janesick

Charge-coupled-device
Charge -coupled- devicecharge-collection
charge -collectionefficiency
efficiency and
and the
the
photon-transfer
photontransfer technique
JamesR.
James
R. Janesick
Kenneth P. Klaasen
Tom Elliott
Propulsion Laboratory
Jet Propulsion
California Institute of Technology
Oak Grove Drive
4800 Oak
4800
Pasadena,
Pasadena,California
California 91109
91109
performance
unprecedented performance
charge-coupled
Thecharge
Abstract.
Abstract. The
-coupled device has shown unprecedented
and
transfer, and
charge transfer,
response, charge
spectral response,
of spectral
areas of
the areas
photon detector in the
as aa photon
as
for
potential for
noise. Recent
readout noise.
Recent experience
experience indicates,
indicates, however, that the full potential
realized in
CCD's charge-collection
the CCD's
charge -collection efficiency
efficiency (CCE)
(CCE)lies
lieswell
well beyond
beyond that
that realized
perforCCE perfordefinitionofofCCE
presentaa definition
we present
paper we
this paper
In this
devices. In
available devices.
currently
currently available
photon-transfer
(the photonmance and
and introduce a standard test tool (the
transfer technique) for
CCE
compare CCE
We compare
parameter. We
CCD parameter.
importantCCD
this important
measuring and optimizing this
in
CCDs, discuss
of CCDs,
types of
characteristics for different types
discuss the
the primary limitations in
characteristics
prospects for
CCE performance,
achieving
achieving high
high CCE
performance,and
andoutline
outline the
the prospects
for future
future
improvement.
charge-coupled
terms: chargeSubject terms:
Subject
coupled devices; charge diffusion;
diffusion; xx-ray
-ray events;
events; frontside
frontside illuminaillumination; backside
backside illumination.
illumination.
1987).
972-980
Optical Engineering 26(10), 972
-980 (October 1987).
CONTENTS
1.
1. Introduction
Charge-collection
2.
2. Charge
-collection efficiency
efficiency (CCE)
(CCE)
Photon-transfer
3.
3. Photontransfer technique
Ideal CCD camera
3.1.
3.1. Ideal
3.2.
3.2. Evaluation of constant K
Evaluation of constant J
3.3.
3.3. Evaluation
included
events included
split events
and split
Partial and
3.4.
3.4. Partial
Photon-transfer
3.5.
3.5. Photon
-transfer curve
3.6. Photon
-transfer histogram
Photon-transfer
3.6.
Photon-transfer
4.
4. Photon
-transfer use
Frontside illumination (TI VPCCD)
4.1.
4.1. Frontside
Backside illumination
4.2.
4.2. Backside
illumination (TI
(TI 3PCCD)
5. Future
improvements in CCE
Future improvements
5.
Acknowledgments
6. Acknowledgments
References
7. References
1. INTRODUCTION
1.
CCDs
CCDs in recent years
years have
have become
become the premier detector for
astronomical
ground-based
and ground
spaceborne and
many spaceborne
use
use in many
-based astronomical
instruments. They were
were selected
selected for
for use
use in
in the Hubble Space
(WF/PC),
Telescope
Telescope Wide
Wide Field
Field Planetary
Planetary Camera (W
F/ PC), the
the GaliGalimany
(SSI), and many
Imager (SSI),
State Imager
Solid State
Orbiter's Solid
leo
leo Jupiter
Jupiter Orbiter's
ground-based
ground -basedimaging
imagingand
andspectroscopic
spectroscopicapplications.
applications. ProPro-ray imager on NASA's
posed space applications include an xx-ray
Space
Advanced
Advanced X-ray
X -ray Astronomical
Astronomical Facility
Facility (AXAF),
(AXAF), a Space
Telescope
Telescope Imaging
Imaging Spectrometer
Spectrometer (SIS), the Solar Optical TeleFlyby
Rendezvous/Asteroid
Comet Rendezvous/
the Comet
scope
scope (SOT),
(SOT), and
and the
Asteroid Flyby
Imaging
Imaging Subsystem
Subsystem (CRAF
(CRAF ISS).
received
1987; revised
13, 1987;
received April 13,
CH-102
Paper CH
Invited Paper
-102 received
revised manuscript received
1987; received
19, 1987;
1987; accepted
15, 1987;
May 15,
accepted for
for publication
publication June 19,
received by
by Managing
Managing
the
at the
presented at
570-02,
Paper570
of Paper
revision of
paper isis a revision
6,1987.
July 6,
Editor July
Editor
1987. This paper
-02, presented
1985, San Diego,
22-23,
Aug.22
Arrays,Aug.
Imaging Arrays,
State Imaging
SPIE conference Solid State
-23, 1985,
Calif.
Calif. The
The paper
paper presented
presented there
there appears
appears (unrefereed)
(unrefereed) in
in SPIE
SPIE Proceedings
Proceedings
Vol. 570.
Engineers.
Photo-Optical
1987 Society of Photo
©
e 1987
-Optical Instrumentation Engineers.
CCD
limit CCD
ultimately limit
parameters that ultimately
fundamental parameters
The
The fundamental
efficiency
charge-transfer
(2) chargenoise,(2)
read noise,
(1) read
are (1)
performance
performance are
transfer efficiency
charge-collection
(4) charge
and (4)
(QE), and
efficiency (QE),
(CTE), (3) quantum
quantum efficiency
-collection
efficiency
efficiency (CCE).
(CCE). At
At their
their present stage of development, it is
(in the 4
noise (in
read noise
low read
have low
that have
devices that
possible to fabricate
fabricate devices
deferred
excellent CTE
range), excellent
15 e~
to 15
a range),
CTE performance
performance(<10
(<10e~
a deferred
entire
the entire
over the
performance over
QE performance
unsurpassed QE
charge),
charge), and
and unsurpassed
potenfull
the
However,
-3
1
A.
11,000
to
1
from
range
spectral
spectral range from 1 to 11,000 A.1 -3 However,
potencharge-collection
of charge
tial of
-collection efficiency
efficiency lies
lies well
well beyond
beyond that
that of
currently
currently available
available devices.
devices. Optimization
Optimization of this important
manufacnew challenge for the CCD manufacrepresents aa new
parameter
parameter represents
is required for many
performance is
CCE performance
High CCE
user. High
turer and user.
the
which the
to which
spectrum to
regions of the spectrum
applications
applications over
over all
all regions
are
CCDs are
CCD is sensitive. In the visible range, for example, CCDs
(charge
sensitivity (charge
highsensitivity
demandhigh
thatdemand
trackers that
used
used in star trackers
geometric
high geometric
with high
loss) in conjunction with
collection
collection without loss)
accuracy (collection
(collection without significant charge diffusion). In
applications
spectrum, applications
the spectrum,
regions of the
EUV regions
the xx-ray
-ray and
and EUV
the
require confinement of signal charge to a single pixel
pixel without
without
loss
loss in
in order
order to accurately determine the energy of the incomincoming
ing photon.
perforCCE perforhigh CCE
achieving high
The means of measuring and achieving
we present a useful
Sec. 22 we
InSec.
paper. In
mance is the subject of this paper.
of parameters that
definition for CCE performance in terms of
definition is
The definition
CCD. The
testing the CCD.
when testing
readily found
are
are readily
found when
responsible for
are responsible
that are
divided
divided into the two primary factors that
and
loss and
chargeloss
namely,charge
performance,namely,
CCE performance,
of CCE
the degradation
degradation of
Sec. 3 we
In Sec.
charge diffusion. In
we introduce
introduce the concept of photon
measuring
ofmeasuring
way of
standard way
as aa standard
used as
technique used
transfer, a technique
CCE characteristics,
characteristics, and develop
develop the
the theoretical
theoretical foundations
show
We show
based. We
method isis based.
photon-transfer
which the photonupon which
transfer method
photon-transfer
of the photonlimitations of
the strengths and limitations
transfer technique
as it is used
used in
in measuring CCE characteristics of the CCD. In
Sec.
Sec. 44 we
we apply
apply the
the photon-transfer
photon -transfer technique in measuring
measuring
10
No. 10
26 No.
Vol. 26
ENGINEERING // October
OPTICALENGINEERING
972 / /OPTICAL
October 1987
1987 // Vol.
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CHARGE-COUPLED-DEVICE
PHOTON-TRANSFER
TECHNIQUE
CHARGE -COUPLED -DEVICE CHARGE-COLLECTION
CHARGE -COLLECTION EFFICIENCY
EFFICIENCY AND
AND THE PHOTONTRANSFER TECHNIQUE
CCE
performance for frontsidefrontside- and
andbackside
backside-illuminated
CCE performance
-illuminated
CCDs
ultimately limit
CCDs and
and discuss
discuss the
the primary
primary factors
factors that ultimately
CCE
each device.
device. Finally,
Sec. 55 we
we discuss
discuss future
future
CCE for
for each
Finally, in Sec.
considerations
considerations for
for further
further improving
improving CCE
CCE for
for the
the CCD.
CCD.
2.
CHARGE-COLLECTION
2. CHARGE
-COLLECTION EFFICIENCY
CCE isis aarelatively
relativelynew
newCCD
CCDperformance
performanceparameter
parameter that
that has
been
Jet Propulsion
Propulsion
been defined,
defined, measured,
measured, and
and optimized
optimized at
at Jet
Laboratory (JPL)
(JPL)and
andelsewhere.
elsewhere. CCE
CCE measures
measures the
the ability of
Laboratory
the CCD to collect all signal charge generated from aa single
single
photon event
event into a single
single pixel.
pixel. High CCE
CCE performance
performance is
is
especially
especially critical
critical for
for EUV
EUV and soft xx-ray
-ray applications (e.g.,
soft xx-ray
soft
-ray imaging
imagingspectrometers),
spectrometers),where
wherethe
the ability
ability of the
CCD to accurately
accurately determine
determine the
energy of
photon
CCD
the energy
of the photon
depends upon collecting
collectingthe
thephotogenerated
photogenerated charge properly.
collection requires
Experience has shown that complete charge collection
requires
that two criteria be met:
met: (1)
(1) There
There must
must be
be no
no trapping.centers
trapping centers
within the CCD to cause signal charge to be lost by recombination,
(2) the
individual photon must
nation, and (2)
the charge
charge of an individual
must be
be
collected
collected within
withinaa single
singlepixel
pixeland
and must
must not be allowed
allowed to
divide
divide among
among several
several pixels.
pixels. Charge
Charge loss
loss causes
causes the
the photon
energy
degrades
energy to
to be
be underestimated,
underestimated, while charge splitting degrades
the precision of charge
charge measurement
measurement by requiring the summation of several noisy pixels.
The
loss and charge
charge splitting
splitting depends
depends
The degree
degree of
of charge
charge loss
upon where
where in
inthe
thepixel
pixelthe
thephoton
photonisisabsorbed.
absorbed. Photons
Photons that
are absorbed within the frontside
frontside depletion
depletionregion
region(see
(see Figs.
Figs. 55
given pixel
pixelare
are typically
typically seen as
as the
the ideal
ideal event
event and
and
and 8) of aa given
are called
called "single-pixel
"single -pixelevents."
events."Photons
Photons absorbed
absorbed below the
depletion region, where the electric field is weaker, create aa
charge cloud
until itit reaches
reaches
cloud that thermally diffuses outward until
the rapidly changing
wells at
changing potential wells
at the lower
lower boundary
boundary of
the pixel
pixel array.
array. At
At that point, the charge cloud may split into
two
pixels.
two or more packets, which are collected in adjacent pixels.
Events of this
Events in
in which
which
Events
this type
type are called "split events." Events
charge
conserved have
have been
been named
named simply
simply "partial
"partial
charge isis not conserved
events"
regions deep
events" and
and are
are usually
usually generated
generated in regions
deep within
within the
the
CCD, where
where loss
occurs.
loss of
of carriers
carriers through
through recombination occurs.
From this discussion,
discussion, aa definition for CCE for an individual
ual photon event
event II can
can be
be presented
presented through the formula
CCE,
CCEI
=
=
(1)
(1)
tion and the
the 800
800 ae remaining
remaining(rspe_1)
Upe-j) split between and collected by two pixels
pixels (1
(Pse
_,). For
se_1).
For this event,
event, aa CCE1
CCEj of
of 0.4
0.4 is
is
calculated
are split
calculated no
no matter
matter in
in what
what proportion
proportion the
the 800
800e~
a are
split
between
between the two affected pixels.
To determine the average CCE performance of a CCD for
a large
large number of
of interacting
interacting photons
photons of
ofthe
thesame
same energy,
energy,
many
splitting and
many events
events are
are measured
measured for charge loss and splitting
then averaged using
using the equation
N
CCE _
i=
Spe - I
(3)
Pse -I
where
N isis the
the number of photon events
where N
events sampled.
Equation (3)
(3) is
is used
used regularly
regularly in
in the
the laboratory
laboratory in characcharacterizing
mechanisms (the partial
terizing the
the two mechanisms
partial and
and split
split events)
events)
responsible for
performance of
the CCD.
CCD.
responsible
for degrading
degrading CCE
CCE performance
of the
However,
manner described
described by
by Eq.
Eq. (3)
(3)
However, measuring CCE in the manner
amount of
ofdata
datareduction.
reduction-since
requires a considerable amount
since many
events must be integrated. Also,
Also, Eq.
Eq. (3)
(3) is
is usable over only a
limited
region (typically,
(typically, A
X<
30 A)
A) because
because for
for
limited spectral
spectral region
< 30
longer wavelengths
wavelengths the
signal generated
generated by an
an individual
individual
longer
the signal
photon becomes too small compared to the
the CCD
CCD read
read noise
noise
floor to reliably resolve the individual event and determine the
amount of
of charge lost and the
the number
number of
ofpixels
pixels affected.
affected.
In this paper we describe
describe another approach
approach to
to evaluating
evaluating
CCE performance for the CCD
CCD that
thatisis applicable
applicable to
toall
all wavewaveThe new
new technique
technique(discussed
(discussedininSec.
Sec. 3)
3) isis
lengths of interest. The
based on the formula
E
CCE=-'
(4)
r/E isiscalled
where CIE
calledthe
theeffective
effectivequantum
quantumyield,
yield,aaquantity
quantity that
that
measures the average number of
of electrons
electrons collected
collected by
by an
an
measures
affected
interacting photon
photon of
ofenergy
energy Ex.
Ex . The
The
affected pixel
pixel for
for an interacting
effective quantum yield
effective
yield r%E
rjE is isrelated
relatedtotothe
thepartial
partial and split
events
events through
E
pe
(5)
Pse
where Spe/
£pe /Pse
the term
termape
£ -i!/Pse
PSeisisthe
theaverage
average value
value of the
/Pse _j.
77; Pse-1
where
where CCEj
CCEI represents
represents the
the fraction of signal electrons, generated by
by aa particular
particular interacting
interacting photon I, that
ated
that isis collected
collected in
any
_j refers
any single
single affected
affected pixel;
pixel; ^e
bpe_I
referstotothe
thepartial
partial event
event and
and
represents the number of signal
signal carriers
carriers generated by a photon
collected by
and collected
by all
all pixels
pixels (the
(the rest
rest being
being lost
lost to recombination); PSe_1
Pse _, refers
referstotothe
thesplit
splitevent
eventand
andrepresents
represents the
the number
of pixels
pixels that
that collect
collect signal
signal electrons
electrons generated
generated by
by a photon;
Tjj is
and m
is defined
defined as
as the
the ideal
ideal quantum
quantum yield, a quantity equal
to the total number of electrons generated for an interacting
interacting
photon
photon of energy
(eV).The
The ideal
ideal quantum
quantum yield
energy EA
Ex (eV).
yield ir/j is
directly
photon energy
energy and is
is found
found
directly proportional
proportionaltoto the
the photon
according
according to
to the
the relationship
E,,
I)i
3.65
(A<1000A)
(À<1000
A) ..
(2)
(2)
As
As an
an example
example of
of using
using Eq.
Eq. (1),
(1), assume
assume that
that an
an interacting
photon generates
(17}), with
recombinagenerates 1000
1000e~e (m),
with 200
200e~e lost to recombina-
PHOTON-TRANSFER
3. PHOTON
-TRANSFER TECHNIQUE
The ideal CCD, which does not generate
generate split
split or
or partial
partial events
events
perfect CCE
CCE performance,
performance,will
will deliver
deliver an
an effeceffecbut exhibits perfect
tive quantum
yield equal
the ideal
ideal quantum
quantum yield
yield (i.e.,
tive
quantum yield
equal to the
r;E
rjj). Today's CCDs are rapidly progressing toward this
this
rlE = rl;).
however, very
placed on
ultimate goal; however,
very strict
strict conditions
conditions are placed
in obtaining
obtaining such
such performance,
performance, as
as we
we shall
shall see
see in
in
the CCD in
Sec.
technologies and
Sec. 4.
4. Because
Because of
of the
the various
various CCD technologies
and manumanufacturers involved in fabricating
fabricating CCDs, a standard "test tool"
performance over
over aa very
very large
large spectral
spectral
for evaluating CCE performance
range is required.
In this section
section we
wediscuss
discussthe
thetechnique
technique of
ofphoton
photon transfer,
transfer,
was used in the past to evaluate
a test tool that was
evaluate CCD
CCD perforperforunits. 1 ItIt was
was realized
mance characteristics
characteristics in
in absolute units.'
realized only
recently that the photon
photon-transfer
recently
-transfer technique also can be applied as
method for
for evaluating
evaluating the
the CCE
CCE perforperforplied
as a standard method
mance of
CCD. In
In the
thediscussion
discussion that
that follows,
follows, we
we first
first
mance
of a CCD.
develop
necessary to
to describe
describe the
the technique,
technique,
develop the equations necessary
OPTICAL
/ October
1987
/ Vol.
OPTICALENGINEERING
ENGINEERING
/ October
1987
/ Vol.2626No.
No.1010/ / 973
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ELLIOTT
JANESICK, KLAASEN,
KLAASEN, ELLIOTT
QE,
QE1
INCIDENTI
PHOTONSI
PI
INTERACTING
INTERACTING
PHOTONS
PHOTONS
ELECTRONS
ELECTRONS
INCIDENT
INCIDENT
PHOTONS
PHOTONS
INTERACTING
INTERACTING
PHOTONS
PHOTONS
L
COLLECTED
COLLECTED
QE
QE
Al
SV
NE
'?'
*R2
R
7
DIGITAL DIGITAL
NUMBER
VOLTS
VOLTS
VOLTS
VOLTS
NUMBER
NUMBER
ELECTRONS
ELECTRONS
TRANSFERRED
TRANSFERRED
VOLT
VOLT
VOLT
SIGNAL
SIGNAL
CHAIN
CHAIN
GAIN
A/DC
A/DC
GAIN
CCD
CCD
SENSITIVITY
I
_JJ
Tft by
through77;
through
A2
S(DN)
SIDNI
CC D
ideal
an ideal
of an
Schematic showing individual transfer functions of
Fig. 1.
Fig.
1. Schematic
CCD camera.
assuming
assuming that
that we
we have
have an
an ideal
ideal CCD
CCD camera
camera with
with no
no partial
split event
or split
event generation.
generation. We
We show
show that
that the ideal quantum
photon-transfer
thephotonthrough the
determined through
be determined
can be
yield TJ
transfer
i can
which
camera, which
CCD camera,
typical CCD
examine a typical
We next examine
approach. We
approach.
includes
includes partial and split event generation, and show that the
photon-transfer
photontransfer technique
technique gives
gives aa reasonable
reasonable approximation
approximation
rjE , defined
yield77E,
quantumyield
for the effective quantum
defined in Eq. (5), which in
performance of the
calculate the
used to calculate
turn is used
the CCE performance
the CCD
sense.
(4)], at least in a relative sense.
[Eq. (4)],
CCD camera
Ideal CCD
3.1. Ideal
3.1.
overall transfer
Figure
Figure 11 isis aa schematic
schematic representation
representation of the overall
debe decamera. The camera can be
ideal CCD camera.
function of
function
of an ideal
are
functions, three
five transfer
scribed in
in terms
terms of
of five
transfer functions,
three that are
scribed
related
related to
to the
the CCD
CCD and
and two
two that are related to the external
signal processing
processing circuitry.
circuitry. The
The input
input to the camera is
CCD signal
given in
given
in units
units of
of incident
incident photons,
photons, and the final output of the
achieved by
is achieved
camera
by encoding
encoding each
each pixel's
pixel's signal
signal into
into a
camera is
12 to 16 bits.
using 12
digital number
bits. The output
output
typically using
(DN), typically
number (DN),
signal
signal SS (DN)
(DN) resulting
resulting from
from aa given
given exposure
exposure of
of the
the CCD
camera
camera shown in Fig. 11 is given by
_ _K
1
(10)
J
measuring
by measuring
possible to
to determine
determine the factors K and JJ by
is possible
It is
each transfer function in Fig. 11 separately and then combining
the
of the
because of
However, because
(9). However,
and (9).
(8) and
Eqs. (8)
these results as in Eqs.
(which
CCD (which
the CCD
of the
parameters of
of parameters
number of
uncertainty in a number
Sv independently), we
QEj, rj{rl, and Sv
prevents us from knowing QED,
great
any great
to any
directly determine
cannot
determine KK or
or J to
practice directly
cannot in practice
we have developed a simple
accuracy. Instead, we
simple technique
technique that
that
requires no knowledge
knowledge of the
the individual
individual transfer functions to
K and J.
determine
factors K
determine the factors
K
constant K
of constant
Evaluation of
3.2. Evaluation
3.2.
generate only one
For the CCD stimulated with photons that generate
one
rl =
(i.e., rj{
electron-hole
electron
-hole(e-h)
(e -h)pair
pairfor
for each
each interaction (i.e.,
(6) reduces
A), Eq. (6)
3000 A),
1;
1; AX >
> 3000
reduces to
to the form
PIK~-I
S(DN)
S
(DN) = PIK
(11)
(I l)
,
interacting
of interacting
number of
represents the
PQE, represents
the number
PI = PQE,
where PI
photons per pixel.
The constant K can be determined by relating the output
(DN)
a§ (DN)
The variance as
a| (DN). The
signal SS (DN)
(DN) to its variance, as
which
errors, which
of errors,
of Eq. (11)
is found using the propagation of
(11) is
perfect
(i.e., perfect
CCD (i.e.,
ideal CCD
the ideal
yields
the following
following equation for the
yields the
charge collection
collection and charge transfer):
-( a S (DN)]2
as (DN)
L
ô PI
aPI
+
[r 3S (DN)12
aK
(12)
+ aR (DN) ,
PQE,r7i SvA,A2 ,,
S(DN)
S
(DN) == PQE0);SvAlA2
(6)
over all
signal (DN)
average signal
where SS (DN)
(DN) represents
represents the
the average
(DN) over
all
where
affected
affected pixels,
pixels, PP isisthe
themean
meannumber
number of
of incident
incident photons
photons per
pixel on the CCD, QED
definedasasthe
theinteracting
interactingquantum
quantum
QEj isisdefined
pixel
is the
efficiency (interacting
efficiency
(interacting photons/incident
photons/ incident photons),
photons), rlrj{ is
ideal
ideal quantum yield defined by Eq. (2), Sv is
is the sensitivity
sensitivity of
of
is the electronic gain of
A, is
on-chip
the CCD on
-chipcircuitry
circuitry(V/e~),
(V/ el, A,
the
of the
A2 isis the
the camera
V), and
and A2
the transfer function of
(V/V),
camera (V/
analog
-to- digital converter
converter (DN/
(DN/ V).
analog-to-digital
QE, and
The quantities QED
and 77}mare
are related
related through
QE =
QE
=
(7)
(7)
ThQEI ,
where QE isis the
the average
average quantum
quantum efficiency (electrons collected/incident
ted/ incident photon).
fundamental
into fundamental
(DN) into
signal SS (DN)
To convert
the output signal
convert the
physical units, it isis necessary
necessarytotofind
findthe
theappropriate
appropriate factors
factors to
signal
or signal
photons or
interacting photons
either interacting
DN units into either
convert DN
convert
are defined by
conversion are
do this conversion
that do
electrons. The constants that
the equations
,A2r! ,
J = (r);SvAIA2)-1
^A2r1 »
K = (SvAIA2)-I
,
,
(8)
(9)
w
(8)
interacting phowhere
where the
the units
units of
of KK and
and JJ are
are e~/DN
e / DN and interacting
respectively. Note
Note that
that Eqs.
Eqs. (8)
(8) and
and (9)
(9) are
are related
related
tons/ DN, respectively.
2
J a1
floor
noise floor
read noise
the read
where we
where
we have
have added
added in
in quadrature the
(e~)KIf2].
a* (e-)
variance aR
(DN) [see
[see Fig.
Fig. 1;1; a£
aÁ(DN)
(DN) = aR
-2].
a£ (DN)
variance
and
(12) and
Eq. (12)
on Eq.
differentiation on
Performing
Performing the required differentiation
(i.e.,
variance (i.e.,
negligible variance
has negligible
constant KK has
assuming
assuming that
that the constant
variance in
the variance
for the
expression for
following expression
aK
thefollowing
findthe
wefind
0),we
cjjt == 0),
S (DN):
2
as (DN) = (-K I
(DN) .
(13)
following
the following
statistics, the
photonstatistics,
ofphoton
because of
PI because
Since ajsj
aPl = PI
Since
(DN)
a§ (DN)
of SS (DN) and as
terms of
in terms
K in
constant K
equation for the constant
results:
K =
K
S (DN)
S(DN)
(DN)
as (DN)
(DN)--4a 2(DN)
(A>3000
(À>3000 A) .
(14)
used, with no
be used,
can be
Equation
(14) is a useful expression and can
Equation (14)
measurements in
output measurements
calibration, to convert output
in DN
further calibration,
electrons.
of electrons.
directly into units of
Evaluation of constant J
3.3. Evaluation
3.3.
wavelengths longer
For wavelengths
longer than
than 3000
3000 A,
A, the
the constants
constants KK and
and JJ
we move into
as we
However, as
1]. However,
= 1].
are equivalent
equivalent [Eq.
[Eq. (10),
(10), rj{rl =
multipleee-h
spectrum, multiple
-ray regions of the spectrum,
-h
the UV, EUV, and xx-ray
resulting in
pairs are generated
generated by each interacting photon, resulting
pairs
in the value J. For these conditions, the
decrease in
and aa decrease
> 11 and
rji >
10
No. 10
26 No.
Vol. 26
October 1987 // Vol.
ENGINEERING // October
/ OPTICALENGINEERING
974 / OPTICAL
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CHARGE-COUPLED-DEVICE
PHOTON-TRANSFER
TECHNIQUE
CHARGE
-COUPLED -DEVICE CHARGE-COLLECTION
CHARGE -COLLECTION EFFICIENCY
EFFICIENCY AND
AND THE PHOTON
-TRANSFER TECHNIQUE
constant
also can be found by
by relating
relating the
the output
output signal
constant JJ also
signal
S (DN),
(DN), given
S
given by
by Eq.
Eq. (6),
(6), to
to its
its variance
variance o$
as (DN). Through
propagation of errors, the variance
variance in
in the
the signal
signal for
for the
the ideal
ideal
CCD can be expressed by
as (DN)
[âS(DN)2
â PI
+
°l\
avi +
z
'as(DN)T
.
J
1e - K
J aK + aR (DN)
an;
.
(15)
Differentiating Eq.
quantum yield
yield
Eq. (15)
(15) and
and assuming
assuming that
that the quantum
r/j has
negligible variance
partial or
or split
split event;
event;
rli
has negligible
variance (i.e.,
(i.e., no partial
61. =
— 0),
0), we
we find
find
a2.
S(DN)
S
(DN)
(XOOOOA)
(X<3000
A)
a£ (DN)
- aR
= aS| (DN) -
J =
(16)
Equations (14)
(14) and (16)
Equations
(16) form
form the basis
basis for
for the
the photon-transfer
photon- transfer
technique. By
By simply
simply measuring
measuring the mean signal and its variance
other spespeance for
for both
both visible
visible photons
photons and
and photons at any other
cific
we can determine the values
values
cific wavelength
wavelength of
of illumination,
illumination, we
K
Once the
known, the ideal
K and
and J.
J. Once
the constants
constants K
K and
and J are known,
quantum yield
yield for
for photons at the wavelength under consideration can be calculated
Eq. (10).
(10).
calculated through Eq.
3.4.
Partial and
and split
split events
events included
3.4. Partial
Up
to
this
point,
we
have assumed
assumed no partial or
or split
split event
event
Up to this
we have
generation within the CCD (i.e., irjEE =
rj{).
We
now
show
that
rl;).
We
now
show
that
=
K/J with
with partial
partialand
andsplit
splitevents
eventsincluded
included gives
the ratio K/J
gives an
an
effective quantum yield
yield rjE,
rjE , which
upper limit for the effective
which in
in turn
gives
performance for
gives an
an upper
upper limit
limit for
for CCE
CCE performance
for the CCD as
as
defined
of partial
partial
defined by
by Eq.
Eq. (4).
(4). We
We also
also show
show that
that as
as the number of
and
split events
events within
CCD decreases,
decreases, the
and split
within the
the CCD
the ratio
ratio K/J
approaches the real
real value
value ofofrlE
rjE and
andininthe
thelimit
limit77E
rjE equals rj^
rl;,
when perfect CCE is achieved.
To analytically
these condianalytically solve
solvefor
for the
the constant
constant J under these
tions, we
we must
must give
give Eq.
Eq. (6)
(6)aanew
newform
form so
so that
that the variances
variances of
the partial and split
split events are included when the overall
overall varivariance of the
the signal
signal isiscalculated.
calculated. Such
Such an
an equation
equation for
for the average
signal in
signal
in any
any given
given pixel
pixel can
can be
be written
written in the form
S(DN)
S (DN) ==P171;M
(CPe
K -I
2(4
Pseat \-1-1
/
S(DN)
S (DN)
'
P.,
+
[as (DN)
(DN) a£ (DN)
(DN) (\P5e + P5e++ epe
- aR
(18)
(18)
a£ is the event
event-to-event
of pixels
where ap
-to -event variance
variance in the number
number of
[ âS(DN)j2
ax
= K
[âS(DN)2
a ,
3*.
It can be
be shown,
shown, again
again using
using propagation
propagation of errors, that the
signal SS (DN), given by Eq.
a| (DN) are
Eq. (17),
(17), and
and its variance as
effective quantum yield by
related to the effective
(17)
Psell'
where
where M
M isis the
the average
average number
number of interacting
interacting photons per
pixel.
informative to
compare the behavior of the
the signal
signal
It is informative
to compare
given
ideal
given by
by Eq.
Eq. (17)
(17) to
to the
the signal given
given in
in Eq. (6) for the ideal
CCD camera
camera without
or split
split events.
events. The
The signal
signal dedeCCD
without partial or
scribed in Eq.
rj{ and
Eq. (6)
(6) isisproportional
proportional to il;
and is
is not
not influenced by
CCE characteristics since CCE is
is assumed
assumed to be perfect.
perfect. In the
the
case
signal isis proportional
case of
of Eq.
Eq. (17),
(17), we
wefind
find that
that the
the signal
proportional to
to
(£pe/
pixel is
ape/ PSC)
PSe)when
whenthe
thenumber
numberof
ofinteracting
interacting photons
photons per pixel
small
1) and interactions are not adjacent
adjacent to
to each
each
small (i.e.,
(i.e., M
M «~ 1)
other
this case,
case, the amount of
of signal
signal
other in
in the
the CCD
CCD array.
array. In this
measured
split event
event behavmeasured isis dependent
dependent on
on both partial and split
ior.
However, when
ior. However,
when the
the number
number of
of interacting
interacting photons
photons per
per
pixel
Pse ), the
pixel isis large
large (i.e.,
(i.e., M
M«
~ PSe),
the signal
signal is
is dependent only on
the partial event [i.e.,
PI^K"-l]
1 ] and the effects of
[i.e., SS (DN)
(DN) ==PIC,peK
the split
split event
event are
are averaged
averaged out.
a^ is
is
that collect signal electrons
electrons per interacting photon and al
event-to-event
the event
-to -eventvariance
variancefor
forthe
the total
total number of electrons
collected.
we have
average of `ape
collected. Here, we
have assumed
assumed that the average
£pe -II
_j/
Pse -i isis equal
£pe _j divided by the average of
Pse_I
equal to
to the average of Cpe1
Pse -i»
"se
_1,which
whichbecomes
becomesnearly
nearlycorrect
correct for
for large
large numbers
numbers of
of
photon events.
events.
Equation (18) also can be written in the form
K_
Je
(19)
where
where Ee isis PSe
Pse + 2(a£/Pse)
Pse (a£/a£e)
2(4/ Pse) ++PSe(GV
ape)and
and K
K and
and J are as
defined
Eqs. (14)
(14) and
and (16),
(16), which
which we
we normally
normally measure
defined in Eqs.
measure
using
photon-transfer
using the photontransfer technique.
The true value
value of
of the
the effective
effective quantum
quantumyield
yield i rjE
given by
E given
Eq. (19)
As the
the number
number of
Eq.
(19) isis less
lessthan
thanK/J
K/J by
by the factor ce"I.1 . As
partial
and split
split events
events decreases,
decreases, the
accuracy of
partial and
the accuracy
of K/J
K/J
improves
improves and
and in
in the
the limit
limit isisexact
exactwhen
wheneE== 11 (i.e.,
(i.e., rjE
rlE=_ rjj).
Therefore, when measuring
measuring the
the effective
effective quantum
quantumyield
yield using
using
the photon-transfer
presence of partial and
photon- transfer technique
technique in the presence
split
K/J gives
gives an
an upper
upper limit
limit for
for flE.
rjE . For
split events,
events, the
the ratio
ratio K/J
example, for the Texas Instruments
(TI) 3PCCD
3PCCD (a
(a CCD
CCD type
type
Instruments (TI)
discussed in Sec.
Sec. 4),
4), we
wefind
findexperimentally
experimentally that for individual
5.9
keV (Fe55)
(Fe55 ) photon
5.9 keV
photon events,
events, one
one out of
of 11
11 events
events splits
splits
between 22 pixels,
pixels, with
with only
only aa few
fewpartial
partial events
events observed.
observed. For
For
this
we calculate
calculate an
an average
average P5e
Pse of
of 1.09
1.09 pixels
pixels with
with
this CCD we
variancesap
= 0.166
0.166 and
and a2
a^ -«0.0.Assuming
Assumingthese
thesevalues,
values, we
variances aP =
find
0.72.Therefore,
Therefore,the
thetrue
truevalue
valueofofrlE
rjE isis actuactufind that ce"I1 ==0.72.
than the
the value
value of
of,lE
rjE measured
measured using
using the
ally smaller by 0.72 than
the
photon-transfer
photon- transfermethod
method (i.e.,
(i.e., K/J).
K/J).
Even though the ratio
ratio K/J
K/ Jdoes
doesnot
notgive
give an
an exact
exact value
value for
for
the
effective quantum
quantity still
the effective
quantum yield,
yield, this
this quantity
still is
is useful
useful in
evaluating and optimizing CCE performance of the CCD, as
we
we shall
shall see
see in
in Sec.
Sec. 4.
4. Therefore,
Therefore, unless otherwise indicated,
we use
K/J as
as found
found through
throughthe
we
use the
the ratio
ratio K/J
transfer
thephotonphoton-transfer
method as our standard
standard measuring
measuringtool
toolinincomparing
comparingrlE
rjE and
CCE performance for different CCDs under different operatoperating
ing conditions,
conditions, while keeping in
in mind
mind that
that the absolute values
of these
1 ).
these quantities
quantities are
are lower
lower (by
(by e"
c I).
Photon-transfer
curve
3.5. Photon
-transfer curve
The constants
constants K
K and JJ can
can be
be found
found either
either graphically
graphically or
or
The
throughEqs.
Eqs. (14)
(14) and
and (16).
(16). We
We examine
examine the
the graphical
graphical
directly through
approach first
first because
because the method
method gives
gives insight
insight into
into the
approach
mechanics of the photonphoton-transfer
mechanics
transfer technique.
The constants K
K and J can be found graphically by plotting
"photon-transfer
curve")
a curve (called the "photontransfer curve
") of noise as (DN)
as
of signal
signal SS (DN),
(DN), typically
typically for aa 20X20
20X20 pixel
pixel
as a function of
array on
on the
the CCD.
CCD. One
One such
such photonphoton-transfer
curve isis shown
transfer curve
shown
in Fig. 2. For
For this
this curve
curve we
we use
use 7000
7000 AA illumination,
illumination, which
which
guarantees that
that TIE
rjE = rl;
rj{ = 1I and
and therefore
therefore can
can be
be used
used in
finding
K. The
The abscissa,
abscissa, SS (DN),
(DN), is
is the average
finding the constant K.
signal level
level of
of the
the 400
400 pixels
pixels with
with the
the array
array uniformly illuminated at some level. (Here, we assume that electrical offset and
OPTICAL ENGINEERING
/ October
975
OPTICAL
ENGINEERING
/ October1987
1987/ /Vol.
Vol.2626No.
No.1010/ / 975
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ELLIOTT
JANESICK, KLAASEN, ELLIOTT
I I I I I I I I I I I
TI3PCCD,
_
TI3PCCD
4000 A
X=
X = 4000
30
-
T= 7000 A
0
t
10
SIGNAL
SHOT NOISE
SLOPE = 1/2
ó
z
20
READ NOISE, oR
101
SLOPE = 0
10
K = 2 e-/DN
100
100
100
J
I
I
I
i
101
102
102
103
103
10*
104
1.5
= K = 1.5
105
105
0.50
DN
SIGNAL
SIGNAL (S),
(S), DN
1).
(T?J =
= 1).
illumination (*1;
Fig.
2. Photon
-transfer curve
curve using
using 7000
7000 A illumination
Photon-transfer
Fig. 2.
0.75
1.0
1.25
1.50
1.75
2.00
2.25
2.50
PHOTONS/DN
INTERACTING PHOTONS
/DN
Fig.
Fig.4.4. Photon-transfer
Photon -transferhistogram
histogram using
using 4000 A illumination
1).
(T* =
=1).
(+F,
10000
10000
rq '' ,"'i
Ea)
,
.,,.i "1
nE12.1Á1=1420
1000
1000
_
71E11216Á1=3
77E(700011=1
ó
.`a .
100
100
Z
2. 1A
1216 Á
10
7000 Á
A
0.001 0.01
0.1
11
10
10
100
100
1000
1000
10000 100000
100000
10000
DN
SIGNAL,
SIGNAL, DN
each
energies, each
photon energies,
three photon
at three
taken at
curves taken
Photon-transfer
Fig.
Fig. 3.
3. Photon
-transfer curves
yielding aa different
different effective quantum yield.
signal
were subtracted
subtracted from the data before the signal
dark current were
level was
wasdetermined.)
determined.)The
The ordinate,
ordinate, as (DN), is the standard
level
exposure.
deviation of the signal of those 400 pixels at each exposure.
pixel-to-pixel
CCDpixel
theCCD
afterthe
found after
-to -pixel
deviation isis found
The standard deviation
accomplished
nonuniformity has been removed. This can be accomplished
same
differencing (pixel
(pixel by
by pixel)
pixel) two
two frames
frames taken at the same
by differencing
light level,
level, calculating
calculatingthe
the standard
standard deviation of the resultant
as
desired as
yields the desired
which yields
difference,and
and dividing
dividing by
by 2,
2, which
difference,
(DN).
aR (DN),
(DN), indicated
indicated in Fig.
Fig. 2,
2, represents the
The read noise aR
intrinsic
noise associated
associated with
with the
the readout circuitry, i.e., the
intrinsic noise
on-chip
CCD on
-chip amplifier
amplifierand
and any
any other
other noise
noise sources
sources that are
level. As the signal is increased, the
signal level.
the signal
of the
independent
independent of
noise eventually becomes
becomes dominated
dominated by the shot noise of the
1/2.
signal and
and isis characterized
characterized by
by aa line
line of slope
slope 1/
2. From Eq.
signal
the
of the
line of
slope 1/1/2
the slope
of the
(14)
we note
note that the intersection of
2 line
(14) we
converdesired converthe desired
represents the
signal axis
signal
axis [i.e.,
[i.e., as
as(DN)
(DN) = 1]1] represents
K.
sion constant K.
The same
graphical approach can be used in determining
same graphical
Fig. 33
example,ininFig.
Forexample,
(16)].For
[Eq.(16)].
the constant J when
when rj{i >>1 1[Eq.
same
photon-transfer
we
transfer curves
curves (taken
(taken with the same
show three photonwe show
wavefields at waveflat fields
CCD
CCD camera
camera and CCD) generated from flat
corresponding
The corresponding
A. The
2.1 A.
1216 A,
lengths
lengths of
of 7000
7000 A,
A, 1216
A, and
and 2.1
wavelengths
these wavelengths
of these
each of
intersections on the signal axis at each
intersections
7000 A
= =r]-m== 11 for 7000
. Since
1.62 X10~3
are 2.3, 0.77,
0.77, and 1.62
X 10 -3.
Sincer]E77E
photon-thisphoton
forthis
illumination,the
thesignal
signalatat as
as (DN)
(DN) = 11 for
illumination,
(i.e.,
K (i.e.,
constant K
transfer
curve represents
represents the
the value
value of constant
transfer curve
wavethe wavefor the
intersections, for
two intersections,
other two
The other
2.3ee~/DN).
K
K ==2.3
-/ DN). The
lengths
lengths 1216
1216AAand
and2.1.
2.1.A,
A,represent
represent values
valuesfor
for JJ that
that can be
be
an
yielding an
J), yielding
used
with K to find
(= KK//J),
rjE (—
find rlE
conjunction with
used in conjunction
interacting
per interacting
pixel per
affectedpixel
peraffected
1420 e~
and 1420
average
average of
of 33e~
e and
e per
respectively.
photon, respectively.
the
e~),),the
1610 el
5.9 keV; rj = 1610
(Ex = 5.9keV;
2.1 A
the case
In the
case of
of2.1
A(Ex
An actual
1420 e~.
of 1420
photontransfer technique yields
yields aa K/J of
e-. An
photon-transfer
individual
measuring individual
by measuring
readily determined by
1215 e~
rjE of 1215
7k
a isis readily
(19)
Eq. (19)
e~ l ininEq.
gives a value for CI
photon
which gives
(5)], which
[Eq. (5)],
events [Eq.
photon events
of 0.88 for CCE perforlimit of
of 0.85.
0.85. From Eq. (4), an upper limit
mance is calculated
calculated using K/ JJ found
found from the photon-transfer
photon- transfer
while a true CCE of 0.75 is
curve, while
is calculated using individual
good
quite good
level of CCE performance isis quite
This level
events. This
photon events.
by today's CCD standards.
3.6.
-transfer histogram
Photon-transfer
3.6. Photon
by
improved by
be improved
can be
The
of determining
determining K
K and
and J can
accuracy of
The accuracy
using Eqs. (14)
(16) directly
directly (as
(as opposed to the graphical
(14) and (16)
3.5). The signal S (DN) and the noise as
Sec. 3.5).
in Sec.
used in
approach used
approach
in the same manner as for the
(DN) are found from the CCD in
aR
noise aR
read noise
photon-transfer
photon- transfer curve
curve discussed
discussed above.
above. The read
is found
found from a dark
dark image. After applying these
these formuformu(DN) is
sensor,
the sensor,
across the
subarrays across
las to many different 20 X20 pixel subarrays
call
we call
formwe
intoaaform
compiled into
K (or J) are compiled
of K
the resulting
values of
resulting values
using
"photon- transfer histogram." An example histogram using
a "photon-transfer
very
produces aa very
4000
A illumination
illumination isis shown
shown in
in Fig. 4. ItIt produces
4000 A
pixel
20X20
many20
Usingmany
1.5e e~/DN.
accurate value of K ==1.5
-/ DN. Using
X20 pixel
device
thedevice
on the
regions on
those regions
of those
subarrays allows elimination of
values for
erroneous values
give erroneous
whichgive
artifacts,which
that contain
blemish artifacts,
contain blemish
be easily recognized as
can be
behaved can
well behaved
not well
K. Areas that are not
as
K.
A
shows. A
Fig. 44 shows.
as Fig.
histogram, as
main histogram,
the main
outside the
points outside
data points
CCD
entire CCD
the entire
over the
be generated over
similar histogram also can be
77E(=
(= K/ J) at a specific wavelength of interest. This
array for rjE
type of histogram is quite valuable in characterizing the varivariability
ability of CCE performance
performance across
across the array of the CCD. In
rjE under different
of rlE
histograms of
Sec.
we depict
depict the use of histograms
Sec. 44 we
operating conditions of the CCD.
PHOTON-TRANSFER
4. PHOTON
4.
-TRANSFER USE
to
technique to
photon-transfer
the photonapply the
we apply
section we
In this section
transfer technique
In
types of CCDs,
different types
two different
fortwo
performancefor
measuring CCE performance
CCD
virtual-phase
namely, the thick TI frontsideilluminated virtual
-phase CCD
frontside-illuminated
three-backside-illuminated
thinTITIbackside
thethin
(TI
-illuminated three
and the
VPCCD) and
(TI VPCCD)
devices are discussed in conThese devices
3PCCD). These
phase CCD (TI 3PCCD).
discussed
tests discussed
in tests
used in
CCDs used
siderable detail elsewhere. !1-~ 33 The CCDs
charge-floor, charge
noise floor,
read noise
same read
the same
here
here have approximately the
for
performance for
efficiency performance
quantum efficiency
transfer efficiency,
efficiency, and quantum
10
No. 10
26 No.
Vol. 26
976 / /OPTICAL
October 1987
1987 // Vol.
ENGINEERING // October
OPTICALENGINEERING
976
Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/21/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
PHOTON-TRANSFER
CHARGE -COUPLED -DEVICE CHARGE-COLLECTION
CHARGE -COLLECTION EFFICIENCY
EFFICIENCYAND
AND THE
THE PHOTON
-TRANSFER TECHNIQUE
CHARGE-COUPLED-DEVICE
SUBSTRATE
500
500
LAYER
EPITAXIAL
EPITAX IAL LAYER
v,
p 11012-cml
p+ 10.011 -cm)
FRONTS IDE
THICK FRONTSIDE
THICK
ILLUMINATED
SiO2
400
EPI INTERFACE
STATES
TII
1
Ec
fl
2µm -
-
Ef
ei
GATE
o
o. 200 200
EVENTS
SPLITEVENTS
AND SPLIT
7 PARTIAL AND
POTENTIAL
z
Mn
Ka
KQ,
100
100 -
ee
i
3.65eV/e~
3.65
eVle-
300 r
? \ 300
POLYS I LICON
5µm
-i
V
1.4e"/DN
1.4e -IDN
1200 A
p+ DIFFUSION
-
E
µmr---
Fe55
5000 A
¡'
fMn Kß
QUAS I -FERMI LEVEL
FOR ELECTRONS
200
200
FREE
800
600
10µm
240 µm
FIELD
400
-H
FIELD
FREE
REGIME
REGIME
SPLIT PARTIAL
SPLIT PARTIAL
EVENTS
EVENTS
1200
DN
SIGNAL,
SIGNAL, DN
1000
1000
1600
1600
1400
1800
1800
2000
2000
CCD,
frontside-illuminated
Fe55 x-ray
Fig.
Fig. 6.
6. Fe55
x -rayhistogram
histogram for
for aa thick
thick frontside
-illuminated CCD,
events.
showing numerous partial and split events.
h`- DEPLETION
REGION
200
200
a
FRONTSIDE
THICK FRONTSIDE
THICK
ILLUMINATED
150 150
Fe55
100 8 100
ELECTRIC
FIELD
BACKSIDE
BACKS
IDE
FRONTS IDE
/IDEAL
IDEAL
50 50
Cross section
Fig.
5. Cross
section of aa thick
thick frontside-illuminated
frontside -illuminated CCD,
CCD, showing
showing
Fig. 5.
and split event
energy band
bandstructure
structure and
and locations
locations at
at which
which partial and
energy
generation occurs.
I
i
00
perforwavelengths used.
the
the wavelengths
used. However,
However, we
we show
show that
that CCE performance for the
the two
two CCDs
CCDs isis significantly
significantly different
different owing
owing to
to the
the
device.
each device.
in each
generated in
events generated
split events
number of partial and split
illumination (TI
4.1.
4.1. Frontside illumination
(TI VPCCD)
the
events for the
split events
we find
find numerous
numerous partial and split
general, we
In general,
is
device is
frontside-illuminated
thick
thick frontside
-illuminatedepitaxial
epitaxialCCD.
CCD. Such
Such a device
primary
5, which shows the primary
schematically represented
represented in
in Fig.
Fig. 5,
schematically
regions
regions within
within the
the CCD
CCD that
that are responsible for generating split
in the substrate region
interact in
events. Photons
Photons that interact
and partial events.
charge cloud
cloud that
that has a high probability of recombiproduce aa charge
holes in this region
of holes
owing to
nation owing
to the high concentration of
existence of
of bulk
bulk interface
interface states
states at
at the
the epitaxial
epitaxial interinterand the existence
face. The physical size
size of the
the charge cloud also is likely to span
the boundary
boundary between
between adjacent
adjacent pixels.
pixels. Such
Such interactions
interactions tend to
to
between
interact between
result
result in
in split
splitand
and partial
partial events.
events. Photons
Photons that interact
also
region also
depletion region
frontside depletion
interface and
epitaxial interface
the
the epitaxial
and frontside
field-free
thefield
diffusionininthe
charge diffusion
to charge
generate
-free
generate split events due to
region and
and partial events due to signal charge
charge diffusing
diffusing through
through
weak field
field produced
produced by
by the p+
p+ diffusion
diffusion into the bulk traps
the weak
5).
Fig. 5).
(see Fig.
interface (see
at the epitaxial
epitaxial interface
Figure 66 shows
shows the
the response
response of
of the
the TI
TI VPCCD uniformly
Fe55 x-ray
illuminated by
illuminated
by an
an Fe55
x -raysource
sourcewith
withaa mean
mean flux
flux of
each pixel on
of each
DN of
The DN
pixels. The
500 pixels.
per500
rayper
approximately
approximately i1 xxray
appromeasured and approis measured
charge is
signal charge
the
containing signal
the CCD containing
response of Fig.
Ideally, the response
priately binned
binned in histogram form. Ideally,
1150 DN
66 should
should show
show only
only two
two prominent
prominent peaks, located at 1150
and
Mn-Ktt
theMn
duetotothe
(1780 e")
1270 DN (1780
and 1270
(1610
(1610e~)
e) and
e) due
-Ka and
events with
F55 source.
Mn-K0
Mn
-Kßxx rays
rays generated
generated by
by the F55
source. The
The events
signals below
signals
below these
these two
two lines
linesare
are the
the result
result of split
split and
and partial
200
200
400
400
J
I
i1
I
i
1400
1200 1400
1000 1200
800
800 1000
t^), ee~
YIELD í'7E1,
QUANTUM YIELD
QUANTUM
600
600
2000
1800 2000
1600
16100 1800
for a thick
r?E for
yieldnE
quantumyield
effectivequantum
of effective
thick frontsideFig.
Fig. 7. Histogram of
CCD.
illuminated CCD.
observed.
events observed.
the events
ofthe
majority of
events
events and
and constitute the majority
yield r]E
effective quantum yield
Figure
Figure 77 shows
shows aa histogram of effective
'7E
TI
same TI
the same
photon-transfer
calculated
calculated by
by the photontransfer method
method for the
Fig. 6.
shown in Fig.
histogram shown
used in generating the histogram
VPCCD used
The histogram is generated by uniformly stimulating the CCD
and
(Fe55 ) and
pixel(Fe55)
perpixel
raysper
about 55 xxrays
of about
mean flux of
with aa mean
with
subarrays
rjE for
calculating
calculating 17E
forseveral
severaldifferent
different 40X40
40X40 pixel subarrays
effective
average effective
anaverage
Fig. 77 an
from Fig.
We find from
sensor. We
across
across the sensor.
which is
pixel//interacting
900 ae~/
of 900
yield of
quantum yield
-/ pixel
interacting photon,
photon, which
is
1610 ee~..
of1610
yieldrlirj{ of
quantumyield
ideal quantum
significantly
significantly less
less than the ideal
is readily calcudevice is
thisdevice
forthis
performancefor
The relative CCE performance
(4).
be 0.56 using Eq. (4).
lated to be
Backside illumination
4.2.
4.2. Backside
illumination (TI
(TI 3PCCD)
substrate
backside-illuminated
the backside
For the
-illuminated CCD,
CCD, in which the substrate
epitaxial interface are removed (Fig. 8), the number of
and epitaxial
been
has been
It has
reduced. It
significantly reduced.
is significantly
events is
split events
partial and split
achieved
beachieved
canbe
100%can
QEofof100%
internalQE
an internal
demonstrated that an
(i.e., ^pe/Tjj
and
thinned and
properly thinned
that isis properly
CCD that
1) for the CCD
= 1)
pe /77i=
CCE
determines CCE
6 The
backside
backside treated.4"
treated.4 -6
Themain
main factor
factor that determines
split
is the split
backside-illuminated
performance
performance for the backside
-illuminated CCD
CCD is
event.
backside-thebackside
forthe
eventsfor
splitevents
ofsplit
numberof
the number
minimize the
To minimize
of
field of
electric field
an electric
that an
illuminated
illuminated CCD,
CCD, itit is
is important that
entire
the entire
throughout the
provided throughout
V/cm
105 V/
greater than 105
greater
cm be
be provided
field
the field
which the
Regionsininwhich
CCD. Regions
the CCD.
of the
depth of
photosensitive depth
/ Vol.
1987
/ October
OPTICAL ENGINEERING
OPTICAL
ENGINEERING
/ October
1987
/ Vol.2626No.
No.1010/ / 977
Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/21/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
ELLIOTT
KLAASEN, ELLIOTT
JANESICK, KLAASEN,
BACKSIDE
BACKSIDE
IDE
FRONTS IDE
FRONTS
e"
e"
e
nn
p
P*-——
800 800
II
DEPLETION
,
DEPLETION
—^11
REGION
P—— REG
1µm
e^ ——I""'!
E
e
e^
e
1
e"
11
600 600
e
500 500
Ev
400
400 -
Si0 2
Si02
OVERLY-THIN
OVERLY -THIN
300
300 -
_^ 111
20
2QA
THIN
17 volts
Vnp
VnP == 17
volts
^NW
~^ Ev\
1
X.
ACCUMULATION
h*- ACCUMULATION
^
LAYER
LAYER
^
BACKSIDE
THIN
THIN BACKSIDE
ILLUMINATED
ILLUMINATED
F055
Fe55
700
700 -
Ef
BACKSIDE
BACKSIDE
CHARGE
CHARGE
900
900
^
-
/IDEAL
/IDEAL
1200 A
200
200 -
6-10µm
100
100 -
backside-illuminated
thin backsideFig.8.8. Cross
Cross section
section of
of a thin
illuminated CCD
CCD that
that is
Fig.
backside charged,
charged,showing
showing energy
energy band
band structure.
structure.
backside
00
i
0
200
200
400
400
It
I
I
1400
1200 1400
1200
1000
800
600
800
1000
600
e(%), e"
YIELD 1'7E1'
QUANTUM
QUANTUM YIELD
'.
1600
1600
2000
1800
1800
' 2000
backside-IJE for
yield TE
for aa thin
thin backside
quantum yield
effective quantum
H istogram of effective
Fig.
Fig. 10. Histogram
illuminated CCD.
3UU
500
2250
EVENTS == 2250
TOTAL EVENTS
': • TOTAL
Ka
Mn Ka
^ /- Mn
; «2.3e~/DN
2.3 e /DN
<yo
N
(1620e")
11620e-1
375 r • 3.
y
65 eV/e3.65
eV /e
z 375
_U
;
-
.:
:
:
125 ~
i
z 125
/ (1780e"):
(1780é I
if
1250
° 250
0
K :
Mn Kß
IrMn
I
Ka
PEAK r
ESCAPE
ESCAPE PEAK
;
CI
0
LrrdL***^*^^
300
300
400
400
500
500
600
600
700
700
U, 1
_
800
800
900
900
DN
(S), DN
SIGNAL
SIGNALIS),
backside-illuminated
Fig. 9.
9. Fe55
x -rayhistogram
histogramfor
for aa thin backside
-illuminated CCD,
CCD,
Fe x-ray
Fig.
events.
split events.
and split
showing very few partial and
large
diffuse to aa large
strength is lower permit the charge cloud to diffuse
split.
and split.
pixel and
one pixel
size, making
making itit likely
likely to
to overlap
overlap more than one
size,
field
high field
thataahigh
For the TI 3PCCD, it has been demonstrated
demonstrated that
using
achieved using
be achieved
can be
region can
/zm region
condition
condition throughout
throughout a 7 µm
backside charging
charging or
or aa flash
flash gate
gate and
and proper bias conditions
backside
n-channel
across the nchanneland
and substrate
substrate (Fig. 8).
across
of a TI
Fe55 x rays of
toFe55
response to
Figure 9 shows a histogram
histogram response
3PCCD that is properly thinned (i.e., thinned to the frontside
Figs. 6 and
Comparing Figs.
edge) and
depletion edge)
and backside treated. Comparing
events isis
split events
and split
partial and
of partial
9,
number of
the number
note that the
we note
9, we
significantly less
less for
for the
the backside-illuminated
backside -illuminated CCD
CCD than
than for
significantly
frontside-illuminated
the frontside
-illuminated CCD.
effective
the effective
of the
histogram of
10 shows
Figure
Figure 10
shows aa TI 3PCCD histogram
photon-the photon
using the
generated using
Fe55 x rays, generated
for Fe55
yield for
quantum yield
on
regions on
two regions
that two
this figure that
from this
We note from
method. We
transfer method.
transfer
different
produce different
thin) produce
overly thin)
and overly
the CCD
(labeled thin and
CCD (labeled
yields. The overly thin region is
quantum yields.
quantum
is slightly
slightlythinner
thinner than
than
depletion
represents where the frontside depletion
the thin region and represents
exhibits
region exhibits
thicker region
backside. The thicker
edge
has reached
reached the backside.
edge has
field-free
largerfield
of aa larger
because of
-free region,
degraded performance because
and
diffusion and
which causes
causes more
more charge
charge splitting
splitting due
due to diffusion
which
yield. The variability of
results in a lower effective
effective quantum
quantum yield.
more
seen more
be seen
can be
membrane can
quantum yield across the CCD membrane
rjE isisdisplayed
which TIE
11, in which
displayedininimage
imageformat
format as a
clearly in Fig. 11,
across the
subarrays across
160,000 subarrays
for 160,000
calculating K/J for
result of calculating
result
right-hand
upperright
the upper
of the
view of
expanded view
12 is an expanded
-hand
Figure 12
CCD. Figure
13 isis aa corresponding
11, and
Fig. 11,
and Fig.
Fig. 13
corresponding printout of
corner of Fig.
rjE . It is seen
fE.
seen from
from Figs.
Figs. 12
12 and
and 13
13 that
that the quantum yield for
this
this device
device varies
varies considerably
considerablyfrom
from 1400
1400e~
e- in
in the
the corners
corners
regions). The
middle (black regions).
the middle
in the
(white
(white regions)
regions)toto 1200
1200e~a in
The
rjE are
differences in
in 77E
arethe
theresult
result of
of thinning
thinning nonuniformities,
differences
middle
the middle
than the
thinner than
where the four corners are physically thinner
employed.
method employed.
of the array because of the thinning method
histogramsfor
foraadifferent
different TI
TI 3PCCD
rjE histograms
14 shows 77E
Figure 14
(V ) across
voltages(VnP)
depletionvoltages
frontside depletion
biased with different frontside
across
n-channel
channel and
and p-substrate.
p- substrate.55 The
The distance
distance that the edge of
the nthe depletion region extends into the
the substrate
substrate isis proportional
proportional
field-free
the field
influences the
therefore influences
and therefore
-free region
region of the
the
V^2 and
to V42
quantum
effective quantum
the effective
that the
see that
we see
figures we
these figures
From these
CCD. From
an
lowered due
is lowered
V is
as Vn
significantly as
yield decreases
decreases significantly
yield
due to
to an
diffusion
field-free
increase
increase in field
-free material,
material, whicn
which causes more diffusion
r]E image over the
showsanan77E
Figure1515shows
splitting. Figure
and charge splitting.
two distinct areas that corV; note two
Vnp —
CCD
CCD array for VnP
= 71 V;
Fig.
in Fig.
indicated in
regions indicated
thin regions
overly thin
and overly
respond to the thin and
respond
14(b).
1 6, isissimilar
rjE histogram,
histogram, shown
shown in
in Fig.
Fig. 16,
similar to
to that
that of
The last r1E
voltage of
depletion voltage
frontside depletion
Fig. 10
elevated frontside
an elevated
has an
10 but has
Fig.
performance
CCEperformance
bestCCE
thebest
represents the
Vn == 27
andrepresents
27 VV and
V
region, an
thin region,
overly thin
the overly
For the
achieved
for the
the TI
TI 3PCCD. For
acnieved for
which yields
measured, which
was measured,
1420 e~
yield of 1420
average quantum
quantum yield
a was
CCE
in CCE
limit in
this limit
that this
believe that
We believe
a relative
CCD == 0.88.
0.88. We
relative CCD
factwo facprimarily to two
due primarily
is due
3PCCD is
performance for the TI 3PCCD
5.9 keV
for aa 5.9
size for
diametersize
cloud diameter
initial cloud
the initial
First, the
tors: First,
keV photon
photon
therefore,
)um); therefore,
diameter «
significant (cloud
event is
(cloud diameter
~ 0.6 µm);
is significant
event
occurs
pixels occurs
pm pixels
3PCCD's1515Am
TI 3PCCD's
the TI
between the
splitting between
charge splitting
even if there
there is
is no
no field-free
field -freematerial.
material. Second,
Second, it isis known
known that
that
regions,
stop regions,
channel stop
field-free
-freeregion
region exists
exists beneath
beneath the channel
a field
occur.
to occur.
splitting to
which
which allows
allows charge
charge diffusion
diffusion and charge splitting
is
where itit is
Ref.7,7, where
detailininRef.
in detail
discussed in
are discussed
Both of
of these effects are
CCE
the CCE
improves the
pixel improves
of the pixel
size of
the size
increasing the
shown that increasing
performance further because of these two factors.
CCE
IN CCE
IMPROVEMENTS IN
5.
FUTURE IMPROVEMENTS
5. FUTURE
backside-thebackside
CCD,the
theCCD,
ofthe
development of
the development
in the
time in
At this time
frontside-illuminated
thefrontside
tothe
superior to
is superior
device is
illuminated
illuminated device
-illuminated
because
is because
This is
device
in achieving
achieving high
high CCE performance. This
device in
backside -illuminated CCD allows field
field control over most
the backside-illuminated
bulk
of the photosensitve volume and elimination of neutral bulk
can
charge can
photogenerated charge
which photogenerated
at which
and trapping
centers at
trapping centers
events.
split events.
and split
partial and
recombine to produce partial
diffuse and recombine
diffuse
backside-illuminated
the backside
for the
Improvements in CCE for
-illuminated CCD
area for
first area
principally in
made principally
will
be made
in two
two areas.
areas. The
The first
will be
10
No. 10
26 No.
Vol. 26
ENGINEERING // October 1987 //Vol.
/ OPTICALENGINEERING
978 / OPTICAL
Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/21/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
PHOTON-TRANSFER
CHARGE-COUPLED-DEVICE
CHARGE
-COUPLED -DEVICE CHARGE-COLLECTION
CHARGE -COLLECTION EFFICIENCY
EFFICIENCY AND
AND THE
THE PHOTON
-TRANSFER TECHNIQUE
1434 1415
1526 1434
1478 1526
1440 1420 1478
1323 1346 1382
1369 1348 1440
1382 1369
1248
125! 1323
1248 1251
1437
1475 1437
1471 1475
1441 1471
1420 1420 1441
1354 1314 1339 1420
1261 1344 1354
1273 1246 1261
1273
1431
1489 1431
1391 1489
1375 1391
1303 1413 1375
1255 1321 1344 1303
1230 1248 1255
1192
1192 1157 1230
1500 1428
1462 1500
1342 1462
1293 1337 1342
1416 1374 1293
1232 1416
1058
1058 1117 1149 1139 1232
1391 1358
1456 1391
1413 1456
1339 1402 1413
1280 1270 1328 1339
1131
1141 1129 1280
1131 1118 1141
1373 1411
1332 1373
1326 1332
1337 1399 1326
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12.
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600
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Fig. 11.
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display of
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effective quantum
quantum yield
yield for
for aa thin
thin
backside-illuminated
backside -illuminatedCCD,
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-hand corner
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depleting the
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complete depletion
Although complete
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tive volume
volume of
of the CCD.
tive
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already has
has been
been demonstrated
demonstrated for
for the
the TI
TI 33PCCD
already
of 77
maximum of
only aa maximum
regions on
on the
the array,
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depletion extends
extends only
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µm. Therefore, high energy
efficiency and
and cosmic
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ray back­
back/urn.
sensor.
characteristics are
are still
still poor for this sensor.
rejection characteristics
ground rejection
fully
depleting itit fully
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the thickness
thickness of
of the
the CCD
CCD and depleting
Increasing
silicon) in
resistivity silicon)
(high resistivity
deep depletion
through
through deep
depletion technology
technology (high
in
yield both high
conjunction with
with backside
backside treatment
treatment should yield
conjunction
CCE and
and high
high energy
energysensitivity
sensitivityfor
forthe
theCCD.
CCD. Work
Work at
at several
several
CCE
this
accomplish this
initiated to accomplish
CCD manufacturers
manufacturers has
has been
been initiated
CCD
goal.
goal.
CCE per­
increase CCE
would increase
jum) would
Second, larger
larger pixels
pixels(—30
(-30 µm)
perSecond,
formance further
further by
by making
making aa larger
larger "target"for
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the incoming
incoming
formance
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event cloud
initial event
the initial
effects of the
reducing the effects
photon and
and reducing
photon
pixel is
the pixel
of the
smaller fraction
diameter. In
In addition,
addition, aa smaller
fraction of
is devoted
devoted
diameter.
regions,
stop regions,
channel stop
to "overhead"
functions such
such as the channel
"overhead" functions
to
which tend
tend to
to increase
increase the
the number
number of
split events
events by
by diffusion.
diffusion.
of split
which
0
200
200
400
400
600
600
800
1000
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QUANTUM YIELDP?E
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Fig. 14.
14. Effective quantum
backside-thinbackside
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histograms for
yield histograms
quantum yield
Fig.
illuminated CCD
CCD using
using frontside
frontside depletion
voltages of
of (a)
(a) 17
17 V,
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illuminated
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(b)
OPTICALENGINEERING
ENGINEERING
/ October
1987
/ Vol.2626No.
No.
979
/ / 979
1010
/ Vol.
1 987
/ October
OPTICAL
Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/21/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
JANESICK, KLAASEN, ELLIOTT
ELLIOTT
7. REFERENCES
REFERENCES
7.
I.I. J.
R. Janesick,
Janesick, T. Elliott,
Elliott, S.
S. Collins,
Collins, M.
M. M.
M. Blouke,
Blouke, and
and J. Freeman,
Freeman,
J. R.
"Scientific charge
charge-coupled
devices;' Opt.
Opt. Eng.
Eng,26(8),
26(8),692
692-714
(1987).
"Scientific
-coupled devices,"
-714 (1987).
2.
2. M.
M. Blouke,
Blouke, J.
R. Janesick,
Janesick, T.
T. Elliott,
Elliott, J.
J. E.
E. Hall,
Hall, M.
M. W.
W. Cowens,
Cowens, and
and
M. M.
J. R.
P.
J. May,
"'Current status
statusofof800X800
800X800charge
charge-coupled-device
imager
P. J.
May, "Current
-coupled -device imager
sensor,"
Eng. 26(9),
26(9), in
in press
press (1987).
(1987),
sensor," Opt.
Opt. Eng.
J, R.
R. Janesick,
Janesick, J.
J. Hynecek,
Hynecek, and
and M.
M. M.
M. Blouke,
Blouke,, "Virtual
"Virtual phase
phase imager
imager for
for
3. J.
Galileo,
"in
C. Geary
Geary and
W.
Galileo,"
in Solid
Solid Stale
State Imagersfor
Imagers for Astronomy,
Astronomy, J.
J. C.
and D.
D. W.
Latham,
Proc. SPIE
SPIE 290,
165-173
(1981)."
Latham, ed.,
ed., Proc.
290, 165
-173 (1981).
4. J.
J. Janesick,
Janesick, T.
T. Elliott,
Elliott, T.
T. Daud,
Daud, J.
J. McCarthy,
McCarthy, and
and M.
M. Blouke,
Blouke, "Backside
"Backside
charging of
in Solid
State Imaging
Imaging Arrays,
charging
of the
the CCD,"
CCD," in
Solid State
Arrays, K.
K. N.
N. Prettyjohns
Prettyjohns
and
E. L.
L. Dereniak,
Dereniak, eds.,
eds., Proc.
Proc. SPIE
and E.
SPIE 570,
570, 46-79
46 -79(1985).
(1985).
J. Janesick,
Janesick, T.
T. Elliott,
Elliott, T.
Daud, and
5. J.
and D.
D. Campbell,
Campbell, "The
CCD flash
flash gate,"
T. Daud,
"The CCD
gate,"
in Astronomy
Astronomy VI,
VI, D.
D. L.
L. Crawford,
in Instrumentation in
Crawford, ed.,
ed., Proc.
Proc. SPIE
SPIE
627,543-582(1986).
627,
543 -582 (1986).
Janesick, D.
D. Campbell,
Campbell, T.
T. Elliott,
Elliott, T.
T. Daud,
Daud, and
and P.
6. J. Janesick,
P. Ottley,
Ottley, "Flash
"Flash
technology for
CCD imaging
imaging in
in the
theUV,"
UV,"ininUltraviolet
UltravioletTechnology,
Technology,
technology
for CCD
R. Huffman,
Huffman, ed.,
ed,, Proc.
Proc. SPIE
SPIE 687,
687, 36-55
R.
36 -55(1986).
(1986).
H. Marsh,
Marsh, and
and, S.
S. Collins,
Collins, "'Present
7. J...
J. Janesick,,
Janesick,T.T. Elliott,,
Elliott, J.
J. McCarthy,
McCarthy, H.
"Present
and,
future CCDs
CCDs for
forUV
UVand
andx x-ray
scientificmeasurements,"
measurements," IEEE
IEEE
and future
-ray scientific
Trans. Nuc.
Nuc. Sci.
Sci.NS
NS-32
(I),, 409
409-416
(.1985).
Trans.
-32 (1),
-416 (1985).
s
Fig.
effective quantum
quantum y
yield
image for
eld image
for the histogram
histogram of
Fig. 15.
15. An
An effective
Fig.
Fig. 14
(b).
14(b).
900
wu
1
800'
800 -
• THIN
BACKS I IDE
THIN BACKSIDE
ILLUMINATED'
ILLUMINATED
I
I
• 1
I
1
i,,
a,A 700
700 z 600 1 600
0
I
r
• V
»= 27
27 volts
volts
Vnp
Fe 55
w
1
Z
200 1 200
00
;
THIN
I
CSL
UJ
300 § 300
0o
1
|Lx/ THIN
E 500 §500
o
ó
o
400 ó 400
100 100
1
R. Janesick:
Janesick: Biography
Biography and
and photograph
photograph appear
appear with the Guest
James R.
Editorial
issue.
Editorial in this issue.
OVERLY -THIN
.OVERLY-THIN
an/
A\ ^I
i D"L IDEAL
,
2DO
,
400
,
600
600
,
800
800
, J.
1000
1000
1200
1200
Ai .,
1400 1600
1400
1600
1800
1800 2000
2000
QUANTUM
YIELD I'k1,
eQUANTUM YIELD(r?E
), e~
Fig.
Fig. 16.
16. Histogram
3PCCD,
H istog ra m of
of best
best effective
effective quantum
quantum yield
yield for
for the
the TI
Till 3
PC C D,
using aa fronts
frontside
voltage of
of 27 V.
V.
using
id e voltage
6. ACKNOWLEDGMENTS
6.
ACKNOWLEDGMENTS
The authors acknowledge many rewarding conversations on
The
the subject
of CCE
(father of
of the
the TI
the
subject of
CCE with
with Morley
Morley Blouke
Blouke (father
3PCCD), Taher Daud, Andy
Andy Collins, Dave Campbell, James
DeWitt, Arsham Dingizian,
DeWitt,
Dingizian, and James McCarthy.
McCarthy,., We
We also
also
thank
Deborah Durham
thank Deborah
this paper.
Durham, for reviewing
reviewing this
paper. The
The
research described
describedwas
wascarried
carried out
out by
by the Jet
research,
Jet Propulsion
Propulsion,
Laboratory, California
California Institute of Technology,
Technology, under concon­
tract with
with the
the National
National Aeronautics
Aeronautics and
and Space
Space Administration.
Administration.
tract
Kenneth P.
IP. Klaasen
Klaasen is
is the
the supervisor
supervisor of
of the
the
P
h otosci e nee Group
G rou p at
at JPL.
J P L. He
H e received
recei ved his
h i s BS
BS
Photoscience
deg
r e e iin
n physics
p hys i cs from
fro m Calvin
C a I v i n College,
Co 11 eg e, Grand
degree
G r a nd
Rapids,
MS in
in aerospace
aerospace engiengi­
Rapids, Mien.,
Mich., and his MS
neering
University of Michigan
Michigan in
neering from
from the University
19 6 9, He
H e has
h a s been
bee n involved
i n vo I ved in
i n many
m a n ysolar
so I a r syssys 1969.
tern exploration
exploration missions,
missions, including
including Mariner
Mariner
tem
1
I
10, the
and currently
currently the
the GaliGali10,
the Viking
Viking Orbiter, and
|
^
leo
Jupiter. He
He has
has served
served as
as the
the
leo mission to Jupiter.
I
experiment representative
representative for
experiment
for the
the imaging
imaging
experiments on
on these
these missions
missions and
and is
is curcur­
experiments
member of
rently aa member
of the
the Galileo
GalileoImaging
ImagingScience
Science Team.
Team. His
His primary
primary
responsibilities have
have included
included imaging
imaging system
system calibration,
calibration, experiment
experiment
planning, and
and mission
mission operations.
operations. He
He has
has published
published papers
papers on
planning,
on the
rotation period
period of
of Mercury,
Mercury, Venus
Venus atmospheric
atmosphericdynamics,
dynamics,and
andthe
thephopho­
rotation
of Mercury,
Mercury, Mars,
Mars, and
tometry of
and the
the Martian
Martianmoons,
moons,Phobos
P hobos and
and Deimos,
Deirnos,
as well as
as several
several on
on various
various spacecraft
as
spacecraft imaging
imaging instruments
instruments and
and
experiments.
1
:/:
Stythe T.
T. Elliott
Elliottwas
wasborn
bornininVan
Stythe
VanNuys,
Nuys, CaliCali­
fornia. He
He received
received his
his BA
fornia.
BA degree in geography
from the California
California State
State University
University at
at NorthNorthPropulsion Laboratory
Laboratory
ridge. He joined the Jet Propulsion
in 1979
1979 and
and isis presently
presently working
workingon
on developdevelop­
charge-coupled
devices for NASA
NASA space
space
ing charge
-coupled devices
imaging systems.
imaging
systems. He
He received
received aa NASA
NASA
in 1986.
1986. He
He isis currently
currently
Achievement Award in
involved with
withthe
thedevelopment
developmentofofCCDs
CCDs used in
involved
the wide
/planetary Hubble
wide field
field/planetary
HubbleSpace
Space TeleTele­
scope camera.
/ OPTICALENGINEERING
980 / OPTICAL
ENGINEERING // October
October 1987
1 987 // Vol.
Vol. 26
26 No.
No. 10
10
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