MIT/Lincoln Labs CCID20 W20C1 CCD Test Results
This is the second standard epi, thinned, backside MIT/Lincoln
Labs 2Kx4K CCD to be characterized in the UCO/Lick detector lab. This CCD
had a wiring problem so it was returned to Lincoln for rework. When the
device returned from Lincoln it was working and it was a very good CCD.
However, after a day in the dewar it stopped working again. The output
amplifiers seem to be working still, but we see no charge transfer. No
obvious electrical problem has been identified and at the current date
(Sept. 16) it is still not working.
The results reported here were obtained before the device failed.
A summary report
is available. Noteworthy points in the report include:
- Parallel clocks. If the
parallel clock negative rail is too low, significant spurious charge is
generated. At -6 volts on the negative rail parallel clocking works fine,
with little or no spurious charge.
- Serial Clocks. Proper serial
clock levels must be chosen to maintain low spurious charge. Based on read
noise measurements, +6v and -3v serial rails seems to produce low spurious
charge.
- CTE. Near perfect CTE is
achieved using the serial and parallel clocks which generate low spurious
charge. This is typical of Lincoln CCDs.
- Read Noise. Read noise is
around 2 electrons. This is as good as or
better than any thin CCD in the world.
Original postscript files are available from our anonymous
ftp server and these provide better resoultion and clarity than is
usually possible on a web page. Check the INDEX
file for a description of the other files available. Here are a few figures
to illustrate device highlights:
- QE curve
- This is a pretty typical QE curve for the CCID20s. The
QE is an average over a fairly large portion of the CCD, so this result
is an average over the brickwall variations.
- Serial CTE
- Near perfect CTE is achieved by the Lincoln CCD design.
- Surface plot
- Hasn't been measured yet.
- Brick wall
- This is the pattern which results from the incomplete
backside laser anneal. This device exhibits a rather high amplitude in
the pattern.
This plot shows the QE measurement
made at a device temperatures of -127°C. We've found that the QE can be
somewhat temperature sensitive, especially in the less sensitive areas
of the brickwall pattern. So this result will change a little with temperature,
with the QE increasing with increasing temperature.
The Lincoln CCID20 design
produces excellent charge transfer efficiency. This plot show a test of
CTE using Fe55 xrays.
No images yet...
Each of these images shows
a flat-field in the same area of the CCD, but at different wavelengths.
The percents shown are derived by taking a single row cut through the image
and computing a percentage as (MAX-MIN)/MEAN. Obviously this emphasizes
maximum variations.
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