MIT/Lincoln Labs CCID20 W62C2 CCD Test Results

This is the first MIT/Lincoln Labs 2Kx4K CCD we've seen with the new and improved boron implant and laser anneal process. The QE non-uniformity has been reduced at most wavelengths. This is a high-resistivity CCD.

A summary report is available. Noteworthy points about this CCD include:

This was a test CCD. It wasn't even rated during the initial phase 1 MIT/LL wafer probe testing. It does have a short that tends to flood the CCD with charge. But at low temperature it is still a useful test-grade device.

Original postscript files are available from our anonymous ftp server and these provide better resolution and clarity than is usually possible on a web page. Here are a few figures to illustrate device highlights:

QE curve: This curve compares the QE of this CCD with an older high resistivity CCD and a low resistivity CCD. The effect of the blue-peaked AR coating is clear.
Serial CTE: CTE is is very good, as usual.
Brick wall: This is the pattern which results from the incomplete backside laser anneal. The pattern is compared to an earlier high resisitivity CCD that used the old processing.
Surface Plots: The surface shape is very good with peak to valley variation less than 20 microns.

This plot compares the QE measurements made of three CCDs. W6C2 and W67C1 were measured as part of the phase 1 work. They both have the standard AR coating supplied by MIT/LL during phase 1. The new coating has peak performance shifted to the blue, and the very significant improvement in blue QE is obvious. The measured QE values can be found in the summary report.

The Lincoln CCID20 design produces excellent charge transfer efficiency. This plot shows a test of serial CTE using Fe⁵⁵ xrays.

The data for these curves were obtained by taking a flat field image at each of the indicated wavelengths and measuring the amplitude of the quantum efficiency variations. 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 and different results will be obtained if a different row is selected. But the general reduction in the amplitude of the variation seen in W62C2, compared to the old process used with W67C1, is clear.

This plot shows how the QE variations change with temperature. A more detailed look at the CCD helps interpret this plot. That analysis shows that just the least-sensitive areas of the CCD increase in sensitivity. This results in a decrease of (MAX-MIN). Other parts of the CCD which show lesser QE variations don't change much, if any, with temperature.

These two plots show the surface shape at room temperature. The same data are show, but in different perspectives.

Back to Lincoln Labs Top Page