UCO/Lick CCD Thinning Project

• First Results
• QE Pinned Condition

The UCO/Lick Detector Development Lab has been working on CCD thinning technology for several years. The first image from one of our thinned Orbit 2Kx4K CCDs was obtained on August 20, 1997.

Congratulations to Bill Brown, Don Booth, Mingzhi Wei, and Kirk Gilmore for all of the work they have put in on this project. We have a long way to go to finish this CCD (oxide growth, AR coating, and possibly a flash-gate) but this just might be an instrument grade device.

First Results (Oct. 20, 1997)

Here is the image! It was obtained when the CCD was cooled to only about -50°C, so there is a high dark, but the CCD looks very clean- no hot columns. Serial charge transfer efficiency also looks very good.

We could not have achieved these results without the Microfabrication Facility at the University of California, Davis. Don Booth, graduate student and now the Facility manager, and Dr. Charles Hunt were instrumental in creating this success, and many others at UC Davis helped in important ways.

QE Pinned Condition (Dec. 19, 1997)

The surface of the CCD was initially in bad shape, with a residue from the chemical thinning step. As a result the QE was poor. As an experiment to improve the surface quality we hand polished a patch of the CCD with a chemical-mechanical polishing agent. The polished patch of the CCD looked very clean and smooth, and after regrowing an oxide on the CCD we gave the device a UV-flood and tested the quantum efficiency. The following image shows the result. The device is QE pinned (or very nearly so) at all wavelengths in the polished patch. Also note that the QE outside the patch is low and irregular. This is a very encouraging result because it means that we now have an established, reliable process from frontside CCD to thin, backside CCD.

Next Step

Next we will polish the remainder of the CCD, regrow the oxide again, and apply an anti-reflection coating.

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