Responsivity Uniformity Enhancements for Backside-Illuminated Charge- Coupled Devices (BICCDs) by Excimer Laser-Assisted Etching
Final rept. May 90-Apr 91,
NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA
Pagination or Media Count:
BICCDs are solid-state electronic imaging devices which read out image charges from wells in an array of pixels. The substrate below the pixel array is typically thinned by chemically etching 100-oriented silicon using a potassium hydroxide KOH etch. The potassium hydroxide anisotropically etches to the 111 crystallographic plane in silicon, leaving smooth sidewalls at an angle of 54.7 degrees to the image plane. This smooth surface acts as a mirror to reflect extraneous light onto the image plane of the BICCD, causing spurious images and reducing the responsivity uniformity RU of the devices. We have developed a noncontact excimer laser-assisted process to promote a chemical reaction between a halocarbon ambient and the silicon. The laser-assisted chemical reaction results in a roughened textured surface which behaves as a light sink. The use of a nonreactive ambient allows us to texture the sidewalls of prepackaged and pretested devices. The sidewalls of fully functional BICCD die have been textured in a Freon-115 chloropentafluoroethane ambient by directing 5000 pulses with laser fluence of about 0.75 Jsq cm upon them. The RU of the devices as well as the background level fat-zero are dramatically improved.
- Manufacturing and Industrial Engineering and Control of Production Systems
- Optical Detection and Detectors