Radiation-hard silicon cryo-CMOS process suitable for charge-coupled devices, and a device made according to this process
AssigneeHughes Electronics Corporation
InventorsChen-Chi P. Chang, James S. Cable
Life of this patent
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Abstract
A silicon-based radiation-hard cryo-CMOS CCD process suitable for fabrication of devices (100) with sub-micron feature sizes. A re-oxidized nitride/oxide (RONO) layer (49″) is preserved in the CCD area (32) while plasma etching is used to define polysilicon 1 gates (50′) in the active FET area of the device. Thereafter, a wet chemical etching process, which does not destroy the integrity of the RONO layer (49″) in the CCD area, is carried out. A channel stop (48) is formed after the field oxidation step in the active FET area to reduce the space required for minimum diode breakdown voltage between the n+ source/drain region and the p+ channel stop.
Claims3
A method of fabricating a silicon-based radiation-hard cryogenic complementary metal oxide semiconductor (cryo-CMOS) charge-coupled device (CCD), said method comprising sequential steps of:
- providing a silicon substrate;
- forming in a CMOS active device area a pair of adjacent wells of opposite doping type in said substrate, and an adjacent CCD area;
- providing a layer of re-oxidized nitride/oxide over said CCD area and said CMOS active device area;
- providing a layer of polysilicon over said layer of re-oxidized nitride/oxide, over said pair of adjacent wells and said adjacent CCD area;
- plasma etching said layer of polysilicon at said pair of wells to define a respective pair of gates for transistors to be formed in said pair of wells;
- and simultaneously protecting said layer of polysilicon and re-oxidized nitride/oxide over said CCD area so that both are substantially not affected by said plasma etching;
- wet-chemical etching said layer of polysilicon over said CCD area to form first polysilicon gates for said CCD area, while substantially not attacking said re-oxidized nitride/oxide layer at said CCD area with said wet-chemical etch.
Dependencies are inferred from the claim text.