Semiconductor device manufacturing: process – Making passive device
Reexamination Certificate
2000-04-12
2002-08-13
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Making passive device
C438S253000, C438S239000, C438S352000, C438S396000, C438S255000
Reexamination Certificate
active
06432791
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to semiconductor integrated circuits, and more particularly to mixed signal integrated circuits and fabrication methods.
Mixed signal integrated circuits (which contain both analog and digital devices) typically include CMOS and bipolar transistors plus capacitors and resistors. Such integrated circuits compromise performance of the various devices in order to reduce process complexity. However, circuits such as 12-bit analog-to-digital converters require precision capacitors with minimal capacitance dependence upon applied voltage. But known mixed signal processes do not provide precision capacitors without undue complexity.
SUMMARY OF THE INVENTION
The invention provides a precision capacitor in a mixed signal process by use of a single polysilicon layer for both MOS gates and capacitor plates but with diffusive doping in the capacitor plates portion and implant doping in the polysilicon gates portion.
This has the advantages of high doping to limit variation of capacitance with applied voltage to the capacitors and avoidance of diffusive doping affecting MOS channel regions.
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Hutter Louis N.
Khan Imran
Ying Peter S.
Brady W. James
Hoel Carlton H.
Lu Chuong Anh
Smith Matthew
Telecky , Jr. Frederick J.
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