Forming twin wells in semiconductor devices

Details Forming twin wells in semiconductor devices Forming twin wells in semiconductor devices

1990-03-30

1991-09-03

Hearn, Brian E.

Fishing, trapping, and vermin destroying

437147, 437 34, 148DIG70, H01L 21302, H01L 2176

Patent

active

050454951

ABSTRACT:
A method of forming a well of one conductivity type in a silicon substrate having a first surface region thereof which is doped with a dopant of one conductivity type and a second surface region thereof which is doped with a dopant of opposite conductivity type. The first and second regions are covered by respective first and second portions of an oxide layer which has been grown on the silicon substrate, the first portion being thicker than the second portion. The substrate is oxidized thereby to increase the thickness of the oxide layer such that the difference in thickness between the first and second portions is reduced. The substrate is also heated to cause diffusion of the dopant of one conductivity type thereby to form a well and of the dopant of opposite conductivity type down into the substrate. The heating step is carried out before, during or after the oxidizing step. The oxide layer is then removed thereby to expose the substrate surface which has a step of around 400 Angstroms in the region of the well boundary.

REFERENCES:
patent: 4027380 (1977-06-01), Deal et al.
patent: 4516316 (1985-05-01), Haskell
patent: 4554726 (1985-11-01), Hillenius et al.
patent: 4925806 (1990-05-01), Grosse
Wolf et al, Silicon Processing for the VLSI ERA, 1986, pp. 198, 219-220.

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