US 5,474,946 AGranted

Reduced mask process for manufacture of MOS gated devices

AssigneeInternational Rectifier Corporation

InventorsJanardhanan S. Ajit, Daniel M. Kinzer

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Abstract

A process for forming a MOS gated device in which an oxide layer is patterned to have adjacent thick and thin oxide layers atop a silicon surface. Polysilicon is then patterned atop the oxide layer with a critical alignment step to the thin oxide layers in the process. Boron is implanted through both the thick and thin regions of the oxide which are exposed by the polysilicon mask to form P type base regions and P type guard rings in the silicon. Arsenic is thereafter implanted at an energy at which arsenic atoms penetrate only the thin oxide exposed by the polysilicon to form self-aligned source regions in the base regions previously formed. A contact opening mask which is critically aligned to the polysilicon mask forms openings for making contact to the silicon. The device is completed using non-critical alignment masking steps.

Claims15

Dependent claims

A process for the manufacture of a MOS gated semiconductor device, comprising the steps of:

(a) forming an insulation layer atop a major surface of a silicon wafer;
(b) patterning said insulation layer in a first mask step to define at least a first area which is thicker than at least a second second area adjacent to said first area;
(c) depositing a layer of polysilicon atop said insulation layer and patterning said polysilicon layer in a second masking step to cover and mask a third area and to expose a fourth area of said second area;
(d) implanting first species atoms at an energy sufficient to penetrate both said first and second insulation areas and diffusing said implanted first species atom to form at least one base region in said silicon wafer in an area exposed by said patterned polysilicon;
(e) implanting second species atoms at an energy sufficient to penetrate said second insulation area but insufficient to penetrate said first insulation area, thereby to form at least one source region in said at least one base region;
(f) and thereafter forming a source contact which contacts said at least one source region and at least one base region.

3 more elements

Dependencies are inferred from the claim text.