Method of forming a semiconductor structure with uniform threshold voltage and punch-through tolerance
First Claim
1. A method of forming a semiconductor structure, comprising the steps of:
- (a) providing a substrate with a major surface;
(b) forming at least one trench in said substrate extending from said major surface;
(c) lining said trench with insulating material;
(d) filling said trench with conductive material;
(e) forming a spacer layer above said conductive material and surrounding said insulating material adjacent said major surface;
(f) patterning a masking layer over said substrate; and
(g) implanting a diffusion layer in said substrate through said masking and spacer layers.
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Accused Products
Abstract
A MOSFET (Metal Oxide Semiconductor Field Effect Transistors) structure is fabricated by first forming a plurality of trenches in a semiconductor substrate which includes a major surface. The trenches are then lined with insulating material and thereafter filled with conductive material. The process of filling the conductive material in the trenches normally involves an over-etching step for preventing any residual material remaining on the major surface. The over-etching of the conductive material in the trenches alters the evenness of the major surface and presents a problem for the later angular ion implantation of the source layer. As a consequence, the source layer formed includes asymmetrical source segments which generates nonuniform threshold voltage and punch-through tolerance in the MOSFET structure. The inventive method provides a spacer layer to compensate for the unevenness of the major surface. Prior to the ion implantation of the source layer, the spacer layer is formed above the conductive material and surrounding the insulating material adjacent the major surface. Source segments thus formed are symmetrical in shape enabling the fabricated MOSFET structure to operate with uniform punch-through tolerance, uniform threshold voltage, and uniform current distribution during normal operation.
101 Citations
21 Claims
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1. A method of forming a semiconductor structure, comprising the steps of:
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(a) providing a substrate with a major surface; (b) forming at least one trench in said substrate extending from said major surface; (c) lining said trench with insulating material; (d) filling said trench with conductive material; (e) forming a spacer layer above said conductive material and surrounding said insulating material adjacent said major surface; (f) patterning a masking layer over said substrate; and (g) implanting a diffusion layer in said substrate through said masking and spacer layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of forming a cell array, comprising the steps of:
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(a) providing a substrate of a first conductivity type;
said substrate includes a major surface;(b) forming a plurality of trenches in said substrate extending from said major surface; (c) lining said trenches with insulating material; (d) filling said trenches with conductive material; (e) forming a spacer layer over said conductive material and surrounding said insulating material adjacent said major surface; (f) forming a masking layer over said major surface; and (g) implanting a source layer of said first conductivity type in said substrate through said masking and spacer layers. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for forming a semiconductor structure, comprising the step of:
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(a) providing a substrate having a major surface; (b) patterning a first masking layer over said substrate; (c) forming at least one trench in said substrate extending beyond said major surface; (d) lining said at least one trench with insulating material; (e) filling said at least one trench with conductive material; (f) forming a spacer layer above said conductive material and surrounding said insulting material adjacent said major surface; (g) implanting a body layer in said substrate through said masking and spacer layers; (h) diffusing said body layer downwardly and sidewardly so as to merge portions of said body layer under said masking and spacer layers together; and (i) implanting a source layer in said substrate through said masking and spacer layers. - View Dependent Claims (20, 21)
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Specification