Method of forming a semiconductor structure having reduced threshold voltage and high punch-through tolerance
DCFirst Claim
1. A method of forming a semiconductor structure comprising the steps of:
- (a) providing a substrate having a major surface;
(b) forming at least one trench in said substrate;
(c) forming a body region of a first conductivity type in said substrate, said body region having a diffusion boundary in said substrate;
(d) forming a source region of a second conductivity type in said body region; and
(e) compensating a portion of said body region by implanting material of said second conductivity type in said body region, said portion being proximal to said source region and spaced from said diffusion boundary of said body region and said major so as to reduce the impurity concentration of said first conductivity type in said portion of said body region.
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Abstract
A power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) device formed on a semiconductor substrate having a body region of a first conductivity type diffused in a semiconductor substrate with an epitaxial layer of a second conductivity type. There is also a source region of a second conductivity type formed in the body region. A portion of the body region adjacent to the source region is compensated by ion implanting a material of the second conductivity type in the portion of the body region such that the impurity concentration of the body region at the portion is reduced. As a consequence, with reduced impurity charge in the body region adjacent to the source, the threshold voltage of the MOSFET device is lowered but at no comprise in punch-through tolerance because the reduction in charge is remote from the origin of the depletion layer which is located at the boundary between the body region and the epitaxial layer.
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Citations
29 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 having a major surface; (b) forming at least one trench in said substrate; (c) forming a body region of a first conductivity type in said substrate, said body region having a diffusion boundary in said substrate; (d) forming a source region of a second conductivity type in said body region; and (e) compensating a portion of said body region by implanting material of said second conductivity type in said body region, said portion being proximal to said source region and spaced from said diffusion boundary of said body region and said major so as to reduce the impurity concentration of said first conductivity type in said portion of said body region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of forming a semiconductor structure having a trench gate with a gate threshold voltage, said method comprising the steps of:
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(a) providing a substrate having a major surface; (b) forming a body region of a first conductivity type in said substrate, said body region having a diffusion boundary in said substrate; (c) forming a source region of a second conductivity type in said body region; and (d) compensating a portion of said body region by implanting material of said second conductivity type in said body region adjacent to said source region and spaced from said diffusion boundary of said body region and said major surface such that the impurity concentration of said portion of said body region is substantially reduced so as to decrease the gate threshold voltage of said trench gate. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method of forming a semiconductor structure having a gate with a gate threshold voltage, said method comprising the steps of:
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(a) providing a substrate having a major surface; (b) forming at least one trench in said substrate extending from said major surface; (c) forming a body region of a first conductivity type in said substrate to a diffusion boundary extending from said major surface; (d) forming a source region of a second conductivity type in said body layer extending from said major surface; and (e) compensating a portion of said body region by implanting material of said second conductivity type in said body region adjacent to said source region and spaced from said diffusion boundary of said body layer and said major surface such that the conductivity of said portion of said body region is substantially reduced so as to decrease the gate threshold voltage of said gate. - View Dependent Claims (26, 27, 28, 29)
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Specification