Method of fabricating high voltage power MOSFET having low on-resistance
First Claim
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1. A method of forming a high voltage MOSFET comprising the steps of:
- providing a substrate of a first conductivity type;
depositing an epitaxial layer on the substrate, said epitaxial layer having a first conductivity type;
forming first and second body regions in the epitaxial layer to define a drift region therebetween, said body regions having a second conductivity type;
forming first and second source regions of the first conductivity type in the first and second body regions, respectively; and
forming a plurality of trenches in said drift region of the epitaxial layer;
filling said trenches with a material having a dopant of the second conductivity type, said trenches extending toward the substrate from the first and second body regions;
diffusing at least a portion of said dopant from said trenches into portions of the epitaxial layer adjacent the trenches;
measuring a breakdown voltage in said epitaxial layer;
comparing the measured breakdown voltage to a predetermined relationship between breakdown voltage and diffusion time to determine a remaining diffusion time to achieve a prescribed breakdown voltage; and
performing an additional diffusion step for said remaining diffusion time.
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Abstract
Test structures for a high voltage MOSFET are provided that includes a substrate of a first conductivity type. An epitaxial layer also of the first conductivity type is deposited on the substrate. A plurality of trenches are located in the drift region of the epitaxial layer. The trenches, which extend toward the substrate from the first and second body regions, are filled with a material that includes a dopant of the second conductivity type. The dopant is diffused from the trenches into portions of the epitaxial layer adjacent the trenches. The test structures allow the simultaneous optimization of the breakdown voltage and on-resistance of the device.
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13 Claims
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1. A method of forming a high voltage MOSFET comprising the steps of:
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providing a substrate of a first conductivity type;
depositing an epitaxial layer on the substrate, said epitaxial layer having a first conductivity type;
forming first and second body regions in the epitaxial layer to define a drift region therebetween, said body regions having a second conductivity type;
forming first and second source regions of the first conductivity type in the first and second body regions, respectively; and
forming a plurality of trenches in said drift region of the epitaxial layer;
filling said trenches with a material having a dopant of the second conductivity type, said trenches extending toward the substrate from the first and second body regions;
diffusing at least a portion of said dopant from said trenches into portions of the epitaxial layer adjacent the trenches;
measuring a breakdown voltage in said epitaxial layer;
comparing the measured breakdown voltage to a predetermined relationship between breakdown voltage and diffusion time to determine a remaining diffusion time to achieve a prescribed breakdown voltage; and
performing an additional diffusion step for said remaining diffusion time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification