Method of forming a trench DMOS having reduced threshold voltage
First Claim
1. A method of manufacturing one or more trench DMOS transistors comprising:
- providing a substrate of a first conductivity type, forming an epitaxial layer of said first conductivity type over said substrate, said epitaxial layer having a lower majority carrier concentration than said substrate;
forming a region of a second conductivity type within an upper portion of said epitaxial layer;
forming A plurality of trenches within said epitaxial layer, said trenches defining one or more body regions within said region of second conductivity type, forming a first insulating layer that lines said trenches;
providing a conductive region within said trenches adjacent to the first insulating layer lining said trenches;
removing a portion of said first insulating layer along at least upper sidewalls of said trenches such that portions of said body regions are exposed along said upper sidewalls;
oxidizing at least said exposed portions of said body regions to form an oxide layer, said oxidizing step resulting in regions of reduced majority carrier concentration within said body regions adjacent said oxide layer; and
forming a plurality of source regions of said first conductivity type within upper portions of said body regions adjacent said trenches, said source regions being adjacent said regions of reduced majority carrier concentration within said body regions.
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Accused Products
Abstract
A method of manufacturing one or more trench DMOS transistors is provided. In this method, one or more or more body regions adjacent one or more trenches are provided. The one or more trenches are lined with a first insulating layer. A portion of the first insulating layer is removed along at least the upper sidewalls of the trenches, exposing portions of the body regions. An oxide layer is then formed over at least the exposed portions of the body regions, resulting in regions of reduced majority carrier concentration within the body regions adjacent the oxide layer. This modification of the majority carrier concentration in the body regions is advantageous in that a low threshold voltage can be established within the DMOS transistor without resorting to a thinner gate oxide (which would reduce yield and switching speed) and without substantially increasing the likelihood of punch-through.
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Citations
24 Claims
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1. A method of manufacturing one or more trench DMOS transistors comprising:
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providing a substrate of a first conductivity type, forming an epitaxial layer of said first conductivity type over said substrate, said epitaxial layer having a lower majority carrier concentration than said substrate;
forming a region of a second conductivity type within an upper portion of said epitaxial layer;
forming A plurality of trenches within said epitaxial layer, said trenches defining one or more body regions within said region of second conductivity type, forming a first insulating layer that lines said trenches;
providing a conductive region within said trenches adjacent to the first insulating layer lining said trenches;
removing a portion of said first insulating layer along at least upper sidewalls of said trenches such that portions of said body regions are exposed along said upper sidewalls;
oxidizing at least said exposed portions of said body regions to form an oxide layer, said oxidizing step resulting in regions of reduced majority carrier concentration within said body regions adjacent said oxide layer; and
forming a plurality of source regions of said first conductivity type within upper portions of said body regions adjacent said trenches, said source regions being adjacent said regions of reduced majority carrier concentration within said body regions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of manufacturing one or more trench DMOS transistors comprising:
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providing an N-type silicon substrate forming an N-type silicon epitaxial layer over said substrate, said epitaxial layer having a tower doping concentration than said substrate;
forming a P-type region within an upper portion of said epitaxal layer, fording a plurality of trenches within said epitaxial layer, said trenches defining one or more P-body regions within said P-type region;
foxing a first oxide layer that lines said trenches;
providing a conductive region within said trenches adjacent the first oxide layer lining said trenches;
removing a portion of said first oxide layer along at least upper sidewalls of said trenches such that portions of said P-body regions are exposed along said upper sidewalls;
oxidizing at least said exposed portions of said P-body regions to form a second oxide layer, said oxidizing step resulting in regions of reduced P-type carrier concentration within said P-body regions adjacent said second oxide layer; and
forming a plurality of N-type source regions within upper portions of said P-body regions adjacent said trenches, said N-type source regions being adjacent said regions of reduced P-type carrier concentration within said P-body regions. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A Tnethod of modifying the majority carrier concentration in a body region within a trench D)MOS transistor comprising:
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providing one or mote or more body regions adjacent one or more trenches, said one or more trenches being lined with a first insulating layer;
removing a portion of said first insulating layer along at least upper sidewalls of said trenches such that portions of said body regions are exposed along said upper sidewalls; and
oxidizing at least said exposed portions of said body regions, said oxidizing step resulting in regions of reduced majority carrier concentration within said body regions adjacent said oxide layer.
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Specification