Process for forming MOS-gated power device having segmented trench and extended doping zone
First Claim
1. A process for forming a trench MOS-gated device, said process comprising:
- providing a substrate having an upper surface and comprising doped monocrystalline semiconductor material of a first conduction type;
forming a trench in an upper layer of said substrate, said trench having a floor and sidewalls, said trench further having a width and extending to a depth substantially corresponding to a width and a depth of the upper segment of an extended trench comprising an upper segment and a bottom segment;
forming a conformal masking oxide layer on said substrate upper layer and on said trench floor and sidewalls;
anisotropically etching said conformal masking oxide layer, thereby removing said masking oxide from said trench floor and forming an opening to substrate semiconductor material underlying said floor;
etching said semiconductor material underlying said trench floor, thereby forming said bottom segment of said extended trench, said bottom segment having a lesser width relative to a greater width of said trench upper segment and extending to a depth corresponding to the total depth of said extended trench;
removing remainder of conformal masking oxide layer from said substrate upper layer and from said trench sidewalls;
substantially filling said extended trench with a dielectric material;
selectively implanting and diffusing a dopant of a second opposite conduction type into said upper layer on one side of said extended trench, thereby forming an extended zone extending from said substrate upper surface into said upper layer;
selectively removing said dielectric material from said upper segment of said extended trench, leaving said bottom segment of said extended trench substantially filled with said dielectric material;
forming floor and sidewalls comprising dielectric material in said upper segment of said extended trench and substantially filling said upper segment with a conductive material, thereby forming a gate region in said upper segment of said extended trench;
forming a doped well region of said second conduction type in said upper layer on the side of said extended trench opposite said extended zone;
forming a heavily doped source region of said first conduction type and a heavily doped body region of said second conduction type in said well region at said upper surface;
forming an interlevel dielectric layer on said upper surface overlying said gate and source regions; and
forming a metal layer overlying said upper surface and said interlevel dielectric layer, said metal layer being in electrical contact with said source and body regions and said extended zone.
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Abstract
A process for constructing a trench MOS-gated device includes: forming in a semiconductor substrate an extended trench that comprises an upper segment and a bottom segment, wherein the bottom segment has a lesser width relative to a greater width of the trench upper segment and extends to a depth corresponding to the total depth of the extended trench. The bottom segment of the trench is substantially filled with dielectric material. The trench upper segment has a floor and sidewalls comprising dielectric material and is substantially filled with a conductive material to form a gate region. A heavily doped source region of the first conduction type and a heavily doped body region of the second conduction type are formed in a surface well region on the side of the extended trench opposite an extended doped zone.
88 Citations
13 Claims
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1. A process for forming a trench MOS-gated device, said process comprising:
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providing a substrate having an upper surface and comprising doped monocrystalline semiconductor material of a first conduction type;
forming a trench in an upper layer of said substrate, said trench having a floor and sidewalls, said trench further having a width and extending to a depth substantially corresponding to a width and a depth of the upper segment of an extended trench comprising an upper segment and a bottom segment;
forming a conformal masking oxide layer on said substrate upper layer and on said trench floor and sidewalls;
anisotropically etching said conformal masking oxide layer, thereby removing said masking oxide from said trench floor and forming an opening to substrate semiconductor material underlying said floor;
etching said semiconductor material underlying said trench floor, thereby forming said bottom segment of said extended trench, said bottom segment having a lesser width relative to a greater width of said trench upper segment and extending to a depth corresponding to the total depth of said extended trench;
removing remainder of conformal masking oxide layer from said substrate upper layer and from said trench sidewalls;
substantially filling said extended trench with a dielectric material;
selectively implanting and diffusing a dopant of a second opposite conduction type into said upper layer on one side of said extended trench, thereby forming an extended zone extending from said substrate upper surface into said upper layer;
selectively removing said dielectric material from said upper segment of said extended trench, leaving said bottom segment of said extended trench substantially filled with said dielectric material;
forming floor and sidewalls comprising dielectric material in said upper segment of said extended trench and substantially filling said upper segment with a conductive material, thereby forming a gate region in said upper segment of said extended trench;
forming a doped well region of said second conduction type in said upper layer on the side of said extended trench opposite said extended zone;
forming a heavily doped source region of said first conduction type and a heavily doped body region of said second conduction type in said well region at said upper surface;
forming an interlevel dielectric layer on said upper surface overlying said gate and source regions; and
forming a metal layer overlying said upper surface and said interlevel dielectric layer, said metal layer being in electrical contact with said source and body regions and said extended zone. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
forming a doped drain zone of said first conduction type extending through said upper layer and into said substrate beneath said well region and said extended zone.
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3. The process of claim 1 wherein said widths of said trench upper segment and said trench bottom segment are in a ratio of about 1.2:
- 1 to about 12;
1.
- 1 to about 12;
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4. The process of claim 1 wherein said trench upper segment and said extended trench each extend to a selected depth, said depths of said upper segment and said extended trench being in a ratio, relative to one another, of about 1:
- 2 to about 1;
8.
- 2 to about 1;
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5. The process of claim 1 wherein said upper layer is an epitaxial layer.
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6. The process of claim 1 wherein said substrate comprises monocrystalline silicon.
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7. The process of claim 1 wherein said dielectric material comprises silicon dioxide.
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8. The process of claim 1 wherein said conductive material in said trench comprises doped polysilicon.
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9. The process of claim 1 wherein said first conduction type is N and said second conduction type is P.
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10. The process of claim 1 further comprising:
forming a plurality of extended trenches in said substrate.
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11. The process of claim 10 wherein said plurality of extended trenches have an open-cell stripe technology.
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12. The process of claim 10 wherein said plurality of extended trenches have a closed-cell cellular topology.
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13. The process of claim 1 wherein said device is selected from the group consisting of a power MOSFET, an insulated gate bipolar transistor, and an MOS-controlled thyristor.
Specification