High density MOS-gated power device and process for forming same
First Claim
1. A high density MOS-gated device comprising:
- a semiconductor substrate;
a doped upper layer of a first conduction type disposed on said substrate, said upper layer comprising a heavily doped source region of said first conduction type and a doped well region of a second and opposite conduction type at an upper surface of said upper layer, said upper surface comprising a contact area for said source region, said upper surface further comprising a recessed portion comprising a contact area for a heavily doped deep body region of said second conduction type in said upper layer, said deep body region underlying said recessed portion; and
a trench gate disposed in said upper layer, said gate comprises a conductive material separated from said upper layer by an insulating layer.
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Abstract
A high density MOS-gated device comprises a semiconductor substrate and a doped upper layer of a first conduction type disposed on the substrate. The upper layer comprises a heavily doped source region of the first conduction type and a doped well region of a second and opposite conduction type at an upper surface. The upper surface, which comprises a contact area for the source region, further includes a recessed portion that comprises a contact area for a heavily doped deep body region of the second conduction type in the upper layer underlying the recessed portion. The device further includes a trench gate disposed in the upper layer and comprising a conductive material separated from the upper layer by an insulating layer. A process for forming a high density MOS-gated device comprises providing a semiconductor substrate comprising a doped upper layer of a first conduction type. A doped well region of a second and opposite conduction type is formed in an upper surface of the upper layer, and a dopant of the first conduction type is implanted in the well region to form a heavily doped source region. A layer of nitride is formed on the upper surface of the upper layer, and the nitride layer and upper layer are selectively etched, thereby forming a trench in the upper layer. The trench is lined with an insulating layer, then filled with a conductive material to form a trench gate. The nitride layer is removed, and a layer of interlevel dielectric material is formed on the trench gate and the upper surface of the upper layer. The interlevel dielectric layer is selectively etched, thereby forming a source region contact area. The source region is selectively etched to form a shallow recess that provides a body region contact area. A dopant of the second conduction type is implanted into the recess, thereby forming a deep body region underlying the recess.
223 Citations
34 Claims
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1. A high density MOS-gated device comprising:
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a semiconductor substrate;
a doped upper layer of a first conduction type disposed on said substrate, said upper layer comprising a heavily doped source region of said first conduction type and a doped well region of a second and opposite conduction type at an upper surface of said upper layer, said upper surface comprising a contact area for said source region, said upper surface further comprising a recessed portion comprising a contact area for a heavily doped deep body region of said second conduction type in said upper layer, said deep body region underlying said recessed portion; and
a trench gate disposed in said upper layer, said gate comprises a conductive material separated from said upper layer by an insulating layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A process for forming a high density MOS-gated device, said process comprising:
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providing a semiconductor substrate comprising a doped upper layer of a first conduction type, said upper layer having an upper surface;
forming a doped well region of a second and opposite conduction type in said upper surface of said upper layer;
implanting a dopant of said first conduction type in said well region, thereby forming a heavily doped source region in said well region;
forming a layer of nitride on said upper surface of said upper layer;
selectively etching said nitride layer and said upper layer, thereby forming a trench in said upper layer;
lining said trench with an insulating layer, then filling said trench with a conductive material, thereby forming a trench gate;
removing said nitride layer and forming a layer of interlevel dielectric material on said trench gate and said upper surface of said upper layer;
selectively etching said interlevel dielectric layer, thereby forming a source region contact area;
selectively etching said source region, thereby forming a shallow recess in said source region, said recess comprising a body region contact area; and
implanting a dopant of said second conduction type into said recess, thereby forming a deep body region underlying said recess. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
forming a screen layer of oxide on said upper surface of said upper layer prior to forming said nitride layer.
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14. The process of claim 12 further comprising:
implanting a dopant of said second conduction type into said source region contact area, thereby forming a shallow body region underlying said source region contact area.
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15. The process of claim 12 further comprising:
forming a metal contact on said source region contact area and on said body region contact area.
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16. The process of claim 12 wherein said upper layer is included within said substrate.
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17. The process of claim 12 wherein said upper layer comprises an epitaxial layer.
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18. The process of claim 12 wherein said first conduction type is N and said second conduction type is P.
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19. The process of claim 12 wherein said substrate comprises monocrystalline silicon and said insulating layer comprises silicon dioxide.
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20. The process of claim 12 wherein said conductive material in said trench gate comprises highly doped polysilicon.
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21. The process of claim 12 wherein said dopant of a first conduction type comprises arsenic or phosphorus.
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22. The process of claim 12 wherein said dopant of a second conduction type comprises boron.
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23. The process of claim 12 wherein said interlevel dielectric material comprises borophosphosilicate glass or phosphosilicate glass.
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24. The process of claim 12 wherein said body contact area is smaller than said source contact area.
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25. The process of claim 12 wherein said device is selected from the group consisting of a power MOSFET, an insulated gate bipolar transistor, and an MOS-controlled thyristor.
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26. In an improved process for forming a high density MOS-gated device including the steps of forming a gate trench in an upper layer of a substrate, forming a well region in the upper layer, implanting a dopant of a first conduction type into the well region to form a source region in the well region adjacent to the gate trench, the improvement comprising:
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selectively etching a portion of the source region, thereby forming a recess comprising a body region contact area, the unetched portion of said source region comprising a source region contact area; and
implanting a dopant of a second conduction type into the recess, thereby forming a deep body region underlying said recess. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
implanting a dopant of said second conduction type into said source region contact area, thereby forming a shallow body region underlying said source region contact area.
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28. The process of claim 26 further comprising:
forming a metal contact on said source region contact area and on said body region contact area.
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29. The process of claim 26 wherein said upper layer is included within said substrate.
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30. The process of claim 26 wherein said upper layer comprises an epitaxial layer.
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31. The process of claim 26 wherein said first conduction type is N and said second conduction type is P.
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32. The process of claim 26 wherein said substrate comprises monocrystalline silicon and said insulating layer comprises silicon dioxide.
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33. The process of claim 26 wherein said conductive material in said trench gate comprises highly doped polysilicon.
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34. The process of claim 26 wherein said body contact area is smaller than said source contact area.
Specification