TRENCH MOSFET WITH SHALLOW TRENCH CONTACT
First Claim
1. A vertical semiconductor power MOS device comprising a plurality of semiconductor power cells with each cell comprising a trenched gate surrounded by a source region encompassed in a body region above a drain region disposed on a bottom surface of a substrate, wherein said MOS cell further comprising:
- a low-resistivity substrate to reduce Rds;
a plurality of trench gates and at least a wider trench gate for gate contact;
a plurality of floating trench gates as termination rings;
a doped area underneath said trench bottom with the same doping type as epitaxial layer but doping concentration is heavier than epitaxial layer, to further reduce Rds;
a source-body contact trench opened through a contact oxide layer covering said cell structure and extending into said body region with the contact trench depth in epitaxial layer shallower than source junction depth;
a gate contact trench opened through said insulating layer and extending into trench-filling material in said trenched gate underneath gate runner metal;
a source metal and gate metal layer formed on a top surface of the MOSFET; and
a drain metal layer formed on a bottom surface of the MOSFET.
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Accused Products
Abstract
A trench MOSFET element with shallow trench contact is disclosed. This shallow trench contact structure has some advantages: blocking the P+ underneath trench contact from lateral diffusion to not touch to channel region when a larger trench contact CD is applied; avoiding the trench gate contact etching through poly and gate oxide when trench gate becomes shallow; making lower cost to refill the trench contact using Al alloys with good metal step coverage as the trench contact is shallower. The disclosed trench MOSFET element further includes an n* region around the bottom of gate trenches to reduce Rds. In some embodiment, the disclosed trench MOSFET provides a terrace gate to further reduce Rg and make self-aligned source contact; In some embodiment, the disclosed trench MOSFET comprises a P* area underneath said P+ region for avalanche energy improvement with lighter dose than said P+ region.
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Citations
24 Claims
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1. A vertical semiconductor power MOS device comprising a plurality of semiconductor power cells with each cell comprising a trenched gate surrounded by a source region encompassed in a body region above a drain region disposed on a bottom surface of a substrate, wherein said MOS cell further comprising:
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a low-resistivity substrate to reduce Rds; a plurality of trench gates and at least a wider trench gate for gate contact; a plurality of floating trench gates as termination rings; a doped area underneath said trench bottom with the same doping type as epitaxial layer but doping concentration is heavier than epitaxial layer, to further reduce Rds; a source-body contact trench opened through a contact oxide layer covering said cell structure and extending into said body region with the contact trench depth in epitaxial layer shallower than source junction depth; a gate contact trench opened through said insulating layer and extending into trench-filling material in said trenched gate underneath gate runner metal; a source metal and gate metal layer formed on a top surface of the MOSFET; and a drain metal layer formed on a bottom surface of the MOSFET. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for manufacturing a trench MOSFET with shallow trench contact comprising the steps of:
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growing an epitaxial layer upon a heavily N doped substrate, wherein said epitaxial layer is doped with a first type dopant, eg., N dopant; forming a trench mask with open and closed areas on the surface of said epitaxial layer; removing semiconductor material from exposed areas of said trench mask to form a plurality of gate trenches; depositing a sacrificial oxide layer onto the surface of said trenches to remove the plasma damage introduced during opening said trenches; removing said sacrificial oxide and said trench mask; implanting whole device with Arsenic ion to form n* area underneath each gate trench; depositing gate oxide on the surface of said epitaxial layer and along the inner surface of said gate trenches; depositing a layer of doped poly or combination doped poly and non-doped poly onto said gate oxide and into said gate trenches; etching back or CMP said doped poly or combination doped poly and non-doped poly from the surface of said gate oxide and leaving enough doped poly or combination doped poly and non-doped poly into said gate trenches to serve as trench gate material; forming silicide on top poly as alternative for low Rg; implanting said epitaxial layer with a second type dopant to form P-body regions; depositing a source mask with open and closed areas to define n+ source regions; implanting whole device with a first type dopant to form source regions; removing said source mask and forming a thick contact oxide onto whole surface; forming a contact mask on the surface of said contact oxide layer and removing oxide material and semiconductor material, as well as poly material from exposed areas of said contact mask to open a plurality of contact trenches; driving in n+ ion of source region by n+ source diffusion to make n+ junction deeper than the trench source contact in silicon; implanting BF 2 ion to form P+ area underneath source contact trench and body contact trench; depositing Ti/TiN/W consequently into contact trenches and on the front surface; etching back W and Ti/TiN to form contact metal plug and depositing a layer of Ti or TiN and then a layer of Al alloys whereon; and forming a metal mask onto said Al alloys with open and closed areas and removing metal material from the exposed areas of said metal mask to form interconnection metal and front metal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification