Trench FET with source recess etch
First Claim
1. A method for fabricating a vertical field effect transistor, comprising:
- forming a recessed conductive gate electrode structure in a trench opening of a semiconductor substrate structure, the recessed conductive gate structure having a top surface which is below an elevated surface region of the semiconductor substrate structure;
forming an implant block layer over the recessed conductive gate electrode structure in the trench opening by depositing an oxide layer to fill the portion of the trench opening above the recessed conductive gate electrode structure and planarizing the oxide layer to form an oxide implant block layer over the recessed conductive gate electrode structure in the trench opening;
implanting dopants of a first conductivity type using one or more angled implants into an upper region of an elevated substrate and trench sidewalls located above the recessed conductive gate electrode structure to form surface implant regions and self-aligned source regions adjacent to the recessed conductive gate electrode structure;
implanting dopants of a second opposite conductivity type into the semiconductor substrate structure to form self-aligned body contact regions adjacent to the self-aligned source regions;
applying a recess etch to the elevated surface region of the semiconductor substrate structure to remove the surface implant region while retaining the self-aligned source regions adjacent to the recessed conductive gate electrode structure and the self-aligned body contact regions adjacent to the self-aligned source regions; and
applying a recess etch to the implant block layer after applying the recess etch to the elevated surface region of the semiconductor substrate structure, thereby forming a recessed implant block layer that is substantially coplanar with the self-aligned body contact regions and self-aligned source regions.
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Accused Products
Abstract
A high voltage vertical field effect transistor device (101) is fabricated in a substrate (102, 104) using angled implantations (116, 120) into trench sidewalls formed above recessed gate poly layers (114) to form self-aligned N+ regions (123) adjacent to the trenches and along an upper region of an elevated substrate. With a trench fill insulator layer (124) formed over the recessed gate poly layers (114), self-aligned P+ body contact regions (128) are implanted into the elevated substrate without counter-doping the self-aligned N+ regions (123), and a subsequent recess etch removes the elevated substrate, leaving self-aligned N+ source regions (135-142) and P+ body contact regions (130-134).
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Citations
16 Claims
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1. A method for fabricating a vertical field effect transistor, comprising:
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forming a recessed conductive gate electrode structure in a trench opening of a semiconductor substrate structure, the recessed conductive gate structure having a top surface which is below an elevated surface region of the semiconductor substrate structure; forming an implant block layer over the recessed conductive gate electrode structure in the trench opening by depositing an oxide layer to fill the portion of the trench opening above the recessed conductive gate electrode structure and planarizing the oxide layer to form an oxide implant block layer over the recessed conductive gate electrode structure in the trench opening; implanting dopants of a first conductivity type using one or more angled implants into an upper region of an elevated substrate and trench sidewalls located above the recessed conductive gate electrode structure to form surface implant regions and self-aligned source regions adjacent to the recessed conductive gate electrode structure; implanting dopants of a second opposite conductivity type into the semiconductor substrate structure to form self-aligned body contact regions adjacent to the self-aligned source regions; applying a recess etch to the elevated surface region of the semiconductor substrate structure to remove the surface implant region while retaining the self-aligned source regions adjacent to the recessed conductive gate electrode structure and the self-aligned body contact regions adjacent to the self-aligned source regions; and applying a recess etch to the implant block layer after applying the recess etch to the elevated surface region of the semiconductor substrate structure, thereby forming a recessed implant block layer that is substantially coplanar with the self-aligned body contact regions and self-aligned source regions. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for fabricating a trench field effect transistor, comprising:
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providing a semiconductor substrate structure having an elevated surface region; forming a plurality of trench openings in the semiconductor substrate structure, where each trench opening is defined by first and second opposite trench sidewalls; forming a recessed conductive gate electrode structure in each trench opening, the recessed conductive gate structure having a top surface which is below the elevated surface region of the semiconductor substrate structure; forming an implant block layer over the recessed conductive gate electrode structure in each trench opening by depositing an oxide layer to fill the plurality of trench openings above the recessed conductive gate electrode structures and planarizing the oxide layer to form an oxide implant block layer over each recessed conductive gate electrode structure; implanting dopants of a first conductivity type using one or more angled implants to form first surface implant regions in the elevated surface region of the semiconductor substrate structure and first sidewall implant regions in the first and second opposite trench sidewalls of each trench opening that extend to a first depth that is below the top surface of the recessed conductive gate electrode structure; implanting dopants of a second opposite conductivity type to form second implant regions between each trench opening in the semiconductor substrate structure to a second depth that penetrates below the elevated surface region of the semiconductor substrate; recessing the elevated surface region of the semiconductor substrate structure to remove the first surface implant regions and part of the second implant regions while leaving at least part of the first sidewall implant regions in the first and second opposite trench sidewalls and a part of the second implant regions in the recessed semiconductor substrate structure; and applying a recess etch to the implant block layer in each trench opening, thereby forming a recessed implant block layer that is substantially coplanar with the first sidewall implant regions remaining after recessing the elevated surface region. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of forming a trench transistor, comprising:
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a) forming a trench in a substrate, the substrate having a surface and the trench having a first upper sidewall and a second upper sidewall; b) forming a recessed gate structure in the trench, the recessed gate structure having a top surface which is below the surface of the substrate to thereby expose the first and second upper sidewalls; c) forming an implant block layer over the recessed gate structure in the trench by depositing an oxide layer to fill the trench above the recessed gate structure and planarizing the oxide layer to form an oxide implant block layer over the recessed gate structure; d) implanting a first dose of dopants such that a portion of the first dose is implanted through the first upper sidewall to form first self-aligned source regions, and a further portion of the first dose is implanted through the surface to form a first surface implant region; e) changing an orientation of the substrate relative to an axis of implantation by a predetermined number of degrees; f) implanting a second dose of dopants such that a portion of the second dose is implanted through the second upper sidewall to form second self-aligned source regions, and a further portion of the second dose is implanted through the surface to form a second surface implant region; g) implanting a third dose of dopants into the substrate without using an implant mask to form a self-aligned body contact regions adjacent to the first and second self-aligned source regions; h) applying a recess etch to the substrate to remove the first and second surface implant region while retaining portions of the first and second self-aligned source regions adjacent to the recessed gate structure and the self-aligned body contact region; and i) applying a recess etch to the implant block layer in the trench, thereby forming a recessed implant block layer that is substantially coplanar with the first and second self-aligned source regions remaining after applying the recess etch to the substrate. - View Dependent Claims (16)
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Specification