Graded MOS transistor junction formed by aligning a sequence of implants to a selectively removable polysilicon sidewall space and oxide thermally grown thereon
First Claim
1. A method for forming a transistor, comprising:
- providing a semiconductor substrate over which a gate conductor having opposed sidewall surfaces is dielectrically spaced; and
depositing an etch stop layer upon the sidewall surfaces, followed by depositing a polysilicon spacer upon the etch stop layer and followed by growing an oxide upon the polysilicon spacer to form a multi-layer spacer.
2 Assignments
0 Petitions
Accused Products
Abstract
A transistor and transistor fabrication method are presented where a sequence of layers are formed and either entirely or partially removed upon sidewall surfaces of a gate conductor. The formation and removal of layers produces a lateral surface to which various implants can be aligned. Those implants, placed in succession produce a highly graded junction having a relatively smooth doping profile. Preferably, the multi-layer spacer structure comprises a polysilicon spacer interposed between a grown oxide and an etch stop. The oxide is grown upon the polysilicon to align a source/drain implant. Either before the source/drain implant or after the source/drain implant, the oxide and polysilicon partially consumed by the oxide is removed to provide a lateral surface to which an MDD implant aligns. A combination of etch stop, polysilicon spacer and grown possibly sacrificial oxide allows a greater ease by which multiple implants can be forwarded into junctions of either an NMOS or PMOS transistor.
69 Citations
11 Claims
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1. A method for forming a transistor, comprising:
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providing a semiconductor substrate over which a gate conductor having opposed sidewall surfaces is dielectrically spaced; and depositing an etch stop layer upon the sidewall surfaces, followed by depositing a polysilicon spacer upon the etch stop layer and followed by growing an oxide upon the polysilicon spacer to form a multi-layer spacer. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for forming an integrated circuit, comprising:
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providing a semiconductor topography upon which a gate conductor having opposed sidewall surfaces is formed; forming a sequence of dielectric layers upon the sidewall surfaces, wherein one of said sequence of dielectric layers comprises a grown oxide which, during thermal growth, partially consumes an immediately underlying, silicon-based dielectric layer, implanting into a junction area within said semiconductor topography after said sequence of dielectric layers is at least partially formed; and implanting into the junction area after said oxide and the partially consumed underlying silicon-based dielectric layer are removed. - View Dependent Claims (9, 10, 11)
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Specification