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US 6,617,217 B2Granted
Reduction in well implant channeling and resulting latchup characteristics in shallow trench isolation by implanting wells through nitride
AssigneeTexas Instruments Incorpated
InventorsMahalingam Nandakumar, Dixit Kapila, Seetharaman Sridhar
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Abstract
Retrograde wells are formed by implanting through nitride films (40). Nitride films (40) are formed after STI (20) formation. By selectively masking a portion of the wafer with photoresist (47) after portions of a retrograde well are formed (45, 50, 55, and 60) the channeling of the subsequent zero degree implants is reduced.
Claims15
A method for forming retrograde well structures, comprising:
- providing a semiconductor substrate with an upper surface;
- forming a pad oxide on said semiconductor surface;
- forming a first nitride structure on a first portion of said pad oxide structure;
- forming a second nitride structure on a second portion of said pad oxide structure;
- forming shallow trench isolation structures in said semiconductor substrate;
- forming a photoresist film over said second nitride structure;
- implanting a first dopant species through said first nitride structure to form a first well region in said semiconductor substrate;
- and
- implanting a second dopant species through said first nitride structure to form a first channel stop region in said semiconductor substrate.
6 more elements
A method for forming retrograde well structures, comprising:
- providing a semiconductor substrate with an upper surface;
- forming a pad oxide on said semiconductor surface;
- forming a first nitride structure on a first portion of said pad oxide structure;
- forming a second nitride structure on a second portion of said pad oxide structure;
- forming shallow trench isolation structures in said semiconductor substrate;
- forming a photoresist film over said second nitride structure;
- implanting a first dopant species through said first nitride structure to form a first well region in said semiconductor substrate;
- implanting a second dopant species through said first nitride structure to form a first channel stop region in said semiconductor substrate;
- removing said first nitride structure thereby exposing said first portion of said pad oxide;
- implanting a third dopant species through said first portion of said pad oxide to form a first punch through region;
- and
- implanting a fourth dopant species through said first portion of said pad oxide to form a first threshold voltage region.
9 more elements
Dependencies are inferred from the claim text.