Method of forming shallow trench isolation for thin silicon-on-insulator substrates
First Claim
1. A method for forming shallow trench isolation on a silicon-on-insulator (SOI) substrate for isolating device areas on said SOI substrate, wherein said SOI substrate comprises a silicon layer on top of a buried oxide layer, the method comprising the steps of:
- forming a gate oxide layer on said silicon layer;
depositing a first polysilicon layer on said gate oxide layer;
depositing a polish stop layer on said first polysilicon layer;
forming a plurality of trenches, wherein said trenches have a depth extending through said polish stop layer, said first polysilicon layer, said gate oxide layer, and said silicon layer;
conformally depositing a silicon oxide layer in said trenches and on said polish stop layer;
removing a first portion of said silicon oxide layer by chemical mechanical polishing, such that the top surface of said silicon oxide layer in said trenches is polished down to the same height as the top surface of said polish stop layer;
removing a second portion of said silicon oxide layer by etching, such that the top surface of said silicon oxide layer is etched down to a height below the top surface of said polish stop layer and above the top surface of said first polysilicon layer;
removing said polish stop layer;
depositing a second polysilicon layer on said silicon oxide layer and said first polysilicon layer; and
forming a polysilicon gate comprised of said first and second polysilicon layers by photolithography masking and etching said first and second polysilicon layers.
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Abstract
A method is disclosed for forming shallow trench isolation (STI) on a thin silicon-on-insulator (SOI) substrate. The method comprises depositing a first polysilicon layer; depositing a polish stop layer on the first polysilicon layer; forming a plurality of trenches in the substrate; filling the trenches with silicon oxide; CMP polishing a first portion of the silicon oxide layer down to the polish stop layer; etching a second portion of the silicon oxide layer down to below the polish stop layer and above the first polysilicon layer; removing the polish stop layer; depositing a second polysilicon layer; and forming a polysilicon gate comprised of the first and second polysilicon layers. Well ion implants may be performed prior to gate formation, thereby preventing exposure of STI oxide to sacrificial oxide growth and removal, eliminating excessive recess in STI structures. STI oxide seam leakage due to polysilicon sidewalls remaining after polysilicon gate etch are also avoided.
60 Citations
36 Claims
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1. A method for forming shallow trench isolation on a silicon-on-insulator (SOI) substrate for isolating device areas on said SOI substrate, wherein said SOI substrate comprises a silicon layer on top of a buried oxide layer, the method comprising the steps of:
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forming a gate oxide layer on said silicon layer;
depositing a first polysilicon layer on said gate oxide layer;
depositing a polish stop layer on said first polysilicon layer;
forming a plurality of trenches, wherein said trenches have a depth extending through said polish stop layer, said first polysilicon layer, said gate oxide layer, and said silicon layer;
conformally depositing a silicon oxide layer in said trenches and on said polish stop layer;
removing a first portion of said silicon oxide layer by chemical mechanical polishing, such that the top surface of said silicon oxide layer in said trenches is polished down to the same height as the top surface of said polish stop layer;
removing a second portion of said silicon oxide layer by etching, such that the top surface of said silicon oxide layer is etched down to a height below the top surface of said polish stop layer and above the top surface of said first polysilicon layer;
removing said polish stop layer;
depositing a second polysilicon layer on said silicon oxide layer and said first polysilicon layer; and
forming a polysilicon gate comprised of said first and second polysilicon layers by photolithography masking and etching said first and second polysilicon layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
forming a sacrificial oxide layer on said silicon layer;
performing threshold ion implantations and source/drain well implantations through said sacrificial oxide layer; and
removing said sacrificial oxide layer.
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Specification