Top corner rounding for shallow trench isolation
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorsHsien-Kuang Chiu, Fang-Cheng Chen, Hun-Jan Tao
Life of this patent
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Abstract
A process for top-corner rounding at the rim of shallow trenches of the type used for STI is described. This is achieved by first forming the trench using a silicon nitride hard mask having a layer of pad oxide between itself and the silicon surface. The silicon nitride is then briefly and selectively etched so that it pulls back from over the trench rim and exposes a small amount of the underlying pad oxide. Rounding by means of sputtering is then effected with the pad oxide serving to protect the underlying silicon until just before rounding takes place. The result is smoothly rounded corners free of facets and overhangs.
Claims20
A process for smoothing an edge, comprising:
- providing a silicon body having a first upper surface that includes a step, having a sharp edge, down to a second upper surface;
- forming on said upper surface a layer of silicon oxide and then forming a layer of silicon nitride on said layer of silicon oxide;
- selectively etching the silicon nitride whereby between about 100 and 250 Angstroms of the silicon oxide is exposed;
- and
- through sputtering, removing said exposed silicon oxide whereby said sharp edge becomes a rounded edge.
A process for rounding top corners of a trench, comprising the sequential steps of:
- providing a silicon body having an upper surface;
- forming a layer of pad oxide on said upper surface;
- depositing a layer of silicon nitride on the layer of pad oxide;
- depositing a layer of photoresist on the layer of silicon nitride and then patterning the photoresist to form a mask;
- using said photoresist mask, etching the silicon nitride thereby forming a hard mask that defines a trench having dimensions;
- using the hard mask, etching through the layer of pad oxide into the silicon body to a preset depth, thereby forming the trench, said trench having a rim;
- using a wet etch, selectively etching the silicon nitride for a time period whereby silicon nitride is pulled back from above said trench rim and between about 100 and 250 Angstroms of the pad oxide is exposed;
- through sputtering, removing said exposed pad oxide and then rounding the trench rim without changing the dimensions of the trench;
- and
- dipping the silicon body in a hydrofluoric solution thereby performing a cleanup etch.
A process for rounding top corners of a trench, comprising the sequential steps of:
- providing a silicon body having an upper surface;
- forming a layer of pad oxide on said upper surface;
- depositing a layer of silicon nitride on the layer of pad oxide;
- depositing a layer of photoresist on the layer of silicon nitride and then patterning the photoresist to form a mask;
- using said photoresist mask, etching the silicon nitride thereby forming a hard mask that defines a trench having dimensions;
- using the hard mask, etching through the layer of pad oxide into the silicon body to a preset depth, thereby forming the trench, said trench having a rim;
- using a dry etch, selectively etching the silicon nitride for a time period whereby silicon nitride is pulled back from above said trench rim and between about 100 and 250 Angstroms of the pad oxide is exposed;
- through sputtering, removing said exposed pad oxide and then rounding the trench rim without changing the dimensions of the trench;
- and
- dipping the silicon body in a hydrofluoric solution thereby performing a cleanup etch.
Dependencies are inferred from the claim text.