Shallow trench isolation formation with improved trench edge oxide

A method of manufacturing a semiconductor device having an insulated trench formed in a semiconductor substrate or in an epitaxial layer on the semiconductor substrate, which method comprises:

• forming a pad oxide layer on a main surface of the substrate or epitaxial layer;
• providing a first mask on the pad oxide layer, the first mask containing a pattern having an opening with a dimension substantially equal to a dimension of the trench;
• etching to remove portions of the underlying pad oxide layer and to form the trench having an internal surface and edges at the main surface;
• removing the first mask;
• forming an oxide liner on the internal surface and edges of the trench;
• depositing a polish stop layer on the oxide liner and the pad oxide layer;
• providing a second mask on the polish stop layer, the second mask containing a pattern having an opening with a dimension greater than a dimension of the trench;
• isotropically etching to remove portions of the polish stop layer such that the oxide liner is exposed;
• removing the second mask;
• depositing an insulating material to fill the trench and cover the polish stop layer;
• and
• planarizing the insulating material such that the polish stop is exposed.

A method of manufacturing an integrated circuit on a semiconductor substrate, which method comprises:

• forming a silicon oxide pad layer on a main surface of the substrate or an epitaxial layer formed on the substrate;
• providing a first photoresist mask on the silicon oxide pad layer, the first mask containing a pattern having an opening with a width substantially equal to a width of the trench of about 0.25.mu. or less;
• etching to remove portions of the underlying silicon oxide pad layer and to form the trench, at a depth of about 2500 .ANG. to about 4000.ANG., the trench having an internal surface and edges at the main surface;
• removing the first mask;
• thermally growing a thin silicon oxide liner on the internal surface and edges of the trench by heating to a temperature of about 1000.degree. C., whereby the silicon oxide liner grown on the trench edges is rounded;
• depositing a silicon nitride polish stop layer on the silicon oxide liner and the silicon oxide pad layer;
• providing a second mask on the silicon nitride polish stop layer, the second mask containing a pattern having an opening with a dimension greater than the width of the trench;
• isotropically etching to remove portions of the silicon nitride polish stop layer such that the silicon oxide liner is exposed;
• removing the second mask;
• depositing an insulating material to fill the trench and cover the silicon nitride polish stop layer, the insulating material comprising silicon dioxide derived from tetraethyl orthosilicate (TEOS) by low pressure chemical vapor deposition (LPCVD), silicon dioxide derived from silane by LPCVD, or a high density plasma oxide;
• chemical-mechanical polishing the insulating material such that the silicon nitride polish stop layer is exposed, whereby the insulating material at the trench edges has a thickness greater than the thickness of the silicon oxide pad layer.