Method for fabricating shallow trench isolation

A method for forming shallow trench isolation, comprising the steps of:

• forming sequentially a mask layer and a pad oxide layer on a substrate;
• forming a opening through said mask layer and said pad oxide layer to expose a portion of said substrate;
• etching said exposed substrate for forming trenches inside said substrate;
• implanting nitrogen ions into the sidewall of said trenches to form a silicon nitride layer wherein the implant energy of said implanting nitrogen ions is between about 1 keV and 10 keV;
• forming a siliconoxynitride layer on said sidewall of said trenches by using a thermal oxidation process wherein the temperature of said thermal oxidation process is between about 650° C. and 900° C.;
• forming a silicon oxide layer on said siliconoxynitride layer and said mask layer by using a high-density plasma chemical vapor deposition process;
• removing the excess portion of said silicon oxide layer over said mask layer to expose said mask layer;
• and
• removing said mask layer.

A method for forming shallow trench isolation, comprising the steps of:

• forming a pad oxide layer on a substrate;
• forming a mask layer on said pad oxide layer;
• forming an opening through said mask layer and said pad oxide layer such that regions of said substrate are exposed;
• etching said exposed regions for forming trenches inside said substrate;
• implanting nitrogen ions into the sidewall of said trenches to form a silicon nitride layer;
• forming a siliconoxynitride layer on said sidewall of said trenches by using a thermal oxidation process wherein the temperature of said thermal oxidation process is between about 650° C. and 900° C.;
• forming a silicon oxide layer on said siliconoxynitride layer and said mask layer by using a high-density plasma chemical vapor deposition process;
• removing the excess portion of said silicon oxide layer over said mask layer to expose said mask layer,
• removing said mask layer;
• and
• removing said pad oxide layer by using hydrofluoric acid (HF).