Shallow trench isolation planarization using self aligned isotropic etch

A method of forming isolation structures in a semiconductor substrate, said method comprising the steps of:

• etching trenches in said substrate, thereby forming substantially unetched areas of said substrate between said trenches;
• depositing a fill material that substantially fills said trenches, said fill material having an upper surface;
• forming a etch barrier on said upper surface of said fill material;
• removing portions of said etch barrier situated over said substantially unetched areas of said substrate thereby exposing portions of said fill material;
• removing said exposed portions of said fill material;
• and
• planarizing said fill material.

A method of forming isolation structures in a semiconductor substrate, said method comprising the steps of:

• etching trenches in said substrate, thereby forming substantially unetched areas of said substrate between said trenches;
• depositing a conformal fill material that substantially fills said trenches, said fill material having an upper surface, elevated areas, and depressed areas;
• forming a conformal etch barrier on said upper surface of said conformal fill material;
• removing portions of conformal etch barrier in said elevated areas thereby leaving it in said depressed areas thereby exposing portions of said conformal fill material;
• removing said exposed portions of said conformal fill material using an isotropic etch;
• and
• polishing said conformal fill material using chemical mechanical polishing.