Method for forming STI structures with controlled step height

A method for forming an isolation structure in a semiconductor device comprising:

• providing a substructure comprising an SiON layer disposed on a silicon nitride layer disposed on a silicon substrate, said SiON layer and said silicon nitride layer having a combined thickness no greater than 900 angstroms;
• etching through said SiON layer, said silicon nitride layer and into said silicon substrate thereby forming a trench having sidewalls formed of said substrate, said silicon nitride layer and said SiON layer;
• forming a dielectric filling said trench and over said SiON layer;
• polishing to reduce a thickness of said dielectric over said SiON layer such that said dielectric remains over said SiON layer;
• after said polishing, using an oxide etch procedure to remove said dielectric from over said SiON layer and to substantially uniformly recede a top surface of said dielectric below a top surface of said SiON layer in said trench;
• and
• removing said SiON layer and said silicon nitride layer.

A method for forming isolation structures in a semiconductor device comprising:

• providing a substructure of a nitrogen-containing layer disposed on a surface of a silicon substrate;
• etching a plurality of openings of different widths through said nitrogen-containing layer and into said silicon substrate thereby forming a corresponding plurality of trenches having different widths;
• forming a dielectric over said nitrogen-containing layer and filling said plurality of trenches;
• polishing said dielectric to reduce a thickness of said dielectric over said nitrogen-containing layer and whereby said dielectric remains over said nitrogen-containing layer;
• after said polishing, using an etch procedure to remove said dielectric from over said nitrogen-containing layer and to substantially uniformly recede a top surface of said dielectric below a top surface of said nitrogen-containing layer in each of said plurality of trenches such that said top surface is no more than about 500 angstroms above said surface of said silicon substrate;
• and
• removing said nitrogen-containing layer to form an isolation structure in each of said plurality of trenches, each isolation structure including said top surface as a top portion thereof and disposed no more than about 500 angstroms above said surface of said silicon substrate.