Shallow trench isolation technique

A method of forming a shallow trench isolation structure in a silicon substrate, said method comprising the steps of:

• forming a pad oxide layer on a silicon substrate and a silicon nitride layer on said pad oxide layer;
• etching a trench in said silicon nitride layer, said pad oxide layer, and said silicon substrate wherein said trench has sidewalls in said silicon substrate;
• prior to oxidizing said trench, exposing said trench to a wet etchant comprising HF so as to etch away a portion of said pad oxide from beneath said silicon nitride layer to thereby expose a portion of the top surface of said silicon substrate;
• oxidizing said trench a first time so as to grow an oxide layer on said trench sidewalls and on said revealed top portion of said silicon substrate;
• after oxidizing said trench a first time, etching said grown oxide layer with a wet etchant comprising HF;
• and
• oxidizing said trench a second time.

A method of forming a trench isolation region in a silicon substrate comprising the steps of:

• forming a trench in said silicon substrate;
• depositing a first oxide layer into said trench;
• sputter etching said first oxide layer so that said sputter etched first oxide layer redeposits in said trench;
• and
• depositing a second oxide layer into said trench over said sputter etched first oxide layer.

A method of forming a shallow trench isolation structure in a silicon substrate, said method of comprising the steps of:

• forming a pad oxide layer on said silicon substrate and a silicon nitride layer on said pad oxide layer;
• etching a trench in said silicon nitride layer, said pad oxide layer, and said silicon substrate wherein said trench has sloped sidewalls in said silicon substrate;
• exposing said trench to a first wet etchant comprising HF so as to etch away a portion of said pad oxide from beneath said silicon nitride layer to thereby expose a portion of the top surface of said silicon substrate;
• oxidizing said trench a first time so as to grow a first oxide layer on said trench sidewalls and on said revealed top portion of said silicon substrate;
• etching said first grown oxide layer with a wet etchant comprising HF so as to remove said first grown oxide layer from said sidewalls of said trench and from said top portion of said silicon substrate;
• and
• oxidizing said trench a second time so as to grow a second oxide layer on said trench sidewalls and on said top portion of said silicon substrate;
• depositing a first oxide layer over said silicon nitride layer and into said oxidized trench;
• sputter etching said first deposited oxide layer;
• depositing a second oxide layer over said sputter etch first oxide layer in said trench and on said silicon nitride layer;
• and
• polishing said second oxide layer and said sputter etch first oxide layer from said silicon nitride layer so as to form a trench isolation structure which is substantially planar to said silicon nitride layer.