Integrated circuit trench device with a dielectric collar stack, and method of forming thereof

A method of forming an isolation collar in a deep trench on a silicon substrate, said method comprising:

• forming a conformal silicon dioxide layer on an interior surface of said trench using a tetraethyloxysilane decomposition (TEOS) process;
• filling a lower portion of said trench with a mask layer, thereby masking a lower sidewall and bottom of said silicon dioxide layer and leaving an upper sidewall of said silicon dioxide layer unmasked;
• forming a conformal silicon nitride layer on said silicon dioxide layer upper sidewall and on an upper surface of said mask layer;
• anisotropically etching said silicon nitride layer to remove horizontal sections of said silicon nitride layer, thereby leaving an upper sidewall of said silicon nitride layer in said trench adjacent said silicon dioxide layer upper sidewall;
• removing said mask layer from said trench to expose said lower sidewall and bottom of said silicon dioxide layer;
• and
• removing said lower sidewall and bottom of said silicon dioxide layer from said trench to expose said silicon substrate surface in said lower portion of said trench.

A method of forming an isolation collar in a deep trench on a silicon substrate, said method comprising:

• forming a pad nitride layer on said silicon substrate;
• forming said deep trench;
• forming a conformal silicon dioxide layer on an interior surface of said trench;
• filling a lower portion of said trench with a mask layer, thereby masking a lower sidewall and bottom of said silicon dioxide layer and leaving an upper sidewall of said silicon dioxide layer unmasked;
• forming a conformal silicon nitride layer on said silicon dioxide layer upper sidewall and on an upper surface of said mask layer;
• anisotropically etching said silicon nitride layer to remove horizontal sections of said silicon nitride layer, thereby leaving an upper sidewall of said silicon nitride layer in said trench adjacent said silicon dioxide layer upper sidewall;
• removing said mask layer from said trench to expose said lower sidewall and bottom of said silicon dioxide layer;
• and
• removing said lower sidewall and bottom of said silicon dioxide layer from said trench to expose said silicon substrate surface in said lower portion of said trench.