Sti cmp under polish monitoring

A method comprising:

• calculating scattering spectra for each of a plurality of oxide thicknesses, producing calculated scattering spectra;
• associating the scattering spectra with the corresponding oxide thickness;
• creating a library of scattering spectra and associated oxide thicknesses;
• providing an oxide layer on a semiconductor wafer;
• reducing a thickness of the oxide layer on a portion of the semiconductor wafer, forming a reduced oxide layer, wherein reducing the thickness of the oxide comprises performing chemical mechanical polishing (CMP) above a pad nitride layer proximate a shallow trench isolation (STI) region;
• measuring scattering spectra of the reduced oxide layer;
• accessing the library of scattering spectra;
• determining a calculated scattering spectra that matches the measured scattering spectra of the reduced oxide layer;
• obtaining the associated oxide thickness of the calculated scattering spectra that matches the measured scattering spectra of the reduced oxide layer;
• and
• repeating the steps of reducing, measuring, accessing, determining, and obtaining until the obtained oxide thickness is zero.

A method comprising:

• calculating scattering spectra for each of a plurality of oxide thicknesses, producing calculated scattering spectra;
• associating the scattering spectra with the corresponding oxide thickness;
• creating a library of scattering spectra and associated oxide thicknesses;
• providing an oxide layer on a semiconductor wafer;
• reducing a thickness of the oxide layer on a portion of the semiconductor wafer, forming a reduced oxide layer;
• measuring scattering spectra of the reduced oxide layer at up to 10 locations per die across the portion of the semiconductor wafer;
• accessing the library of scattering spectra;
• determining a calculated scattering spectra that matches the measured scattering spectra of the reduced oxide layer at each of the multiple locations;
• obtaining the associated oxide thickness of each calculated scattering spectra that matches a measured scattering spectra of the reduced oxide layer;
• identifying a zone in which an obtained oxide thickness is greater than zero;
• reworking the identified zone;
• and
• repeating the steps of measuring, accessing, determining, and obtaining until no obtained oxide thickness is greater than zero.