Polishing with pre deposition spectrum

A method of fabricating a substrate comprising:

• depositing at least one dielectric layer on a metallic layer or semiconductor wafer of the substrate;
• measuring a base spectrum reflected from the substrate, at an optical metrology system, after depositing the at least one dielectric layer but before depositing an outermost layer;
• depositing the outermost layer on the at least one dielectric layer;
• polishing the outermost layer of the substrate;
• during polishing of the outermost layer, measuring a sequence of raw spectra reflected from the substrate, at an in-situ optical monitoring system;
• normalizing each raw spectrum in the sequence of raw spectra to generate a sequence of normalized spectra using the raw spectrum and the base spectrum;
• and
• determining at least one of a polishing endpoint or an adjustment for a polishing rate based on at least one normalized predetermined spectrum from the sequence of normalized spectra.

An integrated circuit fabrication system, comprising:

• a deposition system configured to receive a substrate, and deposit a stack of layers overlying a metallic layer or semiconductor substrate, the stack of layers including a non-metallic layer to undergo polishing and at least one dielectric layer underlying the non-metallic layer;
• a metrology system configured to generate a measurement of a spectrum of light reflected from the substrate after deposition of the at least one dielectric layer and before deposition of the non-metallic layer;
• and
• a polishing system configured to receive the substrate and polish the non-metallic layer on the substrate, wherein the polishing system includes a controller configured to perform operations comprising:
• receiving the measurement of the spectrum of light from the metrology system and store the measurement as a base spectrum,
• receiving measurements of a sequence of raw spectra of light reflected from the substrate during polishing with an in-situ optical monitoring system,
• normalizing each raw spectrum in the sequence of raw spectra to generate a sequence of normalized spectra using the raw spectrum and the base spectrum, and
• determining at least one of a polishing endpoint or an adjustment for a polishing rate based on at least one normalized predetermined spectrum from the sequence of normalized spectra.

A polishing system comprising:

• a carrier configured to mount a substrate, wherein the substrate includes a stack of layers overlying a metallic layer or semiconductor substrate, the stack of layers including a non-metallic layer undergoing polishing and a plurality of deposited dielectric layers underlying the non-metallic layer;
• a platen to receive a polishing pad configured to be in contact with the substrate;
• an in-situ optical monitoring system;
• and
• a controller configured to perform operations comprising:
• storing a post deposition base spectrum, the post deposition base spectrum being a spectrum of light reflected from the substrate after deposition of the plurality of deposited dielectric layers and before deposition of the non-metallic layer;
• receiving, from the in-situ optical monitoring system, measurements of a sequence of raw spectra of light reflected from the substrate during polishing;
• normalizing each raw spectrum in the sequence of raw spectra to generate a sequence of normalized spectra using the raw spectrum and the post deposition base spectrum;
• and
• determining at least one of a polishing endpoint or an adjustment for a polishing rate based on at least one normalized predetermined spectrum from the sequence of normalized spectra.

A computer program product, encoded on one or more non-transitory computer storage media, comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising:

• storing a base measurement, the base measurement being an eddy current measurement of a substrate after deposition of at least one layer overlying a semiconductor wafer and before deposition of a conductive layer over the at least one layer;
• after deposition of the conductive layer over the at least one layer and during polishing of the conductive layer on substrate, receiving a sequence of raw measurements of the substrate from an in-situ eddy current monitoring system;
• normalizing each raw measurement in the sequence of raw measurement to generate a sequence of normalized measurements using the raw measurement and the base measurement;
• and
• determining at least one of a polishing endpoint or an adjustment for a polishing rate based on at least the sequence of normalized measurements.