Phase-Resolved Optical Metrology for Substrates
AssigneeApplied Materials, Inc.
InventorsNedal SALEH, Zhiming JIANG, Xiaodong ZHANG, Arun Ramaswamy SRIVATSA
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Abstract
The methods and apparatus provide phase-resolved optical metrology for determining qualities of a substrate and films thereon. Transmitted and reflected signals are coupled using both amplitude and phase information to improve the metrology information obtained from film layers on the substrate.
Claims20
A method for determining an absorption profile for a film on a substrate, comprising:
- illuminating the substrate with a broadband spectrum;
- obtaining amplitude and phase for reflection beams from a first surface of the substrate;
- obtaining amplitude and phase for transmission beams propagating through the substrate and beyond a second surface of the substrate;
- forming a model of the substrate by coupling the amplitude and phase of the reflection beams and the amplitude and phase of the transmission beams to form a phase-resolved signal with a first sub-signal at a first end of a Standing-Wave-Ratio (SWR) envelope that resolves top layer information and a second sub-signal at a second end of the SWR envelope that resolves substrate bulk information;
- determining the absorption profile of the film on the substrate and the substrate based on the model of the substrate;
- and
- using the absorption profile to perform a corrective action during processing of the film or substrate.
A non-transitory, computer readable medium having instructions stored thereon that, when executed, cause a method for determining an absorption profile for a film on a substrate to be performed, the method comprising:
- illuminating the substrate with a broadband spectrum;
- obtaining amplitude and phase for reflection beams from a first surface of the substrate;
- obtaining amplitude and phase for transmission beams propagating through the substrate and beyond a second surface of the substrate;
- forming a model of the substrate by coupling the amplitude and phase of the reflection beams and the amplitude and phase of the transmission beams to form a phase-resolved signal with a first sub-signal at a first end of a Standing-Wave-Ratio (SWR) envelope that resolves top layer information and a second sub-signal at a second end of the SWR envelope that resolves substrate bulk information;
- and
- determining the absorption profile of the film on the substrate and the substrate based on the model of the substrate.
A metrology apparatus for determining an absorption profile for a film on a substrate, comprising:
- a broadband illumination source configured to produce an infrared (IR) illumination band beam;
- a beam splitter configured to split the IR illumination band beam;
- a fixed mirror configured to receive the IR illumination band beam;
- a movable mirror configured to receive the IR illumination band beam and move to alter resolution of the metrology apparatus;
- a reflection detector configured to obtain amplitude and phase of a reflection of the IR illumination band beam;
- a transmission detector configured to obtain amplitude and phase of a transmission of the IR illumination band beam through the film and the substrate;
- and
- a controller configured to alter a step distance of the movable mirror to less than a shortest wavelength in the IR illumination band beam or to alter a velocity of the movable mirror to a lowest possible continuous velocity wherein the reflection detector and the transmission detector are configured to detect at a sampling rate greater than the velocity divided by a shortest wavelength of the illumination band beam.
Dependencies are inferred from the claim text.