Phase-resolved optical metrology for substrates
Inventors
Saleh, Nedal • Jiang, Zhiming • Zhang, Xiaodong • SRIVATSA, Arun Ramaswamy
Assignees
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Publication Number
US-12429418-B2
Publication Date
2025-09-30
Expiration Date
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.
Core Innovation
The invention determines an absorption profile for a film on a substrate by illuminating the substrate with a broadband spectrum and obtaining amplitude and phase for reflection beams from a first surface of the substrate. It also obtains amplitude and phase for transmission beams propagating through the substrate and beyond a second surface of the substrate, and couples the amplitude and phase into a phase-resolved signal.
A model of the substrate is formed 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 and a second sub-signal at a second end of the SWR envelope. The first sub-signal resolves top layer information, and the second sub-signal resolves substrate bulk information, and the absorption profile of the film on the substrate and the substrate is determined based on the model of the substrate.
The absorption profile is used to perform a corrective action during processing of the film or substrate. In embodiments, the substrate is modeled as an asymmetrical lossy Fabry-Perot etalon, and equations link reflection/transmission amplitudes and phase to absorption parameters for the film and substrate, yielding absorption-profile determination without bare-substrate pre-measurements.
Claims Coverage
The independent claims cover a method, a non-transitory computer readable medium with the same computational method, and a metrology apparatus that measures the required reflection/transmission amplitude and phase and controls mirror motion and sampling to enable SWR phase-resolved modeling. Across the independents, the core inventive structure is the coupling of reflection and transmission amplitude/phase into a phase-resolved SWR-envelope signal that separates top-layer and substrate-bulk information.
Broadband amplitude/phase reflection and transmission for absorption-profile modeling
Illuminating the substrate with a broadband spectrum; obtaining amplitude and phase for reflection beams from a first surface of the substrate; and obtaining amplitude and phase for transmission beams propagating through the substrate and beyond a second surface of the substrate.
Phase-resolved SWR-envelope model separating top-layer and substrate-bulk information
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.
Absorption-profile determination from the SWR-envelope substrate model
Determining the absorption profile of the film on the substrate and the substrate based on the model of the substrate.
Corrective action during processing based on the absorption profile
Using the absorption profile to perform a corrective action during processing of the film or substrate.
Computer-readable medium instructions for the phase-resolved absorption-profile method
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, comprising illuminating the substrate with a broadband spectrum; obtaining amplitude and phase for reflection beams from a first surface; obtaining amplitude and phase for transmission beams propagating through the substrate and beyond a second surface; forming a model by coupling the amplitude and phase to form a phase-resolved signal with a first sub-signal at a first end of an SWR envelope that resolves top layer information and a second sub-signal at a second end that resolves substrate bulk information; and determining the absorption profile based on the model.
IR metrology apparatus with controlled movable mirror and sampling to enable phase detection
A metrology apparatus comprising a broadband illumination source configured to produce an infrared (IR) illumination band beam; a beam splitter; a fixed mirror; a movable mirror configured to receive the IR illumination band beam and move to alter resolution; a reflection detector configured to obtain amplitude and phase of a reflection; a transmission detector configured to obtain amplitude and phase of a transmission 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.
Across the independent claims, the invention centers on coupling broadband reflection and transmission amplitude/phase into a phase-resolved SWR-envelope signal with distinct sub-signals that resolve top-layer versus substrate-bulk information, using a substrate model to determine an absorption profile, and using that absorption profile for corrective action during processing. A corresponding non-transitory computer readable medium and a dedicated IR metrology apparatus with controlled mirror motion and sampling provide the measurement and execution structure for the method.
Stated Advantages
Improves throughput/cost/sensitivity/accuracy and enables on-demand metrology.
Enables absorption-profile determination without bare-substrate pre-measurements.
Documented Applications
Determining an absorption profile for a film on a substrate during processing, and using the absorption profile to perform a corrective action during processing of the film or substrate.
Epitaxial growth and physical vapor deposition (PVD) and chemical vapor deposition (CVD) and resist layer deposition, in which corrective action during processing is performed based on the determined absorption profile.
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