Sub-field overlay correction in lithographic exposure
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Solution Overview
Problem
Current lithographic processes face challenges in effectively controlling overlay errors without negatively impacting throughput, as advanced correction models require more measurements and computing power, which can be economically unviable and limited in correcting certain overlay errors.
Innovation Solution
A method that involves exposing fields on a substrate, obtaining data, defining sub-fields, processing data to produce sub-field correction information, and correcting exposure using this information, allowing for improved overlay control without requiring higher-order correction models, thereby maintaining or enhancing throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If advanced correction models with higher order terms are used to correct overlay errors, then manufacturing precision is improved, but productivity deteriorates due to increased measurement requirements and computing time
Solution Approach 1:
The patent divides the exposure field into multiple sub-fields and applies different correction models to each sub-field. This segmentation allows the system to use simpler correction models for individual sub-fields while achieving overall high precision across the entire field, avoiding the need for computationally intensive high-order models that would reduce throughput.
Solution Approach 2:
The patent implements location-dependent correction by applying different correction parameters and models to different regions (sub-fields) of the exposure field. Each sub-field receives customized correction based on its specific characteristics, enabling precise local correction without requiring complex global models that would impact productivity.
2Manufacturing precision
If more position measurements are made to support advanced correction models, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The patent reduces measurement time by dividing the field into sub-fields and performing measurements and corrections for each sub-field independently. This approach requires fewer total measurements compared to applying a single high-order model to the entire field, thus reducing measurement time while maintaining precision.
Solution Approach 2:
The patent applies correction models with appropriate order for each sub-field rather than using excessive high-order models for the entire field. This partial action approach uses only the necessary measurement data and computing resources for each local region, reducing overall measurement and processing time while achieving sufficient precision.
Data Source
AI summary
A method includes exposing number of fields on a substrate, obtaining data about a field and correcting exposure of the field in subsequent exposures. The method includes defining one or more sub-fields of the field based on the obtained data. Data relating to each sub-field is processed to produce sub-field correction information. A subsequent exposure of the one or more sub-fields is corrected using the sub-field correction information. By controlling a lithographic apparatus by reference to data of a particular sub-field within a field, overlay error can be reduced or minimized for a critical feature, rather than being averaged over the whole field. By controlling a lithographic apparatus with reference to a sub-field rather than only the whole field, a residual error can be reduced in each sub-field.