Lithography Diagnostic Analysis for Overlay Distortion Correction
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Solution Overview
Problem
Modern lithographic processes face challenges in accurately tracing and correcting distortions in substrate patterns due to complex processing steps, leading to non-correctable overlay and alignment residuals, which are difficult to identify and time-consuming to address, and current performance monitoring systems compromise between monitoring time and correction speed.
Innovation Solution
A diagnostic apparatus and method utilizing multivariate analysis to extract diagnostic information from object data, including lithographic patterning and chemical/physical processing operations, to identify component vectors and generate correction data for improving process accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If extensive measurement and mapping operations are performed to model and correct non-linear distortions, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The patent performs measurement and mapping operations before the actual lithographic exposure step. By conducting extensive measurements of alignment marks and creating distortion models in advance, the system prepares correction data that will be applied during subsequent patterning operations, thus improving overlay accuracy without compromising production throughput
Solution Approach 2:
The system anticipates and compensates for non-linear distortions by creating advanced alignment models that predict and correct for processing-induced warpage and lens distortions. This preliminary cushioning against expected errors ensures that even when distortions occur during processing, the overlay accuracy is maintained within specification
2Manufacturing precision
If advanced alignment models are used to correct non-linear distortions, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the complex distortion correction problem into manageable segments by creating separate alignment models for different types of distortions (e.g., wafer warpage, lens distortion, stage positioning errors). Each model focuses on specific spatial frequencies and distortion patterns, making the overall system more tractable and easier to implement while maintaining high correction accuracy
Solution Approach 2:
The system transitions from simple 2D alignment mark detection to 3D spatial modeling that accounts for wafer topography and through-focus variations. By incorporating height information and focal plane variations into the alignment model, the system can correct for non-linear distortions that would be impossible to address with conventional 2D methods
3Measurement precision
If overlay measurements are performed on each individual wafer, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent implements a hybrid measurement strategy where not all wafers undergo complete overlay measurement sequences. Instead, the system uses statistical process control to identify when full measurements are necessary versus when reduced measurement sets suffice, performing measurements on a partial basis while maintaining overall process control and productivity
Data Source
AI summary
In a lithographic process, product units such as semiconductor wafers are subjected to lithographic patterning operations and chemical and physical processing operations. Alignment data or other measurements are made at stages during the performance of the process to obtain object data representing positional deviation or other parameters measured at points spatially distributed across each unit. This object data is used to obtain diagnostic information by performing a multivariate analysis to decompose a set of vectors representing the units in the multidimensional space into one or more component vectors. Diagnostic information about the industrial process is extracted using the component vectors. The performance of the industrial process for subsequent product units can be controlled based on the extracted diagnostic information.