Process Tool Correctables for Semiconductor Overlay Error Control
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Solution Overview
Problem
Conventional semiconductor manufacturing processes face limitations in accurately measuring and correcting overlay errors across semiconductor wafers, leading to misalignment issues and inefficiencies in lithography processes due to fixed sampling methods and inadequate handling of residual variations.
Innovation Solution
A method utilizing a Support Vector Machine (SVM) algorithm to determine process tool correctables by measuring characteristics across multiple fields of wafers, fitting models based on field position, and adjusting processes to minimize residual differences, thereby improving alignment and reducing rework rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed sampling methods are used to measure overlay errors, then measurement simplicity is maintained, but measurement precision and coverage across the wafer deteriorate
Solution Approach 1:
The wafer is divided into multiple fields, and overlay errors are measured at multiple locations across different fields rather than using fixed sampling at single locations. This segmentation approach enables comprehensive coverage of the entire wafer surface, capturing spatial variations in overlay errors that fixed sampling would miss.
Solution Approach 2:
The measurement approach transitions from one-dimensional fixed sampling points to two-dimensional distributed measurement across multiple fields on the wafer. By adding the field position dimension to the measurement scheme, the system captures spatial distribution of overlay errors, significantly improving measurement precision and coverage.
2Manufacturing precision
If conventional overlay correction methods are used, then processing speed is maintained, but manufacturing precision deteriorates due to inadequate handling of residual variations
Solution Approach 1:
The system performs preliminary measurement of overlay errors at multiple fields and locations before the lithography process. By collecting comprehensive measurement data in advance and analyzing spatial patterns, the system prepares accurate correction values that account for field-position dependent variations, improving manufacturing precision without adding time during the actual production process.
Solution Approach 2:
The system implements a feedback loop where overlay error measurements from multiple fields are used to calculate and apply correction values to the lithography tool. The measurements feed into an analysis routine that generates correctables, which are then fed back to adjust the lithography process, continuously improving overlay precision.
3Measurement precision
If comprehensive measurements across multiple fields are performed, then overlay error detection accuracy is improved, but device complexity increases
Solution Approach 1:
The system introduces an intermediary analysis routine that processes the comprehensive measurement data from multiple fields. This intermediary layer aggregates measurements, identifies spatial patterns, and generates correction values, simplifying the overall system architecture while maintaining high measurement precision through distributed sampling.
Data Source
AI summary
The present invention may include performing a first measurement process on a wafer of a lot of wafers, wherein the first measurement process includes measuring one or more characteristics of a plurality of targets distributed across one or more fields of the wafer, determining a set of process tool correctables for a residual larger than a selected threshold level utilizing a loss function, wherein the loss function is configured to fit a model for one or more process tools, as a function of field position, to one or more of the measured characteristics of the plurality of targets, wherein the set of process tool correctables includes one or more parameters of the model that act to minimize the difference between a norm of the residual and the selected threshold, and utilizing the determined process tool correctables to monitor or adjust one or more processes of the process tools.