Wafer Misregistration Correction Using TIS Tilt Compensation
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Solution Overview
Problem
Existing methods for measuring misregistration in semiconductor wafers fail to accurately account for errors caused by localized wafer tilt, leading to inaccuracies in misregistration measurements.
Innovation Solution
A method and system that measure and correct misregistration measurements by calculating the difference in Tool Induced Shift (TIS) between orthogonal and oblique illumination arrangements, using a weighted value to subtract errors caused by wafer tilt, and optimizing metrology device parameters based on these measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional misregistration measurement methods are used, then the measurement process is simple, but the measurement precision deteriorates due to uncorrected wafer tilt errors
Solution Approach 1:
The system performs preliminary measurements of TIS under orthogonal and oblique illumination conditions before the actual misregistration measurement. These preliminary measurements establish a correction profile that is then applied to subsequent measurements, allowing the system to pre-characterize the wafer tilt effects and compensate for them during normal operation.
Solution Approach 2:
The system introduces TIS measurements under different illumination conditions as an intermediary step. By measuring how the tool responds to controlled illumination tilts, the system creates a reference profile that mediates between the raw misregistration measurement and the true value, enabling correction of wafer tilt effects without directly measuring the tilt itself.
2Measurement precision
If TIS measurements are performed under multiple illumination conditions, then the correction accuracy improves, but the measurement time increases
Solution Approach 1:
The TIS characterization under multiple illumination conditions is performed as a preliminary calibration step that needs to be done only once or periodically, rather than before every misregistration measurement. This allows the system to capture the full correction profile in advance and then apply it rapidly to subsequent measurements, amortizing the time cost over many measurements.
Solution Approach 2:
The system creates a correction profile (a digital representation of TIS behavior under various illumination conditions) that can be stored and reused. Instead of repeatedly performing the full multi-condition TIS measurement sequence, the system copies the previously established correction profile and applies it to new measurements, significantly reducing the time required while maintaining correction accuracy.
Data Source
AI summary
A method for correcting misregistration measurements of a semiconductor wafer for errors therein arising from tilt of the wafer including measuring, for at least one location on a wafer, a difference between a Tool Induced Shift (TIS) of a metrology device in a first illumination arrangement with respect to the wafer wherein a surface of the wafer is generally orthogonally illuminated by an illumination source of the metrology device and a TIS of the metrology device in a second illumination arrangement with respect to the wafer, wherein the surface is obliquely illuminated by the illumination source, and correcting a misregistration measurement measured by the metrology device at the at least one location for errors therein arising from tilt of the wafer at the location by subtracting from the misregistration measurement a weighted value of the difference between the TIS in the first and second illumination arrangements.