Overlay Correction Using Asymmetrical Skew Values
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Solution Overview
Problem
Existing semiconductor fabrication methods face challenges in achieving uniformity of overlay correction values, leading to errors in the positioning of patterns on semiconductor substrates during the overlay measurement process.
Innovation Solution
The method involves measuring and calculating various distances and overlay values using processing circuitry to determine skew values, which are then used to adjust the position of photoresist patterns, incorporating an asymmetrical overlay value updated with a weighting coefficient to improve overlay correction uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional overlay measurement process is used to detect distortion between lower and upper patterns, then overlay measurement can be performed at multiple positions, but the uniformity of overlay correction values deteriorates
Solution Approach 1:
The overlay measurement process is segmented into multiple distinct measurement stages: ADI overlay measurement, ACI overlay measurement, and asymmetrical overlay measurement. Each stage measures different aspects of pattern alignment at various positions on the substrate, allowing comprehensive data collection that improves correction uniformity across the entire substrate surface.
Solution Approach 2:
The patent introduces asymmetrical overlay measurement to capture directional differences in pattern misalignment. By measuring overlay in different directions and calculating asymmetrical overlay values, the method accounts for non-uniform distortion patterns that symmetric measurements would miss, thereby improving the uniformity of correction values across the substrate.
2Reliability
If multiple overlay measurement values are obtained from many positions, then comprehensive overlay data is achieved, but the complexity of calculating and correcting overlay errors increases
Solution Approach 1:
The patent performs preliminary measurements and calculations before final overlay correction. ADI and ACI overlay values are measured and calculated in advance, along with asymmetrical overlay values. These preliminary results are then used to determine overlay skew values, which simplify the final correction process by pre-characterizing the distortion patterns.
Solution Approach 2:
The system implements feedback through iterative measurement and correction. Overlay measurement values from multiple positions are fed back into the calculation process to determine skew values, which are then applied to correct the overlay alignment. This feedback loop ensures that correction values are continuously optimized based on actual measured data from the substrate.
Data Source
AI summary
An overlay correction method may include obtaining a first central line of a lower pattern on a substrate, forming a photoresist pattern on the lower pattern, obtaining an ADI overlay value corresponding to a first distance between a second central line of an upper flat surface of the lower pattern and a third central line of the photoresist pattern, obtaining an asymmetrical overlay value corresponding to a second distance between the first and second central lines, form an upper pattern using the photoresist pattern, obtaining an ACI overlay value corresponding to a third distance between the first central line and a fourth central line of the upper pattern, subtracting the ADI overlay value from the ACI overlay value to obtain a first overlay skew value, and adding the asymmetrical overlay value to the first overlay skew value to obtain a second overlay skew value.