Lithography Overlay Correction via Axis-Specific Distortion Segmentation
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Solution Overview
Problem
Current lithography systems face challenges in maintaining high overlay accuracy among layers due to differences in image distortion between projection exposure apparatuses, particularly when adjusting for both linear and nonlinear components, which can lead to misalignment of electrical connections in semiconductor devices.
Innovation Solution
The system selects a reference layer for each axis of the two-dimensional orthogonal coordinate system to adjust distortion and nonlinear components of projected images, using stored information from previously exposed layers to optimize overlay exposure, allowing for precise alignment based on the exposure state of the selected reference layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple projection exposure apparatuses are used to increase productivity, then manufacturing throughput is improved, but overlay accuracy deteriorates due to distortion differences among apparatuses
Solution Approach 1:
The patent applies parameter changes by adjusting the distortion correction parameters for each projection exposure apparatus based on measured distortion characteristics. The system determines specific distortion parameters for each apparatus and uses these to correct the projected images, thereby maintaining overlay accuracy while enabling the use of multiple apparatuses for increased productivity.
Solution Approach 2:
The patent implements feedback by measuring the actual distortion of projected images from each projection exposure apparatus and using this measurement information to adjust and correct subsequent exposures. The distortion measurement results are fed back into the control system to optimize the distortion correction parameters, ensuring consistent overlay accuracy across multiple apparatuses.
2Device complexity
If average distortion of multiple previous layers is used for reference, then distortion matching is simplified, but overlay accuracy deteriorates when circuit design requires axis-specific reference layers
Solution Approach 1:
The patent applies segmentation by dividing the distortion correction process into axis-specific segments. Instead of using a single average distortion reference for all layers, the system separately determines distortion parameters for the X-axis direction and Y-axis direction, allowing each axis to reference appropriate previous layers independently. This segmentation enables precise distortion matching that aligns with circuit design requirements.
Solution Approach 2:
The patent implements dynamics by making the distortion reference selection adaptive and flexible. The system can dynamically select which previous layers serve as references for each axis based on the specific circuit design requirements and distortion characteristics of each apparatus. This dynamic approach allows optimization of overlay accuracy for different circuit configurations without requiring complex manual setup.
3Ease of manufacture
If distortion correction is performed using single reference layer, then processing is simplified, but overlay accuracy deteriorates due to inability to address axis-specific distortion components
Solution Approach 1:
The patent applies dimensionality change by extending the distortion correction from a single reference layer approach to a multi-dimensional approach that considers both the layer dimension and the axis dimension. The system determines distortion parameters separately for X-axis and Y-axis directions, effectively adding an axis dimension to the correction process. This enables comprehensive distortion compensation while maintaining systematic and manageable processing procedures.
Data Source
AI summary
In the case where the previous process (X) and the previous process (Y) are different in step 310, only a distortion amount in an X-axis direction is extracted from image distortion data of the previous process (X) in Step 316 and only a distortion amount in a Y-axis direction is extracted from image distortion data of the previous process (Y) in Step 318, and then in Step 320, image distortion data is created by synthesizing the extracted distortion amounts, and the synthesized image distortion data is used for subsequent adjustment of projected images. With this operation, the distortion of projected images can be adjusted per axis and accordingly overlay exposure with high accuracy can be realized.