Scanner Overlay Correction for Reworked Semiconductor Wafers
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Solution Overview
Problem
In semiconductor processing, maintaining proper alignment between layers during photolithography is challenging due to physical alterations caused by rework processes, such as CMP rework, which affect exposure parameters like wafer scaling coefficients, leading to increased overlay errors.
Innovation Solution
A controller system that differentiates between substrates based on rework processes, applying specific mean corrections to exposure parameters, particularly wafer scaling coefficients, to adjust scanner settings and reduce overlay errors by compensating for the effects of rework processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rework processes (such as CMP rework) are performed on substrates, then manufacturing flexibility and defect correction capability are improved, but physical alterations to the substrate cause increased overlay errors and reduced alignment precision
Solution Approach 1:
The system performs preliminary identification of reworked substrates using process data before exposure, and pre-calculates the appropriate mean correction values for wafer scaling coefficients. This allows the scanner to be pre-configured with the correct correction parameters, eliminating the negative effects of rework processes on overlay precision.
2Ease of operation
If traditional overlay correction methods are used without differentiating reworked substrates, then processing simplicity is maintained, but overlay errors increase due to uncorrected physical alterations from rework
Solution Approach 1:
The system automatically identifies reworked substrates using process data from the fabrication process itself, and self-corrects overlay errors by applying appropriate mean corrections to wafer scaling coefficients. This automated approach maintains processing simplicity while significantly improving overlay accuracy compared to manual methods.
3Manufacturing precision
If mean corrections to wafer scaling coefficients are applied to all substrates, then overlay precision is improved, but unnecessary corrections are applied to non-reworked substrates causing increased process complexity
Solution Approach 1:
The system applies mean corrections to wafer scaling coefficients selectively only to substrates that have undergone rework processes. By using process data to identify which substrates require correction, the system applies local quality adjustments rather than uniform corrections to all substrates, thereby improving overlay precision without unnecessarily increasing process complexity.
Data Source
AI summary
A method of processing first and second semiconductor wafers is provided. Each of the first and second semiconductor wafers has a first layer and a second layer over the first layer. A first lithographic process is performed on the first layer over the first semiconductor wafer using a first inter-field correction and a first intra-field correction. An overlay error of the first lithographic process is determined. A second inter-field correction and a second intra-field correction are computed based on the first inter-field correction, the first intra-field correction, and the measured overlay error. A second lithographic process is performed on the second layer over the second semiconductor wafer, based on the second inter-field correction and the second intra-field correction.