Scanner Overlay Correction for Reworked Substrates
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Solution Overview
Problem
In semiconductor processing, maintaining precise alignment between layers during photolithography is challenging due to alignment errors, which can be exacerbated by rework processes like CMP rework that alter substrate characteristics, affecting exposure parameters and leading to overlay errors.
Innovation Solution
A system with an advanced process control (APC) model and scanner overlay correction module that distinguishes between substrates with and without rework processes, applying specific mean corrections to exposure parameters such as scaling coefficients to adjust for the effects of rework, thereby reducing overlay errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rework processes like CMP rework are performed on substrates, then manufacturing flexibility and defect correction capability are improved, but substrate characteristics are altered causing overlay errors and alignment precision to deteriorate
Solution Approach 1:
The system performs preliminary identification of reworked substrates using process data from previous manufacturing steps. By detecting substrates that underwent rework processes before exposure, the system proactively applies corrected exposure parameters to prevent overlay errors, rather than correcting them after the fact.
Solution Approach 2:
The system modifies exposure parameters (such as scaling coefficients and alignment marks) based on the identified rework history of substrates. By dynamically changing these parameters according to the specific rework process applied, the system compensates for substrate characteristic alterations and maintains overlay precision.
2Ease of manufacture
If standard exposure parameters are used for all substrates, then manufacturing simplicity is maintained, but overlay errors increase for reworked substrates
Solution Approach 1:
The system applies different exposure parameters to different substrates based on their individual rework histories. Instead of using a uniform approach for all substrates, the system tailors the exposure parameters locally to each substrate's specific processing background, ensuring optimal alignment accuracy for each case.
Solution Approach 2:
The system uses feedback from process data collected during previous manufacturing steps to identify which substrates underwent rework. This feedback mechanism enables the system to automatically adjust exposure parameters for subsequent processing, creating a closed-loop control system that maintains precision without manual intervention.
3Device complexity
If overlay APC is applied to all substrates uniformly, then alignment control is simplified, but correction effectiveness decreases for reworked substrates
Solution Approach 1:
The system segments the substrate population into different groups based on their rework history. By dividing substrates into those that underwent rework and those that did not, the system applies appropriate exposure parameters to each segment, improving alignment reliability for reworked substrates without significantly complicating the overall control system.
Data Source
AI summary
A method includes performing a semiconductor fabrication process on a plurality of substrates. The plurality of substrates are divided into a first subset and a second subset. A rework process is performed on the second subset of the plurality of substrates but not on the first subset. A respective mean value of at least one exposure parameter for a lithography process is computed for each respective one of the first and second subsets of the plurality of substrates. A scanner overlay correction and a mean correction are applied to expose a second plurality of substrates on which the rework process has been performed. The mean correction is based on the computed mean values.