Wafer Cooling Time Control for Photomask Overlay Accuracy
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Solution Overview
Problem
Existing semiconductor wafer cooling techniques use a fixed cooling time, which can lead to inconsistent wafer heating across exposure stages, causing photomask misalignment and degraded overlay performance due to thermal expansion and contraction.
Innovation Solution
A learning cooling device that determines a cooling time for a semiconductor wafer based on the pattern mask area, ensuring synchronization between wafer exposure time and cooling time to reduce photomask misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed cooling time is used for all wafers, then the cooling process is simple and fast, but the wafer temperature becomes inconsistent across different exposure stages, causing photomask misalignment
Solution Approach 1:
The cooling time is changed from a fixed static value to a dynamic value that varies according to the pattern mask area. The cooling device adjusts the cooling time based on the specific exposure conditions of each wafer, making the cooling process adaptive rather than rigid. This resolves the contradiction by allowing the system to be both efficient (fast cooling) and precise (aligned photomasks) simultaneously.
Solution Approach 2:
The cooling time parameter is changed based on the pattern mask area parameter. By establishing a relationship between these two parameters, the system optimizes the cooling process for different exposure conditions. Larger pattern mask areas receive different cooling times compared to smaller areas, ensuring consistent wafer temperature and photomask alignment across all exposure stages.
2Manufacturing precision
If the cooling time is extended to ensure consistent wafer temperature, then photomask alignment improves, but the overall processing time increases
Solution Approach 1:
Instead of using a uniformly extended cooling time for all wafers, the system changes the cooling time parameter dynamically based on the pattern mask area. This allows each wafer to receive the minimum necessary cooling time to achieve proper alignment, avoiding unnecessary time extensions while maintaining precision.
Solution Approach 2:
The cooling device determines the appropriate cooling time automatically based on the pattern mask area information, eliminating the need for manual adjustment or conservative over-cooling. The system serves itself by optimizing the cooling process parameters, achieving both precision and time efficiency.
3Manufacturing precision
If different cooling times are applied to different wafers based on exposure time, then overlay performance improves, but the control complexity increases
Solution Approach 1:
The system changes the cooling time parameter based on a single key parameter - the pattern mask area. This straightforward parameter relationship simplifies the control logic compared to considering multiple factors. The cooling device only needs to adjust one parameter (cooling time) based on one input (pattern mask area), maintaining simplicity while achieving improved overlay performance.
Solution Approach 2:
The cooling device uses feedback from the pattern mask area information to automatically determine the appropriate cooling time. This closed-loop approach ensures optimal cooling without requiring complex manual control or monitoring, as the system self-adjusts based on the exposure conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces photomask misalignment between different exposure stages and improves overlay performance by tailoring the cooling time to match the exposure time based on the pattern mask area.
Implementation Method 1
causing the cooling plate to cool the wafer
Implementation Method 2
thermal expansion and contraction
Data Source
AI summary
A cooling controller receives, from one or more sensors, wafer information associated with a wafer. The cooling controller determines a pattern mask area for the wafer based on the wafer information. The cooling controller determines a cooling time for the wafer based on the pattern mask area. The cooling controller causes a cooling plate to cool the wafer for a time duration equal to the cooling time. Determining the cooling time for a wafer based on a pattern mask area provides stable and consistent wafer temperatures for wafers having different mask and layout properties, which reduces mask overlay variation and increases wafer yield.