Wafer Cooling Time Control for Stable Photomask Overlay
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Solution Overview
Problem
Existing semiconductor wafer cooling methods using fixed cooling times fail to account for variations in exposure times across different photomask stages, leading to inconsistent wafer temperatures and photomask misalignment, which degrades overlay performance.
Innovation Solution
A learning cooling device determines a customized cooling time for each wafer based on its pattern mask area, synchronizing exposure and cooling times 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, leading to photomask misalignment
Solution Approach 1:
The cooling time is changed from a fixed static value to a dynamic value that varies based on the pattern mask area. The cooling device adjusts the cooling time automatically according to the specific exposure requirements of each wafer, making the cooling process adaptive rather than rigid.
Solution Approach 2:
The cooling time parameter is modified based on the pattern mask area parameter. By establishing a relationship between these two parameters, the system optimizes the cooling time for each specific exposure scenario, ensuring consistent wafer temperature across different exposure stages.
2Ease of operation
If a fixed cooling time is used for all wafers, then the device operation is simple, but photomask misalignment occurs due to inconsistent wafer temperatures
Solution Approach 1:
The system incorporates feedback by using the pattern mask area information to automatically determine the appropriate cooling time. This feedback mechanism ensures that the cooling process is optimized for each specific exposure scenario without requiring complex manual intervention.
Solution Approach 2:
The cooling device performs self-adjustment by automatically selecting the cooling time based on the pattern mask area. This self-service capability maintains operational simplicity while achieving precise temperature control and consistent photomask alignment.
3Adaptability or versatility
If exposure times vary across different photomask stages, then different pattern details can be achieved, but wafer temperature becomes inconsistent, degrading overlay performance
Solution Approach 1:
The cooling time parameter is adjusted in response to variations in exposure time and pattern mask area. This parameter change ensures that the wafer temperature remains consistent even when exposure conditions vary across different photomask stages, maintaining high overlay performance.
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
This approach ensures consistent wafer temperatures across exposure stages, reducing photomask misalignment and enhancing photomask overlay performance.
Implementation Method 1
A wafer may be cooled by placing the wafer on a cooling plate and causing the cooling plate to cool the wafer
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.