Silica Glass Disc Dimples for Heat Treatment Deformation
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Solution Overview
Problem
In semiconductor manufacturing, silica glass discs used as dummy wafers experience deformation during heat treatment, leading to variations in film thickness on Si wafers due to differences in mechanical characteristics compared to Si wafers. This deformation can cause gaps between the Si wafer and the silica glass disc, affecting gas flow and film thickness uniformity.
Innovation Solution
The formation of regular dimples on the surface of silica glass discs minimizes deformation during heat treatment and increases the surface area. These dimples are created using a laser, such as a CO2, picosecond, or femtosecond laser, and are arranged without directivity to reduce deformation at the distal end of the disc.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the silica glass disc is used as a dummy wafer in place of Si wafer, then the cleaning process is simplified and productivity is improved, but deformation occurs during heat treatment due to difference in mechanical characteristics
Solution Approach 1:
The silica glass disc surface is segmented into multiple dimples distributed across the disc. This segmentation creates multiple localized deformation zones that distribute the overall deformation stress, preventing excessive deformation at any single location and maintaining the disc's functionality as a dummy wafer.
Solution Approach 2:
Dimples with specific local geometry (depth, diameter, spacing) are introduced to modify the mechanical properties of the silica glass disc locally. These local modifications compensate for the material's different mechanical characteristics compared to Si wafers, reducing overall deformation during heat treatment while maintaining the simplified cleaning advantage.
2Manufacturing precision
If regular dimples are formed on the silica glass disc surface, then deformation amount is minimized and surface area is increased, but the complexity of the disc structure increases
Solution Approach 1:
The dimples are designed with optimized parameters (depth, diameter, spacing, density) that balance deformation reduction with structural simplicity. By carefully controlling these parameters, the solution achieves minimal deformation while keeping the surface structure complexity within acceptable limits for manufacturing and usage.
3Area of stationary object
If the surface area of the silica glass disc is increased to match the product wafer, then the gas distribution is improved, but deformation at the distal end portion is accelerated
Solution Approach 1:
The dimples are non-uniformly distributed across the disc surface, with higher density in certain regions and lower density in others. This local variation in dimple distribution compensates for the increased surface area effect, particularly reducing deformation at the distal end portion while maintaining adequate gas distribution across the entire disc.
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 regular dimple formation on silica glass discs reduces deformation to 1 mm or less during heat treatment, enhances surface area, and improves film thickness uniformity on Si wafers, addressing the challenges of deformation and film thickness variation in existing technologies.
Implementation Method 1
the dimples be formed by a laser
Data Source
AI summary
Provided is a silica glass disc in which the deformation amount thereof in heat treatment is minimized, and the surface area of a silica glass surface can be increased. There is provided a silica glass disc, including a dimple forming area in which a large number of dimples are formed on at least one of a front surface or a back surface of a silica glass body, and the dimples in the dimple forming area are regularly formed. It is preferred that the dimples be formed by a laser.