Workpiece Holding Device Thermal Expansion Warping Prevention
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Solution Overview
Problem
In semiconductor processing, the mismatched thermal expansion of stainless steel bases and alumina chuck tables causes warping of the chuck surface, leading to variations in workpiece thickness during grinding.
Innovation Solution
A workpiece holding device with a thermally expandable base and chuck, where a clamping member with gaps in the radial direction presses the chuck's peripheral edge against the base, allowing independent thermal expansion and preventing warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the base and chuck are rigidly connected with bolts, then the structure is simple and strong, but thermal expansion mismatch causes warping of the chuck surface
Solution Approach 1:
The connection between base and chuck is segmented into multiple independent clamping points around the peripheral edge, allowing localized thermal expansion accommodation while maintaining overall structural integrity and surface flatness
Solution Approach 2:
The clamping force parameters are optimized to maintain sufficient holding pressure while allowing micro-movements that accommodate differential thermal expansion between the base and chuck materials
2Measurement precision
If the chuck is tightly fixed to the base, then positioning is precise, but thermal expansion causes warping and thickness variation
Solution Approach 1:
The clamping member acts as an intermediary element between the base and chuck, providing a compliant connection that maintains precise positioning while accommodating thermal expansion through controlled deformation of the clamping mechanism
Solution Approach 2:
The clamping system transitions from a static rigid connection to a dynamic system that can adapt its constraint level based on thermal conditions, allowing the chuck to expand radially while maintaining tangential positioning accuracy
3Manufacturing precision
If a clamping member with gaps is used to prevent warping, then thermal expansion is accommodated, but the device structure becomes more complex
Solution Approach 1:
The clamping member utilizes a flexible blade-like structure with controlled gaps that provides the necessary compliance for thermal expansion while maintaining a simple geometric form and manufacturing process
Solution Approach 2:
The clamping member is designed to automatically adjust its clamping force in response to thermal expansion through elastic deformation, eliminating the need for complex control systems or adjustable mechanisms
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
Enables high-accuracy processing of workpieces without warping on the chuck surface, even when the base thermally expands more than the chuck during processing.
Implementation Method 1
the base and the chuck are each thermally expandable independently while maintaining a state where the clamping member provided in the base presses the peripheral edge of the chuck against the base
Data Source
AI summary
A workpiece holding device capable of processing a workpiece with high accuracy. A holding section 3 in a processing apparatus 1 is a workpiece holding device that rotatably holds a workpiece W to be processed with a grinding stone 21, the workpiece holding device including a base 34, a chuck 33 that is composed of a material exhibiting a lower thermal expansion coefficient than that of the base 34, is placed on the base 34, and can adsorb and hold the workpiece W, and a clamping member 40 that is attached to the base 34 with gaps G1 and G2 between itself and the chuck 33 in a radial direction D of the base 34 and presses a flange 36a of the chuck 33 against the base 34.