Four-Point Wafer Chuck Alignment for High-Stiffness Probing
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Solution Overview
Problem
Current chuck designs for semiconductor wafers have low stiffness and positional variation, compromising the accuracy of adhesion tests during mechanical probe testing due to complex alignment mechanisms and varying penetration depth and force measurements.
Innovation Solution
A chuck with a tilt plate adjustably connected by upper and lower screws, surrounded by springs for pre-load, allowing for precise adjustment and high stiffness with low positional variation, ensuring the chuck remains orthogonal to the wedge-shaped indenter for accurate probing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If 3-point adjustment or gimbal devices are used for chuck tilt alignment, then alignment capability is provided, but stiffness and positional variation deteriorate
Solution Approach 1:
The chuck is divided into a base portion and a tilt plate portion that can be independently adjusted. The tilt plate is segmented from the base, allowing separate tilt adjustment while maintaining the overall structural integrity and stiffness of the chuck body.
Solution Approach 2:
The patent introduces a fourth point of contact (tilt plate) in addition to the three base points, creating a stable pyramid structure. This dimensional addition provides both alignment capability and structural stiffness, resolving the contradiction between adjustability and rigidity.
2Adaptability or versatility
If complex alignment mechanisms are used, then tilt adjustment is enabled, but positional variation increases
Solution Approach 1:
The tilt adjustment function is extracted as a separate tilt plate component that can be independently adjusted relative to the base. This separation allows precise control of tilt angle without affecting the positional stability of the wafer holding surface.
Solution Approach 2:
The patent uses adjustable screw mechanisms to change the geometric parameters (height and angle) of the tilt plate relative to the base. By precisely controlling these parameters, the desired tilt angle is achieved while maintaining minimal positional variation.
3Adaptability or versatility
If multiple adjustment points are used, then alignment flexibility is improved, but adjustment complexity increases
Solution Approach 1:
Multiple adjustment functions (tilt angle control and height adjustment) are merged into a single tilt plate component that adjusts as one unit. This consolidation provides alignment flexibility while reducing the number of separate adjustment mechanisms needed.
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 provides a stable and accurate chuck with high stiffness and low positional variation, improving the precision of adhesion tests by allowing precise tilt adjustments and maintaining contact during the adjustment process, thereby enhancing the accuracy of probing measurements.
Implementation Method 1
A pair of upper springs may surround the pair of upper of screws, a pair of lower springs may surround the pair of lower screws, and the pair of lower springs and the pair of upper springs may have a pre-load between the bottom surface of the chuck and a top surface of the tilt plate.
Data Source
AI summary
An apparatus includes a chuck configured to hold a wafer and a tilt plate disposed beneath the chuck and adjustably connected to the chuck by a pair of upper screws and a pair of lower screws separately arranged in opposite corners of the chuck. Screw heads of the pair of upper screws rest against a top surface of the chuck, such that clockwise rotation of one of the upper screws pushes a corresponding corner of the chuck toward the tilt plate. Screw heads of the pair of lower screws rest against a bottom surface of the chuck, such that counter-clockwise rotation of one of the lower screws pushes a corresponding corner of the chuck away from the tilt plate.