Peripheral Vacuum Clamping for Shadow-Free Wafer Inspection
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Solution Overview
Problem
Vacuum clamping devices with uniformly distributed suction openings hinder visual inspection of wafers due to shadow creation, making it difficult to inspect using reflected or transmitted light.
Innovation Solution
Suction openings are placed in the periphery region of the base plate, allowing for flat clamping and unobstructed visual inspection, with a transparent and flexible film providing additional support for curved wafers, ensuring a strong vacuum and minimal depth of field for optimal optical resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If suction openings are uniformly distributed over the suction surface, then clamping stability is improved, but visual inspection quality deteriorates due to shadow creation
Solution Approach 1:
The suction surface is segmented into two functional zones: a periphery region containing suction openings for stable clamping, and a central region free of openings for high-quality visual inspection. This spatial segmentation allows each zone to optimize its specific function without compromising the other.
Solution Approach 2:
Different regions of the suction surface are assigned different properties: the periphery region has suction openings for mechanical stability, while the central region maintains a smooth, opening-free surface for optical inspection. This local differentiation resolves the contradiction by making each area specialized for its intended purpose.
2Measurement precision
If suction openings are placed in the periphery region, then visual inspection quality is improved by eliminating shadows, but clamping stability may deteriorate
Solution Approach 1:
The suction force is distributed along the periphery circumference rather than being concentrated in central points, creating a stabilizing effect through spatial distribution. This peripheral arrangement generates rotational symmetry in the force distribution, maintaining clamping stability while preserving the central inspection area.
3Adaptability or versatility
If a transparent and flexible film is added to support curved wafers, then adaptability to different wafer shapes is improved, but device complexity increases
Solution Approach 1:
A transparent, flexible film is introduced as an intermediate element between the suction surface and the wafer. This film can conform to curved wafer surfaces while remaining transparent for optical inspection. The film is held taut by the vacuum force itself, eliminating the need for additional support structures or complex 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 nearly complete visual inspection of wafers with maximum contrast and resolution, as the periphery placement of suction openings eliminates shadows and allows for a strong, stable vacuum, facilitating the inspection of flat and curved wafers without interference.
Implementation Method 1
the air inside the vacuum clamping device is sucked off. This generates a pressure difference between the inside and the outside whose boundary layer is the workpiece to be clamped. Consequently, a vacuum is generated between the workpiece, which is in particular a wafer, and the vacuum clamping device.
Data Source
AI summary
Vacuum clamping device for clamping workpieces, in particular for clamping flat substrates, such as wafers for example, comprising a base plate having a suction surface, wherein a plurality of suction openings are formed in the suction surface of the base plate, wherein the base plate can be connected to at least one negative-pressure device via at least one suction line, characterized in that the suction openings are arranged in a peripheral region of the suction surface of the base plate.