Polishing Apparatus V-Ring Seal for Uniform Wafer Pressure
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Solution Overview
Problem
Conventional wafer polishing apparatuses experience discontinuous pressure distribution in boundary areas between concentric press regions, leading to non-uniform polishing, especially when using softer elastic pads, resulting in a staircase pattern on the polished surface.
Innovation Solution
The polishing apparatus employs a rubber V-ring seal ring that allows fluid to flow from a higher-pressure chamber to a lower-pressure chamber, maintaining a differential pressure and enabling continuous pressure variation in the boundary area, ensuring uniform pressure distribution and polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If concentric pressure chambers are used to press the wafer, then uniform pressure distribution is achieved, but discontinuous pressure in boundary areas causes staircase pattern polishing
Solution Approach 1:
The elastic pad serves as an intermediary between the pressure chambers and the wafer. It deforms elastically to bridge the boundary areas between concentric pressure chambers, smoothing out pressure discontinuities and preventing staircase pattern polishing while maintaining uniform overall pressure distribution
Solution Approach 2:
The patent changes the physical state of the pressure transmission medium by using an elastic deformable pad instead of rigid contact. This allows continuous pressure variation in boundary areas through elastic deformation, transforming discontinuous chamber pressure into continuous contact pressure on the wafer surface
2Manufacturing precision
If softer elastic pad material is used, then better polishing quality is achieved, but staircase pattern becomes more remarkable
Solution Approach 1:
The elastic pad acts as a mediator that absorbs and distributes pressure variations. Even with softer material that deforms more easily, the pad's elastic properties smooth pressure transitions at chamber boundaries, preventing staircase patterns while maintaining contact with the wafer surface for high-quality polishing
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 solution allows for continuous variation of pressure distribution between concentric press regions, resulting in highly uniform polishing of the wafer surface, preventing over-polishing and achieving a mirror-like finish.
Implementation Method 1
the seal lip can slightly open to allow passage of fluid from a first one of said chambers which is at a higher pressure to the other one of said chambers which is at a lower pressure
Implementation Method 2
an elastic sheet member being fixed to an edge of the holding plate, the elastic sheet member having a lower face, which is capable of pressing the work onto the polishing pad
Data Source
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AI summary
The polishing apparatus (10) comprises: a polishing head (14) for holding a work (30); a polishing plate (12) having a polishing face; and a driving mechanism for relatively moving the polishing head (14) with respect to the polishing plate (12). The polishing head (14) includes: a holding plate (22); an elastic sheet member (28) being fixed to the holding plate (22), the elastic sheet member (28) having a lower face for pressing the work (30) onto the polishing plate (12); a pressure chamber, to which a pressure fluid is supplied, being formed between the holding plate (22) and the elastic sheet member (28); a seal ring (36) concentrically dividing the pressure chamber into chambers (40, 42), the seal ring (36) having a seal lip (38); and a fluid supply section (29, etc.) for individually supplying the fluid to the divided chambers (40, 42).