Polishing Head Template Deformation for Wafer Flatness
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Solution Overview
Problem
Existing polishing heads fail to consistently maintain flatness and uniformity during the polishing of large silicon wafers, as the positional relation between the work and the template can vary, leading to issues like sag or raised shapes on the outer circumference, making precise adjustments difficult.
Innovation Solution
A polishing head design featuring an annular rigid ring with a rubber film, a mid plate, and a concentric annular template with an inner diameter smaller than the rigid ring, allowing for a 26-45% diameter difference, enabling the inner circumference of the template to deform freely and apply a uniform pressing force, ensuring stable holding and polishing across the work's surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the inner diameter of the template is made smaller than the inner diameter of the rigid ring to enable free deformation, then the uniformity of pressing force is improved, but the structural stability deteriorates
Solution Approach 1:
The template is designed with a thin plate structure that allows flexible deformation. The inner circumference portion of the template can deform freely to adapt to positional variations between the work and template, maintaining uniform pressing force distribution across the work surface while the overall structure remains stable.
Solution Approach 2:
The invention specifies a particular ratio range (26-45%) between the inner diameter difference and the template width, optimizing the balance between deformability and structural stability. This parameter control ensures the template can deform sufficiently to compensate for positional variations while maintaining adequate structural rigidity.
2Manufacturing precision
If the template is made deformable to compensate for positional variations, then the polishing uniformity is improved, but the control difficulty increases
Solution Approach 1:
The template's inner circumference portion automatically deforms in response to positional variations between the work and template without requiring external control mechanisms. This self-adjusting capability compensates for misalignment and maintains polishing uniformity while eliminating complex control systems.
3Manufacturing precision
If the inner diameter difference ratio is increased to improve deformation capability, then the pressing force uniformity is improved, but the template strength decreases
Solution Approach 1:
The invention defines a specific ratio range (26-45%) between the inner diameter difference and template width, optimizing the balance between deformability and strength. This controlled parameter ensures sufficient deformation capability for uniform pressing force while maintaining adequate template strength to prevent breakage during operation.
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 configuration ensures consistent polishing stock removal uniformity, even with slight variations in the positional relation between the work and the template, by allowing the template to deform and maintain a uniform pressing force, thus preventing breakage and ensuring high polishing quality.
Implementation Method 1
a pressurized fluid such as air is poured into a back face of the rubber film, and the rubber film is inflated by a uniform pressure so as to press the work onto the polishing pad
Implementation Method 2
an inner circumference portion of the template can deform freely, and holding of the work by the rubber film and polishing thereof can be carried out by a more uniform pressing force
Data Source
AI summary
The present invention is a polishing head provided with an annular rigid ring, a rubber film bonded to the rigid ring with a uniform tension, a mid plate joined to the rigid ring and forming a space portion together with the rubber film and the rigid ring, and an annular template provided concentrically with the rigid ring in a peripheral portion on a lower face part of the rubber film and having an outer diameter larger than an inner diameter of the rigid ring, in which a pressure of the space portion can be changed by a pressure adjustment mechanism, a back face of a work is held on the lower face part of the rubber film, and a surface of the work is brought into sliding contact with the polishing pad attached onto a turn table for performing polishing, and an inner diameter of the template is smaller than an inner diameter of the rigid ring, and a ratio between an inner diameter difference between the rigid ring and the template and a difference between the inner diameter and an outer diameter of the template is 26% or more and 45% or less. Thereby, a polishing head and the like that can obtain constant flatness stably can be provided.