Tiltable Retaining Ring for Wafer Edge Polishing Control
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Solution Overview
Problem
Conventional polishing apparatuses struggle to precisely control the polishing profile, particularly in the edge portion of wafers, due to non-uniform pressing forces and the influence of varying film-thickness distributions and polishing pad/lubricant types, leading to issues like rounded edges and inconsistent film thickness.
Innovation Solution
A polishing apparatus with a tiltable retaining ring and local load exerting mechanisms, including air cylinders and magnets, to apply precise local forces on the retaining ring, allowing independent vertical and rotational movements, and a pressure ring to control the polishing profile, especially at the wafer edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a retaining ring is used to prevent rounded edges by pressing the polishing surface around the wafer, then the polishing profile in the edge portion can be controlled, but the pressing force becomes non-uniform and affects other regions with large area
Solution Approach 1:
The pressing mechanism is divided into multiple independent air cylinders positioned at different locations (e.g., upstream and downstream sides) of the retaining ring. Each air cylinder can be controlled independently to apply localized pressing force to specific regions of the retaining ring, allowing precise control of the polishing profile in the wafer edge portion without excessively affecting other regions.
Solution Approach 2:
Different regions of the retaining ring are pressed with different forces by positioning air cylinders at specific locations. The pressing force is locally adjusted at the upstream side, downstream side, or other predetermined positions of the retaining ring to optimize the polishing profile for different wafer types and film thickness distributions.
2Manufacturing precision
If the retaining ring is pressed harder to control edge polishing, then the polishing rate in the edge portion increases, but the pressing force distribution becomes more non-uniform
Solution Approach 1:
The pressing force is segmented into multiple independent control zones using separate air cylinders positioned at different locations around the retaining ring. This allows the pressing force to be independently adjusted at the upstream side, downstream side, or other predetermined positions to optimize the polishing profile while maintaining overall force distribution uniformity.
Solution Approach 2:
The pressing force on the retaining ring is made dynamically adjustable through independent control of multiple air cylinders. The pressing force can be changed during the polishing process to adapt to different wafer types, film thickness distributions, and polishing stages, allowing precise control of the polishing rate in the edge portion while maintaining pressure uniformity.
3Manufacturing precision
If different polishing pads or polishing liquids are used to match different film types, then the polishing profile can be optimized, but the cost and complexity of managing multiple consumables increases
Solution Approach 1:
Instead of changing the polishing pad or polishing liquid for different film types, the invention changes the pressing force parameters by adjusting the air cylinder pressure. This allows the same polishing pad and polishing liquid to be used for different film types (e.g., oxide films, metal films) by simply modifying the pressing force distribution to match the specific polishing requirements of each film type.
Data Source
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AI summary
A polishing apparatus polishes a substrate by bringing the substrate into sliding contact with a polishing surface. The polishing apparatus includes: a substrate holder having a substrate holding surface configured to press the substrate against the polishing surface, a retaining ring coupled to the substrate holding surface and configured to surround the substrate, wherein the retaining ring is brought into contact with the polishing surface during operation of the polishing apparatus, the retaining ring being configured to be tiltable independently of the substrate holding surface; a rotating mechanism configured to rotate the substrate holder about its own axis; and at least one local load exerting mechanism configured to exert a local load on a part of the retaining ring in a direction perpendicular to the polishing surface, the at least one local load exerting mechanism being arranged so as not to move in accordance with the substrate holder.