Polishing Apparatus Retainer Ring Fulcrum Positioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional polishing apparatuses face issues with non-uniform surface pressure, edge rounding, powder contamination, thermal expansion, and uneven wear of the retainer ring, leading to suboptimal surface planarization and increased maintenance costs in semiconductor wafer polishing.
Innovation Solution
A polishing apparatus with a retainer ring positioned above the central portion of the top ring body, allowing for tiltable and vertically movable support, using low friction materials and a metal ring for improved rigidity, and a cooling mechanism to prevent thermal expansion, which reduces frictional forces and maintains uniform surface pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the retainer ring is positioned at the outer circumferential portion of the top ring body with a fulcrum, then the structure can receive lateral forces during polishing, but the contact area between the retainer ring and guide is limited causing large frictional forces that limit the retainer ring's capability to apply desired surface pressure
Solution Approach 1:
The fulcrum is repositioned from the outer circumferential portion to the central portion of the top ring body, changing the spatial dimension of force reception. This central positioning creates a larger effective contact area and reduces frictional forces, allowing the retainer ring to maintain better contact with the polishing surface and apply desired surface pressure effectively
2Adaptability or versatility
If the retainer ring is made elastic to allow following of polishing surface undulation, then the retainer ring can adapt to surface variations, but the peripheral portion of the substrate becomes non-uniform in pressing force causing edge rounding
Solution Approach 1:
The retainer ring is designed with non-uniform thickness, creating varying rigidity across different sections. The thicker portions provide greater rigidity to prevent excessive deformation and edge rounding, while thinner portions allow adequate flexibility to follow surface undulation. This local variation in quality enables the retainer ring to simultaneously adapt to surface variations and maintain uniform pressing force distribution
3Manufacturing precision
If the retainer ring is made rigid to maintain uniform pressing force, then edge rounding is prevented, but the retainer ring cannot follow undulation of the polishing surface
Solution Approach 1:
The retainer ring incorporates non-uniform thickness distribution, creating zones of different rigidity. Thicker sections provide the rigidity needed to maintain uniform pressing force and prevent edge rounding, while thinner sections provide the flexibility necessary to follow polishing surface undulation. This localized variation in structural quality resolves the contradiction between rigidity and adaptability
4Force
If the fulcrum is positioned at the outer circumferential portion of the retainer ring, then the structure can receive lateral forces, but unexpected large frictional forces are generated at sliding contact surfaces when the retainer ring tilts
Solution Approach 1:
The fulcrum position is shifted from the outer circumferential region to the central region of the top ring body, fundamentally changing the geometric dimension of force application. This central positioning reduces the moment arm and minimizes tilting motions, thereby reducing frictional forces at sliding contact surfaces while maintaining lateral force reception capability
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 enhances the capability of the retainer ring to apply desired surface pressure, reduces frictional forces, prevents powder contamination, and stabilizes the retainer ring's performance over time, resulting in improved surface planarization and reduced maintenance costs.
Implementation Method 1
a cooling mechanism to prevent thermal expansion
Implementation Method 2
stabilizes the retainer ring's performance over time
Data Source
AI summary
A polishing apparatus is used for polishing a substrate such as a semiconductor wafer to a flat mirror finish. The polishing apparatus includes a polishing table (100) having a polishing surface (101a), a top ring body (2) configured to hold and press a substrate against the polishing surface (101a), and a retainer ring (3) provided at an outer peripheral portion of the top ring body (2) and configured to press the polishing surface (101a). A fulcrum for receiving a lateral force applied from the substrate to the retainer ring (3) during polishing of the substrate is located above a central portion of the substrate.