Retainer Ring Low Friction Coating for Uniform Wafer Pressure
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Solution Overview
Problem
Conventional polishing apparatuses face challenges in applying uniform surface pressure to semiconductor wafers due to non-uniform pressing forces and high frictional forces, leading to insufficient or excessive polishing, particularly at the peripheral edges, which results in edge rounding and reduced capability of the retainer ring to maintain desired surface pressure.
Innovation Solution
The use of a low friction material member with a coefficient of friction of 0.35 or less, such as polytetrafluoroethylene (PTFE) or PEEK·PPS, is applied to the outer circumference of the retainer ring to reduce frictional forces and enhance the capability of the retainer ring in following the polishing surface undulations, allowing for improved surface pressure application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional retainer ring is used without low friction material, then the structure is simple, but the frictional force between the retainer ring and guide is high, reducing the capability to apply desired surface pressure
Solution Approach 1:
The patent applies low friction material (such as PTFE or PEEK·PPS with coefficient of friction of 0.35 or less) to the outer circumference of the retainer ring, changing the friction parameter of the contact surface between the retainer ring and guide, thereby reducing frictional force and enhancing surface pressure application capability
Solution Approach 2:
The patent uses composite material structure by combining the retainer ring base material with low friction material coating or layer, creating a composite component that maintains structural integrity while providing low friction surface properties for reduced energy loss
2Adaptability or versatility
If the retainer ring is made elastic to follow polishing surface undulations, then the following capability is improved, but the pressing force becomes non-uniform causing edge rounding
Solution Approach 1:
The patent applies low friction material specifically to the outer circumference of the retainer ring where it contacts the guide, creating local quality differentiation that reduces friction at the guide interface while maintaining the elastic properties of the retainer ring body for following polishing surface undulations
3Stability of the object's composition
If a retainer ring guide is provided to guide the retainer ring movement, then the movement control is improved, but the frictional force at sliding contact surfaces increases, reducing the following capability
Solution Approach 1:
The patent changes the friction parameter at the sliding contact interface between the retainer ring and guide by applying low friction material to the retainer ring outer circumference, thereby reducing frictional force while maintaining the guide structure for movement control stability
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 significantly reduces frictional forces between the retainer ring and its guide, enabling the retainer ring to apply a desired surface pressure uniformly, thereby preventing edge rounding and ensuring effective polishing across the semiconductor wafer.
Implementation Method 1
A low friction material member, having a coefficient of friction of 0.35 or less, is applied to an outer circumference of a ring member of the retainer ring to bring a low friction material member into sliding contact with a retainer ring guide
Data Source
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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 (2,200) configured to hold and press a substrate W against the polishing surface, a retainer ring (3) provided at an outer peripheral portion of the top ring body (2,200) and configured to press the polishing surface, and a retainer ring guide (410) fixed to the top ring body and configured to be brought into sliding contact with a ring member (408,408a) of the retainer ring to guide a movement of said ring member. Either sliding contact surfaces of the ring member and the retainer ring guide are brought into sliding contact with each other, wherein said sliding contact surfaces of said ring member and said retainer ring guide are coated with lubricant, and a connection (420) sheet is provided between an outer circumferential surface of said ring member and said retainer ring guide, or a low friction material member (602) is provided on an outer circumference of said ring member of said retainer ring to bring said low friction material member into sliding contact with said retainer ring guide.