Substrate Holder With Independent Retaining Rings
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Solution Overview
Problem
Existing substrate holders for polishing wafers face challenges in uniformly controlling the polishing profile, particularly at the edge portions, due to non-uniform pressing forces and the generation of wear particles that can defect the wafer during the polishing process.
Innovation Solution
A substrate holder design featuring an inner and outer retaining ring with independent vertical movement, supported by a spherical bearing that tilts to manage lateral forces and prevent wear particle transmission, ensuring uniform pressing force application and preventing wear particles from reaching the polishing surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single retaining ring is used to control edge portion polishing, then the structure is simple, but the polishing profile cannot be uniformly controlled in both edge portions and neighboring portions
Solution Approach 1:
The retaining ring is divided into two separate rings: an inner retaining ring for controlling edge portion polishing and an outer retaining ring for controlling neighboring portion polishing. Each ring can be independently adjusted and controlled, allowing precise management of polishing profiles in different regions of the wafer edge.
2Reliability
If the retaining ring is fixed vertically, then the structure is stable, but wear particles are generated and can defect the wafer during polishing
Solution Approach 1:
The retaining ring is changed from a fixed vertical position to a dynamically adjustable position. The ring can move vertically and tilt to adapt to lateral forces generated during polishing, reducing wear particle generation while maintaining wafer protection.
Solution Approach 2:
A spherical bearing is introduced as an intermediary mechanism between the retaining ring and the top ring body. This bearing allows the retaining ring to tilt and adjust its position while supporting lateral forces, preventing direct contact that would generate wear particles.
3Manufacturing precision
If the retaining ring presses the wafer edge with high force, then edge portion polishing is improved, but non-uniform pressing force causes excessive polishing and rounded edges
Solution Approach 1:
The pressing force control is segmented into two independent systems: one for the inner retaining ring (edge portion) and one for the outer retaining ring (neighboring portion). This allows optimized pressing forces for each region without causing non-uniformity and rounded edges.
Solution Approach 2:
Different pressing forces are applied to different regions: the inner retaining ring applies appropriate force to the wafer edge portion, while the outer retaining ring applies different force to the neighboring portion. This localized control ensures uniform polishing across different areas.
4Force
If the spherical bearing is positioned far from the polishing surface, then lateral force support is adequate, but the retaining ring tilts excessively and cannot apply uniform pressing force
Solution Approach 1:
The spherical bearing is positioned asymmetrically at a specific distance from the polishing surface, optimized to balance lateral force support with tilt control. This asymmetric positioning allows the retaining ring to receive lateral forces while maintaining sufficient stability for uniform pressing.
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 design effectively controls the polishing profile by managing load changes and reducing wear, leading to improved edge portion polishing and increased wear tolerance of the retaining rings, thus enhancing the substrate holder's performance and preventing wafer defects.
Implementation Method 1
an outer retaining ring arranged radially outwardly of the inner retaining ring and configured to be vertically movable independently of the inner retaining ring and the top ring body; and a spherical bearing configured to support the outer retaining ring and allow the outer retaining ring to tilt
Implementation Method 2
the wafer is pushed against an inner surface of the retaining ring by a frictional force generated between the wafer and the polishing surface
Data Source
AI summary
The substrate holder is a device for holding a substrate and pressing it against a polishing pad. The substrate holder includes: an inner retaining ring vertically movable independently of the top ring body and arranged around the substrate; an inner pressing mechanism to press the inner retaining ring against the polishing surface of the polishing pad; an outer retaining ring to vertically movable independently of the inner retaining ring and the top ring body; an outer pressing mechanism to press the outer retaining ring against the polishing surface; and a supporting mechanism to receive a lateral force applied to the inner retaining ring from the substrate during polishing of the substrate and to tiltably support the outer retaining ring.