Retainer Ring Groove Layout for CMP Pad Rebound and Slurry Discharge
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Solution Overview
Problem
The existing retainer rings for polishing heads in chemical mechanical polishing processes suffer from issues such as pad rebound phenomena, slurry fixation, and edge fast phenomena, leading to defects like scratches on the wafer during the polishing process.
Innovation Solution
A retainer ring design featuring a ring-shaped body with alternating first and second regions, slurry grooves, and rounded grooves that facilitate smooth slurry discharge and reduce pressure contact, preventing pad rebound and slurry fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pressure is applied to the retainer ring through the polishing head, then the wafer is held firmly on the platen, but the polishing pad adjacent to the wafer edge becomes deformed causing pad rebound phenomenon
Solution Approach 1:
The pressure surface is segmented into multiple first regions and second regions arranged alternately in the circumferential direction. The first regions apply pressure to hold the wafer, while the second regions serve as relief zones that prevent excessive deformation of the polishing pad, thereby eliminating pad rebound phenomenon while maintaining firm wafer holding
Solution Approach 2:
Different regions of the pressure surface are given different functions: first regions are designed to apply pressure for wafer holding, while second regions are designed as relief zones to prevent pad deformation. This local differentiation allows the retainer ring to simultaneously achieve firm wafer holding and prevent pad rebound
2Power
If slurry is pushed toward the wafer edge during polishing, then abrasive action is enhanced, but slurry discharge becomes blocked causing edge fast phenomenon
Solution Approach 1:
The pressure surface is segmented into alternating first and second regions, creating channels for slurry flow between them. This segmentation allows slurry to be pushed toward the wafer edge for effective abrasive action while providing designated discharge paths through the second regions, preventing edge fast phenomenon
Solution Approach 2:
The second regions act as intermediary zones that facilitate slurry discharge. These regions serve as channels that mediate between the abrasive action area and the discharge area, allowing slurry to flow smoothly without blocking the discharge path
3Reliability
If slurry adheres to the retainer ring and becomes fixed, then retention is achieved, but scratch defects occur on the wafer during polishing
Solution Approach 1:
Rounded grooves are created in the first regions to extract and remove fixed slurry from the pressure surface. These grooves allow slurry that has adhered to the retainer ring to be taken out and discharged, preventing it from causing scratch defects on the wafer while maintaining effective slurry retention in the polishing zone
Solution Approach 2:
The rounded grooves convert the harmful effect of fixed slurry into a beneficial discharge mechanism. By providing dedicated removal paths for adhered slurry, the design transforms potential scratch-causing material into controlled discharge flow that no longer threatens wafer quality
Data Source
AI summary
The present inventive concept provides a retainer ring for a polishing head, the retainer ring including: a ring-shaped body including a pressure surface having a plurality of first regions and a plurality of second regions alternately positioned in a circumferential direction of the body; a plurality of slurry grooves disposed in the pressure surface to be spaced apart from each other in the circumferential direction of the body and extending from an inner circumferential surface of the body to an outer circumferential surface of the body; and a plurality of rounded grooves disposed in the plurality of first regions and directly connected to the inner circumferential surface of the body, each of the plurality of rounded grooves having a concave groove surface rounded in a cross-sectional view taken along a radial direction of the body.