Retaining Ring Foreign Matter Detection for Polishing Scratches
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Solution Overview
Problem
In semiconductor manufacturing, the increasing number of interconnection layers and miniaturization of photolithographic processes lead to surface irregularities and poor step coverage, necessitating improved surface planarization and CMP techniques to prevent scratches from wafer fragments on the polishing pad.
Innovation Solution
A polishing apparatus equipped with an imaging device and image processor to detect foreign matter, such as wafer fragments, on the inner circumferential surface of the retaining ring, which issues an alarm to prevent scratches during subsequent polishing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the retaining ring is made of resin material to adjust polishing pressure, then the polishing pressure control is improved, but the risk of wafer fragment cutting into the ring and causing scratches increases
Solution Approach 1:
The imaging device captures images of the inner circumferential surface of the retaining ring before polishing operations begin. This preliminary detection allows identification of wafer fragments that have cut into the resin retaining ring, enabling preventive action before these fragments can fall onto the polishing pad and cause scratches during subsequent polishing processes.
Solution Approach 2:
The imaging device and image processing system serve as an intermediary detection mechanism between the retaining ring and the polishing pad. By detecting foreign matter on the retaining ring surface, the system provides early warning before fragments can contaminate the polishing pad, thus preventing the harmful effect of scratches without changing the resin material properties of the retaining ring.
2Object-affected harmful factors
If continuous monitoring is implemented to detect foreign matter, then scratch prevention is improved, but device complexity increases
Solution Approach 1:
The imaging device is integrated into the polishing apparatus structure, utilizing existing operational states (when the carrier is not holding a wafer) to automatically capture images of the retaining ring. The system serves itself by using the natural idle periods in the polishing cycle for detection purposes, eliminating the need for separate continuous monitoring equipment and reducing overall system complexity.
Solution Approach 2:
Instead of continuous monitoring, the imaging device operates periodically when the carrier is in a state where it is not holding a wafer. This periodic detection approach provides sufficient foreign matter detection capability while significantly reducing device complexity and resource consumption compared to continuous monitoring systems.
Data Source
AI summary
A polishing apparatus which can reduce scratches that are generated on a surface of a substrate during polishing by detecting a foreign matter such as a fragment of the substrate on an inner circumferential surface of a retaining ring for holding an edge portion (peripheral portion) of the substrate is disclosed. The polishing apparatus includes a polishing table having a polishing surface, and a top ring having a substrate holding surface to hold a beck surface of a substrate and a retaining ring to retain the substrate on the substrate holding surface. The top ring holds the substrate and presses the substrate against the polishing surface. The polishing apparatus includes an imaging device configured to image an inner circumferential surface of the retaining ring, and an image processor configured to process an image obtained by the imaging device to judge whether there is a foreign matter on the inner circumferential surface of the retaining ring.