Polishing Apparatus Wafer Release Control
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Solution Overview
Problem
The existing polishing apparatuses face challenges in uniformly releasing wafers from the substrate holder, leading to non-uniform pressing forces and potential damage to the wafers, especially with heavier wafers and soft membranes, resulting in inefficient wafer release and potential false detection of release completion.
Innovation Solution
A polishing apparatus with a substrate separation assisting device that ejects a fluid to the contact portion between the wafer and the flexible membrane, and a controller that adjusts the vertically-moving mechanism or tilting device to ensure accurate fluid ejection based on the descent of the contact portion, allowing reliable detection of wafer release through pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a soft flexible membrane is used in the pressure chamber to press the wafer, then the wafer can be held securely during polishing, but the membrane descends significantly when inflated for wafer release, causing inaccurate fluid ejection and unreliable wafer release detection
Solution Approach 1:
A displacement sensor is introduced as an intermediary measurement device to directly measure the descent distance of the flexible membrane. This separate measurement intermediary allows accurate tracking of membrane position without being affected by the membrane's softness or the inflation process, enabling precise control of the fluid ejection timing and amount regardless of membrane compliance.
Solution Approach 2:
The system implements feedback control by using the displacement sensor to continuously monitor membrane descent and adjusting the fluid ejection amount accordingly. The controller receives real-time position feedback from the sensor and dynamically controls the fluid ejection to ensure accurate wafer release detection, compensating for variations in membrane behavior.
2Productivity
If fluid is ejected to assist wafer release from the flexible membrane, then wafer release speed improves, but non-uniform pressing force distribution causes rounded edges and inconsistent release
Solution Approach 1:
The system applies local quality control by using the displacement sensor to detect the specific descent amount at each location and controlling fluid ejection in a localized manner. This allows differentiated fluid application based on local membrane descent characteristics, ensuring uniform release across the wafer surface while maintaining edge integrity.
Solution Approach 2:
The system employs dynamic control by continuously monitoring membrane descent through the displacement sensor and adjusting fluid ejection in real-time. This dynamic adaptation allows the system to respond to changing pressing force distributions during the release process, maintaining uniform wafer release even as conditions change.
3Ease of operation
If the flexible membrane is inflated to separate the wafer from the substrate holder, then wafer release is achieved, but the central portion of the wafer may fail to separate due to lack of deformation, requiring additional release mechanisms
Solution Approach 1:
The system enables self-service release by using the displacement sensor to precisely detect when the membrane has descended sufficiently for complete wafer separation. This automatic detection and control eliminates the need for additional release mechanisms, as the system self-regulates the inflation process to achieve complete release through controlled fluid ejection based on real-time membrane position feedback.
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
Enables quick and secure release of wafers from the substrate holder, reducing the risk of wafer damage and improving productivity by ensuring accurate detection of release completion.
Implementation Method 1
The above-described polishing pad has elasticity. As a result, the pressing force becomes non-uniform in an edge portion of the wafer during polishing of the wafer.
Implementation Method 2
This pressure chamber is supplied with fluid, such as air, to press the wafer against the polishing surface of the polishing pad through the membrane under the fluid pressure.
Data Source
AI summary
A polishing apparatus includes: a polishing table for supporting a polishing pad; a substrate holder having a substrate holding surface and a pressure chamber formed by a flexible membrane, the substrate holder being configured to hold a substrate on the substrate holding surface and press the substrate against the polishing pad via pressure in the pressure chamber; a substrate separation assisting device configured to eject a fluid to a contact portion between the substrate and the flexible membrane so as to release the substrate from the substrate holding surface; and a vertically-moving mechanism configured to vertically move the substrate holder. The substrate holder is moved vertically in accordance with an amount of descent of the contact portion and then the substrate separation assisting device ejects the fluid to the contact portion.