Turntable Temperature Control in Wafer Polishing
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Solution Overview
Problem
Conventional polishing methods cause excessive cooling of the turntable during standby, leading to reduced stock removal and increased variations in flatness, necessitating dummy polishing to restore temperature, which lowers productivity.
Innovation Solution
The method involves controlling the refrigerant flow volume during standby to be less than during polishing and supplying a water retaining liquid at room temperature or more to the polishing pad, while rotating the turntable to maintain heat generation and prevent excessive cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling water is constantly supplied to the turntable unit during standby state, then heat removal effect is maintained, but turntable temperature is lowered excessively causing reduction in stock removal and variations in flatness
Solution Approach 1:
The cooling water supply is changed from continuous to intermittent operation. The control unit stops cooling water supply during standby periods when polishing is not performed, and resumes supply when polishing restarts. This periodic action prevents excessive cooling while maintaining heat removal capability when needed, eliminating the need for dummy polishing operations.
Solution Approach 2:
The control unit monitors the operational state of the polishing apparatus and automatically adjusts cooling water supply based on feedback. When the turntable is in standby state (no polishing), the control unit stops cooling water supply. When polishing resumes, cooling water supply is restarted. This feedback mechanism ensures temperature is maintained within appropriate ranges without manual intervention or dummy operations.
2Temperature
If cooling water is constantly supplied to maintain heat removal, then temperature control is achieved, but energy is wasted during standby state
Solution Approach 1:
Cooling water supply is operated intermittently rather than continuously. The system stops cooling water supply during standby periods when polishing is not performed, and resumes supply when polishing restarts. This periodic operation eliminates unnecessary energy consumption during idle periods while maintaining temperature control capability when polishing is active.
Solution Approach 2:
The control unit automatically manages cooling water supply based on the operational state without requiring external intervention. The system self-adjusts by stopping cooling during standby and resuming during polishing operations, optimizing energy usage autonomously.
3Temperature
If dummy polishing is performed to warm up the turntable, then temperature stability is improved, but productivity is reduced due to additional processing time
Solution Approach 1:
The cooling water supply is stopped in advance during standby periods before polishing restarts. By preventing excessive cooling during the standby period, the turntable temperature is maintained in an appropriate range automatically, eliminating the need for subsequent dummy polishing operations to warm up the turntable before actual polishing can resume.
Solution Approach 2:
The control unit detects when polishing restarts and automatically resumes cooling water supply at the appropriate time. This feedback-based control ensures temperature stability is maintained through proper timing of cooling water supply cessation and resumption, rather than requiring additional dummy polishing steps.
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 approach prevents excessive cooling of the turntable during standby, eliminating the need for dummy polishing and maintaining productivity by stabilizing the turntable temperature.
Implementation Method 1
a refrigerant such as low-temperature cooling water is flowed to a turntable unit to remove the heat
Implementation Method 2
heat is generated from a motor by rotation of the turntable
Implementation Method 3
heat is generated due to friction of the polishing pad, the polishing agent, and the wafer
Implementation Method 4
supply a water retaining liquid to a polishing pad to prevent the polishing pad attached to an upper side of the turntable from being dried
Data Source
AI summary
A polishing method including rubbing a wafer held by holding means against a polishing pad attached to a turntable while cooling the turntable by supplying a refrigerant to a refrigerant flow path provided in the turntable which is driven to rotate by a motor, thereby performing polishing, the polishing method being characterized in that, during standby after end of the polishing of the wafer and before performing the polishing of a next wafer, a flow volume of the refrigerant is controlled to be less than a flow volume of the refrigerant during the polishing where the wafer is polished, the turntable is rotated by the motor, and a water retaining liquid having a temperature adjusted to a room temperature or more is supplied to the polishing pad.