Polishing Apparatus Wafer Detection and Servo Control
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Solution Overview
Problem
Existing polishing apparatuses struggle to rapidly detect wafer detachment from polishing heads during polishing, leading to potential collisions and breakages, which lowers productivity due to the inability to immediately stop the turntable rotation without causing mechanical damage.
Innovation Solution
The apparatus is equipped with wafer-detecting sensors positioned above the peripheral portions of the polishing heads on both upstream and downstream sides of the turntable's rotation direction, capable of outputting a detection signal in 80 μs or less, and features a direct drive servo motor for the turntable driving mechanism to enable immediate and safe stopping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a general optical fiber type wafer-detecting sensor is used, then the sensor can detect wafer detachment, but the detection time is too long (500 μs) to prevent collisions at high rotation rates
Solution Approach 1:
The patent changes the response time parameter of the wafer-detecting sensor from 500 μs to 80 μs or less by selecting a different sensor type, enabling rapid detection that can prevent collisions even at high turntable rotation rates
2Productivity
If the turntable rotation is stopped immediately upon detecting wafer detachment, then collision can be prevented, but mechanical damage occurs to the speed reducer and other components
Solution Approach 1:
The patent performs preliminary action by reducing the turntable rotation rate before stopping, rather than immediate abrupt stopping. This gradual deceleration prevents mechanical damage to the speed reducer and other components while still preventing wafer collisions
Solution Approach 2:
The patent applies beforehand cushioning by using a controlled deceleration process that cushions the mechanical impact on the speed reducer and other components, preventing breakage and tooth skipping that would occur with immediate stopping
3Power
If a speed reducer is used in the turntable driving mechanism, then torque control is improved, but immediate stopping causes breakage of gears, tooth skipping and belt wearing
Solution Approach 1:
The patent performs preliminary action by reducing the rotation rate before stopping the turntable, preventing the sudden torque shock that would cause gear breakage, tooth skipping and belt wearing in the speed reducer
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 configuration allows for rapid detection and prevention of wafer collisions, reducing breakages and increasing productivity by enabling immediate stoppage of the turntable rotation without mechanical damage.
Implementation Method 1
When a wafer comes off from the polishing head 102, the wafer-detecting sensors 106 detects the wafer by light reflection
Data Source
AI summary
A polishing apparatus includes: a plurality of polishing heads for holding a wafer, a polishing pad for polishing the wafer, a rotatable turn table having the polishing pad attached thereto, a turn table driving mechanism for rotating the turn table, a plurality of wafer-detecting sensors for detecting coming off of the wafer from the polishing head during polishing, wherein the polishing apparatus has the wafer-detecting sensor disposed above peripheral portions of the respective polishing heads and on each downstream side in a rotation direction of the turn table with respect to the respective polishing heads. The polishing apparatus can detect coming off of a wafer from a polishing head during polishing more rapidly, and can prevent a breakage of the wafer thereby.