Rotating Optical Sensor for Real-Time Wafer Thickness Control
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Solution Overview
Problem
The existing wafer polishing processes face challenges in accurately measuring the thickness of wafers during polishing, leading to variations in polishing speed and quality due to material deterioration, resulting in inconsistent wafer thickness.
Innovation Solution
A wafer polishing apparatus equipped with a rotating sensor unit that measures the thickness of the wafer in real-time, using light reflection data to calculate the thickness and adjust the polishing process, and a control unit that determines whether to continue polishing based on Global Backside reference Indicate Reading (GBIR) values, ensuring optimal polishing quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed-time polishing process is used, then the polishing process is simple to operate, but the wafer thickness varies due to polishing speed deterioration
Solution Approach 1:
The patent implements real-time thickness measurement during polishing using a sensor that detects the wafer surface position. The measurement value is fed back to the control unit, which automatically adjusts the polishing process parameters (such as polishing time or head speed) to maintain consistent wafer thickness, thereby resolving the contradiction between operational simplicity and manufacturing precision.
2Manufacturing precision
If real-time thickness measurement is implemented, then wafer thickness consistency is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical measurement systems with an optical sensor that non-contactively measures wafer thickness. The sensor unit uses light reflection or transmission principles to detect surface position, eliminating the need for physical contact probes or complex mechanical gauges, thus achieving high measurement precision while minimizing device complexity.
3Stability of the object's composition
If the sensor unit is fixed on the stationary structure, then the measurement system is stable, but the measurement accuracy during rotation decreases
Solution Approach 1:
The patent makes the sensor unit rotatable so that it rotates together with the polishing head during the polishing process. This dynamic configuration allows the sensor to maintain a constant relative position to the wafer surface being measured, ensuring accurate thickness measurements while the polishing head rotates, thereby resolving the contradiction between system stability and measurement precision during rotation.
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 solution enables precise measurement and adjustment of wafer thickness, improving polishing quality by stopping the process when GBIR exceeds predetermined limits, thus maintaining consistent wafer thickness and quality.
Implementation Method 1
a sensor unit for radiating light to the wafer received in the carrier, detecting light reflected by the wafer
Data Source
AI summary
An embodiment comprises: a lower plate; an upper plate which is disposed on the lower plate and rotates; a carrier which receives a wafer and is disposed on the lower plate; and a sensor unit for irradiating light to the wafer received in the carrier, detecting light reflected by the wafer, and outputting detection data according to the detection result, wherein the sensor unit rotates together with the upper plate.