Wafer Edge Shape Measurement by Rotating Displacement Sensor
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Solution Overview
Problem
Existing edge shape measurement techniques for semiconductor wafers face challenges such as difficulty in focusing on the wafer end surface due to its small curvature, leading to diffused reflected light, and issues with focal position adjustment, which hinder accurate edge shape measurement.
Innovation Solution
An edge shape measurement apparatus and method that utilize a displacement sensor rotated around a predetermined point inside the wafer as a center, measuring distances without focusing, using a multicolor confocal displacement sensor to scan the wafer's edge shape by rotational angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If confocal optical system is used to measure wafer end surface, then measurement capability is provided, but focusing becomes difficult due to small curvature of wafer end surface causing diffused reflected light
Solution Approach 1:
The patent replaces the confocal optical system with a displacement sensor that directly measures the distance between the sensor and the wafer end surface. This substitution eliminates the optical focusing mechanism entirely, replacing it with a direct mechanical/electrical measurement approach that does not require focusing adjustment.
Solution Approach 2:
The patent extracts and removes the focusing function from the measurement system. By using a displacement sensor that measures distance directly without requiring light focus, the system eliminates the problematic focusing operation while retaining the core measurement capability.
2Measurement precision
If focal position adjustment is performed with confocal system, then measurement is attempted, but accurate measurement cannot be achieved since distance from sensor to wafer end surface is not directly measured
Solution Approach 1:
The patent replaces the indirect optical measurement method with a direct displacement sensor measurement system. The displacement sensor directly outputs the distance information between the sensor and the wafer end surface, eliminating the need for focal position adjustment and providing accurate direct distance measurement.
Solution Approach 2:
The displacement sensor acts as an intermediary that directly measures and provides distance information without requiring optical focusing. This intermediary device bridges the gap between the measurement system and the wafer end surface, providing accurate distance data without the complications of optical focus adjustment.
3Productivity
If confocal optical system with line-shaped detector is used, then scanning capability is provided, but focal position adjustment becomes difficult and accurate measurement cannot be achieved
Solution Approach 1:
The patent replaces the confocal optical scanning system with a displacement sensor-based scanning system. The displacement sensor directly measures distance during scanning without requiring focal position adjustment, maintaining scanning capability while eliminating the difficult focusing operation.
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 accurate measurement of the edge shape of semiconductor wafers without focusing, overcoming the limitations of previous methods by directly measuring distances with a displacement sensor.
Implementation Method 1
irradiating a wafer end surface as a measurement target with measuring light using a confocal optical system, positioning a focus of the measuring light with a focal position adjustment device, and detecting a defocusing amount
Implementation Method 2
the reflected light is diffused, and it is difficult to put the focus at a pinpoint on the focal point surface of the wafer end surface
Data Source
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AI summary
There is provided an edge shape measurement apparatus (100) and a method of measuring an edge shape capable of accurately measuring the edge shape of a wafer (W) without focusing when scanning with the displacement sensor (12). The displacement sensor (12) configured to measure the edge shape of the wafer (W) having a plate like shape is provided, and is configured to rotationally be driven taking a predetermined point inside the wafer (W) as a rotational center (CTR) in a plane which includes the rotational center (CTR) and is perpendicular to upper and lower surfaces of the wafer (W) while keeping a constant radius (r0) with the rotational center (CTR), and is configured to measure a distance to a point (SP) on a surface of the wafer (W) located on a straight line connecting the rotational center (CTR) and the displacement sensor (12) by a rotational angle (θ).