Surface Height Measurement Apparatus with Dynamic Light Control
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Solution Overview
Problem
In semiconductor manufacturing, existing measurement techniques using white color interference struggle to accurately capture interference fringes due to varying reflectance across different material layers, leading to reduced measurement accuracy and reliability.
Innovation Solution
A measurement apparatus employing a light source, filter, lens mechanical unit, interference unit, and detection unit that adjusts the focus position and light intensity to detect interfering light, allowing for precise calculation of surface height and interface positions by equalizing the intensity of interfering light across varying reflectance regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If white color interference measurement is used to measure surface height, then non-destructive measurement capability is achieved, but measurement accuracy deteriorates when reflectance varies across different material layers
Solution Approach 1:
The patent implements dynamic focus adjustment by moving the objective lens to change the focal position of irradiation light. This allows the measurement system to adapt to different surface heights and focus on specific interfaces (e.g., between material layers) dynamically, thereby maintaining measurement accuracy even when reflectance varies across different layers. The focus position is adjusted based on detected interference fringe positions to optimize measurement at each location.
Solution Approach 2:
The patent changes the wavelength parameter of irradiation light by selecting specific wavelengths (e.g., 405nm, 532nm, 635nm) based on the reflectance characteristics of different material layers. This parameter adjustment optimizes the contrast of interference fringes for each specific layer, thereby improving measurement accuracy across varying reflectance conditions while maintaining non-destructive measurement capability.
2Area of stationary object
If measurement is performed on regions with different reflectance, then comprehensive surface coverage is achieved, but interference fringe capture quality deteriorates
Solution Approach 1:
The patent applies local quality adjustment by using different wavelengths of irradiation light for different regions of the measurement area. Specifically, the system selects optimal wavelengths (405nm, 532nm, or 635nm) based on the reflectance characteristics of each local region's material layer, thereby ensuring high-quality interference fringe capture across the entire surface while maintaining comprehensive coverage.
Solution Approach 2:
The system dynamically adjusts the focus position of the objective lens to capture interference fringes from different depths and interfaces across the measurement area. By moving the lens to different focal positions, the system can clearly capture fringes from various material layers regardless of their reflectance differences, thereby maintaining high capture quality across the entire surface area.
3Measurement precision
If focus position is adjusted to capture interfaces at different depths, then interface detection capability is improved, but measurement time increases
Solution Approach 1:
The patent implements periodic action by systematically adjusting the focus position through multiple predetermined positions to capture interference fringes from different interfaces. Instead of continuous adjustment, the system performs discrete periodic focus adjustments at specific positions, thereby efficiently detecting multiple interfaces (e.g., upper layer surface, lower layer surface) while minimizing measurement time compared to continuous scanning methods.
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 high-accuracy measurement of surface height and shape by recognizing peaks in interfering light intensity, even in regions with different reflectance, thereby improving measurement reliability and accuracy.
Implementation Method 1
a light source that emits irradiation light; an interference unit that causes the irradiation light and reflected light from the material to interfere with each other
Data Source
AI summary
A measurement apparatus includes a filter changing a light amount of an irradiation light, a lens irradiating a surface of a material with the irradiation light, a stage changing a focus position of the irradiation light in a depth direction of the material, an interfering light extractor causing the irradiation light to interfere with reflected light from the material, a detector detecting an intensity of interfering light obtained by interference between the irradiation light and the reflected light, and a controller calculating a height of the surface of the material based on the detected intensity of interfering light while changing a relative focus position of the irradiation light with respect to the material at a given measurement point of the surface of the material. The controller controls the filter or light source based on the detected intensity of interfering light to change the light amount of the irradiation light.