Detection Circuit for Semiconductor Wafer Foreign Matter Inspection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional foreign matter inspection apparatuses for semiconductor wafers face challenges in achieving high accuracy due to noise interference and reduced dynamic range when detecting small foreign matters, especially when the wafer rotation speed increases, leading to deteriorated detection accuracy.
Innovation Solution
A detection circuit with a control circuit that adjusts amplifier response characteristics based on radius position information, allowing for variable control of frequency components and noise reduction, enabling accurate signal detection by optimizing the detection circuit's response characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wafer rotation speed is increased to shorten inspection time, then productivity is improved, but the detection accuracy deteriorates due to increased signal change ratio and noise
Solution Approach 1:
The amplifier's response characteristics are made dynamically adjustable based on the detected signal frequency components. The system automatically adapts the amplifier bandwidth and gain according to the current rotation speed and signal conditions, allowing high-speed inspection while maintaining detection accuracy through real-time parameter optimization.
Solution Approach 2:
The system changes the amplifier's response characteristics (bandwidth, gain) as parameters based on the detected signal frequency. By analyzing the frequency components of the detection signal and adjusting the amplifier parameters accordingly, the system maintains optimal detection performance across varying rotation speeds and signal conditions.
2Measurement precision
If the amplification factor is increased to detect minute foreign matter signals, then measurement precision is improved, but noise interference increases and detection accuracy deteriorates
Solution Approach 1:
The amplifier's gain and bandwidth parameters are dynamically adjusted based on the detected signal frequency components. By optimizing these parameters according to the specific signal conditions, the system achieves high amplification for weak signals while filtering out noise through bandwidth limitation, thus improving detection accuracy without excessive noise amplification.
Solution Approach 2:
The system applies different amplification and filtering characteristics tailored to specific frequency ranges. By matching the amplifier's response characteristics to the expected signal frequency components at different radial positions, the system enhances the desired signal while suppressing noise in other frequency bands, achieving local optimization of signal-to-noise ratio.
3Adaptability or versatility
If the amplifier bandwidth is widened to detect high-frequency signals from outer circumference, then adaptability is improved, but noise increases and detection accuracy deteriorates for inner circumference signals
Solution Approach 1:
The amplifier's bandwidth parameter is dynamically changed based on the radial position and corresponding signal frequency. For outer circumference detection where high-frequency components are present, the bandwidth is widened. For inner circumference detection with lower frequency components, the bandwidth is narrowed to reduce noise. This adaptive parameter adjustment maintains detection accuracy across different positions.
Solution Approach 2:
The system dynamically adjusts the amplifier's frequency response characteristics according to the current detection position and signal conditions. By making the bandwidth and gain time-variable based on radial position feedback, the system optimizes the frequency range for each specific detection scenario, achieving both adaptability and precision.
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 enables highly accurate signal detection by minimizing noise and optimizing frequency band and gain according to the radius position, improving detection accuracy and maintaining dynamic range even at increased wafer rotation speeds.
Implementation Method 1
The PMT 103 multiplies the incident light by the photo multiplier effect and outputs a current in accordance with the incident light intensity
Data Source
AI summary
In a foreign matter inspection apparatus for a semiconductor wafer, a PMT which detects reflection light, an amplifier which amplifies a signal detected by the PMT and in which response characteristics of amplification are controlled by a control signal, an A/D converter which converts the signal amplified by the amplifier into a predetermined code and outputs the code, a control circuit which generates a control signal based on information of the semiconductor wafer having a correlation with the reflection light, and a data processing circuit which detects a foreign matter on the semiconductor wafer based on the code output from the A/D converter are provided.