Electrostatic Capacitance Sensing With Bandpass Noise Rejection
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Solution Overview
Problem
Electrostatic capacitance sensors in semiconductor wafer transfer robots face challenges in accurately detecting minute changes in capacitance due to noise interference from static eliminators and drive sources, which can lead to inaccurate detection of semiconductor wafers, especially with the miniaturization of semiconductors and the adhesion of particles caused by charging.
Innovation Solution
An electrostatic capacitance sensor with a detection unit and amplifier module configuration that uses guard electrodes and bandpass filters to isolate and remove noise, allowing accurate detection of minute capacitance changes without interference from static eliminators or drive sources, and is integrated into a wafer transfer robot to ensure precise semiconductor wafer handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electrostatic capacitance sensor is used to measure the distance between the wafer hand and the semiconductor wafer, then the position detection accuracy is improved, but the detection reliability deteriorates due to noise interference from static eliminators and drive sources
Solution Approach 1:
The patent introduces a bandpass filter as an intermediary component between the detection unit and the control unit. This filter selectively passes only the frequency band of the applied AC voltage, blocking noise from static eliminators and drive sources. The filter acts as a mediator that allows the useful signal to pass while rejecting harmful noise, thereby resolving the contradiction between maintaining detection sensitivity and ensuring detection reliability in noisy environments.
Solution Approach 2:
The patent changes the frequency parameter of the detection system by applying an AC voltage at a specific frequency (e.g., 200 kHz) that is distinct from the noise frequencies generated by static eliminators and drive sources. By operating at this differentiated frequency and using a bandpass filter tuned to this frequency, the system can detect capacitance changes accurately while rejecting out-of-band noise, thus resolving the contradiction between measurement precision and detection reliability.
2Productivity
If the semiconductor wafer is miniaturized to reduce circuit line width, then the integration density is improved, but the detection difficulty increases due to increased particle adhesion from charging
Solution Approach 1:
The patent replaces direct physical contact measurement methods with a non-contact electrostatic capacitance sensing method. By using capacitive coupling between the detection unit and the semiconductor wafer, the system can detect position and presence without mechanical contact. This substitution allows for accurate detection of miniaturized wafers without the mechanical interference and particle adhesion problems that would occur with contact-based methods, thus resolving the contradiction between integration density and detection difficulty.
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
The solution enables stable and accurate detection of semiconductor wafers, reducing particle adhesion and maintaining precise wafer transfer operations even in noisy environments, thus improving the reliability of wafer transfer robots.
Implementation Method 1
detects an electrostatic capacitance generated between an object to be detected and a detection unit that detects the object to be detected
Implementation Method 2
emitting a weak AC that is supplied from a detection circuit of the sensor from the detection unit toward the object to be detected
Implementation Method 3
amplifier module that amplifies the detected electrostatic capacitance
Data Source
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AI summary
Provided is an electrostatic capacitance sensor which can remove an influence of a noise occurring from a static eliminator or a driving source and accurately perform measurement even on electrostatic capacitance detected by a thin-type detection unit which can be passed to a finger surface of a wafer transfer robot. The present invention is provided with an AC supply source 29 which supplies an AC voltage to a detection unit 1a: a parasitic capacitance compensation circuit 33: an operational amplifier 28: a differential amplifier 34: a phase detection means 35: and a low pass filter, wherein an operational amplification output terminal is connected to an inversion input terminal of the differential amplifier 34 through a first band pass filter 30, the AC supply source 29 is connected to a non-inversion input terminal of the differential amplifier 34 through a second band pass filter 31, an output terminal of the differential amplifier 34 is connected to an input terminal of the phase detection means 35, and the phase detection means 35 takes, as a reference signal, an AC signal output from the AC supply source 29.