研究目的
To develop a high-speed CMOS proximity capacitance image sensor with high spatial resolution, high detection accuracy in the attofarad order, and high measurement speed for real-time applications, by reducing noise through innovative circuit design.
研究成果
The developed CMOS proximity capacitance image sensor achieves a detection accuracy of 0.1aF and a frame rate of 60 fps, with significant noise reduction through innovative circuit design. It demonstrates high potential for applications in inspection and imaging, with real-time capabilities and high sensitivity.
研究不足
The sensor's performance may be limited by environmental factors such as temperature and humidity. The spatial resolution is fixed at 16μm pitch, which may not be sufficient for some high-resolution applications. The use of a 0.18μm process technology, while effective, is not the most advanced, potentially limiting further miniaturization or speed improvements.
1：Experimental Design and Method Selection:
The sensor uses a proximity capacitance measurement method with a detection electrode and reference electrode structure. A noise canceling operation synchronized with the reference electrode voltage pulse is introduced to reduce kTC noise and fixed pattern noise (FPN).
2：Sample Selection and Data Sources:
A prototype sensor chip with 16μm pitch 256H×256V pixels is fabricated using a 0.18μm 1-poly 5-metal CMOS process. Measurements are performed with targets such as conductive solids and saline solutions.
3：18μm 1-poly 5-metal CMOS process. Measurements are performed with targets such as conductive solids and saline solutions.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: The sensor chip, a manipulator with a tungsten probe as a reference electrode, an analog front-end (AFE) circuit board with voltage regulators, a 12-bit differential ADC directly connected to VOUT1 and VOUT2, an FPGA board to supply operation pulses to the sensor chip, and a PC for data acquisition and processing.
4：Experimental Procedures and Operational Workflow:
The sensor operates by resetting the detection electrode, applying voltage pulses to the reference electrode, and measuring the output voltage difference to compute capacitance changes. The noise canceling operation involves synchronized switching to cancel noise components.
5：Data Analysis Methods:
Data is analyzed using the FPGA and PC to compute signal-to-noise ratios, temporal random noise, and detection accuracy. Averaging over multiple frames is used to improve accuracy.
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