FPGA 모듈을 이용한 Long Range AFM용 다축 제어 프로그램 개발

Development of Multi-Axis Control Program for Long Range AFM Using an FPGA Module

In general, atomic force microscope (AFM) used for metrological purpose has measuring range less than a few hundred micrometers. We design and fabricate an AFM with long measuring range of $200mm{\times}200mm$ in X and Y axes. The whole stage system is composed of surface plate, global stage, microstage. By combining global stage and microstage, the fine and long movement can be provided. We measure the position of the stage and angular motions of the stage by laser interferometer. A piezoresistive type cantilever is used for compact and long term stability and a flexure structure with PZT and capacitive sensor is used for Z axis feedback control. Since the system is composed of various actuators and sensors, a real time control program is required for the implementation of AFM. Therefore, in this work, we designed a multi-axis control program using a FPGA module, which has various functions such as interferometer signal converting, PID control and data acquisition with triggering. The control program achieves a loop rate more than 500 kHz and will be applied for the measurement of grating pitch and step height.