Development of High Precision Nanometer Level Co-planar Stage

• Main Authors: Hung-Yu Wang, 王宏瑜
• Other Authors: Kuang-Chao Fan
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/95949248695932764714

博士 === 國立臺灣大學 === 機械工程學研究所 === 102 === With the continuing trend toward device miniaturization in many engineering and scientific fields, the need to accomplish highly-precise stage at the micro- or nanoscale has emerged as a critical concern. This research presents a series of key technologies with nanometer level co-planar X-Y stages including Abbe free co-planar stage development, robust motion control scheme, high-resolution sensor, real-time signal correction and subdivision, positioning error calibration and error compensation system established. For the driving resolution and efficiency, as well as the simplification requirement, a piezoelement-based ultrasonic motor HR4 (Nanomotion Co.) is employed in this study. The motor drive provides three main driving modes, namely AC, Gate and DC, for millimeter, micrometer and nanometer displacements, respectively. To compensate for the effects of the variable friction force during stage motion, the gains of the PID controller used to regulate the stage motion are tuned adaptively by a self-tuning neuro-PID based on the feedback signals. The positioning accuracy of the proposed system is evaluated by performing large and small stroke and a series of contouring experiments. The 3rd generation of co-planar stage, the displacement of each axis stage is sensed using a linear diffraction grating interferometer (LDGI) with a nanometer resolution. Furthermore, to obtain a high accuracy positional motion, the error compensation strategy is implemented to eliminate the systematic errors of the stage with error budget. The error budget is obtained by positioning error calibration using a laser interferometer, which optical axis is detected by a quadrant photodetector (QPD) to ensure no cosine error. The positioning error can be controlled to ±20 nm with standard deviation 12 nm after implementing error compensation. In the modified co-planar stage, the x- and y-axis coordinates are measured using the MDFMS which comprising a wavelength-corrected Michelson interferometer, a dual-axis autocollimator and wavelength compensator. In order to meet the requirement for a nanometer level measurement, the method for straightness of mirror in Michelson interferometer and alignment procedures have been developed. Moreover, a mathematical model for real time wavelength correction has been proposed and experimental results show that the MDFMS has a normalized wavelength stability of less than 10-6. Importantly, the MDFMS not only enables the x- and y-axis coordinates to be measured with a nanoscale precision, but also enables the pitch and yaw errors of each axis to be detected such that the Abbe errors in the z-direction can be compensated. Moreover, the autocollimator has an accuracy of ± 0.3 arc-sec over the range of ± 30 arc-sec. Besides, the performance of a high-precision co-planar stage is extremely sensitive to the effects of volumetric accuracy. In the modified co-planar stage, this 6-DOF capability can measure the positioning error, straightness error, squareness error and angular errors of the X and Y motions. In addition, the shape error of the mirror can also be separated by using two MDFMS. The volumetric error compensation can also be done automatically. The results demonstrate that the co-planar stage achieves a nanometer level of accuracy and resolution and is therefore a suitable solution for micro-CMM, micro-lithography and micro-machining applications.