| The line width, step height and line scales of microelectronic masks are three key parameters among five international calibration standards proposed by the nano-metrology group (WGDM7 DG) of Bureau International des Poids et Mesures (BIPM). The measurement and calibration of these parameters have become the tasks which must be performed currently in the area of precision metrology. According to the developing tendency of both international and domestic microelectronic industry, this project attempts to set up a device of measuring mask standards system in cooperation with Chinese National Institute of Metrology. The whole instrument is constructed by two parts, i.e., optical probe and nano-positioning scanning table. Efforts have been mainly focused on the investigation of the latter in this dissertation. The two orthogonal polarization states of the projected beams result in a relative phase shift when reflected by bireflectance thin films, which is treated as the effect of bireflectance. By fabricating the mirrors of cavity with the effect of bireflectance, the He-Ne laser in transverse magnetic field can output dual-frequency laser and it is called bireflectance dual-frequency laser (BDL). A physical model in consideration of not only the effect of bireflectance film and transverse magnetic field but also the mode coupling in the laser cavity is set up. The analysis of the polarization of BDL by means of this model agrees with the experimental result. Due to the direct output of ideal orthogonal polarized linear lights without quarter wave plate(QWP) which is a factor of thermal drift, the BDL can be applied for the interferometer of nano-position for the measurement of microelectronic masks. A nano-positioning Abbe-free stage with the movement range of 150×150×6mm3, has been designed and implemented successfully. The performance of load-carrying of commercial PZT stage has been extended with long range flexure hinges and magnetism-unloading equipment. Based on the bireflectance dual-frequency laser, a height-adjustable interferometer according to the thickness of mask with plane mirrors (HIPM) is proposed. The position table is designed as the precision scanning after the rough movement. The measurement beams of HIPM keeps coincidance with the upper surface of the mask. And the Abbe arm is reduced to be zero and Abbe error can thereby be thoroughly eliminated in the measurement. The precise scanning range of the nano-positioning table is 100μm×100μm. And the positioning resolution is 1nm. The theroetical uncertainty of the position for the nano-positioning tabel is about 17.4nm, which satisfies the requirement of mask measurement. As for the measurement of step height and line scale, simultaneous control has been realized by using a sole computer for the sampling of Lock-in amplifier, PZT driver, sampling and automatic counting of HIPM. A multi-interface software has been programmed for the mask measurement instrument that contains nano-positioning system. Based on the method of confocal intensity measurement, in the mask –measurement system with comprehensive test is employed to measure a chromeplate scale produced by Heidenhain Company. The nominal single-edge positioning uncertainty of scale measurement is 17.4nm, and the uncertainty of scale space is 24.6nm. The experimental results demonstrated that the standard deviation of repeat measurement for the single-edge scale by using 50×objective lens is 24nm; the standard deviation of repeat measurement for the 1mm line scale by using 50×objective lens is approximately 42nm; the standard deviation of repeat measurement for the 40mm line scale by using 20×objective lens is approximately 48nm.
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