ITERATIVE-CONTROL-BASED HIGH-SPEED DIRECT MASK FABRICATION VIA ULTRASONIC-VIBRATION-ASSISTED MECHANICAL PLOWING

摘要

Mechanical indentation and plowing is one of the most widely used methods in probe-based nanolithography. Compared to other probe-based nanolithography techniques such as the Dip-pen and the milliped, mechanical plowing is not restrictive to conductive materials and/or soft materials. However, like other probe-based nanolithgraphy techniques, the low-throughput has hindered the implementation of this technique in practices. The fabrication throughput, although can be increased via parallel-probe, is ultimately limited by the tracking precision of the probe relative to the sample during the plowing process. In this paper, a new iterative learning control technique is proposed and utilized to account for the adverse effects encountered in high-speed, large-range mechanical plowing nanolithography, including the hysteresis, the vibrational dynamics, and the cross-axis dynamics-coupling effects. Moreover, vertical (normal) ultrasonic vibration of the cantilever is introduced during the fabrication process to improve the fabrication quality. This approach is implemented to directly fabricate patterns on a mask with a tungsten layer deposited on a silicon dioxide substrate. The experimental results demonstrated that a relatively large-size pattern of four grooves (20 μm in length) can be fabricated at a high-speed of ～5 mm/sec, with the line width and line depth at ～95 nm and 2 nm, respectively. A fine pattern of the word 'NANO' is also achieved at the speed of～5 mm/sec. Such a high-speed direct lithography of mask with nanoscale line width and depth points the use of mechanical-plowing technique in strategic-important applications such as mask lithography for semiconductor industry.