A Digital Lock-In Amplifier Based Contact Detection Technique for Electrochemical Nanolithography

摘要

This paper presents a digital lock-in amplifier (DLIA) based technique to detect the template-substrate contact in electrochemical nanolithography. This technique is applied to a specially designed electrochemical nanolithography system for verification. The system adopts a macro-micro positioning setup consisting of a fine stepping motor to drive the macropositioning stage and a PZT (lead zirconate titanate, Pb[Zr_xTi_(1-x)]O_3) actuator to drive the micropositioning stage. The template is mounted on a force-displacement sensing module which is attached to the PZT actuated micropositioning stage and the substrate is mounted on a holder which is merged in the solution. When the template approaches the substrate, it is controlled to oscillate at a certain frequency. Two capacitive displacement sensors are used to measure the template oscillation. Afterwards, a digital lock-in amplifier is adopted to separate the oscillation information from the raw signal. The contact is determined by monitoring the separated oscillation information. Finally, experiment tests are conducted to verify the effectiveness of the digital lock-in amplifier. Experimental results demonstrate that the developed DLIA technique makes the template-substrate contact to nanometer accuracy.