Ultrasonic Nanoimprinting in Organic Spin-on-Glass-Coated Si Substrates

Abstract

We have already reported on our success in molding engineering plastics by an ultrasonic nanoimprinting technology. In this paper, we report on our experimental results of ultrasonic nanoimprinting in organic spin-on-glass (SOG)-coated Si substrates. A 753-nm-thick layer of Accuglass 512B, an SOG also known as methyl siloxane, was spin-coated on a sputter-deposited 10-nm-thick Ti layer on a Si substrate. Typically, SOG needs to be baked in a two-step thermal treatment by annealing at a low temperature and then at a high temperature. Therefore, a group of substrates previously heated at 150 °C for 1 min using a hot plate, and another group of substrates previously soft baked at 150 °C followed by hard baking at 450 °C for 1 h in a rapid thermal processor were prepared for tests. Nanoimprinting was carried out under conditions similar to those used in earlier experiments on engineering plastics. In the tests, the frequency and amplitude of ultrasonic vibration were set at 10 kHz and 3 µm, while the contact force and contact time were set to 500 N and 60 s, respectively. In the experiment, we succeeded in transferring mold patterns with linewidths of 500 nm, 700 nm, and 1 µm onto the substrates. The maximum depths of imprinting in the SOG-coated substrates without and with hard baking were 294 and 214 nm, respectively, as measured using a confocal microscope. In addition, the effect of a Ti interlayer and those of the frequency and amplitude of ultrasonic vibration on the depth of imprinting were investigated. The results of these experiments demonstrated the potential wide application of ultrasonic nanoimprinting technology for SOGs as well as for engineering plastics.