Preliminary Study On The Atomic-scale Material Removal Of Silicon Surface

With the rapid development of very large scale integration ciurcuit (VLSI) technique, a much more rigorous request for the surface accuracy and roughness of sbstrates is brought up. Nowadays, the chemical mechanical planarization/polishing (CMP) technique is widely used in integrated circuit (IC) manufacture. However, the experimental study on nano-polishing mechanism is mainly operated by using CMP polishing machine, whose purpose is to reveal the effects of various process parameters on the wafer planarization quality. As a result, the material removal mechanism by single particle in the polishing process is far from understanding. Therefore, it is an important issue to carry out the research of behavior and mechanism of the atomic-scale material removal on monocrystalline silicon surface. The results can not only enrich the basic theory of nanotribology, but also can help to promote the development of CMP technique and IC manufacture.By using an atomic force microscope, the nanowear of monocrystalline silicon was investigated on original silicon surface (with native oxide layer) and hydrophobic silicon surface (without native oxide layer) in various conditions. During the wear tests, the SiO2tips with radius of1μm and a diamond tip with radius of0.3μm were used. Based on the experimental results, the atomic-scale material removal of monocrystalline silicon was studied, and the mechanism was preliminarily discussed. The main experimental results and conclusions can be summarized as follows:1. The wear depth of original silicon (with native oxide layer) increased with the increase of the normal load and presented the trend of atomic layer removal. As the load less than1μN, no obvious wear was detected on original silicon surface. When the normal load increased from1μN to3μN, the nanowear depth increased from1.5nm to2.0nm.2. When the native oxide layer on silicon surface is removed, the tribochemical nanowear on the surface of hydrophobic silicon presents a typical atomic layer removal trend with the increase of the normal load. In addition, the wear depth decreased as the sliding speed increased, and increased as the scanning row distance decreased, and increased to steady level as the relative humidity increased from0%to60%.3. When the contact pressure is lower than the yield stress, the atomic layer removal on monocrystalline silicon surface can be achieved with the help of the tribochemical reaction. The wear depth on silicon surface increased as dissipated energy increased.