Preparation And Characterization Of CrN/SiNx Nano-multilayers And Research Of Thermal Stability Of Multilayers

In the past decades, TiN films deposited by physical vapor deposition (PVD) or chemical vapor deposition (CVD) method have found widespread application in wear resistant situations such as cutting tools or machine parts because of their high hardness, wear resistance, chemical inertness and high temperature stability. Beside the investigation of TiN-based films, recently an increasing amount of attention is focused on other metal nitrides grown by PVD processes, such as CrN, Si₃N₄, MoN, HfN and WN, with specific interest in Cr-N and Si₃N₄. The Cr-N coating system has been investigated extensively in the last 10 years. It was found that CrN coatings exhibit excellent corrosion and wear properties, and have better oxidation resistance, as well as better adhesion to tool steel when compared to TiN films. CrN films deposited by PVD techniques exhibit a potential for practical application in industry. Si₃N₄ is a material with high hardness, thermal and chemical resistance and passivity towards a number of materials. Si₃N₄ films are widely used in verylarge-scale integrated circuits, oxidation masks, gate dielectrics, thin-film transistors, and hard coating materials.It is found that multilayers can combine the properties of the constituent materials and have improved properties when compared to the individual single layer films. Multilayers with optimized interface areas seem to be most promising with respect to an optimum hardness-to-toughness ratio. A few investigations have been reported about the mechanical properties of CrN/SiNx multilayers. But so far no results have been reported about the thermal stability of CrN/SiNx multilayers. Our attempt was to deposit CrN/SiNx multilayers in order to get the multilayers with much better thermal/stability than other multilayers.This thesis consists of two parts:In the first part, CrN/SiNx multilayers have been prepared by magnetron sputtering system in N2/Ar discharge. The structure and topography of the multilayers were characterized by XRR spectroscopy, XRD spectroscopy and AFM. The effects of the work pressure, the substrate bias and the temperature of the substrate on the structure and topography have been discussed.(1) The XRR results show that with the increase of work pressure the modulation periods of the multilayers decrease but the interface widths and topographies increase. The (111) Bragg peak of the multilayers disappeared with the work pressure decreasing from 2. OPa to 0. 4Pa.(2) The layer structures of the multilayers are clearer when the substrate biases are in the range from - 80V to - 140V than in other substrate biases. The (111) and (200) Bragg peaks are all appear when the substrate bias is floating, but (111) Bragg peak disappears when the substrate bias increases to - 170V.(3) As substrate temperature rises the layer structures of the multilayers become bad. The (111) Bragg peak disappears when the temperature increases from room temperature (RT) to 300"C.In the second part, the thermal stability and diffusion behaviour of the multilayers were investigated. The results are as follows:(1) The layer structure of CrN/SiNx multilayers is more obvious than that of TiN/SiNx multilayers because of the poor diffusion between CrN layer and SiNx layer and fast diffusion...