Characteristics of Si-C-N films deposited by microwave plasma CVD on Si wafers with various buffer layer materials

To examine the effects of buffer layer on deposition processes, the Si-C-N films were synthesized by a microwave plasma chemical vapor deposition (MPCVD) system on Si wafers with seven different buffer layer materials, using additional Si columns, CH4 and N-2 gases as raw materials. The buffer layers including Si3N4, Ti, Co, TiN/Co, TiN/W, WSix and TiN were deposited on Si wafers by either CVD or PVD processes. The deposited films were characterized by various techniques. The SEM film morphologies show different features for different buffer layers, including difference in crystal size distribution, crystal shape and preferred orientation. From cathodoluminescence (CL) spectroscopy, the band gaps of the films were varied from 3.76 to 3.95 eV, depending on material of the buffer layers, where 3.86 eV is for films without buffer layers. The field emission measurements indicate that the lowest turn-on field strength can go down to 2 V/mum for the films with Si3N4 buffer layer. The highest turn-on current density is 3.35 muA/cm(2) for films with Co buffer layer. From nano-indentation measurement, the hardness and the reduced modulus of the Si-C-N films can go up to 57 and 342 GPa, respectively. In conclusion, these results also imply that the film properties and film nucleation can be manipulated through applications of buffer layers, which may have a potential application in selective growth of the Si-C-N films for device fabrication. (C) 2001 Elsevier Science B.V. All rights reserved.