ELSEVIER Thin Solid Films 307 (1997) 1-5 j i i m , $ The structure and residual stress in Si containing diamond-like carbon coating Weng-Jin Wu *, Min-Hsiung Hon Department of Materials Science and Engineering (62932), National Che~zgKung Unit,ersity, Tainan 70101, Taiwan Received 29 January 1997; accepted23 April 1997 Abstract Silicon (Si) containing diamond-like carbon films are deposited by RE plasma CVD with reactant gases of CH 4, Sill 4 and Ar. The effects of substrate temperature and RF power on film structure, residual stress and adhesion are studied. The tensile cracking failure mode for films on Coming 7059 glass shows full adherence properties. A structure model is proposed, and the residual stress of the films is compressive. The relation between the structure and the residual compressive stress is investigated. © 1997 Elsevier Science S.A. Keywords: Diamond-likecarbon: Silicon: Residual stress; Structure 1. Introduction Diamond-like carbon films have been widely studied in recent years because of their unique properties such as high hardness, good transparency in IR region and chemi- cal inertness, etc. High residual stress in diamond-like carbon films makes it difficult for application. Doping with other elements such as Ti, W and Si to improve the adhesion and mechanical properties has been studied [1,2]. Introducing silicon to a-C:H to improve properties such as friction coefficient becomes interesting [3,4]. Carbon atoms have both threefold and fourfold coordinated networks depending on the film composition while silicon atoms are arranged in a fourfold coordinated configuration. It is well known that the effect of a small amount silicon addition can increase the sp3:sp 2 ratio and reduce the size of graphite-like islands [5] because silicon does not form ~" bonds. The mechanisms of which such growth stress is generated are not well understood but are known to be a strong function of the coating microstructure [6]. Few studies discussed the relation between the structure and the residual stress of diamond-like carbon films. In this paper, the dependence of the residual stress on the structure of silicon containing diamond-like carbon films is investi- gated. ' Correspondingauthor. 0040-6090/97/$17.00 © 1997 Elsevier Science S.A. All rights reserved. PII S0040-6090(97)0025 1-4 2. Experimental 2.1. Specimen preparation The Si containing diamond-like carbon films are de- posited using a parallel plate, capacitively coupled 13.56 MHz RF plasma system. Electrodes of 8 cm spacing with the grounded gas distributor were used for deposition as shown in Fig. 1. The feed gases consisting of CH 4, Af and Sill 4 were introduced into the system in which the gas flow was measured by mass flow controllers, and the pressure was monitored by a capacitance manometer. The substrates of silicon wafer and Coming 7059 glass were placed on a charged, negatively self-biased internal elec- trode for deposition and allowed the positive ion bombard- ment to take place on the substrate surface during the film growth. The deposition conditions are given in Table t. 2.2. Hardness measurement The hardness of film-substrate composite was mea- sured by Vickers microhardness measurement with a load of 0.245 N with film thickness of 1.0 +0.1 bLm. The hardness calculated in this method will contain contribu- tions from both the substrate and coating. Six tests were performed for each sample, and the standard deviation was estimated to give a more reliable value of hardness, which is meaningful if compared with the value, 550 GPa, mea-