Fracture properties of hydrogenated amorphous silicon carbide thin ﬁlms Y. Matsuda a , S.W. King b , J. Bielefeld b , J. Xu b , R.H. Dauskardt a,⇑ a Stanford University, Stanford, CA 94305, USA b Intel Corporation, Hillsboro, OR 97006, USA Received 12 July 2011; received in revised form 4 October 2011; accepted 8 October 2011 Abstract The cohesive fracture properties of hydrogenated amorphous silicon carbide (a-SiC:H) thin ﬁlms in moist environments are reported. Films with stoichiometric compositions (C/Si  1) exhibited a decreasing cohesive fracture energy with decreasing ﬁlm density similar to other silica-based hybrid organic–inorganic ﬁlms. However, lower density a-SiC:H ﬁlms with non-stoichiometric compositions (C/Si  5) exhibited much higher cohesive fracture energy than the ﬁlms with higher density stoichiometric compositions. One of the non-stoichi- ometric ﬁlms exhibited fracture energy (9.5 J m 2 ) greater than that of dense silica glasses. The increased fracture energy was due to crack-tip plasticity, as demonstrated by signiﬁcant pileup formation during nanoindentation and a fracture energy dependence on ﬁlm thickness. The a-SiC:H ﬁlms also exhibited a very low sensitivity to moisture-assisted cracking compared with other silica-based hybrid ﬁlms. A new atomistic fracture model is presented to describe the observed moisture-assisted cracking in terms of the limited SiAOASi suboxide bond formation that occurs in the ﬁlms. Ó 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Thin ﬁlms; Fracture; Plasticity; Moisture-assisted cracking; Dielectrics 1. Introduction Hydrogenated amorphous silicon carbide (a-SiC:H) thin ﬁlms are a class of organic–inorganic hybrid glasses which contain inorganic network bonds and terminal groups such as methyl and hydrogen. a-SiC:H ﬁlms exhibit excellent thermal and chemical stabilities and unique optical and electrical properties, which are adjustable by controlling the chemical composition [1], the number of terminal groups [2,3] and the ﬁlm porosity. Perhaps their most sig- niﬁcant advantage is that they have molecular structures without SiAOASi bonds, which make them insensitive to moisture-assisted cracking. Moisture-assisted cracking results from a stress-enhanced reaction at the crack tip between water molecules and strained moisture-sensitive SiAOASi bonds, which leads to accelerated bond rupture and crack propagation [4]. Such cracking is a serious reli- ability issue for devices containing silica-based ﬁlms, such as widely used classes of organosilicate hybrid glasses [5–7]. These advantages make a-SiC:H ﬁlms promising can- didates for replacing silica-based materials in applications such as etch stop layers in microelectronic devices and anti-reﬂective coatings in photovoltaics. The integration of a-SiC:H ﬁlms into device technolo- gies, however, is limited by their decreased fracture resis- tance due to the presence of terminal groups and porosity, which reduce ﬁlm network connectivity similar to the case of organosilicate glasses [8–10]. Surprisingly, there has been no study of the fracture resistance nor of the sensitivity to moisture-assisted cracking of a-SiC:H ﬁlms. There have only been studies of these fracture prop- erties for the other forms of SiC. For example, chemical vapor deposition (CVD) polycrystalline SiC has been 1359-6454/$36.00 Ó 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actamat.2011.10.014 ⇑ Corresponding author. Present address: 496 Lomita Mall, Durand Bldg., Rm. 121, Stanford University, Stanford, CA 94305, USA. Tel.: +1 650 725 0679; fax: +1 650 725 4034. E-mail address: dauskardt@stanford.edu (R.H. Dauskardt). www.elsevier.com/locate/actamat Available online at www.sciencedirect.com Acta Materialia 60 (2012) 682–691