후 열처리에 따른 저유전율 SiOC(-H) 박막의 특성연구

Abstract

Recently, materials with a low dielectric constant are required as interlayer dielectrics for the on chip interconnection of ultra-large-scale integration devices to provide high speed, low dynamic power dissipation and low cross-talk noise. The selection of chemical compounds with low polarizability and the introduction of porosity result in a reduced dielectric constant. While porous thin film characterization techniques are beginning to emerge, there is much work to do in order to understand the structure property relationships in porous low-k thin films. an the present study, low-k SiOC(-H) films with nano-pore structure were deposited on p-type Si(100) substrates using UV-source assisted PECVD with a mixture of oxygen gas and DMDMS. FTIR spectroscopy performed in the absorbance mode was used to determine the related Si-O and Si-CH3 bonding configuration in the film, and the bonding structure of the Si-O-C composite films was analyzed using XPS. The characteristics of nano-pore structure in the SiOC(-H) films were investigated by using Bruggeman's effective medium approximation, the dielectric constant of the films was investigated with a metal insulator semiconductor (MIS, Al/SiOC(-H) films/p-Si) structure at 1 MHz. The SiOC(-H) dielectric films were prepared with various compositions and then subsequently annealed for 30 min in a vacuum at 100, 200, 300 and 400 ℃. The dielectric constant decreased from 2.43 to 2.18 and the refractive index decreased from 1.44 to 1.42 in accordance with the increase of porosities from 42.04% to 49.72%. The current voltage analysis indicates that the leakage-current density is 5.55×10-8 A/cm2 at an applied electric field of 1 MV/cm, and the dominant conduction mechanism is found to be Schottky emission in as-deposited and annealed SiOC(-H) films at mid electric field. The spectra of the Si-O-Si asymmetric stretching mode for clearly separated Si-O-Si and Si-O-C bonds indicates the existence of a caged Si-C bond, and this is a reflection of the enhanced porosity in the films. Carbon atoms could be incorporated in the SiOC(-H) films during deposition by -CH3 groups attached to Si atoms in the Si-O-Si networks, and the Si-O-C substructure. Some types of CHn were removed from the bulk of the film due to the annealing process, and some of the Si-O-Si bonds changed into Si-O-C bonds including ring and cage links in which C atoms had been incorporated.