Young Hun Yu

Electrical and Optical Properties of SiOC Films with Low Dielectric Constant

We have prepared the SiOC film by ICPCVD method. The carbon concentration in SiOC film is controlled with a mixture of bis-trimethylsilylmethane (BTMSM) and oxygen gases. We have studied the relation between the carbon concentration and the optical band-gap, relation between the optical band gap and the dielectric constant. The optical band gap increased with carbon concentration and the dielectric constant decreases as the optical band gap increases. The mechanism of lowering dielectric constant with energy gap was discussed by using Penn Model. Introduction A low dielectric material has been required for the multilevel interconnection of the ULSI (ultra large scale integrated circuits) devices for the device performance. The low dielectric constant (low-k) film is used to reduce propagation delay times, cross-talk noise between metal layers, and power dissipation from RC coupling [1]. Recently, many researchers have proposed a variety of organic and inorganic material such as, hydrogensilsequioxane (HSQ), fluorine-doped silicon oxide, fluorinated amorphous carbon, methylsisequioxane (MSQ) and carbon doped silicon oxide (SiOC), as alternatives to SiO2 [2-5]. Silicon oxide-based low-k materials, like SiOC, which contains alkyl groups, have attracted attention as they have greater thermal and mechanical stability than many organic materials. The spatial hindrance of the alkyl groups may produce abundant nano-pores in a film and decrease a dielectric constant [6,7]. Structural properties of SiOC amorphous films are controlled by processing conditions such as annealing temperature and gas flow rate. In amorphous the absorption tail encroaches the into the energy gap [8,9]. But the absorption spectrum, in defect free crystal, terminates abruptly at the energy gap. The changing the energy gap in amorphous modify the electric polarizability and modify the dielectric function [10]. In this paper we have studied the relation between the carbon concentration and optical band gap, between the optical band gap and dielectric constant. We use spectroscopic ellipsometer (SE), Fourier Transformed Infrared (FTIR) absorption spectroscopy to investigate the structural properties of the SiOC film and their relationship to dielectric constant. The bonding configurations have been identified from FTIR, and a strong correlation can be established between the carbon concentration and the optical band gap. Experiments SiOC composite films with nano-pore structure were deposited on p-type Si(100) wafers using a mixture of bis-trimethylsilylmethane (BTMSM) and oxygen by an inductively coupled plasma chemical vapor deposition (ICPCVD) and the post-annealing at 400°C was carried out for 30 minutes in a vacuum. Inductively coupled plasma was generated with a three-turns coil, which was set around a quartz tube and connected to 13.56 MHz radio-frequency (rf) power supply. A base pressure of 10 -6 torr was reached before each deposition. The wafers were kept in a floating potential and were not intentionally heated. The wafers were cleaned using a standard procedure before loading them into the reaction chamber. The BTMSM precursor is a nontoxic, colorless liquid with a boiling point of 137°C * Corresponding Author E-mail : cckyu@cheju.ac.kr Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 814-819 doi:10.4028/www.scientific.net/KEM.270-273.814