Low dielectric constant fluorocarbon films containing silicon by plasma enhanced chemical vapor deposition

Use of low relative dielectric constant (low-k) material as an interlayer dielectric is among important approaches to reduce the RC time delay in high performance ultra-large-scale integrated circuits. Copper metallization is another approach besides the use of low-k material, in reducing the RC delay time, because of its well-known characteristics of low resistivity and high electromigration resistance. Fluorocarbon films containing silicon (SiCF) have been developed in this work for low-k interlayer dielectric applications below 50 nm linewidth technology. The films were prepared by plasma enhanced chemical vapor deposition (PECVD) using gas precursors of tetrafluoromethane as the source of active species and disilane (5 % by volume in helium) as both an active species source and a reducing agent to control the ratio of fluorine to carbon in the films. The basic properties for these low-k interlayer dielectric films were studied along with characterization of their fabrication process. Electrical, mechanical, chemical and thermal properties were evaluated including dielectric constant, electrical field strength, surface planarity, residual stress, hardness, chemical bond structure, and shrinkage upon heat treatment. Deposition process conditions were optimized for film thermal stability while maintaining a relative dielectric constant value as low as 2.0. The average breakdown field strength of the SiCF films was 4.74 MV/cm and its optical energy gap was in the range of 2.2 to 2.4 eV. The hardness and residual stress in the SiCF films deposited under the optimized conditions were respectively measured to be in the range of 1.4 to 1.78 GPa and in the range of 11.6 to 23.2 MPa of compressive stress. For integrated microsystems as well as for ULSI circuits, surface modification of SiCF films by wet chemical treatment and by X-ray irradiation were examined to facilitate copper metallization. Feasibility of copper deposition by recently developed electroless techniques is discussed in conjunction with the studies utilizing wet chemical modification of the film surface. The effect of X-ray irradiation on the chemical structure of the films is also discussed. Additionally, means for selective surface modification of the films are introduced by exposing the films through an X-ray mask

Synthesis and characterization of low pressure chemically vapor deposited boron nitride and titanium nitride films

This study has investigated the interrelationships governing the growth kinetics, resulting compositions, and properties of boron nitride (B-C-N-H) and titanium nitride (Ti-N-Cl) films synthesized by low pressure chemical vapor deposition (LPCVD) using ammonia (NH3)/triethylamine-borane and NH3/titanium tetrachloride as reactants, respectively.Several analytical methods such as the FTIR, UVNisible spectroscopy, XPS, AES, RBS, SEM, and XRD were used to study the stoichiometry and structure of the deposited films. The B-N-C-H films were synthesized over a temperature range of 300 to 8500C at various flow rate ratios of the reactants and total pressure range of 50 to 150 mTorr. The deposits were amorphous in all cases having an index of refraction ranging between 1.76 and 2.47 depending on the composition of the films. The stress of the deposited films varied from +240 to -200 Wa, depending on the deposition parameters. The hardness and Young\u27s modulus were found to be between 5 to 12 GPa and 50 to 120 GPa, respectively. Electrical properties of the BN films were measured using metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) structures. The films did not react with water vapor and exhibited dielectric constant between 3.12 and 5.5. Free standing X-ray windows with thickness varying from 2000Å to 12,000Å, were fabricated using the mildly tensile and compressive films and X-ray transmission studies through these windows indicate significantly lower absorption when compared to the commercially available polymeric X-ray windows. The Ti-N-Cl deposits exhibited an Arrhenius d ependence in the deposition temperature regime of 450 to 600 °C from which an activation energy of ~42 kJ/mol was calculated. The growth rate dependencies on the partial pressures of NH3 (50 to 100 mTorr) and TiC14 (1 to 12 mTorr) yielded reaction rate orders of 1.37 and -0.42 respectively. Films with compositions trending towards stoichiometry were produced as the deposition temperature was decreased and the NH3 partial pressure was increased. The chlorine concentration in the films was observed to decrease from ~8 % (a/o) at the deposition temperature of 450 °C down to ~0.2 % (a/o) at 850 °C. The film density values increased from 3.53 to 5.02 g/cm3 as the deposition temperature was increased from 550 to 850 °C. The resistivity of the films was dependent on changes in deposition temperature and flow rate ratios. The lowest resistivity value of 86 µΩcm was measured for a deposition temperature of 600°C and an NH3/TiCl4 flow ratio of 10/1. The film stress was found to be tensile for all deposits and to decrease with higher deposition temperatures. Nanoindentation measurements yielded values for the hardness and Young\u27s modulus of the films to be around 15 and 250 GPa, respectively. X-ray diffraction measurements revealed in all cases the presence of cubic TiN phase with a preferred (200) orientation. For the investigated aspect ratios of up to 4: 1, the deposits were observed to exhibit conformal step coverage over the investigated range of processing conditions