Optical properties of boron carbide (B5C) thin films fabricated by plasma-enhanced chemical-vapor deposition

Abstract

Ianno, N.J.; Snyder, P.G.; Welipitiya, D.; Byun, D.; and Dowben, Peter A., "Optical properties of boron carbide (B 5 C) thin films fabricated by plasma-enhanced chemical-vapor deposition" (1996) ͑Received 7 September 1995; accepted for publication 11 January 1996͒Variable angle of incidence spectroscopic ellipsometry was used to determine the optical constants near the band edge of boron carbide ͑B 5 C͒ thin films deposited on glass and n-type Si͑111͒ via plasma-enhanced chemical-vapor deposition. The index of refraction n, the extinction coefficient k, and the absorption coefficient are reported in the photon energy spectrum between 1.24 and 4 eV. Ellipsometry analysis of B 5 C films on silicon indicates a graded material, while the optical constants of B 5 C on glass are homogeneous. Line shape analyses of absorption data for the films on glass indicate an indirect transition at approximately 0.75 eV and a direct transition at about 1.5 eV.

The incorporation of Nickel and Phosphorus dopants into Boron-Carbon alloy thin films

“…From the standard Tauc plot [42], the band gap has been determined to be 2.6eV. This value is more consistent with the band gap of B 12 P [43] than for undoped PECVDgrown B 5 C which has a band gap of typically between 0.7 and 0.9eV [1,2]. In contrast to the single-crystal material, the concentration of phosphorus in the B 5 C alloy is 3%.…”

“…Infrared absorption spectra have been obtained for undoped, Ni-doped, and phosphorus-doped boron-carbon alloys. The experimental details have been discussed in greater depth elsewhere [2].…”

“…Like boron carbide, the boron-carbon alloys are refractory materials with melting temperatures in excess of 2400 °C. These alloys typically have band gaps in excess of 0.7eV [1,2] and low numbers of free carriers [1].…”

Annealing effects on the optical properties of semiconducting boron carbide

“…The as-deposited parameter 1ϱ is in very good agreement with average n data within the visible to ultraviolet transparency region, obtained by SE investigations. 26 Here, the results lead to the conclusion that annealing increased the average band gap index of refraction value by ϳ18%.…”

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

“…456,457 These compounds are structurally distinct from B 2 O 3 , BN, and BCN where B is incorporated in either trigonal/sp 2 or tetrahedral/sp 3 linkages with O, N and C. 458 Due to the strong covalent bonding forming the B 12 icosahedra, B 4 C and BO x materials exhibit extremely high values of Young's modulus (>300 GPa) and hardness (>30 GPa) with relatively low values of dielectric constant (≤5). 454,455,459 PECVD a-B 4-5 C:H films have been reported with even lower optical dielectric constants (3-4), 460 and still compelling hardness and mass density values of ∼ 8 GPa 461 and 1.5-1.8 g/cm 3 , 462 respectively. These values are extremely compelling for low-k DB applications, and further optimization of a-B x C:H materials for low-k applications can be anticipated due to the ability of the B 12 icosahedra to arrange themselves in many different distorted arrangements 463 similar to SiO 4 tetrahedra in SiO 2 and low-k a-SiOC:H materials.…”