Deposition. of Boron Thin Films by Pyrolysis of B₁₀H₁₄ in the Molecular Flow Region

Abstract

Boron thin films of 0.1-1.5 pm thickness have been prepared by the pyrolysis of the decaborane (B₁₀H₁₄) at the pressure of molecular flow region (≤10^-4 Torr) and the temperature ranged from 350°C to 1200°C. Sapphire and tantalum were used as the substrate at the temperatures above and below 700°C, respectively.
The crystal structure of the films were examined by means of X-ray and electron diffraction, and the results indicate that the films are amorphous.
The deposition rate of the boron films was proportionate to decaborane partial pressure. The deposition rate is given as a function of the substrate temperature Ts when T_s≤T^*=416°
D=3.65×10^-3·p·exp((E_r -E_d)(1/T_s-1/T^*)/R)(cm/s)
where P is the pressure of decaborane, R is the gas constant. The activation energies for condensation Er and decomposition Ed were found to be 1.1 kcal/mol and 40.1 kcal/mol, respectively. When T_s≤T^*, the deposition rate is dependent only on the condensation at the constant P and is given as
D=3.65 × 10^-3exp(E_r(1/T_s-1/T^*)/R)·P(cm/s)
It was also found that the decaborane was almost completely pyrolised at 416°C.