Mass and energy measurements of the species responsible for cBN growth in rf bias sputter conditions

Abstract

Mass and energy measurements of ions and neutrals impinging on a substrate surface were performed during radio frequency (rf) bias sputter deposition of cubic boron nitride (cBN) thin films in a pure Ar discharge. The sampling system was rf driven to measure the correct energy of ions impinging to the rf driven substrate. The ion energy distributions showed asymmetric bimodal shapes and the energy spreads varied with the masses of ions and the negative substrate bias voltage (Vs). Ar+ was the most dominant ion, and the average energy and energy spread changed with Vs from 90 to 310 eV and from 40 to 140 eV, respectively. The flux ratio of Ar+ to B (Φi/ΦB) increased from 1.0 to 2.3 with a decrease in the target power input. cBN could be deposited above a threshold of the total momentum transfer per depositing boron atoms; 138 (eV amu)1/2, which is comparable to the values reported in the ion beam assisted depositions. Therefore, argon ions with an energy of 135 to 380 eV are considered to be equally contributory for cBN formation. Moreover, nucleation of cBN depends on Φi/ΦB, namely, the flux ratio of ion to boron, and requires accumulation of a certain surface state caused by ion bombardment effects, such as defects generation or densification.

Nanohardness and chemical bonding of boron nitride films

“…[4][5] Recently, similar findings requiring defect generation are found in the mass and energy measurement of species responsible for cBN growth in rf bias sputter conditions. [29][30] V. SUMMARY Boron, BN, and layered B/BN films are sputter deposited from pure boron targets at low tempertaure onto Ni-coated Si substrates. For the set of deposition conditions examined, the films are found to be composed of a mixture of amorphous boron and a defected hexagonal phase as characterized using NEXAFS.…”

Ion Bombardment Effects on Boron Nitride Film Synthesis by Reactive Sputtering with Electron Cyclotron Resonance Plasmas

“…Similar results that the threshold momentum shows substantial deviation from Kester and Messier's case in a high ion flux region are also reported by some other researchers. 12,25) Although various models are proposed as mentioned above, an established model for c-BN synthesis does not exist even today. More theoretical analysis and experimental data are needed to judge which model is the most appropriate.…”