C-BN THIN-FILM FORMATION IN A HYBRID RF-PLD TECHNIQUE

A hybrid radio frequency-pulsed laser deposition (r.f.-PLD) technique was used to deposit BN thin films on Si(100) and Si(111) substrates. H exagonal boron nitride targets were ablated with excimer laser radiati on (lambda = 248 nm, tau = 25 ns) in an N-2/Ar processing gas atmosphe re. Additionally a radio frequency bias (v=13.56 Mhz, P=15-200 W) was capacitively coupled to the substrate, yielding an r.f glow discharge in the processing gas with formation of a d.c. bias voltage up to - 15 00 V, resulting in bombardment of the substrate with processing gas io ns. Langmuir single probe measurements revealed typical ion densities on the order of 10(15) m(-3). The c-BN content of the films as determi ned by FTIR-spectroscopy was up to 60% and depends strongly on the ion to-atom arrival ratio and therefore on the laser pulse repetition rat e and fluence, as well as on the argon-to-nitrogen ratio in the proces sing gas atmosphere. Raman spectroscopy was used to characterize the c rystallinity of the grown films. Most films adhered poorly to the subs trate, indicating the presence of high internal stresses. The formatio n of the c-BN phase is discussed in the light of the currently availab le models for c-BN deposition. (C) 1997 Elsevier Science S.A.