Development of cubic Boron Nitride (cBN) Thin Film Formation Process by Pulsed Laser Ablation

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A method of synthesizing cubic boron nitride (cBN) films using pulsed Nd : YAG (532nm) and KrF (248nm) laser ablation is investigated. BN films are deposited on silicon (100) substrates. The laser beam is focused on the hexagonal BN targets. The composition of the BN film depends on the nitrogen gas pressure. The stoichiometric BN films are obtained under the conditions ; a laser fluence of 3.8 J/cm^2 and the substrate temperature of 650ﾟC and the nitrogen gas pressure of 10.0Pa. Argon gas is mixed with the reactant nitrogen gas and an RF power is applied to the substrate in order to generate a negative DC self-bias and enhance the synthesis of cBN phase for the first time. FT-IR absorption spectroscopy shows that the argon ion bombardment by RF bias plays an important role in the formation of cBN films. Measurements of the optical emission spectrum are performed to estimate the processing plasma state. Auger Electron Spectroscopy shows that the N/B composition ratio depends on the mixture ratio of nitrogen and the reactive emission intensity of B^+ (345.1nm). The surface morphology of the films prepared by the 532 nm laser is rough with lager particulates, whereas much smoother surfaces with fewer and smaller particulates, are obtained with the 248 nm laser. We also prepared tungsten carbide (WC) and carbon nitride (CN) films by pulsed laser ablation method.