Ion-assisted pulsed laser deposition of cubic BN films on Si (001) substrates

Abstract

We report on oriented and adherent cubic BN films grown on (001) faces of silicon using the method of ion-assisted pulsed laser deposition. The structure of the films is cubic zinc-blende with a lattice constant of 3.62 A, as determined by infrared absorption and transmission electron microscopy. The films were found to be poly crystalline, and oriented with the cubic BN [110] axis parallel to the Si [001] direction.In this work we report the successful growth of oriented, adherent, cubic BN films. The films were grown on (001) faces of silicon using the method of ionassisted pulsed-excimer-laser deposition. BN crystallizes into at least three stable phases. The hexagonal form is an insulating, structural analog to graphite with a band gap of ~5 eV. The properties of the wurtzite form are not well documented, but the structure is analogous to hexagonal diamond (or lonsdaleite). The cubic form of BN is structurally and physically similar to diamond. Cubic BN is of interest for its potential as a hightemperature, radiation hard semiconductor, and as an efficient heat-dissipating semiconductor substrate. Since the physical properties of cubic BN are so similar to diamond, and cubic BN can be easily doped both n-and j^-type, it enjoys an advantage over diamond for many semiconductor device applications.Recently, we reported 1 the growth of epitaxial cubic BN films on (001) silicon by pulsed excimer laser deposition. These films were later found to exhibit an epitaxial crystalline-to-amorphous phase transition when the thickness exceeded a critical value of ~200 A. 2 Crystalline-to-amorphous phase transitions have been observed in other epitaxial systems when the growth temperature is well below the melting temperature of the material or when the composition of the material deviates sufficiently from stoichiometry. 3 In our previous studies, 2 -4 we deposited films of BN using a KrF excimer laser. This produces a 248-nm laser line, which is nearly coincident with the optical band gap of the hexagonal BN targets. Auger electron spectroscopy and electron-probe microanalysis of the films indicated that they are compositionally homogeneous throughout the bulk, but tend to be nitrogen deficient.Based on the observation of the epitaxial crystallineto-amorphous phase transition and the nitrogen deficiency of those films, we decided to employ a Kaufman-type ion source to deliver nitrogen ions to the substrate during the laser deposition. In an ionassisted process, broad-beam ion sources are known to improve adhesion of the films to the substrate and increase the density of nucleation sites. The ion beam also tends to reduce the tensile stress in the growing films (presumably via more favorable growth kinetics). A preferred crystal orientation is sometimes established, stronger chemical bonds are often realized, and improved nitride stoichiometries are observed. 5 References that describe the use of ion-assisted techniques to grow cubic BN films can be found in the review by Arya and D'Amico. 6 Generally, BN films grown by io...

Energetics of carbon and oxygen impurities and their interaction with vacancies in cubic boron nitride

“…Recently, considerable efforts have been made in the synthesis of c-BN thin films using a variety of ion-beam-assisted processes [3][4][5][6][7][8][9][10] and several plasma-, ion-, and laser-assisted chemical vapor deposition methods. [11][12][13] These investigations have established that the c-BN formation requires an initial sp 2 -bonded boron nitride layer ͑amorphous and tur-bostratic͒ grown onto the substrate surface.…”

X-ray Absorption Study of Pulsed Laser Deposited Boron Nitride Films

“…The three BN films used in this study were produced by ion-assisted pulsed laser deposition onto heated silicon substrates, as detailed previously. [6] Deposition conditions are summarized in Table 1. Infrared transmission measurements (not shown) on these films revealed absorption at wavelengths characteristic of both the cubic and hexagonal phases, allowing an estimate of their volume fraction.…”

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

“…4) c-BN is attractive to researchers both scientifically and technologically because of its unique features. Since the early 1960's when c-BN was first synthesized by a highpressure and high-temperature method, 5) diverse works have been carried out to synthesize c-BN in the thin-film form using the techniques of ion plating, 6) ion beam assisted deposition (IBAD), 7,8) ion assisted laser ablation, 9,10) magnetron sputtering 11,12) and plasma enhanced chemical vapour deposition (PCVD). 13,14) In almost all references reporting the successful synthesis of a c-BN film, it is found that energetic sure of 1 × 10 −6 Torr by a turbomolecular pump (TMP), then filled with a mixture of Ar and N 2 gases to a working pressure of 4.0 × 10 −3 Torr.…”