Chemical Vapor Deposition of Zirconium Compounds: A Review

Abstract

Coatings of zirconium compounds are used in a wide variety of fields, yet an understanding and descriptions of deposition mechanisms are scant in the public literature. The mechanisms of deposition for metallic zirconium, ZrC, ZrN, ZrO2, ZrB2, and zirconium silicides are discussed based on the direct vapor deposition research of those compounds where possible or compared to complementary titanium systems when direct research is lacking. Both inorganic and organometallic deposition systems are discussed. As a class of compounds, an understanding of the vapor deposition mechanisms can be significantly improved by investigations on metallic zirconium deposition by zirconium halides and hydrogen and by in situ analysis techniques such as Fourier-transform infrared (FTIR) spectroscopy or x-ray photoelectron spectroscopy (XPS).

Early events in the mechanism of single-source chemical vapor deposition of zirconium and hafnium diboride: a computational investigation

“…There is no obviously analogous Lewis base in the deposition mechanism, and therefore it does not necessarily follow that one reaction is representative of the other. Perhaps based on the scheme proposed by Gozum et al, it appears to have been generally assumed 8,45 that the first step of the deposition mechanism involves the dissociation of neutral borane from the M(BH 4 ) 4 complex such that a terminal hydride remains bound to the metal center (with the two BH 3 molecules presumably dimerizing into diborane in the reactor vessel). We observed the possibility of an alternative reaction between two BH 4…”

“…The diverging pathways after generation of Hf-2a agree roughly with the observation that higher reaction temperatures lead to films overstoichiometric in boron. 8,[23][24][25] The large clusters formed in the higher-energy pathway-more favorable at high temperatures-appear to connect this set of reactions with the generation of polyhedral boron clusters through Scheme 5 Proposed scheme of CVD reaction. 43 pyrolysis of diborane: B 3 H 9 has been postulated as an intermediate in the pyrolysis reactions that lead to decaborane (14).…”

“…5,6 TiB 2 and ZrB 2 have found applications in protective coatings for cutting tools, for similar reasons. 7,8 Thin films of these ceramics have also drawn interest as copper and gold diffusion barriers for microelectronics. [9][10][11] Chemical vapor deposition (CVD) has proved to be a powerful technique for generating such films.…”

“…[9][10][11] Chemical vapor deposition (CVD) has proved to be a powerful technique for generating such films. [12][13][14] Two processes dominate the chemical vapor deposition of group 4 transition metal diboride ceramics: independentprecursor systems centered around metal chlorides, 4,8,[15][16][17][18][19] and single-source systems involving metal borohydrides. [20][21][22][23][24][25][26][27][28][29] The single-source technique has significant advantages over the independent-precursor system.…”

“…4,[16][17][18][19]30 The films deposited from a single source are cleaner, free of halogen impurities. 8 While the kinetics of deposition have been studied extensively and this knowledge leveraged to tune the process, 14,22,29 the overall mechanism by which the ceramic is generated has not been elucidated. In this work, we present the results of a computational study of several group 4 metal-borohydride complexes and their reactivities.…”