Titanium Diboride Thin Films by Low-Temperature Chemical Vapor Deposition from the Single Source Precursor Ti(BH₄)₃(1,2-dimethoxyethane)

Abstract

Titanium diboride is a technologically important refractory conductor with a melting point of 3220 °C, a high electrical conductivity, and good wear and corrosion resistance. Thin films of TiB 2 have been obtained at temperatures as low as 170 °C by thermal chemical vapor deposition from the halogen-free single-source precursor Ti(BH 4 ) 3 (CH 3 OCH 2 CH 2 OCH 3 ). Films deposited at temperatures below 200 °C are near stoichiometric, free of impurities, and amorphous as judged by X-ray diffraction. These films exhibit dense nucleation, including on SiO 2 substrates, and have root-mean-square roughness, as measured by atomic force microscopy, of less than 1 nm for films 5-60 nm thick. At growth temperatures between 200 and 600 °C, the films are still amorphous but contain 12-15 atomic % oxygen and 15-20 atomic % carbon; these impurities are incorporated at the expense of boron. For growth at 800 °C and above, the films are crystalline, stoichiometric, and free of impurities. These high-temperature films are oriented in a preferred fashion with respect to the substrate: on Si(100) the films have a (101) orientation when grown at 800 °C but a (001) orientation when the films are grown at 900 °C. An amorphous TiB 2 film, grown at 175 °C to a thickness of 7 nm, performs well as a diffusion barrier: no Cu diffuses across the TiB 2 after thermal annealing at 600 °C for 30 min.

Synthesis and crystal structures of two (cyclopentadienyl)titanium(III) hydroborate complexes, [Cp∗TiCl(BH4)]2 and Cp2Ti(B3H8)

“…We expected that treatment of the pentamethylcyclopentadienyl complex Cp * TiCl 3 with NaB 3 H 8 would afford a titanium B 3 H 8 complex, but instead yields the titanium(III) tetrahydroborate complex [Cp * TiCl(BH 4 )] 2 (1).…”

“…Volatile transition metal tetrahydroborate complexes, M(BH 4 ) x , are attractive CVD precursors for metal boride thin films, which are attracting interest as potential replacements for metal nitrides as copper diffusion barriers in integrated circuits [1][2][3][4][5][6][7][8]. Unfortunately, relatively few binary BH 4 compounds are known: for the d-block transition metals, the only known examples are Ti(BH 4 ) 3 [1], Zr(BH 4 ) 4 [2,3], and Hf(BH 4 ) 4 [4][5][6][7][8].…”

“…Unfortunately, relatively few binary BH 4 compounds are known: for the d-block transition metals, the only known examples are Ti(BH 4 ) 3 [1], Zr(BH 4 ) 4 [2,3], and Hf(BH 4 ) 4 [4][5][6][7][8]. The rarity of such compounds is in part a consequence of the small size and strong reducing power of the BH 4 ligand.…”

Highly conformal film growth by chemical vapor deposition. II. Conformality enhancement through growth inhibition

“…We will compare the model predictions with experimental results from our laboratory, namely, the growth of TiB 2 thin films from the single source precursor Ti͑BH 4 ͒ 3 ͑dme͒ ͑dme=1,2-dimethoxyethane͒ plus additional dme as the inhibitor. 11,12 Let us first consider the effect that a coreactant S ͑hereaf-ter referred to as the inhibitor͒ has on the growth rate of a single source precursor system. As shown in Part I, the simplest approximation is to assume that the precursor P reversibly adsorbs on the surface with a first order Langmuirian behavior, then either desorbs or undergoes an irreversible reaction to form film ͑M ͑s͒ ͒.…”

Titanium diboride thin films produced by dc-magnetron sputtering: Structural and mechanical properties

“…Due to these properties, TiB 2 films have been considered as protective coatings for several applications, including wear and corrosion protection of magnetic recording media and cutting tools [2,3]. Titanium diboride thin films were obtained by various techniques, such as reactive sputtering [4], plasma enhanced CVD [5], ion beam sputtering [6], pulsed laser deposition [7,8] and rf-and dc-magnetron sputtering [9][10][11][12][13][14]. Among these techniques, dc-magnetron sputtering appears to be the most appropriate method for protective coatings applications due to the low deposition temperature, the possibility of using substrates with complicated geometries and the relatively high deposition rate without the use of poison gases.…”