Sputtering boron carbides

Eckardt, T., Bewilogua, K., van der Kolk, G., Hurkmans, T., Trinh, T., Fleischer, W., Improving tribological properties of sputtered boron carbide coatings by process modifications. Surface and Coatings Technology, Vol 126 (2000), pp 69-75... 

The vaporization-cold-substrate condensation process of boron carbide melted by electron-gun heating and plasma torch deposition does not give a well-organized and crystalline B4C-type structure. In CH4 [1.33.10 Pa 1 torr)] an electron-gun evaporation of boron carbide contained in a graphite crucible, followed by a condensation on a water-cooled jacket, gives crystals. Sputtering by H is possible . 

For films sputter deposited from a boron carbide target, k markedly increased at A < 400 nm [55]. This indicates an effect of the incorporated carbon (5-10 at-%, see section 5.5.1) in the films. The cathodoluminescence behavior of hBN and cBN films was investigated by Taylor et al. [80] with respect to possible applications of the large band gap material BN in the deep blue and UV range. 

The resistivities of films sputter deposited with a boron carbide target were lower (10 -10 n cm). Comparing the results of lateral and sandwich measuring arrangements, no essential differences were found [55]. 

Boron carbide in air is immediately, i.e., within seconds, coated by a B2O3 layer, in presence of water by a hydroboric acid layer [172,229]. Oxidation starts at 500-600°C and accelerates significantly above 800-1000°C, depending on the humidity. The weight gain of boron carbide powder being surface-cleaned in glove boxes of 1 ppm O2 and 1 ppm H2O and subsequently Si-sputtered, Ar" " ion implanted, or... 

As a boron nitride film, a B-C-N passivation film can also be deposited by plasma-enhanced CVD in semiconductor devices [9], and hydrogenated boron nitride carbide films are applied for X-ray mask membranes. The radiofrequency (13.56 MHz) plasma-enhanced CVD process uses B2H6, CH4, and Ng or NH3 as source gases, or in a sputtering process with a boron target, CH4, N2, and Ar are used [10 to 18]. A B-C-N mixed phase can also be prepared by N" ion implantation into B4C at 100 keV [19]. 

The co-depositing material for reactive deposition can be from a second sputtering target. However, it is often in the form of a chemical vapor precursor, which is decomposed in a plasma and on the surface. Chemical vapor precursors are such materials as acetylene (C2H2) or methane (CH4) for carbon, silane (SiH4) for silicon, and diborane (B2H6) for boron. This technique is thus a combination of sputter deposition and PECVD and is used to deposit materials such as carbides, borides, and silicides. It should be noted that co-deposition does not necessarily mean reaction. For example, carbon can be deposited with titanium to give a mixture of Ti + C but the deposit may contain little TIC. 

---