Density and deposition rate of chemical-vapour-deposited boron nitride

Abstract

A study is made on the density and deposition rate characteristics of chemical-vapour-deposited boron nitride (CVD-BN) plates synthesized by use of the BCl₃-NH₃-H₂ system at a deposition temperature (T _dep) of 1200 to 2000°C and a total gas pressure (P _tot) of 5 to 60 torr. At aP _tot of 5 torr, all the CVD-BN plates synthesized at eachT _dep above 1300°C had a density greater than 2.O g cm⁻³, and thus showed no noticeable dependence onT _dep. Over theP _tot range from 10 to 60 torr. on the other hand, the density of the plates reached the maximum of 2.08g cm⁻³ at aT _dep of 2000° C. AsT _dep was lowered, the density decreased down to a minimum of 1.40 g cm⁻³ The deposition rate varied with bothT _dep andP _tot and showed a maximum value under a certainP _tot at a givenT _dep. The value ofP _tot where the deposition rate becomes maximum changed depending on theT _dep. The maximum deposition rate was 0.6 mm h⁻¹ for the CVD-BN plates when the density was less than 2.0 g cm⁻³, and 0.4 mm h⁻¹ when the density was above 2.0 g cm⁻³ The effects of deposition conditions on the characteristics of density and deposition rate are discussed in terms of the structure and deposition mechanism.