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 (Tdep) of 1200 to 2000°C and a total gas pressure (Ptot) of 5 to 60 torr. At aPtot of 5 torr, all the CVD-BN plates synthesized at eachTdep above 1300°C had a density greater than 2.O g cm−3, and thus showed no noticeable dependence onTdep. Over thePtot range from 10 to 60 torr. on the other hand, the density of the plates reached the maximum of 2.08g cm−3 at aTdep of 2000° C. AsTdep was lowered, the density decreased down to a minimum of 1.40 g cm−3 The deposition rate varied with bothTdep andPtot and showed a maximum value under a certainPtot at a givenTdep. The value ofPtot where the deposition rate becomes maximum changed depending on theTdep. 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.