DENSITY AND DEPOSITION RATE OF CHEMICAL-VAPOR-DEPOSITED BORON-NITRIDE

A study was made on the density and deposition rate characteristics of chemical vapour deposited boron nitride (CVD-BN) plates synthesized by use of the BCl//3-NH//3-H//2 system at a deposition temperature (T//d//e//p) of 1200 to 2000 degree C and a total gas pressure (P//t//o//t) of 5 to 60 torr. At a P//t//o//t of 5 torr, all the CVD-BN plates synthesized at each T//d//e//p above 1300 degree C had a density greater than 2. 0 g cm** minus **3 and showed no noticeable dependence on T//d//e//p. Over the P//t//o//t range from 10 to 60 torr, the density reached a maximum of 2. 08 g cm** minus **3 at a T//d//e//p of 2000 degree C. As T//d//e//p was lowered, density decreased to a minimum of 1. 40 g cm** minus **3. The deposition rate varied with both T//d//e//p and P//t//o//t and showed a maximum value under a certain P//t//o//t at a given T//d//e//p. The value of P//t//o//t where the deposition rate becomes maximum changed depending on the T//d//e//p. The maximum deposition rate was 0. 6 mm h** minus **1 for the CVD-BN plates when the density was less than 2. 0 g cm** minus **3 and 0. 4 mm h** minus **1 when the density was above 2. 0 g cm** minus **3. The effects of deposition conditions on the characteristics of density and deposition rate are discussed in terms of the structure and deposition mechanism.