An Investigation of MPCVD Synthesis of Boron-rich BN*

Boron-rich Boron Nitride (BN) is a material with high hardness that has often been synthesized by methods that involve high pressure and high temperature. Microwave Plasma Chemical Vapor Deposition (MPCVD) was utilized to nitride a deposited Boron layer on a Silicon substrate using Hydrogen (𝐻2), Diborane (𝐵2𝐻6), and Ammonia (𝑁𝐻3) at pressure and power of 60 Torr and 800 W respectively. By analyzing the Optical Emission Spectra of the process at fixed conditions, it is found that a low flow rate of Ammonia (≤1 𝑠𝑐𝑐𝑚 𝑁𝐻3), along with a high flow rate of Diborane (≥2 𝑠𝑐𝑐𝑚 𝐵2𝐻6), would be helpful in synthesizing Boron-rich thin films. Characterization of different films synthesized found a maximum hardness of 25 GPa from nanoindentation and similar patterns in the substrate shown by optical microscopy, AFM, and SEM. By utilizing OES and characterization results, conditions for Boron-rich BN have been investigated. It is suggest that a five stage process to deposit the Boron layer and nitride it to complete the deposition of BN would be the most effective to maximize the B/N ratio at a starting temperature of 1250° C.