Bias Enhanced Plasma CVD

Electron cyclotron resonance (ECR) is used to deposit c-BN layers. Yokohama et al. [220] considered a negative substrate bias as an essential parameter for the deposition in ECR plasma to accelerate the ions formed in the plasma. A linear coherence was found between the bias and the etching rate of c-BN and h-BN, which was higher for h-BN. Three points are important for the crystal growth  

Typical parameters are 0.5 Pa, plasma gas Ar/N2 mixtures, microwave power 1000 W, substrate temperature 250 °C, and boron precursor B2H6 [221]. 

A very intense inductively coupled plasma (ICP) could be created, using a 13.56-MHz RF-source and coupling the power through a quartz tube into the plasma. Working pressure was 2 x 10-2 mbar and the substrate could be heated up to 800 °C [222]. The precursor was trimethylborazine ((HBN-CH3)3), which was transported in a nitrogen/argon carrier gas. Similar to other deposition processes, prior to the c-BN nucleation an oriented h-BN layer was formed [223]. 

Plasma CVD has been used since the middle of the 1970s. For the creation of the plasma, DC glow discharge [224], RF glow discharge [219, 225-227], microwave plasma [228, 229], or plasma jets [230] are used. 

Under conditions similar to those used for the synthesis of diamond layers, only layers with a small amount of c-BN can be deposited. A lot of publications can be found about the deposition of c-BN with CVD methods, reporting different parameters that are necessary for the growth of c-BN. 

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