Here we report the development of high purity boron thin film growth by low pressure chemical vapour deposition (LPCVD) from solid source precursors - 10-B and 11-B enriched decaborane (B10H14). This boron thin film synthesis was developed and examined for the conformal coating of high aspect-ratio silicon micro pillar structures for the fabrication of high efficiency neutron detectors. Thin boron films were deposited in a resistively heated horizontal tube reactor on silicon substrates with argon as a carrier gas and precursor flow rate controlled by a heated mass flow controller. The roughness, surface structures, and growth rates of the as-deposited films were studied as a function of the key CVD process parameters - growth temperatures, different argon flow rates and process pressures. The control of boron film growth rates were demonstrated to be from 100 to 500 nm/min with judicial choice of CVD parameters. X-ray diffraction analysis indicated that these boron films were amorphous. Force microscopy revealed the low surface roughness of 1.5-3.0 nm for as-deposited boron films. Field emission scanning electron microscopy revealed the very smooth surface of boron films. Conformal filling of 3:1 aspect ratio silicon-pillar structures with various CVD parameters will also be discussed.

This work was partly performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48, UCRL-ABS-223690.