Conformal filling of silicon micropillar platform with ¹⁰boron

A recently proposed micropillar semiconductor platform filled with a high volume of isotopic b 10 oron (B 10) has great potential to yield efficient thermal neutron detectors because B 10 has a high thermal neutron cross section. Here, the authors report the development of conformal filling of high aspect ratio silicon micropillar platforms with B 10 by low pressure chemical vapor deposition (LPCVD) using B 10 -enriched decaborane (B10 H14). The relationships between the pillar structure and the key process parameters including reaction temperature, process pressure, and buffer gas flow rates were investigated to optimize the conformal filling on these structures. Reaction temperature of 420-530 °C, process pressure of 50-450 mTorr, 0.3 SCCM (SCCM denotes cubic centimeter per minute at STP) B10 H14 flow rate, and argon buffer gas flow rate of 0-200 SCCM were used to deposit B 10 materials into the micropillar structures with aspect ratios of 3:1, 6:1, and 10:1. All three mentioned pillar structures were found to be completely (∼100%) filled with B 10 at 420 °C and 50 mTorr. At higher process temperatures, the fill factors of the three pillar structures decreased significantly. The effect of reaction temperature, process pressure, and buffer gas flow rates on the LPCVD deposition mechanism with respect to the structure geometry are also discussed.