Area-selective deposition and B δ-doping of Si(100) with BCl3
Abstract
B-doped δ-layers were fabricated in Si(100) using BCl3 as a dopant precursor in ultrahigh vacuum. BCl3 adsorbed readily at room temperature, as revealed by scanning tunneling microscopy (STM) imaging. Annealing at elevated temperatures facilitated B incorporation into the Si substrate. Secondary ion mass spectrometry (SIMS) depth profiling demonstrated a peak B concentration > 1.2(1) × 1021 cm-3 with a total areal dose of 1.85(1) × 1014 cm-2 resulting from a 30 L BCl3 dose at 150 C. Hall bar measurements of a similar sample were performed at 3.0 K revealing a sheet resistance of Rs = 1.91 k-1, a hole concentration of n = 1.90 × 1014 cm-2 and a hole mobility of μ = 38.0 cm2V-1s-1 without performing an incorporation anneal. Further, the conductivity of several B-doped δ-layers showed a log dependence on temperature suggestive of a two-dimensional system. Selective-area deposition of BCl3 was also demonstrated using both H- and Cl-based monatomic resists. In comparison to a dosed area on bare Si, adsorption selectivity ratios for H and Cl resists were determined by SIMS to be 310(10):1 and 1529(5):1, respectively, further validating the use of BCl3 as a dopant precursor for atomic precision fabrication of acceptor-doped devices in Si.