Area-selective deposition and B $\delta$-doping of Si(100) with BCl${}_3$

Abstract

B-doped $\delta$-layers were fabricated in Si(100) using BCl${}_3$ as a dopant precursor in ultrahigh vacuum. BCl${}_3$ 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) $\times$ 10${}^{21}$ cm${}^{-3}$ with a total areal dose of 1.85(1) $\times$ 10${}^{14}$ cm${}^{-2}$ resulting from a 30 L BCl${}_3$ dose at 150 ${}^{\circ }$C. Hall bar measurements of a similar sample were performed at 3.0 K revealing a sheet resistance of $R_{\mathrm{s}}$ = 1.91 k$\Omega {\square }^{-1}$, a hole concentration of $n$ = 1.90 $\times$ 10${}^{14}$ cm${}^{-2}$ and a hole mobility of $\mu$ = 38.0 cm${}^2$V${}^{-1}$s${}^{-1}$ without performing an incorporation anneal. Further, the conductivity of several B-doped $\delta$-layers showed a log dependence on temperature suggestive of a two-dimensional system. Selective-area deposition of BCl${}_3$ 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 BCl${}_3$ as a dopant precursor for atomic precision fabrication of acceptor-doped devices in Si.