Introducing gallium in silicon and thin film polysilicon using self assembled monolayer doping

Abstract

• Gallium compound synthesized to form Ga molecular monolayers on silicon surface. • Ga monolayer doping in silicon and thin film polysilicon demonstrated. • Junction depth of 200 nm with a dose 1.6*10 15 Ga atoms/cm 2 demonstrated in n -Si. • Near uniform doping in polysilicon films is achieved with 20% electrical activation. Monolayer Doping (MLD) is a technique involving the formation of a self-assembled dopant-containing layer on the substrate. The dopant is subsequently incorporated into the substrate by annealing, forming a diffused region. Following MLD, samples were capped with silicon dioxide and rapid thermal annealed (RTA). In this work, gallium doping using MLD has been demonstrated. Gallium containing compound Tris (2,4 pentanedionato) gallium(III) was synthesized, and shown to be suitable for monolayer doping silicon substrates and deposited thin film polysilicon. Secondary ion mass spectroscopy (SIMS) and spreading resistance probe (SRP) measurements were performed to determine the dopant profiles and dopant electrical activation. These results showed that a dose of 1.6*10 15 atoms/cm 2 was received, and the gallium dopant produced a 0.2 µm junction in n -type silicon. For polysilicon, the entire 0.4 μm film was evenly doped, with a concentration greater than 10 19 atoms/cm 3 throughout.