Synthesis and characterization of Pδ-layer in SiO₂by monolayer doping

Abstract

Achieving the required control of dopant distribution and selectivity for nanostructured semiconducting building block is a key issue for a large variety of applications. A promising strategy is monolayer doping (MLD), which consists in the creation of a well-ordered monolayer of dopant-containing molecules bonded to the surface of the substrate. In this work, we synthesize a P δ-layer embedded in a SiO2 matrix by MLD. Using a multi-technique approach based on time of flight secondary ion mass spectrometry (ToF-SIMS) and Rutherford backscattering spectrometry (RBS) analyses, we characterize the tuning of P dose as a function of the processing time and temperature. We found the proper conditions for a full grafting of the molecules, reaching a maximal dose of 8.3 × 10(14) atoms/cm(2). Moreover, using 1D rate equation model, we model P diffusion in SiO2 after annealing and we extract a P diffusivity in SiO2 of 1.5 × 10(17) cm(2) s(-1).

Control of Doping Level in Semiconductors via Self-Limited Grafting of Phosphorus End-Terminated Polymers

“…Actually surface density of dopant-containing molecules in MLD is intrinsically limited by steric hindrance effects and availability of reactive sites on the pristine surface. For P-containing molecules, a maximum areal dose of ∼8 × 10 14 atoms/cm 2 was reported. , This value is close to the maximum number of P impurities that can be accommodated on silicon surfaces considering the density of available reactive sites. , Slightly lower areal doses of dopant impurities were obtained using bulkier dopant-containing molecules with different chemical composition due to steric hindrance effects . However, optimization of the grafting process is required for each specific dopant-containing molecule to account for its thermal stability and specific chemical interaction with the target substrate.…”

Deep level transient spectroscopic investigation of phosphorus-doped silicon by self-assembled molecular monolayers

“…In this technique, dopant-carrying molecules are first covalently immobilized on the semiconductor surface via surface reactions. Due to surface self-limiting property, the areal dose of dopant molecules can be modulated by varying reaction temperature 6 , reaction time 6 , molecule size 7 , and the composition of the molecules 8 , 9 . Subsequently, the dopants are driven into the semiconductor bulk and activated by thermal annealing.…”

Phosphorus monolayer doping (MLD) of silicon on insulator (SOI) substrates

“…In the case of silicon doping the most prominent issue is the silicon oxide formation at the surface. Phosphorus diffuses through silicon oxide significantly slower than through silicon [16–17]. Although it has been shown that hydrogen-terminated silicon re-oxidizes relatively slowly when stored at room temperature in air [3], the elevated temperatures required for MLD processing carried out in the liquid phase enhances this re-oxidation.…”