Molecular Layer Doping: Non-destructive doping of silicon and germanium

Abstract

Access to the full text of the published version may require a subscription. Abstract -This work describes a non-destructive method to introduce impurity atoms into silicon (Si) and germanium (Ge) using Molecular Layer Doping (MLD). Molecules containing dopant atoms (arsenic) were designed, synthesized and chemically bound in self-limiting monolayers to the semiconductor surface. Subsequent annealing enabled diffusion of the dopant atom into the substrate. Material characterization included assessment of surface analysis (AFM) and impurity and carrier concentrations (ECV). Record carrier concentration levels of arsenic (As) in Si (~5×10 20 atoms/cm 3 ) by diffusion doping have been achieved, and to the best of our knowledge this work is the first demonstration of doping Ge by MLD. Furthermore due to the ever increasing surface to bulk ratio of future devices (FinFets, MugFETs, nanowire-FETS) surface packing spacing requirements of MLD dopant molecules is becoming more relaxed. It is estimated that a molecular spacing of 2 nm and 3 nm is required to achieve doping concentration of 10 20 atoms/cm 3 in a 5 nm wide fin and 5 nm diameter nanowire respectively. From a molecular perspective this is readily achievable. Rights

Chemical approaches for doping nanodevice architectures

“…Inset shows roughness measurements as obtained by atomic force microscopy (AFM). Duffy and co-workers built on the work carried out by Long et al [45] by using an MOVPE-based process to deposit monolayers of P and As on Ge substrates and nanowire devices. [46] Figure 14 (a) shows chemical concentration vs. depth profiles as extracted from SIMS analysis on samples with deposited AsH3.…”

“…Nevertheless, Long et al recently published a study on As-MLD of Ge. [45] The molecule previously utilised by O'Connell and co-workers [40] was used but was dissolved in IPA as opposed to mesitylene. As the hydrogermylation temperature of 200 ο C greatly exceeds the decomposition temperature of the TAA molecule, UV-initiated hydrogermylation was used.…”

State of the Art and Future Perspectives in Advanced CMOS Technology

“…SPD could be carried out in several ways. For three-dimension structures, mono-layer-doping (MLD) is believed to be one of the most promising candidates [ 127 , 128 , 129 ]. The process starts from a self-assembled monolayer formation which is mainly composed of organic dopant.…”

Miniaturization of CMOS

“…This doping method is dominated by a surface chemical reaction between the semiconductor substrate and dopant-containing organic molecules [67,68,69,70,71]. Compared to conventional implantation, MLD introduces fewer defects into the substrates [72,73,74,75] and the dopant-containing molecules could attach uniformly on the surface, which results in a better conformal doping profile [73].…”

“…The solution aqueous HF or NH 4 F was first used to remove the native oxide on the surface and to obtain a hydrogen-terminated surface. Later, the substrate will be immersed into dopants containing liquids or solution of organic materials [70,71,72,73,74,75]. The organic material could be dopant atoms contained in alkene or alkyne.…”