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

Abstract

This paper details the application of phosphorus monolayer doping of silicon on insulator substrates. There have been no previous publications dedicated to the topic of MLD on SOI, which allows for the impact of reduced substrate dimensions to be probed. The doping was done through functionalization of the substrates with chemically bound allyldiphenylphosphine dopant molecules. Following functionalization, the samples were capped and annealed to enable the diffusion of dopant atoms into the substrate and their activation. Electrical and material characterisation was carried out to determine the impact of MLD on surface quality and activation results produced by the process. MLD has proven to be highly applicable to SOI substrates producing doping levels in excess of 1 × 1019 cm−3 with minimal impact on surface quality. Hall effect data proved that reducing SOI dimensions from 66 to 13 nm lead to an increase in carrier concentration values due to the reduced volume available to the dopant for diffusion. Dopant trapping was found at both Si–SiO2 interfaces and will be problematic when attempting to reach doping levels achieved by rival techniques.

Exploring conductivity in ex-situ doped Si thin films as thickness approaches 5 nm

“…Dopant impurities were then introduced to the samples via one of the three following methods; liquid/vapor-source monolayer doping (MLD) of phosphorus, 15 gas-source in-diffusion of arsenic, 17 or beam-line ion implantation of phosphorus. MLD of phosphorus: 15 All chemicals purchased from Sigma-Aldrich were of reagent grade and used as received. The SOI samples were initially sonicated in Milli-Q deionized water for 10 min and dried under a stream of nitrogen gas to remove any debris from the laser dicing process.…”

“…This protective cap was removed after the annealing process. 15 In order to evaluate dopant incorporation, a nominally undoped bulk Si sample was included alongside the SOI samples for each doping method. These bulk samples were used to determine the active doping concentration vs Si depth using electrochemical capacitance voltage (ECV) measurements.…”

“…It is the aim of this work to systematically apply three different ex situ doping techniques to SOI samples with thicknesses ranging from 3 nm to 66 nm. These doping techniques are based on ion implant, 14 liquid/vapor-source in-diffusion, 15,16 and gassource in-diffusion 17 and are verified on bulk Si samples in parallel. Conductivity is primarily determined by electrical testing of transfer length method structures and verified by a micro-four-point probe (μ4PP).…”

Development of metal-free layered semiconductors for 2D organic field-effect transistors

“…In silicon, for example, heteroatoms are incorporated into the bulk lattice, which is typically referred to as ''impurity doping''. [28][29][30][31] Impurity doping of graphene was initially conducted in order to obtain a 2D semiconductor. However, the doping concentration needs to be high and homogeneous enough over the dimensions of the device that no pristine channels of the initial semimetallic material remain.…”

DNA‐Based Strategies for Site‐Specific Doping

“…This monolayer doping approach can produce ultra-shallow junction depth of a few nanometers and is suitable for large-volume production. [15][16][17] However, this approach still requires a litho graphy step to define the area to be doped and the dopant dosage cannot be spatially varied within one doping step.…”