Low‐Temperature PureB CVD Technology for CMOS Compatible Photodetectors

In this chapter, a new technology for low‐temperature (LT, 400°C) boron deposition is developed, which provides a smooth, uniform, closed LT boron layer. This technology is successfully employed to create near‐ideal LT PureB (pure boron) diodes with low, deep junction‐like saturation currents, allowing full integration of LT PureB photodiodes with electronic interface circuits and other sensors on a single chip. In this way, smart‐sensor systems or even charge‐coupled device (CCD) or complementary metal oxide semiconductor (CMOS) ultraviolet (UV) imagers can be realised

Author Correction: A doping-less junction-formation mechanism between n-silicon and an atomically thin boron layer

Electronic InstrumentationQN/High Resolution Electron Microscop

Mechanism of Electronegativity Heterojunction of Nanometer Amorphous-Boron on Crystalline Silicon: An Overview

© 2021 by the authors. The discovery of the extremely shallow amorphous boron-crystalline silicon heterojunction occurred during the development of highly sensitive, hard and robust detectors for low-penetration-depth ionizing radiation, such as ultraviolet photons and low-energy electrons (below 1 keV). For many years it was believed that the junction created by the chemical vapor deposition of amorphous boron on n-type crystalline silicon was a shallow p-n junction, although experimental results could not provide evidence for such a conclusion. Only recently, quantum-mechanics based modelling revealed the unique nature and the formation mechanism of this new junction. Here, we review the initiation and the history of understanding the a-B/c-Si interface (henceforth called the “boron-silicon junction”), as well as its importance for the microelectronics industry, followed by the scientific perception of the new junctions. Future developments and possible research directions are also discussed

Stability, local structure and electronic properties of borane radicals on the Si(1 0 0)

Deposition of a thin B layer via decomposition of B2H6 on Si (PureB process) produces B-Si junctions which exhibit unique electronic and optical properties. Here we present the results of our systematic first-principles study of BHn (n = 0–3) radicals on Si(1 0 0)2 × 1:H surfaces, the initial stage of the PureB process. The calculations reveal an unexpectedly high stability of BH2 and BH3 radicals on the surface and a plausible atomic exchange mechanism of surface Si atoms with B atoms from absorbed BHn radicals. The calculations show strong local structural relaxation and reconstructions, as well as strong chemical bonding between the surface Si and the BHn radicals. Electronic structure calculations show various defect states in the energy gap of Si due to the BHn absorption. These results shed light on the initial stages of the complicated PureB process and also rationalize the unusual electronic, optical and electrical properties of the deposited Si surfaces

Lateral gas phase diffusion length of boron atoms over Si/B surfaces during CVD of pure boron layers

The lateral gas phase diffusion length of boron atoms, LB, along silicon and boron surfaces during chemical vapor deposition(CVD) using diborane (B2H6) is reported. The value of LB is critical for reliable and uniform boron layer coverage. The presented information was obtained experimentally and confirmed analytically in the borondepositiontemperature range from 700 °C down to 400 °C. For this temperature range the local loading effect of the borondeposition is investigated on the micro scale. A LB = 2.2 mm was determined for borondeposition at 700 °C, while a LB of less than 1 mm was observed at temperatures lower than 500 °C.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

A doping-less junction-formation mechanism between n-silicon and an atomically thin boron layer

An Author Correction to this article was published on 12 October 2021. Available at: https://doi.org/10.1038/s41598-017-13100-0.Copyright © 2017 The Author(s). The interest in nanostructures of silicon and its dopants has significantly increased. We report the creation of an ultimately-shallow junction at the surface of n-type silicon with excellent electrical and optical characteristics made by depositing an atomically thin boron layer at a relatively low temperature where no doping of silicon is expected. The presented experimental results and simulations of the ab initio quantum mechanics molecular dynamics prove that the structure of this new type of junction differs from all other known rectifying junctions at this time. An analysis of the junction formation has led to the conclusion that the chemical interaction between the surface atoms of crystalline silicon and the first atomic layer of the as-deposited amorphous boron is the dominant factor leading to the formation of a depletion zone in the crystalline silicon which originates from the surface. The simulation results show a very strong electric field across the c-Si/a-B interface systems where the charge transfer occurs mainly from the interface Si atoms to the neighboring B atoms. This electric field appears to be responsible for the creation of a depletion zone in the n-silicon resulting in a rectifying junction formation between the n-silicon and the atomically thin boron layer

Humidity Sensitivity and Coil Design of a High-Precision Eddy-Current Displacement Sensor

Unlike capacitive displacement sensors, Eddy-Current Displacement Sensors (ECDSs) possess an inherently low sensitivity to environmental conditions, such as the humidity of the ambient air. By elevating the excitation frequency it is possible to mitigate their major limitations regarding stability and resolution, making them of interest for high-precision displacement sensing. However, by increasing the excitation frequency, ECDSs become less immune to environmental conditions, due to the inevitable parasitic capacitance of the sensing coil. In this work, we formulate a requirement for the minimum Self-Resonance Frequency (SRF) of the coil, based on the specified humidity variation and the allowable displacement error. This requirement provides an input for the design of the high-precision ECDS probe

A Novel Interface for Eddy Current Displacement Sensors

In this paper, we propose a novel interface concept for eddy current displacement sensors. A measurement method and a new front-end circuit are also proposed. The front-end circuit demonstrates excellent thermal stability, high resolution, and low-power consumption. The proposed idea is analytically investigated. The demodulation principle, as well as the interface implementation, is also addressed. This interface is being introduced for measuring submicrometer displacements in medium- to high-resolution applications. The interface system consumes less than 12 mW and has an extremely low thermal drift. The interface circuit will be implemented as a system-in-a-package (SIP). The full-scale range of displacement is 1 mm with 50-kHz signal bandwidth and 11-bit resolution (less than 500 nm). The signal conditioning circuit utilizes a standard 0.35- mum complementary metal-oxide semiconductor (CMOS) technology. Simulation results, which were achieved on the basis of experimental results of testing a prototype coil, also confirm the high performance of the interface system, as expected from analytical results. Compared with previous reports, this low-power interface system demonstrates a much lower temperature drift.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc

Stability, geometry and electronic properties of BH_n (n = 0 to 3) radicals on the Si{0 0 1}3×1:H surface from first-principles

A new generation of radiation detectors relies on the crystalline Si and amorphous B (c-Si/a-B) junctions that are prepared through chemical vapor deposition of diborane (B2H6) on Si at low temperature (∼400 C). The Si wafer surface is dominated by the Si{0 0 1}3 1 domains that consist of two different Si species at low temperature. Here we investigate the geometry, stability and electronic properties of the hydrogen passivated Si{0 0 1}3 1 surfaces with deposited BHn (n = 0 to 3) radicals using parameter-free first-principles approaches. Ab initio molecular dynamics simulations using the density functional theory (DFT) including van der Waals interaction reveal that in the initial stage the BH3 molecules/radicals deposit on the Si(-H), forming (-Si)BH4 radicals which then decompose into (-Si)BH2 with release of H2 molecules. Structural optimizations provide strong local relaxation and reconstructions at the deposited Si surface. Electronic structure calculations reveal the formation of various defect states in the forbidden gap. This indicates limitations of the presently used rigid electron-counting and band-filling models. The attained information enhances our understanding of the initial stage of the PureB process and the electric properties of the products.Electronic Instrumentation(OLD) MSE-