Yemin Dong

A comprehensive study of reducing the STI mechanical stress effect on channel-width-dependent Idsat

In this paper, the complex behavior of saturation drain current (Idsat) dependence on channel width was investigated. We compared two types of devices and concluded that the variation of Idsat with changing width is determined by both the y-direction shallow trench isolation mechanical stress (y-stress) effect and the delta width effect. Moreover, a semi-empirical formula was proposed to describe the Idsat dependence on channel width, taking into account these two effects. To reduce the STI stress, we examined several process steps that may contribute to the stress development, and found that a high temperature post-liner-anneal step can obviously reduce the stress effect.

Patterned buried oxide layers under a single MOSFET to improve the device performance

A novel quasi-silicon-on-insulator (Q-SOI) metal-oxide-semiconductor field-effect transistor (MOSFET) has been successfully fabricated, where the drain and source regions were positioned on the patterned buried oxide (BOX) layers while the channel region was left connected to the substrate. The high-quality BOX layers patterned under a single MOSFET were formed by the masked separation by implantation of oxygen technique. The electrical and thermal properties of such a novel Q-SOI device were investigated and the results demonstrated that this Q-SOI device has improved performances over the SOI counterpart because of suppression of the floating-body and self-heating effects.

Room-temperature visible electroluminescence of Al-doped silicon oxide films

A series of Al-doped amorphous silicon oxide films have been grown on p-type silicon (100) substrates by a dual ion beam cosputtering method. Visible electroluminescence (EL) from the devices, made by films with different contents of Al, can be seen with the naked eye under forward bias and reverse bias for films containing sufficient amounts of Al. The EL spectra are found to have a luminescence band peaked at 510 nm (2.4 eV), which is the same result as that obtained from silicon oxide films. With the increase in the amounts of Al, the peak position does not shift, the onset of the bias decreases, and the intensity of EL peak increases. Experiment results show that the doping of Al is beneficial to improving the conduction condition of films while the structure of the films associated with luminescence centers is affected hardly at all.

Low defect density and planar patterned SOI materials by masked SIMOX

Patterned silicon-on-insulator (SOI) materials have been fabricated by masked separation by implantation of oxygen (SIMOX) technique. The formed SOI structure was analyzed by cross-sectional transmission electron microscopy (XTEM). The patterned SOI materials prepared with low-dose and low-energy SIMOX technique exhibit high quality featured by defect free transition of SOI and bulk silicon region and high degree of surface planarity. Furthermore, the buried oxide (BOX) layer is of high integrity at such a low-dose ion implantation. The fabricated excellent quality patterned SOI materials will be the desirable substrates for system-on-a-chip (SOC) applications.

Experimental results on drain and source on insulator MOSFETs fabricated by local SIMOX technology

Abstract To overcome the floating-body effect and self-heating effect of SOI devices, the drain and source on insulator (DSOI) structure [IEEE Int. Solid-State Integr. Circ. Technol. Conf. Proc., 1998, p. 575] is fabricated and tested. The recently developed low dose and low energy local SIMOX technology combined with the conventional CMOS technology is used to fabricate this kind of devices. Using this method, DSOI, SOI and bulk MOSFETs are successfully integrated on a single chip. Test results show that the drain induced barrier lowering effect is greatly suppressed and the drain-to-source breakdown voltage is greatly increased for DSOI devices due to the elimination of the floating-body effect. And the self-heating effect is also reduced and thus the reliability increased. At the same time, the advantage of SOI devices in speed is maintained. The technology makes it possible to integrate low voltage, low power, low speed SOI devices and high voltage, high power, high speed DSOI devices on one chip and it offers option for developing system-on-chip technology.

Formation of ultra-thin silicon-on-insulator materials by low-dose low-energy oxygen ion implantation

Abstract High quality ultra-thin silicon-on-insulator (SOI) materials have been fabricated by low-energy low-dose separation-by-implantation-of-oxygen (SIMOX) method. The thicknesses of the top silicon and the buried oxide (BOX) layers are only 70 and 40 nm, respectively, for the sample implanted with dose of 1.8×10 17 O + / cm 2 at the ion energy of 45 keV. The pinhole density of the BOX layer is less than 0.1 cm −2 , and the thickness uniformity of both the top silicon and the BOX layers over the whole wafer is within 2 nm. The fabricated high quality ultra-thin SOI materials are desirable for the advanced integrated circuits (ICs) manufacturing.

Fabrication of high quality patterned SOI materials by optimized low-dose SIMOX

High quality patterned SOI materials fabricated by optimized low-dose and low-energy SIMOX technique are reported. XTEM results reveal that the formed patterned SOI materials have very flat surface and low defect density transition between the bulk and SOI regions. These excellent quality patterned SOI materials are desirable substrates for system-on-a-chip (SOC) applications.

Comparative study of SOI/Si hybrid substrates fabricated using high-dose and low-dose oxygen implantation

Hybrid substrates comprising both silicon-on-insulator (SOI) and bulk Si regions have been fabricated using the technique of patterned separation by implantation of oxygen (SIMOX) with high-dose (1.5 × 1018 cm−2) and low-dose ((1.5–3.5) × 1017 cm−2) oxygen ions, respectively. Cross-sectional transmission electron microscopy (XTEM) was employed to examine the microstructures of the resulting materials. Experimental results indicate that the SOI/Si hybrid substrate fabricated using high-dose SIMOX is of inferior quality with very large surface height step and heavily damaged transitions between the SOI and bulk regions. However, the quality of the SOI/Si hybrid substrate is enhanced dramatically by reducing the implant dose. The defect density in transitions is reduced considerably. Moreover, the expected surface height difference does not exist and the surface is exceptionally flat. The possible mechanisms responsible for the improvements in quality are discussed.

Fabrication of radiation hardened SOI with embedded Si nanocrystal by ion-cut technique

The ion-cut technique has been proposed to improve the top Si crystalline quality of the radiation hardened silicon-on-insulator (SOI). Si ion implantation prior to wafer bonding and splitting is performed to reduce the lattice damage induced by direct Si implantation through top Si film. Atomic-resolution transmission electron microscopy studies reveal that the top Si film possesses nearly perfect crystalline quality. Photoluminescence spectroscopy, x-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy have corroborated the existence of the embedded Si nanocrystals. The pseudo-MOS transistors are fabricated on the hardened and unhardened SOI wafers for a quick and effective evaluation on the electrical properties of SOI wafers. The results indicate that the improvement in the total ionizing dose tolerance of the hardened SOI wafer can be attributed to the generation of deep electron and proton traps which reduce the positive charge build-up defects in the buried oxides.

Synthesis of an iron-nitrogen co-doped ordered mesoporous carbon-silicon nanocomposite as an enhanced electrochemical sensor for sensitive and selective determination of chloramphenicol

In this study, we developed a sensitive electrochemical sensor for the detection of chloramphenicol (CAP). An iron-nitrogen co-doped ordered mesoporous carbon-silicon nanocomposite (Si-Fe/NOMC) was prepared as follows. First, an SBA-15 surface was treated with an iron and nitrogen co-doped carbon framework obtained from the polymerization of ethylenediamine and carbon tetrachloride via the hard templating method. The mixture was then carbonized at a high temperature (900℃). Finally, the Si-Fe/NOMC modified electrode was fabricated, and employed as a high-performance electrochemical sensor to trace the CAP in drug samples using the large surface area of the hetero-atoms iron, nitrogen and silicon co-doped in the porous structure. Cyclic voltammetry and differential pulse voltammetry tests were determine to assess the efficiency of the sensor. Under optimized conditions, the sensor exhibited rapid current response for CAP in a phosphate buffer solution PBS with pH 7.5. The linear concentration of CAP ranged from 1 μM to 500 μM, with a limit of detection of 0.03 μM (S/N = 3). Furthermore, the electrochemical sensor was used to detect CAP in eye drop samples with satisfactory results.