Gaj Amaratunga

Characterization of a‐C:H:N deposition from CH4/N2 rf plasmas using optical emission spectroscopy

Optical emission spectra (OES) from CH4/N2 rf plasmas, which are used for the deposition of nitrogen‐containing hydrogenated amorphous carbon (a‐C:H:N) thin films, have been characterized. Previously unidentified spectral lines have been assigned to atomic N. Further identified species include CH, H, H2, N2, N+2, N, and CN. Variations between spectra from the pure CH4 or N2 plasmas and the mixed CH4/N2 plasma are discussed. The enhancement of excited nitrogen species, with the addition CH4, is attributed to Penning ionization. The observed OES variations of the CH4/N2 plasma with power, pressure, and CH4/N2 ratio are explained in terms of possible reaction mechanisms and their activation, and correlated with preliminary film growth characteristics.

Diamond-like carbon thin film deposition using a magnetically confined r.f. PECVD system☆

Abstract Diamond-like carbon thin films have been deposited at low temperatures, using local magnetic confinement in a r.f.-powered plasma-enhanced chemical vapour deposition process. The increased plasma density and temperature obtained by magnetically confining the plasma, increases the ionization of the hydrocarbon gas in the deposition chamber. The modified plasma is characterized together with the material properties of the deposited films. A model is proposed to explain the dissociation of species in the plasma and the plasma temperature based on the observed results. Doping of the films using nitrogen gas fed in with the hydrocarbon is also investigated.

Tribological properties of diamond-like carbon films deposited on silicon using r.f. plasma enhanced CVD

The wear properties of diamond-like carbon films deposited on single-crystal silicon using an r.f. plasma enhanced chemical vapour deposition process are analysed as a function of deposition conditions. It is found that the tribological properties of the film are highly dependant on the d.c. self-bias voltage developed between the r.f. driven electrode and the plasma during deposition. The films were tested in dry sliding against steel discs with two different radii of curvature and it was found that the films deposited at higher d.c. self-bias voltages were more wear resistant and offer better protection. When coating failure occurred it was by a process of cracking and delamination.

Performance of 200 V CMOS compatible auxiliary cathode lateral insulated gate transistors

The authors report the performance of various anode-shorted auxiliary cathode lateral insulated gate transistor (ACLIGT) structures fabricated using a 2.5 mu m digital CMOS compatible HVIC process. The reverse breakdown voltage of the ACLIGT is comparable to that of an equivalent anode shorted lateral insulated gate transistor (LIGT). The results indicate that, by placing an auxiliary cathode and an extended p-buried layer of an anode-shorted LIGT, the holes flowing into the p-well can be diverted to overcome the latch-up problems of the LIGT in an ACLIGT. The LIGT shows latch-up at 140 mA, which corresponds to a current density of 340 A/cm/sup 2/ while the ACLIGT structures do not show latch-up. The measured turn-off characteristics of the ACLIGT reveal a turn-off time of less than 250 ns while an equivalent LIGT shows a turn-off time of 350 ns.<<ETX>>

A Monte Carlo study of the kickout mechanism of boron diffusion in silicon

In this article, the results of a study of the diffusion mechanism of boron in silicon based on the Monte Carlo method are presented. The kickout mechanism has been examined for the case of a delta function impurity profile under both inert and oxidation conditions. It is shown that the initial conditions play a significant role in obtaining the mean migration path lengths of the atoms. The kickout mechanism in the case of an initial delta function interstitial impurity profile has been analytically examined. The atomic level computational experiments carried out in this article validate Cowern’s results of ‘‘intermittent diffusion’’ of boron in silicon and yield, the values for λ0, the prefactor for the mean migration path length, which are found to lie between 0.024 and 0.035 nm.

CMOS compatible 250 V lateral insulated base transistors

The performance of various insulated base transistors implemented with a digital CMOS compatible high-voltage integrated circuit process was demonstrated. Design modifications in the lateral insulated base transistor (LIBT) structures have been proposed, and the performance of the improved LIBTs has been compared with that of a conventional LIBT structure. These modifications are based on the effective use of charge-controlled n/sup +/ buried layers to improve the on-state capability of the device. Four different types of LIBT structures have been fabricated and tested. The experimental analysis of the CMOS-compatible LIBTs discussed shows that the n/sup +/ buried layer placed under the p well plays a crucial role in improving the device performance. The improved LIBT structure with n/sup +/ buried layers incorporated near the collector and the p well regions shows the best characteristics with high voltage blocking capability, low specific on-resistance, and a low turn-off delay. A specific on-resistance of 0.016 Omega -cm/sup 2/ and a turn-off delay of 90 ns were obtained in the improved LIBT structure, which can withstand up to 250 V.<<ETX>>