The growth of rf-sputtered silicon carbide thin films has been studied over a wide range of substrate temperatures, producing films with crystal structures from completely amorphous to highly crystalline. The initial 100nm of growth is characterized by ‘void network’ type physical structure throughout the temperature regime studied. This network of polyhedra outlines the dominant physical structure features at the top surface of the film and is shown to grow in average lateral dimension (D) with increasing film thickness (t) as a parabola (D=K·tx). The growth exponent (x) describes the lateral growth rate of these parabolic growth cone columns and decreases with increasing film temperature, bombardment, and hydrogen in the plasma. In the highly crystalline films the lateral crystallite growth rate eventually exceeds the growth of void network columns present in 10–100nm films, producing abrubt increases in size of physical features between 100–1000nm levels. The results show that the evolutionary structure zone model consistently accounts for film growth behavior in the amorphous regime but must be modified for crystalline films.

There are four easily identified stages in the formation of a hydrogenated amorphous silicon film from an electrical discharge in silane. The first stage is the primary reaction between electrons and silane resulting in a mixture of ions and free radicals. The second stage is the transport of these species to the substrate surface accompanied in parallel by a multiplicity of secondary reactions e.g. ion-molecule, photon-molecule, etc. The third stage is the reaction or adsorption of these species with or onto the substrate surface and the fourth stage is the process by which these species or their reaction products incorporate into the growing film or are reemitted from the surface into the gas phase.

Preparation and characterization of microcrystalline silicon are discussed. In addition to the usual characterization techniques using TEM,X-ray, Auger, etc., Raman scattering and electro-reflectance measurements have been extensively incorporated into routine analyses. In particular, conductivity percolation, detection of trace crystallites in an amorphous matrix, measurements of grain-size, doping as well as preferred orientation are fully discussed. The single most important effect on the properties of microcrystalline Si and Ge is the presence of impurities. Thus better technical performances must be preceded by an improvement in vacuum and purer gases used in deposition systems.

Wide gap (>1.9 eV), photoconductive, intrinsic amorphous silicon films were made in a UHV system from Si2H6 -He mixtures. The hydrogen concentrations, optical gaps and photoconductivities were measured. Unlike films made from SiH4, Si2H6-produced films exhibit excellent electronic properties even at low deposition temperatures. The ratio of AM1 photoconductivity to dark conductivity was as high as 107.

A number of microcrystalline silicon films have been deposited by RF sputtering and their structure was investigated by Raman spectroscopy, X-ray scattering, SEM, TEM and IR spectroscopy. The interpretation of these results suggests that the film growth proceeds initially via amorphous island formation and that the degree of crystallization of the final film depends on subsequent solid phase crystallization during the time of growth. The size and the preferred orientation of the crystallites correlates with the columnar growth habit of the films while the rest of the amorphous matrix is shown to exhibit a considerable degree of order.

A plasma reactor has been developed for dry reactive plasma etching and thin semiconductor film deposition. The system combines a multipolar magnetic field layer [1] for charged-particle confinement, and independently controlled substrate biasing. A large volume of dense (1011 cm-3), uniform, quiescent plasma is produced at low working pressure ( 1 mTorr). Anisotropic profiles can be etched into silicon in an SF6-O2 plasma with vertical etch rates ∼l um/min. In a pure silane plasma, good quality polycrystalline silicon films can be deposited at rates 1 to 10 Å/sec., at substrate temperatures 50° to 300° C.

In a low pressure multipole plasma, the energy of the charged species impinging on the substrate can be varied electrostatically. Spectroscopic ellipsometry is used to study the film growth and the surface morphology. Hydrogen evolution is used to investigate the release of hydrogen from the amorphous network. Moderate energy ion bombardment (Eion ‰ 50 eV) is shown to favour the formation of homogeneous high density films with a sharp interface. Weak ion bombardment (Eion ‰ 20 eV) results in a microscopically rough surface. The material strucbural variations are evidenced by hydrogen evolution kinetics.

Fundamental aspects of the interaction between non equilibrium, low pressure oxygen plasma and Si (silicides) are described. The kinetics of oxide growth in oxygen atmosphere, in plasma at low pressure (p<∼ 1 Torr) and low temperature (T < 1 800°C) regimes are reviewed and the Cabrera-Mott mechanism is postulated i.e. the oxidation process is controlled by ion injection at the plasma/oxide interface. The mechanism of electron injection and conduction during plasma anodization is reviewed and discussed in the frame of theory of high current injection in MIS structure. Enhancement of oxide growth rate due to the irradiation (laser), bombardment by electrons or ions is reviewed and compared to the plasma oxidation. Spectacular enhancement of the anodization rate of Si covered by a thin deposited layer of zirconia or hafnia oxide is analyzed. The anodization rate of Si deposit through ∼’ 0.5 mm YSZ single crystal substrate is evoked as an example of potentiality of plasma anodization process. The mechanism of movement of oxygen ions and of cations deduced from 160/180 experiments is discussed. A few examples of applications of Si plasma oxidation processes are presented.

In the first time, hundreds nm thick oxide layers were formed by room temperature plasma anodization of some refractory disilicides. Nuclear microanalysis and Rutherford backscattering techniques were used to study the anodic oxidation of various metal silicides (Hf, Ti and Zr) in a multipolar oxygen plasma set-up. We have found that the low temperature (<100 °C) plasma anodization kinetics of Hf or Zr silicides is two orders of magnitude higher than that of Ti silicide although their thermodynamic and physicochemical behaviour are very similar. 200 nm thick Hf (or Zr) and Si mixed oxide layers have been obtained in one hour plasma anodization. Analysis of RBS spectra indicates that the ratio of Si to metal cation concentration in the bulk of oxide grownis the same than the silicide (HfSi2 or ZrSi2), while in the near surface region of oxide (20 to 30 nm) there is an enrichment in metallic oxide leading to a Si to Hf (or Zr) concentration ratio equal to unity. The spectacular difference between the anodization rates in oxygen plasma of Hf (and Zr) silicides comparing to Ti silicides can be related to the catalytic effect on plasma anodization of the Hf and Zr oxides.

The dissociation of N2 in a microwave discharge has been studied using a gas phase titration between N(4S) and NO. SF6 added in small concentrations (20–100 ppm of N2) is shown to be an efficient catalyst for dissociating N2. Dissociation fractions [N]/[N2 ] of 4–5% have been obtained. The studies suggest how the partial pressure of atomic nitrogen can be maximized. These results have been applied to thermal nitridation of Si in active nitrogen. A strong dependence of the film thickness on the partial pressure of atomic nitrogen (PN) has been shown. In addition to the nitridation rate, the nitrogen fraction [N]/([N] + [O]) also increases with PN.

Thermal nitridation of silicon in both nitrogen and nitrogen-hydrogen plasma has been performed around 1000°C for 5 min to 10 hr. From Auger electron spectroscopy analysis, the formed films contain some oxygen and are identified as oxynitride films in both cases. In nitrogen-hydrogen plasma, high nitrogen fraction( 0.8) in the film is obtained for the nitridation of 5 min. Thus, the addition of hydrogen to nitrogen enhances the nitrgen fraction in the film for such a short nitridation time. The film thickness is almost constant against the nitridation time and is limited to be about 40 Å. Capacitance-voltage characteristics of aluminum gate metal- nitride-semiconductor capacitors show stable behaviors and the fixed charge density at the film-substrate interface is estimated to be the order of 1012 cm−2 in both cases.

Effects of plasma on direct nitridation of Si and SiO2 have been investigated. The reactor consisted of a quartz tube, SiC-coated carbon-susceptors and an RF-induction coil. The electrical probe technique was used to detect floating potential of the susceptor having Si substrates. The voltage distribution between the susceptor and plasma is influenced by nitridation ambient, pressure, reactor geometry and RF power. The predominant species in NH3 plasma is NH radicals which are thought to be negatively charged in an ion sheath formed around the susceptor. The Cabrera-Mott model has been successfully applied to analyze the nitridation mechanism. Plasma enhancement is mainly caused by activation of characteristic velocity of nitridation species rather than by an increase in the electric field appearing in a film. Enhancement due to fluorine incorporation is also explained with the model. Bombardment of ionic species causes sputtering and deposition resulting in damage, contamination and thickness nonuniformity. Optimizing the plasma conditions, decrease in nitridation temperature, increase in growth rate, and improvements in film composition and interfacial structure have been obtained. It has been found that the further nitridation proceeds, the lower Nss becomes. This technique offers various advantages to the VLSI dielectric process.

Applications of plasma anodization technique to Si, GaAs and InP dev-ices fabrication, demonstrated by the author's group, are reviewed. The feature of the technique is an electric field enhanced low temperature oxidation process. Suppression of the generation of oxidation induced stacking faults, the redistribution of impurities in the substrates and the bird's beak formation in selective oxidation process is an advantage in silicon technology. It must be stressed that plasma anodization is only one technique which has been proved to be successful in growing native oxide films on InP substrates for MISFETs fabrication.

Passivation of III-V compounds, especially GaAs, is still a major problem. Surface mechanisms related to stoichiometry defects (free As formation, vacancies) play an important role in the detrimental effects observed on GaAs devices (interface traps, leakage currents, parasitic transients …).

We first analyze the phenomena occuring at GaAs (100) surfaces exposed to several (H2,N2 ) multipolar plasmas, with the following methods : - in situ study of the surface morphology and roughness using ellipsometry and electron diffraction - chemical analysis using photoemission and Auger spectroscopy - electrical analysis in situ (Fermi level position deduced from photoemission, work function measurements) or ex situ (device characterization, C(V) analysis).

Using H2 based plasma treatments, a complete cleaning (oxide and contamination removal) can be obtained at moderate (below 200 °C) temperatures. This process, associated with surface nitridation and dielectric deposition, yield improved surface properties (lower recombination velocity and reduction of devices parasitic effects).

The case of Ga1−xInxAs (100) surfaces (with x varying from 0 to 0.53)is then discussed and a comparative study is given, indicating that native nitridation may also be a good solution,in this case.

Reactive ion etching (RIE) is extensively used as a high resolution pattern transfer process for fabrication of silicon devices. In this work dry etching radiation damage in p-type boron doped, silicon wafers was investigated using a nondestructive surface acoustic wave (SAW) technique. The transverse acoustoelectric voltage (TAV) is monitored across the silicon wafer which is placed in proximity of a SAW delay line. TAV is developed due to the nonlinear interaction between the electric field accompanying SAW and the free carriers near the silicon surface. TAV versus bias voltage (applied across the semiconductor) was obtained to measure the flatband voltage (VFB) shift. The flatband voltage shift of the etched wafer was determined as a measure of the amount of surface charge introduced into the surface by ion bombardment. SiO2 films were etched in C4 F8 and C2 H2 with 2 W/cm2 input power. The ion energy was determined by the self bias dc voltage developed on the cathode. It is shown that a magnetron RF discharge introduces an order of magnitude less damage than non-magnetron discharge.