Hydrogen passivation of the Si(100) surface prepared by a two-stage remote hydrogen plasma treatment has been investigated using Auger Electron Spectroscopy (AES) and Reflection High Energy Electron Diffraction (RHEED). AES analysis was employed to examine the degree of passivation at different temperatures by monitoring the level of impurities, mainly oxygen and carbon, readsorbed on the Si surface after exposure to air for two hours. RHEED analysis was used to investigate the reconstructed surface structure and the results were correlated with the results of AES analysis. It was found that better Si surface passivation is achieved at a lower substrate temperature during the remote hydrogen plasma treatment. Silicon epitaxial growth by Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD) was attempted on the H-passivated Si(100) at 305°C. It was found that epitaxial growth is achievable on these wafers even after 2 hours air exposure without further cleaning prior to growth. We have also observed for the first time electron-beam-induced oxygen adsorption on the Si surface prepared by remote hydrogen plasma clean and have confirmed this by Scanning Auger Microscopy (SAM) at various electron beam current densities. The adsorption of oxygen and carbon on the H-terminated Si surface from the ambient upon 3 keV electron beam irradiation is believed to be associated with either the breakage of the Si-H bond or rearrangement of bonding between Si, H, and O, resulting in a loss of hydrogen passivation.

Using a magnetic field to confine the plasma closer to the cathode has been shown to be advantageous in dry etching technology since this yields a high degree of ionization at low pressures. We report here the results of a study of magnetron reactive ion etching of GaAs using a freon discharge. Various characterization techniques have been employed to understand the etching process and identify the extent of surface damage. The results show that magnetron etching is capable of yielding high etch rates with low damage.

The feasibility of utilizing NF3-halocarbon mixed etchants to anisotropically etch tungsten silicide structures has been investigated. CVD tungsten silicide was etched with various mixtures of CF3Cl and CF2Cl3 to which 0 to 50 vol percent NF3 was added under a variety of conditions. Anisotropy, undercutting, and notching were evaluated using cross-sectional SEM. Relative etch rates and selectivity for each gas mixture were also determined. Halocarbon residues were investigated using XPS and related to side wall passivity.

We have investigated the etch rates, residual lattice damage, surface morphologies and chemistries of InP, InGaAs, AlInAs and GaAs plasma etched in electron cyclotron resonance (ECR) CH4/H2/Ar discharges. The etch rates of InP and InGaAs increase linearly with additional RF biasing of the substrate, and are approximately a factor of two faster than for GaAs. Under our conditions the etch rate of Al0.52Ga0.48As is very low (˜25 Å - min−1) even for the addition of 100 V RF bias. In all of these materials the residual damage layer remaining after dry etching is very shallow (˜20 Å) as evidenced from Schottky barrier height and photoluminescence measurements combined with wet chemical etching. InP shows significant P depletion with the addition of RF biasing during the ECR etching while GaAs retains a near-stoichiometric surface. Hydrogen passivation of shallow donors in n-type GaAs occurs to a depth of ˜3000,Å during exposure to the CH4/H2/Ar discharge for long periods (60 mins). The surface morphologies of the In-based materials become roughened for etching with the addition of RF biasing while GaAs displays smooth, residue-free surfaces under these conditions.

We have studied the plasma etch behavior of four different SOG materials which range from 0 to 14% in their organic content (weight percent of -CH3). A number of gas chemistries were investigated, including SF6/He, CF4/He, C2F6, and CHF3/He. Etch rates of SOG films were determined relative to that of thermal SiO2 as a function of the partial pressure of the fluorine-containing gases. In general, at low partial pressures of the etch gas, where no polymer formation occurs, the SOG films etch faster than thermal oxide. Also, the etch rates increase with an increase in the overall organic content (Si-CH3) of the SOG. While higher SOG etch rates relative to that of thermal SiO2 are attributable to the lower SOG densities, the increase in SOG etch rates with increasing Si-CH3 content probably reflects the effect of decreasing Si-O bond density. Under conditions favoring polymer formation, the SOG etch rates are suppressed relative to that of oxide indicating enhanced polymerization rates on a siloxane SOG surface. Preliminary data obtained using gas chemistries with high F/C ratios suggest that the relative contributuion by F atoms to etching is larger in a siloxane SOG than in SiO2.

Since about 1985 a cascaded arc is used as a particle source in the deposition machine described by Kroesen [1a,1b]. This method of deposition showed to be very fast and efficient to grow amorphous carbon films (a–C:H), varying from graphite and diamond to polymers [1,2]. The most important difference of this method, with respect to R.F. techniques, is that the three most important functions of a deposition process, as there are dissociation/ionization, transport and deposition are spatially separated. The dissociation takes place in a cascaded arc burning on argon. The temperatures in the arc are about 10000–12000 K. At the end of this arc hydrocarbons are injected which are then dissociated and ionized effectively. At the end of the arc the plasma expands supersonically into a vacuum vessel. That means that the plasma cools down and the formed hydrocarbon fractions are transported towards the substrate, where an amorphous carbon film can grow. The quality of the films depend mainly on the amount of energy available for each injected carbon atom. The behavior of the refractive index as a function of this energy could be a confirmation that in our deposition method the carbon ions rather than radicals govern the deposition process [1,3,4]. Therefore the cascaded arc is investigated numerically and experimentally in order to improve the ionization efficiency. The conservation laws for mass, momentum and energy for both the electrons and the heavy particles are solved 2 dimensionally by a control volume numerical method with a non, staggered grid. By Fabry Perot interferometry heavy particle temperatures, electron temperatures and electron densities as a function of the axial position in the cascaded arc are measured. The obtained numerical results are compared to the experimental data, obtained by the optical Fabry Perot diagnostics.

The incidence angle dependence of silicon near-surface contamination caused by CF4 Reactive Ion Beam Etching was studied using on-line variation of SiF4 partial pressure and Auger Sputter Profiling. Initial and steady state etch rates both vanish at grazing incidence and have a smooth maximum at 20–30 deg. It is shown that whatever is the incidence angle, a C, F-blocking overlayer grows involving an etch rate attenuation by a factor which is only slightly dependent on the incidence angle. As the angle increases, with a 500 eV beam, the thickness of the C, F contamination layer decreases monotonically from 1.9 nm down to a constant value of about 1nm achieved beyond a critical angle of 45 deg. Then a “C, F-reactive mixed layer” is seen over the silicon the etching of which is dominated by surface mechanisms. Conversely with the lower angles, the thickness of the “carbonaceous incorporated layer” becomes larger than that of the mixed layer, and volume mechanisms dominate the silicon removal.

Silylation and dry development are the key processes of DESIRE, one of the surface imaging techniques in submicron lithography. The present work was carried out to achieve the improvement of develoment rate and anisotropic resist profile, and to characterize the silylated and dry developed resist. The dependence of silylation on the exposure dose and the presilylation baking temperature was investigated by using Rutherford backscattering spectrometry. The higher dose UV-irradiation results the thicker silylated layer in the dyed resist. The dry development of photoresisl patterns was processed newly by using the plasma of O2/He RIE plasma. It is particularly emphasized to obtain to optimize the RIE process, so that some improvements, i.e., vertical resist profiles with the high anisotropy, good selectivity, and the development rate of 0.4 μm/min were achieved. X-ray photoelectron spectroscopic study indicated that Si in the silylated and dry developed resist was present with the chemical binding states of SiO2 on surface, and SiO. SiC and very small amount of SiO2 in near-Surface region (at about 5 nm depth).

Techniques such as plasma etching, electron-beam lithography, X-ray lithography, ion etching, sputtering and ion implantation are used to Increase the density of Integration of semiconductor devices. All these techniques introduce undesirable radiation damage into the processed device. Annealing techniques are used to reduce or remove completely the radiation induced defects. The conventional postmetallization low temperature (400–450 °C) annealing using Forming gas (10% H2-90% N2) does not anneal all the charge pentres in many device structures. We have employed a novel low temperature (350°C) rf plasma technique using a NH3-N2 gas mixture to anneal bipolar structures. Vertical pnp transistors made with high energy ion implantation and having poor electrical characteristics have been dramatically improved after 30 min annealing with this new technique. The value of the ideality factor of the base current which was about 1.4 before annealing approached the ideal value of 1.0 after 30 min annealing. Optical emission spectroscopy of the NH3-N2 glow discharge shows the presence of NH radicals, atomic hydrogen and nitrogen ion molecules during the plasma annealing. The atomic hydrogen passivates electrically active defects in the oxide and at the Si/SiO2 interface. A nitridation process occurs at the surface of the top BPSG layer, where a thin silicon nitride film is formed and plays the role of a capping layer which inhibits saturation phenomena. Angle-resolved XPS and ellipsometry have been used to analyze the surface of a silicon wafer exposed to this plasma annealing process. A qualitative model is also proposed to explain the mechanisms involved in this novel NH3-N2 rf plasma annealing process.

Plasma emission spectra resulting from rf sputtering Y-Ba-Cu-O targets were observed as a function of time using an optical multichannel analyser. Although most lines of the observed spectra are not attributable to target species, peaks associated with each cation element were resolved. The Ba and Cu peaks can be used as tracking indicators of process conditions. For example, switching from an O2/Ar sputter atmosphere to pure Ar enhanced the Ba peak more than those associated with CuO. The emission spectra from a newly fabricated target exhibited a first-order transient response in seeking equilibrium with the rf plasma. The transient response of a previously sputtered target is also first-order but with a shorter time constant.

Polycrystalline diamond thin films have been deposited on single crystal silicon substrates at low temperatures (<950° C) using a mixture of methane and hydrogen gases by high pressure microwave plasma assisted chemical vapor deposition. Low temperature deposition has been achieved by cooling the substrate holder with nitrogen gas. For deposition at reduced substrate temperature, it has been found that nucleation of diamond will not occur unless methane/hydrogen ratio is increased significantly from its value at higher substrate temperature. Selective deposition of polycrystalline diamond thin films has been achieved at 600° C using our technique previously used at 930° C. Decrease in the diamond particle size and growth rate, and an increase in surface smoothness have been observed with decreasing substrate temperature during the growth of thin films. The morphology is analyzed by scanning electron microscopy and the as-deposited films are identified by Raman spectroscopy.