A multiprojectile version of TRIDYN has been employed to simulate ion-induced effects which occur during ion-beam assisted deposition (IBAD) or plasma-assisted chemical vapour deposition (PECVD) of thin films.

Simulations of the formation of boron nitride films deposited from evaporated boron and energetic nitrogen show an excellent agreement with experimental results for nitrogen concentrations below the stoichiometric limit. For high N/B flux ratios, non-collisional mechanisms (ion-induced outdiffusion, surface trapping of outdiffusing nitrogen) have been included in the simulations, again producing good agreement with the experimental results.

Simulations of the PECVD of hydrocarbon films suffer from the poor knowledge of the neutral and ionic fluxes which contribute to the growth of the layers. Nevertheless, the composition of the films and its dependence on ion energy can be predicted with satisfactory agreement with experimental findings. A simple model of preferential displacement yields a reasonable average ratio of sp2 and sp3 coordinated carbon atoms. The energy dependence of the bond ratio is in contradiction to experimental observation.

Molecular dynamics simulations were used to follow low-energy ion/surface interactions including kinetic energy redistribution in the lattice as a function of time, projectile and lattice atom trajectories, and the nature, number, and depth of residual defects. The simulations were carried out using the Tersoff many-body potential for Si. Irradiation events were initiated with 10 and 50 eV Si atoms incident normal to the Si(001)2×l surface at an array of points in the primitive surface unit cell. Ion-induced epitaxial growth was observed due to both Si projectiles and Si lattice atoms coming to rest at epitaxial positions through direct deposition as well as site exchange occurring via diffusional and collisional processes. 36 simulations of 10 eV (50 eV) Si bombardment resulted in an average stopping position of 0.5 Å (1.6 Å) below the surface, 10 (13) epitaxial events, 7 (24) exchange events between the projectile and a lattice atom, and the formation of 15 (63) interstitials and 0 (36) vacancies. The interstitials preferentially diffuse toward the surface and are annealed out over times corresponding to monolayer deposition at typical Si MBE growth temperatures.

The interaction of low energy Ar+ ions with several surface defect structures on (001) Si has been investigated using molecular dynamics simulation. The simulations suggest that ions with energy less than 20 eV selectively displace surface atoms without causing bulk damage, and that the displacement energies for different defect structures is different. The most important effect of ion bombardment on surface morphology is the increased formation rate of single adatoms, which may lead to smoother surfaces by enhanced coarsening at typical epitaxial temperatures. Simulations results also imply that the migration component of adatom diffusion is not significantly enhanced by ion bombardment at typical epitaxial temperatures (600 – 800 K).

The growth of synthetic diamond thin films is studied by molecular dynamics computer simulations of low energy carbon atom deposition onto a low temperature diamond (111) surface. A previously reported Stillinger Weber potential, reparameterised for sp3 bonding in carbon using Hartree-Fock calculations for small carbon clusters, is used to model the interatomic interactions. The penetration of 1-100eV neutral carbon atoms into a (111) surface of carbon at 100K and the resultant surface atom rearrangements and induced film stress are studied. For intermediate energies (20-60eV) the incident atoms penetrate beneath the exposed (111) surface and increase the lateral compressive stress in the diamond film. It is suggested that diamond films grow from below the exposed surface in a region of locally high stress and tetrahedral coordination. The predicted radial distribution functions agree reasonably with electron diffraction studies of vacuum arc deposited amorphous diamond.

This work presents a molecular dynamics simulation of the intermixing of a metallic bilayer. The aim of the simulation is to elicit, in a more rigourous manner than in standard theoretical approaches, trends and phenomena taking place during the post-collisional stage of the cascade.

Sputtering yields Y(E)at ion energies E keV are shown to be described by the equation Y(E) = A(En - ) where A, n, and the threshold energy Eth are constants characteristic for a particular projectile/target combination. Examination of a wide variety of systems reveals that n = 0.5 provides an excellent universal representation of a large body of data, including physical sputtering of metals by noble gas ions, selfsputtering of metals, as well as physical and chemical sputtering of Si and SiO2. The above value for n is consistent with a 1/r4 power law atom-atom interaction potential within Sigmund's theory of sputtering. Another conclusion is that the effect of Eth on Y(E) must be taken into account at ion energies as high as 1 keV, not just near the sputtering threshold.

We present experiments and a theoretical model for the energy loss distribution of specularly reflected particles after slow (2-5 keV) He ions have been impinging on a Ni(110) surface under grazing incidence. The energy spectra of the backscattered particles are asymmetric with the low-energy tail falling off more slowly than the high-energy tail does.

This asymmetry is accounted for by considering charge exchange events during the interaction with the surface. The main neutralization channel for this system is the Auger-neutralization from the conduction band into the He-1s ground state. The transition rate for this process was calculated from first principles. Assuming that the ‘friction coefficient’ for the system particle-surface depends on the charge state of the particle, we calculate the energy lost by a particle during the interaction as a sum of different contributions belonging to different charge states.

Microstructure evolution has been studied in the early stages of growth of polycrystalline Ge on SiO2 in ultrahigh vacuum by ion beam-assisted deposition, and has been systematically compared to conventional thermal film growth. Experimental results indicate that, at equivalent substrate coverages, films grown by ion beam-assisted deposition exhibit increased island density and decreased island size with respect to thermally-deposited films. The increased island density is not a result of an increased island nucleation rate associated with defects produced in the SiO2 substrate during ion beam-assisted deposition. Instead, a new model for ion beam-induced adatom desorption from islands is proposed to account for the increased island density and decreased island size.

This paper addresses the fundamental aspects of etching semiconductors with inert gas beams in the presence of a suitable precursor gas. In particular, the changes that an energetic bombarding ion/neutral species cause to the surface and sub-surface region of a solid are considered, both in terms of the introduction of damage to the semiconductor and chemical processes that are provoked in the adsorbed states present. The implications for practical etching reactions are then discussed.

Silicon dioxide (SiO2) films were fabricated by microwave ECR plasma processing. Two groups of films were fabricated; group A with the substrates placed in a position directly facing the plasma so that the substrates as well as the on-growing films were subjected to bombardment of energetic particles produced in the plasma, and group B with the substrates placed in a processing chamber physically separated from the plasma chamber in order to prevent or suppress the damaging effects resulting from these energetic particle bombardment. The systems used for fabricating these two different groups of samples are described. The films were deposited at various deposition temperatures. On the basis of the deposition rate as a function of deposition temperature the film growth for group A samples is due mainly to mass-limited reaction, and that for group B samples is due to surface rate limited reaction. The stoichiometric level for group A does not change with deposition temperature though the films density increases with increasing deposition temperature. However, group B samples exhibit an off-stoichiometric property but they become highly stoichiometric as the deposition temperature is increased beyond 200 °C

The feasibility of fabricating ultra-thin SiO2 films on the order of a few nanometer thickness has been demonstrated. SiO2 thin films of approximately 7 nm thickness have been produced by ion flux-controlled Electron Cyclotron Resonance plasma oxidation at low temperature on [100] Si substrates, in reproducible fashion. Electrical measurements of these films indicate that they have characteristics comparable to those of thermally grown oxides. The thickness of the films was determined by ellipsometry, and further confirmed by crosssectional High-Resolution Transmission Electron Microscopy. Comparison between the ECR and the thermal oxide films shows that the ECR films are uniform and continuous over at least a few microns in lateral direction, similar to the thermal oxide films grown at comparable thickness. In addition, HRTEM images reveal a thin (1–1.5 nm) crystalline interfacial layer between the ECR film and the [100] substrate. Thinner oxide films of approximately 5 nm thickness have also been attemped, but so far have resulted in nonuniform coverage. Reproducibility at this thickness is difficult to achieve.

A number of deposition techniques for cubic BN films from the vapor phase at low pressures have been proposed. We show that the essential factor for creating cubic BN films is a negative self-bias applied to the substrate. The optical and mechanical properties of the deposited films are characterized by reflectance and stress measurements, respectively.

Gate dielectric-quality silicon nitride films were deposited on a tunnel oxide from an SiH4/N2 gas mixture using an electron cyclotron resonance (ECR) plasma. Electrical characteristics depend not only upon the quality of the nitride film but also upon the state of the interfacial oxide. Quasi-static and 1 MHz capacitance-voltage measurements show that a nitride film deposited at 200°C on 2 nm thick thermally-grown oxide (tunnel oxide) on an unbiased Si substrate have an interface state density of l.5×1011/cm2-eV. Time-of-flight elastic recoil detection (TOF-ERD) was used to examine the level of mixing between the tunnel oxide and the deposited silicon nitride as a function of bias voltage. TOF-ERD showed that for an applied bias of −350 V (ion energy ≈ 380 eV), the deposition of a 10 nm thick film was completely mixed to form an oxynitride whereas the tunnel oxide remained intact for an unbiased sample. (Interdiffusion resulting from energetic-beam heating was ruled-out as a possibility for the mixing.)

A new electron cyclotron resonance (ECR) plasma etching technology has been developed to realize simultaneously high selectivity, high rate and anisotropic etching for phosphorus doped poly-Si and WSix/poly-Si at a low ion energy. In this technology, a substrate is located around the ECR position (875 gauss position) in an ECR plasma. As a result of ECR position etching, under the low pressure of 5 × 10−4 Torr, a high etching rate and an infinite selectivity to SiO2 etching are realized by using C12/O2 and Cl2/O2/SF6 etching gas.

The dominant factors governing reactive ion etching of Si, SiO, and SiO2 thin films during bombardment with energetic Ar ions in a Cl atmosphere were investigated. Etch rates were determined in-situ by measuring weight loss as a function of ion fluence for films deposited on a quartz micro-balance. Measurements were made as a function of ion energy and Cl pressure using a Kaufman gun for ion energies from 300 to 1500 eV and an electron cyclotron resonance microwave ion source for ion energies from 50 to 600 eV and for Cl pressures ranging from 0.006 to 0.05 Pa. Results were compared to sputtering in Ar alone. The results indicated that the presence of the C1 enhanced the etch rate for all three materials, with the degree of enhancement being inversely proportional to the oxygen content of the film. It was also discovered that there was an optimum pressure for enhancement of the etching and that at the highest pressures, the etching could actually be suppressed. These results are discussed in terms of physisorbed gas layers, the thickness of which depends on the balance between the flux of energetic particles and the gas flux.

Plasma immersion ion implantation (PIII) has been applied to fabricate shallow p-n junction diodes and MOS test structures. BF3 ions created by an electron cyclotron resonance source were implanted into n-type Si(100) at an accelerating voltage of −2 kv. The implant doses ranged from 4 × 1014/cm2 to 4 × 1015/cm2. In some cases, the top layers of the Si(100) substrates were preamorphized by a 3 × 1015/cm2 to 1016/cm2 implant of SiF4 by PIII at −7.2 kV prior to the BF3 implant. The ideality factor exhibited in both non- and preamorphized samples during forward bias is 1.02 to 1.05. Reverse leakages were measured at 30 nA/cm2 at −5V. High frequency capacitance and high field breakdown measurements of the oxide test structures showed no significant damage to the oxide.

We report the results of an ECR hydrogenation time-behavior study on polycrystalline silicon thin film transistors. The device characteristics, such as mobility, subthreshold slope, threshold voltage, off current and on/off current ratio, were measured as a function of the passivation time. It was found that there is an optimal passivation time for this particular TFT structure, and overexposure to ECR hydrogen plasma may cause the degradation of some device parameters.

In this study we show that upon exposure to electron cyclotron resonance hydrogen plasmas, both thermally grown and sputter deposited oxides are degraded, resulting in large shifts of flat band voltage, and increases in fixed charge and interface state density.

The oxidizing activity of an oxygen plasma is investigated in terms of the oxygen content of HoBa2Cu3Ox. thin films. The thermodynamically stable region of HoBa2Cu3Ox. and the region where the HoBa2Cu2Ox films are formed are also determined both in molecular oxygen and in an oxygen plasma. The oxidizing activity of an oxygen plasma is equivalent to that of molecular oxygen at three orders of magnitude higher pressure. The oxygen plasma expands the thermodynamic stability limit toward higher temperatures and the oxidizing activity limit toward lower oxygen pressures. In addition, the interfacial reaction between an oxide superconductor and silicon is investigated. The oxygen ions in HoBa2Cu3O film diffuse into Si even at room temperature, probably enhanced by the strong affinity of silicon for oxygen ions.

Bi-Sr-Ca-Cu-0 thin films were prepared on (110)SrTiO3 by coevaporation with rf oxygen plasma. The non-(00n) crystalline orientations were formed in the Bi2 Sr2Ca2Cu3Oy1 Bi2Sr2 CaCu2Oy2 and Bi2Sr2CuOy3 phases. Furthermore, it was confirmed that the chemical composition and the oxygen plasma condition influenced the crystalline orientation. On the basis of these results, a new idea for the film growth mechanism is proposed.