Results will be presented using a new ultrahigh vacuum system designed to investigate the complex surface chemistries prevailing in plasma-assisted etching processes which use more than one halogen or halogen-hydrogen gas mixtures. In this new apparatus, two separate controllable beams of atoms can be directed onto a surface and energetic ion bombardment of the surface can be introduced. Neutral species evolved or reflected from the surface are monitored with modulated beam mass spectrometry. Etch rates as small as 10−3 Å/sec can be detected. The chemical systems which have been used are Si-F-Cl, Si-F-H and Si-CI-H and some unexpected phenomena observed with these systems will be described. Some catalytic reactions have also been observed with these gases in the presence of polycrystalline Ni and Pd surfaces and another example of an oscillatory surface reaction has been found.

The effects of ion impinging energy on the etching of Si3N4 films in an electron cyclotron resonance (ECR) microwave plasma etching system have been studied. An alternating frequency (10 MHz) bias voltage was used to control the ion impinging energy. The experimental results show that the etching rate in the initial period (less than 3 min) of the etching process is noticeably lower than that in the following period for bias voltage Va > 10 V. The length of the initial period depends on the plasma density. The etching rate in the following period depends on the bias voltage. But the above dependence disappears for Va < 10V. It is found that the surface oxide contribution to the bias effects is negligible. The mass spectrometric measurement of the transient of the etching product SiF4 confirms these bias effects. The effects may be attributed to the ion radiation damage to the subregion lattice even at low ion energies.

HI/H2/Ar discharges are shown to be universal etchants for rn-V semiconductors, giving rise to highly anisotropic features with smooth surface morphologies. At loy dc self bia:s (-100V) and low pressure (1 mTorr), etch rates for all III-V materials of >2000Å min−1 are possible for high HI percentages in the discharges, whereas rates greater than 1 Åm min−1 are obtained at higher pressures and dc biases. These etch rates are approximately an order of magnitude faster than for CH4/H2/Ar mixtures under the same conditions and there is no polymer deposition on the mask or within the reactor chamber with HI/H2/Ar. Auger Electron Spectroscopy reveals residue-free, stoichiometric surfaces after dry etching in this mixture. As i result, photoluminescence intensities from dry etched samples remain high with little apparent damage introduction. Changes in the near-surface carrier concentration due to hydrogen passivation effects are also negligible with HI-based mixtures in comparison to CH4-based dry etching.

The form of ideal surface chemistry that is necessary for chemically assisted ion beam etching (CAIBE), with particular reference to in-situ processing is considered. Whilst to date CAIBE has been almost exclusively carried out with chlorine, distinct advantages exist if a compound that which displays spontaneous reactivity which is limited to one or two monolayers can be used. The role of alkyl halides in this scenario has been investigated through the use of surface spectroscopic probes to investigate the microscopic chemical and ion beam assisted reactivity that may be achieved. Dichloroethane has been found to display promising behaviour.

The presence of highly energetic ionic and neutral species during dry etching generates damage in device structures which significantly reduces their performance. In this study we have utilized photoluminescence spectroscopy (PL) on GaAs/AlGaAs Multi Quantum Well (MQW) structures to assess and compare the relative damage induced by the standard ion beam etch technique and the “less damaging” newer Electron Cyclotron Resonance (ECR) etch technique. MQW structures with well widths of 2.7, 6.4, 10.8, and 81 nanometers (nm) at a distance from the sample surface of 40.5, 83, 130, and 170 nm respectively were grown by molecular beam epitaxy. In order to minimize the effect of the radically different chemistries present in reactive ion etching and in ECR reactive etching we have chosen to initially compare the damage-induced luminescence degradation resulting from Ar irradiation only. The PL intensity is shown to correlate well with the ion dose and energy. At equivalent total surface erosion under Ar irradiation the ECR process is shown to cause significantly less deterioration on QW PL yield. In the ion beam case a dose corresponding to a surface sputtering of less than 100 angstroms of the AlGaAs barrier causes total extinction of the PL from the QW lying at 1000 angstroms below the surface. By comparison under similar conditions no degradation is detected in the ECR irradiation case. Even at higher ECR doses equivalent to removal of up to 30 nm from the top AlGaAs barrier layer only minimal degradation is observed.

A novel ion beam source has been successfully used in both a CAIBE and RIBE configuration, with chlorine as the chemically active gas, to achieve GaAs etching a rates of around 0.1 µm/hour. The energy of species within the beam from the source is estimated at 10 - 25eV. Under these conditions it can be expected that little or no penetration into the GaAs lattice occurs and that the principle origin of lattice disruption, prior to etching, is chemical; a low damage GaAs etching process results. The source, however, gives rise to a coating, derived from the source liner, which must be washed from all etched samples. The presence of such a coating is likely to be the origin of the slow etch rate achieved. After removal of the coating, smooth, mirror like etched surfaces are apparent. These surfaces perform very well when Schottky diodes are constructed from them showing no deviation from the behaviour of control samples.

Novel processing methods are being studied to address the highly selective and directional etch requirements of the ULSI manufacturing era; neutral molecular and atomic beams are two promising candidates. In this study, the potential of 5 eV neutral atomic oxygen beams for dry development of photoresist is demonstrated for application in patterning of CMOS devices. The patterning of photoresist directly on polysilicon gate layers enables the use of a self-contained dry processing strategy, with oxygen beams for resist etching and chlorine beams for polysilicon etching. Exposure to such reactive low-energy species and to the UV radiation from the line-of-sight, high-density plasma source can, however, alter MOSFET gate oxide quality, impacting device performance and reliability. We have studied this process-related device integrity issue by subjecting polysilicon gate MOS structures to exposure treatments of 5–20 eV oxygen beams similar to those used for resist patterning. Electrical characterization shows a significant increase in the oxide trapped charge (30–90x) and interface state density (30–60x) upon low-energy exposure. Current-voltage(IV) and dielectric breakdown characterization show increased low-field leakage characteristics for the same exposure. High-field electron injection studies reveal that the 0.25–V to 0.5–V negative flatband shifts (measured after oxygen beam exposure) can be partially annealed by carrier injection. This could be due to positive charge annihilation or electron trapping, or some combination of both. SEM and electrical analysis of structures exposed to neutral beam processing are presented along with the results of thermal annealing treatments.

A one dimensional mass continuity equation was used to model a low pressure, high radical concentration, non-isothermal oxygen afterglow reactor. The mathematics are very similar to those used to model flames. It was shown that the model, with no adjustable parameters, yielded very good agreement with experimental measures of O-atom flux. The model was manipulated to study the influence of temperature profile, pressure, homogeneous and heterogeneous kinetics, O-atom generation and flow rate on the afterglow plasma.

The reactions of metal oxides including CuO, ZnO, V2O5, and PbO with 1,1,1,5,5,5-hexaflouro- 2,4-pentanedione (hfacH) were investigated. A hot-wall reactor was used to react hfacH with metal oxide powders to form sufficient quantities of volatile reaction products for characterization by Infrared Spectroscopy (IR), Elemental Analysis (EA), Nuclear Magnetic Resonance (NMR), Mass Spectroscopy (MS), Thermogravimetric Analysis and Differential Thermal Analysis (DTA). PbO, ZnO and CuO powders reacted rapidly at 200 °C to form the corresponding metal β-diketonates and V2O5 reacted to give OV(hfac)2. A differential cold-wall reactor was to used to measure etch rates of CuOx films as a function of temperature and hfacH partial pressure. AES and XPS analysis of the laser ablation deposited CuOx film annealed in an O2 atmosphere revealed that the film was composed of CuO and Cu2O. Etch rates of up to a I l.βm/min at hfacH partial pressure of 1 Torr at 270 °C were obtained. Laser induced etching of the same CuOx film with hfacH showed evidence of copper oxide removal.

This paper describes a novel route for removal of surface carbon from heavy-metal fluoride glasses melted in vitreous carbon crucibles. The technique utilizes dry etching with active fluorine produced in a NF3 plasma generated in a microwave cavity.

During ion-assisted growth of thin films from the vapor phase, defect generation and incorporation are of paramount interest. In many cases the wish is to obtain as defect free films as possible, however, in some applications a certain, controllable, defect content is desirable. In this paper experimental results on defect incorporation as a function of ion energy and growth temperature are presented. Results for poly- and single crystalline TiN films as well as for epitaxial Mo/V superlattice films are given. As the ion energy and/or ion flux are increased the amount of defects increases. At low temperatures the defects consist predominantly of point defect clusters and incorporated primary ions while at higher temperatures redistribution of point defects and incorporated primary ions results in dislocation loops and gas bubbles, respectively. However, for low ion energies where the energy transferred to the growing film surface is not high enough to cause atomic displacement events, reduction of defect densities can also be obtained. Furthermore, in the case of Mo/V superlattices it is demonstrated that interfacial mixing and increased interface roughness occurs at ion energies ≥ 25 eV. In the absence of an applied substrate bias the interface widths are determined to be 0.3 nm. For higher energies the widths becomes progressively larger and at a bias of 225 V an interface width of > 0.9 rum is obtained.

Reactive magnetron sputtering (RMS) is a versatile technique for the production of alloy thin film coatings such as hydrides, nitrides, oxides, etc. RMS provides control over (i) film stoichiometry, via the partial pressure of “reactive” gas (H2, N2, etc.) injected, and (ii) film microstructure, via the bombardment of the growing surface by fast neutral or accelerated ionic species. However, few details are known about the fluxes reaching the film surface, and their reactions with it.

This paper reports comprehensive measurements for the RMS growth of hydrogenated amorphous silicon (a-Si:H). The analysis techniques are in situ double modulation mass spectroscopy, plasma probes, isotope replacement experiments, and Monte-Carlo simulations of sputtered particle transport. We determine (i) the composition, energy and angular distributions of the incident flux, (ii) the H coverage of the growing surface, and (iii) the release of H2 from the growing film. For conditions which produce electronic quality a-Si:H, the total H flux arriving at the substrate varies between 0.5–2 times the depositing Si flux; about half of the H flux reflects. The growth surface has excess H varying between 0.5–2 × 1015/cm2, and this surface H coverage is linearly related to the bulk H incorporation. We also find evidence that film density varies with the energy of the arriving sputtered Si atoms.

The thin film processes of the sputter deposition method have been reviewed with special emphasis on the effects of kinetic energy of sputtered particles and ion bombardment during deposition on thin film properties. An overview is first given to describe the thin film process and ion-surface interactions, where the methods of measuring the energy distribution of sputtered ions and the anisotropic-emission-effect sputter deposition are presented. Experimental results for Cr, SiO2 and Ni-Si-B films are presented, and the correlation between the structure and properties of the thin films is discussed. Research in modification of thin films by energetic atoms and ions is an exciting area of materials science in the future.

Ion beam sputter-deposition is a technique currently used by many groups to produce single and multicomponent thin films. This technique provides several advantages over other deposition methods, which include the capability for yielding higher film density, accurate stoichiometry control, and smooth surfaces. However, the relatively high kinetic energies associated with ion beam sputtering may lead to difficulties if the process is not properly controlled. Computer simulations have been performed to determine net deposition rates, as well as the secondary erosion, lattice damage, and gas implantation in the films, associated with primary ions scattered from elemental Y, Ba and Cu targets used to produce high temperature superconducting Y-Ba-Cu-O films. The simulations were performed using the TRIM code for different ion masses and kinetic energies, and different deposition geometries. Results are presented for primary beams of Ar+, Kr+ and Xe+ incident on Ba and Cu targets at 0° and 45° with respect to the surface normal, with the substrate positioned at 0° and 45°. The calculations indicate that the target composition, mass and kinetic energy of the primary beam, angle of incidence on the target, and position and orientation of the substrate affect the film damage and trapped primary beam gas by up to 5 orders of magnitude.

Molecular dynamics simulations of the deposition of atoms on crystalline surfaces have been conducted using the embedded atom method. The following atom-substrate combinations have been employed: 0.1 - 40 eV Ag deposited on (111) and (100) Ag substrates; 0.1 eV Ag deposited on (100) Cu; and 0.1 eV Cu deposited on (100) Ag. The purpose of the calculations for Ag atoms deposited on Ag substrates was to investigate the effects of adatom arrival energy and substrate orientation on the interactions of low-energy atoms with crystal surfaces. The goal of tile Ag oil Cu and Cu on Ag calculations was to observe the mechanisms producing thepreviously-reported asymmetry in epitaxy for these systems. The Ag on Ag deposition simulations demonstrated that the effects of increased atom arrival energies in promoting layerby- layer film growth and producing diffuse substrate-filn interfaces (mixing) were basically the same on the (100) and (111) surfaces. At 0. 1 eV, representative of thennal evaporation, the degree of island formation on the (100) substrate was essentially tile same as previously reported for a (111) Ag substrate. At a given atom arrival energy between 10 and 40 eV, both the redistribution into full monolayers and the mixing by surface exchange interactions were seen to occur more readily on the close-packed (111) growth surface than on the more open (100) surface. The mixing was a stronger function of crystallographic orientation. Cu was observed to grow on (100) Ag as a (100)-oriented film, with the initial film layers transfonned essentially to the bcc structure by a Bain distortion, in agreement with various experimental results. The distortion of the film layers resulted in large-amplitude soft-mode (low-frequency) lattice vibrations. Ag was observed to grow on (100) Cu as a (111)-oriented film, as experimentally observed, with the <110>-type orientations of film and substrate parallel, as predicted by previous calculations of interfacial energy.

We have observed a suppression of island formation and an increase in the thickness limit for layer-by-layer growth of Ge on Si (100) by ion-assisted molecular beam epitaxy. Island suppression is observed both for ion energies at which surface defect generation dominates bulk defect generation and at which the majority of defects generated are bulk defects. This experiment, in conjunction with results of a linear elastic stability model for islanding, reveals that the kinetic mechanism for the suppression of island formation via ion bombardment is the reduction of surface amplitude fluctuations during the early stages of growth.

The purpose of this paper is to discuss the results of experiments that were done to develop a process to reliably produce low-stress a-SixC1−x:H films by PECVD. The films were deposited at 380 °C in a horizontal hot wall reactor using mixtures of silane and methane. The unique feature of the reactor is that, In contrast to others, the plasma was powered by two power sources; one was operated at 450 kHz, the other at 13.56 MHz. The plasma was maintaired in a mixed frequency mode during deposition. The total energy input to the plasma during a duty cycle was kept fixed while the properties of the films were altered by adjusting the relative energy output of each power supply. The energy output of each generator was adjusted by changing their on-times and peak powers. The composition of the films, their Initial stress, and the behavior of their stress during a temperature anneal were studied extensively. The Si/C ratio of the films varied from 0.3 to 3.0. The hydrogen concentration varied from 24 to 32 atomic percent. The initial stress was controlled by frequency mixing, and varied from −400 MPa to + 100 MPa.

The influence of magnetic field on Plasma parameters of ECR plasma were measured by the Langmuir probe technique. And it was shown that the plasma parameters can be controlled by magnetic field. Amorphous silicon films were prepared by ECR plasma CVD method under various magnetic field conditions for the purpose to investigate the effect of plasma density and energy on the property of amorphous silicon films. High plasma density improved the photoconductivity of amorphous silicon but the optical gap and activation of dopant depended on the substrate temperature rather than plasma density.

Polycrystalline CuInSe2 thin films were prepared by coevaporation of the elements under the irradiation of nitrogenions excited by ECR plasma. Nitrogen atoms were doped uniformly in the obtained CuInSe2 films according to the SIMS analysis. The films showed p-type conduction even in the slightly In-rich region where the coevaporation films without the irradiation of nitrogen ions showed n-type conduction. These results show that p-type CuInSe2 thin films even in the slightly In-rich region can be fabricated by the irradiation of ECR excited nitrogen ions during its ternary coevaporation process.

The defect structure of silicon oxynitride films prepared by the ECR Plasma CVD method have been studied by ESR(electron spin resonance) method. The ESR analysis revealed the presence of three paramagnetic defects,that is, Si dangling bonds(g=2.0055 ΔHpp=8 Oe), Si dangling bonds with N atom neighbors(g=2.004, ΔHpp=12 Oe) and E-center(g=2.0016, ΔHpp=4 Oe). These centers strongly depend on the deposition conditions, such as gas flow rate, and microwave powers. The defect density is minimum for the deposition condition of SiON films, under the gas flow O2 /(N2 +02)ratio of 1/3, gas pressure of 8.3x10−4Torr and microwave power of 50OW.