Ion Beam Incidence Angle Research Articles

A reactive ion beam etching and coating system

A reactive ion beam etching system, which can be used for reactive ion beam milling and ion beam coating, has been developed. The effective ion beam diameter is 10 cm with nonunifonnity in beam density less than ± 5%. The etching target is cooled by a semiconductor refrigerator so that the temperature of samples can be kept below 100°C under working conditions. The ion beam energy, density and incident angle can be changed continuously from 200 to 1000 eV, 0 to 1.0 mA/cm 2 and 0° to 90°, respectively. With the help of an improved Kaufman type ion source which is made of graphite and a unique ion beam current feedback system, the stability of the reactive ion beam current using CF 4 gas is up to 0.4% per hour. For ion beam coating spherically dished grids are used, current densities of Ar + up to 18 mA/cm 2 at 1000 eV are achieved at a focal distance of 23 cm. Using CF 4 gas, the etch ratio of SiO 2 to Si is 9, and some other materials such as LiNbO 3 and Bi 12GeO 20 can be etched with good results as well.

Characteristics of submicron patterns fabricated by gallium focused-ion-beam sputtering

Cross sections of the patterns fabricated in (100) GaAs by 100-keV gallium focused ion beam have been studied using a scanning electron microscope (SEM). The probe size of the ion beam is 0.1–0.15 μm at the current of 100 pA. The etched depth becomes saturated at the high dose region (about 5.0×10−6 C/cm) because of the redeposition effect. The pattern profile becomes asymmetric if it is made up of several adjacent lines perpendicular to the beam scanning direction due to the redeposition effect and the increase of sputtering yield for each scan, which is caused by the change of ion beam incident angle. These effects can be eliminated by the use of multiwriting method.

A pattern edge profile simulation for oblique ion milling

An oblique ion milling simulation method is proposed in which etching and redeposition at the pattern side wall are taken into account. The effective etching rate at the pattern side wall is determined as the difference between the etching rate given by the angular dependency and the redeposition rate. The redeposition rate is assumed to be proportional to the etching rate of the material to be etched at the flat surface. A pattern edge profile simulation is carried out for an oblique ion milling of silicon. The simulation results agreed well with the experimental results with a relatively large ion beam incident angle.

Argon and reactive ion beam etching for SAW devices

Ion Beam Etching has played a prominent part in the development of surface accoustic wave (SAW) devices. Two modes have been developed: (1) argon ion beam etching is used for the precision manufacture of grooves in lithium niobate for reflective array pulse compression filters (RAC); (2) reactive ion beam etching in CHF 3 is used for etching grooves in quartz for SAW resonators and surface skimming bulk wave transducers. The etch rate of quartz in CHF 3 increases with the beam current density and is substantially independent of the ion beam incidence angle. Predictable groove profile shaping is demonstrated. Polymerization of the CHF 3 etching gas is shown to be a function of the charge conditions existing on the surface of the substrate. Plasma developable resists of good reactive ion beam etching resistance are shown to have a sub micron line resolution capability.

Silicon nitride and oxynitride films prepared by ion beam reactive sputtering

The composition of particles sputtered from a silicon target during bombardment by nitrogen and oxygen ions was measured. Elementary processes on both the substrate and the target were examined. A model of silicon nitride film formation was proposed, in which the main idea is the interaction of silicon on the substrate with the atomic nitrogen sputtered from the target. The dependence of the film properties on the oxygen concentration in N 2O 2 mixtures was investigated. The relationship between the nitrogen and silicon concentrations in silicon nitride films, the nitrogen ion beam incidence angle and the ejection angle of the sputtered particles was revealed experimentally. In the proposed model this relationship is interpreted as a result of the difference between the angular distribution of silicon and nitrogen atoms sputtered from the target.

Topographical changes induced by low energy ion beam sputtering at oblique incidence

Abstract When niechanically polished Ge, Si, GaAs, LiNbOj, Cd-Ga-garnet, fused quartz and glass surfaces are sputtered by low energy ion beam (from 300 to 1200 eV) at an incident angle of 45°, the surfaces are found to exhibit hillock-like features. The influence of ion beam incident angle, energy, dose and target rotation on surface topography have been investigated. The analysesof hillocks by SIMS and AES show that their formation may not be due to impurity contamination caused by redeposition. A mechanism for hillock formation is proposed. This can be expressed by aformula, through which all the results can be successfully explained.

Single Event Upset Vulnerability of Selected 4K and 16K CMOS Static RAM's

Measurements of single event upset probability for several types of prototype bulk CMOS and CMOS/SOS RAM's have been made using beams of 140 MeV krypton, 160 MeV argon and 33 MeV oxygen ions from the Lawrence Berkeley Laboratory 88-in cyclotron. Upset thresholds, determined by varying the ion species and beam-incidence angles, were used in conjunction with manufacturer-supplied information on device design parameters to estimate values of critical charge for upset. These experimental values are in reasonably good agreement with scaling predictions of Petersen et al. and Pickel. Comparison of the critical charge values deduced from experiment with predictions obtained for the 16K CMOS/SOS devices by means of SPICE and RCAP simulation codes shows discrepancies of approximately a factor of two. These discrepancies indicate the need of additional experimental and theoretical work before an adequate understanding of device response to charged particle bombardment is achieved.

Improvement in gate breakdown voltage for SOS devices

It was attempted to improve low gate breakdown voltage for an air-isolated SOS devices, employing ion-beam etching technology for silicon-island formation. Gate breakdown origin was clarified with SEM observation. As a result, it has been found that 1) low gate breakdown voltage for air-isolated SOS devices is caused by thinner gate oxide at the bottom of a steep silicon-island edge, and 2) ion-beam etching with the ion-beam incident angle over 40° allows the silicon island to have a sidewall angle under 35°, thus resulting in uniform gate oxide thickness. Consequently, the gate breakdown voltage for the air-isolated SOS devices can be improved to as high as that for dielectric isolated SOS devices.

Influence of the bombarding angle on the sputtering yield of heavy atomic and molecular ion bombardment of Ag and Auf

Abstract The sputtering of polycrystalline Ag and Au by heavy atomic and molecular ion bombardment has been measured as a function of the ion beam angle of incidence, θ Comparison is carried out between the measured and calculated values where the calculated values are based upon determination of the surface deposited energy assuming infinite (transport theory) and semi-infinite (Monte-Carlo calculation) media. It is found that the angular dependence, out to 75° from normal incidence, of the measured sputtering yield for Ag and Au bombarded with heavy atomic and molecular ions of Sb and Bi are somewhat different, with the Ag sputtering yields showing a slower rate of increase with θ at large (θ ≳ 70°), than in the case of Au sputtering. Also the sputtering by molecular ions shows a much larger sputtering yield/atom than for the same velocity monatomic bombardment. This enhancement increases non-linearly with the number of atoms/molecule, but decreases with the angle of incidence. It is found that the sputtering yield as a function of angle of incidence becomes increasingly lower than would apparently result for a normal incidence bombardment having the equivalent value of surface deposited energy. This is consistent with increasing ion reflection at larger angles of incidence reducing the molecular ion enhancement factor and a further reduction associated with expected smaller depth topographical features as the angle of incidence increases.

Pattern fabrication by oblique incidence ion-beam etching

Effects of ion-beam incidence angle on etched pattern profiles have been studied. Ion-beam etching was performed using a rotary stage and a Kaufman-type ion gun operated at a 500 V acceleration voltage and a 0.5 mA/cm2 current density. Etched patterns show a unique side wall contour which consists of two distinguishable slopes. The slope angles depend on ion-beam incidence angle and mask thickness. The side wall contour is theoretically interpreted taking into consideration the effects of both ion-beam shadowing and redeposition.

New planar process for 2µm bubble devices with thin film detector

Conventional 2 μm bubble devices with thin permalloy detector have been successfully fabricated using a new planar process. Spacer layer undulation due to underlying conductor patterns is reduced by an organic fluid spin coating, followed by coated layer contour transformation by ion-beam etching. The spacer layer step reduction depends on ion-beam incidence angle. For sputter deposited SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> spacer and spin coated AZ 1350J resist, optimum reduction is obtained at 30° beam angle. Detector figure of merit for a 300 Å thick, 2 μm wide permalloy detector is found to be 1.8% at 25°C. Temperature coefficient for output voltage is -0.36%/°C at 25°C. The output voltage does not depend on drive field amplitudes ranging from 30 to 70 Oe. A 256 kbit chip fabricated using the planar process shows an overall bias margin of 30 Oe at 55 Oe drive field amplitude.

斜め入射イオンエッチングによるパターン形成

Ion-beam etched pattern profiles for an oblique ion-beam incidence have been investigated. The ion-beam etching was performed using a Kaufman type ion gun and a rotating stage. Etched patterns show a unique side wall profile due to ion-beam, shadowing effect. The side wall angle discontinuously changes at the half point of the total etching depth. As the ion-beam incident angle increases, the bottom wall angle becomes lower, while the upper wall angle approaches normal to the sample plane. The bottom wall profile can be interpreted by a theoretical model, taking into consideration the time dependent ion-beam flux distribution. The lateral shift of the upper wall can be explained by considering both etching and redeposition.

Formation of cones during sputtering

Abstract Conditions of cone formation on the sputtered surface of single crystals : re examined. The effects of the various irradiation factors (dose, face orientation, ion beam incidence angle, etc.) on cone formation are studied. The cone formation on sputtered surfaces is primarily explained by crystal growth under the conditions of atom migration and target sputtering.

Annealing of defects at high temperature irradiation of silicon by accelerated ions

Abstract Angular and temperature dependences of ion-electron emission coefficient γ at bombardment of the 〈111〉 face of Si monocrystal by Ar+ ions with the energy of 70 keV and by Kr+ ions with the energy of 30 keV were studied. Two “annealing stages” of radiation defects were observed under irradiation: at T° of 400°C order. When annealing of the near-surface amorphized layer takes place under irradiation and at temperatures above 600°C (T = 0.52 of the melting temperature). It is shown that in contrast to the first stage of defects annealing, the second “stage” does not cause changes of γ = γ(ϕ) angular dependences types (ϕ is the angle of ion beam incidence onto a crystal surface) and leads only to a decrease of γ value. This phenomenon is connected with the processes of considerable density formation of high temperature structure defects resulting in electrons capture. The significance of crystal surface is underlined in formation of these capture centres, as well, as considerable analogy with Ge crys...

スパッタ加工面特性

The ion beam sputter-machining is suitable as a surface finishing process of inorganic materials, and its mechanism is different from the conventional polishing process.The sputter-machining apparatus is constituted in such a way that the gas of ion source is argon and the ion gun is of a duo-plasmatron type which emits the ion beam of 1 mA/cm2 current density at accelerating potential of 20 kV.In the experiment the sputter-machining of BK-7 glass highly polished beforehand was done under the conditions that the ion beam current is 200μA, the incident angle 60°, the rotation speed of workpiece 20 rpm and then the sputtering rate S of 1.2 mol/ion and the machining rate of 14.4A/s in depth were obtained.From the results of experiments the following conclusions were obtained.(1) The machined surface and sputtering rate are largely affected by the incident angle of ion beam. The deteriorated surface appears at an incident angle of 60 degrees.(2) The surface finishing of optical surface can be performed by selecting proper machining conditions for the incident angle, rotation of workpiece and so on.(3) The contamination of workpiece is kept out by the electron neutrizing effect.

Collection and sputtering experiments with noble gas ions

The present paper describes experimental work on the collection of noble gas ions of energies 5–65 keV. We have used an electromagnetic isotope separator to measure saturation values in different materials. The dependence of saturation value on different experimental conditions is investigated, e.g. variations with current density, angle of ion beam incidence and target temperature. In order to provide a simple description of the collection process, we have also measured the sputtering ratios for noble gas ions bombarding different materials. Sputtering is discussed in the light of existing theories for which a few improvements are proposed.