Low Energy Ion Source Research Articles

A 10-s doping technology for the application of low-temperature polysilicon TFTs to giant microelectronics

A bucket-type high-density (0.25-1.2-mA/cm/sup 2/) low-energy (500-2000 V) ion source was utilized for high-speed phosphorus doping directly into a thin polysilicon layer without cap SiO/sub 2/. Doping gas with He dilution was selected to reduce etching of polysilicon film. Excimer laser (XeCl, 8 mm*8 mm) pulse annealing was introduced to activate effectively the doped impurity. The combination of these techniques provided a practically low sheet resistance for the TFT source, drain, and gate with a short time doping. The low-temperature polysilicon TFT fabricated with a doping time of 10 s had characteristics comparable to those of that fabricated by a longer time doping or conventional ion implantation, showing the practicality of this technology and its promise for giant microelectronics. >

Studies of hydrogen ion beam cleaning of silicon dioxide from silicon using in situ spectroscopic ellipsometry and x-ray photoelectron spectroscopy

The removal of a thin oxide layer from a silicon substrate without significant damage has been achieved at temperatures as low as 500 °C using a low-energy hydrogen ion beam produced by a high-intensity and low-energy ion source in a high-vacuum system. In situ spectroscopic ellipsometry was found to be a sufficiently sensitive and nondestructive method for simultaneously monitoring silicon surface cleaning and ion-induced substrate damage. This letter reports the optimum cleaning parameters for silicon (i.e., minimum ion-induced damage with maximum etch rate of SiO2) to be 300 eV ion beam energy, 60° beam incidence, and 500 °C substrate temperature.

Irradiation Effect of Ion Beam in FexN Films Prepared by IRD

Magnetic thin films of Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> N were prepared by so-called "ion reacting deposition." To clarify the effect of ion beam irradiation during deposition, the difference between use of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ions and Ar ions was studied. A low-energy broad-beam ion source (Kaufman type) was directed normal to the substrate, which was set obliquely to the direction of iron vapor incidence. All of the Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> N films consisted mainly of paramagnetic ε-Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-3</sub> N and α-Fe according to Mossbauer measurements; that is, separation into two phases took place in these films. The coercive force H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of iron films prepared by Ar ion beam irradiation decreased with increasing ion current density, while that of Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> N films increased to saturation. This indicates that the ion bombardment did not lead to the increase in H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> . We were able to analyze the film magnetic anisotropy into two different shape anisotropies related to the columnar microstructure of the film. The change in H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and shape anisotropy in Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> N films can be attributed to the anisotropy in the packing density of α-Fe, as estimated from the observed saturation magnetization of the films.

Real-time monitoring of molecular-beam epitaxy processes with coaxial impact-collision ion scattering spectroscopy (CAICISS)

Abstract Coaxial impact-collision ion scattering spectroscopy (CAICISS) is a novel form of low-energy ion scattering spectroscopy (ISS), in which a pulsed-beam low-energy ion source and a time-of-flight ion energy analyzer are placed coaxially so as to cover the experimental scattering angle at 180°. It is demonstrated that CAICISS is useful for monitoring molecular-beam epitaxy (MBE) processes in real time by taking the MBE growth of AlAs on a GaAs(001) substrate as an example.

Preparation of CoxN Thin Films by the Ion Reacting Deposition Method

The formation of cobalt-nitride thin films by the ion reacting deposition method was investigated. A low-energy broad-beam ion source (Kaufman type) was used for ionizing nitrogen. X-ray diffraction spectra revealed that the N-rich cobalt nitrides Co 3 N and Co 2 N were formed only at low ion current densities during deposition. The magnetic properties of the films changed suddenly with increasing Jion. H c was maximum at J ion =1.5 (mA/m2)/(A/s), above which the N-poor compound Co 4 N was formed. The nitrogen which was contained in films but was not involved in the nitriding reaction, was degassed above 250°.

Development of a low energy ion source with multicapillary anode

A new type of hot cathode ion source which has a multicapillary anode and a discharge stabilizer electrode has been developed. There are two special features in this ion source. The gaseous flow is intense and of the collimated beam type, because it is introduced through the multicapillary anode. A high ion current density ( > 5 mA/cm 2) can be obtained because discharge in high vacuum can continue with the help of the stabilizer electrode. At a stabilizer voltage ( V s ) of 50 V, ion current densities of 2.2 and 6.1 mA/cm 2 were obtained at acceleration voltages ( V acc) of 20 and 200 V, respectively. The ion energy was dependent on V d, and the full width at half maximum (FWHM) of its distribution was less than 15 eV. Cu films were etched by this ion source. The etching rate ( E r) was 150 Å/min at V acc = 100 V. The relationship between the etching rate and V acc was represented by E r ∝ ( V acc) α . The values of α were 2.0 in the region of V acc ≤ 100 V and 1.0 for V acc ≥ 100 V.

Hydrogen particle diagnostic based on Pd-MOS diode arrays

The reverse-bias current through a Pd-MOS diode changes when hydrogen is present at the diode interface and this effect provides the bias for a solid-state detector to monitor the flux and energy of hydrogen particles emanating from a beam or plasma. The addition of a coating atop the Pd forms a high-pass energy filter and an array of coated Pd-MOS diodes can function as a compact, hydrogen-specific, energy spectrometer. The response characteristics of an Au-coated Pd-MOS diode array have been measured using a low-energy hydrogen ion source. The array has several desirable characteristics for energetic hydrogen detection. Its response is dosimetric, it discriminates between hydrogen irradiations at different energies, and it can be regenerated by heating briefly to 100–200 °C. These properties make Pd-MOS diode arrays attractive candidates for remote plasma-edge flux and energy monitors in fusion devices.

The accelerator-based mass spectrometry of methane

Accelerator-based Mass Spectrometric (AMS) methods have not been generally applied to the analysis of molecular species because of difficulties with ion sources and the fact that tandem accelerators are not generally applicable. A method has been developed to measure the abundance of fully deuterated methanes, 13 CD 4 and 12 CD 4 , in normal methane by using AMS. A low-energy electron bombardment ion source has been coupled to a single-ended electrostatic accelerator to produce positively charged molecular ions. The ions are accelerated, mass selected, and then dissociated into fragments that are detected by nuclear particle detection methods. In this way information about the composition of the original molecule, as well as the mass, is obtained. Measurements on natural neon, 12 CH 4 , 12 CD 4 , and 13 CD 4 have been made, and new approaches to the stabilization of accelerator voltage and isotopic abundance calibration are presented. Possible applications for analysis of other molecules not easily measured with conventional AMS are considered.

Low-Energy High-Current Ion Source for Ion-Milling Equipment

Summary Ion-milling technique using ion-shower equipments has become practical in several applications, including surface cleaning, fine machining, etc. However, the removal rate is generally not very high comparing with other dry etching processes. On the other hand, in many cases lower ion energy than usual 500eV is desirable, because it is expected that a lower energy bombardment gives less damage on the machined surface. Consequently, a low-energy high-current ion beam is in a great demand. However, the two requirements contradict each other. In a Kaufman type equipment those beam characteristics chiefly depend upon the ion extractor or the grid system. Authors made tests for developing a grid system with high ion extracting efficiency in low range of extracting voltage. Several types of grid systems including conventional two grid system were tested on their applicability, and following conclusions were obtained. Theorectical possibility of conventional two-grid systems was confirmed. However, following two types were found to be more hopeful ones because of their high performance and simpler structure. 1) single grid with insulating layer. 2) Insulator-substrate grid. Especially the insulator-substrate grid was found to be promising for its possibility of wide application.

Study of Beam Divergence of a Low-Energy (1–3 keV) Ion Source

Study of Beam Divergence of a Low-Energy (1–3 keV) Ion Source

Electron Capture Collisions Involving Low-Energy Highly-Stripped Projectiles

Recoil ions produced by fast-ion bombardment of dilute gases are in use at Kansas State University as a source of low-energy highly-charged ions to study electron capture by these projections on neutral targets in the 106-107 cm s-1 velocity range. A progress report on several phases of this program is summarized.

Construction of a simple low-energy high-intensity gas ion source with a multiaperture extractor system

The gas ion source described is useful for a wide range of applications. It is versatile and easy to optimise by changing various geometrical and/or electrical parameters. The source is used as part of an existing apparatus and typical working parameters are presented together with its performance.

High Performance, Low Energy Ion Source

An ion accelerator system using one or two fine mesh tungsten grids has been used in a magnetic multipole containment ion source to produce a continuous positive ion beam variable over a wide range of beam currents and accelerator voltages. The ion source plasma is low noise and uniform to ± 1% density variation over 9 cm diameter. Beams up to 4 cm × 4 cm have been extracted which have low divergence (±1%), uniform current density (±2%), small ion energy speed, beam ion energy variable from 200V to several thousand volts, and current densities variable from ?A per cm2 to tens of milliamperes per cm2, limited only by acceleration grid power loading or sputtering.

Low Energy Ion Source with High Efficiency

A High efficiency ion source which produces low energy ions(100∼500eV)is described. In order to prevent the decrease of ion intensity due to low accelerating potential, negative high voltage is applied to the main slit. Ions are first accelerated to several thousand volts and then decelerated to several hundred volts af ter passing through the main slit. Almost the same ion intensity was obtained compared to ordinary ion source with high accelerating potential. The decrease of resolving power due to low accelerating potential was negligible when the ion source was attached to a double focusing mass spectrometer of second order. This type of ion source is useful for mass analyses of very heavy organic compounds, because very strong magnetic field is not required.

Deionisation of an interrupted vacuum arc

Measurements have been made of time-dependent saturation ion currents flowing to a probe and to the discharge electrodes following the forced extinction of high-current (1–5 kA) vacuum arcs of short duration (≃1 ms) on copper electrodes.The results have been utilised to derive ion-flux distributions irrespective of ion-charge number, assuming collisionless plasma expansion from the cathode spots, and significant differences have been found compared with previous measurements on steady-state discharges.The results on interrupted and steady-state discharges are reconcilable if a source of low-energy ions exists, which is constrained in the cathode-spot region in the steady state and which is released at the zero current condition when the constraining forces vanish.

ECR Ion Source Using Mesh Electrodes and a Space Charge Neutralizer

A low energy (100–500 eV) ion source is developed in which a source plasma is generated by microwave discharge in a magnetic field at ECR condition. Positive potential is applied to the source plasma, and ions are accelerated by the sheath drop in front of a mesh screen. A thermionic electron emitter is provided for neutralizing the beam space charge. The ion beam (3 cm in diameter) has little divergence, and the intensity (up to 50 mA) is nearly independent of the accelerating voltage except for the range below 150 V.

A Laboratory Simulation of the Ionospheric Plasma

CORRECT simulation of the ionospheric plasma surrounding a satellite has been obtained in a large Vacuum chamber by means of a synthesized plasma stream produced by a low energy and high current density ion source. The plasma density and the beam velocity can be varied independently from 103 to 106/cm3 for the density and from 7 to 30 km/sec for the velocity. The electron velocity distribution is Maxwellian and the temperature can be varied between 500 and 2000°K. This plasma wind tunnel is being used for fundamental studies on the wake structure and for testing ionospheric probes. Contents The simulation of the spacecraft motion in the ionospheric plasma can be obtained by means of a synthesized plasma stream directed toward a model of the spacecraft. Several plasma windtunnels working on this principle have been built in recent years.1'2 Most of them have been used only for fundamental research such as satellite wake investigations or the diagnosis of streaming plasmas. Scaling laws are frequently used for these fundamental studies and the experimental conditions are then relatively easy to obtain. However the laboratory calibration of plasma diagnostic instruments which will be used on board a spacecraft does not permit any scaling. These instruments (and the plasma volume which is sampled) are generally of a large size, and the associated electronic circuits are adapted to the ionospheric conditions which must be reproduced exactly in the laboratory (in particular the plasma frequency, the electron gyrofrequency and the electron temperature). The correct simulation of the wake effect on these instruments also requires the ion source to be operated at very low acceleration voltage. Correct simulation is not indispensable for the fundamental studies of the wake structure, but if it could be obtained the use of the scaling laws would be no longer required. Moreover the use of a very low energy ion beam reduces to an insignificant amount the perturbation due to the electrons produced by secondary emission on the obstacles. For these reasons a plasma wind tunnel of large dimensions has been developed with a special effort to obtain, as much as possible, an exact simulation of the ionospheric pla'sma over large volumes. The two principal difficulties have been the development of an ion source working at low accelerating voltage and high current density, and the obtaining of electron temperatures in the range of 500 to 2000°K, which are lower than what is normally obtained in steady state laboratory plasmas. The plasma stream is produced in a vacuum chamber of large dimensions (3 m in diameter and 5 m long). The ultimate pressure is of the order of 10~ 5 N/m2 (1 N/m2 = 0.75 x HT2 Torr). The diagnostic instrument under test or the satellite

Measurements of Beam Emittance in Low Energy Ion Source

Measurements of Beam Emittance in Low Energy Ion Source

Low Energy Ion Source for Chemical Reactions

Low Energy Ion Source for Chemical Reactions

A straight channel multiplier used as a low-energy ion source

Experimental results are presented dealing with the energy distribution of positively charged ions occuring within straight channel multipliers. These ions are produced mainly at the positive potential end of the tube by interaction between cascade electrons and residual gas molecules inside the vacuum chamber. There exists a sharp decrease in the energy distribution of the ions corresponding to the applied high voltage of the straight channel multiplier.