Viktor Kanarov

High resolution energy analyzer for broad ion beam characterization

Characterization of the ion energy distribution function (IEDF) of low energy high current density ion beams by conventional retarding field and deflection type energy analyzers is limited due to finite ion beam emittance and beam space charge spreading inside the analyzer. These deficiencies are, to a large extent, overcome with the recent development of the variable-focusing retarding field energy analyzer (RFEA), which has a cylindrical focusing electrode preceding the planar retarding grid. The principal concept of this analyzer is conversion of a divergent charged particle beam into a quasiparallel beam before analyzing it by the planar retarding field. This allows analysis of the beam particle total kinetic energy distribution with greatly improved energy resolution. Whereas this concept was first applied to analyze 5-10 keV pulsed electron beams, the present authors have adapted it to analyze the energy distribution of a low energy (<or=1 KeV) broad ion beam. In this paper we describe the RFEA design, which was modified from the original, mainly as required by the specifics of broad ion beam energy analysis, and the device experimental characterization and modeling results. Among the modifications, an orifice electrode placed in front of the RFEA provides better spatial resolution of the broad ion beam ion optics emission region and reduces the beam plasma density in the vicinity of analyzer entry. An electron repeller grid placed in front of the RFEA collector was found critical for suppressing secondary electrons, both those incoming to the collector and those released from its surface, and improved energy spectrum measurement repeatability and accuracy. The use of finer mesh single- and double-grid retarding structures reduces the retarding grid lens effect and improves the analyzer energy resolution and accuracy of the measured spectrum mean energy. However, additional analyzer component and configuration improvements did not further change the analyzed IEDF shape or mean energy value. This led us to conclude that the optimized analyzer construction provides an energy resolution considerably narrower than the investigated ion beam energy spectrum full width at half maximum, and the derived energy spectrum is an objective and accurate representation of the analyzed broad ion beam energy distribution characteristics. A quantitative study of the focusing voltage and retarding grid field effects based on the experimental data and modeling results have supported this conclusion.

THIRTY-FIVE CENTIMETER DIAMETER RADIO FREQUENCY ION-BEAM SOURCE

A 35 cm diam inductively coupled rf ion source and its applications for material processing is described. This is the largest commercial rf ion-beam source presently available for ion-beam etching and deposition. It has been used to generate beams of different ions (Ne+, Ar+, Kr+, Xe+, O2+, Cl2+, CH4+,…) at 50–1000 eV of ion energy and corresponding beam currents of 0.15–1.5 A. A presentation of the ion source operation characteristics, along with performance results for various etching and deposition applications are given. Etch uniformities of less than 3% for etch diameters of up to 250 mm are obtained. Etch rates in excess of 100 nm/min for NiFe or silicon dioxide are achievable.

Recent advances in Veeco’s radio frequency ion sources for ion beam materials processing applications (abstract)

In this article we describe an advanced inductively coupled plasma ion source being developed at Veeco for applications in data storage and active optical device fabrication. The new source design minimizes rf capacitive coupling. Capacitive coupling is responsible for erosion of the quartz discharge chamber and high transverse ion energies. Suppression of capacitive coupling, however, can be problematic for some applications due to the fact that, without it, conductive coatings that shield the transfer of inductive power to the plasma can accumulate inside the source. The authors have developed a simple and unique protective device that when installed on the quartz hardware effectively inhibits rf losses in the deposited films, greatly extending the quartz maintenance cycle and overcoming the above problem. Reduction of capacitive coupling is achieved using a slotted Faraday shield inserted between the low-frequency 1.8 MHz rf antenna and the plasma. It is found that the rf power loss to this shield is e...

Ion beam deposition of permanent magnet layers for liftoff processes

Thin film permanent magnet layers of Cr/CoCrPt were prepared by ion beam deposition in a Veeco IBD-350 tool. The magnetic properties were measured as a function of deposition angle, deposition energy, assist energy, and the underlayer and permanent magnet thicknesses. It was found that higher deposition energies and angles (from normal) resulted in larger coercivities. Increasing the assist energy also helped increase the coercivity. The coercivities were in the range of 1400–2100 Oe depending on the deposition conditions, for a Cr-50 A/CoCrPt-250 A film. The squareness, S (the ratio of remnant magnetization to saturation magnetization) and Mrt (remnant magnetization and film thickness product) for these films were about 0.85 and 1.3 memu/cm2, respectively. It was found that underlayers of Cr as thin as 25 A could be used, without significant degradation of magnetic properties. The coercivity had a broad peak between 100 and 200 A of CoCrPt, above which the coercivity gradually decreased. θ–2θ x-ray diffr...

Ion source for ion beam deposition employing a novel electrode assembly

A rf inductively coupled ion source employing a novel electrode assembly for focusing a broad ion beam on a relatively small target area was developed. The primary application of this ion source is the deposition of thin films used in the fabrication of magnetic sensors and optical devices. The ion optics consists of a three-electrode set of multiaperture concave dished grids with a beam extraction diameter of 150 mm. Also described is a variation in the design providing a beam extraction diameter of 120 mm. Grid hole diameters and grid spacing were optimized for low beamlet divergence and low grid impingement currents. The radius of curvature of the grids was optimized to obtain an optimally focused ion beam at the target location. A novel grid fabrication and mounting design was employed which overcomes typical limitations of such grid assemblies, particularly in terms of maintaining optimum beam focusing conditions after multiple cycles of operation. Ion beam generation with argon and xenon gases in en...

Primary beam energy dependence of properties in ion beam sputtered spin–valve films

Spin–valve films with the structure Ta/NiFe/FeCo/Cu(18–30 A)/FeCo/FeMn–70 A/Ta were deposited using a Veeco ion beam deposition (IBD) system, model IBD-350. The physical properties of these spin–valve films as a function of primary ion beam energy have been studied in a primary ion beam energy range of 600–1500 eV. Xe was used as the working gas. The optimal ion beam energy range for the best spin-valve performance has been found to be around 600 eV. Giant magnetoresistance (GMR) values of ΔR/R∼8% have been measured for the spin–valve films deposited in this energy range. A strong dependence on beam energy of magnetic properties for these spin–valve films has been observed in the energy range from 600 to 1500 eV. ΔR/R for spin–valve films with a Cu layer thickness of 22 A decreases from 7.5% at 600 eV monotonically to 6.1% at 1500 eV with increasing ion beam energy. Interlayer coupling field increases from 20 Oe at 600 eV to 37 Oe at 1500 eV. Further reduction in the interlayer coupling field to 13 Oe and...

Investigation of a rf inductively coupled plasma ion source capable of highly uniform and collimated ion-beam generation

In accordance with advanced data storage device fabrication requirements, we have evaluated a new broad-beam rf ion source for ion beam etching and deposition application. This source utilizes a novel reentrant shaped plasma inductively coupled plasma generator for improved radial plasma density uniformity and a dynamic magnetic field for improved static etch uniformity. It has the capability of reproducibly generating extremely uniform ion beams from 500to1500eV with divergence angle <3° and high directionality [Kanarov et al. (patent pending)]. For a 150mm diameter wafer, an etch uniformity of <1% σ/mean in static condition or <0.5% with wafer rotation is obtained over an ion incident angle range of 0°–65°. Recently, we have investigated extending the operation of this source to the critical low energy range, 100–500eV, required for fabricating thin film magnetic head sensors. It was found that, under optimum operating conditions, excellent static etch uniformity (1%–1.5% σ/mean) could be obtained at hi...