Sputtered Target Material Research Articles

Application of the glow discharge mass spectrometry (GDMS) for the multi-element trace and ultratrace analysis of sputtering targets

Glow discharge mass spectrometry using a VG9000 high resolution mass spectrometer has been applied to both the multi-element trace and ultra trace analyses of sputtering target materials, i.e. aluminium-based alloys, cobalt-based alloys, titanium and platinum. Element dependent relative sensitivity factors (RSF) have been determined using reference materials in order to provide the possibility for quantitative analyses. Aluminium-based and cobalt-based alloys have been extensively analysed to demonstrate precision of GDMS analyses. Detection limits in the ng/g and sub-ng/g ranges, i.e. 0.2 ng/g for U and Th have been determined in aluminium-based alloys. Comparative analyses for alloy components in cobalt-based alloys as well as trace concentrations in titanium have been performed. GDMS has been also applied to multi-element depth profile analyses in contaminated and noncontaminated platinum targets.

DC-Magnetron Sputtered Silicon Carbide

AbstractThe preparation and properties of relatively thick films of DC magnetron sputtered SiC films is described. The films were prepared using a new ceramic sputter target material. The new target material is called Hexoloy® SG–90. It is an electrically conductive, dense ceramic material which can be used as a sputter target to yield insulating amorphous SiC thin films on room temperature substrates.

Influence of sputtering target material on the formation of cubic BN thin films by ion beam enhanced deposition

The influence of the sputtering target material on the formation of cubic BN (c-BN) deposited by ion beam enhanced deposition was investigated. Boron or BN films were deposited onto silicon substrates by ion beam sputtering of a pure boron or hexagonal BN (h-BN) sputter-target. An ion beam mixture of argon and/or nitrogen ions was bombarded concurrently onto the growing film. The resulting films were characterized by Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy (XPS). The mass spectra of particles sputtered from the h-BN target were analyzed by secondary ion mass spectrometry (SIMS) using 1–3 keV argon ion beams. Almost single-phase c-BN was deposited using the boron target but, in contrast, c-BN was not formed under any conditions using the h-BN target. The results obtained by XPS and SIMS showed that the h-BN target contained moisture absorbed from the air, and most of the boron atoms were sputtered from the target as compounds of BN, BO or BH when the energy of the sputtering argon ions was less than 2 keV. It is considered that free boron atoms must encounter highly activated nitrogen ions to form c-BN. Nitrogen or other atoms sputtered with boron from the h-BN target seem to interrupt the reaction of boron atoms with the bombarded nitrogen ions to form c-BN.

Improved magnetic behaviour of cobalt-based-alloy sputter-target material

The influence of different grain structures of cobalt alloy sputter targets was examined in terms of magnetic permeability and target utilization. For hexagonal cobalt alloys the best magnetic behaviour can be achieved by a special grain orientation (texture) of the sputter targets, so that the weak magnetic directions are mainly oriented perpendicular to the target surface. Magnetic measurements above the target surface and test sputtering of targets produced by different production techniques demonstrate the possibility of using thicker sputter targets and of higher target utilization, when texture-treated target material is used.

Investigation of angular distributions of ion-induced atomic emission produced under various ion incidence angles

Angular atomic emission distributions of sputtered neutral particles indicate the angular momentum distribution of collision cascades modulated by lattice induced anisotropies of the ejection mechanism. The differential sputtering yield was measured in the angular range between 3° and 80° to the target normal using the collector method: after condensation of the sputtered target material on cooled hemispherical collectors the thickness distributions of the sputtered films were measured in an electron backscattering device. In this way, undistorted angular sputtering yields produced by ion bombardment of monocrystalline Au under various incidence angles were investigated. The results are presented for incidence directions previously checked by ion-induced secondary electron emission. For incidence angles up to 75° to the target normal no deviation from a symmetric emission relative to the surface normal is obvious, whereas the distributions at 80° and 85° show a preference for emission back to the direction of the incident ions.

Characterization of titanium nitride films and sputter target material by 14 MeV neutron activation analysis

Titanium nitride films /3.0 and 3.8 microns/ deposited by the magnetron sputtering technique on silicon substrates and the commercially procured compound sputter target material are characterized for their bulk compositions by non-destructive 14 MeV neutron activation analysis /NAA/. The practical sensitivity and precision obtained under the present experimental conditions are 0.7 mg and 5% in the case of titanium and 0.1 mg and 8% in the case of nitrogen, respectively. The bulk composition of the films seems to conform to stoichiometric nitride, TiN, while the presence of oxygen could not be precluded in the compound target material.

Simulation of focused ion beam milling

The computer program COMPOSITE ( Co mplete M odeling Program of Si licon Te chnology) is a two dimensional process simulator which containts a module for ion beam etching using the well-known string algorithm. This program was modified for focuses ion beam milling, particularly the beam was confined in one direction and the ion beam was given a Gaussian intensity distribution. The program was applied to problems occuring in X-ray mask repair whereby points of emphasis were the shape of the ion beam and redeposition of sputtered target material.

Position and shape of sputtering emission spots measured with hemispherical collectors and electron backscattering

Two-dimensional intensity distributions and angular positions of the emission spots occurring in sputtering experiments with single crystals have been determined for gold and silver targets of different surface orientations under bombardment with argon and oxygen ions. The differential sputtering yield was measured in the whole angular range between 3° and 80° to the target normal using the collector method: after condensation of the sputtered target material on cooled hemispherical collectors the thickness distributions of the sputtered films were measured in a microprocessor controlled electron backscattering device with an angular resolution of 0.2° and a thickness resolution of about 1% of the thickness measuring range. Digital acquisition of the measured data and an image storage unit allow several representation and evaluation methods as e.g., diagrams of constant thickness lines or grey level representations of the emission distributions. Half widths of emission spots have been evaluated in different measuring planes and a strong variation of the maximum spot intensity with the polar emission angle was found.

Angular distributions of heavy particles emitted from a Si target during an ion beam sputter process

Angular distributions of heavy particles — target material and energetic rare gas atoms — emitted from a Si target during a sputter process generated by 10–20 keV rare gas ions have been measured. The influence of beam characteristics — mass, energy, incidence — have been studied. The angular distribution of sputtered target material follows a cos 2 δ function. The rare gas distribution has a sharp shape with a maximum near the direction of the ion beam specular reflection.

Undistorted measurements of differential sputtering yields using the collector method by means of electron backscattering

A method for absolute differential sputtering yield determination is reported. Cooled hemispherical Al-collectors were used to record the complete angular emission distribution of the sputtered target material, avoiding geometrical distortions of the ejection patterns which occur on plane or cylindrical collectors. Incomplete condensation was found to be negligible. The deposit thickness distribution was determined by electron backscattering. Differential sputtering yields and the complete emission distribution for polar angles between 3° and 80° from Ag(111) single crystals under Ar +-ion bombardment were measured for ion energies of 20 keV and 40 keV and a target temperature of 130 K. Polar deviations of 18° ±1° of the weak 〈001〉-spots from the corresponding low-index directions were found. Different half-widths of the strong 〈110〉-spots were observed in the (11̄0)-plane (θ 1 2 = 13.3° ± 0.4°) and in the (001)-plane (ψ 1 2 = 16.7° ± 0.4°) .

Primary and Secondary Ion Deposition of Epitaxial Semiconductor Films From Laser-Induced Plasmas

ABSTRACTPrimary and secondary ion deposition of epitaxial semiconductor films from laser-induced plasmas is reported Laser plasmas were generated by focusing 15 ns, 107 to 108 W/cm2 pulses of 5 eV photons from a KrF excimer laser onto Ge and Si wafer targets. Time-of-flight, current-voltage, and film thickness measurements at secondary (i.e., ion) targets indicated that the ions were emitted, with an average energy of ∼40 eV, in a distribution which was strongly peaked in the normal direction. Primary ion deposition was performed by placing substrates on an ion target/substrate heater biased to give additional ion acceleration as required. Secondary deposition was achieved by biasing the ion target, in this case a wafer of the same material as the laser target, sufficiently negative to sputter target material onto a third electrode. Epitaxial Si on (100) Si and Ge on (100) Si and (100) GaAs were obtained by both methods. Hall effect measurements on heteroepitaxial Ge grown at 1 μm/hr on GaAs substrates by primary deposition showed thatfthe films were p-type with hole concentrations of ∼1018 cm−3 and mobilities of ∼150 cm2/V-sec.

Relations between the orientations of ion bombarded single crystals, resulting surface structures and sputtered spot patterns

Abstract Ion bombarded (111)-oriented single crystals show, under appropriate conditions, an anisotropic distribution of the sputtered target material, e.g. three main and three intermediate sputtered spots. On the bombarded crystal surface a topography with faceted cones (pyramids) can be observed simultaneously. The geometric relations between the orientations of the crystals, the faceted cones and the sputtered spot patterns have been investigated for Ag, Al, Au and Pb single crystals bombarded with energetic Ar ions.

Sputtering of metal alloys containing second-phase precipitates

Glow-discharge optical spectroscopy has been used as a real time monitor of the transient sputtering characteristics of alloy samples containing various amounts of second-phase precipitates. All alloys investigated reached a steady-state sputtering condition in which the chemical composition of the sputtered target material was equal to that of the bulk target. The transient sputtering time required to reach steady state was directly related to the time required to attain a steady-state rate of target surface cone formation and annihilation. Scanning Auger and electron microprobe analyses were used to show that cone formation in these alloys was due to masking of the matrix by slow sputtering second-phase precipitates and surface agglomerates. At steady state, the cone number density was found to be a function of bulk-alloy precipitate density, Ar sputtering pressure, and the sample sputtering rate. Increasing the Ar pressure resulted in increased scattering of sputtered atoms back to the target surface, while changes in overall target sputtering rate affected the surface migration and, hence, surface distribution of low-yield species. The average cone base diameter for Inconel 718, Incoloy 800, and Monel K-500 alloys was approximately 8 μm. The average depths removed during transient dc sputtering at an Ar pressure of 40 mTorr (5.3 Pa) and 2 kV were 1.5 μm for Inconel 718, 1.3 μm for Incoloy 800, and 0.1 μm for Monel K-500. For comparison, high-purity GaAs single-crystal samples sputtered under the same conditions reached steady-state sputtering after the removal of less than 100 Å. In all cases, films deposited on glass substrates at ambient temperature during steady-state sputtering had the same chemical composition as the bulk target. Inconel 718 and Incoloy 800 films also exhibited second-phase precipitates similar to those in the bulk targets.

Columnar grains and twins in high-purity sputter-deposited copper

Columnar grains were normal to the substrate in thick, high-purity copper deposits made by high-rate (80–110 Å/sec) sputter deposition. The grains contained a high density of stacking faults and twin boundaries parallel to the substrate. The columnar grains for a deposit made at 6 °C, 80 Å/sec, and with a −75 V substrate to anode bias were uniformly about 700 Å in diameter, but a deposit made at 100 °C, 110 Å/sec, and with a −20 V bias had a few large grains with diameters up to 13 000 Å and many smaller grains with diameters of about 2500 Å. Deposits made at 100 °C did not recrystallize, but deposits made at −196 °C and at about 10 °C recrystallized at room temperature. Recrystallized regions had annealing twins that were 1000–10 000 Å across. The deposits had (111) crystallographic planes parallel to the substrate before recrystallization, but after recrystallization (100) planes were parallel to the substrate. Chemical analyses for impurity elements in the sputtering target material and a deposit showed four elements not detected in the target material were detectable in the deposit. Krypton gas pickup in the deposits during sputtering was estimated to be less than 5 ppm.