Argon Sputter Etching Research Articles

Thickness dependence of Al0.88Sc0.12N thin films grown on silicon

The thickening behavior of aluminum scandium nitride (Al0.88Sc0.12N) films grown on Si(111) substrates has been investigated experimentally using X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, and residual stress measurement. Al0.88Sc0.12N films were grown with thicknesses spanning 14 nm to 1.1 μm. TEM analysis shows that the argon sputter etch used to remove the native oxide prior to deposition produced an amorphous, oxygen-rich surface, preventing epitaxial growth. XRD analysis of the films show that the AlScN(002) orientation improves as the films thicken and the XRD AlScN(002) rocking curve full width half maximum decreases to 1.34° for the 1.1 μm thick film. XRD analysis shows that the unit cell is expanded in both the a- and c-axes by Sc doping; the a-axis lattice parameter was measured to be 3.172 ± 0.007 Å and the c-axis lattice parameter was measured to be 5.000 ± 0.001 Å, representing 1.96% and 0.44% expansions over aluminum nitride lattice parameters, respectively. The grain size and roughness increase as the film thickness increases. A stress gradient forms through the film; the residual stress grows more tensile as the film thickens, from −1.24 GPa to +8.5 MPa.

Fabrication of narrow-gap nanostructures using electron-beam induced deposition etch masks

We present an optimized procedure to create narrow-gap nanostructures using electron-beam induced deposition etch masks. Incorporation of a Cr sacrificial layer in between Au metal layer and EBID mask improves the etch mask lithography in terms of dimension control and surface flatness. EBID mask writing is performed with a single-pass strategy varying the dose during writing. This patterning strategy allows us to create relatively thick EBID masks with steep, narrow gaps. An argon sputter etch is used to transfer the mask into the underlying material where the low etching rate of sacrificial layer compared to the EBID mask improves transfer of the mask pattern into the metal nanostructure. A Cr wet etch step is then used to remove sacrificial layer and EBID mask material. We show fabrication of Au dimer nanostructures with gap spacing well below 10nm, down to about 5nm, on Si substrates as well as ITO-coated glass. This method may enable the fabrication of nanostructures with small gap spacing and high degree of material purity and flatness on arbitrarily shaped surfaces.

Fabrication of 2D silicon nano-mold based on sidewall transfer

A method based on the sidewall transfer technique for fabricating two-dimensional (2D) nano-mold on a silicon substrate was developed. Instead of using expensive nanolithography, the authors fabricated 2D silicon nano-mold using standard ultraviolet lithography, conformal deposition of gold by radio frequency sputtering, argon sputter etching and deep reactive ion etching (DRIE). This technique enables the generation of very fine geometries with nanoscale dimensions without the electron-beam (e-beam) lithography equipment or other additional lithography techniques. Based on SF 6 , O 2 and C 4 F 8 plasmas, a vertical mold profile and a minimum scallop size of 30 nm were obtained by optimising DRIE parameters. For smooth mold surfaces, the authors report and demonstrate a new mechanism of removing grass obtained during inductively coupled plasma etching. With this technique, very uniform 2D silicon nano-molds consisting of 200 nm wide, 200 nm high and 4.3 mm long bar arrays have been successfully fabricated.

Silicide pre-clean effects on NiPtSi thermal stability for 65 nm technologies and beyond

The effects of different surface preparations on NiPtSi thermal stability were studied. HF wet clean, argon sputter etch and remote plasma pre-clean were used as silicide pre-cleans prior to NiPt sputter deposition and subsequent silicidation on blanket and patterned Si wafers. NiPtSi was characterized using SIMS, ellipsometry, voltage contrast (ES25) testing and electrical performance measurements of 65 nm test structures. Results show that when an in situ remote plasma pre-clean is used in addition to a classical HF wet clean to remove native oxide from the Si substrate prior to NiPt deposition and silicidation, Rs uniformity and SRAM electrical performance as a function of thermal budget are significantly improved. Rs measurements of patterned wafers and SIMS analysis of blanket wafers strongly suggest that the absence of native oxide prior to NiPt deposition and the presence of fluorine at the NiPtSi/Si interface play a key role in improving NiPtSi thermal stability.

A novel method for visualizing hair lipids at the cell membrane complex: Argon sputter etching/scanning electron microscopy1

Hair lipids localized at the cell membrane complex (CMC) play a part in chemical diffusion, cell cohesion, and mechanical strength. There is no method currently available to visualize hair lipids at the CMC. We found that scanning electron microscopy (SEM) of a transversely polished hair plane followed by argon sputter etching (ASE) provides a specific characteristic image consisting of circular patterns (CP) and stitch patterns (SP) at the cortex. Both the CP and the SP are formed as convex structures and are associated with melanin granules and the CMC, respectively. While the convex formation of the CP is not affected by any treatments tested, that of the SP disappeared following treatment of hair fibers with organic solvents and reappeared following incubation of the solvent-treated hair fibers with melting lipids, which suggests that the hair lipids are responsible for the convex SP. Other treatments, such as chemical fixation, thin sectioning, and pre-/post-incubation of the hair plane, reduce or abolish the convex formation of the SP. These findings suggest that the following pathway leads to the convex formation of SP during ASE: (a) joule heat is generated on the surface by violent collisions of argon ions, (b) melting CMC lipids ooze out from the inside to the surface, and (c) CMC lipids that have oozed out are chemically changed, leading to the final convex formation of the SP. With ASE-SEM, visualization of hair lipids as convex structures of SP should enable us to characterize the fine structure and localization of hair lipids and to clarify the roles and functions of the CMC of human hair.

Optical activity in chiral gold nanogratings

Nanogratings consisting of chiral gold particles were fabricated employing electron beam lithography, lift-off and argon sputter etching. Spectra of the transmittance and chirality induced polarization azimuth rotation of nanogratings were measured. A giant specific polarization azimuth rotation (∼10 4 deg/mm) was observed near surface plasmon resonance. We found that the rotation direction changes its sign with a handedness of chiral particles. However, it remains the same for the light incident to the front and back sides of the specific grating, i.e., the effect is reciprocal and manifests conventional optical activity.

Optical emission spectroscopy studies of titanium nitride sputtering on thermoplastic polymers

A magnetron sputter ion plating (MSIP) 13.56 MHz r.f. discharge for titanium nitride (TiN) deposition on thermoplastic polymers was studied by means of optical emission spectroscopy (OES). In this work poly(butylene terephthalate) (PBT) and poly(amide)6.6 (PA) were chosen as substrate materials. Argon sputter etch depth profiling and investigation of the chemical composition by means of X-ray photoelectron spectroscopy (XPS) showed high amounts of oxygen in the films. To determine the source of the oxygen, OES was used to analyze the plasma and to study its spatial and temporal behavior under different sputtering conditions. Results show that a small amount of water, which is always present in the reactor, is one reason for the high oxygen content of the deposited films. The main cause however is water vapor released from the polymer, which is promoted by substrate heating during the coating process. The OES results suggest certain chemical reactions to take place in the plasma, which can be correlated to the chemical composition of the films.

Argon plasma sputter etching induced defect levels in strained, epitaxial p-type Si-Ge alloys

Argon plasma sputter etching-induced electronic defects in boron doped, strained p-type Si 1−xGe x alloys with x = 0 and 0.05 have been investigated by deep level transient spectroscopy (DLTS). Four defects with discrete energy levels, ranging from 0,22–0.55 eV above the valence band, were introduced in p-Si during sputtering. These defects are compared to those introduced during electron beam deposition (EB), alpha particle irradiation and Ar ion beam etching. The most prominent defects in Ar plasma etched samples have similar efectronic properties as a defects detected after electron beam, Ar ion beam etching and alpha particle irradiation. The main defects detected in p-Si was also observed in p-Si 0.95Ge 0.05. One of the dominating peaks has been correlated to the interstitial carbon-interstitial oxygen pair. The decrease in activation energy of this defect for increasing Ge-content from x = 0–0.05 followed the same variation as the band gap in Si 1−xGe x/Si. Its energy level position relative to the conduction band is therefore the same for x = 0 and 0.05 indicating that it is pinned to the conduction band. Defect concentration depth profiling revealed that the main defect introduced during argon plasma sputtering and Ar ion beam etching is located very close to the surface and is deeper than that detected after EB deposition.

Characterization of low-frequency plasma generated in a three-electrode reactor

Electrical characteristic of argon plasma generated in a novel, three-electrode audio frequency (AF) reactor has been investigated by means of a Langmuir single probe movable in the space between reactor electrodes. Both AF potentials of plasma in various places of the reactor and typical current-voltage characteristics have been measured. It has been found that energetic conditions of the plasma, such as electron density and electron temperature, are independent on the coupling capacity C — the only operational parameter used in the reactor. Changes of C have, however, influence on the ion bombardment process taking place in the vicinity of a small electrode. The ion bombardment energy has been roughly estimated. The calculated values are in a good agreement with results of an experiment performed in the reactor with argon sputter etching of a gold film.

Surface Charactreistics of Polyphenylene Sulfide(PPS) Film Treated by Discharge Plasmas.

Polyphenylene sulfide film was treated with low-temperature oxygen, nitrogen, and argon plasmas; argon sputter etching, and low-temperature helium/argon plasma under atmospheric pressure, and then the surface characteristics were investigated by means of critical surface tension and ESCA measurement. Critical surface tension and the O 1S intensities in ESCA spectra were increased considerably after discharge treatments. By helium/argon atmospheric low-temperature plasma treatment, the N 1S and O 1S intensities increased remarkably. From wave form separation of C 1S and S 2p spectra, it was found that oxygens incorporated in the polymer are present in the forms of -C-O-, -COO-, -S(=0)-, and -S(=0) 2−

Patterning of a Ti/Pt/Au metallization for submicron bipolar transistors made by direct write e-beam lithography

To fabricate interdigitated bipolar transistors with lateral dimensions well below 1 μm, electron beam lithography and dry etching have been implemented in an on optical lithography based production process. The most demanding step is the patterning of the Ti/Pt/Au metallization layer traditionally used in these devices. Pattern definition by electron beam lithography is severely hampered by the proximity effect. This problem has been studied in detail and local exposure dose corrections are applied to realize well defined resist patterns. The resist pattern is transferred to the Au/Pt layers by argon sputter etching. In this work with lateral dimensions smaller than the thickness of the metal layers the quality of the etch profiles is seriously degraded by redeposition phenomena. However with a Ti layer patterned by lift-off as etch mask, gaps with a defined width as small as 0.6 μm have been opened.

Reactive sputtering in the ABS TM system

The cathodic arc and unbalanced magnetron (UBM) sputtering processes have been combined into one unit called the ABS TM coating system, the very first of which was installed at BIRL. The arc process is usually used for the substrate sputter etching step, and shutters remain in front of the cathodes to intercept macroparticles. A conventional argon sputter etch is also available, but it takes approximately 100 min to heat a full load of substrates to 300 °C, against 15 min for the arc etch. The longer argon etch roughens the substrate surface, whereas the shorter arc etch can actually lead to a reduction in surface roughness. The UBM process with its high degree of ion bombardment is used for reactive deposition of the coatings. TiN and Ti 0.5Al 0.5N coatings produced in the ABS TM system have excellent hardness and scratch test critical load values. The hardnesses for TiN and Ti 0.5Al 0.5N coatings are 2200 and 2250 kgf mm -2 respectively, and the critical load for TiN on M2 tool steel is 50–60 N for a 2.0 μm thick film. For a 3.0 μm thick Ti 0.5Al 0.5N coating on tool steel, the critical load is 60 N, and on cemented carbide it is greater than 100 N. Field trials with Ti 0.5Al 0.5N coated saw blades and end mills show a 2–3 times improvement in performance compared with TiN coated tools. Cross-sectional transmission electron microscopy shows that the structure of a Ti 0.5Al 0.5N coating on steel is columnar and that it is fully dense.

Argon and oxygen sputter etching of polystyrene, polypropylene, and poly(ethylene terephthalate) thin films

Surface chemical modification of polymer thin films induced by sputter etching was studied by x‐ray photoelectron spectroscopy (XPS) and infrared reflection–absorption spectroscopy (IRRAS). The polymers studied were polystyrene, polypropylene, and poly(ethylene terephthalate) (PET). Oxygen and argon sputter etching of these polymers causes surface oxidation and possibly crosslinking; trends in polymer oxidation can be correlated with the etchant gas, etch power, and initial material properties. For polystyrene and polypropylene, the predominant new functionalities formed are C=O and C–O groups; the breadth of the infrared absorption bands suggests that many different types of these groups exist. For PET, the predominant damage mechanism is crosslinking, with only a slight degree of oxidation resulting from oxygen sputter etching. This work suggests that the information provided by XPS and IRRAS is highly complimentary and will be useful in future studies of polymer functionalization and derivatization.

Surface Characterization of Sputter Etched Polymer Films

AbstractThe surface chemical changes induced in polystyrene, polypropylene and poly(ethylene terephthalate) (PET) by argon and oxygen rf sputter etching were studied by XPS and infrared reflection absorption spectroscopy (IRRAS). Thin (∼5nm) chemically modified surface layers were observed for all three materials. Polystyrene surfaces were oxidized by sputter etching in both oxygen and argon with differing chemical functionality resulting from etching in the different gases. Polypropylene surfaces, by contrast, were oxidized with similar chemical functionality resulting from etching in either gas. PET surfaces were oxidized slightly by oxygen sputter etching and reduced by argon sputter etching. For the model systems chosen, etch mechanisms are suggested based on trends in the chemical modification behavior.

CHANGES OF ABSORPTION IN LPE GROWN (GdBiCa)3Fe5O12 FILMS BY Ar SPUTTER-ETCHING

Change of optical absorption after etching was experimentally studied on Ca and Bi doped GdIG films. When argon sputter-etching was performed on as-grown films for a period of time, absorption decreased to the same level as when reduction treatment was performed in Fe(OH)2 solution. Measurement of lattice constant showed that it increased up to a certain value in both cases of sputter-etching and reducing treatment. Further sputter-etching resulted in the increase of loss, while lattice constant remained unchanged. Change of absorption can be explained by changes in valency of ferric ions, whereas change of lattice constant is mainly attributed to reduction of Pb4+ to Pb2+.

Surface relief of crystalline quartz etched in a planar plasma reactor

Abstract The surface morphology of dry etched crystalline quartz was studied by transmission electron microscopy (replica technique). The experiments were carried out by reactive ion etching (RIE), plasma etching and argon sputter etching. Argon sputter etching does not alter the sample surface. RIE and plasma etching lead to surface roughness when an aluminum electrode is used. The cone-like asperities produced, typical of the beginning of etching, develop into island-like relief during a longer experiment. It is concluded that the surface roughness is caused by the combined action of backscattering of aluminum particles and their protecting effect in a CF 4 plasma.

Annealing of Ar sputter-etch-damaged Si by a Q-switched ruby laser

Argon sputter etching of single crystal Si results in damage of the surface and entrapment of the sputtering gas. In a 6‐kV dc sputtering system these effects have been observed and characterized by Rutherford backscattering. Irradiation by a Q‐switched ruby laser was found to restore the crystal quality and to release the entrapped gas.

Hydrogen passivation of argon sputter-etch induced electrically active defects on Ge, Si, and GaAs

Abstract The passivation of argon sputter-etch induced electrically active defects on Ge, Si, and GaAs surfaces by reaction with atomic hydrogen has been observed using deep level transient spectroscopy. A broad band of defect states, giving rise to non-linear Arrhenius plots, appears to be associated with the induced damage centres. For n-type Ge and p-type Si, a 20-min exposure to atomic hydrogen at 180°C is shown to neutralize the damage created by a 5-min, 6 kV (DC), Ar gas sputter-etch. For n-type GaAs a 1-h exposure at 250°C was sufficient, whilst n-type Si required a 1-h exposure to the hydrogen plasma at 300°C to passivate the damage. In each case, to remove the sputter-etch damage by thermal annealing required temperatures approximately 100°C higher, for periods of approximately 2 h.

Mikrostrukturierung von fotoschablonen mittels nichtreaktiver hochfrequenzionenätzung

An estimate is made of the effective thickness of the resist mask for delineating a pattern into a processed film with minimum dimensional changes during non-reactive ion etching. The selectivity of the etching process, the thickness of the processed film, the evolution of the mask edge profile and the redeposition of the sputtered material are taken into account. In accordance with this estimate, the technological processes of the non-reactive r.f. ion etching of photmasks of Fe 2O 3, chromium and CrO x /Cr/CrO x were investigated using a contact-printed AZ 1350 resist mask. The experimental results thus obtained are interpreted by a model representation of the etching profile and are illustrated by scanning electron microscopy photographs. The conclusion drawn is that non-reactive r.f. ion etching in argon (sputter etching) is a suitable method for the microstructuring of photomasks with micron and submicron dimensions.

Effects of high-intensity electron bombardment on the secondary-emission characteristics of a MgO/Au-cermet film

An experiment to determine the durability of a 75 MgO/25 Au-cermet film secondary-emission cathode has been carried out over a period of 4000 h. A 2-keV electron beam of 2 A/cm2 current density was applied to a single spot and the secondary-electron-yield curve was monitored at regular intervals. To determine changes in chemical composition, Auger analysis was carried out with the same electron beam. Results of these tests indicated a decrease in maximum yield from 8.4 to 3.7 and a corresponding increase in the first crossover energy of 16 to 25 eV. Inspection of the relative intensities of the Auger spectral lines revealed that both Au and Mg increased relative to 0, with the Au line showing a steady increase during the first 500 h and then leveling off after 1500 h for the remainder of the testing period. The discovery of an apparent Au deficiency in the outer layers of the film is in accord with the initially high yield and the expected differential sputtering effects during argon sputter etching prior to the experiment. A surface profilometer measurement indicated that a crater of approximately 500 Å in depth was etched during the bombardment.