Sputter Etching Research Articles

Profile evolution simulator for sputtering and ion-enhanced chemical etching

A plasma etching profile simulator was developed to investigate the evolution of pattern profiles in various materials under different plasma conditions. This simulator is based on a two-dimensional cellular method. The model is fed with input parameters that include angular dependent etch yield, ion and neutral angular distribution, and plasma and material characteristics. It has been tested by comparison with published profiles of Si sputtering and SiO2 ion-assisted chemical etching in argon and chlorine plasmas. Observed microtrenching and bowing have been well reproduced by the simulator. The simulator was further used to examine etching for dimensions below nanometer in low-pressure high-density plasmas. In the case of Si sputtering, trenches of 100 nm depth and 30 nm or less width show unusual lateral etching. Finally, the effect of positive charge accumulation on an insulated mask resulting from negative bias voltage on the wafer was studied. This charge accumulation causes a deflection of ion trajectories. Considering this phenomenon, very isotropic etched profiles were found, in good agreement with in-house experimental profiles of platinum sputtering in argon plasma. The simulator developed is intended to be used for any material and mask combination in order to predict the profile evolution under various plasma conditions and pattern dimensions from micrometer to nanometer.

X-ray diffraction study of gold nitride films: Observation of a solid solution phase

The structure of nitride containing gold films produced by reactive ion sputtering and nitrogen plasma etching is investigated using x-ray photoelectron spectroscopy and x-ray diffraction. It is found that gold nitride is a solid solution of nitrogen atoms dissolved in a fcc gold matrix. Differences between the strain and lattice parameters of gold and gold nitride films were observed and are explained by interstitial nitrogen present in the latter.

Quantitative comparison of adhesion in metal-to-plastic systems

A peel test device was used to monitor metal–polymer adhesion. This technique showed variations in the resulting force within 1%, and enabled the ranking of many systems. A change in the 50 nm-adhesion layer resulted in a variation of the fracture energy by a factor 2.3. A change of the substrate led to a change in adhesion by a factor 40. The peeling results were also combined with attenuated total reflectance Fourier transform infra-red measurements to provide qualitative insight of the bonds at the substrate surface. Differences were also visible after surface pretreatment by plasma or sputter etching with different gases, as changes in interaction bonds as well as in adhesion were observed.

Magnetic Properties of Amorphous Magnetic Film on Self-Assembled Convex Pattern

In this paper, we evaluated magnetic properties of amorphous Tb-Fe-Co magnetic film on self-assembled convex pattern fabricated using conventional sputtering and reactive ion etching equipments. Fabricated pattern had 2-D periodicity of around 28 nm. Tb-Fe-Co film on the pattern indicated that the domain-wall (DW) energy was reduced at the steep region of the pattern, and magnetic reversal behavior became more like Stoner-Wohlfarth mode than DW motion mode. Magnetic force microscope observation showed the magnetic domain whose sizes are as small as 50 nm.

GaAs Microarrays by Noble-Metal Assisted Chemical Etching

Microarrays of n-GaAs were fabricated for both (100) and (111) by colloidal crystal templating, ion sputtering and chemical etching using nanosized Au particles as the etching catalyst. Since self-organized polystyrene spheres were used as a mask, Au particles were selectively deposited at sites resulting in the formation of Au honeycomb pattern on GaAs. Microsized GaAs column arrays were achieved by chemical etching of GaAs, where the honeycomb-patterned Au metals were deposited. Although ordered column structures were obtained for both planes, different anisotropic etching patterns were observed by Au-assisted chemical etching between n-GaAs (100) and (111). The crystal-face orientation strongly affects the etching morphology and the rate of metal-assisted chemical etching.

Room-Temperature Bonding of Oxide Wafers by Ar-beam Surface Activation

Surface activated bonding (SAB) by Ar beam sputter etching has been proved to have ability to bond various semiconductor wafers at room temperature. In this paper, we report SAB of oxide wafers. Various oxide wafers were successfully bonded to Si wafers by SAB. Strong bonding equivalent to bulk strength was achieved without any heat treatments. Among the oxide wafers tested, SiO2 was only a material which was not form strong bond with Si at room-temperature. On the other hand, strength of oxide-to-oxide bonding by SAB was not so strong as bulk materials and was largely dependent on the bonded oxide materials. In case of oxide-to-oxide bonding, SiO2 was again difficult to bond. Deposited thin oxide film such as TiO2 could be bonded by SAB and was effective to improve bonding properties. In summary, oxide wafers were successfully bonded by SAB at room-temperature, however its strength depends on oxide materials.

Polymeric Thermal Microactuator With Embedded Silicon Skeleton: Part II—Fabrication, Characterization, and Application for 2-DOF Microgripper

This paper presents the fabrication, characterization, and application of a novel silicon-polymer laterally stacked electrothermal microactuator. The actuator consists of a deep silicon skeleton structure with a thin-film aluminum heater on top and filled polymer in the trenches among the vertical silicon parts. The fabrication is based on deep reactive ion etching, aluminum sputtering, SU8 filling, and KOH etching. The actuator is 360 mum long, 125 mum wide, and 30 mum thick. It generates a large in-plane forward motion up to 9 mum at a driving voltage of 2.5 V using low power consumption and low operating temperature. A novel 2-D microgripper based on four such forward actuators is introduced. The microgripper jaws can be moved along both the x- and y-axes up to 17 and 11 mum, respectively. The microgripper can grasp a microobject with a diameter from 6 to 40 mum. In addition, the proposed design is suitable for rotation of the clamped object both clockwise and counterclockwise.

Analysis of Structural Distribution of Nitrogen-Incorporated Species at the Interface of Silicon Oxide Films on Silicon Using Time-of-Flight Secondary Ion Mass Spectrometry and Poisson Approximation

Structural distributions of nitrogen-incorporated species at the interface between silicon and SiO2 films for plasma-enhanced chemical vapor deposited (PECVD) SiO2 films have been analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and the Poisson approximation. Depth profiles of the intensity of Si3(+) cluster ions were used to determine the depth-resolution function of the analytical system that causes beam-induced broadening effects in the depth profiles. The full width at half-maximum (fwhm) of the resolution function was approximately 1.6 nm for 22 kV Au3(+) primary ions and sputter etching by Ar(+) at 1 kV. The intensity profile of Si3O2N(+) secondary ion species at the interface was analyzed by assuming a Poisson distribution with a series of delta-layers. Convolution of the postulated signals with the depth resolution function was carried out to simulate depth profiles of Si3O2N(+) ion species, which exhibit slow leading and sharp trailing edges. The analysis showed that the thickness of the delta-layer associated with the most probable existence of nitrogen-incorporated species is approximately 0.8 nm, and the fragmented species decreased from the interface to the SiO2 bulk film with a decay length of approximately 1.5 nm.

Dry etching of AlN films using the plasma generated by fluoride

The plasma produced by the mixture of fluoride and argon (SF 6/Ar) was applied for the dry etching of AlN films. Very high etching rate up to 140 nm/min have been observed. The effects of the bias voltage and the plasma component on the etching results were investigated. It shows that AlN can be effectively etched by the plasma with the moderate SF 6 concentration and the etching rate varies linearly with the bias voltage. The FTIR spectra confirm that AlF 3 is formed due to the chemical reaction of Al and F atoms. The mechanism of AlN etching in F-based plasma is probably a combination between physical sputtering and chemical etching and can be briefly outlined: (i) F − ions reacts with Al atoms to form low volatile product AlF 3 and passivate the surface, and (ii) at the same time the Ar + ions sputter the reaction product from the surface and keep it fluoride free to initiate further reaction. AlF 3 formed on the patterned sidewall play a passivation role during the etching process. The etching process is highly anisotropic with quite smooth surface and vertical sidewalls.

Growth and characterization of the ZnO/ZnS bilayer obtained by chemical spray pyrolysis

ZnO/ZnS bilayer antireflection coatings have been prepared by spray pyrolysis using aqueous solutions of zinc acetate and thiourea or zinc chloride and thiourea. The structure, surface morphology, chemical composition and optical transmittance of the bilayer have been examined as a function of the composition of the initial solution. X-ray photoelectron spectroscopy analysis and Ar ion-beam sputter etching was carried out to obtain a depth profile of bilayer. Neither carbon nor other by-products, which could alter the optical transmittance of the bilayer were found in either the interface or bulk. The differences between the bilayers arise from the annealing of the ZnS underlayer, as well as the precursor used to prepare it.

Characterization of plasma etching induced interface states at Ti∕p-SiGe Schottky contacts

The authors have used current-voltage (I-V) data measured over a wide temperature range (100–300K) complemented by deep level transient spectroscopy (DLTS) for the assessment of the defects introduced in Si0.95Ge0.05 by argon plasma sputter etching. From DLTS, defect concentration depth profiling was extracted and revealed that the main defect introduced during argon plasma sputtering is located very close to the surface. I-V-T analysis shows that the electrical characteristics deviated from the ideal case and indicate the presence of interface states, resulting from the plasma etching induced surface states at Ti∕Si0.95Ge0.05 interface. The interface state density as well as its temperature dependence were obtained from forward bias I-V-T measurements by considering the bias dependence of effective barrier height Φe. It is found that interface states density is temperature dependent although weakly.

Spot Size Converter with Vertically Tapered Waveguide Core Fabricated by Sputter Etching

Superhigh Δ (>1.5%) waveguides are receiving more attention to realize integrated functional circuits. However, one of the problems in the adoption of superhigh Δ waveguides is an increase in coupling loss between a waveguide and a conventional single mode fiber. To overcome this problem we have proposed the use of a spot size converter (SSC) that has a well-designed vertical taper fabricated by sputter etching. In this paper, we describe the fabrication process of this SSC, and particularly discuss the adjustment of an incline angle in sputter etching.

Manufacturing technology for the fabrication a discrete actuator using a magnetic shape memory alloy

To demonstrate the feasibility of combining thin-film fabrication techniques and discrete MSM stripes, a hybrid actuator system was designed. The actuator system consists of four thin-film stators and two discrete MSM stripes mounted in a row. For creating an actuator motion, one of the MSM stripes has to be excited by a pair of stators to cause variant switching. This results in an elongation plus a compression of the second stripe and vice versa. The technologies required for fabricating the thin-film stator are sputter deposition, PECVD, electroplating, etching, and photolithography. This paper describes the fabrication process for a thin-film stator used for the MSM micro actuator system. It also presents technology study results indicating the feasibility of the planned fabrication sequence.

900 keV gold ion sputter etching of silicon and metals

Au ions (900 keV) have been used to directly sputter etch microstructures in silicon, aluminum, copper and silver. The results presented clearly demonstrate that high energy heavy ions can be used to fabricate microstructures in selected metals and silicon in a single step process.

Morphological instability of Cu nanolines induced by Ga+-ion bombardment: In situ scanning electron microscopy and theoretical model

The morphological evolution of copper nanolines induced by focused ion beam at normal bombardment has been investigated by in situ scanning electron microscopy. A periodic array of particles is observed when the width of lines reaches a certain value. The stability of a nanoline is studied in terms of a model based on Nichols and Mullins [Trans. Metall. Soc. AIME 233, 1840 (1965)] instability and curvature-dependent sputtering yield. A critical line width is found by linear analysis. When the line width is below this value, unstable mode whose wave vector is parallel to the line axis develops and a chain of periodic particles forms. When the width is above this critical value, the sputtering etching only leads to the decrease of width. The flux and temperature dependence of wavelength is measured and explained based on this model. The predictions of the model are in good agreement with the experimental results.

Influence of surface cleaning effects on properties of Schottky diodes on 4H–SiC

Ir/4H–SiC and IrO 2/4H–SiC Schottky diodes are reported in terms of different methods of surface pretreatment before contact deposition. In order to find the effect of surface preparation processes on Schottky characteristics the SiC wafers were respectively cleaned using the following processes: (1) RCA method followed by buffered HF dip. Next, the surface was oxidized (5.5 nm oxide) using a rapid thermal processing reactor chamber and circular geometry windows were opened in the oxide layer before metallization deposition; (2) the same as sequence (1) but with an additional in situ sputter etching step before metallization deposition; (3) cleaning in organic solvents followed by buffered HF dip. The I– V characteristics of Schottky diodes were analyzed to find a correlation between extracted parameters and surface treatment. The best results were obtained for the sequence (1) taking into account theoretical value of Schottky barrier height. The contacts showed excellent Schottky behavior with ideality factors below 1.08 and barrier heights of 1.46 eV and 1.64 eV for Ir and IrO 2, respectively. Very promising results were obtained for samples prepared using the sequence (2) taking into account the total static power losses because the modified surface preparation results in a decrease in the forward voltage drop and reverse leakage current simultaneously. The contacts with ideality factor below 1.09 and barrier height of 1.02 eV were fabricated for Ir/4H–SiC diodes in sequence (2).

Aligned defects behaviour of β-FeSi2 thin film on Si(100) substrate prepared by ion beam sputter deposition

β-FeSi2 is one of the possible candidates for a compound semiconductor. Epitaxial β-FeSi2 films grown on a Si substrate are technologically important for microelectronic and silicon-based optoelectronic applications. In earlier studies, we clarified that the treatment of the Si substrate surface greatly influences the crystal structure of the film. Among several surface treatment procedures, it has been reported that the sputter etching (SE) of the substrate with subsequent thermal annealing is fairly effective in obtaining a film that has a favorable epitaxial orientation relationship of β-FeSi2(100)//Si(100) with atomically smooth interface by choosing better conditions. Even though the obtained films have good quality, anomalous patterns were sometime observed in the dark field image of the obtained film by cross-sectional TEM observation. They formed a horizontal line along the β-FeSi2/Si interface. Higher magnification image shows that these spots are aggregated defects. The ‘lines’ tend to appear in the samples, which are irradiated in higher energy. However, they are also occasionally observed in 1 keV Ne+ irradiated sample. It can be related to the diffusion process of the silicon atoms and the defects formed in the silicon through Ne+ irradiation. Formation behavior of these ‘aligned’ defects will be discussed in the present study.

Fabrication and properties of Al 2O 3/Cu/InSnO 3 multilayer cathode electrodes in carbon nanotube field emission display

Multilayer cathode electrodes consisting of Al 2O 3 bufferlayer, Cu conductive layer and InSnO 3 current limiting layer, used in carbon nanotube (CNT) field emission display, were prepared by direct current magnetron sputtering and wet etching. Compared with conventional monolayer cathode electrodes, the multilayer electrodes possess higher current limiting resistance with lower inherent resistance variation. Profilometer measurement indicates the etched edges of the multilayer electrodes were abrupt and regular. Nano Indenter experiment shows that the multilayer electrodes remained intact after annealing treatment and were resistance to scratch damage at loads up to 12.6 mN. X-ray diffraction analysis reveals that no oxidized copper was formed during the annealing treatment. Atomic force microscope images show that the surface of the multilayer electrodes became smoother after plasma bombardment, and the maximum protrusion height decreased from 48.6 nm to 15.4 nm. With the multilayer cathode electrodes, the field emission properties of CNT film cathodes, such as uniformity, lifetime and stability are improved.

Subsurface Biomolecular Imaging of Streptomyces coelicolor Using Secondary Ion Mass Spectrometry

Imaging using time-of-flight secondary ion mass spectrometry (TOF-SIMS) with buckministerfullerene (C(60)) primary ions offers the possibility of mapping the chemical distribution of molecular species from biological surfaces. Here we demonstrate the capability of the technique to provide biomolecular information from the cell surface as well as from within the surface, as illustrated with the distribution of two antibiotics in Streptomyces coelicolor (a mycelial bacterium). Differential production of the two pigmented antibiotics under salt-stressed and normal conditions in submerged cultivations could be detected from the TOF-SIMS spectra of the bacteria, demonstrating the potential of the technique in studying microbial physiology. Although both the antibiotics were detected on the cell surface, sputter etching with C(60)(+) revealed the spectral features of only one of the antibiotics within the cells. Exploratory analysis of the images using principal component analysis assisted in analyzing the spectral information with respect to peak contributions and their spatial distributions. The technique allows the study of not only lateral but also the depthwise distribution of biomolecules, uniquely enabling exploration of the processes within biological systems with minimal system intervention and with little a priori biochemical knowledge of relevance.

SUS304 ステンレス鋼のスパッタエッチングによる円錐状突起物の生成および表面の腐食挙動

The sputter etching of SUS304 stainless steel specimens was carried out, and the formation and growth processes of conical protrusions was investigated. In addition, the polarization behavior of the specimens in 3.5%NaCl aqueous solution and the surface morphology after the polarization test were examined. At an early stage of the sputter etching, the conical protrusions form mainly along grain boundaries. However, with increase in the sputter etching time the protrusions form also within the grains. With further increase in the sputter etching time, some protrusions grow largely and the entire surface is covered by the huge conical protrusions and the irregular small ones around them. The outer layer of the huge protrusion contains larger chromium but smaller nickel amount than matrix, and the interior has almost the same composition as the matrix. This means that the protrusion has a shell structure. For the specimen with short time sputter etching, the corrosion potential becomes nobler and the pitting corrosion potential becomes smaller, while the passive current density is smaller than those of non-sputter-etched specimen. In these specimens, the corrosion occurs preferentially along grain boundaries and around protrusions in grains. For the specimen with long time sputter etching, where the entire surface is covered by protrusions, the pitting corrosion potential increases and the corrosion progresses mainly from the interior of the specimen leaving the surface layer with many protrusions. In some cases, only the outer layer of the shell remains separately as a result of the corrosion of the interior and root of the huge protrusion.