Removal Of Oxide Layer Research Articles

Investigation of thin oxide layer removal from Si substrates using an SiO2 atomic layer etching approach: the importance of the reactivity of the substrate

The evaluation of a plasma-based atomic layer etching (ALE) approach for native oxide surface removal from Si substrates is described. Objectives include removal of the native oxide while minimizing substrate damage, surface residues and substrate loss. Oxide thicknesses were measured using in situ ellipsometry and surface chemistry was analyzed by x-ray photoelectron spectroscopy. The cyclic ALE approach when used for removal of native oxide SiO2 from a Si substrate did not remove native oxide to the extent required. This is due to the high reactivity of the silicon substrate during the low-energy (<40 eV) ion bombardment phase of the cyclic ALE approach which leads to reoxidation of the silicon surface. A modified process, which used continuously biased Ar plasma with periodic CF4 injection, achieved significant oxygen removal from the Si surface, with some residual carbon and fluorine. A subsequent H2/Ar plasma exposure successfully removed residual carbon and fluorine while passivating the silicon surface. The combined treatment reduced oxygen and carbon levels to about half compared to as received silicon surfaces. The downside of this process sequence is a net loss of about 40 Å of Si. A generic insight of this work is the importance of the substrate and final surface chemistry in addition to precise etch control of the target film for ALE processes. By a fluorocarbon-based ALE technique, thin SiO2 layer removal at the Ångstrom level can be precisely performed from an inert substrate, e.g. a thick SiO2 layer. However, from a reactive substrate, like Si, complete removal of the thin SiO2 layer is prevented by the high reactivity of low energy Ar+ ion bombarded Si. The Si surfaces are reoxidized during the ALE ion bombardment etch step, even for very clean and ultra-low O2 process conditions.

Оксидные включения в швах алюминиевых сплавов, полученных методом сварки трением с перемешиванием

The paper reports the results of the impact of different edge surfaces preparation upon the structure of a metal joint and strength characteristics of welds made by a method a friction welding with mixing. As objects of investigations there were chosen plates made of aluminum alloys 1565, 1201, 1915, V-1341, 1420 and 1460 with 5 mm thick with different edge machining for welding: by stripping and degreasing; by machining, for surface oxide layer removal; by AC and DC welding arc for “growing” a surface oxide layer and the further analysis of its distribution in a metal joint after welding. In the paper there are shown the results of metal joint micro-structure investigation and also test results of welds for strength. Oxide distribution from the surface of edge surfaces inside joint metal and its influence upon strength properties of joints is analyzed.

Fabrication of silicon films from patterned protruded seeds.

Thin, flexible silicon crystals are starting up applications such as light-weighted flexible solar cells, SOI, flexible IC chips, 3D ICs imagers and 3D CMOS imagers on the demand of high performance with low cost. Kerfless wafering technology by direct conversion of source gases into mono-crystalline wafers on reusable substrates is highly cost-effective and feedstock-effective route to cheap wafers with the thickness down to several microns. Here we show a prototype for direct conversion of silicon source gases to wafers by using the substrate with protruded seeds. A reliable and controllable method of wafer-scaled preparation of protruded seed patterns has been developed by filling liquid wax into a rod array as the mask for the selective removal of oxide layer on the rod head. Selectively epitaxial growth is performed on the protruded seeds, and the voidless film is formed by the merging of neighboring seeds through growing. And structured hollows are formed between the grown film and the substrate, which would offer the transferability of the grown film and the reusability of the protruded seeds.

Impact of Native Oxide on the Capacitance-Voltage Characteristic of Pseudo-Mos Structure

The pseudo-MOSFET is proposed as a simple approach to evaluating the electrical characteristics of SOI wafers without fabricating any devices [1]. This paper discusses the impact of the native oxide layer that forms on the top and the back surfaces of SOI wafer on the impedance of the pseudo-MOS (Ψ-MOS) structure. Figure 1 shows the Ψ-MOS capacitor structure used to measure the ac response [2]. Humidity is held at 50%. The wafer is dipped in diluted HF solution in order to remove surface oxides just before the impedance measurement. Figure 2 shows the capacitance of the Ψ-MOS capacitor structure measured (i) before the HF treatment, (ii) after the HF treatment of only the back surface of the SOI wafer, and (iii) after the HF treatment of the entire SOI wafer. It turns out that the capacitance saturation value is increased by HF treatment at VG = -10 V and at VG = 25. In order to analyze the above results, we assumed that the change in the capacitance saturation value is influenced by the native oxide layer on the SOI wafer. We drew the Cole-Cole plot [3] of the measured impedance to verify the assumption. Figures 3(a) and 3(b) show Cole-Cole plots of the impedance data for (i), for (ii), and for (iii) at VG = -10 V and at VG = 25 V, respectively. Every plot is an overall result of several measurements made while by changing the probe position. Our previous study suggests that the semicircles in the high and middle frequency ranges in Figs. 3(a) and 3(b) consist of primary components attributed to the probe contact [2]. The semicircle in the low frequency range is attributed to the interface trap at the SOI layer/the BOX layer interface or at the BOX layer/the substrate interface [2]. Figures 3(a) and 3(b) reveal that the semicircle in the low frequency range changes significantly at both negative VG (-10 V) and positive VG (25 V) after HF treatment (ii). Figures 4(a) and 4(b) show the resistance values extracted from the top of the semicircle in the low frequency range for (i), for (ii), and for (iii) at VG = -10 V and VG = 25 V, respectively. At both VG = -10 V and VG = 25 V, the radius of the semicircle in the low frequency decreases with HF treatment. Figures 2 and 3 reveal that the HF treatment increases the capacitance saturation value, while decreasing the semicircle radius in the low frequency range. Assuming a RC series circuit, it turns out that total capacitance decreases as the impedance increases. Therefore, we consider that semicircle radius in the low frequency range decreases with HF treatment due to the removal of the native oxide layer of the SOI wafer. We also consider that the semicircle in the low frequency range consists of a component associated with the surface of the SOI wafer as well as the components associated with interface traps at the SOI/BOX interface and the BOX/substrate interface. We can see in Fig. 4 that the semicircle radius in the low frequency range takes its largest value before HF treatment. Figure 5 shows the time evolution of the highest value of the semicircle in the low frequency range for (iii); the semicircle radius in the low frequency range increases with time at both VG = -10 V and VG = 25 V. Figure 6 shows the total capacitance of impedance measured at 40 Hz for both VG = -10 V and VG = 25 V. The total capacitance at 40 Hz decreases with time at both VG = -10 V and VG = 25 V. This corresponds to the results shown in Figs. 2 and 3. Thus we can assume that the semicircle in the low frequency range reflects the chemical state of the SOI wafer surface before HF treatment because the native oxide layer should reform with time. We conclude that the electrical parameters of SOI wafer can be evaluated more accurately by removing the native oxide layer. Our measurement results suggest the native oxide will induce an erroneous estimation of interface free carrier density when attempting to extract the universal effective mobility with the pseudo-MOS structure. [1] S. Cristoloveanu et al., IEEE Trans. Electron Devices, vol. 47, no. 5, pp. 1018-1027, 2000. [2] I. Yarita et al., IEEE Journal of the Electron Devices Society, vol. 4, pp. 169-173, 2016. [3] K. S. Cole and R. H. Cole , The Journal of Chemical Physics vol. 9, pp. 341-351, 1941. Figure 1

Improvement of Laser Processing for Colloidal Silicon Nanocrystal Formation in a Reactive Solvent

We report the highly improvement of colloidal Si nanocrystal (Si-nc) formation by pulsed-UV-laser irradiation of porous silicon in a HF-contained organic solvent. The Si-nc in such reactive organic solvent exhibits higher photoluminescence quantum yield (∼50–70%) than that in an ordinary organic solvent without HF (∼20%). This enhancement of the quantum yield is caused by HF-induced removal of the surface oxidation layer and subsequent hydrogen termination of the Si surface. These reaction kinetics promote an efficient hydrosilylation between the hydrogen-terminated surface and an organic solvent, resulting in oxygen-free surface terminated by alkyl groups. Furthermore, the preparation yield in the HF-contained solvent is higher and the size distribution of Si-nc becomes more homogeneous than those in the ordinary solvent. These results can be attributed to efficient pulsed-laser-induced fragmentation by the removal of the oxidation layer on the porous Si target surface.

Processing of bulk Al7075 alloy by spark plasma sintering

The main advantages of powder metallurgy processing route are the possibility to produce near-net-shape compacts and to minimize the finish machining and material loss. The main problem in particle consolidation process is to suppress porosity, to remove oxide layers, and to retain the microstructure of powder materials. Spark plasma sintering (SPS) combines concurrent uniaxial pressure and direct heating by a pulsed DC current. Sintering occurs at relatively low temperatures for a short time and does not influence significantly the microstructure in the interiors of original powder particles. The efficiency of SPS in producing compacts with low porosity might be dependent on the distribution of particle size in original powder material. The gas atomized Al7075 powder was sieved to several charges and then sintered by SPS. Microstructure of sintered compacts was studied by light and scanning electron microscopy. The phase composition was investigated using X-ray diffraction. The mechanical behaviour was tested by bending tests.

Photonic crystal nanocavity with a Q factor exceeding eleven million.

Photonic crystal nanocavities that simultaneously possess small modal volumes and high quality (Q) factors have opened up novel research areas in photonics during this decade. Here, we present an important key for the increase of Q factors to ranges beyond ten million. A systematic investigation on photon lifetimes of air-bridge-type heterostructure nanocavities fabricated from silicon on insulator (SOI) substrates indicated the importance of cleaning the bottom side (buried oxide side) of the nanaocavites. Repeated thermal oxidation and an oxide removal process applied after the removal of the buried oxide layer underneath the nanocavities realized an experimental Q factor greater than eleven million, which is the highest experimental Q ever recorded. The results provide important information not only for Si PC nanocavities but also for general Si nanophotonic devices and photonic electronic convergence systems.

Grain Boundary Chemistry and Transport Through Alumina Scales on NiAl Alloys

It is widely accepted that the growth of protective α-Al2O3 scales on Ni-based alloys is governed by the inward diffusion of oxygen through the oxide grain boundaries (GB). However, there is also some outward diffusion of metal ions to the surface, but it is difficult to quantify. In this work we apply atomic force microscopy, scanning electron microscopy and transmission electron microscopy to investigate the outward flux of Al, which manifests as the growth of small ridges along the alumina GBs after the removal of the outermost oxide layer by mechanical polishing or focused ion beam techniques followed by additional oxidation. As a model alumina-former, NiAl with Hf and Zr additions was investigated. In comparison to Zr, Hf was found to reduce the outward Al diffusion. This outward diffusion was six orders of magnitude smaller than the O inward diffusion.

The Motion Characteristics of a Single Cathode Spot in Removing Oxide Layer on Metal Surface by Vacuum Arc

The motion of cathode spots plays a crucial important role in removing oxide layer on a metal surface by vacuum arc. In this paper, the characteristics of the motion of a single cathode spot on metal surface with oxide layer are investigated experimentally. Experiments are conducted in a detachable vacuum chamber. A hollow copper anode with a hole of $10~\text {mm} \times 10$ mm is used in order to observe the 2-D motion of the cathode spot. The motion of the cathode spot during the descaling process is photographed by a high-speed digital camera with an exposure time of $2~\mu \text{s}$ . Experimental results indicate that there are slow motion and fast motion of the cathode spot during descaling process, and the slow motion is the basic characteristic in most of the descaling time. The probability distribution of the cathode spot’s displacement and resident time, the average velocity, and the movement parameter $S^{2}/t$ are analyzed quantitatively. The results indicate that with the increase of gap distance or the decrease of oxide layer thickness, the cathode spot becomes more active.

Tribological behaviour of Zn coated UHSS sliding against hot-work tool steel at high temperatures

The increasing demands for light-weight components in vehicles contribute to the global expansion of hot sheet metal forming technologies. Structural components are typically produced using hot stamping of ultra-high strength steel (UHSS). This process allows forming of complex shapes whilst enabling control of the mechanical properties of the end product. Interest in zinc coated UHSS has increased in recent years in view of the corrosion protection it provides to the final components. There is a need for increased understanding of its tribological behaviour during the interaction with tool steel at elevated temperatures. In this work, tribological studies have been carried out in a novel hot strip tribometer. The aim was to study the effect of different operating conditions on the tribological behaviour of zinc coated UHSS sliding against a hot-work tool steel under un-lubricated conditions. The parameters studied in this work were; temperature, ranging from 400°C to 700°C; and contact pressure, from 5 to 30MPa. The UHSS was initially heated up to austenitising temperature (840°C) and then cooled down to the testing temperature. Upon stabilisation of temperature, the load was applied and sliding was carried out for a total of 1500mm at 100mm/s. The results showed a trend towards decreasing average coefficient of friction as temperature and contact pressure increased. Unstable friction behaviour was observed at low temperature (400°C) and high contact pressure (30MPa) whilst higher temperatures (600°C) facilitated the development of a low and stable friction behaviour. It is proposed that the friction behaviour is controlled by the properties of the zinc phases in the coating developed during heating of the UHSS. The combination of high temperature and sliding conditions result in the removal of the uppermost oxide layer and the phases beneath control the friction behaviour.

Laser Welding of Coated Press-hardened Steel 22MnB5

The press-hardening process is widely used for steels that are used in the automotive industry. Using ultra-high-strength steels enables car manufacturers to build lighter, stronger, and safer vehicles at a reduced cost and generating lower CO2 emissions. In the study, laser welding properties of the coated hot stamped steel 22BMn5 were studied. A constant 900°C temperature was used to heat the steel plates, and two different furnace times were used in the press-hardening, being 300 and 740seconds. Some of the plates were shot blasted to see the influence of the partly removed oxide layer on the laser welding and quality. The welding set-up, welding, and testing of the weld specimens complied with the automotive testing code SEP 1220.

금속결합제 연삭 숫돌의 ELID 전해속도 자동 조절장치 개발

ELID grinding is an excellent technique for the mirror grinding of the variety of the advanced metallic or nonmetallic materials. The focus of this study is the development of an automaticcontrol electrolysis-speed device for the automation of the ELID-grinding process. For the development of the automatic-control electrolysis-speed device, analysis experiments regarding the ELID cycle and oxide-layer removal and creation were conducted according to a truing and dressing process. Also, a comparative experiment was conducted to confirm the variance of the electrolysis speed in accordance with changes of the voltage. The experiment results for the developed automatic-control electrolysis-speed device show that the developed device could control the electrolysis speed according to voltage changes through the use of the data that are monitored during the ELID-grinding process.

Curcit Formation on Glass Substrate Using a Titanium-Copper Oxide Catalytic Adhesion Layer for Copper Plating

Introduction Glass has characteristics such as transparency, smooth surface, chemical and thermal stability, coefficient of thermal resistance similar to silicon, high dielectric constant, electrical insulation and physical strength, deaming it an attractive substrate material for electronic devices. Examples of application are 2.5D/3D electronic device and RF module packaging. Glass can be metallized electroless plating however, problems remain, the most predominant being inadequate adhesion between glass and plated films. Using a catalytic Ti-Cu oxide adhesive layer formed on the glass, adhesion strength of 0.5 kN/m has been obtained1 ) In this study, circuit formation by semi-additive process that’s often used in the formation of fine circuit and the influence of the Ti-Cu oxide layer on post-treatment steps was investigated.Experimental Schott Co., Ltd. Tempax 50 mm × 50mm × t 0.7 mm was used as the test substrate. Circuit formation by the semi-additive process is shown in figure 1. After the circuit formation, the removal of the Ti-Cu oxide layer was accomplished by immersion in an aqueous sodium hydroxide 100 g/dm3, trisodium citrate 5 g/dm3 solution at 80 ℃ for 10 min. Electroless NiP plating was performed as a post-process to evaluate the effectiveness of the Ti-Cu oxide layer removal method.Results and Discussion Circuits of L / S = 50/50~200/200 µm and t=10 µm dimension were formed using the semi-additive process where adhesion after circuit formation was maintained. After the circuit formation, average roughness (Ra) was observed by atomic force microscopy (AFM) and elemental analysis was performed by X-ray photoelectron spectroscopy (XPS). The Ra was 6.4 nm and 14.9 %Ti was detacted prior to removal and when performing electroless NiP plating as the post-treatment, abnormal deposition occurs between the wiring patterns. On the other hand, after performing Ti-Cu oxide layer removal treatment, the Ra was 0.5 nm and 0.3%Ti detected. Abnormal deposition of electroless nickel does not occur, therefore it was possible to deposit the electroless plating selectively on the copper circuit.Conclusions L / S = 50/50 ~ 200/200 um circuits formed on a smooth glass substrate was possible.The adhesion layer of Ti-Cu oxide can be removed by an alkaline solution. By performing the Ti-Cu oxide layer removal process, abnormal deposition of electroless nickel plating in a post-treatment step can be prevented. Acknowledgments This work was funded in part by the “MEXT-supported Program for the Strategic Research Foundation at Private Universities” and the “Tokyo Ohka Foundation for the promotion of Science and Technology.” References 1)K. Okabe, T. Kagami, Y. Horiuchi, O. Takai, H. Honma, and C. E. J. Cordonier, “Copper Plating on Glass Using a Solution Processed Copper-Titanium Oxide Catalytic Adhesion Layer”, Journal of The Electrochemical Society, Vol.163, No.6, p. D201-D205, (2016) Figure 1

Study of the effect of thermal treatment on morphology and chemical composition of silicon-on-insulator

Removing the ultrathin native oxide layer from silicon-on-insulator (SOI) without damaging the Si device layer poses several processing challenges, the main one being the maintenance of the device layer integrity during oxide layer removal. In order to address this challenge and find a low thermal budget process, the thermal decomposition of the ultrathin native oxide in ultrahigh vacuum has been investigated using scanning electron microscopy, atomic force microscopy, scanning tunneling microscopy, and x-ray photoelectron spectroscopy. The evolving morphology and chemical composition of the ultrathin oxide and the SOI device layer were investigated as a function of anneal temperature and duration. Multiple anneal cycles at 750 °C, each lasting for 30–90 s, was found to be an effective method of desorbing the oxide without causing dewetting of the device layer. The total amount of carbon present on the sample was not altered significantly by thermal treatment; however, a change in the chemical composition of the carbon was noted. A simple oxygen plasma-based ex situ cleaning step before annealing was found to be effective in reducing the density of SiC on the annealed sample while keeping the annealed surface atomically smooth.

Effect of surface oxidation layer on tensile strength of Cu-Ni alloy in friction stir welding

Friction stir welding (FSW) of thick Cu-Ni plate was successfully completed. The fracture position after tensile testing was located at the weld nugget zone (WNZ), where surface oxidation occurred. The oxidation morphologies on the surface of the base metal were analyzed by SEM, EPMA and XRD, with the oxide layer being obtained by simple and useful way to analyze the oxide products, namely, collecting oxide powders after immersing of the oxidized specimen into HNO3 solution. The results highlighted that an oxide layer of 30 μm thickness consists of a mixture of two phases, Cu2O and NiO, on the surface of the base metal. After FSW, the thickness of the oxide layer on the surface was decreased to approximately 5 μm, and broken oxide particles, which is NiO, penetrated into the WNZ by the rotating tool. NiO was preferentially formed at the surface after FSW because it has a lower Gibbs free energy value at 950 °C, which is the peak temperature measured during FSW. Oxide layer of Cu-Ni plate was clearly only removed by mechanical method grinding with 1200-grit SiC paper. The removal of oxide layer results in improved mechanical strength.

Dynamics of cathode spots in low-pressure arc plasma removing oxide layer on steel surfaces

The dynamics of cathode spots has been investigated in low-pressure arc plasma for removing oxide layer on low carbon steel surfaces. The motion of cathode spots was observed with a high speed camera, and the arc voltage was analyzed by fast Fourier transform. The spots move on clean steel surface as a random walk, and the low-frequency components dominated the voltage waveform. However, the spots on steel surfaces with oxide layer tend to burn on the rim of the eroded area formed in the previous arcing, and the low-frequency components decrease correspondingly. The “color” of the colored random noise for arc voltage varies from the approximate brown noise for clean steel surface to pink noise for thick oxide layer, where the edge effect of boundary is considered to play a significant role.

Electron-bombarded ⟨110⟩-oriented tungsten tips for stable tunneling electron emission.

A clean tungsten (W) tip apex with a robust atomic plane is required for producing a stable tunneling electron emission under strong electric fields. Because a tip apex fabricated from a wire by aqueous chemical etching is covered by impurity layers, heating treatment in ultra-high vacuum is experimentally known to be necessary. However, strong heating frequently melts the tip apex and causes unstable electron emissions. We investigated quantitatively the tip apex and found a useful method to prepare a tip with stable tunneling electron emissions by controlling electron-bombardment heating power. Careful characterizations of the tip structures were performed with combinations of using field emission I-V curves, scanning electron microscopy, X-ray diffraction (transmitted Debye-Scherrer and Laue) with micro-parabola capillary, field ion microscopy, and field emission microscopy. Tips were chemically etched from (1) polycrystalline W wires (grain size ∼1000 nm) and (2) long-time heated W wires (grain size larger than 1 mm). Heating by 10-40 W (10 s) was found to be good enough to remove oxide layers and produced stable electron emission; however, around 60 W (10 s) heating was threshold power to increase the tip radius, typically +10 ± 5 nm (onset of melting). Further, the grain size of ∼1000 nm was necessary to obtain a conical shape tip apex.

Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;電解酸化水を用いた加熱処理後の無酸素銅材の表面酸化被膜の除去

Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;電解酸化水を用いた加熱処理後の無酸素銅材の表面酸化被膜の除去

Effect of Surface Layer on the Properties of AZ31 Magnesium Alloy Welded Joints

The paper deals with welding of AZ31 magnesium alloy with disk laser with the output power of 2.0kW. The thickness of the base material was 1.7mm. Overlapped welded joints were produced after mechanical removal of the surface oxide layer in the first stage. Laser welding of as received AZ31 magnesium alloy was carried out in the next part of the research. Light microscopy was used to analyze both the macrostructure and microstructure of welded joints. Chemical composition of the base material and weld metal was examined using energy dispersive x-ray microanalysis (EDX). The mechanical properties of welded joints were studied by microhardness measurements and tensile testing. The influence of the oxide layer on the properties of AZ31 magnesium alloy welded joints was assessed.

A Study of mechanical properties of oxide layer removed Co-Cr-Mo abutments

PURPOSE: The aim of this study was to evaluate the influence of the oxide layer removal process in the Co-Cr-Mo (CCM) abutment after casting procedure on the prosthesis settlement and screw stability. MATERIALS AND METHODS: CCM abutments of four different interface conditions (CCM-M; machined, CCM-O; oxide layer formed, CCM-B; blasted, CCM-P; polished after blasted) and gold abutment (Gold-C; Cast with type III Gold alloy) were used. The initial settling values of abutments were evaluated according to the difference of implant-abutment length when the tightening torques were applied at 5 Ncm and 30 Ncm, and the settling values of abutments caused by loading were evaluated according to the difference of implant-abutment length before and after loading with 250 N, 100000 cycle. The loss ratios of removal torque for abutment screws were evaluated according to the difference in value of removal torques under 30 Ncm tightening torque applied before and after cyclic loading. RESULTS: The CCM-P and CCM-B group showed a higher initial settling value compared with the Gold-C group (P&lt;.05), while the Gold-C group showed the highest settling values caused by loading (P&lt;.05) and no significant differences were observed for between CCM groups (P&gt;.05). The loss ratio of removal torque values for the CCM-B, CCM-P groups did not differ significantly from that of the Gold-C group (P&gt;.05). CONCLUSION: Even though the oxide layer was removed by different methods, CCM abutment with internal conical connection structure showed lower abutment settling and similar screw loosening after cyclic loading compared with gold abutment.