Development of electrical enhanced photocatalysis polishing slurry for silicon carbide wafer

2019 ◽  
Vol 234 (3) ◽  
pp. 401-413 ◽  
Author(s):  
Yan He ◽  
Zewei Yuan ◽  
Kai Cheng ◽  
Zhenyun Duan ◽  
Wenzhen Zhao
Keyword(s):  
Silicon Carbide ◽  
Hydroxyl Radical ◽  
Ph Value ◽  
Uv Light ◽  
Removal Rate ◽  
Chemical Oxidation ◽  
Chemical Effect ◽  
Semiconductor Particles ◽  
Clean Manufacturing ◽  
Sic Wafer

Single-crystal silicon carbide, as one of the most promising next-generation semiconductor materials, should be polished with atomically smooth and damage-free surface to meet the requirements of semiconductor applications. The research presented in this paper aims to develop an electrical enhanced photocatalysis polishing method for atomic smoothing of Si-face (0001) 4H-SiC wafer based on the powerful oxidability of UV photo-excited hydroxyl radical on nano semiconductor particles. The research identifies the influences of photocatalyst, electron capturer, UV light, voltage and pH value by designing the orthogonal fading experiments of methyl orange and thus develops several slurries for electrical enhanced photocatalysis polishing accordingly. It also demonstrates that photocatalyst, UV light, electron capturer, and acid environment being necessaries for the electrical enhanced photocatalysis polishing process. Electricity can effectively prevent the recombination of electrons and holes generated on the surface of semiconductor particles and therefore enhance the polishing efficiency. Five photocatalysts including 5 nm TiO2, P25, ZnO, CeO2 and ZrO2 have envious selectivity to the UV light. The slurry with P25 as the photocatalyst and H2O2 as electron capturer presents best polishing performance among, which provides a material removal rate of about 1.18 µm/h and a surface roughness of about Ra 0.0527 nm in an area of 1.0 × 1.0 µm. Furthermore, it also discusses how the UV light irradiation and electricity promotes the chemical oxidation of hydroxyl radical with SiC by forming “Si-C-O”, “Si-O” and “C-O” on SiC surface. The paper concludes that the proposed electrical enhanced photocatalysis polishing is an effective and clean manufacturing method for SiC wafer without rendering toxic chemical effect on environment and human health.

Study on the Photocatalytic Degradation of Diesel Pollutants in Seawater by a Prepared Nano Ag-Droped Zinc Oxide

2014 ◽  
Vol 609-610 ◽  
pp. 311-316
Author(s):  
Xiao Cai Yu ◽  
Dong Dong Hu ◽  
Jin Fang Chen ◽  
Xiao Jie Jin ◽  
Xu Zheng
Keyword(s):  
Reaction Time ◽  
Photocatalytic Degradation ◽  
Calcination Temperature ◽  
Ph Value ◽  
Uv Light ◽  
Removal Rate ◽  
Orthogonal Experiment ◽  
Influential Factors ◽  
Influential Factor ◽  
Sonochemical Method

ZnO and Ag-droped ZnO photocatalysts with different Ag loadings (0.5, 1.0, 1.5, 2.0at%) and different calcination temperature (300, 400, 500, 600, 700°C) were synthesized by a sonochemical method. The morphology and crystal pattern of some prepared catalysts were characterized by XRD and SEM techniques which demonstrated that the prepared catalysts were of hexagonal wurtzite structure. Ag loadings, calcination temperature and other factors, dosage of photocatalyst, reaction time and pH value of seawater, were also taken into consideration in the procedure of photocatalytic degradation reaction under UV light. An orthogonal experiment was carried out to investigate the best combination of factors which can reach the best diesel pollution removal rate and the influence order of factors. Reaction time and dosage of catalyst were the most influential factors in this experiment, and the factor of calcination temperature was the weakest influential factor. The removal rate of diesel can up to 78% when the experiment was undertaken under the very conditions: the dosage of catalyst 2.0g/L, reaction time 2.0h, Ag loading of catalyst 1.0 at%, calcinations temperature 400°C and pH value 8.5.

Thinning of a Two-Inch Silicon Carbide Wafer by Plasma Chemical Vaporization Machining Using a Slit Electrode

2014 ◽  
Vol 778-780 ◽  
pp. 750-753 ◽  
Author(s):  
Yuu Okada ◽  
Hiroaki Nishikawa ◽  
Yasuhisa Sano ◽  
Kazuya Yamamura ◽  
Kazuto Yamauchi
Keyword(s):  
Silicon Carbide ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
High Hardness ◽  
Power Devices ◽  
Plasma Chemical ◽  
Power Transistors ◽  
Device Processing ◽  
High Removal Rate ◽  
Sic Wafer

In recent years, silicon (Si) has been mainly used in power devices, but the limit of its performance is being reached. Therefore, silicon carbide (SiC) power devices have been attracting attention because they enable the fabrication of devices with low power consumption. To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin a SiC wafer with a high removal rate by conventional mechanical processing because its high hardness and brittleness cause cracking and chipping during thinning. Therefore, we have attempted to thin a SiC wafer using plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. In this study, we describe a machining property using a newly developed slit electrode that is composed of two parts and has a slit that allows for a new gas to pass.

Plasma Chemical Vaporization Machining of Silicon Carbide Wafer Using Flat-Bar Electrode with Multiple Gas Nozzles

2012 ◽  
Vol 497 ◽  
pp. 160-164 ◽  
Author(s):  
Yasuhisa Sano ◽  
Kohei Aida ◽  
Hiroaki Nishikawa ◽  
Kazuya Yamamura ◽  
Satoshi Matsuyama ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
High Hardness ◽  
Plasma Chemical ◽  
Power Transistors ◽  
Device Processing ◽  
High Removal Rate ◽  
Mechanical Machining ◽  
Sic Wafer

Silicon carbide (SiC) power devices have received much attention in recent years because they enable the fabrication of devices with a low power consumption. To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin a SiC wafer with a high removal rate by conventional mechanical machining because its high hardness and brittleness cause cracking and chipping during thinning. We have attempted to thin a SiC wafer by plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. In this paper, we describe a machining property using a newly developed flat-bar electrode with multiple gas nozzles for thinning a SiC wafer.

scholarly journals Photoelectrochemical Oxidation Assisted Catalyst-Referred Etching for SiC (0001) Surface

2021 ◽  
Vol 15 (1) ◽  
pp. 74-79
Author(s):  
Daisetsu Toh ◽  
Pho Van Bui ◽  
Kazuto Yamauchi ◽  
Yasuhisa Sano ◽  
◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Uv Irradiation ◽  
Bias Voltage ◽  
Oxidation Rate ◽  
Uv Light ◽  
Removal Rate ◽  
Reaction Site ◽  
Photoelectrochemical Oxidation

In a previous study, we developed an abrasive-free polishing method named catalyst-referred etching (CARE) and used it for the planarization of silicon carbide (SiC) (0001). In this method, Si atoms at step edges are preferentially removed through a catalytically assisted hydrolysis reaction to obtain an atomically smooth and crystallographically well-ordered surface. However, the removal rate is low (< nm/h) and needs to be improved. In this study, we proposed an ultraviolet (UV) light assisted CARE method. In this method, UV light is irradiated onto a SiC surface to generate holes and oxidize the surface. The oxidized area, consisting of SiO2, can be quickly removed to form a nano-pit owing to the higher removal rate of SiO2 compared to that of SiC. The periphery of the nano-pits works as a reaction site, leading to a higher removal rate. To enhance the oxidation rate and form nano-pits, we applied electrochemical bias to the SiC substrate. However, the removal rate did not improve significantly when the bias voltage was higher than 3.0 V. This is because the electrochemical potential of Pt increased with the anodic potential of SiC, which oxidized the Pt surface and degraded the catalyst capability. To avoid this issue, we modified the catalytic pad, where an in-situ refreshment of the Pt surface is possible. As a result, the removal rate increased up to 200 nm/h at a bias of 7.0 V, which is 100 times higher than that of the CARE without UV irradiation. The proposed method is expected to contribute to the enhancement in the productivity and quality of next-generation SiC substrates.

Back-Side Thinning of Silicon Carbide Wafer by Plasma Etching Using Atmospheric-Pressure Plasma

2012 ◽  
Vol 516 ◽  
pp. 108-112 ◽  
Author(s):  
Yasuhisa Sano ◽  
Kohei Aida ◽  
Hiroaki Nishikawa ◽  
Kazuya Yamamura ◽  
Satoshi Matsuyama ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Plasma Etching ◽  
Atmospheric Pressure ◽  
Removal Rate ◽  
Thickness Distribution ◽  
Atmospheric Pressure Plasma ◽  
Back Side ◽  
Wafer Level ◽  
Pressure Plasma ◽  
Sic Wafer

Silicon carbide (SiC) power devices have received much attention in recent years because they enable the fabrication of devices with low power consumption. To reduce the on-resistance in vertical power transistors, back-side thinning is required after device processing. However, it is difficult to thin a SiC wafer with a high removal rate by conventional mechanical machining because its high hardness and brittleness cause cracking and chipping during thinning. In this study, we attempted to thin a SiC wafer by plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. The wafer level thinning of a 2-inch 4H-SiC wafer has been possible without a removal thickness distribution caused by the circular shape of the wafer using the newly developed PCVM apparatus for back-side thinning with a spatial wafer stage.

Chemical Effect on the Material Removal Rate in the CMP of Silicon Wafers

2010 ◽  
Vol 126-128 ◽  
pp. 511-514
Author(s):  
Yong Guang Wang ◽  
Liang Chi Zhang ◽  
Altabul Biddut
Keyword(s):  
Hydrogen Peroxide ◽  
Flow Rate ◽  
Material Removal Rate ◽  
Material Removal ◽  
Ph Value ◽  
Removal Rate ◽  
Chemical Effect ◽  
Alumina Particles ◽  
Chemical Factors ◽  
Slurry Flow Rate

This paper investigates the effects of some chemical factors on the material removal rate (MRR) in chemo-mechanical polishing (CMP) of Si (100) wafers. The CMP was carried out in alkaline slurry using alumina and ceria particles with hydrogen peroxide. When using the alumina particles, the MRR initially decreases with increasing the slurry pH value until pH = 9. Nevertheless, the application of the ceria particles increases the MRR before the pH of the slurry reaches 10. A higher slurry flow rate brings about a greater MRR.

Effect of graphene additions on polishing of silicon carbide wafer with functional PU/silica particles in CMP slurry

2019 ◽  
Vol 12 (05) ◽  
pp. 1950066 ◽  
Author(s):  
Hsien-Kuang Liu ◽  
Chao-Chang A. Chen ◽  
Chun-Jen Chen
Keyword(s):  
Silicon Oxide ◽  
Ph Value ◽  
Removal Rate ◽  
Weight Fraction ◽  
Processing Parameters ◽  
Sonication Time ◽  
Polishing Process ◽  
Improvement Rate ◽  
Sic Wafer ◽  
Polishing Pads

In this paper, a functional ternary slurry consisting of polyurethane (PU) microspheres, graphene oxide (GO) nano platelets and silicon oxide (SiO2) abrasives was used to carry out the polishing process on Si face of 4H-SiC wafers. The processing parameters of the slurry include graphene weight fraction in slurry GO1–GO7 (0.1–0.7[Formula: see text]wt.%), pH value (3–5), and sonication time T5–T15 (5–15[Formula: see text]min). Polishing process is conducted with two kinds of polishing pads A and B, PU and PC (polycarbonate). Results show that material removal rate (MRR) increases with increasing GO weight fraction up to GO5; besides, MRR also increases with increasing sonication time up to T10, and with increasing pH value. Using PU pad, the GO5-T10-pH5-A slurry leads to highest MRR 102.220[Formula: see text]nm/h of the polished SiC wafer. On the other hand, surface roughness improvement rate (SRIR) increases with increasing GO weight fraction up to GO5, and increases with increasing sonication time up to T15. But SRIR is not affected by pH value. Regarding effect of pad type, on average the PU pad results in higher MRR and better SRIR compared with the PC pad. Using PC pad, GO5-T10-pH5-B leads to lower MRR of 87.627[Formula: see text]nm/h. The addition of GO as the ternary slurry demonstrates its better effect on polishing SiC wafers by comparing with the counterpart binary slurry without GO. For example, MRR by the counterpart slurry SiO212-pH5-A is 58.411[Formula: see text]nm/h, which is lower than 102.220[Formula: see text]nm/h by the ternary slurry GO5-T10-pH5-A. Both XPS and Raman spectra demonstrate that the wafer polished by the functional ternary slurry can effectively produce the softer SiO2 reactant layer on SiC wafer, and result in better polishing performance.

Augmented CMP Techniques for Silicon Carbide

2006 ◽  
Vol 527-529 ◽  
pp. 1099-1102 ◽  
Author(s):  
Peter Kuo ◽  
Ian Currier
Keyword(s):  
Silicon Carbide ◽  
Removal Rate ◽  
Mechanical Strain ◽  
Compound Semiconductor ◽  
Subsurface Damage ◽  
Chemical Effect ◽  
Chemical Additives ◽  
Removal Rates ◽  
Silica Slurry ◽  
Made In

Chemical-mechanical polishing (CMP) has proven a powerful tool for the final polishing of semiconductor and compound semiconductor substrates such as silicon, sapphire, gallium arsenide, and indium phosphide. For these materials, conventional CMP techniques have been able to produce removal rates of several μm/hr while achieving pristine, epi-ready surfaces with subsurface damage less than 10[nm]. For certain materials of interest in the compound semiconductor community, particularly silicon carbide (SiC) and the III-V nitrides, conventional CMP techniques perform poorly. These materials are extremely chemically inert, negating the desired chemical effect leading to removal rates of less than 0.1[μm/hr]. These materials are also very brittle and take damage easily, so a significant amount of material must be removed to ensure a sufficiently low subsurface damage for epitaxy. This paper documents the improvements made in the CMP of 4H and 6H SiC by augmenting a colloidal silica slurry with chemical additives and with special treated nano size diamond particles. The chemical additives proved most effective on 4H SiC, enhancing the slurry’s chemical effect and improving its removal rate. For both materials, the addition of the diamond (Chemical-Mechanical Polish with Diamond, CMP-D) greatly enhanced the removal rate and provided strong synergy between mechanical strain and chemical effect resulting in low subsurface damage.

Effect of Powder-Mixed Dielectric on EDM Process Performance

2020 ◽  
Vol 38 (8A) ◽  
pp. 1226-1235
Author(s):  
Safa R. Fadhil ◽  
Shukry. H. Aghdeab
Keyword(s):  
Silicon Carbide ◽  
High Speed ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
High Speed Steel ◽  
Transformer Oil ◽  
Dielectric Fluid ◽  
Peak Current ◽  
Powder Concentration ◽  
Pulse On Time

Electrical Discharge Machining (EDM) is extensively used to manufacture different conductive materials, including difficult to machine materials with intricate profiles. Powder Mixed Electro-Discharge Machining (PMEDM) is a modern innovation in promoting the capabilities of conventional EDM. In this process, suitable materials in fine powder form are mixed in the dielectric fluid. An equal percentage of graphite and silicon carbide powders have been mixed together with the transformer oil and used as the dielectric media in this work. The aim of this study is to investigate the effect of some process parameters such as peak current, pulse-on time, and powder concentration of machining High-speed steel (HSS)/(M2) on the material removal rate (MRR), tool wear rate (TWR) and the surface roughness (Ra). Experiments have been designed and analyzed using Response Surface Methodology (RSM) approach by adopting a face-centered central composite design (FCCD). It is found that added graphite-silicon carbide mixing powder to the dielectric fluid enhanced the MRR and Ra as well as reduced the TWR at various conditions. Maximum MRR was (0.492 g/min) obtained at a peak current of (24 A), pulse on (100 µs), and powder concentration (10 g/l), minimum TWR was (0.00126 g/min) at (10 A, 100 µs, and 10 g/l), and better Ra was (3.51 µm) at (10 A, 50 µs, and 10 g/l).

Investigation of nitrite pathways in sugar beet extraction

2014 ◽  
pp. 626-635 ◽  
Author(s):  
Florian Emerstorfer ◽  
Christer Bergwall ◽  
Walter Hein ◽  
Mats Bengtsson ◽  
John P. Jensen
Keyword(s):  
Sugar Beet ◽  
Laboratory Experiments ◽  
Ph Value ◽  
Full Scale ◽  
Chemical Effect ◽  
Spectrophotometric Detection ◽  
Sugar Factory ◽  
Chemical Effects ◽  
Set Up ◽  
Nitrate And Nitrite

The investigations presented in this work were carried out in order to further deepen the knowledge about nitrite pathways in the area of sugar beet extraction. The article consists of two parts with different experimental set-up: the first part focuses on laboratory trials in which the fate of nitrate and nitrite was studied in a so-called mini-fermenter. These trials were carried out using juice from the hot part of the cossette mixer of an Agrana sugar factory in Austria. In the experiments, two common sugar factory disinfectants were used in order to study microbial as well as microbial-chemical effects on nitrite formation and degradation caused by bacteria present in the juice. The trials demonstrated that the direct microbial effect (denitrification) on nitrite degradation is more pronounced than the indirect microbial-chemical effect coming from pH value decrease by these bacteria and subsequent nitrite loss. The second part describes the findings from laboratory experiments and full scale factory trials using a mobile laboratory set-up based on insulated stainless steel containers and spectrophotometric detection of nitrite in various factory juices. The trials were made at two Nordzucker factories located in Finland (factory A) and Sweden (factory B). The inhibiting effect of the two common sugar factory disinfectants on nitrite formation was evaluated in laboratory trials, whereas the full scale trials focused on one disinfectant. Other trials to evaluate potential contamination sources of thermophilic nitrite producing bacteria to the extraction system, reactivation of nitrite producing bacteria in raw juice and the effect of a pH gradient on bacterial nitrite activity in cossette mixer juice are also reported.

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