• Resources Recycling
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• v.21 no.4
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• pp.60-68
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• 2012

Silicon wafer for making semiconductor devices and solar cell is used in the semiconductor and solar industry, respectively. Silicon wafer is produced by cutting with silicon ingot and sludge contains silicon occurs from cutting process. Generation of silicon sludge is increasing on developing all industry sectors which have need of semiconductor device. These days it has been widely studied for the recycling technologies of the silicon sludge from view points of economy and efficiency. In this paper, patents and paper on the recycling technologies of the silicon sludge were analyzed. The range of search was limited in the open patents of USA (US), European Union (EU), Japan (JP), Korea (KR) and SCI journals from 1982 to 2011. Patents and journals were collected using key-words searching and filtered by filtering criteria. The trends of the patents and journals was analyzed by the years, countries, companies, and technologies.

• Resources Recycling
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• v.17 no.4
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• pp.66-76
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• 2008

Silicon wafer is used in making semiconductor device of various forms in the semiconductor industry. Silicon wafer is produced by cutting silicon ingot and sludge containing silicon results from cutting process. The amount of silicon sludge is increasing owing to the usage of semiconductor device in many industry sectors. These days the recycling technologies of the waste silicon sludge has been widely studied from view point of economy and efficiency. In this study, patents on the recycling technologies of the waste silicon sludge were analyzed. The range of search was limited in the open patents of USA, European Union, Japan, and Korea up to september, 2007. Patents were collected using key-words and filtered by filtering criteria. The trend of the patents was analyzed by the years, countries, companies, and technologies.

• Resources Recycling
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• v.31 no.6
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• pp.60-65
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• 2022

This study presents the carburization process for recycling sludge, which was formed during silicon wafer machining. The sludge used in the carburization process is a mixture of silicon and silicon carbide (SiC) with iron as an impurity, which originates from the machine. Additionally, the sludge contains cutting oil, a fluid with high viscosity. Therefore, the sludge was dried before carburization to remove organic matter. The dried sludge was washed by acid cleaning to remove the iron impurity and subsequently carburized by heat treatment under vacuum to form the SiC powder. The ratio of silicon to SiC in the sludge was varied depending on the sources and thus carbon content was adjusted by the ratio. With increasing SiC content, the carbon content required for SiC formation increased. It was demonstrated that substoichiometric SiC_x (x<1) was easily formed when the carbon content was insufficient. Therefore, excess carbon is required to obtain a pure SiC phase. Moreover, size reduction by high-energy milling had a beneficial effect on the suppression of SiC_x, forming the pure SiC phase.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.3
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• pp.35-41
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• 2023

In this study, silicon sludge generated in semiconductor manufacturing process is recycled and applied as materials for pigments and paints. In detail, metallic impurities are removed from silicon sludge to obtain plate-like silicon sludge powder (SW-sludge), which is then coated with titanium dioxide via sol-gel method (TCS-sludge). SW-sludge and TCS-sludge are dispersed in hydrophilic transparent varnish and sprayed onto glass substrates to observe the possibility for the application as materials for pigments and paints. Notably, the applicability of TCS-sludge-based paint is improved compared to SW-sludge-based paint after the titanium dioxide coating. Moreover, the color of TCS-sludge-based paint turns into white. Accordingly, it is confirmed that the applicability and hydrophilicity are improved by the presence of outer titanium dioxide layer. In this regard, it is expected that the recycled TCS-sludge may be a future material for the application as pigments and paints.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.1
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• pp.1-9
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• 2012

This paper explained about the sludge recycling system which retrieved the silicon and abrasive from solar cell wafer slicing. The basic process of the recycling system was multiple centrifuge and secondary processes of ultra sonic agitation, addition of alcohol-water solution and heating sludge was added for raising separation efficiency. The recycling rate was about 96% and 94% for 2N, 4N silicon respectively. The SiC abrasive recycling rate was about 80%. To retrieve the high purity of 4N silicon, the heat process in vacuum furnace was added to remove remaining impurity components.

• Resources Recycling
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• v.22 no.2
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• pp.37-43
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• 2013

Unlike the conventional slurry type wire sawing, the diamond wire sawing method adopts diamond plated wire as sawing media instead of slurry consisted of both silicon carbide and oil. Wafering with diamond plated wire leaves solid element of the sludge mostly made up of silicon, and it is not difficult to recover 95% or more of silicon by a simple separation process of oil from the sludge. In this study, silicon was recovered from the sludge by drying process and organic and metal impurities were removed by sintering process. As result 3N grade silica was obtained successfully by thermal processing utilized the fact that the recovered silicon readily combines with oxygen due to fine particle size.

• Resources Recycling
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• v.16 no.5
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• pp.41-45
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• 2007

Tetramethylorthosilicate (TMOS) and silica nanopowder were synthesized from the waste silicon sludge containing 15% weight of silicon powder. TMOS, a precursor of silica nanopowder, was firstly prepared from the waste silicon sludge by catalytic chemical reaction. The maximum recovery of the TMOS was 100% after 5 hrs regardless of reaction temperature above $130^{\circ}C$. But the initial reaction rate became faster while the reaction temperature was higher than $150^{\circ}C$. As the methanol feedrate Increased from 0.8 ml/min to 1.4 ml/min, the yield of reaction was not varied after 3 hrs. Then, silica nanopowder was synthesized from the synthesized TMOS by flame spray pyrolysis. The morphology of as-prepared silica nanopowder was spherical and non-aggregated. The average particle diameters ranged from 9 nm to 30 nm and were in proportional to the precursor feed rate, and precursor concentration.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.2
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• pp.45-49
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• 2019

Relatively fine silicon carbide (SiC) crystalline aggregates have been synthesized with the carbonized rice husks, paper sludge, coffee grounds as the carbon sources and the silica powder. The main reaction source to obtain silicon carbide (SiC) aggregates from the mixture of carbon sources and silica was inferred as the gaseous silicon monoxide (SiO) phase, being created from this mixture through the carbothermal reduction reaction. The silicon carbide (SiC) crystalline aggregates, fabricated from the carbonized rice husks and paper sludge, coffee grounds and silica ($SiO_2$) powder, were investigated by XRD patterns, FE-SEM and FE-TEM images. In these specimens, obtained from the carbonized rice husks, paper sludge and silica, XRD patterns showed rather high strong peak of (111) plane near $35^{\circ}$. The FE-TEM images and patterns of specimens, synthesized from carbonized rice husks, paper sludge, coffee grounds and silica under Ar atmosphere, showed relatively fine particles under $1{\mu}m$ and crystalline peak (110) of silicon carbide (SiC) diffraction pattern.

• Resources Recycling
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• v.21 no.5
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• pp.31-37
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• 2012

As a recovery of elemental silicon from the sludge of Si wafer process, a process of mechanical separation-chlorine roasting-electrolysis has been suggested. The silicon sludge consisted of Si, SiC, machine oil, and metallic impurities. The oil and metal impurities was removed by mechanical separation. The Si-SiC mixture was converted to silicon chloride by chlorine roasting at $1000^{\circ}C$ for 1 hr and the silicon chloride was dissolved into an ionic liquid of $[Bmpy]Tf_2N$ as an electrolyte. Cyclic voltammetry results showed an wide voltage window of pure $[Bmpy]Tf_2N$ and a reduction peak of elemental Si from $[Bmpy]Tf_2N$ dissolved $SiCl_4$ on Au electrode, respectively. The silicon deposits could be prepared on the Au electrode by the potentiostatic electrolysis of -1.9 V vs. Pt-QRE. The elemental silicon uniformly electrodeposited was confirmed by various analytical techniques including XRD, FE-SEM with EDS, and XPS. Any impurity was not detected except trace oxygen contaminated during handling for analysis.

• Resources Recycling
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• v.22 no.2
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• pp.22-28
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• 2013

In the present study, the possibility of recovering and recycling the silicon carbide(SiC) from a silicon sludge by removing Fe and Si impurities was investigated. Si and SiC were separated from the silicon sludge using centrifugation. The separated SiC concentrate consisted of Fe, Si and SiC, in which Fe and Si were removed to recover the pure SiC. Leaching with acid/alkali solution was compared with the vapor-phase chlorination. The Fe concentration removed in the SiC was 49 ppm, and it was separated by leaching with 1 M HCl solution at $80^{\circ}C$ for 1 h. The Si concentration removed in the SiC was 860 ppm, and it was separated by leaching with 1M NaOH solution at $50^{\circ}C$ for 1 h. The SiC concentrate was chlorinated in a tubular reactor, 2.4 cm in diameter and 32 cm in length. The boat filled with SiC concentrate was located at the midpoint of the alumina tube, then, the chlorine and nitrogen gas mixture was introduced. The Fe and Si concentration removed in the SiC were 48 ppm and 405 ppm, respectively, at $500^{\circ}C$ reactor temperature, 4 h reaction time, 300 cc/min gas flow rate, and 10% $Cl_2$ gas mole fraction.