Silicon Ingot Slicing Research Articles

Efficient manufacture of high-performance electroplated diamond wires utilizing Cr-coated diamond micro-powder

The slicing of silicon ingots using electroplated diamond wires is a fundamental process in the creation of semiconductor devices such as chips and photovoltaic cells. Composite electroplating, a process that uses nickel (Ni) plating to fix diamond particles onto a steel wire, is a critical step in the manufacturing of these diamond wires. In this work, chromium (Cr)-coated diamond was used to achieve rapid and high-quality composite electroplating, thereby aiding the production of high-performance diamond wire saws. The Cr-coated diamond micro-powder was prepared utilizing vacuum slow evaporation technology at a temperature of 850 °C. This resulted in a uniform and firm Cr coating that was firmly bonded to the diamond surface via Cr3C2. Subsequent electrochemical tests were conducted in the composite electroplating bath. Linear scanning voltammetric curves revealed that the Cr-coated diamond was capable of inducing a more positive shift in the overpotential of Ni deposition, thus enhancing the reaction beyond that of uncoated diamond micro-powder. Additionally, the electrochemical impedance spectra indicated a decrease in charge transfer resistance during composite electroplating, attributable to the conductivity of the Cr-coated diamond. Electroplated diamond wires incorporating Cr-coated diamond demonstrated a greater abrasive density per unit length. SEM results showed that Ni was able to deposit on the Cr-coated diamond surface, resulting in the abrasives being completely covered by the Ni plating. The Cr-coated diamond wire exhibits a stronger resistance to abrasive detachment after cutting, which could increase the diamond-protrusion of the wire. The utilization of Cr-coated diamond micro-powder as an abrasive is anticipated to enhance the manufacturing efficiency of diamond wires and improve product quality, thereby promoting advancements in hard and brittle material processing technology.

Parametric optimization of silicon slicing using wire electro discharge machining

Abstract Silicon covers nearly about 90% of electronic sector that has made slicing a fundamental process for the manufacturing of various components such as integrated circuit, computer chips and solid-state devices. Silicon belong to the class of semi-conductor and has high brittleness due to which slicing using conventional machining processes is difficult, and many defects are to it such as chipping, scratches and large cracks. Wire Electro Discharge Machining (WEDM) is a potential process for slicing of silicon ingots. The present experimental investigation deals with the slicing of mono-crystalline silicon using WEDM process, using brass wire electrode of diameter 250 µm. The responses considered were material removal rate, surface roughness and slicing speed which were measured with the variation of the process parameters viz. open voltage(OV-V), servo voltage(SV-V), pulse on time (Ton -µs), wire tension(WT-g) and pulse off time(Toff -µs). The experimental runs were performed using Taguchi’s L27 (35) orthogonal design. The experimental results were analyzed using Taguchi based Grey Relational Analysis (TGRA) and the optimum parametric setting for the slicing was obtained at OV (111 V), Ton (0.2 µs), Toff (21 µs), WT (600 g) and SV (38 V). ANOVA analysis of the Grey Relational Grade (GRG) shows that pulse on time, wire tension and open voltage are the main contributing factor during slicing.

A low cost additive-free acid texturing process for large area commercial diamond-wire-sawn multicrystalline silicon solar cells

Diamond-wire-sawing (DWS) technique allows slicing of silicon ingots to produce wafers at cheaper price due to its reduced kerf-loss and increased cutting rate. However, there is no cost-effective and industrially viable method available for texturing DWS wafers, especially for multicrystalline silicon (mc-Si) wafers. Currently additive-based acid texturing process is availed by PV manufacturing units for texturing DWS mc-Si wafers. An additive-free, low cost and energy-efficient acid texturing process is demonstrated for DWS mc-Si wafers in industrial production line. Nearly 10% absolute reduction in weighted average reflectance values (WAR) are noticed for the newly textured wafers from that of as-cut DWS mc-Si wafers and the WAR values are comparable to that of existing additive-based acid textured mc-Si wafers. An absolute reduction in emitter saturation current density by ~17 fA-cm-2 and improved implied open circuit voltage of ~5 mV (absolute) are reported for lifetime sample fabricated using newly textured wafers when compared to the additive-based acid textured lifetime samples. An impressive batch average efficiencies of 18.20% and 18.24% are achieved for the additive-free and existing additive-based acid textured mc-Si cells, respectively. Detailed analysis conclude that ~1.5% (relative) enhancement in short circuit current density can be achieved by further process optimization. Cost analysis indicates that 60% of the chemical cost involved the texturing process can be cut down by replacing the existing additive-based acid process with the new method using the same process equipment. Hence, the texturing process presented has great potential for producing large area high efficiency mc-Si cells favoring cost considerations without compromising performance.

Analysis of Electrical Forces in Multi-wire EDM for Semiconductors

Multi-Wire EDM (MWEDM) is being investigated for cutting silicon wafers from ingots in solar industry and IC manufacturing industry. However, practical realization of MWEDM is limited by the forces exerted on the wires. This paper explains nature of forces in case of MWEDM for slicing of silicon ingots, which is distinct from the case of single wire EDM for metal cutting. In particular, the material properties of semiconductor are different from those of the metals and the geometry of the problem is also different. It is shown that the wires in MWEDM exert forces on each other, in addition to those exerted by the workpiece on wires. Quantification of dominant electromagnetic forces is done by analytical means and the results are validated by Finite Element Analysis (FEA) for the cases of 5-wire EDM and 10-wire EDM. Experimentally determined material properties and spark current profiles are used as input to FEA. An algorithm has been developed to calculate the required wire tension considering number of wires, radius of wires, spark current, and wafer thickness. Validation of the algorithm is provided by comparing the results with the experimental data for 40-wire EDM published earlier.

Silicon-Based Composite Negative Electrode Prepared from Recycled Silicon-Slicing Slurries and Lignin/Lignocellulose for Li-Ion Cells

A large amount of kerf loss silicon slurries has been produced in the photovoltaics industry by direct diamond-wire slicing. The high-purity silicon particles in the slurries are suitable for reutilization as anode materials for lithium-ion batteries. In this study silicon particles from the kerf loss of silicon ingot slicing, coupled with lignin or lignocellulose as carbon precursors, are employed to form carbon–silicon composite materials. A pyrolysis thermal treatment in the presence of argon was applied to carbonize the biomass on the silicon materials in order to increase the conductivity of silicon-based anodes. Due to the different carbonaceous precursors, the composites formed different structures. The lignin-silicon electrode with a carbon-coated structure delivered an initial charge capacity of up to 2286 mAh/g and retained 880 mAh/g after 51 cycles at 300 mA/g. On the other hand, the pyrolyzed lignocellulose formed an interconnected structure with silicon particles, providing extra space to acc...

Carbon-Coated Silicon Powders Prepared from Recycled Silicon Ingot Slicing Slurries and Biomass for Negative Electrode Materials of Li-Ion Batteries

Silicon has the potential to replace the graphite as the anode material for LIB due to its high specific capacity and proper working voltage. However, the dramatic volume expansion during the Li-ion insertion and extraction has caused the poor cyclic stability. To improve the cyclic stability of Si anode, we embedded Si into a carbon matrix to form a Si-C composites. In this study, the silicon powders of micrometer size recovered from the silicon ingot slicing slurries and lignin, which is by-product of pulp industry, are employed to fabricate negative electrodes for lithium ion battery. The biomass would well mix with Si particles by magnetic stirring and ultrasonication, and then undergo a pyrolysis process to form Si-C composites. Depends on different carbonaceous precursors, the composites have different structures. The lignin-based Si particles are coated with a carbon layer, and the layer can not only suppress the volume change but also increase the electronic conductivity. The composite electrode exhibits outstanding cycle performance for capacity retention up to 60% after 51 cycles at 300 mA/g. On the other hand, the pyrolyzed lignocellulose formed an interconnected structure with Si particles, which provide extra space to accommodate Si volume variation. It showed excellent electrochemical performance with an initial charge capacity up to 1937 mAh/g and retaining 1275 mAh/g after 100 cycles at 300 mA/g. The utilization of renewable sources and industrial wastes for energy storage materials is well demonstrated in this study.

Recovery of cutting fluids used in polycrystalline silicon ingot slicing

A recovery process for effective separation of silicon, silicon carbide micro powders and polyethylene glycol from the wire sawing slurry is proposed. The separation between silicon and silicon carbide is based on their size difference and surface charging state. The aim of this work is the study of the solid phase and liquid phase separation of silicon carbide and Silicon. Some methods applied for this purpose are the centrifugation process, phase-transfer separation as well as liquid–liquid extraction followed by the regeneration of polyethylene glycol by the distillation process. It is verified experimentally that silicon and silicon carbide micro powder can be effectively separated by phase transfer separation, centrifugation, chemical cleaning, filtering and distillation. In this study, the liquid–liquid extraction was used to separate a particle from a powder mixture. The removal of liquid component from a solution via a solvent separated considerably larger silicon carbide particles. The optimal results showed that Si content can reach 82% in the Si-rich powder and 3.8% wt% in the silicon carbide-rich powder. By separating the mixed powder the content reached 31.2wt% of silicon, 63.3wt% of silicon carbide as the raw material, 5.3wt% of the iron fragment, and 0.2wt% of other impurities.

Multi-objective optimization for silicon wafer slicing using wire-EDM process

Abstract The existing silicon ingot slicing methods adopt contact forces in slicing that could easily cause higher kerf loss and a larger variation in the thickness of the sliced wafers. Wire-EDM is a potential process for slicing of silicon ingots into wafers. This work therefore demonstrates capability of wire-EDM in silicon wafer slicing through a RSM based experimentation involving use of molybdenum wires of 40–120 μm in diameter. During the experiments wafers of various height ranging from 50 to 150 mm were fabricated and capability of the process was assessed in minimizing the kerf width. It was evident that the kerf width reduces from 250 μm to 50 μm, when sliced by a 40 μm diameter wire, which amounts to a reduction in kerf loss by 300%. The slicing speed on the other hand could be increased by 40–50% to 2.5 mm/min over the conventional abrasive slicing. A multi-objective optimization methodology adopted gives parametric conditions that give minimum kerf width at the highest slicing speed and the lowest surface roughness.

Aerosol-assisted extraction of silicon nanoparticles from wafer slicing waste for lithium ion batteries.

A large amount of silicon debris particles are generated during the slicing of silicon ingots into thin wafers for the fabrication of integrated-circuit chips and solar cells. This results in a significant loss of valuable materials at about 40% of the mass of ingots. In addition, a hazardous silicon sludge waste is produced containing largely debris of silicon, and silicon carbide, which is a common cutting material on the slicing saw. Efforts in material recovery from the sludge and recycling have been largely directed towards converting silicon or silicon carbide into other chemicals. Here, we report an aerosol-assisted method to extract silicon nanoparticles from such sludge wastes and their use in lithium ion battery applications. Using an ultrasonic spray-drying method, silicon nanoparticles can be directly recovered from the mixture with high efficiency and high purity for making lithium ion battery anode. The work here demonstrated a relatively low cost approach to turn wafer slicing wastes into much higher value-added materials for energy applications, which also helps to increase the sustainability of semiconductor material and device manufacturing.

Modeling of silicon ingot slicing process by wire–electrical discharge machining

Photovoltaic industry requires the cutting of silicon ingots into wafers in order to get minimum kerf loss, to facilitate manufacturing of thin wafers and to provide high productivity. Existing silicon ingot slicing processes like inner diameter saw and abrasive wire cutting have drawbacks of high kerf loss, lower finish and limitation on the thickness of wafer. In order to have economically viable photovoltaic technology, efficiency of wafer manufacturing process needs to be improved. The wire–electrical discharge machining technology is adopted as a new candidate for silicon slicing and is compared with the existing procedures and testified whether it can inevitably substitute the inner diameter saw or even compete with wire saws in some manufacturing orders. The main focus of this article is to understand the effect of processing parameters on the cutting process, so the parametric conditions delivering high slicing rate and low kerf loss can be achieved. Modeling of wire–electrical discharge machining is difficult as it involves several disciplines such as thermodynamics, hydrodynamics, electrodynamics and electromagnetics. Various researchers have proposed analytical models for electrical discharge machining and wire–electrical discharge machining through the use of electrothermal concepts. However, a comprehensive model that predicts the erosion rate in wire–electrical discharge machining process is needed. This article considers moving the line heat source nature of the wire to predict the temperature profiles of the workpiece in order to calculate the erosion rate. The results thus obtained have been analyzed experimentally, and conclusions have been derived enabling a better understanding of future research prospects and applications.

RESPONSE SURFACE ANALYSIS OF SLICING OF SILICON INGOTS WITH FOCUS ON PHOTOVOLTAIC APPLICATION

Polycrystalline silicon wafers are widely used in Photovoltaic (PV) industry as a base material for the solar cells. The existing silicon ingot slicing methods typically provide minimum wafer thickness of 300–350 μm and a surface finish of 3–5 μm Ra while incurring considerable kerf loss of 35–40%. Consequently, efficient dicing methods need to be developed, and in the quest for developing new processes for silicon ingot slicing, the wire-EDM (electric discharge machining) is emerging as a potential process. Slicing of a 3′′ square silicon ingot into wafers of 500 μm in thickness has been performed to study the process capability. This article analyzes the effect of processing parameters on the cutting process. The objective of the experimental study is improvement in slicing speed, minimization of kerf loss and surface roughness. A central composite design-based response surface methodology (RSM) has been used to study the slicing of polycrystalline silicon ingot via wire-EDM. A zinc-coated brass wire, 100 μm in diameter, has been used as an electrode in the slicing experiments. It has been observed that the optimal selection of the process parameters results in an increase of 40–50% in the slicing rate along with a 20% reduction in the kerf loss as compared to the conventional methods. The machined surfaces on the sliced wafer were free of micro-cracks and wire material contamination, thereby making it useful for electronic applications.

Effect of tensile properties on the abrasive wear of steel saw wires used for silicon ingot slicing

The abrasive wear patterns and the tensile properties of steel saw wires (120μm in diameter) were investigated in order to develop highly reliable saw wires for the application to silicon (Si) ingot slicing. Saw wires that underwent heat treatment at different linear velocities during the patenting process were subjected to 2-body abrasive wear (2-BAW) and 3-body abrasive wear (3-BAW) tests. The 2-BAW and 3-BAW tests of the saw wires showed opposite trends in abrasive wear resistance. The wear loss resulting from the 2-BAW test was mainly determined by the tensile strength and microhardness of the steel saw wire samples, while the wear loss from the 3-BAW test was primarily determined by the elongation, or ductility, of the samples.

Wear Characteristics of ID Saw Blade in Silicon Ingot Slicing Process

In this paper, the wear behavior of the ID (inner diameter) saw blade in the cutting process of silicon ingot was observed with SEM. Its wear mechanism was discussed and the relation between the blade wear and vibration, deflection was analyzed. The results show that the blade worn manners include flatted diamond, micro-fractured diamond, macro-fractured diamond, pulled-out hole, tortoise-fractured bond, and polished bond. In the abnormal working stage of a blade, however, the working surface of the blade is displayed mainly with pulled out diamond, flatted diamond, macro-fractured diamond grains. Abnormal initial tension condition will induce severe vibration and deflection, and so then lots of diamond grits fractured or pulled out too early.