| HS Code | 521783 |
| Product Name | Large Particle Silica Polishing Slurry Electronic/EL Grade |
| Appearance | Milky white liquid |
| Particle Size | 1.0 - 3.0 micrometers |
| Silica Content | 30 - 50 wt% |
| Ph | 9.0 - 11.0 |
| Viscosity | 10 - 50 mPa·s at 25°C |
| Specific Gravity | 1.15 - 1.30 g/cm³ |
| Refractive Index | 1.35 - 1.45 |
| Trace Metal Impurities | Less than 1 ppm each (Fe, Cu, Na, K, Ca, Mg) |
| Shelf Life | 12 months from date of manufacture |
| Storage Temperature | 5 - 30°C |
| Dilution Stability | Stable in deionized water at 1:10 ratio |
As an accredited Large Particle Silica Polishing Slurry Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 5-gallon pails or 55-gallon drums, with contamination-resistant seals to maintain purity and stability for Electronic/EL grade slurry. |
| Container Loading (20′ FCL) | 20' FCL loading of Electronic/EL Grade large particle silica slurry in sealed containers, secured with bracing, spill containment, and moisture protection. |
| Shipping | Shipping as a non-hazardous, aqueous slurry in sealed drums or IBCs. Protect from freezing and direct sunlight to prevent particle settling or agglomeration. Use clean, dedicated equipment to maintain Electronic/EL Grade purity. Standard freight is acceptable; ensure containers are secured upright and labeled per manufacturer guidelines. |
| Storage | Store in a clean, tightly sealed container to prevent contamination and evaporation. Keep in a cool, dry, well-ventilated area, ideally between 5–35°C. Avoid freezing and direct sunlight. Do not allow slurry to dry; keep particles suspended by gentle agitation before use. Use clean, compatible utensils and avoid cross-contamination for electronic-grade purity. |
| Shelf Life | Shelf life is typically 6–12 months when stored sealed at room temperature, avoiding freezing or contamination. |
On 150 mm semi-insulating 4H-SiC substrates received from multi-wire slurry sawing, subsurface lattice damage measured by cross-sectional transmission electron microscopy commonly extends 5–15 µm below the as-sawn surface. Large-particle silica slurry with a D50 centred at 105–130 nm is applied as the first post-lapping CMP step to remove this damaged layer before a finer colloidal silica finish is introduced. The slurry is diluted with ultra-pure water at a volumetric ratio of 1:1 to 1:3, with the exact ratio set by pad groove depth and removal-rate drift. The process runs on a single-side rotary polisher equipped with 500 mm cast-iron platens and a microporous polyurethane pad having Shore D hardness 58–62. Typical parameters include a downforce of 4.0–5.5 psi, platen speed of 55–80 rpm, carrier speed of 45–60 rpm, slurry flow of 90–150 mL/min, and pad temperature held at 30–40 °C. Under these conditions the Si-face stock removal rate falls between 80 nm/min and 160 nm/min, while the C-face removes faster due to the polarity difference of 4H-SiC and can exceed 200 nm/min with the same slurry. Post-polish atomic force microscopy over 10 × 10 µm² scan fields typically returns RMS roughness values of 0.25–0.55 nm after the final fine slurry step. The operational conflict is direct: when the D50 exceeds 130 nm or when the pH drops below 9.8, microscratch density on the Si-face increases rapidly; when the pH is raised above 11.0, hydroxide etching starts to degrade step-terrace morphology and raises surface metal contamination after cleaning. The slurry therefore has to remain within pH 10.0–10.8 using low-sodium potassium hydroxide, with transition-metal cations in the as-shipped liquid maintained below 200 ppb by ICP-MS according to ASTM F1526-20. The terminal product is an epi-ready SiC substrate intended for RF power devices and Schottky diode fabrication, where surface metal contamination after final cleaning is controlled to ≤1×10¹¹ atoms/cm² for sodium, potassium, iron, and copper as verified by total reflection X-ray fluorescence against SEMI M76-0418.
Pad conditioning is performed in situ with a diamond conditioner containing 200–300 µm diamond grit at a sweep frequency of 10–15 sweeps/min; without this conditioning the removal rate decays by 10–15% over 25 wafer passes because large particles compact in the pore structure of the polyurethane pad. Table 1 summarizes representative Si-face removal-rate and defect-density behaviour across the dilution window. Endpoint control is timed because motor-current endpoint is not sufficiently sensitive for 4H-SiC at these removal rates, and post-polish eddy-current thickness mapping is used to confirm total thickness variation below 2.0 µm across a 150 mm substrate. Batch-to-batch removal variation is held within ±8% by recalibrating slurry flow whenever pad groove depth falls below 0.25 mm or when the slurry temperature exceeds 40 °C for more than 5 min. The primary incompatibility is with amine-based post-polish cleaning formulations, which cause silica particle agglomeration on the wafer surface and raise defect counts by more than 3× compared with standard SC1 cleaning at 25 °C.
| Slurry dilution with UPW | D50 | Si-face removal rate | Post-fine-polish RMS roughness | Defects >0.2 µm per 150 mm substrate |
|---|---|---|---|---|
| 1:1 | 110 nm | 155–185 nm/min | 0.32–0.48 nm | 23–41 |
| 1:2 | 110 nm | 120–145 nm/min | 0.28–0.41 nm | 11–18 |
| 1:3 | 110 nm | 85–110 nm/min | 0.25–0.35 nm | 6–10 |
The decision to use a 95–115 nm D50 silica slurry on thinned silicon wafers is driven by the need to remove grind-induced microcracks and residual stress after coarse backgrinding. On a 300 mm silicon wafer processed through a coarse-grind module with #2000 diamond wheels, the backside surface carries subsurface damage to a depth of 1–3 µm, and this damage is not removed by fine colloidal silica at acceptable throughput. The large-particle slurry is diluted 1:2 with ultra-pure water and is supplied to an integrated polishing module at 80–150 mL/min. The process runs with carrier downforce of 2.5–3.5 psi, platen speed of 60 rpm, and pad temperature of 22–28 °C. Under these conditions the slurry removes 1.5–2.5 µm of silicon in 3–5 min and yields a post-process roughness of 0.5–1.2 nm Ra measured by stylus profilometry according to ISO 4287. The pH window is deliberately narrow at 9.5–10.2; above 10.2 the protective front-side tape adhesive swells and loses adhesion, while below 9.5 the removal rate becomes insufficient to clear grind damage in the fixed process time. Sodium-free pH adjusters are required because sodium contamination on the backside can diffuse through the thinned silicon during subsequent thermal processing. The terminal configuration is a thinned logic or memory wafer for through-silicon-via stacking, with total thickness variation after polishing controlled to ±2.0 µm per SEMI M1-0218. Edge chipping is assessed by automated optical inspection around a 200 mm circumference; after process optimization the accepted edge exclusion is 0.5–1.0 mm, and chipping defect counts are held at ≤3 per wafer. The main incompatibility is prolonged exposure to amine-based cleaning concentrates after polishing, which destabilizes residual silica particles and produces localized carbon-rich residues on the thinned backside. Between polish and final rinse, the wafer must not remain in ambient air for more than 2 min because native oxide growth on the freshly polished silicon proceeds at 0.3–0.5 nm/hr and can affect downstream wafer bonding uniformity.
When sapphire LED windows are transferred from loose-abrasive fused alumina lapping to CMP, the immediate benefit is elimination of embedded alumina residues, but the process window narrows considerably. The large-particle silica slurry used on C-plane sapphire has a D50 of 110 nm and a pH of 10.0–10.6, adjusted with high-purity potassium hydroxide. It is diluted 1:1.5 with ultra-pure water before delivery to a single-side polisher equipped with a polyurethane suede pad. The applied downforce is 5.0 psi, platen speed is 40–60 rpm, slurry flow is 100–150 mL/min, and pad temperature is maintained at 40–50 °C to activate the chemo-mechanical reaction between silica and the sapphire surface. Under these conditions the C-plane removal rate is 1.0–1.8 µm/hr, while the A-plane removal rate is 0.6–1.0 µm/hr because the crystallographic orientation alters the hydrolysis rate of the surface layer. Post-polish roughness is Ra ≤0.3 nm over 2 × 2 µm² atomic force microscopy scans and surface texture is specified according to ISO 10110-8. Total thickness variation on 50.8 mm sapphire windows is held below 2.0 µm after final polishing, which is critical because thickness wedges above 2.0 µm shift the photolithographic overlay signature for patterned sapphire substrate production. The slurry’s large particle size presents a specific risk: if pH drifts below 9.8 or if the pad is allowed to dry for more than 30 s between cycles, silica crystallizes in the pad pores and produces crescent-shaped scratches that are not removed by subsequent fine polishing. EDX inspection after the CMP step is used to confirm that aluminum-rich inclusions from the preceding lapping step have been reduced below detection. The terminal product is either an epi-ready sapphire window for high-brightness LED growth or a patterned sapphire substrate that proceeds directly to photolithography. Ultrasonic DI-water cleaning at 35 °C follows the CMP step, and the use of acid-based drying agents is avoided because acidic rinse chemistry destabilizes the alkaline silica dispersion and causes redeposition of agglomerated particles at the wafer edge.
NiP-plated aluminum disk blanks after diamond turning exhibit periodic waviness with amplitudes in the 5–15 nm range and single-point turning marks that cannot be removed by fine colloidal silica alone. For first-stage hard-disk substrate polishing the slurry is a large-particle silica dispersion with D50 of 90–120 nm, pH 2.5–3.5, and an oxidizer-complexing acid system that maintains uniform NiP removal. The process is run on a double-side planetary polisher with 16B carriers, upper and lower plate speeds of 30–45 rpm, plate pressure of 0.6–0.9 psi, slurry flow of 150–250 mL/min, and pad temperature of 25–35 °C. Under these conditions the NiP removal rate is 0.4–0.7 µm/min, which is sufficient to clear diamond-turning marks and reduce peak-to-valley waviness to ≤0.8 nm RMS over 500 × 500 µm² optical interferometer scans. The substrate is a 3.5-inch aluminum disk intended for perpendicular magnetic recording media, and the polishing bay is maintained under ISO 14644-1 Class 4 cleanroom conditions. A pH excursion below 2.0 accelerates NiP corrosion and creates pit defects deeper than 10 nm that can survive the final texture step; a pH excursion above 4.0 causes silica particle settling in the slurry delivery loop and raises microscratch density by more than 2× in the outer-diameter zone. The slurry loop is sized so that the residence time between mix tank and polish point does not exceed 20 min, because settled particles in low-flow corners create hard agglomerates that cannot be redispersed. After polishing, the disks are transferred to a rinse module within 30 s to prevent dried acidic slurry from etching the NiP surface. Table 2 lists the Electronic/EL Grade slurry acceptance parameters that are applied to this process and to the semiconductor-related steps above.
| Parameter | Test method | Acceptance limit |
|---|---|---|
| D50 particle size | ISO 22412:2017 | 105–130 nm or grade-specific ±10% |
| pH | ASTM E70-22 | 9.8–10.6 for alkaline grades; 2.5–3.5 for NiP grades |
| Sodium | ASTM F1526-20 ICP-MS | ≤200 ppb for semiconductor grades; ≤2 ppm for NiP grades |
| Iron | ASTM F1526-20 ICP-MS | ≤100 ppb |
| Copper | ASTM F1526-20 ICP-MS | ≤50 ppb |
| Large particles >0.5 µm | single-particle optical sensing per ISO 21501-2:2019 | ≤5,000 particles/mL |
| Viscosity at 25 °C | ASTM D4212-16 | ≤5 mPa·s |
On single-fiber polishing machines, ferrule end-face geometry is generated by a sequence of diamond film, intermediate slurry, and final slurry steps. The intermediate step uses a large-particle silica slurry with D50 of 80–100 nm, pH 9.0–9.8, and a dilution of 1:1 with deionized water. The polishing load is 0.8–1.2 kgf, the platen speed is 100–140 rpm, and the dwell time is 20–30 s. Under these conditions the zirconia ferrule removal rate reaches 6–12 µm/min, which is sufficient to erase diamond-film scratches and generate a controlled radius of curvature before the final 40–50 nm silica slurry step. The terminal component is a single-mode ceramic ferrule used in patch cords and pigtails, with end-face geometry verified by a phase-shifting interferometer according to IEC 61300-3-16. For a UPC ferrule the radius of curvature is controlled to 15–25 mm, apex offset remains ≤30 µm, and return loss after the final polish exceeds 55 dB. For an APC ferrule the radius is held to 5–12 mm and the angle to 8° ± 0.5°, with the same intermediate slurry step but a longer final polish time. The main incompatibility is chloride-containing pH adjusters, which can initiate microcracks in zirconia ferrules and reduce fiber pull-out strength. The slurry metering on multi-position ferrule polishers must be flushed every 10 min during extended runs because large-particle silica deposits in the delivery nozzle and causes intermittent drop-by-drop flow variation. Published data for the transition from 80–100 nm intermediate silica to 40–50 nm final silica on zirconia ferrules is limited; equipment-specific interferometer yield data are used to define the split. The process is halted when the interferometer apex-offset moving range exceeds 45 µm on 5 consecutive ferrules, because this indicates pad wear has altered the polishing angle and the ferrule fixture requires reconditioning.
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Designated under the model code EL-LPS-120, the product is an aqueous colloidal dispersion of discrete, non-porous synthetic silica particles with a nominal median particle diameter between 110 nm and 130 nm and a coarse tail controlled to D90 ≤ 180 nm by laser diffraction per ISO 13320:2020. The continuous phase is 18.2 MΩ·cm deionized water with ammonium hydroxide as the stabilizing alkali. Solids content is held at 32–36 wt% when measured by loss-on-drying per ISO 3251:2019. The electronic/EL grade designation reflects mobile-ion limits of ≤50 µg/L sodium and ≤100 µg/L potassium, with transition metals controlled to ≤50 µg/L for iron and ≤20 µg/L for copper, chromium, and nickel by ICP-MS per ASTM D5673-16. Final packaging includes depth filtration through a 0.5 µm polypropylene filter to remove oversized agglomerates and process debris.
Compared with conventional electronic-grade colloidal silica with D50 between 40 nm and 60 nm, the large-particle architecture shifts the mechanical component of the Preston removal model upward while retaining the alkaline silica chemistry needed for silicon dioxide hydrolysis. The product is used where stock removal, planarization, and semi-final surface conditioning are required on hard-oxide or compound semiconductor substrates, including c-plane sapphire, 4H-SiC, and PECVD silicon dioxide. The lower specific surface area—BET surface area is typically 25–40 m²/g by ISO 9277:2010—reduces hydrogen-bonded floc formation and allows lower viscosity at high solids than fumed silica grades.
Lot certification includes the values in Table 1. The particle-size window is maintained not only by primary synthesis but also by post-synthesis classification and depth filtration. Because DLS and laser diffraction report different weighting of the distribution, the certificate of analysis lists both the intensity-weighted D50 by ISO 22412:2017 and the volume-weighted D90 by ISO 13320:2020. A shift of more than 5% in D50 after one week of recirculation is used as an early indicator of shear-induced aggregation or microbial growth.
| Parameter | Method | At-release limit |
|---|---|---|
| Appearance | Visual inspection | White to off-white opaque dispersion, free of gel and sediment |
| Median particle diameter D50 | ISO 22412:2017 | 110–130 nm |
| Particle diameter D90 | ISO 13320:2020 | ≤ 180 nm |
| pH at 25 °C | ASTM E70-19 | 10.3–10.8 |
| Viscosity at 25 °C, Brookfield | ASTM D2196-20 | 2.5–3.5 mPa·s |
| Solids content | ISO 3251:2019 | 32–36 wt% |
| Density at 20 °C | ASTM D1475-13 | 1.20–1.23 g/cm³ |
| Sodium | ASTM D5673-16 | ≤ 50 µg/L |
| Potassium | ASTM D5673-16 | ≤ 100 µg/L |
| Iron | ASTM D5673-16 | ≤ 50 µg/L |
| Copper, chromium, nickel | ASTM D5673-16 | ≤ 20 µg/L each |
| Chloride | ASTM D4327-17 | ≤ 10 mg/L |
| Sulfate | ASTM D4327-17 | ≤ 20 mg/L |
| Total organic carbon | ISO 20236:2018 | ≤ 50 mg/L |
Zeta potential at pH 10.5 is maintained below −30 mV by the ammonium hydroxide buffer and silanol deprotonation. Electrophoretic mobility is measured on a 0.1 wt% dilution in 1 mmol/L KCl background electrolyte per ISO 13099-1:2019. This surface charge prevents gel formation during vibration and recirculation, but it is sensitive to hardness cations. Calcium or magnesium above 10 mg/L as CaCO₃ reduces the Debye length and can raise apparent viscosity within 24 h, producing visible ropiness in the return line of a recirculating delivery system.
Tool-specific removal-rate baselines must be established on the target tool; the following ranges are representative for this particle class on polyurethane pads and do not constitute a guaranteed removal rate for unqualified tools. On a 22-inch production rotary CMP tool with a polyurethane pad of Shore D 52–58, in situ diamond conditioning at 0.5–1.0 sweep/min, platen speed 55 rpm, head speed 50 rpm, and downforce 4.5 psi (31 kPa), the removal rate on c-plane sapphire is observed in the range 2.0–2.8 µm/h. Increasing D50 to 150 nm raises removal rate by 10–15%, but AFM roughness Ra on a 10 µm × 10 µm scan increases from 0.18 nm to 0.25 nm, and light-point defects larger than 0.2 µm after SC1 cleaning increase from 4 defects/cm² to 11 defects/cm². The upper specification of 130 nm is therefore set below the observed microscratch cliff-edge.
On 150-mm thermal-oxide wafers, undiluted slurry produces removal rates of 3,000–4,500 Å/min on PECVD SiO₂ at 4 psi downforce, 90 rpm platen speed, and 150 mL/min slurry flow. For endpoint approach, the slurry is diluted 1:1 to 1:3 with 18.2 MΩ·cm DI water, reducing solids and improving planarization efficiency on patterned features with design rules below 90 nm. The large particle size increases the risk of oxide erosion near dense arrays, so a final buff with 40–60 nm colloidal silica may be required for shallow trench isolation or gate oxide planarization.
On the silicon face of 4H-SiC after diamond lapping, the product provides 0.8–1.2 µm/h removal with AFM Ra below 0.5 nm; the lower removal rate compared with sapphire reflects the hardness gap between 9 Mohs sapphire and 9.5 Mohs silicon carbide.
Low-shear rheology remains Newtonian from 1 s⁻¹ to 100 s⁻¹ with deviation below 5%, confirming that the dispersion is not flocculated at rest. The use of a bimodal size distribution, with 10–15 wt% of the silica fraction present as 20–40 nm interstitial particles, reduces packing viscosity and improves pad-wafer lubricity without lowering the average mechanical work per large particle.
The primary difference from fumed silica is particle morphology. Fumed silica consists of chain-like aggregates with high pore volume and broad hydrodynamic diameter, often with a laser-diffraction tail extending beyond 300 nm. The large-particle slurry is composed of discrete spheres with D90 ≤ 180 nm, producing lower coefficient of friction at the pad-wafer interface and fewer chatter marks on 4H-SiC. Table 2 summarizes representative comparative values from public technical bulletins for electronic-grade CMP slurries; the ranges are not lot-specific guarantees.
| Parameter | Large Particle Silica EL | Standard Colloidal Silica | Fumed Silica | Alumina |
|---|---|---|---|---|
| Median particle size D50 | 110–130 nm | 40–60 nm | 100–300 nm aggregate | 150–250 nm |
| pH | 10.3–10.8 | 10.0–10.5 | 9.5–10.5 | 4.0–5.0 |
| Viscosity at 25 °C | 2.5–3.5 mPa·s | 1.5–3.0 mPa·s | 5–15 mPa·s | 2–8 mPa·s |
| Solids content | 32–36 wt% | 25–35 wt% | 15–25 wt% | 10–20 wt% |
| Sodium | ≤ 50 µg/L | ≤ 100 µg/L | ≤ 500 µg/L | ≤ 100 µg/L |
| Removal rate on c-plane sapphire | 2.0–2.8 µm/h | 0.8–1.5 µm/h | 1.5–2.5 µm/h | 5–8 µm/h |
| Post-polish AFM Ra | 0.18–0.30 nm | 0.15–0.25 nm | 0.40–0.80 nm | 0.50–1.00 nm |
| Typical function | Stock removal and semi-final polish | Final buff and low-defect polish | Rough stock removal | Aggressive stock removal |
Alumina and silica chemistries must be isolated. A slurry line that previously carried acidic alumina at pH 4.0–5.0 must be flushed with 3× dead volume of DI water and then with 0.1 M ammonium hydroxide before introducing this product. Residual aluminum above 1 mg/L can form alumino-silicate gel networks that increase viscosity and cause pad glazing. Conversely, when the product is installed on a tool previously used with fumed silica, a pad break-in of 30–60 min at 2 psi downforce with DI water is recommended to remove bound silica aggregates and stabilize pad temperature.
Storage requires high-density polyethylene or PTFE-lined containers at 5–35 °C. Long-term contact with 316L stainless steel is not recommended because alkaline silica leaches iron and chromium and shifts the metal-ion signature. Wetted parts in delivery lines should be polypropylene, PVDF, or halogenated elastomer. Freezing below 5 °C causes irreversible particle aggregation, and heating above 35 °C accelerates silica dissolution and microbial growth. Unopened shelf life is 12 months from the manufacture date; recirculating systems require weekly D50 and pH checks because shear and carbon dioxide absorption can produce pH drift.
The product is amine-free and should not be mixed with amine-based additives. Addition of amine pH adjusters or corrosion inhibitors can cause localized gelation, increase pad hardness, and alter the residence time in the polishing interface. The product is compatible with hydrogen peroxide at concentrations up to 5 wt% for in situ cleaning or slurry activation, but pre-blended peroxide–slurry mixtures should not be held for more than 24 h because peroxide decomposition accelerates silica dissolution.
After polishing, substrates are typically cleaned in an SC1 bath at 65 °C composed of 1:1:5 NH₄OH:H₂O₂:H₂O with megasonic agitation at 950 kHz. Direct transfer to dilute HF before particle removal is not recommended because pH below 2 compresses the electrical double layer and can redeposit silica onto hydrophobic surfaces. For advanced packaging and backside processes, a final DI water rinse with 0.1 wt% surfactant may be used if foam is controlled by vacuum degassing.
The product contains amorphous silica, which is not classified as carcinogenic under CLP. It does not contain substances listed in REACH Annex XIV, and lead, cadmium, mercury, and hexavalent chromium are controlled to ≤5 mg/kg per RoHS Directive 2011/65/EU annex II. Waste streams should be neutralized to pH 6–9 and filtered through 0.45 µm polypropylene filters before discharge; local discharge limits for copper and zinc may require ion exchange.
