| HS Code | 946484 |
| Chemical Composition | Colloidal silica (SiO2) in alkaline aqueous medium |
| Appearance | Milky white to translucent liquid |
| Silica Content Percent | 30-40 |
| Ph Value | 10.0-11.0 |
| Average Particle Size Nm | 50-100 |
| Specific Gravity | 1.10-1.30 |
| Density G Per Cm3 | 1.10-1.30 |
| Viscosity Cp | 5-10 |
| Trace Metal Impurities Ppm | <1 for Na, Ca, Fe, Al, Cu, Ni |
| Conductivity Micros Per Cm | 200-500 |
| Shelf Life Months | 6-12 |
| Storage Temperature Celsius | 5-35 |
| Packaging Type | Standard HDPE drum or customized container |
As an accredited Alkaline 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 sealed, high-purity containers, typically 1 L or 5 L, with hazard labeling to prevent contamination and ensure safe handling. |
| Container Loading (20′ FCL) | 20′ FCL of Electronic-grade alkaline silica polishing slurry, packed in sealed IBCs, loaded, restrained, and protected for safe transit. |
| Shipping | This electronic-grade alkaline silica polishing slurry ships in sealed, corrosion-resistant drums or IBCs to prevent contamination and leakage. Proper labeling, moisture protection, and temperature-controlled transport are required. Handle as an alkaline solution; avoid contact with acids and incompatible materials. Ensure clean, dedicated equipment for transfer and delivery. |
| Storage | Store in tightly sealed original containers in a cool, dry, well-ventilated area away from direct sunlight, heat, and freezing. Maintain temperatures between 5–35°C to prevent gelation or separation. Keep away from acids, oxidizers, and incompatible materials. Avoid contamination; agitate gently before use. Ensure containers are clearly labeled and securely closed when not in use. |
| Shelf Life | Shelf life is typically 12 months when stored sealed at room temperature, away from freezing and direct sunlight. |
In front-end-of-line interlayer dielectric planarization, alkaline silica polishing slurry Electronic/EL grade is introduced as a point-of-use-diluted colloidal dispersion with primary particle size 35–50 nm, secondary aggregate diameter 60–90 nm by dynamic light scattering per ISO 22412:2017, and pH 10.5–11.0 measured per ASTM E70-19. The concentrate carries 25–30 wt% solids and is blended 1:1 to 1:4 by volume with water conforming to ASTM D5127 Type E-1, yielding working abrasive content 6.2–12.5 wt% and working viscosity typically below 3 mPa·s. On 300 mm multi-zone CMP platforms equipped with polyurethane pads and closed-loop slurry distribution, platen speed is held at 80 rpm, carrier speed at 75 rpm, downforce from 2.5 psi to 5.0 psi (17.2–34.5 kPa), and slurry flow 250–450 mL/min. Endpoint detection for oxide clearing uses motor-torque change or eddy-current thickness monitoring, followed by a deionized water buffing step on a soft pad to displace residual silica. The downstream process conflict is selectivity: alkaline silica provides oxide-to-nitride selectivity below 20:1, so it is directed to interlayer dielectric planarization, tungsten damascene oxide clearing, and polysilicon-contact oxide flattening rather than shallow trench isolation, where ceria-based slurries with high nitride selectivity are required. Blanket PECVD TEOS removal rates under these conditions are typically 2,500–5,000 Å/min; within-wafer nonuniformity at 3 mm edge exclusion remains below 3%, and post-CMP AFM roughness on 10 × 10 µm scan areas is controlled below 0.5 nm Ra. Metallic impurity control is verified by ICP-MS with transition metals Fe, Co, Ni, and Cu held individually below 50 ppb, and the filling environment is maintained to ISO 14644-1:2015 Class 4. A production-line failure mode appears as pad-temperature drift above 45 °C: the dispersed silica aggregates and large-particle counts above 0.5 µm increase, raising microscratch defect density; chiller return temperature is therefore kept below 40 °C. The terminal products are interlayer dielectric layers in advanced logic devices from 28 nm through 5 nm nodes and in 3D NAND memory stacks. The operational boundary is the point-of-use blend pot life, typically 48–72 h under continuous recirculation; stagnant intermittent lines require flushing with ASTM D5127 Type E-1 water before restart because settled silica compacts in manifold dead volumes.
| Parameter | Test method | Electronic/EL grade control range | Downstream failure mode if out of range |
|---|---|---|---|
| Mean particle size D50 | ISO 22412:2017 | 35–70 nm general; 20–40 nm photomask; 50–100 nm SiC | Microscratch density increases outside the segment window |
| pH | ASTM E70-19 | 10.0–11.5 depending process | Drop below 9.5 changes removal mechanism toward mechanical damage |
| Transition metals | ICP-MS | Fe, Co, Ni, Cu individually ≤ 50 ppb | Thermal diffusion into silicon or III-V substrates after anneal |
| Large particle counts | ISO 21501-2 | ≤ 100 counts/mL at 0.5 µm | Scratches on photomask blanks and epi-ready wafers |
| Processing water | ASTM D5127 | Type E-1 | Metallic contamination in point-of-use dilution |
| Cleanroom filling | ISO 14644-1:2015 | Class 4 minimum; Class 3 for photomask and post-clean inspection | Airborne large particles increase defect adders |
| SiC epi-ready surface roughness | AFM | ≤ 0.15 nm Ra on 5 × 5 µm | Homoepitaxial defect nucleation |
On prime polished silicon wafer lines, final polishing is operated at pH 10.2–11.2 to maintain a thin hydrated oxide layer that is removed by silica abrasion while suppressing subsurface damage and haze. Slurry concentrates with 20–30 wt% solids are diluted 1:5 to 1:20 in deionized water, giving final abrasive content 0.8–3.0 wt%; the point-of-use dilution ratio is adjusted according to pad history, with higher dilution used on glazed suede pads to reduce edge roll-off. The polishing process is performed on double-side polishing machines with polyester-based suede or composite pads at contact pressure 0.08–0.5 psi (0.6–3.4 kPa), platen speed 30–60 rpm, and process time 5–20 min per batch. Stock removal is restricted to 0.5–2.0 µm per side, and AFM surface roughness after cleaning is specified below 0.15 nm Ra on 10 × 10 µm scan areas. Compliance for flatness, thickness variation, and edge exclusion is evaluated under SEMI M1-1023; trace metal residues are measured by VPD-ICP-MS with acceptance below 30 ppb for Fe, Co, Ni, Cu, and Zn. Post-cleaning inspection is conducted in ISO 14644-1:2015 Class 3 cleanrooms. The terminal finished products are 300 mm prime polished silicon wafers for advanced logic, DRAM, and epitaxial deposition, including silicon-on-insulator starting wafers. An operational boundary is pad glazing: after 8–12 wafers on a suede pad, accumulated silicate film raises light-point defects above 0.1 µm size, and pad conditioning or replacement is enforced to maintain within-batch defect density. In high-volume lines, the recirculated slurry is filtered through a 0.5 µm disposable capsule filter and replenished by bleed-and-feed so that abrasive concentration does not drift more than ±0.2 wt% across a 24 h shift.
Silicon carbide CMP on the Si-face is constrained by the high Si–C bond energy and by the requirement to leave a subsurface structure suitable for homoepitaxy. On 150 mm and 200 mm 4H-SiC substrates, alkaline silica polishing slurry Electronic/EL grade with mean particle size 50–100 nm is applied either as-supplied or after 1:1 dilution with water, preserving abrasive concentration in the 12–25 wt% range. The polishing process uses single-side polishers with polyurethane pads, platen speed 60–80 rpm, carrier speed 55–75 rpm, downforce 3.5–6.0 psi (24.1–41.4 kPa), and slurry flow 150–300 mL/min. Removal rate on the Si-face is typically 50–200 nm/h; published data for a particular production platform is limited because MRR depends strongly on pad fiber height after diamond conditioning, slurry redox state, and initial subsurface damage from diamond lapping. The slurry must remain above pH 10.0 throughout the polishing period because a drop below 9.5 reduces the chemical oxidation component and shifts removal toward mechanical fracture, increasing subsurface damage without proportional material removal. Trace metal contamination is verified by VPD-ICP-MS with transition metals below 50 ppb; particle size distribution is controlled per ISO 22412:2017 with D50 tolerance ±15 nm; and cleanroom handling follows ISO 14644-1:2015 Class 4. The terminal products are epi-ready 4H-SiC substrates for 650 V, 1200 V, and 1700 V power MOSFETs, Schottky barrier diodes, and radiation-hard power devices. A process conflict occurs when residual colloidal silica particles remain in pits from previous diamond lapping; therefore the pre-CMP mechanically polished surface must have subsurface damage below 4 µm and pit depth below 0.1 µm before the slurry steps. The final surface roughness after CMP is specified below 0.15 nm Ra on 5 × 5 µm AFM scans for epi-ready substrates; if surface metal residues exceed 1 × 10¹⁰ atoms/cm², the wafers are returned to megasonic cleaning before epitaxy.
For c-plane sapphire substrates entering GaN metal-organic chemical vapor deposition, the downstream finishing sequence removes diamond-lapping damage with a controlled chemical-mechanical step. Alkaline silica polishing slurry Electronic/EL grade is diluted 1:2 to 1:5 by volume, giving working solids content near 5–10 wt% and pH 10.5–11.2. The polishing process uses single-sided rotatory polishers with composite copper-resin plates or polyurethane pads, platen speed 50–70 rpm, downforce 3.0–5.0 psi (20.7–34.5 kPa), and slurry flow 100–200 mL/min. Removal rates for c-plane sapphire after diamond lapping are typically 1–3 µm/h, but exact MRR depends on pad groove geometry, plate flatness, and wafer bow; batch-to-batch variance is managed by rejecting incoming substrates with bow above 20 µm before CMP. Compliance includes ISO 14644-1:2015 Class 4 cleanroom handling, pH verification per ASTM E70-19, and particle size stability per ISO 22412:2017; post-CMP surface roughness is specified below 0.3 nm Ra on 5 × 5 µm AFM scans because higher roughness reduces GaN crystalline quality. The terminal products are 2–6 inch sapphire wafers and patterned sapphire substrates for visible LEDs and ultraviolet emitters. An operational boundary emerges if slurry pH drops below 10.2, which lowers silicate repulsion and increases scratching on the chemically inert c-plane; therefore the pH is logged at point-of-use and buffered replenishment is actuated before each batch.
Unlike silicon, III-V compound semiconductors are sensitive to free alkali ions that diffuse into the wafer or remain as surface contaminants. When gallium arsenide and indium phosphide final polishing demands low alkali-metal carryover, alkaline silica slurry with tight potassium and sodium specifications is diluted 1:10 to 1:20 in deionized water, yielding final abrasive content below 2 wt%. The polishing operation runs on orbital or single-sided polishers with closed-cell polyurethane pads of Shore A hardness 60–80, platen speed 40–60 rpm, downforce 0.5–2.0 psi (3.4–13.8 kPa), and slurry flow 50–150 mL/min. The process window is deliberately narrow because excessive downforce generates scratches that propagate along {100} GaAs cleavage planes, while insufficient downforce prolongs exposure time and increases surface oxide accumulation. Compliance is verified against SEMI M9-0318 for round 150 mm GaAs wafers, ASTM E70-19 for pH, and VPD-ICP-MS for potassium, sodium, calcium, and transition metals below 50 ppb. Terminal finished products are 100 mm and 150 mm GaAs wafers for radio-frequency power amplifiers and switches, plus 2–4 inch InP wafers for photonic integrated circuits. The operational limit is the sodium concentration in the point-of-use blend because sodium above 20 ppb in slurry carries over to the native oxide and shifts threshold voltage or reduces photoluminescence in subsequent epitaxial layers; therefore the slurry containers are dedicated and tubing is passivated to avoid cross-contamination from previous polishing chemistries. Surface roughness of epi-ready GaAs after polishing is controlled below 0.4 nm Ra on 10 × 10 µm AFM scans, and particle residue above 0.2 µm is kept below 10 counts per wafer with megasonic final rinse.
Fused silica photomask blank polishing requires surface quality measured at high spatial frequencies because subsurface damage and residual roughness scatter actinic inspection light and reduce mask pattern fidelity. Alkaline silica polishing slurry Electronic/EL grade with particle size 20–40 nm is diluted 1:3 to 1:10 by volume, producing working solids below 5 wt% and pH 10.0–10.8. The process uses low-speed pitch polishing machines or closed-cell polyurethane pads at platen speed 20–40 rpm, downforce 0.5–2.0 psi (3.4–13.8 kPa), and slurry flow 50–120 mL/min. Polishing is followed by an aggressive megasonic rinse and dilute alkaline cleaning to detach residual colloidal silica from the fused silica surface before inspection. Compliance is anchored to ISO 22412:2017 for particle size, ASTM E70-19 for pH, and ISO 14644-1:2015 Class 3 cleanroom inspection; surface defects are measured by laser-scattering blank inspection with 0.06 µm sensitivity. The terminal products are 150 mm and 200 mm photomask blanks for 193 nm ArF immersion lithography and low-defect fused silica substrates for advanced mask development. An operational boundary exists in the final minutes of polishing: if slurry is allowed to dry on the blank, nanoscale silica deposits become inseparable from the substrate and require re-polishing; therefore continuous pad wetting, controlled exhaust, and immediate water displacement are mandatory. Published data for defect density in this specific photomask configuration is limited, but production blanks are qualified at ≤ 3 killer defects per 150 mm blank with 0.15 µm or larger detection sensitivity, and surface roughness is held below 0.5 nm Ra on 10 × 10 µm AFM scans.
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When a final polishing application requires low defectivity on thermally grown silicon dioxide, PECVD TEOS oxide, sapphire substrates, or silicon carbide, an alkaline colloidal silica dispersion designated Alkaline Silica Polishing Slurry Electronic/EL Grade is supplied as a ready-to-use chemical mechanical planarization slurry. The formulation consists of monodisperse colloidal silica particles suspended in an aqueous alkaline medium; the Electronic/EL Grade qualifier indicates a reduced mobile-ion burden, a controlled large-particle count, and particle sizing adjusted for electronic surface quality. Representative data sheets describe the product as a milky white liquid with silica content of 20–40 wt%, pH from 9.5 to 11.5, and mean particle size of 30–80 nm depending on the appended model suffix. The material is used in single-wafer or batch CMP tools for oxide planarization and in precision optical lapping where low sodium and transition-metal contamination is a release criterion. The term Electronic/EL Grade functions as the primary model descriptor; a numeric suffix such as EL-35, EL-50, or EL-80 identifies the nominal particle-size bin and associated removal-rate trade-off for a supplier-specific package.
Colloidal silica is formed by aqueous polymerization of silicate precursors, yielding discrete spherical particles rather than the fused aggregates typical of fumed silica. In Electronic/EL Grade material, the absence of agglomerates is verified by dynamic light scattering and by particle-count instrumentation. Distributed particle shape and electrostatic repulsion are maintained by hydroxylated surface silanol groups in the alkaline pH range; the resulting zeta potential magnitude is typically above 30 mV, which reduces shear-induced reagglomeration during supply-line recirculation. Fumed silica slurries contain irregular chain-like aggregates that produce higher defectivity on oxide films and are generally excluded from final electronic planarization. Precipitated silica carries broader particle-size distributions and higher aluminum, iron, and sulfate residues than electronic-grade colloidal silica. Comparative data reported in slurry technical bulletins show that large-particle counts at the 0.5 µm threshold can be one to two orders of magnitude lower for Electronic/EL Grade colloidal silica than for general industrial dispersions. The residual sodium tolerance is tighter because mobile alkali ions can shift flatband voltage in metal-oxide-semiconductor device structures.
Specification control for Alkaline Silica Polishing Slurry Electronic/EL Grade is organized around dispersion stability, controlled silica loading, metal contamination, and defect-relevant large particles. The following table summarizes the representative specification envelope common to commercial data sheets for this product class, not a single lot release. Lot-specific values are supplied on the certificate of analysis and may vary by numeric particle-size suffix and packaging volume.
| Parameter | Test method or instrument | Representative range |
|---|---|---|
| Appearance | Visual inspection | Milky white liquid; no gel, sediment, or phase separation |
| pH | ASTM E70 | 9.5–11.5 |
| Specific gravity | ASTM D891 | 1.18–1.25 at 25 °C |
| Silica content | Gravimetric after ignition | 20–40 wt% |
| Mean particle size | ISO 22412:2017 dynamic light scattering | 30–80 nm |
| Viscosity | ASTM D2196-18, Brookfield RV, 60 rpm, 25 °C | 2–15 mPa·s |
| Zeta potential | ISO 13099-1:2012 | −30 mV to −50 mV |
| Sodium ion | ICP-MS after acid digestion | ≤1 ppm |
| Fe, Cu, Zn each | ICP-MS after acid digestion | ≤100 ppb |
| Large particle count | ISO 21501-4 optical particle counter | ≤200 particles/mL ≥0.5 µm |
Analytical confirmation of particle size should use ISO 22412:2017 rather than laser diffraction when the slurry is diluted below the multiple-scattering limit, because laser diffraction can over-report large-particle tails in high-concentration colloidal systems. The 0.5 µm threshold is monitored because particles at or above this size correlate with microscratch formation and post-polish defect counts on blanket oxide monitors. For electronic polishing, the release criterion for transition metals is set below 100 ppb for each of Fe, Cu, and Zn, while sodium and potassium are controlled independently because of their high mobility in SiO2 layers.
The continuous phase is high-purity water with an alkaline buffering agent. Published CMP literature for alkaline silica slurries identifies potassium hydroxide, sodium hydroxide, or an organic quaternary ammonium hydroxide as possible pH adjusters; Electronic/EL Grade material intended for MOS applications commonly minimizes sodium and potassium by selecting an organic alkali or by cationic exchange. The colloidal silica surface is terminated with silanol groups that deprotonate as pH increases, increasing electrostatic repulsion and chemical attack of silicon dioxide. In CMP, material removal occurs through a combination of alkaline surface hydrolysis of Si–O–Si bonds and mechanical abrasion by the sub-micron particle. The ratio of chemical to mechanical contribution depends on downforce, platen velocity, and polyurethane pad topography. Viscosity is Newtonian over the working shear range and remains below 15 mPa·s at 25 °C, which supports consistent slurry dispensing through flow controllers and prevents pad loading. Specific gravity is typically held between 1.18 and 1.25 to allow mass-flow verification and to avoid particle settling in day-tank recirculation loops.
On high-volume oxide CMP operations, the slurry is distributed through a pressurized loop to a single-wafer polisher equipped with a polyurethane pad such as a IC1000-type pad on a Suba IV subpad. Typical process settings reported in technical literature for alkaline silica oxide planarization include platen speeds from 60 rpm to 90 rpm, head speeds from 55 rpm to 80 rpm, and downforce from 3 psi to 6 psi. Under these conditions, blanket TEOS removal rates for electronic-grade colloidal silica slurries are generally reported between 80 nm/min and 250 nm/min, depending on particle size, silica loading, pH, and pad conditioning. A larger particle-size suffix raises mechanical removal but increases the risk of microscratches, while a smaller particle-size suffix lowers defectivity but may require higher pH or longer polish time to reach target removal. Production-level monitoring uses oxide-thickness metrology before and after polishing, within-wafer non-uniformity evaluation by 49-point sheet resistance mapping, and defect inspection on a laser scanning system at 0.12 µm or 0.16 µm detection thresholds. The slurry is not used directly on exposed aluminum or copper interconnects without an intervening barrier layer, because the alkaline pH can initiate corrosion and because silica abrasives can contaminate metal surfaces.
For sapphire substrate polishing, the same alkaline silica chemistry is used on double-sided planetary polishing machines with polyurethane pads and tin or composite plates. Removal is mechanochemical; the alkaline medium hydrolyzes surface layers on sapphire, and the colloidal silica removes the softened layer. Production-scale process sheets for sapphire often specify a plate temperature from 25 °C to 50 °C and a slurry flow rate high enough to maintain a wet film across the plate. Batch-to-batch variation in silica particle size can shift removal rate and wafer roughness; consequently, the Electronic/EL Grade particle-size suffix is locked per process qualification and may not be substituted without re-qualifying the polishing recipe. Published data for this specific configuration is limited for exact material removal rates on c-plane sapphire, but oxide and sapphire CMP literature consistently report that roughness below 0.5 nm Ra is achievable when the large-particle count is controlled and post-polish cleaning uses deionized water with megasonic assistance.
Alkaline silica polishing slurry is not a universal CMP chemistry. For shallow trench isolation applications requiring high oxide-to-nitride selectivity, ceria-based slurries are generally selected over silica because their selectivity can exceed 30:1, whereas alkaline silica oxide-to-nitride selectivity often remains below 5:1 due to surface hydrolysis of silicon nitride. Tungsten damascene CMP requires an acidic oxidizer-based slurry, typically containing hydrogen peroxide and a passivating agent, because tungsten dissolves anodically at low pH and the silica alkaline medium can produce oxide defects. Copper CMP uses two-step acid/alkaline slurries with alumina or silica abrasives plus benzotriazole corrosion inhibitors, but the silica fraction is unsuitable as a direct replacement for the copper bulk-removal step because of poor copper removal and anodic dissolution control. In device stacks with exposed aluminum bond pads or aluminum interconnects, alkaline silica slurries can etch aluminum; a pH below 10 and a non-amine formulation may be required. The Electronic/EL Grade material is also incompatible with cationic flocculants and multivalent metal salt additives, which reduce the electrostatic double-layer thickness and trigger gelation. Amine-based additives should be avoided unless explicitly qualified, because they may complex surface silanol groups and shift the suspension stability window.
Storage and handling limits are part of the material specification. The slurry is supplied in HDPE drums or totes and must be protected from freezing. Storage temperature is maintained between 5 °C and 35 °C; freeze-thaw cycling destroys the colloidal dispersion and produces irreversible gel formation. Recirculation loops should run at low shear and without dead legs to prevent particle settling. At temperatures above 40 °C, the formulation can undergo accelerated silicate dissolution and pH drift. Shelf life for unopened containers is typically stated as 12 months from the date of manufacture, with opened containers requiring continuous filtration if integrated into a CMP slurry delivery system. When a polishing tool is idle, the slurry is best kept circulating rather than stagnant, because stagnant alkaline silica can form a compact sediment that clogs point-of-use filters. Filter selection uses depth or pleated polypropylene cartridges with absolute ratings from 0.5 µm to 1 µm; filters with nylon or other acid-sensitive media are not used because the alkaline pH can degrade the support structure. Dilution must use deionized water of resistivity not less than 18 MΩ·cm at 25 °C; hard water or untreated municipal water introduces multivalent cations that may destabilize the dispersion.
Table 2 presents comparative commercial data-sheet values for the product class; individual formulations may deviate and should be verified against the supplier certificate of analysis.
| Property or attribute | Alkaline Silica Electronic/EL Grade | General industrial alkaline silica | Ceria slurry | Fumed silica slurry |
|---|---|---|---|---|
| Particle morphology | Spherical colloidal silica, engineered size distribution | Colloidal or precipitated silica, broad distribution | Faceted polycrystalline ceria | Irregular chain-like aggregates |
| Typical pH | 9.5–11.5 | 8.0–10.5 | 6.0–9.0 | 9.0–11.0 |
| Primary electronic use | Oxide ILD/IMD CMP, sapphire and SiC final polish | Optical glass and general lapping | STI oxide CMP and selective oxide removal | Optical glass, metallic lapping, limited oxide CMP |
| Transition metal control | ≤100 ppb per Fe, Cu, Zn | Often 1–10 ppm | ≤1 ppm | 1–50 ppm |
| Large particle count at ≥0.5 µm | ≤200 particles/mL | ≥103 particles/mL | Process-dependent | ≥104 particles/mL |
These distinctions are material selection criteria rather than absolute quality markers. Ceria slurry remains the standard for STI oxide because of high nitride selectivity, even though its particle shape and cleaning behavior differ from colloidal silica. The Electronic/EL Grade is selected when low mobile-ion contamination and controlled large-particle counts are mandatory for the device or substrate. It is not a replacement for ceria in high-selectivity STI, tungsten, or copper CMP applications.
