| HS Code | 361081 |
| Product Name | Nitric Acid Electronic/EL Grade |
| Chemical Formula | HNO3 |
| Cas Number | 7697-37-2 |
| Molecular Weight | 63.01 g/mol |
| Concentration | 69.0-70.0% w/w |
| Assay Purity | ≥69.0% |
| Appearance | Clear, colorless liquid |
| Density | 1.42 g/cm3 at 20°C |
| Boiling Point | 122°C |
| Melting Point | -42°C |
| Refractive Index | 1.397 at 20°C |
| Vapor Pressure | 14 mmHg at 20°C |
| Solubility | Miscible with water |
| Max Individual Metal Impurity | <10 ppb |
As an accredited Nitric Acid Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Nitric Acid Electronic/EL Grade is supplied in a 2.5 L fluorinated polyethylene bottle, sealed for high-purity protection. |
| Container Loading (20′ FCL) | Load nitric acid electronic grade in 20′ FCL using UN-approved containers, secure tightly, segregate from incompatibles, and label hazards. |
| Shipping | Nitric Acid Electronic/EL Grade is a highly corrosive, hazardous oxidizer shipped in compliance with UN 2031 (Class 8) regulations. It must be transported in dedicated, chemically compatible containers with proper venting, secondary containment, and hazard labeling. Ground transport is standard; air and sea require additional approvals. Handling, spill response, and disposal documentation must accompany shipments. |
| Storage | Nitric Acid Electronic/EL Grade requires storage in a clean, dedicated, well-ventilated chemical cabinet. Use tightly sealed containers made of high-purity PTFE, glass, or compatible stainless steel to prevent contamination and corrosion. Keep away from organic materials, reducing agents, bases, and metals. Store below 25°C, protected from light, and clearly label with hazard warnings. |
| Shelf Life | Shelf life is typically 6 months from manufacture date when stored unopened in the original container under recommended conditions. |
Front-end semiconductor wet benches consume electronic-grade nitric acid as the oxidation component of HNA etchants used for isotropic silicon removal, polysilicon thinning, and wafer backside damage removal. The nitric acid stream is specified under SEMI C35; acid lots are released only after ICP-MS cation analysis and anion chromatography confirm that typical trace metal concentrations remain below the cation action limits specified in SEMI C35 for sodium, potassium, iron, copper, and zinc. A representative bath is metered at a volumetric ratio of 4:1:3 for 70 wt% HNO₃, 49 wt% HF, and 99.8 wt% CH₃COOH. The etch mechanism proceeds through HNO₂ autocatalytic regeneration: silicon is oxidized to SiO₂ by HNO₃, and HF dissolves the oxide as H₂SiF₆. At 22–25 °C in a 40 L PTFE/PFA overflow tank with 20 L/min recirculation through a 0.1 µm PTFE depth filter, the removal rate for single-crystal Si(100) in the 4:1:3 bath is typically 1–3 µm/min under spindle agitation. Etch rate drift is continuously recorded by optical thickness sensors; when the rate falls more than 5% from the initial value, or when copper and zinc ICP-MS readings exceed SEMI C35 cation action limits, the bath is dumped. HNO₃-rich formulations near 6:1:1 run at 20 °C and produce smoother surfaces because the process becomes reaction-limited; HF-rich formulations above 1:3:2 generate rough, porous silicon byproducts. The overall reaction 3Si + 4HNO₃ + 18HF → 3H₂SiF₆ + 4NO + 8H₂O releases NO and NO₂, so the wet bench exhaust is routed to a packed-tower scrubber with sodium hydroxide circulation and stack NOx monitoring. After etch, wafers are rinsed with ultrapure water meeting ASTM D5127-13(2018) Type E-1 resistivity limits and dried in a Marangoni dryer. The terminal product is a device wafer with the target silicon recess or removed sacrificial polysilicon layer, measured by scatterometry or stylus profilometry. This bath is incompatible with residual amine-based photoresist strippers, because fluorosilicate precipitates can form and reduce filter life.
In thin-film transistor liquid-crystal display array processing, the wet etch of Mo/Al/Mo source-drain electrode stacks is performed in a phosphoric-acetic-nitric acid mixture, with electronic-grade nitric acid specified to SEMI C35 to avoid mobile alkali residues that shift thin-film transistor threshold voltage. The etchant is blended at 55–65 wt% H₃PO₄, 3–5 wt% HNO₃, 8–12 wt% CH₃COOH, and the balance ultrapure water. Nitric acid functions as the oxidizer for aluminum; without it, aluminum dissolution in phosphoric acid produces hydrogen bubbles that cause local mask undercut and rough sidewalls. The process runs in a 3-chamber linear spray etch tool with 0.2 µm PTFE recirculation filtration and a 2.5 m process chamber. Temperature is held at 40–45 °C by an inline fluoropolymer heat exchanger. Endpoint detection uses transmitted light at 405 nm; the endpoint triggers rinse when light transmission through the panel drops below the pre-set threshold. The process target for CD loss is ≤0.3 µm per edge on a 1.5 µm line/space test coupon, with sidewall taper angle controlled at 25–35° to support subsequent silicon nitride passivation step coverage. Bath density and acid concentration are measured by in situ vibrating-tube density meters every 30 min; nitric acid concentration is re-adjusted by a dosing loop. Production experience shows that if bath temperature exceeds 48 °C, aluminum pitting increases and the undercut limit is no longer met. The bath is dumped when dissolved aluminum builds up beyond 3 g/L as measured by inductively coupled plasma optical emission spectrometry from an in-line sample port. Chloride contamination must remain below the SEMI C35 chloride limit, because chloride accelerates pitting in the aluminum layer. After etch, the panel is rinsed with ultrapure water and dried by air knife. The terminal product is a TFT array glass ready for silicon nitride passivation and indium tin oxide sputtering.
Multi-crystalline silicon photovoltaic cell manufacturing cannot rely on alkaline pyramid texturing across random grain orientations, so acid texturing with an HNO₃/HF/ultrapure water solution is used to generate isotropic etch pits and lower reflectance on as-cut wafers. The nitric acid component is released under SEMI C35 because trace metal contamination from lower-grade acid can reduce minority carrier lifetime after phosphorus diffusion. A typical bath is blended at a volume ratio of 2:1:1.5 to 4:1:2 HNO₃:HF:DI water, where HNO₃ oxidizes silicon and HF dissolves the oxide. The bath temperature is held at 4–10 °C in a chilled PTFE tank with external coolant recirculation, because the reaction is strongly exothermic and higher temperature roughens the surface. Immersion time is 90–180 s; etch depth per side is typically 3–5 µm, depending on grain orientation and initial saw damage. Reflectance at 600 nm is reduced to 18–24% after texturing, measured with an integrating sphere spectrophotometer against a calibrated spectralon reference. The acid bath is sampled every 5 min by an online acid analyzer; when free HF content drops more than 10% from target, fresh acid is replenished. NOx generated at the bath surface is exhausted through a wet scrubber packed with polypropylene media and neutralized with sodium hydroxide. The terminal product is a textured mc-Si wafer ready for emitter diffusion, anti-reflective coating, and screen-printed metallization. Published data for specific reflectance distribution on commercial mc-Si grain boundaries is limited; inline spot checks with reflectance mapping are used for lot acceptance.
Before electrolytic nickel or silver spot plating, copper and Alloy 42 lead frames are processed through a bright-dip bath containing 20–30 vol% HNO₃ and 5–10 vol% H₂SO₄ in ultrapure water. The nitric acid is electronic/EL grade and is controlled under SEMI C35 to prevent residual iron, chloride, and sulfate contamination that causes subsequent silver discoloration and wire-bond lift failures. The bath runs at 25–35 °C in a PVDF tank with integrated fume extraction. Parts are immersed for 30–60 s using a programmable hoist; after rinsing, oxide removal is verified by contact angle measurement below 10° and by Auger electron spectroscopy inspection for residual copper oxide. The terminal product is a clean, low-oxide lead frame surface ready for selective plating. The nitric acid bath life is 8 h; dumps are triggered when dissolved copper concentration reaches 5 g/L as measured by atomic absorption.
MEMS release processing for electroplated accelerometers and gyroscopes uses copper as a sacrificial structural layer, wet-etched after silicon nitride or oxide passivation. Electronic-grade nitric acid diluted to 10–20% HNO₃ with ultrapure water is selected under SEMI C35 because sodium and potassium residues from technical acid can remain on MEMS surfaces and alter capacitive readout. The etch is carried out in a 5 L quartz tank at 20–25 °C, with PTFE wafer carriers and gentle cassette agitation. Copper dissolution in 20% HNO₃ at 25 °C is approximately 1–3 µm/min, while permalloy attack remains below 0.01 µm/min when the bath is free of chloride. The dissolved copper is monitored photometrically in a flow cell; the endpoint is triggered when transmitted light at 660 nm stabilizes, indicating no further copper complex formation. After etching, wafers are rinsed in ultrapure water and dried by supercritical CO₂ to prevent stiction in released microstructures. The terminal product is a released MEMS inertial sensor die with critical dimensions verified by scanning electron microscopy. Operational boundaries: the bath must not exceed 30 °C, because positive photoresist lifting occurs above this temperature; addition of hydrogen peroxide must be avoided when permalloy structures are present, because the mixed oxidizer shifts the open-circuit potential and increases nickel dissolution. Published selectivity data for this specific permalloy-to-copper etch on production MEMS stacks is limited; site qualification uses quartz crystal microbalance test coupons.
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Nitric Acid Electronic/EL Grade is supplied as a high-purity aqueous solution of HNO3 at a nominal assay of 68.0–70.0 wt%; the 68 wt% azeotrope is frequently selected because atmospheric distillation at 121 °C can occur without the assay drift observed from non-azeotropic feeds. The material carries CAS registry number 7697-37-2 and is shipped under UN 2031, Class 8, Packing Group II when the nitric acid concentration does not exceed 70 wt%. Product designations in semiconductor chemical supply chains vary by supplier; common configurations include EL-grade 68% HNO3 in 20 L fluoropolymer drums, 200 L PFA returnable totes, and 5 mL to 1 L high-density polyethylene bottles for analytical or pilot use. The difference between EL, VLSI, and ULSI sub-grades is not primarily assay but trace-metal and particle control. The acid is used in wet etch, cleaning, and passivation operations where cation contamination above the low-ppb level creates device-level defect risk.
Release testing on production lots typically combines inductively coupled plasma mass spectrometry for a defined multi-element panel, ion chromatography for chloride, sulfate, and phosphate, and laser particle counting at 0.2 µm or 0.5 µm thresholds. In high-volume fabs, incoming quality control trend charts show that trace-metal variability is influenced by the raw-acid source, distillation column reflux ratio, and fluoropolymer container conditioning. First-fill lots from new or rinsed PFA totes can exhibit sodium, calcium, and iron excursions at low-ppb levels if the container has not been acid-leached; for this reason, semiconductor users commonly require pre-shipment lot data and reserve the right to return lots that exceed the action limits defined in the purchase specification. Compliance is assessed against SEMI C35 and customer-specific certificates of analysis. ACS reagent or compendial limits are not suitable for this use because their residue and heavy-metal allowances are orders of magnitude less restrictive than the defect budget of advanced metal-oxide-semiconductor or dynamic random-access-memory fabrication.
The distinction is most visible in the release specification. ACS reagent nitric acid permits heavy metals as lead at ≤ 0.5 ppm, chloride at ≤ 0.5 ppm, sulfate at ≤ 2 ppm, and iron at ≤ 2 ppm. Electronic/EL grades routinely specify individual transition metals at ≤ 10 ppb or lower, and the most restrictive ULSI sub-grades drive sodium, potassium, calcium, iron, copper, and zinc below 1 ppb. Anion ceilings of ≤ 100 ppb for chloride and sulfate are common, although some fabs tighten chloride to ≤ 50 ppb to protect metal lines from pitting. Particle counts are not part of the ACS monograph; EL-grade material is instead rated by laser particle count at ≥ 0.2 µm or ≥ 0.5 µm, with typical acceptance criteria of ≤ 25 particles/mL at ≥ 0.5 µm and stricter limits for sub-10 nm process nodes. Exact ceilings vary by supplier and are defined in the purchase specification rather than by a single global standard.
| Parameter | Technical grade | ACS reagent grade | Electronic/EL grade |
|---|---|---|---|
| Assay | variable, often 52–68 wt% | 68–70 wt% | 68–70 wt% |
| Trace metal per element | not controlled | Fe ≤ 2 ppm; heavy metals as Pb ≤ 0.5 ppm | typically ≤ 10 ppb; critical metals ≤ 1 ppb |
| Chloride | not controlled | ≤ 0.5 ppm | ≤ 100 ppb; tighter fabs ≤ 50 ppb |
| Sulfate | not controlled | ≤ 2 ppm | ≤ 100 ppb |
| Particle control | not specified | not specified | LPC at ≥ 0.2 µm or ≥ 0.5 µm; often ≤ 25 particles/mL at ≥ 0.5 µm |
| Packaging | stainless steel or HDPE | glass or HDPE | high-purity PFA/PTFE or nitrogen-blanketed HDPE |
On a wafer surface, sodium and potassium shift flatband voltage and degrade threshold voltage stability in metal-oxide-semiconductor capacitors. Iron, copper, and nickel reduce minority carrier lifetime and can form deep-level traps when incorporated into silicon. Particles in etch or clean baths can obstruct local etching or become embedded in gate dielectrics, producing localized thinning and time-zero dielectric breakdown during electrical testing. Technical-grade acid, and even ACS reagent acid, does not provide the same lot-level control for these species; the cost and packaging differences reflect the dedicated distillation, controlled aging, and fluoropolymer handling required for low-ppb release.
In silicon etching, nitric acid is the oxidizer that converts the silicon surface to silicon dioxide, and hydrofluoric acid dissolves the oxide. The overall reaction for a mixed HF–HNO3 system can be represented as 3 Si + 4 HNO3 + 18 HF → 3 H2SiF6 + 4 NO + 8 H2O. The HF-to-HNO3 ratio controls whether the etch is mass-transport limited or reaction-rate limited. A high HNO3 fraction promotes a smooth chemical-polish etch, while a high HF fraction produces porous silicon and roughened surfaces. Production-scale etch benches commonly control bath temperature within ± 1 °C because the dissociation of HNO3 and the solubility of reaction products, especially H2SiF6, are strongly temperature-dependent. Agitation is supplied by filtered nitrogen sparging or recirculation through 0.1 µm PTFE membrane filters; insufficient agitation creates local depletion of HNO3 at the wafer surface and radial non-uniformity from center to edge.
Electronic/EL-grade material matters here because the etch bath operates as a turnaround reservoir for many wafers. Trace-metal contamination accumulates as the bath ages and can deposit on silicon after oxide removal, especially copper and noble metals that have higher electrochemical nobility than silicon. The low iron, copper, and zinc content of EL-grade nitric acid slows the rate at which the bath reaches defect-generating metal concentrations. Bath lifetime is typically terminated by accumulated silicon loading and viscosity rise rather than acid depletion; when hexafluorosilicic acid reaches the solubility boundary, crystalline precipitates can form in cooler recirculation lines. Used baths are neutralized with calcium hydroxide or sodium hydroxide under controlled dosing, and the evolved NOx is scrubbed before discharge.
Aluminum wet etching uses a phosphoric acid/acetic acid/nitric acid mixture. In this system, HNO3 is commonly maintained between 2 wt% and 5 wt% to oxidize the aluminum surface and regulate the formation of hydrogen gas bubbles. Insufficient nitric acid produces vigorous gas generation and undercut; excess nitric acid accelerates photoresist attack and can shift critical dimension loss beyond the allowed etch bias. Bath temperatures are typically held between 45 °C and 60 °C, depending on the aluminum alloy and linewidth. EL-grade acid is specified for the HNO3 component because chloride and transition-metal impurities in lower-purity acid influence pit formation and post-etch metal contamination.
In pre-diffusion surface preparation, mixtures of HNO3 with H2O2 or H2SO4 are used to remove organic residues and adsorbed metals. The nitric acid component oxidizes carbonaceous contamination and stabilizes the oxidizing potential of the bath. Bath replacement intervals are governed by total organic carbon, metal accumulation, and acid normality; production lots are often changed after a fixed number of wafer lots to avoid cross-lot memory effects. Because nitric acid can leave nitrate residues on hydrophobic silicon surfaces, a subsequent ultrapure water rinse with resistivity monitoring at 18.2 MΩ·cm is required until the rinse water remains above a specified resistivity endpoint.
Nitric Acid Electronic/EL Grade is also used for high-purity passivation of stainless steel in specialty gas and chemical delivery components. A dilution to 20–25 wt% HNO3 circulated at 50–60 °C for 30–60 min is a recognized procedure under ASTM A967 for removal of free iron and the formation of a chromium-enriched passive layer. However, semiconductor components downstream of final filtration are kept in fluoropolymer or quartz because even passivated stainless steel can release trace iron into the chemical stream. Nitric acid of this grade should be stored in dedicated, vented, fluoropolymer or high-purity HDPE containers at temperatures below 40 °C and away from direct sunlight. The storage area must be separated from organic solvents, acetic anhydride, ammonia, and reducing agents; accidental mixing with oxidizable solvents can generate NOx and heat. On receipt, lots should be checked for turbidity, particle count, and container integrity, with any increase in particle count during shelf life investigated as a possible polymer shedding or ingress failure.
