| HS Code | 610054 |
| Product Name | General Metal Etchant Electronic/EL Grade |
| Chemical Family | Acidic aqueous etchant solution |
| Active Constituents | Hydrochloric acid and nitric acid in deionized water |
| Grade | Electronic/EL (high-purity) |
| Physical State | Liquid |
| Color | Clear, colorless to pale yellow |
| Odor | Pungent, acidic |
| Specific Gravity | Approximately 1.20 at 20°C |
| Ph | <1 |
| Solubility | Fully miscible with water |
| Boiling Point | Approximately 100°C (212°F) |
| Freezing Point | Approximately 0°C (32°F) |
| Shelf Life | 12 months from date of manufacture |
| Recommended Storage Temperature | 15°C to 30°C (59°F to 86°F) |
As an accredited General Metal Etchant Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | General Metal Etchant Electronic/EL Grade: 1 gallon in a sealed, corrosion-resistant HDPE container with hazard-labeled, child-resistant cap. |
| Container Loading (20′ FCL) | 20′ FCL: electronic-grade metal etchant loaded in sealed drums, properly secured, labeled, segregated, and ventilated per dangerous goods regulations. |
| Shipping | This chemical requires ground shipping only due to its corrosive nature. It is packaged in leak-proof, UN-approved containers with hazard labeling. Shipments comply with all applicable dangerous goods regulations. Ensure proper handling and storage upon receipt; do not ship by air or standard parcel services. Signature may be required. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight and incompatible substances like bases or oxidizers. Keep the container tightly sealed when not in use to prevent moisture absorption and contamination. Ensure secondary containment and proper labeling. Follow manufacturer’s temperature guidelines; avoid storing near heat sources or reactive metals. |
| Shelf Life | Shelf life is typically six months to one year when stored sealed, cool, and away from light. |
The EL-grade general metal etchant is qualified for wet patterning of aluminium alloy films in wafer-level passive device fabrication. The working bath for aluminium etching on production wet benches is typically a phosphoric acid–acetic acid–nitric acid mixture at a volume ratio of 16:1:1:2, maintained at 40–45 °C in a recirculating quartz or PVDF tank. The nitric acid fraction functions as the oxidiser that regulates the rate of surface oxide removal, while acetic acid acts as a wetting agent that prevents gas-bubble adhesion and controls the taper angle at the photoresist edge. A 300 mm single-wafer spray processor or an immersion batch tool with 18–24 wafer cassettes is operated with 0.1 µm filtration and optional megasonic agitation at 0.8–1.2 W/cm². Endpoint detection on a production line commonly uses optical emission spectroscopy at 396 nm, which terminates the etch when the aluminium signal drops below a threshold set by the control system. Process failure logs from high-volume wafer fabs identify three recurring deviations: edge undercut exceeding 0.3 µm per side when the nitric acid concentration drifts outside the range of 0.8–1.2 % of bath weight, aluminium silicate residue when the dissolved silicon loading exceeds 30 mg/L, and wafer-to-wafer etch depth variation greater than 5 % 3σ when bath temperature control exceeds ±1 °C. The terminal devices after passivation and polymer repassivation are integrated passive devices, RF filters, and redistribution layers for wafer-level chip-scale packages. Lot acceptance for this EL-grade etchant follows SEMI C7 for particle counts, with a limit of ≤100 particles/mL at 0.2 µm, and SEMI C8 for trace metal analysis by ICP-MS. A chloride level below 200 ppb is required to avoid pitting on aluminium-copper interconnects, as determined by ASTM D512 using ion chromatography. The etchant must not be combined with amine-based developers in the same drain system because the resulting pH shift precipitates aluminium hydroxide sludge that clogs the 0.1 µm filter and creates cross-contamination in the wet bench.
| Parameter | Control limit | Reference method |
|---|---|---|
| Particle count ≥ 0.2 µm | ≤100 particles/mL | SEMI C7 |
| Sodium | ≤50 ppb | SEMI C8 ICP-MS |
| Iron | ≤20 ppb | SEMI C8 ICP-MS |
| Copper | ≤20 ppb | SEMI C8 ICP-MS |
| Chloride | ≤200 ppb | ASTM D512 ion chromatography |
In semi-additive printed circuit board fabrication, the copper seed layer after electrolytic panel plating is removed by oscillation spray etching with an EL-grade sulphuric/peroxide formulation. The working bath consists of 5–10 % v/v sulphuric acid, 1–3 % v/v hydrogen peroxide, and a proprietary stabiliser package that suppresses exothermic peroxide decomposition triggered by dissolved copper. Horizontal conveyorised spray etchers with 24–32 nozzles and a conveyor speed of 2–4 m/min operate at 28–32 °C, with air-knife drying immediately after the rinse stage. The etch factor, defined as the ratio of vertical etch depth to lateral undercut, must remain above 3 for 40/40 µm line/space structures; this is achieved by maintaining oxidation-reduction potential between 450 and 550 mV versus Ag/AgCl and by controlling dissolved copper below 35 g/L in the working bath. Pre-drying of panels is required when relative humidity exceeds 60 %, because residual moisture dilutes the peroxide and creates local etch-stop islands that cause open circuits after strip etching. Compliance for the final HDI substrate is assessed against IPC-6012E Class 3 and IPC-A-600J acceptance criteria; ionic cleanliness is tested by IPC TM-650 2.3.25 with a chloride equivalence below 1.5 µg NaCl/cm². The terminal finished product is a high-density interconnect printed circuit board used in automotive radar modules and 5G antenna-in-package substrates.
Galvanic coupling between molybdenum and aluminium in TFT-LCD backplane manufacturing is the principal defect driver when Mo/Al bilayers are patterned with the EL-grade general metal etchant. The bath temperature is held at 32–36 °C for immersion or gentle spray processing; higher temperatures accelerate aluminium dissolution selectively and create undercut at the Mo-Al interface. The formulation is diluted to a phosphoric acid content of 30–45 % by volume with nitric acid held between 0.6 and 1.0 % to balance the etch rate of molybdenum against aluminium. Publicly documented etch rates for this chemical family are approximately 0.1–0.3 µm/min for molybdenum and 0.4–0.8 µm/min for aluminium, with a selectivity to the underlying SiO₂ gate dielectric above 100:1 when acetic acid is maintained above 5 % by volume. Production line data from Gen 8.5 glass substrates show that local galvanic pitting can occur within 20–40 seconds when the redox potential drifts outside the range of 480–560 mV versus Ag/AgCl; the defect is detected post-etch as black spot residues along the data-line edges. Bath loading is limited to 25 mg/L of molybdenum and 50 mg/L of aluminium to prevent precipitation of molybdic acid on the glass surface. Cleanroom requirements follow ISO 14644-1:2015 Class 5 for the wet etch bay, and operator exposure is governed by SEMI S2-0712 for equipment safety. The etched TFT arrays are then coated with photoresist-stripped gate and source-drain electrodes for active-matrix LCD and OLED panels. This layer stack is incompatible with fluoride-containing etchants; any cross-contamination above 5 ppm fluoride causes pinholes in the SiO₂ gate insulator and must be monitored by ion-selective electrode after bath changeover.
Post-DRIE titanium/titanium nitride hardmask removal in MEMS micromachining uses a fluoride-containing EL-grade etchant at 45–50 °C in single-wafer processors equipped with megasonic agitation. The working bath for this operation is a dilute mixture of hydrofluoric acid at 0.2–1 wt% and hydrogen peroxide at 3–5 wt%, with a silicon-containing inhibitor that passivates exposed aluminium interconnect pads. The process removes the TiN diffusion barrier and the underlying titanium adhesion layer after the deep reactive ion etching of silicon, while leaving the aluminium bond pad surfaces intact. Selectivity to aluminium is maintained above 10:1 by the formation of an alumina-fluoride complex that dissolves at a rate below 50 nm/min; the aluminium etch rate is measured on a sacrificial wafer with a four-point probe before production runs. Equipment configuration includes a quartz single-wafer spin processor with a 0.1 µm fluoropolymer filter, chemical temperature control of ±0.5 °C, and exhaust gas scrubbing for hydrogen fluoride vapour. The processing window is narrow: below 45 °C the titanium etch rate drops below 10 nm/min and the hardmask is not cleared in the 120-second process step, while above 50 °C the TiN-to-Al selectivity falls below 5:1 and pitting of the aluminium pads is observed under scanning electron microscopy. The terminal components are inertial MEMS sensors, microbolometers, and pressure sensors where the release of the metal hardmask must not leave polymer residues that affect stiction. The etchant supply system is constructed from PFA and PTFE; stainless steel components are excluded because dissolved ferric ions catalyse peroxide decomposition and create localised hot spots on the wafer edge.
| Metal film stack | Process temperature | Spray pressure / agitation | Endpoint method | Primary defect if outside band |
|---|---|---|---|---|
| Aluminium 1 % Si on SiO₂ | 38–42 °C | 1.2–1.5 kg/cm² spray | optical emission at 396 nm | undercut > 0.3 µm per edge |
| Copper seed foil | 28–32 °C | 0.8–1.2 kg/cm² spray | ORP 450–550 mV vs Ag/AgCl | etch factor < 3 |
| Mo/Al TFT stack | 32–36 °C | 1.0–1.4 kg/cm² spray | time mode with redox potential | galvanic pitting at Mo-Al interface |
| Ti/TiN hardmask | 45–50 °C | megasonic 0.8–1.2 W/cm² | weight loss coupon | Al interconnect attack |
| NiCr 80/20 | 25–30 °C | immersion without ultrasonic | resistance change ≤ 0.1 % | pitting due to chloride |
Thin-film nickel-chromium resistors with 80/20 composition are wet-etched in an aqua regia-type EL-grade bath at 25–30 °C using a volume ratio of 3:1 HCl:HNO₃. The etch must be performed in quiescent immersion without ultrasonic agitation because cavitation damages the 100–300 nm thick NiCr film and creates irregular resistor edges. Endpoint is determined by in-situ resistance change; the bath is stopped when the resistance deviation from target is ≤0.1 %, corresponding to a line width reduction of 0.5–1.0 µm for a 0.8 mm × 0.8 mm resistor geometry. Bath aging is the primary throughput limitation. As dissolved nickel and chromium concentrations rise above 120 mg/L and 80 mg/L respectively, the redox potential shifts and the etch rate becomes non-linear, causing batch-to-batch resistance variation above ±0.5 %. For this reason, bath life is limited to 48 hours or 20 wafer cassettes, whichever occurs first, followed by complete replacement. The terminal finished product is a precision chip resistor or resistor network qualified to IEC 60115-1:2020, with environmental stress testing per AEC-Q200 for automotive-grade parts. The etchant must not be exposed to photoresist stripper solvents because residual organic carbon reacts violently with nitric acid at the 1-L recirculation loop; a dedicated drain line is required.
Leadframe silver spot plating for QFN and DFN packages is preceded by a micro-roughening etch that increases the mechanical adhesion of the plated silver layer to the copper alloy substrate. The working bath is a persulphate-free sulphuric/peroxide EL-grade formulation operated at 30–35 °C in a conveyorised spray system with 1.0–1.5 kg/cm² nozzle pressure. The target etch depth is 0.5–1.5 µm, and the resulting surface roughness is controlled between Ra 0.2 and 0.4 µm on C19400 and C7025 copper alloy leadframes. Production data from reel-to-reel lines show that etch depth uniformity across a 70 mm wide leadframe strip is better than ±10 % only when nozzle spacing is below 25 mm and the conveyor speed is held at 1–2 m/min. Over-etching beyond 1.5 µm creates pits under the silver spot plating and reduces wire-bond pull strength below the 0.12 N/75 µm wire diameter threshold specified in the end-user's qualification plan. The terminal finished product is a leadframe for automotive power discretes, where post-plating adhesion is verified by tape peel testing and thermal cycling at −65 °C to +150 °C for 500 cycles. Compliance for the finished leadframe includes RoHS Directive 2011/65/EU Annex II for restricted substances and REACH Regulation (EC) No 1907/2006 Annex XVII for restriction of nickel in skin-contact applications when applicable. The EL-grade etchant is supplied with a certificate of analysis stating particle counts ≤100 particles/mL at 0.2 µm and chloride below 200 ppb to avoid copper pitting before silver plating.
In crystalline silicon heterojunction cell production, edge isolation of copper-plated front metallization is carried out with a low-chloride sulphuric/peroxide EL-grade etchant in inline horizontal spray systems. The etch step removes 0.3–0.8 µm of copper flash from the cell perimeter and the front surface field regions where plating is undesirable, while the main grid lines are protected by a patterned mask. The process temperature is set at 25–30 °C, and the spray pressure is limited to 0.8–1.2 kg/cm² to prevent delamination of the heterojunction transparent conductive oxide layer. The primary control parameter is the etch depth measured by coulometric thickness analysis on a sacrificial coupon, with replenishment of hydrogen peroxide triggered when the ORP drops below 500 mV versus Ag/AgCl. An incompatibility exists with alkaline texturisation residues: any sodium hydroxide carryover above 5 mg/L raises the pH of the acidic etchant and precipitates copper hydroxide, which blocks the 0.1 µm nozzle filters and creates streak defects on the cell surface. The terminal product is a silicon heterojunction solar cell or shingled module qualified to IEC 61215-1:2021 and IEC 61730-1:2023. Published data for this specific edge isolation configuration is limited; production lines therefore validate the etch rate daily with 25-cell pilot lots before full shift operation.
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General Metal Etchant Electronic/EL Grade is a purified phosphoric acid/nitric acid/acetic acid/water blend formulated for subtractive patterning of aluminum, Al-Si, Al-Cu, and TiW adhesion films in thin-film microelectronics. The formulation’s lot-release window is typically 65.0–75.0 wt% H₃PO₄, 3.0–5.0 wt% HNO₃, 8.0–12.0 wt% CH₃COOH, and the balance deionized water with resistivity ≥ 18.0 MΩ·cm at 25°C. Measured at 25°C, specific gravity ranges from 1.55 to 1.65, while Brookfield viscosity at 40°C is 2.0–4.5 cP. The Electronic/EL Grade is differentiated from technical-grade acid blends by trace metal control: Fe, Cu, Ni, Cr, Na, K, and Zn are each typically ≤ 25 ppb, with total trace metal burden ≤ 200 ppb. Particle counts are controlled to ≤ 100 particles/mL at ≥ 0.2 µm using an optical particle counter calibrated to ISO 21501-2:2019. Lot-specific certificates of analysis report trace metal concentrations by inductively coupled plasma mass spectrometry after dilution; the product is supplied in high-density polyethylene containers under inert nitrogen headspace.
On 100 mm, 150 mm, and 200 mm wafer lines, the etchant is applied by immersion, spray, or puddle processes to define metal interconnects, bond pads, and gate structures. In immersion tools with ultrasonic or megasonic agitation, the etch rate on evaporated Al-1.2Si-0.8Cu at 50°C is typically 1.2–2.4 µm/min, depending on film grain size, prior thermal history, and photoresist loading. The nitric acid component oxidizes the aluminum surface while phosphoric acid dissolves the oxide; acetic acid buffers the reaction and improves wetting without attacking typical novolac resists at film thicknesses above 1.5 µm. Process literature indicates that a ±2°C bath temperature variation shifts the observed etch rate by approximately 0.2–0.4 µm/min in unstirred baths, whereas high-flow spray equipment reduces thermal boundary layer effects and yields more uniform lateral etch profiles. Etch initiation delay is typically 15–45 s on native aluminum oxide layers, after which the reaction proceeds linearly until the film clears.
The principal difference lies in trace metal and particle specifications. Technical-grade phosphoric acid may contain Fe at 500–1500 ppb, Na at 1–5 ppm, and sulfate at 10–50 ppm, whereas Electronic/EL Grade limits alkali metals, transition metals, and chloride/sulfate to sub-100 ppb levels. Residual chloride above 100 ppb can initiate pitting on exposed Al-Cu pads, producing post-etch corrosion. Electronic/EL Grade also maintains controlled nitric acid concentration; technical-grade blends often exhibit wider assay drift because of volatilization during storage, shifting the oxidizing capacity and causing inconsistent etch initiation. The Electronic/EL Grade is filtered through 0.1 µm PTFE or polypropylene filter cartridges before packaging, reducing particle counts to levels compatible with ISO 14644-1:2015 Class 5 rinse environments.
| Parameter | Electronic/EL Grade | Technical Grade | Typical Analytical Method |
|---|---|---|---|
| Fe | ≤ 25 ppb | ≤ 500 ppb | ICP-MS |
| Cu | ≤ 25 ppb | ≤ 200 ppb | ICP-MS |
| Na | ≤ 25 ppb | ≤ 1000 ppb | ICP-MS |
| Chloride | ≤ 100 ppb | ≤ 10 ppm | Ion chromatography |
| Sulfate | ≤ 100 ppb | ≤ 20 ppm | Ion chromatography |
| Particles ≥ 0.2 µm | ≤ 100 particles/mL | Not specified | ISO 21501-2:2019 |
In 200 mm wafer fabs using cassette-to-cassette immersion tools, bath volume is typically 20–40 L per process tank, with recirculation rates of 10–20 L/min. The etchant is maintained at 45–55°C by quartz or PTFE immersion heaters, and etch time is set as end-point detection plus an overetch fraction of 10–20%. Aluminum loading in the bath is controlled below 500 ppm because dissolved aluminum increases solution viscosity and reduces the activity of free phosphoric acid, decreasing etch rate and increasing undercut. Field data from production lines show that batch-to-batch etch-rate variation can be held within ±7% when the bath is replenished with fresh Electronic/EL Grade after each 6–8 h shift and when the water content is adjusted gravimetrically. Substrate dehydration at 150°C for 30 min in a nitrogen purged oven is specified when wafers are stored at relative humidity above 60%, because adsorbed moisture can dilute the etchant film and create localized non-uniform initiation.
An increase in observed etch rate above 2.4 µm/min at a bath setpoint of 45°C in immersion mode is a process excursion, not a benefit. It usually indicates a higher-than-specification nitric acid fraction or the presence of dissolved copper from previous lot carryover, both of which accelerate cathodic half-cell activity. In such cases the lateral undercut on 2.0 µm aluminum lines increases from a nominal 0.3–0.5 µm per edge to more than 0.8 µm per edge, compromising linewidth control for features below 5.0 µm. Bath conductivity at 45°C rises with metal loading; when conductivity exceeds 85 mS/cm, the bath is considered spent for fine-line applications. Thermal control must maintain ±1°C uniformity across the tank, and recirculation flow must be sufficient to achieve a turnover time of 2–3 min, equivalent to 10–20 L/min in a 30 L bath. Under these conditions, the ratio of vertical etch rate to lateral etch rate is typically 2.5:1 to 3.5:1; above 4:1, spray or puddle equipment should be considered.
| Bath Temperature | Al-1.2Si-0.8Cu Etch Rate | Estimated Undercut per Edge |
|---|---|---|
| 40°C | 0.8–1.5 µm/min | 0.2–0.3 µm |
| 45°C | 1.2–2.0 µm/min | 0.3–0.4 µm |
| 50°C | 1.6–2.4 µm/min | 0.4–0.6 µm |
| 55°C | 2.2–3.0 µm/min | 0.6–0.9 µm |
Spray processing in conveyorized equipment operates at lower bath temperatures but higher mass transfer. Typical nozzle pressures are 103–207 kPa, with substrate throughput of 0.5–1.5 m/min; the liquid film thickness on the wafer surface is 0.3–1.0 mm. In spray mode the etch rate at 40°C can be 1.0–2.0 µm/min; because the etchant is continuously impinged, reaction products are removed more efficiently, and undercut is typically 0.2–0.4 µm per edge. However, spray processes are more sensitive to nozzle clogging from precipitated aluminum phosphate. Filters rated at 0.2 µm on the return line reduce particulate accumulation, but filter pressure drop should be monitored and cartridges replaced when differential pressure exceeds 100 kPa. The product is incompatible with amine-based photoresist strippers; if the two chemistries come into contact, an exothermic neutralization can occur, generating localized heating and releasing acetic acid vapor. Rinse after etching with deionized water of resistivity ≥ 18.0 MΩ·cm for 5–10 min until rinse conductivity is below 5 µS/cm prevents post-etch corrosion.
Particle control for Electronic/EL Grade is maintained by a multi-stage filtration architecture. The supply line typically contains a 0.1 µm polytetrafluoroethylene membrane cartridge housed in a fluoropolymer body, while the recirculation loop uses 0.2 µm polypropylene depth filters to trap insoluble aluminum hydroxyphosphates. Liquid particle counts measured at the point of use should not exceed 50 particles/mL at ≥ 0.2 µm for advanced packaging applications. Pumps and filter housings must be constructed of polyvinylidene fluoride, ethylene chlorotrifluoroethylene, or high-purity polypropylene; stainless steel wetted components are unacceptable because the acidic blend leaches Fe, Ni, and Cr, raising trace metal concentrations above the 25 ppb specification within a single shift. Pressure gauges on filter housings should be isolated with fluoropolymer diaphragms to avoid metallic contamination. At bath temperatures of 50°C, the vapor pressure of acetic acid is sufficient to require exhaust ventilation of 0.5–1.0 m/s face velocity at the tool enclosure, and acid fumes should be scrubbed through a packed tower with caustic solution. The process area is typically maintained at ISO 14644-1:2015 Class 5 or better.
Product storage at 15–25°C in original containers prevents acid volatilization and moisture absorption. At temperatures below 10°C, crystallization of phosphoric acid species may occur; if crystals form, the container is heated gradually to 30°C under nitrogen until homogeneity returns. The product should not be combined with reducing agents, strong alkalis, or organic solvents. Under REACH regulation 1907/2006, the material is supplied with an extended safety data sheet identifying phosphoric acid CAS 7664-38-2, nitric acid CAS 7697-37-2, and acetic acid CAS 64-19-7; local exhaust and personal protective equipment requirements follow directive 89/656/EEC.
In high-throughput immersion lines processing more than 200 wafers per shift, bath chemistry drifts because nitric acid undergoes partial decomposition at 50°C and acetic acid evaporates. When the HNO₃ concentration falls below 2.5 wt%, the etch initiation delay increases to 60–120 s, and the surface may develop non-uniform breakthrough. Nitric acid or a proprietary oxidizer replenisher is added with continuous metering while the bath is recirculated through a static mixer; field data show that maintaining a free nitrate concentration equivalent to 3.0–4.0 wt% HNO₃ holds etch-rate variation within ±5% over 8 h. Water loss by evaporation at 50°C increases bath viscosity; a 2–4% water loss raises viscosity by 0.3–0.6 cP and reduces wetting at fine geometries. Gravimetric or refractive-index control is therefore used to maintain water content within 1.0 wt% of the initial formulation. Ex situ analysis by automated titrators provides acid assay every 30 min, while inductively coupled plasma optical emission spectroscopy measures dissolved aluminum and copper every 60 min; baths are discarded when aluminum loading reaches 800 ppm for line/space dimensions above 5 µm, or 300 ppm for dimensions below 5 µm.
Compared with unblended phosphoric acid or commercial aluminum etchant, Electronic/EL Grade reduces post-etch residual metal contamination by 1–2 orders of magnitude as measured by total reflection X-ray fluorescence on blanket aluminum films after a standard deionized water rinse. Users selecting this product for pad redistribution layers or wafer-level packaging should verify etch rate on production sputtered films, because sputtered Al-Cu films with high compressive stress can etch 10–20% faster than evaporated films. The product is not formulated for copper bulk etching; cupric chloride or alkaline permanganate chemistries remain the standard for copper substrate removal. For thin TiW adhesion layers, a separate hydrogen peroxide-based etchant is required because the phosphoric/nitric system leaves tungsten residues unless a post-etch plasma treatment is applied. Published data for specific device integration configurations is limited for sub-65 nm aluminum interconnects, where damascene copper has largely replaced subtractive aluminum.
