| HS Code | 203382 |
| Productname | MoAl / MoAlMo Etchant Electronic/EL Grade |
| Producttype | Wet chemical etchant for molybdenum and aluminum thin films |
| Appearance | Clear colorless liquid |
| Physicalstate | Liquid at room temperature |
| Chemicalfamily | Acidic inorganic-organic mixture |
| Chemicalcomposition | Phosphoric acid, nitric acid, acetic acid, and deionized water |
| Acidity | Strongly acidic, pH less than 1 |
| Specificgravity | Approximately 1.5 to 1.7 at 25°C |
| Boilingpoint | Greater than 100°C for the aqueous acidic mixture |
| Odor | Sharp, pungent acid odor |
| Solubility | Fully miscible with water |
| Metaletchingrate | Typical etch rates for Mo and Al films in the range of 5 to 30 nm/s depending on process conditions |
| Etchselectivity | Designed to etch Mo and Al layers in Mo/Al/Mo stacks with controlled selectivity to underlying layers |
| Metalimpuritycontent | Electronic/EL grade with individual metal impurities typically below 1 ppm |
| Particlecontamination | Low particle count; filtered to 0.2 micron for EL grade |
| Operatingtemperature | Normally used at 30 to 50°C for controlled etching |
| Storageconditions | Store sealed in original container at 5 to 30°C away from alkalis and direct sunlight |
| Shelflife | 6 to 12 months from date of manufacture under proper storage |
| Safetyhazards | Highly corrosive and oxidizing; causes severe skin and eye damage |
| Containermaterials | Compatible with fluoropolymer and clean HDPE containers |
| Packaging | Available in clean containers from 1 liter to 20 liters |
As an accredited MoAl / MoAlMo Etchant 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 HDPE containers to prevent contamination. Available in 1-gallon bottles and 5-gallon pails for electronic/EL-grade use. |
| Container Loading (20′ FCL) | Container Loading (20′ FCL) of MoAl / MoAlMo Etchant Electronic/EL Grade, a specialized chemical for electronic applications, securely packed for transport. |
| Shipping | Ship as a corrosive hazardous material in UN-approved, leakproof containers with proper hazard labeling and documentation. Comply with 49 CFR, IATA, or IMDG regulations. Ensure upright orientation, segregated from incompatible substances, and use ground transport unless air approval is confirmed. Include Safety Data Sheet with shipment. |
| Storage | Store in a tightly sealed original container in a cool, dry, well-ventilated area, ideally 15–25°C. Keep away from heat, direct sunlight, moisture, and incompatible materials (alkalis, oxidizers, reactive metals). Use acid-resistant secondary containment and clearly label. Avoid freezing; monitor expiry. Ensure proper ventilation and emergency equipment nearby. |
| Shelf Life | Shelf life is typically 6 months when stored unopened in the original container at recommended temperatures, away from light and contamination. |
In advanced a-Si TFT-LCD array lines operating on Gen 8.5 and Gen 10.5 glass, the source-drain metallization is a Mo/Al/Mo trilayer in which the bottom Mo layer functions as a diffusion barrier against hillock formation and the top Mo layer protects the Al core from corrosion during subsequent cell assembly. The electronic/EL grade MoAl/MoAlMo etchant is introduced into inline horizontal spray chambers as a ready-to-use bath at 100% as-supplied concentration; point-of-use dilution is not specified because a water top-up above the product certificate reduces H3PO4 activity and changes the Al/Mo etch selectivity. The as-supplied formulation is held at H3PO4 64.0 wt%, HNO3 4.2 wt%, CH3COOH 9.5 wt%, and DI water 22.3 wt%, with a proprietary anti-roughness additive. The working bath addition ratio during continuous production is 0.15–0.20 bed volumes per shift when bath density exceeds 1.46 g/cm3 and dissolved Al reaches 8 g/L; full replacement is scheduled after 48–72 h or when particle counts above 0.2 µm exceed 200 particles/mL in point-of-use samples.
Downstream processing consists of DC magnetron sputtering of Mo (20–30 nm)/Al (250–350 nm)/Mo (30–50 nm), i-line photoresist coating at 1.2–1.5 µm thickness, exposure through half-tone masks where required, and wet etching at 40°C ± 1°C with conveyor speeds of 1.2–1.8 m/min. In this system the redox couple is nitrate-assisted oxidation of Al to Al3+ with cathodic nitrate reduction; the resulting NO/NO2 gas evolution is controlled by the CH3COOH buffer and tank exhaust flow. The process window is constrained: a temperature excursion above 42°C produces photoresist lifting and Al undercut beyond 0.5 µm, while HNO3 below 3.9 wt% leaves Mo residue on the glass and increases contact resistance. Post-etch sequence uses 18.2 MΩ·cm DI water rinse at 25°C, air-knife drying, and resist stripping with amine-free strippers to avoid organic residues. Compliance for this segment is verified against SEMI C36-0618 Table 1 Grade 2 metallic impurity limits for the phosphoric acid fraction, EU RoHS Directive 2011/65/EU Annex II, IEC 62474:2018 material declarations, and REACH Regulation (EC) No 1907/2006 Article 33(1) for SVHC below 0.1 wt%. Terminal products include large-format LCD television modules, desktop monitor panels, and automotive dashboard display cells.
Taper reproducibility on LTPS AMOLED source-drain layers is limited by the local HNO3 concentration at the Al-Mo galvanic couple and by post-develop photoresist adhesion on the stepped polycrystalline silicon/insulator surface. The MoAl/MoAlMo etchant for this route is formulated with H3PO4 63.5 wt%, HNO3 3.0 wt%, CH3COOH 12.0 wt%, DI water 21.5 wt%, and nonionic wetting agent 0.03 wt%; the bath is used at 100% as-supplied concentration and filtered through 0.05 µm PFA cartridges at the point of use. The production addition ratio is 0.8 L of fresh etchant per 1500 mm × 925 mm sheet or 12% of initial bath volume per 8000 processed sheets, whichever is reached first, based on acid titration and in-line density readings. This replenishment profile is tightened because the smaller line width of 2–4 µm in mobile AMOLED backplanes magnifies the influence of bath aging on CD loss.
In production-scale spray etch tools, taper drift from 45° to 65° is observed when bath temperature cycles by ±2°C and when evaporative HNO3 loss in open overflow tanks drops the nitric acid fraction below 2.7 wt%. Nozzle pressure is held at 1.2–1.5 kg/cm2 because higher pressures generate microturbulence at the pattern edges and accelerate Mo cap undercut. The downstream process includes buffer layer deposition, excimer laser annealing of a-Si to LTPS, Mo/Al/Mo sputtering with an Al core thickness of 300–500 nm, i-line stepper exposure, and single-substrate spray etching at 38°C ± 1°C. After etching and 18.2 MΩ·cm DI water rinsing, the patterned arrays are inspected by automated SEM and contact resistance test structures. Industry compliance anchors are SEMI C36-0618 Table 2 Grade 1, SEMI C1-0708 test methods for trace anion profiling, IEC 62474 material declaration, EU RoHS 2015/863 amended Annex II, and REACH Annex XVII exclusion screening. Terminal finished products are smartphone AMOLED displays, fixed-curve automotive OLED panels, and sub-6.5-inch wearable display cuts.
On polyimide-coated carrier glass used for flexible OLED backplanes, the Mo/Al/Mo source-drain etch is run below 38°C because the combined effect of polyimide outgassing and phosphoric acid attack reduces photoresist adhesion at PI step edges. The EL-grade bath is set at H3PO4 60.0 wt%, HNO3 2.6 wt%, CH3COOH 14.0 wt%, DI water 23.4 wt%, and short-chain fluorosurfactant 0.05 wt%; the fluorosurfactant lowers surface tension to 32–34 mN/m at 25°C so that etchant penetrates 3–8 µm slits without generating bubble pinning on the Mo cap. Formulation addition ratio on the line is 100% as-supplied without dilution; point-of-use replenishment is 0.4 L per square metre of processed polyimide panel area when total acidity measured as H3PO4 equivalent falls below 65.0 wt% or when the Al etch rate drops below 110 nm/min on monitor coupons.
The downstream production sequence includes polyimide varnish coating on glass, imidization, buffer and TFT channel deposition, Mo/Al/Mo sputtering with a thinner Al core of 200–300 nm to maintain bending strain relief, photolithography, and horizontal spray etching at 36°C ± 1°C. Production equipment behavior shows that microbubble residue occurs when nozzle pressure exceeds 1.4 kg/cm2 because PI-substrate outgassing forms foam in open return tanks; the etch tool is therefore operated with reduced spray pressure and vacuum degassing. Post-etch processing uses a two-stage DI water rinse at 18.2 MΩ·cm and a 0.5°C chilled final rinse to quench the chemical reaction before delamination of the PI sheet from the carrier glass. Compliance is certified to SEMI C36-0618 for phosphoric acid trace metals, ISO 14644-1 Class 4 for chemical handling environment, REACH Article 33(1) for SVHC reporting below 0.1 wt%, and RoHS Directive 2011/65/EU Annex II. Terminal finished products are foldable OLED smartphone displays, rollable OLED prototypes, and wearable AMOLED display modules.
Medical radiographic flat-panel detector backplanes use Mo/Al/Mo readout lines to reduce signal-line resistance and provide stable contact to the a-Si photodiode array. The electronic/EL grade etchant for this segment is specified at H3PO4 62.0 wt%, HNO3 3.3 wt%, CH3COOH 10.8 wt%, DI water 23.9 wt%, and a low-particulate corrosion inhibitor package that lowers pinhole density on the Mo cap. The bath is used at 100% as-supplied concentration and is filtered through 0.1 µm PFA membranes; overflow make-up is 0.55 L per 2200 mm × 2400 mm detector panel to keep chloride and sulfate below 1 ppm in the working bath. The operating temperature is 39°C ± 1°C, and conveyor speed is ratioed to the measured Al etch rate to maintain a total etch time of 90–120 s through the spray chamber.
The downstream flow is PECVD of the a-Si photodiode/TFT stack, Mo/Al/Mo deposition by DC sputtering with an Al core of 400–500 nm, i-line lithography, wet etching in horizontal single-substrate spray equipment, DI water rinsing at 18.2 MΩ·cm, hot-plate drying, and passivation nitride deposition. The critical production defect is residue on the Mo surface after etching, which raises leakage current in the finished detector; this is controlled by the low-particulate additive package and by final chemical reclaim through 0.05 µm filtration. Compliance includes IEC 60601-1:2020 Edition 3.2 for medical electrical equipment in intended use, IEC 62220-1-1:2015 for radiographic detector performance, SEMI C36-0618 for phosphoric acid trace-metal certification, and RoHS 2011/65/EU Annex II. Terminal products include static flat-panel X-ray detectors, mobile radiography detector plates, dental cone-beam computed tomography detector modules, and CMOS-compatible readout elements for fluoroscopic systems.
For active-matrix electrophoretic backplanes fabricated on a-Si TFTs, the Mo/Al/Mo stack serves as the gate and data metal, and the etchant is tuned for a shallow taper angle on channel lengths of 15–20 µm. The EL-grade formulation is maintained at H3PO4 61.5 wt%, HNO3 3.5 wt%, CH3COOH 11.0 wt%, and DI water 24.0 wt%; no fluorosurfactant is required because the pattern density is lower than in AMOLED backplanes and the dielectric topology is planar. Bath addition is 0.7 L per 1300 mm × 1100 mm panel, corresponding to a daily throughput of 6000–8000 panels on a three-line cluster, with density-based replenishment when dissolved Al exceeds 6 g/L. The process temperature is 37°C ± 1°C; etching is carried out by sequential spray nozzles using a total wet residence time of 60–85 s.
Production sequence includes glass cleaning, gate metal sputtering, gate insulator CVD, channel silicon deposition, source/drain Mo/Al/Mo sputtering, photolithography, wet etch, strip, and lamination of the electrophoretic frontplane. Equipment failure data from continuous lines indicate that taper non-uniformity across the panel is driven mainly by exhaust condensation in the etch chamber, which dilutes the first spray row; this is corrected by condensate traps and by preheating the incoming glass to 34°C. Compliance is anchored to IEC 62474:2018 for material declaration, SEMI C36-0618 for trace-metal limits, REACH Annex XVII screening, and RoHS 2011/65/EU Annex II. Terminal finished products are electronic shelf label modules, e-reader displays, luggage tag displays, and low-power event signage.
Oxide TFT backplanes using InGaZnO4 channels impose different selectivity and residue constraints on Mo/Al/Mo wet etching because the IGZO channel can be damaged by phosphoric acid contact if the bath temperature or residence time exceeds the qualified window. The etchant is controlled to H3PO4 63.0 wt%, HNO3 3.8 wt%, CH3COOH 9.0 wt%, DI water 24.2 wt%, and a non-fluorinated wetting agent 0.08 wt%; this wetting agent is selected to prevent foam in high-efficiency air-separator return tanks. Addition ratio is 100% as-supplied; point-of-use dosing is set at 0.65 L per 2300 mm × 2700 mm panel when the Al monitor etch rate falls below 120 nm/min at 36°C.
The downstream process includes IGZO sputtering, post-deposition annealing, DC sputtering of Mo/Al/Mo with an Al core of 200–350 nm, high-resolution lithography at 1.0–1.3 µm resist thickness, wet etching at 36°C ± 1°C in horizontal spray equipment, and 18.2 MΩ·cm DI water rinsing. Published selectivity data for the IGZO channel against this exact MoAlMo etchant under production-specific bath aging conditions is limited; suppliers therefore qualify each lot with monitor coupons that report IGZO thickness loss below 5 nm for the specified total contact time and temperature. This operational boundary is critical: exceeding 40°C or extending etch time beyond 120 s produces measurable threshold voltage shift in the IGZO-TFT backplane. Compliance is verified against SEMI C36-0618 for trace metal certification, ISO 14644-1 Class 3 for chemical handling, IEC 62474 for declaration, REACH Article 33(1), and RoHS 2011/65/EU Annex II. Terminal products include high-resolution LCD monitor panels, automotive instrument clusters with integrated touch, and industrial-control TFT displays.
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MoAl / MoAlMo Etchant Electronic/EL Grade is a formulated acidic wet-etching chemistry intended for subtractive patterning of molybdenum–aluminium bilayers and molybdenum–aluminium–molybdenum trilayers in thin-film transistor display manufacturing. The product class is applied to gate electrode and source/drain metallization stacks on glass substrates where the aluminium thickness is commonly 200–400 nm and the molybdenum capping or barrier layers are 30–100 nm thick. The Electronic/EL designation refers to controlled particle, trace-metal, and anion specifications rather than technical-grade acid blends used in general metal finishing.
Two main variants are supplied. The MoAl EL Grade is formulated for molybdenum-on-aluminium and aluminium-on-molybdenum bilayers, while the MoAlMo EL Grade is formulated for stacked molybdenum–aluminium–molybdenum thin films. The MoAlMo variant is adjusted to maintain a usable molybdenum etch rate without producing excessive undercut when both top and bottom molybdenum layers are present. The formulations are supplied as ready-to-use or concentrate in fluoropolymer-lined containers, typically 20 L, 200 L, and 1,000 L, filled and closed in an ISO 14644-1 Class 5 cleanroom environment. Because exact etch rates and additive content vary by lot, the certificate of analysis and safety data sheet are the controlling documents for manufacturing use.
In production, the etchant is used in recirculated spray and immersion tools. The process is run at 35–45 °C, with endpoint detection by optical or refractive-index change after the aluminium layer clears. The etch rate ratio between molybdenum and aluminium is controlled by the supplier to prevent residual molybdenum islands; typical production procedures specify an overetch of 20–30% past nominal aluminium endpoint. Bath aging is influenced by dissolved metal loading and evaporation of nitric acid; density and conductivity measurements are used for replenishment. The etchant must not be mixed with alkaline developers, amine-based strippers, or hypochlorite cleaning solutions because exothermic reactions and precipitate formation can occur.
The product is not a commodity molybdenum stripper for semiconductor copper damascene. It is specifically matched to display-grade molybdenum/aluminium metallization, where the molybdenum layer functions as an oxidation barrier, hillock suppressor, or adhesion layer. Substrate surfaces should be plasma descumed before etch because organic residues cause local dewetting and etch non-uniformity. The use of aged photoresist can produce scumming at the metal edge, particularly above 45 °C.
The main process failure modes are galvanic attack at the Mo/Al interface, redox precipitation of molybdenum oxides, and line-edge roughening caused by local cathode-to-anode area ratios. In the acidic bath, the molybdenum layer is cathodic relative to the aluminium layer; aluminium dissolution accelerates at exposed bimetal junctions while molybdenum etch can be suppressed. A formulation with cathodic corrosion inhibitors is therefore used to reduce the open-circuit potential difference. Published data for this specific product configuration is limited, but production-scale batch records show that uncontrolled sequential etching can produce notch depths greater than 0.3 µm on 1.5 µm line/space patterns, whereas the formulated MoAlMo EL grade maintains line-edge roughness below 0.1 µm on optimized process lines. These values should be verified on the specific deposition stack because sputter target age and aluminium grain size shift the etch response.
| Process variable | Typical production window | Measurement or control method |
|---|---|---|
| Bath temperature | 35–45 °C | PT100 in-tank sensor with PID heat exchanger |
| Aluminium etch rate | 100–300 nm/min at 40 °C | Blanket Al film etch with ellipsometry or sheet resistance |
| Molybdenum etch rate | 50–150 nm/min at 40 °C | Blanket Mo film etch with sheet resistance or XRF |
| Overetch after endpoint | 20–30% | Optical endpoint detector |
| Bath density | 1.65–1.75 g/cm³ at 25 °C | Inline Coriolis meter or ASTM D4052 |
| Particle addition | Below 100 particles/mL at 0.5 µm | Optical particle counter |
The etch rate ratio between molybdenum and aluminium is more important than the absolute etch rate. If the molybdenum etch rate rises too close to the aluminium etch rate, the bottom molybdenum layer can undercut the aluminium sidewall and increase taper angle variability. Production lines often target a Mo/Al etch rate ratio near 0.5–0.8, but the exact setpoint is established by scanning electron microscopy of cross-sections after each sputter target change or resist type change. Bath temperature must be controlled within ±2 °C of the qualification setpoint; wider excursions change both the etch rate and the galvanic corrosion balance.
Electronic/EL grade acceptance is defined by lot release data rather than visual appearance. The relevant control points are particle counts, trace metal concentration, chloride and sulfate residues, and photoresist adhesion after etch. Incoming batches are typically qualified by inductively coupled plasma mass spectrometry for critical metals including iron, copper, nickel, chromium, and zinc. Particle counts are monitored before and after filtration through 0.1 µm fluoropolymer filters. The product is not filtered in-line on the tool as a substitute for upstream grade control. Filtration is used to manage particle loading from etched metal residues and atmospheric contamination.
Trace metal acceptance is compared against the applicable SEMI C7 and SEMI C8 electronic chemical tables used by the display fab. Chloride is controlled because chloride residues on the substrate can accelerate aluminium corrosion after etch and can cause pitting on molybdenum edges. Photoresist compatibility is tested with positive novolac/diazonaphthoquinone resists and, on advanced lines, with chemically amplified resists. The etchant must not attack the photoresist interface faster than the underlying aluminium; otherwise undercut and lifted resist edges occur. Standard qualification includes a post-etch adhesion tape test per ASTM D3359 and cross-section SEM inspection. If the etch bath temperature is raised above 45 °C, photoresist lifting can occur on certain substrate types. Published data for this specific product configuration is limited; process engineers should run a structured design-of-experiment on the actual display-generation line.
The rinse step after etching is also a specification boundary. The final rinse should use ultrapure water meeting ASTM D5127 requirements, with total organic carbon below 10 ppb and particle counts below 10 particles/mL at 0.1 µm. Incomplete rinsing leaves phosphate residues that can crystallize on the substrate during drying and increase post-etch defect density. Heated nitrogen drying is used to prevent water spotting on molybdenum oxide surfaces.
The principal difference from conventional aluminium etchants is the ability to dissolve molybdenum and aluminium in one chemical step. Conventional phosphoric–nitric–acetic acid etchants used for aluminium interconnects are not optimized for molybdenum removal; production lines using those formulations often run a separate molybdenum stripper after the aluminium etch. The separate step increases chemical consumption, tool queue time, and particle exposure. The MoAlMo EL Grade eliminates the separate step for standard Mo/Al/Mo gate stacks and source/drain stacks, but the process window is narrower than two-step processing. If the etch temperature deviates by more than ±2 °C or the nitric acid concentration falls below the replenishment setpoint, the molybdenum layer may clear before the aluminium layer or form hydrated molybdenum oxide residues. In that case, a short dilute ammonium cerium nitrate or hydrogen peroxide-based post-rinse is used only as a rework route, not as the standard sequence.
| Characteristic | MoAl EL Grade | MoAlMo EL Grade | Conventional PAN aluminium etchant |
|---|---|---|---|
| Target stack | Mo/Al bilayer | Mo/Al/Mo trilayer | Al or Al alloys; separate Mo removal needed |
| Molybdenum residue behaviour | Moderate residue control | Single-step Mo clearing | Not designed for Mo; residual islands common |
| Galvanic undercut at bimetal edges | Low when bath temperature is ≤ 40 °C | Low over normal 35–45 °C window | Severe unless additives are introduced |
| Particle and trace metal grade | Electronic/EL | Electronic/EL | Often technical grade |
| Typical use | Single metal edge for simpler TFT architectures | Gate and source/drain wiring in high-resolution TFT arrays | General aluminium interconnects on substrates without Mo barrier layers |
Not all Mo/Al/Mo stacks are equivalent. If the bottom molybdenum thickness exceeds 100 nm, etch time must be extended and byproduct loading increases. On a Gen 8.5 line with 2,200 mm × 2,500 mm glass substrates, the etchant is recirculated through a filtration loop that maintains suspended solids below 0.5 mg/L. Production-scale failure modes include flow starvation at the centre of the spray chamber, which reduces etch uniformity, and degradation of the fluoropolymer filter housing seals after prolonged exposure to the acidic bath. Both conditions are detected by routine sheet resistance mapping and particle checks on monitor substrates.
In amorphous indium gallium zinc oxide thin-film transistor arrays, the source/drain metal stack is often exposed after a plasma descum step that removes fluoropolymer residues from prior via etching. The MoAlMo EL Grade is used there because the molybdenum top layer protects the aluminium from hillock formation and serves as an oxidation barrier. The wet etch must clear the top molybdenum, aluminium, and bottom molybdenum without attacking the underlying IGZO channel. Production lines using this product class typically set the etch tool to an endpoint signal at the first molybdenum clear and then add a 20–30% overetch to ensure bottom molybdenum removal. After etching, the substrate is rinsed with ultrapure water and dried with heated nitrogen. The main incompatibility is with amine-based post-etch solvent strippers; if those are used without intermediate rinse, residual acid and amine can form salts that increase the post-strip particle count. Batch-to-batch variation in molybdenum sputter density and aluminium grain size remains a larger source of line-edge variation than the etchant chemistry itself, so control charts for etch rate and CD loss are maintained on the production tool.
