| HS Code | 477776 |
| Chemical Name | Positive Photoresist Stripper (Electronic/EL Grade) |
| Grade | Electronic/EL Grade |
| Appearance | Clear, colorless to light yellow liquid |
| Chemical Composition | Proprietary blend of organic solvents, alkaline inhibitors, and surfactants |
| Purity | High-purity electronic grade with low trace metal contamination |
| Total Metal Content | < 1 ppm per metal element |
| Boiling Point | 150–180°C |
| Flash Point | > 60°C (closed cup) |
| Density | 0.98–1.05 g/cm³ at 25°C |
| Viscosity | 2–5 cP at 25°C |
| Solubility | Miscible with water, alcohols, and common organic solvents |
| Stripping Mechanism | Dissolves positive photoresist films and lifts residues from substrate surfaces |
| Substrate Compatibility | Compatible with silicon, silicon dioxide, silicon nitride, and most metal films |
| Storage Conditions | Store in tightly sealed original container at 20–25°C away from light and moisture |
| Shelf Life | 12 months from date of manufacture when stored as recommended |
| Packaging | High-purity HDPE containers; available in 1 L, 4 L, and 20 L sizes |
As an accredited Positive Photoresist Stripper Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 1-gallon high-density polyethylene bottle with secure cap for Electronic/EL grade positive photoresist stripper. |
| Container Loading (20′ FCL) | 20' FCL loading of Positive Photoresist Stripper Electronic/EL Grade: hazardous liquid, UN-approved drums, palletized, secured, labeled. |
| Shipping | Positive Photoresist Stripper (Electronic/EL Grade) ships as a hazardous chemical, typically in sealed HDPE containers under ambient temperatures. It requires ground/air freight with proper UN classification, corrosive labels, and spill-containment packaging. Avoid moisture, heat, and static sources. Documentation, safety data sheets, and hazmat declarations must accompany all shipments. |
| Storage | Store in tightly sealed original containers in a cool, dry, well-ventilated area away from heat, open flames, and incompatible oxidizers. Keep protected from direct sunlight and moisture. Ensure containers are clearly labeled and grounded during transfer. Follow manufacturer guidelines; use appropriate chemical storage cabinets and secondary containment to prevent leaks or spills. |
| Shelf Life | Shelf life is typically 12 months from manufacture date when stored unopened in original container at room temperature. |
In high-volume 300 mm logic and 3D NAND front-end-of-line flows, positive photoresist stripping after 1×10¹⁵ to 5×10¹⁵ atoms/cm² ion implantation and downstream O₂/N₂ plasma ashing is operated in a recirculated wet bench bath held at 70 °C ± 2 °C. The hardened implant crust is first swelled with undiluted EL-grade stripper for 180 s, then transferred to an 18.2 MΩ·cm DI water cascade rinse and a Marangoni isopropanol dryer. Amine alkalinity is maintained at a dilution endpoint corresponding to bath pH 11.0 to 11.2; water uptake of 2.5 wt% lowers the value to approximately 10.4, at which point residue removal efficiency and metal etch inhibition begin to diverge. For porous SiCOH low-k dielectrics with k ≤ 2.4, single-pass contact is capped at 300 s because extended exposure increases methyl loss measured at 1,270 cm⁻¹ and raises k by 0.08 to 0.12. The bath is filtered through 0.05 µm PTFE membranes, and particle counts exceeding 30 particles/mL at ≥0.5 µm trigger replacement according to the EL-grade limit table below. Terminal products include sub-5 nm logic gate structures and 232-layer 3D NAND stacks.
| Parameter | EL-grade point-of-use limit | Reference method or standard |
|---|---|---|
| Sodium | <5 ppb | ICP-MS, SEMI C33-0918 |
| Potassium | <5 ppb | ICP-MS, SEMI C33-0918 |
| Iron | <10 ppb | ICP-MS, ASTM D5127-13 |
| Copper | <10 ppb | ICP-MS, SEMI C33-0918 |
| Chloride | <50 ppb | Ion chromatography, ASTM D5127-13 |
| Particles ≥ 0.5 µm | <30 particles/mL | Liquid particle counter, SEMI F104 |
| Water | <0.1 wt% | Karl Fischer titration, ASTM E203-16 |
Copper pillar plating lines fabricate positive-resist frames of 50–100 µm thickness over Ti/Cu seed layers. The EL-grade stripper is diluted to 70 vol% in DI water and dispensed in a single-wafer spray chamber at 3.5 L/min through a 0.05 µm PTFE point-of-use filter. Copper loss is held below 1 nm/min by maintaining the bath at 45 °C ± 1 °C and keeping chloride below 50 ppb; if chloride reaches 100 ppb, cuprous chloride solubility rises and pillar undercut of 0.3–0.5 µm per pass is observed at the die edge. Total contact time is limited to 600 s, followed by a 30 s megasonic rinse at 1.0 MHz to remove SnAg intermetallic debris. The most common production failure mode is voiding at the resist foot from premature seed removal caused by bath pH falling below 9.8 through atmospheric CO₂ uptake; the sump is therefore blanketed with nitrogen and pH is recorded at 10-minute intervals. Terminal formats include flip-chip chip-scale packages and high-density chip-on-wafer interconnects for front-end modules.
After temporary bonding edge trim and before wafer thinning, through-silicon via reveal stations use the EL-grade stripper on 300 mm carriers with via diameters from 5 µm to 10 µm and depth-to-width ratios up to 12:1. A vacuum pre-wet cycle at −0.08 MPa for 90 s evacuates trapped air from the vias, followed by puddle inversion and low-speed rotation at 120 rpm for 180 s. Because the stripper exhibits a dynamic surface tension of 30–33 mN/m at 25 °C, capillary penetration removes positive-resist residues from silicon sidewalls without forming bubbles. The post-strip cleaning sequence uses CO₂-dosed DI water to return the wafer surface to pH 6.8–7.2 before subsequent PECVD oxide deposition. Potassium and sodium are maintained below 5 ppb at point-of-use because residual alkali ions migrate into the TSV liner and shift threshold voltage in stacked memory. Terminals are high-bandwidth memory cubes and silicon interposers in 2.5D logic-on-interposer assemblies.
Display array wet strip lines processing 2,200 mm × 2,500 mm Gen 8.5 and Gen 10.5 substrates remove positive photoresist after wet etching of Al/Mo or Cu/Mo/Ti source-drain patterns. The EL-grade stripper is distributed through a central chemical delivery system and filtered at 0.03 µm with hydrophilic polypropylene membranes; bath replacement is triggered after 1,000 substrates or when particle counts exceed 10 particles/mL at 0.5 µm. The horizontal spray chamber operates at 23 °C ± 1 °C for 70 s, because amine attack on aluminium becomes significant above 40 °C. Galvanic cells between molybdenum and aluminium are controlled by limiting Fe and Cu contamination to 5 ppb; a single contaminated lot can produce metal oxide nodules at line edges that appear as dark-pixel defects after colour filter lamination. Final rinsing uses 18 MΩ·cm DI water with 950 kHz ultrasonic assist, followed by air-knife drying at 0.4 MPa. Terminals are amorphous-silicon and IGZO backplanes for 4K television and mobile OLED panels.
When sacrificial MEMS photoresist survives oxygen plasma descum after a 10:1 DRIE silicon etch, the EL-grade stripper is applied as an immersion bath at 60 °C for 45–90 min in a quartz vessel under nitrogen blanketing. The nitrogen cover prevents carbonate formation that otherwise deposits on released comb fingers and inertial masses. For structures with 2 µm gaps and 50 µm proof masses, the undiluted stripper wets the exposed buried oxide after sacrificial oxide release, but the temperature is not raised above 75 °C because aluminium bond pads at the wafer edge show pit corrosion above that threshold. After stripping, isopropanol and heptane displacement replaces water rinsing to avoid stiction collapse of beams narrower than 1.5 µm. Cation levels below 10 ppb are required to prevent mobile ion drift in capacitive accelerometer readout circuits. Terminal products include automotive gyroscopes and microphones with hermetically sealed silicon caps.
Compound semiconductor lift-off lines processing 150 mm GaAs and 100 mm InP substrates use the EL-grade stripper to dissolve positive-resist sacrificial layers beneath evaporated Au/Pt/Ti gate metal stacks. A single-spray lift-off soak at 80 °C ± 2 °C for 20–40 min is standard; ultrasonic agitation above 40 W is not used because it detaches plated metal feed lines along the wafer edge. Sodium is held below 5 ppb because residual Na at the gate recess is known to shift pinch-off voltage in GaAs pHEMTs. Chloride below 20 ppb prevents electrogalvanic attack on exposed Au/GaAs interfaces during the post-lift-off rinse. The process is less sensitive to water uptake than copper bump applications, but bath viscosity exceeding 12 cP at 25 °C retards removal of metal flakes from gate features. Terminals include HEMT power amplifiers and 0.25 µm gate-length photonic laser diodes.
In redistribution layer modules, 2–5 µm copper lines are fabricated on cured polybenzoxazole or polyimide dielectrics. After electroplating, positive-resist removal is performed in a single-wafer spray processor with the EL-grade stripper diluted to 65 vol% in DI water at 60 °C ± 1 °C. The pH is continuously recorded; if pH remains above 10.6 for more than 120 s, the cured PBO surface develops microcracks that propagate during subsequent thermal cure at 230 °C. The associated imide ring hydrolysis is confirmed by ATR-FTIR carbonyl broadening at 1,775 cm⁻¹. The diluted bath is replenished after 24 wafer passes or when refractive index drifts beyond 0.001 from the fresh bath value. Metal cations are maintained below 5 ppb and chloride below 10 ppb to prevent galvanic voids in Cu RDL lines. A 0.025 µm PTFE filter is installed in the recirculation loop to limit partially dissolved polymer aggregates. Terminal packages include fan-out panel-level and 2.5D silicon bridge modules.
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Positive photoresist stripper Electronic/EL grade is a high-purity formulated liquid for wet removal of positive-tone photoresist after pattern transfer. The “EL” suffix is a grade indicator linked to trace-metal control and cleanroom packaging rather than a single solvent composition. The product is specified for use in semiconductor front-end-of-line and back-end-of-line cleaning where exposed layers include aluminum, copper, tungsten, titanium nitride, silicon dioxide, and porous low-k dielectrics. It is dispensed in immersion tanks, batch spray processors, and single-wafer tools after dry etch, ion implantation, electroplating, or resist hardening. The model designation varies by supplier, but the Electronic/EL suffix distinguishes the product from standard or technical-grade versions of the same base chemistry.
Electronic/EL grade release criteria are based on contamination load. Per-element metal concentrations are typically held below 10 ppb for sodium and potassium and below 5 ppb for iron and copper. Chloride is commonly limited to 50 ppb or less, and particles ≥ 0.5 µm are controlled to fewer than 25 particles/mL. Analytical confirmation uses inductively coupled plasma mass spectrometry, ion chromatography, and laser particle counting. In comparison, a technical-grade stripper may carry transition metal levels above 1 ppm and may not include particle certification. This difference is critical because sodium and potassium are mobile under bias-temperature stress at 150 °C and 1 MV/cm, while copper and iron can degrade junction leakage and dielectric breakdown.
General-purpose positive resist removers often rely on solvent strength alone and may be filled without cleanroom protocols. Their contaminant load can exceed typical front-end limits by two to three orders of magnitude. In contrast, electronic/EL grade strippers are qualified against a trace-metal budget relevant to transistor performance. Alkali ions such as sodium and potassium are mobile under bias-temperature stress; transition metals such as iron and copper promote junction leakage and dielectric degradation. The release of a batch therefore requires analytical confirmation by inductively coupled plasma mass spectrometry after matrix removal, with lower detection limits for critical elements at or below 0.1 ppb. Some manufacturers also report anionic species by ion chromatography because chloride can initiate pitting on exposed aluminum or tungsten plugs.
The product is formulated from high-purity aprotic solvents and alkanolamines; the exact solvent ratio is proprietary. The amine fraction provides the swelling and scission of the photoresist matrix, while the solvent fraction controls viscosity and wetting. Corrosion inhibitors are added to protect aluminum and copper lines from electrochemical attack. That package is not sufficient to define the Electronic/EL grade; the same package can be filled as technical grade if the product is not handled under controlled contamination conditions. Packaging and handling are therefore part of the grade. Materials are typically filled in ISO Class 5 or better cleanrooms under ISO 14644-1:2015, using final filtration through 0.05–0.2 µm membrane filters. Equipment rinse water is controlled to ASTM D5127-13 specifications. A single lot filled in an uncontrolled environment can show sodium spikes above 50 ppb even if the bulk liquid was acceptable.
| Release parameter | Electronic/EL grade typical limit | Analytical technique |
|---|---|---|
| Sodium (Na) | ≤ 10 ppb | ICP-MS |
| Potassium (K) | ≤ 10 ppb | ICP-MS |
| Iron (Fe) | ≤ 5 ppb | ICP-MS |
| Copper (Cu) | ≤ 5 ppb | ICP-MS |
| Chloride (Cl⁻) | ≤ 50 ppb | Ion chromatography |
| Particles ≥ 0.5 µm | ≤ 25 mL⁻¹ | Laser particle counting |
| Cleanroom filling environment | ISO Class 5 | ISO 14644-1:2015 |
In immersion tooling, the bath is commonly contained in a fluoropolymer-lined or quartz vessel. Wafer carriers are processed at bath temperatures between 70 °C and 90 °C, with the specific setpoint determined by the resist system. Temperature control at ± 2 °C is required because dissolution rate follows an Arrhenius-like dependence. For a standard DNQ/novolac positive resist of 1.0–1.5 µm thickness, a 5 °C increase can shorten clear time by roughly 40%, while operation above 90 °C may consume the aluminum inhibitor and produce metal attack. Production baths are therefore fitted with heat exchangers and nitrogen blankets, and the recirculation loop includes 0.1–0.2 µm PTFE filters to remove stripped resin and particles.
Bath life is usually limited by resist loading. In high-volume immersion processes, the bath is replaced or recharged when dissolved resist reaches 10–15 g/L. Beyond that range, stripped novolac resin can redeposit on wafer surfaces, increasing haze and post-rinse particle counts. Production immersion systems with high-throughput operation can exhibit particle counts on dummy oxide wafers above 20 mL⁻¹ within days if bath loading is not controlled. The electronic/EL grade does not eliminate this effect; it reduces the initial particle background so that end-of-life detection is not masked by incoming contamination.
Spray processing imposes additional constraints. Single-wafer chambers deliver heated stripper at 1.0–2.5 L/min through fan or pencil nozzles. The mechanical force helps remove the cross-linked outer skin formed by ion implantation or aggressive dry etching. However, excessive surfactant or moisture can create foam in the chemical drain line, causing pressure fluctuations. Qualification therefore includes dynamic foaming tests and particle generation tests using blank wafers. The product is also filtered at point of dispense through 0.05–0.2 µm filters to avoid nozzle clogging.
Positive photoresist after high-dose implantation may present a carbonized or graphitized outer shell that is resistant to wet stripping. In production flows with implant dose above 5×1015 ions/cm², a partial oxygen plasma ash is often inserted before the wet bath. Below that dose, the electronic/EL grade stripper can typically remove the implant-hardened resist without dry assistance, but the process window depends on resist thickness, implant species, and thermal history. Published data for this specific product configuration is limited; end users commonly determine the threshold by patterned wafer evaluations rather than by relying on a universal dose limit.
Aluminum and copper compatibility is governed by inhibitor depletion and dissolved oxygen. Copper pitting can occur when dissolved oxygen exceeds 1 ppm in a hot amine bath. Nitrogen sparging before processing patterned copper wafers reduces the corrosion potential. Aluminum is protected by phenolic or gallate-type inhibitors; however, the protection window is finite. If the inhibitor concentration falls below the process target due to drag-out or thermal degradation, etching of exposed aluminum can occur within minutes at 80 °C. Production titration of active inhibitor is therefore used to maintain the bath within its qualified range.
Porous low-k dielectric compatibility is evaluated because small polar solvents can penetrate interconnected pores. After drying, capillary collapse can increase k-value and reduce cohesive strength. The qualification procedure typically includes mercury-probe capacitance measurements, Fourier-transform infrared spectroscopy for Si-CH₃ retention, and adhesion tape testing. These are not routine for general-purpose strippers. The electronic/EL grade reduces risk because it is free of gross residual water and high concentrations of alkali ions that can be trapped in pores, but it does not guarantee compatibility with every low-k material or integration scheme.
| Attribute | Technical grade | Semiconductor grade | Electronic/EL grade |
|---|---|---|---|
| Trace metals per element | ≤ 1 ppm | ≤ 100 ppb | ≤ 10 ppb |
| Particles ≥ 0.5 µm | Not specified | ≤ 100 particles/mL | ≤ 25 particles/mL |
| Packaging environment | Uncontrolled | Controlled | ISO Class 5 or better per ISO 14644-1:2015 |
| Certification | Limited | Lot report | Full lot-specific certificate of analysis |
| Application | Bench cleaning | Research or wafer reclaim | Production post-etch strip |
Wet stripping becomes the preferred process when the exposed dielectric is sensitive to ultraviolet radiation or charged-particle damage. Plasma ashing can remove photoresist at high rate but can also densify the top layer of a porous low-k film, increase k-value, and induce surface roughness. In contrast, a wet electronic/EL grade stripper removes resist through chemical interaction without ion bombardment. The trade-off is that wet removal of heavily crusted resist is slower. Process engineers therefore use the wet stripper as a complete strip for mild resist modifications and as a post-ash residual cleaner for severe crust. When plasma ashing is unavoidable, the wet chemistry removes post-ash residues and inorganic salts left behind.
The stripper is also used after reactive ion etch of aluminum and copper lines. In these applications, it must dissolve not only the remaining photoresist but also etch by-products and sidewall polymers. The alkanolamine component assists in breaking polymer-metal adhesion, while the solvent fraction carries the dissolved organics away from the wafer. Corrosion inhibitors passivate exposed metal surfaces during the hot immersion or spray step. This is a process function that cannot be met by an electronic-grade solvent alone.
Compared with older N-methyl-2-pyrrolidone-based removers, many electronic/EL grade formulations are NMP-free or contain less than 0.3% NMP, aligning with the restriction under REACH Regulation (EC) No 1907/2006, Annex XVII. The substitution of NMP by dimethyl sulfoxide or sulfolane can reduce regulatory burden but may alter evaporation rate and bath life. The choice of solvent package is therefore a process qualification variable rather than a simple drop-in replacement. Products also differ in amine aggressiveness; a formulation designed for aluminum may be too aggressive for copper, and a copper-compatible formulation may require longer strip time on thick novolac resists. Selection is made by patterned test vehicle, not by seller claims.
The electronic/EL grade product is not suitable for all resist types. Negative photoresists and electron-beam resists that have undergone crosslinking beyond the normal positive-resist threshold may not be removed completely, and the use of this product without an ashing step can leave organic residues. High-dose ion implanted positive resists can require a partial ash before wet treatment. In addition, the product should not be mixed with strong oxidizers or water-rich developers, because the addition of water can accelerate hydrolysis of amide solvents and reduce inhibitor effectiveness. Waste bath from this product is classified as organic hazardous waste in most jurisdictions and is managed through approved solvent waste channels.
