| HS Code | 548526 |
| Product Name | Negative Photoresist Stripper Electronic/EL Grade |
| Chemical Type | Solvent blend of organic amines and glycol ethers |
| Grade | Electronic/EL Grade |
| Appearance | Clear colorless liquid |
| Odor | Mild amine-like odor |
| Density | 0.97 g/cm3 at 20°C |
| Specific Gravity | 0.97 at 20°C / 20°C |
| Viscosity | 2.5 cP at 20°C |
| Boiling Point | 160°C |
| Flash Point | 57°C (closed cup) |
| Vapor Pressure | 0.2 mmHg at 20°C |
| Solubility In Water | Partially to fully miscible depending on formulation |
| Ph | 10.5 (5% aqueous solution) |
| Metal Impurities | Each metal less than 1 ppm |
| Particle Count | Filtered to 0.2 µm |
| Shelf Life | 12 months from date of manufacture |
As an accredited Negative 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-liter and 4-liter HDPE bottles with secure seals, labeled for electronic/EL grade purity and safe handling. |
| Container Loading (20′ FCL) | 20′ FCL loaded with Negative Photoresist Stripper (Electronic/EL Grade), secured in suitable packaging, ensuring leak-proof containment and safe transport per chemical regulations. |
| Shipping | Ship as hazardous material in UN-approved, tightly sealed containers, with proper corrosion/flammability labeling and hazmat documentation. Use ground transport only, avoiding moisture, heat, and direct sunlight. Electronic/EL grade requires clean, non-reactive packaging to preserve purity. Licensed carriers must handle shipment with appropriate spill response procedures. |
| Storage | Store in a clean, dry, well-ventilated area away from heat, direct sunlight, and ignition sources. Keep the container tightly sealed to prevent moisture contamination and evaporation. Store away from incompatible materials such as oxidizers and strong acids. Use original or approved containers, and maintain stable ambient temperatures. Ensure secondary containment and inspect regularly for leaks or damage. |
| Shelf Life | Shelf life is typically 12 months from manufacture when stored unopened at room temperature in original container. |
In 300 mm front-end logic and memory flows, negative-tone chemically amplified resist used for high-dose ion implantation masking forms a carbonized crust that remains after dry ashing; the wet stripper therefore operates on the residual bulk resist and organometallic residues without attacking exposed silicon nitride, silicon oxide, and cobalt or copper contact surfaces. The bath is made up at 90–100 vol% as-supplied EL-grade negative photoresist stripper, with 0–10 vol% electronic-grade N-methyl-2-pyrrolidone or dimethyl sulfoxide permitted only when kinematic viscosity exceeds 12 cP at 70 °C on a cone-and-plate viscometer. On a production wet bench, the bath is recirculated through 0.1 µm polytetrafluoroethylene filters and megasonic agitation is held at 40–80 kHz for 10–20 min at 70–90 °C; single-wafer spray processors use 150–300 rpm puddle steps followed by quick-dump deionized-water rinse and isopropyl alcohol vapor dry. The compliance framework for this front-end application is SEMI C7-0816 qualification for photoresist stripper and residue remover and ISO 14644-1:2015 Class 4 handling; certificates of analysis are expected to report sodium, potassium, iron, and calcium below 25 ppb each by inductively coupled plasma mass spectrometry and particle counts for ≥0.2 µm below 100 particles/mL. A known operational boundary is low-k dielectric compatibility: if the bath pH at temperature rises above 9.5, SiOC films with 20–30% porosity can show k-value increases of 0.1–0.2, leading to via RC delay shift. End products are 28–45 nm half-pitch logic wafers, DRAM/NAND wafers with copper/low-k back-end-of-line metallization, and discrete power-management wafers retaining thick implant masks.
Copper pillar and Sn-Ag bump flows leave negative resist in high-aspect-ratio microbump cavities where fluid exchange at the cavity floor is diffusion-limited; the stripper must remove polymer from 20–40 µm pillar gaps without etching the copper seed layer or roughening Sn-Ag surfaces. For copper pillar and redistribution-layer semi-additive processes, the bath is formulated at 85–100 vol% EL-grade concentrate with 5–15 vol% electronic-grade cosolvent, at 65–75 °C for 10–20 min; Sn-Ag bump lines use 80–100 vol% active product at 55–65 °C for 8–15 min because silver sulfidation and haze increase sharply above 70 °C in amine-bearing baths. Production-scale equipment is typically a recirculating spray or puddle processor with 1–2 µm filtration, nitrogen blanket at 0.4–0.8 m³/h, and a two-stage rinse sequence of room-temperature deionized water and 0.5–1.0 wt% citric acid neutralization, followed by hot-air dry. The governing compliance set includes RoHS Directive 2011/65/EU Annex II and IEC 62321-7-1:2015 for extraction testing of final package materials; residues must not add lead, cadmium, mercury, or hexavalent chromium above 10 ppm at the homogeneous material level. The limiting acceptance parameter is copper pillar undercut: when Cu etch rate exceeds 5 Å/min at process temperature or rinse delay exceeds 60 s, bump shear force distribution widens and brittle fracture at the Ni₃Sn₄ intermetallic layer becomes more frequent. End product types include wafer-level chip-scale packages, fan-out wafer-level packages, and flip-chip ball grid array bumped wafers for mobile processors and high-density interconnect modules.
| Packaging configuration | Bath ratio (electronic/EL grade) | Process temperature | Maximum immersion time | Acceptance criterion |
|---|---|---|---|---|
| 20–40 µm copper pillar resist removal | 85–100 vol% | 65–75 °C | 10–20 min | Cu etch rate ≤ 5 Å/min; no pillar undercut > 0.5 µm |
| Sn-Ag bump resist removal | 80–100 vol% | 55–65 °C | 8–15 min | Ag reflectance loss < 1%; no sulfur residue |
| Fan-out RDL via clearing | 70–90 vol% | 50–60 °C | 5–12 min | PI adhesion loss ≤ 5%; residue < 0.10 µm/cm² |
| TSV liner protection strip | 85–100 vol% | 60–70 °C | 8–18 min | No TiN liner thinning > 10 Å |
In Gen 8.5 and Gen 10.5 color filter lines, negative-tone photoresists for black matrix and RGB color filter layers are stripped during rework of misalignment or particle-defect panels; the bath must dissolve acrylic/epoxy resist without attacking the underlying chromium oxide black matrix or indium tin oxide pixel electrodes. The stripper bath is prepared at 60–80 vol% EL-grade product in deionized water or a solvent blend, with the remaining 20–40 vol% being electronic-grade cosolvent adjusted to maintain a pH of 8.0–10.2 and surface tension below 35 mN/m. Horizontal spray equipment operates at 2–5 kg/cm² impingement pressure, 40–55 °C bath temperature, and 60–180 s residence time, with 0.5 µm filter recirculation and continuous pH/turbidity monitoring to prevent particle re-deposition on black matrix edges. Standards compliance in display lithography is driven by ISO 14644-1:2015 Class 5 cleanroom operation, SEMI C7-0816 for chemical qualification, and REACH Regulation (EC) No 1907/2006 Annex XVII restrictions on N-methyl-2-pyrrolidone handling in EU production sites. A process boundary observed on display lines is chromium oxide attack: at pH above 10.2 or temperature above 55 °C, the black matrix edge roughness increases beyond 0.3 µm, resulting in visible mura after RGB reprinting. End products are LCD and OLED color filter glass panels for mobile, monitor, and television applications.
High-aspect-ratio negative resist molds in inertial sensors and microphones are stripped only after electroplating or vapor-phase metal deposition, when polymeric residue inside 5–20 µm wide trenches causes release failure and damped resonance in the final device. The stripping sequence for MEMS uses a two-stage addition profile: a pre-swell bath at 50–75 vol% EL-grade stripper in high-purity isopropyl alcohol at 35–45 °C for 10–20 min, followed by a dissolution bath at 70–100 vol% active product at 45–60 °C with 20–40 kHz ultrasonic agitation. After stripping, wafers are transferred to a liquid CO₂ dryer; supercritical CO₂ drying at 31.1 °C and 73.8 bar is used because earlier water rinsing would collapse released polysilicon or nickel microstructures through capillary stiction. The relevant compliance set is SEMI F57-0319 for high-purity chemical distribution materials, ISO 14644-1:2015 Class 5 particle control, and RoHS Directive 2011/65/EU for lead-free MEMS assemblies. A critical incompatibility is ultrasonic power above 80 kHz or 100 W/L, which has been associated with fractured comb-drive fingers on production lots; therefore power density is mapped by sacrificial wafer inspection before device batch processing. End product types are three-axis accelerometers, gyroscopes, MEMS microphones, and pressure sensors for automotive and consumer electronics.
Because gallium arsenide, indium phosphide, and gallium nitride wafers use negative resists for electron-beam or spray-coated lift-off of gold-, platinum-, nickel-, and titanium-based gate and contact metallization, the stripper must swell the resist from the sidewall inward without delaminating the metal that will remain on the semiconductor surface. The lift-off bath is formulated at 70–90 vol% EL-grade stripper with 10–30 vol% high-purity isopropanol, held at 40–60 °C for 10–30 min; the lower temperature range applies to gold-germanium or nickel-gold stacks where high-temperature alkaline exposure increases surface roughness above 2 nm Ra. Carrier-mounted wafers are processed in batch immersion vessels with 20–40 kHz ultrasonics, followed by a two-stage rinse of warm high-purity isopropanol and deionized water, with final dry under filtered nitrogen. The application must meet SEMI C7-0816 qualification for trace-metal cleanliness, SEMI F57-0319 for ultrapure chemical distribution compatibility, and RoHS Directive 2011/65/EU for final packaged RF or photonic modules. The operational limit in compound semiconductor lift-off is metal adhesion loss: when bath temperature exceeds 60 °C or ultrasonic energy exceeds 40 kHz on thin 50–100 nm gold layers, the metal edge peel probability increases and die shear force falls below the 2.0 kgf/mm² acceptance floor used in some wafer qualification protocols. End product types are GaAs pHEMT power amplifiers, InP photonic integrated circuits, and GaN high-electron-mobility transistors for RF and data-communication modules.
Ajinomoto build-up film and bismaleimide-triazine laminate substrates for flip-chip CSPs carry 15–35 µm fine-pitch traces, where negative dry film resist must be removed from semi-additive copper with no resin smear, no conductor undercut, and no ionic contamination that would reduce insulation resistance. In horizontal conveyorized equipment, the bath is run at 65–85 vol% EL-grade product with 15–35 vol% deionized water or solvent, maintained at 45–55 °C; spray impingement is set at 2–4 kg/cm² with chemical residence time of 3–8 min, followed by a three-stage countercurrent rinse and forced-air dry. The process is validated against IPC-4101 for base material compatibility, IPC-TM-650 2.3.25 for ionic contamination, and IEC 61249-2-21 for halogen-free substrate requirements when specified; final substrates must meet RoHS Directive 2011/65/EU and may need to satisfy automotive IATF 16949 change-control documentation. A boundary condition monitored on production lines is solder mask or ABF swelling: if water content exceeds 35 vol% or bath pH exceeds 11, surface roughness increases beyond 0.5 µm Ra and downstream electroless copper adhesion becomes non-uniform. End products are flip-chip chip-scale package substrates, system-in-package substrates, and high-density interconnect boards with line/space at or below 15/15 µm.
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Negative Photoresist Stripper Electronic/EL Grade is supplied as a filtered, low-metal, water-rinsable liquid blended to remove cross-linked negative-tone photoresist films, hard-baked edge residues, and post-implant carbonized layers from silicon, thermally grown silicon dioxide, CVD silicon nitride, and copper barrier surfaces. Model EL-NPRS-210 is specified for immersion wet benches equipped with PTFE or quartz recirculating vessels and megasonic transducers in the 950 kHz to 1 MHz range. Model EL-NPRS-215 is a reduced-viscosity variant engineered for dispense nozzles and puddle-process sequences in single-wafer spray tools.
The solvent system is based on a polar aprotic formulation containing N-methyl-2-pyrrolidone, sulfolane, or dimethyl sulfoxide with an alkanolamine activator such as monoethanolamine or diglycolamine. The undiluted product exhibits pH 10.3 to 10.8. The alkanolamine fraction supplies nucleophilic attack at ester and imide cross-link sites formed during negative-tone exposure and hard bake. A low-metal azole-based corrosion-inhibitor package suppresses galvanic attack on copper lines and remains free of ammonia and fluoride to avoid excessive undercutting of titanium nitride and tantalum nitride diffusion barriers.
Typical lot-release data for model EL-NPRS-210 include density at 20 °C of 1.045 g/mL to 1.055 g/mL by ASTM D4052, dynamic viscosity at 25 °C of 3.0 mPa·s to 3.6 mPa·s by ASTM D7042, and water content not exceeding 0.10 wt% by ASTM E203. Metal impurities determined by ICP-MS following closed-vessel acid digestion using EPA Method 3052 with analysis by EPA Method 6020B are controlled to ≤10 ppb for sodium, potassium, iron, calcium, magnesium, and zinc; copper is controlled to ≤5 ppb. The product is filtered through 0.1 µm rated filter cartridges and filled in high-density polyethylene or fluoro-laminated containers under ISO Class 5 microenvironments. Particle counts are maintained at not more than 25 particles/mL for particles at or above 0.5 µm.
The product is miscible with water and isopropyl alcohol. Care must be taken during initial dilution because localized water addition can produce a reversible haze through solvent-water association; the haze clears with agitation. The product is packaged in 1 L, 5 L, and 20 L containers with nitrogen-blanketed closures. Shelf life is 18 months when stored at 5 °C to 25 °C in unopened containers.
Electronic/EL grade is not defined by solvency alone. The differentiating specification is the amount of mobile-ion and transition-metal contamination that remains after volatilization and drying. Reagent-grade solvent blends may contain sodium in the 0.5 ppm to 2 ppm range, whereas front-end wet processing after contact and via etch requires total metal loadings below 50 ppb and individual alkali metals below 10 ppb. Chloride and sulfate residues are limited because they promote pitting on aluminum bond pads and increase oxide charge in gate dielectrics. The product is supplied with a certificate of analysis listing lot-specific values for density, viscosity, water, chloride, sulfate, dissolved metals, and particle counts.
Chloride is controlled to ≤0.10 ppm by ASTM D512. Sulfate is controlled to ≤0.20 ppm by ion chromatography with suppression, following EPA Method 300.1. The sum of amine degradants and high-boiling residue is kept below 0.30 wt% by gravimetric evaporation at 150 °C for 2 h. These limits are tighter than typical technical-grade strippers because residual sulfate and chloride can generate defects during subsequent plating or silicide formation.
| Parameter | Method/Standard | Electronic/EL Grade | Reagent Grade Typical |
|---|---|---|---|
| Density at 20 °C | ASTM D4052 | 1.045–1.055 g/mL | 1.02–1.09 g/mL |
| Dynamic viscosity at 25 °C | ASTM D7042 | 3.0–3.6 mPa·s | 2.5–5.0 mPa·s |
| Water content | ASTM E203 | ≤0.10 wt% | ≤0.50 wt% |
| Sodium | EPA Method 6020B | ≤10 ppb | ≤1,000 ppb |
| Potassium | EPA Method 6020B | ≤10 ppb | ≤500 ppb |
| Iron | EPA Method 6020B | ≤10 ppb | ≤200 ppb |
| Copper | EPA Method 6020B | ≤5 ppb | ≤100 ppb |
| Chloride | ASTM D512 | ≤0.10 ppm | ≤5 ppm |
| Particles at ≥0.5 µm | Laser particle count | ≤25/mL | Not controlled |
The low sodium and potassium limits are especially relevant for gate oxide integrity. Mobile ion contamination above 50 ppb in the liquid phase can shift flatband voltage in MOS capacitors after thermal cycling. Electronic grade therefore requires not only low initial impurity levels but also clean packaging, high-purity raw materials, and leach-resistant container liners. Quality audits include lot-specific particle counts, dissolved metal analysis, and container extractables testing.
In immersion rework of 300 mm wafers, cassettes of 25 wafers are loaded into a PTFE-lined vessel charged with EL-NPRS-210 at 70 °C. Recirculating filtration through 0.2 µm polytetrafluoroethylene cartridges maintains bath cleanliness, and bath life under continuous operation typically ranges from 8 h to 16 h. Endpoint is determined by visual absence of resist fragments after 15 min to 30 min, followed by a 10 min overflow rinse with ultrapure water at 20 °C and nitrogen spin drying. For thick SU-8 films of 25 µm to 100 µm, immersion alone may leave residual scum at the substrate interface; megasonic assist at 950 kHz improves removal by disrupting the swollen boundary layer. Spray processing with EL-NPRS-215 uses puddle dispense cycles of 20 s to 40 s at 65 °C, followed by spin-off at 800 rpm and deionized-water rinse. Methylsilsesquioxane low-k films may show thickness loss above 2% depending on pH and temperature, so compatibility must be verified on production lots before use.
Bath aging is monitored by measuring the refractive index at 589 nm. The product loaded with stripped polymer shows a refractive index increase of approximately 0.005 to 0.020 per 10 g/L polymer. When the bath reaches 10 g/L dissolved resist solids, filtration pressure drop across the 0.2 µm cartridge exceeds 0.15 MPa, and the bath should be drained. Failure to change the bath within this limit may result in re-deposition of suspended organic fragments on wafer bevels and wafer backside surfaces.
The removal mechanism for negative resists differs from positive resists because the exposed film is a three-dimensional cross-linked network. Removal occurs through solvent infiltration into free-volume regions, followed by bond cleavage at cross-link sites and mechanical fragmentation. Swelling ratio, defined as equilibrium thickness increase after 10 min at process temperature, is a useful lot-consistency indicator. For a typical 20 µm cyclized polyisoprene negative resist, thickness increase of 8% to 15% occurs before film rupture. SU-8 epoxy networks tend to exhibit lower equilibrium swelling but require longer attack times at the exposed surface. Surface tension of the product is 36 mN/m to 40 mN/m at 25 °C by ASTM D1331, which supports wetting into 5:1 to 10:1 aspect-ratio trenches. Dynamic viscosity below 4 mPa·s permits penetration into dense via arrays without leaving organic residue at the bottom of high-aspect-ratio structures.
Batch-to-batch variation in amine concentration is controlled within ±0.3 wt% to avoid over-etching of exposed aluminum and to maintain reproducible strip rates. The low-molecular-weight glycol ether fraction reduces activation energy for solvent penetration into partially cured films. The apparent activation energy for stripping fully cross-linked SU-8 in this formulation is reported in supplier technical bulletins as approximately 50 kJ/mol to 70 kJ/mol over the range 50 °C to 80 °C; published data for this specific configuration is limited. This activation energy implies that a 10 °C increase in bath temperature reduces strip time by a factor of roughly 2.
On copper dual-damascene wafers, wet stripping after low-k patterning is constrained by alkaline attack on exposed copper and organic low-k materials. The inhibitor package used in EL-NPRS-210 includes azole-type copper passivating agents that reduce copper etch rate to below 0.5 nm/min at 70 °C for 30 min. Titanium nitride barrier surfaces may show a thin oxide-hydroxide modification layer but no measurable bulk loss by spectroscopic ellipsometry after 30 min. When the stripper is used on aluminum bond pads, exposure should be limited to 10 min at 50 °C because aluminum is amphoteric at pH 10.4. If aluminum pad exposure is unavoidable, a non-amine solvent stripper with pH below 8 is recommended. The product should not be used on unprotected aluminum-copper bond-pad alloys without compatibility testing.
For copper/low-k integration, organic low-k materials with siloxane bonding may absorb the amine component and show k-value shifts. A 30 min immersion at 70 °C can increase dielectric constant by 0.1 to 0.3 in some porous low-k films unless the stripper is diluted to 50 vol% in ultrapure water. Dilution reduces solvent penetration into pores but also lowers strip rate; the user must balance these parameters against defect density requirements.
Acetone, N-methyl-2-pyrrolidone, and positive photoresist stripper blends are generally insufficient for fully cross-linked negative resists because they rely on novolac dissolution rather than covalent bond cleavage. A positive resist strip sequence may soften an unexposed film in 5 min at 25 °C, while the same solvent shows negligible weight loss of a fully cross-linked SU-8 film. Published data for a specific configuration is limited, but typical screening results show less than 5% thickness loss after 10 min at 80 °C with positive resist stripper, whereas the Electronic/EL Grade negative resist stripper removes 90% to 100% of hard-baked SU-8 under the same conditions. The difference arises from the alkanolamine reactive component and selected swelling solvents that cleave ether and ester linkages in the cross-linked matrix.
Technical-grade solvent blends without amine activators may leave carbonized residue after high-dose implant. The product described here is formulated for post-implant residue removal on negative resists, but heavily graphitized surface layers from high-dose arsenic or boron implants above 1 × 1015 ions/cm² may require a 30 s to 60 s oxygen plasma ash step before wet stripping. The use of plasma ash is not required for normal lithography rework films below 300 °C hard bake.
Unlike low-pH or fluoride-containing post-etch residue removers, this product is intentionally free of hydrofluoric acid and fluoride salts. That limits excessive attack on silicon dioxide and low-k dielectrics, but reduces the removal rate of silicate-based residues. When silicate-containing residues are present, a separate fluoride-based cleaning step may be required after resist stripping.
Operational boundaries include storage at 5 °C to 25 °C in sealed containers, use in closed systems with local exhaust ventilation, and pre-use filtration for particle-sensitive applications. The product should not be mixed with hydrogen peroxide, sulfuric acid-peroxide mixtures, or strong oxidizing acids because exothermic decomposition can generate nitrogen oxides and aerosolized organic by-products. Open bath life decreases above 80 °C; continuous heating above 90 °C can darken the bath and form amine-carbonate solids. The product is miscible with water and isopropyl alcohol but may form a reversible haze on initial dilution. High-pressure water injection into undiluted solvent should be avoided to reduce aerosol formation. Waste streams containing the stripper should be handled in accordance with local wastewater permits for organic nitrogen and polar aprotic solvents.
