| HS Code | 190361 |
| Chemical Formula | CH3Cl |
| Molecular Weight | 50.49 g/mol |
| Cas Number | 74-87-3 |
| Appearance | Colorless liquefied gas |
| Purity | ≥99.99% (electronic/EL grade) |
| Boiling Point | -24.2 °C |
| Melting Point | -97.7 °C |
| Liquid Density | 0.915 g/cm3 at 20 °C |
| Vapor Pressure | 4.9 atm at 20 °C (approximate) |
| Solubility | Slightly soluble in water; soluble in acetone, alcohol, benzene, and ether |
| Specific Gravity | 1.78 (vs air) |
| Molecular Dipole Moment | 1.89 D |
As an accredited Methyl Chloride Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in a 200 g stainless steel lecture cylinder with a high-integrity valve, Methyl Chloride Electronic/EL Grade delivers semiconductor-grade purity. |
| Container Loading (20′ FCL) | One 20′ FCL container loaded with Electronic/EL Grade Methyl Chloride, high-purity, packaged safely for transport. |
| Shipping | Methyl Chloride Electronic/EL Grade ships as a liquefied flammable gas under UN1063 in DOT-approved high-pressure cylinders. Proper hazard class 2.1 labels, direction signs, and leakage checks are required. Shipments must meet DOT/TDG/ADR regulations, avoid oxidizers, and be secured upright with pressure-relief and valve protection in place. |
| Storage | Methyl Chloride Electronic/EL Grade should be stored as a liquefied gas in approved, grounded pressure cylinders, away from heat, sparks, and open flames. Keep containers tightly sealed in a cool, dry, well-ventilated area, protected from moisture and direct sunlight. Segregate from oxidizers and reactive metals. Use proper labeling and leak detection. |
| Shelf Life | Methyl Chloride Electronic/EL Grade: shelf life is 12 months from production when stored in sealed containers under specified conditions. |
In electron cyclotron resonance and inductively coupled plasma etch modules configured for indium phosphide ridge-waveguide definition and gallium arsenide heterojunction bipolar transistor emitter mesa exposure, electronic-grade methyl chloride is metered as the chlorine-bearing feed gas in argon-diluted plasma chemistries. The blending envelope reported across production lines spans 18–32 vol% CH3Cl in argon or helium, with total mass flow between 35 sccm and 75 sccm, process chamber pressure held at 2–10 mTorr, and platen temperature maintained between 25°C and 80°C to reduce preferential indium desorption and photoresist reticulation. Under forward ICP power of 300–800 W and RF bias power of 40–120 W, the plasma dissociates CH3Cl into CH3+, CH2Cl+, Cl+, and neutral methyl fragments. The methyl radical pathway forms volatile trimethylindium and trimethylphosphine, while the chlorine pathway forms indium chloride and phosphorus trichloride, enabling anisotropic removal with lower mechanical damage than pure argon sputtering. Production-scale failure modes observed on 100–150 mm wafer lines include methyl radical depletion at high RF bias, producing sidewall notching at the ridge base, and moisture intrusion above 0.2 ppmv in the gas manifold, which shifts etch rate by more than 10% and increases chlorine residue on mask surfaces. Gas distribution for this application is leak-checked according to SEMI F1 integrity procedures, exhaust abatement is verified against SEMI S6 ventilation criteria, and the process bay is controlled to ISO 14644-1:2015, Class 5. Downstream products fabricated from such etched stacks include InP distributed-feedback lasers, electro-absorption modulators, p-i-n photodiodes, monolithically integrated photonic circuits, gallium arsenide heterojunction bipolar transistor wafers, and high-electron-mobility transistor gate-recessed epi wafers. Published data for the exact methyl chloride purity limits in this specific etch configuration is limited; the acceptance profile is normally set by the etch-tool supplier and end-user process qualification rather than by a single public standard.
Synthesis of tetramethylammonium hydroxide from electronic-grade methyl chloride begins with pressure-driven liquid-phase quaternization of trimethylamine in methanol. The molar feed is maintained at 1.00 mol trimethylamine to 1.05–1.10 mol methyl chloride, with reactor temperature held between 30°C and 60°C and reactor pressure between 0.2 MPa and 0.5 MPa in a liquid-filled plug-flow reactor. The excess methyl chloride of 5–10 mol% is applied to drive amine conversion above 99% and to prevent residual trimethylamine from entering the final developer. The resulting tetramethylammonium chloride brine is purified by solvent stripping, ion exchange or bipolar electrodialysis, activated-carbon adsorption for organic residue removal, and final filtration at 0.1 µm or tighter. The release specification for the developer intermediate is established against SEMI C25 tetramethylammonium hydroxide criteria, with chloride held below 0.1 ppm, transition metals controlled below 10 ppb by ICP-MS, and particle counts evaluated as a function of lithographic node rather than as a single universal threshold. Process water used in dilution and washing meets ASTM D5127-13(2020) electronic-grade water requirements. The principal downstream product is 2.38 wt% tetramethylammonium hydroxide aqueous developer used in 193 nm ArF and 248 nm KrF positive-tone photoresist development, post-etch residue removal blends, and buffered anisotropic silicon etch formulations. Batch-to-batch variation in chloride derived from unreacted methyl chloride is the dominant release risk when electrodialysis current efficiency falls below 70%, and the chloride level is therefore monitored by ion chromatography at final filling rather than by reactor sampling alone.
| Parameter | Control window | Method or standard |
|---|---|---|
| Assay | 2.38 wt% ± 0.02 | SEMI C25 |
| Chloride | ≤0.1 ppm | Ion chromatography |
| Transition metals | ≤10 ppb | ICP-MS |
| Particles ≥0.2 µm | ≤20 counts/mL | Laser particle counting |
At fluidised-bed direct-synthesis units that convert metallurgical-grade silicon and electronic-grade methyl chloride into methylchlorosilane intermediates, the feed gas is injected through a distributor plate into a copper-catalysed silicon contact mass maintained at 270–310°C and 1.5–2.5 bar. The contact mass contains copper at 0.8–2.0 wt%, zinc at 0.2–1.0 wt%, and tin or antimony promoters below 0.5 wt% as selectivity modifiers; the methyl chloride partial pressure is adjusted to favour dimethyldichlorosilane formation over methyltrichlorosilane. Higher methyl chloride excess and elevated temperature shift selectivity toward trichlorosilane and tetrachlorosilane fractions, so the production line controls catalyst lifetime, reactor throughput, and downstream monomer distribution simultaneously. The crude product mixture contains primarily dimethyldichlorosilane, methyltrichlorosilane, trimethylchlorosilane, and low-boiling hydrocarbons; separation occurs in pressure distillation columns operated below the decomposition thresholds of the chlorosilane fraction. The electronic-grade feed specification reduces metallic and moisture impurities that would otherwise deactivate the copper catalyst or hydrolyse chlorosilanes prematurely in distillation overheads. Process safety is defined by reactor design alignment with pressure equipment regulations, REACH registration obligations for chlorosilane intermediates under (EC) No 1907/2006, and closed-loop sampling to limit methyl chloride and methylchlorosilane exposure. The distilled methylchlorosilanes are subsequently hydrolysed or converted into siloxane polymers, adhesion promoters, surface modifiers, and chemical vapour deposition precursors used in wafer-level packaging, underfill-compatible coatings, high-density interconnect laminates, and optoelectronic device encapsulation. Terminal product types include electronic-grade polydimethylsiloxane fluids, phenyl-modified silicone encapsulants, silane coupling agents for epoxy-copper adhesion, and low-k dielectric precursors processed in chemical vapour deposition tools.
Electronic-grade methyl chloride functions as the methylating agent in pressure slurry methylation of alkali cellulose for low-ash methyl cellulose binders used in ceramic green tape casting for multilayer ceramic capacitors. The reaction is charged with methyl chloride at 1.5–2.0 mol per anhydroglucose unit, sodium hydroxide at 0.8–1.2 molar equivalents relative to the cellulose hydroxyl pool, and an organic diluent such as toluene or 2-propanol to suspend the partially swollen cellulose. The pressure vessel is held between 55°C and 85°C at a corresponding gauge pressure of 0.7–1.5 MPa; higher temperature reduces viscosity but increases glycol ether by-product formation, while lower temperature leaves residual sodium chloride in the polymer matrix. After methylation, the slurry is neutralised with acetic acid, washed with aqueous methanol until chloride and sodium ions fall below the ash limit, dried under vacuum, and milled to a controlled particle size. The binder used in ceramic tape casting is typically formulated at 5–10 wt% in aqueous or solvent-based ceramic slurries alongside barium titanate and polyvinyl butyral. The critical impurity limit is total ash below 0.05 wt% determined by ASTM D5630, because residual sodium or chloride increases dielectric loss and reduces insulation resistance in the fired ceramic. Compliance for the finished multilayer ceramic capacitor is assessed under IEC 60384-1:2021 generic capacitor requirements and AEC-Q200 for automotive-grade qualification. Downstream terminal products include X7R and C0G multilayer ceramic capacitors, high-frequency class-I ceramic capacitors for RF modules, and green-sheet-derived integrated passive components for semiconductor packaging. Published data for the exact methyl chloride purity required in the methylation reactor is limited; binder manufacturers establish in-house limits based on residual metal levels rather than a public standard.
In anion-exchange membrane lines for alkaline water electrolysis, electronic-grade methyl chloride is used to quaternise tertiary amine functional groups on polymer backbones, converting them to quaternary ammonium chloride moieties before final hydroxide exchange. Methyl chloride is fed at 1.05–1.15 mol per tertiary amine equivalent, with reaction temperature held at 40–70°C and pressure between 0.3 MPa and 0.8 MPa in a solvent-swollen polymer solution. The excess methylating agent is required to achieve a quaternisation degree above 95% because residual tertiary amine groups reduce anion transport and membrane conductivity. After methylation, unreacted methyl chloride is stripped under vacuum and recovered, and the polymer is precipitated, washed, and cast into membranes of 20–60 µm thickness. The quaternary ammonium membranes show hydroxide conductivity in the range of 60–120 mS cm⁻¹ at 80°C when measured with four-probe impedance spectroscopy; values below 50 mS cm⁻¹ generally indicate incomplete quaternisation or residual chloride contamination. Compliance testing for the electrochemical device is established according to IEC 62282-2 fuel cell module test methods and ISO 14644-1:2015 cleanroom assembly environment criteria. Terminal products include anion-exchange membrane electrolyser cells, alkaline fuel cell stacks, and redox flow battery membrane separators. A production-scale failure documented in quaternisation reactors is gel-particle formation when methyl chloride is charged faster than 0.3 mol h⁻¹ per litre of polymer solution, which produces local non-uniform substitution. Published data for the exact electronic-grade methyl chloride acceptance limits in this application remains fragmented, and membrane fabricators typically require moisture below 5 ppmw to prevent polymer neutralisation shifts.
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Chloromethane electronic/EL grade (CAS 74-87-3, EINECS 200-817-4, UN 1063) is a liquefied flammable gas stored under its own vapour pressure. The molecule has a molar mass of 50.49 g mol⁻¹ and a normal boiling point of -24.2 °C at 101.3 kPa. In commercial use, the term “electronic grade” or “EL grade” is not a single industry model number; supplier designations such as “CH₃Cl EL 5N” or “Methyl Chloride Electronic UHP” are catalogue terms, and the binding product definition is the certificate of analysis together with the cylinder preparation class. The product is specified when a methylating agent or chlorine-containing precursor must not introduce transition metals, moisture, sulfur compounds, or non-volatile residue into catalytic or thin-film processes. Because liquid-phase impurities can accumulate during transport, the grade is controlled by package surface quality, vapour-phase analysis, and batch traceability rather than by distillation alone.
Chloromethane has no universal model designation such as a SEMI number. Certificates may carry supplier-specific strings that combine the molecule, grade, and purity class, but a purchasing specification is more reliable when assay and impurity ceilings are listed directly. Electronic/EL material is commonly supplied with a vapour-phase assay not less than 99.99%; tighter supply chains may request 99.999% for catalyst-critical operations. The analytical basis is normally gas chromatography with a pulsed-discharge helium ionisation detector, and calibration gas mixtures are prepared in accordance with ISO 6142 or an equivalent gravimetric method. Assay alone is insufficient because moisture and metallic impurities below the gas-chromatography detection limit can still affect downstream process performance.
| Parameter | Typical Electronic/EL Limit | Analytical Basis |
|---|---|---|
| Vapour-phase assay | ≥ 99.99% to ≥ 99.999% | GC-PDHID |
| Moisture (H₂O) | ≤ 10 ppmv | QCM or CRDS |
| Oxygen (O₂) | ≤ 5 ppmv | GC-DID |
| Total metals | ≤ 10 ppbw per element | Impingement followed by ICP-MS |
| Acidity as HCl | ≤ 1 ppmw | Aqueous impingement/IC |
| Non-volatile residue | ≤ 10 ppmw | Gravimetric after controlled evaporation |
The limits shown are representative order-of-magnitude values. Individual supplier certificates may differ based on cylinder size, detection limits, and the target downstream process. The moisture and acidity ceilings are coupled because hydrolysis of chloromethane to methanol and hydrochloric acid is accelerated by free water and by storage at elevated temperature. In low-pressure vapour delivery, the resulting acid can corrode stainless steel supply lines if moisture is not held below the specified ceiling.
Electronic/EL grade methyl chloride is consumed mainly as a high-purity methylating agent in the copper-catalysed direct synthesis of methylchlorosilanes, including dimethyldichlorosilane and methyltrichlorosilane, which are distilled into precursors for silicon carbide chemical vapour deposition and organosilicate glass films. In a fluidised-bed reactor operated at 250 °C to 300 °C with silicon powder and a copper catalyst, methyl chloride vapour reacts at elevated pressure. Iron, copper, water, and oxygenates in the feed can shift selectivity away from dimethyldichlorosilane and can accelerate catalyst sintering. Electronic/EL grade feed is specified to reduce these catalyst poisons and to prevent carryover of heavy metals into the methylchlorosilane fraction. Direct high-volume semiconductor etch use of methyl chloride is not widely documented in public literature; published data for this specific configuration is limited. Where electronic-grade organosilanes are the product, the distillation train after the Rochow reactor does not correct metallic impurities once they are entrained as chloride-ligand complexes.
Moisture is the most tightly controlled impurity in electronic/EL methyl chloride because it hydrolyses the molecule to methanol and hydrochloric acid during storage. In a cylinder with liquid-phase water accumulation, the acid partitions between liquid and vapour phases, producing an acidic vapour that is not fully removed by ordinary coalescing filters. Metallic impurities such as iron, nickel, chromium, sodium, potassium, calcium, magnesium, zinc, and copper are typically reported as a panel rather than as a single total metals value. The collection method matters because direct gas sampling into an ICP-MS introduces transport losses, whereas impingement in dilute nitric acid followed by ICP-MS quantifies the acid-soluble fraction. Sulfur compounds and non-condensable gases are also controlled in some purchase specifications, although exact limits should be obtained from the certificate of analysis because no unified global standard for electronic/EL methyl chloride exists.
Because chloromethane is a flammable gas, cylinders must be stored away from oxidising gases and ignition sources; lower and upper flammability limits in air are approximately 8.1 vol% and 17.4 vol%, and the autoignition temperature is about 632 °C. Electronic/EL packaging commonly uses electropolished stainless steel cylinders with metal diaphragm or PCTFE-seated valves, but the transport class remains UN 1063, Class 2.1. The gas is incompatible with powdered aluminium, magnesium, and zinc, and with strong bases. Commodity-grade brass regulators or copper tubing should not be used where trace metal release or flammability-relevant mechanical failure may occur. Stainless steel or Monel regulator bodies with purgeable dead volumes are preferred. The product is not a pharmaceutical, food, or drug-grade material; additional requirements such as GMP part 211 or ICH Q3D would apply if methyl chloride is used in an API-related alkylation step.
Particulate control becomes a requirement when the gas is vaporised into a cleanroom distribution system or when downstream reactors contain fixed catalyst beds. In those cases, the cylinder is not simply filled with high-purity product; it is subjected to hot nitrogen purging at 60 °C to 80 °C, vacuum cycling below 20 Pa, and product-vapour passivation before final fill. The passivation step is intended to displace adsorbed moisture and to convert residual surface alkalis into less mobile chloride salts. The vacuum and purge sequence can extend cylinder turnaround time by a factor of two to three compared with commodity chloromethane filling. On a production manifold, the rate-limiting operation is therefore the preparation and analytical quarantine of cylinders, not the distillation of methyl chloride itself. This is a practical reason for the price and lead-time difference between electronic/EL and standard chloromethane: the product value lies in package surface quality and analytical traceability, not in a separate molecular grade.
Typical package sizes for electronic/EL methyl chloride range from 10 L lecture bottles to 440 L ISO containers. Smaller cylinders are more sensitive to surface-to-volume effects and moisture release, so their certificates may show different moisture performance than large packs. The specification is applied after a cylinder conditioning period; residual moisture in valve dead space is removed by purge cycles before sampling. In semiconductor-related supply chains, a two-stage stainless steel regulator with a purgeable pigtail of 316L stainless steel and metal gasket face seal is standard. Polymer hose is avoided because hydrocarbon plasticisers can outgas into the vapour stream.
The grade comparison below is based on typical supplier certificates for technical, chemical-pure, and electronic/EL chloromethane. Values for lower-purity grades are not regulated by a single standard and may vary widely; the table should be read as an order-of-magnitude guide, not as a purchase specification.
| Comparison Parameter | Technical Grade | Chemical-Pure / High-Purity | Electronic/EL Grade |
|---|---|---|---|
| Assay | ≥ 99.5% | ≥ 99.9% | ≥ 99.99% or 99.999% |
| Moisture | Often not specified | ≤ 50 ppmv typical | ≤ 10 ppmv |
| Total metals | Not specified | ≤ 1 ppmw total | ≤ 10 ppbw per element |
| Acidity as HCl | May exceed 10 ppmw | ≤ 5 ppmw typical | ≤ 1 ppmw |
| Non-volatile residue | Not specified | ≤ 50 ppmw typical | ≤ 10 ppmw |
| Cylinder/package | Carbon steel | Carbon or stainless steel | Electropolished stainless steel |
| Analytical certificate | Basic COA | Standard COA | Full COA with ICP-MS metal panel |
The difference between electronic/EL and technical methyl chloride is therefore not simply the assay value; it is the change in package surface, analytical coverage, and impurity ceilings. A lower-purity product that meets the same assay by gas chromatography may still carry dissolved metals or non-volatile residues that are invisible to the vapour-phase assay. For this reason, electronic/EL material should be compared only on certificates that list the same analytical methods, detection limits, and cylinder preparation history. If a supplier certificate does not identify moisture, acidity, or metals methods, it cannot be assumed that the material meets electronic-grade requirements.
The quality of electronic/EL chloromethane is inseparable from the cylinder preparation procedure. Electropolished stainless steel reduces surface area and adsorbed water compared with carbon steel, but it does not eliminate the need for passivation. A fill plant following electronic-grade practice may use hot nitrogen purge at 60 °C to 80 °C, evacuation to less than 20 Pa, and a product-vapour hold before final fill; the sequence is batch-recorded and verified by pressure-rise testing or moisture monitoring. Elastomer and seat materials are selected for low moisture regain; metal diaphragm valves are preferred where leak rates below 1 × 10⁻⁹ mbar L s⁻¹ are required. These controls reduce the release of trace impurities during storage and vapour withdrawal, which is particularly important for low-flow semiconductor or laboratory applications where cylinder residence time can last several months.
Analytical laboratories issuing certificates for electronic/EL methyl chloride should operate under ISO 17025 for the relevant gas analysis methods, and fill plants typically maintain ISO 9001 or equivalent quality management. The substance is registered under REACH where applicable; users in the European Economic Area must apply the registration dossier and exposure scenarios for bulk handling of a flammable liquefied gas. RoHS obligations do not apply to process gases that do not become part of electronic equipment, but the material may be subject to national chemical inventory reporting. Electronic/EL packaging does not alter the hazardous goods classification.
Electronic/EL methyl chloride is specified for high-purity methylation, electronic-grade organosilane synthesis, and other catalytic processes where iron, copper, water, and acidity must be controlled at ppb-to-ppm levels. It is not required for large-scale silicone production where technical-grade purity is acceptable after distillation; in those operations, lower-purity feed is often selected because the distillation train removes volatile impurities and the process tolerance for metals is wider. However, if the downstream distillation train is fabricated from carbon steel, technical-grade methyl chloride may contribute corrosion products that increase maintenance frequencies and reduce catalyst selectivity over repeated campaigns. The choice between technical and electronic/EL material should be based on a mass balance of the downstream purification train, catalyst poison tolerance, and the analytical detection limits of the specified metals panel.
