| HS Code | 501409 |
| Product Name | Carbon Tetrafluoride (CF4) Electronic/EL Grade |
| Chemical Name | Tetrafluoromethane |
| Cas Number | 75-73-0 |
| Molecular Formula | CF4 |
| Molecular Weight | 88.01 g/mol |
| Purity | ≥99.999% |
| Appearance | Colorless gas |
| Odor | Odorless |
| Physical State At 20c | Gas |
| Melting Point | -183.6°C |
| Boiling Point | -127.8°C |
| Critical Temperature | -45.6°C |
| Critical Pressure | 37.5 bar |
| Density At 0c 1atm | 3.93 kg/m³ |
| Vapor Density Relative To Air | 3.03 |
| Solubility In Water | Very slightly soluble |
| Un Number | 1982 |
| Hazard Class | 2.2 (non-flammable, non-toxic gas) |
As an accredited Carbon Tetrafluoride (CF₄) Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Carbon Tetrafluoride (CF₄) Electronic/EL Grade is packaged in high-pressure steel cylinders, with 30 kg net weight per cylinder. |
| Container Loading (20′ FCL) | 20′ FCL: cylinders of electronic-grade Carbon Tetrafluoride (CF₄) securely packed, blocked, and braced for safe transport. |
| Shipping | Ship carbon tetrafluoride (CF₄), Electronic/EL Grade, as a high-pressure compressed gas in DOT-approved cylinders. Proper shipping name: Carbon Tetrafluoride, Compressed; UN1982; Hazard Class 2.2, non-flammable, non-toxic. Protect valves, secure upright, avoid moisture contamination, and use clean, electronics-grade dispensing equipment. |
| Storage | Store Carbon Tetrafluoride (CF₄) Electronic/EL Grade in a secured, upright high-pressure cylinder in a cool, dry, well-ventilated area. Keep away from heat, ignition sources, and oxidizers. Maintain valve protection caps, avoid moisture ingress, and monitor for leaks. Use appropriate gas cabinets and ensure cylinder temperatures remain stable to preserve purity. |
| Shelf Life | Stable for at least 24 months when stored in a sealed cylinder, away from moisture and contaminants. |
In front-end dielectric etch modules, electronic-grade carbon tetrafluoride is metered through mass flow controllers and mixed with oxygen before entering a dual-frequency capacitively coupled plasma reactor. The high-frequency source, typically 13.56 MHz or 60 MHz, controls plasma density; the low-frequency bias, often 2 MHz, modulates ion energy at the wafer surface. For 200 mm thermal oxide and silicon nitride open-area etch, process windows commonly place CF4 flow at 20–50 sccm, O2 at 2–6 sccm, total pressure at 50–200 mTorr, and RF power at 300–700 W. Under these conditions, electron-impact dissociation of CF4 produces CFx radicals and atomic fluorine; oxygen scavenges recombining CF2 and CF3 fragments, shifting the fluorine-to-carbon ratio upward. The volatile products are SiF4 and CO/CO2. Endpoint is monitored by optical emission spectroscopy on the SiF emission band and by process chamber pressure rise. Gas purity conformance is anchored to SEMI C3.22, with moisture and oxygen controlled below 1.0 ppmv and total fluorocarbon homologs below 10 ppmv in common 5N-grade supply contracts. The etched film stack is found in shallow trench isolation, gate sidewall spacers, interlayer dielectric via openings, and passivation contact windows. A process limitation is selectivity to underlying silicon: CF4/O2 etches crystalline silicon when the O2 fraction exceeds roughly 12–15 vol%; therefore, silicon-selective contact etches are formulated with CHF3 or C4F8 additions rather than straight CF4/O2. Published data for exact selectivity at the feature sidewall is tool and photoresist dependent. The terminal products are logic CMOS, analog mixed-signal, and DRAM devices.
| Parameter | Limit | Method |
|---|---|---|
| Moisture | ≤1.0 ppmv | Atmospheric pressure ionization mass spectrometry or FTIR |
| Oxygen | ≤1.0 ppmv | GC-PDHID |
| Nitrogen | ≤5.0 ppmv | GC-PDHID |
| Carbon dioxide | ≤0.5 ppmv | FTIR |
| Carbon monoxide | ≤1.0 ppmv | FTIR |
| Total fluorocarbons | ≤10 ppmv | GC-FID/PDHID |
| Acidity as HF | ≤0.1 ppmw | Ion chromatography after aqueous impinger |
In PECVD and HDP-CVD tools, silicon dioxide, silicon nitride, and oxynitride films deposit on the showerhead, heater pedestal, and chamber walls. A remote plasma source installed upstream of the process chamber dissociates CF4/O2 mixtures at 5–8 kW and 2–6 Torr, delivering fluorine atoms without exposing chamber internals to high-energy ion bombardment. Typical clean recipes use CF4 at 1–3 slm and O2 at 0.5–1.5 slm; clean time is 120–300 s for a 0.5–2.0 µm accumulated film. The etch product stream contains SiF4, CO2, CO, HF, and unreacted CF4. Scrubber systems treat the foreline. Compared with a direct in-situ clean in a capacitively coupled discharge, remote plasma CF4 reduces ion-induced damage to the anodized aluminum chamber body and electrostatic chuck ceramic. The trade-off is lower fluorine utilization at typical source fragmentation efficiencies and longer clean time per micrometer than NF3-based remote clean processes. Process qualification includes particle count after clean below the tool baseline, often ≤50 particles per 150 mm wafer equivalent at 0.09 µm detection threshold, measured by a laser surface scanner. Equipment must comply with SEMI S2 safety guidelines and high-purity gas delivery surface conditions. The resulting operational uptime supports intermetal dielectric, passivation, and hard-mask deposition modules in logic, DRAM, and flash memory flows.
In high-aspect-ratio contact and channel-hole etching for 3D NAND, CF4 serves as the primary fluorine precursor in ICP etching chambers equipped with independent source and bias power. A typical process envelope uses CF4 at 40–100 sccm, Ar at 100–300 sccm, O2 at 5–20 sccm, source power 1500–2500 W, substrate bias 100–400 V, and pressure 5–30 mTorr. The oxygen fraction governs the polymer balance on the sidewall; too little O2 leads to carbon-rich passivation and etch stop, while too much O2 increases bowing and CD enlargement. Through alternating SiO2 and Si3N4 or SiO2 and polysilicon pairs, the fluorine radicals convert silicon species to volatile SiF4, while argon sputter desorbs low-volatility C-N residues. Aspect ratios above 40:1 use pulsed bias to manage charge accumulation at the etch front. Published data for specific 3D NAND stack configurations is limited because stack materials and staircase thicknesses are proprietary. Endpoint for each layer uses OES on SiF or CN emission; pitch between contacts is monitored by scatterometry after partial etch. Gas purity in these chambers is governed by the same SEMI C3.22 CF4 specification, but additional point-of-use purifiers reduce moisture to below 0.1 ppmv. The terminal product is 3D NAND flash memory with stacked wordline layers; the CF4 etch step defines the vertical contacts and channel holes that connect the memory array to peripheral CMOS.
| Downstream tool | CF4/O2 ratio | Pressure range | Primary endpoint signal | Typical etch/clean rate |
|---|---|---|---|---|
| CCP oxide/nitride etcher, 200 mm wafer | 5:1 to 10:1 | 50–200 mTorr | SiF optical emission | 200–500 nm/min |
| Remote plasma PECVD clean | 2:1 to 3:1 | 2–6 Torr | SiF emission or downstream FTIR | 0.5–2.0 µm/120–300 s |
| ICP 3D NAND high-AR etch | 4:1 to 8:1 | 5–30 mTorr | SiF/CN emission ratio | 300–700 nm/min oxide equivalent |
| Large-area TFT display etcher | 3:1 to 6:1 | 100–400 mTorr | SiF emission or optical reflectance | 100–300 nm/min |
| MEMS sacrificial oxide release | 3:1 to 10:1 | 10–100 mTorr | Laser interferometry | 50–200 nm/min |
| PV PECVD remote clean | 2:1 to 3:1 | 2–5 Torr | SiF emission | 0.5–1.5 µm/240–420 s |
In large-area thin-film transistor arrays for liquid-crystal displays, CF4/O2 plasma etches silicon nitride passivation and gate insulator openings on Gen 8.5 or Gen 10.5 glass substrates. Capacitively coupled plasma sources with multiple parallel electrodes operate at 13.56 MHz, with process gas distribution across 2200 mm × 2500 mm or larger carriers. Typical flows are CF4 3–8 slm, O2 0.5–2 slm, pressure 100–400 mTorr, and power density 0.1–0.3 W/cm². The etch target is often a 200–400 nm SiNx layer over thin molybdenum or titanium/aluminum/titanium source-drain metallization. Fluorine-deficient plasma conditions are used when copper interconnects are exposed because free fluorine rapidly forms CuF2 and CuO species that corrode at atmospheric humidity; etch uniformity across the substrate is measured by optical film thickness mapping and must remain within ±10% of the mean. Etch rate for PECVD SiNx under these conditions is typically 100–300 nm/min, depending on RF return loss and gas confinement. The terminal product is a TFT-LCD panel for televisions, monitors, and industrial displays; the CF4 etch step defines the via openings connecting gate and source-drain layers to indium tin oxide pixel electrodes.
For surface-micromachined MEMS devices, CF4/O2 isotropic etching removes sacrificial silicon dioxide layers from beneath polysilicon or silicon structural beams after the overlying mechanical layer is patterned. The process is performed in RIE or ICP tools with CF4 at 15–30 sccm, O2 at 0–5 sccm, chamber pressure 10–100 mTorr, and platen power 50–200 W. Etch rate for PECVD sacrificial oxide is typically 50–200 nm/min, and etch depth is controlled by laser interferometry or timed endpoint. The oxygen fraction is intentionally reduced or eliminated to avoid oxidation of polysilicon; however, pure CF4 can leave fluorocarbon residue on structural sidewalls, requiring a downstream O2 plasma descum. Stiction of released beams after rinsing is avoided by supercritical CO2 drying or vapor HF liquid treatment, not by CF4 plasma. The etch is used for sacrificial oxide thicknesses up to 2 µm; larger gaps require multiple cycles or alternative vapor HF. Compliance with cleanroom particle standards such as ISO 14644-1 and gas purity per SEMI C3.22 is maintained to protect released MEMS structures from particulate contamination. Terminal products include accelerometers, gyroscopes, pressure sensors, inkjet print heads, and RF MEMS switches.
In crystalline-silicon solar cell manufacturing, PECVD of silicon nitride anti-reflective coating deposits SiNx on the wafer carrier, graphite susceptor, and chamber shields after repeated cycles. Remote plasma CF4/O2 cleaning is conducted at 2–5 Torr, with CF4 at 3–5 slm, O2 at 1–2 slm, and remote plasma power at 6–10 kW. Clean time ranges from 240–420 s for 0.5–1.5 µm accumulated nitride thickness. The clean step is initiated before particulate defects exceed the line-specific control limit, often after 4–8 deposition batches. Residual moisture and foreign gases from the gas delivery are controlled to SEMI C3.22 limits because sodium and transition metals from contaminated source gas can diffuse into the anti-reflective layer and reduce minority carrier lifetime. The terminal product is a c-Si solar cell with silicon nitride anti-reflection and passivation coating; the CF4 clean restores chamber emissivity and showerhead conductance without aborting the deposition campaign.
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Carbon tetrafluoride (CF4, CAS 75-73-0) is supplied as a nonflammable, colourless compressed gas with a molar mass of 88.00 g/mol and a normal boiling point of −127.8 °C. The product designated CF4 Electronic/EL, often listed by suppliers as CF4 5N EL or CF4-UHP, is produced by purification of bulk tetrafluoromethane through cryogenic distillation or adsorptive removal of permanent gases, acidic species, and halogenated by-products. The purified material is specified at a minimum assay of 99.999 vol% and is packaged for semiconductor, flat-panel display, and photovoltaic manufacturing. The Electronic/EL grade is not a formal ISO or SEMI classification but a supplier designation indicating that trace impurity specifications, cylinder preparation, and analytical certification are aligned with front-end process requirements. Because CF4 is a permanent gas at ambient temperature, it is delivered in high-pressure cylinders or tube trailers rather than as a liquid; cylinder pressure varies with ambient temperature and transport regulation, and the material is classified under UN 1982 as a nonflammable gas for transport purposes.
Supplier model codes such as CF4-EL-5N or CF4 5N UHP denote the same purification tier but may differ in cylinder size, analytical certificate format, and outlet connection. The Electronic/EL grade is consumed at flow rates from 10 sccm in research etchers to 5 slm in production chamber-clean operations, so packaging is matched to the maximum instantaneous flow and to the requirement that cylinder change-out does not interrupt a process lot.
The principal difference is analytical, not molecular. Industrial-grade CF4 can contain air, moisture, and acid gases at concentrations that are acceptable for non-critical plasma cleaning or refrigerant duty but not for front-end wafer processing. In Electronic/EL grade material, the purification sequence reduces oxygen and nitrogen to prevent oxidation of metal gates and uncontrolled plasma impedance shifts; reduces moisture to limit HF generation in plasma; and removes halogenated C₁–C₃ impurities that could shift etch chemistry. The values in Table 1 are representative commercial specification limits and are not a single universal standard; individual suppliers may report tighter limits for oxygen, total acid gases, or particles.
| Parameter | Electronic/EL Grade | Industrial Grade |
|---|---|---|
| CF4 assay | ≥ 99.999 vol% | ≥ 99.9 vol% |
| H2O | ≤ 1.0 ppmv | ≤ 10 ppmv |
| O2 | ≤ 1.0 ppmv | ≤ 10 ppmv |
| N2 | ≤ 4.0 ppmv | ≤ 50 ppmv |
| CO + CO2 | ≤ 0.5 ppmv each | ≤ 5 ppmv total |
| CH4 | ≤ 0.5 ppmv | ≤ 5 ppmv |
| Total halocarbons | ≤ 1.0 ppmv | ≤ 20 ppmv |
| Total acid gases as HF | ≤ 0.1 ppmv | ≤ 1 ppmv |
| Particles ≥ 0.1 µm | ≤ 10 particles/ft³ | not controlled |
Verification of Electronic/EL grade CF4 on a lot-by-lot basis is performed by gas chromatography with pulsed discharge helium ionisation detection for permanent gases, by cavity ring-down spectroscopy or electrolytic cell analysers for moisture, and by flame ionisation detection or mass spectrometry for halogenated organic impurities. Calibration standards are gravimetrically prepared according to ISO 6142-1:2015; comparison measurement and purity evaluation follow the data-treatment principles of ISO 12963:2017. Cylinder filling is carried out in an environment controlled to ISO 14644-1:2015 Class 3 or better, and the internal surfaces of cylinders and outlet valves are passivated to reduce particle shedding and adsorption of polar impurities during withdrawal. Analytical certificates for Electronic/EL grade shipments typically report the assay, moisture, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane, and total halocarbon values for each cylinder or lot, not just the bulk production batch. Depending on instrument configuration, method detection limits reach 0.05 ppmv for CO and 0.02 ppmv for moisture; suppliers may report these detection limits on certificates when results fall below quantification limits.
During plasma-assisted chamber cleaning of silicon oxide and silicon nitride residues, CF4 is metered through a high-purity mass flow controller calibrated against a nitrogen reference, and is delivered through electropolished 316L stainless-steel gas lines with an internal surface roughness of Ra ≤ 0.25 µm. The gas enters a remote plasma source operating at 2.45 GHz, where CF4 is dissociated into CF3, CF2, CF, and atomic fluorine. Oxygen is added at 5–20 vol% of the total flow to shift the radical population toward atomic fluorine and COF2 and to suppress recombination of fluorine atoms on quartz and ceramic chamber components. A moisture concentration above 1.0 ppmv in the CF4 feed changes the plasma chemistry by generating OH and HF, which can alter the chamber seasoning state and promote particle release from heated liners. Process engineers therefore treat moisture as a chamber-state variable: cylinders showing moisture spikes during high-flow withdrawal are isolated, even if the average certificate value remains within specification. The same reasoning applies to oxygen, because many chamber-clean recipes already add oxygen; uncontrolled O2 in the CF4 supply changes the O2-to-CF4 ratio and can move the clean rate outside the tool’s endpoint-detection window. Published quantitative data correlating specific moisture excursions with clean-rate drift is limited, but the operational threshold of ≤ 1.0 ppmv is widely applied in high-volume semiconductor fabs.
Deposition tools that alternate between SiO2 and Si3N4 films impose a stronger demand on CF4 cleanliness because silicon nitride residues are denser and release NH3 during fluorine-based cleaning. In these systems, the CF4 flow is typically raised from 0.5 slm to 3 slm, and the O2 fraction is adjusted between 5% and 20%, while chamber pressure is held between 1.5 Torr and 5.0 Torr. The chamber wall temperature is maintained in the range of 60 °C to 120 °C to prevent condensation of ammonium fluorosilicate and fluorine-containing residues. Electronic/EL grade material reduces uncontrolled nitrogen and oxygen addition to the plasma; a nitrogen rise of 100 ppmv in the CF4 feed can change plasma impedance and endpoint signature in high-density remote plasma sources, although the exact magnitude is tool-specific and published data for this configuration is limited. When switching from SiO2 to Si3N4 clean recipes, process engineers often observe that the same CF4 flow produces a shorter clean time for SiO2 and a longer clean time for Si3N4 because silicon nitride removal is limited by the availability of fluorine and the volatilisation of nitrogen-containing products.
In dielectric etching applications, CF4 Electronic/EL grade is differentiated from CHF3 and C4F8 primarily by its fluorine-to-carbon ratio. CF4 has an F/C ratio of 4:1, which generates a high density of atomic fluorine and fast but largely isotropic SiO2 removal. CHF3, with an F/C ratio of 3:1, and C4F8, with an F/C ratio of 2:1, produce more CF2 and C2F4 fragments that deposit fluoropolymer on sidewalls and increase selectivity to photoresist, silicon, and silicon nitride. For contact holes with aspect ratios above 3:1, CF4 is therefore not used alone; it is blended with CHF3 or H2 at ratios that vary according to mask type, feature size, and hardmask selectivity. The Electronic/EL grade controls trace metals such as Fe, Ni, Cr, and Na, which can otherwise deposit on the wafer and shift threshold voltage in the formed transistor. Table 2 summarises the comparative characteristics of CF4, CHF3, and C4F8 in semiconductor etch and clean applications.
| Property | CF4 | CHF3 | C4F8 |
|---|---|---|---|
| Fluorine-to-carbon ratio | 4:1 | 3:1 | 2:1 |
| Dominant radical species | F, CF3 | CF2, CHF | CF2, C2F4 |
| Polymer deposition tendency | low | moderate | high |
| Typical application | chamber clean; isotropic oxide/nitride etch | selective oxide/nitride etch | sidewall passivation; high-aspect-ratio dielectric etch |
| 100-year GWP from IPCC AR5 | 7,390 | 14,800 | 10,300 |
Another operational differentiation is between CF4 and NF3 for chamber cleaning. NF3 dissociates at lower power density and offers higher destruction removal efficiency in some remote plasma sources, but it is a toxic oxidising gas that requires a dedicated gas safety system. CF4 is nonflammable and non-corrosive in the cylinder and can be installed in a standard high-purity gas cabinet; however, its C–F bond is stronger, so clean recipes use higher plasma power or longer residence time. The choice between CF4 and NF3 is therefore an equipment-availability and abatement-cost decision rather than a purity decision. The Electronic/EL grade standard for CF4 becomes important when the gas is used in a combined chamber-clean and etch tool where residual nitrogen, oxygen, or metal contamination can affect the subsequent wafer process.
Cylinder change-out procedures for CF4 Electronic/EL service require helium leak checking of the cylinder connection after tightening, followed by vacuum purging to below 1 × 10⁻³ Torr before the cylinder valve is opened. Gas panels and stick components are fabricated from 316L stainless steel with electropolished internal surfaces of Ra ≤ 0.25 µm; sealing is by metal-to-metal face seals, and polymer seals where unavoidable are high-purity polychlorotrifluoroethylene or polyimide. The cylinder valve outlet connection is assigned according to regional compressed gas association requirements, and the cylinder label carries the transport classification for UN 1982, nonflammable gas, with an asphyxiation warning. In high-cylinder-consumption fab areas, cylinder pressure is monitored at the gas cabinet during high-flow chamber-clean events; a pressure drop greater than 50 psi across the connection during purge is treated as a flow restriction or partially opened valve, not a purity issue.
Safety boundaries are determined by the high thermal stability of CF4 and by the toxicity of its decomposition products. CF4 itself has low acute inhalation toxicity but can displace oxygen in enclosed gas cabinets, creating an asphyxiation hazard. In plasma or high-temperature processes, decomposition products include HF, COF2, and fluorine radicals. Exhaust lines must be constructed from fluoropolymer-lined or acid-resistant materials and routed to a point-of-use abatement device; wet scrubbers remove HF but are less efficient for unreacted CF4 because of its chemical stability. CF4 should not be mixed with hydrogen in a storage cylinder or used as a cylinder mixture unless the mixture is prepared by the supplier; CF4/H2 mixtures for etch are usually formed at the mass flow controller. The atmospheric lifetime of CF4 is long, and its 100-year global warming potential is reported as 7,390 relative to CO2 in IPCC AR5. Storage should be below 50 °C and away from strong reducing agents and finely divided metals, because unintended high-temperature contact can generate metal fluorides and carbon oxides.
