Precautions for using laboratory tubular PECVD electric furnace

The laboratory tubular PECVD electric furnace combines high-temperature heating and plasma enhanced chemical vapor deposition technology, which is suitable for thin film deposition on various substrates, but safety regulations and process requirements must be strictly followed during operation. The following are key precautions for use, covering safety, operation, maintenance, and environmental control aspects:

1. Security protection
Personal Protective Equipment (PPE)
Protective clothing: Wear laboratory clothing that is resistant to high temperatures and chemical corrosion, and avoid direct skin contact with high-temperature components or chemical gases.
Gloves: Use heat-resistant gloves (such as aramid or silicone gloves) to operate furnace tubes, heating elements, or freshly deposited samples.
Goggles/face shields: prevent eye injuries from plasma flashes or chemical gas splashes.
Gas mask/respirator: When handling toxic gases (such as SiH ₄, NH ∝), it is necessary to operate in a fume hood and wear a gas mask.
Equipment safety inspection
Leakage protection: Ensure that the equipment is well grounded and regularly check whether the power cord and plug are damaged.
Gas leak detection: Use a gas leak detector (such as a halogen detector) to regularly check for gas leaks at the gas path connections.
Emergency stop function: Familiarize yourself with the location of the emergency stop button on the device to ensure that the power and gas supply can be quickly cut off in case of abnormal situations.
Fire and explosion prevention measures
Flammable gas management: Flammable gases such as hydrogen (H ₂) and silane (SiH ₄) should be stored separately in explosion-proof cabinets, away from heat sources and oxidants.
Ventilation requirements: The equipment must be installed in a well ventilated laboratory, and the exhaust outlet must be connected to the outdoor or exhaust gas treatment system.
Fire extinguishing equipment: equipped with dry powder fire extinguishers or carbon dioxide fire extinguishers, water-based fire extinguishers are prohibited (which may cause hydrogen explosions).

2. Operating standards
Substrate pretreatment
Cleanliness: The surface of the substrate needs to be thoroughly cleaned (such as ultrasonic cleaning, plasma cleaning) to remove oil stains, dust, or oxide layers, otherwise it will affect the adhesion of the film.
Size matching: Ensure that the substrate size is smaller than the inner diameter of the furnace tube to avoid jamming or damaging the furnace tube.
Fixing method: Use quartz boats or graphite fixtures to fix the substrate and prevent it from moving or tilting during the deposition process.
Process parameter setting
Temperature control:
Strictly follow the process requirements to set the temperature curve and avoid overheating (such as SiNx deposition temperature usually being 300-400 ℃).
The heating/cooling rate should be slow (e.g. ≤ 5 ℃/min) to prevent thermal stress cracking of the substrate.
Gas flow rate and ratio:
Accurately control the flow rate of reaction gases (such as SiH ₄, NH ∝, N ₂), with a proportional error of ≤± 1%.
Gas flow meters need to be calibrated regularly to avoid loss of control of film composition due to flow deviation.
Plasma power:
Adjust the power according to the substrate and film type. Excessive power may cause damage to the substrate or cracking of the film.
Before starting the plasma, a carrier gas (such as N ₂) should be introduced to avoid arc ignition.
Loading and unloading
Furnace tube sealing: After loading the substrate, ensure that the flanges at both ends of the furnace tube are well sealed to prevent plasma leakage or external air from entering.
Cooling stage: After sedimentation is completed, the furnace door should be opened only when the temperature of the furnace tube drops below 100 ℃ to avoid high-temperature oxidation or thermal shock.
Sample removal: Use specialized tools (such as tweezers) to remove the sample, and do not touch the high-temperature substrate directly with your hands.

3. Equipment maintenance
Daily cleaning
Furnace tube cleaning: Regularly clean the inner wall of the furnace tube with hydrofluoric acid (HF) or nitric acid (HNO ∝) solution to remove sedimentary residues (such as SiO ₂ SiNx）。
Electrode maintenance: Check whether the plasma electrode (such as the RF electrode) is oxidized or contaminated, and if necessary, polish or replace it with sandpaper.
Gas path cleaning: Blow the gas path with high-purity nitrogen (N ₂) to prevent gas pipeline blockage or cross contamination.
periodic calibration
Temperature sensor: Calibrate the thermocouple or infrared thermometer once a year to ensure accurate temperature display.
Flow meter: Calibrate the Mass Flow Meter (MFC) every six months to ensure the accuracy of gas flow control.
Plasma power meter: Check if the reading of the RF power meter is consistent with the set value, with a deviation of ≤± 5%.
Spare Parts Management
Vulnerable parts reserve: Prepare vulnerable parts such as furnace tubes, sealing rings, electrodes, etc. in advance to avoid equipment shutdown due to component damage.
Compatibility verification: When replacing spare parts, it is necessary to confirm the model matching to avoid equipment failure caused by incompatibility.

4. Environmental control
Laboratory temperature and humidity
Temperature: Keep the laboratory temperature at 20-30 ℃ to avoid temperature fluctuations affecting equipment stability.
Humidity: The humidity should be ≤ 60% to prevent electrical short circuits or substrate oxidation caused by water vapor condensation.
Power stability
Use a regulated power supply or UPS (uninterruptible power supply) to avoid voltage fluctuations (such as ± 10% or more) that can damage equipment or affect film quality.
waste disposal
Gas emissions: The exhaust gas needs to be purified and discharged through exhaust gas treatment systems (such as combustion towers and scrubbing towers) to meet environmental protection requirements.
Solid waste: Sedimentary waste (such as quartz fragments and metal particles) needs to be classified and collected, and disposed of according to the hazardous waste treatment process.

5. Exception handling
Common faults and countermeasures
Plasma cannot start: Check if the gas flow rate, RF power, and electrode connections are normal, and eliminate gas path blockage or power failure.
Thin film cracking or detachment: Reduce deposition temperature or power, optimize substrate pretreatment process (such as adding plasma cleaning step).
Temperature out of control: Immediately press the emergency stop button, check if the temperature control system is malfunctioning, and avoid overheating and damaging the equipment.
Emergency Response Plan
Fire: Cut off power and gas supply, use dry powder fire extinguishers to extinguish the initial fire, and evacuate personnel.
Gas leakage: Quickly close the gas source valve, open the ventilation system, evacuate personnel to a safe area, and report.
Personnel injury: Immediately provide first aid (such as scald washing, chemical burn neutralization) and seek medical treatment.