Precautions for operating a tubular CVD electric furnace for experiments

When operating a tubular CVD electric furnace for experiments, it is necessary to strictly comply with safety regulations and technical requirements. The following key precautions are summarized from four aspects: preparation before operation, monitoring during operation, maintenance after operation, and safety protection:

1. Preparation before operation
Equipment inspection
Furnace body and pipeline: Check whether there are cracks, deformations or blockages in the furnace tube, ensure that the gas path connection is tight and leak free (can be detected with soap water).
Vacuum system: Confirm that the oil level of the vacuum pump is normal, the valve switch is flexible, and the sealing ring is not aged.
Electrical system: Check whether the power cord, temperature controller, and heating element are intact to avoid the risk of short circuit or leakage.
Gas supply: Confirm that the pressure of high-purity gases (such as SiH ₄, NH ∝, N ₂, etc.) in steel cylinders is sufficient, and the calibration of pressure reducing valves and flow meters is accurate.
sample preparation
Cleaning treatment: The substrate materials (such as silicon wafers and glass) need to be cleaned and dried by ultrasound to remove surface oil stains and particles, and avoid contaminating the furnace tube.
Placement: The sample should be evenly distributed in the center area of the furnace tube, avoiding proximity to heating elements or air inlets to ensure temperature uniformity.
Parameter settings
Temperature curve: Set the heating rate, insulation time, and cooling method (such as natural cooling or forced air cooling) according to the material characteristics to avoid sample fracture caused by thermal stress.
Gas flow rate: Accurately control the ratio of reaction gas to carrier gas (such as N ₂, Ar) to prevent excessive reaction or uneven deposition.
Vacuum degree: Adjust the vacuum pump pumping speed according to process requirements to maintain stable furnace pressure (such as low-pressure CVD requiring less than 100 Pa).

2. Monitoring during operation
temperature control
Observe the temperature displayed by the temperature controller in real time to ensure that it is consistent with the set value. If the temperature fluctuation exceeds ± 5 ℃, the experiment should be paused and the heating element or thermocouple should be checked.
Avoid local overheating, especially at the sealed ends of the furnace tube, to prevent material volatilization and contamination of the furnace tube.
Gas flow rate and pressure
Regularly check the reading of the flow meter to prevent membrane defects caused by gas supply interruptions or sudden changes in flow rate.
Monitor the pressure inside the furnace. If the pressure rises abnormally, it may be due to gas path blockage or vacuum pump failure, and the machine needs to be stopped immediately for troubleshooting.
EXCEPTION
Gas leakage: Immediately shut off the gas source, turn on the ventilation system, evacuate personnel to a safe area for maintenance.
Temperature out of control: Cut off power and activate emergency cooling devices (such as water cooling systems) to prevent equipment damage.
Vacuum failure: Pause the experiment, check the oil level, sealing ring or valve status of the vacuum pump, repair and re evacuate.

3. Post operation maintenance
Furnace tube cleaning
After the experiment, blow the furnace tube with high-purity nitrogen for 10-15 minutes to remove residual gases and particles.
Regularly use hydrofluoric acid (HF) or aqua regia to clean the inner wall of the furnace tube and remove sediment (requires professional personnel to operate and wear protective equipment).
equipment maintenance
Heating element: Check if the resistance wire is broken or oxidized, and replace it if necessary.
Vacuum pump: Change the engine oil and clean the impurities inside the pump every 500 hours of operation.
Sealing ring: Regularly apply vacuum grease to prevent air leakage caused by aging and cracking.
Recording and archiving
Detailed recording of experimental parameters (temperature, gas flow rate, pressure, etc.), sample information, and abnormal conditions, providing reference for subsequent process optimization.

4. Security protection
Personal Protection
Wear gas masks, heat-resistant gloves, protective goggles, and lab coats during operation to avoid contact with high-temperature components or toxic gases.
Do not wear metal jewelry to prevent electric shock or burns.
environmental safety
The experimental area is equipped with fire extinguishers, eye wash stations, and emergency shower devices to ensure good ventilation (exhaust volume ≥ 500 m ³/h).
Do not stack flammable materials near the furnace body, and turn off all gas and power sources after the experiment is completed.
Training and Qualification
Operators need to undergo professional training, familiarize themselves with equipment principles, process flow, and emergency response measures.
Regularly organize safety drills to enhance the ability to respond to unexpected accidents.