How is the custom PECVD electric furnace coated?

Customized PECVD (Plasma Enhanced Chemical Vapor Deposition) electric furnace achieves high-quality thin film preparation at low temperatures through plasma assisted chemical vapor deposition technology. The coating process combines physical excitation and chemical reactions, with advantages such as high deposition rate, good film uniformity, and wide substrate adaptability. The following are the detailed steps and technical principles of PECVD electric furnace coating:

1. Preparation before coating
Substrate cleaning and pretreatment
Cleaning: Use chemical solvents (such as acetone, isopropanol) to remove impurities such as oil stains and particles on the surface of the substrate, and then further activate the surface through plasma cleaning (such as O ₂ plasma).
Pre treatment: Low temperature annealing of flexible substrates (such as polyimide) to eliminate internal stress; Surface roughening treatment of metal substrates to enhance film adhesion.
Equipment calibration and parameter setting
Preparation of the cavity: Check the sealing and stability of components such as the vacuum system, gas delivery system, and RF power supply.
Parameter setting: Set process parameters based on target thin film materials (such as SiO ₂, SiN ₓ), including:
RF power: Control plasma density (usually 50-500W).
Pressure: Adjust the concentration of the reaction gas (1-1000 Pa).
Gas flow rate: Precisely control the ratio of precursor gases (such as SiH ₄, N ₂) and carrier gases (such as Ar).
Substrate temperature: Set the deposition temperature (usually 200-450 ℃).

2. Core steps of coating
a. Vacuum pumping and substrate heating
Vacuum pumping: The chamber pressure is reduced to below 10 ⁻ Pa through mechanical and molecular pumps to remove residual gases and impurities.
Substrate heating: Heat the substrate to the set temperature through infrared lamps or resistance heaters to ensure that the reaction gas is fully decomposed on the surface of the substrate.
b. Introduce reaction gas
Gas mixing: Mix precursor gases (such as SiH ₄, NH3) with carrier gases (such as Ar, N ₂) in proportion, and precisely control the flow rate through a mass flow meter.
Gas distribution: Ensure uniform distribution of gas to the surface of the substrate through a spray head or annular gas distributor.
c. Plasma excitation
Radio frequency discharge: Applying high-frequency alternating current (usually 13.56 MHz) between electrodes to ionize gas and form plasma.
Plasma characteristics:
High energy electrons: with an energy of 1-10 eV, they can decompose precursor gas molecules (such as SiH ₄ → SiH ∝⁺+H ⁺).
Active groups: generate highly active species such as SiH ∝⁺ and NH ₂⁻, promoting chemical reactions.
Ion bombardment: Charged particles (such as Ar ⁺) bombard the surface of the substrate, cleaning the surface and enhancing film adhesion.
d. Thin film deposition
Chemical reaction: The active groups react on the surface of the substrate to generate the target thin film material. For example:
Sedimentary SiO ₂: SiH ₄+O ₂ → SiO ₂+2H ₂ ↑
Deposition of SiN ₓ: 3SiH ₄+4NH ∝ → Si ∝ N ₄+12H ₂ ↑
Thin film growth: By continuously introducing reaction gas and maintaining plasma, the thin film grows layer by layer in the form of atomic or molecular layers.
e. Process control and optimization
Real time monitoring: Through equipment such as spectroscopic ellipsometry and quartz crystal micro antennas, the thickness, refractive index, and deposition rate of thin films can be monitored online.
Parameter adjustment: Dynamically adjust parameters such as RF power and gas flow rate based on monitoring results to ensure stable film quality.

3. Post coating treatment
Cooling and Sampling
Natural cooling: Turn off the RF power and heating system, allowing the substrate to slowly cool to room temperature inside the chamber to avoid thermal stress causing film cracking.
Sampling: Remove the substrate in a dust-free environment to avoid contamination.
Thin film characterization and testing
Structural analysis: Use X-ray diffraction (XRD) and transmission electron microscopy (TEM) to analyze the crystal structure of the thin film.
Composition analysis: Determine the chemical composition of the thin film through X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).
Performance testing: Measure key indicators such as film thickness (ellipsometer), refractive index (ellipsometer), adhesion (scratch method), stress (curvature method), etc.

4. Technical advantages and typical applications
a. Technical advantages
Low temperature deposition: avoids damage to the substrate from high temperatures, suitable for heat sensitive materials such as flexible electronics and plastic substrates.
High deposition rate: The deposition rate is faster than ordinary CVD.
Good film uniformity: Higher thickness uniformity meets advanced process requirements.
Strong material controllability: By adjusting plasma parameters, the composition, structure, and stress of the thin film can be precisely controlled.
b. Typical applications
Semiconductor devices: deposited gate dielectric layer (SiO ₂, SiN ₓ), passivation layer, and low-k dielectric material.
Photovoltaic cells: deposition of amorphous/microcrystalline silicon thin films and silicon nitride anti reflection films.
Flexible display: Deposition of transparent conductive oxide (ITO) and water oxygen barrier layer on polyimide substrate.
MEMS devices: deposited structural layers, sacrificial layers, functional coatings.

5. Development Trends
Multi chamber integration: By connecting multiple deposition chambers in series, continuous coating can be achieved to improve production efficiency.
Pulse plasma technology: using pulsed radio frequency power supply to reduce the damage of plasma to the substrate and optimize the quality of the film.
AI Process Control: Integrating machine learning algorithms to optimize process parameters in real-time, improving yield and stability.
Green process development: Using low toxicity precursor gases and efficient waste gas treatment systems to reduce environmental impact.