Principle of laboratory tubular PECVD electric furnace

The principle of laboratory tubular PECVD electric furnace is based on plasma enhanced chemical vapor deposition (PECVD) technology. Its core is to generate plasma by exciting gas with radio frequency or microwave, and use the high activity of plasma to promote chemical reactions, achieving thin film deposition at low temperatures. The following are its specific principles and processes:

1. Core principle
Plasma excitation
In a low-pressure environment, a high-frequency electric field is generated in the reaction chamber through a radio frequency power source (such as 13.56MHz) or microwave, which ionizes gas molecules (such as silane SiH ₄, ammonia NH3, nitrogen N ₂, etc.) and forms a plasma containing particles such as electrons, ions, and active radicals.
The high-energy electrons in plasma collide with gas molecules, causing them to decompose into active groups (such as SiH ∝⁻, H ⁻, NH ₂⁻, etc.), which have extremely high chemical activity and significantly reduce the activation energy of the reaction.
Low-temperature chemical reaction
The active groups diffuse to the substrate surface and undergo chemical reactions at lower temperatures (usually 200-400 ℃) to form the initial components of the solid film (such as Si ∝ N ₄, SiO ₂, etc.).
The reaction by-products (such as H ₂, N ₂, etc.) detach from the surface and are evacuated from the chamber by a vacuum pump.
Thin film growth process
Adsorption and nucleation: Active groups are adsorbed onto the substrate surface, forming crystal nuclei.
Island like growth: Crystal nuclei gradually grow into island like structures.
Continuous film formation: Island like structures merge to form a uniform and continuous thin film.

2. Process flow
gas introduction
Inject precursor gases (such as SiH ₄, NH3) and carrier gases (such as N ₂) into the reaction chamber in precise proportions, and control the flow accuracy through a mass flow meter (MFC).
Plasma excitation
The RF power supply generates a high-frequency electric field inside the cavity, causing gas molecules to ionize and form plasma. The plasma density and energy distribution are regulated by power and pressure.
Chemical reactions and sedimentation
Active groups undergo decomposition, chemical reactions, and other reactions on the substrate surface to generate thin film materials. For example:
Silicon nitride (Si ∝ N ₄): 3SiH ₄+4NH ∝ → Si ∝ N ₄+12H ₂
Silicon oxide (SiO ₂): SiH ₄+2O ₂ → SiO ₂+2H ₂ O
The thickness and composition of the film are precisely controlled through parameters such as reaction time, gas ratio, and power.
By-product discharge
A vacuum pump (such as a molecular pump group) maintains low pressure in the chamber, and by-products (such as H ₂) are continuously extracted to ensure efficient reaction.

3. Technical advantages
Low-temperature sedimentation
The plasma activation effect significantly reduces the reaction temperature (traditional CVD requires 600-1000 ℃), avoiding high temperature damage to flexible substrates (such as polyimide) or heat sensitive materials.
High sedimentation rate
The high-energy particles in plasma accelerate the reaction rate and deposition rate much higher than traditional CVD.
Excellent film quality
Density: Plasma bombardment reduces film pores, resulting in high density.
Adhesion: The active groups form strengthened chemical bonds with the substrate surface, resulting in strong adhesion.
Step coverage: Active particles can cover complex shaped substrates (such as three-dimensional structures) with high step coverage.
Process flexibility
By adjusting parameters such as gas ratio, power, and pressure, various thin films can be deposited (such as SiO ₂, Si ∝ N ₄ SiC、 Amorphous silicon, etc.) and doping (such as p-type/n-type silicon).

4. Application scenarios
Semiconductor manufacturing
Deposition of gate oxide layer (SiO ₂), passivation layer (Si ∝ N ₄), low-k dielectric materials, etc., for use in integrated circuits, TFT-LCD, etc.
solar cell
Preparation of absorption layer and silicon nitride anti reflection layer for amorphous/microcrystalline silicon cells to improve photoelectric conversion efficiency.
Optics and Optoelectronics
Deposition of optical coatings such as anti reflective films, reflective films, filters, and transparent conductive oxides (such as ZnO) for LED and touch screens.
MEMS and Sensors
Manufacturing structural layers, protective layers, and functional coatings (such as piezoelectric thin film AlN) for microelectromechanical systems (MEMS).
Research on New Materials
Synthesize graphene, two-dimensional materials (such as h-BN), nanowires, and explore cutting-edge fields such as quantum computing and flexible electronics.