What are the materials for plasma enhanced PECVD coating electric furnace tubes?

The selection of furnace tube materials for plasma enhanced PECVD (plasma enhanced chemical vapor deposition) coating electric furnaces should take into account requirements such as high temperature resistance, corrosion resistance, insulation, and chemical stability. The following are common furnace tube materials, their characteristics, and application scenarios:

1. Quartz Glass
a. Characteristics and advantages
High temperature resistance: The softening point is about 1730 ℃, and it can work stably for a long time at the commonly used PECVD temperature (≤ 450 ℃). The thermal expansion coefficient is extremely low (5.5 × 10 ⁻⁷/℃), and it is not easy to crack due to temperature fluctuations.
b. Chemical stability: resistant to most acidic gases (such as SiH ₄, NH ∝) corrosion, but avoid contact with strong bases (such as NaOH).
Transparency: Transparent to ultraviolet infrared light, facilitating observation of reactions inside the furnace (such as plasma luminescence), and can also be used in light assisted PECVD processes.
d. Insulation: Volume resistivity>10 ¹⁴Ω· cm at room temperature to avoid leakage of RF electric field and ensure stable excitation of plasma.
Application scenarios
Widely used in laboratory level and small to medium-sized PECVD equipment, such as university research and semiconductor development lines (such as depositing SiO ₂, SiN ₓ thin films).
Suitable for depositing non corrosive thin films, or in combination with corrosion-resistant gases (such as CF ₄, with controlled concentration).

2. Ceramic materials (Al ₂ O ∝, SiC, etc.)
a. Aluminum oxide ceramics (Al ₂ O3)
Characteristics: Alumina ceramics with a purity of ≥ 99.5% have high temperature resistance (melting point 2054 ℃), high hardness (HV ≥ 1500), and good thermal shock resistance (able to withstand a temperature difference of 500 ℃).
Corrosion resistance: Resistant to acid gases (such as HCl, Cl ₂) and molten metal corrosion, but may react with water vapor to generate Al (OH) I3 at high temperatures, requiring control of process humidity.
Insulation: At high temperatures (400 ℃), the volume resistivity remains>10 ΩΩ· cm, making it suitable for high-frequency electric field environments.
b. Silicon carbide ceramics (SiC)
Characteristics: High thermal conductivity (170W/m · K), better thermal stability than alumina, can be used for a long time at 1600 ℃, and has high mechanical strength (bending strength ≥ 400MPa).
Corrosion resistance advantage: resistant to strong corrosive gases (such as NF ∝, SF ₆) and molten silicon erosion, especially suitable for semiconductor etching and coating integration processes.
Application scenarios
Alumina ceramics: used for depositing highly corrosive thin films (such as reactions involving SiCl ₄), or industrial grade equipment that requires wear resistance (such as photovoltaic cell production lines).
Silicon carbide ceramics: high-end semiconductor manufacturing (such as FinFET device deposition gate oxide layer), high-frequency high-power PECVD equipment (reducing heat loss).

3. Composite materials (quartz+ceramic coating, metal+insulation layer)
a. Ceramic coating on quartz surface
Process: Deposition of Al ₂ O ∝ or SiC coating (thickness 5-20 μ m) on the inner wall of the quartz tube to enhance its corrosion resistance.
Advantages: Balancing the transparency of quartz with the corrosion resistance of ceramics, suitable for mixed gas (such as SiH ₄+NF ∝) processes.
b. Metal tube+insulation coating
Design: The inner wall of the stainless steel tube is coated with an Al ₂ O ∝ or zirconia (ZrO ₂) insulation layer, with a thickness of 0.1-1mm, to prevent radio frequency leakage.
Application: Large industrial equipment (such as roll to roll PECVD), reducing costs while meeting insulation requirements.