What is a quartz boat?

Quartz Boat is a key bearing component used in the semiconductor manufacturing process, mainly used for high-temperature processing of wafers, such as diffusion, oxidation and annealing. Its excellent thermal stability, low pollution characteristics and corrosion resistance make it an indispensable material in the semiconductor industry. This article will elaborate on the material, physical properties, classification, application scenarios and differences between quartz boat and PECVD graphite boat.

Ⅰ. Material of Quartz Boat

The main component of quartz carrier is high-purity silicon dioxide (SiO₂), and the purity usually needs to reach more than 99.99% (semiconductor grade). This high-purity quartz material ensures that the quartz carrier will not introduce impurities during the semiconductor manufacturing process to reduce the contamination of metal impurities on the wafer.

According to the preparation process, quartz materials can be divided into two categories:

● Natural quartz: made from crystal purification, with a high hydroxyl content (about 100-200 ppm), low cost, but weak tolerance to high temperature sudden changes.

● Synthetic quartz: synthesized by chemical vapor deposition (CVD) or electrofusion, with low hydroxyl (-OH) content (<1 ppm), better thermal stability, and suitable for high-temperature processes (such as oxidation and diffusion).

In addition, some quartz boats are doped with metals such as titanium (Ti) or aluminum (Al) to improve deformation resistance, or adjust light transmittance to meet the needs of UV processes.

Ⅱ. What are the main physical properties of quartz boats?

● High temperature resistance: The melting point of quartz is as high as 1713°C, and it can work stably at 1200°C for a long time and withstand 1500°C for a short time.

● Low thermal expansion coefficient: The thermal expansion coefficient is only 0.55×10⁻⁶/°C. This excellent performance ensures dimensional stability at high temperatures and avoids cracking due to thermal stress.

● Chemical inertness: Except for hydrofluoric acid (HF) and hot phosphoric acid, quartz can resist strong acids, strong alkalis and most corrosive gases (such as Cl₂, O₂).

● Electrical insulation: resistivity is as high as 10¹⁶Ω·cm, avoiding interference with the electric field distribution of the plasma process.

● Light transmittance: excellent transmittance in the ultraviolet to infrared band (＞90%), suitable for light-assisted processes (such as ultraviolet curing).

III. Classification of quartz boats

According to different design structures and usage scenarios, quartz boats can be divided into the following categories:

● Horizontal Quartz Boat

Applicable to horizontal tube furnaces (Horizontal Diffusion Furnace), used for oxidation, diffusion, annealing and other processes.

Features: Can carry 100-200 wafers, usually with an open or semi-enclosed design.

● Vertical Quartz Boat

Applicable to vertical furnaces (Vertical Furnace), used for LPCVD processes, oxidation and annealing processes.

Features: More compact structure, can increase wafer carrying capacity, and reduce particle contamination during the process.

● Customized Quartz Boat

Designed according to different process requirements, single wafer support or special clamping structure may be used to optimize wafer processing effects.

As a leading quartz boat manufacturer and supplier in China, Veteksemicon can design and manufacture customized quartz carrier products according to your actual needs. For more product details, please refer to:

IV. What are the application scenarios of quartz boat in semiconductor manufacturing?

Quartz boats are widely used in many key process links of semiconductor manufacturing, mainly including the following application scenarios:

4.1 Thermal Oxidation

● Process description: The wafer is heated in a high-temperature oxygen or water vapor environment to form a silicon dioxide (SiO₂) film.

● Features of quartz boat:

1) High heat resistance, can withstand high temperatures of 1000~1200°C.

2) Chemical inertness, quartz boats are resistant to strong acids, strong alkalis and most corrosive gases, so it can avoid affecting the quality of the oxide film.

4.2 Diffusion Process

● Process Description: Impurities (such as phosphorus and boron) are diffused into the silicon wafer under high temperature conditions to form a doping layer.

● Quartz Boat Features:

1) Low contamination, preventing metal contamination from affecting the doping concentration distribution.

2) High thermal stability, with a thermal expansion coefficient of only 0.55×10⁻⁶/°C, ensuring a uniform diffusion process.

4.3 Annealing Process

● Process Description: High temperature treatment is used to remove stress, improve the material crystal structure, or activate the ion implantation layer.

● Quartz Boat Features:

1) With a melting point as high as 1713°C, it can withstand rapid heating and cooling to avoid cracking caused by thermal stress.

2) Precise size control to ensure uniform heating.

4.4 Low Pressure Chemical Vapor Deposition (LPCVD)

● Process Description: In a low pressure environment, a uniform thin film such as silicon nitride (Si₃N₄) is formed through a gas phase reaction.

● Features of quartz boat:

1) Suitable for vertical furnace tubes, can optimize film deposition uniformity.

2) Low particle contamination, improve film quality.

Ⅴ. What are the differences between quartz boat and PECVD graphite boat?

Typical difference scenarios:

● PECVD process: Graphite boats can optimize plasma uniformity due to their conductivity, and do not require the high temperature performance of quartz in low temperature environments (300-400°C).

● High temperature oxidation furnace: Veteksemicon quartz boats are irreplaceable for their high temperature resistance, while graphite is easily oxidized to generate CO/CO₂ at high temperatures in an oxygen environment, which pollutes the chamber.