What is BOAT (Crystal Boat)?

In the semiconductor integrated circuit (IC) manufacturing process, BOAT (Crystal Boat) is a commonly used tool primarily for carrying, transporting, cleaning, and processing chips. Its function is akin to a transport tool, ensuring that chips can smoothly and safely complete various processing steps in complex manufacturing procedures.

1. Definition and Function of BOAT

BOAT is a tool used in the semiconductor manufacturing process to carry and transport chips. Its name "Crystal Boat" metaphorically describes its role in semiconductor manufacturing, like a small boat (dugout canoe) responsible for transporting chips between different processing steps. The manufacturing of semiconductor chips typically involves a series of physical and chemical processes, such as high-temperature heating, cleaning, etching, drying, and chemical treatment. BOAT plays a crucial role in transferring chips from one process step to another.

Specific functions of BOAT include:

- Chip Carrying and Transport:** Safely and accurately transferring chips from one process step to the next.

- Chip Support:** During high-temperature or chemical treatments, BOAT provides support to prevent damage due to deformation or stress concentration.

- Protection and Isolation:** In sensitive processes, BOAT effectively isolates chips from external environments, reducing the risk of contamination and damage.

- Chemical Reaction Medium:** In certain chemical treatment processes, the material of BOAT needs to have corrosion resistance and acid-alkali resistance to ensure that it does not adversely affect the chips during processing.

### 2. Materials and Application Scenarios of BOAT

BOAT is primarily made from quartz and Teflon, with the choice of material depending on process requirements, temperature, and chemical environment. Below we discuss the characteristics and application scenarios of these two materials in detail.

1. Quartz BOAT

Quartz (SiO2) is a very important material widely used in semiconductor manufacturing. Quartz BOAT is primarily used in process steps that require high-temperature treatment. The main advantages of quartz are its excellent high-temperature performance and chemical stability. It remains stable at temperatures exceeding 300°C and does not deform or react with processing gases or chemicals.

Characteristics of Quartz BOAT:

- High Temperature Resistance: Quartz maintains structural stability at high temperatures, often used in processes like oxidation, diffusion, and annealing.

- Excellent Chemical Stability: Quartz has strong resistance to most chemicals (such as acids and bases), meaning it does not get damaged during chemical reactions.

- Transparency: Quartz has good transparency, which allows specific processes that require light exposure to accurately illuminate the chip.

Application Scenarios of Quartz BOAT:

- High-Temperature Processing: Used in processes like diffusion and oxidation, where stability at high temperatures is crucial.

- Annealing Processes: In semiconductor manufacturing, annealing restores or alters material properties through heating, making quartz BOAT ideal for this process.

2. Teflon BOAT

Teflon (PTFE, polytetrafluoroethylene) is a polymer material with excellent chemical stability and corrosion resistance. Teflon BOAT is primarily used in processes involving acidic or alkaline chemicals and is particularly suitable for transporting or processing in corrosive environments.

Characteristics of Teflon BOAT:

- Excellent Chemical Corrosion Resistance:** Teflon has good resistance to most acids, bases, and solvents, making it effective for use in environments like acid cleaning and chemical cleaning.

- Low Friction: Teflon’s low friction properties allow for smooth chip transport, reducing physical damage to the chips.

- High-Temperature Performance: Although Teflon's temperature resistance is not as high as quartz, it performs well in typical temperature ranges (usually below 300°C).

Application Scenarios of Teflon BOAT:

- Chemical Processing: In wet cleaning or chemical etching processes, Teflon BOAT can resist acid and base corrosion, ensuring that chips remain undamaged during treatment.

- Transport Processes: In processes requiring lower temperatures, Teflon BOAT is widely used for chip transport, ensuring smooth passage through various stages.

3. Workflow of BOAT in Semiconductor Manufacturing

To further understand the working principle of BOAT, we can place it within a typical semiconductor production process. Suppose we are conducting a manufacturing process that includes cleaning, chemical treatment, and high-temperature processing:

- Cleaning and Chemical Treatment: In this phase, chips may undergo treatment with acidic solutions to remove surface impurities. The corrosion resistance of Teflon BOAT plays a vital role in this process, as it not only supports the chips but also protects them from acid corrosion.

- Drying and Annealing: After cleaning and chemical treatment, chips need to be dried or annealed. The annealing process requires high temperatures (usually above 300°C), making quartz BOAT the ideal choice due to its stability under high temperatures.

- Transport and Other Processes: Throughout the process, BOAT also plays a role in transport. Chips are transferred via BOAT between different process steps, ensuring they remain uncontaminated and undamaged. Depending on the specific process requirements, the appropriate BOAT material (quartz or Teflon) is selected to ensure smooth operation.

4. Optimization and Selection of BOAT

In actual semiconductor production, selecting the appropriate BOAT is crucial. Engineers need to determine whether to use quartz or Teflon BOAT based on factors such as temperature, chemical environment, and time for each process step. Additionally, the design and shape of BOAT should be customized according to production line requirements to ensure effective carrying and transport of chips across different processing steps.

5. Conclusion

BOAT is an indispensable tool in semiconductor manufacturing, carrying chips and ensuring their safe and precise transport through multiple process steps. Quartz BOAT and Teflon BOAT each have unique advantages and application scenarios, and engineers must select the appropriate BOAT material based on specific process requirements.