In semiconductor manufacturing, thermal processing of wafers involves precise temperature and time controls. It optimizes the microstructure of wafer materials, improves dopant distribution, relieves internal stresses, enhances metal-semiconductor contact performance, and removes surface contaminants and impurities, thereby boosting wafer quality and device performance, and ensuring product reliability and stability.
I. Roles of Thermal Processing
Thermal processing improves wafer material properties and quality by heating wafers to specific temperatures. Its key roles in semiconductor manufacturing are as follows:
1.Enhancing Crystal Structure: Thermal processing enables wafer materials to crystallize into the desired structure on the lattice, endowing wafers with specific electrical, thermal, and mechanical properties.
2.Upgrading Material Quality: By relieving internal stresses in wafers, reducing grain boundaries and crystal defects through thermal processing, the overall material quality is elevated, and the wafer's electrical conductivity, magnetism, and other physical properties are enhanced.
3.Eliminating Impurities and Moisture: During baking, impurities and moisture on the wafer surface are effectively removed, providing a solid foundation for subsequent process steps.
4.Releasing Internal Stresses: Thermal processing relieves internal stresses in wafers, minimizes factors affecting precision, and thereby enhances product reliability and stability.
5.Preparing for Subsequent Processes: Thermal processing is essential for subsequent steps like wafer coating, exposure, and development. It ensures these processes proceed smoothly and guarantees the performance of the final product.
II. Baking Standards for Semiconductor Wafers
Baking standards in thermal processing are determined by considering wafer type, process requirements, and equipment performance. They mainly include baking temperature and time:
1.Baking Temperature: Wafer quality and performance are significantly influenced by baking temperature. Different wafer types, due to their distinct material properties, require varying temperature ranges. For instance, silicon wafers are typically baked at 100℃ - 200℃, while III-V compound semiconductor wafers like gallium arsenide require 200℃ - 300℃. The temperature setting must effectively remove surface impurities and moisture without damaging the wafer material.
2.Baking Time: Baking duration depends on wafer type, temperature, and process requirements. In production, optimal baking time is determined through rigorous testing and validation. Insufficient time may leave impurities and moisture, while excessive time may damage the wafer or affect product performance.
III. Common Oven Equipment
Ovens for semiconductor wafer thermal processing must meet the following requirements. Here are some commonly used types:
1.High-Precision Ovens: Equipped with advanced temperature control systems, they enable precise temperature control and monitoring during baking. Featuring high-precision sensors and intelligent control systems, they monitor and adjust baking temperatures in real-time, ensuring a stable temperature environment for wafers.
2.Clean Ovens: Maintaining high internal cleanliness, they prevent wafer contamination from dust and particles. With dust-free design and efficient filtration systems, they remove airborne particles and harmful gases, providing a clean baking environment.
3.Nitrogen Ovens: To prevent wafer oxidation or contamination during baking, nitrogen-protected ovens are used. The nitrogen-filled inert gas environment shields wafers from oxygen and harmful gases.
4.Automated Ovens: Equipped with automated control systems, they enable precise control and monitoring of baking parameters. With automated loading, unloading, and transfer functions, they enhance production efficiency and product quality.
Thermal processing of semiconductor wafers is crucial in semiconductor manufacturing. Baking standards and oven selection should be based on wafer type and process requirements. With strict baking processes and high-quality ovens, wafer quality and performance can meet standards, ensuring smooth subsequent processes and optimal final product performance.
