Double-Side Polished Sapphire Wafers are high-quality sapphire wafers that have undergone a polishing process on both sides, resulting in a wafer with smooth, flat, and uniform surfaces on both the top and bottom. This dual-polishing process is used to improve the surface quality, flatness, and precision of the wafer, making it suitable for a wide range of advanced applications in the semiconductor, optoelectronic, and optical industries.
Key Characteristics of Double-Side Polished Sapphire Wafers:
Material: Sapphire (Al₂O₃)
Sapphire is a crystalline form of aluminum oxide and is widely known for its high mechanical strength, optical transparency, thermal conductivity, and chemical resistance. These properties make it ideal for use in a variety of high-performance applications, including LED production, semiconductors, optical systems, and MEMS.
Sapphire is also chemically inert, meaning it is highly resistant to corrosion and chemical damage, making it suitable for harsh environments.
Applications:
LED and Optoelectronics: Double-side polished sapphire wafers are commonly used as substrates for the growth of LED layers, particularly for blue and white LED production. The high-quality surface ensures optimal epitaxial layer growth, which is critical for improving LED efficiency and reliability.
Semiconductors: Sapphire wafers are used in various semiconductor applications, such as power devices and microwave components, due to their electrical insulation properties and high thermal conductivity. The dual-polished surface allows for uniform deposition of thin films and consistent processing across the wafer.
Optical Components: The optical transparency and mechanical strength of sapphire make it ideal for optical windows, lenses, viewports, and other high-performance optical components. These wafers are often used in aerospace, military, and medical applications that require durability and clarity in harsh environments.
MEMS (Microelectromechanical Systems): The mechanical properties and flatness of double-side polished sapphire wafers make them suitable for MEMS applications such as sensors, actuators, and microdevices that require high precision and uniformity in fabrication.
Crystal Orientation:
The most common crystallographic orientation for sapphire wafers is the <0001> plane (the c-plane), which is typically used in LED production and semiconductor epitaxy. The c-plane provides the best growth conditions for materials like GaN (gallium nitride), which is used in high-performance LEDs.
Other orientations, such as <1120> (a-plane) or <1102> (r-plane), may also be used for specific applications where different material properties are required, such as optical properties or strain relaxation in semiconductor devices.
Surface Quality:
The double-side polishing process ensures that both surfaces of the wafer are extremely smooth, with low surface roughness (Ra), which is essential for high-precision applications in thin-film deposition and epitaxial growth.
The smooth, polished surfaces minimize defects, improving the yield and performance of devices fabricated on sapphire wafers, such as LEDs, semiconductors, and optical components.
Mechanical and Thermal Properties:
High Strength: Sapphire is incredibly hard (9 on the Mohs scale), making it highly resistant to scratches and abrasion. This hardness is beneficial for applications where wafers need to be handled or processed under harsh conditions.
Thermal Conductivity: Sapphire has excellent thermal conductivity, which allows it to efficiently dissipate heat in high-power devices such as power electronics and LEDs. This property is crucial for improving device performance and longevity.
Thermal Expansion: Sapphire has a relatively low thermal expansion coefficient, meaning it maintains its structural integrity under temperature fluctuations. This is important for precision devices that must remain stable in varying thermal environments.
Thickness and Diameter:
Diameter: Double-side polished sapphire wafers are available in various diameters, including 2 inches, 4 inches, 6 inches, and 8 inches. The 4-inch size is commonly used in LED manufacturing, semiconductor applications, and optical systems.