Single-Side Polished Sapphire Wafers are high-quality wafers made from synthetic sapphire (Al₂O₃) that have undergone a polishing process on one side to achieve a smooth, flat surface. These wafers are commonly used in a wide range of applications in semiconductor, optical, and LED industries due to their excellent optical clarity, high thermal conductivity, chemical stability, and mechanical strength.
Key Characteristics of Single-Side Polished Sapphire Wafers:
Single-Side Polishing:
The single-side polished sapphire wafer has a smooth, flat surface on one side, which is polished to a mirror-like finish, while the other side remains unpolished or has minimal surface treatment.
The polished surface is essential for applications where precise thin-film deposition, photolithography, and optical transmission are needed. This polished surface provides better adhesion for thin films and other materials and allows for uniform layer growth.
Material: Sapphire (Al₂O₃):
Sapphire is a form of aluminum oxide, a crystalline material known for its high hardness, corrosion resistance, and optical transparency across a wide range of wavelengths, including visible and ultraviolet light.
Sapphire wafers are often chosen for their superior mechanical properties and optical clarity, especially in applications where other materials (like silicon) cannot perform well due to environmental conditions or required optical properties.
Applications:
LEDs and Optoelectronics: Sapphire wafers are widely used as substrates for the production of LEDs (Light Emitting Diodes) and laser diodes, particularly in the blue and white LED industries. The smooth surface allows for high-quality deposition of active layers used in LEDs, contributing to higher efficiency and reliability.
Semiconductor Devices: Sapphire wafers are used as substrates for power devices and microwave devices, as they offer high thermal conductivity and excellent electrical insulation properties.
Optical Components: Due to its optical transparency and chemical resistance, sapphire is commonly used in optical components like windows, lenses, and viewports, where high durability and clarity are required.
MEMS (Microelectromechanical Systems): The mechanical strength and smooth surface of single-side polished sapphire wafers make them ideal for MEMS applications, where they serve as substrates for microsensors, actuators, and devices requiring precision fabrication.
High-Temperature and High-Radiation Environments: Sapphire's thermal stability makes it an ideal material for high-temperature applications and environments where devices are exposed to radiation or extreme conditions, such as aerospace, military, and medical technologies.
Diameter and Thickness:
2-inch, 4-inch, 6-inch, or larger diameters are commonly available for single-side polished sapphire wafers. The size depends on the specific application and the equipment used for wafer processing.
The thickness of the sapphire wafer can vary, typically ranging from 200µm to several millimeters depending on the desired application.
Surface Quality:
Polished Surface: The polished surface of the sapphire wafer is essential for ensuring smooth thin-film deposition and uniform etching, which is critical for applications like LED manufacturing and semiconductor processing.
Flatness and Thickness Uniformity: The flatness of the wafer is critical for device yield, especially in photolithography and semiconductor applications. Sapphire wafers are typically manufactured to high standards of flatness and thickness uniformity to ensure that high-performance devices are produced consistently.
Crystal Orientation:
Sapphire wafers are typically oriented with the <0001> crystallographic plane (also known as the c-plane), which is the most common orientation used in optical and semiconductor applications. The c-plane provides optimal properties for LED epitaxial layer growth and other device fabrication processes.
Other orientations like <1120> (a-plane) and <1102> (r-plane) are also used in specific applications, depending on the material's properties required for epitaxial growth and device performance.
Benefits:
High Mechanical Strength: Sapphire is known for its high hardness and resilience, which make the wafer highly resistant to scratches and damage during handling and processing.
Excellent Thermal Conductivity: Sapphire wafers have superior thermal conductivity compared to other materials like silicon, which helps in dissipating heat in high-power devices.
Optical Transparency: Sapphire has high optical transparency, making it ideal for optical windows and devices that need to transmit light without significant absorption or scattering.
Chemical and Environmental Resistance: Sapphire’s chemical inertness and resistance to corrosion make it suitable for use in harsh environments such as high temperatures, vacuum chambers, or high-radiation applications.