1. Material Properties of Sapphire substrate
Crystal Structure:
Sapphire (α-Al₂O₃) belongs to the hexagonal crystal system and exhibits a highly ordered atomic arrangement. This gives sapphire exceptional mechanical stability, allowing it to maintain performance in harsh environments. It provides a reliable and stable substrate environment for semiconductor epitaxial growth, helping reduce defect formation.
High Hardness and Corrosion Resistance:
With a Mohs hardness of 9—second only to diamond—
sapphire has outstanding scratch and wear resistance. Its excellent corrosion resistance enables it to maintain integrity over long periods in acidic and alkaline environments, making it a preferred material for high-reliability applications.
Superior Optical Properties:
Sapphire offers high optical transparency, particularly in the UV to IR wavelength range. This makes it ideal for optoelectronic devices such as LEDs and lasers, ensuring efficient photon transmission and minimal optical loss, which ultimately enhances device performance.
Excellent Thermal Properties:
With a thermal conductivity of up to 42 W/m·K at room temperature, sapphire maintains strong thermal stability even under high temperatures. This enables effective heat dissipation in high-power applications and prevents performance degradation caused by thermal fluctuations.
Lattice Compatibility with GaN:
Sapphire has a lattice mismatch of only 16% with GaN, which helps reduce the defect density in the epitaxial layer, thus improving the optical and electrical performance of the device.
2. Manufacturing Process
2.1 Crystal Growth Technologies
| Method |
Characteristics |
Mainstream Sizes |
| Kyropoulos (KY) |
Cost-effective, optical-grade wafers |
4–6 inches |
| Heat Exchange Method (HEM) |
Large size, low stress |
8–12 inches |
| Edge-Defined Film-Fed Growth (EFG) |
Sheet growth, suitable for LED substrates |
2–4 inches |
Precision Cutting:
Due to sapphire’s high hardness, laser cutting or diamond wire sawing is typically used to ensure precision, minimize material loss, and enhance surface quality.
Polishing and Surface Treatment:
After cutting,
wafers undergo chemical mechanical polishing (CMP) to achieve nanometer-level flatness, which is crucial for high-quality epitaxial growth. This significantly reduces defect rates and improves uniformity.
3. Applications
LED Technology:
Sapphire is the substrate of choice for blue and UV LEDs, providing a stable platform for GaN epitaxy, reducing defect density, and enhancing light emission efficiency and durability.
Lasers and Optical Devices:
Its high hardness and optical clarity make sapphire ideal for high-power laser windows and for use in precision optical lenses and detectors.
Integrated Circuits (ICs) and RF Devices:
Sapphire offers excellent insulation and low dielectric loss, enabling efficient transmission of high-frequency signals and reducing power consumption and EMI in RF and high-speed circuits.
Consumer Electronics:
Sapphire is widely used for camera lens covers and fingerprint recognition modules in smartphones, as well as watch crystals in high-end timepieces, owing to its scratch resistance and transparency.
4. Limitations
Lattice and Thermal Stress Mismatch:
Mismatch with epitaxial materials can generate defects in the epitaxial layer, complicating downstream device processing.
Electrical Insulation Limitations:
As an insulator with a resistivity >10¹¹ Ω·cm at room temperature, sapphire cannot be used in vertical device structures. Electrodes are typically placed only on the surface, which reduces the effective light-emitting area and increases the complexity and cost of photolithography and etching processes.
Limited Thermal Conductivity:
Although better than many insulators, sapphire's thermal conductivity is still a constraint for high-power, large-area LED devices, where efficient heat dissipation is critical.
Difficult to Process:
Its high hardness poses challenges for thinning and cutting during device fabrication. Significant equipment investment is needed for precision processing.
5. Conclusion
Sapphire substrates, with their unique combination of optical, mechanical, and dielectric properties, continue to play an irreplaceable role in semiconductors, optoelectronics, and advanced RF applications. As processing technologies such as stealth laser dicing and nanoimprint lithography advance, sapphire's cost-efficiency and application potential are expected to expand even further.JXT Technology Co.,Ltd is good sapphire substrate supplier, provide high quality,low sapphire wafer price, if you need,just contact us now!
