The Tiny Sapphire Crystal Propelling the "Grand Future" of Semiconductors

The Tiny Sapphire Crystal Propelling the "Grand Future" of Semiconductors

In our daily lives, electronic devices such as mobile phones and smartwatches have become our inseparable companions. These devices are becoming increasingly thin and lightweight while offering more powerful functionalities. Have you ever wondered what lies behind their continuous evolution? The answer is semiconductor materials, and today, we will focus on one of the standout performers in this field: sapphire crystal.

Sapphire crystal, primarily composed of α-Al₂O₃, is formed by the combination of three oxygen atoms and two aluminum atoms through covalent bonding, resulting in a hexagonal crystal structure. Visually, it shares similarities with gem-quality sapphires we commonly see. However, as a semiconductor material, sapphire crystal is more valued for its excellent properties. It exhibits remarkable chemical stability, generally insoluble in water and resistant to corrosion by acids and bases, acting as a "chemical protection guardian" that maintains its characteristics in various chemical environments. Additionally, it boasts good light transmittance, allowing light to pass through smoothly; excellent thermal conductivity, which helps dissipate heat promptly to prevent devices from "overheating"; and outstanding electrical insulation, ensuring stable transmission of electronic signals and preventing leakage issues. Furthermore, sapphire crystal has excellent mechanical properties, with a hardness of nine on the Mohs scale, second only to diamond in nature, making it highly resistant to wear and erosion, and capable of "standing firm" in various complex environments.

The "Secret Weapon" in Chip Manufacturing

(I) Key Material for Low-Power Chips

Today, electronic devices are rapidly evolving towards miniaturization and high performance. Products like smartphones, smartwatches, and wireless earbuds are expected to have longer battery life and faster operation. This places extremely high demands on chips, with low-power chips becoming the industry's pursuit. Traditional chips, as the number of transistors increases and their size shrinks, experience a decline in the insulation performance of dielectric materials at the nanometer scale, leading to current leakage, increased energy consumption, severe device heating, and reduced stability and lifespan.

The research team at the Shanghai Institute of Microsystems and Information Technology of the Chinese Academy of Sciences has, after years of dedicated research, successfully developed artificial sapphire dielectric wafers, providing strong technical support for the development of low-power chips. They employed an innovative metal intercalation oxidation technique to oxidize single-crystal aluminum into single-crystal aluminum oxide, also known as artificial sapphire. This material achieves extremely low leakage current at a thickness of 1 nanometer, effectively solving the challenges faced by traditional dielectric materials. Compared to traditional amorphous dielectric materials, artificial sapphire dielectric wafers have significant advantages in structure and electronic performance, with a state density reduced by two orders of magnitude and greatly improved interfaces with two-dimensional semiconductor materials. The research team utilized this material in combination with two-dimensional materials to successfully fabricate low-power chip devices, significantly enhancing the battery life and operational efficiency of chips. This achievement means that for smartphones, battery life will be greatly extended, eliminating the need for frequent charging; for fields like artificial intelligence and the Internet of Things, low-power chips will enable more stable and longer-lasting device operation, driving faster development in these areas.

(II) The "Perfect Partner" of Gallium Nitride

In the semiconductor field, gallium nitride (GaN) stands out as a shining star due to its unique advantages. As a wide-bandgap semiconductor material with a bandgap of 3.4eV, much larger than silicon's 1.1eV, GaN excels in high-temperature, high-voltage, and high-frequency applications, offering high electron mobility and breakdown electric field strength, making it an ideal material for manufacturing high-power, high-temperature, high-frequency, and high-brightness electronic devices. For example, in the power electronics field, GaN power devices operate at higher frequencies with lower energy consumption, offering significant advantages in power conversion and power quality management. In the microwave communications field, GaN is used to manufacture high-power and high-frequency microwave communication devices, such as power amplifiers in 5G mobile communications, which improve signal transmission quality and stability.

Sapphire crystal and gallium nitride are "Perfect Partner". They exhibit good lattice matching, and although the lattice mismatch is higher than that of silicon carbide, sapphire substrates demonstrate lower thermal mismatch during GaN epitaxy, providing a stable foundation for GaN growth. Additionally, sapphire crystal's good thermal conductivity and optical transparency allow it to rapidly dissipate heat during high-temperature operation of GaN devices, ensuring stable device performance and maintaining light output efficiency. Furthermore, sapphire crystal's excellent electrical insulation effectively reduces signal interference and power loss. Based on the combination of sapphire crystal and gallium nitride, many high-performance devices have been manufactured. In the LED field, GaN-based LEDs have become the market mainstream, widely used in lighting and display applications, from household LED bulbs to large outdoor displays. Lasers also play an important role in optical communications and laser processing.

Expanding the Boundaries of Semiconductor Applications

(I) The "Shield" in Military and Aerospace Fields

Military and aerospace equipment often operates in extremely harsh environments. In space, spacecraft face near-absolute zero temperatures, intense cosmic radiation, and challenges posed by vacuum environments. Military equipment, such as fighter jets, experiences temperatures exceeding 1000°C due to air friction during high-speed flight, along with high overload and strong electromagnetic interference.

Sapphire crystal, with its unique properties, is an ideal material for critical components in these fields. Its high-temperature resistance is outstanding, capable of withstanding temperatures up to 2045°C while maintaining structural stability without deformation or melting, acting as a resilient "high-temperature guardian" to ensure normal device operation. Additionally, its strong radiation resistance means that in cosmic and nuclear radiation environments, sapphire crystal's performance remains almost unaffected, effectively protecting internal electronic components.

Based on these characteristics, sapphire crystal is extensively used in manufacturing high-temperature-resistant infrared windows. In missile guidance systems, infrared windows are crucial components that must maintain good light transmittance under high temperatures and high-speed flight conditions to allow infrared detectors to accurately capture target infrared signals. Sapphire crystal-based infrared windows not only withstand high temperatures but also ensure high infrared light transmittance, significantly improving missile guidance accuracy. In the aerospace field, satellite optical equipment also relies on sapphire crystal, providing stable protection for optical instruments in harsh space environments and ensuring clear and accurate satellite imagery.

(II) The "New Foundation" for Superconductivity and Microelectronics

In the superconductivity field, sapphire crystal serves as an indispensable substrate for superconducting films. Superconducting films have broad application prospects in power transmission, magnetic levitation trains, and nuclear magnetic resonance imaging, enabling zero-resistance electrical conduction and significantly reducing energy loss. However, preparing high-performance superconducting films requires high-quality substrate materials. Sapphire crystal's stable crystal structure and good lattice matching with superconducting materials provide a stable foundation for superconducting film growth. By epitaxially growing superconducting materials like MgB₂ (magnesium diboride) on sapphire crystal, high-quality superconducting films can be prepared, with significant improvements in critical current density and critical magnetic field performance indicators. For example, in power transmission, using superconducting films based on sapphire substrates for cables can greatly enhance power transmission efficiency and reduce energy loss during transmission.

In the microelectronics integrated circuit field, sapphire crystal also plays an important role. Different crystal orientations of sapphire substrates, such as R-plane (<1-102>) and A-plane (<11-20>), exhibit different electrical properties and crystal structures. Utilizing these characteristics, silicon epitaxial layers with specific electrical properties can be grown. R-plane sapphire substrates are commonly used in high-speed integrated circuits, providing good lattice matching for silicon epitaxial layers, reducing crystal defects, and thereby improving integrated circuit speed and stability. A-plane sapphire substrates, due to their high insulation and uniform capacitance characteristics, are widely used in hybrid microelectronics technology. They not only serve as growth substrates for high-temperature superconductors but also help optimize circuit layouts in integrated circuit design, enhancing circuit integration and reliability. High-end electronic devices, such as core chips in high-performance computers and communication base stations, feature sapphire substrates, providing solid support for the development of microelectronics technology.

The Future Blueprint for Sapphire Crystal

Sapphire crystal has already demonstrated significant application value in the semiconductor field, playing an indispensable role in chip manufacturing, military and aerospace applications, superconductivity, and microelectronics. As technology continues to advance, sapphire crystal is expected to achieve breakthroughs in more fields in the future. In the artificial intelligence field, as the demand for computing chip performance continues to rise, there is an urgent need for low-power, high-performance chips. Sapphire crystal, as a key material, is expected to drive further development of artificial intelligence chips and promote broader applications of AI technology in fields like healthcare, transportation, and finance. In the quantum computing field, although still in its early stages, sapphire crystal's excellent properties make it a potential candidate material for quantum chips, supporting breakthroughs in quantum computing technology.

ZMSH specializes in premium sapphire optical windows and GaN-on-sapphire epitaxial wafers tailored for mission-critical applications. Our sapphire windows combine military-grade durability with optical perfection, featuring sub-angstrom surface roughness for superior light transmission across extreme environments. The GaN-on-sapphire platform achieves breakthrough performance with our proprietary defect-reduction technology, delivering <3E6/cm² dislocation density for high-power RF and optoelectronic devices. Through vertically integrated manufacturing from crystal growth to precision finishing, ZMSH enables customers to push the boundaries of photonics and power electronics performance.

ZMSH's AlN-On-Sapphire epitaxial wafer