Epitaxy is the process of "replicating" a single crystal structure along the substrate lattice direction, allowing the growth layer to "inherit" the ordered arrangement of the substrate. This process requires extremely high requirements for surface cleanliness, temperature field, and atmosphere stability, with the aim of obtaining single crystal thin layers with low defects, controllable impurities, and consistent crystal orientation, providing a platform for high-end device manufacturing.
Intrinsic EPI: ultra-low impurities, ultra-high resistivity, key to high-voltage endurance in power, RF and other fields.
Heterogeneous EPI (such as SiGe/Si, III-V/Si): By combining different materials to achieve performance improvements such as bandgap and mobility, it is the core of emerging technologies such as integrated optoelectronics and high-speed communication.
Intrinsic EPI: ultra-low impurities, ultra-high resistivity, key to high-voltage endurance in power, RF and other fields.
Heterogeneous EPI (such as SiGe/Si, III-V/Si): By combining different materials to achieve performance improvements such as bandgap and mobility, it is the core of emerging technologies such as integrated optoelectronics and high-speed communication.
2.1 Gas phase epitaxy (CVD)
The mainstream is hot/cold wall reactors, with gas sources such as SiH ₄, SiCl ₄, etc., supplemented by doping gases such as PH ∝/B ₂ H ₆.
The typical process temperature is 900-1200 ℃, and the thickness can be adjusted from 0.1-20 μ m.
Emerging directions: low-temperature EPI, atomic layer epitaxy (ALE), molecular beam epitaxy (MBE), etc., to enhance interface control and thin layer uniformity.
2.2 Selective Epitaxy
By relying on photolithography masks, "local epitaxy" can be achieved, significantly increasing the structural complexity of integrated circuits.
Commonly used in FinFET Source/Rain strain engineering, SOI local high voltage regions, and RF heterojunction structures.
2.3 Super Junction EPI
Multilayer P/N EPI layers are alternately stacked, with high lateral doping accuracy, requiring extreme growth thickness and doping synchronization control.
3. Latest EPI technology trends and applications
3.1 Large Size/High Voltage/High Uniformity EPI
12 inch (300mm) EPI: driving cost reduction and efficiency improvement in advanced CMOS and power devices.
Ultra thick EPI (>10 μ m): used in the high-voltage drift region of IGBT and SiC MOSFET, requiring extremely high growth rate and uniformity control.
Gallium Nitride on Silicon (GaN on Si)/Silicon Carbide EPI: A New Hotspot for High Frequency and High Voltage Power Applications in Third Generation Semiconductors.
3.2 Highly doped/gradient doped EPI
Utilizing in-situ doping technology to achieve high-precision N/P epitaxial regions, supporting low loss/high-efficiency power switches.
Gradient doping/local ultra-high doping structure, assisting in the development of high-end devices such as RF and HBT.
3.3 EPI Defects and Interface Engineering
Deep oxidation, micro pollution, substrate stress, and other factors can introduce mismatches and dislocations, affecting the device's BV, Ron, and lifespan.
High end EPI manufacturers use atomic level surface treatment (hydrogen reduction, atomic layer cleaning) combined with in-situ monitoring (RHEED, in-situ XRD, etc.) to minimize TDD, impurities, and surface roughness.
EPI technology is becoming a decisive bottleneck for mass production of third-generation semiconductors such as SiC and GaN——
SiC EPI: The commonly used CVD method for growing low defect drift layers is the key to achieving high voltage and high reliability in SiC MOSFETs and SBDs.
GaN epitaxy: MOCVD/MBE, which requires overcoming challenges such as large-area low dislocation, high uniformity doping, and stress control, is the core technology of high-end RF and power chips.
6. Industry Pattern and Trends
China's domestic EPI capabilities have significantly improved: China Resources Microelectronics, Silan Microelectronics, Huahong Hongli, and others have already deployed 12 inch EPI mass production, accelerating the domestic substitution of SiC/GaN EPI.
Localization of equipment: EPI reactors, precision doping systems, etc. are gradually breaking through, reducing dependence on imported equipment.
High end market concentration: The quality of epitaxial wafers directly determines the discourse power of the industry chain for high-end power devices, RF communications, etc.
