Why is SOI so popular in RF chips? The parasitic capacitance is small; High integration density; Fast speed
May 22, 2025
Why is SOI so popular in RF chips? The parasitic capacitance is small; High integration density; Fast speed
SOI stands for Silicon-On-Insulator, which refers to Silicon On an insulating substrate. This technology introduces an embedded oxide layer between the top silicon and the backing substrate. The principle is that by adding insulating substances between silicon transistors, the parasitic capacitance between them can be reduced by twice as much as before.
There are the following three types of
technologies for forming SOI materials:
1. Separation by Implanted Oxygen (SIMOX)
2. Bond and Etch-back SOI (BESOI)
3. Smart-Cut
SOI materials have advantages that body silicon cannot match: they can achieve dielectric isolation of components in integrated circuits and completely eliminate the parasitic latch-up effect in body silicon CMOS circuits. Integrated circuits made of this material also have the advantages of small parasitic capacitance, high integration density, fast speed, simple process, small short-channel effect and being particularly suitable for low-voltage and low-power circuits.
Furthermore, the impedance value of the substrate of the SOI wafer itself can also affect the performance of the component. Therefore, later on, some companies adjusted the impedance value on the substrate to improve the characteristics of the Radio frequency component (RF component). Some of the electrons that were originally supposed to pass through the exchanger will drill into the silicon, causing waste. SOI can prevent electron loss and complement the shortcomings of some CMOS components in the original Bulk wafer. RF SOI is a silicon-based semiconductor process material with a unique three-layer structure of silicon/insulating layer/silicon. It achieves full dielectric isolation between the device and the substrate through an insulating layer (usually SiO2).
Since RF-SOI can achieve higher linearity and lower insertion loss at the best cost performance, it can bring people faster data speed, longer battery life, and more stable and smooth communication quality with higher frequency. For decades, the telecommunications infrastructure market has been driven by macro and micro base stations. Nowadays, with the help of 5G large-scale MIMO active antenna systems, the radio frequency (RF) component industry is choosing an increasing number of RF components. Yole Intelligence, a subsidiary of Yole Group, estimates that the radio frequency market for telecommunications infrastructure was worth $3 billion in 2021 and is expected to reach $4.5 billion by 2025.
Three direction of SOI
RF SOI -is a kind of unique silicon/insulating layer three-layered silicon/silicon semiconductor material technique, it through the buried insulating layer (usually in the form of SiO2) realized the full dielectric isolation device and the substrate. Since RF-SOI can achieve higher linearity and lower insertion loss at the best cost performance, it can bring people faster data speed, longer battery life, and more stable and smooth communication quality with higher frequency. RF-SOI can ensure very high signal linearity and signal integrity.
Power - SOI: the main structure of single crystal top silicon (mono - crystal top material), middle buried oxide layer (buried oxide) and the underlying silicon substrate (silicon base). Due to the thickened Buried Oxide structure of the POWER-SOI wafer, it can effectively overcome the problem that high voltage may penetrate the components and achieve the stability in the use of Power components. Therefore, POWER-SOI is mainly applied in the integration of high-voltage components in the manufacturing technology of BCD (Bipole-CMOS-DMOS) Power integrated
circuits.
FD-SOI ( full depletion silicon on insulator) is a kind of planar t
echnology, structurally, FD - electrostatic properties of SOI transistor is superior to the conventional silicon technology. The buried oxygen layer can reduce the parasitic capacitance between the source and the drain, and effectively suppress the flow of electrons from the source to the drain, thereby significantly reducing the leakage current that leads to performance degradation. Furthermore, FD-SOI also has many unique advantages in other aspects, including backside bias capability, excellent transistor matching characteristics, the ability to use low power supply voltages close to the threshold, ultra-low sensitivity to radiation, and a very high transistor intrinsic operating speed, etc. These advantages enable it to operate in applications in the millimeter-wave frequency band.
Application field of SOI
RF - SOI applied in RF applications, now has become a switch of smartphones and antenna tuner best solution;
POWER - SOI for intelligent POWER conversion circuit, mainly used in automotive, industrial, household appliances consumer high reliability, high performance scene;
FD - SOI has a less silicon geometry size and the advantages of simplified manufacturing process, mainly used in smart phones, the Internet of things, 5 g, such as cars for high reliability, high integration, low power consumption and low cost applications; Optical SOI is applied in optical communication fields such as data centers and cloud computing.
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