0

What is SOI technology?


SOI (Silicon-On-Insulator) is a semiconductor manufacturing technology in which part of the silicon wafer is isolated by an insulating layer (usually silicon dioxide), which can effectively reduce parasitic capacitance and leakage current and improve device performance.


SOI wafers usually consist of three layers:


●Top silicon (Device Layer): This is the silicon layer that eventually forms the semiconductor device. The thickness is usually tens of nanometers to several microns, depending on the specific application.

●Insulating layer (Buried Oxide, BOX): Between the top silicon and the base silicon, there is a thin layer of silicon oxide (SiO₂), usually tens to hundreds of nanometers thick. This layer acts as electrical isolation and reduces the parasitic effects of the device.

●Substrate: The bottom layer is usually a thicker silicon substrate that acts as a mechanical support.

SOI silicon on insulator wafer

Types of SOI


SOI is divided into two common types: FD-SOI and PD-SOI.


In the PD-SOI (Partially Depleted SOI) structure, the channel single-crystal silicon thickness and buried layer thickness are relatively thick, generally the channel single crystal silicon thickness is 50nm-100nm, and the buried oxide layer thickness is 100-200nm. The area close to the insulating layer will form a depletion region, while the area far from the insulating layer still contains free charge, forming an undepleted area.


FD-SOI (Fully Depleted Silicon-On-Insulator), also known as UTB (Ultra-Thin Body) SOI, has extremely thin channel single crystal silicon and buried oxide layer thickness, generally the channel single crystal silicon thickness is 10nm, and the buried oxide layer thickness is 20nm. Since the thickness of the channel single crystal silicon is very thin, it does not need to be doped, so the carriers are completely depleted.

FD-SOI vs PD-SOI

Floating body effect: In PD-SOI transistors, the undepleted body region can store charge, which causes the device threshold voltage to change over time, affecting the stability of the transistor.


Hysteresis: Charge accumulation caused by the floating body effect causes hysteresis on the I-V curve.


Large off current: Undepleted single crystal silicon can increase the leakage current of the transistor in the off state, which has a negative impact on power consumption.


Self-heating effect: Since the insulating layer of FD-SOI hinders heat dissipation, it will cause self-heating of the transistor, which may affect the performance of FD-SOI.


Utilizing the body bias effect: FD-SOI can dynamically adjust the threshold voltage and optimize performance and power consumption through body bias, thereby achieving faster switching of transistors.


Application of SOI technology


SOI technology is widely used in high-performance microprocessors, radio frequency (RF) devices, low-power consumer electronics, and automotive electronics. Especially in scenarios requiring high switching speed, low power consumption and high reliability, SOI technology has shown significant advantages, including but not limited to: high-performance microprocessors and server chips, radio frequency (RF) front-ends and high-speed communication chips, aerospace and military electronics, and high-reliability automotive electronics.



By choosing Semicorex's SOI wafers, you can count on excellent quality and reliability. Our SOI wafers are manufactured using advanced processes to ensure high purity and excellent electrical properties. They are designed to meet the needs of various high-performance applications, whether it's for RF devices, microelectronic circuits, or optoelectronic applications. We also offer customized solutions to meet your specific needs and ensure the success of your project.