The ins and outs of silicon carbide semiconductor materials

What is silicon carbide semiconductor? What is its development history? For a long time, we basically focused on the research of discrete devices and integrated circuits based on silicon semiconductor materials, which are widely used in consumer electronics and industrial control. , communications, automotive electronics, aerospace and other fields, the development brought by it is huge.

As a country with a huge population, most of my country's semiconductor integrated circuits and other products are still imported. The development of semiconductor technology is still not as good as that of foreign countries. According to incomplete statistics, the average annual import volume of integrated circuits from 2014 to 2017 was 2000. More than 100 million U.S. dollars, a huge amount. Just like the current status of the industry, imported devices are always superior to domestic devices in the minds of engineers. When talking about domestic devices, the first thing that comes to mind is the cost. But with the goal of rejuvenating the country through science and technology, will we be willing to accept this status quo? 2014 In 2017, my country established the Integrated Circuit Industry Investment Fund to promote this industry through market-oriented investment. By 2017, nearly 80 billion yuan had been invested.

Since the beginning of the 21st century, improving energy efficiency and reducing energy consumption has become a very critical issue worldwide. The application of silicon semiconductors in the field of power electronics has gradually approached the theoretical limit of silicon materials. In recent years, wide bandgap semiconductors (WBG Semi, WideBand Gap Semiconductor) represented by silicon carbide (SiC) and gallium nitride (GaN) have become more and more popular. It has attracted more and more attention. Among them, silicon carbide semiconductors have begun to be widely used in many industrial fields. Domestic and foreign manufacturers have also invested in the research and development and production of silicon carbide. The spring of WBG Semi, mainly represented by silicon carbide, It's already here.

Comparison of major semiconductor materials

Analysis of the similarities and differences between the properties of wide-bandgap semiconductor materials, mainly represented by silicon carbide semiconductors, and other commonly used semiconductor materials. Silicon carbide (SiC) is composed of carbon (C) atoms and silicon (Si) atoms. Its crystal structure has the characteristics of a homogeneous polytype. The most common ones in the semiconductor field are 3C-SiC and hexagonal sphalerite structures. 4H-SiC and 6H-SiC with wurtzite structure. At the same time, single crystal silicon carbide (SiC) has many superior physical properties than single crystal silicon (Si), which are mainly superior to silicon-based semiconductor materials in terms of high bandgap width, high breakdown electric field and high thermal conductivity. The currently commonly used silicon carbide epitaxial wafer (EpitaxyWafer) is a 4H-SiC crystal structure.

The picture above shows the parameters of the main semiconductor materials. Silicon is the first generation semiconductor material, silicon carbide is the third generation, and the second generation is represented by gallium arsenide (GaAs). This may be a short transition.

At present, most system manufacturers around the world have expanded their investment in silicon carbide semiconductors, while few manufacturers are willing to invest too much in gallium nitride semiconductors for the following reasons:

①The advantage of silicon carbide is that it is more mature than gallium nitride from the mass production level and has better performance.

②The advantage of silicon-based gallium nitride is that the cost is theoretically cheaper than silicon carbide;

③If you want to change this situation, gallium nitride power devices need to be more reliable and provide cheaper system solutions.

Silicon carbide semiconductor chip products mainly include silicon carbide semiconductor power devices and matching silicon carbide MOSFET driver chips. Among them, the main product directions of silicon carbide semiconductor power devices currently include two categories.

One type is the diode type, which mainly includes junction barrier Schottky diodes (JBS Junction Barrier Schottky) and MPS diodes (MPS, Merged PiN Schottky).

One type is field-effect transistors (FETs), including junction field-effect transistors (JFETs), metal-oxide semiconductor field-effect transistors (MOSFETs), etc.

Major SiC manufacturers

At present, most of the mainstream silicon carbide manufacturers are still established foreign brands, and the most important one is undoubtedly Infineon, which has a slightly dominant temperament.

In 2001, Germany's Infineon took the lead in industrializing silicon carbide diode products, and manufacturers such as Cree and ST Microelectronics in the United States followed suit and launched silicon carbide diode products. Infineon also wanted to annex Cree, but failed due to pressure from the government. In Japan, Rohm, Fuji Electric and Renesas are also developing Schottky barrier diodes (SBD) and junction barrier Schottky diodes (JBS). At present, the silicon carbide diode product series already includes products with voltage levels of 600V~1700V and current levels of 50A.

In September 2012, the American company Creat announced the mass production of 6-inch silicon carbide wafers, which was a turning point for silicon carbide to move toward large-scale production and thus become truly market-oriented. The early carbonized MOSFETs started with planar types, including the first and second generations of ROHM of Japan and the first three generations of Cree of the United States. Currently, the German company Infineon is focusing on promoting trench silicon carbide MOSFETs. Domestic manufacturers will certainly not sit still and wait for the development of foreign countries. Domestic manufacturers have also begun to enter the field of silicon carbide power device research, including Tyco Tianrun, Century Jinguang and Basic Semiconductor. According to reports, silicon carbide diodes have entered mass production, and silicon carbide MOS also has finished products.

Common SiC packaging types

Although silicon carbide semiconductor materials have incomparable advantages over silicon semiconductor materials, the relevant power device packaging types in the current mass production stage basically still use silicon power devices. At present, the commonly used packaging type of silicon carbide diodes is still TO220, and the commonly used packaging type of silicon carbide MOSFET is still TO247-3. Of course, the TO247-4 package has also been launched, adding a dedicated source pin for drive control, which improves switching energy efficiency, reduces switching losses, supports higher switching frequencies, and further reduces the size of the power supply.

Silicon carbide module packaging

Compared with silicon IGBT power modules, full silicon carbide power modules can switch at high speeds and can significantly reduce switching losses. In order to optimize the performance and reliability of silicon carbide power devices during use, and effectively combine power devices with different application solutions, research on module packaging has already begun. However, the main bottleneck of module packaging is the high dv/ dt and di/dt, high operating temperature and high electric field strength. Currently, all-silicon carbide power modules are commonly used, which are a combination of silicon carbide MOSFETs and silicon carbide diodes, and the driver chip is usually placed on the driver board outside the power module.

The close integration of silicon carbide power devices and power electronics application solutions will be an important condition for promoting the widespread application of silicon carbide semiconductors. At present, the main applications of silicon carbide are roughly as follows: photovoltaics, new energy vehicles, charging piles, smart grids, etc. Price is one of the factors currently restricting its wide-scale use.

Silicon carbide materials mainly include silicon carbide substrate (Substrate) and epitaxial wafer (EpitaxyWafer). At present, silicon carbide substrate wafers and epitaxial wafers are basically in the hands of several major manufacturers in the United States and Japan. At present, the chip cost of silicon carbide power devices depends largely on the cost of silicon carbide materials. Domestic silicon carbide production is urgently expected within 5 years. Materials have achieved a qualitative breakthrough in quality. The above is the development history of silicon carbide semiconductors, I hope it can be a reference for everyone.