Electric Vehicles
Smart Power
It does not matter whether a hybrid vehicle represents the mild, full or plug-in type, car manufacturers are confronted with the same key issue: how does the electrical energy from the battery get to the electric motor at the right time, and vice versa? This is where power semiconductors come into play. And not just in hybrid vehicles, but in all electrical devices that we encounter in our day-to-day lives. After all, every electric device in a piece of equipment has to be driven at a specific voltage. The market for these power applications is now around 15 percent of all the silicon sold throughout the world, measured by surface area. What’s more, about one quarter of that is made from float zone (FZ) wafers.
FZ wafers are characterized by a high, uniform electrical resistivity, as well as a low oxygen content and few defects. They are found in almost all power devices, across a wide spectrum ranging from very simple devices that have been mass-produced for years to highly complex devices requiring a high level of skill on the part of the manufacturer.
Of particular interest is the “insulated gate bipolar transistor” (IGBT). This relatively new device is noted for its high efficiency and fast switching, making it ideal for applications where saving energy and protecting the environment are important factors. Consequently, IGBTs are found in hybrid vehicles and electric vehicles, in wind turbines and solar installations, as well as in smart grids and modern household appliances, such as refrigerators and air-conditioning systems.
Siltronic is the market leader in 150 and 200 mm FZ wafers.
Siltronic is the market leader in 150 and 200 mm FZ wafers.
Ever More Electronic Components in Vehicles
Although the automotive market is relatively small, the number of electronic components in automobiles is steadily rising. Hybrid and electric vehicles have the highest share of electronic devices. They need IGBTs for power control. The power control unit (PCU) in these cars regulates the transfer of energy between the battery and electric motor. Such PCUs can contain up to 20 IGBTs. IGBT use in the car industry is expected to grow around 30 percent in 2011.
IGBTs are not made from FZ wafers exclusively: conventional epitaxial CZ wafers are also used. However, because of miniaturization and improved performance, FZ wafers are increasingly the preferred choice. There are two major reasons for this: epitaxial wafers need a particularly thick surface layer of epitaxied silicon, around 1 μm for 10 volts or 100 μm for a device designed for 1,000 volts. This makes them relatively expensive and prone to defects, especially when produced on 200 mm wafers.
