Introduction to 13 commonly used semiconductor power devices

Summary of commonly used semiconductor power device knowledge

Power Electronic Devices, also known as power semiconductor devices, are used in high-power (usually tens to thousands of amperes of current and hundreds of volts or more) electronic devices in power conversion and power control circuits. It can be divided into semi-controlled devices, fully controlled devices and uncontrollable devices. Among them, thyristors are semi-controlled devices, with the highest voltage and current capacity among all devices; power diodes are uncontrollable devices with simple structure and principle. Reliable; it can also be divided into voltage-driven devices and current-driven devices, among which GTO and GTR are current-driven devices, and IGBT and power MOSFET are voltage-driven devices.

1. MCT (MOS Control led Thyristor): MOS controlled thyristor

MCT is a new type of MOS and bipolar composite device. As shown in FIG. MCT combines the high impedance, low drive diagram of MOSFET and the power and fast switching speed characteristics of MCT with the high voltage and high current characteristics of thyristor to form a high power, high voltage, fast and fully controlled device. In essence, MCT is a MOS gate controlled thyristor. It can add a narrow pulse to the gate to turn it on or off. It is composed of countless unit cells connected in parallel. Compared with GTR, MOSFET, IGBT, GTO and other devices, it has the following advantages:

(1) High voltage and large current capacity, the blocking voltage has reached 3000V, the peak current reaches 1000 A, and the maximum shut-off current density is 6000kA/m2;

(2) The on-state voltage drop is small and the loss is small, and the on-state voltage drop is about 11V;

(3) Extremely high dv/dt and di/dt tolerance, dv/dt has reached 20 kV/s, di/dt is 2 kA/s;

(4) The switching speed is fast, the switching loss is small, the turn-on time is about 200ns, and the 1000 V device can turn off within 2s;

2. IGCT (Integrated Gate Commutated Thyristors)

IGCT is a new device developed based on thyristor technology combined with IGBT and GTO technologies. It is suitable for high-voltage and large-capacity frequency conversion systems. It is a new power semiconductor device used in giant power electronics complete sets.

IGCT integrates a GTO chip with an anti-parallel diode and gate driver circuit, and then connects its gate driver to the periphery in a low-inductance manner. It combines the stable turn-off capability of the transistor and the advantages of the low on-state loss of the thyristor. In the conduction phase, the performance of the thyristor is exerted, and in the turn-off phase, the characteristics of the transistor are displayed. When the IGCT chip is not connected in series or in parallel, the power of the two-level inverter is 0.5~3 MW, and the power of the three-level inverter is 1~6 MW; if the reverse diode is separated and not integrated with the IGCT, the power of the two-level inverter is 0.5~3 MW. The inverter power can be expanded to 4/5 MW and three-level to 9 MW.

At present, IGCT has been commercialized. The highest performance parameter of the IGCT product manufactured by ABB is 4[1] 5 kV/4 kA, and the highest development level is 6 kV/4 kA. In 1998, Mitsubishi Corporation of Japan also developed a GCT thyristor IGCT with a diameter of 88 mm. The advantages of low loss and fast switching ensure that it can be used in 300 kW ~ 10 MW converters reliably and efficiently without the need for series connection and in parallel.

3. IEGT (Injection Enhanced Gate Transistor) electron injection enhanced gate transistor

IEGT is an IGBT series power electronic device with a withstand voltage of more than 4 kV. It achieves a low on-state voltage by adopting an enhanced injection structure, which has led to a rapid development of large-capacity power electronic devices. IEGT has a potential future as a MOS series power electronic device. It has the characteristics of low loss, high-speed operation, high withstand voltage, intelligent active gate drive, etc., as well as the characteristics of using trench structure and multi-chip parallel connection for self-current sharing, making it It has potential for further expansion of current capacity. In addition, a wide range of distributed products can be provided through module packaging, which has high hopes in large and medium-capacity converter applications. The IECT developed by Toshiba of Japan utilizes the electron injection enhancement effect to combine the advantages of both IGBT and GTO: low saturation voltage drop, safe operating area (the absorption loop capacity is only about one-tenth of GTO), low gate Driving power (two orders of magnitude lower than GTO) and higher operating frequency. The device adopts a flat-plate crimping motor lead-out structure, which has high reliability and its performance has reached the level of 4.5 kV/1500A.

4. IPEM (Integrated Power Elactronics Modules): Integrated power electronic modules

IPEM is a module that integrates many components of a power electronic device. It first packages semiconductor device MOSFET, IGBT or MCT and diode chips together to form a building block unit. Secondly, these building block units are stacked on a high-conductivity insulating ceramic substrate with open holes. Below it are Copper substrate, beryllium oxide ceramic tiles and heat sink. On the upper part of the building block unit, the control circuit, gate driver, current and temperature sensor and protection circuit are integrated on a thin insulating layer through surface mounting. IPEM achieves the intelligence and modularization of power electronics technology, greatly reduces circuit wiring inductance, system noise and parasitic oscillation, and improves system efficiency and reliability.

5. PEBB (Power Electric Building Block) 

PEBB (Power Electric Building Block) is a device or module developed on the basis of IPEM that can handle electric energy integration. PEBB is not a specific semiconductor device. It is an integration of different devices and technologies designed according to optimal circuit structure and system structure. A typical PEBB is shown above. Although it looks a lot like a power semiconductor module, PEBB includes gate drive circuits, level conversion, sensors, protection circuits, power supplies, and passive components in addition to power semiconductor devices. PEBB has energy interface and communication interface. Through these two interfaces, several PEBBs can form a power electronic system. These systems can be as simple as a small DC-DC converter or as complex as a large distributed power system. The number of PEBBs in a system can range from one to any number. Multiple PEBB modules working together can complete system-level functions such as voltage conversion, energy storage and conversion, and impedance matching. The most important feature of PEBB is its versatility.

6. Ultra-high power thyristor

Since the advent of the thyristor (SCR), its power capacity has increased nearly 3,000 times. At this time, many countries have been able to stably produce 8kV/4kA thyristors. At this time, Japan has put into production 8kV/4kA and 6kV/6kA light-triggered thyristors (LTT). The United States and Europe mainly produce electrically triggered thyristors. In the past decade or so, due to the rapid development of self-turnoff devices, the application fields of thyristors have been reduced. However, due to its high voltage and high current characteristics, it has been widely used in HVDC, static var compensation (SVC), and high-power DC power supplies. And it still occupies a very important position in ultra-high power and high-voltage frequency conversion speed regulation applications. It is expected that in the next few years, thyristors will continue to be developed in high-voltage and high-current applications.

At this time, many manufacturers can provide high-voltage and high-current GTOs with a rated switching power of 36MVA (6kV/6kA). The typical turn-off increment of traditional GTO is only 3 to 5. The "squeezing effect" caused by the non-uniformity during the GTO turn-off period makes it necessary to limit the dv/dt during the turn-off period to 500~1kV/μs. For this reason, people have to use bulky and expensive absorption circuits. In addition, its gate drive circuit is more complex and requires larger drive power. So far, gated power semiconductor devices are most commonly used in high-voltage (VBR > 3.3kV), high-power (0.5-20 MVA) traction, industrial and power inverters. Currently, the highest research levels of GTO are 6in, 6kV/6kA and 9kV/10kA. In order to meet the needs of the power system for three-phase inverter power voltage sources above 1GVA, it is very likely to develop 10kA/12kV GTO in the near future, and it is possible to overcome the technology of more than 30 high-voltage GTOs in series, which is expected to make power electronics technology more popular in the world. Applications in power systems have reached a new level.

7. Pulse power closed switching thyristor

The device is particularly suitable for discharge closure switching applications that deliver extremely high peak powers (several MW) and very short durations (several ns), such as lasers, high-intensity lighting, discharge ignition, electromagnetic transmitters, and radar modulators. wait. This device can be quickly switched on at high voltages of several kV, does not require discharge electrodes, has a long service life, is small in size, and is relatively low-priced. It is expected to replace the high-voltage ion thyratrons, ignition tubes, and spark tubes that are still in use. Gap switch or vacuum switch, etc.

The unique structure and process characteristics of this device are: the gate-cathode perimeter is very long and forms a highly intertwined structure. The gate area accounts for 90% of the total chip area, while the cathode area only accounts for 10%; the hole-electron lifetime in the base area Very long, the horizontal distance between gate-cathode is less than one diffusion length. The above two structural features ensure that 100% of the cathode area can be used when the device is turned on. In addition, the device's cathode electrode uses a thicker metal layer to withstand instantaneous peak currents.

8. New GTO device-integrated gate commutated thyristor

There are currently two alternatives to conventional GTO: high-power IGBT modules and new GTO-derived devices - integrated gate commutation IGCT thyristors. IGCT thyristor is a new type of high-power device. Compared with conventional GTO thyristor, it has many good characteristics, such as reliable shutdown without buffer circuit, short storage time, strong turn-on ability, and shut-off gate charge. The total power loss of the application system (including all devices and peripheral components such as anode reactors and snubber capacitors, etc.) is low.

9. High power trench gate structure IGBT (Trench IGBT) module

The IGBT cells in today's high-power IGBT modules usually use trench gate structure IGBTs. Compared with the planar gate structure, the trench gate structure usually adopts 1μm processing accuracy, which greatly increases the cell density. Due to the existence of the gate trench, the junction field effect transistor effect formed between adjacent cells in the planar gate structure device is eliminated. At the same time, a certain electron injection effect is introduced, which reduces the on-resistance. This creates conditions for increasing the thickness of the long base area and improving the withstand voltage of the device. Therefore, the high-voltage and high-current IGBT devices that have appeared in recent years all adopt this structure.

In 1996, Japan's Mitsubishi and Hitachi successfully developed 3.3kV/1.2kA large-capacity IGBT modules. Compared with conventional GTO, their switching time is shortened by 20%, and the gate drive power is only 1/1000 of GTO. In 1997, Fuji Electric successfully developed a 1kA/2.5kV flat-plate IGBT. Since the collector and emitter junctions adopt The flat-plate crimping structure is similar to GTO and adopts a more efficient heat dissipation method at both ends of the chip. What is particularly meaningful is that it avoids a large number of electrode leads inside the high-current IGBT module, improves reliability and reduces lead inductance. The disadvantage is that the chip area utilization rate decreases. Therefore, this kind of high-voltage and high-current IGBT module with a flat-plate crimping structure is also expected to become the preferred power device for high-power and high-voltage converters.

10. Electron injection enhanced gate transistor IEGT (Injection Enhanced Gate Trangistor)

In recent years, Toshiba Corporation of Japan has developed IEGT. Like IGBT, it is also divided into two structures: planar gate and trench gate. The former product is about to be released, and the latter is still under development. IEGT has some advantages of both IGBT and GTO: low saturation voltage drop, wide safe operating area (the absorption loop capacity is only about 1/10 of GTO), low gate drive power (2 lower than GTO order of magnitude) and higher work frequency. In addition, the device adopts a flat-plate crimp-type electrode lead-out structure, which is expected to have high reliability.

Compared with IGBT, the main features of the IEGT structure are that the gate length Lg is longer, and the lateral resistance value of the N-long base region near the gate is higher. Therefore, holes in the N-long base region are injected from the collector, unlike in IGBT. As in, it smoothly flows into the emitter laterally through the P region, but forms a hole accumulation layer in this region. In order to maintain the electrical neutrality of this region, the emitter must inject a large number of electrons into the N-long base region through the N channel. In this way, a high concentration of carriers is accumulated on the emitter side of the N-long base region, and a carrier distribution similar to that in GTO is formed in the N-long base region, thereby better overcoming the problem of high current and high withstand voltage. contradiction. At present, the device has reached the level of 4.5kV/1kA.

11. MOS gated thyristor

MOS gate controlled thyristors make full use of the excellent on-state characteristics, good turn-on and turn-off characteristics of thyristors, and are expected to have good self-turn-off dynamic characteristics, very low on-state voltage drop and high voltage resistance, becoming an important part of power devices in the future. and promising high-voltage and high-power devices in power systems. Currently, there are more than a dozen companies in the world actively conducting research on MCT. There are three main structures of MOS gated thyristors: MOS field controlled thyristor (MCT), base resistance controlled thyristor (BRT) and emitter switching thyristor (EST). Among them, EST may be the most promising structure among MOS gated thyristors. However, it will take a long time for this kind of device to truly become a commercially practical device and reach the level of replacing GTO.

12. Gallium arsenide diode

As the switching frequency of converters continues to increase, the requirements for fast recovery diodes also increase. As we all know, gallium arsenide diodes have superior high-frequency switching characteristics than silicon diodes. However, due to process technology and other reasons, gallium arsenide diodes have a lower withstand voltage, and their practical applications are limited. In order to meet the needs of high-voltage, high-speed, high-efficiency and low-EMI applications, high-voltage gallium arsenide high-frequency rectifier diodes have been successfully developed at Motorola. Compared with silicon fast recovery diodes, the salient features of this new type of diode are: small reverse leakage current degradation with temperature, low switching losses, and good reverse recovery characteristics.

13. Silicon carbide and silicon carbide (SiC) power devices

Among power devices made of new semiconductor materials, the most promising are silicon carbide (SiC) power devices. Its performance index is one order of magnitude higher than that of gallium arsenide devices. Compared with other semiconductor materials, silicon carbide has the following excellent physical characteristics: high bandgap width, high saturated electron drift velocity, high breakdown strength, Low dielectric constant and high thermal conductivity. The above-mentioned excellent physical properties determine that silicon carbide is an ideal semiconductor material in high-temperature, high-frequency, and high-power applications. Under the same withstand voltage and current conditions, the drift region resistance of SiC devices is 200 times lower than that of silicon. Even the conduction voltage drop of high-withstand voltage SiC field effect transistors is higher than that of unipolar and bipolar silicon devices. Much lower. Moreover, the switching time of SiC devices can reach the order of 10nS and has very superior FBSOA.

SiC can be used to manufacture RF and microwave power devices, various high-frequency rectifiers, MESFETS, MOSFETS and JFETS, etc. SiC high-frequency power devices have been successfully developed by Motorola and used in microwave and radio frequency devices. GE is developing SiC power devices and high-temperature devices (including sensors for jet engines). Westinghouse has manufactured very high frequency MESFETs operating at 26GHz. ABB is developing high-power, high-voltage SiC rectifiers and other SiC low-frequency power devices for industrial and power systems.