As one of the important high-power mainstream devices for power electronics, IGBT has been widely used in household appliances, transportation, power engineering, renewable energy and smart grid. In industrial applications such as traffic control, power conversion, industrial motors, uninterruptible power supplies, wind and solar equipment, and frequency converters for automatic control.

The IGBT module is a modular semiconductor product that is packaged by IGBT and FWD through a specific circuit bridge; the packaged IGBT module is directly applied to equipment such as inverter and UPS uninterruptible power supply; IGBT module has energy saving, convenient installation and maintenance, and heat dissipation. Stable and so on; the current market sales are mostly such modular products, generally referred to as IGBT modules; with the promotion of energy conservation and environmental protection concepts, such products will become more and more common in the market.


How IGBT works

IGBTs are a natural evolution of vertical power MOSFETs for high current, high voltage applications and fast end devices. Since a high breakdown voltage BVDSS requires a source-drain path, and this channel has a high resistivity, resulting in a power MOSFET having a high RDS(on) value, the IGBT eliminates these existing power MOSFETs. The main drawback. Although the latest generation of power MOSFET devices have greatly improved the RDS(on) characteristics, at high levels, the power conduction losses are still much higher than the IGBT technology. The lower voltage drop, the ability to convert to a low VCE(sat), and the IGBT structure support higher current densities and simplify the schematic of the IGBT driver compared to a standard bipolar device.

The structure of the IGBT silicon is very similar to that of the power MOSFET. The main difference is that the IGBT adds a P+ substrate and an N+ buffer layer (NPT-non-punch-IGBT technology does not add this part). One of the MOSFETs drives two bipolar devices. The application of the substrate creates a J1 junction between the P+ and N+ regions of the tube. When the positive gate bias causes the P-base region to be inverted below the gate, an N-channel is formed, a current flow occurs simultaneously, and a current is generated in exactly the manner of the power MOSFET.

IGBT and MOSFET are different

MOSFET full name power field effect transistor. Its three poles are source (S), drain (D) and gate (G). The main advantages are good thermal stability and large safe working area. The disadvantages are low breakdown voltage and low operating current.

The IGBT is a combination of a MOSFET and a GTR (power transistor). Its three poles are collector (C), emitter (E) and gate (G). The breakdown voltage can reach 1200V, and the maximum saturation current of the collector has exceeded 1500A. The inverter with IGBT as the inverter device has a capacity of more than 250kVA and an operating frequency of up to 20kHz.


IGBT and MOSFET association

In the early 1980s, DMOS (double diffusion formed metal-oxide-semiconductor) processes for power MOSFET fabrication technology were introduced into IGBTs. At that time, the structure of the silicon chip was a thicker NPT (non-punch through) design. Later, a significant improvement in parametric tradeoffs was achieved by using a PT (punch-through) type of structure, which is a technological advancement over epitaxial wafers and the use of n+ buffer layers designed for a given blocking voltage. Progressive. In the past few years, the DMOS planar gate structure fabricated on epitaxial wafers using PT design has been designed from 5 micron to 3 micron.

In the mid-1990s, the trench gate structure returned to a new concept of IGBT, a new etch process using silicon dry etch technology borrowed from large-scale integration (LSI) processes, but still punch-through ( PT) type chip structure. In this trench structure, a more significant improvement in the trade-off between on-state voltage and off-time is achieved. The critical structure of the silicon chip has also undergone a dramatic transformation, first using a non-punch-through (NPT) structure, which in turn changes to a weak through-pass (LPT) structure, which results in a similar improvement in the safe working area (SOA) with the evolution of the surface gate structure. .

development trend

1, low power IGBT

IGBT application range is generally in the range of 600V, 1KA, 1KHz or above. In order to meet the development needs of the home appliance industry, Motorola, ST Semiconductor, Mitsubishi and other companies have introduced low-power IGBT products, which are used in microwave ovens, washing machines, induction cookers, and electronic rectifiers for the home appliance industry. Applications such as cameras and cameras.


U (trench structure) - The IGBT is grooved on the die, and a trench gate is formed inside the chip cell. By adopting the channel structure, the cell size can be further reduced, the channel resistance can be reduced, the current density can be improved, and the product with the same rated current and the smallest chip size can be manufactured. A number of existing companies produce a variety of U-IGBT products for low voltage drive and surface mount requirements.


NPT (non-punch-through type)--IGBT adopts thin silicon wafer technology, and replaces high-complexity and high-cost thick-layer high-resistance epitaxy with ion injection into the emitter area, which can reduce the production cost by about 25%. The higher the withstand voltage, the greater the difference in cost. It has more characteristics in performance, high speed, low loss, positive temperature coefficient and no locking effect. When designing 600-1200V IGBT, NPT-IGBT has the highest reliability. Siemens can provide 600V, 1200V, 1700V series products and 6500V high voltage IGBTs, and introduce low saturation voltage drop DLC type NPT-IGBT. Ixus, Harris, Intersil, Toshiba and other companies have also developed NPT- IGBT and its module series, Fuji Electric, Motorola, etc. are under development, NPT type is becoming the development direction of IGBT.


In view of the current manufacturers attach great importance to the development of IGBTs, Samsung, and other companies use SDB (Silicon Direct Bonding) technology to produce fourth-generation high-speed IGBT and module products on IC production lines, featuring high speed and low saturation voltage drop. Low tail current, positive temperature coefficient is easy to connect in parallel, excellent performance in 600V and 1200V voltage range, divided into UF, RUF two systems.

5, ultra fast IGBT

International Rectifier IR's research and development focus is to reduce the tailing effect of IGBT, so that it can be quickly turned off. The ultra-fast IGBT developed can minimize the tailing effect, the turn-off time does not exceed 2000ns, and the special high-energy illumination layering technology is adopted. The off time can be below 100ns, and the tailing is shorter. The key products are designed for motor control. There are 6 models available, and they can be used in high power converters.


Based on IGBT, IR has introduced two new devices combining FRD (fast recovery diode). IGBT/FRD is effectively combined to reduce the loss of conversion state by 20%. It is packaged in TO-247 package with rated specifications of 1200V and 25. 50, 75, 100A, for motor drive and power conversion, new technology based on IGBT and FRD facilitates parallel connection of devices, achieves more uniform temperature in multi-chip modules, and improves overall reliability.


7, IGBT power module

IGBT power modules use IC drive, various drive protection circuits, high-performance IGBT chips, new packaging technology, from composite power module PIM to intelligent power module IPM, power electronic building blocks PEBB, power module IPEM. PIM develops to high voltage and high current, and its product level is 1200-1800A/1800-3300V. In addition to IPM for frequency control, the IPM of 600A/2000V has been used for VVVF inverters of electric locomotives. The planar low-inductance package technology is a PEBB with a high-current IGBT module as an active device for missile launchers on ships. IPEM uses PE-chip multi-chip module technology to assemble PEBB, which greatly reduces the circuit wiring inductance and improves system efficiency. The second-generation IPEM has been successfully developed, in which all passive components are buried in the substrate in a buried manner. Intelligent and modularization has become a hot spot for IGBT development.

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