High Voltage Transistor with Isolated Gate
Design and Organization of Production for a Series of Power-Voltage Insulated Gate Bipolar Transistors (IGBT)
Tech Area / Field
- INF-ELE/Microelectronics and Optoelectronics/Information and Communications
3 Approved without Funding
Research and Desigh Company "Belmicrosystems" , Belarus, Minsk
- Scientific-Practical Materials Research Centre NAS of Belarus, Belarus, Minsk\nJSC "Electromodule", Belarus, Minsk reg., Molodechno\nBelarussian State University, Belarus, Minsk
- Japan Semiconductor, Engineering & Consulting Co. Ltd., Japan, Osaka
Project summaryRapid development of power electronics during the last decade is linked with success in development of semiconductor power devices which are widely used in automobile electronics, electrical drivers of industrial automated systems.
At present significant attention is given to semiconductor power device building. Particularly intensive studies are run towards improvement of existing level of electric parameters, development and introduction into production of high speed high voltage transistors and switch high current transistor devices.
Power transistors are widely used at every stage of energy generation, distribution and consumption, and serve as one of the links between devices used in microelectronics and electrical engineering. Main areas of their usage in terms of quantity of applied devices and variety of types of application are: power supply with switch operation modes, electrical motor control, electron circuits for various motor vehicles, control systems for process equipment blocks.
Among power transistors the most promising are bipolar transistors with an insulated gate, foreign name IGBT (Insulated Gate Bipolar Transistor).
IGBT combine advantages of bipolar (hign conductivity) and field (low voltage control) transistors and owing to construction properties allow to increase current density approximately 10 times. Therefore they are used in manufacture of electron power devices of wide application instead of bipolar and field transistors used before. Only in Japan IGBT consumption volume in 1996 reached $1billion at annual growth of 25-30%. Range of IGBT types by International Rectifier (USA) exceeded several hundreds.
The Project goal is design and organization of production of a series of IGBT purposed for power supply application, electron control systems and other power devices. A series of IGBT to 600-1200 V and 10-50 A is planned for development under the Project.
Currently IGBT are not produced in the CIS. Design and organization of manufacture of IGBT will allow to build powerful and compact electron control systems, reduce weight and dimensions of electrical devices, save material and energy resources used in fabrication and operation process.
The construction and technological process developed under the Project serve as the base for high voltage power ICs.
Execution of the Project is directed towards solution of problems of saving energy and resources and reorientation of CIS specialists engaged in production for military application. As the perspective of the Project it is planned to carry out works to expand IGBT nomenclature, improve dynamic/static characteristics that will allow to broaden their application areas.
Development of bipolar power devices in 60-ties has brought along the demand of building more powerful electron devices. Bipolar power devices can be split into two groups: power thyristors and power transistors. In 80-s due to introduction of new technology domination of bipolar devices was put an end to. A new class of power devices combining advantages of bipolar and MOS transistors was developed. Current in these devices is controlled by gate voltage. Signal power received on the gate is significantly lower than in bipolar transistors allowing to use control chains of lower power. Due to their high speed these devices let to raise operating frequency of power systems and on this account improve efficiency and dimensions i.e. solve problems of energy and resource saving. In evolution of power BiMOS devices three stages are distinguished:
1. Creation of power MOS transistors
2. Combination of MOS and bipolar
3. Functional integration of MOS and bipolar
1. Power MOS transistor has high switching speed (1-10 ns to 1 s in bipolar) and high input resistance. Yet high resistance in the open state and high production cost of MOS transistors limited their usage to high switching frequency applications and low-voltage circuits (to 100 V) wherein resistance in the open state looked suitable.
2. In order to get a device with high input and low residual resistance in the open state a technology of integration of discrete MOS and bipolar transistors on one chip in Darlington circuit (control of bipolar by means of power MOS) was developed. Drawbacks of this circuit are related to weak sides of bipolar power devices (low gain <10, demand of high control currents).
3. To provide maximum realization of advantages enabled by MOS control and bipolar conductance it proved necessary to refuse from combination of separate discrete MOS and bipolar transistors and take an approach of combining physical principles of operation of these devices within one structure, that finally brought to building IGBT.
The first IGBT showed good performance at current density 20 times higher than in MOS transistors and 5 times higher than in bipolar transistors with the gain value of 10. However switching time was 10-20 s. Relatively slow switching limited application of these devices to low frequency area. To expand application area including also drivers for electrical devices it became necessary to develop technological process to control charge carrier life time and thus to control transistor switch off time with no worsening of MOS parameters. This has been achieved due to exposure of silicon wafers to e-beam radiation. The process enables control of switching time in the range of 0.2-20 s that made igbt a unique multifunctional device. IGBT was first developed in the research laboratory of General Elektrik and put to the market by Motorola. The device is made on p+ substrate with subsequent growth of epitaxial drift N-layer where vertical DMOS structure is built. In ON state IGBT behaves like a P-i-N diode with direct shift and is capable of operating at current high density.
By construction IGBT differs from vertical MOS transistor as it uses P+substrate instead of N+substrate in MOS transistor. In the operation state positive voltage is supplied to the substrate and gate. Injection of minor charge carriers from the substrate reduces resistance of N drift region significantly. Therefore IGBT resistance in the open state (residual resistance) is significantly lower compared to MOS transistor. Gate voltage can control current through IGBT.
IGBT combines the best qualities of MOS power transistor (voltage control at very high input resistance) and bipolar transistors (high density of allowed direct current). One more important property of these devices is capability to control IGBT characteristics by electron radiation in a wide frequency range. Combination of the above properties makes IGBT the most attractive power device.
The Project goal is development of construction and organization of production of a series of power insulated gate bipolar transistors (IGBT) with improved dynamic characteristics and purposed for power source application, electron control systems for electric motors and other power electron devices.
Main efforts within the Project will be focused on:
· search of new constructive-technological solutions allowing to improve operating characteristics of IGBT transistors;
· development of technological processes to build thick (60-200) and high resistivity (20-100 Ohmґcm) epi-structures;
· running experiments on radiation processing of chips with the aim to control dynamic parameters and on determination of its optimal regimes;
· CAD simulation of impurity distribution profiles, static/dynamic parameters, heat distribution in a transistor cell aimed at optimizing of the construction and fabrication process.
To conduct Project activities it is demanded to involve a group of experts in microelectronics design and foreign collaborators.
Foreign collaborators are planned to be recruited to participate in working out suggestions to the Project and Work Plan. In addition it is expected to share data on the Project current status with the foreign participants, to consider jointly technical reports, to hold consultations on IP rights, to run joint evaluation of fabricated samples.
The Project is planned to be done in BMS R&D Company of Integral, the major designer in microelectronics in Belarus.
Equipment required to fabricate epi-structures, wafer process and TO-218, TO-220 packaging is available at Integral fabs. Packaging of power IGBT with current higher than 50 A is planned at “Electromodule” Joint Stock Company of Molodechno where they have a good expertise in fabrication of power high-voltage modules.
Equipment for radiation process of wafers aimed at controlling dynamic parameters exists in IPSS of Academy of Sciences of the Republic of Belarus and in BSU.
Measurement equipment to evaluate static characteristics is located in Integral. Design and manufacture of equipment to measure dynamic characteristics is to be done at “Elmash” plant of Integral jointly with BSU. Measurement station for static/dynamic parameters of IGBT M3020 can be also purchased in Germany. In the course of the Project a series of IGBT to 600-1200 V and 10-50 A will be designed with subsequent organization of its production.
Design and manufacture of IGBT will allow to build powerful and compact control systems, reduce weight and dimensions of electrical devices, save material and energy resources used in fabrication and exploitation process. The design and technological process developed in the frames of the Project serve as the base for high-voltage power ICs.
The Project Objective is Architecture Design and Set Up of Production of Power Insulated Gate Bi-Polar Transistors (IGBT) Series for Voltage 600-1200 V and current 10-50 A, pertaining improved dynamic parameters and purposed for power supply, electric motor control electronic systems and other power electronic units.
In the course of Project execution the effect of Architecture & Technology parameters at Static &Dynamic Transistor Parameters will be studied, Computer Simulation of Impurity Distribution Profile, Static and Dynamic Parameters, Heat Distribution in Transistor Cell will be carried out.
Foreign collaborators function:
· recruited to participate in working out suggestions to the Project and Work Plan,
· to consider jointly technical reports,
· to hold consultations on IP rights,
· to run joint evaluation of fabricated samples.