Radiation Technologies in Power Semiconductor Devices
The Usage of High Energy Electron Beams to Increase Speed and Reduce Switching Energy Losses in Power Semiconductor Devices (Diodes, Thyristors, Transistors)
Tech Area / Field
- MAT-ELE/Organic and Electronics Materials/Materials
- PHY-SSP/Solid State Physics/Physics
3 Approved without Funding
Scientific-Practical Materials Research Centre NAS of Belarus, Belarus, Minsk
- Royal Institute of Technology / Solid State Electronics, Sweden, Stockholm\nCentre for Electronic Materials, Devices and Nanostructures, UK, Manchester\nTechnische Universität München, Germany, Munich
Project summaryThe objective of the project is to develop and demonstrate the effective radiation-related technology of fabricating the fast-switching power semiconductor devices (PSDs) with low switching energy losses at their operation in the temperature range of 80-400 K.
To attain the project objective we plan:
- To employ the electron accelerators with energies up to 8 MeV, earlier used in military purposes, for controllable introduction of the thermally stable radiation defects into the PSD structures.
- To develop the methods of introducing the thermally stable radiation defects into the pre-determined local regions of a device structure that will provide the device best frequency characteristics, along with the minimum energy losses in conducting state.
The state of the art in the field
The bipolar silicon devices, especially power ones, fabricated by the conventional diffused technology or with the application of ion implantation, have the low switching rate (of about 10-4-10-5 s) that essentially reduces the possibility of their application in modern energy saving equipment and installations. To increase the switching rate of the device structures the diffusion of gold or platinum impurities, which are effective recombination centers of the non-equilibrium charge carriers, is usually used (P.Taylor. Thyristor design and realization, John Wiley and Sons Ltd., Chichester, 1987).
But such a way for the speed increase has some essential drawbacks, namely: gold and platinum have relatively low solubility limit in silicon and they can create the metallic inclusions or accumulate on the imperfections in the device structures. It results in the leakage currents of the reverse biased p-n-junctions increase at elevated temperatures, the blocking voltage decrease, the parameters reproducibility deterioration and as the result the devices output drop. And the increase of the recombination impurities concentration at attaining the maximum speed level of devices results in their loading capacity significant deterioration. Besides, the diffusion process is carried out at high temperatures, it is labor-intensive and hardly controllable.
The experiments, including those performed by the proposed project participants, have shown that some kinds of radiation defects in silicon exhibit the recombination properties, better than those of gold or platinum, and have a high thermal stability that allows one to perform the radiation treatment of devices before their final packaging. So, there is a real possibility to develop the effective methods for increasing the PSD speed by introducing the radiation defects of certain type, with required concentration and into the pre-determined regions of the power device structures. The radiation-related methods of the operation rate increase for low-power devices, usually undergone the low temperature final packaging (<300 °C), have been already developed (see for example 1.. The method of the semiconductor devices speed increase. // USSR certificate No. 497897 appl. 2.07.1973. 2. USA patent No. 3881963. Fast switching thyristors irradiation. Appl. 18.01.1973, filed 06.05.1975).
However, for high-power bipolar semiconductor devices (diodes, thyristors and transistors including those with insulated gate) the theory and practical ways of realizing the radiation-related methods of their speed increase and lowering the switching energy losses have been practically not developed (B.J.Baliga Power semiconductor devices, Boston, MA: PWS, 1995). The proposed project is aimed on the solution of this task.
The impact of the proposed project on the progress in the given field
The proposed project fulfillment will allow:
1. To develop the radiation-related methods for the speed regulation (in limits 10-5-10-8 s) of the serially produced devices with their quality significant increase (leakage currents decrease in 10-50 times and parameters reproducibility increase on 50-60%) without changing the basic technological process providing thus the essential technical and economical effect.
2. To manufacture the multifunctional devices of the different types with optimal static and dynamic parameters trade-off providing minimum energy losses in all modes of exploitation.
3. To exclude from the technological process of the power devices fabrication the use of the noble metals and to reduce production expenditures.
The project participants are the specialists, who earlier dealt with the development of the radiation-tolerant radio-electronic weapons, have a wide experience in the field of radiation physics of solid state, in physics and technique of semiconductors and semiconductor devices. They have published and taken out more than 300 papers and patents and also a series of the monographs, including: F.P. Korshunov et. al., Radiation Effects in Semiconductor Devices, Minsk, Nauka i Technika, 1978, 231 p. V. Grigorenko et al., Simulation and Automatization of the Design of Power Semiconductor Devices, Moscow, Energoatomizdat, 1988, 280 p.
Expected results and their application. The proposed project is assigned to the field of applied investigations. As the result of the four interconnected tasks solution the following results will be attained:
- the physical-mathematical models and simulation programs of the power semiconductor devices with radiation defects will be developed;
- the parameters and accumulation kinetics of the thermally stable (TANN>400 °C) irradiation-induced defects in device structures will be determined and their influence on the device characteristics will be ascertained;
- the effective methods of introducing the radiation defects of a necessary type and with desired depth and area distribution into device structures will be developed;
- the effective technologies of the fast PSD fabrication utilizing irradiation will be developed.
The proposed radiation-related technology will allow one to reduce the devices cost, to expand the temperature range of a device operation, to provide the considerable energy saving. The experimental samples of the diodes, thyristors and transistors manufactured with the help of the radiation related technology will be demonstrated. The fabricated device samples will have considerable performance advantages over the conventional fast diodes, thyristors and transistors. The developed technologies are planning to be used in a serial production. The degree of the project readiness to the introduction into the serial production will depend only on availability of the irradiation installations with required energies of electrons.
Accomplishment of the project will provide the realization of the following ISTS objectives and tasks:
- to give a possibility for the scientists and specialists dealing with radioelectronic weapons to redirect their abilities onto peaceful activity, and allow to use the unique installations (electron accelerators) in the peaceful purposes;
- to provide the integration of scientists of the FSU into the international scientific society;
- to support the applied investigations on solving the important national and international problem - the energy saving problem - by fabrication of the PSDs with low switching energy looses for needs of the power engineering, industry and transport.
Scope of activity: The four basic interconnected tasks will be solved during the project implementation. They include the next ones:
- theoretical analysis of the stationary and transient processes in traditional power devices and choice of the optimal radiation centers distribution into the device structure;
- investigation of the radiation defect formation in the basic silicon materials;
- substantiation of the principles of the technological utilization of the high-energy electron beams;
- practical realization of the radiation-related methods in industrial technology of the power semiconductor devices manufacturing.
With foreign collaborators, Professor D. Shroder from the Munich Technical University (Germany) and Professor B. Svensson from the Royal Institute of Technology (Sweden) a long-term fruitful scientific collaboration has been established already and there are some joint publications. During the project implementation the joint usage of research installations, the mutual checking of the results obtained, an organization of the joint seminars are planned.
Technical attitude and methodology: the experimental structures with p-n-junctions will be fabricated on the basis of Czochralski-grown and floating zone nuclear transmutation-doped silicon. The silicon wafers as well as diode, thyristor and transistor structures will be irradiated on the electron accelerators with energy up to 8 MeV, with application of different irradiation modes and at different temperatures. The measurements of the basic Si material and structure parameters, before and after irradiation and thermal treatments over the wide temperature range (300-600 °C), will be carried out with the use of conventional methods and techniques.
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