SiC power devices for high voltage applications

Silicon Carbide device technology is now evolving from a pure vision to a r eal alternative to silicon devices. The feasibility of SIC devices has been shown for many different types of devices, the development of a working pr oduction technology has started, yield, reliability and costs now being the key issues. At present the high substrate prices keep the manufacturing co sts of SiC high, making it very difficult to enter the device market with S IC on economic terms. Prime applications are those for which SIC offers sub stantial benefits or even a technological breakthrough on the system level. The main application is power conversion when the latest development effor ts on silicon based power switches (e.g. IGBT) allow utilisation of much hi gher switching frequencies, putting very high demands on the free wheeling diode. The system performance is to a large extent limited by the diode rec overy charge-a major source of switching losses. Depending on the voltage r ange, different device concepts are of interest: In the lower voltage range the junction-barrier controlled Schottky (JBS) device is a promising candi date while at voltages beyond 2.5 kV the PIN diodes is the device of choice . Different system requirements-e.g. surge current capability-make the PIN junction superior to a Schottky device for certain applications. With progr ess in material and technology development the 'world's best' result is bec oming less and less important and reproducibility is the issue. Failure ana lysis of defective devices needs to be established with a high number of su bstrate defects being still an obstacle in SIG. High leakage/soft reverse c haracteristics are often encountered and can usually be attributed to local ised defects. It is important to identify their origin and to separate proc ess-induced defects from those already present in the epilayer or substrate . In order to use the high power handling capability of SIC reduction of ma rgins (e.g. in epilayer thickness and doping) is necessary. This requires n arrow bandwidth of process and material variations. For paralleling of SiC devices equal current sharing under static and dynamic conditions is a fund amental requirement from the system side. Top-down calculation gives materi al specifications, which the supplier has to meet. (C) 1999 Elsevier Scienc e S.A. All rights reserved.