Helium irradiated high-power P–i–N diode with low ON-state voltage drop J. Vobeck y * , P. Hazdra, V. Z ahlava Department of Microelectronics, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, 166 27 Praha 6, Czech Republic Received 28 March 2002; received in revised form 30 May 2002; accepted 6 June 2002 Abstract The application of a 300 nm thick platinum silicide (PtSi) layer at the place of the anode contact layer of a soft recovery 2.5 kV/100 A high-power P–i–N diode brought a reduction of the forward voltage drop at several tens percent (for the rating current of 100 A) compared to that of the conventional aluminum and Ti–Ni–Ag layers. This enabled us to greatly improve the trade-off curve between the ON-state and turn-OFF losses of the diode subjected to helium irradiation into the anode and anode junction region. The application of PtSi layers thus opens a new way for the improvement of power devices. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Lifetime control; Helium; Platinum; Power diodes; Silicon 1. Introduction Ion and combined electron–ion irradiation are state- of-the-art techniques for the off-line optimization of electrical parameters of high-power devices [1]. Their principle consists of a controlled introduction of radia- tion defects (acting as deep levels) into appropriate lo- cations in optimal densities. The spatially reduced carrier lifetime leads to a significant improvement of dynamic parameters like turn-OFF time and turn-OFF losses and enlargement of the safe operation area. Un- fortunately, the improvement of the dynamic parameters is off-set by a worsening of static parameters like for- ward voltage drop (ON-state losses), leakage current (OFF-state losses) and/or blocking voltage [2,3]. Any lifetime control technique is attributed to the above mentioned trade-off between the static and dynamic parameters. Thus a permanent effort of researchers is to look for new technologies with a better trade-off. The aim of this paper is to present a way for the further improvement of the trade-off between the ON- state and turn-OFF losses of high-power diodes sub- jected to helium irradiation. The principle is based on a reduction of the forward voltage drop using a very low resistance platinum silicide (PtSi) ohmic contact at the anode compared to that of the traditional aluminum layer or Ti–Ni–Ag stack. The growth of the forward voltage drop V F with irradiation dose and energy re- mains, but the V F of unirradiated device is lowered in tens of percent thus giving a significant shift of the trade- off towards the x-axis. PtSi has been widely used in VLSI technology as a contact layer for its stable features, low resistivity, pos- sibility of fine-line patterning and small silicon con- sumption during silicidation [4]. PtSi was also studied as a source for platinum diffusion into the silicon by means of classical diffusion mechanisms at high temperatures [5,6] or under control of the proximity gettering [7–9]. In both cases, a goal was to introduce a deep acceptor level of substitutional platinum (acting as an efficient re- combination center) and thus control the excess carrier lifetime. In this paper, the PtSi layer is used as a very good contact and not exposed to temperatures higher Solid-State Electronics 47 (2003) 45–50 www.elsevier.com/locate/sse * Corresponding author. Tel.: +420-2-2435-2862; fax +420-2- 2431-0792. E-mail address: vobecky@fel.cvut.cz (J. Vobeck y). 0038-1101/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0038-1101(02)00250-2