Jan Vobecky

High-power P-i-N diode with the local lifetime control based on the proximity gettering of platinum

We demonstrate for the first time a high-power P-i-N diode with local lifetime control using the proximity gettering of platinum in the FZ silicon. The region of maximal damage resulting from the low-dose helium implantation was decorated by substitutional platinum that diffused from the PtSi anode contact at low temperature (700/spl deg/C) through the P/sup +/-P anode doping at the distance of 70 /spl mu/m. The diodes show very low forward voltage drop with negative temperature coefficient and very low leakage current even at elevated temperatures while keeping the major advantages of the ion irradiated devices like low turn-off losses and soft recovery.

A new degree of freedom in diode optimization: arbitrary axial lifetime profiles by means of ion irradiation

A novel approach to lifetime control in fast recovery power diodes, arbitrary axial lifetime profiles by single-step ion irradiation, is presented. The principle is based on irradiation through a single mask which is inserted between the ion source and the device. The density and lateral/axial structures of the mask determine the final lifetime profile. Experimental results show that this new technique is fully capable to replace multiple single-energy ion irradiations and to guarantee superior diode performance.

Radiation-Enhanced Diffusion of Palladium for a Local Lifetime Control in Power Devices

Palladium (Pd) diffusion from a surface layer enhanced by defects from a helium (He) irradiation is shown to provide a local lifetime control in a power p-i-n diode annealed between 350degC and 700degC. An open-circuit voltage decay lifetime measurement is used to identify temperature ranges in which one of two lifetime control mechanisms takes part. Spreading resistance measurements show the doping compensation at the anode junction caused by defects after the Pd diffusion below 725degC. Locally modified doping profiles by introduced defects cause significantly lowered dynamic avalanche (DA) during fast reverse recovery compared to the standard He irradiation as confirmed also by device simulation. Advanced shaping of a shallow doping profile, reducing avalanche generation in the area of peaking electric field under a reverse bias, is suggested as an additional method to suppress the DA in power devices. The diffusion at 650degC gives the best static and dynamic parameters. Breakdown voltage and leakage current are those of untreated diode. Turn-off losses close to the SOA limit are also much lower than in the standard He irradiation, and thermal characteristics are better than after the traditional high-temperature diffusion.

Exploring the Silicon Design Limits of Thin Wafer IGBT Technology: The Controlled Punch Through (CPT) IGBT

The paper introduces a new controlled punch through (CPT) IGBT buffer for next generation devices, which utilise thin wafers technology. The new concept is based on very shallow buffers with optimized doping profiles enabling minimum silicon design thicknesses close to the theoretical limit for a given voltage class. The advanced shaping of the buffer doping profile brings additional degree of freedom in IGBT design. The work was carried out for 1200V IGBTs, but the CPT buffer can be applied with advantages to any voltage class. While this approach is targeting mainly reduced ON-State losses, the IGBT maintains good blocking, soft turn-off, wide SOA and good short circuit capability.

Thin-Wafer Silicon IGBT With Advanced Laser Annealing and Sintering Process

A novel insulated gate bipolar transistor (IGBT) featuring thin-wafer processing and a combined dopant activation laser annealing and contact metal laser sintering is presented. The device concept includes a new back-side boron anode (collector) activation process by laser annealing through a titanium layer to enhance the absorption of the deposited energy from the laser beam. This technology enables improved activation control of the anode injection efficiency for thin-wafer-based IGBTs rated normally below 1700 V. The IGBT concept will therefore be provided with a wider range of performance options on the loss technology curve when compared to state-of-the-art devices processed with conventional activation techniques.

High-power P-i-N diode with local lifetime control using palladium diffusion controlled by radiation defects

We demonstrate for the first time a high-power P-i-N diode with local lifetime control using palladium (Pd) diffusion. Low-temperature (600/spl deg/C-700/spl deg/C) diffusion of Pd is stimulated by radiation defects resulting from alpha-particle irradiation (/sup 4/He/sup 2+/: 10 MeV, 10/sup 12/ cm/sup -2/). The region of maximal radiation damage of Gaussian shape is decorated by substitutional Pd after diffusion from a palladium silicide surface layer through the P/sup +/--P region into the N-base close to the anode junction. Significantly lower leakage current compared to that of standard /sup 4/He/sup 2+/ irradiation and very good ruggedness under fast recovery (di/dt/spl ap/500 A//spl mu/s, V/sub R//spl ap/2 kV) is demonstrated for Pd diffusion at 600/spl deg/C.

Field Shielded Anode (FSA) concept enabling higher temperature operation of fast recovery diodes

In this paper, we introduce the Field Shielded Anode (FSA) concept that enables higher temperature operation of fast recovery diodes with planar junction termination. Conventional diodes utilizing local lifetime control principles show excellent dynamic properties at the expense of a higher leakage current, which is generated during reverse blocking when the space charge region penetrates into the zone containing the radiation defects. In contrast to this, the FSA concept spatially separates the space charge region from the zone with the radiation defects. The ruggedness of conventional diodes can be exceeded with the new FSA concept, while the leakage current is reduced by a factor of ∼4. This was achieved using a special junction extension introduced between the active area and the guard-ring termination. The design parameters and their influence on the softness and the safe-operating area are presented.

The Destruction Mechanism in GCTs

This paper focuses on the causes that lead to the final destruction in standard gate-commutated thyristor (GCT) devices. A new 3-D model approach has been used for simulating the GCT which provides a deep insight into the operation of the GCT in extreme conditions. This allows drawing some conclusions on the complex mechanisms that drive these devices to destruction, previously impossible to explain using 2-D models.

An experimental demonstration of a 4.5 kV “Bi-mode Gate Commutated Thyristor” (BGCT)

In this work we present the first experimental results of a Bi-mode Gate Commutated Thyristor (BGCT). The BGCT is a new type of Reverse Conducting-Integrated Gate Commutated Thyristor (RC-IGCT). In a conventional RC-IGCT, the IGCT and diode are integrated into a single wafer but they are fully separated from each other. The novel BGCT on the other hand features an interdigitated integration of diode- and GCT-areas. This interdigitated integration results in an improved diode as well as GCT area, better thermal distribution, soft turn-off/reverse recovery and lower leakage current compared to conventional RC-IGCTs. We have discussed the advantages of a new diode anode design in BGCT, which is shallower than that of the conventional RC-IGCT. We have successfully demonstrated the BGCT concept with 38 mm, 4.5 kV prototypes and compared the on-state, turn-off and blocking characteristics with conventional RC-IGCTs both in GCT- and diode-modes of operation.

Recent advancements in IGCT technologies for high power electronics applications

In this paper, we review the progress made recently for further developing the Integrated Gate Commutated Thyristor (IGCT) device concept for high power electronics applications. A wide range of newly introduced IGCT technologies are discussed and recent prototype experimental results as well as novel structures and future trends of the IGCT technology are presented. This will provide system designers with a comprehensive overview of the potentials possible with this device concept.