Katsuaki Saito

Reactive Ion Etching of Sputtered PbZr1-xTixO3 Thin Films

Reactive ion etching (RIE) by CCl4 plasma of sputtered PbZr1-xTixO3 (PZT) thin film has been investigated. The etching rate of the as-deposited pyrochlore phase PZT is comparable to that of perovskite which was crystallized by 600°C annealing. Etching rate increased with increasing RF power and reached a plateau at 1.0 W/cm2. Highly anisotropic etching of PZT with little resist damage could be realized by reducing RF power.

A Planar-Gate High-Conductivity IGBT (HiGT) With Hole-Barrier Layer

A high-conductivity insulated gate bipolar transistor (IGBT) (HiGT) with a double diffused MOS structure and an n-type hole-barrier layer surrounding a p-layer (planar HiGT) is presented. The hole-barrier layer prevents the holes from flowing into the p-layer and stores them in the n-layer. The planar HiGT provides a better tradeoff between collector-emitter saturation voltage [VcE(sat)] and turn-off loss than conventional IGBTs, regardless of the injection efficiency of the p-layer on the collector side, while it maintains a high blocking voltage by controlling the sheet carrier concentration of the hole-barrier layer. The planar HiGT has a tough short-circuit capability of more than 10 mus at 125degC, with a saturation current similar to that of conventional IGBTs.

1.7kV trench IGBT with deep and separate floating p-layer designed for low loss, low EMI noise, and high reliability

A novel 1.7kV IGBT with deep floating-p layers separated from trench gates has been developed to realize low loss, low EMI noise, and high reliability. Separating floating-p layers from the trench gates reduces excess V<inf>GE</inf> overshoot, which results in a 51% smaller reverse recovery dV<inf>AK</inf>/dt than the conventional IGBT. The deep floating p-layers weaken the electric field under the trenches, which results in an avalanche breakdown voltage of 2250V. In addition, the E<inf>on</inf> + E<inf>off</inf> for the proposed structure can be reduced by 47% more than that of the conventional one, maintaining a low V<inf>CE(sat)</inf> of 2.3V at 125°C.

Effects of Excited Species in Electron Cyclotron Resonance Plasma on SiN Film Resistivity

Optical emission spectra were measured and the relationship between resistivity of SiN films which were deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) and emission intensities from species excited by electron cyclotron resonance was clarified. With increasing microwave power of lowered reacting pressure or SiH4 gas flow rate, the light intensity from excited ions increased in comparison to the intensity from excited radicals. As a result of increasing excited ion density, the SiN film was condensed and the prismatic structure observed in low-resistivity film was not absent from high-resistivity film.

Novel 3.3-kV advanced trench HiGT with low loss and low dv/dt noise

Novel 3.3-kV trench IGBT with low loss and low dv_AK/dt noise was developed. The structural feature of the IGBTs is deep p-WELL layers separated from trench gates. This structure suppresses excess V_GE overshoot and then reduces recovery dv_AK/dt. Moreover, this effect is enhanced by reducing the resistance of the deep p-WELL layers (R_FP). It was found that, for the first time, the trade-off characteristics between V_CEsat and recovery dv_AK/dt were drastically improved by separating p-WELL layers from trench gates and decreasing R_FP. The recovery dv_AK/dt could be reduced by 79% more than that for the conventional trench IGBT, maintaining a small V_CEsat and E_on equal to the conventional one.

High-Quality, High-Rate SiO2 and SiN Films Formed by 400 kHz Bias Electron Cyclotron Resonance-Chemical Vapor Deposition

A new electron cyclotron resonance (ECR) plasma CVD system is proposed to form high-quality SiO2 and SiN films at high rates. The system applies 400 kHz voltages which ions can follow to the substrate. The system efficiently produces, without heating: 1) SiO2 films in which density and Si-O bond strength are equivalent to those of a thermally oxidized (about 1000° C) film for which deposition rate is higher than 1.2 µ m/min and 2) Si-H bond-free SiN films in which density and resistivity are higher than those of films formed by conventional plasma CVD systems and for which deposition rate is higher than 0.8 µ m/min.

Suppression of reverse recovery ringing 3.3kV/450A Si/SiC hybrid in low internal inductance package: Next high power density dual; nHPD2

Suppression of reverse recovery ringing from 3.3kV Si-IGBT SiC Schottky barrier diode hybrid was verified. Reducing loop inductance, consisting of internal module, busbar connection and capacitor, is effective. To realize low inductance within the module and external connection with busbar, the gap between p and n terminal is minimized whilst maintaining the creepage and clearance required by regulation standards. Functional isolation is adopted instead of basic isolation. We achieved an inductance value 9nH for a 3.3kV, 450A dual IGBT, that leads to the extinction of reverse recovery oscillation. Details of switching characteristics of Si + SiC hybrid module is compared with that of Si IGBT module with low inductance.

p/sup -/-layer punch-through structure with high concentration p-emitter for a light-triggered thyristor

We studied the on-state voltage reduction of a light-triggered thyristor from the viewpoints of reduced thyristor thickness and realization of a high-injection low-lifetime structure. The reduced thickness was achieved through a p/sup -/-layer punch-through structure. The high injection was achieved by a thick, highly-doped p-emitter region. The on-state voltage of a 6-kV 5.5-kA light-triggered thyristor with the p/sup -/-layer punch-through structure and with the thick, high concentration p-emitter was reduced by about 0.2 V.

6-kV, 5.5-kA light-triggered thyristor

A 6-kV, 5.5-kA light-triggered thyristor has been developed for BTB (back-to-back) converter systems. A double-diffused p emitter structure was used to improve the trade-off relationship between on-state voltage and blocking capability, and a high-injection low-lifetime structure was used to improve the trade-off relationship between on-state voltage and reverse recovery charge. The double-diffused p emitter consists of a thin p/sup +/ emitter in the main area and a thick p/sup -/ emitter there and elsewhere. High injection was achieved by increasing the p/sup +/ emitter concentration and decreasing the p/sup -/ emitter thickness. A locally controlled lifetime profile was used to compensate for the high injection efficiency. These structures decreased the on-state voltage by about 0.15 V.

Suppression of self-excited oscillation for common package of Si-IGBT and SiC-MOS

We propose a method to design a module structure avoiding the risk of self-excited (SE) oscillation. By simplifying both the semiconductor device and lumped circuit model, oscillatory conditions can be extracted analytically. Results show good agreement with T-CAD simulation and measurement results of test modules. The method is applied to the design of next generation common package, which has realized very low system inductance. SE oscillation can be prevented for latest generation Si-IGBTs having very small feedback capacitance and SiC-MOS having high output capacitance mounted in the same common package design.