Masahito Otsuki

Formation of Copper Thin Films by a Low Kinetic Energy Particle Process

This paper reports on low kinetic energy particle bombardment of a growing film surface employed to grow high-quality copper thin films on silicon and SiO{sub 2} with ideal metal/substrate interface characteristics. It is shown that the energy of Ar ions concurrently bombarding a growing film surface determines the crystal structure of the film. Under relatively low-energy ion bombardment conditions (100)- or (111)-oriented films are obtained either on (100)Si (111)Si, or SiO{sub 2} surfaces when large ion bombardment energies are employed. It has been found that (111)-oriented films thus created on SiO{sub 2} are metastable and easily transform by thermal annealing into completely (100)-oriented films with large grains of about 100 {mu}m. This unique transformation phenomenon has been successfully applied to the formation of almost single-crystal (100)-oriented Cu islands on SiO{sub 2}. In situ substrate surface cleaning by extremely low energy Ar ion bombardment has enabled the formation of ideal metal/silicon contacts without any postmetallization alloying heat cycles. Excellent adhesion of Cu thin films on SiO{sub 2} has also been demonstrated by the employment of the in situ substrate surface cleaning.

Electrical Properties of Giant‐Grain Copper Thin Films Formed by a Low Kinetic Energy Particle Process

Fomnation of giant-grain copper thin films on SiO 2 by a low-kinetic energy particle process followed by thermal annealing has been investigated. When Cu films are grown on SiO 2 by the process under a sufficient amount of energy deposition, they exhibit almost perfect crystal orientation conversion from Cu(111) to Cu(100) upon themnal annealing. Such crystal orientation conversion is accompanied by the giant grain growth in the film as large as 100 μm. With regard to these phenomena, the effects of the ion flux density and of the ion bombardment energy have been studied

A study on the short-circuit capability of field-stop IGBTs

The short-circuit failure mechanism of 1200 V trench gate field-stop insulated gate bipolar transistor (IGBT) has been investigated in this paper. Experimental testing shows that most of the devices failed during the blocking state after a few hundred microseconds of the short-circuit turn-off condition. This unusual failure mode was analyzed both with experimental and numerical investigation. It has been determined that due to significantly large leakage current, thermal run-away can occur causing device failure after short circuit turn-off. Due to the smaller heat capacity of the FS-IGBT structure, the device temperature after the turn-off becomes so high that the local heating produced by the high temperature leakage current results in the thermal run-away.

The 3rd generation IGBT toward a limitation of IGBT performance

The performance of the third-generation IGBT (insulated-gate bipolar transistor) is described. It is demonstrated that a 600-V/100-A third-generation IGBT has an on-state voltage drop of about 1.7 V and a fall-time of about 150 ns during inductive-load turn-off, which is very close to the limit of IGBT performance predicted by numerical simulation. The device has overcurrent protection, and an average short circuit withstand capability of 30 mu s was obtained. An almost 40% reduction in the switching loss has been realized, as compared with conventional IGBT modules, for a PWM (pulse width modulated) inverter application.<<ETX>>

Analysis on the low current turn-on behavior of IGBT module

This paper presents the noise emission mechanism from IGBT module, which is strongly required to be improved because of EMC regulations. The various 600 V/100 A IGBT module structures were experimentally and numerically tested to improve the current ringing during low current turn-on. As a result, it has been found that the parasitic inductance in the module should be as small as possible to suppress RLC resonant, which consists of parasitic components in the module and the capacitance in the power devices. It is also confirmed that the extra capacitance attached between gate-emitter of IGBT effectively improves the noise emission without increase the switching loss.

Investigation on the short-circuit capability of 1200 V trench gate field-stop IGBTs

The short circuit failure mechanism of newly developed 1200 V/150 A trench gate field-stop IGBT has been investigated. The devices mainly fail after a few hundred microseconds of the short-circuit turn-off. It has been found that the leakage current due to extreme temperature rise in the backside layers results in thermal runaway during off-state. The device with improved backside layer achieved more than 15 /spl mu/s of short circuit capability while keeping the low on-state voltage drop of 1.55 V.

Double gate MOS device having IGBT and MCT performances

A new MOS-bipolar device having IGBT and MCT performances is described. The double gate MOS (DGMOS) can operate at a thyristor action in the on-state and a bipolar transistor action in the turn-off transient state by applying gate signal to two MOS gate electrodes. This new device exhibits very good performance with the almost same low forward voltage drop as a conventional thyristor and the almost same turn-off characteristics as a fast IGBT. This paper reports the new device concept and the results of numerical simulation of its perkormances using two dimensional numerical simulation.

Development of the 1200V FZ-diode with soft recovery characteristics by the new local lifetime control technique

This paper presents the new 1200V FZ-Diode chip using the newly developed local lifetime control technique which is a combination of the electron irradiation and the back-side laser annealing in order to realize the optimum carrier profile. Furthermore, 20% lower resistivity bulk can be utilized due to optimization of the edge termination structure to have a uniform electric field distribution. As a result, the new 1200V FZ-diode with very soft recovery characteristics has been successfully developed without increase of the reverse recovery losses compared to a conventional diode.

Advanced thin wafer IGBTs with new thermal management solution

This paper presents the new design concepts for improving the short-circuit capability of thin wafer power devices, such as field-stop (FS) IGBTs, by thermal management techniques. The experimental results of thin wafer IGBTs, with lead-frame connection via solid copper emitter electrode, have achieved approximately 34% increase in the critical short circuit energy. In addition, compared to the conventional assembling techniques, the new techniques make it possible to keep the lower device temperature during the normal switching operation. It has been found out that 30% reduction in die size can be expected under the conditions of having the same junction temperature increase (/spl Delta/Tj).

Great improvement in turn-on power dissipation of IGBTs with an extra gate charging function

This paper presents a new gate drive circuit using an extra RC-network to realize low turn-on dissipation of IGBTs. The extra capacitance in the gate circuit assists in charging Miller capacitance, therefore the collector voltage tail region during the turn-on period can be reduced drastically without the turn-on dI/sub c//dt increasing. The proposed gate drive method has been achieved 40% reduction in the turn-on switching power dissipation of 1200V-150A IGBT compared with the conventional gate driving.