Yoshihiko Koike

Effect of hydrogenation of the leakage currents of laser-annealed polysilicon TFTs

The effect of hydrogenation on the leakage currents of laser-annealed polysilicon thin-film transistors (TFTs) was investigated for a low-temperature ( >

Advanced high current, high reliable IGBT module with improved multi-chip structure

Advanced IGBT module technology to realize high reliability and high current capability was presented. The 60,000 cycles long term power cycle capability of the low thermal expansion base module was demonstrated. A stress release tall mounting structure and a ceramic metal pull back structure were shown to be essential for high thermal cycle capability. A multi-end main terminal with multichip substrate and high resistivity sense emitter terminal technology was applied to realize high current capability and uniformity in the large high power module.

Noble high thermal conductivity, low thermal expansion Cu-Cu2O composite base plate technology for power module application

Noble high thermal conductivity and low thermal expansion Cu-Cu2O composite base plate was developed and successfully applied to power modules. Metal matrix composite consists of Cu and Cu oxide was demonstrated to show excellent combination of thermal conductivity and thermal expansion. This noble Cu-Cu2O base plate was applied to power module, and high reliability and high thermal conductivity of the module were confirmed. Anisotropic thermal property of Cu-Cu2O base plate by controlling the microstructure of composite was also demonstrated.

Dislocations and Tungsten Concentration Profiles in Tungsten-Silicon Contact Areas

Dislocation formation and impurity distributions in metal-silicon contact areas were investigated by means of cross-sectional transmission electron microscopy (TEM) images and energy-dispersive X-ray measurement. Dislocations were formed in the (111) plane in the [110] direction by annealing at 700°C when W was used as barrier metal. As the diameter of contact holes decreased, dislocations became more significant. Both W and As concentration profiles in the horizontal direction showed maxima at the edges of contact holes. The diffusion length of W in the edge areas was about twice that in the center according to depth profile. This implied that stress in edge areas increased the W diffusion coefficient by a factor of about four.

3300 V 400 A, 600 A and 1200 A high power IGBT modules with high reliability for traction applications

Newly developed 3300 V IGBT modules with current ratings of 400 A, 600 A and 1200 A for traction applications are described. Single or parallel use of these modules can provide coverage of the whole motor range of GTO inverter systems for traction applications. The IGBT modules consist of newly developed IGBT chips with improved terminations for high blocking voltage and soft and fast recovery mode chips with high reverse recovery di/dt capability. The new IGBTs have a lower switching loss as compared with a conventional IGBT. A baseplate with low thermal expansion extends their fatigue lifetime to more than 5 times that of a conventional module. Low thermal impedance is achieved by a simple mode structure with optimal arrangement of IGBT and diode chips for both thermal and electric characteristics. Solder and wire-bonding reliabilities of the modules are kept high throughout the fatigue lifetime despite their large size.