Kazuhiro Kaibara

650 V 3.1 mΩcm 2 GaN-based monolithic bidirectional switch using normally-off gate injection transistor

We report a normally-off GaN-based monolithic bidirectional switch for the first time. The switch consists of a double-gate AlGaN/GaN gate injection transistor (GIT) which serves normally-off operation with high drain current utilizing the hole injection from the p-type gate. The fabricated bidirectional switch exhibits high breakdown voltage of 650 V for both polarities and low on-state resistance (Ron .A) of 3.1 mΩcm2 . The GaN-based bidirectional switch can be applied to AC-AC matrix converters with high efficiency.

Overview and Future Challenge of Ferroelectric Random Access Memory Technologies

We have developed a low-temperature formation technique for ferroelectrics (<500 °C), which is crucial for the ferroelectric random access memory (FeRAM) to be embedded in a leading-edge complementary metal oxide semiconductor (CMOS). A 53-nm-thick Bi4Ti3O12 film was successfully formed by metalorganic chemical vapor deposition at 450 °C and subsequent annealing at 500 °C. It was found that perovskite grains preferentially orient along the (110) and (111) directions and that the fabricated Bi4Ti3O12 capacitors show a remnant polarization (2Pr) of as large as 25.7 µC/cm2. In addition, we have adopted a nondestructive readout operation (NDRO) technique to extend read cycle endurance, in which the switched polarization at reading is automatically rewritten by readout voltage removal. We have demonstrated stable readout characteristics at more than 1011 cycles for 0.18 µm NDRO FeRAMs.

GaN-based multi-junction diode with low reverse leakage current using P-type barrier controlling layer

We present a novel GaN-based diode with low reverse leakage current which ensures the high voltage operation up to 600V. The diode consists of multi-junctions of AlGaN/GaN with a p-GaN overlayer where the anode and cathode are formed on the sidewalls of the channels. The tunneling current which is the origin of the leakage current can be reduced by controlling the potential barrier at the anode sidewall by means of the depletion layer from the p-GaN. The fabricated GaN diode with the p-type barrier controlling layer (BCL) exhibits high forward current of 18A at 1.5V with the breakdown voltages over 600V taking advantages of the reduced leakage current. The fabricated GaN-based diode has smaller RonC of 70 pΩF than 95 pΩF of the commercially available SiC Schottky barrier diode (SBD) indicating that the GaN diode is suitable for power switching. The GaN diode exhibits high conversion efficiency of 98.2 % in the voltage boosting converter at the output voltage of 400V by combining it with a GaN Gate Injection Transistor (GIT). The obtained performance by using the GaN diode is superior to that with a SiC SBD.

A fully integrated GaN-based power IC including gate drivers for high-efficiency DC-DC Converters

In this paper, we present a state-of-the-art integrated GaN power IC capable of operating in a high frequency (MHz) regime. This realizes system size reduction, 60% maximum, of a power IC. The IC consists of two output power transistors (PT) and two gate drivers (GD). The key devices in the IC are normally-off gate injection transistors (GITs) for PT and GD and a normally-on hetero-junction field effect transistor (HFET) for GD. Novel local control of carrier concentration of an identical 2 dimensional electron gas (2DEG) at an AlGaN/GaN interface which made integration of the transistors with such a large threshold voltage difference possible is described. A specially developed post-passivation interconnection process giving low parasitic components is also described. The IC applied to a 12V-1.8V DC-DC converter shows high frequency switching operation well beyond the limit of Si pointing to future improvement in consumer electronics power supply systems.

A 26 GHz Transceiver Chipset for Short Range Radar Using Post-Passivation Interconnection

We demonstrate a 26 GHz SiGe bipolar complementary metal oxide semiconductor (BiCMOS) transceiver chipset for short-range spread-spectrum (SS) radar system. The integrated frequency triplers lower the local oscillation frequency down to 8.8 GHz, and eliminate the carrier leak in the transmitting signal which enables high sensitivity. The on-chip balun connected to the mixer demodulating by the pseudo noise (PN) code in the receiver increases the dynamic range of the receiving signal. Low-loss transmission lines on Si substrate are fabricated by post-passivation interconnection process using thick benzocyclobutene (BCB). We have confirmed the transmitting signal having spread-spectrum with suppressing the carrier leak, the improvement of the dynamic range of the receiver, and the reduction of the transmission loss on Si substrate. We have demonstrated the operation of the 26 GHz ultra wide band (UWB) SS radar, corresponding to detecting a human located at 7 m away from the system.

Electron Backscatter Diffraction Analysis for Polarization of SrBi2(Ta,Nb)2O9 Ferroelectric Capacitors in Submicron Small Area

We investigate the size and crystal orientation of each small grain of ferroelectric SrBi2(Ta,Nb)2O9 (SBTN) films within very small areas by an electron backscatter diffraction (EBSD) analysis technique. The obtained map of the grains reveals that the size of c-axis-oriented grains increases as the average grain size of the films increases. On the other hand, the size of a-axis-oriented grains, each of which has a finite remnant polarization normal to the films, is almost unchanged. The area fraction of the a-axis-oriented grains is in good agreement with the measured polarizations of ferroelectric capacitors with different average grain sizes. This result implies that an increase in the number of relatively small a-axis-oriented grains is effective for increasing the total polarization of the ferroelectric films. The demonstrated analysis technique is very useful for the precise design of future high-density ferroelectric random access memories (FeRAMs) with very small capacitor structures, each of which consists of only a few grains.

Overview and Future Challenge of FeRAM Technologies

Y. Kato, Y. Kaneko, H. Tanaka, K. Kaibara, K. Isogai, and Y. Shimada 1 Semiconductor Device Research Center, Matsushita Electric Industrial Co., Ltd 1-1 Saiwai-cho, Takatsuki, Osaka 569-1193, Japan Phone: +81-72-682-7540 E-mail: kato.yoshihisa@jp.panasonic.com 2 ULSI Process Technology Development Center, Matsushita Electric Industrial Co., Ltd. 19 Nishikujo-kasuga-cho, Minami-ku, Kyoto 601-8413, Japan