Tatsuo Oomori

Successful Development of 1.2 kV 4H-SiC MOSFETs with the Very Low On-Resistance of 5 mΩcm2

4H-SiC MOSFETs comprised of a miniaturized unit cell structure were fabricated. The epilayer channel configuration was employed to effectively improve the MOSFET electrical characteristics. A specific on-resistance of 5 mOmegacm2 with a stable avalanche breakdown of 1.35 kV was successfully recorded. Temperature dependence of the Ron,sp examined and the Ron,sp exhibited still low value of 8.5 mOmegacm2 at 150 degC . The SiC-MOSFETs were put together with SiC-SBDs to realize prototype SiC power modules. A switching energy loss was significantly reduced by employing the SiC module in comparison with a Si-IGBT/Si-FWD module. A three-phase inverter circuit consisted of the SiC module was assembled and stably drove a 3.7 kW/400 V induction motor

Breakthrough in trade-off between threshold voltage and specific on-resistance of SiC-MOSFETs

The threshold voltage of 4H-SiC MOSFET increases drastically by performing wet oxidation after nitridation of gate oxide without significant decrease in the channel effective mobility. The increment of the threshold voltage depends on the wet oxidation conditions, and wet oxidation improves the trade-off between the threshold voltage and the specific on-resistance. We fabricated 600 V 4H-SiC MOSFETs with a threshold voltage of 5.11 V and a specific on-resistance of 5.2 mΩcm2 using the procedure above. The stability of the threshold voltage for the SiC-MOSFETs was confirmed by a HTGB test.

Reduction of crosstalk noise between interconnect lines in CMOS RF integrated circuits

We have numerically investigated crosstalk noise between interconnect lines in CMOS RF integrated circuits. Immersed microstrip line (IMSL) and immersed coplanar waveguide (ICPW) over Si substrate were analyzed to make clear shielding effect of grounded planes to reduce crosstalk noise between parallel interconnect lines. It was shown that the crosstalk between the interconnect lines were extensively reduced by the use of IMSLs or ICPWs, compared with simple lines. However, in layout designs using ICPWs, we need consideration about the transmission loss due to the electromagnetic coupling with the lossy Si substrate. On the other hand, for IMSL configurations, the transmission loss due to the Si substrate is small, because the ground plane shields the signal line from the electromagnetic coupling with the Si substrate.