1800 V, 3.8 A bipolar junction transistors in 4H-SiC

Silicon carbide (SiC) is a very attractive material for high voltage, high power switching devices. Power MOSFETs in SiC have received the most attention, but high performance SiC MOSFETs have yet to be developed due to poor MOS mobility and reliability, especially in 4H-SiC. On the other hand, bipolar devices such as GTOs (Agarwal et al, 1999) have demonstrated high blocking voltages and high on-currents, taking full advantage of the material properties of SiC. In this paper, we report the first demonstration of high voltage NPN bipolar junction transistors in 4H-SiC. The BJTs were able to block 1800 V and showed an on-resistance of 10.8 m/spl Omega/cm/sup 2/ (I/sub C/=2.7 A at V/sub CE/=2 V for a 1 mm/spl times/1.4 mm active area), which outperforms all previously reported SiC power switching devices. Moreover, these transistors show a negative temperature coefficient in the on-resistance characteristics, which enables easy paralleling of the devices. The BJTs were fabricated in 4H-SiC with a 20 /spl mu/m thick, 2.5/spl times/10/sup 15/cm/sup -3/ doped collector layer, 1 /spl mu/m thick, 2.5/spl times/10/sup 17/cm/sup -3/ doped base layer, and 0.75 /spl mu/m thick N+ emitter layer. The N+ emitter fingers were isolated by RIE, and then aluminum was implanted to form base contact regions. The base layer was then RIE etched to isolate the devices, and boron ions were implanted to form JTE termination regions. Alloyed Ni was used for both N-type and P-type ohmic contacts. A Ti/Au layer was then deposited and patterned as overlayer and probing pads.