Low Temperature Hydrophilic SiC Wafer Level Direct Bonding for Ultrahigh-Voltage Device Applications

SiC direct bonding using O-2 plasma activation is investigated in this work. SiC substrate and n(-) SiC epitaxy growth layer are activated with an optimized duration of 60s and power of the oxygen ion beam source at 20 W. After O-2 plasma activation, both the SiC substrate and n(-) SiC epitaxy growth layer present a sufficient hydrophilic surface for bonding. The two 4-inch wafers are prebonded at room temperature followed by an annealing process in an atmospheric N-2 ambient for 3 h at 300 degrees C. The scanning results obtained by C-mode scanning acoustic microscopy (C-SAM) shows a high bonding uniformity. The bonding strength of 1473 mJ/m(2) is achieved. The bonding mechanisms are investigated through interface analysis by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Oxygen is found between the two interfaces, which indicates Si-O and C-O are formed at the bonding interface. However, a C-rich area is also detected at the bonding interface, which reveals the formation of C-C bonds in the activated SiC surface layer. These results show the potential of low cost and efficient surface activation method for SiC direct bonding for ultrahigh-voltage devices applications.

Automated summary

In this study, SiC direct bonding using O-2 plasma activation was investigated, showing a potential low-cost and efficient surface activation method. High bonding uniformity and strength were achieved through C-SAM scanning, with interface analysis revealing the formation of Si-O, C-O, and C-C bonds at the bonding interface through TEM and EDX.