Research on bubble-free Si/SiC hydrophilic bonding approach for high-quality Si-on-SiC fabrication

Abstract

The electrical device fabricated by the Si-on-SiC substrate exhibits superior heat dissipation and minimal RF loss. However, a common challenge in hydrophilic direct bonding is the inevitable formation of bubbles at the Si/SiC interface, which compromises material utilization efficiency. To address this issue, a multi-bonding process was introduced in this research. Experimental findings revealed that this method effectively mitigated interfacial bubble formation, especially when incorporating a multi-step annealing-separating-bonding approach, yielding even more promising results. Ultimately, a bubble-free 3×3 cm2 Si-on-SiC substrate was fabricated. Material characterization techniques confirmed the high crystal quality and minimal surface roughness for the Si functional layer. Transmission electron microscopy further revealed the presence of an amorphous oxide layer (~3.5 nm) at the interface, devoid of any defects or nanovoids. It is believed that with the excellent physical properties, Si-on-SiC will have a broader application prospect in extreme environments.