Mechanism And Surface Damage In Inductively Coupled Plasma Etching Of SiC

Etching is a key process for SiC device fabrication. Due to its hardness and chemical inertness, wet chemical etch has been proven to be incompatible with device processing. Dry etching is, therefore, playing a critical role in processing SiC devices. Among several dry etch methods, Inductively Coupled Plasma (ICP) etching has been widely applied in the SiC device process, because it provides much higher plasma density and at the same time offers the capability of separate control of substrate bias. This means low substrate bias etching with reasonable rate is possible which should lead to minimum etching induced damage.In this paper, SiC was dry etched in ICP system using CF₄/O₂ gas mixtures. Etch rate has been investigated as a function of different parameters, including work pressure, ICP source power, bias power and the flow rate of oxygen. The result shows that high etch rate of SiC can be achieved with high ICP source power, high bias power, a pressure of 1.0Pa and 25% oxygen content within the plasma. And with the methods of X-ray photoelectronic spectrum (XPS) and Atom Force Microscope (AFM), the surface contamination and surface roughness induced in the ICP etching have also been investigated. An optimal etch condition with low surface damage can be obtained, where the ICP source power, bias power, work pressure, CF₄ and O₂ flow rates were 300W, 100W, 0.25Pa, 15sccm and 15sccm, respectively. And Scanning Electronic Microscope (SEM) was also used to study the etch profile. With these analyses, the SiC etch mechanisms are uncovered.In addition, the electrical damage to the surface caused by ICP etching of SiC was further characteristised by fabricating Ni/4H-SiC Schottky diodes onto the surfaces etched within ICP reactor. The results show that with the ICP etching, the performances of the diodes get worse significantly due to the damage and contamination induced in the etching process. In order to reduce the damage, a second etch process with low surface damage is introduced to the etched sample. It is observed that the diodes fabricated on the sample surfaces which were treated with two-step etch process have a better performance than those on the surface treated with one etch process. Therefore, it is believed that the high surface damage which was induced in the high-rate etching can be reduced through adding a second low-damage etch process.