Hi, those are probably carbon residues. Try to reduce CH4, and wash with O2, or other known post etching liquids.

Thanks dear Amir for your insight. What do you mean wash by O2? Do you mean oxygen plasma cleaning? Can you recommend some post etching liquids to me? Thanks

O2 plasma, or in some cases no need for plasma - depends on the tool and etching geometry.

For washing liquid, it really depends on the materials you have inside your bulk.

Your wafer was overheated during the etch. Yes try O2 plasma clean.

Hi H. Zeng,

Like Navid Jahed, I am using AlGaN/GaN materials based HEMT structure, However, I am also observed non conducting Greyish contamination on the sample surface after etching by using ICP consists of Cl2 and BCl3 plasma. Even it is not dissolving in acetone and very hard get rid of that contamination. For me, it look like Photo-resist contamination, due to overheating problem ( as you mentioned). Do you have any Idea to solve this Overheating problem.

Thanks very much

best regards

Satish