Dear members: I have a question about silicon trench wet etching. If etched from back side, for example, 2um mask dimension, how wide the trench will be in the front side with wet etching? I know this depends on the orientation of wafer and the trench direction. According to the book, if the trench is aligned accurately, it is possible to get a vertical side wall, thus, the width in front side will be the same as that in back side, say, 2um. I donot know whether it requires very high accuracy to alignment in order to get vertical side wall. If I do the alignment manualy, generally how thin i can get in the front side? Is there anybody has experience in this area? thanks. Regards, Yilei Zhang