Sacrificial layer etching process in joint channels

A sacrificial layer etching process in joint channels is studied in this paper. If the etching process proceeds from a wide channel to a narrow one, the etching front presents a straight line during the whole process according to the experiments. If the etching process proceeds from a narrow channel connected with a wide channel, it is an arc rather than a straight line when the etching front reaches the wide channel. Some other interesting phenomena are also observed during etching the joint structure. For a narrow?wide channel, the etching rate decreases suddenly near the joint area, while for a wide?narrow channel, the etching rate increases quickly near the joint area and decreases gradually after that. A new model is proposed to explain these phenomena, which is proved to match the experimental data well.