Abstract: A method of etching cavities having different aspect ratios. An etching stop layer is formed on the bottom surface of a substrate, and a mask pattern is formed on the top surface of the substrate. The mask pattern includes a plurality of sacrificial patterns positioned on both a first cavity predetermined region and a second cavity predetermined region. Then, an etching process is performed to remove the substrate not covered by the mask layer. Then, the etching stop layer is removed, as well as the sacrificial patterns and the substrate covered by the sacrificial patterns.

Abstract: A wafer carrier for carrying a wafer includes a transparent base and a conducting layer. The transparent base has dimensions similar to that of the wafer, and bonds the wafer with a bonding layer. The conducting layer is transparent, and can be attracted by an electrostatic chuck so that the electrostatic chuck can deliver the wafer.