In some embodiments, the measuring device 200 is configured to measure the weight of the wafer after the deposition process to the wafer. After the deposition process performing to the wafer, the measuring device 200 measures the weight of the wafer. In some embodiments, the measuring device 200 is equipped in the buffer chamber 130 and measures the weight of the wafer in the buffer chamber 130 after the wafer is transferred from the deposition process chamber. In some other embodiments, the measuring device 200 is equipped in the load lock chamber 120 and measures the weight of the wafer in the load lock chamber 120 after the wafer is transferred from the buffer chamber 130. In alternative embodiments, the measuring device 200 is equipped in the factory interface 110 and measures the weight of the wafer in the factory interface 110 after the wafer is transferred from the load lock chamber 120.

In some embodiment, the weight measured by the measuring device 200 is converted to a thickness of a corresponding material. The conversion will be discussed below with reference to FIGS. 2-3B.

For illustration in FIG. 1, the measuring device 200 is able to be equipped in position A which corresponds to the factory interface 110, positions B-C which correspond to the load lock chambers 120, or positions D-E which correspond to the robot blade 132 of the robot 131 of the buffer chamber 130. The positions A-E in FIG. 1 are given for illustrative purposes. Various positions are within the contemplated scope of the present disclosure.