BUFFER UNIT AND METHOD FOR STORAGING SUBSTRATE TYPE SENSEOR FOR MEASURING OF HORIZONTALITY OF A SUBSTRATE SUPPORT MEMBER PROVIDED ON A TEMPERATURE VARYING ATMOSPHERE

A buffer unit for temporarily storing a substrate includes a housing having a space for storing a substrate therein, one or more slots disposed within the housing for placing a substrate thereon, and a holding unit disposed at a bottom portion of the housing, having a flat and non-inclined top surface, and comprising a built-in wireless charging module. A substrate type sensor is stored at the holding unit.