| 摘要 |
PURPOSE:To improve the stickiness and flatness of a wafer, by dividing a vacuum sucking system into a plurality from the center of a wafer sucking plate to the outside, and by vacuum-sucking sequently at a designated lag time from the center of the vacuum sucking system to the outside. CONSTITUTION:A plurality of vacuum sucking holes 12 are provided on a wafer sucking plate 10 of a wafer sucking device to vacuum-suck a wafer 14 on the sucking plate 10. A vacuum sucking system for applying vacuum sucking forces to the sucking holes 12 is divided into three systems. Namely, it is divided into a central vacuum sucking system 16, an intermediate vacuum sucking system 18 located in the middle, and an outside vacuum sucking system 20 located far outside. The sucking systems 16, 18 and 20 are constituted to have a designated lag in vacuum sucking time mutually. They are combined with a vacuum source through a change-over valve mechanism. Namely, the sucking system 16 first starts vacuum-sucking, then, the sucking system 18 does in a designated time lag, and the sucking system 20 last does in another designated time lag. As a result, no dificient stick occurs at the center, as cimpared to the case of sucking a wafer at the same time. |
