| 摘要 |
<p>PROBLEM TO BE SOLVED: To optimize the vacuum sucking force of a wafer chuck for every sequence. SOLUTION: The wafer chuck 1 for sucking a wafer onto a sucking surface 1a generates the vacuum sucking force through pipes 2a, 2b. A sucking force varying mechanism 20 is provided between this sucking part 10 and a vacuum source 4 to switch the vacuum sucking force between at least two stages. Thus, when the wafer is supplied and when the wafer is retrieved, the sucking part 10 is connected to a first sucking line 21a generating a weaker sucking force, and it is switched to a stronger sucking force through a second sucking line 21b by an electromagnetic valve 22 while it is moved to the focusing position. The throughput can be improved by reducing the time required to generate the vacuum sucking force and to destruct the vacuum.</p> |
