| 摘要 |
<p>PURPOSE:To maintain flatness of wafer surface by controlling the magnetic valve of a vacuum chuck absorber hole according to the condition, measuring the flatness of the wafer surface by a sensor. CONSTITUTION:A wafer is placed on a chuck 11 and absorbed by a hole 12 actuating all the magnetic valves 5. The flatness is measured by a sensor 9 on a measuring rack by keeping 3 projections 7 of the rack 6 and the wafer surface in contact thereby determining a reference surface. A recess of the wafer surface is pushed up breaking vacuum and opening the valve of the hole 12, facing the recess, according to the difference of the output power of the sensor facing the recess of the wafer surface. After the flatness is attained, a uniform and accurate pattern can be imprinted by keeping a perfect contact of a photo mask 10 and the wafer 4 by lifting the vacuum chuck 11.</p> |
