| 摘要 |
PURPOSE:To obtain constant resolution power irrespective of irregular shapes of a mask and a wafer by exposing after confirming the contact of the mask with the wafer. CONSTITUTION:A mask 3 and a wafer 5 are evacuated in vacuum therebetween through a vacuum line 9. An ultrasonic wave oscillator 1 oscillates an intrinsic oscillation frequency determined by the mask 3 and a mask holder plate 4 until the wafer 5 is contacted with the mask 3, outputs the oscillation signal, and an ultrasonic wave receiver 2 receives the output signal. When a wafer chuck 6 rises and the wafer 5 contacts the mask 3, an acoustic impedance from the oscillator 1 to the receiver 2 is affected by the influence of the contact to largely vary. Thus, the intrinsic oscillation frequency of the system is largely varied at the low frequency side to present the large influence at the reception signal, and less varied as the contacting state is improved. An alignment is completed before contacting, and the exposure is started when the output of the receiver 2 becomes a predetermined value.
|
