PURPOSE: To hold the amount of exposure invariably constant by measuring and integrating the intensity of laser light all the time and ending an exposure process when the integral value attains to a specific value.
CONSTITUTION: The rear mirror of a laser 1 has finite transmittivity and a part of laser light from the rear mirror is projected. The intensity of the projected light is detected by a photodiode 7 and amplified by an amplifier 8, which outputs a voltage Va. The output of the amplifier 8 is integrated by an integrator 9. The output Vb of the integrator 9 is proportional to the integral value of the laser light intensity, so the output Vb is also proportional to the intensity of laser light incident to photoresist 6. The output of the integrator corresponding to the desired amount of exposure is denoted as Vc. A comparator 10 compares a reference voltage Vc with the output Vb of the integrator 9 to open and close a shutter. Thus, the amount of exposure is held invariably constant.
MATSUOKA HARUJI
NISHIURA YOUZOU
OKAMOTO KENJI
