PURPOSE: To allow a semiconductor distribution reflection mirror to have a very accurate central wave length by letting infrared rays radiated through a semiconductor layer pass through a first and a second band passing wave filter at a predetermined cycle alternately and by detecting the optical thickness of the semiconductor from the detection output obtained from a phase detector.
CONSTITUTION: A semiconductor layer 22H having a high refractive index is formed on a semiconductor substrate 20. At that time, infrared rays UR radiated from a substrate heating device 40 through the semiconductor layer 22H are let to pass through a band pass wave filter 91a having a central wave length smaller than that of a semiconductor distribution reflection mirror 21 and a band wave filter 91b having a central wave length higher than that of the semiconductor distribution reflection mirror 21 at a predetermined cycle T alternately and then are supplied to an infrared detector 82. The infrared rays intensity detection output DD obtained from the infrared detector 82 is supplied to a phase detector 92. From the detection output of the phase detector 92, the optical thickness of the semiconductor layer 22H is detected. By using infrared rays UR, an apparatus for fabricating a semiconductor distribution reflection mirror can be manufactured easily at low cost and the size of the apparatus can be reduced.
UENOHARA HIROYUKI
KOHAMA TAKETAKA
