| 摘要 |
The present invention relates to measurement of conductivity, particularly to the noncontact measurement of the conductivity using a microwave. A microwave oscillated by an oscillator ( 110 ) using a Gunn diode is applied through an isolator ( 120 ), a circulator ( 130 ), and a horn antenna ( 140 ) to a silicon wafer ( 150 ). The isolator ( 120 ) is used for reducing the standing wave influencing the operation of the instrument. The reflected wave is received by the same horn antenna ( 140 ), detected by a detector ( 160 ) connected to the circulator ( 130 ), and outputted in the form of a voltage. The detector ( 160 ) produces an output voltage proportional to the square of the amplitude of an electric field. Since the amplitude of the reflected wave from a silicon wafer ( 150 ) is proportional to the absolute value of the reflectance, the output voltage is also proportional to the square of the absolute value of the reflectance. The reflectance is in a certain relationship with the conductivity, the conductivity of the silicon wafer ( 150 ) can be determined.
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