Film thickness measuring method and its device null of ultrasonic transducer and ultrasonic sensor and hole

摘要

PURPOSE:To measure the thickness of a thin film formed on the inner circumferential wall of a through hole. CONSTITUTION:A pair of transducers 1a and 1b to form a ultrasonic sensor 110 are installed to a through hole 15 making the conical members 12a at the tips of them opposing each other. The ultrasonic wave transmistted from the conical member 12a of the transducer 1a at the transmitter side is injected to a thin film 17 of the through hole 15 at the incient angle theta set by the angle made by the conical surface of the conical member 12a and the bottom face, where it is reflected and received by the conical member 12a of the transducer 1b at the receiver side at the receiving angle theta. By Fourier-converting at a high speed the time wave form of an electric signal obtained by converting the receiving wave at an FFT computing element 48, a spectrum intensity distribution and a spectrum phase distribution of the reflected waves are formed. A controller 50 detects a dip frequency to the intensity distribution, and a frequency to generate the rotation of phase to the phase distribution respectively, and the thin film thicknesses are calculated respectively depending on these frequencies.