Properties of copper film characterized by scanning acoustic microscope

The scanning acoustic microscope is used to detect the properties of film or coating materials. The ultrasonic wave propagates in the materials with thickness h, sound velocity c, acoustic impedance Z₂ between medium with acoustic impedance Z₁. The echoes from different interfaces overlap and interfere. The interference phenomena are observed in spectrum of echoes. The spectrum has periodic maximums at integral multiples of base frequency f₀. When thickness h is known, speed c of the specimen can be calculated by the relation of f_n = nc/2h. According to the principle, the properties of copper films such as thickness, acoustic impendence and elastic modulus are detected by scanning acoustic microscopy. The experimental results are accorded with the actual properties of specimens.