대구경 선집속 초음파 탐촉자를 이용한 실리콘 판재의 결정방향 측정

국문 초록 (Abstract)

램파(Lamb wave)는 주파수, 파의 두께, 입사각에 따라 다양한 모드가 존재한다. 본 연구에서는 이방성 재료인 (100), (110), (111) 실리콘 판재에서 초음파의 진행방향에 따른 전파 특성에 대하여 연구하였다. 대구경 선집속 탐촉자를 이용하여 초음파를 판재에 입사시킴과 동시에 판재 내에서 발생하는 램파의 파형을 얻었다. 램파는 분산성이 있어서 수신된 파형에는 다양한 주파수의 파가 섞여있다. 이들을 분리하기 위해서 일련의 신호처리를 하였다. 탐촉자와 시험편 사이의 거리를 변화시키면서 얻은 V(t,z) 를 FFT(fast Fourier transform)하여 V(f,z)를 얻고, 특정한 주파수에서 V(z)를 얻었다. 초음파 현미경과 마찬가지로 V(z) 로부터 위상속도를 얻었으며, 시험편을 돌리며 이 과정을 반복하면 진행방향에 따른 위상속도의 변화를 얻을 수 있었다. 진행방향에 따른 파수 및 위상속도를 얻었으며, 이는 결정구조와 잘 일치하였다. 결론적으로 본 연구에 사용된 방법이 판재의 이방성을 평가할 때에 유용할 것으로 판단된다.

다국어 초록 (Multilingual Abstract)

Lamb waves have numerous modes depending on the frequency of the waves, the thickness of the plate and the incident angle. In this experiment, the wave propagation in (100), (110) and (111) single-crystal silicon wafers were investigated. Lamb waves were generated using a line-focused ultrasonic transducer with a large aperture in the wafers, and these waves were detected using the same transducer. The frequency and phase velocity were determined from the incident angle at which a specific mode of Lamb waves were generated. However there are numerous incident angles with the transducer used in this experiment, received signal contains various waves of different frequencies. The V(z) curve for a specific frequency was obtained from V(f, z) which is the FFT (fast Fourier transform) of V(t, z). The phase velocity can be obtained from the V(z) curves by using a method similar to that used in acoustic microscopy. Finally, the phase velocity can be determined as a function of the propagation direction by rotating the silicon wafers. The angular dependences of the wavenumber and Lamb wave phase velocity were obtained, and they show good agreement with the crystalline orientation of the silicon wafers. In conclusion, a line-focused ultrasonic transducer with a large aperture is an epoch tool for evaluating anisotropic plates.

목차 (Table of Contents)

• 초록
• Abstract
• 1. 서론
• 2. 실험장치
• 3. 신호처리
• 4. 결과 및 토의
• 5. 결론
• References

참고문헌 (Reference)

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