이기근 임운현 2018-08 28166 https://aurora.ajou.ac.kr/handle/2018.oak/14021 학위논문(석사)--아주대학교 일반대학원 :전자공학과,2018. 8 본 논문은 Lead zirconate titanate(이하 PZT)를 이용하여 UHF대역의 공진주파수를 가진 초음파 트랜스듀서를 개발하고, PZT를 기존에 MEMS기술에서 절연층으로 사용되던 대신 절연층으로 활용하여 소자의 특성을 향상하려는 시도에 관한 연구이다. PZT 절연층은 초음파 트랜스듀서의 진동 시 음향 임피던스 정합을 용이하게 하였으며, 이는 각각 다른 두 절연층을 가진 같은 구조의 소자들의 S-파라미터 비교를 통해 확인할 수 있었다. 제작된 초음파 소자의 공진주파수와 에너지 전달 확인은 네트워크 분석기를 이용하여 측정하였다. 또한 송수신기간의 음파 전달을 확인하기 위하여 각기 독립된 포트 2곳에 소자를 연결하고 한쪽 포트에만 전기에너지를 인가한 후, 반대쪽 포트의 수신기에서 진동에너지를 전기에너지로 변환시켜 포트로 입력한다. 이 때 전달된 전기에너지를 계산해본 결과 의 전기에너지가 전달되었다. 다양한 소자의 반경을 가진 박막형 트랜스듀서를 제작하여 수직 모드에서의 동작과 주파수 변화를 확인하였다. 또한 고품질의 압전 박막 형성을 위하여 열처리 및 재분극의 후처리 과정을 진행하였고 XRD 회절 분석과 히스테리시스 궤도 분석을 통해 박막의 품질을 확인하였다. S-파라미터 분석을 통해 PZT 절연층에 의한 에너지 변환율 향상과 직류 재분극의 유무에 따른 소자의 특성을 분석하였다. 제 1 장 서 론 ···················································································1 제 2 장 PZT 트랜스듀서의 동작원리 ·························································6 2.1 압전 현상 ···········································································6 2.2 변위 모드 이론 ·····································································8 2.3 음향 임피던스 ·····································································13 제 3 장 초음파 트랜스듀서의 설계 ···························································14 3.1 PZT 초음파 변환기 동작원리 ··················································14 3.2 COMSOL 시뮬레이션·····························································16 제 4 장 트랜스듀서 소자 제작 과정 ·························································20 4.1 트랜스듀서 제작 ··································································20 4.2 후처리 공정 ·······································································25 4.2.1 열처리 과정 ···························································25 4.2.2 재 분극 프로세스 ····················································27 제 5 장 트랜스듀서 특성 분석과 측정결과 ··················································29 5.1 PZT 박막 특성 분석 ·····························································29 5.2 공진주파수 및 전달 특성 측정방법 ············································32 5.3 전달 특성 측정 결과 ·····························································34 5.3.1 반경에 따른 공진 주파수 변화 ·····································34 5.3.2 PZT 절연층에 의한 소자 성능 측정결과 ·························36 5.3.3 직류 재 분극에 따른 특성 비교 ···································38 5.3.4 초음파 트랜스듀서의 에너지 전달 측정 ··························40 제 6 장 결 론 ··················································································42 참 고 문 헌 ······················································································43 Abstract ··························································································46 kor The Graduate School, Ajou University 아주대학교 논문은 저작권에 의해 보호받습니다. RF-스퍼터링으로 형성된 PZT 박막 절연 층을 이용한 고주파 초음파 트랜스듀서 개발 Lim, Un Hyun Thesis 아주대학교 일반대학원 Lim, Un Hyun 일반대학원 전자공학과 2018. 8 Master I804:41038-000000028166 http://dcoll.ajou.ac.kr:9080/dcollection/common/orgView/000000028166 초음파 MEMS Transducer