Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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Research on Fabrication of Silicon Lens for Optical Communication by Photolithography Process

포토리소그래피를 통한 광통신용 실리콘 렌즈 제작 및 특성 연구

  • Park, Junseong (Optoelectronics Convergence Research Center, Chonnam National University) ;
  • Lee, Daejang (Optoelectronics Convergence Research Center, Chonnam National University) ;
  • Rho, Hokyun (Optoelectronics Convergence Research Center, Chonnam National University) ;
  • Kim, Sunggeun (Optoelectronics Convergence Research Center, Chonnam National University) ;
  • Heo, Jaeyeong (Optoelectronics Convergence Research Center, Chonnam National University) ;
  • Ryu, Sangwan (Optoelectronics Convergence Research Center, Chonnam National University) ;
  • Kang, Sung-Ju (School of Chemical Engineering, Chonnam National University) ;
  • Ha, Jun-Seok (Optoelectronics Convergence Research Center, Chonnam National University)
  • 박준성 (전남대학교 광전자융합기술연구소) ;
  • 이대장 (전남대학교 광전자융합기술연구소) ;
  • 노호균 (전남대학교 광전자융합기술연구소) ;
  • 김성근 (전남대학교 광전자융합기술연구소) ;
  • 허재영 (전남대학교 광전자융합기술연구소) ;
  • 류상완 (전남대학교 광전자융합기술연구소) ;
  • 강성주 (전남대학교 화학공학부) ;
  • 하준석 (전남대학교 광전자융합기술연구소)
  • Received : 2018.06.13
  • Accepted : 2018.06.27
  • Published : 2018.06.30
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Abstract

In order to improve the coupling efficiency, a collimator lens that collects the light emitted from the laser diode at a wide angle to the core of the optical fiber is essential. Glass mold method using a mold is widely used as a collimator lens currently used. Although this method is inexpensive to produce, it is difficult to form precisely and quality problems such as spherical aberration. In this study, the precision of surface processing was improved by replacing the existing glass mold method with the semiconductor process, and the material of the lens was changed to silicon suitable for the semiconductor process. The semiconductor process consists of a photolithography process using PR and a dry etching process using plasma. The optical coupling efficiency was measured using an ultra-precision alignment system for the evaluation of the optical characteristics of the silicon lens. As a result, the optical coupling efficiency was 50% when the lens diameter was $220{\mu}m$, and the optical coupling property was 5% or less with respect to the maximum optical coupling efficiency in the lens diameter range of $210-240{\mu}m$.

광결합 효율(Fiber coupling efficiency)을 개선하기 위해서는 Laser diode에서 넓은 각도로 방출된 빛을 광섬유의 중심(Core) 부분으로 모아주는 집광렌즈(Collimating lens)가 필수적이다. 현재 사용되는 집광렌즈는 형틀(Mold)을 이용한 글래스 몰드(Glass mold) 공법이 널리 사용되고 있다. 이 방식은 생산단가가 저렴하지만, 정교한 성형이 어렵고 구면수차와 같은 품질문제가 있다. 본 연구는 기존의 글래스 몰드 공법을 반도체 공정으로 대체함으로써 표면 가공의 정밀도를 높이고, 렌즈의 재질 또한 반도체 공정에 적합한 실리콘으로 변경하였다. 반도체공정은 PR을 이용한 포토리소그래피(Photolithography) 공정과 플라즈마를 이용한 건식 식각(Dry etching) 공정으로 구성된다. 광결합 효율은 실리콘 렌즈의 광학적 특성을 평가하기 위해 초정밀 정렬 시스템을 사용하여 측정되었다. 그 결과, 렌즈 직경 $220{\mu}m$ 일 때의 최대 광결합 효율은 50%로 측정되었고, 렌즈 직경 $210-240{\mu}m$ 범위에서는 최고 광결합 효율 대비 5% 이하의 광결합 특성저하를 보여줌을 확인하였다.

Keywords

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