[20p-A34-1~12] 3.8 Terahertz technologies

4:30 PM - 4:45 PM JST(7:30 AM - 7:45 AM UTC)

[20p-A34-11] Fabrication of terahertz quasi-MIM absorbers for integration with thin-film MEMS bolometers

〇kazuho Harada¹, Zhao Zihao¹, Li Chao¹, Isao Morohashi², Ya Zhang¹ (1.Tokyo Univ. of Agri. &Techno., 2.NICT)

Keywords:

THz absorber,MIM metamaterial,MEMS bolometer

Metal-insulator-metal (MIM) metamaterial absorbers are promising for achieving high terahertz (THz) absorption, which is crucial for the development of high sensitivity THz detectors. Here, we have fabricated a quasi-MIM absorber on high-resistivity silicon substrate, for improving the optical sensitivity of a THz detector using a SOI MEMS resonator. The quasi-MIM absorber is formed by etching a high-resistivity silicon substrate by using reaction ion etching (RIE) to form a groove structure. Then we deposit a 200nm-thick Al film on the top surface of the substrate by thermal evaporation, and the etched and unetched parts naturally become two metal layers, forming the MIM structure together with the silicon substrate as the dielectric layer. A short wet etching process is performed for the Al film to completely separate the two Al layers. This structure features a notable advantage that no extra dielectric layers are introduced, thus is very compact, and very easily fabricated on SOI MEMS beam resonator. We have measured the reflection and transmission spectra of a fabricated quasi-MIM absorber by using a THz time-domain spectroscopy, when THz electromagnetic wave incidents from the Si substrate side. The reflection spectrum shows a valley at ~1.8 THz, indicating that there is a plasmonic resonance at this frequency. The peak absorption is over 95%, demonstrating the effectiveness of the proposed quasi-MIM structure for achieving a high THz absorption coefficient.