Sub-millimeter Wave Devices on Thin Silicon Substrates
Yen-Pin Chang1*, Tse-Jun Chen1, Wei-Chun Lu1, Lingzhen Zeng2, Paul K. Grimes2, C. Edward Tong2, Ming-Jye Wang1
1Institute of Astronomy & Astrophysics, Academia Sinica, Taipei, Taiwan
2Center for Astrophysics, Harvard & Smithsonian, Cambridge,MA, USA
* Presenter:Yen-Pin Chang,
The feature size of device for microwave frequency application is usually proportional to the wavelength, which can be made by the precision CNC machine. As the wavelength becomes shorter, the difficulty and cost of machining increase dramatically. The demand of devices at sub-mm wavelength, such as orthogonal mode transducer (OMT), directional coupler, power combiner, and other passive components, grows quickly in astronomical instrument. Fabricating such devices massively and cheaply are an important issue. We have developed the fabrication process of sub-mm devices on the thin silicon substrate. Such devices are mounted in the host blocks with lower machining precision requirement. Furthermore, the properties of whole device can be adjusted by replacing the chip with different design parameters.
The fabricating process of device on thin silicon substate combines the techniques of deep silicon etching, mechanical lapping and polishing, and the regular RIE etching. The deep silicon etching process can ensure the dimension of silicon substrate with accuracy better than 1 μm. Mechanical lapping/polishing process incorporating with regular RIE can push the thickness accuracy better than 2 μm. Two kinds of devices have been fabricated successfully, attenuator and directional coupler. These devices have been tested and demonstrate excellent performance at frequency bands of 230 and 340 GHz and will be used in the new receiver of sub-millimeter Array (SMA). In this presentation, we will describe the details of fabricating process and the performance of deviecs.

Lingzhen Zeng, Wei-Chun Lu, Paul K. Grimes, Tse-Jun Chen, Yen-Pin Chang, C. Edward Tong, and Ming-Jye Wang† "A Silicon Chip-Based Waveguide Directional Coupler for Terahertz Applications" IEEE Transactions on Terahertz Science and Technology, pp. 698-703,November 2020.

Keywords: Terahartz, attenuator, directional coupler, SMA, OMT