2022 Fiscal Year Annual Research Report
Ultra-compact Sub-mm Heterodyne Focal Plane Array Frontends for Radio Astronomical Observation
| Project/Area Number |
21H01134
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| Allocation Type | Single-year Grants |
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| Research Institution | National Astronomical Observatory of Japan |
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Principal Investigator |
SHAN Wenlei 国立天文台, 先端技術センター, 准教授 (60792570)
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| Co-Investigator(Kenkyū-buntansha) |
江崎 翔平 国立天文台, 先端技術センター, 研究技師 (40794508)
田村 友範 国立天文台, 先端技術センター, 技師 (90897828)
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| Project Period (FY) |
2021-04-01 – 2026-03-31
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| Keywords | Focal Plane Array / Heterodyne / SIS Mixer / Radio Astronomy |
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| Outline of Annual Research Achievements |
Three significant achievements have been made in the development of MMIC SIS mixers. Firstly, a microfabrication method for on-chip resistors was established, allowing for the successful fabrication of NbTiN thin-film resistors with a wide range of resistivity. The method were published in the international journal "Thin Solid Films" and are crucial for the development of MMIC SIS mixers. Secondly, we conducted an experiment to investigate the performance of silicon membrane waveguide transitions, a key component in MMIC mixers. The results, which agreed well with theoretical predictions, were accepted for publication. Lastly, we identified the primary cause of crosstalk in MMIC mixer chips and developed a fabrication process for through-substrate via-holes in the chips. The results showed that conductive via-holes can be fabricated using a non-Bosch silicon etching process and will be published in IEEE Trans. On Applied Superconductivity. These achievements are significant in advancing the understanding of reactive plasma processes and will allow for the continued development of MMIC SIS mixers.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The achievements of the research plan for the 2022 fiscal year are as follows:
Task 1: "Establish a fabrication process for through-substrate via holes (TSV)." We have developed a TSV fabrication process using non-Bosch and DC magnetron sputtering processes and observed a superconducting transition of the Nb films of TSVs at 7.8 K. Task 2: "Revisit the quantum mixing theory and identify the reason for unexpected excess receiver noise measured in the devices fabricated in 2022." We conducted an in-depth study on two important aspects of the noise of SIS mixers, namely RF input noise and IF noise. We are now able to confidently separate the noise components of a SIS mixer and pinpoint the excess receiver noise in some of our devices. Task 3: "Establish an Au-plating process for silicon micro-machined components." We have developed a compact electroplating system. The hardware is now ready, and experiments are underway. Task 4: "Publish the experimental results of thin-film resistor fabrication, which was done in 2022." The thin-film resistor process has been concluded, and the results have been published.
Additionally, we have initiated an on-chip measurement method to assess the transmission loss of superconducting transmission lines at millimeter wavelengths. This method is important because our MMIC mixer experiment results imply unexpected loss of superconducting transmission lines in the signal path before the mixers. Based on the results, we will try to reduce the loss by improving our fabrication process.
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| Strategy for Future Research Activity |
The following studies will be performed in the 2023 fiscal year:(1) Continue to investigate the transmission loss of planar superconducting transmission lines that conduct signals in MMICs. We will further improve the fabrication process to reduce the transmission loss.(2) Carry out studies on the fabrication process of MMICs to improve the fabrication yield and the quality of SIS junctions in terms of the nonlinearity of the IV characteristics. (3) Investigate an alternative method to TSVs to solve the crosstalk problem. In the alternative method, we will try to avoid stimulating the substrate oscillation modes by weakening the coupling.(4) Finally, complete the demonstration of sideband separation configuration with silicon-based MMICs at ALMA Band 4.
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