2021 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 |
There are three major accomplishments in 2021 fiscal year. (1) Based on the study of fabrication of cryogenic thin-film resistors, which is a key technique in this project, we have developed a theoretical model that reveals the mechanism of highly nonlinear current-voltage characteristic of magnetron discharges, and published this finding in Journal of Applied physics. This achievement not only allows us to fabricate cryogenic thin-film resistors with desirable high resistivity, but is a fundamental one that is applicable in a wide range in magnetron sputtering process. (2) We have invented an on-chip measurement method to assess the transmission loss of superconducting transmission lines at millimeter wavelengths. This method is important because it can be implemented at cryogenic temperature and at high frequencies where using a network analyzer is normally difficult. By using this method, we have evaluated the transmission loss in our MMIC mixers and concluded that the transmission loss, although not negligible, is not yet a limiting factor of mixer performance. This conclusion is essential evidence that justifies the application of MMIC technique at millimeter frequencies. (3) We have identified that generation of parallel-plate resonance modes at intermediate frequencies is the reason responsible for the crosstalk in the MMIC mixer chips. According to our study, the best solution is adding through substrate via-holes in the MMIC mixer chips. We have designed a fabrication process and started a fabrication study. Preliminary results showed that the process is feasible.
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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 accomplishment of research plan for 2021 fiscal year is as follows:
Task 1: To complete demonstration of sideband separation configuration on silicon MMICs at ALMA Band 4. We have fulfilled this task by about 70%. The substrate vias-hole process, which is the solution for the cross-talk problem, is still under development. The obtained results are concluded in point 3 of research achievement column (RAC).
Task 2: Thin-film resistor fabrication process will be further studied and improved to obtain NbTiN thin-film resistors. We have fulfilled this task completely. The achievement is concluded in point 1 of RAC.
Task 3: Establishment of 1-micrometer thick SiN membrane fabrication process with PECVD and related membrane transfer process. We decided to postpone this study. Instead, we worked on the investigation of the loss of thin-film transmission lines in our MMIC mixer chips because the later investigation is more urgent. The related results are concluded in point 2 of RAC.
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| Strategy for Future Research Activity |
In line with the overall research plan and based on the results obtained in previous year, in 2022FY following studies will be performed.
(1) Establish fabrication process for through-substrate via holes, which is necessary in resolving the on-chip IF crosstalk problem and finally completing demonstration of sideband separation configuration with silicon-based MMICs at ALMA Band 4.
(2) Revisit the quantum mixing theory and identify the reason for unexpected excess receiver noise measured in the devices fabricated in 2022.
(3) Establish an Au-plating process for silicon micro-machined components.
(4) Publish the experimental results of thin-film resistor fabrication, which was done in 2022.
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Research Products
(8 results)
