在次毫米波段的太空觀測研究之中, 尋找一個低雜訊的觀測元件是令許多科學家極感興趣的。我們藉由本實驗室已發展成熟的鈮/氧化鋁/鈮超導穿隧結之製程技術, 進而發展出一套新的製程方法來製作次微米尺度超導穿隧結之混頻元件。 因為此一元件的寄生電容具有可被忽略的特性, 因而能夠在高頻的訊號源之下仍保有較好的匹配效應, 除此之外亦可在較廣的頻寬範圍內操作。 我們使用一般在鈮/氧化鋁/鈮超導穿隧結之製程中所常用到的自動對正的方法先製作出三夾層的結構, 再配合電子束微影技術, 便可精確製作出0.4um×0.4um大小的超導穿隧結。 我們所製作出來的樣品具備低滲漏, 高超導電流密度, 以及觀察其電流-電壓特性曲線之中, 當外加電壓接近超導能隙電壓時, 會出現十分陡峭的非線性行為。樣品的wRnC乘積值為2.4。
我們首度嘗試使用電子束微影技術中不可或缺的PMMA搭配積體電路產業上常用的polymide, 並成功製作出高品質的次微米尺度超導穿隧結。 我們所發展的這套製程可達到~0.1um×0.1um, 甚至到更小的尺度範圍。
在次毫米的量測中, 我們所使用的接收器是選擇波導管耦合超導穿隧結的方式組裝而成。 關於量測結果方面,一個0.2um^2穿隧介面大小的樣品被測量出具有25hv/k的雜訊溫度值。 由於此一樣品的超導電流密度僅有3,250A/cm^2, 因此很難期待會有好的表現。 如何增加樣品的超導電流密度值, 而且同時顧及介面的強韌度, 是爾後需要努力下工夫的地方。

We are interested in the low noise heterodyne receiver used for the astronomical study in the submillimeter wavelengths range and develop a process to fabricate Nb-based superconductor-insulator-superconductor (SIS) junctions with sub-micron size for the purpose of the reduction in the coupling losses at higher radio frequency (RF) and wide bandwidth operation. We use conventional self-aligned mask trilayer process in addition with E-beam lithography to fabricate SIS junctions with well-defined size of ~0.4um×0.4um and high quality, such as low leakage, high current density of ~10kA/cm^2, and sharp nonlinearity in the I-V curve. The junction has wRnC product value of 2.4.
We first attempt to use PMMA combined with polymide, which is commonly used in the IC process, and successfully fabricate sub-micron SIS with high quality. By this process, the junction size could reach ~0.1um×0.1um and even smaller.
Our SIS receiver’s system is waveguide coupled with SIS junction. Under the 300GHz frequency range measurement, a 0.2um^2 area size junction with supercurrent density of 3,250A/cm^2 performs its noise temperature of about 25hv/k. To improve the SIS mixer junction qualities, especially to increase the supercurrent density with a tough junction, is important for the future studies.

Content
Abstract
Chapter 1 An Approach to Exploring Universe
1.1 Exploration of universe
1.2 Radio astronomy
1.2-1 Big bang explanation
1.2-2 How were the galaxies born
1.3 Detector requirements
1.3-1 Observing instruments
1.3-2 Operation of heterodyne receiver
1.3-3 Brief introduction of heterodyne receivers
1.3-4 Review of SIS receivers
1.3-5 Improvement of RF match to mixers
Chapter 2 Physics of SIS Junctions
2.1 Brief introduction of superconductivity
2.2 SIS tunneling
2.2-1 Quasiparticle tunneling
2.2-2 Josephson tunneling
Chapter 3 Theory of Heterodyne Receivers
3.1 Classical theory of heterodyne receivers
3.2 Receiver noise
3.2-1 Chain stage of receiver
3.2-2 Noise temperature
3.2-3 Y-factor
3.3 Quantum mixer theory
3.3-1 The DC case
3.3-2 LO response (large signal)
3.3-3 Mixing response (small signal)
3.3-4 Three-port approximations
3.4 Conversion gain
3.5 Circuit analysis
3.6 Noise of mixer
3.7 Discussion
Chapter 4 Fabrication Process of Small Area SIS Junctions
4.1 E-beam lithography
4.1-1 Brief introduction
4.1-2 PMMA preparation
4.1-3 Equipment of E-beam Lithography
4.1-4 Results 4.2 Fabrication process
4.2-1 Process illustrations
4.2-2 Fabrication results
4.3 DC measurement results
4.3-1 Equipments for DC measurement
4.3-2 I-V curve results
4.3-3 Fraunhofer diffraction patterns
4.4 Discussion
4.4-1 A brief summary about measurement results
4.4-2 Josephson supercurrent in an ultrasmall Josephson junction
Chapter 5 Mixer Measurement in Submillimeter Wavelength Range
5.1 SIS mixers preparation
5.2 Noise measurement system
5.3 Experimental Result and discussion
5.3-1 Results
5.3-2 Discussion
Chapter 6 Summary
References

Reference
[1] Most content in this paragraph are consulted from “Exploration of the universe” Philadelphia: Saunders College Pub., by George O. Abell, David Morrison, Sidney C. Wolff, 1991.
[2] www.nobel.se
[3] Richards, P. L., T. M. Shen, R. E. Harris, and F. L. Lloyd, "Quasiparticle heterodyne mixing in SIS tunnel junctions," Appl. Phys. Lett., vol. 34, pp. 345-346, 1979.
[4] Dolan, G. J., T. G. Phillips and D. P. Woody, "Low-noise 115 GHz mixing in superconducting oxide-barrier tunnel junctions," Appl. Phys. Lett., vol. 34, pp. 347-349, 1979.
[5] Tucker, J. R., "Quantum limited detection in tunnel junction mixers," IEEE J. Quantum Electron., vol. 15, no.11, pp. 1234-12.58, 1979.
[6] Prober, D. E., “Superconducting terahertz mixer using transition-edge microbolometer,” Appl. Phys. Lett. 62. pp. 2119-2121, 1993.
[7] Dayem, A. H. and R. J. Martin "Quantum interaction of microwave radiation with tunneling between superconductors," Phys. Rev. Lett., vol. 8, no. 6, pp. 246-248, 1962.
[8] P. K. Tein and J. P. Gordan , Phys. Rev. 129, 647, 1963.
[9] L. Ollsen, S. Rudner, E. Kolberg, and C. O. Lindstorm, “A low noise SIS array receiver from radioastronomical applications in 30-50 GHz band” Int. J. IR and MM Waves, vol. 4, pp. 847-858, 1983.
[10] Woody, D. P., R. E. Miller, and M. J. Wengler, ? - 115 GHz receivers for radio astronomy," IEEE Trans. Microwave Theory Tech., vol. 33, no. 2, pp. 90-95. 1985.
[11] Feldman, M. J., S. K. Pan, A. R. Kerr, and A. Davidson, "SIS mixer analysis using a scale model," IEEE Trans. Magn., vol. 19, pp. 494-497, 1983.
[12] Wengler, M. J., D. P. Woody, R. E. Miller, and T. G. Phillips, "A low-noise receiver for millimeter and submillimeter wavelength," Int. J. IR and MM Waves, vol. 6, pp. 697-706, 1985.
[13] Kohjiro, S., S. Kiryii, and A. Shoji, "Surface resistance of epitaxial and polycrystalline NbCN films in the submillimeter wave region," IEEE Trans. Appl. Superconductivity, vol. 3, pp. 1765-1767, 1993.
[14] Wang, Z., A. Kawakami, Y. Uzawa, and B. Komiyama, "High critical-current density NbN/AlN/NbN tunnel junctions fabricated on ambient-temperature MgO substrate," Appl. Phys. Lett., vol. 64, pp. 2034-2036, 1994.
[15] de Lange, G., C. E. Honingh, J. J. Kuipers, H. H. A. Schaeffer, R. A. Pahihuyzen, T. M. Klapwijk, H. Van de Stadt, and M. M. W. M. de Graauw, "Heterodyne Mixing with Nb Tunnel Junctions Above the Gap Frequency," Appl. Phys. Lett., vol. 64, pp. 3039-3041, 1994.
[16] Kooi, J. W., M. S. Chan, M. Bin, B. Bumble, and H. G. LeDuc, "The development of an 850 GHz waveguide receiver using tuned SIS junctions on Si3N4 membranes," Int. J. IR and MM Waves, vol. 16, pp. 349-362, 1995.
[17] Blundell, R., C.-Y.E. Tong, D. C. Papa, R. L. Leombruno, X. L. Zhang, , S. Paine, , J. A. Stern, H. G. LeDuc, and B. Bumble, "A wideband fix-tuned SIS receiver for the 200 GHz operation," IEEE Tran. Microwave Theory and Tech. vol. 43, No. 4, pp. 933-937, 1995.
[18] D'addario, L. R., "An SIS mixer for 90-120 GHz with gain and wide bandwidth," Int. J. IR and MM Waves, vol. 5, no. II. pp. 1419-1442, 1984.
[19] Raisanen, A. V., W. R. McGrath, P. L. Richards, and F. L. Lloyd, "Broadband RF match to 3. millimeter-wave SIS quasi-particle mixer," IEEE Trans. Microwave Theory Tech., vol. 33, no. 12, pp. 1495-1500, 1985.
[20] Shi, S. C., T. Noguchi, J. Inatani, “A 100GHz fixed-tuned waveguide SIS mixer exhibiting broad bandwidth and very low noise temperature” IEEE Transactions on Applied Superconductivity., vol. 7, No. 4, pp 3850-3857, 1997.
[21] Hu, Q., P. L. Richards, “Quasiparticle mixers and detectors,” Ch.5, Superconducting Devices, pp. 169-196, Academic Press, Inc. 1990.
[22] H. Kamerlingh Onnes, Leiden Commun., 120b, 122b, 124c, 1911.
[23] W. Meissner and R. Ochsenfeld, Naturwissenschaft 21,787, 1933.
[24] V. L. Ginzburg and L. Landua, Zh. Eksp. Teor. Fiz. 20, 1064, 1950.
[25] H. London and H. London, Proc. Roy.Soc. (London) A 141, 71, 1935.
[26] H. Fröhlich, Phys. Rev. 79, 845, 1950.
[27] Bardeen, J., L. N. Cooper, and J. R. Schrieffer, "Theory of superconductivity," Phys. Rev., vol. 108, pp. 1175-1204, 1957.
[28] Bednorz, J. G.., and K. A. Müller, Z.Phys. B 64, no.198, 1986.
[29] M. K. Wu et al., Phys. Rev. Lett. 58, 908, 1987.
[30] Tinkham, M., “Introduction to Superconductivity”, New York: McGraw-Hill, 1975.
[31] B. D. Josephson, Phys. Lett 1, 251(1962).
[32] R. Feynmen, “Lectures on Physics” Chapter21 Vol. III, p12-14~p12-18.
[33] V. Ambegaokar, and A. Baratoff, Phys. Rev. Lett. 10, 468(1963a); 11,104(1963b).
[34] Cohen, M. H., L. M. Falicov, and J. C. Phillips, "Superconductive tunneling," Phys. Rev. Lett., vol. 8, no. 8, pp. 316-318, 1962.
[35] Werthamer, N. R., “Nonlinear self-coupling of Josephson radiation in superconducting tunnel junctions," Phys. Rev., vol. 147, no. 1, pp. 255-263, 1966.
[36] Tucker, J. R. and M. J. Feldman, "Quantum detection at millimeter wavelengths," Rev. Mod. Phys., vol. 57, no. 4, pp. 1055-1113, 1985.
[37] Torrey, H. C. and C. A. Whitmer, Crystal Rectifiers, MTT Rad. Lab. Series, vol. 15, New York: McGraw Hill, 1948.
[38] Smith, A. D. and P. L. Richards, “Analysis solutions to superconductor —insulator -superconductor quantum mixer theory,” J. Appl. Phys. Vol. 53, no. 5, 1982.
[39] Shen, T. M., "Conversion gain in millimeter wave quasi-particle heterodyne mixers," IEEE J. Quantum Electronics, vol. 17, no. 7, pp. 1151-1165, 1981.
[40] Feldman, M. J., "Some analytical and intuitive results in the quantum-theory of mixing," J. Appl. Phys., vol. 53, no. 1, pp. 584-592, 1982.
[41] Buttgenbach, T. H., H. G. LeDuc, P. D. Maker, and T. G. Phillips, "A fixed tuned broadband matching structure for submillimeter SIS receivers," IEEE Trans. Appl. Superconductivity, vol. 2, no. 3, pp. 165-175, 1992.
[42] Feldman, M. J., "Quantum noise in the quantum theory of mixing," IEEE Trans. on Magn., vol. mag23, no. 2, pp. 1054-1057, 1987.
[43] Caves, C. M., "Quantum limits on noise in linear amplifiers," Phys. Rev. P, vol. 26, pp. 1817-1839, 1982.
[44] Shin’ichi Morohashi, S. Hasuo, and T. Yamaoka, “Self-align contact process for Nb/AlOx/Nb Josephson junctions” Appl. Phys. Lett. vol. 48(3), no. 20, 1986.
[45] A. Steinbach, P. Joyez, A. Cottet, D. Esteve, M. H. Devoret, M. E. Huber, and John M. Martinis, “Direct Measurement of the Josephson Supercurrent in an Ultrasmall Josephson Junction,” Phys. Rev. Lett. vol. 87, no. 13 pp. 137003-1~137003-4, 2001.
[46] Xiaolei Zhang, “Design of conical corrugated feed horns for wide band high-frequency applications,” IEEE Transactions on Microwave Theory and Tech., vol. 41, No. 8, p. 1263, 1993.
[47] Blundell, R. and C. Y. E. Tong, "Submillimeter receivers for radio astronomy," Proc. IEEE, vol. 80; pp. 1702-1720, 1992.
[48] C. C. Chin, Robert Hu, and Robert Martin, “The Superconducting Receivers of the Sub-mm Array of Taiwan,” CHINESE JOURNAL OF PHYSICS VOL. 36, NO. .L-11 APRIL 1998.
[49] A. R. Kerr, “Low-noise room-temperature and cryogenic mixers for 80-120GHz,” IEEE Tran. Microwave Theory and Tech. vol. 23, no.10, pp. 781-787, 1975.
[50] Kooi, J. W., M. S. Chan, T. G. Philips, B. Bumble, and H. G. LeDuc, "A low-noise 230GHz heterodyne receiver employing .25um2 area Nb/AlOx/Nb tunnel junctions," IEEE Tran. Microwave Theory and Tech. vol. 40, no.5, pp. 812-815, 1992.