다공질 실리콘 산화막 Air-Bridge 기판 위에 제작된 MMIC용 공면 전송선

Coplanar Waveguides Fabricated on Oxidized Porous Silicon Air-Bridge for MMIC Application

  • 박정용 (대전광역시 대전발전연구원) ;
  • 이종현 (경북대학교 전자전기공학부)
  • 발행 : 2003.05.01

초록

본 논문에서는 실리콘 기판상의 전송선로 특성을 개선하기 위하여 표면 마이크로머시닝 기술과 새로운 산화법(H₂O/O₂ 분위기에서 500℃, 1시간 열산화와 1050℃, 2 분간 RTO(Rapid Thermal Oxidation) 공정)을 이용하여 10 ㎛ 두께의 다공질 실리콘 산화막(oxidized porous silicon:OPS) air-bridge 기판 위에 공면 전송선로(Coplanar Waveguide:CPW)를 제작하였다. 간격이 40 ㎛ 신호선이 20 ㎛ 전송선 길이가 2.2 mm인 CPW air-bridge 전송선의 삽입손실은 4 GH에서 -0.28 dB이며, 반사손실은 -22.3 유를 나타내었다. OPS air-bridge 위에 형성된 CPW의 손실이 OPS층 위에 형성된 CPW의 삽입손실보다 약 1 dB 정도 적은 것을 보여주었으며, 반사손실은 35 GHz 범위에서 약 -20 dB를 넘지 않고 있다. 이와 같은 결과로부터 두꺼운 다공질 실리콘 멤브레인 및 air-bridge 구조는 고 저항 실리콘 집적회로 공정에서 고성능, 저가의 마이크로파 및 밀리미터파 회로 응용에 충분히 활용 될 수 있으리라 기대된다.

This paper proposes a 10 ${\mu}{\textrm}{m}$ thick oxide air-bridge structure which can be used as a substrate for RF circuits. The structure was fabricated by anodic reaction, complex oxidation and rnicrornachining technology using TMAH etching. High quality films were obtained by combining low temperature thermal oxidation (50$0^{\circ}C$, 1 hr at $H_2O$/O$_2$) and rapid thermal oxidation (RTO) process (105$0^{\circ}C$, 2 min). This structure is mechanically stable because of thick oxide layer up to 10 ${\mu}{\textrm}{m}$ and is expected to solve the problem of high dielectric loss of silicon substrate in RF region. The properties of the transmission line formed on the oxidized porous silicon (OPS) air-bridge were investigated and compared with those of the transmission line formed on the OPS layers. The insertion loss of coplanar waveguide (CPW) on OPS air-bridge was (about 1 dB) lower than that of CPW on OPS layers. Also, the return loss of CPW on OPS air-bridge was less than about - 20 dB at measured frequency region for 2.2 mm. Therefore, this technology is very promising for extending the use of CMOS circuitry to higher RF frequencies.

키워드

참고문헌

  1. J. Buechler, E. Kasper, P. Russer, and K. Strohm, 'Silicon high-resistivity-substrate millimater-wave technology', IEEE Microwave Theory Tech., Vol. MTT-34, pp. 1516-1521, Dec. 1986 https://doi.org/10.1109/TMTT.1986.1133572
  2. A. C. Reyes, S. M. El-Ghazaly, S. Dorn, M. Dydyk, and D. K. Schroder, 'Silicon as a microwave substrate', in IEEE MTT-S Dig., 1994, pp. 1759-1762 https://doi.org/10.1109/MWSYM.1994.335101
  3. S. R. Taub, 'Temperature dependent performance of coplanar waveguide (CPW) on substrate of various materials', in IEEE MTT-S Dig., 1994, pp. 1049-1051 https://doi.org/10.1109/MWSYM.1994.335175
  4. C. Warns, W. Menzel, and H. Schumacher, 'Transmission lines and passive elements for multilayer coplanar circuits on silicon', IEEE Microwave Theory Tech., Vol. 46, No. 5, pp. 616-622, May. 1998 https://doi.org/10.1109/22.668672
  5. H. Sakai, Y. Ota, K. Inoue, T. Yoshida, K. Takahashi, S. Fujita, and M. Sagawa, 'A novel millimeter-wave IC on Si substrate using flip-chip bonding technology', in IEEE MTT-S Dig., 1994, pp. 1763-1766 https://doi.org/10.1109/MWSYM.1994.335100
  6. B. K. Kim, B. K. Ko, and K. Lee, 'Monolithic planar inductor and waveguide structures on silicon with performance comparable to those in GaAs MMIC', in IEDM Tech. Dig., 1995, pp. 717-720 https://doi.org/10.1109/IEDM.1995.499319
  7. C. M. Nam and Y. S. Kwon, 'Coplanar Waveguides on Silicon Substrate with Thick Oxidized Porous Silicon(OPS) Layer', IEEE Microwave and Guided wave Letters, Vol. 8, No. 11, pp. 369-371, Nov. 1998 https://doi.org/10.1109/75.736246
  8. R. J. Welty, S. H. Park, P. M. Asbeck, K. S. Dancil, and M. J. Sailor, 'Porous silicon technology for RF integrated circuit applications', in Topical Meeting on Silicon Monolithic Integrated Circuit in RF Systems, 1998, pp. 160-163 https://doi.org/10.1109/SMIC.1998.750212
  9. R. L. Peterson and R. F. Drayton, 'Dielectric properties of oxidized porous silicon in a low resistivity substrate', in IEEE MTT-S Dig., 2001, pp. 765-768 https://doi.org/10.1109/MWSYM.2001.967005
  10. Y. M. Kim, K. Y. Noh, J. Y. Park, J. H. Lee, Y. D. Kim, I. S. Yu, and C. S. Cho, 'Fabrication of Oxidized Porous Silicon(OPS) Air-Bridge for RF Application Using Micromachining Technology', JKPS, Vol. 39, Dec. 2001, pp. S268-S270
  11. 남충모 'Selectively Oxidized Porous Silicon (SOPS) Substrate for Packaging', 박사학위논문, 한국과학기술원, 1998
  12. 박사학위논문, 한국과학기술원 Selectively Oxidized Porous Silicon (SOPS) Substrate for Packaging 남충모