Research Summary

Overview: My research interests are in RF/microwave design for integration/packaging/fabrication, circuits, and MEMS.

Motivation and Challenges:

Below are challenges that RF/microwave researchers are working to overcome.

Advanced Integration:
Electrical parasitics at high frequencies are especially difficult to mitigate and require careful electromagnetic (EM) design. For example, consider that 300 micron features have significant EM effects at operating frequencies as low as 10 GHz. A typical "short" wirebond length may be 400 microns long. In order to take advantage of higher frequency bands (ie. unlicensed spectrum at 60 GHz), new methods need to be developed to provide low-cost interconnects.

MEMS:
MEMS have largely been unable to break into the mainstream market due to inavailability of mature MEMS integration. MEMS devices typically require a hermetic enviroment to prevent stiction (static friction) from rendoring MEMS devices inoperable. Fortunately, the MEMS community has now recognized MEMS packaging as a leading challenge towards full scale development. These issues are being worked from both academia and industry.

Highlighted Results

At Endwave, I have designed and developed a number of QFN packages that allow broadband operation from DC to 50 GHz. Both overmolded and air-cavity packages have been designed in order to accomodate a variety of chips. More information will be forthcoming as products are released.

Ph.D. Work:
I have previously worked with Prof. Anh-Vu Pham at UC Davis in the Microwave Microsystems Laboratory pursuing my doctoral degree in electrical engineering. Below are some accomplishments I achieved during that time.

• I had developed organic Liquid Crystal Polymer (LCP) integration techniques with Micro-Electro-Mechanical Systems (MEMS) devices. This technology may allow for new low cost, high performance integration schemes for RF/microwave circuits (up to 67 GHz) by using low-cost organic RF/microwave circuit modules for System-in-Package (SiP), System-on-Package (SoP) packaging schemes. My research on organic circuits is particularly attractive for thin-film low loss RF/microwave circuits that allow compact module designs.
• Careful reliability studies have been performed on the advanced LCP packages. Excellent adhesion seals in excess of 3 lbs/in have been demonstrated. LCP has been demonstrated to show less than 1% Total Mass Loss (TML) and less than 0.1% Collected Volatile Condensible Materials (CVCM) historically required for space applications as determined through ASTM E595 outgassing. I have been able to show that these LCP packages provide hermeticity levels that surpass current requirements for Mil-Std-883, Method 1014. Further, LCP packages are able to withstand a gauntlet of harsh environmental tests ranging from freeze expansion, thermal cycling, and 85C/85%RH life testing.
• Further, I have developed a phase shifter that demonstrates a compact, multi-layer, hybrid, organic LCP/Polyimide integration scheme for RF MEMS switch modules.
• Lastly, a novel amplitude compensation scheme was developed on LCP for Long Time Delay (LTD) circuits to show less than +/-0.4 dB variation over the entire band from DC-10 GHz with 0 ps, 200 ps, 400 ps, and 600 ps delays.

Additional Research: In addition to work directly related to my disseration, I had also spent time developing the following:

• DARPA/Lockheed Martin/GE Integrated Sensor is Structure (ISIS)
• Lockheed Martin/GE Radar-on-Chip (RoC)
• Microwave Carbon Nanotube Sensors,
• V-band Communications,
• Organic Flip-Chip Technology,
• Wafer scale packaging for RF/microwave frequencies,
• Planar, surface mountable, inductors
• and Organic SiP Passives.

Publications of Interest: IEEE Transactions on Microwave Theory and Techniques, IEEE Microwave and Wireless Components Letters, IEEE Journal of Microelectromechanical Systems, IEEE Spectrum, IEEE Microwave Magazine, IEEE Potentials, IEEE Transactions on Advanced Packaging, AFRL Horizons/NASA Tech. Briefs, Microwave Journal, CircuiTree, Chip Scale, and various electronic lists.

Attended Conferences (through Dec. 2007)

• NECA (National Electrical Contractors Association), San Francisco, CA, October 2007
• SEMICON West, San Francisco, CA, July 2007
• IEEE IMS (International Microwave Symposia)
  • Honolulu, HI, June 2007 (poster)
  • San Francisco, CA, June 2006 (poster, 20 min talk - presentated to ~200 people)
  • Long Beach, CA June 2005 (poster)
• MEPTEC (Microelectronics Packaging and Test Engineering Council), San Jose, CA, May 2007 (30 min talk - presented to ~40 people)
• UCD ECE IAB (Industrial Advisory Board) Winter
  • 2007 (poster, 20 min talk - presented to ~50 people, Awarded Best Student Presentation)
  • 2006 (poster)
  • 2005 (poster)
  • 2004 (poster)
• IEEE ECTC (Electronic Components and Technology Conference), San Diego, CA, May 2006
• ASME InterPACK, San Francisco, CA, July 2005 (15 min talk - presented to ~40 people)
• TBA Live, San Jose, CA 2004
• ACM Siggraph, San Diego, CA, 2003
• LinuxWorld, San Francisco, CA, 2002

Tool Proficiencies

I am trained to use tools listed below for fabricating and verifing my circuits.

Acknowledgements

My work is possible with support and/or collaboration from the following:

• 2007 Summer Graduate Student Researcher Award
• GAANN Fellowship Award
• ACCEL Fellowship Award
• General Electric Global Research
• Lockheed Martin Corporation
• Radant MEMS, Inc.
• XCOM Wireless, Inc.

• Nippon Steel Chemical Corporation
• Rogers Corporation
• Dupont Corporation