Application of Uniplanar Structures for High Frequency Material Characterization

1. Application of Uniplanar Structures for High Frequency Material Characterization Can Eyup Akgun1, Rhonda Franklin Drayton1, Daniel I. Amey2, Tim P. Mobley2 Department of Electrical and Computer Engineering, University of Minnesota, Union Street Southeast, Minneapolis, Minnesota, 55455 USA; 2. DuPont Microcircuit Materials, 14 T.W. Alexander Drive, RTP, North Carolina, 27709 USA. 

2. Outline

3. Introduction Goal: To reduce the cost of developing complex integrated systems, diagnostic methods are needed to characterize the material system. Objectives: To implement in situ material characterization methods using modern design techniques To investigate use of planar resonator structures that complement surface and embedded design methods To extend the testable range of planar resonators to cover broadband frequencies up to 50 GHz frequencies.

4. Resonator Methods Resonators are used to extract dielectric constant and loss tangent in materials Current Planar Approaches 20 GHz: Microstrip T-resonator (Amey and Curilla) 30 GHz: Coplanar Waveguide T-resonator with an open-stub (Peterson and Drayton) 40 GHz: Microstrip ring resonators This work: 50 GHz: FGCPW with shorted T- and ring resonator Resonator design depends on satisfying impedance requirements

5. Field Distribution After microstrip, CPWs have become another option in MICs and MMICs and interconnect materials CPW offers: Less dependence on substrate height Eeff less sensitive to impedance changes Does not support parallel-plate modes, hence, less radiation loss than CPW After microstrip, CPWs have become another option in MICs and MMICs and interconnect materials CPW offers: Less dependence on substrate height Eeff less sensitive to impedance changes Does not support parallel-plate modes, hence, less radiation loss than CPW

6. Background: Finite Ground Coplanar Waveguide Design Design Guidelines 50 ohm line (S-g-Wg) (Agilent�s ADS LineCalc) with 3 mil gaps (g) c/b ratio > 3 c/b ratio>3 important for approximating infinite ground casec/b ratio>3 important for approximating infinite ground case

7. Resonator Architectures T-resonator* - Shorted FGCPW w/ single and double stubs Ring resonator* - FGCPW with coupled feeds 1) Conventional feed geometry 2) Inset feed geometry 3) Inset-T feed geometry

8. T-resonator design: FGCPW Approach Wire-bonds are important in suppressing odd-mode excitationWire-bonds are important in suppressing odd-mode excitation

9. Theoretical Characterization: Ansoft�s HFSS E-field Simulations

10. Measurement Method

11. Feedlines: FGCPW Testing method: On-wafer probing using CPW probes with 250 �m pitch (middle of signal line to ground plane separation) TRL calibration- reference plane is shifted to stub junction

12. Characterization: S-parameter response

13. Air-bridge Placement Effects: Balanced T-resonator

14. Ring resonator design: FGCPW Approach

15. FGCPW Ring resonator design-alternate feed designs

16. Ring resonator response

17. Material Characterization Application of Balanced T resonator toward extraction of material properties er Tan ?

18. Material characterization

19. Preliminary Findings

20. Summary/Conclusion FGCPW approach to Balanced T and T resonators demonstrate strong peaks up to 50 GHz. Ring resonances up to 50 GHz are more sensitive to airbridge placement. Dielectric constant values from Balanced T data are consistent with microstrip data. Loss tangent extractions needs further experimental investigation.

21. Acknowledgements NSF Presidential Early Career Award for Scientists and Engineers under grant #ECS-99906017 Dupont Educational Aid Grant Any findings, conclusions or recommendations expressed in this publication are those of the author and do not necessarily reflect the views of the National Science Foundation.