High- Q , Low Impedance Polysilicon Resonators with 10 nm Air Gaps Tiffany J. Cheng and Sunil A. Bhave Cornell Univers

2. Bobby Schneider Electrical Engineering 3/7/2011 High-Q, Low Impedance Polysilicon Resonators with 10 nm Air GapsTiffany J. Cheng and Sunil A. BhaveCornell University, Ithaca, NY 1/19

3. Presentation Overview Discussion Topics • Introduction • Theory • Fabrication Method • Measurement Results • Conclusions 2/19

4. Intro: What did they make? • They made a capacitively transduced micromechanical bar resonator. • Three electrical connections: • Input voltage • Bias voltage (Vp) • Output current 3/19

5. Intro: What does it do? • The resonator vibrates when excited at resonance. • The output current is proportional to the amplitude of vibration. • The resonator can be used to make a filter or an oscillator. ANSYS simulation showing fundamental resonance at 222 MHz Frequency response 4/19

6. Theory • At resonance, the ratio of input voltage to output current is called: • MOTIONAL IMPEDANCE - Rx • The point: They decreased g0 down to 10 nm (where previously only ~30-100 nm had been achieved). • Important strategy:They used a high k insulator to keep it from shorting. 5/19

7. Fabrication 6/19

8. Fabrication 7/19

9. Fabrication 8/19

10. Fabrication 9/19

11. Fabrication 10/19

12. Fabrication 11/19

13. Fabrication 12/19

14. Fabrication 13/19

15. Fabrication 14/19

16. Fabrication 10 nm air gaps! hafnium oxide prevents electrical shorting! 15/19

17. Results • How to extract Rx from S21: • Very good improvement in Rx—down to 1.3 kΩ • -Can interface with low Z0 system. • Hafnia makes the resonators more robust • 10 nm gap is remarkable • -Too small to adequately image in SEM! 16/19

18. Results Very good f Q product as well: • Response of a 530 MHz resonator (with lower Q) 17/19

19. Conclusions • New fabrication process demonstrated • 10 nm gaps achieved • Low Rx allows resonators to be used in lower Z0 systems (1 kΩ) • Devices worked well 18/19

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