MEMS in GaN. Peter Benkart, Ulrich Heinle, Mike Kunze, Ingo Daumiller and Ertugrul Sönmez

Transcription

1 MEMS in GaN Peter Benkart, Ulrich Heinle, Mike Kunze, Ingo Daumiller and Ertugrul Sönmez

2 GaN-MEMS Overview GaN-MEMS actuator GaN-MEMS sensor Application examples: - sensing elements in pressure sensors - proximity sensor with sub-micron resolution Application examples: - varaktors and switches for RF power applications - actuator/resonator for biomedical analysis Advantages of GaN-MEMS - high measurement signal - functionality shown until 300 C (more can be expected) - electronic devices are possible on one chip Advantages of GaN-MEMS - low driving voltages and power dissipation - compact and variable design is possible - suitable for harsh environments

3 GaN-MEMS Process Overview new wafer Si-substrate side view top view

4 GaN-MEMS Process Overview structuring the active layers sensing element mechanical part of the cantilever Si-substrate side view top view

5 GaN-MEMS Process Overview deposition of contacts and passivation passivation ohmic and schottky contacts Si-substrate side view top view

6 GaN-MEMS Process Overview wiring electric wires and contact pads Si-substrate side view top view

7 GaN-MEMS Process Overview structuring the substrate freestanding cantilever Si-substrate silicon frame for mechanical stability side view top view

8 Stability measurement Sensor signal vs time of a cantilever 65,00 180µm 60,00 160µm 120µm Strom (µa) Current (µa) 55,00 deflection 50,00 80µm 60µm 45,00 20µm 40,00 35,00 100µm 40µm beam bent upwards 0µm 30,00 0,00 3,00 6,00 9,00 12,00 15,00 18,00 21,00 24,00 27,00 30,00 (min) timezeit (min) cantilever with a length of 750µm and a width of 200µm at room temperature

9 Sensor signal at high temperature RT 100 C 200 C 300 C relatives Signal (%) relative sensor signal (%) beam bent upwards Hotplate Auslenkung (µm) deflection (µm) 40 45

10 GaN actuator beam GaN is a polar material and lateral stress changes the polarization field Theory predicts the change of the lattice constants by manipulating the polarization field. It should function as actuator. 500µm

11 GaN actuator beam Actuation with square wave voltages of different frequencies Beam length: 800µm Beam width: 200µm Amplitude: ~3,2µm

12 GaN-MEMS Varaktor Actuators Capacity Si-frame Actuator Initial position (Cmin) RF-contact sideview Atuator lower electrode actuated (Cmax)

13 GaN-MEMS varaktor in action Actuators Capacity Square wave driving voltage (1Hz und 2Hz)

14 Capacity variation Varactor capacity vs driving voltage of a GaN-MEMS varaktor 900 Capacity(fF) (ff) Kapazität capacity Aktorspannung Driving voltage (V)(V) actuators

15 Conclusion The piezoelectric effect in GaN opens the possibility for sensors with high signals on one hand. On the other hand, turning the sensor principle upside down, the same material system functions as actuator. This effect allows not only the applications discussed before, but also new fields of application where sensor and actuator are needed in combination.