| AVS 58th Annual International Symposium and Exhibition | |
| MEMS and NEMS Group | Friday Sessions |
| Session MN-FrM |
| Session: | Characterization of Materials and Structures at the Micro- and Nano-scale |
| Presenter: | ChangJung Hsieh, National Taiwan University |
| Authors: | C.J. Hsieh, National Taiwan University J.C. Liou, National Taiwan University C.T. Sun, National Taiwan University Y.C. Lin, National Taiwan University W.-C. Tian, National Taiwan University |
| Correspondent: | Click to Email |
This research focuses on the developments and characterizations of non-invasive tactile blood flow sensors using CMOS MEMS technologies. The capacitive sensing structure consists of two parallel plate capacitors which can be connected in different configurations in cape with different measuring ranges. Sensor detection scope is set to be from 0 to 150 mmHg according to the estimated maximum human vessel pressure. The sensor is fabricated in commercial 2 polysilicon and 4 metal CMOS technology followed by the self-developed post processes. The dimension of each sensor is 400μm in length with the membrane thickness of 1.45μm.
An anisotropic inter metal dielectric layer etch step was utilized on CMOS chips to open wet metal etching holes. After this dielectric layer etch, a metal wet etching process was applied to release sensing structures. In order to protect the metal bonding pads in post CMOS MEMS processes, an Au layer was deposited on the pad areas. Based on the experiment results, the lateral metal sacrificial layer etching rate is 1.85μm per minute and the lateral etching rate underneath gold layer is 2.9μm per minute. We have successfully demonstrated the post CMOS MEMS processes for our sensors.
Initial finite element method analysis results showed that the sensitivities of two different designs are 6.7 and 2.2 fF per mmHg with a dynamic range of 75 and 200 mmHg. The sensor behavior measurement data will be presented.