Design and Construction of a Piezoresistive Pressure Sensor

1
Design and Construction of a Piezoresistive
Pressure Sensor

• Key Paper Presentation
• Student Ariadna Kaplan
• Advisor Stacy Gleixner

2
Pressure Sensor Layers
3
Wet Etching

• SourcePomeroy, William. Surface Micromachined
  Pressure Sensors. Ph. D. Dissertation UC Davis,
  1997.

4
Properties Required for an Anisotropic Etchant

• Etch rate
• Final surface roughness
• Etch stop
• Etch selectivity over other materials.
• Mask material and thickness of the mask.

5
Anisotropic Etching of Silicon in TMAH Solutions.

• Authors Osamu Tabata, Ryouji Asahi, Hirofumi
  Funabashi, Keiichi Shimaoka and Susumu Sugiyama.
• From Toyota Central Research and Development
  Laboratories Inc.
• When 1992
• Importance for my project
• Characterization of the etch properties of TMAH.

6
Details of the Experiment

• Wafers used (100) and (110) orientation.
• Resistivity 30-50 Ohms-cm
• No stirring reflux condenser was used.
• SEM and profilometer were used to measure etch
  rate and quality of the surfaces of the cavity.

7
Results Si Etch Rate as a Function of
Concentration and Temperature
(100) plane
(110) plane
Source O. Tabata, R. Asahi, H Funabashi, K.
Shimaoka, S. Sugiyama. Anisotropic Etching of
Silicon in TMAH Solutions. (1992)
8
Results Etching Rates for Al, SiO2 and Si
Source O. Tabata, R. Asahi, H Funabashi, K.
Shimaoka, S. Sugiyama. Anisotropic Etching of
Silicon in TMAH Solutions. (1992)
9
Principal Characteristics comparison of TMAH
with standard etchant.
10
Conclusions

• TMAH will be used in a concentration of 22wt at
  90C.
• The concentration of Boron should be in the order
  of 1020/cm3.

11
Thank you!