Internal stress compensation and scaling in ultrasensitive silicon pressure sensors

• Published in: IEEE transactions on electron devices 1992-04, Vol.39 (4), p.836-842
• Main Authors: Cho, S.T., Najafi, K., Wise, K.D.
• Format: Article
• Language: English
• Subjects: Biomembranes; Boron; Dielectrics; Etching; Exact sciences and technology; Fabrication; General equipment and techniques; Glass; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Internal stresses; Micromachining; Physics; Sensor phenomena and characterization; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Silicon compounds
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/16.127473

The pressure sensitivity of boron-doped silicon membranes has been characterized as a function of diaphragm dimensions and internal membrane stress. Using an electrostatic technique based on silicon microbridges, the internal stress for p/sup ++/ silicon (on glass), LPCVD silicon dioxide, and LPCVD silicon nitride was measured; typical values are 40, -300, and 950 MPa, respectively. Silicon membranes with several different edge lengths and deposited oxide and/or nitride coatings were characterized for sensitivity. While the pressure sensitivity can be reduced by more than a factor of twenty in the membranes due to boron-induced internal stress, the use of stress-compensating dielectrics can improve this sensitivity by a factor of six or more. Based on this theory and the measured material parameters, scaled experimental devices show typical sensitivities within 10-20% of the theoretical design targets. Pressure sensitivities as high as 2900 ppm/Pa have been achieved.< >