Piezoresistive pressure sensor using nanocrystalline silicon thin film on flexible substrate

• Published in: Sensors and actuators. A. Physical. Vol. 316; p. 112372
• Main Authors: Pandey, Vivek, Mandal, Aparajita, Sisle, Swapnil, Gururajan, M.P., Dusane, R.O.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.12.2020; Elsevier BV
• Subjects: Aluminum; Aluminum induced crystallization; Amorphous hydrogenated silicon; Chemical vapor deposition; Compressed air; Crystallization; Hydrostatic pressure; Machining; Microcrystalline silicon; Micromachining; Nanocrystalline silicon; Nanocrystals; Patterning; Photoresists; Piezoresistive sensor; Piezoresistors; Pressure sensor; Pressure sensors; Raman spectroscopy; Sensors; Silicon films; Silicon substrates; Substrates; Thin films; Wheatstone bridges; Nanocrystalline silicon; Amorphous hydrogenated silicon; Piezoresistive sensor; Microcrystalline silicon; Aluminum induced crystallization; Pressure sensor
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2020.112372

[Display omitted] •Pressure sensor using nc-Si by Aluminum Induced Crystallization on polyimide.•Novel recipe for device-fabrication bypassing the micromachining.•A novel pressure jig to characterize sensors with glue-less fixing.•Sensitivity of 183.10 ± 3.48 mV/mA/MPa for the applied pressure up to 50 psi. A flexible pressure sensor fabricated at processing temperatures as low as 300°C using piezoresistive elements of nanocrystalline silicon (nc-Si) on flexible polyimide substrate is reported. Aluminium induced crystallization (AIC) of Hot Wire Chemical Vapour deposited a-Si:H films is used to obtain the nc-Si films with almost 100 % crystalline fraction as revealed by Raman Spectroscopy, and with a measured piezoresistive gauge factor of 41±3. A novel processing method is adopted, wherein the photoresist itself acts as a mask for the transfer of the pattern on the polyimide diaphragm. This enables bypassing the micromachining step, which otherwise is unavoidable for patterning the sensing elements. A full Wheatstone bridge configuration of nc-Si piezoresistors is realized with acceptable linear response of the output signal for an applied pressure range up to 50 psi and the sensitivity is found to be 183.10±3.48 mV/mA/MPa. A novel pressure jig is also designed with the capability to characterize four sensors simultaneously with an arrangement to apply hydrostatic pressure of compressed air.