Effect of growth and residual stress in AlN (0002) thin films on MEMS accelerometer design
- PDF / 3,034,565 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 84 Downloads / 233 Views
Effect of growth and residual stress in AlN (0002) thin films on MEMS accelerometer design Nidhi Gupta1,2, Shankar Dutta1,* Davinder Kaur3
, Akhilesh Pandey1, Siva Rama Krishna Vanjari2, and
1
Solid State Physics Laboratory, DRDO, Lucknow Road, Timarpur, Delhi 110054, India Department of Electrical Engineering, Indian Institute of Technology Hyderabad, Hyderabad 502285, India 3 Center of Nanotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India 2
Received: 24 May 2020
ABSTRACT
Accepted: 17 August 2020
This paper discusses the growth and evolution of residual stresses in (0002) preferentially oriented aluminum nitride (AlN) layers on Si (111) wafers by sputtering technique for the development of micro-electro-mechanical system (MEMS) accelerometer. The microstructure of the deposited films exhibited vertical columnar structures. Residual stresses in the sputtered AlN films are - 1.2 GPa, - 0.8 GPa, and - 0.25 GPa for the film thickness of 600 nm, 750 nm, and 900 nm respectively. The effect of the residual stress on the piezoelectric MEMS acceleration sensor structure is analyzed. The presence of residual stress reduced the resonant frequency (up to 14.72%) and bandwidth (up to 27.3%) of the accelerometer. The locations of the von-Mises stress maxima are shifted from the beam edges (adjoining to the proof-mass) to the whole proof-mass area. The normalized stress sensitivity (which defines the piezoelectric charge sensitivity) is reduced by two orders due to the residual stress in the AlN layers.
Ó
Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction High precision micro-electro-mechanical system (MEMS) sensors, like accelerometer, gyroscope, inertial switch etc., are being utilized in a variety of space and defense arena [1, 2]. Most of these MEMS sensors employ either piezoresistive, capacitive, or piezoelectric techniques as the sensing principles [3–13]. Among them, piezoelectric accelerometers are being extensively used in high-g, high frequency, high bandwidth, and higher temperature stability applications [1, 3, 11, 14–16]. For piezoelectric
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10854-020-04282-x
accelerometers, most of the research focused on Pb(Zr,Ti)O3 (popularly known as PZT) as a sensing material [1, 13, 15–19]. However, the presence of Pb in the PZT creates hindrances like CMOS incompatibility, non-environment friendly [1, 11, 15, 19]. Moreover, PZT requires high annealing temperature ([ 650 oC) to get desired piezo-properties for sensing applications [16]. To overcome the lacunae of PZT, researchers have started exploring alternative materials like aluminum nitride (AlN) due to its excellent piezoelectric characteristics (attributed to the non-centro-symmetric
J Mater Sci: Mater Electron
wurtzite crystal structure and induced dipole moment); CMOS process compatibility; and environment-friendly nature [20–23]. The maximum piezoelectricity in AlN film is observed along its c-direction. Thus, good
Data Loading...
