Abstract
The reference cantilever method is shown to act as a direct and simple method for determination of torsional spring constant. It has been applied to the characterization of micropaddle structures similar to those proposed for resonant functionalized chemical sensors and resonant thermal detectors. It is shown that this method can be used as an effective procedure to characterize a key parameter of these devices and would be applicable to characterization of other similar MEMS/NEMS devices such as micromirrors. In this study, two sets of micropaddles are manufactured (beams at centre and offset by 2.5 μm) by using LPCVD silicon nitride as a substrate. The patterning is made by direct milling using focused ion beam. The torsional spring constant is achieved through micromechanical analysis via atomic force microscopy. To obtain the gradient of force curve, the area of the micropaddle is scanned and the behaviour of each pixel is investigated through an automated developed code. The experimental results are in a good agreement with theoretical results.
Highlights
MEMS devices utilizing rotation of surfaces controlled by torsional springs have gained a lot of interest
The field of atomic force microscopy is well versed in the calibration of spring constants, albeit for cantilevers, and so it is to this field that the authors have turned for methods which apply to torsional systems
The micropaddle is fabricated from a 519 nm thick low pressure chemical vapor deposition (LPCVD) silicon nitride membrane window (Silson Ltd., England), with a membrane size of 0.5 mm × 0.5 mm, which is supported by a 450 μm thick silicon frame of size 7.5 mm × 7.5 mm
Summary
MEMS devices utilizing rotation of surfaces controlled by torsional springs have gained a lot of interest. Of a cantilever can be evaluated by using its length, width, resonance frequency, and material properties without knowing the exact thickness value [21] All of these methods have uncertainty in the result which makes device performance predictions difficult; that is, in thermal noise analysis, the thermal noise in the probe deflection is related to its spring constant using equipartition theorem [20] and so ultimate resolution is innately linked to accurate knowledge of spring constants. The use of AFM as the reference cantilever has the added advantage that the unknown cantilever can be scanned prior to being pushed and the reference cantilever can be precisely positioned, as spring constant is dependent on the position of the applied force from the anchor It is this reference cantilever method, proposed by Torii et al [12], that has been investigated in this work for its applicability to measuring torsional spring constants. The measurement of the micropaddle torsional spring constant is presented, where the torsional spring constant is determined by pushing a reference cantilever with known spring constant against the micropaddle, using AFM
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
