Modeling of High Frequency Out-of-Plane Single Axis MEMS Capacitive Accelerometer - VLSI Design and Test - page 255

4.2 Accelerometer Design

The accelerometer design is based on the parameters obtained from the folded beam
design shown in Table 1.

Table 1. Optimized design parameters for accelerometer

Parameters Folded Beam (µ m) Proof Mass (µm) Comb Structure (µm)

Length - 100 -

Width - 46 -

Flexure Length 46 - -

Flexure Width 10 - -

Number of fingers - - 10

Finger length - - 20

Finger Width - - 4

Finger Gap - - 2

Finger Overlap - - 15

Structure Height 6 6 6

4.2.1 Analytical Study

Based on the above parameters we have designed the accelerometer and performed
analytical study to calculate total mass of the structure. The material is silicon having
density 2329 Kg/m 3 .
Total mass (excluding fixed fingers) = proof mas + mass of folded beam + mass of
fingers
Mass Total = 64.2804*10 -12 + 57.57288*10 -12 + 22.3584*10 -12
Mass Total = 144.21168*10 -12 Kg
For the structure we performed frequency analysis to determine the proof mass
displacement at different frequencies is shown in Fig. 9.

(a)

(b)

Fig. 9. For frequency range of 1 MHz to 10 MHz, (a) Proof mass displacement, (b) change in
capacitance