To validate the FE model, the measured signal output of an unpackaged pressure sensor was used
to compare with calculated signal output of FE model. Figure 8 shows the FE model and experimental
results of the unpackaged pressure sensor under a pressure loading range of 0–6.9 × 103 Pa and a
temperature loading range of 25–85 °C. The FE model closely matches the experimental data, as
shown in Figure 8. The average error between the FE model and the experimental result was less than
4.2%. The measured results of the unpackaged pressure sensor were collected from five samples. Due
to the doping impurity variation of the piezoresistors, the four piezoresistors of the piezoresistive
pressure sensor had different resistances. The reference pressure in the cavity of the pressure sensor
was vacuum for an absolute pressure sensor, so an initial 1 atmosphere (about 101.3 × 103 Pa) pressure
was applied on the silicon membrane of the pressure sensor at pressure loading of 0Pa. The zero offset
voltage (ΔV) of each pressure sensor was a non-zero value according to Equation 1, and it varied from
sensor to sensor. However, the resistances of the four piezoresistors of the pressure sensor are assumed
to be equal in the FE modeling process. The calculated zero offset value of the FE model was
calculated using a unique ideal sensor chip. This explains why the zero offset voltage of the
experimental measurements is different from that of the FE model results. The FE model was verified
to reliably predict the signal output of the piezoresistive pressure sensor under pressure and
temperature loading.