Triaxial Monolithic Piezoresistive Accelerometers in Foundry CMOS

1996 ii The thesis of Brett Alan Warneke is approved. Figure 3-7 Cross-sectional diagram of an aluminum trace running between oxide plates and contacting a polysilicon piezoresistor. The oxide and first metal overetch into the silicon substrate causes the trace Figure 3-8 SEM of a Skeleton Crew accelerometer with bond wires providing 9.6 µgm of additional proof mass. The plate has been bent up viii slightly with the hinges.. Figure 3-9 Cross-sectional diagram of an oxide beam with embedded polysil-icon piezoresistor showing dimensional variables for analysis. 22 Figure 4-1 Cross-section of thinned beam #7 illustrating the use of gate oxide to change the beam thickness and relative position of the piezore-Figure 4-2 SEM of thinned cantilever array on as described in Table II. Fabricated in Orbit 2µm N-well, MOSIS chip ID: N53B FE (Aletal). 27 Figure 4-3 Test results from bending beams of several different thicknesses and differing relative positions of the piezoresistor within the thin Figure 4-9 Variation of the Wheatstone bridge output with temperature for various driving voltages on beam 1 of the N45Z CC test structure. 37 Figure 4-10 Variation of the Wheatstone bridge output with temperature normalized to the driving voltages on beam 1 of the N45ZCC test Figure 4-13 Variation of the Wheatstone bridge output with temperature normalized to the driving voltages on beam 4 of the N45ZCC test Figure 4-15 Beam 1 Wheatstone bridge output versus time during a XeF2 etch. 42 x Figure 4-16 Variation of the Wheatstone bridge output with temperature for various driving voltages on released beam 1of the N45ZCC test