  This article presents several design techniques to fabricate
micro-electro-mechanical systems (MEMS) using standard complementary
metal-oxide semiconductor (CMOS) processes. They were applied to fabricate high
yield CMOS-MEMS shielded Lorentz-force magnetometers (LFM). The multilayered
metals and oxides of the back-end-of-line (BEOL), normally used for electronic
routing, comprise the structural part of the MEMS. The most important
fabrication challenges, modeling approaches and design solutions are discussed.
Equations that predict the Q factor, sensitivity, Brownian noise and resonant
frequency as a function of temperature, gas pressure and design parameters are
presented and validated in characterization tests. A number of the fabricated
magnetometers were packaged into Quad Flat No-leads (QFN) packages. We show
this process can achieve yields above 95 % when the proper design techniques
are adopted. Despite CMOS not being a process for MEMS manufacturing, estimated
performance (sensitivity and noise level) is similar or superior to current
commercial magnetometers and others built with MEMS processes. Additionally,
typical offsets present in Lorentz-force magnetometers were prevented with a
shielding electrode, whose efficiency is quantified. Finally, several
reliability test results are presented, which demonstrate the robustness
against high temperatures, magnetic fields and acceleration shocks.
