Manufacturing Issues of BEOL CMOS-MEMS Devices

In this paper we present a comprehensive report on the issues found during the manufacturing of high-yield CMOS-MEMS sensors based on vapor-phase hydrogen fluoride (vapor-
$HF$
) oxide etching. During the study we have identified the main issues affecting CMOS-MEMS high-yield manufacturing regarding the silicon oxide as a sacrificial material, the passivation as a release mask, the BEOL as structural material for MEMS design and the aluminum-sputtering as a sealing layer for the MEMS cavity. This study has been carried out by systematically analyzing over 100 full wafers in 10 different runs on four different foundries using
${\mathrm {0.5~ \mu m }}$
,
${\mathrm {0.18~ \mu m }}$
and
${\mathrm {0.15~ \mu m }}$
CMOS processes, containing both test structures and full-sensor designs.