G. Ensell et al., SILICON-BASED MICROELECTRODES FOR NEUROPHYSIOLOGY FABRICATED USING A GOLD METALLIZATION NITRIDE PASSIVATION SYSTEM, Journal of microelectromechanical systems, 5(2), 1996, pp. 117-121
The multimicroelectrode probe (microprobe) is a device used in neuroph
ysiology to record signals from nerve cells, Microprobes typically hav
e a number of gold recording sites supported on a narrow cantilever be
am which is inserted into the tissue, Conducting tracks connect the re
cording sites to bonding pads on the body of the device, The metalliza
tion is insulated, except at the recording sites and bonding pads, by
a passivation layer, Boron etch stop techniques can be used to produce
narrow cantilever beams upon which recording sites are situated, Prev
iously, polysilicon interconnects were used on microprobes fabricated
using boron etch stop techniques, with gold inlaid onto the recording
sites using a lift-off technique, This meant that mechanical jigging w
as required before the final shaping of the probes in potassium hydrox
ide (or other etch) to prevent the etch from attacking the polysilicon
conductors beneath the inlaid gold, The process reported here incorpo
rates a gold metallization layer, in conjunction with a plasma-enhance
d chemical vapor deposition (PECVD) nitride passivation layer. Since b
oth these materials etch very slowly in potassium hydroxide, no mechan
ical jigging, or other steps, need to be taken to protect the front of
the wafer during the shaping stage, This simplifies the fabrication o
f these devices.