Hi everybody,

I was trying to fabricate a high temperature capacitive pressure sensor. I have
made two gold electrodes on pyrex and Si membrane connected to pads by a lines
(100 um width and 150 nm thickness). I used a glass frit to bond two chips
together. The bonding interface forms gap between two electrodes. According to
my design, the gap should be 10 um. The glass frit (originally 50 um thickness)
should flow due to force and temperature in the furnace and decreases its
thickness. The problem was that I couldn't control the force on chips during
heat treatment at 500C because any spring will become loose in high temperature.
So, controling the frit thichness was dificult and also there was a leakage from
some where that there is no good contact between glass frit and si or pyrex.

I also tried to use high temperature epoxy. One with high viscosity generates a
big gap and another one with low viscosity flow into the membrane. Also, anodic
bonding (of different sample with a 10 um cavity) didn't work as I had
connection lines of gold to pads on Si.

Any advise regarding solving the problem by the above solutions or any other
solutions will be highly appreciated.
In case of glass frit, where do you recommend me to buy a thiner glass frit and
how can I work with it to solve the problem?

Thanks,
Reza Rashidi