I'm no etch expert, but I would assume it would be at least 1 degree or
more, (since we're talking about a 500um thickness) so I don't think your
going to make it.
 If you use the following equation for sidewall angle and use 17 for the
(top-bottom) you need a sidewall angle of 89.32.

sidewall angle (degrees) = arctan(thickness/(1/2(top-bottom))*(180/pi)


Subject: [mems-talk] DRIE sidewall angle

What is the expected tolerance for sidewall angle when DRIE 'etching a Si
substrate 500um thick?

I need to etch an arrayed die pattern consisting of two holes 125um and
155um diameter.  The two holes are spaced 150 um apart and the die are ~1mm
apart.  I want to etch 125 um diameter hole through the 500um thick wafer
and obtain a negative sidewall profile no greater than 1 degree and a
backside hole diameter of 125um +17um / -0um.  Likewise, I need the 155um
diameter hole to have a negative sidewall profile no greater than 1 degree
and a backside hole diameter of 155um +17um / -0um.

Thank you in advance for any guidance,

Paul

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