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azonenberg_work>
Testing lift-off patterning of Cr tomorrow, finally confirmed my lab time
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azonenberg_work>
followed by several deep wet etches
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azonenberg_work>
If this works i'll be doing through-silicon vias/trenches this weekend
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azonenberg_work>
IDK if i can hit a 25:1 aspect ratio (20 um hole 500um deep) but i should be able to hit 5:1 at least
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azonenberg_work>
meaning a 100um square hole 500um deep
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azonenberg_work>
i'll also be testing wafer thinning
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azonenberg_work>
do a ~400um deep etch in the center of a die
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azonenberg_work>
then flip over and do another etch on the front with my features
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azonenberg_work>
Hmm, so here's my thought
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azonenberg_work>
Take half a wafer and spin coat in PR
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azonenberg_work>
Expose and develop a contact mask with die-separation lines on it
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azonenberg_work>
Evaporate Cr over the lines
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azonenberg_work>
lift off in acetone
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azonenberg_work>
Now i have a micron of Cr over my dies and nothing in the trenches
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azonenberg_work>
The next step is to KOH etch the entire wafer until i'm around 100um deep
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azonenberg_work>
(the back side would also be Cr coated)
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azonenberg_work>
So now i have hardmask over both sides of the wafer except in the kerf areas
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azonenberg_work>
which are etched ~100um deep
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azonenberg_work>
At this point I spin coat PR and lay down a second contact mask
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azonenberg_work>
This one is a rectangle in the center of each die
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azonenberg_work>
Also coat the back side of the wafer in resist so i dont damage the Cr there
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azonenberg_work>
Etch in HCl until the Cr is removed from the center areas
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azonenberg_work>
Then KOH etch until the dies are separated
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azonenberg_work>
At this point i have a bunch of ~3mm square dies with square outlines
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azonenberg_work>
in the middle of the top is a 400um deep rectangular hole
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azonenberg_work>
maybe 1-2mm square
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azonenberg_work>
I then flip the dies over
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azonenberg_work>
one at a time, spin coat in PR
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azonenberg_work>
expose projection mask with comb drive pattern over the center
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azonenberg_work>
develop, HCl etch
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azonenberg_work>
then KOH a third time (leaving the 400um trench on the underside unmasked)
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azonenberg_work>
the two etches will meet 50um into the die
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azonenberg_work>
leaving me with free-standing features in a 50um silicon plate
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azonenberg_work>
with a nice thick 500um ring around it for mechanical support
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azonenberg_work>
If successful, that's all of the bulk micromachining needed for my comb drive
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azonenberg_work>
i just have to grow thermal oxide, evaporate metal, and pattern the M1 mask
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mrdata>
still, seems like a lot of steps
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azonenberg_work>
lol, it is
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mrdata>
how many layers is the resulting circuit?
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azonenberg_work>
This is for MEMS
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azonenberg_work>
it'd be one metal layer over 3D silicon geometry
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azonenberg_work>
i'll do a CAD model later today and post a render
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azonenberg_work>
Right now, going afk as my battery is about dead:p
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uneducatedsavant>
how do memristors work?
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uneducatedsavant>
how do they actually change resistance?
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mrdata>
if you wnt them to be useful, you should be able to set their resistance many times
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mrdata>
but, i dontknow much about memristors exactly
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uneducatedsavant>
yeah it has something to do with filament formation
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uneducatedsavant>
but i'm not sure how those filaments form
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uneducatedsavant>
or what the filaments are made of
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uneducatedsavant>
is it metal?
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uneducatedsavant>
hmm i wish i knew someone who could help me understand. it's very interesting
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azonenberg>
I dont understand memristance myself but there was someone here who wanted to do work on them
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azonenberg>
i forget who it was