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