MEMS chip

[Andy Resnick]

Hello World! (1st forum post )

This is a decapsulated MEMS (Micro Electro-Mechanical Systems) chip I (most likely) scavenged from a broken phone. This is the sensor that, among other things, controls when the display rotates along with the device. Some folks also use this technology in a classroom setting (https://iopscience.iop.org/article/10.1 ... 552/abdee2).

What you see is a very thin single-crystal piece of Silicon freely suspended and capacitively coupled to another piece of Silicon (those comb-like structures on the left and right), seen better at when zoomed in a bit:

This stitched macro image was acquired under epi-illumination conditions (100W halogen) using a 20mm epi-Luminar w/0.8x reduction lens mounted to an Ultraphot III/b, with my camera (Nikon D810) placed where the 4x5 film holder is located. Stitching was done with Hugin. No post-processing (other than stitching), the stitched image was created using jpgs output from the camera.

Since a lot of people here have extensive experience with sample handling and preservation, I'd greatly appreciate some ideas on how to properly mount these things.

[rjlittlefield]

Andy, welcome aboard!

Judging from the quality of this salvaged chip, I think we should be asking you for advice!

Can you say more about how you decapsulated it?

When you say "how to properly mount these things", what issues are you thinking about?

--Rik

[ChrisR]

Very interesting Andy.
I look forward to understanding more about how these things work. Right now it's too near bed time!
I'm not really clear which parts are floating...

[Andy Resnick]

Andy, welcome aboard!

Judging from the quality of this salvaged chip, I think we should be asking you for advice!

Can you say more about how you decapsulated it?

When you say "how to properly mount these things", what issues are you thinking about?

--Rik

Thanks!

My decapsulation method uses hot sulfuric acid to decompose the epoxy and when that is done, hot nitric acid will open the package.

My mounting question is actually a few related questions:
1) First, I'd like to mechanically stabilize the device. right now it's (carefully) stored in a small specimen box, but not physically attached to anything. I'm not sure if I can simply affix the chip to a slide without (somehow) stabilizing the movable part.
2) Second, most of my lenses are made to be used without a coverslip- and some of those are immersion lenses. I also have some high NA dry lenses and immersion lenses that *are* designed to be used with a coverslip. Mounting any specimen that permits use with the full compliment of lenses has long been a problem.

I don't think there's a simple solution, so I'm also interested to hear how others handle point #2.

Does all that make sense?

[Andy Resnick]

Very interesting Andy.
I look forward to understanding more about how these things work. Right now it's too near bed time!
I'm not really clear which parts are floating...

I have some earlier generations of MEMS chips that are easier to understand because they are constructed more simply. It's hard to see on this image which is the movable part and which is the stationary part, but on the zoomed in image, on the right are 2 interdigitated sections. On each, one side can move while the other is fixed. As the 'tines' change separation distance, the capacitance changes which corresponds to a voltage change. This voltage is read on-chip, and a secondary chip amplifies the voltage signal. At least, that's my primitive understanding

[rjlittlefield]

Today I tripped over the following video which helps to explain how these devices work:

https://www.youtube.com/watch?v=9X4frIQo7x0 "The ingenious micro-mechanisms inside your phone"

The video addresses gyroscopes as well as accelerometers.

--Rik