Laser delayering test

I received my new probe micro-positioner, two S-931 from Signatone and my first idea was to use them to dump the Firmware of the previous PIC16C57 to discover this method, but quickly I needed to delayer this chip. There are many ways to do that the most classic is to use HF by doing a window to selectively remove glass over the traces. Like I said before I don’t have a chemical lab and so I don’t want to use HF (this is a deadly chemical compound). Since I have a spare microscope to do test I bought a Laser from ebay to test some laser surgery on silicon die.

WP_000284

Current Setup

I took a 200mW green one. The choice of green comes from the Signatone website. Before going further I must say that the experiment only had few chance to be a success, 200mW CW laser is not really powerful and burn only black plastic, plus the optic on my microscope is not manufactured for laser use (Mitutoyo have series of objective for that), but I thought that concentrating the laser on a really small surface could do the job. I did the test using my old microscope (on the right):

WP_000287

The results is promising but I need to do a better setup with an other laser, in fact I managed to dig a small hole in the glass of a chip by putting the laser right behind a Neo 40x objective (the objectiv didn’t survive to this test):

DF_large_view BF_close_up BF_large_view DF_close_up

Some pictures in BF and DF of the point of impact.

Future tests

For now I need to find an other Laser, those results confirm the need of a pulsed one (Q-Switched YAG like advise by some people), since finding a TEC/air cooled YAG setup for few bucks is hard I have 4 choices:

Trying 1W Green or IR laser

Maybe that could do the job but I think pulse is necessary to have the max amount of heat at one instant to avoid the dissipation in the die. I will try this anyway when I’ll have enough money (or if someone lend me one ;))

eBaying to find a YAG setup

This option could be the best but need lot of search to find good cavity/lamp and rod in an usable shape (many ebay rod are scratched and I don’t want to polish them) plus will need work to design a good and secured PSU to integrate to the microscope.

Using a tattoo removal machine

There are many cheap tattoo removal machine on eBay (I won’t use those on my body but…) based on Q-Switched YAG laser and delivering IR and Green pulse,  there are two drawbacks, first I’ll need to put water near the setup to cool the laser machine and that’s not wanted for home use, second it’s not so cheap (about 1000$). At the moment it seems to be my best option because I know nobody selling a used setup for a reasonable price (I would love to get a SSY-1).

Signing a contract with the NSA

and stole laser setup before running to Ecuador 😀

So if you know people having used setup or piece of laser etc…. I’ll be interested. No need to say that the full setup will be documented as much as possible to be cloned around the world 🙂