Thursday, May 13, 2010

Inverted metallurgical microscope

A few weeks ago, Tom Ditto was kind enough to lend me this:
A sample image:
It has a number of differences over a standard biological microscope.
First, its primary advantage is that it does not require light to shine through the sample. Instead, light is injected directly into the view path, allowing easy view of opaque objects. I get around this with the biological microscope by shining intense lights to the side of the sample. I'm currently using a small 650W cone shaped halogen on a rheostat. Before I was using a 500W with a roll cage. I don't push it anywhere near full power. I had to make a shield to only allow in the needed amount of light and not toast the microscope with the intense heat it puts off.
Second, it inverts the image. As an example, here is an image of of an Intel 80486 ("486") copyright on the die:
Note it is flipped. After cropping and inverting, a much nicer image is produced:
Those black spots are dirt on the lenses. I've cleaned a lot off, but some of the larger spots are still present. In order to use this analytically, I will obviously have to fully clean it so spots of dirt don't appear where some critical interconnect image should be.
Various filters are available. I haven't played much with these though. I think the options include regular, polarized, and green. Here is a regular image, showing interconnect layers on some DRAM:
With the green filter:
Finally, although many do, for some reason the biological microscope I have doesn't have a movable stage on it. Maybe you were expected to push a slide around with your fingers? On the other hand, this one has an XY knobs for smooth, precise movement of the stage.
For future work, first on the TODO list is a proper camera mount. I'm using a clip on type mount that Tom let me borrow, but, unfortunately, its not stable enough for good images. This should fix alignment issues resulting in fuzzy, darker colors at the bottom and will allow me to zoom in, removing the dark circle. Next, I'm working on fitting some timing pulley's to the XY knobs for CNC control. I have all of the parts assembled for that and could probably due the fit in several hours. However, I need a larger peice of particle board to mount it on. Unfortunatly, I probably won't get back to this until August when I'm done working for the summer. With luck, I'll find someplace to continue work with it at MIT over the summer. Extra lab space anyone?

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