nanolandscape

The crazy-huge mountains of the nanoworld!  The strange waves and scallops are what is left of the protective mask I used to shield the semiconductor material below from a high-energy etching plasma.  The mask held up to the plasma, although it was probably damaged a bit - and then I damaged it further by a couple of rounds in another plasma, that we use to get rid of polymer buildup.  This is what the sample looked like under the microscope after the last plasma cleaning step - fluffy mountains made of thick residual mask. I didn’t care about the fate of the mask - all I cared was that it had done its job, and that I could tell that the etch worked on the unprotected bits of semiconductor.  It did work, as evidenced by the sharp cliff.  Acetone later washed the mask away, leaving the upper surface of the cliff smooth and clean.

A mini-monument, made of semiconductor laser material.  It looks to me a bit like Devil’s Tower.  It’s much, much smaller, though.  Scaling this little nano-tower (600nm high) to the height of Devil’s Tower (386m high) would be like scaling up an average-sized human (~1.7m) to about 1.1 billion meters tall.  This is, as Wolfram Alpha helpfully informs us, about 3x the distance between the earth and the moon.  Every time I do a calculation like this, it still boggles me how tiny these nanostructures are.

So, what is the nanotower doing here?  This is an image of a plasma-etched wafer of semiconductor, the sort we like to make lasers out of.  I was testing the plasma-etching process, so I was just etching simple structures into this wafer.  I did get etching - the top of the tower is where the top surface of the wafer used to be; the tower itself was formed by a tiny dust particle that happened to land on a surface, shielding a bit of the wafer from the plasma.  Unfortunately, I also got this strange fluffy surface on the wafer, signs of problems with the etching gases, or possibly contamination in the chamber.