This is something of a more off-the-beaten path story that I ran into at Semicon West. I talked with a German company called DAS that focuses on environmental remediation. In other words, cleaning up after the rest of you.
Fabs have always needed scrubbers to clean up the wide variety of rather questionable substances that really shouldn’t be out wandering the streets without supervision. Typically, that’s been done in one place: all of the various waste gasses from the different processes would be directed to the Mother of All Gas Confabs to mix and mingle and then – in the ultimate betrayal – to be scrubbed. Sort of like inviting folks with outstanding warrants to pick up their winning lottery tickets and then arresting them when they get there.
But that takes lots of piping and, not inconsequentially, creates some level of risk as the various gasses are allowed to consort with each other. The trend is away from centralized scrubbing and towards point-of-use abatement, meaning that each process or machine has its gasses neutralized at the machine rather than all in one place.
It turns out that there are very different treatments for different waste gas streams – especially when you look beyond just the semiconductor business. Techniques include “burn/wet” treatment (where water scrubs the burn products); electrostatic treatment for dust; “thermal/wet” treatments; oxidation/pyrolysis for LEDs (hydrogen and ammonia); and a new “wet” treatment for lab bench waste.
At Semicon West, they focused on two systems – an existing one and that new one. The Styrax system is a burn/wet unit used for waste gasses from etch, CVD, metal organic CVD (MOCVD), transparent conductive oxide (TCO) deposition, and epitaxy. It’s a water-intensive process (many of these seem to be), but they’ve gotten water usage down to 1 l/min through the use of lye; without it they would need more like 20 l/min.
Then they announced a new system called Salix for single-wafer clean wet bench processes. This is for water-soluble waste gasses, and it has two stages – one for acids, one for alkalis. It doesn’t handle organics (presumably not an issue for this application). It can handle up to 3 x4 inlets, so, I guess in that regard, there’s still some mixage going on… just not at the building level.
You can check out more detail in their Salix release.