Comments by "Grak70" (@Grak70) on "Etch: Lithography's Unheralded Sibling" video.

  1. This is exactly correct. More cowboy engineering in action. The engineers who invented plasma etch used 13.56MHz because it combined RF generators that were commercially available off the shelf with license-free use.
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  2. It’s always etch’s fault. Even when it’s photo’s fault. 💕
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  3. While it’s obsolete for silicon technologies, resist undercut is extensively used as a desirable feature of liftoff patterning where gold is used to carry current (gold has no volatile halides, so it cannot be dry etched). This is still very common in GaAs power amplifier technologies.
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  4. He’s pretty much just trolling at this point to avoid admitting he made a mistake early on. Don’t waste your breath.
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  5. In practice you always trade selectivity for directionality. A heavy non-reactive ion like argon will etch straight down, but it won’t distinguish between layers and the etch products will sputter rather than diffuse away from the surface. Purely chemical reactive species with low ionization will be very selective, but won’t interact with the plasma electric field strongly, so they will etch isotropically like a wet etch. In practice, you either alternate etch chemistry to form a passivation layer that prevents isotropic etching or strike a balance between etch species to achieve the profile you want.
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  6.  @tykjpelk  well you certainly wouldn’t do it for silicon CMOS in any case. Gold contamination forms trap states in the silicon bandgap. You can’t have gold anywhere near a silicon fab.
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  7. Because that part of the radio spectrum is allocated to exactly these kinds of devices. 13.56+/-0.007Mhz is one of the so called “ISM” bands reserved for “industry, science, and medical” use. As such, there are no licensing requirements to use it. Although it’s possible to broadcast and receive in that band, machines that do so typically don’t exist since your data would be corrupted every time someone within 100ft microwaved a burrito.
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  8.  @tykjpelk  sure, if you don’t mind sputtering gold all over everything and failing reliability testing. What works in a university lab or a white paper to get a pretty SEM image rarely works in the field.
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  9.  @tykjpelk  totally gonna start calling mask files “GD slayers” starting this coming Monday.
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