tarlinian (tarlinian.delete@this.gmail.com) on July 1, 2022 6:50 pm wrote:
> Eric P (eric.delete@this.nospam.com) on July 1, 2022 5:26 pm wrote:
> > > I think the notch is still there. It seems to be in the Intel image.
> >
> > > In the 1st and 2nd image it looks to be around 5 o'clock.
> >
> > > In the 3rd image just above (and in the middle of) the "ra" in semiaccurate
> >
> > Thank you for pointing that out. I was referring to the flat section (segment of a circle), like
> > on the TSMC logo. I didn’t notice the V notch before but I agree the Intel wafers do have a V notch.
> > Even the Samsung and TSMC wafers seem to have a V notch at 6 o’clock, but it is less clear due
> > to lighting highlights. I guess this V notch is now used to indicate the crystal orientation.
>
> I have usually heard the feature you describe on smaller wafers referred to as a "flat" in order to
> differentiate it from the fiducial notch you see on 300 mm wafers and many 200 mm wafers. From what
> I've heard, those fiducial features obviously caused even more issues with edge related effects.

My understanding is that they wanted to remove the notch in 450mm wafers for that reason!

David