I've dedicated a chapter called "Alignment" to exactly this issue. We will need at least four alignment crosses (each on each side) and then we need to align it with the help of the mask aligner.

Cheers David

On Wednesday, 21 March 2018 5:05:17 PM HKT Hagen SANKOWSKI wrote:

Hello.

I just grep my folder with essential notes I collected over the years and stumbled across the Overlay problem [1] and [2].

Do we need dedicated structures on the Test-Wafer for that? Just for curiosity how good the machines are and our handling is??

Regards, Hagen

[1] https://de.wikipedia.org/wiki/Overlay_(Halbleitertechnik) [2] https://en.wikipedia.org/wiki/Overlay_control

Btw, the German Wikipedia Article is better than the English one in this case.