Alignment Question for 2-step photolithography using SU-8 

Forum: SU-8 Photoresist Discussion Forum
Date: 2006, Feb 23
From: Razim <rfsamy@gmail.com>

I'm having some problems with aligning two different masks. Lets say I want to perform 2-step photolithography, where I have two different masks to create two different designs which somehow links together on the same wafer. Each mask would have to be separately exposed with the substrate underneath. In these cases, how would I ensure that the first mask and the second mask corelates to the same location on the wafer? I've been reading and asking around, and people have said to use "fudicials" - exact same designs and locations on all the masks in which you can expose a mark onto the wafer, and this mark is used to guide the fudicials on the second and sebsequent masks. However, SU-8 is a negative photoresist, so after exposing, the marks aren't visible unless I develop the wafer. But if I develop the wafer after the first exposure, everything else will be dissolved so I can't expose it a second time with the different mask. How is aligning done in such cases? Thanks, Razim

Messages Inline: Outline:

1. Aligning, 2006, Mar 14

2. Thanks! by razim, 2006, Mar 15

to: "Alignment Question for 2-step photolithography using SU-8"