In 2004, the first bottom resist (BR) was developed in collaboration with the Center for Intelligent Systems (CiS, Erfurt). This bottom resist is non-light sensitive and can be developed in an aqueous alkaline manner.
A “normal” photoresist is then spun onto the bottom layer. The properties of the BR are designed such that the BR layer does not attack the photoresist during coating. The photoresist is subsequently exposed and developed. After complete development, the developer dissolves the bottom resist isotropically. Depending on the respective development time, a more or less pronounced undercut is formed – and thus generates structures which are excellently suited for lift-off processes.
Fig. 1 Differently pronounced undercut of a two-layer system with bottom resist AR-BR 5400
Meanwhile, more than a dozen different bottom resists are commercially available. For several large customers, we adapted the resist precisely according to the requested technology. In 2019, we for the first time produced more than 1,000 litres of these bottom resists.
If you, dear reader, are also looking for a resist with specific properties for your applications, you will certainly find a suitable match in our portfolio or may contact us in this regard.
The high acceptance and usefulness for our customers was reason enough for us to choose AR-BR 5400 as resist of the month of July.