Spin coat photoresist on fluorinated substrate

It is difficult to spin coat a photoresist on a fluorinated substrate due to its ultra-low surface energy.
In my case the substrate (ITO coated glass, or SiNx layer coated on ITO-glass) is coated by PFOTS first. Photolithography followed by RIE are then applied to pattern the PFOTS/SiNx double layer simultaneously. In this way the PFOTS layer is self-aligned with the SiNx.

The spin recipe for the spin coat of AZ5214 photoresist on PFOTS coated layer used is given as follows.

1. 500 rpm, accelaration 100 rpm/sec, time for 5 sec.
2. 4,000 rpm, accelaration 1,000 rpm/sec, time for 40 sec.

The first step is used to coat the fluorinated substrate with photoresist at a low spin speed. As observed from experiment, a fast spin speed can easily throw away most photoresist due to the non-stick property of the fluorinated substrate.

As usual, spin on a HDMS layer first, followed by a AZ5214 layer.