Multi-Height Precision Alignment With Selectively Developed Alignment Marks

The alignment step in fabricating multi-height photoresist masters is a critical and time-consuming process. SU8 masters that combine very thin and thick layers can be difficult to align because of low contrast visibility. We increase visual contrast by selectively developing alignment marks to ease fabrication of masters with thick resist layers deposited on much thinner ones. In addition, we use a vernier calliper based alignment mark to achieve high precision alignment.