In an off-axis levelling procedure a height map of the substrate is generated at a measurement station. The height map is referenced to a physical reference surface of the substrate table. The physical reference surface may be a surface in which is inset a transmission image sensor. At the exposure station the height of the physical reference surface is measured and related to the focal plane of the projection lens. The height map can then be used to determine the optimum height and/or tilt of substrate table to position the exposure area on the substrate in best focus during exposure. The same principles can be applied to (reflective) masks.

 
Web www.patentalert.com

< Method and system for remote wireless video surveillance

< Flash control device, flash control system, master flash device, and remote flash device

> Remote NMR/MRI detection of laser polarized gases

> System for making a photoresist master for a hybrid optical recording disc

~ 00250