Address

Heidelberg Instruments GmbH
Tullastrasse 2
D-69126 Heidelberg
Germany
Phone: (+49) 6221 34 30 0
Fax:     (+49) 6221 34 30 30
Mail:
Web: www.himt.de

Autofocus System

To make exposures with a resolution in the range of one micron or below, our systems need to focus the laser with a high NA lens onto the substrate. Due to the limited depth of focus of these lenses, it is very important for high quality exposures to keep the lens in a constant distance to the substrate. Even slight variations in the focus would result in variations of the linewidth of the exposed structures.

Write Head
Write Head

In order to ensure high quality exposures, the lens that is used to focus the beam onto the substrate is part of a unit called the write head. This write head incorporates an autofocus system that will keep the lens in focus during the entire exposure. The standard system consists of an air-gauge autofocus, which has proven very reliable for exposures on masks and other flat substrates. For special applications, like very small or non-planar substrates, we have developed an improved optical autofocus system. Both system ensure constant structure quality even in long exposures.