Beam delivery component motion control provides a powerful method of automating part processing with UV excimer laser systems. Coordinated movement of the objective lens and the mask along the beam axis provides part thickness compensation without requiring a Z-axis lift stage under the part. Eliminating this axis improves part positioning by reducing the stack height of the part handling stages. Moving the mask and object lens using algorithms derived from the thin lens equation can achieve automatic magnification adjustment. Auto magnification adjustments permit fine feature size adjustments without a mask exchange.
Using a mask aligner allows you to generate multiple feature types as part of an automatic process without operator intervention. This system is analogous to tool bit changers in CNC machining. Both rotary and linear mask aligners are in use in excimer systems. Mask alignment permits high precision overlays, such as counterbore holes. Mask aligners with letter stencils can produce custom serialization marks under computer control. In addition, feature arrays can be produced in workpieces that use multiple overlaid design rules.
Automated beam delivery systems can be realized by mounting optical components on high precision linear motion stages. Precise stage alignment to the beam travel axis is critical to proper operation. Ultra-precise systems are frequently mounted to granite support structures to improve rigidity and thermal stability. A granite substructure provides a large thermal mass, thereby dampening the effects of transient temperature variations on optics position.