AMTC Dresden

Overview
Photomasks are high-purity glass substrates that contain precise images of integrated circuits (or semiconductor chips). Photomasks are an integral part of the fabrication of integrated circuits on silicon substrates (wafers).

State-of-the-art lithography equipment is based on light in the ultraviolet range (DUV = 193 nm) and project the light through the photomask using a complex lens system with high numerical aperture. The intensity distribution of the light creates an image of the design on the wafer. The wafer is coated with photoresist, a photosensitive material. When using negative photoresist, the unexposed areas of the material are removed, so that afterwards the structures can be etched or other materials can be applied.

The three-dimensional integrated circuits are built up layer by layer. The steps described are repeated until the formation of the complete circuit. The current generation of circuits has 25-70 layers, almost each of which requires its own photomask.

For the manufacturing process of the photomask, the following methods are used:

electron beam writing
laser writing
Wet-chemical paint development
plasma etching
Optical AFM and electron beam measurement
Inspection laser and ion beam repair
Ion-induced deposition
Pelliclemontage