Pattern Definition with DUV-Lithography at DTU Danchip

Deep ultra violet (DUV) illumination generated with the help of a KrF laser can be utilized to produce components having sizes of some hundreds of nanometers. This light source with its 248nm wavelength is exploited in the DUV-lithography equipment at DTU Danchip in order to fill the resolution gap between traditional UV-lithography and e-beam lithography.

With the help of a DUV stepper, devices with pattern sizes of 250 nm (see in fig. 1) can be produced on a high volume scale, with a throughput of 30 to 90 wafers per hour on 6” or 8” wafers. For R&D purposes also smaller line widths can be printed - as shown in fig. 2 - utilizing the possibility of beam shape variations that enables to adapt the resolution and the depth of focus of the stepper to the requirements of the fabricated device.

However, generally the highest achievable resolution is dependent on the pattern type - as e.g. pillar, line or hole comprising patterns -, its symmetry and the separations between the different structures. The projection lithography tool FPA-3000EX4 from Canon (max. NA=0,6; 1:5 reduction) produces patterns on the wafer within a maximum chip area of 22x22mm2 that can be stitched together with an accuracy of 3σ=35 nm.

Also alignment to already existing patterns on the wafer can be performed with an accuracy of 3σ=50 nm. These pre-made patterns might be defined in the resist with the help of different lithography methods or - alternatively - already be etched in the wafer.