Dose-dependent structure size with negative resists

The desired structure size also largely depends on the exposure dose used. In the case of overexposure, structures begin to widen which is particularly pronounced during laser exposure. The image series shows 5 µm-columns obtained with different doses. The determined minimum dose is not high enough for a complete build-up of the 5 µm-column, which results in a pointed cone. With increasing doses (30 mJ/cm² and above), the shape of a column is obtained. At higher values (70 mJ/cm² and more), the diameter of the cylinder increases due to the overexposure and the scattered light associated with it. At 120 mJ/cm², already a diameter of 7.5 µm is reached. Overexposure similarly results in larger structures if mask aligners are used for exposure (photolithography). It is thus strongly recommended to determine the optimum dose at the beginning of the application.

Image series 6 with different doses:

7 mJ/cm² 5 µm

40 mJ/cm² 5 µm

70 mJ/cm² 5 µm

90 mJ/cm² 5 µm

120 mJ/cm² 5 µm