Nanoscribe’s 3D microprinter Photonic Professional GT (PPGT) is a versatile tool for structuring photoresists with almost unlimited freedom of design in all three dimensions. However, the device and its technology can be superior to other state of the art structuring techniques even when the full 3D capacity is not required. When a “proper” 2D photoresist pattern is to be printed (i.e., a pattern consisting of photoresist features of equal height), the PPGT is effectively used like a maskless lithography device. Here, the PPGT’s additive manufacturing process excels in three ways:
- Its linewidth and resolution of 200 nm and 500 nm, respectively, extend beyond most other maskless lithography devices and even enter the realm typically reserved for electron beam lithography.
- Due to the additive approach, it is conceptually straightforward to achieve high aspect ratio trenches with vertical sidewalls even in thick-film photoresists.
- It is possible to pattern resists on non-conductive substrate and without the use of vacuum.
When defining so called 2.5D patterns, i.e. patterns in which the height of the final structure varies freely across the sample but no undercuts occur, techniques such as diamond milling or grey scale lithography encounter several limitations. Here, again, an additive 3D printing approach with submicrometer resolution and feature sizes allows for numerous design features that are hard or impossible to realize using other techniques:
- Planes with very different inclinations can be manufactured in close proximity and independently from each other. Even freeform surfaces can be defined with optical quality.
- Sharp edges with radii of curvature down to 300 nm are possible.
- “Buried” angles such as at the intersection of planes deep inside the workpiece can be defined and produced almost freely since no mechanical tool needs to be brought into contact with the final piece.
In addition, process engineering is simplified since tool wear does not need to be taken into account.
These process features make it possible to manufacture 2D and 2.5D masters and prototypes with geometries that are currently impossible or at least challenging to produce using subtractive techniques or greyscale lithography. Throwing in the PPGT’s capacity to structure objects extending over several square centimeters, it becomes economically feasible to produce masters for further replication of the printed objects using techniques such as hot-embossing, stamping or imprinting.
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