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What is the minimum achievable feature size and resolution?

Category: Laser Lithography » Photonic Professional
Tags: feature size, IP-G, IP-L, resolution, SU-8
Last update: 2010-12-13 10:04 | Author: Nanoscribe | Revision: 1.8 |

The minimum feature sizes of structures fabricated by using Nanoscribe's Photonic Professional laser lithography system strongly depend on the photoresist which is used.

For example, SU-8, a common negative-tone resist, shows a prominent proximity effect due to cationic polymerization. The Lewis acid produced during exposure of light diffuses and smears out all fine features. However, this leads to a very low surface roughness. In contrast, Nanoscribe's acrylic based photoresists IP-L and IP-G have a surpressed proximity effect. Hence, 2D structures might have a periodicity of 300nm (sub-120nm line width). Beyond that, we specify 3D photonic woodpile structures with a lateral periodicity of 700nm (approx. 150nm line width).

300nm grating fabricated by DLW using IP-L resist

The resolution of positive-tone photoresists is, however, much lower. The lateral feature sizes for these resits are in the range of about 500nm. This is mainly caused by the poor chemical etching contrast.

Please note that for 3D structures the minimum feature sizes in axial direction must be multiplied by a factor of 2.5-3.5 (resist dependend) due to the elongated shape of the basic building block (i.e., the focal volume which exceeds the threshold for polymerization).

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