Angle controlled imprints using step and stamp imprint lithography

Nanoimprint lithography is an ideal method to fabricate various optical devices, because the resist itself can work as a functional element. New light guide designs based on hybrid grating structures can be fabricated using sequential nanoimprint lithography. These structures may contain elements with various shapes, sizes and orientation. Step and Stamp Imprint Lithography (SSIL) is a suitable method to fabricate large scale master with plurality of optical elements. In our system, a stamp with size of few millimeters can be used for patterning large areas up to 200 mm. For example, the method has been used for fabrication of bendable nickel stamps for Roll-to-Roll nanoimprinting and polymer stamps for UV-nanoimprinting.The imprinting machine equipped with rotating head introduces ability to control, in addition to X/Y positioning, also angular orientation of the stamp. The imprinting head can be rotated between -90° and +90° with accuracy of 0.1°. This makes it a suitable tool to fabricate, for example, directed optical structures in large scale, and thereby only few basic elements are needed to create a large entity. The method is effective tool to fabricate large masters, because the design of the master can be changed by programming new X/Y and angular positions of the basic elements. In this work, the angular positioning accuracy was evaluated by imprinting gratings with 250 nm features into thermoplastic polymer by varying the angle by 15° steps. The quality of the imprints was evaluated by optical and AFM microscopy. The theta angle of the gratings was measured by SEM.