Reversal μCP using hard stamps

In this work, we present a new method of Micro-Contact Printing (μCP) which we call reversal μCP using hard stamps which can be used for the fabrication of different structures like negative index materials, e.g., split ring resonators (SRRs), dots and squares made of gold. Typically soft stamps made of PDMS (polydimethylsiloxane) inked with thiols are used for μCP. The softness of the stamp material entails a lot of problems like deformation of the structures, sagging and pairing of the protruding features and reliability of the process. We use hard stamps which are spin coated with a thiol solution so that the thioles stay in the recessed areas of the stamp. In the following μCP process an EVG®620 is used to bring the stamp and substrate into contact so that the thiols on the stamp diffuse and bind to the gold surface and serve as an etch mask for succeeding wet chemical etching. Using this method overcomes the disadvantage of a soft stamp material. Smallest feature sizes down to 100 nm are shown.