UNDERSTANDING MECHANICAL RESPONSE OF POROUS POLYMERIC STAMPS DURING LARGE-AREA METAL-ASSISTED CHEMICAL IMPRINTING OF SILICON

The patterning of semiconductors with complex 3D hierarchical structures having sub-100 nm resolution is propelling a new generation of optical metasurfaces for applications in optoelectronic interconnects and hyperspectral imaging. These complex structures are now manufacturable with the advent of Metal-assisted chemical imprinting (Mac-Imprint). This technique involves bringing a 3D patterned catalytic stamp into contact with a semiconductor substrate in the presence of an etching solution. Recently, a novel class of catalytic stamps made of Au-coated porous polymeric membranes was developed in order to allow for etching solution storage and mass-transport of the reactants, all of which are essential for fast and accurate Mac-Imprint. Further, the flexibility and stretchability of these porous membranes allows for the use of pressure-based actuation to bring both planar and non-planar substrates in conformal contact with the stamp, replicating the set-up of modern nanoimprinting lithography equipment. Due to the contact-based nature of the Mac-Imprint process, it is vital to understand the mechanical behavior of the stamp. Thus, this work attempts to computationally elucidate the mechanical behavior of the stamp during conformal Mac-Imprint. In particular, the elastic behavior of a stamps laminate made of commercial porous polyvinylidene fluoride (PVDF) with nominal pore sizes of 100 nm and solid polyimide (PI) is modelled using finite element analysis (FEA) in a commercial ANSYS software with material constants, extracted via uniaxial tensile test. The FEA prediction using 2D axisymmetric model is able to capture the induced biaxial stress, strain, deflection and yield of the porous PVDF. To validate simulation results, a deflection test was experimentally performed as a function of air pressure and the obtained results matched with the FEA simulation.