Twente invention makes it easier to apply 3D nanostructures on a chip
Scientists from the University of Twente have developed a method to apply 3D nanostructures to a wafer using a mask in a single step. The technique makes it possible to combine functionalities in the field of electronics, optics and magnetism on a chip.
The scientists’ method enables the etching of 3D nanostructures using techniques compatible with cmos semiconductor processes. According to the University of Twente, this ‘opens the way to mass production of chips in which different functionalities are close together’. Professor Willem Vos of the Complex Photonic Systems department of the MESA+ Institute mentions electronics, optics, magnets and microfluidics as examples.
The etching of nanostructures is currently limited by the use of planar masks. Applying 3d structures is then done by stacking layers, but ensuring a tight alignment limits this method. This would not be a problem with the technique of the people of Twente.
They use a mask layer on two faces of a silicon wafer, which are diagonally adjacent to each other. This can be, for example, the edge of a wafer. Patterns are then projected onto the surfaces with a 2D mask, whereby the top is provided with a pattern a and the bottom with a pattern b.
By projecting the two different two-dimensional patterns via the mask onto the surfaces in a single step, the alignment between the patterns is guaranteed, the researchers claim. Etching holes in two oblique directions creates 3D structures in the silicon where the pores overlap. By making the patterns in the two surfaces differ, several types of structures can be applied.
As a proof-of-concept, the scientists have made a mask with which three-dimensional photonic crystals with a hexagonal structure have been developed. The difference in alignment between the patterns used before was less than 3nm. These types of crystals can be used to control light and eventually play a role in fast optical communication at the nanoscale.
The research was conducted by the Complex Photonic Systems and Transducer Science and Technology department of the MESA+ Institute. It was published Thursday under the heading Method to make a single-step etch mask for 3D monolithic nanostructures in the journal Nanotechnology of the Institute of Physics..