Design for Manufacturing
In the previous chapter, the various lithographic technologies used today to produce digital optical elements on quartz, silicon or other wafers (i.e. mask patterning systems, optical lithography systems, ion etching systems, etc.) were reviewed. The various processes used to produce multilevel and quasi-analog surface relief (multilevel lithography and gray-scale lithography) were also reviewed.
Based on this review, the current chapter provides solutions to optimize the fabrication processes and associated resolutions to produce micro- and nanostructures that are better adapted to the digital optics realm, as has been done for the IC industry. However, one has to remember that basic IC shapes used in standard semiconductor fabrication can be very different to those used in digital optics (parallelogram-type shapes rather than smooth curved shapes).
Design For Manufacturing (DFM) consists of including machine specific characteristics in the design process of an element in order to optimize the fabrication of that element with this specific machine. In microlithography, DFM consists of introducing numeric lithographic models in the design process of the microstructures (micro-electronics or micro-optics) to be patterned on the wafer. Such DFM processes include software and hardware solutions.
13.1 The Lithographic Challenge
In optical lithography, the industry constantly attempts to reduce the minimum printable feature size δx (see Equation (13.1) below), ...