The illumination design of UV LED array for lithography

Abstract

High efficiency coupling of the array of UV light diode light source could be able to replace the traditional mercury light source, while mercury light source requires a large amount of electricity, condenser optics and volume, with hazard environmental issue. It is an urgent need for further requirement of light source for lithography. Although array UVLED could be a replacement of light sources of lithography, there are some existent optical parameters that not fit for optical coupling, such as large divergent cone angle of single chip and half divergent angle of array, which are weak the possibility of application in lithography. Before the broadly accepted by lithography, those shortages have to be overcome. Some techniques, such as designing small divergent cone angle of single chip, or eliminating divergent angle have suggested by fly eye and other methods, yet all of those methods, only improve the coupling efficiency and uniformity of emitted surface in some limited extent. The project is to develop a high coupling efficiency of the optical system used in the array of UV light diodes, which can make the high coupling efficiency, despite UVLED has a small size and large divergent angle. The optical design of illumination has carried out for array UVLED, an illumination optics has designed based on Koehler type illumination, and it has shown reducing the divergent angle to increase in coupling efficiency between the Array UVLED to the mask of lithography. The uniformity of average power has shown excellently fitted for high quality lithography in direct exposure or lens exposure.