Novel photo-lithography is newly proposed named built-in lens mask lithography. The method emulates optical propagation plane in exposure system using binary transmittance and phase mask instead of projection lens. The performance of the built-in lens mask lithography is studied by numerical simulation and experimental study using conventional proximity exposure system. The result shows resolution enhancement in deep focus plane.
Cost effective micro lithography tool is demanded for fine micro devices. However, resolution of a conventional proximity exposure system is not sufficient below several micron feature size for deep focus depth. On the other hand, a reduction projection system is sufficient to resolve it but the cost of the tool is too much high compared to proximity exposure systems. To enhance the resolution of photolithography, there has been proposed a number of novel methods beside shorting of wave length. Some of them are utilized in current advanced lithography systems, for example, the immersion lithography<sup>1</sup> enhances effective NA and the phase shift mask<sup>2</sup> improves optical transmittance function. However, those advanced technology is mainly focused on improvement for advanced projection exposure systems for ultra-fine lithography. On the other hand, coherence holography pattering is recently proposed and expected for 3-dimentional pattering<sup>3-5</sup>. Also, Talbot lithography<sup>6-8</sup> is studied for periodical micro and nano pattering. Those novels pattering are based on wave propagation due to optical diffraction without using expensive optical lens systems. In this paper we newly propose novel optical lithography using built-in lens mask to enhance resolution and focus depth in conventional proximity exposure system for micro lithographic application without lens systems. The performance is confirmed by simulation and experimental works.