A Research Of Projection Lithography System Overlay Alignment

The development of modern optical and IC industry require optical device’sminiaturization, array and centralization, thus produce micro-optics technology.Micro-optics technology is a subject of optical and microelectronics, micromechanical’s combination penetration, research modern optical branch ofsubmicro-sized optical element or optical system.Lithography technology is the precursor and foundation of the large scaleintegrated circuit manufacturing technology and micro-optics and micro mechanicaltechnology,it decides the integration of integrated circuits.The constantly innovationreform of lithography technology determines the development direction of integratedcircuits. Lithography technology experienced contact lithography, proximitylithography, step and repeat projection lithography, step and narrow projectionphotolithography,step and scan projection lithography and other typical lithographytechnology process, extremely ultraviolet carved, X-ray photolithography are in theresearch and useing stage. Next generation lithography techniques such as nanostamping lithography, atomic force lithography are still in the frontier study. The currentIC production’s main application is projection lithography technique.Making binary optical element need after many exposure, development andetchingto complete. Each exposure need a mask，before exposuring,each mask need alignmentthe image which has been exposured to be exposured,it has ability to make sure eachlayer graphics have precise relative positions, this is called setof carved alignment.Theprecision of set of carved is one of the key technology of projectionlithography,alignment accuracy is the main factor that influences the precision of set ofcarved.In this paper, on the basic of contact lithography and proximitylithography,proposeto establish projection lithography system.This system is formed by exposure lightsource, masks, projection lithography lens,3d projection translation worktablecomponents. Everypart has the big role to improve the resolution and the precisionof thegraphicses. The working principle of projection lithography mainly uses the opticalprojection imaging, the graphics on the mask are exposured, through the projectionlithography lens, exposure imaging on the substratewhich is coating photoresist.Thenafter developing,etching, sets of carves alignment and developingagain at,it can get more high resolution graphics. Among them, the setof carved alignment is the keytechnology indicators of the projected lithography, the alignment precision is the keyinfluence factors of carved precision. There are many alignment factors,this paper isbased on the principle of the formation of moiré fringers of grating diffraction of lightand dark stripes,todetermine the relativeposition of the mask and the substrate, then bealigned.This article discusses the basic of imaging factors that impact the reductionprojection lithography system, to optimize the improvement, using of long workingdistance projection lens,designed and built an experimental system which can be usedfor rough dwarf aligned lithography overlay, including designing andprocessingmechanical parts. Application of moiré fringe alignment technology for a set of carved,basic realization of the binary optical element4steps reliefstructure...