Research On A Homogenizer For DMD Lithography Machine

In recent years,with the continuous improvement of chip integration,new maskless lithography technology based on digital micromirror devices(DMD)has received widespread attention.DMD has the advantages of high resolution,high optical efficiency and short response time.DMD lithography technology reduces the difficulty and cost of traditional lithography in the fabrication and processing of masks,simplifies the tedious process of lithography,and improve the working efficiency of the lithography machine.The homogenizer is essential as an important component in the lithography machine.The light intensity of the light directly emitted by the laser is usually non-uniform.Non-uniform light directly illuminating on the DMD for lithography will result in inscribed line width and inconsistent resolution,which seriously affects lithography quality.The microlens array is a common homogenizing system,but they also have some problems when applied to DMD lithography machines.Firstly,the interference patterns on the DMD are obvious and regular because of the periodic structure of microlens array(MLA)and the coherence of the laser;Secondly,Due to its excessive number and volume of the components,it is difficult to integrate;Finally,because DMD is in the direction not perpendicular to the optical axis of the beam homogenize but is 24° to the vertical plane of its vertical plane,the uniformity is poor.In this paper,the shortcomings of the traditional microlens array homogenizing system applied to the DMD lithography machine are studied in depth,and the corresponding solutions are proposed:(1)In view of the interference patterns problem caused by the traditional microlens array for coherent light,a random microlens array is proposed.The periodicity of the sublens position is randomly distributed to break the periodicity of the traditional microlens array.The interference patterns of the target surface are disturbed,and the homogenization effect of the homogenizer for the coherent light is improved.(2)A novel freeform surface microlens array is proposed for the difficulty of integration of traditional microlens arrays.Such a beam homogenizer contains only one freeform microlens array(rfMLA),which minimize the number of components in the system and make system integration easier.And the rfMLA consists of different freeform microlenses.By the individual design of the sublens,efficient and uniform beam shaping results have been obtained in the direction not perpendicular to the optical axis of the beam homogenizer.By randomly designing the size of each sub-lens,the problem of interference patterns for the coherent light is solved.