As the cost of photo masks for display panel is very high, researchers have been developing maskless lithography using electron beam in this system. However the maskless lithography system has typical drawback in some respects. These issues include productivity, size of the system and cost efficiency. To cope with these problems, take reflectance rate and position of spot array into consideration is required. The lithography technology has been focused on studying both reflectance of light from DMDs (digital micromirror devices) and the position of generated spot array. As the lithography technology has been developed steadily, there exists plenty type of maskless lithography nowadays.
DMD-based optical maskless lithography system is gaining substantial attention from researchers and engineers for its outstanding performance concerning cost efficiency and high throughput. Also, accurate alignment of spot array is on requisition under the condition of micro-unit scale. As a result, the maskless lithography system is faced with the problem relevant to accurate alignment. For instance, the actual alignment of spot array has been done by hand although it has a chance to show deleterious effects on productivity.
In this paper, an alignment algorithm was suggested for the purpose of satisfying generation of accurate alignment of spot array. The algorithm is based on concerning kinematics of maskless lithography system. Thus, the suggested algorithm enable to reducing the error that has been measured from the spot array. Defining spot array error that is fitness function of genetic algorithm is introduced at first. An alignment algorithm that has correlation with kinematics of the optical system and spot array error will be represented in sequence. After that, designing 4 DOF align unit will be covered in kinematics analysis chapter. Finally, designing test bed of optical system using vision sensor and align unit is considered in order to validate the suggested alignment algorithm with experiment.
Optical System with 4 ㎛ Resolution for Maskless Lithography Using Digital Micromirror Device
