Design And Research Of Binary Optical Element Applied In Excimer Laser Wavefront Shaping

In MEMS technology, excimer laser micro-processing is a potential for the development of micro-machining tools. In the masking photolithography, the resolution is the key factor in system's performance, and continuously improvement of photolithography resolution has been made efforts to solve the problems. In the masking photolithography system, the uniformity of the distribution of light is very important. Based on the current methods used in excimer laser, we put up the idea that using the binary optical theory to design a BOE for shaping the wave of excimer laser by employing the microelectronic processing techniques, in view of the laboratory's actual use.In this paper, we testified the function of BOE for shaping the wave, and using MATLAB? software to compile the Gerchberg-Saxton algorithm, which confirmed the function of the pure-phase components for wave shaping.Furthermore, we designed the beam splitter in accordance with the binary optical theories. The basic unit is the Fresnel zone plate, and the structure is the single-layer compound eyes. Based on the actual application, we determined the parameters as follows: the effective size of BOE is 33 mm×33mm, the number of arrays is 80×80, the step number is 8, the main focal length is 16.0 mm, the cell aperture is 0.4125 mm. The quartz (JGS1) was selected as the material, because the wave length of KrF excimer laser is in the ultraviolet band.In the process of BOE's fabrication, we calculated the values of various radiuses, firstly. In the light of calculated data, we used the software LEDIT to draw the three masks, and add the corresponding alignment markers. Immediately, the optimal exposure time toward JGS1 is determined as 13s after many experiments, in the meantime, the parameters of the plasma etching are confirmed. According to the requirements of structural components, we obtained the value of etching depth and further determined the etching time for each mask.Final experimental parameters: the exposure time is 13s, the development time is 60s, fixing time is 30s, the gases used are CHF3: 180sccm, SF6: 60sccm; three etching times are T1 = 9min, T2 = 4.5min, T3 = 2.25min, respectively; etching rate is V = 50nm/min.We employed the microscopes and 3D contourgraph to observe the patterns of finished components. In order to understand its performance better, we measured the energy transmissivity, and make it have a comparison with the existing quartz rod arrays. The energy transmissivity of original quartz rod arrays is about 77%, and that of the binary optical Fresnel lens is about 85%, with a significantly increase. The uniformities of BOE in X and Y directions were measured respectively. In the use of masking photolithography, we can clearly see that the element play a role in making the uniformity of excimer laser's energy, and have done some experiments.