| Summary: | 碩士 === 中華大學 === 電機工程學系碩士班 === 88 === The LIGA technology in the field of micro-electro-mechanical system (MEMS), which integrates the processes of X-ray lithography, electroplating, and micromolding, uses the synchrotron radiation as lithography source. However, few can utilize this process because of its high fabrication cost and the lack of access to a synchrotron source. Consequently, recently there has been growing interests in low-cost, commonly available LIGA-like processes in which X-ray lithography is replaced by a cheaper alternative technique such as UV photolithography, deep reactive ion etching (RIE), or excimer laser micromachining. The microstructures fabricated by LIGA-like process have the m-scale precision, which is still suitable for the application of MEMS.
The EPON® SU-8 is a negative, epoxy-type, near-UV photoresist and usually used to fabricate high aspect ratio microstructures. A novel method will be presented in the thesis, which the refractive microlens arrays with SU-8 photoresist is fabricates by excimer laser micromachining, then replicated by this SU-8 photoresist master through hot embossing technique.
The experimental results show that the refractive index of SU-8 photoresist is about 1.58 at the 632.8 nm wavelength and its transmittance is above 85% between 500-1400 nm wavelengths. The refractive microlens arrays can be fabricated rapidly by using excimer laser micromachining. The fill factor of microlens arrays is approximately 100%. The 10x10 microlens array with 75 um in diameter and 3 um in height was fabricated at low ablation rate. It exhibits the smooth surfaces with roughness of 3 nm rms and a P-V value of 21 nm. The maximum optical usage of microlens array is 88.4%. The fifth replica has the characteristic of rms 3 nm roughness and 33 nm P-V value, its transfer efficiency is 96.98%.
In this paper, we have presented a concrete and effective LIGA-like technology. The refractive microlens arrays with high optical quality can be fabricated by this technology. Moreover, it has also been demonstrated that the LIGA-like technology is suitable for low-cost, rapid, and massive production for the industrial application.
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