| 摘要: | 週期性結構之製程技術，近年來以Lloyd’ s mirror干涉系統最為常見。比較單一光束與兩道光路曝光系統，其光路架設精簡、穩定性高、週期調整便利，以及試片載台位置固定，可以降低作業成本的負擔。不過，Lloyd’ s mirror干涉系統，製作次波長結構，旋轉角度須調整至30度以上，會導致表面餘弦的能量損失，使試片的均勻性欠佳，因此製作有其困難。 在本研究中，利用Lloyd’s mirror 干涉微影系統與高於空氣的介質環境作結合，而建立了新穎的菱鏡浸潤式干涉微影的技術。藉由Light tool軟體模擬光線在菱鏡中其軌跡與干涉角度的變化情形。使用波長442nm氦鎘雷射，經由光學系統產生均勻的平行光束，再利用菱鏡波前分光與疊加形成干涉條紋，透過旋轉載台角度可以在光阻上曝出所需的週期性結構。 本研究以菱鏡取代Lloyd’s mirror，可降低空氣擾動，並利用菱鏡內部的全反射，可達到兩光強一致，使條紋對比度增加，由於環境折射率提高，週期可以做得更小。其中，在菱鏡與試片之間浸潤一層水，使菱鏡與試片的震動同步以維持高明晰度，由於水造成的折射率漸變，可使反射率降低，且提高數值孔徑增加干涉條紋解析度，並改善了光線在光阻內多重反射所造成曝光的不均勻。充分地改善並彌補原系統的不足。實驗中已經可以製作出面積1.5cm×1.5cm、週期300nm~500nm的光柵結構。利用此光學干涉系統，對於製作次波長週期性結構，可達到方便快速、穩定均勻的目標。 The Lloyd’s mirror interference system is the most common for fabrication technology of the periodic structure in recent years, Comparison of two beam and Lloyd’s mirror (single beam) exposure systems, advantage of single beam is optical path set up simply, stability highly, period adjusted conveniently, and position of the placement for sample is stable, so the systems can reduce operative cost. However, the rotation angle must be adjusted to above 30 degrees for fabrication sub-wavelength structure by Lloyd's mirror interference system, the larger angle will cause cosine loss of the surface energy, so the uniformity of interference fringes are relatively poor. In the study, establishing a novel prism immersion interference lithography technology by Lloyd's mirror interference lithography system combined with higher than the air dielectric environment. The mathematical simulation was used by the LightTools software which can calculate light track and interference angle in the prism. The He-Cd laser (λ=442nm) can produce a homogeneous parallel beam after through optical system, then the light wave front is divided by the prism, and proceed the two light beam is overlapped to form interference fringes in space areas. Final, the periodic structure can be obtained through change rotation angle by interference exposure. The shake of air can be reduce through prism instead of Lloyd's mirror, and the two light intensity can reach consistent due to internal total reflection in prism, so that the fringe contrast is increased. The period can be made smaller due to increased environmental refractive index. The water is immersed between the prism and the sample, so that vibration of prism is synchronized with the sample to maintain a higher visibility of interference fringes. The reflectivity is decreased due to refractive index of water in middle value, and immersion of water can raise numerical aperture to increases resolution degree, and to improve the uneven stripes that is caused by multiple reflections within the photoresist. The deficiencies of the original system is improved and compensated through the system of interference by prism. In the experiments, the grating structure has been produced in area of 1.5cm×1.5cm, period is 300nm to 500nm. The optical system by prism for the production of sub wavelength periodic structures can be achieved a target of convenient, fast, stable and uniform. |
