使用3D 有限時域差分法分析相位移光罩接觸孔

Abstract

在使用氟化氬並配合高數值孔徑的微影技術去曝65 奈米的圖形以進入了接近0.3 的k1 參數值,以及光罩圖形使用的波長以四倍的量值.此外,相位移光罩為了產生一百八十度的光程差所以去蝕刻一個特定深度的溝.由於波長和高的圖像縱橫比,所以有厚度的光罩效應變成了模擬誤差的來源.尤其對相位移光罩產生很大的影響.以及使用小波長三維精確的電場磁場做模擬. 在以前,因為柯希荷夫邊界條件下,我們得以使用一個較”薄光罩”去近似物體的場,但在次波長微影技術的條件下,不得不需要考慮薄光罩的效應,所以一個新的模擬方法被推出來使用,在基於類似薄光罩在晶圓上產生的場.他的名字叫做有限時域差分法.他是為了在電腦模擬下,把馬克斯威爾方程式離散化.所以我們用這個方法,去分析光罩的電場磁場繞射現象

The using of ArF lithography with high numerical aperture (NA) to print 65nm wafer features translates into a k1 factor approaching values about 0.3 and mask features of the order of the wavelength for 4X magnification. In addition, the Phase-shifting mask (Alt PSM) employ etching with a depths so that have a optical difference in order to make a 180° phase-shifting openings. As a consequence of wavelength sized and high aspect ratio mask features, thick mask effects are becoming a error source of simulation, which are particularly critical for Alt. PSM, and 3D rigorous electromagnetic field simulations in the sub-wavelength regime. In the past, Kirchhoff's Boundary Conditions on the mask surface provides the so-called “Thin Mask” approximation of the object field. But for sub-wavelength lithography, however, it fails to account for thick mask effect A new simulation model is proposed, which is based on a comparison of the fields produced by the thick masks on the wafer. Which is Finite-Difference Time-Domain(FDTD). It can discrete IV the Maxwell’s equation to fit computer’s simulation. We can use FDTD techniques to view rigorous Simulation of electromagnetic scattering and diffraction.