Study of Normal and High Transmittance Embedded Materials, and Simulation of Application of Attenuated Phase-Shifting Mask for 193 nm Lithography
Dr. Loong Wen-an
|Keywords:||嵌附式減光型相移圖罩;高透射率嵌附層材料;螺旋波電漿蝕刻器;純量散射理論;高透射率減光型相移圖罩;Embedded attenuated phase-shifting mask (AttPSM);modified R-T method;high T embedded layer;critical linewidth on mask for single resist line on wafer (CLMSLW);high T AttPSM|
嵌附層氮化矽粗糙表面會產生散射光，所量測的反射率R為18.19%、透射率T為5.61%，較真實之反射率、透射率為低。本論文以純量散射理論近似修正之，修正後反射率為18.41%、透射率為5.68%，應用於R-T法，所求得之折射率n值為2.433，吸收係數k值為0.543，相當接近n & k分析儀所測得之n值2.437與k值0.542。此R-T修正法並應用於其它嵌附層n、k值之測求。
氧化矽鋁薄膜有良好之光學性質，可作為193奈米之高透射率嵌附層材料。此薄膜在相移180度厚度d180 ~ 87奈米時，其透射率為15~35%。作為鉻膜散條之鉻膜厚度約30奈米，加上氧化矽鋁嵌附層d180 ~ 87共約120奈米，接近傳統鉻膜圖罩之鉻膜厚度，經模擬驗證，可提供良好之空間影像解像度。
The design rule of 193 nm lithography is 0.10 mm. Embedded attenuated phase-shifting mask (AttPSM) is one of the important resolution enhancement techniques. The scattered light was generated from the rough surface of SixNy embedded layer. The measured reflectance (R) 18.19% and transmittance (T) 5.61% are smaller than its real R and T. R and T were approximately corrected based on the scalar scattering theory. After correction, R is 18.41% and T 5.68%. The n 2.433 and k 0.543, determined by the modified R-T method were quite close to the n 2.437 and k 0.542, measured by n & k analyzer. The n and k of other embedded materials were also determined by this modified R-T method. The increasing contents of AlN, SixNy and nitrides chemical compositions will increase n and decrease k of normal T embedded material AlSixNy. Therefore, the chemical compositions and optical properties are well correlated. TiSixNy, TiSixOyNz and AlSixOy embedded materials also have shown this correlation. AlSixOy films with T=15~35% under d180 ~ 87 nm have good optical properties as a high T embedded layer in 193 nm. The combined thickness of the Cr layer (~30 nm) as scattering bar and the AlSixOy embedded layer for d180 (~87 nm) is close to the thickness of conventional binary Cr mask, which is 120 nm. It could provide the good resolution of aerial image, proved by simulation studies. By the utilizations of helicon wave plasma etcher and Taguchi design of experiment, the etching selectivity of TiSixOyNz, AlSixNy and AlSixOy over fused silica (SiO2) substrate and e-beam chemically amplified resists were larger than 2:1. The optimized etching conditions were also derived. The 0.2 mm line/space (1:1) etched pattern using AlSixNy and AlSixOy as embedded layer has been fabricated. Compared to the normal T (T<10%) AttPSM, the high T (T>10%) AttPSM assisted with Cr scattering bars could enhance the contrast of aerial image of 0.1 mm isolated line in clear-field mask. An equation was derived, the critical linewidth on mask for single resist line on wafer (CLMSLW) could be decided, enhancing the efficiency of lithography. With T=35% of 0.1 mm isolated line as embedded layer, the optimized width of scattering bars is 0.085 mm, distance between Cr scattering bar and 0.1 mm isolated line is 0.205 mm, and DOF is improved to 0.53 mm under the optimized quadrupole illumination with 0.60/0.21 (σoffset/σradius) in 248 nm lithography. According the 1999 SIA roadmap, the predicted production schedule of 0.10 and 0.07 mm design rule are in the year of 2005 and 2008, respectively. The normal and high T AttPSM are the important resolution enhancement techniques for 0.1 mm design rule in 193 nm lithography, and are of value in both academic study and production application.
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