13 March 2012 Spacer process and alignment assessment for SADP process
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Abstract
Self Aligned Double Patterning (SADP) is now widely accepted as a viable technology for the further extension of 193nm immersion lithography towards the 22nm /18nm technology nodes. SADP was primary introduced for the manufacturing of flash memory due to its 1D design geometry. However, SADP is now becoming a main stream technology for advanced technology nodes for logic product. SADP results in alignment marks with reduced image contrast after completion of spacer patterning. Consequently there is an elevated risk that the alignment performance of the cut lithography layer on the spacer [1] may be negatively impacted. Initial studies indicate that it may be necessary to consider new mark designs. In this paper, we will evaluate different types of SADP processes with the alignment system of the Nikon S620D and S621D immersion scanner. We will discuss the performances and the differences observed due to the SADP materials. Included in this study is an intensive characterization of the morphology of the spacer after SADP process. We will use for this a 3D-AFM from Insight, and characterize the spacer profile of the spacer. Using a standard AFM microscope, we can characterize the surface roughness in the inner and the outer part of the wafer. The self aligned spacer process results in asymmetric spacers. Two types of surface (inside and outside) of the spacer are formed. The impact of this asymmetry is also assessed. The roughness difference, between the two parts, will play an important roll in the alignment contrast.
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L. Lattard, L. Lattard, M. McCallum, M. McCallum, R. Morton, R. Morton, T. Fujiwara, T. Fujiwara, K. Makino, K. Makino, A. Tokui, A. Tokui, N. Takahashi, N. Takahashi, S. Sasamoto, S. Sasamoto, } "Spacer process and alignment assessment for SADP process", Proc. SPIE 8326, Optical Microlithography XXV, 832604 (13 March 2012); doi: 10.1117/12.916362; https://doi.org/10.1117/12.916362
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