Nanoimprint lithography (NIL) processes have the characteristic that a residual resist layer is always present between the nanoimprinted features. This residual resist layer must be removed to obtain usable resist masks for pattern transfer. As this resist layer is removed using oxygen-based plasma processes, the residual thickness nonuniformity translates into feature width dispersion. Thus, the uniformity of this residual thickness after imprint remains an important issue for nanoimprint lithography and a reliable metrology procedure is required for. At present, the standard measurement method is based on scanning electron microscopy (SEM) cross section, which is destructive, time consuming, and may sometimes provide only moderate accuracy. The work presented here will assess and show the interest of scatterometry, which is a nondestructive optical method of metrology that can be easily applied to NIL. This measurement procedure exhibits very good accuracy on the two-dimensional-feature geometry determination, especially for residual thickness. Scatterometry also eases time-consuming studies like residual thickness measurement at the local scale or at the wafer scale. Moreover, this article shows that the imprint uniformity studies provide very interesting information on the mold deformation
With the continuous shrinkage of dimensions in the semiconductor industry, the measurement uncertainty is becoming one of the major component that have to be controlled in order to guarantee sufficient production yield for the next technological nodes production. Thus, CD-SEM and Scatterometry techniques have to face new challenges in term of accuracy and subsequently new challenges in measurement uncertainty that were not really taken into account at the origin of their introduction in production. In this paper, we will present and discuss results about the accuracy requirements related to key applications for advanced technological nodes production. Thus, we will present results related to OPC model precision improvement by using suitable reference metrology model based on the 3D-AFM technique use. An interesting study related to 193 resist shrinkage during CD-SEM measurement will be also presented and therefore the impact on measurement uncertainty will be discussed. Finally we will conclude this paper by showing the potential industrial benefits to use a simple but relevant 3D-AFM reference metrology model use into the semiconductor production environment.
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