Measurement of residual thickness using scatterometry

Abstract

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

Nanoimprinting lithography on 200mm wafers for optical applications

“…Therefore, it should be possible to improve this distribution by improving stamp manufacturing processes. Nevertheless, this relation between the CD and hr values is no more verified for H 0 /H min ratios smaller than 1.73, indicating that such distribution is not only related to stamp design but also related to poor imprint quality [9,10].…”

In-line etching process control using dynamic scatterometry

“…H CD α Figure 7. grating shape modeling with 3 parameters Simulated movie Using our MMFE engine, 4 we simulate an "ellipsometric movie" of 100 frames (the process control lasts 10s and we use 10 frames per second). During this movie, the values of the three parameters are supposed to vary as described in the figure 8 : Figure 8.…”

Physical characterization of nanoimprinted polymer nanostructures using visible light angular scatterometry

“…Previously, spectral scatterometry has been applied to measure the residue thickness of imprinted microscale and sub-m patterns. 11 Other assessment shows that spectral scatterometry faces increasing challenges, such as decreasing sensitivity with CDs Ͻ20 nm ͑Ref. 6͒.…”