Characterization of charging in CD-SEM for 90-nm metrology and beyond

Abstract

Three parameters, measurement times, charging distances, and charging area, are studied with respect to measurement of the local charging effect. We found that the effects of measurement times and charging distances to the local charging is under observation limit and the measured CD deviation is very small. However, the charging area is found to be the most dominant parameter for local charging. A 7-nm CD deviation from this local charging is observed. After the root cause of the local charging is understood and controlled, we use an extra charging area at the opposite side of the measurement site to compensate for the charging effect. The SEM image and CD deviation are greatly improved after this compensation. At last, a novel measurement algorithm is introduced to deal with the actual OPE evaluation. From simulation, the net Coulomb force experienced during the measurement is greatly reduced with the new algorithm compared with that used in the normal measurement sequence. The comparison of the global charging and local charging effects is also discussed in this report.

Elastic constants and dimensions of imprinted polymeric nanolines determined from Brillouin light scattering

“…Information on the cross-sectional geometry was also sought from FESEM of a cleaved section of the specimen, but this measurement was unsuccessful because of apparent plastic deformation of the nanolines during cleaving and more severe effects of charge accumulation on the image. Similar problems with charge accumulation in SEM measurements of nanopatterned polymers are commonly encountered by other researchers [12]. Even in the absence of charging effects, accurate determination of the dimensions and shape of nanopatterned polymers with SEM is a challenging multiparameter problem [13].…”

Research and optimization of electronic charge phenomena on CDSEM imaging of binary photomask

“…After experimenting with several methods, we discovered that spluttering plasma of a mixture of gas onto the photomask can eliminate these electronic charge phenomena with minimum adverse effect instantly and that this photomask is more resistant towards charging. [2] When this sample was viewed under SEM, we observed severer shifting in live view possibly caused by charging on the surface of the mask interact with electron beam from source causing deflections of the beam. [2] This shifting not only cause the image to be blurry but also shifted the beam location on the mask, thus not being able to capture the desired pattern within the designated field of view.…”

“…[2] When this sample was viewed under SEM, we observed severer shifting in live view possibly caused by charging on the surface of the mask interact with electron beam from source causing deflections of the beam. [2] This shifting not only cause the image to be blurry but also shifted the beam location on the mask, thus not being able to capture the desired pattern within the designated field of view. In order to collect accurate and repeatable results from SEM measurement, images are required to be in focus, sharp and clear edge like the image show in Fig 2c . We also noticed that some mask shows a deviation in CD-SEM result after irritation under close approximation to The CD deviation for larger designs like pattern 16 is more obvious than that of smaller patter.…”

“…Images formed during SEM examination are blurry, line edge is widening due to the electronic charge on the photomask interacting with electron beams from SEM, the measurement result is inaccurate and not usable. [2] In this work, we investigate these phenomena and search for methods to reduce such kind of residual charges and their effect on SEM imaging.…”

Homogenization mechanism of the residual surface potential of insulating specimens under electron beam irradiation

“…However, residual charges from previous observations may introduce errors in the inspection of an insulating specimen utilizing the charging effects. In addition, the build-up of charges may affect measurement accuracy and cause pattern placement errors in recent critical dimension SEM and electron beam lithography [18][19][20][21].…”