Abstract
Change in the cross-sectional profile of a photoresist (PR) pattern due to shrinkage was evaluated to investigate the mechanism of electron beam-induced shrinkage. A scanning transmission electron microscope (STEM) was used to observe the cross-sectional profiles of PR lines after atomic-layer deposition of metal oxide and carbon deposition on the sample surface. A HfO2 thin layer enhanced the profile contrast in the STEM measurements without blurring the edge, which enabled the precise cross-sectional measurement of the PR patterns. We found interesting features associated with shrinkage from the detailed profile change obtained using this method, such as a rounding of the pattern top, a necking of the sidewall profile, a rounding of the foot in the pattern on the organic underlying layer, and voltage-independent sidewall shrinkage under a large electron beam dose. These behaviors along with the results from a Monte Carlo simulation are discussed. Consequently, these observations experimentally clarified that the elastic deformation effect and the impact of the secondary electrons emitted from the spaces around the pattern into the sidewall are important to interpret the change in the shape of the pattern induced by shrinkage.
Highlights
The impact of pattern-size deviation from the design value on the device performance is becoming more and more serious as large scale integration devices become more miniaturized.[1]
Three interesting features associated with the PR shrinkage can be identified from these results: the rounding of the top of the patterns, the regression of the bottom antireflective coating (BARC) layer, and the necking profile in the pattern shape, namely, the maximum sidewall recession at the middle height
The change in the crosssectional profile of the PR lines due to shrinkage was investigated in detail
Summary
The impact of pattern-size deviation from the design value on the device performance is becoming more and more serious as large scale integration devices become more miniaturized.[1]. As for the metrology of lithographic features, it is well known that photoresist (PR) materials shrink due to electron-beam (EB) irradiation during the acquisition of SEM images.[5,6,7] The “linewidth slimming” caused by the SEMinduced shrinkage has been an issue because it causes an error in the CD measurements of PR patterns This is especially serious in the case of ArF and most EUV photoresists because their base resins are sensitive to EB irradiation.[7] Lowering the acceleration voltage and/or decreasing the irradiation dose density of the EB are effective ways to reduce the damage itself due to the EB irradiation.[8,9,10] In addition, phenomenological methods for calculating the shrinkage amount of simple patterns, such as the lines and holes, have been developed.[11,12] The original CD before SEM
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