大口径Siウエハ表面形状の計測評価技術に関する研究 : —第1報：ウェーブレット変換を用いたノイズ除去手法の開発—

概要

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In recent semiconductor industry, production and evaluation of ever flatter, thinner and larger Si wafer are required to fulfill the demands in high integration and cost reduction. However, uncertainty in measurement of wafer profile is encountered as a severe problem because the resolution required for analysis of wafer flatness is reaching the limits of available instrument. Thus, the measured profile data always incorporate a certain degree of noise and this noise component behaves to bias the outputs of wafer profile such as SFQR (Site Frontsite least-sQuares focal plane site Range), GBIR (Global Backside Ideal Range), bow, warp and etc.. In order to precisely evaluate the wafer geometry, it is essential to remove the noise from the measured data. Described in this paper is design and development of digital filters for denoising by use of wavelet transform. Compared to the conventional low-pass filters, the developed filter not only provides better performance of decomposition in the spatial frequency domain, but also offers the new capability of filtering in amplitude components.