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2報：ウェーブレット変換を用いたノイズ除去手法の適用—

概要

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In this research, we have been developing the denoising method by use of wavelet transform. In previous report, this method was investigated by comparison with conventional low-pass filter and Fourier transform. It was concluded that wavelet transform was more effective for elimination of white noise and this method was capable of removing the noise not only in the frequency domain, but also in amplitude domain. In this report, the denoising method by use of wavelet transform is applied into evaluation of Si wafer profile data which is acquired by an actual measurement system. As the acquired data includes not only the white noise but also the inherent noise introduced by the measurement system itself, it is found that the proposed method of filtering white noise in both frequency and amplitude domains is insufficient to improve GBIR (Global Backside Ideal Range which is also equal to peak-to-valley). The cutoffs used in the proposed method are then fine-turned via least-square procedure. The results demonstrate the validation of newly designed filter in GBIR improvement.