Design of Digital Filters for Si Wafer Surface Profile Measurement - Noise Reduction by Wavelet Transform -
Recently in semiconductor industry, production of ever flatter, thinner and larger silicon wafers are required to fulfill the demands of high-density packaging and cost reduction. In geometric evaluation of Si wafers, according to SEMI (Semiconductor Equipment and Materials International) standards, the required wafer flatness approaches to the 22 nanometers by year 2016 . For such application, uncertainty of measured data is encountered as a severe problem because high resolution instrument always incorporate a certain degree of noise. In order to precisely evaluate the wafer profile, it is essential to remove the noise from the measured data. Described in this paper is design and development of digital filters for denoising. Compared to the conventional low-pass filters, the developed filter by use of wavelet transform not only provides better performance of decomposition in the spatial frequency domain, but also offers the new capability of denoising in amplitude domain.
Jianhong Zhao, Masanori Kunieda, Guilin Yang and Xue-Ming Yuan
M. Ono et al., "Design of Digital Filters for Si Wafer Surface Profile Measurement - Noise Reduction by Wavelet Transform -", Key Engineering Materials, Vols. 447-448, pp. 544-548, 2010