Junichi Taguchi

Discrimination of clustered defects on wafers using statistical methods

This paper presents a method for discrimination of clustered defects. The histogram of the number of defects per die is approximated to several major distributions. As a result, we found that Poisson distribution is almost equivalent to real data. The advantage of this method is that accurate coordinates are not required. Therefore it can be applied for almost all tools regardless of their accuracy of coordinates.

New particle-inspection system for CMP-planarization-processed metal layers

With the application of chemical mechanical polishing (CMP), particles become the main defect mode among the various modes of defects. Therefore, particle control becomes increasingly important. For the effective particle control, we need to control not only the number of defects but also the size of defects. However, a conventional particle inspection system using laser scattering could not obtain the information of the accurate particle size. We have developed the new system which can obtain the information of accurate particle size by using image processing. The particle size measured by the new system well agrees with the size measured by SEM. With the new system, we can operate the killer particle control effectively.

Improvement of MRI image quality by a directional adaptive filter

In this paper, an image processing method for improving the quality of MRI images is proposed. The directions of various structural elements such as edges are extracted, and a directional adaptive filter is proposed as a one-dimensional smoothing process in the detected directions. The result of applying directional adaptive filtering to MRI images, along with reducing the noise while minimizing structural element degradations, is that the contrast of soft tissue regions can be improved. MRI images have the characteristic of providing high contrast for soft tissue regions, but do not provide very high resolution. Directional adaptive filters are investigated and are shown to be particularly effective for images that possess these qualities, and the MRI performance level is compared to that obtained on X-ray CT images.

Killer defects control on patterned wafers for the sub quarter micron interconnect formation process

Statistical yield modeling has become very practical and effective for defect control since CMP was first applied to the multilevel metallization process in order to achieve surface planarity. This paper presents a study of the defect size to be controlled for the sub-quarter micron interconnect formation process with CMP planarization by estimating the statistical model parameters from experimental data. First, the size distribution, F(x)=ax/sup b/, of defects on PVD processed wafers is obtained. Secondly, the defect sensitivity on sub-quarter micron line and space patterns is estimated. Thirdly, the killer probability during the interconnect formation process is calculated. Finally, we discuss the detection sensitivity of automatic inspection tools for patterned wafers to control killer defects for the sub-quarter micron interconnect formation process.