Study on Nano-inprocess measurement of CMP defects on SiO2 filmed wafer surface

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Light scattering measurements are performed for defects on SiO_2 filmed wafer such as microscratches and PSL (Poly Styrene Latex) particles using the automated 3-D light scattering measurement system originally developed. These microscratches made by FIB (focused ion beam) process are used as equivalent of CMP (Chemical Mechanical Polishing) scratch defects. Several experiments are carried out with these defects that have different sizes.Main results of this study are summarized as follows,(1) CMP defect detection schemes by using numerical analysis based on BEM (Boundary Element Method) have been proposed. Depths and widths of defect are separately obtained by the scattered light intensity distribution. It is shown that the killer defects can be easily categorized in the defect classification map.(2) microscratchs with depth of 30 to 120 nm and width of 250 to 600 nm are made on SiO_2 film surface (film thickness, 0.5 μm) by FIB process. The scattering light from these defects has hig … More h intensity not in the normal but in the backward region for Brewster's angle (55.6 degree) incidence. Besides, the scattering light intensity with s-polarized illumination is higher than with p-polarized one.(3) However, for p-polarized illumination, scattered light from scratches changes sensitively with only 30 nm depth differences of them. The deeper the depth of a scratch is the higher the scattered light intensity is detected. Therefore, it is possible to measureme depth of a scratch with high accuracy based on the scattering light intensity.(4) Scattered light intensity from scratches is not proportional to width of them. When the aspect ratio of depth to width is larger than 3, it is likely that the wider the width becomes, the lower the scattering light intensity is detected.(5) PSL (Poly Styrene Latex) particles on SiO_2 filmed wafer scatters s-polarized light sensitively. Even if the size difference of particles is of less than 100 nm, both the scattering patterns are distinguishable. Especially, the intensities in forward scattering for the size difference is remarkable, for example, the scattering intensity for the particle size of 200 nm is 5.5 times as high as 100 nm.(6) The distribution of the scattering intensity to the scattering angle has a peak at 55 degree for a PSL particle and 0 degree for a microscratch. This result makes it possible to distinguish both the defects. Less