Digital image comparison

Defect detection on a wafer after CMP can be accomplished by a laser scanning technique and/or by a digital image comparison technique. Both types of tools are widely used in the industry. However, neither is sufficient... 

Another method of defect detection is digital image comparison. The tool works by comparing a pixel of one die to that of the preceding and... 

Fig. 10. Defeclivity observed by the digital image comparison method (a) wafer map showing color variation problem after CMP, and (b) the same wafer using a modified computer algorithm.

Chilvers, M. A. and O Callaghan, C., Analysis of ciliary beat pattern and beat frequency using digital high speed imaging comparison with the photomultiplier and photodiode methods, Thorax, 55, 314-317, 2000. 

Figure 1 Comparison between a simple random walk model of particle deposition and an electrochemically deposited copper fractal. (A) 2000 random walks on a square grid, (B) the digitized image (256 x 256 pixels) of copper electrodeposited from 0.75 mol I copper sulfate and 1 moll sulfuric acid in an 11 cm Whatman 541 filter paper at 5V. Both fractals are displayed using Lotus for Windows.

The coordinates system used in the field of the digital image processing (Jahne 1995) is represented in Figure 5.1. This particular coordinate system is inverted in comparison with the usual Cartesian coordinate system we are used to working with. The origin of the axis is situated in the upper left corner. 

The pictures of sample 3, which differs from sample 1 by an increased residence time, are also consistent with an increased mechanical action. It is clear however that the comparison of intermediate situations between themselves will be more difficult, unless quantitative data are derived from the pictures. Work is still under progress to quantify the particles desagglomeradon level (use of digitized image processing) and to estimate the interagglomerate gel phase density (use of Z contrast imaging mode). 

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