Full Image Process Control

The next step is to determine a tolerance matrix. This is the maximum global or local deviation firom the criterion image that will still result in acceptable product. This step requires expert inputs Ifom the process engineer, who has the most intimate knowledge of the process, and knows which site points are most thermally critical to product quality. Since the tolerance matrix exists only in software, it is 

Next is the implementation of controls. The number of control elements deployed usually governs the tightness with which control of the thermal map can be accomplished—but also, to a great extent, the cost of the control system. Here also, on-line IR monitoring of an existing process can help determine what additional control elements are necessary to bring the product within acceptability limits. 

The next step, and a most significant one, is the development and implementation of the algorithm that characterizes the effect of each of the control elements on the overall thermal map of the process. While this algorithm can be calculated theoretically, it is more practically accomplished through statistical analysis of actual on-site experimental measurements. 

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Figure 10.8 Full Image process control using a line scanner and multiple zones (a) before implementation of full image process control (b) after implementation of full image process control (courtesy of FUR Systems, Inc.)-...

Full image process control using a line scanner and... 

The Shape Analyzer is a scientific instrument which is used to analyze the shape, size, and texture of objects. The item for analysis may be the object itself, its photograph, optical or electron micrograph, etc. The shape-size analysis is achieved by converting the profile to a set of shape and size descriptors which are complete, unequivocal and invariant. The texture analysis converts the full image of the object into a set of textural descriptors which are unequivocal, complete and invariant. These shape, size and texture descriptors can be used in research, in quality control, in process control and specifications. Additional details are given in Table 1 and the Appendix. 

In all but the most severe cases, it is likely that appropriate adjustment of hotplate bake processes before and after imaging will be sufficient to create reliable process down to about lpm minimum feature sizes. In addition full utilization of process control capabilities of automated in-line wafer development techniques must be made. 

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