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4.3.3 Consistent Wafer Representation

Tool specialization has led to expert tools dealing with isolated aspects of a wafer only. For example, the SAMPLE [ONStex2html_wrap870080] [Ele91] and PROMIS [SS95] etch and deposition modules operate only on the wafer geometry, causing inconsistencies between the grid-based dopant distribution data and the geometry boundary information, as they do not take care of reconciling the two after updating the geometrygif. To ensure a correct, consistent, and concise wafer representation after each process simulation step, data merge operations have to be performed to reflect geometry alterations in the grid structure, to purge superfluous grid elements, and to merge dopant information from before and after a simulator call (cf. Figure 4.4). Figure 4.8 sketches the data flow in the case of a PROMIS etch operation.

 figure903
Figure 4.8:   Data flow for creating a consistent wafer model after a PROMIS etch operation.

Starting from the geometry information present in the PIF wafer state model, the tool call generates the new wafer geometry reflecting the effects of the simulated etch or deposition process. In the subsequent merge and update operation, segment grids on all segments of the geometry are checked and adjusted to conform with their respective segmentsgif. After the merge and grid-update operation, a complete model of the wafer is available for further processing. For the general case, Figure 4.9 shows the basic flow graph for updating the PIF wafer state representation after termination of a tool.

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Christoph Pichler
Thu Mar 13 14:30:47 MET 1997