Robot pre-positioning in a wafer processing system

DETAILED DESCRIPTION Synchronized, Conflict Resolving Schedulers An aspect of the present invention comprises a method for maximizing throughput and quality in a manufacturing system by scheduling events in the system in a periodic, predictable fashion which eliminates conflicts for system resources.
An example of such a manufacturing system comprises a series of process steps 1, .
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, N, which are performed consecutively on individual units of manufacture.
The individual process steps of the system are conducted in "modules", or "process chambers", and the series of steps is listed in a "recipe".
The manufacturing system also includes resources for transporting the units of manufacture between modules in the series; these resources may include robots.
Conflicts may result between processes in the system when separate modules demand a robot within a time span which is insufficient for the robot to service these modules.
Additionally, it is desirable to schedule the system in a manner which exhibits periodicity, so that events in the system are synchronized to occur at periodic, predictable intervals.
An embodiment of the present invention includes a technique of selectively scheduling delays in various steps of the manufacturing process in order to eliminate all such conflicts, as well enforce periodicity, without degrading throughput or quality of the system.
An Example of Conflict-Resolving Synchronization: Wafer Cluster Tools An example of the type of manufacturing system described above is a wafer cluster tool.
In a wafer cluster tool the modules comprise process chambers, which are organized around a group of wafer transporting resources, or robots, to perform a sequence of process steps on the wafer.
A wafer enters and exits the tool through a buffer called a load port.
Once a robot retrieves a wafer from a load port, the wafer is transported sequentially through the series of modules specified in a recipe.
The time period defined by a wafer's entrance to a module and the wafer's exit from the module is referred to as a module process time