Standalone Platform Houses Integrated Metrology

Although integrated metrology (IM) is viewed as having great merits, undeniably it brings challenges with it. Those who favor standalone systems are convinced that IM is not yet good enough to control a process well, while those on the other side declare that the technology is ready. Short of making the jump into IM, the user has had no practical way to determine what the development state of that technology is, or whether IM would solve particular problems.

This may have become a moot point with the FMS flexible metrology system from Nanometrics Inc. (Milpitas, Calif.). The platform is a 300 mm standalone tool that is based on the company's IM modules. It is designed to allow the user to configure the tool as needed. Because it uses IM modules, it should be of great help to fabs that are considering migrating to an integrated strategy.

With this tool, the company has essentially created an integration platform for all its IM modules — spectroscopic reflectometry, laser profiler, conductive film measurement, universal defect inspection, OCD and ellipsometer.

For example, if someone wanted to do a wafer backside contamination inspection and film thickness measurement, it would be necessary to use two separate metrology tools. The FMS platform, however, allows the user to configure it with up to four identical or different metrology modules. In the case mentioned, the user could select a universal defect inspection module for particle defect measurement, and an ellipsometer to determine film thickness, thus combining the types of metrology that he requires, without the cost and complexity of getting multiple metrology systems, or having to go through a costly and lengthy integration process.

The flexible metrology system is user-configured and has its own stage. (Source: Nanometrics)

The platform offers a hybrid IM strategy by providing what essentially is a middle ground between the pros and cons of IM. The only thing the user seems to be giving up is that the IM module being used is not physically located on the process tool.

Because two of the system's four positions are external, the platform also supports an integrated strategy. If the user has an IM module on a CMP process tool and something happens to it, it is possible to swap the unit and continue doing the diagnostic testing on the broken unit on the FMS tool. The platform makes the value equation for integrated metrology greater, because now in a standalone tool the user has the same metrology, which can be mixed and matched.

The system can be used as an engineering station, and because it can house four modules, it becomes possible to ensure that things like system matching are aligned before recipes are transferred. If the user has a number of integrated tools in CMP, the platform can be used to test a program to determine how well recipes match and, without having the wafer leave the standalone tool, determine whether the recipe will work well when the time comes for it to be ported out to the integrated tools. The new platform provides a good bridge to IM.

According to the company, the platform should cost 25% less than a traditional high-volume 300 mm standalone offering.

For additional information on inspection, measurement and test, go to www.semiconductor.net/imt.