By M. David Levenson
WaferNews Technical Editor
KLA-Tencor has unveiled a new set of automated tools for process window construction and analysis. The Process Window Monitor series automates the construction of process windows based on focus exposure matrices analyzed using KLA-Tencor CD or optical CD metrology tools.
The increased convenience allows production fabs to locate and optimize shifting process windows with minimal delay or disruption. The PWM system facilitates offloading metrology tasks from exposure tools to CD measurement tools, thus increasing production tool availability.
According to Mike Slessor, product marketing manager for lithography module solutions, the PWM system can detect incipient problems like focus tilt or exposure inhomogenities before yields drop noticeably and can suggest corrective action. Litho cells can be matched and the most productive tool for a given task on a given day can be identified. Data can also be downloaded into a Klarity ProDATA file for further analysis. All of that is reputed to result in dramatic savings in manpower and improved production.
KLA has also announced the availability of an etch modeling function for PROLITH lithography simulation tools. This “Etch for Lithographers” simulator captures the influence of the resist dimensions and profile on the pattern transfer process in two and three dimensions, according to Chris Mack, VP of the Finle Division of KLA-Tencor. The after etch process window can be determined for the first time using PROLITH. Since resist can be re-worked, but etched patterns cannot, the improved predictive power should help companies improve wafer disposition decisions and process understanding.
The new system works for single and multiple film stacks, but requires four parameters to be determined for each material and etch stage. It includes real-world effects such as undercutting shadowing and tapering but omits the etch process controls typical of simulators designed for etch engineers. By providing a connection between the litho and etch modules, this new tool may help mediate – or help escalate – disputes in the fab.