Lithography Rework Reduction and Improved Process Control using AIM Targets on Aluminum Layers in the High Volume Production of 110nm DRAM Devices

摘要

AIM grating targets were optimized and implemented on the metal 2 Aluminum layer in high volume production of 110nm DRAM devices. Grating target structures are intrinsically more compatible with Aluminum process design rules, allowing overlay target optimization to better fit the process and better cope with the large grain structure of the Aluminum layer. With the implementation of AIM overlay targets we were able to achieve tighter control of the Aluminum patterning, we also achieved smaller overlay residuals, better matching between post litho and post etch measurements, better modeling and less rework. Above all, AIM targets improve the overlay metrology tool capability and provide a better tool-to-tool matching performance.