AFM application on the topography study of stack cell DRAM processes

The stacked cell design of DRAM processes for lithography considerations has suffered severe topography step-height and unsmooth surface issues. In addition, the stability and uniformity control of thin film processes on the backend process can affect lithography process to a great extent. In this study, the AFM (atomic force microscope) has been used to study topography issues of a typical DRAM process. The detailed information concerning the topography step- height, flow angle, local unsmooth surface, etc., have been clearly identified. These studies provide useful information for future process development and improvement.