Stöckgen, Uwe; Wehner, Susanne; Preuße, Axel; Heinrich, Jens; Groschopf, Johannes (AMD Fab 36 LLC & Co. KG, Wilschdorfer Landstr. 101, MS F36/I22-CM, D-01109 Dresden, Germany)
The demand for process control capability at every wafer radius is growing with the use of larger wafers. Several equipment manufacturers have developed zone control capabilities for deposition processes and CMP. However, there are always characteristic radii with more control capability and such with less. For two subsequent processes, this could mean areas of less capability for one process can be compensated by the other, but the opposite can be challenging. For a process chain from copper ECP to CMP, the major parameter is the copper profile. The most common target is a flat profile in both processes. However, most processes have the center point of their capabilities not exactly there, but rather at a center-thick or edge-thick profile. Using a flat profile would limit the possible process window to react to variations of the previous and of the current process. The number of die at risk is unevenly distributed along wafer radius. However, endpoint detection is easiest in wafer center and more challenging towards wafer edge. A solution is to clear structures last in wafer center. With multi-zone control in ECP and CMP, there are two possibilities: to polish center-slow or to deposit center-thick, but the optimal solution is an integrated one that keeps both processes within their window for all zones.