Cu Corrosion during Post-CMP Clean - Cause and Prevention

Abstract

Copper dual damascene is becoming the standard process for sub-quarter micron microelectronic interconnects. Photo-induced anodic corrosion could occur on a copper p-n junction sctructure during PCMP cleaning process and the prevention of such corrosion is critical for reducing defects and improving overall yield of copper integration. The electron/hole pairs are photo-generated in the p-n junction inducing potential difference. p+ diffused region has a built-in potential of 0.2~0.5 volts against n+ diffused region. Therefore, copper oxidation and etching happen on the p-side and copper re-deposition and growth are shown on the n-side. Tafel curve measurements can be used to provide accelerated corrosion rate data at certain voltage biases that can be charateristic of copper anodic corrosion. From the PCMP cleaning chemistry perspective, increasing copper inhibitor concentration and/or decreasing copper chelator levels are found to protect copper from anodic corrosion at voltage bias. In addition, using additional additives in the PCMP process can further reduce copper anodic corrosion in a PCMP environment.

Investigation of Co surface reaction by in situ measurement for chemical mechanical planarization and post-chemical mechanical planarization cleaning

“…Badawy et al reported the investigation of the oxidation state on a Co surface and suggested that an alkaline solution is preferred to suppress corrosion from the viewpoint of the surface oxidation state. 14,15) Although both acidic and alkaline types of slurry were reported with the various combinations of chelating agents and inhibitors in CMP [16][17][18][19][20] and post-CMP cleaning, [21][22][23][24] the best combination of chemicals has not been determined yet. In this report, we introduced the analysis of open circuit potential (OCP) monitoring to select an inhibitor for Co. OCP is utilized in CMP and post-CMP cleaning areas to see the surface reaction on Cu.…”

Post Cu CMP Cleaning of Polyurethane Pad Debris

“…Much of the previous work on post Cu CMP cleaning process focuses on the optimization of brush gap and contact kinetics during brush clean to enhance cleaning efficiency. 2,3 Addition of inhibitors, surfactants, complexing or chelating agents to post-CMP clean chemicals is also studied extensively [4][5][6] and has become the common practice in the clean chemical industry. In our previous studies, effects of pH and dilution ratio of clean chemical on the cleaning efficiency of PR/FM defects were investigated.…”