The Copper Corrosion and Sulfur Contamination Generated by a Three-Step Copper Chemical-Mechanical Polishing Process
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0914-F09-10
The Copper Corrosion and Sulfur Contamination Generated by a Three-Step Copper Chemical-Mechanical Polishing Process
Chun-Ping Liu1, Yen-Shih Ho2, Tien-Chen Hu3, and Bae-Heng Tseng1 1
Institute of Materials Science and Engineering, National Sun Yat-Sen University, Kaohsiung, 804, Taiwan 2
Department of Electrical Engineering, Kaohsiung University of Applied Sciences, Kaohsiung, 807, Taiwan 3
Institute of Engineering Management, National Chen Kung University, Tainan, 701, Taiwan
ABSTRACT This article shows the root cause of Cu corrosion and sulfur contamination due sulfite vapor reflow through drainpipe of load cup to the original three-step Cu CMP equipment. Since there is quite a large amount of Cu to be removed, the sulfite concentration in wastewater taken from drainpipe of load cup and platen was 32 ppb and 272 ppb, respectively. This is consistent with the defect maps and counts of blanket wafers after polishing in the original three-step Cu CMP equipment. Now, we provide a solution by modifying the arrangement of the drainpipe in original three-step Cu CMP equipment. The sulfite concentration in drainpipe of load cup was decreased to 0.9 ppb. The results of defect maps and counts after polishing on modified three-step Cu CMP equipment are obvious improvement. This is an effective implementation for reduction the defects of Cu corrosion and sulfur contamination from long-term observations. INTRODUCTION In order to reduce interconnect RC delay which in turn will improve the overall device speed, aluminum (Al) interconnects are being replaced with copper (Cu) interconnects in recent years [1]. There are several methods to deposit Cu film, like CVD, sputtering, evaporation, and electrochemical deposition/plating (ECD/ECP). There are some advantages of ECD/ECP: low cost, high deposition rate, low temperature, good gap-fill capability, and high quality of Cu film [2]. Cu ECD/ECP has become the standard process
which be used for sub-micro trench/via filling in advanced Cu interconnect applications. The dual damascene technique and chemical mechanical polishing (CMP) process are employed to fabricate the Cu interconnections [3]. A high yielding Cu damascene process requires defect-free Cu surfaces after Cu polishing. Several yield-limiting defects that appear at the post-CMP Cu wafer surface are: dishing and erosion, metallic residual, scratching on metal and/or dielectric surface, and corrosion, etc.. Some of the defects that appear at the copper CMP actually come from previous process steps, so the right inspection and an understanding of the failure mechanisms allow processes to be modified to reduce the defect levels and improve entire process modules [4]. In this study, we focus on understanding the root cause of Cu corrosion and sulfur contamination generated by a three-step Cu CMP process. Our experiments show high sulfite concentration in wastewater of drainpipe due to large amount of electroplated Cu polished by a three-step copper CMP. Furthermore, the improvement in the arrangement of dr
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