Polishing and Cleaning of Low K Dielectric Material for ild and Damascene
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POLISHING AND CLEANING OF LOW K DIELECTRIC MATERIAL FOR ILD AND DAMASCENE Yuchun Wang, Rajeev Bajaj, Yongsik Moon, David Mai, Kapila Wijekoon, Yufei Chen, Fritz Redeker, CMP Division, Applied Materials, Santa Clara, CA; Dian Sugiarto, Li-Qun Xia, CVD Low K Division, Applied Materials, Santa Clara, CA Summary This paper describes CMP challenges in development of copper-low k process technology. As copper/oxide or copper/FSG backend schemes are being implemented successfully in early manufacturing, development focus has shifted to Cu/OSG (organo-silicate glass) integration development. Cu-OSG presents unique challenges with CMP integration, as these films tend to have much lower hardness than silicon dioxide. Significant process challenges have to be overcome prior to successfully implementing CMP process which does not mechanically damage the softer films and at the same time can achieve planarization requirements expected from CMP process. In addition, the OSG films tend to be hydrophobic leading to a need for developing improved cleaning processes/consumables. It was determined that Applied Materials ElectraPolishTM barrier slurry is extendable to OSG films. Good removal rate and removal profile can be achieved with ElectraPolishTM slurry. A proprietary cleaning solution reduced defect counts by 2 orders of magnitude as detected by SurfScan SS6200 on blanket OSG wafers. The same cleaning solution can be applied to copper/low-k patterned damascene wafers to clean both copper and dielectric surface. Polished OSG films have RMS roughness less than 2 angstroms and copper surface roughness about 5 angstroms with good surface finish. Blanket and patterned wafer results are presented to demonstrate final capability. Future directions for process enhancement are suggested. 1. Introduction Black DiamondTM (or "BD" further in the text of this article) is Applied Materials CVD low k film which has been developed for dielectric application in Cu damascene structure. With k value of 2.9 and below, Black DiamondTM is replacing TEOS to reduce RC delay. There is a need to develop polishing capability for Black DiamondTM, both for copper damascene as well as interlayer dielectric (ILD) planarization in subtractive integration. Black DiamondTM belongs to carbon (or hydrocarbon) doped silicon oxide, or organo-silicate glass (OSG) family. The moiety of carbon and hydrocarbon makes it hydrophobic, which is challenging for both polishing and cleaning. In this paper we report Black DiamondTM polishing and cleaning as ILD and in Cu damascene structure. 2. Polishing and cleaning conditions All the wafers were polished on Applied Materials Mirra polisher with ElectraPolishTM slurry. 4" diamond-conditioning disk by 3M and IC1000 polyurethane pads by Rodel were used
M7.3.1
for main polishing. Politex soft pads from Rodel were used for buffing. Two cleaning solutions were tested for post CMP cleaning. The two cleaning solutions have different wettability characteristics with low-k film. Optiprobe (Thermawave) 121 point diameter scan, with
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