Fundamentals of Post-CMP Cleaning
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0991-C02-01
Fundamentals of Post-CMP Cleaning Jin-Goo Park, and Tae-Gon Kim Division of Materials and Chemical Engineering, Hanyang University, Ansan, 426-791, Korea, Republic of ABSTRACT Post CMP cleaning is necessary for contaminant removal after CMP process. The zeta potential of slurry particle and substrate has been considered to be a critical factor in terms of particle adhesion and removal. The fundamental research such as the calculation and measurement of adhesion forces between slurry particle and wafer surfaces can enhance the understanding of cleaning mechanism and development of cleaning process. The presence of more than two different materials during CMP introduces new defects at the materials interface, corrosion and severe scratches. Device specific chemistry and cleaning process should be introduced and developed for future and current CMP. The highest particle removal efficiency is observed when using cleaning solutions that yields the lowest adhesion force. The effect of frictional and adhesion forces attributed to slurry particles on the quality of Cu surfaces was experimentally investigated during metal CMP process. The magnitude of the adsorption of the organic acid on the slurry particle surfaces can have a significant effect on the frictional behavior as well as the adhesion force. Higher particle adhesion forces resulted in higher friction and might induce defects such as particle contamination and scratches on the polished surface after polishing. The magnitude of particle adhesion force on wafer surfaces in slurries can be directly related to the frictional forces and polished surface quality during CMP process. As low k and poly or bare silicon polishing introduced in fabrication process, the hydrophobicity of these surfaces could affect the defects after polishing. The control of wettability during and after polishing becomes more important in reducing the defects. The organic particles are major defects during metal and poly silicon CMP which may be caused by the surface reaction of organic sources with surfaces. INTRODUCTION With the decrease of a feature size, planarization of both front and back end layers by the CMP process now seems an absolute must for IC fabrication technologies smaller than 0.5 µm [1]. Unfortunately, abrasive particles and metallic contaminations and a damaged layer at the top surface could be generated during CMP process [2]. These particles essentially originate from the used slurries such as SiO2, Al2O3 and CeO2 but also from the polished surface materials and a lesser extent from the polishing equipments. These particles can be physically attached on the wafer surface or even in the worst case partially embedded on the top layer due to the mechanical pressure exerted by the pad. CMP process also leaves a metallic contamination typically in the 1011~1012 atoms/cm2 range. These contaminants arise from the abraded metal lines, metal ions in slurries, and the mechanical environment of the polishers. In front-end applications such as a STI process, the control
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