Persistent Link:
http://hdl.handle.net/10150/194903
Title:
Colloidal and Electrochemical Aspects of Copper-CMP
Author:
Sun, Yuxia
Issue Date:
2007
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Copper based interconnects with low dielectric constant layers are currently used to increase interconnect densities and reduce interconnect time delays in integrated circuits. The technology used to develop copper interconnects involves Chemical Mechanical Planarization (CMP) of copper films deposited on low-k layers (silica or silica based films), which is carried out using slurries containing abrasive particles. One issue using such a structure is copper contamination over dielectric layers (SiO2 film), if not reduced, this contamination will cause current leakage. In this study, the conditions conducive to copper contamination onto SiO2 films during Cu-CMP process were studied, and a post-CMP cleaning technique was discussed based on experimental results. It was found that the adsorption of copper onto a silica surface is kinetically fast (< 0.5 minute). The amount of copper absorbed is pH and concentration dependent and affected by presence of H2O2, complexing agents, and copper corrosion inhibitor Benzotrazole. Based on de-sorption results, DI water alone was unable to reduce adsorbed copper to an acceptable level, especially for adsorption that takes place at a higher pH condition. The addition of complex agent, citric acid, proved effective in suppressing copper adsorption onto oxide silica during polishing or post-CMP cleaning by forming stable copper-CA complexes. Surface Complexation Modeling was used to simulate copper adsorption isotherms and predict the copper contamination levels on SiO2 surfaces.Another issue with the application of copper CMP is its environmental impact. CMP is a costly process due to its huge consumption of pure water and slurry. Additionally, Cu-CMP processing generates a waste stream containing certain amounts of copper and abrasive slurry particles. In this study, the separation technique electrocoagulation was investigated to remove both copper and abrasive slurry particles simultaneously. For effluent containing ~40 ppm dissolved copper, it was found that ~90% dissolved copper was removed from the waste streams through electroplating and in-situ chemical precipitation. The amount of copper removed through plating is impacted by membrane surface charge, type/amount of complexing agents, and solid content in the slurry suspension. The slurry particles can be removed ~90% within 2 hours of EC through multiple mechanisms.
Type:
text; Electronic Dissertation
Keywords:
CMP; Cu-CMP; Electrocoagulation; Copper Contamination; CMP Waste Treatment; Surface Complexation Reactions
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Materials Science & Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Raghavan, Srini
Committee Chair:
Raghavan, Srini

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleColloidal and Electrochemical Aspects of Copper-CMPen_US
dc.creatorSun, Yuxiaen_US
dc.contributor.authorSun, Yuxiaen_US
dc.date.issued2007en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractCopper based interconnects with low dielectric constant layers are currently used to increase interconnect densities and reduce interconnect time delays in integrated circuits. The technology used to develop copper interconnects involves Chemical Mechanical Planarization (CMP) of copper films deposited on low-k layers (silica or silica based films), which is carried out using slurries containing abrasive particles. One issue using such a structure is copper contamination over dielectric layers (SiO2 film), if not reduced, this contamination will cause current leakage. In this study, the conditions conducive to copper contamination onto SiO2 films during Cu-CMP process were studied, and a post-CMP cleaning technique was discussed based on experimental results. It was found that the adsorption of copper onto a silica surface is kinetically fast (< 0.5 minute). The amount of copper absorbed is pH and concentration dependent and affected by presence of H2O2, complexing agents, and copper corrosion inhibitor Benzotrazole. Based on de-sorption results, DI water alone was unable to reduce adsorbed copper to an acceptable level, especially for adsorption that takes place at a higher pH condition. The addition of complex agent, citric acid, proved effective in suppressing copper adsorption onto oxide silica during polishing or post-CMP cleaning by forming stable copper-CA complexes. Surface Complexation Modeling was used to simulate copper adsorption isotherms and predict the copper contamination levels on SiO2 surfaces.Another issue with the application of copper CMP is its environmental impact. CMP is a costly process due to its huge consumption of pure water and slurry. Additionally, Cu-CMP processing generates a waste stream containing certain amounts of copper and abrasive slurry particles. In this study, the separation technique electrocoagulation was investigated to remove both copper and abrasive slurry particles simultaneously. For effluent containing ~40 ppm dissolved copper, it was found that ~90% dissolved copper was removed from the waste streams through electroplating and in-situ chemical precipitation. The amount of copper removed through plating is impacted by membrane surface charge, type/amount of complexing agents, and solid content in the slurry suspension. The slurry particles can be removed ~90% within 2 hours of EC through multiple mechanisms.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectCMPen_US
dc.subjectCu-CMPen_US
dc.subjectElectrocoagulationen_US
dc.subjectCopper Contaminationen_US
dc.subjectCMP Waste Treatmenten_US
dc.subjectSurface Complexation Reactionsen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineMaterials Science & Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRaghavan, Srinien_US
dc.contributor.chairRaghavan, Srinien_US
dc.contributor.committeememberSeraphin, Supapanen_US
dc.contributor.committeememberArnold, Robert G.en_US
dc.contributor.committeememberFarrell, Jimen_US
dc.identifier.proquest2457en_US
dc.identifier.oclc659749956en_US
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