Study On Desorption Mechanism Of Inhibitors On Copper Surface And Its Post-CMP Cleaning

With the gradual development of integrated circuits,the feature sizes of devices are required to be continuously reduced,aluminum and its alloys have been unable to accommodate this change.Copper has completely replaced aluminum as the preferred deep submicron IC metal wiring material due to its excellent properties,such as lower resistivity,RC delay and superior electromigration resistance.At present,chemical mechanical planarization(CMP)is considered to be the most effective method for both global and local planarization requirements,it has been widely used in the dual damascene embedded processes in multilayer copper wiring.However,surface defects and contaminations will be introduced on the wafer surface due to interfacial chemical reactions and abrasive particles,especially organic contaminations represented by corrosion inhibitors,which can form a film to prevent the cleaning solution from contacting the wafer surface.Therefore,it is very important to understand the adsorption and desorption mechanism of inhibitors on copper surface for post-CMP cleaning technology.In this paper,the mechanism of the adsorption and passivation of inhibitors BTA and TAZ on the surface of copper blanket wafer was first studied by comparative experiment.Contact angle,electrochemical impedance spectroscopy(EIS)and X-ray photoelectron spectroscopy(XPS)were tested according to the adsorption characteristics of the two inhibitors under the same environment and different copper surface states.The theoretical results are consistent with the experimental results,and the relationship between the adsorption behavior of inhibitor and the oxide content on copper surface was obtained.It was found that BTA strongly adsorbed on the copper surface treated with citric acid(Cu₂O layer),while TAZ strongly adsorbed on the copper surface treated with citric acid+H₂O₂(Cu O and Cu(OH)₂layer),which proved that the adsorption difficulty of the two inhibitors on the copper surface depends on the content of monovalent copper and divalent copper.This is of great significance to the selection of different inhibitors during polishing.This paper also focuses on the research of post-CMP cleaning solution for copper.The effects of different concentrations of chelating agents and surfactants on the removal of BTA and TAZ were studied,and the effectiveness of each component in the cleaning process was analyzed.Combined with the molecular dynamics calculation,the action mechanism of cleaning solution components was revealed by experimental characterization.In addition,the optimal composition of the new alkaline cleaning solution was determined.Finally,it was found that the combination of 200 ppm FA/O II,200 ppm arginine and 1800 ppm Triton X-100 cleaning solution can effectively remove BTA and other micro defects.The 25 ppm EDTA and 600 ppm LABSA have the most significant effect on TAZ removal.Finally,by adjusting the p H value of the combined cleaning solution,the effect of different p H values on the TAZ removal effect was studied.When the p H value of the cleaning solution was 10.6,the cleaning performance of TAZ was excellent.At the same time,the experiment proves that the surfactant has a certain corrosion inhibition performance,and also helpful to smooth the wafer surface during the post-cleaning process.