Tianbao Du

Mechanism of Copper Removal during CMP in Acidic H 2 O 2 Slurry

Chemical mechanical polishing of copper was performed using as oxidizer and alumina particles as abrasives. Electrochemical techniques were used to investigate the dissolution/passivation behavior of high-purity Cu disk under static and dynamic conditions at pH 4 with varying concentrations. Changes in the surface chemistry of the statically etched Cu disk were investigated using X-ray photoelectron spectroscopy. The Cu removal rate reached a maximum at 1% concentration and decreased with a further increase in concentration. The static etch rate showed the same trend. The etched surface morphology indicates that the removal of copper is primarily the result of electrochemical dissolution of copper at low concentrations. However, at increased concentrations, the copper oxidation rate increases, resulting in a change in the Cu removal mechanism to mechanical abrasion of the oxidized surface.

Electrochemical characterization of copper chemical mechanical polishing

Chemical mechanical polishing (CMP) of copper was performed using H2O2 as oxidizer and alumina particles as abrasives. The interaction between the Cu surface and the slurry was investigated by potentiodynamic measurements taken during the polishing process as well as under static conditions. The Cu removal rate reached a maximum at 1% H2O2 concentration, and decreased with a further increase in H2O2 concentration. The static etch rate showed the same trend. Atomic force microscopic measurements were performed on both the etched surface and polished surface. It was shown that the surface roughness of the polished surface increased as the H2O2 concentration increased. This can be explained by changes in the structure of the passivating layer and the dominating role of the dynamic repassivation during polishing.

Polishing mechanism of tantalum films by SiO 2 particles

Dishing and erosion are major problems in conventional chemical mechanical planarization of copper/barrier layers. Understanding the polishing mechanism of the different materials involved can assist in providing a solution to these issues. Chemical mechanical polishing of tantalum was performed using alumina and silica particles dispersed in deionized water at pH 6. Tantalum shows a higher removal rate in silica slurry compared to alumina slurry. To examine the polishing mechanism of tantalum in silica slurry, the surface structure of the film was investigated by X-ray photoelectron spectroscopy (XPS). Various electrochemical techniques were used to characterize the surface film formation, dissolution and the interaction between silica particles and tantalum film. XPS and electrochemical results indicate that tantalum film may react with silica particles to form Ta-O-Si bonds on the surface. The mechanical tearing of Ta-O-Si bonds leads to the removal of Ta2O5 as a lump, resulting in higher removal rates of tantalum in silica slurry.

Role of oxidizer in the chemical mechanical planarization of the Ti/TiN barrier layer

The electrochemical parameters controlling the polishing rates of Ti and TiN are investigated. In this paper, alumina containing slurry was studied at pH 4 with 5% H2O2 as the oxidizer. Passive film formation on the surface during chemical mechanical polishing (CMP) plays an important role. To understand the oxide growth mechanism and the surface chemistry, X-ray photoelectron spectroscopy was performed. It was found that in the absence of an oxidizer, the removal of Ti and TiN is mainly due to mechanical abrasion of oxide layer or metal layer. However, in the presence of 5% H2O2 as the oxidizer, different removal behavior was observed for Ti and TiN. The removal mechanism of Ti during CMP is mainly due to mechanical abrasion of the oxide layer whereas for TiN it could be attributed to the formation of metastable soluble peroxide complexes.

Effect of Hydrogen Peroxide on Oxidation of Copper in CMP Slurries Containing Glycine and Cu Sulfate

This study compares the oxidative dissolution, passivation, and polishing behavior of copper chemical mechanical polishing in the presence of hydrogen peroxide, glycine and copper sulfate. High purity discs were used to study the dissolution and oxidation kinetics under static and dynamic conditions at pH 4 with varying H 2 O 2 concentrations. Changes in surface chemistry of the statically etched copper-disc were investigated using X-ray photoelectron spectroscopy (XPS). With the addition of glycine and copper sulfate to the slurry, the copper removal rates increased significantly and the maximum removal rate shifted to a H2O2 concentration of 3%. Electrochemical investigation indicates an enhanced dissolution of copper, which might be due to the strong catalytic activity of Cu(II)-glycine complexes in decomposing H 2 O 2 to yield hydroxyl radicals. XPS results suggest that the passivation at higher H 2 O 2 concentrations in the presence of glycine and copper sulfate is provided by the OH radicals adsorbed on Cu surface.

The pH Effect On Chemical Mechanical Planarization Of Copper

This study explores the effect of pH on the chemical mechanical polishing (CMP) characteristics of copper in H 2 O 2 and KIO 3 based slurries under various dynamic and static conditions. High purity copper disc was used to study the dissolution and oxidation kinetics at various pH (2 to 10) with 5% H 2 O 2 or 0.1M KIO 3 . Electrochemical techniques were used to investigate the dissolution/passivation behavior of Cu. The affected surface layers of the statically etched Cu-disc were investigated using X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In 5% H 2 O 2 , the Cu removal rate decreases with an increase in pH and reaches minimum at pH 6, and then increases under alkaline conditions. XPS results indicate that the surface oxide formed at various pH values was responsible for this CMP trend. However, with 0.1M KIO 3 , the CMP removal rates were found to be lower at pH 2. The maximum was observed at pH 4, then the removal rate decreased with the increase of pH. The lower value of removal rate at pH2 was due to the fast interaction between Cu and KIO 3 and the precipitation of CuI on the pad, which makes the pad glassy, resulting in lowered removal rates. This was confirmed by XPS measurements. The decreased CMP removal rates when the pH is higher than 4 might be due to the weaker oxidation power of KIO 3 with the increase of pH.