Gao Baohong

An advanced alkaline slurry for barrier chemical mechanical planarization on patterned wafers

We have developed an alkaline barrier slurry (named FA/O slurry) for barrier removal and evaluated its chemical mechanical planarization (CMP) performance through comparison with a commercially developed barrier slurry. The FA/O slurry consists of colloidal silica, which is a complexing and an oxidizing agent, and does not have any inhibitors. It was found that the surface roughness of copper blanket wafers polished by the FA/O slurry was lower than the commercial barrier slurry, demonstrating that it leads to a better surface quality. In addition, the dishing and electrical tests also showed that the patterned wafers have a lower dishing value and sheet resistance as compared to the commercial barrier slurry. By comparison, the FA/O slurry demonstrates good planarization performance and can be used for barrier CMP.

Non-ionic surfactant on particles removal in post-CMP cleaning

The effect of a non-ionic surfactant on particles removal in post-CMP cleaning was investigated. By changing the concentration of the non-ionic surfactant, a series of experiments were performed on the 12 inch Cu pattern wafers in order to determine the best cleaning results. Then the effect of the surfactant on the reduction of defects and the removal of particles was discussed in this paper. What is more, the negative effect of a non-ionic surfactant was also discussed. Based on the experiment results, it is concluded that the non-ionic surfactant could cause good and ill effects at different concentrations in the post-CMP cleaning process. This understanding will serve as a guide to how much surfactant should be added in order to achieve excellent cleaning performance.

A new cleaning process combining non-ionic surfactant with diamond film electrochemical oxidation for polished silicon wafers

This paper presents a new cleaning process for particle and organic contaminants on polished silicon wafer surfaces. It combines a non-ionic surfactant with boron-doped diamond (BDD) film anode electrochemical oxidation. The non-ionic surfactant is used to remove particles on the polished wafers surface, because it can form a protective film on the surface, which makes particles easy to remove. The effects of particle removal comparative experiments were observed by metallographic microscopy, which showed that the 1% v/v non-ionic surfactant achieved the best result. However, the surfactant film itself belongs to organic contamination, and it eventually needs to be removed. BDD film anode electrochemical oxidation (BDD-EO) is used to remove organic contaminants, because it can efficiently degrade organic matter. Three organic contaminant removal comparative experiments were carried out: the first one used the non-ionic surfactant in the first step and then used BDD-EO, the second one used BDD-EO only, and the last one used RCA cleaning technique. The XPS measurement result shows that the wafers surface cleaned by BDD-EO has much less organic residue than that cleaned by RCA cleaning technique, and the non-ionic surfactant can be efficiently removed by BDD-EO.

A novel cleaner for colloidal silica abrasive removal in post-Cu CMP cleaning*

A novel cleaning solution, named FA/O alkaline cleaner, was proposed and demonstrated in the removal of colloidal silica abrasives. In order to remove both the chemical and physical absorbed colloidal silica abrasives, an FA/OII chelating agent and non-ionic surfactant were added into the cleaner. By varying the concentration of chelating agent and non-ionic surfactant, a series of experiments were performed to determine the best cleaning results. This paper discusses the mechanism of the removal of colloidal silica abrasives with a FA/O alkaline cleaner. Based on the experiment results, it is concluded that both the FA/OII chelating and non-ionic surfactant could benefit the removal of colloidal silica abrasives. When the concentration of FA/OII chelating agent and FA/O non-ionic surfactant reached the optima value, it was demonstrated that silica abrasives could be removed efficiently by this novel cleaning solution.

A new cleaning process for the metallic contaminants on a post-CMP wafer's surface

This paper presents a new cleaning process using boron-doped diamond (BDD) film anode electrochemical oxidation for metallic contaminants on polished silicon wafer surfaces. The BDD film anode electrochemical oxida- tion can efficiently prepare pyrophosphate peroxide, pyrophosphate peroxide can oxidize organic contaminants, and pyrophosphate peroxide is deoxidized into pyrophosphate. Pyrophosphate, a good complexing agent, can form a metal complex, which is a structure consisting of a copper ion, bonded to a surrounding array of two pyrophosphate anions. Three polished wafers were immersed in the 0.01 mol/L CuSO4 solution for 2 h in order to make comparative exper- iments. The first one was cleaned by pyrophosphate peroxide, the second by RCA (Radio Corporation of America) cleaning, and the third by deionized (DI) water. The XPS measurement result shows that the metallic contaminants on wafers cleaned by the RCA method and by pyrophosphate peroxide is less than the XPS detection limits of 1 ppm. And the wafers surface cleaned by pyrophosphate peroxide is more efficient in removing organic carbon residues than RCA cleaning. Therefore, BDD film anode electrochemical oxidation can be used for microelectronics cleaning, and it can effectively remove organic contaminants and metallic contaminants in one step. It also achieves energy saving and environmental protection.