Study On The BTA Removal In Post-CMP Cleaning Of Copper Interconnection For GLSI

With the development of the integrated circuit technology, the integration of chips continues to increase and the feature size of the device becomes smaller and smaller. So the impurities become a prominent danger to the devices. Contaminants on the surface of integrated circuit will affect the electrical properties, yield and reliability of the device, so cleaning becomes a very important part of integrated circuit manufacturing. The cleaning of copper surface after chemical mechanical planarization(CMP) process is a critical step since the surface would be contaminated by a large number of slurry particles such as Si2 O or Al2O3 and organic residues such as benzotriazole(BTA). The presence of organic residues results in a hydrophobic surface, which leads to problems in particle removal and drying. The BTA layer leads to problems in time-dependent dielectric breakdown(TDDB) and the device reliability.This thesis focuses on the problems which exists in cleaning process on benzotriazole(BTA) removal and do the detailed analysis for them. The mechanistic of the BTA adsorb and function during Cu CMP are also analysed. The reaction of Cu and BTA become Cu-BTA which have a complex structure and insoluble on Cu surface. In this paper, a novel alkaline cleaning solution with functionalities of BTA and Cu-BTA removal was designed for advanced post CMP cleaning solution. And the cleaning solution composition and concentration were investigated. The alkaline chelating agent and non-ionic surfactant were used as main compositions of cleaning agent.The firstly, the used concentration of BTA and the dipped time of Cu in BTA solution were detailed analysis. The optimal grow condition of BTA on Cu surface was concluded by contact angle measurement, Metallurgical Microscope and Fourier Transform Infrared Spectrometer measurement. The secondly, the chelating agent was used as cleaning agent on BTA removal. It is characterized by contact angle measurement, static etching rate(SER), electrochemical techniques and the comparison experiment of the same pH KOH, and show that the chelating agent plays a major role on BTA removal. At the same time, the effectively concentration range of chelating agent on BTA removal is concluded. The surfactant is weakly acidic and play a supplementary role. The surfactant was used as cleaning agent on BTA removal that the result is characterized by contact angle measurement and static etching rate(SER). The lastly, the cleaning agent on BTA and other contaminants removal is characterized by contact angle, SER and scanning electrochemical microscopy(SEM) measurement.Alkaline or acidic cleaning solutions are usually preferred over neutral solutions since they can remove BTA better. In this paper, the proposed cleaning solution have some advantages such as high pH, low using concentration, no TMAH and friendly to environment et al. A large number of experiments show that the concentration of chelating agent is less than 200 ppm, the concentration of surfactant is less than 5000 ppm. But the specific concentration of cleaning solution still need further study.