Dynamic NMR Study of Model CMP Slurry Containing Silica Particles as Abrasives

Fadwa Odeh¹*, Abeer Al-Bawab¹ and Yuzhuo Li²

¹ Department of Chemistry, The University of Jordan, Amman 11942, JORDAN

² Department of Chemistry, Clarkson University, Potsdam, NY 13699

Abstract:

With continuous increase in the complexity of current microelectronic devices and integration of Cu as interconnect, it is required that CMP provides a good surface planarity with minimal surface defectivity. One of the prominent roles of the abrasive particles is its ability to interact with chemical components found in the slurry. Surface adsorption of chemical components on to the abrasive particles can alter the intended chemical and mechanical balance of the slurry. Slurries consisting of abrasive particles of similar characteristics but different surface adsorption characteristic may perform differently in a CMP process. Furthermore, the introduction of copper ions during copper CMP may exacerbate the complexity. These copper ions could interact with the chemical components in the slurry to form copper complexes and also could change the adsorption characteristic of the abrasive particles. The formation of the copper complex and the change in the adsorption characteristic of the particles could have a great impact on the copper CMP performance. Performance will be exemplified with silica based slurry.

The longitudinal relaxation times (T₁) of the different components of CMP slurries were measured using Spin Echo-NMR (SE-NMR) at a constant temperature. The fact that NMR is non-invasive and gives information on the molecular level gives more advantage to the technique. The model CMP slurry was prepared in D₂O to enable monitoring of T1 for the various components' protons. SE-NMR provide a very powerful tool to study the various interactions and adsorption processes that take place in a model CMP silica based slurry which contains BTA and/or Glycine and/or Cu⁺² ions, it was found that  BTA is very competitive towards complexation with Cu⁺² ions and  BTA-Cu complex adsorbs on silica surface.