Effect of Structure to Promote Organic Residue Removal during Cu Post-Chemical Mechanical Planarization (p-CMP) Cleaning

Abstract

The extension of Moore’s law remains a focal point as semiconductor manufacturers drive to advance Integrated Circuit (IC) technology by implementing new materials. Chemical Mechanical Planarization (CMP) has emerged as a critical processing step in device fabrication to keep up with these demands. However, one drawback to this process is the generation of killer defects that result from residual contamination (i.e., organic residues, abrasive particles, pad remnants, etc.) that are reliant on post-CMP (p-CMP) cleaning methods. Current Cu p-CMP cleaning methods implement the use of an industry standard polymer brush coupled with cleaning chemistries to remove residual contamination. It has been well established that shear and compressive forces coupled with surface active cleaning chemistries have proven to be efficient albeit with the potential for secondary defectivity (i.e., pitting, etching, scratching). Additionally, current cleaning formulations rely on additives that promote aggressive redox conditions to remove residues through an undercutting mechanism, which leads to the propagation of the aforementioned defect modes. This work focuses on the development of a “softer” approach to Cu p-CMP cleaning by surveying various additives (i.e., -unsaturated carboxylic acids, carboxylic acids, and unsaturated benzaldehydes) to exploit an “overcutting” mode of organic residue removal. By implementing additional modes of interaction (i.e., p-stacking, H-bonding, conformational relationships, etc.), the mode of residue removal can be finely tuned to achieve desired surface-active conditions. This work employs a suite of techniques (i.e., Tafel analysis, OCP vs. time, time-resolved contact angle, shear force analysis) to correlate structure-activity to organic residue removal efficiency and the effects on the coefficient of friction (COF), particle removal efficiency, and the generation of secondary defectivity. Initial results have shown that implementing an “overcutting” mechanism will decrease the overall shear force and significantly reduce the proliferation of p-CMP cleaning defects. Furthermore, adding ancillary structure activity aids in additional modes of residue interaction to alter removal at the liquid-brush interface. Additionally, increased structure-activity has promoted residue-chemistry interactions to form a second passivation layer. Moreover, conformational changes that result in limited accessibility to the a,b-unsaturated double bond promote an “undercutting” mode of removal to become the predominant mode of organic residue mediation.