Evaluation of a Photosensitizer Redox Couple for Oxide Removal Rate Tunability in Shallow Trench Isolation Chemical Mechanical Planarization

Abstract

As technology continues to expand beyond that predicted by Moore’s Law the need to alter chemical mechanical planarization (CMP) processes to meet consumer demands is critical. To achieve higher oxide material removal rates (MRR), slurry formulations have become more complex by implementing rate enhancing additives to increase the slurry’s chemical activity. However, the modulation of MRR in situ requires changes in mechanical parameters, such as downforce, platen speed, and flow rate. These parameters effectively increase the chemical activity of the slurry; however, they can result in greater defectivity due to increased shear force. Therefore, this work employs the use of a photosensitizer redox couple to tune MRR using an external stimulus (i.e., light). Specifically, Rose Bengal (RB) is used to disrupt the adsorbed O2 equilibrium at the CeO2 surface via 1O2 generation. A secondary redox additive is employed to trap the 1O2 thereby preventing readsorption and increasing the number of active surface sites necessary for enhanced MRR. This photosensitized mechanism is supported through the correlation of CMP performance (i.e., MRR) to analytical measurements (i.e., 1O2 generation, contact angle, and quartz crystal microbalance (QCM)) with and without the presence of irradiation.