Temperature Control for High Removal Rate and Low Dishing in TGV CMP

Abstract

Chemical Mechanical Planarization (CMP) is the most well-known process for global planarization of wafer surfaces. The importance of interposers has been growing due to ultra-micronization and densification of semiconductors. Through-Glass-Via used in interposers has over-deposited copper layer after via filling. This copper bulk layer needs to be planarized by CMP for post-processing. At the heterogeneous material interface, defects such as dishing occur due to different material removal selectivities. In addition, the chemical reaction of copper with chemical additives is very sensitive to temperature. Therefore, temperature is an essential consideration for an efficient CMP process. In this study, we compared the effect of slurry additive properties that change with temperature on material removal. For the BTA-based slurry, the initial dishing at high temperature was 95 nm and increased by 25 nm per minute. It shows an increase of more than twice compared to the results at low temperatures. Conversely, for TTA-based slurry used in this study, the initial dishing at high temperature was 70 nm and increased by 15 nm per minute. It shows decrease of more than twice compared to the results at low temperatures. Therefore, we aim to achieve low dishing by utilizing the increasing process temperatures, on the contrary.