Enhancement of Semiconductor Wafer Cleaning by Chelating Agent Addition

Abstract

To realize environmental and cost benefits it is desirable to reduce the RCA cleaning sequence from its historical SC1 ⫹ SC2 combination, in which the particle-removing SC1 solution deposits certain metals, necessitating the metal-removing SC2. One approach is to add a chelating agent to the SC1. Extensive testing of SC1 solutions with addition of the complexing agent 1,2-cyclohexanediaminetetraacetic acid (CDTA) were performed. CDTA was shown to be more stable than other complexing agents in SC1 solutions, facilitating significant bath life extension. Further, SC1 solutions with CDTA were shown to be capable of removing large quantities of metals from contaminated wafers, comparable to SC2, and preventing deposition of metals. An exception is aluminum, which can deposit from SC1 even with large amounts of added CDTA, but which can be removed by a subsequent dilute (1000:1) H2O:HCl step.