Rangarajan Jagannathan

Electroless plating of copper at a low pH level

A new process for electroless copper plating at a pH level of ≤9 is described. The process uses amine borane reducing agents and ligands based on neutral tetradentate nitrogen donors. The use of a variety of buffer systems is demonstrated. Electroless bath performance over a wide range of conditions is presented. The quality of the plated copper is comparable to that obtained by currently used electroless plating processes, and has a resistivity of about 1.8-2 µΩ-cm, depending on bath composition and process parameters. Use of the process is illustrated for forming conductors and filling via holes having submicron minimum dimensions.

Enhancement of Semiconductor Wafer Cleaning by Chelating Agent Addition

To realize environmental and cost benefits it is desirable to reduce the RCA cleaning sequence from its historical SCI + 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 SCI solutions with addition of the complexing agent 1,2-cyclohexanediaminetetraacetic acid (CDTA) were performed. CDTA was shown to he more stable than other complexing agents in SC1 solutions, facilitating significant hath 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 he removed by a subsequent dilute (1000:1) H 2 O:HCl step.