Effect of developer surfactant on lithography process latitudes and post pattern defect concentration

Abstract

The current work was done jointly between Institute of Microelectronics, Singapore and Tokuyama Corporation, Japan. Here the patterning performance of four different developers was evaluated. Three of these were with surfactant and one was without surfactant. The parameters evaluated were resist thickness loss, resist contrast, process windows such as depth of focus and exposure latitudes, across wafer critical dimension (CD) uniformity, and post pattern defect density. Feature sizes of 180 nm and 150 nm were evaluated for litho process latitudes. CD uniformity was also evaluated for 180 nm and 150 nm geometries. The resist loss was found to be minimum for developer A which was without surfactant. The depth of focus and exposure latitude of smaller geometry (150nm lines) in general showed better values for developers with surfactants. Developer solutions with surfactant also gave better across wafer CD uniformity for smaller geometries (150nm). Post pattern defects were found to be least with developer C that which contained nonionic type of surfactant and cationic one. Defects were highest for developer B which contained nonionic type of surfactant. The addition of optimum surfactant to developer has potential for reducing defects to lower levels and achieves better across wafer CD uniformity for smaller geometries.