New FEOL Cleaning Technology for Advanced Devices beyond 45 nm Node

摘要

In FEOL (front-end-of-line) wet cleaning, acid-base chemicals have been employed to remove metallic contamination and oxide films. Ultrasonic irradiation under alkaline-base chemicals such as APM (NH4OH / H2O2 / DIW) is applied frequently to remove particles on silicon substrates. Recently, with scaling down below 50 nm, influence of pattern damage due to physical force such as ultrasonic irradiation has been reported. Hence, for the 3x and 4x nm devices, it will be very difficult to apply ultrasonic irradiation for particle removal process. APM chemical can prevent the re-adsorption of particles on substrates, because the particles-substrates interaction is retained repulsive. However, recently, it has become difficult to use alkaline cleaning for etching of ion-implantation-damaged silicon oxide film and silicon substrate. In this study, we tried to employ dispersant addition into acid-base chemicals and to prevent particles from adsorbing on substrates by controlling surface charge of particles and substrates. Although, according to reports, dispersant or surfactant agent in alkaline chemicals [1] or HF solution [2] was employed in some investigations, such techniques cannot be applied in view of the loss of silicon oxide and silicon substrate. We chose the dispersant agent that is the most effective in HCL acid-base chemicals without loss of^ihcon oxide and silicon substrate, and that is easy to decompose by subsequent ozone water rinse step.