Effects of KIO4 concentration and pH values of the solution relevant for chemical mechanical polishing of ruthenium

Abstract

Ruthenium (Ru), as one of the most promising barrier layer applied for the 14nm node and below technology in the integrated circuits manufacturing, the effects of the polishing variables on the chemical mechanical polishing (CMP) process are not intensively investigated. Corrosion investigation methods combined with CMP experiments were utilized to comprehensively reveal the polishing mechanism affected by the potassium periodate (KIO4) concentration and the slurry pH values. The results of both the static and in-situ corrosion investigation show that the static corrosion rate of Ru is the lowest when the slurry is weak alkaline, but it is the most obviously enhanced by the polishing process under this condition. Considering the different oxidant concentration, the corrosion of Ru distinctively accelerates, and turns to be more like a diffusion-limited mass transfer controlled process when the KIO4 concentration increases. Because the corrosion plays a significant role in the whole CMP process, with a full accounting of other variables, the polishing process of Ru is preferred to be carried out under low down pressure in weak alkaline slurries. Under this condition, the mechanical-enhanced chemical effect is predominating, which is helpful to obtain a good surface quality, and a high material removal rate.