Simulation and in situ monitoring of metallic contamination and surface roughening in wet wafer cleaning solutions

Abstract

The steady decrease in the minimumfeature size of Si integrated circuits has led to an increase in the wafer cleanliness standards necessary to achieve satisfactory device yields. In the foreseeable future, wet cleaning cycles will continue to be used because of their excellent ability to remove particles and native oxides. However, trace metal deposition from contaminated solutions and surface microroughening by localised etching, which are known to impact device yield severely, are important concerns. The thermodynamic basis for simulating the effect of solution composition on cleaning effectiveness is contained in E–pH diagrams, where E is the redox potential of the solution. Successful implementation of advanced cleaning chemistries in the fabrication process depends critically on in line monitoring of cleaning performance. For this purpose, a radio frequency photoconductance decay apparatus has been developedfor the monitoring of cleaning solutions in real time. The sensitivity of the apparatus to trace level Cu deposition from dilute HF and surface roughening in deionised water is demonstrated.

MST/3226