SIMULATION AND IN-SITU MONITORING OF METALLIC CONTAMINATION AND SURFACE ROUGHENING IN WET WAFER CLEANING SOLUTIONS

The steady decrease in the minimum feature size of Si integrated circu its has led to an increase in the wafer cleanliness standards necessar y to achieve satisfactory device yields. In the foreseeable future, we t cleaning cycles will continue to be used because of their excellent ability to remove particles and native oxides. However, trace metal de position from contaminated solutions and surface microroughening by lo calised 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 i mplementation of advanced cleaning chemistries in the fabrication proc ess depends critically on in line monitoring of cleaning performance. For this purpose, a radio frequency photoconductance decay apparatus h as been developed for the monitoring of cleaning solutions in real tim e. The sensitivity of the apparatus to trace level Cu deposition from dilute HF and surface roughening in deionised water is demonstrated. ( C) 1995 The Institute of Materials.