Identification and removal of trace organic contamination on silicon wafers stored in plastic boxes

As semiconductor device geometries continue to shrink, trace volatile organic contamination adsorbing on silicon surfaces has an increasingly detrimental impact on product performance and yield. Therefore, it becomes important to identify the origin of the organic contaminants and to eliminate them from the wafer. When wafers are stored in a plastic box in order to protect them from airborne contaminants, volatile organics from the polymeric construction material adsorb onto the wafter surfaces. A very small quantity of additives in the plastic material are apt to adsorb onto the wafers more easily than the unpolymerized monomers and oligomers outgassing in large quantities. As a result of the evaluation of various wet cleaning solutions in terms of their ability to remove these trace organic contaminants, dilute HF as well as ozonized ultrapure water has been found to completely remove these organic contaminants adsorbing on the silicon surfaces. After wet cleaning, organic contaminants adsorb more easily on the ozonized water-treated silicon surface than on the dilute HF-treated surface. Adsorption of the organic additives on the silicon surfaces can be inhibited by preventing the native oxide growth in a nitrogen atmosphere after dilute HF cleaning. Possible explanations for these phenomena are considered.