Via Resistance Variation Improvement Through Amine Versus Fluorine Based Chemical and O2 Dry Flushing for BiCMOS Technology

Abstract

The paper discussed the via resistance variation using different cleaning chemicals known as the amine and fluorine based chemical for 0.6um BiCMOS technology. Single and chain via resistance showed severe drift with fluorine based clean recipe especially at the wafer edge where the failure rate is approximately 28% for chain via resistance and 12% for single via resistance. The baseline chemical, amine based showed low failure rate of less than 3%. Resistance drift is mainly due to the high Ti/TiN polymer residues which are remained at the bottom of the via holes. This is because 0.6um technology tend to generate more by-products since the etch amount is higher compared to other advanced technology which have smaller critical dimension (CD) size. Focus of the paper is mainly on the recipe optimization with fluorine based chemical where the objective is to have comparable via resistance performance with the amine based chemical. Recipe was optimized for different wet cleaning tool, which includes Batch Spray Type and Single Wafer Type. All optimise recipes showed comparable via resistance performance with the amine based chemical. Apart from that, a study on via resistance by adding O2 flushing etch step was conducted. The study was conducted on dual plasma source chamber and single plasma source chamber for BiCMOS technology. Adding O2 flushing step helps to scavenge some of the polymer on the wafer. Single plasma source chamber with O2 flushing step has better performance on production recipe compared to dual plasma source chamber.