Microscratch testing method for systematic evaluation of the adhesion of atomic layer deposited thin films on silicon

摘要

The scratch test method is widely used for adhesion evaluation of thin films and coatings. Usualcritical load criteria designed for scratch testing of coatings were not applicable to thin atomiclayer deposition (ALD) films on silicon wafers. Thus, the bases for critical load evaluation wereestablished and the critical loads suitable for ALD coating adhesion evaluation on silicon waferswere determined in this paper as LCSi1, LCSi2, LCALD1, and LCALD2, representing the failure pointsof the silicon substrate and the coating delamination points of the ALD coating. The adhesionperformance of the ALD Al2O3, TiO2, TiN, and TaCNþRu coatings with a thickness rangebetween 20 and 600 nm and deposition temperature between 30 and 410 C on silicon wafers wasinvestigated. In addition, the impact of the annealing process after deposition on adhesion wasevaluated for selected cases. The tests carried out using scratch and Scotch tape test showed thatthe coating deposition and annealing temperature, thickness of the coating, and surfacepretreatments of the Si wafer had an impact on the adhesion performance of the ALD coatings onthe silicon wafer. There was also an improved load carrying capacity due to Al2O3, the magnitudeof which depended on the coating thickness and the deposition temperature. The tape tests werecarried out for selected coatings as a comparison. The results show that the scratch test is a usefuland applicable tool for adhesion evaluation of ALD coatings, even when carried out for thin (20 nmthick) coatings.