Growth mechanism of sputter deposited Ta and Ta±N thin ®lms induced by an underlying titanium layer and varying nitrogen ¯ow rates

Tantalum (Ta) and nitrogen-contained tantalum (Ta±N) thin ®lms are sputter deposited on Si-based substrates with and without a titanium adhesion layer. The impact of varying the nitrogen ¯ow rate and the underlying titanium on the phase formation process is investigated using X-ray diffraction analysis, resistivity measurement and scanning electron microscopy. Our results indicate that the titanium layer inhibits the formation of high-resistivity tetragonal b-Ta, and leads to the deposition of low-resistivity cubic a-Ta arising from its epitaxial orientation on the underlying titanium. Consequently, the electrical properties and microstructures of the Ta-based ®lms are signi®cantly changed. # 2001 Elsevier Science B.V. All rights reserved.