Atomic layer deposition of high-quality Pt thin film as an alternative interconnect replacing Cu Available to Purchase

High-quality Pt thin films are prepared by atomic layer deposition (ALD) using metal-organic precursors dimethyl-(N,N-dimethyl-3-butene-1-amine-N) platinum (C₈H₁₉NPt) and with diluted molecular oxygen (O₂) as a reactant. The films are grown at a relatively low temperature of 225 °C on a thermally grown SiO₂ substrate, and the process shows all the necessary qualities of an ideal ALD such as self-limiting growth characteristics and a well-defined ALD temperature window between 200 and 250 °C. Noticeably, the current ALD-Pt process shows a very high growth per cycle of 0.167 nm without an incubation period at 225 °C, and perfect conformality is obtained at a dual trench structure (top and bottom width: 40 and 15 nm) with an aspect ratio of around 6.3. The resistivity of the ALD-Pt film at ∼39 nm in thickness deposited at 225 °C is almost the same (∼10.8 μΩ cm) as its bulk resistivity (10.6 μΩ cm), and it is as low as ∼12 μΩ cm at 25 nm in thickness. Comprehensive analyses using x-ray photoelectron spectroscopy, x-ray diffractometry, transmission electron microscopy (TEM), and x-ray reflectance indicate that the extremely low resistivity of ALD-Pt is due to the formation of highly pure and polycrystalline films with high density (∼21.04 g/cm³) and large grain size (∼48 nm for 25 nm thick film). For comparison, ALD-Ru is deposited at the same equipment and deposition temperature, 225 °C, using (ethylbenzene)(1,3-butadiene)Ru(0) (C₁₂H₁₆Ru) and diluted O₂ as the reactant. The higher resistivity of ∼20 μΩ cm at a similar thickness (∼23.5 nm) with ALD-Pt is obtained, which is much higher than its bulk value (7.6 μΩ cm). TEM analysis suggests that the formation of relatively smaller-sized grains of ALD-Ru is the main reason for it.