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

Abstract

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 (O-2) as a reactant. The films are grown at a relatively low temperature of 225 degrees 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 degrees C. Noticeably, the current ALD-Pt process shows a very high growth per cycle of 0.167 nm without an incubation period at 225 degrees 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 similar to 39 nm in thickness deposited at 225 degrees C is almost the same (similar to 10.8 mu omega cm) as its bulk resistivity (10.6 mu omega cm), and it is as low as similar to 12 mu omega 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 (similar to 21.04 g/cm(3)) and large grain size (similar to 48 nm for 25 nm thick film). For comparison, ALD-Ru is deposited at the same equipment and deposition temperature, 225 degrees C, using (ethylbenzene)(1,3-butadiene)Ru(0) (C12H16Ru) and diluted O-2 as the reactant. The higher resistivity of similar to 20 mu omega cm at a similar thickness (similar to 23.5 nm) with ALD-Pt is obtained, which is much higher than its bulk value (7.6 mu omega cm). TEM analysis suggests that the formation of relatively smaller-sized grains of ALD-Ru is the main reason for it.