Copper Electroplating on Zero-Thickness ALD Platinum for Nanoscale Computer Chip Interconnects

Abstract

Ultra-thin platinum (Pt) films grown by atomic layer deposition (ALD) have been investigated as an alternative to conventional physical vapor deposited (PVD) Cu as seed layer for copper (Cu) electroplating. The wetting angles between the electrolyte and both Pt and Cu seed layers were analyzed using sessile-drop contact-angle analysis prior to plating. Both constant current and pulse reverse current (PRC) were applied to electroplate Cu on both types of blanket seed layers. Scanning electron microscope (SEM) revealed that Cu nucleation density on ALD Pt is lower than on its PVD Cu counterpart, after 30 seconds plating using PRC. Nevertheless, Cu nuclei were observed after only 1.0 minute plating on ALD Pt surfaces, and continuous Cu films were achieved at longer plating times. To fill trench structures coated with ALD Pt/TaN, PRC was applied using the same organic-additive-free electrolyte. Initial results suggest that these seed layers were adequate for ECD fill of trenches with 200 nm feature size and aspect ratio 7:1. The composition and microstructure of the Cu films were analyzed by Auger electron spectroscopy (AES), X-ray diffraction (XRD), and cross-sectional transmission electron microscopy (TEM). Thermal stability of the Cu/Pt system was examined by annealing in forming gas at 450°C for 1 hour and subsequent analysis by XRD and TEM.

In situconductance monitoring of Pt thin film growth by area-selective atomic layer deposition

“…Recently, it has been shown that the catalytic action of Pt seed layers is suitable also for the AS-ALD of other metals like, palladium and copper [15,62,63], making the technique suitable for different type of contacting applications, for example carbon electronics, for which palladium with its high work function and good wetting interactions with nanotubes is well suited [64].…”

Single-electron transport in focused electron beam induced deposition (FEBID)-based nanostructures

“…It is important to underline that the conductance monitoring technique and the GA approach for self-optimization using the in situ monitoring are rather broadly applicable. For instance, Mackus, Hsu, Kaloyeros and collaborators [220,257,258] have shown that the catalytic action of Pt seed layers can be used for AS-ALD of other metals, like palladium and copper, making the technique eligible for different type of contacting applications, for example carbon electronics, for which palladium with its high work function and good wetting interactions with nanotubes is well suited [259]. Moreover, the method could be used for other non-selective metal deposition techniques [260] since the time-resolved feature of this growth monitoring is certainly preserved.…”