Nanometer-thick copper films with low resistivity grown on 2D material surfaces

Yu-Wei Liu,Wei-Chen Tu,Shih-Yen Lin,Chen-Tu Chiang,Po-Cheng Tsai,Dun-Jie Zhang

doi:10.1038/s41598-022-05874-9

Abstract

Thin Copper (Cu) films (15 nm) are deposited on different 2D material surfaces through e-beam deposition. With the assist of van der Waals epitaxy growth mode on 2D material surfaces, preferential planar growth is observed for Cu films on both MoS2 and WSe2 surfaces at room temperature, which will induce a polycrystalline and continuous Cu film formation. Relative low resistivity values 6.07 (MoS2) and 6.66 (WSe2) μΩ-cm are observed for the thin Cu films. At higher growth temperature 200 °C, Cu diffusion into the MoS2 layers is observed while the non-sulfur 2D material WSe2 can prevent Cu diffusion at the same growth temperature. By further increasing the deposition rates, a record-low resistivity value 4.62 μΩ-cm for thin Cu films is observed for the sample grown on the WSe2 surface. The low resistivity values and the continuous Cu films suggest a good wettability of Cu films on 2D material surfaces. The thin body nature, the capability to prevent Cu diffusion and the unique van der Waals epitaxy growth mode of 2D materials will make non-sulfur 2D materials such as WSe2 a promising candidate to replace the liner/barrier stack in interconnects with reducing linewidths.

Highlights

In silicon (Si) industry, copper (Cu) has been widely used for the application of interconnects due to its low resistivity[1,2,3]
By further increasing the deposition rates, a record-low resistivity value 4.62 μΩ-cm for thin Cu films is observed for the sample grown on the WSe2 surface
We have demonstrated 15 nm Cu film deposited on different 2D material surfaces

Summary

Introduction

In silicon (Si) industry, copper (Cu) has been widely used for the application of interconnects due to its low resistivity[1,2,3]. When the TaN film thickness is reduced to below 3 nm, the barrier layer is no longer able to prevent the Cu diffusion to the surrounding dielectrics[14] In this case, a new material with the capability of blocking Cu diffusion in a few nanometer thicknesses will become an urgent need for further interconnect scaling. The results have revealed that the epi-layer formation through the van der Waals epitaxy growth mode on 2D material surfaces has less dependent to the substrate lattice structures. By further expanding this concept to metal crystals, van der Waals epitaxy on 2D material surfaces will help to improve the crystallinity of thick gold (Au) films grown on MoS2 surfaces[17]. The thin thicknesses down to few atomic layers and good wettability of W Se2 to Cu have made it a promising candidate to replace the liner/ barrier stack in interconnects with reducing linewidths

Methods

Results

Conclusion