Plasma-Assisted ALD of Highly Conductive HfNx: On the Effect of Energetic Ions on Film Microstructure

Abstract

In this work, we report on the atomic layer deposition (ALD) of HfN x thin films by employing CpHf(NMe 2) 3 as the Hf(IV) precursor and Ar-H 2 plasma in combination with external RF substrate biasing as the co-reactant. Following up on our previous results based on an H 2 plasma and external RF substrate biasing, here we address the effect of ions with a larger mass and higher energy impinging on HfN x film surface during growth. We show that an increase in the average ion energy up to 304 eV leads to a very low electrical resistivity of 4.1 × 10-4 Ωcm. This resistivity value is achieved for films as thin as ~ 35 nm, and it is an order of magnitude lower than the resistivity reported in literature for HfN x films grown by either CVD or ALD, while being comparable to the resistivity of PVD-grown HfN x films. From the extensive thin film characterization, we conclude that the impinging ions during the film growth lead to the very low electrical resistivity of HfN x films by suppressing the oxygen incorporation and in-grain nano-porosity in the films.

Plasma‐Enhanced Atomic Layer Deposition of Amorphous Tantalum Thin Films for Copper Interconnects Using an Organometallic Precursor

“…Furthermore, Karwal et al. [ 14 ] have shown that the impact of high‐energy ions during the PEALD film growth could significantly improve the chemical and electrical properties of the afforded HfN x films. Second, as a noble gas, argon can stabilize the plasma discharge, making the energy density of the plasma more uniform, and ultimately improving the uniformity of the films.…”

Precise ion energy control with tailored waveform biasing for atomic scale processing

“…Recently, ion energy control during plasma-enhanced atomic layer deposition (ALD) with RF sinusoidal waveform biasing has been demonstrated to enable control over the growth and material properties of thin films. 53,[55][56][57][58] Using the FIG. 6.…”

Advances in ultra-high temperature ceramics, composites, and coatings

“…Nitrides such as ZrN and HfN have similarly strong covalent bonds [59] but their refractory nature makes them especially difficult to synthesize and process. The stoichiometric nitrogen content can be varied in these complexes and relates to their synthetic techniques [63][64][65]. Boride UHTCs, such as HfB 2 and ZrB 2 , benefit from very strong bonding between boron atoms as well as strong metal to boron bonds; the hexagonal close-packed structure with alternating two-dimensional (2D) boron and metal sheets gives these materials high and anisotropic strength as single crystals (Fig.…”