Low electrical resistivity in thin and ultrathin copper layers grown by high power impulse magnetron sputtering

Abstract

Ultrathin copper (Cu) layers are in continuous demand in several areas, such as within microelectronics and space, as well as in instrumentation technology requiring an electrical resistivity as low as possible. However, the performance of modern copper connections is limited by the size-dependent value of the film resistivity, which is known to increase when the layer thickness is reduced to a few tens of nanometer. In this work, the authors have successfully deposited Cu thin films from 20 to 800 nm exhibiting reduced electrical resistivity by using a high power impulse magnetron sputtering (HiPIMS) process. The electrical and microstructural properties of such films were compared to samples deposited by conventional direct current magnetron sputtering (DCMS) within the same thickness range. For films as thin as 30 nm, the electrical resistivity was reduced by $30% when deposited by HiPIMS compared to DCMS, being only three times larger than the copper bulk value. The HiPIMS Cu films exhibit larger grain size and reduced grain boundary density, which reduce the scattering of charge carriers and thereby the resistivity of the thin film. These larger grains are likely due to the highly ionized precursor flux of the HiPIMS discharge, which in the present work is controlled by an external substrate bias. V

The Target Material Influence on the Current Pulse during High Power Pulsed Magnetron Sputtering

“…A full review of these applications would be out of the scope of this paper, so only a few examples will be given. The usage of HPPMS has been demonstrated for different applications such as hard coatings [2][3][4], optical thin films [5][6][7], electrical applications [8][9][10], catalysis [11][12][13], adhesive and/or low friction coatings [14,15], anti-bacterial thin films [16], and conformal coatings [17]. The technique has introduced also some interesting new insight in terms of plasma physics which are presented in a large number of scientific papers, and summarized in a few highly cited reviews [5,[18][19][20].…”

Highly conductive ultrathin Co films by high-power impulse magnetron sputtering

“…In HiPIMS, however, a bias voltage of -100 V is sufficient to achieve a pronounced reduction in sheet resistance, which is in agreement with results reported for Cu. 14 In DCMS, in contrast, large reduction occurs only above -200 V. This shows that achieving the same energy per deposited metal atom in DCMS requires much higher bias voltages due to the low ion current.…”

“…Recently, HiPIMS deposition of Cu has been reported to lead to films with significantly reduced resistivity at thicknesses from 20 to 800 nm. 14 In this paper, we study ionized PVD of thin and ultrathin Co films and focus on the nucleation of Co directly on SiO 2 at room temperature. We use HiPIMS and DCMS for the deposition and investigate the effects of ion energy and ion type on the electrical properties of the films.…”

Plasma Diagnostics in Reactive High-Power Impulse Magnetron Sputtering System Working in Ar + H2S Gas Mixture

“…The electron concentration n e measured by the Langmuir probe at the position of the substrate decreases over this change of Q H 2 S from 10 18 down to 10 17 m −3Coatings 2020, 10, 246 2 of 16 realized. Furthermore, FeS films were found to be excellent low-friction materials working like solid state lubricants in tribological applications [16].High-power impulse magnetron sputtering system (HiPIMS) is a relatively novel approach for the deposition of thin films [17][18][19][20]. This method utilizes very high discharge current densities during the pulse j D > 1 A cm −2 , but, simultaneously, average power applied in the HiPIMS discharge is similar to DC magnetron sputtering.…”

“…High-power impulse magnetron sputtering system (HiPIMS) is a relatively novel approach for the deposition of thin films [17][18][19][20]. This method utilizes very high discharge current densities during the pulse j D > 1 A cm −2 , but, simultaneously, average power applied in the HiPIMS discharge is similar to DC magnetron sputtering.…”