Advanced characterizations of fluorine-free tungsten film and its application as low resistance liner for PCRAM

Abstract

International audienceUsing a metal-organic tungsten based precursor, a fluorine-free tungsten thin film has been obtained. The process deposition recipe includes a plasma-enhanced CVD (PECVD) step and atomic layer deposition (ALD) cycles. A set of physicochemical characterizations including X-ray reflectivity (XRR), in-plane X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WDXRF), plasma profiling time of flight mass spectrometry (PPTOFMS) and microscope observations has been realized in order to study the W thin film structure and properties. The film is perfectly conformal whatever the structure size investigated (from tens of nanometers to micrometers wide). It was also highlighted that the F-free W film exhibits the lowest electrical resistivity phase (α-W) but is not pure. Indeed, in addition to a top surface oxidation, a layer located at the W film / substrate interface is present. This interface layer (IL) contains impurities, including carbon and oxygen, due to ligand decomposition. This IL might be deposited during the soak step or during the PECVD step. The W liner with thicknesses ranging from 3 to 4 nm has been implemented on PCRAM structures in order to evaluate its impact on contact plug resistivity. First electrical results are promising and demonstrate the interest of using a F-free low resistance W liner. At the aspect ratio studied, the gain in terms of contact plug resistivity is about 20% compared to the process of reference using a TiN liner. Modeling shows that this benefit is mainly due to the reduction of interface resistances

Advanced process and electron device technology

“…The molecules are composed of organic chains bonded by silane head group chemistry and terminated with desired functional groups, such as NH 2 -(CH 2 / n -Si(OCH 3 / 3 . For the W contact plugin middle of the line (MOL), Rodriguez et al [28] substituted the conventional TiN/Ti with a fluorine-free tungsten film, and the line resistance of contact plugs could be decreased by approximately 20%. In addition, the alloy has been proposed to be a single barrier/liner to replace the TaN/Ta or TiN/Ti bilayer, such as the Co-Ti and Co-W alloy [29,30] .…”

Tensile and Compressive Mechanical Properties of Polycrystalline Tungsten–Molybdenum Alloy

“…Tungsten (W), due to high melting point, high electrical conductivity, and superior accessibility, [1][2][3][4][5] has been widely used as the word line metal film of 3D NAND flash devices, dynamic random access memory (DRAM) devices, and phase-change memory (PCM) devices [6][7][8][9][10] for decades. Molybdenum (Mo) and tungsten are subgroup six (VIB) elements and have similar physical and chemical properties.…”

Atomistic simulations of mechanical characteristics dependency on relative density, grain size, and temperature of nanoporous tungsten

“…Due to the outstanding characteristics of high electrical conductivity, high melting point, and high thermal conductivity [28][29][30][31][32][33], W has been widely applied as word line metal film in the semiconductor field. The chemical vapor deposition (CVD) method [34] with gas-phase precursors (WF6) is adopted to prepare word line film, and the thickness is usually less than 30 nm.…”