Low-Resistivity Thermal Titanium Nitride ALD for Conductive Layers in Advanced Packaging and Microbatteries

Titanium nitride (TiN) is a highly sought-after material for devices requiring a conformal conductive layer, such as interconnects in semiconductor devices and current collectors in advanced battery technologies. Conventional thermal atomic layer deposition (ALD) of TiN typically demands high temperatures exceeding 500 °C to achieve low resistivity films suitable for device applications—temperatures that surpass the thermal limits of most devices. Although plasma-enhanced ALD (PEALD) can lower resistivity at reduced temperatures, its utility is hindered by step coverage limitations due to restricted delivery of energetic plasma species, such as neutrals/radicals and ions, particularly in high aspect ratio and gap-fill applications. [1] We present a novel thermal ALD TiN process operating at a deposition temperature of 300 °C. This process produces polycrystalline films with high relative density, 5.0 g/cm 3 , and resistivity of approximately 300 µΩ·cm at thicknesses below 20 nm, while achieving over 95% step coverage in ~40:1 aspect ratio features and seamless gap-fill in 5:1 aspect ratio structures. Notably, an inverse correlation between purge time and resistivity was observed, alongside chamber seasoning effects that minimize oxygen contamination in the films. To demonstrate the versatility of this process, two device applications are highlighted. First, we showcase TiN’s effectiveness in seam-free gap-fill as conductive interconnects within nanoscale thermal oxide, SiO₂, features, demonstrating uniform gap fill across a 3-inch wafer with 5:1 aspect ratio features. As shown in Figure 1, ideal gap-fill was success as measured at the center and edge of the 3-inch wafer. Second, the TiN film is applied as a current collector in microbatteries, leveraging anodic aluminum oxide channels for surface area and capacity enhancement. This marks the initial phase of a project to develop microscale batteries using traditional semiconductor manufacturing techniques including ALD. [1] J. Dendooven, et al., J. Electrochem. Soc. 157(4), (2010), G111–G116 Figure 1