Jon Henri

Effect of Reaction Mechanism on Precursor Exposure Time in Atomic Layer Deposition of Silicon Oxide and Silicon Nitride

Atomic layer deposition (ALD) of highly conformal, silicon-based dielectric thin films has become necessary because of the continuing decrease in feature size in microelectronic devices. The ALD of oxides and nitrides is usually thought to be mechanistically similar, but plasma-enhanced ALD of silicon nitride is found to be problematic, while that of silicon oxide is straightforward. To find why, the ALD of silicon nitride and silicon oxide dielectric films was studied by applying ab initio methods to theoretical models for proposed surface reaction mechanisms. The thermodynamic energies for the elimination of functional groups from different silicon precursors reacting with simple model molecules were calculated using density functional theory (DFT), explaining the lower reactivity of precursors toward the deposition of silicon nitride relative to silicon oxide seen in experiments, but not explaining the trends between precursors. Using more realistic cluster models of amine and hydroxyl covered surfaces, the structures and energies were calculated of reaction pathways for chemisorption of different silicon precursors via functional group elimination, with more success. DFT calculations identified the initial physisorption step as crucial toward deposition and this step was thus used to predict the ALD reactivity of a range of amino-silane precursors, yielding good agreement with experiment. The retention of hydrogen within silicon nitride films but not in silicon oxide observed in FTIR spectra was accounted for by the theoretical calculations and helped verify the application of the model.

Patterning with Amorphous Carbon Thin Films

Amorphous carbon hard mask films grown with plasma enhanced chemical vapor deposition are an enabling technology for advanced front-end-of-line patterning technologies. These films must have a low etch rate and be weakly roughened in dielectric etch chemistries, high transparency at lithography alignment wavelengths, and the mechanical properties to mitigate elastic instabilities such as line bending. The deposition process affects all of these parameters through the resulting structure and composition. Highly graphitic films deposited at 550°C are common; however, other process spaces relying on ion bombardment rather than temperature can create less graphitic films with improved film properties like transparency, hardness, and etch selectivity.

Tuning Material Properties of Oxides and Nitrides by Substrate Biasing during Plasma-Enhanced Atomic Layer Deposition on Planar and 3D Substrate Topographies

Oxide and nitride thin-films of Ti, Hf, and Si serve numerous applications owing to the diverse range of their material properties. It is therefore imperative to have proper control over these properties during materials processing. Ion-surface interactions during plasma processing techniques can influence the properties of a growing film. In this work, we investigated the effects of controlling ion characteristics (energy, dose) on the properties of the aforementioned materials during plasma-enhanced atomic layer deposition (PEALD) on planar and 3D substrate topographies. We used a 200 mm remote PEALD system equipped with substrate biasing to control the energy and dose of ions by varying the magnitude and duration of the applied bias, respectively, during plasma exposure. Implementing substrate biasing in these forms enhanced PEALD process capability by providing two additional parameters for tuning a wide range of material properties. Below the regimes of ion-induced degradation, enhancing ion energies with substrate biasing during PEALD increased the refractive index and mass density of TiOx and HfOx and enabled control over their crystalline properties. PEALD of these oxides with substrate biasing at 150 °C led to the formation of crystalline material at the low temperature, which would otherwise yield amorphous films for deposition without biasing. Enhanced ion energies drastically reduced the resistivity of conductive TiNx and HfNx films. Furthermore, biasing during PEALD enabled the residual stress of these materials to be altered from tensile to compressive. The properties of SiOx were slightly improved whereas those of SiNx were degraded as a function of substrate biasing. PEALD on 3D trench nanostructures with biasing induced differing film properties at different regions of the 3D substrate. On the basis of the results presented herein, prospects afforded by the implementation of this technique during PEALD, such as enabling new routes for topographically selective deposition on 3D substrates, are discussed.

Atomic Layer Deposition of Wet-Etch Resistant Silicon Nitride Using Di(sec-butylamino)silane and N2 Plasma on Planar and 3D Substrate Topographies

The advent of three-dimensional (3D) finFET transistors and emergence of novel memory technologies place stringent requirements on the processing of silicon nitride (SiNx) films used for a variety of applications in device manufacturing. In many cases, a low temperature (<400 °C) deposition process is desired that yields high quality SiNx films that are etch resistant and also conformal when grown on 3D substrate topographies. In this work, we developed a novel plasma-enhanced atomic layer deposition (PEALD) process for SiNx using a mono-aminosilane precursor, di(sec-butylamino)silane (DSBAS, SiH3N(sBu)2), and N2 plasma. Material properties have been analyzed over a wide stage temperature range (100-500 °C) and compared with those obtained in our previous work for SiNx deposited using a bis-aminosilane precursor, bis(tert-butylamino)silane (BTBAS, SiH2(NHtBu)2), and N2 plasma. Dense films (∼3.1 g/cm3) with low C, O, and H contents at low substrate temperatures (<400 °C) were obtained on planar substrates for this process when compared to other processes reported in the literature. The developed process was also used for depositing SiNx films on high aspect ratio (4.5:1) 3D trench nanostructures to investigate film conformality and wet-etch resistance (in dilute hydrofluoric acid, HF/H2O = 1:100) relevant for state-of-the-art device architectures. Film conformality was below the desired levels of >95% and attributed to the combined role played by nitrogen plasma soft saturation, radical species recombination, and ion directionality during SiNx deposition on 3D substrates. Yet, very low wet-etch rates (WER ≤ 2 nm/min) were observed at the top, sidewall, and bottom trench regions of the most conformal film deposited at low substrate temperature (<400 °C), which confirmed that the process is applicable for depositing high quality SiNx films on both planar and 3D substrate topographies.

Enabling Robust Copper Fill of High Aspect Ratio Through Silicon Vias

Todays Through Silicon Via (TSV) processes are limited to aspect ratios of 10:1. High performance logic devices drive the need for aspect ratios approaching 20:1 in order to achieve the desired performance while simultaneously reducing costs. The reduced via area required on the wafer enables the designer to utilize less real estate on the die to reduce cost or to potentially add redundant vias to improve yield. However, current conventional processes and techniques are not capable of achieving robust fill on aspect ratios greater than 12:1. This presentation will highlight the technical challenges in achieving robust copper fill on super high aspect ratio TSV structures. Additionally, a compelling, economic solution pathway will be presented that integrates a low temperature conformal high quality dielectric isolation layer, a high step coverage Cu barrier / seed technology and a void free high speed electroplating process with a wide process window that could accelerate the adoption of the high aspect ...