Metal silicides have played an indispensable role in the rapid developments of microelectronics since PtSi was first used to improve the rectifying characteristics of diodes in early 1960s. This wo ...

Metal silicides in CMOS technology : Past, present, and future trends

We review the surface chemistry and kinetics relevant to the chemical vapor deposition (CVD) of metals used for microelectronic applications. Our efforts focus on the surface chemistry of aluminum, tungsten, and copper CVD, which have received the most recent interest for metallization. We first briefly review a variety of topics concerning the applications and the chemistry and kinetics of metal CVD. We also give a brief overview of the application of surface science techniques to the study of CVD-related surface chemistry.

Metal CVD for microelectronic applications: An examination of surface chemistry and kinetics

Vapor growth techniques such as evaporation, sputtering, molecular beam epitaxy (MBE), and chemical vapor deposition (CVD) are usually used for large-area thin film deposition. However, local, or so-called selective, deposition onto desired regions of patterned substrates can be attained. Principally, there exist several categories of selective growth systems. In area-selective growth, the deposition takes place only on one substrate material, and no deposition is obtained on the other. This selectivity is based on a difference in the interfacial reactions between the different substrate materials and the vapor. The interfacial reactions on one substrate material should be inhibited completely to avoid nucleation, whereas the deposition reactions should be stimulated on those substrate areas where the depositon will occur. In phase-selective deposition, different phases are deposited simultaneously and selectively on the different substrate materials. In analogy to the phase-selective deposition,...

Selective vapor-phase deposition on patterned substrates

The room‐temperature electrical resistivity, grain size, and impurity content of tungsten films deposited at low pressure on silicon wafers from tungsten hexafluoride and hydrogen reactants were determined These properties were examined as functions of deposition temperature and film thickness The resistivity is independent of thickness at a value of approximately 135 μΩ cm for films deposited at 300 °C For films deposited at 400 °C, the resistivity decreases from 24 to 85 μΩ cm as thickness increases from 0075 to 1 μm The resistivity behavior is interpreted in terms of grain‐boundary scattering with a zero reflection coefficient for the 300 °C films For the 400 °C films, a reflection coefficient that decreases from 067 to 038 over the above thickness range and a linear dependence of grain size on thickness are utilized For both deposition temperatures, the grain size exhibits a rapid initial growth to 30 nm followed by growth at a slope of 032 with respect to thickness The rapid initial growth is associated with the rapid, self‐limiting tungsten hexafluoride/silicon reaction The oxygen content of the films tracks the trend of the reflection coefficient in that it increases with increased deposition temperature or decreased film thickness Evidence suggests that the oxygen is located predominantly at grain boundaries and may be the primary determinant of boundary scattering Fluorine is found in films at concentrations (003–005 at %) similar to those of oxygen but does not vary with thickness and decreases with increased deposition temperature No evidence is found for surface scattering of carriers suggesting that all are specularly scattered Grain‐boundary scattering, with a constant reflection coefficient, adequately interprets previously published data Utilizing such results, together with the present ones, leads to the conclusions that the grain size is relatively independent of deposition temperature while the intragrain resistivity decreases with temperature and approaches the bulk value for 600 °C deposition

Resistivity, grain size, and impurity effects in chemically vapor‐deposited tungsten films

When two-dimensional (2D) group-VI transition metal dichalcogenides such as tungsten disulfide (WS2) are grown by atomic layer deposition (ALD) for atomic growth control at low deposition temperatures (≤450 °C), they often suffer from a nanocrystalline grain structure limiting the carrier mobility. The crystallinity and monolayer thickness control during ALD of 2D materials is determined by the nucleation mechanism, which is currently not well understood. Here, we propose a qualitative model for the WS2 nucleation behavior on dielectric surfaces during plasma-enhanced (PE-) ALD using tungsten hexafluoride (WF6), dihydrogen (H2) plasma and dihydrogen sulfide (H2S) based on analyses of the morphology of the WS2 crystals. The WS2 crystal grain size increases from ∼20 to 200 nm by lowering the nucleation density. This is achieved by lowering the precursor adsorption rate on the starting surface using an inherently less reactive starting surface, by decreasing the H2 plasma reactivity, and by enhancing the mob...

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Two-Dimensional Crystal Grain Size Tuning in WS2 Atomic Layer Deposition: An Insight in the Nucleation Mechanism

We have analyzed the interfacial structure of selectively deposited LPCVD tungsten on monocrystalline silicon, polycrystalline silicon, and polycrystalline aluminum substrates. Cross-sectional specimens were examined by transmission electron microscopy to determine the amount of substrate consumed by the selective deposition process and to assess the degree of lateral encroachment under masking SiO/sub 2/ layers for different conditions of deposition and surface preparation. The tungsten-silicon interfacial structure was found to depend strongly on the initia surface preparation. Immersion in a dilute HF solution resulted in a smooth interface, while a glow-discharge treatment (CF/sub 4/ + O/sub 2/) led to highly irregular interfaces, which, in extreme cases, contained tunnels extending 1 ..mu..m or more into the silicon substrate. Layers formed in WF/sub 6/ plus H/sub 2/ were found to consist of two layers, of which the lower layer i formed by the substrate reduction of WF/sub 6/.

W. T. Stacy

Papers

Interfacial Structure of Tungsten Layers Formed by Selective Low Pressure Chemical Vapor Deposition