Dries Dictus

Influence of crystallographic orientation on dry etch properties of TiN

A study of the impact of physical vapor deposition conditions on the etch properties of TiN has been conducted using a transformer coupled plasma. This work focuses only on a Cl2-based etch plasma. It is shown that the crystallographic orientation of TiN, observed from x-ray diffraction spectra, has a major influence on the etch behavior. Etch yields at varying dry etch conditions of two types of TiN, with different crystallographic orientations, have been studied quantitatively. The high roughness which is created during plasma exposure was identified as being the result of different etch rates of grains and intergranular material at the grain boundaries. Moreover, it is shown that TiN(111) is more difficult to etch, resulting in more pronounced roughness, than TiN(200), which is easier to etch, resulting in smoother surfaces for certain process conditions.

Unusual Modification of CuCl or CuBr Films by He Plasma Exposure Resulting in Nanowire Formation

In this paper, we present a method for growing copper-based nanowires. The method is based on the unusual modification of a halogenated copper surface by exposure to a helium plasma. The nanowires have diameters ranging between 50 and 150 nm and lengths up to 50 microm. They are polycrystalline, and large parts of the wires have a pronounced core-shell structure with a dense shell and less material inside. The wires are grown in a plasma environment at room temperature, and large amounts can be grown in a matter of minutes. The critical process parameters for the growth process are the gas flow and pressure settings, and the impact thereof will be discussed in detail. In order to gain insight in a possible growth mechanism, our observations are compared with literature on the growth of silver whiskers from halogenated silver crystallites. Finally, photoluminescence spectra of the wires are discussed in view of the analytical data about the stoichiometry and structure of the nanowires.

Impact of metal etch residues on etch species density and uniformity

Uniformity and wafer-to-wafer reproducibility of plasma etch processes are often related to the conditioning of the plasma etch chamber walls. For advanced complementary metal-oxide semiconductor fabrication, numerous metals are used which might deposit on the chamber walls during etch processes and as these metals are not always straightforward to remove, process instabilities can occur. This happens because recombination of atomic species on the chamber walls determines to a certain degree the plasma composition. Therefore, in this article, the impact of metal etch residues, especially titanium and tantalum residues, on plasma composition and uniformity is studied. The chamber walls are analyzed by x-ray photoelectron spectroscopy analysis of so-called floating samples and the densities of Cl, Br, O and F in Cl2, HBr, O2, and SF6 plasmas are monitored by optical emission spectroscopy. Plasma uniformity is checked by measuring etch rates across 300 mm silicon wafers. It is found that chlorine and bromine...

Wet Etch Characteristics of Hafnium Silicate Layers

To facilitate selective removal of the gate dielectric toward the gate electrode, wet etch characteristics of HfSiO x and HfSiO x (N) in acidified HF solutions were determined as a function of several process parameters. Etch behavior of Hf-silicates was found to be little influenced by the various chemical vapor deposition processes. The top part (0-2 nm) of thick Hf-silicate layers etched similar to as-deposited thin layers (<2 nm), while the bulk part etched significantly more slowly. However, etch rates were strongly dependent on composition (lower for Hf-rich silicates). Also, the removal rate of HfSiO,( N) was mainly dependant on the amount of incorporated nitrogen and crystallization temperature. Thermally nitrided layers were easier to remove compared to plasma-nitrided layers. Postnitridation anneals at high temperature in nitrogen environment decreased the etch rate. After removal, Hf concentrations below 1 X 10 11 atoms/cm 2 for most of the HfSiO x (N) layers under study were observed after a short (typically a few seconds) etch process in a single-wafer spin-cleaning tool.

Using Ellipsometry for Assessment of TiN Surface Roughness after Plasma Etch

Continuous downscaling of semiconductor devices that enables high-speed operation and miniaturization of modern integrated circuits brings new challenges for semiconductor manufacturing. Conventional materials used for the gate stack polycrystalline Si as a gate electrode and SiO2 as a gate dielectric can no longer comply with stringent requirements of low gate-leakage current and high source–drain drive current. Aggressive scaling of SiO2 results in increased leakage current, while poly-Si gates suffer from depletion and boron diffusion into the channel region. In order to alleviate these problems, SiO2 is being replaced by dielectrics with high dielectric constant 1 high-k dielectrics while polycrystalline Si is substituted by metallic conductors called metal gates. 2 One of the materials used as metal gate is titanium nitride TiN. It is readily available in semiconductor manufacturing because it is already used as a diffusion barrier for copper metallization and as an antireflective coating ARC for aluminum metallization. One TiN deposition method is physical vapor deposition PVD. Historically, the first PVD TiN was prepared by sputtering of Ti target in the presence of N2 ambient. 3,4 No substrate bias is applied to the substrate that is kept at room temperature. Such a process was used to obtain ARC for patterning of Al metallization, and PVD TiN of that type is sometimes referred to as ARC TiN. Later, when PVD TiN started to be used for diffusion-barrier applications, it was found that the topography coverage of ARC TiN is far from perfect. In order to improve it, a new deposition technique called ionized metal plasma IMP was developed. The main difference between ARC and IMP is that in the IMP source the metal is ionized and a bias is applied to the substrate, resulting in improved topography coverage. 5 The substrate temperature can be varied in the limits of 0–450°C. It is known that the microstructure of PVD TiN depends on power settings and substrate temperature during the deposition process. 6 Usually it has a columnar structure with columns oriented perpendicular to the substrate. When no bias is applied to the substrate and deposition temperature is relatively low close to room temperature, which is the case for ARC TiN, the columns are oriented in 111 direction when the film is relatively thick thicker that several tens of nonometers. 7,8 Application of bias typical for IMP TiN changes the column orientation to 200 or in some cases can result in almost amorphous layers.