G. C. A. M. Janssen

MEASUREMENT OF ION IMPACT ENERGY AND ION FLUX AT THE RF ELECTRODE OF A PARALLEL PLATE REACTIVE ION ETCHER

An experimental study on the ion impact energy distribution and the total ion flux at the driven electrode of a parallel plate reactive ion etcher is presented. Results are shown for 13.56 MHz discharges in Ar, Ar/H2, N2, O2, Cl2, and SF6/He over a pressure range of 0.3–40 Pa. The ion impact energy distribution consists of a collision‐free part and a collision‐induced part. It is observed that in Ar, N2, O2, and Cl2 the collision‐induced part contains single and double peaks at regular energy intervals. This peaked structure is attributed to charge exchange processes in the sheath. Both the collision‐free part and the collision‐induced part of the ion impact energy distribution are well described by a model based on a constant sheath width, a sinusoidal sheath voltage, and a power law for the electric field in the sheath. The only adjustable parameter in the model is the sheath thickness. The sheath thickness has also been determined independently from the total ion current density using the Child–Langmui...

Selective chemical vapor deposition of tungsten using WF6 and GeH4

Germane (GeH4) has, for the first time, been used as a reducing agent for tungsten hexafluoride in selectively depositing tungsten on silicon. As shown by x‐ray diffraction, films deposited below 400u2009°C consist of the β‐W phase with A15 cubic crystal structure. This A15 structure proved to be stabilized by germanium which is probably incorporated in the film as a hitherto unknown W3Ge compound. Annealing for 1 h at 575u2009°C did not change the β‐W structure to the low‐resistivity body‐centered‐cubic α phase of tungsten. The superconducting transition temperature of the films is ≊3 K. The growth rate dependence on temperature, total pressure, and WF6, GeH4, and H2 partial pressure has been investigated. At deposition temperatures above 400u2009°C the deposited films consist of a mixture of the β and α‐W phase.

Cl2 reactive ion etching mechanisms studied by in situ determination of ion energy and ion flux

An experimental study of etching mechanisms in Cl2 reactive ion etching is reported. The ion‐impact energy distribution and ion current density have been measured in situ at the rf electrode of a parallel‐plate reactive ion etcher. This diagnostic method has been used for the first time to unravel etch characteristics in a practical etching environment. Samples of Si, SiO2, Ti, and TiSi2 have been etched both in Cl2 and Ar discharges, and the etch rates have been related to the ion flux and impact energy distribution. The angular impact energy distribution for both ions and neutrals has been calculated numerically in order to study the contribution of fast neutrals and the angular distribution of impinging species to the etch rate. Sputter yields have been determined from the observed etch rate and the ion current density, taking into account the (angular) energy distributions of bombarding ions and neutrals. Comparison of the obtained sputter yields in Ar and Cl2 discharges with corresponding data from (...

Stresses in sputtered Ti‐Si multilayers and polycrystalline silicide films

Titanium silicon multilayers have been produced by alternating sputter deposition. The stress in the as‐deposited layers is a function of the period of the multilayer structure. The multilayers were subsequently annealed to form silicide films. From stress and strain measurements on these films Poisson’s ratio is determined. After annealing, the films exhibit a tensile stress which can be attributed to the difference in thermal expansion coefficient between substrate and silicide film.

Incorporation of argon in titanium silicon multilayer structures during sputter deposition

Titanium silicon multilayer structures have been produced by alternate sputtering of silicon and titanium in an argon plasma. During the sputter process, part of the titanium and silicon layers react to form a silicide at the interfaces. Because of the argon plasma, a certain amount of argon is incorporated in the growing multilayer. A model is presented in which the amount of argon incorporated in the multilayer is a function of the nominal thickness of the individual silicon layers.

The etching mechanism of titanium polycide in a mixture of SF6 and O2

Reactive ion etching of titanium disilicide films on top of undoped polycrystalline silicon has been investigated in order to determine the etching mechanism of the silicide in a fluorine plasma. Mixtures of SF6 and O2 and of CF4 and O2 were used. Vertical and lateral etch rates have been determined as a function of pressure and the amount of oxygen addition. The density of fluorine atoms and positive ions in the plasma has been determined from optical emission spectroscopy and electric probe measurements, respectively. From these results, the fluxes of fluorine to and away from the sample and the ion flux towards the sample have been calculated. With x‐ray photoelectron and Auger electron spectroscopy, the surface constitution after etching has been studied. The TiSi2 layer is etched anisotropically, independent of pressure and the addition of oxygen. A relation between the etch rate and the density of fluorine atoms in the plasma is not found, in contrast with results obtained elsewhere [K. C. Cadien, S...

Growth stress in tungsten carbide-diamond-like carbon coatings

Growth stress in tungsten carbide-diamond-like carbon coatings, sputter deposited in a reactive argon/acetylene plasma, has been studied as a function of the acetylene partial pressure. Stress and microstructure have been investigated by wafer curvature and transmission electron microscopy (TEM) whereas composition and energy distribution functions of positive ions were obtained by electron probe microanalyzer, elastic recoil detection analysis, and mass-energy analyzer (MEA). It has been observed that the compressive stress decreases with increasing acetylene partial pressure, showing an abrupt change from ?5.0 to ?1.6 GPa at an acetylene partial pressure of 0.012 Pa. TEM micrographs show that by increasing the acetylene partial pressure in the plasma from 0 to 0.012 Pa, the microstructure of the coating changes from polycrystalline to amorphous. MEA results show that the most probable energy of positive ions bombarding the substrate during deposition in pure argon and argon/acetylene atmosphere is the same. Based on the results, it is concluded that the huge variation in the compressive stress at low acetylene partial pressures is due to a change in the microstructure of the coating from polycrystalline to amorphous and not to the energy of positive ions bombarding the film.

In Situ Stress Measurements during the reaction of WF 6 with Si(100)

We present measurements on the intrinsic stress developing during chemical vapour deposition of W and WSi 2 from the reaction between WF 6 and Si (100). It will be shown that depending on temperature and WF 6 partial pressure, three growth modes, corresponding with three different stress developments, can be distinguished. The results can be explained with three basic processes. The intrinsic tensile stress during the deposition of self limited W can be as high as 2 GPa.

Scratch test measurements on CrNx coatings

Hard CrNx coatings of various composition were deposited on hot work tool steel by means of reactive sputter deposition in an industrial PVD reactor. All deposited coatings (thickness 3-4 micron) were under compressive stress. The coatings were subjected to scratch testing with a diamond stylus. Two critical loads were determined. The first critical load, Lc1, indicates the onset of chipping and/or spalling. The second critical load, Lc2, indicates complete coating removal inside the track. Micrographs showing the coating failure are presented. Stoichiomeric CrN coatings outperform understoichiometric CrN0.6 coatings in scratch tests. It was found that for all specimens the coating-to-substrate adhesion is very good, independent on composition. Although the values of Lc1 and Lc2 are distinctly different, their dependence on composition is similar.

A study of dry etching mechanisms in CL 2 by Ion energy analysis at the RF-electrode

Abstract A quantitative experimental study on the etching mechanisms of Si, SiO 2 , Ti, and TiSi 2 in Cl 2 reactive ion etching is reported. The ion impact energy distribution and the ion current density have been measured in situ at the rf-electrode of a parallel plate reactor, together with the relevant etch rates. The ion transport through the collisional rf-sheath has been simulated using a Monte Carlo method. A separate method has been used to calculate the energy distribution of bombarding neutrals. This way the contribution of ions and fast neutrals to the sputter yield in Cl 2 RIE plasmas was established. The quantitative approach has been tested against etch results in Ar plasmas in which merely physical sputtering occurs and for which well-defined experimental results are available from the literature.