Jon Tomas Gudmundsson

High power impulse magnetron sputtering discharge

The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulse ...

Ion-assisted physical vapor deposition for enhanced film properties on nonflat surfaces

We have synthesized Ta thin films on Si substrates placed along a wall of a 2-cm-deep and 1-cm-wide trench, using both a mostly neutral Ta flux by conventional dc magnetron sputtering (dcMS) and a mostly ionized Ta flux by high-power pulsed magnetron sputtering (HPPMS). Structure of the grown films was evaluated by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The Ta thin film grown by HPPMS has a smooth surface and a dense crystalline structure with grains oriented perpendicular to the substrate surface, whereas the film grown by dcMS exhibits a rough surface, pores between the grains, and an inclined columnar structure. The improved homogeneity achieved by HPPMS is a direct consequence of the high ion fraction of sputtered species.

Spatial and temporal behavior of the plasma parameters in a pulsed magnetron discharge

We demonstrate the evolution of the electron, energy distribution and the plasma parameters in a high-density plasma in a pulsed magnetron discharge. The high-density plasma is created by applying ...

Electronegativity of low-pressure high-density oxygen discharges

We use a global (volume averaged) model to study the presence of negative ions and metastable species in low-pressure high-density oxygen discharges. We find the negative oxygen ion O- to be the dominant negative ion in the discharge, the density of the negative ion O2- to be small and the density of the negative ion O-3 to be negligible in the pressure range of interest, 1-100?mTorr. Dissociative attachment of the oxygen molecule in the ground-state O2(3?g-) and the metastable oxygen molecule O2(a1?g) are the dominating channels for the creation of the negative oxygen ion O-. At low pressure (<5?mTorr) recombination involving O- and O+ ions is the main loss channel for O- ions. At higher pressure, the detachment on O(3P) becomes the main loss channel for the O- ion. The creation of O-2 is mainly through dissociative attachment of ozone O3. Ozone is almost entirely created through detachment by the collision of O- with the metastable oxygen molecule O2(a1?g). The creation of O-2 is thus greatly influenced by this detachment process and neglecting the detachment has a significant influence on the density of O-2 ions. At low pressure (<10?mTorr) the O-2 ion is mainly lost through recombination while at higher pressure the charge transfer to form O2 is the dominating loss process.

On the effect of the electron energy distribution on the plasma parameters of an argon discharge: a global (volume-averaged) model study

A global (volume-averaged) model is applied to investigate the effect of the electron energy distribution function on the plasma parameters of a high-density, low-pressure, argon discharge. The effective electron temperature increases and the electron density decreases as the electron energy distribution is varied from being Maxwellian to become Druyvesteyn like. The sheath voltage decreases as the electron energy distribution function is varied from being Maxwellian to become Druyvesteyn like for low pressures ({<}2 mTorr) and increases for higher pressures as the electron energy distribution function is varied. Simple global model calculations demonstrated that increasing the operating pressure does not necessary lead to a higher electron density if the electron energy distribution evolves from Maxwellian to become more Druyvesteyn like as the operating gas pressure is increased.

Evolution of the electron energy distribution and plasma parameters in a pulsed magnetron discharge

We demonstrate the creation of high-density plasma in a pulsed magnetron discharge. A 2.4 MW pulse, 100 μs wide, with a repetition frequency of 50 Hz is applied to a planar magnetron discharge to study the temporal behavior of the plasma parameters: the electron energy distribution function, the electron density, and the average electron energy. The electron density in the vicinity of the substrate, 20 cm below the cathode target, peaks at 8×1017 m−3, 127 μs after initiating the pulse. Towards the end of the pulse two energy groups of electrons are present with a corresponding peak in average electron energy. With the disapperance of the high-energy electron group, the electron density peaks, and the electron energy distribution appears to be Maxwellian like. Following the electron density peak, the plasma becomes more Druyvesteyn like with a higher average electron energy.

Oxygen discharges diluted with argon: dissociation processes

We use a global (volume averaged) model to study the dissociation processes and the presence of negative ions and metastable species in a low pressure high density O2/Ar discharge in the pressure range 1?100?mTorr. The electron density and the fractional dissociation of the oxygen molecule increases with increased argon content in the discharge. We relate this increase in fractional dissociation to an increase in the reaction rate for electron impact dissociation of the oxygen molecule which is due to the increased electron temperature with increased argon content in the discharge. The electron temperature increases due to higher ionization potential of argon than for molecular and atomic oxygen. We find the contribution of dissociation by quenching of the argon metastable Arm by molecular oxygen (Penning dissociation) to the creation of atomic oxygen to be negligible. The negative oxygen ion O? is found to be the dominant negative ion in the discharge. Dissociative attachment of the oxygen molecule in the ground state and in particular the metastable oxygen molecule O2(a?1?g) are the dominating channels for creation of the negative oxygen ion O?.

Improved volume-averaged model for steady and pulsed-power electronegative discharges

An improved volume-averaged global model is developed for a cylindrical (radius R, length L) electronegative (EN) plasma that is applicable over a wide range of electron densities, electronegativities, and pressures. It is applied to steady and pulsed-power oxygen discharges. The model incorporates effective volume and surface loss factors for positive ions, negative ions, and electrons combining three electronegative discharge regimes: a two-region regime with a parabolic EN core surrounded by an electropositive edge, a one-region parabolic EN plasma, and a one-region flat-topped EN plasma, spanning the plasma parameters and gas pressures of interest for low pressure processing (below a few hundred millitorr). Pressure-dependent effective volume and surface loss factors are also used for the neutral species. A set of reaction rate coefficients, updated from previous model calculations, is developed for oxygen for the species O2, O2(Δg1), O, O2+, O+, and O−, based on the latest published cross-section set...

A global (volume averaged) model of a nitrogen discharge: I. Steady state

A global (volume averaged) model is developed for a nitrogen discharge in the steady state for the pressure range 1?100?mTorr. The electron energy distribution function is allowed to vary from a Maxwellian to a Druyvesteyn distribution. Varying the electron energy distribution function from a Maxwellian-like to a Druyvesteyn-like influences mainly the density of excited species, ground state species being more important when the distribution is Druyvesteyn-like. We find that the nitrogen discharge is essentially atomic when the pressure is around 1?mTorr and is highly molecular when the pressure is 100?mTorr. The relative reaction rates for the creation and destruction of nitrogen atoms and atomic ions are explored over the pressure range of interest. The model calculations are compared with measurements found in the literature. There is excellent agreement between the model and the measurements for the electron and ion densities as well as the electron temperature. However, a large discrepancy between the model predictions and the measurements of the nitrogen atom density remains unexplained.

Plasma dynamics in a highly ionized pulsed magnetron discharge

We report on electrostatic probe measurements of a high-power pulsed magnetron discharge. Space- and time-dependent characteristics of the plasma parameters are obtained as functions of the process parameters. By applying high-power pulses (peak power of ~0.5 MW), with a pulse-on time of ~100 µs and a repetition frequency of 20 ms, peak electron densities of the order of ~1019 m− 3, i.e. three orders of magnitude higher than for a conventional dc magnetron discharge, are achieved soon after the pulse is switched on. At high sputtering gas pressures (>5 mTorr), a second peak occurs in the electron density curve, hundreds of microseconds after the pulse is switched off. This second peak is mainly due to an ion acoustic wave in the plasma, reflecting off the chamber walls. This is concluded from the time delay between the two peaks in the electron and ion saturation currents, which is shown to be dependent on the chamber dimensions and the sputtering gas composition. Finally, the electron temperature is determined, initially very high but decreasing rapidly as the pulse is turned off. The reduction seen in the electron temperature, close to the etched area of the cathode, is due to cooling by the sputtered metal atoms.