Witold Posadowski

Sustained self‐sputtering using a direct current magnetron source

Sustained self‐sputtering of copper and silver targets has been achieved using a direct current magnetron source. The sputtering was carried out successfully without an inert gas at 8×10−6 Torr. A very high deposition rate was obtained in this mode of operation. The possible mechanism and requirements for sustained self‐sputtering are discussed and other potential material candidates are suggested.

Plasma parameters of very high target power density magnetron sputtering

Abstract The high target power density (up to ∼1000 W cm −2 ) of a magnetron sputtering process was studied by means of optical emission spectroscopy and Langmuir probe characteristics. The goal of this research was to estimate the composition (neutrals and ions) and parameters of the plasma (temperature T e and density n e of electrons) at different technological parameters. Copper targets with a diameter of 50 and 100 mm were sputtered. The argon pressure was changed from 0 (final pressure equal to 1×10 −5 torr) to 5×10 −3 torr. This corresponded to self-sustained (at the final vacuum pressure) and standard argon sputtering modes, respectively. The dominant role of copper ions was observed (404.3 + nm ion line intensity in relation to 402.3 * and 406.3 * excited neutrals line intensities) during both the self-sustained and argon modes of high target power density. The line intensity of copper ions near the etched target surface (cathode voltage fall) increased substantially when the target current increased. The substrate current density (at a distance between target and substrate equal to 9 cm) increased significantly with the decrease of the parallel component of the magnetic field intensity (at constant target current). At this distance, a sputtering rate of ∼5 μm min −1 was achieved for the Cu target of 50 mm in diameter.

Sustained self sputtering of different materials using dc magnetron

Abstract The increase of the target power density causes not only the deposition rate increase, but also gives the possibility of introducing a new way of magnetron sputtering. With high sputtering rates, the secondary ions of sputtered metal begin to play an important role. In the extreme case, the discharge can be sustained with secondary ions only in a so-called ‘pure’ self-sputtering. When this phenomenon occurs the magnetron sputtering process can go on at the final pressure of the vacuum set, (i.e. 4 × 10 −4 Pa). It means that during self-sputtering (SSS) sustained on metal ions the contamination by inert gas particles has been eliminated. The author has proposed an observation of the relation between the minimum values of the target current, (target current density, target power density) and the working gas (argon) pressure, at which the discharge still exists, as an ‘instrument’ of the SSS effect. The paper presents a relation I Tmin ( i Tmin ; Pr Tmin ) versus p wmin , which was measured during Cu, Ag, Ti, Ni, Ta, AI and stainless steel sputtering. The current-voltage characteristics have been measured. The ‘pure’ SSS effect has been observed during Cu, Ta, Ag and stainless steel sputtering. For other materials, the target current increase caused a decrease of the sputtering process pressure. Planar magnetrons of very high efficiency were used. Targets of 50, 100 and 200 mm in diameter were sputtered at power densities up to 300 W/cm 2 .

Directional copper deposition using dc magnetron self-sputtering

A directional copper deposition process has been developed that uses a dc magnetron source operating in self-sputtering mode. The process is performed at 10−5 Torr range pressure where a “long throw” approach can be utilized without discharge enhancement or mechanical collimation due to a very long mean free path of sputtered species. Magnetron sputtering conditions at which the contact hole filling is promoted and substantially enhanced by the self-sputtering process are illustrated and compared to standard sputtering (i.e., short throw, mTorr pressure) in the presence of argon. The experimental parameters of the new process have been explored by depositing Cu on patterned Si wafers with trenches and contact holes of various aspect ratios.

Pulsed magnetron sputtering of reactive compounds

Abstract The Al, Si and Ti targets were sputtered in a reactive atmosphere of argon & oxygen and argon&nitrogen. The pulsed magnetron power supply generated a series of one polarity 160 kHz puises grouped with 2.5 kHz, The amplitude of negative current pulses was constant and equal to 8 A. Target power was accomplished by varying the number of pulses within an interval. The relations between target surface contamination with reactive compounds and power supply parameters were investigated.

Properties of TiNxfilms reactively sputtered in an argon-nitrogen atmosphere

Abstract The dependence of the resistivity and temperature coefficient of resistivity (TCR) of TiN x films on nitrogen pressure is described. The partial nitrogen pressure was varied from 10 −5 Torr to 2×10 −4 Torr. The maximum value of the resistivity (216 μΩ cm) and the lowest negative value of TCR (−33 ppm K −1 ) were obtained in the nitrogen pressure range (2−4)×10 −5 Torr. The minimum value of the resistivity (44 μΩ cm) and the highest positive value of the TCR (1160 ppm K -1 were obtained in the nitrogen pressure range (4−10)×10 −5 Torr. The influence of aging temperature up to 573 K on the resistance changes are shown. X-ray diffraction analysis indicated the presence of oriented or non-oriented TiN in these films.

Structure of thin films prepared by the cosputtering of titanium and aluminium or titanium and silicon

Abstract Structural modifications of thin films prepared by the cosputtering of titanium and aluminum or titanium and silicon in an N 2 Ar atmosphere are reported. The influence of the nitrogen content on the phase composition, microstructure and orientation of the films was analysed. The results obtained were compared with the structural properties of films produced under similar conditions by sputtering single titanium, aluminium and silicon targets.

Low pressure magnetron sputtering using ionized, sputtered species

Abstract The possibility of a self-sustained magnetron sputtering process, without the presence of an inert gas, is demonstrated. The advantages of this process are as follows: the possibility of thin metal film deposition at very low pressures p ⩽ 4 × 10−4 Torr; a very high sputtering rate; an absence of inert gas particles in the deposited films; a possibility of deposition on substrates placed at a distance from the target much smaller than the mean free path; a decrease in the plasma discharge influence on substrate, the substrate can be placed at a greater than usual distance from the target. Low pressure magnetron sputtering using target ions opens new possibilities for thin film deposition. The method combines the advantages of both electron beam evaporation (purity, rate) and sputtering (good adhesion, repeatability, free choice of deposition geometry).

Electric properties of Ti―Si―N thin cermet films deposited in a triode sputtering system with a hot cathode

Abstract The electrical properties of Ti-Si-N films deposited in a triode sputtering system with a hot cathode are presented in this paper. The process conditions P N 2 = 1.6 × 10 -4 Torr, P N 2+Ar = 5 × 10 -4 Torr, and U T = -500 V were selected so as to obtain a mixture of Si 3 N 4 -TiN as a result of reactive sputtering of a two-component Ti-Si target. Films with a TiN composition varying within 55%–95% had a resistivity of about 400 × 10 -8 Ω m and a temperature coefficient of resistance TCR = -20 ppm K -1 , while resistance variations Δ R / r during aging at a temperature T a = 523 K and t a = 1000 h did not exceed 1%.

Pulsed dc self-sustained magnetron sputtering

The magnetron sputtering has become one of the commonly used techniques for industrial deposition of thin films and coatings due to its simplicity and reliability. At standard magnetron sputtering conditions (argon pressure of ∼0.5Pa) inert gas particles (necessary to sustain discharge) are often entrapped in the deposited films. Inert gas contamination can be eliminated during the self-sustained magnetron sputtering (SSS) process, where the presence of the inert gas is not a necessary requirement. Moreover the SSS process that is possible due to the high degree of ionization of the sputtered material also gives a unique condition during the transport of sputtered particles to the substrate. So far it has been shown that the self-sustained mode of magnetron operation can be obtained using dc powering (dc-SSS) only. The main disadvantage of the dc-SSS process is its instability related to random arc formation. In such case the discharge has to be temporarily extinguished to prevent damaging both the magnet...