S. Peter

Comparative experimental analysis of the a-C:H deposition processes using CH4 and C2H2 as precursors

The plasma enhanced chemical vapor deposition of a-C:H films using methane and acetylene as precursors was studied. Noninvasive in situ techniques were used to analyze the plasma processes with respect to the self-bias voltage, the displacement currents to the grounded electrode, the neutral gas composition, the optical sheath thickness as well as current and energy of the ions hitting the powered electrode. The a-C:H films were characterized for their deposition rate, surface roughness, hardness, mass density, and hydrogen content. Ion mean free paths, suitable for low-pressure rf sheaths, have been quantified for both precursors. The film with the highest hardness of 25GPa was formed in the C2H2 discharge when the mean energy per deposited carbon atom was approximately 50eV. The hardness obtained with the CH4 discharge was lower at 17GPa and less sensitive to changes in the process parameters. It was found that the creation of hard (hardness >15GPa) a-C:H films from both precursors is possible if the me...

Two N2+(B2 u+) populations with different Boltzmann distribution of the rotational levels found in different types of N2/Ar discharges—improved estimation of the neutral gas temperature

We investigated the rotational excitation of the nitrogen molecule ion in a pulsed magnetron sputter discharge (Mg target, pressure 0.1–2.0 Pa) and a 150 Pa dc glow discharge in dependence on various process parameters. For this purpose we used optical emission spectroscopy of the 0–0 band of the first negative system of the (FNS0–0) and calculated the rotational temperature by fitting the spectra. Often, the best fit could be achieved assuming two populations of the molecules having two different rotational temperatures. These temperatures and their contributions to the spectrum of the FNS0–0 show a significant dependence on the process parameters. The lower temperature is in the range of 370–800 K and is believed to be equal to the translational temperature of the neutral gas. The higher temperature is in the order of 1500–3000 K and its origin is most probably the excitation of the state by heavy particle impact connected with rotational excitation.

Characterization of the arc evaporation of a hot boron cathode

Cathodic arc discharge with a hot boron cathode has been characterized by high-speed photography, mass spectroscopy and ion energy analysis. During operation, the cathode surface exhibits an extended molten area in which moving cathode spots could be detected by the high-speed cine-camera. This leads to the conclusion that the hot boron cathode exhibits a mixed arc mode including features both of thermionic and spot modes. The charge state distribution, as well as the kinetic energy of the boron ions emerging from the cathode, were measured and conclusions have been drawn with respect to the underlying mechanisms.

Low temperature plasma enhanced chemical vapor deposition of thin films combining mechanical stiffness, electrical insulation, and homogeneity in microcavities

The deposition of hydrogenated amorphous carbon (a-C:H) as well as hydrogenated amorphous silicon carbonitride (SiCN:H) films was investigated in view of a simultaneous realization of a minimum Young’s modulus (>70 GPa), a high electrical insulation (≥1 MV/cm), a low permittivity and the uniform coverage of microcavities with submillimeter dimensions. For the a-C:H deposition the precursors methane (CH4) and acetylene (C2H2) were used, while SiCN:H films were deposited from mixtures of trimethylsilane [SiH(CH3)3] with nitrogen and argon. To realize the deposition of micrometer thick films with the aforementioned complex requirements at substrate temperatures ≤200 °C, several plasma enhanced chemical vapor deposition methods were investigated: the capacitively coupled rf discharge and the microwave electron cyclotron resonance (ECR) plasma, combined with two types of pulsed substrate bias. SiCN:H films deposited at about 1 Pa from ECR plasmas with pulsed high-voltage bias best met the requirements. Pulsed ...

Optical emission spectroscopy of a PCVD process used for the deposition of TiN on cemented carbides

In CVD processes enhanced by plasma excitation of the gaseous species the analysis of the optical emission spectra enables the direct observation of reactive species in the close vicinity of the growing film. In this paper we report on a new OES study of the PCVD process for the deposition of titanium nitride from pulsed DC TiCl4–H2–N2–Ar discharges. From the results we expect a better understanding of the plasma processes used in the coating production. Using optimized conditions of spectra recording, we selected reliable signals (lines/bands) of 12 species (Ti, Ti+, Cl, Cl+, H2, H, N2, N2+, N, N+, Ar and Ar+) involved in the TiN deposition process. The OES measurements were made with successively modified process parameters. An analysis of the waveforms of both the discharge current and the OES signals gave insights into the dynamics of the pulsed discharge. The characteristic temporal evaluation of the discharge was attributed to the slow movement of the ionization front from the cathode to the anode.

Characteristics of the cathodic arc discharge with a hot boron cathode

Recently, the authors developed a cathodic arc evaporation source with a heated boron cathode and successfully applied it to the deposition of cubic BN thin films. The cathode surface area under operation exhibits an extended red-hot area and therefore the so-called distributed arc mode was suspected first. Nevertheless, high-speed photography has revealed that cathode spots exist which move randomly in a similar manner as cathode spots on metal. The discharge mode of the hot boron cathode has been characterized both in Ar and a N/sub 2//Ar atmosphere. The properties of the ion component of the emitted plasma were investigated by energy-resolved mass spectroscopy and conclusions are drawn on the potentials of the boron are evaporation as a deposition process for c-BN films.

Determination of mass and energy distribution of ions in glow discharges

Abstract Equipment was designed for the study of energy and mass distribution of particles hitting the cathode of a glow discharge. Energy and mass analysis were performed using a two-stage differentially pumped plasma monitor. The plasma monitor consisted of a quadrupole mass spectrometer and a modified cylindrical mirror analyser that can measure parallel ion beams. D.c. and pulsed discharges were investigated under conditions typical for plasma assisted chemical vapour deposition and plasma diffusion treatment. Gas atmospheres containing nitrogen, hydrogen, argon and tetramethylsilane (TeMS) were studied at pressures of some millibars. Ions prevailing at the cathode are formed by electron impact ionization of species having low ionization potential. The appearance of ArH + and N 2 H + ions can be explained by ion-molecule reactions. The addition of nitrogen to a TeMS-H 2 -Ar discharge caused a higher degree of fragmentation of the organometallic precursor and an increase in ion energy. Even in the case of d.c. excitation the energy of nearly all the ions exceeds the sputtering threshold of materials (10–30 eV for metals).

Cathodic Arc Evaporation - A Versatile Tool for Thin Film Deposition

Cathodic arc evaporation as a deposition technique (cathodic arc deposition CAD) is rapidly developing, emerging different novel variants. Three new fields of science and technology of CAD are reviewed: i) an analytical model of reactive CAD of metal cathodes, ii) the deposition of amorphous CN x films by filtered carbon arc deposition combined with a nitrogen ion source and iii) the first realization of a CAD process with a hot boron cathode which among others is suitable for cubic boron nitride deposition.

An analysis of the TiN plasmachemical vapor deposition process based on optical emission spectroscopy measurements

Optical emission spectroscopy measurements and film deposition experiments were performed for better understanding and control of the plasmachemical vapor deposition (PCVD) process used in the coating production of Widia/Valenite. The effects of the titanium chloride flow, the nitrogen flow, the mean discharge current density and the pressure were investigated. The coatings were characterized with respect to deposition rate, composition, crystallographic structure and Vickers microhardness. In particular, the dependence on process parameters of emission signals (lines/bands) from 12 species (Ti, Ti + , Cl, Cl + , H 2 , H, N 2 , N + 2 , N, N + , Ar and Ar + ) involved into the TiN deposition process was analyzed. Additional spatially resolved OES measurements of the 12 species revealed in particular that the emission of Ti + arises only from near the cathode surface. Based on an empirical model it was shown that the emission of atomic titanium is related to the intrinsic titanium deposition rate whereas the emission of ionized titanium results from the etching of titanium not yet bounded to nitrogen from the surface.

The effect of additional ion/plasma assistance in CNx-film deposition based on a filtered cathodic arc

Abstract The crucial parameters in CN x -film deposition are the nature of carbon and nitrogen species and their kinetic energy. The filtered cathodic arc produces a highly ionised carbon plasma, containing mainly C + ions. In a standard reactive process, deposition is performed in a reactive gas atmosphere, and there is only little control of the degree of ionisation and kinetic energy of the gas species. Therefore, three types of ion or plasma sources have been used for additional nitrogen bombardment during the deposition of CN x -films: a two-grid Kaufman ion source, a gridless Kaufman source and a hollow anode plasma source. Characterisation of the different types of nitrogen plasma or ion beams was carried out by means of energy resolved mass spectroscopy and electric probe measurements. The films have been analysed for their chemical composition, microstructure and mechanical properties. High energy ion bombardment from the two-grid Kaufman ion source yields films with relatively high nitrogen content (up to 30 at.%) but rather poor mechanical properties. Using the nitrogen beams from the two other sources CN x -films with lower N-content but enhanced mechanical properties have been found.