R.W. Thomae

Niobium oxide thin films formed by plasma immersion oxygen ion implantation

Abstract In analogy to conventional beam-line ion implantation, plasma immersion ion implantation can be combined with a deposition technique to an ion assisted coating process. The structure and composition of a coating and its interface to the substrate can be modified by ion implantation. By means of electron beam evaporation and oxygen plasma immersion ion implantation niobium oxide films were prepared at low substrate temperatures (

Lateral implantation dose measurements of plasma immersion ion implanted non-planar samples

Abstract The homogeneity of plasma immersion ion implantation of non-planar samples was determined by Rutherford backscattering analysis. Half-cylinders made of carbon treated by argon ions served as a model system. The distribution of the implanted argon dose on the top plane and on the side plane of the samples was analysed. The results show a maximum dose at the centre of the top plane and a decrease towards the edges. On the side plane the dose increases from top to bottom. These variations were up to fifty percent. Additionally, a variation in implantation depth depending on the energy of the implanted ions and on the angle of incidence was observed. These effects are due to the sample size and the process parameters determining the dimensions of the plasma sheath which wraps the sample. A possible explanation for these phenomena is based on the assumption that on their way from the plasma to the sample the ions do not follow bent electrical field lines which occur near the edges of a sample.

High current ion implantation by plasma immersion technique

Abstract Plasma immersion ion implantation (PIII) is a novel technique which is under investigation at several laboratories. In this paper we present a short review on existing experiments and work which is done at the Frankfurt PIII experiment.

Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique

Abstract Plasma immersion ion implantation (PIII) is a new technique for surface modifications of materials. In contrast to conventional ion implantation techniques the target is surrounded by the plasma and then pulse biased to high negative voltages. The implantation dose and homogeneity are essentially dependent on plasma density and plasma sheath dynamics. In this paper we present measurements on plasma density and sheath expansion. The plasma is generated in a rf ion source with inductive coupling (13.56 MHz) and diffuses into the target processing chamber. Carbon targets are implanted with Ar ions and analysed by RBS analysis.

Recent developments in ion implantation accelerators

Abstract Ion implantation technology plays an important role in different fields of materials modification and has become a well established industrial technique. In semiconductor device fabrication more than 1000 ion implanters operating in the low- and medium-energy range (≤, 400 keV) are working worldwide. There is also an increasing interest in the improvement of the surface properties of metals, ceramics, and polymers by means of ion implantation. For some of the newer applications the required penetration depth is large, up to several μm, corresponding to an ion beam energy of several MeV. Furthermore, certain processes involve implant doses up to 1018 ions/cm2, which implies that high currents are needed as well. Both requirements — high ion current and high energy — are difficult to fulfill simultaneously by the commonly used static machines. Modem rf linacs combine strong radial focusing with efficient acceleration, which allows for high currents and high energy. In this paper recent developments in this field will be discussed.

Sputter and diffusion processes in a plasma immersion device

Abstract Plasma immersion ion implantation (PIII) is a technique for surface modification. In contrast to conventional ion implantation techniques the target is surrounded by plasma and then pulse biased to high negative voltages. In our experiment the plasma is generated in a radio frequency ion source with inductive coupling (13.56 MHz) and diffuses into the target processing chamber. In this paper we report on the measurements of surface sputtering occurring during oxygen and argon implantation into silicon targets. Surface sputtering accounts for the dose limitation of the implanted ions. By combining vapor-deposition of neutral atoms with implantation and diffusion we obtained layers of stoichiometric silicon and oxygen ratio with thicknesses of > 300 nm.

Design study of high energy, high current rf accelerators for ion implantation

Abstract Ion implantation is of great importance in semiconductor device fabrication. Due to the increasing interest of the microelectronic industry in the implantation of ions in the MeV energy range, high energy beams are required. Furthermore, for several applications the implanted dose is as high as some 1018 ions/cm2, which implies that high currents are needed also. For both requirements the rf linac is well suited. The presented design studies are based on new linac structures (RFQ, MEQALAC, Spiral Loaded Cavity), which fulfill the specific demands of various applications. The discussed systems cover a current range from 1 to 150 mA and an energy range from 0.3 to 6 MeV for ion masses between 10 and 133.

Simultaneous transport of N+ and N2+ ions through a periodic focusing quadrupole channel

Abstract The transport of a mixed beam containing N+ and N2+ ions through a periodic focusing electrostatic quadrupole structure is investigated for 20 and 40 keV beam energy and for a wide range of the zero-current phase advance per cell. The current limit for a mixed beam has been derived by means of the Kapchinski-Vladimirski equations and the matrix formalism. Both the theory and experimental results show that ion beams which contain various ion species are transported in essentially the same way as ion beams which contain only one ion species. The dependence of the current limit on the ion mass and energy, as predicted by the theory, is encountered experimentally. For high injected currents the maximum transmission, which is 85%, is reached for a phase advance per cell of 60°–84°, independent of the particle mass and energy.

Beam diagnostics using an emittance measurement device

Abstract For beam diagnostics aside from Faraday cups for current measurements and analysing magnets for the determination of beam composition and energy the most important tool is an emittance measurement device. With such a system the distribution of the beam particles in phase-space can be determined. This yields information not only on the position of the particles but also on their angle with respect to the beam axis. There are different kinds of emittance measurement devices using either circular holes or slits for separation of part of the beam. The second method (slit-slit measurement), though important for the determination of the rms-emittance, has the disadvantage of integrating over the y - and y ′-coordinate (measurement in xx ′-plane assumed). This leads to different emittance diagrams than point-point measurements, since in xx ′-plane for each two corresponding points of rr ′-plane there exists a connecting line. With regard to beam aberrations this makes xx ′-emittances harder to interpret. In this paper the two kinds of emittance diagrams are discussed. Additionally the influence of the slit height on the xx ′-emittance is considered. The analytical results are compared to experimental measurements in rr ′-, rx ′- and xx ′-phase-space.

Comparison of two types of low-ß RF linacs: MEQALAC and RFQ

Abstract The current limit and the power consumption of a Multiple Electrostatic Quadrupole Array Linear Accelerator (MEQALAC) and a Radio Frequency Quadrupole (RFQ) accelerator are compared theoretically. Design studies are presented for 1 MeV, 24 mA N + accelerators for ion-implantation purposes and for 1.5 MeV, 100 mA D − accelerators. The latter are specified to be used for fusion plasma diagnostics.