Metal deposition with a windowless VUV excimer source
Abstract
A novel lamp configuration for generation of VUV excimer radiation is presented. A silent discharge between parallel dielectric tubes is used to excite the second continua of rare-gas dimers Ar∗2, Kr∗2 and Xe∗2 peaking at 126, 146 and 172 nm, respectively. Subjected to this radiation without intermediate windows palladium acetate films are photolytically decomposed leading to thin palladium layers that can be used as activators for electroless metal plating processes. Deposition rates are investigated as a function of discharge power, gas pressure and wavelength. Compared to earlier experiments with a VUV source consisting of a sealed quartz tube as discharge vessel deposition rates could be increased by two orders of magnitude.
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Cited by (33)
An UV-C/B emitting Xe excimer discharge lamp comprising BaZrSi<inf>3</inf>O<inf>9</inf> – A lamp performance and phosphor degradation analysis
2018, Journal of LuminescenceCitation Excerpt :In a number of modern technologies photochemical techniques have already replaced classical chemical procedures due to their superior cost-effectiveness, environmental compliance, and flexibility [1–3].
This work concerns a highly efficient UV-C emitting phosphor, viz. BaZrSi3O9, which photoluminescence is suitable for a number of photochemical processes, e.g. for air, surface, or water disinfection as well as oxidative purification processes of water. The latter imply direct photolysis as well as photooxidation involving auxiliary components like H2O2. The material was investigated with respect to its application as a conversion layer in Xe excimer discharge lamps (λEm = 172 nm). To this end, substitution of Zr4+ by Hf4+ was performed aiming at an optimization of the preparative process and the resulting VUV conversion efficiency.
As-prepared powder samples were consecutively employed in state-of-the-art dielectric barrier Xe excimer discharge lamps and their performance was compared to YPO4:Bi3+ as a UV-C emitting commercially available reference material (Phillips GmbH). Even the non-optimized BaZr0.8Hf0.2Si3O9 succeeded the standard in terms of long term stability of its luminous flux. Detailed analysis of the material was secured by crystallographic as well as extensive optical and spectroscopic measurements. The latter was supplemented by EPR studies in order to further examine the underlying aging mechanism which governs the phosphor decay during Xe excimer lamp operation.
Photo-induced growth of dielectrics with excimer lamps
2001, Solid-State ElectronicsThe underlying principles and properties of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation (excimer lamps), generated by a dielectric barrier discharge in a rare-gas (Rg) or a mixture of Rg and halogen, are discussed. Compared with conventional sources, these excimer lamps offer narrow-band radiation at various wavelengths from 108–354 nm and over large areas with high efficiencies and high power densities. The variety of available wavelengths offers an enormous potential for new industrial applications in materials processing. Previously, photo-oxidation of silicon, germanium and silicon–germanium and photo-deposition of single- and multi-layered films of silicon oxide, silicon nitride, and silicon oxynitride have been demonstrated by using excimer lamps. This paper reviews the progress on excimer lamp-assisted growth of high dielectric constant (Ta2O5, TiO2 and PZT) and low dielectric constant (polyimide and porous silica) thin films by photo-CVD and sol–gel processing, summarizes the properties of photo-induced growth of Ta2O5 films and discusses the effect and mechanism of low temperature UV annealing with 172 nm radiation. Metal oxide semiconductor capacitors based on the photo-induced Ta2O5 films grown directly on Si at low temperatures exhibit excellent electrical properties. Leakage current densities as low as 5.2×10−7 A cm−2 and 2.41×10−7 A cm−2 at 1 MV cm−1 have been achieved for the as-grown Ta2O5 films deposited by photo-induced sol–gel processing and photo-CVD, respectively-several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) UV annealing step improves these to 10−8 A cm−2. These values are comparable to those only previously achieved for films annealed at high temperatures between 600°C and 1000°C. These properties make the photo-induced growth of Ta2O5 layers suitable alternative to SiO2 for high density DRAM application.
Low temperature photoformation of tantalum oxide
2000, Microelectronics ReliabilityRecently, excimer lamps have opened up the field of intense vacuum ultraviolet (VUV) and ultraviolet (UV) light generation. A number of novel applications of these sources have been successfully demonstrated over the past few years. In this article, photo-induced deposition of tantalum pentoxide (Ta2O5) thin films by photo-CVD and sol–gel processing with the excimer lamps is presented, and the effect of low temperature UV annealing is discussed. Film properties determined using ellipsometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV spectrophotometry, scanning electron microscopy (SEM), capacitance–voltage (C–V) and current–voltage (I–V) techniques, shown that the high quality layers could be produced, rendering the photo-induced technique to be promising for low temperature microelectronic material processing. A significant reduction in the leakage current density of the films has been found after UV annealing using a 172 nm lamp. This is attributed to the reduction of suboxides, impurities, oxygen vacancies and defects in the films as well as the formation of SiO2 on the surface of the Ta2O5. A simple model explaining the observed reduction in the leakage current after UV annealing is proposed. The formation of active oxygen species by the 172 nm irradiation is considered to be the controlling influence that leads to the considerable improvement in the properties of the layer.
Investigations of photo-induced decomposition of palladium acetate for electroless copper plating
1998, Thin Solid FilmsPhoto-induced decomposition of palladium acetate films has been performed by using argon and xenon excimer vacuum ultraviolet (VUV) sources that emit radiation peaking at wavelengths of 126 and 172 nm, respectively. VUV irradiation of a substrate treated with palladium acetate results in the formation of palladium, which acts as a catalyst for subsequent copper plating by means of an electroless bath. A selective copper pattern can thus be formed in a simple process using a contact mask. The surface morphology of films on silicon substrates has been investigated using an atomic force microscope (AFM) and a scanning electron microscope (SEM). Exposure conditions were found to affect the morphology and density of the Pd activation layer. The electrical resistivity of the films, measured by four-point probe, and the adhesion strength of copper on the Pd-nucleated substrate, were both found to be dependent on the thickness of the palladium.
3. Glow Discharges and Wall Stabilized Arcs
1998, Experimental Methods in the Physical SciencesThe chapter presents a discussion on glow discharges, dielectric barrier discharges, wall stabilized arcs, electron cyclotron resonance sources, electron-beam ion trap (EBIT) sources, inductively coupled plasma sources, and capillary discharges. All of these discharges may have different ways to excite bound atomic or molecular states and to ionize constituents of the discharge, but they will all radiate both spectral line radiation and continuum radiation. In some cases, the source conditions can be controlled so one or the other of these types of radiation may dominate. The choice of a source often depends on which type of radiation is desired—for example, if a source exhibits a stable well-characterized continuum spectrum in the vacuum ultraviolet (VUV) region, then this source could be used as a secondary radiometric calibration standard throughout this spectral region. Some of the sources discussed in this chapter were designed and used as sources of spectra—that is, both line and continuum spectra as in the case of the wall stabilized arc. Some other sources that are described were designed for uses other than sources of spectra—for example, the electron cyclotron resonance tool has been primarily used as an ion source.
UV intensity measurement for a novel 222 nm excimer lamp using chemical actinometer
1997, Applied Surface SciencePhotohydrate of uridine in neutral aqueous solution is used for the determination of the ultraviolet (UV) intensity of a novel excimer lamp, employing a dielectric barrier discharge in krypton chloride to provide intense narrow band radiation at λ=222 nm (KrCl*). The intensity measurement is based on UV spectral absorption data. A photokinetic model is presented for the reaction which is generally applicable for any photochemical system. The electrical power dependence of the UV intensity generated as well as the efficiency of the lamps was investigated.