Session FT4: Plasma Deposition I

Electrical and Structural Properties of Copper Thin Films Deposited by Novel RF Magnetized Plasma Sputtering with Gyratory Square-Shaped Arrangement by Bar Permanent Magnets

Rotating square-shaped arrangement by bar permanent magnets has been proposed for uniform target utilization in high-density radio frequency (RF) magnetized sputtering plasma. In this work, copper thin films are grown on unheated Si wafer by RF sputtering technique. The experiments are done in stainless-steel cylindrical vacuum chamber with outer diameter of 235 mm, inner diameter of 160 mm and 195 mm in height, whereas argon (Ar) gas pressure of 1.03 [Pa], rotating the iron yoke with speed of 40 [rpm,] sputtering time of 1.5 [h], and RF input power of 100 [W] at 13.56 [MHz] are realized. The deposited copper film thickness, electrical, structural properties and plasma density are investigated for case (a) without iron cover and case (b) with iron cover, respectively placed on the contact zone between the N-pole and the S-pole magnets. Radial profiles of the deposited copper thin film thickness and resistivity for case (b) are more uniform than case (a). It is found that the resistivities of deposited copper thin film for case (a) and (b) are approximately 7.89×10$^{\mathrm{-8\thinspace }}\Omega $-m and 4.33×10$^{\mathrm{-8\thinspace }}\Omega $-m, respectively at $r \quad =$ 30 mm. From AFM analysis, the uniformity of thin films grown throughout surface is better case (b) than case (a). The roughness of radial profile of the film thickness for case (a) and case (b) are 22.3{\%} and 6.55{\%}, respectively.   

Lateral epitaxial overgrowth of silicon thick films during nanocluster assisted mesoplasma CVD

Mesoplasma epitaxy has been applied to the deposition on a SiO$_{\mathrm{2}}$ masked Si wafer to identify the feasibility of lift-off and layer transfer of the thick epitaxial films. Under a certain deposition condition, the Si epitaxial film was deposited over the patterned mask with 4 µm width. The surface topography on patterned mask has revealed that the epitaxial film grows laterally over the pattern from the Si window and its lateral epitaxial overgrowth (LEO) rate is 4-5 times faster than the vertical growth rate and reaches 2500 nm/sec at the trichlorosilane flow rate of 100 sccm. Growth model was developed, assuming the surface diffusion of the nanoclusters-constituent Si atoms on the mask surface and and also that the Cl etching effect of both SiO2 and Si. The model reproduces reasonably the LEO tendency and identified the shorter diffusion length of 127 nm than that of the conventional CVD, as the unique LEO mode with cluster assisted epitaxy. Furthermore, as predicted by the model, the deposition at greater TCS rates successfully produces LEO on the pattern with wider 8µm mask width as a result of LEO coverage before completion of the mask etching.   

Dynamics of the formation and loss of boron atoms in a H$_2$/B$_2$H$_6$ microwave plasma

For further improvements in doped-diamond deposition technology, an understanding of the complex chemistry in H$_2$/CH$_4$/B$_2$H$_6$ plasmas is of general importance. In this context, a H$_2$/B$_2$H$_6$ plasma ignited by microwave power in a near resonant cavity at high pressure (100-200~mbar) is studied to measure the B-atom density in the ground state. The discharge is ignited in the gas mixture (0-135~ppm B$_2$H$_6$ in H$_2$) by a 2.45~GHz microwave generator, leading to the formation of a hemispheric plasma core, surrounded by a faint discharge halo filling the remaining reactor volume. Measurements with both laser induced fluorescence and resonant absoption with a boron hollow cathode lamp indicate that the B-atom density is higher in the halo than in the plasma core. When the absorption line-of-sight is positioned in the halo, the absorption is so strong that the upper detection limit is reached. To understand the mechanisms of creation and loss of boron atoms, time-resolved absorption measurements have been carried out in a pulsed plasma regime (10 Hz, duty cycle 50~\%). The study focuses on the influence of the total pressure, the partial pressure of B$_2$H$_6$, as well as the source power, on the growth and decay rates of boron atoms when the plasma is turned off.   

Coatings deposition from liquid HMDSO films via conversion in dielectric barrier discharges

The application of plasma discharges for the deposition of coatings is well established in the academic as well as the industrial sector. This is especially true for plasma-enhanced chemical vapour deposition of HMDSO. However, employing thick liquid films is an approach barely recognized, so far. We demonstrate the possibility of introducing thick liquid monomer films into plasma discharges in order to form solid coatings. The underlying processes are discussed including gas kinetics, reactions in the gas and liquid phases as well as at the gas-liquid interface. Finally, conclusions are drawn regarding the plasma-based deposition of highly complex coatings in-between plasma-chemistry and classic polymer chemistry via plasma-enhanced chemical solution deposition.   

Atmospheric Pressure Low Temperature Plasma System for Additive Manufacturing

There is growing interest in using plasmas for additive manufacturing, however these methods use high temperature plasmas to melt the material. We have developed a novel technique of additive manufacturing using a low temperature dielectric barrier discharge (DBD) jet. The jet is attached to the head of a 3D printer to allow for precise control of the plasma's location. Various methods are employed to deposit the material, including using a vaporized precursor or depositing a liquid precursor directly onto the substrate or into the plasma via a nebulizer. Various materials can be deposited including metals (copper using copper (II) acetylacetonate), polymers (PMMA using the liquid monomer), and various hydrocarbon compounds (using alcohols or a 100{\%} methane DBD jet). The rastering pattern for the 3D printer was modified for plasma deposition, since it was originally designed for thermoplastic extrusion. The design constraints for fill pattern selection for the plasma printer are influenced by substrate heating, deposition area, and precursor consumption. Depositions onto pressure and/or temperature sensitive substrates can be easily achieved. Deposition rates range up to 0.08 cm$^{\mathrm{3}}$/hr using tris(2-methoxyethoxy)(vinyl)silane, however optimization can still be done on the system to improve the deposition rate. For example higher concentration of precursor can be combined with faster motion and higher discharge powers to increase the deposition rate without overheating the substrate.   

Opportunities offered by the interaction of plasma and droplets to elaborate nanostructured oxide materials

The association of plasma and spray will permit to process materials where organometallic precursors are not available or economically non-reliable. The injection of aerosols in low pressure plasma results in the rapid evaporation of solvent and the rapid transformation of small amounts of precursors contained in each droplet leading to form nanoscale oxide particles. We developed two configurations of this technique: one is Spray Plasma that permits to deposit this layers on flat substrates; the second one is Fluidized Spray Plasma that permits to deposit thin layers on the surface of solid beads. The aim of this presentation is to describe the principles of this new technique together with several applications. The influence of experimental parameters to deposit various mixed metal oxides will be demonstrated: thin dense layers of nanostructured ZnO for photovoltaic applications, porous layers of La$_{x}$Sr$_{\mathrm{1}}_{-x}$MnO$_{\mathrm{3}}$ as the cathode for fuel cells, ZnO-Cu, NiO layers on solid pellets in fluidized bed for catalysis applications.