Samuel D. Ekpe

Theoretical and experimental determination of the energy flux during magnetron sputter deposition onto an unbiased substrate

The energy flux onto an unbiased substrate is determined theoretically and experimentally for aluminum and copper deposited using a 3 in. magnetron sputtering system. The energy per deposited atom is calculated. Energy per deposited atom trends towards being independent of power and pressure, especially at high magnetron powers. At low powers, the energy per deposited atom increases with pressure due to lower deposition rates. For the magnetron system used, plasma effects are shown to be important in determining the total energy flux to the substrate. Contributions of the electrons and thermal radiation from the target region are included in the model.

Investigation of thermal flux to the substrate during sputter deposition of aluminum

The transient and steady state thermal flux at the substrate during the deposition of aluminum film in a direct current magnetron sputter system has been determined by measuring the resistance of a complementary metal–oxide–semiconductor (CMOS) sensor. The sensor is calibrated using ohmic self-heating before the plasma is switched on. The steady state thermal flux at the substrate was measured to vary from 9.6 to 46 mW/cm2 at a substrate-target distance of 10.8 cm depending on the magnetron power (75–300 W) and gas pressure. Plasma radiation and electron bombardment are noted to be the most significant sources of the thermal flux to the substrate, each contributing about 36% and 29%, respectively, of the total thermal flux at the substrate for a magnetron power of 200 W and gas pressure of 5 mTorr. Thermal radiation is also an important factor, along with kinetic energy and condensation energy. Total energy per deposited atom is calculated to be in the range of 28–52 eV depending on the magnetron power an...

3D numerical simulation of gas heating effects in a magnetron sputter deposition system

3D numerical simulation of gas heating in a magnetron sputtering system is performed. Pressure, magnetron power density and location of the substrate plane in front of the target are shown to affect the gas temperature profile. For the pressure range under study, maximum gas temperature is shown to increase with pressure. By increasing the separation between the target and the substrate, the maximum gas temperature is shown to increase up to the point when most of the particles are assumed thermalized. Cu shows more gas heating than does Al due to its higher sputtering yield and energy transfer efficiency. Sputtered particles are shown to be the major source of gas heating.

Inhomogeneous rarefaction of the process gas in a direct current magnetron sputtering system

The interactions between energetic particles and the sputter gas in a magnetron sputtering system have strong effects on the growth, structures, and properties of the film. These interactions result in inhomogeneous rarefaction of the gas in the space between target and substrate and affect both the transport of particles towards the substrate and the dynamics of the plasma. A hybrid Monte Carlo and fluid model is developed to simulate three-dimensional (3D) gas rarefaction due to the sputtering of metals in argon, neon, and krypton. The governing equations are solved iteratively in a 3D space with a nonuniform grid (octree). Collision events between the sputtered particles and the process gas are assumed as the dominant source of gas heating; however, the effect of the reflected neutrals is also included in the model. Gas rarefaction profiles have been predicted for different process conditions. Model results compare well with experimental ones. The extent of rarefaction depends on process conditions as ...

Measurement of energy flux at the substrate in a magnetron sputter system using an integrated sensor

Knowledge of the energy flux in a sputter deposition system is important for predicting and controlling the properties of the growing film. The use of discrete sensors such as thermocouples for heat measurement has a potential contact problem due to the temperature jump between the surface of the wall and the surrounding gas especially at very low pressures. Embedded sensors such as a microfabricated polysilicon thin film thermistor eliminates the problem associated with thermal connection. In this study, the fabricated sensor is calibrated using ohmic self-heating before the deposition plasma is switched on, and also after the plasma is switched off (passive mode). At low pressures (up to 20 mTorr), pressure has an insignificant effect on the thermal resistance of the sensor. For substrate temperatures up to 250 °C, the sensor response is linear with input power. For a 3 in magnetron system, values of steady state energy flux measured with the sensor range from 5 to 46 mW/cm2 for aluminum (Al) and 14 to ...

Effect of magnetic field strength on deposition rate and energy flux in a dc magnetron sputtering system

Variations in the magnetic field strongly affect the plasma parameters in a magnetron sputtering system. This in turn affects the throughput as well as the energy flux to the substrate. The variation in the magnetic field in this study, for a dc magnetron process, is achieved by shifting the magnet assembly slightly away from the target. Measurements of the plasma parameters show that while the electron density at the substrate increases with decrease in magnetic field, the electron temperature decreases. The cooling of the electron temperature is consistent with results reported elsewhere. The deposition rate per input magnetron power is found to increase slightly with the decrease in magnetic field for the process conditions considered in this study. Results suggest that the energy flux to the substrate tends to show a general decrease with the shift in the magnet assembly.

Comparative Study of Thermal Conductivity Values of Different Percentage Compositions of Ground Arachis hypogea (Groundnut) Husk and Vigna unguiculata (Beans) Husk Compressed Fiberboards

Thermal conductivity values of compressed boards made of ground Arachis hypogea husk and Vigna unguiculata husk as binder at different percentage compositions at a temperature of 303 K were investigated using steady-state method. Other thermal properties including specific heat capacity, density, thermal absorptivity, and diffusivity values were also estimated for the prepared samples. Comparative studies of the determined values for the board at different proportions or ratios of combination of A. hypogeal ground husk with V. unguiculata ground husk reveal that thermal conductivity value decreases with an increase in the percentage content of A. hypogea husk contents. A fitting polynomial regression analysis reveals a correlation coefficient of 99.6%. The range of thermal conductivity values falls within the range of conventional good thermal insulators. Thus, the husks are potential ecofriendly raw materials for insulation board for cold building design and other thermal envelops.

Model of predicting proportion of diesel fuel and engine oil in diesel adulterated SAE 40 engine oil sample

Viscosity of diesel adulterated SAE 40 engine oil at varying proportions of the mixture is presented. Regression, variation of intercept and the power parameters methods are used for developing polynomial and power law functions for predicting proportion of either diesel or engine oil in diesel adulterated SAE 40 engine oil sample. KeyWords : SAE 40 engine oil, diesel, viscosity, adulterated. (Global Journal of Pure and Applied Sciences: 2002 8(4): 513-516)