The Experimental Studies Of Combinationable Plasma Source In Collisional Condition

In recent years, low temperature plasma technology has a wide application in the field of cutting-edg science and technology such as large scale integrated circuit, Mem-s processing, material surface modification, new thin film materials and nano material preparation, where large-area and uniform plasma source with high density play a key role in the fast deposition of large-area and uniform functional materials. Since tradi-tional single-electrode discharge is not suitable for generating such ideal plasma, dis-charge with combination of multiple electrodes attracts much attention for producing large-area and uniform plasma source. However, between high density and uniformity there exists an restriction relationship that high-intermediate gas pressure brings high density, but also results in a bad uniformity. For this reason, discharges were operated under the lower gas pressure in order to attain a large-area and uniform plasma source in the previous study. In this dissertation, under high-intermediate gas pressure and col-lision condition,the nonlinear enhanced effect is discovered in the study of discharge by combining multiple compact internal inductive coils, based on which, a large-area and uniform plasma source with high density is developed under high-intermediate gas pressure and a technical method is also found for adjusting the plasma parameters. Meanwhile, we also propose a method using a single probe with floating tip for accu-rate diagnosing the plasma parameters in the condition of collision and contaminated chamber wall.Discharge with single internal inductive coil can produce a high-density plasma under high-intermediate gas pressure, while the collision affect the uniformity of plas-ma density which shows an radical exponential decay, and We can illuminate the plasma density distribution of single internal ICP in diffusion region by linear loss-diffusion model. Each inductive coil works independently and has no interference in the discharge by combining multiple coils, hence the density of combination of mul-tiple ICPs possess the characteristic of simple linear superposition which improve the uniformity to some extent. What’s more, the density exhibit remarkable nonlinear en-hancement effect that the density distribution in combination of multiple ICPs is larger than the linear summation of each independent single ICP. In considering the process of multi-step ionization in diffusion region based on the linear loss-diffusion model, nonlinear model is successful to explain the nonlinear enhancement effect, so the non- linear enhancement effect is caused by the multi-step ionization and the conclusion is also verified through Helium discharge experiment. Some results of simulation and experiment show that the nonlinear enhancement effect in the central of the mid-plane is associated with the number and the arrangement of the coils, and the distribution of plasma density produced by a single coil discharging independently. There is a re-striction relationship between high density and uniformity, the gas pressure need to be raised to increases the plasma density under fixed discharge power, while the corre-sponding collision restrict the diffusion of particles, resulting in bad radical uniformity. Combination of multiple ICPs can resolve the contradiction. By combining multiple internal ICPs, a large-area plasma source with high density can be directly produced, whose uniformity can further be improved greatly according to the nonlinear enhance-ment effect.Uniform plasma sources in large area with effective diameter of15cm,22cm and30cm are respectively obtained by the combination of six internal ICPs with r of10cm,15cm and20cm. The uniformity of these plasma sources are higher than90%, and the density can be adjusted by changing power with a highest density of1×1019m-3, and all these factors along with uniform electron temperature make the plasma source can be applied in the industry. The relative distribution of plasma density is found to be influenced more by gas pressure and less by discharging power, and the absolute value of plasma density can be adjusted by varying the power. Therefore, uniform plasma source in large area can be produced and quantified by adjusting power under a certain gas pressure.Amorphous silicon thin film deposition is researched in the plasma source with r of10cm through Plasma Enhanced Chemical Vapor Deposition. According to the research, the higher deposition rate can be achieved mainly because of the higher plas-ma density, and in the same condition, the deposition rate will increase with increasing discharge power. In addition, the large-area plasma source can be industrialized based on the capability of large-area thin film deposition.Two problems in the single probe diagnostics are discussed and resolved. The first one is limitation of the electron saturation current which is due to the suffocation of current in probe circuit. The second one is the hysteresis phenomenon in Ⅴ-Ⅰ char-acteristics. When triangular wave is used as scanning voltage, the detected Ⅴ-Ⅰ char-acteristics corresponding to the rising edge and falling edge of triangular wave reveal either left or right offset. Any of them will lead to the distortion of Ⅴ-Ⅰ characteristic curve of single probe. The pollution of vacuum wall, according to the experiment, is blamed for the curve-distortion. To verify it, the single probe characteristic model and equivalent-circuit model are used to simulate the forming of the distortions and the simulation is good in accord with the experiment results. So a novel single probe with floating tip is used to avoid the interference from vacuum wall and get a real and intact probe characteristic curve, and its feasibility has been confirmed by experiment as well as simulation.