Studies On Discharge Characteristics And Applications Of ICP Enhanced Unbalanced Magnetron Sputtering In Cusp-field Confined Magnetron

The present work includes two main parts: The first part mainly investigates a new technique of thin film deposition, referred as to the technology of thin film deposition by ICP enhanced unbalanced magnetron sputtering process in cusp-field confined magnetron. Then it is applied to deposit Cu film of good characteristics under appropriate parameter condition. In the second part, the regularity of plasma parameter, which varies with the air pressure, the power of radio frequency (rf), the cusp magnetic field and different positions in the chamber is studied, by using the emission spectrometry and Langmuir probe.The self-regulating unbalanced magnetron sputtering device and rf winding, which enhance the plasma ionization, are used in ICP (Inductively Coupled Plasma) enhanced unbalanced magnetron sputtering technique. The pulse minus bias voltage is applied to the substrate to increase the velocity of ions arriving at the substrate. The magnetron target is lied above the vacuum chamber, connected with the chamber's upper wall by the insulating polyethylene. There are two groups of permanent magnet outside the discharge chamber: one is three circles of permanent magnet hoop around the outside of the vacuum chamber, and the other is a permanent magnet on the top of the sputtering target. The magnetic fields resulting from the two groups above interact with each other and form a figure of cusp magnetic field. With the confinement of the cusp magnetic field, during the rf discharge and rf enhanced magnetron sputtering discharge, the uniform plasma could be obtained in the middle area of the chamber. The optimum parameters of Cu film deposition are chosen by adjust considering the pressure, the power of rf and the ion current which should not be over large. On the basis of the conventional magnetron sputtering, the permanent magnets outside the column vacuum chamber and above the target interact with each other and form a combined cusp magnetic field, which plays the role of confinement and increases the electron free path, and improves the plasma ionization rate as well. Besides this, the rf power is added through a cylinder antenna to inspire the plasma further and increase plasma density and electron temperature effectively.In this experiment, Ar with the purity of 99.99% is used as discharging gas, and Cu with the purity 99.9% is used as the material of sputtering target. The changing regularity of rf Ar plasma, which varies with the power of radio frequency, the air pressure and the position in the discharge chamber, is investigated by the emission spectrometry. Two given atom and ion spectral lines of Ar are selected. The intensity of spectral lines in RF discharge shows a jumping mode and a hysteresis phenomenon with the change of RF power. When the rf power increases to 400 W, the discharge jumps from E-mode to H-mode, where the line intensity of Ar atom demonstrates an increase jumpily, but the intensity of Ar~+ ion only has a little bit changes. If the RF power decreases from a high power, such as from 1000 W, the discharge jumps from H-mode back to E-mode at 300W. Moreover, under the condition of with or without cusp magnetic field and rf, the change of given atom and ion lines of Ar and Cu is studied by the method of emission spectrometry. In this way, the variety of plasma parameters is investigated qualitatively. The plasma parameters in the discharge chamber are measured by Langmuir probe. The distributing of the plasma parameters (electron temperature, electron density and ion density) at the axis and radial and the influence of cusp magnetic field on plasma parameters are investigated during the process of rf discharge. It has been proved that, with the confinement of cusp magnetic field, parameters of ICP enhanced unbalanced magnetron sputtering plasma are improved obviously.Cu films are deposited on the Si substrate by using this experiment equipment. The films are deposited under three conditions as follows: with rf and without cusp magnetic field, without rf and with cusp magnetic field and with rf and with cusp magnetic field. The morphology and structure of films are examined by scanning electron microscopy (SEM), x-ray diffraction (XRD) and electron spectroscopy (ES). The surface average roughness of the deposited Cu film is characterized by atomic force microscope (AFM) data. The resistivity is measured by four probe method. The results show that rf and cusp magnetic field play an important role in plasma discharge and improve plasma parameters significantly, including electron temperature, electron and ion density. Therefore, the Cu film deposited with rf discharge enhanced ionization and cusp magnetic field confinement has smooth and dense surface, low surface roughness and low resistivity. The scale of the crystal grain is about 100～1000 nm. The reason may be attributed to that the rf discharge and cusp magnetic field could enhance the plasma density, which further improves ion bombardment effect under the same bias voltage. Ion bombardment can influence the growing feature and characteristics of deposited Cu films obviously. From the experiments, the best experiment parameters for the deposition of Cu film with good characteristics can be found. This technique will be contributed to integrated circuit, and is expected to be applied to practical work.