This dissertation mainly includes two parts: simulation and design of (external solenoid coil) circular planar magnetron and low temperature deposition of aluminum-doped zinc oxide (AZO) thin film prepared by reactive magnetron sputtering, respectively. At first, considering conventional circular planar magnetron as an example, we studied the effects of magnetron component parameters by finite-element method (FEM) simulation of magnetic field configuration, analyzed the influence of external solenoid coil arrangement and excitation mode on plasma characteristics and target utilization, and proposed a novel magnetron sputtering method. Additionally, we also investigated the effects of various growth conditions on electrical properties and spatial distribution of the ZnO:Al (AZO) thin films prepared by dc magnetron sputtering at low deposition temperature, with emphasis on the origin of the resistivity inhomogeneity across the substrate.
The results revealed that the using of yoke with a high permeability can remarkably enhances the magnetic field on the target and makes the magnetron more balanced; the magnetic field configuration and unbalanced degree of the magnetron can be significantly influenced by their width rather than their height of inner/ external magnets, and the height of magnets are mainly determined from the perspective of the control of unbalanced degree. As the increase of the thicknesses of target and backboard, the magnetic field on the target surface rapidly reduced and the ignition voltage of glow discharge correspondingly decreased to some extent.
Langmuir probe measurement showed that the coil position had a strong effect on the near-substrate plasma parameters, resulting from the variations of magnetic field configuration in the substrate region. It was a relatively simple and effective method to improve the target utilization by supplying low frequency AC power to the external coil situated around the magnetron. The target utilization efficiency was highly sensitive to the coil position. The coil was more suitable to be placed in the vicinity of the magnetron than near the substrate for improving the target utilization. Compared with that operated in DC mode, the coils excited in AC mode have a minor influence in the I-V characteristics of magnetron and advantage in the maintain the stability of sputtering process. Finally, a novel method was proposed to simultaneously improve target materials utilization and control the near-substrate plasma density in a broad range by choosing an appropriate solenoid coil arrangement and excitation mode.
The crystalline, stress and electrical properties of the films were found to be strongly dependent on growth temperature TS and ion-to-neutral ratio Ji/Jn. Under the low Ji/Jn (<0.3) conditions, the TS exerted a remarkable influence on film quality. The films prepared at 90 °C were highly compressed, exhibiting poor electrical properties and significant spatial distribution. High quality films with low stress and resistivity were produced at higher TS (200 °C). Similarly, at lower TS (90 °C), higher Ji/Jn (~2) dramatically improved the film resistivity as well as its lateral distribution. Moreover, it indicated that the role of ion bombardment is dependent on the mechanism of dissipation of incident species. Ion bombardment is beneficial to the film growth if the energy of incident species Ei is below the penetration threshold EPet (~33 eV for ZnO), while the energy sub-implant mechanism would work, on the other hand, the bombardment degrades the film quality when Ei is over the EPet. The energetic bombardment of negative oxygen ions rather than the positives dominated the resistivity distribution of AZO films, while the non-uniform distribution of active oxygen played a secondary role which was otherwise more notable under conditions of lower TS and Ji/Jn.
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