Fabrication and characterization of non-evaporable nanostructured porous Ti and Ti-Zr-V film getters

• Main Authors: Chien-Cheng Li, 黎建成
• Other Authors: Jow-Lay Huang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/53175178050413228623

博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 96 === According to the progress of microelectromechanical system (MEMS) technologies, the developments of the minimizing vacuum devices have largely increased for the past few years. The features of these devices are the wafer-level bonding fabrications and small vacuum cavity with several micro-gap. The development of the high pumping capacity, porous structure, and low activation temperature of the NEG are the main purpose in the minimizing vacuum devices. This is a key technique to decrease the production costs of bonding fabrications. In this study, the non-evaporable porous thin-film-type getters will be produced by magnetron sputtering. The NEG with high porosity and grain boundaries show a markedly high pumping speed to the gases for improving the capability to absorb the residual gases inside these sealed-off devices. In order to investigate the alloying effect on the activation temperature of the NEG, the research will be studied activation temperature of the NEG, which exhibited activation temperature below 250℃. Highly porous Ti and TiZrV getter film coatings have been successfully grown on (100) silicon substrates using the glancing angle dc magnetron sputtering method. The main deposition parameters that produce the porous Ti and the TiZrV films are the pressure of sputtering gas Ar and glancing angle at room temperature. The evolution of the microstructures of the Ti and the TiZrV films strongly depends on the sputtering flux rate, surface diffusion rate, nucleation rate, compositions, and self-shadowing geometry of the nuclei on the sputtering flux. The larger the glancing angle, the higher the porosity and specific surface area of the Ti and TiZrV films. The weight-gain results strongly depend on several factors, such as specific surface area, the surface structure of the getter film, the diffusion rate of O in the getter film, the reactivity of Ti, Zr, and V on O, and the order of the stabilities of Ti, Zr, and V oxides on the film’s surface. Porous Ti film absorbs oxygen better than porous TiZrV film does due to the its higher surface area and the high diffusion rate of O in Ti films. Highly porous Ti and TiZrV film getters on (100) silicon substrates were used to study the effects of alloy elements on activation process. The effect of activation temperature on the reducing degree of the porous Ti and TiZrV films were investigated by synchrotron radiation photoemission spectroscopy (SRPES). The carbon-element absorbed on the surface of the Ti film, exposed in air, will be transformed to a Ti carbide phase, however, that which is on the surface of the TiZrV film will be completely removed by a heating treatment at 250℃ or above. The oxidized Ti in porous TiZrV film is more easily reduced than that in the porous Ti films. The breakdown of V-O and Ti-O bonds on the TiZrV film surface is easier than that of the Zr-O bond. We suggest that the decrease of reducing temperature of oxidized TiZrV, comparing with that of oxidized Ti, is caused by the displacing reaction of Zr on oxidized Ti or oxidized V. The effects of activation temperature on the reducing degree of the dense and porous TiZrV films were investigated by synchrotron radiation photoemission spectroscopy. The dense and porous TiZrV films have similar composition and thickness, and their specific surface areas are 2 m2/g and 13 m2/g, respectively. Comparing the previous results of the porous TiZrV film, the activation degree of the porous TiZrV film is lower than that of the dense TiZrV film. To complete the activation treatment of the dense and porous TiZrV films, the activation temperature must be higher than 350℃ or the activation time must be longer than 30 minutes. TiZrV films, grown at the deposition angles of 0 and 70, were used for the study of the oxygen-adsorption process. When the deposition angle is 0, the appearance of the film is dense columnar structure. However, the film grown at the glancing angle of 70 is composed of porous and isolated columns, which are made of fine clusters. The activated TiZrV films have the capability to absorb oxygen at room temperature. The component Zr is more easily oxidized than Ti and V components when the TiZrV film is exposed in oxygen. The content of oxidized Ti and oxidized V does not linearly increase with the increase of oxygen exposure when there is a metallic Zr component on the surface of the film. Highly porous TiZrV films on (100) Si wafers were used to study the oxidation state of a film surface after three gas-adsorption/activation cycles using synchrotron radiation photoemission spectroscopy. The oxidation state and composition of porous TiZrV film are highly affected by the present conditions of air-exposure/activation cycles. In the porous TiZrV films after activation treatment, the C content on the surface of the films gradually increased with increasing air-exposure/activation cycles. In the porous TiZrV film after air-exposure treatment, the O content on the surface of the films decreased with increasing of air-exposure/activation cycles. The concentration of Zr on the film surface became rich with increasing of air-exposure/activation cycles. These results are caused by the formation of metal carbides on the film surface.