Mechanical and Diffusion Barrier Properties of Zr(C,N) Thin Films by DC Magnetron Sputtering

• Main Authors: Cheng-Shi Chen, 陳正士
• Other Authors: Chi-Yuan Albert Tsao
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/05055638224035486268

博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 93 === Abstract 　Zirconium-based nitride, carbide and Carbonitride are technologically important materials for many applications because of their outstanding properties including hardness, melting point, corrosion resistance and abrasion resistance. Although the primary function of the Zr(C,N) deposited on Si is the electrical property for metallization applications, the mechanical properties and interfaces are crucial to the successful manufacture and applications of these devices. Therefore, thin film practical adhesion is an important property not only for microelectronics and magnetic recording industries, but also for emerging technologies such as data transmission through optical switches, which are dependent on microelectro-mechanical system. It is possible that the films with high residual stress will spontaneously delaminate. 　In this study, ZrN films were grown on Si (100) substrates using dc magnetron sputtering where the substrate bias was varied from -45 V to 50 V. The results indicate that the introduction of either negative or positive bias results in the degradation of the practical adhesion properties, while the films under zero bias exhibit the best adhesion. In addition, positive bias results in the increase in both the hardness and elastic modulus, while negative bias enhances the hardness and toughness of the ZrN thin films. ZrC films were also grown on Si (100) substrates using magnetron sputtering where the growth temperature (Ts) was varied from 25 oC to 290 oC. The results indicate that there exists an optimum growth temperature at Ts = 120 oC, at which the film exhibits the best adhesion. In addition, lower growth temperatures result in an increase in hardness and a decrease in modulus, while higher growth temperatures degrade fracture toughness. The film structure reveals a change from columnar to equi-axed nanocrystalline at Ts = 290 oC, which has a profound effect on some of the mechanical properties, such as hardness. The flow ratio of N2 to (Ar+N2) was varied from 0 to 4.8% for the growth of amorphous ZrCN films. The result indicated that increasing nitrogen flow ratio, hardness and critical load decrease while elastic modulus and fracture toughness increase. The mechanical properties can be correlated to bond length and short-range ordering. 　As for the evaluation of the ZrN, ZrC and ZrCN as diffusion barriers for the devices, the diffusion coefficient and activation energy of Cu in the ZrN barrier are derived. The results indicate that the thicker (111) oriented crystalline ZrN films with larger grain sizes provide a higher activation energy against Cu diffusion and can act as an excellent diffusion barrier for Cu up to 800˚C. The detailed mechanisms accounted for the better performance are discussed in terms of a proposed grain boundary model. On the other hand, the failure of the Cu/ZrC/Si films is mainly attributed to copper diffusion into Si substrate along the localized defects in the barrier films after the formation of ZrSi2 at the Si/ZrC interface, which provide fast paths for Cu diffusion at 900°C. Accordingly, the complete failure at 900°C results mainly from the formation of Cu3Si and Zr-Si compounds. As for the ZrCN film, the stacked samples were shown to be thermally stable up to about 800°C from Auger electron spectroscopy and x-ray diffraction, where the ZrCN still remains its amorphous phase. The device completely fails at 900°C and the mechanism is discussed in the thesis.