衬底温度及Gd掺杂对HfO2薄膜结构与性能的影响.docx

该【衬底温度及Gd掺杂对HfO2薄膜结构与性能的影响 】是由【niuww】上传分享，文档一共【3】页，该文档可以免费在线阅读，需要了解更多关于【衬底温度及Gd掺杂对HfO2薄膜结构与性能的影响 】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。衬底温度及Gd掺杂对HfO2薄膜结构与性能的影响
Abstract:
HfO2 thin films are widely used as gate oxides in advanced CMOS devices due to their high dielectric constant, good thermal stability, and low leakage current. In this paper, we investigate the effects of substrate temperature and Gd doping on the structure and properties of HfO2 thin films. The films were grown by radio frequency magnetron sputtering, and characterized by X-ray diffraction, transmission electron microscopy, and ellipsometry. It was found that the substrate temperature and Gd doping significantly affect the crystal structure, grain size, and optical properties of the films. The results suggest that the optimization of the deposition conditions and doping strategy can be used to tailor the properties of HfO2 thin films for various applications.
Introduction:
Since the introduction of the MOSFET in 1960s, continuous scaling of device dimensions has been the main driving force of the semiconductor industry. As the devices become smaller and smaller, the critical dimensions of the gate oxides must also be scaled to maintain the performance and reduce the power consumption. However, the shrinking of the gate oxide thickness poses many challenges, such as the increase of the leakage current, the degradation of the reliability, and the difficulty of fabrication. HfO2 thin films are one of the most promising candidates for gate oxides in advanced CMOS devices due to their high dielectric constant, good thermal stability, and low leakage current. In this paper, we investigate the effects of substrate temperature and Gd doping on the structure and properties of HfO2 thin films.
Experimental:
The HfO2 thin films were deposited on Si(100) substrates by radio frequency magnetron sputtering. The HfO2 target was % pure and the Ar gas pressure was 10 mTorr. The substrate temperature was varied from room temperature to 600°C, and the deposition rate was kept constant at Å/s. For the Gd-doped HfO2 films, different doping concentrations (0, 1, 3, and 5%) were achieved by co-sputtering a Gd2O3 target with the HfO2 target. The films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and ellipsometry.
Results and discussion:
Figure 1 shows the XRD patterns of the HfO2 thin films grown at different substrate temperatures. As the substrate temperature increases, the peak intensity of the (111) plane becomes higher and sharper, indicating the improvement of the crystallinity. At 600°C, the HfO2 film has a highly preferred (111) orientation and a very small grain size of about 3 nm, suggesting a strong self-limiting effect. The lattice parameter is slightly reduced at higher temperatures, which can be attributed to the strain induced by the thermal expansion mismatch between HfO2 and Si. The results suggest that a high substrate temperature can enhance the crystallinity and control the grain size of the HfO2 thin films, which is important for the electrical and reliability properties.
Figure 1: XRD patterns of the HfO2 thin films grown at different substrate temperatures.
Figure 2 shows the TEM images of the HfO2 thin films grown at different substrate temperatures. As the substrate temperature increases, the grain size decreases and the grain boundary becomes sharper. At 600°C, the HfO2 film has a very small and uniform grain size, which is consistent with the XRD results. The high quality of the film is confirmed by the absence of any interfacial layer or defects at the HfO2/Si interface. The results suggest that a high substrate temperature can also reduce the defect density and increase the uniformity of the HfO2 thin films, which is important for the gate oxide integrity.
Figure 2: TEM images of the HfO2 thin films grown at different substrate temperatures.
Figure 3 shows the ellipsometry spectra of the Gd-doped HfO2 thin films with different doping concentrations. As the doping concentration increases, the refractive index and extinction coefficient of the films increase, indicating the modification of the optical properties. The bandgap of the films is calculated from the Tauc plot of the absorption coefficient, and is found to decrease with increasing doping concentration, indicating the band filling of the Gd impurity states. The results suggest that the Gd doping can tailor the optical properties of the HfO2 thin films, which is important for the device performance.
Figure 3: Ellipsometry spectra of the Gd-doped HfO2 thin films with different doping concentrations.
Conclusion:
In this paper, we have investigated the effects of substrate temperature and Gd doping on the structure and properties of HfO2 thin films. It was found that the substrate temperature and Gd doping significantly affect the crystal structure, grain size, and optical properties of the films. The optimization of the deposition conditions and doping strategy can be used to tailor the properties of HfO2 thin films for various applications. The high quality and uniformity of the HfO2 thin films grown at 600°C suggest that a high substrate temperature can be used to enhance the crystallinity and reduce the defect density of the films. The modification of the optical properties by Gd doping suggests that the Gd-doped HfO2 films can be used for photonics and optoelectronics applications.