Study On High - K Gate Dielectric And Diffusion Barrier Layer In Atomic Layer Deposition And Their Characteristics

With the shrinking of the dimensions of the integration circuit driving by Moore’s law, quite a few traditional film deposition techniques face great challenges. Atomic layer deposition is a new kind of technology which has great advantage in the precise control of film composition and thickness. It has now been applied in the research of high-k gate dielectrics, diffusion barriers in the back-end technology of integration circuit and various kinds of optical materials. Thus, it is essential to investigate on atomic layer deposition both experimentally and theoretically. This paper mainly focuses on the ALD process of HfO2and TiAN and the material properties of these two films. On the one hand, HfO2films were deposited on Si substrate. The properties of the interfacial layer between HfO2and Si substrate which were annealed at different temperatures were investigated. Furthermore, the oxygen defect properties of HfO2were studied theorically. On the other hand, TiAIN films were deposited by atomic layer deposition (ALD) using titanium tetrachloride (TiCl4), trimethylaluminum (TMA), and ammonia (NH3) with two pulsing sequences of TMA->NH3->TiCl4and Til4->NH3->TMA at different temperatures. The material properties of the films deposited were investigated. Furthermore, First-principles calculations based on density functional theory were also used to investigate the initial surface reaction mechanism for atomic layer deposition of TiAIN films on the SiO2surface using TiCl4, TMA and NH3as precursors. The main content of the work of this thesis can be divided into2parts and can be summarized as follows.In the first part, HfO2films were deposited by atomic layer deposition (ALD) and annealed in temperatures of600and800℃in nitrogen ambient and the chemical properties of the interfacial layer between HfO2and Si substrate were investigated. The XPS results indicated that the interfacial layers were mainly SiO2. When the temperature rises above800℃, the layer content turned into HfSiO4. The Spectroscopic ellipsometry (SE) study showed that HfD2layer thickness decreased with the rising annealing temperature. It may be due to diffusion of the oxygen atoms from HfO2layer into the interfacial layer. First-principles calculations based on hybrid density functional theory were further performed to investigate the defect properties in HfO2. The calculated band gap result is5.6eV which is consistent with the SE result of5.2eV. The oxygen vacancy defect states mainly locate in the middle of the band gap or about1.0eV below the conduction band bottom.In the second part, we investigated atomic layer deposited TiAIN films using titanium tetrachloride (Ticl4), trimethylaluminum (TMA), and ammonia (NH3) with two pulsing sequences of TMA->NH3->TiCl4and TiCl4->NH3->TMAat different temperatures. XRD results the films showed only a few diffraction peaks which indicate an amorphous structure. Both the growth rates of the two pulsing sequences did not show any tendency to saturate along with the increasing of deposition temperature, which may be due to the thermal decomposition of TMA at high temperatures. XPS data showed that the carbon content in the sample of TiCl4->NH3->TMA (30%) is much higher than that of TMA->NH3->TiCl4(10%). Despite of the high C content, the sheet resistance of the films deposited with the sequence of TiCl4-> NH3-> TMA is lower than that of TMA-> NH3-> TiCl4. It may be due to the low reaction barrier of the reaction between TiCl4and NH3which result in more Ti-N bonds.