Deposition And Characterization Of Hf-based High-k And Higher-k Gate Dielectrics On Si And Inp Substrates

With the rapid development of ultra-large scale integrated circuit, the traditional SiO2-gate dielectric has reached its limitation. It is necessary to employ alternative high dielectric constant(high-k) materials. However, some problems follows with the application of high-k gate dielectric, such as high defect density, poor-quality interlace, thermal unstability of high-k/substrate gate stack and so on. Moreover, high speed devices require new channel materials with higher carrier mobility. Ⅲ-Ⅴ group semiconductors have attracted more and more attention. Additionally, new gate dielectrics with higher k (k>30) are demanded for IC application at16nm technology node and beyond. In this paper, CeO2-HfO2(CDH), Gd2O3-HfO2(GDH), HfTiO are selected as gate dielectric materials. Magnetron sputtering or atomic layer deposition (ALD) is employed to deposite high-k oxides on Si or InP substrates. Structure characterizations and electrical properties of these systems are investigated. The main contents of the research are as follows.(1)CDH films are grown on p-type Si(100) by magnetron sputtering. The influence of O2/Ar ratio during deposition and Ce content on the electrical properties of CDH film has been investigated. XPS indicates that CDH film has fewer oxygen vacancies, confirming that Ce doping can help suppress the generation of oxygen vacancy. Pt/CDH/Si MOS capacitor has tower leakage current density and higher maximum accumulation capacitance than Pt/HfO2/Si MOS capacitor. The k value of CDH film is about20, indicating broad prospects for high-k gate dielectric. Additionally, the content of Ce in CDH film and the O2/Ar during deposition also affect the electrical properties of CDH film.(2)GDH films are grown on p-type Si(100) substrate by magnetron sputtering. The GDH/Si gate stack shows significant thermal stability in NH3atmosphere. According to HRTEM images, GDH film keeps amorphous after900℃annealing. GDH film with rapid thermal annealing (RTA) has fewer oxygen vacancies. The content of interfacial silicates and SiOx decreases after RTA. GDH film with RTA has better electrical properties. The leakage current is two orders of magnitude lower and the maximum accumulation capacitance rises. Additionally, the width of hysteresis windows reduces obviously. The effect of NH3annealing temperature on the electrical properties of Pt/GDH/Si MOS structure are investigated. The results show that the leakage current firstly decreases and then increases with the rising temperature. The C-V characteristic performs better at high annealing temperature, including higher maximum accumulation capacitance and a narrower hysteresis window.(3)HfO2film is deposited on p-InP(100) substrate and the chemical states and band alignment of HfO2/InP interface are studied. XPS analysis shows that there are interfacial In2O3and InPO4, which are the products of the reaction between diffused O atoms and InP substrate. In3d and Hf4f core level spectra and valence spectra are employed to obtain the valence band offset of HfO2/InP. A comparison of band structure is made between thick HfO2film without the influence of interface and thin HfO2film with the influence of interface. For thick HfO2film, experimental results indicate that the5.88±0.05eV band gap of HfO2is aligned to the band gap of InP with a conduction band offset△Ec of2.55±0.05eV and a valence band offset△Ev of1.99±0.05eV. For thin HfO2film, the conduction band offset is1.11eV and the valence band offset is3.43eV.(4)GDH film is deposited on p-InP(100) substrate. The interface chemical states and band alignment are investigated and the electrical properties of W/GDH/InP/Ni MOS structure are characterized. HRTEM results illustrate that there is no obvious interface layer between GDH film and InP substrate. XPS shows that O atoms diffuse less in GDH film than in pure HfO2film and thus the generation of interfacial In2O3is suppressed. The6.05±0.05eV band gap of GDH is aligned to the band gap of InP with a conduction band offset△Ec of2.61±0.05eV and a valence band offset△Ev of2.1±0.05eV. W/GDH/InP/Ni MOS capacitor exhibits good electrical properties, including dielectric constant of16and leakage current density of10-5A/cm2(gate voltage at-1V).(5)Higher-k HfTiO film are deposited on thermally oxidized Si(100) substrate using magnetron sputtering and ALD respectively. The electrical characteristics of Pt/HfTiO/SiO2/Si are investigated. The influence of Ti content and RTA on the electrical properties of HfTiO films are studied. Both magnetron-sputtered HfTiO films and ALD-deposited films show high dielectric constant (k>30), but ALD-deposited film has a lower interfaces state density. With the increase of Ti content, the maximum accumulation capacitance rises and the leakage current decreases. After RTA, although the maximum accumulation capacitance becomes smaller, the hysteresis becomes narrower.