Crecimiento de dieléctricos de alta permitividad mediante pulverización catódica de alta presión a partir de blancos metálicos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física Aplicada III (Electricidad y Electrónica), leída el 07/07/2016The integrated circuit based on complementary metal-oxide-semiconductor (CMOS) devices is currently the dominant technology in the microelectronic industry. Their success is based on their low static power consumption and their high integration density. The metal-oxide-semiconductor field effect transistors (MOSFETs) are the main component of this technology. Their dimensions have been decreasing during the last years following the Moore’s law. This downscaling has made possible their continuous performance improvement. However, the size shrinking produced an excessive increase in the leakage current density that made this technology to face several challenges. The introduction of high permittivity (κ) dielectrics permits the use of a thicker insulator film (thus, reducing the leakage current) but with a lower equivalent SiO2 thickness (EOT). Besides, the introduction of these materials also required a change in the poly-Si electrode, that became a pure metal. The main objective of this thesis was the fabrication of metal-insulator-semiconductor (MIS) structures using high κ dielectrics grown from metallic targets. This was performed by means of high pressure sputtering (HPS). The advantage introduced by this system is that, due to the high working pressure, the particles suffer many collisions (because their mean free path is much lower than the target-substrate distance) and get thermalized before reaching the substrate in a pure diffusion process. This way, the semiconductor surface damage is preserved. The key novelty of this work consisted on the fabrication process using metallic targets. A two-step deposition process was developed: first, a thin metallic film is sputtered in an Ar atmosphere and, afterwards, this film was in situ oxidized...Los circuitos integrados basados en los dispositivos CMOS (complementary metal-oxide-semiconductor) son en la actualidad la tecnología dominante de la industria microelectrónica. Su éxito se basa en su bajo consumo de potencia estática y en su alta capacidad de integración. Esto ha hecho que las dimensiones de los transistores de efecto campo metal-óxido-semiconductor (MOSFET, metal-oxide-semiconductor field effect transistor), que es el dispositivo principal de dicha tecnología, se hayan ido reduciendo durante los últimos años de acuerdo a la ley de Moore. A medida que los tamaños se fueron reduciendo, proceso habitualmente denominado escalado, las prestaciones de los transistores mejoraban. Sin embargo, esta continua reducción de los transistores lleva asociada una excesiva corriente de fugas que hace que los transistores dejen de funcionar de una manera óptima. Por tanto, los dieléctricos de alta permitividad (κ) se introdujeron para permitir emplear aislantes de mayor espesor físico (y así reducir las fugas), pero con un menor espesor de óxido de silicio equivalente (EOT, equivalent oxide thickness). El cambio en el material aislante de la puerta lleva asociado también un cambio en el electrodo metálico...Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEunpu

Nano-laminate vs. direct deposition of high permittivity gadolinium scandate on silicon by high pressure sputtering

In this work we use the high pressure sputtering technique to deposit the high permittivity dielectric gadolinium scandate on silicon substrates. This nonconventional deposition technique prevents substrate damage and allows for growth of ternary compounds with controlled composition. Two different approaches were assessed: the first one consists in depositing the material directly from a stoichiometric GdScO_(3) target; in the second one, we anneal a nano-laminate of <0.5 nm thick Gd_(2)O_(3) and Sc_(2)O_(3) films in order to control the composition of the scandate. Metal-insulator-semiconductor capacitors were fabricated with platinum gates for electrical characterization. Accordingly, we grow a Gd-rich Gd_(2-x)Sc_(x)O_(3) film that, in spite of higher leakage currents, presents a better effective relative permittivity of 21 and lower density of defects

Thermal stability study of AlGaN/GaN MOS-HEMTs using Gd2O3 as gate dielectric

Thermal stability of AlGaN/GaN MOS-HEMTs and -diodes using Gd_(2)O_(3) are investigated by means of different thermal cycles and storage tests up to 500ºC for one week. IV DC and pulsed characteristics of the devices before and after the processes are evaluated and compared with conventional HEMTs. Results show that the devices with Gd_(2)O_(3) dielectric layer have lower leakage current and a more stable behavior during thermal treatment processes compared with conventional devices. In fact, an excellent on/off ratio of about 108 and a stable V_(t) is observed after storage at high temperature. The beneficial effects of Gd_(2)O_(3) on trapping effects of MOS-HEMTs are also dis-cussed

Temperature performance of AlGaN/GaN MOS-HEMTs on Si substrates using Gd2O3 as gate dielectric

GaN based high electron mobility transistors have draw great attention due to its potential in high temperature, high power and high frequency applications [1, 2]. However, significant gate leakage current is still one of the issues which need to be solved to improve the performance and reliability of the devices [3]. Several research groups have contributed to solve this problem by using metal–oxide–semiconductor HEMTs (MOSHEMTs), with a thin dielectric layer, such as SiO2 [4], Al2O3 [5], HfO2 [6] and Gd2O3 [7] between the gate and the barrier layer on AlGaN/GaN heterostructures. Gd2O3 has shown low interfacial density of states(Dit) with GaN and a high dielectric constant and low electrical leakage currents [8], thus is considered as a promising candidate for the gate dielectrics on GaN. MOS-HEMTs using Gd2O3 grown by electron-beam heating [7] or molecular beam epitaxy (MBE) [8] on GaN or AlGan/GaN structure have been investigated, but further research is still needed in Gd2O3 based AlGaN/GaN MOSHEMTs

High-k gadolinium scandate on Si obtained by high pressure sputtering from metal targets and in-situ plasma oxidation

This article studies the physical and electrical behavior of Gd2-xScxO3 layers grown by high pressure sputtering from metallic Gd and Sc targets. The aim is to obtain a high permittivity dielectric for microelectronic applications. The films were obtained by the deposition of a metallic nanolaminate of Gd and Sc alternating layers, which is afterwards in-situ oxidized by plasma. The oxide films obtained were close to stoichiometry, amorphous and with minimal interfacial regrowth. By fabricating metal-insulator-semiconductor capacitors we found that a moderate temperature annealing is needed to enhance permittivity, which reaches a high value of 32 while keeping moderate leakage. Finally, the feasibility of interface scavenging in this material with Ti gate electrodes is also demonstrated

Optimization of in situ plasma oxidation of metallic gadolinium thin films deposited by high pressure sputtering on silicon

Gadolinium oxide thin films were deposited on silicon by a two-step process: high pressure sputtering from a metallic gadolinium target followed by an in situ plasma oxidation. Several plasma conditions for metal deposition and oxidation were studied in order to minimize the growth of a SiOx layer at the interface between the high permittivity dielectric and the silicon substrate and to avoid substrate damage. Plasma emission was studied with glow discharge optical spectroscopy. The films were structurally characterized by Fourier transform infrared spectroscopy. Metal-insulator-semiconductor capacitors were fabricated with two different top metals (titanium and platinum) to analyze the influence of deposition conditions and the metal choice. Pt gated devices showed an interfacial SiOx regrowth after a forming gas annealing, while Ti gates scavenge the interface layer

Growth and interface engineering of highly strained low bandgap group IV semiconductors

Highly tensile strained Ge(Sn) layers epitaxially grown on GeSn strain relaxed buffer layer have been presented. Electrical characterization exhibits good interfacial quality of the high-k gate stacks employing HfO2 on Ge and strained Ge. These results mark a first step towards electronic device integration of low bandgap highly tensely strained group IV semiconductors