**4. References**


Synthesis together with the alkoxides was obtained crystalline orthorhombic phase, confirmed by XRD and an exothermal peak without loss of mass by DTA analysis. When the synthesis was performed with separate alkoxides was not possible to obtain only zirconium titanate, probably due to the fact formed crystalline forms anatase, and baddeleyite observed by XRD, which competes with the formation of ZrTiO4, which can be detected only at 700 °C. The ZrTiO4 powders treated thermally at 700°C present. The thermal analysis showed also a great loss of mass, between 40 and 200 ºC approximately, probably due to dehydration. The peaks in DTA at 350 and 550 °C are related to the removal of organic compounds. The water loss was confirmed in the spectrum FTIR. It was observed that the formation of the bands related to the presence of hydroxyl group showed a decrease with the increase of annealing temperatures, and at 700 °C they disappeared, indicating that the material structure no longer contains zirconium hydroxide. The sol-gel process was efficient in the preparation of ZrTiO4 using the two routes compared, but should be studied the addition of other acids, as nitric acid caused the aggregation of the powers.

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**13** 

*Japan* 

**Characterization of Sol-Gel-Derived and** 

Hirofumi Shimizu and Toshikazu Nishide

*College of Engineering, Nihon University Tamura-machi, Koriyama, Fukushima,* 

**Crystallized HfO2, ZrO2, ZrO2-Y2O3 Thin Films** 

**on Si(001) Wafers with High Dielectric Constant** 

A very great number of metal oxide thin films are produced by sol-gel methods. Metallic compounds dissolved in organic solvents are hydrolyzed and polymerized by adding H2O with an acid or a base and heating to obtain metal oxide sols. Metal oxide thin films are

The sol-gel method produces amorphous or crystalline thin gel films of metallic solid compounds by solidifying a sol formed by hydrolyzing and polymerizing a solution containing metallic compounds. Sol-gel processes are widely employed in the field of chemistry to prepare ceramic powders and thin films of hafnium oxide (HfO2) (Nishide et al., 2000) and zirconium oxide (ZrO2) ( Liu et al., 2002) for obtaining high-quality ceramics and insulators, offering the advantages of low cost, relative simplicity, and easy control of the composition of the layers formed. This chapter describes the characterization of sol-gelderived and crystallized HfO2 and ZrO2 thin films intended for use as gate insulators with

In the electronic device field, the continuing miniaturization of silicon (Si) ultra-large-scaleintegration (ULSI) devices has required an ultrathin gate Si dioxide (SiO2) and oxynitride film; upon scaling down to 32-22 nm technology nodes and beyond, thinner SiO2 gate oxide films have been required. At these thicknesses, gate leakage currents due to direct tunneling become comparable to the off-currents of metal-oxide-semiconductor (MOS) field-effect transistors (FETs), increasing the off-state power consumption of the devices. In further scaled-down advanced Si complementary MOS (CMOS) devices, scaling trends have required the substitution of gate SiO2 by insulators with higher dielectric constants (high-*k*) ( Huff & Gilmer, 2004). The aim of using high-*k* materials is to increase the film thickness, thus reducing the tunneling leakage current, while scaling the capacitance of the equivalent oxide thickness (EOT) below the direct tunneling limit of SiO2 ( Huff & Gilmer, 2004). Several high-*k* material candidates, such as HfO2 (Blanchin et al., 2008), ZrO2 (Niinisto et al., 2004), Al2O3, ZrO2-Y2O3 (YANG, 1996), Y2O3 (Nishide & Shibata, 2001),La2O3 (Ng et al., 2005), and gate stack structures have been proposed and some materials have been put into practical use. All of them are

prepared by coating the sols on substrates followed by firing (Kozuka, 2005).

either oxides or silicates of 4d or 5d transition metals or rare earth elements.

high dielectric constants in electronic devices.

**1. Introduction** 

