Precise control of CVD-ZrO 2 film properties based on kinetic information.
- PDF / 128,170 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 54 Downloads / 140 Views
Precise control of CVD-ZrO2 film properties based on kinetic information. Takashi Kawamoto and Yukihiro Shimogaki University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan ABSTRACT ZrO2 films were investigated as high-k gate insulators for possible gate dielectric applications. These thin films were deposited by chemical vapor deposition (CVD). We had investigated kinetics of ZrO2-CVD reaction system and thermal stability of ZrO2 film deposited from zirconium-tetra-tertiary-butoxide (ZTB) and tetrakis-diethylamio-zirconium (TDEAZ) as Zr source. In the case of ZTB, ZTB decomposed into two active intermediate precursors by gas phase reaction. These intermediate precursors also contributed to the film growth. The step coverage, the contents of carbon and oxygen, and film structures depended on the growth precursor contributed to the film growth. Film structures also depended on the deposition temperature. As the films subjected to the rapid thermal oxidation annealing, the film structure changed amorphous into cubic and then into monoclinic. However, in the case of the films deposited at 300oC, the film structure kept amorphous state after 900oC annealing. On the other hand, in the case of TDEAZ, TDEAZ directly deposited on the growing surface and the decomposition of TDEAZ by gas phase reaction did not exist. The films deposited by TDEAZ contained more carbon than by ZTB. The film structure kept amorphous state independent of the deposition temperature. As the films subjected to the rapid thermal oxidation annealing, the film structure changed amorphous into monoclinic and then into amorphous again. This structural change resulted from the decrease of the impurity contents of the residual nitrogen and the residual carbon and the increase of the content of silicon diffused from the substrate in the ZrO2 films. INTRODUCTION The continuous reduction of the gate insulator (SiO2) layer thickness in advanced metal-oxide-semiconductor (MOS) devices leads to excessive gate leakage currents and device reliability problems. In ultrathin SiO2 layers, direct tunneling of electrons becomes important for layers thinner than 1.5nm [1]. In addition, it has been reported recently that for SiO2 layers thinner than 2.5nm, the reliability of the insulating layer becomes a major issue [2,3]. Consequently, alternative gate insulators, with higher dielectric constant than SiO2, are currently being widely investigated for future generations of MOS transistors [4-9]. The use of dielectric layer with higher dielectric constant should allow us to use thicker films with an electrical thickness equivalent to SiO2, and one would thus expect to reduce the leakage current and improve the reliability of the gate dielectric layer. P5.24.1
Among many candidates for replacing SiO2, ZrO2 is one of the major materials because of suitable dielectric constant for gate application and its thermal stability in direct contact with Si [10-13]. However, ZrO2 thin films still have many problems for high-k gate insulator. In the aspect of high-k gate proces
Data Loading...
