• PDF / 1,947,521 Bytes
• 6 Pages / 414.72 x 648 pts Page_size
• 61 Downloads / 254 Views

DOWNLOAD

REPORT

---

ABSTRACT The thermal stability of titanium disilicide (TiSi2) film under dielectric capping layers was studied. Dielectric capping layers prevent changes in sheet resistance and the film stress of the TiSi2 film during annealing at 9000C. The enhancement of thermal stability of the TiSi2 film was dependent on the nature of dielectric; thermal stability of the TiSi2 film was enhanced more effectively by the plasma-enhanced silicon nitride (PE-SiN) capping layer rather than the undoped silicate glass (USG; SiO2) capping layer. The dependence of thermal stability of the TiSi2 film with the nature of dielectrics was due to the difference in stress of dielectrics at anneal temperature. At 9000C, stress of the USG film was nearly twice of that of the PE-SiN film. Agglomeration of the TiSi2 film under the dielectric capping layer at high temperature annealing can be explained by a diffusional flow of atoms called Nabarro-Herring microcreep. As the size of Ti-polycide lines becomes smaller, the nature of the dielectric film on the TiSi2 film will be more important for achieving thermal stability.

INTRODUCTION As devices are reduced further in size, the resistance of the gate electrode starts playing a critical role respect to the signal delay of metal-oxide semiconductor (MOS) devices. The most promising candidates for a suitable low resistance gate-level material in sub-micron MOS devices are refractory disilicides. Among these, TiSi2 has the lowest resistivity and a great potential compatibility with heavily doped polycrystalline silicon gates. However, morphological degradation upon annealing at 9000C or higher temperature has limited its application to future ultra large scale integration (ULSI) processing [1-3]. Thermal stability of TiSi2 films have been investigated widely for microelectric device fabrication [4-9]. During fabrication of devices, many dielectric thin films are stacked on the titanium polycide gate. However, there is little experimental evidences on the effect of the dielectric capping layer on thermal stability of the TiSi2 film. It has been reported that although the thermal stability increased by dielectric overcoat, it was not depend on the nature of dielectric [4]. In this paper, the thermal stability under the dielectric capping layer was studied for the TiSi2 film. Our study showed that the nature of dielectric overcoat on TiSi2 film significantly influences the thermal stability of a TiSi2/Si structure during high temperature annealing, especially, for sub-micron titanium polycide gate line.

EXPERIMENTAL PROCEDURES The experiments were performed on (100)-oriented silicon wafers with a diameter of 150 mm. Each wafer was dipped in 99% H20 + 1% HF solution to remove native 239 Mat. Res. Soc. Symp. Proc. Vol. 317. 11994 Materials Research Society

oxide. Titanium films of 50 nm thickness were sputter deposited after Ar sputter etching of the Si surfaces. The titanium silicide (TiSi2 phase) film was subsequently formed by a solid phase reaction between sputtered Ti and single crystal substrate b