• PDF / 195,465 Bytes
• 7 Pages / 595 x 842 pts (A4) Page_size
• 47 Downloads / 251 Views

DOWNLOAD

REPORT

---

Characterisation of TiO2 films grown at low temperatures for alternative gate dielectric application Jun-Ying Zhang1,2 and Ian W. Boyd1 1 Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, UK 2 Structure Research Laboratory, University of Science and Technology of China, Hefei 230026, People's Republic of China

ABSTRACT In this paper we report the growth of thin titanium oxide films on Si (100) and quartz at low temperatures (≤350°C) by photo-induced chemical vapor deposition (photo-CVD) with 222 nm UV radiation using a novel injection liquid source, which overcomes the reproducible problem in conventional bubblers. The properties of the films formed have been studied using ellipsometry, UV spectrophotometry and Fourier transform infrared spectroscopy (FTIR) measurements. Nanostructured films were observed by atomic force microscopy (AFM). It was found that crystalline TiO2 films could be formed at deposition temperatures as low as 210°C by x-ray diffraction (XRD). The influence of the deposition temperature on the film is discussed. The refractive index as high as 2.5 can be obtained at a deposition temperature of 350°C, while an optical transmittance of between 80-95% in the visible region of the spectrum was obtained at different deposition temperatures. Physical and optical characterization both reveal good film qualities, rendering this technique promising for a wide range of industrial application in low temperature microelectronic and optoelectronic material processing as well as for many heat sensitive compounds.

1

Introduction

The continuous miniaturization of CMOS devices has imposed severe constraints on the performance of the SiO2 gate oxide, with its thickness now approaching the quantumtunneling limit of 20 Å [1-4]. Therefore, it is very desirable to have an alternative insulating layer with a dielectric constant (k) higher than that for SiO2 (3.9) so that the dielectric thickness can then be increased proportionally, thereby reducing the direct tunneling through the gate dielectrics. Amongst the high-k metal oxides dielectrics, titanium dioxide (TiO2) appears to be of considerable interest as an alternative gate insulating layer to replace conventional SiO2 for new generation of dynamic random access memories (DRAMs) as it exhibits a higher dielectric constant (up to 100) than Ta2O5 [5-6]. TiO2 films have been grown by various methods [7-9]. Amongst them plasma-enhanced chemical vapor deposition has received much attention toward developing low temperature growth process. However, plasma-assisted films growth can induce damage due to energetic ion bombardment, contamination, and produce a number of unwanted reactions. Photo-induced CVD offers the advantages of eliminating ion bombardment damage, reducing the number of unwanted reactions and the possibilities of diffusion and intermixing at the semiconductor-oxide K2.10.1

interface due to a low temperature (