Low Temperature Direct-Oxidation of Si using Activated Oxygen Generated by Tungsten Catalytic Reaction
- PDF / 727,948 Bytes
- 6 Pages / 414 x 635.4 pts Page_size
- 84 Downloads / 199 Views
ABSTRACT Ultra-thin silicon dioxide films can be formed at temperatures as low as 220°C by direct oxidation of Si, using active oxygen species generated by tungsten catalytic reaction in a catalytic chemical vapor deposition (Cat-CVD) system. The structural and electrical properties of such a films are investigated. It is found that the density of Si atoms in intermediate oxidation states and the density of films determined from etch rate in dilute HF solution were comparable to those of the films by a conventional thermal oxidation at 900°C. The electrical properties, breakdown electric field and leakage current were also comparable to those of thermally oxidized films.
INTRODUCTION High quality ultra-thin oxide films are required for the next generation of gate oxide in ultra large-scale integrated circuits (ULSI) device. The 1999 version of the International Technology Roadmap for Semiconductors predicts that the gate oxide thickness will be reduced to 1.0-1.9nm in year 2005. Controlling of atomic order oxide growth is required. However, conventional high temperature thermal oxide reactions are too fast to grow the ultra-thin gate oxide, and such a high temperatures cause the diffusion of dopant. Therefore, formation of SiO 2
films at low temperatures is strongly required. In this work, we propose a novel low temperature oxidation of silicon surface using activated oxygen generated by tungsten catalytic reaction in a catalytic chemical vapor deposition (Cat-CVD) system (Cat-oxidation). In the Cat-CVD method [1,21, material gases are decomposed by catalytic cracking reactions at heated catalyzer so that active seeds can be generated without help from plasma nor photochemical excitation. We have also succeeded in surface nitridation of Si [3] and GaAs [4] at 200°C using NH 3gas based on this technique. EXPERIMENTAL Figure 1 shows the schematic diagram of the Cat-CVD apparatus. A tungsten wire with a diameter of 0.5mm and length of 1900mm was used as a catalyzer. It was coiled and spread widely in a space of 100mm X 100mm, keeping it parallel to the substrate holder with a distance of 50mm. The catalyzer was heated by supplying electric power directly on it. The temperature of the catalyzer was measured by an infrared thermometer. The temperature of the substrate was measured by a thermocouple (TC) mounted on the substrate holder (T.J). The surface temperature was also calibrated using a TC directly mounted to the Si substrate (Tu), and it was 207 Mat. Res. Soc. Symp. Proc. Vol. 592 © 2000 Materials Research Society
Heater Substrate holder Infrared thermometer
Fig.1 Schematic diagram of a Cat-CVD apparatus. Table 1 Oxidation conditions Parameter H2 flow rate He diluted O2(5000ppm) flow rate Substrate surface temperature T,.b Catalyzer Temperature Tat Reactor pressure
Set point 100 sccm 10 sccm -220'C 1700 9C 20 Pa
confirmed that the surface temperature was at most a few 10(C higher than Th,1.
The oxidation conditions are summarized in Table 1.An n-type CZ(100) Si wafer with
resistivities of 0.85-1.50cm was
Data Loading...
