Low Temperature Nitridatio of SiO 2 Films using a Catalytic-CVD System
- PDF / 460,958 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 48 Downloads / 224 Views
LOW TEMPERATURE NITRIDATIO OF SiO2 FILMS USING A CATALYTIC-CVD SYSTEM Akira Izumi, Hidekazu Sato and Hideki Matsumura JAIST (Japan Advanced Institute of Science and Technology) Ishikawa 923-1292, JAPAN ABSTRACT This paper reports a procedure for low-temperature nitridation of silicon dioxide (SiO2) surfaces using species produced by catalytic decomposition of NH3 on heated tungsten in catalytic chemical vapor deposition (Cat-CVD) system. The surface of SiO2/Si(100) was nitrided at temperatures as low as 200oC. X-ray photoelectron spectroscopy measurements revealed that incorporated N atoms are bound to Si atoms and O atoms and located top-surface of SiO2. INTRODUCTION Surface nitridation of SiO2 is useful for metal-oxide-semiconductor (MOS) gate dielectric to suppress boron penetration from p+-Si gate [1]. Such treatment should be prepared at low temperatures without plasma enhancement to suppress dopant diffusion and plasma damage. Excessive nitrogen at the SiO2/Si interface may reduce peak carrier mobility in the channel of MOS devices [2]. Therefore, top-surface niridation of SiO2 is required for the suppression of boron penetration without degradation of device. In this paper, we propose a low temperature and plasma-less top-surface SiO2 nitridation technology using species produced by catalytic decomposition of NH3 on heated W in catalytic chemical vapor deposition (Cat-CVD) system. In the Cat-CVD method, deposition gases are decomposed by catalytic cracking reactions with heated catalyzer placed near substrates so that films are deposited at low substrate temperatures without help from plasma excitation. The authors have succeeded in depositing high quality SiNx films using a SiH4 and NH3 gas mixture [3]. High quality amorphous Si [4] and polycrystalline Si films [5] with low hydrogen content have also been obtained using a SiH4 and H2 gas mixture. Applying this technique, we have succeeded in direct surface nitridation of Si at 200oC using NH3 gas [6]. This method is also useful for surface cleaning [7] and nitridation of GaAs [8]. Crystalline Si etching with high etch rate as high as 200nm/min is obtained using H2 gas [9]. This present work is on a similar way of such wide variation of the Cat-CVD application. EXPERIMENTAL Figure 1 shows the schematic diagram of the apparatus for nitridation. The apparatus is
C4.5.1
Fig.1 Schematic diagram of the apparatus for nitridation. basically same as the Cat-CVD apparatus except for the source gases. A tungsten (W) wire with a diameter of 0.5 mm and length of 1300 mm was used as the catalyzer. It was coiled and spread widely in a space of 70 mm x 70 mm, keeping it parallel to a substrate holder with a distance of 60 mm. Therefore, to make the spread area of catalyzer larger, it is possible to make nitridation on large diameter wafers. An n-type CZ Si(100) wafer with a resistivity of 0.85-3.0 Ωcm was cut into 2x2 cm2 pieces. After that they were degreased and cleaned by RCA method. Then, they were dipped in 2% diluted HF for 2 min. After the cleaning, the pieces of
Data Loading...
