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Study of the Influence of Temperature on the Deposition of Sio2 Films from Reaction of Silicone Oil Vapor and Ozone Gas

Arifuzzaman Rajib*
Department of Applied Physics, Electronics and Communication Engineering, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj, Bangladesh.

Susumu Horita
School of Material Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa Prefecture 923-1211, Japan.

Atowar Rahman
Department of Applied Physics and Electronic Engineering, University of Rajshahi, Rajshahi 6205, Bangladesh.

Abu Bakar Md. Ismail
Department of Applied Physics and Electronic Engineering, University of Rajshahi, Rajshahi 6205, Bangladesh.

Abstract/ Executive Summary:

This work reports the influence of deposition temperature on the deposition of SiO₂ films on silicon substrate by using chemical reaction of silicone oil vapor and ozone gas at low temperature. An organic solution as a catalyst at atmospheric pressure has been used to enhance the deposition rate of SiO₂. The deposition rate of SiO₂ films was found to vary with the variation of the concentration of the catalyst and deposition temperature (160°C ~ 260°C). The deposited SiO₂ films were confirmed by Fourier transform infrared (FTIR) spectroscopy. The thickness and refractive index of the as-deposited films were measured by the laser ellipsometry. FT-IR spectra of the as-deposited films were very much similar to those of SiO₂ films found in literature. The deposition temperature was found to influence the deposition rate of SiO₂ strongly. The maximum deposition rate was found to 17.2 nm per minute for the case of 220°C. The deposition temperature also influenced the refractive index of the films. Experimental results showed that the deposition temperature could be a major parameter for the enhancement of the deposition rate.

Keywords: Low-Temperature, SiO2 deposition, APCVD, FT-IR spectroscopy.

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Start Date:

End Date:

Program Area: Resource Development and Management

Non-commodity: Temperature

Objectives:

In this study, APCVD methods have been used to deposit SiO₂ films at low temperature with taking advantage of their easy set-up and lower cost (no extra setup is required for pressure control).

Methodology:

A schematic diagram of the atmospheric pressure chemical vapor deposition (AP) CVD system used for the deposition of silicon oxide films. Here, the conventional APCVD system has been slightly modified by introducing a new line partwhich facilitates to add anorganic solution to the main stream of the system. The chemically cleaned substrates were loaded into the chamber, which was uniformly heated by heater at a deposition temperature. The silicone oil (SO) (TSF-405) was heated to about 50 ºC and vaporized directly by bubbling with N2 gas at a flow rate of 0.35 standard liter per minute (slm) through a stainless tube heated to about 55 °C to avoid the condensation of SO vapor. The organic solution was heated to three different temperatures of 21.9 ºC, 28.1 ºC and 34.1 ºC by another heater and vaporized by bubbling with N2 gas at five different flow rates of 0, 0.05, 0.1, 0.15 and 0.2 slm. After that, the Study of the Influence of Temperature on the Deposition of SiO₂ Films from Reaction of Silicone Oil Vapor and Ozone Gas organic solution was mixed with silicon oil vapor and then flown into the chamber. The ozone was generated by anozonizer from O₂ gas at the flow rate of 0.5 slm and then introduced into the chamber together with the silicone oil and organic solution vapor. The substrates were n-type single crystals silicon with a resistivity of 5-15 -cm. The crystallographic orientation of the substrate was. The dopant of the wafer is phosphorus. The thickness of the substrate = 525 ± 25 µm. They were chemically cleaned by hot ammoniacal solution (NH₄OH : H₂O₂: H₂O = 1 : 1 : 4) and hot acid solution (HCl: H₂O₂ : H₂O = 1 : 1 : 4). After each chemical solution treatment, the chemical oxide was removed by 1% HF solution. In our experimental process,O₃ is decomposed to O₂ and reactive O shown in equation (1). This decomposition is dependent on deposition temperature. Oliver R.Wulf& Richard C. Tolman specified the range of decomposition temperature that is 148 ºC to 179 ºC. Since the O is very chemically active, the overall reaction of the process of reactive oxygen and SO is shown in equation (2). In the first stage, the chemically reactive oxygen atoms are reacted with the methyl (-CH₃) bond of the SO in the gas phase and broken the methyl bond to form hydroxyl (-OH) bond then intermediate products of deca-hydroxyl-cyclo-penta-silaxane (precursors) are formed together with by-products of H₂O and CO₂. In other words, -CH₃ side groups are replaced with hydroxyl (-OH) and silanol bonds of Si-OH cover the sides of the siloxane chains. In the second stage, the – OH groups on the surface are eliminated the by the dehydration reaction with the –OH groups on the precursors. Thickness and Refractive index were measured by laser ellipsometry (ULvac ESM 1A) at a wavelength 632.28 nm, spot size of about 1 nm, angle of incidence 70 º, sampling time 20 ms as well as measured 10 times at the same location.Chemical structures of as deposited films were studied by Fourier Transform Infrared Spectroscopy (Perkin Elmer (Spectrum 100) FT-IR Spectrometer) of wave number range 500 to 4000. When the deposited films are investigated by FT-IR spectrophotometer, the deposited film is kept into the holder and waits 5 to 6 minutes for removing unwanted H₂O and CO₂, which are absorbed in the films.

Source of Information: Rajshahi University Journal of Science & Engineering ISSN 2309-0952 Vol. 44: 1-8, 2016

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Achievement/Findings:

The SiO₂ films were deposited on a silicon substrate at atmospheric pressure and temperature between 160 ºC and 260 ºC by using the chemical reaction between silicone oil vapor and ozone gas as well as an organic solution was used as a catalyst. The deposition rate was too low, e.g., 1 nm/min at 200 ºC for the case of without organic solution. But in our study, the deposition rate was 11.85 nm/min at 200 ºC by using organic solution. The average deposition rate was found to be 13.2 whereas the maximum deposition rate was 17.2 nm per minutes at 220 ºC deposition temperature.The FT-IR spectra showed that the films deposited from 160 ºC to 260 ºC were almost stoichiometric Si oxides. It is confirmed from FT-IR spectra of the as-deposited films. Although weak peaks from Si-OH related bond was found in the FT-IR spectra no peak related to Carbon was observed. The presence of Si-OH bond indicated the presence of small amount of pores in the deposited film that was responsible for the variation in refractive index of the deposited films. The amount of Si-OH were optimized with the help of tuning the deposition temperature that could be occurred due to increase dehydration reaction. From the experimental data it could be concluded that the deposition rate of SiO₂ from the chemical reaction between silicone oil vapor and ozone gas could be enhanced by optimizing the deposition temperature.

Knowledge Management: Journal