Katsuhiko Furukawa

OBSERVATION OF SI CLUSTER FORMATION IN SIO2 FILMS THROUGH ANNEALING PROCESS USING X-RAY PHOTOELECTRON SPECTROSCOPY AND INFRARED TECHNIQUES

SiO2 films having high breakdown characteristics were deposited by a sputtering-type electron cyclotron resonance microwave plasma at room temperature. As-deposited films were annealed in an Ar ambient at temperatures ranging from 450 to 1000 °C. Transmitted infrared (IR) absorption and x-ray photoelectron spectroscopy (XPS) were used to characterize the as-deposited and annealed films. XPS measurements indicated that the as-deposited films had an approximately stoichiometric composition containing a few intermediate SiOx(x≠2) species and Ar atoms around some dangling-bond defects. The dependence of XPS spectra on annealing temperature showed that steep diffusion of the Ar atoms occurs at annealing temperatures of 450–550 °C and the SiOx species separate into SiO2 phase and Si clusters by an annealing process of 750–950 °C. Based on the full width at half-maximum variations of Si 2p XPS spectra and Si–O stretching mode of IR spectra for the annealed films, we discuss the Si cluster formation in SiO2 films...

Effect of preoxidation on deposition of thin gate-quality silicon oxide film at low temperature by using a sputter-type electron cyclotron resonance plasma

We have studied a method of combining preoxidation and subsequent sputter deposition for fabricating Si oxide films with a thickness of less than 10 nm at low temperature by using a sputter-type electron cyclotron resonance plasma system. As a key process to achieving high quality composite oxide structures, plasma preoxidation was investigated under different gas flow rates at a substrate temperature of 130 °C. The optimum conditions for the preoxidation were clarified. The structural properties of Si oxide formed by this method with the preoxidation were characterized and compared with those of Si oxide which was directly sputtered without a preoxidation step. It was found that the method with the preoxidation provided a useful way of establishing an abrupt Si/SiO2 interface region and achieving films which have a lower network disorder degree. This procedure was then followed by a thermal annealing in Ar ambient at 450 °C. A thin Si oxide film was produced with a fixed charge density of less than 1.0×1...

Low-temperature deposition of high-quality silicon dioxide films by sputtering-type electron cyclotron resonance plasma

High-quality silicon dioxide films have been deposited at 130 °C by a sputtering technique using an electron cyclotron resonance microwave plasma. Film properties have been studied as a function of O2 flow rate in the range of 2–8 sccm with a constant Ar flow rate of 8 sccm when other plasma conditions were a microwave power of 700 W, and a radio frequency power of 700 W supplied to a target for sputtering. Dielectric breakdown characteristics have been investigated by ramp current–voltage measurements. Films deposited with an O2 flow rate of 5.3 sccm have a dielectric breakdown field of 10 MV/cm, which is close to that of thermally grown silicon dioxide film. The deposition rate was as high as 23 nm/min. Structural properties of films have also been characterized by ellipsometry and infrared absorption spectroscopy, showing that films with O2 flow rates above 4 sccm have near-stoichiometric composition.

In-situ infrared reflective absorption spectroscopy characterization of SiN films deposited using sputtering-type ECR microwave plasma

Abstract High quality amorphous silicon nitride films have been deposited, without substrate heating, using a sputtering-type electron cyclotron resonance (ECR) microwave plasma. The compositional and structural characterizations have been made by means of a Fourier transform infrared (FT-IR) spectrometer and an ellipsometer. The correlation between the microstructure of a-SixNy films and nitrogen gas fraction relative to argon ( N 2 Ar ) is discussed. In-situ Fourier transform infrared reflection absorption spectroscopy (ISFT-IRRAS) has been used to study the properties of a-Si x N y Si interface. The results from ISFT-IRRAS monitoring indicate that the broadening of a SiN stretching vibration mode, induced by interface stress, decreases with increased film thickness.

Effects of ion irradiation on silicon oxidation in electron cyclotron resonance argon and oxygen mixed plasma

Effects of ion irradiation on oxidation of silicon at a temperature as low as 130 °C in an argon and oxygen mixed plasma excited by electron cyclotron resonance interaction have been investigated. The growth rate of the oxide films increases with increasing incident energy and flux of argon ions, and the thickness increases proportionally to the root square of the oxidation time, which suggests that the growth rate is limited by diffusion of oxidants enhanced by irradiation with argon ions. Effects of substrate bias on the oxidation characteristics have been also investigated. The growth rate increases with increasing positive bias, and the growth kinetics deviate from diffusion limited with increasing thickness. The bias dependence of the growth rate is caused by drift of negative oxidants enhanced by the electric field established in the oxide films. Moreover, it is shown that the electrical properties of the oxide films are improved by applying positive substrate bias. The improvement is due to a reduc...

Electrical characteristics of p–n junction diodes fabricated by Si epitaxy at low temperature using sputtering-type electron cyclotron resonance plasma

This article reports the electrical characteristics of p–n junction diodes that were formed by directly depositing a Sb-doped n-type epilayer on a p-type substrate by using a dc-bias electron cyclotron resonance plasma sputtering system at a low temperature of 400 °C and a conventional vacuum of 5×10−7 Torr. The reverse current density of the n+–p junctions diodes depends on deposition gas pressures and substrate biases. The n+–p junction diodes exhibit, under optimum conditions, a reverse current density as low as 9.5×10−9 A/cm2 at a reverse bias voltage of 5 V and an ideality factor of 1.05. The excellent characteristics of the n+–p junction diode are due to the integrity of interface between n+ epilayer and p-type Si substrate.

In situ FT-IR reflective absorption spectroscopy for characterization of SiO2 thin films deposited using sputtering-type electron cyclotron resonance microwave plasma

Abstract Plasma conditions for depositing high quality SiO 2 thin films using a sputtering-type ECR (electron cyclotron resonance) method have been investigated. Film properties have been studied as a function of an oxygen flow rate, F O 2 , in the range 2–8 sccm with a constant Ar flow rate of 16 sccm. Dielectric breakdown characteristics have been investigated by ramp I - V measurements, indicating that the film prepared with F O 2 = 8 sccm to the thickness of 412 A have a good dielectric breakdown field of 8–10 MV/cm. The deposited films were characterized in terms of refractive index and IR (infra-red) properties using FT-IRRAS (Fourier transform infrared reflective absorption spectroscopy) and ellipsometry. The refractive index of films deposited with more than F O 2 = 3 sccm is close to 1.46 which indicates that the films prepared in this range are approximately stoichiometric. In addition, quantitative analysis of the dominant IR (infra-red) mode shows that the peak frequency and FWHM (full width at half-maximum) of a TO (transverse optical phonon) mode for films prepared with more than F O 2 = 6 sccm are comparable with thermally grown SiO 2 , i.e. v = 1075 cm −1 and FWHM = 70 cm −1 . These observations indicate the optimum operating condition of the sputtering-type ECR apparatus, at which it can produce high quality films for MOS (metal-oxide semiconductor) device manufacture without the need for substrate heating.

Effects of oxygen content on properties of silicon oxide films prepared at room temperature by sputtering-type electron cyclotron resonance plasma

We present the study of the effects of gas-phase oxygen fraction on properties of silicon oxide films prepared in a sputtering-type electron cyclotron resonance plasma discharge. Dielectric breakdown characteristics of the films are considerably improved by an increase in oxygen flow rate, FO2, with a constant Ar gas flow rate of 16 sccm. Films prepared at FO2 of more than 6 sccm have good dielectric breakdown fields of 9–11 MV/cm, which are comparable with those of high quality thermally grown SiO2. Moreover, the increase of FO2 improved structural properties of the films. Detailed measurements of their composition and microstructure were carried out using ellipsometry, chemical etch rate measurement in a mixture of HF, H2O, and HNO3 (P etch), x-ray photoelectron spectroscopy (XPS), and infrared (IR) spectroscopy techniques. Ellipsometry and XPS measurements indicated that films prepared at FO2 of more than 3 sccm are stoichiometric. Dependence of the IR spectra and P etch rate on FO2 of more than 3 sccm...

Optimum discharge condition of DC bias electron cyclotron resonance plasma sputtering for high quality Si epitaxial growth

An electron cyclotron resonance (ECR) plasma sputtering method, combined with DC substrate bias, has been developed to deposit single crystal thin films at the low substrate temperature of 400°C and a conventional base pressure of 5×10-7 Torr. At the optimum discharge condition of deposition pressure of 2.2 mTorr and substrate bias of +10 V, with both the ECR power and the rf power for sputtering of 500 W, crystallographically perfect single crystal deposition was found to be possible. These results have been interpreted as supplying a sufficient ion flux to adatoms while maintaining a sufficiently low ion energy to avoid substrate and film damage during deposition.

Characterization of H–Y zeolite modified by a radio-frequency CF4 plasma

Abstract H–Y zeolite modified by a radio-frequency CF 4 plasma has been characterized using X-ray diffraction, nitrogen adsorption, magic angle spinning nuclear magnetic resonance, ethanol adsorption, energy dispersive X-ray and infrared absorption techniques. The ethanol adsorption measurements indicated that the hydrophobic character of the zeolite was enhanced by the plasma treatment. The energy dispersive X-ray experiments showed that the plasma-treated zeolite contained 7.91 at% of carbon and 9.93 at% of fluorine. The infrared absorption measurements clarified that replacement of –OH groups by –CF 3 or –F groups on the micropore surface of the zeolite was responsible for the hydrophobic surface.