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Featured researches published by Shoichi Mizuo.


Japanese Journal of Applied Physics | 1981

Retardation of Sb Diffusion in Si during Thermal Oxidation

Shoichi Mizuo; Hisayuki Higuchi

Investigation of Sb diffusion in Si during thermal oxidation using LOCOS (LOCal Oxidation of Silicon) shows that diffusion of Sb in Si is retarded during thermal oxidation. This suggests that the diffusion mechanism of Sb differs from those of B and P, which diffuse faster during thermal oxidation. A model which can explain both enhanced and retarded diffusion of impurities in Si during oxidation is proposed. The model assumes that B and P diffuse only by interstitials, Sb diffuses only by vacancies and As diffuses by both vacancies and interstitials.


Journal of Applied Physics | 1983

Effect of Si and SiO2 thermal nitridation on impurity diffusion and oxidation induced stacking fault size in Si

Shoichi Mizuo; Takahisa Kusaka; Akira Shintani; Mitsuo Nanba; Hisayuki Higuchi

The effect of thermal nitridation on impurity diffusion and Oxidation induced Stacking Fault size in Si are clarified by selective nitridation. Enhanced B and P diffusion, retarded Sb diffusion, and growth of OSF’s are found in Si masked with SiO2 films. Retarded B and P diffusion, enhanced Sb diffusion and rapid OSF shrinkage are found in nonmasked Si that has undergone NH3 heat treatment. On the other hand, in N2 or N2+H2 (1:3) ambients, no significant ambient effect on impurity diffusion is found in Si masked with SiO2 films. However, retarded B and P diffusion and enhanced Sb diffusion are found in nonmasked Si with N2 ambient. The results are shown to be consistent with the model that shows that interstitials and vacancies effect thermal equilibrium.


Japanese Journal of Applied Physics | 1982

Anomalous Diffusion of B and P in Si Directly Masked with Si3N4

Shoichi Mizuo; Hisayuki Higuchi

Diffusion of B and P in Si directly masked with Si3N4 films is found to have anomalous characteristics depending on temperature, time, and Si crystal growing method. The discrepancy in diffusion between CZ and FZ substrates under Si3N4 films is explained well assuming the Si–SiO2 interface acts as a sink for super-saturated interstitials. The Si–Si3N4 interface does not have such an effect. It is also found that super-saturated interstitials enhance the diffusion of B and P in CZ Si crystals directly masked with Si3N4 films.


Japanese Journal of Applied Physics | 1982

Effects of Oxidation on Aluminum Diffusion in Silicon

Shoichi Mizuo; Hisayuki Higuchi

Aluminum diffusion in Si affected by thermal oxidation is investigated. Aluminum diffusion in (100) oriented Si is enhanced by thermal oxidation. On the other hand, that in (111) oriented Si is enhanced at low temperature but retarded at high temperature. The difference in the diffusion of Al in Si masked with double-layered SiO2–Si3N4 films and with directly-formed Si3N4 films is found to be very small compared to the case of B and P. Furthermore, the addition of HCl to the oxidizing ambient is found to reduce the anomalous diffusion caused by oxidation. These experimental results are explained assuming that the diffusion of Al in Si proceeds by the interstitialcy mechanism in the Si.


Journal of The Electrochemical Society | 1981

Evaluation of Dislocation Generation at Si3 N 4 Film Edges on Silicon Substrates by Selective Oxidation

Y. Tamaki; S. Isomae; Shoichi Mizuo; Hisayuki Higuchi

The density of dislocations generated at film edges on silicon substrate by selective oxidation is measured and the relation between the selective oxidation conditions and dislocation generation at the film edges is investigated. Dislocations are observed using Secco etching. The results show that the density of dislocations does not continuously increase with oxidation temperature, but decreases markedly at temperatures above 1000°C. A further experiment with recessed oxide structure reveals that the generation of dislocations depends strongly on the cross‐sectional structure of the sample These results are interpreted in terms of viscous flow of film. Another experiment suggests that high pressure oxidation is not effective for suppressing dislocation generation, although it is useful for reducing oxidation time. Finally, collector‐emitter shorts of transistors in bipolar integrated circuits are examined quantitatively using a simple statistical method in relation to the dislocations generated at film edges.


Japanese Journal of Applied Physics | 1982

The Range of Diffusion Enhancement of B and P in Si during Thermal Oxidation

Shoichi Mizuo; Hisayuki Higuchi

The lateral range of oxidation enhanced diffusion (OED) of B and P in Si is investigated using selective oxidation at 1100°C with directly formed Si3N4 films as oxidation resistant masks and FZ Si crystals as substrates. It is found that this OED range of B agrees well with that of P and that the range increases with oxidation time. The value of the range is found to be much larger than previously. The results can be explained using a model in which the range is determined by interstitial diffusion.


Japanese Journal of Applied Physics | 1982

Effects of Backside Oxidation on the Size of Oxidation Induced Stacking Faults at the Front Surface of FZ Si Wafers

Shoichi Mizuo; Hisayuki Higuchi

The effect of backside oxidation on the size of Oxidation induced Stacking Faults (OSF) at the front side of FZ Si wafers has been investigated by Backside Selective Oxidation (BSO). The results show that shrinkage of OSF under directly formed Si3N4 film is interrupted by BSO. However, shrinkage under double-layered SiO2–Si3N4 film is not affected. These results are consistent with the effects of BSO on diffusion of B, P and Sb. The behavior of the OSFs can be explained by the supposition that the Si–SiO2 interface has the effect of preserving the point defect concentration constant and the Si–Si3N4 interface has no such effect.


Japanese Journal of Applied Physics | 1983

Preservation of Point Defect Distribution in FZ Silicon

Shoichi Mizuo; Hisayuki Higuchi

Evidences for the preservation of point defect distribution in FZ Si crystals have been observed by two experimental methods. One is divided selective oxidation and the other is divided backside selective oxidation with Si3N4 as the oxidation resistant films. In both experiments, the selective oxidation is divided into several oxidation steps, and the effects of oxidation division on the range of oxidation effects on impurity diffusion is investigated. The results show that, both laterally and vertically from the oxidizing Si–SiO2 interface, the effect of oxidation on impurity diffusion is determined only by total oxidation time. This suggests that point defect distribution is preserved after heat treatment.


Applied Physics Letters | 1985

Linear rate oxidation of silicon for oxidation effect investigation

Shoichi Mizuo; Hisayuki Higuchi

Oxidation of Si was performed by varying oxygen partial pressure during oxidation. A linear relation between oxide thickness and oxidation time was obtained under a linear increase of oxygen partial pressure. The effect of linear oxidation was examined on B and P diffusion in Si. Linear rate oxidation can be used for investigation of oxidation enhanced or retarded diffusion of impurities and growth kinetics of stacking faults in Si.


MRS Proceedings | 1984

Investigation of Point Defects in Si by Impurity Diffusion

Shoichi Mizuo; Hisayuki Higuchi

Our investigation of impurity diffusion in Si has clarified diffusion mechanisms and the point defect structure for the material. Thermal equilibrium between interstitials and vacancies in high temperature Si was clarified through observation of oxidation-retarded diffusion (ORD) of Sb in Si. Boron, Phosphorus, Aluminum and Galium were found to diffuse mainly due to an interstitialcy mechanism, while Sb did by a vacancy mechanism. Moreover, the atomic number in Si crystal compared to that at lattice sites was seen to play a dominant role in determining point defect concentration. Oxidation of Si and nitridation of SiO 2 on Si lead to an increase in the atomic number of Si crystals and cause an increase in interstitial concentration as well as a decrease in vacancy concentration. On the other hand, nitridation of Si leads to a decrease in atomic number and causes vacancy super-saturation as well as interstitial under-saturation.

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