Junro Sakai

Selective epitaxial growth by UHV-CVD using Si2H6 and Cl2

The conditions under which selective epitaxial growth (SEG) is achieved in UHV-CVD with Si2H6 are determined by the amount of Si2H6 molecules being supplied, and there is a critical gas supply amount (Fc) beyond which SEG will break down and lose its selectivity. The value of Fc is itself determined by two factors, growth temperature and the material used for masking, i.e. SiO2, Si3N4. We found that this limiting factor of Fc was increased through the addition of a small amount of Cl2, and that after such addition, the resulting decrease in growth rate is minimal.

Characterization of Stable Fluorine-Doped Silicon Oxide Film Prepared by Biased Helicon Plasma Chemical Vapor Deposition

Fluorine-doped silicon oxide (SiOF) film prepared by biased helicon plasma chemical vapor deposition with SiF 4 and O 2 is characterized. In this characterization, the SiOF film is compared with that prepared using a nonbiased plasma. SiOF films prepared using a biased plasma are stable in air. Whereas films prepared using a nonbiased plasma are not stable in air and the relative dielectric constant and stress vary in the ranges 3.2 to 3.5 and from -35 MPa to 0 MPa, respectively. Analysis Fourier transform infrared (FT-IR) and thermal desorption mass spectroscopy (TDS) spectra, clarifies the following. (1) Si-F bonds are formed in SiOF films prepared using a biased plasma. (2) Not only Si-F bonds but also F-Si-F bonds are formed in SiOF films prepared using a nonbiased plasma. (3) The F-Si-F bond structure formed in SiOF films absorbs water easily.

Limitations of selective epitaxial growth conditions in gas-source MBE using Si2H6

The limiting conditions of selective epitaxial growth (SEG) on SiO2 patterned Si(001) substrate were studied for Si gas-source molecular beam epitaxy (MBE) by use of 100% Si2H6. In the initial stage of growth, epitaxial Si was selectively grown on a Si surface in the temperature range of 500 to 850°C. On the other hand, polycrystalline Si nucleation on a SiO2 surface was intimately related to the impinging density of the Si2H6 molecules on SiO2, so that SEG was limited by the supply gas volume. Under optimum SEG conditions such as substrate temperature of 700°C and Si2H6 flow rate of 60 SCCM, a SEG layer could be deposited at a rate as high as 645 A/min.

Selective Epitaxial Growth of Si and Si1-xGex Films by Ultrahigh-Vacuum Chemical Vapor Deposition Using Si2H6 and GeH4

Aiming at the precise profile control of Si1-xGex, selective epitaxial growth (SEG) conditions and Si1-xGex growth were investigated by ultrahigh-vacuum chemical vapor deposition (UHV-CVD) using Si2H6 and GeH4. As long as the total amount of Si2H6 did not exceed the critical amount, Si- and Si1-xGex-SEG were both achieved independent of source gas flow rate and substrate temperature. The Ge fraction x of Si1-xGex could be decided by the flow rate ratio between Si2H6 and GeH4, independent of substrate temperature. Fast gas flow switching realized the formation of a Si(120 A)/Si1-xGex(69 A) strained layer superlattice at 587°C.

Structural Analysis for Water Absorption of SiOF Films Prepared by High-Density-Plasma Chemical Vapor Deposition.

Fluorine-doped silicon oxide (SiOF) films, prepared by high-density-plasma chemical vapor deposition, are investigated as to the effect of bond structure on water absorption. In this investigation, two kinds of SiOF films, containing 12% and 8% fluorine atoms, were compared with regard to the change in their bond structure before and after accelerated water absorption. Fourier transform infrared (FT-IR) spectra, thermal desorption mass spectroscopy (TDS) spectra and Raman spectra studies clarified the following. (1) The SiOF film which contains 12% fluorine atoms has more Si–F bonds than that containing 8% fluorine atoms, but it has fewer 3-fold rings. (2) The SiOF film which contains 8% fluorine atoms absorbs little water, and its Si–F bond does not change after water absorption. (3) The 3-fold ring of the SiOF film which contains 12% fluorine atoms has an unstable F–Si–O–Si bond structure. (4) The F–Si–O–Si bond structure of the 3-fold ring is easily changed to the F–Si–OH and Si–OH bond structures due to hydration, upon water absorption.

Structural and Electrical Properties for Fluorine-Doped Silicon Oxide Films Prepared by Biased Helicon-Plasma Chemical Vapor Deposition

Fluorine-doped silicon oxide (SiOF) films, prepared using biased helicon-plasma chemical vapor deposition, are investigated to clarify the relationship between their bond structures and electrical properties. For this purpose, C-V characteristics, I-V characteristics, FT-IR and Raman spectra were measured. In this investigation, two kinds of SiOF films prepared with SiF 4 flow ratios of 0.5 and 1.0 were compared. The SiOF film prepared with a SiF 4 flow ratio of 0.5 has a low leakage current and its relative dielectric constant is 3.6, whereas the film prepared with a SiF 4 flow ratio of 1.0 has a high leakage current and its relative dielectric constant is 3.2. FT-IR and Raman spectra studies clarify the following: (1) The SiOF film with a low leakage current contains Si-F bonds, as well as 3-fold or 4-fold rings. (2) The SiOF film with a high leakage current contains F-Si-F bonds or near-neighbor Si-F bonds in addition to Si-F bonds, but it does not contain 3-fold or 4-fold rings.

The influence of Cl2 on Si1 - xGex selective epitaxial growth and B-doping properties by UHV-CVD

Abstract We report the influence of a small quantity of Cl 2 , which enhanced the selectivity of silicon-selective epitaxial growth (Si-SEG) in UHV-CVD using Si 2 H 6 , on both the epitaxial growth rate and the B-doping properties for each Si and Si 1- x Ge x film. The small quantity of Cl 2 inhibited the Si, Ge and B incorporation, while the selectivity was enhanced. However, it was found, in the case of Si 1- x Ge x -SEG using Cl 2 , that the reduction ratio of both the growth rate and the B incorporation were smaller than those of Si-SEG with the selectivity still more enhanced.

SiGe/Si Heterostructures

2. EXPERIMENTAL Our UHV-CVD system included a stainless steel growth chamber, a water cool ed j acket, and separate nozzles for SiaHe and Clz. A 10001/s turbo-uolecular punp reduced background pressure on the growth chamber to 1.5x10-e Torr. 6-inch (100) Si wafers were nasked with 20004 patterns of either SiOa or SigNa. Wafers were precleaned with a chenical solution (NHa OH:He Oa:Ha O=l :6:20) to form a protective thin oxide layer before loading into the growth chamber. The thin oxide layer on the Si surface was evaporated by a thermal process, during which time the Sia He was supplied. The cl eaning temperature was 8000 C and SieHo was suppl ied at SSCCM wit h 10 sec wit hin t he overal I cl eaning process time of I min. Successful SEG condition was confirmed by RHEED in the growth chamber. The source Bas, pure SieHo, GeHa and Clz, first passed through a mass-flow cont roller and then into the growth chamber trough a nozzle without precracking. SiaHo and GeHl pressure in the growth chamber was 7xl0-a Torr, and Cla pressure was varied from 1xl0-6 to 1x10-5 Torr.

Influence of Gas Desorption from SiOF Film Prepared by High-Density-Plasma Chemical Vapor Deposition upon TiN/Ti Film

The influence of gas desorption from fluorine-doped silicon oxide (SiOF) film prepared by high-density-plasma chemical vapor deposition (CVD) upon TiN/Ti film is investigated. In this investigation, two types of SiOF films, containing 14% and 6% fluorine atoms, are compared with regard to gas desorption and diffusion of fluorine, hydrogen and oxygen atoms into TiN/Ti film on SiOF film, as-deposited on TiN/Ti/SiOF film and after 400°C annealing. In addition, W film was prepared on TiN/Ti/SiOF film in order to examine the practical effect of gas desorption upon adhesion between Ti film and SiOF film. Thermal desorption mass spectroscopy (TDS) and secondary-ion mass spectroscopy (SIMS) spectral studies clarified the following. (1) SiOF film containing 14% fluorine atoms has a high hydrogen-fluoride content due to moisture absorption after exposure to air, while that containing 6% fluorine atoms does not. (2) During deposition of TiN/Ti film at 200°C, many fluorine and hydrogen atoms diffuse from SiOF film containing 14% fluorine atoms and are trapped within the Ti film or the Ti/SiOF interface. (3) During 400°C annealing, more fluorine atoms diffuse from SiOF film containing 14% fluorine atoms and are also trapped within the Ti film. (4) Fluorine atoms trapped within the Ti film degrade the adhesion between Ti film and SiOF film.