Surface Morphology of Si1−x−y GexCy Epitaxial Films Deposited by Low Temperature UHV-CVD

AbstractSi1−x−y GexCy epitaxial films offer wider control of strain and bandgap. In such films the morphology is an important indication of the crystalline quality of the material. We report on the morphology of Si1−x−y GexCy epitaxial thin films deposited by Ultra High Vacuum Chemical Vapor Deposition at a temperature of 550° C and deposition pressures ranging from 1 to 10 mTorr. The precursors used were Si2H6, GeH4 and CH3SiH3. Germanium mole fractions ranging from 0% to 40% were studied with carbon concentrations varying from 2×1019 to 2×1021 atoms/cm3. AFM analysis of the surface indicates that the roughness is a function of both the carbon concentration and the film thickness. For high germanium concentrations with thickness beyond the critical thickness (of Si1−xGex), carbon is found to decrease the surface roughness of the film. Thus the surface morphology confirms the strain compensation provided by carbon which is also observed using XRD. For films below the critical thickness, as the carbon concentration is increased, three dimensional islanding is observed by RHEED and AFM, degrading the epitaxial quality of the material.

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Progression of the Surface Roughness of N+ Silicon Epitaxial Films as Analyzed by AFM

MRS Proceedings ◽

10.1557/proc-399-123 ◽

1995 ◽

Vol 399 ◽

Author(s):

S. John ◽

E. J. Quinones ◽

B. Ferguson ◽

K. Pacheco ◽

C. B. Mullins ◽

...

Keyword(s):

Surface Roughness ◽

High Vacuum ◽

Film Surface ◽

Chemical Vapor ◽

Epitaxial Films ◽

Ultra High Vacuum ◽

Phosphorus Segregation ◽

Surface Mobility ◽

Partial Pressures ◽

Effects Of Ph

ABSTRACTWe report on the morphology of heavily phosphorous doped silicon films grown by ultra high vacuum chemical vapor deposition at temperatures of ∼550° C. The effects of PH3 on epitaxial films have been examined for silicon deposited using SiH4 and Si2H6. It is found that films grown using silane experience an increase in surface roughness with increasing phosphine partial pressure. AFM and RHEED studies indicate 3-D growth. As epitaxy progresses, it is believed that phosphorus segregation on the growing film surface greatly diminishes the adsorption and surface mobility of the silicon bearing species. Initial Si deposition results in a pitted surface, but as growth advances and the phosphorus coverage increases, growth within the pits decreases the surface roughness. In contrast to SiH4, it is found that Si2H6 provides excellent quality, smooth films even at high PH3 partial pressures.

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Nucleation and Growth of Polycrystalline Silicon Films in an Ultra high Vacuum Rapid Thermal Chemical Vapor Deposition Reactor Using Disilane and Hydrogen

MRS Proceedings ◽

10.1557/proc-343-673 ◽

1994 ◽

Vol 343 ◽

Author(s):

Katherine E. Violette ◽

Mehmet C. Öztürk ◽

Gari Harris ◽

Mahesh K. Sanganeria ◽

Archie Lee ◽

...

Keyword(s):

Electron Microscopy ◽

Surface Roughness ◽

Chemical Vapor Deposition ◽

Surface Morphology ◽

Vapor Deposition ◽

High Vacuum ◽

Chemical Vapor ◽

Ultra High Vacuum ◽

Chemical Vapor Deposition Reactor ◽

Thermal Chemical Vapor Deposition

A study of Si nucleation and deposition on SiO2 was performed using disilane and hydrogen in an ultra high vacuum rapid thermal chemical vapor deposition reactor in pressure and temperature ranges of 0.1 – 1.5 Torr and 625 – 750°C. The film analysis was carried out using scanning electron microscopy, transmission electron microscopy and atomic force microscopy. At lower pressures, an incubation time exists which leads to a retardation in film nucleation. At 750°C, the incubation time is 10s at 0.1 Torr and decreases to less than Is at 1.5 Torr. The nuclei grow and form three dimensional islands on S1O2, and as they coalesce, result in a rough surface morphology. At higher pressures, the inherent selectivity is lost resulting in a higher nucleation density and smoother surface morphology. For ˜ 2000 Å thick films, the root-mean-square surface roughness at 750ÅC ranges from 110Å at 0.1 Torr to 40Å at 1.5 Torr. Temperature also strongly influences the film structure through surface mobility and grain growth. At 1 Torr, the roughness ranges from 3Å at 625°C to 60Å at 750°C. The grain structure at 625°C/1Torr appears to be amorphous, whereas at 750°C the structure is columnar. The growth rate at 625°C/1.5 Torr is 1200 Å/min provides a surface roughness on the order of atomic dimensions which is comparable to or better than amorphous silicon deposited in LPCVD furnaces.

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Studies of Ge/Si(100) and Observation of Atomic Steps on Si(100) using Biassed Secondary Electron Imaging in a UHV STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010018029x ◽

1990 ◽

Vol 48 (1) ◽

pp. 308-309

Author(s):

Mohan Krishnamurthy ◽

Jeff S. Drucker ◽

John A. Venablest

Keyword(s):

Secondary Electron ◽

Critical Thickness ◽

Surface Defects ◽

Film Growth ◽

Growth Parameters ◽

High Vacuum ◽

Ultra High Vacuum ◽

Surface Steps ◽

Epitaxial Crystal Growth ◽

Electron Imaging

Secondary Electron Imaging (SEI) has become a useful mode of studying surfaces in SEM[1] and STEM[2,3] instruments. Samples have been biassed (b-SEI) to provide increased sensitivity to topographic and thin film deposits in ultra high vacuum (UHV)-SEM[1,4]; but this has not generally been done in previous STEM studies. The recently developed UHV-STEM ( codenamed MIDAS) at ASU has efficient collection of secondary electrons using a 'parallelizer' and full sample preparation system[5]. Here we report in-situ deposition and annealing studies on the Ge/Si(100) epitaxial system, and the observation of surface steps on vicinal Si(100) using b-SEI under UHV conditions in MIDAS.Epitaxial crystal growth has previously been studied using SEM and SAM based experiments [4]. The influence of surface defects such as steps on epitaxial growth requires study with high spatial resolution, which we report for the Ge/Si(100) system. Ge grows on Si(100) in the Stranski-Krastonov growth mode wherein it forms pseudomorphic layers for the first 3-4 ML (critical thickness) and beyond which it clusters into islands[6]. In the present experiment, Ge was deposited onto clean Si(100) substrates misoriented 1° and 5° toward <110>. This was done using a mini MBE Knudsen cell at base pressure ~ 5×10-11 mbar and at typical rates of 0.1ML/min (1ML =0.14nm). Depositions just above the critical thickness were done for substrates kept at room temperature, 375°C and 525°C. The R T deposits were annealed at 375°C and 525°C for various times. Detailed studies were done of the initial stages of clustering into very fine (∼1nm) Ge islands and their subsequent coarsening and facetting with longer anneals. From the particle size distributions as a function of time and temperature, useful film growth parameters have been obtained. Fig. 1 shows a b-SE image of Ge island size distribution for a R T deposit and anneal at 525°C. Fig.2(a) shows the distribution for a deposition at 375°C and Fig.2(b) shows at a higher magnification a large facetted island of Ge. Fig.3 shows a distribution of very fine islands from a 525°C deposition. A strong contrast is obtained from these islands which are at most a few ML thick and mottled structure can be seen in the background between the islands, especially in Fig.2(a) and Fig.3.

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Challenge to 200 mm 3C-SiC Wafers Using SOI

Materials Science Forum ◽

10.4028/www.scientific.net/msf.483-485.205 ◽

2005 ◽

Vol 483-485 ◽

pp. 205-208 ◽

Cited By ~ 10

Author(s):

Motoi Nakao ◽

Hirofumi Iikawa ◽

Katsutoshi Izumi ◽

Takashi Yokoyama ◽

Sumio Kobayashi

Keyword(s):

Cross Section ◽

Vapor Deposition ◽

Seed Layer ◽

High Vacuum ◽

Chemical Vapor ◽

Ultra High Vacuum ◽

Average Thickness ◽

Entire Region ◽

Transmission Electron ◽

Good Crystallinity

200 mm wafer with 3C-SiC/SiO2/Si structure has been fabricated using 200 mm siliconon- insulator (SOI) wafer. A top Si layer of 200 mm SOI wafer was thinned down to approximately 5 nm by sacrificial oxidization, and the ultrathin top Si layer was metamorphosed into a 3C-SiC seed layer using a carbonization process. Afterward, an epitaxial SiC layer was grown on the SiC seed layer with ultra-high vacuum chemical vapor deposition. A cross-section transmission electron microscope indicated that a 3C-SiC seed layer was formed directly on the buried oxide layer of 200 mm wafer. The epitaxial SiC layer with an average thickness of approximately 100 nm on the seed was recognized over the entire region of the wafer, although thickness uniformity of the epitaxial SiC layer was not as good as that of SiC seed layer. A transmission electron diffraction image of the epitaxial SiC layer showed a monocrystalline 3C-SiC(100) layer with good crystallinity. These results indicate that our method enables to realize 200 mm SiC wafers.

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Microstructure of FCC/BCC Metal Multilayers

MRS Proceedings ◽

10.1557/proc-160-183 ◽

1989 ◽

Vol 160 ◽

Cited By ~ 3

Author(s):

Nigel M. Jennett ◽

D.J. Dingley ◽

Y. Ando

Keyword(s):

Substrate Temperature ◽

Magnetic Moment ◽

High Vacuum ◽

Ultra High Vacuum ◽

Bcc Lattice ◽

A Value ◽

Fcc Lattice ◽

Temperature Window ◽

Backing Layer

AbstractBilayers of Cu/Fe and Cu/V and multilayers of Ni/Fe have been grown under high vacuum and ultra high vacuum conditions respectively with [111] epitaxy. Multilayer layer thicknesses ranged from 3 monolayers to 15 monolayers per layer. Improved epitaxy of the UHV growth was, we believe, due to the better vacuum although perfect material could only be obtained for growth within a narrow and shifting substrate temperature ‘window’. Possible shortfall in the quality of the Cu backing layer epitaxy was averted by a 2hr anneal at 425°C.In the Fe/Ni multilayers the Fe was observed to adopt the FCC lattice rather than the equilibrium BCC lattice for layer thicknesses less than 10 monolayers. This change of structure coincided with a reduction in sample magnetic moment per volume attributed to a collapse of the Fe moment to a value 7 times less than bulk.

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Ultra-high vacuum chemical vapor deposition and in situ characterization of titanium oxide thin films

Journal of Materials Research ◽

10.1557/jmr.1991.1913 ◽

1991 ◽

Vol 6 (9) ◽

pp. 1913-1918 ◽

Cited By ~ 31

Author(s):

Jiong-Ping Lu ◽

Rishi Raj

Keyword(s):

Thin Films ◽

Chemical Vapor Deposition ◽

Titanium Oxide ◽

Vapor Deposition ◽

Photoelectron Spectroscopy ◽

High Vacuum ◽

Chemical Vapor ◽

Titanium Isopropoxide ◽

Ultra High Vacuum

Chemical vapor deposition (CVD) of titanium oxide films has been performed for the first time under ultra-high vacuum (UHV) conditions. The films were deposited through the pyrolysis reaction of titanium isopropoxide, Ti(OPri)4, and in situ characterized by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). A small amount of C incorporation was observed during the initial stages of deposition, through the interaction of precursor molecules with the bare Si substrate. Subsequent deposition produces pure and stoichiometric TiO2 films. Si–O bond formation was detected in the film-substrate interface. Deposition rate was found to increase with the substrate temperature. Ultra-high vacuum chemical vapor deposition (UHV-CVD) is especially useful to study the initial stages of the CVD processes, to prepare ultra-thin films, and to investigate the composition of deposited films without the interference from ambient impurities.

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