In Situ Low Temperature Cleaning and Passivation of Silicon by Remote Hydrogen Plasma for Silicon-Based Epitaxy

1992 ◽  
Vol 259 ◽  
Author(s):  
S. Banerjee ◽  
A. Tasch ◽  
T. Hsu ◽  
R. Qian ◽  
D. Kinosky ◽  
...  
Keyword(s):  
Low Temperature ◽  
Hydrogen Plasma ◽  
High Vacuum ◽  
Substantial Reduction ◽  
Surface Cleaning ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Remote Plasma ◽  
Air Exposure

ABSTRACTRemote Plasma-enhanced Chemical Vapor Deposition (RPCVD), which involves nonthermal, remote plasma excitation of precursors, has been demonstrated to be a novel and attractive technique for low temperature (150-450C) Si and Sil-xGex epitaxy for applications in Si ULSI and novel Si heterostructure devices which require compact doping profiles and/or heterointerfaces. An in situ low temperature remote hydrogen plasma clean in the Ultra-High Vacuum (UHV) deposition chamber in order to achieve a chemically passive, hydrogenated Si surface with minimal O, C and N contamination, is a critical component of the process. The ex situ wet chemical cleaning consists of ultrasonic degreasing and a modified RCA clean, followed by a final dilute HF dip. The in situ clean is achieved by remote plasma excited H, where H introduced through the plasma column is r-f excited such that the plasma glow does not engulf the wafer. In situ AES analysis shows that the remote H plasma clean results in very substantial reduction of the C, O and N contamination on the Si surface. We believe that the H plasma produces atomic H which, in turn, produces a reducing environment and has a slight etching effect on Si and SiO2 by converting them to volatile byproducts. TEM analysis of the wafers subjected to this clean indicate that defect-free surfaces with dislocation loop densities below TEM detection limits of 105 /cm2 are achievable. Corroborating evidence of achieving an atomically clean, smooth Si surface by remote H plasma clean as obtained from in situ RHEED analysis will also be presented. After in situ H cleaning at low pressures (45 mTorr), typically for 30 min. at a substrate temperature of 310 C, we observe both stronger integral order streaks compared to the as-loaded sample and the appearance of less intense half-order lines indicative of a (2 × 1) reconstruction pattern, indicating a monohydride termination. A (3 × 1) reconstruction pattern is observed upon H plasma clean at lower temperatures (250 C), which can be attributed to an alternating monohydride and dihydride termination. Results of air exposure of hydrogenated Si surfaces by AES analysis indicate that the (3 × l) termination is chemically more inert towards readsorption of C and 0. Successful Si homoepitaxy and Si/Sil-xGex heteroepitaxy under a variety of surface cleaning conditions prove that by a combination of these cleaning techniques, and by exploiting the inertness of the H-passivated Si surface, very low defect density films with 0 and C levels as low as 1X1018 cm−3 and 5×1017 cm−3, respectively, can be achieved.

Remote Plasma-Enhanced Chemical Vapor Deposition of Epitaxial Silicon on Silicon (100) at 150°C

1989 ◽  
Vol 165 ◽  
Author(s):  
T. Hsu ◽  
B. Anthony ◽  
L. Breaux ◽  
S. Banerjee ◽  
A. Tasch
Keyword(s):  
Chemical Vapor Deposition ◽  
Low Temperature ◽  
Vapor Deposition ◽  
Hydrogen Plasma ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Ex Situ ◽  
Epitaxial Silicon ◽  
Remote Plasma ◽  
Silicon Epitaxy

AbstractLow temperature processing will be an essential requirement for the device sizes, structures, and materials being considered for future integrated circuit applications. In particular, low temperature silicon epitaxy will be required for new devices and technologies utilizing three-dimensional epitaxial structures and silicon-based heterostructures. A novel technique, Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD), has achieved epitaxial silicon films at a temperature as low as 150°C which is believed to be the lowest temperature to date for silicon epitaxy. The process relies on a stringent ex-situ preparation procedure, a controlled wafer loading sequence, and an in-situ remote hydrogen plasma clean of the sample surface, all of which provide a surface free of carbon, oxygen, and other contaminants. The system is constructed using ultra-high vacuum technology (10-10 Torr) to achieve and maintain contaminantion-free surfaces and films. Plasma excitation of argon is used in lieu of thermal energy to provide energetic species that dissociate silane and affect surface chemical processes. Excellent crystallinity is observed from the thin films grown at 150°C using the analytical techniques of Transmission Electron Microscopy (TEM) and Nomarski interference contrast microscopy after defect etching.

Low Temperature In-Situ Processing for Si-MBE

1991 ◽  
Vol 220 ◽  
Author(s):  
Juergen Ramm ◽  
Eugen Beck ◽  
Albert Zueger
Keyword(s):  
Low Temperature ◽  
Hydrogen Plasma ◽  
Plasma Heating ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Native Oxide ◽  
Wafer Surface ◽  
Process Step ◽  
In Situ Processing

ABSTRACTA basic process sequence for low temperature in-situ processing of metal-insulator-semiconductor (MIS) structures in an ultra-high vacuum (UHV) multichamber system is presented. It includes conditioning of the process chamber by plasma heating, in-situ cleaning of silicon wafers, and conventional silicon molecular beam epitaxy (Si-MBE). The in-situ cleaning is achieved by an argon/hydrogen plasma treatment of the wafer surface at temperatures well below 400° C. The native oxide as well as carbon compounds are removed from the silicon surface. Etch rates for SiO2 are determined for various plasma parameters. Without additional cleaning procedures, silicon films are deposited in another process step using a quadrupole mass spectrometer controlled electron beam evaporator. Epitaxial films are obtained for substrate temperatures as low as 500°C on (100) and 600°C on (111) silicon for deposition rates of 0.05 nm/s.

Self-assembled Ge quantum dots on SiC substrates grown by UHV-CVD

2002 ◽  
Vol 742 ◽  
Author(s):  
C. Calmes ◽  
V. Le ◽  
D. Bouchier ◽  
S. E. Saddow ◽  
V. Yam ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Vacuum ◽  
Chemical Vapor ◽  
High Energy ◽  
Surface Cleaning ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
First Results ◽  
Ge Quantum Dots

AbstractWe report our first results using a ultra high vacuum chemical vapor deposition (UHV-CVD) system to form Ge quantum dots on off-axis SiC substrates. Pure SiH4 and hydrogen-diluted GeH4 were used as gas precursors. The SiC substrates were chemically cleaned using the modified RCA process and the SiO2 layer was removed in-situ under a low SiH4 flow rate at a temperature between 1030°C and 1080°C. The Ge quantum dots were grown at a temperature of 750°C. In-situ reflection high-energy electron diffraction (RHEED) was used to monitor the surface cleaning and the Ge quantum dot growth. Ex-situ scanning electron microscope and atomic force microscopy were used to confirm the presence of Ge dots. The observed dots are smaller (350 Å width and 100 Å height) than similar Ge dots grown on Si.

An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

1988 ◽  
Vol 46 ◽  
pp. 884-885
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove ◽  
R. T. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Metal Base ◽  
In Situ Experiments ◽  
Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

Design for a New Low Energy and Photo-Emission Electron Microscope for Surface Science Studies

1990 ◽  
Vol 48 (1) ◽  
pp. 570-570
Author(s):  
Ruud M. Tromp
Keyword(s):  
Science Studies ◽  
High Vacuum ◽  
Dark Field ◽  
Surface Cleaning ◽  
Geometric Constraints ◽  
Ultra High Vacuum ◽  
Field Mode ◽  
Projection System ◽  
Cathode Lens

A new LEEM/PEEM apparatus has been designed for the study of surfaces and surface processes in Ultra High Vacuum (UHV). The design follows the general layout of the microscope operated succesfully by Prof. Bauer and coworkers, but differs significantly in a number of details. We designed a magnetic/electrostatic cathode lens with a resolution limit close to that of the uniform electrostatic accelerating field between sample and lens. The projection system consists of transfer lens, intermediate lens and projector lens. Total magnification is between 1,000x and 10,000x, with a field of view between 4 and 40 micrometer. The illuminating system features a continuously adjustable range of illumination, such that the loss of image intensity at high magnification can be balanced by a reduction of the illumiated area, without significant loss of electron beam intensity. Both bright field and dark field imaging are possible. The location of the diffraction aperture in the projection column allows for more flexible operation of the microscope in dark field mode. Care has been taken in the design of the microscope to integrate the stringent vacuum requirements with the geometric constraints of the electron optical components. A sample stage, featuring two orthogonal translations and two (eucentric) tilts, sample heating, as well as in situ sample exchange capability has been constructed. All motions are driven by remote control, UHV compatible piezoelectric actuators, eliminating the need for mechanical feedthroughs, and ensuring a short mechanical path between sample and cathode lens. In situ deposition, using e-beam evaporators and/or Knudsen cells will be possible. A sample preparation chamber contains standard surface cleaning and analytical equipment. We will report on the progress in the construction of this machine.

Surface Cleaning Prior to Formation of Si/SiO2 Interfaces by Remote Plasma-Enhanced Chemical Vapor Deposition (RPECVD)

1992 ◽  
Vol 259 ◽  
Author(s):  
H. H. Lamb ◽  
S. Kalem ◽  
S. Bedge ◽  
T. Yasuda ◽  
Y. Ma ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Oxide Layer ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Surface Cleaning ◽  
Ex Situ ◽  
Dangling Bond ◽  
Remote Plasma ◽  
Carbon Contamination

ABSTRACTEx situ UV/O2 cleaning prior to SiO2 deposition by RPECVD results in an SiO2/Si interface with mid-gap Dit values 2-5 times higher than interfaces formed by in situ exposure of HF-etched wafers to plasma-generated atomic O. In situ exposures to plasma-generated atomic H and atomic O are each effective at removing carbon contamination acquired by the UV/O2 cleaned wafers during transfer and introduction to the RPECVD chamber. However, in situ exposure of the photochemical oxide layer to atomic O results in higher mid-gap Dit values, and in situ exposure to atomic H results in creation of dangling bond defects (Pb centers).

Properties of Metal / Polyphenylquinoxaline Interfaces

1994 ◽  
Vol 337 ◽  
Author(s):  
L. Bellard ◽  
J.M. Themlin ◽  
F. Palmino ◽  
A. Cros
Keyword(s):  
Metal Layer ◽  
High Vacuum ◽  
Polymer Surface ◽  
Pure Metal ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Layer By Layer ◽  
Force Microscopy ◽  
Atomic Force

ABSTRACTWe have investigated the microscopic properties of copper and chromium layers deposited on polyphenylquinoxaline (PPQ). PPQ is a thermostable polymer used for multichip module applications. The metal is deposited under ultra-high vacuum conditions and analysed in-situ by X-ray photoemission (XPS) and atomic force microscopy (ex situ). Copper does not react significantly with the PPQ and tends to diffuse into the polymer matrix upon annealing. On the contrary, chromium strongly reacts with the polymer surface at room temperature. With increasing metal coverage, chromium grows in a layer-by-layer mode and the reacted interface is progressively burried under the pure metal layer.

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