Growth Of Silicon Films Research Articles

Temperature Dependence of Structure, Transport and Growth of Microcrystalline Silicon: Does Grain Size Correlate with Transport?

ABSTRACTThe temperature dependence of the growth, structure and transport of plasma-deposited microcrystalline and polycrystalline silicon films have been investigated over the temperature range of 50°C to 350°C. While low substrate temperature yields small grain sizes as expected, high temperature also tends to suppress the grain growth, contrary to the normal behavior observed in thermal CVD (chemical vapor deposition) where crystallinity grows with temperature. In fact, the highest temperature of 350°C corresponds to the lowest degree of crystallinity. Furthermore, it is found that, unlike the polycrystalline Si prepared by thermal CVD, the transport properties of the Si films do not necessarily correlate with the grain size or structural defects. While the largest average grain size of 800–1000 Å was obtained at 200°C, the highest Hall mobility and conductivity were obtained near 250°C, which corresponds to a material with smaller grains and an abundance of voids.

Extreme Supersaturation of Oxygen in Low Temperature Epitaxial Silicon and Silicon-Germanium Alloys

AbstractWe report the low temperature growth (625 - 700 °C) of epitaxial silicon and silicon-germanium alloy films by vapor phase techniques with oxygen concentrations approximately 1020 cm-3. These concentrations are well above the accepted solid solubility for oxygen in silicon. The films, however, have excellent structural and electrical properties with virtually no stacking faults or “haze”. Infrared transmission analysis suggests the possible presence of OH, but the exact nature of the oxygen is not known.

Epitaxial growth of silicon at low temperature by ultrahigh vacuum electron cyclotron resonance plasma chemical vapor deposition

Epitaxial growth of a silicon thin film has been accomplished at a temperature lower than 650 °C by electron cyclotron resonance plasma chemical vapor deposition using an ultrahigh vacuum chamber. Ar plasma from the same electron cyclotron plasma ion source is also used for surface cleaning of the substrate. The relationship between the cleaning condition of a substrate and the quality of an epitaxially grown silicon film is examined in detail. The energy of Ar plasma in the cleaning process should be kept lower than 100 eV in order to obtain films of good crystal quality. Otherwise, damage by Ar ion bombardment cannot be restored by annealing at lower than 700 °C. The epitaxial growth also should be carried out without the accelerating bias voltage to avoid residual compressive stress in the film. An epitaxial film with perfect crystal structure (indicating only a Kikuchi pattern of reflection of high-energy electron diffraction) is obtained at the substrate temperature of 710 °C.

Carrier lifetime in MBE grown Si:Sb and Si:In layers measured by the transient grating method

The carrier recombination dynamics in MBE grown silicon films, doped with Sb or In, are investigated by the transient grating method under strong pumping conditions with 35 ps laser pulses. The temporal decay of the induced gratings gives carrier lifetimes of the order 10-10-10-8 s for doping concentrations in the range 1017-1020 cm-3. A complementary theoretical evaluation of the lifetimes shows the importance of the different kinds of band-to-band Auger recombination increases with increasing doping concentration for Sb-doped Si. For In-doped (1017-1018 cm-3) Si and SRH recombination via in centres dominates. The measured lifetimes agree well with the theoretical values if it is assumed that, at the doping levels, internal stress increases the light absorption coefficient for lambda =0.53 mu m by a factor of up to 2 greater than the pure silicon value.

The growth of polycrystalline silicon films by low pressure chemical vapour deposition at relatively low temperatures

Low pressure chemical deposition at relatively low temperatures carried out by using silane pressures below 100 mTorr leads to structurally well-defined films. Below 10 mTorr the films are characterized as resulting from local epitaxial processes. Deposition on amorphous substrates leads to columnar growth with a (100) preferred orientation with the grains misaligned, thus forming grain boundaries, while with natural seeding the films grow epitaxially. The effective mobility and the threshold voltage of thin film transistors fabricated from these films indicate that they are advantageous over amorphous films.

A spectroscopic ellipsometry study of the growth and microstructure of glow-discharge amorphous and microcrystalline silicon films

Spectroscopic ellipsometry (SE) has been used to study the surface, microstructure, and optical properties of glow-discharge deposited amorphous and microcrystalline silicon films. The SE data has been analyzed using multilayer models, effective medium approximation, and linear regression analysis. The studies have shown that with increasing rf power and silane dilution, a gradual transition from good (dense) a-Si:H to a spongy material with a large density deficit, and then to a microcrystalline material is obtained. A quantitative analysis of the microstructure of a-Si:H films with growth parameters has been carried out. Combined with infrared and x-ray diffraction measurements, the results have been explained in terms of a nucleation and growth model.

ChemInform Abstract: Selective Doped Polysilicon Growth. Effect of Carbon on the Selective Doped Silicon Film Growth.

AbstractIt is demonstrated that the selective growth of doped polysilicon is possible when CH4 is introduced in the growth of epitaxial silicon.

ChemInform Abstract: The Effect of Low Pressure on the Structure of LPCVD Polycrystalline Silicon Films

Abstracthas been investigated by XRD, SEM and TEM.

Study of the chemical reactions' influence on semiconductor films structure formation by the Monte‐Carlo method

AbstractThe investigation by the Monte‐Carlo method of the growth of the silicon epitaxial film at a chloride CVD system has allowed to find out the composition of adsorption layer, the micromechanism of the reactions of Si atoms building‐in into the growing crystalline layer and the growth conditions influence on the growth rate and film surface roughness. The change of adsorptive layer composition in the system SiCl4—HCl—H2 (fraction of adaatoms, silicon atoms built‐in a crystal and molecules SiCl2) depending on temperature has been determined. The change of silicon film growth rate depending on temperature and concentration change of SiH2Cl2 has been established and the contribution of growth mechanism (with participation of adatom, silicon atoms and molecules SiCl2) into the total rate of film growth has been shown.

Selective Doped Polysilicon Growth: Effect of Carbon on the Selective Doped Silicon Film Growth

We have announced selective polysilicon growth technology based on selective epitaxial growth technology (1, 2). In this paper, we report the influence of on the crystallinity of silicon, the doping control with , and the selective growth of silicon. It has become possible to control the transition from epitaxial silicon to polysilicon and . By achieving a definite doping control, the resistivity can be lowered to . A combination of these technologies made it possible to grow selectively doped polysilicon with a flat surface.

The Effect of Low Pressure on the Structure of LPCVD Polycrystalline Silicon Films

Structure and crystal growth of undoped silicon films prepared by low pressure chemical vapor deposition (LPCVD) have been investigated by x‐ray diffraction, and transmission and scanning electron microscopy. We show that for films deposited in silane partial‐pressure range and temperature range , the pressure is a determining factor for crystallite size, texture, and surface roughness. At a fixed temperature, the crystallite size decreases when the pressure increases. At very low pressures the films have a random orientation. At intermediate pressures the films are characterized by a <100> dominant texture and at high pressure, by a strong <110> preferred orientation. The surface roughness is closely related to the preferred orientation.

Characterisation of ar ion laser induced cvd silicon films: deposition, crystallographic texture and phosphorous doping

Pyrolytic dissociation of silane on substrates heated by a cw Ar ion laser beam has been used to deposit polycrystalline silicon thin films. The effects of parameters like laser beam irradiance (power density), dwell time, silane pressure on the silicon deposition are studied. To understand the film growth kinetics, an approximate relationship amongst the film thickness and some of the above parameters is deduced from general chemical thermodynamic considerations. The crystallographic texture of the grown silicon film is studied as a function of laser power. It is found that the texture (preferred orientation) changes from 〈110〉 at low power to 〈111〉 at higher power. Mixtures of silane and phosphine at different partial pressures are used to obtain phosphorous doped polysilicon films. These films show a thermally activated conductivity σ = σ0 exp ( -E a /kT) with the activation energyE a depending on the phosphine partial pressure.

Current Status of Reduced Temperature Silicon Epitaxy by Chemical Vapor Deposition

Current temperatures for the growth of epitaxial silicon films for device applications are in the range of 1050°–1200°C using commercially available CVD reactors. However, the demand for submicron epitaxial layers with abrupt dopant profiles for high performance integrated circuit applications as well as the evolution of mixed technologies and three‐dimensional device structures have generated a strong need for reduced temperature epitaxy in the temperature region at or below 800°C. Several approaches to achieve this are currently under investigation, and these include thermal prebake, plasma‐enhanced epitaxy, chemically enhanced epitaxy, and ultrahigh vacuum processing. In this paper, we review these techniques and consider the limits to low temperature CVD silicon epitaxy.

I n s i t u investigation of the growth of rf glow-discharge deposited amorphous germanium and silicon films

An in situ investigation of the growth of rf glow-discharge amorphous germanium (a-Ge:H) and silicon (a-Si:H) films using fast real-time spectroscopic phase-modulated elipsometry is presented. The influence of the conditions of preparation is studied in both cases. The same behavior is obtained in a-Ge:H and a-Si:H films deposited in similar conditions. In particular, the initial stage of the growth can be described by a nucleation process in both cases, whatever the conditions of preparation. The incomplete coalescence of the nuclei leads to the formation of a surface roughness on a ∼40-Å scale which is observed during film growth. In comparing real-time ellipsometry measurements performed at different wavelengths, a correlation between the internuclei distance and the thickness of the surface roughness is observed. An enhancement of the surface mobility of the reactive species due to an increase of substrate temperature and/or ion-bombardment energy results in an increase in the density of the nucleation centers. The influence of ion bombardment and gas pressure is discussed by comparing the growth of a-Si:H film deposited in a rf discharge to the results of previous studies using a low-pressure multipole plasma.

Growth of single-crystalline silicon films on insulating substrates

The growth of device-worthy silicon crystal films on insulating substrates would offer a new type of semiconductor technology. The crystallization of continuous silicon layers on thermally oxidized silicon wafers was performed by a zone melting process. A number of material characterization techniques have been used to analyse the SOI-structures.

Dielectric Isolation by Growth of Thick Silicon Films on Oxidized Si Wafers

Dielectric Isolation by Growth of Thick Silicon Films on Oxidized Si Wafers

Substrate Annealing and the MBE Growth of Silicon on Sapphire.

AbstractThe effect of predeposition substrate annealing has been investigated for MBE grown silicon films on sapphire substrates (SOS). Films of varying thickness were grown on substrates which had been annealed at either 1450°C or 900°C. The surface morphology and crystal1inity for each film were examined. The silicon thicknesses ranged from 65-400 angstroms and the anneal time for both temperatures was 30 minutes.The results indicate that the predeposition anneal of the sapphire substrate has a dramatic effect on the growth characteristics of the silicon film. The high temperature anneal promotes island growth of the silicon film which is easily resolved in the SEM. These islands are roughly 800 angstroms wide for a 65A thick film and grow to approximately 2200 angstroms for a 250A film. On the other hsuxi, the lower temperature anneal did not result in island formation, when examined by SEM, at any of the film thicknesses. In addition, X ray analysis reveals that the silicon layers for the high temperature anneal are epitaxial with a (100) orientation.

Deposition properties of silicon films formed from silane in a vertical-flow reactor

The growth of silicon films by low pressure chemical vapor deposition in an unique vertical-flow reactor and in a conventional tube reactor is studied, with emphasis on the vertical-flow reactor. For a hydrogen-carried silane process in the vertical-flow reactor, the growth rate depends on both the partial pressure and the flow rate of silane. A growth rate expression incorporating both of these parameters is derived which accounts for a nearly linear dependence on either parameter for small values and saturation at large values. No dependence on hydrogen partial pressure is observed. An Arrhenius-type dependence of growth rate on temperature is observed for both type of reactors, with an activation energy of 1.5 eV. Thickness uniformity of the films deposited in the vertical-flow reactor is compared to that found in the conventional reactor. For high temperatures (above 650 °C) depletion effects degrade the thickness uniformity of the deposited films. Such effects are more pronounced in the conventional reactor than in the vertical-flow reactor. These effects can be attributed to the shorter gas flow path in the vertical-flow reactor. The vertical-flow reactor can be operated without a temperature gradient along the deposition chamber so that uniform film properties can be obtained over the entire load.

Epitaxial growth of silicon and germanium films on CaF 2/Si

The epitaxial growth conditions and the microstructure of (111) and (100) single-crystal films of silicon and germanium were studied using in situ reflection high energy electron diffraction and using transmission electron diffraction and transmission electron microscopy. The films were grown epitaxially by evaporation in an ultrahigh vacuum system onto a CaF 2/epi-Si/Si substrate, where epi-Si is epitaxial silicon, at 450–710°C for Si(111), 450–650°C for Si(100) and 400–550°C for Ge(111) and Ge(100). The epi-Si, 2000 Å thick, was deposited at 580–750°C onto an Si(111) or Si(100) wafer heat treated at 720–750°C in order to overcome the problem of the initial amorphous silicon oxide. The (111)-oriented films contained double-positioning domains, i.e.(111) twins, up to 2 μm in size. Each of the domains contained triangular islands of the complementary domain up to 1000 Å in size. Planar and line defects were concentrated at the (111) twin boundaries. On lowering the growth temperature for Si(111) from 710 to 680°C the defect concentration increased by more than an order of magnitude. Hexagonal-phase particles of up to 2000 Å in size with a density of 10 6 cm -2 were also present in the (111)-oriented films.

Molecular beam epitaxial growth of germanium and silicon films: Surface structure, film defects and properties

Germanium and silicon films were grown on substrates of silicon (germanium and silicon films) and gallium arsenide (germanium films). Reflection high energy electron diffraction was used to investigate superstructure reconstructions on the growth surface as a function of the growth temperature and the film thickness. The greatest number of superstructures was observed during epitaxy of germanium films on Si(111): Si(7 × 7)Ge, Si,Ge(5 × 5), Ge(8 × 2), Ge(7 × 7)Si and Ge(1 × 1). The defects were studied in Ge/Si and Ge/GaAs heterosystems. The surface diffusion was found to have a marked effect on the film surface morphology and as a result of this on the type of misfit dislocations at the interface and on the density of threading dislocations. Electrophysical properties of the films are also discussed.