SiH4 Flow Rate Research Articles

Si Deposition into Fine Contact Holes by Ultrahigh-Vacuum Chemical Vapor Deposition

An ultrahigh-vacuum chemical vapor deposition technique with disilane (Si2H6) molecular flux is applied to fine contact hole filling. Structural observations reveal that a completely buried Si contact has a stacked structure, in which the lower portion consists of pyramidal epitaxial Si, whose height depends not only on the growth temperature and the Si2H6 flow rate but also on the hole diameter, and polycrystalline Si is deposited on the epitaxial Si. The mechanism of selective epitaxy is interpreted in terms of incubation time and facet growth rate depending on growth temperature and Si2H6 flow rate.

Preparation of Nanocrystalline Silicon Quantum Dots by Pulsed Plasma Processes with High Deposition Rates

ABSTRACTA new method for the fabrication of nanocrystalline silicon (nc-Si) in SiH4plasma with very-highfrequency (VHF; 144MHz) excitation is proposed to increase the deposition rate, to control the size, and to minimize size dispersion of nc-Si. Nanocrystalline silicon is formed in the gas phase of the SiH4plasma cell by coalescence of radicals. Supplying Ar enhances the nucleation of nc-Si because of high efficiency of SiH4excitation into SiH2radicals resulting in the nucleation. The deposition rate is thus increased by a factor of 100 to 1012/cm2.h. At the low flow rate of SiH4, smaller nc-Si with small dispersion is obtained. Moreover, when pulsed-SiH4is supplied into Ar plasma, the growth of nuclei is limited by the time when SiH4flows. The size of nc-Si and its dispersion are adjusted by the duration of SiH4gas pulse.

Growth of microcrystalline silicon film by electron beam excited plasma chemical vapor deposition without hydrogen dilution

Unique characteristics have been obtained for silicon films grown by electron beam excited plasma chemical vapor deposition (EBEP-CVD) in comparison with films grown by conventional plasma CVD. The EBEP-CVD growth of silicon films on single-crystal Si and SiO2 substrates was investigated using SiH4 without hydrogen dilution as a function of SiH4 flow rate, discharge current, chamber pressure, substrate temperature, and electron acceleration voltage. Typical growth rate was ∼0.1 nm/s. Characterization by Raman scattering spectroscopy showed that all the films were microcrystalline with a grain size of approximately 10 nm; the peak intensity ratio of the crystalline portion was greater than 0.6. The hydrogen concentration in the silicon layer under “standard” growth condition was determined by elastic recoil detection analysis to be as much as 19 at. %. This high level of hydrogen incorporation, considered to be facilitated by EBEP of SiH4 gas, seems to play a critical role in the growth process.

Compositional characterization of a-SiC:H films by infra-red spectroscopy

Amorphous Si1−xCx:H films (0 < x < 0.6) deposited on c-Si substrates by r.f. plasma-enhanced chemical vapour deposition were studied as functions of the material composition and hydrogen content by infra-red reflectivity and transmission spectroscopy. The films were prepared by glow discharge decomposition of SiH4 and CH4 gases at 50 W r.f. power, 20 Pa of pressure and 300°C of substrate temperature. From analysis of the CH and SiH stretching absorption bands it is shown that the content of hydrogen atoms bonded to Si is not appreciably affected by the precursor CH4/SiH4 flow ratio. On the contrary, the fraction of hydrogen incorporated in CH bonds increases with the relative CH4 to SiH4 flow rate. We analysed the evolution of the refractive index with the growth conditions. In particular, we found that the contribution of the hydrogen content to the minima of the interference fringes in the IR reflectivity spectra is negligible, and all changes in the absolute value are directly attributed to changes in the material composition. This gives a measure of the composition of the film, when comparing the refractive index and the carbon content obtained by X-ray photoelectron spectroscopy.

Deposition of Highly Conductive n+ Silicon Film for a-Si:H Thin Film Transistor

ABSTRACTPlasma enhanced chemical vapor deposition of phosphorus-doped n+ silicon film over a wide range of process conditions has been studied. The deposited films were characterized with SIMS, Raman, and XRD. An unusually abrupt change of resistivity over a small SiH4(1% PH3) flow rate has been observed and was correlated to the variation of the film's morphology from amorphous to micrycrystalline. The grains are less than 50 Å in size and has strong &lt;111&gt; orientation. Amorphous silicon thin film transistors with microcrystalline n+ source and drain contacts have consistently good device characteristics. However, the contact resistance is comparable to the channel resistance when the channel length approaches 1 micrometer.

Effect of Magnesium and Silicon on the lateral overgrowth of GaN patterned substrates by Metal Organic Vapor Phase Epitaxy

Metalorganic vapor phase epitaxy was used to achieve selective regrowth of undoped, Mg- and Si-doped GaN on a silicon nitride patterned mask, capping a GaN epitaxial layer deposited on (0001) sapphire substrate. Hexagonal openings in the mask defined into 10 µm diameter circles separated by 5µm were used as a pattern for the present study. Uniform undoped and Mg-doped GaN hexagonal pyramids, delimited by C (0001) and R {101} facets, were achieved with a good selectivity. Si-doped GaN hexagonal pyramids delimited by vertical {100} facets and (0001) top facet were obtained for a high SiH4 flow rate in the vapor phase. We found that the GaN growth rates VR and VC, measured in the R &lt;101&gt; and C &lt;0001&gt; directions respectively, were drastically affected by the Mg and Si incorporation. By adjusting the Mg partial pressure in the growth chamber, the VR/VC ratio can be increased. Hence, the delimiting top C facet do not vanish as usually observed in undoped GaN selective regrowth but conversely expands. On the other hand, under proper growth conditions, 20µm-high Si-doped GaN columns were obtained.

Silicon Oxynitride Waveguides for Optoelectronic Integrated Circuits

Planar optical waveguides on p-type Si wafers have been fabricated by a photo-induced deposition process. Silicon oxynitride was deposited using a gaseous mixture of SiH4 (2% in Ar), NH3 and N2O under 253.7 nm UV radiation. The oxynitride composition was varied by changing N2O: ( N2O+NH3) ratio while keeping N2O+NH3 and SiH4 flow rates constant. The refractive index varied from 1.46 to 1.95. The optical energy gap increased from 4.8 to 5.7 as the flow rate ratio varied from 0 to 0.25. Si–N bond shifts to higher energy owing to the incorporation of oxygen. A planar waveguide structure was fabricated using thermally grown SiO2 buffer layer of 1.1 µ m thickness. The loss was estimated to be 1.1 dB/cm for TE0 mode at 632.8 nm. The accuracy of measurements is 0.02 dB/cm.

Effects of the Addition of SiF4 to the SiH4 Feed Gas for Depositing Polycrystalline Silicon Films at Low Temperature

Polycrystalline silicon films with a strong (110) texture were prepared on a corning 7059 glass substrate at 400° C by a plasma-enhanced chemical vapor deposition method using a mixture of gases with different SiF4 flow rates ( [SiF4] = 0–0.5 sccm) under a fixed SiH4 flow rate ( [SiH4] = 1 or 0.15 sccm). The effects of the addition of SiF4 to SiH4 on the structural properties of the films were studied by Raman scattering, X-ray diffraction (XRD), atomic force microscopy and stress measurements. For [SiH4] = 1 sccm, the crystallinity and the (110) XRD grain size monotonically increased with increasing [SiF4], and their respective maxima reach 90% and 900 Å. In contrast, for [SiH4] = 0.15 sccm, both the crystallinity and the grain size decreased with [ SiF4]. Mechanisms causing the change in crystallinity are discussed, and it was suggested that an improvement in the crystallinity, due to the addition of SiF4, is likely to be caused by the effect of a change in the surface morphology of the substrates along with the effect of in situ chemical cleaning. On the other hand, both the effect of in situ chemical etching on the growing surface and the effect of a change in the capability for surface migration of adsorbates may provide a minor contribution in determining the crystallinity.

Growth of very low temperature polysilicon film by remote plasma-enhanced chemical-vapor deposition

Silicon thin films have been prepared on SiO2 substrates by remote plasma-enhanced chemical-vapor deposition using H2/SiH4/Ar gases. The film properties were found to critically depend on the variations of deposition parameters, which include the SiH4 flow rate with a fixed H2 flow rate, Ar flow rate, and radio frequency (rf) power. The substrate temperature was fixed at 280±5 °C. The best quality polysilicon film was obtained when the rfpower/Ar ratio was set near 0.5±0.05. In addition, the electrical mobility was observed to increase with the increasing SiH4 flow rate. The effects of the deposition parameters variation were discussed to properly account for the observed properties of the thin films studied.

Effects of Dilution Gases on Si Atoms and SiHx + (x = 0–3) Ions in Electron Cyclotron Resonance SiH4 Plasmas

The behavior of Si atoms and SiHx+ (x=0–3) ions in electron cyclotron resonance (ECR) SiH4/Ar and SiH4/H2 plasmas was investigated by ultraviolet absorption spectroscopy and quadrupole mass spectrometry as a function of microwave power, pressure and SiH4 flow rate ratio. The behavior of ions in SiH4/H2 plasmas is different from that in SiH4/Ar plasmas. This behavior is discussed from the generation and loss of each species. Moreover, the effects of Si atoms and ions on film formation are discussed based on these results.

Reduced Al-Ga interdiffusion in GaAs/AlGaAs multiple quantum well structure by introducing low hydrogen content SiNx capping layer for dielectric cap quantum well disordering

AbstractDielectric cap quantum well disordering (DCQWD) of GaAs/AlGaAs multiple quantum well (MQW) structure was carried out by using SiNx. capping layer grown by plasma enhanced chemical vapor deposition (PECVD). By varying the NH3 flow rate with fixed SiH4 flow rate during the SiNx. growth, the characteristics of the capping film were varied. There was an increase in the energy shift of quantum well photoluminescence (PL) peak after thermal treatment of the samples with rapid thermal annealing (RTA) as the NH3 flow rate was increased, although the thickness of SiNx decreased. This is thought to be due to the increase of hydrogen content in SiNx. film grown at higher NH3 flow rate.

Growth of Si and C δ-doped nipi doping superlattices in GaAs by metal organic vapor phase epitaxy

We have optimized growth conditions of metal organic vapor phase epitaxy (MOVPE) in order to grow Si and C δ-doped nipi doping superlattices in GaAs. Trimethylaluminium (TMAl) and silane (SiH4) were used as p-type and n-type doping precursors, respectively. We report that at 630 °C, full compensation of free electrons and holes can be obtained in the MOVPE-grown Si and C δ-doped nipi doping superlattices over a very wide range of the sheet carrier densities (1012–1013 cm−2) by choosing proper TMAl flow rate and Si δ-doping time or SiH4 flow rate. The experimental results on electrical and optical characterization of Si and C δ-doped nipi doping superlattices in GaAs with 150 Å thick undoped spacer layers are presented.

Behavior of Si atoms in a silane electron cyclotron resonance plasma at high dissociations

The Si atom density at the 3p2 3P2 level in electron cyclotron resonance SiH4/H2 and SiH4/Ar plasmas was measured as a function of total pressure from 0.6 to 3.3 Pa at a microwave power of 400 W and a SiH4 flow rate of 6 sccm using ultraviolet absorption spectroscopy. Parent SiH4 molecules in SiH4/H2 and SiH4/Ar plasmas were found to be considerably dissociated using infrared diode laser absorption spectroscopy. The Si atom density in the SiH4/H2 plasma was larger than that in the SiH4/Ar plasma, which was quite different from that in the capacitively coupled rf SiH4 plasmas. Behaviors of the Si atom density are discussed on the basis of the rate equation for Si atoms. It was concluded from a comparison of the behavior of the density and generation rate of Si atoms that the diffusion loss was comparable to the reaction loss in the removal process of Si atoms in the case of H2 dilution, while the reaction loss was dominant in the case of Ar dilution.

二重管式同軸線路形マイクロ波プラズマCVDにおけるN&lt;sub&gt;2&lt;/sub&gt;/SiH&lt;sub&gt;4&lt;/sub&gt;プラズマのパラメータの空間分布

We have confirmed the new method of probe measurement in N2/SiH4 plasma. Using this method, we have measured the spatial distribution of plasma parameters such as electron temperature Te, electron density ne, plasma space potential Vs, floating potential Vf and sheath voltage Vs-Vf with varying the gas flow rate of SiH4 in the chamber of the double tubed coaxial line type microwave plasma CVD (MPCVD) system. In this paper, we report the spatial distribution of these plasma parameters in the chamber of this MPCVD system. And it is cleared that the plasma is very uniform in the chamber.

Variations in Young's modulus and intrinsic stress of LPCVD-polysilicon due to high-temperature annealing

The effect of high-temperature annealing on Young's modulus E and the intrinsic stress sigma of thin films made of LPCVD-polysilicon was investigated. The films were annealed for 2 hours in a nitrogen atmosphere at temperatures between 600 degrees C and 1100 degrees C. Then Young's modulus and the intrinsic stress were determined by the membrane deflection method. An extended analytical theory for the membrane deflection was developed and the results correspond well with FEM analysis of Pan J.Y. et al. (1990 Technical Digest, IEEE Solid-State Sensor and Actuator Workshop, Hilton Head Island, SC, USA p 70). LPCVD-polysilicon was produced with a SiH4 flow rate of 70 sccm and a total pressure of 100 mTorr at 620 degrees C. The film thickness was 460 nm. For the as deposited films the method of membrane deflection yields a Young's modulus of 151+or-6 GPa and an intrinsic stress of -350+or-12 MPa. After annealing at temperatures higher than the deposition temperature the compressive stress started to decrease with increasing annealing temperature. It relaxed nearly completely after annealing at 1100 degrees C. Young's modulus seems to increase a little with increasing annealing temperature up to 162+or-8 GPa at 1100 degrees C. The values for E and sigma obtained with the membrane deflection method were compared with the values obtained by the method of ultrasonic surface waves. The method of ultrasonic surface waves yields systematically higher values for E. The discrepancy can be explained by the uncertainty of Poisson's ratio of polysilicon.

Mechanism of low-temperature polycrystalline silicon growth from a SiF4/SiH4/H2 plasma

A model for the low-temperature growth of poly-Si by plasma-enhanced chemical-vapor deposition using SiF4/SiH4/H2 gases is presented. The model is based on the existing so-called etching model in which growth and etching take place simultaneously. In this model a set of chemical reactions are postulated. The crucial factors to obtain high-quality poly-Si films are (1) the flux of precursors, (2) the concentration of F radicals in the vicinity of the growing surface which determines the etching rate, and (3) the H-covered surface which ensures long diffusion length of precursors. The flow rate of SiH4 [factor (1)] determines whether the film becomes crystalline or amorphous, and variation in the other gas flow rates and plasma parameters affect factors (2) and (3). According to the model the electrode spacing and rf power predominantly determine the concentration of F radicals diffused to the growing surface, while the gas pressure changes the residence time of radicals which predominantly affects the etching reaction. Natural consequences of the model are that an excess supply of F radicals will in turn deteriorate the crystallinity by stripping the hydrogen covering the surface and increasing nucleation sites. The crystallinity of poly-Si films prepared by changing the above plasma parameters are characterized by x-ray diffraction, and their dependence on the above parameters are found to be consistent with the model. A high degree of hydrogen exchange between the growing surface and the plasma is observed by secondary-ion-mass spectroscopy for the film prepared with SiF4/SiH4/D2 gases.

Synthesis and characterization of ultrafine Si powders from laser induced SiH4 gas reactions

Ultrafine silicon powders with a mean particle diameter of 20–200 nm and a mean crystallite diameter of 18–37 nm were synthesized from high purity SiH4 by laser induced gas phase reactions. The Si powders have been characterized by TEM, XPS, FTIR, XRD and BET techniques, and the effects of processing variables including SiH4 flow rate, laser power, cell pressure and the ArSiH4 ratio on the formation of the Si powders have been studied. Results showed that the powders consisted of monodispersed spherical particles, and agglomerated particles; both types of particles have polycrystalline structure, which resulted from the interparticle collision growth during the formation of the powders. The nonagglomerated spherical particles with a small size werefavored to form with a lower laser power and higher ArSiH4 ratios. The Si powders have O-Si-H surface configuration due to oxidation when exposed to air.

Adhesion between polycarbonate substrate and SiO2 film formed from silane and nitrous oxide by plasma-enhanced chemical vapor deposition

We studied the adhesion of a silicon dioxide film, formed from silane and nitrous oxide gas by plasma-enhanced chemical vapor deposition, to a polycarbonate substrate and the bonding between the film and the substrate by x-ray photoelectron spectroscopy. Adhesion of the SiO2 film to the polycarbonate increases with increasing SiH4 flow rate. All SiO2 film squares produced at a SiH4 flow rate of 10 standard cm3 min−1 exhibited good adhesion to the substrate. An analysis of the x-ray photoelectron spectra indicates that more phenyl groups are decomposed as adhesion increases. The bonding between the SiO2 film and the polycarbonate substrate is discussed on the basis of x-ray photoelectron spectroscopy. The Si–O–C bonding between SiO2 and polycarbonate results in good adhesion between the film and the substrate.

Interaction of Hydrogenated Silicon Nitride Films with Indium Tin Oxide

The whitening mechanism of hydrogenated silicon nitride (SiNx:H) film deposited on indium tin oxide (ITO) film was investigated by means of optical emission spectroscopy (OES), scanning electron microscopy (SEM) and X-ray photoelectron spectrosscopy (XPS) analysis. The degree of whitening of the SiNx:H film on ITO depends on the deposition conditions of SiNx:H, i.e., the SiH4 flow rate and the substrate temperature. Reactive species such as SiHn, decomposed from SiH4 gas, preferentially caused the reduction of ITO. This was followed by formation of In metal and a Si-rich porous layer containing SiO2. An abnormal growth of SiNx:H films caused by these successive reactions led to the whitening.

Silicon epitaxial growth at 300 °C by plasma enhanced chemical vapor deposition from SiH4/H2

This letter presents structural properties of silicon epitaxy grown at 300 °C by plasma enhanced chemical vapor deposition from SiH4/H2. The ratio of H2 to SiH4 flow rate and rf power of plasma was found to play an important role for epitaxial growth. The base pressure of the chamber was greater than 3×10−6 Torr. The substrates were ex situ cleaned by the spin-etch method prior to wafer loading. A H2 baking step was carried out prior to epitaxial deposition. Cross-section transmission electron microscopy and secondary ion mass spectroscopy were used to inspect the quality of Si films. The thickness of the silicon epitaxy is about 0.3 μm, which is grown at a rate of 5.6 nm/min.