Diborane Flow Research Articles

Growth kinetics and boron doping of very high Ge content SiGe for source/drain engineering

We have studied the in-situ boron doping of high Ge content Si 1− x Ge x layers ( x=0.3, 0.4 and 0.5). These layers have been grown at low pressure (20 Torr) and low temperature (600–650 °C) with a heavily chlorinated chemistry on blanket Si(0 0 1) substrates. Such a chemistry yields a full selectivity versus SiO 2 (isolation) and Si 3N 4 (sidewall spacers) on patterned wafers with gate stacks. We have quantified the impact of the diborane flow on the SiGe layer crystalline quality, its resistivity, the SiGe:B growth rate and the apparent Ge concentration. Resistivity values lower than 1 mΩ cm are easily achieved, all the more so for high Ge content layers. The SiGe growth rate increases and the apparent Ge concentration (from X-ray diffraction) decreases as the diborane flow increases. B atoms (much smaller than Si or Ge) indeed partially compensate the compressive strain in the SiGe:B layers. We have also probed the in-situ boron and phosphorus doping of Si at 750 °C, 20 Torr with a heavily chlorinated chemistry. The B ions concentration increases linearly with the diborane flow, then saturates at a value close to 4×10 19 cm −3. By contrast, the P ions concentration increases sub-linearly with the phosphine flow, with a maximum value close to 9×10 18 cm −3. Adding diborane (phosphine) to the gaseous mixture leads to a sharp increase (decrease) of the Si:B (the Si:P) growth rates, which has to be taken into account in device layers. All the know-how acquired will be most handy for the formation of in-situ doped recessed or raised sources and drains in metal-oxide semiconductor devices.

Boron doped diamond deposited by microwave plasma-assisted CVD at low and high pressures

Boron doped diamond is deposited over a range of pressures and chemistries including pressures from 35–120 Torr and gas chemistries including hydrogen–methane–diborane and argon–methane–hydrogen–diborane mixtures. The diamond deposition system is a 2.45 GHz microwave resonant cavity system. Diborane (B 2H 6) gas chemistry has been utilized with flow rates of 2.5–100 ppm. At low pressures of 35 Torr polycrystalline films are deposited using a feed gas mixture of hydrogen and 0.5% methane. At moderate pressures of 95 Torr, diamond films are grown using 60% Ar, 39% H 2 and 1% CH 4. For the high pressure experiments of 120 Torr, polycrystalline films are deposited using 98% H 2 and 2% CH 4. The deposition rate ranges from 0.3 to 1.6 μm/h. This investigation describes the relationship of the diborane flow rate and pressure versus the resulting film morphology, electrical properties, and morphology of the deposited films. The deposition of boron-doped polycrystalline diamond is done on 5 cm diameter silicon and silicon dioxide coated substrates. The resistivity spatial variation across the wafer was ± 5% indicating a good uniformity.

Growth Kinetics and Boron-Doping of Very High Ge Content Si1-xGex for Sources and Drains Engineering

We have studied the in-situ boron-doping of high Ge content Si1- xGex layers (x = 0.3, 0.4 and 0.5). Those layers have been grown at low pressure (20 Torr) and low temperature (600{degree sign}C to 650{degree sign}C) with a heavily chlorinated chemistry (in order to be selective versus SiO2 (isolation) and Si3N4 (sidewall spacers)). We have quantified the impact of the diborane flow on the SiGe layer crystalline quality, its resistivity, the SiGe:B growth rate and the apparent Ge concentration. We have also probed the in-situ boron and phosphorus doping of Si @ 750 {degree sign} C, 20 Torr with a chlorinated chemistry. All the know-how developed will be most handy for the formation of in-situ doped recessed or raised sources and drains.

Growth and characterization of BGaAs and BInGaAs epilayers on GaAs by MOVPE

BGaAs and BInGaAs alloys have been grown by metalorganic vapour phase epitaxy. The epitaxial layers were grown on (0 0 1) GaAs substrates misoriented 1° towards [1 1 0] using diborane, trimethylindium, triethylgallium and arsine as precursors. The influence of diborane flow rate on the growth mode of BGaAs layers was highlighted. We also studied the influence of boron gas-phase concentration and growth temperature on the incorporation of boron and indium into BGaAs and BInGaAs alloys. BInGaAs/GaAs single quantum wells were grown and quantum well emission was observed by photoluminescence at room and low temperature. At 300 K, emission wavelength was up to 1.07 μm.

Low Resistivity Boron Doped Amorphous Silicon-Germanium Alloy Films Obtained with a Low Frequency

AbstractThe structural and electrical properties of boron doped amorphous silicon-germanium alloy films, obtained using a low frequency plasma enhanced chemical vapor deposition (LF PECVD), are presented in this contribution. These thin films were deposited on a substrate heated at 270°C, and by decomposing a mixture of silane, germane, and diborane gases. The chemical bond structure was studied by Infrared Spectroscopy. Our results show that, for a constant diborane flow, the increase of germane flow enhances the incorporation of boron into the film; the peak at 2540 cm−1 becomes larger as the Ge content increases. Transport of carriers was studied by measuring current-voltage curves as a function of temperature. The conductivity increased from 10−6 to 10 (Ω-cm)−1, while the refraction index increased from 3.312 to 4.4458, for an increasing Ge content; this makes the films suitable for optical waveguide applications. On the other hand, the activation energy varied from 0.668 to 0.220 eV when the sample was doped with boron. The AFM images showed that the surface roughness was improved for an alloy with 50% of Ge.

Mechanical Properties of Boron Doped Diamond Films Prepared by MPCVD

ABSTRACTA chemical vapor deposition hydrogen/methane/nitrogen feedgas mixture with unconventionally high methane (15% CH4 by volume) normally used to grow ultra-hard and smooth nanostructured diamond films on Ti-6Al-4V alloy substrates was modified to include diborane (10% B2H6 in hydrogen) for boron-doping. The flow rate for B2H6 was varied to investigate its effect on plasma chemistry, film structure, and mechanical properties. It was found that boron in the plasma can easily be incorporated into diamond films and change the lattice parameter and affect film structure as measured by Raman spectroscopy. Grazing angle x-ray diffraction shows a strong dependence of diamond lattice parameter with diborane flow rate and B2H6:CH4 flow rate ratio. Thermal stability of these films was evaluated by heating in an oxygen environment above 700 °C. Nanoindentation measurements show that the films have high hardness close to that of nanostructured diamond. High film hardness and toughness, combined with good thermal stability and low surface roughness indicate great potential as wear resistant coatings able to withstand high temperature oxidizing environments.

Growth and characterization of high quality B xGa 1− xAs/GaAs(0 0 1) epilayers

In a first step towards the growth of BInGaAs, we have grown and characterized the B x Ga 1− x As/GaAs ternary compound with boron composition up to x=0.06 on GaAs(0 0 1) vicinal substrates. The incorporation behavior of boron has been studied as a function of growth temperature, diborane flux, gallium precursor and carrier gas (hydrogen and nitrogen). A maximum for boron incorporation ( x≈0.04–0.06) is found at 550–600°C depending on the precursor and the carrier gas. The epilayers have good crystalline quality as measured by X-ray rocking curve of the (0 0 4) diffraction peak (full-width at half-maximum of 38 arcsec for x=0.035). However, the surface morphology is very sensitive to the diborane supersaturation in the gas phase. At high diborane flow rate, the surface appears as though it is covered in dust. A low surface roughness of 0.4 nm was measured by atomic force microcopy (AFM) in the best growth conditions. AFM images also show a cross-hatch pattern for the highest boron composition.

MOCVD growth of GaBN on 6H-SiC (0001) substrates

BxGa1−xN films were deposited on 6H-SiC (0001) substrates at 1000°C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. The presence of boron was detected by Auger scanning microprobe, the shift of the (00.2) x-ray diffraction peak, and low-temperature photoluminescence. A single-phase BxGa1−xN alloy with x=1.5% was produced at the gas phase B/Ga ratio of 0.005. Phase separation into wurtzite BGaN and the B-rich phase occurred for a B/Ga ratio in the 0.01–0.2 range. Only BN was formed for B/Ga >0.2. The B-rich phase was identified as h-BN with sp2 bonding based on the results of Fourier transform infrared spectroscopy. As the diborane flow exceeds the threshold concentration, the growth rate of BGaN decreases sharply, because the growth of GaN is poisoned by the formation of the slow growing BN phase. The bandedge emission of BxGa1−xN varies from 3.451 eV for x=0% with FWHM of 39.2 meV to 3.465 eV for x=1.5% with FWHM of 35.1 meV. The narrower FWHM indicates that the quality of GaN epilayer is improved with a small amount of boron incorporation. The PL linewidths become broader as more boron is introduced into the solid solution.

In-situ Kelvin probe and ellipsometry study of the doping of a-Si : H and a-SiC : H layers: : Correlation with solar cell parameters

To underscore the effects of boron doping on the photovoltaic characteristics of a-Si : H based p–i–n solar cells we used the in-situ Kelvin probe technique to determine the evolution of the contact potential at the SnO 2/p interface in two series of solar cells: one with a p(a-Si : H) layer and another with a p(a-SiC : H) layer plus a buffer a-SiC : H layer. In each series, the flow of diborane was varied between 0.5 and 7 sccm. The in-situ Kelvin probe measurements on thick layers indicate that the doping efficiency is higher in a-Si : H than in a-SiC : H layers. In the case of cells with a p(a-Si : H) layer we observe an optimum in V oc as a function of the diborane flow rate. Below this optimum the increase in V oc is correlated to the increase of the contact potential measured by the Kelvin probe. Above the optimum value of the diborane flow, the further increase of the contact potential contrasts with the decrease of V oc. Moreover, we found that V oc of the cells with a p(a-SiC : H) is independent of the diborane flow rate. This unexpected behaviour is interpreted in terms of the diffusion of impurities and changes in the p-layer induced by boron atoms; it is supported by secondary-ion mass spectrometry and in-situ spectroscopic ellipsometry measurements.

Low temperature plasma enhanced chemical vapour deposition boron nitride

In this paper we present our results concerning deposition of large area boron nitride films by the conventional plasma enhanced chemical vapor deposition (PECVD) technique, in a capacitively coupled reactor, from nitrogen (N 2) and diborane (B 2H 6) gaseous mixtures and at pressures lower than 1 Torr and temperatures between 200 and 500°C. Series of samples were grown by changing the RF power, the substrate temperature and the (N 2/B 2H 6) flow ratio. The characterization of the samples was carried out mainly by Fourier transform infrared spectroscopy (FTIR) and thickness measurements. The results have been very promising and samples grown in appropriate conditions show clearly the infrared spectra absorption bands characteristic of hexagonal BN material (h BN), without traces of hydrogen bonding, even at temperatures as low as 200°C. The material structure shows a strong dependence on the RF power and the diborane flow. For the lower studied B 2H 6 flows and the higher RF power, the onset of a cubic phase was observed while the h BN phase peaks decreased and shifted in frequency. However, for lower RF power values and higher B 2H 6 flows the in-plane hexagonal vibration increases and the out-of-plane peak decreases and shifts towards higher frequencies. The temperature did not show a very important effect on the films properties, except for the highest studied value (500°C) for which onset of cubic phase was also observed.

Influence of Diborane Flow Rate on the Structure and Stability of CVD Boron Nitride Films

CVD boron nitride films have been deposited at 800 °C from diborane, ammonia, and hydrogen gas mixtures, using different B2H6 flow rates. The effect of the [B2H6]/[NH3] ratio in the gas mixture on the structure, composition, and the stability of the layers in humid atmospheres has been studied. For low [B2H6]/[NH3] ratios (r ≤ 0.25), the deposition rate is low and some crystalline ordering in the deposit was detected. However, when ratios >0.25 are used, stable amorphous boron nitride films are deposited at deposition rates four times higher (160 nm min-1). The partially turbostratic boron nitride films, deposited at r ≤ 0.25, are unstable in humid atmospheres (80% moisture). The evolution of the unstable films was followed by infrared spectroscopy. It is observed that the turbostratic component in the film is rapidly attacked by the water molecules present in the atmosphere, giving rise finally to boron enrichment in the films. After this stage, the attack rate becomes slower, due to the higher stability...

Incorporation of boron into UHV/CVD-grown germanium-silicon epitaxial layers

Doping of UHV/CVD-grown germanium-silicon epitaxial layers by diborane is reported. The boron concentration is linear in diborane flow rate and is consistent with a surface reaction mechanism in which two surface sites are required for adsorption. The sticking coefficient of diborane on a bare silicon or germanium-silicon surface is found to be about 1.2 × 10-2. Abrupt retrograde profiles can be grown successfully provided a pause is introduced before growing more lightly doped layers.

Heavy Boron Doping in Low‐Temperature Si Photoepitaxy

Heavy boron doping of up to was achieved in a photoepitaxial layer grown at 650°C. Under UV irradiation, the doped carrier concentration was independent of the diborane flow rate in the heavily doped region and doped boron atoms were completely activated up to . Without UV irradiation, no single crystals were grown and very few boron atoms were activated in the heavily doped region. We studied the crystal quality using Raman scattering spectroscopy and found that, under UV irradiation, single crystals could be grown up to . The boron atom activation ratio depended strongly on the crystal quality. UV irradiation markedly increased carrier doping efficiency due to photo‐enhancement of the diborane vapor phase reaction, which we studied using FTIR and the surface reaction of adsorbed species. The electrical properties of low‐temperature photoepitaxial layer with heavy boron doping were studied using a bipolar transistor. Excellent device characteristics were achieved. Low‐temperature photoepitaxy also produced very abrupt boron profiles.

Growth and Doping Kinetics of GexSil-x Structures by Limited Reaction Processing

ABSTRACTWe have investigated the growth rate and boron doping of Sil-xGex epitaxial films grown by Limited Reaction Processing The growth experiments were carried out at a pressure of 6.0 torr with growth temperatures ranging from 625°C to 1000°C. The growth rate increases rapidly upon the additon of a small germane flow to the dichlorosilane in the reaction-rate-limited growth regime, and can not be explained simply by germanium incorporation. The presence of germane can increase the silicon growth rate by up to a factor of one hundred. Boron doping was also studied at high concentrations of boron in Si and Sil-xGex epitaxial films as a function of diborane flow and growth rate supports a simple kinetic model rather than an equilibrium model.

Low Pressure Chemical Vapor Deposition of In Situ Boron‐Doped Polysilicon

The deposition of in situ boron‐doped polysilicon from a mixture of diborane and silane was studied over a temperature range of 450°–600°C, and a diborane/silane flow ratio varying from 0.002 to 0.02. Diborane enhances the deposition rate and suppresses the activation energy of the deposition reaction. Diborane also reduces the temperature of the amorphous/polycrystalline transition. Resistivity after annealing (650° or 900°C) decreases with increasing diborane flow and with decreasing deposition temperature. Minimum resistivity is obtained by depositing the silicon as an amorphous film and annealing at high temperature (≥900°C). Of particular importance to low thermal budget processes, however, is the low resistivity (3.0 mΩ‐cm) obtained by annealing an initially amorphous film at 650°C.

Control of hydrogen content of boron thin films produced in a dc toroidal discharge

Hydrogenated amorphous boron films have been produced by a toroidal glow discharge of B2H6/He mixtures at low pressures (10−2 Torr). Chemically stable pure films with a low hydrogen content can be formed at a moderate substrate temperature (∼200 °C) when the diborane flow rate is raised above 10 sccm with the discharge power lowered below 100 W. The controllability of H content is potentially interesting for applications in the coating of nuclear fusion devices, as well as for use in electronic devices.