Epitaxial Growth Rate Research Articles

Influence of controlled growth rate on tilt mosaic microstructures of nonpolar a-plane GaN epilayers grown on r-plane sapphire

The influence of the epitaxial growth rate on the surface morphology, as well as the crystallinity and optical properties of nonpolar a-plane GaN epilayers grown on r-plane sapphire substrate, has been investigated by x-ray diffraction and photoluminescence studies. The a-plane GaN epilayer grown at faster growth rates revealed a horizontal-pillar-shaped morphology with triangular-pits having sharp corners. While the epilayer grown at a faster growth rate showed a greater difference in the ω tilt-offset angle and line-width value between the on- and off-axes from x-ray diffraction, the a-plane GaN grown at the relatively slower growth rate showed a flat morphology with few pits and small ω tilt-offset difference. Growth of nonpolar a-plane GaN epilayer was optimized, and the effect of the growth rate of the a-plane GaN epilayer and the reason for the difference in the ω tilt-offset line-width value between the c- and m-direction mosaicity of x-ray diffraction were analyzed.

Evaluation of Optical Waveguide by Solid Phase Epitaxial Growth of Amorphous Silicon

This study reports the evaluation of an optical waveguide fabricated on a bulk-Si platform by using an epitaxially grown Si layer. The epitaxial growth of Si is obtained by the solid phase epitaxy (SPE) using a hot furnace annealing method. It is observed that an optical propagation loss of the waveguide decreases with increasing the epitaxially grown area in the waveguide. In this study, an epitaxial growth rate is greatly enhanced by an (100) growth orientation due to the lower atomic close packing density along the (100) orientation. The optical propagation loss is also improved with the (100) growth orientation because of the higher crystalline quality and full epitaxial growth of Si.

Silicon Epitaxial Growth Rate and Transport Phenomena in a Vertical Stacked-Type Multi-Wafer Reactor

The silicon epitaxial growth rate in a trichlorosilane–hydrogen system using a vertical stacked-type multi-wafer reactor, having more than 100 substrate pieces, together with two horizontal gas inlet nozzles for each substrate, was studied by means of numerical calculations. In this study, the authors developed a compact model that consisted of the minimal set of reactor parts, by taking into account the gas flow condition around the stacked susceptors. Because the direction of the gases horizontally injected to the substrate is bent by the gas flowing downward along the stacked susceptors, a part of the horizontally injected gas in the downstream positions is forced to directly go to the exhaust, and not to the substrate. The wafer-to-wafer uniformity of epitaxial thickness is expected to be improved by means of finely adjusting the susceptor position, particularly at the downstream positions.

Low temperature Si:C co-flow and hybrid process using Si3H8/Cl2

In this paper we demonstrate a Si3H8/SiH3CH3/PH3/Cl2 based co-flow process and a “hybrid” co-flow process with interruptions of the deposition. The motivation for the work stems from the desire to improve manufacturability through higher growth rates and higher etch rates commensurate with the drive to lower thermal budgets of integration of Complementary Metal Oxide Semiconductor and memory platforms. For high volume manufacturing, high selective epitaxial growth rates are necessary for enhanced throughput and low cost of ownership. Both high growth rate and low temperatures enable sufficiently high substitutional carbon levels [C]sub in dilute Si:C alloys. The hydride deposition gases Si3H8, SiH3CH3 and PH3 and the etch gas Cl2 were kept separate in the pressurized gas supply lines and injected separately into the reaction chamber thus avoiding premature chemical reactions. The importance and the role of a suitable inert carrier gas are emphasized.

Influence of silicon cluster on epitaxial growth of silicon carbide

Precursor concentration dependences of growth rate, doping concentration and surface morphology have been investigated in the epitaxial growth of 4H-SiC(0001) epilayers with horizontal hot-wall CVD system using various precursor concentrations under constant C/Si ratio. Form the experimental data it is found that silicon cluster which is formed through gas phase nucleation plays an important role in controlling the doping concentration and epitaxial growth rate of the silicon carbide. It was observed that the concentration of silicon clusters cannot reach the equilibrium value in the process by using a low SiH4 concentration, and this phenomenon has not been reported by others.

Silicon epitaxial growth process using trichlorosilane gas in a single-wafer high-speed substrate rotation reactor

A silicon epitaxial growth process in a trichlorosilane–hydrogen system using a single-wafer high-speed substrate rotation reactor was studied by means of experiments and numerical calculations taking into account the transport phenomena and surface chemical reactions. Hydrogen chloride gas produced at the substrate surface is effectively replaced with the source gases of trichlorosilane and hydrogen, due to the effective mass transport provided by high-speed substrate rotation. Because the intermediate species produced due to chemisorption of trichlorosilane fully occupies the silicon surface, the rate of its decomposition by hydrogen gas governs the entire silicon epitaxial growth rate. Thus, the epitaxial growth rate in this reactor simply depends on the hydrogen gas concentration at the silicon substrate surface.

Monochlorosilane for Low Temperature Silicon Epitaxy

Silane (SiH4) and dichlorosilane (DCS) are currently the precursors of choice for the vapor phase epitaxy of silicon at low temperatures (T < 1000 C). Device innovation is pushing down process thermal budgets to the extent that it becomes apparent that in the near future SiH4 and DCS will face challenges in maintaining high growth rates and achieving selectivity at low temperatures. New precursors that produce high growth rates at low deposition temperatures (< 650 C) are needed for advanced epitaxial applications such as recessed source/drain stressors, p-Metal Oxide Semiconductor channel and elevated source/drain structures. In this work, monochlorosilane (MCS) is investigated for the deposition of Si thin films such as blanket Si:P, selective epitaxial Si and Si1-xCx:P. MCS brings a substantial improvement in selective epitaxial silicon growth rate and HCl consumption as compared to DCS.

Low-temperature homoepitaxial growth of 4H–SiC with CH 3Cl and SiCl 4 precursors

In prior research, a possibility to increase the growth rate of the low-temperature epitaxial growth of 4H–SiC was explored by supplementing chloro-carbon precursor CH 3Cl with HCl as an additional source of chlorine. In the current work, SiCl 4 was investigated as a replacement for SiH 4+HCl. The homogeneous nucleation in the gas phase was further reduced compared to SiH 4+HCl growth, thus essentially eliminating the main bottleneck for increasing the growth rate ( R g). However, for low values of the carrier gas flow, premature dissociation of Si gas-phase clusters was found to cause R g non-homogeneity and triangular defect formation. The drastically suppressed homogeneous nucleation opened the window for increasing the carrier gas flow velocity in order to improve the R g homogeneity from upstream to downstream. Nevertheless, generation of triangular defects was significant at R g above 5–6 μm/h. The process window for obtaining good epilayer morphology was found to correspond to Si supply-limited mode. The window was restricted at low values of C/Si ratio by formation of Si-rich islands/droplet and at high C/Si ratio by formation of polycrystalline SiC. The process window became increasingly narrower at higher R g, which serves as a new bottleneck for significantly increasing R g at such low growth temperatures.

Novel chemical precursors and novel CVD strategies enabling low temperature epitaxy of Si and Si:C alloys

In this paper we will discuss non-traditional chemical precursors for carbon-doped silicon (Si:C) that enable improved manufacturability through higher growth rates and new deposition temperature regimes commensurate with the drive to lower thermal budgets of integration of CMOS and DRAM platforms. Among the silicon precursors to be discussed are dichlorodisilane (Si 2Cl 2H 4), dichlorosilane and Silcore® (Si 3H 8). New carbon precursors disilylmethane ((SiH 3) 2CH 2) and propylene (C 3H 6) are discussed and compared with conventional monomethylsilane (SiH 3CH 3). For high volume manufacturing, high selective epitaxial growth rates are necessary for high throughput and low cost of ownership. Both, high GR and low temperatures enable high substitutional carbon levels [C] sub in dilute Si:C alloys. Advantages and disadvantages of different Chemical Vapor Deposition (CVD) strategies such as a co-flow process, a Cyclic Deposition/ Etch (CDE) process and a “hybrid” process are discussed.

Novel CVD Strategies and Novel Chemical Precursors Enabling Low Temperature Epitaxy of Si and Si:C Alloys

In this paper we will discuss non-traditional chemical precursors for carbon-doped Silicon (Si:C) that enable improved manufacturability through higher growth rates and new deposition temperature regimes commensurate with the drive to lower thermal budgets of integration of CMOS and DRAM platforms. Among the silicon precursors to be discussed are dichlorodisilane (DCDS; Si2Cl2H4), dichlorosilane (DCS) and Silcore® (Si3H8). New carbon precursors disilylmethane (DSM, CH2(SiH3)2 and propylene (C3H6) are discussed and compared with conventional (mono-)methylsilane (MMS; SiH3CH3). For high volume manufacturing, high selective epitaxial growth rates are necessary for high throughput and low cost of ownership. Both, high GR and low temperatures enable high substitutional carbon levels [C]sub in dilute Si:C alloys. Advantages and disadvantages of different CVD strategies such as a co-flow process, a cyclic deposition/etch (CDE) process and a "hybrid" process are discussed.

Disilane chemisorption on SixGe1−x(100)-(2×1): Molecular mechanisms and implications for film growth rates

At low temperatures, hydrogen desorption is known to be the rate-limiting process in silicon germanium film growth via chemical vapor deposition. Since surface germanium lowers the hydrogen desorption barrier, Si(x)Ge((1-x)) film growth rate increases with the surface germanium fraction. At high temperatures, however, the molecular mechanisms determining the epitaxial growth rate are not well established despite much experimental work. We investigate these mechanisms in the context of disilane adsorption because disilane is an important precursor used in film growth. In particular, we want to understand the molecular steps that lead, in the high temperature regime, to a decrease in growth rate as the surface germanium increases. In addition, there is a need to consider the issue of whether disilane adsorbs via silicon-silicon bond dissociation or via silicon-hydrogen bond dissociation. It is usually assumed that disilane adsorption occurs via silicon-silicon bond dissociation, but in recent work we provided theoretical evidence that silicon-hydrogen bond dissociation is more important. In order to address these issues, we calculate the chemisorption barriers for disilane on silicon germanium using first-principles density functional theory methods. We use the calculated barriers to estimate film growth rates that are then critically compared to the experimental data. This enables us to establish a connection between the dependence of the film growth rate on the surface germanium content and the kinetics of the initial adsorption step. We show that the generally accepted mechanism where disilane chemisorbs via silicon-silicon bond dissociation is not consistent with the data for film growth kinetics. Silicon-hydrogen bond dissociation paths have to be included in order to give good agreement with the experimental data for high temperature film growth rate.

A power rate law study of silicon germanium selective vapor phase epitaxy kinetics

The selective vapor phase epitaxy (SVPE) kinetics of a Si 1− x Ge x heterostructure is complex. To date, operational kinetics schemes are not available and reactant interactions are not very well understood. This study is a phenomenological investigation of epitaxial film growth rate (GR) and composition. An empirical model is developed specifically to address the kinetics of industrial SVPE processes performed at a pressure above 1 Torr. The response function investigated in this study is very similar to the one applied in the field of heterogeneous catalysis. The relevance of a power rate law (PRL) to Si 1− x Ge x SVPE is assessed with the goodness of fit as well as with a consistency check of the fitting parameters with the chemistry of the process. Despite the lack of a reaction scheme supporting the PRL, trends consistent with the known chemistry of growth kinetics are evidenced, thus confirming the soundness of the method. Partial reaction orders are identified for HCl, SiH 2Cl 2, GeH 4 and B 2H 6.

Development of a High Rate 4H-SiC Epitaxial Growth Technique Achieving Large-Area Uniformity

A vertical hot-wall type epi-reactor that makes it possible to simultaneously achieve both a high rate of epitaxial growth and large-area uniformity at the same time has been developed. A maximum growth rate of 250 µm/h is achieved at 1650 °C. Thickness uniformity of 1.1 % and doping uniformity of 6.7 % for a 65 mm radius area are achieved while maintaining a high growth rate of 79 µm/h. We also succeeded in growing a 280 µm-thick epilayer with excellent surface morphology and long carrier lifetime of ~1 µs on average. The LTPL spectrum shows free exciton peaks as dominant, and few impurity-related or intrinsic defect related peaks are observed. The DLTS measurement for an epilayer grown at 80 µm/h shows low trap concentrations of 1.2×1012 cm-3 for Z1/2 center and 6.3×1011 cm-3 for EH6/7 center, respectively.

Growth of mm-thick orientation-patterned GaAs for IR and THZ generation

Low-pressure hydride vapor phase epitaxy (HVPE) is being used for the regrowth of thick GaAs on orientation-patterned templates for nonlinear optical frequency conversion. We have achieved epitaxial growth rates of 200 μm/h and produced millimeter-thick films in 10-h-long growth runs. A critical problem in the HVPE regrowth of orientation-patterned GaAs is the preservation of the original patterned structure—during thick growth, the domain walls often bend and annihilate. Measurements indicated that the domain wall bending decreased as the growth temperature was reduced. The substrate miscut and the orientation of unpatterned regions also affect the vertical propagation of domain walls. In this paper we discuss the process improvements which have facilitated the production of millimeter-thick layers with nearly vertical domain walls.

Crystal growth of YBCO coated conductors by TFA–MOD method

The crystal growth mechanism of TFA (trifluoroacetates)–MOD (metal organic deposition) derived YBa 2Cu 3O y has been investigated to understand the process for higher production rates of the conversion process. YBCO films were prepared by TFA–MOD on CeO 2/Gd 2Zr 2O 7/Hastelloy C276 substrates. The growth rates of YBCO derived from Y:Ba:Cu = 1:2:3 and 1:1.5:3 starting solutions were investigated by XRD and TEM analyses. YBCO growth proceeds in two steps of the epitaxial one from the substrate and solid state reaction. The overall growth rate estimated from the residual amounts of BaF 2 with time measured by XRD is proportional to a square root of P(H 2O). The trend was independent of the composition of starting solutions, however, the growth rate obtained from the 1:1.5:3 starting solutions was high as twice as that of 1:2:3, which could not be explained by the composition of BaF 2 included in the precursor films. On the other hand, the growth rate measured from the thickness of the YBCO quenched film at the same process time showed no difference between the samples of 1:2:3 and 1:1.5:3. The epitaxial growth rate of 1:1.5:3 was also the same as the overall growth rate of that, which means there was no solid state reaction to form YBCO after the epitaxial growth. The YBCO growth mechanism was found to be as follows; YBCO crystals nucleate at the surface of the substrate and epitaxially grow into the precursor by layer-by-layer by a manner with trapping unreacted particles. The amounts of YBCO and the unreacted particles trapped in the YBCO film are independent of the composition of the starting solution in this step. Unreacted particles react with each other to form YBCO and pores by solid state reaction as long as there is BaF 2 left in the film. The Ba-poor starting solution gives little BaF 2 left in the film and so the solid state reaction is completed within a short time, resulting in the fast overall growth rate.

Correlation of the growth rate for selective epitaxial growth of silicon and oxide thickness and oxide coverage in a reduced pressure chemical vapor deposition pancake reactor

The selective epitaxial growth (SEG) rate of silicon for wafers with various oxide coverages (OCs) (the ratio of oxide area to silicon area on a silicon wafer) and oxide thicknesses, ranging from 0% to 90% and 0to500nm, respectively, in a rf heated cold-wall reduced-pressure chemical vapor deposition (RPCVD) pancake reactor, using the SiH2Cl2–HCl–H2 gas system, was investigated at a chamber pressure of 40Torr and a temperature of 970°C. The highest growth rate is about 175nm∕min, occurred at the oxide coverage of 90% and oxide thickness of 200nm; the lowest growth rate is about 112nm∕min, occurred at the oxide coverage of 30% and oxide thickness of 500nm. The growth rate of a control sample (a bare silicon wafer) is 110nm∕min. According to these data, a semiempirical expression for the SEG rate of undoped wafers in an RPCVD pancake reactor system is developed. The growth rate is exponentially dependent on the oxide coverage and a function of oxide thickness. This expression is suitable for the in situ p-t...

Very High Growth Rate Epitaxy Processes with Chlorine Addition

The growth rate of 4H-SiC epi layers has been increased by a factor 19 (up to 112 μm/h) with respect to the standard process with the introduction of HCl in the deposition chamber. The epitaxial layers grown with the addition of HCl have been characterized by electrical, optical and structural characterization methods. An optimized process without the addition of HCl is reported for comparison. The Schottky diodes, manufactured on the epitaxial layer grown with the addition of HCl at 1600 °C, have electrical characteristics comparable with the standard epitaxial process with the advantage of an epitaxial growth rate three times higher.

In situ Control of Atomic-Scale Si Layer with Huge Strain in the Nanoheterostructure NiSi/Si/NiSi through Point Contact Reaction

Nanoheterostructures of NiSi/Si/NiSi in which the length of the Si region can be controlled down to 2 nm have been produced using in situ point contact reaction between Si and Ni nanowires in an ultrahigh vacuum transmission electron microscope. The Si region was found to be highly strained (more than 12%). The strain increases with the decreasing Si layer thickness and can be controlled by varying the heating temperature. It was observed that the Si nanowire is transformed into a bamboo-type grain of single-crystal NiSi from both ends following the path with low-activation energy. We propose the reaction is assisted by interstitial diffusion of Ni atoms within the Si nanowire and is limited by the rate of dissolution of Ni into Si at the point contact interface. The rate of incorporation of Ni atoms to support the growth of NiSi has been measured to be 7 x 10(-4) s per Ni atom. The nanoscale epitaxial growth rate of single-crystal NiSi has been measured using high-resolution lattice-imaging videos. On the basis of the rate, we can control the consumption of Si and, in turn, the dimensions of the nanoheterostructure down to less than 2 nm, thereby far exceeding the limit of conventional patterning process. The controlled huge strain in the controlled atomic scale Si region, potential gate of Si nanowire-based transistors, is expected to significantly impact the performance of electronic devices.

Very high epitaxial growth rate of SiC using MTS as chloride-based precursor

We present results on chloride-based homoepitaxial growth of 4H-SiC in a hot wall CVD reactor. The addition of chlorinated species to the gas mixture prevents silicon nucleation in the gas phase, thus allowing higher input flows of the precursors resulting in much higher growth rate than that of standard SiC epitaxial growth using only silane, SiH 4, and ethylene, C 2H 4, as precursors. We have achieved growth rates higher than 100 μm/h, as compared to 5 μm/h for the standard case. The chlorinated precursor used is methyltrichlorosilane (MTS), CH 3SiCl 3, but since MTS contains both silicon and carbon, with the C/Si ratio 1, we have also added silane or ethylene to optimise the C/Si ratio in order to improve the morphology of the epitaxial layers. We present studies on how the growth rate depends on both the flow of MTS and C/Si ratio. The morphology of the grown epitaxial layer has been investigated using Nomarski microscope and atomic force microscope showing extremely smooth surface and low epi-defect density. The net doping has been determined using capacitance-voltage measurements. Low temperature photoluminescence and high-resolution X-ray diffraction confirm the high quality of the grown epilayers.

Improvement of AlN crystalline quality with high epitaxial growth rates by hydride vapor phase epitaxy

We have demonstrated that high-quality aluminium nintride (AlN) single crystal can be grown at high growth rates by hydride vapor phase epitaxy (HVPE) with a help of using AlN templates and step growth technique. A colorless and transparent AlN layer with 83 μm thick was grown at a growth rate of 57 μm/h at 1450 °C. Its full-width at half-maximum for {0 0 0 2} plane was 295 arcsec and that for {1 0 1¯ 1} plane was 432 arcsec. Grown AlN layer was transparent in the visible and ultraviolet region and a sharp absorption edge with band gap energy of 5.96 eV was confined.