# Patent

## Title
Methods of forming silicon germanium tin films and structures and devices including the films

## Abstract

Methods of forming silicon germanium tin (SixGe1-xSny) films are disclosed. Exemplary methods include growing films including silicon, germanium and tin in an epitaxial chemical vapor deposition reactor. Exemplary methods are suitable for high volume manufacturing. Also disclosed are structures and devices including silicon germanium tin films.

## Background
FIELD OF INVENTION
The present disclosure generally relates to techniques for forming layers including silicon germanium tin and to structures and devices including such layers. More particularly, various embodiments of the disclosure relate to methods of forming silicon germanium tin layers using germane and/or silane, to methods of forming structures and devices including such layers, to systems for forming the layers and structures, and to structures and devices including the layers.
BACKGROUND OF THE DISCLOSURE
Various electronic devices, such as semiconductor devices, and photonic devices, such as lasers and solar devices, include or may desirably include silicon germanium tin (SixGe1-xSny) layers. For example, SixGe1-xSny layers can be used to form direct band gap devices, quantum well structures, and/or may be used to provide strain in, for example, an adjacent germanium layer to increase carrier mobility in the germanium layer. SixGe1-xSny layers can also be used to form tunable band gap devices as well as optical devices having tunable optical properties. To obtain the desired device properties, the SixGe1-xSny layers generally have a crystalline structure, which generally follows the crystalline structure of an underlying layer, such as a buffer layer.
SixGe1-xSny layers can be deposited or grown using a variety of techniques. For example, vacuum processes, including molecular beam epitaxy and ultra-high vacuum chemical vapor deposition, have been used to form SixGe1-xSny films. Unfortunately, such techniques are slow, expensive, and thus generally not well suited for high-volume manufacturing.
The germanium precursor for such processes typically includes digermane (Ge2H6) or trigermane (Ge3H8). When the film includes silicon, the silicon precursor typically includes a disilane (Si2H6), trisilane (Si3H8), or other higher order silane compounds, or hetero-nuclear Si—Ge compounds with the general formula of (H3Ge)xSiH4-x (x=1-4), (H3Si)xGeH4-x (x=1-4).
Although such processes generally work to deposit or grow crystalline SixGe1-xSny layers, use of digermane, trigermane, or higher order germane precursors and/or disilane or trisilane, is problematic in several respects. For example, formation of films or layers including SixGe1-xSny using digermane or higher order germane precursors, such as trigermane, is not selective when certain carrier gasses (e.g., hydrogen) and/or dopants (e.g., p-type dopants) are used with the precursor. Also, digermane is relatively unstable (explosive) in concentrated form; as a result, an amount of the precursor contained in a vessel may be limited, typically to less than 154 grams, which, in turn, causes throughput of processes using such a precursor to be relatively low. In addition, digermane and higher order germanes are relatively expensive. Similarly, higher order silanes are relatively expensive and can result in relatively slow growth rates. Accordingly, improved processes for forming SixGe1-xSny are desired. Further, improved methods suitable for high-volume manufacturing of structures and devices including a layer of SixGe1-xSny are desired.
SUMMARY OF THE DISCLOSURE
Various embodiments of the present disclosure relate to methods of forming SixGe1-xSny films, to structures and devices including SixGe1-xSny films, and to systems for forming the SixGe1-xSny films. The methods described herein can be used to form SixGe1-xSny films suitable for a variety of applications, including, for example, stressor films in semiconductor devices and tunable bandgap layers in photonic devices. While the ways in which various embodiments of the disclosure address the drawbacks of the prior art methods, films, structures, devices, and systems are discussed in more detail below, in general, the disclosure provides methods of forming SixGe1-xSny using silane and/or germane as precursors. Exemplary methods can be used to form films, structures, and/or devices including SixGe1-xSny in a cost efficient manner and/or can be used to form such films, structures and/or devices in a time efficient manner. Various methods described herein are particularly well suited for use in high volume manufacturing of structures and devices including SixGe1-xSny films.
As used herein, SixGe1-xSny films (also referred to herein as layers) are layers that can include the elements silicon, germanium, and tin. In accordance with various embodiments of the disclosure, the SixGe1-xSny films are crystalline and are epitaxially formed overlying a crystalline substrate or layer. The films can be in the form of an alloy. Exemplary SixGe1-xSny films include from 0 or greater than 0 at % to about 15 at % or about 2 at % to about 15 at % tin, from 0 or greater than 0 at % to about 30 at % or about 1 at % to about 30 at % silicon, or about 55 at % to about 65 at % or about 75 at % to about 95 at % germanium. The layers can include additional elements, such as carbon (e.g., GeSnSiC alloys) and/or other elements, such as phosphorous, boron, or other elements commonly used as dopants, and/or trace amount of other elements.
In accordance with some exemplary embodiments of the disclosure, methods of forming a SixGe SnY layer on a substrate include the steps providing a reactor having a reaction space, providing a substrate within the reaction space, providing silane coupled to the reaction space, providing a germanium precursor (e.g., germane) coupled to the reaction space, providing a tin precursor source coupled to the reaction space, and epitaxially forming a layer of SixGe1-xSny on a surface of the substrate. One or more of the precursors can be mixed at or near an inlet of the reaction chamber—e.g., at an inlet or injection manifold of the reactor. In accordance with further aspects, a cross-flow reactor is used to form the SixGe1-xSny layer(s). In accordance with yet further aspects, a ratio of flowrate of silane to the tin precursor (not including carrier gasses) ranges from about 2 to about 5, or about 2 to about 10, or about 2 to about 15. Exemplary methods can further include providing additional precursors, such as carbon precursors and/or dopant precursors, to the reaction space; such additional precursor(s) can be mixed with one or more of the other precursors at or near the inlet of the reaction chamber and/or further upstream of the reactor.
Other exemplary methods of forming a SixGe1-xSny layer on a substrate include the steps providing a reactor (e.g., a cross-flow reactor) having a reaction space, providing a substrate within the reaction space, providing a silicon source (e.g., silane) coupled to the reaction space, providing germane coupled to the reaction space, providing a tin precursor source coupled to the reaction space, and epitaxially forming a layer of SixGe1-xSny on a surface of the substrate. A ratio of flowrate of silane to the tin precursor ranges from about 2 to about 15 or other silane:tin precursor ratios as set forth herein. Exemplary methods can further include providing additional precursors, such as carbon precursors and/or dopant precursors, to the reaction space; such additional precursor(s) can be mixed with one or more of the other precursors at or near the inlet or further upstream of the reaction chamber.
A reaction space temperature for methods described herein can range from about 200° C. to about 500° C., about 275° C. to about 475° C., or about 300° C. to about 420° C. Exemplary reaction chamber pressures during this step range from about 500 Torr to about 760 Torr, about 600 Torr to about 760 Torr, or about 700 Torr to about 760 Torr. The relatively low temperatures and/or relatively high pressures allow for low throughput times associated with manufacturing structures and devices comprising one or more SixGe1-xSny layers formed as described herein.
In accordance with exemplary aspects of various embodiments of the disclosure, a ratio of flowrates or partial pressures of the precursors can be selected to promote high-quality film formation under high volume manufacturing conditions.
In accordance with additional embodiments of the disclosure, a structure includes one or more SixGe1-xSny films—e.g., formed using a method disclosed herein. Structures can also include additional layers, such as layers typically used to form devices. For example, the structures can include a germanium layer, which can form a buffer layer, and/or a fin layer as part of a FinFET device.
In accordance with yet additional exemplary embodiments of the disclosure, a device includes or is formed using a structure including one or more SixGe1-xSny films.
And, in accordance with yet additional exemplary embodiments of the disclosure, a system for forming one or more SixGe1-xSny films includes a gas-phase reactor including a reaction space, a germanium precursor (e.g., germane) source coupled to the reaction chamber, a tin precursor source coupled to the reaction space, and a silicon precursor (e.g., silane) source coupled to the reaction space. The system can be configured to mix (e.g., have an operational control mechanism configured to cause mixing of) one or more of the precursors (e.g., all precursors) at or near an inlet of a reaction chamber (e.g., at an injection manifold).
Both the foregoing summary and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.



BRIEF DESCRIPTION OF THE DRAWING FIGURES
A more complete understanding of exemplary embodiments of the present disclosure may be derived by referring to the detailed description and claims when considered in connection with the following illustrative figures.
FIG. 1 illustrates a system for forming one or more SixGe1-xSny films in accordance with exemplary embodiments of the disclosure.
FIG. 2 illustrates a method of forming a SixGe1-xSny film in accordance with further exemplary embodiments of the disclosure.
FIG. 3 illustrates an XRD plot showing SixGe1-xSny layers of various compositions grown with fixed SiH4, GeH4, and SnCl4 flows formed in accordance with exemplary embodiments of the disclosure.
FIG. 4 illustrates an RBS plot showing an exemplary SixGe1-xSny layer on Ge buffer with 5% Sn and 8% Si formed in accordance with exemplary embodiments of the disclosure.
FIG. 5 illustrates Raman spectra of various SixGe1-xSny films formed in accordance with exemplary embodiments of the disclosure.
FIGS. 6-13 illustrate exemplary structures according to yet additional exemplary embodiments of the present disclosure.



It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of illustrated embodiments of the present disclosure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE DISCLOSURE
The description of exemplary embodiments of methods, systems, structures, and devices provided below is merely exemplary and is intended for purposes of illustration only; the following description is not intended to limit the scope of the disclosure or the claims. Moreover, recitation of multiple embodiments having stated features is not intended to exclude other embodiments having additional features or other embodiments incorporating different combinations of the stated features.
The present disclosure relates, generally, to methods of forming layers, such as crystalline alloy layers including silicon, germanium, and tin, overlying a substrate. The silicon germanium tin (SixGe1-xSny) layers can include additional elements, such as carbon, which forms part of a crystalline lattice with the silicon germanium tin layer and/or dopants (e.g., p-type dopants, such as boron (B) and/or n-type dopants, such as phosphorous (P) and Arsenic (As)).
Exemplary SixGe1-xSny layers include from 0 or greater than 0 at % to about 15 at % tin, about 2 at % to about 15 at % tin, or about 3 at % to about 12 at % tin. SixGe1-xSny can include greater than 0 at % tin, greater than 2 at % tin, or greater than 3 at % tin. The SixGe1-xSny layers can additionally or alternatively include from 0 or greater than 0 at % to about 30 at % silicon, or about 1 at % to about 30 at % silicon, or about 3 at % to about 25 at % silicon. Exemplary SixGe1-xSny layers can additionally or alternatively include about 55 at % to about 65 at % germanium, or about 60 at % to about 70 at % germanium, or about 80 at % to about 90 at % germanium. When the layers include carbon, the SixGe1-xSnyC layers can include from 0 or greater than 0 at % to about 1 at % carbon, or about 2 at % to about 3 at % carbon, or about 4 at % to about 5 at % carbon.
The SixGe1-xSny layers can be used to form structures and devices suitable for a variety of applications, including strain layers to increase mobility of carriers in other layers in semiconductor devices, as part of quantum well structures and devices, and/or as layers in photonic devices. Exemplary structures and devices are discussed below.
As used herein, a “substrate” refers to any material having a surface onto which material can be deposited. A substrate can include a bulk material such as silicon (e.g., single crystal silicon, single crystal germanium, or other semiconductor wafer) or can include one or more layers overlying the bulk material. Further, the substrate can include various topologies, such as trenches, vias, lines, and the like formed within or on at least a portion of a layer of the substrate. Exemplary substrates include a silicon wafer, a layer comprising germanium overlying silicon, and a layer comprising germanium tin overlying silicon.
Turning now to the figures, FIG. 1 illustrates a system 100 suitable for forming SixGe1-xSny layers on a substrate using the methods described herein. In the illustrated example, system 100 includes a reactor 102, a silane source 104, a germanium (e.g., germane) precursor 106 source, a tin precursor source 108, purge and/or carrier gas source 110, an optional mixer 112, an optional intake plenum 114, and an exhaust (e.g., vacuum) source 116. Sources 104-110 may be coupled to mixer 112 or reactor 102 using lines 118-132 and valves 134-140. Although not illustrated, a system, such as system 100, may include additional sources and corresponding delivery lines for other precursors, such as carbon precursors and/or dopants (e.g., n-type dopants such as phosphorous or arsenic or p-type dopants such as boron). Additionally or alternatively, one or more dopants may be included in one or more of the precursor sources 102-108. Further, although separately illustrated, two or more dopants may be mixed in a common source.
The sources can be relatively pure—e.g., about 99.999% or greater pure or can be mixed with a carrier. In the case of silane, silane source 104 can include about 1 to 10 at % silane in a carrier or about 100 at % silane. Similarly, the germanium precursor source 106 (e.g., germane) can include about 1.5% to about 5 at % or about 10 at % germane in a carrier. Further, exemplary systems can comprise, consist essentially of, or consist of the precursors noted herein.
Reactor 102 can be a standalone reactor or part of a cluster tool. Further, reactor 102 can be dedicated to a particular process, such as a deposition process, or reactor 102 may be used for other processes—e.g., for layer passivation, cleaning, and/or etch processing. For example, reactor 102 can include a reactor typically used for epitaxial chemical vapor deposition (CVD) processing, such as an Epsilon® 2000 Plus, Epsilon® 3200, or Intrepid XP, available from ASM, and may include direct plasma, and/or remote plasma apparatus (not illustrated) and/or various heating systems, such as radiant, inductive, and/or resistive heating systems (also not illustrated). Using a plasma may enhance the reactivity of one or more precursors. The illustrated reactor is a single-substrate, horizontal-flow (cross-flow) reactor, which enables laminar flow of reactants over a substrate 142, with low residence times, which, in turn, facilitates relatively rapid sequential substrate processing. An exemplary CVD reactor suitable for system 100 is described in U.S. Pat. No. 7,476,627, issued to Pomarede et al. on Jan. 13, 2009, the contents of which are hereby incorporated herein by reference, to the extent such contents do not conflict with the present disclosure. The cross-flow reactor was found to produce high-quality SixGe1-xSny layers on a surface of a substrate under conditions that are suitable for high-volume, relatively low-cost manufacturing.
An operating pressure of a reaction chamber 144 of reactor 102 may vary in accordance with various factors. Reactor 102 may be configured to operate at near atmospheric pressure or at lower pressures, which allows relatively fast formation of the SixGe1-xSny layers—e.g., compared to ultra-high vacuum or molecular beam epitaxy techniques. By way of examples, an operating pressure of reactor 102 during layer formation steps ranges from about 500 Torr to about 760 Torr, about 600 Torr to about 760 Torr, or about 700 Torr to about 760 Torr. A reaction space temperature can range from about 200° C. to about 500° C., about 275° C. to about 475° C., or about 300° C. to about 420° C.
Silane source 104 includes silane (SiH4) and can optionally include a carrier. Silane source 104 can optionally include one or more dopant compounds, such as compounds typically used to fabricate photonic and/or semiconductor devices. Exemplary p-type dopant compounds include B2H6 and exemplary n-type dopant compounds include PH3 and AsH3. Use of silane is advantageous over the use of higher order silane compounds, such as disilane, trisilane, tetrasilane (Si4H10), neopentasilane (Si5H12), and higher order silanes, because silane is relatively less expensive and is more readily available. The inventors found that using pressures, a cross-flow reactor, and/or the ratio of reactants disclosed herein allows for formation of high-quality SixGe1-xSny layers using silane—rather than higher order silanes.
Germanium precursor source 106 can include germane (GeH4) and may optionally include one or more carrier gasses and/or dopant compounds, such as compounds typically used to fabricate photonic and/or semiconductor devices—e.g., B2H6 and/or PH3, AsH3.
Use of germane is advantageous over other precursors, such as digermane, trigermane, and other higher-order germanes, used to form SixGe1-xSny layers, because germane is relatively selective when mixed with various carrier gasses (e.g., hydrogen, nitrogen, or the like) and is also relatively selective, even when dopants (e.g., p-type dopants) are used with the precursor. Also, germane is relatively safe, compared to higher order digermanes, and thus can be used and/or transported in higher quantities, compared to higher order germanes. Also, germane can be used as a precursor for other layers, such as germanium, and is more readily available and is less expensive, compared to higher-order germane compounds.
Tin precursor source 108 includes any compound suitable for providing tin to a SixGe1-xSny layer. Exemplary tin precursors include tin chloride (SnCl4), deuterated stannane (SnD4), and methyl and/or halide substituted stannanes, such as compounds having a formula Sn(CH3)4-nXn, in which X is H, D (deuterium), Cl, or Br and n is 0, 1, 2, or 3; ZSn(CH3)3-nXn, in which Z is H or D, X is Cl or Br, and n is 0, 1, or 2; Z2Sn(CH3)2-nXn in which Z is H or D, X is Cl or Br, and n is 0 or 1; or SnBr4. Some exemplary tin precursors suitable for use with the present disclosure are discussed in more detail in application Ser. No. 13/783,762, filed Mar. 4, 2013, entitled TIN PRECURSORS FOR VAPOR DEPOSITION AND DEPOSITION PROCESSES, the contents of which are hereby incorporated herein by reference, to the extent such contents do not conflict with the present disclosure.
Purge and/or carrier gas source 110 may include any suitable purge or carrier gas. Exemplary gasses suitable as carrier and purge gasses include nitrogen, argon, helium, and hydrogen.
System 100 can also include a gas distribution system. An exemplary gas distribution system, which allows for fast switching between gasses (e.g., from sources 104-110) is set forth in U.S. Pat. No. 8,152,922 to Schmidt et al., issued Apr. 10, 2012, entitled “Gas Mixer and Manifold Assembly for ALD Reactor,” the contents of which are hereby incorporated herein by reference, to the extent the contents do not conflict with the present disclosure. The gas distribution system may be used to, for example, mix one or more precursor gasses and a carrier gas (which may be the same or different from a purge gas from gas source 108) prior to the gasses reaching plenum 114 or reactor 102.
Turning now to FIG. 2, an exemplary method 200 of forming a SixGe1-xSny layer is illustrated. Method 200 includes the steps of providing a gas-phase reactor (step 202), providing a substrate within the gas-phase reactor (step 204), providing precursors to a reaction space of the reactor (step 206), and forming a SixGe1-xSny layer overlying the substrate (step 208). Method 200 can optionally include one or more of forming an insulating layer overlying the substrate (step 210), and/or forming a via within the insulating layer (step 212).
During step 202, a gas-phase reactor, such as a CVD reactor suitable for epitaxial growth, is provided. The reactor can be a single-substrate, laminar cross-flow reactor. Suitable reactors are available from ASM, under the name Epsilon® 2000 Plus, Epsilon® 3200, and Intrepid XP.
During step 204, a substrate is provided within a reaction chamber of a reactor. The substrate may be received from a loading load lock of a reactor system and transported to the reaction space, such as a reaction chamber, using a suitable transfer mechanism. During this step, the reaction space can be brought to a suitable pressure and temperature for SixGe1-xSny layer formation, such as the pressures and temperatures noted herein.
At step 206, the silane, germanium precursor, and the tin precursor are provided to the reaction space of the reactor. The precursors can comprise, consist essentially of, or consist of these precursors. The silane, germanium precursor, and tin precursor can be mixed (e.g., at mixer 112) prior to entering the chamber. The silane, germanium precursor, and tin precursor can individually or in various combinations be mixed with one or more carrier gasses prior to entering the reaction space. One or more of the precursors, in any combination, can be mixed with a carrier upstream of the reaction chamber, such as at a mixer, upstream of a mixer, and/or within the respective source. During this step, a partial pressure of silane can range from about 5 Torr to about 20 Torr; a partial pressure of the germanium precursor (e.g., germane) can range from about 300 Torr to about 450 Torr; or a partial pressure of the tin precursor (e.g., tin chloride) can range from about 1 Torr to about 3 Torr.
During step 208, a crystalline layer (e.g., an epitaxial layer) of SixGe1-xSny is formed overlying a substrate. As noted above, an operating pressure of a reaction space during layer formation steps can range from about 500 Torr to about 760 Torr, about 600 Torr to about 760 Torr, or about 700 Torr to about 760 Torr. And, a reaction space temperature can range from about 200° C. to about 500° C., about 275° C. to about 475° C., or about 300° C. to about 420° C.
During step 210, any suitable insulating layer, such as silicon oxide or silicon nitride, is deposited onto the substrate. Then, during step 212, one or more vias are formed within the insulating layer. Reactive ion etching or other suitable technique can be used to form the one or more vias.
In the cases where steps 210 and 212 are performed, the SixGe1-xSny layer formed during step 206 can be selectively formed within the vias. As noted above, use of a germane precursor is advantageous because it is relatively selective when using a variety of carrier gasses, such as hydrogen, and/or when the layer includes one or more dopants, such as p-type dopants.
FIG. 3 illustrates an X-Ray diffraction (XRD) plot of SixGe1-xSny layers of various compositions grown with fixed silane, germane, and tin chloride flow rates over a layer of germanium overlying a silicon substrate. A reaction space temperature during the deposition of the films varied between 300° C. and 375° C. The plot illustrates that a composition of the SixGe1-xSny layers can be adjusted to be lattice matched to germanium or can be increasingly strained.
FIG. 4 illustrates aligned and random yield of Rutherford backscattering spectra of a SixGe1-xSny layer formed overlying a germanium layer on a silicon substrate. The SixGe1-xSny includes about 5% tin and about 8% silicon and was grown at a temperature of about 320° C. The low yield of the aligned spectra relative to the random spectra indicates that the SixGe1-xSny layer is a substitutional alloy.
FIG. 5 illustrates Raman spectra of SixGe1-xSny layers of various compositions, illustrating ternary binding in the films and that the films are substitutional alloys.
FIGS. 6-12 illustrate exemplary structures 600-1200 that can be formed—e.g., using the exemplary systems and/or methods described herein.
Structure 600 includes a substrate 602, a buffer layer 604, and a SixGe1-xSny layer 606 (e.g., epitaxially formed overlying layer 604). Substrate 602 can include, for example, a silicon substrate. Substrate 602 can include additional layers of materials used to form electronic or photonic devices. Buffer layer 604 can include or be, for example, a layer of germanium that is epitaxially formed overlying substrate 602. SixGe1-xSny layer 606 can be formed using, for example, method 200. Structure 600 can be used to form a variety of electronic or photonic devices.
A thickness of buffer layer 604 can range from, for example, about 0.5 to about 0.7, or about 0.8 to about 0.9, or be about one micron thick. A thickness of SixGe1-xSny layer 606 can range from about 1 to about 9, or about 10 nm to about 100 nm in thickness.
Structure 700 is similar to structure 600, except structure 700 includes an additional layer 708. Structure 700 includes a substrate 702, a buffer layer 704, a SixGe1-xSny layer 706, and a germanium layer 708. Substrate 702, buffer layer 704, and SixGe1-xSny layer 706 can be the same as the corresponding substrate and layers described in connection with FIG. 6 and can have the same thicknesses. A thickness of germanium layer 708 can range from about 1 to about 3, or about 4 to about 9 or be about 10 nm thick. Germanium layer 708 can be epitaxially formed overlying SixGe1-xSny layer 706 using, e.g., an epitaxial process with germane as a precursor.
Structure 800 includes a substrate 802, a buffer layer 804, a SixGe1-xSny layer 806, and a germanium tin (GeSn) layer 808 epitaxially formed overlying SixGe1-xSny layer 806. Substrate 802 and layers 804-806 can be the same or similar to corresponding layers described above in connection with FIGS. 6 and 7 and have the same thicknesses. GeSn layer 808 can have a thickness of about 1 to about 3, or about 4 to about 9, or be about 10 nm. GeSn layer 808 can be formed by, for example, using germane and a tin precursor such as tin chloride. GeSn layer 808 can include, for example, about 1 at % to about 8 at % or about 9 at % to about 15 at % tin.
Structure 900 includes a substrate 902, a germanium layer 904, a GeSn layer 906, and a SixGe1-xSny layer 908. The composition of the layers can be the same as the corresponding layers described above in connection with FIG. 8 (with germanium layer 904 corresponding to buffer layer 804). In the illustrated example, buffer layer 904 can have the same thickness as buffer layers 604-804; a thickness of GeSn layer can range from about 100 nm to about 400 nm, or about 500 nm to about 900 nm, or be about 1000 nm. SixGe1-xSny layer 908 can have the same thickness as SixGe1-xSny layers 606, 706, and 806. Structure 900 is similar to structure 800, except GeSn layer 906 and SixGe1-xSny layer 908 are formed in reverse order—compared to the structure illustrated in FIG. 8.
Structure 1000, which is suitable for quantum well structures and devices, includes a substrate 1002, a buffer layer 1004, first SixGe1-xSny layer 1006, GeSn layer 1008, and second SixGe1-xSny layer 1006. The various layers can be formed as described above. Buffer layer 1004, first and second SixGe1-xSny layers 1006 and 1010, and GeSn layer 1008 can have the same thickness noted above. By way of example, buffer layer 1004 can be about 1 micron thick, first SixGe1-xSny layer 1006 and second SixGe1-xSny layer 1010 can each be about 50 nm thick, and GeSn layer 1008 can be about 10 nm thick. Layers 1008-1010 can be repeated a desired number of times to form a quantum well structure.
FIG. 11 illustrates another structure 1100 that is suitable for use as a quantum well structure or device. Structure 1100 includes a substrate 1102, a buffer layer 1104, a first SixGe1-xSny layer 1106, a first Ge layer 1108, a GeSn layer 1110, a second Ge layer 1112, and a second SixGe1-xSny layer 1114. Buffer layer 1104, first and second SixGe1-xSny layers 1106 and 1114, first and second Ge layers 1108 and 1112, and GeSn layer 1110 can have the same thickness noted above. By way of example, buffer layer 1104 can be about 1 micron thick, first SixGe1-xSny layer 1106 can be about 50 nm thick, first Ge layer 1108 and second Ge layer 1112 can be about 50 nm thick, GeSn layer 1110 can be about 10 nm thick, and second SixGe1-xSny layer 1114 can be about 10 nm thick. Layers 1106-1114 can be repeated a desired number of times to form a quantum well structure.
FIG. 12 illustrates yet another structure 1200 in accordance with various embodiments of the disclosure. Structure 1200 includes substrate 1202, first SixGe1-xSny layer 1204, GeSn layer 1206, and second SixGe1-xSny layer 1208. Structure 1200 is similar to structure 1000, except structure 1200 does not include buffer layer 1004. The layers of structure 1200 can be formed using the same techniques used to form structure 1000 and the layers can have the same or similar thicknesses.
FIG. 13 illustrates yet another structure 1300 in accordance with additional exemplary embodiments of the disclosure. Structure 1300 includes a substrate 1302, an insulating layer 1304, a via 1306 formed within insulating layer 1304, a germanium layer 1308 (e.g., epitaxially formed overlying substrate 1302), and a SixGe1-xSny layer 1310 (e.g., epitaxially formed overlying layer 1308). Layers 1308 and/or 1310 can be selectively formed within via 1306—e.g., using method 200. Substrate 1302, germanium layer 1308, and SixGe1-xSny layer 1310 can be the same or similar to respective layers described above and can have the same or similar thicknesses. Insulating layer 1304 can include silicon oxide, silicon nitride, and/or silicon oxynitride. A thickness of insulating layer 1304 can range from about 1 to about 10 nm, or about 10 to about 100 nm.
It is to be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense. In the case of exemplary methods, specific routines or steps described herein can represent one or more of any number of processing strategies. Thus, the various acts illustrated can be performed in the sequence illustrated, performed in other sequences, performed simultaneously, or omitted in some cases.
The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various processes, layers, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.

## Claims

1. A method of forming a SixGe1-xSny layer on a substrate, the method comprising the steps of:
providing a reactor having a reaction space;
providing a substrate within the reaction space;
providing silane coupled to the reaction space;
providing a germanium precursor coupled to the reaction space;
providing a tin precursor source coupled to the reaction space; and
epitaxially forming a layer of SixGe1-xSny on a surface of the substrate,
wherein a pressure in the reaction space is between about 500 Torr and about 760 Torr and a temperature in the reaction space is between about 200° C. and about 500° C.,
wherein a ratio of a flowrate of the silane to a flowrate of the tin precursor is between about 2 to about 15, and
wherein the SixGe1-xSny layer comprises about 2 at % to about 15 at % tin, and about 55 at % to about 65 at % germanium.

2. The method of forming a SixGe1-xSny layer according to claim 1, wherein the germanium precursor comprises germane.

3. The method of forming a SixGe1-xSny layer according to claim 1, wherein, during the step of epitaxially forming a layer of SixGe1-xSny on a surface of the substrate, an operating pressure of the reaction space is between about 600 Torr and about 760 Torr.

4. The method of forming a SixGe1-xSny layer according to claim 1, wherein the layer of SixGe1-xSny comprises about 3 at % to about 12 at % tin.

5. The method of forming a SixGe1-xSny layer according to claim 1, wherein the layer of SixGe1-xSny comprises greater than 0 to about 30 at % silicon.

6. The method of forming a SixGe1-xSny layer according to claim 1, wherein the layer of SixGe1-xSny comprises about 1 at % to about 2 at % carbon.

7. The method of forming a SixGe1-xSny layer according to claim 1, wherein, during the step of epitaxially forming a layer of SixGe1-xSny on a surface of the substrate, a ratio of the silane to the germanium precursor provided to the reaction space is about 2 to about 15.

8. The method of forming a SixGe1-xSny layer according to claim 1, wherein, during the step of epitaxially forming a layer of SixGe1-xSny on a surface of the substrate, a ratio of the silane to the germanium precursor provided to the reaction space is about 3 to about 12.

9. The method of forming a SixGe1-xSny layer according to claim 1, wherein, during the step of epitaxially forming a layer of SixGe1-xSny on a surface of the substrate, an operating temperature within the reaction space is about 275° C. to about 475° C.

10. The method of forming a SixGe1-xSny layer according to claim 1, wherein the step of providing a tin precursor comprises providing a tin source selected from one or more of the group of SnCl4, SnD4, and a methyl and/or halide substituted stannate.

11. The method of forming a SixGe1-xSny layer according to claim 1, wherein the step of epitaxially forming a layer of SixGe1-xSny on a surface of the substrate comprises growing a crystalline layer comprising about 4 at % to about 5 at % carbon.

12. The method of forming a SixGe1-xSny layer according to claim 1, wherein the step of epitaxially forming a layer of SixGe1-xSny on a surface of the substrate comprises growing a crystalline layer comprising 1 at % to about 30 at % silicon.

13. A method of forming a structure comprising a SixGe1-xSny layer, the method comprising the steps of:
providing a cross-flow reactor comprising a reaction space;
providing a substrate within the reaction space; and
forming a crystalline layer comprising SixGe1-xSny on a surface of the substrate using silane and germane,
wherein, during the step of forming, a pressure in the reaction space is between about 500 Torr and about 760 Torr and a temperature is between about 200° C. and about 500° C.,
wherein, during the step of forming, a ratio of the silane to the germane provided to the reaction space is about 2 to about 15,
wherein a ratio of a flowrate of the silane to a flowrate of a tin precursor is between about 2 to about 15, and
wherein the SixGe1-xSny layer comprises about 2 at % to about 15 at % tin, and about 60 at % to about 70 at % germanium.

14. The method of forming a structure comprising a SixGe1-xSny layer of claim 13, wherein the substrate comprises a layer comprising germanium overlying silicon.

15. The method of forming a structure comprising a SixGe1-xSny layer of claim 13, wherein the layer comprising SixGe1-xSny comprises about 3 from greater than 0 at % tin to about 12 at % tin.

16. The method of forming a structure comprising a SixGe1-xSny layer of claim 13, wherein the layer comprising SixGe1-xSny comprises from greater than 0 at % silicon to about 30 at % silicon.

17. The method of forming a structure comprising a SixGe1-xSny layer of claim 13, wherein the layer comprising SixGe1-xSny comprises about 2 at % germanium to about 3 at % carbon.

18. The method of forming a structure comprising a SixGe1-xSny layer of claim 13, further comprising the steps of:
forming an insulating layer overlying the substrate;
forming a via within the insulating layer, and
selectively forming the layer comprising SixGe1-xSny within the via.

19. A structure comprising a crystalline layer of SixGe1-xSny formed according to the method of claim 13.

20. The structure of claim 19, wherein the structure comprises a layer comprising germanium overlying the crystalline layer of SixGe1-xSny.