WO2024124127A1

WO2024124127A1 - Float-zone boule growth using gas precursors

Info

Publication number: WO2024124127A1
Application number: PCT/US2023/083114
Authority: WO
Inventors: David Levi Young; Mark Jon Loboda
Original assignee: Alliance For Sustainable Energy, Llc; Hemlock Semiconductor Operations, Llc
Priority date: 2022-12-09
Filing date: 2023-12-08
Publication date: 2024-06-13

Abstract

Described herein are devices and methods for the production of single crystal boules which utilize in-situ generation of polycrystalline precursors, thereby reducing both energy on monetary costs. A single float zone furnace is used to both generate the polycrystalline starting material from gases and transform the polycrystalline material into a single crystal boule via heating.

Description

FLOAT-ZONE BOULE GROWTH USING GAS PRECURSORS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Patent Application No. 63/386,724, filed December 9, 2023, the contents of which are incorporated herein by reference in their entirety.

CONTRACTUAL ORIGIN

[0002] This invention was made with government support under Contract No. DE-AC36- 08G028308 awarded by the Department of Energy. The government has certain rights in the invention.

SUMMARY

[0003] Described herein are devices and methods for the production of single crystal boules which utilize in-situ generation of polycrystalline precursors, thereby reducing both energy on monetary costs. A single float zone furnace is used to both generate the polycrystalline starting material from gases and transform the polycrystalline material into a single crystal boule via heating. Advantageously, the described devices and methods may also increase the purity of the produced single crystal, allow for increased production rates and allow for facile doping of the crystalline material.

[0004] One useful application of the provided devices and methods is for the generation of high- purity single crystal silicon, which has a variety of applications including semiconductors, photovoltaics, LEDs and electronic devices. However, the devices and methods may be used for the generation of any single crystal material, including Gallium Arsenide, Silicon Nitride, Sapphire and Cadmium Telluride.

[0005] In an aspect, provided is a furnace comprising: a) a chemical vapor deposition (CVD) growth zone for generating a polycrystalline material; b) a gas inlet in physical communication with the growth zone for providing precursor gases; c) a heating zone in physical communication with the float growth zone, comprising a heating element; and d) a movable seed crystal housing in physical communication with the heating zone for holding a seed single crystal and pulling the generated polycrystalline material through the heating zone, wherein the CVD growth zone, the heating zone and the movable seed crystal housing are all contained in a single furnace chamber. [0006] Additionally, the gas precursors may be generated in close proximity to the furnace, for example, by using a fluid bed reactor connected to the furnace capable of generating silicon- containing chemical compounds. An example is generating silanes by flowing HC1 through fluidized bed silicon. The reactor may comprise a quartz shroud to direct the gases to the polycrystalline seed.

[0007] The reactor may be configured so that the boule generation is performed in the upward direction with respect to gravity. The movable crystal housing may hold a seed single crystal, such as single crystal Si. The heating element may be a radio frequency heating coil.

[0008] The reactor may be useful for the production of other semiconducting materials, including for example, GaAs, Ge, GaN and/or sapphire. The seed crystal and precursor gases can be substituted accordingly.

[0009] The growth zone may comprise quartz, for example, a quartz chamber encapsulating the growth zone and the quartz layer may be further encapsulated by a stainless steel chamber. The furnace may have a means for varying pressure, for example, by increasing or decreasing the gas inlet pressure. Varying the pressure allows for further control of the growth the polycrystalline material.

[0010] In an aspect, provided in a method comprising: a) providing a plurality of precursor gases to a float zone furnace; b) reacting the precursor gases in the presence of a polycrystalline seed crystal to form a polycrystalline material; c) heating the polycrystalline material while in contact with a seed single crystal to form a single crystal material; and d) pulling the single crystal material through a heating zone, thereby generating a single crystal boule; wherein the method in performed in a modified single float zone furnace chamber.

[0011] In the example of single crystal silicon, the gas precursors may comprise Hz and a gas comprising Si, such as HSiCh, SiH4, SiCh. Due to the in-situ generation, the polycrystalline seed crystal may be much smaller (i.e., having a shorter length in the direction which the crystal is being pulled), for example, having a vertical length of less than or equal to 50 cm, 25 cm, 20 cm, 15 cm, or optionally, 10 cm. Additionally, the described devices and methods may allow for faster production rates than traditional methods, for example, generating a vertical length of single crystal boule greater than or equal to 1 pm/min, 5 pm/min, 10 pm/min, or optionally, 15 pm/min. The diameter of the polycrystalline rod may be, for example, greater than or equal to 150 mm, 200 mm, or optionally 300 mm.

[0012] The method may also be used to generate GaAs, GaN, Ge or sapphire by adjusting the precursor gases (e.g., Ga, Ge, N, sapphire precursor) and the corresponding seed crystal.

BRIEF DESCRIPTION OF DRAWINGS

[0013] Some embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting.

[0014] Figure 1 provides an exemplary cross-sectional schematic of a float zone furnace as described herein.

[0015] Figure 2 provides an example reactor for the production of Si.

[0016] Figures 3A-3B provide modeled growth rates for Si at 1 atm (Figure 7A) and 10 atm (Figure 7B), the modeling indicates that high temperature and high temperature are necessary to achieve a high enough growth rate to match the necessary pull rate.

[0017] Figure 4 provides a model comparison of growth rate for a 6 inch Si boule.

[0018] Figure 5 illustrates that uniformity increases with a higher TCS mole fraction, uniformity and growth rate are maximized around x = 0.90.

[0019] Figure 6 illustrates growth rate increases with temperature, but it also increased nonuniformity. Growth rate and uniformity are maximized at a temperature of about 1473 K.

[0020] Figure 7 provides an example schematic for a process for the traditional Siemens process for producing Si semiconductors/solar-grade boules.

[0021] Figure 8 shows the two main techniques for growing single-crystal silicon boules. (Left) The Czochralski process uses melted polySi chunks to pull a boule from the melt, (right) The Float Zone process “zone melts” a polySi seed rod into a single-crystal boule.

[0022] Figure 9 provides an example schematic including the reactor described herein where the Seimens process is bypassed and instead HSiCh gas is routed directly into a modified float-zone puller reactor (CVD-Fz).

[0023] Figure 10 provides an example reactor as described herein. REFERENCE NUMERALS

100 Float zone furnace

110 CVD growth zone

120 Heating zone

130 Single crystal zone

140 Gas precursors

150 Poly crystalline material (seed material or generated material)

160 Heating element

170 S eed cry stal hou si ng

180 Seed single crystal

190 Single crystal boule

200 Gas inlet

DETAILED DESCRIPTION

[0024] The embodiments described herein should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein. References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, “some embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0025] As used herein the term “substantially” is used to indicate that exact values are not necessarily attainable. By way of example, one of ordinary skill in the art will understand that in some chemical reactions 100% conversion of a reactant is possible, yet unlikely. Most of a reactant may be converted to a product and conversion of the reactant may asymptotically approach 100% conversion. So, although from a practical perspective 100% of the reactant is converted, from a technical perspective, a small and sometimes difficult to define amount remains. For this example of a chemical reactant, that amount may be relatively easily defined by the detection limits of the instrument used to test for it. However, in many cases, this amount may not be easily defined, hence the use of the term “substantially”. In some embodiments of the present invention, the term “substantially” is defined as approaching a specific numeric value or target to within 20%, 15%, 10%, 5%, or within 1% of the value or target. In further embodiments of the present invention, the term “substantially” is defined as approaching a specific numeric value or target to within 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% of the value or target.

[0026] As used herein, the term “about” is used to indicate that exact values are not necessarily attainable. Therefore, the term “about” is used to indicate this uncertainty limit. In some embodiments of the present invention, the term “about” is used to indicate an uncertainty limit of less than or equal to ±20%, ±15%, ±10%, ±5%, or ±1% of a specific numeric value or target. In some embodiments of the present invention, the term “about” is used to indicate an uncertainty limit of less than or equal to ±1%, ±0.9%, ±0.8%, ±0.7%, ±0.6%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, or ±0.1% of a specific numeric value or target.

[0027] Fig. 1 provides an exemplary cross-sectional schematic of a float zone furnace 100, as described in the present application. A single chamber of the furnace is divided into a CVD growth zone 110, a heating zone 120, and a single crystal zone 130. Gas precursors 140, such as silane gases and hydrogen are fed into the furnace via a gas inlet 200, proximate to the CVD growth zone 110. The gas precursors 140 react in the presence of a polycrystalline material 150 (either a poly crystalline seed or reaction material from previous gas precursors 140) to form additional polycrystalline material 150. The polycrystalline material 150 is then heated in the heating zone 120 via a heating element 160 in the presence of a seed single crystal 180 to form single crystal or monocrystalline material. The new single crystal material can be drawn in the direction of the arrow in Fig. 1 via the seed crystal housing 170, thereby elongating the single crystal material and generating a single crystal boule 190.

[0028] The provided discussion and examples have been presented for purposes of illustration and description. The foregoing is not intended to limit the aspects, embodiments, or configurations to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the aspects, embodiments, or configurations are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the aspects, embodiments, or configurations, may be combined in alternate aspects, embodiments, or configurations other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the aspects, embodiments, or configurations require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. While certain aspects of conventional technology have been discussed to facilitate disclosure of some embodiments of the present invention, the Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects discussed herein. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate aspect, embodiment, or configuration.

Example 1 - Float zone Silicon Boule Growth using Gas Precursors

[0029] In one embodiment, the present application aims to lower the cost, energy input, and carbon footprint of silicon photovoltaics (PV) by circumventing the Siemens process in poly-Si production plants and instead use the high-purity, silicon-containing gases to grow poly-Si rods in-situ during the float-zone (Fz) boule growth process. In large poly-Si plants (e.g., Hemlock Semiconductor), quartz is reduced to metallurgical-grade silicon which is used to produce trichlorosilane gas (“TCS”, HSiCh) and other silanes through distillation. These gases offer the highest purity Si (in terms of metallic impurities) found throughout the process. To produce poly- Si, TCS is mixed with H2 in a large chemical vapor deposition (CVD) chamber where it contacts heated silicon seed rods. The contact with the heated rods results in deposition of silicon on the seed rod. This latter step is known as the Siemens process and represents nearly half the cost of poly-Si, two-thirds of the energy and carbon input. These costs contribute to the wafer being half the cost of the final PV cell. The present application provides a means to eliminate the Siemens process represents a significant path to lowering manufacturing costs for photovoltaics.

[0030] In-situ Polycrystalline Generation: Figs. 7-9 show a Gas-to-Fz furnace described herein. In the traditional Fz method a poly-Si rod is grown by the Siemens process and melted into a single crystal boule by using a crystalline seed crystal and zone melting with an RF heating coil. The Fz boule has fewer impurities (higher lifetime) than a Cz boule due to the absence of a Si melt being in contact with a crucible. The Gas-to-Fz furnace (one embodiment is shown in Fig. 9 takes advantage of the clean growth environment of Fz to make ultra-high lifetime wafers at greatly reduced cost by growing the poly-Si rod in situ using vapor phase deposition. Referring to Fig. 9, the single-crystal boule is formed in the same way as with traditional Fz by passing the poly-Si rod through the zone melting region, but the starting poly-Si seed rod is now very short (10 cm). Silicon containing gases (e.g., HSiCh, SiH4, SiCh) are injected onto the hot, upper surface of the poly-Si seed where they deposit Si at very high growth rates (~20 pm/min). The growing poly-Si seed crystal is pulled downward into the zone heating RF coil where it melts and recrystallizes in the orientation of the seed crystal, as in traditional Fz. Essentially, the Siemens poly-Si deposition process is brought into the Fz furnace, saving cost, capital expenditure, energy, carbon, and time. The advantages of Fz vs Cz boules are numerous including lower impurities, lower oxygen content, fewer consumables, shorter heating cycles, faster pull rates, and less energy consumption. Additionally, dopant gases can be included in the poly-Si growth to provide uniform doping along the length of the boule which is currently a challenge for n-type, phosphorus-doped Cz boules due to a low segregation coefficient. The result is that Fz quality boules can be made at lower cost than Cz boules. The present application provides a path to lower wafer costs and increased module efficiency by providing higher lifetime wafers to the PV industry.

[0031] Increased Rate and Boule Size: In the traditional Fz method a poly-Si rod is grown by the Siemens process and melted into a single crystal boule by using a crystalline seed crystal and zone melting with an RF heating coil. The Fz boule has lower impurities (high lifetime) than a Cz boule due to the absence of the melt being in contact with a crucible. Traditional Fz boules are limited in length and diameter due to the surface tension of the melt region. The new Gas-Recharge Fz Furnace takes advantage of the clean growth environment of Fz to make ultra-high lifetime wafers at greatly reduced cost. First, the starting seed crystal is a short (~10 cm) section of a Cz boule that is lowered into the heating coil region to melt the end of the seed. Second, silicon containing gases (e g., HSiCE, SiH4, SiCE) are injected onto the hot, lower end of the seed crystal to deposit poly- Si onto the boule at very high growth rates (20 pm/min). The seed crystal is pulled up, forcing the poly-Si region through the heating coil where it melts and recrystallizes in the orientation of the seed crystal, as in traditional Fz. The boule may be pulled for much longer lengths and wider diameters (200-300 mm), both on par with Cz boules, due to the lower weight of the boule below the melted region (surface tension limited). Essentially, the Siemens poly-Si deposition process is brought into the Fz furnace, saving cost, energy and time. Additionally, dopant gases can be included to provide uniform doping along the length of the boule which is currently a challenge for n-type, phosphorus-doped boules. The result is that Fz quality boules can be made at lower cost than Cz boules. Thus, the present application lowers wafer costs and increases the efficiency of modules by providing higher lifetime wafers, thereby improving the $/W ratio.

[0032] The described processes require that the poly-Si growth rate at the face of the poly-Si rod match the boule pull speed (~1 mm/hr). Poly-Si can be grown at much higher rates than epitaxial films and the described Fz furnace allows optimization of the gas compound mixtures, temperature, pressure and gas flow to the surface of the Fz rod to obtain the needed growth rates.

Example 2 - Lowering Cost and Environmental Footprint of Solar and Semiconductor- Grade Silicon Boules

[0033] Described herein are devices and methods designed to lower the cost, energy input, and carbon footprint of high purity silicon (Si), a critical material used for photovoltaics (PV) and semiconductor devices, by demonstrating a new, disruptive technology that will revolutionize the silicon wafer industry. Fig. 7 outlines the incumbent process for producing high purity silicon (99.999999999% pure) boules and wafers using the “Siemens” process, large, multi-billion dollar polycrystalline Si (poly-Si) plants, e.g., those operated by team member Hemlock Semiconductor in partnership with Dow Chemical, metallurgical-grade silicon is used to produce silicon- containing gases via reaction with anhydrous HC1. Semiconductor grade trichlorosilane (TCS) (SiHCh) is extracted from the Si-chloride mixture via distillation, and represents the highest purity Si, in terms of metallic impurity concentration, found throughout the process. To produce semiconductor-grade poly-Si, TCS is mixed with H2 in a large chamber and allowed to deposit elemental silicon onto large, electrically resistively heated poly-Si seed rods. This step is known as the Siemens process and represents nearly one-half the cost of poly-Si, two-thirds of the energy and carbon output from electrical generation and has a 90 hour cycle time. These companies use the Czochralski (Cz) crystal growing method to “pull” a cylindrical boule from a molten bath of poly-Si chunks contained in a quartz crucible. The Cz method is slow, has elemental segregation challenges along the length of the boule, and contaminates (Oxygen, Iron, Nickel, etc) build up in the boule as the molten silicon gradually dissolves impurities from the quartz crucible.

[0034] The present application is directed towards lower the cost, embodied energy, and CO2 in the poly-Si process by eliminating the Siemen’s process and instead use the high-purity gases to directly grow poly-Si boules inside a modified float-zone crystal puller. Fig. 9 illustrates how TCS could be routed directly to such a reactor. Fig. 10 shows an illustration an exemplary “chemical vapor deposition float zone” (CVD-Fz) reactor design. In the described CVD-Fz process, TCS that normally would go to the Siemens process is fed directly into the CVD-Fz reactor, where it deposits as fresh Si onto the face of a poly-Si seed boule in situ, as it is being pulled through an RF melting zone. As the boule emerges from the heating zone it recrystallizes into the crystal orientation of the seed boule. The result is a gas-to-boule growth process that, compared to the incumbent technology, uses less energy, produces less CO2, costs less and produces a float-zone boule with semiconductor qualities that are far superior to Cz-pulled boules. Effectively the Siemens process is brought into a float-zone reactor where poly-Si production and boule crystal growth can share a common, localized, and efficient heat source while saving Cz consumables, and poly-Si post processing and transportation costs. The described reactor may also be used to generate other semiconductor materials, for example, GaAs, GaN, Ge, Sapphire and the like.

[0035] Fig. 10 shows a detailed schematic of the reactor. It consists of two major parts: 1) the chemical vapor deposition (CVD) chamber where the silicon-containing gases are allowed to decompose to deposit poly-Si onto a heated seed boule; and 2) the float-zone chamber where the silicon boule is rotated and pulled through a heating zone to melt the poly-Si previously deposited onto the face of the polycrystalline boule and recrystallize into a single-crystal float zone boule. The separation of the CVD gases from the float-zone inert gas is a factor (Argon in Fig. 10). This gas separation is achieved by controlling pressure differentials, gas flows, carefully designed gas baffles, and dynamic gas curtains. The walls of the reactor are built from fused quartz tubes or plates to withstand chemical corrosion, but they, in turn, are contained within a stainless-steel chamber for safety and to allow pressure optimization of the gas decomposition reaction. For the Siemens reaction hydrogen reacts with TCS gas to form elemental silicon and HC1 gas

SiHCl₃ gas^ + H₂ -> Si(s) + 3HCl gas'). “Siemens process” [1] [0036] For the Union Carbide reaction, silane thermally decomposes into elemental silicon and H2

SiH₄ gas) -> Si(s) + 2H₂. “Union Carbide process” [2]

[0037] Fig. 9-10 illustrate the reactor using the Siemens reaction for clarity. Within the CVD portion of the reactor TCS and H2 gases are introduced and allowed to flow over the face of a preprepared cylindrical boule which acts like a substrate for the poly-Si deposition. The reacted gas forms poly-Si at very high growth rates (no need for epitaxial growth) and the unreacted gases are recycled back into the reactor as is done in a siemens reactor. The boule’s face is held within the chemical vapor zone but pulled up and out of the CVD zone at the same rate as the poly-Si deposition rate (100s of pm/min to mm/min). As the boule is pulled through the heating zone (an inductively coupled radio frequency coil) the poly-Si melts. Rotation of the boule ensures thorough mixing of the melt. As the boule passes out of the heating zone it begins to crystallize in the same orientation as the upper part of the boule. The result is a continuous growth of a single crystal, float-zone quality boule. The large upper single-crystal section of the boule can be harvested for wafering, but a small section or “seed boule” will be left to continue the growth process. Note: The first boule used to start the process is a single-crystal boule grown by the traditional Cz or Fz process. This is important to set the orientation of the growing boule, but after the first boule is harvested, the tool makes its own starter boule.

[0038] The CVD-Fz growth rates can be demonstrated via modeling. Using previous kinetic constants for the deposition reaction using TCS, we calculate that it is possible to achieve growth rates comfortably within the 10s to 100s of pm/min range (see Fig. 3). The other half of the process, involving float zone crystallization of Si, is commonly employed in industry.

[0039] Effectively, the Siemens poly-Si deposition process is brought into the Fz furnace, saving cost, CapEx, energy, and carbon. Moreover, because the CVD-Fz process produces Fz-wafers, the quality of the wafers is much higher than Cz wafers. For example, in photovoltaic applications we expect 1-2% absolute efficiency gains compared to cells fabricated with Cz wafers due to the very high minority carrier bulk lifetimes (t > 20 ms) and with lower degradation rates stemming from lower impurity levels. Semiconductor grade wafers will also improve due to the lower oxygen, carbon, and metal impurity levels that cause surface precipitates (e.g., Ni) that short out nanometerscale features in today’s devices. [0040] Furthermore, CVD-Fz boules require fewer consumables (less Argon, no crucibles), use more efficient zone RF heating, less maintenance and higher uptime, and uses far less energy per boule than the Cz process. Additionally, dopant gases can be introduced during the poly-Si growth to provide uniform doping along the length of the boule, which is otherwise a challenge for n-type, phosphorus-doped Cz boules due to a low segregation coefficient. The result is that Fz quality, uniformly doped boules with low impurity levels and high lifetimes can be grown continuously from the gas phase while eliminating the capex, operational costs, and pollution of the Siemens process and the Cz process.

[0041] The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments, exemplary embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the present invention and it will be apparent to one skilled in the art that the present invention may be carried out using a large number of variations of the devices, device components, methods steps set forth in the present description. As will be obvious to one of skill in the art, methods and devices useful for the present methods can include a large number of optional composition and processing elements and steps.

[0042] As used herein and in the appended claims, the singular forms "a", "an", and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to "a cell" includes a plurality of such cells and equivalents thereof known to those skilled in the art. As well, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein. It is also to be noted that the terms "comprising", "including", and "having" can be used interchangeably. The expression “of any of claims XX- YY” (wherein XX and YY refer to claim numbers) is intended to provide a multiple dependent claim in the alternative form, and in some embodiments is interchangeable with the expression “as in any one of claims XX- YY.” [0043] When a group of substituents is disclosed herein, it is understood that all individual members of that group and all subgroups, are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure. For example, when a device is set forth disclosing a range of materials, device components, and/or device configurations, the description is intended to include specific reference of each combination and/or variation corresponding to the disclosed range.

[0044] Every formulation or combination of components described or exemplified herein can be used to practice the invention, unless otherwise stated.

[0045] Whenever a range is given in the specification, for example, a density range, a number range, a temperature range, a time range, or a composition or concentration range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. It will be understood that any subranges or individual values in a range or subrange that are included in the description herein can be excluded from the claims herein.

[0046] All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains. References cited herein are incorporated by reference herein in their entirety to indicate the state of the art as of their publication or filing date and it is intended that this information can be employed herein, if needed, to exclude specific embodiments that are in the prior art. For example, when composition of matter is claimed, it should be understood that compounds known and available in the art prior to Applicant's invention, including compounds for which an enabling disclosure is provided in the references cited herein, are not intended to be included in the composition of matter claims herein.

[0047] As used herein, “comprising” is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of' excludes any element, step, or ingredient not specified in the claim element. As used herein, "consisting essentially of' does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms "comprising", "consisting essentially of' and "consisting of may be replaced with either of the other two terms. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.

[0048] All art-known functional equivalents, of any such materials and methods are intended to be included in this invention. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

Claims

CLAIMS What is claimed is:

1. A furnace comprising: a chemical vapor deposition (CVD) growth zone for generating a polycrystalline material; a gas inlet in physical communication with the growth zone for providing precursor gases; a heating zone in physical communication with the CVD growth zone, comprising a heating element; and a movable seed crystal housing in physical communication with the heating zone for holding a seed single crystal and pulling the generated polycrystalline material through the heating zone to convert the polycrystalline material to a crystalline material, wherein the CVD growth zone, the heating zone and the movable seed crystal housing are all contained in a single furnace chamber.

2. The furnace of claim 1 further comprising a fluid bed reactor in fluidic communication with the gas inlet for generating the precursor gases.

3. The furnace of claim 2, wherein the furnace is connected to a fluid bed reactor which is capable of generating chemical compounds comprising Si.

4. The furnace of claim 3, wherein the fluid bed reactor is capable of generating HSiCh, SiT , SiClz or a combination thereof.

5. The furnace of any of claims 1-4, wherein the float growth zone further comprises a quartz shroud.

6. The furnace of any of claims 1-5, wherein the movable seed crystal housing pulls the generated polycrystalline material through the heating zone in an upwards direction with respect to gravity.

7. The furnace of any of claims 1-6, wherein the movable seed crystal housing further comprises a seed single crystal. The furnace of claim 7, wherein the seed crystal is single crystal Si. The furnace of any of claims 1-8, wherein the heating zone further comprises a radio frequency heating coil. The furnace of any of claims 1-9, wherein the poly crystalline material is Si, GaAs, GaN, Ge or sapphire. The furnace of any of claims 1-10, wherein the CVD growth zone comprises a quartz layer encapsulating the growth zone. The furnace of claim 11, wherein the quartz layer is encapsulated by a stainless steel chamber. The furnace of any of claims 1-12, wherein the furnace further comprises a means for varying internal pressure to control growth rate of the poly crystalline material. A method comprising: providing a plurality of precursor gases to a float zone furnace; reacting the precursor gases in the presence of a polycrystalline seed crystal to form a polycrystalline material; heating the polycrystalline material while in contact with a seed single crystal to form a single crystal material; and pulling the single crystal material through a heating zone, thereby generating a single crystal boule; wherein the method in performed in a single float zone furnace chamber. The method of claim 14, wherein the precursor gases comprise H2 and a gas comprising Si. The method of claim 15, wherein the gas comprising Si is HSiCh, SiT , SiCh or a combination thereof. The method of claim 14, wherein the precursor gases comprise Ga, As, Ge, N2, sapphire or a combination thereof. The method of claim 17, wherein the polycrystalline material comprises GaAs, GaN, Ge or sapphire. The method any of claims 14-18, wherein the polycrystalline seed crystal comprises Si. The method of any of claims 14-19, wherein the seed single crystal comprises Si. The method of any of claims 14-20, wherein the step of heating is performed by a radio frequency heating coil. The method of any of claims 14-21, wherein the step of pulling comprises pulling in the upward direction with respect to gravity. The method of any of claims 14-22, wherein the poly crystalline seed crystal has a vertical length of less than or equal to 25 cm. The method of any of claims 14-23, wherein the method generates the single crystal boule at a rate greater than or equal to 5 pm/min with respect to vertical length.