MXPA01001604A - - Google Patents

Description

METHOD AND SYSTEM TO STABILIZE THE GROWTH OF GLASS OF DENDRÍTICA MESH BACKGROUND OF THE INVENTION The present invention relates to a system and process for the growth of dendritic mesh crystals. More particularly, the present invention relates to a system and process for stabilizing the growth of dendritic mesh crystals. It has long been recognized that dendritic mesh ribbon crystals lend themselves as almost ideal substrates for solar cells due to their high chemical purity, low density of structural defects, rectangular shape and relatively thin crystal size. In addition, solar cells manufactured from dendritic mesh silicon have light energy for electrical energy conversion efficiencies as high as 17.3%, which is comparable to the high efficiencies obtained using expensive processes such as Float Zone silicon and other processes. well-known complexes. Figure 1 shows a diagram of a silicon crystal of dendritic half 10 in the form of a silicon ribbon or sheet emerging as a single crystal from a silicon melt 14 contained in a crucible 12. In order to solidify the 10 mesh silicon crystal during the crystal growth process, the silicon melt 14 is maintained at a few degrees below the freezing point of the silicon (1412 ° C) inside the crucible 12. The silicon crystal 10 is grown typically when extracting upwards on a top dendrite bubble 22 at a speed of approximately 1.5 cm / min. The resulting dendritic mesh silicon crystal 10 includes a portion of silicon mesh 16 bonded by the silicon dendrites 18. The mesh portion 16 is typically approximately 3 to 6 cm wide and approximately 100 μm thick compared to the nominally square dendrites 18, which are typically approximately 700 μm thick. In order to sustain the growth of the above described crystal, the dendrite support structure must be continuously regenerated at the pointed dendrite points 20, below the surface of the silicon melt 14. Unfortunately, the growth processes of the mesh crystal Conventional dendritic suffer from several disadvantages. By way of example, conventional dendritic mesh crystal growth processes are difficult to market because they are "metastable" and subject to premature termination of crystal growth. Although in rare cases a dendritic mesh crystal greater than about 5m can be grown and having a width ranging from about 3 to about 6 cm, minor random disturbances in the growth environment often end in premature growth of the crystal. As a result, most crystals, according to conventional methods, typically cease their growth after 1-2 hours when the crystals are of lengths ranging from about 1 to about 2 or less than the commercially desirable length of 5 hours. more Thus, conventional crystal growth techniques fail to reproducibly provide sufficiently large crystals. As another example, the additional costs and wasted time associated with the premature termination of crystal growth makes the conventional mesh crystal growth process undesirable. After the premature termination of crystal growth, it takes the operator 1 or 2 hours to configure the dendritic mesh crystal growth system to initiate the growth of the next crystal. Consequently, valuable labor costs and time are spent to start the crystal growth again. Still another example, when conventional mesh glass growth techniques are employed, most of the crystals grow under conditions of transient state, instead of steady state conditions. A crystal that starts at a width of about 3 cm is gradually dilated due to transient conditions to a value that is between about 5 and about 6 cm over several meters in length. The finished glass should be trimmed to have a width consistent with the total length. Thus, the solar cells that are currently manufactured from mesh glass tapes produced by conventional techniques, are made in such a way that S B wastes the expense of the surface of mesh crystals, excessively valuable. Therefore, what is needed is a system and method for stabilizing the dendritic mesh crystal growth that can be marketed without suffering from the disadvantages of conventional methods described above. SUMMARY OF THE INVENTION. The present invention provides an improved system and process for growth of dendritic mesh crystals, which substantially outweigh the previously noted problems of premature termination of crystal growth. In one aspect, the present invention provides a process for dendritic mesh growth that includes: providing a fusion; grow a dendritic mesh crystal from the fusion; replenish the fusion during the growth stage of the dendritic mesh crystal; and applying a magnetic field to the fusion during the growth stage of the dendritic mesh crystal. The dendritic mesh crystal of the present invention can be a silicon or germanium crystal. Therefore, the fusion employed in one embodiment of the present invention includes at least one material selected from the group consisting of silicon and germanium. In another embodiment of the present invention, the fusion further includes tin. The step of applying the magnetic field to the fusion may include providing a magnetic field force that allows the dendrites that support the mesh crystal to regenerate continuously below the melting surface. The strength of the magnetic field can generally be greater than or equal to about 400 Gauss and can preferably be between about 400 and about 2500 Gauss. According to one embodiment of the present invention, the growth step includes extracting a silicon bubble crystal from the fusion. The dendritic mesh crystal is extracted at a rate that is generally greater than or equal to about 1.5 cm / min and preferably greater than or equal to about 1.8 cm / min, to ensure that the growth of the dendritic mesh silicon crystal does not cease prematurely. . The refueling step of the melt may include supplying silicon tablets to the melt. The speed of supply of the tablets is generally greater than or equal to 0.20 g / min and preferably may or equal to 0.40 g / min. In an embodiment of the present invention, the step of applying the magnetic field includes producing a magnetic field that is oriented perpendicular to the plane of the mesh crystal. Alternatively, in another embodiment of the present invention, the magnetic field is oriented parallel to the plane of the mesh crystal in the horizontal direction. In yet another embodiment of the present invention, the magnetic field is in the vertical direction and perpendicular to the plane of fusion. In another aspect the present invention provides an apparatus for the growth of the dendritic mesh. The apparatus includes: (1) a crucible that includes a feeding compartment for receiving the tablets to facilitate the replenishment of the fusion and a growth compartment designed to contain a fusion for the growth of the dendritic mesh; and (2) a magnetic field generator configured to provide a magnetic field lasted for the growth of the dendritic mesh. The ciparate of the present invention further includes a growth furnace and the above-mentioned crucible is placed inside the growth furnace. The magnetic field generator, according to one embodiment of the present invention, includes an electromagnet or a permanent magnet, which is installed outside the growth furnace. The magnetic field generator of the present invention can be a superconducting magnet that is installed outside the growth furnace. In embodiments wherein the magnetic pole pieces serve as generators of the magnetic field of the present invention, the magnetic pole pieces include at least one portion that is: located outside the growth furnace. According to one embodiment of the present invention, the magnetic field generator is configured to produce a magnetic field that is oriented perpendicular to the plane of the mesh crystal and the energy consumed by the magnetic field generator is meshed to produce the magnetic field of the magnetic field. enough strength. Alternatively, in another embodiment of the present invention, the magnetic field generator is configured to produce a magnetic field that is oriented in the horizontal direction and parallel to the plane of the mesh crystal. The magnetic field generator can also be configured to produce a magnetic field that is in the vertical direction and perpendicular to the plane of the mesh fusion. In yet another aspect, the present invention provides a dendritic mesh crystal fabricated using a process that includes: providing a fusion; growing a dendritic mesh crystal from the fusion; rebalance the fusion during the growth phase of the dendritic mesh crystal; and applying a magnetic field to the fusion during the growth stage of the dendritic mesh crystal. The step of applying the magnetic field to the fusion may include providing a magnetic field force that allows the dendrites that support the mesh crystal to be generated continuously below the melting surface. These and other features of the present invention will be described in more detail later in the detailed description of the invention and in conjunction with the following figures BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated by way of example and not by way of example. of limitation, in the figures of the accompanying drawings, in which: Figure 1 shows a cross-sectional view of the growth of the dendritic mesh silicon crystal, according to conventional techniques, from a silicon fusion. Figure 2 shows a graphical representation of the dendrite thickness versus dendrite length for a dendritic mesh silicon crystal that was developed using conventional techniques Figure 3 shows a cross-sectional view of a system to stabilize crystal growth of dendritic mesh silicon, according to a modality of the present invention Figure 4 shows a top view of an empty crucible, without the liquid melt, which is employed in the system of Figure 3. Figure 5 shows a separate perspective view of a growth apparatus, in which the growth of the silicon crystal of The dendritic mesh shown in Figure 3 is carried out according to one embodiment of the present invention. Figure 6 shows a separate perspective view of u: growth furnace having incorporated in it the growth equipment of Figure 5 to produce dendritic mesh silicon crystals with magnetic melt stabilization, according to an embodiment of the present invention. Figure 7 shows a graphical representation of the thickness of the dendrite versus the length of the dendrite for a dendritic mesh silicon crystal that is developed according to the present invention. DESCRIPTION OF THE PREFERRED MODALITIES The present invention will now be described in detail with reference to the presently preferred embodiments as illustrated in the accompanying drawings. In the following description, the numbers of specific details are set i in order to provide a complete understanding of the present invention. However, it will be apparent to one of skill in the art that the present invention can be practiced without some or all of the specific details. By way of example, the advantages offered by the systems and processes of the present invention apply but are not limited to the growth of dendritic mesh crystal. Dendritic mesh crystals including germanium can also be grown using the processes and systems of the present invention. In other cases, the steps of the process and / or well-known structures have not been described in detail in order not unnecessarily to obscure the present invention. Although the dendritic mesh crystal growth process has been known for more than 35 years and has the above noted advantages for solar cell applications, the technology is not commercially viable due to its metastable nature. The commercialization of the dendritic mesh crystal growth process has been hampered because the conventional dendritic mesh crystal growth systems and methods employed have failed to recognize the reasons for the premature termination of crystal growth. In addition, the principles of glass growth processes in commercially viable volume, such as that of Czochralski, Float Zone and Britgman, contribute little or nothing to the commercialization of crystal growth processes of dendritic mesh because the glass growth processes in volume, have stable crystal growth and do not suffer from premature termination of crystal growth. The stability of the crystal growth processes in volume, at least partially, results from the fact that the crystals in appreciable mass volume develop from a large melting / crystal interface area. The appreciable crystal mass makes the glass growth processes in volume, relatively insensitive to melting temperature fluctuations in the melting / crystal interface. Consequently the large mass of crystal in the processes of glass growth in volume serves as a thermal resistance. However, the present invention recognizes that the growth of thin-ribbon crystals by the dendritic mesh technique does not have the advantage of this thermal resistance. On the contrary, in order to maintain the crystal growth of the dendritic mesh, two sharp, needle-like dendrites should continue to form, penetrating approximately 5 mm in the fusion. These dendrites are too small to allow sufficient thermal resistance for the mesh crystal to withstand the fluctuations of the melting temperature. As a result, the low mass of dendrites and the small area of fusion interface / cristai. they do not conduct enough thermal resistance to displace the temperature fluctuations, which arise from the convective flow in the fusion fluid. Thus, dendritic mesh crystal growth is fundamentally less stable than crystal growth in volume. Although not intended to be bound by the theory, the present invention identifies the chaotic movement of the convection cells in the melt, as being responsible for the random fluctuations of temperature as well as the physical agitation which leads to the premature termination of the crystal growth process. As explained below, a crucible containing the liquid melt is generally divided into a feed chamber, which accepts the replenishment tablets during the growth of the crystal and a growth chamber from which the growing crystals emerge. Simultaneously to the growth, it places a crystal coming from the fusion and the feeding tablets to replenish the fusion opposite to the requirements in the fusion of silicon - - liquid. In the vicinity of the growth crystal, the liquid must be cooled below its melting point (supercooled) in order to continue cooling the glass cone melting composition. Not far from where the growth crystal emerges, the liquid silicon must be heated above its melting point so that the feeding tablets replenish the melting. Yet?Since the crucible includes a barrier to separate the feeding and growth chambers, it is determined that the barrier alone does not provide the thermal insulation necessary for the stable growth of the crystal. According to the present invention, a magnetic field applied to the melt during the crystal growth process effectively provides the necessary additional thermal insulation between the growth and feed chambers. Under a magnetic field of sufficient strength, the transfer of conductive heat from the heat supply chamber to the cold growth chamber is significantly suppressed. Thus, the application of the magnetic field exerts an advance resistance that effectively suppresses convective heat transfer from the feed chamber to the growth chamber, thus facilitating the task of feeding the melt during the glass growth process. In order to appreciate the effect of random temperature fluctuations on crystal growth in the absence of a magnetic field, it is important to recognize that the thickness of the dendrite provides a reliable indication of the melting temperature in the vicinity of growth of the submerged dendrite. As the local temperature of the fusion surrounding the growth of the dendrite decreases, the dendrite becomes thicker and as the local temperature increases, the dendrite becomes thinner. Thus, the thickness of each dendrite in real time (as the crystal grows) can be measured and recorded, using a video camera and image analysis software, for example, to generate a record of the effective local melting temperature. Figure 2 is provided as an exemplary graphical representation of the thickness of the dendrite versus the length of the dendrite for a crystal that ended at a length of 280 cm. As shown in Figure 2, before termination, the thickness of the dendrite ranges from about 580 to about 880 μm. Various measurements of; the dendrite reveal that the "window" of operation of the thickness of the dendrite for sustained growth is approximately 300 μm wide, approximately centered to approximately 700 μm for the example of Figure 2. These 300 μm wide window The thickness of the dendrite corresponds to a temperature window width of approximately 3 ° C within which the crystal can grow. It is believed that the crystal of Figure 2 ended when the dendrite became too thin because the fusion in the vicinity of those dendrites became too hot. At sufficiently high temperatures, the dendrites no longer regenerate on their own and, therefore, the support structure for the mesh crystal is lost. The crystal of Figure 2 fails due to "desynchronization by too much heat" (indicated as "POTH" in Figure 2) as is commonly known in the art, at a dendrite thickness of approximately 550μm. According to the present invention, the thickness of the dendrite of a growth crystal approaching an upper limit pmallaefinido, indicates that the local melting temperature becomes too cold and that the crystal is in danger of forming an additional dendrite unwanted between 'the two union dendrites. This third dendrite, commonly referred to in the art as "3a", interrupts the growth of the mesh portion thinly and frequently; causes the mesh portion to lose its glass structure. Consequently, the growth crystal runs the risk of ending prematurely. The dendrite of Figure 2, for example, becomes as thick as 280 μn, indicating that the crystal was in danger of prematurely ending by the formation of a 3a in that - moment. The full operation window of 300 μm is consumed during the growth of the 280 cm glass, as shown in Figure 2. Such a variation in the dendrite thicknesses, corresponding to the variation in the melting temperature, is typical and largely uncontrollable by the operator of the glass oven. These variations, according to the present invention, are a reflection of the randomness inherent in the mesh growth process and are the reason for the termination of the crystals at random lengths. Essentially, the likelihood that crystal growth will be sustained over a given period of time (for example, 10 minutes, is constant, regardless of how large the crystal has grown at that time.) Such randomness causes the crystals of mesh terminate prematurely, impregnably, and prevent the crystals from growing "at will." In an effort to combat the aforementioned disadvantages, the present invention in one embodiment provides a process that includes applying a magnetic field of DC of suf? The magnetic field applied to the fusion moves the growth process of the dendritic mesh crystal from a region of metastabilided to a region of stability, thus allowing the growth of the dendritic mesh crystal. stable state of large crystals Figure 3 shows a system 100 for stabilizing the growth of silicate crystal dendritic mesh, according to one embodiment of the present invention. The HE dendrites, the mesh portion 116, the dendrite bubble 122, and the points pointed 120 below the fusion surface are shown in Figure 3 in substantially the same configuration as that shown in Figure 1. Referring to FIG. Figure 3, during the growth of the crystal, the crucible 112 contains the fusion 114 within the growth chamber and the fusion 128 within the feeding chamber. A small opening (not shown to facilitate illustration) in the barrier 126 allows the molten silicon to flow from the feed chamber into the growth chamber. The melt 114 is maintained at sufficiently cold temperatures so that it is below its melting point (supercooled) to continuously cool the melt composition as a crystal. In contrast, the melt 128 is heated above its melting point, so that the tablets being fed melt into the crucible 112. A pair of magnetic field generators 124 flank the crucible 112 and the dendritic mesh crystal in increase. The magnetic field generators 124 are capable of applying a CD magnetic field across the entire fusion 114 to effectively suppress undesired convection. By appropriately placing the near-field magnetic field generators 124 or grid of the system of Figure 3, the magnetic field is oriented either horizontally or vertically. In the horizontal direction, the produced magnetic field can be directed to the fusion in the X direction, that is, parallel or in the plane of the mesh crystal or in the Y direction, ie, perpendicular to the plane of the mesh crystal. In the vertical direction, the magnetic field is directed in the Z direction. Referring to Figure 3, in the X direction, the magnetic field strikes the dendrites 118, in the Y direction the magnetic field strikes the face of the portion of the magnetic field. 116 mesh, and in the Z direction, the magnetic field hits the dendrite bubbles 122 as they are extracted from the melt. Various factors may be considered when deciding which orientation of the magnetic field is preferred in a particular implementation of the present invention. By way of example, a magnetic field generated in the horizontal direction may be preferred either parallel or perpendicular to the plane of the mesh crystal, depending on whether the performance or energy consumption of the magnets is optimized. A magnetic field that is parallel to the plane of the mesh crystal can - provide high performance, for example, increased extraction speed, higher feed rates and greater stability at the expense of relatively higher energy requirements. In contrast, a magnetic field of force similar to that found perpendicular to the plane of the mesh crystal can effectively function under low power consumption at the expense of relatively poorer performance. As another example, the orientations that allow a small space between the magnetic field generators, offer energy consumption mesh through the magnetic coils of the magnetic field generator. In order to effectively suppress fusion convection, generally a magnetic field strength greater than or equal to 400 Gauss and preferably between approximately 400 and approximately 2500 Gauss is found. The necessary magnetic field can be created by magnetic field generators, such as electromagnets, for example conventional iron core magnets and superconducting magnets, or by permanent magnets. The magnetic field generators can be placed in different locations depending on how the crystal growth process is implemented. In those embodiments in which a growth furnace is employed, for example, in the embodiment of Figure 6, the permanent magnet can be installed inside the growth furnace, or alternatively the permanent magnet is installed outside the growth furnace. In addition, in those embodiments where a superconducting magnet is used, the superconducting magnet is generally installed outside the growth furnace. However, in a preferred embodiment, several components of the system shown in Figure 3 are constructed from materials that are substantially undecomposed by the presence of a magnetic field. Figure 4 shows a top view of an empty crucible 112 ', ie, without containing the liquid fusions 114 and 128 shown in Figure 3. According to one embodiment, the crucible 112' includes a growth chamber 132, from from which emerges the growing crystal, which is placed between two feeding chambers 130, which accept the refueling tablets. Those skilled in the art will recognize that it is not necessary to have the growth chamber gummed between two feeding chambers and in another embodiment, the growth chamber can be placed adjacent to a single feeding chamber. The balance between freezing and melting can be precarious, and modest adjustments in heating energy can compromise growth conditions or feeding conditions. In an attempt to achieve the proper balance between the melting and feeding conditions, the barriers 126 provide some measure of thermal insulation between these chambers. However, as mentioned above, the thermal insulation provided by the barriers alone is not sufficient to ensure simultaneous growth and feeding. For this purpose, the present invention applies a magnetic field of sufficient strength to improve the rate at which the silicon tablets can be fed into the melt during the growth of the crystal. Figure 5 shows a growth equipment 150 as an example of an implementation that has incorporated therein, the crucible structure shown in Figure 4. Thus, the dendritic mesh crystal 110, the crucible 112, the mesh portion 116 , the dendrites 118, the silicon fusion 114 and the dendrite bubbles 122 of Figure 5 are substantially in the same configuration as that shown in Figure 3. The growth equipment 150, as explained below, defines the temperature in and merger bin 114 and accommodates the feeding of tablets for refueling during the growth of the crystals. The dendritic mesh crystal is extracted from a growth compartment 184 of the fusion 114, which is contained in a quartz crucible 112 through a slot formed of a curved ribbon in a molybdenum cap (Mo) 170 and a cover 174.

- During the growth of the crystals, a constant depth of the fusion 114 is maintained by replenishing the composition of the melt, generally in the form of tablets, through a feed cavity 178 and into the feed compartment 180. The depth can be generally be between about 7 and about 15 mm and preferably between about 7 and 8 mm. A reflective laser beam (not shown to simplify the illustration) that penetrates the laser slot L82, effectively monitors the surface of the fusion during the crystal growth process from the surface of the growth equipment 150. In order to establish the Feeding ratios of the tablets in the illustrated embodiment, it is preferred to employ a melting level detection system. The resistance heaters 158, 160, 162, 164, and 168 surround and impart sufficient thermal energy through the susceptor 166 to the components of the growth equipment 150 and the growth dendritic mesh crystal to ensure that they are maintained at the proper temperature during the growth of the crystals. As mentioned above, the temperature within the feed compartment 1.80 is maintained above the melting point of the melt composition and the temperature within the growth compartment 184 is maintained at a temperature below the melting point of the composition. of fusion. The thermal insulation between the feed compartment 180 and the growth compartment 184 is facilitated by a barrier, for example a quartz barrier, placed between the compartments. The graphite thermal insulation (not shown to simplify illustration) also surrounds most of the growth equipment 150 to prevent unwanted heat loss. The covers 174 serve to mesh the heat loss from the heat cap 170, adapt the vertical temperature profile of the mesh 110 and effectively cool the mesh in a controlled manner to minimize thermal stress. Figure 6 shows a partial melt stabilization system, according to an embodiment of the present invention, which includes an electromagnet that has been integrated into a standard dendritic mesh crystal growth furnace heated by resistance 200 (hereinafter further referred to as a "growth furnace" to facilitate the expansion: The growth furnace 200 includes a cover 202 for housing growth equipment 236 that is substantially similar to the growth equipment 150 of Figure 5. The growth furnace 200 is equipped with a tablet feeding tube 204 which facilitates the feeding of tablets, for example, 1 mm silicon tablets, typically at room temperature to the feeding compartment of the growth equipment 236 through a feeding cavity in The growth team, however, the magnetic field generators 234, one of which is shown in FIG. e pole pieces, which are connected to magnetic coils 238 and are carried inside the growth furnace 200 and end exactly outside the insulation 216. The corresponding half of the magnetic pole pieces and coils on the left side of the equipment Growth is not shown to simplify the illustration. In this mode, the magnetic field is oriented horizontally in the plane of the mesh. In accordance with the illustrated embodiment of the present invention, the pole pieces 234 may extend toward the furnace cover 202 to just outside the graphite insulation 216 to increase the field strength for a given energy dissipation. The resulting space in the pole pieces 234, which may be approximately 12 inches in diameter, is approximately 19 inches, for example. In this embodiment, a magnetic field force of about 200 Gauss is achieved at the center of the fusion and an energy dissipation of about 20 kW is required in the magnet coils 238. However, other configurations of the pole pieces may be possible., the cover and the insulation. A process, according to one embodiment of the present invention, includes for example, providing a melt in the crucible 112 of Figure 5. A dendritic mesh crystal is grown or extracted using conventional techniques well known to those skilled in the art. in the matter. As the melting composition is depleted with the growing crystal, the tablets are fed into the crucible to replenish the melting composition. A magnetic field of sufficient force is then applied to the fusion, during the crystal growth process. The fusion includes at least one material selected from the group consisting of silicon and germanium and in some embodiments also includes tin. By way of example, the melt may include in addition to a small amount of adulterant, pure silicon or germanium, or silicon and tin, or germanium and tin. According to the present invention, applying the magnetic field to the fusion, effectively allows portions of the two dendrites submerged below the fusion surface to be continuously regenerated. Figure 7 shows a graph of the thickness of the dendrite versus the length of the dendrite for the growth of the silicon dendritic mesh crystal, according to the present invention using the apparatus shown in Figure 6. At a magnetic field strength of Approximately 200 Gauss and an extraction speed of approximately 1.53 cm / min, the mesh crystal of Figure 7 grows to 37.7 m, which at the time of growth was the largest dendritic mesh crystal ever produced, surpassing the record previously known 23 m. However, Figure 7 shows a variation, ie from about 530 μm to about 660 μm, in dendrite thicknesses over a 250 cm length portion typical of a mesh crystal, which has a width of about 3.8 cm and a approximate average thickness: e 113 μm. The crystal growth, according to the present invention, is stabilized because the range of thickness variation of approximately 130 μm as shown in Figure 7 consumes less than half of the available 300 μm window. It is worth remembering that the crystal growth according to conventional techniques consumes the entire 300 μm window, as shown in Figure 2 and ends prematurely by a thermal cause (POTH or 3a). The magnetic stabilization of the fusion according to the present invention, for the growth of the dendritic mesh crystal, significantly reduces convection and offers numerous advantages that are not realized by conventional dendritic mesh crystal growth systems and methods! . As an example, applying a magnetic field significantly reduces the convective heat transfer from the heat supply chamber to the cold growth chamber and therefore effectively provides additional thermal insulation between the feeding and growth chambers. In this form the feeding chamber is maintained at the appropriate elevated temperature without disturbing the growth conditions in the growth compartment. The growth of the crystal according to the present invention is therefore characterized by having a balanced mass flow rate, which is achieved when the rate of feeding of the tablets equals the rate of growth or extraction of the crystal. Thus, the fusion of the present invention is continuously and completely replenished. As another example, the present invention allows a higher rate of tablet feeding during crystal growth. Generally a narrower set of thermal conditions can be found to facilitate both growth and feeding at a rate of about 0.2 g / min without a magnetic field. According to the present invention, the application of a horizontal magnetic field in the plane of the mesh significantly expands the set of conditions that facilitates simultaneous growth and feeding. Feed rates up to approximately 0.4 g / min and higher, almost or more than double that which can be achieved without a magnetic field, are achieved during: the growth of the crystal. The higher extraction rates and the feed rates of the tablets for the fusion, move towards a greater total production for the growth process of the crystal of the present invention. Thus, a crystal growth process is achieved: stronger dendritic mesh. As yet another example, the growth of the dendritic mesh crystal of the present invention provides higher extraction rates, which are not achieved using conventional methods. Those skilled in the dendritic mesh crystal growth technique will recognize that the term "extraction speed" refers to the rate at which the growing mesh crystals are extracted from the fusion during the growth process of the mesh crystal. Extraction speeds as high as approximately 1.8 cm / min and higher, compared to current extraction rates of 1.5 cm / min, are achieved by the system and processes of the present invention. As yet another example, the growth of the crystal according to the present invention provides thinner and smoother dendrites. The thinner dendrites are desirable because smaller amounts of mesh glass are wasted or discarded when the dendrites are cut to make solar cells. It is desirable to have >R dendrites smoother due to the few structural defects (dislocations) that start with smooth dendrites than rough dendrites ("cracked"). The dissociations of the rough dendrites run the risk of propagation from the dendrite to the mesh portion, which serves as the substrate material for the manufacture of solar cells to degrade the electrical properties of the mesh portion. Therefore, it can be seen that new and novel processes and systems for dendritic mesh growth have been described. It will be appreciated by those skilled in the art, that given the teachings herein, it will be noted that there are numerous alternatives and equivalents embodied in the invention described herein. As a result, the invention is not limited by the foregoing exemplary embodiments, but only by the following claims.

Claims (26)

1. CLAIMS 1. A process for dendritic mesh growth, comprising: providing a fusion; grow a crystal of dendritic mesh from the fusion; replenish the fusion during the growth stage of the dendritic mesh crystal; and apply a magnetic field to the fusion during the growth stage of the dendritic mesh crystal.
2. 2. The process of claim 1, wherein the melt includes at least one material selected from the group consisting of silicon and germanium.
3. 3. The process of claim 2, wherein the melting includes tin addition.
4. 4. The process of claim 1, wherein the step of applying the magnetic field to the fusion includes providing a magnetic field force that allows the dendrites that support the mesh crystal to regenerate continuously under the surface of the fusion.
5. The process of claim 4, wherein the step of applying the magnetic field to the fusion includes providing the magnetic field as the two dendrites continuously regenerate beneath the surface of the fusion. - -
6. 6. The process of claim 1, wherein the magnetic field is greater than or equal to about 400 Gauss.
7. 7. The process of claim 6, wherein the magnetic field is between about 400 Gauss and about 2500 Gauss.
8. The process of claim 1, wherein the growth step includes extracting a silicon bubble crystal from the fusion and the dendritic mesh crystal is extracted at a rate that is greater than or equal to about 1.5 cm / min. to ensure that growth does not stop: l Silicon crystal dendritic mesh.
9. 9. The process of claim 8, wherein the extraction speed of the crystal is greater than or equal to about 1.8 cm / min.
10. The process of claim 1, wherein the step of replenishing the melt includes supplying silicon tablets to the melt at a rate that is greater than or equal to 0.20 g / min.
11. 11. The process of claim 10, wherein Silicon tablets are supplied to the melt at a rate that is greater than or equal to 0.4 g / min.
12. The process of claim 1, wherein the step of applying the magnetic field includes producing a magnetic field that is oriented perpendicularly. to the plane of the mesh crystal. -
13. 13. The process of claim 1, wherein the step of applying the magnetic field includes producing a magnetic field that is oriented parallel to the plane of the mesh crystal in the horizontal direction
14. 14. The process of claim 1, wherein the step of applying The magnetic field includes producing a magnetic field that; it is in the vertical direction and perpendicular to the plane of fusion.
15. 15. The process of claim 1, wherein the dendritic mesh crystal is a silicon crystal.
16. An apparatus for the growth of dendritic mesh, comprising: a crucible that includes a feeding compartment for receiving tablets to facilitate the replenishment of the fusion and a growth compartment designed to maintain a fusion for the growth of: the dendritic mesh; and a magnetic field generator configured to provide a magnetic field during the growth of the dendritic mesh.
17. The apparatus of claim 16, further comprising a growth furnace, and the crucible is placed inside the growth furnace.
18. The apparatus of claim 17, wherein the generator c.the magnetic field is a permanent magnet that is installed outside the growth furnace.
19. The apparatus of claim 17, wherein the magnetic field generator is a superconducting magnet that is installed outside the growth furnace.
20. The apparatus of claim 17, wherein the magnetic field generator includes pieces of magnetic poles having at least one portion that is located outside the growth furnace.
21. The apparatus of claim 16, where the magnetic field generator includes an electromagnet or a permanent magnet.
22. The apparatus of claim 16, wherein the electromagnet is configured to produce a magnetic field that is oriented perpendicular to the plane of the mesh crystal and the energy consumed by the electromagnet is meshed to produce the magnetic field of sufficient strength.
23. The apparatus of claim 16, wherein the electromagnet is configured to produce a magnetic field that is oriented in the horizontal direction and parallel to the plane of the mesh crystal.
24. The apparatus of claim 16, wherein the electromagnet is configured to produce a magnetic field that is in the vertical direction and perpendicular to the plane of the mesh fusion.
25. 25 A dendritic mesh crystal fabricated using a process comprising: providing a fusion; growing a dendritic mesh crystal from the fusion; replenishing the fusion during the growth stage of: 1 dendritic mesh crystal; and applying a magnetic field to the fusion during the growth stage of the dendritic mesh crystal.
26. 26. The dendritic mesh crystal of claim 25, wherein the step of applying the magnetic field to the fusion includes providing a magnetic field force that allows the dendrites that support the mesh crystal to be generated continuously under the surface of the fusion.