Quality evaluation method, evaluation silicon manufacturing system, and evaluation silicon manufacturing method

Abstract

To provide a quality evaluation method by which quality evaluation can be easily performed, a manufacturing method of evaluation silicon, evaluation silicon and a manufacturing system of evaluation silicon.SOLUTION: A quality evaluation method comprises a step for generating evaluation silicon, the step including growing polycrystalline silicon on a core 9 in a reactor 20 while generating single-crystal silicon radially extending from the core 9, and a step of performing evaluation using the single-crystal silicon.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a quality evaluation method using an aspect in which polycrystalline silicon is grown on a core wire in a reactor, a manufacturing system for evaluation silicon, a manufacturing method for evaluation silicon, and evaluation silicon. [Background technology]

[0002] Polycrystalline silicon is the raw material for single-crystal silicon used in semiconductors or silicon for solar cells. The Siemens process is a well-known method for producing polycrystalline silicon. The Siemens process generally involves contacting a silane source gas with a heated silicon core wire, and then depositing polycrystalline silicon on the surface of the silicon core wire using the CVD (Chemical Vapor Deposition) method.

[0003] In the Siemens method, silicon core wires are assembled into a torii-gate shape with two vertical and one horizontal core wire, and both ends of the torii-gate silicon core wires are connected to core wire holders and fixed to a pair of metal electrodes placed on a bottom plate. Generally, multiple sets of torii-gate silicon core wires are arranged inside a reactor.

[0004] The torii-shaped silicon core wire is heated to the deposition temperature by passing electricity through it, and a raw material gas, such as a mixture of trichlorosilane and hydrogen, is brought into contact with the silicon core wire, causing silicon to grow in the vapor phase, and a polycrystalline silicon rod of the desired diameter is formed in an inverted U shape.

[0005] As mentioned above, polycrystalline silicon produced by the Siemens process is used as a raw material for single-crystal silicon for semiconductors or silicon for solar cells. These require high purity with low impurity concentrations. Therefore, the raw material gases used in the Siemens process and the components used in the furnace must also be of high purity.

[0006] In this context, various proposals have been made for quality evaluation methods.

[0007] Patent Document 1 discloses a small-scale experimental reactor into which raw material gases are introduced online, and which grows polycrystalline silicon and evaluates its quality.

[0008] Patent Document 2 discloses an apparatus and an evaluation method capable of depositing single crystal silicon and evaluating components inside a furnace used in the Siemens process.

[0009] Furthermore, as a method for producing polycrystalline silicon, Patent Document 3 proposes rod-shaped polycrystalline silicon for use in producing single crystal silicon by the floating zone melting method, characterized in that the single crystal grains in the outer periphery of a coarsened region having coarsened silicon single crystal grains with an area equal to or larger than the minimum cross section of the melted zone during floating zone melting are refined. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] EP2636767 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-145118 [Patent Document 3] Japanese Patent Application Publication No. 03-252397 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0011] In Patent Document 1, small polycrystalline silicon is produced and its quality is evaluated. However, as described in Patent Document 1, it is not possible to evaluate low-concentration impurity concentrations in polycrystalline silicon as is using methods such as photoluminescence and Fourier transform infrared spectroscopy. Therefore, additional operations such as single-crystallization of the obtained polycrystalline silicon are required. Furthermore, in this case, it becomes necessary to consider the segregation of impurities when single-crystallizing.

[0012] In Patent Document 2, inorganic materials used in components of polycrystalline silicon manufacturing equipment are evaluated, and single-crystal silicon is grown and evaluated to evaluate low-concentration impurity concentrations. However, in the embodiment described in Patent Document 2, the source gas flows in a single pass, as in epitaxial growth, and it is not possible to create an environment in which the source gas, as in an actual polycrystalline silicon manufacturing environment, is accompanied by in-furnace circulating gas and rises. Furthermore, new equipment must be built to grow single-crystal silicon for inorganic material evaluation, which leads to increased costs.

[0013] Patent Document 3 proposes a method for producing polycrystalline silicon having coarse silicon single crystal grains, but the purpose of this method is to improve the melting state during float zone melting, and this technology has not been used in areas such as evaluation methods.

[0014] The present invention has been made in consideration of the above problems, and aims to provide a quality evaluation method that allows for easy quality evaluation, a method for manufacturing evaluation silicon, evaluation silicon, and a manufacturing system for evaluation silicon. [Means for solving the problem]

[0015] The quality evaluation method according to the present invention comprises: a step of producing silicon for evaluation, in which polycrystalline silicon is grown on a core wire in a reactor while single-crystal silicon extending radially from the core wire is grown; a step of evaluating using the single crystal silicon; may also be provided.

[0016] The quality evaluation method according to the present invention comprises: Further comprising a removal step of removing the evaluation silicon from the reactor, The evaluation may be performed using the single crystal silicon of the evaluation silicon taken out from the reactor.

[0017] The quality evaluation method according to the present invention comprises: Producing evaluation silicon in a plurality of reactors; Multiple evaluation silicon samples were produced in multiple reactors under the same conditions except for the growth time. Each evaluation silicon may be evaluated.

[0018] In the quality evaluation method according to the present invention, The method for growing polycrystalline silicon on the single crystal silicon core may be the Siemens method.

[0019] In the quality evaluation method according to the present invention, The evaluation target in the evaluation silicon may be one or more of P, As, B, Al, and C.

[0020] The evaluation silicon manufacturing system according to the present invention comprises: a supply pipe for supplying a raw material gas; a plurality of evaluation reactors connected to the supply pipe, each reactor growing polycrystalline silicon while growing single crystal silicon extending radially from a core wire to produce silicon for evaluation; a control unit that controls the supply of a raw material gas to each of the evaluation reactors; Equipped with The timing for starting or stopping the supply of the raw material gas to each of the evaluation reactors may be made different by a command from the control unit.

[0021] The evaluation silicon manufacturing system according to the present invention comprises: further comprising a conventional reactor for growing polycrystalline silicon; It may be possible to simultaneously grow polycrystalline silicon in a normal reactor and grow evaluation silicon in a plurality of evaluation reactors.

[0022] The method for producing evaluation silicon according to the present invention includes the steps of: When growing polycrystalline silicon on the single crystal silicon core, the single crystal silicon may be grown in the growth direction from the surface of the silicon core, and the growth of the single crystal silicon may continue up to at least 5 mm from the outer periphery of the polycrystalline silicon.

[0023] The method for producing evaluation silicon according to the present invention includes the steps of: Growth of single crystal silicon may continue for at least 3 mm from the periphery of the polycrystalline silicon.

[0024] The evaluation silicon according to the present invention is The single crystal silicon may be provided extending from the surface of the core wire in the growth direction, and in cross section, a part or all of the outer periphery of the single crystal silicon may be surrounded by polycrystalline silicon.

[0025] In the evaluation silicon according to the present invention, The single crystal silicon may extend from the surface of the core wire to at least 5 mm from the outer periphery of the polycrystalline silicon.

[0026] In the evaluation silicon according to the present invention, The single crystal may extend from the surface of the core wire to at least 3 mm from the periphery of the polycrystalline silicon.

[0027] In the evaluation silicon according to the present invention, The growth diameter of the single crystal silicon may be 30 mm or less. [Effects of the Invention]

[0028] By applying the present invention to the quality evaluation of polycrystalline silicon, the evaluation can be carried out easily and at reduced cost. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a cross-sectional view of polycrystalline silicon having a single crystal silicon portion formed therein according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view of a reactor according to an embodiment of the present invention. [Figure 3] 1 is a schematic diagram showing an example of a system for producing evaluation silicon used in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, an embodiment of the present invention will be described.

[0031] The quality evaluation method of this embodiment may include a step of producing evaluation silicon, which includes a step of growing polycrystalline silicon on a core wire 9 in a reactor 20, 40 (see FIG. 3) while producing single crystal silicon (referred to as a "single crystal silicon portion 6" in this embodiment) extending radially from the core wire 9 (see FIGS. 1 and 2), and a step of evaluating the single crystal silicon portion 6. A method for growing polycrystalline silicon on the single crystal silicon core wire 9 may be the Siemens method. By adjusting the conditions for the source gas and temperature increase and decrease, the single crystal silicon portion 6 extending radially from the core wire 9 can be produced while growing polycrystalline silicon. The reactors 20, 40 are provided at their bottoms with a supply nozzle 15 through which a source gas is supplied from a supply pipe 10 (see FIG. 3) and an outlet 19 through which the source gas and the like not used in the growth of the polycrystalline silicon are discharged (see FIG. 2). Although FIG. 2 shows a small evaluation reactor 20, a (large) normal reactor 40 of normal size is provided with a greater number of supply nozzles 15 and discharge ports 19 than those shown in FIG. 2.

[0032] In this embodiment, the single crystal silicon portion 6 produced in the process of producing polycrystalline silicon is used, but after a predetermined time has passed, the content ratio of polycrystalline silicon increases and polycrystallization progresses (the content ratio of polycrystalline silicon portion 5 increases), and ultimately a polycrystalline silicon rod made of polycrystalline silicon is produced. As shown in Figure 1, the polycrystalline silicon portion 5 is formed on the periphery of the single crystal silicon portion 6.

[0033] An extraction step of extracting the silicon for evaluation from the reactors 20 and 40 may be performed. In this case, evaluation may be performed using the single crystal silicon portion 6 of the silicon for evaluation extracted from the reactors 20 and 40. The evaluation according to this embodiment is expected to be mainly used for evaluation of the impurity content (evaluation of the raw material gas). It is generally necessary to grow single crystal silicon from polycrystalline silicon. However, according to this embodiment, the operation using the small FZ machine can be performed in a significantly shorter time, which is very beneficial in that evaluation using the single crystal silicon portion 6 can be performed quickly. In other words, this embodiment is very beneficial in that evaluation can be performed using the single crystal silicon portion 6 formed under each growth condition while growing polycrystalline silicon, thereby enabling evaluation of impurities, etc. contained in the single crystal silicon portion 6 at low cost and efficiently.

[0034] As shown in FIG. 3, multiple reactors 20, 40 may be used. FIG. 3 shows an evaluation system having a supply pipe 10 for supplying a source gas such as trichlorosilane (TSC), a conventional reactor 40 connected to the supply pipe 10, and multiple evaluation reactors 20 (three for each conventional reactor 40 in FIG. 3) connected to the supply pipe 10. Sub-gates 70 are provided between the branched supply pipes 10 and the evaluation reactors 20, allowing for individual control of the inflow rate of the source gas supplied to each evaluation reactor 20 and its on / off state. A first main gate 60 is provided on the supply pipe 10 connected to the evaluation reactor 20 after branching the conventional reactor 40 and the evaluation reactor 20, allowing for collective control of the inflow rate of the source gas supplied to each evaluation reactor 20 and its on / off state. A second main gate 80 is provided on the supply pipe 10 connected to the conventional reactor 40, allowing for control of the inflow rate of the source gas supplied to each conventional reactor 40 and its on / off state. Closing the second main gate 80 makes it possible to perform evaluation using only the evaluation silicon using only the evaluation reactor 20. The control unit 50 is connected to the sub gate 70, the first main gate 60, and the second main gate 80 by wire or wirelessly, and the sub gate 70, the first main gate 60, and the second main gate 80 may be controlled as described above in response to commands from the control unit 50.

[0035] According to the embodiment shown in FIG. 3, growth of polycrystalline silicon in the normal reactor 40 and growth of evaluation silicon in a plurality of evaluation reactors 20 can be carried out simultaneously.

[0036] A command from the control unit 50 can make the timing for stopping the supply of the raw material gas to each of the evaluation reactors 20 different. Alternatively, different silicon samples for evaluation may be produced by making the timing for starting the supply of the raw material gas different rather than the timing for stopping it. Alternatively, different silicon samples for evaluation may be produced by making the timing for starting the supply of the raw material gas to each of the evaluation reactors 20 different and then stopping it. In either case, by making the components of the raw material gas to each of the evaluation reactors 20 the same, a more reliable comparison between the silicon samples for evaluation can be performed.

[0037] The control unit 50 may be connected wirelessly or by wire to the plurality of evaluation reactors 20 and the normal reactor 40, and may control the temperatures of the plurality of evaluation reactors 20 and the normal reactor 40. As an example, the method of changing the temperature in each of the plurality of evaluation reactors 20 and the normal reactor 40 may be common, and the source gas for each of the plurality of evaluation reactors 20 and the normal reactor 40 may also be common, and only the timing at which the supply of the source gas to the plurality of evaluation reactors 20 is stopped may be different, thereby making it possible to compare the change over time of the evaluation silicon produced in each evaluation reactor 20 and to compare it with the analysis results (measurement results of the impurity concentration contained in the radial direction, etc.) of the polycrystalline silicon produced in the normal reactor 40.

[0038] The control unit 50 is connected to the storage unit 60, and may perform control based on recipes stored in the storage unit 60. The raw material gas is supplied from the raw material gas supply unit 90, and control over supply from the raw material gas supply unit 90 and control over opening and closing of the sub-opening / closing unit 70, the first main open / close unit 60, and the second main open / close unit 80 may be performed based on recipes stored in the storage unit 60. The supply of raw material gas to each of the multiple evaluation reactors 20 may be stopped by the control unit 50 issuing a command to close the corresponding sub-opening / closing unit 70 based on the recipe stored in the storage unit 60.

[0039] In this embodiment, normal-sized (large) polycrystalline silicon is produced in the normal reactor 40, and small-sized evaluation silicon (which may have a diameter of about 30 to 60 mm) is produced in each of the multiple evaluation reactors 20. In this case, the polycrystalline silicon and the multiple evaluation silicons are produced under the same conditions except for the growth time.

[0040] Conventionally, the generated polycrystalline silicon is analyzed in the radial direction, and the timing at which the impurities entered the polycrystalline silicon is estimated from the radial position of the contained impurities, but when this embodiment is adopted, the growth of polycrystalline silicon in the evaluation silicon can be stopped at an appropriate timing, for example by closing the sub opening / closing part 70, and the impurities contained in the evaluation silicon can be evaluated as appropriate. Therefore, a specific evaluation can be made of the timing at which the impurities were contained.

[0041] In recent years, requirements for impurity concentrations have become stricter, with impurity concentrations on the order of several to several tens of parts per trillion (ppt) for dopant concentrations such as B and P, and several to several tens of parts per trillion (ppt) for heavy metal concentrations. Therefore, confirming the timing of impurity inclusion in real time, as in the present embodiment, is an extremely useful analytical tool, enabling extremely effective determination of single crystal silicon growth conditions, which was difficult using conventional methods. For example, when a system such as that shown in FIG. 3 is employed, observations are made over time in the evaluation reactor 20, and the reactions in the other evaluation reactors 20 and the normal reactor 40 are stopped when the impurity concentration increases, thereby reducing wasteful material consumption and time.

[0042] A small experimental reactor may be used as the evaluation reactor 20 used in producing evaluation silicon in this embodiment. Specifically, it can be performed in a mode similar to the small reactor shown in Patent Document 1 (EP2636767). Regarding the bell jar, quartz or the like is suitable in consideration of not generating contamination.

[0043] As a method for producing silicon for evaluation, the method described in Patent Document 3 (JP Patent Publication No. 03-252397A) may be referred to, and polycrystalline silicon having a required diameter and having single-crystalline silicon portions 6 may be produced.

[0044] In this embodiment, the single crystal silicon portion 6 can be partially formed during the process of producing polycrystalline silicon. Therefore, when performing evaluations that require single crystal silicon, the single crystal silicon portion 6 can be used. Furthermore, this is extremely beneficial in that evaluations can be performed using the single crystal silicon portion 6 formed in the polycrystalline silicon without having to take the trouble of producing single crystal silicon.

[0045] As shown in Figure 1, when viewed in a cross section cut in a direction perpendicular to the direction in which the polycrystalline silicon extends, the single crystal silicon portion 6 extends from the surface of the core wire 9 in the radial growth direction, and part or all of the outer periphery of the single crystal silicon portion 6 may be surrounded by the polycrystalline silicon portion 5.

[0046] When growing polycrystalline silicon on the core wire 9, the single crystal silicon portion 6 may be grown in the growth direction from the surface of the silicon core wire 9, and the growth of the single crystal may be continued up to at least 5 mm from the outer periphery of the polycrystalline silicon portion 5 formed surrounding the single crystal silicon portion 6. The growth of the single crystal may be continued up to at least 3 mm from the outer periphery of the polycrystalline silicon portion 5. In this way, silicon for evaluation can be obtained in which the single crystal silicon portion 6 extends up to at least 5 mm or at least 3 mm from the outer periphery of the polycrystalline silicon portion 5.

[0047] The growth diameter of the single crystal silicon portion 6 may be 30 mm or less. In this case, the single crystal silicon portion 6 extending from the surface of the silicon core 9 in the radial direction of the polycrystalline silicon will extend for 30 mm or less. Note that, although raw material evaluation is required in both the CZ and FZ, using a small embodiment such as this embodiment is advantageous in that it reduces evaluation costs.

[0048] In the grown polycrystalline silicon, by selecting a crystal plane facing a certain direction as the side of the core wire 9, the single crystal silicon portion 6 grows in the growth direction. <110> It is preferable to cut out and use the single crystal silicon portion 6 so that the surface becomes the side surface of the core wire 9. A polycrystalline silicon portion 5 grows around the single crystal silicon portion 6 in the diagonal direction of the cross section of the core wire 2. When the single crystal silicon portion 6 is required for evaluation, the single crystal silicon portion 6 can be used, and when not, the polycrystalline silicon portion 5 can be used.

[0049] A four-probe method may be used to measure the resistivity of the single crystal silicon portion 6. Since the resistivity cannot be measured in the polycrystalline silicon portion 5, it is advantageous to partially generate the single crystal silicon portion 6 as in this embodiment.

[0050] The evaluation target in the evaluation silicon may be one or more of P, As, B, Al, and C. When evaluating donors or acceptors such as P, As, B, and Al, a photoluminescence method is generally used. As the photoluminescence method, the method disclosed in Patent Document 2 (JP 2016-145118 A) may be used. Although the photoluminescence method also requires measurement of single crystal silicon, the present embodiment is advantageous in that evaluation can be performed using the single crystal silicon portion 6.

[0051] When evaluating C, it is common to use Fourier transform infrared spectroscopy to measure Cs, which represents substitutional carbon. In this case, it is necessary to measure single crystal silicon, but the present embodiment is advantageous in that it can be evaluated using single crystal silicon portion 6.

[0052] When evaluating heavy metals, inductively coupled plasma mass spectrometry is generally used. In this case, the sample is dissolved in nitric acid and analyzed, regardless of whether the sample is single crystal or polycrystalline. Therefore, the evaluation can be performed using the polycrystalline silicon region (polycrystalline silicon portion 5) of the silicon to be evaluated. It is preferable to evaluate the polycrystalline silicon portion 5 that is the same as the polycrystalline silicon actually produced, but this is not limited thereto, and the evaluation can also be performed using the single crystal silicon portion 6.

[0053] In addition, according to this embodiment, since the evaluation silicon has both the single crystal silicon portion 6 and the polycrystalline silicon portion 5, the single crystal silicon portion 6 or the polycrystalline silicon portion 5 can be selected according to the needs of the evaluation.

[0054] This method can also be used when evaluating the raw material gas online using an actual conventional reactor 40 (see FIG. 3). It can also be used when evaluating other components that require single crystal silicon.

[0055] When evaluating the components, the influence on the actual conventional reactor 40 can be seen by converting the surface area or volume of each component relative to the amount used in the actual conventional reactor 40. [Example]

[0056] Trichlorosilane, the raw material, was collected from the same tank and stored in a cylinder serving as raw material gas supply unit 90. A portion of the trichlorosilane from raw material gas supply unit 90 was supplied to a conventional reactor 40 capable of epitaxial growth to produce single crystal silicon. The remainder of the trichlorosilane from raw material gas supply unit 90 was supplied to a small evaluation reactor 20. Hydrogen gas was introduced into each reactor in the same manner to perform crystal growth.

[0057] As a result of evaluating the single crystal silicon portion 6 obtained when epitaxially growing polycrystalline silicon in the normal reactor 40 and the single crystal silicon portion 6 obtained when growing polycrystalline silicon in the evaluation reactor 20, it was found that equivalent evaluation was possible. [Industrial Applicability]

[0058] According to the present invention, it is possible to accommodate evaluation methods that require single crystal silicon without incurring additional costs. [Explanation of symbols]

[0059] 5 Polycrystalline silicon section 6 Single crystal silicon section 9 core wire 20 Evaluation reactor 40 Conventional reactor

Claims

1. A quality evaluation method using a manufacturing system having a normal reactor and an evaluation reactor connected to a supply pipe for supplying a raw material gas, comprising: a step of producing evaluation silicon in an evaluation reactor using the Siemens process simultaneously with producing polycrystalline silicon in a normal reactor using the Siemens process, wherein polycrystalline silicon is grown on a core wire in the reactor while single crystal silicon extending radially from the core wire is grown; evaluating the evaluation silicon using the single crystal silicon produced in the evaluation reactor; A quality evaluation method comprising:

2. further comprising a removal step of removing the evaluation silicon from the evaluation reactor, The quality evaluation method according to claim 1 , wherein the evaluation is performed using the single crystal silicon of the evaluation silicon removed from the evaluation reactor.

3. producing evaluation silicon in a plurality of evaluation reactors; A plurality of evaluation silicon samples are produced in a plurality of evaluation reactors under the same conditions except for the growth time. The quality evaluation method according to claim 1 or 2, wherein each evaluation silicon is evaluated.

4. 4. The quality evaluation method according to claim 1, wherein the evaluation target in the evaluation silicon is one or more of P, As, B, Al, and C.

5. A quality evaluation method described in any one of claims 1 to 4, wherein the evaluation reactor is a reactor smaller than the normal reactor.

6. a supply pipe for supplying a raw material gas; a plurality of evaluation reactors connected to the supply pipe, each reactor producing evaluation silicon by growing polycrystalline silicon by the Siemens process while growing single crystal silicon extending radially from a core wire; a conventional reactor connected to the supply pipe for producing polycrystalline silicon by the Siemens process; a control unit that controls the supply of a raw material gas to each of the evaluation reactors; Equipped with It is possible to simultaneously generate polycrystalline silicon in a normal reactor and grow evaluation silicon in multiple evaluation reactors. The timing for starting or stopping the supply of the raw material gas to each of the evaluation reactors can be varied according to a command from the control unit. Evaluation silicon manufacturing system.

7. A manufacturing system for evaluation silicon as described in claim 6, wherein the evaluation reactor is a reactor smaller than the normal reactor.

8. A method for producing evaluation silicon using a production system having a normal reactor and an evaluation reactor connected to a supply pipe for supplying a raw material gas, comprising: A manufacturing method for producing evaluation silicon in the evaluation reactor separately from the production of polycrystalline silicon in the normal reactor, by growing polycrystalline silicon on a single crystal silicon core wire in an evaluation reactor using the Siemens process at the same time as producing polycrystalline silicon in a normal reactor using the Siemens process, by growing the single crystal silicon in the growth direction from the surface of the silicon core wire and continuing the growth of the single crystal silicon up to at least 5 mm from the outer periphery of the polycrystalline silicon.

9. The method for producing evaluation silicon according to claim 8, wherein the growth of single crystal silicon is continued up to at least 3 mm from the outer periphery of the polycrystalline silicon.

10. A method for producing evaluation silicon as described in claim 8 or 9, wherein the evaluation reactor is a reactor smaller than the normal reactor.

Images