Silicon raw material cleaning method and silicon raw material cleaning apparatus

Abstract

To provide a cleaning method of a silicon raw material and a cleaning device of the silicon raw material capable of suppressing clogging of a pump protection filter caused by silicon powder brought into a cleaning liquid, preventing cleaning failure of the silicon raw material by hardly causing circulation failure of the cleaning liquid, and improving an operation rate by reducing a frequency of maintenance work of the cleaning device.SOLUTION: A method for cleaning a silicon raw material, comprising: applying compressed air supplied from a blow nozzle to the silicon raw material to scatter and remove silicon powder adhering to a surface of the silicon raw material; filling the silicon raw material in a cleaning basket having a plurality of holes through which the silicon raw material does not fall; and immersing the silicon raw material in a cleaning tank filled with a cleaning liquid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for cleaning silicon raw material. [Background technology]

[0002] Single crystal silicon is mainly produced by the Czochralski method (CZ method) or the floating zone method (FZ method), and in order to increase the purity of the single crystal, the raw material used must be high-purity silicon. However, normal silicon has a native oxide film and impurities attached to its surface. Therefore, the silicon raw material used to produce single crystal silicon must first have the native oxide film and impurities removed from its surface.

[0003] Figure 6 shows the conventional process from cleaning to packaging of silicon raw materials.

[0004] First, silicon raw material is loaded into a cleaning basket on a transport conveyor (step SA1: loading silicon raw material). This cleaning basket has a plurality of holes to prevent the silicon raw material from falling out. Then, the cleaning basket filled with silicon raw material is transported to a silicon raw material cleaning device by a transport conveyor.

[0005] In the silicon raw material cleaning equipment, first, a pre-washing (step SA2) is performed in which the cleaning basket is immersed and oscillated in a pure water tank, and then an acid wash (step SA3) is performed in which the cleaning basket is immersed and oscillated in a cleaning tank containing a cleaning solution. The cleaning solution used is hydrofluoric acid, nitric acid, hydrochloric acid, hydrogen peroxide, or a mixture of these. After the acid wash, a water wash (step SA4) is performed in a pure water tank to remove the cleaning solution.

[0006] Thereafter, the silicon raw material is transported to a silicon raw material dryer and dried (step SA5), and is then carried out of the silicon raw material dryer by a transport conveyor, and the washed silicon raw material is packed into bags (step SA6: packing).

[0007] A conventional silicon raw material cleaning device is shown in Figure 7, and a method for cleaning silicon raw material using this cleaning device will be described. First, a cleaning tank 101 is filled with cleaning liquid 107, and a cleaning basket 109 filled with silicon raw material 110 is immersed and swung in the cleaning liquid 107. When the cleaning basket 109 is immersed in the cleaning liquid 107, silicon powder that has been adhering to the surface of the silicon raw material 110 floats on the surface of the cleaning liquid 107 or inside the cleaning liquid 107 as floating silicon powder 111.

[0008] Furthermore, when the cleaning basket 109 is immersed, the cleaning liquid 107 overflows into the heat exchange tank 113, and the heat exchange tank 113 is filled with the overflow cleaning liquid 112. The overflow cleaning liquid 112 is then cooled by the cooling heat exchanger 108 provided in the heat exchange tank 113. When the cleaning liquid 107 overflows, large particles of the floating silicon powder 111 are collected by the filter 102 provided on the side of the cleaning tank 101.

[0009] The overflow cleaning liquid 112 is cooled in a cooling heat exchanger 108, passes through a circulation pipe 106, and traps the remaining floating silicon powder 111 in a trap box 103 and a pump protection filter 104, and is then supplied again to the cleaning tank 101 by a circulation pump 105. In this way, the cleaning liquid 107 is circulated.

[0010] The filter 102, trap box 103, and pump protection filter 104 are all constructed with mesh filters placed in resin containers, and the size of the floating silicon powder that is collected decreases in this order.

[0011] In addition, the cleaning liquid 107 is not only circulated, but also replenished in a predetermined amount through a cleaning liquid supply pipe (not shown) each time the silicon raw material in one cleaning basket is cleaned. This is because the cleaning liquid 107 is reduced by coming into contact with the silicon raw material 110 and being consumed in the etching reaction, etc., and is therefore replenished.

[0012] In this way, the silicon raw material is washed by filling a washing basket with the silicon raw material, immersing the washing basket in a washing tank containing a washing liquid, and shaking the washing basket. After a predetermined amount of silicon raw material has been washed using this washing method, the washing liquid is discarded and replaced with new washing liquid.

[0013] During cleaning, the temperature of the cleaning liquid rises due to the heat of reaction generated by the etching reaction between the cleaning liquid and the silicon raw material. Therefore, to prevent variations in the amount of etching due to changes in the temperature of the cleaning liquid, the overflow cleaning liquid 112 is cooled by a cooling heat exchanger 108, and the temperature of the cleaning liquid is measured and managed by a temperature sensor (not shown).

[0014] Patent Documents 1 and 2 disclose methods for cleaning such silicon raw materials.

[0015] Patent Document 1 discloses a method for cleaning a silicon raw material, which involves bringing a lump or granular silicon raw material into contact with a cleaning solution for the silicon raw material to clean the silicon raw material, and then bringing the cleaning solution for the silicon raw material into contact with the silicon raw material again using a circulation pump, and is characterized in that the cleaning solution for the silicon raw material is passed through a circulation pump protection filter and a particulate removal filter in this order and circulated by the circulation pump.

[0016] Patent Document 2 discloses that the number of particles in the cleaning liquid is measured and controlled so that it falls within a range between an upper limit and a lower limit. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-239095 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-233653 Summary of the Invention [Problem to be solved by the invention]

[0018] Silicon raw material is a brittle material that is easily affected by shocks, etc. Therefore, shocks during transportation of the silicon raw material can cause cracks in the surface of the bag containing the silicon raw material, generating silicon powder inside the bag.

[0019] Therefore, when silicon powder smaller than the silicon raw material adheres to the surface of the silicon raw material and is loaded as is into a cleaning basket 109 as shown in Fig. 7, the silicon powder smaller than the silicon raw material eventually passes through multiple holes (numerous drain holes for passing the cleaning liquid) provided in the cleaning basket 109 that are large enough to prevent the silicon raw material from falling out, and flows out into the cleaning liquid in the cleaning tank. The silicon powder that flows out floats or settles in the cleaning liquid.

[0020] Because the floating silicon powder in the cleaning solution is small, it flows out of the cleaning tank into the circulation piping when the cleaning solution is circulating, and some of the floating silicon powder (especially the small ones) reaches the pump protection filter and is captured by the pump protection filter. If a large amount of floating silicon powder is captured by the pump protection filter, the pump protection filter becomes clogged, causing problems with the circulation of the cleaning solution.

[0021] When the cleaning liquid has poor circulation, that is, when the cleaning liquid becomes difficult to flow, the parts of the cleaning liquid that rise in temperature due to the heat of reaction generated by the etching reaction between the cleaning liquid and the silicon raw material and the parts that do not rise in temperature or that are cooled and drop in temperature are not circulated, and temperature unevenness in the cleaning liquid becomes large, resulting in variations in the amount of etching of the silicon raw material and leading to poor cleaning of the silicon raw material.

[0022] Furthermore, if cleaning continues while the pump protection filter is clogged with a large amount of silicon powder, the pump protection filter may eventually break, causing the silicon powder to reach the circulation pump and damage it.

[0023] In the past, to avoid these problems, after a predetermined amount of silicon raw material had been washed, the silicon raw material washing equipment was stopped and maintenance work was carried out to remove the silicon powder (floating silicon powder) that had accumulated on the pump protection filter. However, this maintenance work was required frequently, which resulted in a problem of a decrease in the operating rate of the washing equipment.

[0024] The present invention has been made to solve the above problems, and has an object to provide a method and apparatus for cleaning silicon raw materials that can suppress clogging of a pump protection filter caused by the introduction of silicon powder into the cleaning liquid, thereby making it less likely that poor circulation of the cleaning liquid will occur and preventing poor cleaning of the silicon raw material, and further reducing the frequency of maintenance work on the cleaning apparatus and improving its operating rate. [Means for solving the problem]

[0025] In order to solve the above problems, the present invention provides a cleaning method for cleaning silicon raw material, comprising: blowing compressed air supplied from a blow nozzle onto the silicon raw material to scatter and remove silicon powder adhering to the surface of the silicon raw material; loading the silicon raw material from which the silicon powder has been removed into a cleaning basket having a plurality of holes large enough to prevent the silicon raw material from falling out; immersing the cleaning basket in a cleaning tank filled with a cleaning liquid, thereby bringing the silicon raw material in the cleaning basket into contact with the cleaning liquid and cleaning it; circulating the cleaning liquid in the cleaning tank with a pump; and cleaning the silicon raw material while collecting floating silicon powder floating in the cleaning liquid with a pump protection filter arranged on the water intake side of the pump.

[0026] In this method for cleaning silicon raw material, silicon powder is removed before the silicon raw material is loaded into the cleaning basket, so that the amount of silicon powder carried over into the cleaning solution can be reduced, and the amount of floating silicon powder caused by the silicon powder floating in the cleaning solution when immersed in the cleaning tank is reduced, and the silicon raw material can be cleaned with less floating silicon powder collected by the pump protection filter. Therefore, clogging of the pump protection filter caused by silicon powder is suppressed, and as a result, poor circulation of the cleaning solution is less likely to occur, preventing poor cleaning of the silicon raw material, and further reducing the frequency of maintenance work on the cleaning device, thereby improving the operating rate.

[0027] It is also preferable that the silicon powder scattered by the compressed air supplied from the blow nozzle is collected by an exhaust device disposed on the downwind side of the silicon raw material.

[0028] In this way, by collecting the scattered silicon powder using an exhaust device on the downwind side, the silicon powder can be effectively recovered and the scattered silicon powder can be prevented from diffusing and finding its way into the cleaning tank through unexpected routes.

[0029] In order to solve the above problems, the present invention provides a cleaning device for cleaning silicon raw material, comprising: a blow nozzle that supplies compressed air to the silicon raw material and scatters and removes silicon powder adhering to the surface of the silicon raw material; a cleaning basket that has a plurality of holes large enough to prevent the silicon raw material from falling out and in which the silicon raw material is filled with the silicon raw material from which the silicon powder has been removed; a cleaning tank that is filled with cleaning liquid and in which the silicon raw material filled in the cleaning basket comes into contact with the cleaning liquid when the cleaning basket is immersed, a pump that circulates the cleaning liquid in the cleaning tank; and a pump protection filter that is located on the water intake side of the pump and collects floating silicon powder floating in the cleaning liquid.

[0030] Since such a silicon raw material cleaning device has a blow nozzle that supplies compressed air to scatter and remove silicon powder adhering to the surface of the silicon raw material, it is possible to remove the silicon powder before loading the silicon raw material into the cleaning basket, thereby reducing the amount of silicon powder carried over, and reducing the amount of floating silicon powder caused by the silicon powder floating in the cleaning solution when the cleaning basket is immersed in the cleaning tank, allowing the silicon raw material to be cleaned with little floating silicon powder collected by the pump protection filter. Therefore, clogging of the pump protection filter due to silicon powder is suppressed, and as a result, poor circulation of the cleaning solution is less likely to occur, preventing poor cleaning of the silicon raw material, and further reducing the frequency of maintenance work on the cleaning device and improving the operating rate.

[0031] It is also preferable to have an exhaust device that is arranged on the downwind side of the silicon raw material as viewed from the blow nozzle and that collects the silicon powder scattered by the compressed air supplied from the blow nozzle.

[0032] In this way, if the exhaust device that collects the scattered silicon powder is located on the downwind side, the silicon powder can be effectively collected and the scattered silicon powder can be prevented from diffusing and finding its way into the cleaning tank through unexpected routes. [Effects of the Invention]

[0033] In the silicon raw material cleaning method of the present invention, silicon powder is removed before the silicon raw material is loaded into the cleaning basket, so that the amount of silicon powder carried over into the cleaning solution can be reduced, and the amount of floating silicon powder caused by the silicon powder floating in the cleaning solution when immersed in the cleaning tank is reduced, and the silicon raw material can be cleaned with less floating silicon powder collected by the pump protection filter. Therefore, clogging of the pump protection filter caused by silicon powder is suppressed, and as a result, poor circulation of the cleaning solution is less likely to occur, preventing poor cleaning of the silicon raw material, and further reducing the frequency of maintenance work on the cleaning equipment and improving the operating rate.

[0034] Furthermore, the silicon raw material cleaning device of the present invention has a blow nozzle that supplies compressed air to scatter and remove silicon powder adhering to the surface of the silicon raw material, so that the silicon powder can be removed in advance before loading the silicon raw material into the cleaning basket, thereby reducing the amount of silicon powder carried over, and reducing the amount of floating silicon powder caused by the silicon powder floating in the cleaning solution when the cleaning basket is immersed in the cleaning tank, allowing the silicon raw material to be cleaned with little floating silicon powder collected by the pump protection filter. Therefore, clogging of the pump protection filter due to silicon powder is suppressed, and as a result, poor circulation of the cleaning solution is less likely to occur, preventing poor cleaning of the silicon raw material, and further reducing the frequency of maintenance work on the cleaning device, thereby improving the operating rate. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a flow chart showing an example of a method for cleaning a silicon raw material according to the present invention. [Figure 2] 1 is a block diagram showing an example of a silicon raw material cleaning apparatus according to the present invention. [Figure 3] FIG. 2 is a schematic diagram showing an example of a configuration for removing silicon powder from a silicon raw material. [Figure 4] FIG. 1 is a schematic diagram showing an example of a configuration for removing silicon powder and filling a washing basket with silicon raw material. [Figure 5] FIG. 1 is a schematic diagram showing an example of a configuration for cleaning silicon raw material by immersing a cleaning basket in a cleaning tank. [Figure 6] FIG. 1 is a flow chart showing steps from filling to packaging of conventional silicon raw material. [Figure 7] FIG. 1 is a schematic diagram showing a conventional silicon raw material cleaning device. DETAILED DESCRIPTION OF THE INVENTION

[0036] As described above, there has been a demand for a method and an apparatus for cleaning silicon raw material that can suppress clogging of the pump protection filter due to the introduction of silicon powder into the cleaning liquid, thereby making it less likely that poor circulation of the cleaning liquid will occur and preventing poor cleaning of the silicon raw material, and further reducing the frequency of maintenance work for the cleaning apparatus and improving the operating rate.

[0037] As a result of extensive research into the above-mentioned problems, the present inventors have found that it is effective to reduce the amount of silicon powder carried over into the cleaning solution, which is the fundamental cause, and have thus completed the present invention.

[0038] That is, the present invention is a cleaning method for cleaning silicon raw material, comprising: blowing compressed air supplied from a blow nozzle onto the silicon raw material to scatter and remove silicon powder adhering to the surface of the silicon raw material; loading the silicon raw material from which the silicon powder has been removed into a cleaning basket having a plurality of holes large enough to prevent the silicon raw material from falling out; immersing the cleaning basket in a cleaning tank filled with a cleaning liquid, thereby bringing the silicon raw material in the cleaning basket into contact with the cleaning liquid and cleaning it; circulating the cleaning liquid in the cleaning tank with a pump; and collecting floating silicon powder floating in the cleaning liquid with a pump protection filter arranged on the water intake side of the pump, thereby cleaning the silicon raw material.

[0039] The present invention also provides a cleaning device for cleaning silicon raw material, comprising: a blow nozzle that supplies compressed air to the silicon raw material and scatters and removes silicon powder adhering to the surface of the silicon raw material; a cleaning basket that has a plurality of holes large enough to prevent the silicon raw material from falling out and that is filled with the silicon raw material from which the silicon powder has been removed; a cleaning tank that is filled with a cleaning liquid and in which the silicon raw material filled in the cleaning basket comes into contact with the cleaning liquid when the cleaning basket is immersed, and is cleaned; a pump that circulates the cleaning liquid in the cleaning tank; and a pump protection filter that is located on the water intake side of the pump and collects floating silicon powder floating in the cleaning liquid.

[0040] Incidentally, although prior art such as Patent Document 1 discloses a filter for a cleaning device, it does not mention anything about reducing the amount of silicon powder carried into the cleaning liquid.

[0041] Furthermore, Patent Document 2 discloses measuring and managing the number of particles in the cleaning solution, but does not disclose reducing the amount of silicon powder that becomes particles brought into the cleaning solution.

[0042] The present invention will be described in detail below, but the present invention is not limited thereto.

[0043] FIG. 1 is a flow chart showing an example of the method for cleaning silicon raw material according to the present invention.

[0044] (Step S1: Step of removing silicon powder from silicon raw material) First, compressed air supplied from a blow nozzle is applied to the silicon raw material to scatter and remove silicon powder adhering to the surface of the silicon raw material.

[0045] (Step S2: Step of filling silicon raw material into a washing basket) Next, the silicon raw material from which the silicon powder has been removed in step S1 is loaded into a washing basket having a plurality of holes large enough to prevent the silicon raw material from falling out.

[0046] (Step S3: Immerse the cleaning basket in the cleaning tank) Next, in step S2, the cleaning basket filled with the silicon raw material is immersed in a cleaning tank filled with a cleaning liquid. As a result, the silicon raw material filled in the cleaning basket gradually starts to come into contact with the cleaning liquid from the outer part, i.e., cleaning begins.

[0047] (Step S4: Cleaning the silicon raw material) In step S3, the silicon raw material in the cleaning basket immersed in the cleaning tank is brought into contact with the cleaning liquid and cleaned, and the cleaning liquid in the cleaning tank is circulated by a pump, and the silicon raw material is cleaned while the floating silicon powder in the cleaning liquid is collected by a pump protection filter arranged on the water intake side of the pump.

[0048] In this method for cleaning silicon raw material, silicon powder is removed in advance in step S1, and then the silicon raw material is loaded into the cleaning basket in step S2, so that it is possible to reduce the amount of silicon powder carried over into the cleaning solution, and the amount of floating silicon powder caused by the silicon powder floating in the cleaning solution when immersed in the cleaning tank is reduced, and the silicon raw material can be cleaned with less floating silicon powder collected by the pump protection filter. Therefore, clogging of the pump protection filter caused by silicon powder is suppressed, and as a result, poor circulation of the cleaning solution is less likely to occur, preventing poor cleaning of the silicon raw material, and further reducing the frequency of maintenance work on the cleaning device and improving the operating rate.

[0049] In the above step S1, although not particularly limited, it is preferable to collect the silicon powder scattered by the compressed air supplied from the blow nozzle using an exhaust device arranged downwind of the silicon raw material.

[0050] In this way, by collecting the scattered silicon powder using an exhaust device on the downwind side, the silicon powder can be effectively recovered, and it is possible to prevent the scattered silicon powder from spreading and finding its way into the cleaning tank through unexpected routes, or from deteriorating the working environment.

[0051] While not particularly limited, this embodiment may be combined with the conventional process shown in FIG. 6 as follows. For example, a transport conveyor may be used to move the silicon raw material and the cleaning basket. The cleaning basket may be swung within the cleaning device. When cleaning the silicon raw material, pre-rinsing with water, acid cleaning, and water rinsing may be performed. The cleaning liquid used may be hydrofluoric acid, nitric acid, hydrochloric acid, hydrogen peroxide, or a mixture of these. After cleaning, the silicon raw material may be transported to a silicon raw material dryer for drying, and then removed from the silicon raw material dryer by a transport conveyor for packaging, such as in bags.

[0052] FIG. 2 is a block diagram showing an example of the silicon raw material cleaning apparatus of the present invention.

[0053] The silicon raw material cleaning device 1 is roughly divided into a silicon powder removal section 2 and a cleaning section 3.

[0054] First, the silicon powder removal unit 2 is a part that supplies compressed air to the silicon raw material to scatter and remove silicon powder adhering to the surface of the silicon raw material, and can be typically a blow nozzle.

[0055] Next, the cleaning unit 3 has a cleaning basket that has a plurality of holes large enough to prevent the silicon raw material from falling out and that is filled with the silicon raw material from which silicon powder has been removed, a cleaning tank that is filled with a cleaning liquid and in which the silicon raw material filled in the cleaning basket comes into contact with the cleaning liquid when the cleaning basket is immersed, a pump that circulates the cleaning liquid in the cleaning tank, and a pump protection filter that is disposed on the water intake side of the pump and captures floating silicon powder floating in the cleaning liquid. The cleaning unit 3 is not particularly limited, but a conventional silicon raw material cleaning device can typically be used.

[0056] In the silicon raw material cleaning apparatus 1 of the present invention, the silicon powder removal section 2 includes a blow nozzle that supplies compressed air to scatter and remove silicon powder adhering to the surface of the silicon raw material. This allows the silicon powder to be removed before loading the silicon raw material into the cleaning basket, reducing the amount of silicon powder carried over. Furthermore, in the cleaning section 3, the amount of floating silicon powder caused by the silicon powder floating in the cleaning solution when the cleaning basket is immersed in the cleaning tank is reduced, allowing the silicon raw material to be cleaned with less floating silicon powder collected by the pump protection filter. This suppresses clogging of the pump protection filter due to silicon powder, which in turn reduces the likelihood of poor circulation of the cleaning solution and prevents poor cleaning of the silicon raw material. Furthermore, the frequency of maintenance work on the cleaning device is reduced, improving the operating rate.

[0057] Incidentally, when cleaning silicon raw material using the silicon raw material cleaning apparatus 1 in Figure 2, although this is not particularly limited, a user prepares silicon raw material (before cleaning) 4, cleans it via the routes indicated by arrows 5, 6, and 7, and obtains silicon raw material (after cleaning) 8. More specifically, the silicon raw material (before cleaning) 4 is set in silicon powder removal section 2 via route 5, silicon powder is removed in advance in silicon powder removal section 2, it is moved to cleaning section 3 via route 6, it is cleaned in cleaning section 3, and it is removed from the silicon raw material cleaning apparatus 1 via route 7, and the silicon raw material (after cleaning) 8 is obtained.

[0058] Routes 5, 6, and 7 may involve the movement of silicon raw material, but this may be automated using a conveyor or the raw material may be transported by a worker, and there are no particular limitations on the method of movement.

[0059] Although not particularly limited, it is preferable that the silicon powder removal section 2 has an exhaust device that is positioned downwind of the silicon raw material as viewed from the blow nozzle and that collects the silicon powder scattered by the compressed air supplied from the blow nozzle.

[0060] In this way, if the exhaust device that collects the scattered silicon powder is located on the downwind side, the silicon powder can be effectively collected, and the scattered silicon powder can be prevented from spreading and entering the cleaning tank through unexpected routes, or from worsening the working environment.

[0061] Next, with reference to FIGS. 3 to 5, a more specific embodiment of the method and apparatus for cleaning silicon raw material according to the present invention will be described.

[0062] FIG. 3 is a schematic diagram showing an example of a configuration for removing silicon powder from a silicon raw material.

[0063] 3 is a top view, in which a mat 31 is wound around the conveyor 29, and the silicon raw material 22 is placed on the mat 31. The conveyor 29 is, for example, a roller conveyor, and the silicon raw material 22 moves in the direction of arrow 32 from the back to the front (from the top to the bottom of the paper).

[0064] A blow nozzle 24 is provided on the left side slightly above the conveyor 29, and compressed air 25 is supplied from a blow hole 30 provided on the right side of the blow nozzle 24.

[0065] Therefore, by supplying compressed air 25 from the blow nozzle 24 while moving the silicon raw material 22 on the conveyor 29, the compressed air 25 is applied to the silicon raw material 22 sequentially from the upwind side (left side), and the silicon powder 23 adhering to the surface of the silicon raw material 22 can be scattered to the downwind side (right side) and removed.

[0066] Here, the method for moving the silicon raw material 22 is not limited to a conveyor, but is a preferable method for allowing the compressed air supplied from the blow nozzle to hit the entire silicon raw material.

[0067] Although not particularly limited, it is preferable to collect the scattered silicon powder 23 with an exhaust device 26 arranged on the downwind side (right side) of the silicon raw material 22. In particular, it is preferable to install the exhaust device 26 so that the intake port of the exhaust device 26 is located opposite the blow nozzle 24 across the conveyor 29.

[0068] In this way, by collecting the scattered silicon powder 23 by the exhaust device 26 on the downwind side, the silicon powder 23 can be effectively recovered, and the scattered silicon powder 23 can be prevented from diffusing and getting into the cleaning tank or the like through an unexpected route.

[0069] The blow nozzle 24 that blows compressed air 25 onto the silicon raw material 22 is not particularly limited, but it is preferable to use a resin pipe with a diameter of about 15 mm and to make the overall length the same size as the mat 31. The blow holes 30 provided in the blow nozzle 24 are not particularly limited, but can be holes with a diameter of about 1 mm arranged in a row at intervals of 15 mm.

[0070] The compressed air 25 used to blow the silicon powder 23 is preferably ISO8573-1:2010 [1:6:1] and has an air volume of about 60 L / min, but is not particularly limited thereto.

[0071] Furthermore, it is preferable that the exhaust filter 27 used in the exhaust device 26 has a particle collection efficiency of 99.9995% or more for particles with a particle diameter of 0.15 μm, and the exhaust air volume of the exhaust 34 by the exhaust fan 28 (see FIG. 4) is 60 L / min or more, which is equivalent to the blown compressed air 25, but this is not particularly limited.

[0072] FIG. 4 is a schematic diagram showing an example of a configuration for removing silicon powder and filling the silicon raw material into a washing basket.

[0073] 4 is a front view, in which the silicon raw material 22 on the mat 31 falls into the cleaning basket 21 from the front end of the mat 31 above the conveyor 29 (moves in the direction of arrow 33) as the conveyor 29 moves, and the mat 31 is recovered below the conveyor 29. In this way, the silicon raw material 22 from which the silicon powder 23 has been removed is filled into the cleaning basket 21, which has a plurality of holes 35 large enough to prevent the silicon raw material 22 from falling out. When the silicon raw material 22 is filled into the cleaning basket 21, compressed air 25 is constantly blown out from the blow nozzle 24, and the silicon raw material 22 hits the compressed air 25 while moving before being filled into the cleaning basket 21.

[0074] Furthermore, although not particularly limited, the exhaust device 26 also cleans silicon powder adhering to the silicon raw material 22 and dust generated during the filling operation, and exhausts the cleaned air to a location away from the cleaning chamber, thereby preventing the dust from diffusing inside the cleaning chamber (particularly in the cleaning liquid), and maintaining the cleanliness.

[0075] FIG. 5 is a schematic diagram showing an example of a configuration in which a cleaning basket is immersed in a cleaning tank to clean the silicon raw material.

[0076] Figure 5 is a front view that shows the image of moving the cleaning basket 21 up and down to immerse the cleaning basket 21 in the cleaning tank before cleaning, and then lifting the cleaning basket 21 out of the cleaning tank after cleaning.

[0077] The cleaning basket 21 is immersed in a cleaning tank 41 filled with a cleaning liquid 47, whereby the silicon raw material 22 in the cleaning basket 21 is brought into contact with the cleaning liquid 47 and cleaned, and the cleaning liquid 47 in the cleaning tank 41 is circulated by a circulation pump 45, and the silicon raw material 22 is cleaned while floating silicon powder 51 floating in the cleaning liquid 47 is collected by a pump protection filter 44 arranged on the water intake side of the circulation pump 45.

[0078] 3 and 4, in this embodiment, silicon powder 23 is removed in advance before the silicon raw material 22 is filled into the cleaning basket 21, which reduces the amount of silicon powder carried over into the cleaning solution 47, reduces the amount of floating silicon powder 51 caused by the silicon powder floating in the cleaning solution 47 when the silicon raw material 22 is immersed in the cleaning tank 41, and the silicon raw material 22 can be cleaned with less floating silicon powder collected by the pump protection filter 44. Therefore, clogging of the pump protection filter 44 caused by silicon powder is suppressed, which makes it less likely that poor circulation of the cleaning solution 47 will occur, preventing poor cleaning of the silicon raw material 22 and further reduces the frequency of maintenance work on the cleaning device, thereby improving the operating rate.

[0079] 5 but not explained may be the same as the conventional configuration, and so are assigned the same reference numerals as in the conventional configuration in Fig. 7. However, these are not particularly limited to the same configuration as the conventional configuration.

[0080] For example, in the present invention, silicon powder is removed before the silicon raw material is washed, so that the amount of silicon powder carried over into the washing solution can be reduced. Therefore, since the amount of silicon powder in the washing solution is less than in the past, it is possible to obtain effects such as eliminating the need for the filter 102 and trap box 103 used in the past or simplifying the system. [Example]

[0081] The effect of reducing the frequency of maintenance work for the cleaning device according to the present invention was confirmed using examples and comparative examples, which will be specifically explained below, but the present invention is not limited to these.

[0082] (Comparative Example) Using the conventional silicon raw material cleaning apparatus shown in Figure 7, a basket full of silicon raw material was cleaned according to the conventional silicon raw material cleaning method shown in Figure 6, and the state of the cleaning apparatus after cleaning was checked to determine whether maintenance work such as cleaning was necessary. As a result, in the comparative example, cleaning was required every time cleaning was performed. The cleaning required included cleaning of the pump protection filter, filter, and trap box, and maintenance such as removing silicon powder and debris from the cleaning tank.

[0083] (Example) Cleaning was performed under the same conditions as in the comparative example, except that before filling the cleaning basket with silicon raw material, compressed air supplied from a blow nozzle was applied to the silicon raw material to scatter and remove silicon powder adhering to the surface of the silicon raw material. As in the comparative example, a full basket of silicon raw material was cleaned, and the state of the cleaning device after cleaning was checked, and it was determined that maintenance work such as cleaning was not required. Therefore, a second and third cleaning was performed without maintenance work, and evaluation was performed after each cleaning. As a result, it was determined that maintenance work was not required after the second cleaning, but cleaning was required after the third cleaning.

[0084] From the above, it was found that the embodiment of the present invention can reduce the maintenance frequency to one-third compared to the conventional comparative example.

[0085] The present invention is not limited to the above-described embodiments, which are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0086] 1...Silicon raw material cleaning device, 2...Silicon powder removal unit (blow nozzle), 3...Cleaning section, 4...Silicon raw material (before cleaning), 5, 6, 7...Route, 8...Silicon raw material (after washing), 21...Washing basket, 22...silicon raw material, 23...silicon powder, 24...blow nozzle, 25...Compressed air, 26...Exhaust device, 27...Exhaust filter, 28...Exhaust fan, 29...Conveyor, 30...Blow hole, 31...Mat, 32, 33...arrows, 34...exhaust, 35...multiple holes, 41...cleaning tank, 44...Pump protection filter, 45...Circulation pump, 47...Cleaning liquid, 51...floating silicon powder, 101...cleaning tank, 102...filter, 103...trap box, 104...pump protection filter, 105...circulation pump, 106...circulation piping, 107...cleaning liquid, 108...cooling heat exchanger, 109...cleaning basket, 110...silicon raw material, 111...floating silicon powder, 112...Overflow cleaning liquid, 113...Heat exchange tank. S1~S4...steps, SA1~SA6...steps.

Claims

1. A cleaning method for cleaning a silicon raw material, comprising: Compressed air supplied from a blow nozzle is applied to the silicon raw material to scatter and remove silicon powder adhering to the surface of the silicon raw material; The silicon raw material from which the silicon powder has been removed is filled into a washing basket having a plurality of holes large enough to prevent the silicon raw material from falling out; the cleaning basket is immersed in a cleaning tank filled with a cleaning liquid, thereby bringing the silicon raw material in the cleaning basket into contact with the cleaning liquid and cleaning it; A method for cleaning silicon raw materials, characterized in that the cleaning liquid in the cleaning tank is circulated by a pump, and the silicon raw material is cleaned while floating silicon powder in the cleaning liquid is collected by a pump protection filter arranged on the water intake side of the pump.

2. 2. The method for cleaning silicon raw material according to claim 1, wherein the silicon powder scattered by the compressed air supplied from the blow nozzle is collected by an exhaust device arranged downwind of the silicon raw material.

3. A cleaning apparatus for cleaning silicon raw material, a blow nozzle that supplies compressed air to the silicon raw material to scatter and remove silicon powder adhering to the surface of the silicon raw material; a washing basket having a plurality of holes large enough to prevent the silicon raw material from falling out, and filled with the silicon raw material from which the silicon powder has been removed; a cleaning tank filled with a cleaning liquid, in which the silicon raw material filled in the cleaning basket comes into contact with the cleaning liquid and is cleaned when the cleaning basket is immersed therein; a pump for circulating the cleaning liquid in the cleaning tank; a pump protection filter disposed on the water intake side of the pump and configured to collect floating silicon powder in the cleaning liquid; 1. A cleaning device for silicon raw material, comprising:

4. 4. The silicon raw material cleaning apparatus according to claim 3, further comprising an exhaust device that is disposed downwind of the silicon raw material as viewed from the blow nozzle and that collects the silicon powder scattered by the compressed air supplied from the blow nozzle.

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