JPH04131625U - Polycrystalline silicon sheet manufacturing equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To extrude molten silicon into the mold nozzle,
This equipment is used for the cast ribbon method, in which a product is obtained by continuously drawing a solidified silicone sheet using a drawing jig.The remaining gas inside the device can be discharged, and the molten silicon flows until the drawing jig is filled with molten silicon. Prevents silicon from flowing out of the jig. [Structure] When molten silicon Si flows from the casting channel 6 of the mold nozzle 5 to the gripping end port 7a of the drawer jig 7 communicating therewith, the residual gas in the casting channel 6 flows into the gripping end port 7a.
The gas can be freely discharged into the inert atmosphere 1a through the gas venting pores 12 communicating with the gas. In addition, the temperature-controlled heat source 11 maintains a low temperature from the middle to the tip of the gas venting pore 12, and the molten silicon Si solidifies within the gas venting pore 12.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is based on polycrystalline silicon, which is used in solar cells and other photoelectric conversion elements. This invention relates to improvements in equipment used to manufacture sheets.

0002

[Conventional technology]

Various methods have already been implemented for producing polycrystalline silicon sheets. One of these methods, the ribbon method, is performed in a crucible a in an inert gas atmosphere, as shown in Figure 5. Die c is immersed in molten silicon b existing in The released molten silicon b is cooled and solidified in an inert gas atmosphere outside the die c. With this ribbon technology, the meniscus (surface) of molten silicon b Since the sheet is formed using surface tension (surface tension), a polycrystalline silicon sheet with a uniform thickness can be formed. As a result, when trying to use it as a solar cell device, it is difficult to obtain a Even when trying to form electrodes, it became difficult to apply the Scourin printing method. There is a flaw.

0003 In addition, as mentioned above, ribbon technology attempts to take advantage of wetting with molten silicon. Therefore, many consumables such as die, filament, and substrate are required. However, since carbon, SiC, etc. with good wettability are used, this is molten silicon. becomes a source of impurities. Furthermore, when using the ribbon method, the growth of crystals is The growth rate of the crystal cannot be increased too much, and the quality and quality may be affected. The results are not satisfactory in terms of productivity and production efficiency.

0004 In addition, a separate method called the casting method is also carried out, but the In this method, the silicon base material is heated to form a melt, which is then cast according to the dimensions of the product wafer. The melt is poured into a mold, and the movable parts of the mold press the melt to solidify it. However, when this method is used, wafers with a predetermined shape can be obtained at one time, which improves mass production. Although desired results can be expected with That will happen. Therefore, in this method, the upper and lower surfaces and side surfaces of the mold are exposed to silicon crystals when the melt solidifies. This will inhibit the growth of grains, and the The crystal grains in the vicinity of the solar cell become very fine, making it impossible to obtain large crystal grains. It satisfies the requirement of large crystal grain generation, which is considered desirable for silicon wafers etc. The photoelectric conversion efficiency of the solar cell obtained using the wafer is It also has a defect that makes it extremely bad at 2 to 3%.

[0005] Therefore, in order to overcome the above-mentioned difficulties, the applicant has already proposed the advantages of the above-mentioned casting method. The molten silicon is supplied to the mold nozzle continuously, not discontinuously. As it is supplied, it solidifies inside the mold nozzle, and this solidified silicon Polycrystalline silicon sheets with uniform thickness can be created by continuously pulling out the silicone sheets. can be mass-produced without worrying about contamination by impurities, and can also be manufactured in various thickness dimensions. The thickness can be easily obtained, and the thickness can be made uniform even during the device processing process. We proposed a method to eliminate unnecessary parts and improve yield (hereinafter this method will be referred to as key). (referred to as the "just ribbon method").

[0006] This method is carried out using the manufacturing equipment shown in Figure 4, where 1 is the A furnace body with an inert atmosphere 1a made of an inert gas such as Rougon or a vacuum, and inside it A silicon melting tube 3 heated by heaters 2a, 2b, etc. and a heater 4 A heated mold nozzle 5 is provided, and a mold nozzle 5 is provided to heat the silicon melting tube 3. After being melted by the heater 2a, the silicon base material is heated by an inert gas or the like. In response to the force P, the molten silicon Si is sequentially supplied to the supply port 3a of the silicon melting tube 3, Then, it is fed into the mold nozzle 5 through the injection port 5a of the mold nozzle 5. It is becoming more and more common.

[0007] Here, the mold nozzle 5 consists of a nozzle lower plate 5b and a nozzle upper cover plate 5c, A predetermined groove 5d is formed on the upper surface of the nozzle lower plate 5b, which is not shown in the figure. Both plates 5b and 5c are fixed in a stacked state using screws, etc., which do not have screws, so that a predetermined thickness can be achieved. A casting path 6 of a predetermined width is formed, and 7 in the figure indicates a drawing jig as a drawing means. ing.

One way to carry out the cast ribbon method using this manufacturing apparatus is to put a silicon base material into a silicon melting tube 3 made of quartz or the like, and melt it by operating a heater 2a. (1450°C) and apply pressure P (0.01 to 0.1 kg/cm ² ) by the inert gas to the upper surface of the molten silicon Si. The temperature distribution curve T is such that the temperature decreases from a temperature higher than the melting point of silicon (MP=1420°C) to about 1300°C from the base side of the casting path 6 to the drawing end 5e. The temperature from the solidification region 5f near the drawing end 5e of the casting channel 6 toward the drawing jig 7 is lower than the melting point MP in advance, and the temperature inside the mold nozzle 5 under such temperature conditions is lower than the melting point MP. The molten silicon Si is continuously supplied from the injection port 5a. As a result, the molten silicon Si is solidified from the gripping end 7a of the drawing jig 7 to the solidified region 5f in the mold nozzle 5, thereby forming a solidified silicon sheet MSi.

Once the solidified silicon sheet MSi has been formed in this way, the drawing jig 7 is continuously drawn out in the longitudinal direction of the mold nozzle 5, which is the arrow D. It is preferable to set the pressure P to an operating pressure that is lower than the above-mentioned initial pressure so that the length of the solidification region 5f does not change. In practice, the depth of the groove 5d is 0.5 mm, the width is 25 mm, and the total length is about 250 mm. Carbon is used as the material of the mold nozzle, and a silicon nitride coating is applied to the surface of the mold nozzle. , a mold release agent such as a mixture coating of Si ₃ N ₄ and SiO ₂ is used.

0010 In the above cast ribbon method, a temperature distribution curve T as shown in Fig. 4 is obtained in advance. The temperature is controlled so that the temperature distribution curve is lower than the melting point of silicon in advance. The heating conditions are controlled so that the temperature is high over the entire area, and then the mold nozzle is heated. By controlling the temperature to drop slowly from the tip of the slurry, rapid cooling of the molten silicon is avoided. You may do so.

[0011]

[Problem that the idea aims to solve]

When using the above manufacturing apparatus, the molten silicon Si is transferred to the silicon molten tube as described above. 3, the gas remaining in the casting path 6 immediately after being poured into the mold nozzle 5 As a result, the molten silicon cannot be pulled out and cured. The gripping end opening 7a, which becomes the chuck part of the tool 7, does not flow until it is filled with the gripping end opening 7a. As shown in 4, it has solidified and it is impossible to pull out the solidified silicone sheet MSi. There are some difficulties.

0012 In view of the above-mentioned drawbacks of the conventional device, the present invention is designed to communicate with the gripping end opening at the appropriate location of the drawer jig. A gas vent hole is drilled into the inert atmosphere and the hole is opened into an inert atmosphere. A temperature-controlled heat source is installed to provide an appropriate temperature distribution for the gas venting pores. By doing so, the remaining gas in the casting path can be sufficiently exhausted. to avoid situations such as inability to operate the drawer, and to ensure that the gas The molten silicon that has flowed into the drawing pores flows out from the drawing jig. Its purpose is to ensure that such things are prevented.

[0013]

[Means to solve the problem]

In order to achieve the above objectives, this invention is designed to provide silicon base material in an inert atmosphere. After melting, the molten silicon is heated by a heat source by applying pressure. By continuously sending the molten silicon into the mold nozzle, the molten silicon is The liquid flows into the gripping end of the pull-out jig that is in contact with the pull-out end of the cold nozzle. Then, the melted cylinder at the part near the drawing end of the mold nozzle is removed from the inside of the gripping end. When the molten silicon is solidified, while applying pressure to the molten silicon, By continuously pulling out the pull-out jig, the solidified inside of the mold nozzle is A caster in which the solidified silicone sheet is continuously pulled out from the aforementioned drawer end opening. In the device for carrying out the tribon method, the above-mentioned pull-out jig includes a gripping tool. The gas venting hole that communicates with the end port is directed toward the tip side, and is longer than the overall length of the gripping end port. The hole is long and opens into the inert atmosphere and is used for venting the gas. Form a low-temperature point below the melting point of silicon from the desired point in the pore toward the tip. A polycrystalline silicon system with a temporary temperature-controlled heat source for a flexible pull-out jig. We are trying to provide manufacturing equipment for

[0014]

[Effect]

According to the present invention, when implementing the cast ribbon method, pressure is applied to When the molten silicon in the con melting tube flows into the casting path of the mold nozzle, the The remaining gas in the casting channel is removed from the gripping end of the drawing jig through the gas venting hole. , since the molten silicon is released into the furnace body, the molten silicon is removed from the casting path to the gripping end. After it flows into the mouth and fills it, it flows sufficiently into the gas venting pores. It becomes.

[0015] Here, the degassing pores have a small cross-sectional area, and from the middle to the tip. is controlled by a temperature-controlled heat source so that the temperature is lower than the melting point of silicon. , the molten silicon that has flowed into the gas venting hole solidifies, and therefore the extraction jig This prevents the material from escaping into the inert atmosphere, allowing for trouble-free extraction and treatment. You can pull out tools.

[0016]

【Example】

If the device according to the present invention is described in detail with reference to FIGS. 1 to 3, its basic configuration is shown in FIG. In common with the conventional device explained in 4, the same parts are used in the device of the present invention. are shown with the same reference numerals, and the difference is that the heat source 10 of the mold nozzle 5 and a temperature control heat source 11 for the drawer jig 7, both of which are independent heaters 10a and 10b. ..., independent heaters 11a, 11b..., each independent heater It is possible to give the desired temperature distribution by energizing each separately. Therefore, the drawing jig 7 is provided with gas venting holes 12.

[0017] Here, as shown in FIGS. 2 and 3, the drawer jig 7 has an upper member 7b and a lower member 7b. The side members 7b' are stacked one on top of the other, and these are fixed with carbon locking screws 7c. The upper member 7b consists of a front end 7d and a narrower rear end 7e. , the lower surface 7f of the front end portion 7d has an end opening cutout 7g for forming a gripping end opening 7a. The distal end face 7h is opened and recessed, and the rear end part 7e is penetrated with a fixing vertical hole 7i. The end opening cutout 7g becomes gradually deeper from the tip end surface 7h toward the rear end surface 7e side. It is tilted like that.

[0018] On the other hand, the lower member 7b' also has a front end 7d' and a narrow rear end 7e' connected to each other, A cutout 7g' for an end opening that opens on the tip surface 7h' is inclined and recessed on the upper surface 7f'. In addition, a vertical screw hole 7i' is provided in the rear end portion 7e', and a vertical screw hole 7i' is provided in the rear end surface 7j. In this case, the tap 7l for connecting the drawer rod 7k shown in Fig. 1 is screwed horizontally. It is. The lower surface 7f and upper surface 7f' of the upper member 7b and lower member 7b' are brought into contact with each other. After stacking them together, insert the set screw 7c from the fixing vertical hole 7i as shown in Figure 2, and It is screwed into the screw hole 7i', and the drawer jig 7 configured in this way has a , a wedge shape is formed by combining the end cutouts 7g and 7g' on the tip surfaces 7h and 7h'. The above-mentioned gripping end opening 7a is now opened. The drawer jig 7 thus formed has its tip surfaces 7h, 7h' facing forward. The mold nozzle 5 is brought into contact with the end surface of the mold nozzle 5 where the pull-out end port 5e opens. The above-mentioned gripping end opening 7a is kept in communication.

[0019] Furthermore, in the present invention, the drawer jig 7 is arranged so as to communicate with the gripping end opening 7a. For this purpose, the front end 7d of the upper member 7b is opened. The gas venting hole is formed so as to be long and open at the far end of the end hole 7g. 12 is opened in the longitudinal direction of the member 7b, and this is at the rear end surface of the upper member 7b. , and are opened to an inert atmosphere 1a.

[0020] On the other hand, the temperature-controlled heat source 11 includes independent heaters 11a and 1 such as electric heaters. By controlling the energization to 1b..., the heat source 10 and the mold nozzle are heated. The temperature distribution curve To from the drawer 5 to the drawing jig 7 is as shown in FIG. Up to the middle of the gas venting pore 12, the temperature reaches the melting point of silicon (MP) (1450°C ), but the tip side of point P is a low temperature area where the temperature is lower than the melting point. It can be controlled so that Further, in the illustrated example, three gas venting pores 12 are arranged in parallel as shown in FIG.

[0021] Since the present invention is constructed as described above, cast ribs can be used using this. When trying to manufacture polycrystalline silicon sheets by the If a pressure P using a cylinder or the like is applied to the molten silicon Si in the silicon melting tube 3, The molten silicon Si passes through the supply port 3a, the injection port 5a, the casting path 6, and the withdrawal end port 5e. Further, it flows into the gripping end port 7a of the drawer jig 7, and solidifies at the end port 7a. Once solidified, pull out the pull-out jig 7 in the direction of arrow D. Become.

[0022] Even if there is residual gas in the casting path 6 during the above manufacturing process, this Pressed by the press-fitted molten silicon Si, the casting path 6-drawing end port 5e-grip The molten silicon is discharged to the end port 7a, the gas venting hole 12, and the inert atmosphere 1a. Since there is nothing blocking the flow of water, the water flows smoothly into the gripping end opening 7a. It becomes full and further flows into the gas venting pores 12.

[0023] However, the molten silicon Si that has flowed into the gas venting pores 12 is controlled by temperature control. Due to the temperature control of the heat source 11, the temperature after point P is lower than the melting point MP of silicon. It is cooled by the drawing jig 7, solidifies in the gas venting hole 12, and this Therefore, it does not flow out from the drawer jig 7 into the inert atmosphere 1a.

[0024]

[Effect of the idea] Since the present invention is constructed as described above, it is possible to use the cast ribbon method. If polycrystalline silicon is manufactured using When the gas flows under pressure, it is released into the inert atmosphere from the gripping end through the gas venting hole. Since the molten silicon is poured out, it is difficult to prevent the molten silicon from flowing into the gripping end opening. This not only solves the problem, but also directs the temperature distribution towards the tip of the gas venting pores. Since the temperature can be controlled to fall, the molten silicon is kept in an inert atmosphere. It will not leak inside.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional front view of an embodiment of the polycrystalline silicon sheet manufacturing apparatus according to the present invention, showing the relationship with the temperature distribution state.

FIG. 2 is an enlarged longitudinal sectional front view showing the pull-out jig in FIG. 1;

FIG. 3 is a plan view of the drawing jig shown above.

FIG. 4 is a longitudinal sectional front view showing the temperature distribution state of a conventional polycrystalline silicon sheet manufacturing apparatus.

FIG. 5 is a vertical cross-sectional front view showing a conventional ribbon method polycrystalline silicon sheet manufacturing apparatus.

[Explanation of symbols]

1a Inert atmosphere 5 Mold nozzle 5e Drawer end opening 7 Drawer jig 7a Grip end 10 Heat source 11 Temperature control heat source 12 Pore for gas venting P pressure Si molten silicon MSi solidified silicone sheet

Continuation of front page (72) Creator Tomoya Suzuki 2-3-17 Kikusui Gojo, Shiroishi-ku, Sapporo Shikisha Hokusan Hokusan Research Institute (72) Creator Toshiaki Moritani 2-3-17 Kikusui Gojo, Shiroishi-ku, Sapporo Shikisha Hokusan Hokusan Research Institute

Claims (1)

[Scope of utility model registration request] [Claim 1] After melting a silicon base material in an inert atmosphere, pressure is applied to the molten silicon to continuously send it into a mold nozzle heated by a heat source. , the molten silicon is caused to flow into the gripping end of the drawer jig that is in contact with the drawer end of the mold nozzle, and the molten silicon is solidified from the gripping end to the portion near the drawer end of the mold nozzle. At the point when the silicone is solidified, by continuously pulling out the drawing jig while applying pressure to the molten silicon, the solidified silicon sheet solidified in the mold nozzle is continuously drawn out from the drawing end opening. In an apparatus for carrying out the cast ribbon method in which the drawing jig is pulled out, the drawing jig has a gas venting hole communicating with the gripping end opening facing toward the tip side and extending from the entire length of the gripping end opening. For a drawing jig, the hole is long and is opened into the inert atmosphere, and a low temperature area below the melting point of silicon can be formed from a desired point in the gas venting pore toward the tip side. A polycrystalline silicon sheet production equipment equipped with a temperature-controlled heat source.