JP2005162507A - Polycrystal semiconductor ingot and its manufacturing device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a polycrystal silicon ingot which shows a good unidirectional solidification. <P>SOLUTION: A mold 1 is mounted on a pedestal 4 and can be vertically moved by a driving means 13. A silicon melt contained in the mold 1 is cooled from the bottom of the mold to be gradually solidified toward the top through unidirectional solidification. Here, the pedestal 4 is lowered so that a heating element 17 surrounding the surface of a side wall of the mold 1 is positioned near the solid-liquid interface of the silicon melt to inhibit heat radiation from the side wall surface and to reduce crystal growth from the side wall surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polycrystalline semiconductor ingot manufacturing apparatus for manufacturing a polycrystalline semiconductor ingot such as a polycrystalline silicon ingot used for a solar cell material, a method for manufacturing a polycrystalline semiconductor ingot using the same, and a The present invention relates to a crystalline semiconductor ingot.

  Currently, silicon semiconductors are mainly used as this type of solar cell material. This silicon semiconductor is classified into single crystal, polycrystalline and amorphous from the viewpoint of crystal structure. Among them, polycrystalline silicon is currently most frequently used as a solar cell material because of its excellent balance between manufacturing cost and performance.

  However, since the photoelectric conversion efficiency of polycrystalline silicon is inferior to that of single crystal silicon, in the future, further improvement in photoelectric conversion efficiency is required as the price is reduced.

As a conventional method for producing this polycrystalline silicon, for example, in Patent Document 1, a crucible made of quartz (silicon oxide: SiO ₂ ) is filled with solid silicon, and this is heated and melted. A semi-continuous casting method in which a graphite mold is poured is disclosed.

  Patent Document 2 discloses a heat exchange method in which solid silicon is melted in a quartz crucible in a vacuum and solidified as it is.

  In Patent Document 3, solid silicon charged into the mold bottom is heated and melted with an electron beam gun, and then solid silicon is additionally charged and melted while being heated with an electron beam gun. A method of solidifying molten silicon in one direction upward from the bottom is disclosed.

  Recently, many attempts have been made to produce polycrystalline silicon having high optical and electrical characteristics by improving the conventional method for producing polycrystalline silicon by the heat exchange method. For example, in Patent Document 4, a material having a high porosity and a low thermal conductivity is used for the side wall of the mold, so that heat removal from the side wall surface is suppressed and crystal growth from the side wall surface is reduced. A method for producing good polycrystalline silicon is disclosed.

  Patent Document 5 not only gives a temperature gradient in the vertical direction upward from the bottom as in the conventional manufacturing method, but also uses an auxiliary heater provided on the side surface of the mold at the start of cooling. A method of manufacturing crystalline silicon having crystal grains having a large diameter in the horizontal direction by applying a temperature gradient in a horizontal direction from a part is disclosed.

In Patent Document 6, a sensor such as a thermometer or an ultrasonic distance meter is provided on the side wall surface of a mold, and a solidification rate value obtained from the measured value is compared with a target solidification rate value to provide a heating unit and a cooling unit. A method of stabilizing the coagulation rate by controlling is disclosed.
Japanese Patent Publication No.57-21515 Japanese Patent Publication No.58-54115 JP 62-260710 A JP 2000-135545 A JP 2000-327487 A JP 2001-278613 A

  In a conventional method for producing a polycrystalline silicon ingot, a silicon melt contained in a mold is cooled from the bottom of the mold and gradually solidified upward. However, in the conventional method for manufacturing a polycrystalline silicon ingot, heat is radiated from the side wall surface of the mold to cause crystal growth from the side wall surface of the mold. A bad polycrystalline silicon ingot is produced. In such an ingot, crystallinity as a semiconductor is deteriorated in the peripheral portion, and optical characteristics and electrical characteristics are deteriorated.

  The present invention has been made in view of the above-described conventional circumstances, and produces a polycrystalline semiconductor ingot having good unidirectional solidification, good crystallinity as a semiconductor, and good optical characteristics and electrical characteristics. An object of the present invention is to provide a polycrystalline semiconductor ingot manufacturing apparatus, a method for manufacturing a polycrystalline semiconductor ingot using the same, and a polycrystalline semiconductor ingot manufactured thereby.

  An apparatus for producing a polycrystalline semiconductor ingot according to the present invention includes a mold capable of containing a semiconductor material, a melting means for melting and heating the semiconductor material in the mold, and the semiconductor material in the mold is melted by the melting means. After that, when the molten liquid of the semiconductor material is cooled from one end portion to the other end portion and solidified in one direction, a heating unit that heats the semiconductor material from the side wall surface with the target position of the solid-liquid interface With this, the above-mentioned object is achieved.

  Preferably, in the polycrystalline semiconductor ingot manufacturing apparatus of the present invention, the apparatus further includes a driving unit that relatively moves the mold and the heating unit in one direction, and the driving unit is located at a position corresponding to the solid-liquid interface. At least one of the mold and the heating means is moved so that the heating means is disposed on the substrate.

  Further preferably, the driving means in the polycrystalline semiconductor ingot manufacturing apparatus of the present invention obtains the movement position of the solid-liquid interface based on the calculated solidification rate based on the solidification time of the semiconductor material measured in advance, and sets the obtained movement position to the obtained movement position. The mold and the heating means are relatively moved in one direction so as to match.

  Further preferably, the heating means in the polycrystalline semiconductor ingot manufacturing apparatus of the present invention is provided so as to surround the periphery with a predetermined width with respect to the side wall surface of the mold.

  Further preferably, the driving means in the apparatus for producing a polycrystalline semiconductor ingot of the present invention moves the mold and the melting means relatively in one direction so as to increase the distance between the mold and the melting means. The melt of the semiconductor material is cooled from one end to the other end in the mold to solidify in one direction.

  Further preferably, the melting means in the apparatus for producing a polycrystalline semiconductor ingot according to the present invention is provided so as to cover at least the open upper part of the mold.

  Further preferably, the apparatus further includes a cooling means for cooling the melt of the semiconductor material in the mold from the lower part to the upper part in the polycrystalline semiconductor ingot manufacturing apparatus of the present invention.

  Further preferably, the cooling means in the apparatus for producing a polycrystalline semiconductor ingot of the present invention supplies the coolant to the bottom of the mold or a position near the mold, thereby directing the melt of the semiconductor material in the mold from the bottom to the top. Cool down.

  Furthermore, preferably, the melting means and the heating means in the polycrystalline semiconductor ingot manufacturing apparatus of the present invention are integrally configured.

  Further preferably, the melting means and the heating means in the polycrystalline semiconductor ingot manufacturing apparatus of the present invention are configured separately.

  Further preferably, the semiconductor material in the apparatus for producing a polycrystalline semiconductor ingot of the present invention is silicon.

  The method for producing a polycrystalline semiconductor ingot according to the present invention includes a filling step of filling a semiconductor material in a mold, a filling step of filling the mold with a semiconductor material, and a method for producing a polycrystalline semiconductor ingot by polycrystallizing a semiconductor material; The melting step of melting the semiconductor material and the position of the solid-liquid interface of the semiconductor material when the melt of the semiconductor material is cooled from one end to the other end and solidified in one direction. A heating step of heating from the side wall surface side, whereby the above object is achieved.

  Preferably, in the method for manufacturing a polycrystalline semiconductor ingot according to the present invention, the heating step for heating at least the periphery of the side wall surface of the mold with a predetermined width is disposed at a position corresponding to the solid-liquid interface of the semiconductor material. As described above, there is a moving step of relatively moving the mold and the heating means in one direction.

  Further preferably, in the method for manufacturing a polycrystalline semiconductor ingot according to the present invention, the moving step obtains the moving position of the solid-liquid interface based on the calculated solidification speed based on the solidification time of the semiconductor material measured in advance, The mold and the heating means are relatively moved in one direction so as to match.

  Further preferably, in the method for producing a polycrystalline semiconductor ingot according to the present invention, the moving step includes relatively moving the melting means for melting the semiconductor material in the mold and the mold in one direction so that the mold and the melting are moved. By increasing the distance of the means, the melt of the semiconductor material is cooled from one end to the other end in the mold to solidify in one direction.

  Further preferably, in the method of manufacturing a polycrystalline semiconductor ingot according to the present invention, the moving step lowers the mold or raises at least the heating means of the heating means and the melting means.

  Further preferably, in the method for producing a polycrystalline semiconductor ingot according to the present invention, the method further includes a cooling step of cooling the mold from below, and supplying the coolant to the bottom of the mold or a position near the mold by the cooling step. The molten material is cooled in the mold from the bottom to the top and solidified from the bottom to the top.

  Further preferably, the semiconductor material in the method for producing a polycrystalline semiconductor ingot of the present invention is silicon.

  The polycrystalline semiconductor ingot of the present invention is manufactured by the method for manufacturing a polycrystalline semiconductor ingot according to any one of claims 9 to 15, and thereby the above-described object is achieved.

  The operation of the present invention will be described below with the above configuration.

  In the present invention, the mold is filled with a semiconductor material such as silicon and heated and melted, and then the semiconductor material is melted in one direction (from one end to the other end, for example, the lower part). When moving from the top to the top or from the left end to the right end and solidifying in one direction, the driving means moves the mold and the heating means relatively in one direction. That is, the heating means is moved down by the driving means, or the heating means provided so as to surround the periphery of the side wall surface of the mold is raised by the driving means. For example, the position near the horizontal position is set as the target position. Heating from the side wall surface with the solid-liquid interface position as a target position is suppressed from escaping heat from the side wall surface. As a result, crystal growth from the side wall surface can be suppressed, and a polycrystalline semiconductor ingot having good unidirectional solidification is manufactured.

  According to the present invention, by heating from the side wall surface side of the mold with the solid-liquid interface position as the target position by the heating means provided so as to surround the periphery of the side wall surface of the mold with a predetermined width, Crystal growth can be suppressed and a polycrystalline semiconductor ingot such as a polycrystalline silicon ingot having good unidirectional solidification can be manufactured. The peripheral portion of the ingot thus obtained has improved optical characteristics and electrical characteristics as a semiconductor, and is suitable as a solar cell material.

  In the following, embodiments of the polycrystalline semiconductor ingot manufacturing apparatus and the polycrystalline semiconductor ingot manufacturing method using the same according to the present invention are applied to the polycrystalline silicon ingot manufacturing apparatus and the polycrystalline silicon ingot manufacturing method using the same. The case will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a schematic configuration of a main part in one embodiment of a polycrystalline silicon ingot producing apparatus of the present invention.

  As shown in FIG. 1, the polycrystalline silicon ingot manufacturing apparatus 20 can drive the casting mold 1 located in the center, covers 2 a and 2 b surrounding the casting mold 1, a support base 3 that supports these, and a support base 3. A pedestal 4 as a movable means, a thermocouple 5 for measuring temperature at the tip, induction heating coils 6 and 16 provided on the outer periphery, these molds 1, covers 2a and 2b, and a support base 3 The heating elements 7 and 15 that cover the side wall portion from above, can be accommodated, the thermal insulators 8a and 8b that block internal and external heat, the pyrometer 9, and the tip for temperature measurement are located in the heating element 7. The control thermocouple 10, the control device 11 for controlling the current to the induction heating coils 6 and 16 based on the temperature information from the thermocouple 5 and the control thermocouple 10, and the cooling tank 12 as a cooling means. And drive to move the base 4 up and down And a stage 13.

The mold 1 is made of quartz (silicon oxide: SiO ₂ ) and is a cylindrical or rectangular tube container having a bottom. The mold 1 is installed inside a chamber (not shown). The mold 1 is not limited to quartz but may be made of a refractory material such as graphite, silicon nitride or boron nitride, or may be made of a refractory metal such as mortar, molybdenum or tungsten.

  The covers 2a and 2b are made of graphite or the like and cover the outer peripheral surface of the mold 1 except for the upper portion (open portion).

  The bottom of the mold 1 is horizontally mounted on the support 3 via a cover 2a, and the support 3 is mounted on a pedestal 4 that can be rotationally displaced and moved up and down.

  The pedestal 4 is capable of rotating (rotating displacement) about the vertical line passing through the center of the mold 1 and rotating vertically (up and down displacement) in the vertical direction together with the support 3 using the driving means 13 as a driving source. is there.

  The thermocouple 5 detects the temperature of the bottom surface of the mold 1 by its tip portion, and the detected temperature information is sent to the control device 11.

  The induction heating coil 6 is disposed above the mold 1 at a predetermined interval, and when a high frequency current is passed through the induction heating coil 6, the heating element 7 made of graphite or carbon fiber is induction heated. .

  The heating element 7 is disposed between the mold 1 and the induction heating coil 6 and is disposed so as to cover the open upper portion of the mold 1 with a predetermined distance from the mold 1. When induction heating is performed, the open side of the mold 1 is heated from above by the radiant heat.

  The thermal insulators 8a and 8b are disposed below and on the outside of the heating element 7, and constitute a container that covers and accommodates the mold 1 from above.

  The pyrometer 9 is attached to the inside of the mold 1 so as to face from above, so that radiant heat from the inside of the mold 1 can be detected. By detecting this radiant heat, the surface temperature of the material can be measured. Thereby, it can be determined whether the silicon semiconductor material 14 in the mold 1 has melted or solidified.

  The tip of the control thermocouple 10 is attached so that the temperature of the heating element 7 can be detected.

  The control device 11 receives the detected temperature outputs from the thermocouple 5 and the control thermocouple 10 and controls the heating state by controlling the high-frequency current to the induction heating coil 6 based on them. The induction heating coil 6, the heating element 7 and the control device 11 constitute melting means for melting and heating the silicon semiconductor material 14 in the mold 1.

  The cooling bath 12 can cool the pedestal 4 by supplying cooling water to the pedestal 4 (position near the mold 1) in order to cool the mold 1 from the bottom surface. With the cooling water supplied from the cooling bath 12, the melt of the silicon semiconductor material 14 in the mold 1 can be cooled from the lower part toward the upper part. In the present embodiment, cooling water is used as the refrigerant, but it is also possible to use a refrigerant other than the cooling water.

  The drive means 13 can drive the base 4 to rotate or drive the base 4 up and down. Specifically, the driving unit 13 moves the mold 1 so that the heating element 15 and the induction heating coil 16 are arranged at a horizontal position corresponding to the solid-liquid interface of the silicon semiconductor material 14. The drive control of the driving means 13 is performed by obtaining the movement position of the solid-liquid interface of the silicon semiconductor material 14 based on the solidification speed calculated based on the solidification time of the silicon semiconductor material 14 measured in advance, and matching the obtained movement position. Thus, the mold 1 is lowered.

  The silicon semiconductor material 14 is a material for producing a polycrystalline semiconductor ingot which is accommodated in the mold 1 and crystallized by solidification after melting.

  The heating element 15 is for preventing heat from escaping from the side wall surface of the mold 1. The heating element 15 is provided in a ring shape at the outer peripheral position of the mold 1 that is spaced apart from the heating element 7 by a predetermined distance. And are arranged at predetermined intervals. That is, the heating element 15 is provided in a ring shape surrounding the periphery of the mold 1 with a predetermined width with respect to the side wall surface of the mold 1.

  The induction heating coil 16 is for inductively heating the heating element 15. That is, the induction heating coil 16 is provided in a ring shape that surrounds the outer periphery of the heating element 15 with a predetermined width. After the silicon semiconductor material 14 in the mold 1 is melted by the heating element 15, the induction heating coil 16, and the control device 11, the molten liquid of the silicon semiconductor material 14 is changed from the lower portion that is one end portion to the upper portion that is the other end portion. A heating means is configured to heat from the side wall surface with the position of the solid-liquid interface of the silicon semiconductor material 14 as a target when it is cooled and solidified in one direction.

  With the above configuration, first, when the mold 1 is filled with the silicon semiconductor material 14 and a high-frequency current is passed through the induction heating coil 6, the heating element 7 is induction-heated by the induction heating coil 6, and the radiant heat causes the mold 1 and its The internal silicon semiconductor material 14 is heated from above. Thereby, the silicon semiconductor material 14 can be melted from the upper part toward the lower part. At this time, by rotating the pedestal 4 by the driving means 13, the silicon semiconductor material 14 in the mold 1 can be uniformly heated and melted.

  Next, the cooling water is supplied from the cooling tank 12 to the pedestal 4 to cool the pedestal 4, whereby the molten silicon semiconductor material 14 in the mold 1 starts to solidify from the bottom (lower part) to the upper part. Furthermore, if the pedestal 4 is lowered by the driving means 13 so that the silicon semiconductor material 14 in the mold 1 is moved away from the heating element 7, unidirectional solidification from the bottom to the top in the mold 1 can be promoted. At this time, the gas is sealed from the outside by a chamber so that oxygen gas, nitrogen gas, or the like does not enter the molten silicon semiconductor material 14, and the chamber is kept in a vacuum or an inert gas atmosphere.

  In this case, in the silicon semiconductor material 14, it is necessary to suppress crystal growth from the side wall surface of the mold 1 in order to more surely perform unidirectional solidification from the lower part to the upper part. For this reason, in the present embodiment, when producing polycrystalline silicon, it is necessary until all of the molten silicon semiconductor material 14 in the mold 1 is solidified in each of natural cooling, forced cooling, and gradual cooling. Time is measured in advance. Whether or not the silicon semiconductor material 14 in the mold 1 has solidified can be determined by a change in the signal received by the pyrometer 9. The pyrometer 9 can detect thermal radiation from the silicon semiconductor material 14 filled in the mold 1 and measure the surface temperature of the material. Therefore, when the silicon semiconductor material 14 filled in the mold 1 is melted by heating, the melted state of the material can be determined, and when the silicon semiconductor material 14 is cooled and solidified, the solidified state of the material can be determined.

  Based on the time required for solidification in each of the cases where the silicon semiconductor material 14 in the mold 1 is naturally cooled, forcedly cooled, and gradually cooled, in each case, the silicon semiconductor material 14 melted in the mold 1 is The rate of solidification can be calculated. From this speed, the position of the solid-liquid interface when the silicon melt is unidirectionally solidified from the lower part to the upper part is obtained, and the heating means (heating element 15) provided so as to surround the periphery of the side wall surface of the mold is a silicon semiconductor. The pedestal 4 is lowered and the mold 1 is lowered so as to be arranged near the horizontal position of the solid-liquid interface in the material 14. Thereby, the solid-liquid interface of the silicon semiconductor material 14 is heated by the heating element 15 from the side wall surface, and heat escape from the side wall surface can be suppressed, and crystal growth from the side wall surface of the mold 1 can be suppressed. A polycrystalline semiconductor ingot having good unidirectional solidification can be produced.

  Since the heating element 15 is provided, there is a difference between the solidification rate of the silicon semiconductor material 14 calculated in advance and the actual solidification rate, and correction is necessary. Further, in the present embodiment, the heating means (heating element 15) is disposed near the horizontal position of the solid-liquid interface in the silicon semiconductor material 14 by lowering the pedestal 4, but this is not limiting, and the heating element 15 is not limited to this. The heating element 15 may be arranged near the horizontal position of the solid-liquid interface in the silicon semiconductor material 14 by raising it.

  Here, the manufacturing method of the polycrystalline silicon ingot of the present embodiment will be described in more detail using the flowchart shown in FIG. In addition, each following numerical value is an example, and is not limited to these.

  As shown in FIG. 2, when the production of the polycrystalline silicon ingot is started, first, in step S1, for example, about 140 kg of silicon semiconductor material 14 is filled in the mold 1. The mold 1 has a rectangular tube shape with a bottom surface of 550 mm × 550 mm.

  Next, in step S2, the mold 1 filled with the silicon semiconductor material 14 is placed on the support base 3 while being accommodated in the covers 2a and 2b, and the support base 3 is mounted on the base 4. In this way, preparation for heating is performed. At this time, the pedestal 4 is water-cooled by the cooling water from the cooling bath 12.

  In step S3, an alternating current having a frequency of, for example, about 7 kHz is passed through the induction heating coil 6, induction heating is started, and the temperature of the heating element 7 rises. When the temperature of the heating element 7 rises to about 1420 ° C., which is the melting temperature of silicon, since the heating element 7 is provided above the mold, melting of the silicon semiconductor material 14 progresses from the top to the bottom. To do.

  In step S4, the electric power supplied to the induction heating coil 6 is controlled by the control device 11, and the temperature is controlled so that the temperature in the mold 1 becomes constant.

  Thereafter, the melting of the silicon semiconductor material 14 is confirmed by the pyrometer 9 in step S5.

  In step S6, while the temperature in the mold 1 is gradually lowered, the pedestal 4 is simultaneously lowered, and the solidification of the silicon semiconductor material 14 is started.

  At this time, the pedestal 4 is lowered so that the position of the solid-liquid interface in the silicon semiconductor material 14 matches the position of the heating element 15 at the minimum descending speed 7 mm / h of the pedestal 4. In order to bring the heating element 15 to a predetermined temperature, an alternating current having a frequency of about 7 kHz is supplied to the dielectric heating coil 16 for solidification as well as the induction heating coil 6 for melting. Further, during the solidification of the silicon semiconductor material 14, the base 4 rotates at a speed of 1 rpm in order to reduce the influence of the temperature distribution.

  In step S7, it is determined whether or not the solidification of the silicon semiconductor material 14 is completed based on a change in the cooling rate, etc., and cooling is started after completion of the solidification (heating stop by the heating elements 7 and 15, water cooling, etc.). ).

  When the cooling is finished, the polycrystalline silicon ingot is taken out from the mold 1 in step S8, and all the manufacturing processes are finished.

  Next, the result of evaluating the polycrystalline silicon ingot thus manufactured will be described.

  FIG. 3 is a diagram showing a state when the polycrystalline silicon ingot 17 manufactured according to the present embodiment is viewed from above.

  As shown in FIG. 3, from the manufactured polycrystalline silicon ingot 17, 16 rectangular parallelepiped Nos. 1-No. Cutting was performed to obtain 16. Reference numeral 17a shown by hatching in FIG.

  Further, the direction of the side surface of each rectangular parallelepiped is N, W, S, and E when viewed from above. Note that the NS direction and the WE direction are orthogonal to each other, and the identification number No. 1-No. 16 are sequentially attached.

  4 shows a rectangular parallelepiped No. 1 located on the outer peripheral portion of the polycrystalline silicon ingot 17 shown in FIG. It is a perspective view which shows the measurement position of the crystal growth width from a side wall surface, and a lifetime value about S surface of 2. FIG.

  As shown in FIG. In the S plane of 2, the crystal growth width from the side wall surface and the lifetime of minority carriers generated by light irradiation (lifetime value) at three portions of the straight portion 50 mm, 100 mm and 150 mm from the bottom and parallel to the bottom surface And measured. The lifetime value is an average value in each straight line portion parallel to the bottom surface. The measurement results are shown in Table 1 below.

FIG. 5A shows a rectangular parallelepiped No. manufactured in this embodiment. 2 is a cross-sectional view as seen from the S-plane, and FIG. 5 (b) shows No. 2 in a polycrystalline silicon ingot manufactured by a conventional method in which the solid-liquid interface of the silicon semiconductor material is not heated. It is sectional drawing which looked at the rectangular parallelepiped corresponding to the position of 2 from the S surface. 5A and 5B, the vertical direction indicates the height from the bottom surface, and the horizontal direction indicates the crystal growth width from the side wall surface. A portion indicated by horizontal stripes indicates a portion where crystal has grown from the side wall surface of the mold 1.

  From the results of Table 1 and FIGS. 5A and 5B, the crystal growth width from the side wall surface of the mold 1 is reduced at each location as compared with the conventional method, and the lifetime value is increased. I understand that Since the photoelectric conversion efficiency is higher as the lifetime value is larger, according to the method for producing a polycrystalline silicon ingot of the present invention, a polycrystalline silicon ingot suitable as a semiconductor material for a solar cell can be obtained.

  As described above, according to this embodiment, the mold 1 is mounted on the pedestal 4 and can be moved up and down by the driving means 13. A heating element 15 provided so as to surround the periphery of the side wall surface of the mold 1 when the molten silicon melt accommodated in the mold 1 is cooled from the bottom of the mold and gradually solidified in one direction upward. The pedestal 4 is lowered so as to be arranged in the vicinity of the position of the solid-liquid interface of the silicon melt, thereby suppressing the heat radiation from the side wall surface and reducing the crystal growth from the side wall surface. Thereby, a polycrystalline silicon ingot having good unidirectional solidification can be produced.

  Although not particularly described in the above embodiment, the present invention can be similarly applied to a semiconductor material different from silicon.

  In the above embodiment, the heating element 7 as the melting means and the heating element 15 as the heating means are integrally configured, and the heating element 7 and the heating element 15 are integrally moved up and down. Not limited to this, the heating element 7 as the melting means and the heating element 15 as the heating means are configured separately, and are configured to be moved up and down (lifting / lowering) separately with respect to the mold 1 using the driving means 13. You can also. A vertical movement (lifting / lowering operation) suitable for the heating element 7 and the heating element 15 can be performed.

  Furthermore, in the above embodiment, the driving means 13 is configured to move the mold 1 up and down together with the base 4. However, the present invention is not limited to this, and the mold 1 is fixed and the heating element 7 as the melting means and the heat generation as the heating means. The body 15 may be configured to move up and down integrally, or both may be configured to move up and down. In short, the mold 1, the heating element 15, and the induction heating coil 16 are relatively moved. What is necessary is just to move to one direction (for example, an up-down direction, a left-right direction, etc.). Furthermore, the horizontal position of the heating element 15 can be set with respect to the side wall position (upper and lower position) of the mold 1 by providing a set of the heating element 15 and the induction heating coil 16 at a plurality of upper and lower positions and sequentially supplying power thereto. It can be moved up and down.

  In the above embodiment, the pedestal 4 is lowered to move the silicon semiconductor material 14 in the mold 1 away from the heating element 7. However, the present invention is not limited to this, and the heating element 7 side is raised to raise the heating element 7. The silicon semiconductor material 14 in the mold 1 may be kept away from the mold 1.

  Furthermore, as described above, the present invention has been exemplified using the preferred embodiment of the present invention, but the present invention should not be construed as being limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  For example, in the field of polycrystalline semiconductor ingots such as polycrystalline silicon ingots used for solar cell materials and the like, manufacturing methods thereof, and polycrystalline semiconductor ingot manufacturing apparatuses, heating means provided so as to surround the periphery of the mold sidewall surface are used. By heating the solid-liquid interface from the side wall surface, crystal growth from the side wall surface can be further suppressed, and a polycrystalline semiconductor ingot such as a polycrystalline silicon ingot having good unidirectional solidification can be manufactured. it can. The peripheral portion of the ingot thus manufactured has improved optical characteristics and electrical characteristics as a semiconductor, and can be suitably used as a solar cell material having high photoelectric conversion efficiency.

It is sectional drawing which shows the schematic principal part structure in one Embodiment of the polycrystalline-silicon ingot manufacturing apparatus of this invention. It is a flowchart for demonstrating embodiment in the manufacturing method of the polycrystalline-silicon ingot of this invention. It is a figure for demonstrating the state at the time of cutting out 16 rectangular parallelepiped from the polycrystalline silicon ingot manufactured by the manufacturing method of the polycrystalline silicon ingot of this invention. In the rectangular parallelepiped of FIG. 3, a rectangular parallelepiped No. for explaining the measurement position of the crystal growth width and lifetime value from the side wall surface. FIG. (A) is a rectangular parallelepiped No. in FIG. 2 is a cross-sectional view of the polycrystalline silicon ingot produced by a conventional method in which the solid-liquid interface of the silicon semiconductor material is not heated. It is sectional drawing when the rectangular parallelepiped corresponding to the position of 2 is seen from the S plane.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold 2a, 2b Cover 3 Support stand 4 Base 5 Thermocouple 6 Induction heating coil 7 Heat generating body 8a, 8b Thermal insulator 9 Pyrometer 10 Thermocouple for control 11 Controller 12 Cooling tank 13 Driving means 14 Silicon semiconductor material 15 Heat generating element (For solidification)
16 Induction heating coil (for solidification)
17 Ingot

Claims (16)

A mold that can accommodate a semiconductor material;
Melting means for melting and heating the semiconductor material in the mold;
After the semiconductor material in the mold is melted by the melting means, the semiconductor material is solidified when the molten liquid of the semiconductor material is cooled from one end to the other end to solidify in one direction. A polycrystalline semiconductor ingot manufacturing apparatus having heating means for heating from the side wall surface with the liquid interface position as a target. A driving means for moving the mold and the heating means relatively in one direction;
The polycrystalline semiconductor ingot manufacturing apparatus according to claim 1, wherein the driving unit moves at least one of the mold and the heating unit so that the heating unit is disposed at a position corresponding to the solid-liquid interface.   The driving means obtains a moving position of the solid-liquid interface based on a calculated solidification speed based on a pre-measured solidification time of the semiconductor material, and relatively moves the mold and the heating means in one direction so as to match the obtained moving position. The polycrystalline semiconductor ingot manufacturing apparatus according to claim 2, which is moved to a position.   The polycrystalline semiconductor ingot manufacturing apparatus according to claim 1, wherein the heating means is provided so as to surround the periphery of the mold with a predetermined width with respect to the side wall surface of the mold.   The driving means moves the mold and the melting means relatively in one direction to increase the distance between the mold and the melting means, thereby allowing the molten semiconductor material to flow from one end to the other in the mold. The polycrystalline semiconductor ingot manufacturing apparatus according to claim 1, wherein the apparatus is cooled toward the end portion and solidified in one direction.   The polycrystalline semiconductor ingot manufacturing apparatus according to claim 1, wherein the melting means is provided so as to cover at least an open upper portion of the mold.   The polycrystalline semiconductor ingot manufacturing apparatus according to claim 1, further comprising a cooling unit that cools the melt of the semiconductor material in the mold from the lower part toward the upper part.   The polycrystalline semiconductor ingot manufacturing apparatus according to claim 1, wherein the semiconductor material is silicon. In a method for manufacturing a polycrystalline semiconductor ingot for manufacturing a polycrystalline semiconductor ingot by polycrystallizing a semiconductor material,
A filling step of filling a semiconductor material into a mold;
A melting process for melting the semiconductor material in the mold;
A heating step of heating the semiconductor material melt from one end to the other end to heat from the side wall surface with the position of the solid-liquid interface of the semiconductor material as a target when solidifying in one direction; A method for producing a polycrystalline semiconductor ingot.   In the heating step, the mold and the heating unit are relatively positioned so that the heating unit that heats at least the periphery of the side wall surface of the mold with a predetermined width is disposed at a position corresponding to the solid-liquid interface of the semiconductor material. The method for producing a polycrystalline semiconductor ingot according to claim 9, further comprising a moving step of moving in the direction.   In the moving step, the moving position of the solid-liquid interface is determined based on the calculated solidification speed based on the solidification time of the semiconductor material measured in advance, and the mold and the heating unit are relatively unidirectionally aligned with the determined moving position. The method for producing a polycrystalline semiconductor ingot according to claim 10, wherein   In the moving step, the melting means for melting the semiconductor material in the mold and the mold are relatively moved in one direction, and the distance between the mold and the melting means is increased, whereby the molten liquid of the semiconductor material is removed. The method for producing a polycrystalline semiconductor ingot according to claim 10, wherein the mold is cooled from one end to the other end and solidified in one direction.   The method for manufacturing a polycrystalline semiconductor ingot according to claim 10, wherein the moving step lowers the mold or raises at least the heating means of the heating means and the melting means.   A cooling step of cooling the mold from the bottom, and cooling the molten semiconductor material from the bottom to the top in the mold by supplying a coolant to the bottom of the mold or a position in the vicinity thereof in the cooling step. The method for producing a polycrystalline semiconductor ingot according to claim 9 or 13, wherein the solidification is performed from the lower part to the upper part.   The method for producing a polycrystalline semiconductor ingot according to claim 9, wherein the semiconductor material is silicon. The polycrystalline semiconductor ingot manufactured by the manufacturing method of the polycrystalline semiconductor ingot in any one of Claims 9-15.