JP6590145B2 - Silicon ingot, method for producing the same, and seed crystal - Google Patents

Description

  The present invention relates to a silicon ingot used for a polycrystalline silicon solar cell and the like, a method for producing the same, and a seed crystal.

  Polycrystalline silicon solar cells have relatively high conversion efficiency, can be mass-produced, and have abundant resources necessary for battery production. For this reason, polycrystalline silicon solar cells continue to secure a large share among various types of solar cells.

  A polycrystalline silicon material used for a polycrystalline silicon solar cell is generally manufactured by a cast growth method. The cast growth method is a method in which a silicon bulk polycrystalline ingot is grown in one direction from the bottom of the crucible using a silicon melt placed in the crucible.

  In recent years, quasi-single crystal silicon has attracted attention. Since pseudo-single crystal silicon can be expected to improve conversion efficiency, it has been regarded as a promising material for solar cells.

  In order to produce pseudo single crystal silicon, a mono-like cast method has been developed as a kind of cast growth method. In the mono-like cast method, a single crystal silicon block is laid on the bottom of the crucible, and a grain crystal is grown in one direction from there to form a pseudo single crystal.

  In the mono-like casting method, as shown in FIG. 17, a polycrystallized portion 80 having a random orientation may occur at the upper part on both sides of the grown crystal grain 81. FIG. 18 shows a silicon ingot. Polycrystalline parts with random orientations are observed on both sides of the upper part of the silicon ingot. The polycrystallized part is a process of growing a pseudo single crystal using a seed crystal from a silicon melt, and a large number of crystal grains with a different orientation from the seed crystal are generated from the part in contact with the crucible side wall. The portion occupied by the crystal grains is enlarged.

  In order to overcome the problem of polycrystallization, the inventors of the present application formed an artificial crystal grain boundary by combining seed crystals as shown in Patent Document 1, and made use of this grain boundary. A method to suppress the expansion of the polycrystalline region was devised.

  Further, as shown in Non-Patent Document 1, it has been proposed to improve the quality of the center of the silicon ingot by forming a polycrystalline region near the crucible wall.

  The monolithic casting method still has the following problems.

  As shown in FIG. 17, in the casting method using the crucible 9, dislocations 82 are easily introduced due to volume expansion during solidification. When crystal growth is performed using a seed crystal in which a plurality of single crystal silicon blocks are arranged, dislocation occurs from the grain boundary.

  As shown in FIG. 17, the crucible 9 is used with a release material applied to the side surface and the bottom surface. Impurities 85 derived from the release material diffuse into the crystal grains 81 from the portions in contact with the side and bottom surfaces of the crucible 9. When a silicon ingot having impurities is used for a solar cell, the carrier recombination rate is increased. As shown in FIG. 19, since impurities exist in the vicinity of the crucible side wall of the outer portion of the silicon ingot, the carrier lifetime is short and the lifetime is short, and the central portion is low in impurity diffusion and has a long carrier lifetime. It becomes the life time part. If the diffusion of impurities is wide and the low lifetime part is large, the proportion of the high lifetime part that can be used as a solar cell material decreases, and the yield of silicon ingots also decreases.

JP 2014-24716 A

Advanced production technology of Si solar cells ”, KL-03, 28/10/2013

  The inventor of the present application makes further researches to provide a silicon ingot manufacturing method, a seed crystal, and a silicon ingot capable of growing high-quality pseudo single crystal silicon.

  In the method for producing a silicon ingot according to the present invention, a plurality of single-crystal silicon blocks are arranged in order from the side wall on the crucible bottom, and at least one first dislocation-suppressing grain boundary that suppresses dislocation generation along with crystal growth can be formed. A first dislocation suppression boundary, and at least one dislocation generation boundary capable of forming a dislocation generation grain boundary that is located closer to the side wall than the first dislocation suppression boundary and can generate dislocations along with crystal growth. And arranging the plurality of single-crystal silicon blocks to form a seed crystal, arranging a silicon melt on the seed crystal, cooling the silicon melt, and crystal orientation of the seed crystal In succession, crystal grains are grown in one direction to form a silicon ingot, and the dislocation generation boundary and the first dislocation suppression boundary are formed in the silicon ingot, respectively. Forming the dislocation generation grain boundary and the first dislocation suppression grain boundary taken over, generating dislocations in the crystal grains facing the dislocation generation grain boundary, and the side wall with respect to the first dislocation suppression grain boundary And a growth step for suppressing generation of dislocations in crystal grains facing on the opposite side.

  In the method for producing a silicon ingot according to the present invention, a plurality of single-crystal silicon blocks are arranged in order from the side wall on the crucible bottom, and at least one first dislocation-suppressing grain boundary that suppresses dislocation generation along with crystal growth can be formed. A first dislocation suppression boundary and a dislocation density higher than that of the single crystal silicon block on the side opposite to the side wall side with respect to the first dislocation suppression boundary is located on the side of the sidewall relative to the first dislocation suppression boundary. A dislocation step of disposing a plurality of single crystal silicon blocks to form a seed crystal so as to have a high dislocation single crystal silicon block; and disposing a silicon melt on the seed crystal, Is cooled and inherits the crystal orientation of the seed crystal to grow crystal grains in one direction to form a silicon ingot, and the first ingot in the silicon ingot Forming the first dislocation suppression grain boundary taking over the dislocation suppression boundary and the high dislocation crystal grain in which the dislocation is generated by taking over the high dislocation single crystal silicon block, and forming the side wall on the first dislocation suppression grain boundary. And a growth step for suppressing generation of dislocations in crystal grains facing on the opposite side.

The seed crystal of the present invention is a seed crystal used for producing a silicon ingot by growing silicon crystal grains,
The seed crystal includes a plurality of single crystal silicon blocks arranged in order from an end in a direction perpendicular to a growth direction in which the crystal grains grow, and first dislocation suppression that suppresses dislocation generation along with crystal growth. It is possible to form at least one first dislocation suppression boundary capable of forming a grain boundary and a dislocation generation grain boundary that is located closer to the end portion than the first dislocation suppression boundary and can generate a dislocation accompanying crystal growth. And at least one dislocation generation boundary.

  The seed crystal of the present invention is a seed crystal used for producing a silicon ingot by growing silicon crystal grains, and the seed crystal is an end perpendicular to the growth direction in which the crystal grains grow. A plurality of single crystal silicon blocks arranged in order from the first part, at least one first dislocation suppression boundary capable of forming a first dislocation suppression grain boundary that suppresses dislocation generation with crystal growth, and the first dislocations At least one high dislocation single crystal silicon block located at the end side of the suppression boundary and having a dislocation density higher than that of the single crystal silicon block opposite to the end side with respect to the first dislocation suppression boundary It is characterized by having.

  The silicon ingot according to the present invention is a silicon ingot composed of a plurality of crystal grains grown in one direction inheriting the crystal orientation of a silicon seed crystal, and the silicon ingot includes a first dislocation suppression grain boundary and the first With dislocation generation grain boundaries located on the end side in the direction perpendicular to the crystal grain growth direction from the dislocation suppression grain boundaries, dislocations are generated in the crystal grains facing the dislocation generation grain boundaries, The number of dislocations occurring in crystal grains facing the first dislocation suppression grain boundary on the side opposite to the end portion is less than the dislocations occurring in crystal grains facing the dislocation generation grain boundary. Features.

  The silicon ingot according to the present invention is a silicon ingot composed of a plurality of crystal grains grown in one direction inheriting the crystal orientation of a silicon seed crystal, and the silicon ingot includes a first dislocation suppression grain boundary and the first A high dislocation crystal grain positioned on an end side in a direction perpendicular to the growth direction of the crystal grain from the dislocation suppression grain boundary, and a dislocation is generated in the high dislocation crystal grain, and the first dislocation It is characterized in that the number of dislocations occurring in the crystal grains facing the side opposite to the end portion with respect to the suppression grain boundary is less than the dislocations occurring in the high dislocation crystal grains.

  According to the present invention, since the above-described configuration is provided, it is possible to provide a silicon ingot manufacturing method, a seed crystal, and a silicon ingot capable of growing high-quality pseudo single crystal silicon.

6 is a diagram showing a method for producing a seed crystal of Reference Example 1. FIG. It is a figure which shows the etch pit image of the cut surface of the silicon ingot of the reference example 1. FIG. 3 is a diagram showing a method for producing a seed crystal of Example 1. FIG. 2 is a photograph showing a cut surface of the silicon ingot of Example 1. FIG. It is a figure which shows the etch pit image of the cut surface of the silicon ingot of Example 1. FIG. It is a figure which shows the iron concentration distribution of the dislocation area | region of a crystal grain. It is explanatory drawing of the silicon ingot of Example 1. FIG. It is explanatory drawing of the silicon ingot produced by providing the 3rd dislocation suppression boundary further with respect to the seed crystal of Example 1. FIG. It is explanatory drawing of the silicon ingot produced using the high dislocation single crystal silicon block for the seed crystal of Example 1. It is explanatory drawing of the silicon ingot produced using the seed crystal which replaced with the dislocation generation | occurrence | production boundary of the seed crystal of Example 1, and has arrange | positioned the high dislocation single crystal silicon block. 6 is a diagram showing a method for producing a seed crystal of Example 2. FIG. It is a cross-sectional photograph of the cut surface of the silicon ingot cut | disconnected in the AA arrow line direction of FIG. It is the cross-sectional photograph of the cut surface of the silicon ingot which cut | disconnected the seed crystal part in the direction orthogonal to a Z direction. It is explanatory drawing of the cut surface of the silicon ingot cut | disconnected in the AA arrow line direction of FIG. It is explanatory drawing of the cut surface of the silicon ingot which cut | disconnected the seed crystal part in the direction orthogonal to a Z direction. It is explanatory drawing of the silicon ingot produced using the seed crystal which has replaced the dislocation generation | occurrence | production boundary of the seed crystal of Example 2, and has arrange | positioned the high dislocation single crystal silicon block. It is sectional drawing of the silicon ingot for demonstrating the conventional problem. It is a cross-sectional photograph of a polycrystallized silicon ingot. It is a figure which shows distribution of the lifetime of the carrier in a silicon ingot.

  A method for producing a silicon ingot, a seed crystal, and a silicon ingot according to an embodiment of the present invention will be described in detail.

  A method for producing a silicon ingot includes arranging a plurality of single crystal silicon blocks in order from a side wall on a crucible bottom, and forming at least one first dislocation-suppressing grain boundary that suppresses dislocation generation with crystal growth. A suppression boundary and at least one dislocation generation boundary capable of forming a dislocation generation grain boundary that is located on the side of the side wall from the first dislocation suppression boundary and can generate a dislocation accompanying crystal growth, An arrangement step of disposing a plurality of single crystal silicon blocks to form a seed crystal, disposing a silicon melt on the seed crystal, cooling the silicon melt, and inheriting the crystal orientation of the seed crystal A crystal grain is grown in one direction to form a silicon ingot, and the dislocation generation boundary and the first dislocation suppression boundary are respectively inherited in the silicon ingot. The dislocation generation grain boundary and the first dislocation suppression grain boundary are formed to generate dislocations in the crystal grains facing the dislocation generation grain boundary, and opposite to the side wall with respect to the first dislocation suppression grain boundary. And a growth step for suppressing generation of dislocations in crystal grains facing each other.

  In the arranging step, a seed crystal is formed by arranging a plurality of single crystal silicon blocks on the crucible bottom in order from the side wall. The seed crystal has at least one first dislocation suppression boundary and at least one dislocation generation boundary located on the side of the side wall from the first dislocation suppression boundary.

  The first dislocation suppression boundary can form a first dislocation suppression grain boundary that suppresses dislocation generation as the crystal grows. The dislocation generation boundary can form a dislocation generation grain boundary that can generate dislocations as the crystal grows.

  When a growth process is performed on a seed crystal composed of a plurality of single crystal silicon blocks, crystal grains grow in one direction, taking over the position and orientation of the single crystal silicon block. From the dislocation generation boundary and the first dislocation suppression boundary, a dislocation generation grain boundary and a first dislocation suppression grain boundary taking over the respective positions are formed. “Boundary” refers to a joint between adjacent single crystal silicon blocks, and “grain boundary” refers to a joint between crystal grains grown from adjacent single crystal silicon blocks.

  The first dislocation suppression grain boundary suppresses the occurrence of dislocations in adjacent crystal grains. The dislocation generation grain boundary causes dislocations in crystal grains in contact with the grain boundary. More dislocations of adjacent crystal grains across the dislocation generation grain boundary occur than dislocations of adjacent crystal grains across the first dislocation suppression grain boundary. The crystal grains in contact with the dislocation generation grain boundary relieve external stress caused by volume expansion at the time of dislocation growth, reduce stress applied to crystal grains other than the crystal grains, and dislocations in crystal grains other than the crystal grains. Occurrence can be suppressed. In addition, the crystal grains in which dislocations are generated easily trap impurities entering from the side wall of the crucible. For this reason, by forming a dislocation generation grain boundary, it is possible to suppress the generation of dislocations and the diffusion of impurities in crystal grains other than the crystal grains where dislocations have occurred.

  Moreover, the dislocation generation grain boundary is located on the side wall side from the first dislocation suppression grain boundary. The dislocation generated from the dislocation generation grain boundary is suppressed from propagating to the side opposite to the side wall side, that is, the center side by the first dislocation suppression grain boundary. For this reason, it can suppress that a dislocation | rearrangement generate | occur | produces in the crystal grain of the center side rather than a 1st dislocation suppression grain boundary.

  In addition, the crystal grains in which dislocations are generated can trap impurities diffused from the sidewall. Since the first dislocation suppression grain boundary is formed on the side opposite to the side wall side of the dislocation generation grain boundary, that is, the center side, it is possible to suppress the diffusion of impurities to the center side at the first dislocation suppression grain boundary. Therefore, by cutting out the center side from the first dislocation suppression grain boundary of the silicon ingot and using it as a solar cell material, the region of the high lifetime part having a long carrier lifetime is widened, and the yield of the silicon ingot is increased.

  The dislocation generation grain boundary is located on the side wall side from the first dislocation suppression grain boundary. For this reason, the crystal grains facing the dislocation generation grain boundary located on the side wall side of the first dislocation suppression grain boundary have a dislocation density larger than the crystal grains facing the first dislocation suppression grain boundary on the side opposite to the side wall. Become. For this reason, the dislocation density of the crystal grains facing the dislocation generation grain boundary is preferably larger than the dislocation density of the crystal grains facing the first dislocation suppression grain boundary on the side opposite to the side wall. Furthermore, the dislocation density of the crystal grains facing the dislocation generation grain boundary is preferably 10 times or more larger than the dislocation density of the crystal grains facing the first dislocation suppression grain boundary on the side opposite to the side wall. In this case, it is possible to effectively relieve external stress caused by volume expansion during dislocation growth and trap impurities effectively.

  In the arrangement step, it is preferable to arrange the dislocation generation boundary and the first dislocation suppression boundary in order from the side wall of the crucible. Furthermore, in the arrangement step, it is preferable that the crucible bottom has a quadrangular shape, and the dislocation generation boundary and the first dislocation suppression boundary are arranged in order from the side walls on the four side walls. In this case, a functional defect layer having a dislocation generation grain boundary taking over the dislocation generation boundary and a first dislocation suppression grain boundary taking over the first dislocation suppression boundary is formed at the end of the silicon ingot in contact with the side wall of the crucible. Is done. Since the intrusion of impurities from the side wall of the crucible and the generation of dislocations are suppressed at the first dislocation suppression grain boundaries, the incorporation of impurities and the generation of dislocations are effective in the region opposite to the end portion with respect to the first dislocation suppression grain boundaries. Reduced. In this way, when dislocation generation boundaries and first dislocation suppression boundaries are arranged in order from the side wall of the crucible, only one or more dislocation generation boundaries and first dislocation suppression boundaries may be provided.

  A plurality of single crystal silicon blocks constituting the seed crystal are used. The plurality of single crystal silicon blocks used for the seed crystal may have the same dislocation density.

  Alternatively, the seed crystal is located on the side wall side of the first dislocation suppression boundary and has a high dislocation single crystal silicon having a higher dislocation density than the single crystal silicon block opposite to the side wall side with respect to the first dislocation suppression boundary. You may have a block. In this case, many dislocations are generated in the crystal grains grown by taking over the high dislocation single crystal silicon block. The dislocation density of the crystal grains grown by taking over the high dislocation single crystal silicon block can be made larger than the dislocation density of the crystal grains facing the first dislocation suppression grain boundary on the side opposite to the side wall.

  In the arrangement step, at least one second dislocation suppression boundary that can form a second dislocation suppression grain boundary that suppresses dislocation generation accompanying crystal growth is provided on the opposite side of the side wall with respect to the first dislocation suppression boundary. A plurality of single crystal silicon blocks are formed to form a seed crystal, and in the growth process, a second dislocation suppression grain boundary that takes over the second dislocation suppression boundary is formed in the silicon ingot, and the second dislocation suppression grain boundary is formed. It is preferable to suppress the occurrence of dislocations in the crystal grains facing each other.

  By disposing the second dislocation suppression boundary on the side opposite to the side wall with respect to the first dislocation suppression boundary, that is, on the center side, it is possible to more effectively suppress the occurrence of dislocation on the center side than the first dislocation suppression grain boundary.

  In the arranging step, a plurality of single crystals are provided so as to have at least one third dislocation suppression boundary that can form a third dislocation suppression grain boundary that suppresses dislocation generation along with crystal growth on the side wall side from the dislocation generation boundary. A silicon block is arranged to form a seed crystal, and in the growth process, a third dislocation suppression grain boundary that takes over the third dislocation suppression boundary is formed in the silicon ingot and faces the third dislocation suppression grain boundary on the side wall side. It is preferable to suppress the occurrence of dislocations in the crystal grains.

  Nuclei are formed in the vicinity of the side wall, and a polycrystal having a crystal orientation different from that of the seed crystal may grow. Also in this case, by arranging the third dislocation suppression boundary on the side wall side from the dislocation generation boundary, the growth of the polycrystal having a different orientation from the seed crystal at the third dislocation suppression grain boundary grown from the third dislocation suppression boundary. Can be suppressed. It can suppress that the crystal grain of the center side rather than a 3rd dislocation suppression grain boundary is polycrystallizing.

  When the seed crystal has a third dislocation suppression boundary, it is preferable that the third dislocation suppression boundary, the dislocation generation boundary, and the first dislocation suppression boundary are sequentially disposed from the side wall of the crucible in the arranging step. Further, in the arranging step, it is preferable that the crucible bottom has a quadrangular shape, and the third dislocation suppression boundary, the dislocation generation boundary, and the first dislocation suppression boundary are sequentially arranged from the side walls of the four crucibles. In this case, the end of the silicon ingot that is in contact with the side wall of the crucible is provided with a third dislocation suppression grain boundary that inherits the third dislocation suppression boundary, a dislocation generation grain boundary that inherits the dislocation generation boundary, and a first dislocation suppression boundary. A functional defect layer having the inherited first dislocation suppression grain boundary is formed. In the region on the side opposite to the end portion from the first dislocation suppression grain boundary, not only the mixing of impurities is reduced, but also the polycrystalline growth starting from the side wall of the crucible can be effectively suppressed. Thus, when the dislocation generation boundary and the first dislocation suppression boundary are arranged at the third dislocation suppression boundary in order from the side wall of the crucible, one each of the third dislocation suppression boundary, the dislocation generation boundary, and the first dislocation suppression boundary. It may be only one or a plurality.

  Whether the grain boundary between crystal grains is a dislocation generation grain boundary, a first dislocation suppression grain boundary, a second dislocation suppression grain boundary, or a third dislocation suppression grain boundary is greatly affected by the degree of correspondence of the grain boundaries between crystals. Is done. When the correspondence of the grain boundary is high, it becomes a dislocation generation grain boundary, and when the correspondence of the grain boundary is lower than the dislocation generation grain boundary, the first dislocation suppression grain boundary, the second dislocation suppression grain boundary, and / or the third dislocation suppression grain. Become a world.

  The total thickness of the single crystal silicon blocks facing at least one dislocation generation boundary disposed in the vicinity of one of the pair of opposing side walls of the crucible is preferably 1 mm or more and 100 mm or less, and more preferably 5 mm or more and 100 mm. The following is preferred. Further, even when a high dislocation single crystal silicon block is used, the total thickness of at least one high dislocation single crystal silicon block arranged in the vicinity of one of the pair of opposing side walls of the crucible is 1 mm or more and 100 mm or less. The thickness is preferably 5 mm or more and 100 mm or less. In this case, the crystal grains grown from the high dislocation single crystal silicon block have a thickness suitable for stress relaxation and impurity absorption.

  There is a Σ value as an index representing the degree of correspondence between grain boundaries between crystals. The Σ value can also be determined by the ratio of the unit cell area of the corresponding cell to the unit cell area. The Σ value takes only an odd number, and a Σ value of 1 means that both unit cells between the grain boundaries are the same, and there is no grain boundary. The smaller the Σ value, the better the correspondence between crystals (the degree of correspondence is high) (paragraphs 0004 and 0016 of Japanese Patent No. 4887504).

  The Σ value of the dislocation generation grain boundary is preferably smaller than the Σ value of the first dislocation suppression grain boundary. The Σ value of the dislocation generation grain boundary is preferably smaller than the Σ value of the second dislocation suppression grain boundary. The Σ value of the dislocation generation grain boundary is preferably smaller than the Σ value of the third dislocation suppression grain boundary. The correspondence between crystals at the dislocation generation grain boundary is better than the correspondence between crystals at the first dislocation suppression grain boundary, the second dislocation suppression grain boundary, and the third dislocation suppression grain boundary. For this reason, dislocations at the dislocation generation grain boundary are more easily propagated than the first dislocation suppression grain boundary, the second dislocation suppression grain boundary, and the third dislocation suppression grain boundary.

  The Σ values of the first dislocation suppression grain boundary, the second dislocation suppression grain boundary, and the third dislocation suppression grain boundary may be 27 or more, for example. The Σ value of the dislocation generation grain boundary is preferably 1 or more and 5 or less, for example.

  The grain boundary Σ value can be measured when it is 27 or less, and when it is 29 or more, it is difficult to measure. In this specification, the case where the Σ value is 29 or more is referred to as a random grain boundary. For example, the first dislocation suppression grain boundary, the second dislocation suppression grain boundary, and / or the third dislocation suppression grain boundary is a random grain boundary, and the Σ value of the dislocation generation grain boundary is less than 27, further 21 or less, 17 or less, or 9 or less. It is good to do.

  In order to form the first to third dislocation suppression grain boundaries, the orientations of the single crystal silicon blocks facing each other across the dislocation suppression boundary may be set to be greatly different from each other. In order to form dislocation generation grain boundaries, the orientations of the single crystal silicon blocks facing each other across the dislocation generation boundary may be set so as to approximate each other.

  For example, in order to produce a dislocation occurrence grain boundary of Σ1, a dislocation occurrence boundary may be formed by adjoining single crystal silicon blocks having the same orientation in the arrangement step. The dislocation generation boundary that can form the dislocation generation grain boundary of Σ1 is not particularly limited as long as, for example, the orientations of adjacent single crystal silicon blocks are the same. For example, the orientations of adjacent single crystal silicon blocks are all x (110) y (1-10) z (001), x (210) y (1-20) z (001), or x (310) It may be y (1-30) z (001).

  In order to form the dislocation generation grain boundary of Σ3, in the arranging step, for example, one of the adjacent single crystal silicon blocks is set to x (111) y (11-2) z (1-10), and the other The orientation of the single crystal silicon block may be x (111) y (-1-12) z (-110).

  In order to form the dislocation occurrence grain boundary of Σ5, in the arrangement step, for example, 1) one orientation of adjacent single crystal silicon blocks is x (210) y (1-20) z (001), and the other The orientation of the single crystal silicon block is x (210) y (-120) z (00-1), or 2) the orientation of one of the adjacent single crystal silicon blocks is x (310) y (1 −30) z (001), and the orientation of the other single crystal silicon block may be x (310) y (−130) z (00-1).

In the case where the first dislocation suppression grain boundary, the second dislocation suppression grain boundary, and the third dislocation suppression grain boundary are random grain boundaries, for example, in order to form a random grain boundary, single crystal silicon blocks having the following orientations are formed: Adjacent to each other.
X (210) y (1-20) z (001) single crystal silicon block and x (310) y (1-30) z (001) single crystal silicon block 1-20) z (001) single crystal silicon block and x (111) y (11-2) z (1-10) single crystal silicon block x (310) y (1-30) z (001) single crystal silicon block and x (111) y (11-2) z (1-10) single crystal silicon block

  Regarding the first to third dislocation suppression boundaries and the dislocation occurrence boundary, the orientation (z direction) in the growth direction of the single crystal silicon block facing each other across these boundaries is preferably {001}. In this case, a surface concavo-convex structure with a high antireflection effect of sunlight can be formed by immersing the surface of the obtained silicon ingot in the z direction in a chemical solution.

  When the crystal orientation of the single crystal silicon block facing the boundary of the seed crystal is deviated from the Σ value, the growth orientation is such that the crystal orientation of the surface facing the grain boundary of the crystal grain becomes the Σ value. There is a tendency for deviation to occur. As the deviation angle with respect to the Σ value is larger, dislocations are more likely to occur and the stress relaxation performance during growth is higher. For example, when the first dislocation suppression grain boundary, the second dislocation suppression grain boundary, and / or the third dislocation suppression grain boundary and the dislocation generation grain boundary have the same Σ value, a boundary having a large deviation angle from the Σ value. Is a dislocation occurrence boundary because a grain boundary is likely to generate dislocations, and a boundary having a smaller deviation angle from the Σ value than the dislocation generation boundary is a dislocation suppression boundary because it forms a grain boundary in which dislocations are less likely to occur.

The deviation angle of the crystal orientation of the crystal grain facing the dislocation generation grain boundary with respect to the crystal orientation of the single crystal silicon block facing the dislocation generation boundary is preferably 0 ° or more and 10 ° or less, and more preferably 1 × 10 ^{−5 °} or more and 10 °. It may be the following. If the misalignment angle is too small, dislocations may not be easily generated. If the deviation angle is excessive, it may be difficult to form a grain boundary of the Σ value due to crystal growth.

In addition, the method for producing a silicon ingot has a plurality of single crystal silicon blocks arranged in order from the side wall on the crucible bottom, and at least one first dislocation-suppressing grain boundary that suppresses dislocation generation along with crystal growth. One dislocation suppression boundary and a high dislocation density located on the side of the first dislocation suppression boundary and higher than that of the single crystal silicon block opposite to the side wall with respect to the first dislocation suppression boundary. A disposing single crystal silicon block, and a disposing step of disposing the plurality of single crystal silicon blocks to form a seed crystal;
A silicon melt is disposed on the seed crystal, and the silicon melt is cooled to inherit crystal orientation of the seed crystal to grow crystal grains in one direction to form a silicon ingot, and in the silicon ingot Forming the first dislocation suppression grain boundary that has inherited the first dislocation suppression boundary and the high dislocation crystal grain that has generated the dislocation by taking over the high dislocation single crystal silicon block, and the first dislocation suppression grain boundary. And a growth step for suppressing generation of dislocations in crystal grains facing on the opposite side of the side wall. That is, in the seed crystal, a high-dislocation single crystal silicon block may be disposed on the end side of the first dislocation suppression boundary instead of the dislocation generation boundary.

  Also in this case, many dislocations are generated in the crystal grains grown by taking over the high dislocation single crystal silicon block. The dislocation density of the crystal grains grown by taking over the high dislocation single crystal silicon block can be made larger than the dislocation density of the crystal grains facing the first dislocation suppression grain boundary on the side opposite to the side wall. For this reason, in the crystal grains grown by taking over the high dislocation single crystal silicon block, external stress can be effectively relieved and impurities can be trapped effectively.

  In the arranging step, it is preferable to arrange the high dislocation single crystal silicon block and the first dislocation suppressing boundary in order from the side wall of the crucible. Further, in the arranging step, it is preferable that the crucible bottom has a quadrangular shape, and the high dislocation single crystal silicon block and the first dislocation suppressing boundary are arranged in order from each of the four side walls. In this case, a functional defect having a high dislocation single crystal grown from the high dislocation single crystal silicon block and a first dislocation suppression grain boundary taking over the first dislocation suppression boundary at the end of the silicon ingot in contact with the side wall of the crucible. Layers will be placed. More dislocations of high dislocation crystal grains are generated than dislocations of adjacent crystal grains across the first dislocation suppression grain boundary. High dislocation crystal grains easily trap impurities entering from the side wall of the crucible. By disposing the functional defect layer at the end of the silicon ingot in contact with the side wall of the crucible, it is possible to effectively suppress the intrusion of impurities from the side wall of the crucible with high dislocation crystal grains. As described above, when the high dislocation single crystal silicon block and the first dislocation suppression boundary are arranged in order from the side wall of the crucible, only one or a plurality of the high dislocation single crystal silicon block and the first dislocation suppression boundary may be provided. .

  In the disposing step, when disposing the high dislocation single crystal silicon block and the first dislocation suppression boundary sequentially from the side wall of the crucible, in the disposing step, the crystal is further provided on the side opposite to the side wall with respect to the first dislocation suppression boundary. A growth step comprising forming a seed crystal by arranging a plurality of single crystal silicon blocks so as to have at least one second dislocation suppression boundary capable of forming a second dislocation suppression grain boundary that suppresses dislocation generation with growth. In the method, it is preferable to form a second dislocation suppression grain boundary taking over the second dislocation suppression boundary in the silicon ingot to suppress the occurrence of dislocations in the crystal grains facing the second dislocation suppression grain boundary. Further, in the arrangement step, at least one third dislocation suppression boundary that can form a third dislocation suppression grain boundary that suppresses dislocation generation accompanying crystal growth is provided on the side wall side of the high dislocation single crystal silicon block. , A plurality of single crystal silicon blocks are arranged to form a seed crystal, and in the growth process, a third dislocation suppression grain boundary that takes over the third dislocation suppression boundary is formed in the silicon ingot, and a third dislocation suppression grain boundary is formed. It is preferable to suppress the occurrence of dislocations in the crystal grains facing on the side wall side.

  In this case, in the arrangement step, it is preferable to arrange the third dislocation suppression boundary, the high dislocation single crystal silicon block, and the first dislocation suppression boundary in order from the side wall of the crucible. Further, in the arranging step, it is desirable that the crucible bottom has a quadrangular shape, and the third dislocation suppression boundary, the high dislocation single crystal silicon block, and the first dislocation suppression boundary are arranged in order from the side walls on the four side walls of the crucible. . In this case, at the end of the silicon ingot that is in contact with the side wall of the crucible, the third dislocation suppression grain boundary that inherits the third dislocation suppression boundary, the high dislocation single crystal grown from the high dislocation single crystal silicon block, and the first dislocation A functional defect layer having a first dislocation suppression grain boundary taking over the suppression boundary is formed. Thereby, the growth of the polycrystal starting from the side wall of the crucible can be effectively suppressed. As described above, when the third dislocation suppression boundary, the high dislocation single crystal silicon block, and the first dislocation suppression boundary are arranged in order from the side wall of the crucible, the third dislocation suppression boundary, the high dislocation single crystal silicon block, and the first dislocation are arranged. There may be only one suppression boundary or a plurality of suppression boundaries.

The dislocation density of the high dislocation single crystal silicon block is preferably 1 × 10 ³ / cm ² or more, and more preferably 1 × 10 ⁴ / cm ² or more. A large number of dislocations can be generated in the crystal grains that have inherited the high-dislocation single crystal silicon block, so that crystal grains with more dislocations can be obtained.

  The single crystal silicon block used for the seed crystal of the present embodiment is not limited to the one cut out from the single crystal silicon ingot produced by the Czochralski (CZ) method or the floating zone method. It is possible to reuse the crystal and use a silicon block cut out from the silicon ingot produced by the method of the present invention.

  The crucible used in the present embodiment is made of silica with a horizontal or square horizontal cross-sectional shape, and is used by applying a release agent such as silicon nitride powder on the inner surface. In addition, the method of crystal growth in one direction of the present embodiment includes a method of moving the crucible position downward, a method of moving the heater upward, and a heater output in a temperature gradient in which the lower side is a low temperature and the upper side is a high temperature. Any method can be used as long as crystal growth in one direction is possible, such as a method of gradually lowering the temperature, a method of removing heat from the lower part by opening the shutter, or a combination of these methods.

  In the growth step, a silicon melt is disposed on the seed crystal, the silicon melt is cooled to inherit the crystal orientation of the seed crystal, and crystal grains are grown in one direction from below to form a silicon ingot.

  The silicon melt itself may be charged into a crucible in which a seed crystal is disposed, or a silicon raw material may be disposed on a seed crystal in the crucible to melt the silicon raw material to form a silicon melt. In order to cool the silicon melt, temperature control means (for example, a heating element or / and a cooling medium) capable of controlling the temperature in the crucible may be arranged to cool the silicon melt. For example, the silicon melt may be cooled so that the crystal growth rate is about 0.1 mm / min to 10 mm / min.

The silicon ingot of the present embodiment is a silicon ingot composed of a plurality of crystal grains that have been grown in one direction by inheriting the crystal orientation of the silicon seed crystal, and the silicon ingot includes a first dislocation suppression grain boundary and a first dislocation. The dislocation generation grain boundary is located on the end side in the direction perpendicular to the growth direction of the crystal grain from the suppression grain boundary, and the dislocation is generated in the crystal grain facing the dislocation generation grain boundary. The number of dislocations occurring in the crystal grains facing the dislocation suppression grain boundary on the side opposite to the end is less than the dislocations occurring in the crystal grains facing the dislocation generation grain boundary. It is preferable that a dislocation generation grain boundary and a first dislocation suppression grain boundary are arranged in order from the end. The cross section in the direction perpendicular to the growth direction of the crystal grains of the silicon ingot has a quadrangular shape, and dislocation generation grain boundaries and first dislocation suppression grain boundaries are arranged in order from the four end portions in the vertical direction. Preferably it is. The silicon ingot has a second dislocation suppression grain boundary on the side opposite to the end with respect to the first dislocation suppression grain boundary, and the dislocation generated in the crystal grain facing the second dislocation suppression grain boundary is generated by the dislocation. It is preferable that the number is less than the number of dislocations occurring in the crystal grains facing the grain boundary. The silicon ingot has a third dislocation suppression grain boundary on the end side of the dislocation generation grain boundary, and the dislocation generated in the crystal grain facing the third dislocation suppression grain boundary faces the dislocation generation grain boundary. It is preferable that the number is less than the number of dislocations occurring in the crystal grains.
According to the silicon ingot, dislocations occurring in the crystal grains facing the first dislocation suppression grain boundary on the side opposite to the end are more dislocations than the dislocations occurring in the crystal grains facing the dislocation generation grain boundary. There are few. For this reason, dislocation generation and impurity diffusion in the crystal grains on the center side of the first dislocation suppression grain boundary are suppressed to a small extent.

Further, the silicon ingot of this embodiment may have high dislocation crystal grains instead of dislocation generation grain boundaries. That is, the silicon ingot according to the present embodiment is a silicon ingot composed of a plurality of crystal grains grown in one direction by inheriting the crystal orientation of the silicon seed crystal, and the silicon ingot includes the first dislocation suppression grain boundary, The high dislocation crystal grains are located on the end side in the direction perpendicular to the growth direction of the crystal grains from the one dislocation suppression grain boundary, and dislocations are generated in the high dislocation crystal grains. The number of dislocations occurring in crystal grains facing the grain boundary on the side opposite to the end may be less than the dislocations occurring in high dislocation crystal grains. It is preferable that high dislocation crystal grains and first dislocation suppression grain boundaries are arranged in order from the end. The cross section in the direction perpendicular to the growth direction of the crystal grains of the silicon ingot has a quadrangular shape, and high dislocation crystal grains and first dislocation suppression grain boundaries are arranged in order from the four ends in the vertical direction. Preferably it is. The silicon ingot has a second dislocation suppression grain boundary on the side opposite to the end with respect to the first dislocation suppression grain boundary, and the dislocations occurring in the crystal grains facing the second dislocation suppression grain boundary are high dislocations. It is preferable that the number is less than the number of dislocations occurring in the crystal grains. The silicon ingot has a third dislocation suppression grain boundary on the end side of the high dislocation crystal grain, and the dislocation occurring in the crystal grain facing the third dislocation suppression grain boundary occurs in the high dislocation crystal grain. It is preferable that the number of dislocations is less.
According to the silicon ingot, the number of dislocations occurring in the crystal grains facing the first dislocation suppression grain boundary on the side opposite to the end is less than the dislocations occurring in the high dislocation crystal grains. For this reason, dislocation generation and impurity diffusion in the crystal grains on the center side of the first dislocation suppression grain boundary are suppressed to a small extent.

  The silicon ingot obtained by the present embodiment may be used by cutting out the side opposite to the side wall, that is, the center side with respect to the first dislocation suppression boundary. The grain boundary grown on the center side from the first dislocation suppression boundary is high-quality pseudo-single crystal silicon with few impurities and dislocations. The quasi-single crystal silicon on the center side cut out is suitably used as a solar cell material.

(Reference example)
A method for manufacturing the silicon ingot of this reference example will be described. In order to manufacture a silicon ingot, an arrangement process and a growth process are performed.

  First, in the arranging step, a seed crystal in which a plurality of silicon single crystal blocks were arranged was formed. The plurality of silicon single crystal blocks were manufactured by the CZ method, and three types of blocks A, B, and C were used with respect to crystal orientation.

As shown in FIG. 1, each of the blocks A, B, and C is a rectangle having a planar shape of 5 mm × 45 mm and a height of 30 mm. The block A has a (310) plane in the X (thickness) direction, a (−130) plane in the Y (length) direction, and a (001) plane in the Z (height) direction. Block B has a (111) plane in the X direction, a (11-2) plane in the Y direction, and a (−110) plane in the Z (height) direction. The block C has a (111) plane in the X direction, a (-1-12) plane in the Y direction, and a (1-10) plane in the Z (height) direction. The dislocation densities of blocks A, B, and C were all 0 / cm ² .

  As shown in FIG. 1, blocks A, A, A, A, B, B, C, B, and B were sequentially arranged in the X direction to obtain seed crystals.

  A silica crucible having a space surrounded by a crucible bottom having a size of 50 mm × 50 mm and a side wall having a height of 100 mm was prepared. A release material containing silicon nitride powder was applied to the inner surface of the side wall of the crucible. A seed crystal was placed at the bottom of the crucible. The Z direction of the seed crystal was oriented in a direction perpendicular to the bottom surface of the crucible, the X direction was oriented in one direction of the crucible plane, and the Y direction was oriented in the other direction of the crucible plane.

  In the growth process, 226 g of silicon raw material was placed on the seed crystal in the crucible. The crucible was placed in a heating furnace with a temperature gradient in the vertical direction. The temperature gradient of the heating furnace was increased by about 1 ° C./mm upward. The silicon raw material of the crucible was heated to a temperature not lower than the melting point of silicon (1430 ° C.) in a heating furnace to obtain a silicon melt. At this time, a part of the upper part of the seed crystal was melted together with the silicon raw material, but the lower part of the seed crystal was not melted.

  Next, the crucible was pulled down at a rate of 0.3 mm / min in the heating furnace, and the silicon melt was gradually cooled from the lower side to the upper side. The cooling rate was 0.05 ° C./min. The crystal growth rate was about 0.5 mm / min. Thereby, a silicon ingot was formed.

  FIG. 2 is a view showing an etch pit image of the cut surface of the obtained silicon ingot. In FIG. 2, seed crystals were found in the lower part, and grown crystal grains were found in the upper part. A large number of dislocations occurred in the grown crystal grains, as indicated by white lines.

  Dislocations occurred starting from the grain boundaries inherited from the boundary between the blocks A and A, the grain boundaries inherited from the boundary between the blocks B and B, and the grain boundaries inherited from the boundary between the blocks B and C. On the other hand, dislocation did not occur from the grain boundary that inherited the boundary between the blocks A and B.

  The boundary between blocks A and A, the boundary between blocks B and B, and the boundary between blocks B and C are dislocation generation boundaries that form dislocation generation grain boundaries that can generate dislocations as the crystal grows. . The dislocation generation grain boundary inherited from the dislocation generation boundary has a Σ value of 1, becomes a grain boundary having a deviation angle of about 1 ° from the Σ value of 1, and is a small-angle grain boundary. The deviation angle of the crystal orientation of the crystal grain facing the dislocation generation grain boundary with respect to the crystal orientation of the block A facing the dislocation generation boundary was 0.8 °. The deviation angle of the crystal orientation of the crystal grain facing the dislocation generation grain boundary with respect to the crystal orientation of the block B facing the dislocation generation boundary was 1.1 °. The deviation angle of the crystal orientation of the crystal grain facing the dislocation generation grain boundary with respect to the crystal orientation of the block C facing the dislocation generation boundary was 1 °.

  The boundary between the blocks A and B is a dislocation suppression boundary that can form a dislocation suppression grain boundary that suppresses dislocation generation with crystal growth. The Σ value of the dislocation suppression grain boundary inherited from the dislocation suppression boundary was 29 or more, and was a random grain boundary.

  From this reference example, it was found that dislocations are less likely to occur at grain boundaries having a large Σ value, and dislocations are likely to occur at grain boundaries having a small Σ value. Based on this point, the silicon ingot of Example 1 was manufactured next.

Example 1
The manufacturing method of the silicon ingot of a present Example is demonstrated. In order to manufacture a silicon ingot, an arrangement process and a growth process are performed.

First, in the arranging step, a seed crystal in which a plurality of silicon single crystal blocks were arranged was formed. The plurality of silicon single crystal blocks are manufactured by the CZ method, and two types of blocks A and D are used with respect to crystal orientation. As shown in FIG. 3, the crystal orientation with respect to each direction of the block A used in the present embodiment is the same as the block A of the reference example. Block D has a (210) plane in the X direction, a (−120) plane in the Y direction, and a (001) plane in the Z direction. The dislocation densities of blocks A and D were both the same as 0 / cm ² .

  Blocks A and D were each 45 mm long and 30 mm high, but were prepared with different thicknesses. Blocks A and D having a small thickness (2 mm) were designated as blocks A1 and D1, and three blocks were prepared. Blocks A and D having a thick thickness (18 mm) were designated as blocks A2 and D2, and one each was prepared.

  Blocks A1, A1, A1, D2, A2, D1, D1, and D1 were sequentially arranged between the parallel thin plates 8 with an interval of 45 mm to obtain seed crystals.

  A crucible similar to the reference example was prepared, and a release material was applied to the inner surface of the side wall. One seed crystal as described above was placed at the bottom of the crucible. The Z direction of the seed crystal was oriented in a direction perpendicular to the bottom surface of the crucible, the X direction was oriented in one direction of the crucible plane, and the Y direction was oriented in the other direction of the crucible plane.

  Similarly to the reference example, a silicon ingot was grown by performing a growth process.

  FIG. 4 is a cross-sectional photograph of the cut surface of the obtained silicon ingot. FIG. 5 is an etch pit image of the cut surface. First, as shown in FIGS. 4 and 5, crystal grains grew from the seed crystal in the Z direction.

  As shown in FIG. 5, many dislocations were generated in the crystal grains near the side wall of the crucible. However, on the center side across the boundary between the boundaries between the blocks A1 and D2 and the boundary between the blocks A2 and D1, the occurrence of dislocations is significantly greater than at the end side that was in contact with the side wall. It was suppressed.

  The grain boundaries formed by taking over the boundary between the blocks A1 and A1 located in the vicinity of the end and the boundary between the blocks D1 and D1 were dislocation generation grain boundaries that easily generate dislocations.

  The grain boundaries formed by taking over the boundary between the blocks A1 and D2 and the boundary between the blocks A2 and D1 are first dislocation suppression grain boundaries that suppress the propagation of dislocations to the crystal grains on the center side. I understood it. It was found that the grain boundary formed by taking over the boundary between the blocks D2 and A2 is a second dislocation suppression grain boundary that suppresses the occurrence of crystal grain dislocations.

  As shown in FIGS. 4 and 5, a polycrystal having an orientation different from that of the seed crystal was formed at the end of the silicon ingot. On the other hand, polycrystallization was suppressed for the crystal grains in the central part across the first dislocation suppression grain boundary that took over the boundary between the blocks A1 and D2 and the boundary between the blocks A2 and D1, respectively.

  In FIG. 6, the iron concentration distribution in the crystal grain dislocation generation region was measured by a surface photovoltage method (Surface PhotoVoltage). A release material is applied to the side wall of the crucible, and the release material contains iron as a trace component. When the iron concentration distribution in the dislocation generation region was measured, it was found that iron was present at a remarkably high concentration in the portion where the dislocation was generated. This indicates that a large amount of impurities are trapped in the dislocation region of the crystal grains facing the dislocation generation grain boundary. In this embodiment, since the dislocation generation grain boundary is formed in the vicinity of the side wall, impurities such as iron diffused from the side wall are trapped in the dislocation region of the crystal grain facing the dislocation generation grain boundary. For this reason, the diffusion of impurities into the crystal grains on the center side is suppressed.

  The silicon ingot 7 formed according to this embodiment will be described with reference to FIG. The silicon ingot 7 is formed by growing crystal grains 5 using a seed crystal 6 in which a plurality of single crystal silicon blocks are arranged. Among the boundaries between the blocks arranged in order from the side wall 91 of the crucible 9, the boundary between the blocks A1 and D2 and the boundary between the blocks A2 and D1 are the first dislocation suppression boundary 1 and accompanying crystal growth Thus, the first dislocation suppression grain boundary 51 that suppresses dislocation generation is formed. The boundary between the blocks D2 and A2 is the second dislocation suppression boundary 2, and a second dislocation suppression grain boundary 52 that suppresses the generation of dislocations along with crystal growth can be formed. The boundary between the blocks A1 and A1 and the boundary between the blocks D1 and D1 are dislocation generation boundaries 4 located on the side of the side wall 91 relative to the first dislocation suppression boundary 1, and generate dislocations along with crystal growth. The obtained dislocation generation grain boundary 54 can be formed.

  The first dislocation suppression grain boundary 51 had a Σ value of 29 or more and was a random grain boundary. The second dislocation suppression grain boundary 52 had a Σ value of 29 or more and was a random grain boundary.

  The dislocation generation grain boundary 54 is a grain boundary having a Σ value of 1, a deviation angle of about 1 ° from the Σ value 1, and was a small-angle grain boundary. Deviation angle of crystal orientation of crystal grain 5 facing dislocation generation grain boundary 54 with respect to crystal orientation of blocks A1 and D1 facing dislocation generation boundary 4, crystal orientation of blocks A 1 and D 1 facing first dislocation suppression boundary 1 Of the crystal grain 5 facing the dislocation generation grain boundary 51 and the crystal orientation of the crystal grain 5 facing the dislocation generation grain boundary 52 with respect to the crystal orientation of the blocks A2 and D2 facing the second dislocation suppression boundary 2. The deviation angle of the crystal orientation was 0 ° or more and 5 ° or less in all cases.

  By cutting out a portion of the silicon ingot closer to the center than the first dislocation suppression grain boundary 51 of the crystal grain 5, high-quality pseudo single crystal silicon with few crystal defects can be obtained.

  By the way, in the mono-like cast method employed in the present embodiment, as shown in FIGS. 4 and 7, the silicon ingot is grown from the silicon melt by using a seed crystal, and is in contact with the side wall 91 of the crucible 9. A large number of crystal grains 59 having an orientation different from that of the seed crystal are generated from the end portion, and polycrystallization in which the occupied portion is enlarged occurs. In this example, the expansion of the crystal grains 59 having different orientations was blocked by the first dislocation suppression grain boundaries 51.

  Therefore, it is presumed that dislocation suppression grain boundaries can be effectively suppressed by disposing the dislocation suppression grain boundaries closer to the end portion 70 in contact with the side wall 91 than the dislocation generation grain boundaries 54. That is, as shown in FIG. 8, in the arrangement step, the third dislocation suppression boundary that can form the third dislocation suppression grain boundary 53 that suppresses the generation of dislocations accompanying crystal growth on the side wall 91 side from the dislocation generation boundary 4. 3 may be formed. In order to form the third dislocation suppression boundary 3, the block D1 is disposed between one end 70 of the seed crystal 6 of Example 1 and the block A1, and the other end 70 and the block D1 are arranged. A block A1 is arranged between them. It is presumed that the silicon ingot obtained by crystal growth using the seed crystal 6 is suppressed from polycrystallization at the third dislocation suppression grain boundary 53 taking over the third dislocation suppression boundary 3. For this reason, a higher quality pseudo single crystal is obtained.

  Further, in this embodiment, dislocation generation boundary 4 is arranged in the vicinity of the end portion 70 in contact with the side wall 91, thereby generating dislocations in crystal grains grown in the vicinity of the end portion 70, thereby causing stress relaxation and impurity absorption. Yes. As shown in FIG. 9, instead of the blocks A1 and D1, blocks AD1 and DD1, which are high dislocation single crystal silicon blocks having a higher dislocation density than the blocks A1 and D1, may be used. Also in this case, the crystal grains grown by taking over the blocks AD1 and DD1 generate many dislocations and become high dislocation crystal grains 64. High dislocation crystal grains 64 can relieve stress and absorb impurities. Dislocation propagation and impurity diffusion toward the center side can be effectively suppressed by disposing the first dislocation suppression boundary 1 on the side opposite to the end portion 70 with respect to AD1 and DD1, that is, the center side.

  Further, as shown in FIG. 10, the seed crystal 6 may have a high dislocation single crystal block instead of the dislocation generation boundary of the first embodiment. In this case, in the crucible 9, blocks AD 1 and DD 1, which are high dislocation single crystal blocks having a high dislocation density, are arranged near the side walls 91 on both sides, and a block D 3 having a low dislocation density is arranged in the center. Block D3 is the same as block D2, except that the thickness is approximately twice the thickness of block D2. A first dislocation suppression boundary 1 is formed between the blocks AD1 and D3 and between the blocks DD1 and D3. When a silicon melt is placed on the seed crystal 6 and cooled, a silicon ingot 7 is formed. The crystal grains grown by taking over the high dislocation crystal silicon blocks AD1 and DD1 generate many dislocations and become high dislocation crystal grains 64. At both ends of the silicon ingot 7, there are many dislocations and impurities are accumulated, but the occurrence of dislocations is small in the center and diffusion of impurities is also suppressed.

(Example 2)
In the silicon ingot of this example, the third dislocation suppression boundary is arranged in the seed crystal, and the third dislocation suppression boundary, the dislocation generation boundary, and the first dislocation suppression boundary are formed on all four side walls of the crucible. Is different from the first embodiment. Hereinafter, the manufacturing method of the silicon ingot of a present Example is demonstrated.

First, in the arranging step, a seed crystal in which a plurality of silicon single crystal blocks were arranged was formed. The plurality of silicon single crystal blocks were manufactured by the CZ method, and three types of blocks E, F, and G were used with respect to crystal orientation. As shown in FIG. 11, the crystal orientation of the block E has a (310) plane in the X direction, a (1-30) plane in the Y direction, and a (001) plane in the Z direction. The crystal orientation of the block F has a (210) plane in the X direction, a (1-20) plane in the Y direction, and a (001) plane in the Z direction. The crystal orientation of the block G has a (−211) plane in the X direction, a (01-1) plane in the Y direction, and a (111) plane in the Z direction. The dislocation densities of the blocks E, F, and G were all 0 / cm ² .

  For the blocks E and F, blocks E1, E2, E3, F1, F2, and F3 having different planar shapes were prepared. The planar shape of the blocks E1 and F1 is a rectangle of 32 mm × 64 mm, the planar shape of the blocks E2 and F2 is a rectangle of 5 mm × 64 mm, and the planar shape of the blocks E3 and F3 is a rectangle of 32 mm × 5 mm. It was. The height of all the blocks was 94 mm.

  As shown in FIG. 11, various blocks were arranged to obtain a seed crystal. The bottom wall of the crucible forms a square with a length of 94 mm in each of the X direction and the Y direction. The blocks F2, E2, E2, F1, E1, F2, F2, and E2 were arranged in this order from the side wall of the crucible in the X direction. In the Y direction, the blocks E3, E3, and F3 were arranged in this order on both sides of the block F1, and the blocks F3, F3, and E3 were arranged on both sides of the block E1. Blocks G were arranged at the four corners of the seed crystal.

  A release material was applied to the inner surface of the side wall of the crucible. The above seed crystal was placed at the bottom of the crucible. The Z direction of the seed crystal was oriented in a direction perpendicular to the bottom surface of the crucible, the X direction was oriented in one direction of the crucible plane, and the Y direction was oriented in the other direction of the crucible plane.

  Similarly to the reference example, a silicon ingot was grown by performing a growth process.

  FIG. 12 is a cross-sectional photograph of a cut surface of a silicon ingot cut in the direction of arrows AA in FIG. FIG. 13 is a cross-sectional photograph of a cut surface of a silicon ingot obtained by cutting a seed crystal portion in a direction orthogonal to the Z direction. FIG. 14 is an explanatory diagram of a cut surface of the silicon ingot cut in the direction of arrows AA in FIG. FIG. 15 is an explanatory view of a cut surface of a silicon ingot obtained by cutting a seed crystal portion in a direction orthogonal to the Z direction.

  In the obtained silicon ingot, crystal grains grew from the seed crystal 6 in the Z direction. Numerous dislocations occurred in the crystal grains near the four side walls 91 of the crucible 9. However, as shown in FIG. 12, the center side across the boundary between the blocks F2 and E1 and the two boundaries between the blocks E2 and F1 is significantly dislocated compared to the side wall side. Occurrence was suppressed. Further, as shown in FIG. 13, the occurrence of dislocations was remarkably suppressed on the center side with respect to the boundaries between the blocks F2 and F3 and E1, as compared with the end portion side. Similarly, the occurrence of dislocations was remarkably suppressed on the center side across the grain boundaries that inherited the boundaries between the blocks E2 and E3 and F1, compared to the end side. Therefore, the boundary between the blocks F2 and E1, the boundary between the blocks E2 and F1, the boundary between the blocks F3 and E1, and the boundary between the blocks E3 and F1 are the first that can suppress the occurrence of dislocation. This is the first dislocation suppression boundary 1 that forms the dislocation suppression grain boundary 51.

  The boundary between the blocks E2 and E2, located near the side wall 91 of the crucible 9, the boundary between the blocks E3 and E3, the boundary between the blocks F2 and F2, and the boundary between the blocks F3 and F3 generate dislocations. This is the dislocation generation boundary 4 that forms the dislocation generation grain boundary 54 that is easily formed.

  The boundary between the blocks E1 and F1 on the center side of the seed crystal 6 was the second dislocation suppression boundary 2 that forms the second dislocation suppression grain boundary 52 that suppresses the generation of crystal dislocations. The boundary between the blocks E2 and F2 located near the end portion 70 and the boundary between the blocks E3 and F3 are the third dislocation suppression boundary 3 that forms the third dislocation suppression grain boundary 53 that suppresses the occurrence of dislocation. there were. Polycrystallization was suppressed for the crystal grains opposite to the end portion 70 across the third dislocation suppression grain boundary 53.

  The first dislocation suppression grain boundary 51, the second dislocation suppression grain boundary 52, and the third dislocation suppression grain boundary 53 were all random grain boundaries having a Σ value of 29 or more. The dislocation generation grain boundary 54 is a grain boundary having a Σ value of 1, a deviation angle of about 1 ° from the Σ value 1, and was a small-angle grain boundary. The deviation angle of the crystal orientation of the crystal grain 5 facing the dislocation generation grain boundary 54 with respect to the crystal orientation of each block facing the dislocation generation boundary 4 was 0 ° or more and 5 ° or less.

  The silicon ingot is used by cutting out a portion on the center side from the first dislocation suppression grain boundary 51 of the crystal grain 5. The central portion is high-quality quasi-single crystal silicon with few crystal defects.

  In the present embodiment, the third dislocation suppression boundary, the dislocation generation boundary, and the first dislocation suppression boundary are arranged in order from all the side walls on all the side walls of the crucible. It is possible to effectively suppress dislocation generation and impurity contamination from the entire outer portion of the silicon ingot. For this reason, the yield of a product part can be made still higher compared with the case where the 3rd dislocation suppression boundary, the dislocation occurrence boundary, and the 1st dislocation suppression boundary are arranged only in the X direction or the Y direction.

  In this example, the crystal also grew on the block G arranged at the corner portion of the seed crystal 6. However, since the crystal on the block G is a part excluded from the product part of the silicon ingot at the time of use, any crystal such as dislocation generation or impurity mixing may be used. For this reason, what is arranged at the corner of the seed crystal 6 may have any orientation as long as it is a silicon block. For example, instead of arranging the block G in the corner portion, any of the blocks E2, E3, F2, and F3 on both sides thereof may be extended and arranged. Moreover, it is not necessary to arrange a block in a corner part. In this case, the silicon melt enters the corner portion during the growth process, but there is almost no influence on the product portion of the manufactured silicon ingot. In other words, the silicon melt oozes out from the gap of the corner portion toward the center of the crystal, and in this case, there is no significant influence on the crystal growth.

  In the silicon ingot of this example, in the seed crystal, the third dislocation suppression boundary, the dislocation generation boundary, and the first dislocation suppression boundary are arranged in order from the side walls on all the side walls of the crucible. You may arrange | position a dislocation generation | occurrence | production boundary and a 1st dislocation suppression boundary on all the side walls of a crucible, without using a boundary. Further, as shown in FIGS. 9 and 10, a configuration in which the high dislocation crystal silicon block and the first dislocation suppression boundary are sequentially arranged from the side wall side of the crucible may be provided on all the side walls of the crucible.

  In this embodiment, the dislocation densities of the blocks E and F are the same. However, as shown in FIG. 16, a block composed of a single crystal silicon block having a high dislocation density at the portion facing the first dislocation suppression boundary on the side wall 91 side. ED2, ED3, FD2, and FD3 may be arranged. That is, the bottom of the crucible may be rectangular, and the third dislocation suppression boundary, the high dislocation single crystal block, and the first dislocation suppression boundary may be disposed on all the side walls of the crucible. Also in this case, it is possible to effectively suppress the occurrence of dislocations from the entire outer periphery of the silicon ingot and mixing of impurities. For this reason, the yield of a product part can be made still higher compared with the case where the 3rd dislocation suppression boundary, the block of a high dislocation single crystal, and the 1st dislocation suppression boundary are arranged only in the X direction or the Y direction.

1: First dislocation suppression boundary, 2: Second dislocation suppression boundary, 3: Third dislocation suppression boundary, 4: Dislocation generation boundary, 5: Crystal grain, 51: First dislocation suppression grain boundary, 52: Second dislocation suppression Grain boundary, 53: Third dislocation suppression grain boundary, 54: Dislocation generation grain boundary, 6: Seed crystal, 64: High dislocation crystal grain, 7: Silicon ingot, 70: End

Claims (22)

A plurality of single crystal silicon blocks are arranged in order from the side wall on the crucible bottom, and at least one first dislocation suppression boundary capable of forming a first dislocation suppression grain boundary that suppresses the generation of dislocations along with crystal growth, and the first than dislocation suppression boundaries have at at least one dislocation boundary may form a dislocation generation grain boundaries can generate dislocations with the crystal growth positioned on the side wall, the said first dislocation suppression boundary An arrangement step of arranging the plurality of single crystal silicon blocks to form a seed crystal so that a dislocation generation boundary is opposed ;
A silicon melt is disposed on the seed crystal, and the silicon melt is cooled to inherit crystal orientation of the seed crystal to grow crystal grains in one direction to form a silicon ingot, and in the silicon ingot And forming the dislocation generation grain boundary and the first dislocation suppression grain boundary taking over the dislocation generation boundary and the first dislocation suppression boundary, respectively, and generating dislocations in the crystal grains facing the dislocation generation grain boundary. And a growth step of suppressing generation of dislocations in crystal grains facing the side opposite to the side wall with respect to the first dislocation suppression grain boundary. A plurality of single crystal silicon blocks are arranged in order from the side wall on the crucible bottom, and at least one first dislocation suppression boundary capable of forming a first dislocation suppression grain boundary that suppresses the generation of dislocations along with crystal growth, and the first than dislocation suppression boundaries have at at least one dislocation boundary may form a dislocation generation grain boundaries can generate dislocations with the crystal growth positioned on the side wall, and the dislocation boundary side wall An arrangement step of arranging the plurality of single crystal silicon blocks so as to be parallel to form a seed crystal;
A silicon melt is disposed on the seed crystal, and the silicon melt is cooled to inherit crystal orientation of the seed crystal to grow crystal grains in one direction to form a silicon ingot, and in the silicon ingot And forming the dislocation generation grain boundary and the first dislocation suppression grain boundary taking over the dislocation generation boundary and the first dislocation suppression boundary, respectively, and generating dislocations in the crystal grains facing the dislocation generation grain boundary. And a growth step of suppressing generation of dislocations in crystal grains facing the side opposite to the side wall with respect to the first dislocation suppression grain boundary. A plurality of single crystal silicon blocks are arranged in order from the side wall on the crucible bottom, and at least one first dislocation suppression boundary capable of forming a first dislocation suppression grain boundary that suppresses the generation of dislocations along with crystal growth, and the first At least one dislocation generation boundary that can form a dislocation generation grain boundary that is located on the side of the side wall from the dislocation suppression boundary and can generate dislocations along with crystal growth; and on the side of the side wall from the dislocation generation boundary The plurality of single crystal silicon blocks are arranged to form a seed crystal so as to have at least one third dislocation suppression boundary that can form a third dislocation suppression grain boundary that suppresses the generation of dislocations along with growth. The placement process;
A silicon melt is disposed on the seed crystal, and the silicon melt is cooled to inherit crystal orientation of the seed crystal to grow crystal grains in one direction to form a silicon ingot, and in the silicon ingot Forming the dislocation generation grain boundary, the first dislocation suppression grain boundary, and the third dislocation suppression grain boundary, which have succeeded the dislocation generation boundary, the first dislocation suppression boundary, and the third dislocation suppression boundary , respectively. , Generating dislocations in crystal grains facing the dislocation generation grain boundaries, suppressing generation of dislocations in crystal grains facing the first dislocation suppression grain boundaries on the side opposite to the side walls, and the third dislocations. And a growth step for suppressing the occurrence of dislocations in the crystal grains facing the side wall side with respect to the suppression grain boundary . In the disposing step, the side wall side of the dislocation generation boundary has at least one third dislocation suppression boundary capable of forming a third dislocation suppression grain boundary that suppresses dislocation generation along with crystal growth. A plurality of single crystal silicon blocks are arranged to form a seed crystal,
In the growth step, the third taking over dislocation suppression boundary to form the third dislocation suppressing grain boundary in the silicon ingot during, facing the crystal grains in the side wall side with respect to the third dislocation suppressing grain boundary The method for producing a silicon ingot according to claim 1, wherein generation of dislocation is suppressed. In the arranging step, at least one second dislocation suppression boundary capable of forming a second dislocation suppression grain boundary that suppresses the occurrence of dislocation accompanying crystal growth on the opposite side of the side wall with respect to the first dislocation suppression boundary. A plurality of single crystal silicon blocks are arranged to form a seed crystal,
In the growth step, the second dislocation suppression grain boundary that takes over the second dislocation suppression boundary is formed in the silicon ingot to suppress generation of dislocations in crystal grains facing the second dislocation suppression grain boundary. The manufacturing method of the silicon ingot in any one of Claims 1-4 . The method for producing a silicon ingot according to claim 1, wherein a Σ value of the dislocation generation grain boundary is smaller than a Σ value of the first dislocation suppression grain boundary. With respect to the crystal orientation of the single crystal silicon block facing said dislocation generation boundary claim 1 deviation angle of the crystal orientation of the crystal grains facing the dislocation generation grain boundaries is 10 ° or less 0 ° or more A method for producing a silicon ingot according to 1. The total thickness of the single crystal silicon block which faces at least one said dislocation generation boundaries positioned near one of the side walls of a pair of opposing side walls of the crucible, according to claim 1 to 7 is 1mm or more than 100mm The manufacturing method of the silicon ingot in any one of. The seed crystal is located on the side of the sidewall from the first dislocation suppression boundary, and has a high dislocation density higher than that of the single crystal silicon block on the side opposite to the side of the first dislocation suppression boundary. The manufacturing method of the silicon ingot in any one of Claims 1-8 which have a single crystal silicon block. 10. The silicon ingot according to claim 1 , wherein in the arranging step, the crucible bottom has a quadrangular shape, and the dislocation generation boundary and the first dislocation suppression boundary are arranged in order from the side walls with respect to the four side walls. Method. In the disposing step, the crucible bottom forms a square shape, in order from the respective side walls for the four side walls, said third rearrangement suppression boundary, claim 3 is arranged the dislocation boundary and the first dislocation suppression boundary or 4 Manufacturing method of silicon ingot. A plurality of single crystal silicon blocks are arranged in order from the side wall on the crucible bottom, and at least one first dislocation suppression boundary capable of forming a first dislocation suppression grain boundary that suppresses the generation of dislocations along with crystal growth, and the first A high dislocation single-crystal silicon block located on the side of the dislocation suppression boundary and having a dislocation density higher than that of the single-crystal silicon block on the side opposite to the side wall with respect to the first dislocation suppression boundary. An arrangement step of arranging a plurality of single crystal silicon blocks to form a seed crystal,
A silicon melt is disposed on the seed crystal, and the silicon melt is cooled to inherit crystal orientation of the seed crystal to grow crystal grains in one direction to form a silicon ingot, and in the silicon ingot Forming the first dislocation suppression grain boundary that has inherited the first dislocation suppression boundary and the high dislocation crystal grain that has generated the dislocation by taking over the high dislocation single crystal silicon block, and the first dislocation suppression grain boundary. And a growth step for suppressing the occurrence of dislocations in the crystal grains facing on the side opposite to the side wall. A method for producing a silicon ingot, comprising: 13. The silicon ingot according to claim 12 , wherein, in the arranging step, the crucible bottom has a quadrangular shape, and the high dislocation single crystal silicon block and the first dislocation suppression boundary are arranged in order from each of the four side walls . Production method. A seed crystal used for growing a silicon crystal grain to produce a silicon ingot,
The seed crystal includes a plurality of single crystal silicon blocks arranged in order from an end in a direction perpendicular to a growth direction in which the crystal grains grow, and first dislocation suppression that suppresses dislocation generation along with crystal growth. It is possible to form at least one first dislocation suppression boundary capable of forming a grain boundary and a dislocation generation grain boundary that is located closer to the end portion than the first dislocation suppression boundary and can generate a dislocation accompanying crystal growth. At least one of the dislocation generation boundaries, have a species and the first dislocation suppression boundaries and the dislocation generation boundary, characterized in that the opposing crystals. A seed crystal used for growing a silicon crystal grain to produce a silicon ingot,
The seed crystal includes a plurality of single crystal silicon blocks arranged in order from an end in a direction perpendicular to a growth direction in which the crystal grains grow, and first dislocation suppression that suppresses dislocation generation along with crystal growth. It is possible to form at least one first dislocation suppression boundary capable of forming a grain boundary and a dislocation generation grain boundary that is located closer to the end portion than the first dislocation suppression boundary and can generate a dislocation accompanying crystal growth. At least one dislocation generation boundary, and at least one third dislocation suppression boundary capable of forming a third dislocation suppression grain boundary that suppresses dislocation generation accompanying crystal growth on the end side of the dislocation generation boundary; A seed crystal characterized by comprising: A seed crystal used for growing a silicon crystal grain to produce a silicon ingot,
The seed crystal includes a plurality of single crystal silicon blocks arranged in order from an end in a direction perpendicular to a growth direction in which the crystal grains grow, and first dislocation suppression that suppresses dislocation generation along with crystal growth. At least one first dislocation suppression boundary capable of forming a grain boundary, and located on the end side of the first dislocation suppression boundary, on the side opposite to the end side with respect to the first dislocation suppression boundary A seed crystal comprising: at least one high dislocation single crystal silicon block having a higher dislocation density than the single crystal silicon block. A silicon ingot composed of a plurality of crystal grains that have grown in one direction by inheriting the crystal orientation of a silicon seed crystal,
The silicon ingot, possess a first dislocation suppressing grain boundary, and a dislocation generation grain boundary positioned on the end of the direction perpendicular to the first dislocation suppressing grain boundary growth direction of the crystal grains than the first 1 dislocation suppression grain boundary and the dislocation generation grain boundary face each other, and dislocations are generated in crystal grains facing the dislocation generation grain boundary, opposite to the end with respect to the first dislocation suppression grain boundary. A silicon ingot characterized in that the number of dislocations occurring in crystal grains facing each other is less than the dislocations occurring in crystal grains facing the dislocation generation grain boundary. A silicon ingot composed of a plurality of crystal grains that have grown in one direction by inheriting the crystal orientation of a silicon seed crystal,
The silicon ingot includes a first dislocation suppression grain boundary, a dislocation generation grain boundary located closer to an end side in a direction perpendicular to a crystal grain growth direction than the first dislocation suppression grain boundary, and the dislocation generation grain boundary. And dislocations are generated in the crystal grains facing the dislocation generation grain boundary, and the third dislocation suppression grain boundary located on the end side than the first dislocation suppression grain boundary. Dislocations occurring in crystal grains facing on the side opposite to the end , and dislocations occurring in crystal grains facing on the end side with respect to the third dislocation suppression grain boundary are the dislocation generation grains. Silicon ingot characterized by fewer dislocations occurring in crystal grains facing the boundary. The cross section in the direction perpendicular to the crystal grain growth direction of the silicon ingot has a quadrangular shape, and the four dislocations in the vertical direction, in order from the respective ends , the dislocation generation grain boundary and the first dislocation suppression. The silicon ingot according to claim 17 or 18 , wherein grain boundaries are arranged. The cross section in the direction perpendicular to the growth direction of the crystal grains of the silicon ingot has a quadrangular shape, and the three dislocation suppression grain boundaries and the dislocations are generated in order from the respective end portions of the four end portions in the vertical direction. The silicon ingot according to claim 18 , wherein a grain boundary and the first dislocation suppression grain boundary are arranged. A silicon ingot composed of a plurality of crystal grains that have grown in one direction by inheriting the crystal orientation of a silicon seed crystal,
The silicon ingot includes a first dislocation suppression grain boundary, a high dislocation crystal grain positioned closer to an end portion in a direction perpendicular to the growth direction of the crystal grain than the first dislocation suppression grain boundary, and the high dislocation crystal grain And dislocations are generated in the high dislocation crystal grains, opposite to the end portions with respect to the first dislocation suppression grain boundaries. Dislocations occurring in the crystal grains facing on the side and dislocations occurring in the crystal grains facing on the end side with respect to the third dislocation suppression grain boundary occur in the high dislocation crystal grains. Silicon ingot characterized by fewer dislocations. The cross section in the direction perpendicular to the growth direction of the crystal grains of the silicon ingot has a quadrangular shape, and the three dislocation suppression grain boundaries and the high dislocations are sequentially formed from the four end portions in the vertical direction. The silicon ingot according to claim 21 , wherein crystal grains and the first dislocation suppression grain boundaries are arranged.