JP4282278B2 - Substrate, plate manufacturing method using the substrate, plate and solar cell produced from the plate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a substrate that is brought into contact with a melt containing a semiconductor material to grow a plate-like body of the semiconductor material on the surface thereof, and the surface of the substrate includes a peripheral portion including an edge portion of the substrate and the substrate. The main surface portion is divided into an inner main surface portion, and the main surface portion and the peripheral portion are different from each other in at least one of shape and material. Furthermore, this invention relates to the manufacturing method of the plate-shaped body using this board | substrate. In particular, when silicon is used as the semiconductor material, the obtained plate-like silicon relates to plate-like silicon in which no wraparound portion (burr) to the substrate side is formed in the peripheral portion.
[0002]
[Prior art]
Solar cells are attracting attention as a clean next generation energy alternative to fossil fuels. Above all, polycrystalline silicon solar cells are expected from the viewpoint of relatively high conversion efficiency and cost. Conventionally, a polycrystalline silicon wafer used for a polycrystalline silicon solar cell has been produced by pouring a silicon melt into a mold and gradually cooling it to produce an ingot and then slicing. However, there is a problem that silicon loss due to slicing is large and cost is high because it takes time and effort to slice. In order to promote the spread of solar cells and reduce environmental problems caused by fossil fuels, it is important to reduce the cost of the polycrystalline silicon wafer.
[0003]
For example, a method for directly manufacturing a wafer from a melt, such as the RGS method, has been proposed. In these methods, silicon is grown in parallel with the growth surface of the growth substrate by bringing a graphite substrate or the like into contact with the melt. Therefore, since the area of the portion where the melt and the substrate are in contact with each other is large, the growth rate is fast, which is advantageous for cost reduction.
[0004]
Further, as a method for directly manufacturing a wafer of a predetermined size based on these methods, a method described in Japanese Patent Laid-Open No. 4-342409 has been proposed. In this method, the wafer is divided at the groove portion by bringing a substrate provided with a surface recess composed of a groove having a width and depth of at least 1 mm at a portion corresponding to the wafer edge portion into contact with the melt. This utilizes the phenomenon that the melt does not enter the groove due to the surface tension of the silicon melt, and as a result, the wafer does not grow in the groove.
[0005]
However, when plate-like silicon is produced by this method, a wafer of almost a predetermined size is formed. However, at the edge of the silicon, 100 deeper than the lower surface (contact surface with the substrate) of the silicon is formed. Burrs of micron to 200 microns or more are formed, and problems such as inability to fix silicon with a vacuum chuck used in a production line are expected.
[0006]
Even when considering a process that does not use a vacuum chuck, it is difficult to obtain reproducibility in the shape of the periphery of the wafer, so there is a large shape error between products, and it is expected that it will be difficult to ship the product as it is. The Further, it is possible to flow the wafer peripheral part produced by this method to the production line by cutting with a laser or a dicing apparatus, but there is a problem that the cost increases due to an increase in the number of processes.
[0007]
[Problems to be solved by the invention]
In order to solve these problems and reduce the cost, after the wafer is formed in a predetermined size, the silicon end is directed downward from the lower surface of the silicon so that it can be flowed to the production line as it is. A plate-like silicon having no burr and a manufacturing method thereof are desired. As a result of diligent research, the present inventors have solved the above-mentioned problems by devising the shape and material of the substrate to be brought into contact with the melt, and reduced the number of devices such as solar cells using a plate-like body produced by this method. The cost can be reduced.
[0008]
[Means for Solving the Problems]
The present invention is a substrate that is brought into contact with a melt containing a semiconductor material and on which a plate-like body of the semiconductor material is grown. The substrate has a main surface portion on which the plate-like body grows, and the main surface portion. It has an adjacent peripheral region where the plate-like body does not grow, and at least one of a surface shape or a material of the main surface portion and the peripheral region is different.
[0009]
The present invention is a substrate that is brought into contact with a melt containing a semiconductor material and on which a plate-like body of the semiconductor material is grown. The surface of the substrate includes a peripheral portion including an edge portion and an inner portion thereof. The main surface portion is partitioned, and the peripheral portion and the main surface portion are different in at least one of shape and material. Moreover, it is preferable that the main surface part of the board | substrate of this invention has uneven | corrugated shape. Furthermore, it is preferable that the main surface portion of the substrate has a regular uneven shape, and the peripheral portion has a regular uneven shape different from the uneven shape of the main surface portion. In particular, the main surface portion of the substrate can be formed in a concave shape with respect to the peripheral portion.
[0010]
The substrate of the present invention is characterized in that the peripheral portion higher than the main surface portion of the substrate is different in material from the main surface portion. Moreover, the peripheral part higher than the main surface part of a board | substrate can have uneven | corrugated shape different from the uneven | corrugated shape of this main surface part.
[0011]
Moreover, this invention relates to the manufacturing method of the plate-shaped object using the said board | substrate. Furthermore, this invention relates to the plate-shaped object manufactured using the said board | substrate. The plate-like body has a portion without a wraparound portion (burr) to the substrate side in the peripheral portion. The plate-like body of the present invention is preferably silicon. Furthermore, this invention relates to the solar cell produced using the said plate-shaped silicon.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a substrate that is brought into contact with a melt containing a semiconductor material and forms the semiconductor material on the surface thereof, and the main surface portion and the peripheral portion of the substrate are different in at least one of shape and material. It is characterized by that.
[0013]
The board | substrate used for this invention is demonstrated concretely according to drawing. 1A is a schematic perspective view of the substrate of the present invention, and FIG. 1B is a cross-sectional view taken along the line 1B-1B of FIG. In the figure, a substrate C1 for growing a plate-like body is divided into a peripheral portion 2 including a substrate edge C12 and a main surface portion 1 inside thereof. A plate-like body that can be used for a product mainly grows on the main surface portion 1 and does not grow on the peripheral portion 2 of the main surface portion 1. As shown in FIG. 1B, which is a cross-sectional view taken along the line 1B-1B in FIG. 1A, the peripheral portion 2 is provided with a concavo-convex structure, so that it does not grow into a plate shape. Become. That is, the portion where the plate-like body grows at the boundary between the main surface portion 1 and the peripheral portion 2 is separated from the portion where it does not grow. In the present invention, the plate-like body refers to a plate-like body grown substantially parallel to the main surface portion of the substrate. By increasing the solidification interface between the substrate and the raw material melt, the plate-like body is grown. The speed can be greatly improved, and the productivity is greatly improved.
[0014]
By using the substrate C1 having such a shape, the portion where the plate-like body grows and the portion which does not grow can be separated. By changing the shape of the substrate and the material of the substrate, the method of supporting the raw material melt is changed. It is because it is letting. FIG. 2A is a schematic enlarged view showing the substrate C1 used in FIG. 1 and the melt surface (3A and 3B) on the substrate, and FIG. 2B shows a plate-like body S2 on the substrate. It is a schematic cross section of the state which grew.
[0015]
In FIG. 2B, the melt 3 supplied onto the substrate is solidified on the main surface portion 1 of the substrate to form a plate-like body S2. At this time, as shown in FIG. 2A, the melt surface 3B in contact with the irregularities on the surface of the peripheral portion 2 of the melt 3 supplied onto the substrate is a convex portion of the peripheral portion 2, and is a dot or line. It will be supported by. Thus, the shape of the melt surface 3B can be changed by the surface tension of the raw material melt and the uneven shape of the substrate surface. In the drawing, the silicon melt surface 3B is shown in a state where it slightly hangs down into the concave portion of the substrate, but it can also be made almost flat by the uneven shape of the substrate surface. For example, the uneven pitch P12 used for the peripheral portion 2 is preferably 3 mm or less, and the tip angle α12 of the convex portion is particularly preferably a pyramid shape of 120 ° or less or a shape having an equivalent effect. If the pitch P12 of the concavo-convex shape is 3 mm or more, even if the tip angle is changed, since the raw material melt is supported by the adjacent convex portion, there is a possibility that the raw material enters the concave and convex portion. It will be.
[0016]
Specific examples of the shape of the convex portion here are shown in FIGS. 9 and 10, for example. FIG. 9 shows a structure having pyramid-shaped convex portions 5 on the surface of the substrate, and FIG. 10 shows a structure having a plurality of rows of protrusions having a triangular cross section on the surface of the substrate, which has the same effect as the pyramid shape.
[0017]
In any case, the peripheral portion can support the melt, and the plate-like body does not have to grow on the convex portion. Furthermore, even if the growth of the plate-like body occurs at the convex portion, the solidified solid does not continue between adjacent convex portions and does not grow into a plate shape.
[0018]
In addition, the peripheral part 2 is provided at least one place before and after the moving direction when contacting the melt of the substrate, on both sides in the moving direction, and the width W1 is preferably in the range of 1 mm to 50 mm. More preferably, it is the range from 2 mm to 20 mm. This is because if the thickness is 1 mm or less, it becomes difficult to process the surface shape of the peripheral portion. If the thickness is 50 mm or more, the size of the substrate increases, and it takes time to handle the substrate and heat / cool the substrate. This is because it leads to inferior productivity.
[0019]
1 and 2, the peripheral portion 2 of the substrate C1 is shown as an uneven shape. However, even if the peripheral portion 2 is made of a material different from that of the main surface portion 1, the same effect can be obtained. That is, in FIGS. 1 and 2, the method of supporting the raw material melt is changed by changing the shape of the peripheral portion 2, but the same effect can be obtained by changing the surface material of the peripheral portion 2. .
[0020]
That is, the main surface portion 1 on which the plate-like body is grown is made of a material that easily wets the raw material melt, while the peripheral portion 2 is made of a material that hardly wets the raw material melt. By doing in this way, the part which a plate-shaped body grows in the boundary of the main surface part 1 and the peripheral part 2, and the part which does not grow will be isolate | separated. As described above, the material can be easily separated by changing the material of the main surface portion 1 and the peripheral portion 2. In particular, by changing both the shape of the main surface portion and the peripheral portion of the substrate and the material thereof, separation can be performed with higher accuracy.
[0021]
In addition, as the material used for the main surface portion and the peripheral portion of the substrate when silicon is used as the raw material melt, high purity graphite, glassy carbon, pyrolytic carbon, boron nitride, silicon nitride, silicon carbide, diamond-like carbon, etc. It is preferable to select. This is only required to have at least the above-mentioned material on the surface of the peripheral portion 2, and need not be a molded body. In other words, only the surface of the substrate in contact with the silicon melt may be coated with the above material or the particles thereof. By changing the material in this manner, the wettability between the melt and the peripheral portion 2 can be controlled.
[0022]
FIG. 3A is a schematic perspective view of a substrate C3 for growing a plate-like body, and FIG. 3B is a cross-sectional view taken along 3B-3B in FIG. In this figure, the main surface portion 31 has irregularities finer than the peripheral portion 32. By adopting such a structure, it is possible to separate the portion where the plate-like body grows at the boundary between the main surface portion 31 and the peripheral portion 32 and the portion where it does not grow. Thus, even if the main surface portion 31 is uneven, it can be easily separated. This is because the main surface portion and the peripheral portion are formed with uneven shapes, but the shapes for supporting the melt are different.
[0023]
The pitch P31 of the convex portion of the main surface portion 31 is preferably in the range of 0.5 mm to 5 mm, and the pitch P32 of the convex portion of the peripheral portion 32 is preferably in the range of 0.5 mm to 3 mm. The tip angle of the convex portion of the main surface portion 31 is preferably 90 ° to 150 °, and the tip angle of the peripheral portion 32 is preferably 15 ° to 120 °.
[0024]
When the pitch P31 of the convex part of the main surface part 31 and the pitch P32 of the convex part of the peripheral part 32 are the same, the tip angle of the peripheral part 32 is made small, that is, sharp, in order to delay the growth from the convex part of the peripheral part 32. It will be necessary. Here, the width W3 of the peripheral portion 32 is set in a range of 2 to 40 mm.
[0025]
4A is a schematic perspective view of a substrate C4 for growing a plate-like body, and FIG. 4B is a cross-sectional view taken along 4B-4B in FIG. 4A. In this figure, the surface of the peripheral portion 42 protrudes from the surface of the main surface portion 41 of the substrate C4 on which the plate-like body grows, and the peripheral portion 42 is uneven. By adopting such a structure, a portion where the plate-like body grows and a portion where it does not grow are separated at the boundary between the main surface portion 41 and the peripheral portion 42. In particular, by providing a difference in height between the main surface portion 41 and the peripheral portion 42 as described above, separation becomes very easy. This is because the method of supporting the melt also occurs due to the difference in height. Here, the pitch P42 of the concave and convex portions of the peripheral portion 42 is in the range of 0.5 to 3 mm, and the width W4 of the peripheral portion is in the range of 2 to 40 mm.
[0026]
FIG. 5 (A) is a schematic enlarged view of the substrate used in FIG. 4 and the melt surface (3A and 3B) on the substrate, and FIG. 5 (B) is a plate-like shape grown on the substrate. It is a schematic cross section of the body S5. The melt 3 supplied onto the substrate is solidified on the substrate to form a plate-like body S5. At this time, the melt surface 3B in contact with the irregularities on the substrate surface of the melt 3 supplied onto the substrate is supported by point contact or line contact. As described above, since the melt does not enter the concave portion on the surface of the substrate, the melt supported in the uneven shape is difficult to grow into a plate shape.
[0027]
In particular, the height difference H4 of the substrate is at least a plate to be grown because the obtained plate-like body may be incompletely separated when the height difference between the two surfaces of the main surface portion 41 and the peripheral portion 42 is small. It is preferable that the thickness is larger than the plate thickness h. More preferably, H4> 4h is satisfied. This is because the melt hardly enters the boundary portion between the main surface portion 41 and the peripheral portion 42. The height H4 of the uneven portion is preferably in the range of 1 to 10 mm. Further, the angle α1 of the projections of the concavo-convex portion is set in the range of 15 ° to 120 ° here.
[0028]
FIG. 6A is a schematic perspective view of a substrate C6 for growing a plate-like body, and FIG. 6B is a cross-sectional view taken along 6B-6B in FIG. In the figure, a substrate C6 for growing a plate-like body is divided into four. In other words, the substrate C6 is configured by combining one main surface portion 61 and three peripheral portions 62. Furthermore, a concavo-convex structure is provided on the surface of the substrate constituting the peripheral portion 62. With such a structure, a portion where the plate-like body grows and a portion where it does not grow are separated from each other at the boundary between the main surface portion 61 and the peripheral portion 62. As described above, even when the base plate C6 in which a plurality of substrate members are combined is used, the plate-like body can be separated at the boundary between the main surface portion 61 and the peripheral portion 62. Although FIG. 6 illustrates a structure composed of four substrate members, the number of component members is not particularly limited.
[0029]
The main surface portions (41, 61) of the substrates (C4, C6) shown in FIG. 4 and FIG. 6 are shown as planes, but irregular shapes may also be formed on this surface. The pitch of the convex portions formed on the main surface portion is preferably in the range of 0.5 mm to 5 mm, and the tip angle of the convex portions is preferably 90 ° to 150 °.
[0030]
FIG. 11A is a schematic perspective view of a substrate C11 for growing a plate-like body, and FIG. 11B is a cross-sectional view taken along 11B-11B in FIG. When the substrate C11 is compared with the above-described substrates (C1, C3, C4, C6), every substrate has a main surface portion and a peripheral portion. In the substrate C11, the peripheral portion 112 is a substrate edge portion C112. It is a feature that it does not contain. Even if the substrate of the peripheral portion 112 not including the substrate edge C112 is used, the plate-like body grown on the main surface portion 111 and the plate-like body grown on the peripheral portion 112 can be separated. In other words, at least one of the surface shape or material of the substrate differs at the boundary between the main surface portion and the peripheral portion, so that the method for supporting the melt changes, so that the plate-like body grows and does not grow. It becomes possible to do. Here, the unevenness pitch P112 of the peripheral portion 112 is in the range of 0.5 mm to 3 mm, and the width W11 of the peripheral portion 112 is in the range of 2 to 40 mm.
[0031]
FIG. 12A is a schematic perspective view of a substrate C12 for growing a plate-like body, and FIG. 12B is a cross-sectional view taken along 12B-12B in FIG. The feature of this substrate C12 is that it has a structure that allows two plate-like bodies to be taken out from one substrate. By using such a substrate, mass production is possible, and a cheaper plate-like body can be provided. In this figure, the plate-like body is formed on two main surface portions (121R, 121L) and is separated by a central portion 122C located between the two main surface portions. The surface shape of the central portion 122C preferably forms a linear convex portion as shown in FIG. The width W12C of the central portion 122C is in the range of 2 mm to 15 mm, the unevenness pitch P122 of the peripheral portion 122 is in the range of 0.5 mm to 3 mm, and the width W12 of the peripheral portion 122 is in the range of 2 to 40 mm. Here, a peripheral region where the plate-like body does not grow is formed by the central portion 122C and / or the peripheral portion 122.
[0032]
A plate-like body produced without using the substrate of the present invention will be described for comparison. FIG. 7A is a schematic cross-sectional view when a melt exists on a conventional substrate, and FIG. 7B is a schematic cross-sectional view of a plate-like body grown on the substrate. In FIG. 7A, melt surfaces (3A and 3B) are shown on the inner surface portion 71 and the outer surface portion 72 constituting the surface of the substrate C7. The melt 3 supplied onto the substrate is solidified on the substrate to form a plate-like body S. At this time, the melt surface 3B in contact with the substrate surface of the melt 3 supplied onto the substrate has a shape drooping toward the concave portion of the substrate. Even in the substrate having the shape as shown in the figure, the raw material melt does not completely enter the recesses on the surface of the substrate, but when the raw material melt is solidified, as shown in FIG. The burr 4 is formed between 72. Since the burr 4 is not intentionally cut, the height of the burr part differs. When a plate-like body with burrs is used in a process for producing a product, a shape error between products becomes large, and a yield in the process may be reduced. Moreover, if it uses for the process for producing a product after cut | disconnecting the burr | flash 4, a cutting process will be needed newly and it will become difficult to provide an inexpensive plate-shaped body.
[0033]
When the substrate of the present invention is used, the plate-like body obtained as described above does not have burrs. That is, the plate-like body manufactured using the substrate of the present invention is characterized in that there are no wraparound portions (burrs) to the substrate side. A plate-like body having a portion where no burr exists does not need to be cut when it is subjected to a process for producing a product, and is effective in reducing cutting costs and relaxing cutting conditions. Further, by making all the peripheral portions of the plate-like body into such a substrate shape, it is possible to flow the sheet to the subsequent process without passing through the cutting step, and it is possible to reduce the cost.
(Plate-like body manufacturing equipment)
Next, the manufacturing method of the plate-shaped body using the board | substrate of this invention is demonstrated. FIG. 8 shows a schematic cross-sectional view in the production apparatus for producing the plate-like silicon of the present invention. The apparatus for obtaining the plate-like body of the present invention is not limited to this.
[0034]
The apparatus shown in FIG. 8 has the obtained plate-like body S, the substrate C for growing the plate-like body, the crucible 83, the raw material melt 84, the heater 85, the crucible base 86, the heat insulating material 87, and for raising and lowering the crucible. A base 88 and a shaft 89 connected to the substrate C are provided. However, in this figure, the means for moving the substrate C, the means for raising and lowering the crucible base 86, the means for controlling the heater 85, the means for adding the raw material, the chamber and the pump capable of evacuating, etc. The outside is not described. However, each component of the apparatus needs to be installed in a chamber with good airtightness so that the gas can be replaced with an inert gas after evacuation. At this time, argon, helium, or the like can be used as the inert gas, but argon is more preferable in consideration of cost, and it is more cost-effective to construct a circulation system. Connected. In addition, when silicon is used as a raw material, if a gas containing an oxygen component is used, silicon oxide is generated and adheres to the substrate surface and the chamber wall. Therefore, it is necessary to remove the oxygen component as much as possible. Further, it is preferable to remove silicon oxide particles through a filter or the like in the gas circulation system.
[0035]
As shown in FIG. 8, the substrate C having a temperature equal to or lower than the raw material melt temperature enters the raw material melt 84 in the crucible 83 from the left side in the drawing and is immersed in the raw material melt 84. At this time, the raw material melt is held by the heater 85 above the melting point. In order to obtain a stable plate-like body S, it is necessary to have an apparatus configuration capable of strictly controlling the melt temperature, the atmospheric temperature in the chamber, and the temperature of the substrate C. By adopting such an apparatus configuration, a plate-like body can be obtained with higher reproducibility.
[0036]
The substrate is preferably provided with a structure in which temperature control can be easily controlled. The material of the substrate is not particularly limited, but is preferably a material having good thermal conductivity or a material having excellent heat resistance, and more preferably graphite subjected to high purity treatment or the like. For example, high-purity graphite, silicon carbide, quartz, boron nitride, silicon nitride, alumina, zirconium oxide, aluminum nitride, metal, etc., or a mixture thereof can be used. And an optimal material may be selected according to the purpose. High-purity graphite is more preferable because it is a relatively inexpensive material that is rich in workability. The material of the substrate is industrially inexpensive, and the combination of the melt material and the substrate can be appropriately selected in consideration of various characteristics such as the substrate quality of the obtained plate-like body. Further, when a metal is used for the substrate, there is no particular problem as long as the metal is used at a temperature below the melting point of the substrate, such as constantly cooling, and does not significantly affect the properties of the obtained plate-like body. To facilitate temperature control, it is convenient to use a copper substrate.
[0037]
Substrate cooling means can be roughly classified into two types: direct cooling and indirect cooling. Direct cooling is a means for cooling the substrate by blowing a gas directly, and indirect cooling is a means for indirectly cooling the substrate with gas or liquid. The type of the cooling gas is not particularly limited, but it is preferable to use an inert gas such as nitrogen, argon, or helium for the purpose of preventing oxidation of the plate-like body. In particular, considering cooling capacity, helium or a mixed gas of helium and nitrogen is preferable, but nitrogen is preferable in consideration of cost. The cooling gas can be circulated using a heat exchanger or the like to further reduce the cost, and as a result, inexpensive plate-like silicon can be provided.
[0038]
Furthermore, the substrate preferably has a mechanism that can be heated. That is, it is preferable that the temperature of the substrate not only includes a cooling mechanism but also includes a heating mechanism. A plate-like body grows on the substrate surface of the substrate that has entered the raw material melt. Thereafter, the substrate escapes from the melt, but the substrate side receives heat from the raw material melt, and the temperature of the substrate tends to rise. However, next, when the substrate is immersed in the silicon melt at the same temperature, a cooling mechanism for lowering the temperature of the substrate is required. The mechanism at this time needs to be cooled using the cooling mechanism as described above. However, even with direct cooling or indirect cooling, it is difficult to control the cooling rate, that is, the substrate temperature as needed, and thus a heating mechanism is required.
[0039]
That is, the substrate once escaped from the raw material melt is cooled by the cooling mechanism, and then the temperature of the substrate is controlled using the heating mechanism before being immersed in the raw material melt. The heating mechanism may be a high frequency induction heating method, a resistance heating method, or a lamp heating method.
[0040]
Thus, the stability of the plate-like body is remarkably increased by using the cooling mechanism and the heating mechanism together. The temperature of the melt is preferably controlled by a plurality of thermocouples or a radiation thermometer, and the control temperature is preferably equal to or higher than the melting point. This is because if the control temperature is set in the vicinity of the melting point, the molten metal surface of the raw material melt may solidify due to the substrate coming into contact with the melt. In order to strictly control the melt temperature, it is preferable to immerse the thermocouple in the melt directly, but it is less preferable because impurities from a thermocouple protective tube or the like are mixed into the melt. The control part preferably controls the temperature indirectly by inserting a thermocouple into a crucible or the like.
[0041]
The crucible 83 containing the melt is installed on the heat insulating material 87. This is used to keep the melt temperature uniform, minimize heat removal from the bottom of the crucible, and minimize the temperature distribution in the melt. A crucible base 86 is installed on the heat insulating material 87. The crucible base 86 is connected to a crucible lifting / lowering shaft 88 and needs to be provided with a lifting / lowering mechanism. This is a mechanism for always immersing the substrate C in the melt 84 at the same depth in order to grow the silicon plate on the substrate C.
[0042]
In addition, as a method of keeping the molten metal surface position constant, that is, as a method of replenishing the raw material that has been taken out as a plate-like material, molten raw material polycrystalline body, or sequentially charged as a melt, A method of sequentially charging powder can be used, but a method of keeping the molten metal surface position constant is not particularly limited. However, it is preferable not to disturb the melt surface as much as possible. If the molten metal surface is disturbed, the wave shape generated at that time is reflected on the melt surface side of the plate-like body, which may impair the uniformity of the resulting plate-like body and impair quality stability. Because there is.
(Method for producing plate-like silicon)
Next, the manufacturing method of the plate-shaped body when the substrate of the present invention is used will be described using the plate-shaped body manufacturing apparatus shown in FIG. In particular, here, silicon is used as a raw material. First, a high-purity graphite crucible 83 is filled with a silicon lump whose boron concentration is adjusted so that the specific resistance of the obtained plate-like body is 0.5 to 2 Ω · cm. The crucible is installed in an apparatus as shown in FIG. Next, the inside of the chamber is evacuated, and the inside of the chamber is reduced to a predetermined pressure. Thereafter, Ar gas is introduced into the chamber, and Ar gas is kept flowing from the upper part of the chamber at a flow rate of 10 L / min. The reason why the gas is constantly flowed in this way is to obtain a clean silicon surface.
[0043]
Next, the temperature of the silicon melting heater 85 is set to 1500 ° C., and the silicon lump in the crucible 83 is completely melted. At this time, since the silicon raw material melts and the liquid level becomes low, new silicon powder is added so that the molten metal surface of the silicon melt is positioned 1 cm below the upper surface of the crucible 83. It is preferable that the silicon melting heater is not heated to 1500 ° C. at a time, but is heated to about 1300 ° C. at a heating rate of 5 to 50 ° C./min and then raised to a predetermined temperature. This is because when the temperature is suddenly raised, thermal stress is concentrated on the corners of the crucible and the like, leading to breakage of the crucible.
[0044]
Thereafter, after confirming that the silicon is completely melted, the silicon melt temperature is set to 1410 ° C. and held for 30 minutes to stabilize the melt temperature. Next, the crucible 83 is moved to a predetermined position using the crucible elevating mechanism 88. The silicon melt temperature at this time is preferably 1400 ° C. or higher and 1500 ° C. or lower. This is because, since the melting point of silicon is around 1410 ° C., when the temperature is set to 1400 ° C. or lower, the molten metal surface gradually hardens from the crucible wall. On the other hand, when the temperature is set to 1500 ° C. or higher, the growth rate of the obtained plate-like silicon is slow, and the productivity is deteriorated.
[0045]
Next, plate-like silicon is grown, and the substrate of the present invention is advanced from the left side to the right side of the drawing along the arrow Z as shown in FIG. At this time, the surface of the substrate, for example, the main surface portion 1 in FIG. 1 is brought into contact with the silicon melt, and the substrate is moved so that the front portion F1 of the substrate is in front of the traveling direction. Thus, plate-like silicon is formed on the surface of the main surface portion 1 when the surface of the substrate is in contact with the silicon melt. The trajectory for growing the plate-like silicon on the substrate is not particularly limited. For example, it is preferable to have a structure that can realize an arbitrary trajectory such as a circular trajectory, an elliptical trajectory, or a combination trajectory thereof.
[0046]
1 to 6, the shape of the upper part of the substrate C is formed by the plane F, but is not particularly limited. A more preferable shape is preferably a shape so that the silicon plate grown on the main surface portion 1 does not fall.
[0047]
In particular, the surface temperature of the substrate when entering the silicon melt needs to be equal to or lower than the freezing point of the silicon melt. More preferably, it is 100 degreeC or more and 1100 degreeC or less. If the substrate temperature is 100 ° C. or less, stable control becomes difficult. That is, in the case of continuous production, the substrate waiting to be immersed in the chamber receives radiant heat from the silicon melt, and it is difficult to always maintain it at 100 ° C., resulting in variations in the quality of the obtained silicon plate. It is because it leads to. Moreover, it is not preferable that the temperature of the substrate is 1100 ° C. or higher because not only it takes time to heat the substrate to 1100 ° C., but also the growth rate of the plate-like silicon is slowed and the productivity is deteriorated. In order to adjust the temperature of the substrate, since both the cooling mechanism and the heating mechanism are provided, not only the productivity is improved, but also the yield of the product can be improved and the quality can be stabilized.
[0048]
Here, the manufacturing method of the plate-like silicon has been described. As described above, by appropriately changing the material and shape of the substrate used for the growth, a metal or a group IV (group IV-IV) is used. It can be easily used for producing a plate-like body such as a semiconductor, a group III-V semiconductor, or a group II-VI semiconductor.
[0049]
In addition, as for the general shape of the substrate for manufacturing a plate-like body described above, the edge of the plate-like body shows only a straight quadrangular shape, but it can be applied to any shape, that is, a triangle or a circle. Is possible.
[0050]
Further, here, since the manufacturing apparatus shown in FIG. 8 is used for explanation, plate-like silicon grows on the lower side of the substrate C. However, it is also possible to produce plate-like silicon on the upper side of the substrate C by turning the substrate upside down with a device configuration different from that in FIG.
[0051]
【Example】
(Example 1)
<Production of plate-like silicon>
A silicon raw material whose boron concentration was adjusted so that the specific resistance was 1 Ω · cm was placed in a quartz crucible protected by a high-purity carbon crucible and fixed in the apparatus shown in FIG.
[0052]
First, the chamber was evacuated to about 0.00133 Pa, replaced with Ar gas to normal pressure, and then Ar gas was allowed to flow at 2 L / min. Next, silicon was melted with a heater, and the melt temperature was stabilized at 1425 ° C.
[0053]
Next, the growth substrate having the shape shown in FIG. 1 is controlled so that its surface temperature becomes 200 ° C., and further, the substrate surface is immersed so that it passes through a portion 8 mm below the surface of the molten metal to grow plate-like silicon. I let you. At this time, the used substrate had outer dimensions of 110 mm in width, 105 mm in length, and 30 mm in thickness. Moreover, the width W1 of the peripheral part was 5 mm, the regular convex part was formed in the surface, the pitch P12 of the convex part was 2 mm, and the front-end | tip angle (alpha) 90 degrees used.
[0054]
The size of the plate-like silicon thus obtained was 100 mm × 100 mm, and no burrs protruded toward the growth substrate side at the periphery of the sheet. The thickness of the grown silicon was about 0.35 mm, and it could be easily peeled off from the substrate.
<Method for producing solar cell>
Only the part which grew to the main surface part of the board | substrate was cut | disconnected among the grown plate-shaped silicon | silicone, and it passed through the manufacturing process of the solar cell, and produced the solar cell.
[0055]
In order to clean the obtained plate-like silicon, after performing alkali etching with sodium hydroxide, POCl _Three N on the p-type substrate by diffusion ⁺ A layer was formed. After the PSG film formed on the surface of the plate-like silicon is removed with hydrofluoric acid, n which becomes the light receiving surface side of the solar cell ⁺ A silicon nitride film was formed on the layer using plasma CVD. Next, n formed on the surface to be the back side of the solar cell ⁺ The layer is etched away with a mixed solution of nitric acid and hydrofluoric acid to expose the p substrate, on which the back electrode and p ⁺ Layers were formed simultaneously. Next, an electrode on the light receiving surface side was formed by using a screen printing method. Thereafter, solder dipping was performed to produce a solar cell. AM1.5, 100mW / cm ² Under the irradiation, the characteristics of the solar cell were evaluated according to “Method for Measuring Output of Crystalline Solar Cell (JIS C 8913 (1988))”.
[0056]
The measurement result is a short-circuit current of 30.10 (mA / cm ² ), Open circuit voltage 580 (mV), fill factor 0.750, efficiency 13.1 (%).
(Example 2)
Except that the growth substrate shown in FIG. 3 was used, plate-like silicon was produced by the same method as in Example 1, and solar cells were also produced and evaluated.
[0057]
The substrate used at this time had a pyramid shape with a pitch P31 of regular irregularities of the main surface of 1.5 mm and a tip angle α of 150 °. Further, the width W3 of the peripheral portion was 5 mm, the pitch P32 of the regular uneven projections on the peripheral surface was 2 mm, and the pyramid shape had a tip angle α of 90 °.
[0058]
The size of the obtained plate-like silicon was 100 mm × 100 mm, and no burrs protruded toward the substrate side in the periphery of the plate-like silicon. The obtained plate-like silicon had a thickness of about 0.32 mm and could be easily peeled from the substrate.
[0059]
In the obtained plate-like silicon, only the surface grown from the plane F of the substrate was cut and passed through a solar cell process to produce a solar cell.
[0060]
The measurement result of the produced solar cell characteristics is a short-circuit current of 29.9 (mA / cm ² ), Open circuit voltage 580 (mV), fill factor 0.73, efficiency 12.7 (%).
(Example 3)
Except that the growth substrate shown in FIG. 4 was used, plate silicon was produced in the same manner as in Example 1, and a solar cell was also produced.
[0061]
The substrate used at this time had a height difference H4 of 2 mm between the main surface portion and the peripheral portion. The width W4 of the peripheral portion of the substrate was 5 mm, regular irregularities were present on the surface, the pitch of the convex portions was 1.5 mm, and the shape was a pyramid shape with a tip angle of 90 °.
[0062]
The size of the obtained plate-like silicon was 100 mm × 100 mm, and no burrs protruded toward the substrate side in the periphery of the plate-like silicon. The obtained plate-like silicon had a thickness of about 0.36 mm, and could be easily peeled off from the substrate.
[0063]
In the obtained plate-like silicon, only the surface grown from the plane F of the substrate was cut and passed through a solar cell process to produce a solar cell.
[0064]
The measurement result of the fabricated solar cell characteristics is a short circuit current of 30.2 (mA / cm ² ), An open circuit voltage of 579 (mV), a fill factor of 0.74, and an efficiency of 12.9 (%).
(Example 4)
Except that the growth substrate shown in FIG. 6 was used, plate-like silicon was produced in the same manner as in Example 1, and a solar cell was also produced.
[0065]
The substrate used was a substrate composed of four substrate members, and the height difference H6 between the main surface portion and the peripheral portion was 4 mm. Further, the width W6 of the peripheral portion was 5 mm, the pitch of the regular uneven protrusions on the surface of the peripheral portion was 2 mm, and the pyramid shape had a tip angle of 90 °.
[0066]
The size of the obtained plate-like silicon was 100 mm × 100 mm, and no burrs protruded toward the substrate side in the periphery of the plate-like silicon. Moreover, the thickness of the obtained plate-like silicon was about 0.36 mm at the thick part, and could be easily peeled from the substrate.
[0067]
The measurement result of the produced solar cell characteristics is a short-circuit current of 31.0 (mA / cm ² ), Open circuit voltage 584 (mV), fill factor 0.73, efficiency 13.2 (%).
(Example 5)
A silicon raw material whose boron concentration is adjusted so that the specific resistance of the obtained silicon plate becomes 1 Ω · cm is filled in a quartz crucible protected by a high-purity carbon crucible and installed in the apparatus shown in FIG. did. Then, exhaust was performed using a rotary pump until the pressure in the main body chamber reached 300 Pa. Thereafter, exhaust was further performed using a mechanical booster pump until the pressure reached 6 Pa.
[0068]
Next, the temperature of the crucible is increased to 500 ° C. at a temperature increase rate of 5 ° C./min. Moisture contained in the carbon crucible is removed by holding the pressure in the main chamber for 90 minutes while maintaining the pressure at 6 Pa and the crucible temperature at 500 ° C. After such baking, the output of the inverter is once stopped and the heating of the crucible is stopped. In this state, argon gas is filled until the pressure in the main body chamber reaches 800 hPa.
[0069]
When the inside of the main chamber reaches 800 hPa, the crucible is heated again at a temperature rising rate of 10 ° C./min, and the temperature is raised until the crucible temperature reaches 1500 ° C. By maintaining the temperature of the crucible at 1500 ° C. for 1 hour and stabilizing it, the silicon lump in the crucible eventually melts and becomes a silicon melt. After confirming that the silicon mass is completely dissolved, additional silicon mass is added so that the height of the silicon melt surface is 15 mm from the upper end of the crucible. After confirming that all of the additional silicon lump has been melted, the set temperature of the crucible is lowered to 1430 ° C., and this state is maintained for 30 minutes to stabilize the temperature of the silicon melt.
[0070]
Next, heating is performed so that the temperature of the growth substrate surface becomes 500 ° C., and the substrate is immersed in the silicon melt. At this time, the substrate shown in FIG. 3 was used, and the size of the main surface portion was 165 mm × 155 mm. Regular irregularities exist on the surface of the main surface portion 31 of the substrate, and the pitch P31 of the convex portions is a pyramid shape of 1.5 mm, and the height of the pyramid at that time was 0.20 mm. . Further, regular irregularities exist on the surface of the peripheral portion 32, and the pitch P32 of the convex portions is 1.5 mm and the tip angle is 45 °. The peripheral width W3 was 5 mm.
[0071]
Only one side of the plate-like silicon produced by such a process was cut with a laser to obtain 30 pieces of 155 mm square plate-like silicon.
<Production of solar cell>
A solar cell was fabricated from 155 mm square plate-like silicon. The obtained silicon plate was etched with a mixed solution of nitric acid and hydrofluoric acid also for cleaning. Thereafter, alkali etching was performed using sodium hydroxide. Thereafter, the obtained plate-like silicon is diffused by PSG (phosphorus silicate glass) diffusion. ⁺ A layer was formed. n ⁺ After removing the excess PSG film formed at the time of layer formation with hydrofluoric acid, a silicon nitride film serving as an antireflection film was formed by plasma CVD. Next, n is also formed on the surface to be the back side of the solar cell. ⁺ The layer was etched away with a mixed solution of nitric acid and hydrofluoric acid to expose the p-type substrate. On top of that, by back-printing Al paste, back electrode and p ⁺ Layers were formed simultaneously. Next, the light receiving surface electrode was formed by printing Ag paste. Thereafter, solder coating was performed to obtain a solar cell. The obtained solar cell is AM1.5, 100 mW / cm. ² The solar cell characteristics were performed under irradiation. In addition, the measuring method followed the "crystalline solar cell output measuring method (JIS C 8913 (1988))".
[0072]
The obtained 30 solar cells were measured, and the average value of the results was a short-circuit current of 31.3 (mA / cm ² ), Open circuit voltage 601 (mV), fill factor 0.74, efficiency 13.9 (%).
[0073]
【The invention's effect】
As described above, the plate-like body grown by adopting the substrate according to the present invention does not form burrs, and it is not necessary to cut the plate-like body in the manufacturing process of solar cells, etc. It is effective in relaxing cutting conditions. Further, the use of a silicon sheet produced by this method as a solar cell is useful for reducing the cost of the solar cell and preventing environmental destruction due to the widespread use of solar cells.
[Brief description of the drawings]
1A is a schematic perspective view of a substrate of the present invention, and FIG. 1B is a cross-sectional view taken along 1B-1B in FIG.
FIG. 2A is a schematic cross-sectional view when a melt exists on the substrate of the present invention, and FIG. 2B is a schematic cross-sectional view of a plate-like body grown on the substrate.
3A is a schematic perspective view of a substrate of the present invention, and FIG. 3B is a cross-sectional view taken along 3B-3B in FIG.
4A is a schematic perspective view of a substrate of the present invention, and FIG. 4B is a cross-sectional view taken along 4B-4B in FIG.
5A is a schematic sectional view when a melt exists on the substrate of the present invention, and FIG. 5B is a schematic sectional view of a plate-like body grown on the substrate.
6A is a schematic perspective view of a substrate of the present invention, and FIG. 6B is a cross-sectional view taken along 6B-6B of FIG.
7A is a schematic cross-sectional view when a melt is present on a conventional substrate, and FIG. 7B is a schematic cross-sectional view of a plate-like body grown on the substrate.
FIG. 8 is a schematic cross-sectional view of an apparatus for producing a plate-like body using the substrate of the present invention.
FIG. 9 is an enlarged schematic perspective view of a substrate having convex portions according to the present invention.
FIG. 10 is an enlarged schematic perspective view of a substrate having a convex portion according to the present invention.
11A is a schematic perspective view of a substrate of the present invention, and FIG. 11B is a cross-sectional view taken along 11B-11B of FIG.
12A is a schematic perspective view of a substrate of the present invention, and FIG. 12B is a cross-sectional view taken along 12B-12B in FIG.
[Explanation of symbols]
C substrate, S plate-like body, 1 main surface portion of substrate, 2 peripheral portion, 3 melt, 4 burr, 5 dot-like projection, 6 linear projection.

Claims (5)

A substrate on which a silicon plate is brought into contact with a melt containing silicon and the silicon plate is grown on the surface thereof;
The substrate has a main surface portion on which a plate-like body grows, and a peripheral portion adjacent to the main surface portion where the plate-like body does not grow,
The surface of the main surface portion is a flat surface, and the surface of the peripheral portion has a regular uneven shape,
The concavo-convex shape is a structure having pyramidal protrusions or a structure having a plurality of rows of protrusions having a triangular cross section,
A substrate characterized in that the pitch of the convex and concave portions in the peripheral portion is 0.5 mm to 3 mm, and the tip angle is 15 ° to 120 °. A substrate on which a silicon plate is brought into contact with a melt containing silicon and the silicon plate is grown on the surface thereof;
The substrate has a main surface portion on which a plate-like body grows, and a peripheral portion adjacent to the main surface portion where the plate-like body does not grow,
The surface of the main surface portion and the peripheral portion have a regular uneven shape,
The concavo-convex shape is a structure having pyramidal protrusions or a structure having a plurality of rows of protrusions having a triangular cross section,
The pitch of the concavo-convex convex portion of the main surface portion is shorter than the peripheral portion or the tip of the concavo-convex convex portion of the peripheral portion to such an extent that the plate-like body grows on the main surface portion and does not grow on the peripheral portion. A substrate having an angle smaller than that of a main surface portion. A tip angle of 45 ° to 90 ° range of the convex portion of the uneven shape of the peripheral portion of claim 2, wherein the tip angle of the convex portion of the concavo-convex shape of the front Symbol main surface portion is in the range of 90 ° to 150 DEG ° Board.   The board | substrate in any one of Claims 1-3 in which the main surface part of the board | substrate is formed in concave shape with respect to a peripheral part.   A method for producing a silicon plate-like body using the substrate according to claim 1.

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