JP2009107886A - Method for manufacturing polycrystalline silicon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the collapse accident of a silicon rod by growing the silicon rod uniformly in a longitudinal direction when manufacturing a polycrystalline silicon by Siemens method. <P>SOLUTION: All of a plurality of electrodes satisfy the following conditions (1), (2) and (3), when the peak center of the electrode is represented by A point, the peak center of a supply nozzle for a source gas is represented by B point, a separation distance in a horizontal direction from the electrode center line is represented by D, and a level difference downward from the level of the A point is represented L. The conditions are: (1) in a region A<SB>1</SB>around the electrode satisfying D=80 to 450 mm, at least one B point exists in a region B<SB>1</SB>lower than a plane X satisfying D/L=6 and over a plane Y<SB>1</SB>satisfying D/L=0.8; (2) in the region A<SB>1</SB>around the electrode satisfying D=80 to 450 mm, no B point exists in a region C<SB>1</SB>lower than a plane Y<SB>1</SB>satisfying D/L=0.8 and over a plane Z satisfying L=600 mm; and (3) in a region D around the electrode satisfying D<80 mm, no point B exists in a region E over the plane Z satisfying L=600 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing polycrystalline silicon used for producing solar cell panels, silicon single crystals and the like, and more particularly to a method for producing polycrystalline silicon by the Siemens method.

  Polycrystalline silicon used for manufacturing solar cell panels, silicon single crystals, and the like is mainly manufactured industrially by a method called a Siemens method. In the production of polycrystalline silicon by the Siemens method, a large number of silicon core rods are erected in a reaction furnace called a bell jar. A large number of silicon core rods are fixed on an electrode installed at the bottom of the reaction furnace, and the inside of the reaction furnace is replaced with a predetermined atmosphere, and then heated by energization. In this state, a mixed gas of silane and hydrogen is supplied from a plurality of source gas supply nozzles provided at the bottom of the reaction furnace. As a result, polycrystalline silicon is deposited on the surface of the silicon core rod by thermal decomposition of silane, and the core rod grows, whereby a polycrystalline silicon rod having a predetermined diameter as a product is manufactured. The silicon core rod is formed in an inverted U shape with two wires as a set for energization heating, and is set on a set of electrodes.

  In the production of polycrystalline silicon by the Siemens method, the reactor has been enlarged to increase productivity, and the number of polycrystalline silicon produced at a time has been increased. Recently, several tens or more are produced. Polycrystalline silicon rods are manufactured simultaneously in one reactor.

  Increasing the number of polycrystalline silicon produced causes various problems. One of the problems is difficulty in uniformly supplying the raw material gas to the silicon rod.

  That is, in the manufacture of polycrystalline silicon by the Siemens method, it is necessary to uniformly grow the silicon core rod. This is because, since polycrystalline silicon is a semiconductor, the electrical resistance changes depending on the thickness, and this change promotes the heating temperature difference and further increases the growth difference. For this reason, it is necessary to supply the source gas evenly to all the silicon rods in the reaction furnace.

  However, when the reactor becomes large and the number of silicon rods increases, it becomes difficult to uniformly supply the source gas. For this reason, in addition to increasing the number of raw material gas supply nozzles at the bottom of the furnace with an increase in the size of the reaction furnace and the number of polycrystalline silicon produced, various arrangements have been devised for the arrangement.

  Another problem with the source gas is cooling of the silicon rod with the source gas. This is a phenomenon in which the temperature of the raw material gas is lower than the thermal decomposition temperature of the raw material gas, so that the silicon rod is cooled by the raw material gas, which also increases the growth difference of the silicon rod. For this reason, the arrangement of the raw material gas supply nozzle has been devised including the problem of cooling (see, for example, Patent Document 1).

JP 2006-206387 A

  Another problem in the production of polycrystalline silicon by the Siemens method is the accident of collapse of the silicon rod in the reactor. This is a phenomenon in which a specific silicon rod collapses in the furnace during or after the manufacture, and this triggers many of the silicon rods in the furnace in a chain reaction. When this occurs, the current-carrying rod is grounded, and a discharge may occur between the electrode and the reaction vessel.

  The cause of this collapse accident is thought to be a combination of various factors, but after many of the silicon rods in the furnace collapse, it is difficult to identify the first collapse rod that caused the chain collapse, The cause is extremely difficult to identify.

  An object of the present invention is to produce polycrystalline silicon by the Siemens method for producing polycrystalline silicon, which can achieve uniform growth of the silicon rod while ensuring high productivity, and can effectively prevent the collapse of the silicon rod. Is to provide.

  The present inventors consider that the position of the source gas supply nozzle is also related to the rod collapse accident, which is a particularly serious problem in mass production in a large furnace, and there are various relations between the nozzle position and the rod collapse. We investigated and analyzed from the viewpoint. As a result, the following facts were found.

  Conventionally, the positional relationship between the electrode and the source gas supply nozzle at the bottom of the reactor has been analyzed exclusively from a planar viewpoint (horizontal direction). The vertical positional relationship is never ignored, and certain conditions are satisfied. That is, the upper end position of the nozzle is made sufficiently lower than the upper end position of the electrode.

  That is, the silicon set on the electrode needs to be grown to a uniform thickness from the bottom to the top. If the upper end level of the source gas supply nozzle is not lower than the upper end level of the electrode, the entire amount of gas cannot be supplied uniformly from the bottom to the top of the silicon core rod. For this reason, the upper end level of the source gas supply nozzle is sufficiently lowered than the upper end level of the electrode. However, even if the upper end level of the source gas supply nozzle is lower than the upper end level of the electrode, if the source gas supply nozzle is separated from the electrode, the gas supply to the lower part of the rod near the electrode is insufficient, and the silicon rod is uniformly grown. It becomes difficult. For this reason, the source gas supply nozzle cannot be moved away from the electrode.

  However, when the source gas supply nozzle is brought too close to the electrode, the source gas ejected from the nozzle directly hits the lower part of the silicon rod. The temperature of the raw material gas is extremely lower than the temperature of the rod (the thermal decomposition temperature of silane gas). For this reason, an egre is generated in the lower part of the rod where the source gas collides. Both the poor growth at the bottom of the silicon rod and the occurrence of this aggression are at risk of collapsing.

  For this reason, it is difficult to completely prevent the collapse of the silicon rod by simply devising the planar arrangement position of the electrode and the source gas supply nozzle. Therefore, the present inventor paid attention to the level difference between the upper end of the electrode and the upper end of the source gas supply nozzle, and investigated the relationship between the influence on the growth of the silicon rod and the decrease in collapse. As a result, the following was found.

  In order to supply the source gas to the lower part of the rod, it is necessary to arrange a source gas supply nozzle in the vicinity of the electrode. However, when the nozzle is brought close to the electrode, as described above, the tendency of the raw material gas to collide with the lower portion of the rod and to generate an egress is increased. However, even if the source gas supply nozzle is brought closer to the electrode, if the level of the source gas supply nozzle is increased accordingly, the occurrence of the egress at the lower portion of the rod tends to be suppressed. It is necessary to arrange at least one source gas supply nozzle in a region set in consideration of such a tendency. By doing so, it is possible to supply the necessary raw material gas to the lower part of the rod while preventing the occurrence of the egress of the lower part of the rod.

  On the other hand, in order to supply the source gas to the lower part of the rod, it is necessary to make the upper end level of the source gas supply nozzle lower than the upper end level of the electrode. Regardless of the source gas, there is a danger that the source gas will collide with the lower part of the rod and generate an egress. For this reason, it is necessary to avoid disposing the source gas supply nozzle at a position that is too low. This position is also affected by the horizontal positional relationship between the upper end of the source gas supply nozzle and the upper end of the electrode.

  On the other hand, if the source gas supply nozzle is extremely close to the electrode, the source gas may collide with the lower portion of the rod regardless of the vertical positional relationship, and there is a risk of causing an egress. For this reason, it is also necessary to avoid disposing the source gas supply nozzle at a position that is too close. On the other hand, the source gas supply nozzles such as a position far from the electrode, a position that is too high, and an extremely low position do not affect the rod shape. In other words, at these positions, the source gas supply nozzle may or may not exist.

  The method for producing polycrystalline silicon according to the present invention has been completed on the basis of such knowledge, and a silicon core is fixed on a plurality of electrodes provided at the bottom of the reactor, and these silicon cores are energized. A method for producing polycrystalline silicon by a Siemens method in which polycrystalline silicon is deposited on each silicon core rod by supplying a raw material gas into a reaction furnace from a plurality of raw material gas supply nozzles provided at the bottom in a heated state , The top center of the electrode is A point, the top center of the source gas supply nozzle is B point, the distance in the horizontal direction from the electrode center line is D, and the level difference from the A point level downward is L, All of the plurality of electrodes satisfy both the following conditions 1, 2, and 3.

Condition 1: Within the area A ₁ around the electrode satisfying D = 80 to 450 mm and below the surface X around the electrode satisfying D / L = 6, around the electrode satisfying D / L = 0.8 At least one of the B point exists within region B ₁ above the plane Y ₁ (including the surface X and the plane Y _1).
Condition 2: In the area A ₁ around the electrode satisfying D = 80 to 450 mm and below the surface Y ₁ around the electrode satisfying D / L = 0.8, the surface around the electrode satisfying L = 600 mm There is no point B in the region C ₁ above Z (including the surface Y ₁ but not the surface Z).
Condition 3: There is no point B in the region D around the electrode satisfying D = less than 80 mm and in the region E (including the surface Z) above the surface Z around the electrode satisfying L = 600 mm.

  More preferably, all of the plurality of electrodes satisfy both the following conditions 1 ', 2' and 3 '.

Condition 1 ′: Around the electrode satisfying D / L = 1.15 in the area A ₂ around the electrode satisfying D = 80 to 350 mm and below the surface X around the electrode satisfying D / L = 6 There is at least one B point in the region B ₂ above the surface Y ₂ (including the surface X and the surface Y ₂ ).
Condition 2 ′: within the region A ₂ around the electrode satisfying D = 80 to 350 mm and below the surface Y ₂ around the electrode satisfying D / L = 1.15, around the electrode satisfying L = 600 mm There is no point B in the region C ₂ above the surface Z (not including the surface Y ₂ but including the surface Z).
Condition 3 ′: B point does not exist in the region D around the electrode satisfying D = less than 80 mm and in the region E (including the surface Z) above the surface Z around the electrode satisfying L = 600 mm ( Same as condition 3).

  The reasons for limiting conditions 1, 2, and 3 and conditions 1 ', 2', and 3 'will be described in detail later.

  The method for producing polycrystalline silicon according to the present invention is particularly effective when the number of electrodes per reactor is large, specifically, when the number is 30 or more. Because, if the number of electrodes increases, uniform supply of the source gas to the silicon core rod on the electrodes becomes difficult, so that uniform growth of the silicon rods becomes difficult and damage caused when collapse occurs increases. It is. Note that the number of electrodes is desirably 200 or less in order to suppress damage in the event of a collapse.

The method for producing polycrystalline silicon according to the present invention is also particularly effective when the source gas supply nozzle is a straight pipe type gas nozzle that is vertically upward. This nozzle is a nozzle that blows out the source gas vigorously right above, and is often used in polycrystalline silicon manufacturing furnaces, especially for supplying the source gas sufficiently to the space near the top of the silicon rod in large furnaces. Suitable.
.

  The method for producing polycrystalline silicon according to the present invention defines the positional relationship between the raw material gas supply nozzles around the electrodes for all the electrodes in the reaction furnace in both the horizontal direction and the vertical direction. Even when there are a large number of rods, the source gas can be supplied uniformly and uniformly to each rod. In addition, a silicon rod collapse accident in the furnace can be effectively prevented, thereby contributing to improvement in productivity.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a reaction furnace showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an electrode in the reaction furnace and a raw material gas nozzle, and FIG. 3 is an appropriate positional relationship between the electrode in the reaction furnace and the raw material gas nozzle. It is a schematic diagram for demonstrating.

  In the present embodiment, as shown in FIG. 1, high-purity polycrystalline silicon used for manufacturing a high-performance solar cell panel, a silicon single crystal or the like is manufactured by the Siemens method. The reactor 10 used for the manufacture is a bell jar furnace in which a disc-shaped furnace bottom 11 is covered with a furnace body 12 having a bell-shaped jacket structure. In the furnace bottom portion 11, a large number of electrodes 14, each having two as a set, are installed in a distributed manner. Each electrode 14 is a vertical conductive rod, on which a silicon core rod 13 is fixed vertically and electrically connected (see FIG. 2).

  The silicon core rod 13 is an elongated rod made of polycrystalline silicon, and is connected in series as a pair of two adjacent ones for energization heating. More specifically, the upper portions are connected by a horizontal rod. A gate shape (inverted U-shape) is formed, and one set thereof is fixed on the one set of electrodes 13 described above.

  The furnace bottom 11 is also provided with a large number of source gas supply nozzles 15 dispersed so as not to interfere with the electrode 14, and a plurality of gas discharge holes 16 are provided at the outermost periphery of the furnace bottom 11. It has been. As shown in FIG. 2, the raw material gas supply nozzle 15 is a vertically upward straight pipe type gas nozzle, and is spaced apart from the surrounding electrode 14 in the horizontal direction by a center-to-center distance D ′. The height from the surface of the electrode 14 is set lower than the top level of the electrode 14 by L ′.

  The number of silicon core rods 13 is, for example, 30 (15 sets) or more, and the number of source gas supply nozzles 15 is, for example, approximately half the number of silicon core rods 13.

In operation, the silicon core rod 13 is set in the reaction furnace 10, the reaction furnace 10 is sealed, the atmosphere in the furnace is exhausted by vacuum replacement, and the inside of the furnace is pressurized with H ₂ gas or inert gas. Maintain the atmosphere. In this state, all the silicon core rods 13 are heated to a temperature equal to or higher than the decomposition temperature of silane gas (usually around 1000 ° C.), and the source gas is introduced into the reaction furnace 10 from the source gas supply nozzle 15. The source gas is a mixed gas of silane (usually trichlorosilane) and hydrogen, and is strongly blown up directly from the source gas supply nozzle 15.

  The raw material gas ejected from the raw material gas supply nozzles 15 at various places in the furnace bottom collides with the ceiling surface of the furnace body 12, descends to the periphery along the ceiling surface, and is provided at the outermost peripheral portion of the furnace bottom portion 11. The gas is discharged from the gas discharge hole 15. In this process, the source gas comes into contact with the high temperature silicon core rod 13, and silane is thermally decomposed on the surface of the silicon core rod 13, thereby depositing polycrystalline silicon on the surface and growing the silicon core rod 13. As a result, the silicon rod 20 is formed on the electrode 14.

  Thus, in the polycrystalline silicon manufacturing method of the present embodiment, a large number of polycrystalline silicon rods are simultaneously manufactured by the Siemens method.

  What is important here is the positional relationship in the horizontal and vertical directions between the electrodes 14 provided at various locations on the furnace bottom 11 and the source gas supply nozzles 15 arranged around the electrodes 14. This positional relationship will be described in detail with reference to FIG.

  The center of the top of the electrode 14 is designated as point A, and the center of the top of the source gas supply nozzle 15 is designated as B (see FIG. 2). Further, the horizontal distance from the center line of the electrode 12 is D, and the level difference from the point A level downward is L. When L is large, that is, when there is a point B substantially below point A, the source gas blown from the source gas supply nozzle 15 is also supplied to the lower part of the silicon rod 20 on the electrode 12 and is uniform in the vertical direction. Gas supply is performed. On the other hand, when the level of the source gas supply nozzle 15 increases (L becomes smaller), the supply of the source gas to the lower part of the silicon rod 20 becomes insufficient, and this portion becomes thin and there is a risk of collapse. This is the conventional concept in the vertical direction.

  However, in the region where the horizontal distance D from the point A is small, even if the level difference L is large, there is a risk that the source gas blown from below directly collides with the lower part of the silicon rod 20. Since the temperature of the raw material gas is extremely lower than the rod temperature, if the raw material gas collides directly, an aggression is generated at the collision part, and the aggregation below this rod also causes collapse. In the region where the horizontal distance D is small, the risk of collapse is reduced by reducing the level difference L (raising the nozzle level). As can be seen, both D and L are deeply involved in the collapse of the silicon rod 20, and D / L is an important determination factor.

D / L represents a depression angle from point A. If this is large, the depression angle is small, and conversely, if it is small, the depression angle is large. A negative value of D / L represents an elevation angle. When point B exists in a region below the surface Y ₁ around the electrode that satisfies D / L = 0.8, the source gas supply nozzle 15 directly supplies the source gas to the lower part of the silicon rod 20 on the electrode 12. Collide and create a cause of collapse. Therefore, it is necessary that the point B does not exist in a region below the surface Y ₁ around the electrode that satisfies D / L = 0.8. D / L = 0.8 and electrodes around the surface Y ₁ that satisfies is the conical surface formed by rotating a ramp down line satisfies D / L = 0.8 to electrodes around the center line.

However, in the region where D is large, that is, the region which is separated from the electrode 12 in the horizontal direction, and in the region where L is large, that is, the region which is greatly lowered downward from the electrode 12, the influence of the position of the source gas supply nozzle 15 on the silicon rod 20 is Therefore, the point B may exist below the surface Y ₁ around the electrode that satisfies D / L = 0.8. Specifically, if D> 450 mm or L> 600 mm is satisfied, a point B may exist below the surface Y ₁ around the electrode that satisfies D / L = 0.8.

On the other hand, in order to supply the raw material gas uniformly from the bottom to the top to the silicon rod 20 on the electrode 12, the raw material gas supply nozzle 15 still needs to be positioned below the upper end of the electrode 14, which is also D Affected by. From this point of view, the region B ₁ is lower than the surface X around the electrode satisfying D / L = 6 and is higher than the surface Y ₁ around the electrode satisfying D / L = 0.8, and D ≧ 450 mm is satisfied. It is necessary that at least one point B exists in the region to be performed. The surface X around the electrode satisfying D / L = 6 is a conical surface formed by rotating a downwardly inclined straight line satisfying D / L = 6 around the electrode center line.

  However, even if this condition is satisfied, it is necessary to exclude the source gas supply nozzle 15 from a region extremely close to the electrode 12. This is because the source gas supply nozzle 15 that is extremely close to the electrode 12 causes a collapse at the bottom of the silicon rod 20 on the electrode 12 regardless of the level L, thereby causing a collapse. If it is in the vicinity of the electrode, even if it is above the surface X around the electrode that satisfies D / L = 6, the eyelet is generated in the portion from the lower part of the rod to the middle part. However, if point B exists extremely downward, the adverse effect is mitigated. From this point of view, the region around the electrode satisfying D <80 mm (D) and the region around the electrode satisfying L ≧ 600 mm, that is, the region above the surface Z around the electrode satisfying L = 600 mm (E B) must not exist in

  The area around the electrode that satisfies D> 450 mm, the area around the electrode that satisfies L> 600 mm, that is, the area below the surface Z around the electrode that satisfies L = 600 mm, and the area around the electrode that satisfies D / L = 6 In the region above the surface X (except for the region satisfying D <80 mm), the presence of the point B does not cause a defect of the silicon rod on the electrode 14 due to the influence of gas diffusion or the like. It does not contribute to healthy growth.

In summary, the electrode satisfying D / L = 0.8 in the area A ₁ around the electrode satisfying D = 80 to 450 mm and below the surface X around the electrode satisfying D / L = 6. An area around the electrode satisfying D = 80 to 450 mm, that at least one B point exists in the area B ₁ (including the face X and the face Y ₁ ) above the surrounding face Y ₁ (Condition 1) in the a _1, and does not include a D / L = 0.8 satisfactory electrodes around the surface Y ₁ satisfies L = 600 mm below the electrode around the upper region C within ₁ from the surface Z (the surface Y ₁ The point B is not present (including the surface Z) (condition 2), and the region around the electrode D that satisfies D = less than 80 mm and the region above the surface Z around the electrode that satisfies L = 600 mm It is necessary that point B does not exist in E (including plane Z) (condition 3).

When there is no B point in the region A ₁ and in the region B ₁ , that is, when the condition 1 is not satisfied, the supply of the raw material gas to the lower portion of the silicon rod 20 is insufficient, and the lower portion is thin. There is a risk of collapse. When the point B exists in the area A ₁ and in the area C ₁ , that is, when the condition 2 is not satisfied, the raw material gas directly collides with the lower part of the silicon rod 20 or on the upper part of the silicon rod 20, and an egre is generated below the source As a result, there is a risk of collapse or poor quality. When the point B exists in the region D and in the region E, that is, when the condition 3 is not satisfied, the source gas directly collides from the lower part of the silicon rod 20 to the upper part thereof, and the egregs are generated at the lower part of the rod. Therefore, there is a risk of collapse or poor quality.

Within the region A ₁ governing the condition 1 and within the region B ₁ is an annular region formed by rotating the region surrounded by the thick broken line in FIG. The region A ₁ that dominates the region and the region C ₁ is an annular region where the bottom surface below the annular region is horizontal. The region satisfying D ≧ 80 mm is a region outside a cylindrical surface formed by rotating a vertical line of D = 80 mm around the electrode center line (including the cylindrical surface). Similarly, the region satisfying D ≦ 450 mm is a region inside a cylindrical surface formed by rotating a vertical line of D = 450 mm around the electrode center line (including the cylindrical surface).

More preferably, in the region A ₂ around the electrode satisfying D = 80 to 350 mm and below the surface X around the electrode satisfying D / L = 6, the electrode periphery satisfying D / L = 1.15 At least one of the point B is present (condition 1 '), D = electrode around the region satisfying the 80~350mm on area B within ₂ from the surface Y ₂ (including the surface X and the plane Y ₂₎ of the in the a _2, and free of D / L = 1.15 satisfies electrodes around the surface Y ₂ from the lower by L = 600 mm above the inner region C ₂ from the electrode around the surface Z that satisfies the (surface Y ₂ B point does not exist (including surface Z) (condition 2 '), and within region D around electrode satisfying D = less than 80 mm, and above region Z around electrode satisfying L = 600 mm It is necessary that point B does not exist in E (including plane Z) [condition 3 ′ (same as condition 3)].

Within the region A ₂ governing the condition 1 ′ and within the region B ₂ is an annular region formed by rotating the region surrounded by the thick solid line in FIG. The region A ₂ that dominates “and the region C ₂ is an annular region under the annular region in which the upper surface is an inclined surface and the bottom surface is a horizontal surface.

  Next, the effectiveness of the present invention will be clarified with specific examples.

  Using a small experimental furnace set between the upper and lower electrodes with a single silicon core rod, the influence of the positional relationship between the lower electrode and the source gas supply nozzle on the growth of the silicon rod is measured in the horizontal direction. The positional relationship and the vertical positional relationship were investigated. That is, the properties of the silicon rod formed between the upper and lower electrodes were investigated by changing the horizontal position and the vertical position of the source gas supply nozzles arranged around the electrodes.

  The center of the top of the lower electrode is defined as point A, and the position of point B of the source gas supply nozzle disposed around the electrode is indicated by a to y in FIG. In addition, Table 1 shows the D value and D / L value of these B point positions, and the region to which they belong. Table 1 also shows the relationship between the arrangement conditions of the source gas supply nozzle and the silicon rod properties.

  The D judgment in Table 1 is “◎” if 80 mm ≦ D ≦ 350 mm, “◯” if 350 mm <D ≦ 450 mm, and “x” if D <80 mm or D> 450 mm. The L judgment was “◯” when L> 600 mm, and “X” when L ≦ 600 mm. The D / L judgment is “◎” if 1.15 ≦ D / L ≦ 6, “◯” if 0.8 ≦ D / L <1.15, ““ ”if D / L <0.8 or D / L> 6. × ”.

  When there are a plurality of nozzles, the source gas supply nozzles are arranged equiangularly around the electrode center line, and in the case of two nozzles, they are arranged symmetrically across the electrode center line.

In Test 1, the point B was a position in the region D and E in the vicinity of the electrode, and the egress under the silicon rod was remarkable. In Tests 2, 7, 12, and 18, the point B was at the positions b, g, l, and r above the surface X, and the supply of the raw material gas to the lower part of the silicon rod was insufficient, so the root became narrow. In Tests 6, 11, and 17, since the point B is located at the f, k, and q positions in the area A ₁ and C ₁ below the plane Y ₁ , significant egress occurred at the bottom of the silicon rod.

In tests 3, 4, 8, 9, 13, 14, and 15, point B is located at positions c, d, h, i, m, n, and o in region A ₂ and B ₂ , and an aglet below the silicon is also deposited. There was no shortage. In tests 5, 10, and 16, the point B is below the plane Y ₂ but at the positions e, j, and p in the area A ₁ and B ₁ . It did not lead to a fatal problem. In Tests 19, 20, and 21, since the point B is outside the cylindrical surface of D = 350 mm, but at the s, t, and u positions in the areas A ₁ and B ₁ , the base of the silicon rod is slightly narrower. There was no problem. In the tests 22 and 23, the point B is in the regions A ₁ and B ₁ , but the v and w positions are lower than the plane Y ₂ , so the base of the silicon rod is slightly thin and a slight aggression occurs. It did not lead to a fatal problem.

  In Tests 24 and 25, point B is at the x and y positions below the surface Z and outside the cylindrical surface of D = 450 mm. Therefore, the supply of the raw material gas to the silicon rod alone is insufficient, and the base of the rod is particularly thin. Became a problem.

In the tests 26 and 28, the point B is at _two positions, the h position in the areas A ₂ and B ₂ , the a position in the areas D and E, and the k position in the areas A ₁ and C ₁ . Due to the influence of the position a and the position k, significant aggression occurred at the bottom of the silicon rod.

In tests 27, 29 and 30, point B is located at h position in areas A ₂ and B ₂ , l position above surface X, t position in areas A ₁ and B ₁ , D = 450 mm outside cylindrical surface. Although there are two positions in the y position, no problem occurred because the positions of l, t, and y do not adversely affect. Similarly, in the test 31, the point B is at _two positions, the h position in the areas A ₂ and B ₂ and the x position below the plane Z. However, since the x position does not adversely affect, there is no problem. It was.

The following can be understood from the above test. In order to deposit polycrystalline silicon uniformly from the lower part to the upper part of the silicon rod, at least one of the B points needs to exist in the regions A ₁ and B ₁ , preferably in the regions A ₂ and B ₂ . At the same time, it is necessary to eliminate the points B from the regions D and E in the vicinity of the electrode from the viewpoint of preventing the occurrence of an escaping due to the source gas directly colliding with the lower part of the silicon rod. At the same time, the area A ₁ and the area A ₁ and C ₁ below B _1, preferably it is necessary to eliminate the point B from the area A ₂ and the area A ₂ and C ₂ below the B _2.

  That is, it is clear that the effectiveness of the conditions 1, 2 and 3 is high, and the effectiveness of the conditions 1 ', 2' and 3 'is particularly high within the conditions. The point B in the region unrelated to the conditions 1, 2, and 3 is not indispensable for the growth of the silicon rod, but it does not cause a problem below the rod and may or may not exist.

Next, the above test results were reflected in the operating furnace. The number of electrodes in the operating furnace is 64 (32 sets). Conventionally, there are several electrodes in which the point B exists in the region A ₁ and in the region C ₁ , and specifically, there are several electrodes in which the point B exists in “f” in Table 1. That is, there were several electrodes that did not satisfy the condition 2. Furthermore, there were several electrodes in which the point B does not exist in the region A ₁ and in the region B ₁ . That is, there were several electrodes that did not satisfy Condition 1.

  Therefore, when all the electrodes were changed to the arrangement satisfying the conditions 1, 2, and 3, the conventional collapse frequency was set to 1, and the collapse frequency after the change of the arrangement was 1/10. Furthermore, when all the electrodes were changed to an arrangement satisfying the conditions 1 ', 2' and 3 ', collapse did not occur.

It is a schematic block diagram of the reactor which shows one Embodiment of this invention. It is a schematic block diagram of the electrode and raw material gas nozzle in a reaction furnace. It is a schematic diagram for demonstrating the appropriate positional relationship of the electrode in a reaction furnace, and a raw material gas nozzle. It is a schematic diagram which shows the B point position of the source gas supply nozzle in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reaction furnace 11 Furnace bottom part 12 Furnace main body 13 Silicon core rod 14 Electrode 15 Raw material gas supply nozzle 16 Gas discharge hole 20 Silicon rod

Claims (4)

A silicon core rod is fixed on a plurality of electrodes provided at the bottom of the reactor, and the source gas is reacted from a plurality of source gas supply nozzles provided at the bottom in a state where the silicon core rod is energized and heated. In the method for producing polycrystalline silicon by the Siemens method of depositing polycrystalline silicon on each silicon core rod by supplying it into the furnace,
When the top center of the electrode is point A, the top center of the source gas supply nozzle is point B, the horizontal separation distance from the electrode center line is D, and the level difference from the point A level downward is L, the plurality A method for producing polycrystalline silicon, wherein all of the electrodes satisfy both of the following conditions 1, 2, and 3.
Condition 1: Within the area A ₁ around the electrode satisfying D = 80 to 450 mm and below the surface X around the electrode satisfying D / L = 6, around the electrode satisfying D / L = 0.8 At least one of the B point exists within region B ₁ above the plane Y ₁ (including the surface X and the plane Y _1).
Condition 2: In the area A ₁ around the electrode satisfying D = 80 to 450 mm and below the surface Y ₁ around the electrode satisfying D / L = 0.8, the surface around the electrode satisfying L = 600 mm There is no point B in the region C ₁ above Z (including the surface Y ₁ but not the surface Z).
Condition 3: There is no point B in the region D around the electrode satisfying D = less than 80 mm and in the region E (including the surface Z) above the surface Z around the electrode satisfying L = 600 mm. 2. The method for producing polycrystalline silicon according to claim 1, wherein all of the plurality of electrodes satisfy both of the following conditions 1 ′, 2 ′, and 3 ′.
Condition 1 ′: Around the electrode satisfying D / L = 1.15 in the area A ₂ around the electrode satisfying D = 80 to 350 mm and below the surface X around the electrode satisfying D / L = 6 There is at least one B point in the region B ₂ above the surface Y ₂ (including the surface X and the surface Y ₂ ).
Condition 2 ′: within the region A ₂ around the electrode satisfying D = 80 to 350 mm and below the surface Y ₂ around the electrode satisfying D / L = 1.15, around the electrode satisfying L = 600 mm There is no point B in the region C ₂ above the surface Z (not including the surface Y ₂ but including the surface Z).
Condition 3 ′: The point B does not exist in the region D around the electrode satisfying D = less than 80 mm and in the region E (including the surface Z) above the surface Z around the electrode satisfying L = 600 mm.   2. The method for producing polycrystalline silicon according to claim 1, wherein the number of electrodes per reactor is 30 or more.   2. The method for producing polycrystalline silicon according to claim 1, wherein the source gas supply nozzle is a vertically upward straight pipe type gas nozzle.

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