Method for producing a polycrystalline semiconductor material

Abstract

The subject of the invention is a method for producing a polycrystalline semiconductor material, comprising introducing a reaction gas containing hydrogen and at least one semiconductor component into a reaction chamber of a vapor deposition reactor, the reaction chamber being delimited by a reactor housing and a bottom plate, wherein the reaction gas is introduced through at least one nozzle located in the bottom plate, and wherein the reaction chamber contains at least two filament rods attached to the bottom plate, on which the semiconductor material is deposited, wherein the at least two filament rods differ in length.

Description

[0001] The present invention relates to a method for producing polycrystalline semiconductor materials, comprising introducing a reaction gas containing hydrogen and at least one semiconductor component into a reaction chamber of a vapor deposition reactor, the reaction chamber being enclosed by a reactor shell and a base plate, wherein the reaction gas is introduced through at least one nozzle located in the base plate, and wherein the reaction chamber includes at least two filaments attached to the base plate, on which semiconductor material is deposited, wherein the at least two filaments have different lengths.

[0002] Polycrystalline silicon (PCS) is the starting material used to produce monocrystalline silicon, for example, through the Czochralski process or the floating zone process. Monocrystalline silicon is used in the semiconductor industry to manufacture electronic components (chips).

[0003] Furthermore, polycrystalline silicon is required for the production of polycrystalline silicon, for example, through block casting. Polycrystalline silicon obtained in block form can be used in the manufacture of solar cells.

[0004] Silicon carbide (SiC) has recently been used as a semiconductor material for various electronic devices. SiC is characterized by high radiation hardness, a wide band gap, high saturated electron drift velocity, high operating temperature, and excellent electronic properties, including the absorption and emission of high-energy protons in the blue, violet, and ultraviolet regions of the spectrum. SiC semiconductors can be used at temperatures up to 250°C and they exhibit high oxidation resistance. This results in advantages over pure silicon semiconductors.

[0005] Polycrystalline SiC (poly-SiC) is used as a starting material, for example, to produce single-crystal SiC semiconductor devices via the PVT process.

[0006] Polycrystalline silicon and polycrystalline SiC can be obtained by chemical vapor deposition, which, in the case of polycrystalline silicon, is known as the Siemens process.

[0007] In a bell-shaped vapor deposition reactor, a thin filament rod (support element) is heated through a direct current channel, and a reaction gas containing silicon-containing components and H2 is introduced. For the production of polycrystalline SiC, carbon-containing components are also required. The silicon-containing components are typically silane (SiH4) or chlorosilane / chlorosilane mixtures. A typical example is trichlorosilane (SiHCl3, TCS). For polycrystalline silicon production, SiH4 or TCS mixed with H2 is primarily used. For the production of polycrystalline SiC, for example, methylsilane or a TCS-methane mixture can be used with H2.

[0008] For example, the design of a typical vapor deposition reactor for the production of polycrystalline silicon is described in US 2012 / 0100302 A1. The design of a typical vapor deposition reactor for the production of polycrystalline SiC can be found in US 2023 / 0141427 A1.

[0009] The bottom (base plate) of this reactor typically houses electrodes for receiving filaments. These filaments can be made of silicon, graphite, or SiC and are usually of the same length. Typically, two filaments are connected by bridges to form a filament pair, which forms a circuit via the electrodes. During deposition, the surface temperature of the filaments is typically greater than 1000°C. At these temperatures, the silicon-containing component of the reactant gas, or the silicon- and carbon-containing component, decomposes, and elemental silicon or SiC is deposited from the gas phase onto the filaments. As a result, their diameter increases. After reaching a specific diameter, deposition is stopped, and the resulting rods of semiconductor material (polycrystalline silicon or polycrystalline SiC) are removed. After removing the bridges, cylindrical rods are obtained.

[0010] The distribution of the reactive gas flow in a vapor deposition reactor affects the growth of semiconductor materials. Typically, the goal is to maximize the uniformity of the reactive gas distribution. In particular, as deposition duration increases, the flow of the reactive gas becomes more non-uniform because the increasing diameter of the semiconductor rods occupies an increasing volume of the reaction chamber, which also reduces the distance between the rods. This can lead to non-uniform growth of individual semiconductor rods (deviating from cylindrical growth), potentially resulting in bent semiconductor rods (filament rods typically arranged perpendicular to the substrate) and semiconductor rods with more non-uniform surface and volume morphology, or even breakage.

[0011] Since modern vapor deposition reactors typically contain at least 12 filament rod pairs, the overturning of even one pair can trigger a domino effect. This can lead to significant economic losses, especially when the reactor walls are damaged. Furthermore, overturned rod pairs are often contaminated, and the batch must undergo additional cleaning steps after removal. Additionally, semiconductor rods with non-uniform surface and volumetric morphology often must be assigned to lower quality grades.

[0012] To improve the reaction gas flow, US 2011 / 0151137 A1 describes a shell (or sleeve) arranged around each filament rod along with the tangential gas flow. However, the additional shell increases the complexity of reactor preparation, which is particularly reflected in the longer idle time. Furthermore, the space occupied by the growing semiconductor rods increases significantly, which impacts profitability because fewer rods can be arranged within the reactor.

[0013] US 2013 / 0089488 A1 describes a vapor deposition reactor for polycrystalline silicon having at least 20 filaments, wherein for each filament, in addition to the filaments near the reactor wall, three other adjacent filaments and one to three adjacent gas inlet openings are arranged in the bottom plate at a distance of 15 to 45 cm. With this arrangement, although a uniform reaction gas flow can be achieved at the beginning of deposition, the gas flow tends to become unstable towards the end of deposition with large filament diameters.

[0014] The fundamental objective of this invention arises from the aforementioned drawbacks, namely, to provide a method for depositing polycrystalline silicon and SiC, wherein highly uniform semiconductor rods are obtained regardless of their position in the vapor deposition reactor.

[0015] This objective is achieved by a method for producing polycrystalline semiconductor materials, the method comprising introducing a reactive gas containing H2 and at least one semiconductor component into a reaction chamber of a vapor deposition reactor, the reaction chamber being enclosed by a reactor shell and a base plate, wherein the reactive gas is introduced through at least one nozzle located in the base plate, and wherein the reaction chamber contains at least two filaments attached to the base plate, on which semiconductor material is deposited, wherein the at least two filaments are of different lengths.

[0016] The preferred vapor deposition reactor is a Siemens reactor as described in the introduction.

[0017] These filaments are preferably each a filament pair connected by a bridge having an approximately inverted "U" shape. The free ends of the filament pairs are connected to electrodes anchored in a substrate. The substrate typically has a circular surface, with the filaments preferably arranged rotationally symmetrically about the center point of the substrate. Typical examples of the number of filament pairs in the reactor are 12, 36, 48, 54, 72, 96, or 108. From each filament pair, after deposition and after bridge removal, two semiconductor rods, ideally cylindrical in shape, are obtained. The more uniform the deposition process due to the uniform reaction gas flow, the more uniform the semiconductor rods obtained. The filaments, whether U-shaped or single, can be cylindrical, but other geometries (e.g., triangular or quadrilateral cross-sectional regions) are also possible.

[0018] If the vapor deposition reactor has one nozzle, it is preferably positioned at the center of the substrate. If there are two or more nozzles, they are preferably arranged rotationally symmetrically about the center point of the substrate, or about a nozzle positioned at the center of the substrate.

[0019] Typically, a vapor deposition reactor includes at least one gas outlet opening. This can be centrally or eccentrically arranged in the bottom plate. If two or more gas outlet openings are provided, they are preferably arranged rotationally symmetrically about a central point in the bottom plate. Typically, the gas outlet openings can also be located within the reactor shell.

[0020] The length of the filament (filament length) should be specifically understood as the distance from the upper end of the filament to the base plate. Therefore, the length of the filament is independent of the distance the filament is inserted into the electrode in the base plate. In the case of a pair of U-shaped filaments, the filament length as defined above corresponds to the distance between the base plate and the upper end of the bridge. Preferably, each filament is anchored to the same depth in its electrode, wherein the upper end of the electrode preferably has the same distance from the base plate.

[0021] Surprisingly, it has been found that the distribution of reactant gases in the reaction chamber can be positively influenced, particularly by homogenization, by varying the length of the filaments. This effect has been achieved when at least two filaments (or pairs of filaments) arranged in a vapor deposition reactor have different lengths from each other. For example, the centrally positioned filament can have a shorter length than the surrounding filaments.

[0022] The varying lengths of the filaments allow for control of the pressure on the semiconductor rod caused by the introduced reactive gas, which increases with deposition time. Shorter filaments (semiconductor rods) positioned closer to the nozzle provide a smaller erosion surface for the incoming reactive gas and thus exhibit a lower tendency to tilt or even overturn (see [link to nozzle description]). Figure 3 ).

[0023] Preferably, the length of these filaments increases or decreases as their distance from the center point of the bottom plate increases; more preferably, the length of the filaments increases. Specifically, this is the radial distance from the center point of the bottom plate in the direction of the reactor shell. In other words, the filaments at the center of the reactor preferably have a shorter length than those near the reactor shell.

[0024] Preferably, the filaments are spaced at equal intervals along a radial line from the center point of the bottom plate along the direction of the reactor shell.

[0025] In principle, the filament rod can also be located in the middle of the base plate; however, preferably, the nozzle and / or gas outlet is located there.

[0026] The filaments that are equidistant from the center point of the base plate preferably have the same length.

[0027] Preferably, the filaments are arranged on one or more concentric lines around the center point of the base plate. More preferably, the filaments located on the same concentric lines are equidistant from each other.

[0028] Concentric lines can be circular, triangular, rectangular, pentagonal, hexagonal (or other polygonal shapes). Additionally, star-shaped or wavy concentric lines are also possible.

[0029] The vapor deposition reactor preferably includes 1-4, more preferably 1-3, and especially 2 such concentric lines, with fine filaments arranged on the concentric lines.

[0030] The filaments arranged on the same concentric line preferably have the same length.

[0031] Preferably, at least two groups of filaments are provided, each group containing filaments of the same length, and the lengths of the filaments in each group are different. A group preferably contains two or more filaments.

[0032] The reaction chamber preferably comprises at least two of the aforementioned groups (groups) 1 ,Group 2 ,Group n+1 Each group contains different lengths L Fine wire rods (Group 1: L 1 Group 2: L 2 Group n+1: L n+1 ), the condition is L 1 <L 2 <L (n+1) .

[0033] The preferred number of groups containing filaments is 2 to 4, and typically 4 to 24 filaments of the same length are assembled in one group.

[0034] Preferably, assembled into a set ( 1, 2, n+1 The fine filaments are arranged on concentric lines around the center point of the base plate.

[0035] Different lengths ( L 1 , L 2 , L (n+1) The filaments can also be arranged on the same concentric line. Preferably, the filaments have a periodic sequence related to their length.

[0036] Preferably, the length of the filament rod L 1 , L 2 , L (n+1) The length difference between ΔLL2-L1 ΔL L(n+1)-Ln For length L 1 It is 1% to 25%, preferably 2% to 15%, and more preferably 3% to 8%.

[0037] Length difference ΔL L2-L1 ΔL L(n+1)-Ln It can also be specified relative to the diameter of the base plate. This difference is preferably 1% to 20% of the diameter of the (circular) base plate, more preferably 2% to 15%, and even more preferably 3% to 10%.

[0038] Preferably, the lengths L1, L2, L (n+1) The length difference between ΔL L2-L1 ΔL L(n+1)-Ln They are the same size.

[0039] The semiconductor material to be deposited is preferably polycrystalline silicon. Therefore, the semiconductor component contained in the reaction gas preferably contains at least one silane, more preferably a halosilane.

[0040] Halogenated silanes are preferably selected from those of the general formula H n SiCl 4-n H m Cl 6-m Si2, (CH3) n SiCl 4-n The chlorosilane, wherein n = 1 to 3 and m = 0 to 4. Preferably, the halosilane is TCS or a mixture of dichlorosilane and TCS. Such a reactive gas composition is particularly suitable for the production of polycrystalline silicon according to the Siemens process.

[0041] The semiconductor material to be deposited can also be polycrystalline SiC. In this case, the semiconductor composition preferably contains at least one silane and a carbon component. Alternatively or additionally, the semiconductor composition may include at least one organosilane.

[0042] Semiconductor components can typically be composed of organosilanes because, in this case, a single molecule contains both a C source and a Si source. Organosilanes are preferably selected from those with the general formula (CH3). n H m SiCl 4-n-m (where n = 0 to 3, m = 0 or 1) and Me n Si2Cl 6-n Organochlorosilanes (where n = 1 to 5). The carbon component can be, for example, methane, ethane, propane, butane, and combinations thereof.

[0043] Another aspect of the invention relates to a vapor deposition reactor for producing semiconductor material rods, and particularly to a vapor deposition reactor for carrying out the method described herein.

[0044] The vapor deposition reactor includes a base plate and a reactor shell that form a reaction chamber, at least one nozzle for supplying a reaction gas containing at least one semiconductor component and hydrogen into the reaction chamber, and at least two heatable filaments of different lengths attached to the base plate.

[0045] The vapor deposition reactor is preferably a (Siemens) reactor used for the production of polycrystalline silicon and / or for the production of polycrystalline-SiC.

[0046] The above observations can be used as a reference for the design of the filament rod and other components of the vapor deposition reactor.

[0047] Figure 1 A longitudinal section of the vapor deposition reactor according to the present invention is schematically shown.

[0048] Figure 2 Cross-sections of five (a to e) vapor deposition reactors with different filament configurations according to the present invention are schematically shown.

[0049] Figure 3 The schematic diagram illustrates the reactive gas flow used in the vapor deposition reactor according to the present invention, compared to the prior art.

[0050] List of reference numerals 100, 200, 300 400, 500, 600 700 and 800 vapor deposition reactors 10 base plate 11 center nozzles 12 Reactor Shell 13 nozzles 14 reaction chambers 15 Gas Outlets 16mm fine wire rod (L1) 17 single-bar (L1) 18mm fine wire rod (L2) 19 single bars (L2) 20 bridges 22 electrodes 30 fine wire rods A, B, C or D.

[0051] 31 Single rod (for fine wire rods A, B, C, or D) 33 Inner Circle 35 outer circle 37 Middle Circle Figure 1A gas deposition reactor 100 is shown, which has a reaction chamber 14 enclosed by a bottom plate 10 and a reactor housing 12. In the reaction chamber 14, as an example, four filament rods 16, 18 are arranged, each filament rod having an inverted "U" shape. Each of these filament rods 16, 18 consists of two separate rods 17, 19 connected by a bridge 20. The separate rods 17, 19 are anchored in electrodes 22 in the bottom plate 10. Nozzles 11, 13 are respectively located at the centers of the filament rods 16, 18 and between the filament rods 16, 18, and the nozzles 11, 13 are arranged in the bottom plate 10 to allow reaction gases to enter. In addition, a gas outlet 15 is coaxially arranged around the nozzle 11. In each case, the flow direction of the gas is indicated by a vertical arrow.

[0052] The filament rod 18 has a length L2 , and is arranged near the reactor housing 12. The filament rod 16 has a smaller length L1 , and is arranged more in the center of the reaction chamber 14. The length difference ΔL ( L2 – L1 ) between the filament rods 16, 18 is about 10% of the length L1.

[0053] Figure 2 a) to e) show in cross-section five gas deposition reactors 200, 300, 400, 500, 600 according to the present invention, each gas deposition reactor having filament rods 30 with different configurations. As Figure 1 shown, the filament rods 30 are pairs of filament rods, each pair of filament rods consisting of two separate rods 31 connected by a bridge 20. The filament rods 30 labeled with the same capital letter (A, B, C, D) have the same length, where A < B < C < D applies to the lengths of the filament rods 30. The nozzles 13 are arranged rotationally symmetrically around the central nozzle 11.

[0054] The gas deposition reactor 200 ( Figure 2 a) has four A filament rods 30, which are arranged on a circular line (dashed line, inner circle 33) around the nozzle 11. This inner circle 33 passes through the center points of the bridges 20 of the four A filament rods 30. In addition, eight B filament rods are arranged on an outer circular line (dashed line, outer circle 35). Eight nozzles 13 are arranged between the inner circle 33 and the outer circle 35. Thus, two filament rods 30 are different in terms of their lengths (A and B filament rods), with the B filament rods having a greater length near the reactor housing 12.

[0055] The gas deposition reactor 300 ( Figure 2b) It has two A filaments 30 and two B filaments on its inner circle 33, which are arranged alternately (ABAB). On the outer circle 35, eight filaments 30 of three different lengths (A, B, C) are arranged in the sequence ABCBABCB. The advantage of this arrangement is that it guides the airflow in the direction of the filaments and reduces structural deviations in the central flow direction (e.g., asymmetric inflow through nozzle 11) (see also...) Figure 2 d).

[0056] 400 vapor deposition reactor Figure 2 c) Six radially arranged A filaments 30 are present on its inner circle 33. Twelve B filaments 30 are arranged on its outer circle 35. The vapor deposition reactor 400 has six nozzles 13 arranged between the inner circle 33 and the outer circle 35, and twelve nozzles 13 respectively arranged between the B filaments on the outer circle 35. Additional filament configurations can be used to optimize specific energy consumption. As the number of filaments in the reactor increases (as the reactor size increases), the specific energy requirement can be minimized, and the yield of semiconductor materials can be increased (see also...). Figure 2 e).

[0057] 500 vapor deposition reactor Figure 2 d) A total of 24 filaments 30 of four different lengths (A, B, C, D). Two A filaments 30 and two B filaments are arranged alternately on the inner circle 33. Twelve filaments are arranged alternately (ABAB). On the outer circle 35, twelve filaments 30 are arranged in the sequence BCCDCCBCCDCC with three different lengths (B, C, D). In contrast to the aforementioned vapor deposition reactors 200, 300, and 400, the vapor deposition reactor 500 has an additional intermediate circle 37 on which eight filaments 30 of three different lengths (A, B, C) are arranged in the sequence ABCBABCB. Four nozzles 13 are arranged between the filaments on the inner circle 33, and eight nozzles 13 are arranged between the intermediate circle 37 and the outer circle 35.

[0058] 600 vapor deposition reactor Figure 2 e) Eighteen filaments 30 of four different lengths (A, B, C, D). Three A filaments 30 are arranged on the inner circle 33 surrounding the central nozzle 11. Six filaments of two different lengths (B, C) are alternately arranged on the intermediate circle 37. Nine D filaments 30 are provided on the outer circle 35. Six nozzles 13 are located between the inner circle 33 and the intermediate circle 37, and twelve nozzles 13 are located between the intermediate circle 37 and the outer circle 35 to allow the reaction gas to enter.

[0059] Figure 3a) A known vapor deposition reactor 700 is shown as an example, which has four reactors of equal length. L2 18. Fine filament rod. (e.g.) Figure 1 As shown, the filament rod 18 has an inverted "U" shape, with individual rods 19 arranged continuously. The flow of the reactive gas entering through the central nozzle 11 is indicated by the dashed arrow 40. Two horizontal arrows F L2 This is intended to represent the torque generated by the airflow 40 on the filament 18 arranged around the nozzle 11. This torque increases with the increase of the diameter of the filament 18.

[0060] Figure 3 b) shows a vapor deposition reactor 800 according to the invention, which corresponds to Figure 1 The vapor deposition reactor differs in that individual rods 17 (length L1) of short filament rod 16 and individual rods 19 (length L2) of long filament rod 18 are arranged continuously. The flow of the reaction gas entering through nozzle 11 is indicated by dashed arrows 41 and 42. Two horizontal arrows F L1 The purpose is to indicate the length of the airflow 40, 42 arranged around the nozzle 11. L1 The force generated on the shorter, thinner filament 18. Due to the small length L1 (L2) F L2 L1 F L1 Compared to the known vapor deposition reactor 700, the associated torque (L1) F L1 Significantly lower than L2 F L2 .

[0061] Typically, as torque increases, the risk of tipping or even overturning of the filament rods 16 and 18 increases. Tipping or tilting could cause the filament rods 16 and 18 to lean against each other or against the reactor shell. In addition, the bridge 20 or the electrode 22 may break.

[0062] Example In a vapor deposition reactor (Siemens reactor), according to the method of the present invention (Example 1), as follows: Figure 2 The configuration shown in figure a is used for depositing polycrystalline silicon. The length of the inner filament A is 3100 mm (L1), and the length of the outer filament B is 3200 mm (L2). Therefore, the length difference (100 mm) relative to L1 is approximately 3%. In Comparative Example 1, which was carried out under the same conditions in a reactor with the same structure, all rods had the same length of 3200 mm.

[0063] Also in Figure 2In Example 2, conducted in the vapor deposition reactor (Siemens reactor) shown in Figure a, the length L1 of the inner circumference A filament is 2900 mm, and the length L2 of the outer circumference B filament is 3100 mm. Therefore, the length difference (200 mm) relative to L1 is approximately 7%. For Comparative Example 2 (conducted under the same conditions), all filaments have the same length of 3100 mm.

[0064] Table 1 Table 1 shows the overturning and tilting rates of the embodiments. This rate is calculated as the number of faulty batches divided by the number of batches with and without faults. A batch is considered overturned if a portion of the filament or at least one complete filament has fallen onto the bottom plate. A batch is considered tilted if at least one filament is in contact with the reactor shell or with an adjacent filament. Each batch is evaluated upon removal of the filament (overturning and / or tilting = 1, no overturning and / or tilting = 0). Upper and lower confidence limits are calculated from the values ​​of individual batches using a binomial distribution (according to Wilson).

[0065] Because the filaments are shorter at the center, the average batch weight in Examples 1 and 2 is reduced by only slightly by 1%. The average batch weight corresponds to the average weight of the batch. The weight of the deposition batch corresponds to the sum of the weights of all the filaments.

[0066] Compared to the comparative example, the airflow in Embodiment 1 according to the invention results in more uniform flow around the bridge and between the bar rings. This leads to a more uniform surface and volumetric morphology in Embodiment 1. The lower torque acting on the inner circle due to the gas flow results in significantly fewer overturning and tilting events.

Claims

1. A method for producing polycrystalline semiconductor material, comprising introducing a reaction gas containing hydrogen and at least one semiconductor component into a reaction chamber of a vapor deposition reactor, the reaction chamber being enclosed by a reactor shell and a base plate, wherein the reaction gas is introduced through at least one nozzle located in the base plate, and wherein the reaction chamber includes at least two filaments attached to the base plate, the semiconductor material being deposited on the filaments, wherein the at least two filaments are of different lengths.

2. The method according to claim 1, wherein the length of the filament increases or decreases as the distance of the filament from the center point of the base plate increases, preferably increases.

3. The method according to claim 1 or 2, wherein the filaments at the same distance from the center point of the base plate have the same length.

4. The method according to any one of the preceding claims, wherein the filament rods are arranged on one or more concentric lines around the center point of the base plate.

5. The method according to claim 4, wherein the filaments arranged on the same concentric line have the same length.

6. The method according to any one of the preceding claims, wherein the reaction chamber comprises at least two sets ( 1 , 2 , n+ 1 ) fine filaments, each group containing different lengths L 1 , L 2 , L n+1 Fine filament rod, under the condition that L 1 <L 2 <L (n+1) .

7. The method of claim 6, wherein the assembly is in the form of a group ( 1 , 2 , n+1 The fine filaments are arranged on a concentric line around the center point of the base plate.

8. The method of claim 6, wherein different lengths L 1 , L 2 , L (n+1) The fine filaments are arranged on the same concentric line, preferably in a periodic sequence.

9. The method according to any one of claims 6 to 8, wherein the length L 1 , L 2 , L (n+1) The length difference between Δ L L2-L1 ΔL L(n+1)-Ln It is the length L 1 It is 1% to 25%, preferably 2% to 15%, and more preferably 3% to 8%.

10. The method according to any one of claims 6 to 8, wherein the length L 1 , L 2 , L (n+1) The length difference between Δ L L2-L1 ΔL L(n+1)-Ln It is 1% to 20% of the diameter of the base plate, preferably 2% to 15%, more preferably 3% to 10%.

11. The method according to any one of claims 6 to 10, wherein the lengths L1, L2, L... (n+1) The length difference between ΔL L2-L1 ΔL L(n+1)-Ln They are the same.

12. The method according to any one of the preceding claims, wherein the semiconductor component comprises at least one silane, preferably a chlorosilane.

13. The method according to any one of the preceding claims, wherein the semiconductor component comprises at least one silane and a carbon component, and / or wherein the semiconductor component comprises at least one organosilane.

14. A vapor deposition reactor for producing semiconductor materials, particularly for carrying out the method according to at least one of claims 1 to 13, comprising a base plate and a reactor shell surrounding a reaction chamber, at least one nozzle for feeding a reaction gas containing at least one semiconductor component and hydrogen into the reaction chamber, and at least two heatable filaments attached to the base plate and having different lengths thereof.

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