Method for introducing polycrystalline semiconductor material into a crucible and device therefor
Patent Information
- Application Number
- PCT/EP2026/059328
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-04-17
- Filing Date
- 2026-03-31
- Publication Date
- 2026-10-22
Smart Images
Figure EP2026059328_22102026_PF_FP_ABST
Abstract
Description
[0001] 2024P00010WG / Kl
[0002] Method for introducing polycrystalline semiconductor material into a crucible and apparatus for this purpose
[0003] The present invention relates to a method for introducing polycrystalline semiconductor material, e.g. silicon, into a crucible, wherein a single crystal is to be produced from the polycrystalline semiconductor material by means of the Czochralski method, and to a corresponding device for use in introducing polycrystalline semiconductor material into a crucible.
[0004] State of the art and task
[0005] Semiconductor wafers, such as silicon wafers, are typically produced from a crystal rod, usually a single crystal of the semiconductor material in question. Such a crystal rod or single crystal can be produced, for example, using the Czochralski method. In this process, the single crystal is extracted from a crucible containing molten semiconductor material using a seed. This method is therefore also known as crucible drawing or crucible drawing. The melt itself is obtained by melting polycrystalline, i.e., solid, semiconductor material, which is introduced into the crucible, for example, as a packed bed – meaning the polycrystalline semiconductor material is present in the form of fragments.
[0006] In the production of polycrystalline semiconductor materials, such as polysilicon, the fragments can be fractionated by size using sorting methods (e.g., mechanical or optical). For example, fragments can be placed in specific predefined areas within the crucible according to their size or size class. The division of fragments into size classes is known, for example, from US 2007 / 235574 A1, and the placement of fragments in the crucible is known, for example, from US 6284040 B1. 2024P00010WQ / Kl
[0007] 2
[0008] However, it has now become apparent that problems can arise during the introduction of polycrystalline semiconductor material and the subsequent processing. For example, the crucible can be damaged, and undesirably high pinhole rates (i.e., inclusions of impurities and the like) can occur in the single crystal.
[0009] Against this background, the task is therefore to specify a way to reduce such problems as much as possible, in particular to reduce damage and contamination (pinhole rates).
[0010] General description of the invention
[0011] According to the invention, a method and a device for introducing polycrystalline semiconductor material into a crucible and a device with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.
[0012] The invention relates generally to the growing of single crystals from polycrystalline semiconductor material according to the so-called Czochralski process (also known as the CZ process), and specifically to the introduction of such polycrystalline semiconductor material into a crucible; quartz crucibles are particularly suitable for this purpose. Semiconductor material, e.g., silicon, from which the single crystal is to be formed, is introduced into the crucible in solid, polycrystalline form. Fragments of the polycrystalline semiconductor material are introduced into the crucible or, if necessary, poured in. An apparatus by which the single crystal is then produced typically includes, in addition to the crucible, a suitable growing device for drawing the single crystal from the melt obtained from the polycrystalline semiconductor material. Furthermore, a heat shield is usually provided, the lower end of which is designed as a kind of rim.Furthermore, the device can be evacuated for operation. For a 2024P00010WG / Kl.
[0013] 3
[0014] For a more detailed description of the device, please refer to the following explanations, in particular the description of the figures. The polycrystalline semiconductor material in the crucible is heated to melt it.
[0015] Within the scope of the present invention, it is now proposed that the geometric properties of fragments from a set of fragments of the polycrystalline semiconductor material be determined in an at least semi-automated manner. This can particularly include the use of a 3D acquisition device, especially a 3D scanner, with which the fragments (or at least parts thereof) are captured and then the geometric parameters are determined. However, the use of a camera to capture images of the fragments (or parts thereof) is also conceivable; these images can then be analyzed, for example, using image processing to determine the geometric properties.
[0016] The geometric properties can include parameters such as size (e.g., maximum or average length), but also the specific shape, such as whether fragments have flat sides, edges, or points. Size can range from a few millimeters to several centimeters, sometimes even 10 to 20 centimeters. Depending on their size, the fragments can be classified into one of several different size classes. Each size class can then encompass a specific size range, such as a maximum or average length.
[0017] Examples of size classes are: Class 0 - from 0 to 3 mm, Class 1 - from 1 to 10 mm, Class 2 - from 10 to 40 mm, Class 3 - from 25 to 65 mm, Class 4 - from 50 to 110 mm, Class 5 - from 90 to 250 mm. Often, only classes 2 to 5 are relevant.
[0018] The geometric properties are determined specifically for each individual fraction of the set, i.e., geometric properties are available for each individual fraction, not just a rough classification into one of several size classes.
[0019] Furthermore, for each fragment of at least a subset of the quantity, an insertion position and / or insertion orientation is determined based on the geometric properties of the fragments; this is done specifically for each individual fragment of this subset. This concerns the insertion position or orientation relative to the crucible or within the crucible. In one embodiment, it can also be provided beforehand that the subset is determined based on the geometric properties of the fragments of the quantity, such that only fragments from the quantity that meet at least one predefined criterion, particularly regarding a size restriction, are assigned to the subset. For example, only fragments above a certain size class can be intended for insertion into the crucible or, in particular, into certain areas within the crucible. Thus, for example,Unsuitable polycrystalline semiconductor material for certain crucible areas is pre-filtered. This may be due, for example, to necessary tighter size restrictions than those agreed upon in the specification with the polycrystalline semiconductor material suppliers. In addition to size-related criteria, general geometry-related criteria are also considered; for example, fragments with unfavorable geometries or surface finishes can be filtered out. For instance, it may be stipulated that only fragments of size class 4 (or generally of one or more specific size classes) should be placed on a particular surface of the crucible, whereby these fragments should also meet further criteria regarding their geometric properties, such as having no sharp edges or points. However, these same size class 4 fragments with sharp edges and points can be used in other areas of the crucible.The fragments are then placed into the crucible according to the specified insertion position and / or orientation. This applies particularly to those fragments for which an insertion position and / or orientation has been determined, i.e., especially those from the subset. Specifically, the insertion orientation is determined as a function of the insertion position; that is, the position can be determined first, and then the orientation of the fragment. This allows for a more precise determination of the orientation; for example, a particular orientation might be suitable for a specific position, but not for another.
[0020] The size distribution within a specific size class of polycrystalline semiconductor material, relative to the insertion areas in the crucible, can thus be controlled more precisely and effectively than by simply differentiating by size class. Furthermore, unfavorable geometries can be excluded from insertion into critical areas and instead shifted to less critical areas.
[0021] In particular, this method can prevent or at least reduce damage such as breakage of the crucible or other components. This is primarily because, for example, no fragments with sharp edges or points come into contact with the crucible's surface, which could then damage the surface when the crucible is fully filled. Furthermore, the pinhole rate (e.g., for a critical size greater than 80 pm) can sometimes be significantly reduced. This is possible because the use of certain size classes (especially minimum size classes) results in fewer spaces overall where gas bubbles can accumulate.
[0022] In one embodiment, the quantity of fragments (whose geometric properties are determined) is specified for placement in a selected area of the crucible. Thus, only fragments from this quantity (possibly only a subset after sorting) are placed in the crucible and specifically in the selected area. This allows for a more targeted selection or determination of the placement position and / or orientation. As already mentioned, this makes it possible, for example, to specify fragments with sharp edges and points for particular areas far from the crucible surface.
[0023] Once at least a subset of the fragments has been introduced into the selected area, the geometric properties of the fragments in a further set can be determined. This set is intended for introduction into another (and different) selected area of the crucible. The aforementioned steps—that is, determining the subset, determining the insertion position and / or orientation, and introducing the fragments—can also be performed for this further set. All of this can be repeated for even more selected areas, in particular until the entire crucible is filled or until the desired amount of polycrystalline semiconductor material has been introduced.
[0024] These areas could, for example, be different layers; the crucible can then be filled layer by layer with polycrystalline semiconductor material, with only the amount required for the next layer (or, more generally, the next area) needing to be analyzed. Each of several such amounts could, for example, correspond to the contents of a bag or other container of polycrystalline semiconductor material or fragments.
[0025] In one embodiment, it is also provided that fragments of the polycrystalline semiconductor material are replenished in the crucible; the fragments to be replenished are determined based on specific geometric properties, or they are determined accordingly. This occurs after the fragments have been introduced into the crucible according to the specified insertion position and / or orientation – as explained above – and in particular after at least some of the introduced fragments have already been melted. 2024P00010WQ / Kl
[0026] 7
[0027] The reason for this is that when the fragments melt in the crucible, any free spaces between them disappear, creating more room for additional fragments. These can then usually no longer be placed precisely, so it is more practical to pour them in. For this purpose, a tube or refilling tube, especially a quartz tube, can be used to pour the fragments into the crucible and into the already existing melt.
[0028] Here, too, considering the geometric properties offers particular advantages, as fragments that are too large or irregularly shaped can block the pipe. Therefore, only fragments of certain size classes are used for refilling, for example, only size classes 2 and 3, or only size class 2. This depends primarily on the specific shape and dimensions of the pipe, as well as the definition of the size classes. It is also conceivable that distinctions are made within a single size class, based on specific geometric properties. For example, all fragments of size class 2 can be considered for refilling, but from size class 3, only those that do not exceed a certain average length.It is particularly useful if the fragments to be refilled are determined in advance; this makes it possible to sort out fragments that are unsuitable or unwanted for refilling and instead use them for targeted placement in the crucible or one of the subsequent crucibles (for growing further crystals).
[0029] The described method can be used for manual insertion of the polycrystalline semiconductor material, as well as for semi-automated or fully automated insertion. The insertion of the fragments into the crucible is preferably carried out at least partially automatically. For example, a suitable handling robot could be used. This allows for significantly faster and more precise insertion. Refilling can also be at least partially automated; here, the fragments can be transported to the refill tube and inserted, for example, via a conveyor belt or similar device.
[0030] Once the crucible is filled (to the desired extent) with polycrystalline semiconductor material, it can be melted and the single crystal produced or pulled. As mentioned, more polycrystalline semiconductor material can be added before pulling, but after at least the melting process has begun.
[0031] The invention relates, in addition to the method mentioned, to a device for use in introducing polycrystalline semiconductor material into a crucible. The preceding explanations, features, and advantages of the method also apply accordingly to the device. Besides means for determining the geometric properties of the fragments, e.g., a 3D scanning device or camera with an evaluation or processing unit, the device also includes a determination device for determining the insertion position and / or orientation, and, in one embodiment, also an insertion device for introducing the fragments.
[0032] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.
[0033] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.
[0034] The invention is schematically illustrated in the drawing using an exemplary embodiment and is described below with reference to the drawing.
[0035] Figure description 2024P00010WQ / Kl
[0036] 9
[0037] Figure 1 schematically shows a device for producing a single crystal.
[0038] Figures 2a, 2b, 2c schematically show a process in one embodiment.
[0039] Figure 1 schematically depicts a device 100 used for producing (or growing) a single crystal using the so-called Czochralski method. The device 100 includes a crucible 112, for example, a quartz crucible, which is arranged in a housing 110 of the device 100. The quartz crucible is, in particular, a crucible with a quartz coating. The crucible 112 can, for example, be rotated about a vertical axis. Solid, polycrystalline semiconductor material is first placed in the crucible 112, which can then be melted using a heating device 114 to obtain a melt 120. The semiconductor material can, for example, be silicon. The heating device 114 can, for example, surround the crucible 112 so that the crucible can be heated. This heating device 114 can, for example, be a furnace.
[0040] Furthermore, the device 100 has a drawing device 116, which may include a suitable rope or the like, on which a small single crystal, a so-called seed 122, can be introduced into the melt 120. The seed 120 can then be drawn back up, preferably in such a way that a very thin region forms at the lower end of the seed. This can be achieved by briefly increasing the speed at which the seed is drawn up, so that the liquid semiconductor material from the melt 120 only reaches a small diameter during crystallization on the seed 122. The speed can then be reduced again to form the single crystal 124. For this purpose, a so-called initial cone is typically drawn or formed first, i.e., the diameter of the single crystal 124 initially increases until a
[0041] 10
[0042] Once the desired diameter of, for example, approximately 300 mm is reached, the single crystal 124 can be drawn up at a substantially constant speed until a desired length or height is achieved. It is understood that certain speed adjustments may be necessary to keep the diameter as constant as possible.
[0043] The present invention relates in particular to the introduction of the polycrystalline semiconductor material into the crucible, which can then be melted as described above before the single crystal is pulled from it. A corresponding method in one embodiment will be explained below with reference to Figures 2a, 2b, and 2c.
[0044] Figure 2a shows a quantity 200 of fragments of a polycrystalline semiconductor material, e.g., silicon. Three different fragments are labeled 201, 202, and 203 as examples. Fragment 201 is, for example, a very small fragment, fragment 202 a relatively large fragment, and fragment 203 a medium-sized fragment with a sharp edge or point. This quantity 200 of fragments could, for example, correspond to the contents of a shipping container for polycrystalline semiconductor material. A camera 210, a processing unit 212 (e.g., a computer), and a screen 214 are also shown as examples. Images of the quantity 200 fragments can be captured using the camera 210. The resulting images can then be analyzed using the processing unit, for example, as part of image processing, in order to determine the geometric properties of the fragments.As already mentioned, geometric properties can include quantities such as length, diameter, their averages, or even shapes and the like. Which geometric properties are to be determined can, for example, be specified in advance.
[0045] Instead of a camera with analysis capabilities, a 3D scanner or similar device can also be used. It should be noted that the fragments do not necessarily need to be captured or analyzed from every side. For example, it is conceivable to capture the fragments from only one side, which would allow at least certain geometric properties to be determined, or at least these properties to a sufficient degree.
[0046] For the fragments of at least a subset of the set 200, an insertion position and / or an insertion orientation is determined, based on the geometric properties of the fragments. In particular, an insertion position in the crucible can first be determined, and based on this, an insertion orientation in the crucible can then be determined. The insertion position and / or an insertion orientation can also be determined, for example, using the computation unit 212.
[0047] The geometric properties and the insertion position and / or insertion orientation can then be displayed, for example, on monitor 214. For instance, the geometric properties are labeled 220 and the insertion position 222. This can be done for all fragments that have been analyzed.
[0048] Figure 2b shows crucible 112, into which previously analyzed fragments have been placed. The fragments are placed according to the previously determined insertion position and orientation. The insertion position refers to the position in which the fragment is to be placed in the crucible, for example, whether at the edge or at the bottom. It can also refer to a position between other fragments, and so on. The insertion orientation refers to the orientation or alignment of the fragment, for example, whether a point should face upwards, downwards, or towards the center of the crucible, and so on.
[0049] Figure 2b shows two exemplary areas, 230 and 232, where area 230 represents a bottom layer and area 232 an overlying layer. The previously analyzed quantity 200 can be allocated to area 230. The insertion positions and orientations can therefore be determined to suit the bottom layer. For example, no sharp point should face or touch the bottom of the crucible; consequently, fragment 203 is not positioned directly at the bottom. Furthermore, it is advantageous to utilize the available space as efficiently as possible, which is why smaller and larger fragments can be arranged accordingly, i.e., have appropriate insertion positions. The fragments can then be inserted into the crucible manually or at least semi-automatically.
[0050] Once the fragments have been placed in the crucible, another quantity can be analyzed and then added to a different area. It is understood that, depending on the quantity or number of fragments to be added, as well as the size of the areas, several quantities may be allocated to the same area, followed by one or more further quantities for another area, and so on. In this way, the crucible can be filled to the desired level.
[0051] As already mentioned, an insertion position and / or orientation can be determined for only the fragments of a subset of the set. The geometric properties, however, can be determined for each individual fragment of the set. The subset can be determined based on the geometric properties of the fragments of the set, such that only fragments from the set that meet at least one predefined criterion, particularly regarding a size restriction, are assigned to the subset. In other words, pre-sorting is possible, so that, for example, fragments that are too large or too small are not inserted into the crucible.
[0052] As mentioned earlier, after filling the crucible with the fragments, they can be melted, thus obtaining the molten metal. Figure 2c shows crucible 112 with the molten metal 120. Melting fills any voids, creating more space for additional fragments.
[0053] Fragments of the polycrystalline semiconductor material can then be added to the crucible 112. This can be done, for example, by means of a refilling tube 240, which may be slightly inclined. Fragments can be transported to the refilling tube 242 by means of, for example, a conveyor belt 242, through which the fragments are then introduced into the crucible.
[0054] It should be noted that there is generally no fixed connection between the refill tube and the drawing machine or device. The refill tube can be inserted into the drawing machine, emptied there, and then removed again. The refill tube is typically filled in a separate room at a so-called filling station. There, the polycrystalline semiconductor material can be applied to a transport path. During transport to the refill tube, any fine particles can be sieved out.
[0055] Since such a refill tube typically has only a certain diameter, fragments can become lodged within it. Against this background, one embodiment provides that only fragments of one or more specific size classes are used for refilling via the refill tube, e.g., medium-sized and / or small fragments.
[0056] This can be taken into account earlier during the aforementioned sorting of fragments from the batch of 200. For example, only those fragments unsuitable for refilling via the refill tube can be assigned to the subset to be (directly) placed in the crucible. The fragments sorted out in this way can then be added later via the refill tube. Sorting can also take place at the aforementioned filling station, before and / or during transport. This results in a particularly efficient use of the polycrystalline semiconductor material, i.e., the fragments, while simultaneously improving the pinhole rate and the single-crystal manufacturing process.
Claims
Patent claims 1. Method for introducing polycrystalline semiconductor material into a crucible (112), comprising: • Determining geometric properties (220) of the fragments (201 , 202, 203) from a set (200) of fragments of the polycrystalline semiconductor material in at least a semi-automated manner; • Determine, for the fragments of at least a subset of the set, an insertion position (222) and / or an insertion orientation based on the geometric properties (220) of the fragments; and • Placing the fragments into the crucible according to the specified placement position and / or placement orientation.
2. The method of claim 1, wherein the geometric properties (220) of each of the fragments of the set are determined.
3. Method according to claim 1 or 2, wherein the insertion position (222) is determined for each of the fragments of at least the subset.
4. Method according to one of the preceding claims, wherein the insertion orientation is determined depending on the insertion position (222).
5. Method according to one of the preceding claims, wherein the determination of the geometric properties (220) of the fragments is carried out in at least one of the following semi-automated ways: • using a 3D acquisition device, in particular a 3D scanner, • using a camera (210) and an analysis of images acquired by the camera.
6. A method according to any of the foregoing claims, further comprising: • Determining the subset based on the geometric properties (220) of the fractions of the set such that only fractions from the set are assigned to the subset which satisfy at least one given criterion, in particular with regard to a size restriction, • where the insertion position (222) and / or the insertion orientation are determined only for the fractions of the subset.
7. Method according to one of the preceding claims, wherein the quantity (200) of the fragments is provided for introduction into a selected of several regions (230, 232) of the crucible (112).
8. Method according to claim 7, wherein, after at least the subset of the quantity of fragments has been introduced into the selected area, the geometric properties of the fragments of a further quantity are determined, which is intended for introduction into a further selected of the several areas of the crucible.
9. Method according to one of the preceding claims, wherein the introduction of the fragments of the quantity into the crucible (112) is at least partially automated.
10. Method according to any of the preceding claims, further comprising, after the fragments have been introduced into the crucible (112) according to the determined insertion position and / or insertion orientation, and in particular after at least a part of the introduced fragments has been melted: • Replenishing fragments of the polycrystalline semiconductor material, wherein the fragments to be replenished are or have been determined based on the determined geometric properties.
11. Method for producing a single crystal (124) from a polycrystalline semiconductor material using the Czochralski method from a crucible (112), wherein the polycrystalline semiconductor material has been introduced into the crucible (112) according to a method according to any one of the preceding claims 1 to 10.
12. Device for use in introducing polycrystalline semiconductor material into a crucible, wherein a single crystal is produced from the polycrystalline semiconductor material by means of the Czochralski method, the device comprising: • Means that are set up to determine geometric properties of the fragments from a set of fragments of the polycrystalline semiconductor material in at least a semi-automated manner, and • a determining device that is set up to determine, for the fragments of at least a subset of the set, an insertion position and / or an insertion orientation in the crucible, based on the geometric properties of the fragments.
13. Device according to claim 12, further comprising:
14. A feeding device configured for feeding the fragments into the crucible according to the specified feeding position and / or feeding orientation.
15. A device according to claim 12 or 13, configured to perform a method according to any one of claims 1 to 10.