Device and method for pulling a crystal from a crystal pulling system using the czochralski method
The device with two interconnected chambers addresses the challenge of safely removing monocrystalline rods by enabling simultaneous cooling and reloading, thus reducing setup times and maintaining system productivity.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SILTRONIC AG
- Filing Date
- 2025-12-18
- Publication Date
- 2026-06-25
AI Technical Summary
Existing methods for removing monocrystalline rods from crystal growing systems result in damage or danger due to the heavy and hot nature of the rods, leading to non-productive occupation of the system during loading and removal, necessitating a reduction in setup times.
A device with two interconnected chambers: a first chamber for crystal growth and a second chamber for polysilicon storage, allowing simultaneous crystal cooling and polysilicon loading, enabling safe removal and continuous system operation.
Facilitates safe and efficient removal of crystals while maintaining system productivity by allowing cooling and reloading during crystal removal, reducing setup times and ensuring continuous operation.
Smart Images
Figure EP2025087892_25062026_PF_FP_ABST
Abstract
Description
[0001] 202400029 / Kl
[0002] Device and method for pulling a crystal from a crystal pulling system according to Czochralski
[0003] The invention relates to a device for removing a monocrystalline rod made of semiconductor material from a crystal growing system.
[0004] Crystal growth is an important preliminary step in the production of semiconductor devices. Semiconductor crystal growth methods have been improved to obtain single-crystal semiconductor blocks that can have, for example, a diameter of 200 mm to 300 mm and a length of more than two meters.
[0005] Various commercially available models of crystal growth furnaces that support common crystal growth methods are functionally and structurally similar. A typical crystal growth furnace has a crystal growth chamber at the bottom of the furnace. This chamber usually contains a crucible, heating elements for melting and maintaining the molten state of a batch of crystalline material placed in the crucible, and mechanisms for rotating the crucible to control the uniformity of heat flow within the molten material during the crystal growth process.
[0006] Above the crystal growth chamber rises a towering structure of a crystal pulling chamber. The crystal pulling chamber is typically an upright, essentially cylindrical housing that terminates in an upper structure of a crystal pulling mechanism. The crystal growth chamber and the crystal pulling chamber are connected during the growth process. As a monocrystalline rod continues to grow from the melt in the crystal growth chamber, the crystal pulling mechanism lifts the rod into the crystal pulling chamber at a defined rate.
[0007] Typically, an operator removes the grown rod from the described furnace through a side access door in the crystal-pulling chamber. An opening between the crystal-growing chamber and the crystal-pulling chamber can be closed, while the normally hermetically sealed side access door of the pulling chamber remains open. 202400029 / Kl
[0008] 2
[0009] In the past, removing monocrystalline rods from growth furnaces has caused problems, as the heavy and hot rods can be damaged during removal or, in the worst case, fall off, posing a danger to people and equipment.
[0010] The prior art includes several approaches for extracting monocrystalline rods from crystal growing systems.
[0011] Chinese utility model CN 21 597 162 3 U discloses a device for removing rods from a crystal drawing machine. The device comprises a base and a clamping device arranged on the base, the clamping structure being rotatably arranged in a vertical plane.
[0012] Chinese utility model CN 21 548 141 1 U discloses a cooling and transport device for large-diameter silicon single crystals. The cooling and transport device for large-diameter silicon single crystals comprises a transport vehicle and an air-cooling assembly, wherein the transport vehicle includes a body, support legs for supporting the body, and rollers arranged on the undersides of the support legs.
[0013] Patent US 452 397 2 A describes a device for removing a monocrystalline rod from a crystal drawing furnace, wherein the rod is held with jaws suitable for this purpose.
[0014] Patent application EP 046 047 7 A1 also discloses a device for removing a grown single crystal rod from the single crystal growing devices and transporting it to a predetermined position.
[0015] US Patent 4,350,560 A discloses an apparatus and a method for handling grown rods from a crystal growth furnace, wherein the apparatus and the method comprise: lifting and moving an upper crystal chamber with the crystal carried therein to one side of the furnace; and gently lowering the crystal into a lower crystal chamber located below the upper crystal chamber.
[0016] 3 mer and is arranged on a vehicle with wheels, which allows for easy removal and transport of hot heavy crystals with minimal damage or breakage.
[0017] Chinese utility model CN 202 369 680 U describes a withdrawal device used in crystal pulling to safely and efficiently extract long monocrystalline silicon rods. It consists of several components that work together to ensure stable and reliable operation.
[0018] All the aforementioned points in the prior art have in common that the crystal growing system is occupied for extended periods but not used productively as soon as either the system is being loaded or a finished rod is being removed. In other words, it is necessary to reduce the setup times of the system.
[0019] The object of this invention is therefore to provide a device that makes it possible to reduce setup times. This object is achieved by the devices described in the claims.
[0020] 202400029 / Kl
[0021] 4
[0022] Brief description of the characters
[0023] Fig. 1 shows the principle of the device according to the invention for growing a single crystal. Three characteristic phases A, B, and C of this process are depicted. In phase A, a crystal 105 is pulled from the melt 104, held by the rotation and lifting unit 103. This takes place in the growth chamber 101, which also contains a heat shield 109. During the pulling process, the crystal is drawn into the crystal pulling chamber, hereinafter referred to as the first chamber 102, which is connected to the growth chamber 101 by a detachable connection 112. A second chamber 108, equipped with a lifting unit 107, is not yet connected to the crystal pulling chamber. While the finished crystal 106 cools in the first chamber, the second chamber is loaded with a quartz container 110 filled with silicon, which has a closable opening at its lower end, by means of the lifting unit.In phase C, the first chamber, loaded with the grown crystal, is detached from the growth chamber and pivoted into a removal position where the crystal can be extracted. The second chamber is then pivoted so that it can be connected to the growth chamber, and the polycrystalline silicon is transferred to the crucible and melted there. The empty quartz container 111 remains in the second chamber.
[0024] Abbreviations
[0025] 101 Growth Chamber
[0026] 102 first chamber
[0027] 103 Rotation and lifting unit
[0028] 104 Melt
[0029] 105 Crystals during the draw
[0030] 106 drawn crystal
[0031] 107 Lifting unit, preferably rotary and lifting unit
[0032] 108 second chamber
[0033] 109 Heat shield
[0034] 110 silicon-filled quartz containers
[0035] 111 empty quartz containers
[0036] 112 Detachable connection 202400029 / Kl
[0037] 5
[0038] Detailed description of the invention
[0039] In the Czochralski crystal pulling process, a seed crystal is brought into contact with the melt and, by appropriately controlling the parameters known to those skilled in the art, a section called a thin neck is pulled to eliminate dislocations.
[0040] Subsequently, a conical section of the crystal (initial cone) is drawn, followed by a cylindrical section from which the semiconductor wafers will later be separated. Finally, the crystal is given a conical section, the final cone, before being separated from the remaining melt in the crucible (residual melt).
[0041] The device according to the invention for drawing a crystal from a crystal drawing system according to Czochralski comprises the following elements.
[0042] In a crystal growth chamber (101) is the hot melt (104) of silicon, which in turn is in a crucible, usually made of quartz.
[0043] The growing crystal (105) is placed into a first chamber (102), which is equipped at its upper end with a rotation and lifting unit (103), during the growing process. Therefore, the first chamber (102) is dimensioned to accommodate a fully grown crystal (106). Ideally, the diameter of this chamber is larger than the diameter of the crystal being grown. A diameter greater than 350 mm is particularly preferred.
[0044] The first chamber (102) and crystal growth chamber (101) can be connected by a detachable connection (112). In order to remove the crystal from the crystal growing system, the first chamber (102) is mounted horizontally so that the chamber with the crystal inside it can be pivoted away from the crystal growth chamber (101).
[0045] A locking element that can close the lower end of the first chamber ensures the safe transport of the crystal within the first chamber. 202400029 / Kl
[0046] 6
[0047] When producing crystals using state-of-the-art methods, care must be taken to ensure that the crystal cools down in the first chamber (102) before it can be removed. This time is included in the setup time and can easily take several hours.
[0048] Even if the rod could be removed earlier, no means would be available to ensure that the crystal growing plant could be supplied with new polysilicon.
[0049] The inventors tackled this problem and, after some experimentation, developed the following solution.
[0050] In addition to the first chamber (102), which is primarily available for crystal growing, they propose a second chamber (108) which is arranged parallel to the first chamber and is also mounted to pivot horizontally.
[0051] This second chamber (102) can be filled with polysilicon, for example, while the first crystal is being grown, i.e., while the system is hot. The second chamber is filled using a quartz container (110) filled with silicon, which has a lock valve at the bottom that can be opened. This quartz container is lifted into the chamber by means of a lifting unit (107) attached to the second chamber. Preferably, the second chamber also has a rotation and lifting unit with which the quartz container can also be rotated.
[0052] Preferably, the second chamber at the bottom can be closed in such a way as to ensure that even in the worst case the filled quartz container cannot fall out.
[0053] The inventive method for drawing a crystal involves drawing a crystal using the apparatus described above, wherein the crystal is placed in the first chamber.
[0054] The inventive process also includes separating the first chamber from the crystal growth chamber while the crystal growth chamber still has a temperature greater than 1000°C. The silicon remaining in the crucible is preferably still liquid. 202400029 / Kl
[0055] 7
[0056] The inventive method also provides that the first chamber is pivoted into a removal position. The removal position is understood to be the position in which the crystal can be safely lowered using the lifting unit. Preferably, during removal, the crystal is placed in a specially provided device and then transported away from the crystal pulling system.
[0057] In the inventive process, the second chamber is pivoted onto the crystal growth chamber. According to the invention, the second chamber is loaded with polysilicon, the polysilicon preferably being contained in a quartz container filled with silicon. This quartz container has a lower sluice gate which, when open, provides an opening from which the silicon can be transferred into the still-hot crucible.
Claims
202400029 / Kl 8 Claims 1. Device for pulling a crystal from a crystal pulling system according to Czochralski comprising the following elements: (a) a crystal growth chamber (101), (b) a first chamber (102) which is provided at its upper end with a rotation and lifting unit (103), and the first chamber (102) is dimensioned such that a grown crystal (106) can fit completely inside it, wherein the first chamber (102) and crystal growth chamber (101) can be connected by a detachable connection (112) and wherein the first chamber (102) is mounted to pivot horizontally, (c) a closing element (112) that can close the lower end of the first chamber (102), (d) a second chamber (108) arranged parallel to the first chamber (102) and mounted to pivot horizontally.
2. Device according to claim 1, characterized in that the second chamber (108) is provided with a lifting unit (107) at its upper end.
3. Device according to claim 1, characterized in that the second chamber (108) is provided at its lower end with a closing element that can close the chamber.
4. Device according to claim 2, characterized in that the second chamber (108) is provided at its upper end with a rotation and lifting unit.
5. Device according to claim 1, wherein the diameter of the first chamber is at least 350 mm.
6. Method for growing a crystal comprising the following steps (a) the pulling of a crystal (105, 106) using the apparatus according to claim 1, wherein the crystal (105, 106) is received into the first chamber (102), (b) the separation of the first chamber (102) from the crystal growth chamber (101), 202400029 / Kl 9 while the growth chamber still has a temperature greater than 1000 °C, (c) pivoting the first chamber (102) into an expansion position, (d) the pivoting of the second chamber (108) onto the crystal growth chamber (101), (e) the loading of a crucible located in the plant with polycrystalline silicon through the second chamber, (f) the unloading of the first chamber (102).