TW202302929A - Thermal field control device for crystal pulling furnace and crystal pulling furnace - Google Patents

Abstract

The embodiment of the invention discloses a thermal field control device for a crystal pulling furnace and the crystal pulling furnace, and the thermal field control device comprises a guide cylinder of the crystal pulling furnace, and the guide cylinder is fixedly arranged in the crystal pulling furnace; the heat insulation part is arranged between a silicon melt and a silicon single crystal rod drawn from the silicon melt, so that the heat insulation part and the guide cylinder form a heat shield for blocking heat radiated from the silicon melt to the silicon single crystal rod, and the heat insulation part is made of a material suitable for mechanical transmission; and the heat insulation part driver is used for driving the heat insulation part to move so as to change the distance between the bottom of the heat shielding body and the liquid level of the silicon melt and correspondingly change the heat radiated to the silicon single crystal rod from the silicon melt, so that the required axial temperature gradient is obtained in the silicon single crystal rod.

Description

A thermal field control device for a crystal pulling furnace and a crystal pulling furnace

The invention belongs to the field of semiconductor silicon chip production, and in particular relates to a thermal field control device and a crystal pulling furnace for a crystal pulling furnace.

For the production of semiconductor silicon wafers, usually the single crystal silicon rods are first drawn by direct method, and then the required quality silicon wafers can be obtained after slicing, grinding, polishing and possible epitaxial growth treatment. Among them, for the direct method of pulling single crystal silicon rods, the device used is a crystal pulling furnace, the crucible is placed in the furnace body of the crystal pulling furnace, and the high-purity polycrystalline silicon material is contained in the crucible, and the silicon melt is obtained by heating, and the seed After the crystal is immersed in the silicon melt and undergoes the process of seeding, shouldering, equal diameter, finishing, cooling, etc., the single crystal silicon rod can be finally obtained.

With the shortening of the semiconductor manufacturing process, the requirements for silicon wafers are getting higher and higher. Generally, silicon wafers without crystal growth defects are required, which requires effective control of crystal growth defects in the process of pulling single crystal silicon rods. According to the V/G theory used to determine crystal growth defects, the crystal growth defects in the process of pulling single crystal silicon rods are not only related to the pulling speed V but also related to the axial temperature gradient G of single crystal silicon rods, while single crystal silicon rods The axial temperature gradient G of the rod depends on the thermal field design, and a good thermal field design can help the single crystal silicon rod to have no growth defects.

The factors affecting the thermal field around the pulled monocrystalline silicon rod are comprehensive. The heat in the crystal pulling furnace comes from heating the polycrystalline silicon material to melt the solid polycrystalline silicon material into a silicon melt and melt the silicon. A heater that keeps the body at a certain temperature. Therefore, for example, the heat of the heater will radiate or conduct to the single crystal silicon rod. In addition, since the single crystal silicon rod is drawn from the silicon melt, for example, the silicon melt will also radiate to the silicon rod. Single crystal silicon rods radiate heat. Another example is that the drawn single crystal silicon rods move through the guide tube in the crystal pulling furnace, so the guide tube will block the heat radiated to the single crystal silicon rods. Therefore, it is an urgent problem to provide an efficient thermal field control device so that the axial temperature gradient G of the single crystal silicon rod can be precisely controlled, thereby making the single crystal silicon rod free of growth defects.

In order to solve the above technical problems, the embodiment of the present invention expects to provide a thermal field control device for a crystal pulling furnace and a crystal pulling furnace, which can realize precise control of the axial temperature gradient of a single crystal silicon rod in a simple and effective manner, In this way, the defect-free growth of single crystal silicon can be realized. Technical scheme of the present invention is realized like this: In a first aspect, an embodiment of the present invention provides a thermal field control device for a crystal pulling furnace, the thermal field control device includes: The guide tube of the crystal pulling furnace, the guide tube is fixedly arranged in the crystal pulling furnace; A heat insulating element, the heat insulating element is arranged between the silicon melt and the monocrystalline silicon rod drawn from the silicon melt, so as to form together with the draft tube for blocking radiation from the silicon melt to the single crystal silicon rod A heat shield for the heat of the crystal silicon rod, wherein the heat shield is made of a material suitable for mechanical transmission; a heat shield driver, the heat shield driver is used to drive the heat shield to move to change the distance between the bottom of the heat shield and the liquid surface of the silicon melt and correspondingly change the radiation from the silicon melt to The heat of the single crystal silicon rod is used to obtain the required axial temperature gradient in the single crystal silicon rod.

In a second aspect, an embodiment of the present invention provides a crystal pulling furnace, which includes the thermal field control device according to the first aspect.

The embodiment of the present invention provides a thermal field control device for a crystal pulling furnace and a crystal pulling furnace. The thermal shield is arranged between the silicon melt and the single crystal silicon rod. The distance between the liquid surfaces of the body is changed, or it is equivalent to changing the heat radiated from the silicon melt to the single crystal silicon rod by moving the heat shield, so that the single crystal silicon rod can be controlled in a simple and effective way. The thermal field around the silicon rod is controlled, thereby meeting the requirements of the axial temperature gradient of the single crystal silicon rod, and the guide tube of the crystal pulling furnace is fixedly set, thus avoiding the brittle graphite The material is thus not suitable for mechanically actuating the movement of the nozzle, which would otherwise be prone to rupture, to achieve the aforementioned variation in pitch.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention.

It should be noted that when an element is referred to as being “fixed” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

It is to be understood that the terms "length", "width", "top", "bottom", "front", "rear", "left", "right", "vertical", "horizontal", "top" , "bottom", "inner", "outer" and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying No device or element must have a specific orientation, be constructed, and operate in a specific orientation and therefore should not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of said features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrated; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction relationship between two components. Those with ordinary knowledge in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

Referring to FIG. 1, an embodiment of the present invention provides a thermal field control device 10 for a crystal pulling furnace 1, wherein for the crystal pulling furnace 1, only the crucible 20 and the draft tube 11 are shown in FIG. For other components of the crystal pulling furnace 1 such as furnace body, heater, etc., those skilled in the art are well aware and therefore not shown in FIG. 1 , the thermal field control device 10 may include: The guide tube 11 of the crystal pulling furnace 1, the guide tube 11 is fixedly arranged in the crystal pulling furnace 1, as known to those skilled in the art, the function of the guide tube 11 is to transfer, for example, argon A similar protective gas is introduced to the liquid level L of the silicon melt SM shown in FIG. , the single crystal silicon rod R will move through the guide tube 11, so the guide tube 11 can play a role in shielding the heat radiated from the outside to the single crystal silicon rod R, and the guide tube 11 is made of brittle Made of graphite, it is not suitable for use as a mechanical transmission part, because it is prone to breakage and damage when it is frequently driven; The heat insulating element 12 is arranged between the silicon melt SM and the single crystal silicon rod R drawn from the silicon melt SM, so as to form together with the draft tube 11 to block the heat from the silicon The heat shield 10A of the heat radiated from the melt SM to the single crystal silicon rod R, for example, in FIG. to the single crystal silicon rod R, and the heat radiation path schematically shown by the solid line arrow below the dotted line arrow is not obstructed, so the heat from the silicon melt SM will radiate to the single crystal silicon rod R, wherein, the The material of the heat insulating element 12 is different from that of the draft tube 11, and the heat insulating element 12 is made of a material suitable for mechanical transmission; Heat insulating element driver 13, the heat insulating element driver 13 is used to drive the heat insulating element 12 to move to change the distance D1 between the bottom of the heat shield 10A and the liquid surface L of the silicon melt SM and change accordingly The heat radiated from the silicon melt SM to the single crystal silicon rod R is used to obtain the required axial temperature gradient in the single crystal silicon rod R. For this, it can be easily understood with reference to FIG. When the driver 13 drives the heat insulating element 12 to move upward, the distance D1 increases, so more heat will be radiated from the silicon melt SM to the single crystal silicon rod R, and when the heat insulating element driver 13 drives the heat insulating element 12 downward When moving, the distance D1 decreases, so that less heat is radiated from the silicon melt SM to the monocrystalline silicon rod R.

According to the technical solutions of the above-mentioned embodiments of the present invention, the heat shield 10A is arranged between the silicon melt SM and the single crystal silicon rod R, and the bottom of the heat shield 10A is connected to the liquid surface L of the silicon melt SM. The distance D1 between them is changed, or it is equivalent to changing the heat radiated from the silicon melt SM to the single crystal silicon rod R by moving the heat shield 10A, so that the single crystal silicon rod R is realized in a simple and effective manner. The thermal field around the rod R is controlled, thereby meeting the requirements of the axial temperature gradient of the single crystal silicon rod R, and the draft tube of the crystal pulling furnace 1 is fixedly set, thus avoiding the brittleness caused by The above-mentioned variation of the distance D1 is realized by the movement of the guide tube 11 which is made of graphite material and is therefore not suitable for mechanical transmission or the movement of the guide tube 11 which is prone to breakage.

As above, the heat insulating element 12 is made of a material suitable for mechanical transmission. For this, in an optional embodiment of the present invention, the heat insulating element 12 can be made of stainless steel, which is a low-cost ductile material. So it is different from graphite, or it will not break even if it is driven frequently, so it is suitable for mechanical transmission, but on the other hand, the presence of steel in the crystal puller 1 may lead to the introduction of metal contamination , affect the crystal pulling process or may reduce the quality of the pulled single crystal silicon rod R. For this, the surface area of the heat insulating member 12 can be smaller than the surface area of the draft tube 11. In this way, the same material as the steel Compared with the guide tube 11 as a moving part to realize the above-mentioned variation of the distance D1, the possibility of metal contamination is reduced.

For materials that are suitable for mechanical transmission, for example, for the above-mentioned steel, it is often possible to introduce undesirable pollution in the crystal pulling furnace 1 because of its existence in the crystal pulling furnace 1. For this, in the present invention In an optional embodiment, referring to FIG. 2 , the heat insulator 12 may include a body 120 and a coating 121 covering the body 120 , and the coating 121 is used to prevent polluting impurities of the body 120 from escaping. In this way, while ensuring that the heat insulating element 12 is suitable for mechanical transmission, the introduction of pollution caused by its material is avoided.

In an optional embodiment of the present invention, the insulating member 12 can be made of molybdenum. As known to those skilled in the art, metal molybdenum is a conventional material existing in the crystal pulling furnace 1, and not only does not introduce pollution and has a higher heat radiation reflectivity, which can more effectively realize the function of blocking the heat from the silicon melt SM.

In an optional embodiment of the present invention, referring back to FIG. 1 , the heat insulating member 12 can be cylindrical like the draft tube 11, thereby achieving heat insulation for the single crystal silicon rod R more efficiently, and the insulation The inner peripheral wall 12W of the heat element 12 extends vertically. As mentioned above, the function of the draft tube 11 is to guide the protective gas such as argon to the liquid level L of the silicon melt SM shown in FIG. Therefore, the draft tube 11 needs to have a specific shape in order to form a channel for effectively guiding the protective gas. Specifically, as shown in FIG. 1 , the inner peripheral wall 11W of the draft tube 11 has Therefore, it is easy to receive the relatively large impact force of the guided and flowing protective gas. When the guide tube 11 is driven to move, it will shake due to the impact force of the air flow, and further The connection with the driving device is forced to break, and even when the shaking range is large, it may collide with the single crystal silicon rod R, thus causing the single crystal silicon rod R or the guide tube 11 to fall. However, the heat insulating element 12 does not need to bear the role of guiding the air flow, so its inner peripheral wall 12W can extend vertically as above, thereby avoiding the impact force of the flowing protective gas, even if the heat insulating element 12 is driven to move , and no sloshing will occur. Compared with using the guide tube 11 formed with a channel for guiding the protective gas as a moving part to realize the change of the above-mentioned distance D1, the stability of the part is improved and the production safety is ensured.

In order to further avoid shaking of the heat insulating element 12 , in an alternative embodiment of the present invention, still referring to FIG. 1 , the height of the heat insulating element 12 may be smaller than the height of the draft tube 11 . In this way, when the protective gas flows, the "windward side" of the heat insulating element 12 is further reduced, so the force of the flowing protective gas borne by the heat insulating element 12 is further reduced, thereby further avoiding sloshing.

Optionally, when the diameter of the single crystal silicon rod R is 300mm to 308mm, referring to FIG. Between 20mm and 50mm.

Optionally, in the above case, still referring to FIG. 1 , the distance D3 between the bottom of the draft tube 11 and the liquid surface of the silicon melt can be between 20mm and 60mm. It is easy to understand that the distance D3 determines the maximum value of the distance D1 between the bottom of the heat shield 10A and the liquid surface L of the silicon melt SM, and the minimum value of the distance D1 is determined by the movement of the heat insulating member 12, which can be 10mm . Under the condition that the guide tube 11 is fixed, changing the distance D3 can change the distance D1 between the bottom of the heat shield 10A and the liquid surface L of the silicon melt SM.

In order to realize the heat insulation function of the air guiding cylinder 11 , in an optional embodiment of the present invention, referring to FIG. 3 , the air guiding cylinder 11 may include a casing 110 and an insulating material 111 disposed inside the casing. The housing 110 can be made of high-purity graphite, and can be covered with a silicon carbide coating on the outer surface, and the heat-insulating material 111 can be heat-insulating graphite felt.

Referring to FIG. 4 , the embodiment of the present invention also provides a crystal pulling furnace 1 , which may include the thermal field control device 10 according to the foregoing embodiments of the present invention.

As can be easily understood by referring to FIG. 4, with the continuous growth of the single crystal silicon rod R, the volume of the silicon melt SM in the crucible 20 gradually decreases. The heat radiated from SM to the single crystal silicon rod R changes. On the other hand, because there is less silicon melt SM, the heat that can be radiated by the silicon melt SM itself is reduced, which will also cause the radiation from the silicon melt SM to the single crystal. The heat of the silicon rod R changes, and the combination of these two aspects will cause the axial temperature gradient of the single crystal silicon rod R to change, thereby producing crystal growth defects. In the related art, the distance between the bottom of the draft tube and the liquid surface of the silicon melt is monitored to obtain the axial temperature gradient required by the single crystal silicon rod in this way: Corresponding monitoring As far as the guide tube is concerned, hang the quartz hook at the bottom of the draft tube, use the camera to capture the reflection of the quartz hook on the liquid surface, and measure the distance between the quartz hook and the reflection. Ensure that the distance between the bottom of the draft tube and the liquid surface of the silicon melt meets the requirement for defect-free growth of single crystal silicon rods. However, due to high temperature radiation, liquid level fluctuations, etc., the reflection of the quartz hook on the liquid surface captured by the camera will be very unstable, which will greatly affect the accuracy of monitoring. In this case, the accuracy of the control cannot meet the requirements. It is difficult to avoid crystal growth defects of single crystal silicon rods. Moreover, since the adjustment of the distance between the bottom of the draft tube and the liquid surface of the silicon melt should take into account the coordinated relationship between the rising of the crucible and the pulling speed of the single crystal silicon rod, otherwise melting back or single crystal silicon rods will easily occur. Therefore, the adjustment ability of the above method is limited, especially in the current single crystal silicon rods that are treated with nitrogen to ensure the density of Bulk Micro Defects (BMD). With the increase of nitrogen concentration, the single crystal silicon rods ∆ G gradually increases, resulting in a narrowing of the defect-free casting area of the single crystal silicon rod. In the actual production process, the adjustment of the distance between the bottom of the draft tube and the liquid level of the silicon melt is not enough to improve the defects in the single crystal silicon rod. distribution, causing crystal growth defects in silicon rods.

For this, referring to FIG. 4, in an optional embodiment of the present invention, the crystal pulling furnace 1 may further include: a crucible 20 for containing the silicon melt SM; Crucible driver 30, this crucible driver 30 is used to drive this crucible 20 to move, as schematically shown by the hollow arrow in Fig. The height of the liquid level L of the silicon melt SM is kept constant during the continuous reduction of the amount of the melt SM, Wherein, the thermal field control device 10 may also include: A measuring unit 14, the measuring unit 14 is used to measure the moving distance of the heat insulating element 12; A determining unit 15, the determining unit 15 is used to determine the distance D1 between the bottom of the heat shield 10A and the liquid surface L of the silicon melt SM only according to the moving distance.

In the above-mentioned embodiment, instead of using the quartz hook and its reflection as in the related art, the spacing D1 is obtained simply by measuring the moving distance of the heat insulating member 12. In the case where the measurement accuracy can be guaranteed The lower control precision can be guaranteed correspondingly, so the occurrence of crystal growth defects can be avoided. Moreover, the adjustment method of moving the heat insulating member 12 can realize a larger adjustment range for the axial temperature gradient of the single crystal silicon rod S, and can effectively control crystal growth defects, which is beneficial to the growth of the single crystal silicon rod without growth defects. way to grow.

It should be noted that: the technical solutions described in the embodiments of the present invention can be combined arbitrarily if there is no conflict.

Embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementations, and the above-mentioned specific implementations are only illustrative, rather than restrictive, and those with ordinary knowledge in the art Under the enlightenment of the present invention, many forms can also be made without departing from the gist of the present invention and the protection scope of the claims, all of which belong to the protection of the present invention.

1: Crystal pulling furnace 10: Thermal field control device 10A: Thermal shield 11: Diffuser 11W: inner peripheral wall 110: shell 111: Insulation material 12: Insulation 12W: inner peripheral wall 120: Ontology 121: cladding 13: Thermal insulation driver 14:Measuring unit 15: Determine the unit 20: Crucible 30: Crucible Drive D1: Spacing D2: Spacing D3: Spacing L: liquid level SM: silicon melt R: monocrystalline silicon rod

Fig. 1 shows a schematic diagram of a thermal field control device according to an embodiment of the present invention in a crystal pulling furnace; Fig. 2 is a partial cross-sectional schematic diagram of a heat insulating element according to an embodiment of the present invention; 3 is a partial cross-sectional schematic diagram of a draft guide tube according to an embodiment of the present invention; FIG. 4 is a schematic diagram of a crystal pulling furnace according to an embodiment of the present invention.

1: Crystal pulling furnace

10: Thermal field control device

10A: Thermal shield

11: Diffuser

11W: inner peripheral wall

12: Insulation

12W: inner peripheral wall

13: Thermal insulation driver

20: Crucible

D1: Spacing

D2: Spacing

D3: Spacing

L: liquid level

SM: silicon melt

R: monocrystalline silicon rod

Claims (10)

A thermal field control device for a crystal pulling furnace, the thermal field control device comprising: The guide tube of the crystal pulling furnace, the guide tube is fixedly arranged in the crystal pulling furnace; A heat insulating element, the heat insulating element is arranged between the silicon melt and the monocrystalline silicon rod drawn from the silicon melt, so as to form together with the draft tube for blocking radiation from the silicon melt to the single crystal silicon rod A heat shield for the heat of the crystal silicon rod, wherein the heat shield is made of a material suitable for mechanical transmission; a heat shield driver, the heat shield driver is used to drive the heat shield to move to change the distance between the bottom of the heat shield and the liquid surface of the silicon melt and correspondingly change the radiation from the silicon melt to The heat of the single crystal silicon rod is used to obtain the required axial temperature gradient in the single crystal silicon rod. The heat field control device as claimed in claim 1, wherein the heat insulating element is made of stainless steel, and the surface area of the heat insulating element is smaller than the surface area of the draft tube. The thermal field control device as claimed in claim 1, wherein the thermal insulation member comprises a body and a coating covering the body, and the coating is used to prevent the polluting impurities of the body from escaping. The heat field control device according to any one of claims 1 to 3, wherein the heat insulating element is cylindrical, and the inner peripheral wall of the heat insulating element extends vertically. The heat field control device as claimed in claim 4, wherein the height of the thermal insulation member is smaller than the height of the draft tube. The thermal field control device according to claim 5, wherein the single crystal silicon rod has a diameter of 300 mm to 308 mm, and the distance between the inner peripheral wall and the outer peripheral wall of the single crystal silicon rod is between 20 mm to 50 mm. The thermal field control device according to claim 6, wherein the distance between the bottom of the draft tube and the liquid surface of the silicon melt is between 20 mm and 60 mm. The thermal field control device as claimed in claim 1, wherein the draft tube includes a casing and an insulating material arranged inside the casing. A crystal pulling furnace, comprising the thermal field control device according to any one of Claims 1 to 8. As the crystal pulling furnace described in claim item 9, the crystal pulling furnace also includes: a crucible for containing the silicon melt; a crucible driver for driving the movement of the crucible to keep the liquid level of the silicon melt constant during the continuous reduction of the amount of silicon melt contained in the crucible during the drawing of the single crystal silicon rod , Wherein, the thermal field control device also includes: a measuring unit, the measuring unit is used to measure the moving distance of the thermal insulation; A determining unit is used for determining the distance between the bottom of the heat shield and the liquid surface of the silicon melt only according to the moving distance.

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