Off-axis crystal growth device

Abstract

The present invention provides an off-axis crystal growth device, which belongs to the field of semiconductor technology, and includes a sealed chamber, a lower crucible and an upper crucible. The lower crucible is arranged in the sealed chamber and is used to hold silicon carbide powder. The top of the lower crucible is provided with a gas phase outlet. The bottom of the upper crucible is open and a seed crystal is arranged on the inner side of the top. The seed crystal is arranged coaxially with the upper crucible. The outer side of the top of the upper crucible is connected to a driving mechanism for rotating around its own axis under the drive of the driving mechanism. The upper crucible is arranged in the sealed chamber and is spaced apart from the lower crucible in the vertical direction. The axis of the upper crucible is spaced apart from the axis of the lower crucible in the horizontal direction. By adopting a split off-axis upper crucible and a lower crucible, and arranging the upper crucible to rotate around its own axis under the drive of the driving mechanism, the growth surface of the crystal can maintain a stable convex interface during the growth process, thereby reducing the defects of the silicon carbide crystal and improving the quality of the silicon carbide crystal.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an off-axis crystal growth device. Background Art

[0002] At present, in the silicon carbide crystal growth process based on the PVT method, the shape of the crystal growth surface is one of the important factors affecting the crystal quality. However, the existing crystal growth device generally adopts an integrated quasi-closed growth crucible. The shape of the crystal growth surface is affected by multiple factors such as temperature field distribution, powder graphitization and crucible design. It usually presents a concave interface in the early stage of crystal growth and a convex interface in the middle and late stages of crystal growth. That is, its growth surface cannot maintain a stable shape during the crystal growth process, resulting in more crystal defects and low quality. Summary of the invention

[0003] The object of the present invention is to provide an off-axis crystal growth device, which can keep the growth surface of the crystal at a stable convex interface during the crystal growth process, thereby reducing defects in the silicon carbide crystal and improving the quality of the silicon carbide crystal.

[0004] The embodiment of the present invention is achieved as follows:

[0005] In a first aspect, the present invention provides an off-axis crystal growth device, comprising:

[0006] Sealed chamber;

[0007] A lower crucible is arranged in the sealed chamber and is used to contain silicon carbide powder. A gas phase outlet is arranged on the top of the lower crucible;

[0008] An upper crucible, the bottom of the upper crucible is open and a seed crystal is arranged on the inner side of the top, the seed crystal and the upper crucible are arranged coaxially, the outer side of the top of the upper crucible is connected to a driving mechanism for rotating around its own axis under the drive of the driving mechanism, the upper crucible is arranged in a sealed chamber and is spaced apart from the lower crucible in the vertical direction, and the axis of the upper crucible is spaced apart from the axis of the lower crucible in the horizontal direction.

[0009] In an optional embodiment, the distance between the axis of the upper crucible and the axis of the lower crucible in the horizontal direction is L, and the radius of the seed crystal is r, wherein 1≤L / r≤10.

[0010] In an optional embodiment, the distance between the axis of the upper crucible and the axis of the lower crucible in the horizontal direction is L, and the distance between the gas phase outlet and the growth surface of the seed crystal in the vertical direction is H, where H=(0.5-5)L.

[0011] In an optional embodiment, the upper crucible is driven by a driving mechanism to move in a horizontal direction to adjust the distance between the axis of the upper crucible and the axis of the lower crucible in the horizontal direction.

[0012] In an optional embodiment, the upper crucible is driven by a driving mechanism to move in a vertical direction to adjust the distance between the gas phase outlet and the growth surface of the seed crystal in the vertical direction.

[0013] In an optional embodiment, the outer side of the lower crucible is covered with a heat-insulating layer, and the gas phase outlet is exposed from the heat-insulating layer.

[0014] In an optional embodiment, a first heater is provided between the heat-insulating layer and the lower crucible.

[0015] In an optional embodiment, a second annular heater is disposed above the upper crucible.

[0016] In an optional embodiment, a plurality of air inlets are provided at the bottom of the side wall of the sealed chamber.

[0017] In an optional embodiment, the air pressure in the sealed chamber is less than 1Pa.

[0018] The beneficial effects of the embodiments of the present invention include:

[0019] The eccentric crystal growth device provided by the embodiment of the present invention includes a sealed chamber, a lower crucible and an upper crucible. The lower crucible is arranged in the sealed chamber and is used to hold silicon carbide powder. The top of the lower crucible is provided with a gas phase outlet. The bottom of the upper crucible is open and a seed crystal is arranged on the inner side of the top. The seed crystal is arranged coaxially with the upper crucible. The outer side of the top of the upper crucible is connected to a driving mechanism for rotating around its own axis under the drive of the driving mechanism. The upper crucible is arranged in the sealed chamber and is spaced apart from the lower crucible in the vertical direction. The axis of the upper crucible is spaced apart from the axis of the lower crucible in the horizontal direction. By adopting a split eccentric upper crucible and a lower crucible, and arranging the seed crystal to rotate around its own axis with the upper crucible under the drive of the driving mechanism, the growth surface of the crystal can always maintain a stable convex interface during the growth process, thereby effectively reducing the defects of the silicon carbide crystal and improving the quality of the silicon carbide crystal. On the one hand, the growth of silicon carbide crystals is mainly a step flow growth mode, and the stability of its growth surface is conducive to reducing the collision of step flows and effectively reducing the generation of dislocation defects; on the other hand, the stable micro-convex interface can effectively reduce the stress in the crystal and reduce the risk of cracking. At the same time, the micro-convex growth surface also means that the growth rate at the edge is slightly lower than the growth rate at the center, avoiding the formation of polycrystalline and phase transition due to the excessive growth rate of the crystal edge. In addition, the micro-convex crystal shape is also conducive to improving the crystal output rate and increasing the substrate production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A schematic diagram of the structure of an off-axis crystal growth device provided by an embodiment of the present invention;

[0022] Figure 2 A flow distribution diagram of the vapor phase crystal growth components provided in an embodiment of the present invention.

[0023] Icons: 100-sealed chamber; 200-insulation layer; 300-lower crucible; 310-gas phase outlet; 400-first heater; 410-second heater; 500-upper crucible; 600-seed crystal; 700-driving mechanism; 710-rotating shaft; 720-rotating mechanism; 730-lifting mechanism; 740-translational mechanism; 800-air inlet; 900-silicon carbide powder. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0027] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0028] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0029] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In the related art, the growth surface of the silicon carbide crystal prepared by the silicon carbide crystal growth device based on the PVT method cannot maintain a stable shape during the crystal growth process. Affected by various complex factors, its growth surface usually presents a concave interface in the early stage of crystal growth and a convex interface in the middle and late stages of crystal growth. This unstable shape will lead to more defects in the crystal growth process, seriously affecting the growth quality of the crystal.

[0031] In view of the above situation, the present invention provides an off-axis crystal growth device, which adopts a split off-axis upper crucible and lower crucible structure, and the upper crucible can drive the seed crystal to rotate around its own axis, so that the growth rate of the crystal at the center of the seed crystal is higher than the growth rate at the edge of the seed crystal, and further, the growth surface of the crystal always maintains a stable convex interface during the crystal growth process, thereby reducing crystal defects and improving crystal quality.

[0032] The specific structure, working principle and technical effects of the off-axis crystal growth device provided by the embodiment of the present invention are described in detail below with reference to the accompanying drawings.

[0033] Please refer to Figure 1, the eccentric crystal growth device provided by the embodiment of the present invention includes a sealed chamber 100, a lower crucible 300 and an upper crucible 500. The lower crucible 300 is arranged in the sealed chamber 100, and is used to contain silicon carbide powder 900. The top of the lower crucible 300 is provided with a gas phase outlet 310. The bottom of the upper crucible 500 is open and a seed crystal 600 is arranged on the inner side of the top. The seed crystal 600 is arranged coaxially with the upper crucible 500. A driving mechanism 700 is connected to the outer side of the top of the upper crucible 500, which is used to rotate around its own axis R1 under the drive of the driving mechanism 700. The upper crucible 500 is arranged in the sealed chamber 100 and is spaced apart from the lower crucible 300 in the vertical direction Y. The axis R1 of the upper crucible 500 and the axis R0 of the lower crucible 300 are spaced apart in the horizontal direction X, that is, the gas phase outlet 310 and the seed crystal 600 are staggered in the vertical direction Y. By providing a split upper crucible 500 and a lower crucible 300 with their axes deviated from each other and not overlapping, and arranging the seed crystal 600 of the upper crucible 500 to rotate, high-quality crystals with a growth surface that always maintains a slightly convex shape can be prepared on the seed crystal 600.

[0034] The driving mechanism 700 can adopt different structures as needed. In this embodiment, the driving mechanism 700 includes a rotating shaft 710, a rotating mechanism 720, a lifting mechanism 730 and a translation mechanism 740. The rotating shaft 710 passes through the top wall of the sealed chamber 100. The bottom end of the rotating shaft 710 is connected to the outer side of the top of the upper crucible 500 and is coaxially arranged with the upper crucible 500. The top end is connected to the rotating mechanism 720. The rotating shaft 710 is used to rotate under the drive of the rotating mechanism 720, thereby driving the upper crucible 500 and the seed crystal 600 to rotate around their own axis R1. The rotating mechanism 720 is connected to the lifting mechanism 730, and is used to move along the vertical direction Y under the drive of the lifting mechanism 730. The lifting mechanism 730 is connected to the translation mechanism 740, and is used to move along the horizontal direction X under the drive of the translation mechanism 740. In this way, the driving mechanism 700 can realize the rotation of the upper crucible 500 and the seed crystal 600 around their own axis R1, the movement along the vertical direction Y and the movement along the horizontal direction X.

[0035] An annular second heater 410 is arranged above the upper crucible 500. The second heater 410 is suspended from the top wall of the sealed chamber 100 and is coaxially arranged with the upper crucible 500. In the vertical direction Y, the annular second heater 410 corresponds to the edge position T1 of the seed crystal 600. The second heater 410 is used to heat the upper crucible 500 to adjust the temperature gradient required for crystal growth as needed. It should be noted that the second heater 410 has an inner hole of a preset diameter for the rotating shaft 710 to pass through, and the second heater 410 and the upper crucible 500 have a preset spacing distance, so that the upper crucible 500 can move within a certain range along the vertical direction Y.

[0036] The outer side of the lower crucible 300 is covered with an insulation layer 200, and the gas phase outlet 310 is exposed from the insulation layer 200, that is, the insulation layer 200 covers the other parts of the lower crucible 300 except the gas phase outlet 310. At the same time, a first heater 400 for heating the lower crucible 300 is provided between the insulation layer 200 and the lower crucible 300. The purpose of providing the insulation layer 200 is to reduce the influence of the area where the silicon carbide powder 900 is located (that is, the area where the lower crucible 300 is located) on the crystal growth area (that is, the area where the upper crucible 500 is located), thereby ensuring the growth rate and quality of the crystal on the seed crystal 600.

[0037] For further information, please refer to Figure 1 The distance between the axis R1 of the upper crucible 500 and the axis R0 of the lower crucible 300 in the horizontal direction X is L, the radius of the seed crystal 600 is r, and the distance between the gas phase outlet 310 and the growth surface of the seed crystal 600 in the vertical direction Y is H.

[0038] Among them, the relationship between L and r can be selected as 1≤L / r≤10. The value of L / r is related to the convexity of the crystal growth surface. The larger the L / r value, the smaller the convexity of the crystal growth surface. In this way, the growth morphology of the crystal can be controlled by adjusting the value of L / r, and the convexity of its growth surface can be adjusted to prepare a crystal with a target convexity. In this embodiment, the adjustment of the value of L / r is achieved by a translation mechanism 740, which can realize the movement of the upper crucible 500 and the seed crystal 600 in the horizontal direction X, thereby adjusting the size of L, and then adjusting the value of L / r.

[0039] For the relationship between H and L, H=(0.5-5)L can be selected. The larger the value of H / L, the lower the utilization rate of the silicon carbide powder 900. Thus, the utilization rate of the silicon carbide powder 900 can be adjusted by adjusting the value of H / L, so that the utilization rate of the silicon carbide powder 900 reaches an ideal state. In this embodiment, the adjustment of the value of H / L is achieved by the lifting mechanism 730, which can realize the movement of the upper crucible 500 and the seed crystal 600 in the vertical direction Y, thereby adjusting the size of H, and then adjusting the value of H / L.

[0040] Furthermore, the off-axis crystal growth device provided in this embodiment also has a doping function, which can realize the doping of different types of gases. A plurality of openable and closable gas inlets 800 are provided at the bottom of the side wall of the sealed chamber 100, which are respectively used to introduce different types of doping gases and carrier gases. In this embodiment, two gas inlets 800 are provided, which are respectively used to introduce nitrogen and argon, wherein nitrogen is the doping gas and argon is the carrier gas. During the crystal growth process, the pressure of the entire sealed chamber 100 is less than 1Pa, so that the growth surface of the crystal can be stably and evenly doped with nitrogen. In other embodiments, the number of gas inlets 800 can also be more, and other doping gases and carrier gases can also be introduced into the gas inlets 800.

[0041] The working principle and process of this off-axis crystal growth device are as follows:

[0042] First, according to the convexity requirement of the growth surface of the crystal to be grown, the horizontal position of the upper crucible 500 (i.e., the value of L) is adjusted, and the driving mechanism 700 drives the rotating shaft 710 to move along the horizontal direction X, thereby driving the upper crucible 500 to move to a preset horizontal position. Then, the second heater 410 is installed and suspended on the top wall of the sealed chamber 100, so that the axis of the second heater 410 coincides with the axis R1 of the upper crucible 500.

[0043] Then, the rotating shaft 710 of the driving mechanism 700 drives the upper crucible 500 and the seed crystal 600 to rotate at a constant speed around its own axis R1, and at the same time, the first heater 400 is started. The first heater 400 heats the lower crucible 300, and the silicon carbide powder 900 begins to sublimate to form a vapor phase crystal growth component. After the vapor phase crystal growth component flows out from the gas phase outlet 310, part of it flows to the seed crystal 600 in the upper crucible 500, and finally reaches various parts of the growth surface of the seed crystal 600 to start growing silicon carbide crystals.

[0044] Among them, since the upper crucible 500 and the seed crystal 600 are arranged off-axis relative to the lower crucible 300, after the gas phase crystal growth component flows out from the gas phase outlet 310, the flow distribution at each position and direction is roughly a cosine function (see Figure 2 ), the flow rate is the largest directly above the gas phase outlet 310, and the farther away from the gas phase outlet 310 along the horizontal direction X, the smaller the flow rate. In this way, during the rotation of the seed crystal 600, for the growth surface of the seed crystal 600, the flow rate of the gas phase crystal growth component corresponding to the center position T0 is basically stable (because the position does not change), while the flow rate of the gas phase crystal growth component corresponding to the edge position T1 is smaller than the flow rate at the center position T0 in most areas, and larger than the flow rate at the center position T0 in a small area (that is, for any point at the edge position T1, it is at a position where the flow rate is smaller than the center position T0 most of the time, and is at a position where the flow rate is larger than the center position T0 a small part of the time), so that the crystal growth rate at the center position T0 of the seed crystal 600 will be higher than the crystal growth rate at the edge position T1, so that the grown crystal is always slightly convex (that is, the growth surface is always a convex interface), so as to improve the crystal quality and reduce crystal defects.

[0045] Furthermore, in order to ensure that the crystal growth rate at the center position T0 of the seed crystal 600 is higher than the growth rate at the edge position T1, the second heater 410 can be turned on according to actual conditions during the crystal growth process. The annular second heater 410 can heat the edge position T1 of the seed crystal 600, so that the axial temperature gradient at the center position T0 of the seed crystal 600 is greater than the axial temperature gradient at the edge position T1, thereby ensuring that the crystal growth rate at the center position T0 is higher than the crystal growth rate at the edge position T1, so that the growth surface always presents a convex interface during the crystal growth process, thereby ensuring that the growth surface of the crystal is stable and controllable in shape during the entire growth process.

[0046] At the same time, during the above-mentioned crystal growth process, the driving mechanism 700 can not only drive the upper crucible 500 and the seed crystal 600 to rotate, but also drive the upper crucible 500 and the seed crystal 600 to move along the vertical direction Y according to actual needs and conditions, thereby adjusting the value of H, and then adjusting the value of H / L to adjust the utilization rate of the powder.

[0047] In addition, if doping is required, carrier gas (argon, etc.) and doping gas (nitrogen, etc.) can be introduced through the gas inlet 800, and by controlling the gas pressure in the sealed chamber 100 to be less than 1 Pa, the stability and uniformity of doping can be improved.

[0048] Finally, it should be noted that, according to the conditions of the space above the sealed chamber 100 and the actual needs of crystal growth, a combination of the matching upper crucible 500, seed crystal 600 and drive mechanism 700 can also be provided in multiples and evenly spaced around the axis R0 of the lower crucible 300, so as to achieve the simultaneous growth of multiple crystals, improve production efficiency and reduce powder waste.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An off-axis crystal growth device, characterized in that: include: Sealed chamber (100); a lower crucible (300), the lower crucible (300) being arranged in the sealed chamber (100) and used for containing silicon carbide powder (900), a gas phase outlet (310) being arranged at the top of the lower crucible (300), a heat preservation layer (200) being arranged on the outer side of the lower crucible (300), the gas phase outlet (310) being exposed from the heat preservation layer (200), the heat preservation layer (200) covering the rest of the lower crucible (300) except the gas phase outlet (310), and a first heater (400) being arranged between the heat preservation layer (200) and the lower crucible (300); An upper crucible (500), the bottom of the upper crucible (500) is open and a seed crystal (600) is arranged on the inner side of the top, the seed crystal (600) is arranged coaxially with the upper crucible (500), the outer side of the top of the upper crucible (500) is connected to a driving mechanism (700) for rotating around its own axis under the drive of the driving mechanism (700), the upper crucible (500) is arranged in the sealed chamber (100) and is spaced apart from the lower crucible (300) in the vertical direction, the axis of the upper crucible (500) and the axis of the lower crucible (300) are spaced apart in the horizontal direction, and the gas phase outlet (310) and the seed crystal (600) are arranged in a staggered manner in the vertical direction.

2. The off-axis crystal growth device according to claim 1, characterized in that: The distance between the axis of the upper crucible (500) and the axis of the lower crucible (300) in the horizontal direction is L, and the radius of the seed crystal (600) is r, wherein 1≤L / r≤10.

3. The off-axis crystal growth device according to claim 1, characterized in that: The distance between the axis of the upper crucible (500) and the axis of the lower crucible (300) in the horizontal direction is L, and the distance between the gas phase outlet (310) and the growth surface of the seed crystal (600) in the vertical direction is H, where H=(0.5-5)L.

4. The off-axis crystal growth device according to claim 1, characterized in that: The upper crucible (500) is used to move in a horizontal direction under the drive of the driving mechanism (700) to adjust the distance between the axis of the upper crucible (500) and the axis of the lower crucible (300) in the horizontal direction.

5. The off-axis crystal growth device according to claim 1, characterized in that: The upper crucible (500) is used to move in a vertical direction under the drive of the driving mechanism (700) to adjust the distance between the gas phase outlet (310) and the growth surface of the seed crystal (600) in the vertical direction.

6. The off-axis crystal growth device according to claim 1, characterized in that: An annular second heater (410) is arranged above the upper crucible (500).

7. The off-axis crystal growth device according to claim 1, characterized in that: A plurality of air inlets (800) are provided at the bottom of the side wall of the sealed chamber (100).

8. The off-axis crystal growth device according to claim 1, characterized in that: The air pressure in the sealed chamber (100) is less than 1 Pa.

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