A crystal growth method, apparatus and RF-SOI substrate

Abstract

The application provides a crystal growth method, a device and an RF-SOI substrate, and belongs to the technical field of crystal growth. The crystal growth method comprises the following steps: controlling a first superconducting coil to generate a first current and controlling a second superconducting coil to generate a second current, wherein the value of the first current is not equal to the value of the second current, and the first superconducting coil and the second superconducting coil are oppositely arranged and distributed outside a crucible and are used for generating a magnetic field inside the crucible; and single crystal pulling growth is carried out based on an asymmetric magnetic field generated by the first current and the second current in the crucible. By adjusting the coil current ratio to 1:n, an asymmetric horizontal magnetic field is obtained, and then the melt flow can be inhibited by using the asymmetric horizontal magnetic field, and then an asymmetric convection structure can be obtained based on different inhibition effects of the asymmetric horizontal magnetic field on the melt, so that the oxygen content in the single crystal silicon crystal obtained by the pulling method can be significantly reduced.

Description

Technical Field

[0001] This application relates to the field of crystal growth technology, specifically to a crystal growth method, apparatus, and RF-SOI substrate. Background Technology

[0002] RF-SOI is a silicon-based semiconductor material with a unique three-layer structure (i.e., silicon / insulator / silicon), which achieves full dielectric isolation between the device and the substrate through an insulating buried layer (usually SiO2). Therefore, it has become a core substrate material in 5G radio frequency chip substrates due to its advantages such as low loss, high linearity, high breakdown voltage, high thermal conductivity, high integration capability, and relatively low cost.

[0003] Currently, RF-SOI requires a high-resistivity silicon single-crystal substrate, but because oxygen in the silicon single crystal generates thermal donors, it causes a decrease in resistance. Therefore, this high-resistivity substrate also requires a low oxygen content.

[0004] To reduce the oxygen content in silicon single crystals, traditional 8-inch high-resistivity substrates are grown using crucible-free zone melting (also known as FZ method, i.e., floating zone melting). However, when the crystal size grows to 12 inches, the crucible size and melt volume also increase. The surface tension of the silicon melt is insufficient to support its gravity, so zone melting cannot be used for growth. Only Czochralski methods, such as the Czochralski method, can be used.

[0005] When dealing with 12-inch crystals, although specific magnetic fields (such as horizontal magnetic fields, hook-shaped magnetic fields, etc.) can be applied in the existing Czochralski method to achieve some improvement, it is still impossible to effectively suppress the melt flow problem and solve the problem of high oxygen content in silicon single crystals grown by Czochralski. Summary of the Invention

[0006] In view of this, embodiments of this specification provide a crystal growth method, apparatus, and RF-SOI substrate, which perform Czochralski single-crystal silicon crystal growth based on an asymmetric magnetic field formed by a current ratio.

[0007] The embodiments in this specification provide the following technical solutions:

[0008] This specification provides a crystal growth method, including:

[0009] The first superconducting coil is controlled to generate a first current, and the second superconducting coil is controlled to generate a second current, wherein the values ​​of the first current and the second current are not equal. The first superconducting coil and the second superconducting coil are superconducting coils that are relatively distributed outside the crucible and are used to generate a magnetic field inside the crucible.

[0010] Single crystal Czochralski growth is performed based on the asymmetric magnetic field generated in the crucible by the first current and the second current.

[0011] Preferably, the ratio of the value of the first current to the value of the second current is 1:n, where n is a value not equal to 1.

[0012] Preferably, the first superconducting coil is circular, elliptical, or saddle-shaped; and / or the second superconducting coil is circular, elliptical, or saddle-shaped.

[0013] Preferably, the number of the first superconducting coils is one or more; and / or the number of the second superconducting coils is one or more.

[0014] Preferably, a first superconducting coil is controlled by a first controller to generate a first current, and a second superconducting coil is controlled by a second controller to generate a second current.

[0015] This specification also provides a crystal growth apparatus, including:

[0016] crucible;

[0017] A first superconducting coil and a second superconducting coil, wherein the first superconducting coil and the second superconducting coil are superconducting coils that are arranged opposite to each other outside the crucible and are used to generate a magnetic field inside the crucible;

[0018] A controller is used to control the first superconducting coil to generate a first current and to control the second superconducting coil to generate a second current, wherein the values ​​of the first current and the second current are not equal.

[0019] A Czochralski mechanism for performing single-crystal Czochralski growth based on an asymmetric magnetic field generated within the crucible by the first current and the second current.

[0020] Preferably, the controller includes a first control unit and a second control unit, wherein the first control unit is used to control the first superconducting coil to generate a first current, and the second control unit is used to control the second superconducting coil to generate a second current.

[0021] Preferably, the first superconducting coil is circular, elliptical, or saddle-shaped; and / or the second superconducting coil is circular, elliptical, or saddle-shaped.

[0022] Preferably, the number of the first superconducting coils is one or more; and / or the number of the second superconducting coils is one or more.

[0023] This specification also provides an RF-SOI substrate, which is a substrate obtained by Czochralski growth based on any of the crystal growth methods described in this specification, or the RF-SOI substrate is a substrate obtained by single-crystal Czochralski growth using any of the crystal growth apparatus described in this specification.

[0024] Compared with the prior art, the beneficial effects that at least one technical solution adopted in the embodiments of this specification can achieve include at least:

[0025] By adjusting the coil current ratio to 1:n, the current ratio is no longer 1:1, which generates a horizontal symmetrical magnetic field, thus obtaining an asymmetrical horizontal magnetic field. This asymmetrical horizontal magnetic field can then be used to suppress melt flow. Furthermore, based on the different suppression effects of the asymmetrical horizontal magnetic field on the melt, an asymmetrical convection structure can be obtained, enhancing oxygen volatilization at the free liquid surface. This can significantly reduce the oxygen content in Czochralski single-crystal silicon crystals, enabling the crystal oxygen content to meet the requirements of RF-SOI. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the horizontal symmetrical magnetic field distribution formed by a current ratio of 1:1;

[0028] Figure 2 This is a schematic diagram of the asymmetric magnetic field distribution formed by a current ratio of 1:n;

[0029] Figure 3 This is a schematic diagram of melt flow under different current ratios;

[0030] Figure 4 This is a schematic diagram of a current ratio of 1:1.

[0031] Figure 5 This is a schematic diagram of the current ratio 1:n.

[0032] Figure 6 This is a flowchart of the crystal growth method;

[0033] Figure 7 This is a schematic diagram of the crystal growth apparatus. Detailed Implementation

[0034] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0035] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0037] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0039] The oxygen in silicon single crystals mainly originates from the dissolution of the quartz crucible, and the dissolved oxygen moves with the melt flow. At the free liquid surface, oxygen combines with silicon atoms to form SiO, which then volatilizes. Currently, applying a specific magnetic field in the Czochralski method can improve the growth of single-crystal silicon to some extent.

[0040] For example, existing patent document JP6601420B2 provides a single crystal manufacturing method and a single crystal pulling apparatus, which reduces the oxygen content in the crystal by changing the relative position of the horizontal magnetic field and the melt at different stages of Czochralski silicon single crystal growth. However, on the one hand, this prior art can only obtain the lowest oxygen content.

[0041] The amount is 2.2 × 10 17 Oxygen-deficient silicon single crystals with an oxygen content of approximately (atoms / cubic centimeter) mean that the oxygen content of silicon single crystals is still on the order of 5, around 1E18, which is far from meeting the requirements for RF-SOI.

[0042] For example, existing patent document JP6601420B2 provides a single crystal manufacturing method and a single crystal drawing apparatus, which uses a variable magnetic field to control the shape of the melt-solid-liquid interface of a grown silicon crystal. Using a cusp magnetic field, and through a variable power supply and controller, a generally symmetrical, predominantly horizontal, and transversely...

[0043] Three hook-shaped magnetic field configurations are used, primarily for the crystal growth process. By controlling the configuration of the magnetic field at different stages of crystal growth as needed, the shape of the solid-liquid interface can be controlled. However, as crystal sizes increase to 12 inches, crucible sizes and melt volumes also increase, leading to a corresponding increase in turbulence intensity within the melt. Furthermore, the hook-shaped magnetic field, due to its relatively weak magnetic field strength at the center, presents significant challenges in suppressing melt flow. Therefore, currently, most 12-inch semiconductor silicon single crystal growth processes can only utilize horizontal magnetic fields.

[0044] In view of this, in the in-depth research and exploration of the Czochralski method and its technical solutions for applying magnetic fields, it was found that: Figure 1 As shown, the horizontal magnetic field applied in existing Czochralski methods is mostly generated by superconducting coils on both sides. Typically, a controller controls the superconducting coils on both sides to generate equal currents, thereby producing a nearly symmetrical magnetic induction intensity within the crucible, i.e., a horizontally symmetrical magnetic field distribution within the crucible; for example... Figure 2 As shown, when different currents are generated in the two superconducting coils respectively, the currents in the two superconducting coils are...

[0045] When the current ratios of the two superconducting coils are no longer equal (i.e., the ratio of currents to currents in the two superconducting coils is 1:n instead of 1:1), an asymmetric magnetic field will be generated inside the crucible. The darker the color of the area, the stronger the magnetic field. The arrows indicate the direction of the magnetic field lines.

[0046] Therefore, from Figure 1 As shown in the schematic magnetic field distribution, when the current ratio is 1:1, a symmetrical magnetic induction intensity distribution will be generated, which will form a symmetrical horizontal magnetic field. Figure 2 As shown in the schematic magnetic field distribution, when the current ratio is adjusted to other ratios (such as 1:n, where n is not equal to 1) 5, an asymmetrical magnetic induction intensity distribution will be generated, which will be an asymmetrical horizontal magnetic field.

[0047] Further investigation after changing the current ratio revealed that: Figure 3As shown, under the action of a symmetrical magnetic field, the symmetrical magnetic induction intensity has the same inhibitory effect on the melt on both sides of the crucible, and the melt flow is also symmetrically distributed (e.g., Figure 3 (See the left diagram for illustration), resulting in stronger turbulence in the melt; however, the asymmetric magnetic induction intensity has an inconsistent suppressive effect on the melt on both sides of the crucible, with the side with weaker current experiencing weaker suppression of the melt (e.g., ...). Figure 3 (See the diagram on the right). In addition, due to the stronger natural convection caused by thermal buoyancy, the natural convection on this side will occupy more space. After the oxygen-rich melt rising from the crucible wall is fully volatilized at the free liquid surface, the oxygen content is significantly reduced. When the melt with low oxygen content reaches the crystallization interface, it can significantly reduce the oxygen content concentration of the crystal.

[0048] A careful analysis of the current ratio and the corresponding contour plot also revealed: Figure 4 and Figure 5 These are schematic diagrams of contour plots under different current ratios, from... Figure 4 The schematic cloud diagram shows that when the current ratio is 1:1, the oxygen content at the crystallization interface is around 15 ppma. Figure 5 The schematic cloud diagram shows that when the current ratio is 1:n (e.g., 1:2), the oxygen content at the crystallization interface is around 4 ppma.

[0049] Therefore, by adjusting the current ratio of the superconducting coil outside the crucible, an asymmetric horizontal magnetic field can be provided to the crucible. Under the action of this asymmetric magnetic field, an asymmetric convection structure can be formed in the Czochralski method. This not only helps to reduce the turbulence intensity in the melt, but also significantly reduces the oxygen content in the crystal, so that the crystal grown by the Czochralski method can be used as an RF-SOI substrate.

[0050] The following example illustrates this:

[0051] like Figure 6 As shown in the embodiments of this specification, a crystal growth method is provided, including:

[0052] Step S602: Control the first superconducting coil to generate a first current and control the second superconducting coil to generate a second current, wherein the value of the first current and the value of the second current are not equal. The first superconducting coil and the second superconducting coil are superconducting coils that are relatively distributed outside the crucible and are used to generate a magnetic field inside the crucible.

[0053] As analyzed above, when the current ratio of the superconducting coil outside the crucible is no longer 1:1, the superconducting coil will generate an asymmetric magnetic field inside the crucible. This asymmetric magnetic field can provide an asymmetric horizontal magnetic field distribution for the Czochralski crystal growth, and can also provide different suppression effects on the flow of the melt on both sides of the crucible through the asymmetric magnetic field configuration. On the side with weaker current, the melt is less suppressed, and the natural convection caused by thermal buoyancy is stronger. The natural convection on this side will occupy more space. Since the oxygen in silicon single crystal mainly comes from the dissolution of the quartz crucible, the dissolved oxygen will move with the flow of the melt, and the oxygen will combine with silicon atoms at the free liquid surface to form SiO and volatilize. Therefore, under the action of the asymmetric magnetic field, after the oxygen-rich melt rising from the crucible wall has fully volatilized at the free liquid surface, the melt with low oxygen content reaches the crystallization interface, and the oxygen content is significantly reduced.

[0054] Step S604: Perform single crystal Czochralski growth based on the asymmetric magnetic field generated in the crucible by the first current and the second current.

[0055] By adjusting the current ratio, an asymmetric horizontal magnetic field distribution is formed in the crucible that can be used for Czochralski crystal growth. Based on the different suppression effects of the asymmetric magnetic field on the melt, the melt can form an asymmetric convection structure, which can significantly reduce the oxygen content in single crystal Czochralski growth. Ultimately, this provides a basis for manufacturing RF_SOI substrates with a significantly reduced oxygen content in single crystal Czochralski growth.

[0056] It should be noted that the single crystal Czochralski growth method can be any existing Czochralski method, and there is no limitation here.

[0057] In one example, the superconducting coil can be controlled to generate a corresponding current according to the requirements of the single-crystal Czochralski growth process. The ratio of the value of the first current to the value of the second current is 1:n, where n is a value not equal to 1. It should be noted that n can be a value greater than 1, a value less than 1, or an integer value greater than 1; no specific limitation is made here.

[0058] In one example, the asymmetric magnetic field can consist of one or more pairs of superconducting coils, which can be circular in shape. Therefore, the first superconducting coil is circular; and / or the second superconducting coil is circular. It should be noted that the superconducting coils can also be other shapes, not limited to circular, such as elliptical or saddle-shaped, thereby facilitating the generation of an asymmetric magnetic field distribution within the crucible and the formation of an asymmetric convection structure in the melt after asymmetric suppression of the melt within the crucible. Furthermore, the first and second superconducting coils can have the same or different shapes; no specific limitations are made on their shape and size here.

[0059] In one example, the number of coils can also be one or more, thereby forming the desired asymmetric magnetic field distribution and asymmetric convection structure inside the crucible through the superconducting coil configuration. Therefore, the number of the first superconducting coils can be one or more; and / or the number of the second superconducting coils can be one or more, thereby forming an asymmetric magnetic field based on multiple pairs of superconducting coils and their respective current ratios.

[0060] In one example, by modifying the design of the horizontal magnetic field assembly, the current flowing through the superconducting coil can be controlled independently; that is, a first controller controls the first superconducting coil to generate a first current, and a second controller controls the second superconducting coil to generate a second current. For example, as described above... Figure 2 The diagram illustrates a control scheme for an asymmetric horizontal magnetic field configuration, in which the coils are controlled by separate first and second controllers, thereby enabling a convenient 1:n coil current ratio through individual control.

[0061] Based on the same inventive concept, the embodiments described herein also provide a crystal growth apparatus corresponding to the aforementioned method.

[0062] like Figure 7 As shown, a crystal growth apparatus includes:

[0063] Crucible 701;

[0064] The first superconducting coil 702 and the second superconducting coil 703 are superconducting coils that are arranged opposite to each other outside the crucible and are used to generate a magnetic field inside the crucible.

[0065] The controller 704 is used to control the first superconducting coil to generate a first current and to control the second superconducting coil to generate a second current, wherein the values ​​of the first current and the second current are not equal, for example, the ratio of the two currents is 1:n (n is a value not equal to 1).

[0066] The Czochralski mechanism 705 is used for single crystal Czochralski growth based on the asymmetric magnetic field generated in the crucible by the first current and the second current.

[0067] It should be noted that the crucible, Czochralski mechanism, etc. can be the corresponding parts in the original equipment. Here, the current ratio of the superconducting coils is adjusted by the controller so that the current ratio between the superconducting coils that generate the magnetic field in the crucible is no longer 1:1. In turn, an asymmetric magnetic field is formed inside the crucible through a current ratio of 1:n, which causes the melt in the crucible to also form an asymmetric convection structure.

[0068] In one example, the superconducting coil can be controlled individually. Specifically, the controller may include a first control unit and a second control unit, wherein the first control unit is used to control the first superconducting coil to generate a first current, and the second control unit is used to control the second superconducting coil to generate a second current.

[0069] In one example, the superconducting coil may be circular, but is not limited to, a circular shape. Specifically, the first superconducting coil may be circular, elliptical, or saddle-shaped; and / or the second superconducting coil may be circular, elliptical, or saddle-shaped.

[0070] In one example, there can be one or more first and second superconducting coils. In practice, the controller only needs to ensure that the currents of the two types of superconducting coils are not equal, thereby generating an asymmetric magnetic field.

[0071] Based on the same inventive concept, embodiments of this specification also provide a substrate with low oxygen content for use as an RF-SOI substrate.

[0072] Specifically, the RF-SOI substrate is a substrate obtained by Czochralski growth based on the crystal growth method described in any embodiment of this specification, or the RF-SOI substrate is a substrate obtained by single-crystal Czochralski growth using the crystal growth apparatus described in any embodiment of this specification.

[0073] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the product embodiments described later, since they correspond to the methods, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions in the system embodiments.

[0074] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A crystal growth method, characterized in that, include: A first superconducting coil is controlled by a first controller to generate a first current, and a second superconducting coil is controlled by a second controller to generate a second current; wherein the values ​​of the first current and the second current are not equal, and the first and second superconducting coils are superconducting coils that are relatively distributed outside the crucible and are used to generate a magnetic field inside the crucible. Single crystal Czochralski growth is performed based on the asymmetric magnetic field generated in the crucible by the first current and the second current to reduce the oxygen content concentration in the crystal. By adjusting the current ratio, an asymmetric horizontal magnetic field distribution is formed in the crucible that can be used for Czochralski crystal growth. Based on the different suppression effects of the asymmetric magnetic field on the melt, the melt can form an asymmetric convection structure, thereby significantly reducing the oxygen content in single crystal Czochralski growth.

2. The crystal growth method according to claim 1, characterized in that, The ratio of the value of the first current to the value of the second current is 1:n, where n is a value not equal to 1.

3. The crystal growth method according to claim 1, characterized in that, The first superconducting coil is circular, elliptical, or saddle-shaped; and / or the second superconducting coil is circular, elliptical, or saddle-shaped.

4. The crystal growth method according to claim 1, characterized in that, The number of the first superconducting coils is one or more; and / or the number of the second superconducting coils is one or more.

5. A crystal growth apparatus, comprising the crystal growth method according to any one of claims 1-4, characterized in that, include: crucible; A first superconducting coil and a second superconducting coil, wherein the first superconducting coil and the second superconducting coil are superconducting coils that are arranged opposite to each other outside the crucible and are used to generate a magnetic field inside the crucible; A controller is used to control the first superconducting coil to generate a first current and to control the second superconducting coil to generate a second current, wherein the values ​​of the first current and the second current are not equal. A Czochralski mechanism for performing single-crystal Czochralski growth based on an asymmetric magnetic field generated within the crucible by the first current and the second current.

6. The crystal growth apparatus according to claim 5, characterized in that, The controller includes a first control unit and a second control unit, wherein the first control unit is used to control the first superconducting coil to generate a first current, and the second control unit is used to control the second superconducting coil to generate a second current.

7. The crystal growth apparatus according to claim 5, characterized in that, The first superconducting coil is circular, elliptical, or saddle-shaped; and / or the second superconducting coil is circular, elliptical, or saddle-shaped.

8. The crystal growth apparatus according to claim 5, characterized in that, The number of the first superconducting coils is one or more; and / or the number of the second superconducting coils is one or more.

9. An RF-SOI substrate, characterized in that, The RF-SOI substrate is a substrate obtained by Czochralski growth based on the crystal growth method of any one of claims 1-5, or the RF-SOI substrate is a substrate obtained by Czochralski growth of a single crystal using the crystal growth apparatus of any one of claims 5-8.

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