Crystal growing method, apparatus and rf-soi substrate

Abstract

This application provides a crystal growth method, apparatus, and RF-SOI substrate, applicable to the field of crystal growth technology. The crystal growth method includes: controlling a first superconducting coil to generate a first current and controlling a second superconducting coil 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; and performing single crystal Czochralski growth based on the asymmetric magnetic field generated by the first current and the second current inside the crucible.

Description

Crystal Growth Method, Apparatus and RF-SOI Substrate This application relates to the technical field of crystal growth, and particularly relates to a crystal growth method, apparatus and RF-SOI substrate. RF-SOI is a silicon-based semiconductor process material with a unique three-layer structure (i.e., silicon / insulating layer / silicon). It realizes the full dielectric isolation of components and the substrate through an insulating buried layer (usually SiO 2 ). Therefore, in the substrate materials for 5G radio frequency chips, due to its advantages such as low loss, high linearity, high breakdown voltage, high thermal conductivity, high integration ability and relatively low cost, it has become the core substrate material. Currently, RF-SOI requires a high-resistance silicon single crystal substrate. However, since oxygen in the silicon single crystal will generate thermal donors, resulting in a decrease in resistance. Therefore, this high-resistance substrate also requires a low oxygen content. In order to reduce the oxygen content in the silicon single crystal, traditional 8-inch high-resistance substrates are all grown by the crucible-free floating zone melting method (also known as the FZ method, i.e., the floating zone melting method). When the crystal size develops to 12 inches, the crucible size and the melt volume increase accordingly. The surface tension of the silicon melt is not sufficient to support its gravity, and the floating zone melting method cannot be used for growth. Only the Czochralski method can be used. When dealing with 12-inch crystals, although a specific magnetic field (such as a horizontal magnetic field, a hook-shaped magnetic field, etc.) can be applied in the existing Czochralski method to obtain a certain degree of improvement, it is still unable to effectively suppress the melt flow problem and solve the problem of high oxygen content in the Czochralski silicon single crystal. In view of this, the embodiments of this specification provide a crystal growth method, apparatus and RF-SOI substrate, which grow single crystal silicon crystals by the Czochralski method based on an asymmetric magnetic field formed by the current ratio. The embodiments of this specification provide the following technical solutions: The embodiments of this specification provide a crystal growth method, including: controlling a first superconducting coil to generate a first current, and controlling a second superconducting coil to generate a second current, where 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 relatively arranged outside the crucible and are superconducting coils used to generate a magnetic field inside the crucible; performing single crystal Czochralski growth based on the asymmetric magnetic field generated by the first current and the second current in the crucible. 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. Preferably, the shape of the first superconducting coil is circular, elliptical or saddle-shaped; and / or the shape of the second superconducting coil is circular, elliptical or saddle-shaped. 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. Preferably, 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. An embodiment of this specification further provides a crystal growth device, including: a crucible; a first superconducting coil and a second superconducting coil, where the first superconducting coil and the second superconducting coil are oppositely arranged and distributed outside the crucible and are superconducting coils for generating a magnetic field inside the crucible; a controller for controlling the first superconducting coil to generate a first current and controlling the second superconducting coil to generate a second current, where the value of the first current is not equal to the value of the second current; a Czochralski mechanism for performing single-crystal Czochralski growth based on the asymmetric magnetic field generated by the first current and the second current in the crucible. Preferably, the controller includes a first control unit and a second control unit, where 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. Preferably, the shape of the first superconducting coil is circular, elliptical or saddle-shaped; and / or the shape of the second superconducting coil is circular, elliptical or saddle-shaped. 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. An embodiment of this specification further provides an RF-SOI substrate, where the RF-SOI substrate is a substrate obtained by Czochralski growth based on any one 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 one of the crystal growth devices described in this specification. Compared with the prior art, the beneficial effects that can be achieved by at least one of the above technical solutions adopted in the embodiments of this specification at least include: by adjusting the coil current ratio to 1:n, the current ratio is no longer 1:1 for generating a horizontally symmetric magnetic field, so as to obtain an asymmetric horizontal magnetic field, and then the melt flow can be suppressed by using the asymmetric horizontal magnetic field. Furthermore, an asymmetric convection structure can be obtained based on the different inhibitory effects of the asymmetric horizontal magnetic field on the melt, enhancing the evaporation of oxygen at the free liquid surface, and significantly reducing the oxygen content in the Czochralski single-crystal silicon crystal, so that the crystal oxygen content can meet the requirements of RF-SOI. The embodiments of this application will be described in detail below with reference to the accompanying drawings. The following describes the implementation manners of the present application through specific examples, and those skilled in the art can easily understand the other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all embodiments. The present application can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present application. It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present application, those skilled in the art should 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 described herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functions in addition to one or more of the aspects described herein. It should also be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present application schematically, and only the components related to the present application are shown in the drawings, rather than being drawn according to the number, shape and size of the components in actual implementation. The type, quantity and proportion of each component in actual implementation can be arbitrarily changed, and the layout type of its components may also be more complex. In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the examples can be practiced without these specific details. The oxygen in silicon single crystal mainly comes from the dissolution of quartz crucible, and the dissolved oxygen will move with the flow of the melt. Oxygen will combine with silicon atoms at the free liquid surface to form SiO and volatilize. Currently, applying a corresponding specific magnetic field in the Czochralski method can improve the growth of single crystal silicon to a certain extent. For example, the existing patent document JP6601420B2 provides a single crystal manufacturing method and a single crystal pulling device, which change the relative position of the horizontal magnetic field and the melt at different stages of the Czochralski silicon single crystal growth, so as to reduce the oxygen content in the crystal. However, on the one hand, this existing technology can only obtain the lowest oxygen content of 2.2×10 17The oxygen-deficient silicon single crystal is about [[ID=]], that is, the order of magnitude of the oxygen content in the silicon single crystal is still about 1E18, far from meeting the requirements of RF-SOI. For example, the existing patent document JP6601420B2 provides a single crystal manufacturing method and a single crystal pulling device, that is, a variable magnetic field is used to control the shape of the melt-solid interface of a growing silicon crystal. A cusp magnetic field is used, and through a variable power supply and a controller, three cusp magnetic field configurations that are generally symmetric, mainly horizontal, and mainly transverse are formed. By controlling the magnetic field configuration according to requirements at different stages of crystal growth, the shape of the solid-liquid interface is further controlled. However, when the crystal size develops to 12 inches, the crucible size and the melt volume both increase accordingly. Similarly, the turbulence intensity in the melt increases, and due to the relatively weak magnetic field intensity at the center of the cusp magnetic field, it is difficult to suppress the melt flow. Therefore, at present, a horizontal magnetic field is mostly used for the growth of 12-inch semiconductor silicon single crystals. In view of this, in the in-depth research and improvement exploration of the Czochralski method and its technical solution of applying a magnetic field, it is found that: as shown in Figure 1, in the existing Czochralski method, the applied horizontal magnetic field is mostly generated by superconducting coils on the left and right sides. Usually, the controller controls the superconducting coils on both sides to generate equal currents, so as to generate a nearly symmetric magnetic induction intensity in the crucible, that is, a horizontally symmetric magnetic field distribution is generated in the crucible; as shown in Figure 2, when the superconducting coils on both sides are controlled to generate different currents, the currents of the superconducting coils on both sides are no longer equal, that is, when the current ratio of the superconducting coils on both sides is 1:n instead of 1:1, an asymmetric magnetic induction intensity will be generated in the crucible at this time. The darker the color area, the greater the magnetic field intensity, and the arrow indicates the direction of the magnetic force line. Therefore, from the perspective of the magnetic field distribution shown in Figure 1, when the current ratio is 1:1, a symmetrically distributed magnetic induction intensity distribution will be generated, and its magnetic induction intensity distribution is a symmetric horizontal magnetic field. From the perspective of the magnetic field distribution shown in Figure 2, when the current ratio is adjusted to other ratios (such as 1:n, n is not equal to 1), an asymmetrically distributed magnetic induction intensity distribution will be generated, and its magnetic induction intensity distribution is an asymmetric horizontal magnetic field. In the further exploration after changing the current ratio, it is also found that: as shown in Figure 3, under the action of a symmetric magnetic field, the symmetric magnetic induction intensity has the same inhibitory effect on the melt on both sides of the crucible. At this time, the melt flow is also symmetrically distributed (as shown in the left figure of Figure 3), resulting in a relatively strong turbulence intensity in the melt; while the asymmetric magnetic induction intensity has inconsistent inhibitory effects on the melt on both sides of the crucible. On the side with a weaker current, the melt is less inhibited (as shown in the right figure of Figure 3). 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 volatilizes sufficiently through the free liquid surface, the oxygen content is significantly reduced. The melt with a low oxygen content reaches the crystallization interface again, which can significantly reduce the oxygen content concentration of the crystal. A careful analysis of the contour maps corresponding to the current ratios also reveals that: Figures 4 and 5 are schematic diagrams of contour maps under different current ratios. From the contour map shown in Figure 4, it can be seen that when the current ratio is 1:1, the oxygen content at the crystal interface is about 15 ppma. From the contour map shown in Figure 5, it can be seen that when the current ratio is 1:n (such as 1:2), the oxygen content at the crystal interface is about 4 ppma. Therefore, by adjusting the current ratio of the superconducting coils 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, which is not only beneficial to reducing the turbulence intensity in the melt, but also can significantly reduce the oxygen content in the crystal, enabling the crystal grown by the Czochralski method to be used as an RF-SOI substrate. The following is an example for illustration: As shown in Figure 6, an embodiment of this specification provides a crystal growth method, including: Step S602, controlling the first superconducting coil to generate a first current, and controlling the second superconducting coil to generate a second current, where the value of the first current is not equal to the value of the second current. The first superconducting coil and the second superconducting coil are relatively arranged outside the crucible and are superconducting coils used to generate a magnetic field inside the crucible. As previously analyzed, when the current ratio of the superconducting coils outside the crucible is no longer 1:1, the superconducting coils will generate an asymmetric magnetic field inside the crucible. This asymmetric magnetic field can not only provide an asymmetric horizontal magnetic field distribution for the crystal growth by the Czochralski method, but also provide different inhibitory effects on the flow of the melt on both sides of the crucible under the asymmetric magnetic field configuration. On the side with a weaker current, the melt is less inhibited, 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 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 is fully volatilized through the free liquid surface, the melt with a low oxygen content reaches the crystal interface, and the oxygen content is significantly reduced. Step S604, performing single crystal Czochralski growth based on the asymmetric magnetic field generated by the first current and the second current in the crucible. After adjusting the current ratio, an asymmetric horizontal magnetic field distribution capable of being used for crystal growth by the Czochralski method is formed inside the crucible. And due to the different inhibitory effects of the asymmetric magnetic field on the melt, the melt can form an asymmetric convection structure, thereby being able to significantly reduce the oxygen content in the single crystal Czochralski growth, and ultimately providing a basis for single crystal Czochralski growth with a significantly reduced oxygen content concentration for manufacturing an RF-SOI substrate. It should be noted that the single crystal Czochralski growth method can be the existing Czochralski method, which is not limited here. In one example, according to the requirements of the Czochralski single crystal growth process, the superconducting coil can be controlled to generate corresponding currents, where the ratio of the value of the first current to the value of the second current is 1:n, and 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, and no specific limitation is made here. In one example, the asymmetric magnetic field can be composed of one or more pairs of superconducting coils, and the shape of the coils can be circular. Therefore, the shape of the first superconducting coil is circular; and / or the shape of 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, etc., so that through the setting of the coil shape, it is convenient to generate an asymmetric magnetic field distribution in the crucible and form an asymmetric convection structure of the melt after asymmetric suppression of the melt in the crucible. In addition, the shapes of the first superconducting coil and the second superconducting coil can be the same or different, and no specific limitation is made on the shape and size here. In one example, the number of coils can also be one or more, so as to form the required 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, so as to form an asymmetric magnetic field based on multiple pairs of superconducting coils and their respective current ratios. In one example, through the improved design of the horizontal magnetic field element, the current flowing through the superconducting coil can be controlled separately, that is, the first superconducting coil is controlled by the first controller to generate the first current, and the second superconducting coil is controlled by the second controller to generate the second current. For example, in the control scheme of an asymmetric horizontal magnetic field configuration shown in FIG. 2 above, the coils are controlled by separate first and second controllers respectively, so that it is very convenient to achieve a 1:n coil current ratio through separate control. Based on the same inventive concept, the present embodiment of the specification also provides a crystal growth apparatus corresponding to the foregoing method. As shown in FIG. 7, a crystal growth apparatus includes: a crucible 701; a first superconducting coil 702 and a second superconducting coil 703, where the first superconducting coil and the second superconducting coil are relatively arranged outside the crucible and are superconducting coils for generating a magnetic field inside the crucible; a controller 704 for controlling the first superconducting coil to generate a first current and controlling the second superconducting coil to generate a second current, where the value of the first current is not equal to the value of the second current, for example, the ratio of the two currents is 1:n (n is a value not equal to 1); a Czochralski mechanism 705 for performing Czochralski single crystal growth based on the asymmetric magnetic field generated by the first current and the second current in the crucible. It should be noted that the crucible, the Czochralski mechanism, etc. here 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 a magnetic field in the crucible is no longer 1:1. Furthermore, an asymmetric magnetic field is formed inside the crucible through a current ratio of 1:n, so that the melt in the crucible also forms an asymmetric convection structure. In one example, the superconducting coils can be controlled individually. Specifically, the controller can include a first control unit and a second control unit, where 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. In one example, the shape of the superconducting coil can be circular but is not limited to circular. Specifically, the shape of the first superconducting coil is circular, elliptical or saddle-shaped; and / or the shape of the second superconducting coil is circular, elliptical or saddle-shaped. In one example, both the first superconducting coil and the second superconducting coil can be one or more. In practice, it is only necessary for the controller to control the currents of the two types of superconducting coils not to be equal, so as to generate an asymmetric magnetic field. Based on the same inventive concept, the embodiments of this specification also provide a substrate with low oxygen content for use as an RF-SOI substrate. Specifically, the RF-SOI substrate is a substrate obtained by Czochralski growth based on the crystal growth method described in any one of the embodiments of this specification, or the RF-SOI substrate is a substrate obtained by single crystal Czochralski growth using the crystal growth device described in any one of the embodiments of this specification. In this specification, the same or similar parts among the various embodiments can be referred to each other, and each embodiment focuses on 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 partial descriptions of the system embodiments. As described above, the above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the patent application scope. S602, S604: Steps 701: Crucible 702: First superconducting coil 703: Second superconducting coil 704: Controller 705: Czochralski mechanism To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these accompanying drawings. [Figure 1] is a schematic diagram of the horizontal symmetric magnetic field distribution formed by a current ratio of 1:1; [Figure 2] is a schematic diagram of the asymmetric magnetic field distribution formed by a current ratio of 1:n; [Figure 3] is a schematic diagram of the structure of the melt flow under different current ratios; [Figure 4] is a cloud diagram schematic diagram of a current ratio of 1:1; [Figure 5] is a cloud diagram schematic diagram of a current ratio of 1:n; [Figure 6] is a flowchart of the crystal growth method; [Figure 7] is a schematic diagram of the structure of the crystal growth apparatus.

Claims

1. A crystal growth method, comprising: Controlling a first superconducting coil to generate a first current and controlling a second superconducting coil 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 a crucible and are used to generate a magnetic field inside the crucible; and performing single crystal Czochralski growth based on the horizontally asymmetric magnetic field generated by the first current and the second current inside the crucible.

2. The crystal growth method as described in claim 1, wherein 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 as claimed in claim 1, wherein 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 as described in claim 1, wherein 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. The crystal growth method as described in any one of claims 1 to 4, wherein the first current is generated by controlling the first superconducting coil via a first controller, and the second current is generated by controlling the second superconducting coil via a second controller.

6. A crystal growth apparatus, comprising: A crucible; A first superconducting coil and a second superconducting coil, wherein the first superconducting coil and the second superconducting coil are arranged opposite to each other outside the crucible and are used to generate a magnetic field inside the crucible; a controller for controlling the first superconducting coil to generate a first current and controlling 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; And a Czochralski mechanism for performing single crystal Czochralski growth based on the horizontally asymmetric magnetic field generated in the crucible by the first current and the second current.

7. The crystal growth apparatus as claimed in claim 6, wherein 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 the first current, and the second control unit is used to control the second superconducting coil to generate the second current.

8. The crystal growth apparatus as claimed in claim 6, wherein the first superconducting coil is circular, elliptical, or saddle-shaped, and / or the second superconducting coil is circular, elliptical, or saddle-shaped.

9. The crystal growth apparatus as claimed in claim 6, wherein the number of the first superconducting coils is one or more, and / or the number of the second superconducting coils is one or more.

10. An RF-SOI substrate, wherein the RF-SOI substrate is a substrate obtained by Czochralski growth based on any one of the crystal growth methods described in claims 1 to 5, or the RF-SOI substrate is a substrate obtained by single-crystal Czochralski growth using any one of the crystal growth apparatus described in claims 6 to 9.

Images