Epitaxial structure and preparation system thereof, semiconductor device

Abstract

The present disclosure provides an epitaxial structure, a preparation system thereof and a semiconductor device. The preparation system of the epitaxial structure comprises: a reaction chamber for epitaxially growing a magnetic layer of a gyromagnetic ferrite on a semiconductor substrate; and a first magnetic field generating device for generating a magnetic field in the reaction chamber, wherein the magnetic field has a magnetic field component parallel to the surface of the semiconductor substrate. The preparation system provided by the present disclosure is integrated with the first magnetic field generating device, and by applying a magnetic field with a magnetic field component parallel to the surface of the semiconductor substrate in the reaction chamber, the reaction and crystallization process of reaction gas atoms in the reaction chamber can be affected, so as to change the crystallization orientation, and the in-plane uniaxial magnetic anisotropy can be induced even on a non-textured semiconductor substrate, so as to grow the magnetic layer of the gyromagnetic ferrite with strong crystallographic texture, and further to realize mass production of the magnetic layer of the gyromagnetic ferrite on the non-textured semiconductor substrate.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and in particular to an epitaxial structure and its fabrication system, and a semiconductor device. Background Technology

[0002] Gyromagnetic ferrites are a type of ferrite. When a plane-polarized electromagnetic wave propagates through a gyromagnetic ferrite along a specific polarization direction, the plane of polarization continuously rotates around the direction of propagation. In other words, gyromagnetic ferrites exhibit a gyromagnetic effect on electromagnetic waves propagating within them. Currently, the most widely used gyromagnetic ferrite is the rare-earth garnet-type ferrite YIG. YIG has a complex body-centered cubic structure and belongs to the cubic crystal system. Its molecular formula is Y3Fe5O3. 12 The main characteristics of YIG include: transmittance >80% in the near-mid-infrared band (1.2-5.5μm), resonant linewidth <0.4 Oe, Curie temperature >280℃, and Faraday rotation angle >210° / cm (wavelength 1.55 μm). Due to the property of YIG materials to rotate the polarization direction of electromagnetic waves and light propagating within them, they have wide applications in microwave, optoelectronics, and sensor industries.

[0003] Large-scale chip production in semiconductor factories typically employs Metal-organic Chemical Vapor Deposition (MOCVD) for epitaxial mass production. Current MOCVD equipment in semiconductor factories enables efficient chip mass production. Typical MOCVD equipment supports parallel production of 8×6-inch or 4×8-inch wafers and is currently the mainstream process for large-scale production of power devices and optoelectronic devices. MOCVD uses different organometallic precursor gases and reactant gases to react on the surface of a heated chip substrate to generate the desired semiconductor thin film. Taking GaAs chips as an example, MOCVD is used to generate GaAs chips on a GaAs substrate through the reaction of Ga(CH3)3 and AsH3.

[0004] Ideally, YIG materials are in a single-crystal state. Depending on the application, YIG materials are mainly prepared using two techniques: solid-state preparation and thin-film preparation. Solid-state preparation refers to solid-state sintering methods, while thin-film preparation includes methods such as epitaxy, sputtering, and printing.

[0005] A typical process flow for solid-state sintering includes: mixing Fe₂O₃ and Y₂O₃ through powder grinding, using deionized water as a lubricant, and preparing the YIG ferromagnet by solid-state reaction at 1200℃ for 6 hours. YIG ferromagnets produced by solid-state sintering are bulk solids, not single crystals, and are unsuitable for epitaxial layer growth on layered semiconductor chips. Furthermore, YIG ferromagnets produced by solid-state sintering do not possess their own magnetic field and require external magnetic field excitation.

[0006] Liquid phase epitaxy (LPE) uses a high-temperature molybdate mother liquor, typically at 1100-1200℃, and employs (111) crystal plane Gd3Ga5O 12 Using gadolinium gallium garnet (GGG) single crystals as substrates, a YIG single crystal thin film layer is formed by controlled cooling. GGG single crystals and YIG both belong to the garnet system, and their lattice constants and coefficients of thermal expansion match those of YIG. GGG single crystals are suitable substrate materials for YIG magneto-optical epitaxy films and have wide applications in optical isolators, optical waveguides, and integrated optics. YIG single crystal thin films on GGG substrates are also the main material for bubble memory. Since existing microwave, optoelectronic, or sensor semiconductor chips mainly use materials such as GaAs, InP, GaN, SiC, Si, and SiO2, which differ significantly from GGG single crystal substrates in terms of physicochemical properties such as lattice constants and coefficients of thermal expansion, existing liquid-phase epitaxy methods based on GGG single crystal substrates are not suitable for the GaAs, InP, GaN, SiC, Si, and SiO2 substrates used in these semiconductor chips.

[0007] Sputtering methods mainly include magnetron sputtering and pulsed laser sputtering (PLD). In magnetron sputtering, the target is placed on the cathode, and a strong magnetic field is applied to the target surface to confine charged particles, increasing the plasma density generated on the target before deposition onto the substrate. Laser sputtering uses a laser to excite the target, thus improving sputtering efficiency. YIG targets can be used to prepare YIG thin films on Si, GGG, MgO, and Al2O3 substrates using magnetron or laser sputtering methods. The prepared YIG films are of high quality and have good thickness uniformity. However, due to limitations in plasma concentration and spatial uniformity, it is difficult to perform large-area, high-efficiency epitaxy. Currently, commercially available reactive sputtering equipment can only accommodate three 2-inch substrates, resulting in low epitaxial efficiency. Therefore, it is mainly used in laboratories and is difficult to use for large-area, high-efficiency epitaxial production in semiconductor factories. Furthermore, magnetron or laser sputtering methods struggle to achieve precise control over small amounts of doping elements.

[0008] Therefore, the current fabrication process of ferrite YIG is incompatible with the mainstream chip epitaxial layer fabrication process MOCVD. In other words, it is difficult to mass-produce YIG thin films on substrates such as GaAs, GaN, SiC, InP, Si, and SiO2 used in semiconductor chips using existing MOCVD equipment. Summary of the Invention

[0009] The technical problem to be solved by this disclosure is to overcome the above-mentioned defects in the prior art and provide an epitaxial structure and its preparation system, and a semiconductor device.

[0010] This disclosure solves the above-mentioned technical problems through the following technical solution:

[0011] The first aspect of this disclosure provides a system for preparing an epitaxial structure, comprising:

[0012] The reaction chamber is used for the epitaxial growth of a magnetic layer of gyromagnetic ferrite on a semiconductor substrate;

[0013] A first magnetic field generating device is used to generate a magnetic field in the reaction chamber; wherein the magnetic field has a magnetic field component parallel to the surface of the semiconductor substrate.

[0014] Optionally, the direction of the magnetic field is parallel to the surface of the semiconductor substrate.

[0015] Optionally, the first magnetic field generating device includes a magnetic head, a magnetic yoke, and a coil wound on the magnetic yoke, wherein the magnetic yoke is connected to a pair of magnetic poles of the magnetic head;

[0016] The magnetic yoke penetrates the wall of the reaction chamber, such that one magnetic pole of the magnetic head is located inside the reaction chamber and the other magnetic pole is located outside the reaction chamber.

[0017] Optionally, the preparation system further includes an annealing chamber and a second magnetic field generating device;

[0018] The annealing chamber is used to anneal the semiconductor substrate with an epitaxially grown magnetic layer of gyromagnetic ferrite. The annealing chamber is equipped with a temperature regulating component, which is configured to cause the semiconductor substrate to undergo at least one temperature change process between a first temperature and a second temperature, wherein the first temperature is higher than the second temperature.

[0019] The second magnetic field generating device is used to generate a magnetic field in the annealing chamber that is perpendicular to the surface of the semiconductor substrate.

[0020] Optionally, the second magnetic field generating device includes a superconducting magnet, which includes a superconducting coil and a liquid helium dewar, wherein the superconducting coil is immersed in liquid helium contained in the liquid helium dewar.

[0021] Optionally, the reaction chamber is provided with a tray for placing the semiconductor substrate, and the temperature control component is disposed on the tray.

[0022] Optionally, the preparation system further includes an automated transfer device for transferring the semiconductor substrate from the reaction chamber to the annealing chamber.

[0023] Optionally, the transmission device is further configured to transmit the annealing chamber to the receiving space of the second magnetic field generating device, so that the annealing chamber is placed in the magnetic field generated by the second magnetic field generating device.

[0024] A second aspect of this disclosure provides an epitaxial structure prepared by the preparation system described in the first aspect.

[0025] A third aspect of this disclosure provides a semiconductor device including the epitaxial structure described in the second aspect.

[0026] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this disclosure.

[0027] The positive and progressive effects of this disclosure are as follows: The preparation system provided by this disclosure integrates a first magnetic field generating device, which applies a magnetic field component parallel to the surface of the semiconductor substrate in the reaction chamber, thereby affecting the reaction and crystallization process of the reactant gas atoms in the reaction chamber and changing the crystallization orientation. Even on untextured semiconductor substrates such as GaAs, GaN, SiC, InP, Si, and SiO2, in-plane uniaxial magnetic anisotropy can be induced, thereby growing a magnetic layer of gyromagnetic ferrite with strong crystallographic texture, and thus realizing the mass production of magnetic layers of gyromagnetic ferrite on the aforementioned semiconductor substrates.

[0028] Furthermore, the preparation system provided in this disclosure also integrates an annealing chamber and a second magnetic field generating device. The temperature control component located in the annealing chamber is used to provide variable temperature annealing treatment for the semiconductor substrate. The alternation of high and low temperatures generates periodic huge thermal stress, which promotes the reorganization of atoms and defects, effectively disintegrating and weakening the old in-plane magnetic anisotropy structure. On this basis, the second magnetic field generating device can correct the easy magnetization axis of the magnetic layer by applying a magnetic field perpendicular to the surface of the semiconductor substrate in the annealing chamber, so as to forcibly change it from parallel to the surface of the semiconductor substrate to perpendicular to the surface of the semiconductor substrate, thereby realizing the entire process of preparation of the magnetic layer from induced in-plane texture growth to realization of perpendicular magnetic anisotropy annealing. Attached Figure Description

[0029] Figure 1 A structural block diagram of a preparation system provided for an exemplary embodiment of this disclosure;

[0030] Figure 2 A schematic diagram of a layered structure of an epitaxial structure provided for an exemplary embodiment of this disclosure;

[0031] Figure 3 A cross-sectional schematic diagram of a reaction chamber provided for an exemplary embodiment of this disclosure;

[0032] Figure 4 A three-dimensional schematic diagram of a reaction chamber provided for an exemplary embodiment of this disclosure;

[0033] Figure 5 A structural block diagram of a preparation system provided for an exemplary embodiment of this disclosure;

[0034] Figure 6 A schematic diagram illustrating the effect of variable temperature annealing on correcting easily magnetized shafts, provided as an exemplary embodiment of this disclosure;

[0035] Figure 7 A schematic diagram of the temperature-time curve of a YIG thin film subjected to variable temperature annealing under a magnetic field, provided as an exemplary embodiment of this disclosure;

[0036] Figure 8 A schematic diagram of the magnetic field strength-time curve of a YIG thin film subjected to variable temperature annealing under a magnetic field, provided as an exemplary embodiment of this disclosure;

[0037] Figure 9 This is a partial structural schematic diagram of a preparation system provided for an exemplary embodiment of the present disclosure. Detailed Implementation

[0038] The present disclosure is further illustrated below by way of embodiments, but the present disclosure is not limited to the scope of the embodiments described herein.

[0039] The prefixes such as "first" and "second" used in this disclosure are merely for distinguishing different descriptive objects and do not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes used to distinguish descriptive objects in this disclosure does not constitute a limitation on the described objects. The description of the described objects is given in the claims or the context of the embodiments, and should not be construed as an unnecessary limitation. Furthermore, in the description of this embodiment, unless otherwise stated, "multiple" means two or more.

[0040] like Figure 1 As shown, an exemplary embodiment of this disclosure provides an epitaxial structure fabrication system, including a reaction chamber 101 and a first magnetic field generating device 102.

[0041] Reaction chamber 101 is used for the epitaxial growth of a magnetic layer of gyromagnetic ferrite on a semiconductor substrate. In specific implementations, MOCVD technology can be used for epitaxial growth. In practical applications, semiconductor substrates such as GaAs, GaN, SiC, InP, Si, or SiO2 can be used.

[0042] The first magnetic field generating device 102 is used to generate a magnetic field within the reaction chamber 101; wherein the magnetic field has a magnetic field component parallel to the surface of the semiconductor substrate. In practical applications, the magnetic field is a uniform magnetic field, and the semiconductor substrate rotates at a constant speed during the growth process. The fabrication system provided in this embodiment can efficiently grow high-quality magnetic layers of gyromagnetic ferrite, which have in-plane uniaxial magnetic anisotropy and an easy magnetization axis parallel to the surface of the semiconductor substrate.

[0043] In some examples, the first magnetic field generating device generates a magnetic field with an intensity range of 0.1T to 0.5T and a uniformity better than 10%. In some examples, the magnetic field is a constant magnetic field, a pulsed magnetic field, or a scanning magnetic field.

[0044] The preparation system provided in this embodiment integrates a first magnetic field generating device. By applying a magnetic field component parallel to the surface of the semiconductor substrate in the reaction chamber, it can affect the reaction and crystallization process of the reactant gas atoms in the reaction chamber, thereby changing the crystallization orientation. Even on untextured semiconductor substrates such as GaAs, GaN, SiC, InP, Si, and SiO2, it can induce in-plane uniaxial magnetic anisotropy, thereby growing a magnetic layer of gyromagnetic ferrite with strong crystallographic texture, and thus realizing the mass production of magnetic layers of gyromagnetic ferrite on the aforementioned semiconductor substrates.

[0045] The magnetic field applied by the first magnetic field generating device can suppress the convection of reactant and precursor gases, improve epitaxial uniformity, and enhance film quality. Specifically, during MOCVD vapor phase epitaxy, the Lorentz force suppresses thermal convection of charged reactant atoms on the semiconductor substrate surface. The magnetic field, by influencing surface mobility and nucleation barriers, can increase nucleation density, refine crystal grains, and improve the density of the magnetic layer. Compared to not applying a magnetic field, a magnetic layer closer to a single crystal can be grown.

[0046] The magnetic field applied by the first magnetic field generating device can also induce oriented growth. Specifically, for precursor gases and reactant gases with anisotropic magnetic susceptibility, when reacting in a magnetic field, the reaction products will undergo rotation or directional growth in order to make their easy magnetization axis parallel to the direction of the external magnetic field and reduce the static magnetic energy of the system. That is, the magnetic field will cause the grains to tend to align with a specific crystal axis along the direction of the magnetic field in order to minimize the magnetization energy. This allows magnetic layers with strong crystallographic texture to be induced to grow even on untextured semiconductor substrates such as GaAs and Si.

[0047] In some examples, the direction of the magnetic field is parallel to the surface of the semiconductor substrate. In other examples, the direction of the magnetic field is at an angle to the surface of the semiconductor substrate; that is, the magnetic field has not only a component parallel to the surface of the semiconductor substrate but also a component perpendicular to the surface of the semiconductor substrate. It should be noted that the magnetic field component perpendicular to the surface of the semiconductor substrate is detrimental to inducing in-plane uniaxial magnetic anisotropy and reduces the epitaxial growth rate of the magnetic layer of gyromagnetic ferrite.

[0048] In one optional implementation, the gyromagnetic ferrite is yttrium iron garnet ferrite (YIG), and its magnetic layer can be referred to as a YIG thin film. Specifically, the semiconductor substrate is placed in a reaction chamber, heated to the growth temperature, and a precursor gas and a reactant gas are introduced into the reaction chamber together to react and epitaxially grow a YIG thin film on the surface of the semiconductor substrate.

[0049] The precursor gas includes organic compounds of yttrium (Y) and iron (Fe). In some examples, the organic compound gas of Y is (tris)methylcyclopentadiene yttrium C. 18 H x Y, where x typically has values ​​of 9, 21, etc. In some examples, the organic compound gas of Y is tris(cyclopentadienyl)yttrium C. 15 H 15 Y. In some examples, the organic compound gas of Fe is isopropoxy iron C. a H b FeO c Here, typical values ​​for 'a' are 3, 9, etc., typical values ​​for 'b' are 8, 21, etc., and typical values ​​for 'c' are 1, 3, etc. In some examples, hydrogen, nitrogen, or other inert gases are used as the reactant gas.

[0050] In a specific example, using hydrogen (H2) as the reactant gas, the typical reaction formula is:

[0051] C 18 H x Y + C a H b FeO c + H2 = Y3Fe5O 12 + CO2 +H2O;

[0052] Among the reaction products, Y3Fe5O 12 This refers to YIG, typically a single crystal, grown on a semiconductor substrate in a layered structure. In the above reaction formula, the proportions of CO2 and H2O vary depending on the precursor and reactant gases, and both are discharged as waste gases from the MOCVD reaction chamber. If other reactant gases, such as nitrogen (N2), will generate other waste gases such as NO2. This is achieved by controlling the temperature of the reaction chamber, the temperature of the semiconductor substrate, and the precursor gas CO2. 18 H x Y and C a H b FeO c The growth rate of YIG can be controlled by the flow rate and pressure of the reactant gas H2, etc.

[0053] Figure 2 This illustrates a layered structure used in GaAs HBT epitaxial structures. Figure 2In the example shown, the substrate structure using GaAs HBT, from bottom to top, consists of: a semi-insulating GaAs substrate, an AlGaAs superlattice buffer layer, collector and sub-collector layers, a GaAs base layer, an InGaP emitter layer, a GaAs sub-emitter layer, a GaAs ohmic contact layer, a metal layer M1, an insulating layer, a magnetic metal buffer layer, a YIG magnetic layer Y1, a magnetic metal buffer layer, a metal layer M2, and a passivation layer. Figure 2 In this GaAs chip, the YIG magnetic layer Y1 is located between the metal layer and the substrate, requiring the fabrication of buffer layers between the magnetic layer and the metal layer, and between the magnetic layer and the substrate. If the lattice matching is good, buffer layers may not be necessary. The buffer layer between the magnetic layer and the metal layer serves as insulation; typically, it can be a Si3N4 insulating layer between the metal layers M1 and M2, fabricated using existing technology. The buffer layer between the magnetic layer and the substrate can be an AlGaAs superlattice buffer layer fabricated on a GaAs substrate using existing technology.

[0054] In one alternative implementation, during the growth of the magnetic layer of the gyromagnetic ferrite, a dopant is provided into the reaction chamber to epitaxially grow a magnetic layer of gyromagnetic ferrite containing doped elements. In specific implementations, the doping concentration can be precisely controlled by adjusting the pressures of the precursor gas, the reactant gas, and the dopant.

[0055] In this implementation, rare earth elements or other elements can be introduced for doping, typically such as cerium (Ce), terbium (Tb), gadolinium (Gd), lutetium (Lu), and dysprosium (Dy). 3+ , gallium Ga 3+ Aluminum (Al) 3+ Silicon (Si) 4+ Doping elements such as cobalt (Co), zinc (Zn), and scandium (Sc) require the addition of corresponding rare earth elements or other elemental dopants during the MOCVD reaction process.

[0056] To improve the performance of YIG thin films in superconductivity, magnetism, and other aspects, some examples use rare earth elements such as cerium (Ce), terbium (Tb), gadolinium (Gd), and lutetium (Lu) to replace Y; and in some examples, the rare earth element dysprosium (Dy) is used. 3+ , gallium Ga 3+ Aluminum (Al) 3+ Silicon (Si) 4+ Replace Fe.

[0057] In a specific example, introducing elemental silicon (Si) for doping requires adding a silicon-Si dopant during the reaction process, typically such as silane (Si). x H y In this mixture, x and y can have various ratios, such as x=1, y=4; x=2, y=6; x=3, y=8, etc., typically represented by silane SiH4. A typical reaction formula is:

[0058] C 18 H x Y + C a H b FeO c + SiH4 + H2 = Y3Fe5Si z O 12 + CO2 +H2O;

[0059] Where z is the doping concentration, typically 1 × 10⁻⁶. 18 / cm 3 .

[0060] In some examples, the introduction of rare earth elements for doping requires the addition of dopants such as alkane, methyl, or ethyl compounds as gases during the reaction process. For example, trimethyl rare earth reaction gas Ln(CH3)3 or triethyl rare earth reaction gas Ln(C2H5)3 can be added. Ln can be rare earth elements such as Sc, Y, La, and Lu.

[0061] In this implementation, the performance of the magnetic layer of the gyromagnetic ferrite can be optimized by doping with other elements. Typically, for microwave applications, cobalt (Co), zinc (Zn), and scandium (Sc) doping can improve the Curie temperature and permeability of YIG, thereby optimizing the high-frequency magnetic properties of the YIG thin film. Typically, for optoelectronic applications, Si... 4+ Doping can reduce absorption and improve the optical insertion loss of YIG thin films.

[0062] The following example illustrates the process of preparing YIG thin films using the above-described preparation system:

[0063] The GaAs substrate was placed in the reaction chamber and heated to the growth temperature of 600℃~700℃. A metal-organic source precursor gas of yttrium (Y), thulium (Tm), and iron (Fe), along with oxygen, was introduced to begin Tm doping. 3+ The epitaxial growth of YIG thin films, specifically Tm:YIG thin films. The precursor gas for Y is C. 15 H 15 The precursor gas for Y and Fe is C a H b FeO c The precursor gas for Tm can be tris(cyclopentadienyl)thulium(III)C 15 H 15 Tm.

[0064] Meanwhile, the first magnetic field generating device generates a 0.2 T magnetic field parallel to the substrate surface in the reaction chamber, wherein the substrate rotates at a speed of 20 rpm, which can make the grown Tm:YIG film uniform.

[0065] X-ray diffraction (Φ-scan) revealed that the Tm:YIG thin film grown in this example exhibits a strong in-plane texture. Vibrating sample magnetometer tests showed that the easy magnetization axis of the Tm:YIG thin film is parallel to the direction of the magnetic field applied during growth, demonstrating significant in-plane uniaxial magnetic anisotropy. However, if no magnetic field is applied during the growth of the Tm:YIG thin film, the resulting Tm:YIG thin film has an in-plane polycrystalline structure and is magnetically isotropic, with no obvious easy magnetization direction.

[0066] In one alternative implementation, the first magnetic field generating device includes a magnetic head, a magnetic yoke, and a coil wound around the magnetic yoke, the magnetic yoke being connected to a pair of magnetic poles of the magnetic head. The magnetic yoke penetrates the wall of the reaction chamber, such that one magnetic pole of the magnetic head is located inside the reaction chamber, and the other magnetic pole is located outside the reaction chamber.

[0067] In practice, relays, power switching transistors, and other switches can be used to control the connection and disconnection of the coil circuit. The magnetic field strength can be adjusted by regulating the current flowing through the coil. The larger the current, the stronger the magnetic field.

[0068] In a specific example, refer to Figure 3 and 4 The first magnetic field generating device includes a magnetic head, a ring-shaped magnetic yoke 14, and a coil 15 wound around the magnetic yoke 14. The magnetic yoke 14 is connected to the two magnetic poles of the magnetic head through a top flange 16 of the reaction chamber. The reaction chamber 101 of the fabrication system contains trays for placing semiconductor substrates 13, arranged in a ring on a base 12. There are six trays for placing semiconductor substrates 13, and correspondingly, six magnetic heads. The N pole 17 of all magnetic heads is located in the center of the base 12, and the S pole 18 is located outside the reaction chamber 101. During the epitaxial growth of the semiconductor substrate, the magnetic yoke remains stationary, while the base and trays undergo planetary motion. This causes the trays to continuously change their corresponding magnetic poles. After one rotation, each tray traverses six pairs of magnetic poles. Assuming the base rotates at 10 rpm, it can traverse six pairs of magnetic poles 10 times per minute. This example requires high uniformity of the magnetic field; typically, the uniformity needs to be within 90%.

[0069] In practical applications, precursor gases and reaction gases can be injected into the reaction chamber through multi-layer spray heads on the top flange of the reaction chamber to ensure uniform airflow distribution.

[0070] In an alternative implementation, the first magnetic field generating device is located inside the reaction chamber, specifically including a magnetic head, a magnetic yoke, and a coil wound around the magnetic yoke. The magnetic yoke connects to a pair of magnetic poles of the magnetic head. In a specific example, the reaction chamber contains trays for placing semiconductor substrates, arranged on a chassis. The number of magnetic heads corresponds to the number of trays, with the N poles of all magnetic heads positioned in the center of the chassis and the S poles positioned at the edges. During the epitaxial growth of the semiconductor substrate, the magnetic yoke and chassis rotate synchronously, while the trays rotate independently. This ensures that the relative positions of the magnetic yoke and chassis remain unchanged, and each tray corresponds to the same pair of magnetic poles. Therefore, the requirement for magnetic field uniformity is relatively low; typically, uniformity can be within 80%.

[0071] After growing the magnetic layer of gyromagnetic ferrite, it needs to be annealed in an annealing chamber to optimize the crystal structure and improve the magnetic properties of the magnetic layer. In one possible implementation, such as... Figure 5 As shown, the above-mentioned fabrication system also includes an annealing chamber 103 and a second magnetic field generating device 104. The annealing chamber 103 is used to anneal the semiconductor substrate to which the magnetic layer of the epitaxially grown gyromagnetic ferrite is grown, and the second magnetic field generating device 104 is used to generate a magnetic field perpendicular to the surface of the semiconductor substrate within the annealing chamber. Annealing is a key post-processing step for optimizing the performance of the magnetic layer. Its basic principle is to heat, hold, and cool the semiconductor substrate, using thermal energy to drive atomic diffusion and recombination, thereby eliminating defects, reducing stress, promoting recrystallization, or inducing specific functional properties.

[0072] In this implementation, the annealing chamber is equipped with a temperature regulating component configured to subject the semiconductor substrate to at least one temperature change process between a first temperature and a second temperature, where the first temperature is higher than the second temperature. In specific implementations, the temperature regulating component includes a heating component and a cooling component. Controlling the heating component allows the semiconductor substrate to heat up, and controlling the cooling component allows the semiconductor substrate to cool down. In some examples, the reaction chamber is equipped with a tray for placing the semiconductor substrate, and the temperature regulating component is disposed on the tray.

[0073] In some examples, the second magnetic field generating device includes a superconducting magnet comprising a superconducting coil and a liquid helium dewar, the superconducting coil being immersed in liquid helium contained within the liquid helium dewar. In specific implementations, the magnitude of the current flowing through the superconducting coil can be controlled by an excitation power supply to adjust the magnetic field strength.

[0074] The fabrication system provided in this implementation also integrates an annealing chamber and a second magnetic field generating device. A temperature control component located within the annealing chamber provides variable-temperature annealing for the semiconductor substrate. The alternation of high and low temperatures generates periodic, massive thermal stress. This thermal shock effect provides kinetic energy that strongly promotes the recombination of atoms and defects, effectively dismantling and weakening the existing in-plane magnetic anisotropy structure. Furthermore, the second magnetic field generating device, by applying a magnetic field perpendicular to the semiconductor substrate surface within the annealing chamber, can correct the easy magnetization axis of the magnetic layer, forcibly changing it from parallel to the semiconductor substrate surface to perpendicular to it. Therefore, the fabrication system using this implementation can achieve the entire process of fabricating a magnetic layer, from induced in-plane texture growth to achieving perpendicular magnetic anisotropy annealing.

[0075] It should be noted that the magnetic field strength generated by the second magnetic field generating device must be strong enough to overcome thermal disturbances and material anisotropy. Higher magnetic field strength results in a stronger driving force for domain magnetic moment alignment and a more significant effect. In some examples, the magnetic field strength generated by the second magnetic field generating device typically needs to be above 1T. Considering the increased coil volume due to the increased magnetic field, a magnetic field strength of 1T to 1.5T can be generated to meet the magnetic anisotropy reconstruction requirements of different magnetic layers. Furthermore, the magnetic field generated by the second magnetic field generating device needs to be highly uniform; otherwise, it will lead to non-uniform magnetic anisotropy and performance degradation. In some examples, the uniformity of the magnetic field within the semiconductor substrate is better than 20%. In some examples, the magnetic field generated by the second magnetic field generating device is a pulsed magnetic field. Utilizing the transient peak ultra-high magnetic field of the pulsed magnetic field to correct the easy magnetization axis can reduce the application time of the magnetic field.

[0076] In such Figure 6 In the example shown, the semiconductor substrate 51 is placed in an annealing chamber for variable temperature annealing, and a magnetic field with the direction of A1 is applied in the annealing chamber, causing the easy magnetization axis to change from being parallel to the surface of the semiconductor substrate 51 to being perpendicular to the surface of the semiconductor substrate 51. The direction of A1 is perpendicular to the surface of the semiconductor substrate 51.

[0077] In one optional implementation, the second temperature is lower than the Curie temperature of the magnetic layer, and the second magnetic field generating device is used to stop generating the magnetic field when the temperature of the semiconductor substrate cools to below a third temperature, wherein the third temperature is lower than the Curie temperature but higher than the second temperature. In specific implementations, the third temperature can be set according to the critical region of the Curie temperature; for example, the third temperature can be set to be 1K lower than the Curie temperature. In some examples, the Curie temperature Tc of the YIG thin film is approximately 560K or 287°C.

[0078] In this implementation, when the temperature of the semiconductor substrate drops below the Curie temperature of the magnetic layer, the ferromagnetic order of the magnetic layer begins to solidify, and the directional alignment of the magnetic moments is solidified and frozen in the vertical direction. When the temperature drops further below the third temperature, it indicates that the critical region of the Curie temperature Tc of the magnetic layer has been crossed, and at this time the second magnetic field generating device stops generating the magnetic field.

[0079] In some examples, the first temperature is 50°C to 100°C higher than the growth temperature of the magnetic layer. In some examples, the second temperature is 100°C to 200°C lower than the growth temperature of the magnetic layer. In some examples, the growth temperature of the magnetic layer is 600°C to 800°C.

[0080] In practical applications, the semiconductor substrate undergoing a temperature change process between a first temperature and a second temperature is insufficient to completely overcome the strong shape anisotropy and in-plane horizontal magnetic anisotropy. It needs to undergo this temperature change process multiple times for iterative repair. Each temperature change process is a training for the vertical magnetic anisotropy. After multiple trainings, the vertical magnetic anisotropy is continuously strengthened and accumulated, eventually stably overpowering other magnetic anisotropies and becoming dominant.

[0081] In some examples, the semiconductor substrate undergoes 2 to 20 of the above-mentioned temperature change processes. Figure 6 This is used to illustrate the temperature-time curve of a YIG thin film undergoing variable temperature annealing under a magnetic field. Figure 7 This is used to illustrate the magnetic field strength-time curve of a YIG thin film undergoing variable temperature annealing under a magnetic field.

[0082] The process of the above-mentioned variable temperature annealing treatment is described in detail below:

[0083] First, the magnetic domains are activated in a high-temperature environment. After the semiconductor substrate has grown, it is immediately placed in an annealing chamber. The temperature in the annealing chamber is briefly higher than the growth temperature; it cannot be too high, otherwise it will damage the thin film structure. The annealing chamber must not contain reactive or precursor gases, but it can contain annealing auxiliary gases such as oxygen. In this high-temperature environment, the thin film atoms acquire high migration capabilities, allowing for deep repair of crystal defects before magnetic domain rearrangement and changes in the easy magnetization axis. This typically involves reducing the pinning effect of dislocations and grain boundaries on the domain walls, weakening the various binding forces that maintain the existing in-plane magnetic anisotropy, and enabling the magnetic domains to move.

[0084] Next, a magnetic field is applied during the high-temperature stage to rearrange the magnetic domains and the easy magnetization axis. After activating the magnetic domains, a second magnetic field generating device is used to apply a magnetic field perpendicular to the semiconductor substrate surface to correct the easy magnetization axis of the magnetic layer. This perpendicular magnetic field can be generated by magnetic ions in the magnetic layer, such as Fe. 3+Once the reconfiguration energy is provided to activate the magnetic moments, the magnetic domains can break free from the constraints of their original magnetic moment orientation and be forcibly changed from parallel to perpendicular. After this stage is completed, the easy magnetization axis of the magnetic layer is in a direction perpendicular to the surface of the semiconductor substrate, but it is not stable and is in a metastable state.

[0085] The easy magnetization axis of the magnetic layer is then cured during the cooling phase. During the cooling phase, the direction and intensity of the vertical magnetic field applied by the second magnetic field generating device must remain constant, especially when the temperature drops to the critical region of the Curie temperature Tc, so that the easy magnetization axis will be cured during the cooling process.

[0086] As the temperature of the semiconductor substrate decreases further, moving away from the Curie temperature Tc, the easy magnetization axis of the magnetic layer gradually solidifies, but it is still not stable enough. Some magnetic domains may return to the horizontal direction or deviate from the vertical direction. Therefore, it is necessary to repeat the above process to gradually solidify the magnetic domains and the easy magnetization axis, and finally change the easy magnetization axis from being parallel to the surface of the semiconductor substrate to being perpendicular to the surface of the semiconductor substrate, thereby completely changing the magnetic properties of the magnetic layer.

[0087] Therefore, the above-mentioned variable-temperature annealing process can also be called a magnetically controlled variable-temperature cycle. The following examples compare and contrast the magnetically controlled variable-temperature cycle with isothermal annealing:

[0088] First, samples were prepared by epitaxially growing three different types of YIG thin films on a GaAs substrate, resulting in samples A, B, and C. The easy magnetization axes of all samples were parallel to the substrate surface. Specifically:

[0089] Sample A: Undoped pure YIG thin film;

[0090] Sample B: Doped with Tm 3+ YIG thin film (Tm:YIG); wherein, Tm 3+ Doping with YIG can increase the magnetic anisotropy of YIG thin films;

[0091] Sample C: Al-doped 3+ YIG thin film (Al:YIG); wherein, Al 3+ Partial Fe Substitution 3+ This can reduce the saturation magnetization Ms, thereby weakening the in-plane magnetic anisotropy and indirectly promoting the reversal of the easy magnetization axis.

[0092] Magnetically controlled variable temperature cycle: Ten complete cycles from 700°C to 500°C are performed in an oxygen atmosphere. Each cycle includes: heating to 700°C at a rate of 50°C / min and holding for 10 minutes; cooling to 500°C at a rate of 50°C / min and holding for 5 minutes; and applying a magnetic field perpendicular to the substrate surface in the annealing chamber.

[0093] The samples were treated with magnetically controlled variable temperature cycling and isothermal annealing at 700℃, respectively. The performance comparison results are shown in Table 1. In the table, Ms is the saturation magnetization in kA / m, Hk is the perpendicular anisotropic field in Oe, and ΔH is the ferromagnetic resonance linewidth in Oe.

[0094] Table 1

[0095]

[0096] Referring to Table 1, for sample A, isothermal annealing can only improve crystallization to a limited extent and cannot provide any magnetic anisotropy guidance. The easily magnetized axis maintains the in-plane orientation during growth. Magnetically controlled variable temperature cycling can effectively repair defects and achieve strong perpendicular magnetic anisotropy and extremely low loss in conjunction with the magnetic field.

[0097] For sample B, during isothermal annealing, Tm 3+ The magnetic anisotropy is randomly distributed, making it impossible to form macroscopic perpendicular magnetic anisotropy, and the defect leads to high losses; Tm 3+ The magnetic anisotropy and the magnetically controlled variable temperature cycle work together perfectly to achieve extremely high Hk while maintaining low loss.

[0098] For sample C, during isothermal annealing, low Ms cannot spontaneously lead to perpendicular magnetic anisotropy, and the easy magnetization axis is still dominated by shape anisotropy, which is in-plane direction; during magneto-controlled variable temperature cycling, low Ms combined with high-quality crystal structure, under the guidance of magnetic field, stable perpendicular magnetic anisotropy and excellent microwave performance are achieved.

[0099] In one optional implementation, the fabrication system further includes an automated transfer device for transferring the semiconductor substrate from the reaction chamber to the annealing chamber. In another optional implementation, the automated transfer device is further configured to transfer the annealing chamber to the receiving space of the second magnetic field generating device, so that the annealing chamber is placed in the magnetic field generated by the second magnetic field generating device.

[0100] In some examples, the semiconductor substrate is transferred from the reaction chamber to the annealing chamber for variable-temperature annealing in a vacuum or protective atmosphere to effectively avoid oxidation and contamination caused by atmospheric exposure, maintain interface cleanliness and integrity, reduce the ferromagnetic resonance linewidth of the magnetic layer, increase saturation magnetization, and obtain more uniform magnetic properties.

[0101] In some examples, the automated transfer device includes a robotic arm and a conveyor. The robotic arm transfers the semiconductor substrate from the reaction chamber to the annealing chamber, and the conveyor transfers the annealing chamber to the receiving space of the second magnetic field generating device. In some examples, the conveyor includes a drive mechanism and a conveyor belt. Under the action of the drive mechanism, the connection between the annealing chamber and the reaction chamber is disconnected, and the annealing chamber moves with the conveyor belt to the receiving space of the second magnetic field generating device, so that the annealing chamber is placed in the magnetic field generated by the second magnetic field generating device. In some examples, the robotic arm is a magnetically coupled six-axis robotic arm with a positioning accuracy of ±0.1 mm. In some examples, the drive mechanism is a pneumatic push rod.

[0102] Figure 9 This is a schematic diagram illustrating a partial structure of a specific fabrication system. Figure 9 In the preparation system shown, reaction chamber 101 and annealing chamber 103 are connected by flange 32. Semiconductor substrate 13 is placed on tray 31, and tray 31 is equipped with a temperature control component. A robotic arm 105 is used to transfer the semiconductor substrate 13 from reaction chamber 101 to annealing chamber 103. When the robotic arm 105 has transferred all semiconductor substrates 13 from reaction chamber 101 to annealing chamber 103, the flange 32 between reaction chamber 101 and annealing chamber 103 is disconnected under the action of the transfer device, and annealing chamber 103 is transferred to the receiving space of the second magnetic field generating device 104. It should be noted that... Figure 9 The first magnetic field generating device is not shown.

[0103] The magnetic layer of the gyromagnetic ferrite mass-produced using the MOCVD process disclosed in this embodiment can be integrated with standard semiconductor processes, such as photomasks and photolithography, to mass-produce circuit patterns with complex shapes.

[0104] An exemplary embodiment of this disclosure provides an epitaxial structure prepared by the above-described preparation system. The magnetic layer in the epitaxial structure of this embodiment has a low saturation magnetization, thus requiring little or no external excitation of the magnetic field during application.

[0105] In some examples, the epitaxial structure fabricated using the above-described fabrication system includes a semiconductor substrate and a magnetic layer of gyromagnetic ferrite epitaxially grown on the semiconductor substrate. The magnetic layer of gyromagnetic ferrite exhibits perpendicular magnetic anisotropy, and its easy magnetization axis is perpendicular to the surface of the semiconductor substrate. The epitaxial structure of this example can be used to fabricate microwave devices such as microwave filters, microwave oscillators, microwave circulators, and microwave isolators, and is widely used in communication and radar systems. The epitaxial structure of this example can also be used to fabricate magneto-optical devices such as optical isolators, magneto-optical circulators, and magneto-optical modulators, and is widely used in fiber optic communication and laser systems. The near-single-crystal high-quality gyromagnetic ferrite magnetic layer in the epitaxial structure can effectively reduce the insertion loss of microwave or magneto-optical devices.

[0106] An exemplary embodiment of this disclosure provides a semiconductor device including the epitaxial structure described above. In some examples, the semiconductor device is a magnetic field sensor, a microwave device, or a magneto-optical device. The semiconductor device provided in this embodiment has advantages such as high integration, high performance, and high reliability.

[0107] While specific embodiments of this disclosure have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this disclosure, but all such changes and modifications fall within the scope of protection of this disclosure.

Claims

1. A system for fabricating epitaxial structures, characterized in that, include: The reaction chamber is used for the epitaxial growth of a magnetic layer of gyromagnetic ferrite on a semiconductor substrate; A first magnetic field generating device is used to generate a magnetic field in the reaction chamber; wherein the magnetic field has a magnetic field component parallel to the surface of the semiconductor substrate.

2. The preparation system according to claim 1, characterized in that, The direction of the magnetic field is parallel to the surface of the semiconductor substrate.

3. The preparation system according to claim 1, characterized in that, The first magnetic field generating device includes a magnetic head, a magnetic yoke, and a coil wound on the magnetic yoke, wherein the magnetic yoke is connected to a pair of magnetic poles of the magnetic head; The magnetic yoke penetrates the wall of the reaction chamber, such that one magnetic pole of the magnetic head is located inside the reaction chamber and the other magnetic pole is located outside the reaction chamber.

4. The preparation system according to claim 1, characterized in that, The preparation system also includes an annealing chamber and a second magnetic field generating device; The annealing chamber is used to anneal the semiconductor substrate with an epitaxially grown magnetic layer of ferromagnetic ferrite. The annealing chamber is equipped with a temperature regulating component, which is configured to cause the semiconductor substrate to undergo at least one temperature change process between a first temperature and a second temperature, wherein the first temperature is higher than the second temperature. The second magnetic field generating device is used to generate a magnetic field in the annealing chamber that is perpendicular to the surface of the semiconductor substrate.

5. The preparation system as described in claim 4, characterized in that, The second magnetic field generating device includes a superconducting magnet, which includes a superconducting coil and a liquid helium dewar, wherein the superconducting coil is immersed in liquid helium contained in the liquid helium dewar.

6. The preparation system according to claim 4, characterized in that, The reaction chamber is provided with a tray for placing the semiconductor substrate, and the temperature regulation component is located on the tray.

7. The preparation system according to any one of claims 4-6, characterized in that, The preparation system also includes an automatic transfer device for transferring the semiconductor substrate from the reaction chamber to the annealing chamber.

8. The preparation system according to claim 7, characterized in that, The automatic transfer device is also used to transfer the annealing chamber to the receiving space of the second magnetic field generating device, so that the annealing chamber is in the magnetic field generated by the second magnetic field generating device.

9. An epitaxial structure, characterized in that, The epitaxial structure is prepared by the preparation system according to any one of claims 1-8.

10. A semiconductor device, characterized in that, Includes the epitaxial structure as described in claim 9.

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