Aluminum oxide film production method and Josephson junction production method

Abstract

The application provides an aluminum oxide film preparation method and a Josephson junction preparation method, and relates to the technical field of semiconductors. The aluminum oxide film preparation method comprises the following steps: providing a process chamber, wherein the process chamber is a vacuum chamber, a substrate with a first aluminum film layer on the upper surface is loaded on the base of the process chamber, and the temperature of the base is (25-50) DEG C; O2 is introduced into the process chamber, the pressure in the chamber is kept at a preset pressure, and the thickness of the aluminum oxide film generated on the surface of the first aluminum film layer is kept unchanged; wherein the preset pressure is (25-100) mTorr. The preparation method can obtain an aluminum oxide film with high controllability and uniformity of thickness, accurate stoichiometric ratio, low defects, and high quality.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for preparing alumina thin films and a method for preparing Josephson junctions. Background Technology

[0002] Alumina (AlO) x Thin films, with their excellent insulation properties, chemical stability, and atomic-level flatness, have become indispensable core functional materials in advanced semiconductor and quantum technology fields, with applications covering multiple cutting-edge industries such as superconducting quantum computing, DRAM memory, MRAM magnetic random access memory, and GaN / SiC power semiconductors. In particular, in the field of superconducting quantum computing, the Josephson junction, as the core unit of superconducting qubits, relies heavily on the performance of its intermediate ultrathin AlO₂ layer. x The mass of the tunnel barrier layer, the AlO x Thin films require high precision in controlling quality aspects such as thickness, stoichiometry, and defects.

[0003] In related technologies, low-temperature thermal oxidation or plasma-enhanced oxidation methods are generally used to prepare AlO. x Thin films, however, both preparation methods affect AlO₂ x The thickness control precision of the thin films is relatively low, and the prepared AlO₂₃ is also low. x The stoichiometry and defects of the thin film cannot be guaranteed.

[0004] Therefore, how to prepare alumina thin films with high thickness control accuracy and quality is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing alumina thin films and a Josephson junction, so as to solve the technical problem of how to prepare alumina thin films with high thickness control accuracy and quality.

[0006] To address the above problems, the present invention provides a method for preparing alumina thin films, comprising: A process chamber is provided, which is a vacuum chamber. A substrate with a first aluminum film layer on its upper surface is mounted on a base of the process chamber, and the temperature of the base is [25°C, 50°C]. O2 is introduced into the process chamber, and the chamber pressure is maintained at a preset pressure until the thickness of the aluminum oxide film formed on the surface of the first aluminum film layer remains unchanged; wherein, the preset pressure is [25 mTorr, 100 mTorr].

[0007] The present invention also provides a method for preparing Josephson knots, comprising: The substrate is placed on the base of the deposition chamber for deposition to form a first aluminum film layer as the lower electrode on the upper surface of the substrate. The deposition chamber is used as a process chamber to perform the above method to form an aluminum oxide film on the upper surface of the first aluminum film layer; After evacuating the deposition chamber, the substrate is deposited to form a second aluminum film layer as the upper electrode on the upper surface of the alumina film.

[0008] The alumina thin film preparation method provided by this invention limits the reaction temperature of the first aluminum film layer by setting the base temperature of the process chamber and introducing O2 into the process chamber to form an oxygen atmosphere, thereby enabling the surface of the first aluminum film layer to form an alumina thin film based on the Cabrera-Mott principle. During the alumina thin film growth process, the thickness growth of the alumina thin film can self-limit and stop, and its final thickness is only related to two highly controlled parameters: the reaction temperature and the chamber pressure formed by oxygen. Furthermore, the method has the ability to automatically homogenize the thickness during growth, thereby improving the controllability of the alumina thin film thickness and obtaining an alumina thin film with high thickness accuracy and uniformity. Simultaneously, the alumina thin film growth process also has the ability to suppress oxygen vacancies and self-limit to the thickness at which the stoichiometric ratio is most stable. Moreover, the low-temperature reaction and absence of high-energy ion bombardment damage result in an alumina thin film with an accurate stoichiometric ratio and low defects, ensuring high quality.

[0009] The Josephson junction preparation method provided by this invention, using the above-mentioned alumina thin film preparation method, can prepare a high-quality alumina thin film with high controllability and uniformity of thickness, accurate stoichiometry, and low defects. At the same time, through in-situ integration process, the first aluminum film layer, the alumina film layer, and the second aluminum film layer are prepared in one step in the same deposition chamber without moving the substrate, which can conveniently prepare the Josephson junction and effectively avoid the damage to the quality of each film layer caused by contamination during the transfer process, thereby further ensuring the quality of each film layer and ensuring the quality of the obtained Josephson junction. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of the present invention, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0011] Figure 1 This is a first flowchart of the alumina thin film preparation method provided in an embodiment of the present invention; Figure 2This is a second flowchart of the alumina thin film preparation method provided in an embodiment of the present invention; Figure 3 A flowchart of the Josephson knot preparation method provided in an embodiment of the present invention; Figure 4a TEM image of a Josephson junction prepared by the Josephson junction preparation method provided in the embodiment of the present invention; Figure 4b EDS morphology image of a Josephson junction prepared by the method for preparing a Josephson junction according to an embodiment of the present invention; Figure 4c The elemental composition energy spectrum distribution of the alumina thin film in the Josephson junction prepared by the Josephson junction preparation method provided in the embodiments of the present invention is shown. Figure 5 EDS morphology images of the alumina film at three locations—the center, half radius, and edge—of the Josephson junction prepared by the method provided in the embodiments of the present invention. Detailed Implementation

[0012] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0014] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0015] In related technologies, low-temperature thermal oxidation or plasma-enhanced oxidation methods are generally used to prepare alumina thin films. In the low-temperature thermal oxidation method, a substrate with an aluminum film layer is placed in an oxidation furnace at a temperature higher than 100°C to cause an oxidation reaction on the surface of the aluminum film layer to form an alumina thin film. However, at this temperature, the grains of the aluminum film layer are prone to grow, leading to defects. The uniformity of the oxidation reaction in different regions of the aluminum film layer is poor, and the thickness of the alumina film layer is related to parameters with relatively weak controllability, such as the oxidation reaction rate and oxidation reaction time. As a result, this preparation method has poor controllability over the thickness of the alumina film, and the quality of the alumina film, such as thickness uniformity, stoichiometry, and defects, is also low.

[0016] Plasma-enhanced oxidation typically uses radio frequency power to generate O2 plasma, which is then used to oxidize aluminum film layers with active oxygen atoms to form aluminum oxide films. Although the process temperature is relatively low, the plasma can cause bombardment damage to the generated aluminum oxide films during the oxidation process. Furthermore, the active oxygen atoms have high energy and can easily penetrate the aluminum film layer, leading to over-oxidation. As a result, the thickness control of the aluminum oxide film is poor, and the thickness uniformity, stoichiometry, and defects of the aluminum oxide film are also relatively low.

[0017] This invention provides a method for preparing an alumina thin film. By setting the base temperature of the process chamber to limit the reaction temperature of the first aluminum film layer, and by introducing O2 into the process chamber to form an oxygen atmosphere, an alumina thin film can be formed on the surface of the first aluminum film layer based on the Cabrera-Mott principle. During the growth of the alumina thin film, aluminum ions at the interface of the first aluminum film layer move under the drive of the built-in electrostatic field of the alumina thin film and meet with oxygen ions to form alumina. The strength of the built-in electrostatic field and its driving rate for aluminum and oxygen ions are negatively correlated with the thickness of the alumina thin film. The thickness growth process is self-limiting, with the final thickness dependent only on two highly controlled parameters: reaction temperature and chamber pressure for oxygen formation. Furthermore, it possesses the ability to automatically homogenize the thickness during growth, thereby improving the controllability of the alumina film thickness and yielding alumina films with high thickness accuracy and uniformity. Simultaneously, the alumina film growth process also exhibits the ability to suppress oxygen vacancies and self-limit to the thickness at which the stoichiometric ratio is most stable. Moreover, the low-temperature reaction and absence of high-energy ion bombardment damage result in alumina films with accurate stoichiometry and low defects, ensuring high quality. The alumina film preparation method provided by the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] Figure 1 This is a first flowchart of the alumina thin film preparation method provided in an embodiment of the present invention.

[0019] like Figure 1 As shown, the method for preparing the alumina thin film includes the following steps: S102 provides a process chamber, which is a vacuum chamber. A substrate with a first aluminum film layer on its upper surface is mounted on the base of the process chamber, and the temperature of the base is [25°C, 50°C].

[0020] The process chamber is set as a vacuum chamber to reduce contamination of the first aluminum film layer and the subsequently formed alumina film by residual gases and impurities. Specifically, the substrate with the first aluminum film layer can be placed on the base of the process chamber before evacuating it to create a vacuum chamber; alternatively, the process chamber can be evacuated first before placing the substrate with the first aluminum film layer on the base. The process chamber is evacuated to a background vacuum level of [1×10⁻⁶]. -8 Torr, 1×10 -7 Torr], preferably [1×10] -8 Torr, 5×10 -8 Torr).

[0021] The temperature of the base is set to a relatively low temperature [25℃, 50℃], preferably [30℃, 45℃], and more preferably [35℃, 40℃]. Specifically, the temperature of the base can be any temperature value of 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, and fluctuating above or below 0.5℃. The temperature of the substrate and the first aluminum film layer is approximately equal to that of the base under the heating effect of the base.

[0022] S104 introduces O2 into the process chamber, maintaining the chamber pressure at a preset pressure until the thickness of the aluminum oxide film formed on the surface of the first aluminum film layer remains unchanged.

[0023] O2 is introduced into the vacuum process chamber, and the chamber pressure is maintained at a preset pressure through coordinated control using an O2MFC (Mass Flow Controller) and a vacuum swing valve. The temperature of the first aluminum film layer is limited to a relatively low range (25℃, 50℃). This results in a lower thermal oxidation reaction rate between the first aluminum film layer and O2, leading to a more Cabrera-Mott self-limiting electrostatically driven oxidation reaction. After a very thin alumina base film is formed on the surface of the first aluminum film layer upon contact with O2, electrons can tunnel from the first aluminum film layer to the O atoms on the surface of the alumina base film, forming negatively charged O atoms, due to the much higher electronegativity of O atoms compared to Al atoms. 2- Ions, and positively charged Al is formed on the surface of the first aluminum film layer. 3+Ions are generated, thereby forming a built-in electrostatic field within the alumina-based film. This built-in electrostatic field can drive the Al atoms on the surface of the first aluminum film layer. 3+ Ions diffuse from the aluminum (Al) / alumina (Al2O3) interface to the surface of the alumina substrate film, and react with O on the surface of the alumina substrate film. 2- Ions combine to form aluminum oxide (Al2O3).

[0024] As the reaction continues, the thickness of the alumina-based film increases, and correspondingly, the electrostatic potential difference across the alumina-based film gradually decreases, resulting in a gradual decrease in the strength of the built-in electrostatic field. 3+ The diffusion rate of ions decreases exponentially, and the oxidation rate decreases rapidly accordingly. The thickness increase of the alumina-based film slows significantly, eventually approaching the limiting saturation thickness. 3+ When the diffusion rate of ions approaches zero, the self-limiting electrostatically driven oxidation reaction approaches cessation. Specifically, when the growth rate of the alumina film thickness is less than a preset thickness threshold, such as 0.001 nm / min to 0.002 nm / min, it is considered that the thickness of the alumina film has reached a critical value, and its thickness remains unchanged, not increasing with the extension of oxidation time. This achieves self-limiting cessation of alumina film thickness growth, resulting in an alumina film with constant thickness. That is, the constant thickness of the alumina film in the embodiments of the present invention does not mean absolute constancy, but rather that it approaches the limit saturation thickness, meaning that the thickness change is minimal and negligible, and the thickness remains relatively constant.

[0025] The empirical formula for calculating the critical thickness x of alumina thin films formed by oxidation based on the Cabrera-Mott principle is as follows: ; in, ; ; In the formula, x is the critical thickness of the alumina film, in nm and dimensionless; k1 is a kinetic parameter related to temperature and built-in electrostatic field, in nm. 2 Furthermore, it is dimensionless; k2 is a constant related to temperature and oxygen partial pressure, with units of s. -1 And dimensionless; t is oxidation time, in seconds, and dimensionless; T is reaction temperature, in K, and dimensionless; V M k represents the electrostatic potential difference across the alumina-based film, expressed in V and dimensionless. B Boltzmann constant, in kg·m 2 ·s -2 ·K -1 Furthermore, it is dimensionless.

[0026] It is evident that the critical thickness of the alumina film depends solely on the reaction temperature and oxygen partial pressure—that is, the temperature of the substrate and the chamber pressure formed by oxygen within the process chamber—and is independent of the oxidation time. Consequently, by controlling the substrate temperature and chamber pressure, the thickness of the alumina film can be precisely controlled, thereby achieving precise control over the alumina film thickness and improving its controllability. Furthermore, the thickness no longer changes after the oxidation time exceeds the critical time, indicating a wide process window and good repeatability. Specifically, the control accuracy of the alumina film thickness can reach ±0.03 nanometers.

[0027] Meanwhile, during the formation of the alumina thin film based on the Cabrera-Mott principle, on the one hand, the field strength of the built-in electrostatic field is negatively correlated with the thickness of the alumina base film; therefore, the field strength is even smaller at the micro-protrusions of the alumina base film, where Al... 3+ Ions have weaker migration ability and slower oxidation reactions; however, the electric field strength is greater at the micro-recesses of the alumina-based film, where Al... 3+ The ions have stronger migration capabilities and faster oxidation reactions, thus achieving automatic homogenization of the alumina-based film thickness and improving the uniformity of the formed alumina film thickness; on the other hand, Al 3+ Ions and O -2 Driven by the internal electrostatic field, ions can self-limit and stop at the thickness where the stoichiometry is most stable, making the ratio of Al atoms to O atoms approach 2:3. On the other hand, oxygen vacancies in the alumina base film migrate and annihilate towards the metal side under the driving force of the electric field, resulting in a lower vacancy concentration and a denser alumina film. Furthermore, the low-temperature reaction and the atomic migration temperature within the alumina film make it less prone to dislocations, grain boundaries, and thermal stress cracks. In addition, there is no plasma bombardment damage to the generated alumina film, thereby improving the accuracy of the stoichiometry of the generated alumina film, reducing defect density, and improving the quality of the alumina film.

[0028] In this embodiment of the invention, the preset pressure can be [25 mTorr, 100 mTorr], preferably [30 mTorr, 60 mTorr], and more preferably [40 mTorr, 50 mTorr]. Specifically, the preset pressure can be any pressure value of 25 mTorr, 30 mTorr, 35 mTorr, 40 mTorr, 45 mTorr, 50 mTorr, 55 mTorr, 60 mTorr, 65 mTorr, 70 mTorr, 75 mTorr, 80 mTorr, 85 mTorr, 90 mTorr, 95 mTorr, or fluctuating up or down by 2 mTorr.

[0029] The preset pressure for controlling oxygen formation to be less than 100 mTorr has the following effects: 1) Under low pressure, there is no viscous flow or edge effect and turbulence in the molecular flow within the process chamber, which can avoid pressure gradient and improve the uniform distribution of oxygen molecules; 2) When the oxygen pressure is less than 100 mTorr, the oxidation rate is slower, and oxygen molecules have enough time to diffuse into the deep trenches of the Al film grain boundaries, fill grain boundary defects, and improve the quality of alumina thin films and Josephson junction devices.

[0030] In this embodiment of the invention, the duration of introducing O2 into the process chamber is [30 min, 120 min], preferably [45 min, 90 min], and more preferably [55 min, 70 min]. Specifically, the duration can be any duration of 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, 120 min, or fluctuating by 2 min, to ensure that the oxidation reaction proceeds fully, reduce the oxygen vacancy density, and ensure the uniformity and quality of the generated alumina film; at the same time, it reduces the time wastage caused by excessively long oxidation time, ensuring production efficiency.

[0031] The purity of the O2 introduced into the process chamber is ≥99.999%, preferably high-purity O2 of ≥99.9999%, in order to reduce the pollution caused by impurities carried by the O2 itself being introduced into the process chamber.

[0032] In this embodiment of the invention, before introducing O2 into the process chamber, the method further includes a gas purging step: cyclically performing the following operations: continuously introducing purge gas into the process chamber for a first preset duration, and evacuating the process chamber to become a vacuum chamber.

[0033] Before introducing O2 into the process chamber, a gas purging step is first performed on the process chamber. Step a is performed in sequence: continuously introducing purge gas into the process chamber for a first preset time to fully replace the residual gas and impurities in the process chamber; step b is evacuating the process chamber to become a vacuum chamber to remove residual water vapor, hydrocarbons and other impurities in the process chamber, reducing their incorporation into the aluminum film layer and alumina film. This prevents the alumina film from deviating from the ideal stoichiometry, significantly increasing the defect density, and greatly increasing the number of two-level systems, ultimately severely degrading the superconducting quantum bit performance of the Josephson junction.

[0034] In step a, the first preset time can be [10s, 30s], preferably [15s, 25s], and more preferably 20s. Specifically, it can be any time of 10s, 15s, 20s, 25s, 30s, or fluctuating by 2s, to ensure sufficient replacement of residual gas and impurities in the process chamber and reduce ineffective time consumption, thus ensuring production efficiency. In step a, the purging gas can specifically be high-purity Ar gas with a purity ≥99.999%, preferably ≥99.9999%, to reduce impurities introduced by the purging gas and ensure effective purging and washing of the process chamber.

[0035] In step b, the chamber pressure after evacuation of the process chamber is [1×10]. -8 Torr, 1×10 -7 Torr], preferably [1×10] -8 Torr, 5×10 -8 Torr] is used to ensure the effective removal of residual water vapor, hydrocarbons and other impurities in the process chamber.

[0036] In this process, steps a and b are repeated ≥10 times to fully remove residual water vapor, hydrocarbons and other impurities in the chamber; and the gas washing step ends with step b, making the process chamber a vacuum chamber; specifically, the substrate with the first aluminum film layer can be placed on the base of the process chamber before the gas washing step is performed; or the gas washing step can be performed first, and then the substrate with the first aluminum film layer can be placed on the base of the process chamber.

[0037] In this embodiment of the invention, after the substrate is placed on the base and preheated for at least a second preset time, O2 is introduced into the process chamber. After the substrate is placed on the base, it is preheated for at least the second preset time to ensure that the temperature of the substrate and the aluminum film layer thereon has reached the temperature of the base, and that the temperature uniformity of each region of the substrate is high. Subsequently, O2 is introduced into the process chamber to ensure the uniformity of the Cabrera-Mott self-limiting electrostatically driven oxidation reaction in each region of the aluminum film layer, thereby further improving the thickness uniformity of the generated alumina film.

[0038] Specifically, the second preset duration can be [20s, 40s], preferably [25s, 35s], and more preferably 30s. Specifically, it can be any duration of 20s, 25s, 30s, 35s, 40s, or fluctuating up or down by 2s, to ensure the uniformity of preheating of the substrate and the aluminum film layer on it by the base, and to reduce the reduction in production efficiency caused by the ineffective consumption of time.

[0039] Figure 2 This is a second flowchart of the alumina thin film preparation method provided in an embodiment of the present invention.

[0040] like Figure 2As shown, the method for preparing the alumina thin film includes the following steps: S202 performs a gas purging step on the process chamber: cyclically performs the following operations: continuously introduces purge gas into the process chamber for a first preset duration, and evacuates the process chamber to become a vacuum chamber.

[0041] S204 transfers the substrate with the first aluminum film layer on the upper surface to the base of the process chamber, adjusts the temperature of the base to [25°C, 50°C], and preheats for a second preset time.

[0042] S206 introduces O2 into the process chamber, maintaining the chamber pressure at a preset pressure until the thickness of the aluminum oxide film formed on the surface of the first aluminum film layer remains unchanged.

[0043] Figure 3 This is a flowchart of a Josephson junction preparation method provided in an embodiment of the present invention.

[0044] like Figure 3 As shown, the Josephson junction preparation method includes the following steps: S302 places the substrate on the base of the deposition chamber for deposition processing to form a first aluminum film layer as the lower electrode on the upper surface of the substrate.

[0045] A physical vapor deposition (PVD) chamber is used to deposit a substrate to form a first aluminum film layer on its upper surface. The first aluminum film layer serves as the lower electrode of the Josephson junction, and its thickness can be approximately 100 nm.

[0046] The S304 deposition chamber serves as the process chamber for performing the aforementioned alumina thin film preparation method to form an alumina thin film on the upper surface of the first aluminum film layer.

[0047] In step S302, the substrate on which the first aluminum film layer is formed on the upper surface continues to be held on the base of the deposition chamber, which serves as the process chamber in step S102. After step S302, the process chamber is evacuated or a gas purging step is performed to make the deposition chamber a vacuum chamber. Then, steps S102 and S104 are performed to oxidize and form an aluminum oxide film with the target thickness, high thickness uniformity, accurate stoichiometry, and few defects on the upper surface of the first aluminum film layer. This aluminum oxide film serves as the tunnel barrier layer of the Josephson junction, which can ensure the quality of the Josephson junction.

[0048] After vacuuming the deposition chamber, S306 performs a deposition process on the substrate to form a second aluminum film layer as the upper electrode on the upper surface of the alumina film.

[0049] After the oxidation treatment in step S304 is completed, the O2 supply can be stopped immediately, and the process chamber can be evacuated or a gas purging step can be performed to make the deposition chamber have a vacuum degree of less than 1×10⁻⁶.-7 The vacuum chamber of the Torr deposition chamber; the substrate remains on the base of the deposition chamber without movement, and step S306 is continued for deposition to form a second aluminum film layer on the upper surface of the alumina film. The second aluminum film layer serves as the upper electrode of the Josephson junction, and its specific thickness can be [100nm, 200nm]. Thus, through in-situ integration, the first aluminum film layer, the alumina film layer, and the second aluminum film layer are prepared in one step in the same deposition chamber without moving the substrate, which conveniently prepares the Josephson junction and can effectively avoid the damage to the quality of each film layer caused by contamination during the transfer process, thereby further ensuring the quality of each film layer and the quality of the obtained Josephson junction.

[0050] Specifically, both the first and second aluminum film layers can use Ar gas as the process gas to bombard and sputter the aluminum target material; after the deposition in step S306 is completed, the substrate is cooled to room temperature and transferred out through a vacuum transport system.

[0051] The Josephson junction fabrication method provided in this embodiment has strong equipment compatibility. It can be carried out based on existing physical vapor deposition equipment without the need for additional customized equipment. It can be directly integrated into existing semiconductor mass production lines, such as 12-inch semiconductor mass production lines, thereby significantly reducing mass production costs and equipment investment.

[0052] In this embodiment of the invention, the temperature of the base is [39.5℃, 40.5℃], the preset pressure is [49.5mTorr, 50.5mTorr], and the duration of introducing O2 into the process chamber is [45min, 90min]. In step 304, the temperature of the substrate and its aluminum film layer is 40±0.5℃ (step S102); the chamber pressure is 50±0.5mTorr, and the duration of introducing O2 into the process chamber is 45~90min (step S104), which can prepare the following... Figure 4a and 4b The Josephson knot is shown.

[0053] in, Figure 4a This is a TEM image of a Josephson junction prepared by the method provided in an embodiment of the present invention. Figure 4b EDS morphology image of a Josephson junction prepared by the method provided in the embodiment of the present invention. Figure 4c The elemental composition energy spectrum distribution of the alumina thin film in the Josephson junction prepared by the Josephson junction preparation method provided in the embodiments of the present invention.

[0054] The prepared alumina thin films were comprehensively characterized using high-resolution transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), such as... Figure 4a and 4b As shown, the alumina film prepared using the above process parameters has a thickness of approximately 2.39 nm. The film is continuous and dense, free of defects such as pinholes and cracks, with ordered atomic arrangement, exhibiting a uniform amorphous structure and no crystalline phase precipitation; simultaneously, as Figure 4c As shown, EDS did not detect any impurity elements (trace amounts of C came from the sample surface coating, and Si came from the substrate). The main elements were Al and O, and the impurity concentration was less than 0.1 atomic percentage.

[0055] Figure 5 EDS morphology images of the alumina film at three locations—the center, half radius, and edge—of the Josephson junction prepared by the method provided in the embodiments of the present invention.

[0056] Specifically, three key locations were selected on the 12-inch substrate: the center, a point 150 mm from the center at half the radius, and a point 295 mm from the center at the edge. Simultaneously, three points were selected at equal intervals along the diameter direction to test film thickness and junction parameters, verifying the wafer-level uniformity of this fabrication method. Figure 5 As shown, from top to bottom, the three images in the first row (Center) are cross-sectional EDS energy dispersive spectroscopy (EDS) scans at the center of the alumina film. From the first row, it can be seen that the thickness of the alumina film at the center is approximately 2.4 nm. The three images in the second row (Mid) are cross-sectional EDS energy dispersive spectroscopy (EDS) scans at half the radius of the alumina film. From the second row, it can be seen that the thickness of the alumina film at half the radius is approximately 2.5 nm. The three images in the third row (Edge) are cross-sectional EDS energy dispersive spectroscopy (EDS) scans at the edge of the alumina film. From the third row, it can be seen that the thickness of the alumina film at the edge is approximately 2.0 nm. That is, the maximum deviation of the alumina film thickness is ≤0.5 nm, which meets the Josephson junction's requirement for film thickness uniformity.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing alumina thin films, characterized in that, include: A process chamber is provided, which is a vacuum chamber. A substrate with a first aluminum film layer on its upper surface is mounted on a base of the process chamber, and the temperature of the base is [25°C, 50°C]. O2 is introduced into the process chamber, and the chamber pressure is maintained at a preset pressure until the thickness of the aluminum oxide film formed on the surface of the first aluminum film layer remains unchanged; wherein, the preset pressure is [25 mTorr, 100 mTorr].

2. The method according to claim 1, characterized in that, The temperature of the base is [30℃, 45℃].

3. The method according to claim 1, characterized in that, The preset pressure is [30mTorr, 60mTorr].

4. The method according to any one of claims 1-3, characterized in that, The duration of introducing O2 into the process chamber is [30 min, 120 min]; And / or, the purity of O2 introduced into the process chamber is greater than or equal to 99.999%.

5. The method according to any one of claims 1-3, characterized in that, The temperature of the base is [39.5℃, 40.5℃], the preset pressure is [49.5mTorr, 50.5mTorr], and the duration of introducing O2 into the process chamber is [45min, 90min].

6. The method according to any one of claims 1-3, characterized in that, Before introducing O2 into the process chamber, the method further includes a gas washing step: The following operations are performed in a cycle: continuously introducing purge gas into the process chamber for a first preset duration, and evacuating the process chamber to form a vacuum chamber.

7. The method according to claim 6, characterized in that, The chamber pressure after evacuation of the process chamber is [1×10]. -8 Torr, 1×10 -7 Torr]; And / or, the first preset duration is [10s, 30s]; And / or, the purge gas is Ar gas, and the purity of the purge gas is greater than or equal to 99.999%.

8. The method according to any one of claims 1-3, characterized in that, After the substrate is placed on the base for preheating for at least a second preset time, O2 is then introduced into the process chamber.

9. The method according to claim 8, characterized in that, The second preset duration is [20s, 40s].

10. A method for preparing a Josephson junction, characterized in that, include: The substrate is placed on the base of the deposition chamber for deposition to form a first aluminum film layer as the lower electrode on the upper surface of the substrate. Using the deposition chamber as a process chamber, the method described in any one of claims 1-9 is performed to form an aluminum oxide film on the upper surface of the first aluminum film layer; After evacuating the deposition chamber, the substrate is deposited to form a second aluminum film layer as the upper electrode on the upper surface of the alumina film.

Images