A method and system for fabricating a josephson junction

Abstract

The method and device for preparing a Josephson junction provided by the application belong to the technical field of quantum device preparation. The method comprises the following steps: forming a coplanar waveguide layer on a substrate; forming a pattern on the coplanar waveguide layer; performing surface treatment on the pattern by self-limiting atomic layer etching under a predetermined pressure; forming a first superconducting film layer on the pattern subjected to surface treatment; forming a barrier layer on the first superconducting film layer by atomic layer deposition based on a stoichiometric ratio; and forming a second superconducting film layer on the barrier layer. The method provided by the application avoids surface damage of the coplanar waveguide layer and non-uniformity of the stoichiometric ratio of the barrier layer.

Description

Technical Field

[0001] This invention relates to the field of quantum device fabrication technology, and in particular to a method and system for fabricating Josephson junctions. Background Technology

[0002] Josephson junctions are one of the core components of superconducting quantum devices, typically consisting of two superconducting thin films and a barrier layer (i.e., an oxide layer) sandwiched between them.

[0003] Traditional processes typically employ various ion sources to ionize argon gas and bombard the oxide layer on the surface of superconducting thin films in preparation for the subsequent fabrication of a barrier layer. However, due to the high energy of the high-energy particles, damage can occur to the film or substrate surface, affecting the device's quality factor (Q value). Traditional processes typically employ the following three routes when fabricating oxide layers: (1) using plasma (such as O2 / Ar mixture) to enhance the metal oxidation rate, but this method suffers from the problem of non-stoichiometry between metal atoms and oxygen atoms in the barrier layer, meaning that the reaction process is difficult to control precisely, and the ratio of metal to oxygen in the generated oxide is random and non-uniform; (2) using low-temperature ozone (O3) radicals instead of high-purity O2 to generate an oxide layer at low temperatures, but this method results in insufficient uniformity and thickness of the oxide layer; (3) using low-energy ion beams to clean the surface and etch the surface oxide layer during surface treatment, but this still cannot solve the problem of non-stoichiometry between metal atoms and oxygen atoms in the barrier layer.

[0004] Therefore, there is an urgent need for a method for preparing Josephson knots. Summary of the Invention

[0005] To address the problems existing in the prior art, the first aspect of this application provides a method for preparing Josephson knots, the method comprising:

[0006] A coplanar waveguide layer is formed on the substrate;

[0007] A pattern is formed on the coplanar waveguide layer;

[0008] The pattern is surface-treated by self-limiting atomic layer etching under predetermined pressure;

[0009] A first superconducting film layer is formed on the surface-treated pattern;

[0010] A barrier layer is formed on the first superconducting film layer by atomic layer deposition;

[0011] A second superconducting film layer is formed on the barrier layer.

[0012] Optionally, when the pattern is surface-treated by self-limiting atomic layer etching, the etching energy is less than 0.1 eV / atom.

[0013] Optionally, forming the first superconducting film on the surface-treated pattern includes depositing the first superconducting film in a vacuum environment at room temperature.

[0014] Optionally, the material of the coplanar waveguide layer includes aluminum, tantalum, or niobium.

[0015] Optionally, when the material of the coplanar waveguide layer is aluminum, surface treatment of the pattern by self-limiting atomic layer etching includes:

[0016] When the material of the coplanar waveguide layer is aluminum, Cl2 is continuously applied at a flow rate of 50 sccm for 1 second to allow Cl2 to be adsorbed on the surface of the coplanar waveguide layer, forming a first modified layer.

[0017] BCl3 was continuously applied at a flow rate of 30 sccm for 2 seconds to reduce the first modified layer, thereby removing the first modified layer.

[0018] Repeat the above steps to form a trench of a predetermined depth on the coplanar waveguide layer.

[0019] Optionally, when the material of the coplanar waveguide layer is tantalum, the surface treatment of the pattern by self-limiting atomic layer etching includes:

[0020] When the material of the coplanar waveguide layer is tantalum, HF is continuously applied at a flow rate of 20 sccm for 3 seconds to allow HF to be chemically adsorbed on the surface of the coplanar waveguide layer, forming a second modified layer.

[0021] CH3OH is continuously heated at a flow rate of 10 sccm for 5 s to allow CH3OH to react with the second modified layer, thereby removing the second modified layer;

[0022] Repeat the above steps to form a trench of a predetermined depth on the coplanar waveguide layer.

[0023] Optionally, the thickness of the barrier layer is greater than or equal to 1 nm and less than or equal to 20 nm.

[0024] Optionally, forming a first superconducting film layer on the surface-treated pattern and forming a second superconducting film layer on the barrier layer includes forming a first superconducting film layer on the surface-treated pattern or forming a second superconducting film layer on the barrier layer by electron beam deposition or sputtering deposition.

[0025] Secondly, this application also provides an apparatus for preparing a Josephson junction according to any of the above embodiments, comprising an integrated sample inlet chamber, an etching chamber, a first deposition chamber, a second deposition chamber, a first sample transfer rod, and a second sample transfer rod;

[0026] The first sample transfer rod is used to perform sample transfer between the sample inlet chamber, the etching chamber, and the first chamber;

[0027] The second sample transfer rod is used to perform sample transfer between the first deposition chamber and the second deposition chamber;

[0028] The sample inlet chamber is used to provide a first vacuum environment for the sample;

[0029] The atomic layer etching chamber is configured to perform surface treatment on the pattern of the sample coplanar waveguide layer by self-limiting atomic layer etching under a predetermined process window pressure.

[0030] The first deposition chamber is used to deposit a first superconducting film and a second superconducting film.

[0031] The second deposition chamber is used to form a barrier layer on the first superconducting film layer by atomic layer deposition.

[0032] Optionally, the device further includes an in-situ monitoring device for monitoring process parameters in the etching chamber, the first deposition chamber, and the second deposition chamber.

[0033] Optionally, the first deposition chamber and the second deposition chamber include a sample stage; the sample stage is used to hold the sample and to transfer the sample to the first transfer rod or the second transfer rod.

[0034] The method and apparatus for preparing Josephson knots provided in this application achieve at least the following technical effects:

[0035] The method provided in this application avoids surface damage to the substrate or film by performing surface treatment through self-limiting atomic layer etching under a predetermined window pressure; and forms a barrier layer on the first superconducting film by self-limiting atomic layer deposition, thereby achieving atomic-level control of the stoichiometry of the barrier layer and ensuring the thickness uniformity and thickness of the barrier layer. Attached Figure Description

[0036] Figure 1 An optional flowchart of the method for preparing Josephson knots provided in this application is shown.

[0037] Figure 2 A flowchart of another alternative method for preparing Josephson knots provided in this application is shown.

[0038] Figure 3 A schematic diagram of an alternative structure of the apparatus for preparing Josephson junctions provided in this application is shown.

[0039] Figure 4 A schematic diagram of an alternative structure of the etching chamber provided in this application is shown.

[0040] Figure 5 A schematic diagram of an alternative structure of the first deposition chamber provided in this application is shown.

[0041] Figure 6 A schematic diagram of an alternative structure of the second deposition chamber provided in this application is shown.

[0042] Figure 7 A schematic diagram of an optional structure of the sample stage provided in this application is shown.

[0043] The reference numerals in the figure represent:

[0044] 100 - Sample; 101 - Substrate; 102 - Coplanar waveguide layer; 103 - Photoresist; 104 - First superconducting layer;

[0045] 1-Sample inlet chamber; 2-Etching chamber; 3-First deposition chamber; 4-Second deposition chamber; 51-First transfer rod; 52-Second transfer rod; 6-Sample stage;

[0046] 20-First housing; 21-First power supply; 22-First pump assembly; 23-First gas passage; 24-First electrode; 25-Second electrode;

[0047] 30 - Second housing; 31 - Crystal oscillator; 33 - Evaporation device;

[0048] 40-Third housing; 41-Second power supply; 42-Second pump assembly; 43-Second gas passage; 44-Third electrode; 45-Fourth electrode;

[0049] 61-First sample holder; 62-Sample tray; 63-Second sample holder; 64-Tilting mechanism; 65-Rotation mechanism. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present application.

[0051] Traditional Josephson junction fabrication processes have the following drawbacks:

[0052] (1) Non-stoichiometric problem: In traditional processes, the ratio of metal atoms to oxygen atoms in the barrier layer generated by dynamic oxidation is random, which leads to fluctuations in the band structure, causes differences in the insulating layer barrier, and affects the performance of large-scale quantum bit devices.

[0053] (2) Ion etching is used to treat the sample surface, which introduces lattice defects, increases the tunneling loss of the Josephson junction, and causes the Q value of the quantum device to decay.

[0054] Therefore, embodiments of this application provide, in one aspect, a method for preparing Josephson knots. See also... Figure 1 and Figure 2 The method includes:

[0055] A coplanar waveguide layer 102 is formed on the substrate 101;

[0056] A pattern is formed on the coplanar waveguide layer 102;

[0057] The pattern is surface-treated by self-limiting atomic layer etching under predetermined pressure;

[0058] A first superconducting film 104 is formed on the surface-treated pattern;

[0059] A barrier layer 105 is formed on the first superconducting film layer 104 by atomic layer deposition;

[0060] A second superconducting film 106 is formed on the barrier layer 105.

[0061] According to an embodiment of this application, the coplanar waveguide layer 102 (CPW) includes a center conductor, a ground plane, and a dielectric material layer for connecting and controlling the Josephson junction. According to an embodiment of this application, the fabrication of the coplanar waveguide layer 102 includes measuring the stress value, warpage, and other pre-determined values ​​X of the bare wafer using a stress meter, and depositing a superconducting thin film material on a substrate 101 using techniques such as magnetron sputtering or electron beam deposition to form the CPW layer 102. The superconducting thin film material includes aluminum, tantalum, or niobium. Optionally, the thickness of the CPW layer 102 is greater than 100 nm. After the CPW layer 102 is deposited, the stress value, warpage, and other data Y of the wafer after CPW layer deposition are retested. The stress value in data Y should be as close as possible to 0 MPa. Excessive stress will affect the adhesion of the thin film and patterning processing. Subsequently, photoresist 103 is coated on the surface of the CPW layer, and the Josephson junction is patterned and transferred to the surface of the CPW layer through photolithography (including exposure and development) to form a predetermined pattern (also known as a junction region).

[0062] According to an embodiment of this application, a pattern is surface-treated by self-limiting atomic layer etching (ALE) under a predetermined pressure to remove oxides from the junction surface. The predetermined pressure is a process window pressure suitable for atomic layer etching. For example, the predetermined pressure is less than 0.01 Torr. According to an embodiment of this application, a reactant (gas or plasma) is used to induce a self-limiting reaction with the pattern surface. That is, the reactant reacts with the uppermost atoms of the pattern surface to form a modified layer. When the pattern surface is completely covered by the modified layer, the reaction automatically stops without diffusing to deeper layers. This step only changes the surface properties and removes little or no material. Subsequently, another reactant (removing agent) is used to selectively remove the modified layer. For example, a gas such as BCl3 or HF reacts with the modified layer to form volatile products, which are then volatilized by heating. This step is also self-limiting, removing only the modified layer; the reaction stops once the modified layer is removed. This is because the CPW layer beneath the modified layer is insensitive to the removing agent. This achieves atomic-scale removal precision. Optionally, when surface-treating the pattern using self-limiting atomic layer etching, the etching energy is less than 0.1 eV / atom. For example, the process parameters of ALE etching are monitored by an in-situ monitoring device to achieve closed-loop control, thereby reaching the predetermined etching depth.

[0063] For example, when the superconducting material forming the CPW layer 102 is aluminum, Cl2 is continuously applied at a flow rate of 50 sccm for 1 second, causing Cl2 to be adsorbed on the surface of the coplanar waveguide layer to form the first modified layer.

[0064] BCl3 was continuously applied at a flow rate of 30 standard cubic centimeters per minute (sccm) for 2 seconds to reduce the first modified layer, thereby removing the first modified layer.

[0065] Repeat the above steps to form a trench of a predetermined depth on the coplanar waveguide layer 102.

[0066] As another example, when the material of the coplanar waveguide layer 102 is tantalum, the surface treatment of the pattern by self-limiting atomic layer etching includes:

[0067] When the superconducting material forming the CPW layer is tantalum, HF is continuously applied at a flow rate of 20 sccm for 3 s to allow HF to be chemically adsorbed onto the surface of the coplanar waveguide layer, forming a second modified layer.

[0068] CH3OH was continuously heated at a flow rate of 10 sccm for 5 s to allow CH3OH to react with the second modified layer, thereby removing the second modified layer;

[0069] Repeat the above steps to form a trench of a predetermined depth on the coplanar waveguide layer 102.

[0070] According to the method described in this application, after surface treatment is completed, a first superconducting film 104 is deposited on the patterned surface. The material of the first superconducting film 104 includes aluminum, tantalum, or niobium. The thickness of the first superconducting film 104 is 100 nm to 300 nm. Exemplarily, the deposition of the first superconducting film 104 is performed in a room temperature vacuum environment. Exemplarily, the pressure in the etching chamber reaches a predetermined threshold background vacuum (e.g., 6E). -9 After Torr), the first superconducting film 104 is deposited at room temperature by electron beam deposition or magnetron sputtering. During the deposition process, the film deposition rate and thickness are controlled in a closed loop by a control system such as an in-situ monitoring device (e.g., a crystal oscillator). After deposition is completed, the vacuum is evacuated to the threshold vacuum.

[0071] According to an embodiment of this application, in a vacuum environment, a barrier layer 105 is formed above a first superconducting film layer 104 by atomic layer deposition (ALD) based on a stoichiometric ratio. The barrier layer 105 is an insulating oxide layer, such as aluminum oxide, magnesium oxide, or niobium oxide. Exemplarily, the material of the barrier layer 105 includes Al2O3. Exemplarily, the thickness of the barrier layer 105 is greater than or equal to 1 nm and less than or equal to 20 nm. Optionally, a trimethylaluminium (TMA) precursor is used to undergo a self-limiting reaction with H2O to generate Al2O3. Exemplarily, TMA vapor is pulsed into the vacuum reaction chamber based on a stoichiometric ratio (O / Al = 1.50) to allow TMA to adhere to the surface of the first superconducting film layer. Water vapor conforming to the stoichiometric ratio is then introduced into the reaction chamber, causing a self-limiting reaction between TMA and H2O to generate Al2O3. This process is repeated until a predetermined thickness of Al2O3 is generated.

[0072] According to an embodiment of this application, a second superconducting film layer 106 is formed on a barrier layer 105. The thickness of the second superconducting film layer 106 is 100 nm to 300 nm. Exemplarily, the deposition of the second superconducting film layer 106 is performed in a room temperature vacuum environment. Exemplarily, the pressure in the etching chamber reaches a predetermined threshold background vacuum (e.g., 6E). -9 After Torr), a second superconducting film is deposited at room temperature by electron beam deposition or magnetron sputtering. During the deposition process, the film deposition rate and thickness are controlled in a closed loop by a control system such as an in-situ monitoring device (e.g., a crystal oscillator). After deposition is completed, the vacuum is evacuated to the threshold vacuum. The material of the second superconducting film 106 includes aluminum, niobium, or tantalum. Optionally, the second superconducting film 106 is made of the same material as the first superconducting film 104.

[0073] The process described in this application is applicable to overlap processing routes. This application uses ALD (Al₂O₃) for oxide layer deposition, ensuring that the barrier layer is stoichiometrically precise Al₂O₃ while avoiding damage to the superconducting material surface. Simultaneously, since ALD is a purely thermochemical process, it avoids damage to the first superconducting film layer caused by ion bombardment, thus improving the Q value of the device. See also... Figure 2 The above process, combined with the stacking process, requires only one photolithography alignment, which simplifies the fabrication process of Josephson junctions and results in a higher yield.

[0074] Secondly, this application provides an apparatus for preparing Josephson nodes, used to prepare Josephson nodes according to the method provided in any of the above embodiments. See also Figure 3 The device includes an integrated sample inlet chamber 1, an etching chamber 2, a first deposition chamber 3, a second deposition chamber 4, a first transfer rod 51, and a second transfer rod 52.

[0075] For example, such as Figure 3 As shown, the sample injection chamber 1, etching chamber 2, first deposition chamber 3, and second deposition chamber 4 are linearly arranged. The first sample transfer rod 51 is located at the end of the first chamber 1 furthest from the etching chamber 2, and the second sample transfer rod 52 is located at the end of the second deposition chamber 4 furthest from the first deposition chamber 3. Figure 3 As shown, each chamber is equipped with a sample stage 6. Optionally, each of the sample introduction chamber 1, etching chamber 2, first deposition chamber 3, and second deposition chamber 4 has an independent vacuum system. Vacuum valves are installed between adjacent chambers, achieving physical isolation and communication through the closure of the vacuum valves, and independent pressure control within each chamber through the independent vacuum system. Optionally, when sample transfer between adjacent chambers is required, the vacuum levels of the two chambers are first controlled to be the same, then the vacuum valves are opened to allow the sample transfer rod to enter the corresponding chamber, and the sample transfer is completed through the sample transfer rod. After the sample transfer is completed, the vacuum valves are closed, re-isolating the two chambers.

[0076] According to the embodiments of this application, since the method provided in this application combines ALE etching and ALD deposition, a high vacuum and ultra-clean environment needs to be maintained. Therefore, the device provided in this application includes a sample introduction chamber 1 to provide a buffer and transition zone between the atmospheric environment and the high vacuum process environment. After the sample 100 (wafer) is placed into the sample introduction chamber 1, the internal pressure of the sample introduction chamber 1 is evacuated to a vacuum. Optionally, the sample introduction chamber 1 is evacuated until the internal pressure is 8E. -8 Torr.

[0077] According to the embodiments of this application, such as Figure 4As shown, the etching chamber 2 includes a first housing 20, a first power supply 21, a first pump assembly 22, a first gas channel 23, a first electrode 24, and a second electrode 25. The first electrode 24 and the second electrode 25 are disposed opposite each other within the reaction chamber defined by the first housing 20. The first electrode 24 and the second electrode 25 are electrically connected to the first power supply 21. The first gas channel 23 is fluidly connected to the reaction chamber defined by the first housing 20. Optionally, a flow meter is also provided on the first gas channel 23. The first pump assembly 22 is fluidly connected to the reaction chamber defined by the first housing 20 to create an independent vacuum environment.

[0078] According to the embodiments of this application, such as Figure 5 As shown, the first deposition chamber 3 includes a second housing 30, a crystal oscillator 31, a sample stage 6, and an evaporation device 33. The sample stage 6 holds the sample such that the patterned side of the sample faces the evaporation device.

[0079] According to an embodiment of this application, as shown in Figure 6, the second deposition chamber 4 includes a second housing 40, a second power supply 41, a second pump assembly 42, a second gas channel 43, a third electrode 44, and a fourth electrode 45. The third electrode 44 and the fourth electrode 45 are disposed opposite each other within the reaction chamber defined by the second housing 40. The third electrode 44 and the fourth electrode 45 are electrically connected to the second power supply 41. The second gas channel 43 is fluidly connected to the reaction chamber defined by the second housing 40. Optionally, a flow meter is also provided on the second gas channel 43. The second pump assembly 42 is fluidly connected to the reaction chamber defined by the second housing 40 to create an independent vacuum environment.

[0080] See Figure 3 and Figure 7 The device provided in this application has a sample stage 6 in each chamber for supporting or holding samples. See also Figure 7 The sample stage 6 includes a first sample holder 61, a sample tray 62, a second sample holder 63, a flipping mechanism 64, and a rotating mechanism 65. The first sample holder 61 is C-shaped, and its C-shaped notch matches the shape of the stage notch on the sample transfer rod. The second sample holder 63 is annular. The first and second sample holders 61 and 63 are connected to the rod via rollers, and a pneumatic valve and spring are used to clamp and release the sample tray 62. Optionally, the sample tray 62 provided in this application is suitable for wafers of 8 inches and below. The sample is fixed to the sample tray 62 by a clamping plate and screws.

[0081] When transferring samples, the first sample holder 61 is lowered by controlling the pneumatic valve, and the sample tray 62 is transferred from the sample transfer rod to the first sample holder 61. At this time, the sample tray 62 is fixed to the first sample holder 61. The first sample holder 61 and the sample tray 62 are raised by controlling the pneumatic valve, the sample transfer rod retracts to its initial position, and the control spring lowers the second sample holder 63, so that the sample tray 62 is in contact. At this time, the first sample holder 61 and the second sample holder 63 clamp the sample tray 62 tightly.

[0082] During ALE etching and ALD deposition, the wafer face is facing upwards. During electron beam evaporation, the wafer face is facing downwards. Therefore, if electron beam evaporation is used to deposit the first or second superconducting film, the wafer face is facing downwards. If magnetron sputtering is used to deposit the first or second superconducting film, the wafer face does not need to be facing downwards. In this case, the sample needs to be flipped when transferred between the etching chamber and the first deposition chamber, and between the first deposition chamber and the second deposition chamber. Therefore, the device provided in this application also includes a flipping mechanism 64. The flipping mechanism 64 is connected to a fixed rod via a central shaft, with the center of the sample disk as the flipping center, and can achieve a tilt of ±90° via a motor. The device provided in this application also includes a rotation mechanism 65, which is configured to rotate the sample disk via a motor.

[0083] Example 1

[0084] In some optional embodiments, the method for preparing Josephson knots provided in this application includes:

[0085] Al films were deposited on Si substrates using techniques such as magnetron sputtering or electron beam deposition to form CPW layers; the Si substrate was a 6-inch wafer, and the CPW layer thickness was 300 nm; the substrate stress after CPW layer deposition was close to 0 MPa.

[0086] Photoresist is coated on the surface of the CPW layer, and the predetermined Josephson junction pattern is transferred by photolithography to form a pattern on the surface of the CPW layer.

[0087] The sample (the photolithographically etched substrate) is fed into sample chamber 1;

[0088] Evacuate sample injection chamber 1 until the internal pressure is less than or equal to 8E. -8 Torr;

[0089] The sample is transferred to etching chamber 2, and the etching chamber 2 is evacuated until the internal pressure reaches the process window pressure, for example, less than or equal to 0.01 Torr; the etching temperature is 100°C to 200°C.

[0090] The oxide (Al2O3) on the surface of the CPW layer was removed by ALE etching; the etching gas used was BCl3 / Cl2.

[0091] The sample is introduced into the first deposition chamber 3, and the first deposition chamber 3 is evacuated to bring the internal pressure to the background vacuum (e.g., 6E). -9 Torr);

[0092] The first superconducting film layer is deposited at room temperature by electron beam deposition or magnetron sputtering; the first superconducting film layer is Al and has a thickness of 100 nm; optionally, the film deposition rate and thickness are controlled in a closed loop by a control system such as a crystal vibrator during the deposition process.

[0093] Once the pressure in the first deposition chamber reaches the threshold vacuum, the sample is transferred to the second deposition chamber.

[0094] The second deposition chamber is evacuated. Once the pressure inside the chamber reaches the threshold vacuum, an ALD process is used to deposit a barrier layer on the first superconducting thin film. In this process, a TMA precursor is used to undergo a self-limiting reaction with H2O vapor to form an Al2O3 layer of a predetermined thickness. The etching conditions are: TMA (0.1s) / N2 purge (5s) / H2O (0.1s) @150°C.

[0095] The sample is returned to the first deposition chamber, and a second superconducting film is deposited on the barrier layer using the same process as the first superconducting film.

[0096] Control the pressure in each chamber to reach the predetermined vacuum, balance the pressure in each chamber, and transfer the sample to the sample injection chamber;

[0097] Open the sample injection chamber and remove the sample.

[0098] The Josephson knots prepared by the method and equipment of this application have the technical effects shown in Table 1 below:

[0099] Table 1

[0100]

[0101] In summary, the method provided in this application avoids surface damage to the substrate or film by performing surface treatment through self-limiting atomic layer etching under a predetermined window pressure; and by forming a barrier layer on the first superconducting film layer through self-limiting atomic layer deposition, the stoichiometry of the barrier layer is controlled at the atomic level, ensuring the thickness uniformity and thickness of the barrier layer.

[0102] The equipment provided in this application integrates a sample introduction chamber, an ALE etching chamber, an electron beam (or magnetron sputtering) deposition chamber, and an ALD deposition chamber. The method and equipment provided in this application enable a closed-loop process with zero-damage etching and precise control of stoichiometric deposition.

[0103] The present invention has been described illustratively above and is not limited thereto. The figures shown are only one embodiment of the present invention. If any person skilled in the art proposes a similar structural form without departing from the spirit of the present invention, it shall fall within the protection scope of the present invention.

Claims

1. A method for preparing Josephson knots, characterized in that, The method includes: A coplanar waveguide layer is formed on the substrate; A pattern is formed on the coplanar waveguide layer; The pattern is surface-treated by self-limiting atomic layer etching under predetermined pressure; A first superconducting film layer is formed on the surface-treated pattern; Based on stoichiometry, a barrier layer is formed on the first superconducting film layer by atomic layer deposition; A second superconducting film layer is formed on the barrier layer.

2. The method according to claim 1, characterized in that, When the pattern is surface-treated by self-limiting atomic layer etching, the etching energy is less than 0.1 eV / atom.

3. The method according to claim 1, characterized in that, Forming a first superconducting film on a surface-treated pattern includes depositing a first superconducting film in a vacuum environment at room temperature.

4. The method according to claim 1, characterized in that, The material of the coplanar waveguide layer includes aluminum, tantalum, or niobium.

5. The method according to claim 4, characterized in that, When the material of the coplanar waveguide layer is aluminum, the surface treatment of the pattern by self-limiting atomic layer etching includes: When the material of the coplanar waveguide layer is aluminum, Cl2 is continuously applied at a flow rate of 50 sccm for 1 second to allow Cl2 to be adsorbed on the surface of the coplanar waveguide layer, forming a first modified layer. BCl3 was continuously applied at a flow rate of 30 sccm for 2 seconds to reduce the first modified layer, thereby removing the first modified layer. Repeat the above steps to form a trench of a predetermined depth on the coplanar waveguide layer.

6. The method according to claim 4, characterized in that, When the material of the coplanar waveguide layer is tantalum, the surface treatment of the pattern by self-limiting atomic layer etching includes: When the material of the coplanar waveguide layer is tantalum, HF is continuously applied at a flow rate of 20 sccm for 3 seconds to allow HF to be chemically adsorbed on the surface of the coplanar waveguide layer, forming a second modified layer. CH3OH is continuously heated at a flow rate of 10 sccm for 5 s to allow CH3OH to react with the second modified layer, thereby removing the second modified layer; Repeat the above steps to form a trench of a predetermined depth on the coplanar waveguide layer.

7. The method according to claim 3, characterized in that, The thickness of the barrier layer is greater than or equal to 1 nm and less than or equal to 20 nm.

8. The method according to claim 3, characterized in that, The formation of a first superconducting film layer on a surface-treated pattern and a second superconducting film layer on a barrier layer includes forming a first superconducting film layer on a surface-treated pattern or forming a second superconducting film layer on a barrier layer by electron beam deposition or sputtering deposition.

9. An apparatus for preparing Josephson knots according to any one of claims 1 to 7, characterized in that, It includes an integrated sample inlet chamber, an etching chamber, a first deposition chamber, a second deposition chamber, a first sample transfer rod, and a second sample transfer rod; The first sample transfer rod is used to perform sample transfer between the sample inlet chamber, the etching chamber, and the first deposition chamber; The second sample transfer rod is used to perform sample transfer between the first deposition chamber and the second deposition chamber; The sample inlet chamber is used to provide a first vacuum environment for the sample; The atomic layer etching chamber is configured to perform surface treatment on the pattern of the sample coplanar waveguide layer by self-limiting atomic layer etching under a predetermined process window pressure. The first deposition chamber is used to deposit a first superconducting film and a second superconducting film. The second deposition chamber is used to form a barrier layer on the first superconducting film layer by atomic layer deposition based on stoichiometry.

10. The device according to claim 9, characterized in that, The equipment also includes an in-situ monitoring device for monitoring process parameters in the etching chamber, the first deposition chamber, and the second deposition chamber.

11. The device according to claim 9, characterized in that, The first deposition chamber and the second deposition chamber include a sample stage; the sample stage is used to hold the sample and to transfer the sample to the first transfer rod or the second transfer rod.

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