A method for manufacturing a superconducting circuit, a quantum chip

Abstract

The application discloses a superconducting circuit preparation method and a quantum chip. The preparation method comprises the following steps: providing a vacuum cavity to accommodate a substrate used for preparing a superconducting circuit; forming an adsorption structure in the interior of the vacuum cavity to adsorb gas impurities in the vacuum cavity; forming a superconducting metal layer on the surface of the substrate; oxidizing the superconducting metal layer to form an oxide film on the surface of the superconducting metal layer; and patterning the superconducting metal layer to obtain the superconducting circuit. The superconducting circuit preparation method provided by the application forms an adsorption structure in the interior of the vacuum cavity before forming the superconducting metal layer on the surface of the substrate, adsorbs residual oxygen, water vapor and other gas impurities in the vacuum cavity by using the adsorption structure, further reduces the content of the gas impurities in the vacuum cavity, greatly reduces the impurity content of the superconducting metal layer formed on the substrate, and effectively guarantees that the prepared superconducting circuit has good electrical performance.

Description

Technical Field

[0001] This application belongs to the field of quantum chip technology, specifically a method for fabricating a superconducting circuit and a quantum chip. Background Technology

[0002] A quantum computer is a physical device that performs high-speed mathematical and logical operations, stores and processes quantum information in accordance with the laws of quantum mechanics. In a superconducting quantum computing system, the quantum chip is the core component of the quantum computer. A quantum chip typically contains qubits, and around the qubits are various superconducting circuits with different functions. The qubits transmit signals to external electronic devices through these superconducting circuits.

[0003] Superconducting circuits are typically fabricated by processes such as exposure etching, which involve covering a superconducting metal layer on a substrate. However, existing superconducting circuit fabrication methods often result in unstable signal transmission and poor electrical performance.

[0004] It should be noted that the information disclosed in the background section of this application is intended only to enhance the understanding of the general background of this application, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a method for fabricating a superconducting circuit and a quantum chip to overcome the shortcomings of the prior art. It provides a method for fabricating a high-quality superconducting circuit and a quantum chip.

[0006] One embodiment of this application provides a method for fabricating a superconducting circuit, the method comprising the following steps:

[0007] A vacuum cavity is provided to house the substrate used to support the superconducting circuit;

[0008] An adsorption structure is formed inside the vacuum cavity to adsorb gaseous impurities inside the vacuum cavity;

[0009] A superconducting metal layer is formed on the surface of the substrate;

[0010] The superconducting metal layer is oxidized so that an oxide film is formed on the surface of the superconducting metal layer;

[0011] The superconducting metal layer is patterned to obtain the superconducting circuit.

[0012] The method for fabricating a superconducting circuit as described above further includes the following steps before providing a vacuum cavity to house a substrate for supporting the superconducting circuit:

[0013] The substrate is irradiated with a UV light source to remove impurities from the substrate surface.

[0014] The method for fabricating a superconducting circuit as described above further includes the following steps before providing a vacuum cavity to house a substrate for supporting the superconducting circuit:

[0015] The substrate is cleaned using the BOE cleaning process to remove the natural oxide layer on the substrate surface.

[0016] The method for preparing a superconducting circuit as described above, wherein the step of forming an adsorption structure inside the vacuum cavity includes:

[0017] An adsorbent material is vapor-deposited within the vacuum chamber and deposited inside the vacuum chamber to form the adsorption structure.

[0018] In the superconducting circuit preparation method described above, the adsorbent material is metallic titanium.

[0019] The method for fabricating a superconducting circuit as described above, wherein the step of forming a superconducting metal layer on the surface of the substrate includes:

[0020] Within the vacuum chamber, a superconducting metal material is deposited using an electron beam evaporation process to form the superconducting metal layer on the surface of the substrate.

[0021] The method for fabricating a superconducting circuit as described above, wherein the step of patterning the superconducting metal layer to obtain the superconducting circuit includes:

[0022] A mask layer with a corrosion-resistant pattern is formed on the superconducting metal layer;

[0023] Etching removes the superconducting metal layer not covered by the resist pattern to obtain a circuit pattern on the superconducting metal layer;

[0024] The mask layer is removed to expose the circuit pattern, thereby obtaining the superconducting circuit.

[0025] The method for fabricating a superconducting circuit as described above, wherein the step of forming a mask layer with a resist pattern on the superconducting metal layer includes:

[0026] A photoresist layer is formed on the superconducting metal layer, and the photoresist layer is patterned to obtain the mask layer.

[0027] The fabrication method of the superconducting circuit described above, wherein the step of patterning the photoresist layer to obtain the mask layer includes:

[0028] An exposure and development operation is performed on the photoresist layer to obtain the mask layer.

[0029] Another embodiment of this application provides a quantum chip, wherein the quantum chip includes a superconducting circuit prepared by the preparation method described above.

[0030] Compared with existing technologies, this application provides a method for fabricating a superconducting circuit, comprising the following steps: first, providing a vacuum cavity to accommodate a substrate for supporting the superconducting circuit; then, forming an adsorption structure inside the vacuum cavity to adsorb gaseous impurities within the vacuum cavity; then, forming a superconducting metal layer on the surface of the substrate; and finally, patterning the superconducting metal layer to obtain the superconducting circuit. The method for fabricating a superconducting circuit proposed in this application, before forming the superconducting metal layer on the substrate surface, forms an adsorption structure inside the vacuum cavity. This adsorption structure adsorbs residual gaseous impurities such as oxygen and water vapor within the vacuum cavity, thereby further increasing the vacuum level within the vacuum cavity and further reducing the content of gaseous impurities within the vacuum cavity. This significantly optimizes the formation environment of the superconducting metal layer, thereby greatly reducing the impurity content of the superconducting metal layer formed on the substrate. This effectively ensures that the fabricated superconducting circuit has good electrical performance, which is beneficial for the stable transmission of signals in quantum chips. Attached Figure Description

[0031] Figure 1 A flowchart illustrating the fabrication method of the superconducting circuit provided in this application;

[0032] Figure 2 This is a schematic diagram of the substrate in an embodiment of this application.

[0033] Figure labeling: 1 - substrate, 2 - superconducting metal layer, 3 - mask layer. Detailed Implementation

[0034] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this application to help readers better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0036] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product or device.

[0037] Additionally, it should be understood that when a layer (or film), region, pattern, or structure is referred to as being "on" a substrate, layer (or film), region, and / or pattern, it can be located directly on another layer or substrate, and / or intercalation layers may also be present. Furthermore, it should be understood that when a layer is referred to as being "under" another layer, it can be located directly under that layer, and / or one or more intercalation layers may also be present. Additionally, references to "on" and "under" the layers may be made based on the accompanying drawings.

[0038] A quantum computer is a physical device that performs high-speed mathematical and logical operations, stores and processes quantum information in accordance with the laws of quantum mechanics. In a superconducting quantum computing system, the quantum chip is the core component of the quantum computer. A quantum chip typically contains qubits, and around the qubits are various superconducting circuits with different functions. The qubits transmit signals to external electronic devices through these superconducting circuits.

[0039] Superconducting circuits are typically fabricated from a superconducting metal layer covering a substrate using processes such as exposure etching. Around the qubit (qubit) are various superconducting circuit structures with different functions, such as the drive control signal line (xy-control line, also known as the xy control line or pulse modulation signal line) for XY rotation operations on the qubit, couplers for inter-qubit coupling, readout resonant cavities coupled to the qubits, and readout signal lines coupled to the readout cavities. Additionally, Z-rotation operations on the qubits are performed by control signal lines near the superconducting quantum interference device (squid), called flux control signal lines (z-control line, also known as z control line or frequency modulation signal line). These flux control signal lines are positioned near the superconducting quantum interference device (squid) and are excited by current, coupling with the superconducting quantum interference device (squid) through magnetic flux. It should be noted that the readout signal line, flux control signal line, and drive control line are all part of the superconducting circuitry on the quantum chip, and generally employ coplanar waveguide structures for transmitting microwave signals.

[0040] Existing superconducting circuit fabrication methods often result in unstable signal transmission and poor electrical performance.

[0041] Figure 1A flowchart illustrating the fabrication method of the superconducting circuit provided in this application.

[0042] Figure 2 This is a schematic diagram of the substrate in an embodiment of this application.

[0043] Combined with appendix Figure 1 Appendix Figure 2 As shown in the embodiment of this application, a method for fabricating a superconducting circuit includes the following steps:

[0044] S10. A vacuum cavity is provided to accommodate the substrate 1 for carrying the superconducting circuit. As an example, the substrate 1 can be selected as a sapphire substrate 1, a silicon substrate 1, a gallium nitride substrate 1, etc. The material of the substrate 1 is selected accordingly in different application scenarios, and is not limited to the above examples. For example, the vacuum cavity can be the vacuum deposition cavity of a coating equipment, which provides a vacuum deposition environment for the substrate 1.

[0045] S20. An adsorption structure is formed inside the vacuum cavity to adsorb gaseous impurities inside the vacuum cavity. For example, one specific method is to vapor-deposit an adsorption material inside the vacuum cavity and deposit the adsorption material inside the vacuum cavity to obtain the adsorption structure. The adsorption material can be a vaporizable adsorption material, such as titanium. Using a deposition process (e.g., electron beam evaporation), titanium is vaporized inside the vacuum cavity, causing the titanium to vaporize and form a titanium metal layer inside the vacuum cavity to act as an adsorption structure. The titanium metal layer can further adsorb residual water vapor and oxygen in the vacuum cavity, thereby further reducing the water and oxygen content in the vacuum cavity, further reducing the gaseous impurity content in the vacuum cavity, and further improving the vacuum degree of the vacuum cavity. This helps to prepare a high-quality superconducting metal layer 2 on the substrate 1, and further helps to prepare a high-quality superconducting circuit. In this application, by preparing a titanium metal layer inside the vacuum cavity to act as an adsorption structure, the step of introducing an adsorption structure from outside the vacuum cavity is eliminated.

[0046] It should be noted that during the deposition of the titanium metal layer, a cover can be placed inside the vacuum chamber, allowing the titanium metal to be deposited on the surface of the cover to obtain the titanium metal layer. A shielding structure, such as a shielding sheet, is used to shield the substrate 1 to prevent titanium metal from depositing on its surface. During the electron beam evaporation process for preparing the titanium metal layer, the deposition rate is controlled within... / s, controlling the evaporation time to maintain the thickness of the final titanium metal layer at 10-20nm. The titanium metal layer can further adsorb residual water vapor and oxygen in the vacuum chamber, thereby further reducing the water and oxygen content in the vacuum chamber and further reducing the gas impurity content in the vacuum chamber.

[0047] S30. A superconducting metal layer 2 is formed on the surface of the substrate 1. In specific implementation, a deposition process (such as electron beam evaporation process, atomic layer deposition process, etc.) can be used to evaporate the superconducting material inside the vacuum cavity, thereby depositing and forming a superconducting metal layer 2 on the surface of the substrate 1.

[0048] It should be noted that the superconducting material can be a material that exhibits superconducting properties at or below the superconducting critical temperature, such as aluminum (e.g., a superconducting critical temperature of 1.2 Kelvin) or niobium (e.g., a superconducting critical temperature of 9.3 Kelvin). Specifically, in this embodiment, aluminum is used as the superconducting material, and an aluminum film is deposited on the surface of substrate 1 using a deposition process. Aluminum exhibits superconducting properties in the low-temperature region of the dilution refrigerator. Furthermore, those skilled in the art should recognize that other superconducting materials can be used in the various embodiments described herein.

[0049] S40. Oxidize the superconducting metal layer 2 to form an oxide film on its surface. Specifically, the superconducting metal layer 2 can be oxidized in a pure oxygen environment. For example, when oxidizing the prepared aluminum film, pure oxygen is introduced into the vacuum chamber to create a pure oxygen oxidation environment, thereby oxidizing the surface of the aluminum film and forming a dense oxide film to passivate it. Specifically, oxygen is introduced into the vacuum chamber to achieve a pressure of 500 Torr, and the oxidation is maintained for 10 minutes, resulting in a dense aluminum oxide film on the surface of the aluminum film. This allows the aluminum to be isolated from the atmospheric environment, protecting it from its influence. Compared to the natural oxidation of the aluminum film in the atmosphere, oxidizing it in a pure oxygen environment avoids the negative impact of impurities in the atmosphere on the oxide layer during oxidation. The oxide layer obtained in a pure oxygen environment is denser, providing better protection for the aluminum film.

[0050] S50. The superconducting metal layer 2 is patterned to obtain the superconducting circuit. In this embodiment, the superconducting metal layer 2 prepared by the above process is etched to obtain the superconducting circuit. The etching method is not limited to dry etching, wet etching and other etching processes.

[0051] The method for fabricating a superconducting circuit proposed in this application involves forming an adsorption structure inside a vacuum cavity before forming a superconducting metal layer 2 on the surface of the substrate 1. This adsorption structure adsorbs residual oxygen, water vapor, and other gaseous impurities within the vacuum cavity, thereby further increasing the vacuum level and reducing the content of gaseous impurities. This significantly optimizes the formation environment of the superconducting metal layer 2, thereby greatly reducing the impurity content of the superconducting metal layer 2 formed on the substrate 1. This effectively ensures that the fabricated superconducting circuit has excellent electrical performance, which is beneficial for the stable transmission of quantum chip signals.

[0052] In some embodiments of the present invention, prior to the step of providing a vacuum cavity to accommodate the substrate 1 for supporting the superconducting circuit, the following steps are further included:

[0053] The substrate 1 is irradiated with a UV light source to remove impurities from the surface of the substrate 1. In this embodiment, irradiating the substrate 1 with a UV light source can remove impurities such as organic matter and moisture adhering to the surface of the substrate 1, thereby achieving the effect of cleaning impurities on the substrate 1.

[0054] It should be noted that the UV light source can simultaneously emit ultraviolet light with wavelengths of 254nm and 185nm. These two wavelengths of ultraviolet light can activate organic molecules, decomposing them into ions, free atoms, excited molecules, etc. The UV light source can be used to decompose organic impurities on the surface of substrate 1. Oxygen molecules in the air absorb 185nm ultraviolet light to produce ozone and atomic oxygen. Under irradiation with 254nm ultraviolet light, ozone decomposes into atomic oxygen and oxygen gas. The atomic oxygen combines with organic impurities on the surface of substrate 1 to form volatile gases, such as carbon dioxide and water vapor, which escape from the surface of substrate 1. This thoroughly removes organic matter, water vapor, and other impurities adhering to the surface of substrate 1, thus achieving the purpose of cleaning substrate 1.

[0055] In some embodiments of this application, prior to the step of providing a vacuum cavity to accommodate the substrate 1 for supporting the superconducting circuit, the following steps are also included:

[0056] The substrate 1 is cleaned using the BOE cleaning process to remove the natural oxide layer on the surface of the substrate 1. For example, in this application, a silicon substrate 1 is used, and a film is deposited on the surface of the silicon substrate 1 to prepare a superconducting circuit on the silicon substrate 1. However, in an atmospheric environment, the surface of the silicon substrate 1 is easily oxidized by oxygen in the air, thereby forming a silicon oxide layer on the surface of the silicon substrate 1. The silicon oxide on the surface of the silicon substrate 1 will affect the performance of the prepared superconducting circuit.

[0057] To eliminate the negative impact of the oxide layer on the surface of substrate 1 on the fabrication of superconducting circuits, substrate 1 is cleaned using a BOE cleaning process before being placed into the vacuum chamber. Specifically, the silicon substrate 1 is immersed in BOE etching solution and etched for 10-15 minutes to remove the silicon oxide layer on the surface of the silicon substrate 1. Then, the silicon substrate 1 is removed from the BOE etching solution, rinsed with deionized water, and dried using a spin dryer or a dryer for later use.

[0058] It should be noted that when using BOE etchant to etch and clean the oxide layer on the surface of silicon substrate 1, the BOE etchant can be heated to 40-45℃, thereby accelerating the etching efficiency of the BOE etchant on the oxide layer on silicon substrate 1 and saving the cleaning time of substrate 1.

[0059] In some embodiments of the present invention, the step of forming the superconducting metal layer 2 on the surface of the substrate 1 includes:

[0060] Within the vacuum chamber, a superconducting metal material is deposited using an electron beam evaporation process to form the superconducting metal layer 2 on the surface of the substrate 1. For example, one specific method involves using aluminum as the superconducting material and preparing an aluminum film on the substrate 1 using an electron beam evaporation process inside the vacuum chamber. The aluminum deposition rate is controlled at [value missing]. / S, controlling the evaporation time, so that the final aluminum film thickness is maintained at about 100nm. The aluminum film produced in the vacuum chamber after adsorption by the adsorption structure has higher purity and fewer impurities, which is conducive to the preparation of high-performance superconducting circuits.

[0061] In some embodiments of the present invention, the step of patterning the superconducting metal layer 2 to obtain the superconducting circuit includes:

[0062] S51. A mask layer 3 with an etch-resistant pattern is formed on the superconducting metal layer 2. Specifically, the mask layer 3 can be prepared using photoresist. In practice, a photoresist layer is first formed on the superconducting metal layer 2, and then the photoresist layer is patterned to obtain the mask layer 3. For example, a photoresist layer is coated on the superconducting metal layer 2 using a spin coating process to form a photoresist layer, and an exposure and development operation is performed on the photoresist layer to obtain the mask layer 3. Optionally, the photoresist layer is made using a positive photoresist or a negative photoresist. For example, the photoresist is PMMA photoresist. In specific implementation, the photoresist layer is exposed and developed to form a resist pattern. It should be noted that the pattern formed by the photoresist layer that is not dissolved by the developer is the resist pattern. The superconducting metal layer 2 exposes the area to be etched that is not covered by the resist pattern. It can be understood that the shape of the resist pattern is consistent with the shape of the desired superconducting circuit, thereby obtaining a mask layer 3 with a resist pattern on the superconducting metal layer 2.

[0063] S52. Etch away the superconducting metal layer 2 not covered by the resist pattern to obtain a circuit pattern on the superconducting metal layer 2. For example, in this embodiment, a reactive ion etching process can be used to remove the superconducting metal layer 2 not covered by the resist pattern. By introducing a gas that can chemically react with the superconducting metal layer 2 without reacting with the mask layer 3 during the etching process, the etching of the superconducting metal layer 2 can be achieved. Furthermore, the reactive ion etching process has good etching directionality, and the obtained circuit pattern has a good etching morphology.

[0064] In addition, in this embodiment, the superconducting metal layer 2 not covered by the resist pattern can also be removed by a wet etching process. In the wet etching process, the substrate 1 is immersed in an etching solution that can react with the superconducting metal layer 2 but not with the mask layer 3. The etching solution is used to etch the area on the superconducting metal layer 2 not covered by the resist pattern, thereby achieving the etching of the superconducting metal layer 2.

[0065] S53. Remove the mask layer 3 to expose the circuit pattern, thereby obtaining the superconducting circuit. Clean and remove the mask layer 3 on the substrate 1 to expose the circuit pattern, thereby fabricating the superconducting circuit on the substrate 1.

[0066] Another embodiment of this application provides a quantum chip, wherein the quantum chip includes a superconducting circuit prepared by the above-described preparation method. The superconducting circuit on the quantum chip prepared by the above-described preparation method can effectively ensure that the prepared superconducting circuit has good electrical performance, thereby facilitating the stable transmission of quantum chip signals and effectively ensuring the product quality of the quantum chip.

[0067] It should be noted that the superconducting circuit in the quantum chip described above is prepared using the same method as the superconducting circuit described above, and therefore has the same beneficial effects as the superconducting circuit embodiments described above, so it will not be described again. For the sake of brevity, technical details not disclosed in the quantum chip embodiments of this application will not be elaborated here.

[0068] It should be noted that, as described herein, the terms “deposition process” and / or “deposition procedure” can refer to any process of growing, coating, depositing and / or otherwise transferring one or more first materials onto one or more second materials. Exemplary deposition processes may include, but are not limited to: physical vapor deposition (“PVD”), chemical vapor deposition (“CVD”), electrochemical deposition (“ECD”), atomic layer deposition (“ALD”), low-pressure chemical vapor deposition (“LPCVD”), plasma-enhanced chemical vapor deposition (“PECVD”), high-density plasma chemical vapor deposition (“HDPCVD”), subatmospheric pressure chemical vapor deposition (“SACVD”), rapid thermochemical vapor deposition (“RTCVD”), in-situ radical-assisted deposition, high-temperature oxide deposition (“HTO”), low-temperature oxide deposition (“LTO”), limited reaction process CVD (“LRPCVD”), ultra-high vacuum chemical vapor deposition (“UHVCVD”), metal-organic chemical vapor deposition (“MOCVD”), physical vapor deposition (“PVD”), chemical oxidation, sputtering, electroplating, evaporation, spin coating, ion beam deposition, electron beam deposition, laser-assisted deposition, chemical solution deposition, combinations thereof, and / or similar methods.

[0069] The above description, based on the embodiments shown in the drawings, details the structure, features, and effects of this application. The above description is only a preferred embodiment of this application, but this application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of this application, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and drawings, should be within the protection scope of this application.

Claims

1. A method of fabricating a superconducting circuit, characterized by, The method comprises the following steps: providing a vacuum chamber for accommodating a substrate (1) for carrying the superconducting circuit; forming an adsorption structure in the interior of the vacuum chamber for adsorbing gas impurities in the vacuum chamber; forming a superconducting metal layer (2) on the surface of the substrate (1); patterning the superconducting metal layer (2) to obtain the superconducting circuit; the step of forming the adsorption structure in the interior of the vacuum chamber comprises: evaporating adsorption material in the vacuum chamber and depositing the adsorption material in the interior of the vacuum chamber to obtain the adsorption structure, the adsorption material being titanium metal, and the adsorption structure being a titanium metal layer.

2. The method of making a superconducting circuit of claim 1, wherein, Before the step of providing a vacuum chamber for accommodating a substrate (1) for carrying the superconducting circuit, the method further comprises the following step: irradiating the substrate (1) with a UV light source to remove impurities on the surface of the substrate (1).

3. The method of making a superconducting circuit of claim 1, wherein, Before the step of providing a vacuum chamber for accommodating a substrate (1) for carrying the superconducting circuit, the method further comprises the following step: cleaning the substrate (1) by a BOE cleaning process to remove a native oxide layer on the surface of the substrate (1).

4. The method of making a superconducting circuit of any of claims 1-3, wherein, The step of forming a superconducting metal layer (2) on the surface of the substrate (1) comprises: in the vacuum chamber, evaporating superconducting metal material by an electron beam evaporation process to form the superconducting metal layer (2) on the surface of the substrate (1).

5. The method of making a superconducting circuit of claim 4, wherein, The step of patterning the superconducting metal layer (2) to obtain the superconducting circuit comprises: forming a mask layer (3) with a resist pattern on the superconducting metal layer (2); etching to remove the superconducting metal layer (2) not covered by the resist pattern to obtain a circuit pattern on the superconducting metal layer (2); removing the mask layer (3) to expose the circuit pattern, thereby obtaining the superconducting circuit.

6. The method of making a superconducting circuit of claim 5, wherein, The step of forming a mask layer (3) with a resist pattern on the superconducting metal layer (2) comprises: forming a photoresist layer on the superconducting metal layer (2), and patterning the photoresist layer to obtain the mask layer (3).

7. The method of making a superconducting circuit of claim 6, wherein, The step of patterning the photoresist layer to obtain the mask layer (3) comprises: performing an exposure and development operation on the photoresist layer to obtain the mask layer (3).

8. A quantum chip, characterized by The quantum chip comprises a superconducting circuit prepared by the preparation method of any one of claims 1-7.

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