CN116666935A - Coplanar waveguide resonator and manufacturing method thereof, superconducting quantum chip - Google Patents

Abstract

The application discloses a coplanar waveguide resonant cavity, a manufacturing method thereof and a superconducting quantum chip. The manufacturing method comprises the following steps: providing a substrate; forming a coplanar waveguide resonant cavity made of tantalum on a substrate; and after the coplanar waveguide resonant cavity is contacted with air, passivating the coplanar waveguide resonant cavity by utilizing nitrogen plasma so as to convert the oxide layers on the top surface and the side surface of the coplanar waveguide resonant cavity into tantalum nitride layers. In the passivation treatment process, nitrogen atoms can replace oxygen atoms in an oxide layer on the surface of the coplanar waveguide resonant cavity, and finally the oxide layer is converted into a tantalum nitride layer, so that the purpose of removing the oxide layer is achieved, and meanwhile, the tantalum nitride layer can prevent the oxygen atoms from entering due to insufficient driving force of oxygen, so that the surface oxide layer can be removed without introducing extra microwave loss, and the oxide layer is restrained from being regenerated.

Description

Coplanar waveguide resonator and manufacturing method thereof, superconducting quantum chip

technical field

The invention relates to the technical field of quantum chip manufacturing, in particular to a coplanar waveguide resonant cavity, a manufacturing method thereof, and a superconducting quantum chip.

Background technique

The transmission lines and signal readout lines in the superconducting quantum chip are made of superconducting coplanar waveguide resonators. The inventors of the present application have found in long-term research and development that the lower the microwave loss of the coplanar waveguide resonators, the higher the performance of superconducting qubits. The longer the coherence time. The microwave loss of the coplanar waveguide resonator is mainly caused by the defects of the two-level system, specifically, the microwave loss is mainly affected by the defects of the two-level system existing in the metal-air, metal-substrate and substrate-air interfaces . Therefore, reducing the microwave loss generated by the metal-air interface of the coplanar waveguide resonator can significantly improve the coherence time of superconducting qubits. For tantalum (Ta)-based coplanar waveguide resonators, the microwave loss generated at the metal-air interface mainly comes from the oxide layer (composed of tantalum oxide) on the metal surface and side walls.

At present, the existing technology mainly adopts two methods to remove the oxide layer. One is to use hydrofluoric acid etching to remove the oxide layer, but this will introduce molecular adsorption, which will bring additional charge loss and cause new microwave loss. The other is to use IBE or RIE over-etching to ensure complete removal of the oxide layer, but over-etching will cause etching damage on the surface and side of the coplanar waveguide resonator, resulting in additional microwave loss. And no matter which method is used, as time goes by, a new oxide layer will be formed on the surface of the coplanar waveguide resonator.

Contents of the invention

The purpose of the present invention is to provide a coplanar waveguide resonant cavity and its manufacturing method, superconducting quantum chip, to solve the problem in the prior art that removing the oxide layer will bring additional microwave loss, and can remove the surface oxide layer without Introduces additional microwave losses while inhibiting oxide regeneration.

In order to solve the above technical problems, the present invention provides a method for manufacturing a coplanar waveguide resonator, including:

provide the substrate;

forming a coplanar waveguide resonator made of tantalum on the substrate;

After the coplanar waveguide resonator is in contact with air, nitrogen plasma is used to passivate the coplanar waveguide resonator, so as to convert the oxide layer on the top surface and side surfaces of the coplanar waveguide resonator to nitriding Tantalum layer.

Preferably, before forming the coplanar waveguide resonator made of tantalum on the substrate, it also includes:

The substrate is cleaned.

Preferably, the cleaning of the substrate includes:

Perform NMP ultrasonic cleaning, IPA ultrasonic cleaning, and first DI ultrasonic cleaning on the substrate respectively;

Soaking the substrate into a piranha solution;

The substrate is subjected to the second DI ultrasonic cleaning, the BOE ultrasonic cleaning, and the third DI cleaning respectively.

Preferably, the material of the substrate is Si(111) or Si(100), and the time for the NMP ultrasonic cleaning, IPA ultrasonic cleaning and the first DI ultrasonic cleaning is 5-15min, and the immersion of the substrate The treatment temperature is 100-150°C, the soaking treatment time is 5-15 minutes, the time for the second DI ultrasonic cleaning is 10-20 minutes, the time for the BOE ultrasonic cleaning is less than 5 minutes, and the time for the third DI cleaning 1 to 10 minutes.

Preferably, a coplanar waveguide resonator made of tantalum is formed on the substrate, including:

depositing a tantalum film on the substrate;

The tantalum film is etched to form a coplanar waveguide resonant cavity.

Preferably, the tantalum film is deposited by magnetron sputtering process.

Preferably, the tantalum film is formed under the conditions of a power of 500-700W, a working pressure of 3-5mtorr, an argon gas flow rate of 30-40sccm, and an initial vacuum degree of 3*E-9Torr.

Preferably, the tantalum film is etched by ICP or RIE process.

Preferably, when the tantalum film is etched by the ICP process, the etching power is 400-700W, the working pressure is 5-15mtorr, the flow rate of Cl ₂ is 10-20 sccm, the flow rate of BCl ₃ is 40-50 sccm, and the flow rate of helium is 5 ～15sccm, the working temperature is 20～50℃, and the etching time is 20～40s.

Preferably, the passivation treatment adopts PECVD process.

Preferably, the process of the passivation treatment is:

Putting the substrate into a chamber, and treating it for 5-15 minutes under the conditions of a chamber pressure of 1-3 Torr, a temperature of 300°C, and a radio frequency plasma power of 15-30W;

The substrate is cooled to 100° C. using nitrogen gas at a flow rate of 100˜150 sccm, and the substrate is maintained at 100° C. for 1˜2 hours.

Preferably, the thickness of the coplanar waveguide resonant cavity is 100-150 nm, and the thickness of the tantalum nitride layer is 5-10 nm.

In order to solve the above technical problems, the present invention also provides a coplanar waveguide resonator obtained according to any one of the manufacturing methods of the coplanar waveguide resonator described above.

In order to solve the above technical problems, the present invention also provides a superconducting quantum chip, which has qubit control lines and signal readout lines, and the control lines and/or signal readout lines include common The coplanar waveguide resonator obtained by the method of manufacturing the planar waveguide resonator.

Different from the situation in the prior art, the manufacturing method of the coplanar waveguide resonator provided by the present invention forms a coplanar waveguide resonator made of tantalum on the substrate, and uses nitrogen plasma to treat the coplanar waveguide resonator exposed to air. Passivation treatment, during the passivation treatment process, nitrogen atoms will replace the oxygen atoms in the oxide layer on the surface of the coplanar waveguide resonator, and finally convert the oxide layer into a tantalum nitride layer, achieving the purpose of removing the oxide layer. At the same time, due to The driving force of oxygen is insufficient, and the tantalum nitride layer can prevent the entry of oxygen atoms, so that the present invention can remove the surface oxide layer without introducing additional microwave loss, and at the same time inhibit the regeneration of the oxide layer.

The coplanar waveguide resonator provided by the present invention is obtained according to the manufacturing method of the aforementioned coplanar waveguide resonator. The superconducting quantum chip provided by the present invention has control lines and/or signal readout lines of qubits, control lines and/or signal readout lines The line-taking includes the coplanar waveguide resonator obtained according to the aforementioned manufacturing method of the coplanar waveguide resonator, which has the same technical effect and will not be repeated here.

Description of drawings

FIG. 1 is a schematic flowchart of a method for manufacturing a coplanar waveguide resonator provided by an embodiment of the present invention.

Fig. 2 is a schematic diagram of the atomic arrangement of the surface material before and after passivation of the coplanar waveguide resonator.

FIG. 3 is a schematic flow chart of cleaning a substrate according to an embodiment of the present invention.

Fig. 4 is a schematic flow chart of passivation treatment according to an embodiment of the present invention.

Detailed ways

The specific implementation manner of the present invention will be described in more detail below with reference to schematic diagrams. Advantages and features of the present invention will be apparent from the following description and claims. It should be noted that all the drawings are in very simplified form and use inaccurate scales, and are only used to facilitate and clearly assist the purpose of illustrating the embodiments of the present invention.

In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right" etc. is based on the orientation or positional relationship shown in the drawings , is only for the convenience of describing the present invention and simplifying the description, but does not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

Please refer to FIG. 1 , an embodiment of the present invention provides a method for manufacturing a coplanar waveguide resonator. The manufacturing method includes:

S1: Provide a substrate.

Wherein, for example, the substrate may be a sapphire substrate or a silicon substrate.

S2: forming a coplanar waveguide resonant cavity made of tantalum on the substrate.

Wherein, the thickness of the coplanar waveguide resonant cavity can be set according to actual needs, for example, it is 100-150 nm.

S3: After the coplanar waveguide resonator is exposed to air, nitrogen plasma is used to passivate the coplanar waveguide resonator to convert the oxide layer on the top and side surfaces of the coplanar waveguide resonator into a tantalum nitride layer.

Among them, the coplanar waveguide resonator will inevitably come into contact with air during the manufacturing and storage process, so the surface will be naturally oxidized to form an oxide layer. The material of the coplanar waveguide resonator is tantalum, and the oxide layer on the surface is a tantalum oxide layer. During the passivation process of the coplanar waveguide resonator, nitrogen is ionized under the excitation of an external electromagnetic field to form nitrogen plasma. After being accelerated by an external electric field, the nitrogen plasma bombards the oxide layer and reacts with the oxide layer, which has energy Nitrogen atoms displace oxygen atoms and the oxide layer is converted to a tantalum nitride layer. The thickness of the tantalum nitride layer can be set according to actual needs, for example, it is 5-10 nm.

As shown in Figure 2a, it is a schematic diagram of the atomic arrangement of the surface material before the passivation of the coplanar waveguide resonator. A coplanar waveguide resonant cavity 2 is formed on the substrate 1. The surface material of the coplanar waveguide resonant cavity 2 is tantalum oxide, and the atoms of the surface material only contain tantalum atoms and oxygen atoms. As shown in Figure 2b, it is a schematic diagram of the atomic arrangement of the surface material after passivation of the coplanar waveguide resonator. Most of the oxygen atoms on the surface of the coplanar waveguide resonator 2 are replaced by nitrogen atoms, so that the tantalum oxide is converted into tantalum nitride, and the oxide layer on the surface of the coplanar waveguide resonator is removed. Tantalum nitride is a superconductor at low temperature, and its properties are stable. Under natural storage conditions, due to insufficient driving force of oxygen, tantalum nitride can prevent oxygen atoms from entering, thereby inhibiting the tantalum film from being oxidized for a long time. And the removal of the oxide layer will not cause damage to the coplanar waveguide resonant cavity and the introduction of chemical solvents, so no additional microwave loss will be introduced.

Through the above method, the manufacturing method of the coplanar waveguide resonator provided by the present invention forms a coplanar waveguide resonator made of tantalum on the substrate, and uses nitrogen plasma to passivate the coplanar waveguide resonator after contacting air, During the passivation process, nitrogen atoms will replace the oxygen atoms in the oxide layer on the surface of the coplanar waveguide resonator, and finally convert the oxide layer into a tantalum nitride layer, achieving the purpose of removing the oxide layer. At the same time, due to the driving force of oxygen Insufficiently, the tantalum nitride layer can prevent the entry of oxygen atoms, so that the present invention can remove the surface oxide layer without introducing additional microwave loss, and at the same time inhibit the regeneration of the oxide layer.

In some embodiments of the present application, forming a coplanar waveguide resonator made of tantalum on the substrate, that is, before step S2, further includes: cleaning the substrate. Specifically, referring to FIG. 3, the substrate is cleaned, including:

S201: Perform NMP ultrasonic cleaning, IPA ultrasonic cleaning, and first DI ultrasonic cleaning on the substrate respectively.

Wherein, in this step, NMP ultrasonic cleaning can be performed first, and the first DI ultrasonic cleaning can be performed last.

S202: Soak the substrate in the piranha solution for treatment.

S203: performing the second DI ultrasonic cleaning, the BOE ultrasonic cleaning, and the third DI cleaning on the substrate respectively.

Wherein, in this step, the BOE ultrasonic cleaning can be performed after the second DI ultrasonic cleaning and before the third DI cleaning.

In a specific application, the material of the substrate is Si(111) or Si(100), the time of NMP ultrasonic cleaning, IPA ultrasonic cleaning and the first DI ultrasonic cleaning are all 5-15min, and the soaking temperature of the substrate is 100-150°C, soaking time is 5-15 minutes, the second DI ultrasonic cleaning time is 10-20 minutes, BOE ultrasonic cleaning time is less than 5 minutes, and the third DI cleaning time is 1-10 minutes.

In some embodiments of the present application, forming the coplanar waveguide resonator made of tantalum on the substrate includes: depositing a tantalum film on the substrate; and etching the tantalum film to form the coplanar waveguide resonator. The tantalum film can be deposited by the magnetron sputtering process. In a specific application, the tantalum film is deposited at a power of 500-700W, a working pressure of 3-5mtorr, an argon gas flow rate of 30-40sccm, and an initial vacuum of 3*E-9Torr. formed under the conditions.

Further, the tantalum film can be etched by ICP (Inductively Coupled Plasma) or RIE (Reactive Ion Etching) process. In a specific application, when the tantalum film is etched by the ICP process, the etching power is 400-700W, the working pressure is 5-15mtorr, the flow rate of Cl ₂ is 10-20 sccm, the flow rate of BCl ₃ is 40-50 sccm, and the flow rate of helium is 5-15 sccm, the working temperature is 20-50°C, and the etching time is 20-40s. Among them, Cl ₂ and BCl ₃ are used as etching gas, and helium is used as cooling gas.

In some embodiments of the present application, the passivation treatment adopts PECVD process. Please refer to Figure 4, in a specific application, the process of passivation treatment is:

S301: Put the substrate into the chamber, and process it for 5-15 minutes under the conditions of chamber pressure of 1-3 Torr, temperature of 300° C., and radio frequency plasma power of 15-30 W.

S302: Cool the substrate to 100° C. with nitrogen gas at a flow rate of 100˜150 sccm, and keep the substrate at 100° C. for 1˜2 hours.

The present invention also provides a coplanar waveguide resonator obtained according to the manufacturing method of the coplanar waveguide resonator in the foregoing embodiments.

The present invention also provides a superconducting quantum chip, which has qubit control lines and signal readout lines. surface waveguide resonator.

In the description of this specification, description with reference to the terms "one embodiment", "some embodiments", "example" or "specific example" means that a specific feature, structure, material or characteristic described in connection with the embodiment or example Included in at least one embodiment or example of the invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

The foregoing are only preferred embodiments of the present invention, and do not limit the present invention in any way. Any person skilled in the technical field, within the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the technical solution of the present invention. The content still belongs to the protection scope of the present invention.

Claims (14)

1. A method for manufacturing a coplanar waveguide resonator, characterized in that, comprising: provide the substrate; forming a coplanar waveguide resonator made of tantalum on the substrate; After the coplanar waveguide resonator is in contact with air, nitrogen plasma is used to passivate the coplanar waveguide resonator, so as to convert the oxide layer on the top surface and side surfaces of the coplanar waveguide resonator to nitriding Tantalum layer. 2. The manufacturing method according to claim 1, wherein, before forming a coplanar waveguide resonator made of tantalum on the substrate, further comprising: The substrate is cleaned. 3. The manufacturing method according to claim 2, wherein the cleaning of the substrate comprises: Perform NMP ultrasonic cleaning, IPA ultrasonic cleaning, and first DI ultrasonic cleaning on the substrate respectively; Soaking the substrate into a piranha solution; The substrate is subjected to the second DI ultrasonic cleaning, the BOE ultrasonic cleaning, and the third DI cleaning respectively. 4. manufacturing method according to claim 3, is characterized in that, the material of described substrate is Si (111) or Si (100), described NMP ultrasonic cleaning, IPA ultrasonic cleaning and DI ultrasonic cleaning for the first time The time is 5-15 minutes, the soaking treatment temperature of the substrate is 100-150 ° C, the soaking treatment time is 5-15 minutes, the time of the second DI ultrasonic cleaning is 10-20 minutes, the BOE ultrasonic cleaning The time is less than 5 minutes, and the time for the third DI cleaning is 1-10 minutes. 5. The manufacturing method according to claim 1, wherein the formation of a coplanar waveguide resonator made of tantalum on the substrate comprises: depositing a tantalum film on the substrate; The tantalum film is etched to form a coplanar waveguide resonant cavity. 6. The manufacturing method according to claim 5, wherein the etching is deposited by a magnetron sputtering process. 7. The manufacturing method according to claim 6, characterized in that, the tantalum film has a power of 500-700W, a working pressure of 3-5mtorr, an argon gas flow rate of 30-40sccm, and an initial vacuum degree of 3*E- Formed under the condition of 9Torr. 8. The manufacturing method according to claim 5, wherein the tantalum film is etched by ICP or RIE process. 9. The manufacturing method according to claim 8, characterized in that, when the tantalum film is etched by ICP process, the etching power is 400-700W, the working pressure is 5-15mtorr, and _the Cl flow rate is 10-20sccm, The BCl ₃ flow rate is 40-50 sccm, the helium gas flow rate is 5-15 sccm, the working temperature is 20-50°C, and the etching time is 20-40s. 10. The manufacturing method according to claim 1, wherein the passivation treatment adopts a PECVD process. 11. The manufacturing method according to claim 10, characterized in that, the process of the passivation treatment is: Putting the substrate into a chamber, and treating it for 5-15 minutes under the conditions of a chamber pressure of 1-3 Torr, a temperature of 300°C, and a radio frequency plasma power of 15-30W; The substrate is cooled to 100° C. using nitrogen gas at a flow rate of 100˜150 sccm, and the substrate is maintained at 100° C. for 1˜2 hours. 12. The manufacturing method according to claim 1, wherein the thickness of the coplanar waveguide resonant cavity is 100-150 nm, and the thickness of the tantalum nitride layer is 5-10 nm. 13. A coplanar waveguide resonator obtained according to the manufacturing method of the coplanar waveguide resonator according to any one of claims 1 to 12. 14. A superconducting quantum chip, characterized in that it has a control line and a signal readout line of qubits, and the control line and/or signal readout line comprises the common chip according to any one of claims 1 to 12 The coplanar waveguide resonator obtained by the method of manufacturing the planar waveguide resonator.