阅读说明：本技术 一种铌基约瑟夫森结刻蚀方法 (Niobium-based Josephson junction etching method ) 是由 谷志强 吴志浩 吴愧 蒋中原 车东晨 许开东 于 2019-09-27 设计创作，主要内容包括：一种铌基约瑟夫森结刻蚀方法,属于超导器件制备技术领域。具体方法如下：在真空状态下将待刻蚀样品通过传送装置送至反应离子刻蚀腔,通入刻蚀气体,对待刻蚀样品Nb层进行刻蚀；然后在真空状态下通过传送装置将反应离子刻蚀后的样品送入离子束刻蚀机,通入惰性气体,刻蚀AlO<Sub>x</Sub>/Al层；样品出真空,得到Nb基超导器件。所述刻蚀方法简单、效果好,制得的超导器件良率和产能高,并且所述器件有机物或金属沉积。(A niobium-based Josephson junction etching method belongs to the technical field of superconducting device preparation. The specific method comprises the following steps: conveying a sample to be etched to a reactive ion etching cavity through a conveying device in a vacuum state, introducing etching gas, and etching the Nb layer of the sample to be etched; then the sample after the reactive ion etching is sent into an ion beam etching machine through a conveying device in a vacuum state, inert gas is introduced, and AlO is etched x A layer of/Al; and (5) taking a sample out of vacuum to obtain the Nb-based superconducting device. The etching method is simple and has good effect, the prepared superconducting device has high yield and capacity, and the device is deposited by organic matters or metal.)

1. The niobium-based Josephson junction comprises a mask material, a Nb layer and AlO in sequence from top to bottom_xThe niobium-based Josephson junction etching method is characterized in that the niobium-based Josephson junction is processed under the condition of not interrupting a vacuum environment, and the etching method comprises the following specific steps:

putting a niobium-based Josephson junction sample to be etched into a transmission device in a vacuum state, and transmitting the sample to a reactive ion etching cavity by the transmission device;

step two, introducing etching gas into the reactive ion etching cavity in a vacuum state, and etching the Nb layer of the sample to be etched;

thirdly, conveying the sample to an ion beam etching machine by using a conveying device in a vacuum state, introducing inert gas, and etching AlO_xA layer of/Al;

and step four, vacuumizing the sample to obtain the niobium-based Josephson junction superconducting device after etching.

2. The method of claim 1, wherein the etching process further comprises in-situ etching AlO in step III_xAnd after the Al layer is formed, conveying the sample to a plasma CVD chamber through a conveying device under the vacuum condition for in-situ coating protection, and then performing the operation of the fourth step to ensure that the sample is vacuumized to obtain the etched niobium-based Josephson junction superconducting device.

3. The method of claim 1, wherein AlO is etched in the third step_xAnd modifying the surface of the sample and the side wall of the step by an ion beam etching machine after the Al layer is removed.

4. The method of claim 3, wherein the step of forming the niobium-based Josephson junction is performed in a batch processEtching AlO in the third step_xAnd after the Al layer is formed, modifying the surface of the sample and the side wall of the step by adjusting the energy of an ion beam etching machine to be 50-300 eV and the inclination angle to be 60-80 ℃ so as to remove the deposit.

5. The method of claim 3, wherein AlO is etched through by adjusting the energy of the ion beam etcher to 50-300 eV and the tilt angle to 60-80 ° in the third step_xand/Al layer, and modifying the surface of the sample and the side wall of the step to remove the deposit.

6. The method of claim 1, wherein the mask material is a hard mask or a photoresist mask.

7. The method of claim 1, wherein the etching gas in step two is a fluorine-based gas.

8. The method of claim 1, wherein in step three, the inert gas is Ar, He or Ne.

Technical Field

The invention belongs to the technical field of superconducting device preparation, and particularly relates to a niobium-based Josephson junction etching method.

Background

The phenomenon of superconduction was known as early as 1911. At present, various research and development on superconducting technologies in China are on the way, and enter industrialized operation, and the superconducting technologies are generally operated in the power industry, the communication field, the military field, the medical field and the like. With the development of superconducting technology, the importance of superconducting quantum devices is gradually highlighted, and the superconducting quantum devices are particularly concerned in the field of weak magnetic detection and quantum computing. In superconducting electronics, the fabrication of josephson junctions is a crucial step therein. Superconducting materials exhibit zero resistance only at a particular temperature. Superconducting materials are mainly divided into two categories, high-temperature superconductors and low-temperature superconductors, and generally, a material which has a superconducting phenomenon at the temperature of liquid nitrogen under normal pressure becomes a high-temperature superconductor, and a material which has a superconducting phenomenon at a lower temperature becomes a low-temperature superconductor.

Josephson junctions the british physicist breine, obtained in the nobel prize. Consisting of two superconductors separated by a very thin non-superconducting layer so that electrons can pass through the insulating layer. The current between the superconductors when there is no voltage is called Josephson current (Josephson current), and the movement of electrons through an obstacle is called Josephson tunneling. Two or more junctions joined together by superconducting paths constitute a so-called Josephson interferometer.

In general, the structure of the josephson junction in the device has two types of sandwich structure and planar structure. The sandwich structure becomes a sandwich junction and is generally used for low-temperature superconducting devices; planar structures are commonly used in high temperature superconducting devices.

In low-temperature superconducting devices, the etching of Nb-based devices is a difficult point in the device preparation process. Particularly, the Nb-AlOx/Al-Nb structure is subjected to reactive ion etching, so that the problems of Nb undercut or serious side wall deposition and the like usually occur, and the performance of the device is greatly influenced. The abnormal conditions are shown in fig. 1 and fig. 2 (the Nb-Si-Nb undercut topography and the Nb-Nb deposit topography are also included in fig. 1 and fig. 2). In the case of severe deposition, in addition to organic deposition, there is also much metal deposition, which is difficult to clean and has a significant impact on device performance.

As shown in FIG. 3, the Nb layer and AlO layer are etched during the Josephson junction etching process_xDifferent properties of Al layer, etchingThe etching method is also different, if chlorine-based gas etching is used, AlO_xthe/Al layer is prone to absorb chloride ions and cause corrosion. How to achieve etching of the upper Nb layer and the intermediate AlO_xThe Al layer reduces the damage to the lower Nb layer, and becomes an important process link.

Disclosure of Invention

The technical problem to be solved is as follows: aiming at the technical problems, the invention provides the niobium-based Josephson junction etching method which has the advantages of simple etching method, good effect, high product yield, high productivity and the like.

The technical scheme is as follows: the niobium-based Josephson junction comprises a mask material, a Nb layer and AlO in sequence from top to bottom_xThe method comprises the following steps of (1) forming an Al layer, an Nb layer and a bottom layer material, wherein the niobium-based Josephson junction is processed under the condition of not interrupting a vacuum environment, and the etching method comprises the following specific steps:

putting a niobium-based Josephson junction sample to be etched into a transmission device in a vacuum state, and transmitting the sample to a reactive ion etching cavity by the transmission device;

step two, introducing etching gas into a reactive ion etching cavity (ICP cavity) in a vacuum state, and etching the Nb layer of the sample to be etched;

thirdly, the sample is transmitted to an ion beam etching machine (IBE chamber) by a transmission device in a vacuum state, inert gas is introduced, and AlO is etched_xA layer of/Al;

and step four, vacuumizing the sample to obtain the niobium-based Josephson junction superconducting device after etching.

Preferably, the etching method further comprises in-situ protection, and AlO is etched in the third step_xAnd after the Al layer is formed, conveying the sample to a plasma CVD chamber through a conveying device under the vacuum condition for in-situ coating protection, and then performing the operation of the fourth step to ensure that the sample is vacuumized to obtain the etched niobium-based Josephson junction superconducting device.

Preferably, AlO is etched in the third step_xAfter the Al layer is formed, the surface of the sample and the side wall of the step are etched by an ion beam etching machineModified to remove deposits.

Preferably, AlO is etched in the third step_xAnd after the Al layer is formed, modifying the surface of the sample and the side wall of the step by adjusting the energy of an ion beam etching machine to be 50-300 eV and the inclination angle to be 60-80 ℃ so as to remove the deposit.

Preferably, the third step is to etch through AlO by adjusting the energy of the ion beam etching machine to be 50-300 eV and the inclination angle to be 60-80 DEG_xand/Al layer, and modifying the surface of the sample and the side wall of the step to remove the deposit.

Preferably, the mask material is a hard mask or a photoresist mask.

Preferably, the etching gas in the second step is a fluorine-based gas.

Preferably, the inert gas in the third step is Ar, He or Ne.

Has the advantages that: 1. the method comprises etching Nb with a reactive ion etcher, stopping at AlO_xa/Al layer, etching AlO with IBE_xAl, the etching rate and the etching depth are accurate and controllable, and AlO can be effectively reduced_xDamage to the Nb layer below the Al layer;

2. the IBE has small selection on metal etching, and the smoothness of the side wall can be still ensured by etching a plurality of layers of metal;

3. the etching scheme is suitable for a hard mask or photoresist mask sample, and can ensure no deposition or less deposition on the etching of a large-size pattern, a submicron-sized pattern or a pattern with a smaller size;

4. the method ensures that a sample to be etched is in a condition of not interrupting vacuum during processing, an AlOx/Al layer is arranged between two Nb layers of the sample, wherein an insulating layer AlOx is only 1nm thick, and an Al layer is only 9nm thick. Therefore, the processing is finished under the condition of not interrupting the vacuum, and the performance and the yield of the device are greatly facilitated.

5. The etching method is simple and good in etching effect, and the yield and the capacity of the niobium-based Josephson junction superconducting device are improved.

Drawings

FIG. 1 is a prior art undercut topography, wherein a is a Nb-Si-Nb undercut topography, b is a Nb-AlOx-Al-Nb one undercut topography, and c is a Nb-AlOx-Al-Nb another undercut topography;

FIG. 2 is a prior art severe deposition profile, wherein a is a Nb-Si-Nb deposition profile, b is a Nb-AlOx-Al-Nb deposition profile, and c is another Nb-AlOx-Al-Nb deposition profile;

FIG. 3 is a schematic diagram of the structure of a sample to be etched of a niobium-based Josephson junction before and after etching according to example 1;

FIG. 4 is a schematic diagram illustrating the structure of a sample to be etched of a niobium-based Josephson junction with an in-situ deposited protection film according to example 4 before and after etching;

FIG. 5 is a sample topography of niobium-based Josephson junctions prior to etching;

FIG. 6 is a graph showing the topography of a step-shaped niobium-based Josephson junction with a more serious sidewall deposition after ICP etching;

FIG. 7 is a morphology diagram of a step-shaped niobium-based Josephson junction with a serious side wall deposition after ICP etching and after IBE modification;

FIG. 8 is a topographical view of a Nb step-shaped Nb-based Josephson junction with less pronounced ICP etched Nb sidewall deposition;

FIG. 9 is a diagram of the topography of an IBE-modified Nb step-shaped Nb-based Josephson junction of a device with less obvious Nb sidewall deposition by ICP etching;

fig. 10 is an EDS analysis data graph of the niobium-based josephson junction after etching, wherein the left side of the graph is the EDS analysis data of the Nb-stepped niobium-based josephson junction with less obvious deposition on the ICP-etched Nb sidewall shown in fig. 8, and the right side is the EDS analysis data graph of the Nb-stepped niobium-based josephson junction with less obvious deposition on the ICP-etched Nb sidewall shown in fig. 9 after IBE modification.

Detailed Description

The invention is further described below with reference to the accompanying drawings and specific embodiments.