WO2024140103A1

WO2024140103A1 - Magnetic tunnel junction testing structure, preparation method, and magnetic tunnel junction testing method

Info

Publication number: WO2024140103A1
Application number: PCT/CN2023/137149
Authority: WO
Inventors: 王明; 何世坤; 宫俊录
Original assignee: 浙江驰拓科技有限公司
Priority date: 2022-12-29
Filing date: 2023-12-07
Publication date: 2024-07-04
Also published as: CN118284309A

Abstract

A magnetic tunnel junction testing structure, a preparation method, and a magnetic tunnel junction testing method. The magnetic tunnel junction testing structure comprises: a magnetic tunnel junction unit having a first surface and a second surface opposite to each other; a plurality of conductive plugs arranged on the first surface and the second surface, the plurality of conductive plugs comprising at least one first conductive plug and at least one second conductive plug, the first conductive plug being connected to the first surface, and the second conductive plug being connected to the second surface; a plurality of conductive wires, each conductive wire having a first end and a second end opposite to each other, the first ends being connected to the conductive plugs in one-to-one correspondence so that the conductive wires are connected to the magnetic tunnel junction unit by means of the conductive plugs, and the conductive wires having one-to-one correspondence to the conductive plugs; and a plurality of test electrodes connected to the second ends in one-to-one correspondence. According to the described structure, pin positions are not limited to being set at equal intervals, so that the resolution and accuracy of testing magnetic tunnel junction testing structures can be improved.

Description

Magnetic tunnel junction test structure, preparation method and magnetic tunnel junction test method

Technical Field

The present disclosure relates to the technical field of magnetic electronic device testing, and in particular to a magnetic tunnel junction testing structure, a preparation method, and a magnetic tunnel junction testing method.

Background technique

Magnetic random access memory (MRAM) uses magnetic tunnel junction (MTJ) as the basic unit of information storage. By testing MTJ devices using the final wafer acceptability test (Final WAT), the electrical parameters, magnetic parameters, reliability parameters, etc. of the device can be obtained. By using the in-plane current tunneling measurement (CIPT) technology, the electrical parameters at the film level can be obtained, such as the resistance area product (RA)/magnetoresistance (MR), etc. Both have their own advantages and disadvantages in terms of characterization methods. The former cannot obtain the relevant parameters at the MTJ film level, such as RA/MR, etc., while the latter cannot obtain the final electrical parameters at the device level.

The in-plane current tunneling measurement (CIPT) technique measures the resistance of a magnetic tunnel junction by using a multi-pin probe. The actual top resistance RT of the existing magnetic tunnel junction test structure is too large after process integration, resulting in a too small minimum distance between the probes that can pass through the tunnel barrier layer of the magnetic tunnel junction. This requires that the distance between the probes for testing the magnetic tunnel junction test structure be small enough. However, the current process level results in limited test accuracy of four equally spaced probes, making it difficult to meet the requirement of a small enough distance between the probes.

Summary of the invention

The main purpose of the present disclosure is to provide a magnetic tunnel junction test structure, a preparation method and a test method of a magnetic tunnel junction, so as to solve the problem of low test accuracy of the magnetic tunnel junction test structure in the prior art.

In order to achieve the above-mentioned purpose, according to one aspect of the present disclosure, a magnetic tunnel junction test structure is provided, comprising: a magnetic tunnel junction unit having a first surface and a second surface relative to each other; a plurality of conductive plugs arranged on the first surface and the second surface, the plurality of conductive plugs comprising at least one first conductive plug and at least one second conductive plug, the first conductive plug being connected to the first surface, and the second conductive plug being connected to the second surface; a plurality of conductive wires, each conductive wire having a first end and a second end relative to each other, the first end being connected to the conductive plug in a one-to-one correspondence, so that the conductive wire is connected to the magnetic tunnel junction unit through the conductive plug, and the conductive wire and the conductive plug are in a one-to-one correspondence; a plurality of test electrodes being connected to the second end in a one-to-one correspondence.

Furthermore, the magnetic tunnel junction test structure further includes: a first insulating layer disposed on the first surface, and a first conductive plug penetrating the first insulating layer to the first surface; a second insulating layer disposed on the second surface, and a second conductive plug penetrating the second insulating layer to the second surface.

Furthermore, the above-mentioned magnetic tunnel junction test structure also includes: a first substrate, which is arranged on a side of the first insulating layer away from the first surface, and a part of the multiple conductive wires are arranged at intervals in the first substrate; a second substrate, which is arranged on a side of the second insulating layer away from the second surface, and another part of the multiple conductive wires are arranged at intervals in the second substrate.

Furthermore, the magnetic tunnel junction test structure further includes: a selection circuit having a plurality of input terminals and a plurality of output terminals, wherein the input terminals are connected to the second terminals in a one-to-one correspondence, and the plurality of output terminals are connected to the plurality of test electrodes in a one-to-one correspondence.

Furthermore, the number of the test electrodes is at least 4, and the selection circuit includes at least 4 output terminals.

Further, the number of the first conductive plugs is a first number, the number of the second conductive plugs is a second number, and the first number is equal to the second number.

Further, the first conductive plug has a first orthographic projection on the first surface, the second conductive plug has a second orthographic projection on the first surface, and the first orthographic projection does not overlap with the second orthographic projection.

Furthermore, both the first orthographic projection and the second orthographic projection are multiple and alternately distributed.

According to another aspect of the present disclosure, a method for preparing a magnetic tunnel junction test structure is provided, comprising the following steps: providing a plurality of test electrodes; forming a plurality of conductive wires, each conductive wire having a first end and a second end opposite to each other, the second end being connected to the test electrode in a one-to-one correspondence; forming a plurality of conductive plugs, the plurality of conductive plugs being connected to the first end in a one-to-one correspondence, and the plurality of conductive plugs including at least one first conductive plug and at least one second conductive plug; forming a magnetic tunnel junction unit connected to the plurality of conductive plugs, the magnetic tunnel junction unit having a first surface and a second surface opposite to each other, the first conductive plug being arranged on the first surface, the second conductive plug being arranged on the second surface, and the conductive wire being connected to the magnetic tunnel junction unit through the conductive plugs.

Furthermore, the step of forming a plurality of conductive lines includes: providing a first substrate, forming at least one first conductive line on the first substrate; after the step of forming a first conductive plug, connecting the first conductive line to the first conductive plug in a one-to-one correspondence; after the step of forming a magnetic tunnel junction unit and a second conductive plug, providing a second substrate, forming at least one second conductive line on the second substrate, connecting the second conductive line to the second conductive plug in a one-to-one correspondence.

Furthermore, the step of forming a first conductive plug includes: covering a first insulating dielectric layer on a side of the first substrate having a first conductive line; etching the first insulating dielectric layer to form a first connecting hole that penetrates the first insulating dielectric layer to the first conductive line, and the first connecting hole corresponds one-to-one to the conductive line; and forming a first conductive plug in the first connecting hole.

Furthermore, in the step of forming a magnetic tunnel junction unit, the magnetic tunnel junction unit is formed on a side of the first insulating dielectric layer away from the first substrate, and the step of forming a second conductive plug includes: covering the second insulating dielectric layer on the side of the magnetic tunnel junction unit away from the first insulating dielectric layer; etching the second insulating dielectric layer to form a second connecting hole that penetrates the second insulating dielectric layer to the magnetic tunnel junction unit, and the second connecting hole corresponds one-to-one to the conductive line; and forming a second conductive plug in the second connecting hole.

According to another aspect of the present disclosure, a method for testing a magnetic tunnel junction is also provided, which adopts the above-mentioned magnetic tunnel junction test structure, and the magnetic tunnel junction test structure includes at least four test electrodes, any two of the four test electrodes are used to test the current of the magnetic tunnel junction unit, and the remaining two test electrodes are used to test the potential difference corresponding to the current. The testing method includes: determining a plurality of groups of combinations of two of the four test electrodes, wherein each of the plurality of groups of combinations has two first test electrodes and two second test electrodes, the two first test electrodes are used to test the current of the magnetic tunnel junction unit, and the two second test electrodes are used to test the potential difference corresponding to the current; obtaining the test current of the two first test electrodes corresponding to each group of combinations; obtaining the potential difference of the two second test electrodes corresponding to each group of combinations; obtaining a set of electrode distances corresponding to the two first test electrodes and the two second test electrodes, wherein the electrode distance set includes The first electrode distance and the second electrode distance, the first electrode distance is the distance between a first test electrode and two second test electrodes, and the second electrode distance is the distance between another first test electrode and two second test electrodes; according to the potential difference, resistance value and electrode distance set, a target relationship corresponding to each group of combination methods is obtained; according to the target relationship, the electrical parameters of the magnetic tunnel junction test structure are extracted.

Furthermore, the magnetic tunnel junction unit in the magnetic tunnel junction test structure has a first surface and a second surface, and the first surface and the second surface are respectively connected to at least two test electrodes, and the test current of the two first test electrodes corresponding to each group of combinations is obtained, and the potential difference of the two second test electrodes corresponding to each group of combinations is obtained, including: obtaining the test current between any two test electrodes connected to the first surface, and obtaining the potential difference between the remaining two test electrodes connected to the second surface; or obtaining the test current between any two test electrodes connected to the second surface, and obtaining the potential difference between the remaining two test electrodes connected to the first surface.

By applying the technical solution disclosed in the present invention, a magnetic tunnel junction test structure is provided. Conductive plugs and conductive wires connected to the conductive plugs are arranged on two opposite surfaces of the magnetic tunnel junction unit, so that the magnetic tunnel junction unit of the magnetic tunnel junction test structure can be led out through the multiple conductive plugs and the multiple conductive wires, and multiple test electrodes can be connected, so that needle insertion based on the multiple test electrodes connected to the two side surfaces of the MTJ can be simultaneously performed, thereby realizing the performance test of the MTJ. Compared with the traditional magnetic tunnel junction test structure, the test structure can realize the simultaneous needle insertion measurement on the first surface and the second surface of the MTJ, thereby expanding the needle insertion position of the probe, so that the needle insertion position is not limited to the equal spacing setting, thereby improving the resolution and accuracy of testing the magnetic tunnel junction test structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constituting a part of the present disclosure are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings:

FIG1 is a schematic diagram showing a magnetic tunnel junction test structure provided according to an embodiment of the present disclosure;

FIG2 is a schematic diagram showing another magnetic tunnel junction test structure provided according to an embodiment of the present disclosure;

FIG3 is a schematic diagram showing the relationship between the potential difference Vt and Vb of the MTJ measured by the magnetic tunnel junction test structure provided in this embodiment and the change with x;

FIG. 4 shows a schematic structural diagram of a magnetic tunnel junction test structure with a selection circuit provided according to an embodiment of the present disclosure.

The above drawings include the following reference numerals:
10. Magnetic tunnel junction unit; 210. First conductive plug; 220. Second conductive plug; 30. Conductive line; 40. Selection circuit; 50. Test electrode.

Detailed ways

It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

In order to enable those skilled in the art to better understand the scheme of the present disclosure, the technical scheme in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present disclosure.

It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present disclosure described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, 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 clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

As introduced in the background technology, the actual top resistance RT of the existing magnetic tunnel junction test structure is too large after process integration, resulting in a too small minimum distance between the probes that can pass through the tunnel barrier layer of the magnetic tunnel junction, which requires the probe spacing between the probes for testing the magnetic tunnel junction test structure to be sufficiently small. However, the existing process level results in limited testing accuracy of four equally spaced probes, making it difficult to meet the requirement of a sufficiently small probe spacing between the probes.

In order to solve the above technical problems, according to an embodiment of the present disclosure, a magnetic tunnel junction test structure is provided, as shown in Figures 1 and 2, including: a magnetic tunnel junction unit 10, having a first surface and a second surface relative to each other; a plurality of conductive plugs, arranged on the first surface and the second surface, the plurality of conductive plugs including at least one first conductive plug 210 and at least one second conductive plug 220, the first conductive plug 210 is connected to the first surface, and the second conductive plug 220 is connected to the second surface; a plurality of conductive wires 30, each conductive wire 30 having a first end and a second end relative to each other, the first end being connected to the conductive plug in a one-to-one correspondence, so that the conductive wire 30 is connected to the magnetic tunnel junction unit 10 through the conductive plug, and the conductive wire 30 is in a one-to-one correspondence with the conductive plug; a plurality of test electrodes, connected to the second end in a one-to-one correspondence.

In the above-mentioned magnetic tunnel junction test structure of the present embodiment, conductive plugs and conductive wires connected to the conductive plugs are arranged on two opposite surfaces of the magnetic tunnel junction unit, so that the magnetic tunnel junction (MTJ) unit of the magnetic tunnel junction test structure can be led out through the multiple conductive plugs and the multiple conductive wires, and multiple test electrodes can be connected, so that the needle insertion can be simultaneously based on the multiple test electrodes connected to the two side surfaces of the MTJ, thereby realizing the performance test of the MTJ. Compared with the traditional magnetic tunnel junction test structure, the test structure can realize the simultaneous needle insertion measurement on the first surface and the second surface of the MTJ, thereby expanding the needle insertion position of the probe, so that the needle insertion position is not limited to the equal spacing setting, thereby improving the resolution and accuracy of testing the magnetic tunnel junction test structure.

Specifically, taking the current 4-probe method as an example, the magnetic tunnel junction test structure has four test electrodes, of which two test electrodes (PAD 1′, PAD 2′) are led out with probes for testing current, and the other two test electrodes (PAD 3′, PAD 4′) are led out with probes for testing potential difference. The conventional magnetic tunnel junction test structure in the prior art measures the potential difference _Vt of the MTJ to satisfy the following formula:

The surface where the current needle is located is regarded as the top, and the other surface is the bottom. _RT is the resistance value of the top resistor of the MTJ, and _RB is the resistance value of the bottom resistor of the MTJ. RA is the resistance-area product of the MTJ, which can characterize the thickness of the barrier layer, _K0 represents the 0th-order second-kind modified Bessel function, and a, b, c, d are the distance sets between the test electrodes in the current 4-probe method, including: the electrode distances between PAD 1′ and PAD 3′ and PAD 4′, and the electrode distances between PAD 2′ and PAD 3′ and PAD 4′. Preferably, the four probes are arranged in the same straight line with equal spacing, a=b/2=c/2=d=x, and in this case, the above formula can be simplified to:

According to the above formula, the test accuracy of the traditional magnetic tunnel junction test structure depends on R _T /R _B , that is, it depends on the resistance ratio of the top resistor to the bottom resistor in the MTJ. As shown in Figure 3, it is a schematic diagram of the relationship between Vt and x. It can be seen that when x approaches 0, Vt approaches Rt. In order to improve the fitting accuracy, the sampling point needs to be taken at a position where x is as small as possible, which faces great difficulties in actual operation.

Taking the current 4-probe method as an example, the magnetic tunnel junction test structure has four test electrodes, of which two test electrodes (PAD 1, PAD 2) are led out by probes for testing current, and the other two test electrodes (PAD 3, PAD 4) are led out by probes for testing potential difference. The magnetic tunnel junction test structure provided in this embodiment is used to test the electrical parameters of the MTJ. The magnetic tunnel junction unit of the magnetic tunnel junction test structure can be led out through multiple conductive plugs and multiple conductive wires, that is, the needles are led out from the upper and lower sides of the MTJ at the same time, and the two ends for measuring the potential difference and the two ends for applying the current are located at the upper and lower sides of the MTJ, and the potential difference V _b satisfies the following formula: Among them, the surface where the current needle is located is regarded as the top, and the other surface is the bottom. RT is the resistance value of the top resistor of the MTJ, and _RB is the resistance value of the bottom resistor of the MTJ. RA is the resistance-area product of the MTJ, which can characterize the thickness of the barrier layer, _K0 represents the 0th-order second-kind modified Bessel function, and a, b, c, d are the distances between the test electrodes in the current 4-probe method, including: the electrode distances between PAD 1 and PAD 3 and PAD 4, and the electrode distances between PAD 2 and PAD 3 and PAD 4. Preferably, the four probes are arranged in the same straight line with equal spacing, a=b/2=c/2=d=x, and in this case, the above formula can be simplified to:

According to the above formula, it can be seen that when the magnetic tunnel junction test structure provided in this embodiment is used to test the electrical parameters of the MTJ, the test accuracy does not depend on _RT / _RB , that is, it does not depend on the resistance ratio of the top resistor to the bottom resistor in the MTJ. Therefore, the test structure has better compatibility with the actual production process, and because the needles are output on the opposite sides, the efficiency is higher when designing the position, and there is no need to stick to equal spacing, thereby improving the test resolution.

FIG. 3 is a schematic diagram showing the relationship between V _b and x (x=1, 2, ..., 5). It can be seen from the figure that V _b passes through the origin of the coordinate system and has a much higher accuracy than V _t during the fitting process.

In the magnetic tunnel junction test structure in the present embodiment, the magnetic tunnel junction unit may include a bottom electrode, a magnetic tunnel junction, and a top electrode stacked sequentially.

The materials of the bottom electrode and the top electrode can be independently selected from any one or more of Ta, TaN, Ti, TiN, Co and Ru. Those skilled in the art can reasonably select the types of materials for the bottom electrode and the top electrode based on the prior art.

The core structure of the magnetic tunnel junction (MTJ) includes a free layer, a barrier layer and a reference layer. The free layer and the reference layer are magnetic layers, while the barrier layer is a very thin insulating layer. When the MTJ is working normally, the magnetization direction of the reference layer remains unchanged, the magnetization direction of the free layer can be changed by an external magnetic field or an input current, and the resistance value of the MTJ is determined by the relative magnetization direction of the free layer and the reference layer. When the magnetization directions of the free layer and the reference layer are parallel, the MTJ is in a low resistance state; when the magnetization directions of the free layer and the reference layer are antiparallel, the MTJ is in a high resistance state. Those skilled in the art can reasonably select the types of materials for the free layer, barrier layer and reference layer according to actual needs.

The above-mentioned magnetic tunnel junction can have various forms depending on the application, including but not limited to in-plane MTJ, vertical MTJ, top pinned MTJ, bottom pinned MTJ, double-layer MgO MTJ, single-layer MgO MTJ and polymorphic MTJ.

In order to set the above-mentioned conductive plug, in some optional embodiments, the magnetic tunnel junction test structure in this embodiment also includes a first insulating layer and a second insulating layer (not shown in the figure), wherein: the first insulating layer is arranged on the first surface, and the first conductive plug passes through the first insulating layer to the first surface; the second insulating layer is arranged on the second surface, and the second conductive plug passes through the second insulating layer to the second surface.

In the above optional implementation manner, the materials of the first insulating layer and the second insulating layer may be conventional insulating materials in the prior art, such as silicon dioxide or silicon nitride, which is not specifically limited in the present disclosure.

In order to set the above-mentioned conductive wires connected to the conductive plugs, in some optional embodiments, the magnetic tunnel junction test structure in this embodiment also includes a first substrate and a second substrate (not shown in the figure), wherein: the first substrate is arranged on a side of the first insulating layer away from the first surface, and a part of the multiple conductive wires are arranged at intervals in the first substrate; the second substrate is arranged on a side of the second insulating layer away from the second surface, and another part of the multiple conductive wires are arranged at intervals in the second substrate.

In the above optional embodiments, the material of the first substrate and the second substrate can be single crystal silicon (Si), single crystal germanium (Ge), or silicon germanium (GeSi), silicon carbide (SiC); it can also be silicon on insulator (SOI), germanium on insulator (GOI); or it can also be other materials, such as III-V compounds such as gallium arsenide.

In some optional implementations, the magnetic tunnel junction test structure in this embodiment further includes a selection circuit 40, as shown in FIG4, having multiple input terminals and multiple output terminals, the input terminals of the selection circuit 40 are connected to the magnetic tunnel junction unit 10 by being connected one-to-one with the second terminals of the conductive wires, and the output terminals of the selection circuit 40 are connected one-to-one with the test electrodes 50. By selecting the electrical connection between the magnetic tunnel junction (MTJ) and the test electrodes through the selection circuit, the test electrodes can be saved and the area utilization efficiency of the test structure can be improved.

In the above optional implementation, the number of the above test electrodes can be set to at least 4, and the selection circuit includes at least 4 output terminals, so as to improve the accuracy of the magnetic tunnel junction test structure in testing the electrical parameters of the MTJ therein.

The number of first conductive plugs and second conductive plugs connected to both sides of the magnetic tunnel junction unit can be different. For example, as shown in FIG2 , one side of the magnetic tunnel junction unit 10 is connected with a first conductive plug 210 and the other side is connected with three second conductive plugs 220 .

In order to facilitate the process preparation of the magnetic tunnel junction test structure in this embodiment, in some optional implementations, the number of the first conductive plugs is a first number, the number of the second conductive plugs is a second number, and the first number is equal to the second number. Exemplarily, as shown in FIG1 , there are two first conductive plugs 210 and two second conductive plugs 220.

In order to facilitate the performance test of the MTJ in the magnetic tunnel junction test structure in this embodiment, in some optional implementations, the first conductive plug has a first orthographic projection on the first surface, the second conductive plug has a second orthographic projection on the first surface, and the first orthographic projection and the second orthographic projection do not overlap. Furthermore, the arrangement of the first conductive plug on the first surface and the arrangement of the second conductive plug on the second surface can be set so that both the first orthographic projection and the second orthographic projection are multiple and alternately distributed.

According to another embodiment of the present disclosure, a method for preparing a magnetic tunnel junction test structure is provided, comprising the following steps: providing a plurality of test electrodes; forming a plurality of conductive wires, each conductive wire having a first end and a second end opposite to each other, the second end being connected to the test electrode in a one-to-one correspondence; forming a plurality of conductive plugs, the plurality of conductive plugs being connected to the first end in a one-to-one correspondence, and the plurality of conductive plugs including at least one first conductive plug and at least one second conductive plug; forming a magnetic tunnel junction unit connected to the plurality of conductive plugs, the magnetic tunnel junction unit having a first surface and a second surface opposite to each other, the first conductive plug being arranged on the first surface, the second conductive plug being arranged on the second surface, and the conductive wire being connected to the magnetic tunnel junction unit through the conductive plugs.

By adopting the above-mentioned preparation method of the present embodiment, conductive plugs and conductive wires connected to the conductive plugs are arranged on two opposite surfaces of the magnetic tunnel junction unit, so that the magnetic tunnel junction unit of the magnetic tunnel junction test structure can be led out through the multiple conductive plugs and the multiple conductive wires, and multiple test electrodes can be connected, so that the needle insertion can be simultaneously based on the multiple test electrodes connected to the two side surfaces of the MTJ, thereby realizing the performance test of the MTJ. Compared with the traditional magnetic tunnel junction test structure, the test structure can realize the simultaneous needle insertion measurement on the first surface and the second surface of the MTJ, thereby expanding the needle insertion position of the probe, so that the needle insertion position is not limited to the equal spacing setting, thereby improving the resolution and accuracy of testing the magnetic tunnel junction test structure.

In some optional embodiments, the step of forming the above-mentioned multiple conductive wires includes: providing a first substrate, forming at least one first conductive wire on the first substrate, so that after the step of forming the first conductive plug, the first conductive wire can be connected to the first conductive plug one-to-one; after sequentially forming a magnetic tunnel junction unit and a second conductive plug, one side of the magnetic tunnel junction unit is connected to the first conductive wire through the first conductive plug, providing a second substrate, forming at least one second conductive wire on the second substrate, so that the second conductive wire is connected to the second conductive plug one-to-one, so that the other side of the magnetic tunnel junction unit is connected to the second conductive wire through the second conductive plug.

In the above optional embodiment, the step of forming the first conductive plug may include: covering the first insulating dielectric layer on the side of the first substrate having the first conductive line; etching the first insulating dielectric layer to form a first connecting hole that penetrates the first insulating dielectric layer to the first conductive line, and the first connecting hole corresponds one-to-one to the conductive line; and forming the first conductive plug in the first connecting hole.

In the step of forming a magnetic tunnel junction unit, the magnetic tunnel junction unit is formed on a side of a first insulating dielectric layer away from the first substrate, and the step of forming a second conductive plug may include: covering a second insulating dielectric layer on a side of the magnetic tunnel junction unit away from the first insulating dielectric layer; etching the second insulating dielectric layer to form a second connecting hole that penetrates the second insulating dielectric layer to the magnetic tunnel junction unit, and the second connecting hole corresponds one-to-one to the conductive line; and forming a second conductive plug in the second connecting hole.

Exemplarily, the steps of forming a magnetic tunnel junction unit include: depositing a bottom electrode on a side of a first insulating dielectric layer away from the first substrate, then sequentially depositing a reference layer material, a barrier layer material, and a free layer material on the bottom electrode, obtaining a magnetic tunnel junction including a reference layer, a barrier layer, and a free layer after etching, and depositing a top electrode on the magnetic tunnel junction. Those skilled in the art can reasonably select the types of materials for the free layer, barrier layer, and reference layer according to actual needs.

The first insulating dielectric layer and the second insulating dielectric layer may be silicon oxide layers or silicon nitride layers, but are not limited to the above types. Those skilled in the art may make reasonable selections based on the prior art.

The materials of the first conductive plug and the second conductive plug may include metals such as titanium, tungsten, nickel or tantalum, and may also include metal compounds and/or semiconductor materials. Those skilled in the art may make reasonable selections based on the prior art, and this disclosure does not make specific limitations.

The deposition of the first insulating dielectric layer and the second insulating dielectric layer may be performed by any suitable process, such as chemical vapor deposition, physical vapor deposition (PVD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), high density plasma chemical vapor deposition (HDPCVD), metal organic chemical vapor deposition (MOCVD), remote plasma chemical vapor deposition (RPCVD), plasma enhanced chemical vapor deposition (PECVD), electroplating, other suitable methods and/or combinations of the foregoing.

In order to form the first connecting hole and the second connecting hole, a mask layer may be covered on the surface of the first insulating dielectric layer and the second insulating dielectric layer, and the mask layer may be patterned, and then the surface of the first insulating dielectric layer and the second insulating dielectric layer not covered by the patterned mask layer may be etched to transfer the pattern in the patterned mask layer to the first insulating dielectric layer and the second insulating dielectric layer, thereby obtaining the first connecting hole and the second connecting hole respectively penetrating the two side surfaces of the magnetic tunnel junction unit. The mask layer may be formed of conventional mask materials, such as silicon nitride, and the patterning process of the mask layer may be a photolithography process, which will not be described in detail in this application.

The method for preparing the magnetic tunnel junction test structure in this embodiment will be described below with reference to specific examples.

Exemplarily, the method for forming the magnetic tunnel junction test structure comprises the following steps:

1. Forming a plurality of first metal wires on a first wafer, and electrically connecting the first metal wires to the first test electrodes in a one-to-one correspondence;

2. Depositing a first insulating layer on a surface of one side of the first silicon wafer having a plurality of first metal wires, and forming a first connecting hole in the first insulating layer by photolithography and etching processes;

3. Depositing a first metal plug in the first connecting hole;

4. Depositing a MTJ stack on the first insulating layer so that the MTJ stack is electrically connected to the first metal line through the first metal plug;

5. Deposit a second insulating layer on the MTJ stack, and form a second connecting hole in the second insulating layer by photolithography and etching processes;

6. Depositing a second metal plug in the second connecting hole;

7. Forming a plurality of second metal lines on the second wafer, wherein the second metal lines and the second metal plugs are electrically connected one by one;

8. Electrically connect the plurality of second metal wires to the plurality of second test electrodes in a one-to-one correspondence.

According to another embodiment of the present disclosure, a method for testing a magnetic tunnel junction is also provided, which uses the above-mentioned magnetic tunnel junction test structure, and the magnetic tunnel junction test structure includes at least four test electrodes, any two of the four test electrodes are used to test the current of the magnetic tunnel junction unit, and the remaining two test electrodes are used to test the potential difference corresponding to the current. The test method includes: determining multiple groups of combination modes of two-by-two combinations of the four test electrodes, wherein each group of the multiple groups of combination modes has two first test electrodes and two second test electrodes, the two first test electrodes are used to test the current of the magnetic tunnel junction unit, and the two second test electrodes are used to test the potential difference corresponding to the current; obtaining two first test electrodes corresponding to each group of combination modes Test current of the test electrode; obtain the potential difference between the two second test electrodes corresponding to each group of combinations; obtain the resistance value corresponding to each group of combinations according to the test current and the potential difference; obtain the electrode distance set corresponding to the two first test electrodes and the two second test electrodes, wherein the electrode distance set includes the first electrode distance and the second electrode distance, the first electrode distance is the distance between one first test electrode and the two second test electrodes respectively, and the second electrode distance is the distance between another first test electrode and the two second test electrodes respectively; obtain the target relationship corresponding to each group of combinations according to the potential difference, the resistance value and the electrode distance set; extract the electrical parameters of the magnetic tunnel junction test structure according to the target relationship.

The magnetic tunnel junction unit in the magnetic tunnel junction test structure has a first surface and a second surface, and the first surface and the second surface are respectively connected to at least two test electrodes. In some optional embodiments, the above-mentioned acquisition of the test current of the two first test electrodes corresponding to each group of combination, and the above-mentioned acquisition of the potential difference of the two second test electrodes corresponding to each group of combination, include: acquiring the test current between any two test electrodes connected to the first surface, and acquiring the potential difference between the remaining two test electrodes connected to the second surface.

In other optional embodiments, the above-mentioned obtaining of the test current of the two first test electrodes corresponding to each group of combination, and the above-mentioned obtaining of the potential difference of the two second test electrodes corresponding to each group of combination, include: obtaining the test current between any two test electrodes connected to the second surface, and obtaining the potential difference between the remaining two test electrodes connected to the first surface.

The method for testing the magnetic tunnel junction in this embodiment will be described below with reference to specific examples.

In Example 1, the magnetic tunnel junction test structure shown in FIG. 1 is used, and the magnetic tunnel junction test method includes the following steps:

1. The top electrode of the magnetic tunnel junction unit 10 is led out through the first conductive plug 210 and the conductive wire 30, and the bottom electrode of the magnetic tunnel junction unit 10 is led out through the second conductive plug 220 and the conductive wire 30;

2. The two conductive wires 30 connected to the first conductive plug 210 are connected to two test electrodes (PAD 1, PAD 2), and a constant current I is applied through a current source;

3. The two conductive wires 30 connected to the second conductive plug 220 are connected to the other two test electrodes (PAD 3, PAD 4), and the potential difference U between the two test electrodes is measured;

4. Calculate the resistance value R _b of the bottom electrode;

5. Calculate the electrode distances between PAD 1 and PAD 3 and PAD 4, and the electrode distances between PAD 2 and PAD 3 and PAD 4, and obtain the electrode distance set;

6. Repeat the above steps 2-5 by changing the two different test electrodes to obtain the relationship between the resistance value R _b and the electrode distance set. From this relationship, extract the RA parameter (resistance area product) of the MTJ, which can be used to characterize the thickness of the barrier layer.

In Example 2, the magnetic tunnel junction test structure shown in FIG. 2 is used, and the magnetic tunnel junction test method includes the following steps:

2. Two conductive wires 30 connected to the first conductive plug 210 are connected to a test electrode (PAD I ₁ );

3. The two conductive wires 30 connected to the second conductive plug 220 are connected to the other three test electrodes (PADV ₁ , PADV ₂ , PAD I ₂ );

4. PAD I ₁ and PAD I ₂ apply a constant current I through a current source;

5. Measure the potential difference U between PAD V ₁ and PAD V ₂ ;

6. Calculate the resistance value R _b of the bottom electrode;

7. Calculate the electrode distances between PAD I ₁ and PAD V ₁ and PAD V ₂ , as well as the electrode distances between PAD I ₂ and PAD V ₁ and PAD V ₂ , to obtain an electrode distance set;

8. Repeat the above steps 2-5 by changing the two different test electrodes to obtain the relationship between the resistance value R _b and the electrode distance set. From this relationship, extract the RA parameter of the MTJ.

From the above description, it can be seen that the above embodiments of the present disclosure achieve the following technical effects:

By arranging conductive plugs and conductive wires connected to the conductive plugs on two opposite surfaces of the magnetic tunnel junction unit, the magnetic tunnel junction unit of the magnetic tunnel junction test structure can be led out through the multiple conductive plugs and the multiple conductive wires, and multiple test electrodes can be connected, so that the probe can be simultaneously led out based on the multiple test electrodes connected to the two side surfaces of the MTJ, thereby realizing the performance test of the MTJ. Compared with the traditional magnetic tunnel junction test structure, the test structure can realize the simultaneous probe measurement on the first surface and the second surface of the MTJ, thereby expanding the probe needle position, so that the probe needle position is not limited to the equal spacing setting, thereby improving the resolution and accuracy of testing the magnetic tunnel junction test structure.

The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

A magnetic tunnel junction test structure, comprising:

A magnetic tunnel junction unit having a first surface and a second surface opposite to each other;

A plurality of conductive plugs are disposed on the first surface and the second surface, the plurality of conductive plugs include at least one first conductive plug and at least one second conductive plug, the first conductive plug is connected to the first surface, and the second conductive plug is connected to the second surface;

A plurality of conductive wires, each of the conductive wires having a first end and a second end opposite to each other, the first end being connected to the conductive plug in a one-to-one correspondence, so that the conductive wire is connected to the magnetic tunnel junction unit through the conductive plug, and the conductive wire and the conductive plug are in a one-to-one correspondence;

A plurality of test electrodes are connected to the second ends in a one-to-one correspondence.
The magnetic tunnel junction test structure according to claim 1, further comprising:

A first insulating layer is disposed on the first surface, and the first conductive plug penetrates the first insulating layer to the first surface;

The second insulating layer is disposed on the second surface, and the second conductive plug penetrates the second insulating layer to the second surface.
The magnetic tunnel junction test structure according to claim 2, further comprising:

A first substrate is disposed on a side of the first insulating layer away from the first surface, and a portion of the plurality of conductive lines are disposed at intervals in the first substrate;

The second substrate is arranged on a side of the second insulating layer away from the second surface, and another part of the plurality of conductive lines are arranged at intervals in the second substrate.
The magnetic tunnel junction test structure according to any one of claims 1 to 3, further comprising:

The selection circuit has a plurality of input terminals and a plurality of output terminals, wherein the input terminals are connected to the second terminals in a one-to-one correspondence, and the plurality of output terminals are connected to the plurality of test electrodes in a one-to-one correspondence.
The magnetic tunnel junction test structure according to claim 4, wherein the number of the test electrodes is at least 4, and the selection circuit includes at least 4 of the output terminals.
The magnetic tunnel junction test structure according to any one of claims 1 to 3, wherein the number of the first conductive plugs is a first number, the number of the second conductive plugs is a second number, and the first number is equal to the second number.
The magnetic tunnel junction test structure according to any one of claims 1 to 3, wherein the first conductive plug has a first orthographic projection on the first surface, the second conductive plug has a second orthographic projection on the first surface, and the first orthographic projection does not overlap with the second orthographic projection.
The magnetic tunnel junction test structure according to claim 7, wherein the first orthographic projection and the second orthographic projection are both multiple and alternately distributed.
A method for preparing a magnetic tunnel junction test structure comprises the following steps:

Providing a plurality of test electrodes;

forming a plurality of conductive lines, each of the conductive lines having a first end and a second end opposite to each other, the second end being connected to the test electrodes in a one-to-one correspondence;

forming a plurality of conductive plugs, the plurality of conductive plugs being connected to the first ends in a one-to-one correspondence, and the plurality of conductive plugs including at least one first conductive plug and at least one second conductive plug;

A magnetic tunnel junction unit connected to the plurality of conductive plugs is formed, the magnetic tunnel junction unit having a first surface and a second surface opposite to each other, the first conductive plug being disposed on the first surface, the second conductive plug being disposed on the second surface, and the conductive wire being connected to the magnetic tunnel junction unit through the conductive plug.
The preparation method according to claim 9, wherein the step of forming the plurality of conductive lines comprises:

Providing a first substrate, and forming at least one first conductive line on the first substrate;

After the step of forming the first conductive plugs, the first conductive wires are connected to the first conductive plugs in a one-to-one correspondence;

After the step of forming the magnetic tunnel junction unit and the second conductive plug, a second substrate is provided, and at least one second conductive line is formed on the second substrate so that the second conductive line is connected to the second conductive plug in a one-to-one correspondence.
The preparation method according to claim 10, wherein the step of forming the first conductive plug comprises:

Covering a first insulating dielectric layer on a side of the first substrate having the first conductive line;

Etching the first insulating dielectric layer to form a first connecting hole penetrating the first insulating dielectric layer to the first conductive line, wherein the first connecting hole corresponds to the conductive line one by one;

The first conductive plug is formed in the first communication hole.
The preparation method according to claim 10, wherein, in the step of forming the magnetic tunnel junction unit, the magnetic tunnel junction unit is formed on a side of the first insulating dielectric layer away from the first substrate, and the step of forming the second conductive plug comprises:

Covering a second insulating dielectric layer on a side of the magnetic tunnel junction unit away from the first insulating dielectric layer;

Etching the second insulating dielectric layer to form a second connecting hole penetrating the second insulating dielectric layer to the magnetic tunnel junction unit, wherein the second connecting hole corresponds to the conductive wire one by one;

The second conductive plug is formed in the second communication hole.
A method for testing a magnetic tunnel junction, wherein the magnetic tunnel junction test structure according to any one of claims 1 to 8 is used, the magnetic tunnel junction test structure comprises at least four test electrodes, any two of the four test electrodes are used to test the current of the magnetic tunnel junction unit, and the remaining two test electrodes are used to test the potential difference corresponding to the current, the test method comprising:

Determine a plurality of groups of combinations of two or more of the four test electrodes, wherein each group of the plurality of groups of combinations has two first test electrodes and two second test electrodes, the two first test electrodes are used to test the current of the magnetic tunnel junction unit, and the two second test electrodes are used to test the potential difference corresponding to the current;

Obtaining the test currents of the two first test electrodes corresponding to each group of combination modes;

Obtaining the potential difference between the two second test electrodes corresponding to each group of combinations;

Obtaining a resistance value corresponding to each group of combinations according to the test current and the potential difference;

Acquire an electrode distance set corresponding to the two first test electrodes and the two second test electrodes, wherein the electrode distance set includes a first electrode distance and a second electrode distance, the first electrode distance is the distance between one first test electrode and the two second test electrodes respectively, and the second electrode distance is the distance between another first test electrode and the two second test electrodes respectively;

According to the potential difference, the resistance value and the electrode distance set, a target relationship corresponding to each group of combination modes is obtained;

The electrical parameters of the magnetic tunnel junction test structure are extracted according to the target relationship.
The test method according to claim 13, wherein the magnetic tunnel junction unit in the magnetic tunnel junction test structure has a first surface and a second surface, the first surface and the second surface are respectively connected to at least two of the test electrodes, and the obtaining of the test current of the two first test electrodes corresponding to each group of combination modes, and the obtaining of the potential difference of the two second test electrodes corresponding to each group of combination modes, comprises:

obtaining the test current between any two of the test electrodes connected to the first surface, and

acquiring the potential difference between the remaining two test electrodes connected to the second surface; or

obtaining the test current between any two of the test electrodes connected to the second surface, and

The potential difference between the remaining two test electrodes connected to the first surface is obtained.