Bonding interface construction and strength measurement method based on in-situ TEM technology

Abstract

The invention discloses a bonding interface construction and strength measurement method based on an in-situ TEM technology. The device comprises a micro-cantilever and a sample, the end of the micro-cantilever is fixed, the sample is connected with a displacement control mechanism, the tip of the micro-cantilever and the tip of the sample are arranged in a TEM, a bonding interface is constructed through electric pulses, stretching is performed through the displacement control mechanism, and images are collected in real time. In the TEM, the in-situ electric pole and the micro-cantilever are utilized to realize interface construction and strength real-time measurement through in-situ bonding, different types of interfaces can be constructed according to needs, bonding interface structure regulation and control are realized, the tensile failure process and mechanical properties of bonding interfaces of different structures are researched, and the test result shows that the test result shows that the test result shows that the test result shows that the test result is accurate. And establishing a mutual relation of a bonding interface structure, a failure mechanism and strength. According to the in-situ measurement method, the dynamic change of interface atoms can be tracked in real time, and nano-Newton-precision tensile stress measurement can be achieved in a nano tensile experiment, so that the high-precision quantitative measurement requirements of different material interfaces are met.

Description

Technical Field

[0001] The present invention relates to a method for constructing a bonding interface and measuring its strength based on in-situ TEM technology, belonging to the technical field of interface strength detection devices and detection methods. Background Art

[0002] With the rapid development of advanced packaging technologies, metal bonding technologies at the micron and sub-micron scales have gradually become an important means to improve the packaging density of integrated circuits. However, current research mainly focuses on the qualitative analysis of plastic deformation at the bonding interface, lacking systematic quantitative research on the mechanical properties of different bonding interface types. Although certain research has been conducted on the mechanical tensile properties of different interface structures at home and abroad, limited by experimental conditions and methods, the research on the mechanical properties of bonding interfaces mainly relies on molecular dynamics (MD) simulations, and the experimental work in related fields also lacks detailed mechanism research. In addition, most existing experimental methods rely on fracture analysis and lack dynamic observation of the bonding interface during mechanical loading, especially the instability behavior of the bonding interface.

[0003] Currently, atomic force microscopy (AFM) is widely used in nano-mechanics due to its atomic-level mechanical measurement advantages, but it cannot observe the real-time evolution of the atomic structure of the bonding interface during the force application process. Transmission electron microscopy (TEM) has the advantage of high resolution and can observe the real-time changes in the material structure at the nanoscale. Future research needs to combine the two to observe the atomic-level changes in materials during the loading process, so as to more systematically and comprehensively explore the influence of different bonding interface types on the mechanical properties of materials. Therefore, it is very necessary to construct an in-situ test platform. Summary of the Invention

[0004] Object of the Invention: The first object of the present invention is to provide a method for constructing a bonding interface based on in-situ TEM technology, which can construct and regulate the interface in-situ in TEM; the second object of the present invention is to provide a quantitative detection method for the strength of a bonding interface constructed based on in-situ TEM technology for accurately measuring the stress direction, a method for real-time tracking of atomic dynamic changes, and realizing in-situ observation.

[0005] Technical Solution: The method for constructing a bonding interface based on in-situ TEM technology according to the present invention includes the following steps:

[0006] (1) Adjust the positions of the microcantilever tip (2) and the tip (401) of the sample (4) to be perpendicular to the electron beam direction of the TEM.

[0007] (2) Bring the tip (401) of the sample (4) into contact with the microcantilever tip (2) through the displacement control mechanism (5).

[0008] (3) Apply a pulsed current to bond the tip (401) of the sample (4) to the tip of the microcantilever (2). By varying the magnitude of the pulsed voltage, the size and angle of the constructed bonding interface can be changed, thereby enabling in-situ construction of interfaces at different nanoscale dimensions.

[0009] Furthermore, in step (2), before bringing the tip (401) of the sample (4) into contact with the tip of the microcantilever (2), ensure that no electric field is applied to prevent uncontrollable pulses from being generated during contact.

[0010] Furthermore, in step (3), when bonding, use a pulse generator to set the output signal as a pulse, set the voltage to 1000 - 3000 mV, and set the pulse width to the minimum value.

[0011] A method for measuring the strength of a bonding interface constructed by the bonding interface construction method based on in-situ TEM technology according to the present invention includes the following steps:

[0012] (1) Adjust the positions of the tip of the microcantilever (2) and the tip (401) of the sample (4) to be perpendicular to the direction of the electron beam of the TEM.

[0013] (2) Bring the tip (401) of the sample (4) into contact with the tip of the microcantilever (2) through the displacement control mechanism (5).

[0014] (3) Apply a pulsed current to bond the tip (401) of the sample (4) to the tip of the microcantilever (2) and in-situ construct an interface at the nanoscale.

[0015] (4) Control the sample (4) to displace backward for stretching through the displacement control mechanism (5) and collect an image.

[0016] (5) Analyze the change value of the normal displacement of the tip of the microcantilever (2) in the collected image and calculate the tensile stress of the nanoscale interface strength.

[0017] Furthermore, in step (4), under the condition that the original length of the sample is 100 nm, the strain rate range is 5×10 - 5 s -1 ~1×10 -3 s -1 .

[0018] Furthermore, in step (5), the tensile stress calculation formula is as follows:

[0019]

[0020] In the formula, F Nis the tensile stress, E is the Young's modulus (GPa) of the microcantilever material; w is the width (μm) of the microcantilever; t is the thickness (μm) of the microcantilever; l is the length (μm) of the microcantilever; Δy is the change value of the normal displacement of the cantilever tip;

[0021] Further, the sample is Au, Ag, Cu, W, Nb, Mo, Si, etc.

[0022] Further, the detection device includes an in-situ electrical sample rod. One end of the in-situ electrical sample rod is connected to a fixed end, and the other end is connected to a displacement control mechanism. A microcantilever base is fixedly connected to the fixed end. The lower end of the microcantilever is fixedly connected to the upper end of the microcantilever base. A microcantilever tip perpendicular to it is provided on the upper right side of the microcantilever. The sample is fixedly connected to the front end of the displacement control mechanism, and the microcantilever tip is aligned with the tip of the sample on the right.

[0023] Even further, the displacement control mechanism is a piezoelectric controller.

[0024] Even further, the displacement control mechanism is a piezoelectric controller Mains 220V.

[0025] Even further, the microcantilever, the microcantilever tip, and the microcantilever base are made of metal.

[0026] Even further, the metal can be gold, silver, copper, etc.

[0027] Even further, the ratio of the length, width, and thickness of the microcantilever is (30 - 50):(3 - 5):(1 - 3). Preferably, the ratio of the length, width, and thickness of the microcantilever is 40:3:2.

[0028] Even further, the height of the microcantilever tip is 2 - 10 μm. Preferably, the height of the microcantilever tip is 4 μm.

[0029] Even further, the microcantilever can be set perpendicular or parallel to the ground.

[0030] The quantitative detection device used in the method for constructing and measuring the strength of the bonding interface based on the in-situ TEM technology of the present invention combines the microstructure preparation technology based on focused ion beam (FIB) and the in-situ electrical measurement system. The system is divided into two ends: the fixed end is mainly composed of a microcantilever. One end of the microcantilever is provided with a microcantilever tip perpendicular to it, and the other end is the microcantilever base. The required material layer is coated on the tip and aligned with the tip of the sample material, and is perpendicular to the electron beam irradiation direction; the mobile end fixes the sample material and is connected to the displacement control mechanism. The microcantilever tip and the tip of the sample are placed under a transmission electron microscope, and the change in the normal displacement is observed by real-time image acquisition.

[0031] The present invention realizes the construction of interfaces and the real-time measurement of strength by using an in-situ electrical sample holder and a microcantilever beam in a TEM. It can construct different types of interfaces as needed, track the dynamic changes of interface atoms in real time, and achieve tensile stress measurement with a nano-newton accuracy in a nano-tensile experiment, thereby meeting the high-precision quantitative measurement requirements of different material interfaces.

[0032] Advantages: Compared with the prior art, the present invention has the following remarkable features:

[0033] (1) Through the microcantilever beam structure, the present invention realizes the construction of in-situ bonding interfaces through TEM, accurately regulates the orientation and angle of the bonding interfaces, thereby breaking through the limitations of traditional methods in the design and control of bonding interfaces, and providing greater flexibility and repeatability for further studying the evolution behavior of different bonding interface structures under stress.

[0034] (2) The present invention gives full play to the high spatial resolution and dynamic imaging ability of TEM, realizes the real-time tracking of the atomic-scale morphological changes of materials during the nano-scale tensile process. Compared with AFM, this method can more clearly and meticulously observe the evolution of the bonding interface and the adjustment process of the microstructure of materials during dynamic stretching without affecting the sample environment, filling the gap of the lack of in-situ dynamic characterization of AFM during the nano-tensile process, and providing more comprehensive data support and in-depth research basis for exploring the micro-tensile mechanism of materials. Description of the Drawings

[0035] Figure 1 is a schematic structural diagram of the quantitative detection device in Embodiment 1;

[0036] Figure 2 is a schematic diagram of the nano-tensile in-situ experiment in Embodiment 2, where (a) is a schematic diagram of the front end of the sample holder; (b) is a TEM image of the nano-crystals at the tip of the gold sample probe; (c) is a schematic diagram of the process of constructing the bonding interface; (d) is a schematic diagram of the in-situ tensile test, the yellow dotted line represents the contour during the tensile process, D is the sample diameter, and Δy is the relative displacement at the same position during the tensile process;

[0037] Figure 3 is an example diagram of different interfaces constructed in-situ;

[0038] Figure 4 is a process diagram from the construction of the interface to the fracture of the interface during a single tensile experiment;

[0039] Figure 5 is a measurement diagram of the real-time tensile stress during the nano-tensile process of the present invention. Detailed Embodiments

[0040] Embodiment 1

[0041] AsFigure 1 , a method for constructing a bonding interface based on in-situ TEM technology according to the present invention. The device used includes an in-situ electrical sample rod 7. One end of the in-situ electrical sample rod 7 is connected to a fixed end 6, and the other end is connected to a displacement control mechanism 5. A microcantilever base 3 is fixedly connected to the fixed end 6. The lower end of the microcantilever 1 is fixedly connected to the upper end of the microcantilever base 3. A microcantilever tip 2 perpendicular to the microcantilever 1 is provided on the upper right side of the upper end of the microcantilever 1. The sample 4 is fixedly connected to the front end of the displacement control mechanism 5. The microcantilever tip 2 is aligned with the tip 401 of the sample 4 and is perpendicular to the electron beam of the transmission electron microscope (TEM). The displacement control mechanism 5 is a piezoelectric controller. The microcantilever 1, the microcantilever tip 2, and the microcantilever base 3 are made of metal. The ratio of the length, width, and thickness of the microcantilever 1 is 30-50:3-5:1-3, and the height of the microcantilever tip 2 is 2-10 μm. The microcantilever 1 can be set perpendicular or parallel to the ground.

[0042] The sample 4 is connected to the displacement control mechanism 5. The microcantilever tip 2 and the tip 401 of the sample 4 are placed under the transmission electron microscope to observe the normal displacement change, and the normal displacement change data is obtained by real-time collecting TEM images.

[0043] Example 2

[0044] Using the device described in Example 1 to in-situ construct a gold-gold bonding interface and quantitatively measure the strength of the constructed interface. In this example, the microcantilever 1 is set horizontally. The microcantilever 1, the microcantilever tip 2, and the microcantilever base 3 are made of gold (Au). The ratio of the length, width, and thickness of the microcantilever is 40:3:2, and the height of the microcantilever tip is 4 μm. The following steps are included:

[0045] S1. Through the in-situ electrical sample rod 7, the microcantilever 1, the microcantilever tip 2, the microcantilever base 3, and the sample 4 (single-crystal gold wire, 0.25 mm, purity 99.9 wt.%) are respectively installed at both ends of the in-situ electrical sample rod 7 (Nanofactory STM-TEM holder). Among them, the microcantilever 1, the microcantilever tip 2, and the microcantilever base 3 are installed at the fixed end 6. The microcantilever base 3 is connected to the fixed end 6. The sample 4 is installed at the displacement control mechanism end 5. The microcantilever tip 2 is perpendicular to the direction of the electron beam of the TEM. Then, the in-situ electrical sample rod 7 is placed into the TEM (Titan80-300). The observation direction in the TEM is Figure 2 the top view shown in a of the figure, where the TEM image of the nano-crystals at the tip 401 of the gold sample 4 is as shown in Figure 2 b of the figure.

[0046] Ensure that there is no voltage and current input to the in-situ electrical sample rod 7. Adjust the position of the tip 401 of the single-crystal gold wire sample 4 under TEM through the displacement control mechanism 5 (piezoelectric controller Mains220V) so that it is on the same horizontal plane as the gold microcantilever beam 1. Observe whether there are raised thin regions at the tip 2 of the cantilever beam and the tip 401 of the sample in the TEM respectively. If there are, obtain the diffraction images of the thin regions and judge whether the zone axis of the thin region meets the experimental requirements according to the images until a suitable raised thin region is found. In this embodiment, it is necessary to study the interface constructed on the <111> plane under the gold

[110] zone axis. After obtaining the thin region, perform electron diffraction on the thin region and observe whether the diffraction pattern conforms to the standard diffraction pattern of the face-centered cubic

[110] zone axis. If they are inconsistent, search for or construct a thin region again; if the zone axes are the same but there is an angular deviation, judge the α and β degrees in the deviation direction. The adjustment range of the in-situ electrical sample rod 7 is: -15° < Δα < 15°, and β cannot be adjusted. Therefore, when there is only an α deviation within the adjustment range, adjust to make the Kikuchi line at the diffraction center, and in other cases, reselect / construct a thin region. Align the correct thin regions of the tip 2 of the cantilever beam and the tip 401 of the sample, and then directly proceed to step S3; if a thin region that meets the requirements cannot be found or there is no thin region, proceed to step S2.

[0047] S2. Use the displacement control mechanism 5 to move the tip 401 of the single-crystal gold wire sample 4 forward until it finally contacts the gold microcantilever beam 1. Change the output voltage to -2500 mV and the current limit to 10 mA. At this time, the tip of the sample and the tip of the cantilever beam are melted and connected. Quickly move the single-crystal gold wire sample 4 backward to disconnect the connection and obtain two raised thin regions. Judge whether the zone axis of the thin region meets the experimental requirements through diffraction. If it is not the required zone axis, repeat this step until at least one end obtains the correct zone axis (generally, apply a negative voltage). In this embodiment, applying a negative voltage obtains the required zone axis bulge at the tip 2 of the cantilever beam.

[0048] S3. Retain the displacement control line of the in-situ electrical sample rod 7, disconnect the voltage control line of the in-situ electrical sample rod 7, and instead connect to the signal input of the pulse generator.

[0049] Through the pulse generator: 1. Modify the pulse voltage output to -2000 mV, take the minimum values for the pulse width, rise time width, and fall time width, and apply a single pulse; 2. Observe whether a stable nanowire structure is formed between the sample tip 401 and the cantilever tip 2, and observe whether there is a bonding interface; 3. If a stable connection is not formed between the sample tip 401 and the cantilever tip 2, repeat the application of a single pulse and the observation process in the previous step. If a connection structure is still not formed, repeat the steps of applying the pulse and observing until a stable connection structure is formed; 4. Observe whether the angle and morphology of the bonding interface meet the requirements. If not, adjust the displacement controller 5 to control the sample 4 to retreat until the connection is broken, and then repeat the steps starting from S3 until a bonding interface that meets the requirements is obtained. In this embodiment, a bonding interface is constructed between two gold

[110] zone axes with an included angle greater than 15°, and the bonding interface construction process is as Figure 2 shown in c of

[0050] S4. The nano-tensile experiment process is as Figure 2 shown in d of

[0051] S5. During the nano-tensile process, by real-time acquisition of TEM images, the normal displacement Δy of the gold micro-cantilever tip (2) can be recorded in real time, and then through the mechanical theory formula for measuring the micro-cantilever under TEM:

[0052]

[0053] In the formula, F N is the tensile stress, E is the Young's modulus of the material of the gold micro-cantilever 1, which is 74 GPa; w is the width of the gold micro-cantilever 1, which is 6 μm; t is the thickness of the gold micro-cantilever 1, which is 4 μm; l gold is the length of the micro-cantilever (1), which is 80 μm; calculate the tensile stress during the nano-tensile process of single-crystal gold (sample (4)), so as to obtain a quantitative measurement result of the interface strength at the nano-scale of single-crystal gold based on TEM. This measurement method enables the tensile stress to reach the nano-Newton accuracy, and the data is real and reliable, which is conducive to quantitative analysis and mechanism exploration during the nano-tensile process.

[0054] After the interface breaks, repeat the steps described in S2 and S3 to reconstruct the interface again, which can realize the mechanical measurement of the bonded interfaces with different sizes, angles, and crystal orientations of the same material interface.

[0055] Through the steps described in S2 and S3, bonded interfaces with angles of 20.90 degrees, 34.41 degrees, 36.48 degrees, and 37.62 degrees were constructed respectively. For the bonded interfaces with the above different angles, perform the steps described in S4 respectively. By recording the normal displacement Δy of the tip (2) of the gold microcantilever in real time, and then calculating the tensile stress during the nano-tensile process of single-crystal gold (sample (4)) through the mechanical theory formula for measuring the microcantilever under TEM, the quantitative measurement results of the bonded interface strength at different angles on the nano-scale of single-crystal gold based on TEM can be obtained. This measurement method enables the tensile stress to reach the nano-newton precision, and the data is true and reliable, which is beneficial to quantitative analysis and mechanism exploration during the nano-tensile process.

[0056] Example 3

[0057] The experimental process is the same as that in Example 2. In this example, by changing the voltage magnitude of the pulse, the size and angle of the constructed bonded interface are changed; by quickly breaking the already constructed interface, fracture surfaces with different angles or crystal orientations are obtained, and by repeating the contact and applying the pulse, the construction of bonded interfaces with different angles or crystal orientations can be realized. In this example, the voltages of the pulse generator are set to -1750 mV, -2000 mV, and -2500 mV respectively, and repeat the S3 step in sequence to obtain different in-situ constructed interfaces, as Figure 3 shown. Due to the randomness of the fracture of the bonded interface, Figure 3 The bonded interface shown is only the situation of one experiment. This measurement method can realize the regulation of the bonded interface, thereby realizing the mechanical tests of different types of bonded interfaces.

[0058] Example 4

[0059] Under the tensile force, the nanowire where the bonded interface of the method of the present invention is located will show plastic deformation, and behaviors such as shear, slip, and twinning will occur; cracks may also form somewhere and gradually tear as the displacement increases. The experimental process of this example is the same as that in Example 2, and the deformation situation during the tensile process is given, and the results are as Figure 4 shown. Figure 4 The situations of the bonded interface at the 0th second, 19th second, 34th second, 55th second, and 57th second during the tensile process are respectively shown. As Figure 4 can be seen, the 0th second is the initial state of the tensile sample, slip occurs at the bonded interface at the 19th second, the bonded interface deforms at the 34th second, and at the same time, a migration from bottom to top occurs on the right side of the bonded interface. Cracks appear on the left side of the bonded interface at the 55th second, and the 57th second is the final state where the tensile sample breaks. This measurement method can observe the changes during the tensile process of the sample in real time and make records, asFigure 5 as shown

Claims

1. A method for constructing a bonding interface based on in-situ TEM technology, characterized in that, Comprising the following steps: (1) Adjust the positions of the microcantilever tip (2) and the tip (401) of the sample (4) to be perpendicular to the electron beam direction of the TEM; (2) Bring the tip (401) of the sample (4) into contact with the microcantilever tip (2) through the displacement control mechanism (5); (3) Apply a pulsed current to bond the tip (401) of the sample (4) to the microcantilever tip (2). By varying the voltage magnitude of the pulse, the size and angle of the constructed bonding interface can be changed, thereby achieving in-situ construction of interfaces at different nanoscales.

2. The method for constructing a bonding interface based on in-situ TEM technology according to claim 1, wherein In step (2), ensure that no electric field is applied before bringing the tip (401) of the sample (4) into contact with the microcantilever tip (2) to prevent uncontrollable pulses from being generated during contact.

3. The method for constructing a bonding interface based on in-situ TEM technology according to claim 1, characterized in that, In step (3), when bonding, use a pulse generator to set the output signal as a pulse, the voltage is set to 1000 - 3000 mV, and the pulse width is set to the minimum value.

4. A method for measuring the bonding interface strength constructed by the bonding interface construction method based on in-situ TEM technology according to any one of claims 1-3, characterized in that, Comprising the following steps: (1) Adjust the positions of the microcantilever tip (2) and the tip (401) of the sample (4) to be perpendicular to the electron beam direction of the TEM; (2) Bring the tip (401) of the sample (4) into contact with the microcantilever tip (2) through the displacement control mechanism (5); (3) Apply a pulsed current to bond the tip (401) of the sample (4) to the microcantilever tip (2) and in-situ construct an interface at the nanoscale; (4) Control the sample (4) to displace backward for stretching through the displacement control mechanism (5) and acquire an image; (5) Analyze the change value of the normal displacement of the microcantilever tip (2) in the acquired image and calculate the tensile stress of the nanoscale interface strength.

5. The measuring method according to claim 4, characterized in that, In step (4), the strain rate range is 5×10 -5 s -1 ~1×10 -3 s -1 .

6. The measuring method according to claim 4, characterized in that, In step (5), the tensile stress calculation formula is as follows: Where, F N is the tensile stress, E is the Young's modulus of the material of the micro-cantilever beam (1); w is the width of the micro-cantilever beam (1); t is the thickness of the micro-cantilever beam (1); l gold is the length of the micro-cantilever beam (1), and Δy is the change value of the normal displacement of the cantilever beam tip (2).

7. The measuring method according to claim 4, characterized in that The detection device includes an in-situ electrical sample rod (7). One end of the in-situ electrical sample rod (7) is connected to a fixed end (6), and the other end is connected to a displacement control mechanism (5). A microcantilever base (3) is fixedly connected to the fixed end (6). The lower end of the microcantilever (1) is fixedly connected to the upper end of the microcantilever base (3). A microcantilever tip (2) perpendicular to it is provided on the upper right side of the microcantilever (1). The sample (4) is fixedly connected to the front end of the displacement control mechanism (5), and the microcantilever tip (2) is aligned with the tip (401) of the sample (4) on the right.

8. The measurement method according to claim 4, characterized in that, The displacement control mechanism (5) is a piezoelectric controller.

9. The measuring method according to claim 4, wherein The microcantilever (1), the microcantilever tip (2), and the microcantilever base (3) are made of metal.

10. The measurement method according to claim 4, wherein The ratio of the length, width, and thickness of the microcantilever (1) is (30 - 50):(3 - 5):(1 - 3), and the height of the microcantilever tip (2) is 2 - 10 μm.

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