KR20090044134A - A 4-point bending apparatus for x-ray diffraction system and measuring method for thin film stress-strain curve using the apparatus - Google Patents

Abstract

The present invention relates to a four-point bending device for X-ray diffraction and a method for measuring the stress-strain behavior of thin film material using the same, which can be mounted on an X-ray diffraction device and artificially bends the thin film test piece to generate stress and strain. The point bending device is composed of an upper body for bending, a micrometer of a lower part for adjusting the strength of the bending, and the upper part of the body is fixed to two pairs of thin film test piece supports and two pairs of thin film test pieces to be elevated. A four-point bending device for X-ray diffraction, wherein the two pairs of thin film test piece supporting parts are lifted by a micrometer in connection with the micrometer.

Scanning the thin film test piece deposited with the thin film with a predetermined thickness with a laser displacement meter and measuring the bending curvature of the thin film test piece generated by the deposition residual stress therefrom (S10); Measuring diffraction peak information of the thin film test piece according to the change of the diffraction angle by X-ray diffraction test without bending the thin film test piece (S20); Measuring the bending curvature by using a laser displacement meter by varying the tensile / compressive stress on the surface of the thin film by micrometer rotation of the four-point bending device for X-ray diffraction (S30); And calculating the strain of the thin film test piece by measuring diffraction peak information of the thin film test piece according to the change of the diffraction angle by X-ray diffraction test on the thin film test piece subjected to the tensile / compressive stress at the same time (S30) (S40). It provides a thin film material stress-strain measurement method using a four-point bending device for X-ray diffraction, characterized in that made.

X-ray diffraction, 4-point bending strain, stress-strain, thin film material, microtensile test

Description

4-point Bending Apparatus for X-Ray Diffraction System and Measuring Method for Thin Film Stress-Strain Curve Using the Apparatus}

The present invention relates to a four-point bending device for X-ray diffraction and a method for measuring stress-strain behavior of thin film materials using the same.

Recently, the development and use of functional thin film materials in the semiconductor and electronics industry as well as the industry as a whole are increasing. These thin film materials are formed by depositing thin films having a thickness within several microns by using chemical, physical, and electrochemical methods on a thick substrate.

Measurement of mechanical properties of thin film is very important in the design of thin films, composite devices and systems requiring long-term mechanical durability such as micromechanical devices (MEMS or NEMS) thin films and wear resistant lubricating thin films.

Measurement of the mechanical properties of thin films, in particular the most basic uniaxial tensile strength properties, is usually performed using semiconductor micromachining techniques to pattern the thin films into microaxial uniaxial tensile test specimens, which are separated from the substrate to form a free standing thin film. The test is carried out by pulling the test piece in a micro-tension tester.

The micro tensile tester must maintain a sufficiently high rigidity of the tester compared to the rigidity of the free membrane used as the test piece and the application of a high-precision load cell to measure the load applied to the free film specimen during deformation, with the installation of a special actuator to control fine movements. There is a constraint.

Free film specimens, especially several microns thick, have low stiffness and are susceptible to deformation or destruction during manipulation or handling. As a result, there is a difficulty in micro-tension tests, in which complex structures such as extra ligaments that can support them must be formed, and they must be removed again during the test.

Due to the limitation of the thickness of the free film, the total length of the micro tensile test specimen is limited to the mm level, and unlike the existing standard standard for uniaxial tensile testing of metal materials, a precision transformer capable of checking the gauge distance and measuring the extent to which the strain is elongated in this region Deuce is impossible to attach.

Therefore, by re-depositing a pair of linear metal marks on both ends of the gage length, which is the strain measurement area of the test piece, the interferometric strain / displacement gage is used to measure the increase in distance between the marks when the two ends of the test piece are pulled. ISDG) has also been developed.

In addition, techniques for obtaining microscopic strain information on the surface of specimens using the Electron Spackle Pattern Interferometry (ESPI) interferometer instead of the laser interferometer have been developed, but they have fundamentally complicated optical systems and correspond to the wavelength of the laser used. Displacement can be measured with a level of resolution, making it difficult to measure nm strains and the test procedure has complex disadvantages.

In addition, the multi-stage micromachining process can result in etch damage on the specimen surface, which can lead to unexpected specimen breakage during testing, and by using the specimen size applied in the micromachining design to calculate stress and strain. Large errors in strain may occur.

Therefore, the present invention was devised to solve the above problems, and the object of the present invention is that it does not need to prepare a separate specimen because the deformation is applied as it is a thin film deposited on the substrate, and the position of the load support points The advantage of being able to apply to the thin film not only the tensile load as it is pulled down but also the compressive load to be pushed down, and the uniform load can be applied to the center of the thin film test piece, so it is a gradient of the load generated from the existing three-point bending. The present invention provides a four-point bending device for X-ray diffraction that can solve the problem.

In addition, another object of the present invention is to calculate the stress applied to the thin film test piece by measuring the bending radius of curvature while increasing the bending deformation step by step using a four-point bending device for X-ray diffraction, and at the same time X-ray The present invention provides a method of determining the stress-strain diagram of a thin film test piece by performing a diffraction test and measuring a corresponding strain from the position shift of the diffraction peak.

The object of the present invention as described above, in the four-point bending device for X-ray diffraction for measuring the stress-strain of the thin film test piece by X-ray irradiation and four-point bending, the four-point bending device for X-ray diffraction The upper part of the body for four-point bending, and the micrometer of the lower part to adjust the strength of the bending, the upper part of the body consists of two pairs of fixed thin film test piece support and two pairs of thin film test piece to be elevated The four-point bending apparatus for X-ray diffraction, wherein the two pairs of thin film test piece supporting portions are elevated by a micrometer in connection with the micrometer.

Scanning the thin film test piece on which the thin film is deposited to a predetermined thickness with a laser displacement measuring device and measuring the bending curvature of the deposited substrate generated by the residual stress generated in the deposition state therefrom (S10); Measuring diffraction peak information of the thin film test piece according to the change of the diffraction angle by X-ray diffraction test without bending the thin film test piece (S20); Measuring the bending curvature by using a laser displacement meter by varying the tensile / compressive stress on the surface of the thin film by micrometer rotation of the four-point bending device for X-ray diffraction (S30); And calculating the strain of the thin film test piece by measuring diffraction peak information of the thin film test piece according to the change of the diffraction angle by X-ray diffraction test on the thin film test piece subjected to the tensile / compressive stress at the same time (S30) (S40). It is achieved by a thin film stress-strain measurement method using a four-point bending device for X-ray diffraction, characterized in that.

Further features and advantages of the present invention will become more apparent from the detailed description in the Detailed Description section for carrying out the invention based on the accompanying drawings.

The present invention has the advantage that it does not need to prepare a separate specimen because the deformation is applied as it is a thin film deposited on the substrate, and the tensile load as the position of the load support points up and down, as well as the compression load to push Advantages that can be applied to the thin film and uniform load can be applied to the center of the thin film test piece can solve the problem of the gradient of the load caused by the existing three-point bending.

In addition, the present invention calculates the stress applied to the surface of the thin film, quantitatively measures the degree of deformation of the thin film test piece by grasping the change in the position of the X-ray diffraction peak, and bending bending radius by increasing the bending load of the thin film test step by step The stress applied to the thin film test piece was calculated, and at the same time, the X-ray diffraction test was performed to measure the strain corresponding to the bending stress, thereby determining the stress-strain diagram of the thin film test piece.

Hereinafter, with reference to the accompanying drawings showing a preferred embodiment of the present invention will be described in detail, in adding reference numerals to the components of each drawing, the same components are possible even if displayed on different drawings It should be noted that the same reference numerals are used. In describing the present invention, when it is determined that the detailed description of the related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, the terms or words used in the present specification and claims are consistent with the technical spirit of the present invention on the basis of the principle that the inventor can appropriately define the concept of the term in order to explain the invention in the best way. It must be interpreted as meaning and concept.

The four-point bending apparatus 100 for X-ray diffraction according to the present invention is a top body 10 for four-point bending, the micrometer 20 of the lower to adjust the strength of the bending, a thin film subjected to bending deformation It consists of a test piece 200.

Here, the upper portion of the body 10 is composed of two pairs of fixed thin film test piece support and the two pairs of thin film test piece to be elevated, the two pairs of thin film test piece to be elevated is connected to the micrometer (20) And lifted by the micrometer 20.

In addition, the two pairs of fixed thin film test piece support portions may be provided at both sides in the longitudinal direction of the body 10, and the two pairs of the thin film test piece support portions which are elevated may be provided at the inner side in the longitudinal direction of the body 10. The test piece support part is fixed in the width direction of the upper end of the body 10 and has a pair of fixing pieces 11 having a fitting hole 11a formed at one side thereof, and a fitting hole 11a of the pair of fixing pieces 11. It may consist of a pin 12 to be fitted.

The fitting hole (11a) is preferably made of an oval to help the free rotation of the pin (12), the two pairs of lifting the thin film test piece support, the lower side connected by the micrometer (20) and the connecting pin (22) The structure is fixed to the lifting unit 21 and lifted by the rotation of the micrometer 20.

Here, the lifting unit 21 may further include a pin slider bearing 23 on the outer periphery for precise lifting.

Such the present invention has the advantage that it is not necessary to prepare a separate test piece because the deformation is applied as it is a thin film deposited on the substrate. In addition, there is an advantage that can be applied to the thin film as well as the compression load to pull as the load support points change the position up and down.

In addition, when four-point bending is used, a uniform load can be applied to two pairs of thin film test piece supporting elevating, thereby solving the problem of gradient of load generated from the existing three-point bending.

Meanwhile, the present invention artificially bends a thin film (or substrate, hereinafter thin film) test piece by using the four-point bending apparatus 100 for X-ray diffraction as described above to form an artificial stress on the surface of the thin film. The stress applied to the thin film surface can be calculated by measuring the degree of bending, that is, the radius of curvature of the thin film surface caused by bending, and substituting it into the elastic deformation solution of the thin film.

When the X-rays are irradiated to the crystalline material, diffraction occurs only in a specific direction. The diffraction peaks generated by this diffraction phenomenon are observed only at specific positions because they have unique lattice constants and atomic stacks.

Since the position of the diffraction peak 2θ is inversely proportional to the interplanar distance d of the crystal lattice, the shift of the specific diffraction peak Δ2θ as shown in FIG. 2 indicates that the change of the interplanar distance Δd of the grating is generated. Therefore, the degree of deformation of the material can be quantitatively measured by observing the positional change of the X-ray diffraction peak.

That is, in the thin film material stress-strain behavior measuring method using the four-point bending device for X-ray diffraction according to the present invention, the thin film test piece on which the thin film is deposited to a predetermined thickness is scanned with a laser displacement meter, and the residue generated in the deposition state therefrom. Measuring the bending curvature of the deposited substrate by the stress (S10) and the step of measuring the diffraction peak information of the thin film test piece according to the change of the diffraction angle by the X-ray diffraction test without bending the thin film test piece (S20) and varying the tensile / compressive stress on the surface of the thin film by micrometer rotation of the four-point bending device for X-ray diffraction to measure the bending curvature with a laser displacement meter (S30), and At the same time as (S30), the strain of the thin film test piece was determined by measuring the diffraction peak information of the thin film test piece according to the change of the diffraction angle by X-ray diffraction test on the thin film test piece subjected to the tensile / compression stress. It comprises a step (S40), wherein the calculation of the bending curvature is calculated using the <Equation 1> to average the radius of curvature of the center 50% of the full length of the thin film test piece.

Where R is the bending curvature radius caused by the four-point bending,

a, b, c is the length of each side of the triangle

s is (a + b + c) / 2.

In addition, the calculation of the stress is made by <Equation 2>, the strain is calculated by <Equation 3>.

는 박막에 걸린 응력치를 나타내고,here,

Represents the stress value applied to the thin film,

는 박막의 탄성계수를 나타내고,

Represents the modulus of elasticity of the thin film,

는 기판의 두께를 나타내고,

Represents the thickness of the substrate,

는 박막의 포아슨 비(Poisson's ratio)를 나타내고,

Denotes the Poisson's ratio of the thin film,

은 상기 <수학식1>의

정의와 같다.

Of Equation 1

Same as definition.

은 박막 표면의 변형률을 나타내고,here,

Represents the strain of the thin film surface,

는 증착상태 그대로(혹은 무응력 상태)의 박막 고유 면간거리를 나타내고,

Represents the intrinsic interplanar spacing of the film as it is (or without stress),

는 4점 굽힘응력의 작용으로 변화하는 박막의 면간거리를 나타낸다.

Denotes the interplanar distance of the thin film that is changed by the action of the four-point bending stress.

That is, the present invention calculates the stress applied to the thin film by measuring the bending radius of curvature while increasing the bending load step by step using the four-point bending apparatus for X-ray diffraction of Figure 1, and at the same time X-ray diffraction test By measuring the strain corresponding to the bending stress, it is possible to finally determine the stress-strain diagram of the thin film.

<Example 1>

Both surfaces of a Vitreloy alloy having a size of 32 × 7 × 0.5 mm were polished and used as a substrate, and a thin film of Au was deposited to a thickness of 1 um through sputtering.

The thin film deposited substrate was scanned with a laser displacement meter, and the degree of warpage of the deposited substrate was measured by the residual stress generated in the deposited state. The specimen was placed on the four-point bending device for X-ray diffraction as shown in FIG. 1 (without artificial bending deformation by turning the micrometer), and then subjected to X-ray diffraction test to obtain a diffraction peak according to a change in the rotation angle of the specimen. The information was measured. Here, the X-ray irradiation is between two pairs of thin film test piece support that is elevated.

Thereafter, the elevating part 21 was pushed up by the micrometer 20 to apply a tensile stress to the thin film surface by convexly deforming the thin film deposited substrate, and the degree of bending was measured using a laser displacement meter. The X-ray diffraction test was performed, and the diffraction peak information of the thin film test piece according to the change of the diffraction angle was recorded. These bending strains were accumulated by increasing the rotation of the micrometer 20 in several steps, and at each step, the laser displacement scan record and the diffraction peaks obtained from the thin film were calculated to calculate the stress applied to the thin film based on the bending curvature measurement. The X-ray diffraction test was performed simultaneously to calculate the strain from the degree.

In order to observe the shift of diffraction peak for deformation measurement, it detects X-ray source that generates X-ray, goniometer that can measure diffraction angle and diffraction peak. The detector and the group capable of collecting, recording and storing the diffraction data from the detector are composed of a recorder.

The X-ray source used to obtain the X-ray diffraction pattern was Cukα (1.5405929 mm 3), the radius of the goniometer was 185 mm, the detector was a scintillation counter and the recording device was a computer.

result,

3 shows the bending shape recorded by the laser displacement meter while bending the thin film deposited substrate as it is in several stages. The displacement information recorded over the entire length of the 32 mm substrate is regarded as part of an arc as shown in FIG. The curvature radius was measured by forming.

That is, the radius R of the circle circumscribed with the triangle vertices when the triangle is formed by connecting both ends of the specimen and the individual displacement measurement points as shown in Figure 4 is expressed as Equation (1).

Triangles were formed using all profile measurement points existing between both ends of the bending test piece, and the radius of curvature R values were calculated using Equation 1 and FIG. 4. As a result, as shown in FIG. 5, the change in the radius of curvature R over the entire length of the bending test piece was confirmed. Since the area where the actual bending stress should be measured is the internal width, the radius of curvature of the center 50% of the specimen length was averaged and used as the representative radius of curvature for each bending step.

The bending stress was calculated by substituting the radius of curvature R and the elastic properties of the substrate and the thin film material in equation (2). The elastic modulus and Poisson's ratio of Vitreloy amorphous substrate were 92 GPa and 0.36, and the elastic modulus and Poisson ratio of Au thin film were 50 GPa and 0.25.

As can be seen in FIG. 1, since the thin film test piece in the deposited state has a convex shape downward unlike other artificial bending test pieces, R is substituted with a negative sign. The stress values applied to the surface of the thin film calculated using Equation 2 are shown in Table 1.

 Stress values obtained from as-deposited and bent specimens.

In the diffraction pattern of the Au thin film, nine diffraction peaks were obtained as shown in FIG. 6 in the range of 30 ° to 145 ° diffraction angle (2θ) when Cukα (1.5405 Hz) was used as the X-ray source. Among the nine diffraction peaks, a diffraction peak at 64.45 ° (2θ) was selected as a diffraction peak for measuring the deformation amount according to the bending stress.

Diffraction patterns around 2θ of 64.45 ° were obtained from thin film / substrate test specimens in which the bending state and bending in three steps were increased, and the result is superimposed on FIG. 7. As can be expected from FIG. 2, the diffraction patterns were shifted to the left as the tensile stress increased on the Au thin film surface.

)으로부터 계산할 수 있다. 여기서 반사차수 (reflection order) n은 1로 주어지고, 회절시험에 사용된 X선 파장 λ는 1.5405929 Å으로 주어졌다. 각 회절 패턴의 피크에 해당하는 회절각을 측정하고, 이를 Bragg 법칙에 대입한 결과 면간거리 d는 <표2>와 같이 계산되었다.The changed interplanar distance d at each stress state is Bragg's law (

Can be calculated from Here, the reflection order n is given by 1, and the X-ray wavelength λ used in the diffraction test is given by 1.5405929 Å. As a result of measuring the diffraction angle corresponding to the peak of each diffraction pattern and substituting it into Bragg's law, the interplanar distance d was calculated as shown in <Table 2>.

The change in interplanar distance calculated in <Table 2> can be converted into strain value by substituting <Equation 3>. However, stress and strain are present in the thin film specimens (nil bending) in the deposited state. However, they are insignificant compared to the artificially applied bending stress as shown in <Table 1>. The obtained interplanar spacing was used as the intrinsic interplanar spacing of the stress-free Au thin film.

Changes in the interplanar distance and thin-film strain due to artificial 4-point bendings.

The stress-strain diagram of the Au thin film was completed as shown in FIG. 8 using the stresses and strains obtained in Tables 1 and 2.

Although the present invention has been described in connection with a preferred embodiment, those of ordinary skill in the art will be able to easily make various changes and modifications without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation, and the true scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope are included in the present invention. Should be interpreted as.

1 is a view showing the assembly of the four-point bending device for X-ray diffraction to artificially deform the deposited thin film test piece,

2 is a diagram showing the left and right movement of the X-ray diffraction peak according to the residual stress code applied to the material,

3 is a view showing a shape profile obtained by scanning the surface of an artificial bending deformation thin film test piece with a laser displacement meter,

4 is a diagram illustrating a geometric analysis process of determining a radius of curvature (or inscribed circle radius) assuming the shape profile of FIG. 3 as an arc;

FIG. 5 is a view showing the curvature radius analysis result of FIG. 4 over the entire length of the thin film test specimen subjected to various bending deformations.

6 is a view showing an X-ray diffraction pattern obtained on the surface of the deposited gold thin film,

7 is a view showing that the diffraction peak obtained in the thin film test specimen subjected to artificial bending deformation is moved from the gold thin film diffraction peak as it is deposited due to the applied stress.

8 is a view showing the final result of measuring the stress-strain behavior of the gold thin film using a four-point bending device for X-ray diffraction.

<Description of Symbols for Major Parts of Drawings>

100: 4-point bending device for X-ray diffraction 200: thin film test piece

10: body 20: micrometer

11: fixing piece 11a: fitting hole

12: pin 21: lift

22: connecting pin

Claims (11)

In the four-point bending device 100 for X-ray diffraction to measure the stress-strain of the thin film test piece 200 by X-ray irradiation and four-point bending, The four-point bending device 100 for X-ray diffraction is composed of the upper body 10 for the four-point bending, the lower micrometer 20 to adjust the strength of the bending, The upper portion of the body 10 is composed of two pairs of fixed thin film test piece support, and the two pairs of lifting the thin film test piece support, the two pairs of the lifting thin film test piece support is connected to the micrometer 20 is micro 4-point bending device for X-ray diffraction, which is lifted by the meter (20). The method of claim 1, The two pairs of fixed thin film test piece support portions are provided on both sides in the longitudinal direction of the body 10, and the two pairs of thin film test piece supporting portions are provided on the inner side in the longitudinal direction of the body 10. 4-point bending device for diffraction. The method of claim 1, The thin film test piece support portion is fixed in the width direction of the upper end of the body 10 and a pair of fixing pieces (11) formed with a fitting hole (11a) on one side; And a pin (12) fitted into the fitting hole (11a) of the pair of fixing pieces (11). The method of claim 2, The fitting hole (11a) is a four-point bending device for X-ray diffraction, characterized in that made of an oval to help free rotation of the pin (12). The method of claim 1, The two pairs of lifting test pieces of thin film test piece, The four-point bending device for X-ray diffraction, characterized in that the lift by the rotation of the micrometer 20 is fixed to the lower lifting portion 21 is connected to the micrometer 20 and the connecting pin (22). The method of claim 5, The elevating portion (21) is a four-point bending device for X-ray diffraction, characterized in that it further comprises a pin slider bearing (23) on the outer periphery for precise lifting. Scanning the thin film test piece on which the thin film is deposited to a predetermined thickness with a laser displacement measuring device and measuring the bending curvature of the deposited substrate by the residual stress generated in the deposition state therefrom (S10); Measuring diffraction peak information of the thin film test piece according to the change of the diffraction angle by X-ray diffraction test without bending the thin film test piece (S20); Measuring the bending curvature by using a laser displacement meter by varying the tensile / compressive stress on the surface of the thin film by micrometer rotation of the four-point bending device for X-ray diffraction (S30); Obtaining the strain of the thin film test piece by measuring diffraction peak information of the thin film test piece according to the change of the diffraction angle by X-ray diffraction test on the thin film test piece to which the tensile / compressive stress was applied at the same time (S30); Thin-film stress-strain measurement method using a four-point bending device for X-ray diffraction, comprising a. The method of claim 7, wherein The bending curvature is a thin film stress-strain measurement method using a four-point bending device for X-ray diffraction, characterized in that by <Equation 1>. The method of claim 7, wherein The bending curvature is a thin film stress-strain measurement method using a four-point bending device for X-ray diffraction, characterized in that the average of the radius of curvature of the center 50% of the full length of the thin film test piece. The method of claim 7, wherein The stress calculation is a thin film stress-strain measurement method using a four-point bending device for X-ray diffraction, characterized in that by <Equation 2>. The method of claim 7, wherein The strain is a thin film stress-strain measurement method using a four-point bending device for X-ray diffraction, characterized in that by <Equation 3>.

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