Nanometer film thickness measuring method based on double-layer film buckling structure

Abstract

The invention discloses a nanofilm thickness measuring method based on a double-layer film buckling structure, which comprises the following steps: firstly, transferring a nanofilm to be measured onto a soft film to form a double-layer film system, and the elastic modulus of the soft film is smaller than that of the nanofilm to be measured; then stretching the double-layer film system to manufacture a periodic buckling structure; then measuring and calculating an intrinsic period lambda 0 of the buckling structure; and finally, directly calculating the thickness of the nano film according to the following formula. According to the method, the difficulty of measuring the thickness of the nano-film is remarkably reduced, the testing precision is naturally improved, the thickness of the nano-scale film can be accurately measured, and the method can be used for measuring the thickness of the film of a multi-layer film complex system.

Description

Technical Field

[0001] The invention relates to the field of nanotechnology, and in particular to a method for measuring the thickness of a nano film based on a double-layer film buckling structure. Background Art

[0002] Whether it is the basic properties of thin films or applied research, the thickness measurement of thin films is often necessary. Traditionally, the thickness measurement of single-layer thin films mainly relies on thickness gauges and optical instruments based on beam diffraction interference. Traditional testing methods such as thickness gauges are often only applicable to film thicknesses of microns and above. Optical equipment is also limited by the wavelength of single photons, and the limit of measuring film thickness is at the scale of hundreds of nanometers. When the film thickness is less than tens of nanometers or even drops below ten nanometers, the thickness value measured by the existing film thickness test scheme often has significant errors. In addition, with the development of flexible electronics. The construction of flexible electronic devices often requires composite multiple layers of different types of thin films. In these complex systems, the thickness of any single-layer film may affect the properties and performance of the entire device. Therefore, the thickness measurement of any single-layer film is equally important. Because in complex multi-layer film systems, the separation of any single-layer film is difficult. Therefore, traditional thickness measurement schemes are often not applicable to such systems. Based on the above-mentioned practical difficulties in film thickness measurement, it is very necessary to propose a full solution for measuring the thickness of complex multi-layer film systems.

[0003] The existing thin film thickness measurement technology mainly includes direct measurement by traditional thickness gauges, optical instruments based on beam diffraction interference, etc. The existing methods mainly have the following shortcomings.

[0004] 1. Traditional testing methods such as thickness gauges are often only suitable for measuring films with thickness of microns or above.

[0005] 2. Optical equipment is also limited by the wavelength of a single photon, and the effective measurement limit of film thickness is in the hundreds of nanometers. When the film thickness is less than tens of nanometers or even drops below ten nanometers, the test results of existing test solutions often have significant errors.

[0006] 3. Existing testing methods are not suitable for measuring arbitrary film thickness of complex multi-layer film systems.

[0007] When the hard-soft double-layer membrane system is stretched or squeezed, a buckling array represented by a sinusoidal structure will appear on the surface. The eigenperiod of this type of periodic buckling structure is proportional to the thickness of the hard film. The eigenperiod of the buckled structure formed by the nanoscale hard film can generally reach the micron level. At the same time, the buckled structure is periodic and has the same eigenperiod. The sum of the eigenperiods of multiple buckled structures will reach tens or even hundreds of microns. The length of this scale is easy to measure. Based on this, this patent proposes a solution to measure the eigenperiod of the buckled structure formed by the hard-soft double-layer membrane system under extrusion, and then infer the thickness of the hard nanofilm. Summary of the invention

[0008] The technical problem to be solved by the present invention is to address the defects involved in the background technology and provide a nano film thickness measurement method based on a double-layer membrane buckling structure, which is suitable for thin film thickness measurement in special scenarios and can effectively and accurately measure the film thickness of several nanometers to several microns.

[0009] The present invention adopts the following technical solutions to solve the above technical problems:

[0010] The method for measuring the thickness of a nanofilm based on a double-layer film buckling structure comprises the following steps:

[0011] Step 1), transferring the nanofilm to be tested onto a soft film to form a double-layer film system, wherein the elastic modulus of the soft film is smaller than the elastic modulus of the nanofilm to be tested;

[0012] Step 2), stretching the double-layer membrane system to produce a periodic buckling structure;

[0013] Step 3), measuring and calculating the eigenperiod λ0 of the buckled structure;

[0014] Step 4), the thickness of the nanofilm is directly calculated according to the following formula:

[0015]

[0016] In the formula, E s , μ s are the elastic modulus and Poisson's ratio of the soft film; E m , μ m are the elastic modulus and Poisson's ratio of the hard nanofilm; t m is the thickness of the nanofilm.

[0017] As a further optimization scheme of the nanofilm thickness measurement method based on the double-layer film buckling structure of the present invention, the detailed steps of step 3) are as follows:

[0018] Step 3.1), mark the buckled structure selection area and record the number of buckled structures;

[0019] Step 3.2), relax the double-layer membrane system to make it flat, measure the length of the marked area, divide the length of the marked area by the number of buckled structures, and obtain the intrinsic period λ0 of the buckled structure.

[0020] As a further optimization scheme of the nanofilm thickness measurement method based on the double-layer membrane buckling structure of the present invention, the marking is performed by electron beam irradiation in the step 3.1).

[0021] As a further optimization scheme of the nanofilm thickness measurement method based on the double-layer film buckling structure of the present invention, the thickness of the soft film is between 50 and 100 microns.

[0022] As a further optimization scheme of the nanofilm thickness measurement method based on the double-layer film buckling structure of the present invention, the soft film is a polydimethylsiloxane film.

[0023] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0024] 1. The nanoscale film thickness measurement is converted into the intrinsic period measurement of the buckling structure at the scale of micrometers or even tens or hundreds of micrometers, which significantly reduces the test difficulty and naturally improves the test accuracy;

[0025] 2. Capable of accurately measuring nanoscale film thickness;

[0026] 3. Can be used to measure the film thickness of complex multi-layer film systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the buckling structure of the soft and hard double-layer membrane surface under tension and the electron beam irradiation mark;

[0028] Figure 2 It is a schematic diagram of the state of the double-layer membrane after relaxation and stretching. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0030] The present invention can be implemented in many different forms and should not be considered to be limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete, and will fully express the scope of the present invention to those skilled in the art. In the accompanying drawings, components are enlarged for clarity.

[0031] The present invention discloses a method for measuring the thickness of a nano film based on a double-layer film buckling structure, comprising the following steps:

[0032] Step 1), transferring the nanofilm to be tested onto a soft film to form a double-layer film system, wherein the elastic modulus of the soft film is smaller than the elastic modulus of the nanofilm to be tested;

[0033] That is, the nanofilm to be tested is a relatively hard film, which forms a hard-soft double-layer film system with a soft film with a smaller elastic modulus. The thickness of the soft film is between 1 micron and 200 microns, with 50 to 100 microns being the best. The soft film preferably uses PDMS (poly(dimethylsiloxane)), i.e., polydimethylsiloxane film.

[0034] Step 2), stretching the double-layer membrane system to produce a periodic buckling structure;

[0035] Step 3), measuring and calculating the eigenperiod λ0 of the buckled structure;

[0036] Step 4), the thickness of the nanofilm is directly calculated according to the following formula:

[0037]

[0038] In the formula, E s , μ s are the elastic modulus and Poisson's ratio of the soft film; E m , μ m are the elastic modulus and Poisson's ratio of the hard nanofilm; t m is the thickness of the nanofilm.

[0039] The detailed steps of step 3) are as follows:

[0040] Step 3.1), mark the buckled structure selection area and record the number of buckled structures, such as Figure 1 As shown;

[0041] When marking, electron beam irradiation or other marking tools can be used.

[0042] Step 3.2), relax the double-layer membrane system to make it flat, and measure the length of the marked area, such as Figure 2 As shown, the length of the marked area is divided by the number of buckled structures to obtain the eigenperiod λ0 of the buckled structures.

[0043] Step 3) may also use other methods to obtain the eigenperiod of the buckled structure. For example, by measuring the crack period corresponding to the buckled structure, the eigenperiod of the buckled structure may also be determined.

[0044] The present invention converts the nanoscale film thickness measurement into the measurement of the intrinsic period of the buckling structure at the micron or even tens or hundreds of microns scale, which significantly reduces the test difficulty and naturally improves the test accuracy. It can accurately measure the nanoscale film thickness and can be used for the film thickness measurement of complex multilayer film systems. The measurement accuracy can reach 1 nanometer or even sub-nanometer, or hundreds of nanometers to 1 micrometer.

[0045] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0046] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring the thickness of a nanofilm based on a double-layer film buckling structure, characterized in that: The following steps are involved: Step 1), transferring the nanofilm to be tested onto a soft film to form a double-layer film system, wherein the elastic modulus of the soft film is smaller than the elastic modulus of the nanofilm to be tested; Step 2), stretching the double-layer membrane system to produce a periodic buckling structure; Step 3), measuring and calculating the eigenperiod λ0 of the buckled structure; Step 4), the thickness of the nanofilm is directly calculated according to the following formula: In the formula, E s , μ s are the elastic modulus and Poisson's ratio of the soft film; E m , μ m are the elastic modulus and Poisson's ratio of the hard nanofilm; t m is the thickness of the nanofilm.

2. The method for measuring the thickness of a nanofilm based on a double-layer film buckling structure according to claim 1, characterized in that: The detailed steps of step 3) are as follows: Step 3.1), mark the buckled structure selection area and record the number of buckled structures; Step 3.2), relax the double-layer membrane system to make it flat, measure the length of the marked area, divide the length of the marked area by the number of buckled structures, and obtain the intrinsic period λ0 of the buckled structure.

3. The method for measuring the thickness of a nanofilm based on a double-layer film buckling structure according to claim 2, characterized in that: In the step 3.1), labeling is performed by electron beam irradiation.

4. The method for measuring the thickness of a nanofilm based on a double-layer film buckling structure according to claim 1, characterized in that: The thickness of the soft film is between 50 and 100 microns.

5. The method for measuring the thickness of a nanofilm based on a double-layer film buckling structure according to claim 1, characterized in that: The soft film is a polydimethylsiloxane film.

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