TWM622029U - Non-contact thin film residual stress detection system - Google Patents

Abstract

The present invention mainly discloses a non-contact film residual stress detection system, which mainly includes: a stage, a light source, a spatial filter, an aperture, a lens, a beam splitter, a standard plane mirror, an image capture device, And a control and data processing device; it is characterized in that, after completing the measurement and acquisition of the isoblique interferogram of a substrate and an optical film formed on the substrate, the control and data processing device uses the wavelet transform method to convert the The isotonic interferogram of the substrate and the optical film is converted into a wrapped phase map. Continuing, after sequentially performing phase unwrapping processing, curvature calculation and warpage calculation, and curvature radius fitting calculation, the control and data processing device obtains the X-axis fitting curve of the substrate and the optical film and Y-axis fitting curve. Finally, according to the X-axis fitting curve and the Y-axis fitting curve of the substrate and the optical film, the control and data processing device calculates the residual stress of the optical film by using the Stoney mathematical operation formula.

Description

Non-contact thin film residual stress detection system

The new type relates to the related technical field of the film application field, especially a non-contact type film residual stress detection system.

It is known that an optical film is a dielectric film layer formed on an optical element or a substrate, which is used to produce specific optical effects to change the transmission characteristics of light waves, including light transmission, light reflection, light absorption, light scattering, and light polarization. , and changing the light phase. With the high development of optoelectronic technology and the popularization of optical components and optoelectronic products, the research and development and application of optical thin films are becoming more and more important. It is worth noting that, in the process of forming the optical film on the substrate, the generation of residual stress may cause the optical film to have defects or be deformed and bent, resulting in a decrease in the manufacturing yield and reliability of the optical film.

Engineers who have been involved in film stress measurement for a long time must know that the conventional measurement methods of film stress measurement can be simply divided into two types: contact type and non-contact type. Among them, the probe-type profilometer is a typical contact type film stress measurement method. measurement system. However, the practical application of the contact film stress measurement system has two disadvantages. One is that it is easy to damage the surface integrity of the sample during the measurement process of the film stress measurement, and the other is that the measurement time is long.

On the other hand, engineers who are familiar with the measurement of film residual stress also know that non-contact optical film residual stress measurement methods include: (1) Cahtilever beam method, (2) Newton's ring method ), (3) Laser interference method (Laser interferometric method), and (4) Laser Levered reflection method. Among them, Michelson interferometer, Twyman-Green interferometer and Fizeau interferometer are currently widely used non-contact thin film stress measurement systems.

As far as the prior art is concerned, when the optical interference type non-contact thin film stress measurement system is used to measure the residual stress of the optical thin film, the self-developed Matlab software is usually combined with the two-dimensional fast Fourier transform (FFT) method to process the interference fringes. , and then restore the 3D surface profile of the film through phase unwrapping technology, and then use a Gaussian filter to filter out low-frequency noise, and convert the phase function into a three-dimensional surface profile distribution. Finally, the surface radius of curvature value was determined through numerical fitting analysis to determine the residual stress of the homogeneous and anisotropic optical films.

The Fourier transform method projects the optical interference signal onto a triangular wave, thereby decomposing the optical interference signal into triangular waves of different frequencies. However, practical experience points out that the Fourier transform method is only suitable for dealing with deterministic signals and stationary signals. For time-varying signals and non-stationary signals, the Fourier transform method shows its shortcomings. To sum up, the Fourier transform method cannot describe the regional characteristics of the signal in the time domain, and the Fourier transform method is not good for the abrupt and non-stationary signals.

It can be seen from the above description that the conventional optical interference type non-contact thin film stress measurement system using the Fourier transform method in the signal processing algorithm obviously still has points worth improving. In view of this, the creator of this case tried his best to research and create, and finally developed a non-contact film residual stress detection system.

The main purpose of this new model is to provide a non-contact film residual stress detection system, which mainly includes: a stage, a light source, a spatial filter, an aperture, a lens, a beam splitter, a standard plane mirror, and an image capture An acquisition device, and a control and data processing device; it is characterized in that, after completing the measurement and acquisition of the isoblique interferogram of a substrate and an optical film formed on the substrate, the control and data processing device uses wavelets The transformation method converts the isotonic interferogram of the substrate and the optical film into a wrapped phase map. Continuing, after sequentially performing phase unwrapping processing, curvature calculation and warpage calculation, and curvature radius fitting calculation, the control and data processing device obtains the X-axis fitting curve of the substrate and the optical film and Y-axis fitting curve. Finally, according to the X-axis fitting curve and the Y-axis fitting curve of the substrate and the optical film, the control and data processing device calculates the residual stress of the optical film by using the Stoney mathematical operation formula.

It is worth noting that when converting the isotropic interferogram into the wrapped phase map, the new model uses wavelet transform processing to replace the conventional fast Fourier transform, so that the new non-contact thin film residual stress detection system has the advantages of low cost and high quantity. It has many advantages such as fast measurement and high accuracy.

In order to achieve the above object, the present invention proposes an embodiment of the non-contact film residual stress detection system, which includes: a stage on which a sample to be tested is placed, and an inclination angle of which can be adjusted control, wherein the sample to be tested includes a substrate and an optical film covering the substrate; a light source, arranged along a first optical axis; A spatial filter is arranged along the first optical axis, and a light incident end receives a detection light emitted by the light source, and performs a spatial filtering process on the detection light; an aperture, along the first light a light output end facing the spatial filter to receive the detection light after the spatial filtering process; a lens, arranged along the first optical axis and facing the aperture; a beam splitter, a standard plane mirror, arranged along the first optical axis, with a first side facing the lens; a standard plane mirror, with a first side facing a second side of the beam splitter , and its second surface faces the sample to be tested on the stage; an image capture device is arranged along the first optical axis with a second optical axis perpendicular to it, and uses an image capture device The lens faces a third side surface of the beam splitter; wherein, after the detection light enters the first side surface of the beam splitter through the aperture and the lens, and then enters the standard plane mirror through the second side surface of the beam splitter , so that a first light of the detection light then passes through the second surface of the standard plane mirror and is directed to the sample to be tested, and a second light of the detection light is reflected by the first surface of the standard plane mirror so as to return to the second side of the beam splitter, and finally pass through the third side of the beam splitter and shoot to the camera lens of the image capture device; and a control and data processing device electrically connected to a an adjustment mechanism, which is coupled to the light source and the image capture device; wherein, under the control of the control and data processing device, the non-contact film residual stress detection system measures and obtains the substrate and the optical film respectively. oblique interferogram; The control and data processing device obtains the wrapped phase map of the substrate and the optical film after performing a wavelet transformation process on the isoblique interferogram of the substrate and the optical film; wherein, the substrate and the optical film are continuously processed. After the wrapping phase image of the optical film is subjected to a phase unwrapping process, the control and data processing device obtains the three-dimensional surface profile of the substrate and the optical film; wherein, the substrate and the three-dimensional surface profile of the optical film are continuously curved. After the degree calculation and a warpage degree calculation, the control and data processing device obtains the two-dimensional surface profile of the substrate and the optical film; wherein, a radius of curvature is continuously performed on the two-dimensional surface profile of the substrate and the optical film After the fitting calculation, the control and data processing device obtains the X-axis fitting curve and the Y-axis fitting curve of the substrate and the optical film; finally, according to the obtained X-axis fitting curve of the substrate and the optical film Combined curve and Y-axis fitting curve, the control and data processing device calculates the residual stress of the optical film by using the Stoney mathematical operation formula.

In one embodiment, the control and data processing device is an electronic device, and the electronic device is installed with at least one software, so that a main processor of the electronic device can implement the wavelet transform by loading the at least one software processing, the phase unwrapping processing, the tortuosity calculation, the warpage calculation, and/or the curvature radius fitting calculation, and executing the Stoney math.

In a feasible embodiment, the electronic device is any one selected from the group consisting of industrial computers, cloud computing computers, desktop computers, notebook computers, tablet computers, and smart phones.

In one embodiment, the wavelet transform processing is Morlet wavelet transform processing, and the phase unwrapping processing is Macy phase unwrapping processing.

In one embodiment, the light source is one of a helium-neon laser device or a semiconductor laser device, the lens is a convex lens, and the image capturing device is a CCD camera device.

1: Non-contact film residual stress detection system

10: Carrier

11: Light source

12: Spatial Filter

13: Aperture

14: Lens

15: Optical splitter

151: The first side

152: Second side

153: third side

16: Standard plane mirror

17: Image capture device

18: Control and data processing devices

2: Sample to be tested

FIG. 1 is a schematic perspective view of a novel non-contact film residual stress detection system.

In order to more clearly describe a non-contact film residual stress detection system proposed by the present invention, a preferred embodiment of the present invention will be described in detail below with reference to the drawings.

Please refer to FIG. 1 , which shows a schematic perspective view of a non-contact film residual stress detection system of the present invention. As shown in FIG. 1, the novel non-contact film residual stress detection system 1 includes: a stage 10, a light source 11, a spatial filter 12, an aperture 13, a lens 14, A beam splitter 15 , a standard plate 16 , an image capture device 17 , and a control and data processing device 18 . According to the design of the present invention, the stage 10 is used for a sample to be tested 2 to be placed thereon, and an inclination angle thereof can be adjusted and controlled. It should be known that the system of the present invention is designed to The residual stress of the thin film is measured. Therefore, the sample to be tested 2 includes a substrate and an optical film overlying the substrate.

Continuing with map 1, the light source 11 is one of a Helium-neon laser device or a semiconductor laser device, and is disposed along a first optical axis. In addition, the spatial filter 12 is also disposed along the first optical axis, and a light incident end of the spatial filter 12 receives a detection light emitted by the light source 11, and performs a spatial filtering process on the detection light. In more detail, the aperture 13 is disposed along the first optical axis, and faces a light exit end of the spatial filter 12 to receive the detection light after the spatial filtering process is completed. On the other hand, the lens 14 is a convex lens, which is disposed along the first optical axis and faces the aperture 13 . In addition, the beam splitter 15 is disposed along the first optical axis, and has a first side surface 151 of the lens 14 .

It is worth noting that the standard plane mirror 16 is disposed along the first optical axis, a first surface of the standard mirror 16 faces a second side surface 152 of the beam splitter 15, and a second surface of the standard mirror 16 faces the carrier The sample to be tested 2 on the stage 10 . According to the design of the present invention, the image capturing device 17 is disposed along the first optical axis with a second optical axis orthogonal to it, and a camera lens thereof faces a third side surface 153 of the beam splitter 15 . In this way, as shown in FIG. 1 , after the detection light passes through the aperture 13 and the lens 14 and enters the first side surface 151 of the beam splitter 15 , and then enters the standard through the second side surface 152 of the beam splitter 15 . The plane mirror 16 , so that a first light of the detection light then passes through the second surface of the standard plane mirror 16 and is directed to the sample to be tested 2 , and a second light of the detection light is transmitted by the standard plane mirror 16 . The first surface is reflected to return to the second side 152 of the beam splitter 15, and finally passes through The photographing lens of the image capturing device 17 is emitted through the third side surface 153 of the beam splitter 15 .

In other words, 50% of the detection light incident on the standard mirror 16 through the second side of the beam splitter 15 (ie, the first light) will transmit through the standard mirror 16, and the remaining 50% (ie, the first light) will be transmitted through the standard mirror 16 The second light) will be reflected by the standard mirror 16 . On the other hand, as shown in FIG. 1 , the control and data processing device 18 is electrically connected to an adjustment mechanism of the stage 10 , and is coupled to the light source 11 and the image capture device 17 . In this way, under the control of the control and data processing device 18 , the non-contact film residual stress detection system 1 measures and obtains the isoblique interferograms of the substrate and the optical film, respectively.

According to the design of the present invention, the control and data processing device 18 obtains the wrapped phase map of the substrate and the optical film after performing a wavelet transform on the isoblique interferogram of the substrate and the optical film. In particular, in the present invention, the wavelet transform processing is Morlet wavelet transform processing, that is, a two-dimensional wavelet transform method. The local information of the interference fringe signal can be analyzed by using the Morlet wavelet transform. Generally, the one-dimensional wavelet ψ(x) is assumed to be a function of finite energy, and its average value is zero, as shown in the following formula (1):

Further, expanding the wavelet by the scale parameter (s) and translating it by the position parameter (ξ) generates a series of sub-wavelets, which can be expressed as the following equation (2):

Continuing, for a one-dimensional continuous wavelet W _f can be written as the following formula (3):

In the above formula (3), x represents a spatial variable, and * represents a conjugate complex number.

In more detail, the scale parameter (s) is related to the frequency. When the value of s is small, the analyzed wavelet has the characteristics of rapid oscillation, which is very suitable for the selection of high-frequency components of the signal. Conversely, when the value of s is large, low-frequency signals can be separated. Therefore, for the interference fringes distributed in the x direction, the one-dimensional continuous wavelet W _x can be rewritten as the following formula (4):

In the above formula (4), I ₀ (x, y), V(x, y) and Φ(x, y) are the average intensity of the interference fringes, the fringe contrast and the phase difference, respectively. In formula (4), there is a local maximum in the number corresponding to each pixel, and the absolute value of this value is called a ridge, which can be used to detect frequency changes. These points with significant frequency changes correspond to the phase , and ignoring the noise effect of small frequency changes, the ridge function can be easily converted into a phase function by using this feature, which can be expressed as the following formula (5):

By repeating this process for the y direction, the wrapped phase Φ(x,y) can be obtained, and a phase unwrapping is required to obtain the complete phase function. The wavelet transform method uses only one interferogram for analysis, which is conducive to the rapid restoration of the subsequent wrapping phase Φ(x, y). Therefore, after obtaining the wrapped phase image of the substrate and the optical film, the control and data processing device 18 continues to perform a phase unwrapping process on the wrapped phase image of the substrate and the optical film. The data processing device 18 obtains the three-dimensional surface profiles of the substrate and the optical film. It is worth noting that in order to obtain information on the surface morphology of the thin film, 2π must be added or subtracted when Φ(x, y) is phase unwrapped to deal with the discontinuity of the function. Therefore, the phase unwrapping method adopted in the present invention is Macy's operation method.

可得到待測物(基板表面或光學薄膜表面)的高度h(x,y)，其可以表示為下式(6)：

After that, unwrap the wrapped phase and multiply by

The height h(x, y) of the object to be tested (substrate surface or optical film surface) can be obtained, which can be expressed as the following formula (6):

In the above formula (6), λ is the wavelength of the laser light source, and n is the refractive index of air. After continuously performing a phase unwrapping on the substrate and the wrapped phase image of the optical film, the control and data processing device 18 obtains the three-dimensional surface profile of the substrate and the optical film.

After continuously performing a curvature calculation and a warp calculation on the three-dimensional surface profiles of the substrate and the optical film, the control and data processing device 18 obtains the two-dimensional surface profiles of the substrate and the optical film. Further, after continuing to perform a curvature radius fitting calculation on the two-dimensional surface profile of the substrate and the optical film, the control and data processing device 18 obtains the X-axis fitting curve and the Y axis of the substrate and the optical film. Axial fit curve.

Finally, according to the obtained X-axis fitting curve and Y-axis fitting curve of the substrate and the optical film, the control and data processing device 18 calculates the residual stress of the optical film by using the Stoney mathematical operation formula. Simply put, the interferogram analysis is to reconstruct the surface profile of the optical film with the wavelet transformation method and the phase reduction method in conjunction with the MATLAB program, measure the surface profile of the object to be tested (substrate surface, optical film), and then perform curve fitting to calculate the radius of curvature. , the radius of curvature of the object to be tested (substrate surface, optical film) can be detected. The residual stress value of the film can be calculated by substituting the radius of curvature of the substrate before and after coating into the Stoney formula. Among them, the Stoney formula is shown in the following formula (7):

In the formula in (7), σ is the residual stress of the film, E _s and V _s are the Young's modulus of the substrate material and Poisson's ratio, t _s, and t _f is the thickness of the substrate and each thin film, and the film Thickness is detected by spectrometer combined with self-developed envelope method program. In addition, R ₁ and R ₂ are the values of the radius of curvature before and after substrate coating or heating, respectively.

After using the novel non-contact film residual stress detection system 1 (as shown in FIG. 1 ) to obtain measurement data, finally, the residual stress _{of the optical film (Ta 2} O _{5 ) on the substrate of the sample 2 to be tested is calculated} is -0.191±0.008GPa.

In this way, the above has completely and clearly explained a novel non-contact thin film residual stress detection system. However, it must be emphasized that what is disclosed in the above-mentioned case is a preferred embodiment, and any partial changes or modifications originating from the technical ideas of this case and easy to infer by those who are familiar with the art are all within the scope of this case. the scope of patent rights.

1: Non-contact film residual stress detection system

10: Carrier

11: Light source

12: Spatial Filter

13: Aperture

14: Lens

15: Optical splitter

151: The first side

152: Second side

153: third side

16: Standard plane mirror

17: Image capture device

18: Control and data processing devices

2: Sample to be tested

Claims (7)

A non-contact thin film residual stress detection system, comprising: a stage for a sample to be tested to be set on it, and a tilt angle of which can be adjusted and controlled, wherein the sample to be tested includes a substrate and is covered on the an optical film on the substrate; a light source, arranged along a first optical axis; a spatial filter, arranged along the first optical axis, and a light incident end receives a detection light emitted by the light source, and The detection light is subjected to a spatial filtering process; an aperture is arranged along the first optical axis, and faces a light exit end of the spatial filter to receive the detection light after the spatial filtering process; a lens, along the the first optical axis is arranged and faces the aperture; a spectroscope is arranged along the first optical axis, and has a first side face to the lens; a standard plane mirror is arranged along the first optical axis , and its first side faces a second side of the beam splitter, and its second side faces the sample to be tested on the stage; an image capture device, along the first A second optical axis is arranged orthogonal to the optical axis, and a photographing lens faces a third side surface of the beam splitter; wherein, the detection light passes through the aperture and the lens and enters the first beam splitter. After one side surface, the standard plane mirror is then incident through the second side surface of the beam splitter, so that a first light of the detection light then passes through the second side of the standard plane mirror and is directed to the sample to be tested, and makes all A second light of the detection light is reflected by the first surface of the standard plane mirror to return to the second side surface of the beam splitter, and finally passes through the third side surface of the beam splitter to be directed to the image capture device. photographic lenses; and A control and data processing device, electrically connected to an adjustment mechanism of the stage, and coupled to the light source and the image capture device; wherein, under the control of the control and data processing device, the non-contact film has residual stress The detection system measures and obtains the isoblique interferogram of the substrate and the optical film respectively; wherein, after performing a wavelet transformation process on the isoblique interferogram of the substrate and the optical film, the control and data processing device obtains the substrate and The wrapped phase image of the optical film; wherein, after continuing to perform a phase unwrapping process on the substrate and the wrapped phase image of the optical film, the control and data processing device obtains the three-dimensional surface profile of the substrate and the optical film; wherein , and then continue to perform a curvature calculation and a warp calculation on the three-dimensional surface contour of the substrate and the optical film, the control and data processing device obtains the two-dimensional surface contour of the substrate and the optical film; wherein, and then After continuing to perform a curvature radius fitting calculation on the two-dimensional surface profile of the substrate and the optical film, the control and data processing device obtains the X-axis fitting curve and the Y-axis fitting curve of the substrate and the optical film Finally, according to the obtained X-axis fitting curve and Y-axis fitting curve of the substrate and the optical film, the control and data processing device calculates the residual stress of the optical film by using the Stoney mathematical operation formula. The non-contact film residual stress detection system as claimed in claim 1, wherein the control and data processing device is an electronic device, and the electronic device is installed with at least one software, which enables a main processor of the electronic device to pass the load The at least one software can implement the wavelet transform processing, the phase unwrapping processing, the tortuosity calculation, the warp degree calculation, and/or the curvature radius fitting calculation, and to perform the Stoney math arithmetic. The non-contact film residual stress detection system according to claim 1, wherein the wavelet transform processing is Morley wavelet transform processing, and the phase unwrapping processing is Macy phase unwrapping processing. The non-contact thin film residual stress detection system according to claim 1, wherein the light source is one of a helium-neon laser device or a semiconductor laser device. The non-contact film residual stress detection system according to claim 1, wherein the lens is a convex lens. The non-contact film residual stress detection system according to claim 1, wherein the image capturing device is a photosensitive coupling element photographing device. The non-contact film residual stress detection system according to claim 2, wherein the electronic device is selected from industrial computers, cloud computing computers, desktop computers, notebook computers, tablet computers, and smart phones. Form any of the groups.

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