A measuring device and method for in-situ stress regulation second harmonic wave

Abstract

The application discloses a kind of in-situ stress regulation second harmonic measurement device and measurement method, device includes power regulation and measurement module, microscopic imaging module, stress exerting module and signal acquisition module.Femtosecond laser output as excitation light, femtosecond laser is after adjusting laser power and polarization by power regulation and measurement module by dichroic mirror into microscopic imaging module and is focused to sample on femtosecond laser;Sample is installed on stress exerting module, and quantitative exertion to sample stress is realized;The second harmonic signal of sample is collected by objective lens in microscopic imaging module by reflection mode and enters signal acquisition module by dichroic mirror;Signal acquisition module realizes the filtering of excitation light and focuses into the slit of spectrometer second harmonic signal, and spectrometer is connected with computer, and the second harmonic signal collection under stress quantitative regulation is completed.The application can in-situ measure power dependence and polarization dependence under different quantitative stress second harmonic signal.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of optical nondestructive testing, and particularly relates to a measuring device for in-situ stress regulated second harmonic. BACKGROUND

[0002] The properties of semiconductor materials mainly depend on their crystal structures. The influence of stress on the crystal lattice structure can greatly change the electronic and optical properties, and further affect the performance of electronic devices based on semiconductor materials. Second harmonic is generated in crystals with broken inversion symmetry of crystal structure, and belongs to the second-order nonlinear process of strong light and matter interaction, and is extremely sensitive to the crystal structure, and can be applied to the nondestructive optical detection of semiconductor devices. However, the current commercial second harmonic system can only collect second harmonic signals, and cannot measure the second harmonic under in-situ stress regulation. SUMMARY

[0003] The application aims at the above problems, and provides a measuring device for in-situ stress regulated second harmonic. A uniaxial stress is applied to a material by a stress applying module, and the power dependence and polarization dependence of the second harmonic signal under stress regulation are measured by a microscopic imaging module, a power adjusting and measuring module, a signal collecting module and the like.

[0004] Technical scheme: To achieve the object of the application, the technical scheme adopted by the application is:

[0005] A measuring device for in-situ stress regulated second harmonic, comprising:

[0006] a femtosecond laser, which provides monochromatic femtosecond laser, and a power adjusting and measuring module, a dichroic mirror, a microscopic imaging module, a stress applying module and a signal collecting module arranged in sequence along the optical path of the monochromatic femtosecond laser;

[0007] The femtosecond laser output by the femtosecond laser is adjusted in laser power and polarization by the power adjusting and measuring module, and then enters the microscopic imaging module through the dichroic mirror to focus the laser on the sample on the stress applying module; the reflected second harmonic signal is collected by the microscopic imaging module, and then enters the signal collecting module through the dichroic mirror and the mirror to collect the power dependent second harmonic signal under different stresses.

[0008] The stress applying module is fixed on a three-dimensional displacement platform through an adapter arm, and comprises:

[0009] a one-dimensional displacement platform A, a one-dimensional displacement platform B and a flexible substrate installed between the one-dimensional displacement platform A and the one-dimensional displacement platform B through a pressing plate, wherein the sample is placed on the flexible substrate.

[0010] The power adjustment and measurement module comprises a first half-wave plate, a polarizer, a folding mirror and a power meter, the laser power and polarization are adjusted through the first half-wave plate and the polarizer, the laser power is measured through the folding mirror and the power meter, so that the measurement of the power-dependent second harmonic is realized.

[0011] The folding mirror is a silver mirror installed on a folding mirror frame, and the power is measured by introducing the light into the power meter by lifting the folding mirror.

[0012] The microscopic imaging module comprises an objective lens, a thin film beam splitter, a first lens, an imaging CCD and an illumination light source, wherein the focusing of the laser and the collection of the second harmonic signal are realized through the objective lens, the objective lens is fixed on the three-dimensional displacement platform, the light is introduced into the imaging CCD through the first lens after being split by the thin film beam splitter, and the imaging and alignment of the laser spot are realized.

[0013] The signal acquisition module filters out the excitation light signal of the femtosecond laser through the optical filter, focuses the second harmonic signal on the slit of the spectrometer through the second lens, and the spectrometer is connected with the computer to acquire the second harmonic spectrum.

[0014] It also comprises a second half-wave plate inserted in the light path between the thin film beam splitter and the objective lens, and a polaroid inserted in the light path between the mirror and the optical filter.

[0015] The application further discloses a measurement method based on the measurement device for in-situ stress-controlled second harmonic,

[0016] The monochromatic femtosecond laser generated by the femtosecond laser first enters the power adjustment and measurement module to adjust the power and polarization. The power is adjusted by adjusting the angle of the first half-wave plate relative to the polarizer, the power is measured by introducing the laser into the power meter through the folding mirror, so that the power-dependent second harmonic measurement under the stress control is realized.

[0017] The microscopic imaging module focuses the laser on the surface of the sample in the stress application module through the objective lens, and the objective lens is fixed on the three-dimensional displacement platform.

[0018] The thin film beam splitter focuses a part of the light through the first lens and introduces it into the imaging CCD, the imaging CCD (43) is connected with the computer, the imaging and alignment of the laser spot are realized, and the observation of the sample is realized through the illumination light source.

[0019] The distance between the one-dimensional displacement platforms is adjusted to realize the bending of the flexible substrate and thus apply uniaxial tensile stress to the sample.

[0020] By adjusting the three-dimensional displacement platform, the position of the sample in space is adjusted, so that the sample is aligned with the laser; the second harmonic signal reflected by the sample surface enters the dichroic mirror through the objective lens, and the second harmonic signal that transmits through the dichroic mirror enters the signal acquisition module through the reflecting mirror;

[0021] The filter in the signal acquisition module filters out the excitation light and only the second harmonic signal passes through, the second lens improves the collection efficiency and focuses the second harmonic signal on the entrance slit of the spectrometer, and the spectrometer is connected with the computer to obtain the spectrum of the second harmonic;

[0022] The second half-wave plate and the power adjustment and measurement module are inserted in the optical path, and in the case that the sample is not rotated, the collection of the second harmonic signal dependent on stress regulation is realized by adjusting the angle of the second half-wave plate relative to the polarizer.

[0023] Advantages:

[0024] The stress application module is provided, the sample is placed on the flexible substrate in the stress application module, the flexible substrate is fixed between the two one-dimensional displacement platforms by pressing the tablet, the distance between the one-dimensional displacement platforms is adjusted to realize the bending of the flexible substrate and quantitatively apply uniaxial tensile stress to the sample; the one-dimensional displacement platform is fixed on the adapter arm, the adapter arm is fixed on the three-dimensional displacement platform, and by adjusting the three-dimensional displacement platform, the position of the sample in space can be adjusted, so that the sample is aligned with the laser. By the combination of the second half-wave plate, the polarizer and the power adjustment and measurement module, the measurement of the polarization-dependent second harmonic can be realized without rotating the sample. Through the above stress application module, the quantitative application of uniaxial stress can be realized, and the efficient collection of the second harmonic signal power-dependent and polarization-dependent under stress regulation can be realized.

[0025] The application can solve the problem that the commercial second harmonic system cannot measure the second harmonic in situ under stress regulation, and is expected to be applied in the field of non-destructive optical detection of electronic devices. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of a measurement device for in-situ stress regulation of second harmonic.

[0027] Figure 2 is a second harmonic spectrum under stress regulation. DETAILED DESCRIPTION

[0028] The technical solutions of the application will be further described below in combination with the drawings and examples.

[0029] As Figure 1As shown, the in-situ stress regulation secondary harmonic wave measuring device comprises a femtosecond laser 1, a power adjustment and measurement module 2, a dichroic mirror 3, a microscopic imaging module 4, a stress application module 5 and a signal acquisition module 6.

[0030] The power adjustment and measurement module 2 comprises a first half-wave plate 21, a polarizer 22, a folding mirror 23 and a power meter 24. The dichroic mirror 3 has the characteristics of high reflection to the laser wavelength and high transmission to the frequency-doubled wavelength.

[0031] The microscopic imaging module 4 comprises an objective lens 44, a thin film beam splitter 41, a first lens 42, a CCD camera 43 and an illumination light source 45.

[0032] The stress application module 5 comprises a flexible substrate 52, a one-dimensional displacement platform A 53 and a one-dimensional displacement platform B 54, and an adapter arm 55.

[0033] The signal acquisition module 6 comprises a filter 61, a second lens 62 and a spectrometer.

[0034] The monochromatic femtosecond laser generated by the femtosecond laser 1 first enters the power adjustment and measurement module 2 for power and polarization adjustment. In the power adjustment and measurement module 2, the polarizer 22 is usually fixed horizontally or vertically polarized, and the power is adjusted by adjusting the angle of the first half-wave plate 21 relative to the polarizer 22, thereby performing power-dependent secondary harmonic wave measurement under stress regulation; the folding mirror 23 is a silver mirror installed on a folding mirror holder, and by lifting the folding mirror 23, the light can be introduced into the power meter 24 for power measurement. The femtosecond light with determined power and polarization enters the microscopic imaging module 4 through the dichroic mirror 3. The dichroic mirror 3 has the characteristics of high reflection to the laser wavelength generated by the femtosecond laser 1 and high transmission to the frequency-doubled wavelength, and can efficiently reflect the excitation light while transmitting the secondary harmonic signal.

[0035] The microscopic imaging module 4 focuses the laser on the surface of the sample 51 through the objective lens 44, and the objective lens 44 is fixed on a three-dimensional displacement platform; the thin film beam splitter 41 focuses part of the light through the first lens 42 and introduces it into the imaging CCD 43, and the imaging CCD 43 is connected with a computer, which can realize the observation of the laser spot, and the illumination light source 45 can realize the observation of the sample 51.

[0036] The sample 51 is placed on the flexible substrate 52, which is fixed between the two one-dimensional displacement platforms by pressing the sample 51, and the distance between the two one-dimensional displacement platforms is adjusted to realize the bending of the flexible substrate 52 and thereby apply uniaxial tensile stress to the sample 51; the two one-dimensional displacement platforms are fixed on the adapter arm 55, and the adapter arm is fixed on the three-dimensional displacement platform, and by adjusting the three-dimensional displacement platform, the position of the sample 51 in space can be adjusted, thereby realizing the alignment of the sample and the laser.

[0037] The second harmonic signal reflected by the surface of sample 51 enters dichroic mirror 3 through objective lens 44, and dichroic mirror 3 can achieve high transmission of the second harmonic signal. The second harmonic signal that passes through dichroic mirror 3 enters signal acquisition module 6 through mirror 7.

[0038] The filter 61 in signal acquisition module 6 is a low-pass filter that can filter out the excitation light and only pass the second harmonic signal. The second lens 62 improves the collection efficiency and focuses the second harmonic signal on the entrance slit of the spectrometer. The spectrometer is connected to a computer to obtain the spectrum of the second harmonic.

[0039] As a preferred technical solution of the in-situ stress regulation and measurement device for second harmonic wave of the present application, the second half-wave plate 8 and the analyzer 9 are inserted into the optical path, which can be combined with the power regulation and measurement module 2. Without rotating the sample, the angle of the second half-wave plate 8 relative to the polarizer 22 is adjusted to regulate the stress and collect the second harmonic signal dependent on the polarization.

[0040] The following examples collect the second harmonic signals of gallium selenide under different stresses to specifically illustrate the present application.

[0041] A flexible PC substrate with a thickness of 0.7 mm and a length of 4.8 cm is cut to the appropriate size. A few-layer gallium selenide sample is placed on the PC substrate by mechanical exfoliation and dry transfer. The PC substrate with the gallium selenide sample is fixed between two one-dimensional displacement platforms by pressing and laying. The entire stretching module is fixed on a three-dimensional displacement platform through an adapter arm.

[0042] The femtosecond laser is a fiber laser, the repetition frequency is 80 MHz, the pulse width is 100 fs, the output wavelength is 780 nm, the 780 nm laser is introduced into the power meter by turning up the folding mirror, the angle of the first half-wave plate relative to the polarizer is adjusted to make the power meter display 10 mW; the 780 nm femtosecond light with a power of 10 mW reaches the sample surface through the dichroic mirror, at this time the sample is not stressed, the three-dimensional displacement platform is adjusted, so that the reflected 780 nm light on the sample surface enters the imaging CCD, the laser spot can be observed through the imaging software on the computer, the 20X near-infrared objective lens is installed, the laser spot is focused on the sample surface, the illumination light source is turned on, the sample is observed, and the laser spot is aligned to the sample surface of gallium selenide. The second harmonic signal reflected by the gallium selenide sample surface is collected through the objective lens, filtered through the 650 nm short-wave pass filter to remove 780 nm light, and focused on the slit of the spectrometer through the second lens, the spectrometer is connected with the computer, and the second harmonic spectrum is collected. The one-dimensional displacement platform is moved to bend the flexible substrate, so that the distance between the one-dimensional platforms is 3.70 cm, 3.58 cm and 3.37 cm respectively, and the strain coefficients are 0.5%, 0.6% and 1% respectively, the above spectrum collection steps are repeated under the corresponding strain, the corresponding second harmonic spectra are collected, and the spectral data of the second harmonic under in-situ stress regulation are obtained.

Claims

1. A measurement method for an in-situ stress-controlled second harmonic wave measurement device, wherein the in-situ stress-controlled second harmonic wave measurement device comprises: A femtosecond laser (1) provides a monochromatic femtosecond laser and a power adjustment and measurement module, a dichroic mirror, a microscopic imaging module, a stress application module and a signal acquisition module arranged sequentially along the optical path of the monochromatic femtosecond laser; The femtosecond laser output by the femtosecond laser (1) is adjusted in power and polarization by the power adjustment and measurement module (2) and then enters the microscopic imaging module (4) through the dichroic mirror (3). The microscopic imaging module (4) focuses the laser onto the sample of the stress application module (5). The reflected second harmonic signal is collected by the microscopic imaging module (4) and then enters the signal acquisition module (6) through the dichroic mirror (3) and the reflector in sequence to acquire the power-dependent second harmonic signal under different stresses. The stress application module (5) is fixed to the three-dimensional displacement platform via an adapter arm (55), and includes: One-dimensional displacement platform A, one-dimensional displacement platform B, and a flexible substrate mounted between the one-dimensional displacement platform A and one-dimensional displacement platform B by pressing a sheet, wherein the sample is placed on the flexible substrate; The power adjustment and measurement module includes: a first half-wave plate, a polarizer, a folding mirror, and a power meter. The power is adjusted by adjusting the angle of the first half-wave plate relative to the polarizer, and the laser power is measured by the folding mirror and the power meter. Adjust the distance between one-dimensional displacement platform A (53) and one-dimensional displacement platform B (54), apply quantitative uniaxial tensile stress to the sample by bending the flexible substrate (52); monitor the laser power in real time by using the folding mirror (23) and power meter (24), and adjust the sample position by combining the three-dimensional displacement platform to realize in-situ power-dependent second harmonic signal acquisition under stress control. The microscopic imaging module includes: an objective lens, a thin-film beam splitter, a first lens, an imaging CCD, and an illumination source. The objective lens focuses the laser and collects the second harmonic signal, and is fixed on the three-dimensional displacement platform. The laser beam is split by the thin-film beam splitter and enters the imaging CCD through the first lens to achieve imaging and alignment of the laser spot. The signal acquisition module (6) filters out the excitation light signal of the femtosecond laser (1) through the filter (61), and focuses the second harmonic signal onto the slit of the spectrometer through the second lens (62). The spectrometer is connected to the computer to acquire the second harmonic spectrum. The characteristic feature is that the monochromatic femtosecond laser generated by the femtosecond laser first enters the power adjustment and measurement module (2) for power and polarization adjustment. The power is adjusted by adjusting the angle of the first half-wave plate (21) relative to the polarizer (22). The laser is introduced into the power meter through the folding mirror (23) for power measurement, thereby performing power-dependent second harmonic measurement under stress regulation. The microscopic imaging module (4) focuses the laser onto the surface of the sample (51) in the stress application module (5) through the objective lens (44), and the objective lens (44) is fixed on the three-dimensional displacement platform; The thin-film beam splitter (41) focuses a portion of the light through the first lens (42) and introduces it into the imaging CCD. The imaging CCD is connected to the computer to realize the imaging and alignment of the laser spot. With the help of the illumination source (45), the sample (51) can be observed. Adjusting the distance between the one-dimensional displacement platforms achieves bending of the flexible substrate (52), thereby applying uniaxial tensile stress to the sample (51); Adjust the three-dimensional displacement platform to adjust the position of the sample (51) in space, thereby achieving alignment between the sample and the laser; the second harmonic signal reflected from the surface of the sample (51) enters the dichroic mirror (3) through the objective lens (44), and the second harmonic signal transmitted through the dichroic mirror (3) enters the signal acquisition module (6) through the reflector (7). The filter (61) in the signal acquisition module (6) filters out the excitation light and only the second harmonic signal passes through. The second lens (62) improves the acquisition efficiency and focuses the second harmonic signal onto the entrance slit of the spectrometer. The spectrometer is connected to the computer to obtain the spectrum of the second harmonic. The folding mirror is a silver mirror mounted on a folding mirror frame. By lifting the folding mirror (23), light is introduced into the power meter (24) for power measurement.

2. The measurement method of the in-situ stress-controlled second harmonic measurement device according to claim 1, characterized in that, It also includes a second half-wave plate (8) inserted in the optical path between the thin-film beam splitter and the objective lens, and an analyzer (9) inserted in the optical path between the reflector (7) and the filter (61).

3. The measurement method of the in-situ stress-controlled second harmonic measurement device according to claim 1, characterized in that, The second half-wave plate (8) and polarizer (9) inserted in the optical path can be combined with the power adjustment and measurement module (2) to collect the polarization-dependent second harmonic signal under stress control by adjusting the angle of the second half-wave plate (8) relative to the polarizer (22) without rotating the sample.

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