TWI788180B - Device and method for detecting changes in reflected light - Google Patents

Abstract

The present invention proposes a device and method for detecting changes in reflected light, using the first pupil division The incident light beam is divided into field intensity by the device so that the incident light beam forms a first field intensity distribution on the first surface of the first pupil divider; the collimation and convergence of the incident light beam with the first field intensity distribution is obliquely incident on the surface of the object to form a first pupil divider with the first field intensity distribution A reflected beam having a second field strength distribution; receiving a reflected beam having a second field strength distribution and collimating to form a reflected beam having a third field strength distribution; using a position and shape of a second pupil divider to have a third field strength The distributed reflected light beam is subjected to field strength division, so that the reflected light beam with the third field strength distribution forms a fourth field strength distribution on the first surface of the second pupil divider, the first pupil divider and the second pupil divider Have the same aperture function distribution; obtain the reflected beam with the fourth field intensity distribution, and analyze the change information of the reflected beam with the fourth field intensity distribution within the time interval, so as to make the signal change formed by the light intensity change and the imaging position deviation after analysis Enhanced to improve the detector signal-to-noise ratio.

Description

Device and method for detecting changes in reflected light

The invention belongs to an acousto-optic measuring system and is mainly used for measuring metal films and dielectric films. Specifically, it relates to a device and method for detecting changes in reflected light.

The current principle of acousto-optic measurement in the prior art is as follows: the short-pulse laser 1A is irradiated on the surface of the film sample 2A, the film sample 2A absorbs photons to generate thermoelastic deformation, and the surface forms a deformation zone; the thermoelastic deformation generates sound waves that propagate on the solid surface and inside; The longitudinal sound wave propagates to the interface (the junction between the film and the film of the substrate 3A or the multilayer thin film 6A) to generate the first echo signal 4A; the first echo signal 4A reaches the upper surface, causing further changes in the deformation; the echo signal hits After the upper surface rebounds, the second echo signal 5A is generated after the rebound hits the interface; the second echo signal 5A reaches the upper surface, causing the shape of the bulge to change again, as shown in Figure 1. Of course, the echo signal also May include more than three times. The reflectance change of the incident light beam caused by the shape change is obtained by the photodetector, so that the time interval between two reflectance changes can be obtained, and the thickness value of the film sample can be calculated.

In terms of specific measurement device settings, as shown in Figure 2, the pump laser 1 is incident on the surface of the sample 2 to generate a deformation zone 4, and the incident probe light 5a is hit on the deformation zone 4, because the surface of the film layer when the echo returns The shape of the deformation zone will change, because the further deformation of the deformation zone when the echo signal arrives will have an impact on the reflected detection light 5b. This impact may be the amplitude or Various influences such as phase, generally speaking, the detection module 6 obtains the change of the light reflection amplitude caused by the shape change, so that the time interval of the change of the optical signal amplitude can be obtained, through the film thickness The calculation formula obtains the film thickness value, as shown in the schematic diagrams of FIG. 2 and FIG. 3 . Therefore, the impact of detecting the change of the reflected detection light 5b on improving the precision of the photoacoustic detection device is particularly important.

As shown in Fig. 4, it is a technology for analyzing reflected probe light in the prior art, the probe light 5b reflected by the deformation zone 4 area will be reflected by the first mirror 6c to reflect a half-size circular spot (the position of the mirror 6c The setting is especially important, it has a screening effect on the reflected light spot field of view of the reflected light), this part will continue to be reflected by the second reflector 6d into the second detector 6a, and the other half size that is not reflected by the first reflector 6c The circular light spot will directly enter the first detector 6b. The first reflector 6c is adjusted to the target position by the motor, and the light received by the detector 6a and 6b has a certain light intensity ratio when there is no excitation deformation, such as 1:1. However, when the deformation 4 area is excited and deformed Echo oscillates, and the reflected probe light 5b will undergo a time-dependent slight angle change. At this time, the division effect of the first reflector 6c on the field of view of the spot is no longer half and half. This slight angle change will cause this The readings of the light intensity of the detectors 6a and 6b will change at the same time. Through multiple experiments, the influence of the change of the angle of the reflected detection light 5b and the change of the light intensity readings of the two can be simulated, and then the change of the angle of the reflected detection light 5b and the light intensity can be calculated. The relationship between the changes, the film thickness value can be calculated by measuring the time difference of multiple echo signals.

However, in the above-mentioned technical solution, there are the following problems: the first problem is that the position adjustment accuracy of the first reflector 6c of the applied optical system is extremely high, and its stability is also extremely high. Undertake the role of beam splitting, the requirements for the alignment and stability of the optical path are high, and the assembly of the optical path is relatively difficult; the second aspect is reflected in the complexity of the optical path, which requires the assembly of the first reflector 6c and the second reflector 6d respectively , and in order to meet the requirement that the incident light within a certain angle can be effectively reflected and refracted, the parallel collimation and field of view interlacing between the two also need to be precisely adjusted for a design, and at the same time, two detectors are required to detect the outgoing light. The increase in the use of optical components will also lead to an increase in cost; the third party is reflected in the detection accuracy, due to the use of light splitting in the optical path, the transmitted and reflected light will further damage It is more difficult to detect the change rate of the spot energy decomposition caused by the incident angle deviation caused by the deformation region of the reflected probe light, so the detection signal-to-noise ratio is low, about one part per million, and the detection beam waist The divergence angle is extremely demanding.

In order to solve the above-mentioned problems in the prior art, the present invention proposes a device and method for detecting the change of the reflected light peak value. A pupil divider with the same aperture function is set on the incident light path and the reflected light path of the detection light, and the incident light beam and the reflected light path are provided with a pupil divider. The reflected light beam is disturbed and divided, so that the signal change formed by the light intensity change and the imaging position deviation after analysis is enhanced, and the signal-to-noise ratio of the detector is improved. The structure is simple, easy to implement, and the number of detectors is reduced and the cost is reduced.

In order to solve the above-mentioned technical problems, the present invention first proposes a device for detecting changes in reflected light, which includes: at least one detection light source for generating an incident light beam; at least one first pupil divider arranged behind the light path of the detection light source. The field intensity division of the incident beam is performed so that the incident beam forms a first field intensity distribution on the first surface of the first pupil divider; the first collimating optical element arranged behind the optical path of the first pupil divider is used for collimating Directly converge the incident beam with the first field intensity distribution obliquely incident on the surface of the object to be measured to form a reflected beam with the second field intensity distribution; the second collimating optical element arranged on the reflected light path is used to receive within the field of view The reflected light beam with the second field strength distribution is collimated to form the reflected light beam with the third field strength distribution; the second pupil divider arranged behind the light path of the second collimating optical element is used to receive the light beam with the third field strength Distributed reflected beams are subjected to field intensity splitting such that the reflected beams with the third field intensity distribution in the first The first surface of the two pupil dividers forms a fourth field intensity distribution, the first pupil divider and the second pupil divider have the same aperture function; the detector is used to obtain the reflected light beam with the fourth field intensity distribution , analyzing the change information of the reflected light beam with the fourth field intensity distribution in the time interval.

As a further improvement of the present invention, the first collimating optical element and the second collimating optical element form an optical path collimation system, the first pupil divider is arranged at the entrance pupil position of the optical path collimating system, and the second collimating optical element is arranged The exit pupil position of the optical path collimation system.

As a further improvement of the present invention, the first pupil divider is provided with a plurality of first-type light-passing structures and a plurality of second-type light-passing structures, and the first-type light-passing structures and the second-type light-passing structures have differences in luminous flux , so that the incident beam is split by the disturbance of the first-type light-passing structure and the second-type light-passing structure, and becomes the incident beam with the first field intensity distribution.

As a further improvement of the present invention, the second pupil divider is provided with a plurality of third-type light-passing structures and a plurality of fourth-type light-passing structures, and the third-type light-passing structures and the fourth-type light-passing structures have differences in luminous flux , so that the reflected beam with the third field intensity distribution is further disturbed and divided into the reflected beam with the fourth field intensity distribution.

As a further improvement of the present invention, the first-type light-transmitting structures correspond to the third-type light-transmitting structures one-to-one, and the shapes of the first-type light-transmitting structures and the third-type light-transmitting structures corresponding to each other are the same.

As a further improvement of the present invention, the field of view adjustment of the first collimating optical element is realized by setting the composition structure of the first collimating optical element, so that the image of the first pupil divider is clearly irradiated on the object to be measured; by setting the second The composition structure of the collimating optical element realizes the adjustment of the field of view of the second collimating optical element, so that the reflected light beam with the second field intensity distribution is collimated and enters the second pupil divider.

As a further improvement of the present invention, the first pupil divider (7) and the second pupil divider (8) are axisymmetric with respect to the incident light path and the reflected light path.

As a further improvement of the present invention, the light transmission patterns corresponding to the plurality of first type light transmission structures are different.

In order to solve the above technical problems, the present invention also proposes a method for detecting the change of reflected light, the method includes: using the first pupil divider to divide the incident light beam into field strength so that the incident light beam is at the first pupil divider of the first pupil divider. The surface forms a first field intensity distribution; collimating and converging the incident beam with the first field intensity distribution obliquely incident on the surface of the object to be measured to form a reflected beam with a second field intensity distribution; receiving the reflected beam with the second field intensity distribution and Collimating to form a reflected beam with a third field intensity distribution; using the second pupil divider to receive the reflected beam with a third field intensity distribution for field intensity division, so that the reflected beam with the third field intensity distribution is in the second light The first surface of the pupil divider forms a fourth field intensity distribution, the first pupil divider and the second pupil divider have the same aperture function; a reflected beam with the fourth field intensity distribution is obtained, and the analytical time interval has the fourth Four field strength distributions of reflected beam variation information.

In order to solve the above-mentioned technical problems, the present invention also proposes a film thickness measurement device, including: a burst unit, which bursts a plurality of excitation sources from the upper surface of the film sample to be tested to the bottom surface at one time point, so that At least one deformed area is generated on the surface; the above-mentioned device for detecting the change of the reflected beam is provided, and information on the peak signal intensity change of the polarized reflected beam corresponding to the deformed area is obtained; The calculation unit calculates the thickness of the film sample to be tested according to the time interval corresponding to the peak value.

Compared with the background technology, the technical solution involved in the present invention adopts the pupil division scheme in terms of technical effects, and the scheme obtains the important aspects of improving the detection of the signal change rate through the analysis of the optical system, the incident field strength, the pupil division , field of view of optical collimation and focusing elements and other related parameters, so as to design and optimize this detection scheme, which can significantly improve the detection rate of reflected light changes.

1: Pump light source

1a: Incident pump light

1b: Reflected pump light

2: Film sample

3: Film sample surface

3a: Upper surface

3b: Lower surface

4: Deformation zone

5a: Incident beam

5b: Reflected light

6: Detection module

7: The first pupil divider

8: Second pupil divider

9: The first collimating optical element

10: The second collimating optical element

11: Detector

12: Detector

[FIG. 1] is the overall working principle diagram of the acousto-optic measuring system in the prior art.

[ Fig. 2 ] is a schematic diagram of the structure of the detection optical path for the echo measurement of the acousto-optic measurement technology in the prior art.

[ Fig. 3 ] is a schematic diagram of the time difference between two echo measurements according to the echo measurement in the prior art; [ Fig. 4 ] is a schematic diagram of the optical light path structure of the acousto-optic measurement system in the prior art.

[Fig. 5] is a schematic diagram of the optical path structure of the acousto-optic measuring device realized according to the present invention; [Fig. 6] is a schematic diagram of a specific embodiment of a pupil divider realized according to the present invention; [Fig. 7] is realized according to the present invention A schematic diagram of the imaging information of the pupil splitter; [Figure 8] is a schematic diagram of the correspondence between the light spot without pupil division and the change of the reflection angle;

It should be understood that the following are many different embodiments or examples of different features of this embodiment. Specific examples of components and arrangements are described below for simplicity of describing the embodiments. Of course, these are just examples and not intended to limit specific implementations.

According to one of the embodiments of the present invention, the present invention first proposes a device for obtaining the detection change of reflected light in acousto-optic detection, which can significantly improve the measurement accuracy of the detection light angle change and significantly improve the measurement signal-to-noise ratio.

According to the device for detecting the angle change of reflected light realized by the present invention, as shown in Figure 5, the incident beam 5a is incident on a pupil divider 7 with a certain angle, and the angle is that the incident direction of the incident beam 5a is perpendicular to the surface 3 of the film sample 2 The included angle of the direction is collected and collimated by a lens group 9 and obliquely incident on the sample. On the deformation zone 4 formed in the surface 3 of the sample 2 caused by the pumping laser 1, the reflected light 5b after reflection passes through another lens group. After 10, it passes through another pupil divider 8 and then reaches the detector 11, so that the correlation analysis of the probe light is carried out to obtain the measurement result of the sample 2.

干擾，故探測器10可探測到回聲引起的時間相關性光強變化；解析裝置，再對解析時間間隔內具有第四場強分佈的反射光束變化資訊進行解析，獲得反射光束信號變化。 Wherein, the pupil divider 7 divides the field intensity of the incident light beam 5a so that the incident light beam 5a forms a first field intensity distribution on the first surface of the pupil divider 7, and the lens group 9 arranged behind the pupil divider 7 optical paths further After the incident beam with the first field intensity distribution is collimated and converged, it is obliquely incident on the surface of the object to form a reflected beam 5b with the second field intensity distribution; another lens group 10 receives the collimated beam that can be received within its field of view. The reflected light beam 5b is on the surface of another pupil divider 8, and is formed into a third field intensity distribution, so that the third field intensity distribution characteristic is close to the first field intensity distribution characteristic, because the pupil divider 7 and another pupil divider 8 have the same aperture function division, after another pupil divider 8 receives the reflected beam with the third field intensity distribution, the first surface of another pupil divider 8 is formed into the fourth field intensity distribution and reflected to the detector 12. The detector 12 is used to detect the reflected light beam passing through the pupil divider 8, so as to obtain the light intensity of the reflected light beam. Since the pumping light source (also known as the burst unit) 1 forms an echo in the sample 2, the echo propagates to the deformation region 4 and interferes with the incident beam 5a having the second field intensity distribution to form a reflected beam 5b, which passes through the pupil divider The reflected beam 5b after 7 is also affected by the echo

Interference , so the detector 10 can detect the time-dependent light intensity change caused by the echo; the analysis device analyzes the change information of the reflected beam with the fourth field intensity distribution within the analysis time interval, and obtains the signal change of the reflected beam.

Preferably, the first collimating optical element and the second collimating optical element form an optical path collimation system, the first pupil divider is arranged at the entrance pupil position of the optical path collimating system, and the second collimating optical element is arranged at the optical path collimation system. Because the pupil divider 7 and another pupil divider 8 have the same aperture function, the third field intensity distribution feature is close to the first field intensity distribution feature, so that the pupil division The image of the pupil divider 7 is superimposed on the pupil divider 8 or slightly occluded and misaligned, and after the photoacoustic disturbance produces a signal change, this coincidence or slight misalignment signal will change, by capturing the signal change information within the time interval , more accurate detection results can be obtained.

For the above-mentioned optical system that realizes the measurement of the angle change of reflected light as a whole, the pump light source 1 in the optical components involved is also called the excitation light source, and light sources other than Nd:YAG lasers can be used to optically excite thin films. In an embodiment, the laser may also include Nd:YLF, ion (such as argon and krypton), Ti:sapphire, diode, CO ₂ , ', excimer, dye and metal vapor laser, etc., the above-mentioned pump The function of the pump light source 1 is to generate a deformation zone 4 on the surface of the sample. The parameters of its wavelength, laser pulse energy, period and beam waist can be designed according to the characteristics of the thin film of the sample 2 and its characteristics. In some other studies, the pump light source 1 is converted into a light source with a diffraction pattern incident on the surface of the sample 2 by setting a diffraction element behind the pump light source 1. On this basis, the focused spot The resulting bulge is different, and will have a deformation corresponding to the diffraction pattern, and the change of the formed acousto-optic effect will be more complicated, and it will be more susceptible to interference and change.

In addition, in the specific implementation of the solution involved in the present invention, the type of the pump light source 1 and whether it is consistent with the incident angle of the detected incident light are not strictly limited. In the entire optical detection system, usually through simultaneous The pulse of the pumping light is collected as a reference signal source for the pumping and detecting incident light 5a for triggering the pumping and detection.

Similarly, the above light sources similar to the pump light source except the diode laser can be selected as the probe laser, and the pulsed light sources that can be used to generate the incident beam include Q-switched Nd:YAG, Nd:YLF, Ti: Sapphire, Diode, C0 ₂ ,', Excimer, Dye and Metal Vapor Lasers etc. The incident detection light 5a involved in the design of the present invention also has strong adaptability to the wavelength range, and is not strictly limited, but the collimation requirements for the incident detection light 5a are relatively high, so that it is compatible with The field of view trade-offs of other optical elements in the optical system are coordinated with the design.

As one of the important improvements of the present invention, the pupil divider 7 and the pupil divider 8 are used in the detection optical path, wherein, in the above-mentioned pupil division scheme, it is first necessary to adopt the pupil divider 7 to An optical element with at least two light-passing parts that limits the beam flux, and its light-passing part can be a one-dimensional structure (x horizontal division or y longitudinal division or oblique division of the incident light 5a), or a two-dimensional structure (any shape The grid-like division or any pattern-like division of the incident light 5a) can also be uniform or non-uniform, both of which have the effect of improving the signal-to-noise ratio on the same principle. Among them, the pupil divider 7 preferably has as many beam division structures as possible in the spot direction relative to the incident light 5a. Further, the pupil divider 8 is an optical element that has at least two light-passing parts for the reflected light 5b to limit the beam flux, and its light-passing part can be a one-dimensional structure (x horizontal division or y longitudinal division or oblique Segmented reflected light 5b), or a two-dimensional structure (grid-like segmentation of any shape or any patterned segmented reflected light 5b), can also be uniformly segmented or non-uniformly segmented, all of which have the same principle of improving the signal-to-noise ratio, wherein the pupil The divider 8 preferably has as many division structures as possible in the spot direction of the reflected light 5b.

As shown in Figure 6, it is one of the implementations of the pupil divider according to the present invention, which has a strip-shaped structure with a light-passing part and a beam-shielding part, and the overall pupil divider 7 is a circle with a diameter of D Disc-shaped structure, wherein the light-transmitting part is a strip-shaped through hole, and the shielding beam part is an opaque material. In this embodiment, the periodic strip structure of the light-passing part and the shielding beam part alternately has a light-passing width of a, and the shielding beam The width of the part is b, and the width of the entire periodic structure is d (d=a+b). After the incident probe light 5a passes through the pupil divider 7, after passing through the lens group 9, the image of the pupil divider 7 converges in the deformation zone 4 Above, after being reflected by the film structured light, it is finally received by the detector, and the reflected light 5b will be changed by the acoustic disturbance of the deformation zone 4. This change is the first On the one hand, it will be reflected in that the image of the pupil divider 7 will be deformed to a certain extent. On the other hand, it will be reflected in the position deviation of the image of the pupil divider 7 in the detector imaging part after being disturbed. The strip image will have a slight position deviation on the imaging position of the detector, and this information is reflected on the imaging end of the detector. After being analyzed, compared with the deviation of the circular spot shown in Figure 8, it will carry information about The more multi-dimensional information of the disturbance, so as to obtain more accurate detection results.

Further preferably, the reflected light 5b will pass through another pupil divider 8, and the other pupil divider 8 is a strip-shaped structure with a light-passing part and a light beam shielding part, and the overall pupil divider 8 has a diameter of The disk-shaped structure of D, wherein the light-passing part is a strip-shaped through hole, and the shielding beam part is an opaque material, wherein the alternating periodic strip structure of the light-passing part and the shielding beam part has a light-passing width of a, and the shielding beam The width of the portion is b, and the width of the entire periodic structure is d (d=a+b). The reflected light 5b is collimated and irradiated on the pupil divider 8 after passing through the lens group 10. Preferably, the pupil dividers 7 and 8 The structure is similar, the shape of the corresponding light-transmitting parts is the same, and the size is proportional, and because the lens groups 9 and 10 are also preferably the same mutually symmetrical optical elements in the optical path system, the image of the pupil divider 7 is superimposed on the pupil There may be some slight occlusion and dislocation on the divider 8, and after the photoacoustic disturbance produces a signal change, this coincidence or slight dislocation signal will change, and more information can be obtained by analyzing the detector imaging information.

Of course, in the above cases, the pupil dividers 7 and 8 are preferably symmetrical structures, and the above two optical elements can also be asymmetrical structures. The light-passing part of the pupil divider 8 intersects with the light-limiting part to form a pattern image with two-dimensional information. This asymmetric structure may increase process difficulties during device fabrication.

Further, the positions of the pupil divider 7 and the lens group 9 are chosen to minimize the spot of the incident probe light 5a on the sample surface after being divided, and blurred imaging that is not in focus will significantly increase the difficulty of imaging pattern analysis. Similarly, the positions of the pupil divider 8 and the lens group 10 are selected according to the sample surface The Fourier transform of the diffraction fringes back to the appearance of the pupil divider 7 is clearly imaged on the second surface of the pupil divider 8. Fuzzy imaging will significantly increase the difficulty of imaging pattern analysis.

，隨後入射光束5a經光瞳分割器7分割後，經過透鏡組9匯聚後在形變區4表面的場強分佈為第二場強分佈U(x ₁,y ₁)，即：

Furthermore, in order to improve the signal-to-noise ratio, adjusting the field intensity distribution of the incident probe light beam or the field of view range of the mirror group through theoretical derivation can also modulate the field intensity distribution of the target outgoing probe light spot to improve the signal-to-noise ratio of the detector. The incident light beam 5a will generate diffracted coherent light on the sample surface after passing through the pupil divider 7, and the process is Fourier transform, that is, the field intensity distribution of the incident light beam 5a on the second surface of the pupil divider 7 is U ( x ₀ , y ₀ ), the field intensity distribution of the incident beam 5a on the first surface (rear surface) of the pupil divider 7 is the first field intensity distribution

, then the incident light beam 5a is divided by the pupil divider 7, and the field intensity distribution on the surface of the deformation zone 4 after being converged by the lens group 9 is the second field intensity distribution U ( x ₁ , y ₁ ), namely:

，其場強分佈會近似為入射光束5a經過光瞳分割器7第一表面的第一場強分佈

，由於光瞳分割器7和8具有相同的孔徑函數A(x ₀,y ₀)，通過調製光瞳分割器8的孔徑函數A(x ₀,y ₀)可以實現得到光瞳分割器8第一表面(後表面)的第四場強分佈U(x ₂,y ₂)。而第二場強分佈U(x ₁,y ₁)會受物品表面回聲影響幹擾，形成隨回聲返回時間相關性變化的第三場強分佈，第三場強分佈和光瞳分割器8的孔徑函數A(x ₀,y ₀)再發生疊加錯位可得到隨回聲時間相關性變化的高信噪比信號第四場強分佈U(x ₂,y ₂)，該信號會被探測器11接收。 By modulating the aperture function A ( x ₀ , y ₀ ) of the pupil divider 7, the field intensity distribution of the incident light beam 5a on the surface of the deformation zone 4 can be obtained as U ( x ₁ , y ₁ ), and the lens group 10 will Part of the field intensity distribution U ( x ₁ , y ₁ ) of the reflected light beam 5b is received, and due to the symmetrical optical path system, the field intensity distribution of the reflected light beam 5b formed on the second surface of another pupil divider 8 is the third field intensity distribution

, its field intensity distribution will be approximately the first field intensity distribution of the incident beam 5a passing through the first surface of the pupil divider 7

, since the pupil divider 7 and 8 have the same aperture function A ( x ₀ , y ₀ ), by modulating the aperture function A ( x ₀ , y ₀ ) of the pupil divider 8, the pupil divider 8 can be obtained The fourth field intensity distribution U ( x ₂ , y ₂ ) of a surface (rear surface). The second field intensity distribution U ( x ₁ , y ₁ ) will be interfered by the surface echo of the object, forming a third field intensity distribution that changes with the echo return time correlation, the third field intensity distribution and the aperture function of the pupil divider 8 A ( x ₀ , y ₀ ) is superimposed and misplaced to obtain a fourth field intensity distribution U ( x ₂ , y ₂ ) of a signal with a high signal-to-noise ratio that varies with the time correlation of the echo, and the signal will be received by the detector 11 .

為

入射光束5a到達形變區4表面第二場強分佈為：

Furthermore, the original field intensity distribution of the incident light beam on the second surface of the pupil divider 7 is U ( x ₀ , y ₀ ), and after passing through the pupil divider 7 with an aperture function of A ( x ₀ , y ₀ ), First field intensity distribution after the first surface of the pupil divider 7

for

The second field intensity distribution of the incident light beam 5a reaching the surface of the deformation zone 4 is:

即

The second field intensity distribution of the incident light beam 5a reaching the surface of the deformation zone 4 is U ( x ₁ , y ₁ ), and the reflected light 5b within the field of view of the lens group 10 is collimated to the second surface of the pupil divider 8 to form a third field intensity distribution of

which is

The reflected light beam 5b passes through the pupil divider 8 and forms a fourth field intensity distribution U ( x ₂ , y ₂ ) based on the aperture function A ( x ₀ , y ₀ ), namely

最大化。其中，θ為回聲信號產生的反射探測光5b角度變化，s為探測器接收面積，由於

與U(x ₀,y ₀)、A(x ₀,y ₀)、透鏡組9視場、透鏡組10視場有關係，利用光瞳分割器7的孔徑函數A(x ₀,y ₀)更易於調製。 The field intensity distribution of the reflected light beam 5b on the fourth surface of the pupil divider 8 is U ( x ₂ , y ₂ ), and the formula derivation conclusion: the final signal U ( x ₂ , y ₂ ) is related to U ( x ₀ , y ₀ ), A ( x ₀ , y ₀ ), the field of view of lens group 9, and the field of view of lens group 10 have a clear physical relationship, and the goal is to make

maximize. Among them, θ is the angle change of the reflected detection light 5b generated by the echo signal, and s is the receiving area of the detector, because

It is related to U ( x ₀ , y ₀ ), A ( x ₀ , y ₀ ), the field of view of lens group 9, and the field of view of lens group 10, using the aperture function A ( x ₀ , y ₀ ) of pupil divider 7 Easier to modulate.

；如圖8所示，對於現有技術中不進行光瞳分割的方案來說，信號變化率η ₀=圓形光斑錯位面積/圓形光斑面積=

， 其中：η或者

；由於通常光場強分佈為高斯分佈，結果將會更明顯地看到η≫η₀；因此，使用本發明的光瞳分割方案探測器所探測的信號跳動會較為明顯，而不做分割情況下探測器所探測的信號跳動幅度很小，不易於識別。 As shown in Figure 7, for the pupil division scheme of the present invention, after using the pupil divider 7 and the pupil divider 8 shown in Figure 6, the final signal acquired by the detector 11 is a fringe image with alternating light and dark , the signal change rate after pupil division is η = the change width of each bright fringe/the width of each bright fringe when there is no disturbance =

; As shown in Figure 8, for the scheme that does not carry out pupil division in the prior art, signal rate of change η ₀ =circular spot dislocation area/circular spot area=

, where: η or

; Since the light field intensity distribution is usually a Gaussian distribution, the result will be more clearly seen η≫η ₀ ; therefore, the signal jitter detected by the detector using the pupil division scheme of the present invention will be more obvious, without segmentation The signal jitter detected by the lower detector is very small, which is not easy to identify.

In addition, the main core of the above-mentioned pupil dividers 7 and 8 lies in the division processing of pupils greater than or equal to 2. The specific optical parameters and process consistency of the pupil dividers 7 and 8 can be optimized and designed according to actual application conditions. The production material can be prepared according to the optical process conditions, and considering factors such as the reflection effect in the optical system, it is further preferable to coat the surface or the back of the pupil divider 7 and 8 to reduce the influence of the diaphragm reflection on the probe light 5c etc., or consider the possible diffraction patterns at the edge of the aperture to design filter elements, and keep the design of the first-order fringes, etc., can be further designed according to the above core. At the same time, the aperture itself can be designed to adjust the pupil size, so as to facilitate multiple measurements and reduce the disturbance and error of the measurement results caused by the hardware of the optical system itself. In addition, considering the influence of the stability of the optical system, the above aperture The fixed and adjusted equipment can be designed according to the situation.

The lens groups 9 and 10 are optical element combination systems to complete the collimation of the optical path, as long as they can achieve the corresponding optical functions, and the specific settings are not strictly limited. In addition, setting a gain element to adjust the light intensity on the optical path to compensate for the energy loss caused by the diaphragm can also be designed according to specific conditions.

Samples that can be monitored with the methods and devices of the present invention can be bulk (e.g., solids such as metals or semiconductors), thin films (e.g., polymers, semiconductors, or metal films), fluids, surfaces, or exhibit acousto-optic The effect of time perturbations. Typical samples include metal films used in the semiconductor industry, such as aluminum, tungsten, titanium, titanium: tungsten, titanium or oxide films, etc. Material properties that can be determined in these samples include mechanical, physical (e.g., thickness), elastic, (depth-dependent and/or anisotropic) diffusion, based on adhesion, thermal (e.g., thermal diffusion) and viscosities associated with characteristic. As shown in Figure 7, when the image segmentation caused by aperture segmentation is richer, the information dimensions that can be extracted are richer (a' can reflect the angle change information of reflected light, b' can reflect the information of deformation zone 4 and/or or image distortion information of optical components), for example, the movement of the position change of the diaphragm image can detect the change of the reflected light angle, and the distortion or shape change of the image may mean that the optical characteristics of the deformation zone 4 are caused by As a result, the more patterns are divided, the more common features and specific features can be extracted, so that the scheme used in the present invention can obtain higher analysis accuracy in the subsequent computer analysis of imaging light.

According to another embodiment of the present invention, a method for obtaining reflected light detection changes in acousto-optic detection is proposed, the method includes: using a first pupil divider to perform field intensity division of the incident beam so that the incident beam is in the first pupil The first surface of the splitter forms a first field intensity distribution; converging the incident beam with the first field intensity distribution obliquely incident on the surface of the object to form a reflected beam with the second field intensity distribution; receiving the reflected beam with the second field intensity distribution and collimating to form the reflected beam with the third field intensity distribution; using the second pupil divider to receive the reflected beam with the third field intensity distribution for field intensity division, so that the reflected beam with the third field intensity distribution is used The reflected light beams of the three field intensity distributions form a fourth field intensity distribution on the first surface of the second pupil divider, and the first pupil divider and the second pupil divider have the same aperture function division; Reflected beams with strong distribution, analyzing change information of reflected beams with a fourth field intensity distribution within a time interval. The implementation principle and technical effect of this method are similar to those of the above-mentioned device, and will not be repeated here.

According to another embodiment of the present invention, a film thickness measurement device is proposed, including: a burst unit, which bursts a plurality of excitation sources from the upper surface of the film sample to be tested to the bottom surface at one time point, so that the film thickness on the film sample to be tested At least one deformation area is generated on the surface; the above-mentioned device for detecting the change of the reflected beam is provided to obtain information on the peak signal intensity change of the polarized reflected beam 5b' corresponding to the deformation area; the calculation unit calculates the time interval of the film sample to be tested according to the time interval corresponding to the peak value. thickness. The implementation principle and technical effect of this device are similar to those of the above-mentioned device for detecting changes in reflected light beams, and will not be repeated here.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

1a: Incident pump light

1b: Reflected pump light

2: Film sample

3a: Upper surface

3b: Lower surface

4: Deformation zone

5a: Incident beam

5b: Reflected light

7: The first pupil divider

8: Second pupil divider

9: The first collimating optical element

10: The second collimating optical element

11: Detector

12: Detector

Claims (10)

A device for detecting changes in reflected light, wherein the device includes: at least one detection light source for generating an incident light beam (5a); at least one first pupil divider (7) arranged behind the light path of the detection light source for The incident light beam (5a) is subjected to field intensity division such that the incident light beam (5a) forms a first field intensity distribution on the first surface of the first pupil divider (7); The first collimating optical element (9) after the optical path of the device (7) is used for collimating and converging the incident beam with the first field intensity distribution obliquely incident on the surface of the object to be measured to form a reflected beam with the second field intensity distribution ( 5b); the second collimating optical element (10) arranged on the reflected optical path is used to receive the reflected light beam with the second field intensity distribution within the field of view and collimate to form a reflected light beam with the third field intensity distribution; The second pupil divider (8) arranged behind the light path of the second collimating optical element (10) is used to receive the reflected light beam with the third field intensity distribution for field intensity division, so that the said light beam with the third field intensity distribution The reflected beam of the second pupil divider (8) forms a fourth field intensity distribution on the first surface of the second pupil divider (8), and the first pupil divider (7) and the second pupil divider (8) have the same Aperture function; a detector (11), used for acquiring reflected light beams with a fourth field intensity distribution, and analyzing change information of reflected light beams with a fourth field intensity distribution within a time interval. The device for detecting changes in reflected light according to claim 1, wherein the first collimating optical element (9) and the second collimating optical element (10) form an optical path collimation system, and the first light The pupil divider (7) is arranged at the entrance pupil position of the optical path collimation system, and the second collimating optical element (10) is arranged at the exit pupil position of the optical path collimation system. The device for detecting changes in reflected light according to claim 1 or 2, wherein the first pupil divider (7) is provided with a plurality of first-type light-passing structures and a plurality of second-type light-passing structures, so Said the first The first-type light-passing structure and the second-type light-passing structure have a difference in luminous flux, so that the incident beam (5a) is disturbed and divided by the first-type light-passing structure and the second-type light-passing structure, and becomes the An incident beam with a first field intensity distribution. The device for detecting changes in reflected light according to claim 3, wherein the second pupil divider (8) is provided with a plurality of third-type light-passing structures and a plurality of fourth-type light-passing structures, and the first The three-type light-passing structure and the fourth-type light-passing structure have differences in luminous flux, so that the reflected light beam with the third field intensity distribution is further disturbed and divided into the reflected light beam with the fourth field intensity distribution. The device for detecting changes in reflected light according to claim 4, wherein the first type of light-transmitting structure corresponds to the third type of light-transmitting structure, and the first type of light-transmitting structure and the third type of light-transmitting structure correspond to each other The shapes of the light-passing structures are the same. The device for detecting changes in reflected light as claimed in claim 4, wherein the adjustment of the field of view of the first collimating optical element (9) is realized by setting the composition structure of the first collimating optical element (9), so that The image of the first pupil divider (7) is clearly irradiated on the object to be measured; the second collimating optical element (10) is realized by setting the composition structure of the second collimating optical element (10) The field of view is adjusted so that the reflected light beam (5b) with the second field intensity distribution is collimated and enters the second pupil divider (8). The device for detecting changes in reflected light according to claim 4, wherein the first pupil divider (7) and the second pupil divider (8) are axially symmetrical with respect to the incident light path and the reflected light path. The device for detecting changes in reflected light as claimed in Claim 3, wherein the light transmission patterns corresponding to the plurality of first type light transmission structures are different. A method of detecting changes in reflected light, wherein the method comprises: Utilize the first pupil divider (7) to carry out the field strength division of the incident light beam (5a) so that the said incident light beam (5a) forms a first field intensity distribution on the first surface of the first pupil divider (7) ; collimating and converging the incident beam with the first field intensity distribution obliquely incident on the surface of the object to be measured to form a reflected beam (5b) with the second field intensity distribution; receiving the reflected beam with the second field intensity distribution and collimating to form Have the reflected light beam of the 3rd field intensity distribution; Utilize the second pupil divider (8) to receive the reflected light beam with the 3rd field intensity distribution and carry out field intensity division, make the described reflected light beam with the 3rd field intensity distribution in the described The fourth field intensity distribution is formed by the first surface of the second pupil divider (8), said first pupil divider (7) and the second pupil divider (8) having the same aperture function; Reflected beams with four field intensity distributions, analyzing change information of reflected beams with a fourth field intensity distribution within a time interval. A film thickness measuring device, which includes: a burst unit (1), which bursts a plurality of excitation sources from the upper surface (3a) to the lower surface (3b) of a film sample (2) to be measured at a time point, so that the At least one deformation region is produced on the upper surface of the film sample (2) to be tested; the device for detecting the change of the reflected beam as described in any one of 1-8 is provided, and the information on the peak value change of the polarized reflected beam signal intensity corresponding to the deformation region is obtained; calculation The unit calculates the thickness of the film sample (2) to be tested according to the time interval corresponding to the peak value.

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