Physical appearance recovery method and device suitable for scanning phase shift interference system

Abstract

The invention belongs to the technical field related to microscopic interference, and discloses a morphology recovery method and device suitable for a scanning phase-shift interference system, and the method comprises the steps: (1) employing the scanning phase-shift interference system to collect a series of scanning interference images, calculating the jerk value of each scanning interference image in the vertical direction, and calculating the jerk value of each scanning interference image in the vertical direction; meanwhile, reconstructing the scanning interference image into a three-dimensional interference image; and (2) correcting all time sampling interference signals in the three-dimensional interference image into space sampling interference signals by adopting a vertical direction jerk value, calculating phases of all the space sampling interference signals, and further converting the phases into height values so as to realize characterization of the three-dimensional morphology. According to the invention, the speed is improved and the cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field related to microscopic interference, and more specifically, relates to a morphology recovery method and device suitable for a scanning phase-shifting interference system. Background Art

[0002] Microscopic interferometry technology is widely used in manufacturing fields such as optical component processing quality inspection and structural characterization of micro-electromechanical devices. Among them, monochromatic light phase-shift interferometry, white light vertical scanning interferometry and multi-wavelength interferometry are the most representative. Although these existing microscopic interferometry technologies have their own advantages in vertical height measurement range and measurement accuracy, they are sufficient to meet the static three-dimensional characterization of various micro-nano devices. However, due to the limited field of view, for the measurement range of wafer scale, it is necessary to frequently use the translation stage to switch the field of view and perform axial scanning to obtain sufficient two-dimensional images, so as to restore the surface morphology and stitch the images. In recent years, some scholars have proposed a scanning interferometry system. Different from the traditional interference optical path structure, it uses a tilted reference mirror and moves the sample. A series of interference images are collected in a rapid and continuous scanning process, and finally reconstructed into a traditional three-dimensional interference image and demodulated, thereby realizing surface morphology restoration with a large field of view.

[0003] However, during the sample scanning process, the vertical jump of the linear stage causes the reconstructed three-dimensional interference image to have a large phase error, which is easy to disrupt the interference signal and affect the reconstructed morphology. In order to solve the vertical jump of the linear stage, some scholars have proposed using PZT to compensate for the vertical jump of the linear stage in real time during its movement. However, the response time of PZT is relatively long and cannot meet the requirements of fast sample scanning and high frame rate acquisition, which greatly limits the measurement efficiency and increases the complexity and cost of the hardware. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a morphology restoration method and device suitable for a scanning phase-shift interferometer system, which aims to solve the problem of low speed of the existing morphology reconstruction method.

[0005] To achieve the above object, according to one aspect of the present invention, a morphology restoration method applicable to a scanning phase shift interferometer system is provided, the method comprising the following steps:

[0006] (1) A scanning phase-shifting interferometer system is used to collect a series of scanning interferometer images, and the vertical jump amount of each scanning interferometer image is calculated, and the scanning interferometer images are reconstructed into a three-dimensional interferometer image;

[0007] (2) The vertical jump amount is used to correct all the time-sampled interference signals in the three-dimensional interference image into spatially sampled interference signals, and the phases of all spatially sampled interference signals are calculated and then converted into height values ​​to achieve the characterization of the three-dimensional morphology.

[0008] Furthermore, the stripe direction of each scanning interference image is perpendicular to the scanning direction, and the scanning displacement of the object to be measured occupies an integer number of pixels in each of two adjacent scanning interference images, which is recorded as s.

[0009] Furthermore, the plane area in each scanning interference image is identified, and the vertical runout amount thereof is calculated accordingly.

[0010] Furthermore, based on the position of the sample structure in each scanning interference image and the value of s, the collected scanning interference images are reconstructed into a wide-field three-dimensional interference image.

[0011] Furthermore, the number of pixels p occupied by a period of an interference fringe is at least 4 and at most H, where H is the number of camera pixels along the scanning direction; the scanning speed of the linear translation stage and the camera acquisition frame rate are set so that the scanning displacement of the object to be measured is between every two adjacent frames.

[0012] Furthermore, the scanning interference image occupies s pixels, where s is an integer and does not exceed H / 4.

[0013] Furthermore, the steps for obtaining the vertical jitter of each scanning interference image are as follows:

[0014] S2.1, finding the plane feature area in each scanning interference image;

[0015] S2.2, using the common plane feature area of ​​each adjacent two images, calculate the vertical jump vibDif of the i+1th scanning interference image relative to the i-th scanning interference image i+1 , and set vibDif1=0;

[0016] S2.3. Calculate the cumulative sum of the relative vertical runout vibDif, which is the absolute vertical position runout:

[0017]

[0018] Furthermore, according to the position offset of the sample structure in each scanning interference image, that is, the number of pixels s occupied by the scanning displacement of the sample to be tested in each of two adjacent scanning interference images, a series of scanning interference images are reconstructed into a wide-field three-dimensional interference image; for the interference signal sigPSI of a certain pixel coordinate (m, n) in the reconstructed wide-field three-dimensional interference image m,n , whose time coordinate sequence is [1,…,l,…,L], if sigPSI m,n,1 From the i-th scan image before reconstruction, sigPSI m,n The spatial coordinate sequence is:

[0019] spcOrdm,n =[1,...,l,...L]+[vibPos i ,...,vibPos i+l-1 ,...,vibPos i+L-1 ].

[0020] The present invention also provides a morphology recovery system suitable for a scanning phase-shifting interferometer system, the system comprising a memory and a processor, the memory storing a computer program, and the processor executing the morphology recovery method suitable for a scanning phase-shifting interferometer system as described above when executing the computer program.

[0021] The present invention also provides a computer-readable storage medium, which stores machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions prompt the processor to implement the morphology recovery method applicable to the scanning phase-shift interferometer system as described above.

[0022] In general, compared with the prior art, the above technical solutions conceived by the present invention, the morphology restoration method and device applicable to the scanning phase shift interferometer system provided by the present invention mainly have the following beneficial effects:

[0023] 1. Use the vertical jitter to correct all the time-sampled interference signals in the three-dimensional interference image into spatially sampled interference signals, calculate the phases of all spatially sampled interference signals, and then convert them into height values ​​to achieve the characterization of the three-dimensional morphology, so that the morphology recovery is not affected by the vertical jitter, avoiding the use of complex hardware compensation strategies to reduce the measurement speed and increase the cost.

[0024] 2. The morphology restoration method does not require complex equipment, has simple steps, fewer processes, is easy to implement, and is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a morphology recovery method applicable to a scanning phase-shift interferometer system provided by the present invention;

[0026] Figure 2 is a scanning interference image provided by an embodiment of the present invention;

[0027] Figure 3 is a vertical jitter curve of each scanning interference image provided by an embodiment of the present invention;

[0028] Figure 4 is a two-dimensional image of a certain axial position in the reconstructed wide-field three-dimensional interference image provided by an embodiment of the present invention;

[0029] Figure 5It is a comparison diagram of the interference signal curve of a certain pixel coordinate of the reconstructed wide-field three-dimensional interference image provided by an embodiment of the present invention before and after correction;

[0030] Figure 6 It is a three-dimensional topography image restored by using a corrected wide-field three-dimensional interference image provided by an embodiment of the present invention;

[0031] Figure 7 It is a three-dimensional morphology image restored by using an uncorrected wide-field three-dimensional interference image provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] The present invention provides a morphology recovery method suitable for a scanning phase-shift interferometer system, which directly extracts the vertical jump of the translation stage from a series of acquired scanning interference images and compensates it into the reconstructed interference signal, ultimately achieving accurate morphology recovery without being affected by the vertical jump of the translation stage, avoiding the use of complex hardware compensation strategies that reduce measurement speed and increase costs.

[0034] The morphology restoration method mainly comprises the following steps:

[0035] Step 1: Use a scanning phase-shifting interferometer system to collect a series of scanning interference images, calculate the vertical jump amount of each scanning interference image, and reconstruct the scanning interference image into a three-dimensional interference image.

[0036] The stripe direction of each scanning interference image is perpendicular to the scanning direction. The scanning displacement of the object to be measured occupies an integer number of pixels in each of the two adjacent scanning interference images, which is recorded as s. The plane area in each scanning interference image is identified, and its vertical runout is calculated accordingly.

[0037] According to the position of the sample structure in each scanning interference image and the value of s, the collected scanning interference image is reconstructed into a wide-field three-dimensional interference image.

[0038] Step 2: Use the vertical direction jump amount to correct all the time-sampled interference signals in the three-dimensional interference image into spatially sampled interference signals, calculate the phases of all spatially sampled interference signals, and then convert them into height values ​​to achieve the characterization of the three-dimensional morphology.

[0039] The present invention is further described in detail below with reference to specific embodiments.

[0040] See also Figure 1 A specific embodiment of the present invention provides a morphology recovery method applicable to a scanning phase shift interferometer system, comprising the following steps:

[0041] S1. Adjust the reference mirror in the scanning phase-shift interferometer system so that the interference fringes are perpendicular to the scanning direction, and the number of pixels p occupied by a period of an interference fringe is at least 4 and at most H (H is the number of camera pixels along the scanning direction); set the scanning speed of the linear translation stage and the camera acquisition frame rate so that the scanning displacement of the object to be measured is within every two adjacent frames.

[0042] The scanning interference image occupies s pixels, s is an integer and does not exceed H / 4. Obtain a series of scanning interference images collected by the scanning phase shift interferometer system, one of which is as follows Figure 2 shown.

[0043] S2, calculate the vertical jump amount of each scanning interference image in S1, the specific steps are as follows:

[0044] S2.1, finding the plane feature area in each scanning interference image;

[0045] S2.2, using the common plane feature area of ​​each adjacent two images, calculate the vertical jump vibDif of the i+1th scanning interference image relative to the i-th scanning interference image i+1 , and set vibDif1=0;

[0046] S2.3. Calculate the cumulative sum of the relative vertical runout vibDif, which is the absolute vertical position runout:

[0047]

[0048] The vertical jump amount of each scanning interference image in S1 calculated according to the above steps is as follows: Figure 3 shown.

[0049] S3, according to the position offset of the sample structure in each scanning interference image, that is, the number of pixels s occupied by the scanning displacement of the sample to be tested in each of two adjacent scanning interference images, a series of scanning interference images in S1 are reconstructed into a wide-field three-dimensional interference image. The two-dimensional image of a certain axial position in the reconstructed three-dimensional interference image is as follows: Figure 4 shown.

[0050] S4, using the vertical jump in S2, correct the time-sampled interference signal of each pixel in the three-dimensional interference image in S3 to the correct spatial sampling interference signal. For the interference signal sigPSI of a certain pixel coordinate (m, n) in the reconstructed wide-field three-dimensional interference image m,n, whose time coordinate sequence is [1,…,l,…,L], if sigPSI m,n,1 From the i-th scan image before reconstruction, sigPSI m,n The spatial coordinate sequence is:

[0051] spcOrd m,n =[1,...,l,...L]+[vibPos i ,...,vibPos i+l-1 ,...,vibPos i+L-1 ].

[0052] By calculating the spatial coordinate sequence of the interference signal of all pixel coordinates of the wide-field three-dimensional interference image, the phase error of all time-sampled interference signals caused by vertical jump is corrected and converted into the correct spatially sampled interference signal. Figure 5 The curve diagrams of the interference signal of a certain pixel coordinate of the reconstructed wide-field three-dimensional interference image before and after correction are given. It can be seen that the interference signal converted into a spatial sampling sequence has obvious sinusoidal characteristics.

[0053] S5. Calculate the phase of the spatial sampling interference signal of each pixel point in S4 and convert it into an actual height value to perform three-dimensional morphology characterization.

[0054] According to the interference signal sigPSI of a certain pixel coordinate (m,n) in the wide-field 3D interference image m,n and its spatial coordinate sequence spcOrd m,n Perform sine fitting and obtain its phase value pha m,n , the actual height value is By calculating the height values ​​of all pixel coordinates of the wide-field 3D interference image, the surface morphology h within the wide field of view is obtained. If the number of pixels s occupied by the scanning displacement of the sample to be tested in each of the two adjacent scanning interference images is not 1, the surface morphology h obtained needs to be calculated with a period of s and an amplitude of to compensate for the serrated surface.

[0055] Figure 6 The three-dimensional morphology restored by the above operation using the corrected wide-field three-dimensional interference image is shown. Figure 7 The three-dimensional morphology restored using the uncorrected wide-field three-dimensional interference image is not affected by the vertical jump of the translation stage and can accurately restore the surface morphology of the sample to be tested.

[0056] The present invention also provides a morphology recovery system suitable for a scanning phase-shifting interferometer system, the system comprising a memory and a processor, the memory storing a computer program, and the processor executing the morphology recovery method suitable for a scanning phase-shifting interferometer system as described above when executing the computer program.

[0057] The present invention also provides a computer-readable storage medium, which stores machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions prompt the processor to implement the morphology recovery method applicable to the scanning phase-shift interferometer system as described above.

[0058] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A morphology restoration method suitable for a scanning phase-shift interferometer system, characterized in that: The method comprises the following steps: (1) A scanning phase-shifting interferometer system is used to collect a series of scanning interferometer images, and the vertical jump amount of each scanning interferometer image is calculated, and the scanning interferometer images are reconstructed into a three-dimensional interferometer image; (2) The vertical jump amount is used to correct all the time-sampled interference signals in the three-dimensional interference image into spatially sampled interference signals, and the phases of all spatially sampled interference signals are calculated and then converted into height values ​​to achieve the characterization of the three-dimensional morphology.

2. The morphology restoration method applicable to a scanning phase shift interferometer system according to claim 1, characterized in that: The fringe direction of each scanning interference image is perpendicular to the scanning direction, and the scanning displacement of the object to be measured occupies an integer number of pixels in each of two adjacent scanning interference images, which is recorded as s.

3. The morphology restoration method applicable to a scanning phase shift interferometer system according to claim 2, characterized in that: The plane area in each scanning interference image is identified and its vertical runout is calculated accordingly.

4. The morphology restoration method applicable to a scanning phase shift interferometer system according to claim 3, characterized in that: Based on the position of the sample structure in each scanning interference image and the value of s, the collected scanning interference images are reconstructed into wide-field three-dimensional interference images.

5. The morphology restoration method applicable to a scanning phase-shift interferometry system according to any one of claims 1 to 4, characterized in that: The number of pixels p occupied by a period of an interference fringe is at least 4 and at most H, where H is the number of camera pixels along the scanning direction; the scanning speed of the linear translation stage and the camera acquisition frame rate are set so that the scanning displacement of the object to be measured is between every two adjacent frames.

6. The morphology restoration method applicable to a scanning phase shift interferometer system according to claim 5, characterized in that: The scanning interference image occupies s pixels, where s is an integer and does not exceed H / 4.

7. The morphology restoration method applicable to a scanning phase shift interferometer system according to claim 6, characterized in that: The steps for obtaining the vertical jump amount of each scanning interference image are as follows: S2.1, finding the plane feature area in each scanning interference image; S2.2, using the common plane feature area of ​​each adjacent two images, calculate the vertical jump vibDif of the i+1th scanning interference image relative to the i-th scanning interference image i+1 , and set vibDif1=0; S2.

3. Calculate the cumulative sum of the relative vertical runout vibDif, which is the absolute vertical position runout:

8. The morphology restoration method applicable to a scanning phase shift interferometer system according to claim 7, characterized in that: According to the position offset of the sample structure in each scanning interference image, that is, the number of pixels s occupied by the scanning displacement of the sample to be tested in each of two adjacent scanning interference images, a series of scanning interference images are reconstructed into a wide-field three-dimensional interference image; for the interference signal sigPSI of a certain pixel coordinate (m, n) in the reconstructed wide-field three-dimensional interference image m,n , whose time coordinate sequence is [1,…,l,…,L], if sigPSI m,n,1 From the i-th scan image before reconstruction, sigPSI m,n The spatial coordinate sequence is: spcOrd m,n =[1,...,l,...L]+[vibPos i ,...,vibPos i+l-1 ,...,vibPos i+L-1 ]。 9. A morphology recovery system suitable for a scanning phase-shift interferometer system, characterized in that: The system includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the morphology recovery method applicable to a scanning phase-shifting interferometer system as described in any one of claims 1 to 8 is executed.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores machine-executable instructions. When the machine-executable instructions are called and executed by the processor, the machine-executable instructions prompt the processor to implement the morphology restoration method applicable to a scanning phase-shift interferometry system as described in any one of claims 1 to 8.

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