Over-focus scanning detection device and method based on rolling shutter camera

Abstract

The invention discloses an over-focus scanning detection device and method based on a rolling shutter camera, and the device comprises a laser transmitting module which is suitable for transmitting detection laser; an objective lens adapted to focus the detection laser light; the sample table is suitable for placing a to-be-detected sample, the focused detection laser enters the to-be-detected sample and is reflected by the to-be-detected sample to obtain a reflected laser rolling shutter camera, and the sample table is suitable for carrying out line-by-line scanning on the to-be-detected sample so as to carry out imaging on the reflected laser of each line of scanning area according to a time sequence, when different areas are scanned line by line, the corresponding wavelengths of the reflected laser are different or the corresponding spatial positions of the to-be-detected sample are different.

Description

Technical Field

[0001] The present invention relates to the field of imaging, and more specifically, to an out-of-focus scanning detection device and method based on a rolling shutter camera. Background Art

[0002] The independent development of the semiconductor industry plays a crucial role in economic development and industrial security. After decades of development, the performance of semiconductor micro-nano devices has been greatly improved. With the improvement of performance, the structural feature sizes of micro-nano devices are getting smaller and smaller, and the micro-nano device structures are becoming more and more complex. To ensure the quality and yield of micro-nano devices, it is necessary to measure and analyze the three-dimensional feature sizes of semiconductor micro-nano devices.

[0003] The characteristic sizes of semiconductor micro-nano devices are usually in the order of μm to nm. Traditional measurement methods include electron microscopes, scanning tunneling microscopes, and atomic force microscopes. These methods can only measure surface structures and can only use destructive means for internal structures. At the same time, the measurement speed of these methods is relatively slow. In recent years, non-destructive measurement technologies based on optical methods have become increasingly mature, such as white light interferometry, spectral reflectometry, spectral scatterometry, laser confocal microscopy, etc. These optical methods usually require precise focusing to obtain accurate measurement results. When measuring the surfaces or internal structures at different heights of semiconductor micro-nano devices, re-focusing is required, which affects the measurement speed. At the same time, white light interferometry and spectral reflectometry can only obtain the depth information of trench or hole structures, and spectral scatterometry can only obtain the average results of parameters such as line width, aperture, and sidewall angle of array structures, and cannot comprehensively and truly reflect the structural information of semiconductor micro-nano devices. The through-focus scanning optical microscopy (TSOM) method forms a three-dimensional light field by collecting a series of out-of-focus images. This three-dimensional field reflects the change trend of the light field as the sample moves near the focus. Intercepting the three-dimensional light field along the optical axis direction to obtain a two-dimensional image (i.e., the TSOM image) and analyzing it can achieve rapid non-destructive measurement of multiple geometric parameters of the structure to be measured.

[0004] However, the above-mentioned existing technologies have the following technical defects: The through-focus scanning optical microscopy method needs to collect a series of out-of-focus images, but only a small part of the data is actually used in the measurement process, and a large amount of data is wasted and occupies storage space; Processing a series of collected images and finally generating a TSOM image takes a certain amount of time, reducing the measurement speed of this method; During the measurement process, it is necessary to move the sample or the objective lens along the optical axis direction, which will generate mechanical vibrations affecting the measurement accuracy, and the scanning process takes a long time, affecting the measurement speed. Summary of the Invention

[0005] In view of the above technical problems, embodiments of the present invention provide an out-of-focus scanning detection device and method based on a rolling shutter camera.

[0006] As a first aspect of the present invention, an out-of-focus scanning detection device based on a rolling shutter camera includes:

[0007] A laser emission module, adapted to emit detection laser;

[0008] An objective lens, adapted to focus the detection laser;

[0009] A sample stage, adapted to place a sample to be measured. The focused detection laser is incident on the sample to be measured and reflected by the sample to be measured to obtain reflected laser;

[0010] A rolling shutter camera, adapted to perform line-by-line scanning on the sample to be measured, and image the reflected laser in each scanned line area in sequence to obtain an out-of-focus scanning image of the sample to be measured. Among them, when scanning different areas line by line, the wavelengths of the corresponding reflected lasers are different or the spatial positions of the corresponding samples to be measured are different.

[0011] According to an embodiment of the present invention, the laser emission module includes:

[0012] A continuous laser, adapted to emit continuous laser, and the continuous laser is the detection laser;

[0013] A driving component is further connected to the sample stage. The driving component is adapted to drive the sample stage to move along the optical axis of the objective lens in a preset direction. The rolling shutter camera is adapted to image the reflected laser of the sample to be measured at different positions. The different positions include the focal position of the objective lens and the positions at both ends of the focal point.

[0014] According to an embodiment of the present invention, the above out-of-focus scanning detection device further includes:

[0015] A first control component, adapted to control the exposure time of the rolling shutter camera when the sample stage moves along the optical axis of the objective lens to image the sample to be measured at different spatial positions.

[0016] According to an embodiment of the present invention, the laser emission module includes:

[0017] An ultra-short pulse laser, adapted to emit ultra-short pulse laser;

[0018] A dispersion medium, adapted to spatially separate and arrange different wavelength components in the pulsed laser to broaden the pulse width of the pulsed laser. The broadened pulsed laser is the detection laser. The broadened pulsed laser includes lasers of different wavelengths. Lasers of different wavelengths reach the sample to be measured in sequence in time and are reflected by the sample to be measured. Lasers of different wavelengths reach the rolling shutter camera in sequence after being reflected by the sample to be measured;

[0019] Among them, the rolling shutter camera is applicable to sequentially expose lasers of different wavelengths arriving, and the sample to be measured is located on the focal plane of the objective lens.

[0020] According to an embodiment of the present invention, the above defocus scanning detection device further includes:

[0021] A second control component, which is applicable to control the exposure time of the rolling shutter camera, and when the wavefront of the light of each wavelength arrives at the rolling shutter camera, make a row of pixels of the rolling shutter camera start to expose.

[0022] According to an embodiment of the present invention, the above defocus scanning detection device further includes:

[0023] A semi-transmissive semi-reflective mirror, which is applicable to reflect the detection laser and incident the detection laser onto the sample to be measured, and is also applicable to transmit the reflected laser collected by the objective lens, and the transmitted reflected laser enters the rolling shutter camera.

[0024] According to an embodiment of the present invention, the above defocus scanning detection device further includes:

[0025] A beam shaping module, which is applicable to shape the detection laser into parallel laser light.

[0026] As a second aspect of the present invention, there is also provided a method for detecting a micro-nano device, including:

[0027] Using the above defocus scanning detection device to image the micro-nano device to be measured, and obtaining a defocus scanning image of the micro-nano device to be measured;

[0028] Inputting the image of the micro-nano device to be measured into a trained neural network model, and obtaining the geometric parameters of the micro-nano device to be measured.

[0029] According to an embodiment of the present invention, the training method of the neural network model includes:

[0030] Obtaining training samples, where the training samples include defocus scanning images of micro-nano device samples;

[0031] Inputting the training samples into an untrained neural network model, and outputting a prediction result of the geometric parameters of the micro-nano device samples;

[0032] Analyzing the prediction result, adjusting the parameters of the untrained neural network model, and obtaining a trained neural network model.

[0033] According to an embodiment of the present invention, the micro-nano device to be measured includes an S / L-shaped structure, an array structure or a multi-layer stacked structure;

[0034] The geometric parameters of the micro-nano device to be measured include the contour of the micro-nano device to be measured, the line width, or the width of the trench in the micro-nano device to be measured, the height of the micro-nano device to be measured, the depth of the micro-nano device to be measured, the sidewall angle of the micro-nano device to be measured, the diameters of the particles and holes in the micro-nano device to be measured, the heights of the particles and holes in the micro-nano device to be measured, and the depths of the particles and holes in the micro-nano device to be measured.

[0035] According to an embodiment of the present invention, a rolling shutter camera is used to perform a line-by-line scan on a sample to be measured, so that the start exposure time of each row of pixels of the rolling shutter camera is the same as the time when the wavefront of a certain wavelength reaches the rolling shutter camera. Once all the pixels of the rolling shutter camera are exposed, a TSOM map of wavelength scanning can be obtained without additional data processing. Alternatively, a rolling shutter camera is used to perform a line-by-line scan on a sample to be measured, and the start exposure time of each row of pixels of the rolling shutter camera corresponds to a specific spatial position of the sample to be measured. Once all the pixels of the rolling shutter camera are exposed, a TSOM map of spatial position scanning can be obtained without additional data processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Through the following description of the embodiments of the present invention with reference to the drawings, the above and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0037] Figure 1 The schematic diagram of an over-focus scanning detection device based on a rolling shutter camera provided by an embodiment of the present invention is shown;

[0038] Figure 2 The schematic diagram of an over-focus scanning detection device based on a rolling shutter camera provided by another embodiment of the present invention is shown.

[0039] DESCRIPTION OF THE REFERENCE NUMERALS:

[0040] 1 - Laser emission module;

[0041] 11 - Continuous laser;

[0042] 12 - Ultra-short pulse laser;

[0043] 13 - Dispersion medium;

[0044] 2 - Objective lens;

[0045] 3 - Sample stage;

[0046] 4 - Rolling shutter camera;

[0047] 5 - Sample to be measured;

[0048] 6 - First control component;

[0049] 7 - Driving component;

[0050] 8 - Second control component;

[0051] 9 - Half - transparent and half - reflective mirror;

[0052] 10 - Beam shaping module. Detailed implementation manners

[0053] To make the objectives, technical solutions and advantages of the present disclosure more clear and understandable, the following further elaborates on the present disclosure in detail with reference to specific embodiments and the accompanying drawings.

[0054] Figure 1 The schematic diagram of an over - focus scanning detection device based on a rolling - shutter camera provided by an embodiment of the present invention is shown.

[0055] Figure 2 The schematic diagram of an over - focus scanning detection device based on a rolling - shutter camera provided by another embodiment of the present invention is shown.

[0056] As Figure 1 - Figure 2 shown, the over - focus scanning detection device based on a rolling - shutter camera includes: a laser emission module 1, an objective lens 2, a sample stage 3, and a rolling - shutter camera 4.

[0057] The laser emission module 1 is adapted to emit detection laser light. The objective lens 2 is adapted to focus the detection laser light. The sample stage 3 is adapted to place a sample to be measured. The focused detection laser light is incident on the sample to be measured 5 and is reflected by the sample to be measured 5 to obtain reflected laser light. The rolling - shutter camera 4 is adapted to perform a line - by - line scan on the sample to be measured 5, and image the reflected laser light in each scanned line region in sequence according to the time sequence to obtain an over - focus scanning image of the sample to be measured, wherein the wavelength of the reflected laser light corresponding to different regions during the line - by - line scan is different or the spatial position of the sample to be measured corresponding to different regions is different.

[0058] According to an embodiment of the present invention, the rolling - shutter sensor 4 is realized by the method of line - by - line exposure controlled by a control chip. When the chip starts to expose, the photosensitive elements sense light in sequence according to the first - row pixels, second - row pixels... until the entire photosensitive component is exposed for each row pixel from top to bottom, that is, the exposure times of different row pixels of the rolling - shutter sensor 4 are different.

[0059] According to an embodiment of the present invention, a rolling shutter camera 4 is used to perform line-by-line scanning on a sample 5 to be measured, so that the start exposure time of each row of pixels of the rolling shutter camera 4 is the same as the time when a wavefront of a certain wavelength reaches the rolling shutter camera 4. When all pixels of the rolling shutter camera 4 are exposed, a TSOM map of wavelength scanning can be obtained without additional data processing. Alternatively, a rolling shutter camera 4 is used to perform line-by-line scanning on a sample 5 to be measured. The start exposure time of each row of pixels of the rolling shutter camera 4 corresponds to a specific spatial position of the sample 5 to be measured. When all pixels of the rolling shutter camera 4 are exposed, a TSOM map of spatial position scanning can be obtained without additional data processing.

[0060] According to an embodiment of the present invention, the method of defocus scanning microscopy for obtaining a TSOM map requires collecting a series of defocus images, processing the collected series of defocus images, and finally generating a TSOM map. The method of defocus scanning microscopy only uses a small part of the data in the collected series of defocus images, and a large amount of data is wasted and occupies storage space. In the method proposed by the embodiment of the present invention, a TSOM map is obtained by utilizing the characteristic of line-by-line exposure of a rolling shutter detector, and the amount of data collected is reduced, improving the measurement speed.

[0061] Continue to refer to Figure 1 , according to another embodiment of the present invention, the laser emission module 1 includes: a continuous laser 11. The continuous laser 11 is suitable for emitting continuous laser, and the continuous laser is the detection laser. A driving component 7 (not shown in the figure) is also connected to the sample stage 3. The driving component 7 is suitable for driving the sample stage 3 to move along the optical axis of the objective lens 2 in a preset direction. The rolling shutter camera 4 is suitable for imaging the reflected laser of the sample 5 to be measured at different positions, and the different positions include the focal position of the objective lens 2 and the positions at both ends of the focal point.

[0062] According to an embodiment of the present invention, the preset direction can be, for example, along the optical axis of the objective lens 2 and gradually approaching the objective lens, or can be along the optical axis of the objective lens 2 and gradually away from the objective lens.

[0063] According to an embodiment of the present invention, the above defocus scanning detection device further includes a first control component 6. The first control component 6 is suitable for controlling the exposure time of the rolling shutter camera when the sample stage 3 moves along the optical axis of the objective lens to image the sample 5 to be measured at different spatial positions. The first control component 6 can be, for example, a computer.

[0064] Continue to refer to Figure 2 , the laser emission module 1 includes: an ultrashort pulse laser 12 and a dispersion medium 13.

[0065] The ultrashort pulse laser 12 is suitable for emitting ultrashort pulse laser. The dispersion medium 13 is suitable for separating different wavelength components in the pulsed laser in space and arranging them in sequence to broaden the pulse width of the pulsed laser. The broadened pulsed laser is the detection laser, and the broadened pulsed laser includes lasers of different wavelengths. The lasers of different wavelengths reach the sample to be measured 5 in sequence according to the time sequence and are reflected by the sample to be measured 5. The lasers of different wavelengths reach the rolling shutter camera 4 in sequence after being reflected by the sample to be measured. The rolling shutter camera 4 is suitable for sequentially exposing the lasers of different wavelengths that arrive. The sample to be measured 5 is located on the focal plane of the objective lens. The ultrashort pulse laser output by the ultrashort pulse laser 12 is broadened in the time domain through the dispersion medium 13, so that the broad spectrum of the ultrashort pulse laser is arranged in sequence along the optical axis direction in space according to the wavelength. In the embodiment of the present invention, a defocus scanning image of the sample to be measured is obtained by using each pixel in each row of the rolling shutter camera 4 to expose one wavelength component in the ultrashort pulse laser reflected by the sample to be measured 5. The method provided by the embodiment of the present invention does not require the movement of the sample to be measured 5. According to an embodiment of the present invention, the above defocus scanning detection device further includes: a second control component 8. The second control component 8 is suitable for controlling the exposure time of the rolling shutter camera 4, and when the wavefront of the light of each wavelength reaches the rolling shutter camera 4, making a row of pixels of the rolling shutter camera 4 start to expose. The second control component 8 can be, for example, a computer.

[0066] According to the defocus scanning detection device provided by the embodiment of the present invention, it is not necessary to move the sample to be measured 5 or the objective lens 2 along the optical axis direction of the objective lens 2 during the TSOM measurement. The defocus scanning detection device provided by the embodiment of the present invention, based on the wavelength scanning TSOM method of ultrashort pulse laser, avoids the situation that mechanical vibration is generated due to the movement of the sample to be measured 5 or the objective lens 2, thereby affecting the measurement accuracy. The measurement speed is fast, and the noise introduced by mechanical vibration is avoided.

[0067] According to an embodiment of the present invention, the above defocus scanning detection device further includes: a beam splitter 9. The beam splitter 9 is suitable for reflecting the detection laser and incidenting the detection laser onto the sample to be measured 5, and is also suitable for transmitting the reflected laser collected by the objective lens. The transmitted reflected laser enters the rolling shutter camera 4.

[0068] According to an embodiment of the present invention, the defocus scanning detection device further includes: a beam shaping module 10. The beam shaping module 10 is suitable for shaping the detection laser into parallel laser and expanding the beam of the detection laser.

[0069] According to an embodiment of the present invention, there is also provided a detection method for micro-nano devices, including: operation S1 - operation S2.

[0070] In operation S1, the above defocus scanning detection device is used to image the micro-nano device to be measured, and a defocus scanning image of the micro-nano device to be measured is obtained.

[0071] In operation S2, the image of the micro-nano device to be measured is input into the trained neural network model to obtain the geometric parameters of the micro-nano device to be measured.

[0072] According to an embodiment of the present invention, a database can be established by numerical simulation. The database includes the intensity distribution of the 5TSOM image of the sample to be measured under different conditions (spot size, incident angle, relative position of the spot and the structure of the sample to be measured). The database is established by measuring a series of standard samples with different structural features and different geometric parameters, and the database image that best matches the scanned composite image is selected by comparison. The structural features and geometric parameters corresponding to the matching image are the final measurement results.

[0073] According to an embodiment of the present invention, the mapping relationship between the TSOM image and the corresponding parameter to be measured can be learned by training a neural network through deep learning to predict the parameter to be measured, avoiding the cumbersome work of establishing a database.

[0074] According to an embodiment of the present invention, the training method of the neural network model in operation S2 includes operations S21 - S23.

[0075] In operation S21, training samples are obtained, and the training samples include overfocus scanned images of micro-nano device samples.

[0076] In operation S22, the training samples are input into the untrained neural network model, and the prediction results of the geometric parameters of the micro-nano device samples are output.

[0077] In operation S23, the prediction results are analyzed, and the parameters of the untrained neural network model are adjusted to obtain the trained neural network model.

[0078] According to an embodiment of the present invention, the micro-nano device to be measured includes an S / L-shaped structure, an array structure, or a multi-layer stacked structure;

[0079] The geometric parameters of the micro-nano device 5 to be measured include the contour of the micro-nano device to be measured, the line width, or the width of the groove in the micro-nano device 5, the height of the micro-nano device 5, the depth of the micro-nano device 5, the sidewall angle of the micro-nano device 5, the diameter of the particles and holes in the micro-nano device 5, the height of the particles and holes in the micro-nano device 5, and the depth of the particles and holes in the micro-nano device 5.

[0080] The method provided according to an embodiment of the present invention can also be used to measure the tilt, flatness of a silicon wafer, film thickness uniformity, etc.

[0081] The embodiments of the present invention have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although the embodiments have been described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should all fall within the scope of the present invention.

Claims

1. An over-focus scanning detection device based on a rolling shutter camera, comprising: A laser emission module, adapted to emit detection laser light; An objective lens, adapted to focus the detection laser light; A sample stage, adapted to place a sample to be measured. The focused detection laser light is incident on the sample to be measured and is reflected by the sample to be measured to obtain reflected laser light; A rolling shutter camera, adapted to perform line-by-line scanning on the sample to be measured, and image the reflected laser light in each scanned line region in sequence according to the time sequence to obtain an over-focus scanning image of the sample to be measured. Among them, when scanning different regions line by line, the wavelengths of the corresponding reflected laser light are different or the spatial positions of the corresponding sample to be measured are different.

2. The over-focus scanning detection device according to claim 1, wherein, The laser emission module includes: A continuous laser, adapted to emit continuous laser light, and the continuous laser light is the detection laser light; A driving component is further connected to the sample stage. The driving component is adapted to drive the sample stage to move along the optical axis of the objective lens in a preset direction. The rolling shutter camera is adapted to image the reflected laser light of the sample to be measured at different positions. The different positions include the focal position of the objective lens and the positions at both ends of the focal point.

3. The over-focus scanning detection device according to claim 2, further comprising: A first control component, adapted to control the exposure time of the rolling shutter camera when the sample stage moves along the optical axis of the objective lens, so as to image the sample to be measured at different spatial positions.

4. The over-focus scanning detection device according to claim 1, wherein, The laser emission module includes: An ultra-short pulse laser, adapted to emit ultra-short pulse laser light; A dispersion medium, adapted to spatially separate and arrange different wavelength components in the pulsed laser light to broaden the pulse width of the pulsed laser light. The broadened pulsed laser light is the detection laser light. The broadened pulsed laser light includes laser light of different wavelengths. Laser light of different wavelengths reaches the sample to be measured in sequence according to the time sequence and is reflected by the sample to be measured. Laser light of different wavelengths reaches the rolling shutter camera in sequence after being reflected by the sample to be measured; Among them, the rolling shutter camera is adapted to expose the arriving laser light of different wavelengths in sequence, and the sample to be measured is located on the focal plane of the objective lens.

5. The over-focus scanning detection device according to claim 4, further comprising: A second control component, adapted to control the exposure time of the rolling shutter camera, and when the wavefront of the light of each wavelength reaches the rolling shutter camera, make a row of pixels of the rolling shutter camera start to be exposed.

6. The over-focus scanning detection device according to any one of claims 1-5, further comprising: A semi-transparent semi-reflective mirror, adapted to reflect the detection laser light and incident the detection laser light on the sample to be measured, and is also adapted to transmit the reflected laser light collected by the objective lens. The transmitted reflected laser light enters the rolling shutter camera.

7. The over-focus scanning detection device according to any one of claims 1-5, further comprising: A beam shaping module, adapted to shape the detection laser light into parallel laser light.

8. A detection method for micro-nano devices, comprising: imaging a micro-nano device to be detected by using the defocus scanning detection device according to any one of claims 1-7 to obtain a defocus scanning image of the micro-nano device to be detected; inputting the image of the micro-nano device to be detected into a trained neural network model to obtain geometric parameters of the micro-nano device to be detected.

9. The micro-nano device detection method according to claim 8, wherein, The training method of the neural network model comprises: obtaining training samples, wherein the training samples include defocus scanning images of micro-nano device samples; inputting the training samples into an untrained neural network model and outputting a prediction result of geometric parameters of the micro-nano device samples; analyzing the prediction result and adjusting parameters of the untrained neural network model to obtain a trained neural network model.

10. The micro-nano device detection method according to claim 8, wherein, The micro-nano device to be detected includes an S / L-shaped structure, an array structure or a multi-layer stacked structure; The geometric parameters of the micro-nano device to be detected include the contour of the micro-nano device to be detected, the line width, or the width of the groove in the micro-nano device to be detected, the height of the micro-nano device to be detected, the depth of the micro-nano device to be detected, the sidewall angle of the micro-nano device to be detected, the diameters of particles and holes in the micro-nano device to be detected, the heights of particles and holes in the micro-nano device to be detected, and the depths of particles and holes in the micro-nano device to be detected.

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