Facial profile calculating system and facial profile calculating method
Patent Information
- Application Number
- CN202610893239.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-22
- Publication Date
- 2026-09-25
- Estimated Expiration
- 2046-06-22
AI Technical Summary
[0004]本发明主要解决大翘曲晶圆的面型计算效率低、检测周期长的技术问题
[0033]依据上述实施例的面型计算系统和面型计算方法，其中待测样品被划分为N个局部区域，面型计算系统包括N个面型计算设备，待测样品的N个局部区域被依次调整至干涉仪的视野范围内以进行干涉成像，当待测样品的第p个局部区域处于干涉仪的视野范围内之后，第p个面型计算设备获取第p个局部区域的第二干涉图，基于第二干涉图计算第p个局部区域的面型并发送至拼接计算设备进行拼接，即每个面型计算设备计算一个局部区域的面型，最后拼接得到待测样品完整的面型，可实现各个局部区域面型的并行计算，无需等待，提高了面型计算效率，缩短了检测周期。
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Figure CN122432442B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor testing technology, and more specifically to a surface shape calculation system and a surface shape calculation method. Background Technology
[0002] The surface profile of a wafer is often measured using an interferometer. An interferometer utilizes the phenomenon of light interference to form interference fringes containing height information on the wafer surface. By acquiring the interferogram of the wafer surface, its surface profile can be calculated. Large-warped wafers, due to their warp slope, have local regions that exceed the interferometer's single field of view (numerical aperture NA). Therefore, it is necessary to continuously adjust the tilt of the large-warped wafer, sequentially ensuring that each local region of the large-warped wafer appears within the interferometer's field of view. Finally, the interferograms of all local regions are stitched together to generate the complete interferogram.
[0003] Currently, for wafers with large warpages, it is necessary to divide them into many local regions for imaging and stitching. Each local region requires unpacking and calculating multiple interferograms. For example, in some scenarios, each local region needs to unpack and calculate more than ten interferograms. Wafers with warpages greater than 1800μm require stitching together more than 10 local regions, resulting in a huge amount of data. On a single server, it is common to be able to measure only a dozen wafers per hour. Summary of the Invention
[0004] This invention mainly solves the technical problems of low efficiency in surface shape calculation and long detection cycle of large warp wafers.
[0005] According to the first aspect, one embodiment provides a surface shape calculation system for calculating the surface shape of a sample to be tested. The sample to be tested is divided into N local regions, and the N local regions are sequentially adjusted to the field of view of an interferometer for phase-shifting interferometric imaging. The sample to be tested includes a first sample to be tested. The surface shape calculation system includes a stable state monitoring device and N surface shape calculation devices, where N is an integer not less than 2.
[0006] The stable state monitoring device is used to: after the p-th local region of the first sample under test is within the field of view of the interferometer, acquire the first interferogram of the p-th local region whenever the interferometer performs a phase shift, determine whether the wavelength emitted by the interferometer has stabilized based on the first interferogram of the p-th local region, and send a second interferogram acquisition signal to the p-th surface calculation device after the wavelength has stabilized; where p = 1, 2...N;
[0007] The p-th surface shape calculation device is used to respond to the second interferogram acquisition signal, acquire the second interferogram of the p-th local region, calculate the surface shape of the p-th local region based on the multiple second interferograms of the p-th local region acquired after phase shift, and send the calculated surface shape of the p-th local region to the stitching calculation device for stitching to obtain the complete surface shape of the first test sample.
[0008] In some embodiments, the splicing computing device is the stable state monitoring device, or the splicing computing device is an independent device different from the stable state monitoring device and the N surface type computing devices.
[0009] In some embodiments, the sample to be tested further includes a second sample to be tested;
[0010] If the splicing calculation device is the stable state monitoring device, then during the process of splicing the surface patterns of N local regions of the first test sample, after the first local region of the second test sample is within the field of view of the interferometer, the stable state monitoring device acquires the first interferogram of the first local region of the second test sample every time the interferometer performs a phase shift. Based on the first interferogram of the first local region of the second test sample, it determines whether the wavelength has stabilized. After the wavelength stabilizes, it sends a second interferogram acquisition signal to the first surface pattern calculation device.
[0011] If the splicing calculation device is the independent device, then after all N surface calculation devices have completed the surface calculation and the first local region of the second test sample is within the field of view of the interferometer, the stable state monitoring device acquires the first interferogram of the first local region of the second test sample every time the interferometer performs a phase shift. Based on the first interferogram of the first local region of the second test sample, it determines whether the wavelength has stabilized. After the wavelength stabilizes, it sends a second interferogram acquisition signal to the first surface calculation device.
[0012] In some embodiments, the steady-state monitoring device determines whether the wavelength emitted by the interferometer has stabilized by:
[0013] The steady-state monitoring device continuously acquires multiple first interferograms of the p-th local region and calculates the bit depth of each first interferogram;
[0014] The fluctuation value of the bit depth is calculated based on the bit depth of the multiple first interferograms. If the fluctuation value is within the preset error band, it is determined that the wavelength emitted by the interferometer has stabilized.
[0015] In some embodiments, the steady-state monitoring device calculates the bit depth of each first interferogram in the following manner:
[0016] The steady-state monitoring device performs phase unpacking processing on each first interferogram to obtain the corresponding first phase map;
[0017] Based on the conversion relationship between phase and depth, the depth of each first interferogram is calculated according to the first phase diagram.
[0018] In some embodiments, the first interferogram is a single-pixel interferogram.
[0019] According to a second aspect, one embodiment provides a surface shape calculation system for calculating the surface shape of a sample to be tested, characterized in that the sample to be tested is divided into N local regions, the N local regions are sequentially adjusted to the field of view of an interferometer for interferometric imaging, the sample to be tested includes a first sample to be tested, and the surface shape calculation system includes N surface shape calculation devices.
[0020] Wherein, the p-th surface shape calculation device is used to acquire the second interferogram of the p-th local region after the p-th local region of the first test sample is within the field of view of the interferometer, calculate the surface shape of the p-th local region based on the second interferogram of the p-th local region, and send the calculated surface shape of the p-th local region to the stitching calculation device for stitching to obtain the complete surface shape of the first test sample; wherein, p=1,2...N, and N is an integer not less than 2.
[0021] According to a third aspect, one embodiment provides a surface shape calculation method for calculating the surface shape of a sample to be tested, wherein the sample to be tested is divided into N local regions, the sample to be tested includes a first sample to be tested, and N is an integer not less than 2, the surface shape calculation method includes:
[0022] The first sample to be tested is placed in the interference cavity of the interferometer, so that its first local area is within the field of view of the interferometer;
[0023] Whenever the interferometer performs a phase shift, a first interferogram of the first local region is acquired by a stable state monitoring device. Based on the first interferogram of the first local region, it is determined whether the wavelength emitted by the interferometer has stabilized. After the wavelength stabilizes, a second interferogram acquisition signal is sent to a first surface model calculation device. The first surface model calculation device responds to the second interferogram acquisition signal and acquires the second interferogram of the first local region.
[0024] After the interferometer finishes phase shifting, the first surface shape calculation device calculates the surface shape of the first local region based on multiple second interferograms of the first local region, and sends the calculated surface shape of the first local region to the stitching calculation device;
[0025] The local region surface shape calculation steps are repeated until the surface shapes of all N local regions are obtained. The local region surface shape calculation steps include: adjusting the orientation of the first sample to be tested so that the next local region is within the field of view of the interferometer; each time the interferometer performs a phase shift, the first interferogram of the next local region is acquired through the stable state monitoring device; based on the first interferogram of the next local region, it is determined whether the wavelength has stabilized; after the wavelength stabilizes, a second interferogram acquisition signal is sent to the next surface shape calculation device; the next surface shape calculation device responds to the second interferogram acquisition signal and acquires the second interferogram of the next local region; after the interferometer finishes the phase shift, the next surface shape calculation device calculates the surface shape of the next local region based on multiple second interferograms of the next local region, and sends the calculated surface shape of the next local region to the stitching calculation device.
[0026] The splicing calculation device receives the surface patterns of the N local regions sent by the N surface pattern calculation devices respectively and splices them to obtain the complete surface pattern of the first sample to be tested.
[0027] In some embodiments, the splicing computing device is the stable state monitoring device, or the splicing computing device is an independent device different from the stable state monitoring device and the N surface type computing devices.
[0028] In some embodiments, the sample to be tested further includes a second sample to be tested;
[0029] The surface shape calculation method also includes:
[0030] After the Nth local region of the first sample to be tested is obtained by the Nth surface calculation device, the second sample to be tested is switched into the interference cavity of the interferometer so that its first local region is within the field of view of the interferometer.
[0031] If the splicing calculation device is the stable state monitoring device, then during the process of splicing the surface patterns of N local regions of the first test sample, the stable state monitoring device also acquires the first interferogram of the first local region of the second test sample after each phase shift of the interferometer, and determines whether the wavelength has stabilized based on the first interferogram of the first local region of the second test sample. After the wavelength stabilizes, it sends the second interferogram acquisition signal to the first surface pattern calculation device.
[0032] If the splicing calculation device is the independent device, after all N surface calculation devices have completed the surface calculation, the stability monitoring device acquires the first interferogram of the first local region of the second sample under test after each phase shift of the interferometer, determines whether the wavelength has stabilized based on the first interferogram of the first local region of the second sample under test, and sends the second interferogram acquisition signal to the first surface calculation device after the wavelength has stabilized.
[0033] According to the surface shape calculation system and method of the above embodiments, the sample to be tested is divided into N local regions. The surface shape calculation system includes N surface shape calculation devices. The N local regions of the sample to be tested are sequentially adjusted into the field of view of the interferometer for interferometric imaging. When the p-th local region of the sample to be tested is within the field of view of the interferometer, the p-th surface shape calculation device acquires the second interferogram of the p-th local region, calculates the surface shape of the p-th local region based on the second interferogram, and sends it to the stitching calculation device for stitching. That is, each surface shape calculation device calculates the surface shape of one local region, and finally stitches them together to obtain the complete surface shape of the sample to be tested. This can realize the parallel calculation of the surface shapes of each local region without waiting, improve the surface shape calculation efficiency, and shorten the detection cycle. Attached Figure Description
[0034] Figure 1 This is a schematic diagram of the structure of a surface calculation system according to one embodiment;
[0035] Figure 2 This is a schematic diagram illustrating the sub-aperture division of a large-diameter wafer in one embodiment;
[0036] Figure 3 This is a schematic diagram of wafer orientation adjustment;
[0037] Figure 4 for Figure 2 The surface features of five local regions of the wafer shown;
[0038] Figure 5 for Figure 4 The complete surface shape is formed by piecing together the surface shapes of the five local areas shown.
[0039] Figure 6 This is a schematic diagram of the structure of a surface calculation system according to another embodiment;
[0040] Figure 7 This is a graph showing the oscillation trend of the standard deviation c(t) of the midpoint depth as a function of time t in one embodiment.
[0041] Figure 8 This is a schematic diagram of the structure of the steady-state monitoring device and the surface calculation device in one embodiment;
[0042] Figure 9 This is a flowchart of a surface calculation method according to one embodiment. Detailed Implementation
[0043] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.
[0044] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.
[0045] The serial numbers assigned to components in this document, such as "first," "second," etc., are used only to distinguish the described objects and have no sequential or technical meaning. They should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "A plurality of" means two or more. Unless otherwise specified, the terms "connection" and "linkage" in this invention include both direct and indirect connections (linkages).
[0046] In this embodiment, the sample to be tested, such as a wafer, is divided into N local regions. Each local region is completely within the field of view of a single imaging session of the interferometer, and the N local regions may overlap. The N local regions are sequentially adjusted to the field of view of the interferometer, and interferometric imaging is performed sequentially to obtain the interferogram of each local region for surface shape calculation. Finally, the surface shapes of the N local regions are stitched together to obtain the complete surface shape of the sample to be tested. For example, the first local region is adjusted to the field of view of the interferometer, its interferogram is obtained, and its surface shape is calculated; then the second local region is adjusted to the field of view of the interferometer, its interferogram is obtained, and its surface shape is calculated; and so on, until the surface shapes of all N local regions are obtained and stitched together to obtain the complete surface shape of the sample to be tested. The interferometer can be a single Fizeau interferometer, a double Fizeau interferometer, etc., and is not limited thereto. N is an integer not less than 2.
[0047] Interferometric imaging can employ phase-shifting interferometric imaging techniques, such as the five-step phase-shifting method and the eight-step phase-shifting method. For each local region, multiple interferograms with different phase shifts are acquired using phase-shifting interferometric imaging. Based on these interferograms, the surface profile of the local region is calculated. For each local region, the interferometer performs multiple phase shifts, acquiring one interferogram for the local region after each phase shift. Finally, after all phase shifts are completed, multiple interferograms with different phase shifts are obtained.
[0048] Please refer to Figure 1 This application provides a surface shape calculation system in one embodiment, comprising N surface shape calculation devices 20, and a first sample to be tested. The p-th surface shape calculation device 20 is used to acquire a second interferogram of the p-th local region after the p-th local region of the first sample to be tested is within the field of view of the interferometer, calculate the surface shape of the p-th local region based on the second interferogram, and send the calculated surface shape of the p-th local region to a stitching calculation device for stitching to obtain the complete surface shape of the first sample to be tested. Here, p = 1, 2, ..., N. The stitching method can refer to relevant existing technologies, such as "Research on Sub-Aperture Stitching Detection Method" (Chen Yiwei, Doctoral Dissertation, University of Chinese Academy of Sciences, 2015.4) and "Research on Sub-Aperture Stitching Algorithm for Large-Aperture Plane Detection" (Wu Shixia, Master's Thesis, Xi'an University of Technology, 2013.4), etc.
[0049] like Figure 1 As shown, in some embodiments, one of the surface calculation devices 20 is connected to the detector 100 of the interferometer to acquire a second interferogram from the detector 100, for example... Figure 1The first surface model calculation device 20 is connected to the detector 100 of the interferometer. The remaining surface model calculation devices 20 are connected to the first one, which forwards the second interferogram to the corresponding surface model calculation device 20. This is because commonly used detectors such as CCD sensors have limited interfaces and cannot be connected to all surface model calculation devices individually; therefore, the second interferogram is forwarded through the first surface model calculation device. If the number of interfaces allows, other surface model calculation devices can also be connected to the detector 100 to directly obtain the second interferogram from the detector 100.
[0050] by Figure 2 Taking the wafer shown as an example, Figure 2 The 300mm large-diameter wafer is covered by five sub-apertures, resulting in five localized areas. (Reference) Figure 3 After the wafer is placed into the interference cavity, the first local region is parallel to the interferometer's reference mirror. At this time, the first surface shape calculation device 20 acquires the second interferogram of the first local region for surface shape calculation. Then, the wafer orientation is adjusted so that the second local region is parallel to the interferometer's reference mirror. At this time, the second surface shape calculation device 20 acquires the second interferogram of the second local region for surface shape calculation. The wafer orientation is adjusted again so that the third local region is parallel to the interferometer's reference mirror. At this time, the third surface shape calculation device 20 acquires the second interferogram of the third local region for surface shape calculation. Finally, the surface shapes of five local regions are obtained, as shown below. Figure 4 As shown, the data is sent to a splicing computing device for splicing to obtain the complete surface profile of the wafer, as shown. Figure 5 As shown.
[0051] This application uses N surface shape calculation devices to calculate the surface shape of N local regions respectively, and finally splices them together to obtain the complete surface shape of the sample to be tested. It can realize the parallel calculation of the surface shape of each local region without waiting, which improves the surface shape calculation efficiency of the wafer and shortens the detection cycle.
[0052] After the wafer-carrying chuck in the interferometer is fed into the interference cavity, a fixed waiting time is usually required to wait for the wafer to stabilize and for the wavelength of the laser to stabilize after phase shifting. This process involves a large amount of redundancy and is time-consuming. Moreover, under different environmental conditions, an unreasonable waiting time can easily lead to the acquisition of the interferogram before the wavelength is stable, resulting in increased calculation errors.
[0053] Please refer to Figure 6The surface shape calculation system in one embodiment of this application further includes a stable state monitoring device 10. The stable state monitoring device 10 is used to: after the p-th local region of the first sample to be tested is within the field of view of the interferometer, acquire the first interferogram of the p-th local region every time the interferometer performs a phase shift, determine whether the wavelength emitted by the interferometer has stabilized based on the first interferogram of the p-th local region, and send a second interferogram acquisition signal to the p-th surface shape calculation device 20 after the wavelength stabilizes.
[0054] The p-th surface shape calculation device 20 is used to respond to the second interferogram acquisition signal, acquire the second interferogram of the p-th local region, calculate the surface shape of the p-th local region based on the multiple second interferograms of the p-th local region acquired after the phase shift, and send the calculated surface shape of the p-th local region to the splicing calculation device for splicing to obtain the complete surface shape of the first test sample.
[0055] At this point, the steady-state monitoring device 10 can be directly connected to the detector 100 of the interferometer to obtain the first interferogram from the detector 100, and forward the second interferogram to the first surface calculation device 20, which in turn forwards the second interferogram to the corresponding surface calculation device 20. If the number of interfaces allows, each surface calculation device can also be connected to the detector 100 to directly obtain the second interferogram from the detector 100.
[0056] Taking the first local region as an example, after the first local region is within the field of view of the interferometer, the interferometer performs phase shifting. The stable state monitoring device 10 acquires the first interferogram and determines whether the wavelength emitted by the interferometer has stabilized based on the first interferogram. After the wavelength stabilizes, it sends a second interferogram acquisition signal to the first surface model calculation device 20. The first surface model calculation device 20 responds to the second interferogram acquisition signal and acquires the first second interferogram of the first local region. Then, the interferometer continues to perform phase shifting, and the stable state monitoring device 10 reacquires the first interferogram. Based on the first interferogram, it determines whether the wavelength emitted by the interferometer has stabilized. After the wavelength stabilizes, it sends a second interferogram acquisition signal to the first surface model calculation device 20. The first surface model calculation device 20 responds to the second interferogram acquisition signal and acquires the second second interferogram of the first local region. And so on. After the interferometer finishes phase shifting, the first surface model calculation device 20 acquires multiple second interferograms of the first local region and calculates the surface model of the first local region based on these second interferograms. Subsequently, the stable state monitoring device 10 or the main control device can control the interferometer to adjust the wafer orientation so that the second local region is within the field of view of the interferometer. Then, the interferometer continues to perform phase shifting. The stable state monitoring device 10 acquires the first interferogram of the second local region and determines whether the wavelength emitted by the interferometer has stabilized based on the first interferogram. After the wavelength stabilizes, a second interferogram acquisition signal is sent to the second surface calculation device 20. The second surface calculation device 20 acquires the second interferogram of the second local region and performs surface calculation of the second local region. This process is repeated until the surface calculation of all N local regions is completed.
[0057] In some embodiments, the stable state monitoring device 10 determines whether the wavelength emitted by the interferometer has stabilized by continuously acquiring multiple first interferograms of the p-th local region and calculating the bit depth of each first interferogram; calculating the fluctuation value of the bit depth based on the bit depth of the multiple first interferograms; if the fluctuation value is within a preset error band, it is determined that the wavelength emitted by the interferometer has stabilized.
[0058] The grayscale changes in the interferogram directly reflect its current stability. Bit depth refers to the number of binary bits (bits) used to store a single pixel, determining how many grayscale levels a pixel can represent. Therefore, changes in bit depth reflect the stability of the interferogram. In this embodiment, bit depth is used to determine the stability of the wavelength emitted by the interferometer. The fluctuation value of bit depth can be the standard deviation of bit depth, etc. The stable state monitoring device 10 continuously monitors the changes in the standard deviation of the bit depth of the first interferogram and can generate data in real time. Figure 7The graph shows the oscillation trend of the standard deviation c(t) of the bit depth as a function of time t. In the initial stage after phase shift, the bit depth is unstable and the standard deviation c(t) of the bit depth changes drastically with time t. Then it gradually stabilizes until it enters the preset error band, at which point it is determined that the wavelength emitted by the interferometer has stabilized.
[0059] In some embodiments, the steady state monitoring device 10 calculates the bit depth by bit depth unpacking, that is, by calculating the bit depth of each first interferogram in the following way: the steady state monitoring device 10 performs phase unpacking processing on each first interferogram to obtain the corresponding first phase map; based on the conversion relationship between phase and bit depth, the bit depth of each first interferogram is calculated according to the first phase map.
[0060] Essentially, this process extracts the wrapped phase (principal phase) that is periodically blurred by π / 2 or π / 4 from the first interferogram, and recovers the physically continuous, non-jumping true phase distribution. Then, through the conversion relationship between phase and depth, the actual depth information of the first interferogram is obtained. Specifically, the conversion relationship between phase and depth can be phase-optical path difference-depth. The accuracy of depth unpacking directly determines the reliability of subsequent calculations of parameters such as surface shape, and is the core bridge connecting the interferogram and quantitative measurement results.
[0061] The above embodiments, by setting up a stable state monitoring device to monitor whether the wavelength emitted by the interferometer has stabilized, can ensure that the second interferogram of the sample under test is obtained only after the wavelength has stabilized. At the same time, it can avoid the problem of long redundancy time caused by waiting for a fixed time, thereby improving the efficiency and accuracy of surface calculation.
[0062] The surface shape calculation device 20, the splicing calculation device, and the stable state monitoring device 10 are respectively used for surface shape calculation, splicing the surface shapes of N local regions, and monitoring the wavelength stability, and are examples of such computing devices, such as servers and computers. In some embodiments, the stable state monitoring device 10 and the surface shape calculation device 20 have the same structure. Please refer to... Figure 8 In some embodiments, the stable state monitoring device 10 and the surface shape calculation device 20 include a central processing unit (CPU), a graphics processing unit (GPU), and a data acquisition card. The data acquisition card is used to receive the interferogram output by the detector 100. After the sample under test enters the interferometer cavity, the data acquisition card can perform high-speed image acquisition and transmit the acquired interferogram to the GPU for wavelength stability determination or surface shape calculation. The data acquisition card and the GPU can transmit the interferogram via a PCIe bus. In some embodiments, the detector 100 is connected to the data acquisition card of the stable state monitoring device 10 via a CXP bus to transmit the interferogram. The data acquisition card of the stable state monitoring device 10 can also be connected to the data acquisition card of the first surface shape calculation device 20, and the data acquisition card of the first surface shape calculation device 20 can also be connected to the data acquisition cards of other surface shape calculation devices 20 via a CXP bus.
[0063] In some embodiments, the first interferogram is a single-pixel interferogram, which can minimize the exposure time and the transmission delay of the first interferogram to the steady state monitoring device 10 and further to the GPU, thereby improving the efficiency of surface calculation.
[0064] For surface shape calculation, taking a dual-Fizeau interferometer as an example, before measuring the sample, a cavity image is first taken. That is, the sample is not placed in the interference cavity, and phase-shifting interferometry is performed in the cavity state. The left and right detectors of the interferometer simultaneously acquire the cavity interferogram (when there is no sample, the reference mirror and the cavity reflecting surface form interference), completing the system error calibration. Next, the sample is placed in the interference cavity, keeping the optical path and parameters unchanged, and phase-shifting interferometry is performed on the sample. The left and right detectors simultaneously acquire the second interferograms of the front and back surfaces of the sample. Each detector also acquires a preset number of frames, saving them as a sample interferogram dataset. Taking the five-step phase-shifting method as an example, five second interferograms of the front and back surfaces of the sample are acquired. The original phase of the front surface (related to the front of the sample), the original phase of the back surface (related to the back of the sample), and the original phase of the cavity (related to the system error) are calculated respectively. The calculation formulas are as follows:
[0065] ,
[0066] Where (x,y) represents the coordinates of the pixel, and φ(x,y) refers to the original phase of the front side, the original phase of the back side, or the original phase of the cavity at coordinates (x,y). , , , and These are five interferograms acquired in sequence.
[0067] Due to the periodicity of the arctangent function, the calculated original phase is a wrapped phase (range [-π, π]), requiring phase unwrapping processing. This can be achieved using the branching method or the least squares method to eliminate the phase wrapping phenomenon and obtain a continuous phase. For the front and back continuous phases, subtract them from the cavity continuous phase to deduct systematic errors, obtaining the true front and back phases. Combining the true front and back phases with the optical path characteristics of the dual Fizeau interferometer, the front and back surface profiles of the wafer are calculated.
[0068] In some embodiments, the splicing computing device is a stable state monitoring device 10, or the splicing computing device is an independent device that is different from the stable state monitoring device 10 and the N surface type computing devices 20.
[0069] In some embodiments, the sample to be tested also includes a second sample to be tested. After the Nth surface model calculation device 20 acquires the second interferogram of the Nth local region of the first sample to be tested, the second sample to be tested is switched into the interferometer cavity for measurement. If the stitching calculation device is a stable state monitoring device 10, then during the stitching process of the surface model of the N local regions of the first sample to be tested, and after the first local region of the second sample to be tested is within the field of view of the interferometer, the stable state monitoring device 10 acquires the first interferogram of the first local region of the second sample to be tested whenever the interferometer performs a phase shift. Based on the first interferogram of the first local region of the second sample to be tested, it determines whether the wavelength has stabilized. After the wavelength stabilizes, it sends a second interferogram acquisition signal to the first surface model calculation device 20, so that the first surface model calculation device 20 acquires the second interferogram of the first local region of the second sample to be tested.
[0070] That is, the steady state monitoring device 10 can monitor the wavelength stability of the next sample to be tested while splicing, thereby improving the detection efficiency; at this time, the computing power of the N surface calculation devices is also released, that is, the computing power peaks of the steady state monitoring device and the N surface calculation devices avoid each other, ensuring the efficient operation of the calculation.
[0071] If the splicing calculation device is an independent device, then after all N surface calculation devices 20 have completed the surface calculation and the first local region of the second test sample is within the field of view of the interferometer, the stable state monitoring device 10 acquires the first interferogram of the first local region of the second test sample every time the interferometer performs a phase shift. Based on the first interferogram of the first local region of the second test sample, it determines whether the wavelength has stabilized. After the wavelength stabilizes, it sends the second interferogram acquisition signal to the first surface calculation device.
[0072] If the splicing calculation device is an independent device, then as long as all the surface calculation devices 20 have completed the calculation, the stability monitoring device 10 can perform wavelength stability monitoring of the next sample to be tested.
[0073] Based on the above-described surface calculation system, this application also provides a surface calculation method, please refer to... Figure 9 The surface calculation method of this application includes steps S10 to S50, which are described below.
[0074] Step S10: Place the first sample to be tested into the interference cavity of the interferometer, so that its first local region is within the field of view of the interferometer. Then, the interferometer begins phase shifting.
[0075] Step S20: Whenever the interferometer performs a phase shift, the first interferogram of the first local region is acquired by the stable state monitoring device 10. Based on the first interferogram of the first local region, it is determined whether the wavelength emitted by the interferometer has stabilized. After the wavelength stabilizes, a second interferogram acquisition signal is sent to the first surface model calculation device 20. The first surface model calculation device 20 responds to the second interferogram acquisition signal and acquires the second interferogram of the first local region. The first interferogram can be a single-pixel interferogram.
[0076] For instructions on how to determine whether the wavelength emitted by the interferometer has stabilized, please refer to the relevant explanation above.
[0077] Step S30: After the interferometer finishes phase shifting, the first surface shape calculation device 20 calculates the surface shape of the first local region based on multiple second interferograms of the first local region, and sends the calculated surface shape of the first local region to the splicing calculation device.
[0078] For the calculation method of the face shape, please refer to the relevant instructions above.
[0079] Step S40: Repeat the local region surface calculation step until the surface of all N local regions is obtained.
[0080] The local area surface shape calculation steps include: adjusting the orientation of the first sample to be tested so that the next local area is within the field of view of the interferometer; each time the interferometer performs a phase shift, the first interferogram of the next local area is acquired through the stable state monitoring device 10, and the wavelength is determined based on the first interferogram of the next local area to determine whether the wavelength has stabilized. After the wavelength stabilizes, a second interferogram acquisition signal is sent to the next surface shape calculation device 20; the next surface shape calculation device 20 responds to the second interferogram acquisition signal and acquires the second interferogram of the next local area; after the interferometer finishes phase shifting, the next surface shape calculation device 20 calculates the surface shape of the next local area based on multiple second interferograms of the next local area, and sends the calculated surface shape of the next local area to the splicing calculation device.
[0081] Step S50: The splicing calculation device receives the surface patterns of N local regions sent by N surface pattern calculation devices 20 respectively and splices them to obtain the complete surface pattern of the first test sample.
[0082] In some embodiments, the sample to be tested further includes a second sample to be tested. The surface shape calculation method also includes:
[0083] After the Nth surface calculation device 20 acquires the second interferogram of the Nth local region of the first test sample, the second test sample is switched into the interferometer cavity of the interferometer so that its first local region is within the field of view of the interferometer.
[0084] If the splicing calculation device is a stable state monitoring device 10, then during the splicing process of the surface patterns of N local regions of the first test sample, the stable state monitoring device 10 also acquires the first interferogram of the first local region of the second test sample after each phase shift of the interferometer, and determines whether the wavelength has stabilized based on the first interferogram of the first local region of the second test sample. After the wavelength stabilizes, it sends the second interferogram acquisition signal to the first surface pattern calculation device 20.
[0085] If the splicing calculation device is an independent device, after all N surface calculation devices 20 have completed the surface calculation, the stable state monitoring device 10 acquires the first interferogram of the first local region of the second test sample after each phase shift of the interferometer. Based on the first interferogram of the first local region of the second test sample, it determines whether the wavelength has stabilized. After the wavelength stabilizes, it sends the second interferogram acquisition signal to the first surface calculation device 20.
[0086] The surface shape calculation system and method provided in this application embodiment are as follows: the sample to be tested is divided into N local regions. The surface shape calculation system includes N surface shape calculation devices. When the p-th local region of the sample to be tested is within the field of view of the interferometer, the p-th surface shape calculation device acquires the second interferogram of the p-th local region, calculates the surface shape of the p-th local region based on the second interferogram, and sends it to the stitching calculation device for stitching. That is, each surface shape calculation device calculates the surface shape of one local region, and finally stitches them together to obtain the complete surface shape of the sample to be tested. This can realize the parallel calculation of the surface shapes of each local region without waiting, improve the surface shape calculation efficiency, and shorten the detection cycle.
[0087] In some embodiments, the surface shape calculation system also includes a stability monitoring device for detecting the stability of the wavelength emitted by the interferometer. After confirming that the wavelength emitted by the interferometer is stable, the stability monitoring device triggers the surface shape calculation device to acquire a second interferogram of a local area. This ensures that the second interferogram of the sample under test is acquired only after the wavelength is stable, and avoids the problem of long redundancy time caused by waiting for a fixed time, thereby improving the efficiency and accuracy of surface shape calculation.
[0088] In the above embodiments, implementation can be achieved, in whole or in part, by software, hardware, firmware, or any combination thereof. Furthermore, as those skilled in the art will understand, the principles herein can be reflected in a computer program product on a computer-readable storage medium pre-loaded with computer-readable program code. Any tangible, non-transitory computer-readable storage medium may be used, including magnetic storage devices (hard disks, floppy disks, etc.), optical storage devices (CDs, DVDs, Blu-ray discs, etc.), flash memory, and / or the like. These computer program instructions can be loaded onto a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to form a machine, such that instructions executing on the computer or other programmable data processing apparatus can generate means for performing a specified function. These computer program instructions can also be stored in a computer-readable storage medium that can instruct the computer or other programmable data processing apparatus to operate in a particular manner, such that instructions stored in the computer-readable storage medium can form an article of manufacture, including means for implementing the specified function. The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to perform a series of operational steps on the computer or other programmable apparatus to produce a computer-implemented process, such that instructions executing on the computer or other programmable apparatus can provide steps for implementing the specified function.
[0089] This document describes various exemplary embodiments with reference to them. However, those skilled in the art will recognize that changes and modifications can be made to the exemplary embodiments without departing from the scope of this document. For example, various operational steps and components for performing operational steps can be implemented in different ways depending on the specific application or considering any number of cost functions associated with the operation of the system (e.g., one or more steps can be deleted, modified, or combined with other steps).
[0090] While the principles herein have been illustrated in various embodiments, numerous modifications to the structures, arrangements, proportions, elements, materials, and components, particularly suited to specific environments and operational requirements, may be used without departing from the principles and scope of this disclosure. These modifications and other alterations or alterations will be included within the scope of this document. Those skilled in the art will recognize that many changes can be made to the details of the above embodiments without departing from the fundamental principles of the invention.
Claims
1. A surface shape calculation system for calculating the surface shape of a sample to be tested, characterized in that, The sample to be tested is divided into N local regions, and the N local regions are sequentially adjusted to the field of view of the interferometer for phase-shifting interferometric imaging. The sample to be tested includes a first sample to be tested. The surface model calculation system includes a stable state monitoring device and N surface model calculation devices, where N is an integer not less than 2. The stable state monitoring device is used to: after the p-th local region of the first sample under test is within the field of view of the interferometer, acquire the first interferogram of the p-th local region every time the interferometer performs a phase shift, determine whether the wavelength emitted by the interferometer has stabilized based on the first interferogram of the p-th local region, and send a second interferogram acquisition signal to the p-th surface calculation device after the wavelength has stabilized; wherein, the first interferogram is a single-pixel interferogram, p=1, 2...N; The p-th surface shape calculation device is used to respond to the second interferogram acquisition signal, acquire the second interferogram of the p-th local region, calculate the surface shape of the p-th local region based on the multiple second interferograms of the p-th local region acquired after phase shift, and send the calculated surface shape of the p-th local region to the stitching calculation device for stitching to obtain the complete surface shape of the first test sample.
2. The surface calculation system as described in claim 1, characterized in that, The splicing calculation device is the stable state monitoring device, or the splicing calculation device is an independent device that is different from the stable state monitoring device and the N surface calculation devices.
3. The surface shape calculation system as described in claim 2, characterized in that, The sample to be tested also includes a second sample to be tested; If the splicing calculation device is the stable state monitoring device, then during the process of splicing the surface patterns of N local regions of the first test sample, after the first local region of the second test sample is within the field of view of the interferometer, the stable state monitoring device acquires the first interferogram of the first local region of the second test sample every time the interferometer performs a phase shift. Based on the first interferogram of the first local region of the second test sample, it determines whether the wavelength has stabilized. After the wavelength stabilizes, it sends a second interferogram acquisition signal to the first surface pattern calculation device. If the splicing calculation device is the independent device, then after all N surface calculation devices have completed the surface calculation and the first local region of the second test sample is within the field of view of the interferometer, the stable state monitoring device acquires the first interferogram of the first local region of the second test sample every time the interferometer performs a phase shift. Based on the first interferogram of the first local region of the second test sample, it determines whether the wavelength has stabilized. After the wavelength stabilizes, it sends a second interferogram acquisition signal to the first surface calculation device.
4. The surface calculation system as described in any one of claims 1 to 3, characterized in that, The stability monitoring device determines whether the wavelength emitted by the interferometer has stabilized using the following method: The stable state monitoring device continuously acquires multiple first interferograms of the p-th local region and calculates the bit depth of each first interferogram; The fluctuation value of the bit depth is calculated based on the bit depth of the multiple first interferograms. If the fluctuation value is within the preset error band, it is determined that the wavelength emitted by the interferometer has stabilized.
5. The surface calculation system as described in claim 4, characterized in that, The steady-state monitoring device calculates the bit depth of each first interferogram in the following manner: The steady-state monitoring device performs phase unpacking processing on each first interferogram to obtain the corresponding first phase map; Based on the conversion relationship between phase and depth, the depth of each first interferogram is calculated according to the first phase diagram.
6. A method for calculating surface profile, used to calculate the surface profile of a sample to be tested, characterized in that, The sample to be tested is divided into N local regions, and the sample to be tested includes a first sample to be tested, where N is an integer not less than 2. The surface shape calculation method includes: The first sample to be tested is placed in the interference cavity of the interferometer, so that its first local area is within the field of view of the interferometer; Whenever the interferometer performs a phase shift, a first interferogram of the first local region is acquired by a stable state monitoring device. Based on the first interferogram of the first local region, it is determined whether the wavelength emitted by the interferometer has stabilized. After the wavelength stabilizes, a second interferogram acquisition signal is sent to a first surface model calculation device. The first surface model calculation device responds to the second interferogram acquisition signal and acquires a second interferogram of the first local region. The first interferogram is a single-pixel interferogram. After the interferometer finishes phase shifting, the first surface shape calculation device calculates the surface shape of the first local region based on multiple second interferograms of the first local region, and sends the calculated surface shape of the first local region to the stitching calculation device; The local region surface shape calculation steps are repeated until the surface shapes of all N local regions are obtained. The local region surface shape calculation steps include: adjusting the orientation of the first sample to be tested so that the next local region is within the field of view of the interferometer; each time the interferometer performs a phase shift, the first interferogram of the next local region is acquired through the stable state monitoring device; based on the first interferogram of the next local region, it is determined whether the wavelength has stabilized; after the wavelength stabilizes, a second interferogram acquisition signal is sent to the next surface shape calculation device; the next surface shape calculation device responds to the second interferogram acquisition signal and acquires the second interferogram of the next local region; after the interferometer finishes the phase shift, the next surface shape calculation device calculates the surface shape of the next local region based on multiple second interferograms of the next local region, and sends the calculated surface shape of the next local region to the stitching calculation device. The splicing calculation device receives the surface patterns of the N local regions sent by the N surface pattern calculation devices respectively and splices them to obtain the complete surface pattern of the first sample to be tested.
7. The surface shape calculation method as described in claim 6, characterized in that, The splicing calculation device is the stable state monitoring device, or the splicing calculation device is an independent device that is different from the stable state monitoring device and the N surface calculation devices.
8. The surface shape calculation method as described in claim 7, characterized in that, The sample to be tested also includes a second sample to be tested; The surface shape calculation method also includes: After the Nth local region of the first sample under test is obtained by the Nth surface calculation device, the second sample under test is switched into the interferometer cavity of the interferometer so that its first local region is within the field of view of the interferometer. If the splicing calculation device is the stable state monitoring device, then during the process of splicing the surface patterns of N local regions of the first test sample, the stable state monitoring device also acquires the first interferogram of the first local region of the second test sample after each phase shift of the interferometer, and determines whether the wavelength has stabilized based on the first interferogram of the first local region of the second test sample. After the wavelength stabilizes, it sends the second interferogram acquisition signal to the first surface pattern calculation device. If the splicing calculation device is the independent device, after all N surface calculation devices have completed the surface calculation, the stability monitoring device acquires the first interferogram of the first local region of the second sample under test after each phase shift of the interferometer, determines whether the wavelength has stabilized based on the first interferogram of the first local region of the second sample under test, and sends the second interferogram acquisition signal to the first surface calculation device after the wavelength has stabilized.
Citation Information
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Computer visualization sub-aperture splicing method based on positioning mark
CN115560698A