System and method for measuring deep trench etch structure in 3D NAND

Abstract

The application relates to the field of semiconductor measurement technology, and particularly provides a system and method for measuring a deep trench etching structure in a 3D NAND, aiming at improving a traditional CD-SAXS measurement unit, designing a phase grating on an optical path before probe light is incident on a measured sample, and based on Talbot effect and fractional Talbot effect, the distance between the phase grating and the measured sample is designed as Talbot distance or fractional Talbot distance; the probe light is modulated through the phase grating, so that the probe light intensity distribution irradiated to the sample presents a bright and dark stripe distribution related to the grating structure period and duty cycle; then, through an alignment mechanism, the bright stripe of the incident light beam is aligned to the deep trench etching structure region in the 3D NAND to be measured, and the dark stripe is aligned to the memory hole structure region, so that the light intensity incident to the deep trench etching structure part is enhanced, the light intensity incident to the memory hole part is weakened, and the difficulty of extracting the deep trench nanostructure scattering signal from the total scattering signal is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor measurement technology, specifically providing a system and method for measuring deep trench etched structures in 3D NAND. Background Technology

[0002] 3D-NAND is currently the most widely used non-volatile memory chip, and it is widely used in storage devices of electronic products. For example... Figure 1 As shown, memory holes and slits are essential structures for 3D-NAND. Memory holes are used for signal storage, while slits are used in the 3D-NAND fabrication process to replace silicon oxynitride with tungsten to form the final gate. The critical dimensions (CD) of both memory hole and slit structures have a crucial impact on the performance and yield of 3D-NAND chips.

[0003] Since the invention of 3D-NAND, flash memory manufacturers have been pursuing increased areal density of 3D-NAND memory devices within the same chip area, thereby reducing the cost per bit. In recent years, the development trend of 3D-NAND has been to gradually increase the arrangement period of deep trench etching structures while keeping the arrangement period of memory holes unchanged, thereby increasing the overall storage density of the chip within the same chip area.

[0004] In 3D-NAND, both the via structures and deep trench etched structures have high aspect ratios, posing significant challenges to metrology. Furthermore, with the development of 3D-NAND, the number of stacked layers increases, further increasing the aspect ratio and escalating the metrology challenges. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and optical critical dimensioning (OCD) are commonly used metrology methods for 3D-NAND via and deep trench etched structures. However, SEM and TEM are destructive metrology techniques, expensive and time-consuming, and provide limited statistical feedback for precise process control. With the increasing aspect ratio of 3D-NAND structures, the accuracy of OCD measurements faces increasing challenges.

[0005] Critical Dimension Small Angle X-ray Scattering Measurement (CD-SAXS) is an emerging non-destructive measurement technique for high aspect ratio structures in 3D-NAND. High-energy X-rays penetrate the memory holes and deep trench periodic structures of 3D-NAND chips, generating X-ray scattering patterns. Based on these scattering patterns, the critical dimensions of the memory holes and deep trench etched structures can be accurately determined. Due to the short wavelength of X-rays, CD-SAXS offers unique advantages for the precise measurement of memory holes and deep trench etched structures in 3D-NAND.

[0006] In 3D NAND manufacturing processes, the memory via structure already exists during the deep trench etching process. Therefore, the signal detected by CD-SAXS includes both the scattering signals generated by the periodic structure of the deep trench etching and the scattering signals generated by the periodic structure of the memory via. However, because the density of the deep trench etching structure is much lower than that of the memory via structure, the scattering signal from the deep trench etching structure is greatly interfered with by the scattering signal from the memory via. Figure 2 and Figure 3 As shown, in order to determine the precise dimensions of the deep trench etched structure in 3D NAND, it is necessary to separate and extract the scattering signal corresponding to the deep trench nanostructure from the total scattering signal.

[0007] As 3D NAND manufacturing processes have advanced, flash memory manufacturers, in order to increase the areal density of 3D-NAND memory devices within the same chip area, have gradually increased the arrangement period of deep trench etching structures while keeping the arrangement period of the memory via structure unchanged. This allows them to increase the overall storage density of the chip within the same chip area. However, this has also led to a further reduction in the density of deep trench etching structures. When using existing CD-SAXS systems to measure deep trench etching structures in 3D NAND, the signals belonging to deep trench etching structures in the scattered signals acquired by the CD-SAXS detection system become much weaker. This makes it more difficult for the CD-SAXS algorithm system to accurately separate and extract the scattered signals corresponding to deep trench etching structures from the total scattered signal. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a system and method for measuring deep trench etched structures in 3D NAND. By adding a phase grating, the intensity of X-rays incident on the deep trench etched structure in 3D NAND is increased, while the intensity of X-rays incident on the memory hole structure in 3D NAND is reduced. This effectively solves the problem of accurately separating the scattering signal corresponding to the deep trench etched structure from the CD-SAXS measurement results.

[0009] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0010] On one hand, the system for measuring deep trench etched structures in 3D NAND provided by the present invention includes:

[0011] A light source assembly for providing probe light for CD-SAXS measurements;

[0012] A multi-degree-of-freedom sample stage is used to hold the sample to be tested;

[0013] The detection component is used to collect the scattered signal generated after the detection light shines on the sample under test;

[0014] A phase grating is placed on the optical path of the probe light provided by the CD-SAXS measurement unit before it is incident on the sample to be measured, and is used to modulate the probe light.

[0015] Preferably, it further includes: a vacuum collimation component disposed between the light source component and the multi-degree-of-freedom sample stage, and a vacuum scattering component disposed between the multi-degree-of-freedom sample stage and the detection component.

[0016] Preferably, the detection light provided by the light source assembly is X-ray.

[0017] Preferably, the vacuum collimation assembly includes a vacuum chamber and at least one slit disposed outside the vacuum chamber.

[0018] Preferably, the vacuum collimation assembly includes three slits, wherein two slits are disposed inside the vacuum chamber and one slit is disposed outside the vacuum chamber.

[0019] Preferably, the phase grating is disposed between the vacuum cavity and the slit disposed outside the vacuum cavity.

[0020] Preferably, the multi-degree-of-freedom sample stage can drive the sample under test to move along the X, Y and Z axes, and drive the sample under test to deflect at an angle relative to the probe light.

[0021] Preferably, the detection component includes a two-dimensional array X-ray detector.

[0022] Preferably, the distance between the phase grating and the sample under test is the Talbot distance or a fractional Talbot distance.

[0023] Preferably, Talbot distance The formula for calculation is:

[0024] ;

[0025] in, The period of the phase grating. To detect the wavelength of light;

[0026] Score Talbot distance The formula for calculation is:

[0027] ;

[0028] in, This indicates the Talbot diffraction order, which is the order of the fractional Talbot distance.

[0029] Preferably, when the distance between the phase grating and the sample under test is the Talbot distance, the period of the phase grating is equal to the period of the deep trench etched structure of the sample under test, and the linewidth of the phase grating without phase delay is equal to the linewidth of the deep trench etched structure of the sample under test.

[0030] Preferably, when the distance between the phase grating and the sample under test is a fractional Talbot distance of order m, the period of the phase grating is equal to m times the period of the deep trench etched structure of the sample under test, and the linewidth of the phase grating without phase delay is equal to m times the linewidth of the deep trench etched structure of the sample under test.

[0031] On the other hand, the method for measuring deep trench etched structures in 3D NAND provided by the present invention includes:

[0032] Provide a CD-SAXS measurement device, and set a phase grating in the optical path before the probe light provided by the CD-SAXS measurement device is incident on the sample under test;

[0033] By modulating the probe light with a phase grating, the intensity of the probe light incident on the deep trench etched structure of the sample under test is increased, while the intensity of the probe light incident on the memory hole structure of the sample under test is decreased.

[0034] Preferably, a phase grating is disposed on the optical path before the probe light provided by the CD-SAXS measurement device is incident on the sample under test, and the distance between the phase grating and the sample under test is a Talbot distance or a fractional Talbot distance.

[0035] Preferably, when the distance between the phase grating and the sample under test is the Talbot distance, the period of the phase grating is equal to the period of the deep trench etched structure of the sample under test, and the linewidth of the phase grating without phase delay is equal to the linewidth of the deep trench etched structure of the sample under test.

[0036] Preferably, when the distance between the phase grating and the sample under test is a fractional Talbot distance of order m, the period of the phase grating is equal to m times the period of the deep trench etched structure of the sample under test, and the linewidth of the phase grating without phase delay is equal to m times the linewidth of the deep trench etched structure of the sample under test.

[0037] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0038] This invention adds a phase grating for X-ray probe light to a traditional CD-SAXS measurement system. Utilizing the Talbot effect of the phase grating, it achieves precise control of the light intensity distribution on the sample measurement plane, enhancing the X-ray intensity incident on the deep groove etched structure in the 3DNAND and reducing the X-ray intensity incident on the memory hole structure. This suppresses the intensity of the scattered signal from the memory hole nanostructure during measurement, increases the proportion of the scattered signal from the deep groove etched structure, and reduces the difficulty of accurately extracting the scattered signal corresponding to the deep groove nanostructure, thereby improving the accuracy and reliability of the measurement.

[0039] Furthermore, the design of phase gratings can follow either Talbot imaging or fractional Talbot imaging techniques, making phase grating design more flexible. When the period of deep trench etching structure is extremely small, grating parameter design based on fractional Talbot imaging can greatly reduce the difficulty of grating processing. This allows the system of the present invention to adapt to the characteristics of different 3D NAND nano-etched structures, with good adaptability and flexibility, and to cope with changes in different processes and structures. Attached Figure Description

[0040] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0041] Figure 1 This is a schematic diagram of a 3D NAND structure provided in the background technology;

[0042] Figure 2 The background section describes the scattering and superposition pattern of the memory hole and deep trench etched structure.

[0043] Figure 3 This is a scattering pattern in the background technology when only deep trench etching structures are used;

[0044] Figure 4 This is a schematic diagram of a system for measuring deep trench etched structures in 3D NAND according to an embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of the phase grating, the light intensity of the grating Talbot image, and the distribution of the Slits structure under the Talbot distance condition provided in the embodiments of the present invention;

[0046] Figure 6 This is a schematic diagram of the phase grating, the light intensity of the grating Talbot image, and the distribution of the Slits structure under fractional Talbot distance conditions according to an embodiment of the present invention.

[0047] The reference numerals in the figures include:

[0048] Deep trench etching structure 10, memory hole structure 20;

[0049] Light source assembly 1, vacuum collimation assembly 2, vacuum cavity 21, first slit 22, second slit 23, third slit 24, multi-degree-of-freedom sample stage 3, vacuum scattering assembly 4, detection assembly 5, phase grating 6. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. 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, some operations related to the 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.

[0051] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0052] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0053] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0055] When measuring 3D NAND using existing CD-SAXS metrology equipment, the total scattering signal obtained simultaneously includes scattering signals from deep trench etched structures and memory hole structures. To accurately extract and separate the scattering signal corresponding to the deep trench etched structure from the total scattering signal, an embodiment of this invention proposes a method for measuring deep trench etching in 3D NAND, specifically including the following steps:

[0056] First, an existing CD-SAXS metrology device is provided. This device is used to measure a 3D NAND structure. The scattered signal measured directly by the CD-SAXS metrology device contains a high proportion of the signal from the 3D NAND's memory hole structure. Therefore, this embodiment proposes adding a phase grating to the existing CD-SAXS metrology device to modulate the probe light. This phase grating modulates the intensity distribution of the probe light incident on the surface of the sample, enhancing the intensity of the probe light incident on the deep trench etched structure of the sample and weakening the intensity of the probe light incident on the memory hole structure. This increases the proportion of the scattered signal obtained from the deep trench etched structure in the total scattered signal obtained by the CD-SAXS metrology device.

[0057] Specifically, in order to achieve precise modulation of the probe light, this embodiment of the invention designs a phase grating based on the Talbot effect and the fractional Talbot effect. This mainly requires designing the position of the phase grating in the CD-SAXS measurement optical path, as well as the period and linewidth of the phase grating. Firstly, the phase grating must be placed in the optical path before the probe light is incident on the sample. Furthermore, since the probe light is an X-ray, a monochromatic plane wave, the Talbot effect demonstrates that for periodic objects, if illuminated with a monochromatic plane wave, an image of the object will be observed at periodic distances in the light field behind the object. That is, after the probe light is processed by the phase grating, the intensity distribution of the probe light illuminating the surface of the sample is no longer continuously uniform, but rather presents as bright and dark stripes related to the structural period and duty cycle of the phase grating. Therefore, a phase grating can be set in the optical path, and the distance between the phase grating and the sample under test can be adjusted so that the distance between the phase grating and the sample under test is the Talbot distance or a fraction of the Talbot distance. In this process, the position of the phase grating in the optical path can be adjusted, and the position of the sample under test can also be adjusted appropriately.

[0058] In practice, it is also necessary to design a matching phase grating based on the cycle and size of the deep trench etching structure of the 3D NAND in a specific semiconductor manufacturing line. Specifically, the parameters of the phase grating are designed based on the deep trench etching structure parameters of the sample under test.

[0059] Talbot distance The formula for calculation is:

[0060] ;

[0061] in, The period of the phase grating. To detect the wavelength of light.

[0062] When the distance between the phase grating and the sample under test is the Talbot distance, the period of the phase grating is designed to be equal to the period of the deep trench etched structure of the sample under test. The linewidth of the phase grating in the non-phase delay part is designed to correspond to and be equal to the linewidth of the deep trench etched structure of the sample under test. It can be understood that "corresponding to and being equal" here means that if the linewidth of the deep trench etched structure of the sample under test is uniformly designed, then the linewidth of the phase grating in the non-phase delay part is also uniformly designed, and the two are equal; if the linewidth of the deep trench etched structure of the sample under test is not uniformly designed, the linewidth of the phase grating in the non-phase delay part is also not uniformly designed, and it corresponds one-to-one with the linewidth of the deep trench etched structure of the sample under test.

[0063] Score Talbot distance The formula for calculation is:

[0064] ;

[0065] in, This indicates the Talbot diffraction order, which is the order of the fractional Talbot distance.

[0066] When the distance between the phase grating and the sample under test is a fractional Talbot distance, the period of the phase grating is related to the order of the fractional Talbot distance. Assuming the order of the fractional Talbot distance is m, the period of the phase grating is designed to be m times the period of the deep trench etching structure of the sample under test. That is, the period of the phase grating is m times the period of the deep trench etching structure. The advantage of this design is that when the period of the deep trench etching structure of the sample under test is extremely small, the fabrication difficulty of the phase grating can be reduced. For example, if the period of the deep trench etching structure in the 3D NAND etched structure of the sample under test is 3 micrometers, if a Talbot distance design is used, the period of the phase grating also needs to be fabricated to 3 micrometers. However, with the current level of X-ray grating fabrication technology, fabricating a phase grating with a period of 3 micrometers is extremely difficult and costly, and even if successfully fabricated, the corresponding accuracy is low. Therefore, if a third-order fractional Talbot distance is chosen, i.e. Therefore, the period of the phase grating can be fabricated to 9 micrometers, which can greatly reduce the difficulty of grating fabrication. Correspondingly, the linewidth of the phase grating without phase delay also needs to be designed to be equal to m times the linewidth of the deep trench etched structure of the sample under test.

[0067] The above process can suppress the scattering signal of the memory hole structure in the measurement results. Finally, through the alignment mechanism, the position of the sample under test perpendicular to the direction of the probe light is adjusted so that the bright stripes of the striped beam after the probe light is processed by the phase grating are aligned with the deep trench etched structure area in the 3D NAND of the sample under test, and the dark stripes are aligned with the memory hole structure area in the 3D NAND of the sample under test. Finally, the scattering signal of the extracted deep trench etched structure is obtained by the detection component of the CD-SAXS measurement device. The parameters of the deep trench etched structure can be calculated more accurately through this scattering signal.

[0068] Based on the above method for measuring deep trench etched structures in 3D NAND, this invention also provides a system for measuring deep trench etched structures in 3D NAND. Please refer to [link / reference] for details. Figure 4The system includes a CD-SAXS measurement unit and a phase grating 6. The CD-SAXS measurement unit comprises, sequentially arranged along the probe light propagation path, a light source assembly 1, a vacuum collimation assembly 2, a multi-degree-of-freedom sample stage 3, a vacuum scattering assembly 4, and a probe assembly 5. The light source assembly 1 provides the probe light and contains optical devices such as a monochromator and collimator. The monochromator pre-collimates and monochromates the X-rays, ensuring that the probe light emitted from the light source assembly 1 is a quasi-monochromatic and quasi-parallel X-ray beam. The probe light emitted from the light source assembly 1 enters the vacuum collimation assembly 2, which further improves the collimation of the probe light and achieves precise control of the beam spot size. Specifically, the vacuum collimation assembly 2 structurally includes a slit system and a vacuum cavity 21. The slit system includes a first slit 22, a second slit 23, and a third slit 24. The first slit 22 and the second slit 23 are located inside the vacuum cavity. The first slit 22, the second slit 23, and the optical path between them are all in a vacuum environment. The first slit 22 and the second slit 23 can collimate the probe light entering the vacuum collimation assembly 2 and ensure that the probe light is transmitted in a vacuum environment, reducing the attenuation effect of air on X-rays. The third slit 24 is located on the subsequent optical path of the first slit 22 and the second slit 23, that is, outside the vacuum cavity 21. After the probe light exits through the third slit 24, it illuminates the multi-degree-of-freedom sample stage 3, which carries the sample under test. The multi-degree-of-freedom sample stage 3 is a high-precision multi-degree-of-freedom turntable with high-precision X, Y, and Z motion axes and rotation axes. It is part of the CD-SAXS measurement unit Stage system, and can achieve high-precision displacement and rotation in the X, Y, and Z directions through the multi-degree-of-freedom sample stage 3. It can be understood that the multi-degree-of-freedom sample stage 3 can achieve precise positioning of any point on the sample under test, ensuring that any point on the sample surface is at the measurement point position, i.e., the incident position of the probe light. Simultaneously, it can drive the sample under test to perform angular deflection scanning relative to the optical path axis, adjusting the angle between the plane of the sample under test and the incident angle of the probe light. The vacuum scattering component 4 is a high-vacuum cavity used to transmit the scattered signal obtained from the surface of the sample under test to the detection component 5, reducing the attenuation of the scattered signal by air during transmission. The detection component 5 mainly consists of a two-dimensional array X-ray detector, which is used to detect the scattering signal of the sample under test and to perform CD-SAXS measurement based on the intensity and angular distribution information of the scattering signal.

[0069] To enhance the scattered signal corresponding to the 3D NAND deep trench etched structure in the scattered signal acquired by the detection component 5, this embodiment of the invention adds an X-ray phase grating 6 between the second slit 23 and the third slit 24 in the vacuum collimation component 2. This phase grating 6 is located on the optical path before the probe light is incident on the sample under test, and the distance between it and the sample under test placed on the multi-degree-of-freedom sample stage 3 is a Talbot distance or a fractional Talbot distance. It can be understood here that this distance refers to the distance between the measurement point and a point on the phase grating 6 on the optical path, that is, the distance from the probe light from the phase grating 6 to the measurement point on the surface of the sample under test. The distance between the phase grating 6 and the sample under test can be adjusted by changing the spatial position of the sample under test using the multi-degree-of-freedom sample stage 3, or by adjusting the position of the phase grating 6 on the optical path.

[0070] Talbot distance The specific calculation formula is as follows:

[0071] ;

[0072] in, For the period of phase grating 6, To detect the wavelength of light.

[0073] Score Talbot distance The specific calculation formula is as follows:

[0074] ;

[0075] in, Let be the order of the fractional Talbot distance.

[0076] Since the probe light emitted by the light source assembly 1 has been monochromated by a monochromator and collimated by the vacuum collimation assembly 2, the probe light illuminating the phase grating 6 can be considered a monochromatic plane wave. Therefore, when the distance between the phase grating 6 and the sample under test is the Talbot distance, after the phase grating 6 modulates the probe light, a light field with bright and dark fringes with the same period as the phase grating 6 will be formed on the surface of the sample under test. Furthermore, the distribution of the bright and dark fringes is the same as the duty cycle of the phase grating 6, i.e., Talbo imaging of the phase grating 6, also known as the Talbo effect. Similarly, when the distance between the phase grating 6 and the sample under test is a fractional Talbot distance, after the phase grating 6 modulates the probe light, grating images with different periods, such as second-harmonic or third-harmonic, will be formed on the surface of the sample under test. The period and distribution of the bright and dark fringes of these grating images change proportionally to the period and distribution of the bright and dark fringes of the Talbo images, i.e., fractional Talbot imaging of the phase grating 6, also known as the fractional Talbo effect. Based on the imaging techniques of the Talbot effect and fractional Talbot effect mentioned above, the light intensity distribution on the surface of the sample under test can be precisely controlled by the phase grating 6, and the distance between the phase grating 6 and the sample under test can be adjusted to flexibly switch between Talbot imaging and fractional Talbot imaging.

[0077] After the position of the phase grating 6 in the optical path is determined, the structural parameters of the X-ray phase grating 6 need to be designed to match the period and size of the deep trench etching structure of the sample under test. Specifically, when the distance between the phase grating 6 and the sample under test is the Talbot distance, the period of the phase grating 6 is designed to be equal to the period of the deep trench etching structure of the sample under test; and the linewidth of the phase grating 6 in the part without phase delay is designed to be equal to the linewidth of the deep trench etching structure of the sample under test.

[0078] When the distance between the phase grating 6 and the sample under test is a fractional Talbot distance, the period of the phase grating 6 and the linewidth of the non-phase-delay portion are both integer multiples of the linewidth of the deep trench etching structure. It can be understood that the period of the phase grating 6 is related to the order of the fractional Talbot distance. When the order of the fractional Talbot distance is m, the period of the phase grating 6 is designed to be equal to m times the period of the deep trench etching structure of the sample under test; that is, the period of the phase grating 6 is m times the period of the deep trench etching structure. Correspondingly, the linewidth of the phase grating 6 in the non-phase-delay portion is designed to be equal to m times the linewidth of the deep trench etching structure of the sample under test.

[0079] For example At that time, the period of phase grating 6 should be twice the period of deep trench etched structure, and the linewidth of the phase grating 6 without phase delay is twice the linewidth of deep trench etched structure. At that time, the period of phase grating 6 should be 3 times the period of deep trench etched structure, and the linewidth of the phase grating 6 without phase delay is 3 times the linewidth of deep trench etched structure; and so on.

[0080] The measurement process of the deep trench etched structure in 3D NAND using the above measurement system is roughly as follows: The light source component 1 emits a quasi-monochromatic plane wave (X-ray probe light) that has been monochromated and pre-collimated by a monochromator. After being transmitted and collimated by the vacuum collimation component 2, the probe light is modulated by the phase grating 6 set between the second slit 23 and the third slit 24 to form a bright and dark light field distribution with a period matching the period of the deep trench etched structure of 3D NAND. The linewidth of the bright fringes of the light field is comparable to the linewidth of the deep trench etched structure. Then, the deep trench etched structure of 3D NAND is aligned with the bright fringes of the modulated light field through an alignment mechanism.

[0081] Please refer to the appendix for details. Figure 5 When the distance between the phase grating 6 and the sample under test is the Talbot distance, the probe light is modulated by the phase grating 6 to realize the Talbot image light intensity distribution on the surface of the sample under test. The light intensity of the probe light incident on the deep trench etched structure 10 of the 3D NAND is enhanced, while the X-ray light intensity incident on the memory hole structure 20 is weakened.

[0082] Please see the appendix Figure 6 When the distance between the phase grating 6 and the sample under test is a fractional Talbot distance, the probe light is modulated by the phase grating 6 to realize the fractional Talbot image light intensity distribution on the surface of the sample under test. The light intensity of the probe light incident on the deep trench etched structure 10 of the 3D NAND is enhanced, while the light intensity of the X-ray light incident on the memory hole structure 20 is weakened.

[0083] In both designs described above, it is understood that modulation of the phase grating 6 suppresses the intensity of the scattering signal from the memory hole nanostructure during measurement, increases the proportion of the scattering signal from the deep trench etched structure 10, and reduces the difficulty of accurately extracting the scattering signal corresponding to the deep trench etched structure 10. As for the choice between Talbot imaging and fractional Talbot imaging in actual measurement, it requires comprehensive consideration of factors such as the manufacturing process and structural parameters of the 3D NAND of the sample being measured, the characteristics of the CD-SAXS optical path (light source wavelength and optical path layout), and the required processing technology level of the phase grating 6. When the period of the deep trench etched structure 10 of the sample being measured is only a few micrometers or less, the Talbot distance design requires the period of the phase grating 6 to also be a few micrometers or less. However, given the current process technology and processing costs, the fabrication of a phase grating 6 with an extremely small period is extremely difficult, has low precision, and is very costly. Therefore, using a fractional Talbot distance design can greatly reduce the requirements for the period fabrication of the phase grating 6, thereby reducing the processing difficulty of the phase grating 6. However, the fractional Talbot distance is much shorter than the Talbot distance, so there may be a risk of space limitations. Therefore, the specific Talbot distance and Talbot distance design need to be selected based on the actual measurement situation.

[0084] The Talbot effect differs from lens imaging; it is a form of diffraction imaging and can therefore be explained using diffraction theory. In this embodiment, a phase grating 6 is designed using the Talbot effect and fractional Talbot effect. The phase grating 6 modulates the probe light, thereby suppressing the intensity of the scattering signal from the memory aperture nanostructure during measurement, increasing the proportion of the scattering signal from the deep trench etched structure, and reducing the difficulty of accurately extracting the scattering signal corresponding to the deep trench nanostructure. The phase grating 6 is a periodic object; after monochromaticization and collimation, the probe light conforms to a monochromatic plane wave.

[0085] Furthermore, the diffraction process of a periodic image object is analyzed using the frequency domain analysis method of Fourier optics, thereby explaining the principle of the Talbot effect. For convenience, a one-dimensional periodic object (i.e., phase grating 6) is used as an example (the two-dimensional case is similar). The complex amplitude transmittance of a one-dimensional periodic object can be expressed as:

[0086] (1.1)

[0087] Where p represents the period of the periodic object, if the complex amplitude distribution of the irradiated one-dimensional periodic object is equal to Therefore, the complex amplitude transmittance function of a one-dimensional periodic object can be considered to be a linear superposition of infinitely many plane wave components, and the frequencies of these plane wave components can only take discrete values. The relative amplitude distribution of these plane wave components is used express, Let be a complex exponential function, representing the spatial distribution of the nth harmonic, where i It is the imaginary unit, π is the value of pi, and π is the position variable.

[0088] Taking Fourier transforms of both sides of the equation for calculating the complex amplitude transmittance of a one-dimensional periodic object, we can obtain the spectral distribution function of its light field distribution as follows:

[0089] (1.2)

[0090] in, For Dirac The function represents the frequency. The pulse at the location;

[0091] At a certain distance behind a periodic object, an image of the one-dimensional periodic object can be observed from this position. This plane is called the observation plane. According to the angular spectrum theory of diffraction, the spectral distribution of the light field on the observation plane is as follows:

[0092] (1.3)

[0093] in, This is the spatial spectrum transfer function.

[0094] In the Fresnel diffraction region, we have:

[0095] (1.4)

[0096] in, Z represents the wavelength of the plane wave used to illuminate a one-dimensional periodic object, and Z represents the distance between the observation plane and the object, called the propagation distance. Substitution formula, and utilize The product property of a function and an ordinary function yields:

[0097] (1.5)

[0098] Comparison With formula It can be observed that the spectral distribution of the observation plane, compared to the spectral distribution of the object plane of a one-dimensional periodic object, only introduces a phase shift, which is:

[0099] (1.6)

[0100] Therefore, if the transmission distance Where n represents any positive integer, then we have And then substitute Then we have:

[0101] (1.7)

[0102] Pair Taking the inverse Fourier transform of both ends, we have:

[0103] (1.8)

[0104] The above equation represents the complex amplitude distribution of the light field on the observation plane, and its intensity distribution is:

[0105] (1.9)

[0106] Therefore, when When the light intensity distribution on the observation plane is the same as the light intensity distribution on the object's surface, the image of the object can be observed. Therefore, This is called the Talbot distance, which is the Talbot distance given in the embodiments of this invention. The calculation formula .

[0107] When the diffraction distance is half the first-order Talbot distance, an image of a periodic object can still be observed, but the contrast of the image is reversed compared to the intensity distribution of light transmitted through the object; this is a contrast-inverted image. Similarly, at fractional distances of the first-order Talbot distance, , At fractional positions, grating images with different periods, such as third-order or second-order frequency harmonics, are generated, and the period of these images varies proportionally to the period of the original image. This self-imaging phenomenon is called the fractional Talbot effect, which is the fractional Talbot distance given in the embodiments of this invention. The calculation formula .

[0108] In summary, the above description is merely a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

[0109] The systems, apparatuses, modules, or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, a computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0110] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0111] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0112] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

Claims

1. A system for measuring deep trench etched structures in 3D NAND flash memory, characterized in that, include: A light source assembly for providing probe light for CD-SAXS measurements; A multi-degree-of-freedom sample stage is used to hold the sample to be tested; The detection component is used to collect the scattered signal generated after the detection light shines on the sample under test; A phase grating is placed on the optical path of the probe light provided by the CD-SAXS measurement unit before it is incident on the sample under test. It is used to modulate the probe light so that the bright stripes of the striped beam after the probe light is processed by the phase grating are aligned with the deep groove etched structure area of ​​the sample under test, and the dark stripes are aligned with the memory hole structure area of ​​the sample under test.

2. The system for measuring deep trench etched structures in 3D NAND as described in claim 1, characterized in that, Also includes: A vacuum collimation assembly is disposed between the light source assembly and the multi-degree-of-freedom sample stage, and a vacuum scattering assembly is disposed between the multi-degree-of-freedom sample stage and the detection assembly.

3. The system for measuring deep trench etched structures in 3D NAND as described in claim 2, characterized in that, The detection light provided by the light source assembly is X-rays.

4. The system for measuring deep trench etched structures in 3D NAND as described in claim 2, characterized in that, The vacuum collimation assembly includes a vacuum chamber and at least one slit disposed outside the vacuum chamber.

5. The system for measuring deep trench etched structures in 3D NAND as described in claim 4, characterized in that, The vacuum collimation assembly includes three slits, two of which are located inside the vacuum chamber and one of which is located outside the vacuum chamber.

6. The system for measuring deep trench etched structures in 3D NAND as described in claim 4, characterized in that, The phase grating is disposed between the vacuum cavity and a slit disposed outside the vacuum cavity.

7. The system for measuring deep trench etched structures in 3D NAND as described in claim 1, characterized in that, The multi-degree-of-freedom sample stage can drive the sample under test to move along the X, Y and Z axes, and can also drive the sample under test to deflect at an angle relative to the probe light.

8. The system for measuring deep trench etched structures in 3D NAND as described in claim 1, characterized in that, The detection components include a two-dimensional array X-ray detector.

9. The system for measuring deep trench etched structures in 3D NAND as described in claim 1, characterized in that, The distance between the phase grating and the sample under test is the Talbot distance or fractional Talbot distance.

10. The system for measuring deep trench etched structures in 3D NAND as described in claim 9, characterized in that, Talbot distance The formula for calculation is: ； in, The period of the phase grating. To detect the wavelength of light; Score Talbot distance The formula for calculation is: ； in, This indicates the Talbot diffraction order, which is the order of the fractional Talbot distance.

11. The system for measuring deep trench etched structures in 3D NAND as described in claim 9, characterized in that, When the distance between the phase grating and the sample under test is the Talbot distance, the period of the phase grating is equal to the period of the deep trench etched structure of the sample under test, and the linewidth of the phase grating without phase delay is equal to the linewidth of the deep trench etched structure of the sample under test.

12. The system for measuring deep trench etched structures in 3D NAND as described in claim 9 or 11, characterized in that, When the distance between the phase grating and the sample under test is a fractional Talbot distance of order m, the period of the phase grating is equal to m times the period of the deep trench etched structure of the sample under test, and the linewidth of the phase grating without phase delay is equal to m times the linewidth of the deep trench etched structure of the sample under test.

13. A method for measuring deep trench etched structures in 3D NAND, characterized in that, include: A CD-SAXS measurement device is provided, and a phase grating is set in the optical path of the probe light provided by the CD-SAXS measurement device before it is incident on the sample to be measured. The probe light is modulated by the phase grating, so that the bright stripes of the striped beam after the probe light is processed by the phase grating are aligned with the deep groove etched structure area of ​​the sample under test, and the dark stripes are aligned with the memory hole structure area of ​​the sample under test. This increases the intensity of the probe light incident on the deep groove etched structure of the sample under test and decreases the intensity of the probe light incident on the memory hole structure of the sample under test.

14. The method for measuring deep trench etched structures in 3D NAND as described in claim 13, characterized in that, The phase grating is disposed on the optical path before the probe light provided by the CD-SAXS measurement device is incident on the sample under test, and the distance between the phase grating and the sample under test is the Talbot distance or fractional Talbot distance.

15. The method for measuring deep trench etched structures in 3D NAND as described in claim 13, characterized in that, When the distance between the phase grating and the sample under test is the Talbot distance, the period of the phase grating is equal to the period of the deep trench etched structure of the sample under test, and the linewidth of the phase grating without phase delay is equal to the linewidth of the deep trench etched structure of the sample under test.

16. The method for measuring deep trench etched structures in 3D NAND as described in claim 13, characterized in that, When the distance between the phase grating and the sample under test is a fractional Talbot distance of order m, the period of the phase grating is equal to m times the period of the deep trench etched structure of the sample under test, and the linewidth of the phase grating without phase delay is equal to m times the linewidth of the deep trench etched structure of the sample under test.

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