System and method for measuring deep groove etching structure in 3D NAND

Abstract

The invention relates to the technical field of semiconductor measurement, particularly provides a system and a method for measuring a deep groove etching structure in a 3D NAND, and aims to improve a traditional CD-SAXS measurement unit, design a phase grating on a light path before probe light enters a measured sample, and measure the deep groove etching structure in the 3D NAND based on a Talbot effect and a fractional Talbot effect. The distance between the phase grating and a detected sample is designed to be a Talbot distance or a fraction Talbot distance, the phase grating modulates the detection light, so that the light intensity distribution of the detection light irradiated to the sample is in a light and dark stripe shape related to the grating structure period and the duty ratio, and then through an alignment mechanism, the light intensity distribution of the detection light irradiated to the sample is in the shape of light and dark stripes related to the grating structure period and the duty ratio. According to the method, light fringes of an incident light beam are aligned with a deep groove etching structure region in the 3D NAND to be detected, and dark fringes are aligned with a memory hole structure region, so that the intensity of light entering the deep groove etching structure part is enhanced, the intensity of light entering the memory hole part is weakened, and the difficulty of extracting a deep groove nano-structure scattering signal from a total scattering signal is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor measurement technology, and specifically provides a system and method for measuring a deep trench etching structure in a 3D NAND. Background Art

[0002] 3D-NAND is the most widely used non-volatile memory chip and is widely used in storage devices of electronic products. Figure 1 As shown in the figure, memory holes and slits are essential structures for 3D-NAND. Memory holes are used to store signals, and slits are used to replace silicon oxynitride with tungsten to form the final gate during the 3D-NAND manufacturing process. The critical dimensions (CD) of memory holes and slits have a crucial impact on the performance and yield of 3D-NAND chips. Since the invention of 3D-NAND, flash memory manufacturers have been pursuing to increase the storage area density of 3D-NAND storage devices under 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 improving the overall storage density of the chip under the same chip area.

[0003] The memory hole structure and deep trench etching structure in 3D-NAND are both high aspect ratio structures, which bring great challenges to measurement. And with the development of 3D-NAND, the number of layers of the stacked structure is increasing, the aspect ratio will further increase, and the measurement challenges will also increase further. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical critical dimension measurement (OCD) are commonly used to measure the memory hole structure and deep trench etching structure of 3D-NAND. However, SEM and TEM are destructive measurement technologies, which are expensive and very time-consuming, and provide little statistical feedback for precise process control. As the aspect ratio of the 3D-NAND structure gradually increases, the accuracy of OCD measurement is also increasingly challenged.

[0004] Critical Dimension Small Angle X-ray Scattering (CD-SAXS) is an emerging non-destructive measurement technology for high aspect ratio structures of 3D-NAND. High-energy X-rays penetrate the memory holes and deep groove periodic structures of 3D-NAND chips to generate X-ray scattering patterns. Based on the scattering patterns, the critical dimensions of the memory holes and deep groove etching structures can be accurately inverted. Since X-rays have the advantage of short wavelengths, CD-SAXS has unique advantages in measuring the precise measurement of memory holes and deep groove etching structures of 3D-NAND.

[0005] In the 3D-NAND process, the memory hole structure already exists when the deep trench etching process is performed. Therefore, the signal detected by CD-SAXS will contain both the scattering signal generated by the periodic structure of the deep trench etching structure and the scattering signal generated by the periodic structure of the memory hole. However, since the structure density of the deep trench etching structure is much smaller than that of the memory hole structure, the scattering signal of the deep trench etching structure will be greatly interfered by the scattering signal of the memory hole. Figure 2 and Figure 3 As shown, in order to solve the precise size of the deep groove etching structure in 3D NAND, it is necessary to separate and extract the scattering signal corresponding to the deep groove nanostructure from the total scattering signal.

[0006] With the development of 3D NAND manufacturing process, in order to improve the storage surface density of 3D-NAND storage devices under the same chip area, flash memory manufacturers gradually increase the arrangement period of deep groove etching structure while keeping the arrangement period of memory hole structure unchanged, so as to improve the overall storage density of the chip under the same chip area. This also leads to a further reduction in the density of deep groove etching structure. When the deep groove etching structure in 3D NAND is measured using the existing CD-SAXS system, the signal belonging to the deep groove etching structure in the scattering signal obtained by the CD-SAXS detection system will become more "weak", making it more difficult for the CD-SAXS algorithm system to accurately separate and extract the scattering signal corresponding to the deep groove etching structure from the total scattering signal. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a system and method for measuring the deep groove etching structure in 3D NAND. By adding a phase grating, the X-ray intensity incident on the deep groove etching structure in the 3D NAND is increased, and the X-ray intensity incident on the memory hole structure in the 3D NAND is reduced, which effectively solves the problem of difficulty in accurately separating the scattered signal corresponding to the deep groove etching structure from the CD-SAXS measurement results.

[0008] To achieve the above object, the technical solution created by the present invention is implemented as follows: In one aspect, the present invention provides a system for measuring a deep trench etching structure in a 3D NAND, comprising: A light source assembly, used to provide probe light for CD-SAXS measurement; Multi-degree-of-freedom sample stage, used to carry the sample to be tested; A detection component, used to collect scattered signals generated after the detection light is irradiated on the sample to be tested; The phase grating is arranged on the optical path of the detection light provided by the CD-SAXS measurement unit before it is incident on the sample to be measured, and is used to modulate the detection light.

[0009] Preferably, it also includes: a vacuum collimation component arranged between the light source component and the multi-degree-of-freedom sample stage, and a vacuum scattering component arranged between the multi-degree-of-freedom sample stage and the detection component.

[0010] Preferably, the detection light provided by the light source assembly is X-ray.

[0011] Preferably, the vacuum collimation assembly comprises a vacuum cavity and at least one slit arranged outside the vacuum cavity.

[0012] Preferably, the vacuum collimation assembly comprises three slits, wherein two slits are arranged inside the vacuum cavity and one slit is arranged outside the vacuum cavity.

[0013] Preferably, the phase grating is arranged between the vacuum cavity and a slit arranged outside the vacuum cavity.

[0014] Preferably, the multi-degree-of-freedom sample stage can drive the sample to be measured to move along the X, Y and Z axes, and drive the sample to be measured to perform an angular deflection relative to the detection light.

[0015] Preferably, the detection assembly includes a two-dimensional array X-ray detector.

[0016] Preferably, the distance between the phase grating and the sample to be measured is a Talbot distance or a fractional Talbot distance.

[0017] Preferably, the Talbot distance The calculation formula is: ; in, is the period of the phase grating, is the wavelength of the detection light; Fractional Talbot distance The calculation formula is: ; in, It represents the Talbot diffraction order, that is, the order of the fractional Talbot distance.

[0018] Preferably, when the distance between the phase grating and the sample being measured is the Talbot distance, the period of the phase grating is equal to the period of the deep groove etching structure of the sample being measured, and the line width of the phase grating without phase delay is equal to the line width of the deep groove etching structure of the sample being measured.

[0019] Preferably, when the spacing between the phase grating and the sample to be measured is an m-order fractional Talbot distance, the period of the phase grating is equal to m times the period of the deep groove etching structure of the sample to be measured, and the line width of the phase-delay-free part of the phase grating is equal to m times the line width of the deep groove etching structure of the sample to be measured.

[0020] In another aspect, the present invention provides a method for measuring a deep trench etching structure in a 3D NAND, comprising: Provide a CD-SAXS measurement device, and set a phase grating on the optical path before the detection light provided by the CD-SAXS measurement device is incident on the sample to be measured; The detection light is modulated by a phase grating to increase the intensity of the detection light incident on the deep groove etching structure of the sample under test, and to reduce the intensity of the detection light incident on the memory hole structure of the sample under test.

[0021] Preferably, the phase grating is arranged on the optical path before the detection light provided by the CD-SAXS measurement equipment is incident on the sample to be measured, and the distance between the phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance.

[0022] Preferably, when the distance between the phase grating and the sample being measured is the Talbot distance, the period of the phase grating is equal to the period of the deep groove etching structure of the sample being measured, and the line width of the phase grating without phase delay is equal to the line width of the deep groove etching structure of the sample being measured.

[0023] Preferably, when the spacing between the phase grating and the sample to be measured is an m-order fractional Talbot distance, the period of the phase grating is equal to m times the period of the deep groove etching structure of the sample to be measured, and the line width of the phase-delay-free part of the phase grating is equal to m times the line width of the deep groove etching structure of the sample to be measured.

[0024] Compared with the prior art, the invention can achieve the following beneficial effects: The present invention adds a phase grating for X-ray detection light to the traditional CD-SAXS measurement system and utilizes the Talbot effect of the phase grating to achieve precise control of the light intensity distribution on the sample measurement plane, thereby enhancing the X-ray intensity incident on the deep groove etching structure in 3D NAND and weakening the X-ray intensity incident on the memory hole structure, thereby suppressing the intensity of the scattering signal of the memory hole nanostructure during the measurement process, increasing the intensity proportion of the scattering signal of the deep groove etching structure, reducing the difficulty of accurately extracting the scattering signal corresponding to the deep groove nanostructure, and thus improving the accuracy and reliability of the measurement.

[0025] In addition, the design of the phase grating can follow both Talbot imaging and fractional Talbot imaging technology, making the phase grating design more flexible. When the period of the deep groove etching structure is extremely small, the grating parameter design based on fractional Talbot imaging can greatly reduce the difficulty of grating processing, so that the system of the present invention can adapt to the characteristics of different 3D NAND nano-etching structures, has good adaptability and flexibility, and can cope with changes in different processes and structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 is a schematic diagram of the 3D NAND structure provided in the background technology; Figure 2 The memory hole and deep groove etching structure scattering superposition pattern provided in the background technology; Figure 3 It is the scattering pattern when there is only a deep groove etching structure in the background technology; Figure 4 is a schematic diagram of a system for measuring a deep trench etching structure in a 3D NAND according to an embodiment of the present invention; Figure 5 It is a schematic diagram of the distribution of the phase grating, the grating Talbot image light intensity and the Slits structure under the Talbot distance provided by an embodiment of the present invention; Figure 6 It is a schematic diagram of the distribution of phase grating, grating Talbot image intensity and Slits structure under fractional Talbot distance provided by an embodiment of the present invention.

[0027] Reference numerals include: Deep trench etching structure 10, memory hole structure 20; 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 DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the invention clearer, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the invention and do not constitute a limitation to the invention. Similar components in different embodiments use associated similar component numbers. In the following embodiments, many detailed descriptions are to enable the invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other components, materials, and methods. In some cases, some operations related to the invention are not shown or described in the specification, in order to avoid the core part of the invention being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary sequence, unless otherwise specified that a certain sequence must be followed.

[0030] In the description of the invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0031] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0032] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0033] When measuring 3D NAND using existing CD-SAXS measurement equipment, the total scattering signal obtained contains both deep trench etching structure and memory hole structure scattering signals. In order to accurately extract and separate the scattering signal corresponding to the deep trench etching structure in the total scattering signal, in one embodiment of the present invention, a method for measuring deep trench etching in 3D NAND is proposed, which specifically includes the following steps: First, an existing CD-SAXS measurement device is provided, and a sample to be measured is measured by using the CD-SAXS measurement device. The sample to be measured is a 3D NAND structure. In the scattering signal directly measured by the CD-SAXS measurement device, the memory hole structure signal of the 3D NAND accounts for a relatively high proportion. Therefore, an embodiment of the present invention proposes to add a phase grating for regulating the detection light in the CD-SAXS measurement device to the existing CD-SAXS measurement device, and modulate the intensity distribution of the detection light incident on the surface of the sample to be measured in the CD-SAXS measurement device by the phase grating, thereby enhancing the intensity of the detection light incident on the deep groove etching structure in the sample to be measured, and weakening the intensity of the detection light incident on the memory hole structure in the sample to be measured, thereby increasing the proportion of the scattering signal obtained by the deep groove etching structure in the total scattering signal obtained by the CD-SAXS measurement device.

[0034] Specifically, in order to achieve precise modulation of the detection light, the embodiment of the present invention designs a phase grating based on the Talbot effect and the fractional Talbot effect. It is mainly necessary to design the position of the phase grating in the CD-SAXS measurement light path and the period and line width of the phase grating. First, the phase grating is required to be set on the light path before the detection light is incident on the sample to be measured; in addition, since the detection light is X-ray, which is a monochromatic plane wave, the Talbot effect proves that for a periodic object, if a monochromatic plane wave is used for illumination, the image of the object will be observed at a periodic distance in the light field behind the object, that is, after the detection light is processed by the phase grating, the light intensity distribution of the detection light irradiated on the surface of the sample to be measured is no longer continuously and uniformly distributed, but appears as light 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 to be measured can be adjusted so that the distance between the phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance. In this process, the position of the phase grating in the optical path can be adjusted, and the position of the sample to be measured can also be appropriately adjusted.

[0035] In the specific implementation, it is also necessary to design a phase grating that matches the period and size of the deep groove etching structure of the 3D NAND in a specific semiconductor manufacturing production line, that is, to design the parameters of the phase grating according to the deep groove etching structure parameters of the sample being tested, specifically: Talbot distance The calculation formula is: ; in, is the period of the phase grating, is the wavelength of the detected light.

[0036] When the spacing between the phase grating and the sample to be measured is the Talbot distance, the period of the phase grating is designed to be equal to the period of the deep groove etching structure of the sample to be measured; and the line width of the phase grating in the part without phase delay is designed to be correspondingly equal to the line width of the deep groove etching structure of the sample to be measured. It can be understood that "correspondingly equal" here means that if the line width of the deep groove etching structure of the sample to be measured is uniformly designed, then the line width of the phase grating in the part without phase delay is also uniformly designed, and the two are equal; if the line width of the deep groove etching structure of the sample to be measured is non-uniformly designed, the line width of the phase grating in the part without phase delay is also non-uniformly designed, and is one-to-one equal to the line width of the deep groove etching structure of the sample to be measured.

[0037] Fractional Talbot distance The calculation formula is: ; in, It represents the Talbot diffraction order, that is, the order of the fractional Talbot distance.

[0038] When the spacing between the phase grating and the sample to be tested is a fractional Talbot distance, the period of the phase grating is related to the order of the fractional Talbot distance. Assuming that the order of the fractional Talbot distance is m, the period of the phase grating is designed to be equal to m times the period of the deep groove etching structure of the sample to be tested, that is, the period of the phase grating is m times the period of the deep groove etching structure. The advantage of this design is that when the period of the deep groove etching structure of the sample to be tested is extremely small, the difficulty of preparing the phase grating can be reduced. It can be understood that, assuming that the period of the deep groove etching structure in the 3D NAND etching structure of the sample to be tested is 3 microns, if the Talbot distance design is used, the period of the phase grating needs to be processed to 3 microns. However, for the current level of X-ray grating processing technology, the processing difficulty of a phase grating with a period of 3 microns is extremely high, the cost is also higher, and even if the processing is successful, the corresponding accuracy is also low. Therefore, at this time, if the third-order fractional Talbot distance is selected, that is , then the period of the phase grating can be processed to 9 microns, which can greatly reduce the difficulty of grating processing. Correspondingly, the line width of the phase grating without phase delay also needs to be designed to be equal to m times the line width of the deep groove etching structure of the sample being tested.

[0039] Through the above process, the scattering signal of the memory hole structure in the measurement results can be suppressed. Finally, through the alignment mechanism, the position of the sample under test perpendicular to the direction of the detection light is adjusted, so that the bright stripes of the stripe beam of the detection light after phase grating processing are aligned with the deep groove etching 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 detection component of the CD-SAXS measurement equipment is used to obtain the extracted and separated scattering signal of the deep groove etching structure. The parameters of the deep groove etching structure can be calculated more accurately through the scattering signal.

[0040] Based on the above method for measuring the deep trench etching structure in 3D NAND, the embodiment of the present invention also provides a system for measuring the deep trench etching structure in 3D NAND. Figure 4The system includes: a CD-SAXS measurement unit and a phase grating 6. The CD-SAXS measurement unit includes: a light source component 1, a vacuum collimation component 2, a multi-degree-of-freedom sample stage 3, a vacuum scattering component 4 and a detection component 5, which are arranged in sequence along the optical path of the detection light propagation. Among them, the light source component 1 is used to provide detection light. Optical devices such as a monochromator and a collimator are arranged inside the light source component 1. The monochromator is used to pre-collimate and monochromatize the X-rays to ensure that the detection light emitted by the light source component 1 is a quasi-monochromatic and quasi-parallel X-ray beam. The detection light emitted by the light source component 1 enters the vacuum collimation component 2. The function of the vacuum collimation component 2 is to further improve the collimation of the detection light and realize the precise control of the beam spot size. Specifically, the vacuum collimation component 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, wherein the first slit 22 and the second slit 23 are arranged inside the vacuum cavity, the first slit 22 and the second slit 23 and the optical path therebetween are all in a vacuum environment, the first slit 22 and the second slit 23 can collimate the detection light injected into the vacuum collimation component 2, and ensure that the detection light is transmitted in a vacuum environment, reducing the attenuation effect of air on X-rays, and the third slit 24 is arranged on the subsequent optical path of the first slit 22 and the second slit 23, that is, outside the vacuum cavity 21. After the detection light is emitted from the third slit 24, it is irradiated on the multi-degree-of-freedom sample stage 3 used to carry the sample to be measured. The multi-degree-of-freedom sample stage 3 is a high-precision multi-degree-of-freedom turntable, which has high-precision X, Y and Z motion axes and rotation axes, etc. It is a CD-SAXS measurement unit Stage system, which can be driven by the multi-degree-of-freedom sample stage 3 to achieve high-precision displacement and rotation in the X, Y and Z directions. It can be understood that the multi-degree-of-freedom sample stage 3 can achieve precise positioning of any point on the sample to be measured, so that any point on the surface of the sample to be measured is at the measurement point position, that is, the position where the detection light is incident. At the same time, the sample to be measured can be driven to perform angle deflection scanning relative to the axis of the optical path, and the incident angle of the plane where the sample to be measured is located relative to the detection light can be adjusted. The vacuum scattering component 4 is a high-vacuum cavity, which is used to transmit the scattered signal obtained by scattering from the surface of the sample to be measured to the detection component 5, reducing the attenuation effect of the air on the scattered signal during the transmission process. The detection component 5 is mainly composed of a two-dimensional array X-ray detector, which is used to detect the scattered signal of the sample under test and perform CD-SAXS measurement based on the intensity and angular distribution information of the scattered signal.

[0041] In order to enhance the scattering signal corresponding to the 3D NAND deep groove etching structure in the scattering signal collected by the detection component 5, an embodiment of the present invention adds an X-ray phase grating 6 between the second slit 23 and the third slit 24 in the vacuum collimation component 2. The phase grating 6 is located in the optical path before the detection light is incident on the sample to be measured, and the distance between the phase grating 6 and the sample to be measured placed on the multi-degree-of-freedom sample stage 3 is the Talbot distance or the fractional Talbot distance. It can be understood here that the spacing refers to the distance between the measurement point and the point of the phase grating 6 on the optical path, that is, the distance from the detection light from the phase grating 6 to the measurement point on the surface of the sample to be measured. The spacing between the phase grating 6 and the sample to be measured can be adjusted by adjusting the spatial position of the sample to be measured through the multi-degree-of-freedom sample stage 3, or by adjusting the position of the phase grating 6 on the optical path.

[0042] Talbot distance The specific calculation formula is: ; in, is the period of the phase grating 6, is the wavelength of the detected light.

[0043] Fractional Talbot distance The specific calculation formula is: ; in, is the order of the fractional Talbot distance.

[0044] Since the detection light emitted by the light source component 1 has been monochromatized by the monochromator and collimated by the vacuum collimation component 2, the detection light irradiated on the phase grating 6 can be regarded as a monochromatic plane wave. Therefore, when the distance between the phase grating 6 and the sample to be measured is the Talbot distance, after the phase grating 6 modulates the detection light, a light field of light stripes with the same period as the period of the phase grating 6 will be formed on the surface of the sample to be measured, and the distribution of the light stripes is the same as the duty cycle of the phase grating 6, that is, the 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 to be measured is a fractional Talbot distance, after the phase grating 6 modulates the detection light, grating images of different periods such as the second or third frequency doubling will be formed on the surface of the sample to be measured, and the period and light and dark stripe distribution of these grating images are proportional to the period and light and dark stripe distribution of the Talbo image, that is, the fractional Talbot imaging of the phase grating 6, also known as the fractional Talbo effect. Based on the imaging technology of the Talbot effect and the fractional Talbo effect, the phase grating 6 can be used to accurately control the light intensity distribution on the surface of the sample under test, and the Talbot imaging and the fractional Talbot imaging can be flexibly switched by adjusting the distance between the phase grating 6 and the sample under test.

[0045] After the position of the phase grating 6 in the optical path is determined, it is also necessary to design the structural parameters of the X-ray phase grating 6 that matches it according to the period and size of the deep groove etching structure of the sample to be measured. Specifically, when the spacing between the phase grating 6 and the sample to be measured is the Talbot distance, the period of the phase grating 6 is designed to be equal to the period of the deep groove etching structure of the sample to be measured; and the line width of the phase grating 6 in the part without phase delay is designed to be equal to the line width of the deep groove etching structure of the sample to be measured.

[0046] When the interval between the phase grating 6 and the sample to be measured is a fractional Talbot distance, the period of the phase grating 6 and the line width of the part without phase delay are both integer multiples of the line width of the deep groove 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 groove etching structure of the sample to be measured, that is, the period of the phase grating 6 is m times the period of the deep groove etching structure. Correspondingly, the line width of the phase grating 6 in the part without phase delay is designed to be equal to m times the line width of the deep groove etching structure of the sample to be measured.

[0047] For example When , the period of the phase grating 6 should be twice the period of the deep groove etching structure, and the line width of the non-phase delay part of the phase grating 6 is twice the line width of the deep groove etching structure; When , the period of the phase grating 6 should be three times the period of the deep groove etching structure, and the line width of the phase grating 6 without phase delay is three times the line width of the deep groove etching structure; and so on.

[0048] The measurement process of the deep groove etching structure in 3D NAND by the above-mentioned measurement system is roughly as follows: the light source component 1 emits a quasi-monochromatic plane wave (X-ray detection light) that has been monochromatized and pre-collimated by a monochromator, and then transmits and collimates through the vacuum collimation component 2, and then modulates the detection light through the phase grating 6 set between the second slit 23 and the third slit 24 to form a light and dark light field distribution whose period matches the period of the deep groove etching structure of the 3D NAND, and the line width of the bright fringes of the light field is equivalent to the line width of the deep groove etching structure, and then the deep groove etching structure of the 3D NAND is aligned with the bright fringes of the modulated light field through an alignment mechanism.

[0049] Please refer to the attached Figure 5 When the distance between the phase grating 6 and the sample to be measured is the Talbot distance, the detection light is modulated by the phase grating 6 to realize the Talbot image intensity distribution on the surface of the sample to be measured, the intensity of the detection light incident on the deep groove etching structure 10 of the 3D NAND is enhanced, and the intensity of the X-ray incident on the memory hole structure 20 is weakened.

[0050] Please refer to the attached Figure 6 When the distance between the phase grating 6 and the sample to be measured is a fractional Talbot distance, the detection light is modulated by the phase grating 6 to realize the fractional Talbot image intensity distribution on the surface of the sample to be measured, the intensity of the detection light incident on the deep groove etching structure 10 of the 3D NAND is enhanced, and the intensity of the X-ray incident on the memory hole structure 20 is weakened.

[0051] In the above two designs, it can be understood that by modulating the phase grating 6, the intensity of the scattered signal of the memory hole nanostructure in the measurement process is suppressed, the intensity ratio of the scattered signal of the deep groove etching structure 10 is increased, and the difficulty of accurately extracting the corresponding scattered signal of the deep groove etching structure 10 is reduced. As for the choice of designing Talbot imaging or fractional Talbot imaging in the actual measurement process, it is necessary to comprehensively consider factors such as the production process, structural parameters, CD-SAXS optical path characteristics (light source wavelength and optical path layout) of the specific sample 3D NAND to be measured, and the requirements for the processing technology level of the phase grating 6. When the period of the deep groove etching structure 10 of the sample to be measured is only a few microns or less, the Talbot distance design requires that the period of the phase grating 6 also needs to reach a few microns or less. For the current process level and processing cost, the preparation of the phase grating 6 with a very small period is extremely difficult, the accuracy is low, and the cost is extremely high. Therefore, the use of the fractional Talbot distance design at this time can greatly reduce the period preparation requirements for the phase grating 6, thereby reducing the difficulty of processing the phase grating 6. However, the fractional Talbot distance is several times shorter than the Talbot distance, so there may be a risk of space limitation. Therefore, the Talbot distance and Talbot distance design need to be selected according to the actual measurement situation.

[0052] The Talbot effect phenomenon is different from lens imaging, but is a diffraction imaging, so it can be explained by diffraction theory. In an embodiment of the present invention, the phase grating 6 is designed using the Talbot effect and the fractional Talbot effect, and the phase grating 6 is used to modulate the detection light, thereby achieving the suppression of the intensity of the scattered signal of the memory hole nanostructure during the measurement process, increasing the intensity ratio of the scattered signal of the deep groove etching structure, and reducing the difficulty of accurately extracting the scattered signal corresponding to the deep groove nanostructure. The phase grating 6 is a periodic object, and after the detection light is monochromatized and collimated, it conforms to a monochromatic plane wave.

[0053] Furthermore, the frequency domain analysis method of Fourier optics is used to analyze the diffraction process of periodic image objects, and then explain the principle of Talbot effect. For convenience, a one-dimensional periodic object (i.e., phase grating 6) is taken as an example here (the two-dimensional case is similar). The complex amplitude transmittance of a one-dimensional periodic object can be expressed as: (1.1) Where p represents the period of the periodic object. If the complex amplitude distribution of the illuminated one-dimensional periodic object is equal to , we can assume that the complex amplitude transmittance function of a one-dimensional periodic object is a linear superposition of an infinite number of 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 expressed as express, is a complex exponential function, which represents the spatial distribution of the nth harmonic, where i is the imaginary unit, 𝜋 is pi, and 𝑥 is the position variable.

[0054] By performing Fourier transform on both ends of the equation for calculating the complex amplitude transmittance of a one-dimensional periodic object, the spectrum distribution function of its light field distribution can be obtained:

[0055] (1.2) in, Dirac Function, which means that at frequency The pulse at At a certain distance behind the periodic object, the image of the one-dimensional periodic object can be observed at this position. This plane is called the observation plane. According to the angular spectrum theory of diffraction, the spectrum distribution of the light field on the observation plane is: (1.3) in, is the spatial spectrum transfer function.

[0056] In the Fresnel diffraction region, we have: (1.4) in, represents the wavelength of the illumination plane wave used to illuminate a one-dimensional periodic object, and Z represents the distance between the observation plane and the object, which is called the propagation distance. Substitution formula, and use The product property of the function and the ordinary function gives: (1.5) Contrast With , it can be found that the spectrum distribution of the observation plane only introduces a phase shift compared to the spectrum distribution of the object plane of a one-dimensional periodic object. The phase shift is: (1.6) So, if the propagation distance , where n represents any positive integer, then , and then substitute Formula, then: (1.7) Pair Perform inverse Fourier transform on both ends, and we have: (1.8) The above formula is the complex amplitude distribution of the light field on the observation plane, and its intensity distribution is: (1.9) So, when When , the light intensity distribution on the observation plane is the same as the light intensity distribution on the object surface, that is, the image of the object can be observed, so It is called the Talbot distance, that is, the Talbot distance given in the embodiment of the present invention The calculation formula .

[0057] When the diffraction distance is half of the first-order Talbot distance, the image of the periodic object can also be observed, but the contrast between the image and the light intensity distribution through the object is opposite, that is, it is a contrast-inverted image. Similarly, at the first-order Talbot distance fractional distance, , When the positions are equal, grating images with different periods such as the third-time frequency or the second-time frequency will be generated, and the period of these images changes proportionally with the period of the original image. This self-imaging phenomenon is called the fractional Talbot effect, that is, the fractional Talbot distance given in the embodiment of the present invention The calculation formula .

[0058] In short, the above description is only a preferred embodiment of this specification and is not intended to limit the protection scope of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included in the protection scope of this specification.

[0059] The systems, devices, 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, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0060] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0061] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0062] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A system for measuring deep trench etching structure in 3D NAND, characterized in that: include: A light source assembly, used to provide probe light for CD-SAXS measurement; Multi-degree-of-freedom sample stage, used to carry the sample to be tested; A detection component, used to collect scattered signals generated after the detection light is irradiated on the sample to be tested; The phase grating is arranged on the optical path of the detection light provided by the CD-SAXS measurement unit before it is incident on the sample to be measured, and is used to modulate the detection light.

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

3. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 2, characterized in that: The detection light provided by the light source assembly is X-ray.

4. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 2, characterized in that: The vacuum collimation assembly comprises a vacuum cavity and at least one slit arranged outside the vacuum cavity.

5. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 4, characterized in that: The vacuum collimation assembly comprises three slits, wherein two slits are arranged inside the vacuum cavity and one slit is arranged outside the vacuum cavity.

6. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 4, characterized in that: The phase grating is arranged between the vacuum cavity and a slit arranged outside the vacuum cavity.

7. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 1, characterized in that: The multi-degree-of-freedom sample stage can drive the sample to be measured to move along the X, Y and Z axes, and can drive the sample to be measured to perform an angular deflection relative to the detection light.

8. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 1, characterized in that: The detection assembly includes a two-dimensional array X-ray detector.

9. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 1, characterized in that: The distance between the phase grating and the sample to be measured is a Talbot distance or a fractional Talbot distance.

10. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 9, characterized in that: Talbot distance The calculation formula is: ； in, is the period of the phase grating, is the wavelength of the detection light; Fractional Talbot distance The calculation formula is: ； in, It represents the Talbot diffraction order, that is, the order of the fractional Talbot distance.

11. The system for measuring deep trench etching structure in 3D NAND as claimed in claim 9, characterized in that: When the distance between the phase grating and the sample is Talbot distance, the period of the phase grating is equal to the period of the deep groove etching structure of the sample, and the line width of the phase grating without phase delay is equal to the line width of the deep groove etching structure of the sample.

12. The system for measuring deep trench etching structure in 3D NAND according to claim 9 or 11, characterized in that: When the spacing between the phase grating and the sample to be measured is an m-order fractional Talbot distance, the period of the phase grating is equal to m times the period of the deep groove etching structure of the sample to be measured, and the line width of the phase-delay-free part of the phase grating is equal to m times the line width of the deep groove etching structure of the sample to be measured.

13. A method for measuring deep trench etching structure in 3D NAND, characterized in that: include: Providing a CD-SAXS measuring device, and arranging a phase grating on the optical path of the detection light provided by the CD-SAXS measuring device before it is incident on the sample to be measured; By modulating the detection light with the phase grating, the intensity of the detection light incident on the deep groove etching structure of the sample under test is increased, and the intensity of the detection light incident on the memory hole structure of the sample under test is reduced.

14. The method for measuring deep trench etching structure in 3D NAND according to claim 13, characterized in that: The phase grating is arranged on the optical path before the detection light provided by the CD-SAXS measuring device is incident on the sample to be measured, and the distance between the phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance.

15. The method for measuring deep trench etching structure in 3D NAND according to claim 13, characterized in that: When the distance between the phase grating and the sample is Talbot distance, the period of the phase grating is equal to the period of the deep groove etching structure of the sample, and the line width of the phase grating without phase delay is equal to the line width of the deep groove etching structure of the sample.

16. The method for measuring deep trench etching structure in 3D NAND according to claim 13, characterized in that: When the spacing between the phase grating and the sample to be measured is an m-order fractional Talbot distance, the period of the phase grating is equal to m times the period of the deep groove etching structure of the sample to be measured, and the line width of the phase-delay-free part of the phase grating is equal to m times the line width of the deep groove etching structure of the sample to be measured.

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