3D NAND measurement system and method

Abstract

The invention relates to the technical field of semiconductor measurement, in particular to a 3D NAND measurement system and method, in an existing CD-SAXS measurement light path, a phase grating used for enhancing a scattering signal of a memory hole structure and a phase grating used for enhancing a scattering signal of a deep groove structure are designed on the basis of a Talbot effect or a fractional Talbot effect, and according to the measurement requirement, the phase grating used for enhancing the scattering signal of the memory hole structure and the phase grating used for enhancing the scattering signal of the deep groove structure are designed. A switching device is used for controlling and switching gratings in a measuring light path, detection light is modulated through a phase grating, the light intensity distribution of the detection light irradiated to a sample is in a light and dark stripe shape related to the grating structure period and duty ratio, then the bright stripes are aligned with an area needing to be detected according to an alignment mechanism, and the detection light intensity is adjusted. Dark fringes are aligned with areas needing to be filtered, so that separation and extraction of scattering signals of a memory hole structure and scattering signals of a deep groove structure are enhanced, and mutual interference of the two scattering signals is avoided.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor measurement technology, and specifically provides a 3D NAND measurement system and method. Background Art

[0002] In the process of rapid development of modern information technology, the development of storage technology occupies a very important position. Continuously improving the surface density of storage capacity of storage devices to reduce the cost of each bit of storage capacity is the driving force behind the development of modern storage technology. For this purpose, in 2014, scientists in the semiconductor industry developed 3D NAND technology based on 2D NAND, and continued to improve the aspect ratio of the 3D NAND etching structure in the following decade, thus forming a unique high aspect ratio (HAR) structure in 3D NAND. Etching of extremely high aspect ratio structures is a very critical and challenging process step in the manufacturing process of 3D NAND memory devices, which will significantly affect the performance and yield of the device. Figure 1 As shown, the HAR structure includes memory holes and slits in 3D-NAND. With the continuous vertical scaling of 3D-NAND structures, the aspect ratio of the memory hole structure is greater than 50:1 (the aspect ratio is the ratio of height to diameter) in the most advanced manufacturing process in the industry. In addition, with the increase in the number of oxide / nitride (ON) stacking layers and the continuous development of the use of multiple layers, including the increase in aspect ratio and the obvious bending and warping of the wafer due to increased stress. Therefore, it is becoming increasingly difficult but also increasingly important to accurately characterize the etching process and quality during the development of 3D NAND memory devices and monitor them during the manufacturing process.

[0003] In the current semiconductor manufacturing industry, the measurement technologies that can be used to accurately characterize the etching process and quality during the development of 3D NAND memory devices mainly include: optical critical dimension measurement technology (OCD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Among them, OCD is currently the most widely used online measurement technology in the industry. However, as the aspect ratio of 3D NAND HAR structures is further improved, the resolution of OCD technology is greatly limited due to the limitations of its optical wavelength and reflectivity, and the accurate measurement of 3D NAND HAR structures faces increasing challenges. Although SEM and TEM can achieve accurate measurement of 3D NAND HAR structures, these technologies are destructive measurement technologies, the measurement process is expensive and time-consuming, and there is little accurate process control statistical information that can be provided.

[0004] Critical Dimension Small Angle X-ray Scattering (CD-SAXS) is a transmission-type variable-angle SAXS measurement technology and a non-destructive measurement method. Due to the short wavelength and deep penetration ability of high-energy X-rays, CD-SAXS uses the scattering of X-rays by periodic nanomaterials to simultaneously measure the critical dimensions of the lateral and vertical directions of the HAR structure of the 3D NAND device. Moreover, as the number of stacked layers of 3D NAND devices continues to increase, the CD-SAXS measurement signal intensity will increase accordingly, and the measurement capability will be further enhanced. Therefore, CD-SAXS has unique advantages in the precise measurement of Memory Holes and Slit structures of 3D-NAND.

[0005] When using CD-SAXS to measure 3D-NAND, the spot size of the X-ray beam incident on the sample to be tested is usually tens to hundreds of microns, while the distance between two adjacent deep groove structures is on the order of several microns. There are a large number of memory hole structures distributed between the deep groove structures. Therefore, the signal detected by the CD-SAXS detection system must contain X-ray scattering signals from both the memory hole structure and the deep groove structure. Figure 2 That is the scattering spot of the memory hole structure, such as Figure 3 The X-ray scattering signals of these two structures are superimposed in the form of intensity and detected by the CD-SAXS detection system. The total scattering signal directly measured is as follows: Figure 4 As shown. Therefore, when the CD-SAXS algorithm system solves the memory hole structure in 3D NAND, it is necessary to separate and extract the scattering signal corresponding to the memory hole structure from the total scattering signal; similarly, when the CD-SAXS algorithm system solves the deep groove structure in 3D NAND, it is necessary to separate and extract the scattering signal corresponding to the deep groove structure from the total scattering signal. However, when the existing CD-SAXS system is used to measure the 3D NAND etching structure, the signal belonging to the deep groove structure in the scattering signal obtained by the CD-SAXS detection system will appear very weak, making it difficult for the CD-SAXS algorithm system to accurately separate and extract the scattering signal corresponding to the deep groove structure nanostructure from the total scattering signal. On the other hand, due to the existence of the deep groove structure, when the existing CD-SAXS system is used to measure the memory hole structure in 3D NAND, the scattering signal of the memory hole structure obtained by the CD-SAXS detection system will always be interfered by the scattering signal of the deep groove structure. Therefore, when the CD-SAXS algorithm system solves the critical dimension (CD) of the memory hole structure, it is inevitably interfered by the scattering signal of the deep groove structure, which reduces the accuracy of the measurement results. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a 3D NAND measurement system and method. By designing and switching an X-ray phase grating in the CD-SAXS measurement optical path, the detection light is modulated, thereby effectively realizing the separation and extraction of the scattering signals of the memory hole structure and the scattering signals of the deep groove structure, thereby solving the problem of mutual interference between the scattering signals of the memory hole structure and the scattering signals of the deep groove structure in the existing 3D NAND measurement process.

[0007] To achieve the above object, the technical solution created by the present invention is implemented as follows: The 3D NAND measurement system provided by the present invention includes: a CD-SAXS measurement unit and a first phase grating; When measuring the scattering signal of the memory hole structure, the first phase grating is arranged on the measurement light path before the detection light provided by the CD-SAXS measurement unit is incident on the sample to be measured. The first phase grating is used to modulate the detection light, increase the detection light intensity incident on the memory hole structure of the sample to be measured, and reduce the detection light intensity incident on the deep groove structure of the sample to be measured.

[0008] Preferably, the distance between the first phase grating and the sample to be measured is a Talbot distance or a fractional Talbot distance.

[0009] Preferably, when the spacing between the first phase grating and the sample under test is the Talbot distance, the period of the first phase grating is equal to the period of the memory hole structure of the sample under test, and the line width of the phase-delay-free part of the first phase grating is correspondingly equal to the line width of the memory hole structure of the sample under test.

[0010] Preferably, when the spacing between the first phase grating and the sample under test is an m-order fractional Talbot distance, the period of the first phase grating is equal to m times the period of the memory hole structure of the sample under test, and the line width of the phase-delay-free part of the first phase grating is equal to m times the line width of the memory hole structure of the sample under test.

[0011] Preferably, it further comprises: a second phase grating and a grating switching unit, wherein the grating switching unit is used to move the first phase grating or the second phase grating into the measuring light path, and to move the first phase grating and / or the second phase grating out of the measuring light path.

[0012] Preferably, when the second phase grating is used to measure the scattering signal of the deep groove structure, the second phase grating is arranged on the measurement light path before the detection light provided by the CD-SAXS measurement unit is incident on the sample to be measured, and the distance between the second phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance; When the distance between the second phase grating and the sample under test is the Talbot distance, the period of the second phase grating is equal to the period of the deep groove structure of the sample under test, and the line width of the non-phase-delayed part of the second phase grating is correspondingly equal to the line width of the deep groove structure of the sample under test; When the spacing between the second phase grating and the sample under test is an m-order fractional Talbot distance, the period of the second phase grating is equal to m times the period of the deep groove structure of the sample under test, and the line width of the phase-delay-free part of the second phase grating is equal to m times the line width of the deep groove structure of the sample under test.

[0013] Preferably, a period of the first phase grating is the same as a period of the second phase grating, and a duty cycle of the first phase grating is reciprocal to a duty cycle of the second phase grating.

[0014] Preferably, the grating switching unit comprises a switching positioning stage for adjusting the positions of the first phase grating and the second phase grating, and a controller for controlling the switching positioning stage.

[0015] Preferably, the switching positioning platform includes a vertical axis displacement platform and an optical position detection sensor, the movement axis direction of the vertical axis displacement platform is perpendicular to the measuring optical path, and the optical position detection sensor is used to detect the position of the first phase grating or the second phase grating arranged in the measuring optical path.

[0016] Preferably, the grating switching unit comprises an optical wheel, the first phase grating, the second phase grating and the grating-free hole are arranged on the optical wheel, and the first phase grating, the second phase grating and the grating-free hole are switched by rotating the optical wheel.

[0017] Preferably, the CD-SAXS measurement unit comprises: a light source component, a vacuum collimation component, a stage system, a vacuum scattering component and a detection component, which are arranged in sequence along the measurement light path of the detection light propagation.

[0018] Preferably, the detection light provided by the light source assembly is X-ray.

[0019] Preferably, the vacuum collimation assembly comprises a vacuum cavity and at least one slit arranged outside the vacuum cavity.

[0020] 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.

[0021] Preferably, the first phase grating and the second phase grating are arranged between the vacuum cavity and a slit arranged outside the vacuum cavity.

[0022] Preferably, the Stage system is used to place the sample to be tested, and can drive the sample to be tested to move in the X, Y and Z axes, and drive the sample to be tested to perform an angular deflection relative to the detection light.

[0023] 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, is the order of the fractional Talbot distance.

[0024] The 3D NAND measurement method provided by the present invention uses a 3D NAND measurement system to measure the sample to be measured: Switching the first phase grating to the measurement light path before the detection light provided by the CD-SAXS measurement unit is incident on the sample to be measured, and the distance between the first phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance; or The second phase grating is switched to the measurement light path before the detection light provided by the CD-SAXS measurement unit is incident on the sample to be measured, and the distance between the second phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance; or The first phase grating and the second phase grating are both arranged outside the measuring light path.

[0025] Compared with the prior art, the invention can achieve the following beneficial effects: (1) The present invention adds a first phase grating for X-ray detection light to the traditional CD-SAXS measurement system. The first phase grating is designed based on the Talbot effect or the fractional Talbot effect, thereby achieving precise control of the light intensity distribution on the sample measurement plane, enhancing the X-ray intensity incident on the memory hole structure in the 3D NAND, and weakening the X-ray intensity incident on the deep groove etching structure, thereby suppressing the intensity of the scattering signal of the deep groove etching structure during the measurement process, increasing the intensity ratio of the scattering signal of the memory hole structure, reducing the difficulty of accurately extracting the scattering signal corresponding to the memory hole structure, and thus improving the accuracy and reliability of the measurement.

[0026] (2) The present invention adds two phase gratings for X-ray detection light and a grating switching unit for switching phase gratings to the traditional CD-SAXS measurement system. The grating switching unit can automatically select three optical path structure configurations in the CD-SAXS measurement optical path: a first phase grating, a second phase grating, and no grating. The corresponding optical path configuration can be selected according to specific measurement requirements, thereby obtaining the corresponding measurement effect. Among them, the first phase grating and the second phase grating are both designed based on the Talbot effect or the fractional Talbot effect, which can realize the precise control of the light intensity distribution on the sample measurement plane. When it is necessary to measure the scattering signal of the memory hole structure, the first phase grating can be switched to the CD-SAXS measurement optical path. After modulation by the first phase grating, the X-ray intensity incident on the deep groove structure is significantly weakened, effectively filtering out the interference of the deep groove structure scattering signal on the measurement result, and improving the accuracy of the measurement result; when it is necessary to measure the scattering signal of the deep groove structure, the first phase grating can be removed from the optical path, and the second phase grating can be switched to the CD-SAXS measurement optical path. After modulation by the second phase grating, the X-ray intensity incident on the deep groove etching structure in the 3D NAND is enhanced, and the X-ray intensity incident on the memory hole structure is weakened, thereby realizing the suppression of the scattering signal intensity 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, thereby improving the accuracy and reliability of the measurement. In addition, the two phase gratings can be removed from the CD-SAXS measurement optical path by using a grating switching unit to achieve the total scattering signal measurement of the memory hole structure and the deep groove structure.

[0027] (3) The present invention utilizes a grating switching unit to switch the phase grating, thereby improving the flexibility of the system and making it applicable to various measurement requirements, such as the measurement of scattering signals of deep groove structures and the measurement of scattering signals of memory hole structures. Furthermore, the grating switching unit is used to switch the phase grating, thereby avoiding changes in the axial and radial positions of the phase grating on the optical path during the phase grating switching process, thereby avoiding the need to readjust the position of the phase grating each time the phase grating is replaced.

[0028] (4) In addition, the design of the two phase gratings 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 structural characteristics of 3D NAND with different parameters, has good adaptability and flexibility, and can cope with changes in different processes and structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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 It is the scattering pattern when there is only a memory hole structure provided in the background technology; Figure 3 It is the scattering pattern when there is only a deep groove structure provided in the background technology; Figure 4 It is the memory hole and deep groove structure scattering superposition pattern provided in the background technology; Figure 5 is a schematic diagram of a 3D NAND measurement system provided according to an embodiment of the present invention; Figure 6 It is a schematic diagram of the distribution of the phase grating, the grating Talbot image intensity and the Slits structure under the Talbot distance when measuring the memory hole structure provided by an embodiment of the present invention; Figure 7 Schematic diagram of the distribution of phase grating, grating Talbot image intensity and Slits structure under fractional Talbot distance when measuring the memory hole structure provided by an embodiment of the present invention Figure 8 It is a schematic diagram of the distribution of the phase grating, the grating Talbot image intensity and the Slits structure under the Talbot distance when measuring the deep groove structure provided by an embodiment of the present invention; Fig. 9 It is a schematic diagram of the distribution of the phase grating, the grating Talbot image intensity and the Slits structure under the fractional Talbot distance when measuring the deep groove structure provided by an embodiment of the present invention; Fig.10 It is a schematic diagram of the corresponding relationship between selecting corresponding optical path configuration according to different measurement requirements and its corresponding measurement effect provided by an embodiment of the present invention.

[0030] Reference numerals include: Deep groove 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, Stage system 3, vacuum scattering assembly 4, detection assembly 5, first phase grating 6, second phase grating 7, grating switching unit 8, switching positioning stage 81, controller 82. DETAILED DESCRIPTION

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0036] See also Figure 5In one embodiment of the present invention, a 3D NAND measurement system is provided. When measuring 3D NAND with an existing CD-SAXS measurement device, it is impossible to separate and extract the deep groove structure scattering signal and the memory hole structure scattering signal. In the embodiment of the present invention, a phase grating for regulating the detection light in the CD-SAXS measurement device is added to the existing CD-SAXS measurement device. The detection light is modulated by the phase grating so that the intensity distribution of the detection light irradiated to the sample to be measured presents a distribution of light and dark stripes related to the phase grating structure period and duty cycle. Then, according to the alignment mechanism, the light stripes are aligned with the area to be detected, and the dark stripes are aligned with the area to be filtered out. Specifically, the measurement system includes: a CD-SAXS measurement unit, a first phase grating 6, a second phase grating 7 and a grating switching unit 8. The CD-SAXS measurement unit includes: a light source component 1, a vacuum collimation component 2, a stage system 3, a vacuum scattering component 4 and a detection component 5, which are arranged in sequence along the measurement optical path of the detection light propagation. The light source component 1 is used to provide X-ray 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 assembly 2 structurally includes: a slit system and a vacuum cavity 21, wherein 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 assembly 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 Stage system 3 used to carry the sample to be tested, and the Stage system 3 is a multi-degree-of-freedom turntable, which has high-precision X, Y and Z motion axes and rotation axes, etc., and can be driven by the Stage system 3 to achieve high-precision displacement and rotation in the X, Y and Z directions. It is understandable that the Stage system 3 can realize the 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 highly vacuum chamber, which is used to transmit the scattered signal obtained from the surface of the sample 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 to be tested, and perform CD-SAXS measurement based on the intensity and angle distribution information of the scattered signal.

[0037] In order to achieve the separation and extraction of the scattering signals of the memory hole structure and the deep groove structure in the 3D NAND sample under test, the embodiment of the present invention adds a first phase grating 6 and a second phase grating 7 between the second slit 23 and the third slit 24 in the vacuum collimation assembly 2, and the switching is controlled by the grating switching unit 8. The first phase grating 6, the second phase grating 7 and the grating switching unit 8 are all arranged on the optical path before the detection light is incident on the sample under test, so as to modulate the detection light before it is irradiated on the sample under test.

[0038] The first phase grating 6 is used to improve the measurement effect of the memory hole structure in the 3D NAND. In the process of measuring the scattered signal of the memory hole structure, the detection light is modulated by the first phase grating 6 to increase the intensity of the detection light incident on the memory hole structure of the measured sample, and reduce the intensity of the detection light incident on the deep groove structure of the measured sample. The second phase grating 7 is used to improve the measurement effect of the deep groove structure in the 3D NAND. In the process of measuring the scattered signal of the deep groove structure, the detection light is modulated by the second phase grating 6 to increase the intensity of the detection light incident on the deep groove structure of the measured sample, and reduce the intensity of the detection light incident on the memory hole structure of the measured sample.

[0039] The first phase grating 6 and the second phase grating 7 are fixed and driven by a grating switching unit 8. In an embodiment of the present invention, the grating switching unit 8 includes a switching positioning platform 81 for adjusting the positions of the first phase grating 6 and the second phase grating 7, and a controller 82 for controlling the switching positioning platform 81, wherein the switching positioning platform 81 includes a high-precision vertical axis displacement platform and an optical position detection sensor, the motion axis direction of the vertical axis displacement platform is perpendicular to the measurement optical path, and its motion control accuracy should be above the sub-micron level. The optical position sensor is used to detect the lateral position of the grating after the grating (this is an overview of the first phase grating 6 and the second phase grating 7) is switched to the optical path, and its detection accuracy should reach above the nanometer level. The first phase grating 6 and the second phase grating 7 can be driven to perform linear motion in a direction perpendicular to the measurement optical path through the vertical axis displacement platform to achieve switching of the grating in the measurement optical path.

[0040] As a preferred embodiment, the grating switching unit 8 may also be designed with an optical wheel, and at least three mounting windows are designed on the optical wheel. The first phase grating 6 and the second phase grating 7 are respectively installed in two of the mounting windows, and there is no grating in the other mounting window. The grating in the measuring optical path can be switched by rotating the optical wheel to realize three optical path structure configurations in the CD-SAXS optical path, namely, the first phase grating 6, the second phase grating 7, and no grating holes. The corresponding optical path configuration can be selected according to specific measurement requirements to realize automatic selection of the three configurations of the first phase grating 6, the second phase grating 7, and no grating holes.

[0041] As a preferred embodiment, the grating switching unit 8 may also be provided with a lateral displacement component to adjust the positions of the first phase grating 6, the second phase grating 7 and the grating switching unit 8 along the measuring light path.

[0042] In order to achieve precise modulation of the detection light, the first phase grating 6 and the second phase grating 7 are designed based on the Talbot effect and the fractional Talbot effect. Specifically, it is necessary to design the positions of the first phase grating 6 and the second phase grating 7 in the measuring optical path, as well as the structural parameters of the first phase grating 6 and the second phase grating 7.

[0043] For the first phase grating 6, it is applied to the scattering signal measurement of the memory hole structure of 3D NAND. After the first phase grating 6 is switched to the measurement optical path by the grating switching unit 8, the first phase grating 6 is in the optical path before the detection light is incident on the sample to be measured, and the distance between it and the sample to be measured placed on the stage system 3 is the Talbot distance or the fractional Talbot distance. It can be understood here that the distance refers to the distance between the measurement point and the point of the first phase grating 6 on the optical path, that is, the distance from the first phase grating 6 to the measurement point on the surface of the sample to be measured. The distance between the first 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 stage system 3, or by adjusting the position of the first phase grating 6 on the optical path.

[0044] Talbot distance The specific calculation formula is: ; in, is the period of the phase grating 6, is the wavelength of the detection light.

[0045] Fractional Talbot distance The specific calculation formula is: ; in, is the order of the fractional Talbot distance.

[0046] 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 first phase grating 6 can be regarded as a monochromatic plane wave. Therefore, when the distance between the first phase grating 6 and the sample to be measured is the Talbot distance, after the first phase grating 6 modulates the detection light, a light field of light stripes with the same period as the period of the first 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 first phase grating 6, that is, the Talbo imaging of the first phase grating 6, also known as the Talbo effect. Similarly, when the distance between the first phase grating 6 and the sample to be measured is a fractional Talbot distance, after the first 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 first phase grating 6, also known as the fractional Talbo effect. Based on the imaging technology of the above-mentioned Talbot effect and fractional Talbo effect, the first phase grating 6 can be used to accurately control the light intensity distribution on the surface of the sample under test, and by adjusting the distance between the first phase grating 6 and the sample under test, it is possible to flexibly switch between Talbot imaging and fractional Talbot imaging.

[0047] After the position of the first phase grating 6 in the optical path is determined, it is also necessary to design structural parameters of the first phase grating 6 that match it according to the period and size of the memory hole structure of the sample under test. Specifically, when the spacing between the first phase grating 6 and the sample under test is the Talbot distance, the period of the first phase grating 6 is designed to be equal to the period of the memory hole structure of the sample under test; and the line width of the first phase grating 6 in the part without phase delay is designed to be equal to the line width of the memory hole structure of the sample under test.

[0048] When the spacing between the first phase grating 6 and the sample under test is a fractional Talbot distance, the period of the first phase grating 6 and the line width of the part without phase delay are both integer multiples of the line width of the memory hole structure. It can be understood that the period of the first 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 first phase grating 6 is designed to be equal to m times the period of the memory hole structure of the sample under test, that is, the period of the first phase grating 6 is m times the period of the memory hole structure. Correspondingly, the line width of the first phase grating 6 in the part without phase delay is designed to be equal to m times the line width of the memory hole structure of the sample under test.

[0049] For example When the period of the first phase grating 6 is twice the period of the memory hole structure, the line width of the non-phase-delayed part of the first phase grating 6 is twice the line width of the memory hole structure; When , the period of the first phase grating 6 should be three times the period of the memory hole structure, and the line width of the non-phase-delayed part of the first phase grating 6 is three times the line width of the memory hole structure; and so on.

[0050] The measurement process of the memory hole 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 first 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 memory hole 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 memory hole structure, and then the memory hole structure of the 3D NAND is aligned with the bright fringes of the modulated light field through an alignment mechanism.

[0051] Please refer to the attached Figure 6 When the distance between the first phase grating 6 and the sample to be measured is the Talbot distance, the detection light is modulated by the first 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 memory hole structure 20 of the 3D NAND is enhanced, and the intensity of the X-ray incident on the deep groove structure 10 is weakened.

[0052] Please refer to the attached Figure 7 When the distance between the first phase grating 6 and the sample to be measured is a fractional Talbot distance, the detection light is modulated by the first 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 memory hole structure 20 of the 3DNAND is enhanced, and the intensity of the X-ray incident on the deep groove structure 10 is weakened.

[0053] In the above two designs, it can be understood that by modulating the first phase grating 6, the scattering signal intensity of the deep groove structure 10 during the measurement process is suppressed, the intensity ratio of the scattering signal of the memory hole structure 20 is increased, and the difficulty of accurately extracting the scattering signal corresponding to the memory hole structure 20 is reduced.

[0054] The second phase grating 7 is used for measuring the scattering signal of the deep groove structure of 3D NAND. After the second phase grating 7 is switched to the measurement optical path by the grating switching unit 8, the second phase grating 7 is in the optical path before the detection light is incident on the sample to be measured. Similarly, the distance between the second phase grating 7 and the sample to be measured placed on the Stage system 3 is the Talbot distance or the fractional Talbot distance.

[0055] When the distance between the second phase grating 7 and the sample to be measured is the Talbot distance, after the second phase grating 7 modulates the detection light, a light field of light and dark stripes with the same period as the period of the second phase grating 7 will be formed on the surface of the sample to be measured, and the distribution of the light and dark stripes is the same as the duty cycle of the second phase grating 7, that is, Talbo imaging of the second phase grating 7, also known as the Talbo effect. Similarly, when the distance between the second phase grating 7 and the sample to be measured is a fractional Talbot distance, after the second phase grating 7 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 vary proportionally with the period and light and dark stripe distribution of the Talbo image, that is, fractional Talbot imaging of the second phase grating 7, also known as the fractional Talbo effect. Based on the imaging technology of the Talbot effect and the fractional Talbo effect, the second phase grating 7 can be used to accurately control the light intensity distribution on the surface of the sample under test, and by adjusting the distance between the second phase grating 7 and the sample under test, it is possible to flexibly switch between Talbot imaging and fractional Talbot imaging.

[0056] After the position of the second phase grating 7 in the optical path is determined, it is also necessary to design the structural parameters of the second phase grating 7 that match the period and size of the deep groove structure of the sample to be measured. Usually, the position design of the first phase grating 6 and the second phase grating 7 in the optical path is to select Talbot distance at the same time, or to select fractional Talbo distance at the same time, so that the grating switching unit 8 can switch the grating. At this time, the period of the first phase grating 6 should be the same as the period of the second phase grating 7, and the duty cycle of the first phase grating 6 and the duty cycle of the second phase grating 7 are reciprocal to each other. In special cases, it is also possible that the first phase grating 6 is designed with Talbot distance and the second phase grating 7 is designed with fractional Talbo distance, or the first phase grating 6 is designed with fractional Talbot distance and the second phase grating 7 is designed with Talbo distance. When the first phase grating 6 and the second phase grating 7 are designed with different distances, the period of the first phase grating 6 should be a multiple of the period of the second phase grating 7. Specifically, when the spacing between the second phase grating 7 and the sample to be measured is the Talbot distance, the period of the second phase grating 7 is designed to be equal to the period of the deep groove structure of the sample to be measured; and the line width of the second phase grating 7 in the part without phase delay is designed to be equal to the corresponding line width of the deep groove structure of the sample to be measured.

[0057] When the interval between the second phase grating 7 and the sample under test is a fractional Talbot distance, the period of the second phase grating 7 and the line width of the part without phase delay are both integer multiples of the line width of the deep groove structure. The period of the second phase grating 7 is related to the order of the fractional Talbot distance. When the order of the fractional Talbot distance is m, the period of the second phase grating 7 is designed to be equal to m times the period of the deep groove structure of the sample under test, that is, the period of the second phase grating 7 is m times the period of the deep groove structure. Correspondingly, the line width of the second phase grating 7 in the part without phase delay is designed to be equal to m times the line width of the deep groove structure of the sample under test.

[0058] The measurement process of the deep groove 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 second phase grating 7 set between the second slit 23 and the third slit 24 to form a light field distribution with a period matching the period of the deep groove 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 structure, and then the deep groove structure of the 3D NAND is aligned with the bright fringes of the modulated light field through an alignment mechanism.

[0059] Please refer to the attached Figure 8 When the distance between the second phase grating 7 and the sample to be measured is the Talbot distance, the detection light is modulated by the second phase grating 7 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 structure 10 of the 3D NAND is enhanced, and the intensity of the X-ray incident on the memory hole structure 20 is weakened.

[0060] Please refer to the attached Fig. 9 When the distance between the second phase grating 7 and the sample to be measured is a fractional Talbot distance, the detection light is modulated by the second phase grating 7 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 structure 10 of the 3DNAND is enhanced, and the intensity of the X-ray incident on the memory hole structure 20 is weakened.

[0061] In the above two designs, it can be understood that by modulating the second phase grating 7, the intensity of the scattering signal of the memory hole structure 20 during the measurement process is suppressed, the intensity ratio of the scattering signal of the memory hole structure 20 is increased, and the difficulty of accurately extracting the scattering signal corresponding to the memory hole structure 20 is reduced.

[0062] As for whether the design of the first phase grating 6 and the second phase grating 7 is Talbot imaging or fractional Talbot imaging in the actual measurement process using the first phase grating 6 and the second phase grating 7, 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 3DNAND to be measured, and the requirements for the grating processing technology level. Taking the design of the first phase grating 6 as an example, when the period of the memory hole structure 20 of the sample to be measured is only a few microns or less, the Talbot distance design requires that the period of the first phase grating 6 also needs to reach a few microns or less. However, for the current process level and processing cost, the preparation of the first 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 first phase grating 6, thereby reducing the processing difficulty of the first 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, so it is necessary to select the Talbot distance and the Talbot distance design according to the actual measurement situation. The design of the second phase grating 7 is similar to that of the first phase grating 6, and will not be described in detail here.

[0063] Based on the above 3D NAND measurement system, the embodiment of the present invention further proposes a 3D NAND measurement method, which uses the 3D NAND measurement system to optimize the extraction of the scattering signal of the memory hole structure, optimize the extraction of the scattering signal of the deep groove structure, or measure the total scattering signal of the conventional memory hole structure and the deep groove structure. The 3D NAND measurement system can be used to measure any of the above three measurement requirements. For details, please refer to Fig.10 According to specific measurement requirements, the grating in the CD-SAXS measurement optical path can be switched to configure the optical path. For example, when the measurement requirement is to measure the critical dimension (CD) of the memory hole structure of 3D NAND, the first phase grating 6 is switched to the CD-SAXS measurement optical path. The scattering signal of the deep groove structure will be suppressed, and the scattering signal of the memory hole structure will be enhanced, thereby realizing the extraction of the scattering signal of the memory hole structure, which can effectively improve the CD measurement accuracy of the memory hole structure.

[0064] When the measurement requirement is to measure the CD of the deep groove structure of 3D NAND, the second phase grating 7 is switched to the CD-SAXS measurement optical path. The scattering signal of the memory hole structure will be suppressed, and the scattering signal of the deep groove structure will be enhanced, thereby realizing the extraction of the scattering signal of the deep groove structure, which can effectively improve the CD measurement accuracy of the deep groove structure.

[0065] When the measurement requirement is to measure other nanostructure CDs, the first phase grating 6 and the second phase grating 7 are switched outside the CD-SAXS measurement optical path. The scattering signals of the memory hole structure and the deep groove structure will not be filtered out, thereby realizing the total scattering signal extraction of the memory hole structure and the deep groove structure. This process is the same as the existing ordinary CD-SAXS measurement process.

[0066] The Talbot effect phenomenon is different from lens imaging, but a diffraction imaging, so it can be explained by diffraction theory. In the embodiment of the present invention, the first phase grating 6 and the second phase grating 7 are designed using the Talbot effect and the fractional Talbot effect, and the first phase grating 6 and the second phase grating 7 are used to modulate the detection light, thereby realizing the separation and extraction of the scattered signals corresponding to the memory hole nanostructure and the deep groove structure during the measurement process. The first phase grating 6 and the second phase grating 7 are periodic objects, and after the detection light is monochromatized and collimated, it conforms to a monochromatic plane wave.

[0067] 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 (first phase grating 6, second phase grating 7) is taken as an example (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.

[0068] 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: (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.

[0069] 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 .

[0070] 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 .

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 3D NAND measurement system, comprising: The CD-SAXS measurement unit is characterized by further comprising: The first phase grating is used to measure the scattering signal of the memory hole structure. The first phase grating is arranged on the measurement light path before the detection light provided by the CD-SAXS measurement unit is incident on the sample to be measured. The first phase grating is used to modulate the detection light, increase the detection light intensity incident on the memory hole structure of the sample to be measured, and reduce the detection light intensity incident on the deep groove structure of the sample to be measured.

2. The 3D NAND measurement system according to claim 1, wherein: The distance between the first phase grating and the sample to be measured is a Talbot distance or a fractional Talbot distance.

3. The 3D NAND measurement system according to claim 2, wherein: When the spacing between the first phase grating and the sample under test is the Talbot distance, the period of the first phase grating is equal to the period of the memory hole structure of the sample under test, and the line width of the phase-delay-free part of the first phase grating is correspondingly equal to the line width of the memory hole structure of the sample under test.

4. The 3D NAND measurement system according to claim 2, wherein: When the spacing between the first phase grating and the sample under test is an m-order fractional Talbot distance, the period of the first phase grating is equal to m times the period of the memory hole structure of the sample under test, and the line width of the phase-delay-free part of the first phase grating is equal to m times the line width of the memory hole structure of the sample under test.

5. The 3D NAND measurement system according to claim 1, wherein: Also includes: A second phase grating and a grating switching unit, wherein the grating switching unit is used to move the first phase grating or the second phase grating into a measuring light path, and to move the first phase grating and / or the second phase grating out of the measuring light path.

6. The 3D NAND measurement system according to claim 5, wherein: When the second phase grating is used to measure the scattering signal of the deep groove structure, the second phase grating is arranged on the measurement light path before the detection light provided by the CD-SAXS measurement unit is incident on the sample to be measured, and the distance between the second phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance; When the distance between the second phase grating and the sample under test is the Talbot distance, the period of the second phase grating is equal to the period of the deep groove structure of the sample under test, and the line width of the non-phase-delayed part of the second phase grating is correspondingly equal to the line width of the deep groove structure of the sample under test; When the spacing between the second phase grating and the sample under test is an m-order fractional Talbot distance, the period of the second phase grating is equal to m times the period of the deep groove structure of the sample under test, and the line width of the phase-delay-free part of the second phase grating is equal to m times the line width of the deep groove structure of the sample under test.

7. The 3D NAND measurement system according to claim 6, wherein: The period of the first phase grating is the same as the period of the second phase grating, and the duty cycle of the first phase grating is the reciprocal of the duty cycle of the second phase grating.

8. The 3D NAND measurement system according to claim 5, wherein: The grating switching unit includes a switching positioning stage for adjusting positions of the first phase grating and the second phase grating, and a controller for controlling the switching positioning stage.

9. The 3D NAND measurement system according to claim 8, wherein: The switching positioning platform includes a vertical axis displacement platform and an optical position detection sensor. The movement axis direction of the vertical axis displacement platform is perpendicular to the measuring optical path. The optical position detection sensor is used to detect the position of the first phase grating or the second phase grating arranged in the measuring optical path.

10. The 3D NAND measurement system according to claim 8, wherein: The grating switching unit comprises an optical wheel, the first phase grating, the second phase grating and the grating-free hole are arranged on the optical wheel, and the first phase grating, the second phase grating and the grating-free hole are switched by rotating the optical wheel.

11. The 3D NAND measurement system according to claim 5, wherein: The CD-SAXS measurement unit includes: a light source component, a vacuum collimation component, a stage system, a vacuum scattering component and a detection component which are sequentially arranged along a measurement optical path of the detection light propagation.

12. The 3D NAND measurement system according to claim 11, wherein: The detection light provided by the light source assembly is X-ray.

13. The 3D NAND measurement system according to claim 11, wherein: The vacuum collimation assembly comprises a vacuum cavity and at least one slit arranged outside the vacuum cavity.

14. The 3D NAND measurement system according to claim 13, wherein: 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.

15. The 3D NAND measurement system according to claim 11, wherein: The first phase grating and the second phase grating are arranged between the vacuum cavity and a slit arranged outside the vacuum cavity.

16. The 3D NAND measurement system according to claim 11, wherein: The Stage system is used to place the sample to be tested, and can drive the sample to be tested to move in the X, Y and Z axes, and drive the sample to be tested to deflect an angle relative to the detection light.

17. The 3D NAND measurement system according to claim 2, wherein: 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, is the order of the fractional Talbot distance.

18. A 3D NAND measurement method, characterized in that: The 3D NAND measurement system as claimed in any one of claims 5 to 16 is used to measure the sample to be measured: Switching the first phase grating to the measurement light path before the detection light provided by the CD-SAXS measurement unit is incident on the sample to be measured, and the distance between the first phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance; or Switching the second phase grating to the measurement light path before the detection light provided by the CD-SAXS measurement unit is incident on the sample to be measured, and the distance between the second phase grating and the sample to be measured is the Talbot distance or the fractional Talbot distance; or The first phase grating and the second phase grating are both arranged outside the measuring optical path.

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