Phase grating position measurement system and method for measuring structural parameters

Abstract

The present disclosure provides a phase grating position measurement system and a method for measuring structural parameters. The method comprises: S1, scanning a grating mark (107) using the phase grating position measurement system to obtain a measurement signal; S2, separating measurement signals of each diffraction order from the measurement signal to obtain phase information and light intensity information of each diffraction order; S3, calculating the position information of the grating mark (107) based on the phase information; and S4, calculating the structural parameters of the grating mark (107) based on the light intensity information. The present disclosure utilizes the diffraction field information of the phase grating to obtain the structural information of the grating mark while measuring the position of the grating mark, thereby facilitating analysis of changes in the design structure caused by the grating processing process and the impact on the measurement.

Description

Technical Field

[0001] The present disclosure relates to the technical field of integrated circuit manufacturing, and in particular to a phase grating position measurement system and a method for measuring structural parameters. Background Art

[0002] Phase grating position measurement systems are widely used in the integrated circuit industry due to their high measurement accuracy and minimal environmental impact. These systems typically obtain position information by measuring a periodic grating structure. Due to the complexity of integrated circuit manufacturing processes, grating marks deform after exposure, etching, and chemical mechanical polishing. This asymmetric deformation introduces additional measurement errors. Therefore, information about the microstructure to be measured is crucial for analyzing the impact of these processes.

[0003] To accurately capture the periodic microstructural morphology, scanning microscopic images can be analyzed using methods such as electron microscopy, scanning tunneling microscopy, and atomic force microscopy. While these methods offer high measurement accuracy, they are slow, require strict environmental requirements, and are highly destructive, typically limiting their use to offline analysis and verification. Optical scattering measurement, on the other hand, offers advantages such as speed, high accuracy, and non-destructiveness, and is also widely used for measuring microstructural morphology. Due to the strong coupling between the grating's geometric structure and the grating's diffraction field, reconstructing structural changes during the process, as required, presents a challenge and difficulty in modeling and solving. Summary of the Invention

[0004] (1) Technical issues to be resolved

[0005] In response to the above problems, the present disclosure provides a phase grating position measurement system and a method for measuring structural parameters, which are used to at least partially solve technical problems such as the difficulty in obtaining structural information of grating marks using traditional methods.

[0006] (2) Technical solution

[0007] On the one hand, the present disclosure provides a phase grating position measurement system, comprising: a radiation light source for generating a spatially coherent illumination beam; a collimation system and an aperture stop for converting the illumination beam into a uniform and nearly parallel small-sized illumination beam; an illumination lens assembly, a beam splitter, and a collecting lens assembly for directing the small-sized illumination beam into a grating mark; a collecting lens assembly for converting the diffracted beam generated by the grating mark into a parallel beam; an optical component for causing the parallel beams to interfere; and a focusing lens assembly for converging the interfering parallel beams onto a detector.

[0008] On the other hand, the present disclosure provides a method for measuring structural parameters based on the above-mentioned phase grating position measurement system, including: S1, using the phase grating position measurement system to scan the grating mark to obtain a measurement signal; S2, separating the measurement signals of each diffraction order from the measurement signal, and obtaining the phase information and light intensity information of each diffraction order; S3, calculating the position information of the grating mark based on the phase information; S4, calculating the structural parameters of the grating mark based on the light intensity information.

[0009] Furthermore, S1 includes: an illumination light beam is incident on a grating mark, diffracting to generate diffraction orders of -m to +m; using an optical component to overlap the diffraction orders of -m to +m to generate interference; and using a detector to collect a measurement signal.

[0010] Furthermore, the light intensity information of the measurement signal is expressed as:

[0011]

[0012] Among them, |E m | represents the equal amplitude of the +m diffraction order and the -m diffraction field, M represents the highest diffraction order collected by the collecting mirror group, d represents the grating period, x represents the scanning position, Measure the phase of the signal for each diffraction order.

[0013] Furthermore, S2 includes: separating the measurement signal of each diffraction order from the measurement signal according to the frequency of each diffraction order; and extracting the phase information and light intensity information of each diffraction order according to the measurement signal of each diffraction order.

[0014] Furthermore, S3 includes: calculating the position information x of the grating mark m for:

[0015]

[0016] Where d represents the grating period, m represents the diffraction order, Measure the phase of the signal for each diffraction order.

[0017] Furthermore, the structural parameters in S4 include the duty cycle f and the groove depth h of the grating mark.

[0018] Furthermore, S4 includes: calculating the relative signal intensity R of each diffraction order m :

[0019]

[0020] Here, f represents the duty cycle, h represents the groove depth, m represents the diffraction order, and λ represents the incident wavelength.

[0021] Furthermore, S4 includes: relative signal intensity R of non-zero diffraction orders m , calculate the duty cycle f.

[0022] Furthermore, S4 includes: calculating the groove depth h by combining the zero-order relative signal strength R0 with the duty cycle f.

[0023] (3) Beneficial effects

[0024] The phase grating position measurement system and structural parameter measurement method provided in this disclosure utilizes the diffraction field information of the phase grating to simultaneously measure the grating mark position and obtain structural information about the grating mark. This facilitates analysis of changes in the grating manufacturing process that affect the design structure and their impact on measurement. This method eliminates the need for system reconstruction, increases measurement efficiency, and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The following schematically shows a structural diagram of a phase grating position measurement system according to an embodiment of the present disclosure;

[0026] Figure 2 Schematically shows a marking diagram of structural parameters of a grating mark according to an embodiment of the present disclosure;

[0027] Figure 3 The following schematically shows a flow chart of a method for measuring structural parameters based on a phase grating position measurement system according to an embodiment of the present disclosure;

[0028] Figure 4 Schematically shows the triangle wave measurement signals of -9 to +9 diffraction orders according to an embodiment of the present disclosure;

[0029] Description of reference numerals:

[0030] 101, radiation light source; 102, collimation system; 103, aperture diaphragm; 104, illumination lens assembly; 105, beam splitter; 106, collection lens assembly; 107, grating mark; 108, optical component; 109, focusing lens assembly; 110, detector. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0032] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0033] Various directional words in the present disclosure, such as "front", "back", "left", "right", "up", "down", etc., are only for the convenience of description and are used to describe the relative position relationship between the various components, rather than to limit the present disclosure. Different product placement methods of the present disclosure may result in changes in the various directional descriptions.

[0034] This disclosure provides a phase grating position measurement system, see Figure 1 , including: a radiation light source 101, used to generate a spatially coherent illumination beam; a collimation system 102 and an aperture stop 103, used to convert the illumination beam into a uniform and nearly parallel small-sized illumination beam; an illumination lens group 104, a beam splitter 105 and a collecting lens group 106, used to direct the small-sized illumination beam to the grating mark 107; the collecting lens group 106, used to convert the diffracted beam generated by the grating mark 107 into a parallel beam; an optical component 108, used to cause the parallel beams to interfere; and a focusing lens group 109, used to converge the interfering parallel beams onto the detector 110.

[0035] The radiation source 101 generates a spatially coherent illumination beam. The collimation system 102 and aperture stop 103 produce a uniform, nearly parallel, small-sized illumination beam. The illumination lens assembly 104, beam splitter 105, and collection lens assembly 106 form a 4f optical system, which directs the spatially coherent, small-sized illumination beam into the grating mark 107 to generate diffracted beams of different diffraction orders. The diffracted beams are collected by the collection lens assembly 106 and converted into parallel beams. They then pass through the optical assembly 108, rotating the +m and -m diffraction orders 180°, causing them to overlap and interfere with the original -m and +m diffraction orders, respectively. The beams are then converged by the focusing lens assembly 109 onto the detector 110.

[0036] In the phase grating position measurement device, the grating mark 107 is usually a rectangular phase grating, such as Figure 2 As shown, its characterizing parameters mainly include period d, groove depth h, ridge width a, etc. Here, the duty cycle f is defined as the ratio of the ridge width a to the period d, that is, f=a / d.

[0037] The present disclosure also provides a method for measuring structural parameters based on the above-mentioned phase grating position measurement system, see Figure 3 , including: S1, using a phase grating position measurement system to scan the grating mark 107 to obtain a measurement signal; S2, separating the measurement signals of each diffraction order from the measurement signal, and obtaining the phase information and light intensity information of each diffraction order; S3, calculating the position information of the grating mark 107 based on the phase information; S4, calculating the structural parameters of the grating mark 107 based on the light intensity information.

[0038] The method for measuring structural parameters uses the phase information of the grating mark diffraction field to obtain the grating mark position, and uses the grating diffraction field intensity information to measure the groove depth and duty cycle of the grating mark. Specifically, it includes: scanning the phase grating mark to obtain the measurement signal I; separating the measurement signals of each diffraction order and extracting the phase information. and light intensity information | E m | 2 ; According to the phase information Calculate the grating mark position information x m ; According to the light intensity information |E m | 2 , calculate the grating mark groove depth h and duty cycle f.

[0039] Based on the above embodiment, S1 includes: the illumination light beam is incident on the grating mark 107, diffracting to generate diffraction orders from -m to +m; using the optical component 108 to make the diffraction orders from -m to +m overlap and interfere; and using the detector 110 to collect the measurement signal.

[0040] The illumination beam is incident on the grating mark 107, where it diffracts to generate diffraction orders from -m to +m. Each diffraction order passes through the collecting lens assembly 106, transforming it into a parallel beam. The beam then passes through the optical assembly 108, causing the -m and +m diffraction orders to overlap and interfere. When the grating mark 107 moves, the -m to +m diffraction orders encode the motion stage's displacement information into the phase information of the -m to +m diffraction orders. By extracting the phase information from the interference signal, the motion stage's position information is obtained.

[0041] Based on the above embodiment, the light intensity information of the measurement signal is expressed as:

[0042]

[0043] Among them, |E m | represents the amplitude of the +m diffraction order and the -m diffraction field being equal, M represents the highest diffraction order collected by the collecting mirror group 106, d represents the grating period, x represents the scanning position, Measure the phase of the signal for each diffraction order.

[0044] For example, when the period of the grating mark is 16 μm, the duty cycle is 0.5, the groove depth is 158.25 nm, the incident wavelength is 633 nm, the scanning length is 64 μm, and the collection lens group 106 collects the triangle wave measurement signals of the -9 to +9 diffraction orders, such as Figure 4 shown.

[0045] Based on the above embodiment, S2 includes: separating the measurement signal of each diffraction order from the measurement signal according to the frequency of each diffraction order; and extracting the phase information and light intensity information of each diffraction order according to the measurement signal of each diffraction order.

[0046] Since the measurement signals of each diffraction order are mixed together, it is necessary to separate the measurement signals of each diffraction order and obtain the phase information Δφ of the measurement signals of each diffraction order. m and light intensity information | E m | 2 Since the frequencies of the measurement signals of each diffraction order are different, the diffraction orders can be separated according to the differences in the measurement signals of each diffraction order to obtain the phase information Δφ of the measurement signals of each diffraction order. m and light intensity information | E m | 2 .

[0047] On the basis of the above embodiment, S3 includes: according to the phase information of each diffraction order The position information x of the grating mark 107 is calculated m for:

[0048]

[0049] Where d represents the grating period, m represents the diffraction order, Measure the phase of the signal for each diffraction order.

[0050] According to the above embodiment, according to Figure 4 The measurement signal in the grating can be used to obtain the position information of the grating mark as x m =0nm.

[0051] Based on the above embodiment, the structural parameters in S4 include the duty cycle f and the groove depth h of the grating mark 107.

[0052] The present disclosure utilizes the intensity information of the grating diffraction field to calculate the duty cycle f and groove depth h of the grating structure.

[0053] For the light intensity information of each diffraction order |E m | 2 , where the relative signal intensity R of each diffraction order is defined m for:

[0054]

[0055] According to the above embodiment, according to Figure 4 The relative intensity R of each diffraction order signal is the measured signal m , as shown in Table 1.

[0056] Table 1 Relative signal intensity of each diffraction order (%)

[0057] Diffraction order m 0 1 2 3 4 5 6 7 8 9 <![CDATA[Relative intensity R m > 0.0 100.0 0.0 11.1 0.0 4.0 0.0 2.0 0.0 1.2

[0058] According to Fourier transform theory, when a unit amplitude plane wave is incident normally, the relative signal intensity R of each diffraction order is calculated. m :

[0059]

[0060] Here, f represents the duty cycle, h represents the groove depth, m represents the diffraction order, and λ represents the incident wavelength.

[0061] Based on the above embodiment, S4 includes: calculating the relative signal intensity R of the non-zero diffraction order m , calculate the duty cycle f.

[0062] Taking the second diffraction order R2 as an example, the duty cycle f is:

[0063]

[0064] On the basis of the above embodiment, S4 includes: calculating the groove depth h by combining the relative signal strength R0 of the zero level with the duty cycle f.

[0065] The groove depth h is:

[0066]

[0067] When f = 0.5, the groove depth expression can also be simplified to:

[0068]

[0069] by

[0070] The data in Table 1 shows that the duty cycle f is 0.5 and the groove depth h is 158.25 nm, which are equal to the duty cycle f and groove depth h of the grating mark that generates the measurement signal. Therefore, information about the grating structure can be obtained from the intensity information of the measurement signal in the phase grating position measurement system.

[0071] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A method for measuring structural parameters based on a phase grating position measurement system, the phase grating position measurement system comprising: A radiation light source (101) for generating a spatially coherent illumination beam; A collimation system (102) and an aperture stop (103) are used to convert the illumination beam into a uniform and nearly parallel small-sized illumination beam; an illumination lens group (104), a beam splitter (105) and a collection lens group (106) are used to make the small-sized illumination beam incident on a grating mark (107); a collection lens group (106) is used to convert the diffracted beam generated by the grating mark (107) into a parallel beam; an optical component (108) is used to cause the parallel beams to interfere; and a focusing lens group (109) is used to cause the interfered parallel beams to converge onto a detector (110); the method comprises: S1, using a phase grating position measurement system to scan a grating mark (107) to obtain a measurement signal; S2, separating the measurement signals of each diffraction order from the measurement signal, and obtaining the phase information and light intensity information of each diffraction order; the light intensity information of the measurement signal is expressed as: in, represents the amplitude of +m diffraction order and -m diffraction order being equal, M represents the highest diffraction order collected by the collecting mirror group (106), d represents the grating period, x represents the scanning position, ∆φ m The phase of the signal is measured for each diffraction order; S3, calculating and obtaining position information of the grating mark (107) according to the phase information; S4, calculating and obtaining structural parameters of the grating mark (107) based on the light intensity information; the structural parameters include the duty cycle f and the groove depth h of the grating mark (107); S4 includes: Calculate the relative signal intensity R of each diffraction order m : Here, f represents the duty cycle, h represents the groove depth, m represents the diffraction order, and λ represents the incident wavelength.

2. The method for measuring structural parameters according to claim 1, characterized in that: Said S1 comprises: The illumination beam is incident on the grating mark (107), and diffracts to generate diffraction orders of -m to +m; Using an optical component (108) to cause the diffraction orders of -m to +m to overlap and interfere; The measurement signal is collected using a detector (110).

3. The method for measuring structural parameters according to claim 1, wherein: The S2 includes: Separating measurement signals of the diffraction orders from the measurement signal according to the frequencies of the diffraction orders; Phase information and light intensity information of each diffraction order are extracted according to the measurement signals of each diffraction order.

4. The method for measuring structural parameters according to claim 1, wherein: The S3 includes: The position information x of the grating mark (107) is calculated m for: Where d is the grating period, m is the diffraction order, and ∆φ m Measure the phase of the signal for each diffraction order.

5. The method for measuring structural parameters according to claim 1, characterized in that: The S4 includes: The relative signal intensity R of the non-zero diffraction order m , the duty cycle f is calculated.

6. The method for measuring structural parameters according to claim 5, characterized in that: The S4 includes: The groove depth h is calculated by combining the relative signal strength R0 of the zero order with the duty cycle f.

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