Method and apparatus for measuring overlay error of integrated circuit based on small-angle x-ray scattering

Abstract

This invention provides a method and apparatus for measuring overlay error of integrated circuits based on small-angle X-ray scattering. The method includes acquiring the morphology and key dimensions of an overlay offset measurement mark in the integrated circuit; obtaining the shape factor of the overlay offset measurement mark based on a small-angle X-ray scattering model, combined with the morphology and key dimensions of the overlay error measurement mark; establishing a theoretical scattered light intensity model when small-angle X-rays are incident on the overlay offset measurement mark based on the shape factor of the overlay offset measurement mark; modulating the theoretical scattered light intensity model and determining the peak position of the modulated scattered light intensity at the target diffraction order position; and calculating the overlay error under the overlay offset measurement mark based on the peak position, the target diffraction order position, and the target overlay offset value. This invention can quickly calculate the overlay error of overlay structures with different shapes and improves the accuracy of the measurement results.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit manufacturing technology, and in particular to a method and apparatus for measuring integrated circuit overlay errors based on small-angle X-ray scattering. Background Technology

[0002] With the rapid development of integrated circuit technology, the critical dimension (CD) of integrated circuits is becoming smaller and smaller, and the structural features are becoming more and more complex. Rapid, non-destructive, and accurate measurement of the critical dimension of integrated circuits is an effective means to ensure the quality of integrated circuits. Overlay error is a particularly important parameter, referring to the misalignment between the current lithography layer structure and the previous process layer structure. Generally, the overlay error is required to be no greater than 1 / 3 of the critical dimension. Therefore, rapid measurement and accurate evaluation of overlay error are crucial to ensuring process and device performance.

[0003] Generally, the method for measuring overlay error involves designing overlay marks at the same location on the preceding and following process layers that need to be aligned, and then measuring these marks using an overlay measurement device to obtain the overlay error measurement result. Currently, overlay error measurement is mainly performed based on optical imaging or non-imaging diffraction methods, such as scattering measurement. However, as the critical dimensions of integrated circuits become smaller and their structural features become more complex (e.g., complex 3D structures, structures below 7nm, structures using opaque materials, structures with edge roughness and linewidth roughness, etc.), measurements using traditional optical bands are gradually losing sensitivity.

[0004] In recent years, nanostructure scattering technology based on small-angle X-rays has been gradually developed, and the measurement of overlay error using small-angle X-ray scattering has received increasing attention, but the accuracy of the measurement process needs to be improved.

[0005] Therefore, it is necessary to provide a novel method and apparatus for measuring integrated circuit overlay errors based on small-angle X-ray scattering to solve the above-mentioned problems existing in the prior art. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for measuring the overlay error of integrated circuits based on small-angle X-ray scattering, which can quickly calculate the overlay error of overlay structures with different shapes and improve the accuracy of measurement results.

[0007] To achieve the above objective, the method for measuring integrated circuit overlay error based on small-angle X-ray scattering according to the present invention includes:

[0008] The topography and key dimensions of overlay offset measurement marks in integrated circuits are obtained. The overlay offset measurement marks include a front layer structure mark and a current layer structure mark. Both the front layer structure mark and the current layer structure mark include a periodic structure. The periodic structure includes a plurality of repeating periodic units. The key dimensions include the cross-sectional dimensions of the periodic units, the target overlay offset value between the front layer structure mark and the current layer structure mark, and the vertical distance between the front layer structure mark and the current layer structure mark.

[0009] Based on the small-angle X-ray scattering model, and combining the morphology and structure of the overlay error measurement mark with the key size information, the shape factor of the overlay offset measurement mark is obtained;

[0010] Based on the shape factor of the overlay offset measurement mark, a theoretical scattered light intensity model is established when the small-angle X-ray is incident on the overlay offset measurement mark.

[0011] The theoretical scattered light intensity model is modulated, and the peak position of the modulated scattered light intensity is determined as the target diffraction order position.

[0012] The overlay error under the overlay offset measurement mark is calculated based on the peak position, the target diffraction order position, and the overlay offset target value.

[0013] The beneficial effects of the method for measuring integrated circuit overlay error based on small-angle X-ray scattering described in this invention are as follows: a theoretical scattered light intensity model is established by using the morphology and key size information of the overlay offset measurement mark. The theoretical scattered light intensity is determined by modulating the theoretical scattered light intensity model, so as to determine the peak position of the overlay offset measurement mark at the target diffraction order position according to the theoretical scattered light intensity. The overlay error is calculated according to the relationship between the target diffraction order position, the peak position and the overlay offset measurement mark. Moreover, it is not limited to the shape of the overlay offset measurement mark, which effectively improves the accuracy of the calculation results of the overlay error.

[0014] Optionally, obtaining the shape factor of the overlay offset measurement mark includes:

[0015] Obtain the first shape factor of the preceding structure marker. F 1 and the second shape factor of the layer structure marker F 2;

[0016] Through the first shape factor F 1 and the second shape factor F 2. Calculate the shape factor of the overlay offset measurement mark;

[0017] The calculation process of the shape factor of the overlay offset measurement mark satisfies the following formula:

[0018] ;

[0019] in, The shape factor of the overlay offset measurement mark. and They are the scattering vectors. q The components along the x and z directions, D is the target value of the overlay offset between the previous layer structure mark and the current layer structure mark, and S is the vertical distance between the previous layer structure mark and the current layer structure mark.

[0020] Optionally, the theoretical scattered light intensity model when the small-angle X-rays are incident on the overlay offset measurement mark is expressed by the following formula:

[0021] ;

[0022] in, The theoretical scattered light intensity is... for .

[0023] Optionally, when the cross-sectional shape of the periodic units is rectangular, the peak position satisfies the following formula:

[0024]

[0025] in, The peak position is... The target diffraction order position is the position corresponding to the peak position, where K is a constant, k is the peak ordinal number of the high-frequency modulation term corresponding to the peak position, and the peak ordinal number is determined according to the key size parameter.

[0026] Optionally, when the cross-sectional morphology of the periodic units is trapezoidal, the peak position satisfies the following formula:

[0027]

[0028] in, The peak position is... The target diffraction order position corresponding to the peak position, where K is a constant. This represents the peak position of the left peak. This represents the peak value of the right peak. The first high-frequency modulation term corresponding to the peak position of the left peak. One extreme value, The high-frequency modulation term corresponding to the peak value position of the right peak. Extreme values.

[0029] Optionally, calculating the overlay error under the overlay offset measurement mark based on the peak position, the target diffraction order position, and the target overlay offset value includes:

[0030] Set up a pair of first and second overlay offset measurement marks with opposite overlay offset directions, and obtain the overlay offset of the first and second overlay offset measurement marks respectively;

[0031] At the same target diffraction order position, calculate the first peak position and the second peak position after the peak shift caused by the first and second set offset measurement marks;

[0032] The overlay deviation is calculated based on the first peak position and the second peak position.

[0033] Optionally, when the cross-sectional shape of the periodic unit of both the first overlay offset measurement mark and the second offset measurement overlay mark is rectangular, the overlay deviation satisfies the following formula:

[0034]

[0035] in, The overlay deviation, The first set of offset measurements is the offset of the first set of markings. The second set of offset measurements is the offset of the second set of markings. This refers to the position after the peak value shift caused by the first set of offset measurement marks. The position after the peak shift caused by the second set of offset measurement marks, where k is the peak ordinal number of the high-frequency modulation term corresponding to the first set of offset measurement marks. The target diffraction order position.

[0036] Optionally, when the cross-sectional morphology of the periodic units of both the first and second set of offset measurement marks is trapezoidal, the overlay deviation satisfies the following formula:

[0037]

[0038] in, The overlay deviation, This refers to the position of the diffraction peak shift caused by the first set of offset measurement marks. This refers to the position of the diffraction peak after the second set of offset measurement marks causes a shift. , , The first set of offset measurement marks is marked at the high-frequency modulation terms corresponding to the left peak value and the right peak value. , Peak ordinal number, The target diffraction order position.

[0039] Optionally, calculating the overlay error under the overlay offset measurement mark based on the peak position, the target diffraction order position, and the target overlay offset value includes:

[0040] Select the positions of the first and second diffraction orders in the light intensity scattering spectrum, respectively;

[0041] Calculate the first offset position and the second offset position after the peak offset of the overlay offset measurement mark at the first diffraction order position and the second diffraction order position;

[0042] The overlay deviation is calculated based on the first offset position and the second offset position.

[0043] Optionally, when the cross-sectional shape of the periodic unit of the overlay offset measurement mark is rectangular, the overlay deviation satisfies the following formula:

[0044]

[0045] in, The overlay deviation, This is the position of the first diffraction order. This is the position of the second diffraction order. The offset measurement mark is positioned after the scattering peak shift at the first diffraction order position; The offset measurement mark is the position of the scattering peak after offset at the second diffraction order position. , These are the peak ordinal numbers of the modulation terms corresponding to the overlay marks at the first diffraction order position and the second diffraction order position, respectively.

[0046] Optionally, when the cross-sectional shape of the periodic unit of the overlay offset measurement mark is trapezoidal, the overlay deviation satisfies the following formula:

[0047]

[0048] in, The overlay deviation, This is the position of the first diffraction order. This is the position of the second diffraction order. The offset measurement mark is positioned after the scattering peak shift at the first diffraction order position; The offset measurement mark is the position of the scattering peak after offset at the second diffraction order position. , These are the peak ordinal numbers of the modulation terms corresponding to the left and right peak values ​​when the overlay mark is at the first diffraction order position, respectively. , These are the peak ordinal numbers of the modulation terms corresponding to the left and right peaks when the overlay mark is at the second diffraction order position.

[0049] This invention also discloses a device for measuring integrated circuit overlay errors based on small-angle X-ray scattering, comprising:

[0050] The information acquisition module is used to acquire the morphological structure and key dimension information of the overlay offset measurement mark in the integrated circuit. The overlay offset measurement mark includes a front layer structure mark and a current layer structure mark. Both the front layer structure mark and the current layer structure mark include a periodic structure. The periodic structure includes a plurality of repeating periodic units. The key dimension information includes the cross-sectional dimension of the periodic unit, the target value of the overlay offset between the front layer structure mark and the current layer structure mark, and the vertical distance between the front layer structure mark and the current layer structure mark.

[0051] The shape factor calculation module is used to obtain the shape factor of the overlay offset measurement mark based on the small-angle X-ray scattering model, combined with the morphology and key size information of the overlay error measurement mark;

[0052] The modeling module is used to establish a theoretical scattered light intensity model when the small-angle X-ray is incident on the overlay offset measurement mark based on the shape factor of the overlay offset measurement mark;

[0053] The peak calculation module is used to modulate the theoretical scattered light intensity model and determine the peak position of the modulated scattered light intensity at the target diffraction order position.

[0054] The error calculation module is used to calculate the overlay error under the overlay offset measurement mark based on the peak position, the target diffraction order position and the overlay offset target value.

[0055] The beneficial effects of the device for measuring integrated circuit overlay error based on small-angle X-ray scattering described in this invention correspond one-to-one with the beneficial effects of the method for measuring integrated circuit overlay error based on small-angle X-ray scattering, and will not be repeated here. Attached Figure Description

[0056] Figure 1 This is a flowchart of the method for measuring integrated circuit overlay error based on small-angle X-ray scattering as described in this invention;

[0057] Figure 2 This is a schematic diagram of the rectangular overlay morphology structure in the method for measuring integrated circuit overlay error based on small-angle X-ray scattering described in this invention;

[0058] Figure 3 This is a schematic diagram of the trapezoidal overlay morphology structure in the method for measuring integrated circuit overlay error based on small-angle X-ray scattering described in this invention;

[0059] Figure 4 This is a high-frequency modulation diagram of the scattering curve of the rectangular overlay structure in the method for measuring the overlay error of integrated circuits based on small-angle X-ray scattering described in this invention;

[0060] Figure 5 This is a high-frequency modulation diagram of the scattering curve of the trapezoidal overlay structure in the method for measuring the overlay error of integrated circuits based on small-angle X-ray scattering described in this invention;

[0061] Figure 6 This is a correction term in the rectangular overlay structure of the method for measuring integrated circuit overlay error based on small-angle X-ray scattering described in this invention. A graph showing the functional relationship between t and t;

[0062] Figure 7 In the rectangular overlay structure scattering pattern of the method for measuring overlay error of integrated circuits based on small-angle X-ray scattering described in this invention, the diffraction position q is obtained by fixing the diffraction order in the diffraction pattern. z A schematic diagram illustrating the linear relationship between the overlay offset target value D and the overlay offset measurement mark;

[0063] Figure 8 The diffraction position q in the rectangular overlay structure of the method for measuring integrated circuit overlay error based on small-angle X-ray scattering described in this invention is... z A schematic diagram of the fitted straight line to the target value D of the overlay offset measurement mark;

[0064] Figure 9 The diffraction position q is obtained by fixing the overlay offset target value D of the overlay offset measurement mark in the scattering spectrum of the rectangular overlay structure of the method for measuring overlay error of integrated circuits based on small-angle X-ray scattering as described in this invention. z With diffraction order position q x A schematic diagram of the linear relationship;

[0065] Figure 10 The diffraction peak q is obtained after fixing the target value D of the overlay offset measurement mark in the method for measuring integrated circuit overlay error based on small-angle X-ray scattering described in this invention. z With diffraction order q x A schematic diagram of the linear relationship;

[0066] Figure 11This is a schematic diagram illustrating the absolute error variation between the overlay error obtained from different overlay offset measurement marks based on the same diffraction order and the theoretical overlay error in the method for measuring overlay error of integrated circuits based on small-angle X-ray scattering as described in this invention.

[0067] Figure 12 This is a schematic diagram showing the change in absolute error between the overlay error and the theoretical overlay error obtained by the overlay error extraction method based on different diffraction orders and the same overlay offset measurement mark in the method for measuring overlay error of integrated circuits based on small-angle X-ray scattering described in this invention.

[0068] Figure 13 This is a structural block diagram of the device for measuring integrated circuit overlay errors based on small-angle X-ray scattering, as described in this invention. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed following the word and its equivalents, but do not exclude other elements or objects.

[0070] To address the problems existing in the prior art, embodiments of the present invention provide a method for measuring integrated circuit overlay errors based on small-angle X-ray scattering, referring to... Figure 1 It includes the following steps:

[0071] S101. Obtain the morphological structure and key dimension information of the overlay offset measurement mark in the integrated circuit. The overlay offset measurement mark includes a front layer structure mark and a current layer structure mark. Both the front layer structure mark and the current layer structure mark include a periodic structure. The periodic structure includes several repeating periodic units. The key dimension information includes the cross-sectional dimension of the periodic unit, the target value of the overlay offset between the front layer structure mark and the current layer structure mark, and the vertical distance between the front layer structure mark and the current layer structure mark.

[0072] In some embodiments, the shape of the periodic unit in the overlay offset measurement mark includes a rectangle, trapezoid, or other shapes. When the cross-sectional shape of the periodic unit is rectangular, the reference... Figure 2The key dimensional information includes the rectangle's height h, width w, spacing L, target overlay offset D of the overlay offset measurement mark, and the distance S between the previous layer structure mark and the current layer structure mark; when the cross-sectional shape of the periodic unit is trapezoidal, refer to Figure 3 The key dimensional information includes the height h of the trapezoid, the upper width w1, the lower width w2, the spacing L, the target value D of the overlay offset measurement mark, and the vertical distance S between the previous layer structure mark and the current layer structure mark.

[0073] S102. Based on the small-angle X-ray scattering model, and combining the morphology and structure of the overlay error measurement mark with the key dimension information, obtain the shape factor of the overlay offset measurement mark.

[0074] In some embodiments, obtaining the shape factor of the overlay offset measurement mark includes:

[0075] Obtain the first shape factor of the preceding structure marker. F 1 and the second shape factor of the layer structure marker F 2;

[0076] Through the first shape factor F 1 and the second shape factor F 2. Calculate the shape factor of the overlay offset measurement mark;

[0077] The calculation process of the shape factor of the overlay offset measurement mark satisfies the following formula:

[0078] (2)

[0079] in, The shape factor of the overlay offset measurement mark. and They are the scattering vectors. q The components along the x and z directions, D is the target value of the overlay offset between the previous layer structure mark and the current layer structure mark, and S is the vertical distance between the previous layer structure mark and the current layer structure mark.

[0080] S103. Based on the shape factor of the overlay offset measurement mark, establish a theoretical scattered light intensity model when the small-angle X-ray is incident on the overlay offset measurement mark.

[0081] In this embodiment, the theoretical scattered light intensity model when the small-angle X-rays are incident on the overlay offset measurement mark is expressed by the following formula:

[0082] (2)

[0083] in, The theoretical scattered light intensity is... for .

[0084] In some other embodiments, when the overlay structure type of the previous process layer and the current process layer are both rectangular overlays with the same topographic parameters and uniform electron density distribution, the target shape factor can be simplified to...

[0085] (3)

[0086] Accordingly, the theoretical scattered light intensity satisfies the following formula:

[0087] (4)

[0088] in, The electron density of the air layer, The electron density of the front layer structure, The electron density between the front layer structure and the current structure. To be considered as the electron density of the structure, The shape factor for rectangular overlay when the electron density is 1.

[0089] Furthermore, when Then formula (4) is optimized to:

[0090] (5)

[0091] Since S>h, then when q x When a fixed diffraction order position is taken, the target value of the overlay offset, including the overlay offset measurement mark, is taken as a cosine function of D with respect to q. z High-frequency modulation of the sinc function; see attached diagram for modulation schematic. Figure 4 After modulation by both, the sinc function is merely the envelope, primarily determining the range of light intensity values, while the high-frequency modulation term... This primarily determines the location of the peak. Because the modulation term is in It obtains an extreme value at q, and regarding q z The center of the sinc function is located at q. z = 0, therefore the final peak position will be at a distance of q. z The term closest to 0, i.e.:

[0092] (6)

[0093] This formula, known as the envelope formula, preliminarily verifies the diffraction peak position q. z Diffraction order position q xThe linear relationship between the target value D of the overlay offset is as follows: In addition, if ∆ρ1 ≠∆ρ2, then according to formula (4), the high-frequency modulation term only undergoes scaling and translation in amplitude, and the modulation frequency does not change. The analysis results will be completely consistent with those when ∆ρ1 = ∆ρ2.

[0094] Furthermore, after optimizing formula (5), we obtain:

[0095] (7)

[0096] Regarding the part in parentheses in the above formula (7) concerning q z The function in the envelope formula Performing a Taylor expansion to second-order terms and simplifying by taking the axis of symmetry of the expansion yields a more accurate solution for the peak position, namely:

[0097] (8)

[0098] in, ,remember This refers to the correction term in the Taylor expansion correction formula.

[0099] S104. Modulate the theoretical scattered light intensity model and determine the peak position of the modulated scattered light intensity at the target diffraction order position.

[0100] When the cross-sectional shape of the periodic unit is rectangular, according to formula (8), t is always within a certain range, that is, -π / S ≤ t ≤ π / S, and the corresponding Approximately a constant K, reference Figure 6 The peak position satisfies the following formula (9):

[0101]

[0102] in, The peak position is... The target diffraction order position is the position corresponding to the peak position, where K is a constant, k is the peak ordinal number of the high-frequency modulation term corresponding to the peak position, and the peak ordinal number is determined according to the key size parameter.

[0103] In other embodiments, when the cross-sectional shape of the periodic units is rectangular, reference... Figure 5 The diffraction pattern of a single symmetrical trapezoidal structure is a bimodal sinc curve, which can be approximated as the sum of the squares of two sinc functions located at the center. Therefore, when there is an overlay offset, the initial peak position after modulation will be given by the following envelope formula, i.e.

[0104] (10)

[0105] Where k is satisfied or Integers.

[0106] Furthermore, the scattering curves of the left and right peaks were analyzed separately. By performing a Taylor expansion to the second order, we can obtain more precise positions of the left and right peaks after high-frequency modulation, i.e.:

[0107] (11)

[0108] (12)

[0109] Where k1 is the position of the left peak. q z_L The corresponding high-frequency modulation term has an extremum of k1. k2 represents the peak value position of the right peak. q z_R The corresponding high-frequency modulation term has its 2nd extreme value at that point. .

[0110] The peak position then satisfies the following formula (13):

[0111]

[0112] in, The peak position is... The target diffraction order position corresponding to the peak position, where K is a constant. This represents the peak position of the left peak. This represents the peak value of the right peak. The first high-frequency modulation term corresponding to the peak position of the left peak. One extreme value, The high-frequency modulation term corresponding to the peak value position of the right peak. Extreme values.

[0113] Based on the above formula (13), which is completely similar to the linear formula (9) derived from the rectangular overlay offset measurement mark, it is shown that in the small-angle X-ray scattering spectrum, the peak position is... Target diffraction order position The linear relationship between the target value D of the overlay offset is universal and not limited to morphological features.

[0114] It should be noted that this linear relationship also exists for nanostructures with two sets of etching processes having different morphological characteristics (such as a lower rectangle and an upper trapezoid).

[0115] S105. Calculate the overlay error under the overlay offset measurement mark based on the peak position, the target diffraction order position, and the overlay offset target value.

[0116] In some embodiments, step S105 above includes the following process:

[0117] Set up a pair of first and second overlay offset measurement marks with opposite overlay offset directions, and obtain the overlay offset of the first and second overlay offset measurement marks respectively;

[0118] At the same target diffraction order position, calculate the first peak position and the second peak position after the peak shift caused by the first and second set offset measurement marks;

[0119] The overlay deviation is calculated based on the first derived value position and the second peak position.

[0120] In some further embodiments, when the cross-sectional shape of the periodic units of the first offset measurement mark and the second offset measurement mark are both rectangular, the same diffraction order position is selected. The first set of offset measurement marks is set to the first set of offset measurement marks. Set the second set of offset measurement marks as the second set of offset values. The overlay offsets are respectively D ± + ε Generally speaking, D + =- The positions of the peak values ​​caused by the offset measurement marks of this pair of overlays were extracted respectively. and Then, according to formula (9), we can determine:

[0121] (14)

[0122] in, The peak ordinal number of the high-frequency modulation term corresponding to the first set of offset measurement marks, wherein the positive and negative overlay mark values ​​cause The values ​​are exactly opposites of each other, and the peak ordinal number It is calculated using key dimension information.

[0123] According to the above formula (14), the overlay deviation can be determined to satisfy the following formula:

[0124]

[0125] in, The overlay deviation, The first set of offset measurements is the offset of the first set of markings. The second set of offset measurements is the offset of the second set of markings. For the first set of offset measurement marks This refers to the position after the peak value shift caused by the second set of offset measurement marks. The peak index of the high-frequency modulation term corresponding to the first set of offset measurement marks is given. The target diffraction order position.

[0126] when When = 0, the overlay error satisfies the following formula:

[0127] (16)

[0128] In some embodiments, when the cross-sectional morphology of the periodic units of both the first set of offset measurement marks and the second set of offset measurement marks is trapezoidal, the same diffraction order position is selected. The first set of offset measurement marks is set to the first set of offset measurement marks. Set the second set of offset measurement marks as the second set of offset values. According to formula (13), we can obtain:

[0129]

[0130] In the formula, k'1 and k'2 are the k'1 and k'2 extreme values ​​of the high-frequency modulation term corresponding to the left and right peak values ​​of the first set of offset measurement mark, respectively. Let k = k1 + k2, then the set offset deviation satisfies the following formula (17):

[0131]

[0132] in, The overlay deviation, For the first set of offset measurement marks For the second set of offset measurement marks , , Mark the first set of offset measurements , Peak ordinal number, The target diffraction order position.

[0133] In some other embodiments, the calculation method for the overlay deviation may also employ the following process:

[0134] Select the positions of the first and second diffraction orders in the light intensity scattering spectrum, respectively;

[0135] Calculate the first offset position and the second offset position after the peak offset of the overlay offset measurement mark at the first diffraction order position and the second diffraction order position;

[0136] The overlay deviation is calculated based on the first offset position and the second offset position.

[0137] For example, when the cross-sectional shape of the periodic unit of the overlay offset measurement mark is rectangular, the overlay offset target value D of the same overlay offset measurement mark is set, and two diffraction order positions in the scattering pattern are selected, with the first diffraction order position... The second diffraction order position Extract the positions of the peaks after shift at these two diffraction orders respectively. , Then, according to equation (9), we have:

[0138] (18)

[0139] In the formula, , Let the peak ordinal numbers of the modulation terms corresponding to the overlay marks at the first and second diffraction order positions be respectively. Then, the overlay deviation satisfies the following formula:

[0140] (19)

[0141] Among them, among them, The overlay deviation, This is the position of the first diffraction order. This is the position of the second diffraction order. The offset measurement mark is positioned after the scattering peak shift at the first diffraction order position; The offset measurement mark is the position of the scattering peak after offset at the second diffraction order position. , These are the peak ordinal numbers of the modulation terms corresponding to the overlay marks at the first diffraction order position and the second diffraction order position, respectively.

[0142] In some embodiments, when the cross-sectional shape of the periodic unit of the overlay offset measurement mark is trapezoidal, the same overlay mark D is set, the target value D of the overlay offset measurement mark is set, and two diffraction order positions in the scattering spectrum are selected, the first diffraction order position... The second diffraction order position Extract the positions of the peaks after shift at these two diffraction orders respectively. , Then, according to equation (9), it satisfies the following formula:

[0143]

[0144] In the aforementioned fortifications, for k 11 +k 12 and k 21 +k 22 The requirement is that they cannot both be 0, otherwise it is meaningless. Solving the above two equations simultaneously, we can solve for the overlay error. The overlay deviation satisfies the following formula:

[0145] (20)

[0146] in, The overlay deviation, This is the position of the first diffraction order. This is the position of the second diffraction order. The offset measurement mark is positioned after the scattering peak shift at the first diffraction order position; The offset measurement mark is the position of the scattering peak after offset at the second diffraction order position. , These are the peak ordinal numbers of the modulation terms corresponding to the left and right peak values ​​when the overlay mark is at the first diffraction order position, respectively. , These are the peak ordinal numbers of the modulation terms corresponding to the left and right peaks when the overlay mark is at the second diffraction order position.

[0147] For example, to specifically verify the above solution, the attached document... Figure 2 The rectangular overlay structure shown was simulated, and the key parameters included: bottom width w = 50 nm, overlay morphology height h = 35 nm, spacing of the overlay structures in the x-direction L = 100 nm, vertical distance S = 60 nm between the previous layer structure mark and the current layer structure mark, and electron density difference. = 0.6613、 = 0.7034. When the diffraction order is constant. For the 5th diffraction order, the overlay markers were set to integers from −10 nm to 10 nm. Peak positions were extracted from the simulated scattering curves. ,draw - D curve is attached. Figure 7 As shown in the figure, (8) the fitted straight line is as shown in the appendix. Figure 8 As shown in the figure, the linear relationship exists and is quite obvious, and it matches the analytical formula derived in this invention.

[0148] In another embodiment, when the target overlay offset value D = 5 nm, the diffraction orders are set to 1, 2, 3, 4, 5, 6, and 7, with the remaining key morphology parameters remaining the same as above. The peak positions are extracted from the simulated scattering curves. ,draw - The curve is attached. Figure 9 As shown in the figure, (8) the fitted straight line is as shown in the appendix. Figure 10 As shown in the figure, the linear relationship exists and is quite evident, and it matches the analytical formula derived in this invention.

[0149] In some embodiments, a set of overlay errors under a rectangular overlay morphology structure is simulated and measured using a method based on the same diffraction order but different overlay marks. A first overlay offset target value is set. = 5nm, second set of offset target value = −5nm, the 5th diffraction order was selected as the measurement condition, and the remaining key morphology parameters were consistent with the previous embodiment. The overlay errors were set sequentially as −1 nm : 0.1 nm : 1 nm. The absolute error of the extraction results is shown in the appendix. Figure 11 As shown. According to Figure 11 The data shows that the proposed method can achieve high-precision extraction of overlay error parameters for the same diffraction order but different overlay marks.

[0150] In other embodiments, a set of overlay errors under a trapezoidal overlay morphology structure is simulated and measured based on different diffraction orders and the same overlay mark. The target overlay offset value D = 5 nm is set, and the 6th and 7th diffraction orders are selected as the measurement conditions. The overlay errors are set sequentially as −1 nm : 0.1 nm : 1 nm. The key dimensional information includes the lower base width w1 = 50 nm, the upper base width w2 = 20 nm, the overlay mark height h = 35 nm, the spacing of the overlay structures in the x-direction L = 100 nm, the distance between the two overlay process layers S = 60 nm, and the electron density difference. = 0.6613、 =0.7034, and the extraction result is shown in the attached figure. Figure 12 As shown. According to Figure 12 The data shows that the proposed method can achieve high-precision extraction of overlay error parameters and relatively high-precision extraction of overlay error for different diffraction orders and the same overlay marking.

[0151] The method for measuring integrated circuit overlay error based on small-angle X-ray scattering described in this invention determines the theoretical scattered light intensity by analyzing the morphology and key dimensions of the overlay mark. This allows for the determination of the diffraction peak position of the overlay mark at the target diffraction order based on the theoretical scattered light intensity. The overlay error is then calculated based on the relationship between the target diffraction order position, the diffraction peak position, and the overlay mark. Furthermore, this method is not limited to the shape of the overlay mark, effectively improving the accuracy of the overlay error calculation results.

[0152] This invention also discloses a device for measuring integrated circuit overlay errors based on small-angle X-ray scattering, with reference to... Figure 13 ,include:

[0153] The information acquisition module 1301 is used to acquire the morphological structure and key dimension information of the overlay offset measurement mark in the integrated circuit. The overlay offset measurement mark includes a front layer structure mark and a current layer structure mark. Both the front layer structure mark and the current layer structure mark include a periodic structure. The periodic structure includes a plurality of repeating periodic units. The key dimension information includes the cross-sectional dimension of the periodic unit, the target value of the overlay offset between the front layer structure mark and the current layer structure mark, and the vertical distance between the front layer structure mark and the current layer structure mark.

[0154] The shape factor calculation module 1302 is used to obtain the shape factor of the overlay offset measurement mark based on the small-angle X-ray scattering model, combined with the morphology and structure of the overlay error measurement mark and the key size information.

[0155] Modeling module 1303 is used to establish a theoretical scattered light intensity model when the small-angle X-ray is incident on the overlay offset measurement mark based on the shape factor of the overlay offset measurement mark;

[0156] The peak calculation module 1304 is used to modulate the theoretical scattered light intensity model and determine the peak position of the modulated scattered light intensity at the target diffraction order position.

[0157] The error calculation module 1305 is used to calculate the overlay error under the overlay offset measurement mark based on the peak position, the target diffraction order position and the overlay offset target value.

[0158] In this embodiment, the principles of each module in the device for measuring integrated circuit overlay error based on small-angle X-ray scattering correspond one-to-one with the steps of the aforementioned method for measuring integrated circuit overlay error based on small-angle X-ray scattering, and will not be repeated here.

[0159] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for measuring overlay error of an integrated circuit based on small angle X-ray scattering, characterized in that, The application relates to a method for measuring overlay error of integrated circuit, comprising the following steps: acquiring topographic structure and critical dimension information of an overlay error measurement mark in an integrated circuit, the overlay error measurement mark comprising a front layer structure mark and a same layer structure mark, the front layer structure mark and the same layer structure mark both comprising a periodic structure, the periodic structure comprising a plurality of periodically arranged periodic units, the critical dimension information comprising cross-sectional dimension of the periodic units, overlay error target value of the front layer structure mark and the same layer structure mark, and vertical distance between the front layer structure mark and the same layer structure mark; based on a small-angle X-ray scattering model, combining the topographic structure of the overlay error measurement mark and the critical dimension information, acquiring a shape factor of the overlay error measurement mark, and the calculation process of the shape factor satisfies the following formula: ， wherein is a shape factor of the overlay offset measurement mark, F 1 is a first shape factor of the front layer structure mark, F 2 is a second shape factor of the on layer structure mark, and are components of the scattering vector q in direction x and direction z, D is a target value of an overlay offset between the front layer structure mark and the on layer structure mark, S is a perpendicular distance between the front layer structure mark and the on layer structure mark; based on the shape factor of the overlay error measurement mark, establishing a theoretical scattering light intensity model when the small-angle X-ray is incident on the overlay error measurement mark; modulating the theoretical scattering light intensity model and determining extreme position of high-frequency modulation term of the modulated scattering light intensity as peak position at target diffraction order position, and the peak position and the target diffraction order position and the overlay error target value satisfy a linear relationship; according to the linear relationship among the peak position, the target diffraction order position and the overlay error target value, calculating the overlay error under the overlay error measurement mark based on simulation measurement of different overlay marks at the same diffraction order or simulation measurement of the same overlay mark at different diffraction orders.

2. The method of claim 1, wherein, the theoretical scattering light intensity model when the small-angle X-ray is incident on the overlay error measurement mark is expressed by the following formula: ； wherein is the theoretical scattered light intensity, is the complex conjugate of 3. The method of claim 2, wherein the set of small angle X-ray scattering measurements are obtained from a set of integrated circuit wafers. when the cross-sectional topography of the periodic units is all rectangular, the peak position satisfies the following formula: wherein, is the peak position, is the target diffraction order position, K is a constant, k is a peak number of a high frequency modulation term corresponding to the peak position, and the peak number is determined according to the critical dimension parameter.

4. The method of claim 2, wherein the method is based on small angle X-ray scattering measurements of integrated circuit overlay error. when the cross-sectional topography of the periodic units is all trapezoidal, the peak position satisfies the following formula: wherein, is the peak position, is the target diffraction order position, K is a constant, is the left peak peak position, is the right peak peak position, is the peak number of the high frequency modulation term corresponding to the left peak peak position, is the peak number of the high frequency modulation term corresponding to the right peak peak position.

5. The method of claim 3 or 4, wherein the method is based on small angle X-ray scattering measurements of integrated circuit overlay errors. the calculation of the overlay error under the overlay error measurement mark based on simulation measurement of different overlay marks at the same diffraction order or simulation measurement of the same overlay mark at different diffraction orders according to the linear relationship among the peak position, the target diffraction order position and the overlay error target value comprises the following steps: setting a first overlay error measurement mark and a second overlay error measurement mark with opposite overlay error directions, and acquiring overlay error of the first overlay error measurement mark and overlay error of the second overlay error measurement mark respectively; calculating first peak position after peak value offset caused by the first overlay error measurement mark and second peak position after peak value offset caused by the second overlay error measurement mark at the same target diffraction order position; calculating the overlay error according to the first peak position and the second peak position.

6. The method of claim 5, wherein the set of small angle X-ray scattering measurements are obtained from a set of integrated circuit wafers. when the cross-sectional topography of the periodic units of the first overlay error measurement mark and the second overlay error measurement mark is all rectangular, the overlay error satisfies the following formula: wherein, is the overlay error, is a first overlay amount of the first overlay measurement mark, is a second overlay amount of the second overlay measurement mark, is a first peak position after peak shift caused by the first overlay measurement mark, is a second peak position after peak shift caused by the second overlay measurement mark, is a peak serial number of the first overlay measurement mark corresponding to the high frequency modulation term, is a target diffraction order position.

7. The method of claim 5, wherein the method is based on small angle X-ray scattering measurements of integrated circuit overlay error. when the cross-sectional topography of the periodic units of the first overlay error measurement mark and the second overlay error measurement mark is all trapezoidal, the overlay error satisfies the following formula: wherein, is the overlay error, is the first peak position after a diffraction peak shift caused by the first overlay shift measurement mark, is the second peak position after a diffraction peak shift caused by the second overlay shift measurement mark, , , is the peak number of the high frequency modulation term corresponding to the left peak and the right peak of the first overlay shift measurement mark, is the target diffraction order position.

8. The method of claim 3 or 4, wherein the method is based on small angle X-ray scattering measurement of integrated circuit overlay error. The overlay error under the overlay shift measurement mark is calculated based on different diffraction orders and the same overlay mark according to a linear relationship between the peak position, the target diffraction order position, and the overlay shift target value, and the method comprises the following steps: selecting a first diffraction order position and a second diffraction order position in the light intensity scattering graph respectively; calculating a first peak position after the overlay shift measurement mark causes a peak shift at the first diffraction order position and a second peak position after the overlay shift measurement mark causes a peak shift at the second diffraction order position; calculating the overlay error according to the first peak position and the second peak position.

9. The method of claim 8, wherein the set of small angle X-ray scattering measurements are obtained from a set of integrated circuit wafers. When the cross-sectional morphology of the period unit of the overlay shift measurement mark is rectangular, the overlay error satisfies the following formula: wherein, is the overlay error, is the first diffraction order position, is the second diffraction order position, is a first peak position of the overlay shift measurement mark after peak shift at the first diffraction order position; is a second peak position of the overlay shift measurement mark after peak shift at the second diffraction order position, , are peak numbers of the high frequency modulation terms corresponding to the overlay mark at the first diffraction order position, the second diffraction order position, respectively.

10. The method of claim 8, wherein the set of small angle X-ray scattering measurements are obtained from a set of integrated circuit wafers. When the cross-sectional morphology of the period unit of the overlay shift measurement mark is trapezoidal, the overlay error satisfies the following formula: wherein, is the overlay error, is the first diffraction order position, is the second diffraction order position, is the first peak position of the overlay shift measurement mark at the first diffraction order position after peak shift, is the second peak position of the overlay shift measurement mark at the second diffraction order position after peak shift, , are the peak numbers of the high frequency modulation terms corresponding to the left and right peak positions respectively when the overlay mark is at the first diffraction order position, , are the peak numbers of the high frequency modulation terms corresponding to the left and right peak positions respectively when the overlay mark is at the second diffraction order position.

11. An apparatus for measuring overlay error of an integrated circuit based on small angle X-ray scattering, the apparatus comprising: The method comprises the following steps: An information acquisition module is configured to acquire the morphology structure and key dimension information of an overlay shift measurement mark in an integrated circuit, wherein the overlay shift measurement mark comprises a front layer structure mark and a same layer structure mark, the front layer structure mark and the same layer structure mark each comprise a periodic structure, the periodic structure comprises a plurality of periodically arranged period units, and the key dimension information comprises the cross-sectional dimension of the period unit, an overlay shift target value of the front layer structure mark and the same layer structure mark, and a vertical distance between the front layer structure mark and the same layer structure mark. A shape factor calculation module is configured to acquire the shape factor of the overlay shift measurement mark based on a small-angle X-ray scattering model and in combination with the morphology structure and the key dimension information of the overlay shift measurement mark, and the calculation process of the shape factor satisfies the following formula: ， wherein is a shape factor of the overlay offset measurement mark, F 1 is a first shape factor of the front layer structure mark, F 2 is a second shape factor of the on layer structure mark, and are components of the scattering vector q in direction x and direction z, D is a target value of an overlay offset between the front layer structure mark and the on layer structure mark, S is a perpendicular distance between the front layer structure mark and the on layer structure mark; A modeling module is configured to establish a theoretical scattering light intensity model of the small-angle X-ray incident to the overlay shift measurement mark based on the shape factor of the overlay shift measurement mark. A peak calculation module is configured to modulate the theoretical scattering light intensity model and determine the extreme value position of the high-frequency modulation term of the modulated scattering light intensity as a peak position at a target diffraction order position. An error calculation module is configured to calculate the overlay error under the overlay shift measurement mark based on the same diffraction order and different overlay marks or based on different diffraction orders and the same overlay mark according to a linear relationship between the peak position, the target diffraction order position, and the overlay shift target value.

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