A method for obtaining theoretical spectrum, morphology parameter measurement method and device

Abstract

The present invention relates to a method for obtaining a theoretical spectrum, a method for measuring morphological parameters, and an apparatus. A periodic structure includes a plurality of periodic units, and the method comprises: dividing the morphological model into a plurality of lamellae along a direction Z from the bottom to the top of the periodic structure; obtaining a continuous function of the dielectric constant of the corresponding lamellae along the periodic direction based on the dielectric distribution of each lamellae in the direction Z; then calculating the Fourier coefficient of the dielectric constant of each lamellae; and finally, using a rigorous coupled wave analysis algorithm to calculate the theoretical spectrum of the periodic structure. The present invention avoids approximating the side profiles of the lamellae divided by the model, making the processing of the morphological model in the RCWA calculation more consistent with the actual morphological model of the sample, obtaining a continuous function of the dielectric constant of each lamellae, improving the calculation accuracy of the Fourier coefficient of the dielectric constant, and improving the calculation accuracy and efficiency of the theoretical spectrum.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing processes, and in particular to a method for obtaining a theoretical spectrum, and a method and device for measuring morphological parameters. Background Art

[0002] As the semiconductor industry continues to advance toward deep submicron technology nodes, integrated circuit linewidths continue to shrink, and the dielectric design of integrated circuit devices becomes increasingly complex. Only through strict process control can fully functional circuits and high-speed devices be achieved.

[0003] Optical critical dimension measurement technology is an important part of advanced process control in current semiconductor manufacturing. With advantages such as speed, low cost, and non-destructiveness, it has important applications in advanced process control in semiconductor manufacturing. Optical critical dimension measurement technology is a model-based approach, so fast and accurate optical property modeling and calculation is one of the core elements of optical critical dimension measurement. Among the many optical property modeling and calculation methods, rigorous coupled wave analysis (RCWA) theory is widely used in the optical property modeling and calculation of periodic media due to its high modeling accuracy and wide applicability.

[0004] Ideally, the sidewall angles of the sample morphology designed in the semiconductor manufacturing process are right angles, such as Figure 1 However, due to the limitations of semiconductor processing technology such as photolithography and etching, the actual morphology of the sample may have complex features such as domes, bottom feet, undercuts, or sidewall angle changes that are not 90 degrees, such as Figure 2 In this case, it is necessary to divide the morphology of the sample model according to the requirements of the strict coupled wave analysis algorithm. The usual processing method is to divide the model into a series of slices, such as Figure 3 As shown, take the midline of the height of the layer, such as Figure 4 As shown, the intersection of the center line and the model is perpendicular to the substrate surface, which is approximately the corresponding rectangle, as shown in Figure 5 Based on the layered results, the Fourier coefficient of the dielectric constant of each layer is obtained, and then the RCWA algorithm is used to obtain the theoretical spectrum.

[0005] from Figures 4 to 5 In this modeling method, the model processing is approximate, that is, inaccurate, and the dielectric constant obtained is a discontinuous function, so the Fourier coefficient of the dielectric constant is inaccurate, which will lead to inaccurate theoretical spectrum and low calculation efficiency. Summary of the Invention

[0006] In response to the technical problems existing in the prior art, the present invention provides a method for obtaining a theoretical spectrum, a method and an apparatus for measuring morphological parameters, which can accurately calculate the Fourier coefficient of the dielectric constant, improve the accuracy and calculation efficiency of the theoretical spectrum, and further improve the accuracy and efficiency of the morphological parameter measurement.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] In a first aspect, the present invention provides a method for obtaining a theoretical spectrum for a periodic structure, wherein the periodic structure includes a plurality of periodic units, including:

[0009] Acquire a morphology model of the periodic unit, wherein the morphology model has a plurality of morphology parameters;

[0010] Dividing the topography model into a plurality of layers along a direction Z from the bottom to the top of the periodic structure;

[0011] Based on the dielectric distribution of each layer in the direction Z, obtaining a continuous function of the dielectric coefficient of the corresponding layer along the periodic direction;

[0012] Based on the continuous function, respectively calculating the Fourier coefficient of the dielectric constant of each of the layers;

[0013] The theoretical spectrum of the periodic structure is calculated based on the Fourier coefficients of the dielectric constants of all the layers using a rigorous coupled wave analysis algorithm.

[0014] Furthermore, obtaining a continuous function of the dielectric coefficient of each layer along the periodic direction based on the dielectric distribution of each layer in the direction Z includes:

[0015] Obtaining a periodic medium distribution corresponding to each position of each layer along the periodic direction, wherein the periodic medium distribution includes distributions of D types of dielectric materials along the direction Z, where D is a positive integer;

[0016] Calculating the thickness of each dielectric material along the direction Z, and obtaining the weight of the dielectric material corresponding to each position based on the thickness;

[0017] Based on the dielectric constant of each dielectric material at each position and the weight of the corresponding dielectric material, a continuous function of the dielectric constant of the sheet along the periodic direction is established.

[0018] Furthermore, a continuous function of the dielectric constant of the sheet along the periodic direction is established, including:

[0019] A weighted average is performed on the dielectric coefficients of all the dielectric materials at each position.

[0020] Furthermore, the continuous function of the dielectric constant of the sheet along the periodic direction satisfies:

[0021]

[0022] Among them, ε j (P) is the dielectric constant of any layer j at any position P along the periodic direction, ε jn (P) is the dielectric constant of the dielectric material n of the layer j at position P, p jn (P) is the weight of dielectric material n of slice j at position P. Slice j at position P includes M(P) types of dielectric materials.

[0023] Furthermore, the periodic structure is a one-dimensional periodic model, which is a model that repeats periodically in only one direction:

[0024]

[0025] Where i is the imaginary unit, k is the wave vector, and g is an integer;

[0026] For the morphology model of a single periodic unit, the center point of the period is taken as the origin, the Z direction is taken as the Z axis, and the periodic direction is taken as the X axis to construct an XOZ rectangular coordinate system, ε j (x) is the dielectric constant of the layer j at position P=x, L is the period length of the periodic structure.

[0027] Furthermore, the weight p of the dielectric material n of the layer j at position P=x jn (x), calculated according to the following formula:

[0028] or

[0029] Where h jn (x) is the thickness of the dielectric material n of the layer j at position P=x, H j is the thickness of the layer j, and the sum of the thicknesses of all dielectric materials of the layer j at position P=x is H j .

[0030] Furthermore, the periodic structure is a two-dimensional periodic model, and the two-dimensional periodic model is a model that repeats periodically in two directions perpendicular to each other;

[0031] The Fourier coefficient ε of the dielectric constant of the layer j uv , calculated according to the following formula:

[0032]

[0033] Where i is the imaginary unit, k x is the wave vector in the X direction, k y is the wave vector in the Y direction, u and v are integers;

[0034] Wherein, for the morphology model of a single periodic unit, an XYZ rectangular coordinate system is constructed with the center point of the period as the origin, the Z direction as the Z axis, and the two periodic directions as the XY axes respectively; ε j (x, y) is the dielectric constant of the layer j at position P = (x, y), L x is the period length of the periodic structure in the X direction, L y is the period length of the periodic structure in the Y direction.

[0035] Furthermore, the weight p of the dielectric material n of the layer j at position P = (x, y) jn (x,y), calculated according to the following formula:

[0036] or

[0037] Where h jn The thickness of dielectric material n of (x,y) layer j at position (x,y), H j is the thickness of layer j, and the sum of the thicknesses of all dielectric materials of layer j at position P = (x, y) is H j .

[0038] In a second aspect, the present invention provides a method for measuring a morphology parameter, the method comprising:

[0039] Obtaining a measurement spectrum of the sample to be measured;

[0040] Acquiring a topography model of the sample to be tested, and floating the topography parameters of the topography model to obtain a plurality of topography models corresponding to the sample to be tested;

[0041] The method for obtaining theoretical spectra according to the first aspect of the present invention is used to obtain theoretical spectra corresponding to the plurality of morphology models to construct a theoretical spectrum library;

[0042] searching the theoretical spectrum library for a target theoretical spectrum that matches the measured spectrum;

[0043] The parameters of the sample to be tested are determined according to the morphological parameters of the morphological model corresponding to the target theoretical spectrum.

[0044] In a third aspect, the present invention provides a device for measuring a morphology parameter, the device comprising:

[0045] A metrology unit, used for obtaining a measurement spectrum of a sample to be measured;

[0046] a calculation unit, configured to obtain a theoretical spectrum library using the method for obtaining a theoretical spectrum according to the first aspect of the present invention;

[0047] a fitting unit, configured to determine a target theoretical spectrum matching the measured spectrum from the theoretical spectrum library;

[0048] The output unit extracts the morphological parameters corresponding to the target theoretical spectrum and outputs them as the measured parameters of the sample to be measured.

[0049] The beneficial effects of the present invention are as follows: the present invention avoids the approximation of the side profiles of the lamellae divided by the model, so that the processing of the morphology model in the RCWA calculation is more consistent with the actual morphology model of the sample, and a continuous function of the dielectric constant of each lamella is obtained, thereby improving the calculation accuracy of the Fourier coefficient of the dielectric constant, improving the calculation accuracy and efficiency of the theoretical spectrum, and thus improving the accuracy and efficiency of the morphology parameter measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is the cross-sectional view of the theoretical model;

[0051] Figure 2 This is the cross-sectional view of the actual model;

[0052] Figures 3 to 5 A schematic diagram of processing a model sheet in the prior art;

[0053] Figure 6 A schematic diagram of the medium distribution at position x of a layer j of a morphology model of a one-dimensional periodic structure provided by an embodiment of the present invention;

[0054] Figure 7 A top view of a one-dimensional periodic structure provided by an embodiment of the present invention;

[0055] Figure 8 A schematic diagram of the medium distribution at position (x, y) of layer j of the morphology model of the two-dimensional periodic structure provided by an embodiment of the present invention;

[0056] Figure 9 A top view of a two-dimensional periodic structure provided by an embodiment of the present invention;

[0057] Figure 10 A schematic cross-sectional view of a layer of a morphology model of a one-dimensional periodic structure provided in an embodiment of the present invention;

[0058] Figure 11 For the existing technology Figure 10 The cross-sectional view of the slice shown is after approximate processing;

[0059] Figures 12 and 13 Schematic diagram of processing a morphology model slice of a one-dimensional periodic structure of a trapezoidal structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0061] An embodiment of the present invention provides a method for obtaining a theoretical spectrum, which is used to obtain a theoretical spectrum of a periodic structure, wherein the periodic structure includes a plurality of periodic units, including:

[0062] S100, obtaining a morphology model of the periodic unit, wherein the morphology model has a plurality of morphology parameters;

[0063] S200, dividing the topography model into a plurality of layers along a direction Z from the bottom to the top of the periodic structure;

[0064] S300, based on the dielectric distribution of each layer in the direction Z, obtaining a continuous function of the dielectric coefficient of the corresponding layer along the periodic direction;

[0065] S400, calculating the Fourier coefficient of the dielectric constant of each of the layers based on the continuous function;

[0066] S500: Calculate the theoretical spectrum of the periodic structure based on the Fourier coefficients of the dielectric constants of all the layers using a rigorous coupled wave analysis algorithm.

[0067] The periodic structure is a one-dimensional periodic model or a two-dimensional periodic model, that is, a model that is periodically repeated in only one direction or a model that is periodically repeated in two directions perpendicular to each other.

[0068] Step S300 further includes: obtaining a periodic medium distribution corresponding to each position of each of the slices along the periodic direction, wherein the periodic medium distribution includes a distribution of D types of dielectric materials along the direction Z, where D is a positive integer;

[0069] Calculating the thickness of each dielectric material along the direction Z, and obtaining the weight of the dielectric material corresponding to each position based on the thickness;

[0070] Based on the dielectric constant of each dielectric material at each position and the weight of the corresponding dielectric material, a continuous function of the dielectric constant of the layer along the periodic direction is established. That is, based on the dielectric distribution within the layer - the medium corresponding to each position within the layer, the dielectric constant of the layer is accurately obtained. Compared with the dielectric constant of the layer obtained by structural approximation of the divided layer in the prior art, the method of the present invention can improve the accuracy of the dielectric constant of each layer obtained, thereby improving the accuracy of the theoretical spectrum. At the same time, there is no need to increase the number of divided layers to improve the calculation accuracy as in the prior art. The present invention can improve the calculation efficiency while ensuring the accuracy of the theoretical spectrum.

[0071] In addition, the continuous function is obtained by performing weighted averaging on the dielectric coefficients of all the dielectric materials at each position.

[0072] The continuous function of the dielectric constant of any layer j along the periodic direction satisfies:

[0073]

[0074] Among them, ε j (P) is the dielectric constant of any layer j at any position P along the periodic direction, ε jn (P) is the dielectric constant of the dielectric material n of the layer j at position P, p jn (P) is the weight of dielectric material n of slice j at position P. Slice j at position P includes M(P) types of dielectric materials.

[0075] This functional relationship for the dielectric constant can accurately represent the dielectric constant of sheets with arbitrary geometric structures and profiles, eliminating the approximations of sheet geometry and profiles found in the prior art and addressing the issue of low accuracy in the obtained dielectric constant. For sheets with complex geometries and profiles, the method provided by the present invention better aligns with realistic morphological models, improving the accuracy and efficiency of theoretical spectrum calculations.

[0076] Example 1

[0077] For a one-dimensional periodic model, the method includes the following steps:

[0078] S101: For the morphology model within a single period, an XOZ rectangular coordinate system is constructed with the center point of the period as the origin, the direction from the upper surface of the substrate upward as the Z axis (i.e., the direction from the bottom to the top of the periodic structure as the Z axis), and the periodic direction of the one-dimensional periodic model as the X axis. The position x is the coordinate of any point on the X axis in the layer. L is the period length. Divide the morphology model of the periodic unit into N slices along the Z axis, where N is a positive integer; these slices are called slice 1, slice 2, ..., slice N. The height H corresponding to slice j is obtained. j , j = 1, 2, ..., N. Figure 6 、 Figure 7 As shown, Figure 7 This is a top view of a one-dimensional periodic structure. Each dotted box is a periodic unit. Figure 6 Schematic diagram of the medium distribution at position x of any layer j in the morphology model of a periodic unit of a one-dimensional periodic structure.

[0079] S201 : For a slice j, obtain a continuous function of the dielectric constant based on the dielectric distribution of the slice in the Z-axis direction.

[0080]

[0081] ε j (x) is the dielectric constant of layer j at position x, 1≤j≤N, ε jn (x) is the dielectric constant of medium n at position x of layer j, p jn (x) is the weight of medium n of slice j at position x, and M(x) is the total number of media of slice j at position x.

[0082] The weight p of the medium n of the slice j at position x jn (x) can be calculated according to the following formula:

[0083]

[0084] Where h jn (x) is the thickness of the medium n at position x of the layer j, H j is the thickness of the layer j, and the sum of the thickness of all dielectric materials of the layer j at position x is H j , at this time, the expression of the continuous function of the dielectric constant is:

[0085]

[0086] The weight p of the medium n of the slice j at position x jn (x) can also be calculated according to the following formula:

[0087]

[0088] At this time, the expression of the continuous function of the dielectric constant is:

[0089]

[0090] S301, calculating the Fourier coefficient of the dielectric constant of layer j based on the continuous function of the dielectric constant obtained in step S201, as shown in the following formula:

[0091]

[0092] Where i is the imaginary unit, k is the wave vector, and g is an integer.

[0093] S401, repeating steps S201 to S301, obtaining the Fourier coefficient of the dielectric constant of each layer, and then using the RCWA algorithm to obtain the theoretical spectrum of the one-dimensional periodic model.

[0094] Example 2

[0095] For a two-dimensional periodic model, the method includes the following steps:

[0096] S102: For the morphology model within a single period, an XYZ rectangular coordinate system is constructed with the center point of the period as the origin, the direction from the upper surface of the substrate upward as the Z axis (i.e., the direction from the bottom to the top of the periodic structure as the Z axis), and the two periodic directions of the two-dimensional periodic model as the XY axes. The position (x, y) is any point in the layer. L x is the period length in the X direction, L y is the period length in the Y direction.

[0097] Divide the morphology model of the periodic unit into N slices along the Z axis, where N is a positive integer; these slices are called slice 1, slice 2, ..., slice N, and the height H corresponding to slice j is obtained. j , j = 1, 2, ..., N. Figure 8 、 Figure 9 As shown, Figure 9 This is a top view of a two-dimensional periodic structure. Each dotted box is a periodic unit. Figure 8 Schematic diagram of the medium distribution at position (x, y) of any layer j in the morphology model of the periodic unit of the two-dimensional periodic structure.

[0098] S202 : For layer j, obtain a continuous function of the dielectric constant based on the dielectric distribution of the layer in the Z-axis direction.

[0099]

[0100] ε j (x,y) is the dielectric constant of layer j at position (x,y), 1≤j≤N, ε jn (x,y) is the dielectric constant of medium n at position (x,y) of layer j, p jn(x,y) is the weight of medium n of slice j at position (x,y), M(x,y) is the total number of media at position (x,y) of slice j, L x is the period length in the X direction, L y is the period length in the Y direction.

[0101] The weight p of medium n at position (x,y) for slice j jn (x,y) can be calculated using the following formula:

[0102]

[0103] Where h jn (x,y) is the thickness of medium n at position (x,y) of layer j, H j is the thickness of layer j, and the sum of the thicknesses of all dielectric materials of layer j at position (x, y) is H j , at this time, the expression of the continuous function of the dielectric constant is:

[0104]

[0105] The weight p of medium n at position (x,y) for slice j jn (x,y) can also be calculated according to the following formula:

[0106]

[0107] At this time, the expression of the continuous function of the dielectric constant is:

[0108]

[0109] S302, calculating the Fourier coefficient of the dielectric constant of layer j based on the continuous function of the dielectric constant obtained in step S202, as shown in the following formula:

[0110]

[0111] Where i is the imaginary unit, k x is the wave vector in the X direction, k y is the wave vector in the Y direction, and u and v are integers.

[0112] S402, repeating steps S202 to S302, obtaining the Fourier coefficient of the dielectric constant of each layer, and then using the RCWA algorithm to obtain the theoretical spectrum of the two-dimensional periodic structure.

[0113] Based on the first and second embodiments, taking a one-dimensional periodic structure as an example, the weight p of the medium n at the position x of the layer j is jn The calculation of (x) is further explained.

[0114] Figure 10 is the cross section of sheet j, and its side profile is a curve. The curve of the left profile is f(x), and the curve of the right profile is g(x). j1 The medium is the oblique line area, ε j0 The medium is the area outside the diagonal lines.

[0115] Establish a continuous function of the dielectric constant between positions a and b, and between c and d;

[0116] Between positions a and b, ε j1 The height / thickness of the medium is f(x), ε j0 The height / thickness of the medium is H j -f(x), then the dielectric constant between positions a and b is

[0117] Between positions c and d, ε j1 The height of the medium is g(x), ε j0 The height of the medium is H j -g(x), then the dielectric constant between positions c and d is

[0118] The dielectric constant between position -L / 2 and a is ε j0 ;

[0119] The dielectric constant between positions b and c is ε j1

[0120] The dielectric constant between position d and L / 2 is ε j0 .

[0121] Figure 11 For the existing technology Figure 10 The sectional view of the slice after approximation is shown in the figure. The prior art approximation of slices is to take the midline of the slice height and then make the intersection of the midline and the model perpendicular to the X axis to form a rectangle, which is obviously not accurate enough. Figure 3-5 The dielectric constants of the lamellae obtained by the prior art are approximate and discontinuous, resulting in reduced accuracy of the subsequently obtained theoretical spectrum. However, the embodiments provided by the present invention do not use approximate processing for the lamellae divided by the topography model. They can accurately determine the dielectric constant of the lamellae based on the dielectric distribution in the Z direction at any position along the periodic direction. Furthermore, the obtained dielectric constant of the lamellae is continuous, thereby improving the calculation accuracy and efficiency of the theoretical spectrum.

[0122] Furthermore, the technical solution of the present invention is further explained by taking the morphology model of a one-dimensional periodic structure of a trapezoidal structure as an example.

[0123] S103, establish an XOZ coordinate system, with the periodic direction of the topography model of the upper surface of the substrate as the X axis, the midpoint of the period as the coordinate origin, and the Z axis perpendicular to the upper surface of the substrate. Divide the topography model within the periodic unit into N (N is a positive integer) slices, called slice 1, slice 2, ..., slice N, and obtain the height / thickness corresponding to slice j as H j , j=1,2,…,N. Figure 12 shown.

[0124] S203, for slice j, if Figure 13 As shown, a continuous function of the dielectric constant is obtained, and the same operation is performed on other layers.

[0125] In the figure, slice j, ε j1 The medium is a black trapezoidal area, ε j0 The medium is outside the black trapezoidal area, and the height / thickness of layer j is H j , the length of the upper base of the trapezoid is t, the length of the lower base is b,

[0126] For the two protruding triangles on the left and right sides of the trapezoid, i.e., -b / 2≤x≤-t / 2, t / 2≤x≤b / 2, the dielectric constant at position x is calculated as follows: weight p jn (x) Take the ratio of the height of the medium n at position x to the height of the sheet as an example. At position x, use ε j1 and ε j0 The weighted average of ε at position x j1 The height of the medium h1(x) and ε j0 Height of medium H j -h1(x) and the slice height H j The ratio is the weight corresponding to each medium.

[0127]

[0128]

[0129] In position The dielectric constant is ε j0 .

[0130] In position The dielectric constant is ε j1 .

[0131] The final result is a continuous function of the dielectric constant of layer j:

[0132]

[0133] S303, obtaining the Fourier coefficient of the dielectric constant

[0134]

[0135]

[0136] S403, based on the results of steps S203 to S303, a theoretical spectrum is obtained using the RCWA algorithm.

[0137] In the embodiment of the present invention, the specific expression form of the weight is disclosed as an example, and other expressions are also possible. For example, the weight p of the dielectric material n of the layer j at the position P is jn (P) as an example, the weight function expression can be reasonably constructed to satisfy: when the layer j does not contain dielectric material n at position P, p jn (P) = 0, when the layer j at position P contains only dielectric material n, p jn (P) = 1. As long as the above conditions are met, a continuous dielectric constant of layer j can be constructed.

[0138] Different weights can represent the dielectric coupling effect under different process conditions. Different weight expressions can be used for samples under different process conditions. For example, the exponential form of weight disclosed in the embodiment of the present invention represents the dielectric coupling effect under complex process conditions. It is suitable for certain complex processes and can obtain a more accurate and continuous dielectric coefficient of the layer, thereby improving the accuracy of the obtained theoretical spectrum.

[0139] The more slices are divided, the more accurate the calculated theoretical spectrum is, but the computational efficiency is lower. Taking the theoretical spectrum calculated after 100 slices as a benchmark, the mean square error between the theoretical spectrum obtained after 5 slices in the prior art and the theoretical spectrum obtained after 100 slices in the prior art is 1.84e-6. The mean square error between the theoretical spectrum obtained after 5 slices in the present invention and the theoretical spectrum obtained after 100 slices in the prior art is 1.36e-6. Therefore, under the condition of the same number of slices, the results of the present invention method are more accurate.

[0140] In addition, the mean square error between the theoretical spectrum divided into 5 layers by the prior art and the theoretical spectrum divided into 100 layers by the prior art is 1.84e-6, and the mean square error between the theoretical spectrum divided into 4 layers by the method of the present invention and the theoretical spectrum divided into 100 layers by the prior art is 2.10e-6. Therefore, under the condition of similar mean square error, the method of the present invention has fewer layers than the prior art, so the calculation efficiency is higher.

[0141] The above embodiment uses a one-dimensional trapezoidal structure as an example. In practical applications, the topography model structure is relatively complex, such as when it contains multiple layers of dielectric material and has a complex side profile curve. In such cases, conventional techniques must increase the number of slices to ensure computational accuracy, which reduces computational efficiency. However, the method of the present invention can maintain high accuracy in calculating the theoretical spectrum of a complex topography model even with a small number of slices, without sacrificing computational efficiency. This improves computational efficiency while ensuring the accuracy of the theoretical spectrum.

[0142] The present invention avoids the approximation of the side profiles of the model-divided lamellae, making the processing of the morphology model in the RCWA calculation more consistent with the actual morphology model of the sample, obtaining a continuous function of the dielectric constant of each lamella, improving the calculation accuracy of the Fourier coefficient of the dielectric constant, and improving the accuracy and efficiency of the theoretical spectrum calculation.

[0143] Based on the above embodiment, the present invention further provides a method for measuring a topography parameter, the method comprising:

[0144] Obtaining a measurement spectrum of the sample to be measured;

[0145] Acquiring a topography model of the sample to be tested, and floating the topography parameters of the topography model to obtain a plurality of topography models corresponding to the sample to be tested;

[0146] The method for obtaining the theoretical spectrum of the periodic structure described in the above embodiment is used to obtain the theoretical spectra corresponding to the multiple morphology models to construct a theoretical spectrum library;

[0147] searching the theoretical spectrum library for a target theoretical spectrum that matches the measured spectrum;

[0148] The parameters of the sample to be tested are determined according to the morphological parameters of the morphological model corresponding to the target theoretical spectrum.

[0149] On the basis of the above embodiments, the present invention further provides a device for measuring a morphology parameter, the device comprising:

[0150] A metrology unit, used for obtaining a measurement spectrum of a sample to be measured;

[0151] a calculation unit, configured to obtain a theoretical spectrum library by adopting the method for obtaining a theoretical spectrum of a periodic structure described in the above embodiment; and

[0152] a fitting unit, configured to determine a target theoretical spectrum matching the measured spectrum from the theoretical spectrum library;

[0153] The output unit extracts the morphological parameters corresponding to the target theoretical spectrum and outputs them as the measured parameters of the sample to be measured.

[0154] Based on the method for obtaining the theoretical spectrum in the above embodiment, the present invention further improves the parameter measurement accuracy and efficiency of the morphology model.

[0155] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0156] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for obtaining a theoretical spectrum, for obtaining a theoretical spectrum of a periodic structure, wherein the periodic structure comprises a plurality of periodic units, characterized in that: include: Acquire a morphology model of the periodic unit, wherein the morphology model has a plurality of morphology parameters; Dividing the topography model into a plurality of layers along a direction Z from the bottom to the top of the periodic structure; Based on the dielectric distribution of each layer in the direction Z, obtaining a continuous function of the dielectric coefficient of the corresponding layer along the periodic direction; Based on the continuous function, respectively calculating the Fourier coefficient of the dielectric constant of each of the layers; The theoretical spectrum of the periodic structure is calculated based on the Fourier coefficients of the dielectric constants of all the layers using a rigorous coupled wave analysis algorithm; The continuous function of the dielectric constant of the sheet along the periodic direction satisfies: ， in, is any position of any slice j along the periodic direction The dielectric constant at For slice j at position The dielectric constant of the dielectric material n at For slice j at position The weight of dielectric material n is obtained based on the dielectric material thickness, and the layer j is at position Includes A dielectric material.

2. The method according to claim 1, characterized in that The step of obtaining a continuous function of the dielectric coefficient of each layer along the periodic direction based on the dielectric distribution of each layer in the direction Z includes: Obtaining a periodic medium distribution corresponding to each position of each layer along the periodic direction, wherein the periodic medium distribution includes distributions of D types of dielectric materials along the direction Z, where D is a positive integer; Calculating the thickness of each dielectric material along the direction Z, and obtaining the weight of the dielectric material corresponding to each position based on the thickness; Based on the dielectric constant of each dielectric material at each position and the weight of the corresponding dielectric material, a continuous function of the dielectric constant of the sheet along the periodic direction is established.

3. The method according to claim 2, characterized in that Establishing a continuous function of the dielectric constant of the sheet along the periodic direction includes: A weighted average is performed on the dielectric coefficients of all the dielectric materials at each position.

4. The method according to claim 1, wherein The periodic structure is a one-dimensional periodic model, which is a model that repeats periodically in only one direction; The Fourier coefficient of the dielectric constant of the layer j , calculated according to the following formula: Where i is the imaginary unit, k is the wave vector, and g is an integer; Wherein, for the topography model of a single periodic unit, an XOZ rectangular coordinate system is constructed with the center point of the period as the origin, the direction Z as the Z axis, and the periodic direction as the X axis. That is, the slice j is at position = x The dielectric constant at , is the period length of the periodic structure.

5. The method according to claim 4, characterized in that The slice j is at position = x The weight of the dielectric material n at , calculated according to the following formula: or Where, For the slice j at position = x The thickness of the dielectric material n at is the thickness of the sheet j, and the sheet j is at position = x The sum of the thickness of all dielectric materials at .

6. The method according to claim 1, characterized in that The periodic structure is a two-dimensional periodic model, and the two-dimensional periodic model is a model that repeats periodically in two directions perpendicular to each other; The Fourier coefficient of the dielectric constant of the layer j , calculated according to the following formula: Where, is the imaginary unit, is the wave vector in the X direction, is the wave vector in the Y direction, and is an integer; Wherein, for the topography model of a single periodic unit, an XYZ rectangular coordinate system is constructed with the center point of the period as the origin, the direction Z as the Z axis, and the two periodic directions as the XY axes respectively; That is, the slice j is at position = the dielectric constant at (x,y), , , is the period length of the periodic structure in the X direction, is the period length of the periodic structure in the Y direction.

7. The method according to claim 6, characterized in that The slice j is at position = the weight of the dielectric material n at (x,y) , calculated according to the following formula: or Where, The thickness of dielectric material n of layer j at position (x,y), is the thickness of the slice j, and the slice j is at position =The sum of the thickness of all dielectric materials at (x,y) is .

8. A method for measuring morphological parameters, characterized in that: The method comprises: Obtaining a measurement spectrum of the sample to be measured; Acquiring a topography model of the sample to be tested, and floating the topography parameters of the topography model to obtain a plurality of topography models corresponding to the sample to be tested; The method for obtaining theoretical spectra according to any one of claims 1 to 7 is used to obtain theoretical spectra corresponding to the plurality of morphology models to construct a theoretical spectrum library; searching the theoretical spectrum library for a target theoretical spectrum that matches the measured spectrum; The parameters of the sample to be tested are determined according to the morphological parameters of the morphological model corresponding to the target theoretical spectrum.

9. A device for measuring morphological parameters, characterized in that: The measuring device comprises: A metrology unit, used for obtaining a measurement spectrum of a sample to be measured; a computing unit, configured to obtain a theoretical spectrum library by adopting the method for obtaining a theoretical spectrum according to any one of claims 1 to 7; a fitting unit, configured to determine a target theoretical spectrum matching the measured spectrum from the theoretical spectrum library; The output unit extracts the morphological parameters corresponding to the target theoretical spectrum and outputs them as the measured parameters of the sample to be measured.

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