Optical proximity correction method

Abstract

The invention provides an optical proximity correction method, and the method comprises the steps: providing a target graph which comprises a plurality of first sub-graphs which are distributed in an array, each first sub-graph comprises a rectangle, and each rectangle comprises a short side in the horizontal direction and a long side in the vertical direction; a virtual graph is obtained based on the target graph, two long edges of each first sub-graph are moved inwards by a distance of delta V, two short edges of each first sub-graph are moved outwards by a distance of delta H, a plurality of second sub-graphs are obtained, and the plurality of second sub-graphs are the virtual graph; and performing optical proximity correction based on the virtual graph to obtain a photomask graph. According to the optical proximity correction method provided by the invention, the corresponding virtual graph is obtained based on the target graph, the optical proximity correction is subsequently performed based on the virtual graph, the photomask graph is obtained, and the accuracy of the optical proximity correction can still be ensured in nodes of 10 nm and below.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to an optical proximity correction method. Background Art

[0002] In semiconductor manufacturing, as the design size continues to shrink, the diffraction effect of light becomes more and more obvious. As a result, the optical image produced on the design pattern is degraded, and the actual pattern formed by photolithography on the substrate becomes different from the design pattern. This phenomenon is called the optical proximity effect (OPE: Optical Proximity Effect).

[0003] In order to correct the optical proximity effect, optical proximity correction (OPC: Optical Proximity Correction) was created. The core idea of ​​optical proximity correction is to establish an optical proximity correction model based on the consideration of offsetting the optical proximity effect, and to design the photomask pattern according to the optical proximity correction model. In this way, although the optical proximity effect occurs in the photolithography pattern corresponding to the photomask pattern after photolithography, since the offset of this phenomenon has been considered when designing the photomask pattern according to the optical proximity correction model, the photolithography pattern after photolithography is close to the target pattern that the user actually wants to obtain.

[0004] However, as the design size continues to shrink, the current optical proximity correction method may not be able to effectively converge the correction results in nodes of 10nm and below, affecting the accuracy of the optical proximity correction.

[0005] Therefore, it is necessary to provide a more effective and reliable technical solution that can still ensure the accuracy of optical proximity correction in nodes of 10nm and below. Summary of the invention

[0006] The present application provides an optical proximity correction method, which can still ensure the accuracy of optical proximity correction in nodes of 10nm and below.

[0007] The present application provides an optical proximity correction method, comprising: providing a target pattern, the target pattern comprising a plurality of first sub-patterns distributed in an array, the first sub-pattern comprising a rectangle, the rectangle comprising a short side along a horizontal direction and a long side along a vertical direction; obtaining a virtual pattern based on the target pattern, moving both long sides of each first sub-pattern inward by a distance ΔV and moving both short sides of each first sub-pattern outward by a distance ΔH, to obtain a plurality of second sub-patterns, the plurality of second sub-patterns being the virtual patterns; performing optical proximity correction based on the virtual pattern to obtain a mask pattern.

[0008] In some embodiments of the present application, the ΔV satisfies the following conditions:

[0009]

[0010] Among them, MRC S is the spacing parameter limited by the mask rule; S1 is the horizontal spacing between adjacent first sub-patterns; W is the short side size of the first sub-pattern; MRC W Limits the width parameter for mask rules.

[0011] In some embodiments of the present application, the range of ΔV is 0.1-50 nanometers.

[0012] In some embodiments of the present application, the ΔH satisfies the following conditions:

[0013]

[0014] Wherein, S2 is the vertical spacing between adjacent first sub-graphs; and C is an arbitrary positive number.

[0015] In some embodiments of the present application, C is less than or equal to a minimum fragment value in the optical proximity correction parameter.

[0016] In some embodiments of the present application, the range of C is 0-50 nanometers.

[0017] In some embodiments of the present application, the range of ΔH is 0.1-50 nanometers.

[0018] In some embodiments of the present application, the method for performing optical proximity correction based on the virtual graphic includes: segmenting the virtual graphic, dividing the boundary of the virtual graphic into multiple segments; performing an optical proximity correction operation on the segmented virtual graphic to obtain a corrected graphic; performing simulated lithography on the corrected graphic to obtain a simulated graphic; comparing the edge position error between the simulated graphic and the target graphic, and when the edge position error between the simulated graphic and the target graphic is greater than a threshold, moving the positions of the multiple segments, re-performing the optical proximity correction operation and simulated lithography until the edge position error between the simulated graphic and the target graphic is less than or equal to the threshold, and the corrected graphic corresponding to the simulated graphic is used as the mask graphic.

[0019] In some embodiments of the present application, the virtual graph is segmented based on a segmentation rule.

[0020] In some embodiments of the present application, the length of the long side is greater than the length of the short side.

[0021] The present application provides an optical proximity correction method, which obtains a corresponding virtual pattern based on a target pattern, and subsequently performs optical proximity correction based on the virtual pattern to obtain a mask pattern, which can still ensure the accuracy of the optical proximity correction in nodes of 10nm and below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The following figures describe in detail the exemplary embodiments disclosed in this application. The same reference numerals represent similar structures in several views of the drawings. Those skilled in the art will understand that these embodiments are non-limiting, exemplary embodiments, and the drawings are only for the purpose of illustration and description, and are not intended to limit the scope of this application. Other embodiments may also accomplish the inventive intent in this application. It should be understood that the drawings are not drawn to scale.

[0023] in:

[0024] Figure 1 A flowchart of the optical proximity correction method described in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of the structure of a target graphic in the optical proximity correction method described in an embodiment of the present application;

[0026] Figure 3 It is a structural schematic diagram of the difference between a virtual pattern and a target pattern in the optical proximity correction method described in an embodiment of the present application. DETAILED DESCRIPTION

[0027] The following description provides specific application scenarios and requirements of the present application, with the purpose of enabling those skilled in the art to make and use the content in the present application. It will be apparent to those skilled in the art that various local modifications to the disclosed embodiments are apparent, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the embodiments shown, but to the widest scope consistent with the claims.

[0028] The technical solution of the present invention is described in detail below in conjunction with the embodiments and drawings.

[0029] In some optical proximity correction methods, after providing a target pattern, the edge of the target pattern is cut into small segments. By moving the segment position and performing model simulation, the edge position difference (EPE: Edge Placement Error) between the current simulation pattern and the target pattern is obtained to calculate the segment movement position for the next iteration. Finally, after dozens of iterations, the simulation pattern and the target pattern are made as close as possible. The new pattern obtained after each segment is moved is the OPC correction result, which is used for subsequent mask production. Therefore, the method of accelerating iterative convergence to reduce EPE is the key to the OPC correction process.

[0030] However, as the spacing between patterns continues to shrink, the above method may fail to effectively converge the OPC results in nodes of 10nm and below. Since the two adjacent target patterns are too close, the spacing between the two target patterns is smaller than the MRC setting value (mask rule constrain, which represents the mask production capability and is one of the limiting parameters of the OPC segment movement process). This will prevent the segments that were originally intended to move outward from moving normally due to the MRC restriction, resulting in a large difference between the simulated pattern and the target pattern after OPC correction. If the mask is made based on this result, it will ultimately affect the device performance.

[0031] Based on the above problems, the present application provides an optical proximity correction method, which obtains a corresponding virtual pattern based on the target pattern, and subsequently performs optical proximity correction based on the virtual pattern to obtain a mask pattern, which can still ensure the accuracy of the optical proximity correction in nodes of 10nm and below.

[0032] Figure 1 The optical proximity correction method according to the embodiment of the present application is described in detail below with reference to the accompanying drawings.

[0033] The present application provides an optical proximity correction method, referring to Figure 1 As shown, including:

[0034] Step S1: providing a target pattern, wherein the target pattern includes a plurality of first sub-patterns distributed in an array, wherein the first sub-patterns include a rectangle, and the rectangle includes a short side along a horizontal direction and a long side along a vertical direction;

[0035] Step S2: obtaining a virtual graph based on the target graph, moving the two long sides of each first sub-graph inward by a distance ΔV and moving the two short sides of each first sub-graph outward by a distance ΔH, to obtain a plurality of second sub-graphs, wherein the plurality of second sub-graphs are the virtual graphs;

[0036] Step S3: performing optical proximity correction based on the virtual pattern to obtain a mask pattern.

[0037] The present application provides an optical proximity correction method, which obtains a corresponding virtual pattern based on a target pattern, and subsequently performs optical proximity correction based on the virtual pattern to obtain a mask pattern, thereby avoiding the problem of reduced accuracy of optical proximity correction when the target pattern is at a node of 10nm and below.

[0038] Figure 2 It is a schematic diagram of the structure of the target pattern in the optical proximity correction method described in the embodiment of the present application.

[0039] refer to Figure 1 and Figure 2 As shown, step S1, providing a target pattern 100, the target pattern 100 includes a plurality of first sub-patterns 101 distributed in an array. Specifically, the target pattern 100 includes a plurality of rows of first sub-patterns 101, and the number of first sub-patterns 101 in each row is a plurality. The first sub-patterns 101 in adjacent rows are staggered, that is, the first sub-patterns 101 in adjacent rows are not aligned. The target pattern 100 is a target of optical proximity correction, that is, in an ideal state, the photolithographic pattern formed on the substrate is consistent with the target pattern 100.

[0040] Continue to refer Figure 2 As shown, the first sub-graph 101 comprises a rectangle, and the rectangle comprises a short side along the horizontal direction and a long side along the vertical direction. It should be noted that, unless otherwise specified, the horizontal direction and vertical direction and other azimuth relationships mentioned in the embodiments of the present application are all based on the azimuths in the accompanying drawings.

[0041] In some embodiments of the present application, the length of the long side is greater than the length of the short side.

[0042] Continue to refer Figure 2 As shown, the horizontal spacing between adjacent first sub-patterns 101 is marked as S1. The vertical spacing between adjacent first sub-patterns 101 is marked as S2. The short side dimension (or width) of the first sub-pattern 101 is marked as W.

[0043] In the 10nm and below technology nodes, the horizontal spacing of the adjacent first sub-patterns 101 and the vertical spacing of the adjacent first sub-patterns 101 are very small, which are already smaller than the MRC setting value (mask rule constraint, representing the mask production capability, and one of the limiting parameters of the OPC segment movement process). During the OPC correction process, if the target pattern 100 is directly used as the basis for segmentation and segment movement operations, there may be segments that are originally intended to move outward and cannot move normally due to MRC restrictions, resulting in a large difference between the simulated pattern after OPC correction and the target pattern. If the mask is made based on this result, it will ultimately affect the device performance.

[0044] Based on this, in the technical solution of the present application, the optical proximity correction is not directly started based on the target pattern 100, but the target pattern 100 is first processed to obtain a virtual pattern, the virtual pattern meets the MRC restriction, and then the optical proximity correction is started based on the virtual pattern. In this way, the problem that the accuracy of the OPC correction result is affected due to the target pattern 100 not meeting the MRC restriction can be avoided.

[0045] Figure 3It is a structural schematic diagram of the difference between a virtual pattern and a target pattern in the optical proximity correction method described in an embodiment of the present application.

[0046] refer to Figure 1 and Figure 3 As shown, step S2, based on the target graphic 100, a virtual graphic 200 is obtained, the two long sides of each first sub-graphic 101 are moved inward by a distance ΔV (i.e., the width of the short side is shortened), and the two short sides of each first sub-graphic 101 are moved outward by a distance ΔH (i.e., the length of the long side is increased), to obtain a plurality of second sub-graphics 201, and the plurality of second sub-graphics 201 are the virtual graphics 200.

[0047] The virtual graph 200 needs to meet the MRC restriction.

[0048] First, the width (short side dimension) of each second sub-pattern 201 in the virtual pattern 200 needs to satisfy the mask rule width parameter MRC. W .

[0049] That is, W-2ΔV≥MRC W .

[0050] Second, the horizontal spacing between adjacent second sub-patterns 201 in the virtual pattern 200 needs to meet the mask rule limit spacing parameter MRC. S .

[0051] That is, S1+2ΔV≥MRC S .

[0052] Combining the first and second points above, it can be concluded that the ΔV satisfies the following conditions:

[0053]

[0054] Among them, MRC S is the spacing parameter limited by the mask rule; S1 is the horizontal spacing between adjacent first sub-patterns; W is the short side size of the first sub-pattern; MRC W Limits the width parameter for mask rules.

[0055] In some embodiments of the present application, the range of ΔV is 0.1-50 nanometers.

[0056] In order to improve the OPC convergence efficiency while making the virtual graph 200 meet the MRC restriction, the present application also sets the long side size (length) of the second sub-graph 201 in the virtual graph 200 .

[0057] Specifically, the minimum value of ΔH is half of the vertical spacing between adjacent first sub-graphs 101 in the target graph 100, so that there is a certain amount of opposite projection between the second sub-graphs 201 of the obtained virtual graph 200 to facilitate OPC convergence; the maximum value of ΔH is the minimum value plus a constant C, C can be any positive number, and it is recommended not to exceed the minimum fragment value set in the OPC parameters to facilitate segmentation and convergence.

[0058] In some embodiments of the present application, the ΔH satisfies the following conditions:

[0059]

[0060] Wherein, S2 is the vertical spacing between adjacent first sub-graphs; and C is an arbitrary positive number.

[0061] In some embodiments of the present application, C is less than or equal to a minimum fragment value in the optical proximity correction parameter.

[0062] In some embodiments of the present application, the range of C is 0-50 nanometers.

[0063] In some embodiments of the present application, the range of ΔH is 0.1-50 nanometers.

[0064] In the technical solution of the present application, a corresponding virtual graphic that meets the MRC restrictions is obtained based on the target graphic, and then an optical proximity correction is performed based on the virtual graphic to obtain a mask graphic, which can still ensure the accuracy of the optical proximity correction in nodes of 10nm and below.

[0065] Continue to refer Figure 1 As shown, in step S3, optical proximity correction is performed based on the virtual pattern 200 to obtain a mask pattern.

[0066] In some embodiments of the present application, the method for performing optical proximity correction based on the virtual graphic 200 includes: segmenting the virtual graphic 200, dividing the boundary of the virtual graphic 200 (specifically, the edge of each second sub-graphic 201) into multiple segments; performing an optical proximity correction operation on the segmented virtual graphic 200 to obtain a corrected graphic (or OPC polygon); performing simulated lithography on the corrected graphic to obtain a simulated graphic; comparing the edge position error (EPE: Edge Placement Error) between the simulated graphic and the target graphic, and when the edge position error between the simulated graphic and the target graphic 100 is greater than a threshold, moving the positions of the multiple segments, re-performing the optical proximity correction operation and simulated lithography until the edge position error between the simulated graphic and the target graphic is less than or equal to the threshold, and the corrected graphic corresponding to the simulated graphic is used as the mask graphic.

[0067] In some embodiments of the present application, the virtual graph 200 is segmented based on a segmentation rule. In this embodiment, the virtual graph 200 is segmented based on a segmentation rule. The virtual graph 200 may be segmented by an equal division method, and the boundary of the virtual graph 200 is divided into a plurality of segments.

[0068] Specifically, in this embodiment, the boundary of the second sub-graph 201 of the virtual graph 200 includes a long side and a short side, and the method of segmenting the virtual graph 200 includes: dividing the long side of the second sub-graph 201 into multiple first segments; dividing the short side of the second sub-graph 201 into one or multiple second segments.

[0069] It should be noted that, in other embodiments, the virtual graph 200 may be segmented using a segmentation rule defined by a user, so that the boundary of the virtual graph 200 is divided into a plurality of segments.

[0070] The optical proximity correction operation includes multiple iterative loop calculations. During the optical proximity correction operation, the position of the first fragment moves inward or outward, and the position of the second fragment moves inward or outward, until the iterations of each fragment converge and the edge position error is within a preset range.

[0071] Specifically, the correction pattern (or OPC polygon) satisfies: performing simulated lithography on the correction pattern (or OPC polygon) to obtain a simulated lithography pattern; comparing the position difference between the simulated lithography pattern and the target pattern to obtain an edge position error EPE of the simulated lithography pattern, and the edge position error EPE is within a preset range.

[0072] The traditional OPC correction method of performing splitting and moving operations on the target graphics can no longer meet the process requirements of complex graphics at nodes of 10nm and below. Based on this, the present application proposes a new optical proximity correction method, which can solve the problem that the OPC cannot converge due to the MRC restriction during the correction process caused by the graphics being too close. The technical solution of the present application, based on the target graphics, generates an additional layer of virtual graphics through graphics processing, which is used as the operation object of the first step of OPC segment splitting and moving, while the original target graphics are still used as the actual target for calculating EPE during OPC iteration. According to this method, the initial OPC splitting / moving graphics that meet the MRC requirements can be obtained to ensure the convergence of the OPC results. The applicant's test results show that the OPC EPE obtained by the technical solution of the present application is significantly superior to the traditional method, and the contour line is closer to the target graphics, which shows that the method provided by the present application can effectively help improve the process window and improve the yield.

[0073] The present application provides an optical proximity correction method, which obtains a corresponding virtual pattern based on a target pattern, and subsequently performs optical proximity correction based on the virtual pattern to obtain a mask pattern, which can still ensure the accuracy of the optical proximity correction in nodes of 10nm and below.

[0074] In summary, after reading the contents of this application, those skilled in the art will appreciate that the aforementioned application contents may be presented only in an exemplary manner and may not be restrictive. Although not explicitly stated herein, those skilled in the art will appreciate that this application is intended to encompass various reasonable changes, improvements and modifications to the embodiments. These changes, improvements and modifications are within the spirit and scope of the exemplary embodiments of this application.

[0075] It should be understood that the term "and / or" used in this embodiment includes any or all combinations of one or more of the associated listed items. It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to another element, or there can also be intermediate elements.

[0076] It should also be understood that the terms "comprising", "containing", "including" or "comprising", when used in this application document, indicate the presence of the recorded features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or groups thereof.

[0077] It should also be understood that although the terms first, second, third, etc. can be used to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Therefore, without departing from the teachings of the present application, the first element in some embodiments can be referred to as the second element in other embodiments. The same reference numerals or the same reference signs represent the same elements throughout the specification.

[0078] In addition, the present specification describes exemplary embodiments by reference to idealized exemplary cross-sectional views and / or plan views and / or stereograms. Therefore, differences from the illustrated shapes due to, for example, manufacturing techniques and / or tolerances are foreseeable. Therefore, the exemplary embodiments should not be interpreted as being limited to the shapes of the regions shown herein, but should include deviations in shapes caused by, for example, manufacturing. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shapes of the regions of the device nor to limit the scope of the exemplary embodiments.

Claims

1. An optical proximity correction method, characterized in that: include: Providing a target pattern, the target pattern comprising a plurality of first sub-patterns distributed in an array, the first sub-patterns comprising a rectangle, the rectangle comprising a short side along a horizontal direction and a long side along a vertical direction; Based on the target graph, a virtual graph is obtained, and two long sides of each first sub-graph are moved inward by a distance of ΔV and two short sides of each first sub-graph are moved outward by a distance of ΔH to obtain a plurality of second sub-graphs, wherein the plurality of second sub-graphs are the virtual graphs; An optical proximity correction is performed based on the virtual pattern to obtain a mask pattern.

2. The optical proximity correction method according to claim 1, wherein: The ΔV satisfies the following conditions: Among them, MRC S is the spacing parameter limited by the mask rule; S1 is the horizontal spacing between adjacent first sub-patterns; W is the short side size of the first sub-pattern; MRC W Limits the width parameter for mask rules.

3. The optical proximity correction method according to claim 2, wherein: The range of ΔV is 0.1-50 nanometers.

4. The optical proximity correction method according to claim 1, wherein: The ΔH satisfies the following conditions: Wherein, S2 is the vertical spacing between adjacent first sub-graphs; and C is an arbitrary positive number.

5. The optical proximity correction method according to claim 4, wherein: C is less than or equal to the minimum fragment value in the optical proximity correction parameters.

6. The optical proximity correction method according to claim 5, characterized in that: The range of C is 0-50 nm.

7. The optical proximity correction method according to claim 5, characterized in that: The range of ΔH is 0.1-50 nm.

8. The optical proximity correction method according to claim 1, wherein: The method for performing optical proximity correction based on the virtual pattern comprises: Segmenting the virtual graph, dividing the boundary of the virtual graph into a plurality of segments; Performing an optical proximity correction operation on the segmented virtual image to obtain a corrected image; Performing simulated photolithography on the modified pattern to obtain a simulated pattern; Compare the edge position errors between the simulation pattern and the target pattern. When the edge position error between the simulation pattern and the target pattern is greater than a threshold, move the positions of the multiple fragments, re-perform the optical proximity correction operation and simulate lithography until the edge position error between the simulation pattern and the target pattern is less than or equal to the threshold, and use the corrected pattern corresponding to the simulation pattern as the mask pattern.

9. The optical proximity correction method according to claim 8, wherein: The virtual graph is segmented based on a segmentation rule.

10. The optical proximity correction method according to claim 1, wherein: The length of the long side is greater than the length of the short side.

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