An OPC correction method

Abstract

The present application provides an OPC correction method, which defines a feature pattern according to the OPC publishing experience of product layout; adopts a special segmentation method for the segmentation of specific edges of the feature pattern; corrects the feature pattern based on a conventional OPC correction method, adjusts the target pattern in advance according to the difference between the simulation value and the target value, and carries out subsequent OPC processing based on the adjusted target pattern. The present application defines a feature pattern, carries out special segmentation for the specified edges of the feature pattern, obtains the difference between the simulation value and the target value after OPC, and compensates the difference in the original target pattern, so as to realize reasonable optical proximity effect correction of the feature pattern, match the simulation value and the target value of the feature pattern after OPC, meet the process requirements, and improve the yield of products.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit manufacturing, and specifically relates to an OPC correction method. Background Technology

[0002] With the continuous development of wafer foundry technology, the feature sizes on logic device nodes are approaching or even smaller than the wavelengths of light used in photolithography. According to the principles of light diffraction and interference, light waves undergo diffraction when passing through a photomask, and interference also occurs at different locations on the mask. Therefore, the actual light intensity distribution projected onto the silicon wafer is the result of the superposition of these diffracted and interfering light waves, and it is not exactly the same as the mask pattern. This phenomenon, where the photolithographic pattern deviates from the mask pattern due to light diffraction and interference, is called the Optical Proximity Effect (OPE). In photolithography, the Optical Proximity Effect is unavoidable. Current methods employ OPC technology to minimize the deformation and deviation of the mask pattern projected onto the silicon wafer, ensuring that the exposed pattern meets design requirements.

[0003] OPC stands for Optical Proximity Correction. The general OPC processing flow is as follows: import the layout, perform routine cleanup, generate the target graphic according to process requirements, perform segmentation settings based on the target graphic, and then perform OPC processing based on the model and the OPC program. This method can achieve OPC correction that meets process requirements for 99% of graphics. For weak points where the simulation graphic after OPC correction differs significantly from the target graphic, the OPC program is typically optimized specifically. This operation is a common method for resolving weak points by optimizing the OPC program based on OPC verify results.

[0004] However, for some typical feature graphics, such as U-shaped or H-shaped graphics, the probability of OPC correction being inadequate is very high when the bottom size is within a certain range. Based on the existing OPC method, weak points can only be found in the OPC verify stage and then targeted special processing can be performed, which requires rework, is inefficient, and is not conducive to the mass production and publication of OPC. Summary of the Invention

[0005] The purpose of this invention is to provide an OPC correction method that matches the simulated value and target value of the feature pattern after OPC, thereby meeting process requirements and improving product yield.

[0006] To achieve the above objectives, the present invention provides an OPC correction method, comprising:

[0007] Obtain the product layout and define the feature graphic, which includes two corners and a bottom line segment connecting the two corners;

[0008] The target graphic is generated using a standard OPC program on the product layout.

[0009] The bottom line segment of the feature graphic in the target graphic is divided into three equal parts;

[0010] Perform OPC correction simulation on the target graphic to obtain the simulation values ​​of the center positions of the three segments after simulation.

[0011] Calculate the difference between the simulated values ​​and the target values ​​for the three segments, and compensate for these differences in the settings of the standard OPC program; and,

[0012] The target graphic is corrected based on the compensated OPC program.

[0013] In an optional embodiment of the present invention, the feature pattern is arranged in a U-shape or an H-shape.

[0014] In an optional embodiment of the invention, the length of the bottom line segment of the feature graphic is between 1 times the design critical dimension and 2.5 times the design critical dimension;

[0015] The width of the bottom line segment of the feature graphic is between 1 times the design critical dimension and 1.5 times the design critical dimension;

[0016] The lengths of the line segments on both sides of the connecting corner of the feature graphic are both greater than or equal to twice the design critical dimension.

[0017] In an optional embodiment of the present invention, the feature pattern is further divided into batches, generating multiple batches of feature patterns with different sizes from three aspects: the length of the bottom line segment, the width of the bottom line segment, and the line segments on both sides of the feature pattern.

[0018] In an optional embodiment of the present invention, the setting for compensating the difference to a conventional OPC procedure includes: compensating the difference of each segment to the target value of each segment respectively.

[0019] In an optional embodiment of the present invention, the method for compensating the difference values ​​of each segment to the target value includes:

[0020] After generating the target image using a conventional OPC program, feature graphics are identified on the target image using a software language. The bottom line segment of the feature graphics is divided into three equal parts. The target values ​​of the two segments near the corners are compensated for backward, and the target values ​​of the middle segments are extended.

[0021] In an optional embodiment of the present invention, the backlash compensation value for the two segments adjacent to the corner is N1, and the outer length value for the middle segment is N2.

[0022] N1 = (EPE1 + EPE3) / 2;

[0023] N2 = EPE2;

[0024] Wherein, the length of the bottom line segment of the feature graphic is 1 times the design critical dimension, the width of the bottom line segment of the feature graphic is 1 times the design critical dimension, and the length of the two side line segments of the feature graphic is 3 times the design critical dimension;

[0025] EPE1 and EPE3 are the simulated values ​​of the center positions of the two segments near the corner in the feature graphic, respectively, and EPE2 is the simulated value of the center position of the middle segment in the feature graphic.

[0026] In an optional embodiment of the present invention, the correction of the target graphic based on the compensated OPC program includes:

[0027] Calculate whether the difference between the simulated value and the target value of the feature graphic is within the specified range. If it is not within the specified range, readjust the compensation value in 1 dBu increments until the difference between the simulated value and the target value of the feature graphic is within the specified range.

[0028] In an optional embodiment of the present invention, the method further includes writing the adjusted compensation value into an OPC program, using the adjusted OPC program to generate a target graphic, and performing OPC verification on the generated target graphic.

[0029] In an optional embodiment of the present invention, the calculation formula for the simulation values ​​of the three segment center positions includes:

[0030] EPEi=f2(f1(OPC result),fragment i),

[0031] Where f1 is the model simulation function, f2 is the simulation value calculation function, and i takes the values ​​1, 2, and 3;

[0032] The length of the bottom line segment of the feature graphic is 1 times the design critical dimension, the width of the bottom line segment of the feature graphic is 1 times the design critical dimension, and the length of the two side line segments of the feature graphic is 3 times the design critical dimension.

[0033] In summary, this invention provides an OPC correction method, including obtaining a product layout and defining a feature graphic; employing a special segmentation method for specific edges of the feature graphic; correcting the feature graphic based on conventional OPC correction methods; pre-adjusting the target graphic based on the difference between the simulated value and the target value; and performing subsequent OPC processing based on the adjusted target graphic. This invention, by defining a feature graphic and performing special segmentation on specified edges of the feature graphic, obtains the difference between the simulated value and the target value after OPC, and compensates for this difference in the original target graphic. This achieves reasonable optical proximity effect correction for the feature graphic, matching the simulated value and target value of the feature graphic after OPC, meeting process requirements, and improving product yield. Attached Figure Description

[0034] Figure 1 This is a comparison chart between the target graphic obtained by the conventional OPC processing method and the simulation value.

[0035] Figure 2 A flowchart of an OPC correction method provided in an embodiment of the present invention;

[0036] Figure 3 This is a standard OPC method for segmenting the bottom line segments of feature graphics.

[0037] Figure 4 This invention provides a method for segmenting the bottom line segment of a feature graphic using OPC.

[0038] Figure 5 This is a comparison diagram of the target graphic obtained using the OPC correction method of the present invention and the target graphic obtained using the conventional OPC method.

[0039] Figure 6 This is a comparison chart of simulation values ​​obtained using the OPC correction method of this invention and simulation values ​​obtained using the conventional OPC method. Detailed Implementation

[0040] To make the content of this invention clearer and easier to understand, the following description, in conjunction with the accompanying drawings, further illustrates the invention. Of course, this invention is not limited to this specific embodiment, and common substitutions well-known to those skilled in the art are also covered within the scope of protection of this invention.

[0041] Secondly, the present invention is described in detail using schematic diagrams. When describing the examples of the present invention in detail, for ease of explanation, the schematic diagrams are not enlarged to a certain extent according to the general proportions, and this should not be regarded as a limitation of the present invention.

[0042] For ease of description, some embodiments of the present invention may use spatially relative terms such as “above,” “below,” “top,” and “under” to describe the relationship between one element or component and another (or more) elements or components as shown in the accompanying drawings of the embodiments. It should be understood that, in addition to the orientations described in the drawings, the spatially relative terms are also intended to include different orientations of the device during use or operation. For example, if the device in the drawings is flipped, it is described as an element or component “below” or “under” other elements or components, and will subsequently be positioned “above” or “on” other elements or components. The terms “first,” “second,” etc., used below are used to distinguish between similar elements and are not necessarily used to describe a particular order or temporal sequence.

[0043] Photolithography is a crucial process in integrated circuit manufacturing. It involves creating openings in the surface of a semiconductor wafer (such as silicon dioxide) to allow for the localized diffusion of impurities. In advanced photolithography processes, due to the reduction in the size of the exposure pattern, pre-processing (OPC) of the photomask pattern is necessary to compensate for the optical proximity effect caused by the limited resolution of the optical system. For some typical structural features, the parameter settings in conventional OPC methods, such as fragment settings, backoff parameters, or number of movement wheels, cannot match the simulated and target values ​​after OPC. This results in a significant difference between the actual wafer value and the target value, failing to meet process requirements. Therefore, the OPC recipe needs to be re-optimized. However, during the mass production OPC publication stage, reworking and optimizing the recipe is very inefficient.

[0044] The inventors discovered that these feature graphics in the product layout, within a certain size range, often fail to reach the target due to unreasonable segmentation or improper settings of OPC correction parameters in conventional OPC methods, resulting in poor simulation results after conventional OPC. Figure 1 As shown. Therefore, this invention provides an OPC correction method, which involves defining a feature graphic after obtaining the product layout; employing a special segmentation method for specific edges of this feature graphic; correcting the feature graphic based on a conventional OPC correction method; pre-adjusting the target graphic based on the difference between the simulated value and the target value; and performing subsequent OPC processing based on the adjusted target graphic. This achieves reasonable optical proximity effect correction for the feature graphic, ensuring that the simulated value and target value of the feature graphic match after OPC, meeting process requirements, and improving product yield.

[0045] Figure 2 This is a flowchart illustrating an embodiment of the OPC correction method provided by the present invention. (See reference...) Figure 1 As shown, the OPC correction method provided in this embodiment includes:

[0046] S01: Obtain the product layout and define the feature graphic based on mass production and publishing experience. The feature graphic includes two corners and a bottom line segment connecting the two corners.

[0047] S02: Generate the target graphic from the product layout using a conventional OPC program;

[0048] S03: Divide the bottom line segment of the feature graphic in the target graphic into three equal parts;

[0049] S04: Perform OPC correction simulation on the target graphic to obtain the simulation values ​​of the center positions of the three segments after simulation.

[0050] S05: Calculate the difference between the simulated values ​​and the target values ​​for the three segments, and compensate the difference to the regular OPC program; and,

[0051] S06: Correct the target graphic based on the compensated OPC program.

[0052] Specifically, first, step S01 is executed to obtain the product layout and define the feature graphics in the product layout. The feature graphics include two corners and bottom line segments connecting the two corners. The feature graphics can be defined based on OPC publishing experience of the product layout, considering the combined effects of OPC recipes and model characteristics. For example, the feature graphics can be U-shaped or H-shaped. The length of the bottom line segment of the feature graphics is between 1 and 2.5 times the design critical dimension, and the width of the bottom line segment is between 1 and 1.5 times the design critical dimension. The length of the line segments connecting the corners of the feature graphics is greater than or equal to 2 times the design critical dimension. Here, the design critical dimension (design rule) refers to the minimum line width of the design rule in the product layout.

[0053] In other embodiments of the present invention, the feature graphics are further divided into batches. Within the above-mentioned size range, multiple batches of feature graphics with different sizes are generated from three aspects: the length of the bottom line segment, the width of the bottom line segment, and the line segments on both sides of the feature graphics, and subsequent OPC corrections are performed in batches.

[0054] Next, steps S02 to S04 are executed to generate a target graphic using a conventional OPC program on the product layout. The bottom line segment of the feature graphic in the target graphic is divided into three equal parts. An OPC correction simulation is performed on the target graphic to obtain the simulation value of the center position of the three segments after simulation.

[0055] refer to Figure 3As shown, in a conventional OPC program, the edges of a feature graphic are segmented based on the recipe's segmentation settings. In this embodiment, the bottom line segment of the feature graphic is segmented using a three-equal division method, as follows: Figure 4 As shown. It should be noted that here the bottom line segment of the feature figure is divided into three equal parts only, while the other edges of the feature figure are divided using a general segmentation method.

[0056] After segmentation, the target graphic is subjected to OPC correction simulation to obtain the simulation values ​​of the center positions of the three segments, i.e., the Edge Placement Error (EPE). Taking an example where the length of the bottom line segment of the feature graphic is 1 times the design critical dimension, the width of the bottom line segment of the feature graphic is 1 times the design critical dimension, and the lengths of the two side line segments of the feature graphic are 3 times the design critical dimension, the calculation formula for the simulation values ​​of the center positions of the three segments is as follows:

[0057] EPEi=f2(f1(OPC result),fragment i);

[0058] Where f1 is the model simulation function, f2 is the simulation value calculation function, and i takes the values ​​1, 2, and 3;

[0059] Next, steps S05 and S06 are executed to calculate the difference between the simulation value and the target value of the three segments, and the difference is compensated to the conventional OPC program. The target graphic is then corrected based on the compensated OPC program.

[0060] The setting for compensating the differences to the standard OPC procedure includes: compensating the difference values ​​of each segment to the target value, including:

[0061] After generating the target image using a conventional OPC program, feature graphics are identified on the target image using a software language. The bottom line segments of the feature graphics are divided into three equal parts. The target values ​​of the two segments near the corners are compensated for backward, and the target values ​​of the middle segments are extended.

[0062] Similarly, taking the length of the bottom line segment of the feature graphic as 1 times the design critical dimension, the width of the bottom line segment of the feature graphic as 1 times the design critical dimension, and the length of the two side line segments of the feature graphic as 3 times the design critical dimension as an example, the backoff compensation value of the two segments near the corner is N1, and the outer length value of the middle segment is N2.

[0063] N1 = (EPE1 + EPE3) / 2;

[0064] N2 = EPE2;

[0065] Among them, EPE1 and EPE3 are the simulated values ​​of the center positions of the two segments near the corner in the feature graphic, respectively, and EPE2 is the simulated value of the center position of the middle segment in the feature graphic.

[0066] The correction of the target graphic based on the compensated OPC program includes:

[0067] The difference between the simulated and target values ​​of the feature graph is calculated to see if it is within the specified range (Spec). If it is not within the specified range, the compensation value is readjusted in increments of 1 dBu until the difference between the simulated and target values ​​of the feature graph is within the specified range. Here, dbu is the grid size.

[0068] Next, the adjusted compensation value is written into the OPC program, the adjusted OPC program is used to generate the target graphic, and the generated target graphic is verified by OPC.

[0069] Figure 5 This is a comparison image of the target graphic (adjusted target image) obtained using the OPC correction method of this invention and the target graphic (original target graphic) obtained using the conventional OPC method. Figure 6 This is a comparison chart of simulation values ​​obtained using the OPC correction method of this invention and simulation values ​​obtained using the conventional OPC method. Figure 5 and Figure 6 As shown, the OPC correction method of the present invention can effectively improve the simulation results after OPC of the feature graphic, and the simulation value obtained by the OPC correction method of the present invention improves the bottom pinch problem of the H graphic.

[0070] In summary, this invention provides an OPC correction method. Based on OPC publishing experience of product layouts, and considering the combined effects of OPC recipe and model characteristics, a feature graphic is defined. A special segmentation method is used for the segmentation of specific edges of this feature graphic. The feature graphic is corrected based on conventional OPC correction methods. The target graphic is pre-adjusted according to the difference between the simulated value and the target value, and subsequent OPC processing is performed based on the adjusted target graphic. This invention, by defining a feature graphic and performing special segmentation on specified edges of the feature graphic, obtains the difference between the simulated value and the target value after OPC, and compensates for this difference in the original target graphic. This achieves reasonable optical proximity effect correction of the feature graphic, making the simulated value and target value of this feature graphic match after OPC, meeting process requirements, and improving product yield.

[0071] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. An OPC correction method characterized by, The method comprises the following steps: obtaining a product layout, defining a feature pattern, the feature pattern comprising two corners and a bottom line connecting the two corners; generating a target pattern for the product layout using a conventional OPC program; trisecting the bottom line of the feature pattern in the target pattern; performing OPC correction simulation on the target pattern to obtain simulation values of the center positions of the three segments after simulation, calculating the difference between the simulation values and the target values of the three segments and compensating the difference to the settings of the conventional OPC program; correcting the target pattern based on the compensated OPC program; compensating the difference to the settings of the conventional OPC program comprises compensating the difference of each segment to the target value of each segment respectively; the method of compensating the difference of each segment to the target value of each segment respectively comprises: after generating the target image using the conventional OPC program, recognizing the feature pattern on the target image through software language, trisecting the bottom line of the feature pattern, and performing back compensation on the target values of the two segments adjacent to the corners and performing overlength on the target value of the middle segment; the back compensation value of the two segments adjacent to the corners is N1, and the overlength value of the middle segment is N2, N1 = (EPE1 + EPE3) / 2; N2 = EPE2; wherein the length of the bottom line of the feature pattern is 1 times the design critical dimension, the width of the bottom line of the feature pattern is 1 times the design critical dimension, and the length of the two side lines connecting the corners of the feature pattern is 3 times the design critical dimension; EPE1 and EPE3 are simulation values of the center positions of the two segments adjacent to the corners in the feature pattern, and EPE2 is the simulation value of the center position of the middle segment in the feature pattern.

2. The OPC correction method according to claim 1, wherein The feature pattern is arranged in a U shape or an H shape.

3. The OPC correction method according to claim 2, wherein the length of the bottom line of the feature pattern is between 1 times the design critical dimension and 2.5 times the design critical dimension; the width of the bottom line of the feature pattern is between 1 times the design critical dimension and 1.5 times the design critical dimension; the length of the two side lines connecting the corners of the feature pattern is greater than or equal to 2 times the design critical dimension.

4. The OPC correction method according to claim 3, wherein The method further comprises dividing the feature pattern into batches, generating a plurality of feature patterns with different batch sizes from the length of the bottom line, the width of the bottom line and the two side lines of the feature pattern.

5. The OPC correction method of claim 1, wherein The method of correcting the target pattern based on the compensated OPC program comprises: calculating whether the difference between the simulation value and the target value of the feature pattern is within the specification range, and if not, adjusting the compensation value in steps of 1 dbu until the difference between the simulation value and the target value of the feature pattern is within the specification range.

6. The OPC correction method according to claim 5, wherein The method further comprises writing the adjusted compensation value into the OPC program, generating the target pattern using the adjusted OPC program, and performing OPC verification on the generated target pattern.

7. The OPC correction method of claim 1, wherein The calculation formula of the simulation value of the center position of the three segments comprises: EPEi = f2(f1(OPC result), fragment i), wherein f1 is a model simulation function, f2 is a calculation function of the simulation value, and i takes values of 1, 2 and 3. The length of the bottom line segment of the feature pattern is 1 times the design critical dimension, the width of the bottom line segment of the feature pattern is 1 times the design critical dimension, and the length of the two side line segments of the feature pattern is 3 times the design critical dimension.

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