CN115509081B

CN115509081B - Optical proximity correction method, mask and readable storage medium

Info

Publication number: CN115509081B
Application number: CN202110692382.9A
Authority: CN
Inventors: 孙鹏飞; 王谨恒; 陈洁; 朱斌; 张剑; 曹楠
Original assignee: CSMC Technologies Fab2 Co Ltd
Current assignee: CSMC Technologies Fab2 Co Ltd
Priority date: 2021-06-22
Filing date: 2021-06-22
Publication date: 2025-01-21
Anticipated expiration: 2041-06-22
Also published as: CN115509081A

Abstract

The present invention relates to an optical proximity correction method, a mask plate and a readable storage medium, the method comprising: obtaining a mask plate design pattern; analyzing and dividing the outer edge of the mask plate design pattern into multiple segments, including: for a line pattern that is not parallel to a line end and is adjacent to the line end in the extension direction of the line end, according to the spacing between the line end and the line pattern, and the optical diameter used when establishing an OPC model, calculating the length of the segmented line of the line pattern at a position adjacent to the line end; simulating the mask plate design pattern according to the OPC model to obtain a simulated exposure pattern; adjusting the mask plate design pattern according to the simulated exposure pattern to obtain a mask plate making pattern. The present invention can effectively improve the "ripple" phenomenon, improve the OPC correction accuracy and OPC correction efficiency, and reduce process risks.

Description

Optical proximity correction method, mask and readable storage medium

Technical Field

The application relates to the technical field of semiconductor manufacturing, in particular to an optical proximity correction method, a mask and a readable storage medium.

Background

With the rapid development of Ultra LARGE SCALE Integration (ULSI), integrated circuit fabrication processes are becoming more and more complex and sophisticated. Among them, photolithography is a driving force for the development of integrated circuit manufacturing processes, and is one of the most complex technologies. The improvement in lithography is of great importance for the development of integrated circuits relative to other single fabrication techniques. Before the photolithography process starts, the pattern needs to be copied onto the mask plate by a specific device, and then the pattern structure on the mask plate is copied onto the silicon wafer for producing the chip by a photolithography machine. However, due to the shrinking size of the semiconductor device, the wavelength used for exposure is larger than the size of the ideal pattern of the physical layout design and the spacing between the patterns, and the interference and diffraction effects of the light waves cause great difference between the physical pattern generated by actual lithography and the ideal pattern of the physical layout design, and the shape and spacing of the actual pattern are greatly changed, even the performance of the circuit is affected.

One important reason for this difference is that the optical proximity effect is generated when the wavelength of the light used for lithography is larger than the size of the ideal pattern of the physical layout design and the pitch between the patterns. Therefore, in order to solve the problem, optical proximity correction (OPC, optical Proximity Correction) may be performed on the reticle.

At present, OPC is performed by using computer-aided software tools by correcting a mask plate to solve the graphic distortion after photoetching to the greatest extent.

Disclosure of Invention

Accordingly, it is necessary to provide an optical proximity correction method capable of improving the correction accuracy of OPC.

An optical proximity correction method comprises the steps of obtaining a mask design pattern, analyzing and dividing the outer edge of the mask design pattern into multiple sections, and adjusting the mask design pattern according to the distance between a line end and the line pattern and the optical diameter adopted when an OPC model is built, calculating the length of a segmented line segment of the line pattern at the position adjacent to the line end, wherein the line of the line end and the line pattern form an included angle, simulating the mask design pattern according to the OPC model to obtain a simulated exposure pattern, and adjusting the mask design pattern according to the simulated exposure pattern to obtain a mask plate making pattern.

According to the optical proximity correction method, the segmentation algorithm in the process of analyzing and segmenting (Dissection) the outer edge of the design graph of the mask is improved, segmentation fragments with different lengths are adopted at the positions of the line graph adjacent to the ends of other lines according to different optical environments, so that the 'ripple' phenomenon can be effectively improved, the OPC correction precision and OPC correction efficiency are improved, and the process risk is reduced.

In one embodiment, the step of adjusting the mask design pattern according to the simulated exposure pattern to obtain the mask plate making pattern includes calculating an edge placement error of the simulated exposure pattern and the mask design pattern, and adjusting the mask design pattern according to the edge placement error to obtain the mask plate making pattern.

In one embodiment, the step of adjusting the mask design pattern according to the edge placement error to obtain a mask plate making pattern comprises the steps of A, adjusting the mask design pattern according to the edge placement error, B, simulating the adjusted mask design pattern according to the OPC model to obtain a re-simulated exposure pattern, C, calculating the edge placement error of the re-simulated exposure pattern and the adjusted mask design pattern, D, judging whether a preset condition is met according to the edge placement error calculated in the step C, taking the adjusted mask design pattern as the mask plate making pattern if the preset condition is met, and otherwise, returning to the step A.

In one embodiment, before the step of simulating the mask design pattern according to the OPC model, the method further comprises the step of placing a target point on the outer edge of the mask design pattern, and the step of adjusting the mask design pattern according to the edge placement errors comprises the step of adjusting the mask design pattern according to the value of the edge placement error corresponding to each section of the outer edge so that the value of the edge placement error tends to zero.

In one embodiment, the segment lengthWherein cd is the distance between the line end and the line pattern, OD is the optical diameter adopted when the OPC model is built, l is a tested value, [ ] represents upward rounding, and the unit of Deltax is nanometer.

In one embodiment, Δx is not less than the minimum limit size of the actual plate making of the lithographic plate, and is not greater than the longest length that the segmentation line segment can define.

In one embodiment, l depends on the critical dimensions of the process node.

In one embodiment, the extending direction of the line end is perpendicular to the line pattern.

In one embodiment, the preset condition is that an absolute value of an edge placement error corresponding to the outer edge of each segment of the reticle design pattern is smaller than a preset value.

It is also necessary to provide a mask plate, which is manufactured by using the mask plate making pattern obtained by the optical proximity correction method according to any one of the embodiments.

It is also necessary to provide a readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the optical proximity correction method according to any of the above embodiments.

It is also necessary to provide a computer device comprising a memory and a processor, said memory storing a computer program, said processor implementing the steps of the optical proximity correction method according to any of the embodiments described above when said computer program is executed.

It is also necessary to provide a computer program product comprising a computer program which, when executed by a processor, implements the steps of the optical proximity correction method according to any of the preceding embodiments.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments or the conventional techniques of the present application, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.

FIG. 1 is a schematic diagram of an exemplary reticle design pattern and OPC software simulation exposure pattern;

FIG. 2 is a schematic diagram of reticle design pattern resolution segmentation and simulated exposure in an exemplary OPC process;

FIG. 3 is a schematic diagram of an exemplary parsing split by an Interfeature split command;

FIG. 4 is a flow chart of a method of optical proximity correction in one embodiment;

FIG. 5 is a flow chart of sub-steps of step S440 in the embodiment shown in FIG. 4;

FIG. 6 is a partial reticle design pattern at a critical dimension of 110nm node;

FIG. 7 is a schematic diagram of resolving segmentation and placement target points in a comparative example;

FIG. 8 is a graphic representation of a reticle corresponding to the comparative example of FIG. 7;

FIG. 9 is a schematic diagram of resolving segmentation and placement of target points in one embodiment;

fig. 10 is a comparison of the outline of the reticle pattern at the line pattern segments obtained in the comparison example of fig. 8 and the embodiment of fig. 9.

Detailed Description

In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Embodiments of the application are illustrated in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that when an element or layer is referred to as being "on," "adjacent," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and/or sections, these elements, components, regions, layers, doping types and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or section from another element, component, region, layer, doping type or section. Thus, a first element, component, region, layer, doping type or section discussed below could be termed a second element, component, region, layer or section, for example, a first doping type could be termed a second doping type, and, similarly, a second doping type could be termed a first doping type, a doping type different from the second doping type, such as, for example, the first doping type could be P-type and the second doping type could be N-type, or the first doping type could be N-type and the second doping type could be P-type.

Spatially relative terms, such as "under", "below", "beneath", "under", "above", "over" and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "under" or "beneath" other elements would then be oriented "on" the other elements or features. Thus, the exemplary terms "below" and "under" may include both an upper and a lower orientation. Furthermore, the device may also include an additional orientation (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used herein interpreted accordingly.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. Also, in this specification, the term "and/or" includes any and all combinations of the associated listed items.

Embodiments of the invention are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention, such that variations of the illustrated shapes due to, for example, manufacturing techniques and/or tolerances are to be expected. Thus, embodiments of the present invention should not be limited to the particular shapes of the regions illustrated herein, but rather include deviations in shapes that result, for example, from manufacturing techniques. For example, an implanted region shown as a rectangle typically has rounded or curved features and/or implant concentration gradients at its edges rather than a binary change from implanted to non-implanted regions. Also, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface over which the implantation is performed. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the invention.

An exemplary method for performing Optical Proximity Correction (OPC) by a computer-aided software tool is to first identify the edges of the reticle design pattern by OPC software and divide the edges of the reticle design pattern into a number of small correction line segments, allowing each segment of edges to move freely. The OPC software then simulates the pattern after lithography exposure, and compares it with the reticle design pattern (as shown in FIG. 1), and the difference between them is called edge placement Error (EPE, edge Placement Error), which is an indicator for measuring correction quality. And the OPC software moves the edge position of the mask design graph when running, and calculates the corresponding edge placement error. This process is repeated until the calculated edge placement error reaches an acceptable value. In the OPC process, the segmentation of the mask design graph and the corresponding result are shown in fig. 2, the left half part of fig. 2 shows the positions of the mask design graph and the segmentation points, the segmentation points shown by the black points on the edges of the original layout are segmented into a plurality of correction line segments with different lengths, and the OPC result (i.e. the corrected mask plate making graph) obtained after correction is shown in the right half part of fig. 2.

The positions where the OPC correction amounts are greatest are typically the corners and ends of the line, and the OPC software sets smaller grids at the corners and end-band points of the pattern, making the EPE calculation at these positions more intensive and more perfect. There are two typical methods of dealing with inflection points, namely rule matching segmentation and marking manual segmentation. Taking mentor calibre-WB as an example, a rule matching segmentation command inter-feature is used to project the vertices of adjacent graphics to opposite sides, and a plurality of small segments are segmented according to command parameters, see fig. 3, where small dots are segmentation points. The command has 2 important parameters-num for setting the number of waveplate segments, -ripplelen for controlling the length of the waveplate segments.

Because the rule matching segmentation is based on the whole layout graph, but complex two-dimensional graphs are distributed in the layout graph, and the unified parameter configuration is difficult to meet the requirement under the influence of the optical proximity effect, OPC engineers need to spend a great deal of time to perform experiments to find out a satisfactory segmentation scheme, and then a marked manual segmentation method is adopted to process a key part of the layout so as to obtain a satisfactory segmentation result.

The application provides an optical proximity correction method, which improves a segmentation algorithm when the outer edge of a mask design graph is analyzed and segmented (Dissection), adopts a dynamic segmentation method, and adopts segmentation segments with different lengths according to different optical environments. FIG. 4 is a flowchart of an optical proximity correction method according to an embodiment, including the following steps:

s410, obtaining a mask design graph.

And after the integrated circuit is designed according to the actual requirements, obtaining design patterns of all layers conforming to the requirements as mask design patterns.

S420, analyzing and dividing (Dissection) the outer edge of the mask design graph into a plurality of sections.

The analysis segmentation is to divide the edge of the mask design graph into a plurality of small correction segments (line segments), and each division point divides the edge of the graph into a plurality of correction line segments with different lengths. The analytical segmentation may be performed using OPC software. Step S420 calculates a length Δx of a cut line segment of the line pattern at a position adjacent to the line end according to a distance between the line end and the line pattern and an optical diameter used when the OPC model is established, for the line pattern adjacent to the line end (the line pattern is adjacent to the line end in the extending direction of the line end, and the line pattern is not parallel to the line end). Illustratively, the line pattern is at an angle to the line at which the line ends lie, e.g., the line pattern is perpendicular to the line at which the line ends lie.

S430, simulating the mask design pattern according to the OPC model to obtain a simulated exposure pattern.

OPC software can be used to simulate exposure of the reticle design pattern, and the software can have preset simulated exposure rules which can be modified by a person skilled in the art. The present application is not limited to a specific simulated exposure rule.

S440, adjusting the mask design pattern according to the simulated exposure pattern to obtain a mask plate making pattern.

The optical proximity correction method improves the segmentation algorithm when the outer edge of the mask design graph is analyzed and segmented, and segments with different lengths are adopted at the positions of the line graph adjacent to other line ends according to different optical environments, so that the 'ripple' phenomenon can be effectively improved, the OPC correction precision and OPC correction efficiency are improved, the process window is improved, and the process risk is reduced.

In one embodiment of the present application, step S440 includes calculating an edge placement error of the simulated exposure pattern and the reticle design pattern, and adjusting the reticle design pattern according to the edge placement error to obtain the reticle plate making pattern.

In one embodiment of the present application, the method further includes a step of placing a target point (i.e., a dividing point) on the outer edge (line end and adjacent edge) of the reticle design pattern.

Referring to fig. 5, in one embodiment of the present application, step S440 includes:

S452, adjusting the design graph of the mask plate according to the edge placement error.

In one embodiment of the application, each correction segment of the reticle design pattern is moved according to the edge placement error such that the value of the edge placement error for each correction segment approaches zero or such that the absolute value of the edge placement error for each correction segment approaches a small value.

S454, simulating the adjusted mask design pattern according to the OPC model to obtain a re-simulated exposure pattern.

Step S454 is similar to step S430, and will not be described here.

S456, calculating edge placement errors of the re-simulated exposure pattern and the adjusted mask design pattern.

In one embodiment of the present application, the edge placement error is the position of the simulated exposure pattern minus the position of the reticle design pattern, and the value of the edge placement error may be positive or negative.

After the execution of the step S456 is completed, judging whether a second preset condition is met according to the edge placement error obtained in the step S456, if so, taking the adjusted mask design pattern as a mask plate making pattern, otherwise, returning to the step S452, and adjusting each correction segment of the mask design pattern again.

In one embodiment of the present application, the second preset condition is that an absolute value of an edge placement error corresponding to each of the correction segments is smaller than a preset value. The predetermined value may be a verification value.

In one embodiment of the present application, if the number of times of adjustment in step S452 reaches the preset number of times, no adjustment is performed any more, and the mask design pattern obtained by the last adjustment is used as the mask plate making pattern.

Specifically, step S420 may be an algorithm for changing rule matching cut command inter-feature. In one embodiment of the application, the segment lengths are split

Wherein cd is the distance between the line end and the line pattern, OD is the optical diameter adopted when the OPC model is built, l is a tested value, [ ] represents upward rounding, deltax is in nanometer, the optical diameter defines the size of the square of the optical system space influence, and the influence of all patterns within the OD/2 range is considered when calculating the light intensity of the pattern. In one embodiment of the application, cd, OD and l are also in nanometers.

In one embodiment of the application, Δx is not less than the minimum limit size of the actual plate making of a mask shop (mask shop) reticle, and is not greater than the longest length that a segment can define.

In one embodiment of the application, l depends on the critical dimensions of the process node.

FIG. 6 is a partial reticle design pattern for an exemplary critical dimension (Critical Dimension) at the 110nm node. In fig. 6, the line ends are perpendicular to the line patterns in the extending direction, and the distance cd between the line ends and the line patterns is 120nm. As a comparative example, a regular segmentation method was used in the analysis segmentation step, in which a segmentation segment length of 120nm was used, and target points were placed at the line ends 12 and the line pattern segments 14, as shown in fig. 7. And then simulating the mask design pattern according to the OPC model to obtain a simulated exposure pattern, calculating the edge placement error of the simulated exposure pattern and the mask design pattern at the target position point, correcting the mask design pattern according to the value of the edge placement error, and repeatedly iterating to obtain a mask plate making pattern, as shown in figure 8. As can be seen from fig. 8, the line ends affect the adjacent line patterns due to the influence of the optical proximity effect, and a "moire" phenomenon is generated, which causes a risk of "short" or "open" (pin), resulting in a decrease in OPC accuracy, which causes a process risk.

In one embodiment of the application, when the OPC model is built, the OD takes a value of 960nm, and at a node of 110nm, the recommended value of l takes a value of 720nm, and at this time, the length of Δx takes a value of 90nm, see fig. 9. Fig. 10 is a graph of the comparison of fig. 8 with the comparison of fig. 9 to the line segment of the reticle pattern, in which the "moire" phenomenon is obviously converged, the line width of the reticle pattern is converged from 138.5nm to 132nm, thus improving the OPC correction accuracy, increasing the process window and reducing the process risk.

The application correspondingly provides a mask manufactured by the mask plate making pattern obtained by the optical proximity correction method according to any embodiment.

The present application also provides a readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the optical proximity correction method described in any of the above embodiments.

The application also provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the optical proximity correction method according to any one of the embodiments when executing the computer program.

The present application also provides a computer program product comprising a computer program which, when executed by a processor, implements the steps of the optical proximity correction method according to any of the preceding embodiments.

It should be understood that, although the steps in the flowcharts of the present application are shown in order as indicated by the arrows, these steps are not necessarily performed in order as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least a portion of the steps in the flowcharts of this application may include a plurality of steps or stages that are not necessarily performed at the same time but may be performed at different times, the order in which the steps or stages are performed is not necessarily sequential, and may be performed in rotation or alternately with at least a portion of the steps or stages in other steps or others.

In the description of the present specification, reference to the terms "some embodiments," "other embodiments," "desired embodiments," and the like, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

The technical features of the above embodiments may be arbitrarily combined, and for brevity, all of the possible combinations of the technical features of the above embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims

1. An optical proximity correction method, comprising:

obtaining a mask design graph;

Analyzing and dividing the outer edge of the mask design graph into a plurality of sections, wherein for a line graph adjacent to a line end in the extending direction of the line end, calculating the length of a dividing line segment of the line graph at the position adjacent to the line end according to the distance between the line end and the line graph and the optical diameter adopted when an OPC model is built, wherein the straight line of the line end and the line graph form an included angle;

Simulating the mask design graph according to the OPC model to obtain a simulated exposure graph;

And adjusting the mask design pattern according to the simulated exposure pattern to obtain a mask plate making pattern.

2. The optical proximity correction method according to claim 1, wherein the step of adjusting the reticle design pattern according to the simulated exposure pattern to obtain a reticle plate pattern comprises:

and calculating the edge placement errors of the simulated exposure pattern and the mask design pattern, and adjusting the mask design pattern according to the edge placement errors to obtain a mask platemaking pattern.

3. The optical proximity correction method according to claim 2, wherein the step of adjusting the reticle design pattern according to the edge placement error to obtain a reticle plate pattern comprises:

step A, adjusting the mask design graph according to the edge placement error;

Step B, simulating the adjusted mask design pattern according to the OPC model to obtain a re-simulated exposure pattern;

Step C, calculating the edge placement errors of the re-simulated exposure pattern and the adjusted mask design pattern;

And D, judging whether a preset condition is met according to the edge placement error calculated in the step C, if so, taking the adjusted mask design pattern as a mask platemaking pattern, and otherwise, returning to the step A.

4. The optical proximity correction method according to claim 2 or 3, further comprising the step of placing a target point on an outer edge of the reticle design pattern before the step of simulating the reticle design pattern according to an OPC model;

The step of adjusting the mask design graph according to the edge placement errors comprises the step of adjusting the mask design graph according to the value of the edge placement errors corresponding to the outer edges of each section so that the value of the edge placement errors tends to zero.

5. The optical proximity correction method according to claim 1, wherein the dicing line segment length ;

Wherein cd is the distance between the line end and the line pattern, OD is the optical diameter adopted when the OPC model is built, l is a tested value, [ ] represents upward rounding,In nanometers.

6. The method of claim 5, wherein l is dependent on the critical dimension of the process node.

7. The optical proximity correction method according to claim 1, wherein the extending direction of the line ends is perpendicular to the line pattern.

8. The method of claim 3, wherein the predetermined condition is that an absolute value of an edge placement error corresponding to the outer edge of each of the reticle design patterns is smaller than a predetermined value.

9. A mask plate, characterized in that the mask plate is manufactured by a mask plate making pattern obtained by the optical proximity correction method according to any one of claims 1 to 8.

10. A readable storage medium having stored thereon a computer program, which when executed by a processor realizes the steps of the method according to any of claims 1 to 8.