CN105093808B - Optical proximity correction method for hole layer for avoiding large length-width ratio pattern - Google Patents
Optical proximity correction method for hole layer for avoiding large length-width ratio pattern Download PDFInfo
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Abstract
The invention provides a hole layer optical proximity correction method for avoiding a pattern with a large length-width ratio, which comprises the following steps: A. providing an original graph to be corrected; B. providing an OPC process model; C. calculating the outline of the hole according to the original graph or the graph after OPC and the process model; D. calculating the EPE of each edge of the graph after the OPC; E. judging whether the EPE meets a preset target or not; if not, entering the step F; if yes, entering step I; F. for each graph, judging whether the aspect ratio after OPC is larger than the requirement and whether the lengths of two edges in the length and width directions are larger than twice of the length of the minimum segment; if yes, entering step G, and then entering step H; if not, directly entering the step H; G. segmenting the edge into a plurality of segments on the target layer; H. moving the edge, and returning to the step C; I. and outputting the graph subjected to OPC. The invention can obtain better fidelity in the mask manufacturing process and ensure higher accuracy in the OPC simulation stage.
Description
Technical Field
The invention relates to the technical field of Optical Proximity Correction in a semiconductor manufacturing process, in particular to a method for avoiding a pattern with a large length-width ratio in an Optical Proximity Correction (OPC) process of a hole layer.
Background
With the high-speed development of integrated circuit design, how to reduce the deformation and deviation of the layout pattern after photoetching and inhibit the negative effect of optical proximity effect, thereby improving the yield of chip production and playing a key role in the development of chip manufacturing industry. To address this problem, one method commonly used in the industry at present is optical proximity correction, which reduces the deviation of the lithographic pattern obtained by exposure by changing the shape of the original layout pattern.
In the prior art, the process of optical proximity correction generally includes: carrying out optical simulation on the original layout graph to obtain a simulated graph; and marking the patterns of which the position errors are not within the allowable range by comparing the obtained simulated patterns with the original layout patterns, and correcting the patterns of which the positions are marked in the original layout patterns by adopting a certain correction principle until the simulated patterns meeting the design requirements are obtained.
Because the layout style of the original layout graph changes with designers and has diversity, the direct optical proximity correction of the original layout graph usually obtains a large number of patterns to be marked and corrected, thereby causing the correction process to cost a large amount of labor and time. For this reason, some methods for improving the calibration principle have been proposed, such as: by setting correction rules in advance for components of simple patterns such as line segments, line ends, corners, and the like, the correction rules may include not only some simple correction methods but also a set of these special correction rules. When similar patterns appear in the original layout, the correction rule corresponding to the patterns is applied to the actual correction process so as to reduce the time of the actual correction process, thereby improving the correction efficiency and saving the cost.
In order to eliminate the influence of the optical proximity effect, the pattern on the actually manufactured photomask is different from the expected photoetching pattern, and the pattern on the photomask is subjected to the optical proximity correction processing. In addition, as the feature size (CD) is reduced to a smaller range, the line width of the pattern on the reticle is even 1/3 which is only the wavelength of light, and in addition to the above-mentioned necessary optical proximity correction process, it is usually necessary to provide a Sub-resolution assist pattern (SRAF) around the exposed pattern. The sub-resolution auxiliary patterns are only arranged on the photoetching mask plate, the patterns are not transferred to a semiconductor device after actual exposure, and the functions of increasing the focusing depth of the adjacent exposure patterns and improving the exposure accuracy are achieved.
For more advanced technology nodes, the hole layer (hole layer) design in the back-end process has very dense pitch and very complex structure. Many large length-to-width ratio (big length-to-width ratio) patterns (typically larger than 2.5) will be formed on the Post-proximity correction (Post OPC) layout as long as the minimum edge position error (minimum edge position error) target is reached.
In the mask manufacturing process, the pattern with large aspect ratio has significantly larger characteristic dimension error (negative error in the length direction and positive error in the width direction).
In addition, in the OPC model, the large aspect ratio pattern also has a significantly larger prediction error.
For the above problems caused by the appearance of the pattern with large aspect ratio, the following two methods are generally adopted in the prior art to overcome:
1. optimized scattering bar (scatter bar)
For some patterns, it can effectively change the post-OPC shape. But in a dense pitch there is not enough space to insert scattering bars. It cannot completely solve this problem.
2. Limiting aspect ratio in OPC Menus
This mandatory approach will result in the retention of edge position errors. Some process layers with stringent feature size requirements cannot allow this.
Disclosure of Invention
The invention aims to provide a method for correcting the optical proximity of a hole layer, which avoids a pattern with a large length-width ratio, can obtain better fidelity in the mask manufacturing process and ensure higher accuracy in an OPC (optical proximity correction) simulation stage.
To solve the above technical problem, the present invention provides a method for correcting optical proximity of a hole layer to avoid a pattern with a large aspect ratio, comprising the steps of:
A. providing an original graph to be corrected;
B. providing a process model for optical proximity correction;
C. calculating the outline of the hole according to the original graph or the graph after the optical proximity correction and the process model;
D. calculating the edge position error of each edge of the graph after the optical proximity correction;
E. judging whether the edge position error meets a preset target or not;
F. if the edge position error does not meet the predetermined target, judging whether the aspect ratio after the optical proximity correction is larger than the requirement and whether the length of two edges in the length direction is larger than twice of the minimum segment length for each graph;
G. segmenting the edge into a plurality of segments on the target layer if the aspect ratio after optical proximity correction is larger than the requirement and the length of two edges in the length direction is larger than twice the minimum segment length;
H. moving the edge and returning to the step C again;
I. and if the edge position error meets the preset target, outputting the graph after optical proximity correction.
Optionally, as for the determination result in the step F, if the aspect ratio after the optical proximity correction is not greater than the requirement or the lengths of the two edges in the length direction are not greater than twice the minimum segment length, directly entering step H.
Optionally, step F further includes:
if the edge position error does not meet the preset target, judging whether the lengths of two edges in the width direction after the optical proximity correction are also larger than twice of the minimum segment length or not for each graph; if yes, entering step G, and then entering step H; if not, directly entering the step H.
Optionally, the large aspect ratio means that the aspect ratio of the pattern is greater than 2.5.
Optionally, in the step G, each of the edges is divided into two or three segments.
Compared with the prior art, the invention has the following advantages:
the present invention checks the post-OPC aspect ratio of each pattern and the length of two edges in the length direction and/or the width direction in each OPC cycle, in addition to checking the Edge Position Error (EPE) of each edge as in the prior art. When the aspect ratio is found to be too large and the lengths of two edges in a certain direction are found to be too large, the aspect ratio value of the post-OPC pattern is reduced by dividing the corresponding edge into a plurality of segments larger than the minimum segment length.
By reducing the value of the aspect ratio of the pattern, better fidelity can be achieved in subsequent reticle fabrication processes and higher accuracy in the OPC simulation phase is ensured.
In addition, the invention can achieve the aim of minimum edge position error, is convenient to realize in the OPC flow, and does not generate a large amount of scripts in the OPC menu.
Drawings
The above and other features, properties and advantages of the present invention will become more apparent from the following description of the embodiments with reference to the accompanying drawings, in which:
FIG. 1 is a flow chart of a conventional method for modifying optical proximity of an aperture layer in the prior art;
FIG. 2 is a flowchart of a method for optical proximity correction of an aperture layer to avoid high aspect ratio features according to one embodiment of the present invention;
FIG. 3 is a diagram illustrating the comparison of post-OPC shapes and reticle shapes obtained by the method for optical proximity correction of a hole layer to avoid high aspect ratio patterns according to one embodiment of the present invention with conventional methods for optical proximity correction of a hole layer.
Detailed Description
For comparison, before describing the optical proximity correction method for an aperture layer to avoid a pattern with a large aspect ratio according to the present invention, how the conventional optical proximity correction method for an aperture layer in the prior art is performed will be described. FIG. 1 is a flow chart of a conventional method for modifying optical proximity of an aperture layer in the prior art; FIG. 3 is a diagram illustrating a comparison of post-OPC shapes and reticle shapes obtained by a conventional via layer optical proximity correction method and a via layer optical proximity correction method for avoiding high aspect ratio patterns according to an embodiment of the present invention. As shown in fig. 1 in conjunction with fig. 3, the process includes the steps of:
executing step S201, providing an original graph to be corrected;
step S202 is executed to provide a process model (not shown) for optical proximity correction, which is an OPC algorithm;
step S203 is executed to calculate a simulated contour (contour) of the hole according to the original pattern or the optical proximity corrected pattern (i.e., "post-OPC shape" in fig. 3) and the process model;
step S204 is executed to calculate an edge position error (which is a difference between the post-OPC shape and each edge of the original graph, as shown in fig. 3) of each edge of the optical proximity corrected graph;
step S205 is executed to determine whether the edge position error meets a predetermined target (target, and the final target is the original pattern to be corrected); if not, go to step S206; if yes, go directly to step S207;
executing step S206, moving each edge of the pattern after the optical proximity correction, and returning to execute step S203; and
step S207 is executed to output the graph after the optical proximity correction. The "reticle shape" of the prior art in fig. 3 is the shape of the reticle (mask) made of the pattern after the optical proximity correction according to the present flow.
For conventional aperture layer optical proximity correction methods, there is typically only one segment (unit of movement for optical proximity correction) because its edges are short. In addition, for each OPC cycle, only the respective edge position error of each edge is checked.
The present invention is further described in the following description with reference to specific embodiments and the accompanying drawings, wherein the details are set forth in order to provide a thorough understanding of the present invention, but it is apparent that the present invention can be embodied in many other forms different from those described herein, and it will be readily appreciated by those skilled in the art that the present invention can be implemented in many different forms without departing from the spirit and scope of the invention.
FIG. 2 is a flowchart of a method for optical proximity correction of an aperture layer to avoid high aspect ratio features according to one embodiment of the present invention; FIG. 3 is a diagram illustrating the comparison of post-OPC shapes and reticle shapes obtained by the method for optical proximity correction of a hole layer to avoid high aspect ratio patterns according to one embodiment of the present invention with conventional methods for optical proximity correction of a hole layer. In the present embodiment, a large aspect ratio means that the aspect ratio of the pattern is greater than 2.5. As shown in fig. 2 in conjunction with fig. 3, the process includes the steps of:
executing step S301, providing an original graph to be corrected;
step S302 is executed to provide a process model (not shown) for optical proximity correction, which is an OPC algorithm;
step S303 is executed to calculate a simulated contour of the hole according to the original pattern or the optical proximity corrected pattern (i.e., "post-OPC shape" in fig. 3) and the process model;
step S304 is executed to calculate an edge position error (which is a difference between the post-OPC shape and each edge of the original graph, as shown in fig. 3) of each edge of the optical proximity corrected graph;
executing step S305, judging whether the edge position error meets a preset target; if not, go to step S306; if yes, go to step S309;
step S306 is executed to determine, for each pattern, whether the aspect ratio after the optical proximity correction is larger than the requirement (spec) and whether the lengths of the two edges in the length direction and/or the width direction are larger than twice a minimum segment length (L); if yes, go to step S307, then go to step S308; if not, directly entering step S308;
step S307 is performed to divide each edge into a plurality of segments (e.g., two or three segments) on the target layer;
executing step S308, moving each edge of the graph after the optical proximity correction, and returning to the step S303 again; and
step S309 is executed to output the pattern after the optical proximity correction. The "reticle shape" of the present invention in fig. 3 is the shape of a reticle (mask) made of the pattern after the optical proximity correction according to the present flow.
In contrast, for the aperture layer optical proximity correction method of the present invention, the aperture layer edge may have multiple segments as long as each segment satisfies the minimum segment length value.
In addition, for each OPC cycle, the post-OPC aspect ratio of each pattern and the length of the edge are checked in addition to the edge position error of each edge. When both are found to be too large, the corresponding edge of this graph is segmented into segments larger than the minimum segment length, and then the remaining OPC loop is performed. The edges of the plurality of segments can reduce the aspect ratio value of the post-OPC pattern.
Also as shown in fig. 3, it can be appreciated from the shape obtained after a conventional OPC procedure (prior art), that it has an excessively large aspect ratio, which can have poor fidelity during reticle fabrication, resulting in large simulation errors for wafer data.
The shape obtained after the OPC process of the invention can be seen to have a reduced aspect ratio and better fidelity in the mask manufacturing process, thereby reducing the simulation error of wafer data.
Although both the prior art and the inventive simulated contours can meet the intended target, the novel OPC method of the present invention can reduce the aspect ratio of the pattern.
In summary, the present invention checks the post-OPC aspect ratio of each pattern and the lengths of two edges in the length direction and/or the width direction, in addition to checking the Edge Position Error (EPE) of each edge as in the prior art, in each OPC cycle. When the aspect ratio is found to be too large and the lengths of two edges in a certain direction are found to be too large, the aspect ratio value of the post-OPC pattern is reduced by dividing the corresponding edge into a plurality of segments larger than the minimum segment length.
By reducing the value of the aspect ratio of the pattern, better fidelity can be achieved in subsequent reticle fabrication processes and higher accuracy in the OPC simulation phase is ensured.
In addition, the invention can reach the preset target of the minimum edge position error, is convenient to realize in the OPC flow, and does not have a large amount of scripts in the OPC menu.
Although the present invention has been disclosed in terms of the preferred embodiment, it is not intended to limit the invention, and variations and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention. Therefore, any modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope defined by the claims of the present invention, unless the technical essence of the present invention departs from the content of the present invention.
Claims (4)
1. An optical proximity correction method for avoiding a hole layer with a pattern with a large length-width ratio comprises the following steps:
A. providing an original graph to be corrected;
B. providing a process model for optical proximity correction;
C. calculating the outline of the hole according to the original graph or the graph after the optical proximity correction and the process model;
D. calculating the edge position error of each edge of the graph after the optical proximity correction;
E. judging whether the edge position error meets a preset target or not;
F. if the edge position error does not meet the predetermined target, judging whether the aspect ratio after the optical proximity correction is larger than the requirement and whether the length of two edges in the length direction is larger than twice of the minimum segment length for each graph;
G. segmenting the edge into a plurality of segments on the target layer if the aspect ratio after optical proximity correction is larger than the requirement and the length of two edges in the length direction is larger than twice the minimum segment length;
H. moving the edge and returning to the step C again;
I. if the edge position error meets the preset target, outputting a graph subjected to optical proximity correction;
wherein, in the step F, the method further comprises: if the edge position error does not meet the preset target, judging whether the lengths of two edges in the width direction after the optical proximity correction are also larger than twice of the minimum segment length or not for each graph; if yes, entering step G, and then entering step H; if not, directly entering the step H.
2. The method of claim 1, wherein if the aspect ratio after the optical proximity correction is not greater than the requirement or the length of the two edges in the length direction is not greater than twice the minimum segment length, the step F is directly proceeded to.
3. The method of any one of claims 1-2, wherein the high aspect ratio is that the aspect ratio of the pattern is greater than 2.5.
4. The method according to any one of claims 1 to 2, wherein in step G, each of the edges is divided into two or three segments.
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| CN201410163043.1A CN105093808B (en) | 2014-04-22 | 2014-04-22 | Optical proximity correction method for hole layer for avoiding large length-width ratio pattern |
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106292174B (en) * | 2016-09-27 | 2019-12-20 | 上海华力微电子有限公司 | Method for improving optical proximity correction accuracy |
| CN108663897B (en) * | 2017-03-29 | 2021-06-08 | 中芯国际集成电路制造(上海)有限公司 | Optical proximity correction method |
| CN109254494B (en) * | 2017-07-12 | 2021-11-12 | 中芯国际集成电路制造(上海)有限公司 | Optical proximity correction method |
| CN107908072B (en) * | 2017-12-21 | 2021-04-16 | 上海华力微电子有限公司 | OPC correction method for reducing program running time of connecting hole layer |
| CN110456615B (en) * | 2019-08-13 | 2021-10-15 | 上海华力集成电路制造有限公司 | Optical proximity effect correction method and correction system thereof |
| CN110426915A (en) * | 2019-08-13 | 2019-11-08 | 德淮半导体有限公司 | Optical adjacent correction method |
| CN112415864B (en) * | 2020-11-24 | 2023-04-07 | 上海华力集成电路制造有限公司 | Method for determining OPC minimum segmentation length |
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| CN1311525A (en) * | 2000-03-01 | 2001-09-05 | 日本电气株式会社 | Exposure mask and its mfg. method |
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