阅读说明：本技术 针对特定图形旁波效应的opc方法及通孔层opc处理方法 (OPC method for specific pattern side wave effect and through hole layer OPC processing method ) 是由 江志兴 于 2020-12-08 设计创作，主要内容包括：本发明公开了一种针对特定图形旁波效应的OPC方法,包括：步骤S1,设定OPC模型的曝光阈值,输入目标图形,利用OPC模型模拟所述目标图形曝光后的光强分布,选择光强满足设定光强条件的长方形图形作为选定图形并输出；步骤S2,以所述选定图形中两条长边之间的距离满足设定距离条件的两条长边作为图形边；步骤S3,以所述图形边为目标图形边,在所述选定图形中生成散射条,所述散射条与所述图形边平行；步骤S4,以所述目标图形为目标、所述散射条为辅助图形,进行基于模型的OPC修正,得到最终的OPC图形。本发明还公开通孔层OPC处理方法。本发明通过添加辅助图形(散射条)改变光强分布,从而确保最终的曝光结果既能达到目标尺寸,又能避免产生额外曝光图形。(The invention discloses an OPC method aiming at a specific pattern side wave effect, which comprises the following steps: step S1, setting an exposure threshold of an OPC model, inputting a target graph, simulating the light intensity distribution of the exposed target graph by using the OPC model, and selecting a rectangular graph with light intensity meeting the set light intensity condition as a selected graph and outputting the selected graph; step S2, using two long sides in the selected graph, the distance between which satisfies the set distance condition, as graph sides; step S3, generating scattering bars in the selected graph by taking the graph edges as target graph edges, wherein the scattering bars are parallel to the graph edges; and step S4, carrying out model-based OPC correction by taking the target graph as a target and the scattering bars as auxiliary graphs to obtain a final OPC graph. The invention also discloses an OPC treatment method of the through hole layer. The invention changes the light intensity distribution by adding the auxiliary pattern (scattering strip), thereby ensuring that the final exposure result can reach the target size and avoiding generating additional exposure patterns.)

1. An OPC method aiming at the specific pattern side wave effect is characterized by comprising the following steps:

step S1, setting exposure threshold I of OPC model_thInputting a target graph, simulating the light intensity distribution of the target graph after exposure by utilizing an OPC model, and selecting a rectangular graph with light intensity meeting a set light intensity condition as a selected graph and outputting the selected graph;

step S2, using two long sides in the selected graph, the distance between which satisfies the set distance condition, as graph sides;

step S3, generating scattering bars in the selected graph by taking the graph edges as target graph edges, wherein the scattering bars are parallel to the graph edges;

and step S4, carrying out model-based OPC correction by taking the target graph as a target and the scattering bars as auxiliary graphs to obtain a final OPC graph.

2. The OPC method for the specific pattern side-wave effect of claim 1 further comprising, after step S4:

in step S5, OPC verification is performed.

3. The OPC method for specific pattern side wave effect as claimed in claim 1 or 2, wherein in step S1, said set light intensity condition is light intensity minimum I_minApproach to exposure threshold I_th。

4. The OPC method for specific pattern side-wave effect as claimed in claim 3, wherein said light intensity minimum value I_minThe set light intensity condition is satisfied to be 0.9I_th<I_min<1.1I_th。

5. The OPC method for a specific pattern side wave effect of claim 1 or 2 wherein in the step S2, the pattern edges are paired pattern edges having a distance between 1.4 λ and 1.6 λ, where λ is a light source wavelength.

6. The OPC method for the specific pattern side wave effect as claimed in claim 5, wherein the set distance condition is 1.5 λ.

7. The OPC method of claim 1 or 2 wherein the width of the scattering bars is 1/3 λ and the minimum spacing between the scattering bars and the target pattern is 0.5 λ in step S3, wherein λ is the light source wavelength.

8. A via layer OPC processing method based on the OPC method for a specific pattern-side-wave effect of claim 1, comprising the steps of:

step S1, inputting a target graph, and selecting a rectangular through hole graph as a selected graph;

step S2, judging whether the long side and the short side of the selected graph are both larger than 1 μm, if so, processing according to the standard OPC, otherwise, entering the step S3;

step S3, scattering strips are added in the selected graph, and the scattering strips are parallel to the long edges of the selected graph;

and step S4, carrying out model-based OPC correction by taking the target graph as a target and the scattering bars as auxiliary graphs to obtain a final OPC graph.

9. The via layer OPC processing method of claim 8, wherein the light intensity minimum value I_minThe set light intensity condition is satisfied to be 0.9I_th<I_min<1.1I_th。

10. The via layer OPC processing method of claim 8, wherein in step S3, the width of the scattering bars is 1/3 λ, and the minimum spacing between the scattering bars and the target pattern is 0.5 λ, where λ is a light source wavelength.

Technical Field

The invention relates to semiconductor integrated circuit design, in particular to an OPC method aiming at a specific pattern side wave effect and a via layer OPC processing method, which mainly aim at an extra exposure pattern formed by the side wave effect in the lithography process.

Background

Model-based OPC processes have been widely used in different levels of lithography in deep sub-micron integrated circuit fabrication. The method comprises the steps of establishing a photoetching model corrected by silicon wafer data, well predicting a pattern transfer distortion phenomenon existing under a specific photoetching process condition, then carrying out certain pattern compensation or correction according to the distortion condition simulated by the model, simulating the corrected pattern and checking whether the corrected pattern reaches a target, circulating the steps, and enabling the simulation result of the final pattern to be as close to the target pattern as possible after a certain number of iterations, which is a basic method of model-based OPC (optical proximity correction) processing.

Conventional model-based OPC processing methods have been well suited to correct or optimize optical distortion phenomena caused by optical proximity effects, such as off-target dimensions, corner rounding, etc. Under specific exposure conditions, for some patterns with special sizes and environments, the light intensity secondary peak exceeds the exposure threshold due to the interference effect after light diffraction, and at the moment, additional exposure patterns are generated and imaged outside the target pattern. The extra exposure pattern generated by the secondary wave peak in the micro-lithography process belongs to the side wave effect of the specific pattern under the specific exposure condition and belongs to the defect in the exposure process.

In the existing OPC method, the size and position of the pattern are continuously adjusted to reduce the influence of the interference effect on forming the sub-peak, and although the generation of the extra exposure pattern can be reduced or avoided, it is difficult to simultaneously achieve the convergence of the OPC result, that is, the target pattern size has a certain deviation. Moreover, the conventional OPC method avoids the generation of an extra exposure pattern, and once the process condition changes, there is still a risk of generating an extra exposure pattern after exposure, that is, the process window is small.

Disclosure of Invention

The invention provides an OPC method aiming at the side wave effect of a specific pattern, which can solve the problem that an extra exposure pattern is formed due to the side wave effect in the process of a lithography process.

In order to solve the above technical problem, the OPC method for the specific pattern side-wave effect provided by the present invention comprises the following steps:

step S1, setting exposure threshold I of OPC model_thInputting a target graph, simulating the light intensity distribution of the target graph after exposure by utilizing an OPC model, and selecting a rectangular graph with light intensity meeting a set light intensity condition as a selected graph and outputting the selected graph;

step S2, using two long sides in the selected graph, the distance between which satisfies the set distance condition, as graph sides;

step S3, generating scattering bars in the selected graph by taking the graph edges as target graph edges, wherein the scattering bars are parallel to the graph edges;

and step S4, carrying out model-based OPC correction by taking the target graph as a target and the scattering bars as auxiliary graphs to obtain a final OPC graph.

Further, after step S4, the method further includes:

in step S5, OPC verification is performed.

Further, in step S1, the set light intensity condition is a light intensity minimum value I_minApproach to exposure threshold I_th。

Preferably, the light intensity minimum value I_minThe set light intensity condition is satisfied to be 0.9I_th<I_min<1.1I_th。

Further, in the step S2, the pattern sides are paired pattern sides having a distance between 1.4 λ and 1.6 λ, where λ is the wavelength of the light source.

Preferably, the set distance condition is 1.5 λ.

Further, in step S3, the width of the scattering bars is 1/3 λ, and the minimum distance between the scattering bars and the target pattern is 0.5 λ, where λ is the wavelength of the light source.

Meanwhile, the invention also provides an OPC treatment method of the through hole layer, which comprises the following steps:

step S1, inputting a target graph, and selecting a rectangular through hole graph as a selected graph;

step S2, judging whether the long side and the short side of the selected graph are both larger than 1 μm, if so, processing according to the standard OPC, otherwise, entering the step S3;

step S3, scattering strips are added in the selected graph, and the scattering strips are parallel to the long edges of the selected graph;

and step S4, carrying out model-based OPC correction by taking the target graph as a target and the scattering bars as auxiliary graphs to obtain a final OPC graph.

Further, the light intensity minimum value I_minThe set light intensity condition is satisfied to be 0.9I_th<I_min<1.1I_th。

Further, in step S3, the width of the scattering bars is 1/3 λ, and the minimum distance between the scattering bars and the target pattern is 0.5 λ, where λ is the wavelength of the light source.

Aiming at an extra exposure pattern formed by a side wave effect in the process of a micro-lithography process, the invention firstly finds a specific rectangular pattern with the side wave effect, then adds an auxiliary pattern (scattering bar) in the rectangular pattern to change the light intensity distribution, and carries out OPC correction and verification to obtain a final OPC pattern, thereby ensuring that the final exposure result can reach the target size and avoiding generating the extra exposure pattern.

Drawings

FIG. 1 is a flow chart of an OPC method for specific pattern-side-wave effect according to the present invention;

FIG. 2 is a selected graph resulting from step S1 of the OPC method of the present invention;

FIG. 3 is a graph edge determined in step S2 of the OPC method of the present invention;

FIG. 4 is a schematic diagram of the positions of scattering bars added in step S3 of the OPC method according to the present invention;

FIG. 5 is a schematic diagram of a rectangular pattern after being processed by a conventional OPC method;

FIG. 6 is a schematic diagram of a rectangular pattern after being processed by the OPC method of the present invention;

FIG. 7 is a flowchart of a via level OPC processing method of the present invention;

FIG. 8 is a selected pattern resulting from step S1 of the via layer OPC treatment method of the present invention;

FIG. 9 is a graph of the selected graph of FIG. 8 with at least one edge not greater than 1 μm, as obtained by conventional OPC corrections;

FIG. 10 is a graph of the intensity distribution of the selected pattern of FIG. 8;

FIG. 11 is a schematic illustration of the OPC treatment method of FIG. 8 with scattering bars added when at least one side of the selected feature is not greater than 1 μm;

FIG. 12 is a simulated graph of FIG. 11 with OPC corrections;

FIG. 13 is a graph of the intensity distribution of the selected pattern of FIG. 11.

Detailed Description

Other advantages and effects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown in the accompanying drawings, wherein the specific embodiments are by way of illustration. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. In the following description, specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced or applied in different embodiments, and the details may be based on different viewpoints and applications, and may be widely spread and replaced by those skilled in the art without departing from the spirit of the present invention. In addition, the technical features mentioned in the different embodiments of the present application described below may be combined with each other as long as they do not conflict with each other.

Aiming at an additional exposure pattern formed by the side wave effect in the lithography process, the invention changes the light intensity distribution by adding an auxiliary pattern (scattering strip), in particular to an OPC method aiming at the side wave effect of a specific pattern, as shown in figure 1, and comprises the following steps:

step S1, setting exposure threshold I of OPC model_thInputting a target graph, simulating the light intensity distribution of the target graph after exposure by utilizing an OPC model, selecting a rectangular graph with light intensity meeting a set light intensity condition as a selected graph and outputting the selected graph as shown in FIG. 2;

step S2, using two long sides in the selected graph whose distance between the two long sides meets the set distance condition as graph sides, as shown in fig. 3;

step S3, taking the graph edge as a target graph edge, generating a scattering bar in the selected graph, where the scattering bar is parallel to the graph edge, as shown in fig. 4;

and step S4, carrying out model-based OPC correction by taking the target graph as a target and the scattering bars as auxiliary graphs to obtain a final OPC graph.

Preferably, after step S4, the method further includes: in step S5, OPC verification is performed.

In a preferred embodiment of the invention, the minimum value of the light intensity I is selected_minApproach to exposure threshold I_thAs the selected pattern and output, the rectangular pattern Frag-a of fig. 2. In a more preferred embodiment, the light intensity minimum I_minThe set light intensity condition is satisfied to be 0.9I_th<I_min<1.1I_th。

In a preferred embodiment of the present invention, in the step S2, the pattern sides are paired pattern sides with a distance between 1.4 λ and 1.6 λ, that is, the distance S between two long sides of the rectangular pattern satisfies the condition 1.4 λ < S <1.6 λ, where λ is the wavelength of the light source. Preferably, a pair of long sides with a distance of 1.5 λ between the two long sides is selected as the figure sides, as shown in fig. 3.

In step S3, the width of the scattering bars is 1/3 λ, and the minimum spacing between the scattering bars and the target pattern is 0.5 λ, where λ is the source wavelength.

The above step S1 relates to the nmOPC tool using Mentor, step S2 relates to the SVRF tool using Mentor, and step S3 relates to the nmSRAM tool using Mentor. Of course, other tools may be implemented by those skilled in the art, and the invention is not limited thereto.

In the present invention, a rectangular pattern is selected in which the light intensity satisfies a certain condition (the light intensity exceeding a set value may generate an extra exposure pattern), and the profile (contour) and the target pattern (target) of the specific pattern have a large EPE after the conventional OPC processing, as shown in fig. 5, and the correction does not accurately reach the target value. Fig. 6 shows the profile obtained after the post-OPC treatment of the scattering bars according to the OPC method of the present invention, which is close to the target value, and demonstrates that the correction effect of the OPC method of the present invention is significantly improved, so that it can be clearly seen that the effect of using the scattering bars is significantly better than that of the conventional OPC treatment when the specific pattern is encountered.

The embodiment of the invention aims at the extra exposure pattern formed by the side wave effect in the micro-lithography process, firstly finds the specific rectangular pattern with the side wave effect, then adds an auxiliary pattern (scattering strip) in the rectangular pattern to change the light intensity distribution, and carries out OPC correction and verification to obtain the final OPC pattern, thereby ensuring that the final exposure result can reach the target size and avoiding generating the extra exposure pattern.

Meanwhile, the method for OPC treatment of a via layer based on the above-mentioned OPC method, as shown in fig. 7, includes the steps of:

step S1, inputting a target graph, and selecting a rectangular through hole graph as a selected graph;

step S2, judging whether the long side and the short side of the selected graph are both larger than 1 μm, if so, processing according to the standard OPC, otherwise, entering the step S3;

step S3, scattering strips are added in the selected graph, and the scattering strips are parallel to the long edges of the selected graph;

and step S4, carrying out model-based OPC correction by taking the target graph as a target and the scattering bars as auxiliary graphs to obtain a final OPC graph.

Wherein the light intensity minimum value I_minThe set light intensity condition is satisfied to be 0.9I_th<I_min<1.1I_th。

Wherein, in step S3, the width of the scattering bars is 1/3 λ, and the minimum distance between the scattering bars and the target pattern is 0.5 λ, where λ is the light source wavelength.

The process and effect of the via layer OPC processing method according to the embodiment of the present invention will be further described below by taking the graph (rectangular or long circular) shown in fig. 8 as an example, in conjunction with fig. 7.

According to the pattern shown in fig. 8 (hereinafter, referred to as a long loop pattern), if both the long side and the short side are larger than 1 μm, the target value can be reached without generating an extra exposure pattern by performing correction according to the conventional OPC method.

In the long-loop graph in fig. 8, if one of the long side and the short side (the long side is not greater than 1 μm, the short side is not necessarily greater than 1 μm) or both sides are less than 1 μm, then the side-wave effect phenomenon occurs by using the conventional OPC correction method, as shown in fig. 9.

As can be seen from fig. 9, two additional exposure patterns are generated in each long loop pattern, which occurs because the set value threshold of the light intensity (intensity) is 0.1666 in the conventional OPC processing method, and if the light intensity somewhere in the selected pattern exceeds the set value, the additional exposure pattern is generated, and the light intensity analysis of the long loop pattern shown in fig. 8 finds that the light intensity of the middle pattern of the long loop pattern is 0.1752, as shown in fig. 10, and thus the side wave effect phenomenon occurs.

For the extra exposure pattern generated by the side wave effect of the specific pattern, the method shown in fig. 7 is adopted, and according to Calibre OPCpro and the formula, the scattering bars are added according to the size of the actual pattern, that is, the scattering bars are added inside the long ring pattern, as shown in fig. 11, and simultaneously, auxiliary patterns are added around the long ring pattern according to other rules.

Performing OPC simulations on the pattern (shown in fig. 11) to which the scattering bars were added, it was found that no generation of additional exposure patterns occurred with the addition of the scattering bars, as shown in fig. 12.

The pattern after the addition of the scattering bars was subjected to light intensity analysis, and as shown in fig. 13, the light intensity at the position where the additional exposure pattern was generated using the conventional OPC method was changed from 0.1752 to 0.0976, which is less than a set value (threshold ═ 0.1666), so that no additional exposure occurred.

The present invention has been described in detail with reference to the specific embodiments, which are merely preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Equivalent alterations and modifications made by those skilled in the art without departing from the principle of the invention should be considered to be within the technical scope of the invention.