Optical Proximity Correction Method for Diagonal-to-Diagonal Structures in Layout

Abstract

The present invention discloses an optical proximity correction method for the corner-to-corner structure in a layout, including the following steps: Step S1, find the original pattern of the ion implantation layer lithography layout; the original pattern is a corner-to-corner structure pattern; Step S2, respectively cut off a corner at the original corners of the original pattern; obtain a corner with a notch; Step S3, based on the pattern in Step S2, perform a correction process to obtain a target pattern structure, where the corners of the target pattern are formed with notches, and at the same time, protrusions are formed on the two adjacent corner sides of the corners of the target pattern; Step S4, perform model-based proximity optical effect correction on the target pattern to obtain a simulated photoresist contour line.

Description

Technical Field

[0001] The present invention relates to an integrated circuit manufacturing process, and particularly to an optical proximity correction method for a corner-to-corner structure in a layout. Background Art

[0002] Optical Proximity Correction (OPC) is a lithography enhancement technology that addresses image errors caused by diffraction. OPC is mainly used in the production process of semiconductor devices to ensure that the edges of the designed patterns are etched completely during production. These projected images exhibit irregularities such as line widths that are narrower or wider than the design, which can be compensated for during imaging by changing the mask. Other distortions, such as rounded corners, are more difficult to compensate for due to the resolution limitations of the optical tools. If these distortions are not corrected, they can significantly alter the electrical performance of the fabricated circuit. Optical proximity correction corrects these errors by shifting the edges of the patterns on the mask or adding additional polygons. Based on width and spacing constraints (i.e., rule-based OPC), or by using the results of a compact model for dynamic simulation (i.e., model-based OPC), a look-up table is pre-calculated to determine how to shift the edges of the pattern to find the best solution. The goal of OPC is to make the circuit produced on the silicon wafer as consistent as possible with the original circuit.

[0003] In the front-end SRAM region, there are some corner-to-corner structures that need to satisfy both the distance between the corners of the current layer's pattern (such as B in Figure 1 ), and the current layer's pattern enclosing other layer's patterns inside it (such as A in Figure 1 ). Therefore, there is very little space available for pattern correction using this corner-to-corner structure. As is well known, the shape exposed by a square corner pattern will become circular, which can lead to insufficient distance for enclosing the internal pattern.

[0004] Currently, the method to solve the above technical problem is to grow a circle around the corners of the pattern (such as the Figure 2 structure), but although this method can ensure that the distance inside is satisfied, it cannot ensure that the distance between the outside corners is far enough, and there is a risk of MRC error reporting (at the five-pointed star position in Figure 2 ). Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an OPC processing method that can make full use of the remaining space in the corner-to-corner structure in the layout to achieve the effect of increasing the lithography process window.

[0006] To solve the above technical problem, the present invention discloses an optical proximity correction method for a corner-to-corner structure in a layout, characterized by including the following steps:

[0007] Step S1, find the original pattern of the lithography layout of the ion implantation layer; the original pattern is a pattern with a diagonal-to-diagonal structure.

[0008] Step S2, at the original corners of the original pattern, cut off one corner respectively; obtain notched corners.

[0009] Step S3, based on the pattern in Step S2, perform a correction process to obtain a target pattern structure. The corners of the target pattern are formed with notches, and at the same time, raised portions are formed on two adjacent corner sides of the corners of the target pattern.

[0010] Step S4, perform model-based proximity optical effect correction on the target pattern to obtain a simulated photoresist contour line.

[0011] Preferably, in Step S1, the original pattern is the current layer process pattern, and the current layer process pattern covers the previous layer process pattern in the orthographic projection direction of the substrate.

[0012] Preferably, in Step S2, the vertical distance P between every two opposite notched corners is equal to the minimum distance requirement for mask manufacturing.

[0013] Preferably, in Step S2, the vertical distance P between every two opposite notched corners is equal to 60 nm.

[0014] Preferably, in Step S3, stretch the two adjacent corner sides so that the two adjacent corner sides are formed with a first raised portion and a second raised portion, and the sum of the heights of the first raised portion and the second raised portion is calculated according to the lithography formula.

[0015] Preferably, in Step S4, the simulated photoresist contour line includes arc-shaped corners, and the distance between two opposite arc-shaped corners is a preset distance.

[0016] Preferably, the distance between two opposite arc-shaped corners is 84 nm.

[0017] Preferably, in Step S4, the simulated photoresist contour line includes arc-shaped corners, and the arc-shaped corners are not less than 20 nm away from the previous layer pattern.

[0018] Without affecting the device performance and meeting the design rules, the present invention adjusts the shape parameters of the current layer pattern, introduces size compensation for the distance to the previous layer, reduces the risk of shrinkage or even peeling off of the photoresist, thereby reducing the defect risk caused by pattern distortion, and ensuring the accuracy of ion implantation of the previous layer pattern. Description of the Drawings

[0019] Figure 1 is a schematic diagram of a diagonal-to-diagonal structure in the layout of the prior art.

[0020] Figure 2 It is a schematic diagram of a solution for the corner-to-corner structure in the layout of the prior art.

[0021] Figure 3 It is a schematic diagram of the layout structure after chamfering in an optical proximity correction method for the corner-to-corner structure in the layout of the present invention.

[0022] Figure 4 It is a schematic diagram of the target pattern in an optical proximity correction method for the corner-to-corner structure in the layout of the present invention.

[0023] Explanation of reference numerals

[0024] 10 Process pattern of the current layer 11 First protrusion

[0025] 12 Second protrusion 20 Process pattern of the previous layer

[0026] 30 Simulated photoresist contour line 31 Arc-shaped corner

[0027] P Vertical distance between the notched corners H1 Height of the first protrusion

[0028] H2 Height of the second protrusion W1 Width of the first protrusion

[0029] W2 Width of the second protrusion D1 Distance between two opposite arc-shaped corners

[0030] D2 Distance between the arc-shaped corner and the previous layer pattern Detailed implementation manner

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] The present invention discloses an optical proximity correction method for the corner-to-corner structure in the layout, which is characterized by including the following steps:

[0033] Step S1, find the original pattern of the lithography layout of the ion implantation layer; the original pattern is a pattern with a corner-to-corner structure.

[0034] Preferably, in step S1, the original pattern is the process pattern 10 of the current layer, and the process pattern of the current layer covers the process pattern 20 of the previous layer in the orthographic projection direction of the substrate.

[0035] The process pattern of the previous layer can be FIN (fin) or GATE (gate).

[0036] Step S2, respectively cut off a corner at the original corners of the original pattern; obtain notched corners.

[0037] Preferably, in step S2, the vertical distance P between every two opposite notched corners should be greater than or equal to the minimum distance requirement for mask manufacturing.

[0038] In this embodiment, the vertical distance P is equal to 60 nm.

[0039] Step S3: Based on the pattern in step S2, perform a correction process to obtain a target pattern structure. Notches are formed at the corners of the target pattern, and at the same time, protrusions are formed on two adjacent corner sides of the corners of the target pattern.

[0040] In this embodiment, the OPC software performs optical proximity effect correction on the design pattern according to pre-determined rules. The key to this method is the correction rules, which specify how to correct various exposure patterns. Its form and content will greatly affect the efficiency of OPC data processing and the accuracy of correction.

[0041] The correction rule for this step is to stretch the two adjacent corner sides so that the two adjacent corner sides form a first protrusion and a second protrusion. The heights H1, H2 and widths W1, W2 of the first protrusion and the second protrusion are calculated by EDA software according to the lithography formula.

[0042] Step S4: Perform model-based proximity optical effect correction on the target pattern to obtain a simulated photoresist profile.

[0043] Preferably, the simulated photoresist profile 30 includes arc-shaped corners 31, and the distance D1 between two opposite arc-shaped corners 31 is a preset distance. This preset distance should meet the lithography process window, that is, the photoresist will not peel off. In this embodiment, the distance D1 between two opposite arc-shaped corners is 84 nm.

[0044] In step S4, the simulated photoresist profile includes arc-shaped corners 31, and the distance between the arc-shaped corners 31 and the previous layer process pattern 20 cannot be less than the lithography process window. In this embodiment, the distance D2 between the arc-shaped corners 31 and the previous layer process pattern 20 is not less than 20 nm.

[0045] Without affecting the device performance and meeting the design rules, the present invention reduces the risk of shrinkage or even peeling of the photoresist by adjusting the shape parameters of the current layer pattern and introducing dimensional compensation for the distance to the previous layer, thereby reducing the defect risk caused by pattern distortion and ensuring the accuracy of ion implantation of the previous layer pattern.

[0046] The above are only preferred embodiments of the present invention, and thus do not limit the implementation manners and protection scope of the present invention. Those skilled in the art should be able to realize that all equivalent substitutions and obvious changes made by using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical proximity correction method for the corner-to-corner structure in a layout, characterized in that, It includes the following steps: Step S1, find the original pattern of the lithography layout of the ion implantation layer; the original pattern is a pattern with a diagonal-to-diagonal structure; Step S2, at the original corners of the original pattern, cut off a corner respectively; obtain the notched corners; Step S3, based on the pattern in Step S2, perform a correction process to obtain the target pattern structure. There are notches formed at the corners of the target pattern, and at the same time, there are protrusions formed on the two adjacent sides of the corners of the target pattern; Step S4, perform model-based proximity optical effect correction on the target pattern to obtain the simulated photoresist contour line.

2. The optical proximity correction method for the diagonal-to-diagonal structure in the layout according to claim 1, characterized in that, In Step S1, the original pattern is the current layer process pattern, and the current layer process pattern covers the previous layer process pattern in the orthographic projection direction of the substrate.

3. The optical proximity correction method for the diagonal structure in the layout according to claim 1, wherein , In Step S2, the vertical spacing P between every two opposite notched corners is equal to the minimum spacing requirement for mask making.

4. The optical proximity correction method for the diagonal structure in the layout according to claim 1, characterized in that , In Step S2, the vertical spacing P between every two opposite notched corners is equal to 60 nm.

5. The optical proximity correction method for the diagonal-to-diagonal structure in the layout according to claim 1, characterized in that, In Step S4, the simulated photoresist contour line includes arc-shaped corners, and the distance between two opposite arc-shaped corners is a preset distance.

6. The optical proximity correction method for the diagonal structure in the layout according to claim 5, characterized in that The distance between two opposite arc-shaped corners is 84 nm.

7. The optical proximity correction method for the diagonal-to-diagonal structure in the layout according to claim 5, characterized in that In Step S4, the simulated photoresist contour line includes arc-shaped corners, and the arc-shaped corners are not less than 20 nm away from the previous layer pattern.

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