Optical Proximity Correction Method for Square Hole Patterns

Abstract

The present invention provides an optical proximity correction method for square hole patterns. The method provides a target pattern to be corrected, selects each square hole pattern whose distance from surrounding patterns is less than a set value, and provides a non-overlapping polyline segment on each adjacent edge of the square hole pattern. At least one light intensity sampling point is set on each polyline segment near its vertices. The optical proximity correction is performed on the pattern using the light intensity sampling points. The present invention also provides a method for moving the light intensity sampling points for calculating the line segments of square hole patterns in a through-hole layer, improving the profile of asymmetric environmental holes and optimizing optical proximity correction for photomasks.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an optical proximity correction method for a square hole pattern. Background Art

[0002] As semiconductor chip nodes advance, the minimum CD (critical dimension) and pitch (period) of chip design patterns are shrinking. The design pattern density is getting higher and higher, and the distance between patterns is getting smaller and smaller. This has brought great limitations to OPC (optical proximity correction) mask correction. This is even more serious for the through-hole layer.

[0003] For processes at advanced technology nodes, OPC corrects the design layout based on the lithography process model. The OPC correction process for the layout is as follows: first, the edges of the layout pattern are segmented into fragments (line segments). Then, based on whether the fragment touches the corners of the layout pattern, it is divided into corner fragments and center fragments. For the corner fragment, the endpoint away from the corner of the pattern is used as the sampling point for calculating the light intensity. For the center fragment, the midpoint is used as the sampling point for calculating the light intensity. The layout is convolved with the OPC model to calculate the light intensity of each fragment sampling point, and then combined with the model threshold to obtain the CD value. The CD value is subtracted from the Target value to obtain the movement value of each fragment in the layout. After several cycles, the simulated CD value of the corrected layout meets the Target specification, completing the OPC correction of the layout. Therefore, during the layout OPC correction process, the reasonable fragment segmentation and calculation of the light intensity sampling points determine the OPC correction results. When performing OPC correction on a square hole, the edge of the square hole is divided into two fragments. According to the OPC correction mechanism, the fragments on the edge of the square hole are all corner fragments, so the sampling point for calculating the light intensity point is the same point (such as Figure 1 、 2 When the hole's surrounding environment is inconsistent, the fragment sampling point cannot effectively represent the fragment's environmental characteristics. The fragment can reach the target value after OPC at the sampling point. However, near the pattern corner, far from the calculated light intensity sampling point, due to the rounded corner and the large difference in light intensity between this location and the sampling point environment, the result of OPC correction may be a slanted hole. This pattern profile is not friendly to the subsequent dry etching process and may become a defect, affecting chip yield.

[0004] In order to solve the above problems, a new optical proximity correction method for square hole patterns is needed. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the present invention aims to provide an optical proximity correction method for square hole patterns. This method addresses the problem in the prior art where, according to the optical proximity correction mechanism, the line segments along the edges of the square hole are all angled segments, resulting in the same sampling point for calculating light intensity. When the surrounding environment of the hole is inconsistent, the line segment sampling points cannot effectively represent the environmental characteristics of the line segment. While the line segment can achieve the target value at the sampling point after optical proximity correction, at locations far from the calculated light intensity sampling point, i.e., near the corners of the pattern, the result of optical proximity correction may be an oblique hole due to the rounded corners and the significant difference in light intensity between the sampling point and the surrounding environment. This pattern profile is not friendly to the subsequent dry etching process and may become a defect, affecting chip yield.

[0006] To achieve the above-mentioned and other related objectives, the present invention provides an optical proximity correction method for a square hole pattern, comprising:

[0007] Step 1: Provide a target pattern to be corrected by optical proximity calibration, and select each square hole pattern whose distance to surrounding patterns is less than a set value;

[0008] Step 2: providing a non-overlapping broken line segment on each of two adjacent sides of the square hole pattern;

[0009] Step 3: setting at least one light intensity sampling point on each of the broken line segments and close to two vertices of the broken line segment;

[0010] Step 4: Perform optical proximity correction on the pattern using the light intensity sampling points.

[0011] Preferably, the square hole pattern in step 1 is a through hole pattern connecting upper and lower layer patterns.

[0012] Preferably, the set value in step 1 is 65 nanometers.

[0013] Preferably, in step 2, the broken line segments of the same shape are respectively provided on each two adjacent sides of the square hole pattern.

[0014] Preferably, in step 2, the fold line segments of the same shape are respectively provided on each two adjacent sides of the square hole pattern, and the distances between the two vertices of the fold line segments and their common endpoint are equal.

[0015] Preferably, the first and second segments of the broken line segment in step 2 are perpendicular to each other.

[0016] Preferably, in step 3, the distance between the common endpoint on the broken line segment and the light intensity sampling point is X*Y, where X is the distance between a vertex in the broken line segment and the common endpoint, and Y is greater than 0 and less than 1.

[0017] Preferably, in step 3, the distance between the common endpoint on the broken line segment and the light intensity sampling point is X*0.618, where X is the distance between a vertex in the broken line segment and the common endpoint.

[0018] Preferably, the method of performing optical proximity correction on the pattern using the light intensity sampling points in step 4 includes: simulating the target pattern after photolithography of the layout design pattern according to the light intensity sampling points; re-correcting the mask using the error between the target pattern and the layout design pattern; and simulating the photolithography result of the layout design file using the corrected mask.

[0019] As described above, the optical proximity correction method for square hole patterns of the present invention has the following beneficial effects:

[0020] The invention provides a method for moving sampling points for calculating light intensity of square hole pattern line segments in a through-hole layer, thereby improving the contour of asymmetric environmental holes and optimizing optical proximity correction of photomasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shown is a schematic diagram of setting optical sampling points for a through-hole layer pattern in the prior art;

[0022] Figure 2 The diagram shows the prior art where two fragment light intensity sampling points at the edge of a through-hole layer are merged into one point;

[0023] Figure 3 Shown is a schematic diagram of a local layout of a logic device in the prior art;

[0024] Figure 4 Shown is a schematic diagram of an unmoved optical sampling point in the prior art;

[0025] Figure 5 A schematic diagram showing a mask correction pattern obtained by not moving the optical sampling point in the prior art;

[0026] Figure 6 Shown is a schematic diagram of a simulated exposure profile of the prior art;

[0027] Figure 7 Shown is a schematic diagram of setting optical sampling points for the through-hole layer pattern of the present invention;

[0028] Figure 8 It is a schematic diagram showing that the two fragment light intensity sampling points at the edge of the through-hole layer of the present invention are not merged into one point;

[0029] Figure 9 Shown is a schematic diagram of a moving optical sampling point of the present invention;

[0030] Figure 10Shown is a schematic diagram of the invention name of the mask correction pattern obtained by moving the optical sampling point of the present invention;

[0031] Figure 11 Shown is a schematic diagram of a simulated exposure profile of the present invention;

[0032] Figure 12 Shown is a comparison diagram of simulated exposure profiles between an unmoved optical sampling point and a moved optical sampling point under different light sources according to the present invention;

[0033] Figure 13 Shown is a schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0034] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] See also Figure 13 The present invention provides an optical proximity correction method for a square hole pattern, comprising:

[0036] Step 1: providing a target pattern to be corrected by optical proximity calibration, and selecting each square hole pattern whose distance to surrounding patterns is less than a set value;

[0037] In an embodiment of the present invention, the square hole pattern in step 1 is a through hole pattern connecting upper and lower layer patterns.

[0038] In the embodiments of the present invention, see Figure 3 , which shows a random logic pattern of the metal hole (M0P) layer connecting the gate of a product. In advanced nodes, the M0P layer is used to connect the gate (PO), the source and drain metal layer (M0A) and the hole (V0) layer connecting the metal wire. The pattern type is relatively simple as shown in the figure. Most of the patterns are square holes. The ADI target value is 55nm, but the environment around the square hole is complex. The four sides (1, 2, 3, 4) of the square hole A in the figure have different patterns, and the size of the closest pattern of the 1, 2, and 4 sides is 43, 60, and 43nm. The 3 sides are sparse (ISO). The 1, 2, and 4 sides are too close to other patterns. Each side of the square hole A is divided into Figure 2 In the two fragments shown, the light intensity at the two endpoints of each fragment is very different. Using the endpoints of the line segment to calculate the light intensity sampling points is not appropriate.

[0039] In the embodiment of the present invention, the set value in step 1 is 65 nanometers. It should be understood that due to the different densities of patterns in different processes, the set value may also adopt other values.

[0040] Step 2, please refer to Figure 7 and Figure 8 , a non-overlapping polyline segment is provided on each of two adjacent sides of the square hole figure, and the polyline segment is composed of a first and a second line segment sharing the same common endpoint, and the first and the second line segments are both straight segments, and there is a certain distance between the vertices of the polyline segment on each side of the square hole figure;

[0041] In an embodiment of the present invention, in step 2, broken line segments of the same shape are respectively provided on every two adjacent sides of the square hole pattern.

[0042] In an embodiment of the present invention, in step 2, a broken line segment of the same shape is provided on each two adjacent sides of the square hole pattern, and the distances between the two vertices of the broken line segment and its common endpoint are equal, that is, the lengths of the first and second segments of each broken line segment are equal.

[0043] In an embodiment of the present invention, the first and second segments of the broken line segment in step 2 are perpendicular to each other.

[0044] In an embodiment of the present invention, four corners of the square hole pattern are provided with broken line segments with an angle of 90 degrees, and the lengths of the two broken line segments are equal.

[0045] Step 3, please refer to Figure 7 、 8 , set at least one light intensity sampling point on each broken line segment and close to the two vertices of the broken line segment;

[0046] In an embodiment of the present invention, the distance between the common endpoint on the broken line segment and the light intensity sampling point in step three is X*Y, where X is the distance between a vertex in the broken line segment and the common endpoint, and Y is greater than 0 and less than 1, that is, a light intensity sampling point is set at each of the two vertices close to the broken line segment. It should be noted that more light intensity sampling points can also be set here according to actual process requirements.

[0047] In an embodiment of the present invention, the distance between the common endpoint on the broken line segment and the light intensity sampling point in step 3 is X*0.618, where X is the distance between a vertex in the broken line segment and the common endpoint.

[0048] For example, the lengths of the first and second segments of the broken line segment are both 27.5nm. At this time, the calculated light intensity point of the OPC correction is the endpoint away from the corner of the square hole, and the calculated light intensity sampling points of the two fragments of the same side are at the same position. The calculated value of the calculated light intensity point is 27.5x(1-0.618)=10.05nm. The OPC correction recipe is adjusted so that the calculated light intensity point of the square hole is 10.05nm away from the original calculated light intensity point.

[0049] Step 4: Perform optical proximity correction on the pattern using the light intensity sampling points, and the corrected pattern is used to correct the mask.

[0050] In an embodiment of the present invention, the method of performing optical proximity correction on a pattern using light intensity sampling points in step four includes: simulating a target pattern after photolithography of a layout design pattern according to the light intensity sampling points; re-correcting the mask using an error between the target pattern and the layout design pattern; and simulating the photolithography result of the layout design file using the corrected mask.

[0051] In an embodiment of the present invention, Figure 4 At the light intensity sampling point where the fragment does not move, the two fragments of the square hole are at the same position. Figure 5 The middle one is the corrected mask pattern. Figure 6 for Figure 5 The simulated exposure profile of the mask pattern shown, Figure 9 The light intensity sampling point of the fragment is moved, and the sampling point deviates from the original position by 10nm. Figure 10 is the corrected mask pattern, Figure 11 for Figure 10 The simulated exposure profile of the mask pattern shown, Figure 5 The square hole pattern in the calculation of light intensity is not moved, and the mask pattern correction is presented in a symmetrical correction method. Figure 10 The light intensity sampling point is moved to correct the mask pattern, and a correction method that is more in line with the environment is developed. Figure 6 and Figure 11 The simulated exposure profile results of the modified mask pattern under different light angles are shown in Site 1 and Site 2. Figure 12 Diameter measurements were taken at 0, 45, 90, and 135 degrees, as shown in the table below. Site 1 shows the simulation with the calculated light intensity sampling point unchanged, while Site 2 shows the simulation with the calculated light intensity sampling point moved. This OPC correction method, using the shifted calculation light intensity sampling point, reduces wafer diameter variation and produces smoother holes, making this profile more user-friendly for subsequent processes.

[0052] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0053] In summary, the present invention provides a method for moving sampling points for calculating light intensity for line segments of square hole patterns in a through-hole layer, improving the profile of asymmetric environmental holes and optimizing optical proximity correction for photomasks. Therefore, the present invention effectively overcomes the shortcomings of existing technologies and possesses high industrial value.

[0054] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An optical proximity correction method for a square hole pattern, characterized in that: At least: Step 1: Provide a target pattern to be corrected by optical proximity calibration, and select each square hole pattern whose distance to surrounding patterns is less than a set value; Step 2: providing a non-overlapping broken line segment on each of two adjacent sides of the square hole pattern, wherein the first and second segments of the broken line segment are perpendicular to each other; Step 3: setting at least one light intensity sampling point on each of the folded line segments, wherein the distance between the common endpoint of the folded line segment and the light intensity sampling point is X*Y, where X is the distance between a vertex in the folded line segment and the common endpoint, and Y is greater than 0 and less than 1; Step 4: Perform optical proximity correction on the pattern using the light intensity sampling points.

2. The optical proximity correction method for a square hole pattern according to claim 1, wherein: The setting value in step 1 is 65 nm.

3. The optical proximity correction method for a square hole pattern according to claim 1, wherein: In step 2, the broken line segments of the same shape are respectively provided on each two adjacent sides of the square hole pattern.

4. The optical proximity correction method for a square hole pattern according to claim 3, wherein: In step 2, the same-shaped broken line segments are respectively provided on each two adjacent sides of the square hole pattern, and the distances between the two vertices of the broken line segments and their common endpoint are equal.

5. The optical proximity correction method for a square hole pattern according to claim 3 or 4, wherein: In step 3, the distance between the common endpoint on the broken line segment and the light intensity sampling point is X*0.618, where X is the distance between a vertex in the broken line segment and the common endpoint.

6. The optical proximity correction method for a square hole pattern according to claim 1, wherein: The method of performing optical proximity correction on the pattern using the light intensity sampling points in step 4 includes: simulating the target pattern after photolithography of the layout design pattern according to the light intensity sampling points; re-correcting the mask using the error between the target pattern and the layout design pattern; and simulating the photolithography result of the layout design file using the corrected mask.

7. The optical proximity correction method for a square hole pattern according to claim 1, wherein: The square hole pattern in step 1 is a through hole pattern connecting the upper and lower layer patterns.

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