A method for optimizing a photomask

Abstract

The present invention discloses a mask optimization method, which can avoid the generation of bridging in the mask layout pattern, ensure the lithography effect and improve the product yield rate. The mask optimization method is implemented based on an OPC correction model, and the method includes: providing a target layout; using the OPC correction model to optimize the initial pattern on the target layout to obtain an optimized mask; the OPC correction model is established based on a first correction model, a second correction model and the initial pattern. The first correction pattern is an initial correction pattern for correcting the initial pattern. The structure of the second correction pattern is set according to the minimum distance between adjacent initial patterns, and the second correction pattern is used to correct the first correction pattern that needs to be replaced again.

Description

Technical Field

[0001] The present invention relates to the technical field of transistors, and particularly to a method for optimizing a mask. Background Art

[0002] At present, in ultra-large-scale integrated circuits, the feature size of semiconductor devices has been reduced to dozens of nanometers or even a few nanometers. The higher the degree of integration of integrated circuits, the smaller the feature size of semiconductor devices. In the process of semiconductor processing, in order to meet the requirements of small-size processing of the feature size of semiconductor devices, the lithography process of a lithography machine is mainly used to realize the pattern making of semiconductor devices. However, limited by the resolution ability of the lithography machine, when the pattern on the photomask is reduced to less than the resolution ability of the lithography machine, the problem of insufficient process window will occur. Therefore, generally in the industry, the pattern is corrected through the OPC process to make the size of the lithography pattern on the mask meet the requirements of wafer design.

[0003] The OPC correction process mainly makes different sizes of corrections for different pattern distances in order to meet the design requirements of the wafer. However, when correcting the mask layout pattern, it is very easy to cause bridging between adjacent patterns. For example, when using a mask to make contact holes, the common mask layout patterns mainly include two types: square and rectangular. For contact holes with the same shape and the same size, the shapes and sizes of the photomask patterns used are the same. However, due to design requirements, when the contact holes are distributed densely, that is, the distance between the contact holes is very close or the spacing is very small, if the original correction pattern 1 with the same shape and size of the OPC process is used to correct the adjacent initial pattern 2 of the photomask (i.e., the mask), the phenomenon of pattern bridging 3 (bridge) is very likely to occur, as shown in Figure 1 which affects the manufacturing accuracy of the contact holes. Summary of the Invention

[0004] Aiming at the problem in the prior art that when using the original correction pattern with the same shape and size of the OPC correction model to correct the initial pattern of the mask, bridging is likely to occur between adjacent patterns with a small distance, which affects the subsequent lithography accuracy, the present invention provides a method for optimizing a mask, which can avoid the occurrence of bridging in the mask layout pattern, ensure the lithography effect, and improve the product yield.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for optimizing a mask, which is implemented based on an OPC correction model, and is characterized in that the OPC correction model includes a first OPC correction model and a second OPC correction model. The steps for optimizing the mask include: S1. Providing a target layout, and the target layout includes an initial pattern;

[0007] S2. Establish the first OPC correction model, which is established based on the first correction pattern, and the structure of the first correction pattern is the same as that of the initial pattern;

[0008] S3. Use the first OPC correction model to perform an initial correction on the initial pattern to obtain the first optimized mask containing the initially corrected pattern;

[0009] S4. Establish the second OPC correction model, which is established based on the second correction pattern, and the structure of the second correction pattern is set according to the minimum distance between adjacent initial patterns;

[0010] S5. Measure the distance between two adjacent initial patterns, and select whether to use the second OPC correction model to correct the initially corrected pattern in the corresponding area according to the distance, and correct the first optimized mask through the second OPC correction model to obtain the second optimized mask.

[0011] Its further feature lies in that,

[0012] Further, step S5 includes: S51. Compare the measured distance with a preset distance threshold to determine whether the distance is greater than the distance threshold. If not, no further correction is performed. Otherwise, go to step S52;

[0013] S52. Obtain the area on the first optimized mask where the distance is less than or equal to the threshold, use this area as the area to be corrected again, and use the second correction pattern in the second OPC correction model to correct the first correction pattern in the area to be corrected again to obtain the second optimized mask;

[0014] Further, the first correction pattern is a rectangle and / or a square;

[0015] Further, the second correction pattern is a polygon;

[0016] Further, the polygon includes a first polygon, and the first polygon is a square with notches at four corners;

[0017] Further, the polygon includes a second polygon and a third polygon. Notches are provided at the opposite vertex angles of the second polygon and the third polygon, and the second polygon and the third polygon are mirror-symmetrically arranged;

[0018] Further, the notch is a quadrilateral.

[0019] A manufacturing process for transistor contact holes. Apply the above optimized mask to the manufacturing process of transistor contact holes. The manufacturing process of the contact holes includes: providing a substrate;

[0020] A plurality of the contact holes are formed on the substrate by a photolithography process, and the mask used in the photolithography process is the first optimized mask and / or the second optimized mask.

[0021] It is further characterized in that

[0022] The transistor is an FDSOI transistor;

[0023] The contact hole is rectangular and / or rectangular.

[0024] By using the above method of the present invention, the following beneficial effects can be achieved: in this mask optimization method, in order to avoid bridging of patterns on the target layout during the correction process, the initial pattern is corrected by using the second correction pattern, and the structure of the second correction pattern is set according to the minimum distance between adjacent initial patterns. Therefore, before photolithography, the second OPC correction model established based on this second correction pattern is used to correct the mask layout pattern area with a smaller distance again, effectively avoiding the bridging problem that appears after the mask is corrected by the first correction pattern of the first OPC correction model, ensuring the photolithography effect of subsequent photolithography and improving the product yield. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of bridging of patterns on an existing mask;

[0026] Figure 2 It is a top view structural diagram of the initial pattern of the present invention;

[0027] Figure 3 It is a top view structural diagram of the first correction pattern of the present invention;

[0028] Figure 4 It is a top view structural diagram of the second correction pattern of the present invention;

[0029] Figure 5 It is a top view structural diagram when the initial pattern is corrected by using the first correction pattern;

[0030] Figure 6 It is a top view structural diagram when the initial pattern is corrected by using the first correction pattern and the second correction pattern;

[0031] Figure 7 It is a flowchart of the mask optimization method of the present invention. Detailed Embodiments

[0032] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solution in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "including" and "having" in the specification and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product or equipment that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or equipment.

[0034] See Figures 2 to 7 , a method for optimizing a mask, which is implemented based on an OPC correction model. The steps for optimizing the mask include: S1. Provide a target layout, and the target layout includes an initial pattern 2. See Figure 2 , in this example, the initial pattern includes a square initial pattern and a strip initial pattern. Among them, the distance between the two bottom corners of the square initial pattern 21 above the strip initial pattern and the two top corners of the strip initial pattern 22 is relatively small;

[0035] S2. Establish a first OPC correction model, and the first OPC correction model is established based on a first correction pattern 4 (equivalent to correction pattern 1). The first correction pattern 2 is an initial correction pattern for correcting the initial pattern 2, and the structure of the first correction pattern is the same as the structure of the initial pattern 2. See Figure 3 、 Figure 5 , in this example, the first correction pattern 2 includes a rectangular first correction pattern 42 matching the strip initial pattern and a square first correction pattern 41 matching the square initial pattern. The areas of the rectangular first correction pattern 42 and the square first correction pattern 41 are both larger than the areas of the corresponding initial correction patterns. Therefore, bridging is likely to occur in the adjacent areas of the rectangular first correction pattern 42 and the square first correction pattern 41 used to correct the strip initial pattern 22 and the adjacent square initial pattern 21.

[0036] S3. Use the first OPC correction model to perform an initial correction (i.e., a single correction) on the initial pattern 2 to obtain a first optimized mask including the initial correction pattern.

[0037] S4. Establish a second OPC correction model. The second OPC correction model is established based on a second correction pattern. The structure of the second correction pattern is set according to the minimum distance between adjacent initial patterns, and the second correction pattern 5 is used to further correct the first correction pattern 4 that needs to be corrected.

[0038] S5. Measure the distance between two adjacent initial patterns. According to the measured distance, determine whether to use the second OPC correction model to perform secondary correction (i.e., further correction) on the first correction pattern in the corresponding area. Specifically: S51. Compare the measured distance with a pre-set distance threshold to determine whether the distance is greater than the distance threshold. If not, no further correction is performed. Otherwise, proceed to step S52.

[0039] S52. Obtain the area in the first optimized mask where the distance is less than or equal to the threshold. Use the second correction pattern in the second OPC correction model to correct the first correction pattern in the further correction area, as shown in Figure 5 , to obtain a second optimized mask.

[0040] In this embodiment, the second correction pattern 5 is a polygon, as shown in Figure 4 , Figure 6 , including a first polygon 51, a second polygon 52, and a third polygon 53. The first polygon 51 is a square with notches 6 provided at its four corners. The second polygon 52 and the third polygon 53 are provided with notches 6 at their opposite vertex angles, and the second polygon 52 and the third polygon 53 are mirror images of each other. The notch 6 is a quadrilateral, and the structure of the notch 6 is the same as the right-angle structure of the first polygon or the same as the structure of one vertex angle of the second polygon 52 or the third polygon 53. In this embodiment, notches are provided at the opposite vertex angles of the first polygon and the second polygon, and the first polygon and the second polygon are mirror images of each other. The purpose is to match the shape of the strip-shaped initial pattern 22 shown in Figure 6 , and at the same time prevent bridging between the opposite vertex angles of the second polygon 52 and the third polygon 53 and the corners of the square first correction pattern above them. The square first correction pattern 41 adjacent to the strip-shaped initial pattern 22 and the two adjacent rectangular first correction patterns 42 with a distance lower than the threshold are corrected to the second correction pattern 5, further preventing the occurrence of bridging.

[0041] In this application, not only is the initial pattern on the mask corrected using the first correction pattern to ensure the accuracy of subsequent lithography processes, but also the first correction pattern in the re-correction area on the mask where the adjacent distance is lower than the threshold is further corrected using the second correction pattern. That is, the second OPC correction model is used to correct the square first correction pattern and / or the strip-shaped first correction pattern in the re-correction area into a polygonal second correction pattern. This second correction pattern is mainly used to reduce the side length of the first correction pattern, preventing the size of the first correction pattern from being too large and causing bridging.

[0042] Apply the above optimized mask to the transistor contact hole manufacturing process. The transistor is an FDSOI transistor, but is not limited to FDSOI transistors. Before performing lithography operations on the contact holes using a lithography machine, an initial pattern is fabricated on the initial mask according to the designed shape of the contact holes. In this embodiment, the contact holes include rectangular contact holes and square contact holes. The initial mask is optimized using the above mask optimization method to obtain an optimized mask.

[0043] The manufacturing steps of the contact holes include: A1. Provide a substrate;

[0044] A2. Place the substrate in a lithography machine and etch a number of contact holes on the substrate through the lithography process of the lithography machine to complete the manufacturing of the contact holes. The first correction pattern, the second correction pattern, and the initial pattern in the mask of this application are all fabricated according to the shape of the contact holes to be manufactured. As the main component for connecting the conductive layer and the electrode, or connecting the conductive layer and the conductive layer in a semiconductor device, the manufacturing accuracy of the contact holes determines the performance of the entire device. The contact holes fabricated using the optimized mask can also avoid the bridging problem of the contact holes, thereby improving the manufacturing accuracy of the contact holes and the performance of the entire device.

[0045] In the mask optimization method of this application, the second OPC correction model established based on the second correction pattern is used to re-correct the mask layout pattern area with a smaller pitch, effectively avoiding the bridging problem that occurs after the mask is corrected using the first correction pattern of the first OPC correction model, and ensuring the lithography effect of subsequent lithography. In addition, the manufacturing process of correction patterns with the same shape and size is relatively simple, and the manufacturing process of correction patterns with a square or rectangular structure is also relatively simple for those skilled in the art. Therefore, during the mask correction process, first, the initial pattern on the mask is corrected once using the first correction pattern in the first OPC correction model, and then, according to the minimum distance between two adjacent initial patterns, the second correction pattern in the second OPC correction model is used to re-correct the first correction pattern at the corresponding position, effectively avoiding the generation of the bridging problem while ensuring the simplicity of the manufacturing process.

[0046] The above are only the preferred embodiments of this application, and the present invention is not limited to the above embodiments. It can be understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention shall be considered to be included within the protection scope of the present invention.

Claims

1. A mask optimization method, which is implemented based on an OPC correction model, characterized in that The OPC correction model includes a first OPC correction model and a second OPC correction model. The steps for optimizing the mask include: S1. Provide a target layout, where the target layout includes an initial pattern. S2. Establish the first OPC correction model, which is established based on a first corrected pattern. The structure of the first corrected pattern is the same as that of the initial pattern, and the area of the first corrected pattern is larger than that of the initial pattern. The first corrected pattern is a rectangle and / or a square. S3. Use the first OPC correction model to perform an initial correction on the initial pattern to obtain a first optimized mask including an initial corrected pattern. S4. Establish the second OPC correction model, which is established based on a second corrected pattern. The structure of the second corrected pattern is set according to the minimum distance between adjacent initial patterns. The second corrected pattern is a polygon, which includes a first polygon that is a square with notches at four corners, and the polygon includes a second polygon and a third polygon. The second polygon and the third polygon have notches at their opposite vertex angles, and the second polygon and the third polygon are mirror images of each other. S5. Measure the distance between two adjacent initial patterns, and determine whether to use the second OPC correction model to correct the initial corrected pattern in the corresponding area according to the distance. If so, correct the first optimized mask through the second OPC correction model to obtain a second optimized mask. Step S5 includes: S51. Compare the measured distance with a preset distance threshold to determine whether the distance is greater than the distance threshold. If not, no further correction is performed. Otherwise, proceed to step S52. S52. Obtain the area in the first optimized mask where the distance is less than or equal to the threshold, and use the second corrected pattern in the second OPC correction model to correct the first corrected pattern in the re-correction area to obtain the second optimized mask.

2. The optimized method for a photomask according to claim 1, wherein The notch is a quadrilateral notch.

3. A manufacturing process for transistor contact holes, characterized in that, Apply the mask optimization method described in claim 1 to the manufacturing process of the transistor contact holes. The manufacturing process of the transistor contact holes includes: providing a substrate, and using a lithography process to fabricate a plurality of the contact holes on the substrate. The masks used in the lithography process are the first optimized mask and the second optimized mask.

4. A manufacturing process for a transistor contact hole according to claim 3, characterized in that, The transistor is an FDSOI transistor; the contact holes are rectangles and / or squares.

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