Optical proximity correction method

Abstract

An optical proximity correction method comprises: providing a design layer, the design layer comprising a first design pattern and a second design pattern; obtaining an auxiliary layer according to the design layer, the auxiliary layer comprising a first auxiliary pattern and a second auxiliary pattern; obtaining an initial target layer according to the design layer, the initial target layer comprising an initial first target pattern and an initial second target pattern; and performing a correction process on the initial target layer with reference to the auxiliary layer to obtain a target layer, the target layer comprising a first target pattern and a second target pattern corresponding to the first design pattern and the second design pattern. By adding two auxiliary patterns, i.e., the first auxiliary pattern and the second auxiliary pattern, between the first target pattern and the second target pattern, the stability of the pattern transferred to the photoresist layer in the subsequent exposure process is improved, and the risk of pattern collapse on the photoresist layer is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more particularly to an optical proximity correction method. Background Technology

[0002] Photolithography is a crucial technology in semiconductor manufacturing. It transfers patterns from a photomask to the surface of a silicon wafer, forming semiconductor products that meet design requirements. The photolithography process includes an exposure step, a development step following exposure, and an etching step following development. In the exposure step, light passes through the light-transmitting areas of the photomask and shines onto the silicon wafer coated with photoresist, causing a chemical reaction in the photoresist. In the development step, the different solubility of the developer in the photoresist and the non-photoresist is used to form a photolithographic pattern, transferring the photomask pattern onto the photoresist. In the etching step, the silicon wafer is etched based on the photolithographic pattern formed by the photoresist layer, further transferring the photomask pattern onto the silicon wafer.

[0003] In semiconductor manufacturing, as design dimensions continue to shrink and approach the limits of photolithography imaging systems, the diffraction effect of light becomes increasingly pronounced, leading to optical image degradation of the final design pattern. The actual photolithographic pattern formed is severely distorted relative to the pattern on the mask, resulting in a difference between the actual pattern formed on the silicon wafer and the design pattern. This phenomenon is called the Optical Proximity Effect (OPE).

[0004] To correct the optical proximity effect, Optical Proximity Correction (OPC) was developed. The core idea of ​​OPC is to establish an OPC model based on the consideration of counteracting the optical proximity effect. The photomask pattern is designed according to the OPC model. In this way, although the lithographic pattern and the corresponding photomask pattern have an optical proximity effect, the cancellation of this phenomenon has been considered when designing the photomask pattern according to the OPC model. Therefore, the lithographic pattern after photolithography is close to the target pattern actually desired by the user.

[0005] However, existing optical proximity correction technologies still have many problems. Summary of the Invention

[0006] The technical problem solved by this invention is to provide an optical proximity correction method to reduce the risk of pattern collapse when exposure is transferred to the photoresist layer.

[0007] To address the aforementioned problems, the present invention provides an optical proximity correction method, comprising: providing a design layer, the design layer including a first design graphic and a second design graphic arranged parallel to each other along a first direction, with a first spacing dimension between the first design graphic and the second design graphic; obtaining an auxiliary layer based on the design layer, the auxiliary layer including a first auxiliary graphic and a second auxiliary graphic arranged parallel to each other along the first direction, the first auxiliary graphic and the second auxiliary graphic located between the first design graphic and the second design graphic; obtaining an initial target layer based on the design layer, the initial target layer including an initial first target graphic and an initial second target graphic corresponding to the first design graphic and the second design graphic, with a second spacing dimension between the initial first target graphic and the initial second target graphic, the first spacing dimension being larger than the second spacing dimension; and, with the auxiliary layer as a reference, performing correction processing on the initial target layer to obtain a target layer, the target layer including a first target graphic and a second target graphic corresponding to the first design graphic and the second design graphic, the first auxiliary graphic and the second auxiliary graphic located between the first target graphic and the second target graphic, the first target graphic and the second target graphic having a third spacing dimension, the third spacing dimension being larger than the second spacing dimension.

[0008] Optionally, the initial first target graphic is a rectangle, and the initial first target graphic includes a first long side and a second long side that are opposite to each other, with the first long side being adjacent to the first auxiliary graphic; the initial second target graphic is a rectangle, and the initial second target graphic includes a third long side and a fourth long side that are opposite to each other, with the third long side being adjacent to the second auxiliary graphic.

[0009] Optionally, the method for modifying the initial target layer and obtaining the target layer with reference to the auxiliary layer includes: translating the first long side away from the first auxiliary graphic until the distance between the first long side and the first auxiliary graphic is greater than or equal to the mask rule size, so that the initial first target graphic forms the first target graphic; translating the third long side away from the second auxiliary graphic until the distance between the third long side and the second auxiliary graphic is greater than or equal to the mask rule size, so that the initial second target graphic forms the second target graphic.

[0010] Optionally, the first auxiliary graphic is a rectangle; the second auxiliary graphic is a rectangle.

[0011] Optionally, after obtaining the auxiliary layer, the method further includes: detecting the auxiliary layer to prevent the first auxiliary graphic or the second auxiliary graphic from being exposed to the photoresist layer.

[0012] Optionally, the method for detecting the auxiliary layer to prevent the first auxiliary graphic or the second auxiliary graphic from being exposed to the photoresist layer includes: when it is detected that the first auxiliary graphic or the second auxiliary graphic can be exposed to the photoresist layer, reducing the size of the first auxiliary graphic or the second auxiliary graphic.

[0013] Optionally, after obtaining the target layer, the method further includes: performing optical proximity correction on the target layer several times to obtain a correction layer, wherein the correction layer includes a first correction image and a second correction image corresponding to the first target image and the second target image.

[0014] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0015] In the optical proximity correction method of this invention, the initial target layer is corrected and a target layer is obtained by using the auxiliary layer as a reference. The target layer includes a first target pattern and a second target pattern corresponding to the first design pattern and the second design pattern. The first auxiliary pattern and the second auxiliary pattern are located between the first target pattern and the second target pattern. By adding two columns of auxiliary patterns, namely the first auxiliary pattern and the second auxiliary pattern, a double-slit diffraction effect occurs between the first auxiliary pattern and the second auxiliary pattern in the subsequent exposure process. The light intensity of each diffraction order in the double-slit diffraction process is significantly increased, and the position of the diffraction peak is closer to the center of the first target pattern and the second target pattern. This can greatly improve the stability of the pattern transferred to the photoresist layer and reduce the risk of pattern collapse on the photoresist layer.

[0016] Furthermore, after acquiring the auxiliary layer, the method further includes: detecting the auxiliary layer to prevent the first auxiliary pattern or the second auxiliary pattern from being exposed to the photoresist layer. By detecting the auxiliary layer, the exposure of the first auxiliary pattern or the second auxiliary pattern to the photoresist layer is avoided, and a corresponding redundant device structure is formed on the wafer through subsequent patterning transfer, thereby preventing any impact on other functional device structures. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the pattern morphology structure transferred onto the photoresist layer;

[0018] Figure 2 This is a schematic diagram of adding a column of auxiliary graphics between adjacent target graphics in the target layer;

[0019] Figure 3This is a flowchart of the optical proximity correction method according to an embodiment of the present invention;

[0020] Figures 4 to 8 This is a schematic diagram of the structure of each step of the optical proximity correction method in an embodiment of the present invention. Detailed Implementation

[0021] As described in the background section, existing optical proximity correction techniques still have many problems. These will be explained in detail below with reference to the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of the pattern morphology structure transferred onto the photoresist layer; Figure 2 This is a schematic diagram of adding a column of auxiliary graphics between adjacent target graphics in the target layer.

[0023] With the development of semiconductor technology and the reduction of critical dimensions, when exposure conditions deviate from the optimal values, the transfer of the pattern from the target layer to the photoresist layer can easily result in a larger top dimension and a smaller bottom dimension (e.g., Figure 1 As shown in the figure, this increases the risk of the graphic collapsing.

[0024] Currently, adding auxiliary graphics (i.e., sbars) to the target layer improves exposure resolution, thereby enhancing the stability of the pattern transferred to the photoresist layer after exposure. However, when the spacing between adjacent target graphics 10 in the target layer is small, and only a single column of auxiliary graphics 11 can be added (e.g., ... Figure 2 As shown, the improvement in the stability of the pattern transferred to the photoresist layer after exposure is often not significant. This is because the single-row auxiliary pattern is subjected to single-slit interference during exposure, and the illumination intensity of each diffraction order of the single-slit interference is low, resulting in poor improvement in the stability of the target pattern 10 after exposure and transfer to the photoresist layer.

[0025] Based on this, the present invention provides an optical proximity correction method. By adding two auxiliary patterns, namely the first auxiliary pattern and the second auxiliary pattern, between the first target pattern and the second target pattern, a double-slit diffraction effect will occur between the first auxiliary pattern and the second auxiliary pattern in the subsequent exposure process. The illumination intensity of each diffraction order in the double-slit diffraction process is significantly increased, and the position of the diffraction peak is closer to the center of the first target pattern and the second target pattern. This can greatly improve the stability of the pattern transferred to the photoresist layer and reduce the risk of pattern collapse on the photoresist layer.

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] Figure 3This is a flowchart of an optical proximity correction method according to an embodiment of the present invention, including:

[0028] Step S101: Provide a design layer, the design layer including a first design graphic and a second design graphic arranged in parallel along a first direction, the first design graphic and the second design graphic having a first spacing dimension;

[0029] Step S102: Obtain an auxiliary layer based on the design layer. The auxiliary layer includes a first auxiliary graphic and a second auxiliary graphic arranged parallel to each other along the first direction. The first auxiliary graphic and the second auxiliary graphic are located between the first design graphic and the second design graphic.

[0030] Step S103: Obtain an initial target layer based on the design layer. The initial target layer includes an initial first target graphic and an initial second target graphic corresponding to the first design graphic and the second design graphic. The initial first target graphic and the initial second target graphic have a second spacing dimension, and the first spacing dimension is greater than the second spacing dimension.

[0031] Step S104: Using the auxiliary layer as a reference, the initial target layer is corrected and a target layer is obtained. The target layer includes a first target graphic and a second target graphic corresponding to the first design graphic and the second design graphic. The first auxiliary graphic and the second auxiliary graphic are located between the first target graphic and the second target graphic. There is a third spacing dimension between the first target graphic and the second target graphic. The third spacing dimension is greater than the second spacing dimension.

[0032] The steps of the optical proximity correction method are described in detail below with reference to the accompanying drawings.

[0033] Figures 4 to 8 This is a schematic diagram of the structure of each step of the optical proximity correction method in an embodiment of the present invention.

[0034] Please refer to Figure 4 A design layer 100 is provided, the design layer 100 includes a first design graphic 101 and a second design graphic 102 arranged parallel to each other along a first direction X, and the first design graphic 101 and the second design graphic 102 have a first spacing dimension d1 between them.

[0035] In this embodiment, the first design pattern 101 and the second design pattern 102 in the design layer are ideally formed on the wafer. However, since the final pattern formed on the wafer needs to undergo exposure and pattern transfer, optical proximity effects will occur during the exposure process, and etching deviations will occur during the pattern transfer process. Therefore, the final pattern formed on the wafer will not be completely consistent with the morphology of the first design pattern 101 and the second design pattern 102. It is sufficient to ensure that the deviation between the final pattern formed on the wafer and the first design pattern 101 and the second design pattern 102 is controlled within a certain range.

[0036] Please refer to Figure 5 An auxiliary layer 200 is obtained based on the design layer 100. The auxiliary layer 200 includes a first auxiliary graphic 201 and a second auxiliary graphic 202 arranged parallel to the first direction X. The first auxiliary graphic 201 and the second auxiliary graphic 202 are located between the first design graphic 101 and the second design graphic 102.

[0037] In this embodiment, since the first design pattern 101 and the second design pattern 102 are the final patterns to be formed on the wafer, they do not need to be enlarged or deformed to offset optical proximity effects and etching deviations. Therefore, the first spacing dimension d1 between the first design pattern 101 and the second design pattern 102 is relatively large, which can accommodate two columns of auxiliary patterns, namely, the first auxiliary pattern 201 and the second auxiliary pattern 202 arranged parallel to the first direction X. The positions and spacing dimensions of the first auxiliary pattern 201 and the second auxiliary pattern 202 are first determined using the first design pattern 101 and the second design pattern 102. Subsequently, the initial first target pattern and the initial second target pattern in the initial target layer are corrected using the first auxiliary pattern 201 and the second auxiliary pattern 202 as references.

[0038] In this embodiment, the minimum spacing of the first spacing dimension d1 is the spacing between the first auxiliary graphic 201 and the second auxiliary graphic 202 generated when the design layer 100 is used as the object. That is, the spacing dimension between the first auxiliary graphic 201 and the first design graphic 101, the spacing dimension between the second auxiliary graphic 202 and the second design graphic 102, the width dimension of the first auxiliary graphic 201, the width dimension of the second auxiliary graphic 202, and the sum of the spacing dimensions of the first auxiliary graphic 201 and the second auxiliary graphic 202.

[0039] In this embodiment, the first auxiliary graphic 201 and the second auxiliary graphic 202 have a fourth spacing dimension d4.

[0040] In this embodiment, the first auxiliary graphic 201 is a rectangle; the second auxiliary graphic 202 is a rectangle.

[0041] In this embodiment, the fourth spacing dimension d3 is affected by the mask write capability. It is the minimum acceptable spacing between two adjacent sides of the first auxiliary pattern 201 and the second auxiliary pattern 202 within the mask manufacturing capability range. It is affected by different process nodes and different mask manufacturing processes. The fourth spacing dimension d4 is not a fixed value.

[0042] Please continue to refer to this. Figure 5 In this embodiment, after obtaining the auxiliary layer 200, the method further includes: detecting the auxiliary layer 200 so that the first auxiliary graphic 201 or the second auxiliary graphic 202 cannot be exposed to the photoresist layer.

[0043] In this embodiment, the method for detecting the auxiliary layer 200 to prevent the first auxiliary pattern 201 or the second auxiliary pattern 202 from being exposed to the photoresist layer includes: when the first auxiliary pattern 201 or the second auxiliary pattern 202 is detected to be exposed to the photoresist layer, the first auxiliary pattern 201 or the second auxiliary pattern 202 is scaled down. By detecting the auxiliary layer 200, the subsequent exposure of the first auxiliary pattern 201 or the second auxiliary pattern 202 to the photoresist layer is avoided, preventing the formation of corresponding redundant device structures on the wafer through subsequent patterning transfer, thereby affecting other functional device structures.

[0044] Please refer to Figure 6 An initial target layer 300 is obtained based on the design layer 100. The initial target layer 300 includes an initial first target graphic 301 and an initial second target graphic 302 corresponding to the first design graphic 101 and the second design graphic 102. The initial first target graphic 301 and the initial second target graphic 302 have a second spacing dimension d2, and the first spacing dimension d1 is greater than the second spacing dimension d2.

[0045] In this embodiment, the initial first target pattern 301 and the initial second target pattern 302 in the initial target layer 300 are ideally formed patterns on the photoresist layer. Since the final pattern formed on the photoresist layer needs to be exposed, optical proximity effect occurs during the exposure process. Therefore, the final pattern formed on the photoresist layer will not have a completely identical morphology to the initial first target pattern 301 and the initial second target pattern 302. It is sufficient to ensure that the deviation between the final pattern formed on the photoresist layer and the initial first target pattern 301 and the initial second target pattern 302 is controlled within a certain range.

[0046] As the pattern on the photoresist layer is transferred to the wafer through etching, the pattern gradually shrinks during this process due to etching deviations; that is, the pattern on the photoresist layer becomes larger than the corresponding pattern on the wafer. Therefore, by collecting etching deviation data and considering the optical proximity effect during exposure, the first design pattern 101 and the second design pattern 102 are magnified to obtain the corresponding initial first target pattern 301 and the initial second target pattern 302.

[0047] In this embodiment, the initial first target graphic 301 is a rectangle, and the initial first target graphic 301 includes a first long side 301a and a second long side 301b that are opposite to each other. The first long side 301a is adjacent to the first auxiliary graphic 201. The initial second target graphic 302 is a rectangle, and the initial second target graphic 302 includes a third long side 302a and a fourth long side 302b that are opposite to each other. The third long side 302a is adjacent to the second auxiliary graphic 202.

[0048] In this embodiment, the maximum spacing of the first spacing dimension d1 is such that when the initial target layer 300 is used as the object, the first auxiliary graphic 201 and the second auxiliary graphic 202 can be generated. That is, the spacing dimension between the first auxiliary graphic 201 and the initial first target graphic 301, the spacing dimension between the second auxiliary graphic 202 and the initial second target graphic 302, the width dimension of the first auxiliary graphic 201, the width dimension of the second auxiliary graphic 202, and the sum of the spacing dimensions of the first auxiliary graphic 201 and the second auxiliary graphic 202.

[0049] In this embodiment, since the initial first target graphic 301 and the initial second target graphic 302 are obtained by enlarging the first design graphic 101 and the second design graphic 102, the second spacing dimension d2 between the initial first target graphic 301 and the initial second target graphic 302 is smaller than the first spacing dimension d1.

[0050] In this embodiment, the second spacing dimension d2 is the first spacing dimension d1 minus the spacing between the first side 301a and the corresponding side of the first design pattern 101, and the spacing between the third side 302a and the corresponding side of the second design pattern 102.

[0051] Please refer to Figure 7 Using the auxiliary layer 200 as a reference, the initial target layer 300 is modified to obtain a target layer 400. The target layer 400 includes a first target graphic 401 and a second target graphic 402 corresponding to the first design graphic 101 and the second design graphic 102. The first auxiliary graphic 201 and the second auxiliary graphic 202 are located between the first target graphic 401 and the second target graphic 402. There is a third spacing dimension d3 between the first target graphic 401 and the second target graphic 402. The third spacing dimension d3 is greater than the second spacing dimension d2.

[0052] In this embodiment, by adding two auxiliary patterns, namely the first auxiliary pattern 201 and the second auxiliary pattern 202, between the first target pattern 401 and the second target pattern 402, a double-slit diffraction effect will occur between the first auxiliary pattern 201 and the second auxiliary pattern 202 during subsequent exposure processing. The light intensity of each diffraction order in the double-slit diffraction process is significantly increased, and the position of the diffraction peak is closer to the center of the first target pattern 401 and the second target pattern 402. This can greatly improve the stability of the pattern transferred to the photoresist layer and reduce the risk of pattern collapse on the photoresist layer.

[0053] It should be noted that in this embodiment, the first target pattern 401 is obtained by scaling down the initial first target pattern 301, and the second target pattern 402 is obtained by scaling down the initial second target pattern 302. Although the first target pattern 401 and the second target pattern 402 sacrifice some area, and the corresponding patterns formed on the wafer will also be scaled down to a certain extent, the reduction in the size of the pattern on the wafer will not affect the normal operation of the overall circuit. However, if the pattern collapses on the wafer, it will affect the operation of the overall circuit. Therefore, ensuring the stability of the pattern by reducing its size is acceptable for semiconductor manufacturing processes.

[0054] In this embodiment, the method for modifying the initial target layer 300 and obtaining the target layer 400 with reference to the auxiliary layer 200 includes: translating the first long side 301a in a direction away from the first auxiliary graphic 201 until the distance between the first long side 301a and the first auxiliary graphic 201 is greater than or equal to the mask rule size, so that the initial first target graphic 301 forms the first target graphic 401; and translating the third long side 302a in a direction away from the second auxiliary graphic 202 until the distance between the third long side 302a and the second auxiliary graphic 202 is greater than or equal to the mask rule size, so that the initial second target graphic 302 forms the second target graphic 402.

[0055] It should be noted that in this embodiment, a mask manufacturing rule check is required during the optical proximity correction process to ensure the final pattern convergence and mask fabrication accuracy. Typically, the linewidth and spacing in the mask pattern after optical proximity correction are checked according to the set mask rule constraints (MRC) (including linewidth and spacing values). When the spacing between the first long side 301a and the first auxiliary pattern 201, or the spacing between the third long side 302a and the second auxiliary pattern 202, is smaller than the mask rule constraint, errors may easily occur or the mask fabrication process may fail.

[0056] Please refer to Figure 8 After obtaining the target layer 400, optical proximity correction is performed on the target layer 400 several times to obtain a correction layer 500. The correction layer 500 includes a first correction graphic 501 and a second correction graphic 502 corresponding to the first target graphic 401 and the second target graphic 402.

[0057] In this embodiment, the optical proximity correction refers to the conventional optical proximity correction iteration based on the optical proximity correction model. By exposing the finally obtained correction layer 500, the first correction pattern 501 and the second correction pattern 502 in the correction layer are transferred to the photoresist layer, and then the pattern on the photoresist layer is transferred to the wafer through etching.

[0058] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An optical proximity correction method, characterized in that, include: A design layer is provided, the design layer including a first design graphic and a second design graphic arranged in parallel along a first direction, and a first spacing dimension between the first design graphic and the second design graphic; An auxiliary layer is obtained based on the design layer. The auxiliary layer includes a first auxiliary graphic and a second auxiliary graphic arranged parallel to the first direction. The first auxiliary graphic and the second auxiliary graphic are located between the first design graphic and the second design graphic. An initial target layer is obtained based on the design layer. The initial target layer includes an initial first target graphic and an initial second target graphic corresponding to the first design graphic and the second design graphic. The initial first target graphic and the initial second target graphic have a second spacing dimension, and the first spacing dimension is greater than the second spacing dimension. Using the auxiliary layer as a reference, the initial target layer is corrected and a target layer is obtained. The target layer includes a first target graphic and a second target graphic corresponding to the first design graphic and the second design graphic. The first auxiliary graphic and the second auxiliary graphic are located between the first target graphic and the second target graphic. There is a third spacing dimension between the first target graphic and the second target graphic. The third spacing dimension is greater than the second spacing dimension.

2. The optical proximity correction method as described in claim 1, characterized in that, The initial first target shape is a rectangle, and the initial first target shape includes a first long side and a second long side that are opposite to each other. The first long side is adjacent to the first auxiliary shape. The initial second target shape is a rectangle, and the initial second target shape includes a third long side and a fourth long side that are opposite to each other. The third long side is adjacent to the second auxiliary shape.

3. The optical proximity correction method as described in claim 2, characterized in that, The method for correcting the initial target layer and obtaining the target layer with reference to the auxiliary layer includes: translating the first long side away from the first auxiliary graphic until the distance between the first long side and the first auxiliary graphic is greater than or equal to the mask rule size, so that the initial first target graphic forms the first target graphic; and translating the third long side away from the second auxiliary graphic until the distance between the third long side and the second auxiliary graphic is greater than or equal to the mask rule size, so that the initial second target graphic forms the second target graphic.

4. The optical proximity correction method as described in claim 1, characterized in that, The first auxiliary graphic is a rectangle; the second auxiliary graphic is a rectangle.

5. The optical proximity correction method as described in claim 1, characterized in that, After obtaining the auxiliary layer, the method further includes: detecting the auxiliary layer to prevent the first auxiliary graphic or the second auxiliary graphic from being exposed to the photoresist layer.

6. The optical proximity correction method as described in claim 5, characterized in that, The method for detecting the auxiliary layer to prevent the first auxiliary graphic or the second auxiliary graphic from being exposed to the photoresist layer includes: when the first auxiliary graphic or the second auxiliary graphic is detected to be exposed to the photoresist layer, the first auxiliary graphic or the second auxiliary graphic is reduced in size.

7. The optical proximity correction method as described in claim 1, characterized in that, After obtaining the target layer, the method further includes: performing optical proximity correction on the target layer several times to obtain a correction layer, wherein the correction layer includes a first correction image and a second correction image corresponding to the first target image and the second target image.

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