Method for establishing an OPC model

Abstract

The present invention provides a method for establishing an OPC model, including: collecting focal length energy matrix data; establishing an optical model based on the focal length energy matrix data; using the optical model to simulate a photomask to obtain a simulated ADI critical dimension exposed on a chip, classifying the simulated ADI critical dimension into a first grade, a second grade, and a third grade, and recording the positions of the photomasks corresponding to the first grade, the second grade, and the third grade as a first position, a second position, and a third position respectively; calculating a lithography process window according to the optical model and exposing the chip under the lithography process window; measuring the actual ADI critical dimension of the graphic lines exposed on the chip corresponding to the first position; and establishing an OPC model based on the actual ADI critical dimension. The range of collecting ADI critical dimension measurements is reduced, the number of measured ADI critical dimensions is reduced, the accuracy of the established OPC model is improved, and the production efficiency can also be improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular, to a method for establishing an OPC model. Background Art

[0002] In semiconductor manufacturing, as the design size continues to shrink, the diffraction effect of light becomes more and more obvious. As a result, the optical image of the designed pattern degrades, and the actual pattern formed on the silicon wafer after lithography becomes different from the designed pattern. This phenomenon is called OPE (Optical Proximity Effect).

[0003] To correct the OPE phenomenon, OPC (Optical Proximity Correction) is generated. The core idea of OPC is to establish an OPC model based on the consideration of offsetting the OPE phenomenon, and design the photomask pattern according to the OPC model. Although the photolithography pattern after lithography has the OPC phenomenon relative to the photomask pattern, since the offset of this phenomenon has been considered when designing the photomask pattern according to the OPC model, the photolithography pattern after lithography is close to the target pattern that the user actually hopes to obtain.

[0004] In the prior art, in establishing the OPC model, since the light source or the photomask is a new variable factor, the CD value of the chip corresponding to the photomask due to the optical proximity effect cannot be obtained. Therefore, it is necessary to collect sample data in advance for establishing the OPC model to establish a database. The database can be displayed in the form of a table. The left vertical axis is the critical dimension width of the photomask line diameter (MaskCD Width), and the upper horizontal axis is the photomask line diameter gap (Mask CD Space). Corresponding to the Mask CD Width and MaskCD Space of the photomask, a set of ADI critical dimension Width (pattern line width) of the pattern lines of the chip after exposure and the ADI critical dimension Space (pattern line diameter gap) of the pattern lines of the chip after exposure will be obtained after the chip is exposed. At the beginning of establishing the OPC model, the values of the ADI critical dimension Width and the ADI critical dimension Space must be measured from the actual quantity on the chip. Before measuring the actual value, the process design rules are required to estimate the exposure range corresponding to the photomask on the chip, so as to determine the measurement area range. However, the measurement area range is often set too large, resulting in receiving some unhealthy data (ADI critical dimension), which leads to a reduction in the measurement level or interference with the establishment of the subsequent OPC model. In addition, the measurement of redundant data often needs to occupy the machines on the production line, thus affecting the production efficiency of the chips. Summary of the Invention

[0005] The object of the present invention is to provide a method for establishing an OPC model, which can reduce the measurement range of the ADI critical dimension, reduce the number of measured ADI critical dimensions, improve the accuracy of the established OPC model, and also improve the production efficiency.

[0006] To achieve the above object, the present invention provides a method for establishing an OPC model, including:

[0007] Collecting the focal length energy matrix data during chip exposure;

[0008] Establishing an optical model according to the focal length energy matrix data;

[0009] Using the optical model to simulate the photomask, obtaining the simulated ADI critical dimension exposed on the chip, classifying the simulated ADI critical dimension into a first level, a second level and a third level, and recording the positions of the photomask corresponding to the first level, the second level and the third level as a first position, a second position and a third position respectively;

[0010] Calculating the lithography process window according to the optical model, and exposing the chip under the lithography process window;

[0011] Measuring the actual ADI critical dimension of the pattern line exposed on the chip corresponding to the first position; and

[0012] Establishing an OPC model according to the actual ADI critical dimension.

[0013] Optionally, in the method for establishing an OPC model, the focal length energy matrix data includes: pattern pitch, photomask pattern size, chip exposure pattern size and process window.

[0014] Optionally, in the method for establishing an OPC model, the focal length energy matrix data selects the data of 50 to 100 sampling points on the chip.

[0015] Optionally, in the method for establishing an OPC model, when using the optical model to simulate the photomask, the number of simulated samples is 1000 to 2000.

[0016] Optionally, in the method for establishing an OPC model, the method for classifying the simulated ADI critical dimension into a first level, a second level and a third level includes:

[0017] Deriving the relationship between the optimal exposure focus and the imaging distance of the image under the photomask according to the optical model;

[0018] Obtaining the normalized image logarithmic slope of the relationship; and

[0019] If the normalized image logarithmic slope is greater than the first set value and less than the second set value, the corresponding simulated ADI critical dimension is taken as the first level; if the normalized image logarithmic slope is greater than the second set value, the corresponding simulated ADI critical dimension is taken as the second level; if the normalized image logarithmic slope is less than the first set value, the corresponding simulated ADI critical dimension is taken as the third level.

[0020] Optionally, in the method for establishing the OPC model, the priority order for measuring the actual ADI critical dimension is the actual ADI critical dimension of the graphic line exposed at the first position on the chip, the actual ADI critical dimension of the graphic line exposed at the second position on the chip, and the actual ADI critical dimension of the graphic line exposed at the third position on the chip.

[0021] Optionally, in the method for establishing the OPC model, it further includes: selectively measuring the actual ADI critical dimension of the graphic line exposed at the second position on the chip. If the actual ADI critical dimension of the graphic line exposed at the second position on the chip has been measured, an OPC model is established based on the measured actual ADI critical dimension at the first position and the actual ADI critical dimension at the second position.

[0022] Optionally, in the method for establishing the OPC model, it further includes: selectively measuring the actual ADI critical dimensions of the graphic lines exposed at the second position and the third position on the chip. If the actual ADI critical dimensions of the graphic lines exposed at the second position and / or the third position on the chip have been measured, an OPC model is established based on the measured actual ADI critical dimension at the first position, the actual ADI critical dimension at the second position, and the actual ADI critical dimension at the third position.

[0023] Optionally, in the method for establishing the OPC model, the simulated ADI critical dimension of the second level is used as the control data of the OPC model; the simulated ADI critical dimension of the third level is used as the verification data of the OPC model.

[0024] Optionally, in the method for establishing the OPC model, the ADI critical dimension includes the graphic line width and the graphic line diameter gap.

[0025] In the method for establishing an OPC model provided by the present invention, before collecting the actual ADI critical dimension for establishing the OPC model, an optical model is established based on the focal length energy matrix data, and simulation is performed according to the optical model to obtain the simulated ADI critical dimension. The simulated ADI critical dimension is divided into three levels, and the first position, the second position, and the third position of the photomask corresponding to the simulated ADI critical dimension of the three levels are found respectively. The chip is exposed, and the actual ADI critical dimension on the chip corresponding to the first position is found to establish the OPC model. Compared with the prior art, the range of collecting the ADI critical dimension measurement is reduced, the number of measured ADI critical dimensions is reduced, the accuracy of the established OPC model is improved, and the production efficiency can also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flowchart of the method for establishing an OPC model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The specific embodiments of the present invention will be described in more detail below with reference to the schematic diagrams. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are all in a very simplified form and use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the objectives of the embodiments of the present invention.

[0028] In the following text, terms such as "first" and "second" are used to distinguish between similar elements and are not necessarily used to describe a specific order or time sequence. It is understood that, under appropriate circumstances, these terms used in this way can be replaced. Similarly, if the method described in this article includes a series of steps, and the order of these steps presented in this article is not necessarily the only order in which these steps can be executed, and some of the described steps can be omitted and / or some other steps not described in this article can be added to this method.

[0029] Please refer to Figure 1 , the present invention provides a method for establishing an OPC model, including:

[0030] S11: Collect the focal length energy matrix data when the chip is exposed;

[0031] S12: Establish an optical model based on the focal length energy matrix data;

[0032] S13: Use the optical model to simulate the photomask, obtain the simulated ADI critical dimension exposed on the chip, divide the simulated ADI critical dimension into a first level, a second level, and a third level, and record the positions of the photomask corresponding to the first level, the second level, and the third level as the first position, the second position, and the third position respectively;

[0033] S14: Calculate the lithography process window according to the optical model, and expose the chip under the lithography process window;

[0034] S15: Measure the actual ADI critical dimension of the pattern line exposed on the chip corresponding to the first position; and

[0035] S16: Establish an OPC model based on the actual ADI critical dimension.

[0036] Preferably, the focus energy matrix data includes: pattern pitch, mask pattern dimension mask CD, chip exposure pattern dimension ADI, and process window DOF. The focus energy matrix data can be obtained from previous historical data.

[0037] Preferably, the focus energy matrix data selects the data of 50 to 100 sampling points on the chip. The optical model is used to simulate the photomask, and the number of simulated samples is 1000 to 2000. The number of samples for collecting the focus energy matrix data accounts for about 5%-6% of the number of simulations of the photomask using the optical model.

[0038] Preferably, the lithography process window is calculated according to some physical properties of the optical model, which will not be elaborated here. The simulated ADI critical dimension is divided into the first level, the second level, and the third level according to the value of the normalized image log slope. The optical model derives the relationship between the best exposure focus and the imaging distance of the image under the photomask. The relationship is a polynomial, and its normalized image log slope NILS (Normalized Image Log Slope) can be used as an index for dividing the simulated ADI critical dimension into the first level, the second level, and the third level. If the normalized image log slope NILS is greater than the first set value and less than the second set value, the corresponding simulated ADI critical dimension is taken as the first level. If the normalized image log slope NILS is greater than the second set value, the corresponding simulated ADI critical dimension is taken as the second level. If the normalized image log slope NILS is less than the first set value, the corresponding simulated ADI critical dimension is taken as the third level. The value of the first set value is less than the value of the second set value, and both the first set value and the second set value can be set manually.

[0039] Preferably, the priority order for measuring the actual ADI critical dimension is the actual ADI critical dimension of the pattern line exposed on the chip corresponding to the first position, the actual ADI critical dimension of the pattern line exposed on the chip corresponding to the second position, and the actual ADI critical dimension of the pattern line exposed on the chip corresponding to the third position. In an embodiment of the present invention, it further includes: selectively measuring the actual ADI critical dimension of the pattern line exposed on the chip corresponding to the second position. If the actual ADI critical dimension of the pattern line exposed on the chip corresponding to the second position is measured, an OPC model is established based on the measured actual ADI critical dimension of the first position and the actual ADI critical dimension of the second position. In another embodiment of the present invention, it further includes: selectively measuring the actual ADI critical dimensions of the pattern lines exposed on the chip corresponding to the second position and the third position. If the actual ADI critical dimensions of the pattern lines exposed on the chip corresponding to the second position and / or the third position are measured, an OPC model is established based on the measured actual ADI critical dimension of the first position, the actual ADI critical dimension of the second position, and the actual ADI critical dimension of the third position. That is to say, if time permits, it is also possible to measure the line width and the line diameter gap of the pattern in the range corresponding to the second position on the chip after exposure by the photomask. Similarly, if there is more time, it is possible to continue measuring the line width and the line diameter gap of the pattern in the range corresponding to the third position on the chip after exposure by the photomask. The data measured will all be used to establish the OPC model, and the method for establishing the OPC model will not be elaborated here.

[0040] Preferably, the simulated ADI critical dimension of the second level is used as the control data of the OPC model; the simulated ADI critical dimension of the third level is used as the verification data of the OPC model.

[0041] Preferably, the ADI critical dimension includes the pattern line width and the pattern line diameter gap. The pattern on the photomask has MaskCD Width and Mask CD Space. Therefore, after using the photomask to expose the chip, the pattern on the exposed chip also has a line width and a line diameter gap. So, the simulated ADI critical dimension includes the simulated pattern line width and the simulated pattern line diameter gap, and the actual ADI critical dimension includes the actual pattern line width and the actual pattern line diameter gap.

[0042] In summary, in the method for establishing an OPC model provided by the embodiments of the present invention, before collecting the actual ADI critical dimension for establishing the OPC model, an optical model is established according to the focal length energy matrix data, and simulation is performed according to the optical model to obtain the simulated ADI critical dimension. The simulated ADI critical dimension is divided into three levels, and the first position, the second position, and the third position of the photomask corresponding to the simulated ADI critical dimensions of the three levels are found respectively. The chip is exposed, and the actual ADI critical dimension on the chip corresponding to the first position is found to establish the OPC model. Compared with the prior art, the range of collecting the ADI critical dimension measurement is reduced, the number of measured ADI critical dimensions is reduced, the accuracy of the established OPC model is improved, and the production efficiency can also be improved.

[0043] The above are only the preferred embodiments of the present invention and do not impose any limitation on the present invention. Any person skilled in the art within the technical field of the present invention, without departing from the scope of the technical solution of the present invention, makes any form of equivalent substitution or modification and other changes to the technical solution and technical content disclosed by the present invention, which are all within the content of the technical solution of the present invention and still fall within the protection scope of the present invention.

Claims

1. A method for establishing an OPC model, characterized in that Including: Collecting the focal length energy matrix data during chip exposure; Establishing an optical model based on the focal length energy matrix data; Using the optical model to simulate the photomask, obtaining the simulated ADI critical dimension exposed on the chip, classifying the simulated ADI critical dimension into a first grade, a second grade, and a third grade, and recording the positions of the photomasks corresponding to the first grade, the second grade, and the third grade as a first position, a second position, and a third position respectively; Calculating the lithography process window according to the optical model and exposing the chip under the lithography process window; Measuring the actual ADI critical dimension of the graphic line exposed on the chip corresponding to the first position; And Establishing an OPC model based on the actual ADI critical dimension; The method for classifying the simulated ADI critical dimension into a first grade, a second grade, and a third grade includes: Deriving the relationship between the optimal exposure focus and the imaging distance of the image under the photomask according to the optical model; Obtaining the normalized image log slope of the relationship; and If the normalized image log slope is greater than a first set value and less than a second set value, taking the corresponding simulated ADI critical dimension as the first grade; if the normalized image log slope is greater than the second set value, taking the corresponding simulated ADI critical dimension as the second grade; if the normalized image log slope is less than the first set value, taking the corresponding simulated ADI critical dimension as the third grade.

2. The method for establishing an OPC model according to claim 1, characterized in that The focal length energy matrix data includes: graphic pitch, photomask graphic size, chip exposure graphic size, and process window.

3. The method for establishing an OPC model according to claim 1, wherein, The focal length energy matrix data selects the data of 50 to 100 sampling points on the chip.

4. The method for establishing an OPC model according to claim 1, wherein, Using the optical model to simulate the photomask, and the number of simulated samples is 1000 to 2000.

5. The method for establishing an OPC model according to claim 1, characterized in that, The priority order for measuring the actual ADI critical dimension is the actual ADI critical dimension of the graphic line exposed on the chip corresponding to the first position, the actual ADI critical dimension of the graphic line exposed on the chip corresponding to the second position, and the actual ADI critical dimension of the graphic line exposed on the chip corresponding to the third position.

6. The method for establishing an OPC model according to claim 5, wherein, Also including: Selectively measuring the actual ADI critical dimension of the graphic line exposed on the chip corresponding to the second position. If the actual ADI critical dimension of the graphic line exposed on the chip corresponding to the second position is measured, an OPC model is established according to the measured actual ADI critical dimension of the first position and the actual ADI critical dimension of the second position.

7. The method for establishing an OPC model according to claim 6, characterized in that, Also including: Selectively measuring the actual ADI critical dimension of the graphic line exposed on the chip corresponding to the second position and the third position. If the actual ADI critical dimension of the graphic line exposed on the chip corresponding to the second position and / or the third position is measured, an OPC model is established according to the measured actual ADI critical dimension of the first position, the actual ADI critical dimension of the second position, and the actual ADI critical dimension of the third position.

8. The method for establishing an OPC model according to claim 1, wherein The simulated ADI critical dimension of the second grade is used as the control data of the OPC model; the simulated ADI critical dimension of the third grade is used as the verification data of the OPC model.

9. The method for establishing an OPC model according to claim 1, wherein The ADI critical dimension includes the graphic line width and the graphic line diameter gap.

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