KR100924335B1 - Method for correcting optical proximity using multi-dose simulation - Google Patents

Abstract

After designing the target pattern layout to be transferred onto the wafer, performing optical proximity correction (OPC), and extracting the first simulation contour of the OPC layout using a simulation model, the pattern line width with the target pattern layout (CD) Extract the difference data. After extracting a dose-offset value of exposure energy to compensate for the CD difference, the simulated model is calibrated by applying the extracted dose offset value. After extracting the second simulation contour of the optical proximity calibrated layout using the calibrated model, the optical proximity calibration method for verifying the optical proximity correction by comparing the second simulation contour with the target pattern layout is proposed.

OPC, Simulation Model, Calibration, Dose

Description

Method for correcting optical proximity using multi-dose simulation

1 is a flowchart schematically illustrating an optical proximity correction (OPC) method according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an optical proximity correction layout according to an embodiment of the present invention.

3 is a diagram illustrating a first simulation contour of the optical proximity calibrated layout according to an embodiment of the present invention.

4 is a graph showing a correlation between a pattern line width (CD) difference and an exposure energy dose offset value according to an embodiment of the present invention.

5 is a view showing a second simulation contour of the optically corrected layout according to the embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to an optical proximity correction (OPC) method for a pattern layout when fabricating a photo mask.

 As the degree of integration of semiconductor devices increases, it is required to implement finer patterns in photolithography. However, as the pattern becomes finer, an optical proximity effect due to the influence between neighboring patterns is involved during the exposure process. In order to overcome this problem, a method of suppressing OPE generation by correcting a pattern layout designed to be formed on a photomask for transferring a pattern, for example, optical proximity correction (OPC), has been performed.

The optical proximity correction is a process of predicting a shape in which a target pattern layout is transferred onto a wafer using a simulation model, and correcting the target pattern layout so that the transferred pattern layout matches the target pattern layout. . At this time, in order to perform a more sophisticated OPC, information on the exposure conditions used in the exposure process for transferring the pattern onto the wafer, stack information stacked on the wafer, information on the photoresist (PR) to be used, etc. The process of adding to the model and calibrating the model is involved in the OPC process.

When evaluating the modeling result of simulating OPC layout using this calibrated model, there is a difference between the actual pattern line width (CD) and the pattern line width simulated by modeling on the actual wafer according to the pattern shape. Can be generated. This CD difference is evaluated as root mean square (RMS), and at most 5 nm difference is required in actual OPC process. Therefore, in order to predict a more accurate pattern layout through model simulation and perform more sophisticated OPC, the pattern line width of the simulated layout result and the pattern line width to be implemented on the wafer, that is, the pattern line width of the target pattern layout are more equally matched. There is a need for a method of calibrating or calibrating a model to be evaluated.

The technical problem to be solved by the present invention is to provide an optical proximity correction method that can calibrate a simulation model more precisely and obtain more accurate correction results.

One aspect of the present invention for the above technical problem is, by using a target pattern layout design step to be transferred onto a wafer, optical proximity correction (OPC) for the layout, using a simulation model of the wafer transfer process Extracting a first simulation contour of the optically corrected layout, comparing the first simulation contour with the target pattern layout, extracting pattern line width (CD) difference data, and compensating for the pattern line width difference Extracting a dose-offset value of exposure energy to be applied, calibrating the simulation model by applying the extracted dose offset value, and using the calibrated model, the optically calibrated layout Extracting a second simulation contour of the second simulation contour and the neck; Compared to layout pattern presents the optical proximity correction method comprising the step of verifying the optical proximity correction.

The extracting of the first simulation contour may be performed after initial calibration of the simulation model by inputting one exposure energy dose value to the simulation model.

Extracting the dose-offset value may include setting an area on the layout in which the pattern line width difference is equal to a simulation window area, and compensating for the corresponding pattern line width difference for each window area. Imparting dose offset values to each.

The simulation window area may be divided and set differently for each of the pattern shapes on the layout or for each extension direction of the pattern.

According to the present invention, it is possible to calibrate a simulation model more precisely, and thus it is possible to provide a near-field correction method that can obtain a more accurate correction result.

An embodiment of the present invention provides a simulation method for optical proximity correction (OPC). By simulating the layout using the model under conditions that irradiate different exposure energies for each set unit region or pattern on the pattern layout, the simulation model can be calibrated to fit the layout shape that all the patterns are to achieve. When information is input to the simulation model to impart a constant exposure energy condition to all layout regions, the layout may be simulated with large or small patterns for the target pattern shape to be achieved. A method of OPC layout is proposed by separately separating and setting pattern areas having a size that deviates from the target pattern, extracting different exposure energy conditions as calibration parameters for a set part, and inputting the same into a model to calibrate the layout. do. In other words, we propose an OPC method using multi-dose simulation.

1 is a flowchart schematically illustrating an optical proximity correction (OPC) method according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an optical proximity correction layout according to an embodiment of the present invention. 3 is a diagram illustrating a first simulation contour of the optical proximity calibrated layout according to an embodiment of the present invention. 4 is a graph showing a correlation between a pattern line width (CD) difference and an exposure energy dose offset value according to an embodiment of the present invention. 5 is a view showing a second simulation contour of the optically corrected layout according to the embodiment of the present invention.

Referring to FIG. 1, an OPC method according to an embodiment of the present invention designs a layout of target pattern 201 to be transferred onto an actual wafer, as shown in FIG. 2 ( 101 of FIG. 1). The layout of the target pattern (201 of FIG. 2) may be a layout for a line pattern extending in a predetermined direction.

Optical proximity correction (OPC) is performed on the layout 201 of the target pattern to obtain an OPC layout (203 in FIG. 2) (102 in FIG. 1). This OPC may be performed by using an initial calibrated model and an initial calibrated simulation model prepared for predicting transfer onto a wafer of a pattern layout. In this case, the initial calibration of the model may be performed using modeling variables including information on exposure conditions to be applied to the exposure process for pattern transfer, stack information of the device, photoresist type and characteristics, and the like. At this time, the model is initially calibrated by applying the same constant exposure energy dose to the entire layout area.

The initial calibrated model is used to simulate the OPC layout 203 to extract the first simulation contours 303, 305, as shown in FIG. 3 (103 in FIG. 1). The first simulation contour 303 for the photoresist pattern before the etching process and the first simulation contour 305 of the wafer pattern formed according to the etching after the etching process may be obtained. In this case, a line width difference d may be observed between the layout 301 of the target pattern, which is regarded as the layout of the pattern implemented on the actual wafer, and the first simulation contour 305 of the wafer pattern. Substantially the initial calibrated model must be calibrated to accurately simulate the transfer process, but this line width difference d can be detected by inaccuracies in the measured data or the calculated calibration parameters for calibration. The line width difference data is extracted through the image comparison (104 of FIG. 1). The line width difference data may be collected for each region where the pattern is located.

By using the extracted line width difference data, patterns or regions are classified according to the line width differences, and the classified patterns or regions are set as a simulation window 307 (105 in FIG. 1). The simulation window 307 is set as an area to perform subsequent calibration to compensate for CD difference occurrence. Accordingly, the simulation window 307 is set by classifying the patterns or regions in which the equivalent line width difference is generated.

For example, in an exposure process employing an asymmetric aperture such as a dipole illumination system, the line width may vary depending on the direction of extension of the pattern depending on the orientation of the illumination system. When the dipole illumination system has directionality or asymmetry in the vertical (or horizontal) direction, the simulation window 307 may be set to an area including a pattern extending in the horizontal direction and an area including a pattern extending in the vertical direction, respectively. have.

For each simulation window 307, the CD difference between the target pattern layout 301 of FIG. 3 and the first simulation contour 305 is calculated. Then, the dose offset value of the exposure energy to compensate for this CD difference is extracted using the correlation graph of the line width difference and the dose offset value measured as shown in FIG. 4 (106 in FIG. 1). For example, if the CD difference is 10 nm larger than the first simulation contour 305 relative to the target pattern layout 301, the dose offset value of + 6%, for example, is extracted for linewidth compensation by the data presented in the graph of FIG. Can be.

The extracted dose offset value is assigned to each simulation window 307 to subsequently calibrate the simulation model (127 of FIG. 1). Subsequently, a second simulation is performed on the OPC layout (203 in FIG. 2) using the subsequent calibrated model to obtain second simulation contours 503 and 505 as shown in FIG. A second simulation contour 503 for the photoresist pattern before performing the etching process and a second simulation contour 505 for the wafer pattern formed according to the etching after performing the etching process may be obtained. The OPC result is verified by comparing the second simulation contour 505 with the target pattern layout 501 (108 in FIG. 1).

According to the results presented in FIG. 5, the second simulation contour 505 and the target pattern layout 501 are aligned very accurately. Upon obtaining this correctly aligned verification result, photomask fabrication is performed for the OPC layout 203 (109 in FIG. 1). Since the OPC results reflect the dose offset of various values according to the region, the data of the dose offset value applied to the region is reflected in the photomask fabrication or subsequent exposure process. If the verification fails to obtain the correct alignment, the OPC process may be performed again.

This OPC process can give more precise OPC results by giving various dose offsets for exposure energy conditions. That is, it is possible to prevent the degradation of the OPC accuracy due to the CD difference or the considerably large RMS accompanied by the simulation modeling for the OPC. In addition, it is possible to diversify the performance of the engine that is basically installed in the simulation model. For example, a simulation may be performed to predict the result of the introduction of the auxiliary shape by matching the results on the wafer with sub-resolution features, such as an assist feature, to a dose offset value. have.

According to the present invention described above, it is possible to suppress the effect due to the difference in line width or the significantly larger RMS between the simulation result and the actual pattern, thereby improving the accuracy of optical proximity correction. Accordingly, more accurate optical proximity correction can be realized, and a more precise wafer pattern can be formed.

As mentioned above, although this invention was demonstrated in detail through the specific Example, this invention is not limited to this, It is clear that the deformation | transformation and improvement are possible by the person of ordinary skill in the art within the technical idea of this invention.

Claims (4)

Designing a target pattern layout to be transferred onto the wafer; Optical proximity correction (OPC) on the layout; Extracting a first simulation contour of the optically corrected layout using a simulation model; Extracting pattern line width (CD) difference data by comparing the first simulation contour with the target pattern layout; Extracting a dose-offset value of exposure energy to compensate for the pattern line width difference; Calibrating the simulation model by applying the extracted dose offset value; Extracting a second simulated contour of the optically corrected layout using the calibrated simulation model; And And comparing the second simulation contour with the target pattern layout to verify the optical proximity correction. The method of claim 1, Extracting the first simulation contour The optical proximity correction method is performed after initial calibration of the simulation model by inputting one exposure energy dose value to the simulation model. The method of claim 1, Extracting the dose-offset value Setting an area on the layout in which the pattern line width difference is equal to a simulation window area; And And applying each of the dose offset values to compensate for the difference in the pattern line width for each window region. The method of claim 3, The simulation window area is The optical proximity correction method is divided into different patterns for each of the pattern shape on the layout or the extension direction of the pattern.

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