JP2007115891A - Exposure amount correction method and electron beam exposure apparatus - Google Patents

Abstract

An exposure amount map for proximity effect correction and fogging effect correction in an exposure apparatus using an electron beam is to improve the accuracy of the exposure amount map without increasing the data size.
For an area including a drawing target area, first, an area value is obtained in submesh units, and then the area density is added as an area value in mesh units according to a distribution function such as a weighting coefficient or a Gaussian filter. To do. Further, an area density map is obtained from the area value from the mesh area. An exposure amount map is obtained by using the area density map.
[Selection] Figure 1

Description

  The present invention relates to an exposure correction method and an electron beam exposure apparatus that divide a drawing region irradiated with an electron beam into small meshes, and perform proximity effect correction including a fogging effect based on the drawing information of the mesh, and in particular, an electron beam exposure apparatus. The present invention relates to a method for dividing an area including a drawing target area for an exposure apparatus into mesh-like areas and obtaining an exposure amount map using information on each area.

  A major problem with the electron beam exposure apparatus is accuracy improvement. One of the phenomena affecting the accuracy is the proximity effect. This proximity effect is an error caused by the density of the drawing pattern.

  For example, with respect to the entire area of the object to be drawn, a phenomenon in which the line width is narrow in an isolated pattern with a wide pattern-to-pattern spacing, the area called a solid pattern is wide, and the pattern with a high density is fattened. It is.

  In recent years, the solution of the above problem has become important due to the necessity of miniaturization of the line width called the design rule of the pattern drawn on the drawing object.

  In order to solve the problem that such a pattern is drawn differently from the design value, proximity is obtained using an area density map or an exposure amount map described in Japanese Patent Laid-Open No. 10-229047 (Patent Document 1). There is an exposure amount determination method for effect correction.

  This is because assuming a rectangular mesh of a certain size, the area density of the pattern is obtained for each mesh, and the area density map representing the change in the area density of the entire drawing area is called the area density map. This is a method of drawing a pattern by determining an exposure amount according to the size.

  For example, since the area density is small in the case of the above-described isolated pattern, the exposure amount is increased. On the other hand, the exposure amount is decreased in a pattern having a high area density. In this way, drawing is performed by calculating the actual exposure amount based on the data of the area density map.

  However, in practice, it is necessary to perform processing such as smoothing processing or higher-order approximation processing on the area density map obtained here. The role of proximity effect correction is to correct the backscattering, which is the spread of the electron beam in the resist of the wafer due to the shot, and this smoothing is a means for simulating backscattering. Because there is.

  Generally, as shown in the above-mentioned document, backscattering can be approximated to a Gaussian distribution, so that it can be simulated by adding a filter such as a Gaussian filter.

  Further, considering the change in pattern density in the range of the backscattering diameter described in JP 2000-323385 A (Patent Document 2), the influence of not only the backscattering energy but also the forward scattering energy is considered. Perform high-order approximation. Here, an exposure map is obtained.

  Further, the main exposure amount map is created by the proximity computer (4) in FIG. 2, and the actual exposure amount map is transferred to the proximity circuit (7) in order to calculate the actual exposure amount using the main exposure amount map. There is a need.

  In addition to the proximity effect, a fogging effect can be cited as a cause of deteriorating the drawing accuracy. The fogging effect (fogging effect in English translation) is a phenomenon that occurs mainly when the reflected electrons of the beam irradiated to the object to be drawn are reflected on the deflector of the apparatus and irradiated again on the mask, and similar to the proximity effect. This is an error caused by the density of the drawing pattern.

  A single point of irradiation affects a range of about 60 mm on one side, and the fogging effect affects a wider range than the proximity effect.

  As with the proximity effect correction, the method for correcting the fog effect uses an area density map representing the change in the area density of the entire drawing area. It is necessary to obtain the exposure amount map and transfer it to the proximity circuit.

  In the case of the above conventional method, it is necessary to reduce the mesh size in order to increase the accuracy of the exposure amount map. However, in this case, if the size of the mesh size is reduced, the data size of the exposure amount map becomes enormous by the square, and there is a problem that it takes time to process and transfer this drawing information.

  On the other hand, in the case of the above conventional method, it is necessary to increase the mesh size in order to shorten the processing time for processing and transferring mesh drawing information in the same environment, and the accuracy of the exposure map deteriorates. There is a problem to do.

Japanese Patent Laid-Open No. 10-229047 JP 2000-323385 A

  The present invention has been made in view of the above points, and an object of the present invention is to correct a fogging effect and / or a proximity effect without increasing processing time related to processing and transfer of mesh drawing information. The purpose is to increase the accuracy of correction and obtain a highly accurate exposure amount map without increasing the processing time.

  The present invention relates to an exposure correction method in which a drawing area irradiated with an electron beam is divided into small area meshes, and fogging effect correction and / or proximity effect correction is performed based on the drawing information of the mesh. The sub-mesh is divided, drawing information is obtained in units of sub-mesh, and the sub-mesh drawing information is weighted and added to synthesize the image information in units of meshes.

  As means for synthesizing this sub-mesh drawing information with drawing information in units of meshes, weights according to various distribution functions including a Gaussian distribution may be attached. Further, the sub-mesh may not be aligned on the grid but may be randomly arranged.

  However, as the drawing information of the sub-mesh, all the drawing information of the drawing target pattern is included, and the sub-mesh may not be included twice or included twice. There is a means for knowing that it is included twice, and the drawing information of one of them is eliminated.

  According to the present invention, it is possible to increase the accuracy of fogging effect correction and / or proximity effect correction without increasing the processing time for processing and transferring mesh drawing information, and to increase the exposure time of a highly accurate exposure amount map. There is to ask for.

  In the following, proximity effect correction and fogging effect correction will be described based on an embodiment of an electron beam drawing apparatus.

  FIG. 2 is a schematic diagram of an electron beam drawing apparatus for performing proximity effect correction and fogging effect correction according to the present invention.

  Drawing data is divided into drawing unit areas of the electron beam drawing apparatus by the drawing data calculator 3 shown in FIG.

  In the restoration decomposition circuit 6, the data divided into the drawing unit areas are further decomposed for each shot of the electron beam 12.

  On the other hand, each of the proximity computer 4 and the fogging computer 5 creates an exposure amount map for correcting the proximity effect and an exposure amount map for correcting the fogging effect by the method described later. The proximity computer 4 and the fogging computer 5 have means and functions for obtaining an exposure correction map, but the means and functions can be provided in a proximity circuit described later.

  Further, the proximity circuit 7 receives data obtained by decomposing the exposure amount correction map for correcting the proximity effect and the exposure amount correction map for correcting the fog effect for each shot.

  By the way, the exposure amount correction map for correcting the proximity effect and the exposure amount correction map for correcting the fogging effect are divided on a small mesh in the region 16 including the drawing target region as shown in FIG. ing.

  Therefore, in the proximity circuit 7, as shown in FIG. 3, the figure 17 decomposed for each shot is associated with which mesh of each correction data and the correction value 18 surrounding the figure decomposed for each shot. By interpolating, the correction value for the target graphic can be obtained.

  From the correction value obtained here, the exposure amount magnification of the figure for each target shot can be obtained. Next, the data decomposed for each shot and the exposure amount magnification are input to the tracking circuit 8, where the exposure time of the figure for each shot is determined.

  Thereafter, the data and exposure time decomposed for each shot are input to the DAC circuit 9, converted into an analog signal, and further input to the electron beam drawing apparatus main body 10. In the electron beam drawing apparatus body 10, a figure for each shot is deflected from the electron beam gun 11 by the deflector 13 to the electron beam 12, and irradiated to the desired position of the mask 15 on the stage 14 for the required exposure time. The

  Here, in the present embodiment, the reconstruction decomposition circuit 6 to the tracking circuit 8 are described as hardware, but this can also be realized as software. The processing flow in this case is shown in FIG.

  In 41 of FIG. 4, the data divided into the drawing unit areas are created as graphic data decomposed for each shot. In FIG. 4, for each figure decomposed for each shot, the figure decomposed for each shot is surrounded by the exposure amount map for correcting the proximity effect and the exposure amount map for correcting the fogging effect. By interpolating an exposure amount map, an exposure amount correction value for each figure is obtained, and an exposure amount magnification for each figure is obtained from this value.

  Next, at 43 in FIG. 4, the exposure time of the figure for each target shot is determined from the exposure amount magnification obtained in 42 of FIG.

  Here, an example for calculating the data for correcting the proximity effect and the data for correcting the fog effect in the computer 4 for the proximity and the computer 5 for the fog based on the embodiment of the present invention will be described below. explain.

  In 51 of FIG. 5, the entire region 16 including the drawing target region including the drawing data A19, the drawing data B20, and the drawing data C21 shown in FIG. 6 is divided into submesh 1 regions, and the area value in units of submesh is set. Ask.

  Here, the whole area 16 including the drawing target area may be the whole area of the drawing target object such as a mask or a wafer as shown in the figure, or the data A19 and the drawing data as shown in FIG. It may be obtained by dividing into some drawing information or areas of the drawing object such as B20 and drawing data C21.

  Next, in 52 of FIG. 5, as shown in FIG. 8, the drawing information of the sub-mesh 1 is combined with the drawing information 2 in mesh units. At this time, as the attention mesh M122 in the figure, for example, the drawing information of the sub-mesh of the sub-mesh range 23 to be combined with the attention mesh indicated by diagonal lines is used.

  As the synthesis method, as shown in FIG. 1, the area value which is the drawing information obtained for each sub-mesh is used, for example, a filter having a weighting coefficient shown in the same figure, and the filter center position matches the mesh center position. By adding the area values of all the sub-mesh within the filter size at the position, the area value of 2 mesh units is synthesized.

  This is obtained for all meshes. Actually, the area density of the mesh is obtained from the area and the area value of the mesh. That is, here, the area density map in units of sub-mesh is converted into an area density map in units of mesh.

  Here, the weighted addition as a means for performing synthesis includes various distribution functions such as a Gaussian distribution. By weighted addition using various distribution functions such as a Gaussian distribution, it is possible to synthesize the drawing information for each mesh based on the drawing information for each sub-mesh.

  Further, the sub-mesh or mesh is not arranged in a lattice pattern, and may be present at an arbitrary position.

  FIG. 9 shows an example in which the sub-mesh 1 exists at an arbitrary position and is synthesized with the mesh 2 according to the Gaussian distribution 24.

  In this case, as in the case of the weighted addition described above, the sub-mesh is weighted according to the distance from the Gaussian filter center for all sub-mesh within the filter size at the position where the filter center position and the mesh center position are matched. The area value of 1 is added as the area value of the mesh 2.

  Thereafter, in 53 of FIG. 5, an exposure amount map is created by subjecting the area density map in units of meshes to smoothing processing and high-order approximation processing using a Gaussian filter or the like.

  Finally, in 54 of FIG. 5, the main exposure amount map is transferred to the proximity circuit 7 of FIG.

  In the above-described embodiment, a form obtained from drawing information in units of sub-mesh in the same system as shown in FIG. 2 is described. However, the system for obtaining the drawing information in units of sub-mesh may be a system different from the system that actually performs drawing. As this form example, there is a method as described below.

  For example, when the drawing data is created by a system such as data conversion software different from the electron beam drawing apparatus, the area value file in units of sub-mesh is created.

  Next, the file of area values in units of sub-mesh is transferred to the proximity computer 4 or the fogging computer 5 in FIG. Thereafter, similarly to the above, based on the method of the present invention, the area value of the sub-mesh unit is synthesized with the area value of the mesh unit, the area density map is created, and the exposure map can be created.

  Since the image information obtained by combining the sub-mesh image information in units of meshes is processed and transferred by the proximity computer or the fogging computer, the image information is used in units as fine as the sub-mesh units. Compared to, processing and transfer time is reduced.

  Also, the image information that has been reconstructed by combining in mesh units is different from simply averaged image information in mesh units, and is image information that reflects the weighted addition in sub-mesh units. It is possible to provide a highly accurate drawing in which the proximity effect correction including the correction is performed better.

  Note that the processing and transfer of image information are performed in units of meshes, and the processing and transfer are not performed in units of sub-mesh.

  The present invention can be applied not only to an electron beam drawing apparatus but also to a stepper type exposure apparatus using an electron beam. Further, as the drawing object, a mask is given as an example, but a wafer or the like may be used.

  As described above, according to the embodiment of the present invention, the area density map smoothing process for obtaining the exposure map, the processing of the map by the higher-order approximation process, the creation of the exposure map, and the created exposure map Transfer to another medium can be obtained with high accuracy without increasing the processing time, and an electron beam exposure apparatus and an exposure amount map creation method with high accuracy and high processing speed can be provided.

  In the above embodiment, the fogging effect correction and the proximity effect correction are described. However, the present invention can be applied to any one of the effect correction and the proximity effect correction.

The figure which concerns on the Example of this invention and shows the method (weighting addition use use) which synthesize | combines a submesh with a mesh. 1 is a schematic diagram of an electron beam drawing apparatus according to an embodiment of the present invention. The figure which concerns on the Example of this invention, and shows the calculation method of the correction value of the figure decomposed | disassembled for every shot. The figure which concerns on the Example of this invention and shows the procedure until it calculates | requires exposure amount time by software. The figure which concerns on the Example of this invention and shows the procedure which calculates | requires an exposure amount map. The figure which concerns on the Example of this invention, and divided | segmented the whole area | region including a drawing object area | region with a submesh. The figure which concerns on the Example of this invention and divided | segmented drawing data by the submesh. The figure which related to the Example of this invention, and illustrated the submesh range used in order to synthesize | combine with the drawing information of a mesh unit. The figure which concerns on the Example of this invention and is related to the Example of this invention, and is a figure which shows the method (Gaussian use) which synthesize | combines a submesh into a mesh.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Submesh, 2 ... Mesh, 3 ... Computer for drawing data, 4 ... Computer for proximity, 5 ... Computer for fogging, 6 ... Restoration decomposition, 7 ... Proximity, 8 ... Tracking, 9 ... DAC, 10 ... Electron beam drawing Device main body, 11 ... electron gun, 12 ... electron beam, 13 ... deflector, 14 ... stage, 15 ... mask, 16 ... all area including drawing object, 17 ... figure divided into shot units, 18 ... shot Correction values that enclose each figure that has been decomposed, 19... Drawing data A, 20... Drawing data B, 21... Drawing data C, 22. .

Claims (4)

In an exposure correction method for dividing a drawing region irradiated with an electron beam into meshes of small regions, and performing fogging effect correction and / or proximity effect correction based on the drawing information of the mesh,
Dividing the mesh into sub-mesh of even smaller regions,
An exposure amount correction method, wherein drawing information is obtained in units of the sub-mesh, and the sub-mesh drawing information is weighted and added to the image information in units of the mesh. The exposure amount correction method according to claim 1,
In the exposure correction method, the weighted addition uses various distribution functions including a Gaussian distribution. In an electron beam exposure apparatus that divides a drawing region irradiated with an electron beam into meshes of small regions, and performs fogging effect correction and / or proximity effect correction based on the drawing information of the mesh,
The mesh is further subdivided into sub-mesh of a minimal area, drawing information is obtained in units of the sub-mesh, and the sub-mesh drawing information is weighted and added to synthesize the image information in units of the mesh. Means for obtaining a correction map;
The proximity effect is corrected for the exposure time in real time with reference to the exposure amount for the partial area corresponding to the drawing figure of the exposure correction map, and the drawing figure is drawn by irradiating the electron beam with the corrected exposure time. An electron beam exposure apparatus comprising means for including a controller for performing The electron beam exposure apparatus according to claim 3.
An exposure apparatus using an electron beam, wherein the weighted addition means is various distribution functions including a Gaussian distribution.

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