JPH08227842A - Pattern drawing device - Google Patents

Abstract

PURPOSE: To provide a pattern drawing device which is suitable for efficiently performing proximity-effect correcting work. CONSTITUTION: A area rate, which is stored in a memory 4, is read out and displayed on a graphic display device 1 as a density map. The area rate is further displayed on a control computer 2. A circuit pattern is further overlapped on the area rate map and displayed. With the displays being observed, the area rate map is partially corrected finely as a part of the proximity effect correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern drawing apparatus, and more particularly to a pattern drawing apparatus such as an electronic beam drawing apparatus suitable for correcting a proximity effect phenomenon that occurs when drawing a pattern. Regarding the device.

[0002]

2. Description of the Related Art In a pattern writing apparatus such as an electron beam writing apparatus, an irradiation beam such as an electron beam is controlled by a lens so as to obtain a desired shape and current density, and at the same time, a deflector deflects a sample. This is an apparatus for determining the irradiation position by the irradiation beam and forming a pattern such as an LSI chip on the sample.

In the case of electron beam writing, for example, when writing is performed using this apparatus, the electrons irradiated on the sample collide with the constituent atoms of the resist and the substrate and are scattered, and Energy may be deposited outside the beam irradiation area, and the desired pattern shape may not be obtained. In particular, when the data having a large area pattern shape is close to each other, the deposition energy becomes excessive and the interval between the patterns becomes narrow. Further, in a fine isolated pattern, electrons are scattered to the periphery, so that the deposition energy becomes insufficient in the irradiation region, and the pattern size to be formed becomes small. Such a phenomenon is called a proximity effect phenomenon.

The conventional device uses the following method as a means for correcting this proximity effect phenomenon.

First, a value proportional to the area of a pattern to be drawn (typically an LSI circuit pattern), specifically an area ratio, is obtained. The method decomposes pattern data for drawing into small rectangular pattern data (shot data), and decomposes based on the area and position information of the shot data area. The area ratio of the small pattern data is calculated and cumulatively added to the holding area of the corresponding memory. After that, for the purpose of alleviating the steep area ratio change between shot data and the area ratio cumulative error, uniform smoothing filtering is performed on the entire area ratio map showing the distribution of the area ratio under certain conditions. The area ratio map created in this way is L
In the case of the SI circuit pattern, it is managed for each chip. Further, the correction dose corresponding to the area ratio is obtained by using a dose correction function based on the electron scattering coefficient ratio (ratio of scattering in the resist and scattering in the semiconductor substrate) previously obtained by an experiment. In the actual drawing, the proximity effect phenomenon is corrected by referring to the area ratio map corresponding to the position of the drawing shot and correcting the shot data irradiation amount according to the area ratio.

[0006]

In the above-mentioned prior art, if the optimum input parameters for correction can be determined, high-speed and accurate proximity effect correction can be realized. However, a considerable amount of time is required because it is necessary to repeat drawing experiments to find the optimum parameters for the following, and further it is necessary to become familiar with this method before being used to it.

First of all, problems with the smoothing filter required when creating the area ratio map will be given.
According to the conventional smoothing filtering method applied to the entire area ratio map, fine smoothing is selected according to the configuration and arrangement of the pattern data forming the LSI chip. Since this cannot be done, uneven smoothing occurs. For example, it is difficult to optimize an area ratio map of an LSI chip in which a large area pattern is lined up and a fine pattern is scattered. For this reason, a method of increasing the number of smoothing filters and trying to further reduce the error is taken, but if the number of times is unnecessarily increased, the whole area ratio map becomes too flat, and there are parts that cannot be corrected. come. Actually, the number of times of smoothing is changed and drawing is performed many times to find the best condition.

Next, there will be given a problem in obtaining a corrected irradiation amount corresponding to an area ratio, which is required in actual drawing. The dose correction value is determined by a dose correction function from the electron scattering ratio (the ratio of the forward scattering generated in the resist and the deposition energy of the back scattering generated in the semiconductor substrate) obtained by the experiment. This dose correction function is created based on the double Gaussian approximation, but when using a silicon substrate or the like on which tungsten is adhered, the error becomes large and there are portions where the correction fails.

An object of the present invention is to provide a pattern drawing apparatus suitable for efficiently performing the proximity effect correction work.

[0010]

Means for solving the problems of the present invention are as follows.

1. In a pattern drawing device that irradiates a sample with an irradiation beam to draw a pattern on the sample,
A means for decomposing the pattern into small patterns and a holding area, and a value proportional to the area of each of the decomposed small patterns is held in a corresponding holding area of the holding areas. And a means for displaying an area map showing a distribution of values proportional to the held area, and a means for selecting a partial area of the displayed area map. A value proportional to the area is corrected, and the irradiation amount of the sample by the irradiation beam is corrected according to the corrected value (claim 1).

2. In the pattern drawing apparatus of the problem solving means 1, the value proportional to the area is an area ratio (claim 2).

3. In the pattern drawing apparatus of the problem solving means 2, the area map is a numerical display of the area ratio or a color distinguishable from each other (claim 3).

4. Pattern of problem solving means 1, 2 or 3
In the screen drawing device, the pattern is displayed so as to be superimposed on the area map (claim 4).

5. In the pattern drawing device of the problem solving means 1, 2, 3 or 4, the correction of the value proportional to the area is smoothing filter processing, and means for storing a plurality of processing conditions of the smoothing filter processing is provided. And the processing conditions can be arbitrarily selected and used (claim 5).

6. In the pattern drawing apparatus of the problem solving means 5, the processing conditions include a type of smoothing processing, a smoothing unit, and a smoothing count (claim 6).

7. In the pattern drawing device of the problem solving means 6, the processing condition of the smoothing filter processing selected for a certain pattern is applied to the pattern having the same name as the certain pattern. It is characterized in that it is saved together with the name of the certain pattern (claim 7).

8. In a pattern drawing device that irradiates a sample with an irradiation beam to draw a pattern on the sample,
A means for decomposing the pattern into small patterns and a holding area, and a value proportional to the area of each of the decomposed small patterns is held in a corresponding holding area of the holding areas. And a means for superimposing and displaying the pattern and an area map showing a distribution of values proportional to the held area, and displaying a value proportional to the area of the displayed area map. The irradiation amount of the sample by the irradiation beam is corrected according to the corrected value (claim 8).

9. In the pattern drawing apparatus of the problem solving means 8, the value proportional to the area is an area ratio (claim 9).

10. In the pattern drawing apparatus of the problem solving means 9, the area map is a numerical display of the area ratio or a color distinguishable from each other (claim 10).

11. In the pattern drawing device of the problem solving means 8, 9 or 10, the correction of the value proportional to the area is smoothing filter processing, and means for storing a plurality of processing conditions of the smoothing filter processing is provided. , And the processing conditions can be arbitrarily selected and used (claim 11).

12. In the pattern drawing apparatus of the problem solving means 11, the processing condition includes a type of smoothing processing, a smoothing unit and a smoothing number (claim 12).

13. In the pattern drawing device described in the problem solving means 12, the processing condition of the smoothing filter process selected for a certain pattern is set to the certain pattern.
It is characterized in that it is saved together with the name of the certain pattern so as to be applied to the pattern of the same name as the pattern (claim 13).

14. In a pattern drawing apparatus for irradiating a sample with an irradiation beam to draw a pattern on the sample, the pattern drawing device has a means for breaking down the pattern into small patterns and a holding area, and is broken down. Means for holding a value proportional to the area of the small pattern in the corresponding holding area among the holding areas, and the holding area for each holding area corresponding to the value proportional to the area held in the holding area. A distribution of the dose correction value of the sample by an electron beam, a correction curve showing a relationship between the value proportional to the area and the dose correction value, and means for displaying the pattern. It is characterized (claim 14).

15. In the pattern drawing device of the problem solving means 14, the dose correction value is based on a predetermined reference dose (claim 1).
5).

16. In the pattern drawing apparatus of the problem solving means 15, a value proportional to the area is an area ratio (claim 16).

[0027]

According to the present invention, in a pattern drawing apparatus for irradiating a sample with an irradiation beam to draw a pattern on the sample, means for decomposing the pattern into small patterns and holding A means for holding a value proportional to the area of each of the decomposed small patterns in a corresponding holding area of the holding areas, and a distribution of values proportional to the held area. Means for displaying the area map that it represents,
Means for selecting a partial region of the displayed area map, correcting a value proportional to the area of the selected partial region, and the sample by the irradiation beam according to the corrected value. The irradiation amount of is corrected. For this reason, it becomes possible to perform the work of the proximity effect correction while observing the display, so that the efficiency of the correction work can be improved. In addition, the dose correction, and thus the proximity effect correction, can be performed immediately. Then you will be able to perform finely in part.

According to the present invention, in a pattern drawing apparatus for irradiating a sample with an irradiation beam to draw a pattern on the sample, means for decomposing the pattern into small patterns and holding Means for holding a value proportional to the area of each of the decomposed small patterns in a corresponding holding area of the holding areas, and a proportion to the pattern and the held area. And a means for superimposing and displaying an area map representing the distribution of the values to be displayed, correcting a value proportional to the area of the displayed area map, and irradiating the irradiation beam according to the corrected value. The irradiation amount of the sample due to is corrected. According to this, the difference in the value proportional to the shape and arrangement of the pattern and the area becomes clear, and therefore, the part where the calculation error of the value proportional to the area is large becomes clear, and the proximity effect while observing the display. Since the correction work can be performed, the efficiency of the correction work can be improved.

According to the present invention, in a pattern drawing apparatus for irradiating a sample with an irradiation beam to draw a pattern on the sample, means for decomposing the pattern into small patterns and holding A means for holding a value proportional to the area of the decomposed small pattern in a corresponding holding area of the holding areas, and an area held in the holding area for each holding area. Means for displaying the distribution of the dose correction value of the sample by the electron beam corresponding to the proportional value, the correction curve showing the relationship between the value proportional to the area and the dose correction value, and the pattern. It has and. According to this, the dose correction value distribution for the pattern configuration becomes clear. That is, it becomes easy to verify and correct the dose correction value. This means that the efficiency of the proximity effect correction work can be improved.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electronic beam drawing device is selected as an example of a pattern drawing device, and an embodiment of the present invention will be described by taking this as an example.

Referring to FIG. 1, the electron beam emitted from the electron gun 12 is converged on the sample 15 by the electromagnetic lens 13 and by the deflector 14 controlled by the deflector control circuit 11. Biased.

First, referring to FIGS. 1 and 2, the LSI
The area ratio calculation of the circuit pattern data forming the chip will be described.

The pattern data stored in the large capacity IC memory 4 is a rectangular small pattern by the shot decomposition circuit 5.
And is sent to the area ratio calculation circuit 7 through the proximity effect correction control circuit 6 of the proximity effect correction unit 10 connected later. The area ratio calculation circuit 7 is the center coordinates of the input shot data (LSI chip coordinate system)
Is found in which grid-shaped small area (holding area) on the grid-shaped two-dimensional memory 9 divided by the area ratio calculation circuit 7 for each small area, and the shot corresponding to the small area is obtained. A value proportional to the area of, specifically, the area ratio is stored (held). The shot data is processed in a pipeline manner, and the area ratio is cumulatively added to the corresponding small regions one after another to create an area ratio map.

Next, based on the processing flow of FIG. 3, a method of correcting the area ratio map will be described with reference to FIGS. 1 and 2 and FIGS.

When the area ratio map is smoothed, is it possible to make the area ratio map as described above (S1) and then to perform the area ratio map correction in the circuit pattern of the same name in the past? It is judged (S2), and if past data exists, a smoothing parameter is created based on the data stored in the storage device of the control computer 2. (S9) Then, the smoothing circuit 8 is used to perform optimum smoothing filter processing on each part of the area ratio map (S10).

Next, if there is no record of past processing,
First, smoothing filter processing is performed under initial conditions (S3), and a graphic display of the area ratio map is required (S4).
As shown in FIG. 2, the control computer 2 reads the contents of the area ratio map through the common bus 3, outputs the contents to the graphic display device 1 connected to the computer, and displays them (S5). Reference numeral 16 represents an area ratio grid for displaying an area ratio map. Further, the circuit pattern data 17 stored in the large-capacity IC memory 4 is also read out and displayed in an overlapping manner.
As an output format to the graphic display device, as shown in FIG. 4A, a small area (lattice area) can be selectively color-coded and displayed 18 or a numerical value 19 depending on the area ratio. Further, it is also possible to display an equal area ratio curve, a three-dimensional bar graph, a three-dimensional broken line graph, or the like.

By overlapping and displaying the circuit pattern data and the area ratio map, the difference between the original pattern shape / arrangement and the area density becomes clear, and a large area ratio calculation error or a smooth area is calculated. Since the portion where the optimization filter is not optimal (the portion where the error due to smoothing becomes significant) becomes clear, if there is an inappropriate area (S6), this is set as shown in FIG. 5, for example, the lower left grid point and the upper right grid point. Is extracted by selecting (S7). After that, as shown in FIG. 6, the smoothing type, unit, and number of times are selected from the menuized options (S
7), smoothing area table 24, smoothing filter table 25, number of times table 27, smoothing unit table (smoothing width: for example, 3 × 3 grid is used as a smoothing unit) 2
The parameters (smoothing unit (m, n)
And coefficient parameters), parameters corresponding to the respective areas are sent to the smoothing circuit 8, and smoothing filter processing is executed (S8).

After the smoothing is executed for all the selected areas under the specified smoothing condition, the area ratio map is output again to the graphic display device 1 (S5) and evaluated. If it is satisfied, the circuit pattern name corresponding to the current area ratio map and the final smoothing condition of each part (table shown in FIG. 6)
Is stored in the control computer and is applied to the circuit pattern having the same name from the next time (S9). Therefore, the optimum conditions obtained once can be used while the environment does not change.
After performing the smoothing process, the actual drawing is performed while the irradiation amount is corrected by the area ratio (S11).

Further, the smoothing filter method is a simple averaging filter (FIG. 7 (1)) for a part 28 of the area ratio map.
Expression) and a weighting filter (Expression (2) in FIG. 7) are used. In particular, in the case of the pattern configuration as shown in FIG. 8, when a simple averaging filter is used as the type of smoothing processing condition, the area of the thin pattern sandwiched between the large area pattern and the area is smaller than the actual area. Since the rate is largely corrected and the irradiation amount is conversely small, the pattern becomes thin and causes an electrical short in the LSI. Therefore, weighted filtering is performed. In addition, a new smoothing means
It is also possible to add easily by adding a bull. The smoothing filter can be realized by software on the control computer instead of using the smoothing circuit.

Further, as a direct correction of the area ratio map,
It is also possible to forcibly replace a range of values of the areal density with another value. In this case, the address of the area density map and the changed value are sent to the proximity effect correction control circuit 6 to directly rewrite the contents of the area density map. The address and the changed value of the area density map at this time are stored in the storage device of the control computer 2 together with the circuit pattern name and are reused. Such a case of direct correction is effective in the case where some ultrafine isolated patterns exist in the lattice area of the area density map.

Next, with reference to FIG. 9, a method of determining the correction dose corresponding to the area ratio will be described. First, the dose correction curve for the area ratio obtained by the control computer from the electron scattering coefficient ratio by the calculation formula of FIG. 10 is output to the graphic display device 1 in the format as shown in FIG. 10 and displayed (S12). . Further, since the dose correction value corresponding to each area rate can be known from this dose correction curve, the value obtained by adding the dose correction value to the reference dose in the same manner as the area rate display as shown in FIG. That is, the dose correction value distribution (S13) is output to the graphic display device 1 and displayed (S14). By superimposing and displaying the circuit pattern data on this display, the dose distribution with respect to the pattern configuration becomes clear. When the dose distribution is evaluated and the corrected dose is determined to be optimum (S15), the process ends, but when it is not optimum (S15), the correction curve of FIG. 10 is directly operated ( A range is selected, and two correction values are input.) (S12) The corrected correction curve and dose distribution are displayed again on the graphic output device 1. In this way, the graphic screen is effectively used to determine the corrected irradiation amount (S16).

As is apparent, the validity of the area ratio map can be clearly confirmed by visually verifying the created area ratio map by overlapping it with the pattern data.
As a result, it is possible to surely perform the extraction and correction of the inappropriate area up to the details.

Since the area density map can be partially selected and different smoothing filter processing can be performed, the area ratio map of the LSI chip composed of various circuit patterns can be optimized. Also, when determining the corrected irradiation amount, it is possible to simulate on a computer by visual verification using a graphic display. The optimization of the area ratio map and the optimized irradiation dose by this method were carried out in order to determine the parameters required for creating the area ratio map and calculation of the corrected irradiation dose, and to discriminate many drawing experiments and drawing results. The ability can be kept to a minimum, which saves various resources when performing proximity correction.

Further, by comparing the drawn result with the graphic display screen of the area ratio or dose distribution, the relationship between the area where the proximity effect correction is insufficient, the area ratio distribution and the dose correction value can be clearly understood. The distinction from other factors (factors other than proximity effect) is clear. This is a big decisive factor in determining whether a process is defective.

[0045]

According to the present invention, a pattern drawing apparatus suitable for efficiently performing the proximity effect correction work is provided.

[Brief description of drawings]

FIG. 1 is a block diagram of a pattern drawing apparatus showing an embodiment according to the present invention.

FIG. 2 is a block diagram of a part of FIG. 1 centering on a graphic display device.

FIG. 3 is a flowchart showing an example of smoothing processing according to the present invention.

FIG. 4 is a diagram showing an example of an area ratio map graphic display according to the present invention.

FIG. 5 is a diagram for explaining a partial area selection method of an area map according to the present invention.

FIG. 6 is a diagram showing a table of processing conditions of a smoothing filter according to the present invention.

FIG. 7 is a diagram for explaining a smoothing filter processing method according to the present invention.

FIG. 8 is a diagram showing an example of a pattern.

FIG. 9 is a flowchart of an example of determining a corrected dose according to the present invention.

FIG. 10 is a diagram showing a formula and graph of a dose correction value with respect to an area ratio according to the present invention.

[Explanation of symbols]

1: Graphic display device, 2: Control computer,
4: large capacity IC memory, 5: shot decomposition circuit, 6: proximity effect correction control circuit, 7: area ratio calculation circuit, 8: smoothing circuit, 9: two-dimensional memory, 10: proximity effect correction unit, 11: deflection Control circuit.

Claims (16)

[Claims] 1. A pattern drawing apparatus for irradiating a sample with an irradiation beam to draw a pattern on the sample, wherein a means for decomposing the pattern into small patterns and a holding area are provided. A means for holding a value proportional to the area of each of the decomposed small patterns in a corresponding holding area of the holding areas, and an area representing a distribution of values proportional to the held area. A means for displaying a map and a means for selecting a partial area of the displayed area map are provided,
A pattern is characterized in that a value proportional to the area of the selected partial region is corrected, and the irradiation amount of the sample by the irradiation beam is corrected according to the corrected value. Drawing device. 2. The pattern drawing apparatus according to claim 1, wherein the value proportional to the area is an area ratio. 3. The pattern drawing device according to claim 2, wherein the area map is a numerical display of the area ratio or a color that is distinguishable from each other. A pattern drawing device. 4. The pattern drawing apparatus according to claim 1, 2 or 3, wherein the pattern is superimposed and displayed on the area map. . 5. The pattern drawing apparatus according to claim 1, 2, 3 or 4, wherein the correction of the value proportional to the area is smoothing filter processing, and a plurality of smoothing filter processings are performed. A pattern drawing apparatus characterized in that it is provided with means for storing conditions and the processing conditions can be arbitrarily selected and used. 6. The pattern drawing apparatus according to claim 5, wherein the processing conditions include a type of smoothing processing, a smoothing unit, and a smoothing count. 7. A pattern drawing apparatus according to claim 6, wherein the processing condition of the smoothing filter processing selected for a certain pattern is a pattern having the same name as the certain pattern. The pattern drawing device is characterized in that it is stored together with the name of the certain pattern so as to be applied to. 8. A pattern drawing apparatus for irradiating a sample with an irradiation beam to draw a pattern on the sample, wherein a means for disassembling the pattern into small patterns and a holding area are provided. A means for holding a value proportional to the area of each of the decomposed small patterns in a corresponding holding area of the holding areas, and a value proportional to the pattern and the held area. And a means for displaying an area map representing the distribution of the area overlapped with each other, correcting a value proportional to the area of the displayed area map, and correcting the value by the irradiation beam according to the corrected value. A pattern writing apparatus characterized in that the irradiation amount of a sample is corrected. 9. The pattern drawing apparatus according to claim 8, wherein the value proportional to the area is an area ratio. 10. The pattern drawing apparatus according to claim 9, wherein the area map is a numerical value display of the area ratio or a color distinguishable from each other. A pattern drawing device. 11. The pattern drawing apparatus according to claim 8, 9 or 10, wherein the correction of the value proportional to the area is smoothing filter processing, and a plurality of processing conditions of the smoothing filter processing. A pattern drawing device characterized in that it is provided with a means for storing, and the processing conditions thereof can be arbitrarily selected and used. 12. The pattern drawing apparatus according to claim 11, wherein the processing conditions include a type of smoothing processing, a smoothing unit, and a smoothing count. 13. A pattern drawing apparatus according to claim 12, wherein a smoothing filter processing condition selected for a certain pattern has a pattern having the same name as the certain pattern. The pattern drawing device is characterized in that it is stored together with the name of the certain pattern so as to be applied to. 14. A pattern drawing device for irradiating a sample with an irradiation beam to draw a pattern on the sample, wherein a means for decomposing the pattern into small patterns and a holding area are provided. A means for holding a value proportional to the area of the decomposed small pattern in a corresponding holding area of the holding areas, and proportional to the area held in the holding area for each holding area. A distribution of the dose correction value of the sample by the electronic beam corresponding to the value, a correction curve showing the relationship between the value proportional to the area and the dose correction value, and means for displaying the pattern. A pattern drawing device characterized by being provided. 15. The pattern writing apparatus according to claim 14, wherein the dose correction value is based on a predetermined reference dose. 16. The pattern drawing apparatus according to claim 15, wherein the value proportional to the area is an area ratio.