JPH05341498A - Device and method for designing photomask - Google Patents

Abstract

PURPOSE:To prevent a useless shifter arrangement, and to display a shifter arrangement unable part and a shifter arrangement error. CONSTITUTION:The device is constituted of an automatic arranging part 9 for arranging automatically a phase shifter for giving a phase difference to an incident light for passing through a transparent area in one of a pair of transparent areas in which the shortest distance between the transparent areas is below a threshold and adjacent, on the transparent area of a photomask formed by plural opaque areas and transparent areas, an automatic verifying part 10 for verifying automatically whether the shifter arrangement is correct or not, with respect to the photomask subjected to shifter arrangement as a whole already, and an arranging/verifying part 11 for verifying automatically whether the shifter arrangement is correct or not as for the transparent area to which the shifter arrangement is finished, and arranging automatically the shifter in one of a pair of transparent areas in which the shortest distance between the transparent areas is below a threshold and adjacent as for the transparent area to which the shifter is not arranged yet, with respect to the photomask subjected to shifter arrangement partially already.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for designing a photomask for semiconductor production, and more particularly to an apparatus and method for designing a photomask for semiconductor production suitable for transferring a fine pattern.

[0002]

2. Description of the Related Art Reduction projection in which a photomask on which an original pattern is drawn (hereinafter abbreviated as a mask) is irradiated with partially coherent incident light and photolithography is performed to transfer the pattern on the mask onto a semiconductor substrate. The exposure apparatus is required to have a finer transferable pattern.

The resolution representing how fine a pattern can be transferred by the reduction projection exposure apparatus is, for example, when a mask pattern whose brightness changes periodically is used and two adjacent bright parts on a semiconductor substrate overlap each other. It is evaluated by whether or not it can be separated. As a method of improving this resolution, it is known that a phase difference may be given to incident light passing through a pair of adjacent transparent regions on the mask.

Conventionally, regarding a method of giving a phase difference to incident light passing through a pair of transparent regions adjacent to each other on a mask, IEE Transaction on Electron Devices, ED-29, No. 12 (1982). Year)
Page 1828 (IEEE Transon Electron Devices, Vol E
D-29 No.12 (1982) p1828) Marc D. Levenson et al., “Implementing resolution in photolithography with a phase shifting mask (Inpr
oving Resolution in Photolithography with a Phase
-Shifting Mask) ".

The Levenson-type phase shift mask proposed in this document, as shown in FIG. 18, has a plurality of light-shielding portions (opaque regions) 2 which are original images of a pattern on a mask substrate 1.
And a transparent region is formed, and a phase shifter (hereinafter, simply abbreviated as shifter) 3 made of a transparent material, which gives a phase difference to incident light passing through the transparent region, is arranged in one of a pair of adjacent transparent regions. There is.

The condition of this shifter is d = λ / {2, where d is the film thickness, n is the refractive index, and λ is the wavelength of the incident light.
The relationship (n-1)} is required. Since the light passing through the shifter has a phase difference with other transmitted light, the light intensity becomes 0 at the pattern boundary portion on the semiconductor substrate, and the adjacent bright portions are separated to improve the resolution.

On the other hand, in a paper related to an automatic designing device for automatically designing this Levenson-type phase shift mask, there is a symposium on BLS Technology, JS.
APCAT. No. AP911210 (1991),
95th to 96th pages (Symposium on VLSI Technolo
gy, pp.95-96, Oiso, Japan, May 1991), Nomura Noboru et al.
Fore Phase Shifting Mask (Automatic Pa
ttern Generation System for Phase Shifting Mask)
There is a paper entitled.

In this paper, dynamic random
We are discussing Levenson type phase shift mask automatic design equipment that designed access memory (DRAM).
According to this, a shifter is automatically arranged by the method described with reference to FIG. 18 for each cell that is a set of a plurality of opaque areas and transparent areas, and a warning is issued when there is a place where shifter cannot be arranged. It is designed to give and stop processing.

If there is no place where shifter placement is not possible, after the shifter placement in the cell is completed, it is checked whether the placement state near the boundary between shifter placed cells is appropriate. I am verifying. If there is an error in the shifter arrangement near the boundary between adjacent cells, the shifter arrangements of all transparent areas belonging to one cell are reversed.

[0010] In addition, Andrew Earl Neuloiser (Andrew.
R. Neureuther) et al. “Investigating phase shifting mask layout issues using a CAD tool kit” (Inve
stigating Phase-shifting Mask Layout Issues Using
a CAD Toolkit), the designer decides the reduction ratio for a given design pattern, automatically shifters are placed on the reduced pattern, and there is a place where shifter placement is not possible. For example, an automatic design device for displaying the location is discussed.

However, none of the automatic designing apparatuses has a function of automatically verifying a mask which already has a shifter arrangement as a whole. Therefore, when the shifter arrangement is manually performed, it is not possible to determine whether the shifter arrangement is correct. Furthermore, since it does not have an automatic verification and automatic placement function for a partially placed mask, two adjacent regions 1 as shown in FIG.
A problem occurs when the shifter is automatically arranged on the mask in which the transparent region (hatched portion) extending over 8 and 19 is formed.

That is, at first, when the shifter is arranged in the area 18, if the shifter is arranged on the transparent area extending over the two areas 18 and 19, when the shifter is automatically arranged in the area 19, the partial shifter is already formed. There is a transparent area where shifters are already placed. In such a case, ideally, automatic verification of the shifter arrangement for the transparent area where the shifter has been arranged and automatic shifter arrangement for the transparent area where the shifter has not been arranged are required.

Further, when there is a place where the designer wants to preferentially perform shifter placement, and wants to perform shifter automatic placement on the remaining transparent region after manually placing the shifter on the transparent region, The above-mentioned automatic verification and automatic placement are required.

[0014]

As described above, the conventional
In the method of arranging the shifter on one of the pair of adjacent transparent regions, the resolution is improved by the principle of the Levenson type phase shift mask. However, in this method, it is not determined how close the transparent areas on the mask are adjacent to each other, and the shifter is arranged regardless of the distance between the transparent areas. For this reason, there is a drawback in that the shifter is arranged in a transparent area where it is not necessary to give a phase difference.

On the other hand, since the conventional automatic design apparatus does not have an automatic verification function, there is a problem that it is not possible to judge whether or not the mask is already arranged in the shifter. Further, if there is a portion where shifter placement is not possible, a warning is given and the processing is stopped, or only that portion is displayed, and information for correction has not been displayed.

Further, in the prior art (by Andrew et al.), When layout data having a hierarchy is input, no consideration is given to a method of saving the hierarchy and arranging shifters. Therefore, the layout and layout verification of the shifter are performed after expanding the hierarchy, and the more the pattern repeats, the more layout data increases, and the memory overflow or the data processing time after design increases. Cause problems.

Further, the conventional technique (by Nomura et al.) Has a function of verifying the phase between cells, but when there are a plurality of cells forming a hierarchy, the shifter may be arranged from which cell. It's not clear. In addition, as shown in FIG. 20, in the case where the cell A is composed of the lower cell B and the lower cell C, after the shifter arrangement has already been performed on the cell A, the layout of the cell B is changed and the cell A is changed again. In the case of performing automatic shifter placement, the prior art does not have a storage means that the cell C has already been placed in the shifter, so that the shifter placement is performed again for the cells A, B, and C, which is inefficient. there were.

Therefore, the present invention has been made in view of such conventional circumstances, and the first purpose thereof is to perform an appropriate shifter arrangement according to the shortest distance between a pair of transparent regions. Another object of the present invention is to provide a photomask designing method that allows shifter arrangement without waste.

A second object is to provide an automatic verification function for a mask which is already wholly shifted, and an automatic verification function and an automatic placement function for a partially placed mask, thereby displaying a placement error. Another object of the present invention is to provide a photomask designing device capable of presenting reference information when attempting to make corrections on an unplaceable portion.

Thirdly, when layout data having a hierarchical structure is input, the hierarchical structure is expanded by performing automatic shifter placement and automatic shifter placement verification while maintaining the hierarchical structure. It is an object of the present invention to provide a photomask designing device that can avoid problems such as an increase in the amount of data and an increase in data processing time due to the subsequent operation.

Further, a fourth object is that, as a result of the shifter automatic placement processing or the automatic verification processing, when the phase shifter can be placed in the cell to be processed without contradiction, the shifter has already been placed in the cell. By providing a recognition flag to that effect, it is possible to provide a photomask designing device that can efficiently perform automatic shifter placement processing and automatic verification processing without processing cells multiple times.

[0022]

In order to achieve the above object, the first invention is used in photolithography using partially coherent incident light, and a plurality of opaque areas and transparent areas are formed. When designing a photomask, a phase shifter that gives a phase difference to the incident light passing through the transparent regions is arranged in one of a pair of adjacent transparent regions with the shortest distance between the transparent regions being less than a threshold value. is there.

The second aspect of the present invention is used in photolithography using partially coherent incident light, and sets a plurality of transparent regions of a photomask in which a plurality of opaque regions and transparent regions are formed between transparent regions. Is divided into groups consisting of adjacent transparent areas with a minimum distance of less than a threshold value, and within each group, one of a pair of adjacent transparent areas with a distance less than the threshold value is A phase shifter that gives a phase difference to the incident light is automatically arranged,
With respect to the photomask in which the result and the more detailed information as necessary and more detailed information are displayed, and the photomask in which the phase shifter is already arranged as a whole, a plurality of transparent regions formed on this photomask, If the shortest distance between transparent areas is less than a threshold value, the areas are divided into groups consisting of adjacent transparent areas, and the shifter is temporarily placed in one of a pair of transparent areas that are adjacent and less than the threshold value in each group. Then, compare the placement state of the provisionally placed phase shifter with the placement state of the phase shifter that has already been placed, and if the placement of the phase shifter that has already been placed is incorrect, Automatic verification means that displays the verification result and more detailed information while displaying the comparison of the arrangement state and the arrangement state of the temporarily arranged phase shifter, and To the photomask in which the phase shifter is arranged, the transparent area in which the phase shifter is already arranged, is automatically verified by the method by the automatic verification means, and the transparent area in which the phase shifter is not arranged is The automatic arrangement is performed by the method of the automatic arrangement means, and the arrangement / verification means performs result display and more detailed information display.

Further, the semiconductor substrate is irradiated with the incident light that passes through the pair of transparent regions formed on the photomask, and the threshold value in the first and second inventions,
The shortest distance between the pair of transparent regions at the limit where adjacent bright portions on this semiconductor substrate can be separated is measured by changing the width of the transparent regions, and the maximum value of the shortest distance between the measured transparent regions or The value is larger than that.

The third aspect of the present invention is used in photolithography using partially coherent incident light, and passes through a transparent region on a transparent region of a photomask in which a plurality of opaque regions and transparent regions are formed. A phase shifter that imparts a phase difference to the incident light is automatically arranged on one of a pair of adjacent transparent regions whose shortest distance between the transparent regions is less than a threshold value, and the phase shifter is already arranged as a whole. An automatic verification means for automatically verifying whether or not the arrangement of the phase shifter is correct with respect to the photomask being displayed, and a certain hierarchy is the opaque area and / or cell (a cell is the opaque area and / or one lower hierarchy). When layout data having a hierarchical structure such as a set of cells) is input, the automatic arrangement means and / or the automatic detection means are used. As a result of the processing of the means, when the phase shifter can be arranged in the cell to be processed without contradiction, a recognition flag indicating that the shifter has been arranged is given to the cell, and the recognition flag is added to the layout data. Among the cells not included, a hierarchical structure recognition means for selecting a cell located in the lowest hierarchy as a processing target.

The automatic placement method performed by the automatic placement means of the third aspect of the present invention includes the step of inputting the data of the processing target cell selected by the hierarchical structure recognizing means, and the set element in the processing target cell, The step of dividing into a set of set elements (hereinafter referred to as a group) that are adjacent to each other with the shortest distance from each other being less than a threshold value, and the phase is determined for all the set elements for a group that does not include subordinate cells in the group. And the group that includes the group defined in the lower cell (hereinafter referred to as the lower group) in the group, the topology is determined for the set elements that are not included in the lower group, and between the lower groups and the lower group. The step of determining the relative phase between the set elements that are not included in the lower group, and giving the phase consistently throughout the group. In the case where there is a contradiction in the determination of the phase within the processing target cell and the step of assigning the processing target cell name, the group identification number, and the phase value to the set element included in the group , And a step of presenting the location where the contradiction has occurred to the designer.

Furthermore, the automatic verification method carried out by the automatic verification means of the third invention comprises the step of inputting the data of the processing target cell selected by the hierarchical structure recognizing means, and the aggregate element in the processing target cell, The step of dividing into a set of set elements (hereinafter referred to as a group) that are adjacent to each other with the shortest distance from each other being less than a threshold value, and the phase is determined for all the set elements for a group that does not include subordinate cells in the group. And the group that includes the group defined in the lower cell (hereinafter referred to as the lower group) in the group, the topology is determined for the set elements that are not included in the lower group, and between the lower groups and the lower group. The step of determining the relative phase between the set elements that are not included in the lower group, and giving the phase consistently throughout the group. If it is, the phase determined by the automatic verification means is compared with the previously input phase, and if there is an error, the erroneous portion is presented to the designer, and if there is no error, When a step of assigning a processing target cell name, a group identification number, and a phase value to a set element included in the group and a contradiction in the determination of the phase in the processing target cell, the location where the contradiction occurs And a step of presenting it to the designer.

[0028]

With the above means, in the photomask designing method according to the first aspect of the present invention, the shortest distance between the transparent regions of the mask in which a plurality of opaque regions and transparent regions are formed are adjacent to each other with a minimum distance of less than a threshold value r. Regarding the transparent region, a phase shifter that gives a phase difference to incident light passing through the transparent region is arranged in one of the pair of transparent regions. Further, in the first invention, adjacent transparent areas on the mask are brought closer to each other, and the distance t between the transparent areas on the mask at the limit of separating adjacent bright portions on the semiconductor substrate is set to be the width of the transparent area. Is changed and measured, and the obtained maximum value of t or a value larger than that is used as the threshold value r.

Further, the photomask designing apparatus according to the second invention first inputs pattern data which is arrangement information of a plurality of opaque areas and transparent areas formed on the mask.

When automatic shifter placement is performed, shifter placement is automatically performed on the input pattern data. For automatic verification of shifter placement,
It is verified whether or not the shifter placement position is appropriate for the mask that has already been shifter placed overall. When the pattern data in which the shifters are partially arranged is input, regarding the transparent areas where the shifters are arranged,
It is automatically verified whether the shifter arrangement is appropriate, and the shifter automatic arrangement is performed for the transparent area where the shifter is not arranged. The placement result and more detailed information are displayed for each of the above cases.

When the shifter automatic placement is performed, when the pattern data to be the target of the shifter automatic placement is input, as a result, an execution report in which the shifter automatic placement execution results are summarized for each group is displayed, and as further detailed information, A graph showing the shifter arrangement of a group that can be shifted or the adjacency relationship of transparent areas in the automatic shifter placement area is displayed.

When performing shifter automatic verification, when the shifter arranged pattern data is input, as a result, the execution report in which the automatic verification execution results are summarized for each group is displayed, and the shifter arrangement is possible as more detailed information. And a shifter arrangement for a group in which the correct shifter arrangement has been made, or a graph expressing the adjacency relation of the transparent areas in the shifter arrangement verification target area, or the shifter arrangement that has already been arranged despite the possible shifter arrangement. If there is an error in the placement, the incorrect shifter placement and the correct shifter temporary placement are displayed so that they can be compared.

In the case where automatic shifter placement verification and automatic placement are performed on a partially shifter placed mask, when shifter placed pattern data is partially input, as a result, shifter placement verification / automatic placement is performed. Display the execution report that summarizes the execution results for each group, and as more detailed information, the shifter placement is possible for the group where the shifter placement is possible and the shifter is not placed, and the shifter placement is possible and the correctly placed group,
Or, a graph expressing the adjacency relationship of transparent areas in the shifter placement target area, or even if shifter placement is possible, if there is a placement error in the already placed shifter, the shifter placement that was incorrect Display correct shifter temporary placement for comparison.

Further, in the photomask designing apparatus according to the third aspect of the invention, when layout data having a hierarchical structure is input, a cell located in the lowest hierarchy among cells without shifter-arranged recognition flags is selected. As a processing target (hereinafter referred to as a current cell), phase shifter automatic placement or shifter automatic verification is sequentially performed.

The automatic shifter placement for the current cell is performed as follows. First, the data of the processing target cell selected by the hierarchical structure recognition means is input, and the patterns existing in the processing target area of the shifter automatic arrangement are divided into groups adjacent to each other with the shortest distance from each other being less than a certain threshold value. For groups that do not contain subordinate cells in the group, determine the phase for all patterns, and for groups that include subgroups defined in the subordinate cells in the group, are not included in subgroups. The phase is determined for the pattern, and then the relative phase is determined between the lower groups and between the lower group and the patterns not included in the lower group. If it is possible to give the phase consistently throughout the group,
Cells to be processed for the patterns included in the group,
Three pieces of information, a group identification number and a phase, are given. In this way, when it is possible to give a phase to all the groups in the current cell without contradiction, the hierarchical structure recognizing means gives the current cell a recognition flag in which shifters have been arranged. On the other hand, when a contradiction occurs in the phase determination in the current cell, the contradiction is presented to the designer.

The automatic shifter verification performed on the current cell is performed as follows. First, the data of the processing target cell selected by the hierarchical structure recognizing means is input, and the patterns existing in the processing target area of the shifter placement verification are divided into groups adjacent to each other with the shortest distance from each other being less than a certain threshold value. For groups that do not contain subordinate cells in the group, determine the phase for all patterns, and for groups that include subgroups defined in the subordinate cells in the group, are not included in subgroups. The phase is determined for the pattern, and then the relative phase is determined between the lower groups and between the lower group and the patterns not included in the lower group. If it is possible to give a phase to the entire group without contradiction, the phase determined by the automatic verification means (temporary placement)
And the pre-input phase are compared, and if there is an error, the erroneous portion is presented to the designer, and if there is no error, the processing target cell, the group for the pattern included in the group, Three pieces of information, the identification number and the phase, are given. In this way, when it is possible to give a phase to all the groups in the current cell without contradiction, the hierarchical structure recognizing means gives the current cell a recognition flag in which shifters have been arranged. On the other hand, when a contradiction occurs in the phase determination in the current cell, the contradiction is presented to the designer.

Further, when the layout having the recognition flag in which the shifter has been arranged is changed, the hierarchical structure recognition means removes the recognition flag of the layout and all the recognition flags of the upper cells including the cell as the lower cell.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

First Invention First, an embodiment of the photomask designing method of the first invention will be described in detail with reference to FIGS.

FIG. 1 shows transparent areas a to various sizes and shapes.
g schematically shows a mixed mask on the mask substrate 1. When the threshold value is r, the combinations of the transparent areas in which the shortest distance between the transparent areas is less than r are a and b, b and f, c and d, d and e, e and g, and g and c. is there. Since the resolution is improved by arranging a shifter in one of the transparent areas in such a place, a shifter which gives a phase difference to the partially coherent incident light passing through the pair of transparent areas is provided with one of the transparent areas. Place in the area. For example, suppose that shifters are arranged at a, f, c, and e. FIG. 2 shows an xx ′ cross section of the mask when the shifters are arranged in this manner. In the figure, shifters 3 are arranged in the transparent areas a, c, e.

The threshold value r may be arbitrarily determined based on the experience of the designer, but it can also be determined by the following method.

FIG. 3 shows a mask for obtaining the threshold value r. x is the width of the transparent region 4 and y is the length of the transparent region 4. Since only the threshold value in the x direction is considered, x << y
And the distance between the transparent areas is t. A fixed x
Then, the two transparent regions 4 are brought close to each other, and t _min at the limit is set so that adjacent bright portions on the semiconductor substrate can be separated.
To measure. change x and measure some t _min ,
The maximum value of the measured t _min or a value larger than it is set as the threshold value r.

As described above, according to the first aspect of the invention, when designing a mask using a shifter, the threshold value r is calculated,
On a mask in which transparent regions of various shapes and sizes are mixed, one of a pair of adjacent transparent regions whose shortest distance between the transparent regions is less than a threshold value r is a shifter arrangement target. This makes it possible to fully utilize the resolution improving effect of the Levenson-type phase shift mask and provide a mask with higher resolution.

Further, according to the first invention, it is possible to freely decide whether or not the shifter is arranged in the adjacent transparent area at a distance equal to or larger than the threshold value r. Therefore, the degree of freedom of the shifter arrangement is increased and the shifter is used. The design efficiency of the original photomask is significantly improved.

Second Invention Next, an embodiment of the photomask designing apparatus of the second invention will be described in detail.

FIG. 4 is a block diagram showing the structure of a photomask designing apparatus according to the second invention.

In the figure, this design apparatus is roughly composed of a control unit 5, a pattern data storage unit 6, an input unit 7, and a display unit 8. The control unit 5 includes an automatic shifter placement unit 9, Shifter automatic verification unit 10, shifter placement /
The verification unit 11 and the memory 12 are provided.

The input unit 7 is an input device such as a keyboard or a mouse, and has one function out of the shifter automatic arrangement unit 9, the shifter automatic verification unit 10, and the shifter arrangement / verification unit 11 for a partially shifted mask. It is about to select and instruct execution.

The control unit 5 is composed of a microprocessor and performs data processing described later according to a control program written in the memory 12. Each processing unit 9 to 1
1 is from the memory 12 or the pattern data storage unit 6,
Input the pattern data to be processed.

The input data are processed by the respective processing units 9 ...
Processing is performed in 11, the result is displayed on the display unit 8 such as a CRT, and the data is written in the pattern data storage unit 6 or the memory 12.

The photomask designing device is configured in this way, and the control operation of the control unit 5 when the shifter automatic arrangement unit 9 is selected will be described next with reference to the flowchart of FIG.

The data to be processed is input from the memory 12 or the pattern data storage unit 6 and classified into a group consisting of a set of transparent areas adjacent to each other below a certain threshold value r (steps 101 and 102). Here, although the threshold value r can be arbitrarily determined by the designer,
It is also possible to make the determination by the method described in the invention. The relative phase within a group is uniquely determined, but the relative phase between groups can be freely determined. As described in the first invention, shifters are automatically arranged for each group in one of a pair of adjacent transparent regions with the shortest distance between the transparent regions being less than r (step 10).
3).

Then, the shifter arrangement information and the group information are written in the memory 12 or the pattern data storage unit 6 (step 104). The processing result is displayed in the form of an execution report (step 105). FIG. 6 shows a display example of the execution report.

The contents of the execution report are the total number of groups existing in the shifter automatic arrangement target area, the number of groups that can be shifted and their group numbers, the number of groups that cannot be shifted and cannot be shifted, and their groups. It is a number.

Further, by selecting the shifter layout display or the graph display, more detailed information is displayed (steps 106 to 108). When the shifter arrangement display is selected, the shifter arrangement of the group that was capable of the shifter arrangement is displayed. An example of the display is shown in FIG. In FIG. 7, a shifter (broken line) arranged with a transparent region (hatched portion) is displayed.

FIG. 8 shows a display example when the graph display is selected. A new window 14 is opened in the vicinity of the currently opened window 13 and a graph representing the pattern arrangement of the shifter automatic arrangement processing area is displayed there. Here, the circles in the graph in the window 14 represent the positional relationship of each pattern in the window 13,
The circles and the lines connecting the circles indicate that the transparent areas corresponding to these circles are adjacent to each other with a minimum distance of less than r.

In order to easily associate the transparent area (hatched portion) in the window 13 with the circle mark in the window 14, the group number to which the transparent area belongs and the identification within the group are provided near both the transparent area and the circle mark. Display the number. Window 1
It is also possible to facilitate the distinction by displaying circles and line segments belonging to each group in 4 in different colors for each group.

Further, since the position where the shifter cannot be arranged corresponds to a closed loop composed of an odd number of circles on the graph, the loop 15 in the window 14
By highlighting a loop composed of an odd number of circles such as, it becomes easy to find a portion in the group where shifter placement was impossible.

Next, the control operation of the control section 5 when the shifter automatic verification section 10 or the shifter placement / verification section 11 is selected will be described with reference to the flowchart of FIG.

The data to be processed is input from the memory 12 or the pattern data storage unit 6 and classified into groups (steps 111 and 112). A shifter is provisionally placed on one of a pair of adjacent transparent regions with the shortest distance between the transparent regions being less than r (step 113). The shifter arrangement that has already been arranged is compared with the temporarily arranged shifter arrangement (step 114).

Then, the shifter arrangement information and the group information are written in the memory 12 or the pattern data storage unit 6 (step 115). The verification result is displayed in the form of an execution report (step 116). In Figure 10,
The display example of an execution report is shown.

The contents of the execution report are the total number of groups existing in the shifter placement verification target area, the number of groups that could be shifted and their group numbers, the number of groups that could not be shifted and could not be shifted, and their numbers. The group number, the number of groups that can be arranged, but the number of groups in which there is an error in the already arranged shifter arrangement, and the group number.

Further, more detailed information is displayed by selecting the shifter layout display, the graph display, or the error display (steps 117 to 12).
0). When the shifter arrangement display is selected, the shifter arrangement arranged in the group in which the shifter arrangement is possible is displayed. The display example is the same as in FIG. 7. A display example when the graph display is selected is the same as in FIG.

FIG. 11 shows a display example when the error display is selected. A new window 17 is opened near the currently opened window 16. Despite the shifter placement being possible, the transparent area (shaded area) of the group and the correct temporary shifter placement (broken line) are displayed in the window 17 only for the group that has already been placed but the shifter placement is incorrect.
To display. The original window 16 shows the transparent area (hatched portion) of the group and the erroneous shifter arrangement (broken line) that has already been arranged. Window 16 and window 1
By comparing 7 with each other, it is possible to examine a portion where the shifter arrangement has an error.

Third Invention Next, an embodiment of the photomask designing apparatus of the third invention will be described in detail.

FIG. 12 is a block diagram showing the structure of a photomask designing apparatus according to the third invention.

In the figure, the photomask designing apparatus of this embodiment is roughly composed of a control section 5 ', a pattern data storage section 6, an input section 7, and a display section 8. , A shifter automatic arrangement unit 9 ′, a shifter automatic verification unit 10 ′, a hierarchical structure recognition unit 13, and a memory 12.

The input unit 7 is an input device such as a keyboard or a mouse, and selects one of the functions of the shifter automatic arrangement unit 9'and the shifter automatic verification unit 10 'to instruct execution.

The control unit 5'is composed of a microprocessor and performs data processing described later according to a control program written in the memory 12. When the execution is instructed, the layout data to be processed is input to the hierarchical structure recognition unit 13 from the memory 12 or the pattern data storage unit 6.

The hierarchical structure recognizing unit 13 determines the order of processing the cells in the layout data input, and the shifter automatic arrangement unit 9'or the shifter automatic verification unit 10 'performs a predetermined process in the determined order. .. The result is displayed on the display unit 8 such as a CRT. Further, for cells for which shifter arrangement has been performed without contradiction, the hierarchical structure recognition unit 13 gives a recognition flag of shifter arrangement completion, and the processing result is written in the pattern data storage unit 6 or the memory 12.

Next, the control operation of the hierarchical structure recognition section 13 in the photomask designing apparatus of this embodiment will be described with reference to the flow chart shown in FIG.

Data to be processed is input from the memory 12 or the pattern data storage unit 6. Here, as an example, consider a case where layout data having a hierarchical structure as shown in FIG. 14 is input. The hierarchical structure in FIG. 14 indicates that, for example, the cell A is composed of three cells B, and one cell C and one cell D, respectively. Therefore, from the lower part to the upper part of FIG. Further, it is assumed that the cells with an asterisk (*) have been previously assigned with a shifter-arranged recognition flag.

The hierarchical structure recognizing unit 13 first selects the cell at the lowest position in the hierarchical structure from the cells that do not have the shifter-allocated recognition flag, and designates that cell as the shifter allocation processing target cell (hereinafter referred to as the current cell). (Step 121) and the layout data of the current cell is input to the shifter automatic arrangement unit 9 ′ or the shifter automatic verification unit 10 ′ (Step 123).

Next, the shifter automatic arrangement unit 9'or the shifter automatic verification unit 10 'performs the shifter automatic arrangement process or the shifter automatic verification process on the cell thus input (step 124). In the example of FIG. 14, processing is performed in the order of cell E, cell B, cell D, and cell A.

As a result of the processing of the shifter automatic arrangement unit 9'or the shifter automatic verification unit 10 ', if the shifter can be arranged without any contradiction or error, the hierarchical structure recognition unit 13
A recognition flag in which shifters have been arranged is added to the cell (step 125). In this way, the hierarchical structure recognition unit 1
In 3, the cells to be processed are sequentially determined, and the control operation ends when all the cells have the shifter-arranged recognition flag (step 126).

In addition to this, in the hierarchical structure recognizing unit 13, when the layout is changed after the shifter-arranged recognition flag is given to a cell, the shifter-arranged recognition flag of the cell and the cell are set as lower cells. It also has the function of removing the shifter-arranged recognition flags of all cells including as. For example, if the shifter-arranged recognition flag is added to all the cells in FIG.
When the layout is changed, the shifter arranged recognition flags of the cells B, D, and A are removed.

Next, the control operation of the shifter automatic arrangement unit 9'in the photomask designing apparatus of this embodiment will be described with reference to the flow chart shown in FIG.

First, the current cell data is input from the hierarchical structure recognition section 13 (step 131). The patterns in the cell are divided into a set of adjacent patterns (hereinafter, referred to as a group) when the shortest distance r between them is less than a certain threshold value s (step 132). As the method of determining the threshold value s, the method described in the photomask designing method of the first invention is used.

Here, the grouping will be described using the example shown in FIG. FIG. 16 shows a case where each cell is composed of a group (lower group) generated by a plurality of lower cells. For example, lower group C
-1, B-2, and D-2 and patterns 1 and 2 are included in the same group, but subordinate group D-2
And the lower group C-1 may be included in the same group even if they are not adjacent to each other.

Next, in each group, in the group including the lower group, the shifter automatic arrangement is performed for the patterns not included in the lower group (step 124). If the shifter automatic placement results in a contradiction in the shifter placement, the location is presented to the designer (step 138). Here, the method of automatically arranging shifters and the method of presenting inconsistent points to the designer are the same as those of the photomask designing apparatus of the second invention.

As a result of automatic shifter placement, if shifter placement is possible without contradiction, if shifters are placed between lower groups,
And the relative position between the lower group and the pattern included in the current cell is determined (step 135). That is, at the boundary between a certain lower group and the adjacent lower group or pattern, the phases are determined so that the phases of the adjacent patterns that are less than the threshold value s are mutually inverted. As a result, if a contradiction occurs, the contradiction is presented to the designer (step 138).

On the other hand, if the lower group is not included in the group, shifter automatic arrangement is performed for the group (step 136). As a result of automatic shifter placement,
If there is a contradiction in the shifter layout, the location is presented to the designer (step 138). Further, as a result of automatic shifter placement, if shifter placement is possible without contradiction, three pieces of information of the current cell, group identification number, and phase are added to each pattern (step 137).

The above steps 133 to 138
The processes up to are performed for all groups (step 139).

Incidentally, the three pieces of information of the current cell, the group identification number and the phase given in step 137 are:
In the case where it is applied to one pattern a plurality of times, these pieces of information are sequentially stored and the newest one is recognized as the current state. Further, when the shifter-arranged recognition flag is removed due to a layout change or the like, three pieces of information describing the cell from which the shifter-arranged recognition flag is removed as the current cell are also removed. That is, the current cell, group identification number, and phase information of each pattern must correspond to the cell having the shifter-arranged recognition flag.

Next, the control operation of the shifter automatic verification unit 10 'in the photomask designing apparatus of this embodiment will be described with reference to the flow chart shown in FIG.

First, the current cell data is input from the hierarchical structure recognizing section 13 (step 141), and thereafter, grouping and phase determination are performed, but steps 141 to 1
The processes of 46 and 148 are the same as the processes of steps 131 to 136 and 138 in the shifter automatic arrangement unit 9 ′.

As a result of the automatic placement processing in steps S144 and 145 or step 146, the groups that have no contradiction are compared with the phase input by the designer (step 149). That is, it is verified whether the input phase matches the phase determined as described above (temporary arrangement). The phases determined as described above may be inverted for each group and then compared.

If there is an error in the input phase, the location is presented to the designer (step 150). Here, the method of presenting an error is the same as that of the photomask designing apparatus of the second invention. If there is no error, the three information of the current cell, the group identification number, and the phase is added to each pattern (step 15).
1).

The above steps 143 to 151
The processes up to are performed for all groups (step 152).

[0090]

As described above, according to the first aspect of the present invention, since the shifter is arranged according to the shortest distance of the transparent region, it is possible to prevent wasteful shifter arrangement and improve the design efficiency of the photomask. Can be improved.

According to the second aspect of the invention, the automatic shifter placement function and the automatic verification function are provided for the masks already placed. This makes it possible to present reference information for correcting a portion where shifter placement is impossible or when there is an error in shifter placement.

According to the third invention, when layout data having a hierarchical structure is input, the shifter automatic placement and the shifter automatic verification are performed while maintaining the hierarchical structure. It is possible to avoid problems such as an increase in the amount of data and an increase in data processing time due to the expansion of the structure.

Further, according to the third invention, when the result of the shifter automatic placement processing or the automatic verification processing is that the phase shifter can be placed in the cell to be processed without contradiction, the hierarchical structure recognition means selects the phase shifter. On the other hand, since the recognition flag indicating that the shifter has been arranged is added, the cell is not processed a plurality of times, and the shifter automatic arrangement process and the automatic verification process can be made efficient.

[Brief description of drawings]

FIG. 1 is a plan view of a photomask in which transparent regions of various shapes and sizes are formed for explaining an embodiment according to the first invention.

2 is a cross-sectional view taken along the line x-x 'of FIG.

FIG. 3 is a mask plan view for explaining a method of obtaining a threshold value.

FIG. 4 is a block diagram showing a configuration of an embodiment relating to a photomask designing apparatus of a second invention.

5 is a flowchart showing an operation procedure of the shifter automatic arrangement unit shown in FIG.

6 is a display example of an execution report displayed by the shifter automatic arrangement unit shown in FIG.

FIG. 7 is a display example of shifter arrangement displayed according to the second invention.

FIG. 8 is a display example of a graph display displayed by the second invention.

9 is a flowchart showing an operation procedure of a shifter automatic verification unit and a shifter arrangement / verification unit shown in FIG.

10 is a display example of an execution report displayed by the shifter automatic verification unit and the shifter placement / verification unit illustrated in FIG.

11 is a display example of an error display displayed by the shifter automatic verification unit and the shifter arrangement / verification unit illustrated in FIG.

FIG. 12 is a block diagram showing a configuration of an embodiment relating to a photomask designing apparatus of a third invention.

13 is a flowchart showing an operation procedure of the hierarchical structure recognition section shown in FIG.

FIG. 14 is a hierarchical structure diagram illustrating an example of layout data having a hierarchical structure.

FIG. 15 is a flowchart showing an operation procedure of the shifter automatic arrangement unit shown in FIG.

FIG. 16 is a mask plane for explaining an example of layout data having a hierarchical structure.

FIG. 17 is a flowchart showing an operation procedure of the shifter automatic verification unit shown in FIG.

FIG. 18 is a cross-sectional view of a general Levenson-type phase shift mask.

FIG. 19 is a plan view of a mask for explaining a defect in a conventional shifter arrangement.

FIG. 20 is a mask plan view for explaining an example of layout data having a hierarchical structure.

[Explanation of symbols]

 1 Mask substrate 2 Light-shielding part (opaque region) 3 Phase shifter 4, ag Transparent region x Transparent region width y Transparent region length t Distance between transparent regions 5, 5'Control unit 6 Pattern data storage unit 7 Input Part 8 Display part 9,9 'Shifter automatic placement part 10, 10' Shifter automatic verification part 11 Shifter placement / verification part 12 Memory

Claims (5)

[Claims] 1. When designing a photomask which is used in photolithography with partially coherent incident light and in which a plurality of opaque and transparent regions are formed, the incident light passing through the transparent region is positioned in relation to the incident light. A method for designing a photomask, characterized in that a phase shifter that gives a phase difference is arranged in one of a pair of adjacent transparent regions whose shortest distance between the transparent regions is less than a threshold value. 2. A photomask used in photolithography with partially coherent incident light, wherein a plurality of opaque areas and transparent areas are formed on a transparent area of the photomask, the incident light passing through the transparent area being located above the transparent area. A phase shifter that gives a phase difference is automatically arranged on one of a pair of adjacent transparent areas where the shortest distance between the transparent areas is less than a threshold value, and on a photomask where the phase shifter is already entirely arranged. On the other hand, automatic verification means that automatically verifies that the phase shifter is placed correctly, and for the photomask where the phase shifter is already partially placed, the transparent area where the phase shifter is placed Automatically verifies that the phase shifter placement is correct, and for transparent areas where the phase shifter is not placed,
A photomask provided with at least one means of an arrangement / verification means for automatically arranging a phase shifter in one of a pair of transparent areas adjacent to each other when the shortest distance between the transparent areas is less than a threshold value. Design equipment. 3. A photomask used in photolithography with partially coherent incident light, wherein a plurality of opaque regions and transparent regions are formed on a transparent region of the photomask, the incident light passing through the transparent region being located above the transparent region. A phase shifter that gives a phase difference is automatically arranged on one of a pair of adjacent transparent areas where the shortest distance between the transparent areas is less than a threshold value, and on a photomask where the phase shifter is already entirely arranged. On the other hand, at least one of automatic verification means for automatically verifying whether or not the arrangement of the phase shifter is correct is provided, and a hierarchy has the opaque area and / or cell (the cell is the opaque area and / or one lower layer). When the layout data having a hierarchical structure composed of cells (of cells of And / or as a result of the processing of the automatic verification means, when the phase shifter can be arranged in the cell to be processed without contradiction, a recognition flag indicating that the shifter has been arranged is added to the cell, and in the layout data, A photomask designing apparatus comprising: a hierarchical structure recognition means for selecting a cell located in the lowest hierarchy among cells not having a recognition flag as a processing target. 4. The automatic placement means inputs the data of the processing target cell selected by the hierarchical structure recognizing means, and sets the set element in the processing target cell to a threshold value having a minimum distance from each other. For a group that does not include subordinate cells within the group, the step of dividing into a set of adjacent set elements (hereinafter referred to as a group)
The step of determining the topology for all set elements, and the group defined by the subordinate cells in the group (hereinafter,
A group including a lower group), a phase is determined for a collective element that is not included in the lower group, and a relative phase is determined between the lower groups and between the lower group and the collective elements that are not included in the lower group. And, if it is possible to give a phase to the whole area of the group without contradiction, a step of giving a processing target cell name, a group identification number, and a phase value to a set element included in the group, The phase shifter is arranged by an automatic arrangement method including a step of presenting a place where the contradiction has occurred to a designer when the contradiction occurs in the determination of the phase in the cell. Photomask design device. 5. The automatic verification means inputs the data of the processing target cell selected by the hierarchical structure recognizing means, and sets the set element in the processing target cell to a threshold value having a minimum distance from each other. For a group that does not include subordinate cells within the group, the step of dividing into a set of adjacent set elements (hereinafter referred to as a group)
The step of determining the topology for all set elements, and the group defined by the subordinate cells in the group (hereinafter,
A group including a lower group), a phase is determined for a collective element that is not included in the lower group, and a relative phase is determined between the lower groups and between the lower group and the collective elements that are not included in the lower group. When it is possible to give a phase to the whole area of the group without contradiction, the phase determined by the automatic verification means is compared with the phase input in advance. It is presented to the designer, and if there is no error, the step of assigning the processing target cell name, the group identification number, and the phase value to the set elements included in the group, and the step of determining the phase in the processing target cell. When a contradiction occurs, the placement of the phase shifter is automatically verified by an automatic verification method having a step of presenting the part where the contradiction has occurred to the designer. The photomask design apparatus according to claim 3, wherein the door.