JP4838836B2 - Lithographic data correction apparatus and recording medium storing program for causing computer to perform processing in the apparatus - Google Patents

Description

  The present invention relates to a lithography data correction apparatus, and more particularly to a lithography data correction apparatus that performs proximity effect correction of lithography data of a semiconductor integrated circuit. The present invention also relates to a recording medium storing a program for causing a computer to perform processing in such a lithography data correction apparatus.

  Semiconductor integrated circuits, so-called ICs (Integrated Circuits) and LSIs (Large Scale ICs) that have come to be applied to all industrial fields, are becoming increasingly highly integrated due to significant advances in microlithography and photoresists (Photoresist). Progressing.

  The microlithography is classified according to the type of the source of the apparatus for forming a fine pattern, and includes, for example, photolithography, X-ray lithography, electron beam lithography, and ion beam lithography.

  Here, photolithography will be described as an example of microlithography. Photolithography is a microfabrication method using light (visible, ultraviolet, and far ultraviolet light) as a light source, and has been used from the early stage of semiconductor integrated circuit development. In photolithography, a resist pattern is generated by exposing a resist by irradiating light through a mask pattern as an original drawing.

  By the way, with the miniaturization of mask patterns accompanying high integration of LSIs and the like, it has become difficult to accurately draw physical layouts of LSIs and the like, and it is necessary to correct the mask pattern manufacturing data. It has become. Here, the proximity effect correction refers to correcting a difference between a mask pattern dimension and a resist pattern dimension that are expected to be generated according to layout parameters such as a pattern width and a distance from an adjacent pattern.

  As a method for correcting the proximity effect, for example, there is a method shown in FIG. FIG. 1A shows a method of changing the mask pattern width according to the distance from the adjacent mask pattern. FIG. 1B shows a method of arranging a rectangle at the apex of the mask pattern. FIG. 1C shows a method of disposing a mask pattern that does not resolve between mask patterns. As described above, the mask pattern shape is prevented from being deteriorated by FIGS. 1 (A) to 1 (C).

  Another method of proximity effect correction is, for example, rule base correction. In the rule-based correction, the correction amount is created in advance as a two-dimensional or three-dimensional table with the layout pattern parameters such as the mask pattern width and the distance from the adjacent mask pattern as axes. This table is created, for example, as shown in FIG.

  In the table of FIG. 2, the vertical axis represents the mask pattern width and the horizontal axis represents the distance to the adjacent mask pattern as parameters. For example, the mask pattern width is 0.2 μm and the adjacent mask pattern distance is 0. In the case of 25 μm, the correction amount is 0.01 μm. As described above, in the rule base correction, the mask pattern is corrected according to the table as shown in FIG.

  However, the conventional proximity effect correction method has a problem that appropriate correction cannot be performed according to the layout environment.

  For example, in the method of FIG. 1A, since only the distance to the adjacent mask pattern is considered, it is not possible to perform appropriate correction according to the layout environment. The methods of FIGS. 1B and 1C tend to increase the amount of data from several times to several tens of times, and the amount of data is in units of gigabytes due to high integration of current LSIs. Considering the current situation, the burden on the recording medium is large and the practicality is poor. Further, the proximity effect correction is performed on the portions having different layout environments, so that overcorrection may occur and a short circuit may occur in the mask pattern.

  On the other hand, the rule-based correction has a problem that the shape of the mask pattern after correction becomes more complex and the amount of data increases as finer proximity effect correction is performed, as in FIGS. 1B and 1C. there were. Such an increase in the amount of data makes it difficult to store and transfer data. In addition, as the mask pattern shape becomes more complicated, there is a problem in that similar portions of data are reduced and compression efficiency is lowered.

  The present invention has been made in view of the above points, and a first object of the invention is to provide a lithography data correction apparatus capable of performing proximity effect correction according to a layout environment.

  It is a second object of the present invention to provide a lithography data correction apparatus capable of suppressing an increase in data amount due to proximity effect correction.

  It is a third object of the present invention to provide a recording medium storing a program for causing a computer to perform processing in such a lithography data correction apparatus.

  Accordingly, in order to solve the above-mentioned problem, the present invention according to claim 1 is directed to a rounding calculation error generated when converting data for design layout to data for lithography in a data correction apparatus for lithography that corrects data for lithography. Error correction means for correcting, correction value determining means for determining a correction value for a mask pattern based on the lithography data based on a layout environment around the mask pattern, and deterioration due to exposure among corrections by the correction value Correction portion adjusting means for adjusting a correction portion that does not affect the correction.

  In this way, by correcting the rounding calculation error and adjusting the unnecessary correction portion of the correction portion based on the determined correction value, it is possible to suppress an increase in the corrected mask pattern data.

  For example, the amount of data of mask pattern data is steadily increasing with the high integration of LSI and the like. Therefore, by suppressing the increase in the mask pattern data after correction, processes such as data verification, transfer, and processing can be facilitated.

  According to the present invention, the correction part adjustment unit includes a fine correction part deletion unit that deletes a fine correction part that does not affect exposure among the corrections by the correction value, and the peripheral layout environment. And redundant correction part deletion means for deleting redundant correction parts that do not affect the exposure.

  As described above, the correction effect by the determined correction value is eliminated by removing the fine correction portion that does not affect the exposure and the redundant correction portion that does not affect the exposure due to the surrounding layout environment. It is possible to suppress an increase in the corrected mask pattern data without reducing it.

  According to a third aspect of the present invention, the error correction unit sets the angle formed by the mask pattern based on the lithography data to a double angle of 45 degrees.

  In this way, the rounding calculation error can be eliminated by setting the angle formed by the mask pattern based on the lithography data to a double angle of 45 degrees. When the rounding calculation error disappears, the data portion similar to the mask pattern data increases, and it is possible to greatly compress the data by iterative processing. Accordingly, it is possible to suppress an increase in mask pattern data after correction.

  According to a fourth aspect of the present invention, the correction value determining means corrects the mask pattern according to deterioration due to exposure based on the width of the mask pattern and the distance between the mask pattern and another mask pattern. It has a correction table in which values are set, and a correction value selection means for selecting a mask pattern correction value from the correction table.

  As described above, it is possible to obtain an optimum correction value by having a correction table in which correction values are set based on the width of the mask pattern and the distance between the mask pattern and another mask pattern.

  According to a fifth aspect of the present invention, there is provided a recording medium storing a program for causing the computer apparatus to perform processing in the lithography data correction apparatus for correcting the lithography data, from the design layout data to the lithography data. An error correction procedure for correcting a rounding calculation error occurring when converting to a mask pattern based on the lithography data, a correction value determination procedure for determining a correction value based on a layout environment around the mask pattern, A program having a correction part adjustment procedure for adjusting a correction part that does not affect the correction of deterioration due to exposure among the corrections by the correction value is stored.

  The recording medium for storing this program is a magnetic recording medium for magnetically recording information such as a CD-ROM, a flexible disk, a magneto-optical disk (MO), etc., and an electric information such as a ROM or flash memory. Various types of recording media such as a semiconductor memory for recording data can be used.

  As described above, according to the first aspect of the present invention, the correction of the rounding calculation error is performed, and an unnecessary correction portion of the correction portion based on the determined correction value is adjusted, thereby increasing the mask pattern data after correction. It becomes possible to suppress.

  For example, the amount of data of mask pattern data is steadily increasing with the high integration of LSI and the like. Therefore, by suppressing the increase in the mask pattern data after correction, processes such as data verification, transfer, and processing can be facilitated.

  According to the second aspect of the present invention, the fine correction portion that does not affect the exposure among the correction portions based on the determined correction value, and the redundant correction portion that does not affect the exposure due to the surrounding layout environment are provided. By deleting, it is possible to suppress an increase in mask pattern data after correction without reducing the effect of correction.

  According to the third aspect of the present invention, the rounding calculation error can be eliminated by setting the angle formed by the mask pattern based on the lithography data to a double angle of 45 degrees. When the rounding calculation error disappears, the data portion similar to the mask pattern data increases, and it is possible to greatly compress the data by iterative processing. Accordingly, it is possible to suppress an increase in mask pattern data after correction.

  According to the fourth aspect of the present invention, the optimum correction value is obtained by having the correction table in which the correction value is set based on the width of the mask pattern and the distance between the mask pattern and another mask pattern. Can be obtained.

  According to the fifth aspect of the present invention, in a recording medium storing a program for causing the computer apparatus to perform processing in the lithography data correction apparatus that corrects lithography data, lithography can be performed from design layout data. Correction procedure for correcting a rounding calculation error that occurs when converting to data for correction, and a correction value determination procedure for determining a correction value for a mask pattern based on the lithography data based on a layout environment around the mask pattern And a correction part adjustment procedure for adjusting a correction part that does not affect the correction of deterioration due to exposure among the corrections by the correction value.

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

  FIG. 3 shows a block diagram of an embodiment of a data correction apparatus for lithography according to the present invention. The lithography data correction apparatus 1 of FIG. 3 includes a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 12, a ROM (Read Only memory) 14, and an external storage device 16.

  The CPU 10 reads LSI design layout data from the external storage device 16 and writes it to the RAM 12, and converts the design layout data into mask pattern data. The converted mask pattern data is subjected to proximity effect correction according to a flowchart to be described later, and then written to the external storage device 16.

  The proximity effect correction of the present invention is performed according to the procedure shown in the flowchart of FIG. FIG. 4 shows a flowchart of the first embodiment showing processing of the lithography data correction apparatus of the present invention. In step S <b> 100, the CPU 10 reads out the mask pattern data generated from the design layout data from the external storage device 16 and writes it in the RAM 12.

  In step S 110, a table as shown in FIG. 5 is read from the external storage device 16 and written to the RAM 12. The table can also be read from the ROM 14. The table of FIG. 5 includes a tip correction parameter indicating information necessary for proximity effect correction such as a minimum limit value of mask pattern width, a minimum limit distance between mask patterns, a line correction table used for line correction described later, and an I-shaped correction. The I-shaped correction table used for the T-shaped correction, the T-shaped correction table used for T-shaped correction, and the hammer head table used for adding the hammer head.

  Progressing to step S120 following step S110, a side for performing line correction for controlling the mask pattern width and a side for performing front end correction for controlling the front end portion of the mask pattern are classified. The side for performing line correction and the side for performing front end correction can be classified, for example, according to the ratio of the width X and length Y of the resist pattern shown in FIG. This classification is a phenomenon that occurs particularly in the case of a long and narrow mask pattern. However, when a resist pattern is generated by exposing a resist, it corresponds to the fact that the degree of deterioration differs between the long side and the short side.

  For example, FIG. 7 is an explanatory diagram showing an example of a deterioration state when a resist pattern is generated from an elongated mask pattern. When a resist pattern is generated by exposing the resist based on the mask pattern of FIG. 7, the long side portion deteriorates in an increasing direction as compared with the original mask pattern, and the tip portion corresponding to the short side portion is the original mask. It is deteriorated in the direction of decreasing compared to the pattern. Accordingly, the long side portion and the short side portion of the elongated mask pattern, in other words, the side for performing line correction of the mask pattern and the side for performing tip correction are classified.

  Subsequent to step S120, the process proceeds to step S130, in which the edge to be corrected in the tip classified in step S120 is further classified into an I-shape and a T-shape. This classification corresponds to the fact that the degree of deterioration is different when a resist pattern is generated if the layout environment is different even if the interval between mask patterns is the same.

  For example, FIG. 8 illustrates an example of a case where a resist pattern is generated from a mask pattern in different layout environments. When similar proximity effect correction is performed in the layout environment shown in FIG. 8A and the layout environment shown in FIG. 8B and a resist pattern is actually generated from the mask pattern, the degree of deterioration differs depending on the layout environment. .

  Specifically, the degree of deterioration is larger in the case of the layout environment shown in FIG. 8A, and the degree of deterioration is smaller in the case of the layout environment shown in FIG. 8B. In FIG. 8B, there is a possibility of short-circuiting due to overcorrection even if the correction is properly performed. Therefore, as shown in FIG. 9, the I-shaped tip and the T-shaped tip are classified according to the layout environment. FIG. 9 illustrates an example of an I-shaped tip and a T-shaped tip.

  Progressing to step S140 following step S130, the sides of the mask pattern are divided according to the correction rule. Progressing to step S150 following step S140, the correction values of the sides divided in step S140 are used as the line correction table used for line correction shown in FIG. 5, the I-character correction table used for I-character correction, and the T-character correction. It is determined according to the T-shaped correction table used for the above. Note that a negative correction value described in each table indicates a correction for reducing the drawing, and a positive correction value indicates a correction for expanding the drawing.

  Subsequent to step S150, the process proceeds to step S160, where a portion that falls below the resolution limit when the correction is actually performed with the correction value determined in step S150 is detected. Here, the resolution limit is determined by the resolution limit of the reticle writer and the exposure resolution limit of the resist, and is set to, for example, the tip correction parameter shown in FIG.

  As shown in the tip correction parameter, the resolution limit is different between the I-shaped tip and the T-shaped tip, and if correction is performed with the correction value as it is, the T-corrected portion can be short-circuited due to overcorrection. This is a process for coping with the occurrence of sex.

  Progressing to step S170 following step S160, the correction amount of the portion detected in step S160 is decreased, and a hammer head for compensating the decreased amount is added as shown in FIG. FIG. 10 illustrates an example of a process for adding a hammerhead.

  The correction pattern portion 20 is corrected by the correction value originally determined according to the proximity effect correction in the portion of the T-shaped tip of the mask pattern in FIG. However, in the correction using this correction value, the distance between the mask patterns is less than the resolution limit. If correction is performed with the correction value as it is, there is a possibility that the T-shaped correction portion may be short-circuited due to overcorrection. . Therefore, a hammer head 21 is added to reduce the correction amount of the correction pattern portion 20 determined according to the proximity effect correction and compensate for the decrease.

  Further, in step S170, the T-shaped tip portion of the mask pattern before correction and the portion where the distance between the mask patterns is less than the resolution limit is also shown in FIG. A hammer head 21 is added to correct the direction of retracting the die tip and compensate for the decrease.

  Progressing to step S180 following step S170, the addition of the hammer head detects a portion where the distance between the hammer head and the mask pattern adjacent to the hammer head is less than the resolution limit.

  Progressing to step S190 following step S180, as shown in FIG. 12, the width of the hammer head at the portion detected in step S180 is reduced, and the distance between the hammer head and the mask pattern adjacent to the hammer head is reduced. Correction is performed so that the distance does not fall below the resolution limit. FIG. 12 is an explanatory diagram of an example for correcting the width of the hammer head.

  As described above, optimal proximity effect correction can be performed by the processing shown in the flowchart of FIG.

  Next, another embodiment of the present invention will be described with reference to the drawings. This embodiment is performed according to the procedure shown in the flowchart of FIG. FIG. 13 shows a flowchart of the second embodiment showing the processing of the lithography data correction apparatus of the present invention.

  In step S200, the design layout data is converted into mask pattern data. In general, design layout data is often designed in a unit smaller than a unit that can be expressed by mask pattern data, and a rounding calculation error occurs during data conversion.

  FIG. 14 is an explanatory diagram illustrating an example of the cause of the rounding calculation error. For example, when the design layout data shown in FIG. 14A is converted into mask pattern data, it is unavoidable that rounding calculation errors as shown in FIGS. 14B and 14C occur due to the difference in units. Absent.

  However, the variation in the mask pattern shape due to this rounding calculation error causes an increase in the amount of data. FIG. 15 illustrates an example of a difference in data amount depending on the mask pattern shape. For example, if the mask pattern has the same shape as shown in FIG. 15A, the amount of data is small because it can be expressed by repeating the same data, but if the mask pattern shape varies as shown in FIG. Since it cannot be expressed by repeating, the amount of data increases.

  Therefore, in step S210, the variation in the mask pattern shape based on the rounding calculation error that occurs during data conversion is deleted by correction. FIG. 16 is an explanatory diagram illustrating an example of correcting variations in the mask pattern shape. In general, a rounding calculation error caused by conversion from a fine unit to a coarse unit is one unit. The design layout data generally uses a double angle of 45 degrees.

  Therefore, for example, in the case of FIGS. 16A and 16B, rounding as shown in FIG. 16C is performed by correcting the positions of the vertices 30 and 31 so that the angle is a double angle of 45 degrees. It is possible to eliminate calculation errors.

  Proceeding to step S220 following step S210, proximity effect correction is performed according to the correction rules shown in the table as shown in FIG. FIG. 17 illustrates an example of proximity effect correction. When the proximity effect correction is performed on the mask pattern as shown in FIG. 17A according to the correction rule shown in the table of FIG. 2, the mask pattern is corrected as shown in FIG.

  Specifically, the mask pattern of FIG. 17A is composed of an upper mask pattern 35 and a lower mask pattern 36, and the side of the mask pattern 36 that faces the mask pattern 35 has its mask pattern width. There are three layout environments 37, 38, and 39 depending on the distance between the mask patterns.

  The layout environment 37 has a mask pattern width of 0.2 μm and a distance between mask patterns of 0.25 μm, and a correction amount of 0.01 μm is obtained from the table of FIG. The layout environment 38 has a mask pattern width of 0.2 μm and a distance between mask patterns exceeding 0.3 μm, and a correction amount of 0.03 μm is obtained from the table of FIG.

  The layout environment 39 has a mask pattern width of 0.6 μm and a distance between mask patterns exceeding 0.3 μm, and a correction amount of 0 μm can be obtained from the table of FIG. Therefore, the mask pattern as shown in FIG. 17A is corrected to the mask pattern as shown in FIG.

  However, it is expected that a fine correction portion such as the correction portion 42 in FIG. 17B is not reflected on the resist pattern to be created due to the exposure resolution limit of the resist. On the other hand, when such complicated and fine portions increase, the amount of data increases, which causes a problem.

  Therefore, the process proceeds to step S230 following step S220, and correction is performed to delete complicated and fine portions that are not reflected in the resist pattern created by the correction. When the process of step S230 is performed, the mask pattern in FIG. 17B becomes a simple mask pattern as shown in FIG. Progressing to step S240 following step S230, correction for deleting redundant portions from the mask pattern created by the proximity effect correction in step S220 is performed. FIG. 18 illustrates an example of proximity effect correction.

  When the proximity effect correction is performed on the mask pattern shown in FIG. 18A, the mask pattern is corrected as shown in FIG. In the correction portions 45 and 47 in FIG. 18B, the mask pattern width and the distance between the mask patterns are the same, and the correction amount is the same. Further, the correction portions 46 and 48 in FIG. 18B have the same mask pattern width and the same distance between the mask patterns, and the correction amount is the same.

  However, it has been confirmed that in the actually created resist pattern, the correction portions 47 and 48 are not deteriorated compared to the extent that the correction portions 45 and 46 are deteriorated. Therefore, correction is performed to delete a correction portion with a small degree of deterioration. When the process of step S240 is performed, a mask pattern as shown in FIG.

  Progressing to step S250 following step S240, the mask pattern data after the proximity effect correction is compressed. In the compression processing in step S250, the processing for reducing the data amount of the mask pattern has already been performed in steps S200 to S240, and the mask pattern data can be greatly compressed.

  As described above, the flowchart of FIG. 4 and the flowchart of FIG. 13 have been described separately, but it is naturally possible to perform the two processes in combination, and efficient proximity effect correction and data amount reduction are possible.

  The error correction means described in the claims corresponds to the process in step S210, the correction value determination means corresponds to the process in step S220, and the correction part adjustment means corresponds to the process in steps S230 to S240. The fine correction portion deletion means corresponds to the processing in step S230, the redundant correction portion deletion means corresponds to the processing in step S240, the correction table corresponds to the table in FIG. 2, and the correction value selection means corresponds to step S220. It corresponds to the processing in.

It is explanatory drawing of an example of proximity | contact effect correction | amendment. It is explanatory drawing of an example of the table for rule base correction | amendment. It is a block diagram of one Example of the data correction apparatus for lithography of this invention. It is a flowchart of the 1st Example which shows the process of the data correction apparatus for lithography of this invention. It is an example table which shows a correction rule. It is explanatory drawing of an example of the edge | side used as the object of front-end | tip correction and line correction. It is explanatory drawing of an example which shows the mode of degradation when a resist pattern is produced | generated from an elongate mask pattern. It is explanatory drawing of an example in the case of producing | generating a resist pattern from a mask pattern in a different layout environment. It is explanatory drawing of an example of an I-shaped front-end | tip and a T-shaped front-end | tip. It is explanatory drawing of an example which adds a hammer head. It is explanatory drawing of an example which adds a hammer head. It is explanatory drawing of an example which correct | amends the width | variety of a hammer head. It is a flowchart of 2nd Example which shows the process of the data correction apparatus for lithography of this invention. It is explanatory drawing of an example of the cause which a rounding calculation error generate | occur | produces. It is explanatory drawing of an example of the difference in the data amount by a mask pattern shape. It is explanatory drawing of an example which corrects the variation in a mask pattern shape. It is explanatory drawing of an example of proximity | contact effect correction | amendment. It is explanatory drawing of an example of proximity | contact effect correction | amendment.

Explanation of symbols

1 Lithography Data Correction Device 10 CPU
12 RAM
14 ROM
16 External storage device 20 Correction pattern portion 21 Hammer head 30, 31 Vertex 35, 36 Mask pattern 37, 38, 39 Layout environment 42 Correction portion 45, 46, 47, 48 Correction portion

Claims (5)

In a lithography data correction apparatus for correcting lithography data,
Error correction means for correcting a rounding calculation error that occurs when data for design layout is converted to data for lithography;
A correction value determining means for determining a correction value based on the layout environment around the mask pattern based on the lithography data;
A lithographic data correction apparatus comprising: a correction part adjustment unit that adjusts a correction part that does not affect the correction of deterioration due to exposure among the correction values. The correction part adjusting means includes
Fine correction part deletion means for deleting a fine correction part that does not affect exposure among corrections by the correction value;
2. The lithography data correction apparatus according to claim 1, further comprising redundant correction portion deletion means for deleting redundant correction portions that do not affect exposure due to the peripheral layout environment. The error correction means includes
3. The lithography data correction apparatus according to claim 2, wherein an angle formed by the mask pattern based on the lithography data is a double angle of 45 degrees. The correction value determining means includes
Based on the width of the mask pattern and the distance between the mask pattern and another mask pattern, a correction table in which a correction value is set in accordance with deterioration due to exposure of the mask pattern;
4. The lithography data correction apparatus according to claim 3, further comprising correction value selection means for selecting a correction value of a mask pattern from the correction table. In a recording medium storing a program for causing the computer apparatus to perform processing in a lithography data correction apparatus that corrects lithography data,
An error correction procedure for correcting a rounding calculation error that occurs when data for design layout is converted to data for lithography,
A correction value determining procedure for determining a correction value based on a layout environment around the mask pattern based on the lithography data; and
A recording medium storing a program having a correction portion adjustment procedure for adjusting a correction portion that does not affect the correction of deterioration due to exposure among the correction values.

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