JP4900045B2 - Photomask shading band creating method and shading band data creating apparatus - Google Patents

Description

The present invention relates to a method for creating a light shielding band for a mask or a reticle (collectively referred to as a photomask) used for manufacturing a semiconductor device.
In a process step for manufacturing a semiconductor device, a wafer is exposed by a step-and-repeat method using a stepper. At this time, a light shielding band is provided outside the shot area that needs to be transferred to the wafer on the photomask so that only the shot area is transferred onto the wafer. In such an exposure process, it is necessary to prevent a reduction in exposure pattern accuracy due to exposure light scattering (flare).

  FIG. 6 shows an outline of wafer exposure processing by step-and-repeat. The photomask 1 is mounted on a stepper (not shown), is sequentially moved to a predetermined shot position, exposure processing is performed on the wafer surface, and exposure patterns 2a to 2d are sequentially exposed on the wafer surface.

  FIG. 7 shows an example of a photomask. That is, in the photomask 3, a light shielding band 5 is formed around the shot region 4 where a circuit pattern or the like is formed. In addition, an alignment mark 6 for aligning the photomask with a stepper device is formed outside the light shielding band 5.

  In recent years, the circuit pattern of a semiconductor device has been increasingly miniaturized. In a photomask for manufacturing a semiconductor device having a pattern formed with a minimum line width of 90 nm or 65 nm, the line width of a light-shielding band is 1.5 mm, for example. It is formed with.

  In the exposure process by the stepper device, the exposure light generated by the light source is narrowed down by a masking blade, and leakage of exposure light from the shot area to the outside is suppressed by a light shielding band formed on the photomask.

  FIG. 8 shows a process for creating a shading band by a CAD data creation device for frame data for creating a photomask. First, the coordinates around the shot area determined from the chip size and imposition number inside the shading band, the width of the dicing area, and the width of the shading band (fixed width, for example, 1.5 mm) in the shot area outside the shading band ) Is calculated (step 1), and a shading zone is created based on the coordinates (step 2).

  Next, the interference between the light shielding band and the alignment mark or the like is checked (step 3), and the presence or absence of interference is determined (step 4). If there is no interference, the creation of the shading band is terminated, and if there is interference, an error is output (step 5).

Then, based on the layout data of the light shielding band generated by such processing, the light shielding band is drawn on the mask substrate in the photomask manufacturing process, and a photomask having the light shielding band 5 as shown in FIG. Created.
JP 2002-367890 A JP 2006-220725 A

  In the exposure process using the stepper apparatus as described above, it is known that exposure light is scattered (flared) due to fogging of the optical system components as the usage time elapses. This flare reaches the exposed shot area located outside the light-shielding band and adversely affects the exposure pattern of the shot area.

  For example, as shown in FIG. 9, when the wafer surface is exposed by moving the photomask to the shot position P1, the flare reaches the wafer from the outside of the light shielding band, and the adjacent exposed shot area A is subjected to multiple exposure by the flare. As a result, there is a problem that the accuracy of the exposure pattern in the shot area A is lowered. With the recent miniaturization of the exposure pattern, even a small amount of flare has a serious effect on the accuracy of the exposure pattern, and the probability that a pattern defect will occur is high.

  The flare as described above increases with the use time of the stepper device, and can be reduced by replacing optical parts with increased haze. However, in order to reliably reduce flare, it is necessary to perform maintenance frequently, which increases the maintenance cost and increases the manufacturing cost of the semiconductor device.

  Japanese Patent Application Laid-Open No. 2004-151858 discloses a configuration in which a failure can be detected immediately from an exposure pattern when a failure occurs such that the shading band pattern overlaps the reticle pattern. However, a configuration for reducing exposure due to flare is disclosed. It has not been.

  Patent Document 2 discloses a photomask manufacturing method capable of preventing transfer of a pattern existing outside a chip region onto a wafer, but does not disclose a configuration for reducing exposure due to flare. .

  An object of the present invention is to provide a photomask shading band creating method and shading band data creating apparatus capable of suppressing exposure of shot areas due to flare and reducing maintenance costs.

  The above object is to provide a management value indicating the allowable upper limit of the flare amount by providing in advance a flare management table with the width of the photomask shading band required according to the amount of flare generated in the exposure apparatus and the maintenance cycle of the exposure apparatus. Based on the flare management table, the required shading band width is obtained from the flare management table.

  Further, the object is to store a photomask shading band data required according to the amount of flare generated in the exposure apparatus and the exposure apparatus maintenance cycle in advance as a flare management table; Based on the model information of the exposure apparatus for reading predetermined shading band width data from the flare management table, an input device for inputting a maintenance cycle and a flare amount management value, and information input from the input device, A data creation device that reads out the light shielding band width data from the flare management table and creates frame data having a desired light shielding bandwidth, and a second storage unit that stores the CAD data output from the data creation device. This is achieved by the photomask shading band data creation device provided.

  ADVANTAGE OF THE INVENTION According to this invention, the light-shielding zone preparation method and light-shielding zone preparation apparatus of a photomask which can suppress exposure of the shot area | region by flare and can reduce a maintenance cost can be provided.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a CAD data creation apparatus for forming a light shielding band of a photomask. The input device 11 is used when product information or the like is input to the data creation device 12. The chip size and the number of imposition dicing line widths are input as product information. In addition, the stepper device (exposure device) model and flare management are input. Values, maintenance cycles, etc. are input to the data creation device 12.

  The data creation device 12 is a CAD device and includes a library 13. In the library (first storage means) 13, a plurality of flare management tables A to C are stored in advance. Further, the data creation device 12 stores the shading zone CAD data (shading zone width data) created based on the product information and the flare management table in the output device (second storage means) 14.

  FIG. 2A shows an example of measurement of the distance from the end point of the shot area, that is, the inner edge of the light shielding band, and the flare amount in the stepper apparatus A. The curve L1 shown in the figure shows the measured flare amount immediately after the parts replacement, the curve L2 shows the measured flare amount about six months after the parts replacement, and the curve L3 shows about one year after the parts replacement. Indicates the measured flare amount. The amount of flare decreases as the distance from the end point increases, and increases as time elapses from maintenance such as component replacement.

  If the allowable flare amount is set as the flare management value FC, the flare amount exceeds the flare management value FC within a range of about 0.7 mm from the end point immediately after parts replacement, and about 6 months after the part replacement. The flare amount exceeds the flare management value FC in the range of 1.6 mm, and the flare amount exceeds the flare management value FC in the range of about 3 mm from the end point about one year after the parts replacement.

FIG. 2B shows a measurement example of the distance from the end point of the shot area and the flare amount in another stepper apparatus B.
FIG. 3 shows an example of the flare management table stored in the library 13. FIG. 3A shows a table of flare generation amount measurement results generated based on the flare amount measurement example shown in FIG. In this table, when the maintenance cycle is 1 month to 8 months, the amount of flare generated with a light shielding band width of 1 mm to 8 mm is stored as a table. This shading band width corresponds to the distance from the end point of the shot area in FIG.

  As shown in the figure, the flare amount increases as the maintenance period becomes longer and decreases as the shading band width becomes larger. In the flare management table shown in FIG. 3A, when the flare management value FC is set to 7%, for example, if the maintenance cycle is 6 months, a light shielding band width of 4 mm is required, and the maintenance cycle is 8 months. It can be seen that a 6 mm shading band width is required. FIG. 3B shows a similar flare management table in another stepper apparatus B.

  Next, the shading zone CAD data creation operation by the CAD data creation apparatus shown in FIG. 1 will be described with reference to FIG. First, the model of the stepper device used when manufacturing the target semiconductor device is input by the input device 11 (step 11), and then the flare management table corresponding to the model is selected (step 12).

  Next, a maintenance cycle is determined and input based on the manufacturing period of the target semiconductor device and the number of maintenance operations that can be performed within the manufacturing period (step 13). Then, a flare management value FC for ensuring exposure accuracy is set and input (step 14).

  Then, the data creation device 12 determines a necessary shading band width based on the selected flare management table, the maintenance cycle, and the flare management value FC (step 15), and is necessary for creating the shading band. Is calculated (step 16).

  Next, CAD data of a light shielding band is created based on the calculated coordinates (step 17), and an interference check between the marks such as alignment marks necessary for use in the stepper device and the created light shielding band is performed (step 17). Step 18).

  Then, the presence / absence of interference is determined (step 19), and if there is interference, a punching process is performed to punch out the shading band where the mark interferes (step 20). For example, as shown in FIG. 5, when the alignment mark 6 interferes with the created light shielding band 15, a portion that interferes with the alignment mark 6 is punched out.

  Next, a comparison is made between the width of the light-shielding band created and the minimum width necessary for use in the stepper device (step 21), and it is determined whether or not the minimum width is satisfied (step 22).

If the minimum width is satisfied, the shading zone creation process is terminated. If not, an error is output (step 23), and the creation process is terminated.
In the method for creating a light shielding band as described above, the following effects can be obtained.
(1) It is possible to create a light shielding band that secures a width that can suppress unnecessary exposure due to flare. Accordingly, the accuracy of the exposure pattern in the shot area can be improved.
(2) The shading band width corresponding to the maintenance cycle can be extracted from the flare management table to create the shading band CAD data. Therefore, the maintenance frequency can be reduced by reducing the number of maintenance times.
(3) Since a flare management table corresponding to a plurality of types of stepper devices is provided in advance, a light-shielding band having an optimum width can be created for each type of stepper device.
(4) When the light shielding band and marks such as the alignment mark interfere with each other, a process for punching out the light shielding band of the mark portion can be performed to prevent the interference with the marks. Therefore, even if sufficient space for forming a light shielding band around the shot area cannot be secured due to an increase in the number of impositions on the chip, the necessary light shielding band width is secured while preventing interference with marks. can do.
(5) Based on the flare management table, it is possible to create a shading band having a minimum width necessary for suppressing the flare amount to be equal to or less than the management value FC.

It is a block diagram which shows the CAD data creation apparatus of one Embodiment. (A) (b) is explanatory drawing which shows the measured value of flare generation amount. (A) (b) is explanatory drawing which shows a flare management table. It is a flowchart which shows operation | movement of a CAD data creation apparatus. It is explanatory drawing which shows a photomask. It is explanatory drawing which shows a step and repeat operation | movement. It is explanatory drawing which shows the conventional photomask. It is a flowchart which shows the shading zone preparation process of a prior art example. It is explanatory drawing which shows the exposure operation | movement by step and repeat.

Explanation of symbols

11 Input device (Fig. 1)
12 Data creation device (Figure 1)
13, 14 First and second storage means (FIG. 1)
15 Shading zone (Figure 5)
AC flare management table (Figure 1)
6 Alignment mark (Figs. 5 and 7)
1 Photomask (Figure 6)
2a to 2d Exposure pattern on wafer (FIG. 6)
3 Photomask (Figure 7)
4 Shot area (Fig. 7)
5 Shading zone (Fig. 7)

Claims (5)

  A flare management table is prepared in advance with the width of the light-shielding band of the photomask required according to the amount of flare generated in the exposure apparatus and the maintenance cycle of the exposure apparatus, and the flare is based on the management value indicating the allowable upper limit of the flare amount. A method for creating a shading zone for a photomask, comprising: obtaining a necessary shading zone width from a management table.   2. The method of creating a light-shielding band for a photomask according to claim 1, wherein the flare management table is provided for each type of exposure apparatus. For each type of exposure apparatus, a flare management table is prepared in advance with the width of the light-shielding band of the photomask required according to the amount of flare generated in the exposure apparatus and the maintenance cycle of the exposure apparatus,
A method of creating a light shielding band for a photomask, comprising: obtaining a width of a corresponding light shielding band from the flare management table by selecting a model of an exposure apparatus, a maintenance cycle, and a flare amount management value.   4. The method of creating a light shielding band for a photomask according to claim 1, wherein when the position detection mark of the photomask interferes with the light shielding band, the light shielding band of the position detection mark portion is punched out. . A first storage means for previously storing the shading band data of the photomask required according to the amount of flare generated in the exposure apparatus and the maintenance period of the exposure apparatus as a flare management table;
An input device for inputting model information of an exposure apparatus for reading predetermined shading band width data from the flare management table, a maintenance period, and a flare amount management value;
Based on information input from the input device, a data creation device that reads shading band width data from the flare management table;
A photomask shading zone data creating apparatus, comprising: a second storage means for storing the shading zone width data.

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