TWI699613B - Anti-static photomask - Google Patents

Abstract

The present disclosure relates to an anti-static photomask, including a substrate and a patterned mask layer formed on the substrate. The patterned mask layer includes a conductive strip and a conductive string, wherein the conductive strip includes an end, and the conductive string includes an isolated end. The end of the conductive strip is connected to the conductive string.

Description

Anti-static mask

This disclosure relates to a photomask, and particularly relates to an antistatic photomask.

In today's lithography process, a photomask is required. However, static electricity will accumulate on the photomask during the use of the photomask. If too much static electricity accumulates on the photomask, electrostatic discharge (ESD) may be caused on the photomask pattern, thereby destroying the exposed pattern. For example, in the current photomask, the end of the photomask pattern and adjacent to the metal wire will have a strong electric field due to the accumulation of static charge. These areas with a strong electric field (such as the dotted area corresponding to the static charge e in Figure 2C) have a higher probability of mask chipping, pattern bursting, chromium migration (Cr migriation), haze, etc., making it undesirable The desired pattern is exposed and developed on the wafer, resulting in short circuit or open circuit of the device.

The disclosure relates to an anti-static photomask, which includes a substrate and a patterned mask layer formed on the substrate. The patterned mask layer includes a conductive tape and a conductive strip, the conductive tape includes one end, the conductive strip includes an independent end, and the end of the conductive tape is connected to the conductive strip.

In the antistatic photomask according to some embodiments of the present disclosure, the conductive strip further includes a connecting end, and the conductive strip is connected to the end of the conductive tape by the connecting end. The width of the independent end is greater than the width of the connected end. In other embodiments, the conductive strip further includes another independent end. The patterned mask layer further includes another conductive strip, including an end, and is connected to the conductive strip. The conductive strip further includes another independent end.

In some embodiments, the patterned mask layer further includes another conductive strip including an independent end and a connecting end, and the connecting end of the other conductive strip is connected to the end of the first conductive strip. The width of the conductive strip is greater than the width of the conductive strip. The width of the conductive strip is greater than twice the width of the conductive strip. The patterned mask layer further includes another conductive strip, which is substantially parallel to the aforementioned conductive strip and separated by a distance.

Many different implementation methods or examples are disclosed below to implement different features of the provided target. Of course, these embodiments are only for illustration, and should not be used to limit the scope of the disclosure. In addition, repeated reference signs or labels may be used in different embodiments, and these repetitions are only used to describe the disclosure simply and clearly, and do not represent a specific relationship between the different embodiments and/or structures discussed.

Please refer to FIG. 1, which is a schematic diagram of the photomask 1 (anti-static photomask) according to some embodiments of the disclosure. The photomask 1 includes a substrate 10, a patterned mask layer 20 formed on the substrate 10, a frame 30, a film 40, and a connecting material 50 connecting the substrate 10 and the frame 30. The substrate 10 can be any suitable photomask substrate. The patterned mask layer 20 and the frame 30 may be formed of metal materials (such as MoSi, Cr, etc.), and may be formed on the substrate 10 by a suitable manufacturing process. The film 40 is used to prevent external dust and the like from entering the photomask 1 so as to protect other components (such as the substrate 10, the patterned mask layer 20, and the frame 30). The connecting material 50 is used to connect the substrate 10 and the frame 30, and may include various suitable glue materials.

Next, please refer to FIG. 2A, which is a top view of a portion of the patterned mask layer 20A according to some embodiments of the disclosure. In Figure 2A, the patterned mask layer 20A mainly includes conductive strips 22 and conductive strips 24A formed of the same or similar materials. The conductive tape 22 is a part of the main pattern of the photomask 1, and the conductive tape 22 includes an end 221 that is electrically and physically connected to the connecting end 242A of the conductive strip 24A. The other end of the conductive strip 24A is called an independent end 241A.

It should be noted that the "independent end" referred to herein refers to an end that is not physically connected to other conductive structures (such as the conductive tape 22, the frame 30, or other conductive structures). In addition, although the conductive strip 22 and the conductive strip 24A are shown separately, they can be formed simultaneously by the same process.

In this embodiment, the size of the conductive strip 22 and the conductive strip 24A is related to the wavelength (λ) and the numerical aperture (NA) of the light source used during patterning. For example, the width D2 of the conductive strip 24A can be designed to be smaller than λ/NA (D2<λ/NA), and the width D1 of the conductive strip 22 can be designed to be greater than twice the width D2 of the conductive strip 24A (D1>2 *D2). Therefore, in this way, when the photomask 1 is used for exposure, no corresponding pattern will be generated on the photoresist corresponding to the conductive strip 24A with a smaller width, and only the conductive strip corresponding to the larger width will be generated. Corresponding patterns will be formed at 22 locations. In other words, the conductive strip 24A is an assist feature that is not imaged. In addition, the length L of the conductive strip 24A can be designed to be greater than or equal to twice the width D2 (L≧2*D2) to achieve a better imaging effect.

In addition, by electrically connecting the end 221 of the conductive tape 22 with the conductive strip 24A, the electrostatic charge e of the patterned mask layer 20A can be guided to the independent end 241A of the non-imaging conductive strip 24A to avoid patterning. The end of the main pattern of the mask layer (that is, the end 221 of the conductive tape 22) has problems such as mask chipping, pattern bursting, chromium migration, fogging, etc., thereby reducing the electrostatic charge e to the pattern on the photoresist after exposure Impact. That is, even if the static charge e accumulates on the independent end 241A of the conductive strip 24A and causes electrostatic discharge, since the width of the conductive strip 24A is not sufficient for imaging, no corresponding corresponding to the conductive strip 24A will be formed on the photoresist. Pattern, so this electrostatic discharge will not damage the corresponding pattern on the photoresist.

For example, please refer to Figure 2B and Figure 2C, which are a part of the patterned mask layer 20A and a schematic diagram of the patterned mask layer 20B in another embodiment and its corresponding patterns, respectively. The patterned mask layer 20A and the patterned mask layer 20B form corresponding patterns 26A and 26B, respectively. It should be noted that in Figs. 2B and 2C, the static charge e is accumulated at the independent end 241A and the end 221, respectively. In other words, by providing the conductive strip 24A on the end of the conductive tape 22, the electrostatic charge e accumulated on the end 221 (Figure 2C) can be guided to the independent end 241A (Figure 2B) that is not imaged. ). Therefore, even if electrostatic discharge is caused by the accumulation of electrostatic charge e at the independent end 241A, since the conductive strip 24 is not imaged, even if the independent end 241A has problems such as mask chipping, pattern bursting, chromium migration, fogging, etc. , It will not form the corresponding pattern during exposure, so it can avoid the generation of unwanted patterns at the end of the photoresist corresponding to the main pattern due to electrostatic discharge (for example, prevent the patterned mask layer 20B in Figure 2C The end 221 is at the photoresist during the exposure and the electrostatic charge e discharges the pattern burst), so as to increase the yield of the photolithography process using the photomask 1, and also extend the service life of the photomask 1, Thereby reducing costs. In addition, since the conductive strip 24A is connected to the end 221 of the conductive tape 22 instead of being connected to other places other than the end 221, it will not interfere with the line width of the pattern formed after using the photomask 1. In addition, since the conductive strip 24A also has the characteristics of analysis assistance, the shape of the pattern 26A is closer to the shape (original pattern) of the conductive tape 22 than the shape of the pattern 26B.

It should be noted that although the above-mentioned conductive strip 22 and the conductive strip 24A are shown as extending in substantially the same direction, the disclosure is not limited thereto. For example, in some embodiments, the angle between the conductive strip 22 and the conductive strip may be an angle θ less than 180 degrees. In other embodiments, the conductive strip 22 may be located on the XY plane (ie, the plane parallel to the substrate 10), and the conductive strip may extend in any direction other than the XY plane (for example, the Z direction perpendicular to the substrate 10). . This configuration also allows electrostatic charges e to be guided to the independent ends of the conductive strips, so it can also prevent electrostatic discharge from damaging the photomask 1 and its corresponding patterns, and can also increase design flexibility.

Please refer to FIG. 3A and FIG. 3B, which are schematic diagrams of the patterned mask layer 20C of some embodiments of the present disclosure. In this embodiment, the end 221 of a single conductive strip 22 and the connecting end 242 of two conductive strips 24B are connected to each other. That is, one conductive strip 22 can correspond to two conductive strips 24B. However, the present disclosure is not limited to this. As long as the design permits, one conductive strip 22 can also correspond to more than two conductive strips 24B. In this embodiment, the electrostatic charge e will also be guided to the independent end 241B of the conductive strip 24B, which can prevent the electrostatic discharge from damaging the photomask 1 and its corresponding pattern.

It is worth mentioning that in this embodiment, by connecting the end 221 of a single conductive strip 22 with the connecting ends of multiple conductive strips, the corresponding pattern 26C formed can be made closer to the shape of the conductive strip. Compared with the embodiment in FIG. 2B or FIG. 2C, distortion of the formed corresponding pattern can be further avoided (for example, the situation where the corresponding pattern is rounded is reduced). In some embodiments, as shown in FIG. 3A, the sides 25 of the two conductive strips 24B connected to a single conductive strip 22 are respectively cut to the sides 23 of the conductive strip 22.

Please refer to FIGS. 4A to 4C, which are schematic diagrams of the patterned mask layers 20D and 20E of some embodiments of the present disclosure. First, in FIGS. 4A to 4B, the conductive strip 24C is connected to the end 221 of the conductive strip 22 by the side 243A, instead of the connecting end of the previous embodiment, and the conductive strip 24C is connected to the conductive strip 22. It also has an independent end 241C. In this embodiment, the electrostatic charge e is also guided to the two independent end portions 241C, which can prevent the electrostatic discharge from damaging the photomask 1 and its corresponding patterns. In addition, in this embodiment, by connecting the end point of the conductive tape 22 to the side 243A of the conductive strip 24C, the shape of the corresponding pattern 26D can be formed to be closer to the shape of the conductive tape 22, compared to Figure 2B or As for the embodiment of FIG. 2C, the distortion of the formed corresponding pattern can be further avoided (for example, the situation that the corresponding pattern is rounded is reduced).

Since the conductive strips in this embodiment are not connected with the conductive strips 22 at their ends, it is allowed to connect multiple conductive strips 22 to one conductive strip. For example, please refer to Figure 4C, where the conductive strips 24D of the patterned mask layer 20E can be connected to the ends 221 of more than one conductive strip 22 by the side 243B (Figure 4C shows the connection of three conductive strips 22, but This disclosure is not limited to this), and the conductive strip 24D also has an independent end 241D. In this embodiment, the electrostatic charges e of the plurality of conductive strips 22 will also be guided to the two independent ends 241D of the conductive strips 24D, which can prevent the electrostatic discharge from damaging the photomask 1 and its corresponding patterns. In addition, with this design method, the conductive strip 24D can connect a plurality of conductive strips 22 in series to reduce the potential difference between the conductive strips 22 and the accumulation of static charge, and achieve an effect similar to grounding.

Next, please refer to Figs. 5-7, which are charge distribution diagrams when imaging with various patterned mask layers. The different colors beside the conductive strip 22 represent different electrostatic charge densities. In Figure 5, there are no non-imaging conductive strips, and the conductive strips 22 are separated from each other by a distance. In this situation, the parts with higher charge density will be concentrated on the ends of the conductive strips 22, and because the conductive strips 22 are not electrically connected, their potentials will also be different, so that the The charge density is not uniform, which will cause electrostatic discharge and distortion of the resulting pattern.

In Figure 6, the conductive strips 22 are connected to each other by a conductive strip 24E. In this way, each conductive strip 22 can be electrically conducted, so that each conductive strip 22 has the same potential and disperses static charges. However, since the conductive strip 24E under this condition is not connected to the end of the conductive tape 22, it is still unable to improve the phenomenon of static charge accumulation at the end of the main pattern (such as the conductive tape 22), so there may still be There are problems with electrostatic discharge and distortion of the resulting pattern.

As described in some embodiments of the present disclosure, in Figure 7, one end of the conductive strip 22 of the patterned mask layer is connected to each other by a conductive strip 24F. Therefore, compared with the state in Figure 5, the conductive strips 24F are provided to electrically connect the conductive strips 22 to each other to achieve the effect of dispersing electrostatic charges, so as to reduce the potential difference between the conductive strips 22 and the accumulation of electrostatic charges, to achieve similar The effect of grounding. Compared with the situation in Fig. 6, since the conductive strip 24F is arranged at the end of the conductive tape 22, the electrostatic charge can be further guided to the end of the conductive strip 24F that is not imaged, thereby avoiding the end of the conductive tape 22 The generated electrostatic discharge damages the corresponding pattern and the photomask 1.

In addition, in Figure 7, by providing another conductive strip 24G, the electric field of the patterned mask layer can be changed, thereby further improving the shape of the pattern formed after using the mask 1 and achieving the effect of auxiliary analysis.

Since one end of the conductive strip of the present disclosure is an independent end that is not connected to other conductive structures (such as the conductive tape 22 or the frame 30), the conductive strip of the present disclosure does not need to be connected to the frame 30. Therefore, in some embodiments, it is also allowed to omit the frame 30 of the photomask 1, which can further reduce the cost of the photomask 1.

In summary, the present disclosure provides a photomask with non-imaging conductive strips electrically connected to the main pattern (such as conductive tape) is additionally provided on the patterned mask layer, and the conductive strips are not electrically connected to other conductive structures. Independent end of the connection. By arranging such conductive strips, the problem of corresponding pattern burst caused by the accumulation of static charges on the end of the main pattern can be avoided. In addition, the conductive strips provided according to the present disclosure can also make the corresponding pattern formed by the photomask closer to the desired pattern.

Although the embodiments of the present disclosure and their advantages have been disclosed above, it should be understood that any person with ordinary knowledge in the relevant technical field can make changes, substitutions and modifications without departing from the spirit and scope of the present disclosure. In addition, each patent application scope constitutes an individual embodiment, and the protection scope of the present disclosure also includes each patent application scope and a combination of embodiments.

1: Mask 10: substrate 20, 20A, 20B, 20C, 20D, 20E: patterned mask layer 22: Conductive tape 221: End 23, 25, 243A, 243B: side 24A, 24B, 24C, 24D, 24E, 24F, 24G: conductive strip 241A, 241B, 241C, 241D: independent ends 242A, 242B: connecting end 26A, 26B, 26C, 26D, 26E: pattern 30: frame 40: Film 50: Connection material D1, D2: width e: electrostatic charge L: length

The embodiments of the disclosure will be described in detail below in conjunction with the accompanying drawings. It should be noted that the various features of the embodiments are not drawn to scale and are only used for illustrative purposes. In fact, the size of the element can be arbitrarily enlarged or reduced to clearly show the features of the present disclosure. FIG. 1 is a schematic diagram of a photomask drawn according to some embodiments of the disclosure. 2A to 2B are schematic diagrams of the patterned mask layer and its corresponding patterns of some embodiments of the present disclosure. FIG. 2C is a schematic diagram of the patterned mask layer and its corresponding pattern in an embodiment. 3A to 3B are schematic diagrams of the patterned mask layer and corresponding patterns of some embodiments of the present disclosure. 4A to 4B are schematic diagrams of the patterned mask layer and its corresponding patterns in some embodiments of the present disclosure. FIG. 4C is a schematic diagram of the patterned mask layer and its corresponding patterns in some embodiments of the present disclosure. Figures 5 to 7 are diagrams of charge distribution during imaging with a patterned mask layer in some embodiments.

20A: Patterned mask layer

22: Conductive tape

221: End

24A: Conductive strip

241A: Independent end

242A: connecting end

D1, D2: width

e: electrostatic charge

L: length

Claims (10)

An anti-static photomask includes: a substrate; a frame arranged on the substrate; and a patterned mask layer formed on the substrate, including: a conductive tape including one end; and a conductive strip including An independent end, wherein the end of the conductive strip is connected with the conductive strip, the frame surrounds the conductive strip, and the conductive strip is electrically insulated from the frame. According to the anti-static photomask described in item 1 of the scope of patent application, the conductive strip further includes a connecting end, and the conductive strip is connected to the end of the conductive tape by the connecting end. As described in the second item of the scope of patent application, the width of the independent end is greater than the width of the connection end. According to the antistatic photomask described in item 1 of the scope of patent application, the conductive strip further includes another independent end. According to the anti-static photomask described in item 1 of the scope of patent application, the patterned mask layer further includes another conductive strip, including one end portion, which is connected to the conductive strip. According to the anti-static photomask described in item 5 of the scope of patent application, the conductive strip further includes another independent end. The anti-static photomask described in item 1 of the scope of patent application, wherein the patterned mask layer further includes another conductive strip, including an independent end and a connecting end, the connecting end of the other conductive strip Connect with the end of the conductive tape. The antistatic photomask described in item 1 of the scope of patent application, wherein the width of the conductive strip is greater than the width of the conductive strip. The antistatic photomask described in item 8 of the scope of patent application, wherein the width of the conductive tape is greater than twice the width of the conductive strip. According to the antistatic photomask described in item 1 of the scope of patent application, the patterned mask layer further includes another conductive strip, which is substantially parallel to the conductive strip and is spaced apart by a distance.

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