JP5184916B2 - Reflective mask and method of manufacturing the same - Google Patents

Description

  The present invention relates to a reflective mask suitable for, for example, EUV (Extreme Ultra Violet) lithography and the like, and a manufacturing method thereof in consideration of the influence of flare.

  Conventionally, optical lithography such as i-line lithography with a wavelength of 365 nm, KrF lithography with 248 nm, ArF lithography with 193 nm has been used as a lithography technique used in the manufacturing process of a semiconductor device. Recently, since ArF lithography is no longer satisfying the requirement for resolution, immersion lithography with higher resolution has been actively studied. However, even with this immersion lithography, resolution of 45 nm at a half pitch is the limit. Therefore, EUV having a wavelength of 13.5 nm has been actively studied as a lithography technique with a half pitch of 32 nm.

  As one of the problems of EUV lithography, there is a problem of lens flare. In EUV lithography, the exposure wavelength is as short as 13.5 nm. Due to the relationship between light absorption and refractive index, projection exposure is performed using a reflective lens system instead of a refractive lens system. Exposure light is scattered under the influence of extremely fine surface roughness of the reflection lens composed of the multilayer mirror, and flare which is stray light is generated. Due to this flare, exposure fogging occurs and the pattern dimension changes according to the aperture ratio around the pattern. This is the problem of lens flare. Depending on the roughness of the resist and lens, a dimensional change of 0.7 nm may occur every time the aperture ratio increases by 1%.

  Since the target dimension is at the 32 nm level, this lens flare is a major problem in the manufacture of LSIs in which various patterns coexist with various densities, especially in the manufacture of logic LSIs such as SoC (System on Chip) with many types of patterns. It has become. In EUV lithography, not only lenses but also masks are reflective masks for the same reason.

  In order to solve this lens flare problem, a so-called gray tone mask method has been proposed in which a thin film for reducing EUV light is formed in a part of a field region (for example, Patent Document 1 below). FIG. 3 shows a cross-sectional structure of the main part of a typical mask.

  In FIG. 3, the reflective mask includes a substrate 1 made of a low thermal expansion material such as quartz, a multilayer reflective film 2 formed on the substrate 1, a buffer layer 3 formed on the multilayer reflective film 2, The light-absorbing film 4 is patterned on the buffer layer 3 and the absorber pattern 6 is patterned on the light-reducing film 4. A portion where the multilayer reflective film 2 is exposed via the buffer layer 3 functions as a field portion 5 that reflects EUV light, and is disposed so as to be in contact with the absorber pattern 6.

The multilayer reflective film 2 is made of, for example, a Mo / Si multilayer film and has a function of reflecting EUV light. The absorber pattern 6 is made of, for example, TaBN and has a function of absorbing EUV light. The light reducing film 4 is made of, for example, a SiO ₂ film, a Cr film, a CrN film, or the like, and has a function of attenuating EUV light to some extent. It is done. The buffer layer 3 is made of, for example, Si, and is provided for the purpose of preventing contamination (contamination) and manufacturing, and may be omitted.

  In the mask exposure region, a place other than the pattern portion where the absorber pattern 6 is formed is defined as a field portion. In the gray-tone mask, a normal reflection surface is exposed in the field portion 5 in the vicinity of the absorber pattern 6, and the light-reducing film 44 is formed in a location away from the absorber pattern 6 by a certain distance or more. Yes.

  In a reflective mask without a light-reducing film, the intensity of EUV reflected light from a field portion that is more than a certain distance from the vicinity of the pattern is higher than the level necessary for pattern resolution. Such EUV reflected light with a higher intensity than necessary becomes a flare source, which causes a decrease in pattern resolution and pattern transfer dimensional accuracy.

  Therefore, in the gray tone mask method, the effect of flare is reduced by disposing the light reducing film 4 at a certain distance from the absorber pattern 6 and attenuating the high intensity EUV reflected light by the light reducing film 4. ing.

JP 2006-13494 A

  However, in the conventional gray-tone mask method, no consideration is given to the pattern shape of the light-reducing film, and there are cases where an erroneous determination is made during mask pattern inspection.

  FIGS. 4A to 4D are layout diagrams showing pattern examples of the reflective mask, and the intervals between the two absorption patterns 10 are different. A reflection pattern 11 that reflects exposure light is arranged so as to surround the absorption pattern 10 that absorbs exposure light. Further, a dimming pattern 12 for attenuating the exposure light is disposed at a location away from the absorption pattern 10 by a certain distance or more.

  In FIG. 4A, since the interval between the absorption patterns 10 is small, the dimming pattern 12 does not exist between them. In FIG. 4B to FIG. 4D, since the distance between the absorption patterns 10 is large, the dimming pattern 12 exists between them. In particular, in FIG. 4B, the dimming pattern 12 is too fine. When the line width 112 of the dimming pattern 12 is smaller than the minimum line width 101 of the absorption pattern 10, it is determined as a pseudo defect at the time of mask pattern inspection, resulting in a problem that the mask defect detection sensitivity is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a reflective mask and a method for manufacturing the same that can prevent the influence of flare at the time of exposure while preventing a decrease in defect detection sensitivity during mask pattern inspection.

  According to an embodiment of the present invention, a reflective pattern, an absorption pattern, and a dimming pattern are disposed on the substrate surface of the reflective mask, and the minimum line width of the dimming pattern is D and the minimum line width of the absorption pattern is As L, the relationship of D ≧ L is satisfied.

  According to another embodiment of the present invention, the minimum line width of the dimming pattern is D, the minimum line width of the absorption pattern is L, the reflectance of the reflection pattern with respect to the inspection light used for the mask pattern inspection is Rm, and the inspection The relationship of D ≧ L (Rm / Rg) is satisfied, where Rg is the reflectance of the dimming pattern with respect to light.

  The exposure light includes EUV light, and the reflective mask is preferably used for EUV lithography.

  Further, according to another embodiment of the present invention, a figure in which the absorption pattern is broadened by a predetermined amount is generated, and a portion where the expanded figures overlap is integrated, and the integrated figure is predetermined. A dimming pattern is created by generating a figure that is lessen by the amount.

  According to this embodiment, by adopting a dimming pattern, the influence of flare during exposure is reduced, and the minimum line width of the dimming pattern is optimized, thereby reducing the defect detection sensitivity during mask pattern inspection. Can be prevented.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof may be simplified or omitted.

Embodiment 1 FIG.
FIG. 1A to FIG. 1D are layout diagrams showing pattern examples of a reflective mask according to this embodiment, and the intervals between two absorption patterns 10 are different. Similar to FIGS. 4B to 4D, the reflection pattern 11 that reflects the exposure light is disposed so as to surround the absorption pattern 10 that absorbs the exposure light (for example, EUV light). Further, a dimming pattern 12 for attenuating the exposure light is disposed at a position away from the absorption pattern 10 by a certain distance or more, thereby constituting a gray tone mask.

  In FIG. 1A, since the distance between the absorption patterns 10 is small, the dimming pattern 12 does not exist between them.

  In FIG. 1B, since the interval between the absorption patterns 10 is larger than that in FIG. 1A, there is room for the dimming pattern 12 to be interposed as in FIG. 4B. However, the dimming pattern 12 is omitted because the dimming pattern 12 becomes too fine and causes an erroneous determination in the mask pattern inspection.

  In FIG.1 (c) and FIG.1 (d), the space | interval of the absorption patterns 10 is larger than FIG.1 (b). At this time, when the dimming pattern 12 is interposed, the line width 102 of the dimming pattern becomes larger than the line width 101 of the absorption pattern, so that erroneous determination during mask pattern inspection can be prevented. In order to prevent such a misjudgment, it is generally preferable to satisfy the relationship of D ≧ L, where D is the minimum line width of the dimming pattern and L is the minimum line width of the absorption pattern.

  Next, the reflective mask manufacturing method according to the present embodiment will be described using the pattern layout shown in FIG. 5 as an example. In the pattern layouts illustrated in FIGS. 5A to 5D, the intervals between the two absorption patterns 10 are different.

  First, as shown in FIG. 5A, when the minimum line width 101 of the absorption pattern 10 is L and the predetermined minimum distance 121 between the absorption pattern 10 and the dimming pattern 12 is S, the absorption pattern 10 is A pattern figure 202 broadened by S + L / 2 with the width of one side is generated. A similar expansion process is performed on the absorption pattern 10 shown in FIGS. As a result, as shown in FIGS. 6A to 6D, dilated pattern figures 202, 202b, 202c, 202d, 202e, 202f, 202g, and 202h for each absorption pattern 10 are obtained.

  Next, among the expanded pattern figures, the figures that overlap each other, that is, the figure 202 and the figure 202b, the figure 202c and the figure 202d, the figure 202e and the figure 202f, and the figure 202g and the figure 202h are merged and integrated, respectively, and FIG. ) To FIG. 7D, intermediate graphics 203a, 203b, 203c, 203d, and 203e are generated.

  Finally, as shown in FIGS. 8A to 8D, a graphic is generated by shrinking the integrated intermediate graphics 203a, 203b, 203c, 203d, and 203e by L / 2 on one side. The contraction pattern figures 204a, 204b, 204c, 204d, and 204e thus obtained are employed as reflection patterns (the outside of the pattern is a dimming pattern).

  The line width 104 of the narrowest dimming pattern among the obtained dimming patterns obtained by such pattern expansion / contraction processing is L, and the dimming patterns having smaller line widths are shown in FIGS. It is not generated as shown in c). On the other hand, the minimum interval 121 between the absorption pattern and the dimming pattern is maintained at a predetermined value S.

  When EUV exposure was performed using this mask, the influence of flare was reduced and no resolution failure occurred. In the portion where the absorption pattern interval is 2S + L or less, the dimming pattern does not exist in the meantime, and the area of the reflective surface by the multilayer film increases, but the increase in flare amount is only slight and the resolution is high. The impact on is extremely small. On the other hand, since the minimum line width of the dimming pattern is larger than the minimum line width of the absorption pattern, it is possible to prevent erroneous determination at the time of mask pattern inspection and to prevent a decrease in defect detection sensitivity. As a result, it is possible to prevent a decrease in yield due to erroneous determination of mask defects.

Embodiment 2. FIG.
FIG. 2A to FIG. 2D are layout diagrams showing pattern examples of the reflective mask according to this embodiment, and the intervals between the two absorption patterns 10 are different. Similar to FIGS. 1A to 1D, a reflection pattern 11 that reflects exposure light is disposed so as to surround an absorption pattern 10 that absorbs exposure light (for example, EUV light). Further, a dimming pattern 12 for attenuating the exposure light is disposed at a position away from the absorption pattern 10 by a certain distance or more, thereby constituting a gray tone mask.

  In the present embodiment, the line width 103 of the dimming pattern is optimized in consideration of the difference in reflectance with respect to the inspection light used for the mask pattern inspection. In general, the minimum line width of the dimming pattern is D, the minimum line width of the absorption pattern is L, the reflectance of the reflection pattern with respect to the inspection light used for mask pattern inspection is Rm, and the reflectance of the dimming pattern with respect to the inspection light Is preferably Rg, and the relationship of D ≧ L (Rm / Rg) is preferably satisfied. The wavelength of the inspection light may be different from the wavelength of the exposure light, but is preferably the same as the wavelength of the exposure light.

  For example, when the minimum line width of the dimming pattern is equal to the minimum line width of the absorption pattern, when the reflectance Rm of the reflection pattern is larger than the reflectance Rg of the dimming pattern (Rm> Rg), the reflected light from the reflection pattern is Since it becomes stronger, it is preferable to make the minimum line width of the dimming pattern larger. Conversely, when the reflectance Rm of the reflection pattern is smaller than the reflectance Rg of the dimming pattern (Rm <Rg), the reflected light from the dimming pattern becomes stronger, so the minimum line width of the dimming pattern is made smaller. It is preferable to do.

  With such a configuration, it is possible to adjust the sensitivity of the absorption pattern 10 and the dimming pattern 12 at the time of mask pattern inspection, and it is possible to prevent a decrease in defect detection sensitivity due to a pseudo defect.

  Next, the reflective mask manufacturing method according to the present embodiment will be described using the pattern layout shown in FIG. 5 as an example. In the pattern layouts illustrated in FIGS. 5A to 5D, the intervals between the two absorption patterns 10 are different.

  First, as shown in FIG. 5A, the minimum line width 101 of the absorption pattern 10 is L, the predetermined minimum distance 121 between the absorption pattern 10 and the dimming pattern 12 is S, and is used for mask pattern inspection. A pattern figure 202 in which the absorption pattern 10 is broadened by S + L (Rm / Rg) with a width on one side is generated, where Rm is the reflectance of the reflection pattern for the inspection light and Rg is the reflectance of the dimming pattern for the inspection light. To do. A similar expansion process is performed on the absorption pattern 10 shown in FIGS. As a result, as shown in FIGS. 6A to 6D, dilated pattern figures 202, 202b, 202c, 202d, 202e, 202f, 202g, and 202h for each absorption pattern 10 are obtained.

  Next, among the expanded pattern figures, the figures that overlap each other, that is, the figure 202 and the figure 202b, the figure 202c and the figure 202d, the figure 202e and the figure 202f, and the figure 202g and the figure 202h are merged and integrated, respectively, and FIG. ) To FIG. 7D, intermediate graphics 203a, 203b, 203c, 203d, and 203e are generated.

  Finally, as shown in FIGS. 8 (a) to 8 (d), the integrated intermediate figures 203a, 203b, 203c, 203d, and 203e are generated by shrinking (lessen) only one side L (Rm / Rg). To do. The contraction pattern figures 204a, 204b, 204c, 204d, and 204e thus obtained are employed as the reflection pattern.

  As a result of such pattern expansion / contraction processing, the line width 104 of the narrowest dimming pattern among the obtained dimming patterns is L (Rm / Rg), and the dimming pattern having a smaller line width is shown in FIG. ~ No longer generated as shown in FIG. On the other hand, the minimum interval 121 between the absorption pattern and the dimming pattern is maintained at a predetermined value S.

  When EUV exposure was performed using this mask, the influence of flare was reduced and no resolution failure occurred. Incidentally, in the portion where the absorption pattern interval is 2S + L (Rm / Rg) or less, the dimming pattern does not exist between them, and the area of the reflection surface by the multilayer film increases, but the increase in the flare amount is only slight. The effect on resolution is extremely small. On the other hand, since the minimum line width of the dimming pattern is larger than the minimum line width of the absorption pattern, it is possible to prevent erroneous determination at the time of mask pattern inspection and to prevent a decrease in defect detection sensitivity. As a result, it is possible to prevent a decrease in yield due to erroneous determination of mask defects.

  The present invention is extremely useful industrially in that a semiconductor device including a fine and highly accurate pattern can be manufactured with high production efficiency.

It is a layout figure which shows the example of a pattern of the reflective mask which concerns on 1st Embodiment. It is a layout figure which shows the example of a pattern of the reflective mask which concerns on 2nd Embodiment. It is sectional drawing which shows the structural example of a typical gray tone mask. It is a layout figure which shows the example of a pattern of the conventional reflective mask. It is a layout figure explaining the manufacturing method of the reflective mask which concerns on this invention. It is a layout figure explaining the manufacturing method of the reflective mask which concerns on this invention. It is a layout figure explaining the manufacturing method of the reflective mask which concerns on this invention. It is a layout figure explaining the manufacturing method of the reflective mask which concerns on this invention.

Explanation of symbols

1 substrate, 2 multilayer reflective film, 3 buffer layer, 4 dimming film,
5 Field part, 6 Absorber pattern,
10 Absorption pattern, 11 Reflection pattern, 12 Dimming pattern,
202-202h expansion pattern figure, 203a-203e intermediate figure,
204a-204e Contraction pattern figure.

Claims (5)

A reflective mask in which a reflection pattern that reflects exposure light, an absorption pattern that absorbs exposure light, and a dimming pattern that attenuates exposure light are arranged on the substrate surface,
A reflective mask characterized by satisfying a relationship of D ≧ L, where D is the minimum line width of the dimming pattern and L is the minimum line width of the absorption pattern. A reflective mask in which a reflection pattern that reflects exposure light, an absorption pattern that absorbs exposure light, and a dimming pattern that attenuates exposure light are arranged on the substrate surface,
The minimum line width of the dimming pattern is D, the minimum line width of the absorption pattern is L, the reflectance of the reflection pattern with respect to the inspection light used for mask pattern inspection is Rm, and the reflectance of the dimming pattern with respect to the inspection light is Rg. , D ≧ L (Rm / Rg).   3. The reflective mask according to claim 1, wherein the exposure light includes EUV light. A reflective mask manufacturing method in which a reflection pattern that reflects exposure light, an absorption pattern that absorbs exposure light, and a dimming pattern that attenuates exposure light are arranged on a substrate surface,
Generating a figure expanded by one side S + L / 2 with respect to the absorption pattern, where S is the minimum distance between the absorption pattern and the dimming pattern, and L is the minimum line width of the absorption pattern;
Integrating the parts where the expanded figures overlap;
Generating a figure contracted by L / 2 on one side with respect to the integrated figure and creating a dimming pattern having a minimum line width L. A method for manufacturing a reflective mask, comprising: A reflective mask manufacturing method in which a reflection pattern that reflects exposure light, an absorption pattern that absorbs exposure light, and a dimming pattern that attenuates exposure light are arranged on a substrate surface,
The minimum distance between the absorption pattern and the dimming pattern is S, the minimum line width of the absorption pattern is L, the reflectance of the reflection pattern with respect to the inspection light used for mask pattern inspection is Rm, and the reflection of the dimming pattern with respect to the inspection light Generating a figure expanded by one side S + L (Rm / Rg) with respect to the absorption pattern, where the rate is Rg;
Integrating the parts where the expanded figures overlap;
Generating a figure contracted by one side L (Rm / Rg) with respect to the integrated figure and creating a dimming pattern with a minimum line width L (Rm / Rg). Production method.

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