JP2011238801A - Manufacturing method of reflective mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a reflective mask capable of repairing a defect if a missing part is larger in a bottom part than in an upper part on the side surface of an absorber layer therefore realizing the reflecting mask with high reliability and improved yield.SOLUTION: This is a manufacturing method for a reflective mask which comprises: a substrate; a multilayer film formed on the substrate; and an absorber layer laminate formed in a pattern shape on the multilayer film. The absorber layer laminate includes a first absorber layer formed on the multilayer film, and a second absorber layer formed on the first absorber layer. The reflective mask has a defective part on the side surface of the absorber layer laminate where a missing part in the first absorber layer is larger than in the second absorber layer. The manufacturing method includes: a removal process of the defective part on the side surface where the absorber layer laminate positioned in the defective part on the side surface is removed; and a repair process including a deposition film forming process where the deposition film is formed in the defective part on the side surface after removing the absorber layer laminate.

Description

  The present invention relates to a method for manufacturing a reflective mask used in extreme ultra violet (EUV) lithography.

  A semiconductor element such as a semiconductor integrated circuit repeatedly performs a photolithography process in which exposure light is irradiated onto a mask which is an original on which a circuit pattern is drawn, and the pattern is transferred onto a semiconductor substrate (wafer) via a reduction optical system. By mass production.

  In recent years, semiconductor devices have been miniaturized, and a method for increasing the resolution by shortening the exposure wavelength of photolithography has been studied. In particular, development of EUV lithography having a wavelength of 13.5 nm is progressing.

  In EUV lithography, a transmissive mask cannot be used because of the light absorption of a substance. Therefore, a reflective mask using reflection by a multilayer film such as Mo (molybdenum) and Si (silicon) is used. In general, as a reflective mask for EUV lithography (hereinafter sometimes referred to as an EUV mask), a mask in which a multilayer film is formed on a substrate and an absorption layer is formed in a pattern on the multilayer film is used. (See, for example, Patent Document 1).

  If a defect exists in the absorption layer pattern in the EUV mask, a defect occurs in the circuit pattern transferred onto the wafer. Therefore, in the manufacturing process of the EUV mask, the defect inspection of the absorption layer pattern is usually performed, and when a defect is found, the defect is corrected.

  The EUV mask defect includes a black defect in which an excessive pattern exists and a white defect in which a pattern is missing. As a method for correcting black defects, there is known a method of removing an excess pattern by a gas assist etching method in which a focused ion beam (FIB) or an electron beam (EB) is irradiated while blowing an assist gas. It has been. As a method for correcting white defects, a method is known in which a deposited film is formed in a portion where a pattern is missing by a chemical vapor deposition (CVD) method using FIB or EB.

  In the defect inspection of an EUV mask, deep ultraviolet (DUV) is used as inspection light. The EUV mask is designed with a multilayer film and an absorption layer so as to ensure a high contrast with EUV as exposure light, but the multilayer film and the absorption layer have a reflectivity with respect to DUV used as inspection light. The difference is small. Therefore, the absorption layer is surface-treated so that the reflectance is sufficiently small even for DUV. For example, methods such as forming a natural oxide film on the surface of the absorption layer and introducing oxygen into the surface of the absorption layer are known.

  Since the etching rate differs between the metal material and its oxide, the etching rate differs between the oxide film formed on the surface of the absorption layer and the inside of the absorption layer. Therefore, in the case of black defect correction, when FIB or EB is irradiated while blowing an assist gas, the inside of the absorption layer is etched excessively on the side surface of the absorption layer than the oxide film, and the absorption layer pattern does not have a vertical side surface, So-called side etching is likely to occur. It is known that side etching occurs because the FIB or EB irradiation amount is excessive, the assist gas reacts excessively with the inside of the absorption layer, and the like. Since the EUV light absorption ability is impaired at the side etching occurrence portion as compared with a normal pattern, there is a problem that the pattern accuracy is lowered.

  In order to solve this problem, there has been proposed a technique for suppressing side etching by alternately performing etching and oxidation of an absorption layer a plurality of times and performing etching while forming an oxide film (for example, Patent Document 2 and (See Patent Document 3).

JP 2002-319542 A JP 2009-98369 A JP 2009-210805 A

  If the pattern accuracy is reduced due to the occurrence of side etching, it becomes a defective product, which causes a decrease in yield. Therefore, conventionally, a reflective mask has been manufactured so that side etching does not occur as described above.

  However, in the black defect correction method in which the absorption layer is repeatedly etched and oxidized, it takes time to correct the degree of vacuum and to specify the processing region when etching the absorption layer. Furthermore, it is necessary to make a correction that predicts a strict film thickness considering the three-dimensional structure of the absorption layer.

  In addition, when the mask blank contains foreign matter, the foreign matter is removed during the manufacturing process of the EUV mask, so that the pattern may be lost and the absorption layer pattern may not have a vertical side surface.

  The present invention has been made in view of the above circumstances, and when the lower part is missing from the upper part on the side surface of the absorption layer, it is possible to repair the defect and obtain a highly reliable reflective mask. Furthermore, it is a main object of the present invention to provide a method for manufacturing a reflective mask capable of improving the yield.

  In order to achieve the above object, the present invention includes a substrate, a multilayer film formed on the substrate, and an absorbent layer laminate formed in a pattern on the multilayer film, and the absorbent layer laminate The body has a first absorption layer formed on the multilayer film and a second absorption layer formed on the first absorption layer, and the first absorption layer is formed on the side surface of the absorption layer laminate. A side-face defect portion removing step of removing the absorbent layer laminate located in the side-face defect portion of the reflective mask having a side-face defect portion that is missing from the second absorbent layer, and the absorption layer laminate is removed. There is provided a method for manufacturing a reflective mask, comprising a repairing step including a deposited film forming step of forming a deposited film on the side surface defect portion removing portion.

  According to the present invention, when the reflective mask has a side defect portion in which the first absorption layer is missing from the second absorption layer on the side surface of the absorption layer laminate, the absorption layer located in the side defect portion By removing the stacked body and forming a deposited film on the side surface defect portion removing portion from which the absorption layer stack body is removed, it is possible to repair the side surface defect portion and restore the transfer characteristics of the reflective mask. Therefore, it is possible to dramatically improve the yield of the reflective mask.

  In the above invention, prior to the repairing step, there is a black defect correcting step for removing the absorbing layer laminate located in the black defect portion due to the surplus of the absorbing layer laminate, and the side defect portion is the black defect It is preferable that it is formed in the defect correction process. When the black defect portion is corrected, side etching is likely to occur, which causes a decrease in yield. However, by applying the present invention, the yield can be increased. Further, in the present invention, since the side surface defect portion can be repaired, it is not necessary to correct the black defect portion so that side etching does not occur for a long time as in the prior art. A mask can be manufactured.

  Moreover, in this invention, it is preferable to remove the said absorption layer laminated body located in the said side surface defect part with the probe of a scanning probe microscope in the said side surface defect part removal process. This is because the absorbent layer laminate can be processed with low damage.

  In the present invention, when the reflective mask has a side defect portion in which the first absorption layer is missing from the second absorption layer on the side surface of the absorption layer laminate, the absorption layer stack positioned in the side defect portion By removing the body and forming a deposited film on the side defect removal part from which the absorbent layer stack has been removed, it is possible to repair the side defect and restore the transfer characteristics of the reflective mask. As a result, it is possible to improve the yield.

It is process drawing which shows an example of the manufacturing method of the reflective mask of this invention. It is process drawing which shows the other example of the manufacturing method of the reflective mask of this invention. It is process drawing which shows an example of the black defect correction process in the manufacturing method of the reflective mask of this invention. It is process drawing which shows the other example of the manufacturing method of the reflective mask of this invention. It is the schematic plan view and sectional drawing which show an example of the side surface defect part removal process in the manufacturing method of the reflective mask of this invention. It is the schematic plan view and sectional drawing which show the other example of the side surface defect part removal process in the manufacturing method of the reflective mask of this invention. It is the schematic plan view and sectional drawing which show an example of the deposited film formation process in the manufacturing method of the reflective mask of this invention. It is the schematic plan view and sectional drawing which show the other example of the deposited film formation process in the manufacturing method of the reflective mask of this invention. It is the schematic plan view and sectional drawing which show an example of the reflective mask used for the manufacturing method of the reflective mask of this invention. FIG. 2 is a schematic plan view and a cross-sectional view showing a reflective mask in simulation 1 of Example 1. 6 is a graph showing the relationship between the amount of side etching and the amount of deviation of transfer dimensions according to simulation 1 of Example 1. FIG. 6 is a schematic plan view and a cross-sectional view showing a reflective mask in simulation 2 of Example 1. 6 is a graph showing a relationship between a deposited film thickness and a transfer amount deviation amount according to simulation 2 of Example 1.

  Hereafter, the manufacturing method of the reflective mask of this invention is demonstrated in detail.

  The manufacturing method of the reflective mask of the present invention includes a substrate, a multilayer film formed on the substrate, and an absorption layer laminate formed in a pattern on the multilayer film, and the absorption layer laminate Has a first absorption layer formed on the multilayer film and a second absorption layer formed on the first absorption layer, and the first absorption layer on the side surface of the absorption layer laminate is the first absorption layer. (2) A side surface defect portion removing step of removing the absorption layer laminate located in the side defect portion of the reflective mask having a side defect portion that is missing from the absorption layer, and the absorption layer laminate is removed. And a repairing step including a deposition film forming step of forming a deposition film on the side surface defect portion removing portion.

The reflective mask manufacturing method of the present invention will be described with reference to the drawings.
1A to 1E are process diagrams showing an example of a reflective mask manufacturing method according to the present invention. A reflective mask 1A illustrated in FIG. 1A includes a substrate 2, a multilayer film 3 formed on the substrate 2, a capping layer 4 formed on the multilayer film 3, and a pattern on the capping layer 4. The absorption layer laminate 7 is formed. The absorbent layer stack 7 includes a first absorbent layer 5 formed on the capping layer 4 and a second absorbent layer 6 formed on the first absorbent layer 5. For example, when the 1st absorption layer 5 contains the metal material which is easy to be oxidized, such as Ta (tantalum), the 2nd absorption layer 6 turns into a natural oxide film. In addition, in order to facilitate pattern defect inspection by DUV of a reflective mask for EUV lithography, a material having a low reflectance with respect to DUV of inspection light is used for the second absorption layer 6, and the first absorption layer 5 is used for the first absorption layer 5. A material having a high absorption rate with respect to EUV of exposure light may be used. The reflective mask 1 </ b> A has a side surface defect portion 10 a in which the first absorption layer 5 is excessively missing from the second absorption layer 6 on the side surface of the absorption layer stacked body 7.
First, as shown in FIGS. 1A to 1C, the absorbent layer stack 7 located on the side surface defect portion 10a of the reflective mask 1A is shaved and removed with the probe 11 of the scanning probe microscope (side surface defect). Part removal step). Next, as shown in FIGS. 1D to 1E, FIB or EB13 is irradiated while blowing the source gas 12 on the upper part of the side surface defect removing portion 10b from which the absorption layer laminate 7 has been removed. Then, the deposited film 8 is formed (deposited film forming step). Thereby, the reflective mask 1B in which the side surface defect portion 10a is repaired is obtained (FIGS. 1B to 1E, repair process).

2A to 2D and FIGS. 1A to 1E are process diagrams showing another example of the reflective mask manufacturing method of the present invention. First, as shown in FIG. 2A, the multilayer film 3, the capping layer 4, and the absorption layer laminate 7 including the first absorption layer 5 and the second absorption layer 6 were laminated on the substrate 2. A reflective mask blank 1C is prepared. Next, although not shown in the drawing, a photoresist pattern is formed on the absorption layer laminate 7, and the absorption layer laminate 7 (the first absorption layer 5 and the second absorption layer 6) located in the opening of the photoresist pattern is subjected to plasma. Etching is performed to remove the photoresist pattern, and the absorption layer stack 7 (the first absorption layer 5 and the second absorption layer 6) is patterned as shown in FIG. When processing the absorbent layer laminate 7, as shown in FIG. 2B and FIG. 3A, due to the surplus of the absorbent layer laminate 7 (the first absorbent layer 5 and the second absorbent layer 6). In some cases, a black defect portion 20 is formed. 2B is a cross-sectional view taken along line AA in FIG. 3A, and the multilayer film and the capping layer are omitted in FIG. 3A.
In the case where the black defect portion 20 is detected after the patterning of the absorption layer stack 7 (the first absorption layer 5 and the second absorption layer 6), in order to correct the black defect portion 20, FIG. As shown, FIB or EB22 is irradiated to the black defect portion 20 while the assist gas 21 is being blown, so that the absorption layer stack 7 (the first absorption layer 5 and the second absorption layer 6) located in the black defect portion 20. ) Is etched. As a result, as shown in FIG. 2D, the absorption layer stack 7 (the first absorption layer 5 and the second absorption layer 6) located in the black defect portion 20 is removed. In the absorption layer laminate 7, as described above, the second absorption layer 6 is an oxide film made of the material of the first absorption layer 5, or the second absorption layer 6 has a low reflectance with respect to the DUV of the inspection light. A material is contained and the 1st absorption layer 5 contains the material with a high absorption factor with respect to EUV of exposure light. Therefore, the etching rates of the first absorption layer 5 and the second absorption layer 6 are different, and as a result, the first absorption layer 5 is formed on the side surface of the absorption layer laminate 7 as shown in FIGS. May be excessively removed as compared with the second absorbent layer 6. That is, side etching may occur. This is a side defect portion 10 a in which the first absorption layer 5 is missing from the second absorption layer 6 on the side surface of the absorption layer stack 7. 2D is a cross-sectional view taken along line BB in FIG. 3B, and the multilayer film and the capping layer are omitted in FIG. 3B.
Therefore, in the present invention, in order to repair the side surface defect portion 10a, as shown in FIGS. 1 (a) to 1 (e), the absorbent layer laminate 7 positioned on the side surface defect portion 10a of the reflective mask 1A is provided. Then, the FIB or EB 13 is removed while blowing the source gas 12 on the upper part of the side defect removing part 10b from which the absorption layer stack 7 has been removed by removing with the probe 11 of the scanning probe microscope (side defect removing step). Irradiation forms the deposited film 8 (deposited film forming step). Thereby, the reflective mask 1B in which the side surface defect portion 10a is repaired is obtained (repair process).

FIGS. 4A to 4E are process diagrams showing another example of the reflective mask manufacturing method of the present invention. First, as shown in FIG. 4A, the multilayer film 3, the capping layer 4, and the absorption layer laminate 7 including the first absorption layer 5 and the second absorption layer 6 were laminated on the substrate 2. A reflective mask blank 1C is prepared. During the production of reflective mask blanks, foreign matter may adhere or be mixed. For example, as shown in FIG. 4A, the foreign material 25 may be mixed in the first absorption layer 5. When the absorption layer laminate 7 (the first absorption layer 5 and the second absorption layer 6) is patterned using such a reflective mask blank 1C as shown in FIG. 4B, the patterning of the absorption layer laminate 7 is performed. In the process, the foreign matter 25 is removed, and the first absorbent layer 5 may be missing from the second absorbent layer 6 on the side surface of the absorbent layer laminate 7 as shown in FIG. This is a side defect portion 10 a in which the first absorption layer 5 is missing from the second absorption layer 6 on the side surface of the absorption layer stack 7.
Therefore, in the present invention, in order to repair the side surface defect portion 10a, as shown in FIGS. 4C to 4E, the reflective mask 1A is repaired as shown in FIGS. The absorber layer stack 7 located in the side defect portion 10a is removed with the probe 11 of the scanning probe microscope (side defect portion removing step), and the upper portion of the side defect portion removal portion 10b from which the absorber layer laminate 7 has been removed. Then, FIB or EB13 is irradiated while blowing the source gas 12 to form the deposited film 8 (deposited film forming step). Thereby, the reflective mask 1B in which the side surface defect portion 10a is repaired is obtained (repair process).

  As described above, in the present invention, when the reflective mask has a side surface defect portion in which the first absorption layer is missing from the second absorption layer on the side surface of the absorption layer stack, it is positioned at the side surface defect portion. By removing the absorbent layer stack and forming a deposited film on the side defect removed portion from which the absorbent layer stack has been removed, the side defect is repaired and a reflective mask having good transfer characteristics is manufactured. Is possible. Therefore, in the present invention, even if the reflective mask has a side surface defect portion, the transfer characteristics of the reflective mask can be recovered, so that the yield of the reflective mask can be greatly improved. .

  Hereafter, each process in the manufacturing method of the reflective mask of this invention is demonstrated.

1. Repair Process The repair process in the present invention includes a substrate, a multilayer film formed on the substrate, and an absorbent layer laminate formed in a pattern on the multilayer film, and the absorbent layer laminate is the above A first absorption layer formed on the multilayer film; and a second absorption layer formed on the first absorption layer, wherein the first absorption layer is formed on the side surface of the absorption layer stack. A side-surface defect removing step of removing the absorbent layer stack positioned in the side defect, and a side defect from which the absorbent layer stack is removed, of a reflective mask having a side defect missing from the layer And a deposited film forming step of forming a deposited film on the part removal portion.

  Hereinafter, the side surface defect removing step and the deposited film forming step in the repairing process, and the reflective mask having the side surface defect will be described.

(1) Side defect removing step The side defect removing step according to the present invention includes a substrate, a multilayer film formed on the substrate, and an absorption layer laminate formed in a pattern on the multilayer film. The absorbent layer laminate has a first absorbent layer formed on the multilayer film and a second absorbent layer formed on the first absorbent layer, and the side surface of the absorbent layer laminate has the above-mentioned It is a step of removing the absorbing layer laminate located in the side surface defect portion of the reflective mask having the side surface defect portion in which the first absorption layer is missing from the second absorption layer.

  The method for removing the absorbent layer stack located in the side defect portion is not particularly limited as long as the method can locally remove the absorbent layer stack. For example, a scanning probe microscope (SPM) : Scanning Probe Microscope) or a method of irradiating with an energy beam can be used.

  Among them, the method of removing with an SPM probe is preferable. This is because side etching does not occur in this method. Further, as compared with the method of irradiating with an energy beam, it is possible to reduce damage to the reflective mask when removing the absorption layer stack. In general, SPM is difficult to control in the height direction, and thus there is a risk of scratching the reflective mask surface. However, in the side defect portion in the present invention, the lower first absorption layer is the upper second absorption layer. It is possible to correct without causing such a problem.

  In the case of the removal method using the SPM probe, the SPM probe is not particularly limited, and a commonly used probe can be used, for example, a diamond probe.

In the case of the method of irradiating the energy beam, the energy beam is not particularly limited as long as it can locally etch the absorption layer stack positioned in the side defect portion, but FIB or EB is preferably used. . This is because advanced microfabrication is possible and it is possible to cope with minute side defect portions.
In the case of this method, the absorption layer laminate may be gas-assisted etched by irradiating an energy beam while supplying an assist gas to the absorption layer laminate located in the side surface defect portion. Compared with the case where only the energy beam is used, the absorber layer stack can be satisfactorily etched. In the case of FIB, an assist gas may or may not be used. On the other hand, in the case of EB, an assist gas is necessary.
The irradiation condition of the energy beam is not particularly limited as long as it can locally etch the absorbent layer stack located in the side defect portion and does not cause side etching, and is appropriately selected. .
Conventionally, when a black defect is corrected, when the absorption layer is repeatedly etched and oxidized so that side etching does not occur, there is a problem that correction takes time and labor. On the other hand, in the present invention, even when the condition is set such that side etching does not occur when removing the absorbent layer stack positioned in the side defect portion, the lower first absorption layer is the upper layer in the side defect portion. When the second absorption layer is an oxide film made of the material of the first absorption layer, the thickness of the second absorption layer is thin, and therefore it takes a lot of time and labor. It is possible to modify it.

When removing the absorbent layer stack positioned at the side defect, although not shown, the absorbent layer stack may be removed in the same size as the side defect, as shown in FIGS. 5 (a) and 5 (b). As illustrated, the absorbent layer laminate 7 may be largely removed from the side defect portion 10a, and as illustrated in FIGS. 6A and 6B, the absorbent layer laminate 7 is formed relative to the side defect portion 10a. May be removed small. In order to reliably repair the side defect portion, it is preferable to set so that the absorbent layer laminate is largely removed from the side defect portion, but the first defect layer is missing in the side defect portion. Since the second absorption layer is present, it may be difficult to accurately detect the position of the side defect portion. Therefore, the absorbent layer stack may be removed to be smaller than the side defect portion.
5 (b) is a cross-sectional view taken along the line CC of FIG. 5 (a), FIG. 6 (b) is a cross-sectional view taken along the line DD of FIG. 6 (a), and FIG. In FIG. 6A, the multilayer film and the capping layer are omitted.

  The shape of the side surface defect portion removing portion from which the absorbent layer stack has been removed is not particularly limited as long as the transfer characteristics of the reflective mask can be recovered by the repairing process in the present invention. For example, the shape of the side surface defect portion May be the same or different.

(2) Deposited film forming step The deposited film forming step in the present invention is a step of forming a deposited film on the side surface defect portion removing portion from which the absorption layer laminate has been removed.

As a method for forming a deposited film, a method of irradiating an energy beam while supplying a source gas is usually used.
As the source gas, a gas generally used when a CVD method using FIB or EB is applied can be used. For example, hydrocarbon gases such as phenanthrene, naphthalene, and pyrene, tungsten carbonyl (W (CO) ₆ ), chromium carbonyl (Cr (CO) ₆ ), cobalt carbonyl (Co ₂ (CO) ₈ ), iron carbonyl (Fe (CO) ₅ ) and other metal carbonyls, metal containing gases such as Trimethyl (methylcyclopentadienyl) platinum (MeCpPt (Me) ₃ ), silicon containing tetraethoxysilane (TEOS), 1,3,5,7-Tetramethylcyclotetra-siloxane Gas can be used. A deposited film containing carbon has an advantage that shape control is easy. In addition, a deposited film containing a metal such as tungsten or chromium has an advantage that high light shielding properties can be obtained.
The energy beam is not particularly limited as long as the deposited film can be locally formed on the side surface defect portion removing portion, but FIB or EB is preferably used. This is because advanced microfabrication is possible and it is possible to cope with a minute side defect portion removal portion. Among these, EB is preferable because damage can be reduced.

When forming the deposited film, the deposited film may be formed in the same size as the side defect portion removing portion, or the deposited film may be formed larger than the side defect portion removing portion. You may form a deposited film small with respect to a removal part. In order to reliably repair the side surface defect portion, it is preferable to set so that the deposited film is formed larger than the side surface defect portion removal portion.
Further, when forming the deposited film, the deposited film may be formed in the same size as the side defect portion, or the deposited film may be formed larger than the side defect portion. Thus, the deposited film may be formed small. For example, as shown in FIGS. 5 (a) and 5 (b), the absorbent layer stack 7 is largely removed from the side surface defect portion 10a, and the side surfaces as illustrated in FIGS. 7 (a) and 7 (b). In the case where the deposited film 8 is formed with the same size as the defect removing portion 10b, the deposited film 8 is formed larger than the side defect portion 10a. Further, for example, as shown in FIGS. 6A and 6B, the absorbent layer laminate 7 is removed small with respect to the side surface defect portion 10a, as illustrated in FIGS. 8A and 8B. In the case where the deposited film 8 is formed in the same size as the side defect portion removing portion 10b, the deposited film 8 is formed smaller than the side defect portion 10a. In order to reliably repair the side defect portion, it is preferable to set so that the deposited film is formed to be larger than the side defect portion. Since the absorption layer exists, it may be difficult to accurately detect the position of the side defect portion. Therefore, the deposited film may be formed smaller than the side defect portion. As described above, even when the deposited film is formed to be small with respect to the side surface defect portion, it is possible to obtain a reflective mask exhibiting good transfer characteristics.
7B is a cross-sectional view taken along line EE in FIG. 7A, FIG. 8B is a cross-sectional view taken along line FF in FIG. 8A, and FIG. In FIG. 8A, the multilayer film and the capping layer are omitted.

  The thickness of the deposited film is not particularly limited as long as a desired EUV absorption rate can be obtained. The composition of the deposited film and a buffer between the multilayer film and the absorbing layer stack as will be described later. When a layer is formed, it is appropriately selected according to the thickness of the buffer layer. When forming a deposited film using a hydrocarbon-based gas, the thickness of the deposited film can be, for example, about 5 nm to 200 nm, and preferably within a range of 50 nm to 150 nm. This is because if the deposited film is too thin, it is difficult to obtain a desired EUV absorption rate, and if the deposited film is too thick, it takes time to form the film.

(3) Reflective Mask Having Side Defects The reflective mask used in the repairing process in the present invention is a substrate, a multilayer film formed on the substrate, and an absorption formed in a pattern on the multilayer film. A layer laminate, and the absorbent layer laminate has a first absorbent layer formed on the multilayer film and a second absorbent layer formed on the first absorbent layer, and the absorbent layer laminate In the side surface of the body, the first absorption layer has a side defect portion that is missing from the second absorption layer.
Hereinafter, each configuration in the reflective mask will be described.

(A) Side surface defect portion In the side surface defect portion of the reflective mask according to the present invention, the absorbent layer stack does not have a vertical side surface, and the first absorption layer is formed on the side surface of the absorption layer stack from the second absorption layer. Is also missing.

  The side defect portion is not particularly limited as long as the first absorption layer is missing from the second absorption layer on the side surface of the absorbent layer stack, and the side defect formation factor is not particularly limited. For example, as shown in FIGS. 2B to 2D, the side surface defect portion 10a may be formed when the black defect portion 20 is corrected, as shown in FIGS. 4A to 4C. As described above, the side defect portion 10a may be caused by the foreign matter 25 attached or mixed during the production of the reflective mask blank 1C. Although not shown, the side defect portion is formed of the absorbent layer stack (the first absorption layer and the second absorption layer). It may be formed during the patterning of the absorption layer. Especially, it is preferable that a side surface defect part is formed when correcting a black defect part. When the black defect portion is corrected, side etching is likely to occur, which causes a decrease in yield. However, by applying the present invention, the yield can be increased. Further, in the present invention, since the side defect portion can be repaired, it is not necessary to correct the black defect portion so that side etching does not occur in a long time as in the conventional case, and the reflective mask is efficiently performed. It is because it can manufacture.

The size of the side surface defect portion is not particularly limited. For example, the distance in the direction perpendicular to the end portion of the side surface defect portion on the reflection region side is about 10 nm to 500 nm. When the distance of the side defect portion is too short, the transfer characteristics may not be greatly affected even if the side defect portion is present. When the distance of the side defect portion is too long, the first absorption layer Since it is missing, the self-supporting property of the second absorbent layer may be impaired.
The distance in the direction perpendicular to the end of the side defect portion on the reflection region side is the distance from the end of the side defect portion 10a on the reflection region side as shown in FIGS. This is the distance d in the vertical direction. When the side defect portion is formed when the black defect portion is corrected, the distance d of the side defect portion 10a is also referred to as a side etching amount.
FIG. 9B is a cross-sectional view taken along the line GG of FIG. 9A, and the multilayer film and the capping layer are omitted in FIG. 9A.

(B) Absorbent layer laminate The absorbent layer laminate used for the reflective mask in the present invention is formed in a pattern on the multilayer film, and is formed on the first absorbent layer and the first absorbent layer formed on the multilayer film. The second absorption layer is formed and absorbs EUV in EUV lithography using a reflective mask.

  The material of the first absorption layer is not particularly limited as long as it can absorb EUV. For example, Ta, TaN, TaSi, TaSiN, TaGe, TaGeN, TaB, TaBN, and Ta are the main components. A Ta-based material containing Ta or a Ta alloy such as a material, or a Cr-based material containing Cr, such as a material containing Cr and Cr as a main component and at least one component selected from N, O, and C, is used. Furthermore, WN, TiN, etc. can also be used.

The material of the second absorption layer is not particularly limited as long as it can absorb EUV. For example, the second absorption layer may be an oxide film made of the material of the first absorption layer, or may be formed separately from the first absorption layer.
In particular, the material of the second absorption layer is preferably a material having a low reflectivity of inspection light with respect to DUV in order to facilitate pattern defect inspection with DUV of a reflective mask for EUV lithography. Examples of the material of the second absorption layer include oxides of the Ta-based material, Cr (chromium), and SiO (silicon oxide).

  In the present invention, as described above, it is preferable that the side surface defect portion is formed in the black defect correction step, and therefore, the material of the second absorption layer is more etched than the material of the first absorption layer. It is particularly preferable that is slow. Such a material of the second absorption layer is appropriately selected according to the material of the first absorption layer. As a preferable combination of the materials of the first absorption layer and the second absorption layer, specifically, when the first absorption layer contains the Ta-based material and the second absorption layer contains the oxide of the Ta-based material And so on.

  For example, a magnetron sputtering method, an ion beam sputtering method, a CVD method, a vapor deposition method, or the like is used as a method for forming the first absorption layer.

  The method for forming the second absorption layer is appropriately selected according to the materials of the first absorption layer and the second absorption layer. For example, when the second absorption layer contains an oxide of the material of the first absorption layer, the second absorption layer may be a natural oxide film of the material of the first absorption layer, and oxidizes the surface of the first absorption layer. The second absorption layer (oxide film) may be formed by forming the second absorption layer (oxide film) by introducing the same material as that used when forming the first absorption layer and introducing oxygen. Also good. Specifically, when the first absorption layer contains the Ta-based material and the second absorption layer contains an oxide of the Ta-based material, the Ta or Ta alloy is very easily oxidized. The layer can be a natural oxide film of the material of the first absorption layer. Further, when the second absorption layer does not contain the oxide of the material of the first absorption layer, examples of the film formation method for the second absorption layer include a magnetron sputtering method, an ion beam sputtering method, a CVD method, and an evaporation method. Used.

  As a method for forming the first absorption layer and the second absorption layer in a pattern, a photolithography method is usually used. Specifically, a first absorption layer and a second absorption layer are formed on a substrate on which a multilayer film is formed, a photoresist layer is formed on the second absorption layer, the photoresist layer is patterned, and a photoresist pattern is formed. As a mask, the first absorption layer and the second absorption layer are etched, the remaining photoresist pattern is removed, and the first absorption layer and the second absorption layer are formed in a pattern. A general method can be used as the photolithography method.

(C) Multilayer film The multilayer film used for the reflective mask in the present invention is formed on a substrate.
As a material for the multilayer film, a material generally used for a multilayer film of a reflective mask can be used, and among them, a material having a very high reflectance with respect to EUV is preferably used. This is because the contrast can be increased when the reflective mask is used. As the multilayer film that reflects EUV, a periodic multilayer film of Mo / Si is usually used. In addition, as a multilayer film having a high reflectance in a specific wavelength range, for example, a Ru / Si periodic multilayer film, a Mo / Be periodic multilayer film, a Mo compound / Si compound periodic multilayer film, and a Si / Nb period A multilayer film, a periodic multilayer film of Si / Mo / Ru, a periodic multilayer film of Si / Mo / Ru / Mo, a periodic multilayer film of Si / Ru / Mo / Ru, and the like can also be used.

  The thickness of each layer constituting the multilayer film and the number of stacked layers are different depending on the material to be used and are appropriately adjusted. For example, as the Mo / Si periodic multilayer film, a multilayer film in which a Mo film and a Si film having a thickness of about several nm are stacked by 40 to 60 layers can be used.

The thickness of the multilayer film can be, for example, about 280 nm to 420 nm.
As a method for forming the multilayer film, for example, an ion beam sputtering method, a magnetron sputtering method, or the like is used.

(D) Capping layer In the reflective mask used in the present invention, a capping layer may be formed between the multilayer film and the absorbent layer laminate. The capping layer is provided to prevent oxidation of the multilayer film and to protect the reflective mask during cleaning. By forming the capping layer, when the outermost surface of the multilayer film is a Si film or a Mo film, the Si film or the Mo film can be prevented from being oxidized. If the Si film or the Mo film is oxidized, the reflectance of the multilayer film may be reduced.

The material for the capping layer is not particularly limited as long as it exhibits the above functions, and examples thereof include Si and Ru.
Moreover, as thickness of a capping layer, it can be set as about 2 nm-15 nm, for example.
Examples of the method for forming the capping layer include a sputtering method.

(E) Buffer layer In the reflective mask used in the present invention, a buffer layer may be formed between the multilayer film and the absorbent layer stack. The buffer layer is provided to prevent damage to the lower multilayer film. By forming the buffer layer, it is possible to prevent the lower multilayer film from being damaged when the absorption layer stack is subjected to pattern etching by a method such as dry etching.
In the present invention, when the capping layer is formed on the multilayer film, the capping layer and the buffer layer are usually laminated on the multilayer film in this order.

As the material of the buffer layer, any material having high etching resistance may be used. Usually, a material having a different etching characteristic from that of the absorption layer stack, that is, a material having a high etching selectivity with the absorption layer stack is used. The etching selectivity of the buffer layer and the absorption layer laminate is preferably 5 or more, more preferably 10 or more, and still more preferably 20 or more. Furthermore, the material for the buffer layer is preferably a material having low stress and excellent smoothness. In particular, the smoothness of the buffer layer is preferably 0.3 nmRms or less. From such a viewpoint, it is preferable that the material of the buffer layer has a microcrystalline or amorphous structure.
Examples of such a buffer layer material include SiO ₂ , Al ₂ O ₃ , Cr, and CrN.

Further, the thickness of the buffer layer can be, for example, about 5 nm to 100 nm.
Examples of the method for forming the buffer layer include a magnetron sputtering method and an ion beam sputtering method. When SiO ₂ is used, it is preferable to form SiO ₂ on the multilayer film in an Ar gas atmosphere using an SiO ₂ target by RF magnetron sputtering.

(F) Substrate As the substrate used for the reflective mask in the present invention, those generally used for the reflective mask substrate can be used, and for example, a glass substrate or a metal substrate can be used. Among these, a glass substrate is preferably used. A glass substrate is particularly suitable as a substrate for a reflective mask because good smoothness and flatness can be obtained. Examples of the material of the glass substrate include quartz glass, amorphous glass having a low thermal expansion coefficient (for example, SiO ₂ —TiO ₂ glass), crystallized glass on which β quartz solid solution is precipitated, and the like. Examples of the material for the metal substrate include silicon and Fe-Ni-based invar alloys.

  The substrate preferably has a smoothness of 0.2 nmRms or less and a flatness of 100 nm or less in order to obtain a high reflectance and transfer accuracy of a reflective mask. In addition, unit Rms which shows smoothness is a root mean square roughness, and can be measured using an atomic force microscope. The flatness is a value indicating the warpage (deformation amount) of the surface indicated by TIR (Total Indicated Reading). This value is the difference in height between the highest position on the substrate surface above the focal plane and the lowest position below the focal plane when the plane defined by the least square method based on the substrate surface is the focal plane. Is the absolute value of. The smoothness is smoothness in a 10 μm square area, and the flatness is flatness in a 142 mm square area.

  Moreover, as thickness of a board | substrate, it can be set as about 6 mm-7 mm, for example.

2. Black Defect Correction Process The reflective mask manufacturing method of the present invention includes a black defect correction process for removing the absorber layer stack located in the black defect portion resulting from the surplus of the absorber layer stack before the repair step. It is preferable to have. As described above, when the black defect portion is corrected, side etching is likely to occur, which causes a decrease in yield. However, the yield can be increased by applying the present invention. Further, in the present invention, since it is possible to repair the side defect portion such as side etching, it is not necessary to correct the black defect portion so that side etching does not occur taking a long time as in the prior art, This is because a reflective mask can be manufactured efficiently.

  A method for removing the absorber layer stack located in the black defect portion is not particularly limited as long as it can locally etch the absorber layer stack by irradiating an energy beam. In particular, a method of gas-assisted etching of the absorption layer stack by irradiating an energy beam while supplying an assist gas to the absorption layer stack positioned in the black defect portion is preferably used. This is because the absorbent layer stack can be etched better than when only the energy beam is used. Moreover, since side etching is likely to occur in gas assist etching, it is preferable to apply the present invention.

  The energy beam is not particularly limited as long as it can locally etch the absorption layer laminate positioned in the black defect portion, but FIB or EB is preferably used. This is because advanced microfabrication is possible and it is possible to deal with fine black defects.

3. Side defect inspection step The reflective mask manufacturing method of the present invention preferably has a side defect inspection step for inspecting the side defect of the reflection mask before the repair step. When the black defect correction step is performed, a side defect portion inspection step is performed after the black defect correction step.

  The method for inspecting the side defect portion is not particularly limited as long as it is a method capable of detecting the side defect portion in which the first absorption layer is missing from the second absorption layer on the side surface of the absorbent layer stack, For example, the method using an electron microscope is mentioned.

4). Other Processes The reflective mask manufacturing method of the present invention includes the above-described repair process, black defect correction process, and side defect inspection process, a preparation process for preparing reflective mask blanks, and an absorption patterning for the absorption layer. A layer patterning step or the like may be included.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

The following examples illustrate the present invention in more detail.
[Example 1]
(1) Simulation 1
The effect of the present invention was verified in detail by simulation. The simulator used was EM-Suite made by Panoramic Technology. The simulation was performed using an actual EUV mask structure and an optical system of an EUV transfer apparatus as models.
As shown in FIGS. 10A and 10B, the EUV mask has a multilayer film composed of 40 pairs of molybdenum and silicon (film thickness: 2.8 nm / 4.2 nm) on a substrate 2 made of silicon oxide. 3 and a capping layer 4 (thickness 11 nm) made of silicon are sequentially laminated, and an absorption layer laminate 7 (first absorption layer 5 made of tantalum nitride and tantalum) having a line pattern with a line width of 225 nm is formed on the capping layer 4. The second absorption layer 6) (thickness 51 nm) made of the above oxide was formed. Further, the side etching amount 31 was changed in the range of 0 to 100 nm as the side surface defect portion 10a (side etching occurrence location). 10B is a cross-sectional view taken along the line HH in FIG. 10A, and the multilayer film and the capping layer are omitted in FIG.
The transfer conditions were set in the optical system of an EUV exposure apparatus SFET (Small Field Exposure Tool) manufactured by Canon Inc., and NA = 0.3 and σ = 0.3 / 0.7 (inner / outer). The transfer dimension was calculated from an optical image that was subjected to 1/5 reduction exposure on a wafer.

  FIG. 11 shows the relationship between the side etching amount 31 and the shift amount of the transfer dimension. In addition, since the line width of the absorption layer laminated body 7 is 225 nm and the reduction ratio is 1/5, in FIG. 11, the amount of deviation of the transfer dimension = 0 nm represents the transfer dimension = 45 nm. As can be seen from FIG. 11, when the side etching amount 31 is 30 nm or more, the transfer dimension is expected to vary by 5%. Therefore, when side etching of 30 nm or more occurs, it is necessary to recover EUV transfer characteristics.

(2) Simulation 2
Next, it was verified by simulation that the repairing process in the present invention is effective in recovering EUV transfer characteristics.
As shown in FIGS. 10A and 10B and FIGS. 12A and 12B, the position and shape of the deposited film used in the simulation are absorptions located at the side surface defect portion 10a (side etching occurrence location). The layer stacked body 7 was removed, and verification was performed using a model in which a rectangular deposited film 8 was formed on the side surface defect removing portion 10b from which the absorbing layer stacked body 7 was removed. 12B is a cross-sectional view taken along the line II of FIG. 12A, and the multilayer film and the capping layer are omitted in FIG. The other structure of the EUV mask was the same as that of the EUV mask shown in FIGS. 10 (a) and 10 (b).
The simulation conditions were the same as those in the simulation 1. The deposited film 8 has an optical constant designated as a hydrocarbon.

FIG. 13 shows the relationship between the deposited film thickness and the amount of shift in the transfer dimension under the conditions where the side etching amount 31 is 30 nm, 50 nm, 75 nm, and 100 nm. In addition, since the line width of the absorption layer laminated body 7 is 225 nm and the reduction ratio is 1/5, the shift amount of transfer dimension = 0 nm in FIG. 13 represents the transfer dimension = 45 nm.
As a result of the simulation, by forming a deposited film with an appropriate film thickness for each side etching amount, the displacement amount of the transfer dimension is zero, that is, the transfer size is close to the normal portion, and the repair process in the present invention is the side defect portion. It was confirmed that it was effective in recovering the EUV transfer characteristics of (side etching occurrence location).
According to the simulation result, when the side etching amount is 50 nm, the amount of deviation of the EUV transfer dimension can be made within 5% by depositing the deposited film to about 30 nm. Similarly, when the amount of side etching occurs 100 nm, the amount of deviation of the EUV transfer dimension can be kept within 5% by depositing a deposited film of about 40 nm, preferably about 50 nm. In the simulation, hydrocarbon is assumed as the deposited film, but a metal-containing film such as tungsten or chromium having higher light shielding ability may be used.

[Example 2]
First, a multilayer film composed of 40 pairs of molybdenum and silicon (thickness 2.8 nm / 4.2 nm) and a capping layer (thickness 11 nm) made of silicon are sequentially laminated on a substrate made of silicon oxide. A reflective mask in which an absorption layer stack (a first absorption layer made of tantalum nitride and a second absorption layer made of tantalum oxide) (film thickness 51 nm) was formed in a pattern on the layer was prepared. The pattern of the first absorption layer and the second absorption layer was a line pattern having a line width of 225 nm, and a black defect portion in which a line having a width of 100 nm and a length of 300 nm swelled was formed as a black defect portion.
Next, the black defect portion was removed by gas assist etching in which FIB was irradiated while introducing an etching gas made of xenon fluoride into the black defect portion. As the FIB apparatus, an FIB apparatus SIR7 (gallium ion, acceleration voltage 15 kV) for photomask correction manufactured by SII Nano Technology Co., Ltd. was used. When the black defect part correction | amendment location was observed with the electron microscope, it was confirmed that the side etching has generate | occur | produced in the absorption layer laminated body. At this time, the side etching amount was 100 nm.
Next, by using the above-mentioned FIB apparatus, FIB was irradiated while introducing an etching gas, thereby removing the absorbent layer laminate at the side defect (side etching occurrence location).
Next, using the FIB apparatus, the deposited film was formed by irradiating FIB while introducing the raw material gas into the side surface defect portion removing portion from which the absorption layer stack was removed. At this time, phenanthrene was used as the source gas. As calculated in Example 1 above, the deposited film was deposited with a thickness of 50 nm.

The absorption layer laminated body located at the side defect portion (side etching occurrence location) is removed, and the line pattern including the location where the deposited film is formed is formed on the wafer using an EUV exposure apparatus SFET manufactured by Canon Inc. 1/5 reduction transfer to the resist applied. Next, a resist pattern was obtained by developing the resist.
By observing this resist pattern with a SEM type size measuring machine (CG4000) manufactured by Hitachi High-Technologies Corporation, the transfer characteristics of the repaired portion were evaluated. It was confirmed by SEM observation that a resist pattern equivalent to a normal pattern was formed at a place where the absorbing layer stack was removed and the deposited film was formed at the side defect (side etching occurrence place).

[Example 3]
The same as in Example 2 except that EB was used instead of FIB in the correction of the black defect portion, the removal of the absorption layer laminate positioned in the side defect portion (side etching occurrence location), and the formation of the deposited film. did.
As the EB apparatus, a FIB-SEM double beam apparatus XVision200 manufactured by SII Nano Technology Co., Ltd. was used. At this time, the acceleration voltage of EB was 1 keV, and phenanthrene was used as the source gas.

The absorption layer laminated body located at the side defect portion (side etching occurrence location) is removed, and the line pattern including the location where the deposited film is formed is formed on the wafer using an EUV exposure apparatus SFET manufactured by Canon Inc. 1/5 reduction transfer to the resist applied. Next, a resist pattern was obtained by developing the resist.
By observing this resist pattern with a SEM type size measuring machine (CG4000) manufactured by Hitachi High-Technologies Corporation, the transfer characteristics of the repaired portion were evaluated. It was confirmed by SEM observation that a resist pattern equivalent to a normal pattern was formed at a place where the absorbing layer stack was removed and the deposited film was formed at the side defect (side etching occurrence place).

[Example 4]
In the formation of the deposited film, the FIB is used to correct the black defect portion, and the probe of the scanning probe microscope is used instead of the FIB in the removal of the absorbing layer stack located at the side defect portion (side etching occurrence location). Example 2 was repeated except that EB was used instead of FIB.
A mask defect correcting device SPM6300 manufactured by SII Nano Technology Co., Ltd. was used for the scanning probe microscope.
As the EB apparatus, a FIB-SEM double beam apparatus XVision200 manufactured by SII Nano Technology Co., Ltd. was used. At this time, the acceleration voltage of EB was 1 keV, and phenanthrene was used as the source gas.

The absorption layer laminated body located at the side defect portion (side etching occurrence location) is removed, and the line pattern including the location where the deposited film is formed is formed on the wafer using an EUV exposure apparatus SFET manufactured by Canon Inc. 1/5 reduction transfer to the resist applied. Next, a resist pattern was obtained by developing the resist.
By observing this resist pattern with a SEM type size measuring machine (CG4000) manufactured by Hitachi High-Technologies Corporation, the transfer characteristics of the repaired portion were evaluated. It was confirmed by SEM observation that a resist pattern equivalent to a normal pattern was formed at a place where the absorbing layer stack was removed and the deposited film was formed at the side defect (side etching occurrence place).

[Example 5]
First, a multilayer film composed of 40 pairs of molybdenum and silicon (thickness 2.8 nm / 4.2 nm) and a capping layer (thickness 11 nm) made of silicon are sequentially laminated on a substrate made of silicon oxide. A reflective mask in which an absorption layer stack (a first absorption layer made of tantalum nitride and a second absorption layer made of tantalum oxide) (film thickness 51 nm) was formed in a pattern on the layer was prepared. The pattern of the first absorption layer and the second absorption layer is a line pattern having a line width of 225 nm.
When the reflective mask was subjected to pattern defect inspection using a mask pattern defect inspection apparatus NPI-6000EUVα manufactured by New Flare Technology, Inc., a defect was detected in the line pattern having a line width of 225 nm. When this defect was observed with an electron microscope, side etching with a width of 75 nm and a length of 75 nm was confirmed in the absorption layer laminate.
Next, in the same manner as in Example 2, the absorbent layer laminate at the side surface defect portion (side etching occurrence location) was removed to form a deposited film. At this time, a deposited film having a thickness of 50 nm was formed by irradiating FIB using phenanthrene as a source gas.

The absorption layer laminated body located at the side defect portion (side etching occurrence location) is removed, and the line pattern including the location where the deposited film is formed is formed on the wafer using an EUV exposure apparatus SFET manufactured by Canon Inc. 1/5 reduction transfer to the resist applied. Next, a resist pattern was obtained by developing the resist.
By observing this resist pattern with a SEM type size measuring machine (CG4000) manufactured by Hitachi High-Technologies Corporation, the transfer characteristics of the repaired portion were evaluated. It was confirmed by SEM observation that a resist pattern equivalent to a normal pattern was formed at a place where the absorbing layer stack was removed and the deposited film was formed at the side defect (side etching occurrence place).

DESCRIPTION OF SYMBOLS 1A, 1B ... Reflective type mask 1C ... Reflective type mask blank 2 ... Substrate 3 ... Multilayer film 4 ... Capping layer 5 ... 1st absorption layer 6 ... 2nd absorption layer 7 ... Absorption layer laminated body 8 ... Deposition film 10a ... Side surface defect Part 10b ... Side defect removing part 11 ... Probe of scanning probe microscope 12 ... Source gas 13 ... FIB or EB
20 ... Black defect part 21 ... Assist gas 22 ... FIB or EB

Claims (3)

A first layer having a substrate, a multilayer film formed on the substrate, and an absorption layer stack formed in a pattern on the multilayer film, wherein the absorption layer stack is formed on the multilayer film; A side defect having an absorption layer and a second absorption layer formed on the first absorption layer, wherein the first absorption layer is missing from the second absorption layer on a side surface of the absorption layer laminate. A side defect removing step of removing the absorbent layer stack located in the side defect of the reflective mask having a portion;
A method of manufacturing a reflective mask, comprising: a repairing step comprising: a deposited film forming step of forming a deposited film on the side surface defect portion removing portion from which the absorbent layer stack has been removed.   Before the repairing step, the method has a black defect correcting step of removing the absorbing layer laminate located in the black defect portion due to the surplus of the absorbing layer laminate, and the side defect portion is the black defect correcting step. 2. The method of manufacturing a reflective mask according to claim 1, wherein the reflective mask is formed.   3. The reflective mask according to claim 1, wherein, in the side surface defect portion removing step, the absorbing layer stack positioned at the side surface defect portion is removed with a probe of a scanning probe microscope. Manufacturing method.

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