JP2014053564A - Method for manufacturing reflective mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a reflective mask in such a manner that, upon forming a part such as a designed residual defect, which is in contact with a part of an original mask pattern and has a smaller size than the original mask pattern, as an absorber pattern of the reflective mask, features of the part in a fine size can be obtained conforming to the designed features compared to a conventional methods.SOLUTION: A pattern to be a part with a desired fine size is formed in a hard mask layer formed on an absorption layer of a reflective mask blank; then a mask pattern partially overlapping the pattern formed in the hard mask layer is formed in a resist layer formed on the hard mask layer; and the absorption layer exposed through the pattern formed in the hard mask layer and through the pattern formed in the resist layer is subjected to dry etching.

Description

  The present invention relates to a method of manufacturing a reflective mask for EUV exposure for transferring a mask pattern onto a wafer using extreme ultraviolet light (hereinafter referred to as EUV).

  Currently, as a lithography technique for semiconductor devices, an optical projection exposure method using an ArF excimer laser with a wavelength of 193 nm is mainly used. However, since the resolution limit will eventually be reached, an exposure method using an excimer laser is eventually used. New lithographic techniques to replace are being studied.

  As this new lithography technique, an EUV lithography technique that uses a EUV light having a wavelength of 13.5 nm, which is a shorter wavelength than an excimer laser, to reduce and expose a mask pattern to about ¼ has attracted attention. In this EUV exposure, since the EUV light used for the exposure has a very short wavelength, a refractive optical system cannot be used, and a reflective mask has been proposed (Patent Document 1). .

An example of the reflective mask for EUV exposure (hereinafter referred to as a reflective mask) is shown in FIG. Here, FIG. 11A shows a schematic sectional view of the reflective mask 100, and FIG. 11B shows a partial plan view of the region R shown in FIG. 11A.
For example, as shown in FIG. 11, the reflective mask 100 includes a multilayered structure reflecting layer 112 that reflects EUV light on a substrate 111 that has been optically polished, and EUV light as a mask pattern. And an absorber pattern 113 to be absorbed.
Although not shown, a capping layer for protecting the reflective layer 112 and a buffer layer for preventing etching damage to the reflective layer 112 when the absorber pattern 113 is formed are provided on the reflective layer 112. It may be done. In addition, a low reflection layer may be formed on the upper surface of the absorber pattern 113 in order to facilitate optical inspection.
Further, a conductive layer may be formed on a surface (back surface) opposite to the main surface on which the reflective layer 112 is provided in the substrate 111. This conductive layer is provided to electrostatically attract the back surface of the reflective mask.

Even in the production of the reflective mask, a residual defect (also referred to as a black defect) in which an unnecessary absorber portion is formed in addition to the absorber pattern constituting the original mask pattern, similarly to the conventional photomask. It may occur (Patent Document 2).
Two typical forms are shown in FIG. For example, the residual defect (convex defect) 121 shown in FIG. 12A has a form that protrudes from the edge of the line-shaped pattern portion that is the original mask pattern of the absorber pattern 113. The residue defect (bridge defect) 122 shown in FIG. 12B has a form that bridges between two line-shaped patterns that are the original mask pattern of the absorber pattern 113.

In order to inspect and evaluate the above-mentioned residue defect, a reflection type having a designed residue defect part (designed residue defect part) is designed by designing a pseudo residue defect resembling the shape and size of the target residue defect. It is necessary to manufacture a mask.
In the reflective mask having the design residue defect portion as described above, since the position, shape, size, etc. of the design residue defect portion are known in advance, for example, the sensitivity of the defect inspection apparatus using the reflection mask is known. By performing evaluation or the like, it becomes possible to develop a more practical defect inspection apparatus.
Therefore, conventionally, a method of adding a design residue defect pattern for forming the design residue defect portion to the mask pattern and forming the mask pattern and the design residue defect pattern in one resist in the same process is used. Thus, a reflective mask having the design residue defect portion has been manufactured. An example of the manufacturing method is shown in FIG.

For example, conventionally, as shown in FIG. 13, first, a reflective mask blank 210 having a substrate 211, a reflective layer 212, and an absorption layer 213A is prepared, and a resist layer 216A is formed on the absorption layer 213A ( 13A), the mask pattern and the design residue defect pattern are drawn by electron beam drawing to form a resist pattern 216 including a design residue defect pattern portion 216a in addition to the mask pattern (FIG. 13A). b)), the absorption layer 213A exposed using the resist pattern 216 as a mask is dry-etched (FIG. 13C), and then the resist pattern 216 is removed to form an absorber pattern including a design residue defect 221. A reflective mask 200 having 213 was manufactured.
Although FIG. 13 shows a method for manufacturing a reflective mask having a design residue defect portion of the convex defect type, conventionally, the design residue defect portion of the bridge defect is formed in the same manner. It was.

JP-A-63-201656 JP 2000-98591 A

Here, the dimension required for the absorber pattern of the reflective mask is, for example, a half pitch of a 1: 1 L & S (line and space) pattern is four times the size of a semiconductor lithography node. The half pitch of the absorber pattern is 128 nm.
The size of the design residue defect necessary for inspection and evaluation of the reflective mask is required to be finer than the half pitch of the absorber pattern.
For example, in the case of the convex defect 121 shown in FIG. 12A, the length (L1) of the protrusion is a size of 1/2 or less (64 nm or less) of the half pitch. This size tends to be further refined in the future.

  However, in such a fine size, the design residue defect portion 221 obtained by the above-described conventional manufacturing method has a length of the projection portion as in the residue defect (convex defect) 121 shown in FIG. The resolution of the resist used for forming the absorber pattern is designed even when the length of the portion contacting the line-shaped pattern portion which is the original mask pattern of the absorber pattern 113 is a rectangular shape having a length D1. Because of this limitation, it was a blurred form with a contour that deviated from the designed form.

  More specifically, as shown in FIG. 14A, the design residue defect portion 221 has a hilly form, and the edge of the design residue defect portion 221 and the original mask pattern of the absorber pattern 213 are formed. The angle at which the edges of the line-shaped pattern part intersect is greatly apart from 90 degrees, the length (L1b) of the protrusion becomes smaller than the design value (L1), and the original mask of the absorber pattern 213 The length (D1b) of the portion in contact with the line-shaped pattern portion, which is a pattern, is larger than the design value (D1), and there is a problem that only a reflective mask that is not suitable for practical inspection or evaluation is obtained. It was.

  Also in the case of the bridge type defect, the design residue defect portion 222 obtained by the above-described conventional manufacturing method is, for example, an absorber pattern like the residue defect (bridge type defect) 122 shown in FIG. Even if the length of the portion in contact with the line-shaped pattern portion 113 that is the original mask pattern of 113 is designed in a rectangular shape of D2, the length of the contact portion (D2) is small. Similarly, from the limit of the resolution of the resist used for forming the absorber pattern, as shown in FIG. 14B, the edge of the design residue defect 222 and the line pattern portion which is the original mask pattern of the absorber pattern 213 The angle at which the edges of the contacts intersect with each other is greatly separated from 90 degrees, the central portion is narrowed, and the length (D2b) of the contact portion is larger than the design value (D2). Will in Tsu, there is a problem that is not suitable for practical examination and evaluation.

  The present invention has been made in view of the above-described problems, and an object of the present invention is a portion that is in contact with a portion of an original mask pattern, such as the above-described design residue defect portion, and is more than the mask pattern. In the case where a portion having a fine size is formed as an absorber pattern of a reflective mask, the shape of the fine size portion is set as designed as compared with the prior art. The angle at which the edge of the small-sized portion intersects the edge of the mask pattern portion is closer to the design value than before, and the length of the portion where the fine-sized portion contacts the mask pattern portion is Another object of the present invention is to provide a method of manufacturing a reflective mask that can be made a length closer to the design value than before.

  As a result of various studies, the present inventor firstly formed a pattern that becomes a desired fine size portion such as the design residue defect portion on the hard mask layer formed on the absorption layer of the reflective mask blank. And then forming a mask pattern partially overlapping with the pattern formed on the hard mask layer on the resist layer formed on the hard mask layer, and the pattern formed on the hard mask layer and the resist layer The present invention has been completed by finding that the above-mentioned problems can be solved by dry-etching the absorbing layer exposed from the pattern formed on the substrate.

  That is, the invention according to claim 1 of the present invention partially includes a substrate, a reflective layer made of a multilayer film formed on the main surface of the substrate, and an absorption layer formed on the reflective layer. A reflective mask for EUV exposure having at least an absorber pattern formed by removing the reflective mask blank, the reflective mask blank having at least the substrate, the reflective layer, and the absorbent layer in this order. A step of preparing a reflective mask blank with a hard mask layer in which a hard mask layer is formed on the absorption layer; a step of forming a first resist layer on the hard mask layer; and the first resist layer Forming a first resist pattern by patterning the substrate, and etching the hard mask layer exposed from the first resist pattern to form a hard mask pattern A step of removing the first resist pattern, a step of forming a second resist layer on the hard mask pattern and the absorbing layer exposed from the hard mask pattern, and the second resist layer Forming a second resist pattern partially overlapping the hard mask pattern, etching the second resist pattern and the absorbing layer exposed from the hard mask pattern, and A method of manufacturing a reflective mask, comprising: a step of forming an absorber pattern; a step of removing the second resist pattern; and a step of removing the hard mask pattern.

  In the invention according to claim 2 of the present invention, the hard mask pattern has a plurality of independent patterns separated from each other, and a portion of the independent pattern exposed from the second resist pattern is the absorber pattern. 2. The method of manufacturing a reflective mask according to claim 1, wherein an etching mask for forming the design residue defect portion is formed.

  In the invention according to claim 3 of the present invention, the first resist layer is made of a negative resist, and the reflective mask according to claim 1 or 2 is manufactured. Is the method.

  In the invention according to claim 4 of the present invention, the second resist layer is composed of a positive resist. It is a manufacturing method of a reflective mask.

  Further, in the invention according to claim 5 of the present invention, the first resist layer is made of a resist having a higher resolution than the second resist layer. 5. A method for producing a reflective mask according to any one of 4 above.

  In the invention according to claim 6 of the present invention, the thickness of the first resist layer is thinner than the thickness of the second resist layer. It is a manufacturing method of a reflective mask given in one paragraph.

  In the invention according to claim 7 of the present invention, an overlapping area between the independent pattern and the second resist pattern is different in each independent pattern. It is a manufacturing method of the reflection type mask as described in above.

  Further, in the invention according to claim 8 of the present invention, by changing a relative position between the independent pattern and the second resist pattern, an overlapping area between the independent pattern and the second resist pattern is 8. The method of manufacturing a reflective mask according to claim 7, wherein the independent masks are different.

  Further, in the invention according to claim 9 of the present invention, by changing the shape and / or the area of the independent pattern, the overlapping region of the independent pattern and the second resist pattern is each independent pattern. It is different, It is a manufacturing method of the reflective mask of Claim 7 or Claim 8 characterized by the above-mentioned.

According to the present invention, when a portion that is in contact with a portion of the original mask pattern and is smaller in size than the mask pattern is formed as the absorber pattern of the reflective mask, the fine size is reduced. The shape of the portion of the mask pattern is made as designed as before, more specifically, the angle at which the edge of the fine size portion intersects with the edge of the portion of the mask pattern is set to a design value than before. The length of the portion where the fine size portion contacts the portion of the mask pattern can be made closer to the design value than before.
And the reflective mask which has the design residue defect part suitable for a practical test | inspection and evaluation can be manufactured by making the part of the said fine size into the above-mentioned design residue defect part.
Furthermore, it is possible to develop a more practical defect inspection apparatus by performing sensitivity evaluation of the defect inspection apparatus using the reflective mask obtained by the manufacturing method of the present invention.

It is typical process drawing which shows an example of the manufacturing method of the reflective mask which concerns on this invention. It is a typical process drawing which shows an example of the manufacturing method of the reflective mask which concerns on this invention following FIG. It is a fragmentary top view explaining the principal part of the manufacturing method of the reflective mask based on this invention shown to FIG. 1 and FIG. It is explanatory drawing which shows an example of the relationship between the hard mask pattern and the 2nd resist pattern in the manufacturing method of the reflective mask which concerns on this invention. It is explanatory drawing which shows the other example of the relationship between the hard mask pattern and the 2nd resist pattern in the manufacturing method of the reflection type mask which concerns on this invention. It is explanatory drawing which shows the other example of the relationship between the hard mask pattern and 2nd resist pattern in the manufacturing method of the reflection type mask which concerns on this invention. It is typical process drawing which shows the other example of the manufacturing method of the reflection type mask which concerns on this invention. FIG. 8 is a schematic process diagram illustrating another example of the manufacturing method of the reflective mask according to the present invention subsequent to FIG. 7. It is a fragmentary top view explaining the principal part of the manufacturing method of the reflective mask based on this invention shown to FIG. 7 and FIG. It is a figure explaining the Example using the manufacturing method of the reflective mask which concerns on this invention, and the comparative example using the manufacturing method of the conventional reflective mask. It is explanatory drawing which shows an example of a reflective mask, (a) is sectional drawing, (b) is a partial top view. It is explanatory drawing which shows the example of the residue defect in a reflective mask. It is typical process drawing which shows an example of the manufacturing method of the conventional reflection type mask. It is explanatory drawing which shows the example of the design residue defect part by the manufacturing method of the conventional reflection type mask.

[Reflective mask manufacturing method]
Hereinafter, the manufacturing method of the reflective mask according to the present invention will be described in detail.
The method for manufacturing a reflective mask according to the present invention partially removes a substrate, a reflective layer composed of a multilayer film formed on the main surface of the substrate, and an absorption layer formed on the reflective layer. A reflective mask for EUV exposure having at least an absorber pattern formed in this order, the absorption of the reflective mask blank having at least the substrate, the reflective layer, and the absorbent layer in this order. A step of preparing a reflective mask blank with a hard mask layer having a hard mask layer formed on the layer; a step of forming a first resist layer on the hard mask layer; and Forming a first resist pattern by pattern drawing and etching the hard mask layer exposed from the first resist pattern to form a hard mask pattern Removing the first resist pattern; forming a second resist layer on the hard mask pattern and the absorbing layer exposed from the hard mask pattern; and the second resist layer. Forming a second resist pattern partially overlapping the hard mask pattern, etching the second resist pattern and the absorbing layer exposed from the hard mask pattern, and The method includes a step of forming an absorber pattern, a step of removing the second resist pattern, and a step of removing the hard mask pattern.

Since the above-described steps are included, according to the present invention, a portion that is in contact with a portion of the original mask pattern, such as the above-described design residue defect portion, and that is smaller than the mask pattern. Is formed as the absorber pattern of the reflective mask, the shape of the fine-sized portion can be made as designed as compared with the prior art.
Here, first, a description will be given of a method of manufacturing a reflective mask having the above-mentioned fine defect size design residual defect portion of the convex defect type shown in FIG.

[First Embodiment]
1 and 2 are schematic process diagrams showing an example of a first embodiment of a method for manufacturing a reflective mask according to the present invention.
In order to manufacture the reflective mask 1 having the design defect defect portion of the convex defect type shown in FIG. 12 (a) using the manufacturing method of the present invention, first, as shown in FIG. 1 (a). A reflective mask blank with a hard mask layer is prepared by forming a hard mask layer 14A on the absorbing layer 13A of the reflective mask blank 10 having at least the substrate 11, the reflective layer 12, and the absorbing layer 13A.
In the present invention, the reflective mask blank 10 may be prepared, and the hard mask layer 14A may be formed on the absorption layer 13A.

  Next, a first resist layer 15A is formed on the hard mask layer 14A (FIG. 1B), and pattern drawing is performed by an electron beam drawing apparatus or the like to form a first resist pattern 15 (FIG. 1 (c)), the hard mask layer 14A exposed from the first resist pattern 15 is etched to form a hard mask pattern 14 (FIG. 1D), and then the first resist pattern 15 is formed. It is removed (FIG. 1 (e)).

Next, a second resist layer 16A is formed on the hard mask pattern 14 and the absorption layer 13A exposed from the hard mask pattern 14 (FIG. 2F), and pattern drawing is performed by an electron beam drawing apparatus or the like. Then, the second resist pattern 16 is formed (FIG. 2G).
Here, in the present embodiment, it is important that the second resist pattern 16 partially overlaps the hard mask pattern 14.

  Next, the absorber layer 13A exposed from the second resist pattern 16 and the hard mask pattern 14 is etched to form an absorber pattern 13 including a design residue defect portion 21 (FIG. 2 (h)). Thereafter, the second resist pattern 16 is removed (FIG. 2 (i)), and then the hard mask pattern 14 is removed to obtain the above-described reflective mask 1 (FIG. 2 (j)).

Here, as described above, in the conventional method, the method of forming the mask pattern and the design residue defect pattern in one resist in the same process is used. More specifically, as shown in FIG. 13B described above, in the same electron beam drawing process, a resist pattern 216 including a design residue defect pattern portion 216a in addition to a mask pattern is formed on one resist. Was forming.
Therefore, the design residue defect pattern portion 216a, which is a part of the one resist pattern (resist pattern 216), is subjected to the influence (so-called proximity effect) when patterning the portion of the mask pattern that comes into contact. As a result, the outline was blurred and deviated from the designed form. For example, as shown in FIG. 14A described above, the angle at which the edge of the design residue defect portion 221 and the edge of the line pattern portion that is the original mask pattern of the absorber pattern 213 intersect with each other is greatly separated from 90 degrees. It became a form of a hilly outline.

On the other hand, in the present invention, as described above, a pattern including a portion that becomes the design residue defect portion 21 is formed as the hard mask pattern 14 using the first resist, and after the first resist pattern 15 is removed, A mask pattern (second resist pattern 16) is formed using another resist (second resist).
That is, the mask pattern and the design residue defect pattern are formed in different resists in different processes.
Therefore, the pattern (first resist pattern 15) including the portion that becomes the design residue defect 21 is not affected by the pattern drawing of the mask pattern (second resist pattern 16) (so-called proximity effect). .
For example, as shown in FIG. 3 (a), the shape of the hard mask pattern 14 designed in a rectangular shape is fine, so even if the corners are slightly rounded, The part between the corners) is in the form as designed.
Here, FIG. 3 is a partial plan view for explaining a main part of the reflective mask manufacturing method according to the present embodiment.

  In the present embodiment, the second resist pattern 16 (mask pattern) is formed so as to partially overlap the hard mask pattern 14 (a pattern including a portion that becomes a design residue defect portion). More specifically, as shown in FIG. 3B, since the second resist pattern 16 is formed so as to partially overlap the body portion of the hard mask pattern 14, the overlapping portion thereof. (The angle at which the edges of both patterns intersect) is closer to the design value than before, and the length of the overlapping portion (the body portion of the hard mask pattern 14 and the second resist). The length of the portion in contact with the edge of the pattern 16 is closer to the design value than in the prior art.

Therefore, as described above, the design residue defect portion 21 of the absorber pattern 13 formed by etching the absorption layer 13A exposed from the second resist pattern 16 and the hard mask pattern 14 is shown in FIG. As shown to (c), it becomes a rectangular form as designed conventionally.
More specifically, the angle at which the edge of the design residue defect portion 21 and the edge of the mask pattern portion of the absorber pattern 13 intersect with each other is as designed as before, and the design residue defect portion 21 has the absorber pattern. The length (D1a) of the portion in contact with the 13 mask pattern portions is closer to the design value (D1) than in the prior art.

In the present invention, the pattern drawing for forming the first resist pattern 15 and the pattern drawing for forming the second resist pattern 16 may be pattern drawn using different drawing means.
For example, a spot beam electron beam drawing apparatus is used for pattern drawing for forming the first resist pattern 15, and a variable shaped beam electron beam drawing apparatus is used for pattern drawing for forming the second resist pattern 16. be able to.
Here, although the electron beam drawing by the spot beam can obtain a high resolution, the drawing time becomes long, so that the pattern (the first resist pattern 15) including the portion that becomes the fine design residue defect 21 is obtained. It is preferable to use it for formation. On the other hand, the electron beam drawing by the variable shaped beam is preferably used for forming the mask pattern (second resist pattern 16) because the drawing time can be shortened.

In the present invention, the design residue defect portion having a length close to the design value (L1) can also be formed for the length of the projection portion of the design residue defect portion (L1a shown in FIG. 3C). it can. That is, in the present invention, a design residue defect portion having an area closer to the design value than before can be formed.
As described above, in the conventional method, as shown in FIG. 14A, the design residue defect portion 221 has a hilly form, and the area of the design residue defect portion is controlled as designed. It was difficult.
On the other hand, as described above, in the present invention, as shown in FIG. 3C, the design residue defect portion 21 has a form as designed, that is, a rectangular form as compared with the prior art. Therefore, by controlling the length of the protrusion (L1a shown in FIG. 3C) to a length close to the design value (L1), the area of the design residue defect portion can be controlled as designed. .

However, when using a method of forming the mask pattern and the design residue defect pattern in different resists in different processes as in the present invention, the length of the protrusions is controlled (that is, both In order to control the overlapping region of the pattern), it is usually necessary to form the mask pattern and the design residue defect pattern with high positional accuracy.
As described above, since the size of the design residue defect portion is fine, forming the mask pattern and the design residue defect pattern with high positional accuracy (that is, controlling the overlapping region of both patterns with high accuracy) Usually, this is difficult and requires highly accurate alignment drawing.

However, since the design residue defect portion according to the present invention is formed for the purpose of inspection and evaluation as described above, it does not necessarily have the area as designed at the designed position. .
That is, the reflective mask obtained by the manufacturing method according to the present invention may have a plurality of design residue defect portions having different areas, and any one of the plurality of design residue defect portions according to the design value. As long as it has an area of Information on the position where the design residue defect portion having the area as the design value exists may be obtained by SEM observation or the like.

  In the present invention, the hard mask pattern has a plurality of independent patterns (isolated island patterns) separated from each other, and an overlapping area between the independent pattern and the second resist pattern is different for each independent pattern. Thus, a reflective mask as described above can be manufactured.

For example, as shown in FIG. 4, in the present invention, the independent pattern (14 a to 14 c) and the second resist pattern 16 are changed by changing the relative position of the independent pattern (14 a to 14 c) and the second resist pattern 16. The overlapping area with the second resist pattern 16 can be made different for each independent pattern (14a to 14c).
That is, by changing the relative position between the independent pattern (14a to 14c) and the second resist pattern 16, the protrusion of the independent pattern (14a to 14c) exposed from the second resist pattern 16 is changed. The length (L) can be made different for each independent pattern (14a to 14c) (FIG. 4 (b)).
Therefore, the length (L) of the protrusions is different by dry-etching the absorption layer 13A exposed from the independent patterns (14a to 14c) and the second resist pattern 16 to form the absorber pattern 13. A reflective mask having a plurality of design residue defect portions (21a to 21c) (that is, having different areas) can be manufactured (FIG. 4C).

  Further, in the present invention, by changing the shape and / or area of the independent pattern, the overlapping area between the independent pattern and the second resist pattern may be different for each independent pattern. .

For example, as shown in FIG. 5, in the present invention, the shape of the independent patterns (14 a to 14 c) is changed by changing the lateral length (W) of the independent patterns (14 a to 14 c). Thus, the overlapping area between the independent patterns (14a to 14c) and the second resist pattern 16 can be made different for each independent pattern (14a to 14c).
That is, by changing the shape of the independent pattern (14a to 14c), the length (L) of the protrusion of the independent pattern (14a to 14c) exposed from the second resist pattern 16 is changed to each independent pattern. (14a to 14c) can be different (FIG. 5B).
Therefore, the length (L) of the protrusions is different by dry-etching the absorption layer 13A exposed from the independent patterns (14a to 14c) and the second resist pattern 16 to form the absorber pattern 13. A reflective mask having a plurality of design residue defect portions (21a to 21c) (that is, having different areas) can be manufactured (FIG. 5C).

Further, for example, as shown in FIG. 6, in the present invention, the size of the independent patterns (14a to 14c) is set with the ratio of the length (D) in the vertical direction to the length (W) in the horizontal direction constant. By changing the area of the independent pattern (14a-14c), the overlapping area of the independent pattern (14a-14c) and the second resist pattern 16 is the independent pattern (14a-14c). Can be different.
That is, the length (L) of the protrusion of the independent pattern (14a-14c) exposed from the second resist pattern 16 is changed by changing the area of the independent pattern (14a-14c). (14a to 14c) can be different (FIG. 6B).
Therefore, the length (L) of the protrusions is different by dry-etching the absorption layer 13A exposed from the independent patterns (14a to 14c) and the second resist pattern 16 to form the absorber pattern 13. A reflective mask having a plurality of design residue defect portions (21a to 21c) (that is, having different areas) can be manufactured (FIG. 6C).

[Second Embodiment]
Next, a description will be given of a method for manufacturing a reflective mask having, as the fine size portion, the design residue defect portion of the bridge type defect type shown in FIG.
7 and 8 are schematic process diagrams showing an example of the second embodiment of the reflective mask manufacturing method according to the present invention.
In order to manufacture the reflective mask 2 having the design residue defect portion of the bridge type defect type shown in FIG. 12 (b) using the manufacturing method of the present invention, as in the first embodiment described above. First, as shown in FIG. 7A, a hard mask in which a hard mask layer 14A is formed on the absorption layer 13A of the reflective mask blank 10 having at least the substrate 11, the reflection layer 12, and the absorption layer 13A. A reflective mask blank with a layer is prepared.
The reflective mask blank 10 may be prepared, and the hard mask layer 14A may be formed on the absorption layer 13A.

  Next, a first resist layer 15A is formed on the hard mask layer 14A (FIG. 7B), and pattern drawing is performed by an electron beam drawing apparatus or the like to form a first resist pattern 15 (FIG. 7 (c)), the hard mask layer 14A exposed from the first resist pattern 15 is etched to form a hard mask pattern 14 (FIG. 7D), and then the first resist pattern 15 is formed. It is removed (FIG. 7 (e)).

Next, a second resist layer 16A is formed on the hard mask pattern 14 and the absorption layer 13A exposed from the hard mask pattern 14 (FIG. 8F), and pattern drawing is performed by an electron beam drawing apparatus or the like. Then, the second resist pattern 16 is formed (FIG. 8G).
Here, in the present embodiment, the second resist pattern 16 has two line-shaped patterns that run in parallel, and the two line-shaped patterns are opposite ends of the hard mask pattern 14. The second resist pattern 16 is formed so as to partially overlap with a nearby barrel portion.

  Next, the absorber layer 13A exposed from the second resist pattern 16 and the hard mask pattern 14 is etched to form the absorber pattern 13 including the design residue defect portion 22 (FIG. 8H). Thereafter, the second resist pattern 16 is removed (FIG. 8 (i)), and then the hard mask pattern 14 is removed to obtain the above-described reflective mask 2 (FIG. 8 (j)).

  Here, as described above, in the conventional method, the method of forming the mask pattern and the design residue defect pattern in one resist in the same process is used. Therefore, the design residue defect pattern portion that is a part of the pattern of the one resist is affected by the pattern drawing of the portion of the mask pattern that comes into contact (so-called proximity effect), and the designed form It was in a blurry form with a contour that deviated from. For example, as shown in FIG. 14B described above, the angle at which the edge of the design residue defect 222 intersects with the edge of the line pattern portion that is the original mask pattern of the absorber pattern 213 is greatly separated from 90 degrees. However, the length of the contact portion (D2b) is larger than the design value (D2) while the central portion is narrowed.

On the other hand, in the present embodiment, after the pattern including the portion that becomes the design residue defect portion 22 is formed as the hard mask pattern 14 using the first resist as described above, the first resist pattern 15 is removed. Then, a mask pattern (second resist pattern 16) is formed using another resist (second resist).
That is, the mask pattern and the design residue defect pattern are formed in different resists in different processes.
Therefore, the pattern including the portion that becomes the design residue defect 22 (first resist pattern 15) is not affected by the pattern drawing of the mask pattern (second resist pattern 16) (so-called proximity effect). .
For example, as shown in FIG. 9 (a), the shape of the hard mask pattern 14 designed in a rectangular shape is so fine that even if the corners are slightly rounded, The part between the corners) will be as designed.
Here, FIG. 9 is a partial plan view for explaining a main part of the manufacturing method of the reflective mask according to the present embodiment.

In the present embodiment, as shown in FIG. 9B, the second resist pattern 16 has two line-shaped patterns that run in parallel, and the two line-shaped patterns are: Since the hard mask pattern 14 is formed so as to partially overlap with the body portions in the vicinity of opposite ends of the hard mask pattern 14, the angle of the overlapping portion (the angle at which the edges of both patterns intersect) is designed more than in the prior art. The angle is close to the value.
In addition, the length of the portion where the body portion of the hard mask pattern 14 and the edge of the second resist pattern 16 are in contact with each other is closer to the design value than in the prior art.

Therefore, as described above, the design residue defect portion 22 of the absorber pattern 13 formed by etching the absorption layer 13A exposed from the second resist pattern 16 and the hard mask pattern 14 is shown in FIG. As shown to (c), it becomes a rectangular form as designed conventionally.
More specifically, the angle at which the edge of the design residue defect 22 and the edge of the mask pattern portion of the absorber pattern 13 intersect with each other is as designed as before, and the design residue defect 22 is in the absorber pattern. The length (D2a) of the portion in contact with the 13 mask pattern portions is closer to the design value (D2) than in the prior art.

In the present embodiment, similarly to the above-described first embodiment, the pattern drawing for forming the first resist pattern 15 and the pattern drawing for forming the second resist pattern 16 are differently drawn. It may be used to draw a pattern.
For example, a spot beam electron beam drawing apparatus is used for pattern drawing for forming the first resist pattern 15, and a variable shaped beam electron beam drawing apparatus is used for pattern drawing for forming the second resist pattern 16. be able to.

Next, each element according to the manufacturing method of the reflective mask of the present invention will be described below.
In the present invention, the substrate 11, the reflective layer 12, and the absorption layer 13 </ b> A constituting the reflective mask blank 10 are not particularly limited as long as they are used in a conventional reflective mask. It can be used similarly. Although not shown, the reflective mask blank 10 may have the above-described capping layer and buffer layer.

(Hard mask layer)
The hard mask layer 14A has resistance to the dry etching of the absorption layer 13A, and examples of the material thereof include chromium (Cr), zirconium (Zr), hafnium (Hf), and nitrides and oxides thereof. Is mentioned. The thickness of the hard mask layer 14A is, for example, 3 nm to 15 nm, although it depends on the etching resistance of the material and the processing accuracy according to the size of the transfer pattern.
As a specific example, for example, a hard mask layer made of CrN can be provided by sputtering Cr in a mixed gas atmosphere of Ar and nitrogen.

(First resist layer and second resist layer)
The first resist layer 15A is preferably made of a negative resist, and particularly preferably made of a negative electron beam resist.
The first resist pattern 15 formed from the first resist layer 15A is a resist pattern for forming the design residue defect portion, and the area occupied by the first resist pattern 15 is the entire reflective mask. This is because the pattern drawing time can be shortened by using a negative resist for the first resist layer 15A.
Further, as described above, since the design residue defect portion has a fine size, the means for performing pattern drawing is preferably electron beam drawing. Therefore, the first resist layer 15A is a negative type electron beam resist. It is preferable that it is comprised from these.

On the other hand, the second resist layer 16A is preferably made of a positive resist, and particularly preferably made of a positive electron beam resist.
The second resist pattern 16 formed from the second resist layer 16A is a resist pattern for forming a mask pattern. In addition to the mask pattern, the reflective mask has a region that does not etch the absorption layer. If a positive resist is used for the second resist layer 16A, it is possible to cover the second resist layer without drawing a region other than the mask pattern.
Further, as described above, since the second resist pattern 16 is a resist pattern for forming a mask pattern, the means for performing pattern drawing is preferably electron beam drawing. Therefore, the second resist layer 16A is preferably composed of a positive electron beam resist.

In the present invention, a high-resolution resist can be used as the resist constituting the first resist layer 15A.
As described above, conventionally, a method of forming the original mask pattern and the design residue defect pattern in one resist (the resist constituting the resist layer 216 shown in FIG. 13) in the same process has been used. Then, in order to form a mask pattern occupying a large area with respect to the entire reflective mask within a practical time, it is necessary to use a highly sensitive resist as the one resist.
Here, since it is generally difficult for a resist to have both high sensitivity and high resolution, the resolution of a resist to be used has to be low when priority is given to high sensitivity.

However, in the present invention, the mask pattern and the design residue defect pattern are formed using different resists in different processes. More specifically, the design residue defect pattern is formed with the first resist pattern 15, and the mask pattern is formed with the second resist pattern 16.
Therefore, in the present invention, even if it is necessary to use a high-sensitivity resist for the resist constituting the second resist layer 16A for forming the mask pattern for the reason of the drawing time as described above. As the resist constituting the first resist layer 15A for forming the designed residue defect pattern having a small drawing area, it is necessary to use a highly sensitive resist such as that used for the resist constituting the second resist layer 16A. A resist having higher resolution than that of the resist constituting the second resist layer 16A can be used.
Therefore, in the present invention, the design residue defect pattern can be in the form as designed than before.

  In the present invention, the hard mask layer 14A is an object to be dry-etched using the first resist pattern 15 as an etching mask. Usually, the hard mask layer 14A is thinner than the absorbing layer 13A. . For example, the thickness of the hard mask layer 14A is in the range of about 3 nm to 15 nm, whereas the thickness of the absorption layer 13A is in the range of about 20 nm to 100 nm.

Therefore, the first resist layer 15A has the same resist layer (resist layer 216 shown in FIG. 13) when the mask pattern and the design residue defect pattern are formed in one resist in the same process as in the prior art. The thickness can be reduced compared to
Therefore, in the present invention, the design residue defect pattern can be made as designed as compared with the conventional design.
In the present invention, since the second resist pattern 16 serves as a mask for etching the absorption layer 13A, the thickness of the second resist layer 16A is the same as the conventional mask pattern and design residue defect pattern. Is the same level as the one resist layer (resist layer 216 shown in FIG. 13) in the case of forming the resist in the same resist in the same process.
Therefore, in the present invention, the thickness of the first resist layer 15A can be made thinner than the thickness of the second resist layer 16A.

  Although the reflective mask manufacturing method according to the present invention has been described above, the present invention is not limited to the above-described embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
As a substrate, an optically polished 6-inch square (0.25-inch thick) synthetic quartz substrate is used, and an Si film is formed on its main surface by an ion beam sputtering method using a Si target. 2 nm film is formed, and then a Mo film is formed to 2.8 nm using a Mo target, and this is set as one period, and then 40 periods are laminated. Finally, a Si film is formed to 4.2 nm to form the outermost surface of the reflective layer. A reflective layer made of a multilayer film of Mo and Si was formed.
Next, a capping layer was formed by DC magnetron sputtering using a Ru target in an Ar atmosphere to form a 2.5 nm Ru film on the reflective layer.

Subsequently, a TaN film having a thickness of 35 nm is first formed on the Ru film by a DC magnetron sputtering method using a Ta target in a mixed gas atmosphere of Ar and nitrogen. A TaO film having a thickness of 15 nm was formed in a mixed gas atmosphere to form an absorption layer. Here, the TaO film also serves as a low reflection film during optical inspection.
On the other hand, a CrN film having a thickness of 30 nm is formed on the other main surface of the substrate by a DC magnetron sputtering method in a mixed gas atmosphere of Ar and nitrogen using a Cr target to form a conductive layer. A mask blank was obtained.

  Next, a CrN film having a thickness of 5 nm is formed on the absorption layer of the reflective mask blank by DC magnetron sputtering using a Cr target in a mixed gas atmosphere of Ar and nitrogen to a thickness of 5 nm. A mask layer was formed.

Next, a negative electron beam resist is formed as a first resist layer with a film thickness of 50 nm on the hard mask layer, and a predetermined design residue defect is formed using a spot beam electron beam lithography apparatus with an acceleration voltage of 100 kV. A plurality of rectangular patterns (10 nm × 20 nm) including a portion to be a portion (10 nm × 10 nm convex defect) were drawn and developed to form a first resist pattern.
The positions of the plurality of rectangular patterns were arranged such that the relative positions changed in units of 1 nm with respect to the 1: 1 L & S pattern of the second resist pattern described later.

  Next, the hard mask layer exposed from the first resist pattern is dry-etched using a mixed gas of chlorine and oxygen to form a hard mask pattern, and then the first resist pattern is formed using oxygen plasma. Removed.

  Next, a positive chemically amplified electron beam resist having a thickness of 1200 nm is formed as a second resist layer on the hard mask pattern and the absorption layer exposed from the hard mask pattern, and a variable shaped beam having an acceleration voltage of 50 kV is formed. A mask pattern including a predetermined 1: 1 L & S pattern (line width: 64 nm) portion was drawn and developed to form a second resist pattern.

  Next, the absorber layer exposed from the second resist pattern and the hard mask pattern is dry-etched with fluorine gas to form an absorber pattern, and then the second resist pattern is sulfated with hydrogen peroxide. The reflective mask according to the present invention was obtained by removing with a chemical solution and removing the hard mask pattern by dry etching using a mixed gas of chlorine and oxygen.

  As a result of SEM observation of the reflective mask, as shown in FIG. 10A, the angle at which the edge of the design residue defect 21 and the edge of the mask pattern portion of the absorber pattern 13 intersect is approximately 90 degrees. Yes, the length (L1a) of the protrusion is 10 nm, and the length (D1a) of the portion where the design residue defect portion 21 is in contact with the absorber pattern 13 in the mask pattern portion is 10 nm as designed. It was confirmed that the design residue defect portion 21 (convex defect) having

(Comparative Example 1)
A positive chemically amplified electron beam resist having a film thickness of 1200 nm is formed on the absorption layer of the reflective mask blank obtained in the same manner as in Example 1, and an electron beam drawing apparatus for a variable shaped beam with an acceleration voltage of 50 kV is formed. Then, a mask pattern including a predetermined 1: 1 L & S pattern (line width 64 nm) portion and a predetermined design residue defect pattern (10 nm × 10 nm convex defect) are drawn and developed, and the resist pattern of Comparative Example 1 is developed. Formed.

  Next, the absorption layer exposed from the resist pattern is dry-etched using fluorine gas to form an absorber pattern, and then the resist pattern is removed with a sulfuric acid hydrogen peroxide solution according to Comparative Example 1. A reflective mask was obtained.

  When the above-described reflective mask is observed by SEM, the form of the formed design residue defect 221 (convex defect) is as shown in FIG. 10B. The edge of the design residue defect 221 and the absorber pattern 213 The angle at which the edges of the mask pattern part intersect is far from 90 degrees, the length (L1b) of the protrusion is 5 nm, and the design residue defect part 221 absorbs the mask pattern part. The length (D1b) of the part in contact with the body pattern 213 was confirmed to be a 30 nm hill-like form.

DESCRIPTION OF SYMBOLS 1, 2 ... Reflective mask 10 ... Reflective mask blank 11 ... Substrate 12 ... Reflective layer 13A ... Absorbing layer 13 ... Absorber pattern 14A ... Hard mask layer 14 ..Hard mask pattern 15A ... first resist layer 15 ... first resist pattern 16A ... second resist layer 16 ... second resist pattern 21, 22 ... design residue defect Part 100, 200 ... Reflective mask 210 ... Reflective mask blank 111, 211 ... Substrate 112, 212 ... Reflective layer 213A ... Absorbing layer 113, 213 ... Absorber pattern 121, 122 ... Residual defects 221, 222 ... Design residue defect part 216 A ... Resist layer 216 ... Resist pattern 216 a ... Design residue defect pattern

Claims (9)

At least a substrate, a reflective layer made of a multilayer film formed on the main surface of the substrate, and an absorber pattern formed by partially removing the absorption layer formed on the reflective layer A method for producing a reflective mask for EUV exposure comprising:
Preparing a reflective mask blank with a hard mask layer, wherein a hard mask layer is formed on the absorbent layer of the reflective mask blank having at least the substrate, the reflective layer, and the absorbent layer;
Forming a first resist layer on the hard mask layer;
Applying a pattern to the first resist layer to form a first resist pattern;
Etching the hard mask layer exposed from the first resist pattern to form a hard mask pattern;
Removing the first resist pattern;
Forming a second resist layer on the hard mask pattern and the absorbing layer exposed from the hard mask pattern;
Patterning the second resist layer to form a second resist pattern that partially overlaps the hard mask pattern;
Etching the absorbing layer exposed from the second resist pattern and the hard mask pattern to form the absorber pattern;
Removing the second resist pattern;
Removing the hard mask pattern;
A method for producing a reflective mask, comprising:   The hard mask pattern has a plurality of independent patterns separated from each other, and a portion exposed from the second resist pattern in the independent pattern is an etching mask for forming a design residue defect portion of the absorber pattern. The method of manufacturing a reflective mask according to claim 1, comprising:   The method for manufacturing a reflective mask according to claim 1, wherein the first resist layer is made of a negative resist.   4. The method of manufacturing a reflective mask according to claim 1, wherein the second resist layer is made of a positive resist. 5.   5. The reflective mask according to claim 1, wherein the first resist layer is composed of a resist having a higher resolution than the second resist layer. 6. Production method.   6. The method of manufacturing a reflective mask according to claim 1, wherein the thickness of the first resist layer is thinner than the thickness of the second resist layer.   The method for manufacturing a reflective mask according to claim 1, wherein an overlapping area between the independent pattern and the second resist pattern is different for each independent pattern.   The overlap region between the independent pattern and the second resist pattern is different in each independent pattern by changing a relative position between the independent pattern and the second resist pattern. The manufacturing method of the reflective mask of description. 9. The overlap region between the independent pattern and the second resist pattern is different in each independent pattern by changing the shape and / or area of the independent pattern. A method for producing a reflective mask according to claim 1.

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