JP2002319542A - Reflective mask blank for euv exposure, reflective mask for euv exposure, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an EUV mask of high precision and reflectivity by finding an intermediate layer material capable of forming a precision pattern as an intermediate layer acting also as an etching stopper, related to a method for manufacturing the EUV mask, and the like, and to provide a method for manufacturing a semiconductor in which a pattern is transferred onto a semiconductor substrate using a provided EUV mask. SOLUTION: There are provided a multilayer film 12 on a substrate 11 which reflects EUV light as the EUV mask, an intermediate layer on the multilayer film 12 as an etching stopper 13, and an absorber layer 14 on the intermediate layer which absorbs the EUV light. A material containing at least one element selected from among Cr, N, O, and C is used as the intermediate layer, realizing an EUV mask capable of forming a precision pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective mask blank for EUV exposure, a reflective mask for EUV exposure, a method for manufacturing the same, and a method for manufacturing a semiconductor, which are used for light exposure of EUV light used in semiconductor manufacturing and the like. About. The EUV (Extreme Ultra) described in the present invention is used.
(Violet) light refers to light in a wavelength band of a soft X-ray region or a vacuum ultraviolet region, and specifically has a wavelength of 0.2 to 100.
It is light of about nm.

[0002]

2. Description of the Related Art Conventionally, in the semiconductor industry, a photolithography method using visible light or ultraviolet light has been used as a technique for transferring a fine pattern necessary for forming an integrated circuit having a fine pattern on a Si substrate or the like. Have been. But,
While miniaturization of semiconductor devices is accelerating, shortening the wavelength of conventional light exposure is approaching the exposure limit. In the case of light exposure, the resolution limit of the pattern is said to be の of the exposure wavelength, and even if an F ₂ laser (157 nm) is used, it is 70 n.
m is expected to be the limit. Therefore, EUV lithography (hereinafter, referred to as “EUVL”), which is an exposure technique using EUV light (13 nm) having a shorter wavelength than the F ₂ laser, is expected as an exposure technique of 70 nm or less.

The principle of EUVL image formation is the same as that of photolithography. However, since EUV light absorbs a large amount of all substances and has a refractive index close to 1, refractive optical systems such as light exposure cannot be used. , All use a reflective optical system. As a mask used at that time, a transmission type mask using a membrane has been proposed.
There is a problem that the exposure time becomes long because the membrane absorbs a large amount of UV light, and the throughput cannot be secured. Therefore, at present, a reflective mask for exposure is generally used. Conventional techniques 1 to 3 for obtaining such a reflective mask for EUV exposure will be briefly described with reference to FIG. 2, and then the necessity of an etching stopper used in this manufacturing process and its problems will be described. Will be described.

FIG. 2 is a flow chart schematically showing the production of a reflective mask for EUV exposure according to the prior art. 2. Description of the Related Art An example of a conventional manufacturing process for obtaining a reflective mask for EUV exposure includes (1) a substrate preparing process, (2) a multilayer film forming process on a substrate, and (3) an intermediate layer forming process. Filming step, (4) absorber layer forming step, (5) EB resist coating step, (6) EB
A drawing step, (7) a dry etching step, and (8) an intermediate layer removing step. Hereinafter, each of these steps will be described.

(1) Substrate Preparation Step The substrate 11 preferably has a low coefficient of thermal expansion and is excellent in smoothness, flatness, and resistance to a cleaning liquid used for cleaning an EUV mask. And the like.

(2) Step of Forming Multilayer Film on Substrate As the multilayer film 12, a multilayer film containing Mo and Si is frequently used. For example, when Mo is 28 ° and Si is 42 ° as one cycle, by stacking 30 cycles or more, 13.4 nm is obtained.
Thus, a multilayer film that reflects EUV light having a peak wavelength can be realized. In the case of a multilayer film containing Mo and Si, a Si film is formed as the uppermost layer.

(3) Step of Forming Intermediate Layer On the multilayer film 12 that reflects EUV light, an SiO ₂ film is formed as an etching stopper 23 as an intermediate layer. For the film formation, for example, an RF magnetron sputtering method using a SiO ₂ target is used.

(4) Step of forming absorber layer An absorber layer 14 for absorbing EUV light is formed by a sputtering method. Ta and Cr are used as a film forming material, and a DC magnetron sputtering method is used for the film forming, for example. Through this step, an EUV mask blank is obtained.

(5) EB resist coating step An EUV mask can be manufactured by forming a pattern on the absorber layer 14 of the obtained EUV mask blank. An EB resist is applied to the EUV mask blank obtained in the step (4) and baked at 200 ° C.

(6) EB lithography process A resist pattern is formed on an EUV mask blank coated with an EB resist using an EB lithography machine.

(7) Dry etching step Using the resist pattern as a mask, the EUV absorber layer 14 is dry-etched using chlorine to form an absorption layer pattern.

(8) Step of Removing Intermediate Layer The intermediate layer, ie, Si, remaining on the EUV light reflecting surface
When the etching stopper 23 made of the O ₂ film is removed with a dilute HF aqueous solution, a reflective mask for EUV exposure is completed.

(Necessity of Etching Stopper and Its Problems) The multilayer film 12 for reflecting the EUV light needs to have a high reflectance after the completion of the production. Therefore, in the manufacturing process, particularly in the patterning process, it is necessary to carry out patterning without damaging the multilayer film 12 that reflects EUV light, such as reducing the film thickness or roughening the surface. On the other hand, in the patterning of the absorber layer 14 that absorbs EUV light, although high dimensional accuracy can be obtained by dry etching, the absorber layer 14 that absorbs EUV light can be obtained.
Since it is impossible to etch the lower layer without damage, it is necessary to form an etching stopper 23 as an intermediate layer between the multilayer film 12 and the EUV absorber layer 14. Generally, an SiO ₂ film having a thickness of several hundred degrees or more is used as the etching stopper 23.
In dry etching using l ₂ gas, it sufficiently functions as a stopper. However, if the SiO ₂ film remaining in the part without the pattern is not completely removed at the end of the patterning process, the reflectance of the multilayer film 12 that reflects EUV light will be significantly reduced.

However, if dry etching is used to remove the SiO ₂ film, the uppermost Si film of the multilayer film 12 that reflects EUV light is also etched, which also lowers the reflectance. Therefore, the SiO ₂ film needs to be removed by wet etching with an HF solution or the like. H
Wet etching using an F solution, etc.
This is effective because it does not damage the film, but on the other hand, it has an isotropic etching property, so that the pattern is eroded in the lateral direction, and the pattern may be peeled off. In addition, an SiO ₂ film having a thickness of several hundred degrees or more has a large surface roughness and a high compressive stress, and abnormal discharge is likely to occur during formation of the SiO ₂ film by sputtering.
There is a problem that it is difficult to reduce defects required for the V mask.

Prior Art 2 JP-A-8-213303 discloses a reflective X-ray mask in which an intermediate layer mainly composed of Cr or Ti having an etching ratio with respect to an absorber layer of 5 or more is provided on a multilayer film. Have been. The intermediate layer has a function as an etching stopper layer and a protective layer of the multilayer reflective film when forming a pattern on the absorber layer by etching, and after the absorber pattern is formed, the intermediate layer in the reflection region is removed. Is described.

Prior Art 3 Japanese Patent Application Laid-Open No. 7-333829 discloses that C is used between an absorber layer and a multilayer film.
Pattern formation by etching on the absorber layer by forming the intermediate layer with a material that absorbs less exposure light such as X-rays or extreme ultraviolet rays such as r, Al, Ni, etc. and has a lower etching rate than the absorber layer A technique for preventing a decrease in the reflectivity of the multilayer film without removing the intermediate film later is described.

However, the intermediate films described in the prior arts 1 to 3, such as SiO ₂ , Cr, Al, and Ni, all have poor surface smoothness. For this reason, the absorber layer formed on the intermediate layer whose surface has been roughened also has an absorber layer surface roughened at least as much as the intermediate layer, and as a result, the edge of the absorber pattern is roughened. A problem has been found that adversely affects the transfer accuracy of the reflective mask. Further, the inventors of the present application have a structure in which the intermediate layer is left even after pattern formation by etching as described in the prior art 3 among the prior arts 1 to 3.
In a reflective mask for UV exposure, it has been found that the roughness of the surface of the intermediate layer greatly affects the transfer accuracy of the reflective mask for EUV exposure.

That is, first, when a material having a large surface roughness such as Cr, Al, Ni or the like is used as the intermediate layer remaining in the reflection region, the exposure light is scattered on the surface of the intermediate layer, and eventually the reflection is caused. The rate drops. Secondly, if the material of the intermediate layer is not resistant to the chemicals used in the cleaning process of the reflective mask for EUV exposure, such as Cr, Al, Ni, etc., the intermediate layer deteriorates or the pattern is peeled off. As a result, the reflection of the exposure light becomes non-uniform. Third, if the film stress of the material of the intermediate layer is large, the reflection surface of the reflective mask for EUV exposure may be warped or the like, and the pattern transfer accuracy may be deteriorated. Heretofore, these problems have not been considered at all, and no material has been found to solve them.

The present invention has been made under the above-mentioned background, and has a reflective mask blank for EUV exposure capable of forming a pattern with high accuracy, and an E-mask having a high reflectivity.
It is an object of the present invention to provide a method for manufacturing a semiconductor, characterized in that a pattern is transferred onto a semiconductor substrate by using a reflective mask for UV exposure, a method for manufacturing the same, and a reflective mask for EUV exposure having a high reflectance. .

[0020]

According to a first aspect of the present invention, there is provided a multi-layer film for reflecting EUV light on a substrate, and an intermediate layer on the multi-layer film. A reflective mask blank for EUV exposure having an absorber layer that absorbs EUV light on a layer, wherein Cr is used as the intermediate layer,
EU comprising a material containing at least one element selected from the group consisting of N, O, and C.
It is a reflective mask blank for V exposure.

According to a second aspect of the present invention, there is provided the EUV according to the first aspect, wherein the absorber layer is made of a material containing Ta.
It is a reflective mask blank for exposure.

According to a third aspect of the present invention, there is provided a multi-layer film for reflecting EUV light on a substrate, an intermediate layer on the multi-layer film, and an EUV light absorbing a pattern formed on the intermediate layer. A reflective mask for EUV exposure having a body layer, wherein a material containing Cr and at least one element selected from N, O, and C is used as the intermediate layer. Is a reflective mask for EUV exposure.

According to a fourth aspect of the present invention, there is provided the EUV according to the third aspect, wherein the absorber layer is made of a material containing Ta.
It is a reflective mask for exposure.

According to a fifth aspect of the present invention, a reflective mask blank for EUV exposure according to the first or second aspect of the present invention is used.
EU manufacturing a reflective mask for V exposure
This is a method for manufacturing a reflective mask for V exposure.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor, wherein a pattern is transferred onto a semiconductor substrate using the reflective mask for EUV exposure according to the third or fourth aspect.

[0026]

FIG. 1 shows a reflective mask for EUV exposure according to an embodiment of the present invention (hereinafter, a reflective mask for EUV exposure is an "EUV mask", and a reflective mask blank for EUV exposure is an "EUV mask". It is written as blank.)
FIG. 3 is a conceptual diagram showing that a pattern is exposed and transferred on a Si wafer, for example, using the manufactured EUV mask.

(Embodiment) The manufacture of an EUV mask and the transfer of a pattern onto a semiconductor substrate by the EUV mask according to an embodiment of the present invention will be described below with reference to FIG. In FIGS. 1 and 2, corresponding parts are denoted by the same reference numerals. The manufacture of an EUV mask and the transfer of a pattern onto a semiconductor substrate using the EUV mask include (1) a substrate preparation step, (2) a multilayer film formation step on the substrate, (3) an intermediate layer formation step, (4)
A step of forming an absorber layer, (5) an EB resist coating step,
(6) EB drawing step, (7) dry etching step,
(8) an intermediate layer removing step; and (9) a pattern transfer onto a semiconductor substrate using an EUV mask.

(1) Step of preparing a substrate. The substrate 11 preferably has a low coefficient of thermal expansion and is excellent in smoothness, flatness, and resistance to a cleaning solution used for cleaning an EUV mask. Glass having a low coefficient of thermal expansion, for example, SiO ₂ —TiO ₂ Although a base glass or the like is used, the substrate is not limited to this, and a substrate of crystallized glass, quartz glass, silicon, metal, or the like on which a β-quartz solid solution is precipitated can also be used. Examples of the metal substrate include an invar alloy (Fe
-Ni alloy) or the like can be used. The substrate 11 preferably has a smooth surface of 0.2 nmRms or less and a flatness of 100 nm or less in order to obtain high reflectance and transfer accuracy.

(2) Step of forming a multilayer film on a substrate. As the multilayer film 12, a multilayer film containing Mo and Si is frequently used. As a material capable of obtaining a high reflectance in a specific wavelength range, a Ru / Si periodic multilayer film, a Mo / Be periodic multilayer film, and a Mo compound are used. / Si compound periodic multilayer, Si / Nb periodic multilayer, Si / Mo / Ru periodic multilayer, Si / Mo /
A Ru / Mo periodic multilayer film and a Si / Ru / Mo / Ru periodic multilayer film may be used. However, the optimum film thickness differs depending on the material. In the case of the multilayer film 12 containing Mo and Si, DC
First, a Si film is formed under an Ar gas atmosphere using a Si target by a magnetron sputtering method.
Using a Mo target, a Mo film is formed under an Ar gas atmosphere, and one cycle of the Mo film is formed, and after stacking 30 to 60 cycles, preferably 40 cycles, a Si film is finally formed.

(3) Step of forming an intermediate layer. In order to achieve the object of the present invention described above, the present inventors
As a result of intensive studies, the multilayer film 12 and the EUV absorber layer 1
4, an etching stopper layer 13
The conditions that the material forming must satisfy. That is, first, the material must have a high etching selectivity of 10 or more with respect to the EUV absorber layer 14 containing Ta as a main component. Second, the surface roughness during film formation is sufficiently small. Third, resistance to chemicals such as hot concentrated sulfuric acid / hydrogen peroxide and ammonia / hydrogen peroxide used as a cleaning liquid in the EUV mask manufacturing process. Fourth, the film stress of the etching stopper film after film formation is small. The material for forming the etching stopper 13 layer needs to satisfy the above conditions.

As a material satisfying the above conditions, the present inventors have found a material containing Cr and at least one element selected from the group consisting of N, O, and C. That is, by using a material containing Cr and at least one element selected from the group consisting of N, O, and C as a material for forming the intermediate layer, EUV capable of forming a pattern with high precision The inventors have found that a mask can be manufactured, and have completed the present invention. For example, if N is selected, Cr _1-X
If it is the N _X, especially improved acid resistance, with respect to the cleaning liquid in the EUV mask manufacturing process can be improved durability.
When O is selected to be Cr _1-x O _x , low stress controllability particularly at the time of film formation is improved. Further, when C is selected to be Cr _1-X C _X , dry etching resistance is particularly improved.

Further, the details will be described in “(8) Intermediate layer removing step” described later. When the above-mentioned EUV mask is manufactured, the intermediate layer is formed by reflecting the EUV mask in the reflection region (the pattern of the absorber layer is formed). (A part not to be removed)) Both a step of leaving on the top and a step of removing can be selected.

First, in the case where the intermediate layer is left on the reflection area of the EUV mask, the exposure light passes through the intermediate layer when exposing the manufactured EUV mask. Therefore, in order to suppress a decrease in the reflectance of the reflection region of the EUV mask, it is preferable that the material forming the intermediate layer has a small absorption coefficient. Specifically, the exposure light (in this case, E
The absorption coefficient for a wavelength in the UV region (13 nm) is 0.1.
Material of at most 05, more preferably at most 0.0
35 or less materials are good.

On the other hand, in the case where the intermediate layer is removed from the reflection area of the EUV mask, it is preferable to use a material having a relatively large absorption coefficient as a material for forming the intermediate layer. What happens in a reflective mask is
Usually, the exposure light is not incident perpendicularly to the mask, but is incident at an incident angle of several degrees. Therefore, when the thickness of the pattern of the mask is large, the shadow of the mask pattern is generated, the shape accuracy and the dimensional accuracy are deteriorated, and the pattern image reflected at the time of exposure is blurred, and as a result, the dimensional accuracy of the pattern is deteriorated. This is because there is a problem in that it may occur. For this reason, it is preferable to make the thickness of the pattern itself as thin as possible. Here, since the absorption pattern region of the mask has a laminated structure of the EUV absorber layer 14 and the intermediate layer, to solve the above-described problem, EUV
What is necessary is to reduce the total thickness of the absorber layer 14 and the intermediate layer. For this purpose, not only the EUV absorber layer 14 absorbs the exposure light but also the intermediate layer has the function of absorbing the exposure light.
It is preferable to design the thicknesses of the intermediate layer and the EUV absorber layer 14 based on the idea that the exposure light is sufficiently absorbed by both the layer 4 and the intermediate layer.

For example, if a material having a relatively large absorption coefficient is used for the intermediate layer, the thickness of the intermediate layer can be reduced. Further, for example, when the film thickness is not changed while using a material having a relatively large absorption coefficient for the intermediate layer, the absorption capacity of the intermediate layer is increased, so that the film thickness of the EUV absorber layer 14 can be reduced. In any of the above configurations, the total film thickness of the intermediate layer and the EUV absorber layer 14 can be reduced, and the problem caused by the influence of the pattern shadow can be reduced. From this viewpoint, the intermediate layer and E
The total thickness of the UV absorber layer 14 is preferably set to 100 nm or less. In the case where the intermediate layer is removed from the reflection area of the EUV mask as described above, a problem caused by the influence of the pattern shadow is reduced by using a material having a relatively large absorption coefficient for the intermediate layer. It becomes possible. Here, in the case of adopting a configuration in which the intermediate layer is removed, the material of the intermediate layer has an absorption coefficient of 0.030 for exposure light.
The above are preferably used.

Hereinafter, specific examples of preferred intermediate layers will be described. (In the case of Cr _1-X N _X ) As a film forming method, a film is formed by, for example, DC magnetron sputtering using a Cr target in a mixed gas atmosphere in which nitrogen is added to Ar by 10 to 60%. The film thickness is preferably 40 to 100 °, but if a step of removing the intermediate layer from above the reflection region of the EUV mask is adopted, the film thickness is preferably 30 to 500 °,
More preferably, it is 40 to 400 °. In addition, when considering the influence of the shadow of the pattern described above,
The total thickness of the intermediate layer and the absorber layer is preferably 100 nm or less, more preferably in the range of 30 to 50 nm.

On the other hand, a preferable range of X is 0.05 ≦ X
.Ltoreq.0.5, more preferably 0.07.ltoreq.X.ltoreq.0.4. When X is larger than 0.05, the stress is suppressed and the surface roughness is improved. If X is smaller than 0.5, a sufficient etching selectivity can be obtained. Also, as the content of N increases, the surface roughness tends to decrease and the absorption coefficient tends to decrease. If the intermediate layer is not removed from above the reflection area of the EUV mask in a later step, it is preferable to reduce the absorption coefficient of the intermediate layer in order to suppress a decrease in reflectance. On the other hand, when the intermediate layer is removed from the reflection area of the EUV mask, as described above, in order to reduce the influence of the shadow of the pattern, the intermediate layer and the absorber layer need to have a smaller thickness. Since the larger the absorption coefficient is, the more advantageous it is, it is preferable to reduce the N content as long as the required surface roughness can be ensured. From the above, when the intermediate layer is removed from the reflection region of the EUV mask, N is preferably 5 to 20% (0.05 ≦ X ≦ 0.2), and more preferably N is 5 to 15%. % (0.05 ≦ X ≦ 0.1
5).

[0038] (in the case of Cr _1-X O _X) film forming method, for example, by DC magnetron sputtering using a Cr target, it is deposited in a mixed gas atmosphere with the addition of oxygen to Ar. The film thickness is preferably 40 to 120 °, but if a step of removing the intermediate layer is adopted later, the film thickness may be 30 to 50 °.
It is preferably 0 °, more preferably 40-300 °. On the other hand, a preferable range of X is 0.05 ≦ X ≦ 0.6.

(In the case of Cr _{1 -X} C _X ) The film is formed by, for example, DC magnetron sputtering using a Cr target in a mixed gas atmosphere in which methane gas is added to Ar. The film thickness is preferably 40 to 100 °, but if a step of removing the intermediate layer is adopted later, the film thickness may be 3 °.
It is preferably 0 to 500 °, more preferably 40 to 300 °. On the other hand, a preferable range of X is 0.05 ≦ X ≦ 0.4.
It is.

(In the case of Cr _1-XY N _X C _Y )
For example, a film is formed by a DC magnetron sputtering method using a Cr target in a mixed gas atmosphere in which nitrogen and methane gas are added to Ar. The thickness is preferably from 40 to 100 °, but if a step of removing the intermediate layer is adopted later, the thickness is preferably from 30 to 500 °, more preferably from 40 to 300 °. On the other hand, a preferable range of X is 0.0
5 ≦ X ≦ 0.45, and a preferable range of Y is 0.01 ≦ Y
≦ 0.3.

[0041] (in the case of _{Cr 1-XYZ N X O Y} C Z) film forming method, for example, by DC magnetron sputtering using a Cr target, nitrogen Ar, oxygen and methane gas formed in a mixed gas atmosphere was added Film. The film thickness is 40-1
The thickness is preferably set to 20 °, but if a step of removing the intermediate layer is adopted later, the film thickness is set to 30 to 500 °, and more preferably to
Preferably it is 300 °. On the other hand, a preferable range of X is 0.05 ≦ X ≦ 0.40, and a preferable range of Y is
0.02 ≦ Y ≦ 0.3, and a preferable range of Z is 0.01
≦ Z ≦ 0.2.

In the embodiments described below, a case where Cr _1-X N _X is used as the intermediate layer will be described as an example. When this configuration is adopted, the absorption coefficient of the obtained intermediate layer at an exposure light wavelength of 13.4 nm is set to 0.038 to 0.3.
032.

(4) Step of forming an absorber layer. The following materials are preferable as the material of the EUV absorber layer 14. 1) A material containing Ta as a main component. 2) A material containing Ta as a main component and containing at least B. 3) A material having an amorphous structure containing Ta as a main component. 4) A material having an amorphous structure containing Ta as a main component and containing at least B. (For example, B represented by Ta ₄ B is 25
%) A material containing Ta, B and N (for example, a material having an amorphous structure containing Ta as a main component and containing 15% of B and about 10% of N) However, the above-mentioned material is used. Is not limited to TaSi, TaSi
N, TaGe, TaGeN, WN, Cr, TiN, etc. can also be used.

In an example in which a TaB compound thin film is used as the material of the EUV absorber layer 14, it is preferable to first form a Ta ₄ B film by a DC magnetron sputtering method using a Ta ₄ B target under an Ar gas atmosphere. . Through this step, an EUV mask blank is obtained.

(5) EB resist coating step. An EUV mask can be manufactured by forming a pattern on the absorber layer 14 of the obtained EUV mask blank. An EB resist is applied to the EUV mask blank obtained in the step (5) and baked at 200 ° C.

(6) EB drawing step. 30k on EUV mask blank coated with EB resist
A resist pattern was formed using an eV EB lithography machine.

(7) Dry etching step. Using the resist pattern as a mask, the EUV absorber layer 14 was dry-etched with chlorine at a substrate temperature of 20 ° C. using an ICP-RIE apparatus to form a pattern on the absorber layer 14. At this time, Cr _1-X N X film underlying became a thickness of is slightly etched 30～60A. Further, the resist remaining on the pattern of the absorber layer 14 was removed with hot concentrated sulfuric acid at 100 ° C.

(8) Step of Removing Intermediate Layer (a) In the case where a step of removing the intermediate layer from the reflection surface of the EUV mask is employed, the etching stopper 13 which is the intermediate layer remaining on the EUV light reflection surface is replaced by ( NH ₄₎ When ₂ Ce (NO _{3) 6} "ceric ammonium nitrate" + HClO ₄ + H ₂ O is removed by wet etching with, a reflective mask is completed for EUV exposure.

(B) When the step of leaving the intermediate layer on the reflective surface of the EUV mask is employed. As described in “(3) Step of forming intermediate layer”,
And at least one selected from N, O, and C
The etching stopper 13, which is an intermediate layer containing one or more elements, has an absorption coefficient of 0.05 or less with respect to light having a wavelength (13 nm) in the EUV region and has a sufficient surface roughness during film formation. Since it has the characteristics of being small and having a small film stress of the etching stopper film after film formation, it is possible to complete a sufficiently good reflection mask for EUV exposure even if it remains on the EUV light reflection surface as it is. I can do it. However, in this case, as described in “(3) Intermediate layer forming step”, it is preferable to use a material having a smaller absorption coefficient as the intermediate layer in order to suppress a decrease in reflectance as much as possible. When this step is adopted, the “(8) intermediate layer removing step” can be omitted, which is a preferred embodiment from the viewpoint of man-hours.

(9) Pattern transfer onto a semiconductor substrate using an EUV mask. Here, a pattern transfer onto a semiconductor substrate using an EUV mask will be described with reference to FIG. An apparatus for transferring a pattern onto a semiconductor substrate using an EUV mask includes a laser plasma X-ray source 31, an EUV mask 32, a reduction optical system 33, and the like. EUV light (soft X-rays) obtained from a laser plasma X-ray source 31 is incident on an EUV mask 32, and the reflected light is transferred onto, for example, a Si wafer 34 through a reduction optical system 33.

An X-ray reflection mirror can be used as the reduction optical system 33. The EUV mask 3 is formed by the reduction optical system.
The pattern reflected by 2 is usually reduced to about 1/4. For example, the transfer of the pattern to the Si wafer 34
This can be performed by exposing a pattern to a resist layer formed on the wafer 34 and developing the pattern. When a wavelength band of 13 to 14 nm is used as the exposure wavelength, the transfer is usually performed such that the optical path is in a vacuum. 1
As a material of a multilayer film in a wavelength band of 3 to 14 nm,
A Mo / Si multilayer film having a peak wavelength in this wavelength band can be used. By using the EUV mask obtained in the present embodiment to form a pattern on, for example, a Si wafer, it is possible to form, for example, a highly integrated LS
I, etc., can be manufactured.

(Embodiment 1) Referring to FIG.
Such EUV mask blank and EUV mask manufacturing
Example 1 will be described. In addition, in FIG.
The process is described by a solid line. As the glass substrate 11, the outer shape 6
Low expansion SiO with inch square and thickness of 6.3mm _Two−Ti
O_TwoA glass substrate was used. In addition, the glass substrate 11
Is 0.12 nmRms in 10 μm square by mechanical polishing
Smooth surface and flatness of 142mm square and 100nm or less
Have a degree.

As the multilayer film 12, Mo and Si were laminated. 3. A DC film was formed on the Si film by DC magnetron sputtering at an Ar gas pressure of 0.1 Pa using a Si target.
A 2 nm film is formed, and then, using a Mo target, Ar
At a gas pressure of 0.1 Pa, a Mo film was formed in a thickness of 2.8 nm, and this was taken as one cycle.
is formed to a thickness of nm. Here, the surface roughness on the multilayer film is 0.12 n
mRms.

Next, using a Cr target on the multilayer film 12 and using a gas obtained by adding 20% of nitrogen to Ar as a sputtering gas, an etching stopper 13 composed of a Cr ₁ -XN _x film is applied to the DC. A 6 nm-thick film was formed by magnetron sputtering to form an intermediate layer. Deposited C
In r _1-X N X film, x is 0.25, 13.4 N
The absorption coefficient at a wavelength of m is 0.035, and the film stress is 1
The thickness was +40 MPa in terms of a thickness of 00 nm, and the surface roughness was 0.23 nmRms.

Next, on the Cr _1-X N X film than made an etching stopper 13, as an EUV absorber layer 14, a film containing Ta and B by a DC magnetron sputtering method, a 0.1μm thick To form an EUV mask blank. At this time, the stress of the EUV absorber layer 14 was set to +50 MPa by controlling the sputtering conditions.

Next, using this EUV mask blank, a 16 Gbit-D having a design rule of 0.07 μm was used.
An EUV mask having a pattern for RAM was manufactured by the method described below. First, an EB resist was coated on the EUV mask blank, and a resist pattern was formed by EB drawing and development. Using this resist pattern as a mask, the EUV absorber layer 14 was dry-etched using chlorine to form an absorption pattern on an EUV mask blank, thereby obtaining an EUV mask. At that time, Cr
_1-X N _X etching stopper 13 is an intermediate layer which is composed of film, the film thickness is exposed to chlorine plasma fell to 4nm by over-etching. Here, without removing the etching stopper 13, the wavelength of 13.4 n
When the reflectivity was measured by EUV light at m and an incident angle of 2 °, favorable reflection characteristics of 55% ± 0.5% were obtained within a 130 mm area.

In the EUV mask obtained above, the edge roughness of the pattern of the absorber layer 14 was sufficiently small.
As a result of performing exposure transfer using a pattern transfer apparatus using EUV light on a semiconductor substrate shown in (1), it was confirmed that the semiconductor substrate had sufficient exposure characteristics. EUV mask accuracy is 7
It was confirmed that the required accuracy of the 0 nm design rule was 16 nm or less.

(Embodiment 2) Referring to FIG.
Such EUV mask blank and EUV mask manufacturing
Example 2 will be described. In addition, in FIG.
The process is indicated by a dashed line. Outside as glass substrate 11
6 inch square, low expansion SiO with thickness of 6.3mm _Two−
TiO_TwoA glass substrate was used. Also, the glass substrate 1
1 is a smooth table of 0.12 nmRms by mechanical polishing.
The surface has a flatness of 100 nm or less.

As the multilayer film 12, Mo and Si were laminated. 3. A DC film was formed on the Si film by DC magnetron sputtering at an Ar gas pressure of 0.1 Pa using a Si target.
A 2 nm film is formed, and then, using a Mo target, Ar
At a gas pressure of 0.1 Pa, a Mo film was formed in a thickness of 2.8 nm, and this was taken as one cycle.
is formed to a thickness of nm. Here, the surface roughness on the multilayer film is 0.12 n
mRms.

Next, using a Cr target on the multilayer film 12 and using a gas obtained by adding 30% of nitrogen to Ar as a sputtering gas, etching is performed as an intermediate layer composed of a Cr ₁ -XN _X film. The stopper 13 was formed to a thickness of 15 nm by DC magnetron sputtering. In the formed Cr _1-X N X film, x is 0.4, 13.4
The absorption coefficient at a wavelength of nm was 0.033, and the film stress was +30 MPa in terms of a film thickness of 100 nm. The surface roughness of the Cr _1-X N X film at this time was 0.14NmRms.

Next, a film 14 containing Ta and B is formed as an EUV absorber layer 14 on the etching stopper 13 composed of a Cr ₁ -XN _x film by a DC magnetron sputtering method to a thickness of 100 nm. A film was formed to obtain an EUV mask blank. At this time, the stress of the TaB film is 100
It was +30 MPa in terms of nm film thickness. Also at this time Ta
The surface roughness on the B film was 0.18 nmRms.

Next, using this EUV mask blank, a 16 Gbit-DRA with a design rule of 70 nm was used.
An EUV mask having a pattern for M was produced by the method described below. First, an EB resist was coated on the EUV mask blank, and a resist pattern was formed by EB drawing. Using this resist pattern as a mask, the EUV absorber layer 14 is dry-etched using chlorine to form an absorption pattern on the EUV mask blank, and the Cr _1-X N _X film is removed by wet etching to remove the EUV mask. Obtained. When the reflectance of the obtained EUV mask was measured by EUV light having a wavelength of 13.4 nm and an incident angle of 2 °, it had a good reflection characteristic of 65%. The edge roughness of the pattern of the absorber layer 14 of the EUV mask is sufficiently small. As a result of performing exposure transfer using a pattern transfer apparatus using EUV light on a semiconductor substrate shown in FIG. 3, sufficient exposure uniformity is obtained. I confirmed that. It was also confirmed that the accuracy of the EUV mask was 16 nm or less, which is the required accuracy of the 70 nm design rule.

Example 3 An EUV mask blank and an EUV mask were manufactured in the same manner as in Example 1 except that a Cr _{1 -X} C _X film (x = 0.2) was used as the etching stopper 13. It was set to 3. However, the intermediate layer was formed by DC magnetron sputtering, the atmosphere was 90% Ar + 10% methane gas, and the film thickness was 50 nm. As a result, the absorption coefficient of the formed intermediate layer with respect to light having a wavelength of 13.4 nm was 0.034, the stress of the intermediate layer was +20 MPa in terms of a 100 nm film thickness, and the surface roughness on the intermediate layer was Was 0.25 nmRms. The thickness of the etching stopper 13 after the etching was reduced to 40 nm by over-etching when the absorber pattern was formed. Here, without removing the etching stopper 13, the reflectance of EUV light having a wavelength of 13.4 nm and an incident angle of 2 ° was measured.
A good reflection characteristic of 5% was obtained.

Example 4 As in Example 2, a multilayer film 12 made of Mo and Si was formed on a glass substrate 11. Next, using a Cr target on the multilayer film 12,
Using a gas obtained by adding 30% of nitrogen to Ar as a sputtering gas, an etching stopper 13 as an intermediate layer composed of a Cr ₁ -XN _x film was formed to a thickness of 40 nm by magnetron sputtering. At this time, x is 0.0
It was 8. The wavelength of this Cr _1-X N _X film is 13.4 n.
The absorption coefficient for light of m was 0.036, and the surface roughness on the intermediate layer was 0.28 nmRms.

Next, an absorber layer 14 was formed on the etching stopper 13 composed of the Cr _1-X N _X film.
A film containing Ta and B was formed to a thickness of 55 nm by DC magnetron sputtering. Here, the total thickness of the intermediate layer and the absorber layer was 95 nm. The composition ratio of B in the TaB film was 15 at%, and the surface roughness on the TaB film was 0.3 nmRms. Further, the absorption coefficient of this TaB film for EUV light having a wavelength of 13.4 nm is 0.1.
039. As described above, the EUV of this embodiment
A mask blank was obtained.

Using this EUV mask blank, an EUV mask having a pattern for a 16-bit DRAM having a design rule of 70 nm was manufactured as follows. First, an EB resist was coated on the EUV mask blank, and a resist pattern was formed by EB drawing. Using this resist pattern as a mask, the absorber layer 14 was dry-etched using chlorine gas to form an absorption pattern. Then the remaining resist on the absorber layer 14 is removed with hot concentrated sulfuric acid to obtain an EUV mask further Cr _1-X N _X film on the mask reflection region is removed by dry etching with chlorine gas and oxygen gas .

For the obtained EUV mask, the wavelength 13.
When the reflectance for EUV light at 4 nm and an incident angle of 2 ° was measured, it showed a good reflectance of 65%. Further, in the obtained EUV mask, in addition to the edge roughness of the absorber layer 14 being sufficiently small, the total thickness of the absorber layer and the intermediate layer, that is, the height of the absorption pattern could be reduced to 95 nm. As a result, the problem of blurring of the pattern at the time of exposure can be reduced, and it was confirmed that the pattern had good exposure characteristics in transferring the pattern onto the semiconductor substrate shown in FIG. The accuracy of the obtained EUV mask is 70
This satisfied 16 nm which is the required accuracy of the nm design rule.

(Comparative Example) Referring to FIG.
The ratio of EUV mask blank and EUV mask production
A comparative example will be described. In FIG. 1, the manufacturing process of the comparative example is shown.
It is indicated by a dotted line. 6 inch outer shape as glass substrate 11
Low expansion SiO with corner and thickness of 6.3mm _Two-TiO_TwoAncestry
A glass substrate was used. Further, the glass substrate 11 is
Polishing gives a smooth surface of 0.12nmRms and 100n
m or less.

As the multilayer film 12, Mo and Si were laminated. 3. A DC film was formed on the Si film by DC magnetron sputtering at an Ar gas pressure of 0.1 Pa using a Si target.
A 2 nm film is formed, and then, using a Mo target, Ar
At a gas pressure of 0.1 Pa, a Mo film was formed in a thickness of 2.8 nm, and this was taken as one cycle.
is formed to a thickness of nm. Here, the surface roughness on the multilayer film is 0.12 n
mRms.

Next, a Cr film was formed to a thickness of 15 nm on the multilayer film 12 by using a Cr target, using an Ar gas as a sputter gas, and using a DC magnetron sputtering method as an etching stopper 13. At this time, the absorption coefficient of the Cr film at a wavelength of 13.4 nm is 0.0
39, and the film stress was +500 M in terms of 100 nm film thickness.
It showed a high tensile stress of Pa. At this time, the surface roughness on the Cr film was 0.29 nmRms.

Next, on the etching stopper 13,
As the EUV absorber layer 14, a film 14 containing Ta and B was formed to a thickness of 100 nm by DC magnetron sputtering to obtain an EUV mask blank. At this time, E
The stress of the UV absorber layer 14 is +4 in terms of 100 nm film thickness.
It was set to 0 MPa. At this time, the surface roughness on the EUV absorber layer 14 was 0.45 nmRms.

Next, using this EUV mask blank, a 16 Gbit-DRA with a design rule of 70 nm was used.
An EUV mask having a pattern for M was produced by the method described below. First, an EB resist was coated on the EUV mask blank, and a resist pattern was formed by EB drawing. Using this resist pattern as a mask, the EUV absorber layer 14 was dry-etched using chlorine to form an absorption pattern on the EUV mask blank, and the Cr film was removed by wet etching to obtain an EUV mask. When the reflectance of the obtained EUV mask was measured by EUV light having a wavelength of 13.4 nm and an incident angle of 2 °, it had a reflection characteristic of 65% due to the effect of removing the Cr film. On the other hand, the positional accuracy of this EUV mask caused a large distortion of 25 nm due to the high stress of the Cr film. In addition, the edge roughness increased due to the rough surface of the EUV absorber layer 14 caused by the surface roughness of the Cr film. Therefore, as a result of performing exposure transfer using a pattern transfer apparatus using EUV light on a semiconductor substrate shown in FIG. 3, it was found that the EUV mask manufactured in the comparative example could not obtain sufficient exposure characteristics.

[0073]

In the manufacturing process of an EUV mask or the like, in order to manufacture an EUV mask or the like capable of forming a highly accurate pattern, at least one selected from Cr, N, O, and C as an intermediate layer. By using a material containing one or more elements, an EU having high accuracy and high reflectivity
A V mask or the like can be manufactured, and a semiconductor manufacturing method characterized by transferring a pattern onto a semiconductor substrate using the EUV mask can be realized.

[Brief description of the drawings]

FIG. 1 is a manufacturing flowchart of an EUV mask according to an embodiment of the present invention.

FIG. 2 is a manufacturing flowchart of an EUV mask according to the conventional technique 1.

FIG. 3 shows E on a semiconductor substrate according to an embodiment of the present invention.
It is a conceptual diagram of the pattern transfer apparatus by UV light.

[Explanation of symbols]

 11. Glass substrate 12. Multilayer film 13. Etching stopper 14. Absorber layer 23. Etching stopper 31. Laser plasma X-ray source 32. EUV mask 33. Reduction optical system 34. Semiconductor wafer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H095 BA01 BA10 BB01 BC24 BC27 2H097 CA15 GB00 LA10 5F046 GD01 GD02 GD03 GD10 GD12

Claims (6)

[Claims] 1. A multilayer film reflecting EUV light on a substrate, an intermediate layer on the multilayer film, and an EU layer on the intermediate layer.
A reflective mask blank for EUV exposure having an absorber layer that absorbs V light, wherein the intermediate layer contains Cr and at least one element selected from the group consisting of N, O, and C. A reflective mask blank for EUV exposure, characterized by using a material. 2. The reflective mask blank for EUV exposure according to claim 1, wherein the absorber layer is made of a material containing Ta. 3. A multi-layered film for reflecting EUV light on a substrate, an intermediate layer on the multi-layered film, and an absorber layer for absorbing EUV light having a pattern formed on the intermediate layer. A reflective mask for EUV exposure, wherein a material containing Cr and at least one element selected from the group consisting of N, O, and C is used as the intermediate layer. Reflection type mask. 4. The reflective mask for EUV exposure according to claim 3, wherein the absorber layer is made of a material containing Ta. 5. A method for manufacturing a reflective mask for EUV exposure, comprising using the reflective mask blank for EUV exposure according to claim 1 or 2. 6. A method for manufacturing a semiconductor, comprising: transferring a pattern onto a semiconductor substrate using the reflective mask for EUV exposure according to claim 3 or 4.