JP2005191352A - Method for reproducing substrate with multilayer reflection film of (w2-w1)/w3 as water absorption coefficient, method for producing substrate with multilayer reflection film and method for manufacturing reflection type mask blank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for reproducing a substrate with a multilayer reflection film by which the reproducing cost of the substrate can be reduced because a large-scale apparatus is not required, the damage of the substrate due to the peeling and removal of the multilayer reflection film can be reduced and also the process load of re-polishing is low. <P>SOLUTION: The substrate with the multilayer reflection film constituted of forming the multilayer reflection film on which Mo and Si are alternately laminated on the substrate is brought into contact with a peeling solution consisting of an aqueous solution containing at least one fluorine compound selected from among hydrofluoric acid, hydrosilicofluoric acid and ammonium hydrogendifluoride, and an oxidant consisting of hydrogen peroxide; or an aqueous solution containing at least one fluoride compound selected from among potassium fluoride, sodium fluoride and iodine fluoride, and at least one oxidant selected from among sulphuric acid, nitric acid and hydrogen peroxide, to peel off and remove the multilayer reflection film from the substrate. As a method for contact with the peeling solution, the substrate 4 with the multilayer reflection film which is inserted into a holder 3 is dipped into the peeling solution 2 in a processing tank 1. The surface of the substrate from which the multilayer reflection film is peeled off is accurately repolished. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multilayer reflective film mirror used in an EUV lithography system, which is an exposure technology using extreme ultraviolet (Extreme UltraViolet, hereinafter referred to as EUV) light, and a substrate with a multilayer reflective film used in the production of a reflective mask blank for exposure. It is related with the reproduction | regenerating method of the board | substrate with a multilayer reflective film which peels and removes the multilayer reflective film in a board | substrate, and reproduces | regenerates a board | substrate.

In recent years, in the semiconductor industry, with the miniaturization of semiconductor devices, EUV lithography which is an exposure technique using EUV light is promising. Here, EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, and specifically refers to light having a wavelength of about 0.2 to 100 nm. As an exposure mask used in this EUV lithography, for example, an exposure reflective mask as described in Patent Document 1 has been proposed.
That is, a reflective type in which a reflective film having a multilayer film structure in which two types of layers having different optical constants are alternately laminated on a substrate and an absorber that absorbs soft X-rays or vacuum ultraviolet rays that form a pattern are formed. It is a mask. In an exposure machine (pattern transfer device) equipped with such a reflective mask, the exposure light incident on the reflective mask is absorbed at a portion where the absorber pattern is present, and is reflected by the reflective film at a portion where the absorber pattern is absent. The transferred optical image is transferred onto a semiconductor substrate (for example, a silicon wafer with a resist) through a reflection optical system.

As the reflective film, that is, a reflective film having a multilayer structure (multilayer reflective film), a multilayer film in which a material having a relatively high refractive index and a material having a relatively low refractive index are alternately laminated in the order of several nm are used. Usually used. For example, a multilayer film in which thin films of Si and Mo are alternately stacked is known as one having a high reflectivity for 13 to 14 nm EUV light.
By the way, in such a reflective mask, if there are irregularities on the reflection surface, particularly in the vicinity of the pattern, the reflected light undergoes a phase change caused by the irregularities, and this phase change is caused by the position of the pattern to be transferred. It causes deterioration of accuracy and contrast. When light having a short wavelength, such as EUV light, is used as exposure light, the phase change becomes very sensitive to such irregularities, so that the effect on the transferred image is increased, and the phase derived from small irregularities. The change of cannot be ignored. For example, when EUV light having a wavelength of about 13 nm is used as exposure light, even fine irregularities of about 2 nm can be phase defects. Therefore, after forming a multilayer reflective film on the substrate, a substrate with a multilayer reflective film in which, for example, a convex sub-film defect due to the presence of foreign matter between the substrate and the multilayer reflective film was discovered by surface defect inspection. Cannot be used as a substrate for a reflective mask blank for manufacturing a reflective mask.

However, recent competition for lowering prices of electronic components such as semiconductor devices is becoming increasingly severe, and it is also an important issue to suppress the manufacturing cost of exposure masks. Against this background, after forming a multilayer reflective film on the substrate, the substrate with the multilayer reflective film in which surface defects are found is removed as a defective product, and the multilayer reflective film is peeled off from the substrate and recycled. There is a need for a method to do this. For example, Patent Document 2 below discloses a method of removing a Mo / Si multilayer reflective coating from a super-polished optical support, and the Mo / Si multilayer film is formed by dry etching by reactive ion etching using a chlorine-containing gas. It is described to be removed. Further, in Patent Document 2, as a conventional technique, there is a method of removing a Mo / Si multilayer film by wet etching using both potassium ferrocyanide / alkali hydroxide and hydrofluoric acid / nitric acid etching agents. Has been described.
Japanese Patent No. 2140060 Special Table 2000-506217

However, the Mo / Si multilayer removal by dry etching disclosed in Patent Document 2 has the following problems.
That is, since a large-scale and complex etching apparatus for performing reactive ion etching is used, the running cost is increased. In addition, it is difficult to clean the deposits of the Mo / Si multilayer component adhering in the chamber of the etching apparatus. Furthermore, due to reactive ion etching, an altered layer is formed on the substrate after removing the multilayer film, or damage occurs in the thickness direction of the substrate, and the altered layer and damage are completely removed to regenerate the substrate. In this case, it is necessary to take a lot of machining allowance, and it takes a long time for the re-polishing process, so that the process load is large and the cost is high.
On the other hand, the removal of the Mo / Si multilayer film by wet etching with the specific solution described in Patent Document 2 also has the following problems.
That is, if there is no corrosion-resistant barrier layer between the substrate and the multilayer film, the substrate is damaged by the etching, and even if the substrate is re-polished after re-polishing, the re-polishing process load is large and the cost increases. . For example, in the SiO ₂ —TiO ₂ -based low expansion glass used as a substrate for an EUV reflective mask, the surface roughness due to the etching is particularly large and the damage is large. In order to reduce such damage to the substrate, it is necessary to provide a corrosion-resistant barrier layer (for example, a corrosion-resistant amorphous carbon barrier layer) between the substrate and the multilayer film, which only increases the manufacturing process of the multilayer reflective film-coated substrate. In addition, when the substrate is regenerated, it is necessary to remove the corrosion-resistant barrier layer, and in any case, the cost increases due to the addition of a process.

  The present invention has been made in view of the above-described problems of the prior art, and does not require a large-scale and complicated structure apparatus, and is easy to clean even if a multilayer reflective film component adheres to the processing apparatus used in the present invention. In addition, it is an object of the present invention to provide a method for regenerating a substrate with a multilayer reflective film that can reduce the cost of regenerating the substrate by reducing damage to the substrate due to peeling and removing of the multilayer reflective film and reducing the process load of re-polishing. Another object of the present invention is to provide a method for manufacturing a substrate with a multilayer reflective film and a method for manufacturing a reflective mask blank using the substrate regenerated by this regenerating method.

In order to solve the above-described problems, the present invention has the following configuration.
(Configuration 1) A substrate with a multilayer reflective film in which a multilayer reflective film is formed by alternately laminating two or more materials having different refractive indexes including at least one of molybdenum (Mo) and silicon (Si) on the substrate. Or an aqueous solution containing at least one fluorine compound selected from hydrofluoric acid, silicohydrofluoric acid, and ammonium hydrogen fluoride and an oxidizing agent comprising hydrogen peroxide, or potassium fluoride, sodium fluoride, fluoride. The multilayer reflective film is peeled off from the substrate by contacting with a stripping solution comprising an aqueous solution containing at least one fluorine compound selected from iodine fluoride and at least one oxidizing agent selected from sulfuric acid, nitric acid, and hydrogen peroxide. A method for regenerating a substrate with a multilayer reflective film, wherein the substrate is regenerated.
According to the configuration 1, the multilayer reflective film on the substrate can be peeled and removed to regenerate the substrate by bringing the substrate with the multilayer reflective film into contact with a stripping solution made of a specific aqueous solution. The method for regenerating a substrate with a multilayer reflective film according to the present invention can reduce damage to the substrate due to peeling and removal of the multilayer reflective film. Moreover, it can implement using the processing tank which can contact a board | substrate with a multilayer reflective film with stripping solution, for example, and a large-scale and complicated apparatus is not required. Moreover, even if the removed multilayer reflection film component adheres to the said processing tank, it can be easily cleaned.
The multilayer reflective film formed by alternately laminating two or more kinds of materials having different refractive indexes including at least one of Mo and Si has a high reflectance with respect to EUV light of 13 to 14 nm, for example, a few nm of Mo and Si. This is a Mo / Si multilayer reflective film in which thin films are alternately stacked.
The substrate with a multilayer reflective film is, for example, a substrate with a multilayer reflective film used for manufacturing an EUV reflective mask blank or an EUV reflective mask, or a substrate with a multilayer reflective film used as a multilayer reflective film mirror in an EUV lithography system. .

(Structure 2) The method for regenerating a substrate with a multilayer reflective film according to Structure 1, wherein the multilayer reflective film is peeled and removed from the substrate, and then the surface of the substrate is precisely polished.
According to Configuration 2, the surface of the substrate from which the multilayer reflective film has been peeled and removed can be recovered, for example, to a surface roughness (root mean square roughness (RMS)) of 0.15 nmRms or less. In the case of a glass substrate for an EUV reflective mask, the surface roughness is mirror-polished to an RMS of 0.15 nmRms or less. The method for regenerating a substrate with a multilayer reflective film according to the present invention causes less damage to the substrate due to peeling and removal of the multilayer reflective film, and reduces the process load of re-precise polishing. can do.
(Structure 3) The method for regenerating a substrate with a multilayer reflective film according to Structure 1 or 2, wherein the temperature of the stripping solution is set to room temperature to 80 ° C.
As in Configuration 3, by setting the temperature of the stripping solution in the above range, the multilayer reflective film can be stripped and removed from the substrate in a short processing time, and damage to the substrate can be reduced.

(Structure 4) A multilayer reflective film for reflecting light to be used is formed on a substrate regenerated by the method for regenerating a substrate with a multilayer reflective film according to any one of Structures 1 to 3. A method for manufacturing a substrate with a substrate.
As in Configuration 4, a substrate with a multilayer reflective film using the substrate regenerated according to the present invention can be manufactured.
(Structure 5) At least a multilayer reflective film that reflects exposure light and a multilayer reflective film are provided on the substrate regenerated by the method for regenerating a substrate with a multilayer reflective film according to any one of Structures 1 to 3. A method of manufacturing a reflective mask blank, comprising forming an absorber film that absorbs exposure light.
As in Configuration 5, it is possible to manufacture a reflective mask blank using a substrate regenerated according to the present invention.

  According to the present invention, it is not necessary to use a large-scale and complicated apparatus for peeling and removing the multilayer reflective film from the substrate, and even if the multilayer reflective film component adheres to the processing apparatus, it can be easily cleaned and the substrate is regenerated. Cost can be reduced. In addition, according to the present invention, the substrate is less damaged due to the peeling and removal of the multilayer reflective film, and the re-polishing process load is also reduced. Therefore, the cost for regenerating the substrate can be reduced, and a high-quality substrate can be regenerated. In addition, by forming a multilayer reflective film, an absorber film or the like on the regenerated high-quality substrate, it is possible to manufacture a substrate with a multilayer reflective film or a reflective mask blank.

Next, an embodiment of the present invention will be described.
In one embodiment of the present invention, there is provided a substrate with a multilayer reflective film in which a multilayer reflective film formed by alternately laminating two or more materials having different refractive indexes including at least one of Mo and Si is formed on the substrate. Then, the multilayer reflective film is peeled and removed from the substrate by contacting with a stripping solution comprising the following aqueous solution (A) or (B) to regenerate the substrate.
(A) an aqueous solution containing at least one fluorine compound selected from hydrofluoric acid, silicohydrofluoric acid, and ammonium hydrogen fluoride and an oxidizing agent comprising hydrogen peroxide; (B) potassium fluoride, sodium fluoride, An aqueous solution containing at least one fluorine compound selected from iodine fluoride and at least one oxidizing agent selected from sulfuric acid, nitric acid, and hydrogen peroxide

  As a multilayer reflective film formed by alternately laminating two or more materials having different refractive indexes including at least one of Mo and Si to which the present invention is applied, for example, the reflectance with respect to EUV light of 13 to 14 nm is high. A Mo / Si multilayer reflective film in which Mo and Si are alternately stacked for about 40 cycles can be mentioned. Examples of other multilayer reflective films used in the EUV light region include Ru / Si periodic multilayer reflective films, Mo / Be periodic multilayer reflective films, Mo compound / Si compound periodic multilayer reflective films, and Si / Nb periodic multilayer reflective films. Examples thereof include a film, a Si / Mo / Ru periodic multilayer reflective film, a Si / Mo / Ru / Mo periodic multilayer reflective film, and a Si / Ru / Mo / Ru periodic multilayer reflective film. A substrate with a multilayer reflective film in which these multilayer reflective films are formed on a substrate is used as, for example, a substrate with a multilayer reflective film in an EUV reflective mask blank or an EUV reflective mask, or a multilayer reflective film mirror in an EUV lithography system.

  In the present invention, in order to regenerate the substrate in the substrate with the multilayer reflective film, the substrate with the multilayer reflective film is brought into contact with the stripping solution. As a method of bringing the substrate with a multilayer reflective film into contact with the stripping solution, for example, a method (immersion method) of immersing the substrate with a multilayer reflective film in a treatment tank containing the stripping solution can be mentioned. As another method, a method of spraying a stripping solution directly on the surface of the substrate with a multilayer reflective film (the surface of the multilayer reflective film) with a spray or the like can be mentioned. In particular, the former method of immersing a substrate with a multilayer reflective film in a stripping solution is such that the stripping solution is supplied substantially uniformly over the entire surface of the multilayer reflective film, and the stripping solution penetrates from the end surface of the substrate. It is suitable for. In this case, it is also preferable to apply ultrasonic waves. Further, it is preferable to swing the substrate in the stripping solution during the treatment by the dipping method. This is because the stripping solution does not stagnate in the vicinity of the multilayer reflective film of the substrate, so that the chemical reaction between the multilayer reflective film component and the stripping liquid is promoted, and the multilayer reflective film is preferably peeled off. Examples of means for swinging the substrate include a method of swinging a holder for holding the substrate in the stripping solution in the vertical direction. Further, instead of shaking the substrate, or in addition to shaking the substrate, the stripping solution may be stirred. In addition, it is desirable to replace the used stripping solution as appropriate.

There are no particular restrictions on the processing conditions when the multilayer reflective film is brought into contact with the stripping solution, for example, the concentration, temperature, and processing time of the stripping solution. It is desirable to select appropriately according to the number of layers (film thickness) and the substrate material.
The concentration of the stripping solution is preferably selected as appropriate in the range of, for example, 0.1 to 5% by weight for fluorine compounds and 0.5 to 45% by weight for oxidizing agents. If the concentration of each substance is lower than the exemplified lower limit, the progress of peeling becomes slow, resulting in a longer processing time and difficulty in peeling. On the other hand, when the concentration of each substance is higher than the exemplified upper limit value, peeling progresses quickly, and the processing time can be shortened, but the substrate damage (the surface becomes rough) is large.
The stripping solution temperature is preferably in the range of room temperature to 80 ° C. Here, room temperature is about 20 ° C. When the stripping solution temperature is lower than room temperature, the progress of stripping becomes slow and the processing time becomes long, resulting in difficulty in stripping. On the other hand, when the stripping solution temperature exceeds 80 ° C., the stripping progresses quickly and the processing time can be shortened, but the substrate damage (surface becomes rough) is large. In the present invention, it is particularly preferably in the range of 35 to 65 ° C.
Further, the processing time may be a time sufficient for the multilayer reflective film to be peeled off from the substrate. In the case of the stripping solution of the present invention, although depending on the concentration and temperature of the stripping solution described above or depending on the film thickness of the multilayer reflective film, the action of the present invention is preferably obtained in the range of about 10 to 120 minutes.

The stripping solution used in the present invention is an aqueous solution comprising the above-described aqueous solution (A) or (B) and containing a specific fluorine compound and an oxidizing agent (oxidizing substance). Since such a stripping solution has sufficient fluorine ions activated in an acidic solution, even if it is a multilayer reflection film component that has a very slow dissolution reaction with a fluorine compound unless it is in an acidic solution, such as Si. It is possible to accelerate this dissolution reaction and accelerate the progress of peeling of the multilayer reflective film.
For example, dissolution of a Mo / Si multilayer reflective film composed of alternately laminated films of Mo and Si in a stripping solution composed of an aqueous solution containing hydrofluoric acid and hydrogen peroxide can be expressed by the following chemical reaction formula.
MoSi ₂ + 7H ₂ O ₂ + 14HF → MoF ₆ + 2SiF ₄ ↑ + 14H ₂ O

As a substrate material in a substrate with a multilayer reflective film, amorphous glass (eg, SiO ₂ —TiO ₂ glass) having a low thermal expansion coefficient, quartz glass, crystallized glass on which β-quartz solid solution is precipitated, silicon, metal (eg, Invar alloy) (Fe—Ni alloy) and the like. According to the method of the prior art described above, even in a glass having a low expansion coefficient, particularly damage to the substrate surface after removing the multilayer reflective film can reduce the substrate damage after removing the multilayer reflective film, The present invention is preferred.

In this manner, after removing the multilayer reflective film from the substrate with the multilayer reflective film, the surface of the substrate can be precisely polished to recover the surface roughness of the substrate before the multilayer reflective film is stripped. For example, in the case of a glass substrate for an EUV reflective mask, the surface roughness is reduced to RMS (root mean square roughness) by 0.15 nmRms or less by precision polishing.
Precision polishing is usually performed using a polishing pad while supplying a polishing liquid containing free abrasive grains such as cerium oxide and colloidal silica to the main surface of the substrate. At this time, either a single-side polishing method for polishing one side of the substrate or a double-side polishing method for simultaneously polishing both surfaces of the substrate may be used. In the method for regenerating a substrate with a multilayer reflective film according to the present invention, the damage on the substrate due to peeling and removal of the multilayer reflective film is small, so that the process load of re-precise polishing is small. Accordingly, it is possible to reduce the cost of regenerating the substrate and to regenerate a high-quality substrate.

A substrate with a multilayer reflective film can be manufactured by forming a multilayer reflective film that reflects light to be used (for example, EUV light) on the substrate regenerated by the method for regenerating a substrate with a multilayer reflective film according to the present invention. . The manufactured substrate with a multilayer reflective film is used as a multilayer reflective film mirror in, for example, an EUV lithography system, and of course, it is also used for manufacturing a reflective mask blank for exposure.
Further, on the substrate regenerated by the method for regenerating a substrate with a multilayer reflective film according to the present invention, at least a multilayer reflective film that reflects exposure light (for example, EUV light) and the exposure light provided on the multilayer reflective film are absorbed. By forming the absorber film to be formed, a reflective mask blank for exposure can be manufactured. If necessary, a buffer film for protecting the multilayer reflective film may be provided between the multilayer reflective film and the absorber film, which is resistant to the etching environment during pattern formation on the absorber film. .

  The multilayer reflective film can be formed on the substrate by, for example, DC magnetron sputtering. In the case of the Mo / Si multilayer reflective film, the Si target and the Mo target are alternately used in an Ar gas atmosphere to stack 30 to 60 cycles, preferably about 40 cycles, and finally a Si film is formed as a protective film. . As another film forming method, an IBD (ion beam deposition (also referred to as ion beam sputtering)) method in which an ion beam is applied to a target for forming a multilayer reflective film and ion beam sputtering is used is used. it can.

The buffer film has a function of protecting the lower multilayer reflective film as an etching stop layer when a transfer pattern is formed on the absorber film, and is usually formed between the multilayer reflective film and the absorber film. Note that the buffer film may be provided as necessary.
As the material of the buffer film, a material having a high etching selectivity with the absorber film is selected. The etching selectivity between the buffer film and the absorber film is 5 or more, preferably 10 or more, more preferably 20 or more. Furthermore, a material having low stress and excellent smoothness is preferable, and in particular, it has a smoothness of 0.3 nmRms or less. From such a viewpoint, it is preferable that the material for forming the buffer film has a microcrystalline or amorphous structure.
In general, Ta, Ta alloy, or the like is often used as a material for the absorber film. When a Ta-based material is used as the material of the absorber film, it is preferable to use a material containing Cr as the buffer film. For example, Cr alone or a material in which at least one element of nitrogen, oxygen, and carbon is added to Cr can be used. Specifically, chromium nitride (CrN) or the like is used.
On the other hand, when Cr alone or a material mainly containing Cr is used as the absorber film, the buffer film is made of a material mainly containing Ta, for example, a material containing Ta and B, or Ta and B. A material containing N and N can be used.

  This buffer film may be removed in a pattern according to the pattern formed on the absorber film in order to prevent a reduction in the reflectance of the mask when the reflective mask is formed. If a large material can be used and the film thickness can be sufficiently reduced, the multilayer reflective film may be left without being removed in a pattern. The buffer film can be formed by, for example, a sputtering method such as DC sputtering, RF sputtering, or ion beam sputtering.

  As the material of the absorber film, a material having a high exposure light absorptivity and a sufficiently large etching selection ratio with a film (usually a buffer film or a multilayer reflective film) located below the absorber film is selected. For example, a material having Ta as a main metal component is preferable. In this case, if a material containing Cr as a main component is used for the buffer film, the etching selectivity can be increased (10 or more). A material having Ta as a main metal element is usually a metal or an alloy. Further, those having an amorphous or microcrystalline structure are preferable from the viewpoint of smoothness and flatness. Materials containing Ta as a main metal element include materials containing Ta and B, materials containing Ta and N, materials containing Ta, B and O, materials containing Ta, B and N, and materials containing Ta and Si A material containing Ta, Si and N, a material containing Ta and Ge, a material containing Ta, Ge and N can be used. By adding B, Si, Ge or the like to Ta, an amorphous material can be easily obtained and the smoothness can be improved. In addition, when N or O is added to Ta, resistance to oxidation is improved, so that an effect of improving stability over time can be obtained.

Other absorber film materials include Cr-based materials (chromium, chromium nitride, etc.), tungsten-based materials (tungsten nitride, etc.), and titanium-based materials (titanium, titanium nitride). ) Etc. can be used.
These absorber films can be formed by a normal sputtering method.
As described above, a reflective mask blank using the regenerated substrate is obtained. The reflective mask can be manufactured by forming a predetermined transfer pattern on the absorber film of the reflective mask blank by photolithography.
Next, the embodiment of the present invention will be described more specifically with reference to examples.

(Example 1)
In this embodiment, a substrate with a multilayer reflective film used for manufacturing EUV reflective mask blanks will be described as an example.
On a quartz glass substrate whose surface is mirror-polished to an RMS of 0.15 nm or less by RMS, a Si film is first formed by DC magnetron sputtering using an Si target at an Ar gas pressure of 0.1 Pa and a thickness of 4.2 nm. Then, using a Mo target, an Mo film was formed at 2.8 nm at an Ar gas pressure of 0.1 Pa, and this was set as one period, and after 40 periods were laminated, an Si film was finally formed at 4 nm to obtain a multilayer. A substrate with a reflective film was produced.
When the obtained substrate with a multilayer reflective film was inspected with a surface defect inspection apparatus, a convex subfilm defect in which a foreign substance was thought to be present between the substrate and the multilayer reflective film was found.

Therefore, the multilayer reflective film of the multilayer reflective film-coated substrate having such surface defects was peeled off to regenerate the substrate. As shown in FIG. 1, a holder 3 holding a plurality of multilayer reflective film-coated substrates 4 was immersed in a stripping solution 2 accommodated in a processing tank 1 for a predetermined time, and the multilayer reflective film was peeled from the substrate. As a stripping solution, a mixed aqueous solution of ammonium hydrogen fluoride (1 wt%), hydrogen peroxide (2 wt%) and pure water (97 wt%) was used. The temperature of the stripping solution at this time was 40 ° C., and the treatment time was 30 minutes. During the processing, the substrate 3 was swung in the vertical direction by moving the holder 3.
Thus, when the surface of the board | substrate which peeled the multilayer reflective film which consists of Mo / Si films was observed with the electron microscope, the residue of Mo / Si film was not confirmed. In addition, the surface of the substrate from which the multilayer reflective film has been peeled is slightly roughened by the above-described peeling solution, but the surface roughness (RMS) can be easily restored to 0.15 nmRms or less by re-precise polishing of the substrate surface. The flatness could be reduced to 100 nm or less. Here, the flatness is a value representing the surface warpage (deformation amount) represented by TIR (total indicated reading), and is defined as follows. A plane defined by the least square method based on the substrate surface is defined as a focal plane, and between this focal plane, the highest position on the substrate surface above the focal plane and the lowest position below the focal plane. The absolute value of a certain level difference was defined as flatness.
In the case of peeling off the multilayer reflective film according to the present embodiment, the deposit adhered to the treatment tank can be easily cleaned after being used a plurality of times without replacing the stripping solution, and does not require a large-scale apparatus and is regenerated. There is also an advantage that the cost is low.

(Example 2)
Using the substrate regenerated in Example 1, a multilayer reflective film of Mo / Si film was again formed by DC magnetron sputtering to produce a substrate with a multilayer reflective film.
When the obtained substrate with a multilayer reflective film was inspected with a surface defect inspection apparatus, the above-mentioned convex subfilm defects were not confirmed.
An EUV reflective mask blank and an EUV reflective mask manufacturing method using this multilayer reflective film-coated substrate will be described below.
A chromium nitride (CrN) film having a thickness of 30 nm was formed as a buffer film on the multilayer reflective film of the substrate with the multilayer reflective film. Film formation was performed by a DC magnetron sputtering method using a Cr target and using nitrogen and Ar as sputtering gases. In the formed CrN film, the composition ratio of Cr: N was 0.9: 0.1.
Next, an alloy (TaBN film) made of tantalum, boron, and nitrogen was formed to a thickness of 60 nm as an absorber film on the buffer film made of the CrN film. Film formation was performed by DC magnetron sputtering using a target containing Ta and B, adding 10% nitrogen to Ar. In the formed TaBN film, the composition ratio was 0.8 for Ta, 0.1 for B, 0.1 for N, and the crystalline state was amorphous.
As described above, the EUV reflective mask blanks of this example were obtained.

Next, using this EUV reflective mask blank, an EUV reflective mask having a pattern for a 16 Gbit DRAM having a design rule of 0.07 μm was produced by the following method.
First, a resist for electron beam drawing was applied on the EUV reflective mask blank, and a resist film was formed by baking at 135 ° C., followed by drawing with an electron beam, development, and a resist pattern was formed.
Using this resist pattern as a mask, the absorber film made of a TaBN film was dry-etched using chlorine to form an absorber film pattern.
Further, the resist pattern remaining on the absorber film pattern was removed with hot sulfuric acid at 100 ° C. Next, the buffer film made of the CrN film was dry-etched according to the pattern of the absorber film using a mixed gas of chlorine and oxygen to obtain a patterned buffer film.
As described above, the EUV reflective mask of this example was obtained. When pattern transfer onto a semiconductor substrate was performed using this reflective mask, pattern transfer with high accuracy could be performed.

(Examples 3 to 5)
Next, the stripping solution in Example 1 is a mixed aqueous solution (temperature 35 ° C.) of hydrogen fluoride (0.1 wt%), hydrogen peroxide (1.0 wt%), and pure water (98.9 wt%) (Example 3) Mixed aqueous solution (temperature 45 ° C.) of hydrogen silicofluoride (0.1 wt%), hydrogen peroxide (1.0 wt%) and pure water (98.9 wt%) (Example 4), ammonium hydrogen fluoride (Example 5) except that a mixed aqueous solution (temperature 40 ° C.) of (0.2 wt%), hydrogen peroxide (2.0 wt%), nitric acid (2.0 wt%), and pure water (95.8 wt%) was used. In the same manner as in Example 1, the multilayer reflective film of the multilayer reflective film-coated substrate was peeled off to regenerate the substrate.
Thus, when the surface of the board | substrate which peeled the multilayer reflecting film which consists of Mo / Si films was observed with the electron microscope, the residue of Mo / Si film was not confirmed. In addition, the surface of the substrate from which the multilayer reflective film has been peeled is slightly roughened by the above-described peeling solution, but the surface roughness (RMS) can be easily restored to 0.15 nmRms or less by re-precise polishing of the substrate surface. The flatness could be reduced to 100 nm or less.
In the same manner as in Example 2 described above, a multilayer reflective film of Mo / Si film is formed by DC magnetron sputtering using the substrate regenerated in Examples 3 to 5 described above to produce a substrate with a multilayer reflective film. Furthermore, EUV reflective mask blanks and EUV reflective masks were produced using this multilayer reflective film-coated substrate.
As a result, when the obtained substrate with a multilayer reflective film was inspected with a surface defect inspection apparatus, no convex subfilm defects were confirmed, and a pattern on a semiconductor substrate was obtained using the obtained reflective mask. As a result of the transfer, a highly accurate pattern transfer could be performed.
Next, a comparative example for the above embodiment will be described.

(Comparative example)
Mo / Si multilayer reflection on the same substrate with a multilayer reflective film as in Example 1 by reactive ion etching (RIE) using chlorine-containing gas described in Patent Document 2 (etching conditions described in Patent Document 2) The film was peeled off. As a result, the Mo / Si multilayer reflective film could be peeled off in about 30 minutes. However, substrate damage and altered layers were confirmed in the depth direction by reactive ion etching on the surface of the peeled substrate. They were removed by re-precise polishing of the substrate surface.
In addition, in the case of peeling of the multilayer reflective film by such reactive ion etching, it is difficult to clean the deposits of the multilayer reflective film components adhering in the chamber of the reactive ion etching apparatus, and the apparatus is large-scale. There is a disadvantage that the reproduction cost becomes high.

  As described above, according to the present invention, a large-scale device is not particularly required, and the multilayer reflective film can be peeled off from the substrate using a simple device, and the substrate damage due to peeling is small, so that re-polishing Thus, the process load of the substrate can be reduced, and the cost for regenerating the substrate can be reduced. Although the embodiment of the present invention has been described with reference to examples, it is selected from, for example, fluorine compounds such as potassium fluoride, sulfuric acid, nitric acid, and hydrogen peroxide, regardless of the stripping solution mentioned in the examples. Even when an aqueous solution containing at least one oxidizing agent is used as the stripping solution, the same effect as in the above-described embodiment can be obtained.

It is a schematic block diagram of the immersion method in the Example of this invention.

Explanation of symbols

1 treatment tank 2 stripping solution 3 holder 4 substrate with multilayer reflective film

Claims (5)

A substrate with a multilayer reflective film in which a multilayer reflective film is formed by alternately laminating two or more materials having different refractive indexes including at least one of molybdenum (Mo) and silicon (Si) on a substrate is fluorinated. An aqueous solution containing at least one fluorine compound selected from hydrofluoric acid, silicohydrofluoric acid and ammonium hydrogen fluoride and an oxidizing agent comprising hydrogen peroxide, or selected from potassium fluoride, sodium fluoride and iodine fluoride The multilayer reflective film is peeled and removed from the substrate by contacting with a stripping solution comprising an aqueous solution containing at least one fluorine compound and at least one oxidizing agent selected from sulfuric acid, nitric acid, and hydrogen peroxide, and the substrate is regenerated. A method for regenerating a substrate with a multilayer reflective film. 2. The method for regenerating a substrate with a multilayer reflective film according to claim 1, wherein after the multilayer reflective film is peeled and removed from the substrate, the surface of the substrate is precisely polished. The method for regenerating a substrate with a multilayer reflective film according to claim 1 or 2, wherein the temperature of the stripping solution is from room temperature to 80 ° C. A multilayer reflective film for reflecting light to be used is formed on a substrate regenerated by the method for regenerating a substrate with a multilayer reflective film according to any one of claims 1 to 3. Production method. 4. At least a multilayer reflective film that reflects exposure light, and exposure light provided on the multilayer reflective film on the substrate regenerated by the method for regenerating a substrate with a multilayer reflective film according to claim 1. The manufacturing method of the reflective mask blank characterized by forming the absorber film | membrane to absorb.

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