JP2008103512A - Process for producing reflective mask blank, process for producing reflective mask, and process for fabricating semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing a reflective mask blank and a process for producing a reflective mask in which displacement of the mask caused by flatness of the patterning surface of a mask is prevented when a pattern is transferred. <P>SOLUTION: The process for producing a reflective mask blank comprises a step (S2) for obtaining a mask blank by depositing a multilayer reflective film and an absorber film on a substrate having a major surface polished precisely, a step for acquiring the surface form information of both major surfaces of the mask blank in a predetermined region, and a step (S4) for obtaining the surface form information of the patterning surface of a mask when the mask blank is set on a mask stage. Furthermore, displacement caused by the surface form of the patterning surface of a mask when a pattern is transferred onto a semiconductor substrate is calculated (S5) based on the surface form information of the patterning surface of a mask thus obtained, and the mask pattern is drawn while correcting the displacement in the step for drawing a mask pattern in order to pattern the absorber film of the mask blank. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reflective mask blank and a reflective mask manufacturing method used in semiconductor manufacturing and the like, and a semiconductor device manufacturing method.

  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. However, while miniaturization of semiconductor devices is accelerating, shortening the wavelength of conventional light exposure has approached the exposure limit. In the case of light exposure, the resolution limit of the pattern is said to be 1/3 of the exposure wavelength, and is, for example, about 60 nm using an ArF excimer laser (wavelength 193 nm). Furthermore, with the recent immersion exposure, resolution has been improved, and it is expected that about 45 nm can be resolved, but it is difficult to further improve the optical exposure. Therefore, EUV lithography (hereinafter referred to as “EUVL”), which is an exposure technique using EUV light having a wavelength shorter than that of an ArF excimer laser, is promising as an exposure technique with a resolution higher than 45 nm. Here, EUV (Extreme Ultra Violet) 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.

  EUVL has the same image formation principle as photolithography, but the absorption of all materials to EUV light is large, and the refractive index is close to 1. Therefore, a refractive optical system such as light exposure cannot be used, and all reflections are reflected. An optical system is used. Further, as a mask used at that time, a transmission type mask using a membrane has been proposed conventionally, but there is a problem that the exposure time becomes long because the absorption of the membrane with respect to EUV light is large, and the throughput cannot be secured. Therefore, at present, a reflective mask is generally used.

  For example, in Japanese Patent Publication No. 7-27198 (Patent Document 1) and Japanese Patent Application Laid-Open No. 8-213303 (Patent Document 2), a reflective layer having a multilayer structure is provided on a substrate, and a soft layer is formed on the reflective layer. A reflective mask for exposure is disclosed in which an absorber that absorbs X-rays or vacuum ultraviolet rays is provided in a pattern. FIG. 6 is a schematic cross-sectional view showing an example of such a conventional exposure reflective mask blank and exposure reflective mask. In the reflective mask blank for exposure shown in FIG. 6A, a multilayer reflective film 101 having a multilayer structure is formed on a substrate 100, and an etching stopper layer 102 is formed on the multilayer reflective film 101. An absorption layer 103 is formed on the etching stopper layer 102. A pattern 103a is formed on the absorption layer 103 of the reflective mask blank for exposure, and the unnecessary etching stopper layer 102 on the multilayer reflective film 101 is removed along the absorption layer pattern 103a, thereby exposing for exposure as shown in FIG. A reflective mask is manufactured. The exposure light such as soft X-rays incident on the exposure reflective mask is reflected at the portion where the multilayer reflective film 101 is exposed, and is absorbed without being reflected at the portion where the pattern 103a of the absorption layer is formed. As a result, a pattern (light image) can be formed with a high contrast between the reflection portion and the absorption portion.

Japanese Patent Publication No. 7-27198 JP-A-8-213303 JP 2006-39223 A

  However, in the reflective mask for exposure in which the multilayer reflective film 101 or the like is formed on the substrate 100 as described above, it is necessary to increase the film density of each layer of the multilayer reflective film 101 in order to obtain a high reflectance. Then, the multilayer reflective film 101 inevitably has a high compressive stress. Due to this high compressive stress, the substrate 100 is greatly warped (deformed) on the convex surface as shown in FIG. As a result, the surface of the multilayer reflective film 101 that is a reflective surface of the EUV light is also warped. For example, when a compressive stress of about 400 MPa is applied to a multilayer reflective film of about 0.3 μm thickness on a 6 inch square (152.4 mm × 152.4 mm), 6.35 mm thick quartz glass substrate, 142 mm × 142 mm In this area, warpage (deformation) of about 1000 nm occurs.

  Since the absorption layer 103 and the etching stopper layer 102 formed on the multilayer reflective film 101 are patterned, it is necessary to have a low stress close to zero. The flatness of the mask blank is mainly the film stress of the multilayer reflective film. Dominated by. A reflective mask for EUV light is generally fixed by a vacuum chuck during exposure. Therefore, even if the mask is deformed as shown in FIG. 7, it is possible to correct the mask flatness to some extent by the vacuum chuck, but the flatness of the mask surface (pattern forming surface) can be completely guaranteed. Do not mean. Deformation (warpage) of the mask occurs due to distortion of the substrate itself, film stress such as a multilayer reflective film formed on the substrate, and deformation of the mask substrate due to the vacuum chuck described above. The surface shape is extremely complex.

By the way, when pattern transfer onto a semiconductor substrate, which is a transfer target substrate, is performed using a reflective mask, there is a problem that if the surface shape of the mask surface is not flat, the position on the semiconductor substrate is shifted during exposure. . Referring to FIG. 5, since normal EUV light is exposed from an oblique (angle θ) direction with respect to the mask, if there is an unevenness of the distance d on the mask surface, the reflected light from the mask is reduced by the reduction optical system. When the Si wafer surface, which is a semiconductor substrate, is exposed to 1 / M, the positional deviation of ΔP = (d × tan θ) / M occurs on the Si wafer surface. Such misregistration is a problem because it causes a decrease in overlay accuracy during EUV light exposure. For example, in 45 nm half pitch (DRAM), it is required that the positional deviation due to the flatness of the mask be 1.3 nm or less, and the flatness (flatness) of the mask substrate is 148 mm × 148 mm. In the region, 50 nm or less is required.
However, since flatness of 50 nm or less in a 142 mm × 142 mm region is difficult to produce with good reproducibility and low cost by the substrate polishing technique, it is difficult to satisfy the required value for misalignment during exposure. It was.

In the above-mentioned patent document 3, the mask pattern on the mask is drawn in a predetermined position with the mask chucked by the chuck means of the exposure apparatus based on the flatness change amount data of the mask blank substrate. A method for manufacturing an exposure mask is disclosed in which position correction data of a pattern to be generated is generated and drawing is performed while correcting the drawing position of the pattern, thereby preventing misalignment of the mask pattern.
However, even if the pattern drawing position is corrected based only on the mask blank flatness change amount data, the cause of the misalignment is that the mask surface, the surface shape such as the surface shape and flatness of the back surface, the substrate of the mask substrate Due to the thickness variation and the complicated surface state such as the surface shape and flatness of the mask stage of the exposure apparatus, the method disclosed in Patent Document 3 may not be able to correct with high accuracy. As described above, the reflective mask for EUV light exposure, in particular, requires extremely strict pattern position accuracy. Therefore, surface shape information such as the surface shape and flatness of the mask substrate and the mask blank serving as the mask original plate is used. If it is not obtained accurately and correction with extremely high accuracy is not performed, it is not possible to prevent the displacement of the pattern on the semiconductor substrate due to the flatness of the mask.

  The present invention has been made in view of the above-described conventional problems, and a reflective mask blank and a reflective mask that can prevent positional deviation during pattern transfer due to the flatness of the pattern forming surface of the mask. It aims at providing the manufacturing method of. In addition, a reflective mask blank and a reflection that can prevent misalignment during pattern transfer using an exposure apparatus even if the flatness specification of the substrate in which the flatness of the substrate in the current 142 mm × 142 mm region is 50 nm or less is relaxed. An object of the present invention is to provide a mold mask manufacturing method.

In order to solve the above problems, the present invention has the following configuration.
(Configuration 1) A step of preparing a substrate whose main surface is precisely polished, a multilayer reflective film that reflects exposure light, and an absorber film for a transfer pattern that absorbs exposure light are formed on the substrate. A step of obtaining a reflective mask blank, a step of obtaining substrate surface form information and / or mask blank surface form information of both main surfaces in a predetermined region of the substrate and / or the reflective mask blank, The reflection based on the substrate surface form information and / or the mask blank surface form information and the mask stage surface shape information of a mask stage on which a reflective mask produced by the reflective mask blank of an exposure apparatus is set. Substrate surface morphology of a transfer pattern forming surface in which a reflective mask manufactured using a mold mask blank is set on the mask stage And / or manufacturing process of the reflective mask blank and having a step of obtaining a mask blank surface morphology information.

  According to Configuration 1, substrate surface form information and / or mask blank surface form information in a predetermined region on both the front and back main surfaces of the substrate and / or mask blank is obtained, and the obtained substrate surface form information and / or mask blank is obtained. Based on the surface form information and the mask stage surface shape information of the exposure apparatus, the substrate surface form information and / or the mask of the transfer pattern forming surface in which the reflective mask manufactured using the reflective mask blank is set on the mask stage. In order to obtain blank surface form information, based on the substrate surface form information and / or mask blank surface form information of the mask pattern forming surface obtained in this way, it is caused by the mask blank surface form of the transfer pattern forming surface before and after setting on the mask stage. The amount of pattern misregistration on the transferred substrate can be calculated with high accuracy. In the step of drawing a transfer pattern for patterning the blank absorber film, the transfer pattern is drawn by correcting the amount of displacement, or by using an exposure apparatus (pattern transfer device) using the obtained reflective mask. A semiconductor device in which a fine pattern with high positional accuracy is formed is obtained by correcting and exposing the amount of positional deviation when transferring a pattern onto a semiconductor substrate.

(Structure 2) The method of manufacturing a reflective mask blank according to Structure 1, wherein the surface form information includes at least data of surface flatness and surface shape.
As described in Structure 2, the surface shape information includes at least surface flatness and surface shape data, so that a complicated surface state of a transfer pattern forming surface when a mask blank is set on a mask stage of an exposure apparatus. Can be predicted with high accuracy.

(Structure 3) Reflection having a step of preparing a substrate whose main surface is precisely polished, a multilayer reflection film that reflects at least exposure light, and an absorber film for transfer pattern that absorbs exposure light on the substrate Preparing a mold mask blank, preparing substrate surface form information and / or mask blank surface form information in a predetermined region of both main surfaces of the substrate and / or the reflective mask blank, and providing the substrate surface form information and Fabricated using the reflective mask blank based on the mask blank surface form information and the mask stage surface form information of the mask stage on which the reflective mask produced by the reflective mask blank of the exposure apparatus is set Substrate surface form information and / or mask blank of a transfer pattern forming surface on which a reflection type mask is set on the mask stage The step of preparing the surface form information and the pattern position deviation amount on the transfer substrate due to the substrate surface form information and / or the mask blank surface form change of the transfer pattern forming surface before and after setting on the mask stage. A step of calculating, a step of preparing position correction data of a pattern drawn on the reflective mask blank to correct the positional shift amount based on a calculation result of the positional shift amount, and the reflective mask blank And a step of drawing a transfer pattern for patterning the absorber film, wherein the transfer pattern is drawn according to the position correction data.

  According to Configuration 3, substrate surface form information and / or mask blank surface form information in a predetermined region on both the front and back main surfaces of the substrate and / or mask blank is obtained, and the obtained substrate surface form information and / or mask blank is obtained. Based on the surface form information and the mask stage surface shape information of the exposure apparatus, the substrate surface form information and / or the mask of the transfer pattern forming surface in which the reflective mask manufactured using the reflective mask blank is set on the mask stage. In order to obtain blank surface form information, based on the substrate surface form information and / or mask blank surface form information of the mask pattern forming surface obtained in this way, it is caused by the mask blank surface form of the transfer pattern forming surface before and after setting on the mask stage. The pattern displacement amount on the transferred substrate can be calculated with high accuracy, and the mask In the step of drawing a transfer pattern for patterning the absorber film ranks by drawing a transfer pattern by correcting the positional deviation amount, the semiconductor device can be obtained a fine pattern with high positional accuracy are formed. Further, in the process of drawing the transfer pattern for patterning the absorber film of the mask blank in this way, the amount of misalignment is corrected and the transfer pattern is drawn to make a reflective mask, so that the current 142 mm × 142 mm is obtained. Reflection that can relax the flatness specification of the substrate where the flatness of the substrate in the region is 50 nm or less, and can prevent misalignment during pattern transfer using the exposure apparatus even if the flatness specification of the substrate is relaxed As a mold mask, a semiconductor device in which a fine pattern with high positional accuracy is formed can be obtained.

(Structure 4) The method for manufacturing a reflective mask according to Structure 3, wherein the surface form information includes at least data of surface flatness and surface shape.
As described in Structure 4, the surface shape information includes at least surface flatness and surface shape data, so that a complex surface state of a mask pattern forming surface when a mask blank is set on a mask stage of an exposure apparatus. Can be predicted with high accuracy.

(Structure 5) A step of preparing a reflective mask obtained by the method of manufacturing a reflective mask according to Structure 3 or 4, and pattern transfer of the transfer pattern in the reflective mask onto a transfer substrate using an exposure apparatus And a method of manufacturing a semiconductor device.
When a pattern is transferred onto a semiconductor substrate by an exposure apparatus (pattern transfer apparatus) using the reflective mask obtained in Configuration 3 or 4, exposure is performed without correcting the amount of misalignment, so that high positional accuracy can be achieved. A semiconductor device in which a pattern is formed is obtained.
(Configuration 6) Patterning the absorber film from a reflective mask blank in which a multilayer reflective film that reflects at least exposure light and an absorber film for a transfer pattern that absorbs exposure light are formed on a substrate. A step of preparing a reflection type mask obtained by the above, a substrate surface form information in a predetermined region of at least one of the substrate, the reflection type mask blank, and the reflection type mask, and the mask blank surface Transfer pattern formation in which the reflective mask is set on the mask stage based on any one of the surface form information of the form information and the mask surface form information and the surface form information of the mask stage on which the reflective mask of the exposure apparatus is set And a mask surface shape change of the transfer pattern forming surface before and after being set on the mask stage. A step of calculating a pattern positional deviation amount on the transferred substrate, and a step of correcting and exposing the positional deviation amount when the transfer pattern is transferred onto the transferred substrate by an exposure device; A method for manufacturing a semiconductor device, comprising:

  According to the configuration 6, any one of the surface form information of the substrate surface form information, the mask blank surface form information, and the mask surface form information in a predetermined region of both main surfaces of at least one of the substrate, the mask blank, and the mask. Before and after setting on the mask stage to obtain the mask surface form information of the transfer pattern forming surface with the reflective mask set on the mask stage based on the surface shape information of the mask stage on which the reflective mask of the exposure apparatus is set Since the amount of pattern position deviation on the transfer substrate due to the change in the mask surface shape on the transfer pattern forming surface can be calculated with high accuracy, a pattern on the transfer substrate using an exposure device (pattern transfer device) using a reflective mask A semiconductor in which a fine pattern with high positional accuracy is formed by correcting and exposing the misalignment amount at the time of transfer Location can be obtained.

  According to the present invention, a reflective mask blank and a reflection that can prevent a positional shift at the time of pattern transfer due to the flatness of the pattern forming surface of the mask and obtain a semiconductor device in which a fine pattern with high positional accuracy is formed. A method for manufacturing a mold mask can be provided. Further, according to the present invention, even when the flatness specification of the substrate where the flatness of the substrate in the current 142 mm × 142 mm region is 50 nm or less is relaxed, it is possible to prevent misalignment during pattern transfer using the exposure apparatus. A reflective mask blank and a method of manufacturing a reflective mask can be provided.

FIG. 1 is a flowchart showing a method for manufacturing a reflective mask blank and a reflective mask according to the present invention. FIG. 3 is a sectional view showing the manufacturing process of the reflective mask.
That is, according to FIG. 1, the manufacturing method of a reflective mask blank and a reflective mask according to the present invention includes a substrate preparation step (S1), a film forming step (mask blank preparation) (S2), and (before exposure apparatus setting). Surface shape information acquisition step (S3), surface shape information acquisition step (S4) at the time of exposure apparatus setting, position shift amount calculation step (S5) at the time of pattern transfer, mask pattern drawing step (S6), reflection type mask It consists of each process of a manufacturing process (S7).
Hereinafter, each step will be described step by step with reference to FIG. 3 as appropriate.

(1) Substrate preparation step (S1)
The substrate 1 (see FIG. 3A) is preferably a glass having a low thermal expansion coefficient, excellent in smoothness, flatness, and resistance to a cleaning liquid used for cleaning a mask, etc., and having a low thermal expansion coefficient. For example, SiO ₂ —TiO ₂ glass or the like is used, but the present invention is not limited thereto. Crystallized glass on which β quartz solid solution is deposited, quartz glass, silicon, or a metal substrate can also be used. As an example of the metal substrate, an Invar alloy (Fe—Ni alloy) or the like can be used. The substrate 1 preferably has a smooth surface of 0.2 nmRms or less and a flatness of 100 nm or less in order to obtain a high reflectance and transfer accuracy.

In the present invention, the unit Rms indicating the smoothness is the root mean square roughness and can be measured with an atomic force microscope (AFM). Specific measurement is performed within a range of, for example, 10 μm square, and it is preferable that the smoothness is uniformly provided within the effective area of the mask. Here, in the case of an EUV light exposure mask, the effective area of the mask may be considered to be, for example, a range of about 142 mm square as the effective area.
Further, the flatness described in the present invention is a value representing the warpage (deformation amount) of the surface represented by TIR (Total Indicated Reading), and is defined as follows. That is, the plane defined by the least square method based on the substrate surface 41 in FIG. 2 is the focal plane 42, and then the highest position A of the substrate surface 41 above the focal plane 42 with respect to the focal plane 42, and The absolute value of the height difference between the lowest position B of the substrate surface 41 below the focal plane 42 was defined as flatness. Therefore, the flatness is always a positive number. In the present invention, the measured value in an area of 142 × 142 mm is defined as flatness. For example, a measurement value within an area of 142 × 142 mm at the center of a 6-inch substrate.

(2) Film formation process (mask blank production) (S2)
On the substrate 1, a multilayer reflective film 2 that reflects exposure light, an intermediate layer 3 that mainly functions as an etching stopper, and an absorber layer 4 that absorbs exposure light are sequentially formed to form a reflective mask blank 10 ( 3A) is prepared.

As the multilayer reflective film 2, an alternating laminated film made of Mo and Si is frequently used. As a material capable of obtaining a high reflectance in a specific wavelength range, Ru / Si, Mo / Be, Mo compound / Si compound, An Si / Nb periodic multilayer film, an Si / Mo / Ru periodic multilayer film, an Si / Mo / Ru / Mo periodic multilayer film, an Si / Ru / Mo / Ru periodic multilayer film, or the like may be used. However, the optimum film thickness varies depending on the material. In the case of a multilayer film composed of Mo and Si, a Si film is first formed in an Ar gas atmosphere using a Si target by a DC magnetron sputtering method, and then a Mo film is used in an Ar gas atmosphere using a Mo target. Is formed as a single cycle, and 30 to 60 cycles, preferably 40 cycles, are stacked, and finally a Si film is formed.
By this step, a substrate with a multilayer reflective film is obtained.

The intermediate layer (also referred to as a buffer layer) 3 has a function as an etching stopper for protecting the multilayer reflective film 2 when the upper absorber layer 4 is patterned by etching. Although CrN is frequently used as the material of the intermediate layer 3, depending on the conditions for etching the absorber layer 4, SiO ₂ or the like may be used as a material having high etching resistance. When CrN is used, it is preferable to form a CrN film on the multilayer reflective film 2 using a Cr target by a DC magnetron sputtering method in a mixed gas atmosphere of Ar and nitrogen.

As a material for the absorber layer 4 of exposure light such as EUV light, a material containing Ta as a main component, a material containing Ta as a main component and containing at least B, an amorphous structure material containing Ta as a main component, and Ta as a main component And an amorphous structure material containing at least B (for example, an amorphous structure material containing about 25% of B represented by Ta ₄ B), a material containing Ta, B, and N (for example, B containing Ta as a main component and B Material having an amorphous structure containing about 15% of N and about 10% of N). Furthermore, in order to reduce the reflectivity at the wavelength of inspection light (usually DUV light) used for mask inspection, it is common to increase the contrast of mask inspection by forming an oxide layer on the absorber layer. is there. For example, a material containing Cr as a main component and containing at least one component selected from N, O, and C (for example, a material in which O and C are added to CrN and CrN) is preferable. However, the present invention is not limited to this, and TaSi, TaSiN, TaGe, TaGeN, WN, Cr, TiN, and the like can be used.
In an example in which a TaB compound thin film is used as the material of the absorber layer 4, a TaB film is first formed in a Ar gas atmosphere using a TaB target by a DC magnetron sputtering method, and subsequently in an atmosphere of Ar and oxygen gas, It is preferable to form a TaBO film.

In addition, as a structure of a reflective mask blank, what was shown to Fig.3 (a) is an example to the last, and is not restricted to this. For example, the intermediate layer 3 may be omitted. Further, a stress correction film may be provided in order to correct the warp (deformation) of the substrate 1 formed by the stress of the multilayer reflective film 2 and reduce the stress of the mask blank. For example, even if the multilayer reflective film 2 having a high stress is formed, it is possible to provide a stress correction film that corrects the warp (deformation) of the substrate 1 and controls the stress to be deformed in the pulling direction. As the stress correction film, a strong compressive stress can be easily produced and a smooth film is required. Therefore, for example, an amorphous material mainly containing Ta (TaB or the like), a material mainly containing Si, A material containing Cr is preferred.
The reflective mask blank 10 is obtained through the above steps.

(3) Surface form information acquisition step (before exposure apparatus setting) (S3)
Next, the surface form information in the predetermined area | region of the both main surfaces of the reflection type mask blank 10 obtained above is acquired. As means for acquiring the surface form information of the main surface, it can be obtained by using a flatness measuring device (not shown) using light interference. Using such a flatness measuring apparatus, it is desirable to increase a plurality of measurement points on the main surface of the mask blank (in order to increase accuracy, for example, in the case of a substrate having a size of 152 mm × 152 mm, the measurement points are at least Height information from the reference plane (the focal plane calculated by the least square method and the focal plane 42 in FIG. 2) at the 256 × 256 points) is acquired as the surface shape information of the main surface. Can do. Further, the flatness value of the main surface according to the definition shown in FIG. 2 can be obtained from the acquired height information. Furthermore, the mask blank thickness variation (TTV: Total ThicknessValuation) can be obtained from the surface morphology information of both the main surfaces, and the exposure device set in the next step (S4) using the mask blank thickness variation surface morphology information. It is also possible to acquire surface shape information at the time. It is preferable that the surface form information on both the front and back main surfaces of the mask blank includes at least the height information (surface shape information) and the flatness value as described above.

  The predetermined area for acquiring the surface shape information may be set as appropriate depending on the size of the substrate, the measurement accuracy of the flatness measuring apparatus, the area where the mask stage of the exposure apparatus is in contact with the main surface of the substrate, etc. It is desirable to acquire surface shape information over the entire surface of the substrate, and it is desirable to set at least a region where the mask stage of the exposure apparatus is in contact with the main surface of the substrate. For example, when the substrate size is 6 inches square and the area set by the mask stage (for example, electrostatic chuck) of the exposure apparatus is 142 mm × 142 mm, the predetermined area for acquiring the surface form information is It shall be 142 mm x 142 mm.

(4) Surface form information acquisition process at the time of exposure apparatus setting (S4)
Next, the mask blank is obtained based on the surface form information in a predetermined region of both main surfaces of the front and back surfaces of the reflective mask blank 10 obtained in the step (3) and the surface form information of the mask stage in the exposure apparatus. Surface shape information on the transfer pattern forming surface of the mask blank 10 when a reflective mask manufactured using the mask 10 is set on the mask stage by a vacuum chuck is acquired. The surface pattern information on the transfer pattern forming surface when the reflective mask manufactured using the mask blank 10 is set on the mask stage by a vacuum chuck is a predetermined area on both main surfaces on the front and back of the reflective mask blank 10. Can be obtained by simulation based on the surface shape information inside and the surface shape information of the mask stage in the exposure apparatus. As a simulation method, surface shape information in a predetermined region on both the front and back main surfaces of the reflective mask blank 10 (specifically, information on the thickness variation of the mask blank calculated from the surface shape information on both the front and back main surfaces) ) And the surface shape information of the mask stage in the exposure apparatus, the thickness of the mask blank when the back surface of the reflective mask is set to be in accordance with the vacuum chuck surface and the vacuum chuck surface is the reference surface From the variation, surface shape information of the transfer pattern forming surface can be obtained.

  In this case, as the surface form information of the transfer pattern forming surface of the mask blank in this case, at least the height information (surface shape information) acquired as described above and the flatness value calculated from this height information are used. It is preferable to include.

(5) Position shift amount calculation step during pattern transfer (S5)
Next, based on the surface pattern information of the transfer pattern forming surface obtained in the step (4), the surface pattern of the transfer pattern forming surface when the pattern is transferred onto the semiconductor substrate that is the transfer substrate by the exposure apparatus. The amount of misregistration caused by is calculated. Since the amount of misalignment caused by the surface form of the transfer pattern forming surface when the pattern is transferred onto the semiconductor substrate by the exposure apparatus has the relationship as shown in FIG. 5, the transfer obtained by the process (4) above. By using the surface form information of the pattern formation surface, it is possible to calculate the amount of displacement due to the surface form of the transfer pattern formation surface when the pattern is transferred onto the semiconductor substrate. When calculating the amount of positional deviation, the surface form change obtained from the surface form information of the transfer pattern forming surface before being set in the exposure apparatus and the surface form information of the transfer pattern forming surface when the exposure apparatus is set is calculated. It can be set as d in FIG.

(6) Mask pattern drawing step (S6)
(A) Resist application process. A reflective mask can be manufactured by patterning the absorber layer 4 of the obtained reflective mask blank 10 to form a transfer pattern. First, for example, an electron beam drawing resist is applied on the obtained reflective mask blank 10 and baked.
(B) Drawing process. Pattern drawing is performed on the reflective mask blank coated with the resist using an EB drawing machine. In the present invention, in this pattern drawing step, the transfer pattern is drawn while correcting the positional deviation amount calculated in the step (5). After drawing, the resist is developed to form a resist pattern 5a (see FIG. 3B).

(7) Reflective mask manufacturing process (S7)
Next, using the resist pattern 5a as a mask, the absorber layer 4 is dry-etched, for example, to form the absorber layer pattern 4a (see FIG. 3B). Then, the resist pattern remaining on the absorber layer pattern 4a is removed with, for example, hot concentrated sulfuric acid (see FIG. 3C). Further, the lower intermediate layer 3 is removed by, for example, dry etching along the absorber layer pattern 4a. Through this step, the reflective mask 20 is obtained (see FIG. 3D).

  The obtained reflection type mask was obtained by the present invention because the transfer pattern was formed by correcting (expected) the amount of misalignment caused during pattern transfer due to the surface form of the transfer pattern forming surface. By performing pattern transfer onto a semiconductor substrate using an exposure apparatus using a reflective mask, a semiconductor device on which a fine pattern with high positional accuracy is formed can be obtained.

Further, in the above embodiment, the case where the surface shape information of the mask blank is acquired has been described. In the substrate preparation step (S1), the surface shape information of the substrate in a predetermined region of both main surfaces of the substrate is acquired. Then, based on the surface form information in a predetermined region of both main surfaces on the front and back of the substrate and the surface form information of the mask stage in the exposure apparatus, the mask blank 10 and further the mask blank 10 are used using the substrate. You may acquire the surface form information of the transfer pattern formation surface of a board | substrate when the reflection type mask produced is set to the said mask stage with a vacuum chuck. In that case, a stress correction film is formed to prevent warping of the substrate due to the film stress of the multilayer reflective film or absorber film formed on the main surface of the substrate, and the surface shape information of the substrate and the mask blank It is possible to match the surface morphology information. In addition, when the substrate does not warp due to the film stress of the multilayer reflective film or the absorber film formed on the main surface of the substrate, the surface shape information of the substrate and the surface shape information of the mask blank match. Further, the warpage of the substrate due to the film stress of the multilayer reflective film or absorber film formed on the main surface of the substrate may be predicted by simulation or the like, and the surface shape information of the mask blank may be used. And when a reflective mask manufactured using the mask blank 10 is set on the mask stage by a vacuum chuck based on the surface form information of the obtained mask blank and the surface form information of the mask stage in the exposure apparatus The surface pattern information on the transfer pattern forming surface of the mask blank may be acquired.
In the above embodiment, in the step of drawing a transfer pattern for patterning the absorber film of the mask blank, the case where the calculated misregistration amount is corrected and the transfer pattern is drawn has been described. When the pattern is transferred onto the semiconductor substrate by the exposure apparatus (pattern transfer apparatus) using the obtained reflective mask (without correcting the positional shift amount at the time of drawing), the exposure is performed by correcting the positional shift amount. It may be.

Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples.
(Example 1)
As the substrate 1, a low expansion SiO ₂ —TiO ₂ glass substrate having an outer diameter of 6 inches square and a thickness of 6.35 mm was used. Further, the substrate 1 has a smooth surface of 0.2 nmRms or less and a flatness of 40 nm (132 mm × 132 mm region) by mechanical polishing.

  Next, Mo and Si were laminated on the substrate 1 as the multilayer reflective film 2. By DC magnetron sputtering, an Si film is first formed with an Ar gas of 0.1 Pa using a Si target, and then a Mo film is formed with an Ar gas pressure of 0.1 Pa. A film was formed, and this was defined as one period. After 40 periods were laminated, a Si film was finally formed to a thickness of 11 nm. Here, the stress of the multilayer reflective film 2 was −500 MPa.

  Next, an intermediate layer (etching stopper layer) 3 composed of a CrN film is formed on the multilayer reflective film 2 by using a Cr target and using a mixed gas obtained by adding 20% nitrogen to Ar gas as a sputtering gas. A film having a thickness of 10 nm was formed by a DC magnetron sputtering method. Here, the stress of the intermediate layer 3 was 50 MPa or less.

Finally, a film containing Ta and B (provided that Ta: B = 75: 15 (atomic ratio)) is formed as DC as an EUV light absorber layer 4 on the intermediate layer 3 composed of the CrN film. A 66 nm thick film was formed by magnetron sputtering, and then a TaBO film was formed by DC magnetron sputtering using a mixed gas of Ar and oxygen using TaB as a target. The stress of the EUV light absorber layer 4 was set to 50 MPa or less by controlling the sputtering conditions.
A reflective mask blank was obtained as described above.

  For both main surfaces on the front and back of the obtained reflective mask blank, surface shape information (least square method) in a predetermined area 142 mm × 142 mm using a flatness measuring device (Troppel Corporation: UltraFlat200M) using light interference. (Height information from the focal plane calculated by the above) was acquired and stored in a computer. Based on this surface form information, the surface shape of the main surface (transfer pattern forming surface) on the front side of the mask blank was a convex shape, and the flatness at 142 mm × 142 mm was 150 nm. The surface shape of the main surface on the back side of the mask blank was a concave shape, and the flatness at 142 mm × 142 mm was 130 nm.

Next, based on the acquired surface form information of the mask blank and the surface shape information of the mask stage in the exposure apparatus, the transfer pattern forming surface when the reflective mask obtained by the mask blank is set on the mask stage Surface shape information (height information and flatness data from the focal plane) was obtained by simulation.
Next, based on the obtained surface pattern information on the transfer pattern forming surface, the amount of positional deviation due to the surface pattern of the transfer pattern forming surface when the pattern was transferred onto the semiconductor substrate was calculated.

Next, using this reflective mask blank, a reflective mask having a design rule of 32 nm half pitch (DRAM) was produced by the following method.
First, an EB resist was applied on the reflective mask blank and dried to form an EB resist film.
Next, in the step of drawing the transfer pattern, the transfer pattern was drawn by correcting the positional deviation amount obtained above. After drawing, a resist pattern was formed by development.
Next, using this resist pattern as a mask, the absorber layer 4 made of a laminate of TaBO and TaB was dry-etched using chlorine to form an absorber layer pattern. Thereafter, the resist pattern remaining on the absorber layer pattern is removed, and the intermediate layer 3 composed of the underlying CrN film is removed by etching using a mixed gas of chlorine and oxygen using the absorber layer pattern as a mask. Then, a reflective mask was produced.

  Using the produced reflective mask, pattern transfer onto the semiconductor substrate was performed by an exposure apparatus (pattern transfer apparatus) shown in FIG. As shown in FIG. 4, EUV light (soft X-rays) obtained from a laser plasma X-ray source 31 is incident on the reflective mask 20, and the light reflected here passes through a reduction optical system 32, for example, a Si wafer substrate 33. Transfer on top.

An X-ray reflecting mirror can be used as the reduction optical system 32. The pattern reflected by the reflective mask 20 by the reduction optical system is usually reduced to about ¼. For example, the transfer of the pattern to the Si wafer substrate 33 can be performed by exposing the pattern to a resist film formed on the Si substrate 3 and developing the pattern. When a wavelength band of 13 to 14 nm is used as the exposure wavelength, transfer is usually performed so that the optical path is in a vacuum.
As a result of pattern transfer onto the semiconductor substrate using the reflective mask obtained in this example, it was confirmed that a fine pattern could be formed with high positional accuracy.

(Example 2)
In this example, instead of drawing the transfer pattern by correcting the calculated misregistration amount in the step of drawing the transfer pattern for patterning the absorber film of the mask blank in Example 1, the reflection obtained in this example The second embodiment is different from the first embodiment in that exposure is performed by correcting the amount of displacement when a pattern is transferred onto a semiconductor substrate by an exposure apparatus (pattern transfer apparatus) using a mold mask.

  That is, a reflective mask blank was prepared in the same manner as in Example 1, and using the flatness measuring apparatus, surface shape information in a predetermined region of both main surfaces of the obtained mask blank was acquired, and this acquisition was performed. Based on the surface shape information and the surface shape information of the mask stage in the exposure apparatus, the surface shape information of the transfer pattern forming surface when the reflective mask obtained by the mask blank was set on the mask stage was obtained by simulation. Then, based on the obtained surface pattern information on the transfer pattern forming surface, the amount of positional deviation due to the surface pattern on the transfer pattern forming surface when the pattern was transferred onto the semiconductor substrate was calculated.

And the reflective mask was produced from the said reflective mask blank similarly to Example 1 (however, the correction | amendment of the said positional offset was not performed in the pattern drawing process).
Using the prepared reflective mask, the exposure device (pattern transfer device) shown in FIG. 4 monitors the surface shape information (flatness: flatness) of the reflective mask, and the flatness error is actively controlled by the mask stage. The pattern was transferred onto the semiconductor substrate by exposing the semiconductor substrate so that the pattern was not misaligned. Also in this example, as a result of pattern transfer onto the semiconductor substrate, it was confirmed that a fine pattern could be formed with high positional accuracy.

It is a flowchart which shows the manufacturing method of the reflective mask blank and reflective mask which concern on this invention. It is a conceptual diagram for demonstrating the definition of flatness TIR. It is sectional drawing which shows an example of the manufacturing process of the reflective mask which concerns on this invention. It is a block diagram which shows the structure of exposure apparatus (pattern transfer apparatus). It is a conceptual diagram for demonstrating the position shift resulting from the flatness of a mask. It is sectional drawing of the conventional reflective mask blank and a reflective mask. It is sectional drawing of the conventional reflective mask.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Multilayer reflective film 3 Intermediate layer 4 Absorber layer 10 Reflective mask blank 20 Reflective mask 50 Exposure apparatus (pattern transfer apparatus)

Claims (6)

Preparing a substrate whose main surface is precision polished;
Forming a reflective mask blank by forming at least a multilayer reflective film that reflects exposure light and an absorber film for a transfer pattern that absorbs exposure light on the substrate;
Obtaining substrate surface form information and / or mask blank surface form information of both main surfaces in a predetermined region of the substrate and / or the reflective mask blank;
The reflection based on the substrate surface form information and / or the mask blank surface form information and the mask stage surface shape information of a mask stage on which a reflective mask produced by the reflective mask blank of an exposure apparatus is set. A step of obtaining substrate surface form information and / or mask blank surface form information of a transfer pattern forming surface in which a reflective mask produced using a mold mask blank is set on the mask stage;
A method for producing a reflective mask blank, comprising:   The method of manufacturing a reflective mask blank according to claim 1, wherein the surface form information includes at least data of surface flatness and surface shape. Preparing a substrate whose main surface is precision polished;
Preparing a reflective mask blank having at least a multilayer reflective film that reflects exposure light and an absorber film for a transfer pattern that absorbs exposure light on the substrate;
Preparing substrate surface form information and / or mask blank surface form information in a predetermined region of both main surfaces of the substrate and / or the reflective mask blank, and the substrate surface form information and / or mask blank surface form information; Based on the mask stage surface form information of the mask stage on which the reflective mask produced by the reflective mask blank of the exposure apparatus is set, the reflective mask produced using the reflective mask blank is changed to the mask stage. Preparing the substrate surface form information and / or mask blank surface form information of the transfer pattern forming surface set in
Calculating a pattern positional deviation amount on the transfer substrate due to the substrate surface form information and / or the mask blank surface form change of the transfer pattern forming surface before and after setting on the mask stage;
Preparing position correction data of a pattern drawn on the reflective mask blank to correct the position shift amount based on the calculation result of the position shift amount;
A method of drawing a transfer pattern for patterning the absorber film of the reflective mask blank, the method comprising: drawing a transfer pattern according to the position correction data. .   4. The method of manufacturing a reflective mask according to claim 3, wherein the surface form information includes at least data of surface flatness and surface shape. Preparing a reflective mask obtained by the reflective mask manufacturing method according to claim 3 or 4,
And a step of pattern transfer of the transfer pattern in the reflective mask onto a transfer substrate using an exposure apparatus. It was obtained by patterning the absorber film from a reflective mask blank in which a multilayer reflective film that reflects at least exposure light and an absorber film for a transfer pattern that absorbs exposure light were formed on a substrate. Preparing a reflective mask; and
Surface form of any one of substrate surface form information, mask blank surface form information, and mask surface form information in a predetermined region of at least any one of the substrate, the reflective mask blank, and the reflective mask Obtaining mask surface form information of a transfer pattern forming surface in which the reflective mask is set on the mask stage based on the information and the surface form information of the mask stage on which the reflective mask of the exposure apparatus is set;
A step of calculating a pattern positional deviation amount on the transfer substrate due to a mask surface form change of the transfer pattern forming surface before and after being set on the mask stage;
And a step of performing exposure by correcting the amount of misalignment when the transfer pattern is transferred onto the transfer substrate by an exposure apparatus.

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