JP6287045B2 - Reflective mask and method of manufacturing the same - Google Patents

Description

  The present invention relates to a reflective mask and a manufacturing method thereof, and more particularly to a reflective mask used in a semiconductor manufacturing apparatus using an EUV lithography that uses EUV (Extreme Ultra Violet) as a light source and a manufacturing method thereof.

<Description of EUV lithography>
In recent years, with the miniaturization of semiconductor devices, EUV lithography using EUV having a wavelength of around 13.5 nm as a light source has been proposed. Since EUV lithography has a short light source wavelength and very high light absorption, it needs to be performed in a vacuum. In the EUV wavelength region, the refractive index of most substances is slightly smaller than 1.

  For this reason, in EUV lithography, a transmissive refractive optical system that has been conventionally used cannot be used, and becomes a reflective optical system. Therefore, a photomask used as an original (hereinafter referred to as a mask) must be a reflective mask because a conventional transmission mask cannot be used.

<Description of EUV mask and blank structure>
FIG. 3 shows the structure and manufacturing process of a conventional reflective mask. The reflective mask blank that is the source of the reflective mask is a multilayer reflection on the substrate 1 that exhibits a high reflectance with respect to the exposure light source wavelength. A film 2 and a light absorption film 6 that absorbs the exposure light source wavelength are sequentially formed. Further, a back surface conductive film 3 for an electrostatic chuck in the exposure machine is formed on the back surface of the substrate.

  There is also an EUV mask having a structure having a protective film 5 for protecting the reflective film between the multilayer reflective film and the light absorbing film. When processing from a reflective mask blank to a reflective mask, the light absorbing film 6 is partially removed by EB lithography and etching technology to form a circuit pattern composed of a light absorbing portion and a reflecting portion. The light image reflected by the reflection type mask manufactured in this way is transferred onto the semiconductor substrate through the reflection optical system (Non-Patent Document 1).

<Description of multiple exposure of adjacent chips>
On the other hand, when a transfer circuit pattern is formed on a semiconductor substrate using a reflective mask, chips having a plurality of circuit patterns are formed on one semiconductor substrate. There may be a region where the outer periphery of the chip overlaps between adjacent chips. This is because the chips are arranged at a high density in order to improve productivity to increase the number of chips that can be taken per wafer. In this case, this region is exposed (multiple exposure) a plurality of times (up to four times).

  The chip outer peripheral portion of this transfer pattern is also the outer peripheral portion on the mask, and is usually the absorption layer portion. However, since the reflectance of EUV light on the absorption layer is about 0.5 to 2%, there is a problem that the outer periphery of the chip is exposed by multiple exposure. For this reason, the necessity has arisen for the area | region (henceforth a light-shielding frame) where the chip | tip outer peripheral part on a mask has a higher light-shielding property of EUV light than a normal absorption layer.

<Necessity of microfabrication>
Further, high integration of a large scale integrated circuit requires a thinning technique for a wiring pattern constituting the circuit as an essential element. The reason why pattern miniaturization of large-scale integrated circuits is accelerated is because of its high-speed operation and low power consumption, and the most effective means is that the pattern is miniaturized. For this reason, it is necessary to form a finer pattern on the mask substrate for the purpose of realizing a mask having the above-described thinned wiring pattern.

  In order to form a mask pattern, usually, as shown in FIG. 3, a resist 4 is formed on a mask blank provided with a light absorbing film 6 on a multilayer reflective film 2, and this resist is irradiated with an electron beam. The pattern is drawn and the resist is developed to obtain a resist pattern. Then, by patterning this resist pattern as an etching mask for the light absorption film 6, a mask pattern is obtained. Therefore, in order to obtain a fine mask pattern, it is necessary to make the resist pattern fine.

  If the resist pattern is miniaturized, the aspect ratio (ratio of resist film thickness to pattern width) of the resist that functions as an etching mask for the light absorption film 6 is increased. In general, when the aspect ratio of the resist pattern is increased, a part of the resist pattern may fall down or peel off, resulting in pattern omission.

  In addition, a mask pattern patterned by using a fine resist pattern created by such a method as an etching mask may also be peeled off in a cleaning process, for example, in a foreign matter removal process such as megasonic cleaning, and the quality of the mask is reduced. To do. For this reason, in order to form a higher-definition mask pattern, it is necessary to change the structure of the mask, and there is an examination example of a structure different from a general reflective mask. (Patent Document 1).

  For example, Patent Document 1 includes a single crystal (Si) reflective substrate 10 having a high reflectance with respect to charged particles and a (Cu) mask pattern having a reflectance lower than that of the substrate 1, as shown in FIG. In order to obtain a reflective mask free from shadowing due to the thickness of the light absorption film, a structure in which the surface of the mask pattern is flush with the surface of the substrate 1 has been reported.

  With this structure, there is no shadowing, and the peeling of the mask pattern in the foreign matter removal process by megasonic cleaning or the like is reduced. However, there is no protective film on the surface of the substrate 1, and the mask pattern is formed and exposed for a long time in an exposure apparatus. When used, there is a problem that the surface of the substrate 1 is damaged and affects the reflection characteristics. Further, since the multilayer reflective film 2 is not used as in Non-Patent Document 1, a high reflectance is obtained. Is difficult.

Japanese Unexamined Patent Publication No. 2000-232055

Resist process optimization technique, Information Technology Corporation, 2011, p129

  The present invention has been made in view of the above problems, and provides a reflective mask free from shadowing due to the thickness of a light absorption film without impairing the reflection characteristics of the reflective mask.

As a means for solving the above problems, the invention according to claim 1 is a reflective mask in which a mask pattern and a light shielding frame are provided on a reflective substrate in which a multilayer reflective film is provided on the substrate,
The reflective substrate is provided with a mask pattern and a light shielding frame-shaped digging,
A protective film is formed on the reflective substrate provided with the mask pattern and the light shielding frame-shaped digging, and a light absorption film is formed on the mask pattern and the light shielding frame-shaped digging,
The reflective mask is characterized in that the protective film and the light absorbing film in the mask pattern are flush with each other.

According to the second aspect of the present invention, the multilayer reflective layer is removed in a frame shape outside the region where the mask pattern is formed, and the light absorbing material is filled, and the light absorbing material is also formed on the surface of the multilayer reflective layer. By adopting at least one of whether the depth of the multilayer reflective layer in the frame-shaped part is deep, a light-shielding frame having a structure in which the thickness of the light absorption layer is thicker in the frame-shaped part than the mask pattern The reflective mask according to claim 1 , wherein the reflective mask is formed.

The invention according to claim 3 is a method of manufacturing a reflective mask in which a mask pattern and a light shielding frame are provided on a reflective substrate in which a multilayer reflective film is provided on the substrate,
Forming a mask pattern and a light-shielding frame-shaped dig by etching on the reflective substrate;
A step of laminating a protective film on a reflective substrate provided with the mask pattern and a light shielding frame-shaped digging; a step of forming a light absorption film on the mask pattern and the light shielding frame-shaped digging;
A method of manufacturing a reflective mask, comprising: an etching process in which a light absorption film of the mask pattern portion is flush with a surface of the protective film.

  According to another aspect of the present invention, there is provided a reflective mask characterized in that a mask pattern and a light shielding frame are provided on a reflective substrate, the surfaces of the reflective substrate and the mask pattern are flush, and a protective film is provided on the surface of the reflective substrate. It is possible to provide a reflective mask free from shadowing due to the thickness of the light absorption film without impairing the reflection characteristics of the reflective mask.

It is the cross-sectional conceptual diagram which showed the structure of the reflective mask of this invention, and the process for demonstrating a manufacturing method. It is the cross-sectional conceptual diagram which showed the structure of the reflective mask of this invention, and the process for demonstrating a manufacturing method. It is the conceptual cross-section which showed the structure of the conventional reflective mask, and the process drawing for demonstrating a manufacturing method. It is the conceptual cross-section which showed the structure of the conventional reflective mask, and the process drawing for demonstrating a manufacturing method.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual sectional view showing the structure of a reflective mask according to Embodiment 1 of the present invention, and an explanatory view showing a manufacturing process.

  In the reflective mask of the present invention, a mask substrate and a light shielding frame-shaped dig are provided on a reflective substrate provided with a multilayer reflective film on the substrate, and a light absorption film is provided on the mask pattern and the light-shielding frame-shaped digging. When the reflective substrate surface of the mask pattern part and the light absorbing film are formed and the protective film is formed on the multilayer reflective film, the protective film and the light absorbing film have the same structure. .

<Embodiment 1>
As shown in FIG. 1A, a multilayer reflective film 2 is laminated from one surface of a substrate 1, and a back conductive film 3 is formed on the other surface.

  As shown in FIG. 1B, a resist 4 is applied on the multilayer reflective film 2. A conductive film may be applied on the resist 4.

  FIG. 1C shows a resist development process. The resist 4 is patterned by irradiating a mask pattern and a light shielding frame and developing the resist pattern.

  As shown in FIG. 1D, the multilayer reflective film 2 is etched using the patterned resist as a mask to form a reverse pattern of a predetermined mask pattern in the multilayer reflective film 2 and a groove in a portion that becomes a light shielding frame. To do. Note that when the multilayer reflective film 2 is etched, the multilayer reflective film 2 may not be completely removed, and the depth at which the multilayer reflective film 2 is etched has a mask pattern formed by the light absorption film 6 later. It is sufficient that the depth is equal to or greater than the depth to sufficiently absorb the exposure light source wavelength.

  FIG. 1E shows a film removal process, in which the resist is removed.

  As shown in FIG. 1F, a protective film 5 is formed on the surface of the multilayer reflective film that has been stripped and patterned.

  As shown in FIG. 1G, a light absorption film 6 is formed on the protective film 5 formed.

  As shown in FIG. 1 (h), a resist 7 is applied on the formed light absorption film.

  As shown in FIG. 1I, the resist is patterned so as to open the mask pattern portion.

  As shown in FIG. 1J, the light absorption film 6 in the mask pattern portion is etched or polished so as to be flush with the surface of the protective film.

  As shown in FIG. 1 (k), the resist is peeled off.

<Embodiment 2>
FIG. 2 is an explanatory view showing the structure of a reflective mask according to Embodiment 2 of the present invention and the manufacturing process.

  As shown in FIG. 2A, the multilayer reflective film 2 is laminated from the one surface of the substrate 1, and the back conductive film 3 is formed on the other surface.

  Unlike Embodiment 1, at this time, as shown in FIG. 2B, a protective film 5 is formed on the multilayer reflective film 2.

  As shown in FIG. 2C, a resist 4 is applied on the protective film 5. A conductive film may be applied over the resist.

  FIG. 2D shows patterning of the resist 4, which is irradiated with a mask pattern and a light shielding frame and patterned by a development process.

  As shown in FIG. 2E, using the patterned resist as a mask, the protective film 5 and the multilayer reflective film 2 are etched, and the protective film 5 and the multilayer reflective film 2 have a reverse pattern of a predetermined mask pattern and light shielding. Grooves are formed in the part that becomes the frame. When the protective film 5 and the multilayer reflective film 2 are etched, it is not necessary to completely remove the multilayer reflective film. The depth at which the protective film and the multilayer reflective film are etched in total is determined by the light absorption film 6 later. It suffices if the mask pattern to be formed has a depth equal to or greater than a film thickness sufficient to absorb the exposure light source wavelength.

  As shown in FIG. 2F, the resist is removed.

  As shown in FIG. 2G, a light absorbing film 6 is formed on the surface of the patterned protective film and multilayer reflective film.

  As shown in FIG. 2H, a resist 7 is applied on the formed light absorption film.

  As shown in FIG. 2I, the resist is patterned so as to open the mask pattern portion.

  As shown in FIG. 2J, a step of etching or polishing the light absorption film 6 in the mask pattern portion so as to be flush with the surface of the protective film.

  As shown in FIG. 2 (k), the resist is peeled off.

  Hereinafter, Example 1 of the manufacturing method of the reflective mask of this invention is demonstrated using FIG.

  As shown in FIG. 1A, 40 pairs of Mo and Si are alternately laminated on one surface of the substrate 1 to form a multilayer reflective film 2 (film thickness 280 nm), and CrN is formed on the other surface. The back surface conductive film 3 (film thickness 20 nm) was formed.

  As shown in FIG. 1B, a resist 4 (FEP171: manufactured by FUJIFILM Electronics Materials, Inc., film thickness 200 nm) was applied on the multilayer reflective film 1.

  As shown in FIG. 1C, a mask pattern and a portion serving as a light shielding frame are drawn on the resist 4 using an electron beam drawing machine, and PEB (110 ° C. for 10 minutes) and development (2.38% TMAH). An aqueous solution) was applied, and the resist was patterned.

As shown in FIG. 1D, the multilayer reflective film 2 was etched to a depth of 70 nm by CHF ₃ plasma using a dry etching apparatus using the patterned resist as a mask.

  As shown in FIG. 1E, the resist was stripped using a sulfuric acid stripping solution and ammonia hydrogen peroxide solution.

  As shown in FIG. 1 (f), Ru was sputtered on the patterned multilayer reflective film surface to form a protective film 5 (film thickness 2.5 nm).

  As shown in FIG. 1G, Ta was plated on the formed protective film 5 by electrolytic plating to form a light absorption film 6 (film thickness 200 nm).

  As shown in FIG. 1H, a resist 70 (FEP171: manufactured by Fuji Film Electronics Materials, Inc., film thickness: 300 nm) was applied on the light absorption film 6 formed.

  As shown in FIG. 1 (i), the formed light absorption film 6 was etched with CHF3 plasma using a dry etching apparatus so as to be flush with the surface of the protective film.

  As shown in FIG. 1 (j), the resist was stripped using a sulfuric stripping solution and ammonia hydrogen peroxide solution.

  In FIGS. 1 (j) and (k), a light-shielding portion (light-shielding frame: digging in both the left and right sides in the figure) is formed outside the mask pattern formation region so as to define the mask pattern formation. In addition, the thickness of the light absorbing material outside the mask pattern region is larger than the thickness of the light absorbing material inside the mask pattern region.

  By forming a light shielding frame with low EUV light reflectivity, when a mask pattern is transferred and formed on a silicon wafer in multiple shots, the outer periphery of the mask pattern is exposed between adjacent shots. It will be resolved.

  Hereinafter, Example 2 of the manufacturing method of the reflective mask of this invention is demonstrated using FIG.

  As shown in FIG. 2A, 40 pairs of Mo and Si are alternately laminated on one surface of the substrate 10 to form a multilayer reflective film 2 (film thickness 280 nm), and CrN is formed on the other surface. The back surface conductive film 3 (film thickness 20 nm) was formed.

  As shown in FIG. 2B, Ru was sputtered on the multilayer reflective film 2 to form a protective film 5 (film thickness 2.5 nm).

  As shown in FIG. 2C, a resist 4 (FEP171: manufactured by FUJIFILM Electronics Materials, Inc., film thickness 200 nm) was applied on the protective film 5.

  As shown in FIG. 2 (d), a mask pattern and a portion serving as a light shielding frame are drawn on the resist 4 using an electron beam drawing machine, and PEB (110 ° C. for 10 minutes) and development (2.38% TMAH). An aqueous solution) was applied, and the resist was patterned.

  As shown in FIG. 2E, the protective film 5 and the multilayer reflective film 2 were etched to a total depth of 70 nm by CHF 3 plasma using a dry etching apparatus using the patterned resist as a mask.

  As shown in FIG. 2F, the resist was stripped using a sulfuric acid stripping solution and ammonia hydrogen peroxide solution.

  As shown in FIG. 2G, TaN was sputtered on the surface of the patterned protective film and multilayer reflective film to form a light absorption film 6 (film thickness 150 nm).

  As shown in FIG. 2 (h), a resist 7 (FEP171: manufactured by FUJIFILM Electronics Materials Co., Ltd., film thickness: 300 nm) was applied on the light absorption film 6 formed.

As shown in FIG. 2I, the formed light absorption film 6 was etched with CHF ₃ plasma using a dry etching apparatus so as to be flush with the surface of the protective film.

  As shown in FIG. 2 (j), the resist was stripped using a sulfuric stripping solution and ammonia hydrogen peroxide solution.

  In FIGS. 2 (j) and 2 (k), a light-shielding portion (light-shielding frame: digging in both the left and right sides in the figure) is formed outside the mask pattern formation region so as to define the mask pattern formation. In addition, the thickness of the light absorbing material outside the mask pattern region is larger than the thickness of the light absorbing material inside the mask pattern region.

  In Examples 1 and 2, a reflective mask in which a fine mask pattern and a light shielding frame were formed could be created without impairing the reflection characteristics of the reflective mask.

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Multilayer reflective film 3 ... Back surface conductive film 4 ... Resist 5 ... Protective film 6 ... Light absorption film 7 ... Resist 8 ... Digging 9 ..Mask pattern 10 ... Reflective substrate 20 ... Reflective mask

Claims (3)

A reflective mask in which a mask pattern and a light shielding frame are provided on a reflective substrate in which a multilayer reflective film is provided on the substrate,
The reflective substrate is provided with a mask pattern and a light shielding frame-shaped digging,
A protective film is formed on the reflective substrate provided with the mask pattern and the light shielding frame-shaped digging, and a light absorption film is formed on the mask pattern and the light shielding frame-shaped digging,
A reflective mask, wherein a protective film and a light absorbing film in the mask pattern are flush with each other. The multilayer reflective layer is removed in a frame shape outside the area where the mask pattern is formed, filled with a light-absorbing material, and the light-absorbing material is also formed on the surface of the multilayer reflective layer, or the multilayer reflective layer in the frame-shaped portion The light-shielding frame having a structure in which the thickness of the light absorption layer is thicker than the mask pattern in the frame-shaped portion is adopted by adopting at least one of whether the digging amount is deep or not. the reflective mask according to 1. A method of manufacturing a reflective mask in which a mask pattern and a light-shielding frame are provided on a reflective substrate provided with a multilayer reflective film on the substrate,
Forming a mask pattern and a light-shielding frame-shaped dig by etching on the reflective substrate;
A step of laminating a protective film on a reflective substrate provided with the mask pattern and a light shielding frame-shaped digging; a step of forming a light absorption film on the mask pattern and the light shielding frame-shaped digging;
A method of manufacturing a reflective mask, comprising: an etching process in which a light absorption film of the mask pattern portion is flush with a surface of the protective film.