JP2013074202A - Reflective mask and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective mask enabling accurate exposure transfer while preventing reflection of light from a region other than a circuit pattern region to be exposed.SOLUTION: In a reflective mask blank where a multilayer reflection film, a protective film, an absorption film, and a back conductive film are formed on a substrate, a circuit pattern and a light-shielding frame region on the area other than a circuit pattern formation region are provided, thus constituting a reflective mask. A groove is formed by removing the absorption film, the protective film and the multilayer reflection film in the light-shielding frame region, and a resin layer which absorbs the light of unnecessary wavelengths is formed in the groove.

Description

  The present invention relates to a reflective mask and a reflective mask manufacturing method, and more particularly to a reflective mask and a reflective mask manufacturing method used in a semiconductor device manufacturing apparatus that performs exposure using extreme ultraviolet light as a light source.

  In the manufacturing process of a semiconductor device, with the miniaturization of a semiconductor device, a demand for miniaturization of a photolithography technique is increasing. Already, lithography exposure has been changed from conventional exposure using ArF (argon fluoride) excimer laser light with a wavelength of 193 nm to exposure using light in the EUV (Extreme Ultra Violet) region with a wavelength of 13.5 nm. It is being replaced.

  In the EUV exposure mask, since most substances have high light absorbability with respect to light in the EUV region, a reflection type mask is used unlike a conventional transmission type mask (see, for example, Patent Document 1). ). In Patent Document 1, a molybdenum (Mo) layer and a silicon (Si) layer are alternately laminated on a glass substrate to form a light reflecting film composed of a multilayer film, and tantalum (Ta) is the main component thereon. A technique for forming a mask pattern using a light absorber is disclosed.

  In addition, in an exposure machine that uses EUV light, a refractive optical system that uses light transmission cannot be used for the above reasons, and therefore the optical system of the exposure machine is also of a reflective type. For this reason, deflection using a transmissive beam splitter is impossible. Therefore, there is a drawback that it is impossible to design the optical path of the incident light to the reflective mask and the optical path of the reflected light from the reflective mask to be coaxial. For this reason, in an exposure apparatus using EUV light, a technique is adopted in which reflected light of light incident on the mask with an optical axis inclined about 6 degrees with respect to the normal of the reflective mask is guided to the semiconductor substrate.

  However, in this method, since the optical axis is inclined with respect to the normal of the reflective mask, the wiring pattern of the mask differs from the mask pattern on the semiconductor substrate depending on the incident direction of light with respect to the mask pattern. There arises a problem called the projection effect that becomes the line width. Therefore, in order to suppress or reduce this projection effect, proposals have been made to reduce the thickness of the absorption film forming the mask pattern.

  In this thinning method, since the light attenuation capability necessary to absorb EUV light is insufficient, the reflected light to the semiconductor substrate increases, and the resist film applied on the semiconductor substrate does not need to be exposed. This causes a problem that the light is exposed to light.

  Further, in the semiconductor substrate, in order to expose the chips with multiple surfaces, multiple exposure occurs in the boundary region between adjacent chips. Therefore, in order to prevent the resist in the boundary area of the chip from being unnecessarily exposed, it is proposed to provide a light-shielding frame area having a relatively low reflectance around the mask pattern provided in the reflective mask. Has been. For example, in order to reduce the reflectance of the light-shielding frame region, a configuration is known in which a groove dug from the absorption film of the reflective mask to the light reflection film is provided (see, for example, Patent Document 2).

JP 2007-273651 A JP 2009-212220 A

  Although the EUV light source has a peak of its emission spectrum at 13.5 nm, it is known to emit light in the near-infrared region from a vacuum ultraviolet region other than the 13.5 nm band called out-of-band. . This out-of-band light sensitizes the resist applied to the semiconductor substrate.

  Since the light absorption film using tantalum (Ta) reflects light in the vacuum ultraviolet to deep ultraviolet (Deep Ultra Violet) region, there is a problem due to the out-of-band light incident on the mask pattern formation region. There is no. However, the out-of-band light that has entered the light shielding frame region from which the light absorption film and the reflection film have been removed is transmitted through the substrate, reflected by the conductive film provided on the back surface of the substrate, and irradiated onto the substrate. As described above, since the region that becomes the semiconductor wiring portion in the vicinity of the boundary region between adjacent chips is exposed multiple times, the integrated amount of light of the reflected out-band light becomes a non-negligible size, which affects the size of the wiring pattern. The problem of end up occurs.

  Further, in order to dig into the multilayer reflective layer after the mask pattern is produced, for example, it is necessary to process a total of 80 layers of silicon (Si) and molybdenum (Mo), and generation of particles from the processed surface is inevitable. The quality will be degraded.

  The present invention has been made to solve the above-described problems, and can prevent reflection of far ultraviolet rays from a mask region corresponding to a boundary region of a chip that is subjected to multiple exposure on a semiconductor substrate, and An object of the present invention is to provide a reflective mask with reduced generation of particles.

  The reflective mask according to the present invention includes a substrate, a reflective film formed on the substrate surface, a protective film formed on the reflective film, an absorption film formed on the protective film, and a back surface of the substrate. And a formed backside conductive film. A light shielding frame region in which the absorption film, the protective film, and the multilayer reflective film are partially removed is provided on at least a part of the outside of the circuit pattern region provided in the absorption film, and a resin film is formed in the light shielding frame region. ing.

  The method for manufacturing a reflective mask according to the present invention also includes a method of irradiating an electron beam, ultraviolet light, visible light, or infrared light to a resin applied to the reflective mask to cure the resin, thereby shielding the light shielding frame region. A resin film is selectively formed. In this manufacturing method, the resin applied to the reflective mask is irradiated with ultraviolet light, visible light or infrared light from the side surface of the substrate to cure the resin, thereby selectively forming a resin film in the light shielding frame region. You may do it.

  Moreover, the manufacturing method of the reflective mask which concerns on this invention forms a resin film by apply | coating a resin film selectively to a light-shielding frame area | region with respect to a reflective mask.

  According to the present invention, unnecessary ultraviolet rays can be absorbed by the resin layer provided in the light shielding frame region, so that the substrate to be exposed is irradiated with ultraviolet rays that are transmitted through the substrate and reflected by the back surface conductive film. Can be suppressed. In addition, since the resin layer is formed in the light shielding frame region from which the absorption film, the protective film, and the multilayer reflective film are removed, the generation of particles is reduced.

Sectional drawing of the reflective mask blank which concerns on embodiment of this invention The top view and sectional drawing of the reflective mask which concern on embodiment of this invention Process drawing explaining the manufacturing method of the reflection type mask which concerns on embodiment of this invention Sectional drawing which shows the processing state in the manufacturing process of the reflective mask which concerns on embodiment of this invention Sectional drawing which shows the processing state in the manufacturing process following FIG. 4A. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4B. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4C. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4D. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4E. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4F. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4G. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4H. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4I. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4J. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4K. Sectional drawing which shows the processing state in the manufacturing process following FIG. 4L. Sectional drawing of the reflective mask which concerns on embodiment of this invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the term “film” is used, but the term “film” may be read as “layer”.

  FIG. 1 is a cross-sectional view of a reflective mask blank 10 according to an embodiment. More specifically, it is a mask blank used for exposure using EUV light. The wavelength of EUV light is, for example, 13.5 nm. On one surface of the substrate 11, a multilayer reflective film 12, a protective film 13, and an absorption film 14 are formed in this order. On the other surface of the substrate 11, that is, the surface opposite to the surface on which the multilayer reflective film 12 is provided, a back surface conductive film 15 is laminated and formed. The multilayer reflective film 12, the protective film 13, the absorption film 14, and the back surface conductive film 15 can be formed using a known sputtering method.

  Next, FIG. 2 is a view showing a reflective mask 100 for exposure produced using the reflective mask blank 10 shown in FIG. More specifically, FIG. 2A is a plan view of the reflective mask 100, and FIG. 2B is a cross-sectional view of the reflective mask 100.

  As shown in FIGS. 2A and 2B, a circuit pattern A is provided at the center of the reflective mask 100. A light shielding frame region B is formed so as to surround the outside of the formation region of the circuit pattern A. As shown in FIG. 2B, the light shielding frame region B is a region where the absorption film 14, the protective film 13, and the multilayer reflective film 12 are partially removed. Further, in the present embodiment, the resin layer 23 is provided inside the groove formed by removing the absorption film 14, the protective film 13, and the multilayer reflective film 12 in the light shielding frame region B.

  Next, a manufacturing method of the reflective mask according to this embodiment is shown in FIGS. 3 and 4A to 4M. Here, FIG. 3 is a process diagram showing the manufacturing process, and FIGS. 4A to 4M are cross-sectional views showing the processing state in each process.

  First, a blank shown in FIG. 4A is prepared (step S0), and a circuit pattern A and a region B are formed in the absorption film 14. More specifically, a resist 21 such as a chemical amplification resist or non-chemical amplification resist that reacts with an electron beam is applied to the absorption film 14 (step S1, FIG. 4B), and a predetermined circuit pattern A is drawn (step S1). S2, FIG. 4C). Next, development is performed with an alkaline solution or the like (step S3, FIG. 4D), etching is performed by gas plasma using a fluorine-based gas or a chlorine-based gas using the pattern of the resist 21 formed thereby as a mask, and an absorption film 14 is patterned (step S4, FIG. 4E). Next, the unnecessary resist 21 pattern is removed by performing treatments such as ashing with oxygen plasma, decomposition with an oxidizing chemical such as sulfuric acid or ozone water, or dissolution with an organic solvent (step S5). Next, if necessary, cleaning with acid / alkaline chemicals, ozone or hydrogen gas dissolved in ultrapure water, organic alkaline chemicals, surfactants, etc. (S6), and spin drying using centrifugal force (S7) is performed. The circuit pattern A is formed by the above steps (FIG. 4F).

  Next, the light shielding frame region B is formed. More specifically, a resist 21 that reacts to ultraviolet rays or electron beams is applied on the absorption film 14 on which the circuit pattern A is formed (step S8, FIG. 4G). Next, the pattern of the light shielding frame region B is drawn by exposure or electron beam (step S9, FIG. 4H). Thereafter, development (step S10, FIG. 4I), etching (step S11), removal of the resist 21 (step S12), washing and drying (step S13) are performed to form a light shielding frame region B (FIG. 4J). In the etching process (step S11), fluorine gas plasma or chlorine gas plasma is alternately used to remove a part of the absorption layer 14, the protective film 13, and the multilayer reflective film 12.

  Next, a resin such as photosensitive polyimide, novolac, polyhydroxystyrene, or acrylic resin is applied on the substrate on which the circuit pattern A and the light shielding frame region B are formed (step S14, FIG. 4K). The application of the resin may be performed by a known method such as a spin coating method, or only a necessary portion may be selected and applied.

  As the photosensitive resin, those that do not emit an outgas upon exposure to EUV light or ultraviolet light in a vacuum and those that do not break down the resin are desirable. Moreover, you may adjust the light absorbency with respect to out-of-band light by adding an acid generator, a quencher, a dissolution inhibitor, etc. to the photosensitive resin.

  In addition, as a means for curing the resin, a known method such as electromagnetic wave such as visible light, ultraviolet light, infrared light, heating, pressure, or addition of a curing agent may be adopted depending on the type of resin and the curing agent. it can.

  Next, of the applied resin, the resin 22 in the portion of the light shielding frame region B is selectively cured (step S15). Here, the resin curing method performed in step S15 is exemplified. However, the resin curing method applicable to the present invention is not limited to the following methods. For example, in the following normal drawing method, it is also possible to use a thermosetting resin used in the selective coating method. Further, the resin / curing method to be used can be appropriately selected depending on the required thickness of the resin film, the manufacturing process, and the like. In FIGS. 4L and 4M, a blackened portion denoted by reference numeral 23 represents a cured resin.

<1. Method by normal exposure or normal drawing>
As indicated by an arrow in FIG. 4L, the photosensitive resin 22 in the light shielding frame region B is selectively cured by irradiating only the light shielding frame region B with an electron beam or ultraviolet light from the upper surface of the substrate 11.

<2. Method by horizontal exposure>
As shown in FIG. 4M, exposure light having a wavelength of 150 to 400 nm is incident from the side surface of the substrate 11. The exposure light is reflected at the portion where the multilayer reflective film 12 is formed on the surface of the substrate 11, and the resist 21 on the substrate 11 is not exposed. On the other hand, since the multilayer reflective film 12 is not formed in the light shielding frame region B, the resist 21 is exposed by the incident exposure light, and the resin film 23 is formed.

<3. Method by selective application>
Instead of the method described in the above items 1 and 2, the resin film 23 is formed by selectively applying a resin only to the light shielding frame region B by an inkjet method or the like and curing the resin by heating or the like. Also good. In this case, the resin used does not require photosensitivity and may be any resin that can be cured by heating.

  Thereafter, development processing is performed to remove the uncured resin 22 (step S16), and the reflective mask 100 shown in FIG. 5A or 5B is completed. In the reflective mask 100 shown in FIG. 5A, the resin film 23 is formed so as to reach the surface of the absorption film 14 from the upper surface of the substrate 11, and the thickness thereof is equal to the depth of the groove formed in the light shielding frame region B. Almost equal. On the other hand, in the reflective mask 10 shown in FIG. 5B, the resin film 23 is formed so as to reach a position lower than the surface of the absorption film 14 from the upper surface of the substrate 11, and the height thereof is in the light shielding frame region B. It is smaller than the depth of the formed groove.

  As shown in FIG. 5B, when the resin film 23 is formed on a part of the portion dug out as a light shielding frame, the out-of-band light reflected by the back surface conductive film 15 is exposed on the wafer side (that is, reflected). Even if it reaches the absorption film 14 side of the mold mask 100, the absorbance and film thickness of the resin film 23 can be adjusted so that the resist 21 applied on the semiconductor substrate can be prevented from being exposed to light. preferable.

  By appropriately setting the resin coating film thickness, exposure amount, and development conditions, the resin film 23 formed in the light shielding frame region B is formed so that the absorbance of out-of-band light is 0.5 or more. Thereby, at the time of exposure using the reflective mask 100, unnecessary out-of-band light from the light shielding frame region 32 can be suppressed to 10% or less of the conventional method, and the resist 21 applied on the semiconductor substrate can be suppressed. It is possible to avoid exposure of unnecessary portions. The absorbance here is a dimensionless amount indicating how much the intensity is reduced when light passes through a certain object, and can be measured by a normally used apparatus such as a spectrophotometer.

  The conventional substrate could not remove the light component that once transmitted through the substrate 11 and reflected from the back surface conductive film 15 and returned again only by forming the light shielding frame region B. On the other hand, in the present invention, by forming a resin film that absorbs ultraviolet light in the light shielding frame region B, unnecessary out-of-band light is not guided to the semiconductor substrate side, and the resist coated on the semiconductor substrate is not guided. It became possible to avoid exposure. Further, by providing the resin film 23 in the dug portion of the light shielding frame region B, it is possible to reduce the generation of particles.

  The present invention is not limited to the above-described embodiment as it is, and can be modified and embodied without departing from the gist of the present invention. Various inventions can be envisaged by appropriately combining the matters shown in the specification.

  As an example, in the above-described embodiment, the protective film 13 is provided between the multilayer reflective film 12 and the absorption film 14, but the protective film 13 is not provided, and the absorption film 14 is provided directly on the multilayer reflective film 12. It may be provided. A buffer film may be provided between the multilayer reflective film 12 and the absorption film 14 or between the protective film 13 and the absorption film 14. Furthermore, a conductive film for preventing charge-up during exposure may be provided between the substrate 11 and the multilayer reflective film 12.

  Hereinafter, an embodiment of a method for manufacturing the reflective mask 100 of the present invention will be described.

  First, a reflective mask blank 10 was prepared. This reflective mask blank 10 has a 40-pair multilayer reflective film 12 of Mo and Si designed to have a reflectance of about 64% with respect to EUV light having a wavelength of 13.5 nm on a substrate, and 2 A protective layer 13 having a thickness of 0.5 nm and an absorption layer 14 made of TaSi having a thickness of 70 nm are sequentially formed on the substrate 11.

  After applying a positive chemical amplification resist (FEP171: Fuji Film Electronics Materials) with a film thickness of 300 nm to the reflective mask blank 10 and drawing with an electron beam drawing machine (JBX9000: JEOL), 110 degrees, A resist pattern was formed by PEB (Post Exposure Bake: baking after exposure) and spray development (SFG3000: Sigma Meltech) for 10 minutes.

Next, using a dry etching apparatus, the absorption film 14 was etched by CF ₄ plasma and Cl ₂ (chlorine gas) plasma, and the resist was peeled and washed to produce a reflective mask having an evaluation pattern. As the evaluation pattern, a 1: 1 line & space pattern having a dimension of 200 nm was arranged at the center of the mask so that the defect quality of the mask could be evaluated by a mask inspection machine. The size of the pattern area was 10 × 10 cm.

  Subsequently, the process of forming a light-shielding frame was performed with respect to the pattern area | region of the reflective mask which has the said evaluation pattern. An i-line resist was applied to a reflective mask with a film thickness of 500 nm, and the pattern was drawn and developed by an i-line drawing machine (ALTA) to form a resist pattern in which a region that later becomes a light shielding frame was removed. At this time, the opening width of the resist pattern was 5 mm, and the resist pattern was arranged at a distance of 3 mm from the main pattern region of 10 × 10 cm in the center of the mask.

Next, the multilayer reflective layer at the opening of the resist is etched with CF ₄ plasma using a dry etching apparatus, and the resist is stripped and washed with a sulfuric acid-based stripping solution and ammonia hydrogen peroxide solution. The remaining resist was removed.

  Next, a negative chemical amplification resist (FEN271: FUJIFILM Electronics Materials) was applied in a film thickness of 500 nm on the pattern surface of the reflective mask having the dug portion of the multilayer reflective layer processed as described above. Then, UV light having a wavelength of 254 nm is made incident from the lateral surface of the substrate 11, and the resist is selectively cured only in the light shielding frame region, and PEB and spray development (SFG3000: Sigma Meltech) at 110 degrees and 10 minutes A resin film 23 was formed. As a result, the resin film 23 having the configuration shown in FIG. 5B could be formed. The film thickness was about 250 nm.

  Thus, by covering the light shielding frame region (part) with the resin film, the absorbance with respect to light with a wavelength of 130 nm to 300 nm became 0.5 or more, and the influence of light could be reduced. Further, by covering at least part of the inside of the groove of the light shielding frame region 32 with the resin film 23, generation of particles and the like could be reduced.

  INDUSTRIAL APPLICABILITY The present invention can be used as a reflective mask for performing exposure using light in the EUV region and a method for manufacturing the same.

DESCRIPTION OF SYMBOLS 10 Reflective mask blank 11 Substrate 12 Multilayer reflective film 13 Protective film 14 Absorbing film 15 Back surface conductive film 21 Resist 22 Photosensitive resin 23 Resin film 31 Circuit pattern 32 Light-shielding frame area 101 Reflective mask

Claims (8)

A reflective mask,
A substrate,
A reflective film formed on the substrate surface;
A protective film formed on the reflective film;
An absorption film formed on the protective film;
Comprising a back conductive film formed on the back surface of the substrate;
A light-shielding frame region in which the absorption film, the protective film, and the multilayer reflective film are partially removed is provided on at least a part of the outside of the circuit pattern region provided in the absorption film,
A reflective mask in which a resin film is formed in the light shielding frame region.   2. The reflective mask according to claim 1, wherein an absorbance of the resin film with respect to light having a wavelength of 130 nm to 300 nm is 0.5 or more.   2. The reflective mask according to claim 1, wherein the resin film has a thickness at which an absorbance with respect to light having a wavelength of 130 nm to 300 nm is 0.5 or more.   The reflective mask according to any one of claims 1 to 3, wherein the material of the resin film is at least one of polyimide, polyhydroxystyrene, novolac, and acrylic resin.   The said resin film is selectively formed in the light-shielding frame area | region by hardening using an electron beam, ultraviolet light, visible light, or infrared light, The Claim 1 characterized by the above-mentioned. The reflective mask as described. It is a manufacturing method of the reflective mask in any one of Claims 1-4,
The resin film is selectively formed in the light shielding frame region by curing the resin applied to the reflective mask using an electron beam, ultraviolet light, visible light, or infrared light. A method for manufacturing a reflective mask. It is a manufacturing method of the reflective mask in any one of Claims 1-4,
The resin applied to the reflective mask is irradiated with ultraviolet light, visible light or infrared light from the side surface of the substrate to cure the resin, thereby selectively forming the resin film in the light shielding frame region. A method for manufacturing a reflective mask. It is a manufacturing method of the reflective mask in any one of Claims 1-4,
A method of manufacturing a reflective mask, wherein the resin film is formed by selectively applying a resin film to the light shielding frame region on the reflective mask.

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