JP2005116847A - Photomask and method for manufacturing mask for exposure of charged corpuscular beam by using photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a mask for exposure of charged corpuscular beams such as a mask for exposure of electron beams and a photomask to be used for the method, by accurately aligning a mask pattern formed on the surface side of a mask substrate to a stripe pattern formed on the rear side of the mask substrate without forming an alignment mark on the rear side, so that a silicon oxide layer is not damaged and the mask is not contaminated and damaged. <P>SOLUTION: An alignment mark is constituted of at least two or more different light shielding films on a photomask consisting of a transparent substrate and the light shielding films, an alignment pattern is formed on one light shielding film layer out of the two or more light shielding films, and exposed light is shielded by the alignment mark part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a charged particle beam exposure mask manufacturing method for transferring a mask pattern onto a wafer using a charged particle beam such as an electron beam or an ion beam, which is used for manufacturing a semiconductor device or the like. The present invention relates to a photomask used for alignment of the alignment pattern and a method of manufacturing a charged particle beam exposure mask using the photomask.

  With the miniaturization and high integration of semiconductor integrated circuit elements, instead of the conventional photolithography technology that uses light, an electron beam transfer type that uses a charged particle beam, especially an electron beam, to transfer a desired shape onto a wafer. Lithography technology has been developed, and recently, development is progressing as an EPL (Electron-Beam Projection Lithography) method capable of high throughput. For example, as an electron beam transfer lithography technique, a stencil mask is prepared in which a mask pattern is divided into small areas, and through-hole patterns formed in a predetermined size and arrangement are prepared for each small area. A technique for irradiating a beam and reducing and transferring an electron beam formed by a through-hole pattern onto a wafer that is an exposed substrate is described, and a predetermined pattern divided on a mask is connected on the exposed substrate. A system for forming a device pattern while matching them has been developed (see, for example, Patent Document 1).

  An example of a mask used in the above-described electron beam transfer lithography technique is shown in FIG. FIG. 10 shows an example of an electron beam exposure mask 100 using an 8-inch wafer substrate, FIG. 10A is an overall view of the mask, and two pattern regions (132.57 mm × 54.43 mm) 101 are A pattern is formed by providing a through-hole that transmits an electron beam in a silicon thin film layer called a membrane mask pattern 102. Since the membrane mask pattern 102 is very thin, the pattern region is strut 103 (0.17 mm) from the back side. The membrane mask pattern 102 is reinforced by dividing it with silicon pillars called “width”, thereby reducing the deflection of the pattern region and improving the pattern position system. FIG. 10B is a partially enlarged schematic view of FIG. 10A, and the membrane mask pattern 102 transferred onto the wafer is formed between the struts 103.

  A cross-sectional schematic diagram of a typical conventional manufacturing method of the electron beam exposure mask will be described with reference to FIG. 8 and subsequent FIG. The electron beam exposure mask manufacturing method includes a method of forming a mask pattern on the front surface after forming a strut on the back surface of the mask, and a method of forming a strut on the back surface after forming the mask pattern on the front surface. FIG. 8 and FIG. 9 show a method of preceding the mask pattern formation on the surface.

  In the mask manufacturing process, the membrane side silicon and the strut side silicon are etched in different processes. Therefore, an etching stop layer having a predetermined thickness is required between the silicon and the mask substrate. A silicon oxide film is used. Therefore, as shown in FIG. 8A, an SOI (Silicon On Insulator) substrate 80 having a silicon oxide film between silicon and silicon is mainly used as an electron beam exposure mask substrate. Yes. The SOI substrate 80 has a structure in which two silicon crystal substrates are bonded to each other with a silicon oxide film 83 interposed therebetween. The thickness of the support silicon 81 serving as a mask blank and a mask support (strut) portion is several hundred μm, A silicon thin film layer (called a silicon membrane) 82 for forming a mask pattern has a thickness of several μm, and a silicon blank 83 and a silicon oxide film 83 functioning as an etching stop layer at the time of manufacturing the mask have a thickness of about 1 μm. Is provided.

  On the silicon thin film layer 82 on which the mask pattern of the SOI substrate 80 is to be formed, Cr or the like is sputtered as a masking material for etching the silicon thin film layer 82 to form a hard mask layer 84 (FIG. 8B).

  Subsequently, after forming a resist layer on the hard mask layer 84 on the surface and making the plate, the hard mask layer 84 is etched to form an alignment pattern 84a and a mask pattern 84b by the hard mask layer (FIG. 8C). .

Subsequently, a photoresist layer 85 is formed on the back surface side of the SOI substrate 80, and the alignment mark 84a on the front surface side is detected and aligned with the alignment pattern 76 of the back surface photomask 71, and ultraviolet exposure 77 is performed (FIG. 8). (D)). Next, development is performed to provide resist patterns 85a and 85b for forming strut openings (FIG. 9E). As the backside photomask 71, a conventional chrome mask or see-through mask is used (see, for example, Patent Document 2). FIG. 7 is a schematic cross-sectional view of a conventional backside photomask 71 used at this time. A strut pattern 75 and an alignment pattern 76 are formed on a transparent substrate 72 by a light shielding film 73.
At the time of the above exposure / development, the alignment resist pattern 85a is also formed together with the strut resist pattern 85b. The alignment mark is aligned visually or automatically in the visible region with a microscope or the like using a double-sided aligner. In order to make it easy to find the pattern position, the size of the entire alignment mark is about several mm square. The pattern line width for forming the alignment mark is about several tens of μm.

Next, from the back side of the substrate, the silicon oxide film 83 is used as an etching stop layer, and silicon is dry-etched using an etching gas such as SF ₆ , or an alkali solution such as NaOH solution or KOH solution is heated to wet. The strut 87 is formed by etching. In the back side silicon etching described above, the back side alignment mark portion 86 is etched simultaneously with the strut pattern portion in both dry etching and wet etching. Next, the resist patterns 85a and 85b are removed (FIG. 9F).

  Next, the exposed silicon oxide film 83 is etched (FIG. 9G). Next, from the surface side, using the patterned hard mask layers 84a and 84b as a mask, the exposed silicon thin film layer 82 is dry-etched to provide an electron beam transmitting hole 88 to form a mask pattern 89, which is used for electron beam exposure. A mask 90 is obtained (FIG. 9 (h)).

  As described above, in the conventional method for manufacturing an electron beam exposure mask, when etching back silicon, in the case of dry etching, the influence of the plane orientation is small, and etching proceeds in the vertical direction. As with the strut portion, the alignment mark portion also has a problem that etching proceeds to the silicon oxide layer that is an etching stop layer. On the other hand, in the case of wet etching using an alkaline aqueous solution, there is a problem that etching anisotropy occurs due to a difference in etching speed in the plane direction, an opening becomes larger, and side etching advances and eventually penetrates.

And since the alignment mark part is large in area, the silicon oxide layer of the alignment mark part is destroyed, and etching gas or etching solution wraps around the front side pattern surface, damaging the mask or generating foreign matter due to membrane destruction There is a problem that the mask is contaminated by the adhesion.
Furthermore, in the mask for electron beam exposure, the mask holding at the time of exposure is often performed by electrostatic chuck adsorption, and if the alignment mark portion or the like exists as a thin film in the adsorption area, the thin film is easily contaminated or broken by the adsorption. There was also a problem.

In order to solve the above problem, an alignment mark is proposed in which the alignment mark is configured by a combination of rectangular patterns, and the wet etching of the alignment mark portion is stopped in the middle of the silicon substrate using the plane orientation of silicon. (For example, refer to Patent Document 3).
Further, after the resist pattern is formed on the back surface, a method has been used in which only the alignment mark portion is partially covered with a protective film such as a resist so that etching does not enter.
Japanese Patent No. 2829942 JP 52-69269 A Japanese Patent Laid-Open No. 10-284378

However, the method described in Patent Document 3 has a problem that the mask strength is lowered because etching is performed in the support silicon partway, and in the case of performing dry etching, the etching rate differs depending on the plane orientation. There was a problem that it could not be applied because it did not appear.
In addition, the method of partially covering only the alignment mark part with a protective film such as a resist after forming the resist pattern on the back surface has a problem that it is difficult to apply when the high-density pattern is near the alignment mark, and production There was a problem of inferiority.

  Accordingly, the present invention has been made to solve such problems. The purpose is to accurately align the mask pattern on the front side of the mask substrate and the strut pattern on the back side in the manufacturing method of the charged particle beam exposure mask such as an electron beam exposure mask, and form an alignment mark on the back side. Accordingly, it is an object of the present invention to provide a method of manufacturing a charged particle beam exposure mask and a photomask used therefor, in which the thin film silicon layer and the silicon oxide layer are not destroyed and the mask is not contaminated or damaged.

  In order to solve the above problems, in a photomask composed of a transparent substrate and a light shielding film, at least the alignment mark portion is composed of two or more different light shielding films, and one of the two or more light shielding films of the alignment mark portion. An alignment pattern is formed on the layer, and the alignment mark portion blocks exposure light. With the above structure, even when the entire surface including the alignment mark portion of the photomask is exposed, the mark portion is not transferred.

  A photomask according to a second aspect of the present invention is such that one layer of the light shielding film of the arrangement mark portion is formed of a film containing chromium as a main component.

  A photomask according to a third aspect of the invention is such that one layer of the light shielding film of the arrangement mark portion is a see-through film that transmits alignment light and shields exposure light.

  According to a fourth aspect of the present invention, there is provided a charged particle beam exposure mask manufacturing method, comprising: aligning a surface side pattern and a back side pattern of the charged particle beam exposure mask in the method for manufacturing a charged particle beam exposure mask; At this time, the back side is aligned using the photomask according to any one of claims 1 to 3 and exposed.

  By producing a charged particle beam exposure mask such as an electron beam exposure mask using the photomask of the present invention, the alignment of the front and back patterns of the substrate can be made with high accuracy, and the back side alignment mark on the photomask Is not transferred to the substrate, the backside silicon, which is the support frame other than the struts, is not etched, the mask pattern can be prevented from being damaged or contaminated, and the charged particle beam has a high quality and high positional accuracy pattern. An exposure mask can be obtained.

  Hereinafter, a photomask used in a method for manufacturing an electron beam exposure mask, and an electron beam using the photomask, in the embodiment of the present invention, taking as an example electron beam exposure that is close to practical use in charged particle beam exposure A method for manufacturing an exposure mask will be described with reference to the drawings.

(Photomask)
1 and 2 are partial longitudinal sectional views schematically showing an example of an embodiment of a photomask used for pattern formation on the back surface side of an electron beam exposure mask of the present invention. FIG. 1 and FIG. 2 show an example of an embodiment in which one of two or more different light shielding films in the alignment mark portion is a see-through film that transmits alignment light and shields exposure light.

  As shown in FIG. 1, in the present invention, a photomask 11 includes a transparent substrate 12 such as a low expansion glass substrate or a quartz substrate, a first light shielding film 13 that shields exposure light, and a second light shielding film 14, and includes struts. A pattern 15 and an alignment mark portion 16 are provided. At least the alignment mark portion 16 is composed of two light shielding films, and an alignment pattern is formed in one layer of the two light shielding films. The light-shielding film may be further multi-layered as long as it has two or more layers, but two layers are preferred from the viewpoint of mask manufacturing cost and ease of etching. In the present invention, as shown in FIG. 2, the strut pattern 25 may also be composed of two or more layers of light-shielding films. However, the strut pattern is 1 in terms of pattern resolution, pattern edge accuracy, and the like. It is more preferable to form the light shielding film of the layer. Furthermore, the form shown in FIG. 1 has the advantage that the overlay accuracy with the first light shielding layer 13 may be low by using the second light shielding layer 14 as a see-through film, and is easy to manufacture.

  In the present invention, the light shielding film needs to have a characteristic of shielding exposure light by a single layer. A commonly used photomask material such as a chromium film or a chromium oxide film can be applied to one of the two or more light shielding films used for the alignment mark portion. The alignment mark is aligned visually or automatically in the visible region using a double-sided aligner.

  In the photomask of the present invention, an alignment pattern is formed in one layer of two or more light shielding films, and the alignment pattern on the photomask can be detected with good contrast when aligning the front and back patterns of an SOI substrate or the like. The alignment mark portion including the alignment pattern can be used to shield exposure light. The photomask will be described with reference to the drawings.

  In FIG. 1, the second light-shielding film 14 shown as one layer of the arrangement mark portion 16 composed of two or more light-shielding films is a see-through film that transmits visible light and alignment light and shields exposure light. The alignment pattern is formed on the first light shielding film 13 such as a chromium film, and the second light shielding film 14 is formed as a see-through film covering the alignment pattern. FIG. 2 shows a form in which the second light-shielding film 24 is formed not only on the arament mark portion 26 but also on the first light-shielding film 23 that forms the strut pattern 25. The strut pattern 25 is formed by the light shielding film 23, the alignment pattern is formed by the second light shielding film 24, and the second light shielding film 24 is formed not only on the alignment mark portion 26 but also on the light shielding film 23 of the strut pattern 25. It is a formed form.

  The first light-shielding film 13 in FIG. 1 or the second light-shielding film 24 in FIG. 2 is preferably a film containing chromium as a main component, and is made of chromium, chromium oxide, chromium nitride, chromium oxynitride, chromium carbide, oxynitride carbonization. A chromium thin film is formed into a single layer or a multilayer, and the thickness of the light shielding film is several tens nm to several hundreds nm.

  As the see-through film, a thin film obtained by sputtering or vacuum-depositing a silicon film, a mixed film of silicon and germanium (for example, weight ratio Si: Ge = 99: 1) or the like is used. Since the light-shielding film different from the see-through film shields not only the exposure light but also the visible light, the visible light transmittance of the above-described see-through film only needs to have a see-through property that the alignment pattern can identify. The see-through film is already known as a light-shielding film for a photomask as described in, for example, Patent Document 2, and etching is an aqueous solution containing, for example, ammonium fluoride, silver nitrate, and hydrogen peroxide. Is used.

(Photomask manufacturing method)
FIG. 3 and subsequent FIG. 4 are cross-sectional schematic diagrams showing the manufacturing process of the photomask 11 shown in FIG. 1 of the present invention. As shown in FIG. 3A, a photomask blank is prepared in which a first light-shielding film 13 that shields exposure light is formed on a transparent substrate 12 by sputtering or the like. Next, a photoresist layer 34 is formed on the blanks (FIG. 3B), exposed and developed to form strut resist patterns 15a and alignment resist patterns 16a (FIG. 3C). . Subsequently, the first light-shielding film 13 is etched (FIG. 3D), the resist pattern is peeled off, and a strut pattern 15b formed by the first light-shielding film 13 and an alignment pattern 16b formed by the first light-shielding film 13 are provided. A photomask 31 is formed (FIG. 3E).

  Etching of the first light-shielding film 13 may be wet etching or dry etching. For example, when the first light-shielding film 13 is a film containing chromium as a main component, it is wet with a ceric ammonium nitrate-based etchant. Etching can be performed, or dry etching can be performed with a gas containing chlorine.

  Next, a see-through film that transmits alignment light and shields exposure light is formed on the photomask 31 as a second light-shielding film 14 by sputtering or vacuum deposition (FIG. 4F). Next, a photoresist is applied on the second light-shielding film 14, and plate-making is performed so that a resist pattern 44 is formed so as to cover the alignment pattern 16b (FIG. 4G). At this time, the resist pattern 44 does not need to be accurately aligned with the end of the alignment pattern 16b. It is sufficient to form the resist pattern 44 so that the opening of the alignment pattern 16b is covered. This alignment is extremely easy. It is.

  Next, after etching the second light-shielding film 14, the resist pattern 44 is peeled off to form the photomask 11 of the present invention (FIG. 4H). For example, when the second light shielding film 14 is a silicon film or a mixed film of silicon and germanium, etching is performed with an aqueous solution containing ammonium fluoride, silver nitrate, and hydrogen peroxide. At this time, the first light shielding film 13 mainly composed of chromium is not affected.

(Manufacturing method of electron beam exposure mask)
The manufacturing method of the electron beam exposure mask of the present invention using the above-described photomask of the present invention will be described with reference to FIG. 5 and subsequent FIG. FIG. 5 shows a method of leading the mask pattern formation on the front side. As shown in FIG. 5A, an SOI substrate 50 is used as an electron beam exposure mask substrate. A commercially available substrate can be used as the SOI substrate, the thickness of the support silicon 51 on the back side is 500 to 725 μm, the thickness of the silicon thin film layer 52 on the surface is 0.5 μm to several μm, and the thickness of the silicon oxide film 53. Is about 0.2 to 1 μm.

  On the silicon thin film layer 52 on which the mask pattern of the SOI substrate 50 is formed, Cr or the like is sputtered as a masking material for etching the silicon thin film layer 52 to form a hard mask layer 54 (FIG. 5B).

  Subsequently, after forming a resist layer on the hard mask layer 54 on the surface and making the plate, the hard mask layer 54 is etched to form a surface side alignment pattern 54a and a mask pattern 54b by the hard mask layer (FIG. 5 ( c)).

  As a material of the hard mask layer, a material made of any one of Cr, Ti, Ta, Mo, W, Zr and oxides, nitrides, and oxynitrides of these metals is used. Further, it is formed by vacuum film formation by a method such as sputtering. The hard mask layer 54 is not necessarily required, and a process of directly applying an electron beam resist on the silicon thin film layer 52 and etching the silicon thin film layer 52 based on the resist pattern is also possible. However, when fine pattern etching is performed, it is preferable to provide a hard mask layer 54 in order to increase dry etching resistance.

  Formation of the alignment pattern 54a and the mask pattern 54b of the hard mask layer is performed by applying an electron beam resist and simultaneously by electron beam exposure, or making the alignment pattern 54a using a photoresist and first etching the hard mask layer. It is also possible to form an alignment pattern 54a and then form a mask pattern 54b by patterning electron beam exposure by applying an electron beam resist (not shown).

  Subsequently, a photoresist layer 55 is formed on the back side of the SOI substrate 50, the alignment pattern 13 of the photomask 11 is aligned with visible light at a position corresponding to the alignment pattern 54a on the front side, and ultraviolet (wavelength 436 nm) exposure is performed. 56 (FIG. 5D). At this time, the alignment mark part 16 of the photomask 11 is covered with the second light-shielding film made of the see-through film 14, and the exposure light of the alignment mark part 16 is shielded. Subsequently, by development, only the strut resist pattern 55b is transferred to the back surface of the SOI substrate, and no alignment pattern is formed (FIG. 6E).

Next, the silicon oxide film 53 is used as an etching stop layer, and silicon is dry-etched from the back side of the substrate using an etching gas such as SF ₆ to form the struts 57, and then the photoresist layer 55 is peeled off. (FIG. 6 (f)).
As an etching mask material at the time of dry etching, as described above, a photoresist using a novolak resin having dry etching resistance is applied thick (15 μm), exposed and developed to provide a predetermined resist opening. Alternatively, a silicon-based thin film such as silicon oxide or silicon nitride that can have an etching selectivity ratio with silicon, or a metal thin film such as Cr, Ti, or W is formed in advance and patterned by a photo-etching method as an etching mask It may be used (not shown).
For the deep digging and etching of silicon, a commercially available ICP-RIE apparatus or the like can be used. As the process gas, fluorine-based gas such as SF ₆ , CF ₄ , C ₂ F ₆ , C ₄ F _8, etc. For example, a so-called Bosch (BOSCH) process that performs dry etching with high-density plasma while alternately supplying SF ₆ gas and C ₄ F ₈ gas can be used. Further, in order to increase the etching rate, it is possible to mix a small amount of oxygen or nitrogen within a range that does not affect the mask material.

Next, the exposed silicon oxide film 53 is etched using buffered hydrofluoric acid or the like (FIG. 6G). Next, using the patterned hard mask layers 54a and 54b on the surface side as a mask, the exposed silicon thin film layer 52 is dry-etched to provide an electron beam transmitting hole 58 to form a mask pattern 59. High-precision trench etching is required for dry etching of the silicon thin film layer 52 that forms the mask pattern 59. For example, plasma etching using an HBr-based gas or the like is used. Next, the hard mask layers 54a and 54b are removed by etching to form an electron beam exposure mask 60 (FIG. 6H).
In the method for manufacturing an electron beam exposure mask according to the present invention, the support silicon 51 in the peripheral portion of the mask 60 is not etched, so that it has sufficient strength as a mask.

  A chromium film having a thickness of 70 nm was formed as a first light-shielding film by sputtering on an 8 inch × 8 inch synthetic quartz substrate. Next, this chrome blank was patterned by a normal photomask manufacturing method using a photoresist, and a chrome photomask having a strut pattern and an alignment pattern for processing the back surface of the SOI substrate was manufactured.

  Next, a second light-shielding film made of silicon and germanium (weight ratio Si: Ge = 99: 1) was formed as a see-through film on the entire surface of the chromium photomask to a thickness of 200 nm by sputtering. Next, a photoresist is applied on the second light-shielding film, and the plate is made so as to leave only the second light-shielding film in the alignment mark portion, and 5 ml of 30% hydrogen peroxide solution is added to 1 g of ammonium fluoride / 100 ml of water. Etch with an etching solution to remove unnecessary silicon and germanium layers, then peel off the photoresist, and a two-layer light-shielding film consisting of a chrome film for the strut pattern part and a chrome film and a see-through film for the alignment mark part A photomask for processing the back surface of an SOI substrate composed of

  Next, an 8-inch SOI substrate was prepared as an electron beam exposure mask substrate. In the SOI substrate, the thickness of the back side silicon serving as the support portion of the mask is 725 μm through the silicon oxide film having a thickness of 1 μm, and the silicon thin film layer for forming the mask pattern is 2 μm thick. On this silicon thin film layer, Cr was sputtered to a thickness of 200 nm as a masking material for etching the silicon thin film layer to form a hard mask layer.

  Subsequently, a photoresist layer is formed on the Cr hard mask layer on the surface, plate-making is performed to form an alignment resist pattern, and then Cr is used as a ceric ammonium nitrate etching solution based on the resist pattern. Then, the resist was removed, and an alignment pattern on the surface side of Cr was formed.

  Next, an electron beam resist was applied on the hard mask layer so as to cover the alignment pattern on the surface side, a predetermined mask pattern was drawn with an electron beam exposure apparatus, and developed to form an electron beam resist pattern.

  Next, the exposed Cr hard mask layer was etched based on the electron beam resist pattern, the electron beam resist pattern was removed, and a mask pattern was formed by the hard mask layer together with the alignment pattern previously formed.

  Next, a photoresist using a novolac resin was applied to the backside support silicon to a thickness of 15 μm, and the alignment mark of the photomask was aligned at a position corresponding to the alignment pattern on the front side, and exposed to ultraviolet rays. . At this time, the alignment mark portion of the photomask is covered with a second light-shielding film made of a see-through film, and visible light is transmitted through the see-through film and reflected by the underlying Cr hard mask. Yes, the exposure light is shielded. Subsequently, only the strut resist pattern was transferred to the back surface by development. In the strut pattern, one unit of the opening was 1.13 × 1.13 mm, the width between the openings serving as support silicon (strut) was 170 μm, and the opening was provided with a plurality of units. .

Subsequently, using the Bosch process in which SF ₆ gas and C ₄ F ₈ gas are alternately supplied with an ICP-RIE etching apparatus based on the resist pattern described above, the back side silicon is dry etched to a depth of 725 μm. After forming the struts, the resist pattern was removed with a special stripping solution.

  Next, the silicon oxide film exposed in the opening of the strut was removed by etching using buffered hydrofluoric acid (hydrofluoric acid: ammonium fluoride = 1: 10).

Next, based on the hard mask pattern of Cr on the surface side, the exposed silicon thin film layer was dry-etched using HBr gas to form a mask pattern having electron beam transmission holes. The mask pattern was a 260 nm line and space. Next, Cr of the hard mask layer was removed by etching with a ceric ammonium nitrate-based etchant to form an electron beam exposure mask.
In the mask for electron beam exposure of this example, the opening on the back surface of the mask is 1.13 × 1.13 mm, the strut is 170 μm wide and 725 μm high, and the support silicon maintains the mask strength at the periphery of the mask. The mask pattern made of a silicon thin film layer is a mask having a thickness of 2 μm and a line and space of 260 nm formed therein. An electron beam exposure mask with high accuracy and strength was obtained, in which there was no displacement between the mask pattern and struts, and there was no damage or contamination of the mask.

  A see-through film made of silicon and germanium (weight ratio Si: Ge = 99: 1) was formed by sputtering to a thickness of 200 nm on an 8 inch × 8 inch synthetic quartz substrate as a first light-shielding film by sputtering. Next, a chromium film having a thickness of 70 nm was formed as a second light-shielding film by sputtering. Next, this chromium film was patterned by an ordinary photomask manufacturing method using a photoresist, and a chromium mask having a strut pattern and an alignment pattern was produced.

  Next, a photoresist is applied on the second light-shielding film (chrome film), the plate is made so as to leave only the second light-shielding film of the alignment mark part, and the see-through film is etched using the chromium film as a hard mask, The photoresist was peeled off to produce a photomask in which the strut pattern portion and the alignment mark portion were composed of two layers of light shielding films made of a chromium film and a see-through film. A schematic cross-sectional view of this photomask is shown in FIG.

  Next, an 8-inch SOI substrate similar to that of Example 1 is prepared as an electron beam exposure mask substrate, Cr is sputtered on the silicon thin film layer as a masking material for etching the silicon thin film layer, and a hard mask layer is formed. Formed.

  Subsequently, a resist layer is formed on the Cr hard mask layer on the surface in the same manner as in Example 1, plate-making is performed, Cr is etched based on the resist pattern, the resist is removed, and an alignment pattern on the surface side by Cr And a mask pattern was formed.

  Subsequently, a photoresist was applied to the back side of the SOI substrate, the alignment mark of the photomask was aligned with visible light at a position corresponding to the alignment pattern on the front side, and then exposed to ultraviolet rays. The alignment mark portion of the photomask is covered with a see-through film, and exposure light is shielded. Subsequently, only the strut resist pattern was transferred to the back surface by development.

Next, using the silicon oxide film as an etching stop layer, silicon was dry-etched from the back surface side of the substrate using the etching gas SF ₆ to form struts, and then the photoresist was peeled off.

Next, the silicon oxide film exposed at the opening of the strut was removed by etching using buffered hydrofluoric acid.
Next, using the patterned hard mask layer on the surface side as a mask, the exposed silicon thin film layer was dry-etched to provide an electron beam transmission hole to form a mask pattern, thereby obtaining an electron beam exposure mask.
In this example, there was obtained an electron beam exposure mask with high accuracy and excellent strength, in which there was no displacement between the mask pattern and struts, and there was no damage or contamination of the mask.

Cross-sectional schematic diagram showing an embodiment of a photomask of the present invention used for manufacturing an electron beam exposure mask Cross-sectional schematic diagram showing another embodiment of the photomask of the present invention used for manufacturing an electron beam exposure mask 1 is a schematic cross-sectional view showing a manufacturing process of the photomask of the present invention shown in FIG. FIG. 3 is a schematic cross-sectional view showing the manufacturing process of the photomask of the present invention following FIG. Process sectional drawing which shows the manufacturing method of the mask for electron beam exposure concerning an example of embodiment of this invention Process sectional drawing which shows the manufacturing method of the mask for electron beam exposure concerning the example of embodiment of this invention following FIG. Cross-sectional schematic diagram showing the form of a conventional photomask used in the manufacture of an electron beam exposure mask Process sectional drawing which shows the manufacturing method of the conventional mask for electron beam exposure Process sectional drawing which shows the manufacturing method of the conventional mask for electron beam exposure following FIG. Example of conventional electron beam exposure mask

Explanation of symbols

11, 21 Photomask of the present invention 31, 71 Photomask 12, 22, 72 Transparent substrate 13, 23 First light shielding film 14, 24 Second light shielding film 73 Light shielding film 15, 25, 75 Strut pattern 15a Strut resist Pattern 15b Strut pattern 16, 26, 76 by first light shielding film 16, 26, 76 Alignment mark portion 16a Alignment resist pattern 16b Alignment pattern 34, 55, 85 First light shielding film Photoresist layer 44 Resist pattern 50, 80 SOI substrate 51, 81 Support silicon 52, 82 Silicon thin film layer 53, 83 Silicon oxide film 54, 84 Hard mask layer 54a, 84a Alignment pattern 54b, 84b Mask pattern 55b, 85b Strut resist pattern 56, 7 Ultraviolet exposure 57,87 struts 58,88 electron beam transmission hole 59,89 mask pattern 60,90,100 electron beam exposure mask 85a alignment resist pattern 86 alignment mark portion 101 pattern area 102 membrane mask pattern 103 strut

Claims (4)

In a photomask comprising a transparent substrate and a light shielding film, at least the alignment mark portion is composed of two or more different light shielding films, and an alignment pattern is formed on one layer of the two or more light shielding films of the alignment mark portion. The alignment mark portion shields exposure light. 2. The photomask according to claim 1, wherein one layer of the light shielding film of the alignment mark portion is formed of a film containing chromium as a main component. 3. The photomask according to claim 1, wherein one layer of the light shielding film of the alignment mark portion is a see-through film that transmits alignment light and shields exposure light. 4. 4. The photomask according to claim 1, wherein, in the method for manufacturing a charged particle beam exposure mask, the pattern on the front surface side and the pattern on the back surface side of the charged particle beam exposure mask are aligned. A method for producing a mask for charged particle beam exposure, characterized in that alignment is performed using a mask and exposure is performed.

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