JP2005056981A - Exposure mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the breakage of an exposure mask due to adhesion to a photosensitive material or the breakage of the photosensitive material when the exposure mask is peeled from the photosensitive material such as a photo resist or the like. <P>SOLUTION: The exposure mask 14 is formed of a light shielding metallic film 21 that is provided with an opening 21a with a specified pattern and is formed on a transparent substrate 20, and it is used to expose a photosensitive material by a light given through the metallic film from the side of the transparent substrate 20 in a state where the metallic film 21 is adhered to the photosensitive material. The surface of the metallic film 21 adhered to the photosensitive material is coated with a hydrophilic film 22, thereby improving peeling property between the exposure mask 14 and the photosensitive material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure mask for exposing a photosensitive material such as a photoresist to a predetermined pattern.

The development of optical lithography technology has been supported mainly by advances in reduction projection exposure technology and resist technology. The performance of the reduction projection exposure technique is mainly determined by two basic quantities of resolution RP and depth of focus DOP. When the exposure wavelength of the projection optical system is λ and the numerical aperture of the projection lens is NA, the above two basic quantities are RP = k ₁ λ / NA and DOP = k ₂ λ / NA ² (k ₁ and k ₂ are coefficients. ). In order to increase the resolution of lithography, it is important to reduce the wavelength λ and increase the numerical aperture NA of the projection lens. However, when the NA is increased, the resolution increases, but the depth of focus decreases in inverse proportion to the square of NA. Therefore, as a trend of miniaturization, it is required to decrease the wavelength λ. Therefore, the exposure light is shortened from the g-line having a wavelength of 436 nm to the i-line having a wavelength of 365 nm, and at present, excimer laser beams having wavelengths of 248 nm and 193 nm are mainly used.

  However, in lithography using light, the diffraction limit of exposure light becomes the limit of resolution. Therefore, when a lens array optical system is used, even if an excimer laser beam with a wavelength of 248 nm or 193 nm is used, the line width is reduced to 100 nm. It is said to be the limit. Furthermore, if it is going to obtain | require the resolution of the nanometer order ahead of that, it is necessary to use the electron beam and X-ray (especially SOR light: synchrotron radiation light) lithography technique.

  Electron beam lithography can form a pattern on the order of nanometers with high precision and has a considerably deeper depth of focus than lithography using an optical system. In addition, there is an advantage that direct writing can be performed on a wafer without a mask, but there is a disadvantage that it is far from mass production because of low throughput and high cost.

  On the other hand, X-ray lithography achieves resolution and accuracy that is about an order of magnitude higher than that of excimer laser exposure, both in the case of 1: 1 exposure with a one-to-one mask and in the case of using a reflective imaging X-ray optical system. it can. However, this X-ray lithography has a problem that it is difficult to produce a mask and it is difficult to realize it, and the cost of an apparatus to be used is high.

As a method for solving the above-described problems, recently, exposure light having a pattern having an opening smaller than the wavelength of the exposure light is irradiated with the exposure light, and at that time, the near-field light oozing out from the opening of the exposure mask is used for photo A method of exposing a photosensitive material such as a resist has been proposed. According to this method, it is possible to form a fine pattern having the size of the opening regardless of the wavelength of the exposure light. Patent Document 1 shows an example of an exposure apparatus that uses this near-field light.
Japanese Unexamined Patent Publication No. 2000-112116

  In the above-described exposure apparatus using near-field light, an exposure mask in which a light-shielding metal film having a predetermined pattern of openings is formed on a transparent substrate is generally used. The exposure mask is disposed in a state where the metal film side is in close contact with the photoresist, and in this state, the photosensitive material is exposed to light irradiated through the metal film from the transparent substrate side.

  In the conventional exposure mask that is used in close contact with the photoresist in this way, when peeling from the photoresist after the exposure is completed, a part of the metal film remains attached to the photoresist, and the exposure mask becomes There is a problem that it is damaged or, conversely, the photoresist attached to the metal film is peeled off and damaged from the substrate side.

  The above-mentioned problem is conspicuously recognized in the near-field light exposure apparatus in which the exposure mask and the photoresist are firmly adhered using a negative pressure or the like, but not limited to this, an exposure apparatus using general propagation light Is also recognized in the same way. The above-mentioned problem is similarly recognized in an exposure apparatus that exposes a photosensitive material other than photoresist.

  The present invention has been made in view of the above circumstances, and is an exposure mask that does not adhere to the photosensitive material when it is peeled off from the photosensitive material such as a photoresist, or damage itself. The purpose is to provide.

  As described above, the exposure mask according to the present invention has a light-shielding metal film having a predetermined pattern of openings formed on a transparent substrate, and the metal substrate side is in close contact with a photosensitive material such as a photoresist. In an exposure mask used for exposing a photosensitive material with light irradiated through the metal film from the side, the surface of the metal film that is in close contact with the photosensitive material is subjected to a surface treatment that improves releasability from the photosensitive material. It is characterized by that. Here, “surface treatment for improving releasability” refers to a surface treatment in which releasability is better than when the metal film is in direct contact with the photosensitive material.

  Specifically, as the above-described surface treatment, for example, a treatment for coating a hydrophilic film can be applied. More specifically, as such a hydrophilic film, a film made of a molecular film having a structure in which a hydrophilic group is exposed on the surface opposite to the side in contact with the metal film can be applied. In addition, the molecular film having a structure in which the hydrophilic group is exposed in this manner is desirably formed from a self-assembled monomolecular film.

  On the other hand, the thickness of the hydrophilic film is desirably 10 nm or less, particularly when the exposure mask is used for near-field light exposure.

  In addition, as the surface treatment, a treatment for coating an oil repellent / water repellent film can be applied. More specifically, a film made of a fluorine-based molecular film can be applied as such an oil / water repellent film. Further, the surface energy of the oil / water repellent film is generally preferably 15 dyne / cm or less.

  The film thickness of the oil repellent / water repellent film as described above is also desirably 10 nm or less particularly in an exposure mask used for near-field light exposure.

  Further, as the above-described surface treatment, it is also possible to apply a treatment for entirely etching the surface of the metal film.

  The exposure mask according to the present invention is particularly preferably used for near-field light exposure.

  In the exposure mask according to the present invention, the surface of a metal film that is in close contact with a photosensitive material such as a photoresist is subjected to a surface treatment for improving the peelability from the photosensitive material. When peeling from the material, the film is peeled well from the photosensitive material. Therefore, according to this exposure mask, a part of the metal film remains attached to the photoresist and the exposure mask itself is damaged, or the photoresist attached to the metal film is peeled off from the substrate side. The problem of breakage can be prevented.

  Therefore, according to the present invention, the handleability of the exposure mask is improved and the durability can be improved.

  If the film thickness of the hydrophilic film or oil / water repellent film coated on the surface of the metal film is set to 10 nm or less as the surface treatment, the exposure mask is used for the above-mentioned near-field light exposure. Good exposure is realized. That is, the range of the near-field light that oozes out from the opening of the metal film is generally about several tens of nm or less. Therefore, if the film thickness is 10 nm or less, the near-field light sufficiently reaches the photosensitive material. It will be.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a near-field light exposure apparatus using an exposure mask 14 according to the first embodiment of the present invention. Here, the side shape of the exposure apparatus is partially broken. As shown in the drawing, this exposure apparatus accommodates the substrate 10 having the front surface 10a coated with the photoresist 11 in close contact with the back surface 10b side and the exposure table 12 inside. An exposure light source 16 for irradiating the photoresist 11 with exposure light 15 through a substantially cylindrical photomask holding member 13 disposed in the photomask and an exposure mask (photomask) 14 held on the photomask holding member 13 And.

  As the exposure light source 16, a light source that emits unpolarized exposure light 15 having a wavelength of approximately 400 nm or more, such as g-line (wavelength 436 nm), is used. The exposure mask 14 is formed by forming a light-shielding metal film 21 having a predetermined pattern of openings 21 a on a transparent substrate 20. In particular, the exposure mask 14 of the present embodiment is such that the width of the opening 21a is smaller than the wavelength of the exposure light 15, and the near-field light oozes from the opening 21a when the exposure light 15 is irradiated. It is a mask for light exposure. The metal film 21 is made of a metal such as Cr, Ta, Ag, or Au.

  The upper surface of the exposure table 12 is a substrate holding surface 12a that holds the substrate 10 in close contact. The exposure table 12 is formed with a plurality of exhaust passages 12b penetrating up and down the exposure table 12 and opening at a plurality of positions and a center position of the peripheral edge of the substrate holding surface 12a.

  A seal member 17 is interposed between the exposure table 12 and the exposure mask holding member 13 over the entire circumference of the exposure table 12, and the space between the exposure table 12 and the exposure mask holding member 13 is the seal member. It is divided into 17 top and bottom. The exposure mask holding member 13 is formed with an exhaust passage 13b penetrating the exposure mask holding member 13 laterally at a position above the seal member 17.

  The exhaust passage 13b and the plurality of exhaust passages 12b of the exposure table 12 are connected to an air suction means 19 such as a vacuum pump through a pipe 18. The air suction means 19 together with the pipe 18 and the exposure mask holding member 13 constitute means for pressing the exposure mask 14 against the photoresist 11 on the substrate 10 held on the exposure table 12 so as to be in close contact therewith.

  Next, the operation of this exposure apparatus will be described. The substrate 10 having the front surface 10a coated with the photoresist 11 is placed on the exposure table 12 with the back surface 10b in contact with the substrate holding surface 12a. On the exposure mask holding member 13, the exposure mask 14 having the opening pattern as described above is placed. FIG. 1 shows the above state.

  Thereafter, when the air suction means 19 is driven, air is sucked from the plurality of exhaust passages 12b of the exposure table 12, and the inside thereof is evacuated, so that the substrate 10 becomes the substrate of the exposure table 12 as shown in FIG. It is closely held on the holding surface 12a. At the same time, air is sucked from the exhaust passage 13b of the exposure mask holding member 13, and the space defined in the exposure mask holding member 13 below the exposure mask 14 is also evacuated. 14 bends downward and comes into close contact with the photoresist 11 on the substrate 10.

  In this state, the exposure light source 16 is driven to irradiate the photoresist 11 with the exposure light 15 through the exposure mask 14 (specifically, through the opening 21a of the metal film 21 from the transparent substrate 20). 11 is exposed. That is, the near-field light oozes out from the opening 21a having a width smaller than the wavelength of the exposure light 15, and a fine pattern composed of these openings 21a is transferred and exposed to the photoresist 11.

  Photoresist 11 is a positive resist in which only a portion irradiated with near-field light is soluble in a predetermined developer solution, or a negative type in which only a non-irradiated portion of near-field light is soluble in a predetermined developer solution Any of resists may be used. Then, after the exposure, the photoresist 11 is developed, and the remaining photoresist 11 is used to perform an appropriate etching process on the substrate 10, thereby forming a concavo-convex pattern according to the pattern on the substrate 10. . As the photoresist 11, for example, a two-layer resist disclosed in Japanese Patent Application Laid-Open No. 2001-15427 can be used in addition to a normal photoresist composed of one layer.

  Next, the exposure mask 14 will be described in detail with reference to FIG. As shown in the schematic side view here, in the exposure mask 14, a hydrophilic film 22 is coated on the surface portion of the metal film 21 that is in close contact with the photoresist 11. The hydrophilic film 22 is formed of, for example, a self-assembled monomolecular film (SAM), and as shown in an enlarged view of the part a in the figure, a molecular film 22a composed of a carbon chain, a benzene ring, etc. It is composed of an adsorption group 22b such as SH that adsorbs the molecular film 22a to the metal film 21, and a hydrophilic group 22c such as OH formed on the surface side of the molecular film 22a. In the present embodiment, the hydrophilic film 22 has a thickness of 10 nm or less. In FIG. 1 and FIG. 2, the hydrophilic film 22 is omitted.

  As described above, by providing the hydrophilic film 22 having a structure in which the hydrophilic group 22c is exposed on the surface opposite to the side in contact with the metal film 21, the releasability of the exposure mask 14 from the photoresist 11 is improved. This is better than when the metal film 21 is in direct contact with the photoresist 11. Therefore, when the exposure mask 14 is peeled off from the photoresist 11 after exposure, a part of the metal film 21 remains adhered to the photoresist 11 and the exposure mask itself is damaged, or the metal film 21 The problem that the attached photoresist 11 is peeled off from the substrate 10 and is damaged can be prevented. Therefore, the handling property of the exposure mask 14 is improved, and the durability is improved.

  The range of near-field light that oozes from the opening 21a of the metal film 21 is generally about several tens of nm or less. However, in the present embodiment, the hydrophilic film 22 has a thickness of 10 nm or less. The field light reaches the photoresist 11 sufficiently, and good exposure becomes possible.

  Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, the same elements as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted unless particularly necessary.

FIG. 4 shows a schematic side surface shape of the exposure mask 34 according to the second embodiment of the present invention. In this exposure mask 34, the surface portion of the metal film 21 that is in close contact with the photoresist 11 is coated with an oil / water repellent film 32. The oil / water repellent film 32 is shown by enlarging the portion b in the figure. The oil / water repellent film 32 is made of a molecular film having, for example, a — (CF ₂ ) _n —CF ₃ group, and has a thickness of 10 nm or less.

  As described above, since the oil repellent / water repellent film 32 is provided on the surface of the metal film 21, the releasability of the exposure mask 34 from the photoresist 11 is such that the metal film 21 directly adheres to the photoresist 11. Improve than the case. Therefore, when the exposure mask 34 is peeled off from the photoresist 11 after exposure, a part of the metal film 21 remains adhered to the photoresist 11 and the exposure mask itself is damaged, or the metal film 21 The problem that the attached photoresist 11 is peeled off from the substrate 10 and is damaged can be prevented. Therefore, the handling properties of the exposure mask 34 are improved and the durability is improved.

  Also in this embodiment, since the film thickness of the oil / water repellent film 32 is 10 nm or less, the near-field light reaches the photoresist 11 sufficiently, and good exposure is possible.

  In general, if the oil / water-repellent film 32 is formed with a surface energy of 15 dyne / cm or less, the exposure mask 34 can be provided with a sufficient oil / water-repellent function.

  As described above, the embodiment in which the present invention is applied to the exposure mask used for exposing the photoresist with the near-field light has been described. However, the present invention is not limited to an exposure apparatus using general propagation light, or other than the photoresist. Even when applied to an exposure mask used in an exposure apparatus that exposes a photosensitive material, the same effects as described above can be obtained. However, in the near-field light exposure apparatus in which the exposure mask and the photoresist are firmly adhered using a negative pressure or the like, the exposure mask and the photoresist are particularly difficult to peel off. If the present invention is applied to an exposure mask used for the above, it is more effective.

The partially broken side view which shows the exposure mask by the 1st Embodiment of this invention, and the near-field light exposure apparatus using the same The partially broken side view which shows another state of the exposure apparatus of FIG. Schematic side view of the exposure mask according to the first embodiment Schematic side view of an exposure mask according to the second embodiment of the present invention

Explanation of symbols

10 Board
11 photoresist
12 Exposure stand
12a Substrate holding surface of exposure table
13 Exposure mask holding member
14, 34 Exposure mask
15 Exposure light
16 Exposure light source
17 Seal member
18 Piping
19 Air suction means
20 Transparent substrate
21 Metal film
21a Metal film opening
22 Hydrophilic membrane
32 Oil and water repellent film

Claims (11)

A light-shielding metal film having a predetermined pattern of openings is formed on a transparent substrate,
In an exposure mask used for exposing the photosensitive material with light irradiated through the metal film from the transparent substrate side in a state where the metal film side is in close contact with the photosensitive material,
An exposure mask, wherein the surface of the metal film in close contact with the photosensitive material is subjected to a surface treatment for improving the peelability from the photosensitive material.   The exposure mask according to claim 1, wherein the surface treatment is a treatment for coating a hydrophilic film.   3. The exposure mask according to claim 2, wherein the hydrophilic film is a molecular film having a structure in which a hydrophilic group is exposed on a surface opposite to a side in contact with the metal film.   4. The exposure mask according to claim 3, wherein the hydrophilic film is formed of a self-assembled monomolecular film.   The exposure mask according to any one of claims 1 to 4, wherein the hydrophilic film has a thickness of 10 nm or less.   2. The exposure mask according to claim 1, wherein the surface treatment is a treatment for coating an oil-repellent / water-repellent film.   7. The exposure mask according to claim 6, wherein the oil / water repellent film is made of a fluorine-based molecular film.   8. The exposure mask according to claim 6, wherein the oil / water repellent film has a surface energy of 15 dyne / cm or less.   9. The exposure mask according to claim 6, wherein the oil repellent / water repellent film has a thickness of 10 nm or less.   2. The exposure mask according to claim 1, wherein the surface treatment is a treatment of plasma etching the entire surface of the metal film.   The exposure mask according to claim 1, wherein the exposure mask is used for near-field light exposure.

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