JP2013104960A - Photomask and exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photomask installed on a normal contact exposure apparatus or a proximity exposure apparatus in parallel to an irradiation object body without any necessity of inclining the irradiation object body, and capable of performing diagonal exposure with a plurality of different angles by a single exposure to the irradiation object body.SOLUTION: The photomask emits parallel light that is perpendicular to the photomask and emitted by an exposure apparatus, to an irradiation object body in an inclined manner. The photomask includes a diffraction optical element formed on the irradiation surface side of a transparent substrate, and a pattern of a light transmission part that selectively transmits diffraction light from the diffraction optical element, formed on an emission surface side of the transparent substrate.

Description

  The present invention relates to a photomask for oblique exposure.

  Many electronic parts and optical parts utilizing photolithography technology have been researched and developed in the past. In photolithography, the surface of a substrate (irradiated body) coated with a photoresist is exposed with parallel light through an exposure machine through a photomask to generate a pattern composed of an exposed portion and an unexposed portion. It is a technique, and a surface treatment is applied to a portion where the photoresist is removed after development. Alternatively, the photoresist left after development is used as it is. In general, the end portions of the developed photoresist and the surface-treated substrate pattern are substantially vertical or slightly inclined. However, in recent years, a photolithography technique has been used in which the shape of the end pattern is inclined in a cross-sectional view or a needle-like shape. Such techniques include MEMS, optical waveguide shape fabrication, liquid crystal alignment treatment, and liquid crystal alignment protrusion fabrication. For example, a technique for improving the characteristics of a gallium arsenide field effect transistor by obliquely exposing a substrate is disclosed (Patent Document 2). In addition, a technique is disclosed in which oblique exposure is performed on a mask and a substrate that are aligned in order to form different alignments of alignment films of a liquid crystal display device (Patent Document 6). Furthermore, a technique is disclosed in which oblique exposure is performed on an aligned mask and substrate in order to form a tapered portion on the substrate (Patent Document 8). Other applications of oblique exposure technology include optical waveguides (Patent Document 1), thin film transistors (Patent Document 3), optical diffraction gratings (Patent Document 4), electrodes for plasma display panels (Patent Document 5), and reflective liquid crystal display panels. There are many disclosures such as a reflector having a concavo-convex shape (Patent Document 7) and a micromixer having a concavo-convex shape (Patent Document 9).

JP-A-5-264833 JP-A-6-45363 JP-A-7-226519 Japanese Patent Laid-Open No. 10-10307 JP 2000-30607 A JP 2000-122302 A JP 2001-201619 A JP 2001-235873 A JP 2005-199245 A

  In the oblique exposure technique as described above, the parallel light emitted from the exposure apparatus is irradiated obliquely onto the photomask and the irradiated object. For this reason, it is necessary to install the surface of the emitted light of the exposure apparatus obliquely with respect to the photomask. Therefore, a conventional exposure apparatus that emits parallel light cannot be used as it is, and an apparatus having a new function is required. Further, since the irradiated body is tilted, the irradiation energy varies in the irradiated surface in the large irradiated body. Furthermore, since the irradiated object is irradiated at the same time, only exposure at one angle can be performed. Therefore, when it is desired to form tapered shapes having different angles, it is necessary to expose the same irradiated object a plurality of times.

  The present invention is proposed in view of the above-described problems, and the problem to be solved by the present invention is that there is no need to tilt the irradiated object, and the normal contact exposure apparatus or the proximity exposure apparatus can be connected to the irradiated object. The object is to provide a photomask which can be installed in parallel and can be subjected to oblique exposure at a plurality of different angles with respect to the irradiated object in one exposure.

  As means for solving the above-mentioned problems, the invention according to claim 1 is a photomask that emits parallel light perpendicular to the photomask irradiated from the exposure apparatus while being inclined to the irradiated object, A diffractive optical element is formed on the irradiation surface side of the transparent substrate, and a light transmission portion pattern that selectively transmits diffracted light from the diffractive optical element is formed on the emission surface side of the transparent substrate. It is a photomask.

  The invention according to claim 2 is the photomask according to claim 1, wherein the diffractive optical element includes a diffraction grating.

  The invention according to claim 3 is the photomask according to claim 1 or 2, wherein the diffractive optical element includes a diffractive lens.

  According to a fourth aspect of the present invention, the photomask according to any one of the first to third aspects is obtained by applying a parallel light irradiated perpendicularly from a light source of an exposure apparatus to a photomask on a substrate. It is an exposure method characterized in that it is emitted obliquely to the irradiated object that has been aligned and subjected to oblique exposure.

  The invention according to claim 5 is characterized in that the photoresist is of a negative type, and by developing after exposure, a tapered needle stand and an oblique three-dimensional shape can be formed. The exposure method described.

  According to a sixth aspect of the present invention, the photoresist is a positive type, and by developing after the exposure, a hole having a tapered shape dug in a diagonal direction can be formed. Exposure method.

  In the present invention, the diffractive optical element is formed on the irradiation surface side of the transparent substrate, and the light transmitting portion pattern that selectively transmits the diffracted light from the diffractive optical element is formed on the emission surface side of the transparent substrate. As a result, a photomask having a structure in which parallel light perpendicular to the photomask irradiated from the exposure apparatus is emitted to be tilted to the irradiated body can be obtained. There is no need to tilt the mask. Therefore, even if it is a big to-be-irradiated body, it is hard to produce the variation of irradiation energy. In addition, it is possible to provide a photomask that can be installed in a normal contact exposure apparatus or a proximity exposure apparatus and can perform oblique exposure at a plurality of different angles on an irradiated object in one exposure.

It is explanatory drawing which showed the 1st example of the photomask of this invention, and the exposure process using the same in the cross section. It is explanatory drawing which showed the 2nd example of the photomask of this invention, and the exposure process using the same in the cross section. It is explanatory drawing which showed the 3rd example of the photomask of this invention, and the exposure process using the same in the cross section. It is explanatory drawing which showed the 4th example of the photomask of this invention, and the exposure process using the same in the cross section. It is explanatory drawing which showed the 5th example of the photomask of this invention, and the exposure process using the same in the cross section. It is explanatory drawing which showed the 6th example of the photomask of this invention, and the exposure process using the same in the cross section.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view showing, in section, a first example of the photomask of the present invention and an exposure process using the photomask.
The photomask of the present invention is a photomask 1 that emits parallel light 2 perpendicular to a photomask irradiated from an exposure apparatus (not shown) while being tilted toward an irradiated body 3, and an irradiation surface of a transparent substrate 10. The diffractive optical element 11 is formed on the side, and the pattern of the light transmitting portion 12 that selectively transmits the diffracted light 23 from the diffractive optical element 11 is formed on the emission surface side of the transparent substrate 10. . The irradiation surface refers to the surface irradiated with the parallel light 2 on the upper side of the transparent substrate in the figure, and the emission surface refers to the surface from which the diffracted light 23 on the lower side of the transparent substrate in the figure exits. It is the same.

  The diffractive optical element 11 in this example is a diffraction grating, and the diffraction angle depending on the wavelength is determined from the irradiated parallel light 2 corresponding to the grating period, and multi-order diffracted light 21, 22, 23 is emitted. The light transmission part 12 provided on the light emission surface side of the transparent substrate 10 can be selectively provided by pattern formation of the light shielding film 13, and selectively transmits only the diffracted light 23 having a certain angle in the diffracted light. Thus, the irradiated object 3 can be exposed. On the other hand, other diffracted lights 21 and 22 having an angle different from that of the diffracted light 23 can be shielded by the light shielding film 13 on the exit surface side. Further, in this example, by providing the light shielding film 14 in addition to the diffraction grating 11 on the irradiation surface side, the parallel light 2 that is linearly irradiated can be appropriately shielded first on the irradiation surface side, and the irradiated object 3 It is possible to limit the light emitted toward the light to only the light in the oblique direction by the diffracted light 23.

  In the exposure method of the present invention, the light beam (not shown) of the exposure apparatus is aligned with the photomask 1 by applying the parallel light 2 irradiated onto the above-described photomask 1 perpendicularly to the photoresist 30 on the substrate 30. The oblique exposure that is emission including light in an oblique direction is performed on the irradiated object 3. Adhesion exposure that does not provide a gap between the photomask 1 and the irradiated object 3 during exposure, or proximity exposure that provides a fine gap of 70 μm to 300 μm as the gap can be applied as the exposure method of the present invention. The same applies to other examples. The photoresist 31 in this example is a negative type, that is, a photosensitive resin in which the exposed region is photocured, and the exposed portion becomes a tapered needle-like or oblique three-dimensional shape after the development process. Portions 32 can be formed.

Next, the elements constituting the photomask of the present invention will be described in detail.
The photomask of the present invention can be manufactured using a conventional photolithography technique. The details of the components together with the manufacturing method are exemplified below.

  A pattern of the light transmitting portion 12 is formed on one surface of the transparent substrate 10 by the same method as the conventional photomask manufacturing method. As the transparent substrate, transparent glass can be used, but quartz glass having a low coefficient of thermal expansion and excellent light transmittance in the near ultraviolet region, which is a photosensitive region of a photoresist, is more preferable. In order to form the pattern of the light transmission portion 12, a light shielding film 13 made of, for example, a metal such as chromium is formed on the surface of the transparent substrate with a sufficient light shielding property by a thin and uniform vacuum film formation method. Is applied, and a pattern is drawn with a drawing device, developed, and after etching the metal film using the patterned resist as an etching resist, an unnecessary resist is peeled off.

Next, the diffraction grating 11 is formed on the other side of the transparent substrate 10. The diffraction grating is a light shielding film 1
When the pattern formation of 4 is performed by the same method as the pattern formation of the light shielding film 13, the light shielding film pattern blocks can be arranged in a strip-like slit shape and simultaneously formed with the pattern of the light shielding film 14. However, a diffraction grating that uses a light-shielding film reduces the intensity of diffracted light due to light absorption attenuation. Therefore, aside from manufacturing convenience, a type that does not involve light attenuation and has a higher diffraction efficiency is more suitable. desirable. If the types of diffraction gratings are roughly classified, a relief type consisting of fine irregularities on the surface and a volume type which provides a phase difference by forming a difference in refractive index in the thickness direction depending on the plane position are possible. Among them, the method of forming the groove shape directly on the glass surface of the transparent substrate 10 in a relief type or controlling the shape so that the coated photosensitive resin has a rectangular wave shape or a sawtooth shape as a cross section, This is preferable because it can be easily manufactured using a conventional photolithography method. Furthermore, it is possible to protect the surface of the photomask and increase the strength by surface processing based on the relief shape.

  In manufacturing the photomask 1 of the present invention, in order to form a pattern on both sides of the transparent substrate 10, according to the thickness of the transparent substrate 10 and the inclination angle of the diffracted light 23 to be used, It is necessary to design the alignment state. In addition, it is important to use an exposure machine having an alignment mechanism suitable for front and back positioning. Note that the order of forming the patterns on both sides is not limited to the above description, and the reverse order is possible, and simultaneous formation is also possible in some cases, and the same applies to other examples after the second example described later. is there.

FIG. 2 is a cross-sectional view illustrating a second example of the photomask of the present invention and an exposure process using the photomask.
In this example, the photomask 1 is the same as the first example described above. In the exposure method of this example, the parallel light 2 irradiated perpendicularly to the above-described photomask 1 from a light source (not shown) of an exposure apparatus is coated on the substrate 30 with a photoresist 33 and aligned with the photomask 1. The oblique exposure that is emission including light in an oblique direction is performed on the irradiated object 3. The photoresist 33 in this example is a positive type, that is, a photosensitive resin in which an exposed region is photodecomposed, and the exposed portion forms a hole 34 having a tapered shape that is dug down in a diagonal direction after the development process. can do.

FIG. 3 is a cross-sectional view illustrating a third example of the photomask of the present invention and an exposure process using the photomask.
In this example, the diffractive optical element 11 provided on the irradiation surface side is the same as the diffraction grating 11 of the first example and the second example described above, and the multi-order diffracted lights 21, 22 having different diffraction angles, 23, and the subsequent behavior is the same as in the first and second examples described above. That is, the light transmitting portion 12 provided on the light exit surface side of the transparent substrate 10 can be selectively provided by pattern formation of the light shielding film 13, and the diffracted light 23 having a certain angle among the diffracted light is selectively selected. The irradiated object 3 can be exposed through the light, but the other diffracted lights 21 and 22 are shielded by the light shielding film 13 on the exit surface side.
On the other hand, in this example, unlike the above-described first and second examples, the photomask 1 is perpendicular to the photomask 1 without providing the light shielding film 14 in addition to the diffraction grating 11 on the irradiation surface side. A part of the parallel light 2 irradiated in a straight line is incident as it is, and light emitted perpendicularly toward the irradiated body 3 through the opening pattern of the light shielding film 13 on the emission surface side shown in the light transmission part 12 is diffracted. It becomes possible to add to the light in the oblique direction by the light 23.

In the exposure method of the present invention using the photomask of the third example, parallel light 2 irradiated perpendicularly to the above-described photomask 1 from a light source (not shown) of an exposure apparatus is applied onto the substrate 30 with a photoresist 31. Is applied to the irradiated object 3 aligned with the photomask 1, and exposure including oblique exposure and vertical exposure is performed. That is, in the drawing, the photoresist 31 is irradiated with light in the directions indicated by the two types of block arrows that pass through the light transmitting portion 12. The photoresist 31 in this example is a negative type, that is, a photosensitive resin in which the exposed region is photocured, and the exposed portion becomes a tapered needle-like or oblique three-dimensional shape after the development process. Portions 35 can be formed.

FIG. 4 is an explanatory view showing, in section, a fourth example of the photomask of the present invention and an exposure process using the photomask.
In this example, the photomask 1 is the same as the third example described above. In the exposure method of this example, the parallel light 2 irradiated perpendicularly to the above-described photomask 1 from a light source (not shown) of an exposure apparatus is coated on the substrate 30 with a photoresist 33 and aligned with the photomask 1. The light is emitted to the irradiated body 3 and exposure including oblique exposure and vertical exposure is performed. That is, in the drawing, the photoresist 33 is irradiated with light in the directions indicated by the two types of block arrows passing through the light transmitting portion 12. The photoresist 33 in this example is a positive type, that is, a photosensitive resin in which an exposed region is photodecomposed, and the exposed portion forms a tapered hole 36 that is dug down in an oblique direction after the development process. can do.

FIG. 5 is a cross-sectional view illustrating a fifth example of the photomask of the present invention and an exposure process using the photomask.
In this example, the diffractive optical element 11 provided on the irradiation surface side is the same as the diffraction grating 11 of the first to fourth examples described above, and the multiple-order diffracted light beams 21, 22 having different diffraction angles. 23 and the subsequent behavior is the same as in the first to fourth examples described above. That is, the light transmitting portion 12 provided on the light exit surface side of the transparent substrate 10 can be selectively provided by pattern formation of the light shielding film 13, and the diffracted light 23 having a certain angle among the diffracted light is selectively selected. The irradiated object 3 can be exposed through the light, but the other diffracted lights 21 and 22 are shielded by the light shielding film 13 on the exit surface side.
On the other hand, in this example, the photomask 1 is provided with the light shielding film 14 in addition to the diffraction grating 11 on the irradiation surface side, unlike the third example and the fourth example described above, but the first example described above. And the opening pattern of the light shielding film 13 on the exit surface side is widened in a shape different from that of the second example, and the light transmitting portion 12 is provided as shown in the figure. By forming the above-described structure on the photomask, the parallel light 2 that is perpendicularly irradiated to the photomask 1 perpendicularly to the parallel light 2 incident on the diffractive optical element 11 is separated from the parallel light 2 by a certain distance. A part of the light is incident as it is, and the light emitted perpendicularly toward the irradiated body 3 through the opening pattern of the light shielding film 13 on the light emitting surface side shown in the light transmission part 12 is added to the light in the oblique direction by the diffracted light 23. It becomes possible to do.

  In the exposure method of the present invention using the photomask of the fifth example, parallel light 2 irradiated perpendicularly to the above-mentioned photomask 1 from a light source (not shown) of an exposure apparatus is applied onto the substrate 30 with a photoresist 31. Is applied to the irradiated object 3 aligned with the photomask 1, and exposure including oblique exposure and vertical exposure is performed. That is, in the drawing, the photoresist 31 is irradiated with light in the directions indicated by the two types of block arrows that pass through the light transmitting portion 12. The photoresist 31 in this example is a negative type, that is, a photosensitive resin in which the exposed region is photocured, and the exposed portion becomes a tapered needle-like or oblique three-dimensional shape after the development process. Portions 37 can be formed.

FIG. 6 is an explanatory view showing, in section, a sixth example of the photomask of the present invention and an exposure process using the photomask.
The diffractive optical element 15 of the photomask 1 in this example is a diffractive lens. For example, a relief type diffractive lens in which a fine relief shape whose depth is about the wavelength of light is arranged in a plane as a plurality of concentric patterns, or light transmission. Optical elements that use diffracted light, such as an amplitude-type diffractive lens whose ratio is periodically changed concentrically and a planar Fresnel zone plate in which transmission regions and light-shielding regions are simply arranged concentrically, are used. It is provided on the irradiation surface side of the transparent substrate 10.
In addition, the pattern of the light transmitting portion 12 that selectively transmits the diffracted light 24 from the diffractive lens 15 is formed as the opening pattern of the light shielding film 13 on the emission surface side of the transparent substrate 10. In other examples, the light transmission unit 12 selectively transmits the diffracted light 23 from the diffraction grating 11.

The exposure method of this example is aligned with the photomask 1 by applying a photoresist 31 on the substrate 30 with the parallel light 2 irradiated perpendicularly to the photomask 1 from a light source (not shown) of an exposure apparatus. The oblique exposure that is emission including light in an oblique direction is performed on the irradiated object 3.
The photoresist 31 in this example is a negative type, that is, a photosensitive resin in which the exposed region is photocured, and the exposed portion becomes a tapered needle-like or oblique three-dimensional shape after the development process. Portion 38 can be formed.

Next, the elements constituting the photomask in this example will be described in detail.
A pattern of the light transmitting portion 12 is formed on one surface of the transparent substrate 10 by the same method as the conventional photomask manufacturing method. As the transparent substrate, transparent glass can be used, but quartz glass having a low coefficient of thermal expansion and excellent light transmittance in the near ultraviolet region, which is a photosensitive region of a photoresist, is more preferable. In order to form the pattern of the light transmission portion 12, a light shielding film 13 made of, for example, a metal such as chromium is formed on the surface of the transparent substrate with a sufficient light shielding property by a thin and uniform vacuum film formation method. Is applied, and a pattern is drawn with a drawing device, developed, and after etching the metal film using the patterned resist as an etching resist, an unnecessary resist is peeled off.

  Next, the diffraction lens 15 is formed on the other side of the transparent substrate 10. The case where a Fresnel zone plate is formed as the diffractive lens 15 will be described. The pattern formation of the light shielding film can be performed by a method using a photolithography method in the same manner as the pattern formation of the light shielding film 13. In the photomask manufacturing process of this example, a transmission region and a light shielding region, which were designed in advance in consideration of the thickness of the transparent substrate 10, the wavelength of exposure light when using the photomask, and the exposure gap, were repeatedly arranged concentrically. The Fresnel zone plate pattern can be accurately aligned with the pattern of the light transmitting portion 12 on the opposite surface, that is, the opening pattern of the light shielding film 13.

  In the present invention, the diffractive optical element provided on the irradiation surface side of the transparent substrate 10 constituting the photomask 1 can use the diffraction grating 11 or the diffractive lens 15, but the diffractive grating 11 and the diffractive lens 15 are used together. It is also possible to do. In either case, the pattern of the light transmitting portion 12 that selectively transmits the diffracted light from the diffractive optical element and the pattern of the light shielding film 13 that shields light are formed on the exit surface side of the transparent substrate. On the other hand, as exemplified in the first example, the second example, and the fifth example, the pattern of the light shielding film 14 is appropriately provided on the irradiation surface side of the transparent substrate in combination with various diffractive optical elements. Can do. The shape and arrangement of each pattern constituting the photomask is arbitrarily designed and manufactured in accordance with the pattern shape and arrangement to be finally obtained of the photoresists 31 and 33 formed on the irradiated body 3. The

DESCRIPTION OF SYMBOLS 1 ... Photomask 2 ... Irradiation parallel light 3 ... Subject 10 ... Transparent substrate 11 ... Diffractive optical element (diffraction grating)
12 ... light transmission part 13 ... light shielding film (outgoing surface side)
14 ... Light-shielding film (irradiated surface side)
15 ... Diffraction optical element (diffractive lens)
21, 22, 23 ... diffracted light 24 ... diffracted light 30 ... substrate 31 ... photoresist (negative type)
32, 35, 37, 38 ... 3D shaped part 33 ... Photoresist (positive type)
34, 36 ... portions to be holes

Claims (6)

  A photomask that emits parallel light perpendicular to a photomask irradiated from an exposure apparatus while being tilted toward an irradiated object, and a diffractive optical element is formed on the irradiation surface side of the transparent substrate, and the emission surface of the transparent substrate A photomask, wherein a pattern of a light transmitting portion that selectively transmits diffracted light from a diffractive optical element is formed on the side.   The photomask according to claim 1, wherein the diffractive optical element includes a diffraction grating.   The photomask according to claim 1, wherein the diffractive optical element includes a diffractive lens.   Parallel light irradiated perpendicularly to the photomask according to any one of claims 1 to 3 from a light source of an exposure apparatus is emitted to an irradiated object that is coated with a photoresist on a substrate and aligned with the photomask. An exposure method comprising performing oblique exposure.   5. The exposure method according to claim 4, wherein the photoresist is of a negative type and can be formed into a three-dimensional shape having a tapered needle or an oblique shape by developing after exposure.   5. The exposure method according to claim 4, wherein the photoresist is of a positive type, and a hole having a shape dug in a diagonal direction having a taper can be formed by developing after exposure.

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