JP2006339359A - Method of manufacturing fine structure, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely select an arbitrary portion and microfabricate that portion in the order shorter than the wavelength of visible light while reducing a manufacturing cost. <P>SOLUTION: The method of manufacturing a fine structure comprises a photosensitive film formation process wherein a photosensitive film (103) is formed on a substrate (100); a first exposure process wherein two laser beams (B1 and B2) having a wavelength shorter than that of visible light are made to cross each other to generate interference light, and the interference light is irradiated on the photosensitive film to expose it; a second exposure process wherein light is irradiated (B4) selectively on a predetermined region within a region irradiated with the interference light, to further expose the photosensitive film; and a development process wherein the photosensitive film is developed to express a shape corresponding to the pattern of the interference light on the photosensitive film in the predetermined region which was exposed by the second exposure process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for realizing a fine concavo-convex pattern on the order of a wavelength smaller than the wavelength in the visible light region on a substrate such as glass.

  In recent years, for example, there is an increasing demand for miniaturization in various devices such as optical elements such as polarizing elements and antireflection elements, or semiconductor elements such as transistors, and the like with an order smaller than the visible light wavelength (for example, 100 nm or less). Technological development is underway to achieve fine processing. As means for producing such a sub-wavelength order fine pattern, for example, an exposure method using a stepper or electron beam drawing is known. Recently, a lithography technique using X-rays having a wavelength shorter than that of ultraviolet rays has been proposed (see, for example, Non-Patent Documents 1 and 2).

“Applied Physics”, Japan Society of Applied Physics, 2004, Vol. 73, No. 4, p. 455-461 "Si-based Photonic Crystals and Photonic-Band-Gap Waveguides" M. Notomi et al., Proc. SPIE Vol. 4655, pp. 92-104

  Although the above-described conventional technology can achieve fine processing, both the process margin and the throughput are low, and there is a disadvantage that it is not suitable for mass production. In particular, it has been difficult to reconcile the conflicting demands of precisely selecting an arbitrary position of the object to be processed and performing fine processing and reducing manufacturing costs.

  Therefore, an object of the present invention is to provide a technique that enables an arbitrary position to be accurately selected and fine processing on an order shorter than the visible light wavelength can be performed while reducing the manufacturing cost.

  In the first aspect of the present invention, a photosensitive film forming step of forming a photosensitive film on a substrate and two laser beams having a wavelength shorter than the visible light wavelength are crossed to generate interference light. A first exposure step of exposing the photosensitive film by irradiating with interference light, and selectively irradiating a predetermined area in the irradiation target area with the interference light, thereby making the photosensitive film Further, a second exposure step for exposure and the photosensitive film are developed, and a shape corresponding to the pattern of the interference light is developed on the photosensitive film in the predetermined region exposed in the second exposure step. And a development step. Note that the order of the first exposure step and the second exposure step may be interchanged.

  Here, in this specification, “wavelength shorter than visible light wavelength” means a wavelength of approximately 300 nm or less. The “base material” may correspond to a substrate made of various materials (metal, glass, resin, etc.) and other members.

  By crossing the two laser beams at a certain angle, interference light having a light-dark pattern (interference fringes) having a pitch similar to or less than the wavelength of the laser beam can be obtained. More specifically, the pitch of the interference light can theoretically be achieved up to about ½ of the wavelength of each laser beam. By performing the first exposure step using such interference light, it is possible to form a latent image pattern having an order shorter than the visible light wavelength on the photosensitive film while reducing the manufacturing cost. Moreover, the exposure pattern by an interference light can be sharpened in the desired position of a photosensitive film | membrane by the exposure in a 2nd exposure process. Accordingly, it is possible to select an arbitrary position with high accuracy and perform fine processing on the order shorter than the visible light wavelength.

  The above-described photosensitive film after development can be used as a fine structure itself, but it is also preferable to use the photosensitive film as an etching mask. That is, it is preferable to further include an etching step of etching the photosensitive film as an etching mask and processing the substrate.

  Thereby, the fine structure formed in the photosensitive film can be transferred to the base material, and a fine structure can be obtained at a desired position of the base material.

  Further, prior to the photosensitive film forming step, a processed film forming step for forming a processed film interposed between the substrate and the photosensitive film, and the photosensitive film after development is etched into the etching mask. It is also preferable to further include an etching step of etching and processing the film to be processed.

  In this case, it is possible to transfer the fine structure formed on the photosensitive film to the film to be processed and obtain a fine structure obtained by processing the film to be processed.

  In the photosensitive film forming step, when the total exposure amount is equal to or lower than a predetermined threshold value, the solubility is substantially zero as the photosensitive film, and the total exposure amount is larger than the threshold value. It is preferable to form a film having a characteristic in which the solubility is substantially constant larger than zero, that is, a film having a steep threshold characteristic of the photosensitive film (a film having a large slope of the solubility curve near the threshold). In this case, in the first exposure step and the second exposure step, the exposure amount given to the photosensitive film in each step does not exceed the threshold value, and the integrated value of the exposure amount in each step It is preferable to perform the exposure so that the value exceeds the threshold value.

  As a result, the photosensitive film in the region that is not exposed in the second exposure step has a total exposure amount that does not exceed the threshold value, so that no latent image pattern appears in the region. In addition, the region exposed by the second exposure step has a sharp threshold characteristic, so that a sharper latent image pattern can be obtained.

  In the photosensitive film forming step, when the total exposure amount is equal to or lower than a predetermined threshold value, the solubility is substantially zero as the photosensitive film, and the total exposure amount is larger than the threshold value. In addition, a film having a property that the solubility increases corresponding to the increase in the total exposure amount, that is, a film whose slope of the solubility curve when the threshold value is exceeded is not so large may be formed. Also in this case, in the first exposure step and the second exposure step, the exposure amount given to the photosensitive film in each step does not exceed the threshold value, and the integrated value of the exposure amount in each step It is preferable to perform the exposure so that the value exceeds the threshold value.

  As a result, the photosensitive film in the region that is not exposed in the second exposure step has a total exposure amount that does not exceed the threshold value, so that no latent image pattern appears in the region. Further, the sharpness of the latent image pattern can be variably set by increasing / decreasing the exposure amount in the second exposure step, and fine structures having various shapes can be obtained.

  Preferably, in the second exposure step, the photosensitive film is exposed by scanning a light beam. Here, the light beam may be a laser beam, for example, or may be generated by condensing light emitted from a lamp light source or the like by an optical system.

  Thereby, it is possible to perform exposure in the second exposure step by selecting a relatively narrow region with high accuracy.

  In the second exposure step, the photosensitive film is preferably exposed by light irradiation through an exposure mask having a predetermined light-shielding pattern.

  In this case, it is possible to select a relatively wide area at once and perform exposure in the second exposure step.

  In the second exposure step, it is also preferable to perform light irradiation using interference light obtained by crossing two laser beams.

  For example, by performing light irradiation in the second exposure process using interference light having a pitch of the bright and dark pattern larger than the interference light in the first exposure process, the light is modulated in-plane according to the light and dark pattern of the interference light. Periodic structure can be obtained.

  Preferably, in the first exposure step, one and the other of the two laser beams are incident symmetrically with respect to an axis orthogonal to the exposure surface of the photosensitive film.

  This makes it possible to make the exposure depth, width, or exposure pattern (latent image) pitch of the exposed region more uniform. Therefore, line patterns and the like arranged at equal intervals can be easily obtained.

  Preferably, each of the two laser beams in the first exposure step is linearly polarized light, and the polarization direction thereof is orthogonal to the beam incident surface.

  This makes it possible to obtain clearer interference fringes regardless of the crossing angle of the two laser beams.

  The two laser beams in the first exposure step are preferably obtained by branching one laser beam output from the same laser light source by a branching unit. Here, examples of the “branching unit” include optical elements such as an amplitude division beam splitter, a polarization separation beam splitter, and a diffraction beam splitter.

  Thereby, two laser beams for exposure can be obtained with a simple configuration, and the manufacturing cost can be further reduced.

  More preferably, the branching means generates ± n-order diffracted beams (n is a natural number of 1 or more), and the ± n-order diffracted beams are used as the two laser beams.

  By using a diffracted beam, two laser beams suitable for the present invention can be easily obtained with substantially equal energy and symmetrical traveling directions.

  The second aspect of the present invention is an electronic device that includes the microstructure manufactured by the manufacturing method according to the first aspect of the present invention. Here, examples of the “fine structure” include optical elements (optical thin film devices) having functions such as polarization separation, phase delay, antireflection, and birefringence elimination. A typical example of an electronic device including such an optical element is a liquid crystal projector including a liquid crystal display device using the optical element as a polarizing element.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of an exposure apparatus for performing exposure using interference light. An exposure apparatus 1 shown in FIG. 1 is used for exposing a photosensitive film, and includes a laser light source 10, mirrors 11 and 12, a shutter 13, a diffractive beam splitter 14, a monitor 15, lenses 16a and 16b, and a space. It includes filters 17a and 17b, mirrors 18a and 18b, and a stage 19.

The laser light source 10 outputs one laser beam (light beam) having a wavelength shorter than the visible light wavelength. As such a laser light source 10, various laser oscillators are preferably used. As an example, in this embodiment, a solid-state UV laser Nd: YVO ₄ (fourth harmonic: wavelength 266 nm, maximum output 200 mW, CW oscillation) is used as the laser light source 10. As shown in the figure, the laser beam B0 (for example, the beam diameter of about 1 mm) emitted from the laser light source 10 has its path (optical path) changed by the mirrors 11 and 12, and after passing through the shutter 13, the diffraction beam splitter 14 Incident to

  The shutter 13 is arranged in the course of the laser beam B0 as described above, and has a function of passing or blocking the laser beam B0.

  The diffractive beam splitter 14 is a branching unit that splits one laser beam B0 to generate two laser beams B1 and B2. The diffractive beam splitter 14 is a concavo-convex diffractive element that realizes its function using a shape effect due to a fine concavo-convex shape formed on the surface of quartz or the like. Since the entire splitter is made only of quartz or the like and has high durability, even when irradiated with a high-power UV laser, it is not damaged and can be used almost permanently. The shape and depth of the diffractive beam splitter 14 are optimally designed. When the incident beam is TE polarized light, two diffracted beams (± first order) of equal intensity are generated. In the present embodiment, these ± 1st-order diffracted beams are used as the laser beams B1 and B2. In the present embodiment, the diffractive beam splitter 14 is designed so as to leave a little energy in the zero-order beam. When the optical system is assembled, it is possible to easily set the crossing angle of the laser beams B1 and B2 on the substrate 100 and align the substrate 100 by referring to the zero-order beam B3. Become. Furthermore, since the two branched laser beams B1 and B2 interfere with each other without being reversed left and right, interference fringes with high contrast can be obtained, which is advantageous for forming a pattern with a high aspect ratio.

  Note that ± 2nd order or higher order diffracted beams may be generated by the diffractive beam splitter 14, and the diffracted beams may be used as the laser beams B1 and B2. Further, as the branching means, a simple amplitude division beam splitter or a polarization separation type beam splitter excellent in durability can be used instead of the diffraction beam splitter. In that case, it is necessary to convert one polarization direction of the separated beam into TE using a wave plate.

  The monitor (observation means) 15 receives the zero-order beam B3 and converts it into an electrical signal. By controlling the position of the stage 19 based on the output from the monitor 15, the setting of the crossing angle of the laser beams B1 and B2 on the substrate 100 and the alignment of the substrate 100 are facilitated. Here, for convenience of explanation in FIG. 1, the monitor 15 is disposed closer to the diffraction beam splitter 14 than the substrate 100, but the position of the monitor 15 is not limited to this and can be arbitrarily set. For example, it may be a movable type that is disposed at substantially the same position as the substrate 100 during positioning and moves to another position during exposure. As a simpler observation means, the 0th-order beam B3 may be referred to by using a paper medium that emits fluorescence when irradiated with the 0th-order beam B3.

  The lens 16a is arranged so that one laser beam B1 generated by the diffractive beam splitter 14 is incident thereon, and condenses the laser beam B1. The spatial filter 17a has a pinhole, and is arranged so that the laser beam B1 collected by the lens 16a is incident on the pinhole. That is, a beam expander is configured by the lens 16a and the spatial filter 17a, and the beam diameter of the laser beam B1 is expanded by these. Similarly, the lens 16b is arranged so that the other laser beam B2 generated by the diffractive beam splitter 14 is incident thereon, and condenses the laser beam B2. The spatial filter 17b has a pinhole, and is arranged so that the laser beam B2 collected by the lens 16b is incident on the pinhole. That is, a beam expander is configured by the lens 16b and the spatial filter 17b, and thereby the beam diameter of the laser beam B2 is enlarged. For example, in the present embodiment, each of the laser beams B1 and B2 has its beam diameter expanded to about 200 mm by each beam expander. Because of the action of each of the spatial filters 17a and 17b, the beam wavefront from which unnecessary scattered light has been removed can be used for exposure, so that a clean exposure pattern (latent image) free from defects and noise can be formed.

  The mirror 18a is arranged so that the laser beam B1 after passing through the spatial filter 17a is incident, and reflects the laser beam B1 toward the substrate 100. Similarly, the mirror 18b is arranged so that the laser beam B2 after passing through the spatial filter 17b is incident, and reflects the laser beam B2 toward the substrate 100. These mirrors 18a and 18b function as optical means for setting the course of each laser beam so that the two laser beams B1 and B2 intersect at a predetermined angle to generate interference light.

  The stage 19 supports the substrate 100 and sets its relative position so that the photosensitive film on the substrate 100 can be exposed by interference light (interference fringes) generated by the crossing of the laser beams B1 and B2. . That is, the stage 19 serves as a position setting unit that sets a relative position between the photosensitive film and the generation position of the interference light.

  FIG. 2 is a cross-sectional view illustrating the structure of the substrate 100 and a photosensitive film formed on the upper surface thereof. As shown in FIG. 2A, an antireflection film 102 and a photosensitive film 103 are formed on one surface of the substrate 100.

  The substrate 100 corresponds to the “base material” in the present invention, and substrates made of various materials such as a glass substrate, a resin substrate, or a semiconductor substrate such as silicon can be used.

  The antireflection film 102 has a function of suppressing the back reflection of the interference light when the photosensitive film 103 is exposed by the interference light described above. As the antireflection film 102, any of inorganic materials and organic materials can be adopted as long as the reflection of the interference light can be suppressed by absorbing the interference light or the like. In particular, an organic material such as DUV44 manufactured by Nissan Chemical Industries, Ltd. can be easily peeled off (removed) in a later step. Thereby, a favorable pattern without an interference standing wave can be formed.

  The photosensitive film 103 is formed by using a material that has a property of causing a change in a portion irradiated with light and selectively removing either the light irradiated portion or the non-light irradiated portion by a predetermined process later. Is done. For example, in the present embodiment, the photosensitive film 103 is formed using a chemically amplified resist adjusted for the UV wavelength (λ to 250 nm). Note that the photosensitive film 103 may be formed directly on the substrate 100 without using the antireflection film 102.

  As shown in FIG. 2B, a film (processed film) 101 as a workpiece is interposed between the substrate 100 and the antireflection film 102 (or the photosensitive film 103). Also good. Examples of the film 101 to be processed in this case include a metal film formed by a film forming method such as a sputtering method.

  FIG. 3 is a diagram illustrating interference light generated by crossing two laser beams B1 and B2. As described above, in the present embodiment, interference light having periodic brightness (interference fringes) is generated by causing the laser beams B1 and B2 after the beam diameter to be enlarged to interfere with each other at a predetermined crossing angle. Then, exposure is performed by irradiating the photosensitive film 103 with the interference light.

At this time, if the laser wavelength is λ and the crossing angle is θ, the period P (see FIG. 3) of the interference fringe F is given by the following equation.
P = λ / (2 sin θ) (1)

  At this time, as shown in the drawing, the two laser beams B 1 and B 2 are incident symmetrically with respect to an axis (virtual axis) orthogonal to the exposure surface of the photosensitive film 103. This makes it possible to make the exposure depth, width, or exposure pattern (latent image) pitch of the exposed region more uniform. Therefore, line patterns and the like arranged at equal intervals can be easily obtained. Note that the two laser beams B1 and B2 may be incident asymmetrically with respect to an axis orthogonal to the exposure surface of the photosensitive film 103.

  FIG. 4 is a diagram for explaining the relationship between the interference light and the latent image formed on the photosensitive film 103. As shown in FIG. 4A, the interference light has a periodic light intensity distribution (period P). Then, as shown in FIG. 4B, a latent image pattern 104 is formed on the photosensitive film 103 corresponding to the intensity of irradiation light.

  FIG. 5 is a diagram (graph) showing the relationship of the above equation (1), where the horizontal axis corresponds to the crossing angle θ and the vertical axis corresponds to the period (pitch) P of the interference fringes. As shown in FIG. 5, for example, when the wavelength λ is 266 nm, the period of the interference fringes is P = 150 nm when the crossing angle θ = 62 degrees. The period of the interference light can theoretically be achieved up to about ½ of the wavelength of each laser beam.

On the other hand, the depth Δz of the region where the interference fringes are formed is given by the following equation, where W is the diameter of the incident beam.
Δz <W / sin θ (2)

  Both of the two laser beams B1 and B2 involved in the interference are linearly polarized light, and the direction thereof is orthogonal to the beam incident surface (TE polarized light). By using TE polarized light, it is possible to create clear interference fringes regardless of the crossing angle.

In order to form a resist pattern having a good shape (high aspect and rectangular shape), it is essential to sufficiently increase the contrast of interference fringes. The contrast C of the interference fringes is given by the following equation, where Δx is the displacement of the interference fringes. FIG. 6 is a diagram (graph) showing the relationship of this equation.
C = sin (Δx) / (Δx) (3)

  In order to increase the contrast of the interference fringes, the displacement of the interference fringes during exposure must be minimized. In order to realize this, it is necessary to eliminate disturbance (vibration, air fluctuation). For example, a great effect can be obtained by placing the exposure system shown in FIG. 1 on an anti-vibration bench and taking measures such as covering the exposure system with a cover.

Next, the manufacturing method of the microstructure according to the present embodiment will be described in detail.
7 and 8 are process cross-sectional views illustrating a method for manufacturing a microstructure according to an embodiment. Note that in the following description, a case where the film to be processed 101 is not formed over the substrate 100 (see FIG. 2A) will be described as an example.

(Antireflection film formation process, photosensitive film formation process)
First, as shown in FIG. 7A, an antireflection film 102 and a photosensitive film 103 are formed on one surface of a substrate 100. In this example, a glass substrate having a thickness of 1 mm is used as the substrate 100. The antireflection film 102 is formed to a thickness of about 75 nm by a film formation method such as a spin coating method. The photosensitive film 103 is formed to a thickness of about 450 nm by forming a chemically amplified resist by a film forming method such as a spin coating method. Here, the chemically amplified resist is a mixed solution composed of a resin, an acid generator, and a solvent, and uses an acid generated by a photochemical reaction. Therefore, it is sensitively influenced by a small amount of alkaline impurities such as ammonia, Characteristics vary. Therefore, in this embodiment, it is preferable that the atmosphere when performing this step and the subsequent exposure step and development step is such that the concentration of alkaline impurities is 1 ppb or less. In addition, it is also preferable to add the protective film formation process which forms a protective film on the upper surface of the photosensitive film | membrane 103 after said photosensitive film formation process. For example, a suitable protective film can be formed by using TSP-5A manufactured by Tokyo Ohka Kogyo Co., Ltd. and forming it by spin coating or the like. It is also possible to give this protective film an antireflection function. As a result, the photosensitive film 103 made of a chemically amplified resist can be isolated from the atmosphere and the influence of the outside world can be suppressed.

  FIG. 9 is a diagram for schematically explaining the solubility characteristics of the photosensitive film 103. In FIG. 9, the horizontal axis represents the amount of exposure given to the photosensitive film 103, and the vertical axis represents the solubility. As shown in FIG. 9, the solubility characteristics of the photosensitive film 103 are roughly classified into two types (hereinafter referred to as type A and type B, respectively). As shown in the figure, the type A photosensitive film 103 has a solubility of substantially zero when the total exposure amount is equal to or less than a predetermined threshold th, and when the total exposure amount is greater than the predetermined threshold th. In addition, the solubility curve rises steeply and has a characteristic that becomes a substantially constant value larger than zero. Further, the type B photosensitive film 103 has substantially zero solubility when the total exposure amount is equal to or less than the predetermined threshold th, and the total exposure when the total exposure amount exceeds the predetermined threshold th. It has the characteristic that the solubility gradually increases in accordance with the increase in the amount. In the manufacturing method of the present embodiment, the above type A and type B can be properly used according to the structure of the microstructure desired to be finally obtained. That is, since the solubility of the type A photosensitive film 103 changes in a binary manner, the pattern obtained by baking (baking) and developing the exposed photosensitive film 103 includes a removed part and a remaining part. Have sharply distinct shape profiles (for example, rectangular wave shape profiles). On the other hand, in the type B photosensitive film 103, the change in solubility continuously changes according to the total exposure amount, so the pattern obtained by baking and developing the exposed photosensitive film 103 is removed. The remaining portion and the remaining portion are not so clearly distinguished and have a continuous shape profile (for example, a mountain-like shape profile).

(First exposure step)
Next, as shown in FIG. 7B, two laser beams B1 and B2 having a wavelength smaller than the visible light wavelength (266 nm in this example) are crossed at a predetermined angle to generate interference light. To expose the photosensitive film 103. For example, by setting the crossing angle (see FIG. 3) of the two laser beams B1 and B2 to 62 degrees, an interference fringe with a period of 150 nm is obtained, and the latent image pattern 104 corresponding to the interference fringe (interference light) is obtained. Formed on the photosensitive film 103. In this example, since the laser beams B1 and B2 whose beam diameter is expanded to about 200 mm by the beam expander are used, an area of about 4 inches can be collectively exposed. The time required for exposure is about 30 seconds. Further, when exposing a larger area (for example, about 8 inches), the substrate 100 may be moved step by step. Here, in this step, the intensity of each of the laser beams B1 and B2 is set so that the exposure amount given to the photosensitive film 103 does not exceed the threshold value th (see FIG. 9).

  The exposure with the interference light in the first exposure process may be repeated a plurality of times. At this time, various latent image patterns can be obtained by appropriately changing the relative positional relationship between the interference light and the photosensitive film 103 in each exposure. The latent image pattern will be further described later.

(Second exposure step)
Next, as shown in FIG. 7C, the photosensitive film 103 is further exposed by selectively irradiating a predetermined area in the irradiation target area with interference light. In this step, the exposure amount given to the photosensitive film 103 is such that it does not exceed the above-mentioned threshold th (see FIG. 9), and the integrated value of the exposure amount in the first exposure step and this step described above. Is set such that the intensity of the irradiation light B4 exceeds the threshold value th described above, and exposure is performed. As a result, as shown in FIG. 7D, the latent image pattern 105 appears selectively in a predetermined region irradiated with the irradiation light B4 of the photosensitive film 103. Here, the irradiation light B4 is not limited to the laser light as long as the photosensitive film 103 has a wavelength with which the photosensitive film 103 has reactivity (in this embodiment, a wavelength in the ultraviolet region), such as lamp light obtained by a lamp light source. It is also possible to use light. When laser light is used as the irradiation light B4, the laser beam B0, B1, or B2 obtained by the laser light source 10 described above may be used as the irradiation light B4, and the irradiation light B4 is generated using another laser light source. May be. In the example shown in FIG. 7C, the irradiation light B4 is condensed using a condensing lens to form a spot-like light beam, and a desired region of the photosensitive film 103 is exposed by scanning the light beam. is doing. This makes it possible to accurately expose a relatively narrow range.

  In this step, exposure may be performed using an imaging optical system as shown in FIG. Specifically, in the example shown in FIG. 10, the irradiation light B 4 is irradiated through the exposure mask 21 having a predetermined light shielding pattern, and the light shielding pattern of the exposure mask 21 is connected to the photosensitive film 103 by the imaging lens 20. The photosensitive film 103 is exposed by imaging. According to this example, the photosensitive film 103 can be exposed over a relatively wide area. As the exposure mask 21, a mask whose light transmittance changes in the plane (so-called gray mask) may be used, or a phase shift mask that can be expected to have high resolution may be used. Further, in this step, light irradiation can be performed using interference light obtained by crossing two laser beams. In that case, for example, by exposing with interference light having a bright and dark pattern pitch larger (rough period) than in the first exposure step, the exposure intensity is modulated in-plane according to the pattern of the interference light. Latent image patterns can be formed. In other words, if one-dimensional interference light is used, a latent image pattern modulated in a stripe shape is formed, and if two-dimensional interference light is used, a latent image pattern modulated in a matrix shape is formed, for example.

  FIG. 11 is a diagram illustrating an example of the latent image pattern 105 formed on the photosensitive film 103 through each exposure process. In the example shown in FIG. 11A, a predetermined area surrounded by a dotted line is exposed by scanning with a light beam in the second exposure step (or light irradiation using the exposure mask 21), resulting in a striped latent image. A pattern 105 appears locally. In the example shown in FIG. 11B, a predetermined area surrounded by a dotted line is exposed by light irradiation (or light beam scanning) using the exposure mask 21 in the second exposure step, so that the latent image pattern 105 is obtained. It appears in a relatively wide range. The latent image patterns shown in FIGS. 11A and 11B correspond to the case where the exposure by the interference light in the first exposure process is performed once. In the example shown in FIG. 11C, a predetermined area surrounded by a dotted line is exposed by light irradiation (or light beam scanning) using the exposure mask 21 in the second exposure step, resulting in a latent image pattern. 105 appears in a relatively wide range. In the latent image pattern 105 shown in FIG. 11C, the exposure with the interference light is repeated twice in the first exposure step, and the relative arrangement of the interference light and the photosensitive film 103 is changed between the first time and the second time. A latent image pattern 105 obtained when rotated by 90 degrees is shown. That is, in this example, a latent image pattern 105 is obtained in which striped latent images are formed in directions orthogonal to each other. Such a latent image pattern 105 can also be obtained by performing a single exposure using interference light obtained by crossing three or more laser beams in the first exposure step. In addition, although FIG. 11C illustrates the case where exposure is performed over a relatively wide range in the second exposure step, the exposure may be performed locally.

(Development process)
Next, as shown in FIG. 8A, the photosensitive film 103 after exposure is baked and then developed, so that interference light is applied to the photosensitive film 103 in a predetermined region exposed in the second exposure step. The shape corresponding to the pattern is expressed. Thereby, a resist pattern 106 having a period of 150 nm is obtained. In this embodiment, the resist pattern 106 is used as an etching mask for performing microfabrication on the substrate 100 as will be described as the next step. However, the resist pattern 106 can also be used as a microstructure. It is.

(Etching process)
Next, as shown in FIG. 8B, etching is performed using the developed photosensitive film 103 as an etching mask, and the substrate 100 is processed. In principle, both wet etching and dry etching can be employed as the etching method. In particular, dry etching is preferably performed by a method such as ICP (inductively coupled plasma) or ECR (electron cyclotron resonance). As a result, the resist pattern 106 is transferred to the substrate 100, and a fine structure 107 is formed on the substrate 100 as shown in FIG.

  In the case where the processed film 101 is formed between the substrate 100 and the photosensitive film 103 (see FIG. 2B), the photosensitivity obtained through the same steps as those in FIGS. 7 and 8 described above. By performing etching on the film to be processed 101 using the film 103 as an etching mask, the resist pattern 106 is transferred to the film to be processed 101. Thereby, for example, when a metal film such as an aluminum film is formed as the film to be processed 101, a metal lattice type polarizing element composed of a plurality of aluminum films processed in a stripe shape is obtained.

  FIG. 12 is a schematic perspective view illustrating a structural example of a fine structure that can be formed by the manufacturing method of the present embodiment. FIG. 12A shows a microstructure including a plurality of columnar bodies processed into a stripe shape with a period of about 150 nm. Such a structure may be used as a polarizing element or a phase delay element as described above, or may be used as a substitute for an alignment control film for liquid crystal molecules in a liquid crystal display device. FIG. 12B or FIG. 12C is obtained by performing exposure with interference light in the first exposure process a plurality of times, or by exposure with interference light obtained by crossing three or more laser beams. An example of the microstructure is shown. Such a structure can be used, for example, as a light reflection preventing structure (so-called moth eye) or as a structure for imparting lyophilicity to a desired surface. FIG. 12D illustrates a structure having a plurality of minute recesses. It is also possible to obtain such a fine structure depending on whether a negative type or a positive type is adopted as the photosensitive film 103. Such a structure can be applied, for example, as a photonic waveguide used for processing an optical signal.

  FIG. 13 is a diagram illustrating a specific example of an electronic device. FIG. 13A shows an application example to a rear projector. The projector 270 includes a housing 271, a light source 272, a synthesis optical system 273, mirrors 274 and 275, a screen 276, and a microstructure according to the present embodiment. As a liquid crystal panel 200 including a metal grid type polarizing element. FIG. 13B shows an application example to a front type projector, and the projector 280 includes a liquid crystal panel 200 including an optical system 281 and a metal lattice type polarizing element as a microstructure according to the present embodiment in a housing 282. And an image can be displayed on the screen 283. In addition, electronic devices are not limited to these, and include, for example, a fax machine with a display function, a finder for a digital camera, a portable TV, an electronic notebook, an electric bulletin board, and a display for advertisements. .

  As described above, in the present embodiment, the two laser beams are crossed at a certain angle so that the interference light having a light / dark pattern (interference fringes) having a pitch approximately equal to or less than the wavelength of the laser beam is generated. can get. By performing the first exposure step using such interference light, it is possible to form a latent image pattern having an order shorter than the visible light wavelength on the photosensitive film while reducing the manufacturing cost. Moreover, the exposure pattern by interference light can be made clear in the desired position of a photosensitive film | membrane by exposure in a 2nd exposure process. Accordingly, it is possible to select an arbitrary position with high accuracy and perform fine processing on the order shorter than the visible light wavelength.

  In addition, according to the present embodiment, a wide process margin and high throughput can be secured for the exposure process, so that it can be easily applied to a mass production line.

  In addition, this invention is not limited to the content of the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention.

  For example, the first exposure step and the second exposure step described above can be performed by switching the mutual order. Even in this case, the same exposure result can be obtained.

  Further, as the irradiation light in the second exposure step, in addition to the case where the light intensity is a Gaussian distribution, the light intensity is flattened using an optical means such as a phase difference plate or a computer generated hologram (hat top). May be used. Alternatively, a plurality of arrayed light beams may be generated using optical means such as a diffractive optical element, and a plurality of locations may be exposed simultaneously.

  In the above-described embodiment, the beam generating means for generating two laser beams is configured by the combination of the laser light source and the branching means (diffractive beam splitter). However, the beam generating means is limited to this. It is not a thing. For example, a plurality of laser light sources may be used as the beam generating means according to the present invention.

  In the above-described embodiment, the spherical wave generated by the beam expander including the lens and the spatial filter is used for the interference exposure. However, the plane wave is generated by arranging the collimator lens after the beam expander. It can also be used for interference exposure. Furthermore, various fine patterns can be realized by applying phase modulation to at least one wavefront using various optical elements (lens, phase plate, computer generated hologram, etc.).

It is a figure explaining the structure of the exposure apparatus of one Embodiment. It is sectional drawing explaining the structure of the photosensitive film | membrane etc. which are formed in the upper surface of a board | substrate. It is a figure explaining the interference light generated by crossing two laser beams. It is a figure explaining the relationship between interference light and the latent image formed in a photosensitive film | membrane. It is a figure (graph) which shows the relationship of (1) Formula. It is the figure (graph) which showed the relationship of (3) Formula. It is process sectional drawing explaining the manufacturing method of a microstructure. It is process sectional drawing explaining the manufacturing method of a microstructure. It is a figure which illustrates roughly the solubility characteristic of a photosensitive film | membrane. It is process sectional drawing in the case of performing exposure using an imaging optical system. It is a figure explaining the example of the latent image pattern formed in a photosensitive film | membrane. It is a schematic perspective view explaining the structural example of a fine structure. It is a figure explaining the specific example of an electronic device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exposure apparatus, 10 ... Laser light source, 11, 12 ... Mirror, 13 ... Shutter, 14 ... Diffraction beam splitter, 15 ... Monitor, 16a, 16b ... Lens, 17a, 17b ... Spatial filter, 18a, 18b ... Mirror, DESCRIPTION OF SYMBOLS 19 ... Stage, 20 ... Imaging lens, 21 ... Exposure mask, 100 ... Substrate (base material), 101 ... Film to be processed, 102 ... Antireflection film, 103 ... Photosensitive film, 104, 105 ... Latent image pattern, 106 ... resist pattern, 107 ... fine structure

Claims (13)

A photosensitive film forming step of forming a photosensitive film on the substrate;
A first exposure step of crossing two laser beams having a wavelength shorter than the visible light wavelength to generate interference light and exposing the photosensitive film by irradiating the interference light;
A second exposure step of further exposing the photosensitive film by selectively irradiating a predetermined region in the irradiation target region with the interference light;
A developing step of developing the photosensitive film and developing a shape corresponding to the pattern of the interference light on the photosensitive film in the predetermined area exposed in the second exposure step;
A method for producing a fine structure, including:   The method for producing a microstructure according to claim 1, further comprising an etching step of etching the photosensitive film after development as an etching mask to process the substrate. Prior to the photosensitive film forming step, a processed film forming step of forming a processed film interposed between the base material and the photosensitive film,
Etching using the photosensitive film after development as an etching mask and processing the film to be processed; and
The method for producing a microstructure according to claim 1, further comprising: In the photosensitive film forming step, the solubility of the photosensitive film is substantially zero when the total exposure amount is equal to or less than a predetermined threshold value, and the solubility when the total exposure amount is greater than the threshold value. That has a characteristic that becomes a substantially constant value larger than zero,
In the first exposure step and the second exposure step, the exposure amount given to the photosensitive film in each step does not exceed the threshold value, and the integrated value of the exposure amount in each step is the threshold value. The method for producing a fine structure according to any one of claims 1 to 3, wherein the exposure is performed so as to exceed. In the photosensitive film forming step, as the photosensitive film, the solubility is substantially zero when the total exposure amount is less than or equal to a predetermined threshold value, and when the total exposure amount is greater than the threshold value, Forming a property that increases the solubility corresponding to the increase in total exposure,
In the first exposure step and the second exposure step, the exposure amount given to the photosensitive film in each step does not exceed the threshold value, and the integrated value of the exposure amount in each step is the threshold value. The method for producing a fine structure according to any one of claims 1 to 3, wherein the exposure is performed so as to exceed.   4. The method of manufacturing a microstructure according to claim 1, wherein the second exposure step exposes the photosensitive film by scanning a light beam. 5.   4. The method for manufacturing a microstructure according to claim 1, wherein in the second exposure step, the photosensitive film is exposed by light irradiation through an exposure mask having a predetermined light shielding pattern. 5. .   4. The method for manufacturing a microstructure according to claim 1, wherein in the second exposure step, light irradiation is performed using interference light obtained by crossing two laser beams. 5.   4. The first exposure process according to claim 1, wherein in the first exposure step, one and the other of the two laser beams are incident symmetrically with respect to an axis orthogonal to an exposure surface of the photosensitive film. 5. A manufacturing method of a fine structure.   4. The method for manufacturing a microstructure according to claim 1, wherein each of the two laser beams in the first exposure step is linearly polarized light, and a polarization direction thereof is orthogonal to a beam incident surface. .   The two laser beams in the first exposure step are obtained by branching one laser beam output from the same laser light source by a branching unit. The manufacturing method of the described microstructure.   12. The microstructure according to claim 11, wherein the branching unit generates ± n-order diffracted beams (n is a natural number of 1 or more), and uses the ± n-order diffracted beams as the two laser beams. Production method. An electronic device provided with the fine structure manufactured by the manufacturing method in any one of Claims 1 thru | or 12.

Images