JP2004200577A - Method for forming microstructure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a three-dimensional fine shape by a simple process. <P>SOLUTION: Epoxy resin group photoresist is applied to the surface of a substrate 11 and heated at 50-90°C and a solvent is removed to form a resist layer 12. A die 13 having a V groove extended in a direction perpendicular to paper surface is put on the substrate 11 on which the resist layer 12 is formed through a spacer and the die 13 and the substrate 11 are aligned. Then the die 13 and the substrate 11 are set on a stage having pressurizing and heating means and heated up to 60°C which is close to a glass transition point and the die 13 is pressed to the substrate 11 along a die pushing direction 17. Then the die 13 and the substrate 11 are returned to normal pressure and cooled. Then the die 13 is peeled off from the substrate 11 on which the resist layer 12 is formed. The resist layer 12 is irradiated with ultraviolet light 15 through a photomask 14 having a pattern of a Cr film 14b on the surface of a glass substrate 14a. In an exposed area 16, resin is bridged and cured by acid generated from a photosensitive agent. The resist layer 12 is developed by a developing solution and rinsed, and then the area 16 is cured. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a fine structure, and more particularly to a method for forming a three-dimensional fine pattern.
[0002]
[Prior art]
Lithography technology is widely used as a technique for forming high aspect ratio patterns such as micromachines as well as semiconductor manufacturing as high-precision, high-throughput microfabrication technology. In the field of micromachines, there are many cases where a three-dimensional shape is required such as a mirror or lens for light control, or a flow path or a valve of a microfluidic control device. However, in conventional lithography, a resist is applied to the resist applied to the substrate through a mask and an energy beam is irradiated perpendicularly to the substrate, and the pattern is formed by changing the solubility of the resist in the developing solution. An arbitrary shape can be formed in the direction, but only whether or not there is a resist in the vertical direction can be selected. That is, only a two-dimensional pattern can be formed.
[0003]
In order to solve such a problem, a method of forming a tapered shape on the side surface of the resist pattern by tilting the beam incident direction with respect to the substrate has been proposed (see, for example, Patent Documents 1, 2, and 3). According to these methods, it is described that a V-groove resist pattern and a conical three-dimensional pattern can be formed by changing the inclination direction and performing exposure.
[0004]
Also, a pattern to be enclosed is formed on the substrate, and the resist is filled therein, and then the substrate is tilted so that the horizontal plane of the resist has an angle with respect to the substrate, and is cured in that state. Thus, a method of forming a three-dimensional shape has been proposed (see, for example, Non-Patent Document 1). In this method, the portion of the substrate where the resist is filled and hardened can be arbitrarily selected, and the tilt angle can be arbitrarily changed. However, it is necessary to repeat the process each time, and the throughput is increased. There is a problem in terms of improvement.
[0005]
Further, a method has been proposed in which a three-dimensional shape is formed by leaving the film thickness corresponding to the incident beam intensity on the resist pattern by modulating the intensity of the incident incident energy beam with a mask (for example, Patent Document 4). reference). However, in this method, when a mirror-like shape is produced, there is a problem that the performance as a mirror cannot be obtained because a grating is formed unless a mask whose density is controlled with high gradation is used. Therefore, a high-tone mask is required. However, in order to manufacture such a mask, since complicated conditions are required, there is a problem that the cost of the mask itself increases.
[0006]
On the other hand, if an attempt is made to form a pattern with a high aspect ratio only by the stamping process, there is a problem that when the mold is released, the molding material is peeled off together with the mold. Furthermore, there is a problem that the embossing is impossible depending on the pattern.
[0007]
[Patent Document 1]
JP-A-6-188175 [0008]
[Patent Document 2]
JP-A-6-220341 [0009]
[Patent Document 3]
Japanese Patent Laid-Open No. 7-135142 [0010]
[Patent Document 4]
JP 2000-235873 A [0011]
[Non-Patent Document 1]
Yoonsu choi, et al, IEEE MEMS, 2002, Proc., P176-179
[0012]
[Problems to be solved by the invention]
As described above, in the prior art, there is a problem in terms of throughput and manufacturing cost in forming a three-dimensional fine shape.
[0013]
In view of the above circumstances, an object of the present invention is to provide a method for forming a fine structure that enables a three-dimensional fine shape to be easily produced at low cost.
[0014]
[Means for Solving the Problems]
The fine structure forming method of the present invention includes a step of forming a resist layer on a substrate,
Forming a resist layer with a mold;
Selectively exposing a part of the formed resist layer;
And developing the exposed resist layer to leave one of the exposed region and the region other than the exposed region, and removing the other.
[0015]
The mold may have a molding surface in a direction different from the pressing direction of the mold.
[0016]
Further, in the step of forming the resist layer with a mold, the mold may be stopped at a desired height position on the substrate using a spacer.
Further, the substrate is made of a material that transmits exposure light, and a resist layer is formed after providing a light-shielding film having a predetermined pattern on the substrate, and a part of the resist layer is exposed by exposing from the back surface of the substrate. May be selectively exposed.
[0017]
【The invention's effect】
According to the fine structure forming method of the present invention, since the fine shape is formed by two types of processes, that is, a molding process and a lithography process, the concentration of the light shielding material is controlled as in the prior art. There is no need to use an expensive mask, and there is no need to repeat complicated lithography processes. Therefore, a three-dimensional microstructure can be easily formed at low cost.
[0018]
Furthermore, depending on the combination of the shape of the mold and the mask pattern of lithography, a three-dimensional shape having a high aspect ratio can be easily formed at low cost, and a plurality of fine shapes having different shapes can be formed on the same substrate. It is also possible to form a structure.
[0019]
Further, in the step of forming the resist layer with a mold, when the mold is stopped at a desired height position on the substrate using a spacer, the resist layer can be made to have a desired thickness with high accuracy.
Further, the substrate is made of a material that transmits exposure light, and a resist layer is formed after providing a light-shielding film having a predetermined pattern on the substrate, and a part of the resist layer is exposed by exposing from the back surface of the substrate. Is selectively exposed, it is possible to form a good pattern without being affected by reflected light without using matching oil or the like.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
A method for forming a fine structure according to the first embodiment of the present invention will be described. A cross-sectional view of the formation process is shown in FIG.
[0022]
As shown in FIG. 1 (a), an epoxy resin photoresist (NANO SU-8: manufactured by MicroChem Inc.) is applied on the substrate 11, and heated at 50 to 90 ° C. with a hot plate or a clean oven. The resist layer 12 is formed by removing the solvent. Next, a die 13 made of Si and formed by using anisotropic etching of Si (silicon) crystal and having a V-groove extending in a stripe shape perpendicular to the paper surface is used as a substrate 11 on which a resist layer 12 is formed. The substrate 11 and the mold 13 are aligned with a positioning means such as a double-sided aligner. The mold 13 has a pressing direction 17 that is perpendicular to the surface of the substrate 11 and a molding surface 18 in a different direction, and two V grooves formed by the molding surface 18 extend in parallel to the paper surface. It is formed as follows.
[0023]
In order to make the thickness of the resist layer 12 after being molded by the mold a predetermined value at the end of the surface perpendicular to the pressing direction of the mold 13, the height from the surface is the predetermined thickness. A spacer 13a that defines the thickness between the substrate 11 and the substrate 11 is provided. The spacer is not limited to the spacer provided on the mold 13 as described above and defines the thickness of the resist layer between the substrate and the spacer, but is provided on the mounting table on which the substrate 11 is mounted to adjust the height position of the mold. It is also possible to adjust the height position of the mold provided on both the mold mounting table and the mold mounting table.
Next, as shown in FIG. 1B, the mold 13 and the substrate 11 are set on a stage having pressurization and heating means installed in a vacuum vessel, and the vicinity of the glass transition point while reducing the vacuum vessel. Then, the mold 13 is pressed against the resist layer 12 along the mold pressing direction 17. Then, it returns to normal pressure and cools.
[0024]
Next, as shown in FIG. 1C, the mold 13 is peeled from the substrate 11 on which the resist layer 12 is formed. At this time, in order to facilitate peeling of the mold 13 from the substrate 11, it is desirable to apply a release agent such as a fluorine-based coating agent to the surface of the mold 13 in advance.
[0025]
Next, as shown in FIG. 1 (d), through the photomask 14 having a pattern of the Cr film 14b on the surface of the glass substrate 14a, the ultraviolet light 15 of 350 to 400 nm is perpendicularly directed to the substrate. Irradiate. Thereby, only the shaded portion 16 is exposed. At this time, in order to reduce the influence of reflection due to the difference in refractive index between the resist layer 12 and the air gap, it is desirable to apply the matching oil on the resist layer 12 and then expose the mask 14 to the matching oil for exposure. Alternatively, it is desirable to coat the surface of the resist layer 12 formed by a mold with a non-photosensitive resin that transmits exposure light. Thereby, highly accurate pattern formation becomes possible.
[0026]
Next, PEB (post exposure bake) is performed at 50 to 90 ° C. Thereby, in the exposed area | region, resin is bridge | crosslinked with the acid generate | occur | produced from the photosensitive agent by exposure, and it hardens | cures.
[0027]
Thereafter, as shown in FIG. 1 (e), the resist layer 12 is developed and rinsed with a developer dedicated to SU-8 resist, and the developed region 16 is further cured at 100 to 200 ° C. Complete the pattern.
[0028]
Next, a method for forming a fine structure according to the second embodiment of the present invention will be described. A sectional view of the formation process is shown in FIG.
[0029]
As shown in FIG. 2A, a Cr film 22 as a light shielding film is formed on a glass substrate 21 that is transparent to ultraviolet light of 350 nm or more, and a desired pattern is formed on the Cr film 22. Then, an epoxy resin photoresist (NANO SU-8) is applied on the glass substrate 21 on which the Cr film 22 is formed, heated at 50 to 90 ° C. with a hot plate or a clean oven, the solvent is removed, and the resist layer is removed. Form 23. Next, a mold 24 made of Si and formed by anisotropic etching of Si and formed with a V-groove extending in a stripe shape perpendicular to the paper surface is placed on a glass substrate 21 on which a resist layer 23 is formed via a spacer. The glass substrate 21 and the mold 24 are aligned by alignment means such as a double-sided aligner. The die 24 has a die pressing direction 27 that is perpendicular to the surface of the substrate 21 and a molding surface 28 in a different direction, and two V grooves formed by the molding surface 28 extend in parallel to the paper surface. It is formed as follows.
[0030]
Next, as shown in FIG. 2 (b), a mold 24 and a glass substrate 21 are set on a stage having pressurizing and heating means installed in a vacuum vessel, and the glass transition point is reduced while the vacuum vessel is depressurized. Heating to 60 ° C. in the vicinity, the mold 24 is pressed against the resist layer 23 along the mold pressing direction 27. Then, it returns to normal pressure and cools.
[0031]
Next, as shown in FIG. 2 (c), the mold 24 is peeled off from the glass substrate 21. At this time, if a release agent such as a fluorine-based coating agent is applied to the surface of the mold 24 in advance, it is easy to peel off.
[0032]
Next, as shown in FIG. 2D, the resist layer 23 is exposed by irradiating the back surface of the glass substrate 21 with ultraviolet rays 25 of 350 to 400 nm. As a result, only the shaded portion 26 is exposed. Thereafter, PEB (post exposure bake) is performed at 50 to 90 ° C. to cure the resist in the exposed region 26.
[0033]
Thereafter, as shown in FIG. 2 (e), the resist layer 23 is developed and rinsed with a developer dedicated to NANO SU-8, and the remaining region 26 is further cured at 100 to 200 ° C. to complete the pattern. Let
[0034]
In the second embodiment, since the exposure light is exposed from the back surface of the substrate 21, a good pattern can be formed without being affected by the reflected light without using antireflection means such as matching oil. Is possible.
[0035]
In the case of a shape having a high aspect ratio in the conventional embossing method, when the mold and the resin are peeled off, the resin is peeled off from the substrate and a good shape cannot be obtained. However, according to the present invention, an oblique side surface is formed with respect to the substrate by a mold, and a vertical side surface is formed with respect to the substrate by lithography. Thus, as shown in FIG. 2E, a three-dimensional shape having a high aspect ratio can be easily produced.
[0036]
Furthermore, using a thick film resist such as NANO SU-8 is effective for forming a pattern with a high aspect ratio. In the present embodiment, the resist is not limited to NANO SU-8, and may be a negative resist or a positive resist having a softening point below the deactivation temperature of the photosensitive agent.
[0037]
Further, in the present embodiment, a resist that requires heating is used at the time of molding, but a resist that does not require heating and can be molded only by pressurization may be used.
[0038]
The mold of the embodiment uses a Si substrate that has been patterned by utilizing anisotropic etching of Si, but a mold fabricated by using other microfabrication techniques can also be used.
[0039]
In addition, the shape of the mold may be any of a stripe shape and a discrete shape in the planar shape, and the cross-sectional shape is not limited to the taper shape as in the present embodiment, but the step shape, the curved surface shape or those. Combinations of these shapes may be used, and various shapes that can be molded depending on the mold can be adopted. In particular, if a mold provided with the above combination shape is used, a structure having a plurality of different functions such as MEMS can be easily manufactured.
[0040]
Moreover, in the said embodiment, although the light irradiation direction is made into the perpendicular | vertical direction with respect to a board | substrate, you may irradiate from directions other than a perpendicular direction.
[0041]
Further, an exposure process using different masks may be performed a plurality of times before one development process.
[0042]
Further, a more complicated shape can be produced by repeating the process of the present invention consisting of a resist coating process, a molding process using a mold, an exposure process, and a PEB process a plurality of times.
[0043]
In addition, the substrate can be processed using the fine structure formed according to the present invention as a mask by appropriately adjusting the etching resistance or the like of the resist.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fine structure forming process according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of a fine structure forming process according to a second embodiment of the present invention. ]
11 Board
12 Resist layer
Type 13
13a Spacer
14a glass substrate
14b Cr film
14 Mask
15 Exposure light
17 Pushing direction
18 Molded surface

Claims (4)

Forming a resist layer on the substrate;
Forming the resist layer with a mold;
Selectively exposing a part of the shaped resist layer;
And developing the exposed resist layer to leave one of the exposed region and the region other than the exposed region, and removing the other. 2. The method for forming a microstructure according to claim 1, wherein the mold has a molding surface in a direction different from a direction in which the mold is pressed. 3. The method for forming a fine structure according to claim 1, wherein, in the step of forming the resist layer with a mold, the mold is stopped at a desired height position on the substrate using a spacer. The substrate is made of a material that transmits exposure light,
The resist layer is formed after providing a light-shielding film having a predetermined pattern on the substrate, and a portion of the resist layer is selectively exposed by exposing from the back surface of the substrate. Item 4. The method for forming a microstructure according to Item 1, 2 or 3.

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