JP2000095873A - Formation of polymer pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a polymer pattern at a low cost. SOLUTION: This method for forming a polymer pattern comprises selectively irradiating the pattern formation-predetermined regions 57 of a substrate 51 containing a radical-polymerizable monomer 53 and a free radical-generating agent 53 with light. Thereby, free radicals are generated to addition-polymerize the radiacal-polymerizable monomer 53 by the free radical mechanism, thus forming the polymer of the radical-polymerizable monomer to give the polymer pattern 61.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for forming a polymer pattern.

[0002]

2. Description of the Related Art In the field of communication, construction of a communication network using light is required to realize large-capacity communication. For this reason, development of an optical waveguide has been a major issue.

Conventionally, glass and inorganic crystal materials have been used as materials for optical waveguides. However, these materials are expensive and difficult to process.

Therefore, in recent years, a polymer material (also referred to as a polymer) such as PMMA (polymethyl methacrylate), which is cheaper and easier to process than glass or an inorganic crystal material, has been used. By using such a material, it is possible to form a film-shaped optical waveguide having a larger area and higher flexibility than before. Further, a functional waveguide can be formed by introducing a functional compound or a functional group into the polymer material.

[0005] In order to form such an optical waveguide,
A method of processing a polymer material into a desired pattern shape to form a polymer pattern is indispensable. One such method is reactive etching using oxygen plasma (RI
The E) method was mainly used.

[0006]

However, this R
The apparatus used for the IE method is expensive, and there is a problem that an advanced operation technique is required. In addition, there is a problem that an etching mask corresponding to a pattern shape needs to be formed on a polymer to be etched by a lithography method before performing an etching process. Hereinafter, a specific description will be given.

In order to form a polymer pattern as a core of a polymer optical waveguide by processing a polymer into a desired pattern shape by using the RIE method, for example, FIG.
It is necessary to go through the steps schematically shown in FIG. FIG. 3 is a schematic cross-sectional view sequentially showing main steps for forming a polymer pattern by using the RIE method.

First, a polymer film 103a as a lower clad and a polymer film 103 for forming a core are formed on an underlayer 101.
b and a photoresist film 105 for forming an etching mask are formed in this order (FIG. 3A).

Next, in order to process the photoresist film 105 to obtain an etching mask corresponding to a desired pattern shape, a photomask 1 corresponding to the pattern shape is formed.
07, the photoresist film 105 is selectively exposed. Thus, a pattern latent image 109 is formed in the photoresist film 105 (FIG. 3B). The exposed photoresist film 105 is developed to form a resist pattern 105
x is obtained (FIG. 3C. Here, an example using a negative resist is shown).

Next, using this resist pattern 105x as an etching mask 105x, RIE using oxygen as an etching gas is performed to form an etching mask 105x.
The portion of the polymer film 103b exposed from x is removed. Next, the etching mask 105x is removed. Thereby, the polymer film 103b is formed on the lower clad 103a.
The core 103x of the polymer optical waveguide composed of the remaining portion is formed (FIG. 3D).

Further, a polymer optical waveguide 113 is formed by forming a polymer film 111 as an upper clad so as to fill the etched portion of the polymer film 103b (FIG. 3E).

As is clear from the description with reference to FIG. 3, when a pattern is formed by using the RIE method, the number of steps required for forming the pattern is large and it takes time.

Therefore, it has been desired to develop a method for forming a pattern of a polymer (polymer, polymer) easily and inexpensively.

[0014]

In view of the above, the present inventors have proposed that when a substrate containing a radical generator and a radical polymerizable monomer is irradiated with light, radicals are generated in an irradiated portion of the substrate, The present invention has been completed by paying attention to the fact that the radical polymerizable monomer is added and polymerized to the radical, thereby causing polymerization of the radical polymerizable monomer.

Therefore, according to the method for forming a polymer pattern of the present invention, a region where a polymer pattern is to be formed on a substrate containing a radical polymerizable monomer and a radical generator is irradiated with light, so that the radical generator is Generate radicals to polymerize radical polymerizable monomers,
The method includes a step of forming a polymer of a radical polymerizable monomer in the region where the polymer pattern is to be formed.

The polymer pattern forming region is defined as
This is an area inside the skin including the skin portion of the base material where the polymer pattern is to be formed. The region where the polymer pattern can be formed is, specifically,
This is considered to be a region where light reaches, a region where radicals can be generated from the radical generator by this light, and its vicinity.

Further, the term "substrate" as used in the present invention refers to various substrates on which a polymer pattern is desired to be formed. Typically, it can be a substrate or layer composed of a first material (hereinafter, also referred to as a base material), a radical polymerizable monomer and a radical generator. The first material may be an inorganic material or an organic material, but is preferably an organic material, and more preferably a polymer material. When the substrate is a layer, the layer is preferably formed on any suitable base. As the base, any semiconductor substrate such as a silicon substrate, a glass substrate, a ceramic substrate, a substrate of a polymer material, or the like can be used. An intermediate on which other optical components or electronic components are formed may be the base. Note that the first material is not limited to a single material. Two or more materials may be mixed.

According to this configuration, when light is irradiated to the region where the polymer pattern is to be formed on the base material containing the radical polymerizable monomer and the radical generator, the irradiated portion of the substrate is irradiated with the light. A polymer forms.
Accordingly, a polymer portion having an arbitrary shape (typically, a planar shape) is generated in the base material, and a polymer pattern is obtained by this. Typically, a polymer pattern as a refractive index region different from the base material can be formed in the base material as in the example described later. in this way,
A polymer pattern can be formed only by irradiating the substrate containing the radical polymerizable monomer and the radical generator with light. Therefore, the polymer pattern can be formed in a small number of steps and in a shorter time without going through complicated steps such as the conventional RIE method.

In practicing the present invention, it is more preferable to carry out a step of removing the radical polymerizable monomer remaining in the base material on which the polymer has been formed. According to this configuration, the radical polymerizable monomer remaining unreacted in the substrate without contributing to the above-described polymerization can be removed from the substrate after the polymer pattern is formed. Thereby, in the base material on which the polymer pattern has been formed, a change in characteristics due to the polymerization of the unreacted monomer can be suppressed. Generally, a radical polymerizable monomer requires a radical to initiate its initiation reaction, but the polymerization reaction progresses little by little due to energy other than the radical, that is, energy such as heat or light. Therefore, if the unreacted monomer is not removed,
A change in the characteristics of the polymer pattern, typically, a change in the shape of the pattern may occur. Further, the unreacted radical generator may be removed at the same time.

Here, as a method for removing such unreacted monomers, for example, a substrate on which a polymer pattern has been formed is placed in a reduced-pressure atmosphere to destroy the substrate and the formed polymer. It may be carried out by heating to such an extent that it does not.

In practicing the present invention, it is more preferable that the base material of the above-described base material is at least a material that does not absorb light.

According to this configuration, the base material does not absorb light in a wavelength band in which radicals can be generated from the radical generator. Thereby, the base material made of the base material (first material) has a light transmitting property with respect to light capable of generating radicals from the radical generator. Therefore, light can reach a deep region from the surface of the base material, and a polymer pattern can be formed in that region.

Further, for example, when the base material formed of the base material does not transmit the light because the base material has absorption for light capable of generating radicals from the radical generator. However, by this light irradiation, radicals can be generated in an inner region near the skin of the base material.

In practicing the present invention, it is more preferable that the above-mentioned light is ultraviolet light. This is because there are many generally known radical generators that generate radicals with ultraviolet rays. Therefore, according to this configuration, radicals can be efficiently generated from the radical generator.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention of a method for forming a polymer pattern will be described below with reference to FIG.
In the drawings, the size, shape, and positional relationship of each component are only schematically shown to an extent that the present invention can be understood. In each drawing, the same components are denoted by the same reference numerals, and overlapping description may be omitted.

FIG. 1 is a process diagram illustrating one embodiment of forming a polymer pattern by using the method for forming a polymer pattern of the present invention. FIG. 1 is a cross-sectional view showing a main process of forming a polymer pattern. In the illustrated example, the base member 51 has a light transmitting property with respect to light for generating radicals from the radical generator. However, the case where the base material 51 does not have light transmittance for the light will also be described.

In the invention of the method for forming a polymer pattern, first, a substrate 51 containing a radical polymerizable monomer 53 and a radical generator 55 is prepared (FIG. 1A).

In order to obtain such a base material 51, for example, the first material serving as the base material of the base material is made liquid by adding an appropriate solvent or the like, and the first material is mixed with a radical polymerizable monomer and a radical generator. To prepare a substrate forming solution. After that, the substrate forming solution may be applied to an appropriate substrate, dried and solidified. Alternatively, for a substrate that does not contain a radical polymerizable monomer and a radical generator, that is, for a substrate made of the first material,
The radical polymerizable monomer and the radical generator may be diffused in a gas phase or a liquid phase. For example, when diffusion is performed in a liquid phase, a radical generator and a radical polymerizable monomer are dissolved in an appropriate solvent to form a diffusion solution.
Thereafter, the substrate made of the first material can be diffused by immersing the substrate in the diffusion solution. When diffusion is performed in a gas phase, for example, a substrate made of the first material, a radical polymerizable monomer, and a radical generator are placed in a container. The container is sealed, the pressure in the container is reduced, and the radical polymerizable monomer and the radical generator are heated to such a degree that they become gaseous, and these are heated to the first.
What is necessary is just to diffuse into the base material which consists of said material. The first
The base material made of the above material may be any as long as it can diffuse the radical polymerizable monomer and the radical generator. Also,
In the formation of a substrate using a liquid for forming a substrate, or in the formation of a substrate by diffusion from a gaseous phase or a liquid phase, the formation is preferably performed in a state where light having a wavelength that generates radicals from a radical generator is shielded. It is suitable (not shown).

Next, light is applied to the polymer pattern forming region 57 of the base material 51. For example, the irradiation (exposure) of light to the polymer pattern forming region 57 is performed after the photomask 59 having an opening corresponding to the polymer pattern forming region is placed on the base material 51 ( FIG.
(B)).

When the substrate 51 is transparent to the light used for exposure by this light irradiation, the light reaches the region inside the substrate 51, so that the region to be irradiated (the region 57 where the polymer pattern is to be formed) is irradiated. ) Produces a polymer (FIG. 1 (C)).
In the illustrated example, the light travels from one surface to the other without changing its width. Thus, when the base material is transparent to light, the polymer is formed in the base material 51,
As shown in FIG. 1C, a polymer (polymer) pattern 6
1 is formed. Further, it is desirable that the light used for this irradiation is ultraviolet light and light in a wavelength band near the ultraviolet light. This is because, in general, many radical generators generate radicals by ultraviolet rays.

If the substrate 51 is not transparent to the light used for exposure, light is absorbed inside the substrate 51, so that light energy reaches only a small area near the skin. For this reason, a polymer is formed only in the small irradiated area and the vicinity thereof.

After the formation of the polymer pattern 61, the unreacted monomer may be removed as a preferred embodiment of the present invention. That is, after the polymer pattern 61 is formed as described above, the radical polymerizable monomer 53 remaining in the base material 51 without being reacted is removed (FIG. 1D). In the illustrated example, the radical generator 55 is also removed together with the radical polymerizable monomer 53.

As described above, this removal treatment is performed, for example, by placing a substrate on which a polymer pattern has been formed in an atmosphere under reduced pressure so that the formed polymer and the substrate are not destroyed. It may be performed by heating to a temperature that is low and high enough to volatilize unreacted monomers from the substrate. As described above, by removing the unreacted radical polymerizable monomer 53, it is possible to suppress the secular change of the structure and properties of the polymer pattern 61.

In the embodiment described above, a flat pattern is formed on the surface of a relatively thin substrate as shown in the figure. Typical examples of the use of such a polymer pattern include an optical waveguide and a grating.

Also, instead of the thin substrate as shown in the illustrated example,
A polymer pattern may be formed on a thick substrate. When the base material of the base material does not substantially absorb light that generates radicals from the radical generator, for example, a thick base material containing a radical polymerizable monomer and a radical generator is prepared, and the thickness of the base material is increased. There is a method in which a polymer pattern is formed in a base material by irradiating light having a converging property in the direction of the arrow to generate radicals along the optical path. It is considered that a laser or the like can be used to generate this convergent light. A typical application example of the polymer pattern formed in this way is a linear waveguide.

Here, examples of each of the first material, the radical polymerizable monomer, and the radical generator, which are the above-described base materials of the base material, will be described.

As the first material, for example, polymethyl methacrylate (PMMA), polycarbonate, polyurethane, polyacrylate, polyacrylonitrile and the like can be used. These substances are suitable because they substantially do not absorb light that generates radicals from the radical generator. As described above, a polymer having such light absorption can also be used. At that time, a polymer pattern is formed on the surface of the surface of the substrate irradiated with light and in the vicinity thereof. In addition, even if it is other than such a polymer, it is considered that the present invention is applicable not only to inorganic substances and organic substances, but also can be applied as long as the radical polymerizable monomer and the radical generator can be uniformly contained.

As the radical polymerizable monomer, for example, a radical polymerizable monomer such as methyl methacrylate, acrylonitrile, and methyl acrylate can be used. When the substrate is a polymer, if these radically polymerizable monomers are the monomers (monomers) of the polymer constituting the substrate, the polymer pattern can be formed as a pattern that differs only in density from the substrate. it can. That is, when the base material was formed as a polymer, and the radical polymerizable monomer was used as a radical polymerizable monomer to be a monomer of the polymer to form a polymer pattern, properties such as the refractive index were slightly changed. A polymer pattern can be obtained.

As the radical generator, for example, 2,2
-Dimethyl-2-phenyl-acetophenone (2,2-
dimethyl-2-phenyl-acetoph
eneone), diazo compound, titanocene chloride (titanocene chloride), benzyl (benzil), 1- (4-isopropylphenyl)
-2-Hydroxy-2-methylpropan-1-one (1
-(4-isopropenylphenyl) -2-hy
dropy-2-methylpropan-1-o
n), 2-hydroxy-2-methyl-1-phenylpropan-1-one (2-hydroxy-2-methythy)
1-1-phenylpropan-1-on), azoisobutylnitrile (azoisobutylnitritol)
A substance that is radicalized by light, such as il), can be used.

[0040]

An embodiment of the present invention will be described below in more detail with reference to FIG. The materials used, the equipment used, and the numerical conditions such as temperature, pressure, film thickness, exposure conditions, dimensions of each part, and the like, which are described in the following description, are within the scope of the present invention. This is just one example. Therefore, the present invention is not limited to these conditions.

First, a substrate containing a liquid radical polymerizable monomer and a radical generator was prepared by the following procedure. 1.5 g of P as the first material which is the base material of the base material
MMA was treated with 2-methoxyethyl acetate (2-
(Methylethyl Acetate) at room temperature for 13 hours with stirring. Thereafter, the solution was filtered using a filter. Here, a PTFE (polytetrafluoroethylene) membrane having a pore diameter of 0.45 μm was used as a filter. This filtration removes dust and undissolved matter in the solution and removes 15% by weight of PMM.
A solution was obtained.

Next, this PMMA solution was applied onto the silicon wafer 63 by using a spin coating method. The condition of the spin coating method was 3000 rpm for 40 seconds. After spin coating, the silicon wafer 63 was dried and solidified while being heated at 95 ° C. At this time, a PMMA film 65 was formed on the silicon wafer 63 as a base material made of the first material (FIG. 2A).

Subsequently, methyl methacrylate (MMA) 67 as the radical polymerizable monomer 53 and 2,2-dimethyl-2-phenyl- as the radical generator 55
The acetophenone 69 is diffused into the PMMA film 65 in a gas phase. Therefore, the silicon wafer 63 on which the above-mentioned PMMA film 65 is formed is put into a light-shielded chamber together with 5 g of methyl methacrylate (MMA) and 0.1 g of 2,2-dimethyl-2-phenyl-acetophenone. The pressure in the chamber is 5 mmHg by vacuum means
After that, the inside of the chamber was heated at 88 ° C. for 3 hours. Thereby, MMA and 2,2-dimethyl-2-phenyl-acetophenone were uniformly diffused in the PMMA film 65 (FIG. 2B).

Next, the above-mentioned diffused PMMA film 65, that is, the base material 51, was irradiated with light having a wavelength of 330 nm through a photomask 59 having a 20 μm line and space pattern in a nitrogen atmosphere (FIG. 2
(C)). Thereby, the PMMA film 6 as the base material 51
In the polymer pattern forming region 57 inside 5,
A radical is generated, and the radical is a monomer MM
By addition and polymerization of A, PMMA which is a polymer of this MMA was formed (FIG. 2 (D)). At this time, regions in the base material that are made of the same substance but have different molecular densities (that is, polymer patterns 61) are formed. The nitrogen atmosphere is used to prevent radicals generated in the base material from reacting with oxygen in the atmosphere.

Subsequently, the radical polymerizable monomer 53 (MMA 67) and the radical generator 55 (2,2-dimethyl-2-phenyl-acetophenone) remaining unreacted were obtained from the PMMA film 65 on which the polymer pattern had been formed. 69) is removed. Therefore, the silicon wafer 63 including the PMMA film 65 on which the polymer pattern has been formed is placed in a light-shielded chamber, and the pressure in the chamber is reduced to 5 mmHg by vacuum means.
It was kept at 5 ° C. One hour after the heating, the pressure in the chamber was reduced again to 5 mmHg by using vacuum means. By this operation, unreacted MMA 67 and 2,2-dimethyl-2-phenyl-acetophenone 69 remaining in the PMMA film 65 were removed (FIG. 2E).

When the PMMA film formed as described above was observed with an optical microscope, a line and space pattern of about 20 μm was formed on the PMMA film. In this way, the pattern can be seen with an optical microscope because the refractive index of the part where the radical polymerizable monomer is polymerized and fixed is
This is because it is different from the surroundings.

[0047]

As is apparent from the above description, according to the invention of the method for forming a polymer pattern, a substrate containing a radical polymerizable monomer and a radical generator is prepared, and the polymer pattern of the substrate is prepared. A polymer pattern is formed by selectively irradiating light to a region to be formed and forming a polymer of a radical polymerizable monomer in this region. As described above, according to the present invention, since the polymer pattern can be formed without using the RIE method, the problem when the RIE method is used can be solved. Therefore, a polymer pattern can be formed easily and cheaply as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a diagram provided for describing a method for forming a polymer pattern according to an embodiment.

FIG. 2 is a diagram for explaining a method for forming a polymer pattern according to an example.

FIG. 3 is a process chart of forming a conventional polymer pattern.

[Explanation of symbols]

51: Base material 53: Radical polymerizable monomer 55: Radical generator 57: Polymer pattern forming area 59: Photomask 61: Polymer pattern 63: Silicon wafer 65: PMMA film 67: Methyl methacrylate (MMA) 69: 2 , 2-Dimethyl-2-phenyl-acetophenone

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mitsuro Mita 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Katsutaki Kaibu 1-7-112 Toranomon, Minato-ku, Tokyo Offshore F term (reference) in Electric Industries Co., Ltd. 2H047 PA02 PA12 PA21 PA22 PA28 QA05 QA07 TA43 4F071 AA31 AA33 AA34 AA50 AA53 AE06 AG15 AH12 BB12 4F073 AA14 CA45 FA03

Claims (6)

[Claims] 1. A substrate containing a radical polymerizable monomer and a radical generator is prepared, and a region where a polymer pattern is to be formed on the substrate is selectively irradiated with light, and the region is exposed to the radical polymerizable monomer. A method for forming a polymer pattern, comprising a step of forming a polymer of the above. 2. The method for forming a polymer pattern according to claim 1, further comprising a step of removing the radically polymerizable monomer remaining in the base material on which the polymer has been formed. A method for forming a molecular pattern. 3. The method for forming a polymer pattern according to claim 1, wherein the base material is prepared by diffusing the radical polymerizable monomer and the radical generator into a base material made of a first material. A method for forming a polymer pattern, comprising: 4. The method for forming a polymer pattern according to claim 1, wherein a refractive index region different from the base material is formed in the region by the polymer. 5. The method for forming a polymer pattern according to claim 1, wherein the base material is composed of a first material, the radical polymerizable monomer, and the radical generator. Wherein said material is a material that does not substantially absorb said light. 6. The method for forming a polymer pattern according to claim 1, wherein the light is ultraviolet light.