JP2003149440A - Photonic crystal and manufacturing method thereof - Google Patents

Abstract

[PROBLEMS] To provide a photonic crystal having as few shaping layers as possible and having no problem that a fragile film is easily formed on a rectangular side wall portion of a conventional photonic crystal and defects are easily generated, and a method of manufacturing the same. I will provide a. Kind Code: A1 Abstract: Two types of films having different refractive indices are alternately stacked on a substrate having a periodic structure composed of a concave-convex pattern having a trapezoidal cross-sectional shape, and the cross-sectional shape of a layer having a stationary shape is triangular or A photonic crystal characterized by a trapezoid, and a rectangular cross-sectional pattern formed on the substrate surface, the cross-sectional shape of the pattern is trapezoidal, and the cross-sectional shape is refracted onto a substrate having a trapezoidal pattern. Rate n
1. A method for producing a photonic crystal, comprising: forming a film having a refractive index of n2 and a film having a refractive index of 1 alternately; and shaping the film by ion etching or reactive ion etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photonic crystal used for a light emitting device, a small optical waveguide, etc., in which two or more kinds of materials having different refractive indexes are periodically arranged, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In this type of photonic crystal, a three-dimensional photonic crystal is formed by forming a three-dimensional periodic structure by laminating layers having different dielectric constants on a substrate on which a two-dimensional periodic structure is formed. There is a way to do it. In this case, if the normal stacking conditions are used, the three-dimensional periodic structure is not formed because the surface is rapidly flattened, but an uneven pattern is formed on the substrate and the uneven pattern on the substrate surface is duplicated by the bias sputtering method. However, it was reported that photonic crystals with a three-dimensional periodic structure could be prepared by depositing multilayer films (S. Kawasaki, Electronics Letters
33, 1260, 1997). A specific film formation mode in which a multilayer film is deposited while replicating the concavo-convex pattern on the substrate surface is called a self-cloning mode.

Conventionally, a photonic crystal uses a substrate having an uneven pattern of a rectangular cross section on its surface, and uses high frequency magnetron sputtering to form two films having different refractive indexes on the substrate in a self-cloning mode. It is manufactured by alternately forming a film and laminating. The main steps of forming a three-dimensional photonic crystal in the self-cloning mode are shown below. FIG. 6 is a diagram showing a substrate forming process, 6-1 shows a substrate, and 6-2 shows a state in which the resist pattern 2 is formed on the substrate 1. 6-3 shows a state in which the substrate exposed without being covered with the resist pattern is subjected to reactive ion etching, and then the resist pattern is removed to form an uneven pattern having a rectangular cross section on the substrate. A silicon wafer, a wafer with an oxide film, quartz, or the like is used as the substrate 1, and a periodic resist pattern is formed on this. Using this resist pattern as a mask, reactive ion etching is performed to form an uneven pattern having a rectangular cross section on the substrate surface. Then remove the resist pattern,
Films 4 and 5 having different refractive indexes are alternately formed and laminated on the substrate 3 having an uneven pattern by bias sputtering in which sputtering and ion etching are combined. For example, wavelength 1.
In the case of a photonic crystal intended for optical communication of 55 μm, one in which silicon and silicon oxide are alternately formed and laminated is used.

FIG. 7 shows an example of a sectional structure of a photonic crystal formed by the autocloning method. That is, on the substrate 11 having an uneven pattern of a rectangular cross section on the substrate surface,
A film 6 having a refractive index n1 and a film 7 having a refractive index n2 are alternately laminated. In forming the film, a bias is applied to the substrate while forming the film by the high-frequency magnetron sputtering on the substrate 11 having the uneven pattern of the rectangular cross section on the surface manufactured in the process shown in FIG. in this way,
Etching occurs simultaneously with film formation, and as the films are stacked, the shape of the rectangular cross section shifts to the shape of the triangular cross section. The state in which the shape of the rectangular cross section shifts to the shape of the triangular cross section is called a shaping layer 12, and the state in which the shape of the desired triangular cross section is changed is called a layer 13 having a steady shape.

The main mechanism of this self-cloning is as follows: 1) Silicon or silicon oxide, which is a raw material of a film, is diffused and incident on a substrate having an uneven pattern of a rectangular cross section. The protrusions spread upward, left and right, and the recesses do not progress the film deposition due to the effect of shadows. Furthermore, since the raw material particles are electrically neutral, they are not affected by the DC potential difference generated along the plasma sheath. 2) Gas ions (usually argon) to be etched are incident on a substrate having an uneven pattern of a rectangular cross section. Argon is vertically incident on the substrate due to the DC potential difference. The etching rate of the inclined surface due to ion bombardment is usually maximum at a steep slope of 45-60 °. Therefore, when the effects of 1) and 2) are overlapped, the surface shape changes and the initial rectangle shifts to a desired shape. 3) A part of the raw material particles jumped out from the uneven substrate by etching reaches another part and adheres thereto. Redeposition occurs at the recess. There are three points in which the redeposition phenomenon acts to fill the recessed portion. In this way, by superimposing the ion etching by the bias on the film formation by the high frequency magnetron sputtering, the photonic crystal having the triangular cross section can be formed from the uneven pattern of the rectangular cross section.

[0006]

Even in the production of photonic crystals by the self-cloning method as described above, when a substrate having a concave-convex pattern of a rectangular cross section is used as the substrate, the rectangular cross section has a triangular cross section. A large number of shaping layers are required to migrate, and this shaping layer corresponds to a loss portion as a photonic crystal. Therefore, there has been a demand for minimizing the shaping layer. In addition, when a substrate having an uneven pattern with a rectangular cross section is used, even if a film is formed by high-frequency magnetron sputtering, it is difficult for the film to adhere to the rectangular side wall, so a fragile film is likely to be generated and defects are also generated. There was a problem that it was easy. When attempting to strengthen the adhesion of the side wall portion, there is a problem that more particles sputtered by the ions are scattered and the sputtered particles adhere to the sample stage and the inner wall of the apparatus, causing defects.

[0007]

In view of such a situation, the present inventors can reduce the number of shaping layers, have no problem due to the adhesion to the side wall, and can obtain a high-quality film. As a result of earnestly studying the manufacturing method of the nick crystal,
The present invention has been reached. That is, the gist of the present invention is that the cross-section of a film of a layer having a steady shape is formed by alternately laminating two types of films having different refractive indexes on a substrate having a periodic structure having a concavo-convex pattern having a trapezoidal cross-section. The photonic crystal is characterized in that the shape is a triangle or a trapezoid, and further, the first step of forming an uneven pattern of a rectangular cross section on the substrate surface, and the uneven pattern from the uneven pattern by ion etching or reactive ion etching. A second step of forming a concavo-convex pattern having a trapezoidal cross section, and forming a film having a refractive index n1 on a substrate having the concavo-convex pattern having a trapezoidal cross section, and performing the ion etching or the reactive ion etching to obtain the refractive index n1. The third step of shaping the shape of the film is formed by forming a film having a refractive index n2 on the film having a refractive index n1 and performing ion etching or reactive ion etching.該屈 Oriritsu n
And a fourth step of shaping the shape of the film, wherein the third and fourth steps are alternately performed one or more times.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a process of forming a concavo-convex pattern having a trapezoidal sectional shape on the substrate surface. A pattern of a resist 2 is formed on the substrate 1 so as to form a predetermined periodic structure (1-1), and the substrate 1 is etched using the resist 2 as a mask to form an uneven pattern having a rectangular cross-section (1-). 2). Next, the protrusions 3 having a rectangular cross section are sputter-etched to form the protrusions 4 having a trapezoidal cross section, and an uneven pattern having a trapezoidal cross section is formed. As the material of the substrate 1 used in the present invention, any material can be used as long as it is used for forming a photonic crystal, and examples thereof include a silicon wafer, a wafer with an oxide film, and quartz.

Here, an example of trapezoidal concavo-convex pattern formation will be described by taking a case of a fused silica substrate as an example. A resist is applied to a quartz substrate, and a desired resist pattern is formed by electron beam lithography, X-ray lithography, photolithography, or the like. Appropriate lithographic means may be selected according to the pattern size. Using this resist as an etching mask, a Freon-based etching gas such as C ₂ F ₆ is used to form a quartz pattern having a vertical cross-sectional shape (rectangular cross-section) by reactive ion etching. Then, the remaining resist is peeled off, argon gas is introduced into a parallel plate type ion etching apparatus, and sputter etching is performed to obtain a concavo-convex pattern having a trapezoidal sectional shape. Generally, when the ion irradiation angle is 45 to 60 °, the sputtering speed becomes maximum and a pattern having an inclination of 45 to 60 ° is formed. In the case of the present invention, the RF power was 200 W, the argon gas flow rate was 20 sccm, and the tilt angle was approximately 50 °.

The substrate obtained by the process shown in FIG.
The surface has a one-dimensional periodic structure in which a large number of protrusions having a trapezoidal cross section are arranged in parallel at regular intervals. The pitch of the period of the trapezoidal concave-convex cross section formed on the substrate 1 is preferably half the wavelength λ of the light to be processed by the obtained photonic crystal (≦ λ / 2). This pitch is preferably one tenth or more (≧ λ / 10).

In FIG. 2, a film 6 having a refractive index n1 and a film 7 having a refractive index n2 are formed on a substrate 5 having a concavo-convex pattern having a trapezoidal cross section.
FIG. 3 is a schematic cross-sectional view of a photonic crystal in which layers having a steady shape have a triangular cross-section, which are obtained by alternately stacking This photonic crystal is a crystal having a two-dimensional periodic structure having a substrate surface direction perpendicular to the trapezoid and a periodic structure in a direction perpendicular to the substrate surface. Although FIG. 2 shows that a layer having a steady shape can be obtained with a relatively small number of layers, normally, a photonic crystal has a number of layers of 10 to 200 (a layer of a film having a refractive index n1 and a refractive index of n1). It is preferably the number of pairs when the layer of the film of n2 is a pair). Also,
The number of layers having a steady shape is preferably 10 or more.

The film is formed by forming a film 6 having a refractive index n1 on a substrate 5 having a concavo-convex pattern having a trapezoidal cross section by sputtering and shaping the film by ion etching or reactive ion etching. The step of forming the film 7 having the refractive index n2 by sputtering and shaping the film by ion etching or reactive ion etching is performed alternately. At least one of the film having the refractive index n1 and the film having the refractive index n2 is formed. One of them is preferably formed by electron cyclotron resonance sputtering (hereinafter referred to as ECR sputtering). In the case of ECR sputtering, the part that has been subjected to ion bombardment becomes a good quality film. In the present invention, since a substrate having a concavo-convex pattern having a trapezoidal cross section is used, sufficient ion bombardment can be obtained even on the slope of the periodic concavo-convex pattern. Therefore, the bottom of the pattern, the slope,
In addition, since the upper part is relatively uniformly ion-impacted and the entire surface is ion-impacted, a high quality film can be obtained.

Further, when ECR sputtering is used,
Since it has a very high reactivity, an optically effective and high-quality compound film such as tantalum oxide, zirconium oxide, and aluminum oxide can be easily formed using a metal target.
A nitride such as aluminum nitride or silicon nitride can be easily formed. As described above, since there is a margin in material selection, it is possible to form a photonic crystal made of a combination of materials that cannot be considered by the conventional method. When ECR sputtering is used, the part that receives ion bombardment becomes a good quality film, and the difference in the quality of the film between the part that is not directly bombarded with ion bombardment and the part that is not bombarded is more than in high frequency magnetron sputtering. It becomes remarkable. When a rectangular uneven pattern is present on the substrate surface, a weak film is formed on the rectangular vertical side wall with almost no ion bombardment, and the characteristic of ECR sputtering is lost. On the other hand, if a trapezoidal periodic pattern is formed on the surface of the substrate as in the present invention, sufficient ion bombardment is given even to the slope of the periodic unevenness. Therefore, the ions are bombarded relatively uniformly on the bottom, slope and top of the pattern. Since the entire surface is subjected to ion bombardment, a good quality film can be obtained.

The thickness of each layer is the thickness of a film having a refractive index n1.
1. When the thickness of the film having a refractive index n2 is d2, n1 × d1
And n2 × d2 are preferably in the range of λ / 4 ± λ / 10. FIG. 3 is obtained by alternately forming a film having a refractive index n1 and a film having a refractive index n2 on a substrate 5 having a concavo-convex pattern having a trapezoidal sectional shape, and each layer maintains the trapezoidal sectional shape pattern of the substrate. It is a cross-sectional schematic diagram which shows the photonic crystal of a two-dimensional periodic structure obtained by laminating. When each layer maintains the pattern of the trapezoidal cross-sectional shape of the substrate, it can be said that there is no shaping layer and all layers are layers having a steady shape. That is, as the photonic crystal having the two-dimensional periodic structure, the cross-sectional shape of the film of the layer having a steady shape may be triangular or trapezoidal. After the film is formed,
If the apex of the trapezoid is etched by sputter etching, as the number of layers increases, the shoulder of the trapezoid is removed, resulting in a triangular shape. When a substrate having a trapezoidal cross-section pattern is used as the substrate, the number of shaping layers can be reduced as compared with the case where a substrate having a rectangular cross-section uneven pattern is used. Further, by reducing the time of sputter etching after the film formation, each layer can be laminated while maintaining the trapezoidal cross-sectional pattern of the substrate.

FIG. 4 is a diagram showing an example in which the substrate surface is two-dimensionally processed, and FIG. 4a is a plan view of a hexagonal pattern.
FIG. 4b is an XY sectional view of the substrate. A hexagonal trapezoidal hole is formed in the substrate 1, 8 indicates the slope of the trapezoidal hole, and 9 indicates the bottom of the trapezoidal hole. FIG. 5 is a diagram showing a manufacturing process of a substrate having hexagonal trapezoidal holes,
Mask the surface of the substrate other than the part to make holes with resist,
By ion etching or reactive ion etching,
Make a hexagonal hole with a rectangular cross section. FIG. 5a shows a plan view of the substrate with holes having a rectangular cross section. Then, the edge portion of the hole is removed by sputter etching to form the slope 8 of the hole. FIG. 5b is a plan view of a substrate having trapezoidal holes. Although FIGS. 4 and 5 show an example in which a hole having a trapezoidal cross section is formed, a trapezoidal protrusion may be provided instead of forming a hole. In both the case of the concavo-convex pattern having a one-dimensional trapezoidal sectional shape and the case of a concavo-convex pattern having a two-dimensional trapezoidal sectional shape, the inclination of the slope is preferably 45 to 60 °.

[0016]

EXAMPLES The present invention will be described in more detail below with reference to examples. Obviously, the present invention is not limited to each embodiment. (Example 1) Considering the use for an optical deflector for a wavelength of 1.55 μm, the process shown in FIG.
The concavo-convex pattern having a one-dimensional periodic structure having a concavo-convex pattern having a trapezoidal cross section was formed on a silicon substrate at a pitch of about 0.7 μm. The angle of the slope of the trapezoidal cross section was 50 °.
A silicon oxide film and a silicon film were alternately laminated on this substrate. The film thickness of the silicon oxide film (refractive index 1.46) was 0.27 μm, and the film thickness of silicon (refractive index 3.24) was 0.12 μm. ECR sputtering was used for the silicon oxide film, and the film forming conditions were Ar 20 sccm,
Oxygen 7sccm, microwave power 500W, RF
The power was 200W. The silicon film is formed by high frequency magnetron sputtering, and the film forming conditions are Ar50scc.
m and RF power were 200W. In both the case of the silicon oxide film and the case of the silicon film, sputter etching was performed for 2 to 3 minutes after the film formation to shape the film shape so that the cross-sectional shape of the outermost layer of the film was triangular. The number of laminated layers in the layer having a steady shape was 10. The obtained photonic crystal did not show a fragile film on the side wall, which was observed when using a substrate having an uneven pattern of a rectangular cross section, showed a uniform periodic structure over the entire surface, and a good quality film was formed. .
The number of laminated shaping layers in this crystal was about three.
This photonic crystal was a good optical deflector for a communication wavelength of 1.55 μm.

(Example 2) He-Ne laser (wavelength: 0.
6328 μm) for use as a light source for a deflector, the step shown in FIG. It was formed on a silicon oxide substrate. The angle of the slope of the trapezoidal cross section was 50 °. Tantalum oxide films and silicon oxide films were alternately laminated on this substrate to form 20 layers. The film thickness of the tantalum oxide film (refractive index 2.55) was 0.07 μm, and the film thickness of silicon oxide (refractive index 1.46) was 0.14 μm.
Both the tantalum oxide film and the silicon oxide film were subjected to ECR sputtering, tantalum was used as the target for forming the tantalum oxide film, and silica was used for forming the silicon oxide film, and the film forming conditions were Ar 20 sccm and oxygen 7 sccm.
The microwave power was 500 W and the RF power was 500 W. When laminating the films, the shape was maintained by film formation and subsequent sputter etching so that the shape of the trapezoidal pattern formed on the silicon oxide substrate was maintained. The obtained photonic crystal showed a uniform periodic structure over the entire surface, and a good quality film having no brittle portion was formed.
This crystal has no shaping layer. The polarizer characteristics of this photonic crystal were good as an optical deflector for a He-Ne laser.

(Embodiment 3) Implementation was carried out except that a silicon substrate provided with hexagonal trapezoidal cross-section holes (angle of slope of trapezoidal cross section: 50 °) at a pitch of about 0.7 μm as shown in FIG. A photonic crystal having a stacking number of 105 was obtained in the same manner as in Example 1. The cross-sectional shape of the film of the layer having a steady shape of the obtained photonic crystal was triangular. The number of layers in the layer having a steady shape was 100, and the number of layers in the shaping layer was about 5. The photonic crystal obtained is
It has a uniform periodic structure over the entire surface, and a good quality film with no fragile parts is formed. The wavelength for communication is 1.55 μm.
Was a good light deflector for.

(Embodiment 4) A silicon oxide substrate having hexagonal trapezoidal cross-section holes (angle of slope of trapezoidal cross section: 50 °) with a pitch of about 0.3 μm as shown in FIG. 4 was used. A photonic crystal having 20 layers was obtained in the same manner as in Example 2. The film of each layer of the obtained photonic crystal maintained the uneven shape of the silicon oxide substrate as it was. The obtained photonic crystal showed a uniform periodic structure over the entire surface, and a good quality film having no brittle portion was formed. The polarizer characteristic of this photonic crystal is He-Ne.
It was a good laser light deflector.

(Comparative Example 1) A silicon substrate having a concavo-convex pattern of a one-dimensional periodic structure having a concavo-convex pattern having a rectangular cross-section with a pitch of approximately 0.7 μm was used, and the number of laminated layers was 13.
In the same manner as in Example 1, except that both the silicon oxide film and the silicon film were formed by high frequency magnetron sputtering under the conditions of Ar 50 sccm and RF power of 200 W, a photonic crystal for an optical deflector for a communication wavelength of 1.55 μm. It was created. The obtained crystals had 3 shaping layers and 10 layers having a steady shape. In this crystal, the film quality of silicon oxide is poor at the bottom of the triangle, and
The angle of the triangle was as shallow as 40 °. Therefore, the shape and the optical properties are insufficient.

(Comparative Example 2) A wavelength for communication was obtained in the same manner as in Example 1 except that a silicon substrate having an uneven pattern of a one-dimensional periodic structure having an uneven pattern having a rectangular cross section with a pitch of about 0.7 μm was used. An attempt was made to make a photonic crystal for a light deflector for 1.55 μm. Ions did not reach the bottom corners of the rectangular concavo-convex pattern, resulting in cavities and defects, and the vertical sidewalls became very fragile films, not photonic crystals.

As described above, when a substrate having a concavo-convex pattern having a rectangular cross section is used, the side wall becomes a very fragile film in ECR sputtering, and a good film cannot be obtained. When a film is formed,
The obtained photonic crystal had insufficient uniformity and many defects were observed. On the other hand, according to the method of the present invention, a high-quality film showing a uniform periodic structure over the entire surface and having no fragile portion. It can be seen that a photonic crystal in which is formed is obtained.

[0023]

EFFECTS OF THE INVENTION The photonic crystal of the present invention has no fragile film on the side wall, which is observed when a conventional substrate having an uneven pattern of a rectangular cross section is used, and has a uniform and good quality film over the entire surface. In addition, a film having a regular shape and having a trapezoidal cross-section has no shaping layer, and has a characteristic that a good photonic crystal can be obtained with a relatively small number of layers. In addition, even if the cross-sectional shape of the film of the layer having a steady shape is triangular, the number of layers of shaping layers can be significantly reduced as compared with the case where a substrate having a concavo-convex pattern of a rectangular shape is used. Have.

According to the method for producing a photonic liquid crystal of the present invention, since a substrate having a concavo-convex pattern having a trapezoidal sectional shape is used, a good quality film can be formed over the entire surface and a shaping layer is formed. It can be eliminated or greatly reduced. Further, compared to the case of using a conventional substrate having a concavo-convex pattern with a rectangular cross section, sufficient ion bombardment can be applied to the entire surface, so that a good quality film can be formed on the entire surface and uniformity can be improved.

If a method of forming at least one of the film having the refractive index n1 and the film having the refractive index n2 by ECR sputtering is adopted, the reactivity is very strong.
Using a metal target, an optically effective and high-quality compound film such as tantalum oxide, zirconium oxide, or aluminum oxide can be easily formed. A nitride such as aluminum nitride or silicon nitride can be easily formed. This is because when using a substrate with a rectangular uneven pattern on the surface,
In ECR sputtering, a rectangular vertical side wall is a fragile film with almost no ion bombardment, so ECR sputtering could not be adopted, but since a substrate with a trapezoidal uneven pattern is used as the substrate. That is, a good quality film can be formed over the entire surface, and a compound film with low reactivity can be formed. As described above, since there is a margin in material selection, it is possible to form a photonic crystal made of a combination of materials that cannot be considered by the conventional method.

[Brief description of drawings]

FIG. 1 is a diagram showing a step of forming a trapezoidal concavo-convex pattern on a substrate surface.

FIG. 2 is a photo showing that a layer having a steady shape has a triangular cross section, which is obtained by alternately forming two kinds of films having different refractive indexes on a substrate having a concavo-convex pattern having a trapezoidal cross section. It is a cross-sectional schematic diagram of a nick crystal.

FIG. 3 is a two-dimensional periodic structure obtained by laminating two kinds of films having different refractive indexes on a substrate having a concavo-convex pattern having a trapezoidal sectional shape, each layer being maintained while maintaining the trapezoidal sectional pattern of the substrate. 3 is a schematic cross-sectional view showing the photonic crystal of FIG.

FIG. 4 is a diagram showing an example in which a substrate surface is two-dimensionally processed, FIG. 4a is a plan view of a hexagonal pattern, and FIG. 4b is an XY sectional view of the substrate.

5A and 5B are views showing a manufacturing process of a substrate having hexagonal trapezoidal holes, FIG. 5A is a plan view of a substrate having a rectangular cross section, and FIG. 5B is a plan view showing trapezoidal holes. It is a top view of a substrate.

FIG. 6 is a diagram showing a step of a conventional method of forming an uneven pattern having a rectangular cross section on a substrate.

FIG. 7 is a diagram showing an example of a cross-sectional structure of a photonic crystal formed by an autocloning method.

[Explanation of symbols]

1: substrate, 2: resist, 3: protrusion of rectangular cross section,
4: Projection of trapezoidal cross section, 5: Substrate having a concavo-convex pattern of trapezoidal cross section, 6: Film with refractive index n1, 7: Refractive index n
2 film, 8: slope of trapezoidal hole, 9: bottom surface of trapezoidal hole 11: substrate having an uneven pattern of rectangular cross section on the surface, 12: shaping layer, 13: layer having a steady shape

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Kaneko             2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo             Nutty Advance Technology Co., Ltd.             Inside the company (72) Inventor Kenji Kurihara             2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo             Nutty Advance Technology Co., Ltd.             Inside the company (72) Inventor Chiharu Takahashi             2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo             Nutty Advance Technology Co., Ltd.             Inside the company F term (reference) 2H047 PA04 PA21 PA24 QA01 QA02                       QA04                 2H049 BA02 BA45 BB00 BB06 BB62                       BC08 BC09 BC25

Claims (4)

[Claims] 1. A substrate having a periodic structure composed of a concavo-convex pattern having a trapezoidal cross section, and having different refractive indexes from each other.
A photonic crystal in which films of different types are alternately laminated, and the cross-sectional shape of the film of a layer having a steady shape is triangular or trapezoidal. 2. The photonic crystal according to claim 1, wherein the pitch of the period of the trapezoidal concavo-convex pattern is not more than half the wavelength of the light to be processed by the photonic crystal. 3. A first step of forming an uneven pattern having a rectangular cross section on a substrate surface, and a second step of forming an uneven pattern having a trapezoidal cross section from the uneven pattern by ion etching or reactive ion etching. A third step of forming a film having a refractive index n1 on a substrate having a concavo-convex pattern having a trapezoidal cross section and shaping the film having a refractive index n1 by ion etching or reactive ion etching; and a fourth step of forming a film having a refractive index n2 on the film having a refractive index n1 and shaping the film having a refractive index n2 by ion etching or reactive ion etching.
A method for producing a photonic crystal, wherein the third and fourth steps are alternately performed once or more. 4. The method for producing a photonic crystal according to claim 3, wherein at least one of the film having a refractive index n1 and the film having a refractive index n2 is formed by electron cyclotron resonance sputtering.