JP2000258645A - Three-dimensional periodic structure and two- dimensional periodic structure as well as their manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-dimensional periodic structure formed in such a manner that a photonic band gap effect can be enhanced and a method for manufacturing the same. SOLUTION: The respective materials of the three-dimensional periodic structure periodically laminated with plural kinds of the materials 301 and 302 varying in refractive indices in a thickness direction have a film-like shape having two-dimensional periodic ruggedness or two-dimensional periodic net-like shape within one period of the thickness direction and the intra-surface thickness of the regions consisting of the respective materials are modulated within the surface. The front surfaces and rear surfaces of the respective materials 301 and 302 have the two-dimensional periodic ruggedness structure. The raw material of the certain material is made incident from plural directions within the one period of the thickness direction, by which the ruggedness on the front surface of the material is more stressed than the ruggedness on the rear surface. The other certain material is made weaker in the ruggedness on the upper surface than the ruggedness on the rear surface by deposition having readhesion effect or etching. The thickness of the regions consisting of the respective materials are given modulation within the surface by these stages, by which the photonic band gap effect is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a two-dimensional periodic structure or a two-dimensional periodic structure comprising two or more substances having different refractive indexes which can be used for various optical elements such as a wavelength filter and a polarizer constituting an optical circuit. The present invention relates to a three-dimensional periodic structure and a two-dimensional periodic structure having a photonic band gap effect and a method for manufacturing the same.

[0002]

2. Description of the Related Art A photonic bandgap crystal (hereinafter abbreviated as a photonic crystal) is a material in which two or more substances having different refractive indexes form a lattice with a period slightly shorter than the wavelength of light used. If the refractive indices are sufficiently different, a wavelength band (called a band gap) in which electromagnetic waves cannot propagate at all is formed. The wavelength band and bandwidth of this band gap are mainly determined by the shape and period of the grating and the difference in the refractive index of the material. To obtain a wide band gap, a combination having a large difference in the refractive index is desirable. In particular, a photonic crystal having a three-dimensional periodic structure is advantageous for realizing miniaturization and three-dimensionalization of optical circuit components. However, for use in a wavelength band of optical communication, a photonic crystal having a period of 1 μm or less is used. It is technically difficult to manufacture a two-dimensional periodic structure.

However, in recent years, two or more types of substances are sequentially and substantially sequentially laminated on a substrate having two-dimensionally and substantially periodic irregularities, and at least a part of the laminate is subjected to sputter etching alone. Alternatively, a technique for forming a three-dimensionally substantially periodic structure by using it simultaneously with film formation has been developed. FIG. 1 shows a typical example of the structure of the developed structure. In FIG. 1, on a two-dimensional periodic unevenness formed on a substrate by a fine processing technique, a refractive index l. 46 SiO ₂ and a refractive index of 3.2
When the amorphous silicon (hereinafter a-Si) of No. 4 is alternately laminated and an appropriate condition is selected, a film is deposited while preserving the irregularities on the substrate, and as a result, the three-dimensional period as shown in FIG. A structure is formed. This three-dimensional periodic structure is a net-like structure in which SiO ₂ and aSi are alternately nested within one period in the thickness direction (z direction).

[0004]

However, in the conventional three-dimensional periodic structure shown in FIG. 1, when the optical characteristics are measured, a clear band gap is formed in the z direction, but in the in-plane direction (xy direction). ), No clear band gap could be observed. This is a cross section cut along the AA 'plane in the xy direction, which has a high refractive index a-Si and a low refractive index S-Si.
It has a strong modulation structure in which the relative ratio of iO ₂ changes in the z direction, and the mean refractive index increases and decreases within one cycle, while z
In the direction, a section cut along the BB 'plane,
This is presumed to be due to the fact that the relative proportions of Si and SiO ₂ having a low refractive index are almost the same, resulting in a structure with weak modulation.

FIG. 2 shows another example of the structure of the three-dimensional periodic structure according to the prior art (only the cross section is shown). In this case, the deep irregularities formed on the substrate cause In this example, a zigzag uneven structure is self-formed, and the shape is preserved thereafter to form a three-dimensional periodic structure.
In this case, when viewed within one period in the thickness direction (z direction), the structure becomes a film-shaped two-dimensional structure. However, since the in-plane thickness of each region made of each material is constant, the in-plane A band gap open in all directions could not be obtained.

An object of the present invention is to provide a three-dimensional periodic structure capable of increasing the photonic band gap effect and a method of manufacturing the same in view of the above points.

A further object of the present invention is to provide a two-dimensional periodic structure capable of increasing the photonic bandgap effect and a method of manufacturing the same.

[0008]

Means for Solving the Problems In order to achieve the above object, the present invention is directed to a three-dimensional periodic structure in which a plurality of types of substances having different refractive indexes are periodically laminated in a thickness direction. Within one period in the vertical direction, each substance forms a film shape having two-dimensional periodic irregularities or a two-dimensional periodic mesh shape, and the in-plane thickness of the region composed of each substance is in-plane. It is characterized by being modulated.

Here, preferably, the structure is a structure in which a low-refractive-index substance and a high-refractive-index substance are periodically laminated in the thickness direction. 2
It has a film-like shape with three-dimensional periodic irregularities, and the in-plane thickness of the region made of each material is approximately 0 to 100% in the plane.
Linearly modulated.

Preferably, the structure is a structure in which a low-refractive-index material and a high-refractive-index material are periodically laminated in the thickness direction. It has a film-like shape with three-dimensional periodic irregularities. The refractive index is minimized near a certain surface in the z direction, the refractive index is maximized near another surface in the z direction, and near a certain surface in the x, y directions. , The refractive index becomes maximum, and the refractive index becomes minimum near other planes in the x and y directions.

Also, preferably, the structure is a structure in which a material having a low refractive index and a material having a high refractive index are periodically laminated in a thickness direction, and the low refractive index material is formed within one period in the thickness direction. Is 2
A high-refractive-index material is filled in a hole portion of the mesh, and the in-plane thickness of a region made of each material is modulated in the surface.

Preferably, the structure has a structure in which a low-refractive-index substance and a high-refractive-index substance are periodically laminated in the thickness direction, and the low-refractive-index substance is formed within one period in the thickness direction. Has a film-like shape, and there is a two-dimensional periodic depression in the film,
The concave portion is filled with the high refractive index substance, and the in-plane thickness of the region made of each substance is modulated in the plane.

In order to achieve the above object, the invention of claim 6 is directed to a two-dimensional periodic structure in which a plurality of types of substances having different refractive indexes are periodically laminated in the thickness direction.
Each material has a film shape having one-dimensional periodic irregularities within the period, and the in-plane thickness of the region made of each material is modulated in the plane.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a three-dimensional structure in which a plurality of types of materials having different refractive indices are periodically laminated. With a periodic structure with irregularities
Within a period, a certain substance is irradiated with a raw material from a plurality of directions, so that irregularities on the upper surface of the substance are emphasized more than irregularities on the lower surface, and another substance is formed on the upper surface by deposition or etching having a redeposition effect. The unevenness is weaker than the unevenness on the lower surface, whereby the thickness of the region made of each material is modulated in the plane, and the photonic band gap effect is increased.

Here, preferably, a first step of forming a fine periodic uneven pattern on the surface of the substrate, and two targets of a low refractive index material and a high refractive index material capable of applying a substrate bias to the substrate. A second step of sputtering a high refractive index material by adjusting a substrate bias and a gas pressure so that the concave portion of the pattern is shaped into a relatively shallow wedge shape, and A third step of forming a relatively deep wedge shape by sputtering a low refractive index material on the refractive index material under a condition with a small etching effect or a reattachment effect, and forming a high refractive index material on the low refractive index material. And a fourth step of performing sputtering under a condition where the etching effect and the reattachment effect are large, and thereafter, the second step to the fourth step are sequentially repeated.

[0016] Preferably, a first step of forming a fine periodic concavo-convex pattern on the substrate surface;
A substrate bias can be applied, and the substrate is placed in a sputtering apparatus having two targets of a low refractive index material and a high refractive index material,
A second step of sputtering a high-refractive-index material under the conditions of a substrate bias and a gas pressure having a very large etching effect and re-attachment effect so that the concave portion of the pattern is shaped and flattened leaving a small wedge or projection. And sputtering the low-refractive-index material on the high-refractive-index material by adjusting the substrate bias and gas pressure so as to form a zigzag shape at a predetermined angle.
And a fourth step of entirely etching the cross section of the low-refractive-index layer until the cross-section of the low-refractive-index layer becomes substantially triangular by isotropic etching; and forming a high-refractive-index substance on the triangular low-refractive-index layer. A fifth step of adjusting the substrate bias and gas pressure so as to have a substantially flat surface having small wedges or projections to sputter a high-refractive-index material, and forming a cross-section of the high-refractive-index layer by isotropic etching. And a sixth step of etching the whole until it becomes an inverted triangle, and thereafter, the third to sixth steps are sequentially repeated.

[0017] Preferably, a first step of forming a fine periodic uneven pattern on the surface of the substrate;
A substrate bias can be applied, put into a sputtering apparatus having two targets of a low-refractive index substance and a high-refractive index substance, so that the concave portion of the pattern is shaped into a wedge shape having an angle of about 45 °, A second step of adjusting the substrate bias and the gas pressure to sputter a low refractive index material;
A third step of laminating a high-refractive-index substance on the low-refractive-index substance without applying a bias, and a fourth step of performing dry etching capable of selectively etching the high-refractive-index substance with high anisotropy. And a fifth step of sputtering a low-refractive-index substance on the high-refractive-index substance by adjusting a substrate bias and a gas pressure so that the substance has a wedge shape having an angle of about 45 °. Then, the third to fifth steps are sequentially repeated.

[0018] Preferably, a first step of forming a fine periodic concavo-convex pattern on the substrate surface;
A substrate bias can be applied, put into a sputtering apparatus having two targets of a low-refractive index substance and a high-refractive index substance, so that the concave portion of the pattern is shaped into a wedge shape having an angle of about 45 °, A second step of adjusting the substrate bias and the gas pressure to sputter a low refractive index material;
A third step of laminating a high-refractive-index substance on the low-refractive-index substance without applying a bias, and a fourth step of performing dry etching capable of selectively etching the high-refractive-index substance with high anisotropy. A fifth step of adjusting the substrate bias and gas pressure so that the low-refractive-index substance is formed in a wedge shape having a predetermined angle on the high-refractive-index substance, and isotropic. A sixth step of making a trapezoidal hole in the low-refractive-index layer by performing dry etching capable of etching the low-refractive-index substance more selectively, A seventh step of thinly laminating the thick and convex portions, and a dry etching for selectively etching the high-refractive-index material with high anisotropy are performed. And an eighth step of forming the hole portion. Wherein the sequentially repeating the eighth step from the fifth step.

According to a twelfth aspect of the present invention, there is provided a method of manufacturing a two-dimensional structure in which a plurality of types of materials having different refractive indexes are periodically laminated, wherein each material has a one-dimensional upper surface and a lower surface. In one period in the thickness direction, a certain material is irradiated with a raw material from a plurality of directions, so that the unevenness on the upper surface of the material is emphasized more than the unevenness on the lower surface. The upper surface irregularities are made weaker than the lower surface irregularities by deposition or etching that has a redeposition effect, so that the thickness of the region made of each material is modulated in the plane, and the photonic band gap effect increases. It is characterized by the following.

[0020]

According to the present invention, a plurality of kinds of substances are three-dimensional or
In a structure having a two-dimensional periodic structure, the photonic band gap effect is increased by modulating the in-plane thickness of each substance in the plane. Further, the present invention provides a method of manufacturing a semiconductor device, comprising the steps of: laminating two or more types of substances substantially periodically on two-dimensional or one-dimensional periodic irregularities formed on a substrate by a fine processing technique. By using sputter etching alone or at the same time as film formation on at least a portion of the three-dimensional periodic structure or the two-dimensional periodic structure using a technique for shaping irregularities into a desired shape, As a result, an increase in the photonic band gap effect is obtained.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In the following description, the non-modulation structure means that the ratio of the film thickness of the high-refractive-index material to the low-refractive-index portion occupying one cycle in the laminating direction is anywhere in a plane parallel to the substrate. This means a substantially constant structure, and the modulation structure means a structure in which the film thickness ratio changes depending on the location in the plane.

(First Embodiment) FIG. 3A shows a sectional structure of a three-dimensional periodic structure according to an embodiment of the present invention, and FIG. 3B shows a three-dimensional structure of the three-dimensional periodic structure. Is shown. The structure shown in FIG. 3 is a structure in which a low-refractive-index substance 301 and a high-refractive-index substance 302 are periodically laminated in the thickness direction (z direction), and within one period in the thickness direction. Each material has a film-like shape having two-dimensional periodic irregularities, and the in-plane thickness of the region made of each material is linearly modulated in the plane by 0 to 100%. Structure.

FIG. 4 shows the results of evaluating the band gap in the structure of FIG. 3 by three-dimensional electromagnetic field analysis. Also,
FIG. 5 is for comparison with the evaluation result of the present invention of FIG.
3 shows the results of evaluating the band gap of the conventional structure of FIG. FIG. 4 (b) is an enlarged view of the main part of FIG. 4 (a). In these graphs, the thick broken line indicates the band gap of the TM polarization in the used wavelength band, and a number of others. The thin line indicates the band gap of TM polarization having higher energy. Similarly, FIG. 5B is an enlarged view of the main part of FIG. 5A. In these graphs, a straight line indicates the band gap of the TM polarization, and a thin broken line indicates the TE polarization. The band gap of the wave is shown. FIG. 4C shows a cross-sectional structure corresponding to FIG. 3A, FIG. 5C shows a cross-sectional structure corresponding to FIG. 2, and the maximum in-plane of each region in FIG. This indicates that the three-dimensional electromagnetic field analysis was performed by forming the thickness a to be the same as one period of the used wavelength and the in-plane thickness of each region in FIG. 5 to 0.8a.

Further, in the three-dimensional electromagnetic field analysis shown in FIGS. 4 and 5, the unit cell (unit cell) is set as shown in FIG. 6A, and the hatched portion is amorphous Si of a high refractive index material (refractive index). 3.24), the white part is SiO _{2 of} low refractive index substance
(Refractive index: 1.46) and Nx, N in the x, y, and z directions.
The analysis was divided into y and Nz. The first Brillouin zone (first BZ) in this case is shown in FIG.

As shown in FIG. 5, in the conventional structure without film thickness modulation (unmodulated structure) shown in FIG. 2, a band gap is slightly opened by TE polarization at point M which is an in-plane direction, and TM polarization is increased. Wave gaps do not open. Further, at the point K in the plane, the band gap does not open for both the TE polarization and the TM polarization, so that the three-dimensional photonic crystal is not formed with both the TE and TM polarizations.

On the other hand, as shown in FIG. 4, in the film thickness modulation structure of the present invention shown in FIG. 3, a large band gap opens at the point M where the TM polarization is in the in-plane direction, and at the point K in the plane. Also, since a band gap is observed in the TM polarization and a common band gap is opened in all directions in the plane, a complete three-dimensional photonic crystal is obtained.

(Second Embodiment) FIG. 7 shows a sectional structure of another embodiment of the present invention. Here, a hatched portion indicated by reference numeral 702 is amorphous Si of a high refractive index material (refractive index 3.24), and a white portion indicated by reference numeral 701 is SiO ₂ (refractive index 1.46) of a low refractive index material. This structure
Although the film thickness does not change from 0 to 100% as in FIG. 3 described above, the film thickness changes greatly within the cycle. That is, in the z direction, the refractive index becomes minimum near the A1-A1 'plane, and becomes maximum near the A2-A2' plane. On the other hand, in the x and y directions, the refractive index becomes maximum near the B1-B1 'plane and becomes minimum near the B2-B2' plane.
When this structure is subjected to three-dimensional electromagnetic field analysis, the same effect of increasing the photonic band gap as in the case of the structure in FIG. 3 can be obtained.

(Modifications of First and Second Embodiments) In the structure shown in FIGS. 3 and 7, when the in-plane periodic structure is not two-dimensional but one-dimensional, if the periodic structure is periodically laminated in the thickness direction, Although it has a two-dimensional periodic structure and is useful for a component that controls polarization such as a polarizing element, the film thickness modulation structure also increases the photonic band gap effect in such a two-dimensional periodic structure. It is effective for Although the present invention mainly has a three-dimensional periodic structure, a two-dimensional periodic structure including a one-dimensionally stacked in-plane periodic structure is, of course, included.

As described above, in the structure periodically laminated in the thickness direction, each substance having a different refractive index within one period in the thickness direction has two-dimensional or one-dimensional periodic unevenness. If the in-plane thickness is modulated in the plane within one period in the structure having a film-like shape, an effect of increasing the photonic band gap can be obtained.

(Third Embodiment) FIG. 8 shows a sectional structure of still another embodiment of the present invention. Here, reference numeral 80
The shaded portion indicated by 2 is a high refractive index material, and the white portion indicated by reference numeral 801 is a low refractive index material. In this structure, the low-refractive-index material 801 within one period in the thickness direction forms a two-dimensional periodic net-like shape, and the hole portion is filled with another high-refractive-index material 802. The in-plane thickness of the region is modulated in the plane. Also in this structure, when three-dimensional electromagnetic field analysis is performed, clear band gaps are opened at points M and K by TM polarization.

(Fourth Embodiment) FIG. 9 shows a sectional structure of still another embodiment of the present invention. Here, a shaded portion denoted by reference numeral 902 is a high refractive index material, and a white portion denoted by reference numeral 901 is a low refractive index material. In this structure, the low-refractive index substance 901 within one period in the thickness direction has a film shape, and there is a two-dimensional periodic depression in the film,
This recessed portion is filled with another high refractive index substance 902, and the in-plane thickness of the region made of each substance is modulated in the plane. Also in this structure, when a three-dimensional electromagnetic field analysis is performed, a clear band gap is opened at the point M due to the TM polarization, but the gap is not opened at the point K because the degree of modulation is weak.

(Manufacturing Process) The fabrication of the structure of the present invention shown in FIG. 3, FIG. 6, FIG. 7, and FIG. 2 on
More than one kind of substance is sequentially laminated almost periodically, and sputter etching alone is performed on at least a part of the laminate,
Alternatively, when a manufacturing technique of forming a three-dimensional periodic structure by using the film at the same time as film formation is used, the three-dimensional periodic structure of the present invention can be easily formed.

That is, in the film formation by the bias sputtering, both the adhesion reaction and the etching by the ions coexist, and when the gas pressure or the bias to the substrate is changed, the directional ions and the non-directional The contribution of reactive molecules and the re-adhesion of the etched material changes. When this bias sputtering is performed on an uneven substrate,
Due to the effect that the raw material is incident from a plurality of directions, the irregularities on the upper surface of the material are emphasized more than the irregularities on the lower surface. On the other hand, when the deposition or etching effect having the re-adhesion effect is large, the irregularities on the upper surface of the substance are weaker than the irregularities on the lower surface.

The inventors of the present invention have established a technique of quantitatively controlling these reactions to form a wedge having an arbitrary inclination or to make the surface almost flat, and to complicate the present invention. A three-dimensional periodic structure and a two-dimensional periodic structure have been realized.

(First Example of Manufacturing Process) FIG.
FIG. 9 shows a step of manufacturing the periodic structure according to the second embodiment of the present invention shown in FIG. FIG. 10 shows the state of one side surface (for example, xz plane) of the object. In the case of manufacturing a three-dimensional periodic structure, the other side surface (for example, yz plane) rotated by 90 ° is shown. Is in the same state as FIG.

First, a fine concavo-convex pattern 1002 of 1 μm or less is formed on the surface of a substrate 1001 such as quartz glass by a fine processing technique such as photoetching (step 10-).
1). The concave portion of the concave-convex pattern 1002 is a simple step having a horizontal surface and a vertical surface.

The substrate 1001 is placed in a sputtering apparatus capable of applying a substrate bias and having two targets of a low refractive index material and a high refractive index material.
03 is sputtered (step 10-2). At this time, the substrate bias (bias voltage) and gas pressure are adjusted so that the simple step-shaped concave portion is shaped to have a relatively shallow wedge shape.

This shallow wedge-shaped high refractive index substance 100
3 can be formed into a relatively deep wedge shape by sputtering the low-refractive-index substance 1004 under the condition that the etching effect and the reattachment effect are small (Step 10-).
3).

This deep wedge-shaped low refractive index material 100
When the high refractive index material 1005 is sputtered on the surface 4 under the condition that the etching effect and the reattachment effect are large, the wedge can be made shallow (step 10-4).

Hereinafter, these (Step 10-3) and (Step 1)
By repeating steps 0-4) sequentially, the structure in FIG. 7 can be manufactured (step 10-5).

(Second Example of Manufacturing Process) On the other hand, in order to realize the structure of the periodic structure according to the first embodiment of the present invention shown in FIG. 3 by the bias patterning method, the following contrivance is required. is there. This step is shown in FIG.

First, an uneven pattern 1102 having a period of 1 μm or less is formed on the surface of the substrate 1101 by a fine processing technique (step 11-1). The concave portion of the concavo-convex pattern 1102 is usually a simple step as in FIG. 10, but a similar result is obtained even in a structure such as a zigzag structure (a structure in which a plurality of continuous heads are triangular). can get.

The substrate 1101 is placed in a sputtering apparatus capable of applying a substrate bias and having two targets of a low refractive index material and a high refractive index material.
03 is sputtered (step 11-2). At this time, when the sputtering is performed under the conditions of the substrate bias and the gas pressure where the etching effect and the reattachment effect are extremely large, the simple step-shaped concave portion is shaped and flattened. However, when the surface is completely flattened, a small wedge 1104 that does not matter in optical characteristics is left because the low refractive index material sputtered thereon cannot reproduce the two-dimensional periodic structure on the original substrate.

A low-refractive index material 1105 is sputtered thereon by adjusting the substrate bias and gas pressure so as to form a zigzag shape at an angle of 20 ° to 70 ° (step 11-3).
Next, etching is performed entirely by isotropic etching (for example, ion etching) until the cross section of the low refractive index layer becomes a triangle 1106 (step 11-4).

Then, the high refractive index material 1107 is sputtered by adjusting the substrate bias and gas pressure so that the high refractive index material 1107 has a substantially flat surface having a small wedge (step 11-5).

Thereafter, the whole is etched by isotropic etching until the cross section of the high refractive index layer becomes an inverted triangle 1108 (step 11-6).

The following (Step 11-3) to (Step 1)
Steps 1-6) are sequentially repeated to obtain the structure in FIG. 3 (step 11-7).

Although the process of FIG. 11 is more complicated than that of FIG. 10, since the bias sputtering and the ion etching can be performed by the same apparatus, the structure of FIG. Can be made. In this step, the high refractive index material 110 is provided in the depressions 1102 and 1106.
3 and 1107 are laminated and flattened, and the low refractive index material 110
5, a zigzag structure is formed, but these can be reversed because they can be controlled under the bias sputtering conditions. Also, the case where a small wedge is formed during flattening has been described, but a small projection instead of the small wedge functions in the same manner.

(Third Example of Fabrication Step) FIG. 12 shows a fabrication step of the three-dimensional periodic structure having a net-like two-dimensional periodic structure according to the fourth embodiment of the present invention shown in FIG.

First, a concavo-convex pattern 1202 having a period of 1 μm or less is formed on the surface of the substrate 1201 by a fine processing technique (step 12-1). The concave portion of the concave / convex pattern 1202 is a simple step, as in FIGS.

The substrate 1201 is placed in a sputtering apparatus capable of applying a substrate bias and having two targets of a low refractive index material and a high refractive index material.
03 is sputtered (step 12-2). At this time, the substrate bias and the gas pressure are adjusted so that a simple step-shaped concave portion is shaped to have a wedge shape having an angle of about 45 °.

When the high refractive index material 1204 is laminated thereon without applying a bias, the high refractive index material is laminated thickly on the concave portion and thinly on the convex portion so as to obscure the wedge shape on the lower surface ( Step 12-3).

Then, when dry etching with high anisotropy and capable of more selectively etching the high refractive index material was performed, the projections of the high refractive index material disappeared and the cross section of the high refractive index layer was separated. A triangle 1205 is formed.
2-4).

Next, a low-refractive index material 1206 is sputtered thereon by adjusting the substrate bias and the gas pressure so as to form a wedge shape having an angle of about 45 ° (step 12-).
5).

The following (Step 12-3) and (Step 12)
-4) and (Step 12-5) are repeated to obtain the structure in FIG. 9 (Step 12-6).

(Fourth Example of Manufacturing Process) FIG.
3 of the third embodiment of the present invention shown in FIG.
A manufacturing process of a two-dimensional periodic structure is shown, and this process is a partially modified process of FIG.

First, the concave and convex pattern 130 having a period of 1 μm or less formed on the surface of the substrate 1301 by a fine processing technique.
2, a low refractive index material 1303 is sputtered, and a high refractive index material is further laminated without applying a substrate bias. Then, a dry material having a high anisotropy and capable of more selectively etching the high refractive index material is used. FIG. 1 shows a process from etching to forming a triangle 1305 in which the cross section of the high refractive index layer is separated.
2 (Steps 12-1) to (Step 12-4).

A low-refractive index material 1306 was sputtered thereon by adjusting the substrate bias and the gas pressure so as to form a wedge shape having an angle of about 20 ° to 70 ° (step 13).
-5) After that, dry etching is performed to more selectively etch the isotropic low-refractive-index substance, and a trapezoidal hole 1307 is formed in the low-refractive-index layer (step 13-6). In this way, a reticulated low refractive index layer is obtained.

Next, the high refractive index substance 1308 is thick in the concave portion and thin in the convex portion so as to obscure the wedge shape on the lower surface.
Laminate (Step 13-7).

Next, dry etching with high anisotropy and capable of more selectively etching a high refractive index material is performed.
An inverted trapezoid 1309 in which the cross section of the high refractive index layer is separated is formed at the portion of the net-like hole (step 13-8).

The following (Step 13-5) and (Step 1)
3-6), (Step 13-7), and (Step 13-8) are sequentially repeated to obtain the structure in FIG. 8 (Step 13-).
9).

As described above, in any of the steps, a desired in-period film thickness modulation structure can be obtained by repeating sputtering and etching.

[0064]

Embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment) First, a first embodiment of the present invention corresponding to FIGS. 3 and 11 will be described. Electron beam resist is applied to a synthetic quartz glass substrate.
A 2 μm coating was applied, a conductive film for preventing charge-up was applied, and a 6 μm closest lattice dot pattern with a period of 0.4 μm was exposed by electron beam exposure. After the conductive film is peeled off and the electron beam resist is developed, quartz glass having a depth of 0.2 μm is etched by reactive ion etching using C ₂ F ₆ gas. After removing the resist (Step 11-
1) First, using a known bias sputtering apparatus (not shown) having two targets of SiO ₂ and amorphous Si, first, amorphous Si was applied without applying a substrate RF (high frequency) bias to an Alcon gas pressure of 15 mTo.
When deposited by sputtering at a thickness of 0.7 μm (average value) under conditions of rr and a gas flow rate of 120 SCCM, the concave pattern was buried and almost flattened to the extent that a slight depression of about 0.05 μm was left at the center (step). 11-2).

On this amorphous Si, SiO ₂ was applied with a substrate RF bias of 60 W and an argon gas pressure of 2 mTorr.
r, Gas flow rate When deposited by sputtering at a thickness of 0.5 μm (average value) under the condition of 90 SCCM, a zigzag cross-sectional shape with an average inclination angle of 60 ° was formed (step 11-3).

After that, using SF ₆ gas as an etching gas, RF power 50 W, argon gas pressure 10 mTo
rr, under the conditions of a gas flow rate 150SCCM, the SiO ₂ isotropically 0. 15 μm, etched, 0.4 mm on one side
The cross section was shaped into an isosceles triangle of μm (Step 11-
4).

On this isosceles triangle cross section, the substrate R
When amorphous Si was deposited by sputtering under an argon gas pressure of 10 mTorr and a gas flow rate of 80 SCCM with a thickness (average value) of 0.55 μm without applying an F bias, the concave pattern was buried and 0.1 μm was formed at the center.
The surface was almost flattened leaving a depression of about m (Step 11-
5). Then, using SF ₆ gas as an etching gas, R
Under the conditions of F power of 30 W, argon gas pressure of 8 mTorr, and gas flow rate of 120 SCCM, amorphous Si isotropically etched at 0.2 μm and a side is 0.4 μm.
m was formed into a cross-sectional shape close to an inverse isosceles triangle (step 1
1-6).

Thereafter, each of the above-described steps of depositing and etching SiO ₂ , depositing and etching amorphous Si, is performed in one step.
This was repeated 0 times to produce a structure corresponding to FIG.
1-7).

When the in-plane light transmittance of the manufactured sample was measured, a stop band was observed in all directions in the plane near 1.38 μm, confirming that the sample had a three-dimensional photonic band gap crystal structure. Was done. For comparison,
When a three-dimensional periodic structure corresponding to FIG. 2 according to the prior art was manufactured with the same size, material, and number of layers as the sample, and the light transmittance was measured, the stop band was found to be only TE polarization in the TM direction. Not observed. From this, it was confirmed that the photonic band gap effect was enhanced in the film-like structure having the modulated film thickness shown in FIG.

(Second Embodiment) Next, another embodiment of the present invention corresponding to FIGS. 9 and 12 will be described. An electron beam resist was applied to a synthetic quartz glass substrate at a thickness of 0.2 μm, a conductive film for preventing charge-up was applied, and a 6 μm closest lattice dot pattern having a period of 0.4 μm was exposed by electron beam exposure. After the conductive film is peeled off and the electron beam resist is developed, the quartz glass is etched to a depth of 0.16 μm by reactive ion etching using C ₂ F ₆ gas. After removing the resist (step 12-1 in FIG. 12), S
a bias sputtering apparatus used with two targets iO ₂ and amorphous Si, firstly, SiO ₂
1. Substrate RF bias 70 W, argon gas pressure
Under the conditions of 5 mTorr, gas flow rate of 100 SCCM
When deposited by sputtering with a thickness of 6 μm (average value), it was shaped into a zigzag cross section having an average inclination angle of 45 degrees and a depth of 0.2 μm (step 12-2).

Next, the amorphous Si was deposited by sputtering at a thickness of 0.4 μm (average value) under the conditions of an argon gas pressure of 15 mTorr and a gas flow rate of 120 SCCM without applying an RF bias to the substrate. More deposits were formed, and the zigzag cross-sectional shape was rounded to form a loose uneven structure of 0.05 μm (Step 1).
2-3).

Next, an RF power of 10
0W, gas pressure 1mTorr, gas flow rate 20SCCM
When the amorphous Si is etched under the condition of (1), the convex portion is etched earlier than the concave portion, and the width is 0.3.
Amorphous Si having an inverted triangular cross section having a height of 0.18 μm and a height of 0.18 μm was obtained (Step 12-4).

SiO ₂ was deposited on amorphous Si having an inverted triangular cross-sectional shape by applying a substrate RF bias of 70 W, an argon gas pressure of 2.5 mTorr, and a gas flow rate of 100 S.
When deposited by sputtering with a thickness of 0.5 μm (average value) under the conditions of CCM, it was reshaped into a zigzag cross-sectional shape having an average inclination angle of 45 degrees and a depth of 0.2 μm (step 12-5).

Thereafter, the steps of depositing amorphous silicon, etching and depositing SiO ₂ are repeated 10 times to obtain FIG.
(Step 12-6).

When the in-plane light transmittance of the manufactured sample was measured, TE and TM were measured in the Δ-M direction around 1.4 μm.
In both cases, a surface stop band was observed, but no stop band was observed at point K.

As described above, the embodiment using the combination of SiO ₂ and amorphous Si as the material system and the bias sputtering as the manufacturing technique has been described. However, as is clear from the three-dimensional electromagnetic wave analysis, this embodiment has a three-dimensional photonic crystal structure. It is clear that the above is generally applicable and is not limited to the present substance system and the present production method. For example,
In the present invention, Si ₃ N ₄ , Al ₂ O ₃ or the like can be used as a material having a low refractive index, and Ge, GaAs, or a metal can be used as a material having a high refractive index. Wafer bonding and the like can be used.

[0078]

As described above, according to the present invention,
In a periodic structure in which a plurality of types of materials having different refractive indices are periodically stacked in the thickness direction, each of the materials has two-dimensional or one-dimensional periodic unevenness within one period in the thickness direction. In this case, the photonic band gap effect is enhanced because the in-plane thickness of the region made of each material is modulated in-plane. .

Such a structure of the present invention provides a method of periodically laminating a plurality of types of substances having different refractive indexes on a substrate having irregularities, wherein each of the substances is two-dimensionally formed on the upper surface and the lower surface. It has a three-dimensional irregularity periodic structure, and within one cycle in the thickness direction, a certain substance makes a raw material incident from a plurality of directions, so that the irregularities on the upper surface of the substance are emphasized more than the irregularities on the lower surface. Certain materials can be easily and simply manufactured because the top surface irregularities are made weaker than the bottom surface irregularities by devotion or etching with a redeposition effect, so that the thickness of the region consisting of each material is given in-plane modulation. it can.

Further, the three-dimensional periodic structure or the two-dimensional periodic structure according to the present invention can be used for various filters such as a wavelength filter, an optical switch, an isolator, and a low threshold laser by using the enhanced photonic band gap effect. It can be used for high performance and miniaturization of optical components.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing a conventional three-dimensional periodic structure.

FIG. 2 is a structural sectional view showing another example of a conventional three-dimensional periodic structure.

FIG. 3 shows an in-plane film thickness modulation structure 3 according to the present invention.
It is a structural sectional view showing an example of a three-dimensional periodic structure.

4A and 4B show the results of a three-dimensional electromagnetic field analysis of a three-dimensional periodic structure according to the present invention, wherein FIG. 4A is a graph, FIG. 4B is a partially enlarged view, and FIG.

5A and 5B show the results of a three-dimensional electromagnetic field analysis of a conventional three-dimensional periodic structure, wherein FIG. 5A is a graph, FIG.
(C) is a sectional view.

6 is a schematic diagram showing a unit lattice (a) and a Brillouin zone (b) used in the electromagnetic field analysis in FIGS. 4 and 5. FIG.

FIG. 7 shows an in-plane film thickness modulation structure 3 according to the present invention.
FIG. 9 is a structural cross-sectional view illustrating another example of the two-dimensional periodic structure.

FIG. 8 is a structural sectional view showing an example of a reticulated three-dimensional periodic structure having an in-plane film thickness modulation structure according to the present invention.

FIG. 9 is a structural sectional view showing another example of a reticulated three-dimensional periodic structure having an in-plane film thickness modulation structure according to the present invention.

FIG. 10 is a process chart showing a manufacturing process of the three-dimensional periodic structure structure of FIG. 7 according to the present invention.

FIG. 11 is a process chart showing a manufacturing process of the three-dimensional periodic structure structure of FIG. 3 according to the present invention.

FIG. 12 is a process chart showing a manufacturing process of the three-dimensional periodic structure structure of FIG. 9 according to the present invention.

FIG. 13 is a process chart showing a manufacturing process of the three-dimensional periodic structure of FIG. 8 according to the present invention.

[Explanation of symbols]

101, 301, 701, 801, 901 Low refractive index material 102, 302, 702, 802, 902 High refractive index material 1001, 1101, 1201, 1301 Substrate 1002, 1102, 1202, 1302 Uneven pattern 1003, 1005, 1103 , 1107, 1204
High refractive index material 1004, 1105, 1203, 1303, 1306
Low refractive index substance 1106, 1108, 1305 Triangle 1307 Trapezoidal hole 1308 High refractive index substance 1309 Inverted trapezoid

Continued on the front page (72) Inventor Masaya Notomi 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Shojiro Kawakami 236 Doi, Wakabayashi-ku, Sendai City, Miyagi Prefecture (72) Inventor Takashi Sato 25-6-202 Aramaki Shinmeicho, Aoba-ku, Sendai, Miyagi Prefecture (72) Inventor Yasuo Odera 1-6-1-15 Doi, Aoba-ku, Sendai, Miyagi Prefecture Corp. Kaneko 201 (72) Inventor Takayuki Kawashima Sendai, Miyagi Prefecture No.45-5, Sannai-cho, Kawauchi, Aoba-ku, Yokohama Le Village 203 F-term (reference) 2H047 KA03 KB08 PA04 PA05 PA24 QA02 QA04 RA08 TA05 TA11 2H049 BA01 BA45 BC01 BC25 2H079 CA05 DA16

Claims (12)

[Claims] In a three-dimensional periodic structure in which a plurality of types of substances having different refractive indexes are periodically laminated in a thickness direction, each substance has two-dimensional periodic irregularities within one period in the thickness direction. A three-dimensional periodic structure, wherein the three-dimensional periodic structure has a film shape or a two-dimensional periodic network shape, and a thickness of a region made of each material in a plane is modulated in the plane. 2. A structure in which a low-refractive-index substance and a high-refractive-index substance are periodically laminated in the thickness direction, and each substance is two-dimensionally periodic within one period in the thickness direction. 2. The film according to claim 1, which has a film-like shape having irregularities, and wherein the in-plane thickness of the region made of each substance is linearly modulated by approximately 0 to 100% in the plane. Three-dimensional periodic structure. 3. A structure in which a low-refractive-index substance and a high-refractive-index substance are periodically laminated in the thickness direction, and each substance is two-dimensionally periodic within one period in the thickness direction. In the form of a film having irregularities, the refractive index is minimized near a certain surface in the z direction, the refractive index is maximized near another surface in the z direction,
The refractive index becomes maximum near a certain surface in the x, y directions, and the x, y
The three-dimensional periodic structure according to claim 1, wherein the refractive index is minimized in the vicinity of another surface in the direction. 4. A structure in which a low-refractive-index substance and a high-refractive-index substance are periodically laminated in a thickness direction, wherein the low-refractive-index substance is two-dimensionally formed within one period in the thickness direction. 2. A periodic net-like shape, wherein the holes are filled with the high-refractive-index material, and the in-plane thickness of a region made of each material is modulated in the plane. 3. The three-dimensional periodic structure according to 1. 5. A structure in which a low-refractive-index substance and a high-refractive-index substance are periodically laminated in a thickness direction, wherein the low-refractive-index substance is formed into a film in one cycle in the thickness direction. The film has a two-dimensional periodic dent in the film, and the dent portion is filled with the high refractive index material, and the in-plane thickness of the region made of each material is modulated in the surface. The three-dimensional periodic structure according to claim 1, wherein: 6. In a two-dimensional periodic structure in which a plurality of types of substances having different refractive indices are periodically laminated in the thickness direction, each substance has one-dimensional periodic irregularities within one period in the thickness direction. A two-dimensional periodic structure having a film-like shape, wherein the in-plane thickness of a region made of each material is modulated in the plane. 7. A method for manufacturing a three-dimensional structure in which a plurality of types of substances having different refractive indices are periodically laminated, wherein each substance has a two-dimensional periodic structure of upper and lower surfaces and a thickness direction. In one cycle, a certain substance is irradiated with a source substance from a plurality of directions, so that the irregularities on the upper surface of the substance are emphasized more than the irregularities on the lower surface, and another substance is formed on the upper surface by deposition or etching having a redeposition effect. Is characterized in that the thickness of the region made of each material is modulated in the plane by reducing the unevenness of the lower surface than the unevenness of the lower surface, and the photonic band gap effect is increased.
Method for manufacturing a two-dimensional periodic structure. 8. A first step of forming a fine periodic concavo-convex pattern on a substrate surface, and a sputtering apparatus having a substrate bias application target and two targets of a low refractive index material and a high refractive index material. A second step of adjusting the substrate bias and gas pressure to sputter a high refractive index material so that the concave portion of the pattern is shaped into a relatively shallow wedge shape; A third step of forming a relatively deep wedge shape by sputtering a low refractive index substance under conditions with little etching effect or reattachment effect, and etching a high refractive index substance on the low refractive index substance by etching. A fourth step of performing sputtering under a condition where the adhesion effect is large, and thereafter, repeating the second step to the fourth step sequentially. Production Law. 9. A first step of forming a fine periodic concavo-convex pattern on the surface of a substrate, and a sputtering apparatus having two targets, a low refractive index material and a high refractive index material, to which the substrate can be applied with a substrate bias. And a high refractive index material is sputtered under the conditions of a substrate bias and a gas pressure, which have a very large etching effect and re-adhesion effect, so that the concave portion of the pattern is shaped and flattened leaving a small wedge or projection. A second step of sputtering a low-refractive-index substance on the high-refractive-index substance by adjusting a substrate bias and a gas pressure so as to form a zigzag shape at a predetermined angle; A fourth step of etching the whole of the low refractive index layer by etching until the cross section of the low refractive index layer becomes substantially triangular; A fifth step of sputtering a high-refractive-index substance by adjusting a substrate bias and a gas pressure so that a high-refractive-index layer is formed, and until the cross section of the high-refractive-index layer becomes an inverted triangle by isotropic etching. The method of manufacturing a three-dimensional periodic structure according to claim 7, further comprising: a sixth step of performing etching on the substrate; and thereafter, sequentially repeating the third to sixth steps. 10. A first step of forming a fine periodic pattern on the surface of a substrate, and sputtering the substrate to which a substrate bias can be applied and having two targets of a low refractive index material and a high refractive index material. Put into the device, the concave part of the pattern is shaped and 45 °
The second step is to adjust the substrate bias and gas pressure so as to form a wedge-like shape having an angle of about
A third step of laminating a high-refractive-index substance on the low-refractive-index substance without applying a bias, and a dry-etching method capable of selectively etching the high-refractive-index substance with high anisotropy. A fourth step of performing, and a fifth step of adjusting the substrate bias and the gas pressure to sputter the low refractive index material on the high refractive index material so as to form a wedge shape having an angle of about 45 °. The method of manufacturing a three-dimensional periodic structure according to claim 7, further comprising: sequentially repeating the third to fifth steps. 11. A first step of forming a fine periodic concavo-convex pattern on a substrate surface, and sputtering the substrate to which a substrate bias can be applied and which has two targets of a low refractive index material and a high refractive index material. Put into the device, the concave part of the pattern is shaped and 45 °
The second step is to adjust the substrate bias and gas pressure so as to form a wedge-like shape having an angle of about
A third step of laminating a high-refractive-index substance on the low-refractive-index substance without applying a bias, and a dry-etching method capable of selectively etching the high-refractive-index substance with high anisotropy. A fourth step of performing; and a fifth step of adjusting the substrate bias and gas pressure to sputter the low-refractive-index material on the high-refractive-index material so as to form a wedge-shaped shape having a predetermined angle. A sixth step of making a trapezoidal hole in the low-refractive index layer by performing dry etching capable of more selectively etching the low-refractive index substance, and making the high-refractive index substance blunt the wedge shape on the lower surface. A seventh step of laminating a thick layer on the concave portion and a thin layer on the convex portion, and performing dry etching capable of selectively etching the high-refractive-index material with high anisotropy and separating the cross-section of the high-refractive-index layer, An eighth step of forming a trapezoid in the portion of the net-like hole; Has, then, a method for manufacturing a three-dimensional periodic structure according to claim 7, characterized in that from said fifth step sequentially repeating the eighth step. 12. A method for manufacturing a two-dimensional structure in which a plurality of types of substances having different refractive indexes are periodically stacked, wherein each of the substances has a one-dimensional periodic periodic structure on an upper surface and a lower surface.
Within one cycle in the thickness direction, a certain substance is irradiated with a raw material from a plurality of directions, so that the irregularities on the upper surface of the substance are emphasized more than the irregularities on the lower surface, and another substance has a deposition effect having a redeposition effect. Alternatively, the unevenness of the upper surface is weakened by the etching compared to the unevenness of the lower surface, so that the thickness of the region made of each material is modulated in the plane, and the photonic band gap effect is increased. Method for manufacturing a structure.