JP4186073B2 - Manufacturing method of three-dimensional photonic crystal structure - Google Patents

Description

The present invention, by forming a structure of each layer independently may be formed of defects, a method of manufacturing a three-dimensional photonic crystal structure capable of introducing a locally emitters and nonlinear medium.

Three-dimensional photonic crystal production methods include self-cloning methods such as auto cloning (see Patent Document 1) and artificial opals (opal), and methods using interference patterns such as laser light interference. However, artificial opal, laser light interference, etc. have the disadvantage that defects (necessary for controlling the light level and essential for device application) cannot be introduced at any position. Auto
Cloning is difficult to form a complete bandgap, and only insulators such as SiO2 and polycrystalline materials such as poly-Si can be used, and III-V semiconductor single crystals important for light-emitting device applications cannot be used. Population opal is also insulator and amorphous Si,
Single crystal materials such as amorphous CdS cannot be used. Laser interference has disadvantages, such as using only a specific photosensitive organic material.
As a method for producing a three-dimensional photonic crystal suitable for an optical device, there are a method (A) of Noda and Yamamoto et al. Of Kyoto University and a method (B) of Aoki et al. Of Riken (see Patent Document 2). This will be described.

FIG. 13 is a diagram for explaining the method (A). In this method, as shown in the figure, first, a selective etching stop layer (AlGaAs in the figure) and a photonic crystal forming layer (GaAs in the figure) are formed by epitaxial growth. (ii) Next, a two-dimensional pattern is formed by fine processing. (iii) The materials obtained in (ii) are pasted together after precise alignment so as to form a desired three-dimensional lattice. (iv) The epitaxial growth substrate and the etching stopper layer (AlGaAs in the figure) are removed by selective etching. (v)
Precision positioning, bonding, and selective etching are repeated to form a three-dimensional structure. It is a method.

  Next, FIG. 14 is a diagram for explaining the method (B). As in the method (A) above, after forming a two-dimensional pattern on the epi-wafer, the uppermost photonic crystal forming layer is removed from the growth substrate by selective etching, and they are stacked by directly operating them with a micromanipulator. In this way, a three-dimensional photonic crystal is obtained.

FIG. 14A is a front perspective view of a three-dimensional photonic crystal, and FIG. 14B is an exploded perspective view thereof. The three-dimensional photonic crystal 10 includes a plate-like two-dimensional photonic crystal plate 14a and a two-dimensional photonic crystal plate each having two types of two-dimensional photonic crystals 12a and two-dimensional photonic crystals 12b. 14b are alternately stacked with a period of about the wavelength of light.
The three-dimensional photonic crystal 10 is manufactured by superimposing the two-dimensional photonic crystal plate 14a and the two-dimensional photonic crystal plate 14b, and the superimposition process uses a probe by micro manipulation. Done.

When the micro object 20 is inserted into the through-hole 18 of the two-dimensional photonic crystal plate 14a, a hemispherical portion of the micro object 20 protrudes from the surface of the two-dimensional photonic crystal plate 14a. The pattern of the two-dimensional photonic crystal 12a of the two-dimensional photonic crystal plate 14a in which the micro object 20 is inserted in the through hole 18 is provided with a pattern rotated by 90 degrees, and the two-dimensional photonic crystal plate 14a. The two-dimensional photonic crystal plate 14a and the two-dimensional photonic crystal plate 14b are aligned by fitting the through holes 18 of the two-dimensional photonic crystal plate 14b into the hemispherical portion of the microscopic body 20 protruding from the surface of the two-dimensional photonic crystal plate 14b. And are laminated. By repeating such operations, the three-dimensional photonic crystal 10 having a three-dimensional periodic structure can be manufactured.
The methods (A) and (B) described above can be used at any position because a III-V group semiconductor single crystal, which is used mainly in current optical devices, can be used, and two-dimensional patterns prepared in advance are stacked. Since it is easy to embed crystal defects and light emitters, it is more advantageous in device formation than the other methods described at the beginning.

However, the method (A) is difficult to implement because it requires precise alignment of 1/10 or less of the wavelength by a special method (laser diffraction observation, etc.) in the case of lamination. The method (B) eliminates the complexity of precise alignment required by the method (A) by making positioning holes in the stacked plates. Since it is necessary to directly handle a thin plate of a degree, there is a disadvantage that the area cannot be increased from the viewpoint of the rigidity of the material.
JP 2001-79454 A JP 2003-43274 A

The present invention solves the problem of precision alignment of the above method (A) and the difficulty of manufacturing a large area device of the method (B), and then embeds a defect / light emitting layer at an arbitrary position. and its object is to provide a three-dimensional photonic method for producing a crystalline structure possible.

In the method of manufacturing a three-dimensional photonic crystal structure according to the present invention, a first wafer having a photonic crystal forming layer and a selective etching layer is formed on a first substrate, and the photonic crystal is formed on the second substrate. A second wafer in which the layers are stacked is formed, and an alignment mark and a pattern for one layer of the photonic crystal are formed on the second wafer. The first and second wafers are bonded to each other so that the photonic crystal forming layer of the first wafer faces the pattern on the second wafer, and the substrate and the selective etching layer of the first wafer are selected by selective etching. Is removed, leaving only the photonic crystal formation layer on the pattern on the second wafer, and one photonic crystal layer on the remaining photonic crystal formation layer based on the alignment mark on the second wafer. A pattern is drawn to form a pattern.

  In the present invention, precise alignment as in the method (A) is not required (the positional relationship of the crystal structure is secured by the alignment function of the drawing apparatus), and a thin plate as in the method (B) is used. Since it is not handled directly, it is possible to produce a large area photonic crystal. In addition, since the structure of each layer can be formed independently, defects can be formed, and it is advantageous for device realization such that a light emitter or a nonlinear medium can be locally introduced by changing part of the material to be bonded. It has characteristics.

Hereinafter, the present invention will be described based on examples. 1 to 12 show the steps in producing a three-dimensional photonic crystal according to the present invention.
I. A wafer having a photonic crystal formation layer and a selective etching layer as shown in FIG. 1 is prepared by epitaxial growth or the like. For example, a gallium arsenide (GaAs) substrate, aluminum gallium arsenide (AlGaAs) as a selective etching layer, and gallium arsenide (GaAs) as a photonic crystal formation layer are used. Dissolve the gallium arsenide substrate and the aluminum gallium arsenide layer sequentially using a solution that dissolves only gallium arsenide (eg, ammonia / hydrogen peroxide mixed solution) and a solution that dissolves only aluminum gallium arsenide (eg, buffered hydrofluoric acid). By doing so, only the gallium arsenide layer of the photonic crystal formation layer can be left. In addition, indium phosphide (InP) substrate, indium gallium arsenide phosphorous (InGaAsP) as a selective etching layer, indium phosphide (InP) as a photonic crystal formation layer, gallium arsenide as a substrate, and aluminum gallium arsenide as a selective etching layer , Indium gallium arsenide phosphorous, etc. in the photonic crystal layer, a combination of materials capable of wet or dry etching that dissolves the substrate but does not dissolve the selective etching layer, dissolves the selective etching layer but does not dissolve the photonic crystal layer Can be used.

  II. Separately from the wafer shown in FIG. 1, as shown in FIG. 2, a wafer on which a photonic crystal is laminated is prepared, and an alignment mark and a structure corresponding to one layer of the photonic crystal are formed thereon. The structure is formed, for example, by drawing a fine pattern with an electron beam exposure apparatus and then transferring the pattern onto the wafer by dry etching. When this crystal structure is separated from the wafer after fabrication of the photonic crystal structure, or when a hollow region is provided to form an air bridge, a pattern is formed on the structure having a selective etching layer as shown in FIG. To do.

  When considering an actual photonic crystal device, it is easier to handle it when it is placed on a semiconductor substrate or the like, but in terms of performance, light is concentrated on a semiconductor wafer with a high refractive index, and light is incident on the photonic crystal device. It may be difficult to guide itself. In order to avoid this, it is necessary that the periphery of the photonic crystal is made of air having a low refractive index or is bonded to a dielectric wafer having a low refractive index. For this purpose, by preparing a selective etching layer on the wafer to be laminated in advance, the substrate can be removed after all the structures are laminated.

  Also, when air is used both above and below the photonic crystal structure, the four sides of the photonic crystal end are supported by the lower substrate as shown in FIG. The problem can be avoided and light escape to the semiconductor substrate can be suppressed. For this purpose, a selective etching layer is prepared on the base substrate side to be laminated, and after all the layers are laminated, the structure shown in FIG. 4 can be obtained by dissolving through the gaps of the photonic crystal. .

III. As shown in FIG. 5, the wafer prepared in I is bonded onto the pattern made in II so that the photonic crystal forming layer faces the pattern made in II. The wafer to be bonded must be sized so as not to hide the alignment mark in the pattern made in II.
IV. As shown in FIG. 6, the wafer substrate and the selective etching layer are removed by selective etching, leaving only the photonic crystal forming layer on the structure prepared in II.

V. As shown in FIG. 7, using the alignment drawing function of the drawing apparatus based on the alignment mark, a pattern for one photonic crystal is drawn on the remaining photonic crystal forming layer, and the pattern is formed by etching. Form.
The three-dimensional structure as shown in FIG. 8 is produced by repeating the above.

  Further, in III, a structure obtained by removing the portion where the photonic crystal forming layer is overlapped with the alignment mark as shown in FIG. 9 can be used by bonding as shown in FIG. Thereafter, as shown in FIG. 11, the substrate and the selective etching layer are removed by selective etching. Then, as shown in FIG. 12, the photonic crystal pattern and the alignment mark B are drawn with the alignment mark A as a reference. In this way, when the alignment mark is formed on the bonded material, since the portion to be drawn and the alignment mark portion are present in the adjacent layers in the case of multilayer lamination, errors due to the drawing device can be reduced. .

It is a figure which illustrates the structure with a photonic crystal formation layer and a selective etching layer. It is a figure which illustrates the wafer which formed the photonic crystal pattern and alignment mark for 1 layer. It is a figure which illustrates the photonic crystal pattern and alignment mark for one layer formed in the structure with a selective etching layer. It is a figure which illustrates the structure which made the upper and lower sides of the photonic crystal into air. It is a figure which illustrates the wafer which bonded the structure shown in FIG. It is a figure which illustrates the wafer which left only the photonic crystal formation layer. It is a figure which illustrates drawing the photonic crystal pattern on the bonded photonic crystal formation layer based on the alignment mark, and transferring the pattern by etching. It is a figure which illustrates the completed three-dimensional photonic crystal. It is a figure which illustrates the wafer which removed the photonic crystal layer only in the part which overlaps with an alignment mark. It is a figure which illustrates the structure which bonded the structure of FIG. 2 and the structure of FIG. It is a figure which illustrates the structure which removed the board | substrate and the selective etching layer by the selective etching from the structure of FIG. It is a figure which illustrates drawing the photonic crystal pattern and the alignment mark B on the basis of the alignment mark A. It is a figure explaining the three-dimensional photonic crystal preparation method for optical devices by a prior art. It is a figure explaining the manufacturing method of the three-dimensional photonic crystal for optical devices by another prior art.

Claims (4)

Forming a first wafer having a photonic crystal forming layer and a selective etching layer on a first substrate;
Forming a second wafer in which a photonic crystal forming layer is laminated on a second substrate, forming an alignment mark and a pattern for one layer of the photonic crystal on the second wafer;
The first and second wafers are bonded so that the photonic crystal formation layer of the first wafer faces the pattern on the second wafer,
By selective etching, the substrate and the selective etching layer of the first wafer are removed, leaving only the photonic crystal forming layer on the pattern on the second wafer,
A method for producing a three-dimensional photonic crystal structure comprising drawing a pattern for one layer of a photonic crystal on the remaining photonic crystal formation layer based on an alignment mark on a second wafer, and forming the pattern. The method for producing a three-dimensional photonic crystal structure according to claim 1 , wherein the pattern formation on the second wafer is performed by drawing a fine pattern and then transferring the pattern onto the wafer by dry etching. 2. The method for producing a three-dimensional photonic crystal structure according to claim 1 , wherein the pattern on the second wafer is formed on a structure having a selective etching layer. The first wafer to be bonded to the second wafer is bonded after the photonic crystal forming layer overlapping the alignment mark is removed, and after the substrate and the selective etching layer are removed by selective etching, the alignment is performed. 2. The method for producing a three-dimensional photonic crystal structure according to claim 1 , wherein an alignment mark different from the photonic crystal pattern is drawn on the basis of the mark.