JP7345488B2 - Substrate with alignment marks - Google Patents

Description

The present invention relates to a substrate provided with alignment marks.

In recent years, array-shaped optical elements arranged on a substrate have been frequently used as liquid crystal panels and optical communication components. Since these optical elements are generally used in a stacked state with other components, it is necessary to align the optical axes and the like.

When stacking such an array of optical elements with their optical axes aligned, a technique is used in which alignment marks are provided on the substrate on which each optical element is mounted. .

The alignment mark has a structure that allows it to be visually distinguished from other parts of the substrate. Patent Document 1 discloses a substrate including alignment marks made of metal such as chromium.

Japanese Patent Application Publication No. 2000-235105

However, alignment marks formed of metals such as chromium have high light absorption properties, so when observing alignment marks with a microscope, for example, a part of the back surface opposite to the front surface of the substrate on which the alignment mark is formed is visible. There is a problem in that the marks are hidden behind the alignment marks, reducing the visibility of the back side of the board.

The present invention has been made in view of these circumstances, and its purpose is to provide a substrate with alignment marks that has excellent visibility when observed through the substrate.

In order to solve the above problems, a substrate with an alignment mark according to an aspect of the present invention includes a substrate and an alignment mark formed on a main surface of the substrate. The alignment mark has a plurality of linear recesses or protrusions. The concave portion or the convex portion includes a flat portion parallel to the main surface and an inclined portion inclined with respect to the main surface.

Another aspect of the present invention is also a substrate with alignment marks. This substrate with alignment marks includes a substrate, an alignment mark forming layer provided on the main surface of the substrate, and an alignment mark formed on the alignment mark layer. The alignment mark has a plurality of linear recesses or protrusions. The concave portion or the convex portion includes a flat portion parallel to the main surface and an inclined portion inclined with respect to the main surface.

In the above aspect, the flat part reflects the light irradiated from the normal direction of the main surface in the normal direction of the main surface, and the inclined part reflects the light irradiated from the normal direction of the main surface to the normal direction of the main surface. The light may be reflected in a direction oblique to the linear direction.

In the above aspect, the inclined portion may include a curved surface. The inclined portion may include a flat surface.

In the above embodiment, the refractive index of the material forming the substrate or the alignment mark forming layer may be in the range of 1.2 to 2.7 at a wavelength of 560 nm.

In the above embodiment, the extinction coefficient of the material forming the substrate or the alignment mark forming layer may be less than 1.

In the above embodiment, the surface roughness of the flat portion may be in the range of 0.001 μm to 50 μm.

In the above embodiment, the reflectance of the flat portion to air may be in the range of 0.01% to 30% at a wavelength of 560 nm.

In the above aspect, the visible light transmittance of the flat portion may be 30% or more.

Note that arbitrary combinations of the above-mentioned components and expressions of the present invention converted between methods, devices, systems, etc. are also effective as aspects of the present invention.

According to the present invention, it is possible to provide a substrate with alignment marks that has excellent visibility when observed through the substrate.

FIG. 1 is a schematic plan view of a substrate with alignment marks according to an embodiment of the present invention. 2 is a schematic cross-sectional view taken along line AA of the substrate with alignment marks shown in FIG. 1. FIG. FIG. 2 is a schematic perspective view of an alignment mark and a diagram showing an image formed when the alignment mark is observed with a microscope having a vertical epi-illumination device. FIG. 3 is a diagram for explaining conditions for forming an inclined portion including a curved surface. It is a figure which shows the board|substrate with an alignment mark based on a modification. It is a figure which shows the board|substrate with an alignment mark based on another modification. It is a figure which shows the board|substrate with an alignment mark based on yet another modification. It is a figure which shows the board|substrate with an alignment mark based on yet another modification. It is a figure which shows the board|substrate with an alignment mark based on yet another modification. FIG. 9 is a diagram for explaining conditions for forming an inclined portion including a plane as shown in FIGS. 7 to 9. FIG. FIG. 3 is a diagram for explaining parameters of alignment marks. FIG. 3 is a schematic cross-sectional view of a substrate with alignment marks according to another embodiment of the present invention. FIG. 7 is a schematic cross-sectional view of a substrate with alignment marks according to yet another embodiment of the present invention. FIGS. 14(a) to 14(c) are diagrams showing images of alignment marks. FIG. 3 is a diagram showing an image of an alignment mark. FIGS. 16(a) to 16(d) are diagrams showing a glass optical waveguide substrate. FIGS. 17(a) to 17(d) are diagrams showing a silicon optical waveguide substrate. FIGS. 18A and 18B are diagrams showing images formed when an alignment mark is observed with a microscope having a vertical epi-illumination device. FIGS. 19A and 19B are diagrams showing a state in which a glass optical waveguide substrate and a silicon optical waveguide substrate are stacked. FIGS. 20A and 20B are diagrams showing a state in which a glass optical waveguide substrate and a silicon optical waveguide substrate are bonded together. FIGS. 21(a) to 21(c) are diagrams showing a microlens array substrate. FIGS. 22(a) and 22(b) are diagrams showing a surface emitting laser array substrate. FIGS. 23(a) to 23(c) are diagrams showing a state in which a microlens array substrate and a surface emitting laser array substrate are stacked. FIGS. 24(a) and 24(b) are diagrams showing a state in which a microlens array substrate and a surface emitting laser array substrate are bonded together. FIGS. 25A to 25F are six views of a microlens substrate with alignment marks according to an embodiment of the present invention. FIG. 3 is an enlarged plan view of the alignment mark portion (AB portion) of the microlens substrate. 27 is a sectional view taken along line CC of the alignment mark portion shown in FIG. 26. FIG. FIG. 3 is an enlarged perspective view of the alignment mark portion (AB portion) of the microlens substrate. FIG. 7 is an enlarged plan view of a first modification of the alignment mark portion (AB portion) of the microlens substrate. 30 is a sectional view taken along the line CC of the alignment mark portion shown in FIG. 29. FIG. FIG. 7 is an enlarged perspective view of a first modification of the alignment mark portion (AB portion) of the microlens substrate. FIG. 7 is an enlarged plan view of a second modification of the alignment mark portion (AB portion) of the microlens substrate. 33 is a sectional view taken along the line CC of the alignment mark portion shown in FIG. 32. FIG. FIG. 7 is an enlarged perspective view of a second modification of the alignment mark portion (AB portion) of the microlens substrate. FIG. 7 is an enlarged plan view of a third modification of the alignment mark portion (AB portion) of the microlens substrate. 36 is a sectional view taken along the line CC of the alignment mark portion shown in FIG. 35. FIG. FIG. 7 is an enlarged perspective view of a third modification of the alignment mark portion (AB portion) of the microlens substrate. FIG. 7 is an enlarged plan view of a fourth modification of the alignment mark portion (AB portion) of the microlens substrate. 39 is a sectional view taken along line CC of the alignment mark portion shown in FIG. 38. FIG. FIG. 7 is an enlarged perspective view of a fourth modification of the alignment mark portion (AB portion) of the microlens substrate. FIGS. 41(a) to 41(f) are six views of the optical waveguide substrate with alignment marks according to the embodiment of the present invention.

Hereinafter, a substrate with alignment marks according to an embodiment of the present invention will be described. Identical or equivalent components, members, and processes shown in each drawing are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. Further, the embodiments are illustrative rather than limiting the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

FIG. 1 is a schematic plan view of a substrate 10 with alignment marks according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along line AA of the substrate 10 with alignment marks shown in FIG. The alignment mark-equipped substrate 10 has an alignment mark 14 formed on a part of the substrate 12.

The substrate 12 is a plate-shaped body having a first main surface 12a and a second main surface 12b opposite to the first main surface 12a. The first main surface 12a and the second main surface 12b are parallel. As the material constituting the substrate 12, a material transparent to visible light, for example, an organic material such as glass, an inorganic oxide, an organic-inorganic composite material, or plastic can be used.

Examples of the glass include multi-component glass containing monovalent alkali ions, borosilicate glass (for example, D263 Teco manufactured by SCHOTT, refractive index n=1.53, extinction coefficient k<0.1, linear expansion coefficient: 7. 2ppm/K), quartz substrate (n=1.46, k<0.1, coefficient of linear expansion: 0.55ppm/K), float glass (n=1.52, k<0.1, coefficient of linear expansion: 9 ppm/K). Examples of zero expansion glass include ZERODUR (0.02ppm/K), NEOCERAM (0.00ppm/K), and CLEARCERAM (0.00±0.01ppm/K) (ZERODUR and NEOCERAM are registered with Schott Aktiengesellschaft. CLEARCERAM is a registered trademark of OHARA Co., Ltd.).

Inorganic oxides include silica (n=1.46, k<0.1), titania (n=2.6, k<0.1), and zirconia (n=2.1, k<0.1). , niobium oxide (n=2.1, k<0.1), tantalum oxide (n=2.1, k<0.1), polysilane (n=1.5-2.5, k=0.2) ~0.6) can be exemplified.

Examples of organic-inorganic composite materials include organopolysiloxane compounds, silsesquioxane compounds, and sol-gel materials. Examples of organic materials include polyimide, fluorinated polyimide, epoxy resin, acrylic resin, and silicone.

Among the materials for the substrate 12 described above, glass, silica, polysilane, and organopolysiloxane compounds can be exemplified as desirable materials from the viewpoint of heat resistance and chemical resistance.

The substrate 12 may include an optical element (not shown) such as a waveguide, a diffraction grating, a lens, or a diffractive optical element in a portion thereof. For example, if the substrate 12 is a multi-component glass substrate containing monovalent alkali ions, the monovalent alkali ions contained in the glass base material may be converted into other ions that increase the optical refractive index of the glass base material. By selectively replacing them, it is possible to form a glass substrate on which an embedded optical waveguide is formed. Monovalent alkali ions may be K ions or Na ions, and other ions that increase the refractive index of the glass matrix may be Ag ions and thallium.

In this embodiment, the alignment mark 14 is formed on the first main surface 12a of the substrate 12. The alignment mark 14 includes a plurality of linear recesses 16 formed in the first main surface 12a of the substrate 12. The plurality of recesses 16 are arranged in a direction perpendicular to the longitudinal direction (extending direction) of the recesses 16. The plurality of linear recesses 16 can be formed by a known method such as wet etching, dry etching, transfer method, imprint method, laser processing method, or the like. For example, as a method of forming a recess on a glass substrate by wet etching after forming a mask on the glass substrate, the technique described in JP-A-2000-235105 or JP-A-2000-235178 can be used. Note that the etching may be isotropic etching or anisotropic etching. In the case of isotropic etching, the etching rate in the in-plane direction and the depth direction from the main surface of the substrate 12 is the same, and in the case of anisotropic etching, the etching rate in the in-plane direction and the depth direction are the same. different.

As shown in FIG. 2, each recess 16 is a substantially U-shaped recess (groove) in cross-sectional view. Each recess 16 includes a flat portion 18 and sloped portions 20 formed at both ends of the flat portion 18 . The flat portion 18 is a surface parallel to the first main surface 12a of the substrate 12, as shown in FIG. The inclined portion 20 is a surface inclined with respect to the first main surface 12a of the substrate 12, and in this embodiment, is formed into an arcuate curved surface (concave curved surface) in a cross-sectional view, as shown in FIG. In this embodiment, the ridge portions 21 between adjacent inclined portions 20 in adjacent recessed portions 16 are linear. Further, in this embodiment, the height of the ridge portion 21 is lower than the first main surface 12a of the substrate 12.

FIG. 3 shows a schematic perspective view of the alignment mark 14 and an image 30 formed when the alignment mark 14 is observed with a microscope having a vertical epi-illumination device.

As shown in FIG. 3, the flat portion 18 of the recess 16 in the alignment mark 14 reflects light irradiated from the normal direction of the first main surface 12a of the substrate 12 in the normal direction. The light reflected by the flat portion 18 enters the objective lens of the microscope and is observed as a bright region 32 in an image 30 formed by the microscope.

On the other hand, the inclined part 20 of the recessed part 16 in the alignment mark 14 reflects the light irradiated from the normal direction of the first main surface 12a of the substrate 12 in a direction inclined with respect to the normal direction. Therefore, a portion of the light reflected by the inclined portion 20 does not enter the objective lens of the microscope, and is therefore observed as a so-called dark region 34 in the image 30 formed by the microscope.

Since images of the bright areas 32 and dark areas 34 as described above are formed by each recess 16, when the entire alignment mark 14 is observed under a microscope, a striped pattern in which the bright areas 32 and dark areas 34 are alternately repeated is formed. An image 30 is observed. Using such an image 30, alignment with other substrates can be performed. Note that in this embodiment, one dark region 34 is formed by adjacent sloped portions 20 of adjacent recessed portions 16 .

In the substrate 10 with alignment marks described above, the linear recesses 16 formed in the substrate 12 constitute the alignment marks 14 . When observing the second main surface 12b opposite to the first main surface 12a provided with the alignment mark 14, it is necessary to fill the recess 16 of the alignment mark 14 with a material (for example, (adjusting agent, adhesive, etc.). As a result, reflection (Fresnel reflection) at the inclined portion 20 of the concave portion 16 is substantially eliminated or significantly reduced, so that a clear striped pattern image 30 as shown in FIG. 3 is not observed, and the substrate 12 The second main surface 12b (for example, an optical element mounted on the second main surface 12b) can be observed clearly through the substrate 12 as if the alignment mark 14 were not formed on the second main surface 12b. As described above, according to the present embodiment, it is possible to realize a substrate 10 with an alignment mark that has excellent visibility when observed through the substrate.

The effects of the alignment mark-equipped substrate 10 according to the present embodiment as described above are due to the fact that the alignment mark 14 does not substantially absorb light. In the case of alignment marks made of metal such as chromium, light is absorbed by the material itself used for the alignment marks, so even if a refractive index adjusting agent is applied to the alignment marks, a clear striped pattern will appear when observed under a microscope. image is observed, and therefore visibility on the back side of the substrate is low.

Furthermore, in the case of alignment marks using metals such as chromium, the range of use may be limited in terms of chemical resistance. For example, on a substrate equipped with an alignment mark made of chromium (refractive index n = 3.18, extinction coefficient k = 4.4), ion exchange treatment is performed to form a waveguide while aligning with this alignment mark. In this case, if the substrate is brought into contact with a nitrate compound at high temperatures for ion exchange, there is a risk that the chromium provided to the previously formed alignment marks will dissolve. On the other hand, in the substrate 10 with alignment marks according to the present embodiment, since metal such as chromium is not used to form the alignment marks 14, the above-mentioned situation does not occur during the ion exchange treatment.

FIG. 4 is a diagram for explaining the conditions for forming the inclined portion 20 including a curved surface. As shown in FIG. 4, consider a case where an alignment mark is observed using a microscope equipped with an objective lens OL.

When the inclined part 20 includes a curved surface in cross-sectional view, when α is the angle between the tangential plane TL at the intersection IP of the optical axis AL of the objective lens OL and the inclined part 20 and the plane HL perpendicular to the optical axis AL. , α satisfy the following equation (1).
α>θ ₀ /2=0.5×arcsin(NA/n)...(1)
In equation (1), θ ₀ is the aperture angle of the objective lens OL, NA is the numerical aperture of the objective lens, and n is the refractive index of the medium (usually air) between the objective lens OL and the alignment mark.

As shown in equation (1), if α is larger than 1/2 of the aperture angle θ ₀ of the objective lens OL, then the incident ray a (of the illumination light emitted from the objective lens OL) is parallel to the optical axis AL. The angle formed by the reflected ray b (the ray that passes through the intersection IP of the optical axis AL and the inclined portion 20) and the reflected ray b (the ray from which the incident ray a is reflected at the intersection IP) is smaller than the aperture angle θ ₀ of the objective lens OL. growing. Therefore, the reflected light beam b is not substantially focused by the objective lens OL, and becomes a light beam that does not contribute to the formation of an image by the microscope. Therefore, when the slope portion 20 is formed such that α satisfies the equation (1), the region of the slope portion 20 that satisfies the equation (1) is visually recognized as a dark region. In this case, a clear striped pattern image is formed together with the bright area formed by the reflected light from the flat portion 18.

On the other hand, if the inclined portion 20 is formed such that α does not satisfy equation (1) (that is, if α is 1/2 or less of the aperture angle θ ₀ of the objective lens OL), the reflected light beam b Since the slope portion 20 is within the range where light can be focused by the OL, the slope portion 20 is visually recognized as a bright region. In this case, since the boundary with the bright area formed by the reflected light from the flat portion 18 becomes unclear, there is a possibility that a clear striped pattern image cannot be formed.

In this embodiment, if the refractive index of the material forming the substrate 12 is too low (for example, the same refractive index as air (n=1.0)), sufficient reflection of light from the flat portion 18 may not be obtained, resulting in a clear A striped image cannot be observed. On the other hand, if the refractive index of the material forming the substrate 12 is too high, the reflection of light from the flat portion 18 will be too large, and the transmittance of the substrate 12 will inevitably become low. The visibility of 12b is reduced. As a result, alignment with other substrates may become difficult. Therefore, when the refractive index of the material forming the substrate 12 at a wavelength of 560 nm is ns, it is desirable that the refractive index ns satisfies 1.2≦ns≦2.7, and 1.46≦ns≦2.10. It is more desirable to satisfy 1.48≦ns≦1.70.

Furthermore, in this embodiment, when the absorption of the substrate 12 is small, the loss of transmittance due to reflection is reduced or minimized, so that when the substrate 12 is filled with a substance having an appropriate refractive index as described above, the The visibility of the second main surface 12b can be improved. Therefore, when ks is the extinction coefficient of the material forming the substrate 12 at a wavelength of 560 nm, the extinction coefficient ks preferably satisfies ks<1, and more preferably satisfies ks<0.1.

In addition, in this embodiment, if the surface of the flat part 18 of the recessed part 16 is rough, the irradiated light will be scattered at the flat part 18 and will not be sufficiently focused by the objective lens of the microscope, so that a clear striped image will be observed. There is a possibility that it will not be possible. Therefore, when the surface roughness of the flat portion 18 is defined as Ra, it is desirable that Ra satisfies 0.001 μm≦Ra≦50 μm.

Further, in this embodiment, the reflectance Rs of the flat portion 18 to air satisfies 0.01%≦Rs≦30% at a wavelength of 560 nm, and the visible light transmittance of the flat portion 18 is 30% or more. This is desirable. By satisfying such conditions, excellent positional accuracy can be achieved in alignment with other substrates.

FIG. 5 shows a substrate 50 with alignment marks according to a modified example. This substrate 50 with alignment marks differs from the substrate 10 with alignment marks shown in FIG. 2 in that the height of the ridge 21 is the same as the first main surface 12a of the substrate 12. Also in this modification, when the entire alignment mark 14 is observed with a microscope, a striped pattern image in which bright areas and dark areas are alternately repeated can be observed.

FIG. 6 shows a substrate 60 with alignment marks according to another modification. This substrate 60 with alignment marks differs from the substrate 10 with alignment marks shown in FIG. 2 in that the ridge portion 21 between the inclined portions 20 has a planar shape parallel to the first main surface 12a. When the ridge 21 is made planar in this manner, the light reflected by the ridge 21 enters the objective lens of the microscope and is therefore observed as a bright region in the image formed by the microscope. Also in this modification, when the entire alignment mark 14 is observed with a microscope, a striped pattern image in which bright areas and dark areas are alternately repeated can be observed.

FIG. 7 shows a substrate 70 with alignment marks according to yet another modification. This substrate 70 with alignment marks is different from the substrate 10 with alignment marks shown in FIG. 2 in that the recesses 16 are formed as substantially trapezoidal recesses (grooves) in cross-sectional view, and the inclined portions 20 are flat. different. In this modification, the ridge portions 21 between adjacent slope portions 20 are linear. Further, in this modification, the height of the ridge portion 21 is lower than the first main surface 12a of the substrate 12.

In this modification, the flat portion 18 of the recess 16 reflects light irradiated from the normal direction of the first main surface 12a of the substrate 12 in the normal direction. The light reflected by the flat portion 18 enters the objective lens of the microscope and is observed as a bright region in the image 30 formed by the microscope. On the other hand, the flat inclined portion 20 reflects the light irradiated from the normal direction of the first main surface 12a of the substrate 12 in a direction inclined with respect to the normal direction. Therefore, much of the light reflected by the inclined portion 20 does not enter the objective lens of the microscope, and is therefore observed as a dark region in the image 30 formed by the microscope.

Even when the inclined portion 20 is made into a flat surface in this manner, a striped pattern image in which bright areas and dark areas are alternately repeated can be observed with a microscope. Note that in this embodiment, one dark region is formed by the adjacent inclined portions 20 of the adjacent recesses 16.

FIG. 8 shows a substrate 80 with alignment marks according to yet another modification. This substrate 80 with alignment marks differs from the substrate 70 with alignment marks shown in FIG. 7 in that the height of the ridge 21 is the same as the first main surface 12a of the substrate 12. Also in this modification, when the entire alignment mark 14 is observed with a microscope, a striped pattern image in which bright areas and dark areas are alternately repeated can be observed.

FIG. 9 shows a substrate 90 with alignment marks according to yet another modification. This substrate 90 with alignment marks differs from the substrate 70 with alignment marks shown in FIG. 7 in that the ridge portions 21 between the inclined portions 20 are flat and parallel to the first main surface 12a. When the ridge 21 is made planar in this manner, the light reflected by the ridge 21 enters the objective lens of the microscope and is therefore observed as a bright region in the image formed by the microscope. Also in this modification, when the entire alignment mark 14 is observed with a microscope, a striped pattern image in which bright areas and dark areas are alternately repeated can be observed. Note that the alignment marks shown in FIGS. 2, 5, 6, 7, 8, and 9 may be formed on the first main surface 112a of the substrate 112, as shown in FIGS. 12 and 13, which will be described later.

FIG. 10 is a diagram for explaining the conditions for forming the inclined portion 20 including the plane shown in FIGS. 7 to 9. As shown in FIG. 10, consider a case where an alignment mark is observed using a microscope equipped with an objective lens OL.

When the inclined portion 20 includes a plane in cross-sectional view, the inclined portion 20 is designed so that β satisfies the following equation (2), where β is the angle between the inclined portion 20 and the plane HL perpendicular to the optical axis AL. Form.
β>θ ₀ /2=0.5×arcsin(NA/n) (2)
In equation (2), θ ₀ is the aperture angle of the objective lens OL, NA is the numerical aperture of the objective lens, and n is the refractive index of the medium (usually air) between the objective lens OL and the alignment mark.

As shown in equation (2), when β is larger than 1/2 of the aperture angle θ ₀ of the objective lens OL, the incident ray a (of the illumination light emitted from the objective lens OL) is parallel to the optical axis AL. The angle formed by the reflected ray b (the ray that passes through the intersection IP of the optical axis AL and the inclined portion 20) and the reflected ray b (the ray from which the incident ray a is reflected at the intersection IP) is smaller than the aperture angle θ ₀ of the objective lens OL. growing. Therefore, the reflected light beam b is not substantially focused by the objective lens OL, and becomes a light beam that does not contribute to the formation of an image by the microscope. Therefore, when the slope portion 20 is formed such that β satisfies the equation (2), the slope portion 20 is visually recognized as a dark region. In this case, a clear striped pattern image is formed together with the bright area formed by the reflected light from the flat portion 18.

On the other hand, if the inclined portion 20 is formed such that β does not satisfy equation (2) (that is, if β is less than or equal to 1/2 of the aperture angle θ ₀ of the objective lens OL), the reflected light beam b Since the slope portion 20 is within the range where light can be focused by the OL, the slope portion 20 is visually recognized as a bright region. In this case, since the boundary with the bright area formed by the reflected light from the flat portion 18 becomes unclear, there is a possibility that a clear striped pattern image cannot be formed. In addition, in its cross section, the inclined portion of the recess may be composed of only a curved surface or a plane as described above, or may be composed of a combination of a curved surface and a plane, or may be composed of planes exhibiting a plurality of different βs. Good too. Any method is acceptable as long as it can be used for positioning parts, etc. by obtaining a striped pattern image when viewing the alignment mark in plan.

FIG. 11 is a diagram for explaining parameters of the alignment mark 14. As shown in FIG. 11, the arrangement pitch of the recesses 16 is P, the width of the dark area 34 in the image 30 formed when observed with a microscope is Lb, the length of the flat part 18 is Lw, and the substrate surface of the flat part 18 Let He be the depth from (the first principal surface), and let Hr be the height from the flat part 18 to the ridge part 21.
P is 0.01 μm or more, preferably 0.1 μm or more, and more preferably 1 μm or more. Moreover, P is 1000 μm or less, preferably 500 μm or less.
Lb is 0.001 μm or more, preferably 0.01 μm or more, and more preferably 0.1 μm or more. Further, Lb is 1000 μm or less, preferably 800 μm or less, and more preferably 500 μm or less.
Lw is 0 μm or more, preferably 0.01 μm or more, and more preferably 0.1 μm or more. Further, Lw is 1000 μm or less, preferably 800 μm or less, and more preferably 500 μm or less.
He-Hr has a thickness of 0 μm or more, preferably 0.01 μm or more, and more preferably 0.1 μm or more. Further, He-Hr has a thickness of 1000 μm or less, preferably 800 μm or less, and more preferably 500 μm or less.
Further, the value of Lw+He×2−P is −10 μm or less, and preferably −5 μm or less. Further, the value of Lw+He×2−P is 10 μm or less, and preferably 5 μm or less.
These parameters can be measured using a measuring microscope (OLYMPUS STM7), which will be described later.Measurements of dimensions smaller than 1 μm or 0.1 μm can be performed using, for example, an ultra-high precision coordinate measuring machine (manufactured by Panasonic Production Engineering Co., Ltd.). UA-3P) or a level difference meter (Dektak XT manufactured by Bruker). Further, the structure of FIG. 11 may be formed by wet etching. Wet etching may be isotropic wet etching or anisotropic wet etching. In the case of isotropic wet etching, the etching rate in the in-plane direction and the depth direction from the main surface of the substrate is the same, and in the case of anisotropic etching, the etching rate in the in-plane direction and the depth direction are the same. different.

In the embodiment described above, the alignment mark 14 is formed by forming a plurality of linear recesses 16 on the first main surface 12a of the substrate 12. The alignment mark may be formed by forming a convex portion. Each convex portion includes a flat portion and sloped portions formed at both ends of the flat portion. The flat portion of the convex portion reflects light irradiated from the direction normal to the principal surface of the substrate 12 in the direction normal to the principal surface. The light reflected by the flat portion enters the objective lens of the microscope and is observed as a bright region in the image formed by the microscope. On the other hand, the inclined portion of the convex portion reflects the light irradiated from the normal direction of the principal surface of the substrate 12 in a direction inclined with respect to the normal direction of the principal surface. Therefore, most of the light reflected by the slope does not enter the objective lens of the microscope, and is therefore observed as a dark area in the image formed by the microscope. Each convex portion forms an image of bright and dark areas as described above, so when the entire alignment mark is observed under a microscope, a striped pattern of alternating bright and dark areas is observed. .

FIG. 12 is a schematic cross-sectional view of a substrate 110 with alignment marks according to another embodiment of the present invention. The alignment mark-equipped substrate 110 has an alignment mark forming layer 100 provided on the first main surface 112a of the substrate 112, and an alignment mark 114 formed on the alignment mark forming layer 100.

The substrate 112 is a plate-shaped body having a first main surface 112a and a second main surface 112b opposite to the first main surface 112a. The first main surface 112a and the second main surface 112b are parallel. As a material constituting the substrate 112, a material transparent to visible light, for example, an organic material such as glass, an inorganic oxide, an organic-inorganic composite material, or plastic can be used.

The alignment mark forming layer 100 is a film formed on the first main surface 112a of the substrate 112 and has a thickness of several tens of μm (for example, 40 μm). As a material constituting the alignment mark forming layer 100, a material that is transparent to visible light, such as an organic material such as glass, an inorganic oxide, an organic-inorganic composite material, or a plastic, can be used. Examples of materials desirable from the viewpoint of heat resistance and chemical resistance include organopolysiloxane compounds, silica, and titania.

In this embodiment, the alignment mark 114 is formed in the alignment mark forming layer 100. The alignment mark 114 includes a plurality of linear convex portions 116 formed on the surface of the alignment mark forming layer 100. The plurality of convex portions 116 are arranged in a direction perpendicular to the longitudinal direction (extending direction). The plurality of convex portions 116 can be formed by, for example, a sol-gel nanoimprint method or a transfer method.

Each convex portion 116 includes a flat portion 118 and sloped portions 120 formed at both ends of the flat portion 118. The flat portion 118 is a surface parallel to the first main surface 112a of the substrate 112, as shown in FIG. The inclined portion 120 is a surface inclined with respect to the first main surface 112a of the substrate 112, and in this embodiment, is formed into an arcuate curved surface (convex curved surface) in a cross-sectional view, as shown in FIG. In a modification, the inclined portion 120 may be formed in a plane inclined with respect to the first main surface 112a.

In the alignment mark-equipped substrate 110 configured as described above, the flat portion 118 of the convex portion 116 reflects light irradiated from the normal direction of the first main surface 12a of the substrate 112 in the normal direction. The light reflected by the flat portion 118 enters the objective lens of the microscope and is observed as a bright region in the image formed by the microscope.

On the other hand, the inclined portion 120 of the convex portion 116 reflects the light irradiated from the normal direction of the first main surface 12a of the substrate 112 in a direction inclined with respect to the normal direction. Therefore, much of the light reflected by the inclined portion 120 does not enter the objective lens of the microscope, and is therefore observed as a dark region in the image formed by the microscope.

Since images of bright areas and dark areas as described above are formed by each convex portion 116, when the entire alignment mark 114 is observed under a microscope, a striped pattern image in which bright areas and dark areas are alternately repeated is observed. be done. Using such an image, alignment with other substrates can be performed.

In this embodiment as well, by dropping a substance (for example, a refractive index adjusting agent, adhesive, etc.) having substantially the same refractive index as the material of the alignment mark forming layer 100 on the surface of the alignment mark 114, the inclined portion 120 of the convex portion 116 is Since the reflection (Fresnel reflection) at In this manner, according to this embodiment as well, it is possible to realize a substrate 110 with an alignment mark that has excellent visibility when observed through the substrate.

For the same reason as the substrate 10 with alignment marks described above, when the refractive index of the material forming the alignment mark forming layer 100 at a wavelength of 560 nm is na, the refractive index na satisfies 1.2≦na≦2.7. It is desirable to satisfy 1.46≦na≦2.10, and it is even more desirable to satisfy 1.48≦na≦1.70.

Further, when the extinction coefficient of the material forming the alignment mark forming layer 100 at a wavelength of 560 nm is ka, it is desirable that the extinction coefficient ka satisfy ka<1, and more preferably satisfy ka<0.1. desirable.

Furthermore, when the surface roughness of the flat portion 118 is defined as Ra, it is desirable that Ra satisfies 0.001 μm≦Ra≦50 μm.

Further, it is preferable that the reflectance Rs of the flat portion 118 to air satisfies 0.01%≦Rs≦30% at a wavelength of 560 nm, and the visible light transmittance of the flat portion 118 is 30% or more.

In this embodiment, it is desirable that the height H from the first main surface 112a of the substrate 112 to the top of the alignment mark 114 (that is, the flat portion 118) satisfies H≦0.5 μm. When optical coupling is performed by bonding other optical components to the main surface of a substrate on which a waveguide has been formed by ion exchange treatment, there is a risk that a gap will occur due to unevenness of 10 μm to 500 μm, increasing optical coupling loss. By setting the height from the surface of the substrate 112 to the top of the alignment mark 114 to be less than 0.5 μm, the substrate on which the waveguide is formed and the optical component can be assembled in close contact with each other, thereby improving optical coupling with the optical component. Loss can be reduced.

FIG. 13 is a schematic cross-sectional view of a substrate 130 with alignment marks according to yet another embodiment of the present invention. The substrate 130 with alignment marks according to this embodiment also has an alignment mark forming layer 100 provided on the substrate 112, and alignment marks 131 formed on the alignment mark forming layer 100, similarly to the above-described substrate 110 with alignment marks. .

The alignment mark 131 includes a plurality of linear recesses 132 formed on the surface of the alignment mark forming layer 100. The plurality of recesses 132 are arranged in a direction perpendicular to the longitudinal direction (extending direction) of the recesses 132. The plurality of recesses 132 can be formed, for example, by a sol-gel nanoimprint method or a transfer method.

The shape of the recess 132 may be similar to the recess 16 of the alignment mark-equipped substrate 80 shown in FIG. The recessed portion 132 includes a flat portion 133 and sloped portions 134 formed at both ends of the flat portion 133. In this embodiment, the inclined portion 134 may be formed into a flat surface. In a modification, the inclined portion 134 may be formed into a curved surface.

In the substrate 130 with alignment marks configured as described above, the flat portion 133 of the recess 132 reflects the light irradiated from the normal direction of the main surface of the substrate 112 in the normal direction of the main surface. The light reflected by the flat portion 133 enters the objective lens of the microscope and is observed as a bright region in the image formed by the microscope.

On the other hand, the inclined part 134 of the recessed part 132 reflects the light irradiated from the normal direction of the main surface of the substrate 112 in a direction inclined with respect to the normal direction of the main surface. Therefore, a portion of the light reflected by the inclined portion 134 does not enter the objective lens of the microscope, so that it is observed as a dark region in the image formed by the microscope.

Since each recess 132 forms an image of bright areas and dark areas as described above, when the entire alignment mark 131 is observed under a microscope, a striped pattern image in which bright areas and dark areas are alternately repeated is observed. Ru. Using such an image, alignment with other substrates can be performed.

In this embodiment as well, by dropping a substance (for example, a refractive index adjusting agent, adhesive, etc.) having approximately the same refractive index as the material of the alignment mark forming layer 100 onto the surface of the alignment mark 131, the inclined portion 134 of the recessed portion 132 is formed. Since the reflection (Fresnel reflection) is significantly reduced, the second principal surface 112b can be observed clearly through the substrate 112. In this manner, according to this embodiment as well, it is possible to realize a substrate 130 with alignment marks that has excellent visibility when observing through the substrate.

Next, examples of the present invention will be described.

First, a method for evaluating alignment marks will be explained. The alignment mark was observed using a measuring microscope (OLYMPUS, STM7) equipped with a vertical epi-illumination device and a light source (OLYMPUS, LG-PS2). The objective lenses used are OLYMPUS LMPlanFLN 20x/0.4BD (magnification = 20), OLYMPUS LMPlanFLN 50x/0.5BD (magnification = 50), and OLYMPUS LMPlanFI 100x/0.80BD (magnification = 100). there was.

Substrates with alignment marks shown in FIGS. 2, 5, and 6 were produced, and the alignment marks were observed using a microscope equipped with an objective lens having a magnification of 20. To form the alignment mark, a glass substrate with a chrome mask (ion exchange glass, refractive index: 1.53, extinction coefficient: <0.1) was prepared and etched with a hydrofluoric acid etchant. Alignment marks having shapes shown in FIGS. 2, 5, and 6 were formed by changing the etching time.

FIG. 14(a) shows an image of an alignment mark having the shape shown in FIG. FIG. 14(b) shows an image of an alignment mark having the shape shown in FIG. FIG. 14(c) shows an image of an alignment mark having the shape shown in FIG. As can be seen from FIGS. 14(a) to 14(c), although the widths of the bright and dark regions were different, a clear striped image was observed.

Table 1 below shows the width of the dark area (Lb, see FIG. 11) when the alignment mark is observed while changing the numerical aperture (NA) and magnification of the objective lens of the microscope. In any of the examples shown in Table 1, the medium around the alignment mark is air (refractive index=1.0).

From Table 1, it can be seen that when the numerical aperture NA of the objective lens is increased in the alignment mark 14, which is composed of a concave portion 16 having a flat portion 18 and an inclined portion 20, the reflection is made at a relatively large angle with respect to the optical axis of the objective lens. It can be seen that since the reflected light also enters the objective lens, the width (Lb) of the dark area becomes smaller. That is, in the above equation (1), the value of the aperture angle θ ₀ /2 becomes larger, and the reflected light at a larger angle α is also observed as a bright region, so the width of the dark region (Lb) becomes smaller. .

FIG. 14(c) is an image of an alignment mark in which a plane parallel to the first main surface 12a of the substrate 12 is formed on the ridge 21 between adjacent recesses 16, as shown in FIG. As shown in FIG. 14(c), the flat portion 18 and the ridge portion 21 are observed as a bright region, and the slope portion 20 satisfying the above equation (1) is observed as a dark region. Therefore, a striped image having a pitch that is half the pitch of the mask used to form the alignment mark 14 is observed.

(Example 1)
A glass substrate with a chrome mask (ion exchange glass, ns = 1.53, ks < 0.1, linear expansion coefficient: 0.55 ppm/K) having slit-like openings with various pitches and widths was prepared. , etching was performed with a hydrofluoric acid etchant to form alignment marks (ns=1.53, ks<0.1) having the shape shown in FIG. Here, 17 examples (Examples 1-1 to 1-17) with different alignment mark parameters (see FIG. 11) were produced. Each parameter of Examples 1-1 to 1-17 is shown in Table 2 below.

The alignment mark was observed using a measuring microscope (OLYMPUS, STM7, objective lens: NA = 0.4, magnification: 20x) having a vertical epi-illumination device and a light source (OLYMPUS, LG-PS2). As a result, alignment marks with clearly separated bright areas and dark areas as shown in FIG. 15 were observed. Next, in the same observation system, a refractive index standard solution (n=1.51) was dropped onto the alignment mark to fill the entire recess. As a result, reflections at the slopes of the recesses were significantly reduced, and there were no dark areas in the images observed with the microscope. It was confirmed that light could now pass through the entire substrate and that it was possible to see through to the back surface (second principal surface) of the substrate.

The refractive index and extinction coefficient were measured using a spectroscopic ellipsometer (UVISEL2, manufactured by HORIBA). The incident angle of the measurement light was 60 degrees, the wavelength was 560 nm, and the spot diameter was 1 mm x about 2 mm (ellipse).

(Comparative example 1)
Here, a comparative example of Example 1 will be explained. When a glass substrate with a nickel mask was observed under an optical microscope before being etched with a hydrofluoric acid etchant, the nickel mask area was observed to be dark and the opening area to be observed to be bright. The transmittance of the nickel mask portion was zero. In this state, even if a refractive index standard solution (n=1.8) is dropped onto the alignment mark, the transmittance in the nickel mask area is zero, the appearance of the alignment mark remains dark, and the back side of the substrate ( The second principal surface) could not be observed.

(Example 2)
In Example 2, formation of alignment marks by a transfer method will be described. Example 2 corresponds to a substrate 130 with alignment marks shown in FIG. 13. Here, an organopolysiloxane solution was cured on a substrate to form an alignment mark forming layer, and alignment marks were formed on the alignment mark forming layer.

First, preparation of the organopolysiloxane solution will be explained. 0.1 mol of phenyltriethoxysilane and 0.15 mol of dimethyldiethoxysilane were placed in a beaker and stirred. To this liquid, 0.25 mol of ethanol was added and stirred, and an aqueous solution of formic acid dissolved in 1.75 mol (31.5 g) of water to a concentration of 0.1% by weight was further added thereto and stirred for 2 hours. At the beginning of stirring, the liquid separated into two layers, but after stirring for 2 hours, it became a transparent homogeneous solution. When this solution was heated in an oven at 80° C. for 12 hours, ethanol, formic acid aqueous solution, water produced in the polycondensation reaction, etc. were volatilized. As a result, the solution, which originally had a weight of about 91.2 g and a volume of about 100 cm ³ , had its weight and volume reduced by about 30% to a weight of about 27 g and a volume of about 30 cm ³ . The liquid thus obtained is referred to as "transfer liquid composition A."

Next, formation of alignment marks by the transfer method will be explained. A mold corresponding to the shape of the alignment mark shown in FIG. 8 was prepared as a mold for molding. In addition, a soda lime glass plate having a thickness of 1.0 mm and a size of 25 mm square was prepared as a substrate (glass substrate) (refractive index: ns=1.52, ks<0.1, coefficient of linear expansion: 10 ppm/K). This glass substrate was subjected to ultrasonic alkali cleaning, pure water cleaning, and drying.

Using the above-mentioned substrate, mold, and transfer liquid composition A, alignment marks were formed using the "base material pouring method" so that the film thickness of the portion where no alignment marks were formed was about 40 μm. "Substrate pouring method" is a method in which a liquid containing a curable composition is poured directly onto the substrate surface and heated, resulting in a state in which the coating film has plasticity (including, but not limited to, The mold is pressed at a viscosity of 10 ⁴ to 10 ⁸ poise, heated in that state, and released after the transfer is completed (the liquid has hardened or there is no flow). This is a method of molding and curing by final heating (post-curing). Here, after coating the transfer liquid composition A on the glass substrate, it was heated to about 160° C., and after confirming that the plasticity was maintained, it was pressed with the mold. The pressure during pressing was 2 kg/cm ² , and the heating temperature was raised from 160° C. to 180° C. in 20 minutes and held at that temperature for 40 minutes. Thereafter, the mold was released, and then heated at 350° C. for 15 minutes to obtain a glass substrate on which alignment marks made of an organopolysiloxane film were formed.

The organopolysiloxane film produced as described above was transparent and had a thickness of about 40 μm. The membrane contains 18% by weight and 31% by weight of methyl groups and phenyl groups, respectively. Furthermore, the film contained 60 mol% of dimethylsiloxane and 40 mol% of phenylsiloxane out of the total siloxane. Further, the alignment mark forming layer (organopolysiloxane film) had a refractive index na of 1.51 and an extinction coefficient ka of less than 0.1.

The shape of the concave portion of the alignment mark in Example 2 is approximately the same as the shape shown in FIG. It was .05 μm. The slope angle β (see FIG. 10) of the slope portion was 54.7°. When the alignment mark thus formed was observed with an optical microscope, a clear striped image of bright and dark areas was confirmed. Furthermore, by dropping a refractive index standard solution (n = 1.50) onto the alignment mark to reduce interface reflection at the slope, light can pass through the entire substrate, and the back surface of the substrate (the It was confirmed that it was possible to see through to the 2 main surfaces.

(Example 3)
In Example 3 as well, formation of alignment marks by the transfer method will be explained. Example 3 corresponds to a substrate 110 with alignment marks shown in FIG. 12. Here, a silica layer formed by a sol-gel method was used as an alignment mark forming layer, and alignment marks were formed in the alignment mark forming layer.

First, 0.05 mol of silicon tetraethoxide was weighed, and to this were added 5 times the molar ratio of ethanol and 6 times the molar ratio of water (containing 1 wt% HCl), and the mixture was stirred at room temperature for 30 minutes. This solution was diluted by adding twice the volume of ethanol, and then polyethylene glycol (PEG) with an average molecular weight of 600 was added at a weight ratio of (PEG)/(SiO ₂ )=0.1 to the final product SiO ₂ . The mixture was added and dissolved uniformly, and this was designated as "transfer liquid composition B."

Next, a mold corresponding to the shape of the alignment mark shown in FIG. 12 was prepared as a molding mold. In addition, a 25 mm square plate-shaped borosilicate glass capable of ion exchange with a thickness of 1.0 mm was prepared as a substrate (glass substrate) (refractive index ns = 1.53, ks < 0.1, linear expansion coefficient: 10 ppm). /K). This glass substrate was subjected to ultrasonic alkali cleaning, pure water cleaning, and drying. Transfer liquid composition B was applied onto one main surface of the glass substrate by a spin coating method to form an alignment mark forming layer having a thickness of 0.3 μm. Next, this glass substrate was placed on the stage of a press device capable of pressing in a closed space capable of reducing pressure, and a mold for forming alignment marks was placed on the alignment mark forming layer of the glass substrate.

Next, after reducing the pressure in the space in which the press equipment was installed to approximately 1 x 10 ^-5 Torr, the substrate of the press equipment was pressed with a press pressure of 50 kgf/cm ² , and then heat treated at 100°C for 10 minutes in that state to form alignment marks. The cambium was cured. Thereafter, the pressure was returned to atmospheric pressure and the mold was released. After the mold release, the substrate with the alignment mark was baked in the air at 350° C. for 15 minutes using a clean oven. As a result of this post-curing, ethanol, moisture, etc. in the alignment mark forming layer were evaporated, and the alignment mark forming layer became a glassy amorphous film with a thickness of about 0.2 μm. It is thought that the film contains silica as a main component.

When the cross section of the alignment mark on the glass substrate produced by the above operation was observed by SEM, an alignment mark having the shape shown in FIG. 12 was formed. Convex pitch P: 1 μm, silica layer thickness: 0.25 μm, height to top of convex portion: 0.18 μm, dark area width Lb: 0.5 μm, flat portion length Lw: 0. It was 5 μm. Moreover, the refractive index of the alignment mark forming layer (silica layer) was na=1.46, and the extinction coefficient ka<0.1. Further, the visible light reflectance (one side) of the alignment mark forming layer was about 4%.

The visible light reflectance was determined as follows. Spectral reflectance in the wavelength range of 380 to 780 nm was measured for a portion of the glass substrate on which an alignment mark was formed, where no alignment mark was formed. The spectral reflectance was measured using a spectrophotometer (product name: U-4000, manufactured by Hitachi High-Technology) at a reflection angle of 12°. Next, based on the obtained spectral reflectance, visible light reflectance was calculated according to JIS R3106 (1998).

When the glass substrate on which alignment marks were formed in this manner was observed under an optical microscope, a striped pattern of bright and dark areas could be clearly seen. By dropping a refractive index standard solution (n = 1.48) onto the alignment mark and reducing interface reflection at the inclined part, light is transmitted through the entire substrate, and the back surface of the substrate (second main It was confirmed that it was possible to see through the area.

Further, a glass substrate having an alignment mark having the shape shown in FIG. 13 was obtained in the same manner as in Example 3 above. When the glass substrate on which alignment marks were formed in this manner was observed under an optical microscope, a striped pattern of bright and dark areas could be clearly seen. By dropping a refractive index standard solution (n = 1.48) onto the alignment mark and reducing interface reflection at the inclined part, light is transmitted through the entire substrate, and the back surface of the substrate (second main It was confirmed that it was possible to see through the area.

(Example 4)
Example 4 was the same as Example 3 except that titanium (di-i-propoxide) bis(acetylacetonate) (75% in isopropanol) was used instead of silicon tetraethoxide as the alignment mark forming layer. A glass substrate on which an alignment mark including a convex shape shown in FIG. 12 was formed was manufactured.

It is thought that the alignment mark forming layer of Example 4 contains titania as a main component. Convex pitch P: 1 μm, titania layer thickness: 0.20 μm, height to top of convex portion: 0.15 μm, dark area width Lb: 0.5 μm, flat portion length Lw: 0. It was 5 μm. Moreover, the refractive index of the alignment mark forming layer (titania layer) was na=2.10, and the extinction coefficient ka<0.1. The visible light reflectance (one side) of the alignment mark forming layer was about 12%.

When the glass substrate on which alignment marks were formed in this manner was observed under an optical microscope, a striped pattern of bright and dark areas could be clearly seen. By dropping a refractive index standard solution (n = 1.68) onto the alignment mark to reduce interface reflection at the slope, light can pass through the entire substrate, and the back surface of the substrate (second main It was confirmed that it was possible to see through the area.

(Example 5)
In Example 5, an optical waveguide was formed by performing ion exchange treatment on the glass substrate with alignment marks to give the glass substrate a higher refractive index than other parts. Here, the difference in refractive index between the optical waveguide and the glass substrate was set to 0.0074 (the refractive index of the portion constituting the optical waveguide is higher than the refractive index of other portions).

First, a predetermined optical waveguide pattern was formed on a multicomponent glass substrate containing Na as a monovalent alkali metal component. This patterning was performed by a well-known method in which a Ti film formed by sputtering is processed by a lift-off method using aqueous ammonia (a mixture of aqueous ammonia and hydrogen peroxide).

Next, in the first stage of ion exchange treatment, the glass substrate was immersed in a molten salt containing silver nitrate to exchange Na ions on the surface of the glass substrate with Ag ions. As a result, a predetermined optical waveguide pattern was formed on the surface of the glass substrate.

In the second stage ion exchange treatment, the glass substrate subjected to the first stage ion exchange treatment was immersed in the second molten salt, and an electric field was applied in the thickness direction of the glass substrate. As a result, the optical waveguide formed by the first stage of ion exchange was moved into the glass substrate, forming an embedded optical waveguide. Even after the waveguide was fabricated on the alignment substrate by such a two-step ion exchange method, the alignment mark maintained the same shape as before the waveguide was formed. The visible light reflectance (one side) was about 12%. When observed with an optical microscope, a striped pattern of bright and dark areas could be clearly seen. By dropping a refractive index standard solution (n = 1.51) onto the alignment mark and reducing interface reflection at the inclined part, light is transmitted through the entire substrate, and the back surface of the substrate (second main It was confirmed that it was possible to see through the area. We also measured the insertion loss of the waveguide with respect to wavelength. The wavelength characteristic of the waveguide (the difference in insertion loss between wavelengths of 1.48 μm and 1.58 μm) was 0.34 dB.

(Example 6)
In Example 6, a buried optical waveguide was formed in the same manner as in Example 5 except that thallium nitrate was used instead of silver nitrate and glass containing sodium ions and potassium ions was used.

Even after a waveguide was fabricated on a substrate with alignment marks by a two-step ion exchange method using thallium nitrate, the alignment marks maintained the same shape as before the waveguide was formed. In addition, insertion loss with respect to wavelength was measured. The wavelength characteristic of the waveguide (the difference in insertion loss between wavelengths of 1.48 μm and 1.58 μm) was 0.32 dB.
Further, as a method for forming an optical waveguide inside the glass by an ion exchange method, the techniques described in, for example, Japanese Patent Laid-Open No. 06-3555 and Japanese Patent Laid-Open No. 63-206709 can be used.

(Comparative example 2)
The Ti film (alignment mark portion) of the mask for the waveguide forming ion exchange step in Example 5 maintained its pattern shape even after ion exchange. When the pattern of the Ti film was observed with an optical microscope, a striped pattern of bright areas and dark areas was clearly confirmed, but the transmittance of the Ti mask portion was zero. In this state, even if a refractive index standard solution (n=1.8) is dropped onto the alignment mark, the transmittance in the Ti film region is zero, the appearance of the alignment mark remains dark, and the back surface of the substrate ( The second principal surface) could not be observed.

In the case where a waveguide is formed using a substrate with an alignment mark in which the alignment mark is formed of a chromium film, the chromium is dissolved during the first ion exchange treatment under the same conditions as in Example 5, and the alignment mark is No structure was observed. Furthermore, chromium was dissolved during the first ion exchange treatment under the same conditions as in Example 6, and no alignment mark structure was observed.

(Example 7)
In Example 7, alignment between a glass substrate with alignment marks and a silicon substrate will be described. An optical waveguide device was fabricated by laminating a glass optical waveguide substrate with an optical waveguide formed inside and a silicon (Si) optical waveguide substrate with an optical waveguide formed on the main surface, and coupling the optical waveguides to each other. In this specification, an alignment method using an alignment mark is explained, and the subject matter is the alignment and assembly of a glass optical waveguide substrate and a silicon optical waveguide substrate according to Example 7, and furthermore, the method described below. The present invention is not limited to the alignment and assembly of the microlens array substrate and the surface emitting laser array substrate according to the eighth embodiment.

Silicon optical waveguide substrates make it easy to form active and passive elements such as photoelectric conversion elements on the substrate, so in order to guide the light, it is recommended to combine them with waveguides formed directly on the silicon substrate. It has the advantage of being easy to do. However, silicon optical waveguides tend to have a small mode field diameter because of their high refractive index.

On the other hand, optical fibers and glass optical waveguides are suitable as light guides responsible for transmission over a certain distance, but most of them are made of quartz or multi-component glass and have a relatively large mode field diameter. Therefore, it is desirable to provide an optical waveguide device that can suitably perform optical coupling from a silicon optical waveguide to a glass optical waveguide.

FIGS. 16(a) to 16(d) are diagrams showing a glass optical waveguide substrate 160. FIG. FIG. 16(a) is a schematic left side view of the glass optical waveguide substrate 160. FIG. 16(b) is a schematic plan view of the glass optical waveguide substrate 160. FIG. 16(c) is a schematic right side view of the glass optical waveguide substrate 160. FIG. 16(d) is a schematic front view of the glass optical waveguide substrate 160. This glass optical waveguide substrate 160 has a refractive index ns=1.54 and an extinction coefficient ks<0.1.

The glass optical waveguide substrate 160 includes a glass substrate 161, four optical waveguides 162 formed inside the glass substrate 161, and four alignment marks 163a to 163d formed on the second main surface 161b of the glass substrate 161. Be prepared. Hereinafter, when the four alignment marks 163a to 163d are collectively referred to as "alignment mark 163".

The glass substrate 161 has an outer size of 2 mm x 5 mm and a thickness of 0.2 mm. The optical waveguide 162 is provided close to the first main surface 161a of the glass substrate 161 and parallel to the first main surface 161a. The mode field diameter of the optical waveguide 162 is 5 to 15 μm, and the distance from the center of the mode field to the nearest first principal surface 161a of the glass substrate 161 is 5 μm. The optical waveguide 162 was fabricated within the glass substrate 161 by the above-mentioned two-step ion exchange method.

In Example 7, the shape of the concave portion of the alignment mark 163 was set to the shape shown in FIG. Alignment mark 163 has a first scale. That is, the outer dimensions of the alignment mark 163 are 0.05 mm x 0.25 mm, the arrangement pitch P1 of the recesses is 1 μm, and the width Lb1 of the dark area in the image is 0.2 μm.

The four alignment marks 163 are arranged at four corners of a rectangle, as shown in FIG. 16(b). The alignment mark 163 is precisely aligned with the optical waveguide 162. The two alignment marks 163a and 163d are arranged at opposite corners (upper left and lower right) of the rectangle. The alignment marks 163a and 163d are provided so that the longitudinal direction of the recesses coincides with the direction perpendicular to the longitudinal direction of the optical waveguide 162. The remaining two alignment marks 163b and 163c are located at other opposing corners of the rectangle (upper right and lower left). The alignment marks 163b and 163c are provided so that the longitudinal direction of the recesses coincides with the longitudinal direction of the optical waveguide 162.

17(a) to (d) are diagrams showing a silicon optical waveguide substrate 170. FIG. FIG. 17A is a schematic left side view of the silicon optical waveguide substrate 170. FIG. 17(b) is a schematic plan view of the silicon optical waveguide substrate 170. FIG. 17(c) is a schematic right side view of the silicon optical waveguide substrate 170. FIG. 17(d) is a schematic front view of the silicon optical waveguide substrate 170.

The silicon optical waveguide substrate 170 includes a silicon (Si) substrate 171, a silicon oxide (SiO ₂ ) layer 174 provided on one main surface of the silicon substrate 171, and an optical waveguide 172 formed on the silicon oxide layer 174. and four alignment marks 173a to 173d formed on a silicon substrate 171. Hereinafter, when the four alignment marks 173a to 173d are collectively referred to as "alignment mark 173".

The silicon substrate 171 has an outer size of 2 mm x 10 mm and a thickness of 0.1 mm/0.3 mm. The optical waveguide 172 is made of silicon (Si). The optical waveguide 172 has a substantially rectangular cross section, and the direction in which light propagates is the same as the longitudinal direction of the optical waveguide 172. The optical waveguide 172 has a width of 0.5 μm and a height of 0.3 μm. The silicon optical waveguide substrate 170 may be an optical waveguide substrate including a rib waveguide or a MOS waveguide, in addition to the thin wire waveguide described here.

As shown in FIG. 17D, a portion of the silicon substrate 171 is provided with a stepped portion 175 that is lower than the portion where the silicon oxide layer 174 is provided. Four alignment marks 173 are provided on this stepped portion 175.

The shape of the concave portion of the alignment mark 173 was also the shape shown in FIG. 5 similarly to the alignment mark 163. Alignment mark 173 has a second scale that is different from the first scale of alignment mark 163. That is, the outer dimensions of the alignment mark 173 are 0.05 mm x 0.25 mm, the arrangement pitch P2 of the recesses is 0.9 μm, and the width Lb2 of the dark area in the image is 0.2 μm.

The positions of the four alignment marks 173 and the directions of the grooves are determined to correspond to the alignment marks 163 provided on the glass optical waveguide substrate 160 to be laminated. The four alignment marks 173 are arranged at four corners of a rectangle, as shown in FIG. 17(b). The alignment mark 173 is precisely aligned with the optical waveguide 172. The two alignment marks 173a and 173d are arranged at opposite corners (upper left and lower right) of the rectangle. The alignment marks 173a and 173d are provided so that the longitudinal direction of the recesses coincides with the direction perpendicular to the longitudinal direction of the optical waveguide 172. The remaining two alignment marks 173b and 173c are located at other opposing corners of the rectangle (upper right and lower left). The alignment marks 173b and 173c are provided so that the longitudinal direction of the recesses coincides with the longitudinal direction of the optical waveguide 172.

As described above, the glass optical waveguide substrate 160 and the silicon optical waveguide substrate 170 according to Example 7 are each aligned such that the longitudinal direction of the recesses coincides with the longitudinal direction of the waveguide formed on the substrate. and an alignment mark in which the longitudinal direction of the recess coincides with the direction parallel to the longitudinal direction of the waveguide formed on the substrate. This makes it possible to improve alignment accuracy within a two-dimensional plane.

FIGS. 18(a) and 18(b) show schematic images formed when the alignment mark is observed with a microscope having a vertical epi-illumination device. FIG. 18A shows a schematic image of the alignment mark 163 on the glass optical waveguide substrate 160. FIG. 18(b) shows a schematic image of the alignment mark 173 on the silicon optical waveguide substrate 170. When manufacturing an optical waveguide device by laminating a glass optical waveguide substrate 160 and a silicon optical waveguide substrate 170, an image of the alignment mark 163 shown in FIG. 18(a) and an image of the alignment mark 173 shown in FIG. 18(b) are used. Adjust the positions of both so that they are lined up horizontally. It should be noted that there is no problem even if the alignment mark 163 of the glass optical waveguide substrate 160 is as shown in FIG. 18(b) and the alignment mark 173 of the silicon optical waveguide substrate 170 is as shown in FIG. 18(a) in a reverse combination pattern.

In the seventh embodiment, as described above, the arrangement pitch P1 of the recesses in the alignment mark 163 of the glass optical waveguide substrate 160 is 1 μm, and the arrangement pitch P2 of the recesses in the alignment mark 173 of the silicon optical waveguide substrate 170 is 0.9 μm. It is. That is, the pitch P1 of the alignment marks 163 on the glass optical waveguide substrate 160 and the pitch P2 of the alignment marks 173 on the silicon optical waveguide substrate 170 are different (P1≠P2). By providing a difference of 0.1 μm between the pitches P1 and P2 in this way, it is possible to position or identify the position to be fixed with an accuracy of 0.1 μm, similar to how to read the scale on a caliper. . In another example, P1=1 μm and P2=0.95 μm. In this case, the position to be positioned or fixed can be identified with an accuracy of 0.05 μm.

The width Lb1 of the dark area in the image of the alignment mark 163 on the glass optical waveguide substrate 160 and the width Lb2 of the dark area in the image of the alignment mark 173 on the silicon optical waveguide substrate 170 are determined to facilitate the ease of observing the alignment mark and adjusting the scale. Therefore, it is preferable that they be approximately equal.

As described above, in the seventh embodiment, P1≠P2, but for example, if alignment accuracy is not required so much, alignment marks satisfying P1=P2 may be set on the glass optical waveguide substrate 160 and the silicon optical waveguide substrate 170. may be formed. In this case, the molds for forming the alignment marks can be the same, which is advantageous in terms of cost.

When producing an optical waveguide device by laminating the glass optical waveguide substrate 160 and the silicon optical waveguide substrate 170, it is necessary to precisely adjust the relative positional relationship between the optical waveguides. This is because if the optical waveguides are misaligned, optical loss increases and quality deteriorates. Assuming that the positional relationship between the optical waveguide and the alignment mark is strictly defined on each optical waveguide board, it is easier to recognize it visually than to adjust it while monitoring direct visual information and optical loss of the waveguide. However, it is more efficient to adjust the alignment marks. Satisfactory accuracy can be achieved in the positional relationship between the optical waveguide and the alignment mark by making full use of (photo)lithography technology in semiconductor technology that achieves submicron or less accuracy.

FIGS. 19A and 19B show a state in which a glass optical waveguide substrate 160 and a silicon optical waveguide substrate 170 are stacked. FIG. 19(a) is a schematic plan view, and FIG. 19(b) is a schematic front view. As shown in FIGS. 19(a) and 19(b), the glass optical waveguide substrate 160 and the silicon optical waveguide substrate 170 are stacked such that the glass optical waveguide substrate 160 is located on the stepped portion 175 of the silicon optical waveguide substrate 170. Ru. At this time, the end surfaces of the optical waveguides 162 on the glass optical waveguide substrate 160 and the end surfaces of the optical waveguides 172 on the silicon optical waveguide substrate 170 must be accurately opposed to optically couple the optical waveguides 162 and 172.

To align the glass optical waveguide substrate 160 and the silicon optical waveguide substrate 170, the alignment marks provided on each substrate are observed while being magnified with a microscope, and their relative positions are determined so that the corresponding alignment marks are lined up side by side. or adjust the tilt. Since the optical waveguides and alignment marks on each optical waveguide board have a relative positional relationship with high precision in advance, by positioning the mutual alignment marks, the positional relationship of the mutual optical waveguides can be adjusted. can do.

FIGS. 20A and 20B show a state in which a glass optical waveguide substrate 160 and a silicon optical waveguide substrate 170 are bonded together. Adhesive 190 (n=1.53, k<0.1) is poured between the glass optical waveguide substrate 160 and the silicon optical waveguide substrate 170 for which position adjustment has been completed, and hardened at the portions including the alignment marks 163 and 173. I let it happen. Examples of the adhesive include, but are not limited to, photocurable and thermosetting adhesives.

By filling the recesses of the alignment marks 163 and 173 with the adhesive 190 having a predetermined refractive index, reflections at the slopes of the recesses are substantially eliminated or significantly reduced. When observed with a microscope from the first principal surface 161a side of the optical waveguide substrate 160, no clear striped pattern is visible, and the silicon optical waveguide substrate 160 and the silicon optical waveguide substrate 160 pass through each other as if there were no alignment marks. The optical waveguide substrate 170 can be observed (in FIG. 20A, alignment marks 163 and 173 are omitted to show the state observed with a microscope).

(Example 8)
In Example 8, alignment between a microlens array substrate with alignment marks and a surface emitting laser array substrate will be described.

FIGS. 21(a) to 21(c) are diagrams showing the microlens array substrate 210. FIG. 21(a) is a schematic plan view of the microlens array substrate 210. FIG. 21(b) is a schematic front view of the microlens array substrate 210.

The microlens array substrate 210 is made of glass. The outer dimensions of the microlens array substrate 210 are 0.5 mm x 2.2 mm, and the thickness is 0.2 mm. As shown in the figure, eight axially symmetrical microlenses 212 are formed in a row on one main surface (first main surface 210a) of the microlens array substrate 210. The microlens 212 has a focal length of 0.2 mm and an effective diameter of 200 μm. Further, the arrangement pitch of the eight microlenses 212 is 250 μm. The microlens 212 may be formed by creating a region with a higher refractive index than the surrounding area inside the glass by ion exchange or the like, or may be formed on a glass substrate by the above-mentioned "base material pouring method". Alternatively, it may be formed by a transfer method after forming a lens forming layer.

Four alignment marks 214a to 214d are directly formed on the microlens array substrate 210 at predetermined positions. Hereinafter, when the four alignment marks 214a to 214d are collectively referred to as "alignment mark 214". The alignment mark 214 is precisely aligned with the eight microlenses 212.

In Example 8, the shape of the recessed portion of the alignment mark 214 was set to the shape shown in FIG. Alignment mark 214 has a first scale. That is, the outer dimensions of the alignment mark 214 are 0.5 mm x 0.25 mm, the arrangement pitch P1 of the recesses is 1 μm, and the width Lb1 of the dark area in the image is 0.2 μm.

FIGS. 22A and 22B are diagrams showing a surface emitting laser array substrate 220 with alignment marks. FIG. 22(a) is a schematic plan view of the surface emitting laser array substrate 220. FIG. 22(b) is a schematic front view of the surface emitting laser array substrate 220.

The surface emitting laser array substrate 220 is made of a semiconductor material such as silicon. The outer dimensions of the surface emitting laser array substrate 220 are 0.7 mm x 2.5 mm, and the thickness is 0.2 mm. As shown in the figure, one main surface (first main surface 220a) of the surface emitting laser array substrate 220 has eight surface emitting lasers having optical axes in a direction substantially parallel to the normal to the first main surface 220a. 222 are arranged in a row. The eight surface emitting lasers 222 are arranged at positions corresponding to the eight microlenses 212 on the above-mentioned microlens array substrate 210 on which stacking is planned. The surface emitting laser 222 can be easily configured in an array, and can be laminated with other optical components relatively easily. For example, by integrating with a microlens array as described above, optical coupling with other transmission components such as optical fibers can be efficiently performed. Note that for the sake of simplicity, descriptions of electric circuits, wiring, etc. on the surface emitting laser array substrate 220 are omitted.

Four alignment marks 224a to 224d are directly formed on the surface emitting laser array substrate 220 at predetermined positions. Hereinafter, when the four alignment marks 224a to 224d are collectively referred to as "alignment mark 224". The alignment mark 224 is precisely aligned with the eight surface emitting lasers 222.

The shape of the recessed portion of the alignment mark 224 was also the shape shown in FIG. 5, similarly to the alignment mark 214. Alignment mark 224 has a second scale that is different from the first scale of alignment mark 214. That is, the outer dimensions of the alignment mark 224 are 0.05 mm x 0.25 mm, the arrangement pitch P2 of the recesses is 0.9 μm, and the width Lb2 of the dark area in the image is 0.2 μm.

23(a) to (c) show a state in which a microlens array substrate 210 and a surface emitting laser array substrate 220 are stacked. 23(a) is a schematic plan view, FIG. 23(b) is a schematic front view, and FIG. 23(c) is a schematic right side view.

The microlens array substrate 210 and the surface emitting laser array substrate 220 are arranged such that the optical axis of each microlens 212 arranged on the microlens array substrate 210 and the optical axis of each surface emitting laser 222 arranged on the surface emitting laser array substrate 220 are connected to each other. are aligned so that they match. Alignment marks 214 and 224 are used during this positioning. That is, as in Example 7 above, the relative positions of the microlens array substrate 210 and the surface emitting laser array substrate 220 are adjusted so that the corresponding alignment marks 214 and 224 are aligned side by side, as shown in FIG. 23(a). and tilt are adjusted.

FIGS. 24A and 24B show a state in which the microlens array substrate 210 and the surface emitting laser array substrate 220 are bonded together. Adhesive 230 (n=1.53, k<0.1) is poured between the microlens array substrate 210 and the surface-emitting laser array substrate 220 whose positions have been adjusted. It was cured to produce an optical module. In Example 8, an elongated recess 215 is formed on the lower surface of the microlens array substrate 210. This elongated recess 215 extends over the area below the eight microlenses 212. By providing such an elongated recess 215 in the microlens array substrate 210, a space 216 is formed when the microlens array substrate 210 and the surface emitting laser array substrate 220 are stacked, so that the surface emitting laser 222 and the microlens array substrate 210 are stacked together. Adhesive 230 can be prevented from entering between the lens 212 and the lens 212.

FIGS. 25A to 25F are six views of a microlens substrate with alignment marks according to an embodiment of the present invention. FIG. 25(a) is a rear view of the microlens substrate with alignment marks. FIG. 25(b) is a plan view of the microlens substrate with alignment marks. FIG. 25(c) is a front view of the microlens substrate with alignment marks. FIG. 25(d) is a bottom view of the microlens substrate with alignment marks. FIG. 25(e) is a left side view of the microlens substrate with alignment marks. FIG. 25(f) is a right side view of the microlens substrate with alignment marks.

FIG. 26 is an enlarged plan view of the alignment mark portion (AB portion) of the microlens substrate. FIG. 27 is a cross-sectional view taken along the line CC of the alignment mark portion shown in FIG. 26. FIG. 28 is an enlarged perspective view of the alignment mark portion (AB portion) of the microlens substrate.

FIG. 29 is an enlarged plan view of a first modification of the alignment mark portion (AB portion) of the microlens substrate. FIG. 30 is a cross-sectional view taken along the line CC of the alignment mark portion shown in FIG. 29. FIG. 31 is an enlarged perspective view of a first modification of the alignment mark portion (AB portion) of the microlens substrate.

FIG. 32 is an enlarged plan view of a second modification of the alignment mark portion (AB portion) of the microlens substrate. FIG. 33 is a cross-sectional view taken along the line CC of the alignment mark portion shown in FIG. 32. FIG. 34 is an enlarged perspective view of a second modification of the alignment mark portion (AB portion) of the microlens substrate.

FIG. 35 is an enlarged plan view of a third modification of the alignment mark portion (AB portion) of the microlens substrate. FIG. 36 is a cross-sectional view taken along the line CC of the alignment mark portion shown in FIG. 35. FIG. 37 is an enlarged perspective view of a third modification of the alignment mark portion (AB portion) of the microlens substrate.

FIG. 38 is an enlarged plan view of a fourth modification of the alignment mark portion (AB portion) of the microlens substrate. FIG. 39 is a CC sectional view of the alignment mark portion shown in FIG. 38. FIG. 40 is an enlarged perspective view of a fourth modification of the alignment mark portion (AB portion) of the microlens substrate.

FIGS. 41(a) to 41(f) are six views of the optical waveguide substrate with alignment marks according to the embodiment of the present invention. FIG. 41(a) is a rear view of the optical waveguide substrate with alignment marks. FIG. 41(b) is a plan view of the optical waveguide substrate with alignment marks. FIG. 41(c) is a front view of the optical waveguide substrate with alignment marks. FIG. 41(d) is a bottom view of the optical waveguide substrate with alignment marks. FIG. 41(e) is a left side view of the optical waveguide substrate with alignment marks. FIG. 41(f) is a right side view of the optical waveguide substrate with alignment marks. In this optical waveguide substrate, the alignment mark portion (AB portion) may have the same shape as the alignment mark portion shown in FIGS. 26 to 40.

The present invention has been described above based on the embodiments. Those skilled in the art will understand that this embodiment is merely an example, and that various modifications can be made to the combinations of the constituent elements and processing processes, and that such modifications are also within the scope of the present invention. be.

The present invention can be used for positioning optical elements.

10,50,60,70,80,90,110,130 Substrate with alignment mark, 12,112 Substrate, 14,114,131 Alignment mark, 16,132 Concave portion, 18,118,133 Flat portion, 20,120, 134 slope part, 21 ridge part, 30 image, 32 bright area, 34 dark area, 100 alignment mark forming layer, 116 convex part, 160 glass optical waveguide substrate, 161 glass substrate, 162, 172 optical waveguide, 163, 173, 214 , 224 alignment mark, 170 silicon optical waveguide substrate, 171 silicon substrate, 174 silicon oxide layer, 175 stepped portion, 190, 230 adhesive, 210 microlens array substrate, 212 microlens, 215 elongated recess, 216 space, 220 surface Light emitting laser array substrate, 222 surface emitting laser.

Claims (8)

A substrate and
an alignment mark formed on the main surface of the substrate;
A substrate with an alignment mark, comprising:
The alignment mark has a plurality of linear recesses or protrusions,
The concave portion or convex portion is
a flat portion parallel to the main surface;
an inclined part inclined with respect to the main surface;
Equipped with
The substrate has a first main surface and a second main surface opposite to the first main surface,
A plurality of the alignment marks having an arrangement pitch of P are formed on the first main surface,
In the cross section of the alignment mark, when Lw is the length of the flat part of the alignment mark, and He is the length in the thickness direction between the first main surface and the flat part of the alignment mark,
A substrate with an alignment mark, characterized in that |Lw+He×2−P|≦10 [μm] . The substrate with alignment marks according to claim 1, wherein the inclined portion includes a curved surface. The substrate with alignment marks according to claim 1, wherein the inclined portion includes a flat surface. 4. The substrate with alignment marks according to claim 1, wherein the refractive index ns of the material forming the substrate satisfies 1.2≦ns≦2.7 at a wavelength of 560 nm. 5. The substrate with alignment marks according to claim 1, wherein an extinction coefficient ks of a material forming the substrate satisfies ks<1. 6. The substrate with alignment marks according to claim 1, wherein the surface roughness Ra of the flat portion satisfies 0.001 μm≦Ra≦50 μm. 7. The substrate with alignment marks according to claim 1, wherein the reflectance Rs of the flat portion to air satisfies 0.01%≦Rs≦30% at a wavelength of 560 nm. 8. The substrate with an alignment mark according to claim 1, wherein the visible light transmittance of the flat portion is 30% or more.

Images