JP2011257580A - Method for manufacturing optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a process for manufacturing an optical device and allow an optical element to be positioned with great precision relative to an optical waveguide.SOLUTION: A first layer made of a material having an optical waveguiding property is formed on a substrate 11, and a second layer made of a metallic material is formed on the first layer. The second layer is processed into a first metal pattern of a shape corresponding to an optical waveguide 12, a second metal pattern of a shape corresponding to positioning marks 14a and 14b, and a third metal pattern of a shape corresponding to a joining part 13 respectively. The first layer is processed by etching with the processed second layer serving as a mask into the shapes corresponding to the optical waveguide 12, the positioning marks 14a and 14b, and the joining part 13 respectively. Thereafter, the first metal pattern is removed to complete the optical waveguide 12 of the first layer, and the optical element 2 is mounted on the substrate 1 by use of the positioning marks 14a and 14b of the second metal pattern and the joining part 13 of the third metal pattern.

Description

  The present invention relates to an optical device manufacturing method in which an optical waveguide and an optical element are accurately positioned (aligned) and mounted on a substrate.

In recent years, an optical waveguide is formed on a substrate, and an optical device such as a laser device is accurately positioned (aligned) and mounted on the optical waveguide, and a modularized optical device is used for optical communication, optical information processing, etc. In recent years, it has also been used for laser displays.
In such an optical device, when positioning between the optical waveguide and the optical element, alignment accuracy at a submicron level is required. For the alignment method, an optical element such as a laser element is actually emitted and coupled to one end of an optical waveguide by a lens system, and alignment is performed while monitoring output light from the other end of the optical waveguide. There is an active alignment method.

On the other hand, there is also a passive alignment method in which an optical waveguide and a positioning alignment mark are formed on the same substrate, and the optical element is positioned and mounted without emitting light on the basis of the alignment mark.
In this passive alignment method, the optical waveguide and the optical element can be easily connected simply by patterning the alignment mark for positioning on the substrate with high precision, so that it is excellent in mass production, and an optical transmission / reception module for optical communication, Attention has been focused on cost reduction techniques such as SHG laser modules.
For example, Patent Document 1 discloses an optical waveguide device, which is an optical device based on such a passive alignment method, and a manufacturing method thereof. In the manufacturing method described in Patent Document 1, an alignment marker is formed at the same time that the end face of the core layer is exposed using a patterned metal (chrome) film as a mask 22.

JP 2007-286340 A

  However, the manufacturing method described in Patent Document 1 has the following problems. In the manufacturing method described in Patent Document 1, the thickness of the first film (film for forming the lower cladding layer) formed by plasma CVD and the second film (upper cladding) formed by atmospheric pressure CVD are used. The relative height between the core layer and the light emitting element is determined by the film thickness of the film forming the layer. That is, in order to adjust the relative height of the core layer and the light emitting element, it is necessary to perform film formation and patterning of the first film and film formation and patterning of the second film, respectively, which complicates the process. There is a problem.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to simplify an optical device manufacturing process and to perform positioning of an optical waveguide and an optical element with high accuracy.

In order to achieve the above object, an optical device manufacturing method according to the present invention includes a first step of forming a first layer made of an optical waveguide material on a substrate and a second step made of a metal material on the first layer. A second step of forming the layer, and a third step of processing the second layer into a first metal pattern having a shape corresponding to the optical waveguide and a second metal pattern having a shape corresponding to the positioning mark. And a fourth step of etching the first layer into a shape corresponding to each of the optical waveguide and the positioning mark using the second layer processed in the third step as a mask, and after the fourth step And a fifth step of removing the first metal pattern, and a sixth step of mounting the optical element on the substrate using the second metal pattern having a shape corresponding to the positioning mark. .

Before the first step, there is a substrate processing step for processing the substrate so as to have a first portion and a second portion lower than the first portion. In the third step, The second layer at a position corresponding to the first portion of the substrate is processed into the first metal pattern, and the second layer at a position corresponding to the second portion is changed to other than the first metal pattern. It is desirable to process into a metal pattern.
In the substrate processing step, the second portion of the substrate is a recess having a length dimension and a width dimension that are smaller than the length dimension and the width dimension of the optical element, and is surrounded by the first portion. In the sixth step, the lower surface of the optical element may be abutted against the upper surface of the first portion of the substrate to perform positioning in the height direction.

  Further, in the third step, the second layer is formed with a first metal pattern having a shape corresponding to the optical waveguide, a second metal pattern having a shape corresponding to the positioning mark, and a shape corresponding to the joint portion. In the sixth step, the second metal pattern having a shape corresponding to the positioning mark and the third metal pattern having a shape corresponding to the joint portion are used. The optical element may be mounted on the substrate.

In that case, it is more preferable to have a micro bump processing step for processing the third metal pattern into a micro bump shape between the third step and the sixth step.
In the micro-bump processing step, the third metal pattern can be processed into a micro-bump shape in which a plurality of micro-bumps are all conducted by the remaining portion of the second layer.

In the third step, the third metal pattern may be processed into a microbump shape corresponding to the joint.
In the sixth step, it is desirable to surface-activate and bond the connecting portion on the optical element side and the third metal pattern on the substrate side.
In the second step, the second layer may be formed of Au.

A silicon substrate may be used as the substrate, and a silicon oxide film may be formed on the entire surface of the substrate before the first step.
In the first step, a first layer made of a silicon nitride film (SiN film) may be formed.
In the sixth step, a laser element can be mounted on the substrate as the optical element.

According to the present invention, the first layer made of the optical waveguide material is simultaneously etched into a shape corresponding to the optical waveguide and the positioning mark using the patterned second layer made of the metal material as a mask. And positioning marks can be formed with high positioning accuracy.
According to the present invention, the relative height between the optical element and the optical waveguide is adjusted by the step provided by processing the substrate and the height of each of the first layers. That is, the steps for adjusting the relative height of the optical element and the optical waveguide are only a step of providing a step on the substrate and a step of forming and patterning the first layer. The manufacturing process can be simplified as compared with the conventional technique in which the patterning and the formation and patterning of the second film are necessary.

It is a perspective view which shows the state before and behind mounting an optical element in the board | substrate side block of an example of the optical device manufactured by 1st Example of the manufacturing method of this invention. It is the top view (a) which shows the structure of the board | substrate side block before mounting the optical element of the optical device similarly, and sectional drawing (b) which follows the AA line. It is sectional drawing similar to FIG.2 (b) for demonstrating a part of each process in 1st Example of the manufacturing method of the optical device by this invention. FIG. 4 is a cross-sectional view similar to FIG. 3 for explaining a subsequent process. It is a front view for demonstrating the process of similarly mounting the optical element in the board | substrate side block. It is sectional drawing similar to FIG.2 (b) for demonstrating a part of each process in 2nd Example of the manufacturing method of the optical device by this invention. FIG. 7 is a cross-sectional view similar to FIG. 6 for explaining a subsequent process. It is a front view for demonstrating the process of similarly mounting the optical element in the board | substrate side block. It is the top view (a) which shows the structure of the board | substrate side block of the optical device manufactured by the manufacturing method 3rd Example of this invention, and sectional drawing (b) which follows the BB line. It is sectional drawing similar to FIG.9 (b) for demonstrating a part of each process in 3rd Example of the manufacturing method of the optical device by this invention. FIG. 11 is a cross-sectional view similar to FIG. 10 for explaining a subsequent process. It is a figure for demonstrating the process of similarly mounting an optical element in the board | substrate side block.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
[Examples of optical devices to be manufactured]
First, an example of an optical device manufactured by the manufacturing method of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view showing a state before and after mounting an optical element on a substrate side block of an optical device manufactured by the first embodiment of the manufacturing method of the present invention, and (a) a state immediately before mounting the optical element. (B) shows a state in which an optical element is mounted.
FIG. 2 shows a configuration of a substrate side block before mounting an optical element as an example of the optical device, (a) is a plan view, and (b) shows all cross sections of each part described in (a). It is sectional drawing which followed the AA line made.

As shown in FIG. 1, this optical device comprises a substrate-side block 1 and an optical element 2, and the substrate-side block 1 is close to one end in the longitudinal direction on a substrate 11 having a rectangular planar shape (1/3 of the total length). The optical waveguide 12 is formed in a strip shape along the central portion in the width direction in the first portion 11a. In addition, a pair of strip-shaped joint portions 13 and 13 are formed in parallel with the central portion in the width direction in the remaining second portion 11b in the longitudinal direction, and the side close to the optical waveguide 12 of one of the joint portions 13 Small circular positioning marks (also referred to as alignment marks) 14a and 14b are respectively formed at a position adjacent to the end portion of the other joint portion 13 and a position adjacent to the end portion on the side farther from the optical waveguide 12 of the other joint portion 13.
Note that the second portion 11b is slightly lower than the first portion 11a and has a step, but since it is very small, only the boundary line 15 is shown in FIG.

  On the other hand, the optical element 2 is a flat laser element having a rectangular planar shape in this example, and is located at a position near the lower surface of the central portion in the width direction of one end surface in the longitudinal direction (the end surface on the side close to the optical waveguide in FIG. 1). Although not shown, it has a light emitting point (or light output point). Then, along the longitudinal direction of the lower surface, the pair of strip-like joints 13 and 13 and the pair of positioning marks 14a and 14b of the substrate-side block 1 respectively correspond to the pair of strip-like joints 23 and 23 and the pair of small pieces. Circular positioning marks 24a and 24b are formed.

Thus, the optical element 2 is moved from the state shown in FIG. 1A to the substrate side block 1 in which the positioning marks 14a and 14b and the joint portions 13 and 13 are formed together with the optical waveguide 12 on the substrate 11 (b). As shown in FIG. 4, the positioning marks 24a and 24b on the lower surface thereof are positioned so as to coincide with the positioning marks 14a and 14b on the substrate, and the bonding portions 23 are brought into close contact with the bonding portions 13 on the substrate 11 for bonding. Then, the optical device is completed.
Accordingly, the optical element 2 is placed on the substrate side block 1 with a submicron level alignment accuracy so that the light emitting point of the one end face 2a of the optical element 2 coincides with the center of the end face 12a on the light input side of the optical waveguide 12. Can be mounted on top.

  The bonding between the bonding portions may be performed by a surface activated bonding method. Surface activated bonding technology is activated by removing inactive layers such as oxide films, organic contamination films, and dust (contamination) that cover the surface of materials such as metals by plasma treatment, and so on. This is a technique of bringing them into contact with each other and joining them at a low temperature using the adhesion force between the atoms.

However, even if this technique is used, bonding between flat bonding surfaces cannot be performed unless heated to about 100 to 150 ° C. Therefore, each joint portion is formed of a metal material that is easily plastically deformed, such as gold (Au), and a large number of micro bumps (small convex portions) are formed on one side of the joint surface, that is, the surface of the joint portion on the substrate side. Therefore, bonding at room temperature becomes possible.
Since Au has high electrical conductivity, it is also suitable as an electrode. By bonding the electrode of an optical element having an electrode such as a laser element to a bonding portion of Au and bonding to a bonding portion of Au also serving as an electrode on the substrate side, Bonding can be performed physically and electrically at the same time.

FIG. 2 shows in more detail a plan view (a) in which the substrate side block 1 of the optical device in this embodiment is enlarged and a cross-sectional view (b) along the line AA.
The substrate 11 of the substrate side block 1 is a silicon (Si) substrate, and in FIG. 2 the first portion 11a that forms the optical waveguide 12 on the right side of the boundary line 15 has a joint 13 on the left side and a positioning mark 14a, The second part forming 14b is formed low (thinner thickness is reduced). A silicon oxide film (SiO film) 17 is formed on the entire upper surface of the substrate 11 having a step. The silicon oxide film 17 functions as a clad layer for the optical waveguide 12 and functions as an insulating film for the junction 13.

  The optical waveguide 12 is formed of a silicon nitride film (SiN film) that is an optical waveguide material on the silicon oxide film 17 of the first portion 11a, and a positioning mark 14a on the silicon oxide film 17 of the second portion 11b. , 14b and the joint portion 13 are also formed with pedestals 16a and 16b of the positioning marks 14a and 14b and a pedestal 16c of the joint portion 13 by a silicon nitride film having the same planar shape as that. Since the silicon nitride film has an index of refraction of about 2, it is an optical waveguide material that has an effect of confining light, and has high insulation properties, so that it can be used as an insulating film. Therefore, the optical waveguide 12, the positioning marks 14a and 14b, and the pedestals 16a, 16b, and 16c of the joint portion 13 are all formed of the same silicon nitride film.

The positioning marks 14a and 14b are formed on the small circular bases 16a and 16b made of the silicon nitride film, and the pair of joint portions 13 and 1 are formed on the pair of strip-shaped bases 16c and 16c parallel to the longitudinal direction.
3 are formed of a metal material such as gold (Au), and the upper surface of each joint portion 13 is formed in a micro-bump shape having a large number of micro-bumps (small convex portions) 13a.

If the optical element 2 is positioned and mounted on the upper surface of the substrate block 1 at the position indicated by the phantom line in FIG. 2A, an optical device is obtained.
In this case, since the upper surface of the joining portion 13 on the substrate side block 1 is formed in a microbump shape, joining at room temperature is possible, and the optical element 2 is physically fixed, the electrode of the optical element 2 and the substrate Electrical connection with the electrodes of the side block 1 is made at the same time.

[First embodiment]
Each step of the first embodiment of the optical device manufacturing method according to the present invention will be described with reference to FIGS. FIGS. 3A to 3E and FIGS. 4F to 4J are diagrams for explaining the respective steps, and all are sectional views similar to FIG. 2B. FIGS. 5 (k) and 5 (l) are front views for explaining a process of mounting an optical element on the substrate side block. FIGS. 1 (a) and 1 (b) are views seen from the right side. Equivalent to.

  First, as shown in FIG. 3A, a substrate 11 made of silicon (Si) is prepared, a first portion 11a for forming the optical waveguide, and somewhat lower (thickness). The second portion 11b is formed. In this substrate processing step, for example, a resist film is formed only on the upper surface of the region to be the first portion 11a in the substrate 11, and the region to be the second portion 11b in the substrate 11 is set to a predetermined depth using the resist film as a mask. (Depending on the element to be mounted, for example, 1 to 2 μm) Etching is performed to form a low step portion, and then the resist film is removed.

  Next, as shown in FIG. 3B, a silicon oxide film (SiO film) 17 is formed on the entire upper surface of the substrate 11 having a step. That is, the silicon oxide film 17 is formed to a thickness of, for example, 0.5 μm by a method of oxidizing a silicon substrate to form a silicon oxide film or a method of forming a silicon oxide film by plasma CVD.

Thereafter, a first layer 18 made of a silicon nitride film (SiN film) which is an optical waveguide material is formed on the entire surface of the silicon oxide film 17 on the substrate 11. This is the first step. This silicon nitride film is formed to a thickness of about 3 μm by, for example, plasma CVD.
Then, a second layer 19 made of a metal material (preferably Au) is formed on the first layer 18. This is the second step. The second layer 19 made of this metal material is formed, for example, by vapor deposition or sputtering. Considering the bonding strength of room temperature activation bonding by micro bumps in the sixth step described later, it is preferable to form the second layer 19 by vapor deposition that forms minute irregularities on the film surface.

Next, as shown in FIGS. 3C and 3D, the second layer 19 is formed in accordance with the first metal pattern 19a having the shape corresponding to the optical waveguide 12 and the positioning marks 14a and 14b. In this embodiment, the second metal pattern 19c having a shape corresponding to the joint portion 13 is also processed. This is the third step.
In this step, first, as shown in FIG. 3 (c), a photoresist 31 is applied to the entire upper surface of the second layer 19 and dried, and a mask plate 32 is positioned thereon.

The mask plate 32 is formed on a transparent plate such as glass, for example, a region 32a corresponding to the first metal pattern 19a, a region 32b corresponding to the second metal pattern 19b shown in FIG. Only in the region 32c corresponding to the metal pattern 19c, a pattern is formed of, for example, chromium (Cr). When the photoresist 31 is irradiated with light through the mask plate 32, only the portion of the mask plate 32 corresponding to the region where the chromium pattern is not formed is exposed.
When it is developed by immersing it in a developing solution, only the exposed portion of the photoresist 31 is dissolved and removed, and the portions corresponding to the first metal pattern 19a, the second metal pattern 19b, and the third metal pattern 19c. Only remains.

Dry etching is performed using the remaining pattern of the photoresist 31 as an etching mask, and only the portion of the second layer 19 not covered with the photoresist 31 is selectively removed, and then the photoresist 31 is removed with a release agent. Remove.
As a result, as shown in FIG. 3D, the first metal pattern 19a, the second metal pattern 19b, and the third metal pattern 19c are formed by the second layer 19 made of a metal material such as Au. Is done.

  In the above description, the case where only the exposed portion of the photoresist 31 is dissolved and removed by the developer is described (positive type resist). Separately, only the unexposed portion is the developer. There is also a photoresist (negative resist) that is dissolved and removed by the step S3. When the photoresist 31 is used as the photoresist 31, the mask plate 32 includes the first metal pattern 19a, the second metal pattern 19b, and the third metal pattern 19b. A chromium pattern may be formed in a region other than the portion corresponding to the metal pattern 19c.

  Next, dry etching is performed on the first layer 18 made of the SiN film using the second layer 19 processed as described above in the third step as an etching mask, and the first layer 18 is shown in FIG. 3 (e), a portion 18a to be the optical waveguide 12 having a shape corresponding to the first metal pattern 19a and a portion 18b having a shape corresponding to the second metal pattern 19b to be the positioning marks 14a and 14b. In this embodiment, the portion 18c having a shape corresponding to the third metal pattern 19c to be the joint portion 13 is also processed. This is the fourth step.

  Thereafter, as shown in FIG. 4 (f), a photoresist 33 is applied to the entire surface of the substrate 11 except for the first metal pattern 19a (also formed by photolithography using a mask plate). The second layer 19 is wet-etched using the photoresist 33 as an etching mask, and the first metal pattern 19a not covered with the photoresist 33 is removed. Then, when the photoresist 33 is removed with a release agent, the result is as shown in FIG. This is the fifth step.

  The substrate side block 1 is completed once by the process so far. Here, the second metal pattern 19b and the third metal pattern 19c of the second layer 19 in (f) of FIG. 4 correspond to the pair of positioning marks 14a and 14b and the joint portion 13 in (g) of FIG. Become. Further, the portion 18a of the first layer 18 in FIG. 4F becomes the optical waveguide 12 in FIG. 4G, and the portion 18b and the portion 18c of the first layer 18 in FIG. In FIG. 5G, the pedestals 16a and 16b of the positioning marks 14a and 14b and the pedestal 16c of the joint portion 13 are formed.

  The optical element 2 shown in FIG. 2 may be aligned and mounted on the substrate-side block 1 using the second metal pattern 19b having a shape corresponding to the positioning marks 14a and 14b. However, in this embodiment, before that, it has a micro bump processing step for processing the third metal pattern 19c having a shape corresponding to the joint portion 13 into a micro bump shape.

In the micro bump processing step, first, as shown in FIG. 4 (h), a photoresist 34 is applied to the entire surface of the substrate 11 and dried, and a mask plate 35 is positioned and disposed thereon.
The mask plate 35 is made of chromium on a transparent plate such as glass, for example, in a region 35a corresponding to all regions except for a region corresponding to the joint portion 13 and a portion serving as a micro bump in the region corresponding to the joint portion 13. The pattern is formed. Therefore, the mask plate 35 is transparent only in the portion other than the portion 35a corresponding to the portion to be the micro bump in the region corresponding to the joint portion 13.

When the photoresist 34 is irradiated with light through the mask plate 35, only a portion of the mask plate 35 corresponding to the region where the chromium pattern is not formed is exposed.
When it is soaked in a developing solution and developed, only the exposed portion of the photoresist 34 is dissolved and removed, and the photoresist is formed on the entire region other than the joint portion 13 and on the portion to be a microbump in the joint portion 13. 34 remains.

  Using the remaining pattern of photoresist 34 as an etching mask, dry etching is performed on the bonding portion 13 (third metal pattern 19c), and the portion of the metal film (Au film) not covered with the photoresist 34 Is selectively half-etched to about half the thickness to obtain the state shown in FIG.

  Thereafter, when the photoresist 34 is removed with a release agent, a large number of micro bumps 13a are formed on the surface of the joint portion 13 as shown in FIG. Each of the micro bumps 13a is electrically connected by the remaining portion (half-etched portion) of the joint portion 13, and functions as an integral electrode. Therefore, it is suitable when an element having an electrode such as a laser element is mounted as the optical element 2. Each micro bump 13a is, for example, a circle having a diameter of about 8 μm and a height of about 2 μm.

  In the above description, the case where only the exposed portion of the photoresist 34 is dissolved and removed by the developing solution has been described. However, the photoresist in which only the unexposed portion is dissolved and removed by the developing solution can also be used. In the case where it is used as the photoresist 34, the mask plate 35 may be formed with a chromium pattern only on a portion other than the portion corresponding to the micro bump in the region corresponding to the joint portion 13.

  Using the positioning marks 14a and 14b formed by the second metal pattern 19b on the substrate-side block 1 thus completed, the optical element 2 is formed as shown in (k) and (l) of FIG. Mount. This is the sixth step. At this time, the optical element 2 is physically and electrically bonded to the bonding portion 13 formed by the third metal pattern 19c.

Therefore, plasma cleaning or sputter etching by ion beam is performed on the surfaces of the junction 13 of the substrate side block 1 and the junction 23 of the optical element 2 to remove the oxide film, organic contamination film, and contamination on the surface. It is removed to bring the active state in which the atoms having bonds are exposed.
Then, as shown in FIG. 5 (k), the optical element 2 is placed on the substrate side block so that the positioning marks 24a, 24b on the lower surface of the optical element 2 coincide with the positioning marks 14a, 14b on the substrate side block 1. Position on 1. This positioning is performed as follows, for example.

  The positioning marks 24a and 24b of the optical element 2 and the positioning marks 14a and 14b on the substrate-side block 1 were photographed with a camera using a positioning device (not shown), for example, up to about 30 μm. Check the image. For example, infrared rays are used for photographing each positioning mark. In this case, the optical element 2 and the substrate 11 need to be made of a material that transmits infrared rays. As for the shape of the positioning mark, for example, if one is circular, the other is a donut shape surrounding the circular circle. Both of these marks are observed at the same time, and the center of the circle of each mark is obtained by calculation, and positioning is performed by aligning the positions so as to overlap each other.

  After that, as shown by the arrow, it is lowered vertically and pressurized, and mounted on the substrate side block 1 as shown in FIG. At this time, for example, when the optical element 2 having a size of 0.75 mm × 8 mm is mounted, about 50 kgf is pressurized.

  Thus, the light emitting point of the end face 2a of the optical element 2 is accurately positioned at the center of the end face 12a on the light input side of the optical waveguide 12 on the substrate side block 1, and the optical element 2 is mounted. A large number of micro bumps 13a of the joint portion 13 and the joint portions 23 of the optical element 2 are joined at room temperature by surface activation joining. That is, since it is non-heat-bonding, it has the following advantages. Here, the “components” are the substrate side block 1 (particularly the optical waveguide 12) and the optical element 2.

(1) No component breakage due to residual stress due to difference in thermal expansion coefficient.
(2) Since there is no thermal stress on the component, the functional deterioration of the component does not occur.
(3) Since it is a non-heated solid phase bonding, there is no positional deviation during mounting.
(4) There is no effect of heat on other parts.
(5) Due to the direct bonding of atoms, the bonding layer does not deteriorate with time.

  When the optical element 2 is an element having an electrode such as a laser element, each joint 23 serves also as each electrode, and the optical element 2 is mounted on the substrate side block 1, and each joint 23 is on the substrate side. When bonded to a large number of micro bumps 13 a at each joint 13 of the block 1, the optical element 2 and the substrate side block 1 are also electrically connected to each other through each joint 23 and each joint 13. Each of the joints 13 and 23 is preferably formed of gold (Au) which is easily plastically deformed and has high electrical conductivity.

[Second Embodiment]
Next, each step of the second embodiment of the method of manufacturing an optical device according to the present invention will be described with reference to FIGS. 6 (a) to 6 (e) and FIGS. 7 (f) and 7 (g) are diagrams for explaining the respective steps, and both are sectional views similar to FIG. 2 (b). 8 (h) and 8 (i) are front views for explaining a process of mounting the optical element on the substrate side block, and (a) and (b) of FIG. 1 are respectively viewed from the right side. Equivalent to.

  6 (a) and 6 (b) are the same as FIGS. 3 (a) and 3 (b) in the first embodiment described above. First, in the substrate processing step, an optical waveguide is formed on the substrate 11 made of silicon (Si). A second portion 11b that is somewhat lower (thickness is, for example, 1 to 2 μm thinner) than the first portion 11a for forming the film is formed by etching. Then, a silicon oxide film (SiO film) 17 is formed to a thickness of, for example, 0.5 μm on the entire upper surface of the substrate 11 having a step.

Thereafter, in a first step, a first layer 18 made of a silicon nitride film (SiN film) that is an optical waveguide material is formed on the entire surface of the silicon oxide film 17 on the substrate 11.
In the second step, a second layer 19 made of a metal material (preferably Au) is formed on the first layer 18.

Next, as shown in FIGS. 6C and 6D in the third step, the second layer 19 is formed with the first metal pattern 19a having a shape corresponding to the optical waveguide 12 and the positioning mark. The second metal pattern 19b having a shape corresponding to 14a and 14b is processed, and in the second embodiment, the third metal pattern 19c 'having a microbump shape corresponding to the joint portion 13' is also processed.
In this step, first, as shown in FIG. 6C, until the photoresist 31 is applied to the entire upper surface of the second layer 19 and dried, it is the same as in the first embodiment described above. The mask plate 36 to be positioned and arranged is different from the mask plate 32 used in the first embodiment.

The mask plate 36 is formed on a transparent plate such as glass, for example, a region 36a corresponding to the first metal pattern 19a, a region 36b corresponding to the second metal pattern 19b shown in FIG. A chromium pattern is formed only on the portion 36c corresponding to each micro-bump constituting the third metal pattern 19c 'having a shape. When the photoresist 31 is irradiated with light through the mask plate 32, only a portion of the mask plate 36 corresponding to the region where the chromium pattern is not formed is exposed.

  When it is soaked in a developing solution and developed, only the exposed portion of the photoresist 31 is dissolved and removed, and the first metal pattern 19a, the second metal pattern 19b, and the third metal pattern 19c in the form of micro bumps. Only the portion corresponding to each micro bump constituting ′ remains.

Using the remaining pattern of photoresist 31 as an etching mask, dry etching is performed to selectively remove only the portion of the second layer 19 that is not covered with the photoresist 31, and then the photoresist 31 is removed with a release agent. To do.
As a result, as shown in FIG. 6D, the first metal pattern 19a, the second metal pattern 19b, and the third metal in the micro bump shape are formed by the second layer 19 made of a metal material such as Au. A pattern 19c 'is formed.

  In the above description, the case where only the exposed portion of the photoresist 31 is dissolved and removed by the developer has been described. However, the photoresist in which only the unexposed portion is dissolved and removed by the developer is also available. Yes, when it is used as the photoresist 31, the mask plate 36 corresponds to each micro bump constituting the first metal pattern 19a, the second metal pattern 19b, and the third metal pattern 19c '. A chromium pattern may be formed in a region other than the above.

  Next, in the fourth step, the first layer 18 made of the SiN film is dry-etched using the second layer 19 processed as described above in the third step as an etching mask, and the first layer 18 is subjected to dry etching. As shown in FIG. 6E, the layer 18 is formed in accordance with the portion 18a to be the optical waveguide 12 having a shape corresponding to the first metal pattern 19a and the second metal pattern 19b to be the positioning marks 14a and 14b. The portion 18b having a different shape and the portion 18c having a shape corresponding to the third metal pattern 19c to be the joint 13 in this embodiment are also processed.

  Thereafter, in the fifth step, as shown in FIG. 7F, a photoresist 37 is applied to the entire surface of the substrate 11 except for the first metal pattern 19a (this photoresist 37 also uses a mask plate). Using the photoresist 37 as an etching mask, the second layer 19 is dry-etched to remove the first metal pattern 19a not covered with the photoresist 33. Then, when the photoresist 33 is removed with a release agent, the result is as shown in FIG.

  The substrate side block 1 'is completed through the above steps. Here, the second metal pattern 19b and the third metal pattern 19c ′ of the second layer 19 in FIG. 7 (f) correspond to the pair of positioning marks 14a and 14b and the micro bump shape in FIG. 7 (g). It becomes this junction part 13 '. Further, the portion 18a of the first layer 18 in FIG. 7F becomes the optical waveguide 12 in FIG. 7G, and the portion 18b and the portion 18c ′ of the first layer 18 in FIG. In FIG. 5G, the pedestals 16a and 16b of the positioning marks 14a and 14b and the pedestals 16c 'of the respective micro bumps 13a' of the joint portion 13 'are formed.

  Thus, in the second embodiment, in the third step, the first metal pattern 19a having a shape corresponding to the optical waveguide 12 from the second layer 19 made of a metal material and the positioning marks 14a and 14b are used. When the second metal pattern 19b having the shape is processed, the third metal pattern 19c 'having the microbump shape which becomes the joint portion 13' including the numerous bumps 13a 'is formed. The bump processing step is not necessary, and the manufacturing process is shortened.

Then, in the sixth step, the optical element 2 is mounted on the completed substrate-side block 1 'using the positioning marks 14a and 14b as shown in (h) and (i) of FIG. At this time, the optical element 2 is physically bonded to the bonding portion 13 composed of a large number of bumps 13a ′ formed by the third metal pattern 19c ′.
Therefore, plasma cleaning and sputter etching using an ion beam are performed on the surfaces of the bonding portion 13 ′ of the substrate side block 1 ′ and the bonding portion 23 of the optical element 2 to remove organic contamination films and contamination on the surfaces. Thus, an active state in which atoms having a bond are exposed is obtained.

  Then, as shown in FIG. 8H, the optical element 2 is placed on the substrate side so that the positioning marks 24a, 24b on the lower surface of the optical element 2 are aligned with the positioning marks 14a, 14b on the substrate side block 1 '. Positioning is performed on the block 1 ', and it is lowered vertically as indicated by an arrow. In this example, about 50 kgf is pressurized and mounted on the substrate side block 1' as shown in FIG.

  As a result, the light output point of the end face 2a of the optical element 2 is accurately positioned at the center of the end face 12a on the light input side of the optical waveguide 12 on the substrate side block 1 ', and the optical element 2 is mounted. A large number of micro bumps 13a 'constituting the 1' bonding portion 13 'and the bonding portion 23 of the optical element 2 are bonded at room temperature by surface activation bonding. The advantages are as described above.

  However, since the many micro bumps 13a 'constituting the joint portion 13' of the substrate side block 1 'according to the second embodiment are not electrically connected to each other, an optical element having no electrode such as an SHG element is used. It is suitable for mounting, and is not suitable for mounting an element having an electrode such as a laser element and electrically connecting the connecting portion also serving as the electrode to the connecting portion of the substrate side block.

[Third embodiment]
Next, a third embodiment of the optical device manufacturing method according to the present invention will be described with reference to FIGS.
FIG. 9 shows the structure of the substrate side block of the optical device manufactured in the third embodiment of the manufacturing method of the present invention, (a) is a plan view, and (b) is a cross section of each part described in (a). It is sectional drawing which follows the BB line made to appear.

10 (a) to 10 (e) and FIGS. 11 (f) to 11 (j) are diagrams for explaining the respective steps, and all are sectional views similar to FIG. 9 (b). FIGS. 12 (k) and 12 (l) are front views for explaining a process of mounting the optical element on the substrate side block, and FIGS. 1 (a) and 1 (b) are respectively viewed from the right side. Equivalent to.
Each part shown in these figures is different from each part in the first embodiment described with reference to FIGS. 1 to 5 in its shape and size ratio, etc., but corresponds to each part shown in FIGS. 1 to 5 for convenience of explanation. The same code | symbol is attached | subjected to the part to perform.

In the substrate side block 1 of the optical device shown in FIG. 9, the optical element 2 mounted thereon is shown by phantom lines, but the second portion 11b lower than the first portion 11a of the substrate 11 is replaced by the optical element. 2 differs from the first embodiment in that it has a length dimension x and a width dimension y that are both smaller than the length dimension L and the width dimension W, and is processed as a recess surrounded by the first portion 11a. Yes.
The recess 17a is shown in a state in which the silicon oxide film (SiO film) 17 is formed on the entire surface of the stepped upper surface of the substrate in which the recess is processed as the second portion 11 as described above.

Then, the optical waveguide 12 is formed of a silicon nitride film (SiN film) that is an optical waveguide material on the silicon oxide film 17 of the first portion 11a, and the silicon oxide film 17 of the second portion 11b.
Positioning marks 14a and 14b and joints 13 having a large number of microbumps 13a are formed thereon.

When the optical element 2 is mounted on the substrate-side block 1, as described above, the positioning marks 14a and 14b are used for horizontal (planar) direction alignment, and the lower surface of the optical element 2 is placed on the substrate. Positioning in the height direction can be performed by abutting against the upper surface of the first portion 11a of the first portion (in this example, the thickness is about 0.5 μm through the silicon oxide film 17). Therefore, the optical element 2 can be positioned with high accuracy in the height direction with respect to the optical waveguide 12.
Other configurations are the same as those of the optical device described with reference to FIGS.

Next, each step of the third embodiment of the method of manufacturing an optical device according to the present invention will be described with reference to FIGS.
(A) to (e) in FIG. 10 and (f) to (j) in FIG. 11 are diagrams for explaining the respective steps, and (a) to (e) in FIG. Since it is almost the same as each process of (f)-(j) of FIG. 4, the difference is mainly demonstrated.

FIG. 10A shows a substrate processing step, which is slightly lower than the first portion 11a for forming the optical waveguide on the substrate 11 made of silicon (Si) (thickness is, for example, 1 to 2 μm). The (thin) second portion 11b is formed by etching.
The second portion 11b has a length dimension and a width dimension that are smaller than the length dimension and the width dimension of the optical element 2 to be mounted as described above, and is processed as a recess surrounded by the first portion 11a. The

Then, a silicon oxide film (SiO film) 17 is formed to a thickness of, for example, 0.5 μm on the entire upper surface of the substrate 11 having a step. Reference numeral 17a denotes a recess in which the silicon oxide film 17 is formed.
Thereafter, in a first step, a first layer 18 made of a silicon nitride film (SiN film) that is an optical waveguide material is formed on the entire surface of the silicon oxide film 17 on the substrate 11.
In the second step, a second layer 19 made of a metal material (preferably Au) is formed on the first layer 18.

Next, as shown in FIGS. 10C and 10D in the third step, the second layer 19 is formed with the first metal pattern 19a having a shape corresponding to the optical waveguide 12 and the positioning mark. While processing into the 2nd metal pattern 19b of the shape according to 14a, 14b, the 3rd metal pattern 19c of the shape according to the junction part 13 shown in FIG. 9 is also processed.
This process is also the same as the process described in FIGS. 3C and 3D in the first embodiment, but the first metal pattern 19a has the tip thereof on the first portion 11a of the substrate 1. The second portion 11b is formed away from the boundary line with the recess 17a by a predetermined dimension d. The metal pattern 19b and the third metal pattern 19c are formed in the recess 17a.

  Next, in the fourth step, the first layer 18 made of the SiN film is dry-etched using the second layer 19 processed as described above as an etching mask, and the first layer 18 is shown in FIG. 10 (e), a portion 18a to be the optical waveguide 12 having a shape corresponding to the first metal pattern 19a, and a portion 18b having a shape corresponding to the second metal pattern 19b to be the positioning marks 14a and 14b. Then, it is processed into a portion 18 c having a shape corresponding to the third metal pattern 19 c to be the joint portion 13.

Thereafter, in a fifth step, as shown in FIG. 4F, the first metal pattern 1 on the substrate 11 is formed.
Photoresist 33 is applied to the entire surface except on 9a, and the second metal layer 19 is dry-etched using the photoresist 33 as an etching mask to remove the first metal pattern 19a. Then, when the photoresist 33 is removed with a release agent, the result is as shown in FIG.

  Further, in the microbump processing steps shown in FIGS. 11 (h) to (j), in the same manner as the microbump processing steps described in FIGS. 4 (h) to (i) in the first embodiment, the joint portion 13 is used. The third metal pattern 19c having a shape corresponding to the above is processed into a microbump shape.

  On the substrate-side block 1 thus completed, the optical element 2 is positioned and mounted as shown in FIGS. 12 (k) and 12 (l) by the sixth step. At this time, the positioning in the horizontal direction is performed so that the positions of the centers of the positioning marks 24a, 24b of the optical element 2 and the positioning marks 14a, 14b on the substrate side block 1 are overlapped with each other. It is the same.

  In the third embodiment, as shown in FIG. 12L, the lower surface of the optical element 2 is connected to the upper surface of the first portion 11a of the substrate 1 (in this example, the silicon oxide film 17 is interposed. Since it is extremely thin, it substantially contacts the upper surface of the first portion 11a), and positioning in the height direction is performed. Therefore, the optical element 2 can be positioned with respect to the optical waveguide 12 in the height direction with high accuracy.

  In this state, by pressing the optical element 2 against the substrate side block 1 (for example, 50 kgf), the optical element 2 is formed of a metal material such as Au that is easily plastically deformed and has high electrical conductivity. The connection portion 23 and the joint portion 13 on the substrate side block 1 are integrally joined by surface activation joining. In addition, since a large number of micro bumps 13a are formed at the bonding portion 13 on the substrate side block 1, surface activation bonding is facilitated, and bonding without heating, that is, room temperature bonding is performed. In addition, the micro bump 13a is plastically deformed and crushed by pressurization, the optical element 2 sinks by the amount of the crushed micro bump 13a, and the lower surface of the optical element 2 and the upper surface of the first portion 11a of the substrate 1 abut against each other. Positioning in the vertical direction is performed. The optical element 2 and the substrate-side block 1 are physically coupled (fixed) by the connection between the connection portion 23 and the joint portion 13, and also electrically through the joint portions 23 and the joint portions 13. Connected.

  As described above, according to the manufacturing method of the optical device of each embodiment, the optical element 2 and the light guide are formed according to the step provided by processing the substrate 11 in the substrate processing step and the height of the first layer 18. The relative height with respect to the waveguide 12 is adjusted. That is, the steps for adjusting the relative height of the optical element 2 and the optical waveguide 12 are only a step of providing a step on the substrate and a step of forming and patterning the first layer. The manufacturing process can be simplified as compared with the conventional technique in which the film and patterning and the film formation and patterning of the second film need to be performed, respectively.

[Modification of each example]
In the first embodiment and the third embodiment described above, two joint portions 13 and 13 each having a large number of microbumps formed on the substrate side block 1 are provided in parallel to each other along the longitudinal direction. The number, shape, and forming position are appropriately changed according to the number, shape, and forming position of the joint portion on the optical element side to be mounted.

When an optical element having no electrode is mounted, the optical element is placed on the substrate side block by an adhesive or the like without processing the joints 13 and 13 'from the first layer 18 made of a metal material. You may make it adhere and fix.
When no step is formed on the substrate 1, a layer is formed to make the region corresponding to the first portion 11 a on the substrate 1 higher than the region corresponding to the second portion 11 b by the amount corresponding to the step. You may make it do.

  In each of the above-described embodiments, the method is described as a method of manufacturing a single optical device, but a large plate material such as a silicon wafer is used as a substrate material, and a large number of substrate-side blocks are simultaneously manufactured. After the optical element is mounted on each substrate side block, it may be cut into a single optical device. Alternatively, a large number of substrate-side blocks may be manufactured at the same time, and then divided into a single substrate-side block, and an optical element may be mounted on each substrate-side block to complete each optical device.

  As a substrate material, an insulator substrate or a conductive substrate can be basically used, but a silicon substrate is preferable in consideration of workability. When workability is not considered, a metal plate, an aluminum nitride plate, a glass plate, a quartz plate, a resin plate, or the like can be used.

  As an optical waveguide material, basically, a material having a high refractive index has a large effect of confining light, and thus can be used as an optical waveguide material. The silicon nitride film (SiN film) has a refractive index of about 2, and the Ge-doped silicon oxide film can have a higher refractive index than the silicon oxide film, both of which have a large effect of confining light and can be used as an insulating film. Since it is possible, it can also be used as an optical waveguide and a pedestal.

  The present invention is not limited to the embodiments described above and modifications thereof, and various modifications may be made within the scope defined by the claims.

  The present invention can be applied to manufacture various optical devices in which an optical waveguide and an optical element such as a laser element, LED element, or SHG element are passively mounted on a substrate.

DESCRIPTION OF SYMBOLS 1,1 ': Board | substrate side block 2: Optical element 2a: End surface which has a light emission point 11: Board | substrate 11a: 1st part 11b: 2nd part 12: Optical waveguide 12a: End surface on the optical input side
13 and 13 ': Joint part of board side block 13a, 13a': Micro bump 14a, 14b: Positioning mark of board side block 15: Boundary line 16a, 16b: Base of positioning mark of board side block
16c: pedestal at the junction of the substrate side block 17: silicon oxide film (SiO film)
17a: concave portion 18: first layer made of an optical waveguide material
19: Second layer made of a metal material 19a: First metal pattern
19b: Second metal pattern 19c, 19c ': Third metal pattern 23: Optical element joint 24a, 24b: Optical element positioning marks 31, 33, 34, 37: Photoresist 32, 35, 36: Mask Board

Claims (12)

A first step of forming a first layer of an optical waveguide material on a substrate;
A second step of forming a second layer made of a metal material on the first layer;
A third step of processing the second layer into a first metal pattern having a shape corresponding to the optical waveguide and a second metal pattern having a shape corresponding to the positioning mark;
A fourth step of etching the first layer into a shape corresponding to each of the optical waveguide and the positioning mark, using the second layer processed in the third step as a mask;
A fifth step of removing the first metal pattern after the fourth step;
And a sixth step of mounting an optical element on the substrate using the second metal pattern having a shape corresponding to the positioning mark. Before the first step, the substrate processing step of processing the substrate to have a first portion and a second portion lower than the first portion,
In the third step, the second layer at a position corresponding to the first portion of the substrate is processed into the first metal pattern, and the second layer at a position corresponding to the second portion. The method of manufacturing an optical device according to claim 1, wherein the layer is processed into a metal pattern other than the first metal pattern. In the substrate processing step, the second portion of the substrate is a recess having a length dimension and a width dimension that are smaller than the length dimension and the width dimension of the optical element and surrounded by the first portion. Processed
3. The method of manufacturing an optical device according to claim 2, wherein in the sixth step, positioning in the height direction is performed by abutting a lower surface of the optical element against an upper surface of the first portion of the substrate. . In the third step, the second layer is processed into the first metal pattern and the second metal pattern, and is also processed into a third metal pattern having a shape corresponding to a joint portion,
In the fourth step, using the second layer processed in the third step as a mask, the first layer is etched into a shape corresponding to each of the optical waveguide, the positioning mark, and the joint portion. Processed
4. The method of manufacturing an optical device according to claim 1, wherein the optical element is bonded to the third metal pattern in the sixth step. 5.   5. The optical device manufacturing method according to claim 4, further comprising a microbump processing step of processing the third metal pattern into a microbump shape between the third step and the sixth step. Method.   6. The optical device according to claim 5, wherein, in the microbump processing step, the third metal pattern is processed into a microbump shape in which a plurality of microbumps are all conducted by the remaining portion of the second layer. Manufacturing method.   5. The method of manufacturing an optical device according to claim 4, wherein, in the third step, the third metal pattern is processed into a microbump shape corresponding to a joint portion. 8. The surface activation bonding of the connecting portion on the optical element side and the third metal pattern on the substrate side in the sixth step, according to claim 4. Manufacturing method of optical device.   The method for manufacturing an optical device according to claim 1, wherein the second layer made of gold (Au) is formed in the second step.   The optical device according to any one of claims 1 to 9, wherein the substrate is a silicon substrate, and includes a step of forming a silicon oxide film on the entire surface of the substrate before the first step. Production method.   The method for manufacturing an optical device according to claim 1, wherein the first layer made of a silicon nitride film (SiN film) is formed in the first step.   The optical device manufacturing method according to claim 1, wherein in the sixth step, a laser element is mounted on the substrate as the optical element.

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