JP2002072026A - Optical printed circuit board and optical module using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably mount an optical fiber and an optical semiconductor device by accurately arranging the relative position of a solder bump for flip- chip bonding of an optical fiber-mounted V-groove and the optical semiconductor device and by removing an insulation film formed at the time of V-groove formation and projecting at the V-groove edge, and to improve accuracy in V-groove width measurements by removing the insulation film projecting at the V-groove edge and around it and thereby making accurate discrimination of the V-groove edge possible. SOLUTION: This optical printed circuit board S is provided, on a base plate 1, with an electrode pad 4 for arranging an optical semiconductor device and a mounting groove 8 for arranging an optical waveguide body which is to be connected to the optical semiconductor device. The printed circuit board is characterized by the electrode pad 4 that is formed on a first insulation film 2 formed on a prescribed area of the base plate 1 and that is surrounded with a second insulation film 3 formed in the area excluding at least a peripheral flat part 1a of the mounting grove 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical mounting substrate on which an optical semiconductor element and an optical waveguide are provided, and more particularly, to align the optical axis of an optical fiber to be mounted with the center of the optical axis of the optical semiconductor element. The present invention relates to a self-aligned optical mounting board suitable for the above and an optical module using the same.

[0002]

2. Description of the Related Art When a light emitting semiconductor device such as a laser diode is coupled to an optical fiber, the waveguide of the optical semiconductor device and the optical axis of the optical fiber are aligned in a horizontal and vertical direction with an accuracy of ± 1.0 μm. Otherwise, the light emitted from the light emitting semiconductor element cannot be coupled to the optical fiber. In order to precisely align the optical semiconductor element and the optical fiber, an optical mounting substrate having a V-groove for mounting the optical fiber and a solder bump for flip-chip bonding the optical semiconductor element is used. Further, in order to precisely align the optical axes of the optical semiconductor element and the optical fiber, it is necessary to accurately form the relative positions of the solder bumps and the V grooves.

Heretofore, as shown in Japanese Patent No. 2950767, a first insulating film is formed on the surface of a silicon substrate, and an electrode pad having a predetermined shape is formed on the first insulating film. Forming a second insulating film on the insulating film and the electrode pad, exposing the electrode pad formed by removing the second insulating film so that a predetermined portion does not overlap with a periphery in the electrode pad; Forming an opening and a second opening exposing the silicon substrate at the same time by removing the first and second insulating films without overlapping with the first opening;
And an optical package in which a V-groove is formed in the exposed second opening of the silicon substrate using the second insulating film as an etching mask, and a solder bump is formed on the first opening where the electrode pad is exposed. A method for manufacturing a substrate has been proposed.

[0004] Since the second opening is formed of the second insulating film, it has a function of preventing the flow of solder due to the difference in wettability between the metal and the solder of the insulating film. Therefore, by simultaneously forming the first opening for forming the V-groove and the second opening for positioning the solder bumps, it is possible to align the optical axes of the optical semiconductor element and the optical fiber.

[0005]

However, according to the method disclosed in the aforementioned Japanese Patent No. 2950767, as shown in FIG. 5, after the V-groove is formed, the first and second layers having a thickness of 1 μm or less are formed at the V-groove edge. The shape of the insulating film protrudes, and the first and second insulating films protruding during the solder bump forming process in a later process are broken and adhere to the V-groove slope, the exposed electrode pad surface, and the like. If the broken first and second insulating films adhere to the portion where the V-groove contacts the optical fiber when the optical fiber is mounted, the mounting accuracy of the optical fiber deteriorates. If it gets on the exposed electrode pad,
The solder bumps may be peeled off without adhering to the electrode pads.

In the case where the first and second insulating films protrude from the V-groove edge, it is necessary to recognize the V-groove edge through the first and second insulating films when measuring the formed V-groove width. A measurement error occurs.

Another problem is that the etchant used to form the V-groove may penetrate from the edge of the opening of the second insulating film formed on the electrode pad, and the second insulating film may be peeled off. there were.

Accordingly, the present invention provides a V
The relative position of the groove and the solder bump for flip-chip bonding mounting the optical semiconductor element is accurately arranged, and the insulating film protruding at the V-groove edge generated at the time of V-groove formation is removed.
The optical fiber and the optical semiconductor element can be suitably mounted, and the V-groove edge can be accurately determined by removing the insulating film protruding from the V-groove edge portion and the insulating film around the V-groove. It is possible to improve the V groove width measurement accuracy.

[0009]

In order to achieve the above object, an optical mounting board according to the present invention comprises: an electrode pad on which an optical semiconductor element is provided; and an optical connection to the optical semiconductor element. And a mounting groove for arranging an optical fiber for the optical mounting board, wherein the electrode pad is formed on a first insulating film formed in a predetermined region of the substrate, at least The semiconductor device is characterized in that the mounting groove is surrounded by a second insulating film formed in a region except a peripheral flat portion.

The manufacturing method is characterized in that the mounting groove is formed in the substrate by etching using the second insulating film as an etching mask.

In the optical module of the present invention, in the optical mounting substrate, an optical semiconductor element is disposed on the electrode pad, and an optical fiber is disposed on the mounting groove.

Specifically, for example, the following manufacturing method is employed.

An optical mounting board for forming an electrode pad for disposing an optical semiconductor element and a mounting groove for disposing an optical fiber for optically connecting the optical semiconductor element on the substrate. Forming a first insulating film on the substrate, forming an electrode pad of a predetermined shape on the first insulating film, and forming a first electrode film on the first insulating film and the electrode pad; (2) forming an insulating film; removing a part of the second insulating film to expose a central portion of the electrode pad to form a first opening in the electrode pad forming region; Forming a third insulating film on the entire surface, forming a third opening by removing the peripheral third insulating film including the second opening, and anisotropically etching the second insulating film A V-groove is formed in the exposed portion of the silicon substrate using a mask. A step of the third insulating film and V
The method includes a step of removing the second insulating film around the groove and a step of forming a solder bump on the electrode pad.

Here, in particular, when the silicon substrate is (10
0) It has a crystal plane. Further, the second insulating film is removed so that the second insulating film remains in a state of being superimposed on the peripheral portion of the electrode pad and the silicon substrate around the V groove is exposed. The V-groove is formed in a <110> direction so as to be parallel to a flat surface of the silicon substrate. Further, the silicon substrate is made of KOH solution or
The V groove is etched by dipping in a P solution.

A step of forming a first insulating film on the surface of the silicon substrate and removing the first insulating film in a peripheral portion including a portion for forming a V-groove to form a first opening; (1) a step of forming an electrode pad of a predetermined shape on the upper part of the insulating film;
Forming a second insulating film on the first insulating film and the electrode pad; removing a predetermined portion of the second insulating film in the electrode pad except for the periphery of the electrode pad; Forming a second opening to be exposed and a third opening exposing the silicon substrate by removing the first and second insulating films inside the first opening without being overlapped with the second opening; Forming a third insulating film over the entire surface of the silicon substrate; and forming the first insulating film wider than the third opening.
Forming a fourth opening by removing the third insulating film in a region smaller than the opening, and forming a V on the exposed portion of the silicon substrate by using the second insulating film as an anisotropic etching mask. Forming a groove, the third insulating film and the V
The method includes a step of removing the second insulating film around the groove and a step of forming a solder bump on the electrode pad.

Here, in particular, when the silicon substrate is (10
0) It has a crystal plane. Further, the second insulating film is removed so that the second insulating film remains in a state of being superimposed on the peripheral portion of the electrode pad and the silicon substrate around the V groove is exposed. The V-groove is formed in a <110> direction so as to be parallel to a flat surface of the silicon substrate.

Further, a thick first insulating film is formed on the surface of the silicon substrate, and the first insulating film in the peripheral portion including the portion where the V-groove is formed is removed by isotropic etching. Forming an opening, forming an electrode pad of a predetermined shape on the first insulating film, forming a second insulating film on the first insulating film and the electrode pad, A second step of exposing the electrode pad by removing a predetermined portion of the second insulating film in the electrode pad except for the periphery of the electrode pad;
Forming an opening and a third opening exposing the silicon substrate by removing the first and second insulating films inside the first opening without being overlapped with the second opening; Forming a third insulating film on the entire surface of the silicon substrate; removing the third insulating film in a region wider than the third opening and smaller than the first opening to form a fourth opening; Forming a V-groove in the exposed portion of the silicon substrate using the second insulating film as an anisotropic etching mask; and removing the third insulating film and the second insulating film around the V-groove. And a step of forming a solder bump on the electrode pad.

Here, the silicon substrate is characterized in that it has a (100) crystal plane. Also, the first opening formed on the first insulating film has a slope in cross section so as to gradually narrow from the upper part to the lower part. Further, the second insulating film is removed so that the second insulating film remains in a state of being superimposed on the peripheral portion of the electrode pad and the silicon substrate around the V groove is exposed. The V-groove is formed in a <110> direction so as to be parallel to a flat surface of the silicon substrate.

According to the above manufacturing method, after the first opening and the second opening are formed, the first opening is formed on the second insulating film so as to cover the second opening so as not to be exposed when the V-groove is formed. 3 An insulating film is formed. The third insulating film includes the second opening, and the third opening is formed in a region wider than the second opening. Therefore, when the V-groove is formed, the etchant does not seep from the edge of the first opening on the electrode pad.

Since a solder pad is formed in the first opening formed on the electrode pad, the third insulating film is removed after the formation of the V groove. Further, since the third insulating film does not already exist around the V groove due to the third opening, the first insulating film and the second insulating film can be removed at the same time.

Therefore, the insulating film protruding from the edge of the V-groove is removed before forming the solder pad, so that the protruding insulating film is not broken and adheres to the inside of the V-groove or the exposed electrode pad. . When the width of the V-groove is measured by removing the insulating film at the edge of the V-groove,
The groove edge can be accurately recognized, and the V groove width measurement accuracy is improved.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. <First Embodiment> An optical mounting board of the present invention is shown in FIG.
As shown in FIG. 1B, an electrode pad 4 for disposing an optical semiconductor element on a substrate 3 and a mounting groove 8 for disposing an optical waveguide for optically connecting the optical semiconductor element are formed on the substrate 3. The electrode pad 4 is formed on the first insulating film 2 formed in a predetermined region of the substrate, and is formed at least in a region excluding the peripheral flat portion 1a of the mounting groove 1. The optical mounting substrate S is surrounded by the two insulating films 3.

As shown in FIG. 5, in the optical module using the optical mounting board, the light emitting element 11 as an optical semiconductor element and the light receiving element 1 for monitoring the same are provided on the electrode pads 4 and 4.
2 is an optical module M in which, for example, optical fibers 10 which are optical waveguides for optically connecting the light emitting elements 11 to the mounting grooves 8 are respectively arranged.

Hereinafter, a specific method for manufacturing the optical mounting substrate S will be described.

As shown in FIG. 2A, a first insulating film 2 is formed on the surface of a single-crystal silicon substrate 1 having a predetermined crystal orientation as a main surface, and a predetermined shape is formed on the first insulating film 2. Is formed.

Next, as shown in FIG. 2B, a second insulating film 3 is formed on the first insulating film 2 and the electrode pad 4, and a predetermined portion of the electrode pad 4 excluding the periphery of the electrode pad 4 is formed. The second of the area
The first opening for exposing the electrode pad 4 by removing the insulating film 3 and the first insulating film 2 and the second insulating film 2 which are not overlapped with the first opening and expose the silicon substrate 1 The second opening is formed at the same time.

Next, as shown in FIG. 2C, a third insulating film 7 is formed on the entire surface of the silicon substrate 1. Next, FIG.
As shown in FIG. 7, the third insulating film 7 including the second opening is removed to form a third opening.

Next, as shown in FIG. 2E, the silicon substrate 1 is formed by using the second insulating film 3 as an anisotropic etching mask.
A V-groove 8 is formed in the exposed portion. Next, FIG.
As shown in FIG. 7, the third insulating film 7 and the second insulating film 3 around the V groove 8 are removed to expose the peripheral flat portion 1a of the V groove 8.
Here, particularly, by using the same material (for example, a nitride film) for the second and third insulating films, the side surfaces of the first and second insulating films on the V-groove 8 side are preferably used when removing the third insulating film. Can be removed. Finally, a solder bump 5 is formed on the electrode pad 4 as shown in FIG.

Thus, in the manufacturing process, the area around the V-groove edge and V
Since the insulating film protruding from the groove is removed, the broken insulating film does not adhere to the inside of the V-groove and the electrode pad, and accurate mounting and prevention of solder peeling can be achieved. In addition, since there is no insulating film at the edge of the V-groove, the edge of the V-groove can be accurately recognized, the measurement accuracy is improved, and the yield is improved. <Second Embodiment> Next, a second embodiment of the manufacturing method of the present invention will be described.

First, as shown in FIG. 3A, a first insulating film 2 is formed on the surface of a silicon substrate 1 and the first insulating film 2 in a peripheral portion including a portion where a V-groove 8 is to be formed in advance. Is removed to form a first opening. Next, as shown in FIG. 3B, an electrode pad 4 having a predetermined shape is formed on the first insulating film 2. Next, as shown in FIG. 3C, a second insulating film 3 is formed on the first insulating film 2 and the electrode pad 4, and the second insulating film 3 in a predetermined region of the electrode pad 4 excluding the periphery of the electrode pad 4 is formed. A second opening for exposing the electrode pad 4 by removing the insulating film 3;
By removing the first insulating film 2 and the second insulating film 3 inside the first opening without overlapping with the opening, a third opening exposing the silicon substrate 1 is formed at the same time.

Next, as shown in FIG. 3D, a third insulating film 7 is formed on the entire surface of the silicon substrate 1. Next, as shown in FIG. 3E, the third insulating film 7 in a region wider than the third opening and smaller than the first opening is removed to form a fourth opening. Next, as shown in FIG. 3F, a V-groove 8 is formed in the exposed portion of the silicon substrate 1 using the second insulating film 3 as an anisotropic etching mask. Next, as shown in FIG. 3G, the third insulating film 7 and the second insulating film 3 around the V-groove 8 are formed.
Is removed, and the peripheral flat portion 1a of the V groove 8 is exposed. Finally, a solder bump 5 is formed on the electrode pad 4 as shown in FIG.

Thus, the third insulating film and the second insulating film can be removed at the same time, and the effects of the first embodiment can be obtained, and a simple fabrication with less man-hours can be performed. Third Embodiment Next, a third embodiment of the manufacturing method of the present invention will be described.

First, as shown in FIG. 4A, a thick first insulating film 2 is formed on the surface of a silicon substrate 1. Next, as shown in FIG. 2B, the first insulating film 2 in the peripheral portion including the portion where the V-groove 8 is formed is removed by isotropic etching to form a first opening. Next, as shown in FIG. 4C, an electrode pad 4 having a predetermined shape is formed on the first insulating film 2.

Next, as shown in FIG. 4D, the first insulating film 2 is formed.
And the second insulating film 3 is formed on the electrode pad 4. Next, as shown in FIG.
A second opening for exposing the electrode pad 4 by removing a predetermined portion of the second insulating film 3 excluding the periphery of the first insulating film 2 and the first insulating film 2 inside the first opening not overlapping with the second opening; 2 insulating film 3
Is removed, and a third opening for exposing the silicon substrate 1 is formed at the same time.

Next, as shown in FIG. 4F, a third insulating film 7 is formed on the entire surface of the silicon substrate 1. Next, as shown in FIG. 4G, a fourth opening is formed by removing the third insulating film 7 in a region wider than the third opening and smaller than the first opening.

Next, as shown in FIG. 4H, the silicon substrate 1 is formed by using the second insulating film 3 as an anisotropic etching mask.
A V-groove 8 is formed in the exposed portion. Next, FIG.
As shown in FIG. 7, the third insulating film 7 and the second insulating film 3 around the V groove 8 are removed to expose the peripheral flat portion 1a of the V groove 8.
Finally, a solder bump 5 is formed on the electrode pad 4 as shown in FIG.

Thus, since the first insulating film can be made thick,
By increasing the thickness of the first insulating film, it is possible to easily obtain an optical mounting substrate capable of coping with a high frequency with higher insulating properties.

[0038]

FIG. 2 shows a first embodiment of the present invention.

As shown in FIG. 2A, the surface of a single-crystal silicon substrate 1 whose crystal orientation is (100) is
A silicon oxide film as the first insulating film 2 was formed by thermal oxidation. An electrode pad 4 having a predetermined shape was formed on the first insulating film 2. The electrode pads are formed on the substrate in order from the lower layer, Ti /
Pt / Au (film thickness: in order, 1000/2000 // 5
000) was formed by a vapor deposition method. Further, on the Au, Ti was formed by a 100 ° vapor deposition method in order to increase the adhesion to the second insulating film 3 described later.

Next, as shown in FIG. 2B, a silicon nitride film as a second insulating film 3 is formed on the first insulating film 2 and the electrode pad 4 by a chemical vapor deposition method. A first opening for exposing the electrode pad 4 by removing a predetermined portion of the second insulating film 3 in the electrode pad 4 excluding the periphery of the electrode pad 4, and the first opening which is not overlapped with the first opening; The first insulating film 2 and the second insulating film 2 are removed to remove the silicon substrate 1
The silicon nitride film as the second insulating film 3 was simultaneously removed by photolithography and dry etching to form a second opening for exposing the substrate.

Next, as shown in FIG. 2C, a silicon nitride film as a third insulating film 7 was formed on the entire surface of the silicon substrate 1 by a chemical vapor deposition method.

Next, as shown in FIG. 2D, a third opening was formed by removing the third insulating film 7 around and including the second opening.

Next, as shown in FIG. 2E, a V-groove 8 was formed in the exposed portion of the silicon substrate 1 using the second insulating film 3 as an anisotropic etching mask. A KOH aqueous solution was used for silicon anisotropic etching.

Next, as shown in FIG. 2F, the third insulating film 7 and the second insulating film 3 around the V groove are removed, and the exposed portion 1 is removed.
a was formed.

Finally, as shown in FIG. 2G, a solder bump 5 of an Au / Sn alloy was formed on the electrode pad 4.

The second embodiment will be described with reference to FIG.

As shown in FIG. 3A, a silicon oxide film as a first insulating film 2 is formed on a surface of a silicon substrate 1 having a crystal orientation of (100) by thermal oxidation, and a V-groove is formed in advance. The first insulating film 2 around the formation was removed. Subsequent operations were performed in the same manner as in the first embodiment.

The third embodiment will be described with reference to FIG.

As shown in FIG. 3A, a thick silicon oxide film as a first insulating film 2 is formed on the surface of a silicon substrate 1 having a crystal orientation of (100) by a chemical vapor deposition method. Subsequently, a silicon nitride film was formed as an isotropic etching mask 9, the isotropic etching mask around the V-groove formation was removed in advance, and the first insulating film 2 was removed by isotropic etching. Next, the isotropic etching 9 was removed, and the electrode pad 4 was formed at a predetermined position on the first insulating film 2. Subsequent operations were performed in the same manner as in the first embodiment.

In each of the above examples, the same operation and effect as those of the above embodiment could be obtained.

[0051]

According to the present invention, the relative position accuracy between the solder pad and the V-groove can be made accurate, and the periphery of the V-groove edge and the insulating film protruding from the V-groove can be removed in the manufacturing process. This prevents the insulating film protruding from the V-groove from being broken during a post-process, thereby preventing the insulating film from adhering to the inside of the V-groove or the electrode pad. It is possible to provide a method for manufacturing an optical mounting substrate that solves the problem.

Further, by removing the insulating film around the V-groove edge, the V-groove edge can be accurately recognized at the time of measuring the V-groove width, so that the accuracy of the V-groove width measurement can be improved. A manufacturing method can be provided.

[Brief description of the drawings]

FIGS. 1A and 1B are a top view and a cross-sectional view, respectively, of an optical mounting substrate manufactured according to the present invention.

FIGS. 2A to 2G are cross-sectional views illustrating steps of manufacturing an optical mounting substrate according to the present invention.

3 (a) to 3 (h) are cross-sectional views showing steps of manufacturing an optical mounting board according to the present invention.

FIGS. 4A to 4J are cross-sectional views illustrating steps of manufacturing an optical mounting substrate according to the present invention.

FIGS. 5A and 5B are a plan view and a partial sectional view, respectively, illustrating an optical module according to the present invention.

FIGS. 6A and 6B are a cross-sectional view and a top view, respectively, showing that first and second insulating films protrude from a V-groove edge when a V-groove is formed.

FIGS. 7A and 7B are cross-sectional views showing a state where a second insulating film on an electrode pad is peeled off when a V-groove is formed.

8 (a) to 8 (d) are cross-sectional views showing steps of manufacturing a conventional optical mounting substrate.

[Explanation of symbols]

 1: Silicon substrate 2: First insulating film 3: Second insulating film 4: Electrode pad 5: Solder bump 6: Photoresist 7: Third insulating film 8: V groove (mounting groove) 9: Isotropic etching mask S : Optical mounting board M: Optical module

Claims (2)

[Claims] 1. An optical mounting substrate on which an electrode pad for arranging an optical semiconductor element and a mounting groove for arranging an optical waveguide for optically connecting to the optical semiconductor element are formed on a substrate. The electrode pad is formed on a first insulating film formed in a predetermined region of the substrate, and is formed of a second insulating film formed at least in a region excluding a peripheral flat portion of the mounting groove. An optical mounting board characterized by being enclosed. 2. The optical mounting board according to claim 1, wherein
An optical module comprising: an optical semiconductor element disposed on the electrode pad; and an optical waveguide disposed on the mounting groove.