JPH09128791A - Optical device, its manufacture and optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the availability of light and to improve attaching angle precision of a semiconductor laser by eliminating a vignetting of laser light outgoing from the semiconductor laser. SOLUTION: An etching mask material is formed on a silicon substrate 113, and after an opening with a notched part is provided on the etching mask material, or plural openings are provided close to each other, anisotropy etching is performed, and a hole 115 with the notched part 118 is formed. When the divergent angle of the semiconductor laser 101 is defined to θ and a distance between the end surface of the semiconductor laser 101 and the edge of the hole 115 is defined to (s), by making the depth of the notched part 118 be s×tan(θ/2) or above, the vignetting of the outgoing laser light of the semiconductor laser 101 is eliminated, and further, solder 119 is filled in the notched part 118, and the semiconductor laser 101 is loaded, and then, the attaching angle precision of the semiconductor laser is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate type optical pickup and an optical device using a zigzag optical path, and in particular, the laser light emitted from a semiconductor laser is not broken and the mounting angle accuracy of the semiconductor laser is high. And an optical pickup using the optical device.

[0002]

2. Description of the Related Art A flat integrated optical device (flat optical integrated circuit) is a device in which optical elements are integrated on a transparent flat plate (substrate) such as glass, and an optical path is formed at the interface between the flat plates so as to connect the optical elements. The optical information processing is performed in a zigzag manner using reflection. According to this circuit configuration, attention has been paid to the fact that a compact, stable, and lightweight optical application system can be realized. As an optical device using a conventional flat-plate optical integrated circuit system, there is one shown in FIG. 10 (Shiono, et al.,
JP-A-6-259800 “Japanese Patent Application No. 5-44833”
issue").

FIG. 10 is a cross-sectional view (a) and a plan view (b) showing the basic structure of a conventional optical device and how light is propagated and condensed, and FIG. 11 is the same as that of the conventional optical device. It is sectional drawing (a) and a top view (b) which show the shape of a silicon substrate. The optical device of this conventional example is an example of an optical head that reads out signals from an optical recording element such as a compact disc (CD), an optical disc, or an optical card memory.

In FIG. 10, reflective layers 11a and 11b are formed on the front surface (on the side where the optical disc is located) and the back surface of the transparent substrate 2. The transparent substrate 2 is a light propagation path through which light propagates in a zigzag manner using reflection on the front surface and the back surface.

On the left side of the rear surface of the transparent substrate 2, the plane orientation is (1
00) silicon substrate 13 is integrated. As shown in FIG. 11, the photodetector 6, the electrode pad 14, and the electrode wire 17 are formed on the surface of the silicon substrate 13, and an inverted pyramid-shaped hole 15 is formed on the right side thereof by anisotropic etching. The semiconductor laser 1 is installed on one of the side surfaces of the hole 15 in an oblique direction. The surface of the silicon substrate 13 on which the hole 15 is formed faces the transparent substrate 2, and the hole 15 is transparent. The structure is adhered to the substrate 2 and integrated. The holes 15 are formed by masking the entire surface of the silicon substrate 13 with, for example, a silicon nitride film, and then forming openings by an amount corresponding to the size of the holes 15 and performing anisotropic etching, and obliquely forming θ ₁ = 35.26 °. Form an angle.

[0006] For example, a wavelength of 0.78 installed in this way
Light emitted from the surface emitting end of the semiconductor laser 1 having an optical axis angle of, for example, θ ₁ = 35.26 ° obliquely from the z-axis from the surface emitting end of the semiconductor laser 1 passes through the air, enters the transparent substrate 2, and enters the interface. Propagating light 8 having an optical axis angle of, for example, θ = 22.5 °
Then, the light enters the reflective collimator lens 3 and is reflected / collimated with the angle of the optical axis (propagation angle θ) unchanged (for example, 22.5 °). The collimated light propagates in a zigzag shape, passes through a reflective twin lens 5 also provided on the transparent substrate 2, and the transmitted light (0th-order diffracted light) is a light condensing element. 4, the light is condensed and output in the vertical direction and becomes emitted light 9 to the optical disk 7. The light 10 reflected from the optical disk 7 is also incident on the transmission objective lens 4 and is collimated to become a propagating light 8 ′, which propagates in a zigzag shape and is formed on the transparent substrate 2 by a position signal detecting element (focus / focus). The light enters the reflective twin lens 5, which is a track error signal detection element. The reflection type twin lens 5 has a structure in which two reflection type lenses 5a and 5b having the same specifications and composed of parabolic gratings are arranged in an array. Is divided into two, propagates in a zigzag manner at a propagation angle of the optical axis of, for example, 32 °, and is condensed on the photodetector 6.
A reproduction signal and a focus error signal and a track error signal, which are position signals, are read out from the signal detected by the photodetector 6.

[0007]

A semiconductor laser used for an optical pickup is a gallium arsenide substrate on which an active layer of gallium aluminum arsenide is grown. Usually, it is called a junction down, and the growth layer side is the bottom. Mounted on the mount. This is because the thickness of the growth layer is as small as about 10 μm and the heat dissipation effect is improved by bringing the growth layer side closer to the bonding surface. Laser light emitted from the semiconductor laser diverges due to diffraction and normally spreads by about half angle in the direction perpendicular to the active layer. Therefore, the semiconductor laser light intersects the bonding surface at a distance of about 40 μm from the emitting end face, and it is necessary to bring the emitting end face and the mount end face close to each other in order to prevent the laser light from being blocked.

In the conventional optical head shown in FIG. 11, when the semiconductor laser 1 is mounted on the inclined surface of the silicon substrate 13, the emitting end surface of the semiconductor laser 1 does not come into contact with the transparent substrate 2, and the emitting end surface is inclined. It is necessary to keep the distance from the end face of the device. For example, since the thickness of a normal semiconductor laser is about 0.1 mm, it is necessary to separate it by about 85 μm when θ ₁ is 35.26 °. However, in this case, the laser light is turned off as described above, and the light utilization efficiency is reduced,
There is a problem that unnecessary reflected light increases. Also,
Solder is generally used for joining the semiconductor laser 1 and the silicon substrate 13, but the thickness of the solder layer is about 10 μm, and the size of the semiconductor laser chip is about 250 μm, so the solder layer has a thickness of 0.5 μm. If there is a variation, an angle variation of 0.1 ° occurs, and there is a problem that the mounting accuracy deteriorates.

The present invention has been made in view of the above problems, and an object thereof is to provide an optical device in which the light utilization efficiency of a semiconductor laser is improved and the mounting accuracy is improved by a simple processing means.

[0010]

In order to achieve this object, the present invention provides a substrate, an inclined surface formed on the substrate, a semiconductor laser mounted on the inclined surface, and the inclined surface and the semiconductor laser. A notch is provided in a part of the joint surface on the inclined surface side.

When the distance from the emitting end of the semiconductor laser to the edge of the substrate is s and the divergence angle of the semiconductor laser is θ, the notch depth is set to s × tan (θ / 2) to emit light. The laser light will not be cut off. In addition, by placing solder that joins the semiconductor laser and the inclined surface in the notch, the mounting angle of the semiconductor laser is restricted only by the inclined surface, regardless of the thickness of the solder layer, so that the mounting accuracy can be improved. it can.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A first invention is a substrate or a semiconductor substrate, an inclined surface formed on the substrate or the semiconductor substrate, a semiconductor laser mounted on the inclined surface, and a junction between the inclined surface and the semiconductor laser. A cutout is provided in a part of the surface on the side of the inclined surface.

The second invention is an optical device characterized in that an etching mask material is formed on a semiconductor substrate, an opening having a notch on one side is formed in the mask material, and then anisotropic etching is performed. Is a manufacturing method.

A third aspect of the present invention is a method of manufacturing an optical device, characterized in that an etching mask material is formed on a semiconductor substrate, and a plurality of openings are provided in the mask material in proximity to each other, and then anisotropic etching is performed. Is the way.

The fourth invention comprises a transparent substrate, a plurality of optical elements formed on at least one of the front surface and the back surface of the transparent substrate, a photodetector, and the optical device of the first invention.

The operation of the first invention will be described with reference to FIG. FIG. 12A is a perspective view of the substrate, and FIG.
Is a sectional view. In FIG. 12, 18 is a substrate,
Reference numeral 19 is an inclined surface provided on the substrate, and 20 is a semiconductor laser, which is mounted on the inclined surface 19. Reference numeral 21 is a notch provided in the inclined surface 19, and the semiconductor laser 2
It is provided so as to be close to the 0 active layer. Reference numeral 22 is a solder filled in the notch 21, and joins the inclined surface 19 and the semiconductor laser 20. In FIG. 12B, assuming that the distance from the emission end of the semiconductor laser 20 to the edge of the substrate 18 is s and the divergence angle of the semiconductor laser is θ, the depth of the notch is s × tan (θ / 2). As a result, the emitted laser light can be kept intact. Further, as shown in FIG. 12B, the solder 22 for joining the semiconductor laser 20 and the inclined surface 19 is placed in the notch 21, so that the mounting angle of the semiconductor laser does not depend on the thickness of the solder layer, Since it is regulated only by 19, the mounting accuracy can be improved.

The operation of the second invention is to form an etching mask material (for example, a silicon nitride film) on a silicon substrate by using, for example, a silicon substrate as a semiconductor substrate, and provide the mask material with, for example, a rectangular opening and at the same time, the rectangular opening. When the semiconductor substrate is anisotropically etched by forming a notch on one side, the notch is formed on the inclined surface at the same time as the etching hole having the inclined surface.

The effect of the third invention is that, when a plurality of openings are provided close to the mask material formed in the shape of a semiconductor substrate, the etching holes are connected by the side etching of the openings when anisotropic etching is performed. The notch can be formed by doing so.

The effect of the fourth invention is to increase the light utilization efficiency by propagating the laser light emitted from the optical device of the first invention to the transparent substrate on which the optical element having the condensing function and the beam splitting function is formed. Thus, an optical pickup having excellent light condensing characteristics can be obtained.

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic configuration of an optical device according to a first embodiment of the present invention,
FIG. 2 is a cross-sectional view (a) and a plan view (b) showing how light is propagated and condensed, and FIG. 2 shows the shape of a part of the silicon substrate of the optical device of the first embodiment of the present invention. It is the top view (a) and sectional view (b) shown. The optical device according to the first embodiment of the present invention is a compact disc (CD).
It is an example of an optical pickup that reads out a signal from an optical recording element such as an optical disc, an optical card memory, or the like.

In FIG. 1, 101 is a semiconductor laser, 102 is a transparent substrate, 103 is a reflection type collimator lens, 104 is a transmission type objective lens, 105 is a reflection type twin lens, 106 is a photodetector, 107 is an optical disk, 10
8 is propagating light, 109 is outgoing light, 110 is reflected light, 111
Is a reflective layer, 113 is a silicon substrate, 114 is an electrode pad, 115 is a hole, 117 is an electrode wire, and the above-mentioned configuration and the relationship between components are the same as those described in the conventional example.
As the transparent substrate 102, for example, the thickness (size in the z direction) 3
mm, width (x-direction size) 5 mm, length (y-direction size) 10 mm, for example, BK7 glass, and metal such as Ag, Al, Au, etc. on the front surface (on the side where the optical disk is) and the back surface of the transparent substrate 102. Reflective layers 111a and 111b, which are layers or multilayer films of dielectrics, are formed. The transparent substrate 102 serves as a light propagation path through which light propagates in a zigzag shape by utilizing the reflection on the front surface and the back surface. The transparent substrate 102 may be transparent to the wavelength used. Particularly, a glass substrate such as quartz or BK7 is stable in temperature.

A silicon substrate 113 having a thickness of 600 μm, a width of 5 mm and a length of 3 mm, for example, is integrated on the left side of the back surface of the transparent substrate 102 by, for example, anodic bonding or ultraviolet curing resin or thermosetting resin. . In the case of anodic bonding, the transparent substrate 102 and the silicon substrate 113 are brought into close contact with each other at a predetermined position in a nitrogen atmosphere, a voltage of about 200 V is applied with the transparent substrate 102 as the cathode side and the silicon substrate 113 as the anode side, and Were heated to about 300 ° C.

Next, the features of the present invention will be described with reference to FIG. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. The hole 115 is filled with an inert gas such as nitrogen gas to prevent the semiconductor laser 101 from being oxidized due to a temperature rise. Reference numeral 118 is a notch, which was formed simultaneously with the hole 115 by anisotropic etching of the silicon substrate. Reference numeral 119 is solder. The divergence angle θ within the plane of the paper of the semiconductor laser 101 used in FIG. 2B was 30 °. Further, the hole 11 is formed from the emitting end face of the semiconductor laser 101.
The distance s to the edge of 5 was set to 100 μm. At this time, the depth of the notch 118 is 100 × tan15 ° = 2
By setting the depth to 30 μm, which is deeper than 6.8 μm, the emitted laser light was not eclipsed, and the laser light could be efficiently used. Furthermore, by mounting solder for joining the semiconductor laser 101 and the silicon substrate 113 only in the notch 118, the mounting angle of the semiconductor laser 101 is regulated by the inclined surfaces on both sides of the notch 118, so that the notch 118 can be mounted accurately. I was able to.

Next, referring to FIGS. 3 to 5, the silicon substrate 1 will be described.
The processing method of No. 13 will be described in detail. 3 to 5 are views showing a manufacturing process of the silicon substrate in the present embodiment. In FIG. 3, 113 is a silicon substrate and 120 is an etching mask, for example, silicon formed by a low pressure CVD method. It is a nitride film. FIG. 4A is a sectional view of the silicon substrate, and FIG. 4B is a plan view of the silicon substrate. In the figure, 121 is an opening, which is provided by etching the silicon nitride film by dry etching, for example. Regarding the shape of the opening, a notch was provided on one side of the rectangular opening. FIG. 5A is a sectional view of the same silicon substrate, and FIG. 5B is a plan view of the silicon substrate. In FIG. 5, 115 is a hole and 122 is a notch. Hole 115
The notch 122 was formed by etching a silicon substrate by anisotropic etching. When a silicon substrate is etched with an aqueous potassium hydroxide solution or an alkaline solution such as ethylenediaminepyrocatechol (EDP) or hydrazine, the etching rate of the (100) plane is high,
It is known that the etching rate of the 1) plane is very slow, so that the etching hole has the shape of a quadrangular pyramid surrounded by the (111) plane on the side surface (for example, silicon as a mechanical material KE Petersen). Pro
c. of the IEEE Volume 70 No. 5 p420
~ 1982).

A method of forming a notched hole in a silicon substrate using this technique will be described with reference to FIGS. First, as shown in FIG. 3, an etching mask 1 is formed on a silicon substrate having a (100) plane orientation by low pressure CVD.
A silicon nitride film to be 20 was formed. Next, as shown in FIG. 4, an opening 121 having a notch on one side of the rectangular opening was formed by dry etching the etching mask 120 (silicon nitride film). Next, when anisotropic etching is performed using this silicon nitride film as an etching mask, the (100) plane is initially etched to expose the (111) plane as described above, but the cutout portion of the opening 121 is formed. Then, since the etching of the (212) plane having the next highest etching rate progresses after the (100) plane, the holes 115 and the notches 122 as shown in FIG. 5 were finally formed.

As described above, according to the present embodiment, an etching mask material is formed on the silicon substrate 113, an opening having a notch on one side is formed in the mask material, and then anisotropic etching is performed. A hole 115 having a notch 122 can be formed. By soldering the notch 122 and mounting the semiconductor laser 101 in the hole 115, the laser beam can be prevented from being shaken, and the semiconductor laser 101 can be mounted. The accuracy has also improved.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. The optical device according to the second embodiment of the present invention is also an example of an optical head that reads out a signal from an optical recording element, like the optical device according to the first embodiment. The optical device of the second embodiment of the present invention is different from the optical device of the first embodiment only in the method of manufacturing the silicon substrate, so only the method of manufacturing the silicon substrate of the present embodiment will be described.

6 to 9 are views showing a method for manufacturing a silicon substrate according to the present embodiment. In FIG. 6, 113 is a silicon substrate, 120 is an etching mask,
For example, a silicon nitride film. FIG. 7A shows a cross section of the silicon substrate, and FIG. 7B is a plan view of the silicon substrate. In the figure, 123a and 123b are openings. FIG. 8A shows a cross-sectional view of the silicon substrate.
(B) is a plan view of a silicon substrate. 9A is a cross-sectional view of the silicon substrate, and FIG. 9B is a plan view of the silicon substrate. In FIG. 9, 115 is a hole, and 1
24 is a notch.

A method of manufacturing a silicon substrate will be described below with reference to FIGS. First, as shown in FIG. 6, a silicon nitride film serving as an etching mask 120 was formed on a (100) plane silicon substrate by low pressure CVD. Next, as shown in FIG. 7, two openings were formed separated by 1 μm. The opening was formed by dry etching the silicon nitride film. Next, when anisotropic etching is performed using this silicon nitride film as an etching mask, the (100) plane is etched and the (111) plane appears, but the (111) plane is 400% of the (100) plane. Since it is etched at an etching rate of about 1,
When the (0) plane was etched by about 200 μm, the edges of the (111) planes of the adjacent openings were aligned as shown in FIG. Since various crystal planes including the (100) plane are formed in the portion where the edges are combined, the etching of the (100) plane proceeds when anisotropic etching is further continued. Finally, when the silicon nitride film of the etching mask was removed, holes 115 and notches 124 as shown in FIG. 9 were obtained. At the joint between the hole 115 and the notch 124, as described in the method for manufacturing a silicon substrate in the first embodiment, the etching rate is the second largest (2) after the (100) plane.
12) Since the etching of the surface progressed, the corners were rounded, but the difference from the first embodiment is (212).
Due to the short etching time of the surface, the width of the notch did not widen.

As described above, according to this embodiment, the etching mask material is formed on the silicon substrate 113, and the two openings 123a and 123b are provided in the mask material in close proximity to each other, and then anisotropic etching is performed. By doing so, the hole 115 having the narrow cutout 124 can be formed,
When the semiconductor laser 101 is mounted on the inclined surface of the hole 115 by filling the cutout 124 with solder and the laser light is not blocked, and the width of the cutout is not widened, the angle of the semiconductor laser 101 is regulated. The area is expanded and the mounting accuracy is improved. Although the notch 121 is formed by anisotropic etching of the silicon substrate in the first embodiment, it may be made of another material by another processing means such as laser processing. Also,
Although the silicon substrate having the (100) plane is used in the first embodiment, a silicon substrate having a plane slightly inclined from the (100) plane may be used. Further, instead of enclosing nitrogen gas in the hole 115, if an inert liquid of perfluorocarbon having a refractive index close to that of the transparent substrate 102 is filled, the refractive index matching with the transparent substrate 102 is improved, and the transparent substrate 1
There is an advantage that the reflectance at the interface with 02 can be lowered and the heat dissipation effect is improved. Further, although silicon is used as the semiconductor substrate, it goes without saying that the same effect can be obtained by using gallium arsenide.

[0031]

As described above, according to the first invention, the substrate, the inclined surface formed on the substrate, the semiconductor laser mounted on the inclined surface, and the joint surface between the inclined surface and the semiconductor laser are provided. By providing a notch on a part of the inclined surface side, the laser light of the semiconductor laser is prevented from being shaken, and the mounting accuracy of the semiconductor laser is improved, which is a great effect.

According to the second aspect of the invention, an etching mask material is formed on a semiconductor substrate, an opening having a notch on one side is formed in the mask material, and then anisotropic etching is performed. The inclined surface on which the laser is mounted and the notch can be formed at the same time, and the effect is great.

According to the third aspect of the present invention, an etching mask material is formed on a semiconductor substrate, a plurality of openings are provided in the mask material in proximity to the mask material, and anisotropic etching is performed to mount the semiconductor laser. Has the advantage that

According to the fourth invention, by providing the transparent substrate, the plurality of optical elements formed on at least one of the front surface and the back surface of the transparent substrate, the photodetector and the optical device of the first invention, It is easy to assemble and adjust, and it is possible to obtain a compact and lightweight optical pickup, and the effect is great.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing a basic configuration of an optical device according to a first embodiment of the present invention, and how light is propagated and condensed. FIG. 1B is a plan view of the same.

FIG. 2A is a plan view showing the shape of a silicon substrate of the optical device according to the first embodiment, and FIG. 2B is a sectional view of the same.

FIG. 3 is a sectional view of the silicon substrate according to the first embodiment of the present invention.

FIG. 4A is a cross-sectional view of the silicon substrate according to the first embodiment of the present invention, and FIG. 4B is a plan view of the same.

FIG. 5A is a sectional view of a silicon substrate according to a first embodiment of the present invention, and FIG. 5B is a plan view of the same.

FIG. 6 is a sectional view of a silicon substrate according to a second embodiment of the present invention.

FIG. 7A is a sectional view of a silicon substrate according to a second embodiment of the present invention, and FIG. 7B is a plan view of the same.

FIG. 8A is a sectional view of a silicon substrate according to a second embodiment of the present invention, and FIG. 8B is a plan view of the same.

FIG. 9A is a sectional view of a silicon substrate according to a second embodiment of the present invention, and FIG. 9B is a plan view of the same.

FIG. 10 (a) shows a basic configuration of a conventional optical device,
Sectional view showing how light is propagated and condensed (b) is the same plan view

11A is a sectional view showing the shape of a silicon substrate of a conventional optical device, and FIG. 11B is a plan view of the same.

FIG. 12A is a perspective view for explaining the function of the first invention of the present invention, and FIG. 12B is a sectional view of the same.

[Description of Reference Signs] 101 semiconductor laser 102 transparent substrate 103 reflective collimator lens 104 transmissive objective lens 105 reflective twin lens 106 photodetector 107 optical disk 108 propagating light 109 outgoing light 110 reflected light 111 reflective layer 113 silicon substrate 114 electrode pad 115 hole 117 electrode wire 118 notch 119 solder 120 etching mask 121 opening 122 notch 123a, b opening 124 notch

Claims (5)

[Claims] 1. A substrate, an inclined surface formed on the substrate, a semiconductor laser mounted on the inclined surface, and a cut provided in a part of the junction surface of the inclined surface and the semiconductor laser on the inclined surface side. An optical device consisting of a chip. 2. The optical device according to claim 1, wherein the substrate is a semiconductor substrate. 3. The method of manufacturing an optical device according to claim 2, wherein an etching mask material is formed on the semiconductor substrate, an opening having a notch on one side is formed in the etching mask material, and then the anisotropic A method for manufacturing an optical device, which comprises performing etching. 4. The method of manufacturing an optical device according to claim 2, wherein an etching mask material is formed on the semiconductor substrate, and a plurality of openings are provided close to the etching mask material, and then anisotropic etching is performed. A method for manufacturing an optical device, which is characterized in that 5. An optical pickup comprising a transparent substrate, a plurality of optical elements formed on at least one of a front surface and a back surface of the transparent substrate, a photodetector, and the optical device according to claim 1.