JPH09312439A - Optical element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element with a 111} plane mirror surface and a small dead band region and a manufacturing methodthereof. SOLUTION: A base material forming an optical element according to this invention is provided with a semiconductor laser structure on a GaAs substrate 12 having a 100} as a major surface moreover with a projected laser stripe 11 orthogonal in the [011] direction. An insulating film 21 is formed followed by patterning so as to remove the insulating film from the part excepting for a resonator region. Next, directional etching is performed having the insulating film as a mask so as to etch up to the prescribed surface 23 so as to form a projection part 24 in the same shape with the laser stripe on the prescribed surface. A mirror part 28 is formed by crystal growth on the prescribed surface. In this formation process, 111} B faces 30, 32 are grown from the upper surface, the side surface and the prescribed surface of the projection part simultaneously. Along with this growth, lateral growth begins also from the horizontal surface 6 (a diagonally shaded part in the figure) 34 of the horizontal surface between the 111} B face and the 111} B face 34, and a region of the 111} B face is extended so as to fully function as a laser light boot-up part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called Confoc in which a light emitting element, a reflecting mirror, a light receiving element and the like are monolithically constructed.
The present invention relates to an al Laser Coupler type (confocal laser coupler type, hereinafter simply referred to as CLC type) optical element and a method of manufacturing the same, more specifically, a CLC type optical that is lightweight, downsized, and easy in optical alignment. The present invention relates to an element, for example, an optical element most suitable for an optical pickup used for reading and writing of an optical disk, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a conventional optical pickup for reading and writing an optical disk, optical components such as a semiconductor laser, a photodiode and a beam splitter are individually formed on a substrate in a hybrid structure. This increases the number of optical components that make up the optical pickup, complicates the structure, and requires strict optical alignment accuracy.Therefore, when assembling optical components on a substrate with a hybrid structure, Requires advanced manufacturing techniques,
It was difficult to improve productivity.

Therefore, the applicant of the present invention reduces the number of optical components constituting the optical pickup, simplifies the overall structure, reduces the size, and simplifies the optical alignment accompanying the optical arrangement of the optical components. Therefore, a so-called CLC type optical pickup has been proposed in which a light emitting portion is arranged at a confocal position of a light converging means including a lens and a light receiving portion is formed in the vicinity of the confocal position. An optical device 70 is shown in FIG. 5 as an example of this CLC type optical pickup. Optical device 7
Reference numeral 0 denotes a common semiconductor substrate 78 that includes a light emitting portion 72 formed of a semiconductor laser, a laser light rising portion 74 formed of a semiconductor layer having a triangular pyramid structure, and a light receiving portion 76 formed of a photodiode.
It has a monolithic structure on top of it.

The laser beam rising portion 74 has a rising mirror surface 74a and two reflecting surfaces 74b and 74c, and is formed near the confocal position of the converging means.
4a faces the light emitting portion 72, and the other two reflecting surfaces 74b, c
Is a two-divided photodiode PD _1a , PD _1b and PD _2a , P
It is formed so as to face the light receiving portion 76 made of D _2b . As shown in FIG. 6, the laser light L _F emitted from the light emitting portion 74 is reflected by the rising mirror surface 74 a and goes upward, and after being converged by the light converging means (not shown), the laser light L _F is irradiated onto the optical disk or the like. The illuminator is irradiated. The light is reflected by the object to be irradiated, is converged by the light converging means as the return light L _R , and is irradiated onto the laser light rising portion 74 arranged near the confocal point. The return light L _R is divided by the two reflecting surfaces 74 b and c, respectively, and reflected to form two light receiving portions 76.
The light is received by D _1a , PD _1b and PD _2a , PD _2b .

Now, a conventional method for forming the CLC type optical pickup shown in FIG. 5 will be described. First, FIG.
As shown in (a), an insulating film 50 is formed as a mask pattern forming film in a laser resonator region having a compound semiconductor laminated structure such as a GaAs substrate 42, a lower clad layer 44, an active layer 46 and an upper clad layer 48. To do. Next, directional etching is performed to etch the substrate 42 to a predetermined surface 52, and a laser resonator end face 54 is formed perpendicularly to the resonator direction. As the etching, two-stage etching including first-stage etching and second-stage etching is performed.
First, in the first-stage etching, the substrate surface 5 of the substrate 42 is
Etch to 6. Next, a mask pattern is formed and a second step of etching is performed from the substrate surface 56 to the predetermined surface 5.
Step 2 is performed to form an isosceles triangular prismatic step 58 extending in the direction of the resonator. Next, as shown in FIG. 7B, a compound semiconductor layer is selectively grown by the MOCVD method or the like, and the triangular pyramid-shaped laser light rising portion 74 is formed on the step 58.
Is formed. FIG. 7C is a side cross-sectional view of FIG. 7B and shows the resonator end face 54 and the laser light rising portion 74.
W ₃ between the resonator-side inclined surface of, and the rising mirror surface 80 is a dead zone area.

[0006]

By the way, in an optical element such as a CLC type optical pickup, the wider the dead zone region is, the smaller the light amount of the return light incident on the light receiving portion is. Therefore, the narrower the dead zone region is. good.

Now, the relationship between the return light L _R of the CLC type optical pickup and the dead zone region will be described with reference to FIG. The rising mirror surface 80, which reflects the emitted laser light L _F upward, becomes a dead zone region for the return light L _R due to the nature of the coating layer coated to enhance the reflection efficiency. On the other hand, the irradiation area of the return light L _R expanded due to the diffraction limit is regulated to a constant value by the numerical aperture of the light converging means, so that the light quantity of the return light L _R incident on the light receiving portion becomes wider in the dead zone region. As the width gets wider, the amount decreases, and the optical pickup performance including sensitivity decreases. Therefore, FIG.
As shown in (a), when the triangular pyramid 74 is made large in order to widen the area of the reflection surface 82 of the return light L _R of the laser light rising portion 74, as a result, the distance W between the triangular pyramid and the resonator end surface is increased.
Becomes longer and the dead zone becomes wider. Conversely, FIG. 9 (b)
As shown in FIG.
If it is attempted to reduce the distance W by shortening, the area of the reflection surface 82 that divides the return light becomes smaller, and the amount of the return light L _R incident on the light receiving unit decreases.

By the way, when the {111} A plane or the {110} plane is made to be a rising mirror plane, as shown in FIG. 10 (a), crystals grow on these planes, so that the active layer end face is formed. However, there is an advantage that the interval W between the rising mirror surfaces is narrowed and the dead zone for the returning light is narrowed.
The 1} A plane and the {110} plane are not preferable as the rising mirror surface in terms of the flatness of the plane, the in-plane uniformity of the crystal, and the denseness of the crystal. Therefore, in order to improve the performance of the optical pickup, it is necessary to use the {111} B plane, which has excellent surface flatness, in-plane uniformity of crystals, and compactness, as a rising mirror surface. However, when the {111} B surface is used as the rising mirror surface, {1} is formed in the above-mentioned triangular pyramid forming step.
Since it is difficult to grow a crystal on the 11} B plane, there is a problem that the interval W between the end surface of the active layer and the rising mirror surface is widened and the dead zone region is expanded, as shown in FIG. 10B. It was The {111} B plane is the plane in which As atoms are arranged on the surface layer of the {111} plane of the GaAs crystal substrate, and the {111} A plane is the plane in which Ga atoms are arranged. .

Therefore, an object of the present invention is to provide an optical element having a {111} plane as a rising mirror surface and having a small dead zone region.

[0010]

Means for Solving the Problems The present inventors have found that {100}
Using the substrate whose main surface is the main surface, the convex portion is extended to the surface of the substrate region where the laser beam rising portion is formed, and the compound semiconductor layer is selectively grown on the surface, and the compound semiconductor layer is formed in the lateral direction of the {111} B plane. The present invention has been completed, focusing on solving the above-mentioned problems by causing growth. In order to achieve the above object, an optical element according to the present invention has a main surface {10.
And a semiconductor laser section having a laminated structure of compound semiconductor layers and a GaAs substrate having a plane parallel to the 0} plane or inclined at an angle of 15 ° or less, and arranged near the end face of the semiconductor laser section. The laser light rising portion having a rising mirror surface that reflects the laser light emitted from the end surface of the semiconductor laser portion vertically upward with respect to the substrate surface, and the laser light rising portion on the side opposite to the semiconductor laser portion. It is characterized in that it is provided with a light receiving portion arranged on the substrate surface. The inclination angle of the substrate surface with respect to the {100} plane is preferably 9.7 °. Further, the laser structure of the present invention is formed by a laminated structure of GaAs-based and AlGaAs-based compound semiconductors.

The method for producing the optical element according to the present invention is
A first region formed by laminating a compound semiconductor layer in a laser structure on a GaAs substrate having a plane parallel to the {100} plane which is the main plane or a substrate plane inclined at an angle of 15 ° or less; A second region having a convex portion extending in the cavity direction of the laser structure on a surface formed parallel to the substrate surface at a position lower than the active layer of the laser structure, wherein the end surface of the first region on the second region side is A laser beam emitted from the end face of the first region on the side of the second region by growing a compound semiconductor layer on the face of the second region of the substrate formed so as to be orthogonal to the face of the second region by the selective growth method. It is characterized in that a rising mirror portion having a rising mirror surface that reflects the light vertically upward with respect to the substrate surface is formed.

Another manufacturing method is to use the main surface {10.
A semiconductor laser structure formed by stacking a compound semiconductor layer on a GaAs substrate having a plane parallel to the 0} plane or a substrate plane inclined at an angle of 15 ° or less, and [011] on the upper surface of the semiconductor laser structure. ] A step of forming a mask pattern forming film on the upper surface of a substrate having a convex laser stripe in a direction orthogonal to the direction, and then patterning to form a mask pattern film in the cavity region of the semiconductor laser; Using as a mask, directional etching is performed in a direction orthogonal to the substrate surface to etch to a predetermined surface of the substrate,
A step of forming an end face of the resonator region perpendicular to a predetermined surface and forming a convex portion having the same shape as the laser stripe on the predetermined surface, and crystal growth of a compound semiconductor layer on the predetermined surface having the convex portion by a selective growth method. And a step of forming a laser beam rising portion having a rising mirror surface for reflecting the laser light emitted from the end face of the resonator region in a direction vertically upward with respect to the substrate surface. The selective growth method used in the method of the present invention is not limited to that method.
A CVD method or the like can be used. Further, reactive ion etching (RIE), ECR plasma etching or the like is used for the directional etching. The predetermined surface is a surface on which the laser light rising portion is grown.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Example 1 This example is an example of the optical element according to the present invention.
FIG. 1 is a schematic perspective view of an optical element of this example. As shown in FIG. 1, the optical element 10 of the present embodiment includes a GaAs substrate 12 having a substrate surface inclined at an angle of 9.7 ° with respect to the {100} plane which is the main surface, and the substrate 12. The laser light rising portion 28 and the laser light rising portion 2 which are respectively formed on the semiconductor laser portion 20 and the laser light rising portion 28 which is arranged in the vicinity of the end face 26 of the semiconductor laser portion 20 and has the extending convex portion 27.
8 includes a semiconductor laser section 20 and a light receiving section 22 arranged on the opposite side. The semiconductor laser section 20 includes a lower clad layer 14 made of a compound semiconductor layer, an active layer 16,
The upper clad layer 18 and the like have a laminated structure.
In FIG. 1, 30 is the {111} B surface of the convex portion 27 of the laser beam rising portion 28, and 32 is the {111} B surface of the lower portion of the convex portion 27.
Planes and 34 are {111} B plane 30 and {111} B plane 3
It is a surface in the lateral direction between 2 and (a hatched portion in the drawing) and is a lateral growth surface.

In this embodiment, as described in the second embodiment, when the laser light rising portion 28 and the light receiving portion 22 are grown, the lateral distance between the {111} B surface 30 and the {111} B surface 32 is increased. Since lateral growth also starts in the plane (hatched portion in the drawing) 34 in the direction, and the region of the {111} B plane expands,
It fully functions as a laser light rising mirror surface. Therefore, the optical element 10 can be suitably used as a main part of a CLC type optical pickup.

Example 2 This example is an example in which the method of the present invention is applied to the formation of the optical element 10 of Example 1. The base material for forming the optical element 10 is, as shown in FIG.
A GaAs substrate 12 having a substrate surface inclined at an angle of 9.7 ° with respect to a 0} plane, on which a lower clad layer 14, an active layer 16, an upper clad layer 18, and a cap layer ( (Not shown), and a laminated structure of a compound semiconductor having a convex laser stripe 11 extending in the [011] direction.

First, an insulating film 21 is formed as a mask pattern forming film on the substrate surface and is patterned to remove the insulating film 21 from the region other than the cavity region of the laser structure. Next, as shown in FIG. 2B, using the insulating film 21 as a mask, directional etching by a reactive ion etching method is performed in a direction orthogonal to the substrate surface to expose a predetermined surface of the substrate 12, that is, laser light. Etching is performed up to the raised portion forming surface 23.
As a result, the end face 26 of the resonator region is formed vertically, and the protrusion 24 having the same shape as the laser stripe 11 is formed on the predetermined face 23. Then, an insulating film is formed on the end surface 26 as a protective film. Next, a compound semiconductor layer is selectively grown on the predetermined surface 23 having the convex portion 24 by the MOCVD method or the like to form the laser light rising portion 28 and the light receiving portion 22 shown in FIG. During the process of forming the laser beam rising portion 28, the {111} B surfaces 30 and 32 grow simultaneously from the upper surface and the side surface of the convex portion 24 and the predetermined surface 23. With this growth, the {111} B surface 30 of the convex portion 24 and the {1}
Lateral growth also starts from the lateral surface (hatched portion in the drawing) 34 between the 11} B surface 32 and the area of the {111} B surface expands, and functions sufficiently as the laser beam rising mirror 28. The {111} B plane is formed.

Through the above steps, as shown in FIG. 3 (side sectional view of FIG. 1), in the laser light rising portion 28, the width W _{1 of the} dead zone region is shortened, and the {111} A plane or the {11} A plane is formed.
It is possible to obtain the optical element 10 shown in FIG. 1, which has the same shape as that of the 0} plane used as the rising mirror and has a small dead zone region for the returning light.

Example 3 This example is an example in which the method of the present invention is applied to the formation of a CLC type optical element having a triangular pyramid. First, in the same manner as the conventional example described with reference to FIG. 7, a mask pattern is formed in the laser resonator region having a compound semiconductor laminated structure such as the GaAs substrate 42, the lower clad layer 44, the active layer 46 and the upper clad layer 48. The insulating film 50 is formed as a forming film. Next, directional etching is performed to etch the substrate to a predetermined surface 52 and a resonator end face 54 is formed perpendicular to the resonator direction. As the etching, two-step etching including first-step etching and second-step etching is performed. First, in the first-stage etching, the substrate 4
Etching is performed up to the second substrate surface 56, and then a second step etching is performed from the substrate surface 56 to a predetermined surface 52 using a mask pattern to form an isosceles triangular prismatic step 58 extending in the direction of the resonator. To do. Up to this point, the method is the same as the conventional method shown in FIG. Next, as shown in FIG. 4A, a convex portion 60 extending in the cavity direction is formed on the step 58 by using a mask pattern or the original concave and convex of the semiconductor laser.

Subsequently, a compound semiconductor layer is selectively grown by MOCVD or the like to form a triangular pyramid 62 on the step 58. As a result, as shown in FIG.
Similarly, the {111} B plane 64 of the triangular pyramid 62 expands in the lateral direction and has a shape equivalent to the {111} A plane or the {110} plane. In the present embodiment, the size of the triangular pyramid 62 is kept the same as that of the conventional triangular pyramid (see FIG. 7C), while the distance W ₂ between the active layer and the reflecting surface is shortened and the dead zone region is Decrease.

In Examples 1 to 3, the laser has a convex structure. However, even in a planar laser structure having no convex structure, a convex portion is formed on the predetermined surface 23 or 52 to form a laser. Similar to 1 to 3, it is possible to realize an optical element having a {111} surface as a raised mirror surface and having a small dead zone region.

[0021]

According to the present invention, by providing a convex portion on the surface where the laser beam rising portion is formed, crystal growth is difficult {1
Even if the 11th surface B is used as a rising mirror, {11
As in the case where the 1} A plane or the {110} plane is used as the rising mirror surface, the distance between the end face of the active layer of the laser structure and the rising mirror surface can be shortened, and the dead band region of the returning light can be narrowed. It becomes possible to do. By using the method of the present invention, {111} which has preferable properties as a rising mirror surface, such as surface flatness and in-plane uniformity.
It is possible to form an optical element having the B-side as a rising mirror surface, particularly an optical element having high performance as an optical pickup.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of Example 1 of an optical element according to the present invention.

FIG. 2A and FIG. 2B are respectively the first embodiment.
FIG. 6 is a perspective view of a substrate for each step of manufacturing the optical element of FIG.

FIG. 3 is a diagram for explaining the effect of the method of the present invention.

FIG. 4A, FIG. 4B and FIG.
It is a board perspective view and a sectional view for every process for explaining another example of the method of the present invention.

FIG. 5 is a conceptual perspective view illustrating a configuration of an optical pickup.

FIG. 6 is a schematic diagram illustrating the function of an optical pickup.

7 (a), (b) and (c) are respectively,
9A and 9B are a perspective view and a cross-sectional view of a substrate for each step when forming an optical pickup by a conventional method.

FIG. 8 is a schematic diagram illustrating a dead zone region.

9A and 9B are schematic diagrams for explaining the relationship between the size of the laser beam rising portion and the dead zone region, respectively.

FIG. 10 (a) and FIG. 10 (b) show {1
It is a schematic diagram explaining the difference of the crystal growth of the {111} B plane and the 11} A plane and the {110} plane.

[Explanation of symbols]

10 Examples of optical elements according to the present invention, 12 ... Ga A
s substrate, 14 ... lower clad layer, 16 ... active layer, 1
8: upper clad layer, 20: semiconductor laser section, 21
...... Insulating film, 22 ...... Light receiving part, 23 ...... Predetermined surface, 24 ...
... Convex portion, 26 ... End face, 27 ... Convex portion, 28 ... Laser light rising portion, 30 ... {111} B surface of convex portion of laser light rising portion, 32 ... Laser light rising portion {111} B plane, 34 ... a lateral plane between the {111} B plane 30 and the {111} B plane 32, 42 ... Substrate, 44 ... Lower clad layer, 46 ...... Active layer, 48 ...
... upper clad layer, 50 ... insulating film, 52 ... predetermined surface of substrate, 54 ... resonator end surface, 56 ... substrate surface, 58 ...
Steps in the shape of isosceles triangular prisms, 60 ... convex portions, 62 ...
Triangular pyramid, 64 ... {111} B plane.

Claims (5)

[Claims] 1. A semiconductor laser section having a laminated structure of a GaAs substrate having a plane parallel to a {100} plane as a main surface or a substrate plane inclined at an angle of 15 ° or less, and a compound semiconductor layer. A laser beam rising portion having a rising mirror surface which is arranged near the end surface of the semiconductor laser portion and reflects the laser light emitted from the end surface of the semiconductor laser portion vertically upward to the substrate surface. An optical element comprising a semiconductor laser section and a light receiving section arranged on the opposite side of the raising section on the substrate surface. 2. A compound semiconductor layer is laminated in a laser structure on a GaAs substrate having a plane parallel to a {100} plane which is a main plane or a substrate plane inclined at an angle of 15 ° or less. And a second region having a convex portion extending in the cavity direction of the laser structure on a surface formed parallel to the substrate surface at a position lower than the active layer of the laser structure. A compound semiconductor layer is grown by a selective growth method on the surface of the second region of the substrate formed so that the end face on the second region side is orthogonal to the surface of the second region. A method for manufacturing an optical element, comprising forming a rising mirror portion having a rising mirror surface for reflecting emitted laser light vertically upward with respect to a substrate surface. 3. The method of manufacturing an optical element according to claim 2, wherein the convex portion extends on the upper surface of the first region along an extension line of the convex portion of the second region. 4. The method of manufacturing an optical element according to claim 2, wherein the convex portion of the second region is formed on the upper surface of the triangular columnar base. 5. A semiconductor laser structure in which a compound semiconductor layer is laminated on a GaAs substrate having a plane parallel to a {100} plane as a main plane or a substrate plane inclined at an angle of 15 ° or less. And a mask pattern forming film is formed on the upper surface of a substrate having a convex laser stripe in a direction orthogonal to the [011] direction on the upper surface of the semiconductor laser structure, and then patterned to form a mask pattern in the resonator region of the semiconductor laser. The step of forming a film, and using the mask pattern film as a mask, directional etching is performed in a direction orthogonal to the substrate surface to etch to a predetermined surface of the substrate, and the end face of the resonator region is formed perpendicular to the predetermined surface. The step of forming a convex portion having the same shape as the laser stripe on a predetermined surface, and the crystal growth of the compound semiconductor layer on the predetermined surface having the convex portion by the selective growth method to form an end face of the cavity region. Method for manufacturing an optical element characterized by a step of forming a laser beam rising portion having a raising mirror surface for reflecting upward vertical laser light et emitted to the substrate surface.