JPH10135561A - Optical element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the laser diode manufacturing method with which the falling-out of a passivation film, covering the edge face of an optical waveguide, can be prevented. SOLUTION: In the optical element in which a laser diode 1 is incorporated into a monolithic, the edge face of the optical waveguide of the laser diode 1 is covered by films 25 and 26. The surface of the optical element on the edge face of the optical waveguide, where the films 25 and 26 are formed, is formed lower than the surface part of other optical elements. Also, the surface part of the optical element of the entire edge face of the optical waveguide, where the films 25 and 26 are formed, is formed lower than the surface part of other optical elements. One edge face of the above-mentioned optical waveguide is covered by a low reflectivity film, and other edge face is covered by a high reflectivity film. The surface part of the optical element, where a laser diode 1 is formed, is elevated in band form along the optical waveguide of the laser diode 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device and a method of manufacturing the same, and more particularly to a channel stripe type laser diode, for example, a laser diode having a structure in which a ridge is formed above an active layer to specify an optical waveguide (ridge waveguide). The present invention relates to a technology which is effective when applied to the manufacturing method of the invention.

[0002]

2. Description of the Related Art Semiconductor lasers (laser diodes: LDs) are used as light sources for information processing devices such as digital audio disks, video disks, optical disk files, and laser beam printers, and as light sources for optical communication.

[0003] For example, “Nikkei Electronics” published by Nikkei BP, November 19, 1984, P187-P2
No. 06 describes a high-power semiconductor laser serving as a light source of an information processing device.

This document describes a technique for coating the end face of the optical waveguide with a coating (asymmetric coating of the end face) in order to prevent the deterioration of the end face of the optical waveguide and extend the life of the semiconductor laser. .

[0005] Further, this document discloses an example in which a normal coating film is applied.
In this method, a multilayer film or a single-layer film is attached to the end face so that the front face has low reflectance (5 to 15%). "Is described. It also describes that the reflectance of a normal semiconductor laser is about 32%.

On the other hand, a channel stripe type laser diode having a ridge provided above a flat active layer is described in, for example, "Transactions of the Institute of Electronics, Information and Communication Engineers, C-1 No. 5", May 1990. Published on March 25, pp. 246-252. This document includes a ridge waveguide type GaInAsP / AlGaAsDF.
A B laser is described. This ridge type laser diode is composed of n-AlGaAs on an n-GaAs substrate.
s, GaInAsP (Active), p-AlGaAs
s, p-GaInP (guide layer), p-AlGaAs
(Cladding layer) and p-GaAs (cap layer) are sequentially formed. In the formation of the ridge waveguide structure,
It is described that the GaAs cap layer and the p-AlGaAs clad layer are selectively etched and formed.

[0007]

An end face of a laser diode is provided with an AR (anti-refract) film or an HR (high-refrac) film for the purpose of preventing oxidation of the end face of the optical waveguide and controlling the reflectance.
t) A coating (passivation film) called a film is provided.

[0008] In the analysis of the manufacturing failure of the ridge type laser diode, it was found that there was a peeling failure of the coating.

As a result of analyzing and examining the defective peeling of the film, the surface of the ridge type laser diode is one step higher than other surface portions along the optical waveguide. It has been found that a large force is applied to the raised portion, and the coating covering the end face of the optical waveguide may be peeled off.

FIG. 14 shows a conventional ridge type laser diode alone, that is, an optical element (laser diode chip).
FIG. 1 is a schematic perspective view showing an outline of FIG. The ridge 20 is a portion that rises high above the center of the front surface, and the optical waveguide extends below the ridge 20. In the figure,
The end surface of the optical waveguide, which is to be the light emitting portion 21, is shown by an ellipse.

Further, due to the presence of the ridge 20, the surface of the laser diode chip 1 also has a band-like height (for example, a protruding protruding portion 23 having a height of about 1.1 μm). Further, on both end surfaces of the laser diode chip 1, that is, on the front side and the rear side in FIG. 14, a coating 25 for preventing oxidation and controlling the reflectance of the end face of the optical waveguide is provided.
26 are provided.

FIG. 15 is a sectional view showing a part of a surface along the optical waveguide. On the main surface (upper surface) of the compound semiconductor substrate 2,
Although not shown, a predetermined compound semiconductor layer is formed to form an optical waveguide 22 as shown by a two-dot chain line. An anode electrode 15 is formed on the upper surface of the optical element (laser diode chip) 1, and a cathode electrode 16 is formed on the lower surface. Further, at the left end, the optical waveguide 22
Is provided so as to cover the left end face.

For example, after forming a laser diode vertically and horizontally on a compound semiconductor substrate, the compound semiconductor substrate is cleaved to form a strip. Thereafter, films 25 and 26 are formed on both side surfaces of the strip. Next, after the strip is cut with a cutting scratch, the strip is attached to a tape made of resin. Thereafter, an external force is applied to the strip with a roller or the like so that the strip is cut at the scratched portion and the laser diode chip 1 is cut.
To manufacture.

In this case, a large force acts on the coatings 25 and 26 formed on the end surfaces of the projecting ridges 23. That is, since the protruding protruding portion 23 is higher than the other portions, an external force is concentrated on the protruding protruding portion 23 as indicated by an arrow.

The coatings 25 and 26 are films formed on the side surfaces of the compound semiconductor substrate 2 by vapor deposition or sputtering, and have a small adhesive force to the compound semiconductor substrate as a base material, unlike a monolithic structure, so that the coatings 25 and 26 are large. When a force acts, the film may be easily peeled off, and may be peeled off due to a chip (a chip 24) as shown by a dashed line in FIG. This coating 25,
Due to the peeling of 26, the end face of the optical waveguide 22 is no longer protected, and the end face of the optical waveguide is deteriorated quickly and reliability is reduced.

Further, since the films 25 and 26 are also films for controlling the reflectance, the peeling of the films 25 and 26
The state of the light output from the end face of the optical waveguide 22 changes, and does not become the designed value, and the predetermined light output characteristic cannot be obtained.

The peeling of the coatings 25 and 26 may occur when an external force is applied even when the laser diode chip 1 is handled.

An object of the present invention is to provide an optical element in which a coating covering an end face of an optical waveguide is less likely to fall off, and a method for manufacturing the same.

Another object of the present invention is to provide a laser diode having high reliability and predetermined characteristics and a method of manufacturing the same.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0021]

The following is a brief description of an outline of typical inventions disclosed in the present application.

(1) An optical device in which a laser diode is monolithically incorporated, wherein the end surface of the optical waveguide of the laser diode is covered with a coating, and the optical waveguide in which the coating is formed is The surface of the optical element at the end face is one step lower than the surface of the other optical element.
The optical element surface portion on the entire end face of the optical waveguide on which the coating is formed is one step lower than the other optical element surface portions.
One end face of the optical waveguide is covered with a low reflectivity film, and the other end face is covered with a high reflectivity film. The surface portion of the optical element on which the laser diode is formed is raised in a strip along the optical waveguide of the laser diode.

Such an optical element is manufactured by the following manufacturing method.

A step of forming a predetermined compound semiconductor layer on the main surface side of the compound semiconductor substrate to form a plurality of laser diodes and the like in a matrix and a step of forming predetermined electrodes on the main surface and the back surface of the compound semiconductor substrate; And cleaving the compound semiconductor substrate along a direction orthogonal to the optical waveguide of the laser diode to form a strip, and dividing the strip to form an optical element including the laser diode. Forming a coating on an exposed end face of the optical waveguide in the state of the strip or the state of the optical element, after forming a laser diode or the like on the compound semiconductor substrate. Selectively etching the main surface side surface of the compound semiconductor substrate so that the film forming portion is lower than the main surface of the compound semiconductor substrate,
Thereafter, the electrodes are formed. A main surface side surface portion of the compound semiconductor substrate corresponding to the optical waveguide is higher than other main surface side surface portions.

According to the means (1), the surface of the optical element at the end face portion of the optical waveguide on which the coating is formed, that is, both end portions of the protruding protrusion are one step lower than the other portions. Therefore, even if a force is applied to the protruding ridge with a roller or the like, the roller or the like does not contact the raised portion or the film that has become lower, so that a large force does not act on the film covering both ends of the optical waveguide. In addition, it is possible to prevent the occurrence of film damage such as cracks in the film, chipping or peeling of the film, stabilization of the characteristics of the laser diode, and improvement of the production yield.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments of the present invention, components having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

(Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention.
FIG. 2 is a schematic perspective view of an optical element (laser diode chip), and FIG. 2 is a schematic sectional view of the optical element.

In the first embodiment, the emission wavelength is 680 nm.
An example in which the present invention is applied to a ridge-type laser diode suitable for a light source for an information processing device will be described.

As shown in FIG. 1, the optical element (laser diode chip) 1 of the first embodiment is formed of a rectangular body, and has a structure in which laser light is emitted from the light emitting portions 21 at both ends of the laser diode chip 1. I have.

Laser diode chip 1 of the first embodiment
Is a ridge-type laser diode, which has a band-shaped ridge 20 whose center is raised high in the compound semiconductor layer on the main surface side of the compound semiconductor substrate 2. An optical waveguide extends below the ridge 20. In FIG. 1, a portion which is an end face of the optical waveguide and becomes a light emitting portion 21 is indicated by an ellipse.

Also, due to the presence of the ridge 20, the surface of the laser diode chip 1 is also formed in a belt-like shape (for example, a protruding protrusion 23 having a height of about 1 μm). In addition, coatings 25 and 26 are provided on both end surfaces of the laser diode chip 1, that is, on the front side and the rear side in FIG. 1 for the purpose of preventing the end face of the optical waveguide from being oxidized and controlling the reflectance.

The coating 25 is provided on the front emission surface, and forms an AR film (low reflectance film) 30 having a low reflectance. Further, the coating 26 is provided on the rear emission surface, and is an HR film (high reflectance film) 31 having a high reflectance. The AR film 30 is made of, for example, a SiO ₂ film having a thickness of about 170 nm, and has a reflectance of about 15%. The HR film 31 has, for example, a structure in which four layers of a SiO ₂ film and an amorphous silicon film (a-Si film) are stacked, and has a reflectance of about 80%. The HR film 3
1 has a thickness of about 0.5 μm as a whole.

FIG. 2 is a sectional view of a plane along the optical waveguide.
On the main surface (upper surface) of the compound semiconductor substrate 2, although not shown, a predetermined compound semiconductor layer is formed, and an optical waveguide 22 as shown by a two-dot chain line is formed. An anode electrode 15 is formed on the upper surface of the optical element (laser diode chip) 1, and a cathode electrode 16 is formed on the lower surface. Further, the coating film 2 covers both end surfaces of the optical waveguide 22.
5, 26 are provided.

On the other hand, this is one of the features of the present invention, and the coatings 25 and 26 are one step lower in height. In order to lower the coatings 25 and 26 one step, the compound semiconductor layers at the upper edges of both ends of the laser diode chip 1 are selectively etched to a predetermined thickness. by this,
Grooves 35 are formed at the upper edges of both ends of the laser diode chip 1. As will be described later, since the thickness of the P-type buried cap layer on the ridge is about 3 μm, the depth of the groove 35 is set to about 1.5 to 2 μm.

The coatings 25 and 26 are formed by vapor deposition or sputtering after electrodes are provided on the upper surface of the compound semiconductor layer after etching and the rear surface of the compound semiconductor substrate 2. Are etched, the upper edges (upper surfaces) of the coatings 25 and 26 are also 1.5 to 2 times smaller than the surface of the protruding protrusion 23.
μm lower. Since the projecting ridge 23 is only about 1 μm higher than the surrounding surface, the coating 25,
The upper edge 26 is lower by about 0.5 to 1 μm than the surface height around the protrusion 23.

Therefore, in manufacturing the laser diode chip 1, the roller is pressed against the strip to divide the strip, thereby manufacturing the laser diode chip 1. At this time, even when the roller is in contact with the anode electrode 15 surface,
The surface of the roller does not come into contact with the upper end surfaces of the coatings 25 and 26 which have been lowered one step. As a result, coating damage such as peeling, chipping, and cracking of the coatings 25 and 26 due to the application of external force does not occur. Since the coatings 25 and 26 can be prevented from being damaged, the end face of the optical waveguide 22 is protected, reliability is improved, and the yield is improved. In addition, coating 2
Due to the presence of 5, 26, the forward output light and the backward output light can also maintain a predetermined light output.

Next, the specific structure of the optical element will be described. FIG. 3 is a schematic cross-sectional view of the optical device according to the first embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along line AA of FIG.

The optical element (laser diode chip) 1
As shown in FIG. 3, the ridge structure has an internal current confinement type.

The laser diode chip 1 is made of N-type GaAs
s, an N-type buffer layer 3 made of an N-type GaAs layer having a thickness of about 0.1 μm provided on a main surface (upper surface) of the compound semiconductor substrate 2, and the N-type buffer layer An N-type cladding layer 4 of N-type AlGaInP having a thickness of about 1.3 μm provided on the N-type cladding layer 3 and an active layer 5 of GaInP provided on the N-type cladding layer 4
A P-type cladding layer 6 of P-type AlGaInP having a thickness of about 0.2 μm provided on the active layer 5;
A first etch stop layer 7 of P-type GaInP having a thickness of about 0.1 μm provided on the mold cladding layer 6, and a width of about 5 μm and a thickness of about 1 μm along the center of the first etch stop layer 7. A ridge 8 made of P-type AlGaInP provided and a thickness of about 0.1 provided on an upper surface of the ridge 8.
Etch stop second layer 9 made of Pm-type GaInP 9 μm
An N-type current blocking layer 10 of about 1.0 μm thick made of N-type GaAs provided so as to cover both sides of the ridge 8 and the second etch-stop layer 9 and the first etch-stop layer 7; A P-type buried cap layer 11 of P-type GaAs covering the N-type current block layer 10 and the second etch stop layer 9 and having a thickness of about 3 μm.

Further, both sides of the laser diode chip 1 are subjected to mesa etching, and each compound semiconductor layer formed on the compound semiconductor substrate 2 is selectively removed. The etching reaches the compound semiconductor substrate 2 beyond each compound semiconductor layer. A region excluding the portion along the center of the P-type buried cap layer 11 is covered with an insulating film 12, and the exposed P-type buried cap layer 11 is provided with an anode electrode 15 made of gold. On the back surface of the compound semiconductor substrate 2, a cathode electrode 16 made of gold is provided.

This laser diode chip 1 has a width of 30
0 μm, length (depth) 700 μm, and height 100 μm.

The portion of the active layer 5 corresponds to the optical waveguide 22.
However, both ends of the optical waveguide 22 are covered with the films 25 and 26 as described above. That is, the coating 25 is provided on the front emission surface, and is an AR film (low reflectance film) 30 having a low reflectance. In addition, the coating 26
Are HR films (high reflectance films) 31 provided on the rear emission surface and having high reflectance. The AR film 30 is made of, for example, a SiO ₂ film having a thickness of about 170 nm, and has a reflectance of about 15%. The HR film 31 has, for example, a structure in which four layers of a SiO ₂ film and an a-Si film are stacked, and has a reflectivity of about 80%. The HR film 31 has a thickness of about 0.5 μm as a whole.

On the other hand, this is one of the features of the present invention. As shown in FIG. 4, the upper edge portions of both ends of the laser diode chip 1 have the uppermost P-type buried cap layer 11 of 1.5 to 1.5. The groove 35 is formed by etching at a depth of 2 μm. The groove 35 is provided over a length of about 1 μm from the end of the laser diode chip 1.

The thickness of the ridge 8 is about 1 μm, and the thickness of the second etch stop layer 9 overlapping the ridge 8 is 0.1 μm.
Since it is μm, the protruding height on the surface of the protruding ridge 23 of the P-type buried cap layer 11 grown following it is about 1 μm.

Therefore, the P-type buried cap layer 1
1 is etched by about 1.5 to 2 μm, the anode electrode 15 is formed on the upper surface of the P-type buried cap layer 11.
And the coatings 25 and 26 are formed so as to cover the end surface of the anode electrode 15.
Since the upper edge surface is at the same height as the groove bottom 13 of the groove 35, it is lower than the surface of the projecting ridge 23 as well as the surface on both sides of the projecting ridge 23 (FIG. 3 (see the groove bottom 13 by the two-dot chain line).

Next, a method of manufacturing such a laser diode chip (optical element) will be described with reference to FIGS.

First, as shown in FIG. 5, a compound semiconductor substrate 2 made of N-type GaAs having a thickness of several hundred μm is prepared.

Next, as shown in FIG. 5, a conventional MOCVD (metalorganic)
An N-type buffer layer 3 composed of an N-type GaAs layer having a thickness of about 0.1 μm and an N-type AlGaInP layer having a thickness of about 1.3 μm are formed by a chemical vapor deposition (IC) method.
-Type cladding layer 4, an active layer 5 of GaInP, a P-type cladding layer 6 of P-type AlGaInP having a thickness of about 0.2 μm, an etch stop first layer 7 of P-type GaInP having a thickness of about 0.1 μm, and a thickness of about 0.1 μm. About 1 μm P-type AlGaIn
A ridge formation layer 40 made of P and an etch stop second layer formation layer 41 made of P-type GaInP having a thickness of about 0.1 μm are sequentially formed.

A plurality of laser diodes are formed on the compound semiconductor substrate 2 vertically and horizontally as described later.
Therefore, the compound semiconductor substrate 2 in this manufacturing stage includes the wafer 45 including the compound semiconductor layer formed on the main surface side.
Will be referred to.

Next, on the main surface side of the wafer 45, a plurality of strip-shaped masks 46 having a width of about 5 μm are provided in parallel by ordinary photolithography (in FIG.
(Only the book is shown), and the etch stop second layer forming layer 41 and the ridge forming layer 40 are etched using the mask 46 as an etching mask. At this time, since the first etch stop layer 7 acts as an etching stop layer, the thickness of the ridge 8 is formed with high precision,
The formation of a laser diode with stable characteristics can be achieved.

Next, an N-type current blocking layer 10 of about 1.0 μm thick made of N-type GaAs is formed on the first etch-stop layer 7, the ridge 8, and the second etch-stop layer 9 by MOCVD. After that, the mask 46
Is removed. The N-type current blocking layer 10 covers the side surfaces of the ridge 8 and the second layer 9 of the etch stop.

Next, as shown in FIG. 8, a P-type buried cap layer 11 of P-type GaAs having a thickness of about 3 μm is formed on the N-type current block layer 10 and the second etch stop layer 9 by MOCVD. I do. This MOCVD
In the formation of the P-type buried cap layer 11 by the method,
Since the crystal growth is performed corresponding to the projecting ridges of the ridge 8 and the second layer 9 of the etch stop, the projecting crystal ridges 47 are formed. The height of the protruding crystal protrusion 47 protrudes substantially the same as the height of the ridge 8 and the second etch stop layer 9.
It is about 1 μm.

Next, as shown in FIG.
After selectively forming the mask 48 on the main surface side of the groove 5, the region mask 49 to be the end face portion of the optical waveguide is etched by, for example, wet etching to form the groove 35. The depth d of the groove 35 shown in FIGS.
It is about 5 to 2 μm. The width of the groove 35 is about 2 μm. When the wafer 45 is cut into strips, cleavage is performed along the center line of the groove 35. Therefore, after cleavage, the length of the groove 35 in the optical waveguide direction is about 1 μm.

FIG. 10 is a plan view of the wafer 45. A portion shown by a two-dot chain line is a cleavage line 50 for forming a strip, or a dividing line 51 for cutting the strip to form a single optical element (laser diode chip). Further, two dashed lines shown at narrow intervals are the optical waveguides 22. A two-dot chain line orthogonal to the optical waveguide 22 is a cleavage line 50, and a two-dot chain line parallel to the optical waveguide 22 is a dividing line 51. The hatched portion becomes the groove 35.
A region surrounded by a two-dot chain line is a portion where a single laser diode chip (optical element) is formed. Therefore, the groove 35 is provided along the cleavage line 50 and along the edge of the wafer 45 that is parallel to the cleavage line 50.

Next, as shown in FIG.
The main surface side is subjected to mesa etching along the dividing line 51, and each compound semiconductor layer formed on the compound semiconductor substrate 2 is selectively removed. The etching reaches the compound semiconductor substrate 2 beyond each compound semiconductor layer.

Next, the insulating film 12 is formed on the entire main surface side of the wafer 45. After the insulating film 12 is selectively removed by a conventional etching technique, an anode electrode 15 made of a gold-based material is formed on the P-type buried cap layer 11 corresponding to the ridge 8 by vapor deposition or the like.

Next, the back surface of the wafer 45, that is, the lower surface of the compound semiconductor substrate 2 is etched to a predetermined thickness so that the thickness of the wafer 45 is about 100 μm. To form a cathode electrode 16 made of a gold-based material by vapor deposition or the like.

Next, after the wafer 45 is cleaved along the cleavage line 50 (see FIG. 10) to produce an elongated strip, the films 25 and 26 are formed on both sides of the strip by sputtering or the like.
To form

As shown in FIG. 4, the coating film 25 is provided on the front emission surface and has an AR film having a low reflectance (low reflectance film).
It is 30. Further, the coating 26 is provided on the rear emission surface, and is an HR film (high reflectance film) 31 having a high reflectance. The AR film 30 is made of, for example, a SiO ₂ film having a thickness of about 170 nm, and has a reflectance of about 15%. The HR film 31 is made of, for example, SiO 2
_{It has} a structure in which four layers of _two films and an a-Si film are stacked,
The reflectance is about 80%. The HR film 31 has a thickness of about 0.5 μm as a whole.

The coatings 25 and 26 are formed only on the compound semiconductor substrate 2 from the base material, on each compound semiconductor layer formed on the main surface side of the compound semiconductor substrate 2, the anode electrode 15, and the side surface of the insulating film 12. Therefore, the upper surfaces of the films 25 and 26 are formed on the groove bottoms 13 of the grooves 35 provided along the cleavage lines 50.
And the height of the protruding ridge 23 and the flat surfaces on both sides of the protruding ridge 23 are respectively 1 to 1.5.
μm lower.

As a result, when the strip is cut and bonded to a resin tape when forming the laser diode chip 1 by cutting the strip, and as shown in FIG. In the work for dividing, since the upper end surfaces of the coatings 25 and 26 are located at the bottom of the groove 35 which is narrow and deeper than the groove width,
The pressing pieces, the rollers and the like do not directly contact the upper surfaces of the coating films 25 and 26, and the peeling and falling off of the coating films 25 and 26 can be prevented.

A laser diode chip (optical element) as shown in FIGS.
1 is manufactured.

This laser diode chip 1 has a width of 30
0 μm, length (depth) 700 μm, and height 100 μm.

Such a laser diode chip 1 is
Assembled in a predetermined package. For example, the laser diode chip 1 is incorporated in a can package as shown in FIG.

The optoelectronic device 70 shown in FIG. 13 includes a plate-shaped stem 71 which is a main component of the assembly and a cap 72 which is hermetically fixed to the main surface of the stem 71. The stem 71 is a circular metal plate having a thickness of several mm, and a heat sink 73 made of copper is fixed to a central portion of a main surface (upper surface) of the stem 71 with a brazing material or the like. The laser diode chip 1 is fixed to a side surface of the heat sink 73 via a submount 74. The laser diode chip 1 is fixed to the heat sink 73 via the submount 74 such that the rear emission surface faces the main surface of the stem 71. As a result, the light output of the front emission surface becomes higher than the light output of the rear emission surface.

On the other hand, a light receiving element 75 for receiving the laser light emitted from the lower end (rear emission surface) of the laser diode chip 1 and monitoring the light output of the laser light is fixed to the main surface of the stem 71. . The light receiving element 75 is fixed to an inclined surface 76 provided on the main surface of the stem 71 via a bonding material (not shown). This is because the reflected light on the light receiving surface of the light receiving element 75 of the laser light emitted from the laser diode chip 1 is prevented from entering the window of the cap 72, so that the reflected light is not emitted out of the package and the far field This is to prevent the image from being disturbed.

On the other hand, the stem 71 has three leads 7
7 is fixed. One lead 77 is electrically and mechanically fixed to the back surface of the stem 71, and the other two leads 77 penetrate the stem 71 and are electrically connected to the stem 71 via an insulator 78 such as glass. Insulated and fixed. The upper ends of the two leads 77 projecting from the main surface of the stem 71 are connected to the respective electrodes of the submount 74 and the light receiving element 75 via wires 79, respectively. The electrodes of the laser diode chip 1 and the heat sink 73 are also electrically connected by wires 79.

A metal cap 72 having a window 80 is hermetically fixed to the main surface of the stem 71 to seal the laser diode chip 1, the light receiving element 75 and the like. The window 80 of the cap 72 is made of a transparent glass plate 81.
The glass plate 81 is hermetically fixed to the cap 72 via a bonding material (not shown). The laser light emitted from the front emission surface of the laser diode chip 1 passes through the glass plate 81 and is emitted outside the package formed by the stem 71 and the cap 72.

According to the optical device 1 of Embodiment 1 and the method for manufacturing the same, the following effects can be obtained.

(1) According to the method for manufacturing an optical device of the present invention, the surface of the optical device at the end face of the optical waveguide on which the coating is formed, that is, both end portions of the protruding protrusion are one step higher than other portions. Since the height is lowered, even if a force is applied to the protruding protruding portion by a roller or the like, the roller or the like does not contact the protruding portion or the film that has become lower, so that the film covering both ends of the optical waveguide is large. No force is applied, and coating damage such as peeling, chipping, and cracks can be prevented.

(2) According to the above (1), since damage to the coating protecting the end face of the optical waveguide can be prevented, oxidation of the end face of the optical waveguide can be prevented by the coating, so that the reliability of the laser diode can be increased and the lifetime can be increased. Can be achieved.

(3) According to the above (1), damage to the coating for controlling the reflectance provided at the end face of the optical waveguide can be prevented, so that the forward emission light and the backward emission light can be set accurately, and the threshold current Characteristics such as I _th , slope efficiency η _s , and monitor current I _s can be stabilized.

For example, the threshold current failure rate and the monitor current failure rate were each reduced from several percent to 0.5% or less.

Further, the slope efficiency could be kept within a certain range.

(4) According to the above (1), the coating provided on the end face of the optical waveguide can be prevented from being damaged, so that the manufacturing yield can be improved and the manufacturing cost of the optical device can be reduced.

(5) By the above (1) to (4), it is possible to inexpensively provide an optical device which can stabilize the characteristics of the laser diode and achieve a long life.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. Needless to say, for example, in the above-described embodiment, the entire upper edges of both ends of the optical element are lowered. However, even if the end upper edges of the optical element corresponding to the end face of the optical waveguide and the periphery thereof are partially lowered, The same effects as in the embodiment can be obtained.

In the above embodiment, the optical element has a structure in which one laser diode is incorporated. For example, an optical element having a modulator for controlling the laser diode and a driver circuit for driving and controlling the laser diode are incorporated. However, the same effects as those of the above-described embodiment can be obtained in the OEIC.

Further, the laser diode is not limited to the ridge type, but may be a laser diode having a buried heterostructure in which the surface portion of the optical element on which the laser diode is formed becomes higher in a band along the optical waveguide of the laser diode. It may be.

Further, the present invention can be applied to a laser diode having a flat structure in which a part of the surface of the optical element is not raised, as a technique for preventing the coating covering the end face of the optical waveguide from peeling off.

[0081]

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, in the laser diode chip, the height of the upper surface of the coating covering the end face of the optical waveguide is lower than the other height of the surface of the laser diode chip. In handling and manufacturing the diode chip, external force is less likely to be applied to the coating, and damage such as peeling or falling off of the coating does not occur. As a result, since the end face of the optical waveguide can be protected, the reliability and the life of the laser diode are increased.

(2) Further, since damage to the coating provided on the end face of the optical waveguide does not occur, the forward emission light and the backward emission light of the laser diode can be controlled with high accuracy, and the laser having excellent characteristics can be obtained. A diode can be provided.

(3) Since the coating provided on the end face of the optical waveguide is less likely to be damaged, the manufacturing cost of the optical device can be reduced.

(4) Since the coating provided on the end face of the optical waveguide is less likely to be damaged, the reliability of the bonding of the optical element can be increased, and the manufacturing cost of the optoelectronic device incorporating the optical element can be reduced. Can also be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an optical element (laser diode chip) according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the optical device according to the first embodiment.

FIG. 3 is a schematic cross-sectional view of the optical element according to the first embodiment.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a schematic cross-sectional view showing a state in which a multi-layer growth layer is formed on the main surface of the compound semiconductor substrate in the method for manufacturing an optical device according to the first embodiment.

FIG. 6 is a schematic cross-sectional view showing a state in which a ridge is formed in the method for manufacturing an optical element according to the first embodiment.

FIG. 7 is a schematic cross-sectional view showing a state where current blocking layers are formed on both sides of the ridge in the method for manufacturing an optical device according to the first embodiment.

FIG. 8 is a schematic cross-sectional view showing a state in which a P-type buried cap layer is formed in the method for manufacturing an optical element of the first embodiment.

FIG. 9 is a schematic cross-sectional view showing a state in which a groove is formed along a cleavage line in the method for manufacturing an optical element of the first embodiment.

FIG. 10 is a schematic plan view showing a state of a wafer in which a groove is formed along a cleavage line in the method for manufacturing an optical element of the first embodiment.

FIG. 11 is a schematic cross-sectional view showing a state in which an anode electrode is formed in the method for manufacturing an optical element according to the first embodiment.

FIG. 12 is a schematic cross-sectional view showing a strip formed by cleaving a wafer in the method of manufacturing an optical element according to the first embodiment.

FIG. 13 is a perspective view of the optoelectronic device incorporating the optical element of the first embodiment, with a part thereof being cut away.

FIG. 14 is a schematic perspective view showing an outline of a conventional ridge-type laser diode.

FIG. 15 is a partial schematic cross-sectional view showing a peeled state of an end face film in a conventional ridge type laser diode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical element (laser diode chip), 2 ... Compound semiconductor substrate, 3 ... N-type buffer layer, 4 ... N-type cladding layer,
5 Active layer, 6 P-type cladding layer, 7 Etch stop first layer, 8 Ridge, 9 Etch stop second layer, 10
... N-type current blocking layer, 11 ... P-type buried cap layer,
12: insulating film, 13: groove bottom, 15: anode electrode, 16
... Cathode electrode, 20 ... Ridge, 21 ... Light emitting part, 22
... optical waveguide, 23 ... protruding ridge, 24 ... chipped piece, 2
5, 26 coating, 30 AR film, 31 HR film, 35
Groove, 40: Ridge forming layer, 41: Etch stop second layer forming layer, 45: Wafer, 46: Mask, 47: Projecting crystal ridge, 48: Mask, 50: Cleavage line, 51: Break line, 60 ... Strips, 70 ... Optoelectronic devices, 71 ... Stems,
72: cap, 73: heat sink, 74: submount, 75: light receiving element, 76: inclined surface, 77: lead,
78: insulator, 79: wire, 80: window, 81: glass plate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideo Taguchi 5-2-1, Josuihonmachi, Kodaira-shi, Tokyo Inside Semiconductor Division, Hitachi, Ltd. 20-1 chome Semiconductor Division, Hitachi, Ltd.

Claims (6)

[Claims] 1. An optical element in which a laser diode is monolithically incorporated, wherein the end face of an optical waveguide of the laser diode is covered with a coating, and the end face of the optical waveguide on which the coating is formed. An optical element characterized in that a part of the optical element surface is one step lower than other optical element surface parts. 2. The optical device according to claim 1, wherein the surface portion of the optical device over the entire end face of the optical waveguide on which the coating is formed is one step lower than the surface portions of the other optical devices. 3. The optical device according to claim 1, wherein one end face of the optical waveguide is covered with a low reflectivity film, and the other end face is covered with a high reflectivity film. 4. The optical device according to claim 1, wherein a surface portion of the optical element on which the laser diode is formed is formed in a strip along the optical waveguide of the laser diode. An optical element as described in the above. 5. A step of forming a predetermined compound semiconductor layer on the main surface side of the compound semiconductor substrate to form a plurality of laser diodes and the like in a matrix, and forming predetermined electrodes on the main surface and the back surface of the compound semiconductor substrate. Performing the step of cleaving the compound semiconductor substrate along a direction orthogonal to the optical waveguide of the laser diode to form a strip; and forming the optical element including the laser diode by dividing the strip. And forming a coating on an exposed end face of the optical waveguide in a state of the strip or the optical element, wherein a laser diode or the like is formed on the compound semiconductor substrate. After that, the main surface side surface of the compound semiconductor substrate is selectively etched so that the film forming portion is lower than the main surface of the compound semiconductor substrate, and then the electrode is formed. A method for manufacturing an optical element, comprising: 6. The method of manufacturing an optical device according to claim 5, wherein a main surface side surface portion of the compound semiconductor substrate corresponding to the optical waveguide is higher than another main surface side surface portion.