JP3976875B2 - Semiconductor laser device and mounting method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser element that can be precisely mounted in a non-light emitting state and a mounting method thereof.
[0002]
[Prior art]
The alignment accuracy required when optically coupling light emitted from a semiconductor laser element (hereinafter referred to as LD) with an optical waveguide, for example, an optical fiber, is about ± 1 μm in the direction perpendicular to the optical axis. In order to ensure this accuracy, conventionally, as shown in FIG. 6, the LD 101 is oscillated after being mounted on the mounting substrate 103 so that the light emitting surface 101a is perpendicular to the mounting substrate 103 surface. A method (active alignment method) has been employed in which the optical fiber 102 is aligned while monitoring the output, and the optical fiber 102 is fixed at a position where a desired light output can be obtained.
[0003]
By the way, the demand for optical modules is expected to increase in the future, and there is a demand for cost reduction and mass production of optical modules. As a method for mounting the LD at that time, a passive alignment method in which precise alignment is performed without oscillating the LD is considered to be effective, and development is being promoted in various directions.
As a conventional passive alignment method, for example, as shown in FIG. 7, the alignment markers 104 and 105 processed on the light emitting surface 101 a and the surface of the mounting substrate 103 with the light emitting surface 101 a of the LD 101 facing downward are mounted on the mounting substrate. A method is generally used in which the LD 101 and the mounting substrate 103 are aligned by observing using the light 106 having a wavelength that transmits both the material forming 103 and the LD 101. The mounting substrate 103 is mainly made of Si from the viewpoint of processability and cost, and the light used as transmitted light is infrared light having a wavelength of 1.1 μm or more.
[0004]
[Problems to be solved by the invention]
In order to mount the LD with high accuracy by the passive alignment method, it is necessary that the LD and the alignment marker on the mounting substrate are processed with submicron positional accuracy. A conventional marker on an LD is formed by aligning a photomask on the surface of a semiconductor layer stacked on a semiconductor substrate, and forming a photoresist film at a position where a marker is to be formed with respect to a light emitting portion. After the electrode pattern was formed, the portion where the electrode pattern was removed by the lift-off of the electrode pattern (where the photoresist film was present) was used as a marker.
However, this method has a limit in accuracy when aligning the photomask with the LD surface, and it is difficult to accurately position the marker with respect to the light emitting portion. Further, when a rectangular marker is used and the marker length is shorter than the element length of the LD, there is a problem that the accuracy of the setting angle of the mounting substrate with respect to the optical axis of the LD is lowered.
[0005]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 is provided in a stripe-like light emitting part and at a predetermined distance from the light emitting part and parallel to the light emitting part. The LD has a stripe-shaped V-groove, and a metal film is formed on a surface including the V-groove.
[0006]
According to a second aspect of the present invention, there is provided a stripe-shaped light-emitting portion and a stripe-shaped V-groove provided at a predetermined distance from the light-emitting portion and parallel to the light-emitting portion. An LD mounting method for mounting an LD having a metal film formed on a surface thereof on a mounting substrate having a stripe-shaped alignment marker, wherein the alignment marker on the mounting substrate is a pattern on the surface of the mounting substrate. A stripe-shaped portion surrounded by a metal film that has a width wider than the V-groove, and the surface having the V-groove of the LD is opposed to the surface having the alignment marker on the mounting substrate. The light passing through the mounting substrate is incident from the back surface of the substrate, and the V groove and the alignment marker are aligned using the difference in the amount of reflected light from the surface of the LD having the V groove. .
As described above, since the present invention uses the difference in the amount of reflected light on the surface of the LD having the V-groove, the shape of the groove does not have to be strictly V-shaped, and has a shape that produces a difference in the amount of reflected light. I just need it.
[0007]
When light is applied perpendicularly to the metal film on the surface of the LD according to claim 1, the light strikes the side wall obliquely in the V-groove, and the amount of reflected light in the direction perpendicular to the surface of the LD is lower than in other parts. Equivalently, the reflectance is lower than the other parts. Accordingly, contrast of light and dark is applied to the LD surface, and the V-groove portion becomes relatively dark, so that the position of the V-groove can be recognized.
Note that an LD in which a stripe-shaped V-groove parallel to the light-emitting portion is accurately formed at a predetermined distance from the stripe-shaped light-emitting portion can be realized by the invention of the already-filed application (Japanese Patent Application No. 5). -212337). That is, when forming the light emitting portion by forming the active layer in a stripe shape, the active layer is simultaneously formed in a stripe shape at a predetermined interval to provide a stripe active layer that becomes a non-light emitting portion, The stripe-shaped active layer portion other than the stripe-shaped active layer portion is filled with a semiconductor layer having a refractive index lower than that of the active layer, and a stripe-shaped V-groove is provided above the stripe-shaped active layer portion serving as a non-light emitting portion.
[0008]
The invention according to claim 2 utilizes the above-described characteristics of the LD according to claim 1. That is, when light that passes through the mounting substrate is incident from the back surface of the mounting substrate, the light is transmitted through the alignment marker portion of the mounting substrate, is incident on the surface of the LD, and is reflected there. By recognizing the relative positional relationship between the V-groove and the alignment marker by this reflected light, the V-groove and the alignment marker can be aligned. Therefore, according to the present invention, the LD can be accurately and easily positioned on the mounting substrate by the passive alignment method. Note that if the V-groove is formed to be sufficiently long with respect to the element length in the optical axis direction of the LD, for example, to reach both ends of the element, the accuracy of the mounting angle of the mounting substrate with respect to the optical axis of the LD can be improved. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIGS. 1A to 1E are explanatory diagrams of a manufacturing process of an embodiment of an LD 300 according to the present invention. The process is as follows. That is,
1) On the p-InP substrate 301, an InGaAsP active layer 302 and an n-InP clad layer 303 are sequentially laminated. Next, stripe-shaped dielectric masks 311 and 312 having a width of 1.5 μm are formed at a predetermined interval (for example, 100 μm), and active layers 302a and 302b and n-InP cladding layers 303a and 303b are formed in a mesa stripe shape by etching. (FIG. 1A).
The dielectric masks 311 and 312 can be formed at a precise interval at a time by masking.
2) Next, using the dielectric masks 311 and 312 as selective growth masks, a p-InP buried layer 304, an n-InP buried layer 305, and a p-InP buried layer 306 are sequentially stacked to form a p / n / p buried layer. Form. At this time, the buried layer does not grow on the dielectric masks 311 and 312 (FIG. 1B).
3) A resist mask 313 is formed so as to cover the dielectric mask 312 (FIG. 1C).
4) Next, after removing the dielectric mask 311 using the resist mask 313, the resist mask 313 is removed. The dielectric mask 312 remains.
5) Next, an n-InP cladding layer 307 and an n-InGaAsP cap layer 308 are grown. Then, the n-InP cladding layer 307 and the n-InGaAsP cap layer 308 are stacked on the upper surface of the active layer 302a serving as the light emitting portion, but do not grow on the upper surface of the active layer 302b. Therefore, a striped V-shaped groove 314 is formed on the upper surface of the active layer 302b (FIG. 1D). The V groove 314 is used as a marker.
6) Finally, metal films 309, 310 (for example, Cr, Ti, Pt, Ni, Au) for the p electrode and the n electrode are formed on the surface including the V groove 314 (FIG. 1 (e)).
[0010]
When light is applied perpendicularly to the surface of the LD 300 manufactured in this way, the reflected light in the vertical direction from the surface becomes weaker in the V groove 314 portion than in other portions, and the position of the V groove 314 is optically recognized. can do.
As the metal film 310 becomes thicker, the shape of the edge of the V-groove 314 falls and the position accuracy for optically recognizing the V-groove 314 decreases. In order to prevent this, it is preferable to make the thickness of the metal film 310 on the V groove 314 thinner than the periphery. For example, a thin metal film of several hundreds of millimeters is formed on the entire surface of the LD, and then a thick metal film of about 1 μm is formed except on the V groove 314.
[0011]
Next, the mounting substrate will be described.
FIG. 2 is a side view of the mounting substrate 600. The mounting substrate 600 is patterned on the Si substrate 601 with a photoresist 602 (FIG. 2 (a)), and after depositing a metal film 603 for electrodes, the photoresist 602 is removed and placed at a desired position. A stripe-shaped marker 604 having a width of 20 μm (a portion where the Si substrate 601 is partially exposed) is formed (FIG. 2B). Reference numeral 601a denotes an oxide film (SiO ₂ ) formed on the surface of the Si substrate 601.
When a V-groove for positioning an optical fiber is formed on the mounting substrate 600, it can be formed by cutting at a desired distance with the center of the marker 604 as a reference. Further, the oxide film 601a in the region for forming the optical fiber positioning V-groove is removed by patterning with a mask and performing dry etching such as RIE using C ₂ F ₆ as a reactive gas or wet etching with hydrofluoric acid. Thereafter, when immersed in an aqueous potassium hydroxide solution, only the portion from which the oxide film 601a has been removed is anisotropically etched, and a V-groove having a slope angle of 54.7 ° can be formed.
[0012]
Next, a method for aligning the LD 300 and the mounting substrate 600 will be described with reference to FIGS. The method is as follows. That is,
1) First, the LD 300 is held by the holder 701 with the light emitting surface facing down, and is moved by the controller 705 onto the mounting substrate 600 placed on the XY stage 702 that moves on the plane.
Next, the holder 701 is lowered and brought closer until the distance between the surface of the LD 300 and the surface of the mounting substrate 600 reaches about 20 μm. This distance is a distance that allows focusing on both the mounting substrate 600 and the LD 300 when observing at a magnification of about 50 times, and avoiding contact between the LD 300 and the mounting substrate 600.
In the present embodiment, the size of the LD 300 is 250 width × length 300 × 80 μm height. The stripe-shaped V groove 314 serving as a marker of the LD 300 has a width of 10 μm and a depth of 7 μm, and is formed at a position 100 μm away from the active layer 302a serving as a light emitting portion.
The marker 604 on the mounting substrate 600 side is a metal extraction pattern with a width of 20 μm.
[0013]
2) Next, when observed with the infrared microscope 703 from the lower side of the mounting substrate 600, the following images are observed.
Infrared light passes through a portion of the marker 604 formed on the mounting substrate 600, is reflected by the metal film 310 on the surface of the LD 300, and returns. As shown in FIG. 3B, the image obtained by the infrared microscope 703 includes a reflection image 603a of the metal film 603 of the mounting substrate 600, a reflection image 314a of the V groove 314 of the LD300, and a metal film 310 around the V groove 314. The reflection image 310a. These reflected images 603a, 314a and 310a have a contrast of light and dark, and the reflected image 314a is darker than the reflected image 310a.
Here, the reflected images 603a, 314a and 310a obtained by the infrared microscope 703 are input to the image processing device 704, and the reflected images 314a and 310a of the reflected images 314a and 310a are calculated from changes in the illuminance of the image (for example, by calculating a spatial differential value of illuminance). Detect the position of both ends. Then, the controller 705 moves the X / Y stage 702 in a plane so that the shift amount of the center point of the width of the reflected images 314a and 310a is minimized, thereby aligning the LD 300 and the mounting substrate 600. At this time, the angle is adjusted by rotating the θ stage 706 so that the shift amount of the center line is minimized at both ends of the LD 300 in the optical axis direction.
[0014]
3) Next, the holder 701 is lowered to apply a desired excessive weight to the LD 300, and the solder thin film 708 formed on the metal film 603 of the mounting substrate 600 is melted by heating with the heater 707, and the LD 300 and the mounting substrate 600 are joined. To do.
The solder thin film 708 may be formed on the LD 300 side. Also, as this solder thin film 708, Au and Sn were alternately stacked several hundreds of A at a weight ratio of Au: Sn = 80: 20, and the total thickness was about 2 μm. A good bond was formed.
[0015]
(Embodiment 2)
FIG. 4 is an explanatory diagram of an alignment process of another embodiment of the LD mounting method according to the present invention.
In this embodiment, V grooves 605 covered with a metal film 603 are formed on both sides of the marker 604 of the mounting substrate 600 in the first embodiment.
When observed with the infrared microscope from the lower side of the mounting substrate 600, the images obtained by the infrared microscope are the reflection image 603a of the metal film 603 of the mounting substrate 600, the reflection image 605a of the V groove 605, and the reflection of the V groove 314 of the LD 300. The image 314a and the reflection image 310a of the metal film 310 around the V groove 314 are formed. These reflected images 603a, 605a, 314a and 310a have a contrast of light and dark, and the reflected images 314a and 605a are darker than the reflected images 310a and 603a. In the present embodiment, the LD 300 and the mounting substrate 600 are aligned based on the positional relationship between the reflected images 314a and 605a.
In the present embodiment, the reflected image 605a of the V-groove 605 can be recognized with better contrast than the marker 604 region, so that the alignment accuracy and workability are improved as compared with the first embodiment. Note that the V groove 605 formed by etching by masking has higher positional accuracy than the marker 604 formed by the lift-off method, which also contributes to improved alignment accuracy.
[0016]
(Embodiment 3)
FIG. 5 is an explanatory diagram of an alignment process of still another embodiment of the LD mounting method according to the present invention.
In this embodiment, the V groove 605 is exposed without forming the metal film 603 on the V groove 605 of the mounting substrate 600 in the second embodiment. Forming the metal film 603 serving as an electrode pattern on the V-groove 605 complicates the process, but this embodiment is not necessary and simplifies the process.
When observed with an infrared microscope from the lower side of the mounting substrate 600, the images obtained with the infrared microscope are the reflected image 605a of the V-groove 605 of the mounting substrate 600, the reflected image 314a of the V-groove 314 of the LD300, and the periphery of the V-groove 314. It consists of a reflection image 310a of the metal film 310. The reflected image 605a does not reflect from the metal film 603 and thus is not as clear as the second embodiment, but appears to be raised by the reflected light from the metal film 310 of the LD300.
[0017]
【The invention's effect】
When the LD according to claim 1 is used and the LD is mounted on the mounting substrate by the method according to claim 2, it is possible to accurately and easily position the LD on the mounting substrate by a passive alignment method. effective.
[Brief description of the drawings]
FIGS. 1A to 1E are explanatory views of a manufacturing process of an embodiment of an LD according to the present invention.
FIGS. 2A and 2B are explanatory views of a manufacturing process of a mounting substrate used in an embodiment of an LD mounting method according to the present invention. FIGS.
FIGS. 3A and 3B are an explanatory diagram of a mounting system and an explanatory diagram of an alignment process, respectively, used in an embodiment of an LD mounting method according to the present invention.
FIG. 4 is an explanatory diagram of an alignment process of another embodiment of the LD mounting method according to the present invention.
FIG. 5 is an explanatory diagram of an alignment process of still another embodiment of the LD mounting method according to the present invention.
FIG. 6 is an explanatory diagram of a mounting method using a conventional active alignment method.
FIG. 7 is an explanatory diagram of a mounting method using a conventional passive alignment method.
[Explanation of symbols]
300: LD
301: p-InP substrate
302, 302a, 302b: active layer,
303, 303a, 303b, 307: n-InP clad layer
304, 306: p-InP buried layer,
305: n-InP buried layer,
308: cap layer,
309, 310: Metal film
310a, 314a, 603a, 605a: Reflected image
311, 312: Dielectric mask,
313: resist mask,
314, 605: V groove
600: Mounting board
601: Si substrate
601a: Oxide film
602: Resist mask
603: Metal film
604: Marker
701: Retaining tool
702: XY stage
703: Infrared microscope
704: Image processing apparatus
705: Controller
706: θ stage
707: Heater
708: Solder thin film

Claims (4)

And stripe-shaped light-emitting portion, provided at a predetermined distance away from said light emitting portion has a parallel stripe V-grooves to the light emitting portion, and a metal film is formed on the surface including the V-groove The metal film has a thickness in a portion on the V-groove smaller than a thickness in a peripheral portion of the V-groove .   A stripe-shaped light emitting portion and a stripe-shaped V-groove that is provided at a predetermined distance from the light-emitting portion and is parallel to the light-emitting portion, and a metal film is formed on the surface including the V-groove A semiconductor laser device mounting method for mounting a semiconductor laser device on a mounting substrate having a stripe-shaped alignment marker, wherein the mounting substrate alignment marker is surrounded by a patterned metal film on the surface of the mounting substrate. The striped portion having a width wider than the V-groove, the surface having the V-groove of the semiconductor laser element and the surface having the alignment marker on the mounting substrate are made to face each other, and from the back surface of the mounting substrate The semiconductor laser is characterized in that light transmitted through the mounting substrate is incident and the V groove and the alignment marker are aligned using the difference in the amount of reflected light from the surface of the semiconductor laser element having the V groove. Implementation method for the device.   3. The mounting substrate alignment marker includes the stripe-shaped portion surrounded by a patterned metal film on the surface of the mounting substrate, and a V-groove having the metal film formed on the surface. Mounting method of the semiconductor laser device.   3. The method of mounting a semiconductor laser device according to claim 2, wherein the alignment marker for the mounting substrate comprises the stripe-shaped portion surrounded by a patterned metal film on the surface of the mounting substrate and a V-groove.

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