JPH07210893A - Semiconductor beam splitter and its production - Google Patents

Abstract

PURPOSE:To obtain a high precision small-sized beam splitter by forming a unidirectional masking on a semiconductor substrate, growing a crystal of a material having a specified band gap, and applying a dielectric multilayer coating film on slopes of the crystal. CONSTITUTION:A unidirectional mask 11 is formed on a semiconductor substrate 10. The mask 11 is used to selectively crystallize a material having a larger band gap than the wavelength of the semiconductor laser used as a light source. Thus, a chavron semiconductor crystal is formed in the direction of the mask 11. By coating the slopes of the crystal 12 with a dielectric multilayer film 13, the slopes become a semi-transmitting plane and a high precision small-size semiconductor beam splitter is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam splitter for splitting an optical path used in an optical pickup and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a beam splitter is often used as a splitting optical system in an optical pickup or the like. This beam splitter is constructed by bonding two flat surfaces of optical glass via a thin film made of plastic or the like.

According to the beam splitter having such a structure, the thin film interposed between the optical glasses acts as a semi-transmissive surface so that the light beam incident on one of the optical glasses reaches this thin film. The incident light beam partially passes through the thin film and is partially reflected by the thin film. Thus, it is divided into two light beams, a transmitted light beam and a reflected light beam.

[0004]

However, in the beam splitter configured as described above, downsizing is demanded along with downsizing of an optical pickup or the like in which the beam splitter is to be incorporated. However, due to its structure, There are limits to miniaturization.

Therefore, since the optical path length of the optical pickup and the like becomes relatively long, the light amount loss on the way becomes relatively large. On the other hand, in order to suppress the light amount loss, it is necessary to make each optical element large in order to increase the transmitted light amount, which causes a contradiction. Further, there is a problem that the manufacturing cost becomes high in response to the miniaturization.

Further, when mounting the miniaturized beam splitter on an optical pickup or the like, a predetermined mounting precision is required, and therefore a high level of technique is required for the mounting work, resulting in a high assembly cost. There was also the problem of being lost.

In view of the above points, the present invention has an object to provide a semiconductor beam splitter and a method of manufacturing the same which are configured with high precision and small size.

[0008]

According to the present invention, the above object is to provide a material having a band gap larger than the wavelength of a semiconductor laser used as a light source, which is masked in one direction on a semiconductor substrate. By growing a crystal, a semiconductor crystal extending in the mask direction is formed,
This is achieved by a method for manufacturing a semiconductor beam splitter, which is characterized in that the slope of this semiconductor crystal is coated with a dielectric multilayer film to make this slope a semi-transmissive surface.

Further, according to the present invention, the above object is made of a material having a band gap larger than the wavelength of a semiconductor laser used as a light source, which is selectively crystal-grown on a semiconductor substrate by a unidirectional mask. The present invention is achieved by a semiconductor beam splitter, which comprises a mountain-shaped semiconductor crystal extending in the mask direction and a dielectric multilayer film coated on the slope of the mountain-shaped semiconductor crystal.

The semiconductor beam splitter according to the present invention is
Preferably, a semiconductor laser is formed on the semiconductor substrate in the vicinity of the chevron-shaped semiconductor crystal.

In the semiconductor beam splitter according to the present invention, preferably, a photodetector is formed on the semiconductor substrate, and the chevron-shaped semiconductor crystal is formed thereon.

[0012]

According to the above structure, the semiconductor beam splitter is formed of the semiconductor crystal selectively grown on the semiconductor substrate by the mask extending in the [001] direction. For this reason, for example, when a (110) crystal plane is generated from the edge portion on one side of the mask, the crystal growth rate is slow on the (110) crystal plane, so that an angle of 45 degrees is formed with respect to this substrate. The (110) crystal plane is accurately formed. Regarding the edge portion on the other side of the mask, similarly, a (1-10) crystal plane is formed. Thus, a chevron-shaped semiconductor crystal having slopes formed on both sides of the substrate at an angle of 45 degrees is formed.

Here, this chevron-shaped semiconductor crystal is made of a material having a band gap larger than the wavelength of the semiconductor laser used as the light source, as described above. For example, when the emission wavelength of the semiconductor laser is 780 nm, the energy is about 1.59 eV, and therefore the Al 0.35 having a band gap equal to or larger than this energy is used.
Ga0.65As (Eg = 1.83 eV) is used as a material for the semiconductor crystal, and the atmospheric pressure MOCVD method or the reduced pressure MO is used.
It is epitaxially grown by the CVD method or the like.

The slope of the mountain-shaped semiconductor crystal thus formed, that is, the (110) crystal plane is transparent to the light beam from the semiconductor laser which is the light source.
The dielectric multilayer is coated to obtain the desired spectral ratio. As a result, the sloped surface is configured as a semi-transmissive surface.

When a semiconductor laser is formed on the semiconductor substrate in the vicinity of the mountain-shaped semiconductor crystal, the semiconductor laser and the semiconductor beam splitter are
Since they are integrally formed on the semiconductor substrate, they need not be aligned with each other during assembly. Therefore,
Assembling can be easily performed, and mounting accuracy is improved.

When the photodetector is formed on the semiconductor substrate and the chevron-shaped semiconductor crystal is formed on the photodetector, the intensity of light incident on the semiconductor beam splitter can be easily adjusted. In addition to being monitorable, the photo-detecting element for monitoring does not require any mounting space.

Here, as the light detecting element, for example, a photodiode or a phototransistor is used. In any case, it can be easily formed by selectively growing a thin film on a semiconductor substrate, but especially in the case of a photodiode, it can be formed at low cost because of its simple structure. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to FIGS. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

1 to 5 show a first embodiment of a method of manufacturing a semiconductor beam splitter according to the present invention in the order of steps. In FIG. 1, a mask 11 made of SiO2 or the like extending in one direction is formed on the surface of the semiconductor substrate 10 made of GaAs or the like, which is the (100) plane. In the illustrated case, the mask 11 extends in the [001] direction (front side of the drawing).

Next, as shown in FIG. 2, this mask 11 is used.
From above, a material having a bandgap larger than the wavelength of the semiconductor laser used as a light source, for example, in the case where the emission wavelength of the semiconductor laser is 780 nm, it has a bandgap of this energy or more, Al0.35Ga
0.65 As (Eg = 1.83 eV) is epitaxially grown by a normal pressure MOCVD method or a low pressure MOCVD method.

As a result, on the semiconductor substrate 10,
The semiconductor crystal 12 having (110) and (1-10) crystal planes extending at an angle of 45 degrees from both edges of the mask 11 is naturally formed.

Subsequently, as shown in FIG. 3, the surface of the semiconductor crystal 12 formed as described above is coated with a dielectric multilayer film 13 in order to obtain a desired spectral ratio. Thus, the semiconductor beam splitter 14 is completed.

In this case, the semiconductor beam splitter 14
Will have its slope formed by the (110) crystal face and the (1-10) crystal face. As a result, the sloped surface is accurately aligned with the (100) surface of the semiconductor substrate 10 with an accuracy on the order of the crystal level of the semiconductor.
While being formed at 5 degrees, the spectral angle is the direction of the crystal axis,
That is, it is determined in the [001] direction (direction before the paper surface). Therefore, a compact and highly accurate beam splitter can be easily obtained at low cost.

Here, as shown in FIG. 4, the semiconductor substrate 1
After removing the mask 11 from above 0, electrodes are formed in the laser mount portion on the semiconductor substrate 10 in the vicinity of the semiconductor beam splitter 14, and the laser diode 15 which is a semiconductor laser is mounted thereon.

Alternatively, as shown in FIG. 5, in the vicinity of the semiconductor beam splitter 14, from above the mask 11,
A laser diode 17 mounted on a Si pedestal 16 having electrodes formed thereon is mounted on the semiconductor substrate 1.

In either case, the beam splitter 14 and the laser diode 15 or 17 as a light source are integrally formed on the semiconductor substrate 10. Therefore, the distance between the laser diodes 15 and 17 and the beam splitter 14 is set to be extremely short, so that the entire optical system is made compact, the optical path length is shortened, and the loss is reduced.

6 to 10 show a second embodiment of the method of manufacturing a semiconductor beam splitter according to the present invention in the order of steps. In FIG. 6, a N-AlG layer is formed on the (100) surface of the semiconductor substrate 20 made of GaAs or the like.
The aAs layer 21, the active layer 22, and the P-AlGaAs layer 23 are sequentially epitaxially grown.

After that, as shown in FIG. 7, the cavity facet 24 of the semiconductor laser is formed by performing an etching process by the RIE method or the like.

Subsequently, as shown in FIG. 8, a semiconductor laser 26 is formed on the semiconductor substrate 20 by forming a dielectric multilayer protective film 25 on the cavity facet 24 of the semiconductor laser.

Next, as shown in FIG. 9, a material having a band gap larger than the wavelength of the semiconductor laser used as the light source, for example, the emission wavelength of the semiconductor laser is 7
In the case of 80 nm, Al0.35Ga0.65As (Eg = 1.83) having a bandgap of this energy or more.
eV) is epitaxially grown by a normal pressure MOCVD method or a low pressure MOCVD method. As a result, on the semiconductor substrate 20, 4 from the side edge of the semiconductor laser 26.
The semiconductor crystal 27 having a crystal plane extending to form an angle of 5 degrees is naturally formed.

Then, as shown in FIG. 10, a dielectric multilayer film 28 is coated on the surface of the semiconductor crystal 27 formed as described above in order to obtain a desired spectral ratio, and a semiconductor laser is applied. An electrode 29 is formed on top of 26.

Thus, the semiconductor laser 26 and the semiconductor beam splitter 30 are integrally formed on the semiconductor substrate 20.

In this case, the semiconductor beam splitter 30
Will have its slope formed by the (110) crystal face and the (1-10) crystal face. As a result, the sloped surface is accurately aligned with the (100) surface of the semiconductor substrate 10 with an accuracy on the order of the crystal level of the semiconductor.
While being formed at 5 degrees, the spectral angle is the direction of the crystal axis,
That is, it is decided in the [001] direction.

Therefore, a compact and highly accurate beam splitter can be obtained easily and at low cost. Furthermore, since the semiconductor laser 26 and the semiconductor beam splitter 30 are integrally formed in the vicinity of each other,
The entire optical system is downsized and the optical path length is shortened,
Further, the mounting accuracy of the semiconductor laser 26 can be easily improved without requiring high technology.

FIG. 11 shows another embodiment of the semiconductor beam splitter according to the present invention. That is, in FIG. 11, the photodiode 41 is previously formed as a photodetector by doping P + on the N-GaAs substrate 40. On the surface of the semiconductor substrate 40 provided with such a photodiode 41, as shown in, for example, FIGS. 1 to 4, a portion other than the light receiving portion of the photodiode 41 is masked with SiO 2 or the like, and a semiconductor material is placed on the mask. The beam-splitter 42 is formed by forming a mountain-shaped semiconductor crystal by epitaxial growth, and coating the dielectric multilayer film on the slope.

Further, an electrode is formed in the laser mount portion on the semiconductor substrate 40 in the vicinity of the beam splitter 42, and a laser diode 43 which is a semiconductor laser is mounted thereon.

According to the semiconductor beam splitter 42 having such a structure, most of the laser light emitted from the laser diode 43 is reflected by the left slope of the semiconductor beam splitter 42, and only a small part thereof is reflected. The light enters the semiconductor beam splitter 42 and is reflected on the inside of the slope on the right side. As a result, the light is incident on the light receiving portion of the photodiode 41 formed on the surface of the semiconductor substrate 40. Thus, the output of the laser diode 43 can be monitored based on the output signal of the photodiode 41, and the output of the laser diode 43 can be made constant by sending the output signal to a control circuit (not shown). It becomes possible to hold.

FIG. 12 shows still another embodiment of the semiconductor beam splitter according to the present invention. In this embodiment, a plurality of semiconductor beam splitters 51 and 52 extending in the [001] direction are formed on a semiconductor substrate 50. As a result, the laser light emitted from the laser diode 53 mounted closely on the semiconductor substrate 50 is reflected upward by the slopes 51a and 52a of the semiconductor beam splitters 51 and 52. Therefore, from the laser light from one laser diode 53, two upward light beams can be obtained.

As described above, in the above embodiments, the semiconductor beam splitter is formed of the semiconductor crystal selectively grown on the semiconductor substrate by the mask extending in one direction. Are formed with an accuracy of the order of the crystal level of the semiconductor so as to form an angle of 45 degrees with respect to the surface of the semiconductor substrate.

Therefore, in addition to being downsized,
The accuracy is easily improved without requiring advanced technology. Thus, a low cost and high precision beam splitter can be obtained. As a result, the optical path length in the beam splitter is significantly shortened, so that the loss of light quantity is reduced and various optical systems in which the present beam splitter is to be incorporated are made compact as a whole.

When a semiconductor laser such as a laser diode is mounted in proximity to the semiconductor beam splitter on the semiconductor substrate on which the semiconductor beam splitter is formed, the semiconductor laser and the semiconductor beam splitter are Since the interval of can be extremely small, the optical system can be further miniaturized. Since the semiconductor laser and the semiconductor beam splitter are integrally formed on the semiconductor substrate, the mutual mounting accuracy of these is improved.

Further, when the photodetector is formed on the semiconductor substrate and the semiconductor beam splitter is formed on the photodetector, the photodetector for monitoring the output of the semiconductor laser is provided. Since it is formed integrally with the beam splitter, the entire optical system including the photodetector is made compact.

In the above-described embodiments, the case of the beam splitter disposed adjacent to the light source of the optical pickup has been described, but the present invention is not limited to this, and the present invention can be applied to various optical systems including a splitting optical system. It is obvious that the semiconductor beam splitter according to

[0044]

As described above, according to the present invention, it is possible to provide a semiconductor beam splitter having a high optical accuracy and a small size, and a manufacturing method thereof.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a state in which a mask is formed on a semiconductor substrate in a first embodiment of a method of manufacturing a semiconductor beam splitter according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a state in which a semiconductor crystal is formed on a mask on the semiconductor substrate of FIG.

3 is a schematic cross-sectional view showing a semiconductor beam splitter in which a dielectric multilayer film is formed on the surface of the semiconductor crystal of FIG.

FIG. 4 is a schematic cross-sectional view showing a structure in which a laser diode is directly mounted on a semiconductor substrate in the vicinity of the semiconductor beam splitter shown in FIG.

5 is a schematic cross-sectional view showing a configuration in which a laser diode is mounted on a semiconductor substrate via a Si pedestal in the vicinity of the semiconductor beam splitter of FIG.

FIG. 6 is a schematic cross-sectional view showing a state in which a thin film constituting a laser diode is formed on a semiconductor substrate in a second embodiment of the method of manufacturing a semiconductor beam splitter according to the present invention.

7 is a schematic cross-sectional view showing a state in which a resonator end face is formed on the thin film of FIG.

8 is a schematic cross-sectional view showing a laser diode in which a dielectric multilayer film is formed on the end face of the resonator of FIG.

9 is a schematic cross-sectional view showing a state in which a semiconductor crystal is formed on the semiconductor substrate of FIG. 8 from above the laser diode.

10 is a schematic cross-sectional view showing a state in which a dielectric multilayer film is formed on the surface of the semiconductor crystal of FIG. 9 and electrodes are formed on the surface of the laser diode.

FIG. 11 is a schematic cross-sectional view showing another embodiment in which the photodetector of the semiconductor beam splitter according to the present invention is integrally incorporated.

FIG. 12 is a schematic sectional view showing still another embodiment of the semiconductor beam splitter according to the present invention.

[Explanation of symbols]

 10 semiconductor substrate 11 mask 12 semiconductor crystal 13 dielectric multilayer film 14 semiconductor beam splitter 15 laser diode 16 Si pedestal 17 laser diode 20 semiconductor substrate 21 N-AlGaAs layer 21 22 active layer 22 23 P-AlGaAs layer 24 resonator end face 25 dielectric multilayer Film 26 Semiconductor Laser 27 Semiconductor Crystal 28 Dielectric Multilayer Film 29 Electrode 30 Semiconductor Beam Splitter 40 Semiconductor Substrate 41 Photodiode 42 Semiconductor Beam Splitter 43 Laser Diode 50 Semiconductor Substrate 51 Semiconductor Beam Splitter 52 Semiconductor Beam Splitter 53 Laser Diode

Claims (5)

[Claims] 1. A semiconductor crystal that extends in the mask direction is masked in one direction on a semiconductor substrate, and a material having a bandgap larger than the wavelength of a semiconductor laser used as a light source is grown on the semiconductor crystal to grow a semiconductor crystal in the mask direction. A method of manufacturing a semiconductor beam splitter, which comprises forming and coating a sloped surface of the semiconductor crystal with a dielectric multilayer film to make the sloped surface a semi-transmissive surface. 2. A mountain-shaped semiconductor crystal extending in the mask direction, which is made of a material having a band gap larger than the wavelength of a semiconductor laser used as a light source, which is selectively crystal-grown on a semiconductor substrate by a mask in one direction. And a dielectric multi-layer film coated on the slope of this mountain-shaped semiconductor crystal, and a semiconductor beam splitter. 3. The semiconductor beam splitter according to claim 2, wherein a semiconductor laser is formed on the semiconductor substrate in the vicinity of the chevron-shaped semiconductor crystal. 4. The semiconductor beam splitter according to claim 2, wherein a photodetecting element is formed on the semiconductor substrate, and the chevron-shaped semiconductor crystal is formed thereon. 5. A material having a band gap larger than a wavelength of a semiconductor laser used as a light source, which is epitaxially grown on a (100) plane which is a surface of a semiconductor substrate by a mask extending in a [001] direction. A chevron-shaped semiconductor crystal extending in the mask direction, and the chevron-shaped semiconductor crystal with respect to the substrate (100) plane 45
A semiconductor beam splitter, comprising: a dielectric multilayer film coated on (110) and (1-10) crystal planes forming an angle of degrees.