JPH11109159A - Manufacture of semiconductor wavelength plate type polarization rotating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor wavelength plate type polarization rotating element used for optical communication, optical exchange, and optical information processing. SOLUTION: In a method for manufacturing a semiconductor wavelength plate type polarization rotating element consisting of two semiconductor waveguides formed on a semiconductor substrate and arranged in parallel to each other in different heights from the substrate surface, this method comprises steps of forming a difference in level on a semiconductor substrate 21; developing a semiconductor layer forming the core of the waveguide on the semiconductor substrate 21; working the semiconductor layer forming the core of the waveguide into mutually parallel stripes having a rectangular section to form waveguide cores 23a, 23b one each in the respective parts of the upper and lower step parts of the difference in level on the semiconductor substrate 21; and developing the same semiconductor material 25 as the semiconductor substrate 21 on the semiconductor substrate 21 so as to bury the two waveguide cores 23a, 23b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to optical communication, optical switching,
The present invention relates to a method for manufacturing a semiconductor wave plate type polarization rotation element used for optical information processing and the like.

[0002]

2. Description of the Related Art In constructing a system using light such as optical communication, optical switching, and optical information processing, optical elements such as wave plates are often used in bulk components. A wavelength plate having a plate thickness at which the phase difference between two orthogonal linearly polarized components is π is called a λ / 2 plate. This λ / 2 plate has a function of rotating the plane of polarization of linearly polarized light.

However, the commonly used bulk λ /
The size of the two plates is large, and there is a problem that the matching with the semiconductor material is not good. In order to solve such a problem, a semiconductor polarization rotator having a buried structure manufactured on a semiconductor substrate includes two waveguides (a first InGaAsP waveguide layer) as shown in FIGS. (Hereinafter referred to as “first waveguide”) 121, second InGaAs
An sP waveguide layer (hereinafter, referred to as a “second waveguide”) 122), the first waveguide 121 and the second waveguide 122 are located in parallel, and a straight line connecting the centers of the two waveguides and a substrate The angle (θ ′) formed by a straight line parallel to is set to 45 °, and the two equivalent refractive indices counted from the lowest order of the unique waveguide modes of the two waveguides are n ₁ and n ₂ ( n ₁ >
n ₂ ), the length L ₂ is defined by the following “Equation 1”, and the ratio of the light confinement coefficient of the first waveguide 121 to the TE / TM mode is almost 1. In the drawings, reference numeral 111 denotes an InP substrate and 112 denotes an InP buried layer.

[0004]

(Equation 1)

This element has a function of rotating the output light polarization by 2θ from the incident light polarization, assuming that the angle between the incident light polarization and the crystal axis of the wave plate is θ. This allows
For example, it is possible to realize a polarization control device that is effective for eliminating odd-number dependence of a semiconductor optical amplifier.

Next, a conventional method for manufacturing a rotating element will be described. 8 to 12 are views showing a series of manufacturing processes of a rotary element according to the related art.

As shown in FIG. 8, an InP layer 13 of 1 μm and a wavelength of 1.3 μm are formed on an InP substrate 14 as a second waveguide.
InGaAsP12 having a composition corresponding to m is grown to 0.5 μm to form an SiO ₂ film 11 having a thickness of 0.2 μm. Next, as shown in FIG. 9, the SiO ₂ film 11 is patterned to a width of 0.5 μm by dry etching to be used as a mask. Then, the second waveguide 12 and the In layer 13 are processed to a width of 0.5 μm by dry etching. Thereafter, as shown in FIG. 10, the InP layer 15 is buried to the height of the second waveguide 12 to reduce the influence of the stripe, and the SiO ₂ film 11 serving as a mask is removed. Then, an InP layer 16 of 1 μm and a 1.3 μm InGaAsP layer 17 of 0.5 μm as a first waveguide are again formed thereon.
Then, an SiO ₂ film 18 serving as a mask is formed to a thickness of 0.2 μm. Furthermore, as shown in FIG. 11, the SiO ₂ film 18 0.
The first waveguide 17 is processed to a width of 5 μm, and the first waveguide 17 is patterned to 0.5 μm by dry etching using the mask as a mask. Finally, the SiO ₂ film 18 is removed, and FIG.
2, the InP layer 19 is buried and completed.

[0008]

However, in the conventional manufacturing method, it is necessary to perform a total of four crystal growth steps in order to realize a wave plate type semiconductor polarization rotating element. Due to the large number, there were problems such as a prolonged manufacturing process and an increase in cost. Further, there is a problem that dust or the like adhered during crystal growth or in another process is likely to cause abnormal growth during the next stage of crystal growth, thereby deteriorating the yield of element fabrication.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor wave plate type polarization rotator which is formed on a semiconductor substrate and is parallel to different heights from the substrate surface. Forming a step on a semiconductor substrate, and forming a semiconductor layer serving as a core of the waveguide on the semiconductor substrate. Growing step, processing the semiconductor layer to be the core layer into mutually parallel stripes having a rectangular cross-section, and forming a waveguide on each of the upper and lower steps of the step on the semiconductor substrate. The method includes a step of forming a core and a step of growing the same semiconductor material as the semiconductor substrate so as to embed the two waveguide cores on the semiconductor substrate.

According to a second aspect of the present invention, there is provided a method for manufacturing a semiconductor wave plate type polarization rotating element comprising two semiconductor waveguides formed on a semiconductor substrate and arranged in parallel at different heights from the substrate surface. Forming a step on a semiconductor substrate, and selectively forming a selective growth mask having stripe-shaped openings parallel to each other on each of an upper portion and a lower portion of the step on the semiconductor substrate having the step. Forming a stripe-shaped semiconductor waveguide core having a rectangular cross section in each of the upper and lower openings of the step; removing the selective growth mask; Growing the same semiconductor material as the semiconductor substrate so as to bury the waveguide core on the substrate.

According to the present invention, the number of crystal growth steps is set to 2
This makes it possible to suppress the prolongation of the manufacturing process and the increase in cost, which are problems when forming the semiconductor wave plate type polarization rotating element by the four growth processes as in the prior art. Is done. In addition, it is possible to improve the yield of device fabrication that has been deteriorated due to abnormal growth during crystal growth at a stage during crystal growth or dust attached in another process.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

(Embodiment 1) This embodiment shows one embodiment of a method of manufacturing a semiconductor wave plate type polarization rotating element according to claim 1 of the present invention.

1 to 4 show a first embodiment of the present invention.
ing. First, as shown in FIG.
μm SiO_TwoForm film 22 and use dry etching
And patterning. And use it as a mask,
Form 1.5μm step on InP substrate 21 by light etching
To achieve. After that, the SiO_TwoRemove the film 22 and as shown in FIG.
1.3 μm InGaAsP to be the first waveguide and the second waveguide
Layer 23 is grown to a thickness of 0.5 μm. In addition, a mask
SiO_TwoThe film 24 is formed with a thickness of 0.2 μm. Next, as shown in FIG. 3, the first waveguide and the second waveguide
To form SiO _TwoFilm 24 for dry etching
It is further processed to a width of 0.5 μm. Then, the first waveguide and the second waveguide
Use this mask to form a waveguide and dry
The first waveguide 23 is processed to a width of 0.5 μm by etching.
a and the second waveguide 23b are formed. Finally, as shown in FIG._Two
By removing the film 24 and embedding the InP layer 25,
The conductor wave plate type polarization rotating element is completed.

(Embodiment 2) This embodiment shows an embodiment of a method for manufacturing a semiconductor wave plate type polarization rotating element according to [claim 2] of the present invention.

FIGS. 5 to 7 show a second embodiment of the present invention. As in the first embodiment, as shown in FIG.
A 0.2 μm SiO ₂ film 32 is formed on a substrate 31 and is patterned by using dry etching. Then, using it as a mask, dry etching
A 1.5 μm step is formed on the nP substrate 31. Thereafter, the SiO ₂ film 32 is removed, and a 0.2 μm SiO ₂ film 34 is formed again as shown in FIG. Then, in order to use it as a selective growth mask, an arbitrary portion of the SiO ₂ film 34 is removed by dry etching. Then, a first waveguide and a second waveguide are formed in the selected region.
The 1.3 μm InGaAsP layers 33a and 33b are selectively grown. Finally, as shown in FIG. 7, SiO ₂ is the mask
By removing the film 34 and embedding the InP layer 35, a semiconductor wave plate type polarization rotator is completed.

[0017]

As described above, the use of the manufacturing method according to the present invention makes it possible to reduce the number of crystal growth steps to two in the manufacture of a semiconductor wave plate type polarization rotator. As a result, it is possible to suppress a longer manufacturing process and an increase in cost than in the conventional four-time growth. In addition, it is possible to improve the yield of element fabrication that has been deteriorated due to abnormal growth during crystal growth at a stage during crystal growth or due to dust or the like adhered in another process.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing a first embodiment.

FIG. 2 is a manufacturing process diagram showing a first embodiment.

FIG. 3 is a manufacturing process diagram showing the first embodiment.

FIG. 4 is a manufacturing process diagram showing the first embodiment.

FIG. 5 is a manufacturing process diagram showing a second embodiment.

FIG. 6 is a manufacturing process diagram showing a second embodiment.

FIG. 7 is a manufacturing process diagram showing a second embodiment.

FIG. 8 is a series of manufacturing process diagrams according to the prior art.

FIG. 9 is a series of manufacturing process diagrams according to a conventional technique.

FIG. 10 is a series of manufacturing process diagrams according to a conventional technique.

FIG. 11 is a series of manufacturing process diagrams according to a conventional technique.

FIG. 12 is a series of manufacturing process diagrams according to the related art.

FIG. 13 is a sectional view of a semiconductor polarization rotation element.

FIG. 14 is a perspective view of a semiconductor polarization rotation element.

[Explanation of symbols]

Reference Signs List 21 InP substrate 22 SiO ₂ film 23 InGaAsP layer 23a First waveguide 23b Second waveguide 24 SiO ₂ film 25 InP layer 31 InP substrate 32 SiO ₂ film 33 InGaAsP 33a First waveguide 33b Second waveguide 34 SiO ₂ film 35 InP layer

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor wave plate type polarization rotating element comprising two semiconductor waveguides formed on a semiconductor substrate and arranged in parallel at different heights from the substrate surface, wherein a step is formed on the semiconductor substrate. Forming a semiconductor layer serving as a core of the waveguide on the semiconductor substrate; and processing the semiconductor layer serving as the core layer into mutually parallel stripes having a rectangular cross section. A step of forming one waveguide core at each of an upper portion and a lower portion of a step on the semiconductor substrate; and forming the same waveguide substrate on the semiconductor substrate so as to embed the two waveguide cores. And a step of growing a semiconductor material. 2. A method for manufacturing a semiconductor wave plate type polarization rotator comprising two semiconductor waveguides formed on a semiconductor substrate and arranged in parallel at different heights from the substrate surface, wherein a step is formed on the semiconductor substrate. Forming a selective growth mask having a stripe-shaped opening parallel to each other in each of the upper and lower steps of the step on the semiconductor substrate having the step; Selectively growing a stripe-shaped semiconductor waveguide core having a rectangular cross-section in each of the upper and lower openings of the step; removing the selective growth mask; and forming the waveguide on the semiconductor substrate. Growing a semiconductor material identical to that of the semiconductor substrate so as to bury the core.