JP2677225B2 - Manufacturing method of surface emitting laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a surface emitting laser, and more particularly to a method for manufacturing a multi-wavelength device capable of emitting light of a plurality of wavelengths.

[0002]

2. Description of the Related Art A conventional method for integrating compound semiconductor devices having different characteristics, such as optical semiconductor devices having different wavelengths, on the same substrate surface is to perform crystal growth once, patterning in the atmosphere, and then again. The following techniques for growing crystals are known.

The first is the method described in Applied Physics Letters, Volume 58, pp. 2698-2700, which has an oscillation wavelength of 0.
An 85 μm GaAs / AlGaAs laser structure is formed by the molecular beam epitaxial growth (MBE) method, and then the laser portion is removed by patterning in a stripe pattern at a pitch of 250 μm. InGaAs laser structure is grown to integrate a two-wavelength laser.

Second, the Japanese Journal of Applied Physics.
32, pages 600 to 603, and relates to a method for manufacturing a vertical cavity laser, which comprises growing one vertical cavity by the MBE method, and then patterning the vertical cavity 125-125. The upper reflecting mirror is removed in a stripe shape at a pitch of 250 μm, and the upper reflecting mirror layer is grown again by the MBE method to integrate a laser with a single resonator and a detector (light receiving element) with a double resonator.

[0005]

In the above conventional example, the crystal growth substrate must be taken out into the atmosphere after the crystal growth in an ultrahigh vacuum, and after the patterning, the crystal growth must be performed again in the growth chamber. Thus, in such a method, not only the process becomes complicated, but also the device characteristics are formed by one-time crystal growth due to deterioration of quality of re-grown crystals and contamination and defects introduced at the interface. Will be inferior to.

Further, in a device such as a reflecting mirror of a surface emitting laser that requires highly accurate film thickness control, the growth process is performed in two steps.
When divided into times, there is a fatal problem that the upper and lower reflecting mirrors have different wavelengths. The present invention has been made in view of this point, and an object of the present invention is to perform all steps in a method of manufacturing a surface emitting laser in which an etching step is inserted between two crystal growths and to expose the substrate to the atmosphere. Therefore, it is possible to perform the process without exposing the device, simplify the process, and manufacture the device with high quality.

[0007]

In order to achieve the above object, according to the present invention, (1) a lower Bragg reflector layer, an active layer and an intermediate layer are successively epitaxially grown in this order on a semiconductor substrate. A step, (2) a step of selectively etching away a partial region of the intermediate layer to a predetermined film thickness, and (3) a step of epitaxially growing an upper Bragg reflector layer on the intermediate layer, And a method for manufacturing a surface emitting laser, characterized in that the above steps are performed without exposing the semiconductor substrate to the atmosphere between the steps.

Preferably, in the second step (2), a mask having an opening of a predetermined pattern is arranged on the semiconductor substrate, and an electron beam and hydrogen chloride gas are simultaneously irradiated through the mask for etching. To do. Further, preferably, the crystal growth apparatus in which the steps (1) and (3) are carried out and the processing apparatus in which the step (2) is carried out are connected by a vacuum transfer path. During the process, the semiconductor substrate is moved between the devices via the transfer path.

[0009]

In the present invention, in the processing of the intermediate layer of the surface emitting laser,
By adopting the electron beam excited hydrogen chloride gas etching method, which allows selective etching to be performed as it is, the complexity of the conventional atmospheric extraction process can be avoided, and contamination of the substrate due to exposure to the atmosphere can be avoided. ,
It is possible to prevent deterioration of the quality of the grown film. Therefore,
According to the present invention, the simplification of the process and the improvement of the quality of the device can be realized. Further, by using a mask having an arbitrary opening at the time of electron beam excitation etching, it is possible to avoid poor throughput, which was a problem in the conventional method using electron beam drawing.

This method will be described with reference to FIG. GaAs
The electron beam 103 is irradiated through the mask 102 arranged on the s substrate 101, and at the same time, the hydrogen chloride gas 104 is supplied through the nozzle 105 to perform electron beam excited etching. As a result, the etching proceeds only in the area irradiated with the electron beam. This etching rate is very slow and the substrate temperature is 7
0 ° C, gas pressure: 2 × 10 ^-5 Torr, electron beam accelerating voltage: 1
0.2 nm / min under the etching condition of 0 kV (Semiconductor Science and Technology (S
emiconductor Science and Technology) Volume 6, 934-93
Page 6). Therefore, highly accurate processing is possible. Further, since the etching does not proceed at all in the region where the electron beam is not irradiated, highly accurate mask shape transfer is possible.

[0011]

Next, embodiments of the present invention will be described in detail with reference to the drawings. [First Embodiment] FIGS. 2A to 2C show the first embodiment of the present invention.
5A to 5C are cross-sectional views in order of the steps for explaining the manufacturing method of the embodiment, and FIG. 3 is a cross-sectional view of the surface-emission laser manufactured according to the first embodiment. This example relates to a process of integrating a vertical cavity surface emitting laser of two wavelengths.

First, an n-type GaAs layer (thickness 71.2 nm) and an n-type A are formed on a GaAs substrate 201 by the MBE method.
A lower Bragg reflector layer 202 consisting of 15 pairs of 1As layers (thickness 84.7 nm) is grown. The Bragg reflector layer 202 has a high reflectance of 99.9% or more in the wavelength band of 950 nm to 1050 nm. After forming the lower Bragg reflector layer 202, In
Active layer 203 made of _0.18 Ga _0.82 As and having a thickness of 10 nm
And a film thickness of 305.4 nm consisting of Al _0.25 Ga _0.75 As
The intermediate layer 204 is sequentially crystal-grown [FIG. 2 (a)].
The thickness of the intermediate layer 204 at this time corresponds to a film thickness (so-called λ thickness) for oscillating at a wavelength of 1020 nm.

Next, an ultra-high vacuum transfer path (vacuum degree: 10 ^-10 Torr) is transferred from the crystal growth chamber to the processing chamber where the sample is etched.
Transport through. This processing chamber is equipped with an electron beam source and a reactive gas introduction mechanism. A movable etching mask 205 is set directly above the sample. The mask 205 used here has a thickness of 100 μ which has been subjected to corrosion resistance treatment.
m metal plate with a pitch of 500 μm and a width of 250 nm
With a striped opening.

This mask 205 is set at a position 100 μm directly above the substrate, and an electron beam 206 and hydrogen chloride (HCl) gas 207 are simultaneously irradiated to carry out electron beam excited hydrogen chloride gas etching [FIG. 2 (b)]. The substrate temperature is room temperature, the electron beam acceleration energy is 500 eV, and the hydrogen chloride gas pressure is 2
It was conducted at × 10 ^-5 Torr. As shown in FIG. 2B, since the electron beam is vertically incident on the sample, the mask shape can be accurately transferred onto the sample.

Further, at room temperature, the hydrogen chloride gas does not etch the GaAs substrate which has not been irradiated with the electron beam at all, and the etching proceeds only in the electron beam irradiated region. 14nm in this process
Etching processing is performed to set the remaining thickness of the intermediate layer in the processing region to 291.4 nm. As a result, the processing area has a wavelength of 9
The film thickness corresponds to a λ thickness of 80 nm. After completion of this etching process, the sample is again transported to the crystal growth chamber through the ultra-high vacuum transport path. Here, again by the MBE method, p-type A
An upper Bragg reflector layer 208 consisting of 20 pairs of 1As layer (thickness 84.7 nm) and p-type GaAs layer (thickness 71.2 nm) is grown. This makes it possible to form a vertical cavity of a surface emitting laser having two wavelengths of 980 nm (region A) and 1020 nm (region B) [FIG. 2 (c)].

Next, as shown in FIG. 3, the upper Bragg reflector layer 208 is processed into a post shape having a size of 6 μm square in order to form a surface emitting laser of two wavelengths on the crystal growth substrate thus formed. did. After that, a proton injection region 209 is formed around the post to confine the current path only under the post.

Then, a silicon oxide film or the like is deposited by the CVD method to form an insulating film 210, a window is formed on the posts, and then a p-side electrode 211 is formed by depositing a metal film and patterning the metal film. . Further, a groove exposing the intermediate portion of the lower Bragg reflector layer 202 is formed, and the n-side electrode 212 is formed at the bottom of the groove, and the manufacturing process of this embodiment is completed. When the oscillation wavelengths of the region A and the region B of the surface emitting laser thus formed were measured,
It was confirmed that the laser was oscillating at the wavelengths of ₁ = 982 nm and λ ₂ = 1019 nm, which were almost designed.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. this is,
The present invention relates to a manufacturing method for integrating a vertical cavity laser of 8 wavelengths. In the second embodiment, as shown in FIG.
3 of 301, 302, 303 shown in (b) and (c)
Types of masks are used. Each mask has a film thickness of 100 μm
It is formed by the metal plate of
The stripe-shaped opening 301a with a width of 250 μm is 500
They are lined up in the vertical direction at a μm pitch. Also, the mask 302
Then, the stripe-shaped openings 302a having a width of 250 μm are arranged laterally at a pitch of 500 μm.
In, stripe-shaped openings 303a having a width of 500 μm are arranged in the vertical direction at a pitch of 1000 μm. These three masks can be arbitrarily attached and detached in the etching chamber.

Similar to the case of the first embodiment, the n-type GaAs layer (thickness 71.
2 nm) and n-type AlAs layer (thickness 84.7 nm) 15
Paired lower Bragg reflector layer, In _0.18 Ga _0.82 A
10 nm thick active layer of Al, _0.25 Ga _0.75 A
An intermediate layer made of s and having a film thickness of 305.4 nm is successively grown. At this time, the thickness of the intermediate layer is 1020
This corresponds to the λ thickness in nm.

Next, the sample is transferred to the processing chamber and the mask 301 is removed.
Is placed on the sample, and the intermediate layer is etched by 2 nm by simultaneously irradiating it with an electron beam and hydrogen chloride gas. At this time, as shown in FIG. 5A, the etching region 401 in the intermediate layer is formed in a stripe shape in the lateral direction. Next, the mask 302 is placed on the sample, and the intermediate layer is etched by 4 nm. At this time, as shown in FIG. 5B, the etching region 402 is formed in a stripe shape in the vertical direction. Further, the mask 303 is placed on the sample, and the intermediate layer is etched by 8 nm. At this time, as shown in FIG. 5C, the etching region 403 is formed in a stripe shape in the horizontal direction.

The numerical values in FIG. 5 are the initial film thickness 30 of the intermediate layer.
It shows the thickness reduced from 5.4 nm. The thickness of the intermediate layer is 291.4n as a result of the above three etching steps.
This means that the film was formed in 8 steps in steps of 2 nm from m to 305.4 nm. This film thickness corresponds to eight wavelengths from 980 nm to 1020 nm when converted into wavelength λ.

After completion of this etching process, the sample is conveyed again to the crystal growth chamber through the ultrahigh vacuum conveying path. Here, the p-type AlAs layer (thickness 84.7n) is again formed by the MBE method.
m) and a p-type GaAs layer (thickness 71.2 nm) consisting of 20 pairs of upper Bragg reflector layers. This makes it possible to form a vertical cavity laser with 8 wavelengths in steps of about 5 nm from 980 nm to 1020 nm.

Next, the crystal growth substrate thus formed is subjected to a treatment for current constriction and further p-side and n-side electrodes are formed. Then, a device in which a vertical cavity laser of 8 wavelengths is integrated is formed. Can be formed.

[0024]

As described above, according to the method of manufacturing a surface emitting laser of the present invention, the lower Bragg reflector layer, the active layer, the intermediate layer having regions having different film thicknesses, and the upper Bragg reflector layer are exposed to the atmosphere. Since it is formed without taking it out,
In addition to simplifying and facilitating the process, it becomes possible to avoid contamination and defects introduced at the regrowth interface during regrowth after patterning in the atmosphere. Therefore, according to the present invention, it is possible to manufacture a multi-wavelength device in which lasers of a plurality of wavelengths are integrated with high quality, and it is possible to improve the manufacturing yield and reduce the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an electron beam excited hydrogen chloride gas etching step for explaining the operation of the present invention.

FIG. 2 is a process sectional view for explaining the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a surface emitting laser formed according to the first embodiment of the present invention.

FIG. 4 is a plan view of three types of masks used in the second embodiment of the present invention.

5A to 5C are plan views in order of processes for explaining the second embodiment of the present invention.

[Explanation of symbols]

 101 GaAs substrate 102 Mask 103 Electron beam 104 Hydrogen chloride gas 105 Nozzle 201 GaAs substrate 202 Lower Bragg reflector layer 203 Active layer 204 Intermediate layer 205 Mask 206 Electron beam 207 Hydrogen chloride gas 208 Upper Bragg reflector layer 209 Proton injection region 210 Insulation Film 211 p-side electrode 212 n-side electrode 301, 302, 303 mask 301a, 302a, 303a opening 401, 402, 403 etching region

Claims (5)

(57) [Claims] 1. A step of: (1) continuously epitaxially growing a lower Bragg reflector layer, an active layer, and an intermediate layer on a semiconductor substrate in this order; and (2) a partial region of the intermediate layer having a predetermined film thickness. Until the above, and (3) a step of epitaxially growing an upper Bragg reflector layer on the intermediate layer, the above steps without exposing the semiconductor substrate to the atmosphere between the steps. A method of manufacturing a surface emitting laser, comprising: 2. In the second step (2), a mask having an opening of a predetermined pattern is arranged on the semiconductor substrate, and an electron beam and hydrogen chloride gas are simultaneously irradiated through the mask for etching. The method for manufacturing a surface emitting laser according to claim 1, wherein 3. The method of manufacturing a surface emitting laser according to claim 2, wherein in the second step (2), a plurality of masks having different opening patterns are used to perform etching a plurality of times. 4. The method of manufacturing a surface emitting laser according to claim 1, wherein each layer is grown by a molecular beam epitaxial growth method in the first (1) and the third (3) epitaxial growth steps. 5. The crystal growth apparatus in which the steps (1) and (3) are performed and the processing apparatus in which the step (2) is performed are connected by a vacuum transfer path, 2. The method for manufacturing a surface emitting laser according to claim 1, wherein the semiconductor substrate is moved between the devices via the transfer path between the steps.