JP2013093439A - Method for manufacturing surface-emitting semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a surface-emitting semiconductor laser capable of preventing the inhibition of an oxidation reaction of a layer to be formed into a current constriction layer in a step of forming the current constriction layer.SOLUTION: A method for manufacturing a surface-emitting semiconductor laser 100 which is a method for manufacturing a surface-emitting semiconductor laser having a columnar portion 20 including at least a part of a resonator includes the steps of: forming a silicon-containing film on a side face 21 of the columnar portion 20 while forming the columnar portion 20 by etching using gas containing SiCl; removing a silicon-containing film 110 by etching using fluorine-based gas; and oxidizing at least one layer out of layers constituting the columnar portion 20 from the side face of the columnar portion 20 to form a current constriction layer 28.

Description

  The present invention relates to a method for manufacturing a surface emitting semiconductor laser.

  In a surface emitting semiconductor laser (VCSEL), for example, a semiconductor multilayer film is formed on a substrate, and the semiconductor multilayer film is patterned to form a columnar portion serving as a resonator, and a semiconductor multilayer film constituting the columnar portion is formed. Of these, at least one layer is oxidized from the side surface to form a current confinement layer.

Here, in the step of forming the columnar portion described above, for example, as disclosed in Patent Document 1, a mixed gas of silicon tetrachloride (SiCl ₄ ) and argon (Ar) is used as an etching gas. By using a gas containing SiCl ₄ in this manner, lateral etching is suppressed and a good columnar shape can be obtained.

JP 2002-198359 A

However, as described above, when the columnar portion is formed using a gas containing SiCl ₄ , a silicon-containing film is formed on the side surface of the columnar portion, thereby inhibiting the oxidation reaction of the semiconductor layer serving as the current confinement layer was there. Therefore, for example, the current confinement layer may not be formed in a desired shape, for example, a difference in oxidation rate occurs in the plane of the semiconductor layer that becomes the current confinement layer and the shape of the current confinement layer becomes asymmetric. .

  One of the objects according to some aspects of the present invention is to provide a method for manufacturing a surface-emitting type semiconductor laser capable of suppressing inhibition of an oxidation reaction of a layer that becomes a current confinement layer in a step of forming a current confinement layer. It is to provide.

A method of manufacturing a surface emitting semiconductor laser according to the present invention includes:
A method of manufacturing a surface emitting semiconductor laser having a columnar portion including at least a part of a resonator,
Forming a silicon-containing film on a side surface of the columnar portion while forming the columnar portion by etching using a gas containing SiCl ₄ ;
Removing the silicon-containing film by etching using a fluorine-based gas;
Forming a current confinement layer by oxidizing at least one of the layers constituting the columnar portion from the side surface;
including.

  According to such a method for manufacturing a surface emitting semiconductor laser, the silicon-containing film formed on the side surface of the columnar portion can be removed by performing etching using a fluorine-based gas. Therefore, in the step of forming the current confinement layer, the oxidation reaction of the layer that becomes the current confinement layer can be suppressed from being inhibited by the silicon-containing film formed on the side surface of the columnar portion.

In the method for producing a surface emitting semiconductor laser according to the present invention,
The fluorine-based gas may be a gas containing any of CF ₄ , CHF ₃ , and C ₄ F ₆ .

  According to such a surface emitting semiconductor laser manufacturing method, in the step of forming the current confinement layer, the oxidation reaction of the layer that becomes the current confinement layer is inhibited by the silicon-containing film formed on the side surface of the columnar portion. Can be suppressed.

In the method for producing a surface emitting semiconductor laser according to the present invention,
In the step of removing the silicon-containing film, O ₂ gas may be mixed with the fluorine-based gas.

  According to such a method for manufacturing a surface-emitting type semiconductor laser, both the removal of the silicon-containing film and the ashing of a resist or the like can be performed in the step of removing the silicon-containing film.

In the method for producing a surface emitting semiconductor laser according to the present invention,
In the step of forming the columnar part and the silicon-containing film, a gas in which SiCl ₄ and Ar are mixed may be used.

  According to such a surface emitting semiconductor laser manufacturing method, in the step of forming the current confinement layer, the oxidation reaction of the layer that becomes the current confinement layer is inhibited by the silicon-containing film formed on the side surface of the columnar portion. Can be suppressed.

Sectional drawing which shows typically the surface emitting semiconductor laser which concerns on this embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser which concerns on this embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser which concerns on this embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser which concerns on this embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser which concerns on this embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser which concerns on this embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser which concerns on this embodiment.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

1. Surface Emitting Semiconductor Laser First, a surface emitting semiconductor laser according to the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a surface emitting semiconductor laser 100 according to this embodiment.

  As shown in FIG. 1, the surface emitting semiconductor laser 100 includes a substrate 10, a lower mirror 22, an active layer 24, an upper mirror 26, a current confinement layer 28, a first electrode 30, and a second electrode 32. And the insulating layer 40.

  As the substrate 10, for example, a first conductivity type (for example, n-type) GaAs substrate or the like can be used.

On the substrate 10, a first conductivity type (for example, n-type) lower mirror 22 is formed. The lower mirror 22 is, for example, a distributed Bragg reflection (DBR) mirror in which low refractive index layers (not shown) and high refractive index layers (not shown) are alternately stacked. The low refractive index layer can be composed of, for example, an n-type Al _0.9 Ga _0.1 As layer. The high refractive index layer can be composed of, for example, an n-type Al _0.15 Ga _0.85 As layer. The number of stacked layers (number of pairs) of the low refractive index layer and the high refractive index layer is not particularly limited, but may be, for example, 30 to 40 pairs.

An active layer 24 is formed on the lower mirror 22. The active layer 24 has, for example, a multiple quantum well (MQW) structure in which three quantum well structures each composed of a GaAs well layer and an Al _0.3 Ga _0.7 As barrier layer are stacked.

On the active layer 24, an upper mirror 26 of the second conductivity type (for example, p-type) is formed. The upper mirror 26 can be, for example, a DBR mirror in which low refractive index layers (not shown) and high refractive index layers (not shown) are alternately stacked. The low refractive index layer can be composed of, for example, a p-type Al _0.9 Ga _0.1 As layer. The high refractive index layer can be composed of, for example, a p-type Al _0.15 Ga _0.85 As layer. The number of stacked layers (number of pairs) of the low refractive index layer and the high refractive index layer is not particularly limited, but may be, for example, 30 to 40 pairs. The uppermost layer of the semiconductor multilayer film constituting the upper mirror 26 may be a layer (contact layer) in ohmic contact with the second electrode 32.

  Note that the composition and the number of layers constituting the lower mirror 22, the active layer 24, and the upper mirror 26 are not particularly limited, and can be appropriately adjusted as necessary.

  The lower mirror 22, the active layer 24, and the upper mirror 26 can constitute a vertical resonator. The p-type upper mirror 26, the active layer 24 not doped with impurities, and the n-type lower mirror 22 constitute a pin diode. A part of the upper mirror 26, the active layer 24, and the lower mirror 22 can constitute a columnar semiconductor deposited body (hereinafter referred to as “columnar portion”) 20. That is, a part of the resonator is included in the columnar part 20. Although not shown, the entire resonator may be included in the columnar portion 20. The planar shape of the columnar portion 20 is, for example, a circle.

  As shown in FIG. 1, for example, at least one of the layers constituting the upper mirror 26 can be a current confinement layer 28. The current confinement layer 28 is formed in a region close to the active layer 24. As the current confinement layer 28, for example, an oxidized AlGaAs layer can be used. The current confinement layer 28 is an insulating layer having an opening. The current confinement layer 28 is formed in a ring shape, for example. The planar shape of the opening of the current confinement layer 28 is, for example, a circle.

  A first electrode 30 is formed on the lower mirror 22. The first electrode 30 is electrically connected to the lower mirror 22. Although not shown, the first electrode 30 may be formed on the back surface of the substrate 10 (the surface opposite to the surface on which the lower mirror 22 is formed).

  A second electrode 32 is formed on the upper mirror 26 and the insulating layer 40. The second electrode 32 is electrically connected to the upper mirror 26. The second electrode 32 has an opening on the columnar portion 20. By the opening, a region where the second electrode 32 is not provided is formed on the upper surface of the upper mirror 26. This region is the laser light emission surface. The planar shape of the emission surface is, for example, a circle. A current is injected into the active layer 24 by the first electrode 30 and the second electrode 32. The first electrode 30 and the second electrode 32 are used for driving the surface emitting semiconductor laser 100.

  The insulating layer 40 is formed on the lower mirror 22. The insulating layer 40 is formed so as to surround the columnar part 20. The insulating layer 40 can electrically separate the second electrode 32 and the lower mirror 22.

  The surface emitting semiconductor laser 100 is used, for example, as a light source of an atomic oscillator using CPT (Coherent Population Trapping), an illumination device, or the like.

2. Manufacturing Method of Surface Emitting Semiconductor Laser Next, a manufacturing method of the surface emitting semiconductor laser according to the present embodiment will be described with reference to the drawings. 2-7 is sectional drawing which shows typically the manufacturing process of the surface emitting semiconductor laser which concerns on this embodiment.

  As shown in FIG. 2, for example, an n-type GaAs substrate is prepared as the substrate 10. Next, the semiconductor multilayer film 101 is formed on the substrate 10 by, for example, epitaxial growth while modulating the composition. As a method for epitaxial growth, for example, MOCVD (Metal-Organic Chemical Vapor Deposition) method, MBE (Molecular Beam Epitaxy) method or the like can be used. The semiconductor multilayer film 101 is formed by sequentially laminating semiconductor layers constituting the lower mirror 22, the active layer 24, and the upper mirror 26. Note that when the semiconductor multilayer film to be the upper mirror 26 is grown, at least one layer in the vicinity of the active layer 24 can be used as the semiconductor layer 28a to be oxidized later to become the current confinement layer 28. As the semiconductor layer 28a to be the current confinement layer 28, for example, an AlGaAs layer having an Al composition of 0.95 or more can be used.

  As shown in FIG. 3, a resist R is formed on the semiconductor multilayer film 101. The resist R is formed by performing exposure processing and development processing after forming a resist film.

As shown in FIG. 4, the semiconductor multilayer film 101 is anisotropically etched using the resist R as a mask to form a lower mirror 22, an active layer 24, and an upper mirror 26 having desired shapes. Thereby, the columnar part 20 is formed. Etching of the semiconductor multilayer film 101 is performed using a gas containing SiCl ₄ . More specifically, the semiconductor multilayer film 101 is etched using a mixed gas of SiCl ₄ and Ar.

When the semiconductor multilayer film 101 is etched using a gas containing SiCl ₄ , the columnar portion 20 is formed as shown in FIG. 4, and the silicon-containing film 110 is formed on the side surface 21 of the columnar portion 20. That is, in this step, the silicon-containing film 110 is formed on the side surface 21 of the columnar portion 20 while the columnar portion 20 is formed by etching the semiconductor multilayer film 101 using a gas containing SiCl ₄ . Here, the silicon-containing film 110 is a film containing silicon as its material. The silicon-containing film 110 may be a film made of a silicon compound such as silicon oxide, for example. By forming the silicon-containing film 110 on the side surface 21 of the columnar portion 20, lateral etching is suppressed and a good columnar shape is obtained.

As shown in FIG. 5, the silicon-containing film 110 is removed by etching using a fluorine-based gas. As the fluorine-based gas, for example, a gas containing any of CF ₄ , CHF ₃ , and C ₄ F ₆ can be used. Furthermore, the resist R can be removed by mixing the fluorine-based gas with O ₂ gas and performing etching. That is, in this step, both the removal of the silicon-containing film 110 and the removal of the resist R (ashing) can be performed by using a mixed gas of fluorine-based gas and O ₂ gas.

  As shown in FIG. 6, the current confinement layer 28 is formed by oxidizing the semiconductor layer 28a to be the current confinement layer 28 from the side surface. For example, the current confinement layer 28 is formed by oxidizing the semiconductor layer 28a from the side surface by introducing the substrate 10 on which the columnar portion 20 is formed by the above-described process into a water vapor atmosphere at about 400 ° C. The side surface of the semiconductor layer 28 a constitutes the side surface 21 of the columnar portion 20. Here, the silicon-containing film 110 formed on the side surface 21 (side surface of the semiconductor layer 28a) of the columnar portion 20 in the step of forming the columnar portion 20 is removed by etching using a fluorine-based gas as described above. Yes. Therefore, inhibition of the oxidation reaction of the semiconductor layer 28a that becomes the current confinement layer 28 by the silicon-containing film 110 can be suppressed. Therefore, for example, the oxidation rate can be made uniform in the plane of the semiconductor layer 28a, and the current confinement layer 28 can be formed in a desired shape.

  As shown in FIG. 7, an insulating layer 40 is formed on the lower mirror 22 so as to surround the columnar portion 20. The insulating layer 40 is formed by forming a layer made of polyimide resin or the like on the upper surface of the lower mirror 22 and the entire surface of the columnar portion 20 using a spin coat method or the like, and patterning this layer using a photolithography technique, an etching technique, or the like. It is formed by. In this way, the insulating layer 40 having a desired shape can be formed.

  As shown in FIG. 1, the first electrode 30 and the second electrode 32 are formed. The electrodes 30 and 32 can be formed in a desired shape by a combination of a vacuum deposition method and a lift-off method. In addition, the order in which each electrode 30 and 32 is formed is not specifically limited.

  Through the above steps, the surface emitting semiconductor laser 100 can be manufactured.

  The method for manufacturing the surface-emitting type semiconductor laser 100 according to this embodiment has the following features, for example.

As described above, the method for manufacturing the surface emitting semiconductor laser 100 includes the step of removing the silicon-containing film 110 by etching using a fluorine-based gas. Thereby, the silicon-containing film 110 formed on the side surface 21 of the columnar portion 20 can be removed by etching using a gas containing SiCl ₄ . Therefore, in the step of forming the current confinement layer 28, it is possible to prevent the silicon-containing film 110 from inhibiting the oxidation reaction of the semiconductor layer 28a that becomes the current confinement layer 28. Therefore, for example, the oxidation rate can be made uniform in the plane of the semiconductor layer 28a, and the current confinement layer 28 can be formed in a desired shape. Thereby, the characteristic and reliability of an apparatus can be improved.

According to the method for manufacturing the surface emitting semiconductor laser 100, in the step of removing the silicon-containing film 110, the fluorine-containing gas is mixed with O ₂ gas to use the silicon-containing film 110 and the resist R (see FIG. Ashing). Therefore, the manufacturing process can be simplified.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 10 Board | substrate, 20 Columnar part, 21 Side surface, 22 Lower mirror, 24 Active layer, 26 Upper mirror, 28 Current confinement layer, 28a Semiconductor layer, 30 1st electrode, 32 2nd electrode, 40 Insulating layer, 100 Surface emitting semiconductor Laser, 101 semiconductor multilayer film, 110 silicon-containing film, R resist,

Claims (4)

A method of manufacturing a surface emitting semiconductor laser having a columnar portion including at least a part of a resonator,
Forming a silicon-containing film on a side surface of the columnar portion while forming the columnar portion by etching using a gas containing SiCl ₄ ;
Removing the silicon-containing film by etching using a fluorine-based gas;
Forming a current confinement layer by oxidizing at least one of the layers constituting the columnar portion from the side surface;
A method of manufacturing a surface-emitting type semiconductor laser comprising: The method for manufacturing a surface emitting semiconductor laser according to claim 1, wherein the fluorine-based gas is a gas containing any one of CF ₄ , CHF ₃ , and C ₄ F ₆ . 3. The method of manufacturing a surface emitting semiconductor laser according to claim 1, wherein in the step of removing the silicon-containing film, O ₂ gas is mixed with the fluorine-based gas. 4. The surface-emitting type semiconductor laser according to claim 1, wherein a gas mixture of SiCl ₄ and Ar is used in the step of forming the columnar part and the silicon-containing film. 5. Method.

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