WO2016009911A1

WO2016009911A1 - Vertical-cavity surface-emitting laser manufacturing method

Info

Publication number: WO2016009911A1
Application number: PCT/JP2015/069613
Authority: WO
Inventors: 崇資植田; 鈴木　新; 關　仁士
Original assignee: 株式会社村田製作所
Priority date: 2014-07-18
Filing date: 2015-07-08
Publication date: 2016-01-21
Also published as: TW201607190A

Abstract

In the present invention, in a vertical-cavity surface-emitting laser manufacturing method, a lateral surface of an oxidation layer is exposed due to the processing of a laminated body which includes the oxidation layer, and then a current constriction layer is formed according to a heated water vapor oxidizing process. The heated water vapor oxidizing process includes: a step in which a substrate (110), which includes the processed laminated body, is placed on a stage (102) provided inside of a chamber (101) the interior of which can be made airtight; a step in which, in a purified water tank (122) which is outside of the chamber (101), a water vapor gas is generated by heating the purified water in a vacuum atmosphere; and a step in which the water vapor gas is subjected to flow-rate control and supplied to the inside of the chamber (101) which has a vacuum atmosphere.

Description

Manufacturing method of vertical cavity surface emitting laser

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

A vertical cavity surface emitting laser (VCSEL: Vertical Cavity Surface Emitting Laser) is a laser device that outputs laser light in a direction perpendicular to a substrate surface by forming an optical resonator in a direction perpendicular to the substrate surface. Usually, in the VCSEL, a current confinement structure is formed in order to concentrate the current in the light emitting region.

In many cases, an opening structure formed by oxidizing the outer peripheral side of an AlAs (aluminum arsenic) layer is used as the current confinement structure. Specifically, the oxidation of the AlAs layer is carried out by holding the substrate on which the laminate (object to be oxidized) processed into a mesa shape so that the AlAs layer is exposed on the side surface in heated steam at 400 to 500 ° C. Is executed. In this case, the temperature distribution in the substrate is preferably within ± 1 ° C.

A method described in Japanese Patent Application Laid-Open No. 2011-18876 (Patent Document 1) is known as a method for making the temperature distribution in the substrate uniform. In the method of this document, the upper surface of the heat radiating plate on which the substrate is placed is processed into a spherical shape following the warp during the thermal oxidation of the substrate on which the oxidation target is formed.

JP 2011-18876 A

The method described in the above Japanese Unexamined Patent Publication No. 2011-18876 (Patent Document 1) has the following problems. First, since the amount of warpage of the substrate varies depending on the temperature of the substrate, it is difficult to accurately grasp the amount of warpage during heating oxidation. Further, the amount of warpage of the substrate varies depending on the structure of the epitaxial film formed on the substrate and the growth conditions thereof, and thus varies depending on the product type (model number). For this reason, in order to implement | achieve the method of said literature, it will be necessary to prepare the heat sink from which the curvature of an upper surface differs for every kind of product, and is not easy.

The present invention has been made in consideration of the above-described problems, and the object of the present invention is to form a current confinement layer by a heating steam oxidation method in the manufacture of a vertical cavity surface emitting laser. It is to equalize the temperature distribution in the substrate and the oxidation distribution of the object to be oxidized.

In one aspect, the present invention provides a method for manufacturing a vertical cavity surface emitting laser, and includes a stacked body including first and second reflecting mirror layers, an active layer, and an oxidized layer serving as a current confinement structure on a substrate. A step of forming the layered structure into a mesa shape so that at least a side surface of the oxidized layer is exposed, and a current confinement by oxidizing the oxidized layer from the side surface after processing the stacked body into a mesa shape Forming a structure. The step of forming the current confinement structure includes a step of placing a substrate having a processed laminated body on a stage provided inside a chamber that can be hermetically sealed, and a pure structure outside the chamber. In a water tank, the method includes the steps of generating water vapor gas by heating pure water in a vacuum atmosphere, and supplying the water vapor gas by controlling the flow rate into a vacuum atmosphere chamber.

According to the above manufacturing method, the steam gas generated by heating pure water in a vacuum atmosphere is supplied as an oxidizing gas into the chamber, so that the oxidizing gas is blown using an inert gas such as nitrogen gas as a carrier. Compared with this method, the diffusion efficiency of the gas is high as much as the inert gas does not exist, and the oxidizing gas can be supplied uniformly to the oxidation target layer of the laminate. In addition, since the oxidizing gas is not strongly blown, it is possible to suppress the occurrence of a temperature drop of the substrate and the accompanying variation in temperature distribution, and the degree of progress of oxidation of the oxidized layer can be made uniform. Thereby, the oxidation distribution of the oxidation target can be made uniform.

Preferably, the stage includes a heating unit for heating the substrate and a support member for supporting the substrate at three points of the peripheral portion of the substrate.

In the above configuration, since the substrate is supported by the supporting member at the three peripheral edge portions of the substrate, the contact area between the stage and the substrate can be minimized, and the amount of heat that escapes through the stage by heat conduction is minimized. Can be stopped. Also, since the heat conduction through the oxidizing gas is small because it is in a vacuum atmosphere, the radiant heat is dominant between the stage and the substrate, and the temperature distribution on the surface of the substrate due to the warpage of the substrate is uneven. Generation | occurrence | production etc. can be suppressed and it becomes possible to stabilize quality at a high level by equalizing the progress degree of oxidation of the layer to be oxidized of the laminate.

Preferably, the step of forming the current confinement structure further includes a step of confirming the progress of oxidation of the oxidation target layer of the stacked body by infrared rays from an observation window provided on the top surface of the chamber.

In the above configuration, since the chamber is in a vacuum atmosphere, no convection of oxidizing gas occurs, and heat does not easily escape from the observation window provided on the top surface. Therefore, variations in temperature distribution on the surface of the substrate placed on the stage can be avoided. In addition, it is not necessary to provide a mechanism for moving the stage up and down in order to change the distance between the stage and the observation window during the progress of oxidation and when observing the degree of progress, and the overall manufacturing cost can be reduced. It becomes.

Therefore, according to the present invention, in the production of a direct cavity surface emitting laser, the temperature distribution in the substrate and the oxidation distribution of the object to be oxidized are more uniform than in the prior art when the current confinement layer is formed by the heating oxidation method. Can be

It is a top view which shows typically the structure of VCSEL. FIG. 2 is a diagram schematically showing a cross-sectional structure along the line II-II in FIG. 1. It is the figure which expanded a part of FIG. It is a distribution map of Al composition of each layer of FIG. FIG. 5 is a cross-sectional view schematically showing a multilayer epitaxial film in a VCSEL manufacturing process. It is sectional drawing which shows typically formation of a mesa post structure in the manufacturing process of VCSEL. It is sectional drawing which shows typically the oxidation of the outer peripheral part of a current confinement layer in the manufacturing process of VCSEL. It is sectional drawing which shows typically formation of a moisture-proof film | membrane in the preparation process of VCSEL. It is sectional drawing which shows typically formation of a contact electrode in the manufacturing process of VCSEL. It is sectional drawing which shows typically formation of a polyimide pattern in the preparation process of VCSEL. It is sectional drawing which shows typically formation of a pad electrode in the preparation process of VCSEL. It is a flowchart which shows the preparation process of VCSEL. It is sectional drawing which shows the structure of an oxidation furnace typically. It is a flowchart which shows the procedure of a heating steam oxidation process (step S140 of FIG. 12). It is sectional drawing which expanded and showed the principal part of the stage 2 shown in FIG. 13 typically.

Hereinafter, embodiments will be described in detail with reference to the drawings. In the following, the structure of the VCSEL and the manufacturing method thereof will be described, and then the oxidation method that is a feature of the present invention will be described in detail. In the following description, the same or corresponding parts are denoted by the same reference numerals, and the description thereof may not be repeated.

[Configuration of VCSEL]
FIG. 1 is a plan view schematically showing the configuration of a VCSEL. FIG. 2 is a diagram schematically showing a cross-sectional structure along the line II-II in FIG. FIG. 3 is an enlarged view of a part of FIG. 2 and 3 are schematic diagrams, and the thickness of each layer in the drawings is not proportional to the actual thickness of the device. Also, the thicknesses of the layers in FIGS. 2 and 3 are not proportional to each other.

Referring to FIGS. 1 to 3, the VCSEL 1 is disposed inside the substrate 10, the semiconductor

multilayer reflector layers

11, 15, the

clad layers

12, 14, the active layer 13, and the semiconductor multilayer reflector layer 15. The current confinement layer 16, the anode electrode layer 19, and the cathode electrode layer 20 are provided.

In this embodiment, a GaAs (gallium arsenide) semiconductor substrate exhibiting an N-type conductivity is used as the substrate 10. A cathode electrode layer (back electrode layer) 20 is formed on the back surface of the substrate 10. Although different from the cases shown in FIGS. 1 to 3, a non-doped GaAs substrate exhibiting semi-insulating properties may be used as the substrate 10. In this case, the cathode electrode layer 20 is formed on the surface of the DBR layer 11.

On the substrate 10, a semiconductor multilayer reflector (DBR: Distributed Bragg Reflector) layer 11 made of a compound semiconductor having N-type conductivity is formed. The DBR layer 11 includes, for example, a structure in which Al _0.15 Ga _0.85 As and Al _0.9 Ga _0.1 As are alternately stacked with an optical film thickness λ / 4. Si (silicon) is doped to give an N-type conductivity, and its concentration is, for example, 2 to 3 × 10 ¹⁸ [cm ⁻³ ]. Si coordinates to a Ga (Al) site and easily becomes a donor.

Al _X Ga _(1-X) As (aluminum, gallium, arsenic) is a mixed crystal semiconductor of GaAs and AlAs. The higher the Al composition (X), the wider the energy gap and the lower the refractive index. Since the lattice constant hardly changes depending on the Al composition (X), an Al _x Ga _(1-x) As film having any Al composition (X) can be epitaxially grown on the GaAs substrate. In this specification, when the Al composition (X) is not specified, it may be described as AlGaAs.

An active region for generating laser light is formed on the DBR layer 11. The active region includes the clad

layers

12 and 14 and the active layer 13 having an optical gain sandwiched between the

clad layers

12 and 14. In the active layer 13, a multiple quantum well (MQW) in which a quantum well layer and a barrier layer are stacked in multiple layers is formed. The active layer 13 is a non-doped region where impurities are not introduced.

The cladding layers 12 and 14 can be non-doped or partially doped depending on the design of the resistance value of the device. In this embodiment, a part of the cladding layers 12 and 14 in contact with the N-type and P-type DBR layers 11 and 15 is doped with an impurity having the same conductivity type as that of the adjacent DBR layers 11 and 15.

An upper DBR layer 15 made of a compound semiconductor having a P-type conductivity is formed on the active region. The upper DBR layer 15 constitutes an optical resonator together with the lower DBR layer 11. Except for the current confinement layer 16, the DBR layer 15 is made of, for example, Al _0.15 Ga _0.85 As and Al _0.9 Ga _0.1 As each having an optical film thickness of λ / 4 (λ). (Represents the wavelength of the laser beam) and includes an alternately stacked structure. In order to give a P-type conductivity, C (carbon) is doped, and its concentration is, for example, 2 to 3 × 10 ¹⁸ [cm ⁻³ ]. C is easily coordinated to the As site and becomes an acceptor.

Here, the conductivity type may be reversed, the substrate 10 may be a P-type semiconductor substrate, the lower DBR layer 11 may be P-type, and the upper DBR layer 15 may be N-type. . In this specification, when the first and second conductivity types are described, one of the first and second conductivity types is P-type, and the other is N-type.

Furthermore, a current confinement layer 16 is formed in a part of the upper DBR layer 15 to efficiently inject current into the active region and bring about a lens effect. As shown in FIG. 3, the current confinement layer 16 has an unoxidized portion 18 at the central portion and an oxidized portion 17 of a substantially insulator around the central portion. In this structure, an oxidized layer to be the current confinement layer 16 is formed of Al _X Ga _(1-X) As satisfying 0.95 ≦ X ≦ 1 (when X = 1, that is, including AlAs), After the epitaxial multilayer film including the layers is processed into a mesa post shape, the layer to be oxidized is selectively oxidized from the surroundings in a heated steam atmosphere. Since only the unoxidized portion 18 in the central portion becomes a current path, current can be efficiently injected into the active region.

As shown in FIGS. 1 and 2, a moisture-proof insulating film 21 (also referred to as a moisture-resistant film) is formed on an epitaxial multilayer film having a mesa post structure. An opening is formed in the insulating film 21 above the mesa post so that the surface of the DBR layer 15 is exposed. An anode electrode layer 19 (ring electrode layer) is connected to the exposed surface of the DBR layer 15. A pad electrode 23 for bonding is connected to the anode electrode layer 19. A polyimide pattern 22 is provided between the pad electrode 23 and the DBR layer 11 in order to reduce parasitic capacitance.

[Al composition distribution]
4 is a distribution diagram of the Al composition of each layer in FIG. The vertical axis of FIG. 4 indicates the Al content (X) of Al _X Ga _(1-X) As, and the horizontal axis indicates the depth direction of the VCSEL in arbitrary units (AU). When X = 0, it means GaAs, and when X = 1, it means AlAs.

Referring to FIG. 4, in DBR layers 11 and 15, a low refractive index layer having a high Al content and a high refractive index layer having a low Al content are alternately laminated. The region adjacent to the cladding layers 12 and 14 in the DBR layers 11 and 15 corresponds to the first low refractive index layer. In the case of FIG. 4, the current confinement layer 16 is formed at a position farthest from the active layer 13 in the first low refractive index layer of the DBR layer 15. The current confinement layer 16 may be disposed on a lower layer side (for example, a position adjacent to the clad layer 14) in the first low refractive index layer. The P-type doped region 31 extends from the DBR layer 15 to a part of the cladding layer 14.

The current confinement layer 16 is formed inside the first low-refractive index layer constituting the DBR layer 15, but may be arranged closer to the active layer 13 such as the inside of the cladding layer 14. Is possible. Therefore, more generally speaking, the current confinement layer 16 is disposed in the DBR layer 15 or between the DBR layer 15 and the active layer 13. Alternatively, the current confinement layer 16 can be disposed on the substrate 10 side with respect to the active layer 13, and may be disposed inside the DBR layer 11 or between the DBR layer 11 and the active layer 13.

[Production process of VCSEL]
5 to 11 are cross-sectional views schematically showing a VCSEL manufacturing process. FIG. 12 is a flowchart showing a VCSEL manufacturing process. Hereinafter, a method for manufacturing the VCSEL 1 shown in FIGS. 1 to 4 will be described with reference to FIGS.

Referring to FIG. 5, multilayer epitaxial films 11 to 16 are formed on a semiconductor substrate 10 (here, an N-type GaAs substrate). For the formation of the epitaxial film, a method such as MOCVD (Metal Organic Chemical Vapor Deposition) or MBE (Molecular Beam Epitaxy) is suitable.

Specifically, the DBR layer 11 showing the N-type conductivity is first formed on the GaAs substrate 10 (step S100 in FIG. 12). The DBR layer 11 is formed in 30 to 40 layers with a pair of optical film thicknesses such that the high refractive region and the low refractive region are each λ / 4. As the high refractive material, Al _x Ga _(1-X) As having about X = 0.1 can be used, and as the low refractive material, Al _x Ga _(1-X) As having about X = 0.9 can be used. In order to obtain an N-type conductivity, about 2 × 10 ¹⁸ [cm ⁻³ ] is introduced with Si as an impurity.

Next, an active layer 13 including a quantum well (QW) is formed on the N-type DBR layer 11 so as to be sandwiched between the cladding layers 12 and 14 (steps S105 to S115 in FIG. 12). The thickness and material of the active layer 13 and the cladding layers 12 and 14 can be appropriately adjusted according to the oscillation wavelength. For example, GaAs can be used as the material of the active layer 13 and the oscillation wavelength can be adjusted to 850 nm.

Next, P-type DBR layers 15 and 15A are formed on the cladding layer 14 (steps S120 to S130 in FIG. 12). Similarly to the N-type DBR layer 11, the P-type DBR layers 15 and 15A are formed to have about 20 layers with a pair of optical film thicknesses such that the high refractive region and the low refractive region are each λ / 4. As the high refractive material, Al _x Ga _(1-X) As having about X = 0.1 can be used, and as the low refractive material, Al _x Ga _(1-X) As having about X = 0.9 can be used. In order to obtain a P-type conductivity, about 2 × 10 ¹⁸ [cm ⁻³ ] is introduced with C as an impurity.

However, in the case of the structure shown in FIGS. 1 to 4, an oxidized layer to be the current confinement layer 16 is formed in the first low refractive index layer in contact with the cladding layer. Specifically, for example, an Al _X Ga _(1-X) As layer 15A (where X = 0.65) is formed on the cladding layer 14 with a C (carbon) of about 2 to 3 × 10 ¹⁸ [cm ⁻³ ]. ) while forming introducing (step S120 in FIG. 12), then, by increasing the Al composition X 0.95 or more, Al _X Ga _(1-X) as layer as the layer to be oxidized (where 0 .95 ≦ X ≦ 1) is formed while introducing C (carbon) of about 2 to 3 × 10 ¹⁸ [cm ⁻³ ] (step S125 in FIG. 12).

Since the layer to be oxidized that should become the current confinement layer 16 is distorted due to volume shrinkage during the oxidation treatment, it is desirable that the layer be 40 nm or less in order to suppress the influence of the strain. As described with reference to FIG. 4, the oxidized layer may be formed at a position near the upper layer or at a position near the lower layer in the first low refractive index layer.

Referring to FIG. 6, the epitaxial multilayer film (laminated body) formed on substrate 10 as described above is processed into a mesa post pattern of, for example, φ30 μm to form a current confinement structure (step S135 in FIG. 12). . The mesa post pattern is formed by photolithography and dry etching techniques. The dry etching needs to be performed until at least the side surface of the oxidized layer to be the current confinement layer 16 is exposed. In the case of FIG. 6, the dry etching is performed to a depth at which the surface of the lower DBR layer 11 is exposed.

Referring to FIG. 7, next, the substrate with the epitaxial multilayer film processed into the mesa post pattern is heated to 450 ° C. or higher in a water vapor atmosphere, so that the oxidized film to be the current confinement layer 16 is changed to its outer peripheral portion. The oxidation portion 17 is formed by selectively advancing oxidation from (step S140 in FIG. 12). The oxidation time is adjusted so that the unoxidized portion 18 in the central portion becomes φ10 μm. The cross-sectional shape of the mesa post pattern and the shape of the current confinement layer 16 are not particularly limited, and may be a square or a rectangle other than a circle.

Referring to FIG. 8, next, a silicon nitride film or a silicon oxide film is formed as moisture-resistant film 21 (step S145 in FIG. 12). For the formation of the moisture resistant film 21, a technique such as CVD or sputtering can be applied. On the top of the mesa post, an opening for the contact electrode layer is formed by photolithography and dry etching (step S150 in FIG. 12).

Referring to FIG. 9, next, a P-type contact electrode layer (anode electrode layer) 19 is formed in the opening at the top of the mesa post, for example, by photolithography and vapor deposition (step S155 in FIG. 12). As the P-type contact electrode layer 19, for example, a laminated film made of Ti (titanium), Pt (platinum), and Au (gold) can be used.

Referring to FIG. 10, next, polyimide pattern 22 is formed for the purpose of capacity reduction under pad electrode 23 (step S160 in FIG. 12). Referring to FIG. 11, next, pad electrode 23 connected to P-type contact electrode layer 19 is formed by, for example, photolithography and sputtering film formation (step S165 in FIG. 12).

Thereafter, as shown in FIGS. 1 to 3, after adjusting the thickness of the substrate 10, the back electrode layer 20 is formed (step S170 in FIG. 12). As the back electrode layer 20, for example, a laminated film made of Au, Ge, and Ni can be used. Furthermore, the VCSEL 1 is completed by performing an annealing process (step S175 in FIG. 12) for making ohmic contact between the electrode layers 19 and 20 and the semiconductor layer.

[Details of forming method of current confinement structure]
Next, a method for forming a current confinement layer by heating steam oxidation (step S140 in FIG. 12), which is a characteristic part of the present invention, will be described.

FIG. 13 is a cross-sectional view schematically showing the configuration of the oxidation furnace. Referring to FIG. 13, an oxidation furnace 150 includes a chamber 101 that can be hermetically sealed, and a stage 102 on which a substrate 110 having a processed stacked body is placed. . The stage 102 is provided with a heating unit (not shown) such as a heater for heating the substrate. The stage 102 is fixed in the chamber 101 by a fixing member 129. Examples of the heating unit include a heating mechanism using a resistance heater or an infrared lamp heater, but are not particularly limited.

An oxidizing gas supply pipe 105 is provided on the wall surface of the chamber 101. After the chamber 101 is evacuated by evacuation of the pump 126, water vapor gas is supplied into the chamber 101 from the supply port 151 as an oxidizing gas.

The oxidizing gas supply unit 120 is provided outside the chamber 101 and includes at least an oxidizing gas supply pipe 105, a pump 126, valves 121a to 121d, a pure water tank 122,

ribbon heaters

123 and 124, and a controller 125. Steam gas is supplied as an oxidizing gas from the supply port 151 of the oxidizing gas supply pipe 105 of the oxidizing gas supply unit 120 into the chamber 101.

The oxidation furnace 150 further includes a control unit 140 that controls operations of a heating unit provided in the stage 102, valves 121a to 121d,

ribbon heaters

123 and 124, a controller 125, a pump 126, an infrared microscope 108, and the like. The control unit 140 is configured based on a computer.

FIG. 14 is a flowchart showing the procedure of the heating steam oxidation step (step S140 in FIG. 12). Of the steps in FIG. 14, steps S 205 to S 240 can be executed under the control of the control unit 140.

Referring to FIGS. 13 and 14, first, after placing the substrate 110 in which the laminated band is processed into a mesa post shape on the stage 102 in the chamber 101 (step S <b> 200), the valve 121 b is opened and the pump 126 is used. The inside of the pure water tank 122 is evacuated by sucking the air inside the tube (step S205). Then, the pure water stored in the pure water tank 122 is heated by the ribbon heater 123 to generate water vapor gas (step S210).

Next, the chamber 121 is evacuated by closing the valve 121b and opening the valve 121a (step S215). And after heating the board | substrate 110 to predetermined temperature with a heater etc. (step S220), water vapor | steam gas is induced | guided | derived into the chamber 101 by opening the

valves

121c and 121d (step S225).

The opening and closing of each valve described above is summarized in Table 1 for each procedure. In Table 1, the valve 121b is “closed” at the start of pure water heating. This is because the valve 121b at the start of pure water heating is once the inside of the pure water tank 122 is in a vacuum state. This is because it may be closed.

The flow rate of the water vapor gas is adjusted (flow rate control) by the controller 125. In order to prevent condensate (liquefaction of water vapor gas), it is desirable to provide a ribbon heater 124 at an important point.

The layer to be oxidized on the substrate 110 is oxidized from the surroundings by the water vapor gas induced into the chamber 101. Since the chamber 101 is in a vacuum state, heat transfer due to convection hardly occurs. By keeping the gap between the stage 102 and the substrate 110 around several millimeters, the heat transfer by convection becomes smaller. As a result, the heat transfer due to radiation accounts for the majority, so the temperature distribution on the surface of the substrate 110 can be easily achieved without depending on the temperature distribution on the surface of the stage 102, the warpage of the substrate 110, the flatness of the surface of the stage 102, or the like. It becomes possible to make uniform.

In addition, although the observation window 113 is provided on the top surface of the chamber 101, since heat transfer due to convection hardly occurs, the temperature distribution of the substrate 110 can be obtained even when the stage 102 and the observation window 113 are brought close to each other. This variation does not occur. Further, since the chamber 101 is in a vacuum state, oxidative gas convection does not occur, and the heat of the substrate 110 is less likely to escape from the observation window 113. That is, since the substrate 110 may be disposed close to the observation window 113, the progress of oxidation of the substrate 110 can be confirmed from the observation window 113 via the infrared microscope 108 even during the oxidation process ( Step S230). Further, since it is not necessary to provide a mechanism for moving the stage 102 up and down, the cost can be reduced and the oxidation time as a whole can be shortened.

When the predetermined oxidation time has elapsed (or when the predetermined amount of oxidation has been reached), the supply of water vapor gas is stopped (step S235). Thereafter, the substrate 110 is cooled to near room temperature (step S240) and taken out from the oxidation furnace chamber 159 (step S245).

It should be noted that stage 102 of the oxidation apparatus according to the present embodiment preferably includes a support member that supports substrate 110 at three points on the outer peripheral portion of substrate 110. By supporting the substrate 110 at three points, the contact area between the stage 102 and the substrate 110 can be minimized. Thereby, the heating of the substrate 110 is dominated by the heat transfer by radiation from the stage 102 to the substrate 110 rather than the heat conduction by the contact between the stage 102 and the substrate 10. As a result, the temperature distribution of the substrate 110 can be made uniform, and stable oxidation can be ensured.

FIG. 15 is a cross-sectional view schematically showing an enlarged main part of the stage 102 shown in FIG. FIG. 15A is a plan view showing the substrate 110 placed on the stage 102, and FIG. 15B is a front view showing the substrate 110 placed on the stage 102.

As shown in FIG. 15, the substrate 110 includes three support members 130 that support the substrate 110 at three points in the peripheral portion. Since the planar shape of the substrate 110 is circular, it is preferable to provide the three support members 130 at equiangular intervals at the peripheral portion, that is, so that the central angles formed by the three support members 130 are 120 degrees. This is because the substrate 110 can be stably supported by providing the support members 130 at equal angular intervals.

Even when the substrate 110 is warped, there is no variation in the temperature distribution on the surface of the substrate 110 between the portion where the warp is generated and the portion where the warp is not generated. Therefore, the temperature distribution on the surface of the substrate 110 does not vary due to the warp generated in the substrate 110, and the oxidation can proceed uniformly.

[effect]
According to the above embodiment, since the water vapor gas generated by heating pure water in a vacuum atmosphere is supplied into the chamber as an oxidizing gas, the oxidizing gas is sprayed using an inert gas such as nitrogen gas as a carrier. Compared with the conventional method, the diffusion efficiency of the gas is high as much as the inert gas does not exist, and the oxidizing gas can be supplied uniformly to the oxidation target layer of the laminate. In addition, since the oxidizing gas is not strongly blown, it is possible to suppress the occurrence of a temperature drop of the substrate and the accompanying variation in temperature distribution, and the degree of progress of oxidation of the oxidized layer can be made uniform. Thereby, the oxidation distribution of the oxidation target can be made uniform.

[Modification]
In the above embodiment, the stacked body including the DBR layers 11 and 15, the cladding layers 12 and 14, the active layer 13, and the oxidized layer to be the current confinement layer 16 is processed into a mesa post shape. Alternatively, the laminate may be processed into a recess structure. Also in the case of the recess structure, an oxidation portion is formed so as to surround an unoxidized portion by the progress of oxidation from the side surface of the oxidized layer that should become the current confinement layer 16.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 VCSEL, 10 substrate, 11, 15 semiconductor multilayer reflector layer (DBR layer), 12, 14 cladding layer, 13 active layer, 16 current confinement layer, 17 oxidized portion, 18 unoxidized portion, 19 contact electrode layer (anode) Electrode layer), 20 back electrode layer (cathode electrode layer), 21 moisture resistant film (insulating film), 22 polyimide pattern, 23 pad electrode, 25 high resistance region, 30 N-type doped region, 31 P-type doped region, 101 chamber, 102 stage, 108 infrared microscope, 110 substrate, 113 observation window, 120 oxidizing gas supply unit, 130 support member, 151 supply port.

Claims

Forming a laminated body including first and second reflecting mirror layers, an active layer, and an oxidized layer to be a current confinement structure on a substrate;
Processing the laminate so that at least the side surface of the oxidized layer is exposed;
Forming a current confinement structure by oxidizing the layer to be oxidized from the side after processing the laminated body,
Forming the current confinement structure comprises:
Placing the substrate having the laminated body after processing on a stage provided inside a chamber capable of airtight inside;
Generating water vapor gas by heating pure water in a vacuum atmosphere in a pure water tank outside the chamber;
A method of manufacturing a vertical cavity surface emitting laser, comprising the step of supplying the water vapor gas to the chamber in a vacuum atmosphere while controlling the flow rate.
The stage is
A heating unit for heating the substrate;
The method for manufacturing a vertical cavity surface emitting laser according to claim 1, further comprising: a support member that supports the substrate at three points on a peripheral portion of the substrate.
The step of forming the current confinement structure further comprises a step of confirming the progress of oxidation of the oxidation target layer of the stacked body by infrared rays from an observation window provided on the top surface of the chamber. 3. A method for producing a vertical cavity surface emitting laser according to 2.