WO2024048882A1

WO2024048882A1 - Laser device manufacturing method

Info

Publication number: WO2024048882A1
Application number: PCT/KR2023/002714
Authority: WO
Inventors: 유준상
Original assignee: 주식회사 오이솔루션
Priority date: 2022-08-31
Filing date: 2023-02-27
Publication date: 2024-03-07
Also published as: KR20240031544A

Abstract

The present invention relates to a laser device manufacturing method. The disclosed present invention comprises the steps of: laminating a first conductive clad layer, an active layer, a second conductive clad layer, and an ohmic contact layer in order on a substrate; forming a first mask layer on the ohmic contact layer, and then, by using same as a mask, etching the second conductive clad layer, the active layer, and the first conductive clad layer, along with the ohmic contact layer; forming a semi-insulating clad layer having rabbit ear-shaped protrusion parts, on the second conductive clad layer, the active layer, the first conductive clad layer, and the ohmic contact layer which have been exposed by the etching; removing the first mask layer, forming a second mask layer on the semi-insulating clad layer and the ohmic contact layer, and then selectively etching the second mask layer so as to expose the rabbit ear-shaped protrusion parts; and planarizing the semi-insulating clad layer by removing the exposed protrusion parts of the semi-insulating clad layer by using the etched second mask layer as a mask.

Description

Laser device manufacturing method

The present invention relates to an integrated optical device, and more specifically, to a laser device that can maintain the upper surface of the semi-insulating clad layer flat by removing sharp protrusions in the shape of rabbit ears created on the semi-insulating clad layer. It is about manufacturing method.

In general, for ultra-high-speed optical signal transmission of 10G bps or more in optical communication, the 1550nm wavelength band, which has a low absorption rate of optical fiber, is mainly used, and an electro-absorption modulator and a distributed-feedback laser diode are used. : DFB LD) combined laser (electro-absortion modulated laser: hereinafter referred to as EML) is used.

In the case of such an integrated device, electrical isolation between the integrated distributed feedback laser diode and the field absorption optical modulator, or between the semiconductor optical amplifier and the field absorption optical modulator or distributed feedback laser diode, or optical isolation, is used in the device. It is an important factor that determines performance.

Figure 1 is a diagram showing the configuration of an EML integrated optical device with an EMBH (Etched Mesa Buried Hetero-structure) structure.

Referring to FIG. 1, the EMBH structure integrated optical device includes an n-type substrate 11, an n-type lower clad layer 12 formed on the n-type substrate 11, and an n-type lower clad layer 12 formed on the n-type lower clad layer 12. An active layer 13, a p-type upper clad layer 14 formed on the active layer 13, an ohmic contact layer 15 formed on the p-type upper clad layer 14, and a p-type lower clad layer 12 ) It is composed of a semi-insulating clad layer 17 formed to surround the upper and side walls of the active layer 13, the p-type upper clad layer 14, and the side walls of the ohmic contact layer 15.

Here, the integrated optical device of the existing EMBH structure has the p-type upper clad layer 14 only on the active layer 13, so the capacitance can be reduced. Therefore, there is an advantage that there is no need to etch the surrounding unnecessary p-type upper clad layer.

However, since the devices are connected by the p-type upper clad layer 14, they must be insulated through ion implantation or etching processes, and the problems inherent in each process remain.

In addition, in the integrated optical device of the EMBH structure, the width of the p-type upper cladding layer 14 for current injection is narrow, so the resistance, including contact resistance with the electrode, increases.

As shown in Figure 1, the integrated optical device having an EMBH (Etched Mesa Buried Hetero Structure) structure has sharp protrusions in the shape of rabbit ears on the surface of the semi-insulating (SI) clad layer 17. (18) is formed.

Therefore, due to the sharp protrusions 18 in the shape of rabbit ears, while cutting the substrate into a plurality of bars, the sharp protrusions 18 in the shape of rabbit ears collide with each other and break into particles.

In addition, as shown in FIG. 2, sharp protrusions 18 in the shape of rabbit ears are formed on the semi-insulating clad layer 17 around the electrode 22, so that thin electrodes may break.

In order to protect the active area, the height of the electrode 22 must be higher than the rabbit ear-shaped protrusion 18 by a certain thickness t, so a metal material layer to form the electrode 19, for example, For example, Au consumption increases, which has the disadvantage of increasing not only the manufacturing cost but also the manufacturing time.

Therefore, the purpose of the present invention is to maintain the height of the semi-insulating (SI) clad layer, but to provide a laser device manufacturing method that can reduce particle contamination caused by cracking of the protrusions by removing sharp protrusions in the shape of rabbit ears. .

In addition, the purpose of the present invention is to provide a laser device manufacturing method that can significantly reduce product damage by flattening the semi-insulating clad layer and reduce manufacturing costs by reducing the consumption of metal materials.

The present invention for achieving the above object includes the steps of sequentially stacking a first clad layer of a first conductivity type, an active layer, a second conductivity type clad layer, and an ohmic contact layer on a substrate, and applying a first mask on the ohmic contact layer. forming a forming material layer and patterning it to form a first mask layer; etching the ohmic contact layer using the first mask layer as a mask; and etching the ohmic contact layer using the first mask layer as a mask. etching the second conductive clad layer, the active layer, and the first conductive clad layer; and etching the exposed second conductive clad layer, the active layer, the first conductive clad layer, and the ohmic contact layer. forming a semi-insulating clad layer with rabbit ear-shaped protrusions on the semi-insulating clad layer; removing the first mask layer; and forming a semi-insulating clad layer on the semi-insulating clad layer and the ohmic contact layer. forming a mask layer, selectively etching the second mask layer to expose the rabbit ear-shaped protrusions of the semi-insulating clad layer, and removing the exposed protrusions of the semi-insulating clad layer to Planarizing the upper surface of the semi-insulating clad layer, removing the second mask layer and forming an electrode on the exposed ohmic contact layer.

The laser device manufacturing method according to the present invention includes etching the second conductive clad layer, the active layer, and the first conductive clad layer using the first mask layer as a mask, the second conductive upper clad layer and The active layer and the first conductive lower clad layer may be sequentially etched to form a mesa structure.

In the laser device manufacturing method according to the present invention, the step of selectively removing the second mask layer to expose the rabbit ear-shaped protrusions corresponds to the protrusions of the ohmic contact layer and the semi-insulating clad layer surrounding it. A process of placing an exposure mask on an upper side of the second mask layer so that a portion of the second mask layer is exposed, irradiating UV to the exposed portion of the second mask layer using the exposure mask as a mask, and then performing a UV development process. It may include a process of removing the irradiated portion of the second mask layer to expose the protrusion.

According to the laser device manufacturing method according to the present invention, the semi-insulating clad layer may include any one of a transition element or a lanthanide-based or actinium-based element.

According to the laser device manufacturing method according to the present invention, the first mask layer may include SiO ₂ or SiNx.

According to the laser device manufacturing method according to the present invention, the second mask layer may include a photoresist material.

According to the laser device manufacturing method according to the present invention, the first conductive lower clad layer may include an n-type InP material, and the second conductive upper clad layer may include a p-type InP material.

According to the laser device manufacturing method according to the present invention, the active layer has an MQW (Multi Quantum well) structure in which well layers and barrier layers are alternately stacked, and the composition of the well layers and barrier layers may include InAlGaAs or InGaAsP.

According to the laser device manufacturing method according to the present invention, the semi-insulating clad layer is composed of InP material, and the dopants that enable the InP material to have semi-insulating properties include Fe, Co, and Cr. , Mn, Ti, and Ru may be included as transition metals.

As described above, according to the laser device manufacturing method according to the present invention, sharp protrusions in the shape of rabbit ears generated when forming a semi-insulating clad layer are removed through an etching process using a photo mask. By doing so, the upper surface of the semi-insulating clad layer is flattened, greatly reducing damage to the product.

In addition, the laser device manufacturing method according to the present invention flattens the upper surface of the semi-insulating clad layer by removing the protrusions formed on the semi-insulating clad layer, so that when cutting the existing substrate into multiple bars, rabbit ears are used. As the sharp protrusions in the shape of (rabbit ears) break, contamination caused by particles is reduced, thereby reducing problems occurring on the surface of the product.

In addition, the laser device manufacturing method according to the present invention removes the protrusions formed on the semi-insulating clad layer to flatten the upper surface of the semi-insulating clad layer, so there is no need for a metal layer such as a metal material forming an electrode, such as Au. Since there is no need to form it too thick, not only can manufacturing costs be reduced, but manufacturing time can also be shortened.

Figure 1 is a diagram showing the configuration of an integrated optical device with an EMBH (Etched Mesa Buried Hetero-structure) structure according to the prior art.

Figure 2 is a diagram schematically showing a state in which a thick electrode material layer is formed due to protrusions of a semi-insulating clad layer in an integrated optical device with an EMBH (Etched Mesa Buried Hetero-structure) structure according to the prior art.

Figures 3A to 3K are cross-sectional process views for explaining the laser device manufacturing method according to the present invention.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings.

The present embodiments may be modified in other forms or various embodiments may be combined with each other, and the scope of the present invention is not limited to each embodiment described below.

Even if matters described in a specific embodiment are not explained in other embodiments, they may be understood as descriptions related to other embodiments, as long as there is no explanation contrary to or contradictory to the matter in the other embodiments.

For example, if a feature for configuration A is described in a specific embodiment and a feature for configuration B is described in another embodiment, the description is contrary or contradictory even if an embodiment in which configuration A and configuration B are combined is not explicitly described. Unless otherwise stated, it should be understood as falling within the scope of the rights of the present invention.

In the description of the embodiment, when an element is described as being formed “on or under” another element, or under) includes both two elements being in direct contact with each other or one or more other elements being placed between the two elements (indirectly). Additionally, when expressed as "on or under," it can include not only the upward direction but also the downward direction based on one element.

Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention.

In this embodiment, the technical idea of the present invention is explained based on the configuration of the laser device of the integrated optical device, but the idea of the present invention is not limited to the laser device of the integrated optical device and can also be applied to other types of tunable lasers. Of course.

Figures 3A to 3K are cross-sectional views of the manufacturing process for explaining the laser device manufacturing method according to the present invention.

First, referring to FIG. 3A, a first conductivity type, for example, n-type substrate 101 is placed on a first conductivity type, for example, n-type lower clad layer 102, an active layer of a multiple quantum well (MQW) structure ( 103), a second conductive type, for example, p-type upper clad layer 104 and an ohmic contact layer 105 are sequentially stacked. At this time, the substrate 101 is formed of an n-type InP material as an example, but it is not limited to this and may be formed using other materials.

Additionally, the n-type lower clad layer 102 of the first conductivity type may include an InP material, but is not necessarily limited thereto.

Additionally, the active layer 103 may have an MQW (Multi Quantum well) structure in which well layers and barrier layers are alternately stacked. The composition of the well layer and the barrier layer may include, but are not necessarily limited to, InAlGaAs or InGaAsP.

Additionally, the p-type upper clad layer 104, which is the second conductivity type, may include an InP material, but is not necessarily limited thereto.

Additionally, the ohmic contact layer 105 may include an InGaAs material, but is not necessarily limited thereto.

Next, referring to FIG. 3B, a first mask material layer (not shown) is formed on the ohmic contact layer 105 using SiO ₂ or SiNx to form a Buried Hetero (BH) structure. At this time, the forming material of the first mask material layer (not shown) may include SiO ₂ or SiNx, but is not necessarily limited thereto.

Next, the first mask layer 106 is formed by selectively etching the first mask material layer (not shown).

Next, referring to FIG. 3C, the ohmic contact layer 105 is selectively etched through an etching process using the first mask layer 106 as a mask. At this _time , when etching _the ohmic contact layer 105 _, the ohmic contact layer ( 105) can be wet etched. Here, the selective etchant includes H ₂ PO ₄ : H ₂ O = 1 : 1 : 5, but is not necessarily limited thereto.

Next, referring to FIG. 3D, the upper clad layer 104, the active layer 103, and the lower clad layer 102 are sequentially etched through a mesa etching process using the first mask layer 106 as a mask. This forms a BH (Buried Hetero) structure.

At this time, a vertical mesa is formed in advance up to the active layer 103 through a dry etching process using the first mask layer 106 as an etch mask, and then a non-selective etchant, such as HBr: H ₂ O ₂ : H ₂ O = 10 : 2 : 100 can be used to etch.

Through the etching process, the p-type InP upper clad layer 104 is formed in an inverse mesa structure, and the InGaAs active layer 103 and the n-type lower clad layer 102 are formed in a mesa structure.

The formation of the inverse mesa utilizes the characteristics of the wet etching process, in which the reaction with the etchant is significantly reduced, and is etched at an angle of approximately 60 degrees due to the inherent characteristics of the InP material.

After forming the p-type upper clad layer 104 of the inverted mesa structure, when it encounters the InGaAs active layer 103, the ancestor changes and it is no longer etched with the inverse mesa structure but with the mesa structure. In addition, the process of FIG. 3D is possible only with a wet etching process, but as described above, combining the dry etching process and the wet etching process can shorten the process time.

Meanwhile, in order to reduce series resistance, it is important to thin the thickness between the active layer 103 and the ohmic contact layer 105, that is, the thickness of the p-type upper clad layer 104. Although it is possible in the case of a thick upper clad layer, in order to obtain series resistance characteristics or good high-frequency response characteristics of the optical device, it is desirable to have a minimum thickness, for example, the thickness of the p-type upper clad layer 104, of 0.8 to 2.0 μm. do.

Next, referring to FIG. 3E, a semi-insulating clad layer 107 is formed on the sidewall of the BH structure formed through the mesa etching process. At this time, protrusions 108 in the shape of rabbit ears are formed around the side walls of the BH (Buried Hetero) structure. Additionally, the semi-insulating clad layer 107 may include a transition element or any one of a lanthanide-based or actinium-based element, but is not necessarily limited thereto.

In addition, the semi-insulating clad layer 107 is made of InP material to block current and electrically separate devices on the sidewalls of the inverted mesa and mesa structures. At this time, transition metals such as Fe, Co, Cr, Mn, Ti, and Ru can be mainly used as dopants that allow the InP material to have semi-insulating properties. In this embodiment, the leakage current The case of doping with low Fe is given as an example, but it is not necessarily limited to this.

The sidewall of the BH structure includes the ohmic contact layer 105, the upper clad layer 104, the active layer 103, and the lower clad layer 102 sidewall.

Forming an inverted mesa in the form of an EMBH (Etched Mesa Buried Hetero-structure) has the advantage of reducing direct force resistance.

Next, referring to FIG. 3F, the first mask layer 106 is removed, and photoresist is applied to the entire upper surface of the ohmic contact layer 105 and the semi-insulating clad layer 107 to form a second mask layer 109. forms.

Next, referring to FIG. 3g, an exposure mask 110 is placed on the upper part of the second mask layer 109, and the exposure mask 110 is used as a mask to UV expose the second mask layer 109. exposed through. At this time, the exposure mask 110 is composed of an opening (not shown) and a blocking part (not shown), and the opening (not shown) is connected to the ohmic contact layer 105 below the second mask layer 109 and its It is located at a position corresponding to the rabbit ear-shaped protrusion 108 of the surrounding semi-insulating clad layer 107.

Next, referring to FIG. 3H, UV exposure is performed through the opening (not shown) of the exposure mask 110 to selectively etch the exposed portion of the second mask layer 109 to form the semi-insulating clad layer. The protrusion 108 of (107) is exposed.

Next, referring to FIG. 3I, the exposed protrusions 108 of the semi-insulating clad layer 107 are etched to flatten the upper part of the semi-insulating clad layer 107.

Next, referring to FIG. 3J, the selectively etched second mask layer 109 is removed to expose the semi-insulating clad layer 107 and the ohmic contact layer 105 from which the protrusions 108 have been removed.

Next, referring to FIG. 3K, a metal material, such as Au, is deposited on the entire upper surface of the ohmic contact layer 105 and the semi-insulating clad layer 107, and then selectively etched through a mask process to form the ohmic contact layer 105. An electrode 112 for a laser device is formed on the contact layer 105.

At this time, physical vapor deposition (PVD) methods such as sputtering, E-beam evaporation, and thermal evaporation are used as a method of forming the metal material for forming the electrode.

In the embodiment, the case of depositing a metal using an electron beam deposition method is described as an example, but the present invention is not necessarily limited to this and the metal can be deposited using the various deposition methods described above.

At this time, the deposition thickness of the metal material layer does not need to be as thick as in the prior art. The reason is that, as shown in FIG. 2, in the prior art, in order to form the electrode 22 due to the rabbit ear-shaped protrusion 18 formed on the semi-insulating clad layer 17, the metal material layer is formed with a certain thickness t. It must be formed thickly.

However, in the case of the present invention, the upper surface of the semi-insulating clad layer 107 is flattened by removing the protrusions 108 of the semi-insulating clad layer 107, so that the electrode 112 is formed on the ohmic contact layer 105. Since there is no need to form a thick metal material, not only the cost of manufacturing the device but also the manufacturing process time can be reduced.

As described above, according to the laser device manufacturing method according to the present invention, the sharp protrusions in the shape of rabbit ears generated when forming the semi-insulating clad layer are removed through an etching process using a photo mask, thereby forming the semi-insulating clad layer. The upper surface is flattened, greatly reducing damage to the product.

In addition, the present invention flattens the upper surface of the clad layer by removing the protrusions formed on the semi-insulating clad layer, so when cutting the existing substrate into a plurality of bars, sharp protrusions in the shape of rabbit ears are removed. When it breaks, particle contamination caused by particles colliding is reduced, so contamination occurring on the surface of the product is reduced.

In addition, since the present invention flattens the upper surface of the clad layer by removing the protrusions formed on the semi-insulating clad layer, the manufacturing cost can be reduced by eliminating the need to form the metal material layer forming the electrode unnecessarily thick, thereby reducing the manufacturing cost. The manufacturing time can also be shortened.

Although the above description focuses on examples, this is only an example and does not limit the present invention, and those skilled in the art will understand that the examples are as follows without departing from the essential characteristics of the present example. You will see that various variations and applications are possible. For example, each component specifically shown in the examples can be modified and implemented. And these variations and differences in application should be construed as being included in the scope of the present invention as defined in the appended claims.

Claims

sequentially stacking a first conductive type first clad layer, an active layer, a second conductive type clad layer, and an ohmic contact layer on a substrate;

forming a first mask forming material layer on the ohmic contact layer and patterning the layer to form a first mask layer;

etching the ohmic contact layer using the first mask layer as a mask;

etching the second conductive clad layer, the active layer, and the first conductive clad layer using the first mask layer including the ohmic contact layer as a mask;

Forming a semi-insulating clad layer having rabbit ear-shaped protrusions on the etched and exposed second conductive clad layer and active layer, and the first conductive clad layer and ohmic contact layer. step;

removing the first mask layer and forming a second mask layer on the semi-insulating clad layer and the ohmic contact layer;

selectively removing the second mask layer to expose rabbit ear-shaped protrusions;

flattening the upper surface of the semi-insulating clad layer by removing the exposed protrusions of the semi-insulating clad layer; and

A laser device manufacturing method comprising: removing the second mask layer and forming an electrode on the exposed ohmic contact layer.
According to claim 1,

In the step of etching the second conductive type clad layer, the active layer, and the first conductive type clad layer using the first mask layer as a mask, the second conductive upper clad layer, the active layer, and the first conductive type lower clad layer A laser device manufacturing method characterized in that the layers are sequentially etched to form a mesa structure.
According to claim 1,

The step of removing the exposed portion of the second mask layer to expose the rabbit ear-shaped protrusions,

A process of placing an exposure mask on an upper side of the second mask layer so that a portion of the second mask layer corresponding to the protrusion of the semi-insulating clad layer in the ohmic contact layer and its surrounding area is exposed;

Manufacturing a laser device comprising the step of irradiating UV to the exposed portion of the second mask layer using the exposure mask as a mask and then removing the irradiated portion of the second mask layer to expose the protrusion. method.
According to claim 1,

A method of manufacturing a laser device, wherein the semi-insulating clad layer includes a transition element or a lanthanum-based or actinium-based element.
According to claim 1,

The semi-insulating clad layer is made of an InP material, and the dopant that allows the InP material to have semi-insulating properties is a transition metal of Fe, Co, Cr, Mn, Ti, and Ru ( A laser device manufacturing method comprising any one of transition metal).
According to paragraph 1,

The first mask layer is a laser device manufacturing method, characterized in that it includes SiO 2 or SiNx.
According to paragraph 1,

A method of manufacturing a laser device, wherein the second mask layer includes a photoresist material.
According to paragraph 1,

A method of manufacturing a laser device, wherein the first conductive lower clad layer includes an n-type InP material, and the second conductive upper clad layer includes a p-type InP material.
According to paragraph 1,

The active layer is an MQW (Multi Quantum well) structure in which well layers and barrier layers are alternately stacked, and the composition of the well layers and barrier layers includes InAlGaAs or InGaAsP.