KR100330591B1 - Method of making semiconductor laser diode - Google Patents

Abstract

PURPOSE: A method of making semiconductor laser diode is provided to easily carry out a step of forming a current blocking layer. CONSTITUTION: A method comprises sequentially forming a buffer layer(13), a lower clad layer(14), an active layer(15), an upper layer(16) and a cap layer(18) on a substrate(12). A mask is formed on a stacked structure, and a ridge is formed at a center thereof by etching both ends of the cap and upper clad layers by a predetermined depth. A current blocking layer(17) is formed on the upper clad and cap layers through an electron beam deposition method. Annealing is carried out at a resolution atmosphere for a predetermined time. After removing the mask, the first metal layer(20) and the second metal layer are formed on an upper part of the current blocking and cap layers and on a lower part of the substrate.

Description

Manufacturing method of semiconductor laser diode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser diode, and more particularly, to fabricating a laser diode having an improved process of forming a current blocking layer in a compound semiconductor laser diode having a ridge type waveguide structure. It is about a method.

In general, lasers generated by induced emission are characterized by unidirectional light, directivity, and high intensity. Gas lasers such as helium-neon lasers, argon lasers, and YAG lasers There are various types, ranging from solid state lasers such as ruby lasers to semiconductor lasers that are small and easy to modulate by modulating bias current at high frequencies.

The semiconductor laser as described above is a semiconductor device including the concept of Quantum Electron based on a PN junction, and artificially induces electron-hole recombination by injecting a current into a thin film made of a semiconductor material, that is, an active layer. Light will be emitted corresponding to the reduced energy following recombination.

The semiconductor laser diode is smaller in size, lower in price, and more particularly in intensity control through current control than a solid laser such as a He-Ne gas laser or an Nd: YAG laser. As an information processing device such as a disc player (CDP), an optical memory, a high-speed laser printer, and an optical communication device, the application range is being expanded by replacing a conventional gas laser such as helium-neon.

On the other hand, in recent years, the performance of semiconductor lasers has been improved epitaxially for the development of materials for determining wavelengths and for device structures for determining characteristics and reliability such as critical current, light output, oscillation efficiency, single wavelength, and spectral line width. Epitaxial) The remarkable development is being made by the growth technology and the fine processing technology. In particular, the epitaxial growth technology replaces the conventional liquid phase epitaxy (LPE) method with the method of metal organic chemical vapor deposition (hereinafter referred to as "MOCVD") and molecular beam epitaxy. MBE), etc., enable atomic layer level control.

1 shows a vertical cross section of a compound semiconductor laser diode having a conventional ridge waveguide structure, which forms a current blocking layer using the above-described MOCVD technique.

First, the structure of the conventional ridge type optical waveguide semiconductor laser diode shown in FIG. 1 is as follows. That is, the buffer layer 3, the lower clad layer 4, the active layer 5, and the upper clad layer 6 are sequentially stacked on the upper surface of the substrate 2 to form a laser oscillation layer. In addition, the upper cladding layer 6 of the laser oscillation layer formed as described above is formed of a ridge structure that serves as a conduction channel having a central portion protruding therefrom and a shoulder portion formed at both sides thereof. In addition, a cap layer 8 continuously forms an upper layer portion of the ridge structure on the ridge structure of the upper cladding layer 6, and a current blocking layer is formed on the side of the ridge structure of the upper clad layer 6 and on the upper surface of the shoulder. 7) is laminated. In addition, an n-metal layer 1 is formed on a lower surface of the substrate 2, and a p-metal layer 10 is completely covered on the current blocking layer 7 and the cap layer 8. have.

Referring to the manufacturing method of the semiconductor laser diode according to the prior art having the structure as described above is as follows.

That is, the buffer layer 3, the lower cladding layer 4, the active layer 5, and the upper cladding layer 6 and the capping layer 8 are first grown on the upper surface of the substrate 2 by an epitaxy process and sequentially. Laminated.

Then, both edges of the cap layer 8 and the upper clad layer 6 are etched by wet etching in order to lower the critical driving current on the central upper surface of the sequentially stacked structure as described above. Form a ridge structure.

Thereafter, the current blocking layer 7 is selectively grown on the ridge structure side of the upper cladding layer 6 and the upper surface of the shoulder. According to the related art, in this step, excellent thermal conductivity and thermal expansion coefficient of ZnSe or SiO ₂ are used. In order to grow a single crystal by using an aduct-source MOCVD method.

Finally, the n-metal layer 1 is formed on the bottom surface of the substrate 2 and the p-metal layer 10 is completely covered on the current blocking layer 7 and the cap layer 8 to complete the device. .

However, in the conventional laser diode manufacturing method as described above, ZnSe or SiO ₂ , which is a material having excellent thermal conductivity and high thermal expansion coefficient, is used as the current blocking layer. In this step, an expensive auxiliary-source MOCVD equipment is required. Since there is a problem that acts as a cause of the cost increase.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to manufacture a step of forming a current blocking layer in a method of manufacturing a compound semiconductor laser diode having a ridge type optical waveguide structure. It is to provide a method for manufacturing a laser diode improved to be able to perform the process more simply and easily.

In the manufacturing method according to the present invention uses an E-beam (Electron Beam) deposition technique for forming a current blocking layer to achieve the above object.

Therefore, the method of manufacturing a laser diode according to the present invention in order to achieve the above object,

A first growth step of sequentially stacking a buffer layer, a lower clad layer, an active layer, and an upper clad layer and a cap layer sequentially on the substrate;

An etching step of forming a ridge in the center by forming a mask on the laminated structure after the first growth and etching both ends of the cap layer and the upper clad layer by a predetermined depth by photo lithography;

Depositing a current blocking layer on the upper cladding layer and the cap layer by E-beam deposition;

A heat treatment step of heat-treating the resultant of stacking the current blocking layer for a predetermined time in a reducing atmosphere at a predetermined temperature;

And removing a mask formed on the upper surface of the cap layer, and depositing a first metal layer and a second metal layer on the upper surface of the current blocking layer and the cap layer and the lower surface of the substrate, respectively.

In the method of manufacturing a laser diode according to the present invention, in particular, in the heat treatment step, it is preferable to heat-treat the resulting product by laminating the current blocking layer for 10 to 20 minutes in a reducing atmosphere in a temperature range of 300 ° C. or less. More preferably, the heat treatment is maintained for 15 minutes in a reducing atmosphere of 230 to 270 ° C temperature range can be most usefully applied. In the deposition step, the composition of the current blocking layer deposited by the E-beam is preferably ZnSe. In each manufacturing step of the present invention, the material of the substrate and the buffer layer is n-GaAs, and the lower cladding layer Preferably, the material is n-AlGaInP, the active material is GaInP, and the first and second upper cladding layers are p-AlGaInP.

Hereinafter, exemplary embodiments of a method of manufacturing a semiconductor laser diode according to the present invention will be described in detail with reference to the accompanying drawings.

2 to 4 are vertical cross-sectional views illustrating a step-by-step manufacturing process of a semiconductor laser diode according to the present invention, in which FIG. 2 is a step of sequentially forming a laser oscillation layer on a substrate, and FIG. 3 is a step of forming a mask. 4 and 5 illustrate a step of forming a ridge structure by etching both edges of the cap layer and the upper clad layer. 6 shows a step of depositing a current blocking layer on the upper surface of the ridge structure through E-beam deposition and performing heat treatment as a manufacturing step forming a characteristic element of the present invention. Opening the upper surface of the photolithography and depositing a metal layer to show the step of completing the device.

First, referring to FIG. 2, the buffer layer 13, the lower clad layer 14, the active layer 15, the upper clad layer 16, and the cap layer 18 are sequentially epitaxially processed on the substrate 12. Primary growth is performed by lamination.

Subsequently, as illustrated in FIG. 3, an SiO ₂ dielectric film 21 is formed on the upper surface of the cap layer 18, and an etch mask is formed through patterning.

Next, as illustrated in FIG. 4, the cap layer 18 is formed in a stripe shape having a predetermined width by selective etching, and both edges of the upper clad layer 16 are etched by a predetermined width and depth. The central portion forms a protruding ridge structure.

Then, through the E-beam deposition on the upper surface of both shoulders, the inclined portion and the cap layer 18 of the upper cladding layer 16 forming the above-mentioned ridge structure as a stage element characterizing the manufacturing method according to the present invention. A ZnSe current blocking layer 17 is deposited and laminated. In this case, the current blocking layer 17 deposited by the E-beam is formed in the form of columnar grains so that buckling occurs due to stress when the p-metal layer is subsequently deposited. In the manufacturing method, the resultant, in which the ZnSe current blocking layer 17 is laminated, is maintained for 15 minutes in a reducing atmosphere in a temperature range of 230 to 270 ° C., thereby performing heat treatment, thereby preventing occurrence of the above buckling phenomenon. .

After the heat treatment step, the SiO ₂ dielectric film mask 21 formed on the top surface of the cap layer 18 is removed (FIG. 7), and the n-metal layer 11 on the bottom surface of the substrate 12 as shown in FIG. ) And the p-metal layer 20 is formed on the current blocking layer 17 and the cap layer 18 to complete the fabrication of the device.

As described above, the step of forming the current blocking layer on the upper surface of the upper cladding layer and the cap layer in manufacturing a compound semiconductor laser diode having a ridge type optical waveguide structure, conventionally using an expensive secondary-source MOCVD equipment In the manufacturing method of the present invention, the current blocking layer is deposited by E-beam deposition, and the resultant is heat treated by maintaining the resultant in a reducing atmosphere at a predetermined temperature for a predetermined time. It is intended to be simple and easy.

1 is a vertical cross-sectional view of a semiconductor laser diode having a conventional ridge waveguide structure,

2 to 8 is a vertical cross-sectional view showing a step-by-step manufacturing process of a semiconductor laser diode according to the present invention,

2 is sequentially forming a laser oscillation layer on a substrate,

FIG. 3 shows forming a dielectric film mask on the upper surface of the laser oscillation layer shown in FIG.

4 and 5 illustrate etching of both edges of the cap layer and the upper clad layer to form a ridge structure;

FIG. 6 shows a step of depositing a current blocking layer on the upper surface of the ridge structure through E-beam deposition as a characteristic step of the present invention, and performing a predetermined heat treatment, and FIGS. 7 and 8 show ridges. The upper surface of the structure is opened by photolithography, and a cap layer is grown on the upper surface to complete the device.

* Explanation of symbols for main parts of the drawings

11..n-metal layer 20..p-metal layer

12. Substrate 13. First buffer layer

14. Lower cladding layer 15. Active layer

16. Upper cladding layer 17. ZnSe current blocking layer

18. Cap layer 21. Dielectric film

Claims (5)

A first growth step of sequentially stacking a buffer layer, a lower clad layer, an active layer, and an upper clad layer and a cap layer sequentially on the substrate; An etching step of forming a ridge in the center by forming a mask on the stacked structure after the first growth and etching both ends of the cap layer and the upper clad layer by a predetermined depth by photo lithography; Depositing a current blocking layer on an upper surface of the upper clad layer and the cap layer through e-beam deposition; A heat treatment step of heat-treating the resultant of stacking the current blocking layer for a predetermined time in a reducing atmosphere at a predetermined temperature; A second deposition step of removing the mask formed on the upper surface of the cap layer, and depositing a first metal charge and a second metal layer on the upper surface of the current blocking layer and the cap layer and on the lower surface of the substrate, respectively. Method of manufacturing a diode. The method of claim 1, The method of manufacturing a laser diode, characterized in that for heat treatment by maintaining the resultant layer laminated the current blocking layer in the heat treatment step in a reducing atmosphere in the temperature range of 300 ° C or less for 10 to 20 minutes. The method according to claim 1 or 2, The method of manufacturing a laser diode, characterized in that for heat treatment by maintaining the resultant laminated the current blocking layer in the heat treatment step for 15 minutes in a reducing atmosphere of 230 to 270 ° C temperature range. The method of claim 1, The method of manufacturing a laser diode, characterized in that the composition of the current blocking layer deposited by the E-beam in the deposition step is ZnSe. The method of claim 1, The material of the substrate and the buffer layer is n-GaAs, the material of the lower cladding layer is n-AlGaInP, the material of the active layer is GaInP, the material of the first and second upper cladding layer is a semiconductor laser, characterized in that p-AlGaInP. Method of manufacturing a diode.