KR890004644B1 - Radiation diode array manufacturing method - Google Patents

Abstract

The manufacturing method for the LED for application to FAX or photo copier comprises steps of : (a) epitaxial growth of a p-type AlGaAS(32), a n-type AlGaAS(33) and a n-type GaAS(34) with a fixed thickness in sequence on the GaAS substrate(31); (b) forming ptype region(35) by diffusing Zn at a fixed part of the epitaxial layer; (c) forming an ohmic contact(45) by etching the n-type GaAS(34); (d) forming a P-N junction, which is light emitting region, by etching a part of the p-type AlGaAS(32) and the p-type AlGaAS(32) and the n- type AlGaAS(33);(e) forming a protective film on the top layer;

Description

Manufacturing method of light emitting diode array

Figure 1a is a cross-sectional view of a conventional light emitting diode array using zinc diffusion.

2b is a cross-sectional view of a light emitting diode array using mesa etching in the related art.

2 is a perspective view of the light emitting diode array of the present invention.

3A to 3L are manufacturing process diagrams of the light emitting diode array of the present invention.

* Explanation of symbols for main parts of the drawings

1, 11, 31: GaAs substrate 2: n-type GaAsP

3, 35: zinc diffusion region 4, 16, 39: P-type electrode

5, 15, 38: n-type electrode 12, 32: P-type AlGaAs active layer

13, 33: n-type AlGaAs transmission layer 14, 34: n-type GaAs cap layer

37 PSG protective film 35 P-type conversion layer

30 light emitting region 36 Pn junction portion

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array of light emitting devices that are components of optical printer heads used for facsimile terminals and copiers. In particular, each device is composed of light emitting diodes, and a P-type electrode and an n-type electrode exist on the same side of the device. A light emitting diode array in which light emitting portions are formed by etching.

With the development of information equipment, various types of printers that require high speed, high quality, and low price have been developed as output devices, and printers using high density semiconductor light emitting diode arrays have been developed to meet such demands.

In addition, unlike the printer using a semiconductor laser, the optical type printer of the light emitting diode array, which is an electric photographic print field, has high reliability, fewer parts, and a small optical path length due to the elimination of mechanical moving parts such as a multi-faceted mirror. The LED diode array has been widely used in facsimile machines, copiers, printers, and the like because of its high speed and high quality recording characteristics.

FIG. 1A is a light emitting diode array made by diffusing zinc into a GaAsP semiconductor, and FIG. 1B is an AlGaAs light emitting diode array using Mesa etching.

The light emitting diode of FIG. 1A is composed of a GaAs substrate 1, an n-type GaAsP layer 2, a zinc diffusion region 3, a P-type electrode 4 and an n-type electrode 5 as shown in FIG. Since the light emitting diode of the Pn junction is made by diffusing zinc into the n-type GaAsP layer 2, the light emitting diode becomes a homojunction and the light output is low, resulting in a slow printing speed.

As shown in FIG. 1B, the light emitting diode of FIG. 1B includes a GaAs substrate 11, a P-type AlGaAs active layer 12, an n-type AlGaAs transmission layer 13, an n-type cap layer 14, an n-type electrode 15, and a P-type electrode. It is composed of (16) and the structure of the light emitting diode AlGaAs is heterojunction (Heterojunction), theoretically 10 times more output than GaAsP.

However, since the light emitting diode has a current flowing vertically to the device structure, a substrate having a P-type or n-type conduction type and low defects is required, and an active layer, a transmission layer, and a cap layer near 800 ° C on a substrate fabricated at 1200 ° C or higher. When the epitaxial layer of is grown, a defect occurs at the boundary between the substrate and the epitaxial layer, and the defect directly affects the device.

In addition, since the P-type electrode 16 and the n-type electrode 15 are on different surfaces, the electrode formation must be performed separately. Therefore, a large amount of gold (Au), which is the main raw material for electrode formation, has a disadvantage in that the manufacturing cost increases.

Accordingly, an object of the present invention is to form a device on the high purity epitaxial layer so as to be free from defects occurring at the boundary between the epitaxial layer and the substrate by using a heterojunction AlGaAs system with high luminous output, and to form a P-type electrode and an n-type electrode. It is to provide a method of manufacturing a light emitting diode array to form all at once.

Therefore, the present invention for achieving the above object of the present invention is a first step of epitaxial growth of the P-type active layer, n-type transmissive layer, n-type cap layer in turn on a semi-insulating GaAs substrate with good insulation effect, and A second process of diffusing zinc to form a P-type conversion layer on a predetermined portion of the epitaxial layer surface, a third process of etching an n-type cap layer to form an n-contact resistance part pattern, and a process of the transmission layer and the active layer A fourth process of separating a portion of each device by etching a portion through a photolithography process, a fifth process of forming a protective film on the top of the device for surface stabilization, and a sixth process of forming an active part on the surface of the device Characterized in that made.

Hereinafter will be described in detail with reference to the present invention. 2 shows a GaAs substrate 31, a P-type AlGaAs active layer 32, an n-type AlGaAs transmission layer 33, an n-type cap layer 45, a PSG protective film 37, as shown in the perspective view of the light emitting diode of the present invention. The n-type electrode 38, the P-type conversion region 35, and the P-type electrode 39 are formed, and the region 30 is a light emitting portion separated by etching.

3a to 3l are manufacturing process diagrams of the light emitting diode array of the present invention, and FIGS. 3a, 3c, 3e, 3g, 3i, and 3k are front cross-sectional views of the light emitting diode array. 3b, 3d, 3f, 3h, 3j, and 3l show side cross-sectional views of the light emitting diode array.

3A and 3B illustrate a process of forming a P-type AlGaAs active layer, an n-type AlGaAs permeable layer, and an n-type GaAs permeable layer in order on a GaAs substrate. The starting material is a liquid phase on the substrate using a GaAs substrate having good insulation effect. The P-type AlGaAs active layer 32, the type AlGaAs transmissive layer 33, and the n-type GaAs cap layer are grown sequentially using the crystal growth method.

In this embodiment, a semi-insulating GaAs substrate is used, but both P-type and n-type GaAs substrates may be used.

3C and 3D illustrate a process of diffusing zinc to form a P-type conversion region on a predetermined portion of the epitaxial layer. The nitride film 40 is deposited on the epitaxial layer 34 by CVD (Chemical Vapor Deposition). ), Then a window 41 for zinc diffusion is formed by conventional photolithography, and zinc is diffused to convert the region 35 into a P-type.

3e and 3f are processes for etching an n-type cap layer to form a resistive contact pattern, and after removing the nitride film 40 on the top of FIGS. 3c and 3d, the photoresist is applied, and then a general photolithography process is performed. The resistive contact portion 45 is formed by the method and the photoresist remaining in the acetone solution is removed.

3g and 3h are processes for etching each of the n-type transmission layer and a portion of the P-type active layer to separate regions of each element, and after the photoresist is applied to the entire surface of FIGS. 3e and 3f, ordinary photolithography is performed. By etching the portion of the n-type AlGaAs transmissive layer 34 and the portion of the P-type AlGaAs active layer 38 by a method, a Pn junction portion 36, which is a light emitting region, is formed separately.

3i and 3j show a process of forming a protective film on the top of the device for surface stabilization, and the PSG (Phosphosilicate Glass) film 37 is formed on the top of the 3g and 3h by the conventional CVD method. After that, the upper portion of the region 45 and the region 35 is exposed to form an electrode by a conventional photolithography method.

, Ni는 100

, Au는 2000

순차적으로 증착시킨 후 통상의 사진식각법으로 P형전극(39)과 n형전극(38)을 형성시키며 저항접촉을 좋게하기 위해 400℃ 수소분위기에서 3분동안 열처리하여 소자의 제작을 끝낸다.3k and 3l are processes for forming an electrode on the surface of the device, and Au-Ge is 600 on the entire surface of the device.

, Ni is 100

Au is 2000

After sequentially depositing, the P-type electrode 39 and the n-type electrode 38 are formed by a conventional photolithography method, and heat treatment is performed in a hydrogen atmosphere at 400 ° C. for 3 minutes to improve resistance contact.

Although the Au-Ge / Ni / Au electrode is generally used as an n-type electrode material, the contact resistance of the Au-Ge / Ni / Au electrode is not excellent with respect to the P-type region 35, but the contact area of the P-type electrode 39, which is a common electrode, is large. Since the P-type electrode 39 and the n-type electrode 38 can be formed at the same time using Au / Ge / Ni / Au since they do not affect the characteristics of.

Therefore, the light emitting diode array as described above has a high luminous efficiency because the device is formed on the epitaxial layer having excellent crystal quality, and since the P and n electrodes are on the same side, it is easy to form electrodes and easy to measure in the wafer state. Since common type electrodes are used, driving to a general integrated circuit is easy.

In addition, it is possible to increase the insulation effect by applying a reverse voltage to the substrate after forming it on the n-type substrate instead of the semi-insulating substrate, and the device fabrication of hetero crystal growth structure in which the GaAs layer is grown on the silicon substrate currently under research It is possible to manufacture the optical integrated circuit including the driving circuit because it is possible to operate on the surface rather than the vertical structure.

Claims (3)

In the method of manufacturing a light emitting diode array, epitaxial growth of a P-type AlGaAs active layer 32, an n-type AlGaAs transmissive layer 33, and an n-type GaAs cap layer 34 on a semiconductor GaAs substrate 31 is performed in order. A first process, a second process of diffusing zinc in a predetermined portion of the grown epitaxial layer to form a P-type conversion region 35, and etching the n-type GaAs cap layer 34 to form a predetermined resistance contact portion ( A third step of forming 45), and a fourth step of etching a portion of the n-type AlGaAs transmissive layer 33 and the P-type AlGaAs active layer 32 to form a Pn junction portion 36, which is a light emitting region, and A fifth process of forming a protective film 37 on the top of the device for surface stabilization, and the n-type electrode 38 is formed in contact with the resistance contact portion 45 formed above, and the P-type electrode 39 to be common A light emitting diode array manufacturing method, characterized in that formed on the surface of the P-type conversion region (35). The method of manufacturing a light emitting diode array according to claim 1, wherein the GaAs substrate has an insulating property or a GaAs substrate having an insulating effect. In the fifth process of claim 1, Au-Ge, Ni and Au are sequentially deposited on the semiconductor substrate to simultaneously form a P-type electrode and an n-type electrode so that the P-type electrode and the n-type electrode are on the same side. A method of manufacturing a light emitting diode array.

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