JPH06326357A - Light emitting diode array - Google Patents

Abstract

PURPOSE:To make an electrode wiring part flat by separating light emitting diodes from each other by forming diffusion layers in parallel with the diodes and, at the same time, electrically separating the diodes from each other by forming grooves in the vertical direction. CONSTITUTION:After a partial row where a light emitting diode section is formed is coated with a selective diffusion mask 5 of SiN, p-type diffusion layers 7 for constricting currents are formed in parallel with the row where the light emitting diode section is formed on both side of the row by selectively diffusing Zn. Then the row is divided into a plurality of light emitting diode sections by forming separating grooves 8 by etching the row to the middle of a p-type Ga1-xAlxAs layer 2 in the direction perpendicular to the direction of the row. Therefore, the electrode wiring part of this light emitting diode array can be made flat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode array formed by selective diffusion.

[0002]

2. Description of the Related Art A light emitting diode array is widely used as a light source for a display device or a head light source for a printer device. Here, an example of a conventional light emitting diode array will be described with reference to the drawings.

FIG. 3 (A) is a plan view showing a conventional light emitting diode array, and FIG. 3 (B) is a sectional view taken along line B of FIG.
It is a -B sectional view. In this light emitting diode array, a p-type Ga _1-X Al _X As layer 22 and an n-type Ga _1-Y Al _Y As layer 23 are sequentially epitaxially grown by LPE (liquid phase epitaxy) on a p-type GaAs substrate 21. By setting the mixed crystal ratio X to be about 0.10 to 0.35 and making the mixed crystal ratio Y higher than the mixed crystal ratio X, the p-type Ga _{1 -X} Al _X As layer 22 is formed. Of the n-type Ga _{1 -Y} Al _Y As layer 23 and p
The injection efficiency of electrons supplied to the type Ga _1-x Al _x As layer 22 is increased and the minority carriers injected in the p-type Ga _1-x Al _x As layer 22 are confined. And S
A p-type Ga _1-x Al _x A is formed by a hydrochloric acid or phosphoric acid-based etchant using an etching mask such as io ₂ or SiN.
The light emitting diode portions are separated by etching up to the middle of the s layer 22 in the direction parallel to the array direction and the direction perpendicular to the array direction. Further, after forming the insulating protective film 24 thereon,
Al is vapor-deposited, an ohmic electrode 26 is formed on each light emitting diode portion by using a lithography technique and an etching technique, and an electrode 29 is provided on the back surface of the p-type GaAs substrate 21.

This type of light emitting diode array has a structure in which a compound semiconductor layer having a conductivity type opposite to that of the substrate is formed on or inside a p-type or n-type compound semiconductor substrate, or the same conductivity as the substrate. In a structure in which a compound semiconductor layer having a conductivity type opposite to that of the substrate is formed on or over the surface of the compound type semiconductor layer, the light emitting diode unit is a light emitting diode unit of a compound semiconductor layer having an opposite conductivity type. Parts other than the above are removed by etching to a layer having the same conductivity type as that of the substrate thereunder to separate them, and then electrodes for energization are formed in the respective light emitting diode sections.

The light-emitting diode array shown in FIG. 4 has an n-type GaA structure as shown in the enlarged sectional view of FIG.
An n-type GaAsP layer 32 is crystal-grown on an s substrate 31, a p-type selective diffusion layer 37 is provided by selectively diffusing impurities such as Zn, and an insulating protective film 34 such as SiN is formed thereon. By depositing Al on the GaAs substrate 31 and providing the ohmic electrode 36 by using the lithography technique and the etching technique, and by providing the electrode 39 on the back surface of the GaAs substrate 31, as shown in FIG. The diffusion layers 37) form a light emitting diode array in a straight line.

A light emitting diode array of this type is a p-type or n-type compound semiconductor substrate, or
A plurality of light emitting diode sections are formed by selectively diffusing impurities having a conductivity type opposite to that of the substrate to a portion to be each light emitting diode section in a compound semiconductor layer having the same conductivity type as the substrate laminated on this substrate. An electrode for energizing each of the light emitting diode portions is formed.

[0007]

In the light emitting diode array having the structure as shown in FIG. 3, the periphery of each light emitting diode portion is etched to form a groove in order to separate the individual light emitting diode portions. Al electrode 26 provided on the upper surface
Will be wired across the step due to the etching groove, and the wiring will be broken in the Al vapor deposition step, or the thickness of the resist above and below the step when the wiring pattern is formed by photolithography using resist. There is a problem in that it is not possible to uniformly manufacture each light emitting diode portion of the light emitting diode array, such as unevenness and a difference in light intensity at the time of exposing the resist to ultraviolet light, which causes variations in wiring width. Further, in order to minimize such problems, there is a problem that it is necessary to precisely control the etching depth and its shape.

Further, in the light emitting diode array having the structure as shown in FIG. 4, in order to form the selective diffusion layer having the conductivity type opposite to that of the substrate to be the individual light emitting diode portions, the surface protection film (impurity diffusion) is formed. Impurities are diffused by opening a window for the light emitting part in the (prevention film), and the impurities also diffuse laterally below the surface protective film from the edge of the diffusion window in accordance with the depth of diffusion. Therefore, the diffusion amount in the lateral direction corresponding to the initially planned diffusion depth is predicted in advance, and the size and interval of the diffusion layers are considered so that the diffusion layers of the individual light emitting diode units do not contact each other in the column direction. Then, it was necessary to design the size and interval of the diffusion window with respect to the surface protective film. Further, when forming electrodes for energizing the light emitting diode portions, the electrode pattern is accurately aligned with the position of the light emitting diode portions, particularly with respect to the column direction, in order to securely connect the electrodes to the respective light emitting diode portions. There was a need.

Therefore, an object of the present invention is to provide a high density light emitting diode array which can be easily manufactured.

[0010]

As means for achieving the above object, in a light emitting diode array in which a plurality of light emitting diodes are formed in a row on a compound semiconductor substrate by selective diffusion, each of the light emitting diodes is It is separated by a diffusion layer formed by the selective diffusion in a direction parallel to the light emitting diode row, and electrically separated by a groove formed deeper than the diffusion layer in a direction vertical to the light emitting diode row. It is intended to provide a characteristic light emitting diode array.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the light emitting diode array of the present invention, first, selective diffusion is performed to form a diffusion layer so that a plurality of light emitting diode portions are connected in the column direction, and then in a direction perpendicular to the column direction. A light emitting diode portion is divided into a plurality of portions by forming a separation groove only in the.

A first embodiment of the light emitting diode array of the present invention will be described with reference to FIGS. 1 (A) and 1 (B). FIG. 1A is a partially enlarged sectional perspective view showing a light emitting diode array in the process of manufacturing according to the present invention, and FIG. 1B is a partially enlarged sectional perspective view showing a completed state. First, a method of manufacturing the light emitting diode array will be described. As shown in FIG. 1A, a p-type Ga _1-X Al _X As layer 2 and an n-type Ga _1-Y Al _Y As are formed on a p-type GaAs substrate 1. Layer 3 is sequentially epitaxially grown by LPE (liquid phase epitaxy) or the like, and the value of mixed crystal ratio X is about 0.10 to 0.35, and the value of mixed crystal ratio Y is higher than the value of this mixed crystal ratio X. by, p-type Ga _1-X Al X and the light transmittance with respect to the emission wavelength from the as layer 2, the n-type Ga _1-Y Al Y as layer 3 through the p-type G
The injection efficiency of electrons supplied to the a _1-x Al _x As layer 2 is increased, and the minority carriers injected into the p-type Ga _1-x Al _x As layer 2 are confined. Then, after applying a selective diffusion mask 5 of SiN to the partial row in which the light emitting diode portion is formed, Zn is selectively diffused to form a p-type diffusion layer 7 for current confinement on both sides of the row to be the light emitting diode portion. It is formed in parallel with the row to be the light emitting diode section.

Next, as shown in FIG. 2B, the selective diffusion mask 5 is removed, and then wet etching is again performed using an etchant of hydrochloric acid or phosphoric acid using an etching mask of SiO ₂ , SiN or the like. Or by dry etching using chlorine-based gas, the direction perpendicular to the column direction of the light emitting parts (direction separating each light emitting diode part)
Then, the p-type Ga _1-x Al _x As layer 2 is partially etched to form a separation groove 8 to separate into a plurality of light emitting diode portions. Further, after forming the insulating protective film 4 of SiN or the like, an AuBu alloy or the like is vapor-deposited on the insulating protective film 4, and the ohmic electrode 6 is formed by using the lithography technique and the etching technique. The ohmic electrode 6 may be formed before forming the separation groove 8. Further, an electrode 9 is also provided on the back surface of the p-type GaAs substrate 1.

In the light-emitting diode array having such a structure, the p-type diffusion layers 7 are formed on both sides of the row of the light-emitting diode sections in parallel with the row to confine the current. The diode part may be separated only between the respective light emitting diode parts. Since the ohmic electrode 6 can be wired while avoiding the separation groove, no step is generated, and the wiring is broken in the Al vapor deposition step.
When forming the wiring pattern, there is no unevenness in the thickness of the resist and variation in the wiring width due to the difference in light intensity when the resist is exposed to ultraviolet light. As a result, each light emitting diode unit can be manufactured uniformly. At this time, the etching for forming the isolation groove 8 of the light emitting diode portion is
Etching may be performed to a depth that reaches the p-type Ga _1-x Al _x As layer 2 or more, and control may be performed with an accuracy that does not affect the light emitting area of the light emitting diode portion.

Further, when the separation groove 8 for separating each light emitting diode portion is formed after the ohmic electrode 6 is provided, it is not necessary to precisely align the position in the column direction when patterning the ohmic electrode 6. Since the separation groove 8 for separating the light emitting diode portion may be formed according to the pattern of the ohmic electrode 6, the photolithography process can be easily performed.

A second embodiment of the light emitting diode array of the present invention will be described with reference to the partially enlarged sectional perspective view shown in FIG. The light emitting diode array shown in FIG.
The n-type GaAsP layer 12 is crystal-grown on the n-type GaAs substrate 11, and an insulating protective film 14 such as SiN is formed on a portion other than the portion connected to the light emitting diode portion in the column direction. Impurities such as Zn are selectively diffused in the partial column where the light emitting diode portion is formed using 14 as a selective diffusion mask to provide a p-type selective diffusion layer 17.

Next, the etching mask is used to perform a wet etching using a hydrochloric acid or phosphoric acid type etchant or a dry etching using a chlorine type gas to perform a vertical direction with respect to the column direction of the light emitting diode portions (each light emitting diode portion is N-type GaAsP layer 1 in the separating direction)
2 is etched halfway to form a separation groove 18 and separate into a plurality of light emitting diode portions. In addition, Al
Is deposited, the p-type ohmic electrode 16 is provided by using the lithography technique and the etching technique, and the n-type GaA is formed.
The n-type ohmic electrode 19 made of AuGeNi alloy or the like is also provided on the back surface of the s substrate 11.

Finally, on the surface of the light emitting diode array, S
The light emitting diode array is formed by forming a non-reflection coating film (AR film) 13 such as iN. In addition,
The ohmic electrode 16 may be formed before the separation groove 18 is formed. The light emitting diode array having such a structure has the same effect as that of the first embodiment. Also,
In this light emitting diode array, after providing the selective diffusion layer 17 connected to the partial row in which the light emitting diode portion is formed,
Since the separation groove 18 is separated into a plurality of light emitting diode portions by etching, it is not necessary to precisely design the selective diffusion window when the selective diffusion layer 17 is formed. Accuracy need not be considered.

[0019]

The light emitting diode array of the present invention is separated by the diffusion layer in the direction parallel to the light emitting diode array and is electrically isolated by the groove formed in the direction perpendicular to the light emitting diode array deeper than the diffusion layer. Therefore, the portion where the electrodes are wired can be flattened, the wiring may be broken in the wiring process, or the wiring pattern may be formed between the upper part and the lower part of the step when the wiring pattern is formed by the photolithography technique using the resist. It is possible to prevent variations in the thickness of the resist that have occurred and variations in the wiring width due to differences in light intensity when the resist is exposed to ultraviolet light.

Further, the etching depth control for separating the light emitting diode portions is performed by controlling the etching depth so that the compound semiconductor layer in which the light emitting diode portions are formed can be completely separated unless the etching depth reduces the light emitting area. More than that, it is not necessary to do it precisely. Furthermore, when a window is opened for each light emitting diode unit to perform selective diffusion,
The diffused impurities also diffuse laterally below the surface protective film from the edge of the diffusion window corresponding to the diffusion depth. Therefore, the amount of diffusion in the lateral direction with respect to the expected diffusion depth is predicted in advance, and It was necessary to design the size and spacing of the diffusion window with respect to the surface protective film so that the final final size and the diffusion layers of the individual light emitting diode sections would not come into contact with each other in the column direction. Then, since it suffices that the light emitting diode portions are diffused in a form in which they are connected in the column direction, it is not necessary to design the selective diffusion window so precisely.

When the etching for separating the respective light emitting diode portions is carried out after the electrodes are formed, it is not necessary to precisely align the electrode pattern with the position of the light emitting diode portions, particularly with respect to the position in the column direction. Since the light emitting diode portion may be etched and separated according to the electrode pattern after formation, there is an effect that the photolithography process can be easily performed.

[Brief description of drawings]

FIG. 1A is a first view of a light emitting diode array of the present invention.
FIG. 3B is a partially enlarged sectional perspective view showing the manufacturing process of the embodiment of FIG.
FIG. 3 is a partially enlarged sectional perspective view showing the completed state.

FIG. 2 is a partially enlarged sectional perspective view showing a second embodiment of the light emitting diode array of the present invention.

FIG. 3A is a plan view showing an example of a conventional light emitting diode array, and FIG. 3B is a sectional view taken along line BB in the array direction.

FIG. 4A is an enlarged sectional view showing another example of a conventional light emitting diode array, and FIG. 4B is a plan view of the same.

[Explanation of symbols]

1,21 p-type GaAs substrate 2,22 p-type Ga _1-X Al _X As layer 3,23 n-type Ga _1-Y Al _Y As layer 4,14,24,34 insulating protection film 5 selective diffusion mask 6,9 , 16, 19, 26, 29, 36, 39 Ohmic electrode 7, 17, 37 p-type selective diffusion layer 8, 18 Separation groove 11, 31 n-type GaAs substrate 12, 32 n-type GaAsP layer 13 Antireflection coating film (AR film)

Claims (1)

[Claims] 1. A light emitting diode array in which a plurality of light emitting diodes are formed in rows on a compound semiconductor substrate by selective diffusion, wherein each light emitting diode is formed by the selective diffusion in a direction parallel to the light emitting diode row. A light emitting diode array, wherein the light emitting diode array is separated by a diffusion layer and is electrically separated by a groove formed deeper than the diffusion layer in a direction perpendicular to the light emitting diode rows.