JP2003197960A - Light emitting diode array and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a light emitting diode array which is equipped with electrodes of evaporation metal film that can be formed in an optional direction and high in degree of freedom of design. <P>SOLUTION: A method of manufacturing a light emitting diode array 1 comprises a first process of cutting grooves 31 in the surface of a semiconductor layer 23 by scanning a laser beam on the semiconductor layer 23 on the surface of a wafer 2 and of forming a plurality of light emitting diodes 30 each surrounded with the groove 31, a second process of forming an insulating film 24 on the surface of the wafer 2, a third process of boring a hole communicating with the light emitting diode 30 in the insulating film 24, and a fourth process of evaporating a metal film (discrete minus electrode 26) whose one end is brought into contact with the semiconductor layer 23 through the intermediary of the above hole and other end extends beyond the range of the light emitting diode 30, passing above the groove 31. <P>COPYRIGHT: (C)2003,JPO

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 and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, in a zinc-zinc-type III-V group compound semiconductor crystal, there is a strong anisotropy in the rate of chemical etching and the cleavage direction. Therefore, as a single crystal wafer for device formation, , (100) plane or a plane orientation close to this is used.

For example, as shown in FIG.
When chemical etching is performed in the <1-11> direction and <0-11>, which is perpendicular to this direction, the ridge angle of each mesa becomes an acute angle in the <011> direction. The direction close to this is called the reverse mesa direction. On the other hand, the <0-11> direction where the ridge angle is obtuse or a direction close to this is called the forward mesa direction. Here, -1 indicates that the direction of the vector is opposite to 1.

It is generally known that the following phenomenon occurs when a metal film is deposited on the surface of this wafer. That is, as shown in FIG. 8A, in the etched portion in the reverse mesa direction, the vapor-deposited metal film 16 is discontinuous at the mesa edge portion. On the other hand, in the etching portion in the forward mesa direction, FIG.
As shown in FIG. 7, the step breakage of the deposited metal film 16 does not occur.
7 and 8, 12 is a crystal substrate and 13 is an insulating film.

The manufacturing procedure of the monolithic light emitting diode array by the conventional chemical etching disclosed in Japanese Patent Publication No. 3-63830 will be described below. Figure 5
Is a top view of the conventional LED array 1 shown in FIG.
Shows a perspective view of the BB 'cross section of FIG. 5, respectively.

In the figure, 21 is a p-type GaAs substrate, 22 is an epitaxially grown p-type Ga _1-x Al _x As layer, and the value of the mixed crystal ratio x is within the range of x = 0.10 to 0.35. , Which is appropriately determined according to the desired emission wavelength. 23 is p-type Ga
N-type Ga epitaxially grown on the _1-x Al _x As layer 22
_{It is a 1-y} Al _y As layer, and its mixed crystal ratio y is higher than the mixed crystal ratio x, so that the light transmission property with respect to the emission wavelength from the p-type Ga _1-x Al _x As layer 22 is This n-type Ga _1-y Al _y As layer 2
The electron injection efficiency from 3 is increased and the minority carriers injected into the p-type Ga _1-x Al _x As layer 22 are confined. Here, an active layer functioning as a light emitting layer may be provided between the p-type layer 22 and the n-type layer 23.

Reference numeral 26 denotes an electrode portion 2 of the n-type Ga _1-y Al _y As layer 23.
It is an individual negative electrode for wiring connected to 9, and is formed by depositing a metal film.

Reference numeral 24 is an individual negative electrode 26 and an electrode portion 2.
It is a phosphor silicate glass (PSG) film provided to insulate the n-type Ga _1-y Al _y As layer 23 other than 9. In addition, P on the electrode portion 29 of each light emitting diode portion 30
The SG film 24 has been removed by hydrofluoric acid, and one end of the individual negative electrode 26 passes through the hole to form the n-type Ga _1-y Al _y As layer 2
3 is contacted.

Reference numeral 30a is a ridge portion in the reverse mesa direction.
b is a ridge in the forward mesa direction. Each rectangular light emitting diode section 30 is completely isolated by these ridges 30a and 30b. Therefore, the ridge portions 30a in the reverse mesa direction face each other between the adjacent light emitting diode portions 30.

Here, each individual negative electrode 26 is drawn out from the electrode portion 29 along the ridge portion 30b in the forward mesa direction. Therefore, each individual negative electrode 26 does not break due to a step break at the ridge 30b.

In this structure, the individual negative electrode 26
When a forward current is applied to the light emitting diode section 30 by applying a voltage between the common positive electrode 27 and the common positive electrode 27, the n-type Ga _1-y Al _y As layer 23 is changed to the p-type Ga _1-x Al _x As layer 22. Electrons are injected to cause radiative recombination, and light is emitted upward from the light emitting diode unit 30.

[0012]

By the way, in the conventional light emitting diode array 1, the ridge portion 30a in the reverse mesa direction is formed.
When the individual negative electrode 26 is pulled out through the top, the ridge 3
At 0a, the vapor-deposited metal film is interrupted and broken. Therefore, as described above, each individual negative electrode 26 is drawn out from the electrode portion 29 through the ridge portion 30b in the forward mesa direction. Therefore, the manufacture of the light emitting diode array 1 is
There is a problem in that the degree of freedom in design is impaired due to restrictions on the crystal structure of the wafer 2.

When each light emitting diode section 30 emits light, light is emitted from the upper surface of the light emitting diode section 30 to above the wafer 2. At this time, light leakage also occurs from the ridges 30a and 30b. In particular, the light leaked from the ridge portion 30a in the reverse mesa direction is not included in the ridge portions 30 of the adjacent light emitting diode portions 30.
Since it reaches a and is reflected at a position away from the light emitting portion, the directivity of light is disturbed. Therefore, the printer using the light emitting diode array 1 has a problem that the printing quality and the resolution are deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a light emitting diode array having a high degree of freedom in designing, in which electrodes of a vapor-deposited metal film can be formed in an arbitrary direction, and a manufacturing method thereof. .

[0015]

In order to achieve the above object, the light emitting diode array of the present invention comprises a wafer having at least one semiconductor layer grown so that a pn junction surface is formed on the substrate. , Surrounded by a groove deeper than the pn junction surface engraved on the wafer surface,
A plurality of light emitting diode portions regularly arranged on the wafer surface, an insulating film formed on the wafer surface on which the light emitting diode portion is formed, a hole provided in the insulating film and communicating with the light emitting diode portion, and one end Is in contact with the semiconductor layer through the hole, and the other end of the metal film electrode extends over the groove and out of the range of the light emitting diode section.

According to this, since the periphery of each light emitting diode portion is surrounded by the groove, the ridge portion of the reverse mesa by chemical etching cannot be formed, and the metal film electrode extending outside the range of the light emitting diode portion is stepped by the groove. There is no danger of cutting. Therefore, the electrode can be pulled out freely in any direction.

Further, in the method for manufacturing a light emitting diode array of the present invention, a groove is formed in the surface of the semiconductor layer by scanning a laser beam on the semiconductor layer on the surface of the wafer, and the light emitting diode part surrounded by the groove is formed. A step of forming a plurality on the wafer surface, a step of forming an insulating film on the wafer surface, a step of providing a hole communicating with the light emitting diode portion in the insulating film, and one end contacting the semiconductor layer through the hole And forming a metal film having the other end extending over the groove and out of the range of the light emitting diode portion. According to this, since the groove carved on the surface of the wafer by the irradiation of the laser beam has a semicircular cross section, even if a metal film is formed on the surface of the wafer, the vapor-deposited metal film is stepped at the groove portion. There is no danger of cutting.

Further, in the method for manufacturing a light emitting diode array of the present invention, a groove is formed in the surface of the semiconductor layer by scanning a laser beam on the semiconductor layer on the surface of the wafer, and the light emitting diode part surrounded by the groove is formed into the groove. By forming a plurality of steps on the wafer surface and scanning a laser beam on the semiconductor layer on the wafer surface to form a groove in the semiconductor layer surface, and enclosing a predetermined number of the continuous light emitting diode portions with the groove, a group is formed. As a separate step, a step of forming an insulating film on the surface of the wafer, a step of providing a hole in the insulating film that communicates with the light emitting diode portion, one end contacts the semiconductor layer through the hole, A step of forming a metal film whose end extends over the groove and out of the range of the light emitting diode portion. According to this, a predetermined number of continuous light emitting diode portions can be surrounded by a groove cut by laser irradiation and separated as a group on the surface of the wafer.

In this case, the light emitting diode section can be formed in a rectangular, circular or elliptical shape by scanning the laser beam in a rectangular, circular or elliptical shape.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of the light emitting diode array 1, and FIG. 2 is a perspective view taken along the line AA ′ of FIG. 1 and 2, the same parts as those of the conventional light emitting diode array 1 shown in FIGS. 5 and 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

A procedure for manufacturing the light emitting diode array 1 according to the present invention will be described with reference to FIGS. First, a wafer 2 in which at least one semiconductor layer is grown so that a pn junction surface is formed on a substrate is prepared. The surface of this wafer 2 (consisting of the p-type GaAs substrate 21, the p-type Ga _1-x Al _x As layer 22 and the n-type Ga _1-y Al _y As layer 23) is irradiated with a strong laser beam. At this time, the laser beam is scanned so as to draw a rectangle. As a result, the groove 31 is engraved in a rectangle,
The light emitting diode section 30 surrounded by the groove 31 is formed. The laser beam may be scanned not only in a rectangular shape but also in a circular shape or an elliptical shape. Then, by repeating the scanning of the laser beam, a plurality of light emitting diode units 30 are formed on the surface of the wafer 2 and arranged as a whole. After that, the same laser beam may be scanned on the surface of the wafer 2 as shown in FIG. 4, and a predetermined number of continuous light emitting diode portions 30 may be surrounded by a groove 32 to be separated as a group. The depth of the grooves 31 and 32 can be changed by changing the laser scanning speed.

As shown in FIG. 3, the groove 31 has a semi-circular cross section, and has a sharp ridge portion 30a due to the anisotropy of the crystal structure as seen in chemical etching.
(See FIG. 2) is not formed. The cross section of the groove 32 described later is also similar to the groove 31. When the mesa is formed on the surface of the wafer 2 by chemical etching, the ridges in the forward direction and the reverse direction are mixed around the mesa. However, since the groove is formed on the surface of the wafer 2 by the laser beam, the periphery of the mesa forming the light emitting diode unit 30 is
The shape has only ridges in the forward direction. Groove 3 described later
The region surrounded by 2 is the same as the mesa forming the light emitting diode unit 30.

Next, after forming a PSG film 24 as a protective film on the surface of the wafer 2, each light emitting diode section 3 is formed.
The portion of the PSG film 24 corresponding to the 0 electrode portion 29 is removed by hydrofluoric acid to form a hole. As further other end with one end through the hole is in contact with the n-type Ga _1-y Al _y As layer 23 is pulled out to the outside of the light emitting diode 30 through the upper groove 31, thereby depositing a metal film in a strip .

Here, the cross section of the groove 31 is, as described above,
Since it has a semi-circular shape, the vapor-deposited metal film has no possibility of being cut off on the groove 31. As a result, as shown in FIG. 1, the individual negative electrode 2 is moved in any direction from the electrode portion 29.
6 can be pulled out, and the degree of freedom in designing the light emitting diode array 1 is improved.

Further, as shown in FIG. 2, in order to prevent the light from the adjacent light emitting diode portions 30 from entering, the adjacent light emitting diode portions 30 have independent grooves 31 around each of them. That is, since the light emitting diode portions 30 are separated by the rectangular grooves 31, the surface of the wafer 2 remains as it is between the adjacent light emitting diode portions 30. Therefore, when the light emitting diode sections 30 emit light, the range where light leaks from other than the upper surface is limited to the frame of the rectangular groove 31 formed at the periphery at most, so that the light emitting diode sections 30 are stably exposed from the upper surface. It can emit highly directional light.

1 and 2, the groove 31 is drawn thick in order to emphasize the cross-sectional shape of the groove 31 formed by laser etching, but the groove 31 that is actually engraved is quite thin. That is, since the laser beam is a beam that converges at one point, it can be said that laser etching is suitable for making fine cutting grooves.

In the embodiment shown in FIG. 4, a predetermined number of continuous light emitting diode portions 30 are formed in the groove 32 on the surface of the wafer 2.
An example of enclosing with and separating as a group is shown. A plurality of groups surrounded by the groove 32 are arranged on the surface of the wafer 2. The depth of the groove 32 is deeper than the depth of the groove 31. The groove 32 is set to a depth that allows electrical isolation between the groups, and has a depth that reaches at least the substrate 21.

The PSG film 2 in the region surrounded by the groove 32
A hole 33 is formed in the hole 4. The hole 33 is located outside the groove 31. N-type Ga located under the PSG film 24
_{The 1-y} Al _y As layer 23 is removed immediately below the hole 33 and over a range slightly wider than the hole 33 so that the p-type Ga _1-x Al _x As layer 22 is exposed from the hole 33. The removal of the n-type Ga _1-y Al _y As layer 23 can be performed by chemical etching or laser light irradiation. For example, it is desirable to perform laser light irradiation using the device used to form the groove 31.

The individual electrode 26 and the common electrode 34 are arranged on the surface of the wafer 2. The individual electrode 26 corresponds to the electrode 26 of FIG. 1 and is used to specify one light emitting diode unit 30 in the group. Common electrode 3
Reference numeral 4 corresponds to the electrode 27 of FIG. 1, and although it can be arranged on the back surface of the wafer 2 as shown in FIG. 1, it is arranged on the front surface of the wafer 2 in this example. The common electrode 34 is
In order to specify the groups, they are arranged for each group defined by the groove 32. One end of the electrode 34 has a hole 33.
Is connected to the p-type Ga _1-x Al _x As layer 22 via. The other end of the electrode 34 exits the region surrounded by the groove 32 and forms a pad region located on the surface of the wafer 2.
The groove 32 defining the group shares the portion located between the light emitting diode portions 30. By sharing it, it is possible to cope with a case where the pitch of the light emitting diode sections 30 is narrow.

The above element is formed by the following manufacturing method. That is, by scanning the semiconductor layer on the surface of the wafer 2 with a laser beam, grooves 3 are formed on the surface of the semiconductor layer.
1 is carved, and the light emitting diode section 30 surrounded by this groove 31
Forming a plurality of wafers on the wafer surface. By scanning the semiconductor layer on the surface of the wafer 2 with a laser beam, a groove 32 is formed in the surface of the semiconductor layer, and a predetermined number of continuous light emitting diode units 30 and a region common thereto are surrounded by the groove to form a group. The process of separating. In order to form a common electrode for the light emitting diode units 30 in the group,
Etching the wafer surface. By this etching, a part of the n-type layer 23 is removed, and the holes 33
The p-type layer 22 is exposed from a position corresponding to. A step of forming an insulating film 24 on the surface of the wafer. The insulating film 24
A step of forming a hole for an individual electrode connected to the light emitting diode section and a hole 33 for a common electrode in the. A step of stacking a metal film on the insulating film and patterning the metal film to form the individual electrode 26 and the common electrode 34.

In the above embodiment, p-type GaAs is used as the substrate crystal.
However, it is also possible to use n-type GaAs.
When GaAs is used, the common electrode side may be the negative electrode and the individual electrode side may be the positive electrode. Further, a wafer 2 having a composition other than the above may be used as the compound semiconductor.

[0032]

As described above, according to the present invention, since the groove is formed around the light emitting diode portion by laser etching, the metal is passed through the groove without interruption in any direction from the electrode portion of the light emitting diode portion. An electrode film can be formed. Therefore, regardless of the electrode extraction direction,
It is possible to realize a light emitting diode array having a high degree of design freedom.
Further, by irradiating the wafer surface with a laser beam, a predetermined number of continuous light emitting diode portions can be surrounded by grooves to be separated as a group, and light emission can be controlled individually in each group.

Further, since the surface of the wafer remains as it is between the adjacent light emitting diode portions, it is possible to stably radiate light of high directivity from the upper surface of each light emitting diode portion.

[Brief description of drawings]

FIG. 1 is a top view showing a light emitting diode array of the present invention.

FIG. 2 is a perspective view of a cross section taken along the line AA ′ of FIG.

FIG. 3 is a plan view of the cross section.

FIG. 4 is a top view showing a wafer in which a light emitting diode unit is separated.

FIG. 5 is a top view showing a conventional light emitting diode array.

FIG. 6 is a perspective view of a cross section taken along the line BB ′ of FIG.

FIG. 7 is an explanatory diagram showing a mesa shape formed by chemical etching.

FIG. 8 is a cross-sectional view in the reverse mesa direction (a) and the forward mesa direction (b).

[Explanation of symbols]

1 light emitting diode array 2 wafer 21 p type GaAs substrate 22 p type Ga _1-x Al _x As layer 23 n type Ga _1-y Al _y As layer 26 individual negative electrode 27 common positive electrode 29 electrode part 30 light emitting diode part 31, 32 grooves

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shoji Inaba             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. F-term (reference) 4E068 AD00 DA10                 5F041 AA25 CA02 CA35 CA36 CA74                       CA75 CA77 CB11 CB25

Claims (4)

[Claims] 1. A wafer having at least one semiconductor layer grown to form a pn junction surface on a substrate,
A plurality of light emitting diode portions which are surrounded by mutually independent grooves deeper than the pn junction surface engraved on the wafer surface and which are regularly arranged on the wafer surface;
An insulating film formed on the surface of the wafer on which the light emitting diode portion is formed, a hole provided in the insulating film and communicating with the light emitting diode portion, one end contacts the semiconductor layer through the hole, and the other end And a metal film electrode extending over the groove and out of the range of the light emitting diode section. 2. A step of forming a groove on the surface of the semiconductor layer by scanning a laser beam on the semiconductor layer on the surface of the wafer to form a plurality of light emitting diode portions surrounded by the groove on the surface of the wafer, and the wafer. A step of forming an insulating film on the surface; a step of providing a hole communicating with the light emitting diode portion in the insulating film; one end contacting the semiconductor layer through the hole; the other end passing over the groove; And a step of forming a metal film extending out of the range of the light emitting diode portion. 3. A step of forming a groove on the surface of the semiconductor layer by scanning a laser beam on the semiconductor layer on the surface of the wafer, and forming a plurality of light emitting diode portions surrounded by the groove on the surface of the wafer. By scanning on the semiconductor layer on the surface of the wafer, to form a groove in the surface of the semiconductor layer, and a step of separating a predetermined number of the continuous light emitting diode portions in the groove to separate them as a group, and on the surface of the wafer A step of forming an insulating film, a step of providing a hole communicating with the light emitting diode part in the insulating film, and one end contacting the semiconductor layer through the hole and the other end passing over the groove and the light emitting diode part And a step of forming a metal film extending out of the range. 4. The method for manufacturing a light emitting diode array according to claim 2, wherein the laser beam is scanned in a rectangular shape, a circular shape, or an elliptical shape.