JPH0613715A - Edge light emitting element and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily form a thin element of a semiconductor layer by a method wherein an electrode film is formed on both sides of the semiconductor layer, and the electrode film of an end light-emitting element, where light is emitted from the side face, is cleaved without patterning. CONSTITUTION:This edge light-emitting element is formed by laminating a compound semiconductor layer and electrode films 12 and 13 formed on both surfaces of a semiconductor wafer 1, and a beam of light is emitted from the side face. The outermost layer of Au films 3 and 7 of the electrode films 12 and 13 are formed thick 1500 to 2500Angstrom .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end face light emitting device which emits light from an end face (side face) of a semiconductor chip and a method for manufacturing the same. More specifically, the present invention relates to an end face light emitting device in which a gold film of an electrode film formed on both surfaces of a semiconductor substrate is thinned to facilitate cleavage, and a manufacturing method thereof.

[0002]

2. Description of the Related Art An edge emitting element that emits light from an edge of a semiconductor chip with a semiconductor laser, a super luminescent diode, or the like is provided on almost the entire front and back surfaces of a semiconductor wafer 21 having a pn junction formed on a semiconductor substrate such as GaAs. A metal coating is formed as the electrode films 22 and 23. As this electrode film, an AuGe film or a Ti film for forming ohmic contact with the semiconductor wafer 21 is formed, and an Au film is formed on the uppermost film to facilitate die bonding or wire bonding. It is formed of a plurality of metal films.

After that, the semiconductor wafer 21 is cut and separated to manufacture each semiconductor chip. In the edge emitting element, each chip is made to emit light from the cut surface.
If the cut surface is not perfectly flat, light will not be emitted in one direction. Therefore, in this type of edge emitting device, it is not suitable to cut with a diamond cutter to separate each semiconductor chip, and the semiconductor chip is cut and separated by cleavage.

Of the above-mentioned electrode films, the Au film is 3000-1000.
Since it is formed to have a thickness of 0Å and Au has ductility and malleability, the semiconductor wafer 21 is likely to be cleaved along the crystal plane, but the Au film is difficult to cut. Therefore, the electrode films 22 and 23 at the positions where the semiconductor wafer 21 is cleaved are removed in advance, and a plurality of grooves 24 and 25 are formed in the vertical and horizontal directions of the electrode films 22 and 23 as shown in FIGS. It is necessary to form a patterned pattern. The pattern forming step includes an exposure step and an etching step. In the exposure step, a resist is applied on the semiconductor wafer 21, and the applied resist is exposed and developed to form a pattern. When applying this resist,
The semiconductor wafer 21 is attracted by a vacuum chuck and applied by spin coating while rotating. In the etching process, the resist films formed in the exposure process are used as masks to etch the electrode films 22 and 23 that are base films to form patterns of the electrode films 22 and 23.

[0005]

When a semiconductor wafer is cleaved and chips are produced by this conventional technique, it is necessary to fix the wafer with a vacuum chuck and rotate it in the resist coating step in the exposure step. In this case, when the thickness of the semiconductor wafer is 150 μm or less, the semiconductor wafer is easily broken due to the gripping force of the semiconductor wafer by the vacuum chuck. On the other hand, if the gripping force of the vacuum chuck is weakened so that the semiconductor wafer is not cracked, centrifugal force acts on the semiconductor wafer due to the rotation of the vacuum chuck, and the semiconductor wafer is separated from the vacuum chuck.

Therefore, forming a pattern on the electrode film in manufacturing a thin edge emitting semiconductor chip leads to an increase in the defective rate, and the pattern cannot be formed. On the other hand, in the edge emitting element, it is necessary to utilize the cleavage plane as described above (for example, Ryoichi Ito et al., “Semiconductor Laser” page 23 (1989)), and cleavage is required for chip formation, but the electrode If the film is thick, the electrode film cannot be cut at the time of cleavage, and there is a problem that a thin (150 μm or less) semiconductor chip for edge emitting cannot be obtained.

An object of the present invention is to reduce the thickness of the Au film formed on both sides of a semiconductor wafer so that it can be easily made into a semiconductor chip without patterning, and the end face having a small thickness of the semiconductor chip can be formed. It is to provide a light emitting element.

[0008]

In the edge emitting device according to the present invention, a semiconductor chip is formed by laminating a compound semiconductor layer of a p-type layer and an n-type layer, and electrode films are formed on the entire surfaces of both sides of the semiconductor chip. An end face light emitting device which emits light from a side surface of the semiconductor chip, wherein the outermost layer of the electrode film is formed of an Au film, and the Au film is formed in a range of 1500 to 2500Å. is there.

Further, in the semiconductor laser according to the present invention, at least the lower clad layer, the active layer, the first upper clad layer, the current limiting layer, the second upper clad layer and the cap layer are formed on the compound semiconductor substrate as the compound semiconductor layer. And an outermost layer of the electrode film is formed of an Au film, and the Au film is formed to have a thickness of 1500 to 2500Å. To do.

Further, the manufacturing method of the edge emitting device according to the present invention is (a) a step of laminating a compound semiconductor layer on a compound semiconductor substrate to form a light emitting semiconductor wafer, and (b) an outermost layer of Au on both sides of the semiconductor wafer. A step of forming an electrode film so as to form a film, (c) a step of forming a semiconductor chip by cleaving the semiconductor wafer along a crystal plane, and (d) a step of die-bonding and wire-bonding the semiconductor chip It is characterized by that.

[0011]

According to the present invention, the electrode film is cut by the cleavage of the semiconductor wafer without patterning, and the thickness of the Au film is controlled by finding the thickness of the Au film that can surely perform die bonding or wire bonding. Because it has been
Cleavage can be easily performed without forming a pattern on the electrode film, and a semiconductor chip for an edge emitting device having a thin semiconductor layer with good bonding properties can be obtained without causing a defect in forming a semiconductor chip. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The edge emitting device of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a partial cross sectional view showing a state in which electrode films are formed on both sides of a semiconductor wafer for a semiconductor laser. In the figure, 1 is a semiconductor wafer, for example, as shown in FIG.
The detailed structure is as shown in. Ie 20
Lower clad layer 11 on GaAs substrate 10 with thickness of 0 to 500 μm
Is, for example, n-type Al _x Ga _1-x As (0.3 ≦ x ≦ 0.
7) layer having a thickness of about 1.3 μm, which is epitaxially grown by MBE (Molecular Beam Epitaxy) method, and on top of that, an undoped Al _x Ga _1-x As (0 ≦ x ≦ 0.2) layer is epitaxially grown, and a p-type Al _x Ga _1-x As (0.3 ≦ x ≦ 0.7) layer is further formed thereon as the first upper cladding layer 15.
An n-type GaAs layer is further epitaxially grown to a thickness of about 0.6 μm as a current limiting layer 16 on the n-type GaAs layer, and an n-type GaAs layer is formed thereon as an evaporation preventing layer 17.
Type Al _x Ga _1-x As (0.05 ≦ x ≦ 0.2) layer is 0.1 μm
Epitaxial growth is performed and stripe grooves are formed by etching to limit the range of current flow. When the stripe groove is etched, the Ga of the current limiting layer 16 is
Etching is performed so that the As layer remains about 0.1 μm so that the Al _x Ga _1-x As layer, which is the first upper cladding layer 15, is not directly exposed.

Then, the substrate is put into the MBE apparatus again, and the surface of the substrate is irradiated with arsenic molecular beam, and the substrate is heated at 740 ° C to 760 ° C.
Heat to. At this temperature, the GaAs layer re-evaporates, but the Al _x Ga _1-x As (x ≧ 0.05) layer does not re-evaporate, so only the GaAs layer in the stripe groove is removed and the Al _{x of} the first upper cladding layer 15 is removed. The Ga _1-x As layer is exposed (thermal etching step). At this time, G of the current limiting layer 16
Since the evaporation prevention layer 17 is formed on the surface of the aAs layer,
It does not evaporate, only the stripe groove part evaporates. Then, a second MBE process was performed to form about 1 p-type Al _x Ga _1-x As (0.3 ≤ x ≤ 0.7) layer as the second upper cladding layer 18.
μm and the p-type GaAs layer as the cap layer 19 is about 2
μm is epitaxially grown and laminated. After that, Ga
The As substrate side is polished by lapping to make a thin layer, and electrode films 12 and 13 are formed on the upper and lower sides, respectively.

Electrode films are formed on the upper and lower surfaces of this semiconductor wafer.
12 and 13 are each formed of a plurality of metal films by a vapor deposition method or a sputtering method. First, the top electrode film 12 is 1000Å
A Ti film 2 having a thickness of 2000 and an Au film 3 having a thickness of 2000 Å are formed. The upper surface side of the semiconductor wafer 1 is B as an impurity.
Since e is doped to about 1 × 10 ¹⁹ cm ^−3, it is easy to make ohmic contact and a Ti film is directly formed. The Ti film 2 is formed as a barrier metal so that Au does not enter the semiconductor layer and reacts therewith and does not deteriorate the element. Since the Ti film 2 is inferior in malleability and ductility to Au, the Ti film 2 has a large thickness. The limit is not so problematic and is formed in the range of 500 to 2000Å. Further, the Au film 3 has a thickness of 15 as described later.
By setting 00 to 2500Å, the semiconductor wafer can be cleaved without patterning the electrode film, and the semiconductor chip can be fixed to the lead terminals and die bonding for electrical connection and the electrodes and leads of the semiconductor chip can be made with gold wires. Wire bonding for electrical connection can be performed without any trouble.

Further, since Si is doped on the back surface side of the semiconductor wafer 1 as an impurity so as to have a concentration of about 2 × 10 ¹⁸ cm ⁻³ to form an n-type, it is difficult to form an ohmic contact and GaAs is formed. First, the semiconductor substrate A
uGe (for example, the proportion of Ge is 12 at%) film 4 has 2000 Å,
It is formed by a vapor deposition method or a sputtering method. Further, the Ni film 5 for improving the adhesion of the film is 100 Å, the Ti film 6 as the barrier metal is 500 Å, and finally the Au film 7 for securely performing the die bonding for adhering the semiconductor chip with good electric contact. 2000Å formed.

This back side electrode film is also made of AuGe, Ni, T
The respective films of i are inferior in malleability and ductility as compared with Au, and like the above-mentioned upper surface side, the limitation of these film thicknesses does not pose a problem so much, and the conventionally used 1500 to 2500, 50 to 150, and 500 respectively. ~
It is formed to 1000 Å, but the Au film 7 is 1500 to
Formed to 2500Å.

Next, the thickness of the Au film used as the electrode film will be described. As described above, the thickness of the semiconductor wafer 1 is 15
When the thickness is 0 μm or less, cracking occurs in the semiconductor wafer 1 when patterning the electrode film, and the yield is reduced. On the other hand, when patterning is not performed, the electrode film is not cut when the semiconductor wafer is cleaved, and edge emission The yield of semiconductor chips does not increase. Therefore, as a result of intensive studies by the inventors, by controlling the thickness of the Au films 3 and 7 having high malleability and ductility in the electrode film to 1500 to 2500 Å, the semiconductor film can be formed without patterning the metal film. It has been found that when the wafer 1 is cleaved, the electrode film can be cut and separated into semiconductor chips, and electrical connection can be surely made during die bonding and wire bonding.

That is, first, a Ti film or an A film other than the Au film is formed.
The uGe film, the Ni film, etc. are kept constant with the above-mentioned thickness,
The semiconductor wafer 1 is formed to a thickness of 60 μm, and the Au films 3 and 7 are formed.
Cleavability and bondability (no bonding failure) of the semiconductor wafer were investigated when the values were changed to 1000, 1500, 2000, 2500, 3000, 4000Å. The results shown in Table 1 were obtained when the yield was 90% or more as good and as good, and as bad.

[0020]

[Table 1]

As is clear from Table 1, the thickness of the Au film is
By selecting 1500 to 2500Å, both cleavage and bonding properties are excellent, and semiconductor chips can be formed without patterning. In addition, most of the defective bonding properties at 1000Å are due to peeling of wire bonding,
This is because the bonding strength of the bonding is weak, and some of them have large contact resistance and deteriorated light emission characteristics.

Next, the AuGe film 4 and the Ti films 2 and 5 are set to 4000 Å and 1000 Å, which are double the thickness of the above-mentioned example, respectively.
Cleavability and bondability were similarly examined by setting the u films 3 and 7 to 2000 Å. As a result, all of them are good, and even if the metal film such as the AuGe film or the Ti film is formed thick, the semiconductor wafer 1
It has no effect on the cleavage property of Cu, and only Au film is 1500-2500Å
It was found that the cleavage property and the bonding property are satisfied by forming the film.

In the above embodiment, the lower cladding layer, the active layer, etc. are laminated on the n-type GaAs substrate and the p-type G is formed on the upper surface.
In the example of the semiconductor laser in which the aAs layer is formed, the example in which the upper electrode film is two layers and the lower electrode film is four layers has been described, but the same can be applied to edge emitting elements other than the semiconductor laser. Is not limited to this example, and other combinations of laminated layers may be used. Further, if the n-type and p-type are formed in reverse, the laminated structure of the electrode film changes, and the semiconductor substrate is not GaAs but InP
The structure of the electrode film may change due to changes such as
In both cases, Au is bonded to the outermost layer due to its bonding property.
A film is formed, and the thickness of the Au film is 1500 to 2500Å as described above.
By forming the film, the semiconductor wafer can be cleaved without patterning the electrode film, and the die bonding and the wire bonding can be performed well.

[0024]

According to the present invention, of the electrode films formed on both surfaces of the semiconductor wafer for the edge emitting device, the Au film is 15
Since it is formed as thin as 00 to 2500Å, it can be separated into each semiconductor chip by cleaving the semiconductor wafer without patterning the electrode film.

As a result, it is not necessary to pattern the electrode film, the number of steps can be greatly reduced, and defective products due to cracking of a semiconductor wafer during resist coating for patterning do not occur, which greatly contributes to cost reduction. .

Moreover, since the semiconductor wafer can be cleaved without patterning the electrode film, the thickness of the semiconductor wafer is reduced.
Even a thin film of 100 μm or less can be formed into a semiconductor chip with a good yield. For example, like a semiconductor laser chip used in the three-beam method, in order to avoid reflection of a branched beam due to a diffraction grating of return light, the thickness of the semiconductor chip is increased. Can be made as thin as 80 μm or less, and an edge emitting device having a thin semiconductor layer can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing a state where electrode films are formed on both surfaces of a semiconductor laser wafer which is an embodiment of the present invention.

FIG. 2 is a cross-sectional explanatory diagram illustrating a structure of a semiconductor layer of a semiconductor laser.

FIG. 3 is a perspective view showing a state where an electrode film is patterned, which is one manufacturing process of a conventional edge emitting device.

FIG. 4 is a plan view of the semiconductor wafer of FIG.

[Explanation of symbols]

 1 Semiconductor wafer 3, 7 Au film 12, 13 Electrode film

Claims (3)

[Claims] 1. An end face light emitting device in which a semiconductor chip is formed by stacking compound semiconductor layers of a p-type layer and an n-type layer, electrode films are formed on the entire surfaces of both sides of the semiconductor chip, and light is emitted from the side surface of the semiconductor chip. The outermost layer of the electrode film is formed of an Au film, and the Au film is formed at 1500 to 2500Å. 2. A compound semiconductor substrate on which at least a lower clad layer, an active layer, a first upper clad layer, a current limiting layer, a second upper clad layer and a cap layer are formed as compound semiconductor layers, and electrodes are formed on the upper and lower surfaces. A semiconductor laser having a film formed, wherein the outermost layer of the electrode film is formed of an Au film, and the Au film is formed in a thickness of 1500 to 2500Å. 3. A step of laminating a compound semiconductor layer on a compound semiconductor substrate to form a light emitting semiconductor wafer, and (b) forming an electrode film on both surfaces of the semiconductor wafer so that the outermost layer is an Au film. A step, (c) a step of cleaving the semiconductor wafer along a crystal plane to form a semiconductor chip, and (d) a step of die-bonding and wire-bonding the semiconductor chip, a method for manufacturing an edge-emitting device. .