JPH0587998B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a light emitting device, for example, a semiconductor laser device that emits (emits) laser light from a resonator end of an end face, or an integrated optical device having such a semiconductor laser device portion. Regarding light emitting elements such as devices (OEIC elements).

[Background technology]

Regarding semiconductor laser elements that serve as light sources for optical communications or information processing devices such as digital audio disks and video disks, for example,
“Technological innovation in semiconductor lasers” by Oka et al., Semiconductor World, May 1982, p. 25.
Discussed in the literature entitled.

In addition, prior art (Nikkei Electronics, 1981
September 14th issue, pp. 138-152: Semiconductor lasers that meet the demands of audio disks: Fushiki et al.) In the semiconductor laser element (hereinafter simply referred to as a laser chip), a wafer on which electrodes are formed is separated ( cleavage);
It is also disclosed that the electrode has a multilayer metal structure, and gold (Au) is often used as the main material.

However, with this technology, shooting defects are caused by protruding Au parts (overhanging electrode parts) that occur when the Au that serves as electrodes stretches and is torn off when the wafer is cut, and the edges of the electrodes are damaged by external force when handling the laser chip. They are not aware of problems such as shot defects due to overhang.

That is, in conventional laser chips of this type, during manufacture, the electrodes provided on one side of the laser chip tend to protrude due to the following reasons, and shorts occur in the pn junction. The inventor has found that this makes it easier.

A laser chip has a structure in which a multilayer growth layer is formed on the main surface of a thick substrate of approximately 100 μm, and the laser beam is emitted from the end face of the active layer, which is one of the constituent layers of the multilayer growth layer. At least one electrode is provided on the upper surface side of the multilayer growth layer. The distance between the electrode on this multilayer growth layer and the active layer is extremely short, for example, 4 to 5 μm. For this reason, if the electrode on the multilayer growth layer overhangs and hangs down from the periphery of the laser chip, this overhanging electrode portion may straddle the pn junction and contact a region of a different conductivity type, or contact the pn junction, resulting in short will cause the condition. As mentioned above, the electrodes on the multilayer growth layer are highly malleable.
Since it is made of Au, the Au stretches and is torn off when the wafer is divided, resulting in an overhanging electrode portion at the periphery of the laser chip.
In particular, when cutting a wafer, the wafer is folded in a curved shape to prevent damage to the multilayer growth layer, so the Au on the multilayer growth layer is torn into pieces. This results in a state where the overhanging electrode portion is likely to occur. In addition, the laser chip is handled with vacuum tweezers or the like, and at this time, the contact pressure of the vacuum tweezers causes the electrodes made of Au on the multilayer growth layer to extend.
An electrode portion protrudes from the periphery of the laser chip.

[Purpose of the invention]

An object of the present invention is to provide a light-emitting element of excellent quality in which shot defects due to electrodes are less likely to occur.

Another object of the present invention is to provide a light emitting device having a structure that facilitates wafer cutting.

Another object of the present invention is to provide a light emitting device having a structure that is easy to handle.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the BH type semiconductor laser device of the present invention has a multilayer growth layer of which the active layer is one of the constituent layers, and an Au
By providing a thick shot prevention layer made of silicon with low electrical resistance between the electrodes, which mainly consist of Also, even if the electrode partially overhangs and hangs down at the peripheral edge of the laser chip when cutting the wafer, this overhanging electrode will never reach the pn junction, reducing the chance of shoots occurring due to the overhanging electrode. can be achieved.

〔Example〕

FIG. 1 is a perspective view showing a BH type semiconductor laser device according to an embodiment of the present invention. Also, Figure 2~
FIG. 7 is a diagram showing a wafer, which is a workpiece in each manufacturing process in the manufacture of a BH type semiconductor laser device, and FIG. 2 is a cross-sectional view of the wafer, which is a workpiece, and FIG. Figure 4 is a cross-sectional view of a wafer that has been subjected to buried growth treatment, Figure 5 is a cross-sectional view of a wafer that has been treated with zinc diffusion treatment, and Figure 6 is a cross-sectional view of a wafer that has been treated with a shot prevention layer. 7 is a cross-sectional view of the wafer with electrodes formed thereon. Further, FIG. 8 is a perspective view of a laser chip having a protruding electrode portion, and FIG. 9 is a schematic view showing the state in which the laser chip is mounted.

The BH type semiconductor laser device (laser chip) in this embodiment has a structure as shown in FIG. Further, the laser chip is manufactured through the manufacturing steps shown in FIGS. 2 to 7.

In this example, a buried heterostructure (BH:
An example in which the present invention is applied to a semiconductor laser device with a buried-hetero structure will be described.

For an explanation of the structure of the laser chip, see Figure 2~
This will be explained by explaining the manufacturing state shown in FIG.

When manufacturing a laser chip, first a compound semiconductor thin plate (wafer) 1 as shown in FIG. 2 is prepared. This wafer 1 consists of a substrate 2 of n-type InP, a buffer layer 3 of n-type InP, an active layer 4 of InGaAsP, and an active layer 4 of It consists of a multilayer growth layer 7 consisting of a cladding layer 5 of type InP and a cap layer 6 of p-type InGaAsP, and a double heterojunction structure is constituted by the buffer layer 3, active layer 4, and cladding layer 5. The substrate 2 has a thickness of about 200 μm, the active layer 4 has a thickness of 0.15 μm, and each of the other layers has a thickness of about 1 to 2 μm.

Next, as shown in FIG. 3, an insulating film (SiO ₂ ) is formed on the main surface (upper surface) of the wafer 1 by CVD (chemical vapor deposition), and this insulating film is removed by photolithography. partially removed,
<110> A large number of striped masks 8 with a width of 5 to 6 μm are formed parallel to the cleavage direction. Thereafter, the semiconductor layer of the wafer 1 exposed through the mask 8 is etched with an etching solution such as bromethanol. Etching is performed so as to reach the middle of the buffer layer 3 or the surface layer of the substrate 2. In this embodiment, the etching reaches halfway through the buffer layer 3. As a result of anisotropic etching, the upper part of the active layer 4 covered by the mask 8 becomes an inverted mesa part whose cross section is an inverted triangle, and remains in a stripe shape along the <110> direction of the crystal, and the active layer 4 remains in a stripe shape along the <110> direction of the crystal. layer 4
The area below is a mesa shaped like a parabola. Note that the interval between each mask is approximately 400 μm.

Next, the mask 8 partially extending over the main surface of the wafer 1 is removed. After that, as shown in Figure 4, p-type InP is etched into the recessed area by etching.
blocking layer 9, n-type InP buried layer 1
A cap layer 11 of 0.0, n-type InGaAsP is sequentially buried by an epitaxial method.

Next, as shown in FIG. 5, an insulating film 12 made of SiO ₂ or the like is partially formed on the main surface of the wafer 1 by photolithography. This insulating film 1
2 is not provided on the surface of the striped mesa portion. Therefore, using this insulating film 12 as a mask, zinc (Zn) is implanted into the main surface of the wafer 1.
Zinc diffusion region 1 reaching the middle depth of cladding layer 5
3 is formed. This zinc diffusion region 13 becomes an ohmic layer of a contact electrode.

Next, as shown in FIG. 6, a shoot prevention layer 14 made of silicon (Si) having low electrical resistance is formed on the main surface of the wafer 1. This shot prevention layer 14 is formed by, for example, a manufacturing method such as an epitaxial growth method, a sputtering method, or a vapor deposition method.
Formed to a thickness of 10 μm. Shoot prevention layer 14
As will be described later, as shown in FIG.
6 is thick to prevent shot from coming into contact with pn junctions, etc.

Next, the back surface of the wafer 1 is etched, so that the total thickness of the wafer 1 is about 100 μm. Thereafter, as shown in FIG. 7, an anode electrode 15 is provided on the main surface of the wafer 1, and a cathode electrode 17 is provided on the back surface. The anode electrode 15 is Cr/
Au and the cathode electrode 17 are made of AuGeNi/Pd/Au, both of which are formed by vapor deposition and alloy processing.

Next, an external force is applied to one end of the wafer 1 using a diamond tool or the like, and cleavage scratches are made at regular intervals along the cleavage plane of the crystal. Thereafter, bending stress is applied to the wafer 1 from the outside to cleave it, forming strip-shaped pieces.
Next, this fragment is made with a diamond tool or the like to make scratches (scribes) at regular intervals in the direction perpendicular to the cleavage line in the scribe area, and is divided along the scribe by cracking, resulting in a large number of pieces. A laser chip 18 is formed.

At this time, when the wafer 1 is divided by cleavage and cracking due to bending stress, the electrode on the multilayer growth layer 7, that is, the Au layer that will become the anode electrode 15 is torn off and divided. As a result, the highly malleable Au layer stretches and splits, resulting in an overhanging electrode portion 16 that partially protrudes (overhangs) at the periphery of the laser chip 18, as shown in FIG. However, according to the inventor's experimental investigation, etc., the projecting length of the projecting electrode portion 16 does not reach 10 μm at most.
The tip of the protruding electrode portion 16 hardly crosses over the pn junction and comes into contact with another conductivity type region, or comes into contact with the pn junction, and the occurrence of shoots can be prevented.

On the other hand, regarding the wafer 1 according to this embodiment,
Since the multilayer growth layer 7, which should not be damaged, is covered with a shot prevention layer 14 as thick as 10 μm,
When dividing the wafer 1, the wafer 1 can be divided by repeatedly folding both sides of the divided portion up and down. Therefore, if this repeated folding and dividing method is adopted, the division can be performed quickly and the workability of dividing the wafer into parts will be improved.

Furthermore, when the laser chip 18 is handled with a tool such as vacuum tweezers, the anode electrode 15 is extended by the contact pressure of the vacuum tweezers.
Even if a part of the laser chip 18 protrudes from the periphery of the laser chip 18, since the thick shot prevention layer 14 is provided under the anode electrode 15, the tip of this protruding electrode portion 16 will not exceed the p-n junction as described above. Contact with other conductivity type regions or contact with pn junctions hardly occurs, and the occurrence of shoots can be prevented.

On the other hand, the external shape of the laser chip 18 is as shown in FIG. 1 and FIG. When a predetermined voltage is applied to
oscillates.

Note that this laser chip 18 is connected to the anode electrode 1.
5 or via the cathode electrode 17 on a support plate. For example, the 9th
The figure shows an example of a laser chip 18 in which the anode electrode 15 surface is the connection surface, and the laser chip 18 is fixed to a support plate 21 via a solder 20.

In this case, the laser chip 18 can also be directly attached to a heat sink such as a stem.
That is, conventionally, the laser chip 18 is fixed to the stem (heat sink) using an auxiliary support plate called a submount. This is because the size of the laser chip 18 is small and difficult to handle, and when the multilayer growth layer 7 side is the fixed surface side, the laser beam 18 is small and difficult to handle.
Since the distance between the light emitting position 9 and the fixing surface is short, a few μm, the distance between the laser beam 19 and the laser beam 19 is small, so the distance between the laser beam 19 and the laser beam 19 is small, so the distance between the laser beam 19 and the laser beam 19 is small. After being fixed to a large submount, it is fixed to a support plate 21 such as a stem (heat sink). However, in this embodiment, although the former's ease of handling with respect to the laser chip size is not improved, the latter's solder 20 swells up and blocks the laser beam 19.
This can be avoided by providing a thick shot prevention layer 14 of 10 μm between the two. Therefore, when mounting the laser chip 18, there is no need to pay much attention to the swelling of the solder, and the laser chip 18 can be directly fixed to the support plate 21 in the same way as in the conventional case where the laser chip 18 is fixed to a submount.

On the other hand, when the cathode electrode 17 side is the fixed surface, the active regions such as the active layer 4 are covered with a thick shoot prevention layer 14, and this shot prevention layer 14 acts as a buffer, so that the anode electrode 15 The wire connected to can also be connected to a location corresponding to the active area, eliminating the need for highly accurate positioning of wire bonding and improving work efficiency.

〔effect〕

1. In the semiconductor laser device of the present invention, the distance between the pn junction portion exposed on the peripheral surface of the device and the anode electrode 15 adjacent thereto is such that the distance between the shot prevention layer 14
Since the anode electrode 15 is longer than the conventional one due to the interposition of the laser chip 18, even if the anode electrode 15 is extended during chip formation or chip handling and the electrode material overhangs and hangs down from the periphery of the laser chip 18, the overhanging electrode portion will not be affected. It is almost impossible for the tip of 16 to come into contact with a pn junction or the like, resulting in a short shot defect, and it is possible to provide a light emitting element with excellent quality.

2. From 1 above, since the frequency of shot defects can be reduced, the yield can be improved and the manufacturing cost of semiconductor laser devices can be reduced.

3 As mentioned in 1 above, in the semiconductor laser device of the present invention, since the active regions such as the active layer 4 are covered with the thick shot prevention layer 14, when handled with a tool such as vacuum tweezers, the shot based on the anode electrode 15 is prevented. Defects can be handled without special care. Therefore, the ease of handling the semiconductor laser device is improved.

4 In the semiconductor laser device of the present invention, as described in 1 above, the active regions such as the active layer 4 are covered with the thick shot prevention layer 14, so that when the wafer 1 is made into chips, it can be folded back in opposite directions. Therefore, the chipping speed becomes faster and work efficiency improves.

5 As mentioned in 1 above, in the semiconductor laser device of the present invention, the active regions such as the active layer 4 are covered with the thick shot prevention layer 14, so when mounting the chip, the height of the active layer 4 is higher than that of the conventional device. Therefore, shielding failure of the laser beam 19 by the solder 20 is less likely to occur. As a result, the laser chip 18 can be directly fixed to the support plate 21 such as a stem without using a submount as in the past, and the manufacturing cost of the light emitting electronic device is reduced by reducing the number of parts and assembly man-hours. mitigation can be achieved.

6. From 1 to 5 above, the semiconductor laser device of the present invention can achieve improved yield, improved reliability, and improved workability in its manufacture, so manufacturing costs can be reduced, and the semiconductor laser device of the present invention can be incorporated. A reduction in the manufacturing cost of the light emitting electronic device can also be achieved.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the above Examples, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say. For example, even if the shot prevention layer 14 is made of other conductive material, the same effect as in the embodiment described above can be obtained. At least the shot prevention layer 14
The material may be any material as long as it has good adhesion to the anode electrode 15, the multilayer growth layer 7, and the insulating film 12, has good divisibility when the wafer 1 is cleaved, and is electrically conductive. Further, the thickness of the shot prevention layer 14 is further increased so that the active layer 4 is located at the center position in the thickness direction of the laser chip 18, so that the laser chip 18 can be fixed to the support plate 21 without worrying about its vertical direction. This eliminates the need for vertical alignment of chips during chip bonding, improving workability in chip bonding. Further, the present invention can be similarly applied to semiconductor laser elements having other structures, and similar effects can be obtained.

[Application field]

The above explanation has mainly been about the case where the invention made by the present inventor is applied to semiconductor laser device manufacturing technology, which is the background field of application, but the invention is not limited thereto. It can be applied to other light emitting element manufacturing technologies such as optical devices (OEIC elements).

The present invention is applicable to at least a light emitting device having a monolithic structure.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a BH-type semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a wafer showing the manufacturing state of the BH-type semiconductor laser device, and FIG. 3 is a wafer that is similarly mesa-etched. Figure 4 is a cross-sectional view of a wafer that has also been subjected to buried growth treatment, Figure 5 is a cross-sectional view of a wafer that has also been treated with zinc diffusion treatment, and Figure 6 is a cross-sectional view of a wafer that has also been treated with a shoot prevention layer. FIG. 7 is a cross-sectional view of the wafer with electrodes formed thereon, FIG. 8 is a perspective view of a laser chip having a protruding electrode portion, and FIG. 9 is a view of the laser chip being mounted. It is a schematic diagram. DESCRIPTION OF SYMBOLS 1... Compound semiconductor thin plate (wafer), 2... Substrate, 3... Buffer layer, 4... Active layer, 5... Cladding layer, 6... Cap layer, 7... Multilayer growth layer, 8... Mask , 9...Blocking layer, 10
...Embedding layer, 11...Cap layer, 12...
Insulating layer, 13... Zinc diffusion region, 14... Shoot prevention layer, 15... Anode electrode, 16... Extended electrode portion, 17... Cathode electrode, 18... Laser chip, 19... Laser light, 20... Solder, 21...Support plate.

Claims (1)

[Scope of Claims] 1. Forming a multilayer growth layer including an active layer on the main surface of a substrate made of a semiconductor, etching the multilayer growth layer into a mesa shape, and burying the depressed portion caused by the etching, An insulating film is formed on the entire surface except for the multilayer grown layer, and a diffusion region is selectively provided in the multilayer grown layer using the insulating film as a mask, and an active layer that is one of the constituent layers of the multilayer grown layer and the main layer of the substrate are formed. In the method for manufacturing a light emitting element, electrodes are formed on the main surface side and the back surface side, respectively, and electrodes are provided on the main surface side and the back surface side and are electrically connected to regions of a predetermined conductivity type located above and below the active layer, respectively, the substrate. a step of laminating a multi-layer growth layer parallel to the mask, a shoot prevention layer laminated with conductive silicon in contact with the diffusion region over the entire surface of the insulating film used as a mask, and a shoot prevention layer laminated over the entire surface of the shoot prevention layer. 1. A method for manufacturing a light emitting device, comprising the step of forming an electrode on the main surface side made of a gold layer.