JPS6347358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming an end face protection film of a semiconductor light emitting device, particularly a semiconductor laser device.

[Technical background of the invention and its problems]

FIG. 1 shows a semiconductor light emitting device, particularly a ternary semiconductor laser device made of GaAlAs. The example shown is n type.
On one side of the GaAs substrate 7, an n-type GaAlAs layer 6,
active layer 5, p-type GaAlAs layer 4, p-type GaAs layer 3,
An insulating film 2, an anode electrode 1 provided by opening a hole in the insulating film 2, and a cathode ohmic electrode 8 on the other side. In such devices, the active layer has a very small light-emitting area of 0.02 to 0.1 μm x 3 to 5 μm, from which light output of several mW, sometimes tens of mW, is extracted, and the light output per unit area is very small. The output is
It reaches as much as 10 ⁶ W/cm ² . For this reason, it is no exaggeration to say that the operating life is now increasing, and that the limit of the operating life depends on the formation of the protective film at the end of the semiconductor laser resonator. This semiconductor laser device end face protection film is formed by depositing a dielectric film of SiO ₂ , Al ₂ O ₃ , Si ₃ N ₄ , etc. on both end faces of the semiconductor laser resonator using known methods such as sputtering, E-gun, and CVD. This is done by depositing half a wavelength thick. At this time, adhesion of the dielectric film to each electrode surface of the anode electrode 1 and the cathode electrode 8 must be avoided because it makes mounting on a heat sink and wire bonding of the electrodes difficult. Therefore, it is necessary to mask the electrode surface in the process of attaching a protective film to the end face. However, semiconductor laser chips are usually extremely small, for example 0.4 x 0.3 x 0.1 mm, and it is difficult to mask the electrode surfaces of such chips. Therefore, as shown in Fig. 2 or 3, the semiconductor laser chip is mounted and then an end face protection film is attached.
Alternatively, a bar-shaped sample in which semiconductor laser chips are connected as shown in FIG. 4 is folded up and an end face protection film is attached thereto.

In the example shown in FIG. 2, a semiconductor laser chip 13 is attached to a stem 9 to which a pin diode 10 is attached via a heat sink 11 and a submount 12. In this device, the mounting of the semiconductor laser chip on the heat sink and the wire bonding are completed before the end face protection film is attached, so that the attachment of the dielectric film to the electrode surface is no longer a problem. However, in this example, of the pair of laser end faces, the end face facing the stem is obstructed by the stem, so directional film adhesion methods such as sputtering or E-guns are not suitable. Not suitable. Furthermore, since the stem body is placed inside the device, it takes up a lot of space and is not suitable for mass production.

In the example shown in FIG. 3, the electrode post 14 is provided on the submount 12 in advance, and wire bonding to the laser chip 13 is completed only on the submount. That is, after soldering the semiconductor laser chip 13 and the electrode post 14 onto the Cu or Si submount 12, wire bonding is performed between them, a plurality of these are mounted on a fixing jig, and an end face protection film is attached. Thereafter, it is fixed to the heat sink 11 by soldering as shown in the figure. However, in this example, since the semiconductor laser device is divided into individual elements, it takes time and effort to arrange them when attaching the protective film, and requires many steps such as providing electrode posts. Therefore, like the above example, it has a weakness in mass production.

In the example shown in FIG. 4, a plurality of bar-shaped semiconductor laser devices 13 are closely arranged on a fixing jig 16 to form an end face protection film. Each arrayed sample is held down by the stop jig 15, but if there are minute irregularities on the wafer surface, a slight gap will be created between the bars, so that the dielectric film will not fit into this gap when forming the dielectric film. After entering the mount,
There is a problem in that the yield in the bonding process is reduced. Furthermore, in a similar method, the edge protection film is
It can only be attached to one side in one application, and in order to form a protective film on both sides, the device must be turned over and the attachment repeated, which is a two-time process and there is a risk that one end face may be contaminated by jigs, etc. There is also.

In each example, when the end face protection film is formed by sputtering, the reflecting surface of the semiconductor laser, that is, the surface on which the protection film is formed, is positioned parallel to the sputtering target. Generally, in the sputtering method, the sputtered particles, that is, the particles forming the dielectric protective film, have an energy of several tens of eV when the film is formed.
Particles with such energy that directly hit the reflective surface of the semiconductor cause damage to the reflective surface of the semiconductor during the formation of the protective film, create stress between the semiconductor surface and the film, and cause surface leakage when current is applied. It also leads to

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming end face protection with excellent yield and efficiency, in which a protective film with low stress is simultaneously formed on both end faces while masking the electrode faces of a semiconductor laser device.

[Summary of the invention]

For example, when forming a thin film using the sputtering method,
Normally, the film-forming surface of the sample is placed parallel to, or opposite to, the sputtering target.
If the sample is thick, a film of uniform thickness will be formed on the surface of the sample perpendicular to the target up to a certain distance from the top surface. This phenomenon is called the wrap-around phenomenon. This wrap-around film is not directly exposed to the energy of the sputter particles during sputtering, causing less damage to the semiconductor film-forming surface and making it possible to form a film with less stress. This invention utilizes this wraparound. That is, as shown in FIG. 5, both end faces 19 of the semiconductor laser device 13, which has a metal mask 21 placed on the sample stage 18, are placed as sputter targets 1.
By placing the protective film at a position perpendicular to 7, a protective film with less stress can be formed on both end faces at the same time by wrapping around the formed film. Furthermore, since the surface 20 of the semiconductor laser device 13 parallel to the sputter target 17 is the surface to which wire bonding is applied, the area that can be bonded is set using the metal mask in order to prevent insulation due to the adhesion of the film. It is covered with 21.

[Embodiments of the invention]

FIG. 6 shows the jig arrangement used in the embodiment method of this invention. The sample support jig 22 made of molybdenum has a groove 23 tapered on both sides, which makes it easier for the end face protection film to wrap around the reflective surface of the laser device placed in this groove. It plays a role in determining the set position. A bar-shaped sample 13' in which semiconductor laser devices are arranged in a strip-like manner is placed in this groove. The number of semiconductor laser devices in the bar-shaped sample, ie, the length of the bar-shaped sample, is free within the length of the groove. Since the top surface of the bar-shaped sample is the surface to which wire bonding is applied,
In order to prevent the formed film from adhering, a metal mask 21' made of Monbuden is used to cover an area of 100 μm or more that can be wire bonded. The position of the metal mask 21' is determined by a wedge-shaped pin 24, and the sample 13' is fixed by this metal mask 21'. By setting the above-mentioned jig so that both end faces of the semiconductor laser device are perpendicular to the sputter target of the high frequency 13.56 MHz sputtering device, a protective film is simultaneously formed on both end faces of the semiconductor laser device. In this example, an Al ₂ O ₃ film is used. The growth rate of the edge protection film is 40 to 50% of the growth rate of the film attached to the plane parallel to the sputter target.
At 110-120Å/min, the thickness of the semiconductor laser device is approx.
It is formed with a uniform thickness of 80 μm.

FIG. 7 shows the jig arrangement used in another example method. When the length of the bar-shaped sample, that is, the number of semiconductor lasers arranged in a strip shape, is constant, the sample is positioned by forming a rated groove in the sample support jig 22 to fix the sample 13'. . The upper surface of this sample is covered with a metal mask 21',
The position of the mask is determined by wedge-shaped pins 24.

In the above-mentioned embodiment, the semiconductor laser devices connected in a strip shape are placed one by one in the groove of the sample support jig, but it is also possible to stack a similar sample on top of the strips, so that a large number of semiconductor laser devices can be stacked at once. It is possible to form an end face protection film for a semiconductor laser device. Further, this method may be employed not only in the sputtering method but also in other thin film forming methods such as E-gun and CVD methods. Examples of the film forming material include SiO ₂ and Si ₃ N ₄ .

〔Effect of the invention〕

According to the present invention, it is possible to simultaneously form a protective film with less stress on both end faces of a semiconductor laser device, thereby improving manufacturing yield and efficiency.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a DH semiconductor laser device, Figures 2 and 3 are mounting diagrams of the semiconductor laser device, Figure 4 is a jig for forming an end face protective film, and Figure 5 explains the method of the present invention. The sputter target arrangement diagrams shown in FIGS. 6 and 7 are all of the protective film forming jig used in the embodiment method. In each figure, 1... anode ohmic electrode, 2...
...Insulating film, 3...p-GaAs layer, 4...p-
GaAlAs layer, 5... active layer, 6... n-GaAlAs
layer, 7... n-GaAs substrate, 8... cathode ohmic electrode, 9... stem, 10... pin diode, 11... heat sink, 12... submount, 13, 13'... semiconductor laser device, 14
...Electrode post, 15...Sample fixing jig, 16...
...Sample holding jig, 17...Spatter target,
18...Sample stage, 19...Resonator end face, 2
0...Wire bonding surface, 21, 21'...
...Metal mask, 22... Support jig, 23... Placement groove, 24... Wedge pin.

Claims (1)

[Claims] 1. A pair of opposing reflecting surfaces each consisting of a cleavage plane;
A method for forming a protective film made of a dielectric material on the reflective surface of a semiconductor laser device, which comprises at least a surface to be fused to a heat sink and a surface to be wire-bonded to the semiconductor laser device, the method comprising: A semiconductor laser characterized in that a dielectric film is formed on the reflective surface by sputtering the dielectric protective film forming surface, which serves as the reflective surface of the laser element, positioned perpendicularly to a sputter target made of a dielectric material. Method for forming a device end face protective film. 2. A method for forming a semiconductor laser device end face protection film according to claim 1, characterized in that the wire bonding surface is sputtered below a metal mask. 3 A plurality of semiconductor laser elements are arranged in a row so that the reflective surfaces are continuous, the surface to be fused to the heat sink is in close contact with the support jig surface over the entire surface, and the surface to be wire bonded is at least as long as necessary for wire bonding. 3. The method of forming a semiconductor laser device end face protection film according to claim 2, wherein the area is held in close contact under a mask and sputtered.