JPH11284279A - Manufacture of semiconductor laser element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce exposure of an end surface being liable to deterioration as little as possible, by forming an end surface protecting film not at the same time but gradually by using film forming equipment which can form only one end surface protecting film in a first process. SOLUTION: A jig 6 for fixing a laser bar is so set on a holder 7 that a light outputting end surface 5a of the laser bar face a vapor depositing source 10. A chamber 8 of a vapor depositing apparatus is vacuumized via a duct 9, vapor depositing material is evaporated from the vapor depositing source 10 when specified vacuum is obtained, and film formation is started. A protective film 12a' having a thickness (t') less than a specified value is formed on the light outputting end surface 5a and, continuously, a protective film 12a' having a thickness (t') is formed on a light outputting end surface 5b. The holder 7 is turned over again, additional film formation is performed on the protective film 12a' of the light outputting end surface 5a, and a protective film 12a having a specified thickness (t) is formed. As a result, additional film formation is performed on the protective film 12a' of the light outputting end surface 5a of the other side, and an end surface protective film having a specified thickness is gradually formed, so that only one side end surface is not exposed for a long time, and reliability of a laser is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming method used for forming a protective film having a predetermined reflectance on an end face of a semiconductor laser chip.

[0002]

2. Description of the Related Art As shown in FIG. 5, most semiconductor lasers are provided with a protective film 12a having the same reflectance as the light emitting end faces 5a and 5b of a GaAs laser chip 5. When the protective film 12a is made of Al ₂ O ₃ , as an example, the refractive index (n) of the Al ₂ O ₃ film is set to n = 1.6.
0, when the refractive index of the laser chip 5 is calculated as n = 3.50, the reflectance of the protective film 12a changes as shown in FIG. 6 by changing the thickness of the protective film 12a. (FIG. 6 shows a calculation result at a laser oscillation wavelength of 7800 °.) On the other hand, in the case of a high-power laser having an optical output of 20 mW or more, as shown in FIG. In order to increase the light output Pf of the
a is designed to have low reflection and the rear surface 5b is designed to have high reflection. In this case, the Al ₂ O ₃ protective film 12a on the main emission surface side 5a
Is set to a low reflection of about 15% or less, and the film thickness corresponding to this reflectance is about 700 to 1700 °. In addition, the protective film 13 on the rear surface side 5b is composed of a first layer and a third layer 13
a of an Al ₂ O ₃ film corresponding to a thickness λ / 4 (λ: wavelength) and amorphous Si corresponding to a thickness λ / 4 of the second and fourth layers 13b. The last fifth layer 13c is an Al ₂ O ₃ film having a thickness of λ / 4.
The reflectance is as high as about 85% or more.

Next, a method for forming a protective film having the above-described reflectance on the light emitting end face of a semiconductor laser chip will be described below.

First, as shown in FIG. 8, a light emitting portion (channel) 3 is provided between an electrode 2 of a semiconductor laser wafer 1 and the electrode 2.
After a cleavage line is formed in a live direction preferably in the direction orthogonal to the above, the wafer 1 is cleaved into a laser bar (laser chip in a bar state) 5 as shown in FIG. Next, FIG.
The laser bar 5 is stacked on the laser bar fixing device 6 as shown in FIG. At this time, in all the laser bars, the main emission surface 5a and the rear emission surface 5a of the laser chip (bar) are arranged.
Set so that b is in the same direction. Next, a protective film having a predetermined reflectance is formed on the light emitting end surface of the laser bar 5 fixed to the laser bar fixing device 6, in which case,
Generally, a vacuum evaporation apparatus as shown in FIG. 11 is used.

[0005] This vacuum deposition apparatus includes a holder 7 holding a deposition source 10 and the above-mentioned laser bar fixing device 6 in a chamber 8, and a crystal oscillator 11 for monitoring a deposited film thickness.

Hereinafter, a film forming procedure will be described with reference to FIGS. When depositing a protective film on both end surfaces 5a and 5b of the laser chip, first, the chamber 8 is passed through the duct 9.
Vacuum the inside. Then, after reaching a predetermined degree of vacuum, the evaporation material is evaporated from the evaporation source 10 and the light emitting end face 5 of the laser is emitted.
A protective film 12a is deposited on a. After the vapor deposition is completed, the holder 7 is rotated by 180 ° to deposit the protective film 12a on the other light emitting end face 5b of the laser. The vapor deposition is performed while monitoring the film thickness by the quartz oscillator 11, and the vapor deposition is stopped when a predetermined film thickness is reached. In the case of a high-output type laser, the low-reflection protective film 1 on the front surface (main emission surface) side is exactly the same as the procedure described above, as shown in FIG.
After the formation of 2a, the high-reflection protective film 13 on the rear side
Is formed.

[0007]

As described above, when forming an end face protective film of a laser chip, the end face is exposed and heated in a film forming chamber of a vapor deposition machine until a film forming material is deposited. Will be. Despite being under a condition of a high degree of vacuum, the end face gradually deteriorates due to oxidation or the like with the passage of time, and the reliability as a laser element decreases. In particular, in the case of a high-power laser, the light output during laser oscillation is about 5 to 20 times that of a general low-power laser. Need to be protected from deterioration due to

[0008]

According to the present invention, a film forming apparatus capable of forming only one end face protective film in one step is provided.
An object of the present invention is to form the edge protection film little by little rather than forming the edge protection film all at once, thereby exposing the easily degraded end face as much as possible.

A method of manufacturing a semiconductor laser device according to the present invention (claim 1) includes a step of forming a laser bar by cleaving a wafer, and a first step of forming a protective film on one cleavage end face of the laser bar. And a second step of forming a protective film on the other cleavage end face of the laser bar. The first step and the second step are sequentially repeated to obtain a protective film having a predetermined thickness. By accomplishing this, the above object is achieved.

After laminating a semiconductor laser chip in a bar state divided from a wafer by cleavage on a bar fixing jig, a protective film having a predetermined reflectance is formed on a light emitting end face composed of a cleavage end face of the semiconductor laser chip. In this case, a protective film thinner than a predetermined thickness is alternately formed on both light emitting end faces, and finally a film having a predetermined thickness is formed on both light emitting end faces, thereby exposing the end faces which are easily deteriorated. Time can be reduced.

In the method of manufacturing a semiconductor laser device according to the present invention (claim 2), the first step is repeated twice, and the second step is performed once during the first step. Achieve the above objectives.

Here, first, a protective film having a thickness smaller than a predetermined thickness is formed on one of the light emitting end faces, and then a film is formed to a predetermined thickness on the other light emitting end face. A film is formed to a predetermined thickness on the light-emitting end face on which the film has been formed.

As a result, it is possible to more optimally reduce the exposure time of the end face which is easily deteriorated.

A method for manufacturing a semiconductor laser device according to the present invention (claim 3) solves the above-mentioned problem by being characterized in that the first step and the second step are continuously repeated.

During film formation, the jig for fixing the laser bar is constantly rotated at a predetermined speed to form a film on both light emitting end surfaces to a predetermined film thickness.

This makes it possible to protect both light emitting end faces from deterioration due to oxidation or the like in a shorter time.

In the method for manufacturing a semiconductor laser device according to any one of claims 1 to 3, after forming a protective film having a predetermined thickness on both light emitting end faces, the multilayer is continuously formed only on one of the light emitting end faces. Film formation may be performed to form a protective film having an asymmetrical reflectance. ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to shorten the exposure time of the light emission end surface of a laser element, and it becomes possible to suppress end surface deterioration by oxidation etc.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor laser device according to the present invention will be described with reference to examples.

FIG. 1 shows a first embodiment. FIG.
Among them, A1 to A4 schematically show the inside of the vapor deposition machine following the steps, and B1 to B4 show the state of vapor deposition on the laser bar after the steps.

First, as shown in FIG. 1A1, a laser bar fixing jig 6 on which laser bars are stacked is set on a holder 7 in a vapor deposition machine such that a light emitting end face 5a of a laser bar (laser chip) faces a vapor deposition source 10. I do. Next, the chamber 8 of the evaporator is evacuated through the duct 9. When a predetermined degree of vacuum is reached, the evaporation material is evaporated from the evaporation source 10 to start film formation. As shown in FIG. 1B1, a protective film 12a ′ having a thickness t ′ smaller than a predetermined thickness is formed on the light emitting end face 5a.

Subsequently, as shown in FIGS. 1A2 and B2, the holder 7 is turned by 180 ° and a protective film 12a ′ having a thickness smaller than a predetermined film thickness is similarly applied to the other light emitting end face 5b. The film is formed. Thereafter, the holder 7 is again moved to 180
1A3 and B3, an additional film is formed on the protective film 12a 'on the light emitting end face 5a to form a protective film 12a having a predetermined thickness t, as shown in FIGS. 1A3 and B3.

Next, the film forming holder 7 is again turned over by 180 °, and as shown in FIGS. 1A4 and B4, an additional film is formed on the protective film 12a 'on the other light emitting end face 5a to a predetermined thickness. The protective film 12a having a thickness t is formed.

As described above, by forming the end face protective film little by little, the one end face is not exposed for a long time, and the reliability of the laser is improved.

FIG. 2 shows a second embodiment.

First, as shown in FIG. 2A1, a laser bar fixing jig 6 on which laser bars are stacked is set on a holder 7 in a vapor deposition machine such that a light emitting end face 5a of a laser bar (laser chip) faces a vapor deposition source 10. .

Next, the chamber 8 of the evaporator is evacuated through the duct 9. After reaching a predetermined degree of vacuum, a vapor deposition material is vapor-deposited from the vapor deposition source 10 and, as shown in FIG.
a ′ is formed. Subsequently, as shown in FIGS. 2A2B2, the holder 7 is inverted by 180 °, and a protective film 12a having a predetermined thickness t is formed on the other light emitting end face 5b. Thereafter, the holder 7 is again turned over by 180 °, and FIG.
As shown in A3B3, the protective film 12 on the light emitting end face 5a
An additional film is formed on a ′, and a protective film having a predetermined thickness t is formed.

FIG. 3 shows a third embodiment.

First, as shown in FIG. 3A, a laser bar fixing jig 6 on which laser bars are stacked is placed on a holder 7 in a vapor deposition machine such that the light emitting end face 5 a or 5 b of the laser bar (laser chip) faces the vapor deposition source 10. Set to

Next, the chamber 8 of the vapor deposition machine is evacuated through the duct 9. When a predetermined degree of vacuum is reached, the evaporation source 10
The vapor deposition material is further evaporated to start film formation. At this time, the rotation of the holder 7 on which the laser bar fixing jig is set is reduced by one rotation.
00 starts at the same time.

This rotation is always performed at an arbitrary speed from the start to the end of the vapor deposition. That is, while the vapor deposition is being performed, the two light emitting end faces 5a and 5b of the laser alternately face the vapor deposition source 10 at a certain interval.

By rotating in this manner, FIG. 3B
As shown in FIG. 5, both light emitting end faces 5a and 5b can be protected almost simultaneously by the protective film 12a.

Here, the film thickness control method of the present invention will be described. Assuming that the desired film thickness of the protective film 12a is t, the film thickness set in the apparatus is T, and the deposition coefficient is α, in the method according to the present invention, α = 2 in principle. Becomes However, since there is a time during which rotation does not contribute to film formation, it is desirable that α actually takes a value exceeding 2 depending on the rotation speed. For example, t = 2200 °, α =
In the case of 3.0, T becomes T = 2200Å × 3.0 = 6600Å. That is, in this case, the vapor deposition may be terminated when the film thickness monitored by the crystal unit 11 becomes 6600 °.

FIG. 4 shows a fourth embodiment.

This embodiment is used when a protective film is formed on the above-described high output type (asymmetrical reflectance) laser chip. As shown in FIGS. 4A1 and B1, first, protective films 12a on both light emitting end faces 5a and 5b are formed by any of the methods described in the first, second, or third embodiment.

Next, at the same time when the deposition of the protective films 12a on both end faces is completed, the light emitting end face 5b on the rear face side of the laser chip is directed to the deposition source 10, as shown in FIG. 4A2. Thereby, as shown in FIG. 4B2, the second and fourth layers of the amorphous Si film 13b on the rear side and the third and fifth layers of Al ₂
O ₃ films 13a and 13c are formed by vapor deposition.

At this time, the vapor deposition of the second and subsequent layers on the rear side is performed in a state where the inversion or rotation of the holder 7 in the vapor deposition machine is stopped.

[0037]

According to the present invention, it is possible to form a protective film on both light emitting end faces of a semiconductor chip in a shorter time, so that it is possible to suppress the end face deterioration of the laser chip due to oxidation or the like, and it becomes possible to suppress the laser element. Greatly improves the reliability.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a second embodiment of the present invention.

FIG. 3 is a diagram for explaining a third embodiment of the present invention.

FIG. 4 is a diagram for explaining a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a conventional example.

FIG. 6 is a diagram showing a conventional example.

FIG. 7 is a diagram showing a conventional example.

FIG. 8 is a diagram showing a conventional example.

FIG. 9 is a diagram showing a conventional example.

FIG. 10 is a diagram showing a conventional example.

FIG. 11 is a diagram showing a conventional example.

FIG. 12 is a diagram showing a conventional example.

FIG. 13 is a diagram showing a conventional example.

[Explanation of symbols]

5 laser bar 5a, 5b beam emitting end face 6 laser bar fixing jig 7 holders 8 chamber 9 duct 10 evaporation source 11 quartz oscillator 12a, 12a ', 12b, 12b ' protective film 13a, 13c Al ₂ O ₃ film 13b amorphous Si film

Claims (3)

[Claims] 1. A step of forming a laser bar by cleaving a wafer, a first step of forming a protective film on one cleavage end face of the laser bar, and a second step of forming a protective film on the other cleavage end face of the laser bar. And a method of manufacturing a semiconductor laser device, wherein the first step and the second step are sequentially repeated to obtain a protective film having a predetermined thickness. 2. The method according to claim 1, wherein the first step is repeated twice, and the second step is performed once during the first step. . 3. The method according to claim 1, wherein the first step and the second step are continuously repeated.