JPH02273982A - Semiconductor laser inspection method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an inspection method for determining whether a semiconductor laser is good or defective after it has been manufactured. For the purpose of providing an inspection method, a first cladding layer 7 of the same conductivity type as the substrate 1, an active N8 layer, and a second cladding layer of the opposite conductivity type to the base vi1 are sequentially formed on a substrate 1 of one conductivity type. In the semiconductor laser in which a cladding N9 is formed, grooves 13 are provided in the substrate 1 in a lattice pattern to expose the laser beam emitting end face processing 2, and the semiconductor lasers are individually divided, and the first semiconductor laser is directed in the forward direction. A bias is applied to emit the laser beam 14, and a reverse bias is applied to a second semiconductor laser adjacent to and facing the laser beam emitting end face of the first semiconductor laser, and the laser beam 14 is received. The first semiconductor laser is inspected by detecting a photocurrent flowing through the second semiconductor laser.

(Field of Industrial Application) The present invention relates to an inspection method for determining whether a semiconductor laser is good or bad after manufacturing it.

In recent years, demand for semiconductor lasers has increased as optical devices for transmitting and receiving optical communications that enable high-speed communications. In addition to the performance, reliability, ease, and time reduction of inspection during manufacturing are desired.

[Conventional technology]

Conventionally, there have been two main methods for testing semiconductor lasers.

The first method is to form several hundred to several dozen semiconductor lasers on a 1- to 2-inch square substrate and inspect the substrate before it is cut out one by one.

This method will be explained using FIGS. 3(a) and 3(b).

FIG. 3(a) is a perspective view when the board is inspected, and FIG. 3(b) is a partial cross-sectional view of FIG. 3(a).

As shown in the figure, grooves are usually formed in a lattice shape by etching on a substrate 1 in order to divide the substrate into individual semiconductor laser chips, and hundreds of semiconductor lasers are formed. Touch each of these with the test needle,
A forward bias is applied by the semiconductor laser driving means 4 to cause the semiconductor laser to which the needle is applied to emit light. Then, as shown in Figure 3(b), the laser beam is emitted approximately 20 mm from the substrate surface.
Since the light is emitted with a wide spread, it is received by a light receiving means 2 such as a photodiode, and the output photocurrent is detected by a photocurrent detecting means 3. Based on this data, the laser oscillation threshold current and the like are measured to inspect whether the semiconductor laser is good or bad.

The second method involves folding the semiconductor laser substrate and creating a length of 20 m.
The test involves cutting out a piece with a size of approximately 200 to 400 am and a width of 200 to 400 am.

This method will be explained using FIG. 3(C).

As shown in the figure, a substrate 1 on which grooves are formed in a lattice pattern is folded to form a line of semiconductor lasers 5. Then, the inspection unit 1G is applied to each semiconductor laser, and a forward bias of 'C5 is applied by the semiconductor laser driving means 4 to cause the semiconductor laser to emit light. Then, the laser beam is received by a light receiving means 2 such as a photodiode, the output photocurrent is detected by a photocurrent detecting means 3, and the threshold current etc. are measured to inspect whether the semiconductor laser is good or bad. The idea is to do so.

Since the laser beam from the body laser is received, there have been problems such as variations in the positional relationship between each semiconductor laser to be inspected and the light receiving means, and poor reproducibility. If reproducibility is poor, there are inconveniences such as not being able to compare with previous data when you want to repeat the test, reducing the reliability of the test.

In addition, even in the second method shown in FIG. 3(C), since the semiconductor laser is cut out into a small row and inspected, the operability is poor and the inspection takes a long time, and the semiconductor laser may be scratched. There was such a problem.

Therefore, it is an object of the present invention to provide a method for testing a semiconductor laser, which has less variation in test results, good reproducibility, and excellent work efficiency.

[Problem to be solved by the invention]

However, in the first method shown in FIGS. 3(a) and 3(b), a light receiving means such as a photodiode is arranged near the laser beam emitting surface of the substrate 1, In the present invention, a forward bias is applied to a semiconductor laser formed by dividing a substrate into a lattice shape to cause the laser to emit laser light, and semiconductor lasers that are adjacent in the resonator direction and have a reverse bias applied thereto are , receives the emitted laser light, extracts the photocurrent, measures the characteristics of the semiconductor laser, and inspects whether it is good or bad.

[Effect]

In the present invention, as a means for receiving laser light from a semiconductor laser to be inspected, adjacent semiconductor radars are reverse biased and used as light receiving elements, so inspection can be performed with the substrate in its original state. Therefore, operability during inspection is very good, and inspection time is shortened.

In addition, the distance between the laser emitting end face and the light receiving surface is very close,
Furthermore, since everything is constant on the substrate, not only is the coupling efficiency high, but there is also less variation and excellent reproducibility.

〔Example〕

Figure 1 (a), (b) and Figure 2 (a), (b)
) An embodiment of the present invention will be described using the following.

FIG. 1(a) is a cross-sectional view of the semiconductor laser viewed from a direction perpendicular to the cavity direction, and FIG. 1(b) is a
) is a plan view seen from above, showing a state in which semiconductor lasers 15 are formed on a substrate in a lattice-like manner.

The semiconductor laser shown in FIG. 1(a) is an n-type 1n
An n-type 1nP cladding layer 7 is sequentially formed on a substrate 1 made of P.
(Film thickness: 1.5 μm, 4 degrees lXl0” cm−3).

InGaAsP active layer 8 (film thickness: 0.13 μm, non-doped, λ-1, 3 μm).

p-type 1nP cladding layer 9 (thickness: 1.3 μm concentration 5×1
0”cm-3).

p-type InGaAsP contact layer 10 (thickness: 0.3μ
m, concentration lXl0Iqc m-3) electrode 11 (film thickness: 1 μm).

Next, in order to separate each semiconductor laser and form a laser beam emitting end face 12, a grid-shaped groove 13 having a width of 50 to 100 μm and a depth of 20 to 50 μm is formed using chlorine (cfz) as a reactive gas. , ion acceleration voltage 300V.

Output: 300 W, pressure: 5 x 10-' torr,
The film is formed by active ion beam etching (RIBE) at room temperature.

By this RIBE, the substrate 1 is divided into lattice shapes as shown in FIG. 1(b) to form semiconductor lasers. One semiconductor laser 15 has a substantially square shape of 200 to 300 μm square when viewed from above.

After this, in order to increase the intensity of the laser beam emitted from the emission side end surface 12a, a reflective film is formed on the laser beam receiving side end surface 12b.
The SiO□ film 16 has a thickness equal to 2 of the wavelength λ of the emitted light.
Membrane shape 6. However, this SiO□ film 16 film type 600%
Since it does not reflect light, it does not interfere with light reception.

Among the semiconductor lasers formed in this way, FIG. 1(a)
The test needles 6a and 6b are brought into contact with the electrodes 11 of two semiconductor lasers adjacent in the cavity direction, respectively, as shown in FIG.

Then, a forward bias of 1 to 1.5 cm is applied to the PN junction of the laser by the semiconductor laser driving means 4 through the inspection needle 68 to one of the semiconductor lasers 100, and the laser beam 14 is emitted.

In this case, since the conductivity type of the substrate 1 is n type, the needle 6a has a positive
A negative voltage is applied to the electrode 11 on the substrate 1 side.

The other semiconductor laser 200 receives the emitted laser beam 14 by applying a reverse bias of 2 to 3 2 by the photocurrent detection means 3 through the inspection needle 6b, and detects the photocurrent. At this time, the forward bias applied by the semiconductor laser driving means 4 and the reverse bias applied by the photocurrent detection means 3 are at the same potential at the electrode 11 on the substrate 1 side.

There are three main inspection items before assembling a semiconductor laser:

■ Inspection of the threshold value to check the minimum current that allows laser emission ■ Inspection of the emission peak wavelength at which the spectral density of the laser beam is maximum ■ Inspection of the interval of the spectral half-width at which the maximum value of the spectral density of the laser beam is A Among these, the most suitable test for determining whether a semiconductor laser is good or bad is the threshold test. If the crystallinity is poor due to some abnormality in the manufacturing stage, this threshold value will become high and the semiconductor laser will become unusable. Good products can be eliminated.

As described above, in the present invention, a semiconductor laser adjacent to the semiconductor laser to be inspected is used as a detection means, and inspection is performed based on the data obtained from the photocurrent detection means 3. However, the semiconductor laser on the light receiving side has a light receiving characteristic. is not understood,
There are concerns that correct test results may not be obtained.

However, in a semiconductor laser as a light receiving element to which a reverse bias is applied, the relationship between the intensity of the received light and the output current has linearity as shown in FIG. 2(a). Therefore, even if there are variations in the characteristics between different light-receiving elements as shown in a, b, and c as shown in the figure, there will be differences in the slope in the threshold test as shown in Figure 2 (b). It's nothing more than that. Therefore, it is possible to find a change point P, that is, a threshold value, at which spontaneous emission light changes to laser oscillation light.

Therefore, even if a semiconductor laser whose light-receiving characteristics is unknown is used as a light-receiving means, it is possible to determine whether adjacent semiconductor lasers are good or bad.

After the inspection of the semiconductor lasers is completed as described above, the needles 6a and 6b are shifted by one grid and similar inspections are performed one after another to inspect the semiconductor lasers on the entire substrate. After all inspections are completed, the substrate 1 is folded along the grooves 13 and the semiconductor lasers 15 are cut out one by one.

In the embodiment described above, only one semiconductor laser was tested, but if multiple test needles are used and care is taken to prevent the laser beams of the semiconductor lasers being tested from influencing each other,
Multiple semiconductor lasers can be tested at the same time.

As described above, in one embodiment, the semiconductor laser can be inspected in the substrate state, and the operability is good, so the inspection time can be shortened without damaging the semiconductor laser. Further, since the distance between the semiconductor laser to be inspected and the semiconductor laser to which a reverse bias is applied, which is the light receiving means, is very close and constant, the coupling efficiency is high and the reproducibility of the inspection is also good.

Although the present invention has been described above with respect to a semiconductor laser whose substrate has an n-type conductivity, a semiconductor laser whose substrate has a p-type conductivity can be similarly inspected.

〔effect〕

As described above, in the present invention, the semiconductor laser can be inspected in the state of the substrate, so the operability during inspection is good.
This has the effect of shortening the inspection time.

Furthermore, since not only high binding efficiency is obtained but also good reproducibility, the reliability of the test is improved.

Therefore, the present invention greatly contributes to shortening the inspection time and improving reliability of semiconductor lasers.

FIG. 3A to FIG. 3C are diagrams illustrating a conventional technique.

1... Substrate 2... Light receiving means 3... Photocurrent detection means 4... Semiconductor laser driving means 5...
Semiconductor laser 6a, 6b... Test needle 7... N-type 1nP cladding layer 8... InGaAsP active layer 9... P-type InP cladding layer lO... Contact layer 11... Electrode 12a...
- Output side end face 12b... Light receiving side end face 13... Groove 14... Laser light 14... Laser light 15... Semiconductor laser 16... Electrode 17... Si0g film

[Brief explanation of drawings]

FIGS. 1(a) and (b) are diagrams explaining one embodiment of the present invention, and FIGS. 2(a) and (b) show the characteristics of a semiconductor laser (0,
) (b) Diagrams explaining the characteristics of semiconductor conductor books 2 Diagrams 1; ヱL, +, The liquid of Ma.

Claims (1)

[Claims] A first cladding layer (7) of the same conductivity type as the substrate (1) and an active layer (8) are sequentially formed on the substrate (1) of one conductivity type.
and a second cladding layer (9) of the opposite conductivity type to the substrate (1).
In the semiconductor laser formed with the above, grooves (13) are provided in the substrate (1) in a lattice pattern to expose the laser beam emitting end face (12), and the semiconductor lasers are individually divided to form a first semiconductor laser. A forward bias is applied to emit the laser beam (14), and a reverse bias is applied to a second semiconductor laser adjacent to and facing the laser beam emitting end face of the first semiconductor laser, and the laser beam (14) is emitted. A method for inspecting a semiconductor laser, comprising: inspecting the first semiconductor laser by receiving light (14) and detecting a photocurrent flowing through the second semiconductor laser.