JPH0529707A - Manufacture of internal current constriction type semiconductor laser element - Google Patents

Abstract

PURPOSE:To improve efficiency of measurement and evaluation work for deciding quality of elements under the bar condition after forming a cleavage on a wafer in order to reduce mistake on judgement for the measurement by providing a substrate to a vacuum deposition source with an inclination at the time of vacuum deposition of electrodes on the surface of a second contact layer. CONSTITUTION:A SiO2 film 9a is deposited on the entire surface of a wafer and the SiO2 film is removed leaving the SiO2 film 9a only on the area for isolating elements. next, a current constriction layer 8 of a second contact layer 7b is grown. When a p-side electrode 10 is to be formed on a contact layer 7, a wafer is set with inclination against the vacuum deposition source using the inclined vacuum deposition technique. Vacuum deposition to the on of the side surfaces of the second contact layer 7b provided opposed to the vacuum deposition source is shielded by the other second contact layer 7b and thereby the electrode 10 between elements is isolated. After formation of the electrode of n-side, under the bar condition after formation of cleavage, characteristics of elements are measured. Thereby, the yield during measurement can be improved and productivity of elements can also be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an internal current confinement type semiconductor laser device.

[0002]

2. Description of the Related Art An internal current constriction type semiconductor laser device having a structure shown in FIG. 2 is known, and has excellent characteristics which cannot be obtained by a usual external current confinement type semiconductor laser device. FIG. 2 is a schematic cross-sectional view of the internal current confinement type semiconductor laser device seen from the front. As shown in FIG. 2, this device has a first cladding layer 2, an active layer 3, a second cladding layer 4 on a GaAs substrate 1. , Etching stop layer 5, third
The clad layer 6 and the contact layer 7 are formed in this order, and both side surfaces of the stripe-shaped mesa formed in the third clad layer 6 and the contact layer 7 parallel to the laser light traveling direction are filled with the current confinement layer 8. is there. The current confinement layer 8 has a role of a light absorption layer, and the etching stop layer 5
By appropriately selecting the width of the third cladding layer 6 viewed from the front, stable transverse mode oscillation of the device is possible, and further, the current confinement layer 8 has a smaller active layer 3 than the external current confinement type device. Since it is close to the light emitting region, current concentrates in a part of the active layer 3 and the oscillation threshold current can be reduced.

Thus, the internal current confinement type semiconductor laser
The device has a structure suitable for high output, and is usually
Manufactured in this way. 3 (a) to 3 (d) are the main
It shows the order of steps, and the same parts as those in FIG.
It is represented by. First, the substrate 1 (n-GaAs, thickness 30)
0 μm, carrier concentration 3 × 10¹⁸/cm³) On the reduced pressure M
Using the OCVD method (metalorganic vapor phase epitaxy),
Layer 2 (n-Al_xGa_1-xAs, thickness 1.5 μm, key
Carrier concentration 5 × 10¹⁷/cm³), Active layer 3 (p-Al_x
Ga_1-xAs, thickness 0.1 μm, carrier concentration 3 × 10
¹⁷/cm³), The second cladding layer 4 (p-Al_xGa_1-xA
s, thickness 1.5 μm, carrier concentration 5 × 10¹⁷/ C
m³), Etching stop layer 5 (p-Al_yGa_1-y
As, thickness 0.1 μm, carrier concentration 5 × 10¹⁷/ C
m³), The third cladding layer 6 (p-Al_xGa _1-xAs,
Thickness 1.2 μm, carrier concentration 1 × 10¹⁸/cm³), No.
One contact layer 7a (p-GaAs, thickness 0.5 μ
m, carrier concentration 1 × 10¹⁸/cm³) Grows sequentially
It However, active layer 3, second cladding layer 4, etching
Al composition z, x, y of the stop layer 5 and the third cladding layer 6
Is set so that z <y <x. [Figure 3
(A)].

Next, the SiO ₂ film 9 is formed on the entire upper surface of this laminated body.
Are deposited by sputtering, a photoresist is applied and patterned, a SiO ₂ film 9 having a width of 5 μm is formed in a stripe shape, and the resist is removed. Then, the SiO ₂ film 9 is used as a mask to first remove a sulfuric acid-based etching solution (sulfuric acid). : Hydrogen peroxide water: water = 10: 1: 1), and then an iodine-based etching solution (iodine: hydrogen peroxide water: water = 100: 1: 1) is used to form the third clad layer 6 and the first contact. The layer 7a is etched, and the third cladding layer 6 is partially etched to form a stripe-shaped mesa portion [FIG. 3 (b)].
At this time, the etching stop layer 5 is utilized by utilizing the difference in etching rate with respect to the Al composition of the iodine-based etching solution.
At this position, the etching of the third cladding layer 6 can be stopped. For example, the Al composition x of the third cladding layer 6 is 0.45, and the Al composition y of the etching stop layer 5 is 0.
When it is set to 2, the etching rate ratio is 5: 1, and the etching of the third cladding layer 6 is stopped by utilizing this difference in etching rate.

Next, the current confinement layer 8 (n-GaA) is again formed by using the low pressure MOCVD method with the SiO ₂ film 9 attached.
s, thickness 1.7 μm, carrier concentration 5 × 10 ¹⁹ / cm ³ )
Are selectively grown on both sides of the mesa portion [FIG. 3 (c)].

Then, the SiO ₂ film 9 is removed, and M
The second contact layer 7b of p-GaAs is regrown by 3 μm by using the OCVD method, and the contact layer 7 is formed so as to be integrated with the first contact layer 7a formed first. This is to prevent the solder material from blocking the light emitting region when the surface of the element on the active layer 3 side is mounted on the heat sink so as to enhance the heat radiation effect when the element oscillates. [FIG.3 (d)].

The laminated structure as described above is performed for a large number of elements formed on a semiconductor wafer which becomes the substrate 1. The AuZn, n side is formed as the p-side ohmic electrodes 10 on the upper and lower surfaces of the wafer, respectively. By forming AuGe as the ohmic electrode 11 and then cleaving it into a bar shape and further chipping, the internal current confinement type semiconductor laser device shown in FIG. 2 can be obtained.

[0008]

However, when the internal current confinement type semiconductor laser device is manufactured by the above method,
There are the following problems. It takes a considerable time to individually measure the electrical characteristics of a large number of chips before assembling the obtained semiconductor laser device chips into products and to select good products from these. That is.
The size of each chip is extremely small, with vertical and horizontal dimensions of about 0.3 mm square, so if this sorting is done manually, it will take a very long time, and even if automatic measurement is performed, this It is very difficult to accurately align such small chips in the laser beam emission direction. In the state of the bar cleaved from the wafer before being made into chips, the size is 0.3 mm square and the length is about 20 mm, so if the characteristics are measured in this state, it will be easy to handle and the time required will be short. However, it is difficult to separate the characteristics of each chip formed on the bar, and an erroneous determination may be made in distinguishing a good product from a defective product. That is, since the bar-shaped wafer contains a plurality of elements and they are not separated from each other, if currents flow in superposition, the apparent currents are too large to obtain the desired optical output, and the individual With regard to the element, the non-defective product is treated as a defective product.

The present invention has been made in view of the above-mentioned points, and an object thereof is to perform a characteristic measurement for determining the quality of an element in a bar state after wafer cleavage in manufacturing an internal current confinement type semiconductor laser element. SUMMARY OF THE INVENTION It is an object of the present invention to provide a manufacturing method capable of efficiently performing a measurement operation and making a measurement error.

[0010]

In order to solve the above-mentioned problems, the present invention forms a current confinement layer in the process of manufacturing an internal current confinement type semiconductor laser device and then separates the device on the surface thereof. The second contact layer is selectively grown after the SiO ₂ film is patterned in parallel with the laser beam traveling direction. When the electrode is vapor-deposited on the surface of the second contact layer, the substrate is placed against the vapor deposition source. The element is arranged so as to be inclined with respect to the laser light traveling direction, and an electrode is formed in a direction parallel to the laser light traveling direction only on one of both side surfaces of the second contact layer which are adjacent and opposed to each other.

[0011]

According to the present invention, since the elements are separated at the stage of epitaxial growth by using the above method, when the characteristics are measured in the bar state after the cleavage of the wafer, the characteristics of individual elements can be measured in a short time. There is no erroneous determination of pass / fail, and the yield at the time of measurement is improved.

[0012]

EXAMPLES The present invention will be described below based on examples. The method of the present invention is the same as the conventional method up to the step of selectively growing the current confinement layer 8 of FIG. 3C on both sides of the mesa portion, and therefore the description thereof is omitted and the subsequent steps are illustrated in FIG. Although the description will be made with reference to (c) to (c), in order to illustrate the isolation portion of the element, it is shown as a region having two element structures for convenience of description. FIG. 3A in FIGS. 1A to 1C
Parts common to (d) are represented by the same reference numerals.

In the present invention, first, S corresponding to FIG.
iO ₂ After the film 9 is removed, by adhering SiO ₂ film 9a on the entire wafer surface again, SiO only point to separate the element ₂
SiO ₂ adhered to other parts except the film 9a
The film 9a is removed [FIG. 1 (a)].

Next, the second contact layer 7b is regrown to 3 μm by MOCVD again. At this time, as in the case of growing the current confinement layer 8, the selective growth of the second contact layer 7b is performed, and the first contact layer 7 is formed.
The contact layer 7 formed integrally with a is completely separated for each element [FIG. 1 (b)].

A plurality of contact layers thus formed
In the case of forming the p-side electrode 10 on the contact layer 7 , the side surfaces of the second cladding layer 4 which are adjacent to each other with the SiO ₂ film 9a sandwiched therebetween face each other with an inclination. Using a vapor deposition technique, this wafer is set at an angle to the vapor deposition source. When the electrode material is vapor-deposited, one of the side surfaces of the second contact layer 7b, which is inclined and faces the other side, is blocked from vapor deposition by the other second contact layer 7b, and vapor deposition is not performed on that surface. Electrode 1 between
0 can also be separated [Fig. 1 (c)].

Next, after forming an n-side electrode (not shown), it is cleaved into a bar shape and chipped to obtain an internal current confinement type semiconductor laser device using the method of the present invention.
The internal current confinement type semiconductor laser device obtained in this manner is measured for the characteristics of the devices belonging to the bar in the state of the bar after the end of cleavage, and at the same time, the bar-shaped one manufactured by the conventional method is also measured. The rate of misjudgment at the time of measurement in the separation work of good products and defective products was compared. As a result, in the element manufactured by the method of the present invention, the number of erroneous judgments of quality is 2
%, Whereas the element produced by the conventional method is 38%, and by using the method of the present invention,
% Could also reduce judgment errors. This is because the large number of elements formed on the measured bar are well separated from each other and do not electrically affect each other.

In the method of the present invention, the p-side electrode 10 is formed on the contact layer 7 from the state of FIG. 1 (b) instead of using the oblique deposition method.
7 surface, that is, the entire surface of the second contact layer 7b,
Even if the p-side electrode 10 is attached and then patterned to separate the elements, an element having the same structure as described above can be obtained. The error in the pass / fail judgment at the time of measuring the element characteristics of the bar thus manufactured is only 1%, and in this case as well, it is shown that the elements are often separated.

[0018]

According to the present invention, in manufacturing an internal current confinement type semiconductor laser device, a current confinement layer is formed, and then a SiO ₂ film for isolating the device is patterned on the surface thereof in parallel with the laser light traveling direction. , When the characteristics are measured in the bar state after the wafer is cleaved because the elements were separated at the stage of epitaxial growth by selectively growing the second contact layer and depositing the electrode on the surface of the second contact layer. Since the quality of the characteristics of each element is not erroneously judged efficiently, the yield at the time of measurement can be improved, and the productivity of the element can be improved.

[Brief description of drawings]

1A to 1C are manufacturing process diagrams of an internal current confinement type semiconductor laser device according to the present invention.

FIG. 2 is a schematic cross-sectional view of an internal current confinement type semiconductor laser device.

3A to 3D are manufacturing process diagrams of an internal current confinement type semiconductor laser device.

[Explanation of symbols]

1 substrate 2 first clad layer 3 active layer 4 second clad layer 5 etching stop layer 6 third clad layer 7 contact layer 7a first contact layer 7b second contact layer 8 current confinement layer 9 SiO ₂ film 9a SiO ₂ Membrane 10 p-side electrode 11 n-side electrode

Claims (2)

[Claims] 1. A semiconductor substrate having at least a first cladding layer, an active layer, a second cladding layer, and a third cladding layer on a main surface thereof.
And a first contact layer are sequentially formed, and the second clad is formed on both side surfaces parallel to the laser light traveling direction in a region where the first contact layer contacts the upper surface of the mesa formed in the third clad layer. A current confinement layer having a conductivity type opposite to that of the layer is buried, and the current confinement layer is in contact with the second contact layer on the surface of the second cladding layer opposite to the active layer, and the first contact layer and the first contact layer. A method of manufacturing an internal current confinement type semiconductor laser device, comprising forming a plurality of device structures having a second contact layer integrated on the substrate, wherein the device is separated on the surface after forming the current confinement layer. SiO ₂
A method of manufacturing an internal current constriction type semiconductor laser device, comprising: a step of patterning a film parallel to a laser light traveling direction; and a step of selectively growing the second contact layer. 2. When forming an electrode on the surface of the selectively grown second contact layer according to claim 1 by an evaporation method,
The substrate is arranged so as to be inclined with respect to the vapor deposition source with respect to the laser beam traveling direction of the device, and electrodes are formed on one of both side surfaces of the second contact layer which are adjacent and opposed to each other in a direction parallel to the laser beam traveling direction. A method of manufacturing an internal current constriction type semiconductor laser device, comprising: