JPH01292883A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent the characteristics of each semiconductor laser from being deviated by radiating light from the upper part of an etching liquid toward a layer to be etched and by controlling the thickness of film of the layer to be etched while observing light which is reflected on the reflection surface below the layer to be etched and returns onto the etching liquid. CONSTITUTION:Light equivalent to white light is irradiated from the upper part of an etching liquid 8 toward an active layer 3. When a film thickness d of a clad layer 4 is fully thin for the liquid thickness of the etching liquid 8, the irradiated light passes through the etching liquid 8 and the clad layer 4 and then most of it is reflected by the interface with the active layer 3, thus returning to an area above the etching liquid 8 again. Thus, the color changes continuously as etching advances and change in color is constantly monitored by using an image pickup tube, a solid image pickup element etc., and etching is stopped when a specified color corresponding to a desired film thickness d is reached to allow the film thickness d to be controlled easily. It allows a semiconductor laser without any deviation of characteristics to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor laser used for, for example, compact discs, laser beam printers, optical disc memories, and the like.

[Conventional technology]

FIG. 2 is a perspective view showing an example of a semiconductor laser. In this figure, 1 is an n-type substrate, 2 is an n-type cladding layer epitaxially grown on the substrate 1, 3 is an active layer,
4 is a p-type cladding layer, 4a is a striped ridge portion formed by etching, 5 is an n-type current blocking layer formed by second epitaxial growth on the cladding layer 4, and 6 is a p-type cladding layer. 7 is a contact layer, 7 is an upper electrode,
d indicates the thickness of the cladding layer 4 in a region other than the ridge portion 4a.

As described above, the film thickness d of the cladding layer 4 is one of the parameters that influences many of the characteristics of the semiconductor laser including the ridge portion 4a, such as the operating current value for obtaining a constant output value and the radiation angle of the beam. be. Conventionally, the thickness d of the cladding layer 4 has been controlled by forming the cladding layer sufficiently thicker than the desired thickness in advance, and then changing the chemical etching time when forming the striped ridge portions 4a. He was blaming himself by controlling him.

(Problems to be Solved by the Invention) In the conventional semiconductor laser manufacturing method as described above, the film thickness d of the cladding layer 4 is controlled by the chemical etching time.
When using H2O2:H20=1:10:10, etc., as can be seen from the graph in FIG. 3, the etching rate changes as the etching time elapses, making it possible to stably control the film thickness d of the cladding layer 4. There was a problem in that it was difficult to do so, and large variations occurred in the characteristics of the semiconductor laser.

The present invention was made to solve this problem, and its purpose is to provide a method for manufacturing semiconductor lasers that can stably control the thickness of the cladding layer and that does not cause variations in the characteristics of each semiconductor laser. do.

[Means to solve the problem]

In the method for manufacturing a semiconductor laser according to the present invention, when performing chemical etching, light is irradiated from above the etching solution toward the layer to be etched, and the light is reflected by a reflective surface below the layer to be etched and returns onto the etching solution again. This method includes a step of controlling the thickness of the layer to be etched while observing the etching process.

[Operation] In this invention, only the light other than the wavelength components absorbed by the layer to be etched returns to the etching solution, but the wavelength components absorbed gradually change due to changes in film thickness as etching progresses. The thickness of the layer to be etched can be determined from the color tone or intensity of the light that returns to the surface of the liquid.

〔Example〕

FIG. 1 is a diagram for explaining the method of manufacturing a semiconductor laser according to the present invention, and here shows the etching process of the semiconductor laser having the structure shown in FIG. In this figure, the same reference numerals as in FIG. 2 indicate the same parts, 8 indicates an etching solution, and 9 indicates reflected light.

Next, specific steps will be explained.

First, a cladding layer 2. Active layer 3. After sequentially growing the cladding layer 4, chemical etching (here, wet etching) is performed to form a striped ridge portion 4a on the cladding layer 4 as a layer to be etched. At this time, for example, light corresponding to white light containing many wavelength components is irradiated from above the etching liquid 8 toward the active layer 3 . As shown in FIG. 1, if the thickness d of the cladding layer 4 is sufficiently thinner than the thickness of the etching solution 8, the irradiated light will
．． After passing through the cladding layer 4, most of it is reflected at the interface with the active layer 3 and returns to the etching solution 8 again, with a film thickness d=λ(2N+1)/4n (N=0.1,
2. Since the wavelength components satisfying the condition (---------) are absorbed by the cladding layer 4, light other than the wavelength components returns to the outside. In other words, the color tone changes successively as the etching progresses, and while etching is performed, the change in color tone is constantly monitored using an image pickup tube, solid-state image sensor, etc., and a predetermined value corresponding to the desired film thickness d is determined. If you stop etching when the color tone is reached, you can easily reduce the film thickness d.
can be controlled.

Then, as shown in FIG. 2, the current blocking layer 5. The device is completed by sequentially growing the contact layer 6 and further forming the picture electrode.

In addition, in the above embodiment, a method was described in which the film thickness d is detected by a change in the color tone of reflected light when polychromatic light is irradiated, but it is also possible to detect a change in the intensity of a specific wavelength component using a wavelength selection filter or the like. In addition to determining the film thickness d by irradiating monochromatic light from the beginning, it is possible to
It is also possible to determine the film thickness d from the change in intensity of .

Furthermore, it is not necessary to use any special equipment to monitor changes in the color tone of the reflected light, and it goes without saying that the film thickness d can be sufficiently detected by directly detecting changes in color tone with the naked eye.

〔Effect of the invention〕

As explained above, when performing chemical etching, this invention irradiates light from above the etching solution toward the layer to be etched, and observes the light that is reflected from the reflective surface below the layer to be etched and returns to the etching solution. However, since the process of controlling the thickness of the layer to be etched is included, the thickness of the layer to be etched can be determined from the color tone or intensity of the light that is not absorbed by the layer to be etched and returns onto the etching solution. Since the etching layer can be easily controlled to a desired thickness, it is possible to realize a semiconductor laser with uniform characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an embodiment of the semiconductor laser manufacturing method of the present invention, FIG. 2 is a perspective view showing an example of the semiconductor laser, and FIG. 3 is a graph showing changes in the characteristics of the etching solution. . In the figure, 1 is a substrate, 2.4 is a cladding layer, 3 is an active layer, 4a is a striped ridge portion, 5 is a current blocking layer, 6 is a contact layer, 7 is an upper electrode, 8 is an etching solution, and 9 is an etching liquid. The reflected light and d are the film thickness. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 1 6a Thickness Figure 2 Figure 3 Time T- Procedural amendment (voluntary) = 1□5i28 ・Indication of case Patent application No. 124208/1988/Invention Name of Semiconductor Laser Manufacturing Method, Relationship with the Amendment Person Case Patent Applicant Representative Moriya Shiki 4, Attorney 5, ? lfl In column 6 of the detailed description of the invention in the correct subject specification, [semiconductor laser according to this invention] in line 14 on page 3 of the description of amendment is amended to read "semiconductor laser according to this invention."that's all

Claims (1)

[Claims] When performing chemical etching, light is irradiated from above the etching solution toward the layer to be etched, and while observing the light that is reflected by the reflective surface below the layer to be etched and returns onto the etching solution, the layer to be etched is A method of manufacturing a semiconductor laser, comprising a step of controlling film thickness.