JPH0149029B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an optical semiconductor device in which a light emitting surface of a semiconductor laser, an edge-emitting light emitting diode, etc. is formed by etching.

[Conventional technology]

In recent years, development and research into optical integrated circuits has been active, and in this case, a semiconductor laser is naturally incorporated into the optical integrated circuit.

Generally, the mirror surface (laser end face) in an individual type semiconductor laser is formed by cleavage.
At present, mirror surfaces obtained using this technique have shown the best performance.

However, in the case of optical integrated circuits, semiconductor elements having other functions in addition to the semiconductor laser are monolithically integrated.

Therefore, if cleavage techniques such as those applied to individual type semiconductor lasers are used for such optical integrated circuits, the substrate will be separated.
It is either impossible to implement or only obtainable on a very small scale.

Therefore, the mirror surface of the semiconductor laser was processed using reactive ion etching (RIE).
Attempts have been made to form the mirror surface by applying a dry etching method such as the method, or a wet etching method using a chemical mixture, etc., but it is not possible to obtain a mirror surface of good quality as in the case of cleavage.

FIG. 2 shows an explanatory diagram of the main parts of a sample and an apparatus for explaining the conventional technique of forming a mirror surface by dry etching.

In the figure, 1 is a rotating table, 2 is a rotating shaft, 3 is a wafer on which optical semiconductor devices are fabricated, 4 is a photoresist film, 5 is a reactive or non-reactive ion beam, and 6 is a rotating direction. Each indicates a pointing arrow.

In this prior art, the optical semiconductor elements on the wafer 3 are covered with a photoresist film 4, the wafer 3 is temporarily fixed on the rotary table 1, and the rotary table 1, and therefore the wafer 3, is moved as indicated by the arrow 6. Etching is performed by irradiating the wafer with a reactive ion beam 5 while rotating as instructed, and a mirror surface is formed by removing the portion shown by the broken line in the wafer 3.

FIG. 3 shows a cut-away oblique view of essential parts of a semiconductor laser in which a mirror surface has been formed by the technique explained in connection with FIG. 2, and the same parts as those explained in connection with FIG. 2 are indicated by the same symbols.

In the figure, 7 indicates a mirror surface, and 8 indicates a striped electrode.

As can be understood from the above, when the prior art explained with reference to FIG. 2 is applied, the third
As seen in the figure, a large number of streaks are formed on the mirror surface 7.

[Problem that the invention seeks to solve]

The reason why a large number of streaks are formed on the mirror surface 7 formed according to the conventional technique is due to the photo film, which is a mask film.
The main cause is that the shape of the end face of the resist film 4 is directly transferred to the wafer 3, and it is impossible to obtain optical flatness and verticality of the mirror surface 7 using the conventional technique. Incidentally, as explained with reference to FIG.
Rotating can only serve to alleviate the non-uniformity of the reactive ion beam 5. Further, it is well known that the edges of the photoresist film 4 as described above have irregularities of about 1000 Å.

The present invention employs a very simple technique when forming a mirror surface of an optical semiconductor device using an etching method, thereby eliminating all the streaks that would be generated on the mirror surface obtained by implementing the conventional technique, and thereby achieving an optical To make it possible to form a flat and perpendicular mirror surface.

[Means for solving problems]

In the method for manufacturing an optical semiconductor device of the present invention, a mask film such as a photoresist film is formed to cover the optical semiconductor elements and other necessary parts of a wafer in which various elements are fabricated, and then the wafer is rotated. The wafer is temporarily fixed by pasting it on a table, and then the rotating table is rotated about a direction parallel to the surface on which the wafer is temporarily fixed, and reactive ions are etc. A mirror surface of the optical semiconductor element is formed by irradiating the photodiode with etching.

[Effect]

According to the above means, the streaks that would normally occur on the mirror surface of an optical semiconductor element are scraped away by ions from the sides, depending on the relationship between the direction of ion irradiation and the rotation direction of the wafer, and as a result, ,
The mirror surface is optically flat and vertical.

〔Example〕

FIG. 1 shows an explanatory view of the main parts of a wafer and an etching apparatus at key points in the process for explaining one embodiment of the present invention, and the same parts as those explained with reference to FIGS. 2 and 3 are designated by the same symbols. I have been instructed.

In this embodiment, a rotating shaft 2 is fixed to the side surface of a rotating table 1, and is configured to rotate in the direction of an arrow 6.

Therefore, the wafer 3 temporarily fixed to the surface of the rotating table 1 is etched every time the rotating shaft 2 rotates by 180 degrees.

In the figure, the reactive ion beam 5 is irradiated vertically, but since the rotation axis 2 and therefore the rotary table 1 are set at an angle, the reactive ion beam 5 is irradiated at an angle φ with respect to the surface of the wafer 3. This means that the light is incident at an angle. Although the wafer 3 is attached to the front and back sides of the rotary table 1, this is for the purpose of increasing work efficiency and is not essential.

When forming the mirror surface 7 of the optical semiconductor device as described above, streaks are generated on the mirror surface 7 at a position where the surface of the wafer 3 is substantially opposed to the reactive ion beam 5. As the beam 3 rotates, the reactive ion beam 5 is irradiated from the side of the streak and is scraped off, so the flatness of the mirror surface 7 becomes good, and the incident angle of the reactive ion beam 5 changes. By appropriately adjusting φ, the verticality of the mirror surface 7 can also be improved.

In the above embodiment, a flat plate-shaped rotary table 1 was used, but the rotary table 1 is not limited to this, and mass productivity can be improved by using a polygonal column-shaped one such as a triangular prism, a quadrangular prism, etc. do.

In the above embodiment, when the optical semiconductor device assembled on the wafer 3 is a GaAlAs/GaAs double heterostructure semiconductor laser, the photoresist film 4 serving as a mask film is positive type, and the photoresist film 4 to be irradiated is As a result of an experiment using argon (Ar) ions with an accelerating voltage of 500 [V] as ions, a flat and vertical mirror surface 7 was obtained at φ = 15°, and the threshold current I _th has a mirror surface due to cleavage. It wasn't much different.

[Effects of the Invention] In the method for manufacturing an optical semiconductor device of the present invention,
A mask film such as a photoresist film is formed to cover the optical semiconductor elements and other necessary parts of the wafer in which various elements have been fabricated, and then the wafer is temporarily attached to a rotating table. Then, etching is performed by irradiating the surface of the wafer with reactive ions or the like from an oblique direction while rotating the rotating table about a direction parallel to the surface on which the wafer is temporarily fixed. This forms the mirror surface of the optical semiconductor element.

If this is done, streaks will be generated on the mirror surface at positions where the surface of the wafer is substantially opposite to the ion irradiation direction, but as the wafer rotates, the ions will scrape off the streaks from the sides. As a result, the flatness of the resulting mirror surface is significantly improved, and by adjusting the direction of ion irradiation with respect to the wafer, it is possible to improve the perpendicularity of the mirror surface. Therefore, it is possible to obtain good properties that are almost the same as those of mirror surfaces produced by ordinary cleavage.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the main parts of a wafer and etching apparatus for explaining one embodiment of the present invention, FIG. 2 is an explanatory diagram of the main parts of a sample and etching apparatus for explaining the conventional technique, and FIG. 3 is an explanatory diagram of the main parts of the etching apparatus for explaining the conventional technique. Each of them shows a cut-away oblique view of a main part of a semiconductor laser to explain the mirror surface formed by the technique. In the figure, 1 is a rotating table, 2 is a rotating shaft, 3 is a wafer, 4 is a photoresist film which is a mask film,
5 is a reactive ion beam, 6 is an arrow representing the direction of rotation of the rotating shaft 2, 7 is a mirror surface of a semiconductor laser, 8 is a stripe electrode, and φ is an incident angle of the reactive ion beam 5, respectively.

Claims (1)

[Claims] 1. A mask film is formed to cover the optical semiconductor elements and other necessary parts of a wafer in which various elements have been fabricated, and then the wafer is temporarily fixed to a rotating table, and then the rotating table is temporarily attached to the wafer. An optical device comprising the step of forming a mirror surface of an optical semiconductor element by irradiating the surface of the wafer with ions from an oblique direction while rotating the wafer about a direction substantially parallel to the fixed surface. A method for manufacturing a semiconductor device.