JPS61292390A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To form a gold reflective film without a risk of short-circuiting by a method wherein, after the end plane of a semiconductor laser is coated with a silicon nitride film, gold is evaporated on the surface of it and lifted off except the desired area. CONSTITUTION:The P-type electrodes 13 and 14 of semiconductor laser arrays 11 and 12 are closely arranged parallel to each other so as to form a silicon nitride film 16 and a gold reflective film 17 on the end plane including an active layer 15 with electron cyclotron resonance plasma CVD method. The silicon nitride film is supersonic-processed with fluoric acid so as to fully remove the silicon nitride applied on the side plane 18. Thus, the reflective film 17 on it is lifted off, and the other region is kept coated. By this method, the reflective film of gold is fully separated from the electrodes, thereby completely preventing the reflective film from causing short-circuiting of the electrodes or current leakage.

Description

[Detailed Description of the Invention] [1Ill Required] The present invention is a method for manufacturing a semiconductor laser, which prevents the p and n electrodes of the semiconductor laser from being short-circuited when forming a reflective film of gold on the end face of the semiconductor laser. After depositing a silicon nitride film using the electron cyclotron resonance plasma CVD method with selective etching properties, gold is deposited on the surface of the silicon nitride film, and then lift-off is performed except for the required areas.
A gold reflective film is formed to prevent short circuits.

[Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor laser, and particularly to a method of forming a reflective film on an end face.

In recent years, the use of semiconductor lasers for high-performance communications has rapidly increased, and they are being used extremely widely.

In this semiconductor laser, a reflective film is formed using a gold material or the like on one end face of the active layer in order to improve luminous efficiency.

However, in the conventional method of forming a reflective film for a semiconductor laser, when gold is deposited on the end facet of the semiconductor laser, the gold may short-circuit to both the p and n electrodes. There is a problem in that leakage current flows to the end face, resulting in a decrease in efficiency and short circuits, and there is a desire to improve this problem.

[Conventional technology] FIG. 3 is a schematic perspective view of a semiconductor laser element.

Consists of indium phosphorus (InP) and compounds containing it.
There is a semiconductor laser 1 in which a plurality of layers are stacked, an active layer 2 that emits light is formed in a part of the stack, and an n-electrode 3 and a p-electrode 4 are provided on both sides.

A silicon nitride film 5, a reflective film 6 coated with gold, and a silicon nitride protective film 7 are formed on the end face of the semiconductor laser element.

FIGS. 4(111) to 4(C) are schematic cross-sectional views of main parts for explaining the manufacturing process of forming a reflective film on the end face portion of a conventional semiconductor laser.

FIG. 4(a) is a cross section of the stacked layers of the semiconductor laser device 1, in which an n-electrode 3 and a p-electrode 4 are formed at both ends including the active layer 2.

A silicon nitride film 5 is formed on this end face by an electron cyclotron resonance plasma CVD method so as to have a thickness of 1/4 of the emission wavelength in order to improve light transmission.

FIG. 4 (bl is a silicon nitride film 5 on the semiconductor laser element)
A reflective film 5 is formed by vapor-depositing a gold material from an angle of approximately 45 degrees as shown by the arrow on the surface on which the reflective film 5 is formed.

This diagonal vapor deposition is performed at an angle where gold does not adhere to one electrode side, so that the n-electrode 3 and the p-electrode 4 do not have a short circuit caused by the gold material deposited on them. If the surface is inclined to , the film will be formed on a rough surface.

FIG. 4(C) shows a silicon nitride film 5 on the semiconductor laser element.
A protective silicon nitride film 7 is further formed on the surface on which the gold reflective film 6 has been deposited, and is carried out by plasma CVD.

This method of forming a reflective gold film has the disadvantage that the deposited gold film wraps around to the electrode side, causing a short circuit.

[Problems to be Solved by the Invention] In the conventional method of forming a reflective film on the end face of a semiconductor laser, the vapor-deposited film of gold material goes around to the electrode side and connects the p-electrode and n-electrode on both sides of the device. There are problems such as short circuits and leakage current flowing through the laminated layers and the active layer.

[Means for Solving the Problems] The present invention has been proposed to solve the above problems, and the means for solving the problems is to form a silicon nitride film on the end face of a semiconductor laser by electron cyclotron resonance plasma CVD. by forming a protective layer of gold film on the entire surface,
By lifting off the silicon nitride film leaving a predetermined area, it is possible to prevent the deposited gold material from adhering to the p-electrode and n-electrode, and finally, a protective film of silicon nitride film is formed on the surface of the reflective film. By doing so, a complete reflective film is formed.

[Function] The present invention was proposed in order to prevent the deposited gold film from adhering to the electrode side in the formation of a conventional reflective film for a semiconductor laser. of,
It is formed by an electron cyclotron resonance plasma CVD method that is selective in etching depending on the direction of deposition, and then a gold material is deposited on the entire surface, and then lift-off is performed in a predetermined area to create a perfect reflective film that does not short-circuit with electrodes. By forming a gold film and forming a highly reflective film on the end face of the semiconductor laser, a highly reliable semiconductor laser can be provided.

[Example] FIGS. 1(a) to 1(dl) are schematic cross-sectional views of main parts for explaining a manufacturing method for forming a reflective film on the end face portion of a semiconductor laser according to the present invention.

FIG. 2 shows that a semiconductor laser device or an array of semiconductor laser devices 11, 12 has an active layer 15 and is of p-type or n-type.
The cross-sectional view of FIG. 1 is similar to that of A of FIG. FIG.

In FIG. 1(a), for example, the p-type electrodes 13.14 of the semiconductor laser element array 11.12 are arranged closely in parallel,
A silicon nitride film 16 with a thickness of approximately 2000 mm and a reflective film 17 of gold with a thickness of approximately 1000 mm are formed on the end face including the active layer 15 by electron cyclotron resonance plasma CVD.
form.

Figure 1) is electron cyclotron resonance plasma CVD
Taking advantage of the fact that the silicon nitride film formed by this method has different etching rates depending on the surface to which it is adhered, the silicon nitride film that had adhered to the side surface 18 was treated with ultrasonication using hydrofluoric acid. By completely removing the reflective film 17, the reflective film 17 on the reflective film 17 is lifted off, and the other regions remain coated.

In FIG. 1, a silicon nitride film 19 is formed to a thickness of approximately 1,000 wafers by the CVD method.

FIG. 1(d) is a cross-sectional view of a completed semiconductor laser in a state where a plurality of semiconductor laser elements are separated into single units.

According to the manufacturing method of the present invention, the gold reflective film is completely isolated from the electrode, and the reflective film can completely prevent the electrode from causing a short circuit or leakage current.

[Effects of the Invention] As described above in detail, the reflective film of the semiconductor laser according to the present invention has no short circuit between electrodes, no leakage between laminated layers, etc.
There are significant benefits that a high quality semiconductor laser can provide.

[Brief explanation of the drawing]

1(!I) to 1(d) are schematic cross-sectional views of main parts for explaining the manufacturing method for forming a reflective film on a semiconductor laser of the present invention, and FIG. 2 is an array of semiconductor laser elements. FIG. 3 is a schematic perspective view of a semiconductor laser element, and FIG. 4 (a
) to FIG. 4(C) are schematic % formulas for explaining the manufacturing process of forming a reflective film on a conventional semiconductor laser. 11.12 is a semiconductor laser element array, 13.14 is a p
type electrode, 15 is an active layer, 16 is a silicon nitride film,
17 is a reflective film, 18 is a side surface, and 19 is a silicon nitride film. Figure 2

Claims (1)

[Claims] After forming a silicon nitride film (16) on the entire reflective surface of a semiconductor laser by electron cyclotron resonance plasma CVD, a reflective film (17) is formed on the surface of the silicon nitride film (16). , and then lifting off the reflective film (17) by removing the silicon nitride film in a region other than the region facing the active layer (15), leaving the reflective film in a predetermined region. Laser manufacturing method.