JPH077862B2 - Semiconductor laser manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a ridge waveguide type semiconductor laser used as a light source for optical fiber communication and optical information processing.

[Conventional technology]

Fig. 2 shows, for example, Electronics Letters, Vol. 22, No. 21, p. 1145 (1986) by CJ Armisted (CJARMIS
TEAD et.al., Electron. Lett., Vo1.22, No. 21, p. 1145 (19
86)) is a cross-sectional view showing the method of manufacturing the conventional ridge waveguide type semiconductor laser shown in FIG.
P substrate, 2 InGaAsP active layer, 3 InGaAsP anti-melt back (AMB) layer, 4 p-InP clad layer, 5 p-InGaAs
P contact layer, 6 is a SiO ₂ film used as an etching mask when etching the contact layer 5 and the p-InP clad layer 4, 7 is a photoresist, 9 is a p-side electrode, 10 is an n-side electrode, and 11 is a passivation layer. It is a SiO ₂ film.

Next, the manufacturing method of the conventional example will be described.

First, an InGaAsP active layer 2, an InGaAsP antimeltback layer 3, a p-InP clad layer 4, and a p-InGaAsP contact layer 5 are sequentially grown on the n-InP substrate 1 by a liquid phase epitaxial method or the like, and a SiO ₂ film 6 is formed. It is formed by a plasma CVD method or the like. Then, a photoresist stripe 7 is formed by ordinary photolithography, and the SiO ₂ film 6 is etched by using the photoresist as a mask (FIG. 2A). Then Si
Using the O ₂ film 6 as an etching mask, the p-InGaAsP contact layer 5 and the p-InP cladding layer 4 are etched with a selective etching solution (FIG. 2 (b)). Then, after removing the resist 7 and the SiO ₂ film 6, S is formed by plasma CVD or the like.
An iO ₂ film 11 is formed (FIG. 2 (c)). After that, a resist pattern is formed by normal photolithography so that only the SiO ₂ film 11 on the ridge can be removed, and the SiO ₂ film is etched using the resist as an etching mask (FIG. 2 (d)). Then, the p-side electrode 9 and the n-side electrode 10 are formed to complete the device.

[Problems to be Solved by the Invention]

Since the conventional method for manufacturing a ridge waveguide type semiconductor laser is configured as described above, highly accurate mask alignment is required to remove the passivation film only on the ridge, and the photoresist on the ridge is Although it is thinner than the surrounding portion, its thickness depends on the ridge width and height, so that there is a problem that it is difficult to keep the exposure and development conditions constant, and there is a problem particularly when the ridge width is reduced. Further, the conventional manufacturing method has a problem that the width of the contact hole on the ridge is narrower than the ridge width and the contact resistance is increased due to a mask alignment margin for forming the electrode contact on the ridge.

The present invention has been made to solve the above problems, and an object thereof is to obtain a method of manufacturing a semiconductor laser capable of removing the passivation film on the ridge in a self-aligned manner.

[Means for Solving the Problems]

The method for manufacturing a semiconductor laser according to the present invention is an electron cyclotron resonance chemical vapor deposition (ECR-CV) method in which the photoresist used for forming the ridge waveguide structure is left.
A passivation film is formed by the method D) and only the passivation film on the photoresist is selectively removed by etching.

[Action]

In the present invention, since the passivation film on the photoresist formed by the ECR-CVD method has a faster etching rate than that formed on the semiconductor, only the passivation film on the resist can be removed by etching.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a method of manufacturing a semiconductor laser according to an embodiment of the present invention, and the same reference numerals as those in FIG. 2 denote the same or corresponding parts. Reference numeral 8 is a SiN _x passivation film formed by the ECR-CVD method.

Next, the manufacturing method will be described.

The steps up to FIG. 1B are the same as the conventional one.
Next, with the photoresist 7 and the SiO ₂ film 6 used as the etching mask as they are, SiN _x is formed at room temperature on the entire surface by ECR-CVD. Since the ECR-CVD method has directionality, it is obliquely deposited with respect to the substrate surface as shown by the arrow in FIG. 1 (c). When etching the SiN _X film by an etching solution composed of hydrogen fluoride and ammonium fluoride, who SiN _X film formed on the photoresist 7 is etched faster. This is what towards those in the SiN _X film and the SiN _X film formed on a semiconductor formed on the resist is formed on the resist by using a property called etching rate becomes faster, whereby the first FIG. As shown in (d), the SiN _x film on the photoresist 7 can be selectively removed. Next, after removing the photoresist 7 with a stripping solution or the like, the SiO ₂ film 6 is etched again with an etching solution composed of hydrogen fluoride and ammonium fluoride. This utilizes the difference in etching rate depending on the materials of the SiO ₂ film and the SiN _x film. That is, since towards the SiO ₂ film is faster etching rate than the SiN _X, in which SiO ₂ film 6 is removed. In this way, only the passivation film 8 on the ridge is removed, and further the SiO ₂ film 6 is removed, after which the p-side electrode 9 and n
By forming the side electrode 10, the element shown in FIG. 1 (e) is completed.

As described above, in the present embodiment, since the formation of the ridge structure and the formation of the electrode contact on the ridge can be manufactured by self-alignment by one photolithography, the conventional photolithography for forming the ridge structure and the formation of the ridge on the ridge can be performed. It is not necessary to perform highly accurate mask alignment, which was necessary because photolithography was performed twice for forming the electrode contact. In the conventional manufacturing method,
The width of the contact hole on the ridge is narrower than the ridge width due to the mask alignment margin for forming the electrode contact on the ridge, but the passivation film on the entire surface of the ridge can be removed by the method of this embodiment. Therefore, there is an effect that the contact resistance can be reduced.

Although the method of manufacturing a semiconductor laser using a conductive n-InP substrate has been described in the above embodiment, the present invention is directed to a device using a semi-insulating InP substrate or a p-InP substrate, and a GaAs
It may be applied to an element using another material such as a system material, and the same effect as that of the above-described embodiment is obtained.

〔The invention's effect〕

As described above, according to the present invention, in the method of manufacturing the ridge waveguide type semiconductor laser, the ECR-CV is used while leaving the photoresist used for forming the ridge waveguide structure.
Since the passivation film is formed by the D method and only the passivation film on the photoresist is selectively etched by utilizing the difference in etching rate to form the electrode contact on the ridge, the number of times of photolithography is reduced. There is an effect that the high-performance semiconductor laser can be easily manufactured by reducing the number and eliminating the need for mask alignment.

[Brief description of drawings]

FIG. 1 is a sectional process view showing a method for manufacturing a semiconductor laser according to an embodiment of the present invention, and FIG. 2 is a sectional process view showing a conventional method for manufacturing a semiconductor laser. 4 is a p-InP clad layer, 5 is a p-InGaAsP contact layer, 6
Is SiO ₂ film, 7 is photoresist, 8 is SiN by ECR-CVD method
_X membrane. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshiyuki Oishi 8-1-1 Tsukaguchihonmachi, Amagasaki-shi, Hyogo Central Research Laboratory, Sanryo Electric Co., Ltd. (72) Teruhito Matsui 8-chome, Tsukaguchihonmachi, Amagasaki-shi, Hyogo No. 1-1 Sanryo Electric Co., Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor laser for manufacturing a ridge waveguide type semiconductor laser, wherein an insulating film is formed by an ECR-CVD method while leaving a photoresist used for forming a ridge waveguide structure. A method of manufacturing a semiconductor laser, which further comprises a step of selectively etching and removing only a portion of the insulating film on the resist.