JPH05218564A - Manufacture of light semiconductor element - Google Patents

Abstract

PURPOSE:To provide the method of collective growth/process for manufacturing a current block layer and an active layer by selective growth so as to get a light semiconductor element being a large-area wafer and excellent in uniformity and reproducibility. CONSTITUTION:In the first place, a pair of current block layers are manufactured by MOVPE selective growth, and then only the SiO2 film 21 between the current block layers is removed to make an n-InP clad layer 4, an active layer 5, a p-InP clad layer 6, and a p-InGaAs cap layer 7. Hereby, a light semiconductor element of large area and highly uniform can be gotten since the light semiconductor is not etched. Moreover, a high-performance element can be materialized since the current block layer is made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical semiconductor device used for optical communication, optical information processing and the like.

[0002]

2. Description of the Related Art Semiconductor lasers used for optical communication and optical information processing are required to have higher performance. On the other hand, in order to meet the demands for optical communication for subscribers and the demands for low cost, it is necessary to fabricate high yield devices using large area wafers. In order to meet these requirements, it is necessary to perform crystal growth by a vapor phase growth method such as a metal organic vapor phase epitaxy method (MOVPE) capable of high-area and uniform growth. Further, by using vapor phase growth, it is possible to fabricate a quantum well semiconductor laser having various characteristics such as low threshold, high efficiency operation, and narrow spectral line width operation. 3 and 4 show a typical method of manufacturing a semiconductor laser for optical communication using MOVPE. Here, it is a distributed feedback (DFB) laser that operates in a single mode, and current confinement is performed by a buried ridge structure.
First, after forming a grating on the n-type indium phosphorus (InP) substrate 1, n-type indium gallium
Arsenic / phosphorus (InGaAsP) guide layer 8, InGaAs
The P active layer 5 and the p-type InP clad layer 6 are laminated (see FIG.
(A)) Next, the SiO ₂ film 21 is formed in a stripe shape having a width of 2 μm (FIG. 3B), and mesa etching is performed until the substrate 1 is reached (FIG. 3C). After that, p-type I on the entire surface
The nP layer 2 and the p ⁺ -type InGaAsP cap layer 7 are grown (FIG. 4D), and the high resistance region 31 in which protons are implanted is formed around the active layer to confine the current (FIG. 4). (E)).

[0003]

In order to manufacture a large number of semiconductor lasers as described above, it is important to use a large-area wafer and to precisely control the layer structure.
The layer thickness can be sufficiently controlled by using a vapor growth method such as MOVPE, but the waveguide width is conventionally controlled by mesa etching using SiO ₂ as a mask, and is sufficiently controlled by side etching or the like. There was a problem such as not being able to obtain sex. For example, in the mesa etching shown in FIG. 3C, even if the width of the SiO ₂ film 21 is exactly 2 μm, the width of the active layer varies due to the variation of the mesa structure and the side etching during the etching of the active layer. .. In particular, in a process using a large-diameter wafer such as a 2-inch substrate, the variation within the wafer surface becomes considerably large.
In addition, there is a problem that the active layer is damaged even by the dry etching method with good controllability. Variations in the active layer and waveguide width and defects in the active layer affect device characteristics such as threshold current, oscillation wavelength, beam pattern, and reliability, so not only does the yield of the device decrease, but There was a problem that it was difficult to obtain the action of and there was a need for improvement.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide a method for manufacturing an optical semiconductor device with high performance and high yield.

[0005]

According to the present invention, a step of forming two dielectric thin film stripes facing each other with an optical waveguide forming region interposed therebetween on a semiconductor substrate, and the above-mentioned method other than the dielectric thin film stripes are provided. In a method of manufacturing an optical semiconductor device, which comprises a selective growth step of laminating a semiconductor multilayer film including an active layer on a semiconductor substrate, a dielectric thin film stripe is formed in the center of the optical waveguide forming region, and a pair of current block layers is formed. The step of forming by selective growth, the step of removing the dielectric thin film stripe formed in the center of the optical waveguide formation region and the step of exposing a part of the semiconductor substrate subsequent to this step, A selective growth step of stacking a semiconductor multilayer film including an active layer in addition to the body stripe is further included.

[0006]

In the method of the present invention, the current blocking layer is formed by selective growth before forming the active layer. This current blocking layer is [011] on the surface of the semiconductor substrate in the (100) direction.
Since two dielectric thin film stripes such as SiO ₂ films are formed in the direction and are selectively grown by MOVPE, the part sandwiched between the stripes has a flat surface (100) surface and a smooth side surface (111) surface. It grows like a ridge. Therefore, the width of the active layer can be determined only by patterning the SiO ₂ film without using a technique such as mesa etching that lacks uniformity, and the controllability and reproducibility are excellent, and the active layer is formed after the current block layer is formed. Therefore, it is possible to manufacture a semiconductor laser having good characteristics with few interface recombination components.

In the method of the present invention, the p-InP cladding layer and the p ⁺ -InGaAs cap layer are also formed by selective growth. Thus, the device fabrication process SiO ₂
It is constituted only by patterning and selective growth of a dielectric thin film such as, and there is no need to use etching of a semiconductor which is the root of various problems. In this way, devices can be manufactured by batch growth / process with excellent uniformity and reproducibility using a large-area wafer, and the advantages of forming active layers by selective growth can be maximized.

[0008]

1 and 2 show a method of manufacturing a buried ridge structure semiconductor laser using the method according to the present invention. (10
A SiO ₂ film 21 (thickness: about 2000 Å) is deposited on the surface of the n-InP substrate 1 having the 0) orientation by the CVD method, and the width is 10 μm by the photolithography method.
m, and two stripes with an interval of 5 μm, and a stripe with a width of 1 μm in the center of the two stripes (see FIG. 1).
(A)). Then, Zn-doped p is formed by reduced pressure MOVPE.
-InP layer 2 (layer thickness 1 μm, carrier concentration 5 × 10 ¹⁷ c
m ⁻³ ), Si-doped n-InP layer 3 (layer thickness 0.5 μm
m, carrier concentration 1 × 10 ¹⁸ cm ⁻³ ) was selectively grown (FIG. 1B). The layer thickness is a value in the current block layer sandwiched between SiO ₂ films. Then, to remove the stripe-shaped SiO ₂ film 21 having a width 1μm of the region sandwiched between the pair of current blocking layers (Fig. 1 (c)), SiO left ₂ film 21
N-InP clad layer 4 (layer thickness 1 μm, carrier concentration 1 × 10 ¹⁸ cm ⁻³ ), InGaAsP active layer 5
(1.55 μm composition, layer thickness 800 Å),
p-InP clad layer 6 (layer thickness 1.5 μm, carrier concentration 5 × 10 ¹⁷ cm ⁻³ ), p ⁺ -InGaAs cap layer 7 (layer thickness 0.3 μm, carrier concentration 1 × 10 ¹⁹ cm ⁻³ ).
Selectively grown (FIG. 2 (d)), and Si formed on the entire surface again
Only the upper part of the active region of the O ₂ film 21 is removed in a stripe shape having a width of 2 μm (FIG. 2 (e)), and the p-side electrode 32 and the n-side electrode 33 are formed to complete the laser (FIG. 2 (f)). ). When this laser was evaluated with a cavity length of 300 μm, the threshold current was 10 mA on average, the standard deviation was 0.2 mA, and the slope efficiency was 0.3 W / A on average and 0.04 W / A on standard deviation. Active layer width is 2.0 μm on average, standard deviation 0.12
was μm. This result is improved as compared with the result of the conventional example, and it was confirmed that the uniformity of device characteristics is improved by using the present invention. By using MOVPE growth capable of such large-area and high-uniform growth, it becomes possible to manufacture a low-priced semiconductor laser with a high characteristic yield. In this embodiment, bulk InGa is used as the active layer.
Although AsP was used, the characteristics can be further improved by using a quantum well structure (MQW). In addition to the pnpn thyristor structure, the structure of the current block layer is InGaA.
Further improvement in characteristics can be achieved by using a wide-gap layer of s or a high resistance layer such as Fe-doped InP.

[0009]

As described above, when the method for manufacturing an optical semiconductor device of the present invention is used, etching of a semiconductor having poor uniformity and reproducibility is completely unnecessary, and a device having a uniform active layer and a uniform waveguide width. Can be manufactured with good controllability. By carrying out this method by batch growth / process using a large-area wafer, it has become possible to manufacture low-priced semiconductor lasers of high characteristics with high yield.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a method for manufacturing a semiconductor laser according to the present invention.

FIG. 2 is a cross-sectional view showing an embodiment of a method for manufacturing a semiconductor laser according to the present invention.

FIG. 3 is a diagram for explaining a conventional method for manufacturing a semiconductor laser.

FIG. 4 is a diagram for explaining a conventional method for manufacturing a semiconductor laser.

[Explanation of symbols]

1 n-InP substrate 2 p-InP layer 3 n-InP layer 4 n-InP clad layer 5 active layer (including quantum well structure) 6 p-InP clad layer 7 p-InGaAs cap layer 8 n-InGaAsP guide layer 21 SiO ₂ film 31 Proton injection region 32 p-side electrode 33 n-side electrode

[Procedure amendment]

[Submission date] March 18, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

In the method of the present invention, the current blocking layer is formed by selective growth before forming the active layer. This current blocking layer is [011] on the surface of the semiconductor substrate in the (100) direction.
Two dielectric thin film stripes such as SiO ₂ film are formed in the direction, and selective growth is performed by MOVPE. Therefore, the surface sandwiched between the stripes is a (100) surface with a flat surface and a smooth (111) B surface. It grows like a ridge. Therefore, the width of the active layer can be determined only by patterning the SiO ₂ film without using a technique such as mesa etching that lacks uniformity, and the controllability and reproducibility are excellent, and the active layer is formed after the current block layer is formed. Therefore, it is possible to manufacture a semiconductor laser having good characteristics with few interface recombination components.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

1 and 2 show a method of manufacturing a buried ridge structure semiconductor laser using the method according to the present invention. (10
A SiO ₂ film 21 (thickness: about 2000 Å) is deposited on the surface of the n-InP substrate 1 having the 0) orientation by the CVD method, and the width is 10 μm by the photolithography method.
m 2 and two stripes with an interval of 5 μm, and a stripe with a width of 1 μm was formed at the center of the two stripes (FIG.
(A)). Then, Zn-doped p is formed by reduced pressure MOVPE.
-InP layer 2 (layer thickness 1 μm, carrier concentration 5 × 10 ¹⁷ c
m ^-3 ), Si-doped n-InP layer 3 (layer thickness 0.5 μm,
A carrier concentration of 1 × 10 ¹⁸ cm ^-3 ) was selectively grown (Fig. 1).
(B)). The layer thickness is a value in the current block layer sandwiched between SiO ₂ films. Next, the stripe-shaped SiO ₂ film 21 having a width of 1 μm in the region sandwiched between the pair of current block layers is removed (FIG. 1C), and the remaining SiO ₂ film 21 is used to form the n-InP clad. Layer 4 (layer thickness 1 μm, carrier concentration 1 × 10 ¹⁸ cm ⁻³ ), InGaAsP active layer 5 (1.
55 μm composition, layer thickness 800 Å), p-I
nP clad layer 6 (layer thickness 1.5 μm, carrier concentration 5 ×
10 ¹⁷ cm ^-3 ), a p ⁺ -InGaAs cap layer 7 (layer thickness 0.3 μm, carrier concentration 1 × 10 ¹⁹ cm ^-3 ) was selectively grown (FIG. 2D), and SiO ₂ formed again on the entire surface. Only the upper part of the active region of the film 21 is removed in a stripe shape having a width of 2 μm (FIG. 2E), and the p-side electrode 32 and the n-side electrode 33 are removed.
Was formed to complete the laser (FIG. 2 (f)). When this laser was evaluated with a cavity length of 300 μm, the threshold current was 10 mA on average, the standard deviation was 0.2 mA, and the slope efficiency was 0.3 W / A on average and 0.04 W / A on standard deviation. The average width of the active layer is 2.0 μm with a standard deviation of 0.12 μm
Met. This result is improved as compared with the result of the conventional example, and it was confirmed that the uniformity of device characteristics is improved by using the present invention. By using MOVPE growth capable of such large-area and high-uniform growth, it becomes possible to manufacture a low-priced semiconductor laser with a high characteristic yield. In this embodiment, bulk InGaAs is used for the active layer.
Although P is used, the characteristics can be further improved by using a quantum well structure (MQW). In addition to the pnpn thyristor structure as the structure of the current block layer, the characteristics can be further improved by using a wide-gap layer of InGaAs or a high resistance layer such as Fe-doped InP.

Claims (1)

[Claims] 1. A step of forming, on a semiconductor substrate, two dielectric thin film stripes opposed to each other with an optical waveguide forming region interposed therebetween, and an active layer is included on the semiconductor substrate other than the dielectric thin film stripes. In a method for manufacturing an optical semiconductor element, which comprises a selective growth step of laminating a semiconductor multilayer film, a step of forming a dielectric thin film stripe in the center of the optical waveguide formation region, and forming a pair of current block layers by selective growth, Subsequent to this step, a step of removing the dielectric thin film stripe formed in the center of the optical waveguide forming region to expose a part of the semiconductor substrate, and, following this step, including an active layer in addition to the dielectric stripe. A method of manufacturing an optical semiconductor device, further comprising a selective growth step of stacking semiconductor multilayer films.