Semiconductor device manufacturing method

Abstract

An active layer (2) and an n-type semiconductor layer (3) are formed in this order on a p-type semiconductor layer (1). Using an insulating film pattern (4) as a mask, the n-type semiconductor layer (3) and the active layer (2) are dry-etched to form a ridge (5). A first block layer (7) made of an n-type semiconductor is formed directly on the p-type semiconductor layer (1) on both sides of the ridge (5), with dry etching residues (6) still adhering to the side surfaces of the ridge (5). After the first block layer (7) is formed, the residues (6) are removed. After the residues (6) are removed, a second block layer (8) made of a semiconductor other than n-type is formed between the first block layer (7) and the active layer (2).

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor device and a manufacturing method thereof. [Background technology]

[0002] In the manufacture of buried-type laser devices, when a ridge is formed by dry etching a semiconductor layer with SiCl4 gas using an insulating film pattern as a mask, Si-based residues are formed on the surface of the ridge. Conventionally, the Si-based residues are removed using an oxidizing agent and diluted BHF, and then current blocking layers are formed on both sides of the ridge (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-172059 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the first layer of the current blocking layer formed on the sidewalls of the ridge became a leakage path. If the first layer was made thicker to ensure stable growth, the width of the leakage path would widen. This resulted in an increase in leakage current and a deterioration in device characteristics.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its object is to provide a semiconductor device and a manufacturing method thereof that can improve element characteristics. [Means for solving the problem]

[0006] A method for manufacturing a semiconductor device according to the present disclosure includes the steps of: sequentially forming an active layer and an n-type semiconductor layer on a p-type semiconductor layer; dry-etching the n-type semiconductor layer and the active layer with a gas containing a Si compound to form a ridge; forming first block layers made of an n-type or undoped semiconductor directly on the p-type semiconductor layer on both sides of the ridge while leaving residues of the Si compound produced by the dry etching attached to the side surfaces of the ridge; removing the residues after forming the first block layer; and, after removing the residues, forming a second block layer made of a semiconductor other than the n-type between the first block layer and the active layer. [Effects of the Invention]

[0007] In this disclosure, the first blocking layer is selectively formed while the Si compound residues generated by dry etching remain attached to the side surfaces of the ridge, thereby separating the first blocking layer from the active layer. Because the first blocking layer, which is the first layer of the current blocking layer, does not contact the active layer, leakage current lateral to the active layer can be reduced. As a result, current efficiency is improved, leading to improved device characteristics. [Brief explanation of the drawings]

[0008] [Figure 1] 1A to 1C are cross-sectional views showing a manufacturing process of a semiconductor device according to an embodiment. [Figure 2] 1A to 1C are cross-sectional views showing a manufacturing process of a semiconductor device according to an embodiment. [Figure 3] 1A to 1C are cross-sectional views showing a manufacturing process of a semiconductor device according to an embodiment. [Figure 4] 1A to 1C are cross-sectional views showing a manufacturing process of a semiconductor device according to an embodiment. [Figure 5] 1A to 1C are cross-sectional views showing a manufacturing process of a semiconductor device according to an embodiment. [Figure 6] 1A to 1C are cross-sectional views showing a manufacturing process of a semiconductor device according to an embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing a semiconductor device according to a comparative example. [Figure 8] 1 is a cross-sectional view showing a semiconductor device according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 to 6 are cross-sectional views showing the manufacturing process of a semiconductor device according to an embodiment of the present invention, which is a buried type laser element.

[0010] First, as shown in Figure 1, an active layer 2 and an n-type semiconductor layer 3 are formed in this order on a p-type semiconductor layer 1. The p-type semiconductor layer 1 is a p-InP substrate and a p-InP regrowth layer epitaxially grown thereon, or a p-Inp substrate. The active layer 2 is AlInGaAs, AlInGaAsP, InGaAsP, or the like. An insulating film is formed on the n-type semiconductor layer 3, and the insulating film is patterned to form a pattern 4.

[0011] 2, using the insulating film pattern 4 as a mask, the n-type semiconductor layer 3, the active layer 2, and a portion of the p-type semiconductor layer 1 are dry-etched with a gas containing a Si compound such as SiCl4 gas to form a ridge 5. Residues 6 of the Si compound produced by the dry etching adhere to the side surfaces of the ridge 5. The residues 6 are Si compounds such as Si, SiO, and SiClx.

[0012] 3, first block layers 7 made of n-type semiconductor are selectively formed directly on the p-type semiconductor layer 1 on both sides of the ridge 5 while the residues 6 remain attached to the side surfaces of the ridge 5. At this time, the first block layers 7 are not formed on the side surfaces of the ridge 5 to which the residues 6 have attached.

[0013] Next, as shown in FIG. 4, the residue 6 is removed by wet processing using an oxidizing agent and diluted BHF. Next, a second block layer 8 is formed between the first block layer 7 and the active layer 2. The second block layer 8 is in direct contact with the side surfaces of the first block layer 7 and the active layer 2. The second block layer 8 is an undoped InP layer. However, the second block layer 8 may be made of any semiconductor other than n-type, such as undoped, lightly p-type doped, or semi-insulating. A third block layer 9 made of p-InP and a fourth block layer 10 made of n-InP are sequentially formed on the second block layer 8. The first to fourth block layers 7 to 10 of the current block layer are formed by epitaxial growth. The material of the first to fourth block layers 7 to 10 is not limited to InP, and other compound semiconductors may also be used.

[0014] Next, as shown in FIG. 5, the pattern 4 is removed, and a contact layer 11 made of n-InP is formed on the n-type semiconductor layer 3 of the ridge 5 and the fourth block layer 10 of the current block layer.

[0015] Next, as shown in FIG. 6, the contact layer 11, the first to fourth block layers 7 to 10, and a portion of the p-type semiconductor layer 1 are etched to form a mesa structure. Insulating films 12 and 13 are formed on the side surfaces of the mesa structure. An opening is formed in the insulating film 13 on the top surface of the mesa structure. A front surface electrode 14 is formed so as to be connected to the contact layer 11 through this opening. A back surface electrode 15 is formed on the back surface of the p-type semiconductor layer 1. Through the above steps, the semiconductor device according to this embodiment is manufactured.

[0016] Next, the effects of this embodiment will be described in comparison with a comparative example. Fig. 7 is a cross-sectional view showing a semiconductor device according to the comparative example. In the comparative example, a first layer of the current blocking layer is formed on the side surface of the active layer 2. If n-InP were formed as the first layer, the current flowing through the active layer 2 would decrease, so a p-InP blocking layer 16 is formed as the first layer. However, this p-InP blocking layer 16 beside the active layer 2 becomes a leak path, resulting in increased leak current and current consumption.

[0017] FIG. 8 is a cross-sectional view showing a semiconductor device according to an embodiment. In this embodiment, the first block layer 7 is selectively formed while the residue 6 remains attached to the side surfaces of the ridge 5, thereby separating the first block layer 7 from the active layer 2. Because the first block layer 7, which is the first layer of the current blocking layer, does not contact the active layer 2, the leakage current lateral to the active layer 2 can be reduced. As a result, the current efficiency is improved, leading to improved device characteristics. Although leakage current occurs when the p-type semiconductor layer 1 and the p-type second block layer 8 are slightly in contact with each other, the leakage current is smaller than in the comparative example. Furthermore, by using the residue 6, it is not necessary to re-grow a mask covering the side surfaces of the ridge 5, thereby reducing the number of processes.

[0018] Furthermore, to prevent the first block layer 7 from contacting the active layer 2, the lower surface of the first block layer 7 is set lower than the lower surface of the active layer 2. However, if the thickness of the first block layer 7 is constant, it is necessary to deeply etch the p-type semiconductor layer 1 during the formation of the ridge 5 so that the first block layer 7 does not contact the active layer 2, which increases the current injection resistance of the p-type semiconductor layer 1. In contrast, in this embodiment, the first block layer 7 is epitaxially grown while the residue 6 remains attached to the side surfaces of the ridge 5, so the thickness of the first block layer 7 decreases as it approaches the ridge 5. This prevents the first block layer 7 from contacting the active layer 2 even if the etching depth of the p-type semiconductor layer 1 is shallow. Because the first block layer 7 can be made thick, the first block layer 7 can be stably grown without relying on film thickness controllability. [Explanation of symbols]

[0019] 1 p-type semiconductor layer, 2 active layer, 3 n-type semiconductor layer, 4 pattern, 5 ridge, 6 residue, 7 first block layer, 8 second block layer

Claims

[Claim 1] forming an active layer and an n-type semiconductor layer in sequence on a p-type semiconductor layer; forming a ridge by dry etching the n-type semiconductor layer and the active layer with a gas containing a Si compound; forming a first block layer made of an n-type or non-doped semiconductor directly on the p-type semiconductor layer on both sides of the ridge while leaving residues of a Si compound produced by dry etching attached to the side surfaces of the ridge; removing the residue after forming the first blocking layer; and after removing the residue, forming a second block layer made of a semiconductor other than an n-type semiconductor between the first block layer and the active layer.

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