阅读说明：本技术 光半导体元件及其制造方法 (Optical semiconductor element and method for manufacturing the same ) 是由 堀口裕一郎 西川智志 秋山浩一 福永圭吾 外间洋平 铃木洋介 于 2018-10-02 设计创作，主要内容包括：具备：半导体基板(2)；第1半导体层(3),设置于半导体基板(2)上；台面波导(44),设置于第1半导体层(3)的主面上；埋入层(5),以使第1半导体层(3)的上表面的一部分露出的方式,覆盖第1半导体层(3)的上表面；以及台面构造(8),设置于第1半导体层(3)的被埋入层(5)覆盖的部分和第1半导体层(3)露出的部分的边界,一方的侧面被埋入层(5)覆盖,另一方的侧面露出,通过降低在埋入层(5)中发生的应力,例如,能够抑制向埋入层(5)发生裂纹,提高可靠性。(The disclosed device is provided with: a semiconductor substrate (2); a 1 st semiconductor layer (3) provided on a semiconductor substrate (2); a mesa waveguide (44) provided on the main surface of the 1 st semiconductor layer (3); an embedded layer (5) that covers the upper surface of the 1 st semiconductor layer (3) so as to expose a part of the upper surface of the 1 st semiconductor layer (3); and a mesa structure (8) provided at the boundary between the portion of the 1 st semiconductor layer (3) covered with the embedded layer (5) and the portion of the 1 st semiconductor layer (3) exposed, one side surface being covered with the embedded layer (5) and the other side surface being exposed, and by reducing stress generated in the embedded layer (5), for example, it is possible to suppress the occurrence of cracks in the embedded layer (5) and improve reliability.)

1. An optical semiconductor element, comprising:

a semiconductor substrate;

a 1 st semiconductor layer disposed on the semiconductor substrate;

a mesa waveguide provided on a main surface of the 1 st semiconductor layer;

a buried layer covering the upper surface of the 1 st semiconductor layer so that a part of the upper surface of the 1 st semiconductor layer is exposed; and

and a mesa structure provided at a boundary between a portion of the 1 st semiconductor layer covered with the embedded layer and a portion of the 1 st semiconductor layer exposed, one side surface of the mesa structure being covered with the embedded layer and the other side surface being exposed.

2. The optical semiconductor element according to claim 1,

the mesa formation is provided at a portion of the boundary where the boundary is curved.

3. The optical semiconductor element according to claim 1 or 2,

an electrode provided on the 1 st semiconductor layer and electrically connected to the 1 st semiconductor layer,

the mesa formation and the boundary are arranged in a manner surrounding the electrode,

the electrode is provided in a portion where the 1 st semiconductor layer is exposed.

4. The optical semiconductor element according to claim 2,

at least a part of the curved portion is a part of a polygon having a circular arc shape or an obtuse angle in a plan view.

5. The optical semiconductor element according to claim 3,

the electrode is led out to the upper surface of the buried layer,

the mesa structure surrounds a portion where the 1 st semiconductor layer and the electrode are electrically connected.

6. The optical semiconductor element according to claim 1, comprising:

the 1 st electrode is arranged on the upper surface of the mesa waveguide and is electrically connected with the mesa waveguide;

the 2 nd electrode is arranged on the 1 st semiconductor layer and is electrically connected with the 1 st semiconductor layer; and

an electrode pad electrically connected to the 1 st electrode,

the buried layer covers the semiconductor substrate, the 1 st semiconductor layer, and the mesa waveguide in a region where the 1 st electrode and the electrode pad are provided, the 1 st electrode and the electrode pad are provided on an upper surface of the buried layer,

the mesa structure is provided along an end portion of the buried layer in such a manner that the end portion is located on an upper surface of the mesa structure,

a part of the upper surface of the mesa structure is covered with the embedded layer on the side of the region where the embedded layer is provided, along an end portion of the embedded layer, and is exposed on the side opposite to the side of the region where the embedded layer is provided.

7. The optical semiconductor element according to claim 6,

the mesa structure is provided in a portion where an end portion of the embedded layer is bent.

8. The optical semiconductor element according to any one of claims 1 to 7,

the buried layer formed on the upper surface of the mesa structure has a 1 st thickness smaller than a 2 nd thickness of the buried layer formed on the main surface of the 1 st semiconductor layer.

9. The optical semiconductor element according to any one of claims 1 to 8,

the width of the mesa formation is greater than the width of the mesa waveguide.

10. The optical semiconductor element according to any one of claims 1 to 9,

the buried layer is a resin containing benzocyclobutene or polyimide resin.

11. A method for manufacturing an optical semiconductor element, comprising:

forming a 1 st semiconductor layer on a semiconductor substrate;

forming a mesa waveguide and a mesa structure on a main surface of the 1 st semiconductor layer;

forming an embedded layer so as to cover the semiconductor substrate, the 1 st semiconductor layer, the mesa waveguide, and the mesa structure; and

a step of removing a part of the buried layer to expose a part of the main surface of the 1 st semiconductor layer,

in the exposing step, a part of the main surface of the 1 st semiconductor layer is exposed so that the buried layer is left on one side surface of the mesa structure and the other side surface of the mesa structure is exposed.

12. The method for manufacturing an optical semiconductor element according to claim 11,

the method comprises a step of forming an electrode electrically connected to the 1 st semiconductor layer on the 1 st semiconductor layer,

in the step of forming the mesa structure, the mesa structure is formed so as to surround the electrode,

in the exposing step, the 1 st semiconductor layer is exposed in a region where the mesa structure surrounds the electrode.

13. The method for manufacturing an optical semiconductor element according to claim 11, comprising:

forming a 1 st electrode electrically connected to the mesa waveguide on the upper surface of the mesa waveguide and the buried layer;

forming a 2 nd electrode electrically connected to the 1 st semiconductor layer on the 1 st semiconductor layer; and

a step of forming an electrode pad electrically connected to the 1 st electrode on the buried layer,

in the step of forming the mesa structure, the mesa structure is formed so as to surround a region where the 1 st electrode and the electrode pad are provided,

in the exposing step, the embedded layer is removed except for a region where the 1 st electrode and the electrode pad are provided.

14. The method for manufacturing an optical semiconductor element according to any one of claims 11 to 13,

in the step of forming the mesa waveguide and the mesa structure, the mesa waveguide and the mesa structure are simultaneously formed in the same process.

Technical Field

The present invention relates to an optical semiconductor element and a method for manufacturing the same.

Background

For example, an optical semiconductor element used in a conventional Mach-Zehnder (Mach-Zehnder) modulator includes an optical waveguide having a high mesa structure, the optical waveguide including: the light-emitting device includes a lower cladding layer including an n-type semiconductor layer provided on a semiconductor substrate, a core layer provided on the lower cladding layer and functioning as a light-sealing layer having a Multi Quantum Well (MQW) structure, and an upper cladding layer including a p-type semiconductor layer provided on the core layer.

The conventional optical semiconductor element includes a buried layer made of a resin such as benzocyclobutene (BCB) so as to cover the semiconductor substrate, the lower cladding layer, and the optical waveguide having the mesa structure. In the buried layer, openings reaching the main surface of the lower clad and the upper surface of the optical waveguide are formed, and electrodes electrically connected to the lower clad and the upper clad are formed in the openings, respectively.

Patent document 1 discloses a method for manufacturing an optical semiconductor element used in a mach-zehnder modulator, in which an optical waveguide having a high mesa structure is covered with an embedded layer made of a resin, and an electrode is provided on the embedded layer.

Patent document 2 discloses a method for manufacturing an optical semiconductor element used in a mach-zehnder modulator, in which a thick embedded layer is formed on an optical waveguide having a high mesa structure by applying a resin as the embedded layer in two separate applications.

Disclosure of Invention

In the optical semiconductor element used in the mach-zehnder modulator as in patent documents 1 and 2, in order to provide an electrode on the main surface of the lower cladding layer, it is necessary to provide an opening portion reaching the main surface of the lower cladding layer in the embedded layer.

However, in the optical semiconductor element as in patent document 1 and patent document 2, since the opening is formed in the under clad layer and the side surface of the buried layer is exposed to a thickness of several μm, the optical semiconductor element undergoes a temperature change in a heating step in a wafer process, soldering at the time of element mounting, or the like, and stress occurs in the resin as the buried layer. Therefore, there is a problem that stress concentrates on the outer periphery of the opening of the embedded layer, particularly on a portion where the opening is bent, and cracks occur in the resin as the embedded layer. In particular, when the thickness of the embedded layer is increased in order to increase the distance between the electrode and the semiconductor, the stress further increases, and the problem of occurrence of cracks becomes remarkable.

The present invention has been made to solve the above-described problems of the conventional art, and an object thereof is to provide an optical semiconductor element and a method for manufacturing the same, which can reduce stress generated in a buried layer, thereby suppressing, for example, generation of cracks in the buried layer and improving reliability.

In order to achieve the above object, an optical semiconductor device according to the present invention includes: a semiconductor substrate; a 1 st semiconductor layer disposed on the semiconductor substrate; a mesa waveguide provided on a main surface of the 1 st semiconductor layer; an embedded layer covering the upper surface of the 1 st semiconductor layer so as to expose a part of the upper surface of the 1 st semiconductor layer; and a mesa structure provided at a boundary between a portion of the 1 st semiconductor layer covered with the embedded layer and a portion of the 1 st semiconductor layer exposed, one side surface being covered with the embedded layer and the other side surface being exposed.

Further, a method for manufacturing an optical semiconductor device according to the present invention includes: forming a 1 st semiconductor layer on a semiconductor substrate; forming a mesa waveguide and a mesa structure on a main surface of the 1 st semiconductor layer; forming a buried layer so as to cover the semiconductor substrate, the 1 st semiconductor layer, the mesa waveguide, and the mesa structure; and a step of removing a part of the buried layer to expose a part of the main surface of the 1 st semiconductor layer, wherein in the exposing step, the part of the main surface of the 1 st semiconductor layer is exposed so that the buried layer is left on one side surface of the mesa structure and the other side surface of the mesa structure is exposed.

The optical semiconductor element and the method for manufacturing the same according to the present invention configured as described above can provide an optical semiconductor element and a method for manufacturing the same, which can reduce stress generated in the embedded layer, for example, suppress the occurrence of cracks in the embedded layer, and improve reliability.

Drawings

Fig. 1 is a plan view showing the structure of an optical semiconductor device according to embodiment 1 of the present invention.

Fig. 2 is a sectional view showing the structure of an optical semiconductor element according to embodiment 1 of the present invention.

Fig. 3 is a sectional view showing a method for manufacturing the optical semiconductor element as viewed from a cut line AA in fig. 1.

Fig. 4 is a sectional view showing a method for manufacturing the optical semiconductor element as viewed from a cut line BB in fig. 1.

Fig. 5 is a sectional view for explaining a process of forming the 2 nd opening portion of fig. 3.

Fig. 6 is a diagram for explaining an effect of the optical semiconductor element according to embodiment 1 of the present invention.

Fig. 7 is a plan view showing the structure of an optical semiconductor element according to embodiment 2 of the present invention.

Fig. 8 is a sectional view showing the structure of an optical semiconductor element according to embodiment 2 of the present invention.

(description of reference numerals)

1: an optical semiconductor element; 2: a semiconductor substrate; 3: 1 st semiconductor layer; 4: a mesa waveguide; 5: a buried layer; 6: 1 st opening part; 7: a 1 st electrode; 8: a mesa structure; 9: a 2 nd opening part; 10: a 2 nd electrode; 11: a 2 nd semiconductor layer (core layer); 12: a 3 rd semiconductor layer; 13: an electrode pad; 14: a photoresist; 41: a branching section; 42: a modulation unit; 43: a coupling section; 44: 1 st optical waveguide; 45: a 2 nd optical waveguide; 51: the boundary between the No. 2 opening and the embedded layer; 52: a curved portion; 53: and an end portion of the buried layer.

Detailed Description