SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME

• US 20170068047A1
• Filed: 08/22/2016
• Published: 03/09/2017
• Est. Priority Date: 09/04/2015
• Status: Active Grant

• Current Assignee: Photonics Electronics Technology Research Association, Renesas Electronics Corporation
• Original Assignee: Photonics Electronics Technology Research Association, Renesas Electronics Corporation
• Inventors: USAMI, TATSUYA, SAKAMOTO, KEIJI, YAMAMOTO, YOSHIAKI, WATANUKI, SHINICHI, WAKABAYASHI, MASARU, MOGAMI, TOHRU, HORIKAWA, TSUYOSHI, KINOSHITA, KEIZO
• Granted Patent: US 10,162,110 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/132 by deposition of thin films
• CPC Class Codes: G02B 6/136 by etching

Abstract

A semiconductor device is provided with an insulating layer formed on a base substrate, an optical waveguide composed of a semiconductor layer formed on the insulating layer, and an insulating film formed along an upper surface of the insulating layer and a front surface of the optical waveguide. A peripheral edge portion of a lower surface of the optical waveguide is separated from the insulating layer, and the insulating film is buried between the peripheral edge portion and the insulating layer.

Claims

1. A semiconductor device comprising:

a base substrate;

an insulating layer formed on the base substrate;

a first optical waveguide composed of a semiconductor layer formed on the insulating layer; and

a first insulating film formed along an upper surface of the insulating layer and a front surface of the first optical waveguide,

wherein a first peripheral edge portion of a first lower surface of the first optical waveguide is separated from the insulating layer, and

the first insulating film is buried between the first peripheral edge portion and the insulating layer.

2. The semiconductor device according to claim 1, further comprising:

two of the first optical waveguides disposed to be spaced apart from each other in a first direction when seen in a plan view; and

a second insulating film formed on the first insulating film,

wherein the second insulating film is buried between the two first optical waveguides, with the first insulating film interposed therebetween.

3. The semiconductor device according to claim 2, further comprising:

a third insulating film formed on the second insulating film,

wherein the second insulating film has a flat upper surface.

4. The semiconductor device according to claim 2,

wherein the insulating layer is formed on the base substrate in a first region on a main surface side of the base substrate and in a second region on the main surface side of the base substrate, and

the two first optical waveguides are formed on the insulating layer in the first region,

the semiconductor device further comprising:

two second optical waveguides composed of the semiconductor layer formed on the insulating layer in the second region; and

a fourth insulating film formed on the second insulating film in the first region,

wherein the two second optical waveguides are disposed to be spaced apart from each other in a second direction when seen in a plan view,

a first distance between the two first optical waveguides in the first direction is narrower than a second distance between the two second optical waveguides in the second direction,

the first insulating film is formed along a front surface of each of the two second optical waveguides,

a second peripheral edge portion on a second lower surface of each of the two second optical waveguides is separated from the insulating layer,

the first insulating film is buried between the second peripheral edge portion and the insulating layer,

the second insulating film is formed on the first insulating film in the first region, and

the fourth insulating film is formed on the first insulating film in the second region.

5. The semiconductor device according to claim 2,

wherein the insulating layer is formed on the base substrate in a third region on a main surface side of the base substrate and in a fourth region on the main surface side of the base substrate, and

the two first optical waveguides are formed on the insulating layer in the third region,

the semiconductor device further comprising:

two third optical waveguides composed of the semiconductor layer formed on the insulating layer in the fourth region;

a fifth insulating film formed on the second insulating film in the third region; and

a sixth insulating film formed on the first insulating film in the fourth region,

wherein the two third optical waveguides are disposed to be spaced apart from each other in a third direction when seen in a plan view,

a third distance between the two first optical waveguides in the first direction is narrower than a fourth distance between the two third optical waveguides in the third direction,

the first insulating film is formed along a front surface of each of the two third optical waveguides,

a third peripheral edge portion on a third lower surface of each of the two third optical waveguides is separated from the insulating layer,

the first insulating film is buried between the third peripheral edge portion and the insulating layer,

the second insulating film is formed on the first insulating film in the third region and on the sixth insulating film in the fourth region, and

the fifth insulating film is formed on the second insulating film in the fourth region.

6. A method for manufacturing a semiconductor device comprising the steps of:

(a) preparing a semiconductor substrate having a base substrate, an insulating layer formed on the base substrate, and a semiconductor layer formed on the insulating layer;

(b) patterning the semiconductor layer to form a first optical waveguide composed of the semiconductor layer; and

(c) forming a first insulating film along an upper surface of the insulating layer and a front surface of the first optical waveguide,

wherein upon carrying out the step (b), a first gap is formed between a first peripheral edge portion of a first lower surface of the first optical waveguide and the insulating layer, and

in step (c), the first gap is buried by the first insulating film.

7. The method for manufacturing a semiconductor device according to claim 6,

wherein the step (b) further comprises the steps of:

(b1) patterning the semiconductor layer to form the first optical waveguide; and

(b2) cleaning a front surface of the insulating film after the step (b1), and

upon carrying out the step (b2), the first gap is formed.

8. The method for manufacturing a semiconductor device according to claim 7,

wherein the insulating layer contains oxygen and silicon, and

in the step (b2), the front surface of the insulating layer is cleaned by using a cleaning liquid containing hydrofluoric acid.

9. The method for manufacturing a semiconductor device according to claim 6,

wherein in the step (c), the first insulating film made of silicon oxide is formed by chemical vapor deposition through use of a tetraethoxy silane gas, a first gas containing a tetraethoxy silane gas and an oxygen gas, a second gas containing a silane gas and a nitrous oxide gas, or a third gas containing dichlorosilane and a nitrous oxide gas.

10. The method for manufacturing a semiconductor device according to claim 9, further comprising the step of:

(d) forming a second insulating film made of silicon oxide on the first insulating film by chemical vapor deposition through use of a fourth gas containing a tetraethoxy silane gas and an ozone gas,

wherein in the step (b), two of the first optical waveguides are formed to be disposed to be spaced apart from each other in a first direction, when seen in a plan view, and

in the step (d), the second insulating film is buried between the two first optical waveguides with the first insulating film interposed therebetween.

11. The method for manufacturing a semiconductor device according to claim 10, further comprising the step of:

(e) forming a third insulating film made of silicon oxide on the second insulating film by plasma chemical vapor deposition.

12. The method for manufacturing a semiconductor device according to claim 11, further comprising the step of:

(f) planarizing an upper surface of the second insulating film after the step (d), prior to the step (e).

13. The method for manufacturing a semiconductor device according to claim 11,

wherein in the step (a), the semiconductor substrate having the insulating layer formed on the base substrate in a first region on a main surface side of the base substrate and in a second region on the main surface side of the base substrate is prepared,

in the step (b), two of the first optical waveguides are formed in the first region and two of second optical waveguides made of the semiconductor layer are formed in the second region,

the two second optical waveguides are disposed to be spaced apart from each other in a second direction when seen in a plan view,

a first distance between the two first optical waveguides in the first direction is narrower than a second distance between the two optical waveguides in the second direction,

upon carrying out the step (b), a second gap is formed between a second peripheral edge portion of a second lower surface of each of the two second optical waveguides and the insulating layer,

in the step (c), the first insulating film is formed along a front surface of each of the two second optical waveguides, and the second gap is buried by the first insulating film, and

in the step (d), the second insulating film is formed on the first insulating film in the first region and the second region,

the method further comprising the step of:

(g) removing the second insulating film from the second region after the step (d), prior to the step (e),

wherein in the step (e), the third insulating film is formed on the second insulating film in the first region and the third insulating film is formed on the first insulating film in the second region.

14. The method for manufacturing a semiconductor device according to claim 11,

wherein in the step (a), the semiconductor substrate having the insulating layer formed on the base substrate in a third region on a main surface side of the base substrate and in a fourth region on the main surface side of the base substrate is prepared,

in the step (b), two of the first optical waveguides are formed in the third region and two of third optical waveguides made of the semiconductor layer are formed in the fourth region,

the two third optical waveguides are disposed to be spaced apart from each other in a third direction when seen in a plan view,

a third distance between the two first optical waveguides in the first direction is narrower than a fourth distance between the two third optical waveguides in the third direction,

upon carrying out the step (b), a third gap is formed between a third peripheral edge portion of a third lower surface of each of the two third optical waveguides and the insulating layer, and

in the step (c), the first insulating film is formed along a front surface of each of the two third optical waveguides, and the third gap is buried by the first insulating film,

the method further comprising the steps of:

(h) forming a fourth insulating film made of silicon oxide on the first insulating film in the third region and the fourth region, by plasma chemical vapor deposition after the step (c); and

(i) removing the fourth insulating film from the third region after the step (h), prior to the step (d),

wherein in the step (d), the second insulating film is formed on the first insulating film in the third region and the second insulating film is formed on the fourth insulating film in the fourth region, and

in the step (e), the third insulating film is formed on the second insulating film in the third region and the fourth region.