JP2012009488A - Method of manufacturing ridge type semiconductor optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a ridge type semiconductor optical element capable of preventing variation in width of a lower portion of a ridge.SOLUTION: An active layer 12, a p-type InP layer 14, and a p-type InP layer 16 are sequentially formed on an n-type InP substrate 10. Next, a lower portion 20 of a ridge is formed by dry etching of the p-type InP layer 16. Subsequently, the periphery of the lower portion 20 of the ridge is buried in an InGaAsP layer 22 until the height at which the top surface of the lower portion 20 of the ridge is not covered. Subsequently, a p-type InP layer 24 is formed on the lower portion 20 of the ridge and the InGaAsP layer 22. Next, an upper portion 28 of the ridge is formed on the lower portion 20 of the ridge by dry etching of the p-type InP layer 24 such that the width of the top surface of the upper portion 28 of the ridge is wider than the width of the lower portion 20 of the ridge. Next, the InGaAsP layer 22 is selectively removed with respect to the p-type InP layer 14, the lower portion 20 of the ridge, and the upper portion 28 of the ridge.

Description

  The present invention relates to a method for manufacturing a ridge-type semiconductor optical device in which the width of the upper surface of the upper portion of the ridge is wider than the width of the lower portion of the ridge. .

  In the ridge-type semiconductor optical device, an inverted mesa ridge structure in which the width of the upper surface is wider than the width of the lower surface is used (see, for example, Patent Document 1). Thereby, the area of the upper surface of the ridge can be increased, and the contact resistance with the electrode can be reduced. In addition, since the width of the lower portion of the ridge can be narrowed, high-speed response can be realized by reducing the capacitance.

Japanese Patent Laid-Open No. 2-199891

  In the conventional method for manufacturing a ridge type semiconductor optical device, an inverted mesa ridge structure is formed by wet etching. For this reason, there is a problem that the width of the lower portion of the ridge varies due to manufacturing variations in the etching angle and the ridge height.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for manufacturing a ridge-type semiconductor optical device that can suppress variations in the width of the lower portion of the ridge.

  The method for manufacturing a ridge-type semiconductor optical device according to the present invention includes a step of sequentially forming an active layer, a first semiconductor layer, and a second semiconductor layer on a semiconductor substrate, and dry etching the second semiconductor layer. Forming a lower ridge, embedding the periphery of the lower ridge with a buried layer to a height that does not cover the upper surface of the lower ridge, and forming a third semiconductor layer on the lower ridge and the buried layer. Patterning the third semiconductor layer to form an upper ridge on the lower ridge; and selectively removing the buried layer with respect to the first semiconductor layer, the lower ridge, and the upper ridge. And the width of the upper surface of the upper portion of the ridge is wider than the width of the lower portion of the ridge, and the material of the buried layer is the first semiconductor layer, the lower portion of the ridge, and the ridge. Different from the part of the material.

  According to the present invention, variation in the width of the lower portion of the ridge can be suppressed.

It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 1 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 1 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 1 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 1 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 1 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 1 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 1 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 2 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 2 of this invention. It is sectional drawing for demonstrating the manufacturing method of the ridge type semiconductor optical element which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
A method for manufacturing a ridge-type semiconductor optical device according to the first embodiment of the present invention will be described with reference to the drawings. This semiconductor optical device is a ridge type semiconductor laser in which both sides of the ridge are not covered with a semiconductor.

  First, as shown in FIG. 1, an active layer 12, a p-type InP layer 14, and a p-type InP layer 16 are sequentially formed on an n-type InP substrate 10. Then, a resist pattern 18 is formed on the p-type InP layer 16 by photolithography or the like.

  Next, as shown in FIG. 2, the p-type InP layer 16 is dry-etched using the resist pattern 18 as a mask to form a ridge lower portion 20. The ridge lower portion 20 has a vertical ridge structure in which the width of the upper surface is equal to the width of the lower surface.

  Next, as shown in FIG. 3, the periphery of the ridge lower portion 20 is buried with an InGaAsP layer 22 to a height that does not cover the upper surface of the ridge lower portion 20. Thereafter, the resist pattern 18 is removed.

  Next, as shown in FIG. 4, a p-type InP layer 24 is formed on the ridge lower portion 20 and the InGaAsP layer 22. Then, a resist pattern 26 is formed on the p-type InP layer 24 by photolithography or the like.

  Next, as shown in FIG. 5, the p-type InP layer 24 is dry-etched using the resist pattern 26 as a mask to form an upper ridge 28 on the lower ridge 20. Here, the width of the upper surface of the ridge upper portion 28 is made wider than the width of the ridge lower portion 20.

  Next, as shown in FIG. 6, the resist pattern 26 is removed. Then, the InGaAsP layer 22 is selectively removed from the p-type InP layer 14, the ridge lower portion 20, and the ridge upper portion 28 by wet etching using tartaric acid.

  Next, as shown in FIG. 7, the side surfaces of the ridge lower portion 20 and the ridge upper portion 28 and the upper surface of the p-type InP layer 14 are covered with an insulating film 30. An opening is formed in the insulating film 30 on the upper surface of the ridge upper portion 28. A p-electrode 32 is formed on the ridge upper portion 28, and an n-electrode 34 is formed on the lower surface of the n-type InP substrate 10. The ridge type semiconductor optical device according to the first embodiment is manufactured through the above steps.

  According to the present embodiment, since the area of the upper surface of the ridge upper portion 28 can be increased, the contact resistance between the ridge upper portion 28 and the p-electrode 32 can be reduced. Furthermore, since the width of the ridge lower part 20 can be narrowed, a high-speed response can be realized by reducing the capacity.

  Further, by forming the ridge lower portion 20 by dry etching, it is possible to suppress the variation in the width of the ridge lower portion 20 regardless of the manufacturing variation in the etching angle and the ridge height.

Embodiment 2. FIG.
A method for manufacturing a ridge-type semiconductor optical device according to the second embodiment of the present invention will be described with reference to the drawings. Constituent elements similar to those in Embodiment 1 are denoted by the same reference numerals, and repeated description may be omitted.

  First, similarly to the first embodiment, the steps shown in FIGS. 1 to 4 are performed. Next, as shown in FIG. 8, the p-type InP layer 24 is wet-etched with HBr using the resist pattern 26 as a mask to form an upper ridge 28 on the lower ridge 20.

  Here, the width of the upper surface of the ridge upper portion 28 is made wider than the width of the ridge lower portion 20. Further, the ridge upper portion 28 has a reverse mesa ridge structure in which the upper surface is wider than the lower surface.

  Next, as shown in FIG. 9, the resist pattern 26 is removed. Then, the InGaAsP layer 22 is selectively removed from the p-type InP layer 14, the ridge lower portion 20, and the ridge upper portion 28 by wet etching using tartaric acid.

  Next, as shown in FIG. 10, the side surfaces of the ridge lower portion 20 and the ridge upper portion 28 and the upper surface of the p-type InP layer 14 are covered with an insulating film 30. An opening is formed in the insulating film 30 on the upper surface of the ridge upper portion 28. A p-electrode 32 is formed on the ridge upper portion 28, and an n-electrode 34 is formed on the lower surface of the n-type InP substrate 10. The ridge type semiconductor optical device according to the second embodiment is manufactured through the above steps.

  In this embodiment, the p-type InP layer 24 is wet-etched to form the ridge upper portion 28 having a reverse mesa ridge structure. Thereby, since the insulating film 30 is more likely to adhere to the side surfaces of the ridge lower portion 20 and the ridge upper portion 28 than in the first embodiment, it is possible to prevent the insulating film 30 from being peeled off. In addition, the same effects as those of the first embodiment can be obtained.

10 n-type InP substrate (semiconductor substrate)
12 Active layer 14 p-type InP layer (first semiconductor layer)
16 p-type InP layer (second semiconductor layer)
20 Lower ridge 22 InGaAsP layer (buried layer)
24 p-type InP layer (third semiconductor layer)
28 Ridge upper portion 30 Insulating film

Claims (4)

Forming an active layer, a first semiconductor layer, and a second semiconductor layer in this order on a semiconductor substrate;
Forming a lower ridge by dry etching the second semiconductor layer;
Embedding the periphery of the lower portion of the ridge to a height that does not cover the upper surface of the lower portion of the ridge with a buried layer;
Forming a third semiconductor layer below the ridge and on the buried layer;
Patterning the third semiconductor layer to form an upper ridge on the lower ridge;
Selectively removing the buried layer with respect to the first semiconductor layer, the ridge lower part and the ridge upper part,
The width of the upper surface of the ridge upper part is wider than the width of the ridge lower part,
The method of manufacturing a ridge-type semiconductor optical device, wherein a material of the buried layer is different from materials of the first semiconductor layer, the lower portion of the ridge, and the upper portion of the ridge.   2. The method of manufacturing a ridge type semiconductor optical device according to claim 1, wherein the lower portion of the ridge has a vertical ridge structure in which the width of the upper surface is equal to the width of the lower surface. An insulating film covering the ridge lower part and the side surface of the ridge upper part;
Wet etching the third semiconductor layer when forming the ridge top;
3. The method of manufacturing a ridge-type semiconductor optical device according to claim 1, wherein the upper portion of the ridge has an inverted mesa ridge structure in which the width of the upper surface is wider than the width of the lower surface. The material of the buried layer is InGaAsP,
The material of the first semiconductor layer, the ridge lower part and the ridge upper part is InP,
The method for manufacturing a ridge-type semiconductor optical device according to claim 1, wherein wet etching using tartaric acid is performed when the buried layer is removed.

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