JP4804261B2 - Semiconductor optical device manufacturing method and semiconductor optical device semiconductor substrate - Google Patents

Description

  The present invention relates to a method of manufacturing a semiconductor optical device and a semiconductor substrate for a semiconductor optical device, and more particularly to a method of manufacturing a semiconductor optical device using a quaternary semiconductor as a cladding layer and a semiconductor substrate used for manufacturing the semiconductor optical device. .

  Since semiconductor optical devices such as semiconductor lasers widely used in optical communication systems and the like are desirably capable of stably obtaining high output, the present applicant also uses a quaternary semiconductor as an n-type cladding layer. An optical element has already been proposed (see, for example, Patent Document 1).

  As shown in the perspective view (a) of FIG. 3, the conventional semiconductor optical device 40 disclosed in Patent Document 1 includes an active layer 34 having a multiple quantum well structure as a first optical confinement structure (SCH) layer. And an n-type cladding layer 32 made of indium / gallium / arsenic / phosphorus (InGaAsP) and a p-type cladding layer 36 made of indium / phosphorus (InP) through the second SCH layer 35 and the second SCH layer 35. is doing.

  Then, as shown in FIG. 3 (b), the refractive index of the first SCH layer 33 and the second SCH layer 35 is made smaller than the refractive index of the active layer 34, and the n-type cladding layer 32 and the p-type are formed. By making it higher than the refractive index of the clad layer 36, the carrier and light are simultaneously concentrated in the same region, thereby improving the light emission efficiency.

  However, if light is confined excessively in the active layer 34, the generated light is absorbed by the active layer 34 and the output is reduced.

  Therefore, in a high-power semiconductor laser, it is effective to reduce the optical confinement factor of the active layer 34, the first SCH layer 33, and the second SCH layer 35. However, if the optical confinement factor is reduced, the light distribution is reduced. Becomes larger, and the amount of light that oozes into the n-type cladding layer 32 and the p-type cladding layer 36 increases.

  In particular, when the amount of light leaking to the p-type cladding layer 36 made of InP increases, light loss due to light absorption between valence bands increases. Inter-valence band light absorption can be reduced by reducing the impurity concentration in InP. However, if the impurity concentration is reduced, the electrical resistance of the p-type cladding layer 36 increases, so that the semiconductor optical device 40 is used at a high current. In some cases, the light output decreases due to heat generation.

  Further, as the light distribution becomes wider, it is necessary to secure the thicknesses of the n-type cladding layer 32 and the p-type cladding layer 36 to some extent. However, when the thickness of the p-type cladding layer 36 is increased, the electrical resistance of the p-type cladding layer 36 increases, resulting in a decrease in light output due to the heat generation described above.

  FIG. 4 is an enlarged view (a) of a portion surrounded by a dotted line in FIG. Light distribution in the case where the refractive index of the n-type cladding layer 32 is larger than the refractive index of the p-type cladding layer 36, compared to the light distribution (dotted line) when the refractive indexes of the n-type cladding layer 32 and the p-type cladding layer 36 are equal. (Solid line) is biased toward the n-type cladding layer 32 side.

Therefore, in the semiconductor optical device according to the above proposal, by making the refractive index of the n-type cladding layer 32 larger than the refractive index of the p-type cladding layer 36 and biasing the light distribution toward the n-type cladding layer 32, A decrease in light output and an increase in light loss are avoided.
Japanese Patent No. 3525257

  However, when the light distribution is biased to the n-type cladding layer as shown in FIG. 4, the thickness of the n-type cladding layer needs to be sufficiently thick, preferably 5 micrometers or more. In order to laminate the mold clad layer, it took about 2 hours, and there was a problem that it took a manufacturing time.

  The structure in which the light distribution is biased to the n-type cladding layer can be applied not only to a laser but also to an optical amplifier and a super luminescent diode (SLD). If an intermediate product with multiple layers is manufactured in large quantities at once, the optical functional layer such as the active layer and the p-type cladding layer are stacked on this intermediate product, thereby substantially reducing the manufacturing time of the semiconductor optical device. it can.

  The present invention has been made in view of the above knowledge, and an object of the present invention is to provide a method of manufacturing a semiconductor optical device and a semiconductor substrate for a semiconductor optical device that can shorten the manufacturing time.

According to the method for manufacturing a semiconductor optical device of the present invention, an n-type cladding layer of InGaAsP having a composition wavelength of 0.97 micrometers or less and a predetermined thickness of 5 micrometers or more is laminated on an n-type semiconductor substrate made of InP. Forming a protective film made of InGaAs or InGaAsP having a composition wavelength of 1.3 micrometers or more on the upper surface of the n-type cladding layer, and forming the protective film using selective etching remove and a protective film removed step Ru is exposed in a clean state suitable for re-stacking the upper surface of the n-type cladding layer, an upper surface of the n-type cladding layer exposed by removing the protective film , an optical functional layer laminate stacking the optical function layer corresponding to the semiconductor optical element to be manufactured, smaller than refractive index of the n-type cladding layer on the upper surface of the optical function layer Including a p-type cladding layer stacked stacking a p-type cladding layer have refractive index, a.

With this manufacturing method, the manufacturing time of the semiconductor optical device can be shortened.
Also, with this manufacturing method, the thickness of the n-type cladding layer can be made sufficiently thick against the deviation of the light distribution toward the n-type cladding layer.

In the semiconductor substrate for a semiconductor optical device of the present invention, an n-type cladding layer, an optical functional layer, and a p-type cladding layer having an optical refractive index smaller than the optical refractive index of the n-type cladding layer are sequentially formed on the n-type semiconductor substrate. A semiconductor substrate for a semiconductor optical device, which is an intermediate product of the semiconductor optical device to be manufactured, the n-type semiconductor substrate made of InP, and a composition wavelength of 0.97 micrometers or less laminated on the n-type semiconductor substrate of a predetermined thickness the n-type cladding layer and 5 or more micrometers in InGaAsP, is formed in the upper surface of the n-type cladding layer, InGaAs or composition wavelength is 1.3 micrometers or more InGaAsP, the n It includes a protective film for protecting the upper surface of the mold cladding layer, wherein the protective film, the upper surface of the n-type cladding layer the optical functional layer corresponding to the semiconductor optical device to be manufactured In forming, it is removed by selective etching, and has a structure, characterized in that to expose the upper surface of the n-type cladding layer in a clean state suitable for re-lamination.

With this configuration, the upper surface of the n-type cladding layer can be kept clean for a long period of time.
Also, with this configuration, the thickness of the n-type cladding layer can be made sufficiently thick against the deviation of the light distribution toward the n-type cladding layer.

  The present invention relates to a method for manufacturing a semiconductor optical device and a semiconductor substrate for a semiconductor optical device capable of reducing the manufacturing time of a semiconductor optical device by manufacturing an intermediate product in which an n-type cladding layer is laminated on an n-type semiconductor substrate. It can be provided.

  Hereinafter, embodiments of a method for manufacturing a semiconductor optical device according to the present invention will be described with reference to the drawings.

(First embodiment)
As shown in FIG. 1, the method for manufacturing a semiconductor optical device according to the first embodiment of the present invention comprises eight steps (a) to (h).

(A) n-type cladding layer stacking step: an n-type cladding layer 12 is stacked on an n-type semiconductor substrate 11;
It is appropriate to use indium phosphorus (InP) as the n-type semiconductor. As the n-type cladding layer 12, it is appropriate to use indium / gallium / arsenic / phosphorus (InGaAsP). The composition wavelength of InGaAsP is preferably 0.97 micrometers or less.

  InGaAsP needs to be laminated so as to coincide with the lattice spacing of the n-type semiconductor substrate 11 made of InP, and it takes 2-3 hours to laminate them to a predetermined thickness of 5 micrometers or more. Become.

(B) Protective film formation step: A protective film 13 is formed on the upper surface of the n-type cladding layer 12.
In order to keep the upper surface of the n-type cladding layer 12 clean for a long period of time, it is appropriate to use, for example, indium gallium arsenide (InGaAs) having a composition different from that of InGaAsP as the protective film 13. The protective film 13 may be InGaAsP having a compositional difference that allows selective etching with the n-type cladding layer 12 and having a composition wavelength larger than 1.3 micrometers. At this stage, the semiconductor optical device semiconductor substrate 10 in which the n-type cladding layer 12 and the protective film 13 are stacked on the n-type semiconductor substrate 11 is completed.

  (C) Protective film removal step: The protective film 13 is removed from the semiconductor substrate 10 for a semiconductor optical device by a method such as selective etching, and the clean upper surface of the n-type cladding layer 12 is exposed.

(D) Optical functional layer lamination step: The optical functional layer 14 is laminated on the upper surface of the n-type cladding layer 12 from which the protective film 13 has been removed.
As the optical functional layer 14, a layer having functions such as a laser, an optical amplifier, and an SLD can be formed.

(E) p-type cladding layer stacking step: a p-type cladding layer 15 having an optical refractive index smaller than the optical refractive index of the n-type cladding layer 12 is stacked on the upper surface of the optical functional layer 14.
It is appropriate to use InP as the p-type cladding layer 15.

  (F) Mesa shape forming step: A SiNx film is deposited on the entire surface by a plasma CVD method or the like, and this is formed into a stripe shape by a photolithography process, and is immersed in an etching solution to form a mesa shape.

  (G) Embedding step: After the p-type lower buried layer 16 and the n-type upper buried layer 17 are stacked by the MOVPE method using the SiNx film as a growth inhibition mask, both sides of the mesa are buried. Then, the SiNx film is removed. Thereafter, the upper layer portion 18 of the p-type cladding layer 15 is grown on the entire surface.

  (H) Electrode forming step: A p-type contact layer 19 is grown on the upper layer portion 18, a p-electrode 20 is formed on the upper surface of the p-type contact layer 19, and an n-electrode 21 is formed on the lower side of the n-type semiconductor substrate 11. .

  Finally, the semiconductor optical device wafer manufactured through steps (a) to (h) is separated into individual semiconductor optical devices using a separation method such as cleaving and dicing.

  As described above, the semiconductor substrate 10 for a semiconductor optical device in which the n-type cladding layer 12 having a predetermined thickness of 5 micrometers or more is laminated is mass-produced and stored as an intermediate product at one time. If a semiconductor optical device semiconductor substrate 10 with the protective film 13 removed is used when manufacturing a semiconductor optical device such as an SLD, the time required for manufacturing the semiconductor optical device can be substantially reduced. It becomes possible.

( Reference embodiment)
As shown in FIG. 2, the method for manufacturing a semiconductor optical device according to the reference embodiment includes seven stages (a) to (g). Note that description of steps similar to those in the first embodiment described above is omitted.

(A) n-type cladding layer stacking step: an n-type cladding layer 12 is stacked on an n-type semiconductor substrate 11;
The layer thickness of the n-type cladding layer 12 is a thickness obtained by adding a cutting thickness t for cutting in the cutting step (b) to a predetermined thickness of 5 micrometers or more. At this stage, the semiconductor optical device semiconductor substrate 30 in which the n-type cladding layer 12 is laminated on the n-type semiconductor substrate 11 is completed.

(B) Cutting stage: The n-type cladding layer 12 is cut by a cutting thickness t.
A clean surface of the n-type cladding layer 12 can be exposed by cutting the n-type cladding layer 12 of the semiconductor substrate 10 for a semiconductor optical device by a cutting thickness t by a method such as selective etching. This etching may be performed in a semiconductor lamination apparatus such as a MOVPE apparatus.

  (C) Optical functional layer lamination step: The optical functional layer 14 is laminated on the upper surface of the n-type cladding layer 12 cut by the cutting thickness t.

  (D) p-type cladding layer stacking step: a p-type cladding layer 15 having an optical refractive index smaller than the optical refractive index of the n-type cladding layer 12 is stacked on the upper surface of the optical functional layer 14.

  (E) Mesa shape forming step: A SiNx film is deposited on the entire surface by a plasma CVD method or the like, and this is formed into a stripe shape by a photolithography process, and is immersed in an etching solution to form a mesa shape.

  (F) Embedding step: After the p-type lower buried layer 16 and the n-type upper buried layer 17 are stacked by the MOVPE method using the SiNx film as a growth inhibition mask, both sides of the mesa are buried. Then, the SiNx film is removed. Thereafter, the upper layer portion 18 of the p-type cladding layer 15 is grown on the entire surface.

  (G) Electrode formation step: A p-type contact layer 19 is grown on the upper layer portion 18, a p-electrode 20 is formed on the upper surface of the p-type contact layer 19, and an n-electrode 21 is formed on the lower side of the n-type semiconductor substrate 11. .

  Finally, the semiconductor optical device wafer manufactured through steps (a) to (g) is separated into individual semiconductor optical devices using a separation method such as cleaving and dicing.

  As described above, the semiconductor substrate 30 for a semiconductor optical device in which the n-type cladding layer 12 having a thickness obtained by adding a predetermined thickness of 5 μm or more and the cutting thickness t is laminated as an intermediate product and mass-produced at once. In addition, when a semiconductor optical device such as a semiconductor laser, an optical amplifier, or an SLD is manufactured, if the semiconductor substrate 30 for semiconductor optical device having a cutting thickness t is used, it is necessary to manufacture the semiconductor optical device. Time can be substantially shortened.

  As described above, the method for manufacturing a semiconductor optical device and the semiconductor substrate for a semiconductor optical device according to the present invention have an effect that the manufacturing time of the semiconductor optical device can be shortened, and are effective as a semiconductor substrate or the like.

Sectional drawing which shows the manufacturing stage of the manufacturing method of the semiconductor optical element of 1st Embodiment which concerns on this invention Sectional drawing which shows the manufacturing stage of the manufacturing method of the semiconductor optical element of reference embodiment A perspective view and refractive index characteristics of a conventional semiconductor optical device The enlarged view of FIG. 3 and the figure which shows a light distribution characteristic

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 30 Semiconductor substrate for semiconductor optical elements 11 n-type semiconductor substrate 12 n-type cladding layer 13 protective film 14 optical functional layer 15 p-type cladding layer

Claims (2)

An n-type cladding layer stacking step of stacking an n-type cladding layer of InGaAsP having a composition wavelength of 0.97 micrometers or less and a predetermined thickness of 5 micrometers or more on an n-type semiconductor substrate made of InP;
Forming a protective film made of InGaAs or InGaAsP having a composition wavelength of 1.3 micrometers or more on the upper surface of the n-type cladding layer;
The Remove the protective film, the protective film removed step Ru is exposed in a clean state suitable for re-stacking the upper surface of the n-type cladding layer by selective etching,
An optical functional layer laminating step of laminating an optical functional layer corresponding to a semiconductor optical device to be manufactured on the upper surface of the n-type cladding layer exposed by removing the protective film;
A p-type cladding layer stacking step of stacking a p-type cladding layer having a light refractive index smaller than that of the n-type cladding layer on the upper surface of the optical functional layer. A semiconductor that is an intermediate product of a semiconductor optical device in which an n-type cladding layer, an optical functional layer, and a p-type cladding layer having a light refractive index smaller than that of the n-type cladding layer are sequentially formed on an n-type semiconductor substrate A semiconductor substrate for an optical element,
The n-type semiconductor substrate made of InP;
The n-type cladding layer laminated on the n-type semiconductor substrate and having a composition wavelength of InGaAsP of 0.97 micrometers or less and a predetermined thickness of 5 micrometers or more;
Wherein formed in the upper surface of the n-type cladding layer, InGaAs or composition wavelength is from more than InGaAsP 1.3 micrometers, anda protective film for protecting the upper surface of the n-type cladding layer,
The protective layer, when forming the optical functional layer corresponding to the semiconductor optical device to be produced on surfaces of the n-type cladding layer are removed by selective etching, the re-stacking an upper surface of the n-type cladding layer A semiconductor substrate for a semiconductor optical device , characterized by being exposed in a suitable clean state .

Images