JP2003031904A - Method of manufacturing semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of the interval between the light-emitting points of two semiconductor layers, having different structures by forming the lasers by using a common mask. SOLUTION: In the first gain-guiding type semiconductor laser, an active layer 6 emits light at a position below a stripe-like oxide film 36. In the index- guiding type second semiconductor laser, an active layer 18 emits light at a position below an oxide film 38. Therefore the interval between the light- emitting points of the two lasers varies, depending upon the interval between the oxide films 36 and 38. Since the oxide films 36 and 38 are formed through etching, by using stripe-like photoresist layers 32 and 34, obtained by exposing and developing a photoresist by using a single exposure mask as masks, the interval between the light-emitting points is set with very high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor laser device in which a semiconductor laser having a gain guide structure and a semiconductor laser having an index guide structure are provided on a common semiconductor substrate.

[0002]

2. Description of the Related Art CD (Compac) which is an information recording medium
t Disk) and DVD (Digital Versa)
Information recorded on an optical disk such as a tile disk) is reproduced by irradiating the surface of the optical disk with laser light from a semiconductor laser and receiving the reflected light with a photodiode or the like to generate an electric signal.

Semiconductor lasers used for irradiating the above laser light include those having a gain guide structure and those having an index guide structure, each of which has its advantages and disadvantages. As described above, the laser light irradiated onto the optical disk by the semiconductor laser and reflected by the optical disk not only enters the light receiving element such as a photodiode but also the semiconductor laser itself, resulting in so-called return light noise. To do. In order to suppress this return light noise, it is effective to use a semiconductor laser with a gain guide structure. However, in terms of luminous efficiency, the index guide structure having high current confinement efficiency and high light confinement efficiency is excellent.

Further, the wavelength of the laser beam used for reproducing information is different between CD and DVD, and CD is 750 to 89.
A wavelength of about 0 nm is used, while 630 for DVD
A wavelength of about 690 nm is used. Therefore, an optical disk device capable of reproducing information from both CD and DVD media for the sake of convenience needs to be provided with two types of semiconductor lasers in order to generate laser beams of these two types of wavelengths. Then, a semiconductor laser having a gain guide structure is used for giving priority to suppression of return light noise for reproducing a CD, while for reproducing a DVD,
Since it is difficult to adopt a gain guide structure from the viewpoint of device life, a semiconductor laser with an index guide structure is used. When a semiconductor laser with an index guide structure is used for DVD reproduction, it is disadvantageous in terms of return light noise, but this problem causes pulsation of the oscillation mode due to the formation of a supersaturated absorption region due to the light absorption effect of the current block layer. This can be avoided.

When two semiconductor lasers having different wavelengths are used, it is necessary to accurately set the distance between the semiconductor lasers, and hence the distance between the light emitting points. As described above, a light receiving element such as a photodiode is used for receiving the reflected light, and the light receiving element is provided for each semiconductor laser and arranged at an interval corresponding to the interval between the two semiconductor lasers. Therefore, when the interval between the light emitting points is inaccurate, the reflected light does not properly enter the light receiving element, and the light receiving sensitivity is lowered.

[0006]

In order to accurately set the light emitting point interval of two semiconductor lasers, it is common to form each semiconductor laser on a different chip and arrange each chip adjacently. It is more advantageous to form two semiconductor lasers having different structures on the semiconductor substrate.
Further, even when semiconductor lasers having different structures are formed on a common semiconductor substrate, it is better to form each semiconductor laser using a common mask than to form each semiconductor laser individually. No problem,
The two semiconductor lasers can be arranged with higher positional accuracy.

Therefore, an object of the present invention is to provide a method of manufacturing a semiconductor laser device which realizes an improvement in the accuracy of the emission point spacing of two semiconductor lasers by forming two semiconductor lasers having different structures using a common mask. To provide.

[0008]

According to the present invention, in order to achieve the above object, a first semiconductor laser having a gain guide structure and a second semiconductor laser having an index guide structure are arranged side by side on a common semiconductor substrate. A method of manufacturing a semiconductor laser device, comprising:
A first laminated structure which forms the first semiconductor laser and has an active layer sandwiched by clad layers is formed in an island shape, and the second semiconductor laser is formed on the entire surface of the semiconductor substrate. A first cladding layer, an active layer,
And the second clad layer is sequentially laminated to form a second laminated structure, and the second laminated layer including at least a lower portion of the first clad layer is formed on the first laminated structure. The upper part of the second laminated structure is removed, leaving a partial layer of the structure, an oxide film is formed on the entire surface of the semiconductor substrate, and photolithography is performed using a single exposure mask to remove the oxide film. On the partial layer of the second laminated structure on the first laminated structure, and on the second laminated structure formed at the second semiconductor laser formation location on the semiconductor substrate, respectively. The oxide film is patterned in a stripe shape, and the surface of the second clad layer at the portion where the second semiconductor laser is formed is etched by using the oxide film as a mask, and the second semiconductor is formed on the entire surface of the semiconductor substrate. Les The material of the current blocking layer constituting the laser is deposited by MOCVD, and the material of the current blocking layer and the partial layer of the second laminated structure are masked from above the first laminated structure with the oxide film. Then, ion implantation is performed on the surface portion of the first laminated structure by using the oxide film and the partial layer of the second laminated structure under the oxide film as a mask to form an insulating layer. Characterize.

In the gain guide structure semiconductor laser, the active layer emits light at a position below the stripe-shaped oxide film formed on the first laminated structure during manufacturing, and in the index guide structure semiconductor laser, The active layer emits light at a position below the stripe-shaped oxide film formed on the second cladding layer. Therefore, the distance between the light emitting points of the two semiconductor lasers is determined by the distance between the stripe-shaped oxide films. Further, in the present invention, since the oxide film is patterned by photolithography using a single exposure mask, the light emitting point interval is set with extremely high accuracy.

Further, according to the present invention, the second laminated structure formed on the first laminated structure as described above has a partial layer including at least a lower portion of the first clad layer and an ion layer formed later. Leave to use as a mask during injection. Then, even if MOCVD for depositing the material of the current blocking layer of the second semiconductor laser is performed, the first cladding layer is not deteriorated by the heat thereof. Therefore, ion implantation is performed using the partial layer of the second laminated structure as a mask.
It is possible to form the above-mentioned insulating layer which constitutes the semiconductor laser.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to the drawings. 1A to 1E
2A to 2E are sectional side views showing respective steps in an example of the method for manufacturing a semiconductor laser device according to the present invention, and FIGS. 2A to 2E are sectional side views showing respective steps following the step of FIG. 1E. is there. In the present embodiment, as an example, the first guide having a gain guide structure for reproducing information from a CD is provided.
And the second semiconductor laser having an index guide structure for reproducing information from the DVD are formed adjacent to each other on the same semiconductor substrate. The wavelength of laser light generated by the first semiconductor laser is approximately 750 to 890 nm, and the wavelength of laser light generated by the second semiconductor laser is approximately 630 to 690 nm. In this embodiment, a large number of first and second semiconductor lasers are formed on a semiconductor substrate, but FIGS. 1 and 2 show a set of first and second semiconductor laser devices constituting one semiconductor laser device. The location of the semiconductor laser is shown.

First, as shown in FIG.
AlGaA on the semiconductor substrate 2 made of As
An n-type clad layer 4, an active layer 6, and a p-type clad layer 8 made of s are sequentially formed, and GaAs is further formed thereon.
A cap layer 10 made of is formed. Then, the first laminated structure 12 which is patterned into an island shape by known photolithography to form a first semiconductor laser 12
To get

Next, as shown in FIG. 1B, the first
In order to form a second semiconductor laser at a position adjacent to the laminated structure 12 of FIG.
N-type buffer layer 14 made of P, n-type cladding layer 16 made of GaInP, GaInP well and AlGa
Active layer 18 made of InP barrier, p-type clad layer 20 made of GaInP, p-type intermediate layer 2 made of GaInP.
4 and the cap layer 22 made of GaAs are laminated in this order to form the second laminated structure 26.

The first and second laminated structures 12,
Each layer of 26 can be formed by MOCVD (metal organic chemical vapor deposition). By using the MOCVD method, it is possible to form a film with a uniform thickness in a wide range on the semiconductor substrate 2 with good controllability, to ensure the uniformity of crystal composition, and to form a steep hetero interface.

Then, as shown in FIG. 1C,
On the first laminated structure 12, the surface of the second laminated structure 26 formed adjacent to the first laminated structure 12 is covered with a photoresist layer 28, and etching is performed using this as a mask. , Leaving at least a partial layer of the second laminated structure 26 including the lower part of the n-type cladding layer 16,
The upper portion of the second laminated structure 26 is removed. In this embodiment, as an example, the etching is stopped at the active layer 18, the cap layer 22, the p-type intermediate layer 24, and the p-type cladding layer 20 above the active layer 18 are removed, and the n-type cladding layer 16 is removed. And the active layer 18 is left as the partial layer.

In this etching, for example, H3PO
4; the cap layer 22 is removed by a selective etchant such as H2O2; H2O, and the p-type intermediate layer 24 is removed by a selective etchant such as HCl; H2O.
For example, the p-type cladding layer 20 is removed by a selective etchant such as H2SO4; H2O.

Next, as shown in FIG. 1D, CV
An oxide film 30 (SiO2) 20 is formed on the entire surface by the D method.
After depositing a thickness of 0 nm to 300 nm and further forming a resist layer thereon, the photoresist layer is patterned by exposure using a single exposure mask and subsequent development to form a first laminated layer. Oxide film 30 on structure 12
And a second laminated structure 26 in the second semiconductor laser formation position, which is adjacent to the first laminated structure 12.
Striped photoresist layers 32 and 34 are formed on the upper oxide film 30, respectively. Here, the photoresist layers 32 and 34 extend in stripes in a direction orthogonal to the paper surface. Then these photoresist layers 3
The oxide film 30 is etched using ammonium fluoride with the masks 2 and 34 as a mask, and the pattern of the stripe-shaped photoresist layers 32 and 34 is transferred to the oxide film 30 as shown in FIG. , Striped oxide film 3
6 and 38 are formed.

Continuing, as shown in FIG.
The active layer 18 and the oxide film 36 on the first laminated structure 12
Is covered with a photoresist layer 40, and then the second laminated structure 26 in the second semiconductor laser forming portion is formed.
The cap layer 22, the p-type intermediate layer 24, and the upper layer portion of the p-type clad layer 20 are removed by etching using the oxide film 38 as a mask. As a result, under the oxide film 38,
A stripe ridge 42 is formed by a part of the p-type cladding layer 8.

In this etching, for example, H3PO
4; the cap layer 22 is removed by a selective etchant such as H2O2; H2O, and the p-type intermediate layer 24 is removed by a selective etchant such as HCl; H2O.
For example, the p-type cladding layer 20 is etched to a predetermined depth with a selective etchant such as H2SO4; H2O.

Next, as shown in FIG. 2B, GaAs is deposited by MOCVD on the entire surface of the semiconductor substrate to form the current blocking layers 44 on both sides of the oxide film 38. At this time, GaAs is selectively deposited on the active layer 18 on the first laminated structure 12 and the p-type clad layer 20 of the second laminated structure 26 at the second semiconductor laser forming location, and an oxide film is formed. It does not deposit on 36 and 38.

After that, as shown in FIG. 2C, the second laminated structure 26 at the second semiconductor laser forming portion is covered with a photoresist layer 46, and the second laminated structure 26 shown in FIG. The deposited layer 48 (current blocking layer) formed by the MOCVD method on the laminated structure 12 of No. 1 is H3PO4; H2O2;
It is removed by etching using a selective etchant such as H2O. The oxide film 36 and the lower active layer 18 are not removed by this etching. Subsequently, by using the oxide film 36 as a mask and performing etching using a selective etchant such as HCl;
The active layer 18, the n-type clad layer 16 and the n-type buffer layer 14 on the second layer 2 are removed ((B) of FIG. 2).

Then, as shown in FIG. 2D, the oxide film 36 and the partial layer of the second laminated structure 26 centering on the n-type cladding layer 16 therebelow are used as a mask.
For example, B + ions are implanted to form the insulating layer 50 on both sides of the oxide film 36 on the surface of the first laminated structure 12.
Then, as shown in FIG. 2E, after removing the photoresist layer 46, the oxide films 36 and 38 are removed with ammonium fluoride, and further the oxide film 36 is removed with HCl.
The active layer 18, the n-type clad layer 16 and the n-type buffer layer 14 which are the lower layers are removed. Further, electrodes (not shown) are formed on the striped cap layers 10 and 22 to complete the basic structure of the first and second semiconductor lasers 52 and 54.

In the first semiconductor laser 52 having the gain guide structure thus formed, the active layer 6 emits light under the stripe-shaped cap layer 10, and in the second semiconductor laser 54 having the index guide structure, the cap is formed. Layer 2
The active layer 18 emits light at a position 2 below. Therefore, the distance L between the light emitting points of the two semiconductor lasers ((E) in FIG. 2) is
It is determined by the distance between the oxide films 36 and 38, and in the present embodiment, the oxide films 36 and 38 are formed by photolithography using a single exposure mask as described above. It is set with high accuracy.

In addition, in the present embodiment, as described above, the second laminated structure 26 formed on the first laminated structure 12 is not entirely removed, but the n-type cladding layer is removed. 16 is left for later use as a mask. Then, the n-type cladding layer 16 is subjected to MOCVD as described above to deposit the material of the current blocking layer 50 forming the second semiconductor laser, and it is not altered even if exposed to a high temperature of about 600 ° C. There is no. Therefore, n under the oxide film 36
Ion implantation is performed using the mold cladding layer 16 as a mask.
It is possible to form the insulating layer 50 that constitutes the semiconductor laser. Conventionally, a photoresist has been used as a mask for such ion implantation. If a photoresist layer is formed as a mask instead of the n-type clad layer 16 as in the prior art also in this embodiment, the heat generated by the MOCVD for forming the current blocking layer 50 causes The photoresist layer is deteriorated and does not function as a mask. Therefore, the insulating layer 50 cannot be formed by the conventional method.

Further, in the present embodiment, after the material of the current block layer 44 is deposited by MOCVD to form the second semiconductor laser 54, ion implantation is performed on the surface portion of the first laminated structure 12. Then, the insulating layer 50 is formed. Therefore, as in the case where the insulating layer 50 is formed before the current blocking layer 44, the resistivity of the insulating layer 50 is
It does not happen that the insulating layer 50 does not play its role because it is lowered by the heat for performing MOCVD.
In the present embodiment, the stripe-shaped oxide films 36, 38 on the first and second laminated structures 12, 26 are formed.
Is not formed individually for each of the first and second laminated structures 12 and 26, but is formed by the same process as described above ((D) and (E) of FIG. 1), In this respect, the process is simplified.

In the present embodiment, when removing the second laminated structure 26 formed on the first laminated structure 12, the etching is stopped at the active layer 18 and the cap layers 22 and p are removed. The type intermediate layer 24 and the p-type clad layer 20 are removed, but a layer serving as a mask when the current blocking layer 44 is formed later may be formed on the first laminated structure 12. Therefore, if a sufficient thickness can be ensured, the active layer 18 can be removed, and further, the upper layer portion of the n-type cladding layer 16 can be removed. Also,
Conversely, etching may be stopped before the active layer 18 and only the upper portion of the p-type cladding layer 20 may be removed.

[0027]

As described above, the present invention provides a semiconductor laser device in which a first semiconductor laser having a gain guide structure and a second semiconductor laser having an index guide structure are arranged side by side on a common semiconductor substrate. A method of manufacturing, wherein a first laminated structure, which constitutes the first semiconductor laser and has an active layer sandwiched by cladding layers, is formed in an island shape on the semiconductor substrate, and the entire surface of the semiconductor substrate is formed. And a first clad layer, an active layer, and a second clad layer for forming the second semiconductor laser are sequentially laminated to form a second laminated structure, and the first laminated structure is formed. The upper part of the second laminated structure is removed, leaving at least a partial layer of the second laminated structure on the body, the partial layer including at least the lower part of the first cladding layer. An oxide film is formed on the entire surface, and by photolithography using a single exposure mask, on the partial layer of the second laminated structure on the first laminated structure, and on the semiconductor substrate. The oxide film is patterned into a stripe shape on the second laminated structure formed at the second semiconductor laser forming location, and the second cladding layer surface at the second semiconductor laser forming location is formed. Etching is performed using the oxide film as a mask, the material of the current block layer that constitutes the second semiconductor laser is deposited on the entire surface of the semiconductor substrate by MOCVD, and the current block is formed on the first laminated structure. The layer material and the partial layer of the second laminated structure are removed by using the oxide film as a mask, and the oxide film and the oxide film are formed on the surface of the first laminated structure. Fine said ion implantation is carried out the partial layer of the second laminated structure under an oxidative film as a mask and forming an insulating layer.

In the gain guide structure semiconductor laser, the active layer emits light at a position below the stripe-shaped oxide film formed on the first laminated structure during manufacturing, and in the index guide structure semiconductor laser, The active layer emits light at a position below the stripe-shaped oxide film formed on the second cladding layer. Therefore, the distance between the light emitting points of the two semiconductor lasers is determined by the distance between the stripe-shaped oxide films. Further, in the present invention, since the oxide film is patterned by photolithography using a single exposure mask, the light emitting point interval is set with extremely high accuracy.

Further, in the present invention, the second laminated structure formed on the first laminated structure as described above has a partial layer including at least a lower portion of the first clad layer and an ion layer formed later. Leave to use as a mask during injection. Then, even if MOCVD for depositing the material of the current blocking layer of the second semiconductor laser is performed, the first cladding layer is not deteriorated by the heat thereof. Therefore, ion implantation is performed using the partial layer of the second laminated structure as a mask.
It is possible to form the above-mentioned insulating layer which constitutes the semiconductor laser.

Furthermore, in the present invention, after depositing the material of the current blocking layer by MOCVD to form the second semiconductor laser, ion implantation is performed on the surface portion of the first laminated structure to form an insulating layer. Since the insulating layer is formed, the resistivity of the insulating layer is not lowered by the heat for performing MOCVD, and the insulating layer does not lose its role. In the present invention, the stripe-shaped oxide film on the first laminated structure and the stripe-shaped oxide film on the second cladding layer at the second semiconductor laser forming location are not formed individually but are the same. Since the steps are performed at once, the steps are simplified in this respect.

[Brief description of drawings]

1A to 1E are cross-sectional side views showing respective steps in an example of a method for manufacturing a semiconductor laser device according to the present invention.

2A to 2E are cross-sectional side views showing respective steps following the step of FIG. 1E.

[Explanation of symbols]

2 ... Semiconductor substrate, 4 ... N-type cladding layer, 6 ... Active layer, 8 ... P-type cladding layer, 10 ... Cap layer, 12
... first laminated structure, 14 ... n-type buffer layer, 1
6 ... n-type clad layer, 18 ... active layer, 20 ... p-type clad layer, 22 ... cap layer, 24 ... p-type intermediate layer, 26 ... second laminated structure, 30 ... oxidation Membrane, 32
...... Photoresist layer, 34 ...... Photoresist layer, 3
6 ... Oxide film, 38 ... Oxide film, 40 ... Photoresist layer, 42 ... Stripe ridge, 44 ... Current blocking layer, 46 ... Photoresist layer, 48 ... Deposition layer, 5
0 ... Insulating layer, 52 ... First semiconductor laser, 54 ...
… Second semiconductor laser.

Claims (15)

[Claims] 1. A method of manufacturing a semiconductor laser device comprising a first semiconductor laser having a gain guide structure and a second semiconductor laser having an index guide structure arranged side by side on a common semiconductor substrate, the method comprising: A first laminated structure, which constitutes the first semiconductor laser and has an active layer sandwiched by clad layers, is formed in an island shape on a substrate, and the second semiconductor laser is formed on the entire surface of the semiconductor substrate. A first clad layer, an active layer, and a second clad layer for constituting are sequentially laminated to form a second laminated structure, and at least the first laminated structure is formed on the first laminated structure. Leaving the partial layer of the second laminated structure including the lower portion of the clad layer, removing the upper portion of the second laminated structure, forming an oxide film on the entire surface of the semiconductor substrate, Formed by photolithography using one exposure mask on the partial layer of the second stacked structure on the first stacked structure and on the second semiconductor laser formation location on the semiconductor substrate. And patterning the oxide film in a stripe shape on the second laminated structure, and etching the surface of the second clad layer at the second semiconductor laser forming location using the oxide film as a mask. The material of the current block layer forming the second semiconductor laser is deposited by MOCVD on the entire surface of the semiconductor substrate, and the material of the current block layer and the second stack structure are formed on the first stacked structure. The partial layer of the body is removed using the oxide film as a mask, and the oxide film and the first oxide film under the oxide film are formed on the surface portion of the first laminated structure. The method of manufacturing a semiconductor laser device, which comprises the partial layer of the laminated structure forming the insulating layer by ion implantation as a mask. 2. The second laminated structure body of the second laminated structure body is left on the first laminated structure body, leaving at least a partial layer of the second laminated structure body including at least a lower portion of the first cladding layer. 2. The method of manufacturing a semiconductor laser device according to claim 1, wherein when the upper portion is removed, a portion below the active layer of the second laminated structure is left. 3. The method of manufacturing a semiconductor laser device according to claim 1, wherein a first cap layer is formed on the surface of the first laminated structure. 4. When laminating the first cladding layer, the active layer, and the second cladding layer for forming the second semiconductor laser, a buffer layer is first formed on the entire surface of the semiconductor substrate. Is formed, the first clad layer, the active layer, and the second clad layer are laminated thereon, and an intermediate layer is further formed on the second clad layer. The method for manufacturing a semiconductor laser device according to claim 1. 5. The method of manufacturing a semiconductor laser device according to claim 4, wherein a second cap layer is formed on the intermediate layer. 6. The second cap formed on the second clad layer when etching the surface of the second clad layer at the portion where the second semiconductor laser is formed by using the oxide film as a mask. The method for manufacturing a semiconductor laser device according to claim 5, wherein the layer and the intermediate layer are etched by using the oxide film as a mask. 7. The method of manufacturing a semiconductor laser device according to claim 1, wherein the wavelength of light generated by the first semiconductor laser is longer than the wavelength of light generated by the second semiconductor laser. 8. The method of manufacturing a semiconductor laser device according to claim 1, wherein the semiconductor substrate is made of GaAs. 9. The method of manufacturing a semiconductor laser device according to claim 1, wherein the clad layer and the active layer forming the first laminated structure are made of AlGaAs. 10. The method of manufacturing a semiconductor laser device according to claim 3, wherein the first cap layer is formed of GaAs. 11. The method of manufacturing a semiconductor laser device according to claim 1, wherein the first and second clad layers forming the second semiconductor laser are formed of AlGaInP. 12. The method of manufacturing a semiconductor laser device according to claim 1, wherein the active layer forming the second semiconductor laser is formed of GaInP and AlGaInP. 13. The material of the current blocking layer is GaA.
2. The method for manufacturing a semiconductor laser device according to claim 1, wherein s is s. 14. The method of manufacturing a semiconductor laser device according to claim 5, wherein the second cap layer forming the second semiconductor laser is formed of GaAs. 15. The method of manufacturing a semiconductor laser device according to claim 4, wherein the buffer layer and the intermediate layer are formed of GaInP.