JP2009141130A - Semiconductor laser and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser with improved ESD resistance and a method for manufacturing the same.
A reflection film including a compressive stress of 700 to 2000 MPa is formed on an end face of a semiconductor laser body by an ECR sputtering method. The inventors have found that when high compressive stress is applied to the reflective film formed on the semiconductor laser body, light absorption at the end face is reduced, and as a result, ESD resistance is improved. Therefore, according to the film forming process in the semiconductor laser manufacturing method according to the present invention, a semiconductor laser having high ESD resistance can be obtained.
[Selection] Figure 2

Description

  The present invention relates to a semiconductor laser and a manufacturing method thereof.

  Patent Documents 1 to 4 below disclose semiconductor lasers in which a predetermined reflective film is formed on an end face to improve laser characteristics and control reflectance.

Among these, Patent Document 1 and Patent Document 2 suggest that the internal stress of the reflective film formed on the semiconductor end face affects the semiconductor laser characteristics. Further, these patent documents disclose an invention for improving the reliability of a semiconductor laser by reducing internal stress. Patent Document 3 and Patent Document 4 disclose DFB (Distributed Feedback) semiconductor lasers that oscillate at a single wavelength.
JP 2005-175111 A Japanese Patent Laid-Open No. 2002-2223026 JP-A-8-78776 JP-A-11-163466

  However, the above-described semiconductor laser does not have sufficiently high electrostatic discharge resistance (hereinafter referred to as “ESD resistance”, ESD: electrostatic discharge), and therefore, improvement of the ESD resistance of the semiconductor laser has been demanded.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a semiconductor laser with improved ESD resistance and a method for manufacturing the same.

  In order to achieve the above object, a method for manufacturing a semiconductor laser according to the present invention includes a film forming step of forming a reflective film containing a compressive stress of 700 to 2000 MPa on an end face of a semiconductor laser body by an ECR sputtering method. It is characterized by that.

  As a cause of the low ESD resistance of the semiconductor laser, it is conceivable that the surface of the semiconductor laser in contact with the reflection film provided on the end face is deteriorated due to light absorption. The inventors have found that when the reflective film formed on the semiconductor laser body contains a high compressive stress, the light absorption at the end face is reduced, and as a result, the ESD resistance is improved. Therefore, according to the film forming process in the semiconductor laser manufacturing method according to the present invention, a semiconductor laser having high ESD resistance can be obtained.

  The film forming step of the semiconductor laser manufacturing method according to the present invention includes a step of forming a first layer made of aluminum oxide on the end face, a second layer having a refractive index different from that of the first layer, and a first layer. And alternately laminating the layers on the first layer. As a result, it is possible to effectively increase the reflectance of the reflective film, and at the same time, it is possible to obtain a semiconductor laser having high ESD resistance.

  In a preferred embodiment, the second layer is preferably made of either titanium oxide or amorphous silicon. In this case, it is possible to obtain a semiconductor laser having a high ESD resistance and a high ESD resistance effect according to the present invention.

  In addition, the film forming step of the semiconductor laser manufacturing method according to the present invention may include a step of forming an aluminum film on the end surface of the semiconductor laser body before forming the first layer. According to this manufacturing method, since the adhesion between the end face of the semiconductor laser and the reflective film is improved, it is possible to obtain a semiconductor laser having high ESD resistance and at the same time, occurrence of peeling of the reflective film is reduced.

  A semiconductor laser according to the present invention includes a semiconductor laser body and a reflective film that is provided on an end surface of the semiconductor laser body and contains a compressive stress of 700 to 2000 MPa.

  The semiconductor laser according to the present invention includes a plurality of first layers arranged alternately and a plurality of second layers having a refractive index different from that of aluminum oxide. The thickness of the first layer is 1.5 times or more of λ / (4 × n), where n is the refractive index of the first layer and λ is the laser oscillation wavelength of the semiconductor laser. Has a film thickness of λ / (4 × n), and one of the first and second layers is made of aluminum oxide, and the other of the first and second layers has a refractive index different from that of aluminum oxide. It is preferable to consist of materials.

  Since the compressive stress included in the reflective film can be increased by increasing the film thickness of any one of the first layers as described above, the effect of improving the ESD resistance of the semiconductor laser can be increased. it can.

  According to the present invention, a semiconductor laser with improved ESD tolerance and a method for manufacturing the same are provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate descriptions are omitted.

(First embodiment)
In the present embodiment, a description will be given by taking a distributed feedback semiconductor laser (hereinafter referred to as “DFB laser”) used for optical communication or the like as an example of the semiconductor laser. FIG. 1 is a diagram illustrating a method of manufacturing a semiconductor laser according to the first embodiment. FIG. 2 is a diagram showing a flow of a manufacturing method of the semiconductor laser according to the first embodiment.

<Preparation process>
First, in step S101 of FIG. 2, the semiconductor laser body 12 is prepared as shown in FIG. The semiconductor laser body 12 is configured by sequentially laminating a semiconductor substrate 12S, a first conductivity type cladding layer 12A, an active layer 12B, a diffraction grating layer 12C, and a second conductivity type cladding layer 12D. . As a constituent material of the semiconductor laser body 12, a III-V group compound semiconductor material can be used, and an InP-based material, a GaAs-based material, an AlAs-based material, a GaN-based material, or a mixed crystal material thereof can be used. . The active layer 12B is made of, for example, GaInAsP and can output light having a wavelength of 1310 nm. The semiconductor laser body 12 can be obtained by, for example, sequentially forming semiconductor layers on a semiconductor substrate 12S made of InP and then cleaving the semiconductor substrate. The unevenness of the diffraction grating layer 12C is formed using, for example, a photolithography method.

<Film formation process>
As a film forming step, a first layer made of aluminum oxide is formed on the end face of the semiconductor laser body 12, and a second layer and a first layer having a refractive index different from those of the first layer are formed on the first layer. A reflective film in which the layers are alternately stacked is formed. In this embodiment, a titanium oxide film is formed as the second layer. In addition, this embodiment includes a step of forming an aluminum film on the end face of the semiconductor laser body before forming the first layer.

<Cleaning step and aluminum film forming step>
FIG. 3 is a diagram schematically showing a film forming apparatus 20 for forming the reflective films 14 and 16 of the semiconductor laser according to the present embodiment. The film forming apparatus 20 shown in FIG. 3 is an ECR sputtering apparatus, and can form various coating films on the end face E1 and the end face E2 of the semiconductor laser main body 12, respectively.

The film forming apparatus 20 includes a vacuum chamber 22, a jig J that is installed in the vacuum chamber 22 and holds the semiconductor laser body 12, and a sputtering target T that is installed in the vacuum chamber 22 and made of aluminum. A sputtering target made of titanium is further installed in the vacuum chamber 22. A high frequency power source PW1 such as an RF power source is connected to the sputtering target T, for example. In addition, the film forming apparatus 20 uses a microwave MW to generate a plasma P in the vacuum chamber 22 and a magnetic power source PW2 surrounding the vacuum chamber 22 to control the shape of the plasma P and the like. A coil C1. The vacuum chamber 22 has a supply port 22a for supplying the gas G1 that generates the plasma P, and an exhaust port 22b for exhausting the gas G2. Examples of the gas G1 include an inert gas such as argon gas (Ar) and nitrogen gas (N ₂ ), oxygen gas (O ₂ ), and the like.

  Next, as shown in FIG. 1B, the semiconductor laser body 12 set on the jig J is placed in the vacuum chamber 22 of the film forming apparatus 20 (S102). The end face E2 is cleaned by exposing the end face E2 of the semiconductor laser body 12 to the plasma P1 generated from the inert gas (S103). Further, the aluminum film 16C is formed on the end face E2 by exposing the sputtering target T to the plasma P1 (S104). The film thickness of the aluminum film 16C is 3 nm. The plasma P1 is an example of the plasma P shown in FIG. Argon gas can be used as the inert gas.

  In the cleaning step and the aluminum film formation, the plasma P1 is preferably generated from an inert gas supplied so that the pressure in the vacuum chamber 22 is less than 0.06 Pa. When the pressure is less than 0.06 Pa, the mean free path of active particles (for example, atoms, ions, or radicals) in the plasma P1 becomes long, and it is considered that the sputtering target T is easily sputtered. Therefore, the sputtering target T is sputtered even if the high-frequency power from the high-frequency power source PW1 is not substantially applied to the sputtering target T. More preferably, the pressure in the vacuum chamber 22 is 0.03 Pa or less. The pressure in the vacuum chamber 22 can be adjusted by the flow rate of the inert gas or the displacement.

<Aluminum oxide film formation process>
Next, an aluminum oxide film 16A is formed on the aluminum film 16C (S105). The aluminum oxide film 16A is formed by, for example, a sputtering method using the film forming apparatus 20. A sputtering target made of aluminum is exposed to plasma generated from a mixed gas of an inert gas and oxygen gas, and a bias voltage is applied to the sputtering target using a high-frequency power source. At this time, the surface of the aluminum film 16C shown in FIG. 1B is oxidized by being exposed to plasma generated from a mixed gas of an inert gas and an oxygen gas. Further, the aluminum oxide film 16A is laminated on the oxidized aluminum film by exposing the sputtering target to plasma and applying a bias voltage to the sputtering target using a high frequency power source. Argon gas can be used as the inert gas.

<Titanium oxide film formation process>
Next, a titanium oxide film 16B is formed on the aluminum oxide film 16A (S106). The titanium oxide film 16B is also formed by a sputtering method using the film forming apparatus 20. A sputtering target made of titanium is exposed to plasma generated from a mixed gas of an inert gas and oxygen gas, and a bias voltage is applied to the sputtering target using a high-frequency power source. Thereby, the titanium oxide film 16B is formed.

  Furthermore, if necessary, the aluminum oxide film 16A and the titanium oxide film 16B are alternately stacked (repetition of S105 and S106), and the reflection film 16 composed of a plurality of layers is formed.

  Thereafter, the reflective film 14 in which the aluminum oxide film 14A and the titanium oxide film 14B are sequentially laminated is formed on the other end face E1 of the semiconductor laser in the same manner, and then taken out from the film forming apparatus, as shown in FIG. The semiconductor laser 10 is obtained (S107).

  FIG. 4 is a diagram schematically showing the semiconductor laser 10 according to the first embodiment. The semiconductor laser 10 includes a semiconductor laser body 12, a reflective film 14 provided on the end face E1, and a reflective film 16 provided on the end face E2. The reflection film 14 is an AR film (low reflection film), and the reflection film 16 is an HR film (high reflection film). Therefore, when power is supplied from the power source 18 to the cladding layer 12A and the cladding layer 12D, the laser light L is emitted from the reflective film 14 side of the semiconductor laser 10.

  The reflective film 14 has a two-layer structure and includes an aluminum oxide film 14A provided on the end face E1. A titanium oxide film 14B is provided on the aluminum oxide film 14A. Note that there may be a plurality of the aluminum oxide films 14A and the titanium oxide films 14B, and in this case, it is preferable that they are alternately stacked.

  The reflective film 16 has a six-layer structure and includes an aluminum oxide film 16A provided on the end face E2. A titanium oxide film 16B is provided on the aluminum oxide film 16A. In the present embodiment, the aluminum oxide film 16A and the titanium oxide film 16B are alternately stacked. As described above, there may be a plurality of aluminum oxide films 16A and titanium oxide films 16B. In this case, it is preferable that the aluminum oxide films 16A and the titanium oxide films 16B are alternately stacked.

  The semiconductor laser 10 obtained by the above manufacturing method has a high compressive stress contained in the reflective film and a high ESD resistance.

  The compressive stress of the reflective film of the semiconductor laser can be controlled by adjusting the gas pressure and power during film formation in the ECR sputtering method using the apparatus shown in FIG. For example, the compressive stress of the reflective film tends to decrease by increasing the gas pressure or decreasing the power during film formation. Conversely, by reducing the gas pressure and increasing the power during film formation, it is possible to increase the compressive stress of the produced reflective film. Specifically, a reflective film having a high compressive stress can be formed by setting the gas pressure during film formation to 0.02 to 0.1 Pa and the power during film formation to 500 to 600 W. Therefore, it is preferable to form the reflective film under these manufacturing conditions.

Note that the conditions for forming the reflective film used in the following detailed description are as follows.
Gas pressure during aluminum oxide film formation: 0.08 Pa,
Electric power when forming an aluminum oxide film: 500 W
Gas pressure during titanium oxide film formation: 0.03 Pa,
Electric power when forming the titanium oxide film: 600 W.

<Stress measurement method>
The stress of the semiconductor applied to the end face of the semiconductor laser obtained by the above manufacturing method can be obtained from the wave number shift of the Raman scattering peak derived from InP. The wave number shift is obtained by measuring the end face of a semiconductor laser having a reflective film by microscopic laser Raman spectroscopy. When the end face of the semiconductor laser was measured by microscopic laser Raman spectroscopy, it was shown that a tensile stress of 3000 MPa worked on the semiconductor at the end face of the semiconductor laser along a plane parallel to the end face. In this semiconductor laser, the aluminum oxide film 16A is laminated on the end face of the semiconductor laser 10 so as to have a film thickness of 201 nm, and the titanium oxide film 16B is laminated thereon so as to have a film thickness of 142 nm. The reflective film 16 has a total film thickness of 1029 nm.

  On the other hand, the stress contained in the reflective film can be obtained by measuring the warp of the reflective film formed on the 2-inch InP substrate. The compressive stress contained in the reflective film having the same total six-layer structure (total film thickness 1029 nm) as described above was determined by this method, and was found to be 1600 MPa along the surface parallel to the end face of the semiconductor laser (in the surface direction of the InP substrate). It was shown to have compressive stress. The reflective film used for the stress measurement of the above two methods is formed under the same conditions by the same method. Therefore, from the measurement result of the above film stress, when a reflective film having a compressive stress of 1600 MPa measured on the warp of the 2-inch InP substrate is formed on the semiconductor laser end face, the semiconductor side of the semiconductor laser end face is 3000 MPa. It was found by microscopic laser Raman spectroscopy that the tensile stress was applied.

<Evaluation of ESD resistance>
Inventors conducted the experiment shown below in order to investigate ESD tolerance of said semiconductor laser. That is, after the reflective film was formed on the 2-inch InP substrate under the same conditions as the reflective film according to the present embodiment, the ESD degradation rate of the semiconductor laser when a voltage of 1 kV was applied was measured. Based on the measured value, the relationship between the stress of the reflective film and the ESD deterioration rate was obtained. In FIG. 5, the horizontal axis represents compressive stress, and the vertical axis represents ESD degradation rate. The compressive stress on the horizontal axis is a value obtained by measuring the warp of the InP substrate provided with the reflective film. In FIG. 5, the characteristic line C1 shown as Al ₂ O ₃ / TiO ₂ uses an aluminum oxide film (Al ₂ O ₃ ) and a titanium oxide film (TiO ₂ ) as a reflective film as in this embodiment. It was.

  As a result, as shown in FIG. 5, as the compressive stress of the reflective film increases, the ESD deterioration rate decreases and the ESD resistance is improved.

  As described above, the inventors have found that high ESD resistance can be obtained by increasing the compressive stress in the reflective film. Hereinafter, the compressive stress of the reflective film in the semiconductor laser 10 will be described.

  The stress generated in the vicinity of the end face E2 of the semiconductor laser body 12 when a reflective film (1600 MPa) having a high compressive stress is employed will be described along the xyz coordinate axes shown in FIG.

  FIG. 6 is a diagram for explaining the compressive stress in the reflective film 16 of the semiconductor laser 10 according to the present embodiment. In order to explain the direction in which the stress acts, the xyz orthogonal coordinate axes are set based on the end face E2 of the semiconductor laser 10 on the reflective film 16 side. As shown in FIG. 6, the stacking direction of the semiconductor laser body 12 is a y-axis, the direction in which the active layer 12B extends is the z-axis, and the direction perpendicular to the y-axis and the z-axis is the x-axis.

  7 to 9 are graphs showing the relationship between the distance (μm) in the z-axis direction from the end face E2 of the semiconductor laser 10 and the magnitude of stress (MPa) at that position. 7 to 9 show stresses in the x-axis direction, the y-axis direction, and the z-axis direction, respectively. 7 to 9, when the magnitude of the stress is positive, it is a tensile stress, and when it is negative, it is a compressive stress.

  As shown in FIGS. 7 and 8, the x stress (stress in the x-axis direction) and the y stress (stress in the y-axis direction) are positive values in the vicinity of the end surface E2 (range from the end surface E2 to 10 μm). . This indicates that tensile stress is generated in a direction (xy plane) parallel to the end surface E2, and it is considered that the semiconductor laser body 12 is distorted. At a position separated from the end face E2 by 10 μm or more, almost no stress is generated.

  On the other hand, as shown in FIG. 9, the z stress (stress in the z-axis direction) is a positive value in the range from the end face E2 to 2 μm, and it can be seen that the tensile stress is working. However, in the range of 3 μm or more from the end face E2, z stress shows a negative value, and compressive stress works. As described above, the stress in the z-axis direction is inverted from the tensile stress to the compressive stress at the portion entering the inside from the end face E2. This compressive stress is in the range of 3 μm to 70 μm from the end face E2, and it can be seen that the compressive stress is generated in this range.

  Next, a change in the band gap in the semiconductor laser body of the semiconductor laser 10 provided with the reflective film (1600 MPa) having a high compressive stress will be described with reference to FIG.

  FIG. 10 is a diagram showing the band gap wavelength in the semiconductor laser 10. The horizontal axis in FIG. 10 indicates the distance (separated position) in the z-axis direction from the end surface E2. As shown in FIG. 10, since the band gap wavelength is longer than 1310 nm in the range where the distance from the end face E2 is up to 2 μm, light having a wavelength of 1310 nm is absorbed. However, the band gap wavelength is shorter than 1310 nm at a position 2 μm or more inside from the end face E2. That is, in this range, light having a wavelength of 1310 nm is not absorbed.

  Conventionally, it has been considered that providing a semiconductor laser with a reflective film having a high compressive stress is not preferable because defects such as film peeling and film cracking occur and affect semiconductor laser characteristics. Therefore, in general, a reflection film that hardly generates compressive stress is formed on the end face of the semiconductor laser. Therefore, conventionally, the band gap energy in the vicinity of the end face of the semiconductor laser body is small, and the oscillation is absorbed by the end face member, so that deterioration is promoted and sufficient ESD resistance cannot be obtained.

  On the other hand, since the semiconductor laser 10 according to the present embodiment includes the reflective film 16 having a high compressive stress, a high compressive stress is generated inside the semiconductor laser body 12, and as a result, a large band gap energy is generated in the vicinity of the end face E2. It was confirmed by calculation that a part was formed. Since light absorption is suppressed by this, degradation in the vicinity of the end face is suppressed, and ESD resistance can be improved as compared with the conventional case.

  The compressive stress contained in the reflective film is preferably 700 MPa to 2000 MPa when formed on an InP substrate and measured using the warp of the InP substrate. When the reflective film is formed under the condition that the compressive stress included in the reflective film exceeds 3000 MPa, the reflective film may peel off in the heat cycle test (−40 ° C. to + 85 ° C., 100 cycles). For this reason, a reflective film having a compressive stress of 2000 MPa or less is preferable in that film peeling can be suppressed.

  About peeling of a reflecting film, it can also be suppressed by forming an aluminum oxide film after forming an aluminum film on the end surface of a semiconductor laser in a film-forming process like the manufacturing method of this embodiment. This is because the adhesion between the end face of the semiconductor laser and the reflective film is enhanced by forming the aluminum film.

<Changing the thickness of the reflective film>
In addition, the inventors investigated the relationship between the layer structure of the reflective film, the reflectance, and the compressive stress in the semiconductor laser according to the present embodiment. Table 1 shows the reflectance in a reflective film in which an aluminum oxide film (for example, Al ₂ O ₃ ) and titanium oxide (for example, TiO ₂ ) are combined.

As the compressive stress, a value obtained by a method of measuring the warpage of the reflective film formed on the 2-inch InP substrate was used. The film formation method followed this embodiment. The film forming conditions at that time were as follows.
Gas pressure during film formation of Al ₂ O ₃ : 0.08 Pa,
Electric power when forming Al ₂ O ₃ : 500 W
Gas pressure during TiO ₂ film formation: 0.03 Pa,
Electric power for TiO ₂ film formation: 600 W.
The result is shown as Al ₂ O ₃ / TiO ₂ in FIG. FIG. 11 is a diagram showing the relationship between the thickness of the reflective film and the compressive stress. It was found that the compressive stress increases with increasing film thickness. When a semiconductor film is laminated with a film thickness (= λ / (4 × n)) obtained by dividing 1/4 of the laser oscillation wavelength λ of the semiconductor laser by the refractive index n of the film of the layer, a highly reflective film is obtained. Referring to Table 1, it is shown that the film thickness of each layer when the total film thickness is 1308 nm is 201 nm, 142 nm, 201 nm, 142 nm, 480 nm, and 142 nm. When the film thickness of one of the laminated films is 1.5 times larger than λ / (4 × n), such as a layer having a film thickness of 480 nm, the reflectance is maintained at a desired value. The compressive stress contained can be increased as it is (without the reflectance becoming too high). Thus, it is preferable to increase the film thickness of one of the laminated films as the reflective film according to this embodiment. Note that the position of one layer may be changed by increasing the thickness of the laminated film. Further, in order to increase the film thickness, a layer made of a material different from Al ₂ O ₃ and TiO ₂ can be added.

  In addition, it is preferable that the upper limit of the total film thickness of the reflective film which concerns on this embodiment is a grade which the film | membrane peeling of a reflective film does not generate | occur | produce. Specifically, the total film thickness of the reflective film is preferably about 2000 nm or less.

(Second Embodiment)
Next, a semiconductor laser including an amorphous silicon (a-Si) film instead of a titanium oxide film will be described as a second embodiment of the present invention.

  The manufacturing method of the semiconductor laser according to this embodiment is the same as that of the first embodiment except that an amorphous silicon film is formed instead of the titanium oxide film in the film forming process of the first embodiment. As a result, the semiconductor laser obtained by the semiconductor laser manufacturing method according to the present embodiment is a film in which the portions indicated by the titanium oxide films 14B and 16B in the structure of the semiconductor laser 10 shown in FIG. Changed to

  Also in the semiconductor laser according to the present embodiment, as in the first embodiment, an increase in compressive stress in the reflective film is realized, and ESD resistance is improved.

FIG. 5 shows the results of measuring the ESD degradation rate when a voltage of 1 kV was applied with respect to the ESD tolerance of the semiconductor laser according to the present embodiment. In FIG. 5, the characteristic line C2 shown as Al ₂ O ₃ / a-Si indicates that an aluminum oxide film (Al ₂ O ₃ ) and amorphous silicon (a-Si) are used as a reflective film as in this embodiment. It is the result used.

  As shown in FIG. 5, as the stress of the reflective film increased, the ESD degradation rate decreased, confirming improvement in ESD resistance. This effect was equivalent to that of the semiconductor laser using the titanium oxide film according to the first embodiment.

Furthermore, the relationship between the layer structure of the reflection film of the semiconductor laser according to the present embodiment, the reflectance, and the compressive stress was also examined in the same manner as in the first embodiment. Table 2 shows the reflectance in a reflective film in which an aluminum oxide film (for example, Al ₂ O ₃ ) and amorphous silicon (a-Si) are combined.

As the compressive stress, a value obtained by a method of measuring the warpage of the reflective film formed on the 2-inch InP substrate was used. The film formation method followed this embodiment. The film forming conditions at that time were as follows.
Gas pressure during film formation of Al ₂ O ₃ : 0.08 Pa,
Electric power when forming Al ₂ O ₃ : 500 W
Gas pressure during a-Si film formation: 0.1 Pa,
Power during a-Si film formation: 500 W.
The result is shown as Al ₂ O ₃ / a-Si in FIG. Similar to the first embodiment, it was found that the compressive stress increases as the film thickness increases. Referring to Table 2, it is shown that the film thickness of each layer when the total film thickness is 1200 nm is 300 nm, 100 nm, 500 nm, 200 nm, and 100 nm. A film thickness obtained by dividing the film thickness of one layer of the laminated film by ¼ of the laser oscillation wavelength λ of the semiconductor laser by the refractive index n of the film of the layer, such as a layer having a film thickness of 500 nm. By forming a layer having a thickness greater than (= λ / (4 × n)), the compressive stress can be increased while keeping the reflectance in a desired range. Thus, it is preferable to increase the film thickness of one of the laminated films as the reflective film according to this embodiment. Further, in order to increase the film thickness, it is also possible to add a layer of a different material than the Al ₂ O ₃ and a-Si.

  Also in this embodiment, as in the first embodiment, it is preferable that the upper limit of the total film thickness of the reflective film is such that peeling of the reflective film does not occur. Specifically, the total film thickness of the reflective film is preferably about 2000 nm or less.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the first and second embodiments, the reflective film 14 is an AR film and the reflective film 16 is an HR film. However, the AR film and the HR film may be reversed depending on the laser structure. The number of layers of the reflective film 14 and the reflective film 16 is shown as an example.

  Further, in the film forming process, the semiconductor laser end face was cleaned and an aluminum film was formed on the end face, and then the aluminum oxide film was formed. However, the aluminum oxide film was formed without passing through the cleaning process and the aluminum film forming process. It may be formed on top. That is, the aspect which does not implement S103 and S104 among the flows of the manufacturing method in FIG. 2 may be sufficient. In the above-described embodiment, the DFB laser is described as an example of the semiconductor laser. However, the present invention can also be applied to a Fabry-Perot laser having a reflection film on the end face.

It is a figure which shows a part of manufacturing method of the semiconductor laser 10 which concerns on 1st Embodiment of this invention. 1 is a flowchart showing a method for manufacturing a semiconductor laser 10 according to a first embodiment of the present invention. It is a figure which shows typically the film-forming apparatus for forming the reflective film of the semiconductor laser 10 which concerns on 1st Embodiment of this invention. 1 is a diagram schematically showing a semiconductor laser 10 according to a first embodiment of the present invention. It is a figure which shows the result of having measured the ESD degradation rate of the semiconductor laser which concerns on 1st Embodiment and 2nd Embodiment of this invention. It is a figure explaining the compressive stress in the reflective film of the semiconductor laser which concerns on 1st Embodiment of this invention. It is a figure which shows x stress among the compressive stress which acts on the semiconductor laser main body shown in FIG. It is a figure which shows y stress among the compressive stress which acts on the semiconductor laser main body shown in FIG. It is a figure which shows z stress among the compressive stress which acts on the semiconductor laser main body shown in FIG. It is the figure which showed the band gap wavelength in the semiconductor laser main body shown in FIG. It is a figure which shows the relationship between the film thickness of the reflective film of the semiconductor laser which concerns on 1st Embodiment of this invention, and 2nd Embodiment, and compressive stress.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Semiconductor laser, 12 ... Semiconductor laser main body, 14, 16 ... Reflective film, 14A, 16A ... Aluminum oxide film, 14B, 16B ... Titanium oxide / amorphous silicon film E1, E2 ... End face, L ... Laser beam.

Claims (6)

  A method for manufacturing a semiconductor laser, comprising a film forming step of forming a reflective film containing a compressive stress of 700 to 2000 MPa on an end face of a semiconductor laser body by an ECR sputtering method. The film forming step includes
Forming a first layer of aluminum oxide on the end face;
Laminating the second layer having a refractive index different from that of the first layer and the first layer on the first layer alternately;
The method of manufacturing a semiconductor laser according to claim 1, comprising:   The method of manufacturing a semiconductor laser according to claim 2, wherein the second layer is made of one of titanium oxide and amorphous silicon. The film forming step includes
4. The method for manufacturing a semiconductor laser according to claim 2, further comprising a step of forming an aluminum film on the end face of the semiconductor laser body before forming the first layer. A semiconductor laser body;
A reflective film that is provided on an end face of the semiconductor laser body and encloses a compressive stress of 700 to 2000 MPa;
A semiconductor laser. The reflective film is
Having a plurality of first layers and a plurality of second layers arranged alternately,
The film thickness of any one of the first layers is such that the refractive index of the first layer is n and the laser oscillation wavelength of the semiconductor laser is λ. 5 times or more, the film thickness of the other layers is λ / (4 × n),
Either one of the first and second layers is made of aluminum oxide,
6. The semiconductor laser according to claim 5, wherein the other of the first and second layers is made of a material having a refractive index different from that of aluminum oxide.

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