JP2008004835A - Manufacturing method for semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for semiconductor laser with a small current flowing therethrough in a reverse direction. <P>SOLUTION: A semiconductor laser chip 42 is mounted on a jig 40 installed in a chamber 12. Next, the semiconductor laser chip 42 is heated. Further, a thermocouple 38 installed on the jig 40 is used to measure the temperature of the semiconductor laser chip 42, and a vacuum deposition method by an electronic beam A1 is used to form a protective film 58a on an end face 48a of the semiconductor laser chip 42. Here, when the temperature of the semiconductor laser chip 42 becomes higher than a predetermined temperature, the formation of the protective film 58a is started. In this way, semiconductor laser 60 is manufactured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor laser manufacturing method.

A method of forming a protective film on an end face of a semiconductor laser chip by using a vacuum vapor deposition method (EB vapor deposition method) using an electron beam is known (for example, see Patent Document 1).
JP 2001-177179 A

  Usually, in order to measure the temperature in the chamber of the vacuum deposition apparatus, a thermocouple is disposed outside the chamber. However, the thermocouple arranged outside the chamber cannot accurately measure the temperature of the semiconductor laser chip installed in the chamber. The present inventors have found that the temperature of the semiconductor laser chip at the time of forming the protective film greatly affects the characteristics of the finally manufactured semiconductor laser. When the formation of the protective film is started while the temperature of the semiconductor laser chip is low, not only the characteristics of the protective film itself change, but also in the reverse direction (n side to p side) in the semiconductor laser with the protective film formed, The breakdown voltage when a reverse bias voltage is applied decreases, and the value of the current flowing in the reverse direction increases. As a result, the electrostatic discharge (ESD) resistance of the semiconductor laser is reduced.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of manufacturing a semiconductor laser having a small value of current flowing in the reverse direction.

  In order to solve the above-described problems, a method of manufacturing a semiconductor laser according to the present invention includes a step of supporting a semiconductor laser chip on a support body installed in a chamber, a step of heating the semiconductor laser chip, and the support body. A step of measuring the temperature of the semiconductor laser chip using an installed temperature sensor, and a step of forming a protective film on an end face of the semiconductor laser chip by using a vacuum evaporation method using an electron beam, The formation of the protective film is started when the temperature of the laser chip becomes equal to or higher than a predetermined temperature.

  According to the semiconductor laser manufacturing method of the present invention, the actual temperature of the end face of the semiconductor laser chip can be measured, and after confirming that the temperature is equal to or higher than a predetermined temperature, the formation of the protective film can be started. . As a result, a semiconductor laser having a small current value flowing in the reverse direction when a reverse bias voltage is applied can be obtained.

  The predetermined temperature is preferably 240 ° C. or higher and 400 ° C. or lower. When the predetermined temperature is less than 240 ° C., the value of the current flowing in the reverse direction in the obtained semiconductor laser tends to increase. On the other hand, when the predetermined temperature exceeds 400 ° C., the quality of the protective film tends to be altered.

  According to the present invention, a method of manufacturing a semiconductor laser having a small value of current flowing in the reverse direction is 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.

  FIG. 1 is a diagram schematically illustrating an example of a vacuum deposition apparatus. The vacuum deposition apparatus 10 shown in FIG. 1 is for forming a protective film 58a on the end face 48a of one or a plurality of semiconductor laser chips 42.

Examples of the material of the protective film 58a include aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), zirconium oxide (ZrO ₂ ), and tantalum oxide (Ta _2). Examples thereof include dielectric materials such as O ₅ ) and amorphous silicon.

  The vacuum deposition apparatus 10 includes a chamber 12 such as a vacuum chamber, an electron gun 14 that is disposed in the chamber 12 and emits an electron beam A1, and a hearth 16 on which the electron beam A1 from the electron gun 14 is incident. The hearth 16 accommodates a vapor deposition material for forming the protective film 58a. The electron beam A1 from the electron gun 14 is bent by, for example, a magnetic field and enters the hearth 16. When the electron beam A1 enters the hearth 16, the vapor deposition material in the hearth 16 is heated by the electron beam A1. As a result, the vapor deposition material in the hearth 16 evaporates, and the source gas A2 that is the source material of the protective film 58a is released from the hearth 16. A shutter 18 may be provided in the chamber 12 for blocking the released source gas A2 as necessary.

An ion gun 20 that emits ions A3 such as Ar ⁺ is disposed in the chamber 12. When the source gas A2 and the ions A3 reach the end face 48a of the semiconductor laser chip 42, a protective film 58a is formed.

  A jig 40 (support) for supporting the semiconductor laser chip 42 is disposed opposite to the hearth 16 and the ion gun 20. Another support may be used instead of the jig 40. The jig 40 is attached to, for example, a dome-shaped top plate 24. One end 22 a of the shaft 22 is attached to the top plate 24. The other end 22 b of the shaft 22 is attached to the chamber 12 via a joint mechanism 36. A drive unit 34 for rotating the shaft 22 is connected to the shaft 22. Thereby, since the jig | tool 40 rotates centering on the axis | shaft 22, the film thickness uniformity of the protective film 58a improves.

  The jig 40 is provided with a thermocouple 38 (temperature sensor). Instead of the thermocouple 38, another temperature sensor may be used. The thermocouple 38 may extend along the top plate 24 and the axis 22. A signal from the thermocouple 38 is input to the control unit 32 via the joint mechanism 36 and the wiring 32b. The control unit 32 is, for example, a computer. When the shaft 22 rotates, since the thermocouple 38 and the wiring 32b are electrically connected via the joint mechanism 36, the thermocouple 38 rotates, but the wiring 32b does not rotate. The joint mechanism 36 includes, for example, a brush that electrically connects the thermocouple 38 and the wiring 32b. The controller 32 is electrically connected to the ion gun 20 via the wiring 32a. The ion gun 20 can emit or stop the ions A3 according to a signal from the control unit 32. When the ion A3 is emitted, the formation of the protective film 58a is started, and when the emission of the ion A3 is stopped, the formation of the protective film 58a is completed.

  In the chamber 12, a film thickness measuring device 30 for measuring the film thickness of the protective film 58a may be disposed. The film thickness measuring device 30 is, for example, an optical film thickness measuring device. The film thickness measuring device 30 is disposed to face the top plate 24. Further, in the chamber 12, a crystal resonator 28 for monitoring the thickness of the protective film 58a may be disposed. The crystal resonator 28 is disposed opposite to the ion gun 20.

  In the chamber 12, for example, one or a plurality of heaters 26 for heating the inside of the chamber 12 are arranged. FIG. 2 is a top view schematically showing an arrangement example of the plurality of heaters 26. The heaters 26 are preferably arranged at equal intervals along the side wall of the chamber 12. The chamber 12 has a side wall provided with a door portion 12a for taking in and out the jig 40.

  Next, a method for manufacturing the semiconductor laser according to the embodiment will be described. The semiconductor laser manufacturing method according to the present embodiment is implemented by using, for example, the above-described vacuum evaporation apparatus 10. Hereinafter, with reference to FIGS. 1 to 9, a method for manufacturing the semiconductor laser 60 (see FIG. 9) will be described as an example of the method for manufacturing the semiconductor laser according to the present embodiment. For example, the semiconductor laser 60 is obtained by sequentially performing the following steps.

(Preparation process)
A semiconductor laser chip 42 shown in FIG. 3 is prepared. FIG. 3 is a perspective view schematically showing an example of a semiconductor laser chip. The semiconductor laser chip 42 has an active region 46 and a clad 48 that covers the active region 46. The active region 46 is exposed at one end surface 48 a and the other end surface 48 a of the semiconductor laser chip 42. The semiconductor laser chip 42 is obtained, for example, by dividing a semiconductor wafer in which a plurality of semiconductor layers are stacked on a compound semiconductor substrate. Specifically, for example, the semiconductor wafer is cleaved (scratched) and then cleaved. In one embodiment, the shape of the semiconductor laser chip 42 is a rectangular parallelepiped having a length of 300 μm, a width of 10 mm, and a height of 100 μm.

(Installation process)
As shown in FIGS. 4 and 5, the semiconductor laser chip 42 is attached to the jig 40. FIG. 4 is a plan view schematically showing an example of a support on which the semiconductor laser chip is supported. FIG. 5 is an enlarged perspective view of a part of the semiconductor laser chip and the support shown in FIG. The jig 40 includes a base portion 50 in which a recess 50a for receiving the semiconductor laser chip 42 is formed, and a plurality of silicon plates that are received in the recess 50a and sandwich the semiconductor laser chip 42 so that the end surface 48a is exposed. 56. Semiconductor laser chips 42 and silicon plates 56 are alternately arranged in the recesses 50a. A pressing portion 54 that presses the semiconductor laser chip 42 through the silicon plate 56 is accommodated in the recess 50 a. Thereafter, the jig 40 is attached to the top plate 24.

  Thereafter, if necessary, when the vacuum in the chamber 12 is started and a predetermined pressure is reached, the heater 26 is turned on and the electron beam A1 is emitted from the electron gun 14 to evaporate the deposition material in the hearth 16. To melt. Thereafter, the electron beam A1 is stopped.

(Heating process)
As shown in FIG. 1, the semiconductor laser chip 42 is heated using, for example, a heater 26. The semiconductor laser chip 42 may be heated by heating the jig 40.

(Temperature measurement process)
As shown in FIG. 1, the temperature of the semiconductor laser chip 42 is measured using a thermocouple 38 installed in a jig 40 that supports the semiconductor laser chip 42. The temperature of the semiconductor laser chip 42 is calculated by the control unit 32 based on the signal from the thermocouple 38. A signal from the thermocouple 38 is input to the control unit 32 through the wiring 32a and recorded.

  FIG. 6 is a graph showing the relationship between the temperature of the semiconductor laser chip 42 and the elapsed time since the heater 26 was turned on. The horizontal axis of the graph indicates the elapsed time (minutes) since the heater 26 was turned on. The vertical axis of the graph indicates the temperature (° C.) of the semiconductor laser chip 42 measured by the thermocouple 38. A solid line T <b> 1 in the graph indicates a change with time of the temperature of the semiconductor laser chip 42. As can be seen from the graph, the temperature of the semiconductor laser chip 42 increases with the passage of time until the elapsed time reaches 40 minutes.

(Protective film formation process)
As shown in FIGS. 1 and 7, a protective film 58a is formed on the end face 48a of the semiconductor laser chip 42 by using a vacuum vapor deposition method using an electron beam A1. FIG. 7 is a perspective view schematically showing an example of a semiconductor laser chip in which a protective film is formed on the end face. Among the vacuum deposition methods, the ion-assisted deposition method using both the electron beam A1 and the ions A3 is preferable.

  Here, when the temperature of the semiconductor laser chip 42 becomes equal to or higher than a predetermined temperature, the formation of the protective film 58a is started. For example, the formation of the protective film 58a is started by emitting ions A3 from the ion gun 20. In the example shown in FIG. 6, it is preferable to start forming the protective film 58a when the temperature of the semiconductor laser chip 42 becomes 240 ° C. or higher.

When the material of the protective film 58a is aluminum oxide (Al ₂ O ₃ ) or titanium oxide (TiO ₂ ), the predetermined temperature is preferably 240 ° C. or higher and 400 ° C. or lower. When the predetermined temperature is less than 240 ° C., the value of the current flowing in the reverse direction in the obtained semiconductor laser 60 tends to increase. On the other hand, when the predetermined temperature exceeds 400 ° C., the film quality of the protective film 58a tends to be altered.

  As shown in FIG. 8, the protective film 58b is formed on the end face 48b of the semiconductor laser chip 42 by using the same method as the formation of the protective film 58a. FIG. 8 is a perspective view schematically showing an example of a semiconductor laser chip in which protective films are formed on both end faces.

(Cutting process)
The semiconductor laser chip 42 is divided along a dividing line CL drawn so as to separate adjacent active regions 46 from each other. Specifically, for example, after the semiconductor laser chip 42 is scribed (damaged), it is cleaved.

  Through the above steps, a semiconductor laser 60 is obtained as shown in FIG. FIG. 9 is a perspective view schematically showing an example of a semiconductor laser. The semiconductor laser 60 shown in FIG. 9 includes a protective film 58ap and a protective film 58bp formed from the protective film 58a and the protective film 58b, respectively, and a clad 48p formed from the clad 48. The laser light L of the semiconductor laser 60 is emitted to the outside through, for example, the protective film 58bp. In this case, the protective film 58bp is a low reflection film, and the protective film 58ap is a high reflection film.

  According to the semiconductor laser manufacturing method of the present embodiment, the formation of the protective film 58a and the protective film 58b can be started after the temperature of the semiconductor laser chip 42 is sufficiently high. When the protective film is formed at a high temperature, an oxide film is formed on the end face of the semiconductor laser chip, so that the current flowing in the reverse direction is expected to increase. However, contrary to this prediction, in this embodiment, the detailed mechanism is unknown, but the semiconductor laser 60 with a small value of the current flowing in the reverse direction can be obtained. As a mechanism, for example, it is conceivable that moisture and deposits attached to the end surface 48a of the semiconductor laser chip 42 are removed. As a result, the ESD tolerance of the semiconductor laser 60 is improved.

  As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Example 1)
The semiconductor laser chip was fixed to a jig, and the jig was attached to a vacuum deposition apparatus. Then, the temperature of the semiconductor laser chip was measured using the thermocouple installed in the jig. When this temperature reached 250 ° C., formation of the Al ₂ O ₃ film was started. In this manner, Al ₂ O ₃ films were formed on both end faces of the semiconductor laser chip. The pressure in the chamber at the time of film formation was 1 × 10 ⁻² Pa. Further, the semiconductor laser chip was scribed using a scribing device, and then cleaved to produce the semiconductor laser of Example 1.

(Example 2)
A semiconductor laser of Example 2 was fabricated in the same manner as in Example 1 except that another type of scribe device was used.

(Comparative Example 1)
A semiconductor laser of Comparative Example 1 was fabricated in the same manner as in Example 2 except that the formation of the Al ₂ O ₃ film was started when the temperature of the semiconductor laser chip reached 230 ° C.

(Evaluation results)
For the semiconductor lasers of Example 1, Example 2, and Comparative Example 1, the relationship (IV characteristics) between the current flowing in the opposite direction and the voltage was calculated.

FIG. 10 is a graph showing the relationship between the current flowing in the reverse direction of the semiconductor laser and the voltage. The horizontal axis of the graph indicates the voltage V _r (V) applied in the reverse direction of the semiconductor laser. The vertical axis of the graph represents current I _r (A) flowing in the reverse direction of the semiconductor laser. A solid line I1 in the graph indicates the IV characteristic of the semiconductor laser of Example 1. A solid line I2 in the graph indicates the IV characteristic of the semiconductor laser of Example 2. A solid line I3 in the graph indicates the IV characteristic of the semiconductor laser of Comparative Example 1. As can be seen from the graph, at the same voltage, the current value in Example 1 and Example 2 is smaller than the current value in Comparative Example 1.

Example 1, to prepare a semiconductor laser of Example 2 and Comparative Example 1 by 10, respectively, to calculate the average value and standard deviation of the current I _r in the case of the voltage V _r for example -2.0 V. The average value of the current _{I r} in the first embodiment is 6.2NA, the standard deviation was 0.8 nA. The average value of the current _{I r} in the second embodiment is 6.7NA, standard deviation was 1.7NA. The average value of the current _{I r} in Comparative Example 1 is 11.1NA, standard deviation was 3.6NA.

It is a figure which shows an example of a vacuum evaporation system typically. It is a top view which shows typically the example of arrangement | positioning of a some heater. It is a perspective view which shows an example of a semiconductor laser chip typically. It is a top view which shows typically an example of the support body with which a semiconductor laser chip is supported. FIG. 5 is an enlarged perspective view of a part of the semiconductor laser chip and the support shown in FIG. 4. It is a graph which shows the relationship between the temperature of a semiconductor laser chip, and the elapsed time after turning on a heater. It is a perspective view which shows typically an example of the semiconductor laser chip in which the protective film was formed on the end surface. It is a perspective view which shows typically an example of the semiconductor laser chip in which the protective film was formed on both the end surfaces. It is a perspective view showing an example of a semiconductor laser typically. It is a graph which shows the relationship (IV characteristic) of the electric current and voltage which flow in the reverse direction of a semiconductor laser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 ... Chamber, 38 ... Thermocouple (temperature sensor), 40 ... Jig (support), 42 ... Semiconductor laser chip, 48a, 48b ... End surface of semiconductor laser chip, 58a, 58b ... Protective film, 60 ... Semiconductor laser, A1 ... Electron beam.

Claims (2)

Attaching a semiconductor laser chip to a support installed in the chamber;
Heating the semiconductor laser chip;
Measuring the temperature of the semiconductor laser chip using a temperature sensor installed on the support;
Forming a protective film on the end face of the semiconductor laser chip using a vacuum deposition method using an electron beam;
Including
A method of manufacturing a semiconductor laser, wherein the formation of the protective film is started when the temperature of the semiconductor laser chip becomes equal to or higher than a predetermined temperature. The method for manufacturing a semiconductor laser according to claim 1, wherein the predetermined temperature is 240 ° C. or higher and 400 ° C. or lower.

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