JPH0846289A - Manufacturing method of semiconductor laser - Google Patents

Abstract

PURPOSE:To manufacture a high reliable semiconductor laser by causing no damage at all to an ohmic contact region in the bonding step. CONSTITUTION:The first semiconductor clad layer 23, a semiconductor active layer 24, the second semiconductor clad layer 25 etc. are laminated on a semiconductor substrate 21 furthermore, an insulating film 27 having a striped aperture part 270 in width exceeding 100mum is formed to make an ohmic contact with an upper electrode 28 for the constitution of the title semiconductor laser element 10. Next, this semiconductor laser element 10 is provided on a heat sink 40 so that the laser element 10 may be pressurized from the region 100 out of the ohmic contact region 280 to be die-bonded for making the semiconductor element 10 effect the junction with the heat sink 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser,
In particular, it is suitable as a high-power semiconductor laser for distance measurement that constitutes the eyes of a robot or a laser radar system.

[0002]

2. Description of the Related Art In the case of a laser radar system in which a semiconductor laser is used to detect an object 100 m away, the semiconductor laser is required to have a large output of several tens W in pulse driving. The structure of this high power semiconductor laser is shown in FIG.

An n-GaAs layer 22 and an n-Al _X Ga _1-X As clad layer 23 are laminated on an n-GaAs substrate 21, and a GaAs active layer 24 and a p-Al _X Ga _1-X layer are formed thereon.
An As clad layer 25 and a p-GaAs layer 26 are laminated. Further, an insulating film 27 made of SiO ₂ is formed, a window (opening) 270 is formed in the insulating film 27, and a p-type electrode 28 made of Cr / Au is formed thereon. The p-type electrode 28 and the p-GaAs layer 2
Ohmic contact with 6 is made to form an ohmic contact region 280 (which coincides with the window portion 270).

Here, the width of the window portion 270 is the stripe width, and the light emitting region 241 in the active layer 24 matches the stripe width. High power semiconductor lasers have a stripe width of at least 100μ in order to obtain an output of several tens of W class.
m (400 μm in the case shown in FIG. 9) or more is required. In contrast to such a large output semiconductor laser, there is a small output semiconductor laser that obtains an output in the tens of mW class with a driving current of about tens of mA. However, since the stripe width of this one is several μm (for example, 5 μm), Stripe width is 1
A high-power semiconductor laser is defined by having a thickness of 00 μm or more.

The semiconductor laser device 1 thus constructed
0 is fixed to the heat sink 40 made of Cu because the inside of the element generates heat during light emission. Therefore, the n-type electrode 29 and the Au / Sn solder layer 30 are formed on the back surface of the n-GaAs substrate 21. That is, while the solder layer 30 is being heated, the die-bonding position 50 is set at the substantially central portion of the element, and the bonding tool 51 is used.
The pressure is applied at a pressure of about kg / cm ² , and die bonding is performed to fix the heat sink 40.

After the die bonding as described above, a bonding wire made of Au is pressed while applying ultrasonic vibration to bond it with the p-type electrode 28 which is the upper electrode.

[0007]

However, as the injection current to the high-power semiconductor laser thus constructed is increased to increase the optical output, the device life (reliability) is increased.
Is reduced. This is because the stress applied from the outside by die bonding or wire bonding causes damage inside the crystal to generate a crystal defect, and the defect grows as the optical output increases.

As described above, the major factor that causes the long-term reliability of the device to be lost by applying pressure to the device by die bonding or wire bonding is deterioration of the crystal layer including the ohmic contact region 280. This is because if the interface between the semiconductor forming the ohmic contact and the electrode metal is damaged, it becomes difficult for a current to flow there, and as a result, a non-uniform current flow occurs in the light emitting region 241. Further, since the active layer 24 forming the light emitting region 241 is formed several microns from the upper part of the device, if the pressure applied by die bonding or wire bonding is large, crystal defects also occur in the active layer 24. In such a case, as shown in FIG. 10, a region 24a in the active layer 24 where no light is emitted occurs. When a current of several tens of amperes is instantaneously passed through the element like a semiconductor laser, such non-uniform current flow particularly greatly affects the reliability of the element.

Then, in die bonding, a solution to such a problem is disclosed in JP-A-53-14469.
4 and JP-A-55-6877. Each of these has an element structure in which a light emitting region does not fall within a region sandwiched by two surfaces, a slip plane (111) plane with respect to the crystal plane (100) plane and a plane symmetrical to this, with the bonding position as the apex. Alternatively, the device structure has a groove that holds the slip surface.

However, in all of the above publications, the substrate side (n-GaAs substrate 21 side in FIG. 9) is used.
The bonding pressure is applied to the substrate side with the side facing up. In a semiconductor laser such as a high-power semiconductor laser having a stripe width of at least 100 μm or more, when the substrate side is faced up and the light emitting region side is solder-bonded as in the above publication, a Ga forming a heat sink and a semiconductor laser
Due to the difference in thermal expansion between materials such as As, stress is applied to the active layer, and the reliability of the device is reduced. Therefore, in order to obtain reliability, it is desirable to mount the substrate with the light emitting region side facing up and the substrate side as the joint surface with the heat sink.

Further, in wire bonding, as shown in FIG. 11, solder pellets 80 are provided at the wire bonding locations so as not to apply mechanical shock to the element.
After that, the pellet is heated to make the solder in a semi-molten state, and the wire 70 is bonded thereon. However, if the above-mentioned method is adopted, since the solder is in a semi-molten state during wire bonding, ultrasonic vibration may not be applied to the solder well, and the solder may drip to the active layer 24. There is a nature. In addition, solder pellets of several tens of microns must be placed on the surface of the electrode 28, which causes a problem of extremely poor mass productivity.

The present invention has been made in view of the above problems, and provides a novel method for manufacturing a semiconductor laser which does not cause the above-mentioned element defect due to stress during die bonding or wire bonding in a high power semiconductor laser. The purpose is to do.

[0013]

In order to achieve the above-mentioned object, the present invention provides a semiconductor substrate (21) having at least a first semiconductor cladding layer (23) and a semiconductor active layer. Semiconductor laser component (22-2) having a layer (24) and a second semiconductor cladding layer (25)
6) is laminated, and has a width of 100 μm on the upper surface.
An insulating film (27) having the above stripe-shaped opening (270) is formed, and an upper electrode (28) is formed in the opening (270) and is the uppermost layer (26) of the semiconductor laser component.
A step of preparing a semiconductor laser device (10) formed so as to make ohmic contact with the semiconductor laser device, a step of installing the semiconductor laser device (10) on a pedestal (40), and the upper electrode (28) when viewed from the upper surface. ) Is deviated from the region (280) in ohmic contact, and pressure is applied from the upper surface to die-bond the semiconductor laser element (10) onto the pedestal (40). There is.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the step of die bonding is a step of pressurizing from above the insulating film (27). In the invention described in claim 3, claim 1
In the invention described in (1), the semiconductor laser component (2
2 to 26), at least the semiconductor active layer (24)
The component parts (23 to 26) that are located on the upper side of the base plate are formed in a mesa shape, and the flat part (1) is formed on the upper part of the remaining component parts (22).
01) is formed, and the die bonding step is a step of applying pressure from above the flat portion (101).

According to the fourth aspect of the present invention, at least the first semiconductor clad layer (23), the semiconductor active layer (24) and the second semiconductor clad layer (25) are provided on the semiconductor substrate (21). Semiconductor laser components (22-2
6) is laminated, and has a width of 100 μm on the upper surface.
An insulating film (27) having the above stripe-shaped opening (270) is formed, and an upper electrode (28) is formed in the opening (270) and is the uppermost layer (26) of the semiconductor laser component.
A step of preparing a semiconductor laser device (10) formed so as to make ohmic contact with the semiconductor laser device, a step of installing the semiconductor laser device (10) on a pedestal (40), and a step of applying the semiconductor laser device (10) on the insulating film (27). A pressure dispersion plate (60, 61) is installed, and pressure is applied from above the pressure dispersion plate (60, 61),
And a step of die-bonding the semiconductor laser element (10) on the pedestal (40).

According to a fifth aspect of the invention, in the invention of the fourth aspect, the step of die bonding comprises:
The pressure distribution plate (61) is attached to the upper surface of the pressure distribution plate (61) and the upper electrode (2).
8) a step of fixing the semiconductor laser element (10) to the semiconductor laser element (10) in an electrically connected state, and a step of wire bonding to the upper surface of the pressure dispersion plate (61) after the die bonding. It is characterized by having.

The invention according to claim 6 is characterized in that, in the invention according to claim 4, the pressure dispersion plate (60) has a plurality of heat dissipation grooves formed on the surface for wire bonding. There is. In the invention according to claim 7, a semiconductor laser structure having at least a first semiconductor clad layer (23), a semiconductor active layer (24), and a second semiconductor clad layer (25) on a semiconductor substrate (21). Stacking the elements (22-26), and component parts (23-26) of the semiconductor laser components (22-26) above at least the semiconductor active layer (24).
And forming a flat portion (101) on top of the remaining component parts (22), and forming a stripe-shaped opening (width 100 μm or more) on the upper surface of the mesa. 270) and forming an insulating film (27) on the upper surface of the semiconductor laser component (22-26), and on the insulating film (27) and the opening (270).
An upper electrode (28) is formed on the upper portion and the opening (270) is formed.
Ohmic-connecting the upper electrode (28) formed on the upper surface (26) of the semiconductor laser component, and the upper electrode (28) formed on the insulating film (27) in the flat portion (101). ) And wire bonding step.

The reference numerals in parentheses of the above means indicate the correspondence with the concrete means described in the embodiments described later.

[0019]

In the invention described in claim 1,
The semiconductor laser device is placed on a pedestal, and when viewed from the upper surface, at a position outside the region where the upper electrode is in ohmic contact, pressure is applied from the upper surface for die bonding. Therefore, since the ohmic contact region is not damaged, a non-uniform current flow does not occur in the active layer, and a highly reliable semiconductor laser can be obtained.

The die bonding can be performed by applying pressure from above the insulating film formed on the upper surface of the semiconductor laser device as described in claim 2. Further, the die bonding can be performed by applying pressure from above the flat portion formed on the semiconductor laser element formed on the mesa, as in the invention according to the third aspect.

According to another aspect of the present invention, the semiconductor laser device is installed on the pedestal, and the pressure dispersion plate is installed on the insulating film formed on the upper surface of the semiconductor laser device. Pressure is applied from above to perform die bonding. Therefore, the pressure at the time of die bonding is dispersed by the pressure distribution plate, so that the ohmic contact region is not damaged and a highly reliable semiconductor laser can be obtained.

According to a fifth aspect of the invention, the pressure dispersion plate is fixedly installed on the semiconductor laser device in a state where the upper surface of the pressure dispersion plate is electrically connected to the upper electrode, and after the die bonding, the pressure dispersion plate. Wire bonding is performed on the upper surface. Therefore, wire bonding can be performed by using the pressure distribution plate used for die bonding as it is.

Further, as in the invention described in claim 6, by forming a plurality of heat dissipation grooves on the wire bonding surface of the pressure distribution plate, heat dissipation characteristics can be improved. In the invention of claim 7,
Wire bonding is performed on the upper electrode on the flat portion formed on the semiconductor laser element formed on the mesa.

Therefore, since wire bonding is performed at a position away from the ohmic contact region, a highly reliable semiconductor laser can be obtained without damaging the ohmic contact region.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows Ga having an electrode stripe structure.
_{As-Al X Ga 1-X} As double hetero shows a perspective view of a junction type semiconductor laser, part of the same reference numerals as in FIG. 9 shows the same configuration as it.

This semiconductor laser is manufactured as follows.
Is done. First, on the n-GaAs substrate 21, n-GaA
s layer 22, n-Al_XGa_1-XAs clad layer 23
GaAs active layer 24, p-Al_XGa
_1-XAs clad layer 25, p-GaAs layer (coordinate with the electrode
Contact layer 26 in sequence to MOCVD (Metal Organic
Laminate by the Chemical Vapor Deposition method. Well
Moreover, SiO is formed on the upper surface of the p-GaAs layer 26.₂ Or Si
₃N_FourThe insulating film 27 made of is formed by the plasma CVD method.
A film is formed and a window is opened by etching to form a window portion 270.
It Then, on the insulating film 27, a p-type film made of Cr / Au is formed.
The electrode 28 is formed by an electron beam evaporation method, and ohmic
A contact region 280 is formed.

Furthermore, A is formed on the back surface of the n-GaAs substrate 21.
An n-type electrode 29 made of uGe / Ni / Au is formed by an electron beam evaporation method, and heat treatment is performed to make ohmic contact. In any case, the above ohmic contact can be obtained by heat treatment at about 360 ° C. Then, the Au / Sn solder layer 30 is formed by the electron beam evaporation method. Finally, the end face is cleaved to form the semiconductor laser device 10.

This semiconductor laser device 10 is transported onto the heat sink 40 and bonded using vacuum tweezers. The heat sink 40 as this pedestal is made of Cu, Fe, or the like, and the surface thereof is provided with a metal having a high conductivity such as gold by plating, vapor deposition, sputtering, or the like. The semiconductor laser element 10 and the heat sink 40 are joined to each other by heating up to about 300 ° C. with a heater under a heat sink (not shown) to melt the Au / Sn solder layer 30 and pressurizing it with a bonding tool 51.

In the present embodiment, the place 50 to be die-bonded by the bonding tool 51 is set on the upper portion 10 of the insulating film 27 other than the ohmic contact region 280.
It is set to 0. The bonding tool 51 is made of a ceramic such as Al ₂ O ₃ or a super steel alloy, and the pressing portion of the bonding tool 51 has a diameter of 100 μm.
And a pressure of about 200 kg / cm ² per unit area is applied.

Also for the wire bonding performed after this die bonding, the ohmic contact region 280 is used.
Other than the above, it is performed on the upper portion 100 of the insulating film 27 to prevent damage to the ohmic contact region 280. The vertical and horizontal dimensions of the semiconductor laser device 10 are 50
The thickness was 0 μm × 600 μm, and the thickness of the device was 100 μm.

FIG. 2 shows the life test results when the semiconductor laser manufactured by this method was driven at room temperature with a driving current of 20 A (optical output of 20 W) and a driving cycle of 10 KHz and an emission width of 50 nsec. As shown in FIG. 2, according to this embodiment, since the ohmic contact region 280 is not damaged, higher reliability can be obtained as compared with the conventional joining method.

The pressure applied by the bonding tool 51 may be applied to the upper portion 100 of the insulating film 27 at two or more places at once. (Second Embodiment) In this second embodiment, as shown in FIG. 3, the semiconductor laser device 10 shown in FIG. 1 is configured so that pressure is applied by a bonding tool 51 via a pressure plate dispersion plate 60. It was done. The pressure dispersion plate 60 is
This is a GaAs substrate having a plate thickness of 100 μm.

The pressure plate dispersion plate 60 is removed after the die bonding, and the upper portion 1 of the insulating film 27 other than the ohmic contact region 280 is removed as in the first embodiment.
Wire bonding is performed at 00. Also in this embodiment, not only the ohmic contact region 280 is not damaged, but also the light emitting region 241 is not stressed at all, so that extremely high reliability can be obtained as shown in FIG.

The material of the pressure dispersion plate 60 is GaAs.
Besides, use Si substrate, ceramic plate, metal plate, etc.
You may Especially good thermal conductivity and thermal expansion coefficient to GaAs
Materials such as close ones are preferred. (Third Embodiment) In the third embodiment, as shown in FIG.
Bond the wire 70 on the pressure distribution plate 61.
It is a scam. The pressure dispersion plate 61 has a specific resistance of 4
× 10 ^-3A low resistance Si substrate of Ωcm is used.
Further, Au vapor is vapor-deposited on the upper surface and the lower surface of the pressure dispersion plate 61.
A deposition film 62 is formed, and Au / Sn is further formed on the lower surface.
The solder layer 63 is formed.

In this embodiment, the semiconductor laser device 10 is installed at a predetermined position of the heat sink 40, and the pressure dispersion plate 61 is installed on the semiconductor laser device 10. After that, the Au / Sn solder layers 30 and 63 are heated to about 300 ° C. by a heater (not shown) under the heat sink 40 to melt the semiconductor laser 10 and the heat sink 40.
Also, the semiconductor laser device 10 and the pressure dispersion plate 61 are joined together.

Then, similarly to the second embodiment, the pressure dispersion plate 6
1 is used for die bonding, and then the pressure dispersion plate 6
A wire 70 made of Au and having a diameter of 30 μm is wire-bonded on the surface 0. FIG. 5 is a sectional view of FIG. Since the Au / Sn solder layer 63 has poor wettability with the insulating film 27 made of SiO ₂ or Si ₃ N ₄ , when the solder 63 is pressed while being heated, the solder 63 flows into the groove of the stripe,
The groove is completely filled.

In the semiconductor laser manufactured according to this embodiment, the pressure applied to the element can be dispersed by the pressure distribution plate 61, and the light emitting region 241 is not stressed at all. Therefore, during wire bonding and die bonding, the crystal layer including the ohmic contact region 280 and the active layer 24 including the light emitting region 241 are not damaged, and as shown in FIG. Sex is obtained.

The light emitting region 241 and the pressure distribution plate 61
Is very close to several microns, so the pressure distribution plate 6
If a material having a higher thermal conductivity than GaAs such as Si is used for 1, the heat generated in the light emitting region 241 at the time of driving the element can be dissipated from the pressure distribution plate 61, so that a semiconductor device with higher reliability can be obtained. Obtainable. As the material of the pressure distribution plate 61, the coefficient of thermal expansion is close to that of GaAs,
Further high thermal conductivity such as AlN, SiC, c
Ceramics such as BN and metals such as Mo, CuW and Kovar may be used. When a material having poor electric conductivity is used, if the Au vapor deposition film 62 is formed on the entire surface of the pressure dispersion plate 61, a current flows through the vapor deposition film 62, so that the electric resistance of the pressure dispersion plate 61 is not a problem.

Further, as shown in FIG. 6, the upper surface of the pressure distribution plate 61 may be formed in a concavo-convex shape to form a plurality of heat dissipation grooves. Such an uneven shape can be formed by photoetching the upper surface of the Si pressure distribution plate 61. By increasing the surface area of the pressure distribution plate 61 in this way, heat dissipation is further improved and extremely high reliability can be obtained. In the Fourth Embodiment The fourth embodiment, as shown in FIG. _{7, n-Al X Ga 1} -X As cladding layer 23, Ga
As active layer _{24, p-Al X Ga 1} -X As cladding layer 2
5, the p-GaAs layer 26 is laminated in a mesa shape.

In order to have such a structure, n-GaAs
After stacking the substrate 21 to the p-GaAs layer 26,
The mesa portion is formed by etching, and the n-GaAs layer 2
An insulating film 27 and a p-type electrode 28 are formed on the flat portion of 2 and the upper surface of the mesa. In this embodiment, the location 50 to which the pressure is applied by the bonding tool 51 is the flat portion 101 outside the mesa shape.

The wire bonding performed after this die bonding is performed at the bonding position 52 on the flat portion 101 outside the mesa shape, as shown in FIG. Also in this embodiment, not only the ohmic contact region 280 is not damaged, but also the light emitting region 2 is not damaged.
Since 41 is not stressed at all, extremely high reliability can be obtained as shown in FIG.

Regarding wire bonding, except for the flat portion 101, the insulating film 27 is used as in the first embodiment.
It may be performed in the upper part 100 of the. Other Embodiments The pedestal on which the semiconductor laser device 10 is mounted may be another semiconductor substrate or circuit board other than the heat sink 40.

Before mounting the semiconductor laser device 10, a submount may be mounted with Si, Ge, diamond or the like having a conductive material and a solder layer on the surface. Also,
In the above embodiment, the stripe type semiconductor laser made of AlGaAs material is used, but a semiconductor laser using other III-V group compound material may be used. Further, the stripe width may be any value other than 400 μm as long as it is 100 μm or more. Further, it may be used for a direct current (CW) semiconductor laser other than the pulse driven semiconductor laser.

Further, the solder material is not limited to Au / Sn, but may be Au / Si, Sn / Pb, In or the like.

[Brief description of drawings]

FIG. 1 is a perspective view of a semiconductor laser showing a first embodiment of the present invention.

FIG. 2 is a characteristic diagram illustrating effects of the first to fourth examples.

FIG. 3 is a perspective view of a semiconductor laser showing a second embodiment of the present invention.

FIG. 4 is a perspective view of a semiconductor laser showing a third embodiment of the present invention.

5 is a partial cross-sectional view of the semiconductor laser device in FIG.

FIG. 6 is a perspective view showing a modification of the third embodiment.

FIG. 7 is a perspective view of a semiconductor laser showing a fourth embodiment of the present invention.

FIG. 8 is a perspective view showing a state in which wire bonding is performed on the one shown in FIG.

FIG. 9 is a perspective view showing a configuration of a conventional semiconductor laser.

FIG. 10 is an explanatory diagram illustrating a conventional problem.

FIG. 11 is a diagram showing a conventional method for performing wire bonding.

[Explanation of symbols]

10 semiconductor laser device 21 n-GaAs substrate 22 n-GaAs layer 23 n-Al _X Ga _1-X As clad layer 24 GaAs active layer 25 p-Al _X Ga _1-X As clad layer 26 p-GaAs layer 27 insulating film 28 p-type electrode 280 ohmic contact region 40 heat sink 51 bonding tool 70 bonding wire

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriyuki Matsushita 1-1, Showa-cho, Kariya city, Aichi prefecture

Claims (7)

[Claims] 1. A semiconductor laser component having at least a first semiconductor clad layer, a semiconductor active layer, and a second semiconductor clad layer laminated on a semiconductor substrate, the upper surface of which has a width of 100 μm or more. A step of preparing a semiconductor laser device in which an insulating film having a stripe-shaped opening is formed, and an upper electrode is formed in the opening so as to make ohmic contact with the uppermost layer of the semiconductor laser component; A step of placing the element on a pedestal, and a step of pressing from the upper surface at a position outside the region where the upper electrode is in ohmic contact when viewed from the upper surface, and die-bonding the semiconductor laser element on the pedestal A method of manufacturing a semiconductor laser, comprising: 2. The method of manufacturing a semiconductor laser according to claim 1, wherein the step of die bonding is a step of applying pressure from above the insulating film. 3. A step of forming at least a component portion of the semiconductor laser component above the semiconductor active layer in a mesa shape, and forming a flat portion on an upper portion of the remaining component portion. The method of manufacturing a semiconductor laser according to claim 1, wherein the step of die-bonding is a step of pressing from above the flat portion. 4. A semiconductor laser component having at least a first semiconductor clad layer, a semiconductor active layer, and a second semiconductor clad layer is laminated on a semiconductor substrate, and has a width of 100 μm or more on an upper surface. A step of preparing a semiconductor laser device in which an insulating film having a stripe-shaped opening is formed, and an upper electrode is formed in the opening so as to make ohmic contact with the uppermost layer of the semiconductor laser component; A step of installing the element on a pedestal, and a step of installing a pressure dispersion plate on the insulating film, applying pressure from the pressure dispersion plate, and die-bonding the semiconductor laser element on the pedestal. A method for manufacturing a semiconductor laser, which comprises: 5. The die bonding step includes a step of fixedly installing the pressure dispersion plate on the semiconductor laser device in a state where an upper surface of the pressure distribution plate and the upper electrode are electrically connected to each other. The method of manufacturing a semiconductor laser according to claim 4, further comprising a step of wire-bonding to the upper surface of the pressure dispersion plate after the bonding. 6. The method of manufacturing a semiconductor laser according to claim 5, wherein the pressure dispersion plate has a plurality of heat dissipation grooves formed on a surface to which the wire is bonded. 7. A step of laminating a semiconductor laser component having at least a first semiconductor clad layer, a semiconductor active layer, and a second semiconductor clad layer on a semiconductor substrate, and at least the semiconductor laser component among the semiconductor laser components. A step of forming a component portion above the active layer in a mesa shape, and forming a flat portion on an upper portion of the remaining component portion; and a stripe-shaped portion having a width of 100 μm or more on the upper surface formed in the mesa shape. Forming an insulating film on the upper surface of the semiconductor laser component having an opening, and forming an upper electrode on the insulating film and on the opening,
A step of ohmic-connecting the upper electrode formed in the opening and the uppermost layer of the semiconductor laser component; and a step of wire-bonding the upper electrode formed on the insulating film in the flat portion. A method for manufacturing a characteristic semiconductor laser.