CN101039014B - Optical semiconductor device - Google Patents

Abstract

The invention discloses an optical semiconductor device. The object is to provide an optical semiconductor device in which residual stress applied to a semiconductor laser chip is applied in a desired direction and within a certain range to improve the performance and reliability of the semiconductor laser and improve mass productivity. The optical semiconductor device 20 of the present invention includes a semiconductor laser chip 21 , a base 23 on which the semiconductor laser chip 21 is mounted, and a solder layer 24 sandwiched between the upper surface of the base 23 and the lower surface of the semiconductor laser chip 21 . The semiconductor laser chip is bent upward into a convex shape.

Description

Optical semiconductor device

technical field

The present invention relates to optical semiconductor devices, and more particularly to high-performance optical semiconductor devices used in rewritable magneto-optical disks, high-speed and large-capacity optical communications, and the like. the

Background technique

In order to meet the advanced information society, high-speed and large-capacity optical communication technology is urgently required in the communication means represented by the network, and more high-speed and large-capacity optical communication technology is urgently required as a device for storing large-capacity information obtained through communication. rewritable optical disk technology. Under such circumstances, optical semiconductor devices such as semiconductor lasers have become the main devices of optical communication technology and optical disk technology, and such optical semiconductor devices are required to have higher performance, higher functions and higher reliability. the

The technique of connecting a semiconductor laser chip to a submount is a main technique for improving the performance of the optical semiconductor device. FIG. 10 shows a configuration example of a conventional optical semiconductor device as an example. the

FIG. 10 is a diagram showing a main part of an optical semiconductor device 10 used as a light source for optical communication. An optical semiconductor device 10 includes a silicon substrate 3 and a distributed feedback semiconductor laser chip 1 . A silicon dioxide film 5 is formed on the upper surface of the silicon substrate 3 , and an electrode pattern 6 is formed on the silicon dioxide film 5 . A flux layer 7 is provided on the electrode pattern 6 , and the semiconductor laser chip 1 is bonded to the electrode pattern 6 through the flux layer 7 . the

A mesa portion 8 is formed at the central portion of the lower surface of the semiconductor laser chip 1 , and a flux layer 7 is applied to the portion other than the mesa portion 8 on the lower surface of the semiconductor laser chip 1 . That is, there is a gap 9 between the mesa portion 8 and the silicon dioxide film 5 . The active layer 2 is present on the mesa 8 , and the active layer 2 is a layer that emits laser light and is provided near the lower surface of the semiconductor laser chip 1 . the

In the optical semiconductor device 10, when the semiconductor laser chip 1 is mounted on the silicon substrate 3, firstly, molten flux is provided on the electrode pattern 6, and secondly, the semiconductor laser chip 1 is provided Put it on the molten flux, and then use the cooling method to let the flux solidify. Here, since the thermal expansion coefficient of the semiconductor laser chip is generally different from that of the silicon substrate, the active layer 2 may be warped or residual stress may be generated in the active layer 2 when the flux is cooled and solidified. the

However, as described above, since there is a gap between the mesa portion 8 and the silicon dioxide film 5 , the active layer 2 is not in contact with the solder layer 7 . Distortion of the active layer 2 can be significantly reduced, or the possibility of residual stress occurring in the active layer 2 can be reduced. As a result, the distributed feedback type optical semiconductor device 10 can perform a single-mode operation at a stable oscillation wavelength (for example, refer to Patent Document 1). the

For example, an optical semiconductor device (not shown) shown in Patent Document 2 has substantially the same configuration as the above-mentioned optical semiconductor device 10 , but has a semiconductor laser chip in which no mesa is formed. At this time, since the coefficient of thermal expansion of the semiconductor laser chip is different from that of the mounting substrate on which the semiconductor laser chip is mounted, residual stress occurs in the active layer of the semiconductor laser chip mounted on the mounting substrate. This residual stress may destabilize the characteristics of the diffraction lattice of the active layer. However, due to the existence of the above-mentioned gap, the instability of the characteristics of the diffraction lattice of the active layer can be reduced, and stable oscillation characteristics can be obtained. the

For example, Patent Document 3 discloses the following structure in order to reduce the above-mentioned residual stress, improve laser characteristics when the semiconductor laser chip is operated at high temperature, and improve the reliability of the semiconductor device. A groove is provided on a portion of the upper surface of the mounting substrate facing the stage portion, and the flux layer is formed in stripes along the groove. Since no flux is provided around the mesa (mesa peripheral portion) in the lower surface of the semiconductor laser chip, the above-mentioned residual stress can be reduced. In addition, a solder layer substantially parallel to the groove is provided on the lower surface of the semiconductor laser chip outside the peripheral portion of the mesa. The melting point of this flux is higher than the melting point of the flux arranged in stripes along the groove. With this structure, the semiconductor laser chip can be electrically connected to the mounting substrate, and at the same time, high heat dissipation of the semiconductor laser device can be ensured. (For example, refer to Patent Document 3)

[Patent Document 1] JP-A-2002-314184 Gazette

[Patent Document 2] Japanese Patent Laid-Open No. 11-87849

[Patent Document 3] JP-A-2003-23200 Gazette

As described above, if a gap is provided between the lower surface of the semiconductor laser chip and the upper surface of the mounting substrate, residual stress in a direction parallel to the resonator end face of the semiconductor laser chip can be reduced. However, in order to achieve higher performance and higher reliability of the optical semiconductor device, it is also desirable to reduce the residual stress in the resonator direction of the semiconductor laser chip. the

With the need for higher output of optical semiconductor devices, the resonator of the semiconductor laser chip must be made longer, and as a result, the length of the semiconductor laser chip becomes longer. When the chip length of the semiconductor laser chip is long, it is necessary to control the residual stress in the resonator direction of the semiconductor laser chip. If the residual stress is not controlled, for example, in a high-output semiconductor laser for a magneto-optical disk, each optical semiconductor device in a lot will exhibit a different polarization ratio, or the operating current value at the initial stage of burn-in will vary. Variations differ among optical semiconductor devices within a lot. In addition, the difference in the polarization ratio within the lot and the difference in the above-mentioned change in the operating current value become large. In addition, the polarization ratio is one of the main characteristics of semiconductor lasers for magneto-optical disks. the

Contents of the invention

The present invention has been made in view of the points described above, and an object of the present invention is to provide an optical semiconductor device capable of reducing residual stress in a resonator direction of a light emitting element. the

The optical semiconductor device of the present invention includes a light-emitting element, a base on which the light-emitting element is installed on the upper surface, and a connection layer sandwiched between the upper surface of the base and the lower surface of the light-emitting element, and the light-emitting element is curved upward to be convex. shape. the

(the effect of the invention)

According to the present invention, the residual stress applied to the semiconductor laser chip can be applied in a desired direction and within a certain range. In this manner, it is possible to provide an optical semiconductor device capable of improving the performance and reliability of the semiconductor laser and improving mass productivity. the

A brief description of the accompanying drawings

Fig. 1 is a schematic structural diagram showing the optical semiconductor device in the first embodiment of the present invention, Fig. 1 (a) is a schematic structural diagram of the mounted state of the optical semiconductor device viewed from above, and Fig. 1 (b) is The sectional view of the IB-IB line shown in Fig. 1(a). the

FIG. 2 is a schematic view showing a mounted state of the semiconductor laser chip of the first embodiment of the present invention. the

FIG. 3 is a phase diagram of a solder composed of gold and tin. the

FIG. 4 is a graph showing the relationship between the bending of the optical semiconductor chip and the operating current value. the

Fig. 5 is a schematic structural view of the solder connection of the optical semiconductor device in the second embodiment of the present invention, and Fig. 5 (a) is a schematic diagram when the solder is unevenly placed on the upper surface of the submount (submount) Structural diagram, Fig. 5(b) is a schematic structural diagram when a recess is provided on the upper surface of the submount. the

6 is a schematic structural diagram showing an optical semiconductor device assembled in a metal package in a second embodiment of the present invention, FIG. 6(a) is a schematic diagram showing an internal main structure, and FIG. 6( b) is a schematic view of the internal main structure viewed from the direction of the arrow shown in FIG. 6( a ). the

Fig. 7 is a schematic structural diagram showing an optical semiconductor device in a third embodiment of the present invention, Fig. 7(a) is a schematic diagram showing an internal main structure, and Fig. 7(b) is a schematic diagram of Fig. 7(a) A schematic cross-sectional view of line VIIB-VIIB shown. the

8 is a schematic structural view showing an optical semiconductor device in a fourth embodiment of the present invention, and FIG. The cross-sectional view of line VIIIB-VIIIB shown in FIG. 8( a ). the

Fig. 9 is a schematic structural view showing the optical semiconductor device in the fifth embodiment of the present invention, Fig. 9 (a) is a schematic structural view of the mounted state of the optical semiconductor device viewed from above, and Fig. 9 (b) is A cross-sectional view of line IXB-IXB shown in FIG. 9( a ). the

FIG. 10 is a schematic configuration diagram of a conventional optical semiconductor device. the

(simple explanation of symbols)

10, 20, 30, 40, 50, 60, 70, 80-optical semiconductor device; 1, 21, 31, 41, 71, 81-semiconductor laser chip (light-emitting element); 3, 23, 33, 43-submount Platform (base platform); 7, 24, 34, 44-solder layer (connection layer); 24b-central portion in the direction of the optical axis; 24a, 24c-ends in the direction of the optical axis; 43b-recess; 75-element body; 76, 86 - protrusions; 122 - active layer. the

Detailed ways

Hereinafter, an optical semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. In addition, the description of the same symbols attached in the drawings may be omitted. the

(first embodiment)

1( a ) is a top view showing the structure of an optical semiconductor device 20 according to the first embodiment, and FIG. 1( b ) is a cross-sectional view taken along line IB-IB shown in FIG. 1( a ). the

The optical semiconductor device 20 includes a semiconductor laser chip (light emitting element) 21, a submount (submount) 23, a solder layer (connection layer) 24, and a metal base 2, as shown in FIG. 1(a). The semiconductor laser chip 21 is bonded on the upper surface 23a of the submount 23 via the flux layer 24, and the submount 23 is separated by The illustrated solder layer is bonded to the upper surface of the metal base 25 . In addition, the submount 23 may be made of silicon, or may be made of a material (silicon carbide, aluminum nitride, etc.) having a thermal expansion coefficient smaller than that of the semiconductor laser chip 21, which is a high heat dissipation material. Moreover, the metal base 25 is a part of the package which is not shown in figure. the

Hereinafter, the semiconductor laser chip 21 and the solder layer 24 will be described in detail. the

In the semiconductor laser chip 21, laser light 22 is emitted from an active layer (not shown). The active layer is provided on the lower surface 21 a of the semiconductor laser chip 21 than the upper surface 27 . Since the laser light 22 is emitted along the arrow shown in FIG. 1( b ), the direction of the arrow is the resonator direction of the semiconductor laser chip 21 and the optical axis direction of light emitted from the optical semiconductor device 20 . Furthermore, among the end faces of the semiconductor laser chip 21, the end faces 21b and 21c extending substantially perpendicular to the optical axis direction serve as reflection mirrors of the resonator. the

And, the semiconductor laser chip 21 is upwardly bent into a convex shape, as shown in FIG. In other words, it bends upwards to draw an arc with a radius of curvature r1 and a central angle θ. When the semiconductor laser chip 21 is bent upwards into a convex shape like this, compared with when the semiconductor laser chip 21 is bent downwards into a convex shape, the initial characteristics can be improved in a plurality of optical semiconductor devices 20 in a lot. (For example, the polarization ratio, the symmetry of the spread angle of the laser light, and the linearity of the current-light output characteristic) are the same as the change of the operating current value in the initial stage of burning. Therefore, high performance and high reliability in the optical semiconductor device 20 can be achieved. the

The solder layer 24 is filled in the gap between the lower surface 21 a of the semiconductor laser chip 21 and the upper surface 23 a of the submount 23 . As mentioned above, since the semiconductor laser chip 21 is curved upward into a convex shape, and the upper surface 23a of the submount 23 is a flat surface, the gaps at both ends of the gap in the optical axis direction are narrower than those at the optical axis. Clearance at the central part in the axial direction. In the solder layer 24, the thickness of the central part 24b located in the optical axis direction is made smaller than the thickness of both end parts 24a and 24c located in the optical axis direction. the

Furthermore, it is preferable that the solder layer 24 contains tin and gold, and that the melting point of the solder layer 24 is close to the temperature at which the semiconductor device is used (hereinafter referred to as "use temperature"). This is because when the semiconductor laser chip 21 is connected to the submount 23 with flux, the semiconductor laser chip 21 is bonded on the flux of melting earlier, and then the flux is allowed to cool and solidify. If the temperature is lower, the stress generated when the flux is solidified can be reduced. And, in order to allow welding The melting point of the flux layer 24 is close to the temperature during use, and it is preferable to allow the flux layer 24 to contain more tin. The reason for this will be described using the phase diagram shown in FIG. 3 . the

Figure 3 shows the phase diagram of tin and gold. The vertical axis of FIG. 3 shows the melting point temperature of the solder, and the horizontal axis of the figure shows the composition ratio of tin to gold. the

When melting and solidifying a solder containing more gold than tin, that is, when melting and solidifying a solder having a composition ratio of tin to gold of less than 50%, the solder is solidified at 280°C to become a gold-rich eutectic solder . the

On the other hand, when melting and solidifying a solder having a composition ratio of tin to gold of about 90%, the solder is solidified at 217°C. As mentioned above, in order to make the melting point of the flux close to the temperature at the time of use, it is preferable to use a flux rich in tin. the

In the solder layer 24, the composition ratio of tin to gold is such that the composition ratio of the central portion 24b in the optical axis direction is larger than the composition ratio of the both end portions 24a, 24c in the optical axis direction. This point will be described again when the method of manufacturing the optical semiconductor device 20 is described. the

The present inventors produced a laser device that emits red laser light, and investigated the initial characteristics of the laser light. Furthermore, the composition of the flux layer 24 was investigated. the

First, the semiconductor laser chip 21 of the manufactured laser device will be described. Its material is AlGaInP material with a wavelength of 650nm, its maximum waveform light output is 300mW, its chip length is 1500μm, its chip width is 300μm, and its chip thickness is 110μm. Also, lots with an average value of Δb1 shown in FIG. 1 of −0.12 μm, lots with an average value of Δb1 shown in FIG. 1 of 0.3 μm, and lots with an average value of Δb1 shown in FIG. 1 of 0.5 μm were prepared. . In addition, initial operating current values of a plurality of laser devices belonging to each lot were investigated. Fig. 4 shows the measurement results. The horizontal axis in FIG. 4 represents the bending amount Δb1, and the vertical axis in the figure represents the operating current value. the

As shown in FIG. 4 , in a lot with an average value of the bending amount Δb1 of −0.12 μm, that is, when the semiconductor laser chip 21 is bent downward in a convex shape, the operating current value greatly differs among optical semiconductor devices. On the other hand, in the lot where the average value of the bending amount Δb1 is 0.3 μm, the operating current value is substantially constant in each of the optical semiconductor devices 20 , 20 , . . . . the

In addition, the initial characteristics of the laser light emitted by the semiconductor laser chip 21 in the lot in which the average value of the bending amount Δb1 was 0.3 μm was investigated. As a result of the investigation, a plurality of optical semiconductor devices 20, 20, ... in the lot showed Roughly the same initial characteristic value, the initial characteristic value in the lot The difference is small. And, the average value of the initial characteristic value presented by a plurality of optical semiconductor devices 20, 20, ... is averaged, and the result of the average value of the calculated initial characteristic value shows that the average value is a more ideal value. Therefore, it is estimated that if the semiconductor If a laser device is manufactured using the laser chip 21, a high-performance and highly reliable laser device can be provided. Therefore, the amount of curvature Δb1 is preferably 0.3 μm, and since the radius of curvature r1 is 900 mm when the amount of curvature Δb1 is 0.3 μm, it is known that the radius of curvature r1 is preferably 900 mm or more. the

In addition, in a lot with an average value of the amount of curvature Δb1 of 0.5 μm, the maximum value of Δb1 is 1.0 μm, and the radius of curvature is 281 mm when Δb1 is 1.0 μm. The radius of curvature is about 900 mm in a lot having an average value of the amount of curvature Δb1 of 0.3 μm. Therefore, it is known that the best semiconductor laser chip 21 is curved upwards into a convex shape, and draws an arc with a radius of curvature of 280 mm or more, and more ideally bends upwards into a convex shape, and draws an arc with a radius of curvature of 900 mm. above the arc. the

Here, the bending amount Δb1 was calculated by measuring and analyzing the light interference band obtained by irradiating the semiconductor laser chip with laser light. Since the measurement limit of the optical interference band of laser light is 0.05 μm, when the semiconductor laser chip 21 with a chip length of 1500 μm is curved upward in a convex shape, the upper limit of the curvature radius is 6000 mm. However, the longer the chip length of the semiconductor laser chip 21 is, the larger the upper limit of the curvature radius is. Therefore, when the semiconductor laser chip 21 having a chip length of 3000 μm is bent upward in a convex shape, the upper limit of the radius of curvature is 22500 mm. the

In addition, when the semiconductor laser chip 21 was cut and the bending amount Δb1 was measured from its cross-sectional shape, the initial characteristic value of the laser light and the operating current at the initial stage of firing could be adjusted in a batch in which the average value of the bending amount Δb1 was 0.02 μm. Value changes are the same. When the amount of curvature Δb1 is 0.02 μm, the upper limit of the radius of curvature of the semiconductor laser chip 21 having a chip length of 3000 μm is 56250 mm. It can be seen from the above that it is preferable that the semiconductor laser chip 21 is curved upwards in a convex shape, and draws an arc with a curvature radius of not less than 280 mm and not more than 56250 mm. the

To sum up, it is preferable that the semiconductor laser chip 21 bends upwards into a convex shape, draws an arc with a radius of curvature between 280mm and 56250mm, and more ideally bends upwards into a convex shape, and draws an arc with a radius of curvature between 280mm and 56250mm. Arc above 280mm and below 22500. the

In addition, the inventors of the present application investigated the solder layer 24 after the above test was completed. As a result of the investigation, the thickness of the solder layer 24 was 4.8 μm at the central portion 24b in the direction of the optical axis, and at Both end portions 24a and 24c in the optical axis direction are 3.8 μm. Furthermore, gold and tin are contained in the solder layer 24 . It can be considered that the gold in the solder layer 24 originates from the melted portion formed in the gold-plated layer of the semiconductor laser chip 21, and the tin in the solder layer 24 originates from the tin solder layer containing tin in order to install the semiconductor laser chip 21. The melted portion of the solder layer on the upper surface 23 a of the submount 23 . the

The inventors of the present invention bent the semiconductor laser chip downward into a convex shape, and investigated the initial characteristics of the laser light emitted from the semiconductor laser chip. As a result, it was found that a plurality of optical semiconductor devices in a lot showed different initial characteristics, and the difference in a lot was large, so it was difficult to mass-produce laser devices. Then, the semiconductor laser chip bent downward into a convex shape was assembled to manufacture a stacked type optical semiconductor device, and the stacked type optical semiconductor device was baked . As a result, the average value of the initial operating current value and The amount of change at which the initial operating current value starts to change is larger than that of a semiconductor laser chip bent upward in a convex shape.

In addition, even if the semiconductor laser chip is bent upward into a convex shape, if the curvature radius r1 is less than 250 mm, a very large stress will be applied to the semiconductor laser chip compared with the case where the curvature radius r1 is greater than 250 mm. , so that the average value of the operating current value is larger. When the average value of the operating current value is large, when the optical semiconductor device is installed in the optical pickup device, the optical semiconductor device will emit more heat, so the temperature of the optical semiconductor device is greatly increased. ideal. Therefore, it is preferable to make the radius r1 of curvature equal to or greater than 250 mm, and to bend the semiconductor laser chip 21 upward into a convex shape. the

When the semiconductor laser chip 21 is mounted on the submount via the solder layer 24 as described above, residual stress is applied to the semiconductor laser chip 21 (especially the active layer) in a certain direction and within a certain range. However, as shown in FIG. 1( b ), when the semiconductor laser chip 21 is bent into a convex shape, the initial characteristic values in the batch can all be approximately the same initial characteristic value, and the initial characteristic value of the firing can be reduced. The change in current value is the same. Although the specific reason is unclear, the inventors of this case think so. That is, this is because when the semiconductor laser chip 21 is bent upward into a convex shape, the portion close to the active layer in the lower surface 21a of the semiconductor laser chip 21 shrinks, so that the gain in the optical axis direction and the like can be suppressed. The reason is different. the

Next, a method of manufacturing the optical semiconductor device 20 according to this embodiment is shown. Using this manufacturing method, the semiconductor laser chip 21 is mounted on the upper surface 23a of the submount 23 with flux. Next, a method of mounting the semiconductor laser chip 21 with flux will be described. the

First, flux is provided on the upper surface 23 a of the submount 23 . the

Next, the submount 23 on which the flux is placed is heated from above and below to melt the flux. Then, the semiconductor laser chip 21 is held by heated vacuum tweezers and pressed against the melted solder. With this method, the semiconductor laser chip 21 can be mounted on the upper surface 23a of the submount 23 with flux. the

Then, stop the heat from below and let the flux solidify. the

At this time, since the lower surface 21a of the semiconductor laser chip 21 is cooled earlier than the upper surface 27, the laser chip is bent upward in a convex shape. Here, it is preferable that the thermal expansion coefficient of the submount 23 is slightly larger than that of the semiconductor laser chip 21 . This is because if the thermal expansion coefficient of the sub-mount 23 is greater than that of the semiconductor laser chip 21, the shrinkage of the sub-mount 23 becomes larger than when the thermal expansion coefficient of the sub-mount 23 is smaller than that of the semiconductor laser chip 21. Therefore, it is possible to suppress the semiconductor laser chip 21 from being bent downward into a convex shape. the

And, since the semiconductor laser chip 21 is bent upward into a convex shape as described above, the gap between the lower surface 21a of the semiconductor laser chip 21 and the upper surface 23a of the submount 23 is the central portion in the optical axis direction. The gap is larger than the gap at both ends in the optical axis direction. Therefore, the melted flux moves from both end portions in the optical axis direction to the center portion in the optical axis direction to fill the gap. At this time, since gold has a higher melting point than tin, tin mainly moves from both end portions in the optical axis direction to the center portion in the optical axis direction. As a result, the ratio of tin to gold is such that the ratio of the central portion 24b in the optical axis direction is higher than the ratio of the both end portions 24a, 24c in the optical axis direction. In addition, the inventors investigated the ratio of tin to gold in the solder layer 24 by X-ray micro analysis (hereinafter referred to as XMA method), and confirmed that the ratio is at the center of the optical axis direction. The ratio of 24b is larger than the ratio of both ends 24a and 24c in the optical axis direction. the

In addition, since the tin in the central portion 24b in the optical axis direction is more than the tin in the both end portions 24a, 24c in the optical axis direction, the melting point of the solder in the central portion 24b in the optical axis direction is lower than that in the optical axis direction both end portions 24a, 24c. The melting point of the flux is 24c. Therefore, when the flux is solidified, the flux at both end portions 24 a and 24 c in the optical axis direction is first solidified, and then the flux at the central portion 24 b in the optical axis direction is solidified. The semiconductor laser chip 21 is bent upward in a convex shape. the

(second embodiment)

FIG. 5 schematically shows how solder is put on the upper surface 33 a of the submount 33 . Fig. 5 (a) schematically shows the figure of an example in the present embodiment, and Fig. 5 (b) schematically shows A diagram of another example in this example. the

In the second embodiment of the present invention, the tin content in the central portion in the optical axis direction can be made higher than in the first embodiment described above. The details are as follows. the

In FIG. 5( a ), although the upper surface 33 a of the submount 33 is flat, the flux placed on the upper surface 33 a of the submount 33 is uneven. Specifically, the flux in the central portion 34a in the optical axis direction of the upper surface 33a of the submount 33 and the flux in the peripheral portions 34b and 34c sandwiching the central portion 34a are more than those in other portions. In this way, tin can be enriched in the central portion 34a in the optical axis direction. the

In FIG. 5( b ), recesses 43 b , 43 b , and 43 b are formed on the upper surface 43 a of the submount 43 . Specifically, recessed portions 43 b , 43 b , 43 b are formed in the center portion in the optical axis direction of the upper surface 43 a of the submount 43 and the peripheral edge portions sandwiching the center portion. When flux is put on such an upper surface 43a to form a uniform flux layer 44, more solder can be placed in the portion where the recesses 43b, 43b, 43b are formed than the portion where the recesses 43b, 43b, 43b are not formed. flux. In this way, the tin in the central portion 44a in the optical axis direction can be increased more than the tin in the both end portions 44b and 44c in the optical axis direction. the

As mentioned above, in Fig. 5(a) and Fig. 5(b), since the semiconductor laser chip can be bent upward into a convex shape, the residual stress applied to the semiconductor laser chip can be applied in a certain direction. And within a certain range. Accordingly, the initial characteristic values of a plurality of optical semiconductor devices in a lot can be made the same, and the change in the operating current value in the initial stage of firing can be made the same. the

Fig. 6 has shown in the structure shown in Fig. 5 (a) after utilizing flux to mount semiconductor laser chip 31, then sub-installation platform 33 is bonded in the structural diagram of the optical semiconductor device 50 that forms in the metal packaging body . Figure 6 (a) is a schematic view showing the internal structure of the optical semiconductor device 50 in a state where the cover (not shown) of the optical semiconductor device 50 is removed, and Figure 6 (b) is a schematic view showing the internal structure of the optical semiconductor device 50 from the 6( a ) is a schematic diagram of the internal structure of the optical semiconductor device 50 viewed from the direction of the arrow. In addition, although the semiconductor laser chip 31 does not bend upward in a convex shape in FIG. 6( b ), it actually bends upward in a convex shape. the

Semiconductor laser chip 31 is mounted on submount 33 in a state of being bent upward in a convex shape, and submount 33 is mounted on metal block 52 with a flux having a melting point lower than that of solder layer 24 . The metal block 52 is integrally formed with the metal package 53 , and the electrode terminals 54 a , 54 b , and 54 c are integrally formed with the metal package 53 . The electrode terminal 54b is electrically connected to the gold The metal package 53 is a ground terminal of the optical semiconductor device 50 . Furthermore, the electrode terminal 54 a is an electrode terminal for injecting a current into the optical semiconductor device 50 , and a positive voltage is applied from the electrode terminal 54 a to the electrode terminal 54 b (ground terminal). The electrode terminal 54 a is connected to the semiconductor laser chip 31 through a conductive wire 55 . the

The present inventors investigated the uniformity of the initial characteristics of the optical semiconductor device 50 shown in FIG. 6 and the change in the operating current value in the initial stage of firing. Specifically, the electrode terminals 54 a and 54 b are electrically connected, and a current is injected into the semiconductor laser chip 31 . The optical semiconductor device 50 outputted laser light 56 having a wavelength of 650 nm and a waveform light output of 250 mW. Since the residual stress applied to the semiconductor laser chip 31 is applied in a certain direction and within a certain range, the multiple semiconductor lasers in the batch exhibit the same initial characteristic value, and the operating current value at the initial stage of burning presents a uniform Variety. the

(third embodiment)

FIG. 7 is a schematic configuration diagram showing the configuration of an optical semiconductor device 60 according to a third embodiment of the present invention. Fig. 7 (a) is a schematic view showing the state after the cover (not shown) mounted on the upper part of the package of the optical semiconductor device 60 is removed, and Fig. 7 (b) is the state shown in Fig. 7 (a). Sectional view of line VIIB-VIIB. the

The optical semiconductor device 60 shown in Figure 7 (a) is such an optical integrated device, comprising: a semiconductor laser chip 21, a light receiving element 62, a processing circuit (not shown) of a light receiving signal, a reflector 63, a diffraction lattice (without Figure), light-receiving element chip 64, package body 65, silicon substrate 66 and electrode terminals 67, 67, . . . In this optical semiconductor device 60 , a light-receiving element chip 64 is provided on a silicon substrate 66 , and a light-receiving element 62 and a signal processing circuit for a light-receiving signal are bonded to the light-receiving element chip 64 with solder. Furthermore, the light receiving element chip 64 is bonded to the package body 65 with a conductive paste. the

The operation of the optical semiconductor device 60 will be described. First, after a current is injected into the electrode terminals 67 , 67 , . . . of the package 65 , the semiconductor laser chip 21 is driven to emit laser light 69 . The laser beam 69 is emitted parallel to the surface of the light receiving element chip 64 (L1 shown in FIG. 7( b ), is reflected at the reflection point 68 of the reflector 63, and is emitted vertically upward (L2 shown in FIG. 7( b ), That is, it is emitted from the optical semiconductor device 60 . The laser light 69 emitted from the optical semiconductor device 60 returns to the optical semiconductor device 60 after reading the signal on the magneto-optical disk, and is branched by a diffraction lattice (not shown) that is bonded to the package top of the package 65. The light receiving element 61 receives it. Light-receiving element 61 pairs of received light signal The signal is amplified and calculated, and the amplified and calculated optical signal is input to the processing circuit of the light signal. the

When the present inventors injected current into the electrode terminals 67 , 67 , . Since the residual stress applied to the semiconductor laser chip 21 is applied in a certain direction and within a certain range, multiple semiconductor lasers in the batch exhibit the same initial characteristic value, and the operating current value in the initial stage of burning presents the same change . the

Although a detailed description of the optical semiconductor device 60 shown in FIG. 7( a ) is omitted, the semiconductor laser chip 21 is curved upward in a convex shape as shown in FIG. 7( b ). In addition, the thickness of the central part 24b in the optical axis direction of the solder layer 24 is greater than the thickness of both end parts 24a and 24c in the optical axis direction, and the central part 24b in the optical axis direction has more tin than the two end parts 24a in the optical axis direction. , 24c tin. the

(fourth embodiment)

FIG. 8 is a structural view showing an optical semiconductor device 70 according to a fourth embodiment of the present invention, FIG. 8( a ) is a top view thereof, and FIG. 8( b ) is VIIIB shown in FIG. 8( a ). - Sectional view of line VIIIB. the

In the optical semiconductor device 70 according to this embodiment, the semiconductor laser chip 71 has an element body 75 and protrusions 76 , 76 . The element body 75 is bent upwards into a convex shape, drawing an arc with a radius of curvature r2 and a central angle θ2, which is the semiconductor laser chip 21 described in the first embodiment above. In addition, the end faces 75b and 75c of the semiconductor laser chip 71 serve as reflection mirrors of the resonator, respectively. the

Each protrusion 76 is provided on the peripheral portion of the upper surface of the element body 75 , and as shown in FIG. In this embodiment, since the laser light 22 is emitted along the longitudinal direction of the sides constituting the upper surface of the element body 75, each protrusion 76 is substantially perpendicular to the optical axis along the sides constituting the upper surface of the element body 75. The direction in which the direction extends. In addition, a part of the upper surface 76 a of each protrusion 76 exists above the most upwardly curved portion of the semiconductor laser chip 21 . the

Furthermore, each protrusion 76 is preferably formed by gold plating, and is preferably made of a material having a thermal conductivity higher than that of the element body. Furthermore, it is preferable to form the length in the left-right direction in FIG. 8 to be 100 μm, the depth in FIG. 8 to be 300 μm, and the thickness to be 5 μm. the

In this embodiment, as in the above-mentioned first embodiment, the average value of the bending amount Δb2 is prepared. The initial operating current of a plurality of optical semiconductor devices belonging to each lot was determined for a lot with a value of -0.12 μm, a lot with an average value of the amount of warpage Δb2 of 0.3 μm, and a lot with an average value of the amount of warpage Δb2 of 0.5 μm. value was investigated. The same results as in the first embodiment described above were obtained. the

And, the optical semiconductor device 70 shown in FIG. 8(a) and FIG. 8(b) was mounted in a metal package, and the device shown in FIG. The variation was investigated, and it turned out that the variation of the initial characteristic value and operating current value was the same within the lot. the

Next, the manufacturing method of the optical semiconductor device 70 of this embodiment is shown. the

First, flux is provided on the upper surface 23 a of the submount 23 . the

Next, for example, a flat collet is brought into contact with the protrusions 76 , 76 of the semiconductor laser chip 71 to sandwich the semiconductor laser chip 71 . the

Next, the flat chuck is heated in a state where the flat chuck is brought into contact with the protrusions 76 , 76 of the semiconductor laser chip 71 . At the same time, the submount 23 is heated from below to heat the entire semiconductor laser chip 71 . Since the flux is melted by this heating, the semiconductor laser chip 71 is pressed against the melted flux. the

Next, the heating of the flat chuck and the heating of the submount 23 from below are stopped, and the flux is solidified. the

Now, the path that the heat of semiconductor laser chip 71 escapes has two, from semiconductor laser chip 71 via solder layer 24, the first path that escapes to sub-installation platform 23; , the second escape route to the flat chuck. Here, since the both end portions in the optical axis direction of the semiconductor laser chip 71 are different from the central portion in the optical axis direction, a part of the semiconductor laser chip 71 is in contact with air, so the cooling rate is fast. Both ends of the semiconductor laser chip 71 in the optical axis direction are cooled earlier than the central portion of the semiconductor laser chip 71 in the optical axis direction. In addition, since the flux shrinks while solidifying, both ends of the semiconductor laser chip 71 in the optical axis direction are stretched by the submount 23 side. It can be considered that the result is that the semiconductor laser chip 71 is bent upward in a convex shape. the

As described above, the phenomenon that the flux solidifies sequentially from both end portions 24 a and 24 c in the optical axis direction toward the central portion 24 b is remarkable when a flux composed of gold and tin is used. In addition, the inventors of the present application analyzed the solder layer 24 by the XMA method, and confirmed that the ratio of tin in the central portion 24b in the optical axis direction is higher than the ratio of tin in the both end portions 24a, 24c in the optical axis direction. . the

(fifth embodiment)

FIG. 9 shows a schematic configuration diagram of an optical semiconductor device 80 according to a fifth embodiment of the present invention. FIG. 9( a ) is a schematic structural view of the optical semiconductor device 80 of this embodiment seen from above, and FIG. 9( b ) is a cross-sectional view along line IXB-IXB shown in FIG. 9( a ). the

In this embodiment, as shown in FIG. 9(b), as in the above-mentioned first embodiment, the semiconductor laser chip 81 is bent upward into a convex shape, specifically, curved upward into a convex shape, as shown in FIG. An arc whose radius of curvature is r3 and center angle is θ3. the

Furthermore, in this embodiment, as shown in FIGS. 9( a ) and 9 ( b ), a semiconductor laser chip 81 has an element body 75 and protrusions 86 , 86 . However, the protruding portions 86, 86 are respectively provided at positions closer to the center of the upper surface of the semiconductor laser chip 81 than in the fourth embodiment described above. Thus, when the main substrate is diced to simultaneously manufacture a plurality of optical semiconductor devices 80, 80, . . . , dicing is easier than in the fourth embodiment described above. the

In addition, as described above, the inventors of the present application also confirmed the performance of the optical semiconductor device 80 according to the present example, and details thereof are omitted here. the

That is, an optical semiconductor device 80 outputting red laser light was produced by using an AlGaInP-based material with a wavelength of 650 nm as the semiconductor laser chip 81, and the relationship between the initial characteristics and the reliability of the optical semiconductor device 80 and the amount of curvature Δb3 was investigated. , substantially the same results as those obtained in the first embodiment above were obtained. the

And, the optical semiconductor device 80 shown in FIG. 9(a) and FIG. 9(b) was mounted in a metal package, and the device shown in FIG. The variation was investigated, and it turned out that the variation of the initial characteristic value and operating current value was the same within the lot. the

(other embodiments)

The first to fifth embodiments described above may also have the following configurations. the

The AlGaAs-based semiconductor laser device with a wavelength of 780nm band and the AlGaInP-based semiconductor laser device with a wavelength of 650nm band have been described as optical semiconductor devices. Blue laser devices and ultraviolet laser devices can be used. Furthermore, a device that emits multi-wavelength laser light such as two-wavelength laser light and three-wavelength laser light can also be used as an optical semiconductor device. the

A semiconductor laser chip can be formed as a single chip, or a plurality of chips can be mixed and mounted together. In addition, a semiconductor laser chip is an example of a light-emitting element, and an end-emitting type can also be used Light-emitting diode chips instead of semiconductor laser chips. the

Each protrusion is made of gold, but it may also be made of a metal or a semiconductor whose thermal conductivity is substantially the same as that of the light-emitting element. In addition, each protrusion may be formed by processing the material of the light emitting element. When a laser chip made of an AlGaInP-based semiconductor having a wavelength of 650 nm is used as the semiconductor laser chip, the submount is made of GaAs. Therefore, a substrate made of GaAs may also be etched to form protrusions. the

(Industrial Utilization Possibility) 

The present invention provides an optical semiconductor device capable of improving the performance and reliability of semiconductor lasers and improving mass productivity by applying residual stress on semiconductor laser chips in a desired direction and within a certain range. And optical disk equipment and systems, etc. are useful. the

Claims (12)

1. An optical semiconductor device, characterized in that: Including: light emitting element, a base, the above-mentioned light-emitting element is mounted on the upper surface, and a connection layer sandwiched between the upper surface of the above-mentioned base and the lower surface of the above-mentioned light-emitting element; The above-mentioned light-emitting element is bent upward into a convex shape, The above connection layer contains gold and tin, The light emitting element emits light propagating substantially parallel to the upper surface of the base; The ratio of tin to gold in the above-mentioned connection layer is that the ratio of the central part of the light emitted by the light-emitting element in the direction of the optical axis is higher than the ratio of the end parts in the direction of the optical axis; In the central portion in the direction of the optical axis, tin exists more than gold. 2. The optical semiconductor device according to claim 1, characterized in that: The above-mentioned light-emitting element is curved such that the radius of curvature is not less than 250 m and not more than 22500 mm. 3. The optical semiconductor device according to claim 1, characterized in that: The content of tin in the connection layer is greater than the content of gold in the connection layer in terms of weight ratio. 4. The optical semiconductor device according to claim 1, wherein the thickness of the connection layer is such that the thickness of the central portion in the optical axis direction of the light emitted by the light emitting element is greater than the thickness of the end portions in the optical axis direction. 5. The optical semiconductor device according to claim 1, characterized in that: A recess is formed at the center of the upper surface of the base; The connection layer is disposed on a part of the upper surface of the base platform where the recess is not formed, and fills the recess; The ratio of tin to gold is such that the ratio inside the concave portion is higher than the ratio of the portion of the upper surface of the base where the concave portion is not formed. 6. The optical semiconductor device according to claim 1, characterized in that: The above-mentioned light-emitting element has a plate-shaped element body bent upward into a convex shape, and a protrusion provided on the peripheral portion of the upper surface of the element body; At least a part of the upper surface of the protrusion is present at a position above the upper surface of the uppermost part of the element body, The above-mentioned element body, viewed from above, is rectangular; The protruding portion extends in a direction substantially perpendicular to an optical axis direction of light emitted from the element body. 7. The optical semiconductor device according to claim 6, characterized in that: The thermal conductivity of the protrusion is higher than the thermal conductivity of the element body. 8. The optical semiconductor device according to claim 1, characterized in that: The above base is a silicon substrate. 9. The optical semiconductor device according to claim 8, characterized in that: At least one of a light-receiving element, a circuit element, and a reflector is mounted on the upper surface of the silicon substrate. 10. The optical semiconductor device according to claim 1, characterized in that: The above-mentioned submount is made of metal or semiconductor whose heat dissipation property is higher than that of the light-emitting element. 11. The optical semiconductor device according to claim 1, characterized in that: An active layer that emits light is provided at a position closer to the lower surface than the upper surface inside the light emitting element. 12. The optical semiconductor device according to claim 1, wherein the light-emitting element is a semiconductor laser chip or an end-emission type light-emitting diode chip.

Images