JP2000183440A - Stem for semiconductor laser element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the stem for a semiconductor laser element suitable for a high output semiconductor laser, having high heat radiating property, high reliability and improved positional accuracy in assembling. SOLUTION: This stem for a semiconductor laser element is provided with a round-shaped base part 11 and a post part 12, having a chip adhering surface 12a where a semiconductor chip is adhered and which is connected to the upper surface of the base part 11. In this case, the base part 11 is formed of iron or an iron base alloy, the post part 12 is formed by copper or a copper base alloy, and the percentage of the contract area between the base part 11 and the post part 12 to the circular area of the base part 11 is set at 7.9% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stem for a semiconductor laser device and a method of manufacturing the same. The present invention relates to an element stem and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIGS.
A plan view and a front view of a stem used for a semiconductor laser device for an optical disk of up to 50 mW are shown. The stem 10 ′ has notches 11 a, 11 a for positioning and a notch 11 b for direction indication, and leads 13, 13. Hole 11 for passing
c, a post portion 12 made of a rectangular parallelepiped joined on a circular base portion 11c having a post portion, and a post vertical surface at the center of the base portion 11 as a chip bonding surface 12a.
The semiconductor laser chip is configured to be bonded to the surface 12a by soldering or the like.

The base portion 11 is generally made of an iron-based alloy (for example, an iron-nickel alloy). Leads 13 extending vertically through the base portion 11 have a low melting point glass in order to maintain insulation and airtightness. 15 and attached
Further, a common lead 14 is welded to the bottom surface of the base portion 11. After the electrodes of the semiconductor laser chip bonded to the chip bonding surface 12a of the post portion 12 are connected to the leads 13 and 13 by wire bonding, the cap with the window is welded to the stem 10 'to assemble the semiconductor laser element. Is completed.

In recent years, visible light red light output has been 3 to 50 m.
As the semiconductor laser element of W, for example, FIG.
The stem shown in the plan view and the front view is used in FIG. In the stem 10 ″, unlike the stem of FIG. 9, the circular base portion 11 and the semicircular post portion 12 are integrally formed of copper, particularly oxygen-free copper having low thermal resistance, and the semiconductor laser chip is Then, it is bonded to the chip bonding surface 12a provided on the side surface where the thickness of the copper plate constituting the post portion 12 appears by soldering or the like.

[0005] The base 11 has no leads, and another stem having leads is attached to the bottom surface of the base 11. For this reason, a substantially semicircular hole 11d for penetrating the lead is formed in the base portion 11, and grooves 12b for the lead are formed on both sides of the chip bonding surface 12a of the post portion 12. .

[0006]

By the way, in the conventional stem 10 'shown in FIG.
Generally, copper, particularly oxygen-free copper having a low thermal resistance, is used, so that the thermal resistance between the semiconductor laser chip and the post part 12 is small, but the contact area between the post part 12 and the base part 11 is small. Is about 1.5 mm × 1.5 mm = 2.25 mm ² , and the area of a circle drawn by the 9 mmφ base portion 11 is about 6 mm.
In addition to only 3.5% of 3.6 mm ² , thermal resistance between the post 12 and the base 11 is large because the base 11 is made of an iron-based alloy. Therefore, there is a problem that an excessive load is required for Peltier temperature control for adjusting the chip temperature in order to release heat generated from the semiconductor laser chip.

Further, in a semiconductor crystal constituting a semiconductor laser chip, crystal defects are easily induced by impact or strain, and when operated for a long time, dislocations generated from these defects reach the active layer. There is a problem that the crystal is deteriorated, the luminous efficiency is remarkably reduced, and the device driving is stopped. In order to avoid this problem, a method of bonding a semiconductor laser chip to the chip bonding surface 12a on the post portion 12 side with a soft solder, for example, indium or the like, is generally widely used. This does not mean that the chip should be fixed by soldering. It does not give an impact to the chip, and the bonding surface on the chip side and the chip bonding surface 12a on the post 12 side.
By maintaining uniform adhesion while maintaining the parallelism, the desired reliability over time can be obtained.

However, in the stem 10 'using the post portion 12 as shown in FIG. 9, prior to bonding the chip to the chip bonding surface 12a on the post portion 12, the chip on the post portion side 12 with respect to the chip-side bonding surface. Adhesive surface 12
When trying to know the parallelism of a with a high degree of accuracy, although it can be confirmed only by this post part 12 itself,
Since the lateral width of the pochip bonding surface 12a is small and a soft indium is adhered thereon, it is extremely difficult to bring a jig into contact with the portion in the element assembling process to perform parallel alignment. Further, for example, if a laser displacement meter is used, parallel alignment can be performed in a non-contact manner, but if this method is attempted, there is a problem that the manufacturing apparatus becomes expensive.

Further, in the conventional stem 10 "shown in FIG. 10, since oxygen-free copper having low thermal resistance is used for the base portion 11 and the post portion 12, heat from the chip can be effectively released. Can be used in the normal infrared region (800 nm
It can be said that the configuration is suitable for a visible red laser diode that generates a large amount of heat as compared with a chip for the vicinity (980 nm). However, even with this stem having good heat dissipation, the following problems occur.

First, as a first problem, the length of the resonator of the chip is limited. For example, in a general broad-area high-power laser, the cavity length is set to 0.1 in order to lower the drive current density per unit light output and to improve the long-term drive reliability of the device.
It is about 7 to 1.5 mm. However, in the stem 10 ", the press process is used in the manufacturing process, so that the thickness of the copper plate is limited to 1.2 to 1.5 mm. Therefore, the dimension of the flat bonding surface 12a for bonding the chip is set. However, the maximum length is about 1.2 mm, and it is not possible to mount a chip having a longer resonator length.Therefore, it is conceivable to increase the thickness of the copper plate. In addition to the necessity of increasing the height, the increase in the amount of deformation of the copper plate causes inconvenience such as an increase in dimensional error (distortion).

As a second problem, when assembling the semiconductor laser into a module, it is difficult to improve the positional accuracy if copper is used as a member constituting the module. That is, when assembling this semiconductor laser device into a module, as shown in FIG. 9, if the base portion 11 is made of an iron alloy harder than copper, copper is used as a member constituting the module. By fitting the semiconductor laser element to the module-constituting copper member, the module can be fixed with good heat dissipation and good positional accuracy.

However, the stem 10 "shown in FIG.
In this case, since the portion of about 9 mmφ serving as the base portion 11 is made of a copper material, it is difficult to improve the positional accuracy with a copper member of the same material. Also, the material of the module constituent copper member is
Although it is possible to change to beryllium copper or the like which is harder than copper, the cost is increased, which is not preferable.

[0013] A third problem is that it is necessary to retrofit a stem with leads. In the case of the stem 10 ′ shown in FIG. 9, the lead 13 can be fixed to the base 11 made of an iron-based alloy with low-melting glass 15 with insulation and airtightness. In the case where is made of copper, since there is no low-melting glass having substantially the same thermal expansion coefficient, a stem having leads must be formed as a separate part and attached to the bottom surface of the base portion 11. For this reason, the number of components increases, and it is necessary to connect the copper member for chip bonding and the stem for lead by welding or the like.
Is disadvantageous in cost as compared with

Further, as a fourth problem, a similar problem occurs in the parallel alignment described for the stem 10 'shown in FIG. If the flat surfaces 12c, 12c on both sides of the grooves 12b, 12b of the post portion 12, the center chip bonding surface 12
a, if these planes 12
Although c and 12c can be used to parallelize the chip bonding surface 12a on the post portion with respect to the bonding surface on the chip side, since the post portion 12 is formed by deforming a copper plate by press working, Due to the accuracy of this processing method, it is difficult to manufacture the flat surfaces 12c, 12c so as to be stably the same as the chip bonding surface 12a. Therefore, as in the case of the stem 10 'shown in FIG. 9, the parallel state of the chip bonding surface 12a on the post portion 12 side with respect to the chip bonding surface can only be confirmed on the chip bonding surface 12a, so that the parallel setting is performed. It is extremely difficult.

In view of such circumstances, the present invention avoids the above-mentioned problems, and can improve heat radiation and reliability, and improve the assembling position accuracy, suitable for a high-power semiconductor laser. The purpose is to provide a stem.

[0016]

SUMMARY OF THE INVENTION The present invention provides a stem for a semiconductor laser device having a circular base portion and a post portion having an adhesive surface to which a semiconductor laser chip is adhered and joined to the upper surface of the base portion. Wherein the ratio of the contact area between the base and the post to the area of the circle defined by the base is 7.9% or more, preferably 10% or more, and more preferably 15% or more. is there.

In this case, it is preferable that the base portion is formed of iron or an iron-based alloy, for example, an iron-nickel alloy, and the post portion is formed of copper or a copper-based alloy, for example, a copper-tungsten alloy. .

It is desirable that the post portion has, on both sides of the chip bonding surface, flat surfaces used for parallelizing the chip bonding surface to the chip when the semiconductor laser chip is bonded to the chip bonding surface. .

Further, the present invention provides a method for manufacturing a stem for a semiconductor laser device having a base portion and a post portion having a chip bonding surface to which a semiconductor laser chip is bonded and bonded to the base portion. When the semiconductor laser chip is bonded to the chip bonding surface, a plane used for parallelizing the chip bonding surface with respect to the chip is collectively formed in a step of processing the chip bonding surface.

[0020]

According to the stem for a semiconductor laser device of the present invention, the ratio of the contact area between the base and the post to the area of the circle defined by the base is increased. The thermal resistance has been greatly reduced, and the heat generated in the high-power semiconductor laser device can be effectively released. Therefore, iron or an iron-based alloy can be used for the base portion, and the semiconductor laser element can be fixed with good heat dissipation and good positional accuracy by using copper for the members constituting the module.

The post portion has, on both sides of the chip bonding surface, planes used for parallelizing the chip bonding surface on the post portion side with the chip side bonding surface when bonding the semiconductor laser chip to the chip bonding surface. Because it is equipped, by pressing each parallelizing jig mechanically against these planes, without touching the chip bonding surface,
The parallel alignment can be performed with high accuracy.

According to the method of manufacturing a stem for a semiconductor laser device of the present invention, when a semiconductor laser chip is bonded, a plane used for parallelizing the chip bonding surface to the chip is collectively used in the step of processing the chip bonding surface. Thus, these planes can be formed accurately and easily.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1A and 1B are a plan view of a stem for a high-power semiconductor laser device according to the present invention and an AA thereof.
FIG. 2 is a sectional view taken along a line, FIG.
1 shows a cross-sectional view along the line BB in FIG.

The stem 10 includes a circular base 11 having a diameter of 9 mmφ, and a semi-cylindrical post 12 joined to the base 11. The base portion 11 is made of iron or an iron-based alloy (for example, iron-nickel alloy), and has a notch 11 for positioning along the both ends of one circular diameter.
a, 11a, a notch 1b for direction indication, and holes 11c, 11c through which two leads 13, 13 are provided. As shown in FIG. 4, the post part 12 is made of copper (particularly oxygen-free copper) or a copper-based alloy (for example, copper alloy).
Tungsten alloy) cylinder is cut in half in the axial direction,
The relief grooves 12b, 12 of the leads 13, 13 are formed on the cut surface.
After forming b, by dividing into desired lengths,
It is manufactured in a semi-cylindrical shape. Therefore, the escape grooves 12b, 1
2b, the chip bonding surface 12a and the escape grooves 12b, 12
Processing to make the outer surfaces 12c, 12c of b outside the same plane included in the same plane can be easily performed with high precision. However, the method of processing the post portion 12 is merely an example, and is not limited to this. In short, the chip bonding surface 12a and the surfaces 12c, 12c on both sides thereof
May be accurately included in the same plane.

Next, the surface of the post portion 12 corresponding to the chord of the semicircle is formed by the positioning notches 11a, 1a of the base portion 11.
It is joined on the base part 11 by silver solder so as to match the diameter passing through 1a.

In this case, in order to prevent the silver solder from flowing onto the chip bonding surface 12a, as is apparent from FIGS. 2 and 3, the base 1 is attached to the base of the chip bonding surface 12a.
It is preferable to form the groove 12d in advance along the joint surface with the groove 1. Then, the common lead 14 is welded to the bottom surface of the base portion 11, and the holes 11 b and 11
Leads 13 and 13 are attached to b using low-melting glass 15 to maintain insulation and airtightness.

As described above, in the stem 10 for a semiconductor laser device of the present embodiment, the semi-cylindrical post portion 12 having a size extending to both outer sides of the lead holes 11b, 11b formed in the base portion 11 is formed. The contact area between the post part 12 and the base part 11 is 1
It becomes 0.9 mm ² approximately, a nearly 5 times the contact area 2.25 mm ² in the stem 10 'shown in FIG. That is,
9mmφ about 17% of the base portion 11 a circle of area of about 63.6 mm ² to draw the the equivalent to (stem in 10 'about 3.5% shown in FIG. 9), using an iron or iron-based alloy base portion 11 However, the thermal resistance between the post portion 12 and the base portion 11 has been greatly reduced, and the heat generated in the high-power semiconductor laser device can be effectively released.

Also, in the case of the stem 10 ″ shown in FIG. 10, since the post portion 12 and the base portion 11 are integrally formed of the same copper material, members of different materials come into contact with each other. Although there is no portion corresponding to the contact area in the sense, the area of the portion corresponding to the contact area between the post portion 12 and the base portion 11 is 5.0 mm ² from the shape thereof. This is twice as large as this, and has a heat radiation performance equal to or higher than that of the stem 10 ″ shown in FIG. 10 made entirely of copper while using iron or an iron-based alloy. In fact, 5 in the 800nm band
When the shift amount of the oscillation peak wavelength with respect to the current of the 0 nm broad area laser device was measured, it was 10 to 12 nm / A for the stem 10 ′ shown in FIG. 9 and 8 to 10 nm / A for the stem 10 ″ shown in FIG. / A, when the stem 10 of the present embodiment is used, 7 to 9 nm / A
And a decrease in thermal resistance was confirmed.

The chip bonding surface 12a of the post 12
The reason for providing the flow stop groove 12d for silver solder at the root of
This is because when the silver solder flows, the flatness of the chip bonding surface 12a is impaired. Further, the semiconductor laser chip is bonded to the chip bonding surface 12a of the post portion 12 by using an indium which is a soft solder with a small distortion applied to the chip. In this case, uniform bonding is impossible due to the repelling of the flow-out portion, and an increase in thermal resistance between the chip and the chip bonding surface 12a and a local distortion due to generation of voids cause deterioration of device characteristics, especially This leads to a decrease in reliability.
It is necessary to bond the chip to the chip bonding surface 12a with good solder wettability. For example, if the solder film thickness to be used is 5 μm, it is necessary to prevent unnecessary distortion from being applied to the semiconductor laser chip. , Chip bonding surface 12a
Has a flatness of at least the thickness of the solder, that is, 5 μm
Must be:

Therefore, as shown in FIGS. 2 and 3,
A groove 12 for stopping the flow of silver solder is provided at the base of the chip bonding surface 12a.
By providing d, the flatness of the chip bonding surface 12a is prevented from lowering. The width and depth of the groove 12d are also related to the amount of silver solder used at the time of joining. However, if the width is too large, the contact area between the post portion 12 and the base portion 11 is reduced. Importantly, its width and depth are about 0.5 mm, preferably about 0.1 mm.

As shown in FIG. 5, with respect to the stem 10 manufactured as described above, the chip bonding surface is held while the chip bonding surface 12a of the post portion 12 is horizontal. The semiconductor laser chip 20 horizontally supported by the jig 22 is bonded (die-bonded) to the semiconductor laser chip 12a using indium solder. In this case, since the surfaces 12c, 12c on both sides of the chip bonding surface 12a are formed by the same cut surface as the chip bonding surface 12a, the surface 1c
2c and 12c are also horizontal, and as shown in FIG.
Is used for parallelizing the chip bonding surface 12a on the post 12 side with respect to the chip side bonding surface.

That is, by mechanically pressing the parallelizing jig 21 against the surfaces 12c, 12c, the parallelizing can be performed with high accuracy without touching the chip bonding surface 12a with solder.

In this case, the post portion 12
When the surfaces 12c, 12c of the post portion 12 are mechanically pressed against the jigs 21, 21 in a state where the chip bonding surface 12a is not horizontal, as shown in FIG.
Since only the jig 21 is in contact with the jig 21, the relatively soft copper post 12 may be deformed, and parallelization may not be performed accurately. As a countermeasure, as shown in FIG. 8, an arc portion of the post 12 has a surface 1 parallel to the chip bonding surface 12a.
2e is formed in advance, and while the surface 12e is kept horizontal, the post portion 12 is pushed upward, so that the surfaces 12c, 12c
Is pressed against the jigs 21 and 21 so that the post 1
2 can be prevented. Thereby, the semiconductor laser chip 20 is attached to the chip bonding surface 12 of the post portion 12.
a can be bonded horizontally.

Further, the chip bonding surface 12 of the post 12
a, the semiconductor laser chip 20 is tilted and touched, the chip 20 rotates, and a rotational shift occurs at the bonding position, and the emitted light is tilted by 1 ° or more with respect to the stem reference plane of the base portion 11 (out of specification). ), The yield was sometimes reduced. However, by providing the surface 12e on the post portion 12 and performing the above-described paralleling method, the defects were drastically reduced, and the yield was greatly improved.

Next, a method for actually manufacturing the stem 10 having the above-described configuration will be described in more detail.

Specific Example 1 (In the case of using indium for bonding the semiconductor laser chip 20) The base portion 11 made of iron or an iron-based alloy is provided with notches 11a, 11a for positioning and a notch 11b for direction indication, and a lead. Holes 11c, 11c through which the holes 13 pass are provided, and are manufactured by punching. The post part 12 is manufactured by cutting a columnar oxygen-free copper into half in the axial direction as shown in FIG. 4 and further cutting the same into a desired length. In this case, before or after the division, the escape grooves 12b,
12b is formed on the cut surface.

Next, the post part 12 is silver-brazed to the base part 11, the common lead 14 is welded to the base part 11, and the lead 1 is inserted into the holes 11 c, 11 c of the base part 11.
3 and 13 are assembled with the base portion 11 by the low-melting glass 15 with insulation and airtightness. Thereafter, for example, nickel plating is performed by a method such as the Watt method, and further, only the leads 13 and 13 to be wire-bonded to the chip 20 are partially plated by electrolytic gold plating to complete the stem 10.

The chip bonding surface 12 of the post 12
In order to prevent a decrease in wettability of the solder, which is likely to occur when an indium of soft solder is used to bond the chip 20 to the chip 20a, and to suppress the generation of whiskers which occur with time, the chip bonding surface 12a of the completed stem 10 On top, a metal film combining nickel only, nickel and platinum, or titanium and platinum or the like is formed to a thickness of about 50 to 500 nm by combining the vacuum evaporation method and the electron beam evaporation method. Then, an indium is adhered by a vacuum evaporation method to a thickness of about 0.5 to 5 μm.

The stem 10 is connected to the semiconductor laser chip 2
As shown in FIG. 6, the semiconductor laser chip 20 is mounted at a predetermined position on the chip bonding surface 12a with a chip bonding surface 12a parallel to the chip 20, as shown in FIG. After being put together, the temperature is raised to melt the solder and then cooled to bond. In order to prevent the oxidation of the solder, it is desirable that the atmosphere at the time of bonding be low in moisture and oxygen.
It is performed in nitrogen mixed with about 2%. Next, wire bonding is performed between the chip 20 and the leads 13 and 13, and the cap with a window is welded to the base portion 11 in dry nitrogen to complete the semiconductor laser device.

Example 2 (When Gold-tin Alloy Solder is Used for Bonding Semiconductor Laser Chip 20) The base 11 is made of the same material and method as in Example 1, but the post 12 has a thermal expansion closer to that of GaAs. It is made of a copper-tungsten alloy whose composition is adjusted to have a coefficient, and is manufactured by the method shown in FIG. Then, specific example 1
Similarly, the post part 12 is silver brazed to the base part 11, the common lead 14 is welded to the base part 11, and the leads 13, 13 are connected to the holes 11 c, 11 c of the base part 11 by the low melting glass 15. The base part 11 is assembled with insulation and airtightness. Thereafter, for example, nickel plating is performed by a method such as the Watt method, and further, the leads 13 to be wire-bonded to the chip 20 are formed.
Only 13 is partially plated by electrolytic gold plating,
The stem 10 is completed.

In the case of this example, since the melting point of the gold-tin alloy is high, in order to prevent the solder material from breaking through the nickel barrier layer and being sucked into the post portion 12, nickel, platinum, gold or titanium, platinum, gold or A metal film composed of a combination of molybdenum, platinum, gold, etc. is applied to the chip bonding surface 12a for about 50
It is formed to a thickness of about 500 nm, and further, gold tin is deposited thereon to a thickness of about 0.5 to 5 μm while adjusting it to a eutectic composition by a vacuum evaporation method. The later steps are
This is the same as the specific example 1.

[Brief description of the drawings]

FIG. 1 is a plan view of a stem for a high-power semiconductor laser device according to the present invention and a cross-sectional view thereof along line AA.

FIG. 2 is a perspective view without the lead.

FIG. 3 is a sectional view taken along the line BB in FIG.

FIG. 4 is an explanatory view showing an example of a method for manufacturing a post portion.

FIG. 5 is a diagram showing a state in which a semiconductor laser chip is bonded to a post part.

FIG. 6 is a diagram showing a state where the chip bonding surface of the stem is kept parallel to the chip by a paralleling jig when the semiconductor laser chip is bonded to the post part.

FIG. 7 is a view showing a state in which the post portion is inclined and abutted against the paralleling jig when the semiconductor laser chip is bonded to the post portion.

FIG. 8 is a view showing a state in which the post portion is correctly abutted on the paralleling jig when the semiconductor laser chip is bonded to the post portion, since the post portion has a surface parallel to the chip bonding surface.

FIG. 9 is a plan view and a front view of a conventional stem for a semiconductor laser device.

FIG. 10 is a plan view and a front view of a conventional stem for a semiconductor laser device.

[Explanation of symbols]

 10, 10 ', 10 "stem 11 base portion 12 post portion 12a chip bonding surface of stem portion 12c surface included in the same plane as chip bonding surface 13 lead, 14 20 semiconductor laser chip 21 parallel setting jig

Claims (6)

[Claims] 1. A semiconductor laser device stem having a circular base portion and a post portion having a chip bonding surface to which a semiconductor laser chip is bonded and bonded to an upper surface of the base portion, wherein the base portion is drawn. A stem for a semiconductor laser device, wherein a ratio of a contact area between the base portion and the post portion to an area of a circle is 7.9% or more. 2. The stem for a semiconductor laser device according to claim 1, wherein the ratio is 10% or more. 3. The stem for a semiconductor laser device according to claim 1, wherein the ratio is 15% or more. 4. The method according to claim 1, wherein said base portion is formed of iron or an iron-based alloy, and said post portion is formed of copper or a copper-based alloy.
4. The semiconductor laser stem according to any one of the above. 5. The post portion has, on both sides of the chip bonding surface, flat surfaces used for parallelizing the chip bonding surface to the chip when the semiconductor laser chip is bonded to the chip bonding surface. The stem for a semiconductor laser device according to any one of claims 1 to 4, wherein: 6. A method of manufacturing a stem for a semiconductor laser device having a base portion and a post portion having a chip bonding surface to which a semiconductor laser chip is bonded and bonded to the base portion, wherein the chip bonding of the post portion is performed. A step of forming a plane used for parallelizing the chip bonding surface to the chip at the time of bonding the semiconductor laser chip to a surface in a step of processing the chip bonding surface; Manufacturing method.