JPH0553315B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat sink for mounting a semiconductor laser array used in optical communication devices, optical information processing devices, and the like.

[Conventional technology]

When independently driving a large number of semiconductor lasers arranged in an array, a single optical disk is used as a light source to introduce light as a signal carrier into an array of optical waveguide wiring formed on a substrate. It is widely used as a light source for multi-beam optical heads that have multiple optical beams in the head. The distance between the semiconductor laser arrays used for these is 50 μm ~
In order to avoid thermal interference between individual semiconductor elements and increase reliability, heat sinks are placed on the growth layer side including the active layer from above the semiconductor laser structure, rather than on the substrate side. It is desirable that they be fused.

Normally, when silicon (Si) is used as a heat sink for a single semiconductor laser, a gold electrode provided on the surface of the semiconductor laser that has a crystal growth layer, and a Si
This is done by fusing a thick tin film on the Si surface, and the tin on the Si surface is formed to a thickness of several μm in order to absorb the difference in thermal expansion coefficient between the semiconductor laser and the Si. ing.

[Problem that the invention seeks to solve]

An example of a semiconductor laser array that has been realized satisfying these conditions is a semiconductor laser array in which grooves are provided between semiconductor laser elements by etching or cutting, etc. to electrically isolate the elements. A metal tin film compatible with a semiconductor laser array is formed by vapor deposition on a beryllium oxide substrate that has electrical insulation properties and high thermal conductivity using a metal mask, etc., and this tin film and the semiconductor laser array are bonded together. It is fused by alloying with a film of gold or the like provided on the surface. In this conventional method of forming a tin film using a mask, the array pitch is 150~
It could not be applied to a thin array with an array pitch of about 50 μm.

The usual manufacturing method for silicon crystal, which is often used as a heat sink for a single semiconductor laser, is to use a silicon wafer with a thickness of about 300 μm as a substrate, and to form a mesh at intervals of 1 mm to 3 mm.
The method used is to make cuts several tens of μm wide and 100 to 200 μm deep, deposit Sn on the entire surface, and then concentrate stress on the cuts to break into individual heat sink chips.

To make a heat sink for a semiconductor laser array using high-resistance silicon, the electrical isolation between the arrays can be made by making cuts similar to (but shallower than) the cuts made to cut each chip. A possible method is to vapor-deposit Sn after this. However, in this case, since the Sn to be deposited is thick, a film is also formed on the side walls of the cut grooves, making it impossible to achieve electrical isolation. Furthermore, as a simple method, it is possible to uniformly form Sn without cutting incisions for separation, and then pattern the Sn film by a combination of photolithography and chemical etching of Sn, or by laser trimming. However, in the chemical Sn etching method, the surface of the Sn vapor deposited film is altered by the resist film formed as a mask, and in the laser trimming method, the Sn that occurs on both sides of the trimmed area is
The re-adhesion of the semiconductor laser causes burrs to form, making it difficult to fuse with the semiconductor laser.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat sink for an array semiconductor laser which eliminates these problems, allows easy separation according to the laser elements, and enables high-density packaging.

[Means for solving problems]

In the structure of the present invention, in a heat sink for an array semiconductor laser in which a high-resistance silicon substrate is fused to the array semiconductor laser, the heat sink is placed at a position corresponding to approximately the middle of the light emitting point position of the array semiconductor laser in the direction of the resonator of the array semiconductor laser. Grooves are provided in the silicon substrate surface along the respective directions, and the cross-sectional shapes of these grooves perpendicular to the groove direction are such that the groove width at the bottom of the grooves is wider than the groove width on the side of the surface to which the array semiconductor laser is fused. It is characterized by being widely formed.

[Effect]

By adopting the configuration of the present invention, the cross-sectional shape of the groove along the resonance direction of the semiconductor laser formed on the surface of the silicon substrate to which the array semiconductor laser is fused can be adjusted so that the width of the cross-section is at the substrate depth position than the fusion surface position. Because it can be formed wide, even if Sn, which is one of the soft metals used for fusion of each laser element, is deposited thickly, it will not adhere to the side walls of the groove, and the electricity between the semiconductor laser elements after fusion will be reduced. It is possible to avoid physical conduct. Furthermore, since there is no need to apply photoresist or the like on the Sn film after the Sn film has been deposited, the surface of the Sn film does not change in quality.
Good fusion can be achieved.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view showing the configuration of an embodiment of the present invention. In the figure, 1 is a high resistance used as a heat sink.
Si, 2 is a Si crystal layer containing boron (B) provided on the surface of this Si 1, 3 is a semiconductor laser array fused to the heat sink 1, and here, each laser element can be driven independently just by separating the electrodes. It uses an embedded laser. 4 is Si for fusion
Sn vapor deposited film provided on the surface of crystal layer 2, 5 sagging
Sn, 6 is a groove that electrically isolates individual laser elements.

In this embodiment, the cross-sectional shape of the groove 6 is narrow at the joint portion of the heat sink 1 with the semiconductor laser 3 and widened inside the substrate. It just accumulates like Sn5 at the bottom of the groove 6 without adhering to the side walls of the groove. Therefore, the electrode 3 of each laser element
There is no conduction between a, 3b, and 3c, and each laser element can be driven independently.

Such a groove 6 can be formed as follows. That is, the Si crystal layer 2 containing B can be formed as a crystal layer by epitaxial growth or as a B-implanted layer by ion implantation into the high-resistance Si substrate 1. This B-containing layer 2 is etched into grooves using a photoresist mask and KOH as an etching liquid. Furthermore, a mixture of ethylenediamine and pyrocatechol was heated to 116°C.
When the Si substrate 1 is heated to the boiling point of and immersed in this mixed solution, etching occurs at a rate of about 50 μm per hour. At this time, since the etching speed of the Si layer 2 containing B is extremely slow, the Si 1 is etched in a hole shape with the B containing layer 2 on the other side, and as shown in the figure, the Si layer 2 is etched at the welded part with the laser. A groove 6 is formed which is narrow in width and wide in the deep part.

[Effects of the Invention] As described above, according to the present invention, the groove 6 corresponding to the laser element can be easily formed, so that a heat sink for a semiconductor laser array suitable for high-density packaging can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention. 1... Si for heat sink, 2... Si crystallinity containing B, 3... semiconductor laser array, 4... Sn vapor deposited film, 5... Tamatsuta Sn, 6... etching groove,
3a, 3b, 3c...Laser element electrode, 3
d...Common electrode.

Claims (1)

[Claims] 1. In a heat sink for an array semiconductor laser in which a high-resistance silicon substrate is fused to an array semiconductor laser, the silicon substrate is heated toward the resonator direction of the array semiconductor laser at a position corresponding to approximately the middle of the light emitting point position of the array semiconductor laser. Each groove is provided in the substrate, and the cross-sectional shape of each of these grooves perpendicular to the groove direction is such that the groove width at the bottom of each groove is wider than the groove width on the side of the surface to which the array semiconductor laser is fused. A heat sink for array semiconductor lasers featuring: