JPH0677584A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a semiconductor laser in which thermal characteristics are improved and which has a stable wavelength. CONSTITUTION:This semiconductor laser comprises a chip 110 having a laser resonator and bonded to an electrode plate 101, and a heat pass wire 103 provided as a heat radiator at a side of a substrate of the chip 110. Electrodes 102a, 102b, 102c, 102d are formed on the plate 101, and the electrodes 102a, 102b are electrically connected to the resonator. The wire 103 is brought into contact with the substrate of the chip 110, and a wire which performs excellent function as a heat radiator is used. It is electrically connected to the electrodes 102c, 102d, and a current flows between the electrodes 102a, 102b and 102c, 102d to output a laser light from the resonator of the chip 110.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly to a multi-beam semiconductor laser having a plurality of beams which can be independently driven on the same semiconductor chip.

[0002]

2. Description of the Related Art Currently, semiconductor lasers are widely used in laser printers and optical disks, but the drawing speed of the printer and the data transfer speed of the optical disk are not necessarily sufficiently high. In this case, if two laser beams that are close to each other and can be driven independently can be provided on one semiconductor laser substrate, then a system having double the writing speed or data transfer speed with one optical system can be created. Since such a multi-beam semiconductor laser is expected to be produced, research on such a multi-beam semiconductor laser has recently been conducted. This type of laser currently used is of the AlGaAs type,
The wavelength is about 0.78 to 0.84 μm. In this material system, as a method for electrically separating the beams, a method of diffusing impurities between the beams to increase the resistance, or a method of etching deeper than the active layer at the time of beam formation and then lowering the refractive index A method of burying with a high resistance crystal is known.

Further, a multi-beam semiconductor laser having a wavelength of 0.6 to 0.7 micron using AlGaInP as a main material has been filed by the inventor of the present invention (for example, it has not been published yet, Japanese Patent Application No. 4-33334, 4). -524
27, 4-149490). The use of this red semiconductor laser can be expected to increase the speed of a laser printer and increase the capacity of an optical disk.

[0004]

In a multi-beam semiconductor laser, one beam (referred to as beam A) is turned on and an adjacent beam (referred to as beam B) is lit.
When the beam B is turned on and off, heat is generated by turning on and off the beam B. This heat is transmitted to the laser resonator of the beam A to raise the temperature, and the phenomenon that the output of the beam A fluctuates occurs (thermal crosstalk). This causes a decrease in operational reliability of the multi-beam semiconductor laser, which causes a problem for practical use.

In order to suppress the thermal crosstalk as described above, it is improved by improving the heat dissipation of the chip. As one of the methods, "1991 Autumn Applied Physics Society 11p-
ZM-18, Murata et al. ", Which will be briefly described as follows. The electrode of the multi-beam laser is printed on the Si wafer to create an electrode plate,
A chip on which a multi-beam semiconductor laser is formed is die-bonded to this electrode plate by epi-down (substrate side up). Then, a heat radiator called a heat path wire is attached to the substrate side. By providing the heat pass wire, heat dissipation is improved. However, it was not always possible to sufficiently suppress thermal crosstalk.

[0006]

In order to solve the above-mentioned problems, a method of manufacturing a semiconductor laser according to the present invention is a semiconductor in which a chip having a laser resonator on its substrate is die-bonded with the substrate facing upward. A method of manufacturing a laser, characterized by including a step (wet etching, mechanical polishing, etc.) of thinning a chip from the substrate side after die bonding.

After the step of thinning, there is a step of providing a radiator on the substrate side (for example, a heat sink of a laser stem, a heat path wire, thick gold plating, etc.).

The chip is characterized by having a plurality of laser resonators.

A semiconductor laser in which a chip having a laser resonator on its substrate is die-bonded, the chip has a thickness of 40 μm or less, and a radiator is provided on the substrate. Characterize.

The chip has a plurality of beams on the substrate,
A multi-beam semiconductor laser is configured so that each beam can be driven independently of each other by providing a common electrode on the back surface of the substrate and an electrode separated for each beam on the front surface, and the active layer of each beam (for example, ( Al) GaInP
(Including the case where the Al composition ratio is zero) and the clad layer (for example, Al (Ga) InP (including the case where the Ga composition ratio is zero) is used as the strained multiple quantum well isolation confinement type It has a heterostructure and gives compressive strain) as a common layer, and the upper clad layer between the beams is thinner than that of the beam portion.

[0011]

The chip provided with the laser resonator is obtained by subjecting the wafer to a predetermined process and slicing it.
At this time, it is desirable that the wafer (substrate) be thick to some extent in order to maintain mechanical strength, and it is desirable that the substrate be thin in order to suppress heat resistance in order to dissipate heat. Since the semiconductor laser manufacturing method of the present invention has a step of thinning the chip from the substrate side after die bonding, the chip can be manufactured on a wafer having a certain thickness, and the semiconductor laser manufactured by the method is Since the substrate is thin, the heat generated in the laser resonator can be well dissipated from the substrate side.

By providing the radiator on the substrate side, the semiconductor laser manufactured by the radiator has better heat dissipation.

When the chip is formed of the multi-beam semiconductor laser as described above, a multi-beam semiconductor laser with very little thermal crosstalk can be obtained. In particular,
It is useful in a GaInP or AlGaInP laser in which it is difficult to form a structure in which an active layer divided for each beam is buried, and has an effect that a multi-beam semiconductor laser having a shorter wavelength can be used as compared with an AlGaAs laser.

[0014]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of an embodiment of the present invention. In this semiconductor laser, a chip 110 (having a thickness of about 40 μm) provided with a laser resonator is bonded on an electrode plate 101, and a heat pass wire 103 is provided as a radiator on the substrate side of the chip 110. .

On the electrode plate 101, electrodes 102a, b, c and d are formed by depositing gold and gold tin on a silicon substrate,
The electrodes 102a and 102b are electrically connected to the laser resonator of the chip 110. The heat path wire 103 is in contact with the substrate of the chip 110, and is made of, for example, copper so as to function well as a heat radiator. Then, the laser light is electrically connected to the electrodes 102c and d, and a current is passed between the electrodes 102a and 102b and the electrodes 102c and 102d, whereby laser light is output from the laser resonator of the chip 110.

The chip 110 is a multi-beam semiconductor laser chip, and has a laser resonator on its substrate. FIG. 2A shows the configuration of this chip 110. This chip 110 comprises a Se-doped GaAs substrate 201 and a Se-doped AlGaInP cladding layer 20.
3 (thickness 2000 angstrom), active layer 204 of strained multiple quantum well structure, Zn-added AlGaInP cladding layer 205, Si-added GaAs current blocking layer 20.
6 are sequentially stacked, and a Zn-added GaInP cap layer 2 is formed.
07 is provided. The contact layer 20 made of GaAs to which Zn is added is formed on the cap layer 207.
8 and electrodes 209 are provided. Then, the silicon nitride film 212 is provided between the regions A and B for outputting the beam, and is formed so as to fill the groove 211 for separating the regions A and B.

FIG. 2B is an energy band diagram showing the strained multiple quantum well structure of the active layer 204. As shown in the figure, the active layer 204 includes a well layer 241 having a thickness of 100 angstrom and made of undoped Ga _0.47 In _0.57 P, and an undoped (Al _0.4 Ga _0.6 ) _0.5 I layer separating the well layer 241.
The barrier layer 242 of n _0.5 P (thickness 80 Å) and the light confinement layer 243 (thickness 800 Å) made of the same material as the barrier layer 242,
The active layer has a multiple quantum well structure so that the active layer is subjected to compressive strain.

The semiconductor laser of FIG. 1 is manufactured as follows.

First, the chip 110 is manufactured with a thickness of about 70 μm. The chip 110 is manufactured as follows.

The clad layer 2 is formed on the GaAs substrate 201.
03, the active layer 204, the cladding layer 205, and the cap layer 207 are sequentially epitaxially grown at 740 ° C., and then the silicon nitride film 221 is formed (FIG. 3A).
The n- and p-clads 203, 204 have a dope pink amount of 2 × 10 ¹⁷ cm ⁻³ and 4 × 10 ¹⁷ cm ⁻³ , respectively, and the thickness is 1 μm.
m. The silicon nitride film 221 is patterned so as to serve as a mask when the portion indicated by the broken line is removed by etching in the next step. Buffered hydrofluoric acid was used as an etchant for this patterning. The width of the two patterned silicon nitride films 221 is 5 μm, and the distance between the centers of the two is 15 μm.

Next, mesa etching is performed. Here, mixed acid (sulfuric acid: hydrogen peroxide: water = 50 ° C) is added to the etchant.
Etching is performed for 6 minutes using 3: 1: 1) to leave the upper clad layer 5 at 2000 angstroms (FIG. 3B). Then, GaAs added with Si (impurity concentration is 2 × 10 ¹⁷ cm
^-3 ) is grown to form the current blocking layer 206. The silicon nitride film 221 is removed with an etchant of hydrofluoric acid: water = 1: 1 (FIG. 3C). After that, a silicon nitride film is formed on the entire surface, and the silicon nitride film 222 is left only between the regions where the laser resonator is formed by resist patterning and etching (FIG. 3D).

Then, Zn-added GaAs (impurity concentration: 1 × 10 ¹⁹ cm ⁻³ ) is grown to 1 μm to form a contact layer 208 separated at the portion where the silicon nitride film 222 is left (FIG. 4). (E)). After that, the silicon nitride film 222 is removed, and a patterned silicon nitride film 212 is formed on the separated portion of the contact layer 208 (FIG. 4F). After the Ti / Pt / Au3 layer metal film 209 'is vapor-deposited on the entire surface (FIG. 4G), the resist pattern 230 is removed with acetone, and the electrode 209 is left for each beam by lift-off. The substrate is etched from the back to a thickness of about 70 μm, and the temperature is 1 ° C at 400 ° C in a nitrogen atmosphere.
After a minute of alloying treatment, a wafer having a multi-beam laser resonator is obtained.

After thinly applying a resist on both surfaces of this wafer, the wafer is cleaved into a bar having a resonator length of about 500 μm. A protective film of silicon nitride is deposited and the resist is removed with acetone. Since the resist is applied to both surfaces of the wafer, silicon nitride is provided only on the cleavage surface of the protective film, that is, the end surface of the laser resonator. And 4
The chip 110 is obtained by cutting it to a width of about 00 microns.

On the other hand, a resist is applied in a predetermined pattern, gold and gold tin (tin 20%) are vapor-deposited, and then the resist is removed. As a result, an electrode plate 101 is obtained in which the electrodes 102a, b, c, d having a gap of about 50 microns (distance between the electrodes 209) near the center of the silicon substrate are formed by wrist-off (FIG. 5A).

Next, die bonding is performed at a temperature of about 300 ° C. with the substrate 201 of the chip 110 facing upward so that the electrode 209 of the chip 110 and the electrodes 102a and 102b are in electrical contact with each other (see FIG. b)). Then, the etchant (ammonia water: hydrogen peroxide water: water = 9: 6: 2)
In step 5), the substrate 201 is etched until it becomes about 30 microns. A resist is applied to the entire surface of the electrode plate 101 except for the portion where the chip 110 is provided (here, the resist may cover a part of the chip 110). A metal that makes ohmic contact with the substrate 201 is formed. For example, as described in "J.Appl.Phys.62 (3), 1 August 1987", palladium and germanium are vapor-deposited and annealed to G.
e / PdGe is formed.

Then, the heat pass wire 103 is bonded to the chip and the electrode plate 101 using tin and lead at about 250 ° C. (FIG. 5 (c)). After that, the entire substrate 201 (FIG. 5C) is die-bonded at about 160 ° C. using indium for a heat sink of a copper stem, and an electrode 102 is formed.
Wire bonding of a, b, c and d is completed.

As described above, since the laser resonator is formed on the wafer in a state where the substrate is thick, that is, in a state where the mechanical strength of the substrate is high, it is easy to handle in the process and resistant to thermal stress. . And chip 11
Since 0 is die-bonded and the substrate 201 is etched to be thin, good handling can be maintained.

When a current was passed through this semiconductor laser to cause laser oscillation, laser beams having different wavelengths were obtained. In the case of the chip as shown in FIG. 2, since the threshold current for oscillating the laser is low, the heat generation is small.
Since the substrate 201 of 10 is thin, heat generation is extremely small. Since the thickness d (FIG. 2) of the cladding layer 205 is thin, the heat in the region where the laser resonator is formed does not easily reach the next laser resonator region, and thermal crosstalk is reduced. In addition, since the thermal resistance of the substrate 201 is small, the heat radiation from the laser resonator, which is the heat source, is good. And heat pass wire 10
3 functions as a heat radiator, and the heat radiation is good. Since the effect of suppressing the thermal crosstalk is great in this way, even if one of the laser resonators is driven in a pulse shape, the fluctuation of the other output is small.

The present invention is not limited to the above-mentioned embodiment, but various modifications can be made.

For example, although an example in which a heat path wire is used as the heat radiator is shown, it may be a heat sink of the laser stem or thick gold plating as long as it functions as the heat radiator. Further, although an example of etching is used to thin the substrate, an etchant having another composition may be used, and mechanical polishing may be used as long as it does not damage the laser resonator. Further, although the chip 110 is shown as having a multi-beam semiconductor laser, a single-beam semiconductor laser may be used. The Al composition ratio of AlGaInP in the active layer may be zero. The Al composition ratio of AlGaInP in the clad layer may be zero.

[0031]

As described above, according to the semiconductor laser of the present invention, since the substrate of the chip is thin and the heat generated in the laser resonator is well dissipated from the substrate side, the thermal characteristics are improved and stable. Laser light of the specified wavelength can be obtained. Particularly, in the case of a chip configured with a multi-beam semiconductor laser, thermal crosstalk is reduced, stable laser oscillation can be obtained, and excellent multi-beam laser light can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram of a chip.

FIG. 3 is a manufacturing process diagram of a chip.

FIG. 4 is a manufacturing process diagram of a chip.

FIG. 5 is a manufacturing process diagram of an embodiment of the present invention.

[Explanation of symbols]

101 ... Electrode plate, 102a, b, c, d ... Electrode, 103
... heat pass wire, 110 ... chip, 204 ... active layer, 203 ... cladding layer.

Claims (6)

[Claims] 1. A method of manufacturing a semiconductor laser in which a chip having a laser resonator on its substrate is die-bonded with the substrate facing upward, the chip being attached from the substrate side after the die-bonding. A method of manufacturing a semiconductor laser, comprising a step of thinning. 2. The method according to claim 1, further comprising a step of providing a radiator on the substrate side after the step of thinning.
A method for manufacturing the semiconductor laser described. 3. The method for manufacturing a semiconductor laser according to claim 1, wherein the chip has a plurality of laser resonators. 4. The chip has a plurality of beams on the substrate, and a common electrode is provided on the back surface of the substrate and electrodes separated for each beam are provided on the surface to drive each beam independently of each other. A multi-beam semiconductor laser is constructed so that the active layer and the clad layer of each beam are integrated as a common layer, and the thickness of the upper clad layer between the beams is thinner than that of the beam part. The method for manufacturing a semiconductor laser according to claim 1, wherein 5. A semiconductor laser in which a chip having a laser resonator on its substrate is die-bonded, the chip has a thickness of 40 μm or less, and a radiator is provided on the substrate. A semiconductor laser characterized in that. 6. The chip has a plurality of beams on the substrate, and a common electrode is provided on the back surface of the substrate and electrodes separated for each beam are provided on the surface to drive the beams independently of each other. A multi-beam semiconductor laser is constructed so that the active layer and the clad layer of each beam are integrated as a common layer, and the thickness of the upper clad layer between the beams is thinner than that of the beam part. The semiconductor laser according to claim 5, wherein