JP2672405B2 - Manufacturing method of super luminescent diode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a super luminescent diode (hereinafter referred to as "SLD") having high brightness and high speed response characteristics, and more specifically, it is used for a fiber gyro and an LED printer. The present invention relates to an SLD manufacturing method.

[0002]

2. Description of the Related Art A light emitting element which constitutes a fiber gyro, an LED printer or the like is required to have high brightness and high speed response. However, for example, current LEDs (light-emitting diodes) cannot be used because they have poor response, and semiconductor lasers (which have good response) are dangerous when irradiated to the human eye, and drive with high differential efficiency. There is a problem that the circuit becomes complicated and difficult to use. Therefore, as an intermediate existence between the LED and the semiconductor laser, an SLD having a structure for limiting the laser oscillation of the semiconductor laser to some extent is used.

Conventionally, in this SLD, one of two facing laser light emitting end faces of a semiconductor laser is roughened by etching, or one of the emitting end faces is formed by wet etching, and then this SLD is formed. It is manufactured by a method in which a semiconductor layer (so-called window layer) having a wider forbidden band than the active layer (laser oscillation layer) is provided on the emitting end face by the LPE (liquid phase epitaxy) method.

[0004]

However, the above S
Among the LD manufacturing methods, the method in which one of the emission end surfaces is roughened by etching makes it difficult to obtain reproducibility of etching and causes variations in the characteristics of the manufactured element. Moreover,
After etching, the etching interface is oxidized in the atmosphere, and as a result, a defect is generated in the etching interface, which lowers the reliability of the device (lifetime deterioration). Also, a method of providing a semiconductor layer (window layer) having a wider forbidden band than the active layer by the LPE method after wet-etching one of the emission end faces has a large variation in the wet etching within the substrate surface, and therefore the device characteristics Variation occurs. Furthermore, LPE
There is a problem that there are many instability factors such as the shape of the emission end face changing due to meltback during growth, and the thickness of the window layer varying within the substrate surface.

Therefore, an object of the present invention is to provide a method for producing an SLD which has stable characteristics and good reliability and can be produced with good reproducibility.

[0006]

In order to achieve the above object, a method of manufacturing an SLD according to a first aspect of the present invention is such that one of two facing laser light emitting end faces of a semiconductor laser emits a laser beam. SL having a structure for limiting laser oscillation by providing a window layer made of a semiconductor having a bandgap wider than the layer
A manufacturing method of D, wherein a mask layer serving as an etching mask is provided on the surface of the semiconductor laser layer formed on the substrate, and openings having a predetermined pattern are formed in the mask layer.
And a second step of etching the semiconductor laser layer by a reactive ion etching method to form a groove reaching the surface of the substrate in the same pattern as the opening, without exposing the substrate to the atmosphere. A third step of growing a wide bandgap semiconductor to be a window layer on the substrate by a phase growth method and filling the groove formed in the second step, and forming the window layer on the substrate. The method further comprises a fourth step of cleaving the semiconductor-embedded groove and the portion where the semiconductor laser layer is formed to respectively form one emission end face having the window layer and the other emission end face. And

A method of manufacturing an SLD according to a second aspect is the method of manufacturing the SLD according to the first aspect, in which the reactive ion etching apparatus and the vapor phase growth apparatus are evacuated to a substrate transfer path. After performing the second step in the reactive ion etching apparatus, the substrate is loaded into the vapor phase growth apparatus via the substrate transport path, and the second step is performed in the vapor phase growth apparatus. The third step is performed.

[0008]

In the method of manufacturing the SLD according to the first aspect, since the groove for forming the window layer is formed by dry etching by the RIE (reactive ion etching) method, the inner surface of the groove is formed.
The (etching interface) is highly accurate, has good reproducibility, and is finished in a stable shape. Therefore, the characteristics of the manufactured element are stable. Moreover, the window layer is formed by VPE instead of LPE.
Since it is grown by the (vapor phase growth) method, the device characteristics are further stabilized. Further, after etching, the crystal growth (window layer formation) is performed without exposing the substrate to the atmosphere, so that the etching interface is not oxidized. Therefore, crystal defects do not occur at the etching interface (that is, the re-growth interface), the lifetime deterioration is avoided, and the reliability is improved.

When the window layer is formed by the LPE method, the material of the window layer grows on the mask layer as well.
In the case of the PE method, it is possible to grow only in the trench by selecting the growth conditions appropriately (selective growth). Therefore, according to the manufacturing method of the present invention, it is not necessary to purposely remove the unnecessary crystal on the mask in the subsequent step, and the step is simplified.

According to the method of manufacturing an SLD of claim 2, R
The substrate can be reliably transferred from the second step of performing the IE method to the third step of performing the VPE method without exposing the substrate to the atmosphere.

[0011]

EXAMPLES The method for producing the SLD of the present invention will be described in detail below with reference to examples.

3 (a) and 3 (b) are SLDs to be manufactured, respectively.
When viewed from the laser light emitting direction, the view is shown from the side. This SLD is a p-type GaAs substrate 2
01 as a semiconductor laser layer as an n-type GaAs current confinement layer 2
And 02, a p-type _{Ga 0. 5 Al 0. 5} As cladding layer 203, a p-type _{Ga 0. 85 Al 0. 15} As active layer (laser oscillation layer) 204, n-type Ga _{0. 5} Al _{0. 5} An As clad layer 205 and an n-type GaAs contact layer 206 are laminated, and one of the two laser light emitting end faces 230, 231 facing each other is provided with an emitting end face 231.
Undoped Ga ₀ of the wide forbidden band width than the active layer _204.5
And a al _{0. 5} As window layer 207. 220,22
Reference numeral 1 indicates an electrode.

This SLD is manufactured as follows.

First, as shown in FIG. 1A, the LPE
An n-type GaAs layer is formed on the p-type GaAs substrate 201 by the growth method.
(Impurity concentration n = 3 × 10 ¹⁸ cm ⁻³ ) 202 is grown to a thickness of 1 μm.

Next, after applying a resist on the n-type GaAs layer 202 and performing alignment, as shown in FIG. 1B, the p-type GaAs substrate 2 is wet-etched.
The channel groove 210 reaching 01 is formed. Here, the composition of the etching solution is H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 1.
6: 1: 16, the temperature of the etching solution is 10 ° C., and the etching time is 40 seconds.

Next, as shown in FIGS. 1C and 1D, L
Substrate 20 in which the groove 210 is formed by PE growth method
On 1, p-type _{Ga 0. 5 Al 0. 5} As layer ^{(n = 1 × 10 18 cm} -3) 2
03 thickness 0.2 [mu] m, p-type _{Ga 0. 85 Al 0. 15} As layer (n = 1
× 10 ¹⁸ cm ^-3) 204 thickness 0.1 [mu] m, n-type Ga _{0. 5} Al _0.
5 As layer (n = 1 × 10 ¹⁸ cm ⁻³ ) 205 with a thickness of 1 μm, n-type G
An aAs layer (n: 5 × 10 ¹⁸ cm ⁻³ ) 206 is grown to a thickness of 2 μm. Note that FIG. 1 (c) shows a view from the laser light emitting direction, and FIG. 1 (d) shows a view from the side.

Next, as shown in FIG. 1E, a mask layer 215 made of SiO ₂ or Si ₃ N ₄ is formed on the n-type GaAs layer 206, resist is applied, and alignment is performed. Width 40μ in the direction perpendicular to channel groove 210
A stripe-shaped opening 215a of m or more is provided. Opening 2
The pitch of 15a is, for example, 1,000 μm (= 1 mm).

After the resist is peeled off, the substrate 105 in this state is introduced into the load lock chamber 102 as a substrate transfer path shown in FIG. 2 (the RIE apparatus 1 is provided in the load lock chamber 102 via the flange 104).
03 and the vapor phase growth apparatus 101 are attached. ). The load lock chamber 102 is evacuated to 10 ⁻⁵ Torr or less, and the substrate 105 is transported by the load lock 106 and introduced into the RIE apparatus 103. Then, as shown in FIG. 6E, chlorine (C) is formed by RIE by using the mask layer 215 as a mask and passing through the opening stripes 215a.
l ₂₎ using a gas (gas pressure to 10 ^-4 Torr), with the conditions of the ion extraction voltage 500V, dry etching the semiconductor laser layer. As a result, a groove 217 reaching the p-type GaAs substrate 201 is formed. Since it is formed by the RIE method, by selecting appropriate conditions,
It is possible to finish the etching interface (the inner surface of the groove 217) with high accuracy (within ± 10% at 2 inches) with good reproducibility and a stable shape.

Then, as shown in FIG. 2, the substrate 105 in this state is not exposed to the atmosphere, and the load lock 10
It is introduced into the vapor phase growth apparatus (MOCVD reaction furnace) 101 via 6. Then, as shown in FIG. 1 (f), on the substrate 105 by MOCVD (metal organic chemical vapor deposition) method, to grow a non-doped _{Ga 0. 5 Al 0. 5} As to the groove 217 is filled. Thereby, the window layer 207 is formed.
As is known, by appropriately selecting the growth condition, it is possible to prevent the crystal growth only in the groove 217 and prevent the crystal growth on the mask layer 215 (selective growth).

Next, as shown in FIG. 1G, the substrate 105 is taken out from the reaction furnace 101, and the mask layer 215 is removed.
Then, the electrodes 220 and 221 are formed on the n-type GaAs layer 206 and the p-type GaAs substrate 201, respectively.

Finally, the substrate 105 is attached to each window layer 20.
Cleavage is performed at the center of 7 and the center of the window layers 207, 207 adjacent to each other to complete the fabrication of the device. The length between the laser light emitting end faces 230 and 231 of the device is 500 μm.

Thus, the groove 2 in which the window layer 207 is to be provided
Since 17 is finished in a stable shape with high accuracy and good reproducibility by the RIE method (process), it is possible to suppress variations in the characteristics of the manufactured elements and to make the characteristics stable. Further, since the window layer 207 is formed by vapor phase growth instead of LPE growth method (step), the inner surface of the groove 217 is not melted back to change its shape. Therefore, the device characteristics can be further stabilized. In addition, since the substrate 105 is transported without being exposed to the atmosphere and the window layer 207 is provided when proceeding from step to step, generation of crystal defects due to oxidation on the inner surface (regrowth interface) of the groove 217 is prevented. it can. Therefore, the deterioration of the life of the element can be prevented and the reliability can be improved. Further, in the process, crystal growth is prevented from occurring on the mask layer 215 by selective growth, so that it is not necessary to remove unnecessary crystals on the mask layer 215 in a later process, and the process can be simplified as compared with the related art. You can

In this embodiment, the semiconductor laser layer (heterostructure) is made of a GaAs-based material by the LPE growth method, but the invention is not limited to this. For example, other III-V or II-VI group materials such as InGaAlP-based and InGaAsP-based materials may be used. The semiconductor laser layer may be formed by MOCVD or MBE.
It may be formed by a (molecular beam epitaxial growth) method.

[0024]

As is apparent from the above, the S of claim 1
According to the method of manufacturing the LD, S having stable characteristics and good reliability
The LD can be manufactured with good reproducibility.

When the window layer is formed by the LPE method, the material of the window layer grows on the mask layer, but V
When using the PE method, it is possible to grow only in the groove by selecting the growth conditions appropriately (selective growth).
Therefore, there is no need to remove unnecessary crystals on the mask,
The manufacturing process of the element can be simplified.

According to the method of manufacturing an SLD of claim 2, R
The substrate can be reliably transferred from the second step of performing the IE method to the third step of performing the VPE method without exposing the substrate to the atmosphere.

[Brief description of the drawings]

FIG. 1 is a process diagram illustrating a method of manufacturing an SLD according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an apparatus used for manufacturing an SLD by the above manufacturing method.

FIG. 3 is a diagram showing a structure of an SLD to be manufactured.

[Explanation of reference numerals] 101 vapor phase growth furnace 102 load lock chamber (substrate transfer path) 103 RIE (reactive ion etching) device 104 flange 105 substrate 106 load lock (substrate transfer system) 201 p-type GaAs substrate 202 n-type GaAs current Constriction layer 203 p-type Ga ₀ . ₅ Al ₀ . ₅ As clad layer 204 p-type Ga ₀ . ₈₅ Al ₀ . ₁₅ As active layer 205 n-type Ga ₀ . ₅ Al ₀ . ₅ As clad layer 206 n-type GaAs contact layer 207 Non-doped Ga ₀ . ₅ Al ₀ . ₅ As Window layer 210 Channel groove 215 Mask layer 215a Opening 217 Groove 220,221 Electrode 230,231 Laser light emitting end face

Claims (2)

(57) [Claims] 1. A structure in which a window layer made of a semiconductor having a band gap wider than that of a laser oscillation layer is provided on one of the two laser light emission end surfaces of a semiconductor laser which face each other to limit laser oscillation. In the method for manufacturing a super luminescent diode described above, a mask layer serving as an etching mask is provided on the surface of a semiconductor laser layer formed on a substrate, and an opening having a predetermined pattern is formed in the mask layer. And a second step of etching the semiconductor laser layer by a reactive ion etching method to form a groove reaching the surface of the substrate in the same pattern as the opening, and vapor-phase growth without exposing the substrate to the atmosphere. By the method, a wide bandgap semiconductor to be a window layer is grown on the substrate,
The third step of filling the inside of the groove formed in the second step, and the groove in which the semiconductor to be the window layer is embedded and the portion where the semiconductor laser layer is formed on the substrate are cleaved to form the window. A method of manufacturing a superluminescent diode, comprising a fourth step of forming one of the emission end faces having a layer and the other of the emission end faces. 2. The method for manufacturing a super luminescent diode according to claim 1, wherein the reactive ion etching apparatus and the vapor phase growth apparatus are connected via a substrate transport path capable of being evacuated. After performing the second step in the reactive ion etching apparatus, the substrate is loaded into the vapor phase growth apparatus via the substrate transport path, and the third step is performed in the vapor phase growth apparatus. A method for manufacturing a super luminescent diode, which comprises: