JPH0548209A - Semiconductor optical device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a structure which enable the contact resistance of a metallic electrode with a semiconductor contact layer to be low stably, in a semiconductor optical device having a semiconductor contact layer which is in connection with a metallic electrode. CONSTITUTION:On a semiconductor contact layer 6, formed is a metallic electrode 13 for contacting, which is in ohmic connection with the semiconductor contact layer 6. Then, on the metallic electrode 13 for contacting, an insulation film 8 is formed. Further, on the insulation film 8, formed is a metallic electrode 12 for leading, which is in connection with the metallic electrode 13 at an opening part 11 provided in the insulation film 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device, and more particularly to a semiconductor optical device capable of stably lowering the contact resistance between a semiconductor contact layer and a metal electrode connected to the semiconductor contact layer, and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 3 is a sectional process view showing an example of a conventional method for manufacturing a semiconductor optical device. The semiconductor optical device shown here is, for example, Mitsubishi Electric Technical Report, Vol. 64, No. 10 (1990
Years), PPIBH (P-substrate Partially
This is an Inverted Buried Hetero-structure) laser that removes regions on both sides of the active region by etching etc. to form a mesa shape, thereby reducing the junction capacitance in the laser element and realizing high-speed modulation characteristics. is there.

In FIG. 3, 1 is a p-InP substrate, 2 is a p-InP clad layer, 3 is an InGaAsP active layer, 4
Is an n-InP clad layer, 5 is a p-InP block layer,
6 is an n-InGaAsP contact layer, 7 is a mesa, 8 is a SiO film, 9 is a SiO ₂ film window opening photoresist,
10 is a photoresist window, 11 is a SiO ₂ film window, and 12 is an n-side electrode.

Next, the manufacturing process will be described. First, by repeating crystal growth and etching, as shown in FIG.
A mesa including the nGaAsP active layer 3 is formed (mesa width 7). Forming the mesa in this manner reduces the junction area of the p-InP substrate 1, the n-InP clad layer 4, and the p-InP block layer 5, and reduces the parasitic capacitance generated by these to minimize high-speed modulation characteristics. Is to improve. Therefore, the mesa width 7 is set to a narrow value of about several μm to 20 μm. Next, as shown in FIG. 3B, a SiO ₂ film 8 is formed to electrically insulate the junction exposed on the side surface of the mesa, and then a SiO ₂ film window opening photoresist 9 is applied. Then, as shown in FIG. 3C, the photoresist window 10 is patterned on the mesa, and the SiO _{2 is formed} by a method such as dry etching with CF _{4.
A two-} film window 11 is formed. Then, after removing the SiO ₂ film window opening photoresist 9, finally, an n-side electrode 12 is formed as shown in FIG. 3 (d) to complete a semiconductor laser.

Next, the operation will be described. In the semiconductor laser completed through the above steps, the p-InP block layer 5 and the SiO ₂ film 8 sandwiched between the n-InP clad layers 4 are formed.
Since the current is blocked more, the current injected from the P-side electrode is sequentially p-InP substrate 1, p-InP clad layer 2, I
nGaAsP active layer 3, n-InP clad layer 4, n-
In that flows to the InGaAsP contact layer 6 and the n-side electrode 12 and is in contact with the only pn junction in the current path
The required laser oscillation occurs in the GaAsP active layer 3.

[0006]

Since the conventional semiconductor laser is constructed as described above, the n-side electrode, which plays a role of connection with an external circuit, simultaneously receives n through the SiO ₂ film window.
-It plays a role of contacting the InGaAsP contact layer, but as shown in FIG. 3 (b), the thickness of the SiO ₂ film window opening photoresist 9 can be uneven on the mesa. The width of
Since it is difficult to form the SiO ₂ film window 11 with high accuracy, the contact resistance between the n-side electrode and the n-InGaAsP contact layer tends to be high, which impairs the high-speed modulation characteristics and high reliability of the semiconductor laser. there were.

The present invention has been made to solve the above problems, and provides a high-performance semiconductor optical device capable of high-speed modulation and exhibiting high reliability, and a method of manufacturing the same.

[0008]

A semiconductor optical device according to the present invention, which has a semiconductor contact layer connected to a metal electrode, is formed on the semiconductor contact layer and has a desired resistance value with the semiconductor contact layer. A metal electrode for contact that makes an ohmic contact in an area sufficient to obtain the insulating film, an insulating film formed on the metal electrode for contact, and an opening formed in the insulating film and provided in the insulating film. And a metal electrode for extraction connected to the metal electrode for contact.

Further, in the method for manufacturing a semiconductor optical device according to the present invention, a semiconductor having a structure in which both sides of the active region are removed by forming a stripe-shaped groove from the contact layer side in order to reduce the junction capacitance in the element. In a method of manufacturing an optical device, a region on both sides of an active region is removed from a contact layer side to form a mesa having a laminated structure including the contact layer, and the contact layer is formed on a contact layer made of a semiconductor crystal. A contact metal electrode that is in ohmic contact with an area sufficient to obtain a desired resistance value is formed, and after forming the mesa, a lead electrode that is electrically connected to the contact metal electrode is formed. It is a thing.

[0010]

In the present invention, a contact metal electrode, which is formed on the semiconductor contact layer and is in ohmic contact with the semiconductor contact layer in an area sufficient to obtain a desired resistance value, is provided separately from the lead metal electrode. Since the structure is provided, the contact resistance between the semiconductor contact layer and the metal electrode can be stably lowered.

Further, according to the present invention, in a method of manufacturing a semiconductor optical device in which an element is formed in a mesa shape to reduce a junction capacitance in the element, the contact is formed on a contact layer made of a semiconductor crystal before forming a mesa. Since the contact metal electrode that makes ohmic contact with the layer in a sufficient area to obtain the desired resistance value is formed, it is possible to perform patterning of the contact metal electrode on a flat wafer and to stabilize the contact. As a result, a sufficient contact area between the contact layer and the metal electrode can be obtained, and a high-performance semiconductor optical device can be manufactured.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional structural view showing a semiconductor laser having a mesa structure for capacitance reduction, which is an example of a semiconductor optical device according to an embodiment of the present invention.
-InP substrate, 2 is a p-InP clad layer formed on the substrate 1, and 3 is an InGaAsP active layer formed on the p-InP clad layer 2. Reference numeral 4 is an n-InP cladding layer formed on both sides of the mesa formed by etching and removing the active layer 3 and the cladding layer 2 until they reach the substrate 1, and 5 is an n-InP cladding layer. P- formed on the layer 4 to embed the mesa
It is an InP block layer. 4'is a block layer 5 and an n-InP clad layer formed on the mesa, and 6 is an n-I
n-InGaAsP formed on the nP clad layer 4 '
The contact layer, 13 is a contact n-side electrode formed on the contact layer 6.

Next, the manufacturing process will be described. 2 is a cross-sectional process diagram showing a method for manufacturing the semiconductor laser shown in FIG. 1, in which the same reference numerals as those in FIG. 1 designate the same or corresponding parts, 14 is a photoresist for forming a contact n-side electrode, and 15 is a photo resist. The resist is left, 16 is the contact n-side electrode, and 17 is a photoresist mask for forming a mesa. In the manufacturing method according to this embodiment, n-InGaAsP is used.
Immediately after forming the contact layer 6, without forming a mesa, a contact n-side electrode 13 is formed and a contact n-side electrode forming photoresist 14 is applied, as shown in FIG. Then, as shown in FIG.
Patterning the side electrode forming photoresist 14;
A photoresist residue 15 is formed, and using this as an etching mask, a contact n-side electrode residue 16 is formed. After that, as shown in FIG. 2C, the photoresist residue 15 is formed.
To remove. Then, as shown in FIG. 2D, a photoresist mask 17 for forming a mesa is formed, and by using this, a mesa 7 is formed for the first time as shown in FIG. 2E. Further, as shown in FIG. 2 (f), the photoresist mask 17 for forming the mesa is removed, then, as shown in FIG. 2 (g), a SiO ₂ film 8 is formed, and a SiO ₂ film window is opened. Photoresist 9 is applied. Then, as shown in FIG. 2 (h), a photoresist window 10 is formed in the SiO ₂ film window opening photoresist 9 on the mesa, and using this,
For example, by a method such as dry etching with CF ₄ ,
The SiO ₂ film window 11 is formed. Thereafter, as shown in FIG. 2 (i), the SiO ₂ film window opening photoresist 9 is removed, and finally, an extraction n-side electrode 12 to be connected to an external circuit is formed.

In this embodiment, as shown in FIG. 2A, since the contact n-side electrode forming photoresist 14 is applied before the mesa is formed, that is, when the wafer is flat. The film thickness of the resist can be made very uniform, which allows the photoresist to remain 15
The width of the contact n side electrode 16 can be precisely controlled as a result. In the n-side polarity, the n-InGaAsP contact layer 6 and n
The electrical resistance between the side electrodes 12 is the contact n side electrode remaining 1
6 and the n-InGaAsP contact layer 6 are almost determined by the contact resistance. Therefore, when the width of the contact n-side electrode leaving 16 is precisely controlled by the method according to the present embodiment, the contact resistance is sufficiently low, and It can be controlled to a constant value.

The operation of the semiconductor laser of this embodiment is almost the same as that shown in the conventional example, but since the contact resistance is reduced, a semiconductor laser having high speed modulation and high reliability can be realized. Further, the uniformity of the contact resistance between the wafers in the manufacturing process and the uniformity within the wafer surface are also greatly improved, resulting in a high yield.

[0016]

As described above, according to the present invention, in the semiconductor optical device, the connection electrode to the external circuit and the contact electrode to the crystal are separately provided. Can be reduced, which has the effect of improving the performance of the device and improving the yield.

Further, according to the present invention, in the method of manufacturing a semiconductor optical device in which regions on both sides of the active region are removed to form a mesa shape, a contact electrode to the crystal is formed before forming the mesa to form the mesa. Since the connection electrode to the external circuit is formed after the formation, the contact metal electrode can be patterned on the flat wafer, which is stable and stable.
There is an effect that a sufficient contact area between the contact layer and the metal electrode can be obtained, and a high-performance semiconductor optical device can be manufactured.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a semiconductor optical device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional process diagram showing a method for manufacturing a semiconductor optical device according to an embodiment of the present invention.

FIG. 3 is a cross-sectional process diagram showing a conventional method for manufacturing a semiconductor optical device.

[Explanation of symbols]

1 P-InP Substrate 2 P-InP Clad Layer 3 InGaAsP Active Layer 4 n-InP Clad Layer 5 P-InP Block Layer 6 n-InGaAsP Contact Layer 7 Mesa 8 SiO ₂ Film 9 SiO ₂ Film Window Opening Photoresist 10 Photo Resist window 11 SiO ₂ film window 12 n-side electrode 13 contact electrode 14 contact n-side electrode forming photoresist 15 photoresist remaining 16 contact n-side electrode remaining 17 mesa forming photoresist mask

Claims (2)

[Claims] 1. A semiconductor optical device having a semiconductor contact layer connected to a metal electrode, the ohmic contact being formed on the semiconductor contact layer and contacting the semiconductor contact layer in an area sufficient to obtain a desired resistance value. A contact metal electrode to be connected, an insulating film formed on the contact metal electrode, and a lead-out formed on the insulating film and connected to the contact metal electrode at an opening provided in the insulating film. A semiconductor optical device comprising a metal electrode. 2. A structure having a semiconductor contact layer connected to a metal electrode, wherein both sides of the active region are removed by forming a stripe-shaped groove from the contact layer side in order to reduce the junction capacitance in the device. In the method of manufacturing a semiconductor optical device, the method further comprises: removing regions on both sides of an active region from the contact layer side to form a mesa having a laminated structure including the contact layer on the contact layer made of a semiconductor crystal. Forming a contact metal electrode in ohmic contact with the contact layer in an area sufficient to obtain a desired resistance value; and covering the mesa and the mesa side wall after forming the mesa,
And a step of forming an insulating film having an opening through which the contact metal electrode is exposed, and a step of forming an electrode for connecting to an external circuit connected to the contact metal electrode at the opening on the insulating film. A method for manufacturing a semiconductor optical device, comprising: