JPH07273370A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To provide an optical semiconductor device which has a small capacitance between a light-emitting element and a semiconductor substrate and has a good operating characteristic at the high-speed operation. CONSTITUTION:This optical semiconductor device is constituted of a recessed section which has slant faces 2a, 2b and a bottom face 4 and which is formed on the surface of an n-type semiconductor substrate 1, an insulating layer 5 and an electrode 6 for mounting an element, both of which are formed on the bottom face 4, a semiconductor laser element 7 which is located on the electrode 6 through a solder layer, a p-type semiconductor region formed in the n type semiconductor substrate 1 below the semiconductor laser element 7, a pn junction which forms an interface between the p-type semiconductor region and the n-type semiconductor substrate 1, and a photo detector which is formed of an n-type semiconductor region. In this device, the pn junction region formed in the semiconductor substrate and the insulating layer are serially connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device used for optical recording, optical communication, optical measurement and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, an optical semiconductor device is one that converts an optical signal into an electrical signal or an electrical signal into an optical signal by photoelectric conversion. For example, JP-A-62-2
There is an optical semiconductor device having a structure described in Japanese Patent No. 50528. FIG. 6A shows the configuration of the optical semiconductor device,
A circuit diagram is shown in FIG.

In this optical semiconductor device, a first coating layer 102 formed on the surface of the semiconductor substrate 101 on the one main surface side.
And the second coating layer 103 and the semiconductor substrate 1
A light receiving element 104 formed between the first coating layer 102 and a part of the surface of 01, and a semiconductor laser element 105 arranged on the second coating layer 103 via a solder layer 106, A half mirror 108 formed by multilayer coating via an adhesive layer 109, and a prism 107 formed with the half mirror 108 as a bottom surface.
Composed of and.

FIG. 6B shows a circuit configuration of the optical semiconductor device having such a configuration, which will be described. Here, FIG.
In the constituent members shown in FIG. 6B, the same members as those shown in FIG. 6A are designated by the same reference numerals, and the description thereof will be omitted.

In this optical semiconductor device, the semiconductor laser element 105, a power source 111 for driving the semiconductor laser element 105, a capacitor 112 including a semiconductor substrate 101, first and second coating layers 102 and 103, and a solder layer 106. And an operational amplifier 113 that detects the output of the light receiving element 104.

Next, the operation of the optical semiconductor device thus configured will be described. First, a part of the emitted light 110 a from the semiconductor laser element 105 driven by the power supply 111 is reflected by the surface 107 a of the prism 107, and the path 110
An object such as an optical disk (not shown) is irradiated via f. Further, the reflected light from the object reaches the surface 107a again via the path 110f, partly enters the prism 107, passes through the half mirror 108 and the adhesive layer 109 via the path 110r, and reaches the light receiving element 104. Reached and the intensity of the reflected light is converted into an electrical output.

The output of the light receiving element 104 is detected by the operational amplifier 113 and sent to the outside. On this occasion,
In order to prevent the current for driving the semiconductor laser element 105 flowing through the solder layer 106 from affecting the light receiving element 104, the first or second coating layers 102, 10
The solder layer 106 and the semiconductor substrate 101 are electrically separated by using an electrically insulating material for either one of the three. Thus, in the conventional optical semiconductor device,
A small optical semiconductor device having both a light source and a light receiving function has been realized.

[0008]

However, the above-described conventional optical semiconductor device has the following problems. As is apparent from FIG. 6A, the semiconductor substrate 101
And the solder layer 106 includes the first and second coating layers 10
A parallel plate capacitor is formed via 2 and 103.

This corresponds to the capacitor 112 shown in the circuit of FIG. 6 (b). Therefore, the solder layer 106
-Electrical capacitance (C _mos : referred to as MOS capacitance when the insulating layer is silicon oxide, hereinafter referred to as MOS capacitance) occurs between the coating layers 102 and 103 and the semiconductor substrate 101. The value of this MOS capacitance varies depending on the potential difference applied between the solder layer 106 and the semiconductor substrate 101 and the carrier concentration of the semiconductor substrate 101, but as a maximum approximate value, C _mos = ε ₀ × ε ₁ × ε ₂ × S / (T ₁ × ε ₂ + t ₂ ×
It can be represented by ε ₁ ). Here, ε ₁ and ε ₂ are relative permittivities of the coating layers 102 and 103, ε ₀ is a vacuum permittivity,
S is the area of the electrode, t ₁ and t ₂ are the coating layers 102,
The thickness is 103.

Since this C _mos causes deterioration of the high-speed operation characteristics of the semiconductor laser device 105 as a parasitic capacitance, it has to be made as small as possible. For that purpose, a method of increasing the thicknesses t ₁ and t ₂ of the coating layer can be considered.

However, when the thicknesses t ₁ and t ₂ of the insulating layers are increased in order to reduce the parasitic capacitance, the semiconductor laser element 105 to the solder layer 106, the coating layers 103 and 10 are formed.
Then, the heat radiation path to the semiconductor substrate 101 via 2 becomes an obstacle, and the heat radiation of the semiconductor laser element 105 deteriorates.

This conventional example is an example in which the coating layer is two layers, but the same problem occurs even when the coating layer is one layer or three or more layers. Therefore, the conventional optical semiconductor device is
There is a trade-off relationship between reduction of parasitic capacitance between semiconductor substrates and improvement of heat dissipation of a semiconductor laser device. Therefore, there is a problem that it is difficult to obtain a small-sized optical semiconductor device having excellent high-speed operation characteristics and good heat dissipation. Therefore, an object of the present invention is to provide an optical semiconductor device having a small electric capacitance between a light emitting element and a semiconductor substrate and excellent operating characteristics at high speed.

[0013]

In order to achieve the above object, the present invention provides a semiconductor substrate having an electronic device formed in the vicinity of its surface, an insulating layer formed on at least the electronic device on the semiconductor substrate, Provided is an optical semiconductor device including a light emitting element arranged on an insulating layer and a pn junction region formed in the semiconductor substrate below the light emitting element and connected in series with the insulating layer. Here, the light emitting element is a concept including a semiconductor laser element and a light emitting diode.

[0014]

In the optical semiconductor device having the above-described structure, the pn junction formed in the semiconductor substrate under the light emitting element is coupled in series with the electric capacity generated by the electrically insulating layer interposed between the light emitting element and the semiconductor substrate. Generated electric capacitance, the parasitic capacitance between the light emitting element and the semiconductor substrate is reduced, and high-speed operation is possible without hindering the heat dissipation of the light emitting element.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. An outline of an optical semiconductor device as a first embodiment according to the present invention will be described with reference to FIGS.

First, FIG. 1 is a perspective view seen from above, and FIG. 2 (a) is a view showing a sectional structure of a main part.
(B) is a figure which shows the equivalent circuit. In this optical semiconductor device, the sloped surface 2 is removed from the surface side of the n-type semiconductor substrate 1 into a tapered concave shape by etching or the like.
a, 2b and the bottom surface 4 are formed. A reflection surface 3 made of a metal thin film is formed on a part of the slope 2b. An insulating layer 5 and an element mounting electrode 6 are formed on the bottom surface 4, and a semiconductor laser element 7 is arranged via a solder layer (not shown). In the figure, 8a represents the forward emission light of the semiconductor laser element 7 by the semiconductor laser element 7, 8b represents the reflected light of the forward emission light from an object (not shown), and 9 represents the semiconductor laser element 7. There is backward emission light.

In the sectional structure, a p-type semiconductor region 10 formed in the n-type semiconductor substrate 1 below the semiconductor laser element 7 and a pn junction 10a forming a boundary surface of the p-type semiconductor region 10 are formed. There are a light receiving element 12 formed of a p-type semiconductor region and a signal electrode 13 of the light receiving element 12. Further, an external connection electrode 15 for connecting to the outside, the semiconductor laser element 7, a bonding wire 14 for wiring between the external connection electrode 15, an external connection electrode 16 drawn out from the electrode 6 and the electrode 13, And 17 are provided.

In this embodiment, the electronic device formed in the vicinity of the surface of the semiconductor substrate is a light receiving element as an example. However, the electronic device is not limited to this, and may be a transistor or an integrated circuit thereof. Further, as the light emitting element,
The effect of the present invention is remarkable when an element driven by an alternating current is used.

FIG. 2B shows an equivalent circuit of a drive circuit including the optical semiconductor device shown in FIG. In this circuit,
The optical semiconductor device described above is provided with a power supply 17 for driving the laser element 7 and an operational amplifier circuit 20 for detecting a signal from the light receiving element 12. Also, electrode 6-insulating layer 5-p
And a pn junction 10 between the type semiconductor regions 10.
The capacitor 19 is formed by a.

Next, the operation of the optical semiconductor device thus configured will be described. In this optical semiconductor device, a MOS capacitance (C _mos ) is generated between the electrode 6-insulating layer 5-p type semiconductor region 10 formed below the electrode 6. In addition, a pn junction capacitance (C _j ) is generated in the pn junction 10a between the p-type semiconductor regions 10-n semiconductor substrate 1. Therefore, the electric capacitance C _total between the electrode 6 and the n-type semiconductor substrate 1
Is a series combination of these, 1 / C _total = 1 / C
_{From mos} + 1 / C _j C _total = 1 / (1 / C _mos + 1 / C _j ) = C _mos × C _j / (C _mos + C _j ), where C _mos > 0 and C _j > 0, so C _j <C _mos +
C _j , that is, C _j / (C _mos + C _j ) <1, therefore C _total <C _mos .

As described above, according to the optical semiconductor device of this embodiment, it is possible to obtain the effect of reducing the parasitic capacitance of the semiconductor laser element 7 without increasing the thickness of the insulating layer 5. Therefore, in this optical semiconductor device, due to the presence of the pn junction formed in the semiconductor substrate below the light emitting element, the electric capacity coupled in series with the electric capacity generated by the electric insulating layer interposed between the light emitting element and the semiconductor substrate. And the parasitic capacitance between the light emitting element and the semiconductor substrate are reduced,
An effect that good high-speed operation characteristics can be obtained without impairing the heat dissipation of the light emitting element is obtained.

Next, FIG. 3 shows the structure of an optical semiconductor device as a second embodiment according to the present invention. Here, the same components as those shown in FIG. 2 in the components of the second embodiment are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 3A is a diagram showing a sectional structure of a main part of the optical semiconductor device, and FIG. 3B is a diagram showing an equivalent circuit. In this optical semiconductor device, a light receiving element 21 formed of a p-type semiconductor region is further provided in the configuration shown in FIG. 2, and a pn junction 21a that forms a boundary of the light receiving element 21 is formed.

In the optical semiconductor device having such a configuration, the light receiving element 21 functions as a light receiving element for receiving the backward emission light 9 of the semiconductor laser element 7, and also functions as reducing the parasitic capacitance of the electrode 6. This function will be described with reference to the circuit diagram of FIG. As is clear from the circuit diagram of FIG. 3B, the capacitor 18 and the light receiving element 21 are connected in series between the element mounting electrode 6 and the semiconductor substrate 1. Here, the light receiving element 21 has the p-type shown in FIG.
Since an electric capacitance is generated in the junction region of the n-junction 21a, the electric capacitance between the element mounting electrode 6 and the semiconductor substrate 1 is a series combination of the electric capacitances of the capacitor 18 and the light receiving element 21.

Therefore, as in the first embodiment, the effect of reducing the parasitic capacitance of the electrode 6 is obtained. In this embodiment, the electrode 6 for mounting the element and the signal electrode 13 of the light receiving element are provided.
Regarding the electric capacitance between the two, the effect described above cannot be obtained, but the signal electrode 13 is naturally connected to a signal processing circuit such as the operational amplifier 20 for the purpose.
It is not directly connected to the power supply potential or the ground potential.

Therefore, the element mounting electrode 6 and the signal electrode 1
The capacitance generated during 3 does not adversely affect the operation of the semiconductor laser device 7 and does not impair the effects of this embodiment. In the optical semiconductor device of the second embodiment, since the light receiving element and the pn junction formed under the light emitting element are common, it is possible to arrange the light receiving element in a region adjacent to the light emitting element, and the entire device. Since the light receiving element can be arranged in the vicinity of the emitting end face of the light emitting element, the emitted light can be efficiently received.

Next, FIG. 4 shows a sectional structure of an optical semiconductor device as a third embodiment according to the present invention. Here, in the constituent members of the third embodiment, the same members as those shown in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In this optical semiconductor device, a light receiving element 31 formed of a p-type semiconductor region and a p-type semiconductor region 32 formed below the semiconductor laser element 7 are provided. By forming this region, a pn junction 32a that forms a boundary of the p-type semiconductor region 32 is formed. In addition, the p-type semiconductor regions 31, 3
An n-type semiconductor region 33 separating the two is formed. Such a configuration can be realized by forming the p-type semiconductor regions 31 and 32 as a series of p-type semiconductor regions in advance and then forming the n-type semiconductor region 33 by a method such as ion implantation. Further, the impurity diffusion regions can be separated by a method of physically separating them by etching or the like.

The third embodiment has the above structure.
Similar to the first and second embodiments described above, the effect of reducing the parasitic capacitance between the electrode 6 and the semiconductor substrate 1 can be obtained. In the optical semiconductor device of the third embodiment, since the light receiving element is separated from the pn junction formed below the light emitting element, the action of reducing the electric capacity of the light receiving element and the electric capacity of the light receiving element can be achieved. The reduction has the effect of realizing an optical semiconductor device including a light-receiving element with high response.

Next, FIG. 5 shows a sectional structure of an optical semiconductor device as a fourth embodiment according to the present invention, which will be described. Here, the members of the fourth embodiment which are the same as those shown in FIG. 2 are designated by the following reference numerals and the description thereof is omitted.

In this optical semiconductor device, in addition to the structure shown in FIG. 2, the external connection electrode 15 connected to the light emitting element 7 by the bonding wire 14 and the n-type semiconductor substrate 1 below the external connection electrode 15 are provided. The p-type semiconductor region 41 provided therein is provided, and further, a pn junction 41 a that forms a boundary of the p-type semiconductor region 41 is formed.

The p-type semiconductor region 41 can be formed in the same process as the p-type semiconductor region 10 and the light receiving element 12. The pn junction 41a can obtain the effect of reducing the electric capacitance between the external connection electrode 15 and the n-type semiconductor substrate 1 based on the same principle as in the first embodiment.

In the optical semiconductor device of the fourth embodiment, the pn junction formed in the semiconductor substrate below the wiring layer connected to the light emitting element causes the electrical insulation layer to generate electricity between the wiring layer and the semiconductor substrate. To obtain good high-speed operation characteristics by reducing the capacitance between the wiring layer and the semiconductor substrate and reducing the parasitic capacitance of the entire light-emitting element drive system by the action of generating capacitance coupled in series with the capacitance. You can

The present invention having the above embodiment can be configured as follows. (1). Corresponding to Examples 1 to 3 (FIGS. 1 to 4) A semiconductor substrate having an electronic device formed on its surface, an insulating layer formed on at least the electronic device on the semiconductor substrate, and light emission arranged on the insulating layer. Provided is an optical semiconductor device having an element and a pn junction region connected in series with the insulating layer formed in the semiconductor substrate below the light emitting element.

In this optical semiconductor device, the pn junction formed in the semiconductor substrate below the light emitting element generates an electric capacity generated in series with the electric capacity generated by the insulating layer between the light emitting element and the semiconductor substrate. As a result, the parasitic capacitance between the light emitting element and the semiconductor substrate is reduced, and good high-speed operation characteristics can be obtained without hindering the heat dissipation effect of the light emitting element.

(2). Corresponding to Example 2 (FIG. 3) In the above (1), a semiconductor substrate on which an electronic device including a light receiving element is formed near the surface, an electric insulating layer formed on the semiconductor substrate, and an electric insulating layer on the electric insulating layer An optical semiconductor device characterized in that a light emitting element arranged, a pn junction formed in the semiconductor substrate below the light emitting element, and the pn junction and the light receiving element are formed by a common impurity diffusion region. I will provide a.

With this optical semiconductor device, since the light receiving element and the pn junction formed below the light emitting element are common, the light receiving element can be arranged in the vicinity of or adjacent to the light emitting element. Therefore, the entire device can be downsized, and the light receiving element can be arranged near the emission end face of the light emitting element, so that the emitted light can be efficiently received.

(3). Corresponding to Example 3 (FIG. 4) In the above (1), a semiconductor substrate on which an electronic device composed of a light receiving element is formed in the vicinity of the surface, an electric insulating layer formed on the semiconductor substrate, and an electric insulating layer on the electric insulating layer The pn junction and the pn junction are formed by two or more impurity diffusion regions that are formed by disposing the light emitting element and a pn junction formed in the semiconductor substrate below the light emitting element, and separating a common impurity diffusion region formed in advance. Provided is an optical semiconductor device having a light receiving element formed therein.

In addition to the effect (2) obtained by the optical semiconductor device, this optical semiconductor device reduces the electric capacity of the light receiving element because the light receiving element is separated from the pn junction formed under the light emitting element. be able to.

Therefore, this optical semiconductor device can be further realized as an optical semiconductor device provided with a light-receiving element having high responsiveness by reducing the electric capacity of the light-receiving element. (4). Corresponding to Example 4 (FIG. 5) A semiconductor substrate having an electronic device formed in the vicinity of the surface, an electric insulating layer formed on the semiconductor substrate, a light emitting element arranged on the electric insulating layer, and the electric insulation. An optical semiconductor device comprising: a wiring layer formed on a layer and connected to the light emitting element; and a pn junction formed in the semiconductor substrate below the wiring layer.

In this optical semiconductor device, the pn junction formed in the semiconductor substrate below the wiring layer connected to the light emitting element couples the wiring layer and the semiconductor substrate in series with the electric capacitance generated by the electric insulating layer. To generate a given electrical capacity. Therefore, the series coupling of the capacitance of the electrical insulation layer and the capacitance of the pn junction reduces the capacitance between the wiring layer and the semiconductor substrate, and reduces the parasitic capacitance of the entire light emitting element drive system, thereby achieving favorable high-speed operation. The characteristics are obtained.

[0042]

As described above in detail, according to the present invention, an electrical insulating layer is formed and interposed between a light emitting device by a pn junction formed in a semiconductor substrate below the light emitting device and the semiconductor substrate. Electric capacity generated by the insulating layer, and pn
The electric capacity due to the joined impurity layers is coupled in series,
It is possible to provide an optical semiconductor device in which the parasitic capacitance between the light emitting element and the semiconductor substrate is reduced, the heat dissipation of the light emitting element is not hindered, and the operating characteristics at high speed are excellent.

[Brief description of drawings]

FIG. 1 is a perspective view of the appearance of an optical semiconductor device as a first embodiment according to the present invention as seen from above.

2 (a) is a diagram showing a cross-sectional structure of a main part of the optical semiconductor device shown in FIG. 1, and FIG. 2 (b) is a diagram showing an equivalent circuit thereof.

FIG. 3A is a diagram showing a sectional structure of a main part of an optical semiconductor device as a second embodiment according to the present invention, FIG.
(B) is a figure which shows the equivalent circuit.

FIG. 4 is a diagram showing a sectional structure of a main part of an optical semiconductor device as a third embodiment according to the present invention.

FIG. 5 is a diagram showing a cross-sectional structure of a main part of an optical semiconductor device as a fourth embodiment according to the present invention.

FIG. 6 is a diagram showing a configuration and a circuit of a conventional optical semiconductor device.

[Explanation of symbols]

1 ... N-type semiconductor substrate, 2a, 2b ... Slope, 3 ... Anti-slope,
4 ... Bottom surface, 5 ... Insulating layer, 6, 13 ... Electrode, 7 ... Semiconductor laser element, 8a ... Front emission light, 8b ... Reflected light, 9 ... Rear emission light, 10 ... P-type semiconductor region, 10a ... Pn junction part , 12 ... Light receiving element, 14 ..., 15, 16, 17 ... External connection electrodes, 18, 19 ... Capacitor, 19 ..., 20 ...
Op-amp circuit (op-amp).

Claims (1)

[Claims] 1. A semiconductor substrate on which an electronic device is formed near the surface, an insulating layer formed on at least the electronic device on the semiconductor substrate, a light emitting element disposed on the insulating layer, and a light emitting element of the light emitting element. Formed below in the semiconductor substrate,
An optical semiconductor device, comprising: a pn junction region connected in series with the insulating layer.