JPH0329193B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an optical semiconductor device that performs wavelength detection using a semiconductor device.

<Prior Art> Conventionally, the following devices have been developed by the present inventors as optical semiconductor devices that perform light detection using semiconductor devices. That is, by utilizing the property that the degree of light absorption in the thickness direction of a semiconductor substrate depends on the wavelength of irradiated light, at least two PN junctions are formed at different depths inside the semiconductor substrate, and each PN junction is
The photocurrent output ratio at the junction is made to correspond to the wavelength of the irradiated light. FIG. 2 is a cross-sectional view of an optical semiconductor device 1 developed by the present inventors, in which, for example, an epitaxial layer 3 exhibiting N-type conductivity is provided on a P-type silicon substrate 2; A relatively shallow P ⁺ diffusion is swirled into the layer 3 to provide a P-type region 4 and a first PN junction 5 located deep between the P-type substrate 2 and the N-type epitaxial layer 3 is formed. , a second PN junction 6 located shallowly between the N-type epitaxial layer 3 and the P ⁺ region 4 is formed. In conventional phototransistors, the base-emitter PN junction, which corresponds to the second PN junction, is provided in a very limited area of the semiconductor region because it does not immediately contribute to photoelectric conversion. In the developed optical semiconductor device 1, since photocurrent is also taken out from the second PN junction 6, the diffusion region is designed so that the second PN junction 6 is generated in a relatively wide range within the N-type epitaxial region 3. The pattern is designed.

Reference numeral 7 denotes a P ⁺ isolation region provided through the N-type pitaxial layer 3 . Electrodes 8, 9, and 10 are provided in ohmic contact with the P type substrate 2, the N type epitaxial region 3, and the P ⁺ region 4, respectively ^.
A translucent insulating film 11 (for example, SiO ₂ film) such as an antireflection film is deposited on the semiconductor layer covering the semiconductor layer.

FIG. 3 is an equivalent circuit diagram of the optical semiconductor device 1,
The P-type substrate 2 and the N-type epitaxial region ₃ form a first photodiode PD 1 , and the N-type epitaxial region 3 and the P ⁺ region 4 form a second photodiode PD ₂ .

FIG. 4 is a diagram showing the spectral sensitivity characteristics of the optical semiconductor device 1 having the above structure, where curve A is from the first photodiode PD ₁ having a deep PN junction, and curve B is from the second photodiode PD ₂ having a shallow PN junction. The relationship between the wavelength (λmμ) of the irradiated light and the sensitivity obtained from the above is shown, with the first photodiode PD ₁ absorbing the long wavelength component, and the second photodiode PD ₂ absorbing the short wavelength component.

FIG. 5 shows a wavelength detection circuit using the optical semiconductor device 1 described above, in which the optical output currents I _PD1 and I _PD2 of the first photodiode PD ₁ and the second photodiode PD ₂ are derived, respectively, into an operational amplifier circuit with high input impedance. OP ₁ and OP ₂ are entered. The operational amplifier circuit
OP ₁ and OP ₂ both have logarithmic compression diodes D ₁ and D ₂ with logarithmic compression characteristics in their feedback paths.
is connected and input photodiode PD ₁ ,
The optical output current of PD ₂ is logarithmically compressed and output.
The output signals V _OP1 and V _OP2 derived from both operational amplifier circuits OP ₁ and OP ₂ are then connected to a resistor R ₁ or a resistor R ₂ respectively.
It is input to the terminal or terminals of operational amplifier _OP3 via. Here, the resistance values of the resistors R ₁ , R ₂ , R ₃ , and R ₄ connected to the operational amplifier OP ₃ are set in advance as R ₁ = R ₂ ,
By designing to have the relationship R ₃ = R ₄ ,
Vout, which is proportional to the value obtained by subtracting the above V _OP1 and V _OP2 as the operational amplifier output, is the output of both photodiodes PD ₁ and PD _2.
The value obtained by logarithmically compressing the ratio of the optical output current I _PD1 and I _PD2 of
Obtained as a value proportional to ogI _PD1 /I _PD2 .

The solid line data in Figure 6 is the output of the wavelength detection circuit above.
This is a diagram showing the relationship between Vout and the wavelength (λmμ) of the irradiation light, and it can be seen that a nearly linear relationship is obtained, and an output signal having a value corresponding to the wavelength of the irradiation light can be obtained. Therefore, if the spectral sensitivity characteristics of the optical semiconductor device are determined in advance, the relationship between the optical output ratio and the wavelength is uniquely determined, and when the optical semiconductor device is irradiated with light of unknown wavelength, the wavelength detection circuit The wavelength can be measured by the output.

However, the data indicated by the solid line above is data when the irradiation light enters the central part of the optical semiconductor device 1, and
When the irradiation light is incident on the periphery or side surface of the optical semiconductor device 1, the characteristics deviate from the solid line data and become as shown by the broken line. In other words, the photocurrent ratio differs depending on the position where the irradiation light is incident.

Now, when the optical semiconductor device 1 is sealed with a hermetic seal and a cap with a lens is provided on the surface,
Since the irradiation light is concentrated at the center of the optical semiconductor device 1, there are relatively few problems. However, if the optical semiconductor device 1 is molded with resin, the irradiation light will be incident not only from the center but also from the periphery or side surfaces, and in such a case, the photocurrent ratio will depend on the incident position of the irradiation light. The difference makes reliable wavelength detection difficult.

<Purpose> The present invention has been made in view of the above-mentioned conventional points, and provides an optical semiconductor device that can perform highly reliable wavelength detection even when irradiation light is incident not only from the center but also from the periphery or side surfaces. Its purpose is to provide.

<Example> An example of the optical semiconductor device according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a side sectional view of an embodiment of an optical semiconductor device according to the present invention. A P-type silicon substrate 2 is used as a substrate of the optical semiconductor device 1, an epitaxial layer 3 exhibiting N-type conductivity is provided on the P-type silicon substrate 2, and a relatively shallow layer 3 is provided in the N-type epitaxial layer 3. P ⁺ diffusion is swirled to provide a P type region 4 . According to this structure, the first PN located deep between the P-type substrate 2 and the N-type epitaxial layer 3
A junction 5 is formed between the N-type epitaxial layer 3 and
Second PN junction 6 located shallowly between P ⁺ region 4
is formed. 7 is an N-type epitaxial layer 3
This is a P ⁺ isolation region provided through the . The P type substrate 2, the N type epitaxial region 3 ^, and the P ⁺ region 4 are provided with electrodes 8, 9, and 10, respectively, which are in ohmic contact. A light-transmitting insulating film 11 (for example, SiO ₂ film) such as a prevention film is deposited. Further, the electrode 9 is located on the periphery of the P-type region 4 on the transparent insulating film 11 .
It extends and is deposited so as to cover the N type epitaxial region 3 and the P ⁺ isolation region 7 around the periphery. A third photodiode 12 is formed at a position covering the P ⁺ isolation region 7 and an area further outside thereof. The third photodiode 12 is kept short-circuited. That is, a third photodiode 12 consisting of an N-type epitaxial layer 13, a P ⁺ isolation region 7, and a P-type region 2 is formed in the peripheral area of the chip, and a P-type region 14 by P ⁺ diffusion and an N-type region 14 by N ⁺ diffusion are formed. A mold region 15 is formed, and both are short-circuited by an aluminum electrode 16 (one short-circuit portion is sufficient). Note that the P type region 14 and the N type region 15 are P type regions 14 and N type regions 15.
It is efficient to form the type region 4 and the N-type region 17 at the same time. The effective light-receiving area of the third photodiode 12 is outside the dashed-dotted lines (A) and (B) in FIG. That is, the boundaries of the effective light receiving area between the photodiode formed by the second PN junction 6 and the third photodiode 12 are the dashed-dotted lines (A) and (B). According to the structure shown in FIG. 1 described above, a large amount of minority carriers generated by light incident on the periphery or side surface of the optical semiconductor device 1 is absorbed by the third photodiode 12. In this structure, there is no need to consider the diffusion length of minority carriers due to incident light from the periphery or side, and the dimensions outside the boundary line (dotted chain lines (A) and (B)) of the effective light receiving area can be reduced. This has the advantage that the overall size of the device can be reduced. Next, FIG. 7 shows a side sectional view of an embodiment of a structure that is a further improvement of FIG. 1. In the figure, 18 is an interlayer insulating material made of phosphor glass, polyimide resin, etc., which covers the aluminum film 19 through the interlayer insulating material.
9 shields the gap between the electrodes 9 and 16 from light. By providing the aluminum film 19, the degree of freedom in electrode wiring can be increased.

<Effects> According to the present invention, it is possible to provide an optical semiconductor device that is miniaturized, prevents the adverse effects of light incident from the peripheral portion or side portion, and obtains an accurate relationship between optical output ratio and wavelength. can.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of an embodiment of an optical semiconductor device according to the present invention, FIG. 2 is a side sectional view of a conventional optical semiconductor device, FIG. 3 is an equivalent circuit diagram, and FIG. 4 is a diagram of spectral sensitivity characteristics. Graph diagram, Figure 5 is a circuit diagram of the wavelength detection circuit,
FIG. 6 is a graph showing the relationship between the wavelength detection circuit output and the wavelength of irradiated light, and FIG. 7 is a side sectional view of another embodiment of the optical semiconductor device according to the present invention. In the figure, 1...
... Optical semiconductor device, 2 ... Substrate, 3 ... N type epitaxial layer, 4 ... P type region, 5 ... First PN
Junction, 6... Second PN junction, 7... P ⁺ isolation region, 8, 9, 10... Electrode, 11...
Transparent insulating film, 12... third photodiode,
13... N-type epitaxial layer, 14... P-type region, 15... N-type region, 16... aluminum electrode, 17... N-type region, 18... interlayer insulator, 1
9...Aluminum film.

Claims (1)

[Claims] 1 A first photodiode and a second photodiode are formed by two PN junctions having different depths in the thickness direction of the semiconductor substrate, and the first photodiode and the second photodiode are connected to each other when irradiated with light. In an optical semiconductor device provided with electrodes for respectively deriving photocurrents generated in each PN junction,
An optical semiconductor device characterized in that a third photodiode maintained in a short-circuited state is formed at a position covering an isolation region provided around each of the PN junctions and a region further outside the isolation region.