JP2006041432A - Optical semiconductor device and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly consolidate a fast and high light acceptance sensitivity photo-diode (PD) and a fast and highly pressure-proof transistor on the same semiconductor substrate. <P>SOLUTION: In an opto-electronic integrated circuit (OEIC) wherein a transistor and a light receiving element are consolidated on the same semiconductor substrate, a p-type first epitaxial layer 22 is formed, and then, an n-type second epitaxial layer 23 is formed, the structure of which makes it possible to materialize an epitaxial layer's film thickness most suitable for a higher performance of a vertical PNP transistor 3 and a photo-diode 4, and thus, such a structure is feasible as can fully exercise each element's characteristics improvement, thus resulting in an enhancement of the OEIC's characteristics. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical semiconductor device in which a light receiving element and a transistor are mixedly mounted on the same substrate, and a method for manufacturing the same.

  The light receiving element is an element that converts an optical signal into an electric signal, and is used in various fields. In particular, in the field of optical discs such as CD and DVD, it is important as a key device of an optical pickup device that reads and writes signals recorded on the optical disc. In recent years, there has been a so-called optoelectronic integrated circuit (OEIC) in which a photodiode as a light receiving element and various electronic elements such as a bipolar transistor, a resistor, and a capacitor are mounted on the same substrate in response to a demand for higher performance and higher integration. In the OEIC, a light receiving element having high light receiving sensitivity, high speed, and low noise characteristics and a high speed, high performance bipolar transistor are required to be mounted together.

  A conventional optical semiconductor device will be described below.

  FIG. 8 is a cross-sectional view of an optical semiconductor device (OEIC) in the prior art. This OEIC includes a silicon substrate as a semiconductor substrate, a vertical PNP transistor (V-PNP transistor) as a bipolar transistor, and a pin photodiode as a light receiving element. 1 is a low-concentration p-type silicon substrate, 2 is an n-type epitaxial layer formed on the silicon substrate 1, 3 is a V-PNP transistor formed in the n-type epitaxial layer 2, and 4 is formed in the n-type epitaxial layer 2. Pin photodiode.

  In the V-PNP transistor 3, 5 is a high-concentration p-type emitter layer, 6 is an n-type base layer formed under the emitter layer 5, 7 is a p-type collector layer formed under the base layer 8, 8 is a high-concentration n-type buried layer formed under the collector layer 7, 9 is an emitter electrode, 10 is a base electrode, and 11 is a collector electrode. Currents flowing through the emitter layer 5, the base layer 6, and the collector layer 7 are taken out from the emitter electrode 9, the base electrode 10, and the collector electrode 11, respectively.

  A high-concentration p-type isolation layer 12 electrically insulates and isolates elements such as the V-PNP transistor 3 and the photodiode 4.

  In the photodiode 4, 13 is a cathode layer formed of the n-type epitaxial layer 2, 14 is a high concentration n-type cathode contact layer formed on the cathode layer 13, and 15 is a cathode electrode formed on the cathode contact layer 14. is there.

  Reference numeral 16 denotes a high-concentration p-type anode contact layer also used as a separation layer, and reference numeral 17 denotes an anode electrode formed on the anode contact layer 16. The anode region is a region of the low-concentration p-type silicon substrate 1 below the cathode layer 13, and the anode contact layer 16 is used for holes and the cathode contact layer 14 is used for electrons. Via the cathode electrode 15 and taken out as current. Reference numeral 18 denotes a light receiving surface formed on the cathode contact layer 14, and an antireflection film is often provided to reduce reflection at the interface of incident light.

  The operation of the OEIC configured as described above will be described below.

  Light enters from the light receiving surface 18 and is absorbed by the cathode layer 13 and the silicon substrate 1 serving as the anode, generating electron / hole pairs. At this time, when a reverse bias is applied to the photodiode 4, a depletion layer spreads on the silicon substrate 1 side having a low impurity concentration, and among the electron-hole pairs generated in the vicinity of the depletion layer, electrons are supplied to the cathode contact layer 14. The holes reach the anode contact layer 16 separately by diffusion and drift, and a photocurrent is generated. In response to this photocurrent, the electronic circuit formed by the V-PNP transistor 3, the resistance element, and the capacitance element is amplified and signal-processed and output to become an optical disc recording and reproduction signal.

  However, in this structure, in order to ensure the withstand voltage of the V-PNP transistor 3, the n-type epitaxial layer 2 normally requires a film thickness of 2.5 μm or more. On the other hand, the photocurrent in the photodiode 4 is roughly divided into a diffusion current component and a drift current component. Since the diffusion current is dominated by diffusion of minority carriers to the end of the depletion layer, a drift current component due to an electric field in the depletion layer The response speed is slower than the above, which causes the frequency characteristics of the photodiode 4 to deteriorate. Therefore, in order to increase the speed of the photodiode 4, it is necessary to completely deplete the vicinity of the PN junction, and it is advantageous that the thickness of the n-type epitaxial layer 2 is thin. Usually, it is 1.0 μm or less. Therefore, it is difficult to integrate the high-speed V-PNP transistor 3 and the high-speed photodiode 4 on the same substrate.

  As a method for solving this problem, a technique for selectively etching the epitaxial layer of the photodiode portion has been proposed.

  Hereinafter, a conventional optical semiconductor device that selectively etches the epitaxial layer of the photodiode portion will be described with reference to FIG. 9 (see Patent Document 1).

  Reference numeral 19 denotes an etching region formed by selectively etching the n-type epitaxial layer 2 of the photodiode 4. In this structure, by changing the depth of the etching region 19, the thickness of the cathode layer 13 can be easily controlled independently of the thickness of the n-type epitaxial layer 2, and the thickness can be reduced to 1.0 μm or less. Become. That is, the thick film of the n-type epitaxial layer 2 of the V-PNP transistor 3 and the thin film of the cathode layer 13 can be realized simultaneously. It is advantageous that the thickness of the cathode layer 13 is thin (usually 1.0 μm or less). Therefore, the high-speed V-PNP transistor 3 and the high-speed photodiode 4 can be integrated on the same substrate.

  In the prior art of FIG. 8, as a second problem, for example, when infrared light or the like is incident on silicon, the light enters from the surface to a depth of about 30 μm because the absorption coefficient is small. Usually, the depletion layer extends to the anode side, but its length is at most 10 μm or less. Therefore, when infrared light is incident, carriers generated outside the depletion layer reach the end of the depletion layer by diffusion and become a current, resulting in a diffusion current that becomes a slow component and cannot be increased in speed. It is.

  In order to solve this problem, a technique for forming a high-concentration buried layer in a silicon substrate has been proposed for further increasing the speed of OEIC.

  Hereinafter, a conventional optical semiconductor device that selectively etches the epitaxial layer of the photodiode portion will be described with reference to FIG. 10 (see Patent Document 2).

  Reference numeral 20 denotes a high-concentration p-type buried layer formed on the silicon substrate 1, and reference numeral 21 denotes a p-type epitaxial layer formed on the silicon substrate 1.

In this structure, the p-type epitaxial layer 21 is completely depleted by the operating voltage of the photodiode 4 by selecting a low concentration and a thickness of about several to 10 μm. Further, when the p-type buried layer 20 is formed at a high concentration of two digits or more with respect to the silicon substrate 1, carriers formed in the silicon substrate 1 by light such as infrared light that penetrates deeply are generated due to the concentration difference. They are recombined by the potential barrier and do not become current components. In other words, the drift current component is dominant in the carrier current on the anode side in the photocurrent, which is advantageous for speeding up.
Japanese Unexamined Patent Publication No. 2003-37259 (page 4, FIG. 1-3) Japanese Patent Laid-Open No. 9-219534 (page 4-5, FIG. 3-5)

  However, in the case of FIG. 9, a step of about several μm occurs in the etching region 19, so that the process of forming the cathode contact layer 14 and the cathode electrode 15 becomes complicated. The resist film thickness used for pattern formation is required to be thick for coverage, and it is particularly difficult to miniaturize the pattern. Further, when a wiring or the like is formed at the step portion, the wiring is likely to be disconnected, and there is a problem that the degree of freedom of the pattern of the photodiode 4 is limited.

  In addition, a pattern in which a plurality of photodiodes 4 are adjacent to each other is often used. In this case, photocurrent characteristics (scan characteristics) when light is scanned in the lateral direction are important. However, when light hits the stepped portion of the etching region 19, irregular reflection occurs, and the incidence of light into the photodiode 4 becomes unstable, resulting in a problem that stable scanning characteristics cannot be obtained.

  In the case of FIG. 10, the p-type epitaxial layer 21 usually needs a low concentration and a thickness of about several to 10 μm in order to improve the light receiving sensitivity to infrared light. Is formed by implantation or the like, it is difficult to form deeper than 5 μm. Therefore, the p-type epitaxial layer 21 having a low concentration is interposed between the anode contact layer 16 and the p-type buried layer 20, and the series resistance of the photodiode 4 cannot be reduced. Therefore, there arises a problem that the frequency characteristic that depends on the CR product cannot be increased.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and an object thereof is to provide an optical semiconductor device in which a high-speed transistor and a high-light-receiving sensitivity / high-speed light-receiving element are appropriately mounted on the same substrate, and a method for manufacturing the same. And

A first optical semiconductor device according to the present invention includes:
A first conductivity type first epitaxial layer formed on a first conductivity type semiconductor substrate;
A second epitaxial layer of a second conductivity type formed on the first epitaxial layer;
A light receiving element formed in the first and second epitaxial layers;
The semiconductor substrate and the transistor formed in the first and second epitaxial layers are provided.

  Here, the first conductivity type and the second conductivity type indicate either a p-type or an n-type semiconductor. When the first conductivity type is p-type, the second conductivity type is n-type. Conversely, when the first conductivity type is n-type, the second conductivity type is p-type.

  The optical semiconductor device is characterized in that the conductivity type of the first epitaxial layer formed on the semiconductor substrate is the same as that of the semiconductor substrate, and the conductivity type of the second epitaxial layer formed on the first epitaxial layer. However, the conductivity type is opposite to that of the first epitaxial layer and the semiconductor substrate.

  In the prior art, the PN junction of the light receiving element is formed by the semiconductor substrate and the epitaxial layer thereon, or the conductivity types are separated from each other through the high-concentration buried layer of the same conductivity type with respect to the semiconductor substrate. The first and second epitaxial layers are formed. On the other hand, in the above configuration of the present invention, the PN junction of the light receiving element is formed by the first epitaxial layer and the second epitaxial layer having different conductivity types, apart from the semiconductor substrate. . There is no high concentration buried layer between the semiconductor substrate and the first epitaxial layer.

  The total film thickness of the first epitaxial layer and the second epitaxial layer forming the PN junction is set to a film thickness sufficient to ensure the depth of the active region of the transistor, and high performance characteristics such as high breakdown voltage of the transistor Secure. In this case, if the thickness of the upper second epitaxial layer is reduced, the cathode layer of the light receiving element is also reduced, and the amount of carriers absorbed on the cathode side is reduced. That is, since the diffusion current component is reduced and the photocurrent is dominated by the drift current component, high-speed response of the light receiving element is enabled.

  Through the above synergy, a high-speed light receiving element and a high-speed, high-performance transistor can be formed on the same substrate. Moreover, since the surface of the light receiving element is formed flat and no step is generated, the process can be simplified and miniaturized. Furthermore, the light scanning characteristic is also stabilized.

A second optical semiconductor device according to the present invention includes:
A buried layer of a first conductivity type having a higher concentration than the semiconductor substrate formed on the semiconductor substrate of the first conductivity type;
A first epitaxial layer of a first conductivity type formed on the semiconductor substrate;
A second epitaxial layer of a first conductivity type formed on the first epitaxial layer;
A third epitaxial layer of the second conductivity type formed on the second epitaxial layer;
A light receiving element formed in the second and third epitaxial layers;
And a transistor formed in the first, second and third epitaxial layers.

  This configuration is mainly designed to obtain high light receiving sensitivity with respect to infrared light. In this case, the PN junction of the light receiving element is formed by the second epitaxial layer and the third epitaxial layer.

  According to a third optical semiconductor device of the present invention, in the second optical semiconductor device, an anode contact buried layer connected to the buried layer is selectively formed in the first epitaxial layer. It has a configuration.

  Infrared light having a relatively long wavelength enters a semiconductor substrate relatively deeply, and electron / hole pairs are generated there. Carriers generated in the semiconductor substrate are recombined by the potential barrier formed by the buried layer, thereby reducing the diffusion current component and increasing the speed. The first epitaxial layer and the second epitaxial layer form an anode region. If the film thickness of the first epitaxial layer is reduced, the anode contact buried layer in the first epitaxial layer can be shortened and buried. Connection with the layer becomes possible. As a result, it is possible to reduce the series resistance and increase the speed of the light receiving element.

  In the above, the semiconductor substrate, the first and second epitaxial layers, and further the third epitaxial layer are usually made of silicon. The transistor includes a case where it is a vertical PNP transistor.

  As for the film thickness of the epitaxial layer forming the PN junction, the film thickness of the first epitaxial layer is 1.0 μm or more and the film thickness of the second epitaxial layer is 1.0 μm or less. including. Or the case where the film thickness of the said 2nd epitaxial layer is 1.0 micrometer or more and the film thickness of the said 3rd epitaxial layer is 1.0 micrometer or less is included. The upper epitaxial layer of the PN junction is preferably thinner.

  The first epitaxial layer and the second epitaxial layer forming the PN junction are related to the depth of the active region of the transistor, and as the total film thickness of both epitaxial layers is increased, high performance characteristics such as higher breakdown voltage of the transistor are secured. Is done. In this case, if the thickness of the upper epitaxial layer is reduced, the cathode layer of the light receiving element is also reduced, and the amount of carriers absorbed on the cathode side is reduced. That is, since the diffusion current component is reduced and the photocurrent is dominated by the drift current component, high-speed response of the light receiving element is enabled. In order to satisfy this condition, the thickness of the lower epitaxial layer is preferably 1.0 μm or more, and the thickness of the upper epitaxial layer is preferably 1.0 μm or less.

A first optical semiconductor device manufacturing method according to the present invention includes:
Growing a first conductive type first epitaxial layer on a first conductive type semiconductor substrate;
Growing a second conductivity type second epitaxial layer on the first epitaxial layer;
Forming a light receiving element in the second epitaxial layer;
Forming a transistor in the first and second epitaxial layers.

  According to this manufacturing method, the first epitaxial layer having the same conductivity type as that of the semiconductor substrate is formed on the semiconductor substrate, and the second epitaxial layer having a different conductivity type is further formed thereon, on which the light receiving element is formed. In addition, an optical semiconductor device in which a transistor is formed can be obtained. Therefore, the first optical semiconductor device having the high-speed light-receiving element and the high-speed and high-performance transistor, the surface of the light-receiving element being flat, and the light scanning characteristic being stabilized is effectively promoted. Can do.

A second method for manufacturing an optical semiconductor device according to the present invention includes:
A step of forming a high-concentration buried layer by implanting high-energy dopant into the first conductive type semiconductor substrate in a first conductive type;
Growing a first conductivity type first epitaxial layer on the semiconductor substrate;
Growing a second conductivity type second epitaxial layer on the first epitaxial layer;
Forming a light receiving element in the second epitaxial layer;
Forming a transistor in the first and second epitaxial layers.

A third method for manufacturing an optical semiconductor device according to the present invention includes:
Forming a first conductivity type buried layer on the first conductivity type semiconductor substrate, the concentration of the first conductivity type being higher than that of the semiconductor substrate;
Growing a first conductivity type first epitaxial layer on the semiconductor substrate;
Growing a second conductivity type second epitaxial layer on the first epitaxial layer;
Forming a light receiving element in the second epitaxial layer;
Forming a transistor in the first and second epitaxial layers.

  In the second manufacturing method, a buried layer having the same conductivity type as that of the semiconductor substrate is formed by high energy implantation of a dopant, and the buried layer is formed in the semiconductor substrate. In contrast, the third manufacturing method does not require particularly high energy, and a buried layer is formed on the semiconductor substrate by normal implantation.

  According to the second or third manufacturing method, after the high-concentration buried layer having the same conductivity type as that of the semiconductor substrate is embedded in the semiconductor substrate, the first conductivity type having the same conductivity type as that of the semiconductor substrate is formed on the semiconductor substrate. Thus, an optical semiconductor device in which a second epitaxial layer of a different conductivity type is formed thereon and a light receiving element and a transistor are formed thereon is obtained. Accordingly, the second light-receiving element has a high-speed light-receiving element and a high-speed and high-performance transistor, the surface of the light-receiving element is flat, the light scanning characteristic is stabilized, and the second light receiving sensitivity is particularly high for infrared light. The production of the optical semiconductor device can be effectively advanced.

A fourth method for manufacturing an optical semiconductor device according to the present invention includes:
Forming a first conductivity type buried layer on the first conductivity type semiconductor substrate, the concentration of the first conductivity type being higher than that of the semiconductor substrate;
Growing a first conductivity type first epitaxial layer on the semiconductor substrate;
Growing a second epitaxial layer of a first conductivity type on the first epitaxial layer;
Growing a third epitaxial layer of a second conductivity type on the second epitaxial layer;
Forming a light receiving element in the third epitaxial layer;
Forming a transistor in the second and third epitaxial layers.

A fifth method for manufacturing an optical semiconductor device according to the present invention includes:
Forming a first conductivity type buried layer on the first conductivity type semiconductor substrate, the concentration of the first conductivity type being higher than that of the semiconductor substrate;
Growing a first conductivity type first epitaxial layer on the semiconductor substrate;
Forming an anode contact buried layer by implantation so that a concentration peak reaches a predetermined depth from the surface during the first epitaxial;
Growing a second epitaxial layer of a first conductivity type on the first epitaxial layer;
Growing a third epitaxial layer of a second conductivity type on the second epitaxial layer;
Forming a light receiving element in the third epitaxial layer;
Forming a transistor in the second and third epitaxial layers.

  The fourth, fifth and fifth manufacturing methods are characterized by comparison with the first to third manufacturing methods in that the epitaxial layer is grown in three stages. The difference between the fourth manufacturing method and the fifth manufacturing method is that, in the fifth manufacturing method, an anode contact buried layer is formed by implantation so that a concentration peak reaches a predetermined depth from the surface during the first epitaxial. There is a process to do.

  According to the fourth or fifth manufacturing method, the PN junction of the light receiving element is formed by the second epitaxial layer and the third epitaxial layer. As a result, the first to third manufacturing methods are used. An optical semiconductor device having the same structure as the above can be obtained. That is, a high concentration buried layer having the same conductivity type as that of the semiconductor substrate is embedded in the semiconductor substrate, and then a first epitaxial layer having the same conductivity type as that of the semiconductor substrate is formed on the semiconductor substrate, and the same is formed thereon. A second epitaxial layer of conductivity type is formed, and a third epitaxial layer of different conductivity type is further formed thereon, and an optical semiconductor device having a light receiving element and a transistor formed thereon is obtained. Therefore, it has a high-speed light-receiving element and a high-speed, high-performance transistor, the surface of the light-receiving element is flat, the light scanning characteristics are stabilized, and, moreover, an optical semiconductor device with particularly high light-receiving sensitivity to infrared light. Manufacturing can proceed effectively. In particular, according to the fifth manufacturing method, since the anode contact buried layer is formed in the first epitaxial layer so that the concentration peak reaches a predetermined depth, the series resistance is small and the light receiving element can operate at high speed. Realize.

  According to the optical semiconductor device or the method of manufacturing an optical semiconductor device of the present invention, the epitaxial layer of the transistor portion is made thick and the light receiving element portion is made thin at the same time, so that the high-speed transistor and the high-speed light receiving element are the same. It can be integrated on a substrate. In addition, the semiconductor surface can be a flat surface without a step, and the process can be simplified and further miniaturized. Furthermore, the light scanning characteristics can be stabilized. In addition, since the high-concentration anode contact buried layer is formed by implantation under a high energy condition, the series resistance of the light receiving element can be reduced to increase the speed. When the buried layer for layer separation is formed, both high-speed response and high light receiving sensitivity can be achieved for infrared light.

  Embodiments of an optical semiconductor device (OEIC) according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1 of an optical semiconductor device)
FIG. 1 is a cross-sectional view showing the configuration of the optical semiconductor device according to the first embodiment of the present invention. In FIG. 1, 1 is a low-concentration p-type silicon substrate, 22 is a low-concentration p-type first epitaxial layer formed on the silicon substrate 1, and 23 is formed on the p-type first epitaxial layer 22. The n-type second epitaxial layer formed.

  3 is a V-PNP transistor, 4 is a photodiode, 5 is an emitter layer, 6 is a base layer, 7 is a collector layer, 8 is an n-type buried layer, 9 is an emitter electrode, 10 is a base electrode, and 11 is a collector electrode. . 12 is a separation layer, 13 is a cathode layer, 14 is a cathode contact layer, and 15 is a cathode electrode. Reference numeral 16 denotes an anode contact layer, 17 denotes an anode electrode, and 18 denotes a light receiving surface, which are the same as those in the conventional configuration.

  The operation of the optical semiconductor device of the present embodiment configured as described above will be described below.

  The basic operation is the same as that described with reference to FIG. When light enters from the light receiving surface 18, it is absorbed by the cathode layer 13 and the low-concentration p-type first epitaxial layer 22, which is the anode, and the silicon substrate 1, generating electron / hole pairs, and the electrons are cathode contact layer 14. In addition, the holes reach the anode contact layer 16 by being separated into diffusion and drift, and a photocurrent is generated. For example, when the concentration of the n-type second epitaxial layer 23 is higher than that of the p-type first epitaxial layer 22 by one digit or more, the interface between the cathode layer 13 and the p-type first epitaxial layer 22, That is, in the vicinity of the PN junction, the depletion layer extends toward the p-type first epitaxial layer 22 and hardly extends toward the cathode layer 13. Here, when the n-type second epitaxial layer 23 is thinned (for example, 1.0 μm or less), the cathode layer 13 is also thinned, and the amount of carriers absorbed on the cathode side is reduced. That is, since the diffusion current component is reduced and the photocurrent is dominated by the drift current component, the photodiode 4 can respond at high speed.

  On the other hand, in this embodiment, since the film thicknesses of the p-type first epitaxial layer 22 and the n-type second epitaxial layer 23 can be determined independently, the film thickness of the p-type first epitaxial layer 22 is By increasing the thickness (for example, 1.5 μm or more), it is possible to sufficiently secure the depth (for example, 1.5 μm or more) of the active region of the V-PNP transistor 3, thereby realizing high performance characteristics such as high breakdown voltage. It becomes easy.

  As a result, the high-speed photodiode 4 and the high-speed and high-performance V-PNP transistor 3 can be formed on the same substrate. That is, a structure capable of maximizing the improvement of the characteristics of each element is possible, and the characteristics can be improved as an OEIC.

  Further, since no step is generated on the surface of the photodiode 4, the process can be simplified and miniaturized as compared with the case where there is a step. Furthermore, the light scanning characteristic can be stabilized.

(Embodiment 2 of an optical semiconductor device)
FIG. 2 is a cross-sectional view showing the configuration of the optical semiconductor device according to the second embodiment of the present invention. In FIG. 2, 24 is a high-concentration p-type buried layer formed by implantation or the like in the silicon substrate 1, 25 is a p-type first epitaxial layer formed on the silicon substrate 1, and 26 is a p-type buried layer. This is a p-type second epitaxial layer formed on the first epitaxial layer 25. Reference numeral 27 denotes an n-type third epitaxial layer formed on the p-type second epitaxial layer 26. 28 is a high concentration p-type anode contact buried layer selectively formed in the p-type first epitaxial layer 25, and 29 is the p-type first epitaxial layer 25 of the photodiode 4 and the p-type first epitaxial layer 25. 2 is an anode region formed by two epitaxial layers 26.

  In the second embodiment, the anode region 29 is usually formed at a low concentration so that it is sufficiently depleted by the operating voltage of the photodiode 4. Further, the p-type buried layer 24 has a concentration two or more digits higher than that of the silicon substrate 1, and carriers formed in the silicon substrate 1 are recombined by a potential barrier generated by the concentration difference, thereby reducing the diffusion current component and increasing the speed. We are trying to make it. The anode contact buried layer 28 is connected to the anode contact layer 16 and the p-type buried layer 24 in order to reduce the resistance component of the photodiode 4. In order to obtain a high light receiving sensitivity with respect to infrared light, the film thickness of the anode region 29 needs to be about several to 10 μm. Here, by setting the thickness of the p-type second epitaxial layer 26 to several μm, the thickness of the p-type first epitaxial layer 25 can be formed to be 5 μm or less, and by implanting under high energy conditions. The anode contact buried layer 28 can be formed so that the peak concentration is 2 μm from the surface of the p-type first epitaxial layer 25, and can be connected to the p-type buried layer 24.

  According to this structure, holes generated in the depletion layer by light absorption are extracted from the anode electrode 17 from the p-type buried layer 24 via the anode contact buried layer 28 and the anode contact layer 16. Since each layer is set to a high concentration, the resistance component becomes small, and the speed of the photodiode 4 can be increased.

(First Embodiment of Manufacturing Method of Optical Semiconductor Device)
FIG. 3 is a cross-sectional view showing each step of the first embodiment of the method of manufacturing the optical semiconductor device in the present invention. 30 is a low-concentration p-type silicon substrate, 31 is a p-type buried layer for an isolation layer, 32 is an n-type buried layer for a transistor region, 33 is a p-type first epitaxial layer, and 34 is a p-type for a collector layer. The type buried layer 35 is an n type buried layer for the transistor region, and 36 is an n type second epitaxial layer.

  First, a p-type buried layer 31 for a separation layer and an n-type buried layer 32 for a transistor region are selectively formed in a silicon substrate 30 by ion implantation or the like (FIG. 3A).

  Next, a p-type first epitaxial layer 33 is grown on the silicon substrate 30 (FIG. 3B).

  Next, a p-type buried layer 34 for the collector layer and an n-type buried layer 35 for the transistor region are selectively formed in the p-type first epitaxial layer 33 by ion implantation or the like (FIG. 3C).

  Further, an n-type second epitaxial layer 36 is grown on the p-type first epitaxial layer 33 (FIG. 3D).

  Finally, the V-PNP transistor 3 and the photodiode 4 are formed in the n-type second epitaxial layer 36 (FIG. 3E).

(Second Embodiment of Manufacturing Method of Optical Semiconductor Device)
FIG. 4 is a cross-sectional view showing each process of the second embodiment of the method of manufacturing the optical semiconductor device in the present invention. Reference numeral 37 denotes a p-type buried layer for layer separation.

  First, a p-type buried layer 37 for layer separation is formed in the silicon substrate 30 by ion implantation using a high energy condition (FIG. 4A). At this time, the peak concentration position of the p-type buried layer 37 is selectively formed at a position several μm deep from the surface of the silicon substrate 30.

  Next, a p-type buried layer 31 for the separation layer and an n-type buried layer 32 for the transistor region are selectively formed in the silicon substrate 30 by ion implantation or the like (FIG. 4B).

  Further, a p-type first epitaxial layer 33 is grown on the silicon substrate 30 (FIG. 4C).

  Next, a p-type buried layer 34 for the collector layer and an n-type buried layer 35 for the transistor region are selectively formed in the p-type first epitaxial layer 33 by ion implantation or the like (FIG. 4D).

  Further, an n-type second epitaxial layer 36 is grown on the p-type first epitaxial layer 33 (FIG. 4E). Finally, the V-PNP transistor 3 and the photodiode 4 are formed in the n-type second epitaxial layer 36 (FIG. 4F).

(Embodiment 3 of the manufacturing method of an optical semiconductor device)
FIG. 5 is a cross-sectional view showing each step of Embodiment 3 of the method for manufacturing an optical semiconductor device in the present invention.

  First, a p-type buried layer 37 for layer separation is formed in the silicon substrate 30 by ion implantation or the like (FIG. 5A).

  Next, a p-type first epitaxial layer 33 is grown on the silicon substrate 30 (FIG. 5B).

  Next, the p-type buried layer 31 for the isolation layer and the n-type buried layer 32 for the transistor region are ion-implanted into the p-type first epitaxial layer 33 using high energy conditions. It is selectively formed so as to be a position several μm deep from the surface of the silicon substrate 30 (FIG. 5C).

  Next, a p-type buried layer 34 for the collector layer and an n-type buried layer 35 for the transistor region are selectively formed in the p-type first epitaxial layer 33 by ion implantation or the like (FIG. 5D).

  Further, an n-type second epitaxial layer 36 is grown on the p-type first epitaxial layer 33 (FIG. 5E).

  Finally, the V-PNP transistor 3 and the photodiode 4 are formed in the n-type second epitaxial layer 36 (FIG. 5F).

(Fourth Embodiment of Manufacturing Method of Optical Semiconductor Device)
FIG. 6 is a cross-sectional view showing each step of Embodiment 4 of the method for manufacturing an optical semiconductor device in the present invention. Reference numeral 38 denotes a p-type first epitaxial layer, 39 denotes a p-type second epitaxial layer, and 40 denotes an n-type third epitaxial layer.

  First, a p-type buried layer 37 for layer separation is formed in the silicon substrate 30 by ion implantation or the like (FIG. 6A). Next, a p-type first epitaxial layer 38 is grown on the silicon substrate 30 (FIG. 6B). Next, the p-type buried layer 31 for the separation layer and the n-type buried layer 32 for the transistor region are selectively formed in the p-type first epitaxial layer 38 by ion implantation or the like (FIG. 6C). ). Further, a p-type second epitaxial layer 39 is grown on the p-type first epitaxial layer 38 (FIG. 6D). Next, a p-type buried layer 34 for the collector layer and an n-type buried layer 35 for the transistor region are selectively formed in the p-type second epitaxial layer 39 by ion implantation or the like (FIG. 6E). Further, an n-type third epitaxial layer 40 is grown on the p-type second epitaxial layer 39 (FIG. 6F). Finally, the V-PNP transistor 3 and the photodiode 4 are formed in the n-type third epitaxial layer 40 (FIG. 6G).

(Fifth Embodiment of Manufacturing Method of Optical Semiconductor Device)
FIG. 7 is a cross-sectional view showing each step of Embodiment 5 of the method for manufacturing an optical semiconductor device in the present invention. Reference numeral 41 denotes a high concentration p-type anode contact buried layer.

  First, a p-type buried layer 37 for layer separation is formed in the silicon substrate 30 by ion implantation or the like (FIG. 7A).

  Next, a p-type first epitaxial layer 38 is grown on the silicon substrate 30 (FIG. 7B).

  Next, an anode contact buried layer 41 is formed in the p-type first epitaxial layer 38 by ion implantation using a high energy condition. The position of the peak concentration of the anode contact buried layer 41 is selectively formed so as to be several μm deep from the surface of the silicon substrate 30.

  Further, a p-type buried layer 31 for the isolation layer and an n-type buried layer 32 for the transistor region are selectively formed (FIG. 7C).

  Further, a p-type second epitaxial layer 39 is grown on the p-type first epitaxial layer 38 (FIG. 7D).

  Next, a p-type buried layer 34 for the collector layer and an n-type buried layer 35 for the transistor region are selectively formed in the p-type second epitaxial layer 39 by ion implantation or the like (FIG. 7E).

  Further, an n-type third epitaxial layer 40 is grown on the p-type second epitaxial layer 39 (FIG. 7F).

  Finally, the V-PNP transistor 3 and the photodiode 4 are formed in the n-type third epitaxial layer 40 (FIG. 7G).

  In the above description of the embodiment, a silicon substrate is used. However, the present invention is not necessarily limited to a silicon substrate. For example, a germanium substrate or a compound semiconductor widely used in a long wavelength region may be used. Good.

  In the above description, a pin photodiode is used as the light receiving element. However, it goes without saying that the present invention can also be applied to a normal pn-type photodiode, avalanche photodiode, and phototransistor. Also, a V-PNP transistor was used as the transistor. Needless to say, the present invention can also be applied to NPN transistors and MOS transistors.

  In the above description, the p-type is used as the semiconductor substrate and the first epitaxial layer. However, it goes without saying that the n-type is applicable.

  The optical semiconductor device or the optical semiconductor device manufacturing method of the present invention is useful for a so-called OEIC (optoelectronic integrated circuit) in which high-speed and high-performance transistors and high-speed and high light-receiving sensitivity light-receiving elements are integrated on the same substrate.

Sectional drawing which shows the structure of Embodiment 1 of the optical semiconductor device in this invention Sectional drawing which shows the structure of Embodiment 2 of the optical semiconductor device in this invention Sectional drawing which shows each process of Embodiment 1 of the manufacturing method of the optical semiconductor device in this invention Sectional drawing which shows each process of Embodiment 2 of the manufacturing method of the optical semiconductor device in this invention Sectional drawing which shows each process of Embodiment 3 of the manufacturing method of the optical semiconductor device in this invention Sectional drawing which shows each process of Embodiment 4 of the manufacturing method of the optical semiconductor device in this invention Sectional drawing which shows each process of Embodiment 5 of the manufacturing method of the optical semiconductor device in this invention Sectional drawing which shows the structure of the optical semiconductor device in a prior art Sectional drawing which shows the structure of the optical semiconductor device in another prior art Sectional drawing which shows the structure of the optical semiconductor device in another prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 N type epitaxial layer 3 V-PNP transistor 4 Photodiode (light receiving element)
5 emitter layer 6 base layer 7 collector layer 8 n-type buried layer 9 emitter electrode 10 base electrode 11 collector electrode 12 separation layer 13 cathode layer 14 cathode contact layer 15 cathode electrode 16 anode contact layer 17 anode electrode 18 light receiving surface 19 etching region 20 p-type buried layer 21 p-type epitaxial layer 22 p-type first epitaxial layer 23 n-type second epitaxial layer 24 p-type buried layer 25 p-type first epitaxial layer 26 p-type second epitaxial layer 27 n-type third epitaxial layer 28 anode contact buried layer 29 anode region 30 silicon substrate 31 p-type buried layer for isolation layer 32 n-type buried layer for transistor region 33 p-type first epitaxial layer 34 collector layer For Type buried layer 35 n type buried layer for transistor region 36 n type second epitaxial layer 37 p type buried layer for layer separation 38 p type first epitaxial layer 39 p type second epitaxial layer 40 n Type third epitaxial layer 41 anode contact buried layer

Claims (13)

A first conductivity type first epitaxial layer formed on a first conductivity type semiconductor substrate;
A second epitaxial layer of a second conductivity type formed on the first epitaxial layer;
A light receiving element formed in the first and second epitaxial layers;
An optical semiconductor device comprising: the semiconductor substrate; and a transistor formed in the first and second epitaxial layers. A buried layer of a first conductivity type having a higher concentration than the semiconductor substrate formed on the semiconductor substrate of the first conductivity type;
A first epitaxial layer of a first conductivity type formed on the semiconductor substrate;
A second epitaxial layer of a first conductivity type formed on the first epitaxial layer;
A third epitaxial layer of the second conductivity type formed on the second epitaxial layer;
A light receiving element formed in the second and third epitaxial layers;
An optical semiconductor device comprising: a transistor formed in the first, second, and third epitaxial layers.   The optical semiconductor device according to claim 2, wherein an anode contact buried layer connected to the buried layer is selectively formed in the first epitaxial layer.   The optical semiconductor device according to claim 1, wherein the semiconductor substrate and the first and second epitaxial layers are made of silicon.   The optical semiconductor device according to claim 2, wherein the semiconductor substrate and the first, second, and third epitaxial layers are made of silicon.   The optical semiconductor device according to claim 1, wherein the transistor is a vertical PNP transistor.   5. The optical semiconductor device according to claim 4, wherein the film thickness of the first epitaxial layer is 1.0 μm or more and the film thickness of the second epitaxial layer is 1.0 μm or less.   The optical semiconductor device according to claim 5, wherein the film thickness of the second epitaxial layer is 1.0 μm or more and the film thickness of the third epitaxial layer is 1.0 μm or less. Growing a first conductive type first epitaxial layer on a first conductive type semiconductor substrate;
Growing a second conductivity type second epitaxial layer on the first epitaxial layer;
Forming a light receiving element in the second epitaxial layer;
Forming a transistor in the first and second epitaxial layers. A step of forming a high-concentration buried layer by implanting high-energy dopant into the first conductive type semiconductor substrate in a first conductive type;
Growing a first conductivity type first epitaxial layer on the semiconductor substrate;
Growing a second conductivity type second epitaxial layer on the first epitaxial layer;
Forming a light receiving element in the second epitaxial layer;
Forming a transistor in the first and second epitaxial layers. Forming a first conductivity type buried layer on the first conductivity type semiconductor substrate, the concentration of the first conductivity type being higher than that of the semiconductor substrate;
Growing a first conductivity type first epitaxial layer on the semiconductor substrate;
Growing a second conductivity type second epitaxial layer on the first epitaxial layer;
Forming a light receiving element in the second epitaxial layer;
Forming a transistor in the first and second epitaxial layers. Forming a first conductivity type buried layer on the first conductivity type semiconductor substrate, the concentration of the first conductivity type being higher than that of the semiconductor substrate;
Growing a first conductivity type first epitaxial layer on the semiconductor substrate;
Growing a second epitaxial layer of a first conductivity type on the first epitaxial layer;
Growing a third epitaxial layer of a second conductivity type on the second epitaxial layer;
Forming a light receiving element in the third epitaxial layer;
Forming a transistor in the second and third epitaxial layers. Forming a first conductivity type buried layer on the first conductivity type semiconductor substrate, the concentration of the first conductivity type being higher than that of the semiconductor substrate;
Growing a first conductivity type first epitaxial layer on the semiconductor substrate;
Forming an anode contact buried layer by implantation so that a concentration peak reaches a predetermined depth from the surface during the first epitaxial;
Growing a second epitaxial layer of a first conductivity type on the first epitaxial layer;
Growing a third epitaxial layer of a second conductivity type on the second epitaxial layer;
Forming a light receiving element in the third epitaxial layer;
Forming a transistor in the second and third epitaxial layers.

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