JP2007250917A - Optical semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to mount a high-photosensitivity photodiode for a monitor and a high-speed/high-performance transistor together on one and the same semiconductor substrate. <P>SOLUTION: A silicon substrate 1 is low-concentrated and of p-type. The photodiode for the monitor is formed by pn junction of a highly-concentrated n-type cathode layer 19 which is selectively formed on the silicon substrate 1. A light receiving element is composed of a first inclined plane 10, a second inclined plane 11, and a mirror basal plane 12 which are formed by etching the silicon substrate 1 in a micromirror part 3 for incident radiation from the first inclined plane 10. In this case, the first inclined plane 10 and the second inclined plane 11 form a predetermined angle with respect to the major surface of the silicon substrate 1. The mirror basal plane 12 is parallel to the major surface of the silicon substrate 1. A depletion layer 20a which is formed by pn junction between the silicon substrate 1 and the n-type cathode layer 19, and a depletion layer 20b which is formed of the first inclined plane 10, are connected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical semiconductor device and a method for manufacturing the same, and more particularly to a structure and a method for forming a light receiving element for monitoring in which a laser diode, a laser beam raising mirror, and a light receiving element are mixedly mounted on the same substrate.

  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, due to the demand for higher performance and higher integration, it has been configured as a so-called optoelectronic integrated circuit (OEIC) in which photodiodes as light receiving elements and various electronic elements such as bipolar transistors, resistors and capacitors are mounted on the same substrate. Yes. In response to further miniaturization and higher integration, an OEIC in which a laser diode, which is a light emitting element, and a 45 ° micromirror for starting up laser light are integrated is widely used. 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.

FIG. 7 shows a conventional optical semiconductor device.
This example illustrates an OEIC in which a low-concentration p-type silicon substrate 1, a monitoring photodiode 2 formed on the silicon substrate 1, and a micromirror unit 3 are configured on the same substrate. Reference numeral 15 denotes a laser diode.

  In the monitoring photodiode 2, 4 is a high-concentration n-type cathode layer, 5 is a high-concentration p-type anode contact layer, 6 is a LOCOS isolation layer, 7 is a cathode electrode, 8 is an anode electrode, 9 is an oxide film, etc. This is a field film to be formed. A p-type silicon substrate 1 and an n-type cathode layer 4 form a PN junction to form a monitoring photodiode 2, and photocurrent is taken out from the cathode electrode 7 and the anode electrode 8.

  The micromirror unit 3 is formed by anisotropic wet etching of the silicon substrate 1 using, for example, an alkaline aqueous solution such as potassium hydroxide, and the first inclined surface 10 on the monitoring photodiode side and the anti-monitoring side. It is composed of a second slope 11 on the photodiode side and a mirror bottom surface 12. Here, the first inclined surface 10 and the second inclined surface 11 form a predetermined angle with respect to the main surface of the silicon substrate 1, and the mirror bottom surface 12 is parallel to the main surface of the silicon substrate 1. For example, if a substrate with a (100) 9.7 ° off is used as the plane orientation of the silicon substrate 1, the (111) plane is extremely slow in etching rate for the alkaline aqueous solution. The plane orientation of 11 is the (111) plane. Since the (100) plane and the (111) plane form an angle of 54.7 °, the angles of the first inclined surface 10 and the second inclined surface 11 with respect to the main surface of the silicon substrate 1 are 64.3 °, respectively. 45 °. Reference numeral 13 denotes an insulating film formed of an oxide film, a nitride film, or the like formed on the first inclined surface 10 and the second inclined surface 11 and the mirror bottom surface 12. Reference numeral 14 denotes an insulating film formed on the second inclined surface 11, for example. This is a mirror reflection film made of a metal film such as Au.

  The laser diode 15 is placed on the mirror bottom surface 12 via a laser lower electrode 16. A front light 17 and a rear light 18 which are signal lights emitted from the laser diode 15 to the optical disk or the like are emitted.

  The front light 17 and the rear light 18 emitted from the laser diode 15 are parallel to the main surface of the silicon substrate 1. When the second inclined surface 11 is formed at 45 ° with respect to the main surface of the silicon substrate 1, the front light 17 rises in the vertical direction by the mirror reflection film 14 and is irradiated onto the optical disk or the like, and the reflected light is formed on the silicon substrate 1. A signal detection photodiode (not shown) is incident and converted to a photocurrent, and is amplified and signal processed by an electronic circuit formed by a transistor, a resistor element, and a capacitor element on the silicon substrate 1, and is output. It becomes a recording or reproduction signal of an optical disk.

  However, although the power of the front light 17 is determined by the current value flowing through the laser diode 15, there is a large individual difference in current-power characteristics. Therefore, to accurately adjust the power, the power of the emitted light is monitored and fed back. Therefore, auto power control (APC) for adjusting the current flowing to the laser diode 15 is required.

  Here, the rear light 18 is also emitted from the laser diode 15, and the power ratio of the front light 17 and the rear light 18 is uniquely determined by the type of the laser diode 15. The back light 18 is received by the monitoring photodiode 2 and converted into a photocurrent, and the magnitude of the photocurrent can be monitored and APC can be applied.

A part of the back light 18 is reflected by the first inclined surface 10, but a part of the back light 18 enters the silicon substrate 1 and is absorbed by the silicon substrate 1 to generate electron / hole pairs. Since the cathode layer 4 is formed on the entire lower portion of the field film 9, the generated electrons reach the PN junction formed by the silicon substrate 1 and the cathode layer 4 and are taken out from the cathode electrode 7. Some holes are recombined in the silicon substrate 1, but some holes are extracted to the outside through the anode contact layer 5 and the anode electrode 8. This photocurrent is subjected to APC as a monitor current to adjust the power of the laser diode 15.
JP-A-5-327131

  In recent years, there has been a demand for higher speed transistors, and in order to achieve this, it is necessary to make transistors and wiring rules finer, and to shallow the diffusion layers of transistors. However, since the step of the micromirror part 3 is as large as about 50 μm, it is necessary to use a thick film resist (film thickness of about 15 μm) in the process after the formation of the micromirror part 3, and miniaturization is difficult. Therefore, it is necessary to form the micromirror part 3 having a large design rule after forming the transistors and wirings of the miniaturization rule.

  However, in the above configuration, the cathode layer 4 needs to be formed after the micromirror part 3 is formed, and heat treatment is necessary to activate the impurities. However, after forming the shallow diffusion layer and the wiring of the transistor, the temperature is 500 ° C. The above heat treatment cannot be performed. That is, there arises a problem that the miniaturization rule transistor and wiring cannot be compatible with the monitoring photodiode having the above-described configuration.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an optical semiconductor device in which a high-speed transistor and a monitoring photodiode are mounted on the same substrate, and a method for manufacturing the same.

  An optical semiconductor device according to claim 1 of the present invention is an optical semiconductor device in which a light emitting element and a light receiving element are mounted on the same substrate, and is provided on a first conductive type semiconductor substrate and a main surface of the semiconductor substrate. Provided on the side surface of the groove portion, the light emitting element provided on the bottom surface of the groove portion, the second conductive type diffusion layer provided on the main surface of the semiconductor substrate adjacent to or adjacent to the groove portion, and The light receiving element comprises a PN junction of the semiconductor substrate and the diffusion layer, a first depletion layer generated on the semiconductor substrate side from the PN junction, and a side surface of the groove from the semiconductor substrate side The second depletion layer generated in the step is connected.

  An optical semiconductor device according to a second aspect of the present invention is the optical semiconductor device according to the first aspect, further comprising a semiconductor layer of a second conductivity type provided on the semiconductor substrate, and the diffusion layer is made of the semiconductor layer. To do.

  An optical semiconductor device according to a third aspect of the present invention is the optical semiconductor device according to the first aspect, wherein the second conductive type semiconductor layer provided on the semiconductor substrate, an isolation insulating layer that separates the semiconductor layer, and the semiconductor substrate The semiconductor device further includes a buried layer of a second conductivity type provided between the semiconductor layers, and the diffusion layer includes the separated semiconductor layer and the buried layer.

  An optical semiconductor device according to a fourth aspect of the present invention is the optical semiconductor device according to any one of the first to third aspects, wherein the groove portion has a side surface forming a predetermined angle with respect to a main surface of the semiconductor substrate, and a main surface of the semiconductor substrate. It consists of the bottom face which is parallel to the surface.

According to a fifth aspect of the present invention, in the optical semiconductor device according to the first or third aspect, the insulating film extends on the semiconductor substrate between the groove and the diffusion layer.
According to a sixth aspect of the present invention, there is provided the optical semiconductor device according to any one of the first to fifth aspects, wherein the field film provided on the semiconductor substrate and the gate provided on the field film or the isolation insulating layer. An electrode is further provided.

According to a seventh aspect of the present invention, in the optical semiconductor device according to any one of the first to sixth aspects, the insulating film is an oxide film or a nitride film.
An optical semiconductor device according to an eighth aspect of the present invention is characterized in that, in any one of the first to seventh aspects, the insulating film is formed of a multilayer film having a different refractive index.

  An optical semiconductor device according to a ninth aspect of the present invention is the optical semiconductor device according to any one of the first to eighth aspects, wherein the insulating film has a film thickness that maximizes the transmittance with respect to the wavelength of the emitted light of the light emitting element. It has a refractive index.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the impurity concentration of the semiconductor substrate is 1 × 10 ¹⁵ cm ⁻³ or less.
An optical semiconductor device according to an eleventh aspect of the present invention is the optical semiconductor device according to any one of the first to tenth aspects, wherein the diffusion layer has an impurity concentration higher than that of the semiconductor substrate and is close to the diffusion layer. A high-concentration diffusion layer of the first conductivity type provided in the semiconductor layer is further provided.

  A method for manufacturing an optical semiconductor device according to claim 12 of the present invention is a method for manufacturing an optical semiconductor device in which a light emitting element and a light receiving element are mounted on the same substrate, on the main surface of the first conductive type semiconductor substrate. A step of selectively forming a diffusion layer of a second conductivity type, a step of forming a field film on the semiconductor substrate, and forming a groove in the main surface of the semiconductor substrate adjacent to or adjacent to the diffusion layer The method includes a step, a step of forming an insulating film on a side surface of the groove portion, and a step of installing the light emitting element on the bottom surface of the groove portion after forming the insulating film.

  According to claim 13 of the present invention, in the method for manufacturing an optical semiconductor device according to claim 12, in the step of forming the diffusion layer, a buried layer of a second conductivity type is selectively formed on the main surface of the semiconductor substrate. The method includes a step, a step of forming a semiconductor layer of a second conductivity type on the semiconductor substrate, and a step of forming an isolation insulating layer that separates the semiconductor layer.

According to a fourteenth aspect of the present invention, in the method for manufacturing an optical semiconductor device according to the twelfth or thirteenth aspect, the step of forming the groove portion selectively opens the field film or the isolation insulating layer. And anisotropic wet etching the semiconductor substrate from the opening.
According to a fifteenth aspect of the present invention, there is provided a method for manufacturing an optical semiconductor device according to any one of the twelfth to fourteenth aspects, wherein the insulating film is formed by a CVD method or a sputtering method.

  The optical semiconductor device and the manufacturing method thereof according to the present invention have the above-described configuration, and the depletion in which carriers that have reached the depletion layer formed under the first slope are formed at the PN junction of the monitoring photodiode. Since it can be taken out as a photocurrent through the cathode and through the cathode layer, a highly sensitive and stable monitoring photodiode can be realized. In addition, since the implantation / heat treatment process is not required after the formation of the micromirror, it is possible to integrate the transistors / wirings of the miniaturization rule and the monitoring photodiode, and to achieve both the high-speed transistor and the high-sensitivity monitoring photodiode.

Hereinafter, each embodiment of the present invention will be described with reference to FIGS.
In addition, the same code | symbol is attached | subjected and demonstrated to what comprises the same effect | action as FIG.
(First embodiment)
FIG. 1 shows a first embodiment of an optical semiconductor device of the present invention.

In FIG. 1, 1 is a low-concentration p-type silicon substrate, 2 is a monitoring photodiode, and 3 is a micromirror part. Reference numeral 15 denotes a laser diode.
In the monitoring photodiode 2, 5 is a high-concentration p-type anode contact layer, 6 is a LOCOS isolation layer, 7 is a cathode electrode, 8 is an anode electrode, and 9 is a field film.

  In the micromirror part 3, 10 is a first slope, 11 is a second slope, 12 is a mirror bottom, 13 is an insulating film, 14 is a mirror reflection film, 16 is a laser lower electrode of the laser diode 15, and 17 is front light. , 18 are backlights, which are the same as the conventional configuration. A groove 50 is formed in the main surface of the silicon substrate 1 by the first inclined surface 10, the mirror bottom surface 12, and the second inclined surface 11.

  A cathode layer 19 as a high concentration n-type diffusion layer formed on the silicon substrate 1 has an impurity concentration higher than that of the silicon substrate 1, and includes a first inclined surface 10, a mirror bottom surface 12, a second inclined surface 11, and the like. Is provided on the main surface of the semiconductor substrate 1 in the vicinity of or adjacent to the groove portion 50 formed in (1). The monitoring photodiode 2 includes the high-concentration p-type anode contact layer 5 as a high-concentration diffusion layer of the first conductivity type. The monitoring photodiode 2 is composed of a PN junction between the cathode layer 19 and the silicon substrate 1.

  Reference numeral 20 denotes a depletion layer, which is composed of a depletion layer 20 a formed by the monitoring photodiode 2 and a depletion layer 20 b formed by the first slope 10. Reference numeral 20-2 denotes a boundary region between the first slope 10 and the cathode layer 19, where the depletion layer 20a and the depletion layer 20b are connected.

The basic operation of the laser diode is the same as the conventional description shown in FIG. Since the silicon substrate 1 is at least one digit lower than the impurity concentration of the cathode layer 19, the depletion layer 20 a extends to the silicon substrate 1 side. For example, when the concentration of the silicon substrate 1 is 1 × 10 ¹⁴ cm ⁻³ and the reverse bias applied to the monitoring photodiode 2 is 5 V, the depletion layer 20a of about 9 μm extends to the silicon substrate 1 side. Further, since the silicon substrate 1 has a low concentration, a depletion layer 20b is always generated on the silicon substrate 1 side due to the surface level Nss at the interface between the insulating film 13 and the silicon substrate 1. For example, when the concentration of the silicon substrate 1 is 1 × 10 ¹⁴ cm ⁻³ and Nss = 1 × 10 ¹¹ cm ⁻² , the depletion layer 20b extends to the silicon substrate 1 side by about 10 μm. Here, when the distance between the first slope 10 and the cathode layer 19 is several μm or less, the depletion layer 20a and the depletion layer 20b are always connected.

For example, when a nitrogen film formed by a plasma CVD method is used as the insulating film 13, the surface level Nss is generally about 1 × 10 ¹⁰ to 1 × 10 ¹² cm ⁻² and an oxide film formed by a sputtering method. Is used, the surface level Nss becomes 1 × 10 ¹¹ to 1 × 10 ¹³ cm ⁻² , and a state in which the depletion layer 20a and the depletion layer 20b are always connected can be realized.

  Here, when the back light 18 is incident from the first inclined surface 10, the light is absorbed in the silicon substrate 1 to generate electron / hole pairs. Electrons absorbed to the outside of the depletion layer 20 reach the depletion layer 20a or 20b by diffusion, then reach the cathode layer 19 by drift, and are taken out from the cathode electrode 7 to the outside. On the other hand, holes are extracted to the outside through diffusion through the anode contact layer 5 and the anode electrode 8 and become a photocurrent. In this configuration, not only the light absorbed in the vicinity of the PN junction of the monitoring photodiode 2 but also the carriers generated by the light absorbed in the vicinity of the first inclined surface 10 contribute to the photocurrent. It is possible to increase the ratio of the photocurrent to, that is, the light receiving sensitivity. For example, since red light (λ = 650 nm) used for DVD absorbs 95% of light at 10 μm in silicon, it is almost the same as the width of the depletion layer 20b in the above example. 90% or more of the generated carriers can contribute to the photocurrent.

  In addition, since there is no step of forming a diffusion layer after the formation of the micromirror portion 3 in this configuration, a heat treatment step is not necessary, and the transistor can be shallowed and the transistor / wiring can be miniaturized and integrated with a high-speed transistor. Can be realized.

  Further, by adjusting the film thickness and refractive index of the insulating film 13, it is possible to reduce the reflection of the back light 18 on the first inclined surface 10. For example, when the first inclined surface 10 forms an angle of 64.3 ° with respect to the main surface of the silicon substrate 1, the wavelength of the back light 18 is 650 nm, a nitride film is used as the insulating film 13, and the refractive index is 2.00. The film 13 has a thickness of 90 nm, and the transmittance of the back light 18 is 95% or more.

  Furthermore, by using a multilayer film with different refractive indexes as the insulating film 13 and optimizing the film thickness of each layer, it becomes possible to improve the transmittance with respect to a plurality of wavelengths. Even in the case of a dual wavelength laser diode compatible with both, a highly sensitive monitoring photodiode 2 corresponding to this can be realized. For example, an oxide film (film thickness: 72 nm, refractive index: 1.45) is used as the lower layer as the multilayer film, and a nitride film (film thickness: 90 nm, refractive index: 2.00) is used as the upper layer. When the angle of 64.3 ° is formed with respect to the surface and the wavelength of the back light 18 is 650 nm, the transmittance of the back light 18 in the insulating film 13 is 99% or more.

  The boundary region 20-2 has a configuration in which the silicon substrate 1 and the insulating film 13 are in direct contact with each other. With this configuration, not only on the first slope 10 but also in the boundary region 20-2, the interface state Nss at the interface between the silicon substrate 1 and the insulating film 13 can be increased, the depletion layer can be extended, and the depletion layer 20a And the depletion layer 20b can be stably connected.

(Second Embodiment)
FIG. 2 shows a second embodiment of the optical semiconductor device of the present invention.
The second embodiment is a modification of the first embodiment, in which an n-type epitaxial layer 21 is added on the silicon substrate 1 instead of the n-type cathode layer 19 of the first embodiment. It is a structure advantageous for integration with a high-performance transistor. The monitoring photodiode 2 is formed by a PN junction between the n-type epitaxial layer 21 and the silicon substrate 1. Since the n-type epitaxial layer 21 is exposed on the first slope 10, the depletion layer 20a and the depletion layer 20b are always connected regardless of the substrate concentration and the surface level Nss at the interface between the insulating film 13 and the silicon substrate 1. Thus, a high light receiving sensitivity characteristic can be obtained stably. The other configuration of the n-type epitaxial layer 21 is the same as that of the first embodiment.

(Third embodiment)
FIG. 3 shows a third embodiment of the optical semiconductor device of the present invention.
As shown in FIG. 3, 21 is an n-type epitaxial layer formed on the silicon substrate 1, 22 is an n-type buried layer selectively formed at the interface between the silicon substrate 1 and the n-type epitaxial layer 21, and 23 is silicon. The p-type buried layer is selectively formed on the substrate 1 so as to be connected to the anode contact layer 5. Other configurations are the same as those of the first embodiment.

  The optical semiconductor device of this embodiment has a configuration in which an n-type epitaxial layer 21 is added to the first embodiment, and has a structure that is advantageous for improving the performance of the transistor (speeding up, reducing parasitic components, etc.). Integration with high-speed, high-performance transistors is possible.

  Further, the monitoring photodiode 2 is configured by a PN junction between the n-type buried layer 22 and the silicon substrate 1, and the PN junction can be formed at a deep position from the surface with respect to the first embodiment. Therefore, the ratio of carriers that reach the PN junction increases, and the light receiving sensitivity can be improved.

The n-type buried layer 22 and the p-type buried layer 23 can be shared with the buried layer of the bipolar transistor, and can be integrated without adding a mask process.
A gate electrode can also be provided on the LOCOS isolation layer 6 that isolates the n-type epitaxial layer 21.

(Fourth embodiment)
FIG. 4 shows a fourth embodiment of the optical semiconductor device of the present invention.
As shown in FIG. 4, 24 is a boundary region between the first slope 10 and the n-type buried layer 22, and 25 is a gate electrode formed on the insulating film 13. Other configurations are the same as those of the first embodiment.

  The optical semiconductor device of the present embodiment has a configuration in which the boundary region 24 does not have the LOCOS isolation layer 6 and the silicon substrate 1 or the n-type epitaxial layer 21 and the insulating film 13 are in direct contact with the configuration of the third embodiment. is there. With this configuration, the interface state Nss at the interface between the silicon substrate 1 and the insulating film 13 can be increased similarly to the first inclined surface 10, the depletion layer 20 can be extended, and the depletion layer 20a and the depletion layer 20b can be stabilized. Can be connected.

  Furthermore, the gate electrode 25 is provided on the insulating film 13, and a voltage is applied to the gate electrode 25, whereby the width of the depletion layer 20 in the boundary region 24 is further increased, and high sensitivity and stability can be achieved. In addition, the depletion layer 20 can be reduced by adjusting the voltage applied to the gate electrode 25, and can also be used as a switching element that stops the movement of carriers absorbed in the depletion layer 20b and adjusts the photocurrent. it can.

(Fifth embodiment)
FIG. 5 shows a manufacturing method of the optical semiconductor device shown in FIG.
26 is a region for a monitor photodiode, 27 is a region for a micromirror part, 28 is a low-concentration p-type silicon substrate, 29 is a high-concentration n-type diffusion layer, 30 is a high-concentration p-type diffusion layer, 31 Is a LOCOS separation layer, 32 is a cathode electrode, 33 is an anode electrode, 34 is a field film such as an oxide film, 35 is a first slope, 36 is a second slope, 37 is a mirror bottom, 38 is an insulating film, 39 is A laser lower electrode 40 is a laser diode.

  First, as shown in FIG. 5A, an n-type diffusion layer 29 and a p-type diffusion layer 30 are selectively formed in the silicon substrate 28 by diffusion or implantation, and then the n-type diffusion layer 29 and the p-type diffusion layer are formed. A LOCOS isolation layer 31 is formed between the layers 30.

  Next, as shown in FIG. 5A, after forming a field film 34 on the silicon substrate 28 and opening a part thereof, the cathode electrode 32 and the p-type diffusion layer 30 are connected to the n-type diffusion layer 29. The anode electrode 33 is selectively formed by sputtering or the like so as to be connected.

  Next, as shown in FIG. 5C, after opening the field film 34 in the micromirror region 27, the silicon substrate 28 is anisotropically wet etched with an alkaline aqueous solution such as KOH using this as a mask. . At this time, if a (100) 9.7 ° off substrate is adopted as the plane orientation of the silicon substrate, the (111) plane is formed on the slope because the etching rate of the (111) plane is extremely slow relative to other plane orientations. First slope 35 (64.3 ° with respect to the main surface of the silicon substrate), second slope 36 (45 ° with respect to the main surface of the silicon substrate), mirror bottom surface 37 (parallel to the main surface of the silicon substrate) Is formed.

  Thereafter, as shown in FIG. 5D, an insulating film 38 made of a nitride film or the like is formed by a CVD method. Finally, as shown in FIG. 5E, a laser lower electrode 39 made of Au or the like is formed on the mirror bottom surface 37 by vapor deposition or sputtering, and then the laser diode 40 is bonded.

(Sixth embodiment)
FIG. 6 shows a method of manufacturing the optical semiconductor device shown in FIG.
41 is a high-concentration n-type buried layer, 42 is a high-concentration p-type buried layer, 43 is an n-type epitaxial layer, 44 is an anode contact layer, and 45 is a gate electrode. Other configurations are the same as those in FIG.

  First, as shown in FIG. 6A, after an n-type buried layer 41 and a p-type buried layer 42 are selectively formed in the silicon substrate 28 by diffusion or implantation, an n-type epitaxial layer 43 is grown.

  Next, as shown in FIG. 6B, after the LOCOS isolation layer 31 is selectively formed between the n-type buried layer 41 and the p-type buried layer 42 and in the micromirror part 27, the anode contact layer 44 is buried in the p-type buried layer. It is selectively formed so as to be connected to the layer 42.

  Next, as shown in FIG. 6C, after forming a field film 34 on the silicon substrate 28 and opening a part thereof, the cathode electrode 32 and the p-type diffusion layer 30 are connected to the n-type diffusion layer 29. The anode electrode 33 is selectively formed by sputtering or the like so as to be connected, and then the LOCOS isolation layer 31 and the field film 34 of the micromirror part 27 are opened.

  As shown in FIG. 6D, after the silicon substrate 28 is anisotropically wet etched with an alkaline aqueous solution such as KOH using the LOCOS separation layer 31 as a mask, the first slope 35 and the periphery of the first slope 36 are surrounded. The LOCOS isolation layer 31 and the field film 34 are removed.

Thereafter, as shown in FIG. 6E, an insulating film 38 made of a nitride film or the like is formed by a CVD method.
Next, as shown in FIG. 6F, a gate electrode 45 is formed on the insulating film 38 by vapor deposition or sputtering, and a laser lower electrode 39 made of Au or the like is formed on the mirror bottom surface 37 by vapor deposition or sputtering. After the formation, the laser diode 40 is bonded.

  In this embodiment, the nitride film formed by the CVD method is used as the insulating film. However, the insulating film is not necessarily limited to the nitride film. For example, the oxide film and the nitride film formed by the CVD method or the sputtering method are used. It may be a multilayer film of oxide films.

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

In the present invention, the n-type is used as the silicon substrate, but it goes without saying that the present invention can also be applied using a p-type.
In each of the above embodiments, the impurity concentration of the silicon substrate 1 has been described as being 1 × 10 ¹⁴ cm ⁻³ , for example, but may be 1 × 10 ¹⁵ cm ⁻³ or less.

  The present invention is useful for a so-called OEIC structure in which a laser diode, a high-speed and high-performance transistor, and a light-receiving element with high light-receiving sensitivity are integrated on the same substrate, and a method for forming the same.

Sectional drawing which shows the optical semiconductor device which concerns on 1st Embodiment Sectional drawing which shows the optical semiconductor device which concerns on 2nd Embodiment Sectional drawing which shows the optical semiconductor device which concerns on 3rd Embodiment Sectional drawing which shows the optical semiconductor device which concerns on 4th Embodiment Process drawing of the manufacturing method of the optical semiconductor device which concerns on FIG. Process drawing of the manufacturing method of the optical semiconductor device which concerns on FIG. Sectional view showing a conventional optical semiconductor device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Photodiode for monitoring 3 Micromirror part 4 Cathode layer 5 Anode contact layer 6 LOCOS isolation layer 7 Cathode electrode 8 Anode electrode 9 Field film 10 First slope 11 Second slope 12 Mirror bottom face 13 Insulating film 14 Mirror Reflective film 15 Laser diode 16 Laser lower electrode 17 Front light 18 Back light 19 Cathode layer 20 Depletion layer 20-2 Boundary region 21 n-type epitaxial layer 22 n-type buried layer 23 p-type buried layer 24 Boundary region 25 Gate electrode 26 For monitoring Photodiode region 27 Micromirror region 28 Silicon substrate 29 n-type diffusion layer 30 p-type diffusion layer 31 LOCOS isolation layer 32 cathode electrode 33 anode electrode 34 field film 35 first slope 36 second slope 37 Mirror Bottom 38 Insulating film 9 laser lower electrode 40 laser diode 41 n-type buried layer 42 p-type buried layer 43 n-type epitaxial layer 44 anode contact layer 45 a gate electrode 50 groove

Claims (15)

An optical semiconductor device having a light emitting element and a light receiving element mounted on the same substrate,
A first conductivity type semiconductor substrate; a groove provided on a main surface of the semiconductor substrate; the light emitting element provided on a bottom surface of the groove; and provided on the main surface of the semiconductor substrate adjacent to or adjacent to the groove. A second conductivity type diffusion layer and an insulating film provided on the side surface of the groove,
The light receiving element includes a PN junction between the semiconductor substrate and the diffusion layer, a first depletion layer generated from the PN junction toward the semiconductor substrate, and a second depletion layer generated from the side surface of the groove toward the semiconductor substrate. And an optical semiconductor device characterized by being connected to each other. The optical semiconductor device according to claim 1, further comprising a semiconductor layer of a second conductivity type provided on the semiconductor substrate, wherein the diffusion layer is made of the semiconductor layer. A second conductive type semiconductor layer provided on the semiconductor substrate; an isolation insulating layer separating the semiconductor layer; and a second conductive type buried layer provided between the semiconductor substrate and the semiconductor layer. Prepared,
The optical semiconductor device according to claim 1, comprising the semiconductor layer separated from the diffusion layer and the buried layer. The said groove part consists of the side surface which makes a predetermined angle with respect to the main surface of the said semiconductor substrate, and the bottom face which is parallel with respect to the main surface of the said semiconductor substrate. An optical semiconductor device according to 1. 4. The optical semiconductor device according to claim 1, wherein the insulating film extends on the semiconductor substrate between the groove and the diffusion layer. 5. 6. The optical semiconductor according to claim 1, further comprising a field film provided on the semiconductor substrate and a gate electrode provided on the field film or the isolation insulating layer. apparatus. The optical semiconductor device according to claim 1, wherein the insulating film is an oxide film or a nitride film. The optical semiconductor device according to claim 1, wherein the insulating film is formed of a multilayer film having a different refractive index. 9. The optical semiconductor device according to claim 1, wherein the insulating film has a film thickness and a refractive index that maximize a transmittance with respect to a wavelength of light emitted from the light emitting element. . The optical semiconductor device according to claim 1, wherein an impurity concentration of the semiconductor substrate is 1 × 10 ¹⁵ cm ⁻³ or less. The diffusion layer has an impurity concentration higher than that of the semiconductor substrate, and further includes a high-concentration diffusion layer (5) of the first conductivity type provided in the semiconductor substrate or the semiconductor layer in the vicinity of the diffusion layer. 11. The optical semiconductor device according to claim 1, wherein the optical semiconductor device is characterized in that: A method of manufacturing an optical semiconductor device in which a light emitting element and a light receiving element are mounted on the same substrate,
Selectively forming a second conductivity type diffusion layer on the main surface of the first conductivity type semiconductor substrate;
Forming a field film on the semiconductor substrate;
Forming a groove in the main surface of the semiconductor substrate adjacent to or adjacent to the diffusion layer;
Forming an insulating film on a side surface of the groove,
And a step of installing the light emitting element on the bottom surface of the groove after forming the insulating film. The step of forming the diffusion layer includes
Selectively forming a second conductivity type buried layer on the main surface of the semiconductor substrate;
Forming a second conductivity type semiconductor layer on the semiconductor substrate;
13. The method of manufacturing an optical semiconductor device according to claim 12, further comprising a step of forming an isolation insulating layer that isolates the semiconductor layer. The groove forming step includes:
Selectively opening the field film or the isolation insulating layer;
14. The method of manufacturing an optical semiconductor device according to claim 12, further comprising anisotropic wet etching of the semiconductor substrate from the opening. The method of manufacturing an optical semiconductor device according to claim 12, wherein the insulating film is formed by a CVD method or a sputtering method.

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