JP2022152358A - Optical semiconductor element and manufacturing method thereof - Google Patents

Abstract

To provide an optical semiconductor element capable of suppressing generation of polycrystalline grains caused by a deposition process of a selective epitaxial growth method.SOLUTION: An optical semiconductor element includes: a semiconductor substrate having a single crystal layer as an outermost layer; an insulation film which is formed on the single crystal layer and has a main opening and at least one dummy opening which are made mutually apart; a main epitaxial film which is selectively epitaxially grown in the main opening on the single crystal layer; and a dummy epitaxial film which is selectively epitaxially grown in the dummy opening on the single crystal layer. The main epitaxial film is a film bearing a part of a function of the optical semiconductor element. The dummy epitaxial film is a film not bearing a part of a function of the optical semiconductor element. A clearance between the main epitaxial film and the dummy epitaxial film is in a range of 4 μm or larger and 100 μm or smaller.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to an optical semiconductor device formed using a selective epitaxial growth method and a manufacturing method thereof.

In recent years, silicon photonics technology has been used in research and development to integrate optical semiconductor devices such as optical active devices (e.g. light receivers or optical modulators) and optical passive devices (e.g. optical waveguides or optical multiplexers/demultiplexers) on silicon layers. is being done. For example, active research and development is being conducted to integrate Ge optical semiconductor devices made of germanium (Ge), which is a Group IV semiconductor like silicon (Si), on a silicon layer. It is known that germanium or silicon-germanium films epitaxially grown on silicon layers by selective epitaxial growth can be used to form photodetectors and optical modulators in optical transceiver integrated circuits.

The following Non-Patent Document 1 discloses a Ge photodetector formed using an SOI (Silicon-On-Insulator) substrate. This Ge photodetector has a germanium film epitaxially grown by a selective epitaxial growth method as a light absorption layer. Non-Patent Document 2 below discloses a Si optical modulator formed using an SOI substrate. This Si optical modulator has an optical waveguide structure including a silicon germanium film epitaxially grown by a selective epitaxial growth method.

J. Fujikata et al., "High-performance surface illumination-type Ge photodetector for optical interconnection on 300-diameter of SOI substrate," Extended Abstracts of the 2017 International Conference on Solid State Devices and Materials, Sendai, 2017, pp. 145 -146. J. Fujikata et al., "High speed and highly efficient Si optical modulator with strained SiGe layer," Proceedings of IEEE International Conference on Group IV Photonics 2015, Vancouver, BC, Canada, 2015, pp. 13-14.

In the film formation process of the selective epitaxial growth method, an insulating film having an opening is formed on the single crystal layer, and an epitaxial film such as a germanium film or a silicon germanium film is selectively epitaxially grown on the single crystal layer within the opening. and a step of allowing However, even in a situation where sufficient selectivity of the epitaxial film is considered to be secured by adjusting the film formation conditions such as the flow rate of the raw material gas and the substrate temperature during epitaxial growth, low-density polycrystals are formed on the insulating film. The inventors have found that grains occur. Since such polycrystalline grains remain in the optical semiconductor element and absorb signal light, there is a problem that the element performance is deteriorated.

In view of the above, an object of the present disclosure is to provide an optical semiconductor device and a method of manufacturing the same that can suppress the generation of polycrystalline grains due to the film formation process of the selective epitaxial growth method.

An optical semiconductor device according to a first aspect of the present disclosure is an optical semiconductor device that functions as an optical passive device or an optical active device, comprising: a semiconductor substrate including a single crystal layer as an outermost layer; an insulating film having a main opening and at least one dummy opening separated from each other; a main epitaxial film selectively epitaxially grown on the single crystal layer within the main opening; and the dummy on the single crystal layer. a dummy epitaxial film selectively epitaxially grown within the opening, wherein the main epitaxial film is a film having a part of the function of the optical semiconductor element, and the dummy epitaxial film is a part of the function of the optical semiconductor element. The distance between the main epitaxial film and the dummy epitaxial film is 4 μm or more and 100 μm or less.

A method for manufacturing an optical semiconductor device according to a second aspect of the present disclosure includes steps of preparing a semiconductor substrate including a single crystal layer as an outermost layer; forming an insulating film on the single crystal layer; forming a resist pattern on an insulating film; forming a main opening and a dummy opening in the insulating film by etching using the resist pattern; and forming the main opening and the dummy opening by selective epitaxial growth. and simultaneously and parallelly growing a main epitaxial film and a dummy epitaxial film on the single crystal layer, wherein the main epitaxial film is a film responsible for part of the function of the optical semiconductor element, and the dummy epitaxial film The film is a film that does not perform part of the function of the optical semiconductor element, and the separation distance between the main epitaxial film and the dummy epitaxial film is in the range of 4 μm or more and 100 μm or less.

According to the present disclosure, a dummy epitaxial film is formed in the dummy opening in addition to the main epitaxial film, and the separation distance D between the main epitaxial film and the dummy epitaxial film is limited to 4 μm or more and 100 μm or less. Therefore, during the film formation process of the selective epitaxial growth method, the precursor migrating on the insulating film has a high probability of reaching the region of the dummy opening and being single-crystallized before forming polycrystalline nuclei. It is possible to suppress the generation of polycrystalline grains on the insulating film. Therefore, it is possible to suppress performance deterioration of the optical semiconductor element.

1 is a cross-sectional view showing an example of a schematic configuration of an optical semiconductor device according to the present disclosure; FIG. 1. It is sectional drawing for demonstrating the partial process of the manufacturing method of the optical semiconductor element shown in FIG. 1. It is sectional drawing for demonstrating the partial process of the manufacturing method of the optical semiconductor element shown in FIG. 1. It is sectional drawing for demonstrating the partial process of the manufacturing method of the optical semiconductor element shown in FIG. 1. It is sectional drawing for demonstrating the partial process of the manufacturing method of the optical semiconductor element shown in FIG. 1. It is sectional drawing for demonstrating the partial process of the manufacturing method of the optical semiconductor element shown in FIG. 1. It is sectional drawing for demonstrating the partial process of the manufacturing method of the optical semiconductor element shown in FIG. 1. It is sectional drawing for demonstrating the partial process of the manufacturing method of the optical semiconductor element shown in FIG. 1. It is sectional drawing for demonstrating the partial process of the manufacturing method of the optical semiconductor element shown in FIG. 1 is a schematic cross-sectional view showing a conventional structure; FIG. FIG. 4 is a top view schematically showing an epitaxial film pattern formed for an experiment to examine foreign matter defect density; It is a figure which shows an experimental result in tabular form. 13 is a graph created from the numerical values in the table of FIG. 12; 4 is a graph calculated based on the complementary distribution function; It is a top view which shows roughly the structure of the optical-semiconductor element of other embodiment. It is a top view which shows roughly the structure of the optical-semiconductor element of further another embodiment.

Next, various embodiments and modifications thereof will be described in detail with reference to the drawings. It should be noted that constituent elements denoted by the same reference numerals throughout the drawings have the same configuration and the same function.

FIG. 1 is a cross-sectional view showing an example of a schematic configuration of an optical semiconductor device 1 according to the present disclosure. The optical semiconductor device 1 can be formed to function as an optical active device such as a light receiver or an optical modulator, or an optical passive device such as an optical multiplexer or an optical demultiplexer.

As shown in FIG. 1, the optical semiconductor element 1 is formed of a semiconductor substrate 10P including a single crystal layer 13P as the outermost layer, an insulating film 20P formed on the single crystal layer 13P, and an insulating film 20P. Main epitaxial film 22 selectively epitaxially grown within main opening 20a, dummy epitaxial film 23 selectively epitaxially grown within dummy opening 20d formed in insulating film 20P, main epitaxial film 22 and dummy epitaxial film 23, contact holes 24a and 24b penetrating the interlayer insulating film 24 in the vertical direction (thickness direction of the interlayer insulating film 24), and buried in the contact holes 24a and 24b, respectively. and wiring layers 28 and 29 formed on the interlayer insulating film 24 so as to be electrically connected to the contact plugs 26 and 27, respectively.

The semiconductor substrate 10P of this embodiment includes a supporting substrate (supporting layer) 11, an embedded insulating film 12 formed on the supporting substrate 11, and a single crystal layer which is a single crystal silicon layer formed on the embedded insulating film 12. It is an SOI (Silicon-On-Insulator) substrate made of 13P.

The main opening 20a and the dummy opening 20d are formed to penetrate the insulating film 20P in the vertical direction (thickness direction of the insulating film 20P) and reach the upper surface of the single crystal layer 13P. The dummy opening 20d is formed in a peripheral region spaced apart from the main opening 20a by the separation distance D. As shown in FIG. The main epitaxial film 22 is formed by epitaxially growing a single crystal film or a plurality of single crystal films in the main opening 20a using the single crystal layer 13P as a base by a selective epitaxial growth process. The dummy epitaxial film 23 is formed by epitaxially growing a single crystal film or a plurality of single crystal films in the dummy opening 20d using the single crystal layer 13P as a base by a selective epitaxial growth method.

The main epitaxial film 22 and the dummy epitaxial film 23 are formed concurrently in the same film forming process. In the film forming process, the film forming precursor that migrates on the insulating film 20P has a high probability of entering either the main opening 20a or the dummy opening 20d before forming polycrystalline nuclei on the insulating film 20P. Since it can be reached and single-crystallized, the probability that the film formation precursor will be polycrystallized can be reduced. This makes it possible to suppress the occurrence of polycrystalline grains, ie foreign matter defects, on the insulating film 20P.

The inventors adjusted the size of the dummy opening 20d, and also adjusted the distance D between the main opening 20a and the dummy opening 20d, that is, the distance D between the main epitaxial film 22 and the dummy epitaxial film 23. It was found that the occurrence of foreign matter defects can be remarkably suppressed. From the viewpoint of suppressing the occurrence of foreign matter defects, it is preferable that the separation distance D is within a range of 100 μm or less. If the separation distance D is too short, light may leak from the main epitaxial film 22 to the dummy epitaxial film 23, so the separation distance D is preferably 4 μm or more. From the viewpoint of more effectively suppressing the occurrence of foreign matter defects, the separation distance D is preferably within a range of 50 μm or less, and particularly preferably within a range of 20 μm or less. Furthermore, in order to suppress the occurrence of foreign matter defects, the shape of the dummy opening 20d when viewed from above can be made rectangular with an area of 1 μm×1 μm or more.

The main epitaxial film 22 and the dummy epitaxial film 23 are, for example, a Ge film or a silicon-germanium (SiGe) film whose constituent material is germanium (Ge), which is the same Group IV semiconductor as the constituent material (Si) of the single crystal layer 13P. Alternatively, it is preferably formed as a laminate including a Ge film and a SiGe film, but is not limited to this. The main epitaxial film 22 and the dummy epitaxial film 23 are not limited to the Ge film, the SiGe film, and the laminate as long as they are epitaxial films epitaxially grown on the single crystal layer 13P.

For example, when the optical semiconductor device 1 is formed as a light receiver, the main epitaxial film 22 is a light-receiving film for receiving light propagating in the single crystal layer 13P patterned to function as an optical waveguide, or It functions as a light-receiving film that receives light incident from the front surface side (upper side in FIG. 1). The main epitaxial film 22 may be formed to function at least partially in the PIN structure. For example, single crystal layer 13P made of p-type silicon, main epitaxial film 22 made of i-type Ge layer or i-type SiGe layer, and n-type silicon film (not shown) bonded to the upper surface of main epitaxial film 22 A PIN structure may be formed. As described above, the optical semiconductor device 1 can be formed to have the function of an optical active device or an optical passive device other than a light receiver. The main epitaxial film 22 is a film having a part of the function of the optical semiconductor element 1 , whereas the dummy epitaxial film 23 is a film not having a part of the function of the optical semiconductor element 1 .

In the example of FIG. 1, the contact plug 26 is embedded in the interlayer insulating film 24 between the main epitaxial film 22 and the wiring layer 28, but there is also a configuration in which the contact plug 26 is not embedded. In the example of FIG. 1, the contact plug 27 is buried in the interlayer insulating film 24 between the single-crystal layer 13 and the wiring layer 29 in the lateral region of the main epitaxial film 22. A form in which the plug 27 is not embedded is also possible.

Next, an example of a method for manufacturing the optical semiconductor element 1 shown in FIG. 1 will be described below with reference to FIGS. 2 to 9 are schematic cross-sectional views for explaining steps of the manufacturing method.

First, a semiconductor substrate 10 as shown in FIG. 2 is prepared. This semiconductor substrate 10 includes a supporting substrate (supporting layer) 11 , a buried insulating film 12 such as a silicon oxide film formed on the supporting substrate 11 , and a monocrystalline silicon layer formed on the buried insulating film 12 . 1 is an SOI substrate having a crystal layer 13. FIG.

Next, a predetermined region of the single crystal layer 13 shown in FIG. 2 is subjected to pretreatment such as impurity ion implantation, etching using a known lithographic technique, or a combination of impurity ion implantation and etching. As a result, semiconductor substrate 10P having single crystal layer 13P as the outermost layer is fabricated as shown in FIG.

Next, an oxide film, a nitride film or an oxynitride film is deposited on the single crystal layer 13P by, for example, a chemical vapor deposition method (CVD method: Chemical Vapor Deposition) to obtain a thickness of 0.1 μm as shown in FIG. An insulating film 20 having a thickness of about 2 μm is formed.

Next, the insulating film 20 is patterned using lithography. Specifically, as shown in FIG. 5, a resist pattern 21 having openings 21a and 21d is formed on the insulating film 20. Then, as shown in FIG. Next, the insulating film 20 is selectively etched by anisotropic etching using the resist pattern 21 as a mask, and then the resist pattern 21 is removed. As a result, an insulating film 20P having a main opening 20a and dummy openings 20d is formed on the single crystal layer 13P as shown in FIG. The dummy opening 20d may be formed in a rectangular shape having an area of 1 μm×1 μm or more when viewed from above (viewed from above). Upper surfaces 13a and 13d of the single crystal layer 13P are exposed at the main opening 20a and the dummy opening 20d, respectively.

Next, by a CVD method such as an ultra-high vacuum chemical vapor deposition method (UHV-CVD method: Ultra-High Vacuum Chemical Vapor Deposition) or a reduced pressure chemical vapor deposition method (RP-CVD method: Reduced-Pressure Chemical Vapor Deposition), In the main opening 20a and the dummy opening 20d, one or more single crystal films are epitaxially grown using the upper surfaces 13a and 13d of the single crystal layer 13P as bases. The single crystal film can be formed as a Ge film or a SiGe film. Thereby, as shown in FIG. 7, the main epitaxial film 22 is formed in the main opening 20a, and the dummy epitaxial film 23 is formed in the dummy opening 20d.

The film formation conditions at this time are, for example, film formation temperature (wafer temperature): 380° C. to 520° C., source gas: germane (GeH ₄ ) gas, carrier gas: hydrogen (H ₂ ) gas, film formation control gas: Chlorine gas, deposition rate: 5 nm/minute to 80 nm/minute. The thickness of each of the main epitaxial film 22 and the dummy epitaxial film 23 may be controlled depending on the function of the optical semiconductor element 1 so as to be within the range of approximately 300 nm to 2000 nm, for example. A buffer layer (not shown) may be formed between main epitaxial film 22 and single-crystal layer 13P to alleviate lattice mismatch with single-crystal layer 13P serving as a base. By providing such a buffer layer, generation of threading dislocations due to lattice mismatch can be suppressed. For example, a SiGe film with a low Ge content or a Ge film formed at a low temperature can be used as the buffer layer. For example, by depositing a Ge film with a thickness of about 100 nm as a buffer layer at a substrate temperature of 380° C., the threading dislocation density can be reduced to about 10×10 ⁷ cm ⁻² .

Further, after growing a Ge film or SiGe film as the main epitaxial film 22, heat treatment may be performed at a high temperature (approximately 800 to 900° C.). This makes it possible to form a high-quality main epitaxial film 22 with fewer crystal defects in the Ge film or SiGe film.

By adjusting the separation distance D between the main opening 20a and the dummy opening 20d, it is possible to suppress the occurrence of polycrystalline grains, ie foreign matter defects, on the insulating film 20P. In the film formation process of the selective epitaxial growth method, the film formation precursor migrates on the insulating film 20P. If the separation distance D is too large, the deposition precursor has a high probability of forming polycrystalline grains on the insulating film 20P before reaching the areas of the main opening 20a and the dummy opening 20d. From the viewpoint of suppressing the generation of polycrystalline grains, the separation distance D is preferably within a range of 100 μm or less. From the viewpoint of more effectively suppressing the generation of polycrystalline grains, the separation distance D is preferably 50 μm or less, particularly preferably 20 μm or less. FIG. 10 is a schematic cross-sectional view showing a conventional structure having such polycrystalline grains 23X and 23Y. As shown in FIG. 10, an opening 100a is formed in the insulating film 100P, and the main epitaxial film 22 is formed in this opening 100a, but the dummy opening and the dummy epitaxial film are not formed. Polycrystalline grains 23X and 23Y are formed on the insulating film 100P.

After the structure shown in FIG. 7 is formed, an insulating film such as an oxide film, a nitride film or an oxynitride film is deposited on the insulating film 20P, the main epitaxial film 22 and the dummy epitaxial film 23. Then, as shown in FIG. Then, the upper surface of the insulating film is flattened by chemical mechanical polishing (CMP). After that, by patterning this insulating film by lithography and etching, as shown in FIG. 24b is formed.

Next, as shown in FIG. 9, contact plugs 26 and 27 made of a conductive metal such as tungsten (W) are buried in the contact holes 24a and 24b by, eg, CVD. After that, wiring layers 28 and 29 made of a material such as aluminum (Al) or copper (Cu) are formed on the contact plugs 26 and 27 to fabricate the optical semiconductor device 1 shown in FIG.

FIG. 11 is a top view schematically showing an epitaxial film pattern formed using an SOI substrate for experiments to examine polycrystalline grain density, ie foreign matter defect density. For this experiment, an opening pattern consisting of a plurality of openings is formed in an insulating film (silicon oxide film) on an SOI substrate, and then Ge epitaxial films GP(0,0) to GP are formed in these openings. (2,2) was epitaxially grown. The film formation conditions during epitaxial growth were H ₂ gas flow rate 12 SLM, Ge gas flow rate 1 SLM, total pressure 10 Torr, Ge partial pressure 1.54 Torr, film formation temperature 500° C., and film formation rate 0.22 μm/min. Each of the epitaxial films GP(0,0) to GP(2,2) has a rectangular shape with a side length L when viewed from above. The spacing distance between laterally adjacent epitaxial films is D, and the spacing distance between vertically adjacent epitaxial films is also D. As shown in FIG.

FIG. 12 is a diagram showing experimental results in tabular form. The table of FIG. 12 shows the relationship between the combination of the separation distance D and the length L of one side of the epitaxial film pattern of ^FIG . showing. For example, for the combination of D=4 μm and L=1 μm, a polycrystalline grain density of 5/cm ² was observed. FIG. 13 is a graph created from the numerical values in the table of FIG. In this graph, the horizontal axis corresponds to the length L (unit: μm) of one side, and the vertical axis corresponds to the foreign matter defect density (unit: pieces/cm ² ), which is the polycrystalline grain density. A polycrystalline grain density of about 70 grains/cm ² was observed in the absence of the epitaxial film pattern. According to this graph, it can be seen that the effect of reducing polycrystalline grains strongly depends on the separation distance D, and a large effect is obtained when the separation distance D is within a range of 100 μm or less. Further, when the separation distance D is within a range of 50 μm or less, particularly when the separation distance D is within a range of 20 μm or less, a remarkable effect is exhibited.

Such an effect can be rationalized by considering that the film forming precursor adsorbed on the surface of the insulating film migrates on the surface in a random manner and reaches the opening pattern before forming polycrystalline grains. can be explained in a simple way.

The above effects can also be considered in terms of mathematical stochastic processes. In general, when the state of the system at time t is represented by a random variable X(t) and the set of times to be considered is represented by Ta, {X(t), tεTa} is called a stochastic process. Here, the state of the system shall be considered as a scalar quantity. The position of the deposition precursor corresponds to the state of the system. It is known that when the time step size and the moving width of the particle in the random walk of the particle are close to zero (in the case of continuous time and continuous state), the motion of the particle can be considered as Brownian motion. . The mathematical definition of Brownian motion is:

A continuous-time and continuous-state stochastic process {X(t), t≧0} is Brownian motion (process) when the following conditions (A) to (C) are satisfied.
(A) X(0)=0.
(B) have independent increments;
(C) For any t>0, s≧0, X(t+s)−X(s) follows a normal distribution with mean 0 and variance σ ² t. Therefore, the probability P(X(t+s)-X(s)≤x) that X(t+s)-X(s)≤x can be expressed by the following equation (1).

The distribution function Φ(z) in Equation (1) is expressed by Equation (2) below.

In particular, Brownian motion when σ=1 is called standard Brownian motion. Let {B(t), t≧0} denote the stochastic process of standard Brownian motion. In particular, regarding the standard Brownian motion {B(t), 0≤t≤T} in the interval [0, T], if its maximum value is R(T), then R(T)>a(>0). It is known that the complementary distribution function P(R(T)>a) representing probability is given by the following equation (3).

FIG. 14 is a graph calculated based on the complementary distribution function P(R(T)>a). In this graph, the horizontal axis corresponds to the variable a, and the vertical axis corresponds to the value of the complementary distribution function P(R(T)>a). In FIG. 14, the distribution curve F ₁₀ is the curve for variance σ ² t=10, the distribution curve F ₂₀ is the curve for variance σ ² t=20, and the distribution curve F ₅₀ is the curve for variance σ ² t=50. The curve distribution curve F ₁₀₀ is the curve for variance σ ² t=100. The complementary distribution function P (R (T) > a) represents the probability that the maximum distance (maximum movement distance) R (T) over which the Brownian motion particles (film formation precursor) move by time T exceeds a. can be called a thing. When one side of the dummy epitaxial film is sufficiently large, the deposition precursor adhering to the region between the dummy epitaxial films or the region between the dummy epitaxial film and the main epitaxial film is about 1/2 of the separation distance D. It is thought that the particles will be stably adsorbed to the epitaxial growth region if they travel a distance of . Therefore, equation (3) can be considered to represent the relationship between the separation distance D and the reduction amount of foreign matter defects.

As described above, in the optical semiconductor device 1 and the manufacturing method thereof of the above-described embodiment, in addition to the main epitaxial film 22, the dummy epitaxial film 23 is formed in the dummy opening 20d. 23 is limited to a range of 4 μm or more and 100 μm or less. Therefore, the precursor migrating on the insulating film 20P during the selective epitaxial growth process has a high probability of reaching the region of the dummy opening 20d and being single-crystallized before forming polycrystalline nuclei. Therefore, it is possible to effectively suppress the generation of polycrystalline grains on the insulating film 20P. In the conventional optical semiconductor device and its manufacturing method, even in a situation where the selectivity of the epitaxial film is sufficiently ensured by adjusting the film formation conditions, 10/cm ² to 100/cm 2 on the insulating film. There is a problem that polycrystalline grains having a very low density of 1/cm ² are generated, and these polycrystalline grains deteriorate the performance of the optical semiconductor device. On the other hand, in the above-described embodiment, the generation of polycrystalline grains on the insulating film 20P is effectively suppressed, so it is possible to suppress performance deterioration of the optical semiconductor element 1. FIG.

From the viewpoint of suppressing the occurrence of foreign matter defects by improving the probability that the film formation precursor reaches the area of the dummy opening 20d, the data ratio of the dummy epitaxial film 23 (the area of the dummy epitaxial film 23 is the total area ratio) is preferably adjusted within the range of 1% to 20%.

Furthermore, in the optical integrated circuit in which the optical semiconductor element 1 is integrated, the high light absorption coefficient of the dummy epitaxial film 23 is utilized to absorb stray light (unnecessary light other than signal light) in the optical integrated circuit. The function of a stray light absorber to be removed can be given to the dummy epitaxial film 23 . For example, stray light may occur due to unexpected reflection or scattering of signal light propagating inside the optical integrated circuit, or part of the light incident from an external light source may become stray light without coupling with the optical waveguide inside the optical integrated circuit. can be. Such stray light can be absorbed by the dummy epitaxial film 23 and removed.

Next, FIGS. 15 and 16 are top views schematically showing configurations of optical semiconductor elements 2 and 3 of other embodiments, respectively. Each of the optical semiconductor elements 2 and 3 is configured as an optical waveguide type light receiver. 15 and 16, the illustration of the insulating film is omitted for convenience of explanation.

The optical semiconductor device 2 shown in FIG. 15 includes an optical waveguide structure 30 formed by patterning a single crystal layer (outermost layer) of an SOI substrate, a main epitaxial film 32 formed on the optical waveguide structure 30, dummy epitaxial films 33 ₁ to 33 ₁₀ formed in _a peripheral region surrounding the main _epitaxial film 32; Contact plugs 35 ₁ to 35 ₃ and 36 ₁ to 36 ₃ formed to conduct to the single-crystal layer (a part of the optical waveguide structure 30) in lateral regions, and contact plugs 34 ₁ to 34 6 have contact plugs 34 1 to 34 ₆ at their upper ends. An upper wiring layer 37 formed to be conductive, an upper wiring layer 38 formed to be conductive to the upper ends of the contact plugs 35 ₁ to 35 ₃ , and a conductive upper end to the contact plugs 36 ₁ to 36 ₃ . and a formed upper wiring layer 39 . The main epitaxial film 32 functions as a light receiving film.

_On the _other hand _, optical _{semiconductor} device ₃ shown in FIG _. , and upper wiring layers 37 , 38 , 39 . The optical semiconductor element 3 further includes dummy epitaxial films 33 ₂₁ to 33 ₃₆ formed in a peripheral region surrounding the main epitaxial film 32 . Compared with the dummy epitaxial films 33 ₁ to 33 ₁₀ of the optical semiconductor element 2, the dummy epitaxial films 33 ₂₁ to 33 ₃₆ of the optical semiconductor element 3 are densely arranged in a region closer to the main epitaxial film 32. The data rates of the epitaxial films 33 ₂₁ - 33 ₃₆ are higher than those of the dummy epitaxial films 33 ₁ - 33 ₁₀ . Therefore, it can be expected that the foreign matter defect density of the optical semiconductor element 3 is lower than that of the optical semiconductor element 2 . In addition, stray light is generated when part of the light incident on the optical semiconductor devices 2 and 3 or part of the light propagating in the optical semiconductor devices 2 and 3 is not coupled with the optical waveguide structure 30 or the main epitaxial film 32. However, such stray light can be expected to be absorbed by the dummy epitaxial films 33 ₁ to 33 ₁₀ and 33 ₂₁ to 33 ₃₆ and removed.

Although various embodiments and modifications thereof have been described above, the above-described embodiments and modifications thereof are merely examples and do not limit the scope of the present invention. It should be understood that changes, additions and improvements may be made to the above embodiments as appropriate without departing from the spirit and scope of the invention. The scope of the present invention should be construed based on the claims, and should be understood to include equivalents thereof.

INDUSTRIAL APPLICABILITY An optical semiconductor device and a manufacturing method thereof according to the present disclosure can be suitably used for optical active devices and optical passive devices formed using a selective epitaxial growth method and manufacturing methods thereof.

1 to 3: optical semiconductor element, 10, 10p: semiconductor substrate (SOI substrate), 11: support substrate (support layer), 11: support substrate, 12: buried insulating film, 13, 13P: single crystal layer (single crystal silicon layer), 20, 20P: insulating film, 20a: main opening, 20d: dummy opening, 21: resist pattern, 22: main epitaxial film, 23: dummy epitaxial film, 23X, 23Y: polycrystalline grains, 24: interlayer Insulating films 24a, 24b: contact holes 26, 27: contact plugs 28, 29: wiring layers 30: optical waveguide structure 32: main epitaxial films 33 ₁ to 33 ₁₀ , 33 ₂₁ to 33 ₃₆ : dummy epitaxial Films 34 ₁ to 34 ₆ , 35 ₁ to 35 ₃ , 36 ₁ to 36 ₃ : contact plugs 37 to 39: upper wiring layer 100P: insulating film 100a: opening.

Claims (16)

An optical semiconductor device that functions as an optical passive device or an optical active device,
a semiconductor substrate including a single crystal layer as the outermost layer;
an insulating film formed on the single crystal layer and having a main opening and at least one dummy opening separated from each other;
a main epitaxial film selectively epitaxially grown on the single crystal layer within the main opening;
a dummy epitaxial film selectively epitaxially grown in the dummy opening on the single crystal layer;
The main epitaxial film is a film responsible for part of the function of the optical semiconductor element,
The dummy epitaxial film is a film that does not play a part of the function of the optical semiconductor element,
The distance between the main epitaxial film and the dummy epitaxial film is 4 μm or more and 100 μm or less,
An optical semiconductor device characterized by: 2. The optical semiconductor device according to claim 1, wherein said separation distance is in the range of 4 [mu]m or more and 50 [mu]m or less. 3. The optical semiconductor device according to claim 1, wherein said dummy opening has a rectangular shape with an area of 1 [mu]m*1 [mu]m or more. 4. The optical semiconductor device according to claim 1, wherein said single crystal layer is a silicon layer. The optical semiconductor device according to claim 4,
the semiconductor substrate is an SOI substrate including a supporting layer, a buried insulating film formed on the supporting layer, and a single crystal silicon layer formed on the buried insulating film;
The optical semiconductor device, wherein the silicon layer is composed of the single crystal silicon layer. 6. The optical semiconductor device according to claim 4, wherein each of said main epitaxial film and said dummy epitaxial film comprises a germanium film or a silicon germanium film. 7. The optical semiconductor device according to claim 1, wherein said dummy epitaxial film has a data rate of 1% or more and 20% or less. 8. The optical semiconductor device according to claim 1, wherein said main epitaxial film functions as a light receiving film. A method for manufacturing an optical semiconductor device,
preparing a semiconductor substrate including a single crystal layer as the outermost layer;
forming an insulating film on the single crystal layer;
forming a resist pattern on the insulating film by lithography;
forming a main opening and a dummy opening in the insulating film by etching using the resist pattern;
simultaneously epitaxially growing a main epitaxial film and a dummy epitaxial film on the single crystal layer in the main opening and the dummy opening by a selective epitaxial growth method;
The main epitaxial film is a film responsible for part of the function of the optical semiconductor element,
The dummy epitaxial film is a film that does not play a part of the function of the optical semiconductor element,
The distance between the main epitaxial film and the dummy epitaxial film is 4 μm or more and 100 μm or less,
A manufacturing method characterized by: 10. The manufacturing method according to claim 9, wherein said separation distance is in the range of 4 [mu]m or more and 50 [mu]m or less. 11. The manufacturing method according to claim 9, wherein the dummy opening has a rectangular shape with an area of 1 [mu]m*1 [mu]m or more. 12. The manufacturing method according to any one of claims 9 to 11, wherein said monocrystalline layer is a silicon layer. The manufacturing method according to claim 12,
the semiconductor substrate is an SOI substrate including a supporting layer, a buried insulating film formed on the supporting layer, and a single crystal silicon layer formed on the buried insulating film;
The manufacturing method, wherein the silicon layer is the single crystal silicon layer. 14. The manufacturing method according to claim 12, wherein each of said main epitaxial film and said dummy epitaxial film comprises a germanium film or a silicon germanium film. 15. The manufacturing method according to any one of claims 9 to 14, wherein the data rate of said dummy epitaxial film is in the range of 1% or more and 20% or less. 16. The manufacturing method according to any one of claims 9 to 15, wherein said main epitaxial film functions as a light receiving film.

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