JP7348337B2 - Semiconductor device and semiconductor device manufacturing method - Google Patents

Description

The present invention relates to a semiconductor device and a method for manufacturing a semiconductor device.

Front side illumination (FSI) is known as a structure of solid-state imaging devices such as CMOS (Complementary MOS (metal-oxide-semiconductor field-effect transistor)) image sensors. A front-illuminated solid-state imaging device has a structure in which a wiring layer provided with wiring and a microlens that condenses incident light are laminated in this order on a semiconductor layer having a photodiode. In a front-illuminated solid-state imaging device, light from an object to be imaged that has passed through a microlens passes through gaps in wiring and reaches a photodiode.

As a technique related to a front-illuminated solid-state imaging device, a technique is known in which a film having a relatively high refractive index is provided on the light incident surface of the photodiode in order to obtain desired characteristics between the photodiode and the photodiode. For example, Patent Document 1 discloses a front-illuminated solid-state imaging device in which a silicon carbide antireflection film having a refractive index higher than that of a silicon oxide film used as an insulating film is provided on the light incident surface of a photodiode. Disclosed.

Japanese Patent Application Publication No. 2008-294242

In front-illuminated solid-state imaging devices, as a technique for providing a film with a relatively high refractive index on the light incidence surface of the photodiode, for example, as in the technology described in Patent Document 1 mentioned above, reflection of light on the light incidence surface of the photodiode is used. In order to prevent this, an antireflection film having a refractive index higher than the refractive index of air and lower than the refractive index of the semiconductor layer is provided on the light incident surface of the photodiode. When the semiconductor layer is made of silicon (Si), for example, a silicon nitride film (SiN), a silicon carbide film (SiC), or the like can be used as the antireflection film. However, such an anti-reflection film generates a relatively large stress near the interface with the photodiode, and this stress causes crystal defects inside the semiconductor substrate, resulting in noise in the signal output from the photodiode. becomes. Therefore, in order to prevent the occurrence of crystal defects caused by such stress, a buffer layer made of, for example, a silicon oxide film (SiO ₂ ) is provided between the photodiode and the antireflection film to alleviate the stress. Countermeasures can be considered. However, since the refractive index of the silicon oxide film (SiO ₂ ) is lower than the refractive index of the silicon nitride film (SiN) or the like constituting the antireflection film, the antireflection effect of the antireflection film is reduced.

As a technology to provide a film with a relatively high refractive index on the light incident surface of a photodiode, for example, a film made of a material with a high refractive index is used to improve the efficiency of light utilization on the light incident surface side of a photodiode. A light condensing section such as a waveguide or an intralayer lens is provided. In this case, as a material with a high refractive index, a silicon nitride film, a silicon oxynitride film (SiON), or the like can be used. However, since such a light condensing part is made of a material with a high refractive index, it generates relatively large stress near the interface with the photodiode, similar to the antireflection film described above, and this stress causes damage to the inside of the semiconductor substrate. Crystal defects occur in the photodiode, resulting in noise in the signal output from the photodiode. Therefore, in order to prevent the occurrence of crystal defects caused by such stress, it is possible to take measures to alleviate stress by providing a buffer layer made of, for example, a silicon oxide film between the photodiode and the light condensing section. . However, since a buffer layer having a refractive index lower than that of the light collecting part is provided between the light collecting part and the photodiode, light collecting efficiency decreases.

The present disclosure has been made in view of the above points, and provides an object to suppress the occurrence of crystal defects inside a light receiving part in a semiconductor device that constitutes a front-illuminated solid-state imaging device without impairing desired characteristics. An object of the present invention is to provide a semiconductor device and a method for manufacturing the semiconductor device that can perform the following steps.

A semiconductor device of the present disclosure includes a light receiving section provided inside a semiconductor layer having a first conductivity type and having a second conductivity type different from the first conductivity type, and a light receiving section on a light incident side of the light receiving section. , a buffer layer provided in contact with the light receiving section and made of amorphous silicon; an insulating film provided on the light incident side of a region of the semiconductor layer other than the region where the light receiving section is formed; a light condensing section provided on the incident side and having a refractive index higher than the refractive index of the insulating film and lower than the refractive index of the buffer layer .

The semiconductor device of the present disclosure also includes a light receiving section provided inside a semiconductor layer having a first conductivity type and having a second conductivity type different from the first conductivity type; a buffer layer made of amorphous silicon and provided in contact with the light-receiving section ; and a buffer layer provided on the light incident side of the semiconductor layer and the buffer layer and made of at least one of a silicon nitride film and a silicon oxynitride film. and a light condensing section provided on the light incident side of the insulating film and having a refractive index lower than the refractive index of the buffer layer .

Further, the method for manufacturing a semiconductor device of the present disclosure includes a step of forming a light receiving portion having a second conductivity type different from the first conductivity type inside a semiconductor layer having a first conductivity type; a step of forming a buffer layer made of amorphous silicon on the light incident side of the semiconductor layer in contact with the light receiving section ; and a step of forming an insulating film on the light incident side of a region of the semiconductor layer other than the region where the light receiving section is formed. and forming, on the light incident side of the buffer layer, a light condensing portion having a refractive index higher than the refractive index of the insulating film and lower than the refractive index of the buffer layer .

Further, the method for manufacturing a semiconductor device of the present disclosure includes a step of forming a light receiving portion having a second conductivity type different from the first conductivity type inside a semiconductor layer having a first conductivity type; forming a buffer layer made of amorphous silicon on the light incident side of the semiconductor layer and the buffer layer in contact with the light receiving section; The method includes the steps of forming an insulating film composed of at least one of the insulating films, and forming a light condensing portion having a refractive index lower than the refractive index of the buffer layer on the light incident side of the insulating film.

According to the present disclosure, in a semiconductor device that constitutes a front-illuminated solid-state imaging device, it is possible to suppress the occurrence of crystal defects inside a light receiving portion without impairing desired characteristics.

FIG. 1 is a cross-sectional view showing an example of the configuration of a semiconductor device according to a first embodiment. 1 is a diagram showing an example of a method for manufacturing a semiconductor device according to a first embodiment; FIG. 1 is a diagram illustrating an example of a method for manufacturing a semiconductor device according to a first embodiment; FIG. 1 is a diagram showing an example of a method for manufacturing a semiconductor device according to a first embodiment; FIG. 1 is a diagram showing an example of a method for manufacturing a semiconductor device according to a first embodiment; FIG. 1 is a diagram showing an example of a method for manufacturing a semiconductor device according to a first embodiment; FIG. 1 is a diagram showing an example of a method for manufacturing a semiconductor device according to a first embodiment; FIG. 1 is a diagram showing an example of a method for manufacturing a semiconductor device according to a first embodiment; FIG. 1 is a diagram showing an example of a method for manufacturing a semiconductor device according to a first embodiment; FIG. FIG. 3 is a cross-sectional view showing another example of the configuration of the semiconductor device of the first embodiment. FIG. 3 is a cross-sectional view showing an example of the configuration of a semiconductor device according to a second embodiment. FIG. 7 is a diagram illustrating an example of a method for manufacturing a semiconductor device according to a second embodiment. FIG. 6 is a diagram illustrating an example of a method for manufacturing a semiconductor device according to a second embodiment. FIG. 7 is a diagram illustrating an example of a method for manufacturing a semiconductor device according to a second embodiment. FIG. 7 is a diagram illustrating an example of a method for manufacturing a semiconductor device according to a second embodiment. FIG. 7 is a diagram illustrating another example of the method for manufacturing a semiconductor device according to the second embodiment. FIG. 7 is a diagram illustrating another example of the method for manufacturing a semiconductor device according to the second embodiment. FIG. 7 is a diagram illustrating another example of the method for manufacturing a semiconductor device according to the second embodiment. FIG. 7 is a cross-sectional view showing an example of the configuration of a semiconductor device according to a third embodiment. FIG. 7 is a diagram illustrating an example of a method for manufacturing a semiconductor device according to a third embodiment. FIG. 7 is a diagram illustrating an example of a method for manufacturing a semiconductor device according to a third embodiment.

An example of an embodiment of the disclosed technology will be described below with reference to the drawings. In each drawing, the same or equivalent components and parts are given the same reference numerals, and duplicate explanations will be omitted as appropriate.

[First embodiment]
FIG. 1 is a cross-sectional view showing an example of the configuration of a semiconductor device 100 that constitutes a front-illuminated solid-state imaging device of this embodiment.

The semiconductor device 100 has an SOI (Silicon on Insulator) substrate 1 in which a substrate layer 12, a buried oxide film 11, and a semiconductor layer 10 are stacked, and for example, a semiconductor layer made of n-type single crystal silicon. 10 has a p-type light receiving section 30 constituting a photodiode. Among the conductivity types in this embodiment, n-type is an example of the first conductivity type of the present disclosure, and among the conductivity types in this embodiment, p-type is an example of the second conductivity type of the present disclosure. In this embodiment, the light-incidence side surface of the light-receiving section 30 is the same as the light-incidence side surface S1 of the semiconductor layer 10 (so-called flush). Note that the semiconductor layer 10 is provided with a plurality of photodiodes having a configuration similar to that shown in FIG. Each of these photodiodes constitutes a plurality of pixels in the solid-state imaging device.

The light receiving section 30 generates charges according to the amount of light incident from the surface S1 side of the semiconductor layer 10. The surface of the light receiving section 30 on the light incident side is covered with a buffer layer 40. In this embodiment, the buffer layer 40 is made of n-type amorphous silicon (a-Si), which has a conductivity type opposite to that of the light receiving section 30. The buffer layer 40 is in contact with the light receiving section 30.

The light incident side surface of the buffer layer 40 is covered with a high refractive index layer 42 having a refractive index higher than that of an insulating film 29 made of an insulator such as silicon oxide (SiO ₂ ), which will be described later. . Here, the refractive index of silicon oxide constituting the insulating film 29 is about 1.5. As the high refractive index layer 42, for example, a silicon nitride film (SiN) having a refractive index of about 2 can be used. By configuring the high refractive index layer 42 with a material having a higher refractive index than the refractive index of the insulating film 29, the high refractive index layer 42 prevents reflection of light irradiated onto the light incident side surface of the light receiving section 30. Functions as an anti-reflection film to prevent

Further, inside the semiconductor layer 10, a p-type floating diffusion 24 is provided with a gap between it and the light receiving section 30. Further, inside the semiconductor layer 10, an element isolation region 21 made of an insulator such as SiO ₂ is provided. The element isolation region 21 electrically isolates the plurality of photodiodes provided inside the semiconductor layer 10 .

A gate electrode 23 is provided in a region corresponding to a region between the light incident side surface of the light receiving section 30 and the floating diffusion 24 with a gate insulating film 22 interposed therebetween. The gate electrode 23 is connected to a wiring 27 via a contact plug 25 made of a conductor. Furthermore, the floating diffusion 24 is connected to a wiring 28 via a contact plug 26 made of a conductor. The light incident side surface S1 of the semiconductor layer 10 is covered with an insulating film 29 made of an insulator such as SiO ₂ , and the gate electrode 23, contact plugs 25 and 26, and wirings 27 and 28 are insulated. It is buried inside the membrane 29.

An example of a method for manufacturing the semiconductor device 100 will be described below with reference to FIGS. 2A to 2G.

First, an SOI substrate 1 on which a substrate layer 12, a buried oxide film 11, and a semiconductor layer 10 are stacked is prepared (FIG. 2A).

Next, for example, using a well-known STI (Shallow Trench Isolation) method, an element isolation region 21 made of an insulator such as SiO ₂ is formed inside the semiconductor layer 10 (FIG. 2B).

Next, a gate insulating film 22 made of an insulator such as SiO ₂ is formed on the surface of the semiconductor layer 10 using, for example, a known thermal oxidation method. Subsequently, a polysilicon film is deposited on the surface of the gate insulating film 22 using, for example, a known CVD (Chemical Vapor Deposition) method, and this polysilicon film is patterned using a known photolithography technique. By doing so, the gate electrode 23 is formed (FIG. 2C). Note that after forming the polysilicon film, ion implantation may be performed to lower the resistance of the gate electrode 23.

Next, impurity ions made of a group 3 element such as boron (B) are implanted into the semiconductor layer 10 near the gate electrode 23 by a known ion implantation method. Thereafter, impurity ions are activated by heat treatment. As a result, a p-type light receiving section 30 constituting a photodiode is formed inside the semiconductor layer 10. Subsequently, impurity ions made of a group 3 element such as boron are implanted into the semiconductor layer 10 at a position facing the light receiving section 30 with the gate electrode 23 in between. Thereafter, impurity ions are activated by heat treatment. As a result, a p-type floating diffusion 24 is formed inside the semiconductor layer 10 at a position facing the light receiving section 30 with the gate electrode 23 therebetween (FIG. 2D).

Next, using a known plasma CVD method or catalytic CVD (Cat-CVD) method, a buffer layer 40 made of amorphous silicon and having a thickness of about 10 nm to 50 nm is formed on the light incident side surface of the light receiving section 30. do. In this CVD, for example, silane gas (SiH ₄ ) and hydrogen gas (H ₂ ) can be used as material gases (FIG. 2E).

Next, a high refractive index layer 42 made of, for example, a silicon nitride film (SiN) is formed on the surface of the buffer layer 40 using a known plasma CVD method. In this CVD, for example, silane gas (SiH ₄ ), ammonia gas (NH ₃ ), and nitrogen gas (N ₂ ) can be used as material gases (FIG. 2F). The layer thickness of the high refractive index layer 42 is set according to the wavelength range of light sensed by the semiconductor device 100 as a solid-state imaging device. For example, when the wavelength range of light sensed by the semiconductor device 100 is in the infrared wavelength range, the layer thickness of the high refractive index layer 42 can be, for example, about 120 nm.

Next, an insulating film 29 made of an insulator such as SiO ₂ is formed on the surface of the semiconductor layer 10 using, for example, a known CVD method. Subsequently, a contact hole reaching the gate electrode 23 and a contact hole reaching the floating diffusion 24 are formed in the insulating film 29, and a conductive material such as tungsten (W) is filled in these contact holes to form the contact plugs 25, 26. form. Subsequently, a conductive film made of a conductive material such as aluminum is formed on the surface of the insulating film 29, and this conductive film is patterned using a known photolithography technique to connect to the contact plugs 25 and 26, respectively. Then, interconnections 27 and 28 are formed. After that, an insulating film 29 is further formed to cover the wirings 27 and 28 (FIG. 2G).

As described above, the semiconductor device 100 of the present embodiment includes the light receiving section 30 that constitutes a photodiode provided inside the n-type semiconductor layer 10, and the A buffer layer 40 made of amorphous silicon, an insulating film 29 provided on the light incident side of the semiconductor layer 10 and the buffer layer 40, and an insulating film 29 provided between the buffer layer 40 and the insulating film 29. a high refractive index layer 42 having a refractive index higher than the refractive index.

Since the high refractive index layer 42 has a refractive index higher than that of the insulating film 29, the high refractive index layer 42 functions as an antireflection film. By interposing the buffer layer 40 between the semiconductor layer 10 and the high refractive index layer 42, the influence of stress caused by the high refractive index layer 42 on the light receiving section 30 is alleviated, and the occurrence of crystal defects within the light receiving section 30 is suppressed. is suppressed. The buffer layer 40 is made of amorphous silicon, and its refractive index is approximately the same as the refractive index of the light receiving section 30 and higher than the refractive index of the high refractive index layer 42. Therefore, the buffer layer 40 exhibits a stress relaxation function without reducing the antireflection effect provided by the high refractive index layer 42.

Note that the conductivity type of the buffer layer 40 may be the opposite conductivity type to that of the light receiving section 30. As a method for setting the conductivity type of the buffer layer 40 to be the conductivity type opposite to that of the light receiving section 30, the following method may be used, for example. After forming the buffer layer 40 on the light incident side surface of the light receiving section 30 (see FIG. 2E), before forming the high refractive index layer 42, phosphorus (P) or arsenic (As) is added by a known ion implantation method. ) and the like are implanted (doped) into the buffer layer 40. Subsequently, the impurity ions implanted into the buffer layer 40 are activated by irradiating the surface of the buffer layer 40 with a Nd:YLF laser. This imparts n-type conductivity to the buffer layer 40 (FIG. 2H). According to such laser annealing treatment, heat treatment of the entire device becomes unnecessary. In addition, the ion implantation process and laser annealing process in this step are processes for the buffer layer 40, and by appropriately setting the acceleration voltage and laser power during ion implantation, damage to the light receiving section 30 due to these processes can be prevented. Can be suppressed. For example, when forming the buffer layer 40 by a plasma CVD method or a catalytic CVD (Cat-CVD) method (see FIG. 2E), a material gas containing silane gas (SiH ₄ ) and hydrogen gas (H ₂ ) and phosphorus ( A mixed gas containing an impurity gas containing a Group 5 element such as P) or arsenic (As) may be used. Thereby, conductivity can be imparted to the buffer layer 40 at the stage of film formation of the buffer layer 40.

In this way, by setting the conductivity type of the buffer layer 40 in contact with the light receiving section 30 to be the opposite conductivity type to that of the light receiving section 30, the buffer layer 40 can prevent noise caused by the interface state on the surface of the light receiving section 30. It also functions as a pinning layer to suppress This constitutes a solid-state imaging device with less noise. Therefore, by setting the conductivity type of the buffer layer 40 in contact with the light receiving section 30 to be the opposite conductivity type to that of the light receiving section 30, the buffer layer 40 has the function of mitigating the influence of stress caused by the high refractive index layer 42 on the light receiving section 30. and functions as a pinning layer that suppresses noise generation.

Further, as in the semiconductor device 100 shown in FIG. 3, a wiring 48 electrically connected to the buffer layer 40 may be provided so that a voltage can be applied to the buffer layer 40. By applying a voltage to the buffer layer 40, the surface potential of the light receiving section 30 can be controlled. When providing the wiring 48 electrically connected to the buffer layer 40, for example, after forming the high refractive index layer 42 on the surface of the buffer layer 40 (see FIG. 2F), the wiring 48 is passed through the high refractive index layer 42, and the buffer layer 48 is provided. A contact hole is formed that reaches layer 40. As described with reference to FIG. 2G, when forming the wirings 27 and 28 connected to the contact plugs 25 and 26, respectively, the wirings 27 and 28 are formed on the surface of the insulating film 29 using the well-known photolithography technique. The contact plug 46 and the wiring 48 are formed by patterning the conductive film. After that, an insulating film 29 is further formed to cover the wirings 27, 28, and 48.

Further, in this embodiment, amorphous silicon is used as the material for the buffer layer 40, but polysilicon can also be used instead of amorphous silicon. In this way, even when the buffer layer 40 is made of polysilicon, the same effect as when the buffer layer 40 is made of amorphous silicon can be obtained. The buffer layer 40 made of polysilicon can be formed using the well-known CVD method, as in the case of amorphous silicon. Furthermore, when imparting conductivity to the buffer layer 40 made of polysilicon, it can be done by a known ion implantation method, as in the case of amorphous silicon. Alternatively, conductivity may be imparted to the buffer layer 40 by introducing an impurity gas when forming the buffer layer 40 by CVD.

[Second embodiment]
FIG. 4 is a cross-sectional view showing an example of the configuration of the semiconductor device 100 that constitutes the front-illuminated solid-state imaging device of this embodiment. Similar to the semiconductor device 100 of the first embodiment, the semiconductor device 100 includes a p-type light receiving section 30 forming a photodiode provided inside the n-type semiconductor layer 10, and a p-type light receiving section 30 provided on the light incident side of the light receiving section 30. and a buffer layer 40 made of amorphous silicon.

The semiconductor device 100 of this embodiment differs from the semiconductor device 100 of the first embodiment in the following points. That is, as shown in FIG. 4, the semiconductor device 100 of this embodiment has a light condensing section 50 formed on the buffer layer 40 instead of the high refractive index layer 42 included in the semiconductor device 100 of the first embodiment. Be prepared. The light condensing section 50 includes a high refractive index layer 51 that constitutes a waveguide 54 that reaches the light incident side surface of the buffer layer 40, and a lens section 52 that covers the light incident side surface of the high refractive index layer 51.

The high refractive index layer 51 has a refractive index higher than that of the insulating film 29. When the insulating film 29 is made of SiO ₂ , for example, SiN or a silicon oxynitride film (SiON) can be used as the high refractive index layer 51 . The refractive index of SiON can be adjusted between the refractive index of SiO ₂ and the refractive index of SiN by changing the composition.

The lens portion 52 covers at least the light incident side surface of the high refractive index layer 51 (the opening of the waveguide 54), and as an example, in this embodiment, the lens portion 52 covers the light incident side surface of the insulating film 29 around the opening of the waveguide 54. Areas across the surface are also covered. Note that when the size of the opening of the waveguide 54 is smaller than the size of the surface of the light-incidence side of the light-receiving section 30, in other words, a part of the surface of the light-incidence side of the light-receiving section 30 is not in contact with the waveguide 54. In this case, the lens portion 52 may cover a region corresponding to the surface of the light receiving portion 30 on the light incident side. The lens portion 52 has a high refractive index, for example, a refractive index higher than that of the insulating film 29. As the material constituting the lens portion 52, for example, SiN or SiON can be used similarly to the above-described high refractive index layer 51. Note that the material constituting the lens portion 52 and the material constituting the high refractive index layer 51 may be the same or different, but the refractive index of the lens portion 52 is the same as that of the high refractive index layer 51. Preferably, it is lower than the rate.

The light focused by the lens section 52 reaches the light incident side surface of the light receiving section 30 via the waveguide 54. In addition, the lens part 52 of this embodiment functions as an in-layer lens for improving light condensation, and a color filter and a color filter (not shown) are arranged on the light incident side of the lens part 52 in order from the one closest to the lens part 52. A microlens is provided.

An example of a method for manufacturing the semiconductor device 100 of this embodiment will be described below with reference to FIGS. 5A to 5D. The method for manufacturing the semiconductor device 100 of this embodiment is the same as the method for manufacturing the semiconductor device 100 of the first embodiment up to the step of forming the buffer layer 40 (FIG. 2E).

Thereafter, the insulating film 29, contact holes 25 and 26, and wirings 27 and 28 are formed (FIG. 5A) in the same manner as in the first embodiment (see FIG. 2G) without forming the high refractive index layer 42.

Next, using a known photo-etching technique, the insulating film 29 in a region corresponding to the light incident side surface of the buffer layer 40 is removed to form an opening 60 (FIG. 5B).

Next, the opening 60 is filled with a material (here, SiN) having a refractive index higher than that of the insulating film 29 using a known high-density plasma-CVD method (FIG. 5C). . Note that the surface of the high refractive index layer 51 on the light incident side is flattened by removing the SiN formed in the portion other than the opening 60 by, for example, chemical mechanical polishing or plasma etching.

Next, an insulating film made of a material having a refractive index higher than that of the insulating film 29 (here, SiN) is formed on the light incident side surfaces of the insulating film 29 and the high refractive index layer 51. Then, a lens-shaped photoresist pattern is formed on this insulating film, and the insulating layer film is etched using the photoresist pattern as a mask, thereby forming a lens portion 52 (FIG. 5D). As a result, the light condensing section 50 including the high refractive index layer 51 that becomes the waveguide 54 and the lens section 52 is formed.

As described above, the semiconductor device 100 of the present embodiment includes a p-type light receiving section 30 forming a photodiode provided inside the n-type semiconductor layer 10, and a p-type light receiving section 30 provided on the light incident side of the light receiving section 30, A buffer layer 40 made of amorphous silicon, an insulating film 29 provided on the light incident side of the semiconductor layer 10 in an area other than the area where the light receiving section 30 is formed, and an insulating film 29 provided on the light incident side of the buffer layer 40. 29.

The high refractive index layer 51 has a refractive index higher than that of the insulating film 29 and has a function of increasing light utilization efficiency. The buffer layer 40 is interposed between the light-incidence side surface of the light-receiving section 30 and the high refractive index layer 51, thereby alleviating the influence of stress caused by the high-refractive index layer 51 on the light-receiving section 30. The occurrence of crystal defects within is suppressed. The buffer layer 40 is made of amorphous silicon, and its refractive index is approximately the same as the refractive index of the light receiving section 30 and higher than the refractive index of the high refractive index layer 51. Therefore, the buffer layer 40 exhibits a stress relaxation function without reducing the light utilization efficiency of the high refractive index layer 51.

Note that the method for forming the light condensing portion 50 is not limited to the method described above, and for example, as described below with reference to FIGS. 5E to 5G, the high refractive index layer 51 is formed before the insulating film 29. It may also be a method of forming. After forming the buffer layer 40 as described above (see FIG. 2E), a high refractive index layer 51 is formed over the entire light incident side surface S1 of the semiconductor layer 10 using a known CVD method (FIG. 5E). Next, using a known photo-etching technique, the high refractive index layer 51 in a region other than the light incident side surface of the buffer layer 40 is removed to form an opening 62 (FIG. 5F). Next, as described with reference to FIG. 2G, the insulating film 29, contact plugs 25 and 26, and wirings 27 and 28 are formed in the opening 62 (FIG. 5G). Thereafter, as described with reference to FIG. 5D, the lens portion 52 is formed on the light incident side surfaces of the insulating film 29 and the high refractive index layer 51.

Further, in the semiconductor device 100 of this embodiment, the conductivity type of the buffer layer 40 in contact with the light receiving section 30 can be made to be the opposite conductivity type to that of the light receiving section 30, similarly to the semiconductor device 100 of the first embodiment. be. Further, like the semiconductor device 100 of the first embodiment, the semiconductor device 100 of this embodiment is configured such that a wiring 48 electrically connected to the buffer layer 40 is provided so that a voltage can be applied to the buffer layer 40. It's okay. Furthermore, in the semiconductor device 100 of this embodiment, polysilicon can be used instead of amorphous silicon as the material for the buffer layer 40, similarly to the semiconductor device 100 of the first embodiment.

[Third embodiment]
FIG. 6 is a cross-sectional view showing an example of the configuration of the semiconductor device 100 that constitutes the front-illuminated solid-state imaging device of this embodiment. Similar to the semiconductor device 100 of the first embodiment, the semiconductor device 100 includes a p-type light receiving section 30 forming a photodiode provided inside the n-type semiconductor layer 10, and a p-type light receiving section 30 provided on the light incident side of the light receiving section 30. and a buffer layer 40 made of amorphous silicon.

The semiconductor device 100 of this embodiment differs from the semiconductor device 100 of the first embodiment in the following points. That is, as shown in FIG. 6, the semiconductor device 100 of the present embodiment includes a high refractive index layer 55 and a lens portion 52 instead of the insulating film 29 and the high refractive index layer 42 included in the semiconductor device 100 of the first embodiment. It is equipped with Note that in this embodiment, the lens section 52 corresponds to an example of the light condensing section of the present disclosure.

The high refractive index layer 55 has a relatively high refractive index, specifically a higher refractive index than _SiO2 . For example, SiN or SiON can be used as the high refractive index layer 55.

The lens portion 52 also has a relatively high refractive index, specifically a higher refractive index than SiO ₂ . As the material constituting the lens portion 52, for example, SiN or SiON can be used similarly to the high refractive index layer 55 described above. Note that the material constituting the lens portion 52 and the material constituting the high refractive index layer 55 may be the same or different, but the refractive index of the lens portion 52 is higher than that of the high refractive index layer 55. Preferably, it is lower than the rate.

The light focused by the lens section 52 reaches the light incident side surface of the light receiving section 30 via the high refractive index layer 55. In addition, the lens part 52 of this embodiment functions as an in-layer lens for improving light condensation, and a color filter and a color filter (not shown) are arranged on the light incident side of the lens part 52 in order from the one closest to the lens part 52. A microlens is provided.

An example of a method for manufacturing the semiconductor device 100 of this embodiment will be described below with reference to FIGS. 7A and 7B. The method for manufacturing the semiconductor device 100 of this embodiment is the same as the method for manufacturing the semiconductor device 100 of the first embodiment up to the step of forming the buffer layer 40 (FIG. 2E).

Thereafter, without forming the high refractive index layer 42, for example, a well-known CVD method is used to coat the surface of the semiconductor layer 10 with a high refractive index layer made of an insulator made of a material having a relatively high refractive index (here, SiN). Form layer 55. Subsequently, a contact hole reaching the gate electrode 23 and a contact hole reaching the floating diffusion 24 are formed in the high refractive index layer 55, and a conductor such as tungsten (W) is filled in these contact holes to form the contact plug 25. , 26. Subsequently, a conductive film made of a conductive material such as aluminum is formed on the surface of the high refractive index layer 55, and this conductive film is patterned using a known photolithography technique to form contact plugs 25 and 26, respectively. Connected wiring lines 27 and 28 are formed. After that, a high refractive index layer 55 is further formed to cover the wirings 27 and 28 (FIG. 7A).

Thereafter, as described in the second embodiment with reference to FIG. 5D, the lens portion 52 is formed on the light incident side surface of the high refractive index layer 55.

As described above, the semiconductor device 100 of the present embodiment includes a p-type light receiving section 30 forming a photodiode provided inside the n-type semiconductor layer 10, and a p-type light receiving section 30 provided on the light incident side of the light receiving section 30, A buffer layer 40 made of amorphous silicon, and a high refractive index film provided on the light incident side of the semiconductor layer 10 and the buffer layer 40 and made of at least one of a silicon nitride film (SiN) and a silicon oxynitride film (SiON). layer 55 and a lens portion 52 provided on the light incident side of the high refractive index layer 55.

The high refractive index layer 55 has a relatively high refractive index, specifically a refractive index higher than that of SiO ₂ , and has a function of increasing light utilization efficiency. The buffer layer 40 is interposed between the light-incidence side surface of the light-receiving section 30 and the high refractive index layer 55, thereby alleviating the influence of stress caused by the high-refractive index layer 55 on the light-receiving section 30. The occurrence of crystal defects within is suppressed. The buffer layer 40 is made of amorphous silicon, and its refractive index is approximately the same as the refractive index of the light receiving section 30 and higher than the refractive index of the high refractive index layer 55. Therefore, the buffer layer 40 exhibits a stress relaxation function without reducing the efficiency of light utilization by the lens portion 52 and the high refractive index layer 55.

Note that in the semiconductor device 100 of this embodiment, the conductivity type of the buffer layer 40 in contact with the light receiving section 30 can be set to be the opposite conductivity type to that of the light receiving section 30, similarly to the semiconductor device 100 of the first embodiment. be. Further, like the semiconductor device 100 of the first embodiment, the semiconductor device 100 of this embodiment is configured such that a wiring 48 electrically connected to the buffer layer 40 is provided so that a voltage can be applied to the buffer layer 40. It's okay. Furthermore, in the semiconductor device 100 of this embodiment, polysilicon can be used instead of amorphous silicon as the material for the buffer layer 40, similarly to the semiconductor device 100 of the first embodiment.

As explained above, the semiconductor device 100 of each of the above embodiments has the buffer layer 40 provided between the light receiving section 30 and the high refractive index layer (42, 51, 55), so that In the semiconductor device 100 constituting the solid-state imaging device, the occurrence of crystal defects inside the light receiving section 30 can be suppressed without impairing desired characteristics.

In each of the above embodiments, the conductivity type of the semiconductor layer 10 and the buffer layer 40 is n-type, and the light receiving section 30 and floating diffusion 24 are p-type, but the conductivity of each of these components You can also invert the mold.

10 Semiconductor layer 29 Insulating film 30 Light receiving section 40 Buffer layer 42, 51, 55 High refractive index layer 50 Light condensing section 52 Lens section 100 Semiconductor device

Claims (11)

a light receiving section provided inside a semiconductor layer having a first conductivity type and having a second conductivity type different from the first conductivity type;
a buffer layer made of amorphous silicon and provided on the light incident side of the light receiving section in contact with the light receiving section ;
an insulating film provided on a light incident side of a region of the semiconductor layer other than the region where the light receiving section is formed;
a light condensing section provided on the light incident side of the buffer layer and having a refractive index higher than the refractive index of the insulating film and lower than the refractive index of the buffer layer ;
semiconductor devices including The semiconductor device according to claim 1, wherein the light condensing section includes a high refractive index layer that is in contact with the buffer layer, and a lens section that covers a region on the light incident side of the high refractive index layer. a light receiving section provided inside a semiconductor layer having a first conductivity type and having a second conductivity type different from the first conductivity type;
a buffer layer made of amorphous silicon and provided on the light incident side of the light receiving section in contact with the light receiving section ;
an insulating film provided on the light incident side of the semiconductor layer and the buffer layer and made of at least one of a silicon nitride film and a silicon oxynitride film;
a light condensing section provided on the light incident side of the insulating film and having a refractive index lower than the refractive index of the buffer layer ;
semiconductor devices including The insulating film is a high refractive index layer having a higher refractive index than silicon oxide.
The semiconductor device according to claim 3. The light condensing section is a lens section that covers a region on the light incident side of the insulating film.
The semiconductor device according to claim 4. The lens portion has a refractive index lower than the refractive index of the high refractive index layer.
The semiconductor device according to claim 2 or claim 5. the buffer layer is of the second conductivity type;
The semiconductor device according to any one of claims 1 to 6 . 8. The semiconductor device according to claim 1, wherein the buffer layer is made of polysilicon instead of the amorphous silicon. forming a light receiving portion having a second conductivity type different from the first conductivity type inside a semiconductor layer having a first conductivity type;
forming a buffer layer made of amorphous silicon on the light incident side of the light receiving section in contact with the light receiving section ;
forming an insulating film on the light incident side of a region of the semiconductor layer other than the region where the light receiving section is formed;
forming a light condensing portion having a refractive index higher than the refractive index of the insulating film and lower than the refractive index of the buffer layer on the light incident side of the buffer layer;
A method for manufacturing a semiconductor device including: forming a light receiving portion having a second conductivity type different from the first conductivity type inside a semiconductor layer having a first conductivity type;
forming a buffer layer made of amorphous silicon on the light incident side of the light receiving section in contact with the light receiving section ;
forming an insulating film provided on the light incident side of the semiconductor layer and the buffer layer and made of at least one of a silicon nitride film and a silicon oxynitride film;
forming a light condensing portion having a refractive index lower than the refractive index of the buffer layer on the light incident side of the insulating film;
A method for manufacturing a semiconductor device including: The manufacturing method according to claim 9 or 10 , wherein the buffer layer is made of polysilicon instead of the amorphous silicon.