Patent Publication Number: US-2022231175-A1

Title: Photoelectric conversion apparatus and equipment

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a photoelectric conversion apparatus and equipment. 
     Description of the Related Art 
     Photoelectric conversion elements in which a protective film made of aluminum oxide is provided on a silicon substrate having a photoelectric conversion layer have been proposed. International Publication No. WO 2013/115275 (PTL 1) describes that dangling bonds present near the interface of a silicon substrate are likely to be terminated by adding hydrogen to the protective film on the silicon substrate to suppress the recombination of the carrier in the interface of the silicon substrate. 
     PTL 1 describes that the concentration of hydrogen included in the protective film made of aluminum oxide provided on the silicon substrate is adjusted. However, the dark current cannot be sufficiently suppressed only by adjusting the hydrogen concentration. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present disclosure provides a photoelectric conversion apparatus in which the dark current is suppressed in view of the above-mentioned disadvantages. 
     The present disclosure relates to a photoelectric conversion apparatus comprising a semiconductor layer including a plurality of photoelectric conversion portions and having a first surface and a second surface that is the surface opposite to the first surface, a wiring structure disposed on the second surface side of the semiconductor layer, and a metal compound film disposed on the first surface side of the semiconductor layer. The metal compound film contains hydrogen and carbon. The concentration of the hydrogen in the interface on the semiconductor layer side of the metal compound film is 1×10 21  atoms/cm 3  or more and 1×10 22  atoms/cm 3  or less. The concentration of the carbon in the interface on the semiconductor layer side of the metal compound film is 5×10 20  atoms/cm 3  or more and 1×10 22  atoms/cm 3  or less. 
     Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view for explaining a photoelectric conversion apparatus. 
         FIGS. 2A to 2D  are graphs of relationships between hydrogen concentration or carbon concentration and dark current for explaining a photoelectric conversion apparatus. 
         FIGS. 3A to 3D  are graphs of relationships between the ratio of hydrogen concentration to carbon concentration and dark current for explaining a photoelectric conversion apparatus. 
         FIG. 4  is a schematic view for explaining equipment including a photoelectric conversion apparatus. 
         FIG. 5A to 5F  are schematic cross-sectional views for explaining a method for manufacturing a photoelectric conversion apparatus. 
         FIG. 6A to 6D  are schematic cross-sectional views for explaining the method for manufacturing a photoelectric conversion apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments for implementing the present disclosure will now be described with reference to the drawings. In the following description and drawings, common reference numerals are given to common configurations across multiple drawings. 
     Accordingly, common configurations will be described with reference to each other of the plurality of drawings, and the description of the configuration with a common reference numeral will be appropriately omitted. Configurations with similar names but different reference numerals may be distinguished by attaching numerals, such as first configuration, second configuration, and third configuration, as appropriate. In the present specification, the description of “xx or more and yy or less” and “xx to yy” indicating the numerical range means the numerical range including the lower limit and the upper limit which are the end points, unless otherwise specified. 
     Configuration of Photoelectric Conversion Apparatus 
       FIG. 1  is a cross-sectional view of a photoelectric conversion area (imaging area) of a photoelectric conversion apparatus  930  according to the present embodiment. The photoelectric conversion apparatus  930  includes a semiconductor layer  100  having a plurality of photoelectric conversion portions  101 ,  102 , and  103 . 
     The semiconductor layer  100  is a single-crystal silicon layer having a thickness of, for example, 1 to 10 μm or 2 to 5 μm. The semiconductor layer  100  has a rear surface  1001  constituting a light-receiving surface (light incidence surface) of each of the photoelectric conversion portions  101 ,  102 , and  103 . The photoelectric conversion portions  101 ,  102 , and  103  can each be a photodiode. 
     The rear surface  1001  is one of the two main surfaces of the semiconductor layer  100 , and the semiconductor layer  100  has a front surface  1002  that is the other of the two main surfaces of the semiconductor layer  100 . Hereinafter, the rear surface  1001  and the front surface  1002  may be referred to as a first surface and a second surface, respectively. The front surface  1002  is provided with a transistor including a gate electrode  400 , and a wiring structure  440  constituted of a plurality of wiring layers  410  and  420  and an interlayer insulation film  430  is provided on the front surface  1002 . That is, the wiring structure  440  is provided on the second surface side of the semiconductor layer  100 . The transistor including the gate electrode  400  includes, for example, a transfer transistor, an amplification transistor, a reset transistor, and a selection transistor, and these transistors constitute a pixel circuit. 
     On the light-receiving surface of the photoelectric conversion portions  101 ,  102 , and  103 , a silicon compound film  300 , which is a film of a compound of silicon and at least one of oxygen, nitrogen, and carbon, such as a silicon oxide film, a silicon nitride film, or a silicon carbide film, is provided. The composition of the silicon compound film  300  can be represented by SiO x N y C z . Here, any of x, y, and z is larger than 0, and those other than that larger than 0 in x, y, and z may be 0 or not be 0. The silicon compound film can include, for example, hydrogen (H), boron (B), fluorine (F), phosphorus (P), chlorine (Cl), and argon (Ar), in addition to silicon (Si), oxygen (O), nitrogen (N), and carbon (C). When x&gt;0, x≥y≥0, and x≥z≥0, the silicon compound film  300  is a silicon oxide film. When y&gt;0, y≥x≥0, and y≥z≥0, the silicon compound film  300  is a silicon nitride film. When z&gt;0, z≥x≥0, and z≥y≥0, the silicon compound film  300  is a silicon carbide film. For example, an SiON film can be classified into a silicon oxide film or a silicon nitride film depending on the amounts of O and N. 
     Furthermore, an insulation layer  150  and a metal compound film  200  are stacked on the light-receiving surface of the photoelectric conversion portions  101 ,  102 , and  103  in this order from the light-receiving surface side. In other words, the insulation layer  150  and the metal compound film  200  are disposed on the first surface side of the semiconductor layer  100 . In the present embodiment, the insulation layer  150  and the metal compound film  200  are disposed between the silicon compound film  300  and the semiconductor layer  100 . The detail of the metal compound film  200  will be described later. In the present embodiment, the insulation layer  150  is disposed between the semiconductor layer  100  and the metal compound film  200  but is not limited thereto. The insulation layer  150  need not be disposed, and the metal compound film  200  may be disposed directly on the semiconductor layer  100 . That is, the metal compound film  200  may be disposed on the semiconductor layer  100  so as to be in contact with the semiconductor layer  100 . 
     The insulation layer  150  is disposed on the first surface side of the photoelectric conversion portions  101 ,  102 , and  103 . The insulation layer  150  may have s function of reducing the interface state and accordingly can also be called a layer of reducing the interface state. The insulation layer  150  may be formed by oxidizing the rear surface  1001  of the semiconductor layer  100  and is constituted of silicon oxide (SiO 2 ) in the present embodiment. Incidentally, as described later, the metal compound film  200  can be formed by an atomic layer deposition (ALD) method. The insulation layer  150  can also be secondarily formed in the rear surface  1001  of the semiconductor layer  100  when the metal compound film  200  is formed by the ALD method. The thickness of the insulation layer  150  is not particularly limited and may be 1 atomic layer or more and 50 nm or less, 0.1 nm or more and 10 nm or less, 0.2 nm or more and 5 nm or less, or 0.3 nm or more and 2 nm or less. When the thickness of the insulation layer  150  is 10 nm or less or 1 nm or less, hydrogen possessed by the metal compound film  200  is likely to transmit. Consequently, even if the insulation layer  150  is formed between the semiconductor layer  100  and the metal compound film  200 , the action of terminating the dangling bonds in the interface of the semiconductor layer  100  by hydrogen possessed by the metal compound film  200  is unlikely to be decreased. 
     A microlens array including a plurality of microlenses  871 ,  872 , and  873  is provided on the rear surface  1001 . One microlens  871  among the microlenses  871 ,  872 , and  873  is disposed above the photoelectric conversion portion  101 . One microlens  872  among the microlenses  871 ,  872 , and  873  is disposed above the conversion portion  102 . One microlens  873  among the microlenses  871 ,  872 , and  873  is disposed above the photoelectric conversion portion  103 . It can also be said that in a planar view from a direction perpendicular to the rear surface  1001 , the microlens  871  overlaps the photoelectric conversion portion  101 , the microlens  872  overlaps the photoelectric conversion portion  102 , and the microlens  873  overlaps the photoelectric conversion portion  103 . Each of the microlenses  871 ,  872 , and  873  is made of, for example, a resin. 
     Another interlayer lens array including a plurality of interlayer lenses  831 ,  832 , and  833  is provided between the microlens array including the plurality of microlenses  871 ,  872 , and  873  and the semiconductor layer  100 . The interlayer lenses  831 ,  832 , and  833  are each provided in, for example, a dielectric film  820  such as a silicon nitride film. The interlayer lenses  831 ,  832 , and  833  in this example are upper convex lenses but may be lower convex lenses or biconvex lenses. 
     An insulating material film  810 , such as a silicon oxide film, is provided between the interlayer lenses  831 ,  832 , and  833  and the silicon compound film  300 . An insulating material film  840 , such as a silicon oxide film, is provided between the interlayer lenses  831 ,  832 , and  833  and the microlenses  871 ,  872 , and  873 . Light collection by the interlayer lenses  831 ,  832 , and  833  is performed due to the difference in refractive index between the insulating material film  840  and the interlayer lenses  831 ,  832 , and  833  made of silicon nitride. A color filter array including color filters  861 ,  862 , and  863  is provided between the interlayer lenses  831 ,  832 , and  833  and the microlenses  871 ,  872 , and  873 . It can also be said that in a planar view from a direction perpendicular to the rear surface  1001 , the color filter  861  overlaps the photoelectric conversion portion  101 , the color filter  862  overlaps the photoelectric conversion portion  102 , and the color filter  863  overlaps the photoelectric conversion portion  103 . For example, the color filter  861  is a red filter, the color filter  862  is a green filter, and the color filter  863  is a blue filter. A planarizing film  850  is provided between the color filters  861 ,  862 , and  863  and the interlayer lenses  831 ,  832 , and  833  and/or between the color filters  861 ,  862 , and  863  and the microlenses  871 ,  872 , and  873 . The planarizing film  850  is made of, for example, a resin. 
     A light-shielding member  710  is provided between the insulating material film  810 , such as a silicon oxide film, and a silicon compound film  300 . A light-shielding wall  720  is provided on the light-shielding member  710 . The light-shielding wall  720  can be provided so as to penetrate at least one of the insulating material film  810 , the dielectric film  820 , and the insulating material film  840 . The light-shielding wall  720  can be disposed so as to surround the interlayer lenses  831 ,  832 , and  833 . 
     The optical structure of one pixel is defined mainly by a microlens, a color filter, an interlayer lens, and a photoelectric conversion portion. For example, the optical structure of a pixel including the photoelectric conversion portion  102  is defined by the microlens  872 , the color filter  862 , the interlayer lens  832 , and the photoelectric conversion portion  102 . However, some of the microlens, the color filter, and the interlayer lens can be omitted. 
     A semiconductor substrate  600  is stacked to the semiconductor layer  100 . A transistor including a gate electrode  500  is disposed on a surface of the semiconductor substrate  600 . On the surface of the semiconductor substrate  600  (between the semiconductor substrate  600  and the wiring structure  440 ), a wiring structure  540  is provided. The wiring structure  540  is constituted of a plurality of wiring layers  510  and  520  and an interlayer insulation film  530 . The transistor including the gate electrode  500  constitutes a driving circuit for driving a pixel circuit including a photoelectric conversion portion or a control circuit for controlling the photoelectric conversion apparatus  930 . The transistor including the gate electrode  500  constitutes an AD conversion circuit for performing analog-to-digital (AD) conversion of the analog signal obtained from the pixel circuit. The transistor including the gate electrode  500  constitutes a digital signal processing circuit for processing the digital signal obtained by the AD conversion. The electrical connection between the wiring structure  440  and the wiring structure  540  is accomplished by wiring through direct bonding of a wiring layer or a through-via passing through the semiconductor layer  100 . The electrical connection between the wiring structure  440  and the wiring structure  540  may be accomplished by a bump between the wiring structure  440  and the wiring structure  540  or by wire bonding. When the semiconductor substrate  600  is used as a mere supporting substrate, the transistor including the gate electrode  500  and the wiring structure  540  can be omitted. 
     Metal Compound Layer 
     The metal compound film  200  is a monolayer film of a metal compound layer or a multilayer film of metal compound layers. The metal compound layer constituting the metal compound film  200  is any of a metal oxide layer, a metal nitride layer, and a metal carbide layer. In particular, the metal compound layer may be a metal oxide layer from the viewpoint of the high light transmittance. As a specific material constituting the metal compound layer, for example, an oxide, a nitride, or a carbide including at least one element selected from hafnium (Hf), aluminum (Al), zirconium (Zr), tantalum (Ta), and titanium (Ti) can be used. The material constituting the metal compound layer may be a compound represented by MO l N m C n . Here, any of l, m, and n is larger than 0, and those other than that larger than 0 in 1, m, and n may be 0 or not be 0. In particular, 1 can be larger than 0. M may be any of hafnium (Hf), aluminum (Al), zirconium (Zr), tantalum (Ta), and titanium (Ti). Examples of the material constituting the metal compound layer include, in addition to the above, an oxide, a nitride, or a carbide including at least one element selected from lanthanum (La), praseodymium (Pr), cerium (Ce), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y). The metal compound layer may include at least one layer selected from a hafnium oxide layer, a zirconium oxide layer, an aluminum oxide layer, a titanium oxide layer, and a tantalum oxide layer. 
     The metal compound film  200  may include a layer having a negative fixed electric charge. In other words, the metal compound film  200  may be a fixed electric charge film having a negative fixed electric charge. When the metal compound film  200  is composed of a plurality of metal compound layers, among the plurality of metal compound layers, the metal compound layer nearest the semiconductor layer  100  may be the layer having a negative fixed electric charge. When the metal compound film  200  has a negative fixed electric charge, an inversion layer is formed on the rear surface  1001  side (the side of the surface in contact with the metal compound film  200 ) of the semiconductor layer  100 . Consequently, the interface of the semiconductor layer  100  is pinned by the inversion layer, and occurrence of a dark current is therefore suppressed. 
     The metal oxide layer can have a fixed electric charge when the composition of the metal and oxygen in the metal oxide layer deviates from the stoichiometric ratio. When the composition is low in the metal or high in oxygen relative to the stoichiometric ratio, the metal oxide layer can have a negative fixed electric charge. For example, when aluminum oxide is used as the metal oxide layer nearest the semiconductor layer  100  among the layers constituting the metal compound film  200 , the composition may be low in aluminum or high in oxygen relative to the stoichiometric ratio. 
     The metal compound film  200  of this example is a laminated film including a first metal compound layer  210  and a second metal compound layer  220  from the side near the semiconductor layer  100 . The thickness of the metal compound film  200  is the sum of the thickness of the first metal compound layer  210  and the thickness of the second metal compound layer  220 . The thickness of the first metal compound layer  210  may be smaller than the thickness of the second metal compound layer  220 . 
     The first metal compound layer  210  may has a negative fixed electric charge as described above and can function as a charge fixing layer for fixing the non-signal charge of the semiconductor layer  100 . The second metal compound layer  220  can function as an antireflection layer for light incident on the semiconductor layer  100 . The first metal compound layer  210  is the layer nearest the semiconductor layer  100  among the plurality of layers constituting the metal compound film  200 . The first metal compound layer  210  may be any of a hafnium oxide layer, a zirconium oxide layer, an aluminum oxide layer, a titanium oxide layer, and a tantalum oxide layer or may be an aluminum oxide layer. The second metal compound layer  220  may be any of a hafnium oxide layer, a zirconium oxide layer, an aluminum oxide layer, a titanium oxide layer, and a tantalum oxide layer or may be a hafnium oxide layer or a tantalum oxide layer. 
     When the semiconductor layer  100  is a silicon layer and performs photoelectric conversion of visible light, the metal compound film  200  may have the following configuration: the first metal compound layer  210  is, for example, an aluminum oxide (Al 2 O 3 ) layer having a thickness of 5 to 20 nm, and the second metal compound layer  220  is, for example, a tantalum oxide (Ta 2 O 5 ) layer having a thickness of 25 to 100 nm. Furthermore, an insulation layer  150  is disposed between the semiconductor layer  100  and the first metal compound layer  210 , and the insulation layer  150  can be, for example, a silicon oxide (SiO 2 ) layer having a thickness of 0.1 to 5 nm. 
     In the present embodiment, a rear-surface-irradiation-type photoelectric conversion apparatus in which the rear surface  1001  forms a light-receiving surface has been described, but the present disclosure can also be applied to a front-surface-irradiation-type photoelectric conversion apparatus in which the front surface  1002  forms a light-receiving surface. In addition, in the present embodiment, a complementary metal oxide semiconductor (CMOS) image sensor has been described as the photoelectric conversion apparatus, but the present invention is not limited thereto. The photoelectric conversion apparatus can be applied to an arbitrary sensor, such as a charge coupled device (CCD) image sensor. 
     Hydrogen Concentration and Carbon Concentration in Metal Compound Layer 
     The metal compound film  200  contains hydrogen and carbon. In the present embodiment, the first metal compound layer  210  includes hydrogen and carbon. In addition, in the present embodiment, the first metal compound layer  210  is constituted of aluminum oxide and has a negative fixed electric charge. 
     Hydrogen Concentration 
     The dangling bonds of the material constituting the semiconductor layer  100 , the dangling bonds being capable of being present in the interface of the rear surface  1001  of the semiconductor layer  100 , are terminated by that the first metal compound layer  210  includes hydrogen. The termination of dangling bonds suppresses the recombination of the carrier in the rear surface  1001  of the semiconductor layer  100 , resulting in suppression of dark current. Incidentally, even if another layer, such as the insulation layer  150 , lies between the first metal compound layer  210  and the semiconductor layer  100 , when the another layer is a sufficiently thin layer, hydrogen passes through the another layer to terminate dangling bonds. 
     Accordingly, from the viewpoint of suppressing the dark current by termination of the dangling bonds of the interface of the rear surface  1001  of the semiconductor layer  100 , the concentration of hydrogen included in the first metal compound layer  210  may be high to some extent. In particular, among the interfaces of the first metal compound layer  210 , hydrogen present in the interface near the semiconductor layer  100  (i.e., the interface on the semiconductor layer side) highly contributes to the termination of dangling bonds, and thereby the hydrogen concentration in the interface near the semiconductor layer  100  may be high. Specifically, the hydrogen concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be 1×10 21  atoms/cm 3  or more. 
     In contrast, if hydrogen is excessively included in the first metal compound layer  210 , a large amount of free hydrogen that does not contribute to termination of dangling bonds of the semiconductor layer  100  and also does not bond to the metal compound constituting the first metal compound layer  210  can be present. It is inferred that such hydrogen is present as hydrogen ions (H f ) in the first metal compound layer  210 . If a large amount of hydrogen ions are present in the first metal compound layer  210 , the negative fixed electric charge of the first metal compound layer  210  is decreased, and the effect of suppressing the dark current can be decreased. Consequently, the concentration of hydrogen included in the first metal compound layer  210  may be low to some extent. In particular, if hydrogen ions are present in the interface near the semiconductor layer  100  among the interfaces of the first metal compound layer  210 , since a decrease in the negative fixed electric charge is likely to occur, the hydrogen concentration in the interface near the semiconductor layer  100  may be low. Specifically, the hydrogen concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be 1×10 22  atoms/cm 3  or less. In addition, the hydrogen concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be 5×10 21  atoms/cm 3  or less and may be less than 3×10 21  atoms/cm 3 . 
     When the above is put together, the hydrogen concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be 1×10 21  atoms/cm 3  or more and 1×10 22  atoms/cm 3  or less. In addition, the hydrogen concentration may be 1×10 21  atoms/cm 3  or more and 5×10 21  atoms/cm 3  or less and further preferably 1×10 21  atoms/cm 3  or more and less than 3×10 21  atoms/cm 3 . When the hydrogen concentration is within the above-mentioned range, the dark current can be suppressed. 
     The hydrogen concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be the hydrogen concentration in a height region from 0 to 3 nm with the interface on the semiconductor layer  100  side of the first metal compound layer  210  as the reference height (0 nm). Here, the direction from the semiconductor layer  100  toward the first metal compound layer  210  is defined as the forward direction. 
     In the first metal compound layer  210 , the hydrogen concentration distribution in the layer thickness direction may be heterogeneous. In other words, in the first metal compound layer  210 , the hydrogen concentration may vary along the layer thickness direction. That is, the hydrogen concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  and the hydrogen concentration in a portion away from the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be different from each other. In the following description, the former hydrogen concentration is referred to as interfacial hydrogen concentration, and the latter hydrogen concentration is referred to as hydrogen concentration in film. The hydrogen concentration in film may be the hydrogen concentration in the region 3 nm or more away from the interface on the semiconductor layer  100  side of the first metal compound layer  210 . 
     The hydrogen concentration in film may be lower than the interfacial hydrogen concentration. When the hydrogen concentration is low, the crystallinity of the first metal compound layer  210  can be enhanced. Consequently, the mechanical intensity is increased, and also the moisture resistance can be improved. The hydrogen concentration in the first metal compound layer  210  may monotonically decrease with an increase in the distance from the interface on the semiconductor layer  100  side in the region between the interface on the semiconductor layer  100  side and a plane 3 nm away from the interface on the side opposite to the semiconductor layer  100 . In such a case, both suppression of dark current by termination of dangling bonds in the interface of the semiconductor layer  100  and high moisture resistance and high mechanical intensity of the first metal compound layer  210  can be achieved. The hydrogen concentration in film of the first metal compound layer  210  may be 5×10 20  atoms/cm 3  or more and 2×10 21  atoms/cm 3  or less. Incidentally, the concentrations of hydrogen and carbon of the metal compound film  200  such as the first metal compound layer  210  can be adjusted by film formation atmosphere, film formation temperature, and heat treatment conditions after film formation. 
       FIGS. 2A to 2D  are graphs showing relationships between the hydrogen concentration and the average value of dark current and relationships between the carbon concentration and the average value of dark current in the first metal compound layer  210 , when the semiconductor layer  100  is constituted of silicon and the first metal compound layer  210  is constituted of aluminum oxide.  FIG. 2A  shows a relationship between interfacial hydrogen concentration and the average value of dark current,  FIG. 2B  shows a relationship between hydrogen concentration in film and the average value of dark current. As shown in  FIG. 2A , the dark current tends to be suppressed with an increase in the interfacial hydrogen concentration. When the interfacial hydrogen concentration is 1×10 21  atoms/cm 3  or more and 1×10 22  atoms/cm 3  or less, the value of dark current is low. As shown in  FIG. 2B , also in the hydrogen concentration in film, the dark current tends to be suppressed with an increase in the hydrogen concentration in film, and when the hydrogen concentration in film is 5×10 20  atoms/cm 3  or more and 2×10 21  atoms/cm 3  or less, the value of dark current is low. Here, although the case in which the semiconductor layer  100  is constituted of silicon and the first metal compound layer  210  is constituted of aluminum oxide has been considered, the above is the same also when the semiconductor layer  100  and the first metal compound layer  210  are constituted of other materials. 
     Carbon Concentration 
     As described above, if hydrogen is excessively contained in the first metal compound layer  210 , a large amount of free hydrogen can be present in the first metal compound layer  210 . Such free hydrogen can reduce the dark current-suppressing effect. Accordingly, in the present embodiment, carbon is added to the first metal compound layer  210 . The carbon included in the first metal compound layer  210  can be present in bonding with a metal element represented by M, as represented by, for example, M-CH 2 — or M-C—O—. The first metal compound layer  210  can be formed by a film formation method using an organic metal as a raw material, such as an ALD method and a metal organic chemical vapor deposition (MOCVD) method, as described later. Particularly, when the layer is formed by such a film formation method, carbon is likely to present in bonding with the metal element in the above-mentioned form. When the first metal compound layer  210  contains a certainly large amount of carbon, even if a large amount of hydrogen is contained and a large amount of hydrogen that does not contribute to termination of dangling bonds in the interface of the semiconductor layer  100  is present, such hydrogen is captured by carbon. Consequently, it is possible to suppress the negative fixed electric charge from being decreased by liberation of hydrogen in the first metal compound layer  210 . 
     When the first metal compound layer  210  includes carbon, the refractive index of the first metal compound layer  210  is reduced. The carbon concentration of the first metal compound layer  210  and the refractive index of the first metal compound layer  210  are in reverse proportion to each other, and the higher the carbon concentration of the first metal compound layer  210 , the lower the refractive index of the first metal compound layer  210 . Generally, the semiconductor layer  100  has a high refractive index, and the refractive index of the semiconductor layer  100  is higher than the refractive index of the first metal compound layer  210 . If the refractive index of the first metal compound layer  210  is too low, the difference of the refractive indices of the first metal compound layer  210  and the semiconductor layer  100  becomes large, and the reflectance between the first metal compound layer  210  and the semiconductor layer  100  becomes large. Accordingly, from the viewpoint of the efficiency of light incident on the semiconductor layer  100 , the refractive index of the first metal compound layer  210  need not be very low, and the carbon concentration of the first metal compound layer  210  may be accordingly low to some extent. Incidentally, even if an insulation layer  150  is disposed between the semiconductor layer  100  and the first metal compound layer  210 , when the thickness of the insulation layer  150  is sufficiently small, the influence of the insulation layer  150  on the reflection of light between the semiconductor layer  100  and the first metal compound layer  210  can be ignored. For example, when the thickness of the insulation layer  150  is 50 nm or less, the reflection of light between the semiconductor layer  100  and the first metal compound layer  210  can be dominated by the refractive index of the semiconductor layer  100  and the refractive index of the first metal compound layer  210 . 
     Based on the above, the carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be 5×10 20  atoms/cm 3  or more and 1×10 22  atoms/cm 3  or less. In addition, the carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be 1×10 21  atoms/cm 3  or more or 2×10 21  atoms/cm 3  or more. When the carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  is 5×10 20  atoms/cm 3  or more, liberation of hydrogen can be suppressed, and the dark current-suppressing effect can be enhanced. When the carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  is 1×10 22  atoms/cm 3  or less, the crystallinity of the first metal compound layer  210  can be suppressed from decreasing. The carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be the carbon concentration in a height region from 0 to 3 nm with the interface on the semiconductor layer  100  side of the first metal compound layer  210  as the reference height (0 nm), as in the interfacial hydrogen concentration. 
     In the first metal compound layer  210 , the carbon concentration distribution in the layer thickness direction may be heterogeneous. In other words, in the first metal compound layer  210 , the carbon concentration may vary along the layer thickness direction. That is, the carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  and the carbon concentration in a portion away from the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be different from each other. In the following description, as in the case of hydrogen concentration, the former carbon concentration is referred to as interfacial carbon concentration, and the latter carbon concentration is referred to as carbon concentration in film. The carbon concentration in film may be the carbon concentration in the region 3 nm or more away from the interface on the semiconductor layer  100  side of the first metal compound layer  210 . 
     The carbon concentration in film of the first metal compound layer  210  may be 1×10 19  atoms/cm 3  or more and 1×10 21  atoms/cm 3  or less. 
       FIG. 2C  shows a relationship between interfacial carbon concentration and the average value of dark current,  FIG. 2D  shows a relationship between carbon concentration in film and the average value of dark current. As shown in  FIG. 2C , the dark current tends to be suppressed with an increase in the interfacial carbon concentration. When the interfacial carbon concentration is 5×10 20  atoms/cm 3  or more and 1×10 22  atoms/cm 3  or less, the value of dark current is low. As shown in  FIG. 2D , also in the carbon concentration in film, the dark current tends to be suppressed with an increase in the carbon concentration in film, and when the carbon concentration in film is 1×10 19  atoms/cm 3  or more and 1×10 21  atoms/cm 3  or less, the value of dark current is low. Here, although the case in which the semiconductor layer  100  is constituted of silicon and the first metal compound layer  210  is constituted of aluminum oxide has been considered, the above is the same also when the semiconductor layer  100  and the first metal compound layer  210  are constituted of other materials. 
     Ratio of Hydrogen Concentration and Carbon Concentration 
     As described above, since carbon contained in the first metal compound layer  210  has a function of capturing excess hydrogen in the first metal compound layer  210 , in the viewpoint of suppressing dark current, the ratio of the carbon concentration and the hydrogen concentration in the first metal compound layer  210  is also important. The reduction in the refractive index of the first metal compound layer  210  can be suppressed by adjusting the ratio of the hydrogen concentration and the carbon concentration in the first metal compound layer  210  to an appropriate value, while suppressing dark current by the hydrogen-capturing effect of carbon. Hereinafter, the ratio of the hydrogen concentration to the carbon concentration in the first metal compound layer  210  (hydrogen concentration/carbon concentration) will be considered. 
     If the ratio, hydrogen concentration/carbon concentration, is too high, excess hydrogen that does not contribute to the termination of dangling bonds in the interface of the semiconductor layer  100  cannot be captured by carbon, and free hydrogen is likely to be generated in the first metal compound layer  210 . As a result, as described above, the negative fixed electric charge possessed by the first metal compound layer  210  is reduced, and the dark current-suppressing effect is reduced. Accordingly, the hydrogen concentration/carbon concentration may be low to some extent. Specifically, the hydrogen concentration/carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  may be 1.5 or less. In addition, the hydrogen concentration/carbon concentration in the film of the first metal compound layer  210  may be 10 or less. Consequently, the dark current can be effectively suppressed. 
       FIGS. 3A to 3D  are graphs showing relationships between the ratio of the hydrogen concentration to the carbon concentration (hydrogen concentration/carbon concentration) in the first metal compound layer  210  and the dark current when the semiconductor layer  100  is constituted of silicon and the first metal compound layer  210  is constituted of aluminum oxide.  FIG. 3A  shows a relationship between the hydrogen concentration/carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  and the maximum value of dark current, and  FIG. 3B  shows a relationship between the hydrogen concentration/carbon concentration in the interface on the semiconductor layer  100  side of the first metal compound layer  210  and the minimum value of dark current. As shown in  FIG. 3A , when the hydrogen concentration/carbon concentration in the interface exceeds 1.5, the maximum value of dark current significantly increases, and the dark current can be suppressed by adjusting the hydrogen concentration/carbon concentration to 1.5 or less.  FIG. 3C  shows a relationship between the hydrogen concentration/carbon concentration in the film of the first metal compound layer  210  and the maximum value of dark current, and  FIG. 3D  shows a relationship between the hydrogen concentration/carbon concentration in the film of the first metal compound layer  210  and the maximum value of dark current. As shown in  FIG. 3C , when the hydrogen concentration/carbon concentration in the film exceeds 20, the maximum value of dark current significantly increases, and the dark current can be suppressed by adjusting the hydrogen concentration/carbon concentration to 10 or less. Here, although the case in which the semiconductor layer  100  is constituted of silicon and the first metal compound layer  210  is constituted of aluminum oxide has been considered, the above is the same also when the semiconductor layer  100  and the first metal compound layer  210  are constituted of other materials. 
     Other Embodiments 
       FIG. 4  is a schematic view of equipment  9191  including a photoelectric conversion apparatus  930 . The equipment  9191  further includes at least one of an optical system  940 , a controller  950 , a processor  960 , a memory  970 , a display  980 , and a mechanical device  990 , in addition to the photoelectric conversion apparatus  930 . The optical system  940  is associated with the photoelectric conversion apparatus  930  and forms an image in the photoelectric conversion apparatus. The controller  950  controls the photoelectric conversion apparatus  930 . The processor  960  processes the signal output from the photoelectric conversion apparatus  930 . The memory  970  stores the information obtained by the photoelectric conversion apparatus  930 . The display  980  displays the information obtained by the photoelectric conversion apparatus  930 . The mechanical device  990  is operated based on the information obtained by the photoelectric conversion apparatus  930 . The mechanical device  990  may be a moving device for moving the photoelectric conversion apparatus  930  in the equipment  9191  or moving the whole equipment  9191 . An anti-vibration (image stabilizer) function can be realized by moving the photoelectric conversion apparatus  930  in the equipment  9191 . 
     The photoelectric conversion apparatus  930  may include an electric device  910  and a mount member  920 , but the mount member  920  need not be present. The electric device  910  is a semiconductor device including a semiconductor layer. The electric device  910  includes a photoelectric conversion area  901  where the photoelectric conversion portion is disposed and a peripheral circuit area  902  where a peripheral circuit (not shown) is disposed. The peripheral circuit includes the above-mentioned driving circuit, AD conversion circuit, digital signal processing circuit, control circuit, and so on. The photoelectric conversion area  901  and the peripheral circuit area  902  may be disposed on a single semiconductor layer, but in this example, they may be arranged on separate semiconductor layers (semiconductor substrates) laminated with each other. 
     The mount member  920  includes, for example, a ceramic package or a plastic package, a printed wiring board, a flexible cable, solder, and wiring bonding. The optical system  940  is, for example, a lens, a shutter, a filter, and a mirror. The controller  950  is, for example, a semiconductor device, such as an ASIC. The processor  960  is, for example, a semiconductor device, such as a central processing unit (CPU) or an application specific integrated circuit (ASIC), constituting an analog front end (AFE) or a digital front end (DFE). The display  980  is, for example, an EL display or a liquid crystal display. The memory  970  is a volatile memory, such as an SRAM and a DRAM, or a non-volatile memory, such as a flash memory and a hard disk drive, and is, for example, a magnetic device or a semiconductor device. The mechanical device MCHN includes a moving part or a promoting part, such as a motor or an engine. 
     The equipment  9191  shown in  FIG. 4  can be electronic equipment, such as an information terminal having a photographing function (e.g., smart phone and wearable terminal) and a camera (e.g., interchangeable lens camera, compact camera, video camera, and monitoring camera). The mechanical device  990  of a camera can drive a part of the optical system  940  for zooming, focusing, or shutter operation. Furthermore, the equipment  9191  can be transportation equipment (moving body), such as a vehicle, a ship, a flight vehicle, and an artificial satellite. 
     The mechanical device  990  of transportation equipment can be used as a moving device. The equipment  9191  as transportation equipment is suitable for transporting the photoelectric conversion apparatus  930  or assisting and/or automating driving (maneuvering) by the photographing function. The processor  960  for assisting and/or automating of driving (maneuvering) can perform processing for operating the mechanical device  990  as a moving device based on information obtained by the photoelectric conversion apparatus  930 . In addition, the equipment  9191  can be analytical equipment or medical equipment. 
     The photoelectric conversion apparatus  930  according to the present embodiment can provide a high value to a designer, manufacturer, seller, purchaser, and/or user thereof. Accordingly, the value of the equipment  9191  can also be increased by mounting the photoelectric conversion apparatus  930  on the equipment  9191 . Therefore, determination of installation of the photoelectric conversion apparatus  930  of the present embodiment on the equipment  9191  is advantageous for increasing the value of the equipment  9191  in manufacturing and selling the equipment  9191 . 
     Method for Manufacturing Photoelectric Conversion Apparatus 
     A method for manufacturing the photoelectric conversion apparatus will be described using  FIGS. 5A to 5F and 6A to 6D . 
     As shown in  FIG. 5A , a semiconductor substrate  1000  in which a transistor including a photoelectric conversion portion and a gate electrode  400  and a wiring structure (not shown) are formed is turned over and is joined with a supporting substrate (not shown). The supporting substrate may be a semiconductor substrate  600 . The semiconductor substrate  1000  is provided with an element isolation portion  201  having an STI structure on the front surface  1002  side. In addition, the semiconductor substrate  1000  is provided with an insulating region  216  where a groove having a depth deeper than the element isolation portion  201  is filled with an insulating material on the front surface  1002  side. 
     Subsequently, as shown in  FIG. 5B , the semiconductor substrate  1000  is thinned from the side opposite to the front surface  1002  until the thickness becomes about several to several tens micrometers which allows the insulating region  216  to pass through the semiconductor substrate  1000  to form a semiconductor layer  100  having a front surface  1002  and a rear surface  1001 . The method for thinning is, for example, back grinding, chemical mechanical polishing, or etching. 
     Subsequently, as shown in  FIG. 5C , a first metal compound layer  210 , a second metal compound layer  220 , and a silicon compound film  300  are formed on the rear surface  1001  of the semiconductor layer  100 . As the method for forming the first metal compound layer  210 , for example, a film formation method using an organic metal gas as a raw material, such as an ALD method or an MOCVD method, can be used. In the present embodiment, the first metal compound layer  210  is an aluminum oxide layer. The hydrogen concentration and the carbon concentration in the aluminum oxide film and in the interface with the semiconductor layer  100  can be adjusted by the conditions for forming the aluminum oxide layer. Incidentally, although it is not shown in  FIGS. 5A to 5F and 6A to 6D , an insulation layer  150  with a thickness of about 1 nm is formed between the rear surface  1001  of the semiconductor layer  100  and the first metal compound layer  210 . In the present embodiment, the insulation layer  150  is a silicon oxide layer and can be formed by oxidizing the rear surface  1001  of the semiconductor layer  100  made of silicon when the first metal compound layer  210  is formed by an ALD method. 
     The method for forming the second metal compound layer  220  is, for example, an ALD method, an MOCVD method, a PVD method, or a CVD method. The second metal compound layer  220  is, for example, a tantalum oxide layer or a titanium oxide layer. 
     The silicon compound film  300  can be arbitrarily selected from materials that are generally used in semiconductor apparatuses, such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a carbon-containing silicon oxide film, and a fluorine-containing silicon oxide film. The layer structure of the silicon compound film  300  may be a single layer structure made of one material or a laminated layer structure made of a plurality of materials. 
     Subsequently, a groove for embedding a metal structure is formed in the silicon compound film  300 . Subsequently, as shown in  FIG. 5D , a conductor film  700  is formed over the entire surface of the silicon compound film  300 . At that time, the conductor film  700  embeds the groove of the silicon compound film  300 . The conductor film  700  is, for example, a tungsten film, an aluminum film, or a copper film. 
     Subsequently, as shown in  FIG. 5E , the conductor film  700  is patterned. The patterning is performed by photolithography and etching. A part of the conductor film  700  becomes light-shielding members  710  and  711  by the patterning, and another part becomes a guard ring  714 . The light-shielding member  711  serves as a light shield for an optical black pixel and a peripheral circuit. Incidentally, at the same time as the formation of the light-shielding member  711  and the guard ring  714 , a via  713  and a guard ring  712  for connecting the light-shielding member  711  and the guard ring  714  to the semiconductor layer  100  are formed in grooves of the silicon compound film  300 . The guard rings  712  and  714  are disposed so as to surround the outside of the insulating region  216  in a planar view with respect to the front surface  1001 . 
     Subsequently, as shown in  FIG. 5E , an insulating material film  810  is formed. The insulating material film  810  can be arbitrarily selected from materials that are generally used in semiconductor apparatuses, such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a carbon-containing silicon oxide film, and a fluorine-containing silicon oxide film. The layer structure of the film may be a single layer structure made of one material or a laminated layer structure made of a plurality of materials. 
     Subsequently, a groove is formed by etching from the surface of the insulating material film  810 , a conductor is then formed by a PVD method or a CVD method and embeds the groove, and the conductor on the substrate surface is removed by, for example, a chemical mechanical polishing or etchback. Consequently, as shown in  FIG. 5F , a light-shielding wall  721  is formed in the insulating material film  810 . The number of the layers of the metal film can be arbitrarily selected. 
     Subsequently, a dielectric film  820  is formed on the insulating material film  810 , and the dielectric film  820  is processed by, for example, photolithography and etching to form an interlayer lens  832  on the dielectric film  820  as shown in  FIG. 6A . The dielectric film  820  can be arbitrarily selected from materials that are generally used in semiconductor apparatuses, such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a carbon-containing silicon oxide film, and a fluorine-containing silicon oxide film. The layer structure of the film may be a single layer structure made of one material or a laminated layer structure made of a plurality of materials. 
     Subsequently, an insulating material film  840  is formed, a groove is formed by etching from the surface of the insulating material film  840 , and the groove is then embedded with a conductor over the entire substrate surface by a PVD method or a CVD method. As shown in  FIG. 6B , a light-shielding wall  722  is formed in the insulating material film  840  by removing the conductor on the substrate surface by, for example, chemical mechanical polishing or etchback. The light-shielding wall  721  and the light-shielding wall  722  are in contact with each other, and the light-shielding wall  721  and the light-shielding wall  722  function as the light-shielding wall  720  shown in  FIG. 1 . Insulating material film  840  can be arbitrarily selected from materials that are generally used in semiconductor apparatuses, such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a carbon-containing silicon oxide film, and a fluorine-containing silicon oxide film. The layer structure of the film may be a single layer structure made of one material or a laminated layer structure made of a plurality of materials. The material of the light-shielding wall  722  may be, for example, tungsten. 
     Subsequently, as shown in  FIG. 6C , a planarizing film  850 , color filters  862  and  863 , and a microlens  872  are formed. A blue color filter  863  covers the light-shielding member  711 . 
     The planarizing film  850  can be arbitrarily selected from materials that are generally used in semiconductor apparatuses, such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a carbon-containing silicon oxide film, a fluorine-containing silicon oxide film, and a resin film. The layer structure of the film may be a single layer structure made of one material or a laminated layer structure made of a plurality of materials. 
     Subsequently, as shown in  FIG. 6D , an aperture  888  is formed in the semiconductor layer  100  by dry etching. A pad (not shown) made of aluminum previously provided to the wiring structure  440  or the wiring structure  540  shown in  FIG. 1  is exposed to the bottom of the aperture  888 . A wafer including the semiconductor layer  100  is then diced into a chip, and packaging is performed to connect a wire bonding chip to the pad through the aperture  888  to obtain a photoelectric conversion apparatus. 
     The embodiments included in the present disclosure include not only what is described as text, but also all matters that can be read from the text and matters that can be read from the attached drawings. In the present embodiment, components can be added, deleted, or replaced without departing from the idea of the disclosure. 
     While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-007474, filed Jan. 20, 2021, which is hereby incorporated by reference herein in its entirety.