JP5888985B2 - Photoelectric conversion element, photoelectric conversion device using the same, and imaging system - Google Patents

Description

  The present invention relates to a photoelectric conversion device having a light guide structure.

In a photoelectric conversion device including a plurality of photoelectric conversion elements, in order to increase the number of photoelectric conversion units and / or to downsize the photoelectric conversion device, it is necessary to reduce the width of the light receiving surface. Therefore, the sensitivity of the photoelectric conversion unit itself may be reduced. Therefore, the sensitivity of the photoelectric conversion element can be improved by increasing the utilization efficiency of incident light.
In order to increase the utilization efficiency of incident light, as described in Patent Document 1, it is effective to provide an optical waveguide on the light receiving surface of a photoelectric conversion unit (light receiving unit).

JP 2010-103458 A

  An object of the present invention is to improve the utilization efficiency of incident light.

  A first aspect of the present invention for solving the above problem is a photoelectric conversion element comprising a photoelectric conversion unit and an optical path member provided on the photoelectric conversion unit and surrounded by an insulating film. A first portion and a second portion having a refractive index lower than the refractive index of the first portion, and in a certain plane parallel to the light receiving surface of the photoelectric conversion unit and parallel to the light receiving surface In another plane closer to the light receiving surface than the certain plane, the second portion is continuous with the first portion and surrounds the first portion, and the refractive index of the second portion is the insulating layer. The refractive index is higher than the refractive index of the film, and the thickness of the second portion in the other plane is smaller than the thickness of the second portion in the certain plane.

  In addition, a second aspect of the present invention for solving the above-described problem is a photoelectric conversion element including a photoelectric conversion unit and an optical path member provided on the photoelectric conversion unit and surrounded by an insulating film. The member includes a first portion made of silicon nitride and a second portion made of silicon nitride and having a silicon nitride density lower than that of the first portion, and each of the insulating films is oxidized. Including a first insulating layer and a second insulating layer made of silicon or silicate glass, and in a certain plane parallel to the light receiving surface of the photoelectric conversion portion, the second portion is the first portion and the second portion It is located between the first insulating layer, and the second portion is continuous with the first portion and surrounds the first portion, and is parallel to the light receiving surface of the photoelectric conversion unit and more than the certain plane. In another plane close to the light receiving surface, the second part Is located between the first part and the second insulating layer, and the second part is continuous with the first part and surrounds the first part, and the second part in the certain plane The thickness of the second portion in the other plane is smaller than the thickness of the portion.

  A third aspect of the present invention for solving the above problems is a photoelectric conversion element comprising a photoelectric conversion unit and an optical path member provided on the photoelectric conversion unit and surrounded by an insulating film, wherein the optical path member is A first portion made of silicon nitride and a second portion made of silicon nitride and having a lower ratio of silicon to nitrogen than the first portion, each of the insulating films being made of silicon oxide Or a first insulating layer and a second insulating layer made of silicate glass, and the second portion is the first portion and the first in a plane parallel to the light receiving surface of the photoelectric conversion unit. And the second portion is continuous with the first portion and surrounds the first portion, and is parallel to the light receiving surface of the photoelectric conversion unit and more than the certain plane. In another plane close to the light receiving surface, the second part Is located between the first part and the second insulating layer, and the second part is continuous with the first part and surrounds the first part, and the second part in the certain plane The thickness of the second portion in the other plane is smaller than the thickness of the second portion.

  According to the present invention, the utilization efficiency of incident light can be improved.

It is a cross-sectional schematic diagram of a photoelectric conversion element for explaining an example of the photoelectric conversion element. It is a partial cross-sectional schematic diagram of the photoelectric conversion element explaining an example of the first embodiment. It is a schematic diagram explaining 1st Embodiment. It is a one part cross-sectional schematic diagram of the photoelectric conversion element explaining an example of 2nd Embodiment. It is a one part cross-sectional schematic diagram of the photoelectric conversion element explaining an example of 3rd Embodiment. It is a one part cross-sectional schematic diagram of the photoelectric conversion element explaining an example of 4th Embodiment. It is a one part cross-sectional schematic diagram of the photoelectric conversion element explaining an example of 5th Embodiment. It is a one part cross-sectional schematic diagram of the photoelectric conversion element explaining an example of 6th Embodiment. It is a schematic diagram explaining an example of a photoelectric conversion apparatus and an imaging system.

  First, the outline | summary of the photoelectric conversion element 1 is demonstrated using FIG. FIG. 1 is a schematic cross-sectional view illustrating an example of a photoelectric conversion element.

  The photoelectric conversion element 1 includes a photoelectric conversion unit 110. A photoelectric conversion device can be formed by arranging a plurality (multiple) of photoelectric conversion elements 1 in a one-dimensional or two-dimensional manner. The photoelectric conversion device will be described later with reference to FIG. 9, but the photoelectric conversion device may further include a peripheral circuit for controlling a signal obtained from the photoelectric conversion element 1.

  The photoelectric conversion unit 110 is provided on the substrate 100. In the photoelectric conversion device, one substrate 100 includes a plurality of photoelectric conversion units 110, and each of the plurality of photoelectric conversion units 110 forms part of a separate photoelectric conversion element 1.

  The upper surface of the photoelectric conversion unit 110 in the drawing is the light receiving surface 111. A virtual (geometric) plane including the light receiving surface 111 is referred to as a first plane 1001. Typically, the photoelectric conversion unit 110 is formed by introducing impurities deeper than the main surface 101 of the semiconductor substrate 100. Therefore, the light receiving surface 111 of the photoelectric conversion unit 110 typically substantially coincides with at least a part of the main surface 101 of the substrate 100, and the first plane 1001 includes the main surface 101 of the substrate 100.

  However, the photoelectric conversion unit 110 may be formed deeper than the bottom surface of the recess by providing a recess in the main surface 101 of the semiconductor substrate 100. Alternatively, it may be formed as a thin film having a MIS type structure or a PIN type structure on the main surface of a glass plate or the like. In these cases, the main surface 101 of the substrate 100 and the light receiving surface 111 of the photoelectric conversion unit 110 are not necessarily in the same plane.

On the substrate 100 (on the main surface 101), an insulating film 200 that covers at least one main surface 101 of the substrate 100 on which the photoelectric conversion unit 110 is disposed is provided. That is, the lower surface of the insulating film 200 is in contact with the main surface 101 of the substrate 100.
In the example of FIG. 1, the insulating film 200 covers the main surface 101 of the substrate 100 and the light receiving surface 111 of the photoelectric conversion unit 110. The insulating film 200 has an insulating property (conductivity lower than the conductivity of the substrate 100) such that the plurality of photoelectric conversion units 110 do not conduct with each other. Typically, the insulating film 200 is transparent. Although the insulating film 200 may be a single layer film made of one kind of material, the insulating film 200 is typically a multilayer film in which a plurality of layers made of different materials are laminated.

  An example of the insulating film 200 in the case of a multilayer film will be described. The insulating film 200 includes a first insulating layer 205, a second insulating layer 206, a third insulating layer 207, a fourth insulating layer 208, a fifth insulating layer 209, a sixth insulating layer 210, and a seventh insulating layer in order from the main surface 101 side. The insulating layer 211, the eighth insulating layer 212, the ninth insulating layer 213, the tenth insulating layer 214, and the eleventh insulating layer 215 are sequentially stacked. The insulating film 200 includes a twelfth insulating layer 216 located between a part of the second insulating layer 206 and a part of the third insulating layer 207.

Among these insulating layers, the second insulating layer 206, the fifth insulating layer 209, the seventh insulating layer 211, the ninth insulating layer 213, and the eleventh insulating layer 215 are made of silicon oxide (SiO ₂ ). The third insulating layer 207 is made of BPSG (borophosphosilicate glass), but instead of BPSG, PSG (phosphosilicate glass), BSG (borosilicate glass), or silicon oxide (SiO ₂ ) may be used. . Among these insulating layers, the first insulating layer 205, the fourth insulating layer 208, the sixth insulating layer 210, the eighth insulating layer 212, the tenth insulating layer 214, and the twelfth insulating layer 216 are made of silicon nitride (Si ₃ N ₄ ).

  A wiring 217 may be provided inside the insulating film 200. The wiring 217 may be a multilayer wiring, and FIG. 1 shows an example in which the wiring 217 includes a first wiring layer 2171, a second wiring layer 2172, and a plug layer 2173. The plug layer 2173 is located between the first wiring layer 2171 and the second wiring layer 2172, and connects the first wiring layer 2171 and the second wiring layer 2172 to each other. Although an example in which two wiring layers are provided has been described, a wiring layer may be further provided between the first wiring layer 2171 and the second wiring layer 2172 to form three or more wiring layers. For the wiring 217, a conductive material such as copper, aluminum, tungsten, tantalum, titanium, or polysilicon can be used. A typical wiring 217 is opaque and has a metallic luster. A gate electrode 218 of a transfer gate having a MOS structure is provided on the main surface 101 of the semiconductor substrate 100. The gate electrode 218 is made of polysilicon and connected to the first wiring layer 2171 through a plug (not shown).

  An example of the wiring 217 is given. The plug (not shown) contains tungsten as a main component and can be formed by a single damascene method. The first wiring layer 2171 is mainly composed of copper and can be formed by a single damascene method. The plug layer 2173 and the second wiring layer 2172 are mainly composed of copper and can be integrally formed by a dual damascene method. At this time, the fourth insulating layer 208, the sixth insulating layer 210, and the eighth insulating layer 212 can be used as an etching control layer and a copper diffusion preventing layer, and the tenth insulating layer 214 can be used as a copper diffusion preventing layer. Note that the first wiring layer 2171, the second wiring layer 2172, the contact layer 2173, and the plug can have a barrier metal whose main component is tantalum or the like in the vicinity of the interface with the insulating film 200.

  The insulating film 200 has an opening (hole) 201. Although the opening 201 can be a through hole or a recess, FIG. 1 shows a configuration in which the opening 201 is a recess. The insulating film 200 has an upper surface 202 that is substantially flat and parallel to the main surface 101 of the substrate 100. Here, the eleventh insulating layer 215 forms the upper surface 202 of the insulating film 200. A virtual (geometric) plane including the upper surface 202 is referred to as a second plane 1002. The second plane 1002 is parallel to the first plane 1001, and the first plane 1001 and the second plane 1002 are substantially separated by the thickness of the insulating film 200. The opening 201 is continuous with the upper surface 202. Specifically, the opening 201 includes a bottom surface 203 and a side surface 204. Here, the twelfth insulating layer 216 forms the bottom surface 203. A virtual (geometric) plane including the bottom surface 203 is referred to as a third plane 1003. The bottom surface 203 is located in a region corresponding to the light receiving surface 111. Specifically, the bottom surface 203 is positioned so as to enter an orthogonal projection from the light receiving surface 111 in a direction parallel to the main surface 101 (a direction parallel to the first plane 1001 and the third plane 1003). In this way, the light receiving surface 111 and the bottom surface 203 are opposed to each other through part of the insulating film 200. The third plane 1003 is parallel to the second plane 1002 (and the first plane 1002), and the second plane 1002 and the third plane 1003 are substantially separated by the depth of the opening 201. The side surface 204 is continuous with the top surface 202 and the bottom surface 203. Therefore, the side surface 204 extends substantially between the second plane 1002 and the third plane 1003. Note that the cross-sectional shape of the opening 201 is U-shaped, and the boundary between the bottom surface 203 and the side surface 204 may not be clear in practice. Even in that case, the third plane 1003 includes at least a point closest to the substrate 100 (the bottom of the opening 201) on the surface of the insulating film 200 opposite to the substrate 100 side. As described above, “the surface of the insulating film 200 opposite to the substrate 100 side” has the upper surface 202, the bottom surface 203, and the side surface 204. The surface of the insulating film 200 on the substrate 100 side is the lower surface of the insulating film 200. As is clear from the above description, the distance between the first plane 1001 and the third plane 1003 substantially corresponds to the difference between the thickness of the insulating film 200 and the depth of the opening 201.

The depth of the opening 201 is preferably ¼ or more of the thickness of the insulating film 200, and more preferably ½ or more of the thickness of the insulating film 200. The depth of the opening 201 is preferably longer than the wavelength of incident light. The wavelength of typical incident light is 0.55 μm for green, and the distance between the second plane 1002 and the third plane 1003 corresponding to the depth of the opening 201 is preferably 0.55 μm or more. Therefore, the thickness of the insulating film 200 is preferably thicker than 0.55 μm. More preferably, the thickness of the insulating film 200 is 1.0 μm or more. Or greater when extremely thickening the insulating film 200 stress, for it takes time to manufacture, in practice, the thickness T _I of the insulating film 200 is 10μm or less, preferably not more than 5.0 .mu.m.

  The planar shape of the side surface 204 of the opening 201 (the shape of the opening 201 in a plane parallel to the first plane 1001) is a closed loop shape, and may be a circle, an ellipse, a rounded rectangle, a rectangle, or a hexagon. Can do. Here, it is circular. The bottom surface 203 is also circular. The width (diameter) of the opening end of the opening 201 (side surface 204 in the second plane 1002) is typically 10 μm or less, and preferably 5.0 μm or less. The present invention has a particularly remarkable effect when the width of the opening end is 2.0 μm or less.

  The cross-sectional shape of the opening 201 (the shape of the opening 201 in a plane that passes through the central axis and is perpendicular to the first plane 1001) may be an inverted trapezoid, a regular trapezoid, a rectangle, a square, or the like as shown in FIG. It can be made into the step form which combined.

  An optical path member 220 is located in the opening 201. Since light passes through the optical path member 220, the optical path member 220 is transparent. The term “transparent” as used herein is sufficient if it has sufficient transparency with respect to light in a wavelength region where photoelectric conversion is substantially performed, and may have wavelength selectivity.

  The optical path member 220 is located inside the opening 201. Therefore, the optical path member 220 is located on the photoelectric conversion unit 110 and is surrounded by the insulating film 200. Specifically, the optical path member 220 is surrounded by the side surface 204 of the opening 201 and is in contact with the side surface 204 of the insulating film 200. The optical path member 220 is also in contact with the bottom surface 203 of the opening 201. More specifically, the optical path member 220 includes the third insulating layer 207, the fourth insulating layer 208, the fifth insulating layer 209, the sixth insulating layer 210, the seventh insulating layer 211, the eighth insulating layer 212, the insulating film 200, Surrounded by a ninth insulating layer 213, a tenth insulating layer 214, and an eleventh insulating layer 215. The optical path member 220 is in contact with the twelfth insulating layer 216 that forms the bottom surface 203 of the opening 201. In this way, the optical path member 220 is located in an area corresponding to the photoelectric conversion unit 110 (an orthogonal projection area of the light receiving surface 111). When the opening 201 is not a recess but a through hole, the light receiving surface 111 forms the bottom surface 203 of the opening 201. In other words, the optical path member 220 is in contact with the photoelectric conversion unit 110. The depth of the opening 201 is substantially equal to the thickness of the insulating film 200.

  The shape of the optical path member 220 substantially matches the shape of the opening 201. In the present embodiment, the optical path member 220 has a truncated cone shape, but may have a truncated pyramid shape, a prismatic shape, or a cylindrical shape according to the shape of the opening 201. The optical path member 220 is preferably rotationally symmetric with respect to the central axis. The width (diameter) of the optical path member 220 is typically 10 μm or less, and preferably 5.0 μm or less. The present invention has a particularly remarkable effect when the width of the opening end is 2.0 μm or less.

  The refractive index of at least a part of the optical path member 220 is higher than the refractive index of the insulating film 200. In the following description, the “refractive index of the insulating film 200” will be described as the refractive index of the material constituting most of the insulating film 200. The refractive index of a part of the optical path member 220 may be equal to or lower than the refractive index of the insulating film 200. In the present invention, the simple refractive index means the absolute refractive index. Although the refractive index varies depending on the wavelength, it is at least a refractive index with respect to the wavelength of light that can generate a signal charge in the photoelectric conversion unit 110. Furthermore, when the photoelectric conversion element 1 has a wavelength selection unit such as a color filter, the wavelength of light transmitted through the wavelength selection unit is used. However, practically, the wavelength of incident light may be regarded as 0.55 μm, which is a green wavelength that is sensitive to human eyes. In the following description, the refractive index will be described with respect to 0.55 μm.

  When the refractive index of the outermost layer of the optical path member 220 is higher than the refractive index of the insulating film 200 and the optical path member 220 and the insulating film 200 form an interface, total reflection occurs at the interface in terms of geometrical optics, and the optical path Incident light can be guided into the member 220, and as a result, can be guided to the light receiving surface 111.

  As a waveguide structure, a configuration is known in which an opaque film is provided between the optical path member and the side surface of the insulating film so that the optical path member and the insulating film are not in contact with each other (for example, Japanese Patent Laid-Open No. 2002-118245). ). When an opaque film is provided, the amount of light leaking from the side surface 204 that causes stray light can be reduced. Furthermore, when the opaque film is a film having a metallic luster (such as a metal film), metal reflection occurs in the opaque film, and incident light can be guided to the light receiving surface in the optical path member. However, when the opaque film is positioned between the optical path member 220 and the side surface 204, the light incident on the insulating film 200 without entering the optical path member 220 does not enter the optical path member 220, so that the light utilization efficiency is remarkably high. It will decline. On the other hand, when the optical path member 220 is in contact with the side surface 204 of the insulating film 200 without providing the opaque film, the light incident on the insulating film 200 can be incident on the optical path member 220 from the insulating film 200. Utilization efficiency can be improved.

The material (transparent material) of the optical path member 220 may be an organic material (resin) or an inorganic material. However, inorganic materials are preferred because they are chemically stable. Examples of the resin include siloxane-based resins and polyimide. As the inorganic material, silicon nitride (Si ₃ N ₄ ), silicon oxynitride (SiO _x N _y ), and titanium oxide (TiO ₂ ) are preferable. The optical path member 220 may be made of a single material or may be made of a plurality of materials. The rough values of the refractive index of the materials exemplified as the materials of the optical path member 220 and the insulating film 200 are given. 1.4 to 1.5 for silicon oxide, 1.6 to 1.9 for silicon oxynitride, 1.8 to 2.3 for silicon nitride, 2.5 to 2.7 for titanium oxide, BSG, PSG, BPSG Is 1.4 to 1.6. Note that the significant figures of the refractive index values described here are two digits, and the second decimal place is rounded off. The above values are examples, and even for the same material, the refractive index can be set as appropriate because the non-stoichiometric composition ratio and material density change by changing the film formation method. It is. In addition, the refractive index of a general resin is 1.3 to 1.6, and even a high refractive index resin is 1.6 to 1.8, but by including a high refractive index inorganic material such as a metal oxide, The effective refractive index can be increased. Examples of the high refractive index inorganic material contained in the resin include titanium oxide, tantalum oxide, niobium oxide, tungsten oxide, zirconium oxide, zinc oxide, indium oxide, and hafnium oxide.

  Although details will be described later using an embodiment, in the present invention, the optical path member 220 includes a first high refractive index region and a second high refractive index region having a refractive index higher than the refractive index of the first high refractive index region. And a refractive index distribution as shown in FIG. And this refractive index distribution can be formed in the part (center part and peripheral part) which comprises at least one part of the optical path member 220, and was occupied with the same material (same material). Practically, the optical path member 220 preferably has a refractive index of 1.6 or more. Further, practically, the difference between the maximum value and the minimum value of the refractive index in the refractive index distribution of the portion occupied by the one material is preferably 0.025 or more, and 0.050 or more. More preferably. Typically, the difference between the maximum value and the minimum value of the refractive index is 0.50 or less, and practically 0.25 or less. In the refractive index distribution, the boundary between the first high refractive index region and the second high refractive index region may be clearly observable, but may not be clearly observable. For example, when the refractive index changes gently from the central axis toward the insulating film 200, the boundary between the first high refractive index region and the second high refractive index region will not be clearly observable. In such a case, the boundary between the first high refractive index region and the second high refractive index region can be determined as follows. That is, an intermediate value ((maximum value + minimum value) / 2) between the maximum value and the minimum value of the refractive index of the portion made of the same material in the optical path member 220 is obtained. In the refractive index distribution in the optical path member 220, a line connecting the intermediate points can be defined at the boundary between the first high refractive index region and the second high refractive index region. Naturally, the first high refractive index region includes a portion having the minimum refractive index, and the second high refractive index region includes a portion having the maximum refractive index.

The “same material” means materials having the same stoichiometric composition. Therefore, materials that deviate from the stoichiometric composition (that is, non-stoichiometric composition is different), crystallinity, material density, concentration of additives (less than the main material), impurities (1 wt% or less) In addition, materials having different concentrations can be regarded as “the same material”. For example, the stoichiometric composition ratio of silicon nitride is Si: N = 3: 4. However, within the range where the stoichiometric composition ratio is the same, materials having different actual Si / N ratios may be used. Consider the same material. For example, single crystal silicon and polysilicon (polycrystalline silicon) are regarded as the same material. Note that materials having different stoichiometric compositions are not the same material. For example, titanium monoxide (TiO) and titanium dioxide (TiO ₂ ) are both oxygen and titanium compounds (titanium oxides), but are stoichiometrically different materials. As described above, silicon nitride has a significantly higher refractive index than silicon oxide and has a wider range of refractive index than silicon oxynitride. Therefore, as a material having the refractive index distribution of the optical path member 220, Is preferred. When silicon nitride is used for the optical path member 220, the above refractive index distribution can be formed by changing the silicon nitride film forming method during film formation. In addition, when a resin in which metal oxide particles are dispersed is used for the optical path member 220, the refractive index distribution described above can also be obtained by changing the concentration of a high refractive index inorganic material such as metal oxide particles contained in the resin. Can be formed. The refractive index distribution of the optical path member 220 may be formed of different materials. However, the present invention can achieve a remarkable effect by forming a refractive index profile with the same material by the method described above.

  The formation method of the optical path member 220 and the insulating film 200 is not particularly limited. Typically, after an insulating film 200 having the opening 201 is formed by etching the insulating film without the opening 201, the material of the optical path member 220 is deposited in the opening 201 to form the optical path member 220. The first forming method can be adopted. In addition, each time each insulating layer constituting the insulating film 200 is formed, a second step of repeating the step of etching each insulating layer to provide an opening and the step of depositing the material of the optical path member 220 in the opening is repeated. A forming method may be adopted. Alternatively, a third forming method may be employed in which after the optical path member 220 is first disposed, a part of the insulating layer of the insulating film 200 is disposed around the optical path member 220. Alternatively, a fourth forming method may be employed in which the optical path member 220 is formed by modifying a part of the insulating film corresponding to the optical path member 220 after forming the insulating film without the opening 201.

  In the example of FIG. 1, the example which employ | adopted the 1st formation method is shown. The twelfth insulating layer 216 constitutes part of the insulating film 200 and constitutes the bottom surface 203 of the opening 201. The twelfth insulating layer 216 is disposed on the light receiving surface 111 and a part of the gate electrode 218. The area of the twelfth insulating layer 216 in the planar direction is larger than the area of the bottom surface 203. The area of the twelfth insulating layer 216 in the planar direction is smaller than the areas of the first insulating layer 205 and the second insulating layer 206. Here, the bottom surface 203 of the opening 201 is located within the range where the third insulating layer 207 exists. In other words, the third insulating layer 207 is located in the third plane 1003. The bottom surface (third plane 1003) of the opening 201 is preferably located closer to the semiconductor substrate 100 than the first wiring layer 2171.

  The twelfth insulating layer 216 can function as an etching stopper when the opening 201 is formed in the multilayer insulating film 200. In order to function as an etching stopper, a material different from the layer in contact with the upper surface of the twelfth insulating layer 216 (here, the third insulating layer 207 made of BPSG) is used. FIG. 1 shows a mode in which the bottom surface 203 is positioned closer to the photoelectric conversion unit 110 than the top surface of the twelfth insulating layer 216 as a result of the twelfth insulating layer 216 being slightly etched when the opening 201 is formed. . As a result, the twelfth insulating layer 216 forms a small part of the side surface 204 in the immediate vicinity of the bottom surface 203. The twelfth insulating layer 216 as an etching stopper may not be etched at all. In this case, the twelfth insulating layer 216 forms only the bottom surface 203.

  Between the second insulating layer 206 and the photoelectric conversion unit 110, a layer having a refractive index between the refractive index of the second insulating layer 206 and the refractive index of the photoelectric conversion unit 110 (here, a first layer made of silicon nitride). When the insulating layer 205) is provided, the transmittance from the optical path member 220 to the photoelectric conversion unit 110 is improved.

  As described above, at least the optical path member 220 and the insulating film 200 form a waveguide structure, and light incident on the photoelectric conversion element 1 is mainly propagated to the photoelectric conversion unit 110 via the optical path member 220.

  A transparent film 319 is provided on the optical path member 220 and the insulating film 200.

  The second medium refractive index layer 320, the low refractive index layer 321, the first medium refractive index layer 322, and the second lens base are arranged in this order from the transparent film 319 side on the side opposite to the light receiving surface 111 side with respect to the transparent film 319. A layer 323, a second lens body layer 324, a second lens body coating layer 325, a planarizing film 326, a color filter layer 327, a first lens base layer 328, and a first lens body layer 329 are laminated. Although details of these layers will be described later, the present invention is not limited to this configuration, and various modifications may be made. For example, at least one of the first lens body layer 329 (and the first lens base layer 328) and the second lens body layer 324 (and the second lens base layer 323) may be omitted. When the second lens body layer 324 (and the second lens base layer 323) is omitted, the planarizing film 326 may be omitted. Further, the color filter layer 327 may be omitted, or the color filter layer 327 may also function as the planarization film 326.

  The transparent film 319 controls the distance (optical path length) from the outermost surface of the photoelectric conversion element 1 (here, the surface of the first lens body layer 329) to the insulating film 200 and the optical path member 220. A typical transparent film 319 has a thickness of 0.080 μm or more. On the other hand, when the transparent film 319 is made extremely thick, the amount of light incident on the optical path member 220 decreases. The thickness of the transparent film 319 is preferably less than or equal to the depth of the opening 201, and more preferably less than or equal to half the depth of the opening 201. A typical transparent film 319 has a thickness of 0.50 μm or less.

  The material of the transparent film 319 may be different from the material of the optical path member 220, but is preferably the same material. When the material of the transparent film 319 is the same as the material of the optical path member 220, the optical path member 220 and the transparent film 319 may be integrated, and the boundary between the optical path member 220 and the transparent film 319 may not be clearly observed. As described above, the optical path member 220 is located inside the opening 201 (between the second plane 1002 and the third plane 1003), and the transparent film 319 exists outside the opening 201. Therefore, by determining whether the transparent material exists inside the opening 201 or outside the opening 201, the optical path member 220 and the transparent film 319 can be distinguished. In the observation image of the cross section of the photoelectric conversion element 1, the inner and outer sections of the opening 201 virtually extend the upper surface 202 of the insulating film 200 over the opening 201 (the upper ends of the side surfaces 204 are virtually straight lines). Is possible).

  The above is the outline of the photoelectric conversion element 1. Next, an embodiment of the refractive index distribution of the optical path member 220 will be described with reference to FIGS. 2 and 4 to 8 show only the substrate 100 of FIG. 1, the portion from the first plane 1001 to the second plane 1002, and the transparent film 319. FIG. Since the configuration of the portion above the transparent film 319 is common and can be changed as appropriate, description thereof is omitted. Moreover, in each drawing, the same code | symbol is attached | subjected to the member or part which show | plays the same function, and detailed description is abbreviate | omitted.

<First Embodiment>
2A is a cross-sectional view of a part of the photoelectric conversion element 1 according to the first embodiment in a direction perpendicular to the main surface 101 (and the light receiving surface 111), and FIG. 2B is a diagram illustrating the first embodiment. FIG. 2 is a cross-sectional view of a part of the photoelectric conversion element 1 according to 1 in a direction parallel to the main surface 101 (and the light receiving surface 111).

  2A shows a fourth plane 1004, a fifth plane 1005, and a sixth plane 1006 in addition to the first plane 1001, the second plane 1002, and the third plane 1003 described with reference to FIG. Yes. The fourth plane 1004 is located between the second plane 1002 and the third plane 1003, and is a plane located at an equal distance from the second plane 1002 and the third plane 1003. That is, the fourth plane 1004 is located between the second plane 1002 and the third plane 1003. The fifth plane 1005 is located between the second plane 1002 and the fourth plane 1004, and the sixth plane 1006 is located between the third plane 1003 and the fourth plane 1004. That is, the fifth plane 1005 is a plane that represents the upper part (half of the incident side) of the optical path member 220, and is here a plane that is located at an equal distance from the second plane 1002 and the fourth plane 1004 for convenience. Similarly, the sixth plane 1006 is a plane that represents the lower part (half of the emission side) of the optical path member 220, and is here a plane that is located at an equal distance from the third plane 1003 and the fourth plane 1004 for convenience. .

  In FIG. 2B, S1 indicates a cross section on the second plane 1002, S2 indicates a cross section on the fifth plane 1005, S3 indicates a cross section on the fourth plane 1004, and S4 indicates a cross section on the sixth plane 1006. S5 shows a cross section in the vicinity of the optical path member 220 side of the third plane 1003, specifically, the lower end of the portion formed by the third insulating layer 207 of the side surface 204.

  The optical path member 220 has at least a central portion 222 and a peripheral portion 221. The peripheral portion 221 is located between the central portion 222 and the insulating film 200.

  The peripheral portion 221 surrounds the central portion 222. The peripheral portion 221 is made of the same material as the central portion 222. At least a part made of a material different from the material of the peripheral part 221 and the central part 222 does not exist between at least a part of the peripheral part 221 and a part of the central part 222, and extends from the central part 222 to the peripheral part 221. The same material is continuous. Therefore, it can be said that the peripheral portion 221 is continuous with the central portion 222. It is desirable that a portion made of a material different from both materials does not exist between the entire peripheral portion 221 and the entire central portion 222. As in the example illustrated in FIG. 2, the peripheral portion 221 is preferably in contact with the insulating film 200.

  In the present embodiment, the refractive index of the peripheral portion 221 is higher than the refractive index of the insulating film 200. The refractive index of the central portion 222 is higher than the refractive index of the peripheral portion 221. For this reason, the refractive index of the central portion 222 is also higher than the refractive index of the insulating film 200.

  Thus, the optical path member 220 is made of a high refractive index material having a refractive index higher than that of the insulating film 200. The high refractive index material has a refractive index distribution that includes a first high refractive index region and a second high refractive index region having a refractive index higher than that of the first high refractive index region. Have. In the present embodiment, the peripheral portion 221 is a first high refractive index region, and the central portion 222 is a second high refractive index region. FIG. 2A shows a state in which the refractive index is significantly different between the central portion 222 and the peripheral portion 221. For example, when the refractive index of the central portion 222 is 1.90 and the refractive index of the peripheral portion 221 is 1.83, in the cross-sectional observation image of the optical path member 220 in the direction perpendicular to the main surface 101, observed with an electron microscope, It can be confirmed that the image has a contrast between the central portion 222 and the peripheral portion 221.

  In order to form a refractive index profile using silicon nitride, for example, the following method can be cited. As a first method, first, a first silicon nitride film is formed on the side surface 204 by relatively reducing the amount of silicon component relative to the amount of nitrogen component of the film forming material. After that, on the first silicon nitride film, the amount of the silicon component relative to the amount of the nitrogen component of the film formation material is made larger than that when the first silicon nitride film is formed, so that the second silicon nitride film is formed. Form a film. At this time, one of the amount of the nitrogen component and the amount of the silicon component may be the same when forming the first silicon nitride and when forming the second silicon nitride, or both are different. It may be. By this first method, the optical path member 220 in which the first silicon nitride film forms the peripheral portion 221 and the second silicon nitride film forms the central portion 222 can be formed. This is because the ratio of silicon (Si) to nitrogen (N) (Si / N) is relatively high with respect to the non-stoichiometric composition even if the stoichiometric composition ratio is Si: N = 3: 4. This is because silicon nitride has a higher refractive index than silicon nitride, which has a relatively low ratio of silicon to nitrogen. In a silicon nitride film formed by a conventional film formation method such as a CVD method, the ratio of silicon to nitrogen is generally 1/2 to 3/2, and 3/5 to 1 is typical. The ratio of silicon to nitrogen in the silicon nitride film can be 3/4, and the refractive index of silicon nitride whose actual composition matches the stoichiometric composition can be 2.0.

  As a second method, first, a first silicon nitride film having a relatively low material density is formed on the side surface 204 by relatively increasing the incident energy of the film forming material. After that, the incident energy of the film forming material is made lower than that when the first silicon nitride film is formed on the first silicon nitride film, and the material density higher than that of the first silicon nitride film is obtained. A silicon nitride film 2 is formed. Thereby, the optical path member 220 in which the first silicon nitride film forms the peripheral portion 221 and the second silicon nitride film forms the central portion 222 can be formed. This is because a dense silicon nitride film having a relatively high silicon nitride density has a higher refractive index than a coarse silicon nitride film having a relatively low silicon nitride density.

  The thickness of the peripheral portion 221 decreases as it approaches the light receiving surface 111. This will be described in detail with reference to FIG. DS1, DS2, DS3, DS4, and DS5 represent the width (diameter) of the opening 201 in each of the cross sections S1 to S5. In the present embodiment, the side surface 204 has a forward taper shape with respect to the light receiving surface 111, and the relationship is DS1> DS2> DS3> DS4> DS5.

  DL1, DL2, DL3, DL4, and DL5 represent the width (diameter) of the central portion 222 in each of the cross sections S1 to S5. The central axis passes through the central portion 222, and the central portion 222 continuously extends along the central axis without interruption. In the present embodiment, the central portion 222 has a truncated cone shape, and the outer surface of the central portion 222 (the surface on the peripheral portion 221 side) has a forward tapered shape with respect to the light receiving surface 111. The outer surface of the central portion 222 is concentric with the central axis and is rotationally symmetric with respect to the central axis. The relationship is DL1 <DL2 <DL3 <DL4 <DL5. DL5 is a value smaller than DS5, but is very close to DS5.

  TH1, TH2, TH3, and TH4 represent the thickness (width) of the peripheral portion 221 in each of the cross sections S1 to S4. In the present embodiment, the inner surface of the peripheral portion 221 (the surface on the central portion 222 side) and the outer surface of the peripheral portion 221 (the surface on the insulating film 200 side) have a reverse taper shape with respect to the light receiving surface 111. The relationship is TH1> TH2> TH3> TH4> TH5. Here, TH5 (not shown) represents the thickness of the peripheral portion 221 in the cross section S5, and is a value corresponding to (DS5-DL5) / 2, which is extremely close to zero. As described above, the peripheral portion 221 continuously extends along the side surface 204 of the insulating film 200 without interruption.

Here, the ratio (TH1 / TH5) between the maximum value (TH1) and the minimum value (TH5) of the thickness of the peripheral portion 221 is almost infinite, but at least the minimum value of the thickness of the peripheral portion 221 is the maximum value. Or less (maximum value / minimum value ≧ 2). The wavelength of light incident on the optical path member 220 is λ, the refractive index of the insulating film 200 is n ₀ , the refractive index of the peripheral portion 221 is n ₁ , and the maximum thickness of the peripheral portion 221 is λ / 2√ (n ₁ ² -N ₀ ² ) is preferred. Further, it is preferable that the minimum value of the thickness of the peripheral portion 221 is smaller than λ / 4√ (n ₁ ² −n ₀ ² ). The thickness of the peripheral portion 221 is preferably the maximum value in the upper part of the optical path member 220 (from the second plane 1002 to the fourth plane 1004). In addition, the thickness of the peripheral portion 221 is preferably a minimum value below the optical path member 220 (from the fourth plane 1004 to the third plane 1003).

  Even in a portion where the thickness of the peripheral portion 221 is between the minimum value and the maximum value, it is preferable that the thickness in a plane closer to the light receiving surface 111 is ½ or less. In the example shown in FIGS. 2A and 2B, the thickness (TH3) of the peripheral portion 221 in the fourth plane 1004 is ½ of the thickness (TH1) of the peripheral portion 221 in the second plane 1002. Yes. Further, the thickness (TH4) of the peripheral portion 221 in the sixth plane 1006 is less than ½ of the thickness (TH2) of the peripheral portion 221 in the fifth plane 1005.

  FIG. 3 shows an electric field intensity distribution when light parallel to the central axis of the optical path member 220 is incident on the optical path member 220 in the present embodiment. Specifically, the three electric field strength distributions are distributions of electric field strengths at three positions having different heights in the optical path member 220 in a plane parallel to the light receiving surface 111. The position on the horizontal axis indicates the height in the optical path member 220.

  From the viewpoint of wave optics, it can be considered that light tends to concentrate in a region having a high refractive index. Therefore, the electric field strength of the central portion 222 is higher than the electric field strength of the peripheral portion 221 at a position where the thickness of the central portion 222 having a higher refractive index than that of the peripheral portion 221 is large. In addition, since most of the light propagates through the central portion 222, light leaking from the optical path member 220 to the insulating film 200 can be reduced. Therefore, it is considered that light loss is suppressed. For this reason, the utilization efficiency of the light incident in parallel to the central axis of the photoelectric conversion element 1 can be improved.

  The light parallel to the central axis of the photoelectric conversion element 1 is light that is substantially incident perpendicularly to the light receiving surface of the photoelectric conversion unit 110, and is typical of light incident on the photoelectric conversion unit 110. Therefore, the photoelectric conversion element 1 with high sensitivity can be obtained. Note that light incident parallel to the central axis of the photoelectric conversion element 1 is preferably focused inside the optical path member 200, and more preferably focused between the second plane 1002 and the fourth plane 1004. . Typically, light incident parallel to the central axis of the photoelectric conversion element 1 is focused in the central portion 222. On the other hand, light incident obliquely on the central axis of the photoelectric conversion element 1 is mainly focused in the peripheral portion 221.

  In the present embodiment, the thickness of the peripheral portion 221 gradually decreases as it approaches the photoelectric conversion unit 110. Therefore, at the position where the thickness of the peripheral portion 221 is small, it is difficult for the same amount of light to propagate through the peripheral portion 221 as the position where the thickness is large. Therefore, the light that can no longer propagate through the peripheral portion 221 transitions to the central portion 222. In the present embodiment, since the same material is continuous in the peripheral portion 221 and the central portion 222, the light loss in this transition is suppressed. In general, the refractive index changes discontinuously at the interface between different materials. On the other hand, it can be considered that the peripheral portion 221 and the central portion 222 are made of the same material, so that the refractive index continuously changes at the boundary between the peripheral portion 221 and the central portion 222.

  The light emitted from the wide central portion 222 is less likely to be diffracted between the optical path member 220 and the photoelectric conversion unit 110 than when emitted from the peripheral portion 221 having a small thickness (width). Therefore, it is considered that the light emitted from the optical path member 220 is diffracted and the loss due to not entering the photoelectric conversion unit 110 is suppressed.

  As described above, in the present embodiment, light loss is suppressed while suppressing light loss between the optical path member 220 and the insulating film 200, in the optical path member 220, and between the optical path member 220 and the photoelectric conversion unit 110. Propagation is considered to improve sensitivity.

  As shown in the present embodiment, it is preferable that the thickness of the peripheral portion 221 is continuously reduced as it approaches the light receiving surface 111. That is, it is preferable that the thickness of the peripheral portion 221 decreases monotonously in a narrow sense as the distance to the light receiving surface 111 is shortened. The thickness of the peripheral portion 221 may intermittently become thinner as it approaches the light receiving surface 111, that is, the thickness of the peripheral portion 221 may decrease monotonously in a broad sense with respect to the shortening of the distance to the light receiving surface 111. However, when the thickness is intermittently reduced, it is considered that the transition to the central portion 222 is relatively small in the portion where the thickness of the peripheral portion 221 is constant. For this reason, when the peripheral portion 221 is thinned rapidly, a transition to the insulating film 200 is likely to occur in addition to a transition to the central portion 222, which may cause a loss.

For the three models in which the wavelength of incident light is 550 nm (green light), the refractive index of the insulating film 200 is 1.46, and the refractive index of the optical path member 220 is 1.83 to 1.90. Thus, the sensitivity when light parallel to the central axis of the optical path member 220 is incident on the optical path member 220 was examined. The first model is a model in which the optical path member 220 does not have a refractive index distribution in which the refractive index of the central portion and the refractive index of the peripheral portion are both 1.83. The second model is a model in which the optical path member 220 does not have a refractive index distribution in which the refractive index of the central portion and the refractive index of the peripheral portion are both 1.90. The third model is a model corresponding to this embodiment in which the refractive index of the central portion 222 is 1.90 and the refractive index of the peripheral portion 221 is 1.83. When the sensitivity of the first model was normalized to 1.00, the normalized sensitivity of the second model was 1.04, whereas the normalized sensitivity of the third model was 1.05. Thus, for the first model, by making the refractive index of the central portion 222 higher than the refractive index of the peripheral portion 221, and for the second model,
By making the refractive index of the peripheral portion 221 lower than the refractive index of the central portion 222, the sensitivity of the photoelectric conversion element 1 can be improved.

  When the insulating film 200 is a multilayer film, the refractive index of a part of the multilayer film may be equal to or higher than the refractive index of the peripheral portion 221 of the optical path member 220, and more than the refractive index of the central portion 222. Such a layer having a refractive index equal to or higher than the refractive index of the first high refractive index region is referred to as a high refractive index insulating layer. On the other hand, the remaining layers of the multilayer film having a refractive index lower than the refractive index of the peripheral portion 221 of the optical path member 220, in other words, having a refractive index lower than the refractive index of the first high refractive index region are reduced to a low refractive index. Called an insulating layer. The refractive index of the high refractive index insulating layer is higher than the refractive index of the low refractive index insulating layer.

  In the case of the present embodiment, the third insulating layer 207, the fifth insulating layer 209, the seventh insulating layer 211, the ninth insulating layer 200, which are made of silicon oxide or silicate glass and form the side surface 204 of the opening 201. The insulating layer 213 and the eleventh insulating layer 215 are low refractive index insulating layers. These low refractive index insulating layers surround the optical path member 220. For example, when the refractive index of the central portion 222 is 1.83 and the refractive index of the peripheral portion 221 is 1.90, the third insulating layer 207, the fifth insulating layer 209, the seventh insulating layer 211, and the ninth insulating layer 213 When the refractive index of the eleventh insulating layer 215 is 1.46, these insulating layers are low refractive index insulating layers. The second insulating layer 206 is also a low refractive index insulating layer, but does not form the side surface 204 of the opening 201.

  FIG. 2B shows the side surface 204 in the cross section in each plane. In detail, as can be understood from FIG. 2A, the side surface 204 in each cross section is formed by a different insulating layer. Has been. Specifically, the side surface 204 in the cross section S1 is the eleventh insulating layer 215, the side surface 204 in the cross section S2 is the ninth insulating layer 213, and the side surface 204 in the cross section S3 is the seventh insulating layer 211 in the cross sections S4 and S5. The side surfaces 204 and the third insulating layer 207 are formed respectively.

  On the other hand, since the peripheral portion 221 and the central portion 222 are made of silicon nitride, the fourth insulating layer 208, the sixth insulating layer 210, and the eighth insulating layer 200 are made of silicon nitride and form the side surface 204 of the opening 201. The insulating layer 212 and the tenth insulating layer 214 are high refractive index insulating layers. These high refractive index insulating layers surround the optical path member 220. For example, when the refractive index of the central portion 222 is 1.83 and the refractive index of the peripheral portion 221 is 1.90, the fourth insulating layer 208, the sixth insulating layer 210, the eighth insulating layer 212, and the tenth insulating layer When the refractive index of the layer 214 is 2.03, these insulating layers are high refractive index insulating layers. Note that the first insulating layer 205 is also a high refractive index insulating layer, but does not form the side surface 204 of the opening 201. In this example, the high refractive index insulating layer is made of the same material as that of the peripheral portion 221 and the central portion 222, and the low refractive index insulating layer is made of a material different from the material of the peripheral portion 221 and the central portion 222.

However, it is not preferable that a layer (high refractive index insulating layer) having a refractive index higher than that of the optical path member 220 forms most of the side surface 204 of the opening 201. This is because the light incident on the optical path member 220 may propagate through the high refractive index insulating layer and leak from the opening 201. Therefore, the side surface 204 of the opening 201 formed by the high refractive index insulating layer is preferably less than half the area of the entire side surface 204 of the opening 201, and more preferably less than ¼. In other words, the layer (low refractive index insulating layer) lower than the refractive index of the optical path member 220 in the multilayer film may constitute half or more, preferably 3/4 or more of the entire area of the side surface 204 of the opening 201. preferable. The area of the side surface 204 formed by each layer can be adjusted by appropriately setting the thickness of each layer and the angle of the side surface 204. The thickness of one low refractive index insulating layer is typically 0.10 μm or more and 0.60 μm or less. The thickness of one high refractive index insulating layer is preferably λ / 2n _0H or less, where λ is the wavelength of light incident on the optical path member 220 and n _0H is the refractive index of the high refractive index insulating layer. More preferably, it is _0H or less. The thickness of the high refractive index insulating layer is typically 0.010 μm or more and 0.10 μm or less.

Second Embodiment
4A is a cross-sectional view of a part of the photoelectric conversion element 1 according to the second embodiment in a direction perpendicular to the main surface 101 (and the light receiving surface 111), and FIG. 4B is a second embodiment. FIG. 2 is a cross-sectional view of a part of the photoelectric conversion element 1 according to 1 in a direction parallel to the main surface 101 (and the light receiving surface 111).

  Also in this embodiment, the peripheral portion 221 is a first high refractive index region, and the central portion 222 is a second high refractive index region having a higher refractive index than the first high refractive index region (peripheral portion 221).

  Definitions of the first plane 1001, the second plane 1002, the third plane 1003, the fourth plane 1004, the fifth plane 1005, the sixth plane 1006, S1 to S5, DS1 to 5, DL1 to 5, and TH1 to 5 are shown in FIG. Since it is the same as (a) and (b), description is abbreviate | omitted.

  Also in this embodiment, as in the first embodiment, the side surface 204 has a forward tapered shape. On the other hand, the central portion 222 has a cylindrical shape, and the outer surface of the central portion 222 (surface on the peripheral portion 221 side) is perpendicular to the light receiving surface 111. The relationship is DL1 = DL2 = DL3 = DL4 = DL5. The inner surface (surface on the central portion 222 side) of the peripheral portion 221 is perpendicular to the light receiving surface 111, but the outer surface (surface on the insulating film 200) of the peripheral portion 221 is relative to the light receiving surface 111. It has a reverse taper shape. The relationship is TH1> TH2> TH3> TH4> TH5.

  A modification (not shown) of this embodiment will be described. The side surface 204 of the insulating film 200 may not be tapered and may be perpendicular to the light receiving surface 111 (DS1 = DS2 = DS3 = DS4 = DS5). In that case, the outer surface of the central portion 222 may have a forward taper shape with respect to the light receiving surface 111 (DL1 <DL2 <DL3 <DL4 <DL5). In addition, the side surface 204 of the insulating film 200 may have an inversely tapered shape so that DS1 <DS2 <DS3 <DS4 <DS5. In that case, the outer surface of the central portion 222 may have a forward tapered shape with a smaller inclination than the side surface 204 with respect to the light receiving surface 111. That is, by setting DS1-DL1> DS2-DL2> DS3-DL3> DS4-DL4> DS5-DL5, the relationship TH1> TH2> TH3> TH4> TH5 can be realized.

<Third Embodiment>
FIG. 5A is a cross-sectional view of a part of the photoelectric conversion element 1 according to the third embodiment in a direction perpendicular to the main surface 101 (and the light receiving surface 111), and FIG. 5B is a third embodiment. FIG. 2 is a cross-sectional view of a part of the photoelectric conversion element 1 according to 1 in a direction parallel to the main surface 101 (and light receiving surface 111).

  Also in this embodiment, the peripheral portion 221 is a first high refractive index region, and the central portion 222 is a second high refractive index region having a higher refractive index than the first high refractive index region (peripheral portion 221).

  Definitions of the first plane 1001, the second plane 1002, the third plane 1003, the fourth plane 1004, the fifth plane 1005, the sixth plane 1006, S1 to S5, DS1 to 5, DL1 to 5, and TH1 to 5 are shown in FIG. Since it is the same as (a) and (b), description is abbreviate | omitted.

  Also in this embodiment, as in the first embodiment, the side surface 204 has a forward tapered shape. On the other hand, a part of the upper portion of the central portion 222 (portion from the second plane 1002 to the fifth plane 1005) has a cylindrical shape. The remaining upper part of the central part 222 (the part from the fifth plane 1005 to the fourth plane 1004) and the lower part of the central part 222 have a regular truncated cone shape. Then, DL1 = DL2 <DL3 <DL4 <DL5. In addition, the outer surface of the peripheral portion 221 (the surface on the insulating film 200 side) has a reverse taper shape with respect to the light receiving surface 111. The relationship is TH1> TH2> TH3> TH4> TH5.

<Fourth embodiment>
FIG. 6A is a cross-sectional view of a part of the photoelectric conversion element 1 according to the fourth embodiment in a direction perpendicular to the main surface 101 (and the light receiving surface 111), and FIG. 6B is a fourth embodiment. FIG. 2 is a cross-sectional view of a part of the photoelectric conversion element 1 according to 1 in a direction parallel to the main surface 101 (and light receiving surface 111).

  Also in this embodiment, the peripheral portion 221 is a first high refractive index region, and the central portion 222 is a second high refractive index region having a higher refractive index than the first high refractive index region (peripheral portion 221).

  Definitions of the first plane 1001, the second plane 1002, the third plane 1003, the fourth plane 1004, the fifth plane 1005, the sixth plane 1006, S1 to S5, DS1 to 5, DL1 to 3, and TH1 to TH3 are shown in FIG. Since it is the same as (a) and (b), description is abbreviate | omitted.

  Also in the present embodiment, as in the first embodiment, the side surface 204 has a forward tapered shape, and has a relationship of DS1> DS2> DS3> DS4> DS5. On the other hand, in the present embodiment, the peripheral portion 221 and the central portion 222 are located between the second plane 1002 and the sixth plane 1006 and are not located between the sixth plane 1006 and the third plane 1003. However, it is different from the first to third embodiments. In the present embodiment, the optical path member 220 has an exit part 2221 having a higher refractive index than the peripheral part 221. The exit portion 2221 has a refractive index higher than that of the insulating film 200 and typically has a refractive index comparable to that of the central portion 222. Therefore, in the present embodiment, the peripheral portion 221 is the first high refractive index region, and the central portion 222 and the emission portion 2221 have the second high refractive index higher than that of the first high refractive index region (the central portion 222). It is a refractive index region.

  The emission part 2221 is located between the third plane 1003 and the sixth plane 1006. That is, the emission part 2221 is located between the central part 222 and the photoelectric conversion unit 110, specifically, between the bottom surface 203 and the central part 222 shown in FIG. The emission part 2221 is made of the same material as the central part 222 (and the peripheral part 221), and is continuous with the central part 222. DL4 and DL5 shown in FIG. 6B represent the width (diameter) of the emission portion 2221. The emission part 2221 has an inverted truncated cone shape.

  In the present embodiment, as in the third embodiment, a part of the upper portion of the center portion 222 (portion from the second plane 1002 to the fifth plane 1005) has a cylindrical shape. Further, the remaining part of the upper part of the central part 222 and a part of the lower part of the central part 222 (parts from the fourth plane 1004 to the sixth plane 1006) have a regular truncated cone shape.

  The remaining upper portion of the central portion 222 (the portion from the fifth plane 1005 to the fourth plane 1004) and the lower portion of the central portion 222 (the portion from the fourth plane 1004 to the sixth plane 1006) have a regular truncated cone shape. ing. Then, DL1 = DL2 <DL3 <DL4 <DL5. Note that the emission portion 2221 is in contact with the insulating film 200 and has a relationship of DL4 = DS4 and DL5 = DS5. The relationship is TH1> TH2> TH3> TH4.

<Fifth Embodiment>
FIG. 7A is a sectional view of a part of the photoelectric conversion element 1 according to the fifth embodiment in a direction perpendicular to the main surface 101 (and the light receiving surface 111), and FIG. 7B is a fifth embodiment. FIG. 2 is a cross-sectional view of a part of the photoelectric conversion element 1 according to 1 in a direction parallel to the main surface 101 (and light receiving surface 111).

  Also in this embodiment, the peripheral portion 221 is a first high refractive index region, and the central portion 222 is a second high refractive index region having a higher refractive index than the first high refractive index region (peripheral portion 221).

  Definitions of the first plane 1001, the second plane 1002, the third plane 1003, the fourth plane 1004, the fifth plane 1005, the sixth plane 1006, S1 to S5, DS1 to 5, DL3 to 5, and TH3 to 5 are shown in FIG. Since it is the same as (a) and (b), description is abbreviate | omitted.

  Also in the present embodiment, as in the first embodiment, the side surface 204 has a forward tapered shape, and has a relationship of DS1> DS2> DS3> DS4> DS5. On the other hand, in the present embodiment, the peripheral portion 221 and the central portion 222 are located between the fifth plane 1005 and the third plane 1003 and are not located between the second plane 1002 and the fifth plane 1005. However, it is different from the first to fourth embodiments.

  In the present embodiment, the optical path member 220 has an incident portion 2212 having a lower refractive index than the central portion 222. The refractive index of the incident portion 2212 is higher than the refractive index of the insulating film 200, and typically has the same refractive index as that of the peripheral portion 221. Therefore, in the present embodiment, the peripheral portion 221 and the incident portion 2212 are the first high refractive index region, and the central portion 222 has a higher refractive index than the first high refractive index region (the peripheral portion 221 and the incident portion 2212). A second high refractive index region.

  The incident portion 2212 is located between the second plane 1002 and the fifth plane 1005. That is, the incident part 2212 is located between the transparent film 319 and the peripheral part 221. The incident portion 2212 is made of the same material as the peripheral portion 221 (and the central portion 222), and is continuous with the peripheral portion 221. DL1 and DL2 shown in FIG. 7B represent the width (diameter) of the incident portion 2212. The incident portion 2212 has an inverted truncated cone shape.

  In the present embodiment, the central portion 222 has a conical shape, but may have a truncated cone shape. The relationship is DL3 <DL4 <DL5. Note that the incident portion 2212 is in contact with the insulating film 200 and has a relationship of DL4 = DS4 and DL5 = DS5. The relationship is TH1> TH2> TH3> TH4. Such a conical or frustoconical center portion 222 can also be formed by applying a spindt-type electron-emitting device manufacturing method (for example, rotational evaporation).

<Sixth Embodiment>
FIG. 8A is a cross-sectional view of a part of the photoelectric conversion element 1 according to the sixth embodiment in a direction perpendicular to the main surface 101 (and the light receiving surface 111), and FIG. 8B is a diagram illustrating the sixth embodiment. FIG. 2 is a cross-sectional view of a part of the photoelectric conversion element 1 according to 1 in a direction parallel to the main surface 101 (and the light receiving surface 111).

  Also in this embodiment, the peripheral portion 221 is a first high refractive index region, and the central portion 222 is a second high refractive index region having a higher refractive index than the first high refractive index region (peripheral portion 221).

  Definitions of the first plane 1001, the second plane 1002, the third plane 1003, the fourth plane 1004, the fifth plane 1005, the sixth plane 1006, S1 to S5, DS1 to 5, DL1 to 4, and TH1 to 4 are shown in FIG. Since it is the same as (a) and (b), description is abbreviate | omitted.

  In the present embodiment, the optical path member 220 has an emission part 2211. The emission part 2211 is continuous with the peripheral part 221, and the emission part 2211 is made of the same material as the peripheral part 221. The refractive index of the emission part 2211 is lower than the refractive index of the central part 222. The exit portion 2211 is preferably thin. In the present embodiment, the peripheral portion 221 and the emission portion 2211 are first high refractive index regions, and the central portion 222 has a higher refractive index than the first high refractive index region (the peripheral portion 221 and the emission portion 2211). 2 High refractive index region. In FIG. 8B, TH5 represents the width (diameter) of the emission portion 2221. Here, TH5 = DS5.

  In the first to sixth embodiments described above, the form in which the peripheral portion 221 is in contact with the side surface 204 of the insulating film 200 has been described. However, the peripheral portion 221 is not in contact with the side surface 204 of the insulating film 200, and one or more layers constituting a part of the optical path member 220 are interposed between the peripheral portion 221 and the side surface 204 of the insulating film 200. May be.

  For example, the optical path member 220 may have a low refractive index layer (not shown) having a refractive index lower than that of the peripheral portion 221 between the peripheral portion 221 and the insulating film 200. The refractive index of the low refractive index layer is preferably higher than the refractive index of the insulating film 200, and more preferably lower than the refractive index of the central portion 222. The material of the low refractive index layer may be the same as or different from the material of the peripheral portion 221 (and the central portion 222). When such a low refractive index layer is provided, light loss can be reduced. Further, this low refractive index layer may surround the peripheral portion 221.

  Further, for example, the optical path member 220 is a high refractive index layer (non-reflective layer) having a refractive index higher than the refractive index of the peripheral portion 221 and made of a material different from the material of the peripheral portion 221 between the peripheral portion 221 and the insulating film 200. May be included). However, if the refractive index of such a high refractive index layer is made extremely higher than the refractive index of the peripheral portion 221 and / or if the thickness of the high refractive index layer is made extremely thick, light incident on the optical path member 220 will be described. Is considered to concentrate on the high refractive index layer. Therefore, the effect according to the present embodiment may not be sufficiently obtained. Therefore, it is preferable that the refractive index difference between the peripheral portion 221 and the high refractive index layer is smaller than the refractive index difference between the peripheral portion 221 and the central portion 222. In any cross section, the thickness of the high refractive index layer is preferably smaller than the thickness of the peripheral portion 221. The high refractive index layer or the low refractive index layer as described above can fulfill the functions of defining the shape of the peripheral portion 221 and improving the adhesion of the optical path member 220 to the opening 201. In the case where an organic material (resin) is used as the material of the peripheral portion 221 and the central portion 222, the high refractive index layer or the low refractive index layer functions as a protective layer (passivation layer) for the organic material. Silicon nitride is preferably used as the material for such a protective layer.

  Note that a region made of a material different from the central portion 222 or a void (void) may be present inside the central portion 222 and surrounded by the central portion 222. However, when the refractive index of such a region is lower than the refractive index of the central portion 222, or when the refractive index of this region is higher than the refractive index of the peripheral portion 221, it is desirable to eliminate these regions as much as possible.

The transparent film 319 common to the first to sixth embodiments will be described. As shown in FIGS. 2 and 4 to 8, a transparent film 319 is provided on the upper surface 202 of the insulating film 200. The transparent film 319 is made of the same material as the peripheral portion 221 and the central portion 222, and has a refractive index higher than that of the insulating film 200 (herein, the eleventh insulating layer 215). The refractive index of the transparent film 319 is preferably higher than the refractive index of the central portion 222, and more preferably about the same as the refractive index of the peripheral portion 221. That is, assuming that the refractive index of the transparent film 319 is n ₃ , the refractive index of the central portion 222 is n ₂ , and the refractive index n ₁ of the peripheral portion 221 is (n ₁ + n ₂ ) / 2 <n ₃ <(3n ₁ −n ₂ ) / 2.

The transparent film 319 will be described in more detail. As shown in the first embodiment (FIG. 2), the second embodiment (FIG. 4), the third embodiment (FIG. 5), the fourth embodiment (FIG. 6), and the sixth embodiment (FIG. 8), transparent The film 319 includes a first region 3191 and a second region 3192. The second region 3192 of the transparent film 319 is continuous with the central portion 222 which is the second high refractive index region. The first region 3191 of the transparent film 319 is continuous with the peripheral portion 221 that is the first high refractive index region, and is located on the insulating film 200. The refractive index of the second region 3192 is higher than that of the first region 3191, and the transparent film 319 has a refractive index distribution. The first area 3191 surrounds the second area 3192. In this way, the light incident on the transparent film 319 can be guided to the central portion 224 of the optical path member 220, and the light utilization efficiency can be improved. Even if there is light propagating in a direction to enter the upper surface 202 of the insulating film 201 instead of the opening 201, the transparent film 319 can guide the light to the optical path member 220. That is, since the light enters the first region 3191 of the transparent film 319 before entering the insulating film 201, the light has a higher refractive index than the insulating film 201 having a lower refractive index (first region 3191). Try to propagate inside. The light propagating through the transparent film 319 enters the peripheral portion 221 made of the same material as the first region 3191 of the transparent film 319 with low loss. In addition, the light in the first region 3191 easily propagates to the second region 3192 or the central portion 222 having a higher refractive index than the first region 3191. Therefore, the light use efficiency can be improved. In order to obtain such an effect, the wavelength of light incident on the optical path member 220 is λ, the refractive index of the transparent film 319 is n ₃ , and the thickness of the transparent film 319 is not less than λ / 4n _{3 and not} more than 2λ / n _3. It is preferable. In the fifth embodiment shown in FIG. 7, the transparent film 319 is continuous with the incident portion 2212, and the transparent film 319 has the same refractive index as the incident portion 2212. The transparent film 319 has substantially no refractive index distribution. As described above, it is preferable that the first region 3191 and the second region 3192 have a refractive index distribution because light can be concentrated on the second region 3192 continuous with the central portion 222.

<Details of photoelectric conversion element>
An example of the photoelectric conversion element 1 will be described in detail with reference to FIG.

An N ⁺ type semiconductor region 112 is provided in a semiconductor substrate 100 made of N type silicon. An N-type semiconductor region 113 is provided in the periphery including the lower portion of the N ⁺ -type semiconductor region 112. A P-type semiconductor region 114 is provided below the N-type semiconductor region 113. The N ⁺ type semiconductor region 112 can mainly function as a charge storage region. The N ⁺ type semiconductor region 112, the N type semiconductor region 113, and the P type semiconductor region 114 can constitute a part of the photoelectric conversion unit 110.

  The incident-side surface (upper surface in FIG. 1) of the first lens base layer 328 forms an ideal spherical surface, substantially spherical surface, or aspherical surface (hereinafter collectively referred to as a curved surface) convex toward the incident side. That is, it has a convex lens shape. Thereby, the light incident on the lens body layer 329 approaches the central axis and is condensed. The lens base layer 328 and the lens body layer 329 are made of the same organic material (resin), and the lens base layer 328 and the lens body layer 329 are in contact with each other. That is, the lens base layer 328 and the lens body layer 329 are provided substantially integrally. It is often difficult to observe the boundary between the lens base layer 328 and the lens body layer 329. In that case, a plane connecting the ends of the curved region of the lens body layer 329 can be set as a virtual boundary. The first lens base layer 328 may be omitted, and the first lens body layer 329 and the color filter layer 327 may be in contact with each other.

  The physical properties (especially the refractive index) of the material of the first lens body layer 329 and the shape of the curved surface (especially its curvature, height, width) greatly affect the position of the focal point. In general, the greater the curvature, the farther the focal point is from the first plane 1001. The physical properties (particularly the refractive index) and thickness of the material of the lens base layer 328 affect the distance at which the collected light approaches the central axis in the lens base layer 328, and thus become one of the factors that determine the focal point. A typical first lens body layer 329 has a refractive index of 1.6 to 2.0.

  The color filter layer 327 is made of an organic material (resin) containing a color material. A dye can be used as the color material, but a pigment may be used. The physical properties (particularly the refractive index) and thickness of the material of the color filter layer 327 affect the distance that the light refracted at the interface between the lens base layer 328 and the color filter layer 327 approaches the central axis in the color filter layer 327. This is one of the factors that determine the focal point 500. A typical color filter layer 327 has a thickness of 0.1 to 1.0 μm and a refractive index of 1.4 to 1.6.

  The planarizing film 326 is made of an organic material (resin) and has a function of adjusting the distance between the first lens body layer 329 and the second lens body layer 324. Further, the second lens body layer 324 is flattened with respect to the curved shape, and has a function of suppressing the inclination of the optical path in the color filter layer 327, the first lens base layer 328, and the first lens body layer 329. ing. The thickness of the thinnest portion of the planarizing film 326 is typically 0.1 to 0.5 μm. The refractive index of the planarizing film 326 is 1.4 to 1.5.

  The second lens base layer 323 and the second lens body layer 324 are made of silicon nitride, and the second lens body layer 324 has a convex lens shape (plano-convex lens shape). Note that the refractive index of the second lens body layer 324 is higher than the refractive index of the planarizing film 326. Therefore, the light condensed by the first lens body layer 329 can be further condensed.

  The second lens body coating layer 325 is made of silicon oxide and has a refractive index between the refractive index of the second lens body layer 324 and the refractive index of the planarization film 326. Thus, when the second lens body coating layer 325 has a refractive index between the refractive index of the second lens body layer 324 and the refractive index of the planarization film 326, the planarization film 326 to the second lens body layer 324 is provided. Incident light increases. This is because reflection at the interface between the planarizing film 326 and the second lens body layer 324 that may occur when the second lens body coating layer 325 is not provided can be suppressed, and the transmittance can be increased.

The thickness of the second lens body coating layer 325 is preferably smaller than the thickness of the second lens body layer 324 and not more than ½ of the thickness of the second lens body layer 324. The thickness of the second lens body coating layer 325 is preferably (M−0.5) / 4n ₃₂₅ times to (M + 0.5) / 4n ₃₂₅ times the wavelength of incident light, and M / 4n ₃₂₅ of the wavelength of incident light _. More preferably, it is doubled. Here, M is an odd number, and n ₃₂₅ is the refractive index of the second lens body coating layer 325. M is preferably 1 or 3, and more preferably 1. When the thickness of the second lens body coating layer 325 is set in this way, interference between the reflected light on the surface of the second lens body layer 324 and the reflected light on the surface of the second lens body coating layer 325 can be weakened. It has a function of suppressing reflection from the viewpoint of wave optics.

  A first intermediate refractive index layer 322 is provided between the second lens base layer 323 and the low refractive index layer 321, and the second intermediate refractive index layer 320 is provided between the low refractive index layer 321 and the transparent film 319. Is provided. The material of the first medium refractive index layer 322 and the second medium refractive index layer 320 is made of silicon oxynitride, and the material of the low refractive index layer 321 is silicon oxide.

  The upper surface of the first intermediate refractive index layer 322 forms an interface with the lower surface of the second lens base layer 323, and the refractive index of the first intermediate refractive index layer 322 is lower than the refractive index of the second lens base layer 323. . The upper surface of the low refractive index layer 321 forms an interface with the lower surface of the first medium refractive index layer 322, and the refractive index of the low refractive index layer 321 is lower than the refractive index of the first medium refractive index layer 322. Therefore, the first intermediate refractive index layer 322 has a refractive index between the refractive index of the second lens base layer 323 and the refractive index of the low refractive index layer 321. The upper surface of the second intermediate refractive index layer 320 forms an interface with the lower surface of the low refractive index layer 321, and the refractive index of the second intermediate refractive index layer 320 is higher than the refractive index of the low refractive index layer 321. The lower surface of the second intermediate refractive index layer 320 forms an interface with the upper surface of the transparent film 319, and the refractive index of the second intermediate refractive index layer 320 is lower than the refractive index of the transparent film 319. Therefore, the second middle refractive index layer 320 has a refractive index between the refractive index of the low refractive index layer 321 and the refractive index of the transparent film 319. As described above, the first medium refractive index layer 322, the low refractive index layer 321 and the second medium refractive index layer 320 are all lower than the refractive indexes of the second lens base layer 323 and the second lens body layer 324. The first medium refractive index layer 322, the low refractive index layer 321 and the second medium refractive index layer 320 are collectively referred to as a low refractive index film. Note that at least one of the first medium refractive index layer 322 and the second medium refractive index layer 320 may be omitted from the low refractive index film, and the low refractive index film may be a single layer film or a two layer film. It is possible to omit the low refractive index film.

Since the refractive index of the low refractive index film 321 is lower than the refractive index of the first medium refractive index layer 322, the low refractive index layer 321 approaches the central axis of the opening 201 and the optical path member 220 according to Snell's law. Refract. Therefore, the amount of light incident on the opening 201 (optical path member 220) can be increased. Even without the first intermediate refractive index layer 322, the refractive index of the low refractive index film 321 is lower than the refractive index of the first intermediate refractive index layer 322, so that similar refraction can be generated. However, due to the difference in refractive index between the second lens base layer 323 and the low refractive index layer 321, incident light may be reflected at the interface between the second lens base layer 323 and the low refractive index layer 321. Further, due to the difference in refractive index between the low refractive index layer 321 and the transparent film 319, incident light may be reflected at the interface between the low refractive index layer 321 and the transparent film 319. The reflectance R at this time can be represented by R = (n ₃₂₁ −n ₃₁₉ ) ² / (n ₃₂₁ + n ₃₁₉ ) ² . Here, n ₃₂₁ is the refractive index of the low refractive index layer 321, and n ₃₁₉ is the refractive index of the transparent film 319. In the example of FIG. 1, both the refractive index difference between the second lens base layer 323 and the first medium refractive index layer 322 and the refractive index difference between the first medium refractive index layer 322 and the low refractive index layer 321 are the same. The difference in refractive index between the two-lens base layer 323 and the low refractive index layer 321 is smaller. Therefore, the transmittance from the second lens base layer 323 to the low refractive index layer 321 can be improved, and the amount of light incident on the low refractive index layer 321 can be increased. Since the refractive index of the transparent film 319 is higher than the refractive index of the second medium refractive index layer 320, the transparent film 319 is refracted in a direction away from the central axis of the opening 201 and the optical path member 220 according to Snell's law. Therefore, the light flux incident on the peripheral portion 221 (or the peripheral portion 223) can be increased. In addition, the angle with respect to the side surface 204 can be reduced, the luminous flux incident on the side surface 204 can be increased at an incident angle greater than the critical angle, and the amount of light leaking from the side surface 204 of the opening 201 can be reduced. Even when the second middle refractive index layer 320 is not provided, the same refraction can be caused by making the refractive index of the low refractive index layer 321 lower than the refractive index of the transparent film 319. In the example of FIG. 1, both the refractive index difference between the low refractive index layer 321 and the second middle refractive index layer 320 and the refractive index difference between the second middle refractive index layer 320 and the transparent film 319 are low refractive index layers. It is smaller than the refractive index difference between 321 and the transparent film 319. Therefore, the transmittance from the low refractive index layer 321 to the transparent film 319 can be improved, and the amount of light incident on the transparent film 319 can be increased.

The thickness of the first medium refractive index layer 322 is preferably (M−0.5) / 4n ₃₂₂ times to (M + 0.5) / 4n ₃₂₂ times the wavelength of incident light, and M / 4n ₃₂₂ of the wavelength of incident light _. More preferably, it is doubled. Here, M is an odd number, and n ₃₂₂ is the refractive index of the first medium refractive index layer 322. M is preferably 1 or 3, and more preferably 1. When the thickness of the first middle refractive index layer 322 is set in this way, the reflected light at the interface between the first middle refractive index layer 322 and the second lens base layer 323, the first middle refractive index layer 322, and the low refractive index. It has a function of suppressing reflection from the viewpoint of wave optics, which weakens interference of reflected light at the interface with the layer 321.

Similarly, the thickness of the second intermediate refractive index layer 320 is preferably (M−0.5) / 4n ₃₂₀ times to (M + 0.5) / 4n ₃₂₀ times the wavelength of the incident light, and the M of the wavelength of the incident light is preferably set. / 4n is more preferably ₃₂₀ times. Here, M is an odd number, and n ₃₂₀ is the refractive index of the second middle refractive index layer 320. M is preferably 1 or 3, and more preferably 1.

  In order to increase the refraction approaching the central axis in the low refractive index film within the range where the thickness of each layer is limited, the thickness of the first medium refractive index layer 322 and the thickness of the low refractive index layer 321 are as follows. It is good to set to. First, the relative refractive index of the second lens base layer 323 and the first medium refractive index layer 322 is compared with the relative refractive index of the first medium refractive index layer 322 and the low refractive index layer 321. The thickness of the exit side medium (one of the first medium refractive index layer 322 and the low refractive index layer 321) having the larger relative refractive index is set to the thickness of the medium on the smaller exit side (the first medium refractive index layer 322 and the low refractive index layer 321). It is made larger than the thickness of the other of the rate layer 321. Here, the relative refractive index is (refractive index of the incident-side medium) / (refractive index of the outgoing-side medium), and is a value larger than 1 in this embodiment. In the description so far, the simple description of “refractive index” means the absolute refractive index. According to Snell's law, the larger the relative refractive index, the larger the exit angle. Therefore, by increasing the thickness of the exit side medium having the larger relative refractive index, the emitted light can be made closer to the central axis. it can. For example, when the refractive index of the second lens base layer 323 is 2.00, the refractive index of the first medium refractive index layer 322 is 1.72, and the refractive index of the low refractive index layer 321 is 1.46, 2. 00 / 1.72 <1.72 / 1.46. Accordingly, the thickness of the low refractive index layer 321 may be made larger than the thickness of the first medium refractive index layer 322.

<Photoelectric conversion device and imaging system>
An example of the photoelectric conversion device 10 and an imaging system 30 using the same will be described with reference to FIG. The photoelectric conversion device 10 can be used as, for example, an imaging sensor, a distance measuring sensor, or a photometric sensor. The photoelectric conversion device 10 may have a plurality of functions among functions as an imaging sensor, a distance measuring sensor, and a photometric sensor.

  An imaging system 30 including the photoelectric conversion device 10 and a signal processing device 20 that receives the electrical signal output from the photoelectric conversion device 10 and processes the electrical signal can also be constructed. FIG. 9 is a diagram illustrating an example of the imaging system 30. The electrical signal is output from OUT1 and OUT2 of the photoelectric conversion device 10. Here, an example in which two output paths OUT1 and OUT2 are provided is shown, but there may be one output path or three or more output paths. The electric signal is input to IN of the signal processing device 20. The electrical signal may be a current signal, a voltage signal, an analog signal, or a digital signal. An optical signal may be used instead of the electrical signal.

  When the photoelectric conversion device 10 is used as an image sensor, the signal processing device 20 is configured to output an image signal from OUT3 by inputting an electric signal to IN. When the photoelectric conversion device 10 is used as a focus detection distance measuring sensor, the signal processing device 20 inputs an electric signal to IN to drive a lens provided in front of the photoelectric conversion device 10. A drive signal is configured to be output from OUT3. When the photoelectric conversion device 10 is used as a photometric sensor, the signal processing device 20 is configured to output from the OUT3 a control signal for controlling the shutter and adjusting the exposure time by inputting an electrical signal to the IN. . The shutter may be a mechanical shutter or an electronic shutter. However, in the case of an electronic shutter, the photoelectric conversion device 10 is substantially controlled. The photoelectric conversion device 10 of the present invention is particularly suitable for use as an image sensor, and a good image can be obtained.

  An example of the photoelectric conversion device 10 in the imaging system 30 illustrated in FIG. 9 will be described. In this example, a pixel amplification type photoelectric conversion device is used as the image sensor as the photoelectric conversion device 10. In FIG. 9, the photoelectric conversion device 10 includes a pixel region 611, a vertical scanning circuit 612, two readout circuits 613, two horizontal scanning circuits 614, and two output amplifiers 615. An area other than the pixel area 611 is also referred to as a peripheral circuit area.

  A large number of photoelectric conversion elements 1 are two-dimensionally arranged in the pixel region 611. Each photoelectric conversion element 1 corresponds to one pixel. The interval (pixel pitch) between the central axes of the photoelectric conversion elements 1 adjacent to each other is typically 10 μm or less, preferably 5.0 μm or less, and more preferably 2.0 μm or less. In the peripheral circuit area, a read circuit 613, for example, a column amplifier, a CDS circuit, an adder circuit, and the like are provided, and a signal read out from a pixel in a row selected by the vertical scanning circuit 612 via a vertical signal line. Amplification, addition, etc. The column amplifier, the CDS circuit, the addition circuit, and the like are arranged for each pixel column or a plurality of pixel columns, for example. The horizontal scanning circuit 614 generates a signal for sequentially reading the signals from the reading circuit 613. The output amplifier 615 amplifies and outputs the signal of the column selected by the horizontal scanning circuit 614.

  The above configuration is only one configuration example of the photoelectric conversion device 10 and is not limited to this. The readout circuit 613, the horizontal scanning circuit 614, and the output amplifier 615 are arranged one above the other with the pixel region 611 sandwiched therebetween in order to form two output paths (OUT 1 and OUT 2).

  Examples of the typical imaging system 30 include cameras such as a still camera and a video camera. The imaging system 30 can also include moving means (not shown) that allows the photoelectric conversion device 10 to move. Examples of the moving means include wheels that use an electric motor, a reciprocating engine, a rotary engine, or the like as a power source. Moreover, propulsion apparatuses, such as a propeller, a turbine engine, a rocket engine, are also mentioned as a moving means. Such an imaging system including a moving unit can be realized by mounting the photoelectric conversion device 10 and the signal processing device 20 on an automobile, a railway vehicle, a ship, an aircraft, an artificial satellite, or the like.

DESCRIPTION OF SYMBOLS 100 Substrate 110 Photoelectric conversion part 200 Insulating film 220 Optical path member 221 Peripheral part 222 Central part 319 Transparent film

Claims (23)

In a photoelectric conversion element comprising a photoelectric conversion unit and an optical path member provided on the photoelectric conversion unit and surrounded by an insulating film,
The optical path member includes a first portion and a second portion having a refractive index lower than the refractive index of the first portion,
The second portion continues to the first portion in a certain plane parallel to the light receiving surface of the photoelectric conversion unit and in another plane parallel to the light receiving surface and closer to the light receiving surface than the certain plane. And surrounding the first portion, and the refractive index of the second portion is higher than the refractive index of the insulating film,
The photoelectric conversion element, wherein a thickness of the second portion in the other plane is smaller than a thickness of the second portion in the certain plane. It said first portion and said second portion is a silicon nitride as a material, and said second portion is rather the density of silicon nitride is lower than the first portion,
The insulating film includes a first insulating layer and a second insulating layer each made of silicon oxide or silicate glass,
Within said one plane, the second portion is positioned between the first insulating layer and the first portion, and said first portion with said second portion continuous with the first portion Box,
In the other plane, the second portion is located between the first portion and the second insulating layer, and the second portion is continuous with the first portion, and the first portion is the photoelectric conversion device according to claim 1, wherein enclose it. It said first portion and said second portion is a silicon nitride as a material, and said second portion is the ratio of the silicon rather low for nitrogen than the first portion,
The insulating film includes a first insulating layer and a second insulating layer each made of silicon oxide or silicate glass,
Within said one plane, the second portion is positioned between the first insulating layer and the first portion, and said first portion with said second portion continuous with the first portion Box,
In the another plane, the second portion is located between the first portion and the second insulating layer, and the second portion is continuous with the first portion and surrounds the first portion. the photoelectric conversion device according to claim 1, wherein the free it.   The thickness of the said 2nd part in said another plane is 1/2 or less of the thickness of the said 2nd part in the said certain plane, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. Photoelectric conversion element.   5. The photoelectric conversion element according to claim 1, wherein a width of the optical path member in the other plane is smaller than a width of the optical path member in the certain plane. 6.   6. The photoelectric conversion element according to claim 1, wherein a width of the first portion in the other plane is larger than a width of the first portion in the certain plane. 7. . The optical path member is provided in an opening composed of a side surface of the insulating film that is continuous with the upper surface of the insulating film and surrounds the optical path member, and a bottom surface that is continuous with the side surface,
A plane including the light receiving surface is a first plane, a plane including the top surface and parallel to the first plane is a second plane, and the bottom surface is between the first plane and the second plane. Located in a third plane parallel to one plane,
The plane parallel to the first plane and located at the same distance from the second plane and the third plane is defined as a fourth plane, and the certain plane is positioned between the second plane and the fourth plane. The photoelectric conversion element according to claim 1, wherein the another plane is located between the third plane and the fourth plane. The width of the optical path member in the other plane is larger than the width of the optical path member in the fourth plane, and the first in the other plane is larger than the width of the first portion in the fourth plane. The photoelectric conversion element according to claim 7 , wherein the width of the portion is large. The insulating film includes a first insulating layer and a second insulating layer each having a refractive index lower than that of the second portion, and each of the insulating films is higher than the first insulating layer and the second insulating layer. A multilayer film including a third insulating layer and a fourth insulating layer having a high refractive index,
Each of the first insulating layer, the second insulating layer, the third insulating layer, and the fourth insulating layer surrounds the optical path member, and the first insulating layer is the third insulating layer. The first insulating layer is located in the certain plane, and the second insulating layer is located in the other plane. The photoelectric conversion element according to claim 1. Inside the insulating film, a first wiring layer mainly composed of copper and a second wiring layer mainly composed of copper are provided,
The insulating film is a multilayer film including a first diffusion prevention layer for copper contained in the first wiring layer and a second diffusion prevention layer for copper contained in the second wiring layer,
4. The photoelectric conversion element according to claim 2, wherein the first insulating layer is located between the first diffusion prevention layer and the second diffusion prevention layer. 5.   11. The optical path member includes a third portion having a refractive index lower than that of the second portion between the first portion and the photoelectric conversion unit. The photoelectric conversion element of Claim 1.   The photoelectric conversion element according to claim 1, wherein the optical path member is in contact with the insulating film, and the width of the optical path member is 2.0 μm or less.   The photoelectric conversion element according to claim 1, wherein the second portion is in contact with the insulating film.   A low refractive index layer having a refractive index lower than that of the second portion or a high refractive index layer having a refractive index higher than that of the second portion between the second portion and the insulating film. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is provided.   Refractive indexes of the first portion and the second portion are continuous from the axis passing through the first portion in the certain plane and the other plane toward the insulating film perpendicular to the light receiving surface. It has changed, The photoelectric conversion element of any one of Claims 1 thru | or 14 characterized by the above-mentioned.   16. The thickness of the second portion between the certain flat surface and the another flat surface is continuously reduced as it approaches the light receiving surface. Photoelectric conversion element. The wavelength of light photoelectrically converted by the photoelectric conversion unit is λ, the refractive index of the insulating film is n ₀ , and the refractive index of the second portion is n ₁ .
A thickness of the second portion in the certain plane is larger than λ / 2√ (n ₁ ² −n ₀ ² );
17. The photoelectric conversion element according to claim 1, wherein a thickness of the second portion in the another plane is smaller than λ / 4√ (n ₁ ² −n ₀ ² ). . A transparent film extending on the insulating film from above the optical path member is provided, and the transparent film includes a first region continuous with the second portion and a second region continuous with the first portion. And
The first region surrounds the second region in a plane parallel to the light receiving surface,
The photoelectric conversion element according to claim 1, wherein a refractive index of the second region is higher than a refractive index of the first region.   The photoelectric conversion element according to any one of claims 1 to 18, wherein the first portion and the second portion have the same stoichiometric composition.   On the opposite side of the optical path member from the photoelectric conversion unit, a first lens body layer, a second lens body layer positioned between the first lens body layer and the optical path member, and the second A low refractive index film positioned between the lens body layer and the optical path member, wherein the low refractive index film has a refractive index lower than that of the second lens body layer. The photoelectric conversion element according to any one of claims 1 to 19.   The photoelectric conversion element according to claim 1 or 9, wherein the material of the second portion is silicon nitride, or the material of the first portion is a resin.   A photoelectric conversion device comprising a pixel region in which a plurality of pixels including the photoelectric conversion element according to any one of claims 1 to 21 are arranged, wherein the pixel region includes the certain plane and the different region. Wiring located in the plane is provided inside the insulating film, and is perpendicular to the light receiving surfaces of the photoelectric conversion elements adjacent to each other, in the one plane and in the other plane, A photoelectric conversion device characterized in that an interval between axes passing through one portion is 5.0 μm or less.   A photoelectric conversion device in which a plurality of photoelectric conversion elements according to any one of claims 1 to 21 are arranged, a signal processing device that receives a signal output from the photoelectric conversion device and processes the signal, An imaging system comprising:

Images