WO2022019307A1

WO2022019307A1 - Photoelectric conversion element

Info

Publication number: WO2022019307A1
Application number: PCT/JP2021/027180
Authority: WO
Inventors: 祥二川人
Original assignee: 国立大学法人静岡大学
Priority date: 2020-07-22
Filing date: 2021-07-20
Publication date: 2022-01-27
Also published as: JPWO2022019307A1

Abstract

This photoelectric conversion element 1 comprises: a photoelectric conversion unit 30 that receives light and generates an electrical charge; an electrical charge accumulation detector 70 that accumulates electric charges received from the photoelectric conversion unit 30; an optical confinement unit 50 having a back-surface-side reflection layer 50B and a front-surface-side reflection layer 50F provided on the photoelectric conversion unit 30, the optical confinement unit 50 confining light in the photoelectric conversion unit 30 so that the light reciprocates in the photoelectric conversion unit 30; and a light direction conversion unit 60 including an outer lens 10 positioned on the back-surface-side-reflection-layer 50B side, the light direction conversion unit 60 determining the direction in which the light in the photoelectric conversion unit 30 advances. The light direction conversion unit 60 is positioned on the outer side of a region sandwiched by the back-surface-side reflection layer 50B and the front-surface-side reflection layer 50F, and causes light to advance in a direction away from the optical axis Z of the outer lens 10 each time reflection of the light between the back-surface-side reflection layer 50B and the front-surface-side reflection layer 50F is repeated.

Description

Photoelectric conversion element

The present invention relates to a photoelectric conversion element.

The spectrum of sunlight has a large intensity drop near the wavelength of 940 nm due to the influence of absorption by water vapor. Imaging devices such as TOF cameras reduce the influence of sunlight by using this wavelength band. Silicon is often used as a material for constituting an image pickup device. The light absorption coefficient of silicon is about 1/10 of visible light in the wavelength band of 940 nm. That is, the light absorption efficiency is low. For example, it is assumed that the thickness (x) of the photoelectric conversion unit included in the image pickup apparatus is 5 × 10 ^-4 cm (5 μm). This thickness is that of a typical CMOS image sensor. Then, it is assumed that the light absorption coefficient (α) of silicon in the wavelength band of 940 nm is 250 cm ^-1. According to the equation (1), the light absorption rate (B) obtained from the assumed thickness of the photoelectric conversion unit (x = 5 × 10 ^-4 cm) and the light absorption coefficient (α = 250 cm ^{-1) is 11.} It is 8%.

Special Table 2018-525837 Japanese Unexamined Patent Publication No. 2019-114642

Absorbance in silicon is proportional to the distance (optical path length) that light travels inside silicon. Then, even if the light absorption coefficient (α) is low, the amount of light absorbed by the silicon can be increased by ensuring a sufficient optical path length in the photoelectric conversion unit. For example, the elements disclosed in

Patent Documents

1 and 2 have a structure in which light that has passed through the photoelectric conversion unit is returned to the photoelectric conversion unit again. The optical path length obtained by these structures is longer than that in the case of passing through the photoelectric conversion unit only once. However, in the art, it has been desired to further increase the sensitivity of an image pickup apparatus provided with a photoelectric conversion element.

Therefore, the present invention provides a photoelectric conversion element capable of increasing the sensitivity.

The photoelectric conversion element according to the present invention has a photoelectric conversion unit that receives light to generate a charge, a charge storage detection unit that stores the charge received from the photoelectric conversion unit, and a first surface side of the photoelectric conversion unit. It has a first reflective layer provided in the above and includes an opening for receiving light, and a second reflective layer provided on the second surface side of the photoelectric conversion unit which is opposite to the first surface. Light that includes a light confinement unit that confine light in the photoelectric conversion unit and a first lens arranged on the first surface side so that the light reciprocates in the photoelectric conversion unit, and determines the traveling direction of the light in the photoelectric conversion unit. The light direction changing unit comprises a direction changing unit, and the optical direction changing unit is arranged outside the region sandwiched between the first surface and the second surface, and is arranged between the first surface and the second surface. Each time the light is repeatedly reflected, the light is advanced in a direction away from the optical axis of the first lens.

In this photoelectric conversion element, light is reflected a plurality of times between the first reflection layer and the second reflection layer. A photoelectric conversion unit exists between the first reflective layer and the second reflective layer. That is, the light reciprocates a plurality of times in the photoelectric conversion unit. Then, since the optical path length of the light in the photoelectric conversion unit is extended, it becomes possible for the photoelectric conversion unit to sufficiently absorb the light. As a result, the sensitivity can be increased.

In one form of photoelectric conversion element, in the cross-sectional shape including the optical axis of the first lens, the line segment indicating the surface that receives light is the first curved portion and the line segment farther from the optical axis than the first curved portion. The curvature of the second curved portion may be smaller than the curvature of the first curved portion, including the curved portion of 2. According to this configuration, each time the light is repeatedly reflected between the first surface and the second surface, light traveling in a direction away from the optical axis of the first lens can be generated.

In one form of photoelectric conversion element, in the cross-sectional shape including the optical axis of the first lens, the line segment indicating the surface that receives light may include a portion defined as an arc. Also with this configuration, it is possible to generate light traveling in a direction away from the optical axis of the first lens each time the reflection of light between the first surface and the second surface is repeated.

In one form of photoelectric conversion element, in the cross-sectional shape including the optical axis of the first lens, the line segment indicating the surface that receives light may include a portion defined as a parabola. Also with this configuration, it is possible to generate light traveling in a direction away from the optical axis of the first lens each time the reflection of light between the first surface and the second surface is repeated.

In one form of photoelectric conversion element, in the cross-sectional shape including the optical axis of the first lens, the line segment indicating the surface that receives light is the first straight line portion and the first straight line portion that is farther from the optical axis than the first straight line portion. The second tilt angle between the virtual reference axis and the second straight section including the two straight sections and orthogonal to the optical axis is the first tilt between the virtual reference axis and the first straight section. It may be larger than the corner. Also with this configuration, it is possible to generate light traveling in a direction away from the optical axis of the first lens each time the reflection of light between the first surface and the second surface is repeated.

In one form of photoelectric conversion element, the shape of the first lens may be a shape symmetrical with respect to the optical axis. According to this configuration, the traveling direction of light when the photoelectric conversion unit is viewed in a plane can be made radial.

In one form of photoelectric conversion element, the shape of the first lens may be a shape in which the cross-sectional shape is stretched in a direction orthogonal to the optical axis. According to this configuration, the traveling direction of light when the photoelectric conversion unit is viewed in a plane can be set in a desired direction.

In one form of photoelectric conversion element, the optical direction conversion unit may further include a second lens arranged between the first lens and the first surface in addition to the first lens. Also with this configuration, in the light incident on the photoelectric conversion unit from the opening of the first reflective layer, the component of the light emitted again from the opening can be reduced. Therefore, the sensitivity can be further increased.

In one form of photoelectric conversion element, in the cross-sectional shape including the optical axis of the second lens, the line segment indicating the surface that receives light is the third curved portion and the third curved portion farther from the optical axis than the third curved portion. The curvature of the fourth curved portion may be smaller than the curvature of the third curved portion, including the curved portion of 4. Also with this configuration, it is possible to generate light traveling in a direction away from the optical axis of the first lens each time the reflection of light between the first surface and the second surface is repeated.

In one form of photoelectric conversion element, in the cross-sectional shape including the optical axis of the second lens, the line segment indicating the surface that receives light may include a portion defined as an arc. Also with this configuration, it is possible to generate light traveling in a direction away from the optical axis of the first lens each time the reflection of light between the first surface and the second surface is repeated.

In one form of photoelectric conversion element, in the cross-sectional shape including the optical axis of the second lens, the line segment indicating the surface that receives light may include a portion defined as a parabola. Also with this configuration, it is possible to generate light traveling in a direction away from the optical axis of the first lens each time the reflection of light between the first surface and the second surface is repeated.

In one form of photoelectric conversion element, in the cross-sectional shape including the optical axis of the second lens, the line segment indicating the surface that receives light is the third straight line portion and the third straight line portion farther from the optical axis than the third straight line portion. The fourth tilt angle between the virtual reference axis perpendicular to the optical axis and the fourth straight section, including the four straight sections, is the third tilt between the virtual reference axis and the third straight section. It may be larger than the corner. Also with this configuration, it is possible to generate light traveling in a direction away from the optical axis of the first lens each time the reflection of light between the first surface and the second surface is repeated.

In one form of photoelectric conversion element, the optical direction conversion unit may include a reflection unit arranged on the second surface side. Also with this configuration, in the light incident on the photoelectric conversion unit from the opening of the first reflecting layer, the component of the light emitted again from the opening can be reduced. Therefore, the sensitivity can be further increased.

In one form of photoelectric conversion element, the light confinement portion further has a first partition wall portion surrounding the photoelectric conversion portion, and one end surface of the first partition wall portion cooperates with the first reflection layer to perform photoelectric printing. The other end surface of the first partition wall portion may be flush with the second surface of the photoelectric conversion unit so as to sandwich a part of the conversion unit. According to this configuration, light can be better confined in the photoelectric conversion unit.

In one form of the photoelectric conversion element, the light confinement portion further has a second partition wall portion surrounding the photoelectric conversion portion, and one end surface of the second partition wall portion is flush with the first surface of the photoelectric conversion portion. The other end face of the second partition wall portion may cooperate with the second reflective layer to sandwich a part of the photoelectric conversion portion. According to this configuration, it is possible to better confine the light in the photoelectric conversion unit and provide a path for taking out the electric charge generated in the photoelectric conversion unit.

In one form of the photoelectric conversion element, the light confinement portion further has a third partition wall portion surrounding the photoelectric conversion portion, and one end surface of the third partition wall portion is flush with the first surface of the photoelectric conversion portion. The other end face of the third partition wall portion may be flush with the second surface of the photoelectric conversion portion. According to this configuration, light can be reliably confined in the photoelectric conversion unit.

In one form of the photoelectric conversion element, the photoelectric conversion unit may include a portion overlapping with the opening of the first reflection layer, and the charge accumulation detection unit may not include a portion overlapping with the opening of the first reflection layer.

In one form of the photoelectric conversion element, the optical confinement portion is a pixel region having a photoelectric conversion region including a pn junction portion formed by the photoelectric conversion portion and a charge storage detection region including a charge storage detection portion when viewed from the incident direction of light. In addition, an outer partition wall portion surrounding the photoelectric conversion region and the charge accumulation detection region may be included so as to confine the light incident from the opening.

In one form of the photoelectric conversion element, one end surface of the outer partition wall portion is in contact with the semiconductor region constituting the pn junction, and the other end surface of the outer partition wall portion is flush with the second surface of the photoelectric conversion portion. May be good.

In one form of the photoelectric conversion element, one end surface of the outer partition wall portion is flush with the first surface of the photoelectric conversion portion, and the other end surface of the outer partition wall portion is in contact with the semiconductor region constituting the pn junction. May be good.

In one form of the photoelectric conversion element, one end surface of the outer partition wall portion is flush with the first surface of the photoelectric conversion portion, and the other end surface of the outer partition wall portion is the second surface and surface of the photoelectric conversion portion. It may be one.

In one form of the photoelectric conversion element, the light confinement portion is provided between the photoelectric conversion region and the charge accumulation detection region when viewed from the incident direction of light, and the inner partition wall optically separates the charge accumulation detection region from the photoelectric conversion region. May include parts.

In one form of the photoelectric conversion element, one end surface of the inner partition wall portion is in contact with the semiconductor region constituting the pn junction, and the other end surface of the inner partition wall portion is flush with the second surface of the photoelectric conversion portion. May be good.

In one form of the photoelectric conversion element, one end surface of the inner partition wall portion is flush with the first surface of the photoelectric conversion portion, and the other end surface of the inner partition wall portion is in contact with the semiconductor region constituting the pn junction. May be good.

In one form of the photoelectric conversion element, one end surface of the inner partition wall portion is flush with the first surface of the photoelectric conversion portion, and the other end surface of the inner partition wall portion is the second surface and surface of the photoelectric conversion portion. It may be one.

According to the present invention, a photoelectric conversion element capable of increasing sensitivity is provided.

FIG. 1 is a cross-sectional view of the photoelectric conversion element of the first embodiment. FIG. 2 is an enlarged cross-sectional view showing DTI, which is the first configuration shown in FIG. FIG. 3 is an enlarged cross-sectional view showing DTI, which is the second configuration. FIG. 4 is an enlarged cross-sectional view showing DTI, which is the third configuration. 5 (a) is a contour diagram showing the shape of the lens main surface of the outer lens, and FIG. 5 (b) is a cross-sectional shape of the outer lens in the XX'cross section shown in FIG. 5 (a). (C) is a cross-sectional shape of the outer lens in the YY'cross section shown in FIG. 5 (a). FIG. 6 is a cross-sectional view for explaining the confinement of light in the photoelectric conversion element. FIG. 7 is a perspective view showing the shape of the outer lens and the formed light irradiation region. FIG. 8 is a diagram for explaining the shape of the outer lens of the modified example 1. FIG. 9 is a diagram showing a photoelectric conversion element to which the outer lens of Modification 1 is applied. FIG. 10 is a diagram for explaining the shape of the outer lens of the modified example 2. FIG. 11 is a diagram showing a photoelectric conversion element to which the outer lens of Modification 2 is applied. FIG. 12 is a diagram showing a photoelectric conversion element to which the outer lens of Modification 3 is applied. FIG. 13 is a diagram for explaining the shape of the outer lens of the modified example 4. FIG. 14 is a diagram showing a photoelectric conversion element to which the outer lens of the modified example 4 is applied. FIG. 15 is a cross-sectional view of the photoelectric conversion element of the second embodiment. FIG. 16 is a cross-sectional view of the photoelectric conversion element of the third embodiment. FIG. 17 is a cross-sectional view of the photoelectric conversion element of the fourth embodiment. FIG. 18 is a cross-sectional view of the photoelectric conversion element of the fifth embodiment. FIG. 19 is a cross-sectional view of the photoelectric conversion element of the sixth embodiment. FIG. 20 is a perspective view showing the shape of the outer lens included in the photoelectric conversion element of the seventh embodiment and the formed light irradiation region. 21 (a) and 21 (c) are views showing the cross-sectional shape of the outer lens of another shape in the seventh embodiment, and FIG. 21 (b) is a diagram showing the outer lens of another shape in the seventh embodiment. It is a figure which shows the irradiation area of the light formed by. 22 (a) is a contour diagram showing the shape of the lens main surface of the outer lens of the eighth embodiment, and FIG. 22 (b) is a cross-sectional shape of the outer lens in the X1-X1'cross section and the X2-X2' cross section. FIG. 22 (c) shows the cross-sectional shape of the outer lens in Y1-Y1'cross-section and Y2-Y2'. FIG. 23 is a diagram showing a light irradiation region formed by a modification of the outer lens of the eighth embodiment. FIG. 24 is a cross-sectional view of the photoelectric conversion element of the ninth embodiment. FIG. 25 (a) is a cross-sectional view showing a first step for manufacturing the photoelectric conversion element of the ninth embodiment, and FIG. 25 (b) is a cross-sectional view showing the second step. FIG. 26A is a cross-sectional view showing a third step for manufacturing the photoelectric conversion element of the ninth embodiment, and FIG. 26B is a cross-sectional view showing the fourth step. 27 (a) is a cross-sectional view showing a fifth step for manufacturing the photoelectric conversion element of the ninth embodiment, and FIG. 27 (b) is a cross-sectional view showing the sixth step. FIG. 28 (a) is a cross-sectional view showing a seventh step for manufacturing the photoelectric conversion element of the ninth embodiment, and FIG. 28 (b) is a cross-sectional view showing the eighth step. FIG. 29 (a) is a cross-sectional view showing a first step in another method for manufacturing the photoelectric conversion element of the ninth embodiment, and FIG. 29 (b) is a cross-sectional view showing the second step. FIG. 30A is a cross-sectional view showing a third step in another method for manufacturing the photoelectric conversion element of the ninth embodiment, and FIG. 30B is a cross-sectional view showing the fourth step. FIG. 31 is a cross-sectional view showing a fifth step in another method for manufacturing the photoelectric conversion element of the ninth embodiment. FIG. 32 is a cross-sectional view of the photoelectric conversion element of the tenth embodiment. FIG. 33 is a plan view of the photoelectric conversion element of the eleventh embodiment. FIG. 34 is a plan view showing the structure of the photoelectric conversion element of the eleventh embodiment and the formed light irradiation region. FIG. 35 is a plan view showing a first arrangement example of the photoelectric conversion element of the eleventh embodiment. FIG. 36 is a plan view showing a second arrangement example of the photoelectric conversion element of the eleventh embodiment. FIG. 37 is a plan view showing the structure of the photoelectric conversion element of the eleventh embodiment and the formed light irradiation region. FIG. 38 is a plan view of the photoelectric conversion element of the twelfth embodiment. FIG. 39 is a plan view showing the structure of the photoelectric conversion element of the twelfth embodiment and the formed light irradiation region. FIG. 40 is a diagram illustrating the analysis model used in Calculation Examples 1, 2, and 3. FIG. 41 is a perspective view of the outer lens used in Calculation Example 1. FIG. 42 is a perspective view of the outer lens used in Calculation Example 2. FIG. 43 is a perspective view of the outer lens used in Calculation Example 3. FIG. 44 is a first contour diagram showing the result of calculation example 1. FIG. 45 is a second contour diagram showing the result of calculation example 1. FIG. 46 is a first contour diagram showing the result of calculation example 2. FIG. 47 is a second contour diagram showing the result of calculation example 2. FIG. 48 is a diagram showing light rays according to the result of calculation example 2. FIG. 49 is another diagram showing a light ray according to the result of the calculation example 2. FIG. 50 is a first contour diagram showing the result of calculation example 3. FIG. 51 is a diagram showing light rays based on the result of calculation example 3. FIG. 52 is another diagram showing a light ray according to the result of the calculation example 3. FIG. 53 (a) is a second contour diagram of the calculation example 3, and FIG. 53 (b) is a third contour diagram of the calculation example 3. FIG. 54 (a) is a fourth contour diagram of Calculation Example 3, and FIG. 54 (b) is a fifth contour diagram of Calculation Example 3. FIG. 55 (a) is a sixth contour diagram of Calculation Example 3, and FIG. 55 (b) is a seventh contour diagram of Calculation Example 3.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description is omitted.

The photoelectric conversion element 1 shown in FIG. 1 is a so-called back-illuminated pixel. The photoelectric conversion element 1 includes an outer lens 10 (first lens, optical direction conversion unit 60), a main spacer 20, a photoelectric conversion unit 30, a wiring unit 40, and a light confinement unit 50.

The outer lens 10 determines the direction of the light R incident on the photoelectric conversion unit 30 together with the main spacer 20. That is, the outer lens 10 constitutes the optical direction conversion unit 60 together with the main spacer 20. The outer lens 10 has a lens incident surface 11 and a lens emitting surface 12. The refractive index of the outer lens 10 is n = 1.58 as an example. The details of the outer lens 10 will be described later.

The main spacer 20 determines the distance from the outer lens 10 to the photoelectric conversion unit 30. The refractive index of the main spacer 20 is, for example, n = 1.58. That is, the refractive index of the main spacer 20 is the same as the refractive index of the outer lens 10. The main spacer 20 has a spacer incident surface 21 and a spacer emitting surface 22.

In the photoelectric conversion element 1 of the present embodiment, in order to cause multiple reflections in the photoelectric conversion unit 30, the incident position and angle of light incident on the photoelectric conversion unit 30 are important. These incident positions and angles are determined according to the shape and characteristics (refractive index) of the optical component through which light passes. In the case of the photoelectric conversion element 1, the outer lens 10 and the main spacer 20 correspond to this. That is, the photoelectric conversion element 1 has an optical direction conversion unit 60 composed of an outer lens 10 and a main spacer 20. That is, the optical direction conversion unit 60 is configured to guide light to the photoelectric conversion unit 30 so as to cause multiple reflections. Since the optical direction conversion unit 60 is configured to guide light to the photoelectric conversion unit 30, it is arranged outside the photoelectric conversion unit 30.

The photoelectric conversion unit 30 absorbs light R. The photoelectric conversion unit 30 generates an electric charge according to the absorbed light R. The photoelectric conversion unit 30 has a back surface 30B (first surface) and a front surface 30F (second surface). The photoelectric conversion unit 30 is made of silicon. According to silicon, the refractive index of the photoelectric conversion unit 30 is n = 3.64. That is, the refractive index of the photoelectric conversion unit 30 is larger than the refractive index of the outer lens 10. Further, the refractive index of the photoelectric conversion unit 30 is larger than the refractive index of the main spacer 20.

The photoelectric conversion unit 30 has a p + type first semiconductor region 31, a p-type second semiconductor region 32, an n-type third semiconductor region 33, and a p + type fourth semiconductor region 34. The first semiconductor region 31 constitutes the back surface 30B of the photoelectric conversion unit 30. The first semiconductor region 31 is in contact with the second semiconductor region 32. The second semiconductor region 32 is in contact with the first semiconductor region 31, the third semiconductor region 33, and the fourth semiconductor region 34, respectively. The third semiconductor region 33 is in contact with the second semiconductor region 32 and the fourth semiconductor region 34. The second semiconductor region 32 and the third semiconductor region 33 form a pn junction and function as a photodiode. That is, the photoelectric conversion unit 30 made of silicon that absorbs light R includes a photodiode. The structure of the photodiode is preferably an embedded photodiode, but it may be a light receiving element such as a photogate. The fourth semiconductor region 34 constitutes the surface 30F of the photoelectric conversion unit 30. The fourth semiconductor region 34 is in contact with the second semiconductor region 32 and the third semiconductor region 33. Further, the fourth semiconductor region 34 is in contact with the back surface 40B of the wiring portion 40.

The light confinement portion 50 includes a back surface side reflection layer 50B (first reflection layer), a front surface side reflection layer 50F (second reflection layer), an antireflection layer 51, and a DTI 52 (Deep Trench Isolation, first partition wall). Part) and. The antireflection layer 51 is formed on the back surface 30B of the photoelectric conversion unit 30. The antireflection layer 51 is composed of, for example, silicon oxide (SiO ₂ ) and silicon nitride (SiN). The antireflection layer 51 covers the entire pixel area defined by the DTI 52.

The back surface side reflective layer 50B and the front surface side reflective layer 50F are made of metal. That is, the back surface side reflective layer 50B and the front surface side reflective layer 50F are metal layers. The back surface side reflective layer 50B and the front surface side reflective layer 50F are made of, for example, aluminum (Al), copper (Cu), or tungsten (W). The back surface side reflective layer 50B is formed on the antireflection layer 51. The back surface side reflective layer 50B includes an incident opening 50B1 and a boundary opening 50B2. The incident aperture 50B1 intersects the optical axis Z. The position of the boundary opening 50B2 corresponds to the position of the DTI 52. The antireflection layer 51 is exposed through the incident opening 50B1 and the boundary opening 50B2. The antireflection layer 51 contacts the main spacer 20 via the incident opening 50B1 and the boundary opening 50B2. The surface-side reflective layer 50F is formed inside the wiring portion 40.

The DTI 52 optically partitions the adjacent photoelectric conversion elements 1. In the DTI 52, a substance having a refractive index smaller than that of silicon (refractive index 3.64 @ 940 nm) is embedded in a trench formed in a silicon substrate constituting the photoelectric conversion unit 30. Examples of the substance having a small refractive index include SiO ₂ (refractive index of about 1.45). As a result, the DTI 52 has a function of reflecting light R. That is, the DTI 52 totally reflects the light R incident at an angle.

The DTI 52 surrounds the third semiconductor region 33. The width from one DTI 52 to the other DTI 52 is larger than the width of the third semiconductor region 33. FIG. 2 is an enlarged view of one DTI 52. The DTI 52 is formed in the second semiconductor region 32 and the fourth semiconductor region 34. The surface side end surface 52s of the DTI 52 is in contact with the wiring portion 40. The DTI 52 penetrates the fourth semiconductor region 34. An electrode 43p is provided at a portion of the wiring portion 40 in contact with the surface side end surface 52s. The electrode 43p electrically connects the DTI 52 to the surface reflective layer 50F. The DTI 52 extends from the front surface of the second semiconductor region 32 (front surface 30F of the photoelectric conversion unit 30) toward the back surface of the second semiconductor region 32 (back surface 30B of the photoelectric conversion unit 30). The DTI 52 having such a structure is formed by processing from the surface 30F of the photoelectric conversion unit 30. The back surface side end surface 52t of the DTI 52 is located in the second semiconductor region 32. A part of the second semiconductor region 32 exists between the back surface side end surface 52t and the first semiconductor region 31. That is, the DTI 52 does not penetrate the second semiconductor region 32.

The DTI 52 is not limited to the configuration shown in FIG. The DTI 52 has three configurations including the first configuration shown in FIG. 2 in the relationship between the back surface side end surface 52t and the back surface 30B of the photoelectric conversion unit 30 and the relationship between the front surface side end surface 52s and the front surface 30F of the photoelectric conversion unit 30. Can be adopted.

FIG. 3 is an enlarged view of the DTI 52A (third partition wall portion) having the second configuration. In the second configuration, the DTI 52A, the back surface side end surface 52t is flush with the back surface 30B of the photoelectric conversion unit 30, and the front surface side end surface 52s is flush with the surface 30F of the photoelectric conversion unit 30. That is, the DTI 52A penetrates the photoelectric conversion unit 30. The back surface side end surface 52t is in contact with the antireflection layer 51. Further, the back surface side reflective layer 50B is not provided in a small area above the back surface side end surface 52t. That is, the back surface side reflective layer 50B has a boundary opening 50B2 which is a gap. The front end surface 52s is electrically connected to the electrode 43p exposed on the back surface 40B of the wiring portion 40. The DTI 52A optically separates the inside of the photoelectric conversion unit 30. Therefore, the second configuration, DTI52A, is advantageous in that it enhances the light absorption efficiency. Further, the DTI 52A electrically separates the inside of the photoelectric conversion unit 30. That is, the DTI 52A blocks the transfer of charge.

FIG. 4 is an enlarged view of the DTI 52B (second partition wall portion) having the third configuration. In the DTI 52B having the third configuration, the back surface side end surface 52t is flush with the back surface 30B of the photoelectric conversion unit 30. The back surface side end surface 52t comes into contact with the antireflection layer 51. On the other hand, the surface side end surface 52s is not flush with the surface 30F of the photoelectric conversion unit 30. The front end surface 52s is separated from the surface 30F of the photoelectric conversion unit 30. That is, the DTI 52B does not penetrate the photoelectric conversion unit 30. Such a DTI 52B is formed by processing from the back surface 30B of the photoelectric conversion unit 30. The surface side end surface 52s is in contact with the second semiconductor region 32 of the photoelectric conversion unit 30. Then, the second semiconductor region 32 of the photoelectric conversion unit 30 is not separated below the surface side end surface 52s. A part 32s of the second semiconductor region 32 can be used as a charge transfer path. That is, the region (32s) that the DTI 52B does not penetrate can be used for transferring the charge to the charge storage detection unit 70 (see FIG. 33) via the MOS transistor structure. It should be noted that light R may leak from the region where the DTI 52B does not penetrate. In this case, measures for leakage of light R may be taken as appropriate.

Refer to Fig. 1 again. The wiring portion 40 has a back surface 40B and a front surface 40F. The wiring unit 40 has a first wiring layer 41, a second wiring layer 42,

electrodes

43 and 43p, and a silicon oxide region 44. The silicon oxide region 44 constitutes the back surface 40B of the wiring portion 40 and the front surface 40F of the wiring portion 40. The first wiring layer 41, the second wiring layer 42, and the

electrodes

43, 43p are embedded in the silicon oxide region 44. Further, the surface-side reflective layer 50F is also embedded in the silicon oxide region 44. The first wiring layer 41 is electrically connected to the second wiring layer 42 via the electrode 43.

The outer lens 10 will be described in more detail. The lens incident surface 11 of the outer lens 10 has a different curvature depending on the location. That is, the lens incident surface 11 is not a curved surface having a constant curvature. For example, regarding the curvature of the outer lens 10, in the cross-sectional shape including the optical axis Z of the outer lens 10, the line segment indicating the surface that receives light is the first curved portion and the optical axis Z rather than the first curved portion. It can be explained that the curvature of the second curved portion includes the second curved portion far from the curve portion and is smaller than the curvature of the first curved portion. For example, as shown in FIG. 5A, in the lens incident surface 11, the first region L5a corresponds to the first curved portion, and the second region L5b corresponds to the second curved portion. The curvature of the second region L5b is smaller than the curvature of the first region L5a. This configuration can be easily understood with reference to FIGS. 5 (a), 5 (b) and 5 (c).

FIG. 5A is a contour line view of the lens incident surface 11 in a plan view. As shown in FIG. 5A, the outer lens 10 has a rotationally symmetric shape centered on the optical axis Z. 5 (b) and 5 (c) are cross-sectional views showing the positions of the contour lines. The cross section 10a in FIG. 5 (b) corresponds to the X1-X1'cross section in FIG. 5 (a). The cross section 10b of FIG. 5B corresponds to the X2-X2'cross section of FIG. 5A. The cross section 10c of FIG. 5 (c) corresponds to the Y1-Y1'cross section of FIG. 5 (a). The cross section 10d in FIG. 5 (c) corresponds to the Y2-Y2'cross section in FIG. 5 (a). The axes of FIGS. 5 (b) and 5 (c) indicate the positions of the contour lines of FIG. 5 (a). For example, the numbers on the axes of FIGS. 5 (b) and 5 (c) correspond to the numbers attached to the contour lines of FIG. 5 (a). In FIG. 5A, for example, the region surrounded by the contour lines (11) is defined as the first region L5a, and the region surrounded by the contour lines (1) to the contour lines (6) is defined as the second region L5b. May be good. Then, the first region L5a intersects the optical axis Z. Further, the second region L5b surrounds the first region L5a.

It can be said that the outer lens 10 having such a shape has a plurality of focal positions. For example, as shown in FIG. 1, the position of the focal point FP1 at the top of the outer lens 10 (first region L5a) is higher than the position of the focal point F2 at the peripheral portion of the outer lens 10 (second region L5b). Far from. In other words, the focal length at the top of the outer lens 10 is shorter than the focal length at the periphery of the outer lens 10.

The state of light absorption in the photoelectric conversion element 1 will be described with reference to FIGS. 6 and 7. It is assumed that the lights R6a and R6b are parallel lights. The directions of the light R6a and R6b are parallel to the optical axis Z.

It can be said that the shape of the outer lens 10 which is a microlens is a conical shape with rounded vertices. According to such a lens shape, the light R6a and R6b that have passed through the outer lens 10 are incident on the photoelectric conversion unit 30 from the incident aperture 50B1. Then, the reflected light becomes donut-shaped (ring-shaped) in the surface-side reflective layer 50F. After that, the diameter of the ring is expanded near the surface, and the ring shape becomes thinner once. Then, while expanding the radius and the diameter of the ring, the reflection is repeated between the front surface side reflection layer 50F and the back surface side reflection layer 50B. As a result, as long as the light R6a and R6b stay in the photoelectric conversion unit 30 made of silicon, the optical R6a and R6b continue to be absorbed by the photoelectric conversion unit 30, so that the photoelectric conversion continues.

As a specific first example, the state of the light R6a incident on the second region L5b on the lens incident surface 11 will be described with reference to FIG. When the light R6a passes through the lens incident surface 11, the traveling direction of the light R6a changes. The change in the traveling direction is based on the incident angle of the light R6a with respect to the lens incident surface 11. Further, the change in the traveling direction is also based on the difference in the refractive index between the refractive index of air and the refractive index of the outer lens 10. The light R6a is incident on the main spacer 20 from the lens emitting surface 12. The refractive index of the outer lens 10 is the same as the refractive index of the main spacer 20. That is, since there is no difference in the refractive index between the outer lens 10 and the main spacer 20, the traveling direction of the light R6a does not change. The light R6a passes through the incident opening 50B1 of the back surface side reflective layer 50B and then passes through the antireflection layer 51. After that, the light R6a is incident on the photoelectric conversion unit 30. The refractive index of the first semiconductor region 31 of the photoelectric conversion unit 30 does not match the refractive index of the main spacer 20. Therefore, the traveling direction of the light R6a changes when it is incident on the photoelectric conversion unit 30. The light R6a incident on the photoelectric conversion unit 30 passes through the first semiconductor region 31, the second semiconductor region 32, the third semiconductor region 33, and the fourth semiconductor region 34. Then, it is incident on the wiring portion 40. These plurality of semiconductor layers do not have a significant difference in refractive index. Therefore, the traveling direction of the light R6a does not substantially change. That is, the light R6a travels straight in the photoelectric conversion unit 30.

The refractive index (3.64) of the photoelectric conversion unit 30 is different from the refractive index (1.45) of the silicon oxide region 44 of the wiring unit 40. Therefore, upon incident incident on the wiring portion 40, the traveling direction of the light R6a changes according to the difference in the refractive index. The light R6a incident on the wiring portion 40 reaches the surface-side reflective layer 50F. The position where the light R6a is incident on the surface-side reflective layer 50F is away from the optical axis Z. The light R6a is reflected by the surface-side reflective layer 50F.

The traveling direction of the light R6a after reflection depends on the angle of incidence of the light R6a on the surface side reflection layer 50F. The reflected light R6a is incident on the photoelectric conversion unit 30 from the wiring unit 40. The light R6a travels straight in the photoelectric conversion unit 30. Then, the light R6a reaches the back surface side reflective layer 50B. That is, the light R6a reflected by the surface-side reflective layer 50F does not return to the incident opening 50B1. The light R6a reflected by the back surface side reflection layer 50B passes through the photoelectric conversion unit 30 again and then reaches the front surface side reflection layer 50F. After that, the light R6a approaches the DTI 52 while reciprocating between the back surface side reflective layer 50B and the front surface side reflective layer 50F. Then, the light R6a that has reached the DTI 52 is reflected by the DTI 52. After that, the light R6a reciprocates between the back surface side reflective layer 50B and the front surface side reflective layer 50F, and is separated from the DTI 52. Finally, the component of the light R6a that was not absorbed by the photoelectric conversion unit 30 reaches from the photoelectric conversion unit 30 to the main spacer 20 via the incident opening 50B1.

In the structure shown in FIG. 6, the ratio of the thickness of the photoelectric conversion unit 30 to the pixel size (width of the light receiving region) is shown as 1: 2. As an example, the thickness of the photoelectric conversion unit 30 is 5 μm, and the pixel size (width of the light receiving region) is 10 μm. Then, the light R6a passes through the photoelectric conversion unit 30 eight times. In this case, the optical path length of the optical R6a is 40.8 μm. In the photoelectric conversion unit 30, the absorption length of light having a wavelength of 940 nm is about 40 μm. That is, if there is no loss due to reflection, the quantum efficiency can be increased to about 64%.

Next, as a second example, the state of the light R6b incident on the first region L5a on the lens incident surface 11 will be described. The light R6b also enters the photoelectric conversion unit 30 from the incident opening 50B1 in the same manner as the light R6b incident on the first region L5a. Then, the optical R6b reciprocates the photoelectric conversion unit 30 a plurality of times. In the second example, the incident angle when the light R6b first enters the surface-side reflective layer 50F after passing through the incident opening 50B1 is smaller than that in the first example. As a result, the number of times the light R6b is reflected by the photoelectric conversion unit 30 is 22 times. That is, the number of round trips of the photoelectric conversion unit 30 of the optical R6b is larger than the number of round trips of the optical R6a of the first example. Then, the optical path length of the photoelectric conversion unit 30 in the second example is about 110 μm. If there is no loss due to reflection, the quantum efficiency can be increased to about 94%.

When the photoelectric conversion element 1 is viewed as a whole, it can be assumed that the number of reflections (optical path length) exists between the first example and the second example. Then, the quantum efficiency of the photoelectric conversion element 1 can be increased to about 80%.

FIG. 7 is a perspective view illustrating the second example by another expression. FIG. 7 illustrates a ray of one light R7a. As shown in FIG. 7, the outer lens 10 has a symmetrical shape around the optical axis Z. Then, when the light R7a incident on the same position along the optical axis Z reaches the surface-side reflective layer 50F, it is incident on the position equidistant from the optical axis Z. In other words, the position incident on the surface-side reflective layer 50F is a circle centered on the optical axis Z. Since the incident angles of the light R7a are equal to each other at each position, the directions from the front surface side reflection layer 50F to the back surface side reflection layer 50B are also equivalent. As a result, the position of being incident on the surface-side reflective layer 50F again is a similar circle. In this case, since the light R7a is approaching the DTI 52, in other words, the radius of the position where the light R7a is incident on the surface side reflective layer 50F for the second time is the radius of the position where the light R7a is incident on the surface side reflective layer 50F for the first time. Greater than the radius of the incident position. By repeating such reflections, the positions where the light R7a is incident on the surface-side reflective layer 50F draw concentric circles. In the following description, changing the traveling direction of the light R7a so that it is incident on the surface-side reflective layer 50F at a position equidistant from the optical axis Z is referred to as “light molding”.

<Action effect>
The light source of the TOF camera, which measures the distance by irradiating the object with light and measuring the flight time while the light is reflected by the object and returns, measures the distance outdoors in the presence of sunlight. In order to cope with this, laser light in the 940 nm band, in which the spectral intensity of sunlight is relatively low due to absorption of water vapor in the atmosphere, is often used. However, it cannot be said that the absorption coefficient of silicon, which is a semiconductor, is sufficiently large for light in this wavelength band. Therefore, it was not possible to increase the quantum efficiency in the photoelectric conversion layer of about several μm to about 10 μm of the conventional CMOS image sensor. Therefore, it cannot be said that sufficient sensitivity for outdoor distance measurement has been achieved.

The photoelectric conversion element 1 reflects light R a plurality of times between the back surface side reflection layer 50B and the front surface side reflection layer 50F. A photoelectric conversion unit 30 exists between the back surface side reflection layer 50B and the front surface side reflection layer 50F. That is, the light R reciprocates the photoelectric conversion unit 30 a plurality of times. Then, since the optical path length of the light R in the photoelectric conversion unit 30 is extended, it becomes possible for the photoelectric conversion unit 30 to sufficiently absorb the light R. As a result, the sensitivity can be increased.

That is, the photoelectric conversion element 1 of the first embodiment reflects light R a plurality of times between the front surface side reflection layer 50F and the back surface side reflection layer 50B provided with the incident opening 50B1. As a result, it is possible to lengthen the substantially optical path length inside the photoelectric conversion unit 30 made of silicon, so that the near-infrared sensitivity can be improved. According to the outer lens 10 of the first embodiment, the distribution of the light intensity in the surface-side reflective layer 50F can be made annular (doughnut-shaped). According to this intensity distribution, most of the light R is projected onto the back surface side reflective layer 50B. The combination of the outer lens 10 of the first embodiment, which has a large curvature at the top and a small curvature at the side, and the main spacer 20 arranged between the outer lens 10 and the photoelectric conversion unit 30, is annular. It is possible to obtain the distribution of light intensity. As a result, according to the photoelectric conversion element 1 of the present embodiment, sufficient sensitivity can be achieved for distance measurement outdoors.

The refraction angle from the main spacer 20 to the photoelectric conversion unit 30 for causing multiple reflections inside the photoelectric conversion unit 30 made of silicon and the incident position with respect to the incident opening 50B1 are the incident angles of the light incident on the outer lens 10. It is directly determined by the inclination of the reflecting surface on the incident surface. The reflective surface is a surface perpendicular to the normal of the surface of the outer lens 10.

In the cross-sectional shape of the outer lens 10 including the optical axis Z, the surface that receives light has a condition that causes multiple reflection even when the line segment indicating the surface includes a plurality of straight lines. Further, the line segment indicating the surface of the outer lens 10 that receives light is a curve, and there is a condition that causes multiple reflection even if the curvature of the curve is the same. That is, the outer lens constituting the optical direction conversion unit is not limited to the outer lens 10 of the first embodiment. The outer lens cooperates with other optical components to emit light in a direction away from the optical axis Z each time light is repeatedly reflected between the back surface 30B of the photoelectric conversion unit 30 and the front surface 30F of the photoelectric conversion unit 30. A configuration may be adopted in which the traveling direction of the light can be changed so that the light travels. Hereinafter, some modifications of the outer lens will be described. Even when the outer lenses of Modifications 1 to 4 are adopted, the light parallel to the optical axis Z incident on the outer lens is reflected by the surface-side reflective layer 50F after passing through the incident aperture 50B1, and further the incident aperture. It is reflected by the back surface side reflective layer 50B around 50B1. That is, the optical direction changing unit including the outer lens can generate multiple reflections. As used herein, "multiplex" means at least two or more reflections.

<Modification 1>
The outer lens 10S1 of the modification 1 will be described with reference to FIGS. 8 and 9. The outer lens 10S1 has a composite conical shape. In the following description, the compound conical shape refers to a multi-stage shape having inclinations of a plurality of angles. That is, in the cross-sectional shape of the outer lens 10S1 of the first modification, the tilt angle increases as the distance from the optical axis Z increases. The tilt angle here means the angle of the contour line with respect to the virtual reference axis ZA orthogonal to the optical axis Z in the cross-sectional shape of the outer lens 10S1 including the optical axis Z. The tilt angle is more preferably a finite angle.

The outer lens 10S1 shown in FIGS. 8 and 9 is an example of an outer lens having a composite conical shape. Therefore, the specific numerical values are not limited to the examples shown in FIGS. 8 and 9 and the specific numerical values described below. Specific numerical values may be appropriately set according to the specific configuration of the photoelectric conversion element 1S1.

FIG. 8 is a schematic diagram for explaining the composite conical shape. The line segment C1 shown in FIG. 8 indicates a surface that receives light in the cross-sectional shape of the outer lens 10S1 of the first modification. The line segment C1 has a first straight line portion C1a, a second straight line portion C1b, and a third straight line portion C1c between the apex C1t and the end point C1e. The first straight line portion C1a includes the apex C1t. The third straight line portion C1c includes the endpoint C1e. The second straight line portion C1b is arranged between the first straight line portion C1a and the third straight line portion C1c. That is, the second straight line portion C1b connects the first straight line portion C1a to the third straight line portion C1c.

The first straight line portion C1a has a first inclination angle A1a. The inclination angle is an angle between the virtual reference axis ZA orthogonal to the optical axis Z and the first straight line portion C1a. Similarly, the second straight line portion C1b has a second tilt angle A1b and the third straight line portion C1c has a third tilt angle A1c. The second tilt angle A1b is larger than the first tilt angle A1a. The third tilt angle A1c is larger than the second tilt angle A1b.

FIG. 9 is a cross-sectional view showing a main part of the photoelectric conversion element 1S1 provided with the outer lens 10S1 having the composite conical shape described with reference to FIG. The photoelectric conversion element 1S1 includes an outer lens 10S1, a main spacer 20, and a photoelectric conversion unit 30.

The following numerical values can be exemplified for each component included in the photoelectric conversion element 1S1.
Outer lens: thickness t1 = 2.8 μm, width t4 = 10 μm, refractive index n = 1.8.
Main spacer: thickness t2 = 7 μm, width t4 = 10 μm, refractive index n = 1.8.
Photoelectric conversion unit: thickness t3 = 20 μm, width t4 = 10 μm, refractive index n = 3.6.

Further, FIG. 9 illustrates a light ray indicating the light incident on the outer lens 10S1. The angles of the normal line N on the lens surface and the axis line parallel to the optical axis Z at the incident position are shown as angles A2a, A2b, and A2c, respectively. The following can be exemplified as the numerical values of each angle.
Angle A2a = 20 °
Angle A2b = 30 °
Angle A2c = 40 °

The light incident from the vicinity of the optical axis Z of the outer lens 10S1 is reflected by the front surface side reflection layer 50F and then incident on the back surface side reflection layer 50B. That is, the light incident from the vicinity of the optical axis Z is not emitted from the incident opening 50B1 to the outside of the photoelectric conversion unit 30 due to the first reflection by the surface-side reflective layer 50F. Similarly, the light incident from the end portion of the outer lens 10S1 is also reflected by the front surface side reflection layer 50F and then incident on the back surface side reflection layer 50B. That is, the light incident from the end portion of the outer lens 10S1 is not emitted from the incident aperture 50B1 to the outside of the photoelectric conversion unit 30 due to the first reflection by the front surface side reflection layer 50F. Therefore, the photoelectric conversion element 1S1 provided with the outer lens 10S1 of the modification 1 can also suitably confine the light in the photoelectric conversion unit 30.

<Modification 2>
The outer lens 10S2 of the modification 2 will be described with reference to FIGS. 10 and 11. The portion that receives light in the cross-sectional shape showing the contour of the outer lens 10S2 includes a curved portion. In the second modification, the curve is an arc. Then, the entire portion of the cross-sectional shape showing the contour of the outer lens 10S2 that receives light exhibits a shape in which the curve is copied with the optical axis Z as the axis of symmetry. Part of the curve does not have to include the axis of the arc parallel to the optical axis Z.

The line segment C2 shown in FIG. 10 shows a surface that receives light in the cross-sectional shape including the optical axis Z in the outer lens 10S2 of the modification 2. In the cross-sectional shape of the outer lens 10S2 including the optical axis Z, the line segment C2 indicating the surface that receives light includes a portion defined as an arc. More specifically, the line segment C2 corresponds to a part CA1 of the arc CA. The arc CA has a virtual reference axis ZA parallel to the optical axis Z. The virtual reference axis ZA and the optical axis Z are separated from each other in a direction orthogonal to the optical axis Z. Such a line segment C2 has one value as the curvature, and in this respect, it differs from the outer lens 10 of the embodiment shown by the curve including a plurality of curvatures.

FIG. 11 is a cross-sectional view showing a main part of the photoelectric conversion element 1S2 provided with the outer lens 10S2 described with reference to FIG. The photoelectric conversion element 1S2 includes an outer lens 10S2, a main spacer 20, and a photoelectric conversion unit 30.

The following numerical values can be exemplified for each component included in the photoelectric conversion element 1S2.
Outer lens: thickness t1 = 2.9 μm, width t4 = 10 μm, refractive index n = 1.8.
Main spacer: thickness t2 = 6 μm, width t4 = 10 μm, refractive index n = 1.8.
Photoelectric conversion unit: thickness t3 = 20 μm, width t4 = 10 μm, refractive index n = 3.6.

Further, FIG. 11 shows a light ray indicating the light incident on the outer lens 10S2 as in FIG. 9. The angles of the normal line N of the lens surface and the axis line parallel to the optical axis Z at the incident position are shown as angles A3a, A3b, A3c, A3d, and A3e, respectively. The following can be exemplified as the numerical values of each angle.
Angle A3a = 20 °
Angle A3b = 25 °
Angle A3c = 30 °
Angle A3d = 35 °
Angle A3e = 40 °

Light incident from the vicinity of the optical axis Z of the outer lens 10S2 (for example, optical Lar) is reflected by the front surface side reflection layer 50F and then incident on the back surface side reflection layer 50B. That is, the light incident from the vicinity of the optical axis Z of the outer lens 10S2 is not emitted from the incident aperture 50B1 to the outside of the photoelectric conversion unit 30. Similarly, the light incident from the end of the outer lens 10S2 (for example, light Lbr, Lbl) is also reflected by the front surface side reflection layer 50F and then incident on the back surface side reflection layer 50B. That is, the light incident from the end portion of the outer lens 10S2 is not emitted from the incident aperture 50B1 to the outside of the photoelectric conversion unit 30. Therefore, the photoelectric conversion element 1S2 provided with the outer lens 10S2 of the modification 2 can also suitably confine the light in the photoelectric conversion unit 30.

In the outer lens 10S2 shown in FIG. 11, the right end Er of the lens on the right side of the paper surface and the left end El of the lens on the left side of the paper surface are defined. Light Lbr is incident on Er at the right end of the lens. Light Lbl is incident on the left end El of the lens. It is assumed that the light Lbr and Lbl are parallel to the optical axis Z. Further, the light Lar is incident on a position slightly to the right of the optical axis Z.

The light Lbr is incident on the photoelectric conversion unit 30 at the position Lbrp1. Then, the light Lbr is reflected by the front surface side reflection layer 50F and then incident on the position Lbrp2 on the back surface side reflection layer 50B. Further, the light Lbl is incident on the photoelectric conversion unit 30 at the position Lblp1. Then, the light Lbl is reflected by the front surface side reflection layer 50F and then incident on the position Lblp2 on the back surface side reflection layer 50B. Further, the optical Lar is incident on the photoelectric conversion unit 30 at the position Larp1. Then, the light Lar is reflected by the front surface side reflection layer 50F and then incident on the position Larp 2 on the back surface side reflection layer 50B.

Here, comparing the distance from the optical axis Z to the position Lblp1 and the distance from the optical axis Z to the position Lbrp2, the distance from the optical axis Z to the position Lbrp2 is larger than the distance from the optical axis Z to the position Lblp1. big. Further, comparing the distance from the optical axis Z to the position Lblp1 and the distance from the optical axis Z to the position Larp2, the distance from the optical axis Z to the position Larp2 is larger than the distance from the optical axis Z to the position Lblp1. .. Then, the incident opening 50B1 is provided so as to pass through the position Lbrp1 and the position Lblp1.

That is, in the outer lens 10S2 of the modification 2, the opening end of the incident aperture 50B1 is determined by the position (position Lbrp1, Lblp1) where the light Lbr and Lbl incident on the position far from the optical axis Z are incident on the photoelectric conversion unit 30. There is.

In short, the inclination of the tangent line of the lens surface with respect to the light Lar and Lbr in the outer lens 10S2, the refractive index of the lens material of the outer lens 10S2, and the thickness of the main spacer 20 are on the right side of the light Lbr and the optical axis Z on the outermost periphery of the right lens. After the light Lar substantially overlapping the optical axis Z is incident on silicon (photoelectric conversion unit 30), it is reflected once by the second reflective layer (front surface side reflective layer 50F) and then reflected once by the first reflective layer (back surface side reflective layer). 50B) so that the position Lbrp2 and the position Larp2 where the second reflection is performed are located farther from the optical axis Z than the position Lblp1 where the light Lbl on the outermost periphery of the lens on the opposite side (left side) is incident on the photoelectric conversion unit 30. It is set. Then, a part of the back surface side reflective layer 50B constituting the first reflective layer is provided from the left end of the pixel to the position between the position Lbrp2 (or the position Larp2) and the position Lblp1. Another part of the back surface side reflective layer 50B constituting the first reflective layer is provided on the opposite side of this and the optical axis Z as an axis target.

<Modification 3>
FIG. 12 is a cross-sectional view showing a main part of the photoelectric conversion element 1S3 provided with the outer lens 10S3 whose opening end of the incident aperture 50B1 is determined by another factor. The photoelectric conversion element 1S3 includes an outer lens 10S3, a main spacer 20, and a photoelectric conversion unit 30.

The following numerical values can be exemplified for each component included in the photoelectric conversion element 1S3.
Outer lens: thickness t1 = 3.9 μm, width t4 = 10 μm, refractive index n = 1.56.
Main spacer: thickness t2 = 12.5 μm, width t4 = 10 μm, refractive index n = 1.56.
Photoelectric conversion unit: thickness t3 = 5 μm, width t4 = 10 μm, refractive index n = 3.6.

Further, FIG. 12 shows a light ray indicating light incident on the outer lens 10S3 as in FIG. 9. The angles of the normal line N on the lens surface and the axis line parallel to the optical axis Z at the incident position are shown as angles A4a and A4b, respectively. The following can be exemplified as the numerical values of each angle.
Angle A4a = 20 °
Angle A4b = 55 °

Further, the following numerical values can be additionally exemplified for each component included in the photoelectric conversion element 1S3.
The radius t5 of the arc that defines the outer lens is 10.5 μm.
The deviation between the arc axis ZB and the optical axis Z t6 = 3.7 μm.
The width of the back surface reflective layer t7 = 2.9 μm.
The diameter of the incident opening t8 = 4.2 μm.

The outer lens 10S2 of the second modification was determined by the position where the light Lbr and Lbl incident on the position where the incident aperture 50B1 is far from the optical axis Z are incident on the photoelectric conversion unit 30. On the other hand, in the outer lens 10S3 of the modification 3, the incident aperture 50B1 is determined by the position where the light Lar incident on the optical axis Z is incident on the photoelectric conversion unit 30.

Specifically, the light Lbr is incident on the photoelectric conversion unit 30 at the position Lbrp1. Then, the light Lbr is reflected by the front surface side reflection layer 50F and then incident on the position Lbrp2 on the back surface side reflection layer 50B. Further, the optical Lar is incident on the photoelectric conversion unit 30 at the position Larp1. Then, the light Lar is reflected by the front surface side reflection layer 50F and then incident on the position Larp 2 on the back surface side reflection layer 50B.

Comparing the distance from the optical axis Z to the position Larp1 and the distance from the optical axis Z to the position Lbrp2, the distance from the optical axis Z to the position Lbrp2 is larger than the distance from the optical axis Z to the position Larp1. The incident opening 50B1 is provided so that its end portion passes between the position Lbrp2 and the position Larp1.

In short, after the optical Lbr on the outermost periphery (right side) of the lens is incident on silicon (photoelectric conversion unit 30), it is reflected once by the second reflective layer (front surface side reflective layer 50F), and is reflected once by the first reflective layer (back surface side reflection). The position Lbrp2 where the second reflection is performed on the layer 50B) is located on the right side of the optical axis Z and at a position farther from the optical axis Z than the position where the optical Lar substantially overlapping the optical axis Z is incident on the silicon (photoelectric conversion unit 30). Therefore, the inclination of the tangent line of the lens surface, the refractive index of the material constituting the microlens which is the outer lens 10S3, and the thickness of the main spacer 20 are determined. Then, a first reflective layer (reflective layer 50B on the back surface side) is provided from the left end of the pixel to a position between the position Lbrp2 and the position Larp1. A first reflective layer (reflective layer 50B on the back surface side) is also provided on the side opposite to the optical axis Z.

<Modification example 4>
In the modified examples 2 and 3, an example in which the curve is a part of the arc has been described. Curves are not limited to arcs. As shown in FIG. 13, the line segment C4 indicating the portion that receives light in the cross-sectional shape showing the contour of the outer lens 10S4 of the modified example 4 may include a portion defined as a parabolic CB. That is, the cross-sectional shape showing the outline of the outer lens 10S4 may be a shape in which a part of the parabola CB having an axis parallel to the optical axis Z is copied with the optical axis Z as the axis of symmetry. The partial CB1 of the parabola CB may not include the axis ZB of the parabola CB parallel to the optical axis Z. If it is permissible to generate light that does not reflect multiple times to some extent, the axis ZC of the parabola CB parallel to the optical axis Z may be included.

FIG. 14 is a cross-sectional view showing a main part of a photoelectric conversion element 1S4 provided with an outer lens 10S4 including a line segment C4 defined as a parabolic CB. The photoelectric conversion element 1S4 includes an outer lens 10S4, a main spacer 20, and a photoelectric conversion unit 30.

The following numerical values can be exemplified for each component included in the photoelectric conversion element 1S4.
Outer lens: thickness t1 = 3 μm, width t4 = 10 μm, refractive index n = 1.8.
Main spacer: thickness t2 = 6 μm, width t4 = 10 μm, refractive index n = 1.8.
Photoelectric conversion unit: thickness t3 = 20 μm, width t4 = 10 μm, refractive index n = 3.6.

Further, FIG. 14 shows a light ray indicating light incident on the outer lens 10S4 as in FIG. 9. The angles of the normal line N on the lens surface and the axis line parallel to the optical axis Z at the incident position are shown as angles A5a, A5b, A5c, A5d, and A5e, respectively. The following can be exemplified as the numerical values of each angle.
Angle A5a = 20 °
Angle A5b = 25 °
Angle A5c = 30 °
Angle A5d = 35 °
Angle A5e = 40 °

Even with the outer lens 10S4 of the modification 4, both the light incident from the vicinity of the optical axis Z and the light incident from a position away from the optical axis Z are reflected from the incident aperture 50B1 to the photoelectric conversion unit 30 as a result of the first reflection. It is not emitted to the outside of. Therefore, the photoelectric conversion element 1S4 provided with the outer lens 10S4 of the modification 4 can also suitably confine the light in the photoelectric conversion unit 30.

<Second Embodiment>
In the photoelectric conversion element 1 of the first embodiment, all the light R reflected for the first time by the front surface side reflection layer 50F reaches the back surface side reflection layer 50B. That is, the light R reflected for the first time by the surface-side reflective layer 50F does not reach the incident opening 50B1. Such light R is realized by the shape of the outer lens 10 in the first embodiment. However, a configuration capable of guiding the light R first reflected by the front surface side reflection layer 50F to the back surface side reflection layer 50B can be realized by a configuration different from the shape of the outer lens 10.

As shown in FIG. 15, the photoelectric conversion element 1A of the second embodiment includes an outer lens 10A, a main spacer 20A, an inner lens 61A (second lens, optical direction conversion unit 60A), an inner spacer 62A, and the like. A photoelectric conversion unit 30A and a wiring unit 40A are provided. The photoelectric conversion element 1A of the second embodiment has a DTI 52A (see FIG. 3) having a second configuration. The photoelectric conversion element 1A differs from the photoelectric conversion element 1 of the first embodiment in the configuration of the outer lens 10A.

Further, the photoelectric conversion element 1A is different from the photoelectric conversion element 1 of the first embodiment in that the inner lens 61A and the inner spacer 62A are further provided. The photoelectric conversion element 1A includes an inner lens 61A that the photoelectric conversion element 1 of the first embodiment does not have. The inner lens 61A has a shape corresponding to the outer lens 10 of the first embodiment. That is, the photoelectric conversion element 1A of the second embodiment adopts a double microlens structure including an outer lens 10A and an inner lens 61A. In the photoelectric conversion element 1A of the second embodiment, a spherical microlens is adopted as the outer lens 10A for capturing light R, and a microlens having a conical shape with rounded vertices is adopted as the inner lens 61A. That is, in the second embodiment, the components that guide the light to the photoelectric conversion unit 30A are the outer lens 10A, the main spacer 20A, the inner lens 61A, and the inner spacer 62A. These optical components constitute the optical direction conversion unit 60A in the second embodiment.

The photoelectric conversion element 1A guides the light R first reflected by the front surface side reflection layer 50F to the back surface side reflection layer 50B. Since the photoelectric conversion unit 30A and the wiring unit 40A are the same as the photoelectric conversion unit 30 and the wiring unit 40 of the first embodiment, detailed description thereof will be omitted. Hereinafter, the outer lens 10A, the inner lens 61A, and the inner spacer 62A will be described in detail.

The outer lens 10A of the second embodiment has a spherical lens incident surface 11A. The focal point of the outer lens 10A is set inside the photoelectric conversion unit 30A. The positional relationship between the outer lens 10A and the inner lens 61A can be adjusted by the main spacer 20A. The inner lens 61A includes an optical axis Z. For example, the optical axis of the inner lens 61A coincides with the optical axis of the outer lens 10A. Further, all the light rays of the light R passing through the outer lens 10A intersect with the light incident surface of the inner lens 61A.

The photoelectric conversion element 1A of the second embodiment includes an outer lens 10A and an inner lens 61A. The inner lens 61A exhibits the same function as the outer lens 10 of the first embodiment. That is, as the shape of the inner lens 61A, the shape of the outer lens 10 of the first embodiment may be adopted. Further, as the shape of the inner lens 61A, any one of the outer lenses 10S1 to 10S4 of the modified examples 1 to 4 may be adopted. The inner spacer 62A adjusts the positional relationship between the inner lens 61A and the photoelectric conversion unit 30A. The refractive index (n2) of the inner lens 61A and the inner spacer 62A is larger than the refractive index (n1) of the outer lens 10A. Conversely, the refractive index of the outer lens 10A is smaller than the refractive index of the inner lens 61A. In other words, the refractive index (n2) of the inner lens 61A and the inner spacer 62A is larger than the refractive index (n1) of the main spacer 20A (n2> n1). The range of the refractive index of the outer lens 10A is about 1.55 to 1.6. Then, the refractive index of the inner lens 61A is about 2.0. As a result, refraction occurs when the light R is incident on the inner lens 61A from the main spacer 20A. That is, the traveling direction of the light R changes.

The inner lens 61A and the inner spacer 62A are arranged between the main spacer 20A and the photoelectric conversion unit 30A. The back surface of the inner spacer 62A is in contact with the back surface side reflective layer 50B and the antireflection layer 51. An inner lens 61A is provided on the main surface of the inner spacer 62A. The inner lens 61A and the inner spacer 62A are an integral part. The main surface of the inner lens 61A and the main surface of the inner spacer 62A are in contact with the main spacer 20A. The main spacer 20A may be omitted.

The photoelectric conversion element 1A of the second embodiment can also increase the sensitivity in the same manner as the photoelectric conversion element 1 of the first embodiment.

Further, in the photoelectric conversion element 1A provided with the inner lens 61A, the spot diameter SD of the light R becomes smaller at the incident opening 50B1 of the back surface side reflection layer 50B. When the lens of the camera is opened (when the F number is set small), the incident angle of the light R becomes large. Since the photoelectric conversion element 1A realizes the small spot diameter SD as described above, the light R is not irradiated from the main spacer 20A side to the back surface side reflective layer 50B even if the incident angle of the light R is large. Therefore, the photoelectric conversion element 1A of the second embodiment is advantageous in increasing the sensitivity because the loss of light R is suppressed.

In other words, the photoelectric conversion element 1A of the second embodiment can reduce the spot diameter SD of the light R in the incident opening 50B1 as compared with the photoelectric conversion element 1 of the first embodiment. According to this aspect, even when the incident angle of the light R changes, the light R can be surely passed through the incident opening 50B1. In other words, it is possible to suppress a state in which the light R that has passed through the inner lens 61A does not enter the photoelectric conversion unit 30A by reaching the back surface side reflective layer 50B. Therefore, since all the incident light R is guided to the photoelectric conversion unit 30A, it is possible to suppress a decrease in sensitivity due to a change in the incident angle.

Further, when the usage mode is such that the incident direction of the light R is constant, the area of the incident opening 50B1 may be reduced. According to this configuration, it is possible to suitably suppress the light R reciprocating inside the photoelectric conversion unit 30A from exiting from the incident opening 50B1 to the inner spacer 62A again. Therefore, the light R can be better confined in the photoelectric conversion unit 30A.

<Third Embodiment>
For example, the photoelectric conversion element 1 of the first embodiment may be further provided with an inner lens 61B. As shown in FIG. 16, the photoelectric conversion element 1B of the third embodiment includes an outer lens 10B, a main spacer 20B, an inner lens 61B, an inner spacer 62B, a photoelectric conversion unit 30B1, and a wiring unit 40B1. Be prepared. Of these, the outer lens 10B, the main spacer 20B, the inner lens 61B, and the inner spacer 62B constitute the optical direction conversion unit 60B. The photoelectric conversion element 1B of the third embodiment has a DTI 52 (see FIG. 2) which is the first configuration. Since the outer lens 10B, the main spacer 20B, the photoelectric conversion unit 30B1 and the wiring unit 40B1 are the same as the outer lens 10, the main spacer 20, the photoelectric conversion unit 30 and the wiring unit 40 of the first embodiment, detailed description thereof will be omitted. do. Hereinafter, the inner lens 61B and the inner spacer 62B will be described in detail.

The main surface of the inner lens 61B is spherical. The photoelectric conversion element 1B includes an outer lens 10B and an inner lens 61B. The refractive index (n2) of the inner lens 61B and the inner spacer 62B is larger than the refractive index (n1) of the outer lens 10B and the main spacer 20B (n2> n1).

The photoelectric conversion element 1B of the third embodiment can also increase the sensitivity in the same manner as the photoelectric conversion element 1 of the first embodiment.

The photoelectric conversion element 1A of the second embodiment includes an outer lens 10A and an inner lens 61A. The photoelectric conversion element 1B of the third embodiment includes an outer lens 10B and an inner lens 61B. For example, the photoelectric conversion element 1B may include an outer lens 10A and an inner lens 61B. That is, the photoelectric conversion element 1A of the third embodiment may adopt the shape of the outer lens 10 of the first embodiment as the shape of the outer lens. Further, as the shape of the outer lens, any one of the outer lenses 10S1 to 10S4 of the modified examples 1 to 4 may be adopted. Further, the shape of the outer lens 10 of the first embodiment may be adopted as the shape of the inner lens. Further, as the shape of the inner lens, any one of the outer lenses 10S1 to 10S4 of the modified examples 1 to 4 may be adopted.

<Fourth Embodiment>
In the photoelectric conversion element 1B of the third embodiment, the refractive index (n2) of the inner lens 61B is larger than the refractive index (n1) of the outer lens 10B. This relationship of refractive index may be reversed. That is, the refractive index (n2) of the inner lens 61C may be smaller than the refractive index (n1) of the outer lens 10C, as in the photoelectric conversion element 1C of the fourth embodiment shown in FIG. The photoelectric conversion element 1C of the fourth embodiment is a configuration example in which the refractive index (n2) of the inner lens 61C is smaller than the refractive index (n1) of the outer lens 10C (n2 <n1).

The photoelectric conversion element 1C of the fourth embodiment includes an outer lens 10C, a main spacer 20C, an inner lens 61C, an inner spacer 62C, a photoelectric conversion unit 30C, and a wiring unit 40C. Of these, the outer lens 10C, the main spacer 20C, the inner lens 61C, and the inner spacer 62C constitute the optical direction conversion unit 60C. Since the outer lens 10C, the main spacer 20C, the photoelectric conversion unit 30C and the wiring unit 40C are the same as the outer lens 10, the main spacer 20, the photoelectric conversion unit 30 and the wiring unit 40 of the first embodiment, detailed description thereof will be omitted. do. In this case, the inner lens 61C is a concave lens. The photoelectric conversion element 1C of the fourth embodiment can also increase the sensitivity in the same manner as the photoelectric conversion element 1 of the first embodiment.

<Fifth Embodiment>
In the first to fourth embodiments, the light R is formed by an outer lens or an inner lens. More specifically, the light R was molded before reaching the surface reflective layer 50F. That is, the molding of the light R is completed before the light R is incident on the photoelectric conversion unit 30, and all the light R reflected for the first time by the front surface side reflection layer 50F reaches the back surface side reflection layer 50B. The molding of the optical R is not limited to this configuration. Specifically, the molding of the light R may be performed at the time of the first reflection. Hereinafter, a configuration in which the light R is formed at the time of the first reflection will be described in detail with reference to FIG. The photoelectric conversion element 1D of the fifth embodiment includes a mirror 63 (reflecting portion) having a convex shape instead of the outer lens 10.

The photoelectric conversion element 1D of the fifth embodiment includes an outer lens 10D, a main spacer 20D, a photoelectric conversion unit 30D, a wiring unit 40D, and a light confinement unit 50D. The main spacer 20D sets the distance from the outer lens 10D to the photoelectric conversion unit 30D to a predetermined value. As a result, the focal point of the outer lens 10D is located inside the photoelectric conversion unit 30D. Since the photoelectric conversion unit 30D and the wiring unit 40D are the same as the photoelectric conversion unit 30 and the wiring unit 40 of the first embodiment, detailed description thereof will be omitted.

The mirror 63 has the same function as the outer lens 10 of the first embodiment. In the fifth embodiment, the outer lens 10D, the main spacer 20D, and the mirror 63 constitute the optical direction conversion unit 60D. The mirror 63 is provided at a position intersecting the optical axis Z. The mirror 63 is tilted with respect to a direction parallel to the optical axis Z. That is, a slope is formed on the surface of the mirror 63, which is a reflector. For example, if the direction facing the optical axis Z is inward and the opposite direction is outward, the mirror 63 is outward. It can be said that the main surface of the mirror 63 is a conical surface. The normal of the mirror 63 has a predetermined angle other than 0 degrees with respect to the optical axis Z. In this embodiment, the mirror 63 is integrated with the surface-side reflective layer 50FD. The mirror 63 is embedded in the wiring portion 40D. For example, the mirror 63 may be said to be a convex portion in which a part of the surface-side reflective layer 50FD is projected in a conical shape.

If the light R passing through the outer lens 10D is incident on the reflecting surface perpendicular to the optical axis Z, the reflected light R is focused on the optical axis Z. Then, the light R again exits from the photoelectric conversion unit 30D through the incident opening 50B1.

On the other hand, when the light R passing through the outer lens 10D is incident on the mirror 63 tilted with respect to the optical axis Z, the incident angle of the light R is different from the incident angle on the reflecting surface perpendicular to the optical axis Z. More specifically, as the angle of incidence increases, so does the angle of reflection. That is, the traveling direction of the light R is more outwardly biased. As a result, the reflected light R is not focused on one point on the optical axis Z. The reflected light R is focused on the circumference centered on the optical axis Z. Then, all the reflected light R reaches the back surface side reflection layer 50B, and then reciprocates between the back surface side reflection layer 50B and the front surface side reflection layer 50FD.

The photoelectric conversion element 1D of the fifth embodiment is formed by adding a dedicated process to the mirror 63. In the step of forming the mirror 63, the mirror 63 is formed so that the reflection angle increases the number of reflections. As a result, the same effect as that of the photoelectric conversion element 1 of the first embodiment in which the outer lens 10 is adopted can be expected. That is, the photoelectric conversion element 1D of the fifth embodiment can also increase the sensitivity in the same manner as the photoelectric conversion element 1 of the first embodiment.

<Sixth Embodiment>
The configuration for forming the light R by reflection is not limited to the mirror 63 of the fifth embodiment. A configuration capable of condensing the light R reflected on the circumference centered on the optical axis Z may be appropriately adopted. For example, FIG. 19 shows a photoelectric conversion element 1E of a sixth embodiment having another reflection structure instead of the mirror 63 of the fifth embodiment. The photoelectric conversion element 1E of the sixth embodiment pseudo-realizes the mirror 63 of the fifth embodiment by using a part of the wiring layer used for the image sensor and the integrated circuit.

The photoelectric conversion element 1E of the sixth embodiment includes an outer lens 10E, a main spacer 20E, a photoelectric conversion unit 30E, a wiring unit 40E, and a light confinement unit 50E. Of these, the outer lens 10E, the main spacer 20E, and the pseudo mirror structure 64 constitute the optical direction conversion unit 60E. Since the photoelectric conversion unit 30E and the wiring unit 40E are the same as the photoelectric conversion unit 30 and the wiring unit 40 of the first embodiment, detailed description thereof will be omitted.

The pseudo mirror structure 64 is a pseudo reflection structure composed of the silicon oxide region 44 in the wiring portion 40E and the

wiring layers

45a, 45b, 45c, 45d. The pseudo mirror structure 64 is a laminated structure of the silicon oxide region 44 and the

wiring layers

45a, 45b, 45c, 45d. The widths of the

wiring layers

45a, 45b, 45c, and 45d increase from the back surface side to the front surface side along the optical axis Z. In other words, the wiring layer 45d arranged on the front surface 40F side of the wiring portion 40E is wider than the wiring layer 45a arranged on the back surface 40B side of the wiring portion 40E. Both ends of the

wiring layers

45a, 45b, 45c, and 45d are in contact with the silicon oxide region 44. That is, the

wiring layers

45a, 45b, 45c, 45d used as the pseudo mirror structure 64 are physically separated from the wiring layers 41, 42 used for electrical connection. The light R passes through the silicon oxide region 44, but does not pass through the

wiring layers

45a, 45b, 45c, and 45d. According to such a configuration, the light R can reach the surface 40F side of the wiring portion 40E. The arrangement of the

wiring layers

45a, 45b, 45c, and 45d can be said to be stepped. When the size of one step of this staircase structure is sufficiently small with respect to the wavelength of the light R, it can be approximated as a reflecting surface at the angle of the slope.

The photoelectric conversion element 1E of the sixth embodiment can also increase the sensitivity in the same manner as the photoelectric conversion element 1 of the first embodiment.

<7th Embodiment>
The outer lens 10 of the first embodiment had the same cross-sectional shape including the optical axis Z. In other words, the outer lens 10 is a rotating body in which a predetermined cross-sectional shape is rotated around the optical axis Z. The outer lens 10 is not limited to such a rotating body. For example, as another example of the shape of the outer lens, the cylindrical outer lens 10F shown in FIGS. 20 and 21 can be mentioned. When this shape is adopted, the light R is incident on the photoelectric conversion unit 30 from the incident opening 50B1. Then, as shown in FIG. 21, the light R reaching the surface-side reflective layer 50F irradiates the two elongated cigar-shaped regions. The reflected light becomes thinner near the front surface and is reflected by the back surface side reflective layer 50B. After that, the reflection is repeated between the front surface side reflection layer 50F and the back surface side reflection layer 50B while expanding the diameters of the major axis and the minor axis. As a result, as long as the light R stays in the photoelectric conversion unit 30 made of silicon, the light R is absorbed by the photoelectric conversion unit 30 and the photoelectric conversion continues.

More specifically, the outer lens 10F of FIG. 20 has a predetermined cross-sectional shape extended along the sweep axis SL orthogonal to the optical axis Z. Such a three-dimensional shape can also be referred to as a cylindrical type. Then, the cross-sectional shape of the outer lens 10F orthogonal to the sweep axis SL is the same at every place. The cross-sectional shape orthogonal to the sweep axis SL may be, for example, the same as the cross section of the outer lens 10 of the first embodiment, and the cross-sectional shape orthogonal to the sweep axis KL may be a substantially trapezoidal shape. good. The outer lens 10F of FIG. 21 has a first region L14a and a second region L14b. Even in the outer lens 10F, the second curvature of the second region L14b is smaller than the first curvature of the first region L14a. In the outer lens 10 of the first embodiment, the first region L5a is surrounded by the second region L5b in an annular shape. On the other hand, in the outer lens 10F of the seventh embodiment, the first region L14a is sandwiched by the second region L14b. More specifically, the second region L14b sandwiches the first region L14a along the axis KL orthogonal to both the optical axis Z and the sweep axis SL.

According to the outer lens 10F of FIG. 21, the surface-side reflective layer 50F is irradiated with light R in an elliptical shape. The long axis direction of the elliptical irradiation region IR is along the direction of the sweep axis SL. On the other hand, the minor axis direction of the elliptical irradiation region IR is along the direction of the axis KL. The pair of irradiation regions IR are line-symmetrical with the sweep axis SL in between. That is, a pair of irradiation region IRs corresponding to each other are formed with the sweep axis SL interposed therebetween. The irradiation region IR gradually moves away from the optical axis Z while expanding the length of the short axis and the length of the long axis. As a result, the optical path length of the light R in the photoelectric conversion unit 30F1 can be sufficiently secured.

<8th Embodiment>
A more suitable example of the outer lens will be described. The outer lens 10G shown in FIG. 22 reflects light R multiple times by forming a substantially triangular shape (see FIG. 22B) whose curvature changes smoothly in the vertical direction (direction of the sweep axis SL). On the other hand, the outer lens 10G reduces the component of light reflected in the horizontal direction by making the cross-sectional shape in the horizontal direction (direction of the axis KL) a substantially spherical shape (see FIG. 22C).

FIG. 22A is a contour diagram of the outer lens 10G in a plan view. 22 (b) and 22 (c) are cross-sectional views showing the positions of the contour lines. The cross section 15a in FIG. 22B corresponds to the X1-X1'cross section in FIG. 5A. The cross section 15b in FIG. 22B corresponds to the X2-X2'cross section in FIG. 22A. The cross section 15c in FIG. 22 (c) corresponds to the cross section Y1-Y1'in FIG. 22 (a). The cross section 15d in FIG. 22 (c) corresponds to the cross section Y2-Y2'in FIG. 22 (a). The axes of FIGS. 22 (b) and 22 (c) indicate the positions of the contour lines of FIG. 22 (a). The region surrounded by the contour lines (8) corresponds to the first region L15a. Then, the second region L15b is formed so as to sandwich the first region L15a along the sweep axis SL.

FIG. 23 schematically shows the irradiation region IR of the light R formed by the outer lens 10G in a plan view. For example, in the light R applied to the cross section of Y1-Y1', the first reflected light has a spot shape (see IR1). The spot-shaped light component is absorbed by one round trip inside the photoelectric conversion unit 30. After that, the light R exits from the photoelectric conversion unit 30, so that a loss occurs. However, the light component that becomes a loss is relatively sufficiently small in view of the entire light incident on the photoelectric conversion unit 30.

<9th embodiment>
The photoelectric conversion element 1 of the first embodiment is a so-called back-illuminated type. The outer lens 10 used in the photoelectric conversion element 1 of the first embodiment may be used in the surface-illuminated photoelectric conversion element 1H as shown in FIG. 24. That is, even in the surface-illuminated photoelectric conversion element 1H, it is possible to increase the quantum efficiency by adopting the outer lens.

As shown in FIG. 24, the photoelectric conversion element 1H of the ninth embodiment includes an outer lens 10H, a main spacer 20H, a photoelectric conversion unit 30H, a wiring unit 40H, an optical confinement unit 50H, a support substrate 71H, and the like. Has. Of these, the outer lens 10H, the main spacer 20H, and the wiring unit 40H constitute an optical direction conversion unit 60H. The photoelectric conversion element 1H is different from the photoelectric conversion element 1 of the first embodiment in the arrangement of the photoelectric conversion unit 30H and the wiring unit 40H. Further, the photoelectric conversion element 1H is different from the photoelectric conversion element 1 of the first embodiment in that the support substrate 71H is provided.

The photoelectric conversion element 1H is provided with a wiring portion 40H between the main spacer 20H and the photoelectric conversion portion 30H. The photoelectric conversion element 1H of the ninth embodiment has a DTI 52 (see FIG. 2) which is the first configuration. The surface 40F of the wiring portion 40H is in contact with the main spacer 20H. The back surface 40B of the wiring unit 40H is in contact with the antireflection layer 51 provided on the back surface 30B of the photoelectric conversion unit 30H. In the wiring portion 40H, the light R is transmitted through the light transmission region 46H near the optical axis Z. Therefore, the first wiring layer 41 and the second wiring layer 42 that do not allow light R to pass through are not formed in the light transmission region 46H. That is, in the light transmission region 46H, the back surface 40B of the wiring portion 40 to the front surface 40F of the wiring portion 40 are integrally formed of silicon oxide. The surface-side reflective layer 50F is embedded in the wiring portion 40H closest to the photoelectric conversion portion 30H. The surface-side reflective layer 50F has an incident opening 50F1 provided in a portion constituting the light transmission region 46H.

The photoelectric conversion element 1H of the ninth embodiment can also increase the sensitivity in the same manner as the photoelectric conversion element 1 of the first embodiment.

Next, a method of manufacturing the image pickup apparatus 101 including the photoelectric conversion element 1H of the ninth embodiment will be described. In the method of manufacturing the image pickup apparatus 101, an intermediate wafer is first prepared by a step of forming a standard surface-illuminated image pickup apparatus. Next, the intermediate wafer is thinned, leaving a low concentration layer for the photodiode (second semiconductor region 32) and a p + layer for the electrodes (fourth semiconductor region 34). Next, the back surface side reflective layer 50B is formed. Next, the support substrate is bonded from the back surface. Finally, a lens unit including the outer lens 10G is formed. As a result, the photoelectric conversion element 1H having a structure in which light R is multiple-reflected inside the photoelectric conversion unit 30 made of silicon is obtained. Hereinafter, a method of manufacturing the image pickup apparatus 101 will be described in more detail.

FIG. 25A shows a state immediately after the step of forming the CMOS (CIS step) is completed. In the example of FIG. 25A, the second semiconductor region 32, the third semiconductor region 33, and the fourth semiconductor region 34 constituting the wiring unit 40H and the photoelectric conversion unit 30H are shown. First, a semiconductor layer to be later a second semiconductor region 32 is provided on the semiconductor region 31S. The thickness of the semiconductor layer is, for example, 20 μm. Then, the third semiconductor region 33 and the fourth semiconductor region 34 are provided on the semiconductor layer, respectively. After that, a step of forming the DTI 52 is performed. The DTI 52 is formed between the fourth semiconductor regions 34 formed adjacent to each other. As a result, the second semiconductor region 32, the third semiconductor region 33, and the fourth semiconductor region 34 constituting the photoelectric conversion unit 30H are formed, respectively. Subsequently, the wiring portion 40H is formed. The thickness of the wiring portion 40H is, for example, 5 μm.

Next, as shown in FIG. 25 (b), the first support substrate 81 is bonded. The first support substrate 81 is adhered to the surface 40F of the wiring portion 40.

Next, as shown in FIG. 26 (a), turn it over so that the first support substrate 81 is located on the lower side. Subsequently, the semiconductor region 31S located on the upper side is thinned. The semiconductor layer remaining after being thinned is the first semiconductor region 31. The thickness of the first semiconductor region 31 may be 1 μm or more and 2 μm or less. Further, the thickness of the first semiconductor region 31 may be 3 μm or more and 5 μm or less.

Next, as shown in FIG. 26B, the back surface side reflective layer 50B is provided. The back surface side reflective layer 50B may be an aluminum layer. Next, as shown in FIG. 27 (a), the second support substrate 82 is bonded. The second support substrate 82 is adhered to the back surface side reflective layer 50B. Next, as shown in FIG. 27 (b), the second support substrate 82 is turned over so as to be located on the lower side. Subsequently, the first support substrate 81 is removed.

Next, as shown in FIG. 28A, the lens unit 83 is formed in the wiring portion 40H. The lens unit 83 is a combination of a plurality of outer lenses 10H. Subsequently, as shown in FIG. 28 (b), the wafer is housed in the package 84. At this time, the back surface of the second support substrate 82 is fixed to the bottom surface of the package 84. Next, the wire 85 is bonded to the electrode pad 45 provided in the peripheral portion of the wiring portion 40H. Finally, the opening of the package 84 is closed by a plate 86 that is transparent to the light R. Through the above steps, an image pickup apparatus 101 including a plurality of photoelectric conversion elements 1H can be obtained.

The image pickup apparatus 101 including a plurality of photoelectric conversion elements 1H can be manufactured by a simpler process.

Prepare the intermediate wafer 104 shown in FIG. 29 (a). The intermediate wafer 104 includes a semiconductor substrate 87a, a semiconductor layer 87b including a second semiconductor region 32, a third semiconductor region 33, and a fourth semiconductor region 34, and a wiring portion 40H. A DTI 52 is formed on the semiconductor layer 87b. A surface-side reflective layer 50F is formed on the wiring portion 40H. The manufacturing process up to this point may be referred to as, for example, a "pre-process". Next, as shown in FIG. 29 (b), the semiconductor substrate 87a is thinned. Specifically, the thickness of the semiconductor substrate 87a is reduced from 750 μm to 200 μm. That is, the entire semiconductor substrate 87a is thinned. Next, in the semiconductor substrate 87a, the region L22a provided with the structure constituting the photoelectric conversion element 1H is thinned. For the partial thinning of the semiconductor substrate 87a, the thickness of the portion corresponding to the region L22a is reduced from 200 μm to about 21 μm or more and 25 μm. As a step of partially scraping the semiconductor substrate 87a, for example, an etching process can be adopted. The thinned portion becomes the first semiconductor region 31.

Subsequently, as shown in FIG. 30A, the back surface side reflective layer 50B is formed. The back surface side reflective layer 50B is an aluminum film formed by a sputtering method. Next, as shown in FIG. 30B, a lens unit 83H including a plurality of outer lenses 10H is formed on the surface 40F of the wiring portion 40H. Then, as shown in FIG. 31, it is mounted in the package 84. The specific procedure of the step shown in FIG. 30 (b) and the step shown in FIG. 31 may be the same as the steps shown in FIGS. 28 (a) and 28 (b) described above.

<10th Embodiment>
The photoelectric conversion element 1A of the second embodiment is also a so-called back-illuminated type. The inner lens 61A adopted for the photoelectric conversion element 1A of the second embodiment may be adopted for the surface-illuminated photoelectric conversion element 1K as shown in FIG. 32. That is, the photoelectric conversion element 1K of the tenth embodiment includes an outer lens 10K and an inner lens 61K.

The photoelectric conversion element 1K of the tenth embodiment includes an outer lens 10K, a main spacer 20K, an inner lens 61K, an inner spacer 62K, a wiring portion 40K, a photoelectric conversion portion 30K, an optical confinement portion 50K, and a support substrate. It has 71K and. Of these, the outer lens 10K, the main spacer 20K, the inner lens 61K, the inner spacer 62K, and the wiring portion 40K constitute an optical direction conversion portion 60K. The photoelectric conversion element 1K is different from the photoelectric conversion element 1A of the second embodiment in the arrangement of the photoelectric conversion unit 30K and the wiring unit 40K. Further, the photoelectric conversion element 1K is different from the photoelectric conversion element 1A of the second embodiment in that the support substrate 71K is provided.

The photoelectric conversion element 1K of the tenth embodiment can also increase the sensitivity in the same manner as the photoelectric conversion element 1 of the first embodiment.

<11th Embodiment>
FIG. 33 is a plan view of the photoelectric conversion element 1T of the eleventh embodiment. In the eleventh embodiment, particular attention is paid to the DTI structure 55T.

The DTI structure 55T shown in FIG. 33 is intended to further enhance the absorption of light R that contributes to the generation of electric charges in the photoelectric conversion unit 30. The pixel area 90T surrounded by the DTI structure 55T corresponds to one pixel. The pixel region 90T includes a photoelectric conversion region 91T and a charge accumulation detection region 92T. The planar shape of the photoelectric conversion region 91T is a regular octagon. The planar shape of the charge accumulation detection region 92T is a square. One side of the photoelectric conversion region 91T, which is a regular octagon, protrudes outward, and the protruding portion is the charge accumulation detection region 92T. The length of one side of the charge accumulation detection region 92T is equal to the length of one side of the photoelectric conversion region 91T.

The photoelectric conversion region 91T includes a photodiode formed by a second semiconductor region 32 and a third semiconductor region 33 (see FIG. 1). Further, the center of the photoelectric conversion region 91T coincides with the center of the incident aperture 50B1. For example, the shape of the incident opening 50B1 may be a regular octagon. In other words, the planar shape of the photoelectric conversion region 91T may be similar to the planar shape of the incident opening 50B1.

The charge accumulation detection area 92T includes a plurality of charge accumulation detection units 70. More specifically, all of the plurality of charge accumulation detection units 70 are arranged in the charge accumulation detection region 92T, and are not arranged in the photoelectric conversion detection region 91. The plurality of charge storage detection units 70 are connected to a photodiode formed by the second semiconductor region 32 and the third semiconductor region 33. The charge generated by the photoelectric conversion unit 30 is distributed to the charge accumulation detection unit 70 at predetermined timing intervals.

By referring to FIG. 34, the action and effect of the photoelectric conversion element 1T of the eleventh embodiment can be easily understood. FIG. 34 shows a plan-viewed photoelectric conversion element 1T shown in FIG. 33 overlaid with an irradiation region IR of light R in the surface-side reflective layer 50F shown in FIG. 7. The photoelectric conversion element 1T of the eleventh embodiment includes an outer lens. The photoelectric conversion element 1T of the eleventh embodiment may include another optical molding component (inner lens 61A or the like) included in the photoelectric conversion element 1A or the like. That is, the photoelectric conversion element 1T of the eleventh embodiment may have a configuration in which the light R is formed concentrically.

Then, the light R is irradiated to a plurality of annular regions centered on the optical axis Z, and gradually spreads outward. Since the photoelectric conversion region 91T is a regular octagon, the distance from the optical axis Z to the DTI structure 55T is equal in eight directions. That is, the progress of light R is not hindered in a specific direction. As a result, the light R that repeats reflection can be suitably absorbed by the photoelectric conversion unit 30T.

Here, when the light R is incident on the charge storage detection unit 70, the charge may be generated in the charge storage detection unit 70 as well. Since the charge storage detection unit 70 stores the charges distributed based on a predetermined rule, the stored charges without following the rules are noise. The charge accumulation detection region 92T is arranged so as to be adjacent to the photoelectric conversion region 91T. According to this arrangement, the charge accumulation detection unit 70 is sufficiently separated from the optical axis Z. As a result, the light R is repeatedly reflected and sufficiently absorbed until it reaches the charge accumulation detection region 92T. Therefore, the light R incident on the charge accumulation detection region 92T can be substantially ignored.

Note that, in FIG. 33, the DTI structure 55T is not shown at the boundary between the photoelectric conversion region 91T and the charge accumulation detection region 92T. The charge accumulation detection region 92T is optically separated from the photoelectric conversion region 91T and needs to be electrically connected. Therefore, for example, a DTI 52B having a third structure shown in FIG. 4 may be provided at the boundary between the photoelectric conversion region 91T and the charge accumulation detection region 92T. According to this arrangement, the light R moving from the photoelectric conversion region 91T to the charge accumulation detection region 92T can be further reduced, and the light R can be confined in the photoelectric conversion region 91T. That is, since the DTI 52B casts a shadow on the charge accumulation detection region 92T, it is possible to make it difficult for the light R to hit the PN junction constituting the charge accumulation detection region 92T. As a result, the parasitic sensitivity of the charge accumulation detection unit 70 can be reduced.

On the other hand, DTI52A having a second structure may be adopted as the partition wall surrounding the photoelectric conversion region 91T. Similarly, the DTI 52A having the second structure may be adopted as the partition wall surrounding the charge accumulation detection region 92T. According to the DTI 52A having the second structure, the photoelectric conversion elements 1T adjacent to each other can be reliably separated optically and electrically.

According to the DTI structure 55T shown in FIG. 33, as shown in FIG. 35, an image pickup device 101T in which a plurality of photoelectric conversion elements 1T are arranged in a grid pattern can be configured. The grid-like arrangement means a state in which a plurality of photoelectric conversion elements 1T are arranged along axes orthogonal to each other. For example, in a certain photoelectric conversion element 1T, the three sides constituting the charge accumulation detection region 92T are the photoelectric conversion regions 91T of each photoelectric conversion element 1T adjacent to the photoelectric conversion element 1T in the vertical, horizontal, and diagonal directions. It touches each side. According to the grid arrangement, the intervals (pitch) of the photoelectric conversion elements 1T along the horizontal direction can be made equal. Similarly, the intervals (pitch) of the photoelectric conversion elements 1T along the vertical direction can be made equal.

The image pickup apparatus 101T provided with the photoelectric conversion element 1T of the eleventh embodiment includes an outer lens 10T that causes multiple reflection of light in the photoelectric conversion unit 30T. In the DTI structure 55T shown in FIG. 33, the distance from the incident opening 50B1 of the back surface side reflective layer 50B to the charge accumulation detection unit 70 is the longest. Further, the DTI structure 55T reduces the volume around which the light R wraps around. Therefore, the DTI structure 55T can satisfactorily reduce the parasitic sensitivity caused by the non-demodulation component light directly incident on the charge accumulation detection region 92T. As a result, the photoelectric conversion element 1T of the eleventh embodiment can exhibit high quantum efficiency with respect to near-infrared light.

According to the DTI structure 55T shown in FIG. 33, another arrangement as shown in FIG. 36 can be adopted. The arrangement shown in FIG. 36 is a staggered arrangement. Further, it can be said that the arrangement shown in FIG. 36 is a so-called honeycomb structure arrangement. When the photoelectric conversion element 1T is arranged with a pitch (P) in the horizontal direction, the photoelectric conversion element 1T adjacent in the vertical direction is arranged at a position ½ of a certain pitch (P). With such an arrangement, horizontal and vertical resolution can be increased.

Further, the photoelectric conversion element 1T may include an outer lens having the shape shown in FIG. 22. FIG. 37 is a plan-viewed photoelectric conversion element 1T shown in FIG. 33 overlaid with an irradiation region IR of light R in the surface-side reflective layer 50F shown in FIG. 23. When the outer lens having the shape shown in FIG. 22 is provided, the sweep axis SL of the outer lens is arranged so as to be parallel to the axis connecting the photoelectric conversion region 91T and the charge accumulation detection region 92T. Then, the irradiation region IR of the light R does not proceed from the incident opening 50B1 toward the charge accumulation detection region 92T. Therefore, it is possible to suitably suppress the generation of noise due to the incident light R on the charge accumulation detection region 92T.

<12th Embodiment>
In the eleventh embodiment, the DTI structure 55T forming the regular octagonal photoelectric conversion region 91T is exemplified. The shape of the photoelectric conversion region 91T is not limited to a regular octagon. As shown in FIG. 38, the photoelectric conversion region 91R may be rectangular. FIG. 38 is a plan view of a TOF type photoelectric conversion element 1R having 4 taps and 1 drain. In FIG. 39, the irradiation region IR shown in FIG. 21B is superimposed on the photoelectric conversion element 1R of FIG. 38. A shadow is created by the DTI structure 55R in order to reduce the sensitivity of parasitism to the charge accumulation detection unit 70. Further, the outer lens 10F shown in the seventh embodiment causes the reflected light to travel in a direction orthogonal to the direction of the charge accumulation detection unit 70. As a result, since the light R is confined in the photoelectric conversion unit 30, it is suppressed that the light R is directly incident on the charge accumulation detection region 92R.

In the photoelectric conversion element 1R of the twelfth embodiment, the shape of the pixel region 90R is substantially rectangular in a plan view. The pixel region 90R has a rectangular photoelectric conversion region 91R and a rectangular charge storage detection region 92R. By providing the DTI 52A in the pixel region 90R, it is divided into a photoelectric conversion region 91R and a charge accumulation detection region 92R. DTI52A is adopted as the four partition walls surrounding the pixel region 90R. Although not shown in FIG. 38, for example, a DTI 52B having a third structure shown in FIG. 4 may be provided between the DTI 52A partitioning the pixel region 90R.

In the photoelectric conversion region 91R, a photodiode formed by the second semiconductor region 32 and the third semiconductor region 33 is arranged. Further, in the illustration of FIG. 38, a pair of drains 72 are arranged in the photoelectric conversion region 91R. The other charge accumulation detection unit 70 is arranged in the charge accumulation detection region 92R.

When such a pixel region 90R is adopted, the photoelectric conversion element 1R adopts the optical molding component of the seventh embodiment. As shown in FIG. 39, the molded light repeatedly reflects along a predetermined axis KL. The axis KL is orthogonal to the direction in which the photoelectric conversion region 91R and the charge accumulation detection region 92R are arranged in the example of FIG. 38. Therefore, the outer lens 10P is arranged so that the direction in which the photoelectric conversion region 91R and the charge accumulation detection region 92R are lined up coincides with the sweep axis SL. Then, the region where the molded light is incident is aligned in a direction orthogonal to the direction in which the photoelectric conversion region 91R and the charge accumulation detection region 92R are aligned. As described above, when the direction in which the light is diffused is a specific direction, the photoelectric conversion region 91R may be rectangular.

Hereinafter, the results of performing some calculations (calculation examples 2, 3, and 4) for confirming the effect of the outer lens will be described. In addition, the results of calculations (calculation example 1) for confirming the effect of the outer lens, which is a comparative example, will also be described.

First, the analysis model used in the simulation will be described with reference to FIG. 40. As shown in FIG. 40, the analysis model 103P includes an outer lens 10P. The analysis model 103M includes an outer lens 10M. The analysis model 103N includes an outer lens 10N. In FIG. 40, three

outer lenses

10P, 10M, and 10N are superimposed and shown. The configurations of the main spacer 20 and the photoelectric conversion unit 30 are the same in Calculation Examples 1 to 4.

The following are set as parameters that define the shape of the outer lens 10P of Calculation Example 1. FIG. 41 is a perspective view of the outer lens 10P used in the calculation example 1.
Lens diameter: 8.4 μm
Lens thickness: 5.0 μm
Base thickness: 0.8 μm
Offset: 1
Base: 1
Rate: 1

The following are set as parameters that define the shape of the outer lens 10M of Calculation Example 2. As can be understood by comparing with the outer lens 10P of the calculation example 1, the outer lens 10M of the calculation example 2 has a large curvature at the top and a small curvature at the side. FIG. 42 is a perspective view of the outer lens 10M used in Calculation Example 2.
Lens diameter: 8.4 μm
Lens thickness: 5.0 μm
Base thickness: 0.8 μm
Offset: 1000
Base: 1
Rate: 1

The following are set as parameters that define the shape of the outer lens 10N of Calculation Example 3. FIG. 43 is a perspective view of the outer lens 10N used in the calculation example 3. The lens thickness of the outer lens 10N is different from the lens thickness of the outer lens 10M. The parameters of the other outer lens 10N are the same as the parameters of the outer lens 10M.
Lens diameter: 8.4 μm
Lens thickness: 3.0 μm
Base thickness: 0.8 μm
Offset: 1000
Base: 1
Rate: 1

The refractive index of the

outer lenses

10P, 10M, and 10N was 1.58.

The first layer L1 corresponds to the main spacer 20. The details of the first layer L1 and the second layer L2 are as follows.
First layer L1: Microlens material, refractive index (1.54 to 1.58)
Second layer L2: Dielectric multilayer film (material: silicon nitride, silicon oxide), refractive index (1.46 to 1.92)

The third layer L3 corresponds to the photoelectric conversion unit 30. The details of the third layer L3 are as follows.
Third layer L3: Material / Silicon (Si), Refractive index (automatic setting)

The conditions of the light incident on the

outer lenses

10P, 10M, and 10N were set as follows.
Wavelength: 870 nm
Direction: Vertical incident (ζ = 0 °, φ = 0 °)
Light intensity: 1 W / cm ^-2
Incident position: Two-dimensional arrangement (60 points (X) x 60 points (Y) = 3600 points)

Using the above conditions, a numerical simulation was performed by the ray tracing method. Then, as a result of the numerical simulation, the distribution of the light intensity was obtained as a contour diagram.

<Calculation example 1 (comparative example)>
In Calculation Example 1, the outer lens 10P was adopted. 44 and 45 are contour diagrams of the distribution of light intensity. In the contour diagram of FIG. 44, it was found that the region A37a had the strongest light intensity, and the light intensity decreased as the region A37b was approached. Further, according to FIG. 44, a region A37a having a strong light intensity appeared in the vicinity of the surface of the photoelectric conversion unit 30 (Z = 0.0 μm). Further, FIG. 45 is a contour diagram in which a portion of FIG. 44 where Z = 15 μm is viewed in cross section. For example, the position where Z = 15 μm can be regarded as the position where the surface-side reflective layer 50F (see FIG. 1) is arranged. Then, according to FIG. 45, it was found that the region having strong light intensity was generated in the region A38a near the center and the region A38b near the periphery. That is, it was found that the outer lens 10P does not have an annular shape in the light intensity distribution. According to such a distribution, the light R irradiating the region A38a near the center is reflected by the surface-side reflective layer 50F and then exits from the photoelectric conversion unit 30 through the incident opening 50B1 (see FIG. 1). It ends up. That is, of the incident light R, a light component that does not generate an electric charge is generated in the photoelectric conversion unit 30.

<Calculation example 2>
In Calculation Example 2, the outer lens 10M was adopted. 46 and 47 are contour diagrams of the distribution of light intensity. In the contour diagram of FIG. 46, it was found that the region A39a had the strongest strength, and the strength decreased as the region A39b was approached. Further, according to FIG. 46, a region A39a having a strong light intensity appeared in the vicinity of the surface of the photoelectric conversion unit 30 (Z = 0.0 μm). Further, FIG. 47 is a contour diagram in which a portion in FIG. 46 where Z = 15 μm is viewed in cross section. In Calculation Example 2, it was found that the light intensity of the region A40a near the center was weak, gradually increased toward the outside, reached the maximum value in the region A40b, and then decreased. That is, it was found that the outer lens 10M has an annular shape in the light intensity distribution. According to such a distribution, for example, when the light radiated to the region A40b is reflected by the front surface side reflection layer 50F, it does not exit from the photoelectric conversion unit 30 through the incident opening 50B1 but toward the back surface side reflection layer 50B. move on. Therefore, it was found that the outer lens 10M can change the traveling direction so as to suitably confine the light R in the photoelectric conversion unit 30.

By the way, refer to the contour diagram of FIG. 46 again. Focusing on the distribution of the light intensity of the third layer L3 in the contour diagram of FIG. 46, it was found that the light R spreads in the third layer L3 (photoelectric conversion unit 30) (see arrow S39). The spread of the light R in the third layer L3 can be better understood by looking at the ray diagram of FIG. The cause of the spread of this light R was considered. FIG. 49 illustrates only one of the light rays shown in FIG. 48. The light ray L41a indicates incident light. The light ray L41c indicates refracted light. As shown in FIG. 49, it is considered that the cause of the spread of the light R is that the intersection L41p of the optical axis Z of the outer lens 10M and the light rays L41a and L41c is located on the surface of the third layer L3. ..

<Calculation example 3>
Therefore, we investigated the factors that suppress the spread of light R. We paid attention to the lens thickness as an element that suppresses the spread of light R. In Calculation Example 3, the thickness of the outer lens 10N was set to 3 μm.

According to the contour diagram shown in FIG. 50, it was found that the distribution of the light intensity in the third layer L3 was narrowed down in the range L43a in the range of Z = 0 μm to 10.0 μm. This situation can be clearly understood from the region L44a in the ray diagram of FIG. The cause of this distribution of light R was considered. FIG. 52 illustrates only one of the light rays shown in FIG. 51. The light ray L45a indicates incident light. The light ray L45c indicates refracted light. As shown in FIG. 52, it is considered that the cause of the distribution of the light R is that the intersection L45p of the optical axis Z of the outer lens 10N and the light ray L45c is located inside the third layer L3.

In addition, the shape of the light intensity distribution in the third layer L3 was confirmed. 53, 54 and 55 are contour diagrams of light intensity at different cross-sectional positions. FIG. 53 (a) corresponds to Z = 0 μm, and FIG. 53 (b) corresponds to Z = 5 μm. FIG. 54 (a) corresponds to Z = 10 μm, and FIG. 54 (b) corresponds to Z = 15 μm. FIG. 55 (a) corresponds to Z = 20 μm, and FIG. 55 (b) corresponds to Z = 25 μm. As shown in each figure, it was found that the light intensity distribution was annular in each cross section.

1,1A, 1B, 1C, 1D, 1E, 1H, 1K, 1R, 1T ...

Photoelectric conversion element

10,10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H, 10K, 10M, 10N, 10P, 10T ... outer lens, 30,30A, 30B1,30C, 30D, 30E, 30F1,30H, 30K, 30T ... photoelectric conversion unit, 30B ... photoelectric conversion unit back surface (first surface), 30F ... photoelectric conversion unit surface (first surface) 2), 50, 50D, 50E, 50H, 50K ... Optical confinement part, 61A, 61B, 61C, 61K ... Inner lens, 63 ... Mirror (reflection part), L5a, L14a, L15a ... First region, L5b, L14b, L15b ... second region, R, R6a, R6b, R7a ... light, Z ... optical axis.

Claims

A photoelectric conversion unit that receives light and generates an electric charge,
A charge storage detection unit that stores the charge received from the photoelectric conversion unit, and a charge storage detection unit.
A first reflective layer provided on the first surface side of the photoelectric conversion unit and including an opening for receiving the light, and a second surface side of the photoelectric conversion unit opposite to the first surface. A light confinement portion that confine the light in the photoelectric conversion unit so that the light reciprocates in the photoelectric conversion unit.
It includes a first lens arranged on the first surface side, and includes an optical direction conversion unit that determines the traveling direction of the light in the photoelectric conversion unit.
The optical direction changing unit is arranged outside the region sandwiched between the first surface and the second surface, and the light of the light between the first surface and the second surface. A photoelectric conversion element that advances the light in a direction away from the optical axis of the first lens each time the reflection is repeated.
In the cross-sectional shape including the optical axis of the first lens, the line segment indicating the surface that receives the light includes the first curved portion and the second curved portion that is farther from the optical axis than the first curved portion. Including the part
The photoelectric conversion element according to claim 1, wherein the curvature of the second curved portion is smaller than the curvature of the first curved portion.
The photoelectric conversion element according to claim 1, wherein in the cross-sectional shape including the optical axis of the first lens, the line segment indicating the surface that receives the light includes a portion defined as an arc.
The photoelectric conversion element according to claim 1, wherein in the cross-sectional shape including the optical axis of the first lens, the line segment indicating the surface that receives the light includes a portion defined as a parabola.
In the cross-sectional shape including the optical axis of the first lens, the line segment indicating the surface that receives the light is a first straight line portion and a second straight line portion farther from the optical axis than the first straight line portion. Including the part
The second tilt angle between the virtual reference axis orthogonal to the optical axis and the second straight line portion is larger than the first tilt angle between the virtual reference axis and the first straight line portion. , The photoelectric conversion element according to claim 1.
The photoelectric conversion element according to any one of claims 2 to 5, wherein the shape of the first lens is a shape symmetrical with respect to the optical axis.
The photoelectric conversion element according to any one of claims 2 to 5, wherein the shape of the first lens is a shape obtained by extending the cross-sectional shape in a direction orthogonal to the optical axis.
Any of claims 1 to 7, wherein the optical direction changing unit further includes, in addition to the first lens, a second lens arranged between the first lens and the first surface. The photoelectric conversion element according to claim 1.
In the cross-sectional shape of the second lens including the optical axis, the line segment indicating the surface that receives the light includes a third curved portion and a fourth curve that is farther from the optical axis than the third curved portion. Including the part
The photoelectric conversion element according to claim 8, wherein the curvature of the fourth curved portion is smaller than the curvature of the third curved portion.
The photoelectric conversion element according to claim 8, wherein in the cross-sectional shape including the optical axis of the second lens, the line segment indicating the surface that receives the light includes a portion defined as an arc.
The photoelectric conversion element according to claim 8, wherein in the cross-sectional shape including the optical axis of the second lens, the line segment indicating the surface that receives the light includes a portion defined as a parabola.
In the cross-sectional shape including the optical axis of the second lens, the line segment indicating the surface that receives the light is a third straight line portion and a fourth straight line portion farther from the optical axis than the third straight line portion. Including the part
The fourth tilt angle between the virtual reference axis orthogonal to the optical axis and the fourth straight line portion is larger than the third tilt angle between the virtual reference axis and the third straight line portion. The photoelectric conversion element according to claim 8.
The photoelectric conversion element according to any one of claims 1 to 12, wherein the optical direction conversion unit includes a reflection unit arranged on the second surface side.
The light confinement portion further has a first partition wall portion surrounding the photoelectric conversion portion.
One end surface of the first partition wall portion cooperates with the first reflective layer to sandwich a part of the photoelectric conversion portion.
The photoelectric conversion element according to any one of claims 1 to 13, wherein the other end surface of the first partition wall portion is flush with the second surface of the photoelectric conversion unit.
The light confinement portion further has a second partition wall portion surrounding the photoelectric conversion portion.
One end surface of the second partition wall portion is flush with the first surface of the photoelectric conversion portion.
The photoelectric conversion element according to any one of claims 1 to 14, wherein the other end surface of the second partition wall cooperates with the second reflective layer to sandwich a part of the photoelectric conversion portion.
The light confinement portion further has a third partition wall portion surrounding the photoelectric conversion portion.
One end surface of the third partition wall portion is flush with the first surface of the photoelectric conversion portion.
The photoelectric conversion element according to any one of claims 1 to 15, wherein the other end surface of the third partition wall portion is flush with the second surface of the photoelectric conversion unit.
The photoelectric conversion unit includes a portion of the first reflective layer that overlaps with the opening.
The photoelectric conversion element according to any one of claims 1 to 16, wherein the charge accumulation detection unit does not include a portion of the first reflective layer that overlaps with the opening.
The light confinement portion is opened in a pixel region having a photoelectric conversion region including a pn junction formed by the photoelectric conversion portion and a charge storage detection region including the charge storage detection unit when viewed from the incident direction of the light. The photoelectric conversion element according to any one of claims 1 to 13, which includes an outer partition wall portion surrounding the photoelectric conversion region and the charge accumulation detection region so as to confine the light incident from the light.
One end face of the outer partition wall is in contact with the semiconductor region constituting the pn junction.
The photoelectric conversion element according to claim 18, wherein the other end surface of the outer partition wall portion is flush with the second surface of the photoelectric conversion unit.
One end surface of the outer partition wall portion is flush with the first surface of the photoelectric conversion unit.
The other end face of the outer partition wall is in contact with the semiconductor region constituting the pn junction.
The photoelectric conversion element according to claim 18.
One end surface of the outer partition wall portion is flush with the first surface of the photoelectric conversion unit.
The photoelectric conversion element according to claim 18, wherein the other end surface of the outer partition wall portion is flush with the second surface of the photoelectric conversion unit.
The light confinement portion is provided between the photoelectric conversion region and the charge storage detection region when viewed from the incident direction of the light, and has an inner partition portion that optically separates the charge storage detection region from the photoelectric conversion region. The photoelectric conversion element according to any one of claims 18 to 21, which includes.
One end face of the inner partition wall is in contact with the semiconductor region constituting the pn junction.
22. The photoelectric conversion element according to claim 22, wherein the other end surface of the inner partition wall is flush with the second surface of the photoelectric conversion unit.
One end surface of the inner partition wall portion is flush with the first surface of the photoelectric conversion unit.
22. The photoelectric conversion element according to claim 22, wherein the other end surface of the inner partition wall is in contact with a semiconductor region constituting the pn junction.
One end surface of the inner partition wall portion is flush with the first surface of the photoelectric conversion unit.
22. The photoelectric conversion element according to claim 22, wherein the other end surface of the inner partition wall is flush with the second surface of the photoelectric conversion unit.