Photoelectric conversion element and its manufacturing method

Abstract

A method for manufacturing a photoelectric conversion element according to one embodiment of the present application includes the following steps: a step of preparing a substrate, wherein the substrate includes: a semiconductor substrate having a main surface, a first electrode located above the main surface, a plurality of second electrodes located above the main surface and arranged in one dimension or two dimensions, and a photoelectric conversion film that at least covers the plurality of second electrodes; a step of forming a mask layer on the photoelectric conversion film, wherein the mask layer includes a coating portion that covers a portion of the photoelectric conversion film that overlaps with the plurality of second electrodes when viewed from above and has conductivity; and a step of removing a portion of the photoelectric conversion film by immersing the substrate and the mask layer in an etchant.

Description

Technical Field

[0001] The present application relates to a photoelectric conversion element and a method for manufacturing the same. Background Art

[0002] An imaging device having a photoelectric conversion unit disposed above a semiconductor substrate is known. This structure is also called a stacked type, and for example, Japanese Patent Publication Nos. 2006-032714, 2011-228648, 2015-056554, and 2003-234460 disclose imaging devices having a photoelectric conversion film disposed above a semiconductor substrate.

[0003] In the stacked structure, a CCD (Charge Coupled Device) circuit or a CMOS (Complementary Metal Oxide Semiconductor) circuit for signal readout is provided on a semiconductor substrate supporting a photoelectric conversion unit. According to the stacked structure, since the portion responsible for photoelectric conversion is located above the semiconductor substrate, a high aperture ratio can be easily obtained. In addition, the advantage of having sensitivity (sensitivity) even in the near-infrared region that does not show absorption with respect to Si can be obtained. For reference, the entire disclosure of Japanese Patent Publication No. 2006-032714, Japanese Patent Publication No. 2011-228648, Japanese Patent Publication No. 2015-056554 and Japanese Patent Publication No. 2003-234460 is cited in this specification.

[0004] As a material for forming a photoelectric conversion film, an organic material is typically used. Japanese Patent Publication No. 2006-032714 discloses a patterning method using dry etching for an organic material layer as a photoelectric conversion film. Japanese Patent Publication No. 2011-228648 and Japanese Patent Publication No. 2015-056554 propose suppressing white damage defects by reducing the stress applied to the organic photoelectric conversion film. Here, "white damage defects" refers to the following phenomenon: due to reasons such as local concentration of stress, the photoelectric conversion film is damaged, and dark current is generated in the damaged area, thereby generating a bright part like white damage in the image. Summary of the invention

[0005] The manufacturing method of the photoelectric conversion element of the non-limiting exemplary embodiment of the present application includes the following steps: a step of preparing a substrate, wherein the substrate includes: a semiconductor substrate having a main surface, a first electrode located above the main surface, a plurality of second electrodes located above the main surface and arranged in one dimension or two dimensions, and a photoelectric conversion film covering at least the plurality of second electrodes; a step of forming a mask layer on the photoelectric conversion film, wherein the mask layer includes a coating portion covering a portion of the photoelectric conversion film that overlaps with the plurality of second electrodes when viewed from above and has conductivity; and a step of removing a portion of the photoelectric conversion film by immersing the substrate and the mask layer in an etchant.

[0006] The general or specific scheme can be realized by elements, devices, apparatuses or systems. In addition, the general or specific scheme can also be realized by any combination of elements, devices, apparatuses, systems and methods.

[0007] Additional effects and advantages of the disclosed embodiments are made clear by the specification and drawings. The effects and / or advantages are provided by each embodiment or feature disclosed in the specification and drawings, and not all embodiments or features are required to obtain one or more of them. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a diagram schematically showing a cross section of an exemplary photoelectric conversion element obtained by the production method according to an embodiment of the present application.

[0009] Figure 2 When viewed from the main surface side of the semiconductor substrate Figure 1 Schematic top view of the photoelectric conversion element shown.

[0010] Figure 3 Yes means Figure 2 A diagram showing an exemplary circuit configuration of a pixel shown.

[0011] Figure 4 Yes means Figure 2 A schematic cross-sectional view of an exemplary device structure of a pixel is shown.

[0012] Figure 5 This is a diagram schematically showing a cross section of another exemplary photoelectric conversion element obtained by the production method according to the embodiment of the present application.

[0013] Figure 6 This is a flowchart showing an outline of a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0014] Figure 7It is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0015] Figure 8 It is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0016] Fig. 9 is a schematic cross-sectional view showing an example of the structure of a photoelectric conversion film.

[0017] Fig.10 About Fig. 9 Energy diagram of the photoelectric conversion film illustrated in FIG.

[0018] Fig.11 It is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0019] Fig.12 It is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0020] Fig.13 It is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0021] Fig.14 It is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0022] Fig.15A It is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0023] Fig. 15B This is a schematic cross-sectional view showing, in an enlarged manner, a side end portion of the photoelectric conversion film after a step of removing a portion of the photoelectric conversion film by wet etching.

[0024] Fig. 15C This is a schematic cross-sectional view showing, in an enlarged manner, a side end portion of the photoelectric conversion film after a step of removing a portion of the photoelectric conversion film by wet etching.

[0025] Fig.16A It is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application.

[0026] Fig. 16B This is a schematic cross-sectional view showing an enlarged side end portion of the photoelectric conversion structure after the counter electrode is formed.

[0027] Fig.17This is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to another exemplary embodiment of the present application.

[0028] Fig.18 This is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to another exemplary embodiment of the present application.

[0029] Fig.19 This is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to another exemplary embodiment of the present application.

[0030] Fig. 20 This is a schematic cross-sectional view for explaining a method for manufacturing a photoelectric conversion element according to another exemplary embodiment of the present application.

[0031] Fig.21 This is a schematic cross-sectional view showing the structure of the laminated body of Comparative Example 1.

[0032] Fig. 22 It is a schematic cross-sectional view showing the structure of the laminated body after etching.

[0033] Explanation of symbols

[0034] 10 pixels

[0035] 14 Electron blocking film

[0036] 14s electron blocking layer

[0037] 16. Hole blocking film

[0038] 16s hole blocking layer

[0039] 16C, 16D, 140C, 146C mask layer

[0040] 16m, 134 organic layer

[0041] 100A, 100B Photoelectric conversion element

[0042] 110 first electrode

[0043] 120 second electrode

[0044] 130A, 130B Photoelectric conversion structure

[0045] 130q, 130r, 130s photoelectric conversion film

[0046] 132 Photoelectric conversion layer

[0047] 136 Oxide semiconductor layer

[0048] 140 pairs of electrodes

[0049] 140m transparent conductive layer

[0050] 150 protective layer

[0051] 160 Interlayer insulation layer

[0052] 190 Semiconductor substrate

[0053] 191, 192, 193, 194, 195 impurity regions

[0054] 200, 200A, 200B, 200C, 210 Base

[0055] 300 Etching Agent

[0056] 540 Photoelectric conversion unit

[0057] 550 Readout Circuit

[0058] 560 covered part DETAILED DESCRIPTION

[0059] An outline of one aspect of the present application is as follows.

[0060] [Project 1]

[0061] The method for manufacturing a photoelectric conversion element of item 1 of the present application comprises the following steps:

[0062] A step of preparing a substrate, the substrate comprising: a semiconductor substrate having a main surface, a first electrode located above the main surface, a plurality of second electrodes located above the main surface and arranged one-dimensionally or two-dimensionally, and a photoelectric conversion film covering at least the plurality of second electrodes;

[0063] forming a mask layer on the photoelectric conversion film, the mask layer including a covering portion covering a portion of the photoelectric conversion film overlapping with the plurality of second electrodes in a plan view and having conductivity; and

[0064] A step of removing a portion of the photoelectric conversion film by immersing the substrate and the mask layer in an etchant.

[0065] According to the configuration of item 1, since a portion of the photoelectric conversion film is removed by wet etching, the stress of the photoelectric conversion film is relieved and the generation of damage defects can be suppressed. In addition, since a conductive mask layer is used when wet etching is applied, the portion of the mask layer remaining after etching can be used as, for example, a charge blocking layer or a light-transmitting electrode.

[0066] [Project 2]

[0067] In the method for manufacturing a photoelectric conversion element according to item 1,

[0068] The step of forming the mask layer includes forming the mask layer using an organic material.

[0069] An etching rate of the mask layer in the step of removing a portion of the photoelectric conversion film may be lower than an etching rate of the photoelectric conversion film in the step of removing a portion of the photoelectric conversion film.

[0070] According to the configuration of item 2, since the photoelectric conversion film can be preferentially dissolved in wet etching, even if an organic material is used as the material of the mask layer, the mask layer can remain on the photoelectric conversion film after wet etching.

[0071] [Item 3]

[0072] In the method for manufacturing a photoelectric conversion element according to item 2, the organic material may be a photoelectric conversion material.

[0073] According to the configuration of item 3, the portion remaining after etching in the covering portion, which is a part of the mask layer, can be used as a part of the photoelectric conversion structure, for example, a charge blocking layer.

[0074] [Item 4]

[0075] In the method for manufacturing a photoelectric conversion element according to item 1,

[0076] The step of forming the mask layer may include a step of forming the mask layer using an oxide semiconductor material.

[0077] According to the configuration of item 4, the remaining portion of the covering portion as a part of the mask layer after etching can be used as a part of the photoelectric conversion structure, such as a charge blocking layer, and a higher voltage can be applied to the organic photoelectric conversion film to improve the photoelectric conversion efficiency.

[0078] [Item 5]

[0079] The method for manufacturing a photoelectric conversion element according to any one of items 2 to 4,

[0080] Here, after the step of removing a portion of the photoelectric conversion film, the method may further include a step of forming a light-transmitting third electrode, wherein the light-transmitting third electrode covers the covering portion and electrically connects the covering portion to the first electrode.

[0081] According to the configuration of Item 5, the covering portion can be used as a light-transmitting counter electrode.

[0082] [Item 6]

[0083] In the method for manufacturing a photoelectric conversion element according to item 1,

[0084] The step of forming the mask layer may include a step of forming the mask layer using a transparent conductive material.

[0085] According to the configuration of item 6, the covering portion, which is a part of the mask layer, can be used as a light-transmitting electrode.

[0086] [Item 7]

[0087] The method for manufacturing a photoelectric conversion element according to item 6,

[0088] Here, after the step of removing a portion of the photoelectric conversion film, the method may further include a step of forming a third electrode that electrically connects the covering portion and the first electrode.

[0089] According to the configuration of Item 7, it is possible to form a counter electrode including the covering portion in a part thereof.

[0090] [Item 8]

[0091] In the method for manufacturing a photoelectric conversion element according to any one of items 1 to 7,

[0092] The semiconductor substrate may include a readout circuit electrically connected to the plurality of second electrodes.

[0093] [Item 9]

[0094] In the method for manufacturing a photoelectric conversion element according to any one of items 1 to 8,

[0095] The step of preparing the substrate may also include the following steps:

[0096] forming the plurality of second electrodes above the main surface; and

[0097] After the step of forming the plurality of second electrodes, a step of forming the photoelectric conversion film on the main surface is performed.

[0098] [Item 10]

[0099] The photoelectric conversion element of item 10 of the present application comprises:

[0100] a semiconductor substrate having a main surface;

[0101] a first electrode located above the major surface;

[0102] a plurality of second electrodes located above the main surface and arranged one-dimensionally or two-dimensionally;

[0103] a photoelectric conversion film covering at least the plurality of second electrodes; and

[0104] A conductive layer includes a covering portion that covers a portion of the photoelectric conversion film that overlaps with the plurality of second electrodes in a plan view.

[0105] In a cross section perpendicular to the main surface, the conductive layer extends outward along a surface of the conductive layer beyond a side end portion of the photoelectric conversion film.

[0106] [Item 11]

[0107] In the photoelectric conversion element according to item 10,

[0108] In the cross section, the photoelectric conversion film may have a tapered side surface.

[0109] [Item 12]

[0110] In the photoelectric conversion element according to item 10,

[0111] The conductive layer may also be formed of an organic material.

[0112] [Item 13]

[0113] In the photoelectric conversion element according to item 12,

[0114] The organic material may also be a photoelectric conversion material.

[0115] [Item 14]

[0116] In the photoelectric conversion element according to item 10,

[0117] The conductive layer may also be formed of an oxide semiconductor material.

[0118] [Item 15]

[0119] The photoelectric conversion element according to any one of items 12 to 14,

[0120] It may further include a light-transmitting third electrode, the light-transmitting third electrode covers the covering portion and electrically connects the covering portion and the first electrode.

[0121] [Item 16]

[0122] In the photoelectric conversion element according to item 10,

[0123] The conductive layer may also be formed of a transparent conductive material.

[0124] [Item 17]

[0125] The photoelectric conversion element according to item 16,

[0126] It may further include a third electrode that electrically connects the covering portion and the first electrode.

[0127] [Item 18]

[0128] In the photoelectric conversion element according to any one of items 10 to 17,

[0129] The semiconductor substrate may include a readout circuit electrically connected to the plurality of second electrodes.

[0130] Below, the embodiments of the present application are described in detail with reference to the accompanying drawings. It should be noted that the embodiments described below all represent general or specific examples. The numerical values, shapes, materials, constituent elements, configurations of constituent elements and connection forms, steps, the order of steps, etc. shown in the following embodiments are only examples, and their purpose is not to limit the present application. The various schemes described in this specification can be combined with each other as long as no contradiction occurs. In addition, for the constituent elements in the following embodiments that are not recorded in the independent claims representing the highest concept, they will be described as optional constituent elements. In the following description, constituent elements having substantially the same function are sometimes represented by common figure marks, and the description is omitted.

[0131] Figure 1 FIG. 1 schematically shows a cross section of an exemplary photoelectric conversion element obtained by the production method according to an embodiment of the present application. Figure 1 The photoelectric conversion element 100A shown generally includes: a semiconductor substrate 190 having a main surface 190a; a first electrode 110 and a plurality of second electrodes 120 arranged on the main surface 190a side of the semiconductor substrate 190; a photoelectric conversion structure 130A covering the plurality of second electrodes 120; and a light-transmitting counter electrode 140 covering at least the upper surface 130a of the photoelectric conversion structure 130A. The counter electrode 140 is formed of a transparent conductive material represented by indium tin oxide (ITO) and the like. It should be noted that the terms "light-transmitting" and "transparent" in this specification refer to at least a portion of the light of the wavelength that can be absorbed by the photoelectric conversion structure 130A, and do not need to transmit light in the entire wavelength range of visible light. In addition, the terms "above", "upper surface" and "lower surface" in this specification are used to indicate the relative configuration between components, and do not limit the posture of the photoelectric conversion element of the present application.

[0132] Figure 1Although not shown in the figure, a driving circuit for driving the photoelectric conversion element 100A, a readout circuit for reading a signal corresponding to the illumination, etc. are formed on the semiconductor substrate 190 supporting the photoelectric conversion structure 130A. The semiconductor substrate 190 is not limited to a substrate whose entirety is a semiconductor, and may be an insulating substrate having a semiconductor layer provided on the surface of the side where the plurality of second electrodes 120 are formed.

[0133] like Figure 1 As schematically shown in FIG. 1 , the counter electrode 140 extends above the first electrode 110 and is connected to the first electrode 110. That is, the counter electrode 140 is configured such that a specific voltage can be applied to the counter electrode 140 via the first electrode 110 during operation of the photoelectric conversion element 100A.

[0134] As described later, a plurality of second electrodes 120 are arranged one-dimensionally or two-dimensionally above the main surface 190a. A readout circuit is connected to each of the second electrodes 120. In the illustrated example, the photoelectric conversion element 100A has the same structure as a stacked imaging device and can be used as a digital camera, a light sensor, or the like.

[0135] In this example, the photoelectric conversion structure 130A includes: a photoelectric conversion layer 132 covering the plurality of second electrodes 120; and an organic layer 134 on the photoelectric conversion layer 132. The organic layer 134 may be a charge blocking layer such as a hole blocking layer or an electron blocking layer. The organic layer 134 may also have a photoelectric conversion function.

[0136] exist Figure 1 In the structure illustrated in FIG. 1 , the photoelectric conversion element 100A further includes a protective layer 150 and an interlayer insulating layer 160. The protective layer 150 is formed of a light-transmitting insulating material and covers the counter electrode 140. The interlayer insulating layer 160 is located between the main surface 190a and the photoelectric conversion structure 130A. Figure 1 As schematically shown in FIG. 1 , the interlayer insulating layer 160 electrically separates two adjacent second electrodes 120 . In addition, the interlayer insulating layer 160 electrically separates the first electrode 110 and the plurality of second electrodes 120 .

[0137] Figure 2 1 is a schematic top view of the photoelectric conversion element 100A when viewed from the main surface 190a side of the semiconductor substrate 190. For convenience of explanation, Figure 2 The figure shows the reference Figure 1 The structures other than the photoelectric conversion structure 130A, the counter electrode 140 and the protective layer 150 are described.

[0138] like Figure 2As schematically shown in , the photoelectric conversion element 100A has an imaging region 500 including a plurality of pixels 10. Here, the imaging region 500 can be said to be a region having a repeated structure of pixels 10, each of which is a unit including a second electrode 120 and a readout circuit connected to the second electrode 120. In this example, the plurality of second electrodes 120 are arranged in a plurality of rows and columns on the main surface 190a side of the semiconductor substrate 190, and thus a rectangular imaging region 500 is formed on the main surface 190a side of the semiconductor substrate 190. The configuration of the plurality of second electrodes 120 is not limited to Figure 2 For example, by arranging the plurality of second electrodes 120 one-dimensionally, the photoelectric conversion element 100A can be used as a line sensor. The number of the plurality of second electrodes 120 is also arbitrary.

[0139] On the other hand, the first electrode 110 is located in the peripheral region 510 outside the imaging region 500 and is connected to a voltage supply circuit (not shown) via a circuit or wiring formed on the semiconductor substrate 190. A specific voltage is applied to the first electrode 110 during operation of the photoelectric conversion element 100A.

[0140] like Figure 2 As schematically shown in FIG. 1 , the photoelectric conversion element 100A includes a plurality of row signal lines R0, R1, . . . R provided for each row of a plurality of pixels 10. i ……R m-1 and a plurality of output signal lines S0, S1 ... S arranged in each column of a plurality of pixels 10 j ……S n-1 Here, m is an integer greater than 0, and one or more pixels 10 belonging to the same row are electrically connected to the corresponding row signal line. n is an integer greater than 0, and one or more pixels 10 belonging to the same column are electrically connected to the corresponding output signal line.

[0141] Row signal lines R0, R1...R i ……R m-1 For example, they are address signal lines. These row signal lines extend to a row driver region 520 where transistors constituting a row scanning circuit are formed, and are connected to the row scanning circuit, for example. Output signal lines S0, S1, ... S j ……S n-1 The output signal lines S0, S1, ... S j ……S n-1 A column scanning circuit that performs noise suppression signal processing represented by correlated double sampling, analog-to-digital conversion, and the like on output signals read out from the pixels 10 can be connected.

[0142] Figure 3 2 shows an exemplary circuit configuration of the pixel 10. For simplicity, here, among the plurality of pixels 10, the pixel located at the i-th row and the j-th column is taken out and shown.

[0143] Figure 3 The pixel 10 shown in FIG. 1 includes: a photoelectric conversion unit 540 including a second electrode 120, a counter electrode 140, and a photoelectric conversion structure 130A; and a readout circuit 550 connected to the second electrode 120. The counter electrode 140 is connected to the photoelectric conversion structure 130A. Figure 3 The first electrode 110 (not shown) is connected to the wiring 142, and receives a specific voltage from a voltage supply circuit (not shown) during operation. A specific voltage is applied to the counter electrode 140 via the wiring 142, so that the potential of the counter electrode 140 is higher than the potential of the second electrode 120 functioning as a pixel electrode, for example, so that positive charges among the charges generated in the photoelectric conversion structure 130A by the incidence of light can be collected by the second electrode 120 as signal charges.

[0144] exist Figure 3 In the structure illustrated in FIG. 1 , the readout circuit 550 includes a signal detection transistor 32 and an address transistor 34. The signal detection transistor 32 and the address transistor 34 are typically field effect transistors formed on the semiconductor substrate 190. Hereinafter, an example using an n-channel MOSFET as a transistor will be described.

[0145] The gate of the signal detection transistor 32 is connected to the second electrode 120, and the drain is connected to the power supply line 22 which functions as a source follower power supply. The node 44 between the photoelectric conversion unit 540 and the gate of the signal detection transistor 32 constitutes at least a part of the charge storage region for storing the signal charge generated by the photoelectric conversion unit 540. The address transistor 34 is connected to the signal detection transistor 32 and the output signal line S j By turning on the address transistor 34, a voltage signal corresponding to the illumination is read out to the output signal line S j .

[0146] In the example shown in the figure, the readout circuit 550 further includes a first reset transistor 36, a second reset transistor 38, a first capacitor 41, and a second capacitor 42. In addition, in this example, the photoelectric conversion element 100A has an inverting amplifier 24 arranged for each column of the plurality of pixels 10. The inverting input terminal of the inverting amplifier 24 is connected to the output signal line S j As shown in the figure, the first reset transistor 36 and the second reset transistor 38 are connected in series between the feedback line 25 connected to the output terminal of the inverting amplifier 24 and the second electrode 120.

[0147] The first capacitor 41 is connected in parallel with the first reset transistor 36 in which one of the source and the drain is connected to the second electrode 120. One electrode of the second capacitor 42 is connected to the node 46 between the first reset transistor 36 and the second reset transistor 38. The other electrode of the second capacitor 42 is connected to the accumulation control line 52, and when operating, a specific voltage is applied to the other electrode of the second capacitor 42. In addition, typically, the second capacitor 42 has a larger capacitance value than the first capacitor 41.

[0148] By controlling the potential of the first reset control line 26 connected to the gate of the first reset transistor 36 and the second reset control line 28 connected to the gate of the second reset transistor 38, a feedback loop can be formed to electrically feed back part or all of the output signal of the signal detection transistor 32. By forming a feedback loop, the influence of the kTC noise generated by the disconnection of the first reset transistor 36 and the second reset transistor 38 can be reduced. The details of such noise elimination using feedback are described in Japanese Patent Gazette No. 2017-046333. In addition, according to Figure 3 In the circuit structure illustrated in the example, the first reset transistor 36 can also function as a transistor for gain switching. The details of such mode switching are also described in Japanese Patent Publication No. 2017-046333. For reference, the entire disclosure of Japanese Patent Publication No. 2017-046333 is cited in this specification.

[0149] Figure 4 The schematic diagram shows an exemplary device structure of the pixel 10. The semiconductor substrate 190 has: impurity regions 191, 192, 193, 194, 195; and an element isolation region 196 for electrically isolating the readout circuit 550 provided for each pixel 10 between the pixels 10. The impurity regions 191, 192, 193, 194, 195 are typically N-type diffusion regions. In addition, Figure 4 In order to avoid excessive complexity of the drawing, the signal detection transistor 32, the address transistor 34 and the first reset transistor 36 among the elements constituting the readout circuit 550 are shown as representatives.

[0150] The signal detection transistor 32 includes: the impurity region 193 and the impurity region 194 among the impurity regions 191, 192, 193, 194, and 195; and a gate electrode 32e disposed on the semiconductor substrate 190 via a gate insulating layer. The address transistor 34 includes: a gate insulating layer and a gate electrode on the semiconductor substrate 190; and the impurity region 194 and the impurity region 195. In this example, the address transistor 34 and the signal detection transistor 32 share the impurity region 194.

[0151] The first reset transistor 36 includes: an impurity region 191 and an impurity region 192; and a gate insulating layer and a gate electrode on a semiconductor substrate 190. Figure 4 As schematically shown in FIG. 1 , the element isolation region 196 is also provided between the first reset transistor 36 and the signal detection transistor 32 .

[0152] The interlayer insulating layer 160 includes a plurality of insulating layers each formed of, for example, silicon dioxide, and covers the readout circuit 550 formed on the semiconductor substrate 190. The pixel 10 has a conductive structure 170 inside the interlayer insulating layer 160 that electrically connects the second electrode 120 to the readout circuit 550. The conductive structure 170 includes a via formed of a metal such as copper, a plug formed of polysilicon, and the like. Figure 4 As schematically shown in FIG. 1 , the second electrode 120 and the impurity region 191 and the gate electrode 32 e of the signal detection transistor 32 are electrically connected to each other.

[0153] The counter electrode 140 of the photoelectric conversion unit 540 is located on the side where light from the subject arrives. The counter electrode 140 is typically provided in the form of a single electrode layer that is continuous across a plurality of pixels 10. The photoelectric conversion structure 130A can also be provided in the form of a single photoelectric conversion structure that is continuous across a plurality of pixels 10. An optical filter 182 such as a color filter, a microlens 184, etc. can be arranged on the main surface of the counter electrode 140 on the opposite side to the photoelectric conversion structure 130A.

[0154] Figure 5 The cross section of another exemplary photoelectric conversion element obtained by the manufacturing method according to the embodiment of the present application is schematically shown. Figure 5 The photoelectric conversion element 100B shown in FIG. Figure 1 The photoelectric conversion element 100A described above is mainly different in that the photoelectric conversion element 100B includes a photoelectric conversion structure 130B instead of the photoelectric conversion structure 130A.

[0155] like Figure 5 As schematically shown in FIG. 1 , the photoelectric conversion structure 130B includes: a photoelectric conversion layer 132 covering the plurality of second electrodes 120; and an oxide semiconductor layer 136 on the photoelectric conversion layer 132. The oxide semiconductor layer 136 can function as a hole blocking layer, for example, similarly to the above-mentioned organic layer 134. The oxide semiconductor layer 136 can also have a photoelectric conversion function. The photoelectric conversion structure 130B can include, for example, an oxide semiconductor layer as an electron blocking layer.

[0156] (Exemplary method for manufacturing a photoelectric conversion element)

[0157] Figure 6This is a flowchart showing an outline of a method for manufacturing a photoelectric conversion element according to an exemplary embodiment of the present application. Figure 6 The method for manufacturing a photoelectric conversion element exemplified in the above generally includes the following steps: a step of preparing a substrate including a semiconductor substrate, a plurality of electrodes and a photoelectric conversion film ( Figure 6 Step S1); forming a conductive mask layer covering a portion of the photoelectric conversion film on the photoelectric conversion film ( Figure 6 and a step ( S2 ) of removing the portion of the photoelectric conversion film not covered by the mask layer by immersing the substrate and the mask layer in an etchant. Figure 6 Step S3).

[0158] <Step of Preparing a Base>

[0159] First, a substrate is prepared, which includes: a semiconductor substrate having a main surface, a plurality of electrodes located above the main surface, and a photoelectric conversion film covering at least the plurality of electrodes. The substrate can be prepared by purchasing, or by sequentially forming a plurality of electrodes and a photoelectric conversion film on one main surface side of the semiconductor substrate as described below.

[0160] Here, first, an n-type silicon substrate as a supporting substrate is prepared, and a p-well layer is formed on one main surface of the n-type silicon substrate. After that, a signal detection transistor 32 and the like are formed on the main surface side where the p-well layer is formed, thereby forming a readout circuit 550. Thus, a semiconductor substrate 190 is obtained. The formation of the readout circuit 550 can be applied to a known semiconductor process. As described above, the semiconductor substrate 190 is not limited to a substrate whose entirety is a semiconductor. For example, a glass substrate, a quartz substrate, etc. can also be used as a supporting substrate. As long as an electronic circuit can be set inside and / or on the substrate, it can be used as a supporting substrate. A p-type silicon substrate can also be used instead of an n-type silicon substrate.

[0161] Then, if Figure 7 As shown, a plurality of second electrodes 120 as pixel electrodes are formed on the main surface 190a side of the semiconductor substrate 190. Here, in the process of forming the plurality of second electrodes 120, the first electrode 110 is also formed on the main surface 190a side.

[0162] Typically, an insulating film is formed to cover the main surface 190a where the readout circuit 550 is formed, and then the first electrode 110 and the plurality of second electrodes 120 are formed on the insulating film. Figure 2 As described above, the plurality of second electrodes 120 are arranged in the imaging region 500 , whereas the first electrode 110 is arranged in the peripheral region 510 .

[0163] Physical vapor deposition (PVD) and chemical vapor deposition (CVD) can be applied to the formation of the first electrode 110 and the plurality of second electrodes 120. As materials for the first electrode 110 and the second electrode 120, wiring materials commonly used in the field of semiconductor integrated circuits can be used. Examples of materials for the first electrode 110 and the second electrode 120 are precious metals such as Ag, Pt, Au, or transparent conductive materials such as ITO. The materials for the first electrode 110 and the second electrode 120 do not need to be common.

[0164] In the case of forming a finer electrode pattern, for example, the first electrode 110 and the second electrode 120 may be formed by removing unnecessary portions by dry etching after deposition of the electrode material. By using Al, Ti, Mo, Ta, W, or an alloy containing one or more of them, conductive silicide or nitride, or polycrystalline Si as the material of the first electrode 110 and the second electrode 120, high-precision patterning can be performed by dry etching.

[0165] After the first electrode 110 and the second electrode 120 are formed, the space between two adjacent second electrodes 120 and between the first electrode 110 and the second electrode 120 is filled with an insulating material, and the surfaces of the first electrode 110, the second electrode 120 and the insulating material layer are processed in such a way that the surfaces are aligned. Figure 7 The interlayer insulating layer 160 is formed as schematically shown in FIG. Figure 7 In FIG. 1 , the lower surface of the first electrode 110 and the lower surface of the second electrode 120 are drawn as if they are in contact with the main surface 190 a, but this is merely a schematic illustration of the configuration of the first electrode 110 and the second electrode 120. Figure 4 As described above, the first electrode 110 and the second electrode 120 can be electrically connected to the readout circuit 550 via the conductive structure disposed inside the interlayer insulating layer 160. In particular, each of the second electrodes 120 is connected to the gate of the corresponding signal detection transistor 32 via a plug or the like, thereby being electrically connected to the corresponding readout circuit 550.

[0166] Next, a photoelectric conversion film is formed to cover at least the plurality of second electrodes 120. Figure 8As shown, a photoelectric conversion film 130r is formed to cover the entire main surface 190a side of the semiconductor substrate 190. In the example described below, an organic material is used as the material of the photoelectric conversion film 130r. The photoelectric conversion film 130r typically includes an organic p-type semiconductor and an organic n-type semiconductor. The photoelectric conversion film 130r can be formed using any of a dry film forming method and a wet film forming method. As a dry film forming method, for example, a vacuum evaporation method can be applied, and as a wet film forming method, an inkjet method, a spray method, a nozzle printing method, a spin coating method, a dip coating method, a casting method, a die coating method, a roller coating method, a rod coating method, a gravure coating method, etc. can be applied. By forming the photoelectric conversion film 130r, as Figure 8 As shown, the base 200 having the photoelectric conversion film 130r on the main surface 190a side can be obtained.

[0167] Fig. 9 An example of the structure of the photoelectric conversion film 130r is schematically shown. In this example, the photoelectric conversion film 130r has a stacked structure including a plurality of layers formed of organic materials. The stacked structure has the following structure: an electron blocking film 14, a p-type semiconductor film 13p, a mixed film 13x, an n-type semiconductor film 13n, and a hole blocking film 16 are stacked in order from the second electrode 120 side. The p-type semiconductor film 13p is located between the mixed film 13x and the electron blocking film 14, and functions as a hole transport layer. The n-type semiconductor film 13n is located between the mixed film 13x and the hole blocking film 16, and functions as an electron transport layer. Fig. 9 This is an example of a structure in which the positive charges among the positive and negative charges generated by photoelectric conversion are collected by the second electrode 120, and the holes are used as signal charges. In addition, in the case of a structure in which the negative charges among the positive and negative charges generated by photoelectric conversion are collected by the second electrode 120, and the electrons are used as signal charges, the stacking order of each film included in the photoelectric conversion film 130r is reversed. That is, the hole blocking film 16 and the n-type semiconductor film 13n are arranged on the second electrode 120 side, and the electron blocking film 14 and the p-type semiconductor film 13p are arranged on the opposite side to the second electrode 120.

[0168] Fig.10 About Fig. 9 Energy diagram of the photoelectric conversion film 130r illustrated in FIG. Fig.10 The lower side of the rectangle in Schematically represents the energy level of the highest occupied molecular orbital (HOMO) of the material of each layer. The upper side of the rectangle Schematically represents the energy level of the lowest unoccupied molecular orbital (LUMO) of the material of each layer. Fig.10 The bold horizontal line in illustratively represents exemplary Fermi levels of the counter electrode 140 and the second electrode 120. Hereinafter, the energy level of the highest occupied molecular orbital may be referred to as the HOMO energy level, and the energy level of the lowest unoccupied molecular orbital may be referred to as the LUMO energy level.

[0169] like Fig.10 As shown, typically, the HOMO energy level of the electron blocking film 14 is lower than the HOMO energy level of the p-type semiconductor film 13p, and the LUMO energy level of the electron blocking film 14 is higher than the LUMO energy level of the p-type semiconductor film 13p. The electron blocking film 14 is formed of, for example, aromatic amine compounds such as 4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (α-NPD) as an organic p-type semiconductor, stilbene derivatives, pyrazoline derivatives, porphine derivatives, phthalocyanine derivatives, triazole derivatives, oxazole derivatives, imidazole derivatives, phenylenediamine derivatives, aromatic amine derivatives, fluorene derivatives, amino-substituted chalcone derivatives, fluorenone derivatives, hydrazone derivatives, or silazane derivatives. The electron blocking film 14 has a function of reducing dark current generated by electrons injected from the second electrode 120 into the photoelectric conversion film 130r.

[0170] Organic p-type semiconductors are mainly represented by hole-transporting organic compounds, which refer to organic compounds that have the property of easily donating electrons. More specifically, they refer to organic compounds that have a low ionization potential when two organic compounds are used in contact. Therefore, any organic compound can be used as an organic p-type semiconductor as long as it shows electron-donating properties.

[0171] Examples of organic p-type semiconductors include triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds such as α-sixithiophene (α-6T) and P3HT, phthalocyanine compounds, cyanine compounds, merocyanine compounds, oxonol compounds, polyamine compounds, indole compounds, pyrrole compounds, pyrazole compounds, polyarylene compounds, condensed aromatic carbocyclic compounds (e.g., naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives such as rubrene, pyrene derivatives, perylene derivatives, fluoranthene derivatives), and metal complexes having nitrogen-containing heterocyclic compounds as ligands, etc. Without being limited to these, any organic compound having a smaller ionization potential than an organic compound used as an organic n-type semiconductor can be used as an organic p-type semiconductor.

[0172] The hole blocking film 16 has a function of reducing dark current generated by holes injected from the counter electrode 140 into the photoelectric conversion film 130r. As a material for the hole blocking film 16, for example, an organic n-type semiconductor can be used. As described later, an oxide semiconductor material can also be used as a material for forming the hole blocking layer.

[0173] As an organic material for forming the hole blocking film 16, for example, fullerene, fullerene derivatives, copper phthalocyanine, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), acetylacetone complex, BCP, Alq, etc. can be used. The hole blocking film 16 is an example of the above-mentioned organic layer 134. If the transmittance of the hole blocking film 16 in the visible region to the near-infrared region is high, more light can reach the stacked structure 13L including the p-type semiconductor film 13p, the mixed film 13x and the n-type semiconductor film 13n. As a material for the hole blocking film 16, a material that does not have a large absorption at a wavelength at which the stacked structure 13L shows absorption can be selected. Alternatively, the thickness of the hole blocking film 16 can be minimized. The thickness of the hole blocking film 16 depends on the specific composition of the stacked structure 13L and the thickness of the electrode 140, but the thickness of the hole blocking film 16 can be in the range of 2nm to 50nm.

[0174] Organic n-type semiconductors are mainly represented by electron-transmitting organic compounds, which refer to organic compounds that have the property of easily accepting electrons. More specifically, they refer to organic compounds that have a high electron affinity when two organic compounds are used in contact. Therefore, any organic compound can be used as an organic n-type semiconductor as long as it shows electron-accepting properties.

[0175] An example of an organic n-type semiconductor is C 60 and C 70 Fullerene, phenyl C 61 butyric acid methyl ester (PCBM) and other fullerene derivatives, fused aromatic carbocyclic compounds (for example, naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives), 5- to 7-membered heterocyclic compounds containing nitrogen atoms, oxygen atoms or sulfur atoms (for example, pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole, oxazole, indazole, benzene The organic n-type semiconductor may be an organic compound having a ligand such as imidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine, triazolopyrimidine, tetrazaindene, oxadiazole, imidazopyridine, pyrrolidine, pyrrolopyridine, thiadiazopyridine, dibenzoazepine, tribenzoazepine, etc.), subphthalocyanine (SubPc), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, perylenetetracarboxylic acid diimide compounds (PTCDI), and metal complexes having nitrogen-containing heterocyclic compounds as ligands. The organic compound may be used as an organic n-type semiconductor as long as it has a larger electron affinity than an organic compound used as an organic p-type semiconductor.

[0176] In the case where the electron blocking film 14 is provided in the photoelectric conversion film 130r, the material of the second electrode 120 is selected from the above-mentioned materials in consideration of the bonding strength, stability, difference in electron affinity and difference in ionization potential between the second electrode 120 and the electron blocking film 14. For the material of the counter electrode 140, the bonding strength, stability, difference in ionization potential and difference in electron affinity between the adjacent layers can also be considered and selected from known materials. In addition, in the case where the hole blocking film 16 is not provided and the work function of the counter electrode 140 is relatively large, for example, about 4.8 eV, the potential barrier between the counter electrode 140 and the stacked structure 13L becomes smaller, and hole injection from the counter electrode 140 to the stacked structure 13L is likely to occur. As a result, there is a possibility of increased dark current. However, in the present embodiment, since the hole blocking film 16 is interposed between the counter electrode 140 and the stacked structure 13L, the effect of suppressing dark current can be expected.

[0177] When the stacked structure 13L is formed of an organic semiconductor material, the photoelectric conversion film 130r may include a stacked structure of an electron-donating organic compound and an electron-accepting organic compound, in other words, a heterojunction. Alternatively, it may include a layer having a bulk heterojunction structure. The photoelectric conversion film 130r may also be a combination of these.

[0178] The light incident on the photoelectric conversion film 130r can be absorbed by either or both of the electron-donating organic compound and the electron-accepting organic compound. The photoelectric conversion structure 130A includes a bulk heterojunction structure layer, which can make up for the short carrier diffusion length in the photoelectric conversion film and improve the photoelectric conversion efficiency. The bulk heterojunction structure is described in detail in Japanese Patent No. 5553727. For reference, the entire disclosure of Japanese Patent No. 5553727 is cited in this specification.

[0179] <Step of Forming a Conductive Mask Layer on the Photoelectric Conversion Film>

[0180] Next, a mask layer is formed on the photoelectric conversion film 130r. As described later, in the embodiment of the present application, a portion of the photoelectric conversion film 130r is removed by wet etching, thereby forming a photoelectric conversion structure 130A including the photoelectric conversion film 130r in a portion thereof. The mask layer functions as an etching mask for protecting a portion of the photoelectric conversion film 130r located in the imaging region 500.

[0181] In one embodiment of the present application, a mask layer is formed of an organic material and / or a transparent conductive material, and the mask layer at least covers the portion of the photoelectric conversion film 130r that overlaps with the plurality of second electrodes 120 when viewed from above. For example, the portion of the hole blocking film 16 other than the portion located on the imaging region 500 is selectively removed, and the remaining portion of the hole blocking film 16 can be used as a mask layer. That is, by patterning the hole blocking film 16, a Fig.11 The mask layer 16C shown includes the covered portion 560 in part thereof. As described later, the mask layer may be formed of one or more of an organic material, an oxide semiconductor material, and a transparent conductive material, and the mask layer may cover at least the portion of the photoelectric conversion film overlapping with the plurality of second electrodes 120 .

[0182] The layout of the hole blocking film 16 can be performed, for example, as follows: after the hole blocking film 16 is formed by vacuum evaporation or coating, photolithography and etching are applied to selectively remove the portion of the hole blocking film 16 other than the portion located on the imaging area 500, thereby performing layout. The pattern of the organic photoelectric conversion material can also be directly formed by inkjet printing, offset printing, gravure printing, flexographic printing or screen printing. Alternatively, the pattern of the organic photoelectric conversion material can also be formed by vacuum evaporation via a mask. From the perspective of the influence of the resist, developer or release agent on the photoelectric conversion film, the application of vacuum evaporation via a mask is advantageous compared to the case of applying photolithography. In addition, it is not necessary to completely remove the portion of the hole blocking film 16 located in the peripheral area 510. The mask layer 16C can have a portion located in the peripheral area 510 in addition to the covering portion 560.

[0183] like Fig.11 As schematically shown in FIG. 1 , the covering portion 560 of the mask layer 16C covers the portion of the photoelectric conversion film 130q that overlaps with the plurality of second electrodes 120 when viewed from above. Here, the photoelectric conversion film 130q is a stacked structure made of the electron blocking film 14, the p-type semiconductor film 13p, the mixed film 13x, and the n-type semiconductor film 13n. In addition, after the hole blocking film 16 is patterned, the covering portion 560 of the mask layer 16C can also maintain the function as a hole blocking film. Therefore, the stacked structure of the electron blocking film 14, the p-type semiconductor film 13p, the mixed film 13x, the n-type semiconductor film 13n, and the covering portion 560 of the mask layer 16C can also be referred to as a photoelectric conversion film.

[0184] When the mask layer is formed of an organic material, an organic compound having a lower etching rate than the material of the photoelectric conversion film 130q with respect to an etchant used in a wet etching process described later is used as the material of the mask layer. Thus, the photoelectric conversion film 130q can be preferentially dissolved in the wet etching, and the covering portion 560 can remain on the photoelectric conversion film 130q after the wet etching.

[0185] In particular, when a part of the hole blocking film 16 is used as the mask layer 16C, in the step of forming the photoelectric conversion film 130r, the hole blocking film 16 is formed using an organic material whose etching rate with respect to the etchant used in the wet etching of the photoelectric conversion film 130q is lower than that of the photoelectric conversion film 130q. As described above, the hole blocking film 16 as the organic layer 134 can have a photoelectric conversion function. That is, the material forming the hole blocking film 16 can be an organic photoelectric conversion material. In other words, the photoelectric conversion material can be used as the material of the mask layer 16C.

[0186] The mask layer can also be formed by a transparent conductive material instead of an organic material. If the transparent conductive material is used as a hard mask material, first, the transparent conductive material is deposited on the photoelectric conversion film 130r by sputtering or coating, and then photolithography and etching are applied to selectively remove the portion of the transparent conductive material film located on the peripheral area 510. As a transparent conductive material for forming the mask layer, the same transparent conductive material as the material of the electrode 140 can be used. As in the case of using an organic material in the formation of the mask layer, a pattern of the transparent conductive material can be directly formed on the photoelectric conversion film 130r by an inkjet method. Alternatively, a pattern of the transparent conductive material can also be formed by a vacuum evaporation method via a mask. From the perspective of the influence of the resist, developer or release agent on the photoelectric conversion film, it is advantageous to apply a vacuum evaporation method via a mask compared to the case of applying photolithography.

[0187] By patterning the transparent conductive material film, portions of the transparent conductive material film other than the portion located on the imaging region 500 are selectively removed, such as Fig.12 As shown in FIG. 5 , a conductive mask layer 140C having a covering portion 560 can be formed. Fig.11 Similar to the example described above, the covering portion 560 of the mask layer 140C covers the portion of the photoelectric conversion film 130r that overlaps with the plurality of second electrodes 120 in a plan view. Fig.11 As in the example described above, it is not necessary to completely remove the portion of the transparent electrode material film located in the peripheral region 510 . The mask layer 140C may include a portion located in the peripheral region 510 in addition to the covering portion 560 .

[0188] Alternatively, the mask layer may be formed by patterning both the hole blocking film 16 and the film of the transparent conductive material on the hole blocking film 16. Fig.13 As shown, a mask layer 146C having a covering portion 560 may be formed on the photoelectric conversion film 130q, the covering portion 560 including a portion of the hole blocking film 16, namely the organic layer 16m, and a portion of the transparent conductive material film, namely the transparent conductive layer 140m. The covering portion 560 of the mask layer 146C still covers the portion of the photoelectric conversion film 130q that overlaps with the plurality of second electrodes 120 when viewed from above.

[0189] <Step of Removing a Part of the Photoelectric Conversion Film by Wet Etching>

[0190] Next, the substrate 200 and the mask layer are immersed in an etchant, thereby removing a portion of the photoelectric conversion film. Fig.11 The substrate 200A having the mask layer 16C formed of the hole blocking film 16 as shown in FIG. 1 is immersed in the etchant 300. As described above, the etching rate of the mask layer 16C for the etchant 300 is lower than the etching rate of the photoelectric conversion film 130q. Therefore, by immersing in the etchant 300, Fig.14 As schematically shown in FIG. 1 , the portion of the photoelectric conversion film 130q not covered by the mask layer 16C can be selectively removed to form a photoelectric conversion structure 130A having a shape corresponding to the covering portion 560. The portion remaining after the wet etching process in the covering portion 560 and the portion remaining after the wet etching process in the photoelectric conversion film 130q correspond to Figure 1 The organic layer 134 and the photoelectric conversion layer 132 shown in FIG. In this example, the portion remaining after the wet etching process in the covering portion 560 is completed can function as a hole blocking layer.

[0191] As long as the etching rate of the photoelectric conversion film 130q is greater than the etching rate of the mask layer 16C, any liquid can be used as the etchant 300. As for the etching rates of the mask layer 16C and the photoelectric conversion film 130q, the etching rates can be controlled by parameters such as the molecular polarity of the etchant and the presence or absence of aromatic rings. An example of the etchant 300 is acetone or a mixed solution of acetone and ethanol.

[0192] In use Fig.12 The base body 200B shown or Fig.13 In the case of the substrate 200C shown in FIG. 1 , it is sufficient to immerse these substrates in the etchant 300 instead of the substrate 200A. For example, by immersing the substrate 200B in the etchant 300, as shown in FIG. Fig.15AAs schematically shown in FIG. 1 , the portion of the photoelectric conversion film 130r not covered by the covering portion 560 can be selectively removed to form a photoelectric conversion structure 130A having a shape corresponding to the covering portion 560. In the case where wet etching is performed by immersing the substrate 200C in the etchant 300, the photoelectric conversion structure 130A is formed. Fig.14 Similarly to the example described above, it is sufficient to use, as the etchant 300 , a liquid having a higher etching rate for the photoelectric conversion film 130 q than for the organic layer 16 m in the mask layer 146C.

[0193] Fig. 15B and Fig. 15C Yes Fig.14 FIG. 1 is a cross-sectional view showing an enlarged side end of the photoelectric conversion film 130q after a process of removing a portion of the photoelectric conversion film 130q by wet etching. Since wet etching is isotropic etching, the portion of the photoelectric conversion film 130q covered by the mask layer 16C is etched inwardly in the horizontal direction relative to the side surface of the mask layer 16C by the etchant 300. As a result, as shown in FIG. Fig. 15B and Fig. 15C As shown in FIG. 19 , the mask layer 16C is extended outward along the surface of the mask layer 16C further than the side end of the photoelectric conversion film 130q. In a cross section perpendicular to the main surface 190a, the side surface of the photoelectric conversion film 130q has Fig. 15B A straight tapered shape as shown or Fig. 15C In addition, Fig.15A In the case of the process shown in which a portion of the photoelectric conversion film 130 r is removed by wet etching using the mask layer 140C formed of a transparent conductive material, the side surface of the photoelectric conversion film 130 r has the same shape.

[0194] <Step of Forming a Light-Transmitting Electrode>

[0195] Here, first, for Fig.11 The following process will be described for the case where the substrate 200A shown in FIG. 1 is immersed in the etchant 300 to form the photoelectric conversion structure 130A. After the photoelectric conversion film 130q and the covering portion 560 of the mask layer 16C are wet-etched to obtain the photoelectric conversion structure 130A, as shown in FIG. Fig.16A As shown in FIG. 5 , a counter electrode 140 is formed as a light-transmitting third electrode, which covers the portion used as the covering portion 560. The counter electrode 140 extends at least to the position of the first electrode 110 and also covers the upper surface 110a of the first electrode 110. By forming the counter electrode 140, the hole blocking film 16 and the first electrode 110 are electrically connected via the counter electrode 140.

[0196] The counter electrode 140 may be formed by, for example, high frequency magnetron sputtering, for example, by depositing a transparent electrode material such as ITO in an Ar atmosphere of 1 Pa.

[0197] If it is through Fig.12 The base body 200B shown or Fig.13 In the case where the substrate 200C shown in FIG. 1 is immersed in the etchant 300 to form the photoelectric conversion structure 130A, the counter electrode 140 including the light-transmitting covering portion 560 in a portion thereof can be formed by depositing the transparent electrode material, thereby obtaining the same Fig.16A The example shown has the same structure.

[0198] Fig. 16B Yes Fig.16A The cross-sectional view is an enlarged view of the side end of the photoelectric conversion structure 130A after the formation of the counter electrode 140. By using the etchant 300 to remove a portion of the photoelectric conversion film 132, the portion of the photoelectric conversion film 132 covered by the organic layer 134 is etched inward from the side of the organic layer 134 in the horizontal direction, so that a gap 570 is generated between the counter electrode 140 and the side of the photoelectric conversion film 132.

[0199] Typically, after the formation of the counter electrode 140, a protective layer 150 is formed to cover the structure on the semiconductor substrate 190. By forming the protective layer 150, the degradation of the photoelectric conversion structure 130A caused by direct exposure to external gases can be suppressed. Examples of the protective layer 150 are single-layer films of aluminum oxide, silicon oxide, silicon nitride or silicon oxynitride, or stacked films containing two or more of them. The formation of the protective layer 150 can be applied to PVD methods such as sputtering, plasma CVD methods, catalyst CVD methods, atomic layer deposition (ALD) methods, etc. Alternatively, high-frequency magnetron sputtering can also be applied. For example, the protective layer 150 can also be formed by depositing aluminum oxide in a manner covering the counter electrode 140 under an atmosphere of 1Pa of Ar and O2.

[0200] Through the above process, we can obtain Figure 1 Here, an example of using an organic material as the material of the electron blocking film 14 and the material of the hole blocking film 16 is described, but as described below, the electron blocking layer and / or the hole blocking layer may be formed of an oxide semiconductor. In this case, for example, an oxide semiconductor layer or a combination of an oxide semiconductor layer and a transparent conductive layer 140m may be used as a mask layer.

[0201] <Step of Preparing a Base>

[0202] Next, another method for manufacturing a photoelectric conversion element of one embodiment of the present application is described. As in the above example, a substrate is first prepared, the substrate comprising: a semiconductor substrate having a main surface, a plurality of electrodes located above the main surface, and a photoelectric conversion film covering at least the plurality of electrodes. For example, a semiconductor substrate 190 is prepared, and a plurality of second electrodes 120 and a first electrode 110 are formed on the main surface 190a side of the semiconductor substrate 190. In addition, an interlayer insulating layer 160 is formed. Thus, Figure 7 The structure shown.

[0203] Next, a photoelectric conversion film is formed to cover at least the plurality of second electrodes 120. Here, first, an electron blocking layer 14s is formed to cover at least the plurality of second electrodes 120 on the main surface 190a side of the semiconductor substrate 190. Examples of the material of the electron blocking layer 14s are calcium oxide, chromium oxide, chromium copper oxide, manganese oxide, cobalt oxide, nickel oxide, copper oxide, gallium copper oxide, strontium copper oxide, niobium oxide, molybdenum oxide, indium copper oxide, indium silver oxide, iridium oxide, and the like.

[0204] When such a material is used, the electron blocking layer 14s will not be removed even if the above-mentioned etchant 300 is used. Therefore, patterning is performed at the stage of depositing or coating the material of the electron blocking layer 14s. For example, after the material of the electron blocking layer 14s is applied by vacuum evaporation or coating, photolithography and etching are applied to selectively remove the portion of the film of the material of the electron blocking layer 14s located on the peripheral area 510. Alternatively, the pattern of the oxide semiconductor can be formed by vacuum evaporation or sputtering through a mask. Thus, as Fig.17 As shown, the electron blocking layer 14 s can be formed to cover the region to be the imaging region 500 .

[0205] By forming the electron blocking layer 14s from an oxide semiconductor material, the resistance becomes smaller than when the electron blocking layer 14s is formed from an organic material, so that the voltage drop in the electron blocking layer 14s is small, and thus a higher voltage can be applied to the organic photoelectric conversion film. Therefore, the photoelectric conversion efficiency can be improved without changing the bias applied between the second electrode 120 and the counter electrode 140. In addition, by using an oxide semiconductor material as the material of the electron blocking layer 14s, even if an organic film is formed on the electron blocking layer 14s by a coating method in a subsequent process, there is no need to worry about the dissolution of the electron blocking layer 14s due to the solution of the material of the organic film. Therefore, it is easier to form a stacked structure that functions as a photoelectric conversion structure.

[0206] Next, a p-type semiconductor film 13p, a mixed film 13x, and an n-type semiconductor film 13n are formed on the main surface 190a side. Fig.18As shown in the figure, the p-type semiconductor film 13p, the mixed film 13x, and the n-type semiconductor film 13n may be formed not only on the electron blocking layer 14s but also in a manner covering the region to be the peripheral region 510. Thus, a substrate 210 having the photoelectric conversion film 130s including the electron blocking layer 14s, the p-type semiconductor film 13p, the mixed film 13x, and the n-type semiconductor film 13n on the main surface 190a side is obtained.

[0207] <Step of Forming a Conductive Mask Layer on the Photoelectric Conversion Film>

[0208] Then, if Fig.19 As shown in FIG. 1 , a mask layer 16D is formed to cover at least the portion of the stacked structure of the p-type semiconductor film 13p, the mixed film 13x, and the n-type semiconductor film 13n that overlaps with the plurality of second electrodes 120 when viewed from above. Here, an oxide semiconductor layer is formed as the mask layer 16D. The portion of the oxide semiconductor layer located on the region to be the imaging region 500 functions as a covering portion 560. As described later, after the etching process is completed, the portion of the oxide semiconductor layer corresponding to the covering portion 560 can function as a hole blocking layer.

[0209] Examples of materials for the mask layer 16D are oxide semiconductors such as titanium oxide, tin oxide, indium oxide, tungsten oxide, niobium oxide, and zinc oxide. The formation of the hole blocking layer as the mask layer 16D can be applied in the same way as the electron blocking layer 14s. For example, after the oxide semiconductor material is imparted to the n-type semiconductor film 13n by vacuum evaporation or coating, photolithography and etching are applied to selectively remove the portion of the oxide semiconductor material film located on the peripheral area 510. Alternatively, a pattern of the oxide semiconductor can be formed by vacuum evaporation or sputtering via a mask. In addition, the pattern of the oxide semiconductor can be directly formed by inkjet printing, offset printing, gravure printing, flexographic printing, or screen printing. Thus, a mask layer 16D having a covering portion 560 can be formed.

[0210] <Step of Removing a Part of the Photoelectric Conversion Film by Wet Etching>

[0211] Next, the base 210 and the mask layer 16D are immersed in an etchant 300, thereby removing a portion of the photoelectric conversion film 130s. The mask layer 16D is insoluble in the etchant 300. By immersing in the etchant 300, Fig. 20As schematically shown in FIG. 1 , the portion of the photoelectric conversion film 130s not covered by the mask layer 16D can be selectively removed to form a photoelectric conversion structure 130B having a shape corresponding to the covering portion 560. The portion remaining after the wet etching process in the covering portion 560 and the portion remaining after the wet etching process in the photoelectric conversion film 130s correspond to Figure 5 The oxide semiconductor layer 136 and the photoelectric conversion layer 132 shown in FIG. In this example, the portion remaining after the wet etching step in the covering portion 560 can function as the hole blocking layer 16s.

[0212] about Fig. 20 The energy diagram of the photoelectric conversion structure 130B shown can be compared with the reference Fig.10 The energy diagram in the example described is the same. However, here, since an oxide semiconductor is used as the material of the electron blocking layer 14s and the hole blocking layer 16s, it is sufficient to replace the upper side of the rectangle representing the electron blocking film 14 and the hole blocking film 16 with the bottom of the conduction band of the electron blocking layer 14s and the hole blocking layer 16s, and replace the lower side with the upper end of the valence band of the electron blocking layer 14s and the hole blocking layer 16s. By using an oxide semiconductor material as the material of the hole blocking layer 16s, the resistance is small and the voltage drop is small, as in the case where the electron blocking layer 14s is formed of an oxide semiconductor material, so that a higher voltage can be applied to the organic photoelectric conversion film to improve the photoelectric conversion efficiency.

[0213] <Step of Forming a Light-Transmitting Electrode>

[0214] Next, with reference Fig.16A Similarly to the example described above, the counter electrode 140 as the third light-transmitting electrode covering the cover portion 560 is formed. Figure 5 The photoelectric conversion element 100B shown in FIG. 10B. As in this example, the layer of the oxide semiconductor material as the hole blocking layer 16s may also be used as an etching mask. Fig.13 Similarly to the described example, the transparent conductive layer 140 m may be formed on the covering portion 560 of the mask layer 16D, and the photoelectric conversion film 130 s may be etched using the mask layer 16D and the transparent conductive layer 140 m as an etching mask.

[0215] In the above embodiment, the electron blocking layer is arranged on the second electrode 120 side, and the hole blocking layer is arranged on the counter electrode 140 side. Conversely, when the hole blocking layer is arranged on the second electrode 120 side and the electron blocking layer is arranged on the counter electrode 140 side, the electron blocking layer or the transparent electrode layer may be used as an etching mask to perform etching of the photoelectric conversion film.

[0216] According to the embodiment of the present application, in the etching of the photoelectric conversion film, since a mask layer formed of at least one of an organic material, a transparent conductive material, and an oxide semiconductor material is used, the process of removing the etching mask after etching can be omitted. In particular, by using an organic photoelectric material as the material of the mask layer, a portion of the mask layer, i.e., the portion remaining after etching in the coating portion 560, can be used as a portion of the photoelectric conversion structure 130A, such as a charge blocking layer. In addition, by using a transparent conductive material as the material of the mask layer, a counter electrode 140 including the coating portion 560 in a portion thereof can be formed.

[0217] In addition, in the embodiment of the present application, the layout of the photoelectric conversion film 130r or the photoelectric conversion film 130q is performed by applying wet etching. According to the application of wet etching, as described later with reference to the embodiment, it is possible to suppress dark current and suppress the generation of white damage defects. Therefore, the effect of improving the yield can be obtained. It is speculated that this is because: just after the photoelectric conversion film is formed, a stress difference is generated at the interface between the photoelectric conversion film 130r, 130q and the second electrode 120 and the interface between the photoelectric conversion film 130r, 130q and the mask layer, but by performing wet etching, the stress is relieved.

[0218] In the embodiment of the present application, for a structure that can function as a device including a photoelectric conversion film, a selective layout of the photoelectric conversion film is performed by wet etching, and the etching mask is also used as a conductive structure after the wet etching. Therefore, the stress in the photoelectric conversion structure can be relaxed, and at the same time, the photoelectric conversion element is obtained in a state where the etching mask remains. In addition, by applying wet etching to the etching of the photoelectric conversion film instead of the commonly used dry etching, the degradation of the sensitivity near the surface formed by dry etching can be avoided.

[0219] Example

[0220] White damage defects are caused by generating a dark current in the photoelectric conversion structure that is larger than the surrounding area. Therefore, the amount of white damage defects can be evaluated by the size of the dark current flowing in the photoelectric conversion structure. Here, samples that imitate the photoelectric conversion structure applied to the photoelectric conversion element are made, and the size of the dark current in each sample is measured, thereby studying the white damage defect suppression effect of the embodiment of the present application.

[0221] (Reference Example 1, Comparative Example 1)

[0222] Samples of Reference Example 1 and Comparative Example 1 were prepared in the following steps. First, a glass substrate having a thickness of 0.7 mm and an ITO film having a thickness of 150 nm on one main surface as a lower electrode was prepared. Next, (OC2H5)8Sn(OSi(C6H 13 )3) A mixed solution of 2Nc and PCBM (manufactured by Frontier Carbon Corporation) was used to form a mixed film. In the mixed solution used for film formation, (OC2H5)8Sn(OSi(C6H 13 )3) 30 mg / ml chloroform solution with a weight ratio of 2Nc to PCBM of 1:9. In addition, in the following structural formula, Et represents C2H5 and Hex represents C6H 13 The thickness of the mixed film obtained at this time is about 250 nm.

[0223]

[0224] Furthermore, C was deposited with a thickness of 50 nm on a portion of the mixed film as a photoelectric conversion layer through a first metal shadow mask by vacuum deposition. 60 Then, by sputtering, a second shadow mask with a smaller opening is used to form a shadow mask at C 60 An ITO film with a thickness of about 30 nm is formed on the layer as the upper electrode. 60 The layer acts as a hole blocking layer. Fig.21 The structure of the laminated body obtained at this time is schematically shown.

[0225] With a bias voltage of 5 V applied between the upper electrode and the lower electrode, the current density generated between the upper electrode and the lower electrode was measured in a nitrogen atmosphere using a semiconductor device parameter analyzer B1500A manufactured by Keysight Technologies Inc. The result was 2.3×10 -4 (mA / cm 2 The measured value obtained at this time is regarded as the value of the dark current of the sample of Comparative Example 1.

[0226] Next, the laminated body was immersed in acetone in a nitrogen atmosphere to perform wet etching of the mixed film as the photoelectric conversion layer. After 5 minutes, the laminated body was taken out from the acetone as an etchant to prepare a sample of Reference Example 1.

[0227] Fig. 22 The structure of the stacked body after etching is schematically shown. Fig. 22 As schematically shown in FIG. 1 , for the sample of Reference Example 1, the uncoated C60 The portion covered by the layer is removed by wet etching. The etching rate of the mixed film at this time is 50nm / min. Here, C 60 Insoluble in acetone. 60 The etching rate of the layer can be considered to be 0 nm / min.

[0228] As in Comparative Example 1, the current density generated between the upper electrode and the lower electrode of the sample of Reference Example 1 was measured in a nitrogen atmosphere, and the result was 7.5×10 -5 (mA / cm 2 ) value.

[0229] (Reference Example 2, Comparative Example 2)

[0230] First, similarly to the sample of Comparative Example 1, a sample having Fig.21 Next, the current density generated between the upper electrode and the lower electrode was measured in a nitrogen atmosphere in the same manner as in Comparative Example 1, and the dark current was 1.0×10 -4 (mA / cm 2 The dark current value obtained at this time is taken as the measured value of the sample of Comparative Example 2.

[0231] Next, the laminate was immersed in a mixed solution of acetone and ethanol under a nitrogen atmosphere to perform wet etching of the mixed film as the photoelectric conversion layer, thereby producing a laminate having Fig. 22 The stacked body has the same structure as shown. The ratio of acetone and ethanol in the mixed solution used at this time is 3:1 by volume. After the stacked body is immersed in the mixed solution for 6 minutes, the stacked body is taken out from the mixed solution as an etchant and used as a sample of Reference Example 2. The etching rate of the mixed film is 40nm / min. As in Reference Example 1 and Comparative Examples 1 and 2, the current density generated between the upper electrode and the lower electrode is measured in a nitrogen atmosphere, and the dark current is 1.6×10 -5 (mA / cm 2 )’s measured value.

[0232] (Reference Example 3, Comparative Example 3)

[0233] Similar to the samples of Comparative Examples 1 and 2, Fig.21 Next, the current density generated between the upper electrode and the lower electrode was measured in a nitrogen atmosphere in the same manner as in Comparative Examples 1 and 2, and the dark current was 3.5×10 -3 (mA / cm 2 The dark current value obtained at this time is taken as the measured value of the sample of Comparative Example 3.

[0234] As an etchant, a mixed solution of acetone and ethanol in a volume ratio of 2:1 was used, and the immersion time of the stack was changed to 8 minutes. The mixed film was selectively wet-etched in the same manner as the sample of Reference Example 2 to produce a sample of Reference Example 3. The etching rate of the mixed film was 30 nm / min. As in the above examples, the current density generated between the upper electrode and the lower electrode was measured in a nitrogen atmosphere, and the dark current was 2.5×10 -4 (mA / cm 2 )’s measured value.

[0235] (Reference Example 4, Comparative Example 4)

[0236] Similar to the samples of Comparative Examples 1 to 3, Fig.21 Next, the current density generated between the upper electrode and the lower electrode was measured in a nitrogen atmosphere in the same manner as in Comparative Examples 1, 2, and 3, and the dark current was 4.2×10 -5 (mA / cm 2 The dark current value obtained at this time is taken as the measured value of the sample of Comparative Example 4.

[0237] As an etchant, a mixed solution of acetone and ethanol in a volume ratio of 1:1 was used, and the immersion time of the stack was changed to 12.5 minutes. The mixed film was selectively wet-etched in the same manner as the samples of Reference Examples 2 and 3 to produce a sample of Reference Example 4. The etching rate of the mixed film was 20 nm / min. As in the above examples, the current density generated between the upper electrode and the lower electrode was measured in a nitrogen atmosphere, and the dark current was 1.9×10 -5 (mA / cm 2 )’s measured value.

[0238] Table 1 below shows the measured values ​​of dark current for each sample of Reference Examples 1 to 4 and Comparative Examples 1 to 4.

[0239] Table 1

[0240]

[0241] It can be seen from Table 1 that for the samples of Comparative Examples 1 to 4, the measured values ​​of the dark currents deviate to a certain extent, but if the measured values ​​of the dark currents of the samples of the corresponding reference examples are referred to, the dark current values ​​of all the samples are reduced by the implementation of wet etching. That is, it can be seen that by performing wet etching on the photoelectric conversion film, the dark current value is reduced, and the white damage defect suppression effect can be obtained. It is speculated that the reduction in the dark current value is caused by the relaxation of the stress of the mixed film by performing wet etching. This suggests the following possibility: when the structure including the photoelectric conversion film is immersed in the etchant, the molecules in the photoelectric conversion film are in a state that is easy to move, and in the process of being lifted out of the etchant and dried, the molecules are rearranged into a stable state, and there is a possibility that the etchant partially penetrates into the photoelectric conversion film.

[0242] The above-mentioned reference examples 1 to 4 can be said to be equivalent to etching the organic layer C of the mixed film as the photoelectric conversion film at a lower etching rate. 60 However, when the ITO film as the upper electrode is used as an etching mask and an oxide semiconductor material is used instead of C 60 According to the embodiment of the present application, it is possible to simultaneously achieve the relaxation of stress generated at the interface between the photoelectric conversion film and other members and the removal of a portion of the photoelectric conversion film by etching.

Claims

1. A method for manufacturing a photoelectric conversion element, comprising the following steps: A step of preparing a substrate, the substrate comprising: a semiconductor substrate having a main surface, a first electrode located above the main surface, a plurality of second electrodes located above the main surface and arranged one-dimensionally or two-dimensionally, and a photoelectric conversion film covering at least the plurality of second electrodes; forming a mask layer on the photoelectric conversion film, the mask layer including a covering portion covering a portion of the photoelectric conversion film overlapping with the plurality of second electrodes in a plan view and having conductivity; and A step of removing a portion of the photoelectric conversion film by immersing the substrate and the mask layer in an etchant.

2. The method for manufacturing a photoelectric conversion element according to claim 1, wherein: The step of forming the mask layer includes forming the mask layer using an organic material. An etching rate of the mask layer in the step of removing a portion of the photoelectric conversion film is lower than an etching rate of the photoelectric conversion film in the step of removing a portion of the photoelectric conversion film.

3. The method for manufacturing a photoelectric conversion element according to claim 2, wherein: The organic material is a photoelectric conversion material.

4. The method for manufacturing a photoelectric conversion element according to claim 1, wherein: The step of forming the mask layer includes the step of forming the mask layer using an oxide semiconductor material.

5. The method for manufacturing a photoelectric conversion element according to claim 2, wherein: After the step of removing a portion of the photoelectric conversion film, the method further includes the step of forming a light-transmitting third electrode, the light-transmitting third electrode covering the covering portion and electrically connecting the covering portion to the first electrode.

6. The method for manufacturing a photoelectric conversion element according to claim 1, wherein: The step of forming the mask layer includes a step of forming the mask layer using a transparent conductive material.

7. The method for manufacturing a photoelectric conversion element according to claim 6, wherein: After the step of removing a portion of the photoelectric conversion film, the method further includes the step of forming a third electrode that electrically connects the covering portion and the first electrode.

8. The method for manufacturing a photoelectric conversion element according to claim 1, wherein: The semiconductor substrate includes a readout circuit electrically connected to the plurality of second electrodes.

9. The method for manufacturing a photoelectric conversion element according to claim 1, wherein: The process of preparing the substrate includes the following steps: forming the plurality of second electrodes above the main surface; and After the step of forming the plurality of second electrodes, a step of forming the photoelectric conversion film on the main surface is performed.

10. A photoelectric conversion element comprising: a semiconductor substrate having a main surface; a first electrode located above the major surface; a plurality of second electrodes located above the main surface and arranged one-dimensionally or two-dimensionally; a photoelectric conversion film covering at least the plurality of second electrodes; and a conductive layer including a covering portion, the covering portion covering a portion of the photoelectric conversion film that overlaps with the plurality of second electrodes in a plan view, In a cross section perpendicular to the main surface, the conductive layer extends outward along the surface of the conductive layer further than a side end portion of the photoelectric conversion film. In the cross section, the photoelectric conversion film has a tapered side surface at an outermost end thereof.

11. The photoelectric conversion element according to claim 10, wherein The conductive layer is formed of an organic material.

12. The photoelectric conversion element according to claim 11, wherein The organic material is a photoelectric conversion material.

13. The photoelectric conversion element according to claim 10, wherein The conductive layer is formed of an oxide semiconductor material. 14 . The photoelectric conversion element according to claim 11 , further comprising a light-transmitting third electrode, wherein the light-transmitting third electrode covers the covering portion and electrically connects the covering portion and the first electrode.

15. The photoelectric conversion element according to claim 10, wherein The conductive layer is formed of a transparent conductive material. 16 . The photoelectric conversion element according to claim 15 , further comprising a third electrode electrically connecting the covering portion and the first electrode.

17. The photoelectric conversion element according to claim 10, wherein The semiconductor substrate includes a readout circuit electrically connected to the plurality of second electrodes.

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