U.S. patent application number 17/444431 was filed with the patent office on 2021-11-25 for photoelectric conversion element, imaging device, and electronic apparatus.
The applicant listed for this patent is SONY GROUP CORPORATION. Invention is credited to YU KATO, NOBUYUKI MATSUZAWA, YOSHIAKI OBANA, ICHIRO TAKEMURA.
Application Number | 20210366965 17/444431 |
Document ID | / |
Family ID | 1000005767361 |
Filed Date | 2021-11-25 |
United States Patent
Application |
20210366965 |
Kind Code |
A1 |
KATO; YU ; et al. |
November 25, 2021 |
PHOTOELECTRIC CONVERSION ELEMENT, IMAGING DEVICE, AND ELECTRONIC
APPARATUS
Abstract
A photoelectric conversion element including a first electrode
and a second electrode that are disposed to face each other and a
photoelectric conversion layer that is provided between the first
electrode and the second electrode. The photoelectric conversion
layer contains at least a subphthalocyanine or a subphthalocyanine
derivative, and a carrier dopant, in which the carrier dopant has a
concentration of less than 1% by volume ratio to the
subphthalocyanine or the subphthalocyanine derivative.
Inventors: |
KATO; YU; (KANAGAWA, JP)
; TAKEMURA; ICHIRO; (KANAGAWA, JP) ; OBANA;
YOSHIAKI; (KANAGAWA, JP) ; MATSUZAWA; NOBUYUKI;
(TOKYO, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SONY GROUP CORPORATION |
TOKYO |
|
JP |
|
|
Family ID: |
1000005767361 |
Appl. No.: |
17/444431 |
Filed: |
August 4, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16920030 |
Jul 2, 2020 |
11107849 |
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17444431 |
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16064717 |
Jun 21, 2018 |
10727262 |
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PCT/JP2016/088926 |
Dec 27, 2016 |
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16920030 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/307 20130101;
H01L 27/14612 20130101; Y02E 10/549 20130101; H01L 27/14665
20130101; H01L 51/4253 20130101; H01L 27/14638 20130101; H01L 31/10
20130101; H01L 51/0078 20130101; H01L 27/146 20130101; H01L 51/42
20130101; H01L 51/002 20130101; H01L 27/14621 20130101; H01L
27/1464 20130101; H01L 51/5262 20130101; H01L 27/14647 20130101;
H04N 5/335 20130101 |
International
Class: |
H01L 27/146 20060101
H01L027/146; H01L 31/10 20060101 H01L031/10; H01L 27/30 20060101
H01L027/30; H01L 51/00 20060101 H01L051/00; H01L 51/42 20060101
H01L051/42; H01L 51/52 20060101 H01L051/52; H04N 5/335 20060101
H04N005/335 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2016 |
JP |
2016-004383 |
Mar 25, 2016 |
JP |
2016-062422 |
Claims
1. A photoelectric conversion element, comprising: a first
electrode; a second electrode that faces the first electrode; and a
photoelectric conversion layer between the first electrode and the
second electrode, wherein the photoelectric conversion layer
comprises at least a subphthalocyanine or a subphthalocyanine
derivative, and a carrier dopant, the carrier dopant has a
concentration of less than 1% by volume ratio to the
subphthalocyanine or the subphthalocyanine derivative, and the
photoelectric conversion layer has a maximum absorption wavelength
in a range between 450 nm and 650 nm.
2. The photoelectric conversion element according to claim 1,
wherein an absorption coefficient at the maximum absorption
wavelength is more than two times an absorption coefficient at 450
nm.
3. The photoelectric conversion element according to claim 1,
wherein an absorption coefficient at the maximum absorption
wavelength is more than five times an absorption coefficient at 450
nm.
4. The photoelectric conversion element according to claim 1,
wherein an absorption coefficient at the maximum absorption
wavelength is more than ten times an absorption coefficient at 450
nm.
5. The photoelectric conversion element according to claim 1,
wherein an absorption coefficient at the maximum absorption
wavelength is more than ten times an absorption coefficient at 650
nm.
6. The photoelectric conversion element according to claim 1,
wherein an absorption coefficient at the maximum absorption
wavelength is more than twenty times an absorption coefficient at
650 nm.
7. The photoelectric conversion element according to claim 1,
wherein an absorption coefficient at the maximum absorption
wavelength is more than thirty times an absorption coefficient at
650 nm.
8. The photoelectric conversion element according to claim 1,
wherein the carrier dopant is at least one of triphenylmethane
derivative represented by a following formula (1), acridine
derivative represented by a following formula (2), xanthene
derivative represented by a following formula (3), and
benzimidazole derivative represented by a following formula (4):
##STR00012## where R1 to R13 denote, each independently: hydrogen
atom; halogen atom; a linear chain, branched, or cyclic alkyl
group; thioalkyl group; thioaryl group; arylsulfonyl group;
alkylsulfonyl group; amino group; alkylamino group; arylamino
group; hydroxy group; alkoxy group; acylamino group; acyloxy group;
phenyl group; carboxy group; carboxoamide group; carboalkoxy group;
acyl group; sulfonyl group; cyano group; and nitro group; or a
derivative, wherein R1 to R13 form a cycle by bonding with each
other, and a to h are each an integer of 0 or more.
9. The photoelectric conversion element according to claim 1,
wherein the subphthalocyanine derivative is at least one of
compounds represented by following formulae (5) and (6):
##STR00013## where R14 to R25 and X denote, each independently:
hydrogen atom; halogen atom; a linear chain, branched, or cyclic
alkyl group; thioalkyl group; thioaryl group; arylsulfonyl group;
alkylsulfonyl group; amino group; alkylamino group; arylamino
group; hydroxy group; alkoxy group; acylamino group; acyloxy group;
phenyl group; carboxy group; carboxoamide group; carboalkoxy group;
acyl group; sulfonyl group; cyano group; nitro group; heterocyclic
group; or a derivative, wherein mutually adjacent R14 to R25 form a
cycle by bonding with each other, and M denotes boron, or a
divalent or trivalent metal.
10. The photoelectric conversion element according to claim 1,
wherein the photoelectric conversion layer includes a p-type
semiconductor, and the p-type semiconductor comprises a
quinacridone derivative.
11. The photoelectric conversion element according to claim 10,
wherein the photoelectric conversion layer further includes a
n-type semiconductor, and the n-type semiconductor comprises a
fullerene derivative.
12. An imaging device, comprising: a plurality of pixels, wherein
each of the plurality of pixels comprises at least one organic
photoelectric conversion section, and each of the at least one
organic photoelectric conversion section comprises: a first
electrode; a second electrode that faces the first electrode; and a
photoelectric conversion layer between the first electrode and the
second electrode, wherein the photoelectric conversion layer
comprises at least a subphthalocyanine or a subphthalocyanine
derivative, and a carrier dopant, the carrier dopant has a
concentration of less than 1% by volume ratio to the
subphthalocyanine or the subphthalocyanine derivative, and the
photoelectric conversion layer has a maximum absorption wavelength
in a range between 450 nm and 650 nm.
13. The imaging device according to claim 12, wherein an absorption
coefficient at the maximum absorption wavelength is more than two
times an absorption coefficient at 450 nm.
14. The imaging device according to claim 12, wherein an absorption
coefficient at the maximum absorption wavelength is more than five
times an absorption coefficient at 450 nm.
15. The imaging device according to claim 12, wherein an absorption
coefficient at the maximum absorption wavelength is more than ten
times an absorption coefficient at 450 nm.
16. The imaging device according to claim 12, wherein the at least
one organic photoelectric conversion section and at least one
inorganic photoelectric conversion section are stacked in each of
the plurality of pixels, and the at least one inorganic
photoelectric conversion section is configured to execute a
photoelectric conversion of a wavelength region different from a
wavelength region of the at least one organic photoelectric
conversion section.
17. An electronic apparatus, comprising: an imaging device that
comprises a plurality of pixels, wherein each of the plurality of
pixels comprises at least one organic photoelectric conversion
section, and each of the at least one organic photoelectric
conversion section comprises: a first electrode; a second electrode
that faces the first electrode; and a photoelectric conversion
layer between the first electrode and the second electrode, wherein
the photoelectric conversion layer comprises at least a
subphthalocyanine or a subphthalocyanine derivative, and a carrier
dopant, the carrier dopant has a concentration of less than 1% by
volume ratio to the subphthalocyanine or the subphthalocyanine
derivative, and the photoelectric conversion layer has a maximum
absorption wavelength in a range between 450 nm and 650 nm.
18. The electronic apparatus according to claim 17, wherein an
absorption coefficient at the maximum absorption wavelength is more
than two times an absorption coefficient at 450 nm.
19. The electronic apparatus according to claim 17, wherein an
absorption coefficient at the maximum absorption wavelength is more
than five times an absorption coefficient at 450 nm.
20. The electronic apparatus according to claim 17, wherein an
absorption coefficient at the maximum absorption wavelength is more
than ten times an absorption coefficient at 450 nm.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 16/920,030 filed on Jul. 2, 2020, which
claims priority from U.S. patent application Ser. No. 16/064,717
filed on Jun. 21, 2018, now U.S. Pat. No. 10,727,262, which is a
U.S. National Phase of International Patent Application No.
PCT/JP2016/088926 filed on Dec. 27, 2016, which claims priority
benefit of Japanese Patent Application No. JP 2016-004383 filed in
the Japan Patent Office on Jan. 13, 2016 and also claims priority
benefit of Japanese Patent Application No. JP 2016-062422 filed in
the Japan Patent Office on Mar. 25, 2016. Each of the
above-referenced applications is hereby incorporated herein by
reference in its entirety.
TECHNICAL FIELD
[0002] The disclosure relates to a photoelectric conversion element
and an imaging device using a subphthalocyanine or a
subphthalocyanine derivative, and an electronic apparatus including
the same.
BACKGROUND ART
[0003] In recent years, there has been progress in miniaturization
of a pixel size in a solid-state imaging device such as a CCD
(charge coupled device) image sensor or a CMOS (complementary metal
oxide semiconductor) image sensor. This leads to a phenomenon in
the number of photons that enter a unit pixel, thus leading to
lowered sensitivity as well as a lowered S/N ratio. Further, in a
case where a color filter is used in which primary color filters of
red, green, and blue are two-dimensionally arrayed for
colorization, pieces of light of green and blue are absorbed by the
color filter, for example, in a red pixel, thus causing the
sensitivity to be lowered. Further, an interpolation process is
performed between pixels upon generation of each color signal, thus
causing occurrence of a so-called false color.
[0004] Accordingly, for example, PTL 1 discloses an image sensor
using an organic photoelectric conversion film having a multi-layer
structure in which an organic photoelectric conversion film having
sensitivity to blue light (B), an organic photoelectric conversion
film having sensitivity to green light (G), and an organic
photoelectric conversion film having sensitivity to red light (R)
are sequentially stacked. In this image sensor, the sensitivity is
improved by extracting each of the signals B/G/R separately from
one pixel. PTL 2 discloses an imaging device in which a single
organic photoelectric conversion film is formed, a signal of a
single color is extracted with this organic photoelectric
conversion film, and signals of two colors are extracted using a
silicon (Si) bulk spectroscopy. In so-called laminated imaging
devices (image sensors) disclosed in PTL 1 and PTL 2, incident
light is mostly subjected to photoelectric conversion and thus
read, which allows efficiency of use of visible light to be nearly
100%. Further, color signals of three colors, R, G, and B are
obtained at each light-receiving unit, making it possible to
generate an image with high sensitivity and high resolution (false
color becomes unconspicuous).
[0005] For an organic semiconductor serving to absorb green light
particularly among organic semiconductors configuring an organic
photoelectric conversion film, a subphthalocyanine derivative
having superior selectivity in absorption wavelength is widely
used. However, the subphthalocyanine derivative is low in carrier
mobility, which has caused an issue in which it is not possible to
obtain sufficient photoresponse from an imaging device using the
subphthalocyanine derivative.
[0006] An example of a method of improving conductivity
characteristics of a carrier includes a method of doping a target
layer with a carrier. For example, PTL 3 discloses a photoelectric
conversion element in which transporting a carrier from an anode
and a cathode to a photoelectric conversion layer is facilitated by
doping with a dopant a photoelectric conversion layer containing
poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-
-benzothiadiazole)],
poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophene
diyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophene diyl]
(PCDTBT).
CITATION LIST
Patent Literature
[0007] PTL 1: Japanese Unexamined Patent Application Publication
No. 2003-234460
[0008] PTL 2: Japanese Unexamined Patent Application Publication
No. 2005-303266
[0009] PTL 3: Japanese Unexamined Patent Application Publication
No. 2014-107465
SUMMARY OF INVENTION
[0010] However, in a case where a photoelectric conversion layer
using a subphthalocyanine derivative is simply doped with a dopant,
there has been an issue of insufficient improvement of conductivity
characteristics of a carrier or deterioration of the
characteristics.
[0011] It is desirable to provide a photoelectric conversion
element, an imaging device, and an electronic apparatus that make
it possible to improve photoresponse while maintaining superior
wavelength selectivity of a subphthalocyanine and a
subphthalocyanine derivative.
[0012] A photoelectric conversion element according to an
embodiment of the disclosure includes: a first electrode and a
second electrode that are disposed to face each other; and a
photoelectric conversion layer that is provided between the first
electrode and the second electrode, and contains at least a
subphthalocyanine or a subphthalocyanine derivative, and a carrier
dopant, in which the carrier dopant has a concentration of less
than 1% by volume ratio to the subphthalocyanine or the
subphthalocyanine derivative.
[0013] An imaging device according to an embodiment of the
disclosure is provided in which pixels each have one or a plurality
of organic photoelectric conversion sections, and includes, as an
organic photoelectric conversion section, the photoelectric
conversion element according to the embodiment of the disclosure
above.
[0014] An electronic apparatus according to an embodiment of the
disclosure is provided with an imaging device, in which pixels each
have one or a plurality of organic photoelectric conversion
sections, and the electronic apparatus includes, as an organic
photoelectric conversion section, the photoelectric conversion
element according to the embodiment of the disclosure above.
[0015] In the photoelectric conversion element, the imaging device,
and the electronic apparatus according to the respective
embodiments of the disclosure, the photoelectric conversion layer
provided between the first electrode and the second electrode that
are disposed to face each other is formed using at least the
subphthalocyanine or the subphthalocyanine derivative, and the
carrier dopant having a concentration less than 1% by volume ratio
to the subphthalocyanine or the subphthalocyanine derivative. This
makes it possible to improve mobility of the carrier of the
photoelectric conversion layer containing the subphthalocyanine
derivative.
[0016] In the photoelectric conversion element, the imaging device,
and the electronic apparatus according to the respective
embodiments of the disclosure, the photoelectric conversion layer
is formed using at least the subphthalocyanine or the
subphthalocyanine derivative, and the carrier dopant having a
concentration less than 1% (by volume ratio) to the
subphthalocyanine or the subphthalocyanine derivative. This makes
it possible to improve mobility of the carrier of the photoelectric
conversion layer, leading to the improvement of photoresponse. It
is to be noted that the effects of the disclosure are not
necessarily limited to the effects described above, and may be any
of the effects described in the specification.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a cross-sectional view of an outline configuration
of a photoelectric conversion element according to an embodiment of
the disclosure.
[0018] FIG. 2 is a plan view of a positional relationship among an
organic photoelectric conversion layer, a protective layer (top
electrode), and a contact hole being formed.
[0019] FIG. 3A is a cross-sectional view of a configuration example
of an inorganic photoelectric conversion section.
[0020] FIG. 3B is another cross-sectional view of the inorganic
photoelectric conversion section illustrated in FIG. 3A.
[0021] FIG. 4 is a cross-sectional view of a configuration
(extraction of electrons on lower side) of an electric charge
(electron) accumulation layer of an inorganic photoelectric
conversion section.
[0022] FIG. 5A is a cross-sectional view describing a method of
manufacturing the photoelectric conversion element illustrated in
FIG. 1.
[0023] FIG. 5B is a cross-sectional view of a step subsequent to
FIG. 5A.
[0024] FIG. 6A is a cross-sectional view of a step subsequent to
FIG. 5B.
[0025] FIG. 6B is a cross-sectional view of a step subsequent to
FIG. 6A.
[0026] FIG. 7A is a cross-sectional view of a step subsequent to
FIG. 6B.
[0027] FIG. 7B is a cross-sectional view of a step subsequent to
FIG. 7A.
[0028] FIG. 7C is a cross-sectional view of a step subsequent to
FIG. 7B.
[0029] FIG. 8 is a cross-sectional view of a main part describing a
working of the photoelectric conversion element illustrated in FIG.
1.
[0030] FIG. 9 is a schematic diagram describing a working of the
photoelectric conversion element illustrated in FIG. 1.
[0031] FIG. 10 is a cross-sectional view of a schematic
configuration of a photoelectric conversion element according to a
modification example of the disclosure.
[0032] FIG. 11 is a functional block diagram of an imaging device
using the photoelectric conversion element illustrated in FIG. 1 as
a pixel.
[0033] FIG. 12 is a block diagram of an outline configuration of an
electronic apparatus (imaging unit) including the imaging device
illustrated in FIG. 11.
[0034] FIG. 13 is a characteristic graph illustrating a relation
between a dopant concentration and photoresponse in experiment
example 1.
[0035] FIG. 14 is a characteristic graph illustrating a relation
between a dopant concentration and photoresponse in experiment
example 2.
[0036] FIG. 15 is an I-V characteristic graph in experiment example
3-1.
[0037] FIG. 16 is an I-V characteristic graph in experiment example
3-2.
[0038] FIG. 17 is an I-V characteristic graph in experiment example
3-3.
[0039] FIG. 18 is an absorption spectrum graph in experiment
example 4.
MODES FOR CARRYING OUT THE INVENTION
[0040] In the following, some embodiments of the disclosure are
described in detail with reference to drawings. It is to be noted
that description is given in the following order.
[0041] 1. Embodiment (a photoelectric conversion element containing
a subphthalocyanine or a subphthalocyanine derivative, and a dopant
in an organic photoelectric conversion layer)
[0042] 1-1. Basic Configuration
[0043] 1-2. Manufacturing Method
[0044] 1-3. Workings and Effects
[0045] 2. Modification Example (a photoelectric conversion element
in which a plurality of organic photoelectric conversion layers are
stacked)
[0046] 3. Application Examples
[0047] 4. Examples
1. EMBODIMENT
[0048] FIG. 1 illustrates a cross-sectional configuration of a
photoelectric conversion element (photoelectric conversion element
10) according to an embodiment of the disclosure. The photoelectric
conversion element 10 constitutes a single pixel in, for example,
an imaging device (described later) such as a CCD image sensor or a
CMOS image sensor. The photoelectric conversion device 10 has a
structure in which an organic photoelectric conversion section 11G
and two inorganic photoelectric conversion sections 11B and 11R are
stacked in a vertical direction. The organic photoelectric
conversion section 11G and the inorganic photoelectric conversion
sections 11B and 11R each selectively detect corresponding one of
pieces of light of different wavelength regions to perform
photoelectric conversion. Further, the photoelectric conversion
element 10 includes a multi-layer wiring layer (multi-layer wiring
layer 51) and pixel transistors (including later-described transfer
transistors Tr1 to Tr3) formed on side of a front face (a face S2
opposite to a light-receiving face) of a semiconductor substrate 11
on which the inorganic photoelectric conversion sections 11B and
11R are provided.
[0049] According to the photoelectric conversion element 10 of the
present embodiment, the organic photoelectric conversion section
11G is formed using a subphthalocyanine or a subphthalocyanine
derivative and a carrier dopant.
[0050] (1-1. Basic Configuration)
[0051] The photoelectric conversion element 10 has a stacked
structure of one organic photoelectric conversion section 11G and
two inorganic photoelectric conversion sections 11B and 11R. This
allows for obtainment of respective color signals of red (R), green
(G), and blue (B) using a single element. The organic photoelectric
conversion section 11G is formed on a back face (face S1) of the
semiconductor substrate 11, and the inorganic photoelectric
conversion sections 11B and 11R are formed to be embedded inside
the semiconductor substrate 11. Description is given below of a
configuration of each section.
[0052] (Organic Photoelectric Conversion Section 11G)
[0053] The organic photoelectric conversion section 11G is an
organic photoelectric conversion element that uses an organic
semiconductor to absorb light (here, green light) of a selective
wavelength region, thus generating an electron-hole pair. The
organic photoelectric conversion section 11G has a configuration in
which an organic photoelectric conversion layer 17 is interposed
between a pair of electrodes (bottom electrode 15a and top
electrode 18) that extract a signal electric charge. As described
later, the bottom electrode 15a and the top electrode 18 are
electrically coupled to electrically-conductive plugs 120a1 and
120b1 each embedded inside the semiconductor substrate 11, through
a wiring layer and a contact metal layer.
[0054] Specifically, in the organic photoelectric conversion
section 11G, interlayer insulating films 12 and 14 are formed on
the face S1 of the semiconductor substrate 11. The interlayer
insulating film 12 has through-holes provided in respective regions
that face the later-described electrically-conductive plugs 120a1
and 120b1. Electrically-conductive plugs 120a2 and 120b2 are
embedded in the respective through-holes. In the interlayer
insulating film 14, wiring layers 13a and 13b are embedded in
respective regions that face the electrically-conductive plugs
120a2 and 120b2. The bottom electrode 15a and a wiring layer 15b
electrically separated from the bottom electrode 15a by the
insulating film 16 are provided on the interlayer insulating film
14. Among those, the organic photoelectric conversion layer 17 is
formed on the bottom electrode 15a, and the top electrode 18 is so
formed as to cover the organic photoelectric conversion layer 17. A
protective layer 19 is so formed on the top electrode 18 as to
cover a face of the top electrode 18, although the detail is
described later. A contact hole H is provided in a predetermined
region of the protective layer 19. A contact metal layer 20 is
formed on the protective layer 19 which fills the contact hole H
and extends up to an upper face of the wiring layer 15b.
[0055] The electrically-conductive plug 120a2, together with the
electrically-conductive plug 120a1 and the wiring layer 13a,
functions as a connector together with the electrically-conductive
plug 120a1, and forms a transmission path of an electric charge
(electron) from the bottom electrode 15a to a later-described
electricity storage layer for green 110G. The
electrically-conductive plug 120b2 functions as a connector
together with the electrically-conductive plug 120b1, and forms,
together with the electrically-conductive plug 120b1, the wiring
layer 13b, the wiring layer 15b, and the contact metal layer 20, a
discharge path of an electric charge (hole) from the top electrode
18. The electrically-conductive plugs 120a2 and 120b2 are desirably
configured by, for example, a stacked film of a metal material such
as titanium (Ti), titanium nitride (TiN), and tungsten, in order to
allow the electrically-conductive plugs 120a2 and 120b2 to function
also as a light-shielding film. Further, the use of such a stacked
film is desirable because this enables a contact with silicon to be
secured also in a case where the electrically-conductive plugs
120a1 and 120b1 are each formed as an n-type or p-type
semiconductor layer.
[0056] The interlayer insulating film 12 is desirably configured by
an insulating film having a small interface state in order to
reduce the interface state with the semiconductor substrate 11
(silicon layer 110) and to suppress occurrence of a dark current
from an interface with the silicon layer 110. As such an insulating
film, for example, a stacked film of a hafnium oxide (HfO.sub.2)
film and a silicon oxide (SiO.sub.2) film may be used. The
interlayer insulating film 14 is configured by a monolayer film
containing one of silicon oxide, silicon nitride, and silicon
oxynitride (SiON), for example, or alternatively is configured by a
stacked film containing two or more thereof.
[0057] The insulating film 16 is configured by a monolayer film
containing one of silicon oxide, silicon nitride, and silicon
oxynitride (SiON), for example, or alternatively is configured by a
stacked film containing two or more thereof. The insulating film 16
has a planarized face, for example, and has a substantially
stepless shape and pattern with respect to the bottom electrode
15a. The insulating film 16 has a function of electrically
separating the bottom electrodes 15a of the respective pixels from
one another in a case where the photoelectric conversion element 10
is used as a pixel of the solid-state imaging device.
[0058] The bottom electrode 15a is provided at a region that faces
light-receiving faces of the inorganic photoelectric conversion
sections 11B and 11R formed inside the semiconductor substrate 11
and covers the light-receiving faces. The bottom electrode 15a is
configured by an electrically-conductive film having
light-transmissivity, and includes ITO (indium tin oxide), for
example. However, as a constituent material of the bottom electrode
15a, a dopant-doped tin oxide (SnO.sub.2)-based material or a zinc
oxide-based material in which aluminum zinc oxide (ZnO) is doped
with a dopant may be used, besides the ITO. Examples of the zinc
oxide-based material include aluminum zinc oxide (AZO) doped with
aluminum (Al) as a dopant, gallium (Ga)-doped gallium zinc oxide
(GZO), and indium (In)-doped indium zinc oxide (IZO). Aside from
those described above, for example, CuI, InSbO.sub.4, ZnMgO,
CuInO.sub.2, MgIN.sub.2O.sub.4, CdO, and ZnSnO.sub.3 may be used.
It is to be noted that, in the present embodiment, a signal
electric charge (electron) is extracted from the bottom electrode
15a. Therefore, in the later-described solid-state imaging device
using the photoelectric conversion element 10 as a pixel, this
bottom electrode 15a is formed in a manner to be separated on a
pixel-by-pixel basis.
[0059] The organic photoelectric conversion layer 17 includes
either one or both of an organic p-type semiconductor and an
organic n-type semiconductor, and allows for transmission of light
of another wavelength region while subjecting light of a selective
wavelength region to photoelectric conversion. Here, the organic
photoelectric conversion layer 17 has a maximum absorption
wavelength in a range of no less than 450 nm and no more than 650
nm, for example.
[0060] In the present embodiment, the organic photoelectric
conversion layer 17 is formed using a subphthalocyanine or a
subphthalocyanine derivative represented by the following formulae
(5) or (6), for example, and a carrier dopant. The carrier dopant
provides a carrier to the subphthalocyanine or the
subphthalocyanine derivative in the organic photoelectric
conversion layer 17, to thereby improve the conductivity of the
carrier in the organic photoelectric conversion layer 17.
##STR00001##
(where R14 to R25 and X denote, each independently: hydrogen atom;
halogen atom; a linear chain, branched, or cyclic alkyl group;
thioalkyl group; thioaryl group; arylsulfonyl group; alkylsulfonyl
group; amino group; alkylamino group; arylamino group; hydroxy
group; alkoxy group; acylamino group; acyloxy group; phenyl group;
carboxy group; carboxoamide group; carboalkoxy group; acyl group;
sulfonyl group; cyano group; nitro group; heterocyclic group; or a
derivative thereof. Any mutually adjacent R14 to R25 may form a
cycle by bonding with each other. M denotes boron, or a divalent or
trivalent metal.)
[0061] Specific examples of the subphthalocyanine or the
subphthalocyanine derivative represented by the above formulae (5)
and (6) include the following formulae (5-1) to (5-14), and the
formulae (6-1) and (6-2).
##STR00002## ##STR00003## ##STR00004## ##STR00005##
[0062] The carrier dopant is preferably an organic material. The
organic material has high stability in air and is larger in
molecular size as well. Therefore, diffusion of a carrier dopant
after discharging the carrier is suppressed, making it possible to
prevent a characteristic defect from occurring. Furthermore, in a
case where the subphthalocyanine or the subphthalocyanine
derivative functions as an n-type semiconductor in the organic
photoelectric conversion layer 17, it is preferable to select a
dopant that is able to donate electrons to the subphthalocyanine or
the subphthalocyanine derivative, i.e. select an organic material
that functions as an electron dopant. An electron dopant with
superior stability in air has a deep HOMO level and involves
difficulty in oxidization in the atmosphere, and is accompanied
with, upon doping, a chemical reaction, or an elimination reaction
or an addition reaction of, for example, hydrogen, carbon oxide,
nitrogen, or hydroxyl radical. Herein, a chemical reaction refers
to a reaction accompanied with breaking or generating of a chemical
bond. Examples of such an electron dopant include a
triphenylmethane derivative represented by the following formula
(1), an acridine derivative represented by the following formula
(2), a xanthenes derivative represented by the following formula
(3), and a benzimidazole derivative represented by the following
formula (4). At least one of these electron dopants is preferably
used for the organic photoelectric conversion layer 17 according to
the present embodiment.
##STR00006##
(where R1 to R13 denote, each independently: hydrogen atom; halogen
atom; a linear chain, branched, or cyclic alkyl group; thioalkyl
group; thioaryl group; arylsulfonyl group; alkylsulfonyl group;
amino group; alkylamino group; arylamino group; hydroxy group;
alkoxy group; acylamino group; acyloxy group; phenyl group; carboxy
group; carboxoamide group; carboalkoxy group; acyl group; sulfonyl
group; cyano group; and nitro group; or a derivative thereof.
Further, R1 to R13 may form a cycle by bonding with each other and
a to h are each an integer of 0 or more.)
[0063] Examples of the electron dopants represented by the above
formulae (1) to (4) include the following formulae (1-1), (1-2),
(2-1), (3-1), (3-2), and (4-1) to (4-3).
##STR00007##
[0064] It is to be noted that it is possible to form the organic
photoelectric conversion layer 17, for example, using a coating
method or a vapor deposition method; however, in a case of forming
using a vapor deposition method in particular, it is possible to
use a precursor of the above-described materials. Examples of the
precursors of the above formulae (1-1), (1-2), (2-1), (3-1), (3-2),
and (4-1) to (4-3) include the following formulae (1-1'), (1-2'),
(2-1'), (3-1'), (3-2'), and (4-1') to (4-3').
##STR00008##
[0065] It is to be noted that, specifically, the precursors of the
above-described electron dopants are transformed to the electron
dopants represented by the above formulae (1-1), (1-2), (2-1),
(3-1), (3-2), and (4-1) to (4-3), for example, through the
following processes. Description is given by exemplifying a
chloride, which is a precursor of crystal violet, represented by
the formula (1-1'), for example. First, a vapor deposition boat
containing a chloride of crystal violet is heated. Hydrogen (H) is
added to the chloride of crystal violet in the vapor evaporation
boat for reduction, to thereby generate leuco salt of crystal
violet (formula (1-1)). The mixing of the leuco salt of crystal
violet with the subphthalocyanine or the subphthalocyanine
derivative allows for working as an electron dopant. Specifically,
electrons are discharged and H is eliminated, to thereby generate
cation of crystal violet.
[0066] For the doping amount of a carrier dopant, the dopant
concentration (by volume ratio) to the subphthalocyanine or the
subphthalocyanine derivative in the organic photoelectric
conversion layer 17, for example, is preferably less than 1%.
Although described in detailed later, in a case where the dopant
concentration is no less than 1%, conductivity of a carrier in the
organic photoelectric conversion layer 17 may not be improved, and
further, the conductivity of the carrier may be lowered, leading to
deterioration of photoresponse. It is noted that, in a case where
two or more kinds of carrier dopants (electron dopants) described
above are combined and used, for example, the total dopant
concentration combining all the carrier dopants used for the
organic photoelectric conversion layer 17 to the subphthalocyanine
or the subphthalocyanine derivative is preferably less than 1%. The
conversion from volume ratio to mole ratio is calculated by the
following expression.
(m=Ddopant/Mdopant)/(Dhost/Mhost).times.V (Numerical Expression
1)
(m: mole concentration, M: molecular weight (g/mol), D: film
density (g/cm.sup.3), V: volume concentration)
[0067] For the organic photoelectric conversion layer 17, it is
preferable to further use, as a p-type semiconductor, a
quinacridone or a derivative thereof represented by the following
formulae (7-1) and (7-2). Use of the subphthalocyanine or the
subphthalocyanine derivative, and a carrier dopant, as well as the
quinacridone or the derivative thereof allows for the improvement
of separation efficiency of exciton and the increase of
photoelectric current. Further, efficiency of electron transport as
well as efficiency of hole transport are secured, to thereby ensure
the conductivity of electrons and holes. Further, for the organic
photoelectric conversion layer 17, it is preferable to further use,
as an n-type semiconductor, a fullerene or a derivative thereof.
Use of the fullerene or the derivative thereof makes it possible to
improve efficiency of electron transport.
##STR00009##
It is to be noted that the subphthalocyanine or the
subphthalocyanine derivative may function as a p-type
semiconductor, depending on a combination of materials constituting
the organic photoelectric conversion layer 17. In such a case, for
a carrier dopant, it is preferable to select a dopant that is able
to donate holes to the subphthalocyanine or the subphthalocyanine
derivative, i.e. select an organic material that functions as a
hole dopant. Examples of such a material include a
tetracyanoquinodimethane derivative, a
tetracyanonaphtoquinodimethane derivative, and a fullerene fluoride
derivative.
[0068] Any other unillustrated layer may be provided between the
organic photoelectric conversion layer 17 and the bottom electrode
15a and between the organic photoelectric conversion layer 17 and
the top electrode 18. For example, an underlying film, a hole
transport layer, an electron blocking film, the organic
photoelectric conversion layer 17, a hole blocking film, a buffer
film, an electron transport layer, and a work function adjustment
film may be stacked in order from side of the bottom electrode
15a.
[0069] The top electrode 18 is configured by the
electrically-conductive film having light-transmissivity similarly
to that of the bottom electrode 15a. In the solid-state imaging
device using the photoelectric conversion element 10 as a pixel,
the top electrode 18 may be separated on a pixel-by-pixel basis, or
may be formed as an electrode common to the respective pixels. The
top electrode 18 has a thickness of 10 nm to 200 nm, for
example.
[0070] The protective layer 19 includes a material having
light-transmissivity, and is, for example, a monolayer film
containing one of silicon oxide, silicon nitride, and silicon
oxynitride, or alternatively is a stacked film containing two or
more thereof. The protective layer 19 has a thickness of 100 nm to
30000 nm, for example.
[0071] The contact metal layer 20 is configured by a stacked film
containing one of titanium, tungsten, titanium nitride, and
aluminum, for example, or alternatively two or more thereof.
[0072] The top electrode 18 and the protective film 19 are so
provided as to cover the organic photoelectric conversion layer 17,
for example. FIG. 2 illustrates a planar configuration of the
organic photoelectric conversion layer 17, the protective film 19
(top electrode 18), and the contact hole H.
[0073] Specifically, a peripheral part e2 of the protective layer
19 (applicable likewise to the top electrode 18) is located outside
a peripheral part e1 of the organic photoelectric conversion layer
17. The protective layer 19 and the top electrode 18 are formed to
be expanded outward beyond the organic photoelectric conversion
layer 17. In detail, the top electrode 18 is so formed as to cover
an upper face and side faces of the organic photoelectric
conversion layer 17 and to extend up to a portion on the insulating
film 16. The protective layer 19 is formed to cover an upper face
of such a top electrode 18 and to have a planar shape equivalent to
that of the top electrode 18. The contact hole H is provided in a
non-opposed region to the organic photoelectric conversion layer
17, of the protective layer 19 (region outside the peripheral part
e1), causing a portion of a surface of the top electrode 18 to be
exposed. A distance between the peripheral part e1 and the
peripheral part e2 is, for example, 1 .mu.m to 500 .mu.m, although
the distance is not particularly limited. It is to be noted that,
although FIG. 2 illustrates a single rectangular contact hole H
provided along an edge side of the organic photoelectric conversion
layer 17, the shape and the number of the contact hole H are not
limited thereto; other shapes (e.g., circular shape and square
shape) may be adopted, and a plurality of contact holes H may be
provided.
[0074] A planarization layer 21 is so formed on the protective
layer 19 and the contact metal layer 20 as to cover the whole face.
An on-chip lens 22 (microlens) is provided on the planarization
layer 21. The on-chip lens 22 condenses light incident from above
to each light-receiving face of the organic photoelectric
conversion section 11G, and the inorganic photoelectric conversion
sections 11B and 11R. In the present embodiment, the multi-layer
wiring layer 51 is formed on side of the face S2 of the
semiconductor substrate 11, thus making it possible to allow the
respective light-receiving faces of the organic photoelectric
conversion section 11G and the inorganic photoelectric conversion
sections 11B and 11R to be disposed closer to one another. Thus, it
becomes possible to reduce a variation in sensitivity among
respective colors occurring depending on an F value of the on-chip
lens 22.
[0075] It is to be noted that, in the photoelectric conversion
element 10 according to the present embodiment, a signal electric
charge (electron) is extracted from the bottom electrode 15a, and
thus the solid-state imaging device using the photoelectric
conversion element 10 as a pixel may adopt the top electrode 18 as
a common electrode. In this case, the above-described transmission
path including the contact hole H, the contact metal layer 20, the
wiring layers 15b and 13b, and the electrically-conductive plugs
120b1 and 120b2 may be formed at at least one location for all the
pixels.
[0076] In the semiconductor substrate 11, for example, the
inorganic photoelectric conversion sections 11B and 11R and the
electricity storage layer for green 110G are formed to be embedded
in a predetermined region of the n-type silicon (Si) layer 110.
Further, the electrically-conductive plugs 120a1 and 120b1 are
embedded in the semiconductor substrate 11. The
electrically-conductive plugs 120a1 and 120b1 serve as a
transmission path of an electric charge (electron or hole (hole))
from the organic photoelectric conversion section 11G. In the
present embodiment, the back face (face 51) of the semiconductor
substrate 11 serves as a light-receiving face. On side of the front
face (face S2) of the semiconductor substrate 11, a plurality of
pixel transistors (including transfer transistors Tr1 to Tr3)
corresponding, respectively, to the organic photoelectric
conversion section 11G and the inorganic photoelectric conversion
sections 11B and 11R, are formed, and a peripheral circuit
configured by a logic circuit, etc., is formed.
[0077] Examples of the pixel transistors include a transfer
transistor, a reset transistor, an amplifying transistor, and a
selection transistor. Each of these pixel transistors is
configured, for example, by a MOS transistor, and is formed in a
p-type semiconductor well region on side of the face S2. A circuit
that includes such pixel transistors is formed for each of the
photoelectric conversion sections of red, green, and blue. Each of
the circuits may have a three-transistor configuration that
includes three transistors in total, configured by the transfer
transistor, the reset transistor, and the amplifying transistor,
for example, among these pixel transistors. Alternatively, each of
the circuits may have a four-transistor configuration that includes
the selection transistor in addition thereto. Here, illustration
and description are given only of the transfer transistors Tr1 to
Tr3 among these pixel transistors. Further, the pixel transistor
other than the transfer transistors may be shared by the
photoelectric conversion sections or by the pixels. Furthermore, a
so-called pixel-shared structure may also be applied in which a
floating diffusion is shared.
[0078] The transfer transistors Tr1 to Tr3 each include a gate
electrode (gate electrode TG1, TG2, or TG3) and a floating
diffusion (FD113, FD114, or FD116). The transfer transistor Tr1
transfers, to a later-described vertical signal line Lsig, a signal
electric charge (electron, in the present embodiment) corresponding
to a green color that is generated in the organic photoelectric
conversion section 11G and is accumulated in the electricity
storage layer for green 110G. The transfer transistor Tr2
transfers, to the later-described vertical signal line Lsig, a
signal electric charge (electron, in the present embodiment)
corresponding to a blue color that is generated in the inorganic
photoelectric conversion section 11B and is accumulated. Likewise,
the transfer transistor Tr3 transfers, to the later-described
vertical signal line Lsig, a signal electric charge (electron, in
the present embodiment) corresponding to a red color that is
generated in the inorganic photoelectric conversion section 11R and
is accumulated.
[0079] The inorganic photoelectric conversion sections 11B and 11R
are each a photodiode (Photo Diode) that has a p-n junction. The
inorganic photoelectric conversion sections 11B and 11R are formed
in order from side of the face S1 on an optical path in the
semiconductor substrate 11. Among these, the inorganic
photoelectric conversion section 11B selectively detects blue light
and accumulates a signal electric charge corresponding to the blue
color. The inorganic photoelectric conversion section 11B is formed
to extend, for example, from a selective region along the face S1
of the semiconductor substrate 11 to a region near an interface
with the multi-layer wiring layer 51. The inorganic photoelectric
conversion section 11R selectively detects red light and
accumulates a signal electric charge corresponding to the red
color. The inorganic photoelectric conversion section 11R is
formed, for example, in a region in a lower layer (on face S2 side)
than the inorganic photoelectric conversion section 11B. It is to
be noted that the blue (B) is a color that corresponds to a
wavelength region from 450 nm to 495 nm, for example, and the red
(R) is a color that corresponds to a wavelength region from 620 nm
to 750 nm, for example. It is acceptable so long as the inorganic
photoelectric conversion sections 11B and 11R are able to detect
light of a portion or all of the respective wavelength regions
described above.
[0080] FIG. 3A illustrates a detailed configuration example of the
inorganic photoelectric conversion sections 11B and 11R. FIG. 3B
corresponds to a configuration in another cross-section in FIG. 3A.
It is to be noted that, in the present embodiment, description is
given of a case where, among a pair of an electron and a hole
generated by photoelectric conversion, the electron is read as a
signal electric charge (case where an n-type semiconductor region
serves as a photoelectric conversion layer). Further, in the
drawing, "+(plus)" in a superscript manner attached to "p" or "n"
indicates that p-type or n-type impurity concentration is high.
Furthermore, among the pixel transistors, the gate electrodes TG2
and TG3 of the transfer transistors Tr2 and Tr3 are also
illustrated.
[0081] The inorganic photoelectric conversion section 11B includes,
for example, a p-type semiconductor region (hereinafter, simply
referred to as "p-type region", applicable likewise to the case of
n-type) 111p to serve as a hole accumulation layer, and an n-type
photoelectric conversion layer (n-type region) 111n to serve as an
electron accumulation layer. The p-type region 111p and the n-type
photoelectric conversion layer 111n are each formed in a selective
region near the face S1. A portion of each of the p-type region
111p and the n-type photoelectric conversion layer 111n is bent and
so formed and extend as to reach the interface with the face S2.
The p-type region 111p is coupled to an unillustrated p-type
semiconductor well region on side of the face S1. The n-type
photoelectric conversion layer 111n is coupled to the FD113 (n-type
region) of the transfer transistor Tr2 for the blue color. It is to
be noted that a p-type region 113p (hole accumulation layer) is
formed near an interface between the face S2 and each of the end
portions of the p-type region 111p and the n-type photoelectric
conversion layer 111n on side of the face S2.
[0082] The inorganic photoelectric conversion section 11R is
formed, for example, between p-type regions 112p1 and 112p2 (hole
accumulation layers), with an n-type photoelectric conversion layer
112n (electron accumulation layer) being interposed therebetween
(having a p-n-p stacked structure). A portion of the n-type
photoelectric conversion layer 112n is bent and so formed and
extend as to reach the interface with the face S2. The n-type
photoelectric conversion layer 112n is coupled to the FD 114
(n-type region) of the transfer transistor Tr3 for the red color.
It is to be noted that the p-type region 113p (hole accumulation
layer) is formed at least near the interface between the face S2
and an end portion of the n-type photoelectric conversion layer
111n on side of the face S2.
[0083] FIG. 4 illustrates a detailed configuration example of the
electricity storage layer for green 110G. It is to be noted that
description is given here of a case where, between a pair of an
electron and a hole generated by the organic photoelectric
conversion section 11G, the electron is read as a signal electric
charge from side of the bottom electrode 15a. Further, FIG. 4 also
illustrates the gate electrode TG1 of the transfer transistor Tr1
between the pixel transistors.
[0084] The electricity storage layer for green 110G includes an
n-type region 115n that serves as an electron accumulation layer. A
portion of the n-type region 115n is coupled to the
electrically-conductive plug 120a1, and accumulates electrons
supplied from side of the bottom electrode 15a via the
electrically-conductive plug 120a1. The n-type region 115n is also
coupled to the FD 116 (n-type region) of the transfer transistor
Tr1 for the green color. It is to be noted that a p-type region
115p (hole accumulation layer) is formed near an interface between
the n-type region 115n and the face S2.
[0085] The electrically-conductive plugs 120a1 and 120b1, together
with the later-described electrically-conductive plugs 120a2 and
120b2, each function as a connector between the organic
photoelectric conversion section 11G and the semiconductor
substrate 11, and forms a transmission path for electrons or holes
generated in the organic photoelectric conversion section 11G. In
the present embodiment, the electrically-conductive plug 120a1 is
in electric conduction with the bottom electrode 15a of the organic
photoelectric conversion section 11G, and is coupled to the
electricity storage layer for green 110G. The
electrically-conductive plug 120b1 is electrically conducted to the
top electrode 18 of the organic photoelectric conversion section
11G, and serves as a wiring line for discharge of holes.
[0086] These electrically-conductive plugs 120a1 and 120b1 are each
configured, for example, by an electrically-conductive type
semiconductor layer, and are each formed to be embedded in the
semiconductor substrate 11. In this case, the
electrically-conductive plug 120a1 may be of an n-type (because it
serves as the transmission path of electrons). The
electrically-conductive plug 120b1 may be of a p-type (because it
serves as the transmission path of holes). Alternatively, the
electrically-conductive plugs 120a1 and 120b1 may each include, for
example, an electrically-conductive film material such as tungsten
embedded in a through-via. In this case, for example, in order to
suppress short circuit with silicon, a side face of the via is
desirably covered with an insulating film containing a material
such as silicon oxide (SiO.sub.2) or silicon nitride (SiN).
[0087] The multi-layer wiring layer 51 is formed on the face S2 of
the semiconductor substrate 11. In the multi-layer wiring layer 51,
a plurality of wiring lines 51a are provided through an interlayer
insulating film 52. In this manner, the multi-layer wiring layer 51
is formed on side opposite to the light-receiving face in the
photoelectric conversion element 10, which makes it possible to
achieve a so-called backside illumination type solid-state imaging
device. A support substrate 53 containing silicon, for example, is
joined to the multi-layer wiring layer 51.
[0088] (1-2. Manufacturing Method)
[0089] For example, it is possible to manufacture the photoelectric
conversion element 10 as follows. FIGS. 5A, 5B, 6A, 6B, 7A, 7B, and
7C illustrate a manufacturing method of the photoelectric
conversion element 10 in order of steps. It is to be noted that
FIGS. 7A, 7B, and 7C illustrate only a configuration of a main part
of the photoelectric conversion element 10. It is to be noted that
a method of fabricating the photoelectric conversion element 10 to
be described below is merely an example, and thus a method of
fabricating the photoelectric conversion element 10 (and a
later-described photoelectric conversion element 30) according to
an embodiment of the disclosure is not limited to examples
below.
[0090] First, the semiconductor substrate 11 is formed.
Specifically, a so-called SOI substrate is prepared, in which the
silicon layer 110 is formed on a silicon base 1101 with a silicon
oxide film 1102 being interposed therebetween. It is to be noted
that a face on side of the silicon oxide film 1102 of the silicon
layer 110 serves as a back face (face S1) of the semiconductor
substrate 11. FIGS. 5A and 5B illustrate the structure illustrated
in FIG. 1 in a vertically inverted state. Subsequently, as
illustrated in FIG. 5A, the electrically-conductive plugs 120a1 and
120b1 are formed in the silicon layer 110. In this situation, it is
possible to form the electrically-conductive plugs 120a1 and 120b1,
for example, by forming through-vias in the silicon layer 110 and
thereafter embedding, inside the through-vias, tungsten and barrier
metal such as the above-described silicon nitride. Alternatively,
for example, ion implantation into the silicon layer 110 may be
adopted to form an electrically conductive impurity semiconductor
layer. In this case, the electrically-conductive plugs 120a1 and
120b1 are formed, respectively, as an n-type semiconductor layer
and a p-type semiconductor layer. Thereafter, for example, the
inorganic photoelectric conversion sections 11B and 11R each having
the p-type region and n-type region illustrated in FIG. 3A are
formed by ion implantation in regions having different depths
inside the silicon layer 110 (so as to overlap each other).
Further, the electricity storage layer for green 110G is formed by
ion implantation at a region adjacent to the
electrically-conductive plug 120a1. In this manner, the
semiconductor substrate 11 is formed.
[0091] Subsequently, the pixel transistor including the transfer
transistors Tr1 to Tr3, and the peripheral circuit such as a logic
circuit are formed on side of the face S2 of the semiconductor
substrate 11. Thereafter, as illustrated in FIG. 5B, the wiring
lines 51a of a plurality of layers are formed on the face S2 of the
semiconductor substrate 11 through the interlayer insulating film
52, to thereby form the multi-layer wiring layer 51. Subsequently,
the support substrate 53 including silicon is joined onto the
multi-layer wiring layer 51. Thereafter, the silicon base 1101 and
the silicon oxide film 1102 are peeled off from side of the face 51
of the semiconductor substrate 11 to expose the face 51 of the
semiconductor substrate 11.
[0092] Next, the organic photoelectric conversion section 11G is
formed on the face 51 of the semiconductor substrate 11.
Specifically, as illustrated in FIG. 6A, first, the interlayer
insulating film 12 configured by the stacked film of a hafnium
oxide film and a silicon oxide film as described above is formed on
the face 51 of the semiconductor substrate 11. For example, the
hafnium oxide film is formed by an atomic layer deposition (ALD)
method, and thereafter, for example, the silicon oxide film is
formed by a plasma chemical vapor deposition (CVD) method.
Thereafter, contact holes H1a and H1b are formed at positions
facing the respective electrically-conductive plugs 120a1 and 120b1
of the interlayer insulating film 12. The electrically-conductive
plugs 120a2 and 120b2 including the above-described material are so
formed as to fill the contact holes H1a and H1b, respectively. In
this situation, the electrically-conductive plugs 120a2 and 120b2
may be each formed to expand to a region that is desired to be
light-shielded (to cover the region that is desired to be
light-shielded). Alternatively, a light-shielding film may be
formed at a region separated from the electrically-conductive plugs
120a2 and 120b2.
[0093] Subsequently, as illustrated in FIG. 6B, the interlayer
insulating film 14 including the above-described material is formed
by the plasma CVD method, for example. It is to be noted that,
after the formation of the film, a surface of the interlayer
insulating film 14 is desirably planarized by a chemical mechanical
polishing (CMP) method, for example. Next, contact holes are opened
at positions facing the electrically-conductive plugs 120a2 and
120b2 of the interlayer insulating film 14. The contact holes are
filled with the above-described material to form the wiring layers
13a and 13b. It is to be noted that the CMP method, for example,
may be desirably used thereafter to remove a residual wiring layer
material (such as tungsten) on the interlayer insulating film 14.
Next, the bottom electrode 15a is formed on the interlayer
insulating film 14. Specifically, first, the above-described
transparent electrically-conductive film is formed over the entire
surface of the interlayer insulating film 14 by a sputtering
method, for example. Thereafter, a photolithography method is used
(exposure and development of a photoresist film, post-bake, etc.
are performed), and a selective portion is removed by dry etching
or wet etching, for example, thus forming the bottom electrode 15a.
In this situation, the bottom electrode 15a is formed at a region
that faces the wiring layer 13a. Further, upon the process of the
transparent electrically-conductive film, the transparent
electrically-conductive film is allowed to remain also at a region
that faces the wiring layer 13b, thereby forming the wiring layer
15b that constitutes a portion of the transmission path of holes,
together with the bottom electrode 15a.
[0094] Subsequently, the insulating film 16 is formed. In this
situation, first, the insulating film 16 including the
above-described material is formed, for example, by the plasma CVD
method over the entire surface on the semiconductor substrate 11 to
cover the interlayer insulating film 14, the bottom electrode 15a,
and the wiring layer 15b. Thereafter, as illustrated in FIG. 7A,
the formed insulating film 16 is polished, for example, by the CMP
method. Thus, the bottom electrode 15a and the wiring layer 15b are
exposed from the insulating film 16, and a step difference between
the bottom electrode 15a and the insulating film 16 are moderated
(desirably planarized).
[0095] Next, as illustrated in FIG. 7B, the organic photoelectric
conversion layer 17 is formed on the bottom electrode 15a. In this
situation, the above-described carrier dopant and the
subphthalocyanine or the subphthalocyanine derivative are patterned
to be formed by a vacuum deposition method, for example. It is to
be noted that, as described above, when other organic layers (such
as electron blocking film) are formed as an upper layer or a lower
layer of the organic photoelectric conversion layer 17, it is
desirable to form the layers successively in a vacuum process
(through a vacuum consistent process). Further, the film-forming
method of the organic photoelectric conversion layer 17 is not
necessarily limited to the above-described vacuum deposition
method; any other method, for example, a printing technique may be
used.
[0096] Subsequently, as illustrated in FIG. 7C, the top electrode
18 and the protective layer 19 are formed. First, the top electrode
18 configured by the above-described transparent
electrically-conductive film is formed, by the vacuum deposition
method or the sputtering method, for example, over the entire
surface of the substrate to cover the upper face and the side faces
of the organic photoelectric conversion layer 17. It is to be noted
that the top electrode 18 is desirably formed with the organic
photoelectric conversion layer 17 through the vacuum consistent
process, because characteristics of the organic photoelectric
conversion layer 17 are easily varied under influences of moisture,
oxygen, hydrogen, etc. Thereafter (before patterning of the top
electrode 18), the protective layer 19 including the
above-described material is formed by the plasma CVD method, for
example, to cover the upper face of the top electrode 18.
Subsequently, the protective layer 19 is formed on the top
electrode 18, and thereafter the top electrode 18 is processed.
[0097] Thereafter, etching by means of the photolithography method
is used to collectively remove a selective portion of each of the
top electrode 18 and the protective layer 19. Subsequently, the
contact hole H is formed on the protective layer 19, for example,
by the etching by means of the photolithography method. In this
situation, the contact hole H is desirably formed in a region not
facing the organic photoelectric conversion layer 17. Even after
the formation of the contact hole H, the photoresist is peeled off,
and washing using chemical solution is performed in a manner
similar to that described above. Thus, it follows that the top
electrode 18 is exposed from the protective layer 19 at the region
facing the contact hole H. Therefore, in consideration of
generation of a pin hole as described above, the contact hole H is
desirably provided by avoiding the region where the organic
photoelectric conversion layer 17 is formed. Subsequently, the
contact metal layer 20 containing the above-described material is
formed using the sputtering method, for example. In this situation,
the contact metal layer 20 is so formed on the protective layer 19
as to fill the contact hole H and to extend up to the upper face of
the wiring layer 15b. Finally, the planarization layer 21 is formed
over the entire surface of the semiconductor substrate 11, and
thereafter the on-chip lens 22 is formed on the planarization layer
21 to complete the photoelectric conversion element 10 illustrated
in FIG. 1.
[0098] As a pixel of the solid-state imaging device, the
photoelectric conversion element 10 as described above, for
example, obtains a signal electric charge as follows. That is, as
illustrated in FIG. 8, when light L is incident through the on-chip
lens 22 (not illustrated in FIG. 8) to the photoelectric conversion
element 10, the light L passes through the organic photoelectric
conversion section 11G and the inorganic photoelectric conversion
sections 11B and 11R in order, and undergoes photoelectric
conversion of each color of red, green, and blue through the
passing process. FIG. 9 schematically illustrates a flow in which
the signal electric charge (electron) is obtained on the basis of
the incident light. Description is given below of a specific
operation of signal obtainment in each of the photoelectric
conversion sections.
[0099] (Obtainment of Green Signal by Organic Photoelectric
Conversion Section 11G)
[0100] Green light Lg of the light L incident on the photoelectric
conversion element 10 is first detected (absorbed) selectively in
the organic photoelectric conversion section 11G to undergo the
photoelectric conversion. Accordingly, an electron Eg of the
electron-hole pair generated is extracted from side of the bottom
electrode 15a, and thereafter is accumulated into the electricity
storage layer for green 110G through a transmission path A (wiring
layer 13a and electrically-conductive plugs 120a1 and 120a2). The
accumulated electron Eg is transferred to the FD 116 upon a reading
operation. It is to be noted that a hole Hg is discharged from side
of the top electrode 18 through a transmission path B (contact
metal layer 20, wiring layers 13b and 15b, and
electrically-conductive plugs 120b1 and 120b2).
[0101] Specifically, the signal electric charge is accumulated as
follows. That is, in the present embodiment, for example, a
predetermined potential VL (<0 V) is applied to the bottom
electrode 15a, and a potential VU (<VL) lower than the potential
VL is applied to the top electrode 18. It is to be noted that the
potential VL is supplied, for example, from the wiring line 51a
inside the multi-layer wiring layer 51 to the bottom electrode 15a
through the transmission path A. The potential VL is supplied, for
example, from the wiring line 51a inside the multi-layer wiring
layer 51 to the top electrode 18 through the transmission path B.
Accordingly, in a state where an electric charge is accumulated
(where the unillustrated reset transistor and the transfer
transistor Tr1 are each in an OFF state), the electron, among the
electron-hole pair generated in the organic photoelectric
conversion layer 17, is guided toward side of the bottom electrode
15a having a relatively high potential (the hole is guided toward
side of the top electrode 18). In this manner, the electron Eg is
extracted from the bottom electrode 15a, and is accumulated in the
electricity storage layer for green 110G (n-type region 115n, in
detail) through the transmission path A. Further, the accumulation
of the electron Eg also causes the potential VL of the bottom
electrode 15a in electric conduction with the electricity storage
layer for green 110G to fluctuate. This amount of the variation in
the potential VL corresponds to the signal potential (here,
potential of a green signal).
[0102] Further, upon the reading operation, the transfer transistor
Tr1 is turned into an ON state, and the electron Eg accumulated in
the electricity storage layer for green 110G is transferred to the
FD116. This causes the green signal based on a light reception
amount of the green light Lg to be read by the later-described
vertical signal line Lsig through unillustrated another pixel
transistor. Thereafter, the unillustrated reset transistor and the
transfer transistor Tr1 are turned into an ON state, and the FD116
being the n-type region and an electricity storage region of the
electricity storage layer for green 110G (n-type region 115n) are
reset to a power supply voltage VDD, for example.
[0103] (Obtainment of Blue Signal and Red Signal by Inorganic
Photoelectric Conversion Sections 11B and 11R)
[0104] Subsequently, blue light and red light of the pieces of
light having been transmitted through the organic photoelectric
conversion section 11G are absorbed in order, respectively, in the
inorganic photoelectric conversion section 11B and the inorganic
photoelectric conversion section 11R to each undergo the
photoelectric conversion. In the inorganic photoelectric conversion
section 11B, an electron Eb corresponding to incident blue light is
accumulated in the n-type region (n-type photoelectric conversion
layer 111n), and the accumulated electron Ed is transferred to the
FD 113 upon the reading operation. It is to be noted that the hole
is accumulated in the unillustrated p-type region. Likewise, in the
inorganic photoelectric conversion section 11R, an electron Er
corresponding to the incident red light is accumulated in the
n-type region (n-type photoelectric conversion layer 112n), and the
accumulated electron Er is transferred to the FD 114 upon the
reading operation. It is to be noted that the hole is accumulated
in the unillustrated p-type region.
[0105] As described above, in the state where the electric charge
is accumulated, the negative potential VL is applied to the bottom
electrode 15a of the organic photoelectric conversion section 11G.
Thus, the p-type region (p-type region 111p in FIG. 2) being the
hole accumulation layer of the inorganic photoelectric conversion
section 11B tends to have an increased hole concentration.
Accordingly, it becomes possible to suppress occurrence of a dark
current at the interface between the p-type region 111p and the
interlayer insulating film 12.
[0106] Upon the reading operation, similarly to the above-described
organic photoelectric conversion section 11G, the transfer
transistors Tr2 and Tr3 are turned into an ON state, and the
electrons Eb and Er accumulated, respectively, in the n-type
photoelectric conversion layers 111n and 112n are transferred,
respectively, to the FD113 and FD114. This causes each of the blue
signal based on a light reception amount of the blue light Lb and
the red signal based on a light reception amount of the red light
Lr to be read by the later-described vertical signal line Lsig
through unillustrated another pixel transistor. Thereafter, the
unillustrated reset transistor and the transfer transistors Tr2 and
Tr3 are turned into an ON state, and the FD113 and FD114 being the
n-type region are reset to the power supply voltage VDD, for
example.
[0107] In this manner, by stacking the organic photoelectric
conversion section 11G and the inorganic photoelectric conversion
sections 11B and 11R in the vertical direction, it becomes possible
to detect pieces of color light of red, green, and blue separately
without providing a color filter, thus allowing a signal electric
charge of each color to be obtained. This makes it possible to
suppress optical loss (reduction in sensitivity) caused by color
light absorption by the color filter as well as occurrence of a
false color associated with a pixel interpolation process.
[0108] (1-3. Workings and Effects)
[0109] It is necessary for a photoelectric conversion element
(imaging element) used for an imaging device such as a CCD image
sensor or a CMOS image sensor to have superior wavelength
selectivity and high photoresponse. a subphthalocyanine derivative
is typically used widely as an organic semiconductor serving to
absorb green light. However, the subphthalocyanine derivative is
low in carrier mobility, which has caused an issue in which it is
not possible to obtain sufficient photoresponse in a case of using
as an imaging device. Therefore, a technology has been desired
which improves conductivity characteristics while maintaining
superior wavelength selectivity of the subphthalocyanine
derivative.
[0110] Examples of a method of improving conductivity
characteristics of a carrier include a method of doping a target
layer with a carrier. However, as described above, in the case
where the photoelectric conversion layer using the
subphthalocyanine derivative is simply doped with a dopant by
several percents, it is found that the conductivity characteristics
of the carrier tend not to be sufficiently improved. Further, in
some cases, light-absorption characteristics may be lowered.
[0111] In contrast, the subphthalocyanine or the subphthalocyanine
derivative and a carrier dopant having a concentration less than 1%
by volume ratio to the subphthalocyanine or the subphthalocyanine
derivative are used to form the photoelectric conversion layer 17
in the present embodiment. This allows mobility of the carrier of
the organic photoelectric conversion layer 17 to be improved.
[0112] Thus, in the photoelectric conversion element 10 according
to the present embodiment, the photoelectric conversion layer 17 is
formed using the subphthalocyanine or the subphthalocyanine
derivative and the carrier dopant having a concentration less than
1% (by volume ratio) to the subphthalocyanine or the
subphthalocyanine derivative. This allows mobility of the carrier
of the organic photoelectric conversion layer 17 to be improved.
Accordingly, it is possible to improve photoresponse while
maintaining superior wavelength selectivity of the
subphthalocyanine or the subphthalocyanine derivative. In other
words, it is possible to provide an imaging device and an
electronic apparatus (imaging unit) having superior spectroscopic
characteristics and high photoresponse.
2. MODIFICATION EXAMPLE
[0113] FIG. 10 illustrates a cross-sectional configuration of a
photoelectric conversion element 30 according to a modification
example of the disclosure. Similarly to the photoelectric
conversion element 10 of the above-described embodiment, the
photoelectric conversion element 30 constitutes a single pixel in,
for example, an imaging device such as a CCD image sensor or a CMOS
image sensor.
[0114] The photoelectric conversion element 30 of the modification
example includes a red photoelectric conversion section 40R, a
green photoelectric conversion section 40G, and a blue
photoelectric conversion section 40B in order on a silicon
substrate 61, with an insulating layer 62 being interposed
therebetween. An on-chip lens 32 is provided on the blue-color
photoelectric conversion section 40B, with a protective layer 33
and a planarization layer 31 being interposed therebetween. A
electricity storage layer for red 310R, a electricity storage layer
for green 310G, and a electricity storage layer for blue 310B are
provided in the silicon substrate 61. Light that enters the on-chip
lens 32 undergoes photoelectric conversion at the red photoelectric
conversion section 40R, the green photoelectric conversion section
40G, and the blue photoelectric conversion section 40B, and
respective signal electric charges are transmitted from the red
photoelectric conversion section 40R to the electricity storage
layer for red 310R, from the green photoelectric conversion section
40G to the electricity storage layer for green 310G, and from the
blue photoelectric conversion section 40B to the electricity
storage layer for blue 310B. The signal electric charge may be
either an electron or a hole that is generated from the
photoelectric conversion.
[0115] The silicon substrate 61 includes, for example, a p-type
silicon substrate. The electricity storage layer for red 310R, the
electricity storage layer for green 310G, and the electricity
storage layer for blue 310B provided in this silicon substrate 61
each include a corresponding n-type semiconductor region. Signal
electric charges supplied from the red photoelectric conversion
section 40R, the green photoelectric conversion section 40G, and
the blue photoelectric conversion section 40B are accumulated in
the respective n-type semiconductor regions. The respective n-type
semiconductor regions of the electricity storage layer for red
310R, the electricity storage layer for green 310G, and the
electricity storage layer for blue 310B are formed by doping the
silicon substrate 61 with an n-type impurity such as phosphorus (P)
or arsenic (As). It is to be noted that the silicon substrate 61
may be provided on a support substrate (not illustrated) containing
glass, for example.
[0116] The insulating layer 62 includes, for example, silicon oxide
(SiO.sub.2), silicon nitride (SiN), silicon oxynitride (SiON), and
hafnium oxide (HfO.sub.2). The insulating layer 62 may be so formed
as to have a plurality of types of insulating films stacked. The
insulating layer 62 may also be configured by an organic insulating
material. A plug and an electrode (neither unillustrated) are
provided in this insulating layer 62. The plug and the electrode
couple the electricity storage layer for red 310R with the red
photoelectric conversion section 40R, the electricity storage layer
for green 310G with the green photoelectric conversion section 40G,
and the electricity storage layer for blue 310B with the blue
photoelectric conversion section 40B.
[0117] The red photoelectric conversion section 40R includes a
first electrode 41R, a photoelectric conversion layer 42R, and a
second electrode 43R in this order from a position close to the
silicon substrate 61. The green photoelectric conversion section
40G includes a first electrode 41G, a photoelectric conversion
layer 42G, and a second electrode 43G in order from a location
close to the red photoelectric conversion section 40R. The blue
photoelectric conversion section 40B includes a first electrode
41B, a photoelectric conversion layer 42B, and a second electrode
43B in order from a location close to the green photoelectric
conversion section 40G. An insulating layer 44 is provided between
the red photoelectric conversion section 40R and the green
photoelectric conversion section 40G, and an insulating layer 45 is
provided between the green photoelectric conversion section 40G and
the blue photoelectric conversion section 40B. Red color light (for
example, wavelength of 600 nm to 800 nm), green color light (for
example, wavelength of 450 nm to 650 nm), and blue color light (for
example, wavelength of 400 nm to 600 nm) are respectively absorbed
selectively by the red photoelectric conversion section 40R, the
green photoelectric conversion section 40G, and the blue
photoelectric conversion section 40B, to thereby each generate an
electron-hole pair.
[0118] The first electrode 41R, the first electrode 41G, and the
first electrode 41B respectively extract the signal electric
charges (electric charges) generated in the photoelectric
conversion layer 42R, the photoelectric conversion layer 42G, and
the photoelectric conversion 42B. The first electrodes 41R, 41G,
and 41B are, for example, provided on a pixel-by-pixel basis. The
first electrodes 41R, 41G, and 41B are each configured by, for
example, an electrically-conductive material having
light-transmissivity, and specifically, ITO (Indium-Tin-Oxide). The
first electrodes 41R, 41G, and 41B may be each configured by a tin
oxide (SnO.sub.2)-based material or a zinc oxide (ZnO)-based
material, for example. Examples of the tin oxide-based material
include a material in which a tin oxide is doped with a dopant.
Examples of the zinc oxide-based material include aluminum zinc
oxide (AZO) in which a zinc oxide is doped with aluminum (Al) as a
dopant, gallium zinc oxide (GZO) in which a zinc oxide is doped
with gallium (Ga) as a dopant, and indium zinc oxide (IZO) in which
a zinc oxide is doped with indium (In) as a dopant. Aside from
those described above, for example, IGZO, CuI, InSbO.sub.4, ZnMgO,
CuInO.sub.2, MgIn.sub.2O.sub.4, CdO, and ZnSnO.sub.3 may be used.
The first electrodes 41R, 41G, and 41B each have a thickness
(thickness in a stacked direction, hereinafter, simply referred to
as thickness) of 50 nm to 500 nm, for example.
[0119] The photoelectric conversion layers 42R, 42G, and 42B each
absorb light of a selective wavelength region and subject the light
to photoelectric conversion, and transmit light of another
wavelength region. The photoelectric conversion layers 42R, 42G,
and 42B include respective organic dyes that absorb pieces of light
of selective wavelength regions each corresponding to the
photoelectric conversion sections 40R, 40G, and 40B. The
photoelectric conversion layers 42R, 42G, and 42B each have a
thickness of 0.05 .mu.m to 10 .mu.m, for example. The photoelectric
conversion layers 42R, 42G, and 42B include a similar configuration
to each other excluding the wavelength regions of absorbed light
differing from each other.
[0120] Examples of the organic dyes include the subphthalocyanine
or the subphthalocyanine derivative represented by the above
formula (5) or (6) and the quinacridone or the quinacridone
derivative represented by the above formulae (7-1) and (7-2). Aside
from those, examples of an organic dye that absorbs blue color
include a coumarin derivative, a silole derivative and a fluorine,
examples of an organic dye that absorbs green light include a
dipyrrin derivative, a squalene derivative, and a perylene
derivative, and examples of an organic dye that absorbs red color
include zinc phtalocyanine.
[0121] In the modification example, a layer, which is formed with
use of the subphthalocyanine or the subphthalocyanine derivative as
an organic dye, among the photoelectric conversion layers 42R, 42G,
and 42B, is so formed as to include a carrier dopant as well as the
subphthalocyanine or the subphthalocyanine derivative. In this
situation, the doping amount of the carrier dopant preferably has a
concentration less than 1% by volume ratio to the subphthalocyanine
or the subphthalocyanine derivative. This allows mobility of the
carrier of the photoelectric conversion layer 42G (or the
photoelectric conversion layers 42R and 42B) using the
subphthalocyanine or the subphthalocyanine derivative to be
improved.
[0122] The second electrodes 43R, 43G, and 43B respectively extract
holes generated by the photoelectric conversion layers 42R, 42G,
and 42G. The holes extracted from the respective second electrodes
43R, 43G, and 43B are discharged into a p-type semiconductor region
(unillustrated) in the silicon substrate 61, for example, via each
transmission path (unillustrated). The second electrodes 43R, 43G,
and 43B are each configured by a electrically conductive material
such as gold (Au), silver (Ag), Copper (Cu), and aluminum (Al), for
example. Similarly to the first electrodes 41R, 41G, and 41B, the
second electrodes 43R, 43G, and 43B may be configured by a
transparent electrically conductive material. In the photoelectric
conversion element 30, the holes extracted from the second
electrodes 43R, 43G, and 43B are discharged. Therefore, in a case
where a plurality of photoelectric conversion elements 30 are
provided (for example, a later-described imaging device 1 of FIG.
11), the second electrodes 43R, 43G, and 43B may be provided
commonly to each of the photoelectric conversion elements 30 (unit
pixel P in FIG. 11). The second electrodes 43R, 43G, and 43B each
have a thickness of 0.5 nm to 100 nm, for example.
[0123] The insulating layer 44 insulates the second electrode 43R
and the first electrode 41G. The insulating layer 45 insulates the
second electrode 43G and the first electrode 41B. The insulating
layers 44 and 25 include a metal oxide, a metal sulfide, or an
organic substance, for example. Examples of the metal oxide include
silicon oxide (SiO.sub.2), aluminum oxide (Al.sub.2O.sub.3),
zirconium oxide (ZrO.sub.2), titanium oxide (TiO.sub.2), zinc oxide
(ZnO), tungsten oxide (WO.sub.3), magnesium oxide (MgO),
oxidization niobium (Nb.sub.2O.sub.3), tin oxide (SnO.sub.2), and
oxidization gallium (Ga.sub.2O.sub.3). Examples of the metal
sulfide include zinc sulfide (ZnS) and magnesium sulfide (MgS). A
material configuring the insulating layers 44 and 25 preferably has
a bandgap of no less than 3.0 eV. The insulating layers 44 and 25
each have a thickness of 2 nm to 100 nm, for example.
[0124] The protective layer 33 that covers the second electrode 43B
prevents water or other substance from entering the red
photoelectric conversion section 40R, the green photoelectric
conversion section 40G, and the blue photoelectric conversion
section 40B. The protective layer 33 includes a material having
light-transmissivity. A monolayer film containing silicon nitride,
silicon oxide, or silicon oxynitride, for example, or stacked
layers containing them is used for the protective layer 33.
[0125] The on-chip lens 32 is provided on the protective layer 33
with the planarization layer 31 being interposed therebetween. An
acrylic resin material, a styrenic resin material, an epoxy resin
material, or other material may be used for the planarization layer
31. The planarization layer 31 may be provided as necessary, and
the protective layer 33 may serve as the planarization layer 31.
The on-chip lens 32 condenses light incident from above to each
light-receiving face of the red photoelectric conversion section
40R, the green photoelectric conversion section 40G, and the blue
photoelectric conversion section 40B.
[0126] Any other unillustrated layer may be provided between the
first electrode 41R and the photoelectric conversion layer 42R,
between the first electrode 41G and the photoelectric conversion
layer 42G, between the first electrode 41B and the photoelectric
conversion layer 42B, or between the photoelectric conversion layer
42R and the second electrode 43R, between the photoelectric
conversion layer 42G and the second electrode 43G, and the
photoelectric conversion layer 42B and the second electrode
43B.
[0127] An electron transport layer may be provided, for example,
between the first electrode 41R and the photoelectric conversion
layer 42R, between the first electrode 41G and the photoelectric
conversion layer 42G, and between the first electrode 41B and the
photoelectric conversion layer 42B. The electron transport layer
promotes supplying electrons generated in the photoelectric
conversion layers 42R, 42G, and 42B, respectively to the first
electrodes 41R, 41G, and 41B. The electron transport layer is
configured by, for example, titanium oxide (TiO.sub.2) or zinc
oxide (ZnO). Further, the electron transport layer may be so formed
to stack titanium oxide and zinc oxide. The electron transport
layer has a thickness of 0.1 nm to 1000 nm, for example, and
preferably has a thickness of 0.5 nm to 200 nm.
[0128] A hole transport layer may be provided, for example, between
the photoelectric conversion layer 42R and the second electrode
43R, between the photoelectric conversion layer 42G and the second
electrode 43G, and between the photoelectric conversion layer 42B
and the second electrode 43B. The hole transport layer promotes
supplying holes generated in the photoelectric conversion layers
42R, 42G, and 42B, respectively to the second electrodes 43R, 23G,
and 23B. The hole transport layer is configured by, for example,
molybdenum oxide (MoO.sub.3), nickel oxide (NiO), or vanadium oxide
(V.sub.2O.sub.5). Further, the hole transport layer may be
configured by an organic material such as PEDOT
(Poly(3,4-ethylenedioxythiophene)) and TPD
(N,N'-Bis(3-methylphenyl)-N,N'-diphenylbenzidine). The hole
transport layer has a thickness of 0.5 nm to 100 nm, for
example.
[0129] As described above, in the modification example, the
photoelectric conversion layer (for example, the photoelectric
conversion layer 42G) containing the subphthalocyanine or the
subphthalocyanine derivative is doped with the carrier dopant
having a concentration less than 1% (by volume ratio) to the
subphthalocyanine or the subphthalocyanine derivative. This allows
mobility of the carrier in the photoelectric conversion layer 42G
to be improved as in the above-described embodiment, making it
possible to improve photoresponse while maintaining superior
wavelength selectivity of the subphthalocyanine or the
subphthalocyanine derivative. In this manner, doping with an
appropriate amount of the carrier dopant the photoelectric
conversion layer containing the subphthalocyanine or the
subphthalocyanine derivative achieves exerting the effect of
allowing mobility of the carrier of the photoelectric conversion
layer to be improved regardless of the configuration of the
photoelectric conversion element.
3. APPLICATION EXAMPLES
Application Example 1
[0130] FIG. 11 illustrates an overall configuration of the imaging
device (imaging device 1) that uses, as each pixel, the
photoelectric conversion element 10 (or the photoelectric
conversion element 30) described in the above-described embodiment.
The imaging device 1 is a CMOS imaging sensor. The imaging device 1
has a pixel section 1a as an imaging area on the semiconductor
substrate 11. Further, the imaging device 1 includes, for example,
a peripheral circuit section 130 including a row scanning section
131, a horizontal selection section 133, a column scanning section
134, and a system controller 132 in a peripheral region of the
pixel section 1a.
[0131] The pixel section 1a includes, for example, a plurality of
unit pixels P (equivalent to the photoelectric conversion elements
10) that are two-dimensionally arranged in rows and columns. To the
unit pixels P, for example, pixel drive lines Lread (specifically,
row selection lines and reset control lines) are wired on a
pixel-row basis, and vertical signal lines Lsig are wired on a
pixel-column basis. The pixel drive line Lread transmits a drive
signal for reading of a signal from the pixel. One end of the pixel
drive line Lread is coupled to an output terminal corresponding to
each row of the row scanning section 131.
[0132] The row scanning section 131 is configured by a shift
register, an address decoder, etc. The row scanning section 131 is,
for example, a pixel drive section that drives the respective unit
pixels P in the pixel section 1a on a row-unit basis. Signals
outputted from the respective unit pixels P in the pixel row
selectively scanned by the row scanning section 131 are supplied to
the horizontal selection section 133 via the respective vertical
signal lines Lsig. The horizontal selection section 133 is
configured by an amplifier, a horizontal selection switch, etc.,
that are provided for each vertical signal line Lsig.
[0133] The column scanning section 134 is configured by a shift
register, an address decoder, etc. The column scanning section 134
sequentially drives the respective horizontal selection switches in
the horizontal selection section 133 while scanning the respective
horizontal selection switches in the horizontal selection section
133. The selective scanning by the column scanning section 134
causes signals of the respective pixels that are transmitted via
the respective vertical signal lines Lsig to be sequentially
outputted to horizontal signal lines 135, and to be transmitted to
the outside of the semiconductor substrate 11 through the
horizontal signal lines 135.
[0134] A circuit part including the row scanning section 131, the
horizontal selection section 133, the column scanning section 134,
and the horizontal signal lines 135 may be formed directly on the
semiconductor substrate 11, or may be provided in an external
control IC. Alternatively, the circuit part may be formed on
another substrate coupled with use of a cable, etc.
[0135] The system controller 132 receives a clock, data instructing
an operation mode, etc., that are supplied from the outside of the
semiconductor substrate 11. The system controller 132 also outputs
data such as internal information of the imaging device 1. The
system controller 132 further includes a timing generator that
generates various timing signals, and performs drive control of
peripheral circuits such as the row scanning section 131, the
horizontal selection section 133, and the column scanning section
134 on the basis of the various timing signals generated by the
timing generator.
Application Example 2
[0136] The above-described imaging device 1 is applicable to any
type of electronic apparatus (imaging unit) having an imaging
function, for example, a camera system such as a digital still
camera and a video camera, and a mobile phone having the imaging
function. FIG. 12 illustrates an outline configuration of an
electronic apparatus 2 (camera) as an example thereof. This
electronic apparatus 2 may be, for example, a video camera that is
able to photograph a still image or a moving image. The electronic
apparatus 2 includes, for example, the imaging device 1, an optical
system (optical lens) 310, a shutter unit 311, a drive section 313
that drives the imaging device 1 and the shutter unit 311, and a
signal processing section 312.
[0137] The optical system 310 guides image light (incident light)
obtained from a subject to the pixel section 1a in the imaging
device 1. The optical system 310 may be configured by a plurality
of optical lenses. The shutter device 311 controls a period in
which the imaging device 1 is irradiated with light and a period in
which the light is blocked with respect to the imaging device 1.
The drive section 313 controls a transfer operation of the imaging
device 1 and a shutter operation of the shutter device 311. The
signal processing section 312 performs various signal processes on
a signal outputted from the imaging device 1. An image signal Dout
after the signal process is stored in a storage medium such as
memory, or outputted to a monitor, for example.
4. EXAMPLES
[0138] In the following, various types of samples relating to the
embodiments and the modification example according to the
disclosure were fabricated to evaluate photoresponse, I-V
characteristics, and absorption spectrum.
[0139] (Experiment 1)
[0140] First, in experiment example 1-1, an ITO electrode serving
as a bottom electrode was provided on a quartz substrate by means
of sputtering, following which a film of a photoelectric conversion
layer is formed. Specifically, butylquinacridone (BQD) represented
by the above-described formula (7-2), subphthalocyanine fluoride
(F.sub.6-SubPc-Cl) represented by the formula (5-2), and leuco
crystal violet (LCV) represented by the formula (1-1), for example,
were so subjected to co-deposition with the volume ratio of
1:1:0.001, as to form a film of an organic photoelectric conversion
layer having a thickness of 100 nm. Here, BQD serves as hole
transport, while F.sub.6--SubPc-Cl serves as electron transport.
Subsequently, a film of AlSiCu having a thickness of 100 nm was
formed on the organic photoelectric conversion layer by means of an
evaporation method to fabricate a photoelectric conversion element
having this film serving as a top electrode.
[0141] Aside from those described above, in experiment examples 1-2
to 1-4, the photoelectric conversion elements each having an
organic photoelectric conversion layer containing BQD,
F.sub.6--SubPc-Cl, and LCV, respectively with the volume ratios of
1:1:0.005 (experiment example 1-2), 1:1:0.01 (experiment example
1-3), and 1:1:0.05 (experiment example 1-4) were fabricated.
Further, a photoelectric conversion element was fabricated using a
method similar to those of experiment examples 1-1 to 1-4 excluding
use of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole (DMBI)
represented by the above-described formula (4-1) in place of LCV of
experiment examples 2-1 to 2-4. Furthermore, as a comparative
example, a photoelectric conversion element having an organic
photoelectric conversion layer containing BQD and F.sub.6--SubPc-Cl
(1:1 by volume ratio) was fabricated without using a carrier
dopant. These experiment examples 1-1 to 1-4 and 2-1 to 2-4 and the
comparative example were evaluated in terms of photoresponse as
follows. Table 1 collectively shows types of carrier dopants used
for the comparative example and the experiment examples 1-1 to 1-4
and 2-1 to 2-4, concentrations (%) of the carrier dopants to the
subphthalocyanine derivative, presence/absence of effect, and
photoresponse time (a.u.).
[0142] Photoresponse was evaluated by measuring, using an
oscilloscope, the speed of a light current value observed during
light irradiation falling down after stopping the light
irradiation. Specifically, the amount of light (green light) with
which a photoelectric conversion element is irradiated from a light
source via a filter was set to 1.62 .mu.W/cm.sup.2, and the bias
voltage applied between electrodes was set to -1 V (0 V to a top
electrode, and -1 V to a bottom electrode). A steady current
thereof was observed in this state, following which the light
irradiation was stopped to observe how the current was attenuated.
Subsequently, a dark current value was subtracted from an obtained
current-time curve. Using the current-time curve thus obtained, the
time necessary for the current value after stopping the light
irradiation to having been attenuated down to 3% of the current
value that was observed in the steady state was set as an index of
photoresponse.
TABLE-US-00001 TABLE 1 Presence/ Concentration absence
Photoresponse Dopant (%) of effect time (a.u.) Comparative -- 0 --
1.0 example Example 1-1 Formula 0.1 o 0.26 (1-1) Example 1-2
Formula 0.5 o 0.25 (1-1) Example 1-3 Formula 1 .times. 1.0 (1-1)
Example 1-4 Formula 5 .times. 1.2 (1-1) Example 2-1 Formula 0.02 o
0.46 (4-1) Example 2-2 Formula 0.1 o 0.51 (4-1) Example 2-3 Formula
1 .times. 2.3 (4-1) Example 2-4 Formula 5 .times. 3.6 (4-1)
[0143] FIGS. 13 and 14 respectively illustrate the experiment
examples 1-1 to 1-4 and the experiment examples 2-1 to 2-4, and
illustrate a transition response during which the top electrode was
applied with 0 V, the bottom electrode was applied with -1 V, and
the green light of 1.62 .mu.W/cm.sup.2 with which a photoelectric
conversion element has been irradiated was switched to an
unirradiated state at the timing of t=0. As seen from FIGS. 13 and
14, when the carrier dopant concentration was less than 1%, the
photoresponse was improved as compared to that of the comparative
example. Specifically, the photoresponse was improved approximately
four times in the experiment examples 1-1 and 1-2 using LCV as a
carrier dopant. Further, the photoresponse was improved
approximately double in the experiment examples 2-1 and 2-2 using
DMBI as a carrier dopant.
Experiment 2
[0144] Further, photoelectric conversion elements (experiment
examples 3-1 to 3-3) were fabricated in which LCV, acridine orange
(AOB) represented by the formula (2-1), and DMBI are used for the
respective photoelectric conversion layers as carrier dopants, and
each of voltage-current characteristics (I-V characteristics)
thereof was measured. The configurations of elements in each of
experiment examples 3-1 to 3-3 are as follows.
[0145] In the experiment example 3-1, an ITO film as a bottom
electrode was provided on a quartz substrate, following which a
film of an organic photoelectric conversion layer having a
thickness of 100 nm with the volume ratio of F.sub.6--SubPc-Cl to
LCV being 1:0.01 was formed on the ITO film. Thereafter, a lithium
fluoride (LiF) film having a thickness of 0.5 nm was formed.
Finally, an AlSiCu film was formed as a top electrode on the LiF
film to thereby fabricate a photoelectric conversion element
(experiment example 3-1).
[0146] In the experiment example 3-2, an AlSiCu film was formed as
a bottom electrode on a quartz substrate, and thereafter, a lithium
fluoride (LiF) film having a thickness of 0.5 nm was formed on the
AlSiCu film. Subsequently, an organic photoelectric conversion
layer having a thickness of 100 nm with the volume ratio of
F.sub.6--SubPc-Cl to AOB being 1:0.01 was formed on the LiF film,
and thereafter, a lithium fluoride (LiF) film having a thickness of
0.5 nm was formed. Finally, an AlSiCu film was formed as a top
electrode on the Lif film to thereby fabricate a photoelectric
conversion element (experiment example 3-1). In the experiment
example 3-3, a photoelectric conversion element including a similar
configuration to that of the experiment example 3-2 excluding use
of DMBI as a carrier dopant was fabricated.
[0147] Further, in the comparative examples 3-1 to 3-3 with respect
to the experiment examples 3-1 to 3-3, photoelectric conversion
elements each including a similar configuration to those of
experiment examples 3-1 to 3-3 were fabricated, except that each of
them not containing a carrier dopant.
[0148] FIGS. 15 to 17 respectively illustrate the I-V
characteristics of the experiment example 3-1 and the comparative
example 3-1, the experiment example 3-2 and the comparative example
3-2, and the experiment example 3-3 and the comparative example
3-3. It is found from FIGS. 15 to 17 that the doping with the
carrier dopant the organic photoelectric conversion layer
containing F.sub.6--SubPc-Cl allows the carrier dopant to act on
F.sub.6--SubPc-Cl, to thereby improve the conductivity of the
carrier (here, electron). The resulting improvement of the
conductivity owing to the doping with the carrier dopant was also
confirmed in view of the rise of the Fermi level shown in Table 2,
for example. Specifically, the Fermi level was evaluated by an
ultraviolet photoelectron spectroscopy, a result of which the Fermi
level (eV) rose by 0.2 eV in the experiment example 3-1 with a
carrier dopant being doped, as compared to the comparative example
3-1 without a carrier dopant.
TABLE-US-00002 TABLE 2 Presence/ Fermi level Dopant absence of
effect (eV) Comparative -- -- -4.5 example 3-1 Example 3-1 Formula
(1-1) o -4.3
[0149] FIG. 18 illustrates an absorption spectrum of the
photoelectric conversion elements in the experiment example 3-1 and
the comparative example 3-1. It is found from FIG. 18 that doping
with the carrier dopant does not influence wavelength selectivity
of F.sub.6--SubPc-Cl.
[0150] Further, doping with the carrier dopant the organic
photoelectric conversion layer containing F.sub.6--SubPc-Cl allows
the conductivity of the carrier to be improved, which makes it
possible to reduce drive voltage.
[0151] Description has been given hereinabove referring to the
embodiment and the modification example; however, content of the
disclosure is not limited to the foregoing embodiment and the like,
and various modifications may be made. For example, the numbers of
organic and inorganic photoelectric conversion sections, and the
ratio therebetween are not limitative as well. Two or more organic
photoelectric conversion sections may be provided, or color signals
of a plurality of colors may be obtained only by the organic
photoelectric conversion sections. Furthermore, the organic
photoelectric conversion section and the inorganic photoelectric
conversion section are not limited to have a vertically-stacked
structure, and may be arranged side by side along the substrate
surface.
[0152] Moreover, the foregoing embodiment and the modification
example exemplify the configuration of the backside illumination
type imaging unit; however, the content of the disclosure is also
applicable to an imaging unit of a front side illumination type.
Further, the imaging device (photoelectric conversion element) of
the disclosure does not necessarily include all of the components
described in the foregoing embodiment, and may include any other
layer, conversely.
[0153] It is to be noted that the effects described herein are
merely examples and are not necessarily limitative; the effects may
further include other effects. It is to be noted that the present
disclosure may have the following configurations.
[0154] [1]
[0155] A photoelectric conversion element including:
[0156] a first electrode and a second electrode that are disposed
to face each other; and
[0157] a photoelectric conversion layer that is provided between
the first electrode and the second electrode, and contains at least
a subphthalocyanine or a subphthalocyanine derivative, and a
carrier dopant,
[0158] in which the carrier dopant has a concentration of less than
1% by volume ratio to the subphthalocyanine or the
subphthalocyanine derivative.
[0159] [2]
[0160] The photoelectric conversion element according to [1], in
which the carrier dopant includes an organic material.
[0161] [.sup.3]
[0162] The photoelectric conversion element according to [1] or
[2], in which, upon doping, the carrier dopant is accompanied with
chemical reaction.
[0163] [4]
[0164] The photoelectric conversion element according to [1] or
[2], in which, upon doping, the carrier dopant is accompanied with
elimination reaction or addition reaction of hydrogen, carbon
oxide, nitrogen, or hydroxyl radical.
[0165] [5]
[0166] The photoelectric conversion element according to any one of
[1] to [4], in which the carrier dopant includes an electron
dopant.
[0167] [6]
[0168] The photoelectric conversion element according any one of
[1] to [5], in which the carrier dopant is one or more of
triphenylmethane derivative represented by a following formula (1),
acridine derivative represented by a following formula (2),
xanthenes derivative represented by a following formula (3), and
benzimidazole derivative represented by a following formula
(4):
##STR00010##
[0169] where R1 to R13 denote, each independently: hydrogen atom;
halogen atom; a linear chain, branched, or cyclic alkyl group;
thioalkyl group; thioaryl group; arylsulfonyl group; alkylsulfonyl
group; amino group; alkylamino group; arylamino group; hydroxy
group; alkoxy group; acylamino group; acyloxy group; phenyl group;
carboxy group; carboxoamide group; carboalkoxy group; acyl group;
sulfonyl group; cyano group; and nitro group; or a derivative
thereof. Further, R1 to R13 may form a cycle by bonding with each
other. a to h are each an integer of 0 or more.
[0170] [7]
[0171] The photoelectric conversion element according to any one of
[1] to [6], in which the subphthalocyanine derivative is one or
more of compounds represented by following formulae (5) and
(6):
##STR00011##
[0172] where R14 to R25 and X denote, each independently: hydrogen
atom; halogen atom; a linear chain, branched, or cyclic alkyl
group; thioalkyl group; thioaryl group; arylsulfonyl group;
alkylsulfonyl group; amino group; alkylamino group; arylamino
group; hydroxy group; alkoxy group; acylamino group; acyloxy group;
phenyl group; carboxy group; carboxoamide group; carboalkoxy group;
acyl group; sulfonyl group; cyano group; nitro group; heterocyclic
group; or a derivative thereof. Any mutually adjacent R14 to R25
may form a cycle by bonding with each other. M denotes boron, or a
divalent or trivalent metal.
[0173] [8]
[0174] The photoelectric conversion element according to any one of
[1] to [7], in which the photoelectric conversion layer includes a
p-type semiconductor.
[0175] [9]
[0176] The photoelectric conversion element according to [8], in
which the p-type semiconductor includes a quinacridone
derivative.
[0177] [10]
[0178] The photoelectric conversion element according to [8] or
[9], in which the photoelectric conversion layer further includes
an n-type semiconductor.
[0179] [11]
[0180] The photoelectric conversion element according to [10], in
which the n-type semiconductor includes a fullerene derivative.
[0181] [12]
[0182] An imaging device in which pixels each include one or a
plurality of organic photoelectric conversion sections, the organic
photoelectric conversion sections each including:
[0183] a first electrode and a second electrode that are disposed
to face each other; and
[0184] a photoelectric conversion layer that is provided between
the first electrode and the second electrode, and contains at least
a subphthalocyanine or a subphthalocyanine derivative, and a
carrier dopant,
[0185] in which the carrier dopant has a concentration of less than
1% by volume ratio to the subphthalocyanine or the
subphthalocyanine derivative.
[0186] [13]
[0187] The imaging device according to [12], in which, in each of
the pixels, the one or the plurality of organic photoelectric
conversion sections and one or a plurality of inorganic
photoelectric conversion sections are stacked, the one or the
plurality of inorganic photoelectric conversion sections performing
photoelectric conversion of a wavelength region different from that
of the organic photoelectric conversion section.
[0188] [14]
[0189] The imaging device according to [13], in which
[0190] the inorganic photoelectric conversion section is embedded
in a semiconductor substrate, and
[0191] the organic photoelectric conversion section is provided on
first face side of the semiconductor substrate.
[0192] [15]
[0193] The imaging device according to [14], in which
[0194] the organic photoelectric conversion section performs the
photoelectric conversion of green light, and
[0195] the inorganic photoelectric conversion section that performs
the photoelectric conversion of blue light and the inorganic
photoelectric conversion section that performs the photoelectric
conversion of red light are stacked in the semiconductor
substrate.
[0196] [16]
[0197] An electronic apparatus with an imaging device, in which
pixels each have one or a plurality of organic photoelectric
conversion sections, the organic photoelectric conversion sections
each including:
[0198] a first electrode and a second electrode that are disposed
to face each other; and
[0199] a photoelectric conversion layer that is provided between
the first electrode and the second electrode, and contains at least
a subphthalocyanine or a subphthalocyanine derivative, and a
carrier dopant,
[0200] in which the carrier dopant has a concentration of less than
1% by volume ratio to the subphthalocyanine or the
subphthalocyanine derivative.
[0201] This application is based upon and claims priority from
Japanese Patent Application Nos. 2016-004383 filed with the Japan
Patent Office on Jan. 13, 2016 and 2016-062422 filed with the Japan
Patent Office on Mar. 25, 2016, the entire contents of which are
hereby incorporated by reference.
[0202] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations, and
alterations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
or the equivalents thereof.
* * * * *