JP6482185B2 - Solid-state image sensor - Google Patents
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- 238000006243 chemical reaction Methods 0.000 claims description 113
- 239000013078 crystal Substances 0.000 claims description 90
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims description 60
- 229910052711 selenium Inorganic materials 0.000 claims description 60
- 239000011669 selenium Substances 0.000 claims description 60
- 238000003384 imaging method Methods 0.000 claims description 58
- 239000000758 substrate Substances 0.000 claims description 28
- 229910052714 tellurium Inorganic materials 0.000 claims description 6
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 claims description 6
- 230000035945 sensitivity Effects 0.000 description 22
- 238000000034 method Methods 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
- 239000004065 semiconductor Substances 0.000 description 9
- 238000009826 distribution Methods 0.000 description 6
- 238000001771 vacuum deposition Methods 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000010030 laminating Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 229910052951 chalcopyrite Inorganic materials 0.000 description 1
- -1 chalcopyrite compound Chemical class 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- KYKLWYKWCAYAJY-UHFFFAOYSA-N oxotin;zinc Chemical compound [Zn].[Sn]=O KYKLWYKWCAYAJY-UHFFFAOYSA-N 0.000 description 1
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
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- 229910052719 titanium Inorganic materials 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Description
本発明は、固体撮像素子に関する。 The present invention relates to a solid-state imaging device.
近年、固体撮像素子の多画素化および高フレームレート化が急速に進んでいる。このため、１画素あたりで発生する電荷量が減少し、固体撮像素子の感度をより一層向上させることが要求されている。 In recent years, the number of pixels of a solid-state image sensor and the increase of the frame rate are rapidly progressing. For this reason, the amount of charge generated per pixel is reduced, and it is required to further improve the sensitivity of the solid-state imaging device.
この要求に対応するために、基板上に形成された信号読み出し回路上に、下部電極と光電変換膜と透明電極とを、この順に積層した固体撮像素子が提案されている（例えば、特許文献１および特許文献２参照）。このような固体撮像素子では、透明電極側から固体撮像素子に入射した光が、信号読み出し回路に遮られることなく光電変換膜で受光される。このため、光の利用効率が高く、高感度の固体撮像素子が実現できる。 In order to meet this requirement, a solid-state imaging device has been proposed in which a lower electrode, a photoelectric conversion film, and a transparent electrode are stacked in this order on a signal readout circuit formed on a substrate (for example, Patent Document 1). And Patent Document 2). In such a solid-state imaging device, light incident on the solid-state imaging device from the transparent electrode side is received by the photoelectric conversion film without being blocked by the signal readout circuit. For this reason, the light use efficiency is high, and a highly sensitive solid-state imaging device can be realized.
また、特許文献２には、高感度の固体撮像装置として、光電変換膜の結晶粒径を１画素の大きさよりも大きく成長させて、１個の画素内に存在する結晶粒界密度を下げることで、光電流の低損失での取出しを可能としたものが提案されている。 In Patent Document 2, as a high-sensitivity solid-state imaging device, the crystal grain size of a photoelectric conversion film is grown larger than the size of one pixel to lower the crystal grain boundary density existing in one pixel. Thus, there has been proposed one capable of taking out photocurrent with low loss.
しかしながら、従来の固体撮像素子では、撮像した画像に現れる固定パターンノイズが大きく、これを低減することが要求されていた。
本発明は、上記の事情に鑑みてなされたものであり、固定パターンノイズの低減された高画質の画像が得られる固体撮像素子を提供することを課題とする。
However, in the conventional solid-state imaging device, the fixed pattern noise that appears in the captured image is large, and it has been required to reduce this.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solid-state imaging device capable of obtaining a high-quality image with reduced fixed pattern noise.
本発明者は、上記課題を解決すべく、光電変換層に多結晶膜からなる光電変換膜を用いた固体撮像装置において、光電変換膜の結晶粒径と固定パターンノイズとの関係に着目し、鋭意検討した。その結果、光電変換膜の最大結晶粒径を、画素サイズ以下とすることで、撮像した画像の固定パターンノイズを低減できることを見出し、本発明を完成するに至った。 In order to solve the above problems, the present inventor paid attention to the relationship between the crystal grain size of the photoelectric conversion film and the fixed pattern noise in the solid-state imaging device using the photoelectric conversion film made of a polycrystalline film as the photoelectric conversion layer. We studied diligently. As a result, it has been found that the fixed pattern noise of the captured image can be reduced by setting the maximum crystal grain size of the photoelectric conversion film to be equal to or smaller than the pixel size, and the present invention has been completed.
すなわち、本発明は、以下の発明に関わるものである。
［１］信号読み出し回路を有する基板上に、第１電極と光電変換層と第２電極とが、この順に積層された固体撮像素子であって、前記光電変換層が多結晶膜であって結晶セレン膜からなる光電変換膜を有し、前記光電変換膜の最大結晶粒径Ａと、３μｍ以下である画素サイズＢとの関係が、以下の式（１）を満足することを特徴とする固体撮像素子。
Ａ／Ｂ≦１．０ ‥（１）
（式（１）において、Ａは＞０である。）
［２］前記光電変換膜の平均結晶粒径Ｃと、画素サイズＢとの関係が、以下の式（２）を満足することを特徴とする［１］に記載の固体撮像素子。
Ｃ／Ｂ≦０．１０ ‥（２）
（式（２）において、Ｃは＞０である。）
［３］前記第１電極が下部電極であり、前記第２電極が透明電極であることを特徴とする［１］または［２］に記載の固体撮像素子。
That is, the present invention relates to the following inventions.
[1] A solid-state imaging device in which a first electrode, a photoelectric conversion layer, and a second electrode are stacked in this order on a substrate having a signal readout circuit, and the photoelectric conversion layer is a polycrystalline film and is crystallized. A solid having a photoelectric conversion film made of a selenium film , wherein the relationship between the maximum crystal grain size A of the photoelectric conversion film and the pixel size B of 3 μm or less satisfies the following formula (1): Image sensor.
A / B ≦ 1.0 (1)
(In the formula (1), A is> 0.)
[2] The solid-state imaging device according to [1], wherein the relationship between the average crystal grain size C of the photoelectric conversion film and the pixel size B satisfies the following formula (2).
C / B ≦ 0.10 (2)
(In the formula (2), C is> 0.)
[3] The solid-state imaging device according to [1] or [2] , wherein the first electrode is a lower electrode and the second electrode is a transparent electrode.
本発明の固体撮像素子は、光電変換層が多結晶膜からなる光電変換膜を有し、前記光電変換膜の最大結晶粒径Ａと、画素サイズＢとの関係がＡ／Ｂ≦１．０を満足するものであるので、撮像した画像の固定パターンノイズを低減でき、高画質の画像が得られる。 The solid-state imaging device of the present invention has a photoelectric conversion film in which the photoelectric conversion layer is a polycrystalline film, and the relationship between the maximum crystal grain size A of the photoelectric conversion film and the pixel size B is A / B ≦ 1.0. Therefore, the fixed pattern noise of the captured image can be reduced, and a high-quality image can be obtained.
以下、本発明の実施形態について、図面を用いて詳細に説明する。但し、本発明は、以下の実施形態に限定されるものではなく、本発明の趣旨及びその範囲から逸脱することなく、その形態及び詳細を様々に変更し得ることは当業者であれば容易に理解される。したがって、本発明は、以下に示す実施形態の記載内容に限定して解釈されるものではない。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and it is easy for those skilled in the art to change the modes and details in various ways without departing from the spirit and scope of the present invention. Understood. Therefore, the present invention should not be construed as being limited to the description of the embodiments below.
「固体撮像素子」
図１は、本発明の固体撮像素子の一例を示した断面模式図である。図１に示す固体撮像素子１０は、基板１上に、下部電極２（第１電極）と、光電変換層３と、透明電極４（第２電極）とがこの順に積層されたものである。図１に示す固体撮像素子１０は、ＣＭＯＳ（Complementary Metal Oxide Semiconductor、相補型金属酸化膜半導体）型固体撮像素子である。また、図１に示す固体撮像素子１０は、基板１の光電変換層３側から光を入射するものである。
"Solid-state imaging device"
FIG. 1 is a schematic cross-sectional view showing an example of the solid-state imaging device of the present invention. A solid-state imaging device 10 shown in FIG. 1 is obtained by laminating a lower electrode 2 (first electrode), a photoelectric conversion layer 3 and a transparent electrode 4 (second electrode) on a substrate 1 in this order. A solid-state imaging device 10 shown in FIG. 1 is a CMOS (Complementary Metal Oxide Semiconductor) type solid-state imaging device. Moreover, the solid-state image sensor 10 shown in FIG. 1 enters light from the photoelectric conversion layer 3 side of the substrate 1.
図１に示す基板１は、信号読み出し回路（不図示）を有する半導体基板である。信号読み出し回路としては、各画素の光電変換層３に蓄積された電荷を、画素毎に増幅器で電荷から電圧に変換するとともに増幅してから、固体撮像素子１０を備えた電子機器（不図示）の信号処理手段に送るものが形成されている。このような信号読み出し回路を有する半導体基板としては、従来、ＣＭＯＳ型固体撮像素子の信号読み出し回路を有する半導体基板として用いられている公知のものなどを用いることができる。 A substrate 1 shown in FIG. 1 is a semiconductor substrate having a signal readout circuit (not shown). As the signal readout circuit, the electric charge accumulated in the photoelectric conversion layer 3 of each pixel is converted from electric charge to voltage by an amplifier for each pixel and amplified, and then an electronic device (not shown) provided with the solid-state imaging device 10 To be sent to the signal processing means. As the semiconductor substrate having such a signal readout circuit, a known substrate or the like conventionally used as a semiconductor substrate having a signal readout circuit of a CMOS type solid-state imaging device can be used.
基板１の信号読み出し回路上には、下部電極２が形成されている。図１に示す固体撮像素子１０においては、下部電極２が、基板１に埋め込まれるように形成され、画素電極を兼ねるものとなっている。下部電極２に用いられる材料としては、例えば、Ａｌ（アルミ）、Ｗ（タングステン）、Ｍｏ（モリブデン）、Ｔｉ（チタン）などが挙げられる。 A lower electrode 2 is formed on the signal readout circuit of the substrate 1. In the solid-state imaging device 10 shown in FIG. 1, the lower electrode 2 is formed so as to be embedded in the substrate 1 and also serves as a pixel electrode. Examples of the material used for the lower electrode 2 include Al (aluminum), W (tungsten), Mo (molybdenum), and Ti (titanium).
図１に示す光電変換層３は、接合層（不図示）と、接合層上に形成された多結晶膜からなる光電変換膜とからなるものである。
接合層は、多結晶膜からなる光電変換膜の直下に配置される。接合層は、接合層の直下に配置される層と、多結晶膜からなる光電変換膜との密着性を向上させるものである。接合層は、テルル（Ｔｅ）、ビスマス（Ｂｉ）、アンチモン（Ｓｂ）から選ばれる１種からなるものであることが好ましい。特に、多結晶膜からなる光電変換膜が結晶セレン膜である場合、接合層は、テルル（Ｔｅ）からなるものであることが好ましい。
The photoelectric conversion layer 3 shown in FIG. 1 includes a bonding layer (not shown) and a photoelectric conversion film made of a polycrystalline film formed on the bonding layer.
The bonding layer is disposed immediately below the photoelectric conversion film made of a polycrystalline film. The bonding layer improves the adhesion between the layer disposed immediately below the bonding layer and the photoelectric conversion film made of a polycrystalline film. The bonding layer is preferably made of one selected from tellurium (Te), bismuth (Bi), and antimony (Sb). In particular, when the photoelectric conversion film made of a polycrystalline film is a crystalline selenium film, the bonding layer is preferably made of tellurium (Te).
接合層の膜厚は、０．１〜３ｎｍの範囲であることが好ましい。接合層は、多結晶膜からなる光電変換膜の下層の全面に連続して形成されていてもよいし、接合層の厚みを薄くすることによって多結晶膜からなる光電変換膜の下層の一部に形成されていない領域が存在していてもよい。接合層の膜厚が、０．１ｎｍ以上であると、接合層の直下に配置される層と、多結晶膜からなる光電変換膜との高い密着性が得られ、好ましい。また、接合層の膜厚が、３ｎｍ以下であると、接合層が光電変換膜中の結晶欠陥となって、暗電流増加の要因となることを防止できる。 The thickness of the bonding layer is preferably in the range of 0.1 to 3 nm. The bonding layer may be formed continuously over the entire surface of the lower layer of the photoelectric conversion film made of the polycrystalline film, or a part of the lower layer of the photoelectric conversion film made of the polycrystalline film by reducing the thickness of the bonding layer. There may be a region that is not formed. When the film thickness of the bonding layer is 0.1 nm or more, high adhesion between the layer disposed immediately below the bonding layer and the photoelectric conversion film made of a polycrystalline film is preferable. Moreover, when the film thickness of the bonding layer is 3 nm or less, it can be prevented that the bonding layer becomes a crystal defect in the photoelectric conversion film and causes an increase in dark current.
多結晶膜からなる光電変換膜としては、例えば、結晶セレン、多結晶シリコン、カルコパイライト系化合物材料（例えばＣｕＩｎＧａＳｅなど）からなるものが挙げられる。多結晶膜からなる光電変換膜としては、これらの中でも特に、結晶セレン膜が好ましい。光電変換層３の多結晶膜からなる光電変換膜が、結晶セレン膜を有する場合、高い光吸収性能と視感度に近い分光感度特性とを有するものとなる。したがって、高画質の画像が得られる固体撮像素子１０となる。 Examples of the photoelectric conversion film made of a polycrystalline film include a film made of crystalline selenium, polycrystalline silicon, or chalcopyrite compound material (for example, CuInGaSe). Among these, a crystalline selenium film is particularly preferable as a photoelectric conversion film made of a polycrystalline film. When the photoelectric conversion film made of the polycrystalline film of the photoelectric conversion layer 3 has a crystalline selenium film, the photoelectric conversion layer 3 has high light absorption performance and spectral sensitivity characteristics close to visual sensitivity. Therefore, the solid-state imaging device 10 can obtain a high-quality image.
多結晶膜からなる光電変換膜が結晶セレン膜からなるものである場合、光電変換膜の膜厚は、０．２μｍ以上であることが好ましく、０．５μｍ以上であることがより好ましい。結晶セレン膜の膜厚が０．２μｍ以上である場合、光電変換膜として良好に機能する。また、結晶セレン膜の膜厚は、薄いほど結晶粒径が小さくなり、画素間における光電変換膜の感度の差の小さい光電変換層３が得られやすいものとなる。このため、結晶セレン膜の膜厚は、４μｍ以下であることが好ましく、２μｍ以下であることがより好ましい。 When the photoelectric conversion film made of a polycrystalline film is made of a crystalline selenium film, the thickness of the photoelectric conversion film is preferably 0.2 μm or more, and more preferably 0.5 μm or more. When the thickness of the crystalline selenium film is 0.2 μm or more, it functions well as a photoelectric conversion film. Further, the thinner the film thickness of the crystalline selenium film, the smaller the crystal grain size, and it becomes easier to obtain the photoelectric conversion layer 3 having a small difference in sensitivity of the photoelectric conversion film between pixels. For this reason, the film thickness of the crystalline selenium film is preferably 4 μm or less, and more preferably 2 μm or less.
多結晶膜からなる光電変換膜の最大結晶粒径Ａと、画素サイズＢとは、以下の式（１）を満足する関係を有している。画素サイズは、略正方形である一画素の一辺の長さである。
Ａ／Ｂ≦１．０ ‥（１）
固体撮像素子１０で撮像した画像の固定パターンノイズは、画素毎のノイズ量の差で形成される。Ａ／Ｂが１．０を超えると、光電変換膜の結晶粒界が全くない画素が形成されたり、結晶粒界が僅かしかない画素が形成されたりする場合がある。また、Ａ／Ｂが１．０を超えると、結晶粒界の長さが他の画素と比較して非常に長い画素が形成される場合がある。このため、Ａ／Ｂが１．０を超えると、各画素の光電変換膜の感度の差が大きくなり、画素毎のノイズ量の差が大きくなる。
The maximum crystal grain size A of the photoelectric conversion film made of a polycrystalline film and the pixel size B have a relationship satisfying the following formula (1). The pixel size is the length of one side of a pixel that is substantially square.
A / B ≦ 1.0 (1)
Fixed pattern noise of an image captured by the solid-state image sensor 10 is formed by a difference in noise amount for each pixel. When A / B exceeds 1.0, a pixel having no crystal grain boundary of the photoelectric conversion film may be formed, or a pixel having few crystal grain boundaries may be formed. On the other hand, when A / B exceeds 1.0, a pixel having a very long grain boundary as compared to other pixels may be formed. For this reason, when A / B exceeds 1.0, the difference in the sensitivity of the photoelectric conversion film of each pixel increases, and the difference in the amount of noise for each pixel increases.
これに対し、Ａ／Ｂが、１．０以下であると、各画素の光電変換膜の結晶粒径が平均化され、結晶の大きさに起因する画素間の光電変換膜の感度の差が小さいものとなる。よって、画素毎のノイズ量の差が抑制され、固定パターンノイズが低減する。結晶の大きさに起因する各画素の光電変換膜の感度の差をより一層低減するためには、Ａ／Ｂは、０．６以下であることが好ましい。 On the other hand, if A / B is 1.0 or less, the crystal grain size of the photoelectric conversion film of each pixel is averaged, and the difference in sensitivity of the photoelectric conversion film between the pixels due to the size of the crystal is It will be small. Therefore, the difference in the amount of noise for each pixel is suppressed, and the fixed pattern noise is reduced. In order to further reduce the difference in sensitivity of the photoelectric conversion film of each pixel due to the size of the crystal, A / B is preferably 0.6 or less.
しかし、Ａ／Ｂを０．３未満にすると、固定パターンノイズを低減する効果が飽和する。したがって、Ａ／Ｂは０．３以上であることが好ましい。
また、最大結晶粒径Ａの小さい光電変換膜を得るために、光電変換膜の膜厚を薄くした場合、高い感度が得られにくくなる。具体的には、例えば、最大結晶粒径Ａが１μｍ未満の光電変換膜を形成するために光電変換膜の膜厚を薄くすると、光電変換膜における長波長の光の感度が低下する場合がある。このため、画素サイズＢが例えば３μｍ以下と小さい場合、Ａ／Ｂは０．３以上であることが好ましい。
However, if A / B is less than 0.3, the effect of reducing fixed pattern noise is saturated. Therefore, A / B is preferably 0.3 or more.
In addition, when the thickness of the photoelectric conversion film is reduced in order to obtain a photoelectric conversion film having a small maximum crystal grain size A, it is difficult to obtain high sensitivity. Specifically, for example, when the photoelectric conversion film is thinned to form a photoelectric conversion film having a maximum crystal grain size A of less than 1 μm, the sensitivity of long-wavelength light in the photoelectric conversion film may be reduced. . For this reason, when the pixel size B is as small as 3 μm or less, for example, A / B is preferably 0.3 or more.
多結晶膜からなる光電変換膜の最大結晶粒径Ａは、以下に示す方法により測定できる。
光電変換膜を走査型電子顕微鏡（Scanning Electron Microscope、ＳＥＭ）を用いて撮影し、面積０．７ｍｍ２の領域の画像に含まれる結晶粒子の最大面積を算出する。次に、結晶粒子が円であると仮定して、最大面積の直径を算出し、最大結晶粒径とした。
The maximum crystal grain size A of the photoelectric conversion film made of a polycrystalline film can be measured by the following method.
The photoelectric conversion layer using a scanning electron microscope (Scanning Electron Microscope, SEM) were taken using to calculate the maximum area of the crystal particles contained in the image of an area 0.7 mm 2 region. Next, assuming that the crystal grains are circles, the diameter of the maximum area was calculated and used as the maximum crystal grain diameter.
多結晶膜からなる光電変換膜の平均結晶粒径Ｃと、画素サイズＢとは、以下の式（２）を満足する関係を有している。
Ｃ／Ｂ≦０．１０ ‥（２）
Ｃ／Ｂが、０．１０以下であると、各画素の光電変換膜の結晶粒径がより一層平均化され、結晶の大きさに起因する画素間の光電変換膜の感度の差がより小さいものとなる。したがって、画素毎のノイズ量の差が抑制され、より一層固定パターンノイズが低減する。結晶の大きさに起因する各画素の光電変換膜の感度の差をより一層低減するためには、Ｃ／Ｂは、０．０９以下であることが好ましい。
The average crystal grain size C of the photoelectric conversion film made of a polycrystalline film and the pixel size B have a relationship satisfying the following formula (2).
C / B ≦ 0.10 (2)
When C / B is 0.10 or less, the crystal grain size of the photoelectric conversion film of each pixel is further averaged, and the difference in sensitivity of the photoelectric conversion film between the pixels due to the crystal size is smaller. It will be a thing. Therefore, the difference in the amount of noise for each pixel is suppressed, and the fixed pattern noise is further reduced. In order to further reduce the difference in the sensitivity of the photoelectric conversion film of each pixel due to the size of the crystal, C / B is preferably 0.09 or less.
しかし、Ｃ／Ｂを０．０８未満にすると、固定パターンノイズを低減する効果が飽和する。したがって、Ｃ／Ｂは０．０８以上であることが好ましい。
また、平均結晶粒径Ｃの小さい光電変換膜を得るために、光電変換膜の膜厚を薄くした場合、高い感度が得られにくくなる。具体的には、例えば、平均結晶粒径Ｃが０．２５μｍ未満の光電変換膜を形成するために光電変換膜の膜厚を薄くすると、光電変換膜における長波長の光の感度が低下する場合がある。このため、画素サイズＢが例えば３μｍ以下と小さい場合、Ｃ／Ｂは０．０８以上であることが好ましい。
However, if C / B is less than 0.08, the effect of reducing fixed pattern noise is saturated. Therefore, C / B is preferably 0.08 or more.
In addition, when the thickness of the photoelectric conversion film is reduced in order to obtain a photoelectric conversion film having a small average crystal grain size C, it is difficult to obtain high sensitivity. Specifically, for example, when the photoelectric conversion film is thinned to form a photoelectric conversion film having an average crystal grain size C of less than 0.25 μm, the sensitivity of long wavelength light in the photoelectric conversion film decreases. There is. For this reason, when the pixel size B is as small as 3 μm or less, for example, C / B is preferably 0.08 or more.
多結晶膜からなる光電変換膜の平均結晶粒径Ｃは、以下に示す方法により測定できる。
光電変換膜を走査型電子顕微鏡（ＳＥＭ）を用いて撮影し、面積０．７ｍｍ２の領域の画像に含まれる結晶粒子の総面積を結晶粒子の総個数で割り、平均面積を算出する。次に、結晶粒子が全て円であると仮定して、平均面積の直径を算出し、平均結晶粒径とした。
The average crystal grain size C of the photoelectric conversion film made of a polycrystalline film can be measured by the following method.
The photoelectric conversion film is photographed using a scanning electron microscope (SEM), and the total area of the crystal particles included in the image of the area having an area of 0.7 mm 2 is divided by the total number of crystal particles to calculate the average area. Next, assuming that the crystal grains are all circles, the diameter of the average area was calculated and used as the average crystal grain size.
画素サイズＢは、３μｍ以下であることが好ましい。画素サイズＢが３μｍ以下であると、高画質の画像が得られやすくなる。 The pixel size B is preferably 3 μm or less. When the pixel size B is 3 μm or less, a high-quality image is easily obtained.
透明電極４としては、例えば、ＩＴＯ（酸化インジウムスズ）、ＩＺＯ（酸化亜鉛スズ）などを用いることができる。 As the transparent electrode 4, for example, ITO (indium tin oxide), IZO (zinc tin oxide), or the like can be used.
「製造方法」
図１に示す固体撮像素子１０は、例えば、以下に示す方法により製造できる。
まず、基板１として、信号読み出し回路を有する半導体基板を用意する。次いで、基板１の信号読み出し回路上に、真空蒸着法、スパッタリング法など従来公知の方法を用いて、下部電極２を形成する。
次に、下部電極２の形成された基板１上に、例えば、真空蒸着法、スパッタリング法など公知の方法を用いて、テルルなどからなる接合層（不図示）を形成する。
"Production method"
The solid-state image sensor 10 shown in FIG. 1 can be manufactured by the method shown below, for example.
First, a semiconductor substrate having a signal reading circuit is prepared as the substrate 1. Next, the lower electrode 2 is formed on the signal readout circuit of the substrate 1 by using a conventionally known method such as a vacuum deposition method or a sputtering method.
Next, a bonding layer (not shown) made of tellurium or the like is formed on the substrate 1 on which the lower electrode 2 is formed by using a known method such as a vacuum evaporation method or a sputtering method.
次に、接合層上に、真空蒸着法など公知の方法を用いて、多結晶膜からなる光電変換膜を形成する。このことにより、接合層と、多結晶膜からなる光電変換膜とからなる光電変換層３が形成される。
多結晶膜からなる光電変換膜の最大結晶粒径または、最大結晶粒径および平均結晶粒径は、多結晶膜からなる光電変換膜の材料、膜厚、成膜時の雰囲気および温度などの条件のうちから選ばれる１つ以上の項目を変化させることにより、制御できる。
Next, a photoelectric conversion film made of a polycrystalline film is formed on the bonding layer using a known method such as a vacuum deposition method. Thereby, the photoelectric conversion layer 3 which consists of a joining layer and the photoelectric converting film which consists of a polycrystalline film is formed.
The maximum crystal grain size or the maximum crystal grain size and the average crystal grain size of a photoelectric conversion film made of a polycrystalline film are the conditions such as the material, film thickness, atmosphere and temperature during film formation of the photoelectric conversion film made of a polycrystalline film Control can be performed by changing one or more items selected from among the items.
多結晶膜からなる光電変換膜として、結晶セレン膜を形成する場合、例えば、以下に示す方法により、結晶セレン膜を形成することが好ましい。まず、真空蒸着法により、接合層上にアモルファスセレン膜を形成する。その後、大気中で５０〜２１５℃の熱処理温度で１０秒〜２分間の加熱処理を行うことにより、アモルファスセレン膜を結晶化し、結晶セレン膜とする。 When a crystalline selenium film is formed as a photoelectric conversion film made of a polycrystalline film, it is preferable to form the crystalline selenium film by, for example, the following method. First, an amorphous selenium film is formed on the bonding layer by vacuum deposition. Then, the amorphous selenium film is crystallized by performing a heat treatment for 10 seconds to 2 minutes at a heat treatment temperature of 50 to 215 ° C. in the atmosphere to obtain a crystalline selenium film.
また、多結晶膜からなる光電変換膜として、例えば、結晶セレン膜を形成する場合、膜厚を変化させることにより、所定の最大結晶粒径または、最大結晶粒径および平均結晶粒径を有する結晶セレン膜を形成することが好ましい。
本発明者は、結晶セレン膜の結晶粒径を制御するべく検討した。その結果、結晶セレン膜は、膜厚を小さくするほど、最大結晶粒径および平均結晶粒径が小さくなることを見出した。そして、以下に示す方法により、容易かつ高精度で所定の最大結晶粒径および平均結晶粒径を有する結晶セレン膜が得られることを確認した。
初めに、結晶セレン膜の膜厚と、最大結晶粒径または、最大結晶粒径および平均結晶粒径との関係を調べる。そして、得られた結果に基づいて、必要とされる最大結晶粒径または、最大結晶粒径および平均結晶粒径となる膜厚で、結晶セレン膜を形成する。結晶セレン膜の膜厚は、例えば、結晶化によって結晶セレン膜とされるアモルファスセレン膜の厚みを制御する方法により、調整できる。アモルファスセレン膜の厚みは、成膜時間を変化させる方法などにより制御できる。
Further, as a photoelectric conversion film made of a polycrystalline film, for example, when a crystalline selenium film is formed, a crystal having a predetermined maximum crystal grain size or a maximum crystal grain size and an average crystal grain size can be obtained by changing the film thickness. It is preferable to form a selenium film.
The inventor has studied to control the crystal grain size of the crystalline selenium film. As a result, it has been found that the maximum crystal grain size and the average crystal grain size of the crystalline selenium film are reduced as the film thickness is reduced. It was confirmed that a crystalline selenium film having a predetermined maximum crystal grain size and average crystal grain size can be obtained easily and with high accuracy by the following method.
First, the relationship between the film thickness of the crystalline selenium film and the maximum crystal grain size or the maximum crystal grain size and the average crystal grain size is examined. Then, based on the obtained results, a crystalline selenium film is formed with a required maximum crystal grain size or a film thickness that provides the maximum crystal grain size and the average crystal grain size. The film thickness of the crystalline selenium film can be adjusted by, for example, a method of controlling the thickness of the amorphous selenium film that is converted into a crystalline selenium film by crystallization. The thickness of the amorphous selenium film can be controlled by a method of changing the deposition time.
次に、高周波（ＲＦ）スパッタ法など公知の方法を用いて、光電変換層３上に透明電極４を形成する。
以上の工程により、図１に示す固体撮像素子１０が得られる。
Next, the transparent electrode 4 is formed on the photoelectric conversion layer 3 using a known method such as a radio frequency (RF) sputtering method.
Through the above steps, the solid-state imaging device 10 shown in FIG. 1 is obtained.
図１に示す固体撮像素子１０は、信号読み出し回路を有する基板１上に、下部電極２と、光電変換層３と、透明電極４とがこの順に積層されたものであり、光電変換層３が多結晶膜からなる光電変換膜を有し、光電変換膜の最大結晶粒径Ａと、画素サイズＢとの関係が、Ａ／Ｂ≦１．０を満足するものである。このため、図１に示す固体撮像素子１０では、各画素における光電変換膜の結晶粒界に起因する感度の差が平均化され、光電変換膜の結晶の大きさに起因する画素間の光電変換膜の感度の差が小さくなる。よって、画素毎のノイズ量の差が抑制され、撮像した画像の固定パターンノイズが低減し、高画質の画像が得られる。 A solid-state imaging device 10 shown in FIG. 1 is obtained by laminating a lower electrode 2, a photoelectric conversion layer 3, and a transparent electrode 4 in this order on a substrate 1 having a signal readout circuit. It has a photoelectric conversion film made of a polycrystalline film, and the relationship between the maximum crystal grain size A of the photoelectric conversion film and the pixel size B satisfies A / B ≦ 1.0. For this reason, in the solid-state imaging device 10 shown in FIG. 1, the difference in sensitivity due to the crystal grain boundary of the photoelectric conversion film in each pixel is averaged, and the photoelectric conversion between the pixels due to the crystal size of the photoelectric conversion film. The difference in film sensitivity is reduced. Therefore, the difference in the amount of noise for each pixel is suppressed, the fixed pattern noise of the captured image is reduced, and a high-quality image can be obtained.
図１に示す固体撮像素子１０において、光電変換膜の平均結晶粒径Ｃと、画素サイズＢとの関係が、Ｃ／Ｂ≦０．１０を満足する場合、より一層各画素における光電変換膜の結晶粒界に起因する感度の差が平均化され、光電変換膜の結晶の大きさに起因する画素間の光電変換膜の感度の差が小さくなる。したがって、撮像した画像の固定パターンノイズがより一層少なくなり、より高画質の画像が得られる。 In the solid-state imaging device 10 shown in FIG. 1, when the relationship between the average crystal grain size C of the photoelectric conversion film and the pixel size B satisfies C / B ≦ 0.10, the photoelectric conversion film in each pixel is further increased. The difference in sensitivity due to the crystal grain boundary is averaged, and the difference in sensitivity of the photoelectric conversion film between pixels due to the crystal size of the photoelectric conversion film is reduced. Therefore, the fixed pattern noise of the captured image is further reduced, and a higher quality image can be obtained.
図１に示す固体撮像素子１０は、信号読み出し回路を有する基板１上に、下部電極２と、光電変換層３と、透明電極４とがこの順に積層されたものであるので、透明電極４側から固体撮像素子１０に入射した光が、信号読み出し回路に遮られることなく光電変換層３で受光される。このため、図１に示す固体撮像素子１０は、光の利用効率が高く、高感度のものとなる。 The solid-state imaging device 10 shown in FIG. 1 has a lower electrode 2, a photoelectric conversion layer 3, and a transparent electrode 4 laminated in this order on a substrate 1 having a signal readout circuit. The light incident on the solid-state imaging device 10 is received by the photoelectric conversion layer 3 without being blocked by the signal readout circuit. For this reason, the solid-state imaging device 10 shown in FIG. 1 has high light utilization efficiency and high sensitivity.
図１に示す固体撮像素子１０は、ＣＭＯＳ型固体撮像素子であり、各画素の光電変換層３に蓄積された電荷を、画素毎に増幅器で電荷から電圧に変換するとともに増幅してから、固体撮像素子１０を備えた電子機器の信号処理手段に送るものである。したがって、画素毎のノイズ量には、各画素の光電変換膜の感度の差に起因するノイズに加えて、画素毎に設けられている増幅器の特性に起因するノイズも含まれる。このため、ＣＭＯＳ型固体撮像素子では、固定パターンノイズが大きくなりやすい。本実施形態の固体撮像素子１０は、各画素の光電変換膜の感度の差によるノイズが小さいものであるため、ＣＭＯＳ型固体撮像素子における画素毎のノイズ量の差を抑制でき、固定パターンノイズを抑制できる。 A solid-state image pickup device 10 shown in FIG. 1 is a CMOS solid-state image pickup device. The charge accumulated in the photoelectric conversion layer 3 of each pixel is converted from charge to voltage and amplified by an amplifier for each pixel, and then solid-state. The signal is sent to a signal processing means of an electronic device provided with the image sensor 10. Therefore, the noise amount for each pixel includes noise due to the characteristics of the amplifier provided for each pixel in addition to the noise due to the difference in sensitivity of the photoelectric conversion film of each pixel. For this reason, fixed pattern noise tends to be large in a CMOS solid-state imaging device. Since the solid-state imaging device 10 of this embodiment has a small noise due to the difference in sensitivity of the photoelectric conversion film of each pixel, the difference in the amount of noise for each pixel in the CMOS type solid-state imaging device can be suppressed, and fixed pattern noise can be reduced. Can be suppressed.
「他の例」
本発明の固体撮像素子は、上述した実施形態の固体撮像素子に限定されるものではない。例えば、図１に示す固体撮像素子１０においては、基板１の光電変換層３側から光を入射するものを例に挙げて説明したが、基板１の光電変換層３と反対側から光を入射するものであってもよい。この場合、図１に示す固体撮像素子１０の下部電極２および信号読み出し回路を有する基板１として、透光性を有するものを用いる。
"Other examples"
The solid-state image sensor of the present invention is not limited to the solid-state image sensor of the above-described embodiment. For example, in the solid-state imaging device 10 shown in FIG. 1, the light incident from the photoelectric conversion layer 3 side of the substrate 1 is described as an example, but the light is incident from the opposite side of the substrate 1 from the photoelectric conversion layer 3. You may do. In this case, the substrate 1 having the lower electrode 2 and the signal readout circuit of the solid-state imaging device 10 shown in FIG.
図１に示す固体撮像素子１０は、ＣＭＯＳ型固体撮像素子であるが、本発明の固体撮像素子は、ＣＣＤ（Charge Coupled Device、電荷結合素子）型固体撮像素子であってもよい。この場合、信号読み出し回路として、全ての画素の光電変換層に蓄積された電荷を１つの増幅器に転送し、その増幅器で電荷から電圧に変換するとともに増幅してから、固体撮像素子を備えた電子機器の信号処理手段に送るものが形成されている半導体基板を用いる。このような信号読み出し回路を有する半導体基板としては、例えば、従来のＣＣＤ型固体撮像素子の信号読み出し回路を有する半導体基板として用いられている公知のものなどを用いることができる。 The solid-state imaging device 10 shown in FIG. 1 is a CMOS solid-state imaging device, but the solid-state imaging device of the present invention may be a CCD (Charge Coupled Device) type solid-state imaging device. In this case, as a signal readout circuit, the charges accumulated in the photoelectric conversion layers of all the pixels are transferred to one amplifier, converted from charge to voltage by the amplifier and amplified, and then provided with an electron equipped with a solid-state imaging device. A semiconductor substrate on which what is sent to the signal processing means of the device is formed is used. As a semiconductor substrate having such a signal readout circuit, for example, a known substrate used as a semiconductor substrate having a signal readout circuit of a conventional CCD type solid-state imaging device can be used.
図１に示す固体撮像素子１０の光電変換層３のように、光電変換層は、多結晶膜からなる光電変換膜の他に接合層などの他の層を有するものであってもよいし、多結晶膜からなる光電変換膜のみからなるものであってもよい。
また、光電変換層の有する光電変換膜は、図１に示す固体撮像素子１０のように、多結晶膜からなる１層の光電変換膜のみであってもよいし、多結晶膜からなる１層の光電変換膜に加えて、さらに１層以上の光電変換膜を有していてもよい。光電変換層が複数の光電変換膜を有するものである場合、複数の光電変換膜は全て異なる光電変換膜であってもよいし、複数の光電変換膜のうち一部または全部が同じ光電変換膜であってもよい。また、光電変換層が複数の光電変換膜を有するものである場合、積層された光電変換層間には、電極と相関絶縁膜と電極とがこの順で配置されていることが好ましい。
Like the photoelectric conversion layer 3 of the solid-state imaging device 10 shown in FIG. 1, the photoelectric conversion layer may have another layer such as a bonding layer in addition to the photoelectric conversion film made of a polycrystalline film, It may be composed only of a photoelectric conversion film composed of a polycrystalline film.
Further, the photoelectric conversion film included in the photoelectric conversion layer may be only one photoelectric conversion film made of a polycrystalline film as in the solid-state imaging device 10 shown in FIG. 1, or one layer made of a polycrystalline film. In addition to the photoelectric conversion film, one or more photoelectric conversion films may be further included. When the photoelectric conversion layer has a plurality of photoelectric conversion films, the plurality of photoelectric conversion films may all be different photoelectric conversion films, or some or all of the plurality of photoelectric conversion films are the same photoelectric conversion film. It may be. Moreover, when a photoelectric converting layer has a some photoelectric converting film, it is preferable that the electrode, the correlation insulating film, and the electrode are arrange | positioned in this order between the laminated | stacked photoelectric converting layers.
以下、本発明を実施例に基づいて具体的に説明する。なお、本発明はこれらの実施例にのみ限定されるものではない。
「実施例１」
以下に示す方法により、図１に示す固体撮像素子１０を形成し、評価した。
画素サイズが３μｍであるＣＭＯＳ型固体撮像素子の信号読み出し回路を有する半導体基板を用意し、信号読み出し回路上に下部電極２を形成した。
Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.
"Example 1"
The solid-state imaging device 10 shown in FIG. 1 was formed and evaluated by the following method.
A semiconductor substrate having a signal readout circuit of a CMOS type solid-state imaging device having a pixel size of 3 μm was prepared, and the lower electrode 2 was formed on the signal readout circuit.
次に、下部電極２の形成された基板１上に、真空蒸着法を用いて、膜厚０．１ｎｍのテルルからなる接合層を形成した。次に、接合層上に、真空蒸着法を用いて、アモルファスセレン膜を形成した。その後、大気中で２００℃の熱処理温度で１分間の加熱処理を行うことにより、アモルファスセレン膜を結晶化し、膜厚０．５μｍの結晶セレン膜を形成した。このことにより、テルル膜と結晶セレン膜とからなる光電変換層３を形成した。 Next, a bonding layer made of tellurium having a thickness of 0.1 nm was formed on the substrate 1 on which the lower electrode 2 was formed, using a vacuum deposition method. Next, an amorphous selenium film was formed on the bonding layer by vacuum evaporation. Thereafter, heat treatment was performed in the atmosphere at a heat treatment temperature of 200 ° C. for 1 minute to crystallize the amorphous selenium film, thereby forming a 0.5 μm thick crystalline selenium film. Thus, a photoelectric conversion layer 3 composed of a tellurium film and a crystalline selenium film was formed.
このようにして得られた実施例１の結晶セレン膜の表面を、走査型電子顕微鏡（ＳＥＭ）を用いて撮影し、上述した方法を用いて、結晶セレン膜の最大結晶粒径および平均結晶粒径を調べた。その結果、結晶セレン膜の最大結晶粒径は１．４３μｍであり、平均結晶粒径は０．３０μｍであった。図２は、実施例１の結晶セレン膜の表面を、走査型電子顕微鏡（ＳＥＭ）を用いて撮影した写真である。図２に示すように、実施例１の結晶セレン膜では、画素サイズである３μｍを超える粒径を有する結晶は見られなかった。 The surface of the crystalline selenium film of Example 1 obtained in this way was photographed using a scanning electron microscope (SEM), and the maximum crystal grain size and average crystal grain of the crystalline selenium film were obtained using the method described above. The diameter was examined. As a result, the maximum crystal grain size of the crystalline selenium film was 1.43 μm, and the average crystal grain size was 0.30 μm. FIG. 2 is a photograph of the surface of the crystalline selenium film of Example 1 taken using a scanning electron microscope (SEM). As shown in FIG. 2, in the crystalline selenium film of Example 1, no crystals having a particle size exceeding the pixel size of 3 μm were observed.
次に、室温でＤＣ（直流）スパッタ法を用いて、光電変換層３上にＩＴＯからなる透明電極４を形成した。
以上の工程により、実施例１の固体撮像素子を得た。
Next, a transparent electrode 4 made of ITO was formed on the photoelectric conversion layer 3 by using a DC (direct current) sputtering method at room temperature.
Through the above steps, the solid-state imaging device of Example 1 was obtained.
「実施例２」
結晶セレン膜として膜厚１．０μｍの結晶セレン膜を形成したこと以外は、実施例１と同様にして実施例２の固体撮像素子を得た。
また、実施例１と同様にして、透明電極４を形成する前に結晶セレン膜の表面を、走査型電子顕微鏡（ＳＥＭ）を用いて撮影し、結晶セレン膜の最大結晶粒径および平均結晶粒径を調べた。その結果、結晶セレン膜の最大結晶粒径は１．７９μｍであり、平均結晶粒径は０．３３μｍであった。
"Example 2"
A solid-state imaging device of Example 2 was obtained in the same manner as in Example 1 except that a crystalline selenium film having a thickness of 1.0 μm was formed as the crystalline selenium film.
Similarly to Example 1, the surface of the crystalline selenium film was photographed using a scanning electron microscope (SEM) before forming the transparent electrode 4, and the maximum crystal grain size and the average crystal grain of the crystalline selenium film were taken. The diameter was examined. As a result, the maximum crystal grain size of the crystalline selenium film was 1.79 μm, and the average crystal grain size was 0.33 μm.
「比較例１」
結晶セレン膜として膜厚２．０μｍの結晶セレン膜を形成したこと以外は、実施例１と同様にして比較例１の固体撮像素子を得た。
また、実施例１と同様にして、透明電極４を形成する前に結晶セレン膜の表面を、走査型電子顕微鏡（ＳＥＭ）を用いて撮影し、結晶セレン膜の最大結晶粒径および平均結晶粒径を調べた。その結果、結晶セレン膜の最大結晶粒径は４．１４μｍであり、平均結晶粒径は０．４０μｍであった。図３は、比較例１の結晶セレン膜の表面を、走査型電子顕微鏡（ＳＥＭ）を用いて撮影した写真である。図３に示すように、比較例１の結晶セレン膜では、画素サイズである３μｍを超える粒径を有する結晶が見られた。
"Comparative Example 1"
A solid-state imaging device of Comparative Example 1 was obtained in the same manner as Example 1 except that a crystalline selenium film having a thickness of 2.0 μm was formed as the crystalline selenium film.
Similarly to Example 1, the surface of the crystalline selenium film was photographed using a scanning electron microscope (SEM) before forming the transparent electrode 4, and the maximum crystal grain size and the average crystal grain of the crystalline selenium film were taken. The diameter was examined. As a result, the maximum crystal grain size of the crystalline selenium film was 4.14 μm, and the average crystal grain size was 0.40 μm. FIG. 3 is a photograph of the surface of the crystalline selenium film of Comparative Example 1 taken using a scanning electron microscope (SEM). As shown in FIG. 3, in the crystalline selenium film of Comparative Example 1, crystals having a grain size exceeding the pixel size of 3 μm were observed.
実施例１、実施例２、比較例１において測定した結晶セレン膜の最大結晶粒径および平均結晶粒径を図４および表１に示す。図４は、結晶セレン膜の膜厚と、結晶セレン膜の最大結晶粒径および平均結晶粒径との関係を示したグラフである。図４において白丸（○）は最大結晶粒径を示し、黒丸（●）は平均結晶粒径を示す。 The maximum crystal grain size and average crystal grain size of the crystalline selenium film measured in Example 1, Example 2, and Comparative Example 1 are shown in FIG. FIG. 4 is a graph showing the relationship between the thickness of the crystalline selenium film and the maximum crystal grain size and average crystal grain size of the crystal selenium film. In FIG. 4, white circles (◯) indicate the maximum crystal grain size, and black circles (●) indicate the average crystal grain size.
図４および表１に示すように、膜厚の薄い結晶セレン膜ほど、最大結晶粒径および平均結晶粒径が小さいことが確認できた。 As shown in FIG. 4 and Table 1, it was confirmed that the smaller the thickness of the crystalline selenium film, the smaller the maximum crystal grain size and the average crystal grain size.
実施例１、実施例２、比較例１の固体撮像素子を用いてそれぞれ画像を撮像し、グレー１色の部分から抜き出した４００画素（２００画素×２００画素）について輝度の分布を調べた。その結果を図５〜図７に示す。
図５〜図７は、固体撮像素子を用いて撮像した画像の輝度の分布を示したヒストグラムであり、図５は実施例１の固体撮像素子を用いたヒストグラムであり、図６は実施例２の固体撮像素子を用いたヒストグラムであり、図７は比較例１の固体撮像素子を用いたヒストグラムである。
Images were captured using the solid-state imaging devices of Example 1, Example 2, and Comparative Example 1, respectively, and the luminance distribution was examined for 400 pixels (200 pixels × 200 pixels) extracted from the gray one color portion. The results are shown in FIGS.
5 to 7 are histograms showing the luminance distribution of an image picked up using a solid-state image sensor, FIG. 5 is a histogram using the solid-state image sensor of Example 1, and FIG. 7 is a histogram using the solid-state image sensor of Comparative Example 1. FIG.
また、図５〜図７に示す実施例１、実施例２、比較例１の輝度の分布について標準偏差σを算出した。その結果、実施例１の標準偏差σは２２．７９、実施例２の標準偏差σは２３．４０、比較例１の標準偏差σは３２．６１であった。
図５〜図７および標準偏差から分かるように、結晶セレン膜の膜厚が０．５μｍである実施例１の固体撮像素子および結晶セレン膜の膜厚が１．０μｍである実施例２の固体撮像素子では、結晶セレン膜の膜厚が２．０μｍである比較例１の固体撮像素子と比較して、標準偏差σが小さく、輝度のばらつきが小さかった。
Also, the standard deviation σ was calculated for the luminance distributions of Example 1, Example 2, and Comparative Example 1 shown in FIGS. As a result, the standard deviation σ of Example 1 was 22.79, the standard deviation σ of Example 2 was 23.40, and the standard deviation σ of Comparative Example 1 was 32.61.
As can be seen from FIGS. 5 to 7 and the standard deviation, the solid-state imaging device of Example 1 in which the film thickness of the crystalline selenium film is 0.5 μm and the solid of Example 2 in which the film thickness of the crystal selenium film is 1.0 μm. In the imaging device, the standard deviation σ was small and the variation in luminance was small compared to the solid-state imaging device of Comparative Example 1 in which the film thickness of the crystalline selenium film was 2.0 μm.
また、実施例１、実施例２、比較例１の固体撮像素子の画素サイズは３μｍである。上記の結果より、結晶セレン膜の最大結晶粒径Ａと画素サイズＢとの関係がＡ／Ｂ≦１．０を満足する実施例１および実施例２では、光電変換膜の結晶の大きさに起因する各画素の光電変換膜の感度の差が小さいことが確認できた。
また、上記の結果より、結晶セレン膜の平均結晶粒径Ｃと画素サイズＢとの関係がＣ／Ｂ≦０．１０を満足する実施例１では、光電変換膜の結晶の大きさに起因する各画素の光電変換膜の感度の差が非常に小さいことが確認できた。
Moreover, the pixel size of the solid-state imaging device of Example 1, Example 2, and Comparative Example 1 is 3 μm. From the above results, in Example 1 and Example 2 in which the relationship between the maximum crystal grain size A of the crystalline selenium film and the pixel size B satisfies A / B ≦ 1.0, the crystal size of the photoelectric conversion film is It was confirmed that the difference in the sensitivity of the photoelectric conversion film of each pixel due to the difference was small.
Further, from the above results, in Example 1 in which the relationship between the average crystal grain size C of the crystalline selenium film and the pixel size B satisfies C / B ≦ 0.10, this is caused by the crystal size of the photoelectric conversion film. It was confirmed that the difference in sensitivity of the photoelectric conversion film of each pixel was very small.
また、実施例１、実施例２、比較例１の標準偏差σから分かるように、Ａ／Ｂ≦１．０を満足する実施例１と実施例２とでは、標準偏差σの差が小さかった。また、実施例１および実施例２と、Ａ／Ｂ≦１．０を満足しない比較例１とでは、標準偏差σの差が大きかった。 Further, as can be seen from the standard deviation σ of Example 1, Example 2, and Comparative Example 1, the difference in standard deviation σ was small between Example 1 and Example 2 that satisfied A / B ≦ 1.0. . Further, in Example 1 and Example 2 and Comparative Example 1 that does not satisfy A / B ≦ 1.0, the difference in standard deviation σ was large.
１…基板、２…下部電極（第１電極）、３…光電変換層、４…透明電極（第２電極）、１０…固体撮像素子 DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Lower electrode (1st electrode), 3 ... Photoelectric conversion layer, 4 ... Transparent electrode (2nd electrode), 10 ... Solid-state image sensor
Claims (3)
前記光電変換層が、テルルからなる接合層と、前記接合層上に形成された多結晶膜であって結晶セレン膜からなる光電変換膜とからなり、前記光電変換膜の最大結晶粒径が１μｍ以上であり、前記最大結晶粒径Ａと、３μｍ以下である画素サイズＢとの関係が、以下の式（１）を満足することを特徴とする固体撮像素子。
Ａ／Ｂ≦１．０ ‥（１）
（式（１）において、Ａは＞０である。） A solid-state imaging device in which a first electrode, a photoelectric conversion layer, and a second electrode are stacked in this order on a substrate having a signal readout circuit,
The photoelectric conversion layer is composed of a bonding layer made of tellurium, formed on said bonding layer and the polycrystalline film is a photoelectric conversion layer made of crystalline selenium film, maximum crystal grain size of the photoelectric conversion layer is 1μm A solid-state imaging device in which the relationship between the maximum crystal grain size A and the pixel size B of 3 μm or less satisfies the following formula (1).
A / B ≦ 1.0 (1)
(In the formula (1), A is> 0.)
Ｃ／Ｂ≦０．１０ ‥（２）
（式（２）において、Ｃは＞０である。） The solid-state imaging device according to claim 1, wherein a relationship between an average crystal grain size C of the photoelectric conversion film and a pixel size B satisfies the following formula (2).
C / B ≦ 0.10 (2)
(In the formula (2), C is> 0.)
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