JP2982206B2 - Solid-state imaging device - Google Patents
Solid-state imaging deviceInfo
- Publication number
- JP2982206B2 JP2982206B2 JP2058988A JP5898890A JP2982206B2 JP 2982206 B2 JP2982206 B2 JP 2982206B2 JP 2058988 A JP2058988 A JP 2058988A JP 5898890 A JP5898890 A JP 5898890A JP 2982206 B2 JP2982206 B2 JP 2982206B2
- Authority
- JP
- Japan
- Prior art keywords
- region
- photoelectric conversion
- charge
- charge transfer
- type
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Solid State Image Pick-Up Elements (AREA)
Description
【発明の詳細な説明】 ［産業上の利用分野］ 本発明は固体撮像素子に関し、特に、受光部に埋め込
み型のフォトダイオードを用いて半導体基板表面で発生
する暗電流を低減せしめた固体撮像素子に関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device, and more particularly, to a solid-state imaging device in which a dark current generated on the surface of a semiconductor substrate is reduced by using an embedded photodiode in a light receiving section. About.
［従来の技術］ 第３図（ａ）は、この種従来の固体撮像素子の主要部
断面図である。同図に示すように、ｎ型半導体基板１上
にｐ型ウェル２が形成され、ｐ型ウェルの表面に形成さ
れた接合の深いｎ型領域３の表面に、接合の浅いp+型領
域４が形成されている。ｐ型ウェル２の表面には更に電
荷転送部のｎ型領域９と各領域を分離するチャネルスト
ップ11が形成され、また、半導体基板上には絶縁膜10を
介して電荷転送電極８と遮光膜５が形成されている。[Prior Art] FIG. 3A is a sectional view of a main part of a conventional solid-state imaging device of this kind. As shown in FIG. 1, a p-type well 2 is formed on an n-type semiconductor substrate 1, and a shallow p + -type region 4 is formed on the surface of a deep junction n-type region 3 formed on the surface of the p-type well. Are formed. On the surface of the p-type well 2 are further formed a channel stop 11 for separating the n-type region 9 of the charge transfer portion from each other, and a charge transfer electrode 8 and a light shielding film on the semiconductor substrate via an insulating film 10. 5 are formed.
埋め込み型に形成されているフォトダイオードのｎ型
領域３には、遮光膜５の開口部６から入射した光により
発生した電子が蓄積される。フォトダイオードと電荷転
送部の間にはｐ型の読み出しゲート領域7aが設けられて
おり、該ゲート領域上に設けられた電荷転送電極８に適
切な電圧を印加することにより、フォトダイオードのｎ
型領域３に蓄積された電子を電荷転送部のｎ型領域９へ
読み出すことができる。In the n-type region 3 of the buried photodiode, electrons generated by light incident from the opening 6 of the light shielding film 5 are accumulated. A p-type read gate region 7a is provided between the photodiode and the charge transfer section. By applying an appropriate voltage to the charge transfer electrode 8 provided on the gate region, the n-type
The electrons accumulated in the mold region 3 can be read out to the n-type region 9 of the charge transfer section.
このような固体撮像素子において、正常な読み出し動
作を行わせるには、p+型領域４と読み出しゲート領域7a
とが接触しないようにすることが、換言すれば、フォト
ダイオードのｎ型領域３の一部がp+型領域４より読み出
しゲート領域7a寄りに形成されていることが必要であっ
た。In such a solid-state imaging device, in order to perform a normal read operation, the p + type region 4 and the read gate region 7a are required.
In other words, it is necessary that a part of the n-type region 3 of the photodiode is formed closer to the read gate region 7a than the p + -type region 4.
［発明が解決しようとする課題］ 上述した従来の固体撮像素子では、フォトダイオード
のｎ型領域３の一部がp+型領域４よりも電荷転送部寄り
に形成されているために、フォトダイオードのｎ型領域
は電荷転送電極８の下の上記部分で絶縁膜の界面と接し
てしまう。従って、フォトダイオードから電荷転送部に
かけての電位分布は第３図（ｂ）に示されるようにな
り、そのため、絶縁膜10と半導体基板との界面で発生す
る雑音電荷がｎ型領域３に蓄積される。この電荷は信号
電荷に混入して暗電流成分となるので、従来の固体撮像
素子では、S/Nの低下、固定パターンノイズの発生が避
け難かった。[Problem to be Solved by the Invention] In the above-described conventional solid-state imaging device, since a part of the n-type region 3 of the photodiode is formed closer to the charge transfer portion than the p + -type region 4, the photodiode The n-type region is in contact with the interface of the insulating film in the above-described portion below the charge transfer electrode 8. Therefore, the potential distribution from the photodiode to the charge transfer portion is as shown in FIG. 3 (b). Therefore, noise charges generated at the interface between the insulating film 10 and the semiconductor substrate are accumulated in the n-type region 3. You. Since this charge mixes with the signal charge to become a dark current component, it has been difficult to avoid a reduction in S / N and generation of fixed pattern noise in the conventional solid-state imaging device.
［課題を解決するための手段］ 本発明の固体撮像素子は、ｎ型光電変換領域の電荷読
み出しゲート領域と接する部分を除く表面上にp+型領域
を設けた、いわゆる埋め込み型フォトダイオードを有す
るものであって、少なくともｎ型光電変換領域の電荷読
み出しゲート領域と接する部分の表面はｐ型不純物の導
入によりｐ型化されている。すなわち、本発明において
は、埋め込み型フォトダイオードのｎ型領域は全て半導
体基板内部に埋め込まれ、絶縁膜と接することがないよ
うになされている。そして電荷読み出しゲート領域から
電荷転送領域上にかけて形成されている電荷転送電極は
ｎ型光電変換領域上にまで延在している。[Means for Solving the Problems] The solid-state imaging device of the present invention has a so-called embedded photodiode in which ap + -type region is provided on the surface of the n-type photoelectric conversion region except for a portion in contact with the charge readout gate region. The surface of at least a portion of the n-type photoelectric conversion region which is in contact with the charge readout gate region is made p-type by introducing a p-type impurity. That is, in the present invention, the entire n-type region of the buried photodiode is buried inside the semiconductor substrate so as not to come into contact with the insulating film. The charge transfer electrode formed from the charge readout gate region to the charge transfer region extends to the n-type photoelectric conversion region.
［実施例］ 次に、本発明の実施例について図面を参照して説明す
る。Example Next, an example of the present invention will be described with reference to the drawings.
第１図は、本発明の一実施例を示す要部断面図であ
る。同図において、第３図（ａ）に示す従来例の部分と
同等の部分には同一の参照番号が付されているので重複
する説明は省略するが、本実施例の従来例と相違する点
は、フォトダイオードのp+型領域４から電荷転送部のｎ
型領域９に渡る領域に、ｎ型領域３の導電型を反転させ
る濃度のｐ型不純物が導入されて、この部分が読み出し
ゲート領域７となされている点である。このように構成
すれば、フォトダイオードのｎ型領域３が絶縁膜と半導
体表面との界面で接することはなくなる。FIG. 1 is a sectional view of an essential part showing one embodiment of the present invention. In the figure, the same parts as those of the conventional example shown in FIG. 3 (a) are denoted by the same reference numerals, and duplicate explanations are omitted, but the points different from the conventional example of this embodiment are omitted. Is from the p + type region 4 of the photodiode to n of the charge transfer section.
The point is that a p-type impurity having a concentration that inverts the conductivity type of the n-type region 3 is introduced into a region extending over the mold region 9, and this portion serves as the read gate region 7. With this configuration, the n-type region 3 of the photodiode does not come into contact with the interface between the insulating film and the semiconductor surface.
このような固体撮像素子は、常法によりフォトダイオ
ードのｎ型領域３と電荷転送部のｎ型領域９およびp+型
のチャネルストップ11を形成した後、読み出しゲート部
に適切な量のボロンをイオン注入法で注入することによ
り容易に作成することができる。In such a solid-state imaging device, after forming the n-type region 3 of the photodiode, the n-type region 9 of the charge transfer portion, and the p + -type channel stop 11 by an ordinary method, an appropriate amount of boron is applied to the readout gate portion. It can be easily formed by performing ion implantation.
本実施例において、フォトダイオードのｎ型領域３の
不純物濃度が２×1016cm-3であるとき、読み出しゲート
領域７のｐ型ウェル２の表面部分の不純物濃度を１×10
17cm-3程度になるようにすれば、転送電極下の絶縁膜
（SiO2膜）の膜厚を60nmとして電荷転送電極に12V以上
の読み出しパルスを印加することにより、フォトダイオ
ードのｎ型領域３内に蓄積された信号電荷を完全に電荷
転送部のｎ型領域９へ読み出すことができる。そして、
この場合にフォトダイオードのｎ型領域は絶縁膜と接し
ていないので、暗電流による固定パターンノイズが発生
することはなくなる。In this embodiment, when the impurity concentration of the n-type region 3 of the photodiode is 2 × 10 16 cm −3 , the impurity concentration of the surface portion of the p-type well 2 of the read gate region 7 is 1 × 10 16
If the thickness is set to about 17 cm -3, the thickness of the insulating film (SiO 2 film) under the transfer electrode is set to 60 nm, and a read pulse of 12 V or more is applied to the charge transfer electrode, so that the n-type region of the photodiode is formed. 3 can be completely read out to the n-type region 9 of the charge transfer section. And
In this case, since the n-type region of the photodiode is not in contact with the insulating film, fixed pattern noise due to dark current does not occur.
第２図は、本発明の他の実施例を示す要部断面図であ
る。本実施例の先の実施例と異なる点は、電荷転送電極
８の側面に絶縁膜のサイドウォール12が形成され、か
つ、フォトダイオードのｎ型領域３のp+型領域４と接す
る部分にｎ型領域３より不純物濃度の高い第２のｎ型領
域13が形成されている点である。本実施例によれば、フ
ォトダイオードの第２のｎ型領域13とフォトダイオード
のp+型領域４との接合容量が増加する分フォトダイオー
ドの第１のｎ型領域３の不純物濃度を減らせるため、読
み出しゲート領域７へ導入されるｐ型不純物の量をそれ
ほど上げなくとも、フォトダイオードのｎ型領域３が絶
縁膜と半導体表面の界面に接するのを防止することがで
きる。FIG. 2 is a sectional view of a main part showing another embodiment of the present invention. This embodiment is different from the previous embodiment in that a sidewall 12 of an insulating film is formed on the side surface of the charge transfer electrode 8 and an n-type region 3 of the photodiode is in contact with the p + -type region 4 at n-type. The point is that a second n-type region 13 having a higher impurity concentration than the type region 3 is formed. According to the present embodiment, the impurity concentration in the first n-type region 3 of the photodiode can be reduced by an increase in the junction capacitance between the second n-type region 13 of the photodiode and the p + -type region 4 of the photodiode. Therefore, the n-type region 3 of the photodiode can be prevented from contacting the interface between the insulating film and the semiconductor surface without increasing the amount of the p-type impurity introduced into the read gate region 7.
第２図に示した固体撮像素子は、以下のようにして作
成することができる。まず、従来例と同様に、ｎ型半導
体基板１の表面にｐ型ウェル２を形成し、ｐ型ウェル２
の表面の所定領域にフォトダイオードのｎ型領域３と電
荷転送部のｎ型領域９およびp+型領域であるチャネルス
トップ11を形成する。次に、フォトダイオードのｎ型領
域３の一部領域およびｎ型領域３と電荷転送部のｎ型領
域９との間にボロンを導入して読み出しゲート領域７を
形成する。このとき導入されるボロンのドーズ量は、ｎ
型領域３の導電型がｐ型に反転する程度に選択される。
次に、絶縁膜10の表面上に電荷転送電極８を形成し、こ
の電荷転送電極８をマスクとしてフォトダイオードのp+
型領域４をイオン注入法で形成する。次いで、電荷転送
電極８の膜厚程度の絶縁膜を設け、RIE等の異方性エッ
チングによりサイドウォール12を形成する。フォトダイ
オードの第２のｎ型領域13は、サイドウォール12をマス
ク材としてイオン注入法でフォトダイオードのp+型領域
12よりも深く注入することにより形成する。最後に、絶
縁膜で電極を覆い、所定の領域に遮光膜５を形成すれば
第２図に図示した固体撮像素子が形成される。The solid-state imaging device shown in FIG. 2 can be manufactured as follows. First, as in the conventional example, a p-type well 2 is formed on the surface of an n-type
The n-type region 3 of the photodiode, the n-type region 9 of the charge transfer portion, and the channel stop 11 which is the p + -type region are formed in a predetermined region on the surface of the substrate. Next, a read gate region 7 is formed by introducing boron into a part of the n-type region 3 of the photodiode and between the n-type region 3 and the n-type region 9 of the charge transfer section. The dose of boron introduced at this time is n
The conductivity type of the mold region 3 is selected so as to be inverted to the p-type.
Next, a charge transfer electrode 8 is formed on the surface of the insulating film 10, and the p +
The mold region 4 is formed by an ion implantation method. Next, an insulating film having a thickness of about the thickness of the charge transfer electrode 8 is provided, and a sidewall 12 is formed by anisotropic etching such as RIE. Second n-type region 13 of the photodiode, p + -type region of the photodiode by ion implantation to the side wall 12 as a mask material
It is formed by implanting deeper than 12. Finally, the electrodes are covered with an insulating film, and a light-shielding film 5 is formed in a predetermined region, whereby the solid-state imaging device shown in FIG. 2 is formed.
なお、以上の実施例では、読み出しゲート領域全体に
ｐ型不純物が導入されていたが、これを変更して、ｎ型
領域３のp+型領域４に覆われていない部分のみにｐ型不
純物を導入するようにしてもよい。In the above embodiment, the p-type impurity is introduced into the entire readout gate region. However, this is changed so that only the portion of the n-type region 3 which is not covered by the p + -type region 4 is p-type impurity. May be introduced.
［発明の効果］ 以上説明したように、本発明は、埋め込み型フォトダ
イオードのｎ型領域が電荷転送電極下の絶縁膜と半導体
表面との界面に接することがないようにしたものである
ので、本発明によれば、暗電流を低減せしめることがで
き、暗電流に起因する固定パターンノイズを抑制するこ
とできる。[Effects of the Invention] As described above, the present invention prevents the n-type region of the buried photodiode from contacting the interface between the insulating film below the charge transfer electrode and the semiconductor surface. According to the present invention, dark current can be reduced, and fixed pattern noise due to dark current can be suppressed.
第１図、第２図は、それぞれ本発明の実施例を示す断面
図、第３図（ａ）は、従来例の断面図、第３図（ｂ）
は、その電位分布図である。 １……ｎ型半導体基板、２……ｐ型ウェル、３……フォ
トダイオードのｎ型領域、４……フォトダイオードのp+
型領域、５……遮光膜、６……遮光膜の開口部、７、7a
……読み出しゲート領域、８……電荷転送電極、９……
電荷転送部のｎ型領域、10……絶縁膜、11……チャネル
ストップ、12……サイドウォール、13……フォトダイオ
ードの第２のｎ型領域。1 and 2 are sectional views showing an embodiment of the present invention. FIG. 3 (a) is a sectional view of a conventional example, and FIG. 3 (b).
Is a potential distribution diagram thereof. 1 ... n-type semiconductor substrate, 2 ... p-type well, 3 ... n-type region of photodiode, 4 ... p + of photodiode
Mold region, 5: light shielding film, 6: opening of light shielding film, 7, 7a
...... Readout gate region, 8 ... Charge transfer electrode, 9 ...
N-type region of the charge transfer section, 10... Insulating film, 11... Channel stop, 12... Sidewall, 13... Second photodiode n-type region.
Claims (2)
れた、光電変換を行い光電変換電荷を蓄積しておく第２
導電型の光電変換・電荷蓄積領域と、前記第１導電型半
導体層の表面領域内に形成された、前記光電変換・電荷
蓄積領域において発生した信号電荷の転送を受ける第２
導電型の電荷転送領域と、前記光電変換・電荷蓄積領域
の前記電荷転送領域と対向する一部領域を除く前記光電
変換・電荷蓄積領域の表面に形成された高不純物濃度の
第１導電型領域と、前記光電変換・電荷蓄積領域の前記
一部領域の表面上を覆い該一部領域の表面上から前記電
荷転送領域にかけて形成された第１導電型の読み出しゲ
ート領域と、絶縁膜を介して前記読み出しゲート領域上
および前記電荷転送領域上に形成された電荷転送電極
と、を具備する固体撮像素子であって、前記電荷転送電
極は前記光電変換・電荷蓄積領域の前記一部領域上をも
覆うように前記光電変換・電荷蓄積領域上にまで延在し
ていることを特徴とする固体撮像素子。A first conductive type semiconductor layer formed in a surface region of the first conductive type semiconductor layer for performing photoelectric conversion and storing photoelectrically converted charges;
A conductive type photoelectric conversion / charge storage region and a second region formed in the surface region of the first conductivity type semiconductor layer and receiving a signal charge generated in the photoelectric conversion / charge storage region.
A conductive type charge transfer region, and a high impurity concentration first conductivity type region formed on the surface of the photoelectric conversion / charge storage region excluding a part of the photoelectric conversion / charge storage region facing the charge transfer region. A first-conduction-type read gate region formed on the surface of the partial region of the photoelectric conversion / charge accumulation region and extending from the surface of the partial region to the charge transfer region; A charge transfer electrode formed on the readout gate region and the charge transfer region, wherein the charge transfer electrode also covers a part of the photoelectric conversion / charge storage region. A solid-state imaging device, which extends to cover the photoelectric conversion / charge accumulation region.
物濃度の第１導電型領域と接する部分の少なくとも一部
が光電変換・電荷蓄積領域の他の部分より不純物濃度が
高くなされ、かつ、該光電変換・電荷蓄積領域の他の部
分より不純物濃度が高くなされた領域は前記読み出しゲ
ート領域とは接していないことを特徴とする請求項１記
載の固体撮像素子。2. A photoelectric conversion / charge accumulation region, wherein at least a part of a portion of the photoelectric conversion / charge accumulation region which is in contact with the high impurity concentration first conductivity type region has an impurity concentration higher than other portions of the photoelectric conversion / charge accumulation region, and 2. The solid-state imaging device according to claim 1, wherein a region having an impurity concentration higher than that of another portion of the photoelectric conversion / charge accumulation region is not in contact with the readout gate region.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2058988A JP2982206B2 (en) | 1990-03-10 | 1990-03-10 | Solid-state imaging device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2058988A JP2982206B2 (en) | 1990-03-10 | 1990-03-10 | Solid-state imaging device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03261172A JPH03261172A (en) | 1991-11-21 |
| JP2982206B2 true JP2982206B2 (en) | 1999-11-22 |
Family
ID=13100228
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2058988A Expired - Lifetime JP2982206B2 (en) | 1990-03-10 | 1990-03-10 | Solid-state imaging device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2982206B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6690423B1 (en) | 1998-03-19 | 2004-02-10 | Kabushiki Kaisha Toshiba | Solid-state image pickup apparatus |
| JP2004349715A (en) * | 2004-06-21 | 2004-12-09 | Sony Corp | Image sensor |
| WO2011043432A1 (en) * | 2009-10-09 | 2011-04-14 | 国立大学法人静岡大学 | Semiconductor element and solid-state image pickup device |
| JP6668600B2 (en) | 2015-03-19 | 2020-03-18 | セイコーエプソン株式会社 | Solid-state imaging device and method of manufacturing the same |
| JP6609948B2 (en) | 2015-03-19 | 2019-11-27 | セイコーエプソン株式会社 | Solid-state imaging device and manufacturing method thereof |
| JP2016178145A (en) | 2015-03-19 | 2016-10-06 | セイコーエプソン株式会社 | Solid-state imaging element and manufacturing method thereof |
-
1990
- 1990-03-10 JP JP2058988A patent/JP2982206B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03261172A (en) | 1991-11-21 |
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