JPH08130299A - Ccd solid state image sensor and manufacture thereof - Google Patents
Ccd solid state image sensor and manufacture thereofInfo
- Publication number
- JPH08130299A JPH08130299A JP6267322A JP26732294A JPH08130299A JP H08130299 A JPH08130299 A JP H08130299A JP 6267322 A JP6267322 A JP 6267322A JP 26732294 A JP26732294 A JP 26732294A JP H08130299 A JPH08130299 A JP H08130299A
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- JP
- Japan
- Prior art keywords
- diffusion layer
- type
- concentration
- ccd solid
- impurity diffusion
- 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.)
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Links
Landscapes
- Solid State Image Pick-Up Elements (AREA)
- Transforming Light Signals Into Electric Signals (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、ＣＣＤ固体撮像装置お
よびその製造方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CCD solid-state image pickup device and a method for manufacturing the same.
【０００２】[0002]
【従来の技術】以下、従来のＣＣＤ固体撮像装置につい
て説明する。2. Description of the Related Art A conventional CCD solid-state image pickup device will be described below.
【０００３】図４は、従来のＣＣＤ固体撮像装置の断面
構造を示している。図４において、１１はｎ型半導体基
板、１２はｎ型半導体基板１１の表面部に形成された第
１のｐ型ウェル領域、１３はｎ型拡散層、１４はノイズ
低減用ｐ型拡散層、１５は第２のｐ型ウェル領域、１６
はｎ型ウェル領域、１７は分離用ｐ型拡散層、１８はゲ
ート酸化膜、１９はゲート電極、２０は遮光膜、２１は
アルミ遮光部、２２は保護膜であって、第１のｐ型ウェ
ル領域１２およびｎ型拡散層１３によって、光電変換を
行い信号電荷を生成するフォトダイオード部が構成さ
れ、第２のｐ型ウェル領域１５およびｎ型ウェル領域１
６によって、信号電荷を転送する電荷転送部が構成され
ている。FIG. 4 shows a sectional structure of a conventional CCD solid-state image pickup device. In FIG. 4, 11 is an n-type semiconductor substrate, 12 is a first p-type well region formed on the surface of the n-type semiconductor substrate 11, 13 is an n-type diffusion layer, 14 is a noise reducing p-type diffusion layer, 15 is a second p-type well region, 16
Is an n-type well region, 17 is a p-type diffusion layer for separation, 18 is a gate oxide film, 19 is a gate electrode, 20 is a light-shielding film, 21 is an aluminum light-shielding portion, and 22 is a protective film. The well region 12 and the n-type diffusion layer 13 constitute a photodiode section that performs photoelectric conversion to generate a signal charge, and the second p-type well region 15 and the n-type well region 1 are formed.
6 constitutes a charge transfer section for transferring the signal charge.
【０００４】以下、前記のように構成されたＣＣＤ固体
撮像装置の動作を説明する。ノイズ低減用ｐ型拡散層１
４の上方から光が入射すると、ノイズ低減用ｐ型拡散層
１４、ｎ型拡散層１３および第１のｐ型ウェル領域１２
において光電変換がおこなわれ、電子・ホール対が発生
する。発生した電子は、前記フォトダイオード部のｎ型
拡散層１３に集まり、信号電荷として蓄積される。次
に、ゲート電極１９にパルス信号が印加されると、信号
電荷は、前記電荷転送部のｎ型ウェル領域１６に読み出
された後、外部取り出し段まで転送され、外部に取り出
される。これにより、各ＣＣＤ固体撮像素子に入射した
光の強度を判定することができる。The operation of the CCD solid-state image pickup device constructed as described above will be described below. Noise reduction p-type diffusion layer 1
When light enters from above 4, the noise reduction p-type diffusion layer 14, the n-type diffusion layer 13, and the first p-type well region 12 are formed.
At, photoelectric conversion is performed, and electron-hole pairs are generated. The generated electrons gather in the n-type diffusion layer 13 of the photodiode section and are accumulated as signal charges. Next, when a pulse signal is applied to the gate electrode 19, the signal charges are read out to the n-type well region 16 of the charge transfer section, transferred to the external extraction stage, and taken out to the outside. This makes it possible to determine the intensity of light incident on each CCD solid-state image sensor.
【０００５】ここで、ノイズ低減用ｐ型拡散層１４は、
ＣＣＤ固体撮像装置製造の際に基板表面付近に形成され
た欠陥によるノイズを低減するためのものであり、ｎ型
拡散層１３の上にｐ型拡散層を形成することによって、
ｎ型拡散層１３の上部が空乏化することを防いでいる。
ノイズ低減用ｐ型拡散層１４は、ゲート電極１９をマス
クとしてイオン注入を行うことにより形成される。Here, the noise reducing p-type diffusion layer 14 is
This is for reducing noise due to defects formed in the vicinity of the surface of the substrate when the CCD solid-state imaging device is manufactured. By forming the p-type diffusion layer on the n-type diffusion layer 13,
The upper part of the n-type diffusion layer 13 is prevented from being depleted.
The noise reducing p-type diffusion layer 14 is formed by performing ion implantation using the gate electrode 19 as a mask.
【０００６】ノイズ低減用ｐ型拡散層１４の形成におい
ては、不純物濃度をあまり高くしないよう留意すべきで
ある。なぜならば、ノイズ低減用ｐ型拡散層１４の不純
物濃度が高いとホール濃度も高くなり、このため、光電
変換により発生した電子とホールとが再結合する確率が
増大するので、信号電荷の消滅が起こりやすくなるから
である。これによって、ＣＣＤ固体撮像装置の光感度が
低下する。In forming the noise reducing p-type diffusion layer 14, care should be taken not to make the impurity concentration too high. This is because when the impurity concentration of the noise reducing p-type diffusion layer 14 is high, the hole concentration is also high, and thus the probability that electrons and holes generated by photoelectric conversion are recombined is increased, so that the signal charge disappears. Because it is easy to happen. This reduces the photosensitivity of the CCD solid-state image pickup device.
【０００７】特に短波長領域においては、吸収係数が大
きいので、ほとんどすべての光子が、ｎ型拡散層１３に
達することなくノイズ低減用ｐ型拡散層１４内において
光電変換される。したがって、ノイズ低減用ｐ型拡散層
１４の不純物濃度が高いと、大部分の信号電荷が消滅し
てしまうことになり、短波長領域における光感度が著し
く低下する。Particularly in the short wavelength region, since the absorption coefficient is large, almost all photons are photoelectrically converted in the noise reducing p-type diffusion layer 14 without reaching the n-type diffusion layer 13. Therefore, if the impurity concentration of the noise reducing p-type diffusion layer 14 is high, most of the signal charge will be lost, and the photosensitivity in the short wavelength region will be significantly reduced.
【０００８】従来の技術においては、ドーズ量６×１０
13／ｃｍ2 程度、注入エネルギー５０ｋｅＶ程度の条件
でボロンを注入することにより、低濃度でかつ深い構造
を有するノイズ低減用ｐ型拡散層１４を形成するという
方法がとられている。In the prior art, a dose amount of 6 × 10
A method of forming a noise reducing p-type diffusion layer 14 having a low concentration and a deep structure by implanting boron under the conditions of about 13 / cm 2 and an implantation energy of about 50 keV is adopted.
【０００９】[0009]
【発明が解決しようとする課題】しかしながら、前記従
来技術には以下のような問題がある。However, the above-mentioned prior art has the following problems.
【００１０】図５は、ノイズ低減用ｐ型拡散層１４の受
光面近傍における内部特性を示しており、図４のＣ−Ｄ
線における状態を示している。図５からわかるように、
不純物濃度はノイズ低減用ｐ型拡散層１４中央部におい
て最も高く一定となり、両端に近づくにしたがい徐々に
低くなる分布を示す。したがって、受光時の電位はノイ
ズ低減用ｐ型拡散層１４中央部で最も低く一定となり、
電荷転送部のｎ型ウェル領域１６へ近づくにつれて徐々
に高くなる。FIG. 5 shows the internal characteristics in the vicinity of the light-receiving surface of the noise reducing p-type diffusion layer 14, and is shown in FIG.
The state in the line is shown. As you can see from Figure 5,
The impurity concentration is highest and constant in the central portion of the noise reducing p-type diffusion layer 14, and shows a distribution that gradually decreases toward both ends. Therefore, the electric potential at the time of receiving light becomes the lowest and constant in the central portion of the noise reducing p-type diffusion layer 14,
It gradually increases as it approaches the n-type well region 16 of the charge transfer portion.
【００１１】また図６は、ノイズ低減用ｐ型拡散層１４
における基板深さ方向の内部特性を示しており、図４の
Ｅ−Ｆ線における状態を示している。図６からわかるよ
うに、不純物濃度は基板表面付近で最も高く基板内部へ
向かうにつれて徐々に低くなる。したがって、受光時の
電位は基板表面付近で最も低く、フォトダイオード部の
ｎ型拡散層１３に近づくにつれて徐々に高くなる。Further, FIG. 6 shows a p-type diffusion layer 14 for noise reduction.
4 shows the internal characteristics of the substrate in the depth direction, and shows the state along the line EF in FIG. As can be seen from FIG. 6, the impurity concentration is highest near the surface of the substrate and gradually decreases toward the inside of the substrate. Therefore, the potential at the time of receiving light is the lowest near the surface of the substrate and gradually increases as it approaches the n-type diffusion layer 13 of the photodiode section.
【００１２】この電位分布により、受光面近傍において
光電変換により発生した電子は、図７に示すように、拡
散とドリフトによりフォトダイオード部のｎ型拡散層１
３へ向かい信号電荷となると同時に、拡散により受光面
近傍を水平方向に移動し、電位の勾配に沿って電荷転送
部のｎ型ウェル領域１６まで到達し、スミア成分とな
る。Due to this potential distribution, the electrons generated by photoelectric conversion in the vicinity of the light receiving surface are diffused and drifted, as shown in FIG.
At the same time as 3 toward the signal charge, it becomes a signal charge, and at the same time, it moves in the horizontal direction near the light receiving surface by diffusion, reaches the n-type well region 16 of the charge transfer portion along the gradient of the potential, and becomes a smear component.
【００１３】このスミア成分を減らすためには、ノイズ
低減用ｐ型拡散層１４の不純物濃度を上げて、拡散によ
り受光面近傍を水平方向に移動する電子がホールとの再
結合により消滅する確率を上げればよい。しかし、ノイ
ズ低減用ｐ型拡散層１４の不純物濃度を上げると、フォ
トダイオード部のｎ型拡散層１３ヘ向かう信号電荷がホ
ールとの再結合により消滅する確率も増大してしまい、
ＣＣＤ固体撮像装置の光感度が低下する。特に短波長領
域において、ほとんどすべての光子がｎ型拡散層１３ま
で達することなくノイズ低減用ｐ型拡散層１４内におい
て光電変換されるので、光感度が著しく低下する。In order to reduce the smear component, the impurity concentration of the noise reducing p-type diffusion layer 14 is increased so that electrons moving horizontally in the vicinity of the light receiving surface due to diffusion will disappear by recombination with holes. You can raise it. However, if the impurity concentration of the noise reducing p-type diffusion layer 14 is increased, the probability that the signal charge toward the n-type diffusion layer 13 of the photodiode portion will disappear due to recombination with holes also increases,
The photosensitivity of the CCD solid-state imaging device is reduced. Particularly in the short wavelength region, almost all photons are photoelectrically converted in the noise reducing p-type diffusion layer 14 without reaching the n-type diffusion layer 13, so that the photosensitivity is remarkably lowered.
【００１４】以上説明したように、従来の技術では、ス
ミアを低減するためにノイズ低減用ｐ型拡散層１４の不
純物濃度を上げると、光感度も低下してしまうという問
題がある。As described above, the conventional technique has a problem that if the impurity concentration of the noise reducing p-type diffusion layer 14 is increased to reduce smear, the photosensitivity is also lowered.
【００１５】本発明は、前記従来技術の問題を解決する
もので、光感度を低下させることなくスミアの低減を実
現できるＣＣＤ固体撮像装置およびその製造方法を提供
することを目的とする。The present invention solves the above-mentioned problems of the prior art, and an object of the present invention is to provide a CCD solid-state image pickup device capable of reducing smear without lowering photosensitivity and a manufacturing method thereof.
【００１６】[0016]
【課題を解決するための手段】前記の目的を達成するた
め、請求項１の発明が講じた手段は、半導体基板上に、
ｎ型不純物拡散層を有し光電変換により信号電荷を生成
するフォトダイオード部と信号電荷を転送する電荷転送
部とが交互に形成され、前記フォトダイオード部のｎ型
不純物拡散層の上にノイズを低減するためのノイズ低減
用ｐ型不純物拡散層が形成されたＣＣＤ固体撮像装置を
前提とし、前記ノイズ低減用ｐ型不純物拡散層は、前記
電荷転送部側の両側部にそれぞれ形成された不純物濃度
が相対的に高い高濃度領域と、前記高濃度領域同士の間
の中央部に形成された不純物濃度が相対的に低い低濃度
領域とからなる構成とするものである。[Means for Solving the Problems] In order to achieve the above-mentioned object, the means taken by the invention of claim 1 is to provide a semiconductor substrate on a semiconductor substrate.
Photodiode sections having n-type impurity diffusion layers and generating signal charges by photoelectric conversion and charge transfer sections for transferring signal charges are alternately formed, and noise is generated on the n-type impurity diffusion layers of the photodiode sections. Assuming a CCD solid-state imaging device in which a noise-reducing p-type impurity diffusion layer is formed, the noise-reducing p-type impurity diffusion layer is formed on both sides of the charge transfer portion. Is a relatively high concentration region, and a low concentration region having a relatively low impurity concentration formed in the central portion between the high concentration regions.
【００１７】請求項２の発明は、請求項１の発明に係る
固体撮像装置の製造方法であって、半導体基板上に、ｎ
型不純物拡散層を有し光電変換により信号電荷を生成す
るフォトダイオード部と信号電荷を転送する電荷転送部
とが交互に形成され、前記フォトダイオード部のｎ型不
純物拡散層の上にノイズを低減するためのノイズ低減用
ｐ型不純物拡散層が形成されたＣＣＤ固体撮像装置の製
造方法を対象とし、前記フォトダイオード部のｎ型不純
物拡散層にドーズ量が相対的に低い第１のイオン注入を
行うことにより不純物濃度が相対的に低いｐ型低濃度領
域を形成した後、前記ｐ型低濃度領域における前記電荷
転送部側の両側部にドーズ量が相対的に高い第２のイオ
ン注入を行うことにより不純物濃度が相対的に高いｐ型
高濃度領域を形成することにより、前記ｐ型低濃度領域
と前記ｐ型高濃度領域とからなるノイズ低減用ｐ型不純
物拡散層を形成する工程を備えている構成とするもので
ある。According to a second aspect of the present invention, there is provided a method of manufacturing a solid-state image pickup device according to the first aspect of the invention, wherein n is formed on the semiconductor substrate.
Photodiode portions having a type impurity diffusion layer and generating signal charges by photoelectric conversion and charge transfer portions transferring signal charges are alternately formed, and noise is reduced on the n-type impurity diffusion layer of the photodiode portion. A method for manufacturing a CCD solid-state image pickup device having a p-type impurity diffusion layer for noise reduction is provided for the first ion implantation with a relatively low dose amount in the n-type impurity diffusion layer of the photodiode section. After the p-type low concentration region having a relatively low impurity concentration is formed by performing the second ion implantation, second ion implantation having a relatively high dose amount is performed on both sides of the p-type low concentration region on the charge transfer portion side. As a result, a p-type high-concentration region having a relatively high impurity concentration is formed, thereby forming a noise-reduction p-type impurity diffusion layer including the p-type low-concentration region and the p-type high-concentration region. It is an arrangement which comprises a step.
【００１８】請求項３の発明は、請求項２の発明の構成
に、前記第１のイオン注入は、ドーズ量が３×１０13／
ｃｍ2 〜３×１０14／ｃｍ2 、注入エネルギーが３０ｋ
ｅＶ〜８０ｋｅＶの条件でボロンを用いて行い、前記第
２のイオン注入は、ドーズ量が５×１０13／ｃｍ2 〜４
×１０14／ｃｍ2 、注入エネルギーが３０ｋｅＶ〜６０
ｋｅＶの条件でボロンを用いて行う構成を付加するもの
である。A third aspect of the present invention is the structure of the second aspect, wherein the first ion implantation has a dose amount of 3 × 10 13 /
cm 2 to 3 × 10 14 / cm 2 , implantation energy is 30 k
The second ion implantation is performed at a dose of 5 × 10 13 / cm 2 to 4 by using boron under the condition of eV to 80 keV.
× 10 14 / cm 2 , implantation energy is 30 keV-60
A configuration in which boron is used under the condition of keV is added.
【００１９】[0019]
【作用】請求項１の構成により、ノイズ低減用ｐ型拡散
層は、中央部に位置する不純物濃度が相対的に低い低濃
度領域と両側端部に位置する不純物濃度が相対的に高い
高濃度領域とから構成されるので、ノイズ低減用ｐ型拡
散層内の受光面近傍における基板面方向の不純物濃度
は、中央部で低く両側端部で高くなる。したがって、受
光時の電位は、中央部で高く両側端部で低い分布を持
つ。According to the structure of claim 1, in the p type diffusion layer for noise reduction, a low concentration region having a relatively low impurity concentration located at the center and a high concentration having a relatively high impurity concentration located at both end portions. The impurity concentration in the substrate surface direction in the vicinity of the light receiving surface in the p-type diffusion layer for noise reduction is low in the central portion and high in both end portions. Therefore, the electric potential at the time of receiving light has a distribution that is high at the central portion and low at both end portions.
【００２０】このため、受光面付近で光電変換により発
生した電子は、拡散により水平方向へ移動しても、ノイ
ズ低減用ｐ型拡散層の両側端部における電位の勾配によ
って、電荷転送部のｎ型ウェル領域への到達は抑止され
る。また、高濃度領域において、ホールとの再結合によ
り電子が消滅する確率が上がる。このことにより、スミ
アの増大が抑制される。Therefore, even if the electrons generated by photoelectric conversion near the light receiving surface move in the horizontal direction by diffusion, due to the potential gradient at both end portions of the noise reducing p-type diffusion layer, the n of the charge transfer portion is affected. Reaching the mold well region is suppressed. Further, in the high concentration region, the probability that electrons will disappear due to recombination with holes increases. This suppresses the increase in smear.
【００２１】請求項２の構成により、フォトダイオード
部のｎ型不純物拡散層にドーズ量が相対的に低い第１の
イオン注入を行うことにより不純物濃度が相対的に低い
低濃度領域を形成した後、前記低濃度領域における前記
電荷転送部側の両側部にドーズ量が相対的に高い第２の
イオン注入を行うことにより不純物濃度が相対的に高い
高濃度領域を形成するので、中央部に位置する不純物濃
度が相対的に低い低濃度領域と両側端部に位置する不純
物濃度が相対的に高い高濃度領域とからなるノイズ低減
用ｐ型不純物拡散層が形成される。According to the structure of claim 2, after forming the low concentration region having a relatively low impurity concentration by performing the first ion implantation having a relatively low dose amount in the n-type impurity diffusion layer of the photodiode portion. Since the high concentration region having a relatively high impurity concentration is formed by performing the second ion implantation having a relatively high dose amount on both sides of the low concentration region on the side of the charge transfer portion, the high concentration region having a relatively high impurity concentration is formed. The p-type impurity diffusion layer for noise reduction is formed of the low-concentration region having a relatively low impurity concentration and the high-concentration regions having a relatively high impurity concentration located at both ends.
【００２２】請求項３の構成により、ドーズ量が３×１
０13／ｃｍ2 〜３×１０14／ｃｍ2、注入エネルギーが
３０ｋｅＶ〜８０ｋｅＶの条件でボロンを用いて第１の
イオン注入を行い、ドーズ量が５×１０13／ｃｍ2 〜４
×１０14／ｃｍ2 、注入エネルギーが３０ｋｅＶ〜６０
ｋｅＶの条件でボロンを用いて第２のイオン注入を行う
ので、中央部に位置する不純物濃度が相対的に低い低濃
度領域と両側端部に位置する不純物濃度が相対的に高い
高濃度領域とからなるノイズ低減用ｐ型不純物拡散層が
確実に形成される。According to the structure of claim 3, the dose amount is 3 × 1.
The first ion implantation is performed using boron under the conditions of 0 13 / cm 2 to 3 × 10 14 / cm 2 and implantation energy of 30 keV to 80 keV, and the dose amount is 5 × 10 13 / cm 2 to 4
× 10 14 / cm 2 , implantation energy is 30 keV-60
Since the second ion implantation is performed using boron under the condition of keV, a low-concentration region having a relatively low impurity concentration located in the central portion and a high-concentration region having a relatively high impurity concentration located at both end portions are formed. The p-type impurity diffusion layer for noise reduction consisting of is surely formed.
【００２３】[0023]
【実施例】以下、本発明の一実施例について、図面を参
照しながら説明する。An embodiment of the present invention will be described below with reference to the drawings.
【００２４】図１は、本発明の一実施例に係るＣＣＤ固
体撮像装置の断面構造を示している。図１において、１
１はｎ型半導体基板、１２はｎ型半導体基板１１の表面
部に形成された第１のｐ型ウェル領域、１３はｎ型拡散
層、１４はノイズ低減用ｐ型拡散層、１５は第２のｐ型
ウェル領域、１６はｎ型ウェル領域、１７は分離用ｐ型
拡散層、１８はゲート酸化膜、１９はゲート電極、２０
は遮光膜、２１はアルミ遮光部、２２は保護膜であっ
て、第１のｐ型ウェル領域１２およびｎ型拡散層１３に
よって、光電変換を行い信号電荷を生成するフォトダイ
オード部が構成され、第２のｐ型ウェル領域１５および
ｎ型ウェル領域１６によって、信号電荷を転送する電荷
転送部が構成されている。FIG. 1 shows a sectional structure of a CCD solid-state image pickup device according to an embodiment of the present invention. In FIG. 1, 1
1 is an n-type semiconductor substrate, 12 is a first p-type well region formed on the surface of the n-type semiconductor substrate 11, 13 is an n-type diffusion layer, 14 is a noise reducing p-type diffusion layer, and 15 is a second P-type well region, 16 n-type well region, 17 p-type diffusion layer for isolation, 18 gate oxide film, 19 gate electrode, 20
Is a light-shielding film, 21 is an aluminum light-shielding portion, and 22 is a protective film. The first p-type well region 12 and the n-type diffusion layer 13 constitute a photodiode portion for performing photoelectric conversion to generate a signal charge, The second p-type well region 15 and the n-type well region 16 form a charge transfer unit that transfers signal charges.
【００２５】ノイズ低減用ｐ型拡散層１４は、ＣＣＤ固
体撮像装置の製造時に基板表面付近に形成される欠陥に
よるノイズを低減するためのものであって、本実施例の
特徴として、中央部に位置する不純物濃度が相対的に低
い低濃度領域１４ａと両側端部に位置する不純物濃度が
相対的に高い高濃度領域１４ｂとからなる。The noise reducing p-type diffusion layer 14 is for reducing noise due to defects formed near the surface of the substrate during manufacturing of the CCD solid-state image pickup device, and is characteristic of the present embodiment. The low-concentration region 14a having a relatively low impurity concentration and the high-concentration region 14b having a relatively high impurity concentration located at both ends are located.
【００２６】図２は、図１のＡ−Ｂ線における、不純物
濃度および受光時の電位の分布を示している。本実施例
において、ノイズ低減用ｐ型拡散層１４の受光面近傍に
おける基板面方向の不純物濃度は、図２に示すように、
中央部で低く一定となり両側端部で高くなる。したがっ
て、受光時の電位は、中央部で高く両側端部で低い分布
を持つ。また、ノイズ低減用ｐ型拡散層１４の中央部に
おける基板深さ方向の不純物濃度および受光時の電位の
分布は、図６に示している従来技術のものと同様であ
る。FIG. 2 shows the distribution of the impurity concentration and the potential at the time of receiving light, along the line AB in FIG. In this embodiment, the impurity concentration in the substrate surface direction in the vicinity of the light receiving surface of the noise reducing p-type diffusion layer 14 is as shown in FIG.
It becomes low and constant at the center, and becomes high at both ends. Therefore, the electric potential at the time of receiving light has a distribution that is high at the central portion and low at both end portions. Further, the impurity concentration in the substrate depth direction and the potential distribution at the time of receiving light in the central portion of the noise reducing p-type diffusion layer 14 are the same as those of the conventional technique shown in FIG.
【００２７】このとき、受光面近傍で光電変換により発
生した電子は、拡散により水平方向に移動しても、ノイ
ズ低減用ｐ型拡散層１４の両側端部に位置する高濃度領
域１４ｂによってできた電位の勾配により、電荷転送部
のｎ型ウェル領域１６への到達は抑止される。また、高
濃度領域１４ｂにおいてはホール濃度も高いので、電子
がホールとの再結合により消滅する確率が上がることに
なり、スミア成分となる電子を低減することができる。At this time, the electrons generated by photoelectric conversion in the vicinity of the light-receiving surface are formed by the high-concentration regions 14b located at both ends of the noise-reducing p-type diffusion layer 14 even if the electrons move horizontally due to diffusion. Due to the potential gradient, the charge transfer portion is prevented from reaching the n-type well region 16. In addition, since the hole concentration is high in the high concentration region 14b, the probability that electrons will disappear due to recombination with holes is increased, and the electrons that become smear components can be reduced.
【００２８】また、ノイズ低減用ｐ型拡散層１４の中央
部においては、従来と同様に不純物濃度は低くホール濃
度も低いので、受光面近傍で発生した電子がフォトダイ
オード部ｎ型拡散層１３へ向かう過程でホールと再結合
し消滅する確率は低く、光感度は低下しない。ノイズ低
減用ｐ拡散層１４内でほとんどの光子が光電変換される
短波長領域においても、光感度は低下することはない。In the central portion of the noise reducing p-type diffusion layer 14, the impurity concentration is low and the hole concentration is low as in the conventional case, so that electrons generated in the vicinity of the light receiving surface enter the photodiode portion n-type diffusion layer 13. The probability of recombination and disappearance with holes in the process of traveling is low, and the photosensitivity does not decrease. Even in the short wavelength region where most photons are photoelectrically converted in the noise reducing p diffusion layer 14, the photosensitivity does not decrease.
【００２９】このように、中央部で不純物濃度が低く両
側端部で不純物濃度が高い構造を有するノイズ低減用ｐ
型拡散層１４を形成することにより、高い光感度と低ス
ミアを同時に可能とするＣＣＤ固体撮像装置を実現でき
る。As described above, the noise reducing p having the structure in which the impurity concentration is low in the central portion and the impurity concentration is high in the both end portions.
By forming the mold diffusion layer 14, it is possible to realize a CCD solid-state imaging device capable of simultaneously achieving high photosensitivity and low smear.
【００３０】以下、前記構造のＣＣＤ固体撮像装置の製
造方法におけるノイズ低減用ｐ型拡散層１４の形成工程
について説明する。The steps of forming the noise reducing p-type diffusion layer 14 in the method of manufacturing the CCD solid-state image pickup device having the above structure will be described below.
【００３１】図３（ａ）は、ノイズ低減用ｐ型拡散層１
４を形成するためボロン注入を行う直前のＣＣＤ固体撮
像装置の断面構造を示している。ｎ型半導体基板１１の
上に、第１のｐ型ウェル領域１２、ｎ型拡散層１３、第
２のｐ型ウェル領域１５、ｎ型ウェル領域１６、分離用
ｐ型拡散層１７、ゲート酸化膜１８およびゲート電極１
９が、すでに形成されている。FIG. 3A shows a p-type diffusion layer 1 for noise reduction.
4 shows a cross-sectional structure of the CCD solid-state imaging device immediately before performing boron implantation to form No. 4. On the n-type semiconductor substrate 11, the first p-type well region 12, the n-type diffusion layer 13, the second p-type well region 15, the n-type well region 16, the isolation p-type diffusion layer 17, and the gate oxide film. 18 and gate electrode 1
9 has already been formed.
【００３２】ノイズ低減用ｐ型拡散層１４の形成工程と
しては、まず、ゲート電極１９をマスクとして、注入エ
ネルギー：３０ｋｅＶ〜８０ｋｅＶ、ドーズ量：３×１
０13／ｃｍ2 〜３×１０14／ｃｍ2 の条件により、ボロ
ンを用いた第１のイオン注入を行う。図３（ｂ）は、第
１のイオン注入直後のＣＣＤ固体撮像装置の断面構造を
示している。ノイズ低減用ｐ型拡散層１４中央部に位置
する低濃度領域１４ａが形成される。In the step of forming the p-type diffusion layer 14 for noise reduction, first, with the gate electrode 19 as a mask, the implantation energy is 30 keV to 80 keV and the dose is 3 × 1.
The first ion implantation using boron is performed under the condition of 0 13 / cm 2 to 3 × 10 14 / cm 2 . FIG. 3B shows a sectional structure of the CCD solid-state imaging device immediately after the first ion implantation. A low concentration region 14a located in the central portion of the noise reducing p-type diffusion layer 14 is formed.
【００３３】次に、注入エネルギー：３０ｋｅＶ〜６０
ｋｅＶ、ドーズ量：５×１０13／ｃｍ2 〜４×１０14／
ｃｍ2 の条件による、ボロンを用いた第２のイオン注入
を、前記低濃度領域１４ａの両端の位置に、半導体製造
マスクを用いてプロセス最小寸法程度の幅を持たせて行
う。図３（ｃ）は、第２のイオン注入直後のＣＣＤ固体
撮像装置の断面構造を示している。ノイズ低減用ｐ型拡
散層１４両側端部に位置する高濃度領域１４ｂが形成さ
れる。Next, implantation energy: 30 keV-60
keV, dose: 5 × 10 13 / cm 2 to 4 × 10 14 /
The second ion implantation using boron under the condition of cm 2 is performed at the positions of both ends of the low concentration region 14a with a width of about the minimum process dimension using a semiconductor manufacturing mask. FIG. 3C shows a sectional structure of the CCD solid-state imaging device immediately after the second ion implantation. High-concentration regions 14b located at both ends of the noise reducing p-type diffusion layer 14 are formed.
【００３４】なお、第２のイオン注入の注入エネルギー
の条件範囲は、ゲート酸化膜１８の膜厚が３０ｎｍ〜１
００ｎｍの範囲内において、高濃度領域１４ｂにおける
基板深さ方向の不純物濃度分布のピーク位置が基板表面
より０．１μｍ程度以内におさまるように、ドーズ量の
条件範囲は、スミア成分が従来技術の１／３以下になり
且つ高濃度領域１４ｂの横方向への広がりが電荷転送部
ｎ型ウェル領域１６に影響をおよぼさないように、シミ
ュレーションおよび実験により最適化したものである。The condition range of the implantation energy of the second ion implantation is that the thickness of the gate oxide film 18 is 30 nm to 1
In the range of 00 nm, the smear component is 1 of the conventional technique so that the peak position of the impurity concentration distribution in the substrate depth direction in the high-concentration region 14b is within about 0.1 μm from the substrate surface. It is optimized by a simulation and an experiment so that it becomes equal to or less than / 3 and the lateral expansion of the high concentration region 14b does not affect the charge transfer portion n-type well region 16.
【００３５】この後、９００℃〜１１００℃の熱処理を
行い、ノイズ低減用ｐ型拡散層１４を形成した後、遮光
膜２０、アルミ遮光部２１および保護膜２２を形成し、
本発明の一実施例に係るＣＣＤ固体撮像装置を完成す
る。図３（ｄ）は、完成したＣＣＤ固体撮像装置の断面
構造を示している。After that, heat treatment at 900 ° C. to 1100 ° C. is performed to form the p type diffusion layer 14 for noise reduction, and then the light shielding film 20, the aluminum light shielding portion 21 and the protective film 22 are formed.
A CCD solid-state imaging device according to an embodiment of the present invention is completed. FIG. 3D shows a sectional structure of the completed CCD solid-state imaging device.
【００３６】[0036]
【発明の効果】請求項１の発明に係るＣＣＤ固体撮像装
置によると、装置製造時にできる欠陥によるノイズを低
減するためのノイズ低減用ｐ型拡散層を、中央部に位置
する不純物濃度が相対的に低い低濃度領域と両側端部に
位置する不純物濃度が相対的に高い高濃度領域とから構
成したため、受光面近傍における基板横方向の不純物濃
度は中央部で低く両側端部で高くなり、受光時の電位分
布は中央部で高く両側端部で低くなるので、拡散によっ
て水平方向へ移動する電子は、電位の勾配のために電荷
転送部のｎ型ウェル領域へ達しにくくなる。また、両側
端部に位置する高濃度領域において、ホールとの再結合
により消滅する確率が増す。したがって、スミア成分と
なる確率は小さくなる。According to the CCD solid-state image pickup device of the first aspect of the present invention, the p-type diffusion layer for noise reduction for reducing noise due to defects formed during device fabrication has a relative impurity concentration at the central portion. Since it is composed of a low-concentration low region and a high-concentration region with relatively high impurity concentration located at both ends, the impurity concentration in the lateral direction of the substrate near the light-receiving surface is low at the center and high at both ends. Since the potential distribution at this time is high at the central portion and low at both end portions, electrons moving in the horizontal direction due to diffusion are less likely to reach the n-type well region of the charge transfer portion due to the potential gradient. In addition, in the high-concentration regions located at both ends, the probability of disappearance due to recombination with holes increases. Therefore, the probability of becoming a smear component becomes small.
【００３７】このため、ノイズ低減用ｐ型拡散層の不純
物濃度を上げることなく、スミアの発生を抑制すること
ができる。つまり、本発明のＣＣＤ固体撮像装置による
と、光感度を従来技術の水準に維持しつつ、スミアを低
減することができる。短波長領域においても、高光感度
を保証すると同時に、スミアを低減することが可能とな
る。Therefore, it is possible to suppress the occurrence of smear without increasing the impurity concentration of the noise reducing p-type diffusion layer. That is, according to the CCD solid-state imaging device of the present invention, smear can be reduced while maintaining the photosensitivity at the level of the conventional technique. Even in the short wavelength region, it is possible to ensure high photosensitivity and simultaneously reduce smear.
【００３８】実際には、従来技術の光感度を維持しつ
つ、スミアレベルを１／３以下に低減することができ
た。In practice, the smear level could be reduced to 1/3 or less while maintaining the photosensitivity of the prior art.
【００３９】請求項２の発明に係るＣＣＤ固体撮像装置
の製造方法によると、ドーズ量が相対的に低い第１のイ
オン注入を行い不純物濃度が相対的に低い低濃度領域を
形成し、次に、前記低濃度領域における電荷転送部側の
両側部に、ドーズ量が相対的に高い第２のイオン注入を
行い不純物濃度が相対的に高い高濃度領域を形成するこ
とにより、中央部に位置する不純物濃度が相対的に低い
低濃度領域と両側端部に位置する不純物濃度が相対的に
高い高濃度領域とからなるノイズ低減用ｐ型不純物拡散
層を形成するので、請求項１の発明に係るＣＣＤ固体撮
像装置を簡易かつ確実に製造することができる。According to the method of manufacturing the CCD solid-state image pickup device of the second aspect of the present invention, the first ion implantation having a relatively low dose amount is performed to form a low concentration region having a relatively low impurity concentration, and , The high concentration region having a relatively high impurity concentration is formed by performing the second ion implantation having a relatively high dose amount on both sides of the low concentration region on the charge transfer portion side, and thus is located in the central portion. According to the invention of claim 1, since the p-type impurity diffusion layer for noise reduction is formed of the low-concentration region where the impurity concentration is relatively low and the high-concentration regions where the impurity concentration is relatively high, which are located at both ends. The CCD solid-state imaging device can be manufactured easily and reliably.
【００４０】請求項３の発明に係るＣＣＤ固体撮像装置
の製造方法によると、ドーズ量：３×１０13／ｃｍ2 〜
３×１０14／ｃｍ2 、注入エネルギー：３０ｋｅＶ〜８
０ｋｅＶの条件でボロンを用いて第１のイオン注入を行
い、ドーズ量：５×１０13／ｃｍ2 〜４×１０14／ｃｍ
2 、注入エネルギー：３０ｋｅＶ〜６０ｋｅＶの条件で
ボロンを用いて第２のイオン注入を行うことにより、中
央部に位置する不純物濃度が相対的に低い低濃度領域と
両側端部に位置する不純物濃度が相対的に高い高濃度領
域とからなるノイズ低減用ｐ型不純物拡散層を確実に形
成するので、請求項１の発明に係るＣＣＤ固体撮像装置
を簡易かつより確実に製造することができる。According to the method of manufacturing the CCD solid-state image pickup device of the third aspect of the present invention, the dose amount is from 3 × 10 13 / cm 2 to
3 × 10 14 / cm 2 , implantation energy: 30 keV to 8
The first ion implantation is performed using boron under the condition of 0 keV, and the dose amount is 5 × 10 13 / cm 2 to 4 × 10 14 / cm.
2. Implantation energy: By performing the second ion implantation using boron under the condition of 30 keV to 60 keV, the low concentration region where the impurity concentration is relatively low in the central portion and the impurity concentration in both end portions are Since the p-type impurity diffusion layer for noise reduction, which is composed of a relatively high concentration region, is reliably formed, the CCD solid-state imaging device according to the invention of claim 1 can be manufactured simply and more reliably.
【図１】本発明の一実施例に係るＣＣＤ固体撮像装置の
断面図である。FIG. 1 is a sectional view of a CCD solid-state imaging device according to an embodiment of the present invention.
【図２】前記一実施例に係るＣＣＤ固体撮像装置におけ
る、ノイズ低減用ｐ型拡散層の基板表面部における横方
向の不純物濃度および受光時の電位の分布を示す図であ
って、図１のＡ−Ｂ線における状態を示している。2 is a diagram showing a lateral impurity concentration and a potential distribution at the time of receiving light in the substrate surface portion of the p type diffusion layer for noise reduction in the CCD solid-state imaging device according to the one embodiment, FIG. The state at the line AB is shown.
【図３】（ａ）〜（ｄ）は、本発明の一実施例に係るＣ
ＣＤ固体撮像装置の製造方法の各工程を示す断面図であ
る。3 (a) to (d) are C according to an embodiment of the present invention.
FIG. 8 is a cross-sectional view showing each step of the manufacturing method of the CD solid-state imaging device.
【図４】従来のＣＣＤ固体撮像装置の断面図である。FIG. 4 is a sectional view of a conventional CCD solid-state imaging device.
【図５】前記従来のＣＣＤ固体撮像装置における、ノイ
ズ低減用ｐ型拡散層の基板表面部における横方向の不純
物濃度および受光時の電位の分布を示す図であって、図
４のＣ−Ｄ線における状態を示している。5 is a diagram showing a lateral impurity concentration in a substrate surface portion of a p-type diffusion layer for noise reduction and a potential distribution at the time of receiving light in the conventional CCD solid-state image pickup device, and FIG. The state in the line is shown.
【図６】前記従来のＣＣＤ固体撮像装置における、ノイ
ズ低減用ｐ型拡散層の基板深さ方向の不純物濃度および
受光時の電位の分布を示す図であって、図４のＥ−Ｆ線
における状態を示している。FIG. 6 is a diagram showing the impurity concentration in the substrate depth direction of the noise reduction p-type diffusion layer and the potential distribution during light reception in the conventional CCD solid-state imaging device, taken along the line EF of FIG. 4; It shows the state.
【図７】前記従来のＣＣＤ固体撮像装置における、受光
時の動作を示す模式図である。FIG. 7 is a schematic view showing the operation of the conventional CCD solid-state imaging device when receiving light.
１１ ｎ型半導体基板 １２ 第１のｐ型ウェル領域 １３ ｎ型拡散層 １４ ノイズ低減用ｐ型拡散層 １４ａ 低濃度領域 １４ｂ 高濃度領域 １５ 第２のｐ型ウェル領域 １６ ｎ型ウェル領域 １７ 分離用ｐ型拡散層 １８ ゲート酸化膜 １９ ゲート電極 ２０ 遮光膜 ２１ アルミ遮光部 ２２ 保護膜 11 n-type semiconductor substrate 12 first p-type well region 13 n-type diffusion layer 14 noise reduction p-type diffusion layer 14a low concentration region 14b high concentration region 15 second p-type well region 16 n-type well region 17 for separation p-type diffusion layer 18 gate oxide film 19 gate electrode 20 light-shielding film 21 aluminum light-shielding portion 22 protective film
Claims (3)
し光電変換により信号電荷を生成するフォトダイオード
部と信号電荷を転送する電荷転送部とが交互に形成さ
れ、前記フォトダイオード部のｎ型不純物拡散層の上に
ノイズを低減するためのノイズ低減用ｐ型不純物拡散層
が形成されたＣＣＤ固体撮像装置において、 前記ノイズ低減用ｐ型不純物拡散層は、前記電荷転送部
側の両側部にそれぞれ形成された不純物濃度が相対的に
高い高濃度領域と、前記高濃度領域同士の間の中央部に
形成された不純物濃度が相対的に低い低濃度領域とから
なることを特徴とするＣＣＤ固体撮像装置。1. A photodiode section having an n-type impurity diffusion layer for generating signal charges by photoelectric conversion and charge transfer sections for transferring signal charges are alternately formed on a semiconductor substrate. In a CCD solid-state imaging device having a p-type impurity diffusion layer for noise reduction for reducing noise formed on an n-type impurity diffusion layer, the p-type impurity diffusion layer for noise reduction is provided on both sides of the charge transfer section side. And a low-concentration region with a relatively low impurity concentration formed in the central portion between the high-concentration regions. CCD solid-state imaging device.
し光電変換により信号電荷を生成するフォトダイオード
部と信号電荷を転送する電荷転送部とが交互に形成さ
れ、前記フォトダイオード部のｎ型不純物拡散層の上に
ノイズを低減するためのノイズ低減用ｐ型不純物拡散層
が形成されたＣＣＤ固体撮像装置の製造方法であって、 前記ノイズ低減用ｐ型不純物拡散層を形成する工程は、 前記フォトダイオード部のｎ型不純物拡散層にドーズ量
が相対的に低い第１のイオン注入を行うことにより不純
物濃度が相対的に低いｐ型低濃度領域を形成した後、前
記ｐ型低濃度領域における前記電荷転送部側の両側部に
ドーズ量が相対的に高い第２のイオン注入を行うことに
より不純物濃度が相対的に高いｐ型高濃度領域を形成す
ることにより、 前記ｐ型低濃度領域と前記ｐ型高濃度領域とからなるノ
イズ低減用ｐ型不純物拡散層を形成する工程であること
を特徴とするＣＣＤ固体撮像装置の製造方法。2. A photodiode portion having an n-type impurity diffusion layer for generating signal charges by photoelectric conversion and charge transfer portions for transferring signal charges are alternately formed on a semiconductor substrate, and the photodiode portions of the photodiode portions are formed. A method of manufacturing a CCD solid-state imaging device, comprising a p-type impurity diffusion layer for noise reduction formed on an n-type impurity diffusion layer, the method comprising: forming the p-type impurity diffusion layer for noise reduction. Form a p-type low-concentration region having a relatively low impurity concentration by performing first ion implantation with a relatively low dose amount in the n-type impurity diffusion layer of the photodiode part, and By performing second ion implantation with a relatively high dose amount on both sides of the concentration region on the side of the charge transfer portion, a p-type high concentration region with a relatively high impurity concentration is formed, A method of manufacturing a CCD solid-state imaging device, which comprises a step of forming a p-type impurity diffusion layer for noise reduction, which comprises a p-type low-concentration region and the p-type high-concentration region.
×１０13／ｃｍ2 〜３×１０14／ｃｍ2 、注入エネルギ
ーが３０ｋｅＶ〜８０ｋｅＶの条件でボロンを用いて行
い、前記第２のイオン注入は、ドーズ量が５×１０13／
ｃｍ2 〜４×１０14／ｃｍ2 、注入エネルギーが３０ｋ
ｅＶ〜６０ｋｅＶの条件でボロンを用いて行うことを特
徴とする請求項２に記載のＣＣＤ固体撮像装置の製造方
法。3. A dose amount of the first ion implantation is 3
Boron is used under the conditions of × 10 13 / cm 2 to 3 × 10 14 / cm 2 and implantation energy of 30 keV to 80 keV, and the second ion implantation is performed at a dose amount of 5 × 10 13 /
cm 2 to 4 × 10 14 / cm 2 , implantation energy is 30 k
The method for manufacturing a CCD solid-state image pickup device according to claim 2, wherein boron is used under a condition of eV to 60 keV.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06267322A JP3124451B2 (en) | 1994-10-31 | 1994-10-31 | CCD solid-state imaging device and method of manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06267322A JP3124451B2 (en) | 1994-10-31 | 1994-10-31 | CCD solid-state imaging device and method of manufacturing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08130299A true JPH08130299A (en) | 1996-05-21 |
| JP3124451B2 JP3124451B2 (en) | 2001-01-15 |
Family
ID=17443216
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06267322A Expired - Fee Related JP3124451B2 (en) | 1994-10-31 | 1994-10-31 | CCD solid-state imaging device and method of manufacturing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3124451B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6384436B1 (en) | 1998-12-04 | 2002-05-07 | Nec Corporation | Photoelectric transducer and solid-state image sensing device using the same |
| JP2010283232A (en) * | 2009-06-05 | 2010-12-16 | Nippon Hoso Kyokai <Nhk> | Back-illuminated solid-state imaging device, and photographing device including the same |
| WO2014185643A1 (en) * | 2013-05-13 | 2014-11-20 | 주식회사 레이언스 | Image sensor using photodiode |
-
1994
- 1994-10-31 JP JP06267322A patent/JP3124451B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6384436B1 (en) | 1998-12-04 | 2002-05-07 | Nec Corporation | Photoelectric transducer and solid-state image sensing device using the same |
| JP2010283232A (en) * | 2009-06-05 | 2010-12-16 | Nippon Hoso Kyokai <Nhk> | Back-illuminated solid-state imaging device, and photographing device including the same |
| WO2014185643A1 (en) * | 2013-05-13 | 2014-11-20 | 주식회사 레이언스 | Image sensor using photodiode |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3124451B2 (en) | 2001-01-15 |
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