JP2007006261A - Driving method for solid-state imaging element and solid-state imaging apparatus - Google Patents

Driving method for solid-state imaging element and solid-state imaging apparatus Download PDF

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JP2007006261A
JP2007006261A JP2005185352A JP2005185352A JP2007006261A JP 2007006261 A JP2007006261 A JP 2007006261A JP 2005185352 A JP2005185352 A JP 2005185352A JP 2005185352 A JP2005185352 A JP 2005185352A JP 2007006261 A JP2007006261 A JP 2007006261A
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state imaging
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Masaru Sato
優 佐藤
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Fujifilm Holdings Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To obtain a driving method for a solid-state imaging element and a solid-state imaging apparatus in which excessive charges can be swept out to a substrate with a little power consumption. <P>SOLUTION: The present invention relates to a driving method for a solid-state imaging element 100 which forms, on a top layer of a substrate 11, a number of pixels 41 disposing photo-electric transducers 3 in a matrix shape; vertical transfer sections 5 provided adjacently to the pixels 41 for transferring signal charges generated by the pixels in a column direction; horizontal transfer sections 7 disposed at one end side in the column direction of each of the vertical transfer sections 5 for transferring signal charges transferred from the vertical transfer sections 5 in a row direction; an output amplifier 9 connected to the downstream side of the horizontal transfer sections 7 in a charge transfer direction; and an overflow drain adjacent to the photoelectric transducers 3, wherein during a period of time from reading of signal charges from the photoelectric transducers 3 to the vertical transfer sections 5 to transferring of all the read signal charges to the output amplifier 9, a bias voltage for sweeping out the charges of the photoelectric transducers 3 to the side of the substrate 11 is applied to the overflow drain. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、オーバーフロードレイン（ＯＦＤ）構造のＣＣＤ（Ｃｈａｒｇｅ Ｃｏｕｐｌｅｄ Ｄｅｖｉｃｅ）を用いた固体撮像素子の駆動方法及び固体撮像装置に関する。   The present invention relates to a method for driving a solid-state image sensor using a charge coupled device (CCD) having an overflow drain (OFD) structure and a solid-state image pickup apparatus.

ＣＣＤ撮像素子等の固体撮像素子は、例えば、デジタルカメラ、デジタルビデオカメラ、カメラ付き携帯電話機などの画像を記録する携帯電子機器に搭載される。
図４は固体撮像素子の概略構成を表す平面模式図である。
この種の固体撮像素子１は、二次元状に配列された複数のフォトダイオード（光電変換部）３と、各フォトダイオード３で発生した信号電荷をフォトダイオード３の列方向に読み出して、この列方向に順次転送する複数列の垂直シフトレジスタ（以下、垂直電荷転送路とも呼称する）５と、これらの垂直シフトレジスタ５の端部に配置されそれぞれの垂直シフトレジスタ５からの信号電荷を水平方向に転送する水平シフトレジスタ（以下、水平電荷転送路とも呼称する）７と、さらに水平シフトレジスタ７の電荷転送方向先端側に配置され、転送されてくる信号を電圧値に変換して出力する出力アンプ９と、を備えている。この固体撮像素子１は、一般に電荷結合素子（ＣＣＤ）と呼ばれる。 A solid-state image sensor such as a CCD image sensor is mounted on a portable electronic device that records an image, such as a digital camera, a digital video camera, or a camera-equipped mobile phone.
FIG. 4 is a schematic plan view illustrating a schematic configuration of the solid-state imaging device.
This type of solid-state imaging device 1 reads a plurality of photodiodes (photoelectric conversion units) 3 arranged two-dimensionally and signal charges generated in each photodiode 3 in the column direction of the photodiodes 3. A plurality of columns of vertical shift registers (hereinafter also referred to as vertical charge transfer paths) 5 that sequentially transfer in the direction, and signal charges from the vertical shift registers 5 arranged at the ends of these vertical shift registers 5 in the horizontal direction And a horizontal shift register (hereinafter also referred to as a horizontal charge transfer path) 7 for transferring to the output of the horizontal shift register 7 and an output for converting the transferred signal into a voltage value and outputting it. And an amplifier 9. This solid-state imaging device 1 is generally called a charge coupled device (CCD).

図５は図４のI−I断面の構造を表す模式図である。
固体撮像素子１では、図５に示すように、ｎ型のシリコン基板１１の表面にｐ型の不純物ウェル層１３が形成され、さらにその上にＳｉｎ／ＳｉＯ2／ＳｉＮ膜（ＯＮＯ膜）からなる絶縁層１５が形成されている。また、不純物ウェル層１３の表面から高濃度のｐ型不純物層１７と、さらにその下部にｎ型不純物層１９が形成され、これにより光に感応して電荷を発生する光電変換部（フォトダイオード）３が構成されている。 FIG. 5 is a schematic diagram showing the structure of the II cross section of FIG.
In the solid-state imaging device 1, as shown in FIG. 5, a p-type impurity well layer 13 is formed on the surface of an n-type silicon substrate 11, and further a Sin / SiO 2 / SiN film (ONO film) is formed thereon. An insulating layer 15 is formed. In addition, a high-concentration p-type impurity layer 17 is formed from the surface of the impurity well layer 13, and an n-type impurity layer 19 is further formed below the p-type impurity layer 17, thereby generating a charge in response to light. 3 is configured.

また、フォトダイオード３の読み出しゲート２１を挟んだ側方には、ｎ型不純物層２３が形成され、このｎ型不純物層２３の下部に高濃度のｐ型不純物層２５が形成されている。ｎ型不純物層２３上方の絶縁層１５の表面には第２の電極２７が形成され、この第２の電極２７は絶縁層２９により覆われている。
さらに、固体撮像素子１では、フォトダイオード３と垂直電荷転送路となるｎ型不純物層２３とを含む１画素領域を囲むように、高濃度のｐ型不純物層からなる素子分離帯３１が形成されている。 Further, an n-type impurity layer 23 is formed on the side of the photodiode 3 across the read gate 21, and a high-concentration p-type impurity layer 25 is formed below the n-type impurity layer 23. A second electrode 27 is formed on the surface of the insulating layer 15 above the n-type impurity layer 23, and the second electrode 27 is covered with an insulating layer 29.
Furthermore, in the solid-state imaging device 1, an element isolation band 31 composed of a high-concentration p-type impurity layer is formed so as to surround one pixel region including the photodiode 3 and the n-type impurity layer 23 serving as a vertical charge transfer path. ing.

図６は図５のII−II断面における電位分布の模式図である。
このような構成を有する固体撮像素子１において、第２の電極２７に対して十分に高い電圧を印加することで、図６に示すように、フォトダイオード３の電位に対して垂直シフトレジスタ５に向かっての障壁（Ｐウェル領域）３３がなくなり、蓄積された信号電荷Ｄは全て垂直シフトレジスタ５に移動する。フォトダイオード３に蓄積される信号電荷Ｄの電荷量は、図６のポテンシャル分布図に示すように、Ｐ型のウェル領域３５で構成されるオーバーフローバリアのポテンシャルバリアの高さによって決定される。即ち、このオーバーフローバリアは、フォトダイオード３に蓄積される飽和信号電荷量を決めるものであり、蓄積電荷量がこの飽和信号電荷量を越えた場合に、その越えた分の電荷がポテンシャルバリアを越えて基板１１側へ掃き出される。 FIG. 6 is a schematic diagram of a potential distribution in the II-II cross section of FIG.
In the solid-state imaging device 1 having such a configuration, by applying a sufficiently high voltage to the second electrode 27, the vertical shift register 5 is applied to the potential of the photodiode 3 as shown in FIG. There is no barrier (P well region) 33 toward it, and all the accumulated signal charge D moves to the vertical shift register 5. The charge amount of the signal charge D accumulated in the photodiode 3 is determined by the height of the potential barrier of the overflow barrier formed by the P-type well region 35 as shown in the potential distribution diagram of FIG. That is, this overflow barrier determines the saturation signal charge amount accumulated in the photodiode 3, and when the accumulated charge amount exceeds this saturation signal charge amount, the excess charge exceeds the potential barrier. To the substrate 11 side.

オーバーフローバリアのポテンシャルは、基板バイアスの電圧値によって決まる。換言すれば、基板バイアスの電圧値により、フォトダイオード３の飽和信号電荷量が設定される。   The potential of the overflow barrier is determined by the voltage value of the substrate bias. In other words, the saturation signal charge amount of the photodiode 3 is set by the voltage value of the substrate bias.

図７は従来の固体撮像素子の駆動タイミングチャートである。
固体撮像素子１では、電荷蓄積期間Ｔ、即ち露光期間の前後において、フォトダイオード３に蓄積された電荷が完全に基板１１に掃き捨てられる電圧（完全基板掃き出し電圧）を、パルス（電子シャッターパルス電圧ＯＦＤ２）として読み出し前に印加することにより、不要な信号電荷を掃き捨て、実効的な露光期間を電子的に制御することができる。このときの露光期間は、最後の電子シャッターパルスＰｅから読み出しパルスＰｗまでの期間となる。 FIG. 7 is a drive timing chart of a conventional solid-state image sensor.
In the solid-state imaging device 1, a voltage (complete substrate sweep voltage) at which the charge accumulated in the photodiode 3 is completely swept away by the substrate 11 before and after the charge accumulation period T, that is, the exposure period, is converted into a pulse (electronic shutter pulse voltage). By applying it as OFD2) before reading, unnecessary signal charges can be swept away and the effective exposure period can be electronically controlled. The exposure period at this time is a period from the last electronic shutter pulse Pe to the readout pulse Pw.

また、パルスを印加することで、実効的な露光期間を電子的に制御するものに、例えば特許文献１に開示される固体撮像装置がある。この固体撮像素子では、信号電荷の加算モード時において、例えば２画素分の信号を加算して転送する場合、フォトダイオード部の飽和信号をフレーム読み出し時の約１／２になるように、基板バイアス電圧（オーバーフロードレイン電圧；ＯＦＤ）を設定することで、画素信号加算に伴って垂直転送部及び水平転送部で信号電荷が溢れることを防止している。   Moreover, there exists a solid-state imaging device disclosed by patent document 1 as what controls an effective exposure period electronically by applying a pulse, for example. In this solid-state imaging device, in the signal charge addition mode, for example, when signals for two pixels are added and transferred, the substrate bias is set so that the saturation signal of the photodiode portion is about ½ of that during frame reading. By setting the voltage (overflow drain voltage; OFD), it is possible to prevent the signal charge from overflowing in the vertical transfer unit and the horizontal transfer unit with the addition of the pixel signal.

特開２０００−３０７９６１号公報JP 2000-307961 A

しかしながら、動画モードなどＣＣＤイメージセンサが連続動作する状況においては、メカニカル・シャッターの代わりに電子シャッターを用いて露光期間を制御すると、電子シャッターパルスＰの発生に起因して電力消費量が増大する問題が生じた。即ち、従来のように、シリコン半導体基板の純度がさほど高くない場合では、ＯＦＤ電圧を高く設定する必要があり、そのような高い電圧信号は、印加期間の短いパルスとする以外には信号生成が困難であった。一般に、このようなパルス信号を生成すると、他のバイアス信号等と比較して、駆動回路に余分な負担がかかるため、消費電力を大幅に増大させた。特にデジタル式の撮像装置にあっては、消費電力がバッテリーによる駆動時間に大きく影響を及ぼすため、消費電力を如何に抑えるかが課題となっていた。   However, in a situation where the CCD image sensor continuously operates such as a moving image mode, if the exposure period is controlled using an electronic shutter instead of the mechanical shutter, the power consumption increases due to the generation of the electronic shutter pulse P. Occurred. That is, when the purity of the silicon semiconductor substrate is not so high as in the prior art, it is necessary to set the OFD voltage high, and such a high voltage signal is not generated except for a pulse with a short application period. It was difficult. In general, when such a pulse signal is generated, an extra load is applied to the drive circuit as compared with other bias signals and the like, so that power consumption is greatly increased. In particular, in a digital imaging apparatus, power consumption greatly affects the driving time of a battery, so how to suppress power consumption has been a problem.

本発明は上記状況に鑑みてなされたもので、少ない消費電力で余分な電荷を基板へ掃き出しできる固体撮像素子の駆動方法及び固体撮像装置を提供することにある。   The present invention has been made in view of the above situation, and it is an object of the present invention to provide a solid-state imaging device driving method and a solid-state imaging device capable of sweeping extra charges to a substrate with low power consumption.

本発明に係る上記目的は、下記構成により達成される。
（１）光に感応して電荷を発生する光電変換部を複数行、複数列に亘って行列状に配置した多数個の画素と、これら各画素に隣接して設けられ前記各画素が発生した信号電荷を列方向に転送する複数の垂直転送部と、前記各垂直転送部の列方向一端側に配置され該垂直転送部から転送される前記信号電荷を行方向に転送する水平転送部と、該水平転送部の電荷転送方向下流側に接続された出力アンプ部と、前記各光電変換部に隣接するオーバーフロードレインと、を基板表面層に形成した固体撮像素子の駆動方法であって、前記光電変換部から前記垂直転送部に前記信号電荷を読み出してから、該読み出した前記信号電荷の全てが前記出力アンプまで転送されるまでの期間、前記光電変換部の電荷を前記基板側へ掃き出すためのバイアス電圧を前記オーバーフロードレインに印加することを特徴とする固体撮像素子の駆動方法。 The above object of the present invention is achieved by the following configuration.
(1) A large number of pixels in which a photoelectric conversion unit that generates charges in response to light is arranged in a matrix over a plurality of rows and a plurality of columns, and the pixels are provided adjacent to the pixels. A plurality of vertical transfer units that transfer signal charges in the column direction; a horizontal transfer unit that is arranged on one end side in the column direction of each vertical transfer unit and that transfers the signal charges transferred from the vertical transfer unit in the row direction; A method for driving a solid-state imaging device, comprising: an output amplifier unit connected to a downstream side of the horizontal transfer unit in a charge transfer direction; and an overflow drain adjacent to each of the photoelectric conversion units. For sweeping out the charge of the photoelectric conversion unit to the substrate side during a period from when the signal charge is read from the conversion unit to the vertical transfer unit until all of the read signal charge is transferred to the output amplifier. Bias voltage The driving method of a solid-state imaging device and applying to the overflow drain.

この固体撮像素子の駆動方法では、フォトダイオードに蓄積された電荷を完全に基板に掃き捨てるための完全基板掃き出し電圧が、バイアス電圧としてオーバーフロードレインに印加可能となり、従来の駆動方法のように、基板掃き出し電圧を電子シャッターパルス電圧として印加する必要がなくなる。なお、低電圧のバイアス電圧で電位ポテンシャルの障壁（Ｐウェル）を低くすることは、近年にあって容易に得られるようになった高純度の半導体を用いることで可能となる。   In this solid-state imaging device driving method, a complete substrate sweeping voltage for completely sweeping away the electric charge accumulated in the photodiode to the substrate can be applied to the overflow drain as a bias voltage, and the substrate is driven like the conventional driving method. There is no need to apply the sweep voltage as an electronic shutter pulse voltage. Note that the potential potential barrier (P well) can be lowered with a low bias voltage by using a high-purity semiconductor that has been easily obtained in recent years.

（２）前記バイアス電圧は、前記オーバーフロードレインの領域に形成される電位ポテンシャルの障壁を、前記光電変換部に蓄積された電荷が前記基板側に掃き出すことのできる電圧であることを特徴とする（１）記載の固体撮像素子の駆動方法。 (2) The bias voltage is a voltage that allows a charge accumulated in the photoelectric conversion unit to be swept out to the substrate side through a potential potential barrier formed in the overflow drain region. 1) The method for driving a solid-state imaging device according to 1).

この固体撮像素子の駆動方法では、バイアス電圧が印加されることで、オーバーフロードレインの領域に形成される電位ポテンシャルの障壁が、光電変換部に蓄積された電荷を基板側に掃き出すことのできる低さとなり、フォトダイオードに蓄積される蓄積電荷量がＰウェル領域を越えて基板側へ掃き出される。   In this solid-state imaging device driving method, a bias voltage is applied so that the potential potential barrier formed in the overflow drain region is low enough to sweep out charges accumulated in the photoelectric conversion unit to the substrate side. Thus, the amount of charge accumulated in the photodiode is swept to the substrate side beyond the P well region.

（３）固体撮像素子と、被写体像を前記固体撮像素子に結像する光学系と、前記固体撮像素子の前記出カアンプ部から出力されてくる信号を処理し画像を生成する信号処理部と、この生成された画像を表示する表示部と、を備えた固体撮像装置であって、前記固体撮像装置により静止画撮影を行う場合に、前記固体撮像素子を（１）又は（２）記載の固体撮像素子の駆動方法で動作させ、前記表示部に被写体像をモニタ表示させる制御部を備えたことを特徴とする固体撮像素子。 (3) a solid-state imaging device, an optical system that forms a subject image on the solid-state imaging device, a signal processing unit that processes a signal output from the output amplifier unit of the solid-state imaging device, and generates an image; A solid-state imaging device including a display unit that displays the generated image, and when the solid-state imaging device performs still image shooting, the solid-state imaging device is the solid-state imaging device described in (1) or (2) A solid-state image pickup device comprising a control unit that is operated by a driving method of the image pickup device and displays a subject image on the display unit.

この固体撮像装置では、電子シャッターパルス電圧が印加されずに、制御部によって一定のバイアス電圧がオーバーフロードレインに印加されることで、光電変換部の電荷が基板側へ掃き出される。したがって、従来、パルス電圧動作によって消費された電力が低減され、少ない消費電力で被写体像が表示部にモニタ表示可能となる。   In this solid-state imaging device, the electric shutter pulse voltage is not applied, but a constant bias voltage is applied to the overflow drain by the control unit, so that the electric charge of the photoelectric conversion unit is swept to the substrate side. Therefore, conventionally, the power consumed by the pulse voltage operation is reduced, and the subject image can be displayed on the display unit with less power consumption.

本発明に係る固体撮像素子の駆動方法によれば、光電変換部から垂直転送部に信号電荷を読み出してから、読み出した信号電荷の全てが出力アンプまで転送されるまでの期間、光電変換部の電荷を基板側へ掃き出すためのバイアス電圧をオーバーフロードレインに印加するので、従来の駆動方法のように、フォトダイオードに蓄積された電荷を完全に基板に掃き捨てるための完全基板掃き出し電圧を、電子シャッターパルス電圧として印加する必要がなく、駆動回路に余分な負担がかからず、消費電力を低減することができる。   According to the method for driving a solid-state imaging device according to the present invention, a period from when the signal charge is read from the photoelectric conversion unit to the vertical transfer unit until all of the read signal charge is transferred to the output amplifier, A bias voltage is applied to the overflow drain to sweep the charge to the substrate side. Therefore, as in the conventional driving method, a full substrate sweep voltage for completely sweeping the charge accumulated in the photodiode to the substrate is applied to the electronic shutter. There is no need to apply it as a pulse voltage, no extra load is applied to the drive circuit, and power consumption can be reduced.

本発明に係る固体撮像装置によれば、固体撮像装置により静止画撮影を行う場合に、固体撮像素子を前記固体撮像素子の駆動方法で動作させ、表示部に被写体像をモニタ表示させる制御部を備えたので、駆動回路に余分な負担をかける電子シャッターパルス電圧を印加せずに、一定のバイアス電圧を印加して光電変換部の電荷を基板側へ掃き出せる。この結果、従来のパルス電圧動作によって消費された電力を低減でき、デジタル式の撮像装置においてバッテリーによる駆動時間を延長することができる。   According to the solid-state imaging device according to the present invention, when performing still image shooting with the solid-state imaging device, the control unit that causes the solid-state imaging device to operate by the driving method of the solid-state imaging device and displays the subject image on the display unit. Since it is provided, a constant bias voltage is applied without applying an electronic shutter pulse voltage that imposes an extra burden on the drive circuit, and the charge of the photoelectric conversion unit can be swept out to the substrate side. As a result, the power consumed by the conventional pulse voltage operation can be reduced, and the battery driving time can be extended in the digital imaging device.

以下、本発明に係る固体撮像素子の駆動方法及び固体撮像装置の好適な実施の形態について、図面を参照して詳細に説明する。
図１は本発明に係る固体撮像素子の平面模式図である。なお、図４〜図７に示した部材及び部位と同等の部材及び部位には同一の符号を付して説明するものとする。
本実施の形態によるＣＣＤ等の固体撮像素子１００は、光に感応して電荷を発生する光電変換部（フォトダイオード）３を複数行、複数列に亘って行列状に配置した多数個の画素４１と、これら各画素４１に隣接して設けられ各画素４１が発生した信号電荷を列方向に転送する複数の垂直転送部（垂直シフトレジスタ）５と、各垂直シフトレジスタ５の列方向一端側に配置され垂直シフトレジスタ５から転送される信号電荷を行方向に転送する水平転送部（水平シフトレジスタ）７と、この水平シフトレジスタ７の電荷転送方向下流側に接続され転送されてくる信号を電圧値に変換して出力する出力アンプ部（出力アンプ）９と、各フォトダイオード３に隣接するオーバーフロードレインと、を基板１１（図５参照）表面層に形成している。なお、本実施の形態では、基板１１がオーバーフロードレインとなる。 Preferred embodiments of a solid-state imaging device driving method and a solid-state imaging device according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a schematic plan view of a solid-state imaging device according to the present invention. In addition, the same code | symbol shall be attached | subjected and demonstrated to the member and site | part equivalent to the member and site | part shown to FIGS.
The solid-state imaging device 100 such as a CCD according to the present embodiment has a large number of pixels 41 in which photoelectric conversion units (photodiodes) 3 that generate charges in response to light are arranged in a matrix over a plurality of rows and columns. A plurality of vertical transfer units (vertical shift registers) 5 provided adjacent to the respective pixels 41 for transferring the signal charges generated by the respective pixels 41 in the column direction, and one end in the column direction of each vertical shift register 5 A horizontal transfer unit (horizontal shift register) 7 for transferring the signal charge transferred from the vertical shift register 5 in the row direction, and a signal connected to the downstream side of the horizontal shift register 7 in the charge transfer direction as a voltage An output amplifier section (output amplifier) 9 that converts the value into an output and an overflow drain adjacent to each photodiode 3 are formed on the surface layer of the substrate 11 (see FIG. 5). In the present embodiment, the substrate 11 serves as an overflow drain.

固体撮像装置１００は、駆動信号を入力する素子駆動部４３とを備えている。素子駆動部４３は、水平同期信号ＨＤ、垂直同期信号ＶＤに基づいて、固体撮像素子１００を駆動するための種々のパルス信号を生成するタイミング信号生成部４５と、タイミング信号生成部４５から供給された種々のパルスを所定レベルのドライブパルス（垂直転送パルス、水平転送パルス）にして固体撮像素子１００に供給するドライバ４７と、タイミング信号生成部４５からのタイミング信号に基づき固体撮像素子１００にドレイン電圧ＶＤＤを印加する基板電圧発生部４９と、を含んで構成される。固体撮像素子１００は、これら素子駆動部４３からの出力信号に基づいて駆動制御される。   The solid-state imaging device 100 includes an element driving unit 43 that inputs a driving signal. The element drive unit 43 is supplied from a timing signal generation unit 45 that generates various pulse signals for driving the solid-state imaging device 100 based on the horizontal synchronization signal HD and the vertical synchronization signal VD, and the timing signal generation unit 45. The driver 47 that supplies various pulses as drive pulses (vertical transfer pulse, horizontal transfer pulse) at a predetermined level to the solid-state image sensor 100 and the drain voltage applied to the solid-state image sensor 100 based on the timing signal from the timing signal generator 45. And a substrate voltage generator 49 for applying VDD. The solid-state imaging device 100 is driven and controlled based on output signals from these device driving units 43.

この固体撮像素子１００では、素子駆動部４３のタイミング信号生成部４５から基板電圧発生部４９へタイミング信号が送出されることで、フォトダイオード３から垂直シフトレジスタ５に信号電荷を読み出してから、読み出した信号電荷の全てが出力アンプ９まで転送されるまでの期間、フォトダイオード３の電荷を基板１１側へ掃き出すためのドレイン電圧ＶＤＤ（バイアス電圧）が、オーバーフロードレイン（基板１１）に印加される。   In the solid-state imaging device 100, the timing signal is sent from the timing signal generation unit 45 of the element driving unit 43 to the substrate voltage generation unit 49, so that the signal charge is read from the photodiode 3 to the vertical shift register 5 and then read out. During the period until all of the signal charges are transferred to the output amplifier 9, the drain voltage VDD (bias voltage) for sweeping out the charges of the photodiode 3 to the substrate 11 side is applied to the overflow drain (substrate 11).

ここで、このバイアス電圧は、オーバーフロードレインの領域に形成される電位ポテンシャルの障壁（Ｐウェル領域）を、フォトダイオード３に蓄積された電荷が基板１１側に掃き出すことのできる電圧となっている。これにより、電位ポテンシャルの障壁が、フォトダイオード３に蓄積された電荷を基板１１側に掃き出すことのできる低さとなり、フォトダイオード３に蓄積される蓄積電荷量がＰウェル領域を越えて基板１１側へ掃き出し可能となっている。つまり、従来、印加されていた電子シャッターパルスを、バイアス電圧に代えることで、電圧の変調のみで余分な電荷の掃き出しを行い、従来のパルス動作によって消費される電圧を低減している。   Here, this bias voltage is a voltage at which charges accumulated in the photodiode 3 can be swept out to the substrate 11 side through a potential potential barrier (P well region) formed in the overflow drain region. As a result, the potential potential barrier becomes low enough to sweep out the charge accumulated in the photodiode 3 to the substrate 11 side, and the accumulated charge amount accumulated in the photodiode 3 exceeds the P well region and is on the substrate 11 side. Can be swept out. That is, by replacing the conventionally applied electronic shutter pulse with a bias voltage, the excess charge is swept out only by voltage modulation, and the voltage consumed by the conventional pulse operation is reduced.

図２は本発明に係る固体撮像素子の駆動タイミングチャートである。
固体撮像素子１００では、電荷蓄積期間Ｔ、即ち露光期間において、フォトダイオード３に蓄積された電荷が完全に基板１１に掃き捨てられる電圧（完全基板掃き出し電圧）を、バイアス電圧ＯＦＤ２として印加する。この不要な信号電荷を掃き捨てする期間は、前の読み出しパルスＰ１が印加される読出処理が終了した後ｔ１から、次の読み出しパルスＰ２が印加される読出処理前の電荷蓄積期間Ｔの直前ｔ２までとなって繰り返される。 FIG. 2 is a drive timing chart of the solid-state imaging device according to the present invention.
In the solid-state imaging device 100, during the charge accumulation period T, that is, the exposure period, a voltage at which the charges accumulated in the photodiode 3 are completely swept away by the substrate 11 (complete substrate sweep voltage) is applied as the bias voltage OFD2. The period during which the unnecessary signal charges are swept away is t2 after the read process to which the previous read pulse P1 is applied and immediately before the charge accumulation period T before the read process to which the next read pulse P2 is applied. Repeat until.

固体撮像素子１００の駆動方法では、近年にあって容易に得られるようになった高純度の半導体を用いることで、低電圧で電位ポテンシャルの障壁（Ｐウェル）を低くすることが可能となる。これにより、フォトダイオード３に蓄積された電荷を完全に基板１１に掃き捨てるための完全基板掃き出し電圧が、バイアス電圧としてオーバーフロードレインに印加可能となる。このため、従来の駆動方法のように、基板掃き出し電圧を電子シャッターパルス電圧として印加する必要がなくなる。なお、完全基板掃き出し電圧は、従前では３０Ｖを要していたが、高純度の半導体基板を用いることで、２０Ｖ程度まで電圧値を抑えることができる。   In the driving method of the solid-state imaging device 100, it is possible to lower the potential potential barrier (P well) at a low voltage by using a high-purity semiconductor that has been easily obtained in recent years. As a result, a complete substrate sweep voltage for completely sweeping away the charge accumulated in the photodiode 3 to the substrate 11 can be applied to the overflow drain as a bias voltage. Therefore, unlike the conventional driving method, it is not necessary to apply the substrate sweep voltage as an electronic shutter pulse voltage. In addition, the complete substrate sweeping voltage conventionally required 30 V, but the voltage value can be suppressed to about 20 V by using a high purity semiconductor substrate.

したがって、本実施の形態による固体撮像素子１００の駆動方法によれば、フォトダイオード３から垂直転送部に信号電荷を読み出してから、読み出した信号電荷の全てが出力アンプ９まで転送されるまでの期間、フォトダイオード３の電荷を基板１１側へ掃き出すためのバイアス電圧をオーバーフロードレインに印加するので、従来の駆動方法のように、掃き出し電圧を、電子シャッターパルス電圧として印加する必要がなく、駆動回路に余分な負担がかからず、消費電力を低減することができる。   Therefore, according to the method for driving the solid-state imaging device 100 according to the present embodiment, the period from when the signal charge is read from the photodiode 3 to the vertical transfer unit until all of the read signal charge is transferred to the output amplifier 9. Since the bias voltage for sweeping out the electric charge of the photodiode 3 to the substrate 11 side is applied to the overflow drain, it is not necessary to apply the sweep voltage as an electronic shutter pulse voltage as in the conventional driving method, and the drive circuit An extra burden is not applied and power consumption can be reduced.

次に、本発明に係る固体撮像素子が用いられた固体撮像装置の例を説明する。
図３は本発明に係る固体撮像装置の概略構成図である。
上記した固体撮像素子１００は、例えば固体撮像装置であるデジタルスチルカメラ２００に好適に用いることができる。
このデジタルスチルカメラ２００は、固体撮像素子１００と、被写体像を固体撮像素子１００に結像する光学系５１と、固体撮像素子１００の出力アンプ部９から出力されてくる信号を処理し画像を生成する信号処理部５３と、この生成された画像を表示する表示部５５とを基本構成要素として備える。 Next, an example of a solid-state imaging device using the solid-state imaging device according to the present invention will be described.
FIG. 3 is a schematic configuration diagram of a solid-state imaging device according to the present invention.
The solid-state imaging device 100 described above can be suitably used for a digital still camera 200 that is a solid-state imaging device, for example.
The digital still camera 200 processes the signals output from the solid-state imaging device 100, the optical system 51 that forms a subject image on the solid-state imaging device 100, and the output amplifier unit 9 of the solid-state imaging device 100, and generates an image. The signal processing unit 53 that performs this processing and the display unit 55 that displays the generated image are provided as basic components.

また、デジタルスチルカメラ２００には、固体撮像装置１００と光学系５１との間に設けられるメカニカル・シャッター５７と、固体撮像装置１００を駆動するドライブ回路５９と、固体撮像装置１００から読み出されたアナログ画像信号をデジタル画像信号に変換するアナログ／デジタル変換部６１と、信号処理部５３で信号処理された画像信号を記憶する記録部６３と、制御部６５とを備える。   Further, the digital still camera 200 is read from the solid-state imaging device 100, a mechanical shutter 57 provided between the solid-state imaging device 100 and the optical system 51, a drive circuit 59 for driving the solid-state imaging device 100, and the like. An analog / digital conversion unit 61 that converts an analog image signal into a digital image signal, a recording unit 63 that stores an image signal processed by the signal processing unit 53, and a control unit 65 are provided.

信号処理部５３は、アナログ／デジタル変換部６１から出力されるデジタル画像信号の出力先を切り替えるスイッチ５３ａと、スイッチ５３ａを通して取り込んだデジタル画像信号を動画処理する動画処理部５３ｂと、スイッチ５３ａを通して取り込んだデジタル画像信号を静止画処理する静止画処理部５３ｃと、動画処理部５３ｂ及び静止画処理部５３ｃの処理結果を受け取りその他の画像処理を行う共通信号処理部５３ｄとを備える。   The signal processing unit 53 includes a switch 53a for switching the output destination of the digital image signal output from the analog / digital conversion unit 61, a moving image processing unit 53b for moving the digital image signal acquired through the switch 53a, and an input through the switch 53a. The digital image signal includes a still image processing unit 53c that performs still image processing, and a common signal processing unit 53d that receives processing results of the moving image processing unit 53b and the still image processing unit 53c and performs other image processing.

そして、制御部６５は、ドライブ回路５９や信号処理部５３、記録部６３の制御に加え、固体撮像装置１００により静止画撮影を行う場合に、固体撮像素子１００を上記の駆動方法で動作させ、表示部５５に被写体像をモニタ表示させる制御を行う。   Then, in addition to controlling the drive circuit 59, the signal processing unit 53, and the recording unit 63, the control unit 65 operates the solid-state imaging device 100 with the above driving method when performing a still image shooting with the solid-state imaging device 100. Control for displaying the subject image on the display unit 55 is performed.

このデジタルスチルカメラ２００では、従来の固体撮像素子の場合のように電子シャッターパルス電圧が印加されず、制御部６５によって一定のバイアス電圧がオーバーフロードレインに印加され、フォトダイオード３の電荷が基板側へ掃き出される。これにより、従来、パルス電圧動作によって消費された電力が低減され、少ない消費電力で被写体像が表示部５５にモニタ表示可能となる。   In the digital still camera 200, an electronic shutter pulse voltage is not applied as in the case of the conventional solid-state imaging device, a constant bias voltage is applied to the overflow drain by the control unit 65, and the charge of the photodiode 3 is transferred to the substrate side. Swept out. Thus, conventionally, the power consumed by the pulse voltage operation is reduced, and the subject image can be displayed on the display unit 55 with less power consumption.

したがって、本実施の形態による固体撮像装置２００によれば、静止画撮影を行う場合に、固体撮像素子１００を上記の駆動方法で動作させ、表示部５５に被写体像をモニタ表示させる制御部６５を備えたので、駆動回路に余分な負担をかける電子シャッターパルス電圧を印加せずに、一定のバイアス電圧を印加してフォトダイオード３の電荷を基板１１側へ掃き出せる。この結果、従来のパルス電圧動作によって消費された電力を低減でき、デジタル式の撮像装置においてバッテリーによる駆動時間を延長することができる。   Therefore, according to the solid-state imaging device 200 according to the present embodiment, the control unit 65 that causes the solid-state imaging device 100 to operate by the above driving method and displays the subject image on the display unit 55 when performing still image shooting. Since it is provided, a constant bias voltage is applied without applying an electronic shutter pulse voltage that imposes an extra burden on the drive circuit, and the charge of the photodiode 3 can be swept out to the substrate 11 side. As a result, the power consumed by the conventional pulse voltage operation can be reduced, and the battery driving time can be extended in the digital imaging device.

本発明に係る固体撮像素子の平面模式図である。It is a plane schematic diagram of the solid-state image sensor concerning the present invention. 本発明に係る固体撮像素子の駆動タイミングチャートである。3 is a drive timing chart of the solid-state imaging device according to the present invention. 本発明に係る固体撮像装置の概略構成図である。1 is a schematic configuration diagram of a solid-state imaging device according to the present invention. 固体撮像素子の概略構成を表す平面模式図である。It is a plane schematic diagram showing schematic structure of a solid-state image sensor. 図４のI−I断面の構造を表す模式図である。It is a schematic diagram showing the structure of the II cross section of FIG. 図５のII−II断面における電位分布の模式図である。It is a schematic diagram of the potential distribution in the II-II cross section of FIG. 従来の固体撮像素子の駆動タイミングチャートである。It is a drive timing chart of the conventional solid-state image sensor.

符号の説明Explanation of symbols

３ フォトダイオード（光電変換部）
５ 垂直シフトレジスタ（垂直転送部）
７ 水平シフトレジスタ（水平転送部）
９ 出力アンプ部
１１ 基板
３３ Ｐウェル領域（障壁）
４１ 画素
５１ 光学系
５３ 信号処理部
５５ 表示部
６５ 制御部
１００ 固体撮像素子
２００ デジタルスチルカメラ（固体撮像装置） 3 Photodiode (photoelectric converter)
5 Vertical shift register (vertical transfer unit)
7 Horizontal shift register (horizontal transfer unit)
9 Output amplifier section 11 Substrate 33 P well region (barrier)
41 pixels 51 optical system 53 signal processing unit 55 display unit 65 control unit 100 solid-state imaging device 200 digital still camera (solid-state imaging device)

Claims (3)

光に感応して電荷を発生する光電変換部を複数行、複数列に亘って行列状に配置した多数個の画素と、
これら各画素に隣接して設けられ前記各画素が発生した信号電荷を列方向に転送する複数の垂直転送部と、
前記各垂直転送部の列方向一端側に配置され該垂直転送部から転送される前記信号電荷を行方向に転送する水平転送部と、
該水平転送部の電荷転送方向下流側に接続された出力アンプ部と、
前記各光電変換部に隣接するオーバーフロードレインと、を基板表面層に形成した固体撮像素子の駆動方法であって、
前記光電変換部から前記垂直転送部に前記信号電荷を読み出してから、該読み出した前記信号電荷の全てが前記出力アンプまで転送されるまでの期間、前記光電変換部の電荷を前記基板側へ掃き出すためのバイアス電圧を前記オーバーフロードレインに印加することを特徴とする固体撮像素子の駆動方法。 A large number of pixels in which photoelectric conversion units that generate charges in response to light are arranged in a matrix over a plurality of rows and columns;
A plurality of vertical transfer units provided adjacent to each of the pixels and transferring the signal charges generated by the pixels in the column direction;
A horizontal transfer unit arranged on one end side in the column direction of each vertical transfer unit and transferring the signal charges transferred from the vertical transfer unit in a row direction;
An output amplifier connected to the downstream side of the horizontal transfer unit in the charge transfer direction;
A method for driving a solid-state imaging device in which an overflow drain adjacent to each photoelectric conversion unit is formed on a substrate surface layer,
During the period from when the signal charges are read from the photoelectric conversion unit to the vertical transfer unit until all of the read signal charges are transferred to the output amplifier, the charges of the photoelectric conversion unit are swept to the substrate side. A bias voltage for applying a voltage to the overflow drain is provided. 前記バイアス電圧は、前記オーバーフロードレインの領域に形成される電位ポテンシャルの障壁を、前記光電変換部に蓄積された電荷が前記基板側に掃き出すことのできる電圧であることを特徴とする請求項１記載の固体撮像素子の駆動方法。   2. The bias voltage is a voltage that allows a charge accumulated in the photoelectric conversion portion to sweep out to a substrate side a potential potential barrier formed in the overflow drain region. Driving method for a solid-state image sensor. 固体撮像素子と、
被写体像を前記固体撮像素子に結像する光学系と、
前記固体撮像素子の前記出力アンプ部から出力されてくる信号を処理し画像を生成する信号処理部と、
この生成された画像を表示する表示部と、を備えた固体撮像装置であって、
前記固体撮像装置により静止画撮影を行う場合に、前記固体撮像素子を請求項１又は請求項２記載の固体撮像素子の駆動方法で動作させ、前記表示部に被写体像をモニタ表示させる制御部を備えたことを特徴とする固体撮像装置。 A solid-state image sensor;
An optical system for forming a subject image on the solid-state image sensor;
A signal processing unit that processes a signal output from the output amplifier unit of the solid-state imaging device and generates an image;
A display unit for displaying the generated image, and a solid-state imaging device,
A control unit that operates the solid-state imaging device by the driving method of the solid-state imaging device according to claim 1 and performs monitor display of a subject image on the display unit when taking a still image by the solid-state imaging device. A solid-state imaging device comprising:
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JPS63105579A (en) * 1986-10-23 1988-05-10 Sony Corp Solid-state image pickup device
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