CN102856332A - Large-size four-transistor active pixel sensor (4T APS) for rapidly transferring charges - Google Patents
Large-size four-transistor active pixel sensor (4T APS) for rapidly transferring charges Download PDFInfo
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- CN102856332A CN102856332A CN2012101033681A CN201210103368A CN102856332A CN 102856332 A CN102856332 A CN 102856332A CN 2012101033681 A CN2012101033681 A CN 2012101033681A CN 201210103368 A CN201210103368 A CN 201210103368A CN 102856332 A CN102856332 A CN 102856332A
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Abstract
The invention relates to a large-size 4T APS for rapidly transferring charges and aims to improve the charge transfer efficiency and reduce charge residues. The utilized technical scheme is that the large-size 4T APS comprises a pinned photodiode area, a pass transistor transmission gate (TG) and a reset transistor (RST), a source follower (SF) and a strobe transistor single event latch-up (SEL). The pinned photodiode area and pass transistor TG grid electrodes are in U-shaped structures, and axes of the two U-shaped structures are overlapped and the two U-shaped structures are opened in a same direction. Pass transistor TG grids are arranged at the bottom of the U-shaped structure of the pinned photodiode area and arranged to be partially overlapped with the bottom of the U-shaped structure of the pinned photodiode area. The pinned photodiode area is extended towards the opening direction along the axis of the U-shaped structure to form an extended area parallel with two arms of the U-shaped structure. A floating diffusion (FD) area and a grid electrode and a leakage electrode of the RST are arranged successively nearby the bottom axis of the U-shaped structure of the pinned photodiode area and in the extended area. The large-size 4T APS for rapidly transferring charges is mainly used for designing and manufacturing pixel sensors.
Description
Technical field
The present invention relates to a kind of structure of 4T pixel of electric charge fast transfer, specifically, relate to the large scale four pipe CMOS active pixel sensor of electric charge fast transfer.
Background technology
Lasting reduction and cmos image sensor (CMOS Image Sensors along with the standard CMOS logic process, CIS) the continuous improvement of manufacturing process, cmos image sensor constantly bring into play its at aspects such as integration, power consumption, randow addressings the relative advantage to ccd image sensor, become the main flow device in solid state image sensor field.Four pipe active pixel (Pinned-Photodiode Four Transistors-Active Pixel Sensor based on clamp diode, PPD 4T-APS) have low-dark current, can eliminate the characteristics such as reset noise and low streaking, be the main dot structure that present CIS adopts.
The basic structure of PPD 4T-APS as shown in Figure 1, wherein 1 is P type substrate, 2 are clamp diode N district, 3 is surperficial clamper layer, 1-3 consists of clamp diode jointly, in order to collect the photoinduction electric charge; 4 and 6 are respectively the grid level of transfer tube TG and reset transistor RST, 5 is TG and the total source class of RST, be called again floating empty diffusion region (Floating Diffusion, FD), 7 is the leakage level of RST, VDD links to each other with the pixel supply voltage, and 4-7 consists of transfer tube TG and reset transistor RST jointly, in order to resetting of the transfer that realizes the photoinduction electric charge and clamp diode.The grid level of source class follower SF links to each other with FD, and drain electrode links to each other with VDD, and source class and gate tube SEL share, the leakage level of SEL and column bus (Column Bus, CB) link to each other, SF and SEL consist of the buffering reader of pixel jointly, the photovoltage signal of changing in order to read the photoinduction electric charge.In said structure, the photogenerated charge of collecting among the PD need to be transferred to FD after resetting through the transmission channel under the TG grid, impels FD voltage to change, and finally forms the photovoltage signal.
Before the PD exposure, need the electric charge of clamp diode N district (2) storage is transferred to FD node (6), should exhaust fully in the zone.Will cause larger random noise and image retention if can not realize shifting fully of electric charge.Because large scale pixel charge storage region is larger, distant with TG grid (4) easily the residual of electric charge occur at the middle part in clamp diode N district (2), the accumulation of electric charge especially occurs at the middle part in clamp diode N district (2).Reduce the doping content in clamp diode N district (2) and can improve the reduction that this problem still can cause the absorption efficiency of trap capacity and longwave optical with the degree of depth that reduces clamp diode N district (2).
Summary of the invention
The present invention is intended to solution and overcomes the deficiencies in the prior art, and it is residual that the efficient that the raising electric charge shifts reduces electric charge.For achieving the above object, the technical scheme that the present invention takes is, the large scale four pipe CMOS active pixel sensor of electric charge fast transfer, comprise clamp diode district, transfer tube TG and reset transistor RST, source class follower SF, gate tube SEL, clamp diode district and transfer tube TG grid are U-shaped structure, the dead in line of two U-shaped structures, opening are in the same way, transfer tube TG grid is arranged on the bottom of the U-shaped structure in clamp diode district, and transfer tube TG grid arranges with the base section of the U-shaped structure in clamp diode district overlapping; The clamp diode district prolongs the formation prolongation zone parallel with U-shaped structure two arms along the axis of U-shaped structure towards opening direction, reaches the prolongation zone and be disposed with the grid level of floating empty diffusion region FD, reset transistor RST, the leakage level of RST near the bottom axis of the U-shaped structure of diode region.
Two arms of the U-shaped structure in clamp diode district form H type structure towards U-shaped structural openings direction reverse extending; The U-shaped structure of transfer tube TG grid only keeps two arms, is symmetricly set on the middle whippletree of H type structure two ends, the controlled sequential Complete Synchronization of two arms that the U-shaped structure of transfer tube TG grid only keeps.
Technical characterstic of the present invention and effect:
Reduce the width in clamp diode district, be not easy to occur the accumulation of electric charge at middle part, clamp diode N district;
The length of TG grid increases, and electric charge is shifted to the FD node by a plurality of directions simultaneously, and because the average distance of clamp diode district and grid becomes near, and electric field action strengthens to some extent, the speed that electric charge shifts is improved;
Because reducing of clamp diode sector width, the scope of clamp diode N district's doping content and the degree of depth can appropriateness be relaxed, and the absorption efficiency of trap capacity and long wavelength light can be improved.
Description of drawings
Fig. 1 is 4T active pixel principle schematic.
Fig. 2 is conventional pixel structure vertical view.L among the figure
TGLong for grid, what refer to is exactly the length of the vertical direction of grid and source or drain region intersection.L
OLCrossover region length.
Fig. 3 is the dot structure vertical view of the present invention's the first example.
Fig. 4 is the dot structure vertical view of the present invention's the second example.
Fig. 5 is the image element circuit figure of the present invention's the second example.
Embodiment
Two parts that the present invention is adjusted into axisymmetric U-shaped structure or separates by the rectangle clamp diode zone with general large scale pixel are connected to the FD node by U-shaped TG grid or two TG grid.The average distance that is transferred to the TG grid by reducing electric charge in the clamp diode zone has improved efficient that electric charge shifts, and to have reduced electric charge residual.
As shown in Figure 2, the clamp diode of conventional pixel zone (1-3) generally is designed to rectangle.When the size of pixel increased, the distance of charge storage region and grid just relative change was far away, the accumulation of electric charge easily occurred at the middle part in rectangle clamp diode district.The shape in the clamp diode district (1-3) of the present invention by adjusting pixel shortens electric charge and is transferred to average distance with TG grid (4), makes the large scale pixel can realize electric charge transfer effect near small-sized pixel.
The embodiment of the invention 1: pixel knot top and the bottom full symmetric, the size of pixel is generally between 5 μ m * 5 μ m～15 μ m * 15 μ m.The clamp diode of this pixel zone (1-3) and TG grid all are U-shaped structure, and the length of TG grid (4) is generally between 0.5 μ m～2 μ m, and the overlapping region of clamp diode district (1-3) is between 0 μ m～0.5 μ m.The FD node, reset transistor RST, source follower, row select pipe to be positioned at the centre of pixel, are surrounded by U-shaped clamp diode district (1-3).
The embodiment of the invention 2: dot structure top and the bottom full symmetric, the size of pixel are generally between 5 μ m * 5 μ m～15 μ m * 15 μ m.The clamp diode zone (1-3) of this pixel is split up into two symmetrical parts, be positioned at FD node (5), reset transistor RST (6), source follower (9), row is selected the both sides of pipe SEL (11), is connected to FD node (5) by TG grid (4a) and TG grid (4b) respectively.The length of TG grid (4) is generally between 0.5 μ m～2 μ m, and the overlapping region of clamp diode district (1-3) is between 0 μ m～0.5 μ m.Wherein TG grid 4a controls with identical sequential with 4b.
The embodiment of the invention 1: the dot structure vertical view as shown in Figure 3, pixel is of a size of 10 μ m * 10 μ m; The clamp diode zone (1-3) of pixel is the U-shaped structure, and shape is symmetrical.TG grid (4) are positioned at the inboard in U-shaped clamp diode district (1-3), and TG grid (4) are similarly U-shaped structure, and the length of TG grid (4) is 0.7 μ m, with the overlapping region of clamp diode district (1-3) be 0.1 μ m.FD node (5), reset transistor RST (6), source follower (9), row select pipe SEL (11) to be positioned within the opening in U-shaped clamp diode zone (1-3).
The embodiment of the invention 2: the dot structure vertical view as shown in Figure 4, pixel is of a size of 10 μ m * 10 μ m; The clamp diode of pixel zone (1-3) is divided into (1-3a) of full symmetric and (1-3b) two parts; Clamp diode zone (1-3a) and (1-3b) independently TG grid 4a and 4b are connected to FD node (5) by two respectively; The length of TG grid (4) is 0.7 μ m, and the overlapping region of clamp diode district (1-3) is between the 0.1 μ m.FD node (5), reset transistor RST (6), source follower (9), row select pipe SEL (11) all be positioned at pixel clamp diode zone (1-3a) and (1-3b) between.The circuit structure diagram of this pixel as shown in Figure 5, TG grid (4a) connect together with TG grid (4b), by the transfer of same control signal control electric charge.
Claims (2)
1. the large scale four of an electric charge fast transfer is managed CMOS active pixel sensor, comprise clamp diode district, transfer tube TG and reset transistor RST, source class follower SF, gate tube SEL, it is characterized in that, clamp diode district and transfer tube TG grid are U-shaped structure, the dead in line of two U-shaped structures, opening are in the same way, transfer tube TG grid is arranged on the bottom of the U-shaped structure in clamp diode district, and transfer tube TG grid arranges with the base section of the U-shaped structure in clamp diode district overlapping; The clamp diode district prolongs the formation prolongation zone parallel with U-shaped structure two arms along the axis of U-shaped structure towards opening direction, reaches the prolongation zone and be disposed with the grid level of floating empty diffusion region FD, reset transistor RST, the leakage level of RST near the bottom axis of the U-shaped structure of diode region.
2. the large scale four pipe CMOS active pixel sensor of electric charge fast transfer as claimed in claim 1 is characterized in that, two arms of the U-shaped structure in clamp diode district form H type structure towards U-shaped structural openings direction reverse extending; The U-shaped structure of transfer tube TG grid only keeps two arms, is symmetricly set on the middle whippletree of H type structure two ends, the controlled sequential Complete Synchronization of two arms that the U-shaped structure of transfer tube TG grid only keeps.
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| CN2012101033681A CN102856332A (en) | 2012-04-10 | 2012-04-10 | Large-size four-transistor active pixel sensor (4T APS) for rapidly transferring charges |
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| CN2012101033681A CN102856332A (en) | 2012-04-10 | 2012-04-10 | Large-size four-transistor active pixel sensor (4T APS) for rapidly transferring charges |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108417593A (en) * | 2018-02-27 | 2018-08-17 | 上海集成电路研发中心有限公司 | Imaging sensor, dot structure and its control method |
| CN112331688A (en) * | 2020-11-04 | 2021-02-05 | 中国电子科技集团公司第四十四研究所 | CCD structure capable of simultaneously realizing large signal processing and high-frequency transfer |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6107655A (en) * | 1997-08-15 | 2000-08-22 | Eastman Kodak Company | Active pixel image sensor with shared amplifier read-out |
| CN1992316A (en) * | 2005-12-29 | 2007-07-04 | 东部电子股份有限公司 | CMOS image sensor |
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- 2012-04-10 CN CN2012101033681A patent/CN102856332A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6107655A (en) * | 1997-08-15 | 2000-08-22 | Eastman Kodak Company | Active pixel image sensor with shared amplifier read-out |
| CN1992316A (en) * | 2005-12-29 | 2007-07-04 | 东部电子股份有限公司 | CMOS image sensor |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108417593A (en) * | 2018-02-27 | 2018-08-17 | 上海集成电路研发中心有限公司 | Imaging sensor, dot structure and its control method |
| CN108417593B (en) * | 2018-02-27 | 2020-11-27 | 上海集成电路研发中心有限公司 | Image sensor, pixel structure and control method thereof |
| CN112331688A (en) * | 2020-11-04 | 2021-02-05 | 中国电子科技集团公司第四十四研究所 | CCD structure capable of simultaneously realizing large signal processing and high-frequency transfer |
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Application publication date: 20130102 |