(19) (12) EUROPEAN PATENT SPECIFICATION (11) EP 1 417 829 B1 (45) Date of publication and mention of the grant of the patent: 08.04.2009 Bulletin 2009/15 (21) Application number: 02751534.5 (22) Date of filing: 17.07.2002 (51) Int Cl.: H04N 1/19 (2006.01) H04N 3/15 (2006.01) H04N 9/04 (2006.01) (86) International application number: PCT/IB2002/003107 (87) International publication number: WO 2003/013126 (13.02.2003 Gazette 2003/07) (54) IMAGE RECORDING DEVICE WITH IMPROVED IMAGE STORAGE TRANSITION BILDAUFNAHMEGERÄT MIT VERBESSERTER BILDSPEICHERÜBERGABE DISPOSITIF D ENREGISTREMENT D IMAGES AVEC TRANSITION AMELIOREE DU STOCKAGE D IMAGES (84) Designated Contracting States: DE (30) Priority: 02.08.2001 EP 01202927 (43) Date of publication of application: 12.05.2004 Bulletin 2004/20 (73) Proprietor: DALSA CORPORATION Waterloo, Ontario N2V 2E9 (CA) (72) Inventors: BOSIERS, Jan, T., J. NL-5656 AA Eindhoven (NL) KLEIMANN, Agnes, C., M. NL-5656 AA Eindhoven (NL) (74) Representative: Smeets, Eugenius Theodorus J. M. c/o Octrooibureau Smeets, Poelhekkelaan 16 5644 TN Eindhoven (NL) (56) References cited: EP-A- 0 720 387 EP-A- 0 757 496 WO-A-98/17051 WO-A-99/62245 PEEK H L ET AL: "AN FT-CCD IMAGER WITH TRUE 2.4 X 2.4 MUM2 PIXELS IN DOUBLE MEMBRANEPOLY-SI TECHNOLOGY" INTERNATIONAL ELECTRON DEVICES MEETING 1996. TECHNICAL DIGEST.IEDM 96. SAN FRANCISCO, DEC. 8-11, 1996, INTERNATIONAL ELECTRON DEVICES MEETING (IEDM), NEW YORK, IEEE, US, 8 December 1996 (1996-12-08), pages 907-910, XP000753851 ISBN: 0-7803-3394-2 EP 1 417 829 B1 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). Printed by Jouve, 75001 PARIS (FR)
1 EP 1 417 829 B1 2 Description with reference to the annexed drawings, in which: [0001] An image recording device for application as a so-called Digital Still Camera is often provided with an FT-CCD (Frame Transfer-Charge Coupled Device) and usually requires a real-time preview mode, for example for an electronic viewfmder such as an LCD screen, a display on a television in accordance with the NTSC or PAL standard, or for camera functions such as horizontal and vertical automatic focusing. [0002] The invention relates to such an image recording device, comprising: - an image section with gates and with a number of picture elements (pixels) arranged in rows and columns; - a storage section with gates and with image storage elements arranged in rows and columns for (temporarily) at least partially storing charge absorbed by the pixels, wherein the charge is transferred to the storage elements; - a transition that is present between the image section and the storage section and a transition region that comprises the transition and parts of the image section and the storage section, and wherein the gates of the image section and the storage section outside the transition region have substantially the same length. [0003] Such an FT-CCD with a storage section of limited size is known, for example, from the international patent application WO 98/17051 (PCT/IB97/01201) that has been published on 23 April 1998. Although a charge dump is performed with a vertical overflow drain in this known image recording device, and a sampled image is thus transported to the storage section, the speed hereof is in need of improvement, while the further performance of the sensor, such as a high maximum charge value Qmax and a high frame shift frequency, must be retained and charge overflow must be avoided. [0004] According to the present invention, which has for its object to obviate the above problems, an imagerecording device of the kind mentioned in the opening paragraph is characterized that one or more gates in the transition region have a larger length than the gates outside the transition region. [0005] According to a further aspect of the present invention, the doping concentration below one or more gates in the transition region is modified with respect to the doping below the gates outside the transition region. [0006] As a result of the present invention, the dumping of charge during subsampling is facilitated, i.e. fewer problems occur at high speeds, while a charge overflow between charge packages is also avoided as much as possible at high speeds. [0007] Further advantages, features and details of the present invention will be elucidated on the basis of the following description of a preferred embodiment thereof 5 10 15 20 25 30 35 40 45 50 55 Fig. 1 is a diagrammatic view of a preferred embodiment of an image recording device according to the present invention; Fig. 2 is a diagrammatic view of a device as shown in Fig. 1 for the purpose of elucidating the operation thereof; Fig. 3 is a diagrammatic view of a possible preferred embodiment of the device shown in Figs. 1 and 2; Figs. 4A and 4B are diagrammatic views serving to explain the operation of the device shown in Figs. 1-3; and Figs. 5A and 5B are a view in cross-section and a plan view, respectively, of part of an image recording device according to the present invention in which the device according to the present invention can be applied. [0008] An image recording device 10 (Fig. 1) comprises a recording part 11 and a storage part 12, with a transition 13, diagrammatically indicated with a broken line, between the parts 11 and 12. Furthermore, a so-called horizontal read-out register 14 is connected to the recording part. [0009] The diagrammatic view of Fig. 2 further shows vertical channels 23 along which the charge can be transported from the recording part 11 to the storage part 12 in the direction of an arrow A. Four-phase driven electrodes A1 to A4 for gates arranged above channels 23 in the image recording area are connected to clock lines 24, 25, 26, and 27, respectively, while electrodes B1 to B4 in the storage area are connected to clock lines 28, 29, 30, 31, respectively. Clock lines 24 to 31 are driven from a diagrammatically indicated clock driving circuit 32. [0010] The present embodiment relates to a fourphase image recording device. In a practical embodiment, the recording part 11 comprises 1280 horizontal lines and 960 vertical channels, wherein the electrodes A1 to A4 are repeated in each case. The storage part 12 then has a smaller capacity of for instance 240 lines by 960 vertical channels, i.e. a notably smaller number of lines than the image recording part. [0011] As can be seen in Fig. 3, electrodes A1, A2, A3, A4, B1, B2, B3 B4, B1 forming the gates are arranged close to the transition 13 on an insulating layer 34 on the channels 23, under which a p-type layer 35 is provided on a substrate 36 which is brought to the desired voltage by a voltage source 37. Also shown in Fig. 3 is a diagrammatically indicated light-screening layer 38 which prevents light from penetrating into the storage part 12 and which is preferably integrated into the circuit in a manner not shown. [0012] In the embodiment shown in Fig. 3, the gates A2, A3, A4, A1, A2, A3, A4, B1, B2, B3, B4, B1 close to the transition 13 have the following lengths: A2=0.8 m 2
3 EP 1 417 829 B1 4 A3 = 0.8 m A4 = 0.8 m A1 = 1.0 m A2 = 1.2 m A3 = 2.4 m A4=1.0 m Bl==1.4 m B2=1.4 m B3=1.2 m B4=1.0 m B1 = 0.8 m whereas the other gates (not shown) further removed from the transition all have a length of about 0.8 m. [0013] The p-well at the transition was lower-doped, in the present embodiment by narrowing the implementation width under the last two image electrodes to 1.6 m, as opposed to 2.4 m at the other gates. [0014] In contrast to the diagram of Fig. 4A, in which six clock cycles are shown in a four-phase CCD at normal charge transport, the diagram of Fig. 4B shows the drive diagram in subsampling, wherein the surplus charge must be drained to the substrate at the third clock cycle and lateral leakage thereof must be avoided. At clock cycle t4 there remains only one blocking gate (A3) between the charge package that needs to be drained below A4 and the charge package of the pixel lying thereabove. At clock cycle t3 the maximum charge capacity amounts to, for example, only 30,000 electrons, whereas that at step t4 it is no more than 25,000 electrons. The surplus must also be drained rapidly to the substrate at clock cycle t4. [0015] Owing to the design of the lengths of the gates as described above, a practically symmetrical separation is sufficiently realized from both the previous charge package below A1 and A2 and the subsequent one below B3 and B4. [0016] As a result of the lower p-well doping and/or higher n-channel doping under the gate A4, and partially under the gates A3, B1 and B2, close to the transition, a lower barrier to the substrate and a higher channel potential are locally obtained. Dumping of charge is accelerated owing to the lower barrier. The higher channel potential avoids flowing away of any residual charge still present below A4 at the moment this just (dis)connects to a previous or subsequent charge package situated, for example, below gate A3 or B1 or B2. [0017] Simulations have shown that the above changes in p-well or n-channel doping and gate lengths avoid charge flowing away to the substrate in an undesired manner during normal transport or remaining behind owing to poor transport. [0018] Two-dimensional and three-dimensional effects also lead to better charge reset conditions below the relatively long "disconnected" gates close to the transition (A3 + A4 + B1 + B2 = 6.2 m). The charge package therebelow is enclosed by longer switched-on gates than below a package of gates of constant length wherein A3 5 10 15 20 25 30 35 40 45 50 55 + A4 + B 1 + B2 would amount to about 3.7 m. [0019] In the example of a four-phase pixel of Fig. 5A (shown in cross-section) and 5B (shown in plan view), in which the longer gates close to the transition in accordance with the above description are preferably used, further details of which are described in the article by H. Peek et al. An FT-CCD image with true 2.4 x 2.4 m 2 pixels in double membrane poly-si technology (IEDM 1996 pp. 35.3.1-4), four gates with a length of 0.9 m of polysilicon 52 are each situated on an insulating layer 51, while an n-channel 53 extends between two stop areas 54. A so-called profiled peristaltic implant 55 for enlarging the well, i.e. the charge capacity, is situated between the oxide layer and the n-channel, while a p-well 56 is situated on the n-substrate 57 under the n-channel 53. [0020] The present invention is not limited to the above preferred embodiments thereof; the rights sought are defined by the following claims, within the scope of which many modifications can be envisaged. Claims 1. An image recording device (10), comprising: - an image section (11) with gates (Ai) and a number of picture elements (pixels) arranged in rows and columns; - a storage section (12) with gates (Bi) and image storage elements arranged in rows and columns for (temporarily) at least partially storing charge absorbed by the pixels, wherein the charge is transferred to the storage elements; - a transition (13) that is present between the image section (11) and the storage section (12) and a transition region that comprises the transition (13) and parts of the image section (11) and the storage section (12), and wherein the gates (Ai,Bi) of the image section (11) and the storage section (12) outside the transition region have substantially the same length, characterized in that one or more gates (A1, A2,A3,A4, B1, B2, B3, B4) in the transition region have a larger length than the gates outside the transition region. 2. An image recording device as claimed in claim 1, characterized in that the first two gates (B1,B2) in the part of the transition region forming part of the storage section (12) have a length which is 50 % larger than the length of the gates (Bi) of the storage section (12) outside the transition region. 3. An image recording device as claimed in claim 1 or 2, characterized in that the second gate of a part of the transition region forming part of the image sec- 3
5 EP 1 417 829 B1 6 tion (11), as seen from the transition (13), has a length of approximately 2.5 to 3 times the length of a gate (Ai) of the image section (11) outside the transition region. 4. An image recording device as claimed in anyone of the preceding claims, characterized in that the doping below one or more gates (A4,A3,B1,B2) in the transition region is modified with respect to the doping below the gates (Ai,Bi) outside the transition region. 5. An image recording device as claimed in claim 4, characterized in that during operation of the device the channel potential obtained under one or more gates (A4,A3,B1,B2) in the transition region is higher than that obtained below the gates (Ai,Bi) outside the transition region. 6. An image recording device as claimed in claim 4 or 5, characterized in that the modified doping implies that the doping concentration below the one or more gates (A4,A3,B1,B2) in the transition region is lower than the doping concentration below the gates (Ai, Bi) outside the transition region. 7. An image recording device as claimed in claim 4 or 6, characterized in that the modified doping is characterized by a lower doping concentration constituted by a lowered doping. Patentansprüche 1. Bildaufzeichnungs-Bauelement (10), das Folgendes umfasst: - eine Bildsektion (11) mit Gates (Ai) und einer Anzahl von Bildelementen (Pixel), die in Zeilen und Spalten angeordnet sind; - eine Speichersektion (12) mit Gates (Bi) und Bildspeicherelementen, die in Zeilen und Spalten angeordnet sind, zum (vorübergehenden) mindestens teilweisen Speichern von Ladung, die durch die Pixel aufgenommen wurde, wobei die Ladung zu den Speicherelementen übertragen wird; - einen Übergang (13), der zwischen der Bildsektion (11) und der Speichersektion (12) vorhanden ist, und eine Übergangsregion, die den Übergang (13) und Teile der Bildsektion (11) und der Speichersektion (12) umfasst, und wobei die Gates (Ai, Bi) der Bildsektion (11) und der Speichersektion (12) außerhalb der Übergangsregion im Wesentlichen die gleiche Länge haben, dadurch gekennzeichnet, dass ein oder mehrere 5 10 15 20 25 30 35 40 45 50 55 Gates (A1, A2, A3, A4, B1, B2, B3, B4) in der Übergangsregion länger sind als die Gates außerhalb der Übergangsregion. 2. Bildaufzeichnungs-Bauelement nach Anspruch 1, dadurch gekennzeichnet, dass die ersten zwei Gates (B1, B2) in dem Teil der Übergangsregion, der einen Teil der Speichersektion (12) bildet, eine Länge haben, die 50 % größer ist als die Länge der Gates (Bi) der Speichersektion (12) außerhalb der Übergangsregion. 3. Bildaufzeichnungs-Bauelement nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das zweite Gates eines Teils der Übergangsregion, der einen Teil der Bildsektion (11) bildet, von dem Übergang (13) aus gesehen, eine Länge von ungefähr dem 2,5- bis 3-fachen der Länge eines Gates (Ai) der Bildsektion (11) außerhalb der Übergangsregion aufweist. 4. Bildaufzeichnungs-Bauelement nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass die Dotierung unter einem oder mehreren Gates (A4,A3, B1, B2) in der Übergangsregion im Vergleich zur Dotierung unter den Gates (Ai, Bi) außerhalb der Übergangsregion modifiziert ist. 5. Bildaufzeichnungs-Bauelement nach Anspruch 4, dadurch gekennzeichnet, dass während des Betriebes des Bauelements das Kanalpotenzial, das unter einem oder mehreren Gates (A4, A3, B1, B2) in der Übergangsregion erhalten wird, höher ist als das, was unter den Gates (Ai, Bi) außerhalb der Übergangsregion erhalten wird. 6. Bildaufzeichnungs-Bauelement nach Anspruch 4 oder 5, dadurch gekennzeichnet, dass die modifizierte Dotierung impliziert, dass die Dotierungskonzentration unter dem einen oder den mehreren Gates (A4, A3, B1, B2) in der Übergangsregion geringer ist als die Dotierungskonzentration unter den Gates (Ai, Bi) außerhalb der Übergangsregion. 7. Bildaufzeichnungs-Bauelement nach Anspruch 4 oder 6, dadurch gekennzeichnet, dass die modifizierte Dotierung durch eine geringere Dotierungskonzentration gekennzeichnet ist, die durch eine geringere Dotierung gebildet wird. Revendications 1. Dispositif d enregistrement d images (10), comprenant : - une section d image (11) avec des grilles (Ai) et une pluralité d éléments d image (pixels) 4
7 EP 1 417 829 B1 8 agencés en rangées et colonnes ; - une section de stockage (12) avec des grilles (Bi) et des éléments de stockage d image agencés en rangées et colonnes pour stocker au moins partiellement (temporairement) une charge absorbée par les pixels, dans lequel la charge est transférée aux éléments de stockage ; - une transition (13) qui est présente entre la section d image (11) et la section de stockage (12) et une région de transition qui comprend la transition (13) et des parties de la section d image (11) et de la section de stockage (12), et dans lequel les grilles (Ai,Bi) de la section d image (11) et de la section de stockage (12) en dehors de la région de transition ont substantiellement la même longueur, 5 10 15 de dopage en dessous des grilles (Ai,Bi) en dehors de la région de transition. 7. Dispositif d enregistrement d images selon la revendication 4 ou 6, caractérisé en ce que le dopage modifié est caractérisé par une concentration de dopage plus basse constituée par un dopage diminué. caractérisé en ce que une ou plusieurs des grilles (A1,A2,A3,A4,B1,B2,B3,B4) dans la région de transition ont une longueur plus grande que les grilles en dehors de la région de transition. 20 2. Dispositif d enregistrement d images selon la revendication 1, caractérisé en ce que les deux premières grilles (B1,B2) dans la partie de la région de transition faisant partie de la section de stockage (12) ont une longueur qui est 50% plus grande que la longueur des grilles (Bi) de la section de stockage (12) en dehors de la régions de transition. 3. Dispositif d enregistrement d images selon la revendication 1 ou 2, caractérisé en ce que la seconde grille d une partie de la région de transition faisant partie de la section d image (11), vue depuis la transition (13), a une longueur d approximativement 2,5 à 3 fois la longueur d une grilles (Ai) de la section d image (11) en dehors de la région de transition. 25 30 35 4. Dispositif d enregistrement d images selon une quelconque des revendications précédentes, caractérisé en ce que le dopage en dessous d une ou plusieurs grilles (A4,A3,B1,B2) dans la région de transition est modifié par rapport au dopage en dessous des grilles (Ai,Bi) en dehors de la région de transition. 5. Dispositif d enregistrement d images selon la revendication 4, caractérisé en ce que, pendant le fonctionnement du dispositif, le potentiel de canal obtenu sous une ou plusieurs grilles (A4,A3,B1,B2) dans la région de transition est plus grand que celui obtenu en dessous des grilles (Ai,Bi) en dehors de la région de transition. 40 45 50 6. Dispositif d enregistrement d images selon la revendication 4 ou 5, caractérisé en ce que le dopage modifié implique que la concentration de dopage en dessous de la ou des grilles (A4,A3,B1,B2) dans la région de transition soit inférieure à la concentration 55 5
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EP 1 417 829 B1 REFERENCES CITED IN THE DESCRIPTION This list of references cited by the applicant is for the reader s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard. Patent documents cited in the description WO 9817051 A [0003] WO IB9701201 A [0003] 10