JP2624334B2 - Driving method of solid-state imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a driving method of a solid-state imaging device.

2. Description of the Related Art In recent years, the development of solid-state imaging devices has progressed, and some of them are comparable or superior to imaging tubes in terms of performance. Among them, the inter-line transfer type CCD solid-state imaging device (hereinafter referred to as IT-CCD)
Abbreviations) have particularly excellent properties and have been put to practical use.

Hereinafter, a conventional configuration of an IT-CCD will be described with reference to the drawings.

FIG. 3 is an overall configuration diagram of the IT-CCD. In FIG. 3, 1 is a photoelectric conversion element, 2 is a vertical CCD (hereinafter abbreviated as VCCD) for vertically transferring signal charges stored in the photoelectric conversion element 1, and 3 is a signal for transferring signal charges transferred by VCCD2 in a horizontal direction. Transfer CCD (hereinafter abbreviated as HCCD) to transfer to 4
An output amplifier that detects the signal charge transferred by D3,
It is.

FIG. 4 is an enlarged view of a broken line portion A in FIG. In this figure, the light shielding film is omitted. 5 after reading from the photoelectric conversion element 1 a charge transfer electrode of VCCD 2, the transfer electrodes applied with phi ₁ pulse to be transferred, the transfer electrodes applied with phi ₂ pulses to perform only transfer 6, 7 applied with phi ₁ pulse transfer electrodes transfer electrodes, applied the phi ₃ pulses having the same role as 8 transfer electrodes applied with phi ₄ pulses to perform only the transfer, the or between the photoelectric conversion element 1 9, be a separation region separating between VCCD2 the photoelectric conversion element The P-type layer has a high concentration in order to ensure separation. In the solid-state imaging device driven by the field mode, the charge generated in the photoelectric conversion element 1 is read out from the photoelectric conversion element 1 to the VCCD 2 by the transfer electrodes 5 and 7, and is transferred to the transfer electrodes 5, 6,.
After the electric charges of two adjacent photoelectric conversion elements 1 are mixed as a pair by 7, 8, the transfer is performed by the transfer electrodes 5, 6, 7, and 8.

FIG. 5 is a sectional view taken along the line B-C in FIG. 10 is an n-type layer of a substrate, 11 is an n-type layer of a photoelectric conversion element, 12 is an n-type layer of VCCD, 13 is a separate P-type layer, 14 is a depletion layer of VCCD, 15 is generated charge, and 16 is a light shielding film. , 17 is light.

The region sandwiched between the n-type layer 11 of the photoelectric conversion element and the n-type layer 12 of the VCCD is used to transfer electric charges at a low voltage from the n-type layer 11 of the photoelectric conversion element.
It has a low concentration so that it can be read out to the n-type layer 12 of VCCD. Therefore, when the high voltage applied to the transfer electrode 5 applied with phi ₁ pulse, the depletion layer 14 of VCCD is spread in the region, generating charge 15 by the light 17 which is incident is likely to enter the n-type layer 12 of VCCD, thus smear This leads to an increase in the signal. In order to eliminate this, among the transfer pulses of the VCCD, the transfer electrodes 5 and 7, which have the role of reading out the charge from the n-type layer 11 of the photoelectric conversion element to the n-type layer 12 of the VCCD, are low during most of the transfer pulse period. The voltage is applied.

FIG. 6 is a drive timing chart of the solid-state imaging device. φ
₅ is a vertical blanking pulse. 18 is the vertical blanking period, 19 is the effective scanning period, 20 is the photoelectric conversion element 1
A read pulse for reading charges to VCCD2, and 21 is a transfer pulse amplitude for transferring charges. The charge generated in the photoelectric conversion element 1 is read out to the VCCD 2 by the readout pulse 20 during the vertical blanking period 18 and is transferred by the transfer pulse amplitude 21. phi ₁ and phi ₃ of applied pulses, in order to prevent an increase of the smear suppressing a depletion layer expands in the VCCD, effective scanning period
Most of the period of 19 is a low-level potential.

FIG. 7 is a pulse timing chart applied to the transfer electrodes during the vertical blanking period 18 in FIG. t ₁ , t ₂ , t ₃ , t ₄ , and t ₅ each indicate time.

FIG. 8 is a sectional potential diagram between D and E in FIG. 4 at each time in FIG. 22 is a charge. potential diagram t ₁ shows a state after the charge 22 is read out from the photoelectric conversion element 1 to VCCD2 by the transfer electrode 5 applied with phi ₁ pulse. potential of t ₂ further shows a state after the charge from the photoelectric conversion element 1 to the VCCD 2 22 is read by the transfer electrode 7 applied the phi ₃ pulses. potential t ₃ diagram illustrates how the charge 22 under the transfer electrode 5 when the field mode drive 7 are mixed. potential diagram t ₄ shows a state in which prevented the increase of the smear to the transfer electrodes 5 and 7 to the Low level. potential diagram t ₅ illustrates how the transfer electrodes 8 becomes a High level potential. At this time, as can be seen from FIG. 4, since both sides of the transfer electrode 8 are the separation regions 9 having a high concentration, even if the transfer electrode 8 becomes the high level potential, the VCCD is transferred to the photoelectric conversion element 1 side. The depletion layer 14 does not spread and there is no large increase in smear.

However, in the above configuration, the charge 22 is φ ₂
Accumulated only under the transfer electrode 6 to which the pulse is applied,
Under the transfer electrodes 8 exerted a phi ₄ pulse has a state where there is no electric charge 22, capacity to transfer the charges of VCCD2 is, capacity to transfer the charges of VCCD2 for thus determined only by the capacity of the transfer electrodes 6 It will be smaller.

Means for Solving the Problems In order to solve the above problems, a method for driving a solid-state imaging device according to the present invention reads a plurality of photoelectric conversion elements arranged in a matrix and electric charges generated in the photoelectric conversion elements, In a solid-state imaging device including a transfer unit having a plurality of transfer electrodes for transferring, a driving method has a period in which a charge serving as one output signal is divided and accumulated below the transfer electrode.

Operation With this configuration, it is possible to increase the capacity that can be accumulated in the transfer unit by dividing and accumulating the charge serving as one output signal under a number of transfer electrodes of the transfer unit.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a pulse timing chart applied to a transfer electrode during a vertical blanking period in an embodiment of the present invention. Time t _6, the pulse timing at t _7, t ₈ is the same as t _1, t _2, t ₃ of a conventional pulse timing diagram of Figure 7, t _9, t
_At the pulse timing of ₁₀ , t ₁₁ ,
It is divided and accumulated under one transfer electrode.

FIG. 2 is a sectional potential diagram under the transfer electrode at each time of FIG. The potential diagrams up to t ₆ , t ₇ and t ₈ are the same as the potential diagrams at t ₁ , t ₂ and t _{3 in} the potential diagram of FIG. According to t ₉ and t ₁₀ , at the time of t ₈ , the transfer electrodes 5, 6,
The electric charge 22 accumulated under 7 is transferred to below the transfer electrodes 6, 7, 8. Thereafter, the time t _11, the transfer electrode 7 to prevent the increase of the smear becomes the Low level potential, divides the charge as a single signal that has been the case accumulated into two transfer electrodes 6 and 8 Can be accumulated.

Effect of the Invention As described above, according to the present invention, once a charge output as one signal is transferred, the transfer electrode performing the read transfer is set to the low-level potential, and divided below the two transfer electrodes performing the transfer. This is the timing of the transfer electrodes that can be accumulated and stored, so that an increase in smear can be prevented and the capacity of the charges that can be transferred by the vertical transfer unit can be increased, and the practical effect is large.

[Brief description of the drawings]

FIG. 1 is a pulse timing chart applied to a transfer electrode during a vertical blanking period in an embodiment of the present invention, and FIG.
Sectional potential diagram under the transfer electrode at each time in the figure,
3 is an overall configuration diagram of the IT-CCD, FIG. 4 is an enlarged view of a broken line portion A in FIG. 3, FIG. 5 is a cross-sectional view between B and C in FIG. 4, and FIG. FIG. 7 is a drive timing chart of FIG.
FIG. 8 is a timing chart of the pulse applied to the transfer electrode during the vertical blanking period shown in FIG.
It is sectional electric potential diagram between -E. 1 ... photoelectric conversion element, 2 ... vertical transfer CCD (VCCD), 3
…… horizontal transfer CCD (HCCD), 4 …… Output amplifier section, 5…
... Transfer electrode to which φ ₁ pulse is applied, 6... Transfer electrode to which φ ₂ pulse is applied, 7... Transfer electrode to which φ ₃ pulse is applied, 8
...... phi ₄ pulses applied transfer electrodes 9 ...... isolation region 10
... n-type layer of substrate, 11 ... n-type layer of photoelectric conversion element, 12 ...
... n-type layer of VCCD, 13 ... p-type layer of isolation, 14 ... depletion layer of VCCD, 15 ... generated charge, 16 ... light shielding film, 17 ... light, 18 ...
... vertical blanking period, 19 ... effective scanning period, 20 ...
Read pulse, 21: transfer pulse amplitude, 22: electric charge.

Claims (2)

(57) [Claims] A plurality of photoelectric conversion elements arranged in a matrix and signal charges stored in the photoelectric conversion elements are read;
In the method for driving a solid-state imaging device including a transfer unit having a plurality of transfer electrodes for transferring, each signal charge stored in an adjacent photoelectric conversion element is read out by the transfer electrode and then mixed under the transfer electrode. A period in which the mixed charge is divided and accumulated under a plurality of transfer electrodes other than the transfer electrode used for reading out the signal charge. Method. 2. A photoelectric conversion unit in which first and second photoelectric conversion elements adjacent to each other in a column direction are arranged two-dimensionally, and a plurality of signal transfer units for vertically transferring signal charges accumulated in the photoelectric conversion unit. A vertical transfer unit having a transfer electrode, wherein a first transfer electrode and a second transfer electrode are arranged among the plurality of transfer electrodes in correspondence with the first photoelectric conversion element; A third transfer electrode and a fourth transfer electrode arranged corresponding to the conversion element, and a third transfer electrode arranged so as to be adjacent to the second transfer electrode; An electrode for reading and transferring a signal charge from each of the first and second photoelectric conversion elements; and a second and fourth transfer electrode for driving the solid-state imaging device that transfers the signal charge. From the second photoelectric conversion element to below the first and third transfer electrodes respectively Reading the first and second signal charges, and then mixing the first and second signal charges under the first, second and third transfer electrodes to form a mixed charge; Driving the solid-state imaging device having a period in which the mixed charge is divided and stored under the second and fourth transfer electrodes after being transferred under the second, third, and fourth transfer electrodes. Method.