JPH02164185A - Drive method for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To keep a sweep out time of an undesired charge within a vertical blanking period by adopting the drive method that there exists a processing period in which all transfer voltage waveforms applied to a transfer electrode of a transfer section are of the same polarity at the same time. CONSTITUTION:When clocks phi1, phi2 are of the same potential, a potential well generated in an HCCD 3 has only a potential due to the density difference of n-channel impurity from under the electrode in the HCCD. The electrode overflowed from the HCCD flows to a diffusion layer 5 naturally at the HCCD or a diffusion layer 8 of an output amplifier section with diffusion when the maximum potential under an IG gate 9 or an OG gate 10 is selected to be the maximum potential under each electrode of the HCCD 3. The speed of natural diffusion of the electric charge is sufficiently faster than the speed carrying the electric charge by the drive of the HCCD 3, then the overflowed charge is diffused naturally at the outside of HCCD momentarily. Thus, the undesired charge is all swept out to the HCCD within the vertical blanking period T.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for driving 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 to or even superior to image pickup tubes in terms of performance.

Among them, an interline transfer type COD solid-state imaging device (hereinafter abbreviated as IT-COD) has particularly excellent characteristics and has been put into practical use.

Hereinafter, the conventional configuration of IT-COD 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) that vertically transfers the signal charge accumulated in the photoelectric conversion element 1, and 3 is a horizontal CCD that transfers the signal charge transferred by VCCD 2. horizontal transfer CCD (hereinafter H
(abbreviated as CCD), 4 is an output amplifier section that detects the signal charge transferred by HCCD 3, and 5 is an HCC that serves as a drain to sweep out unnecessary charges overflowing from the HCCD.
This is the diffusion layer at the D end.

FIG. 4 is a conventional pulse timing diagram.

φ1 and φ2 are drive pulses for the two-phase drive HCCD, and φ3 is a vertical blanking pulse. TI is one field period, T2 is valid period, T3 is vertical blanking period, T4
is part of the HCOD drive pulse. Among the charges generated by the photodiode, the signal charge is transferred to T2 by VCCD.
The unnecessary charge is taken out to the HCCD 3 during the period T3, and the unnecessary charge is taken out to the HCCD 3 during the period T3. The charge taken out to the HCCD is read out from the output amplifier by pulses φ1 and φ2.

FIG. 5 is an enlarged view of the period T4 in FIG. 4.

In the case of a two-phase drive HCCD, φI and φ2 are in opposite phases to each other.

FIG. 6 is a cross-sectional view between A-A' in FIG. 3 and t in FIG.
It is a potential diagram at time l. (a) is a sectional view. 6 is the diffusion layer of the HCCD transfer channel, 7 is the HCC
Transfer electrode D, 8 is a diffusion layer of the output amplifier section, 9 is an output electrode that separates the diffusion layer 8 of the output amplifier section and the HCCD 3 (hereinafter abbreviated as ○G gate), 10 is the diffusion layer 8 of the HCCD 3 and the end of the HCCD. This is a shielding input electrode (hereinafter abbreviated as IG gate).

V+, V2, V3, V4, φl, and φ2 are voltages applied to each electrode or diffusion layer.

(b) is a potential diagram within the semiconductor in the region shown in (a). This potential diagram is a potential diagram at time tl in Figure 5, with a predetermined voltage applied to V, tV2V, , V, a high pulse voltage applied to φ1, and a low pulse voltage applied to φ2. There is. 11 is the charge in the potential well within the HCCDS. In the case of this two-phase drive HCCD, as shown in (b), the charges stored in the well under one electrode are sequentially taken out as one unit to the diffusion layer 8 of the output amplifier section.

FIG. 7 is a cross-sectional view and a potential diagram during the vertical blanking period T3. (a) is a cross-sectional view, and (b) is a potential diagram, in which a large amount of unnecessary charge is injected from the VCCD 2 to the HCCD 3. 12 is HCCD
This is the charge overflowing from 3.

Among the large amount of charge injected from VCCD2, HCCD
The charge 12 overflowing from the
Alternatively, it diffuses into the diffusion layer 5 at the edge of the HCCD and flows out, but most of it remains in the potential well created by the potentials of φ1 and φ2.

The charges in the potential well are transferred to the diffusion layer 7 of the output amplifier by driving the HCCD 3 during the vertical blanking period T3.
swept away.

Problems to be Solved by the Invention However, in the above configuration, a large amount of charge remaining in the potential well during the vertical blanking period is as shown in FIG.
As shown in b), since the amount of charge that can be carried out per time is limited, it takes a long time to sweep out all the unnecessary charges remaining in the HCCDS. Therefore, the vertical blanking period T is shorter than the effective period T2.
3, some of the unnecessary charges will enter the valid period T2, and a false signal due to the unnecessary charges will be generated on the monitor screen.

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 transfers charges generated in the photoelectric conversion elements to a plurality of photoelectric conversion elements arranged in a matrix. Among the charges generated in the photoelectric conversion element in a solid-state imaging device equipped with a transfer section, unnecessary charges that do not become signal charges are swept out in one transfer direction or in a direction opposite to the one transfer direction using the transfer section. In this case, the driving method has a predetermined period in which all the transfer voltage waveforms applied to the transfer electrodes of the transfer section have polarities in the same direction at the same time.

Effect: With this configuration, most of the unnecessary charges within HCCDa overflow from HCCD3 and are quickly swept out of HCCDa by natural diffusion of electrons.

The charge remaining in the HCCDS is only the charge 11 in the potential well generated due to the difference in the concentration of n-type impurities in the HCCDS, and since the amount of charge is small, the vertical blanking period Since the length can be shortened to fit within the range, false signals due to unnecessary charges can be prevented from appearing on the monitor screen.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a drive timing chart in an embodiment of the present invention. T5 is the HCCD drive pulse φ! ,φ2
T6 is a period in which both the HCCD and the HCCD have the same potential, and the unnecessary charge remaining in the HCCD is swept out of the HCCD by driving the HCCD.

During periods φI and φ2 of T5, the DC potential is equal to the low potential of the drive pulse of the HCCD 3. During the period T6, φ1 and φ2 are in opposite phases to each other like the valid period T2, and unnecessary charges remaining in the HCCDa are swept out to the diffusion layer 8 of the output amplifier section by driving the HCCD3.

FIG. 2 is a sectional view and a potential diagram of the period T5 in FIG. 1. T5 period φ! When and φ2 become the same potential, H
The potential well generated in the CCDS is only the potential due to the difference in concentration of n-type impurities under the electrodes in the HCCD. Therefore, the amount of charge 11 in the potential well decreases, and most of it becomes charge 12 overflowing from the HCOD. H
The charge 13 overflowing from the CCD is sent to the IG gate 9 or O
If the maximum potential under the G gate 10 is set higher than the maximum potential under each electrode of the HCCD 3, the diffusion layer 8 of the output amplifier section or the diffusion layer 5 at the end of the HCCD, which has a higher potential than the potential inside the HCCD 3, naturally diffuses and flows out. Since the speed at which charges naturally diffuse is sufficiently faster than the speed at which charges are transported by driving the HCCD 3, the charge 12 overflowing from the HCCD, which accounts for most of the unnecessary charges in the HCCD 3, spontaneously diffuses outside the HCCD in an instant. . At this time, HCC
Since the charge 11 in the potential well, which is the unnecessary charge remaining in D, is small, the period T6 during which the unnecessary charge is swept out of the HCCD by driving the HCCD can be extremely shortened. Therefore, since all unnecessary charges can be swept out of the HCCD within the vertical blanking period T3, the effective period T
No unnecessary charge is mixed into the signal output to 2,
It can prevent false signals appearing on the monitor screen.

In FIG. 2, during the period T5 in which the HCCD drive pulses φ1φ2 are both at the same potential, φ1 and φ2 are both at the HCCD3.
The DC potential is equal to the low potential of the drive pulse of the HCOD, but in this case, the potential inside the semiconductor under the transfer electrode 6 of the HCOD is low, so the unnecessary charge transferred from the VCCD2 is transferred to the VCCD2 side. It may also flow backwards. Therefore, setting both the periods φ1 and φ2 of T5 to a high potential of the drive pulse of the HCCD 3 is more effective in preventing the backflow of charges to the VCCD 2. At this time, the maximum potential below the IG gate 9 or OG gate 10 needs to be higher than the maximum potential below each electrode of the HCCD 3.

Further, although both φ■ and φ2 are at DC potential during the period Tr in FIG. 2, the same effect can be obtained even if φ1 and φ2 are pulses in the same phase.

In the embodiment of the present invention, the unnecessary charges that have entered the HCCD3 are swept out of the HCCDS, but the VC
Even when unnecessary charges that have entered the CD2 are swept out of the VCCDZ, by making the potential of the transfer electrode of the VCCD2 similar to that of the electrode of the HCCD3, the period during which unnecessary charges are swept out of the VCCD2 can be shortened. For example, VCCD
This is extremely effective when sweeping out smear signals in the 2nd drive or sweeping out unnecessary charges when driving an electronic shutter.

Effects of the Invention As described above, the present invention eliminates most of the unnecessary charges that have entered the HCCD 3 by providing a period T5 in which the drive pulses φ1 and φ2 of the HCCD 3 are both at the same potential within the vertical blanking period T3. Charge 1 overflowing from HCCD3
It can be done with 2.

The charge 12 overflowing from the HCCD 3 is transferred to H using the principle that charge naturally diffuses from a low potential to a high potential.
By quickly sweeping out unnecessary charges to a region with a higher potential than the CCD 3, the period during which unnecessary charges are swept out can be kept within the vertical blanking period, which has a great practical effect.

[Brief explanation of the drawing]

Fig. 1 is a drive timing diagram in an embodiment of the present invention, Fig. 2 is a sectional view and potential diagram during the period T5 in Fig. 1, Fig. 3 is an overall configuration diagram of the IT-CCD, and Fig. 4 is a diagram of the conventional 5 is an enlarged view of the period T4 in FIG. 4, FIG. 6 is a sectional view and potential diagram of FIG. 3, and FIG. 7 is a sectional view of the vertical blanking period. 1...Photoelectric conversion element, 2...Vertical transfer C0D (VCCD), 3-...-Horizontal transfer CCD
(HCCD), 4... Output amplifier section, 5...
... Diffusion layer at the end of HCCD, 6 ... Diffusion layer of transfer channel of HCCD, 7 ... Transfer electrode of HCCD, 8 ... Diffusion layer of output amplifier section, 9...
...Output electrode (OG gate), 10...Input electrode (IG agate, II...Charge in the potential well in the HCCD, 12...Overflowing from the HCCD charge.

Claims (3)

[Claims] (1) In a solid-state imaging device including a plurality of photoelectric conversion elements arranged in a matrix and a transfer section that transfers charges generated by the photoelectric conversion elements, the charges generated by the photoelectric conversion elements are transferred to the transfer section. When sweeping in one transfer direction or in a direction opposite to the one transfer direction using A driving method for a solid-state imaging device. (2) All of the transfer voltage waveforms applied to the transfer electrodes are simultaneously
2. The method of driving a solid-state imaging device according to claim 1, wherein the signal charge has a predetermined period in which the potential has a high polarity. (3) If there is a separation electrode between the area where the charges swept out using the transfer electrode are collected and the electrode at the end in one transfer direction or the electrode at the end in the opposite direction to the transfer direction, the transfer electrode The separation electrode has a voltage such that the maximum potential under the separation electrode is equal to or higher than the maximum potential under each of the transfer electrodes during a predetermined period in which all of the transfer voltage waveforms applied to the transfer voltage waveforms have polarities in the same direction at the same time. Characteristic claim 1
A method for driving a solid-state imaging device according to section 1.