JPH05130511A - Driving method for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To perform FIT transfer capable of performing smear suppression and to suppress blooming in a FIT transfer period even when an object with remarkably high luminance is image-picked up by increasing a substrate voltage in the FIT transfer period. CONSTITUTION:The voltage of a substrate 14 is set at a low level that is a constant driving voltage during a period 4 before a readout pulse 2 is applied. The chevron of potential of a P well 13 is set at a high state, and the saturation capacity of a photoelectric conversion part 6 goes to the maximum level. When the discharge pulse 1 of pseudo signal charge is applied, the pseudo signal charge that exists in a vertical transfer part 7 is transferred to a signal discharge part 11. Thence, when the pulse 2 is applied, the signal charge of the photoelectric conversion part 6 is read out to the vertical transfer part 7. Simultaneously with the application of a FIT transfer pulse 3, the voltage of the substrate 14 is increased higher than the driving voltage in a period other than that of the FIT transfer. The chevron of potential of the P well 13 goes to a low state, and the signal charge generated at the photoelectric conversion part 6 in the FIT transfer period is extracted to a substrate 14 side without generating overflow, therefore. no blooming occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a solid-state image pickup device, and more particularly to a measure for controlling a voltage applied to a substrate.

[0002]

2. Description of the Related Art Recently, in a solid-state image pickup device, one method for realizing high image quality is to provide a photoelectric conversion part, a vertical transfer part, a horizontal transfer part, a signal detection part, and a signal discharge part. The structure in which the storage part is provided is used. Therefore, the above-described solid-state imaging device will be described below with reference to the drawings.

First, as shown in FIG. 2, the basic structure of a solid-state image pickup device is such that a photoelectric conversion section 6, a vertical transfer section 7, and a storage section are provided in a P well 13 provided on an N-type substrate 14. 8
, Horizontal transfer unit 9, signal detection unit 10, and signal output unit 1
1 are formed. The arrow in FIG. 2 indicates the transfer direction of signal charges.

On the other hand, FIG. 4 shows a part of the conventional drive pulse and the voltage of the substrate 14. In this FIG.
(A) is a composite blanking signal, (b) is the vertical transfer unit 7
Pulse 1 (hereinafter referred to as sweep pulse 1) for transferring the false signal charge of the above to the signal discharge part 11, and pulse 2 for reading out the signal charge accumulated in the photoelectric conversion part 6 to the vertical transfer part 7.
(Hereinafter, referred to as read pulse 2) and photoelectric conversion 6
The pulse 3 for transferring the signal charge read from the vertical transfer unit 7 to the vertical transfer unit 7 (hereinafter, this transfer is referred to as FIT transfer,
Pulse 3 is called FIT transfer pulse 3. (C) shows the voltage of the substrate 14.

Therefore, a method of driving this solid-state image pickup device will be described.

First, the sweep pulse 1 is output during the vertical blanking period.
By the sweep pulse 1, the pseudo signal charges accumulated in the vertical transfer unit 7 during the FIT transfer period and the vertical scanning period are transferred to the signal discharging unit 11 and discharged. Next, the signal pulse is read from the photoelectric conversion unit 6 to the vertical transfer unit 7 by the read pulse 2. Then, the signal charges are transferred at high speed from the vertical transfer section 7 to the storage section 8 by the FIT transfer pulse 3.
The signal charges stored in the storage section 8 are sequentially transferred to the horizontal transfer section 9 one by one in the vertical scanning period, and are output from the signal detection section 10.

By this driving method, the transfer from the vertical transfer unit 7 to the storage unit 8 can be performed in a short time, and the charges generated by the light directly incident on the vertical transfer unit 7
That is, smear is greatly suppressed.

The voltage of the substrate 14 is higher than the potential of the transfer gate 12 between the photoelectric conversion unit 6 and the vertical transfer unit 7 as shown by the solid line in FIG.
It is set to a certain constant value such that the peak of the potential of the P well 13 between them becomes slightly lower. Thus, the substrate 14
By setting the voltage of 1 to a constant value, the supersaturated charges are extracted to the substrate 14 side without impairing the amount of signal saturated charges, forming a so-called vertical overflow drain.

[0009]

However, in the above-described method for driving the solid-state image pickup device, the voltage of the substrate 14 is always set to a constant value. Therefore, when an extremely high-luminance subject is imaged, the FIT transfer is performed. During the period, signal charges exceeding the saturation capacity of the photoelectric conversion unit 6 are generated, and the transfer gate 1 of FIG.
There has been a problem that a phenomenon in which charges overflow from the potential of 2 to the vertical transfer unit 7 (hereinafter, this phenomenon is referred to as blooming) occurs.

The present invention has been made in view of the above points, and an object of the present invention is to provide a driving method of a solid-state image pickup device capable of preventing blooming occurring during the FIT transfer period.

[0011]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the measures taken by the present invention are:
A pulse voltage higher than the period other than the T transfer period is applied to the substrate.

Specifically, in a semiconductor layer of opposite conductivity type provided on a semiconductor substrate of one conductivity type, a photoelectric conversion section, a vertical transfer section, a storage section, a horizontal transfer section, and a signal detection section. , A solid-state imaging device in which a signal discharging unit is formed.

A pulse higher than the constant drive voltage is applied during a FIT transfer period in which a constant drive voltage is applied to the substrate while the signal charges read from the photoelectric conversion unit to the vertical transfer unit are transferred to the storage unit. A voltage is applied to the substrate.

[0014]

With the above structure, in the present invention, the potential of the semiconductor layer is lowered during the FIT transfer period, and all signal charges exceeding the saturation capacity of the photoelectric conversion portion are swept out to the substrate side. As a result, blooming is suppressed even when capturing an extremely high-luminance subject.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, in the solid-state image pickup device, a photoelectric conversion section 6 and a vertical transfer section are provided in a P well 13 which is a semiconductor layer of opposite conductivity type provided on an N type substrate 14 of one conductivity type. 7, a storage unit 8, a horizontal transfer unit 9, and a signal detection unit 10
And a signal discharge part 11 are formed, and the arrow indicates the transfer direction of the signal charge.

On the other hand, FIG. 1 shows a part of the driving pulse of the solid-state image pickup device and the voltage of the substrate 14 in the embodiment of the present invention, (a) is a composite blanking signal, and (b) is. , Sweep pulse 1 for transferring the false signal charge of the vertical transfer unit 7 to the signal discharge unit 11, read pulse 2 for reading the signal charge accumulated in the photoelectric conversion unit 6 to the vertical transfer unit 7, and vertical transfer from the photoelectric conversion 6 The signal charge read to the unit 7 is stored in the storage unit 8.
Transfer pulse consisting of FIT transfer pulse 3 for transfer to
(C) shows the voltage of the substrate 14.

Next, a method of driving the solid-state image pickup device configured as described above will be described below together with its operation.

First, during the period 4 until the read pulse 2 is applied, the voltage of the substrate 14 is set to a low level which is a constant drive voltage. In this state, as shown in FIG. 3, the peak of the potential of the P well 13 is in a high state as shown by the solid line, and the saturation capacity of the photoelectric conversion unit 6 is maximized.

On the other hand, when the sweep-out pulse 1 of the false signal charge is applied, the false signal charge existing in the vertical transfer section 7 is transferred to the signal discharging section 11. Next, when the read pulse 2 is applied, the signal charge of the photoelectric conversion unit 6 is read to the vertical transfer unit 7.

Then, at the same time that the FIT transfer pulse 3 is applied, the voltage of the substrate 14 is made higher than the drive voltage of the substrate 14 in the period other than the FIT transfer period (see (c) in FIG. 1). Then, in this state, as shown in FIG.
As shown in FIG. 5, the potential peak of the P well 13 is in a low state as shown by the broken line, and the signal charges generated in the photoelectric conversion unit 6 during the FIT transfer period do not overflow into the vertical transfer unit 7 and the substrate 14 side. Blooming does not occur because it is pulled out to.

Thereafter, the signal charges stored in the storage section 8 are sequentially transferred to the horizontal transfer section 9 one by one in the vertical scanning period, and output from the signal detection section 10.

During the period 5 for accumulating the signal charge used for the image, the voltage of the substrate 14 is set to the low level, and the peak of the potential of the P well 13 is as shown by the solid line in FIG. Therefore, the dynamic range is not impaired.

[0024]

As described above, according to the present invention, the FIT
Since the substrate voltage is increased during the transfer period, FIT transfer capable of suppressing smear can be performed, and at the same time, even when an extremely high-luminance object is imaged,
Since the occurrence of blooming during the FIT transfer period can be suppressed, its practical effect is great.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a drive pulse and a substrate voltage of a solid-state imaging device of the present invention.

FIG. 2 is a configuration diagram of a solid-state imaging device.

FIG. 3 is a characteristic diagram of a potential near a photoelectric conversion unit, a vertical transfer unit, and a P well.

FIG. 4 is a waveform diagram showing drive pulses and substrate voltage of a conventional solid-state imaging device.

[Explanation of symbols]

 1 Sweeping pulse 2 Readout pulse 3 FIT transfer pulse 6 Photoelectric conversion unit 7 Vertical transfer unit 8 Storage unit 9 Horizontal transfer unit 10 Signal detection unit 11 Signal discharge unit 12 Transfer gate 13 P well 14 Substrate

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location H01L 29/796 (72) Inventor Toshihide Nobusada 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electronics Industrial Co., Ltd. (72) Inventor Yasuyuki Toyota, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electronics Industrial Co., Ltd. 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electronics Industrial Co., Ltd.

Claims (1)

[Claims] 1. A photoelectric conversion part, a vertical transfer part, a storage part, a horizontal transfer part, a signal detection part, and a signal in a semiconductor layer of the opposite conductivity type provided on a semiconductor substrate of one conductivity type. In the solid-state imaging device in which the discharge unit is formed, a constant drive voltage is applied to the substrate, and the constant charge is transferred during the FIT transfer period in which the signal charge read from the photoelectric conversion unit to the vertical transfer unit is transferred to the storage unit. A driving method for a solid-state imaging device, which comprises applying a pulse voltage higher than the driving voltage to the substrate.