JPH05235318A - Solid-state image pickup device and its driving method - Google Patents

Abstract

PURPOSE:To perform the transfer of signal charge at low voltage and at high speed and prevent a transfer electrode from leaving signal charge. CONSTITUTION:The horizontal charge transfer part made on a silicon substrate 3 has six pieces of transfer charges 1a and 1b in its one repeat unit, and the distribution of impurities inside the semiconductor substrate 3 below the odd transfer electrodes 1b among these transfer electrodes is different from that of the impurities inside the semiconductor substrate 3 below the even transfer electrodes 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device and a driving method thereof.

[0002]

2. Description of the Related Art In recent years, solid-state image pickup devices have rapidly spread in place of image pickup tubes for both industrial and home use, and there is a strong demand for their size and weight reduction.

A drawing of a conventional solid-state image pickup device will be described below.
Will be described with reference to. Figure 3 (a) shows conventional solid-state imaging.
FIG. 3B is a schematic cross-sectional view of the main part of the horizontal charge transfer portion of the device.
Pulse voltage was applied to each electrode in the same solid-state imaging device
Figure 3 (c) is a potential diagram when applied to each electrode
It is a waveform diagram of a pulse voltage. In these figures, 1
a and 1b transfer the signal charges formed by the polycrystalline silicon film.
It is a transfer electrode for sending. The transfer electrodes 1a and 1b
Is each electrode per horizontal pitch_H1, Ф_H21 for each
A total of four are arranged. 2 is an insulating film, 3 is a film
The silicon substrate 4 and the silicon substrate 3 have the same conductivity type as the silicon substrate 3.
Pure layer, Ф_H1, Ф_H2Is a pulse voltage transfer electrode 1a, 1b
It is an electrode for applying to. Electrode Φ_H1, Ф_H2To Figure 3
When a pulse voltage as shown in (c) is applied, time t =
t₁ In case of, the potential shape on the upper side of FIG.
And the signal charge is_H2Under the transfer electrode 1b of the first layer of
To be distributed. Next time t = t₂ At the bottom of Fig. 3 (b)
Side potential shape, and the electrode Φ_H2First layer transfer
The signal charge distributed under the electrode 1b is _H1One layer
It moves under the eye transfer electrode 1a and is distributed. like this
By repeating the operation, the signal charge is transferred to the output section.
To send. By adopting the horizontal two-layer drive system as described above
Therefore, the drive circuit of the horizontal charge transfer unit can be simplified, and solid-state imaging is possible.
The device is compact and lightweight.

[0004]

However, in the above-mentioned conventional structure, the horizontal charge transfer portion is provided with four transfer electrodes at one horizontal pitch. For example, when one horizontal pitch is 10 μm, about 2 transfer electrodes are provided. Although it is designed to have a length of 0.5 μm, such a long transfer electrode has a problem that the required transfer efficiency cannot be realized with a low voltage swing when horizontal charge transfer is performed at high speed.

That is, when the transfer electrodes 1a and 1b are formed on the silicon substrate 3 via the insulating film as shown in FIG. 4A, a low voltage swing as shown in FIG. This is because the fringing field is weak at the center of the transfer electrode 1a, and the signal charges are left behind in that portion.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a solid-state image pickup device capable of transferring signal charges at high speed with a low voltage pulse, and a driving method thereof.

[0007]

In order to achieve this object, the solid-state image pickup device of the present invention has six or more transfer electrodes arranged in one horizontal pitch of the horizontal charge transfer section, and transfers each one. It has a configuration in which the electrodes are shortened.

[0008]

With this structure, a strong fringing field can be obtained in the central portion of the transfer electrode even when driven at a low voltage, and as a result, a solid-state image pickup device with high transfer efficiency can be realized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a schematic cross-sectional view of a main part of a horizontal charge transfer portion of a solid-state imaging device according to an embodiment of the present invention,
FIG. 1B is a potential diagram when a pulse voltage is applied to each electrode in the solid-state imaging device, and FIG. 1C is a waveform diagram of the pulse voltage applied to each electrode. In these figures, the same parts as those of the conventional example shown in FIG. Φ _H1 , Φ _H2 , and Φ _H3 are electrodes for applying a pulse voltage to the transfer electrodes 1a and 1b.
As shown in FIG. 1A, one transfer electrode 1a and one transfer electrode 1b are provided for each electrode Φ _H1 , Φ _H2 , and Φ _H3 per horizontal pitch.
A total of 6 are arranged. These three electrodes Φ _H1 , Φ _H2 ,
The pulse voltage and DC voltage shown in FIG. 1C are applied to Φ _H3 . At time t = t ₁ , the signal charge is distributed under the transfer electrode 1b of the first layer of Φ _H1 , and at time t = t ₂ , it is moved under the transfer electrode 1a of the first layer of Φ _H3 and distributed. To do.
By repeating this operation, the signal charges are guided to the output section.

Next, a solid-state image pickup device according to a second embodiment of the present invention will be described with reference to the drawings. Figure 2
FIG. 2A is a schematic cross-sectional view of a main part of a horizontal charge transfer portion of a solid-state imaging device according to a second embodiment of the present invention, and FIG. 2B is a potential when a pulse voltage is applied to each electrode in the solid-state imaging device. FIG. 2C is a waveform diagram of the pulse voltage applied to each electrode. In these figures, the same parts as those of the conventional example shown in FIG. Note that Φ _H1 , Φ _H2 , and Φ _H3 transfer the pulse voltage to the transfer electrode 1
It is an electrode for applying to a and 1b. In this embodiment, six transfer electrodes 1a and 1b are arranged in one horizontal pitch, and each of the transfer electrodes 1a and 1b has three transfer electrodes 1a and 1b.
It is connected to two electrodes Φ _H1 , Φ _H2 and Φ _H3 . The pulse voltage shown in FIG. 2C is applied to these electrodes Φ _H1 , Φ _H2 , and Φ _H3 , and at time t = t ₁ , the signal charge is distributed under the transfer electrode 1a of the second layer of Φ _H2. However, at the time t = t ₂ , it is moved and distributed under the transfer electrode 1b of the first layer of Φ _H3 . By repeating this operation, the signal charges are guided to the output section.

[0011]

According to the present invention, a solid-state image pickup device capable of transferring signal charges at low voltage and at high speed can be realized, and its industrial value is high.

[Brief description of drawings]

FIG. 1A is a schematic cross-sectional view of a main part of a horizontal charge transfer portion of a solid-state imaging device according to an embodiment of the present invention, and FIG. 1B is a potential diagram when a pulse voltage is applied to each electrode in the solid-state imaging device. (C) is a waveform diagram of a pulse voltage applied to each electrode of the solid-state imaging device

FIG. 2A is a schematic cross-sectional view of a main part of a horizontal charge transfer portion of a solid-state imaging device according to a second embodiment of the present invention, and FIG. 2B is a schematic diagram when a pulse voltage is applied to each electrode in the solid-state imaging device. Potential diagram (c) is a waveform diagram of the pulse voltage applied to each electrode of the solid-state imaging device

3A is a schematic cross-sectional view of a main part of a horizontal charge transfer portion of a conventional solid-state imaging device, FIG. 3B is a potential diagram when a pulse voltage is applied to each electrode in the solid-state imaging device, and FIG. Waveform diagram of pulse voltage applied to electrodes

4A and 4B are potential diagrams showing a state of a fringing field in a conventional solid-state imaging device.

[Explanation of symbols]

 1a Transfer Electrode 1b Transfer Electrode 3 Silicon Substrate (Semiconductor Substrate) 4 Impurity Layer (Impurity Distribution in Semiconductor Substrate)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuyuki Toyota 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electronics Industrial Co., Ltd.

Claims (4)

[Claims] 1. A horizontal charge transfer part formed on a semiconductor substrate has 6 transfer electrodes in one repeating unit, and the horizontal charge transfer part has an odd number of transfer electrodes among the 6 transfer electrodes. A solid-state imaging device, wherein the impurity distribution in the lower semiconductor substrate is different from the impurity distribution in the semiconductor substrate below the even-numbered transfer electrodes. 2. The first, second and third of the six transfer electrodes
The solid-state imaging device according to claim 1, wherein the third, fourth, fifth, and sixth transfer electrodes are taken out through three different electrodes. 3. A solid-state image pickup device according to claim 2, wherein a DC voltage is applied to one of the three electrodes of the solid-state imaging device, and pulse voltages having phases different by 180 degrees are applied to the remaining two electrodes. A method for driving an imaging device. 4. The solid-state imaging device according to claim 2, wherein the phase of the pulse voltage applied to one of the three electrodes of the solid-state imaging device differs from the phase of the pulse voltage applied to the remaining two electrodes by 180 degrees. Driving method.