JPH03142969A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To eliminate residual images by installing a transfer electrode serving as a reading electrode stretching on both surfaces from photoelectric conversion side toward a transfer part. CONSTITUTION:When light enters an N-type impurity region 1 as the light sensitive part, electric charge is generated and stored. When a reading pulse is applied on a transfer electrode 4 in the vertical blanking period, the potential of a transfer part just under the transfer electrode becomes deeper from the light sensitive part side toward the transfer part side in a potential profile along the A-A' section. This is based on what is called narrow channel effect, and the change stored in the N-type impurity region 1 is read in an N-type impurity region 2 as the transfer part. Thereby the potential of the transfer part just under the transfer electrode can be made deeper from the light sensitive part side toward the transfer part side, so that residual images can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device that can be used for image sensors, image scanners, and the like.

[Prior Art] A solid-state imaging device uses a solid-state element as a photoelectric conversion element. For example, it integrates a large number of photoelectric conversion elements using phototransistors or photodiodes, and applies the principle that a photocurrent flows when exposed to light. It is used for image signal processing such as facsimiles.

In recent years, solid-state imaging devices have rapidly become popular, replacing image pickup tubes, both for industrial and home use. However, so-called dark current, in which charges generated even when no light is incident, is extracted as a signal, is an issue that needs improvement. It is believed that a buried photodiode structure is effective against this dark current.

Hereinafter, a conventional solid-state imaging device as described above will be described with reference to the drawings.

FIG. 3 shows a photosensitive section and a charge transfer section of a conventional solid-state imaging device.

In FIG. 3, 1 is a light receiving area. 2 is a charge transfer section. 3 is a transfer electrode. 4 is a transfer electrode that also serves as a readout electrode. 5 is a separation area. 6 is a readout area.

The operation of the solid-state imaging device configured as described above will be described below.

First, when light enters the n-type impurity region 1 as a photosensitive portion, charges are generated and accumulated. When a read pulse is applied to the transfer electrode 4 during the vertical blanking period, the potential profile along the cross section AA' in FIG. 3 becomes as shown in FIG. 4. The charges accumulated in the n-type impurity region 1 through the readout section 6 are read out to the n-type impurity region 2 as a transfer section.

[Problems to be Solved by the Invention] However, in the above configuration, as is clear from a in FIG. In order to completely transfer the signal charge from the photosensitive section to the charge transfer section,
Unable to read. For this reason, it has had the disadvantage of producing an afterimage.

In order to solve the problems of the prior art described above, the present invention provides a solid-state imaging device that can eliminate afterimages.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration. That is, the present invention includes a photoelectric conversion section formed on the surface of a semiconductor region of one conductivity type by a region of a conductivity type opposite to the one conductivity type, and a photoelectric conversion section of the opposite conductivity type that transfers signal charges formed in the photoelectric conversion section. In a solid-state imaging device provided with a transfer section formed in a region, the shape of an electrode serving both readout and transfer for reading signal charges from the photoelectric conversion section to the transfer section is such that The solid-state imaging device is characterized in that it extends on both sides toward the transfer section.

Furthermore, in the present invention, it is preferable that the readout electrode is independent of the transfer electrode.

[Function] According to the configuration of the present invention described above, the potential of the readout section directly under the readout electrode becomes deeper on the transfer section side due to the so-called narrow channel effect, so that the accumulated signal charges are not completely read out. Become. Therefore, the problem of remaining afterimages, which was a drawback of the prior art, is solved.

[Examples] Hereinafter, the present invention will be explained in more detail using Examples. Note that the present invention is not limited to the following examples.

FIG. 1 shows a photosensitive section and a charge transfer section of a solid-state imaging device in an embodiment of the present invention.

In Fig. 2, 1 is a light receiving area. 2 is a charge transfer section. 3 is a transfer electrode. 4 is a transfer electrode that also serves as a readout electrode. 5 is a separation area. 6 is a readout area.

In such a solid-state imaging device, the shape of the electrode 4, which serves both for reading and transferring signal charges from the photoelectric conversion section to the transfer section, is provided so as to spread on both sides from the photoelectric conversion section toward the transfer section.

The operation of the solid-state imaging device configured as described above will be described below.

First, when light enters the n-type impurity region 1 as a photosensitive portion, charges are generated and accumulated. Then, when a read pulse is applied to the transfer electrode 4 during the vertical blanking period, the potential profile along the cross section A-A in FIG. 1 changes as shown in FIG. The potential of the area becomes deeper from the photosensitive area side to the transfer area side. This is due to the so-called narrow channel effect. The charges accumulated in n-type impurity region 1 are read out to n-type impurity region 2 as a transfer section.

As described above, according to this embodiment, by providing the transfer electrode 4 that also serves as a readout electrode and extending from the photoelectric conversion unit side toward the transfer unit, the potential of the transfer unit directly below the transfer electrode can be increased. Since the depth can be increased from the photosensitive section side to the transfer section side, afterimages can be eliminated.

Further, in the embodiment described above, the readout electrode 4 may be provided independently of the transfer electrode 3. This is because it is possible to achieve a point-to-point effect that can eliminate residual afterimages.

Although this example is a solid-state imaging device that uses electrons as signal charges, the P-vacancy region constituting this device is replaced with an n-type region, and the n-type region is replaced with a P-vacancy region to convert holes into signal charges. It may also be a solid-state imaging device.

[Effects of the Invention] As described above, the present invention can eliminate afterimages by providing a transfer electrode that also serves as a readout electrode that spreads on both sides from the photoelectric conversion unit side toward the transfer unit, and has practical advantages. The effects are huge.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a solid-state imaging device according to a first embodiment of the present invention, FIG. 2 is a diagram for explaining the operation in the embodiment of the present invention, and FIG. 3 is a structural diagram of a conventional device. FIG. 4 is a diagram for explaining the operation of the conventional device. 1... Light receiving area 2... Charge transfer section 3... Transfer electrode 4... Transfer electrode 5 which also serves as a readout electrode... Separation area 6... Readout area Fig. 1, Fig. 3

Claims (2)

[Claims] (1) On the surface of a semiconductor region of one conductivity type, a photoelectric conversion section formed of a region of a conductivity type opposite to the one conductivity type, and a region of the opposite conductivity type that transfers the signal charge formed in the photoelectric conversion section. In a solid-state imaging device provided with a transfer section formed of:
A solid-state imaging device characterized in that the solid-state imaging device extends on both sides from the photoelectric conversion unit side toward the transfer unit. (2) The solid-state imaging device according to claim 1, wherein the readout electrode is independent of the transfer electrode.