JPH0427162A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To obtain a solid state image sensor in which an after image is not generated even if a photodiode is formed by providing other conductivity type impurity region having the same degree of impurity concentration as that of an impurity region of a photodiode on a boundary part under a transfer gate. CONSTITUTION:An incident light to an image sensing unit having other conductivity type impurity region 5 of the same degree of impurity concentration as that of an impurity region of a photodiode 1 on a boundary under a transfer gate between the photodiode 1 and a transfer channel is photoelectrically converted by the photodiode 1 to generate charge. The generated charge is transferred from the photodiode 1 to an n-channel CCD 2 through the region 5 when a transfer gate 3 is turned ON. In this case, since a MOS transistor in which the CCD 2, the gate 3 and the region 5 respectively become a drain, a gate and a source, is formed, complete charge transfer can be performed under voltage control of the gate 3, and no after image is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device used in a video integrated camera and the like.

[Conventional technology]

In recent years, the characteristics of solid-state image sensors have significantly improved, and the fields in which solid-state image sensors are used are rapidly expanding.

On the other hand, increasing the number of pixels has always been desired. Generally, when the number of pixels of a solid-state image sensor is increased, the area per pixel becomes smaller, and there is a problem that the amount of charge accumulated by the photodiode (hereinafter referred to as "maximum amount of charge handled") cannot be obtained sufficiently. . As a method of increasing the maximum amount of charge that can be handled without changing the area of the photodiode, it is effective to form the photodiode by an implantation method in which impurities are deeply implanted.

FIG. 2 is a cross-sectional structural diagram of an imaging section in a conventional solid-state imaging device. In Figure 2, 1 is a photodiode that performs photoelectric conversion, 2 is an n-channel COD that transfers the charge generated in photodiode 1, and 3 is photodiode 1.
4 is a p-type substrate, and 6 is an oxide film.

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

Light incident on the imaging section generates charges through photoelectric conversion in the photodiode 1. The generated charge is transferred to the transfer gate 3
is in the on state, the signal is transferred from the photodiode 1 to the n-channel CCD 2.

[Problem to be solved by the invention]

By forming photodiode 1 using a conventional implantation method that deeply implants impurities, it is possible to increase the maximum amount of charge that photodiode 1 can handle. Sometimes, because the photodiode 1 is deep, a potential barrier remains between the photodiode 1 and the n-channel CCD 2 even if the transfer gate 3 is turned on. For this purpose, from photodiode 1 to n-channel CCD
2 cannot be transferred smoothly, and the afterimage characteristics deteriorate.

An object of the present invention is to provide a solid-state imaging device in which no afterimage occurs even when a photodiode is formed by an implantation method in which impurities are deeply implanted.

[Means for Solving the Problems] The solid-state imaging device of the present invention is characterized in that an impurity region of another conductivity type having the same impurity concentration as the impurity region of the photodiode is provided in the interface portion under the transfer gate. Features.

[Effect]

According to the configuration of the present invention, an impurity region of another conductivity type having the same impurity concentration as the impurity region of the photodiode is provided at the interface between the photodiode and the transfer channel under the transfer gate. Therefore, no potential barrier is formed between the photodiode and the COD when charges generated in the photodiode are transferred to the CCD.

Therefore, charge can be smoothly transferred from the photodiode to the CCD.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a solid-state imaging device according to an embodiment of the present invention. In FIG. 1, reference numeral 5 denotes an n-type impurity region having the same concentration as the n-type impurity region of the photodiode 1, and the other configurations are the same as in the conventional example.

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

Light incident on the imaging section generates charges through photoelectric conversion in the photodiode 1. The generated charge is transferred to the transfer gate 3
When is in the on state, the light is transferred from the photodiode l to the n-channel CCD 2 via the n-type impurity region 5. In this case, n-channel CCD2. Since the transfer gate 3 and the n-type impurity region 5 form a MOS transistor serving as a drain, a gate, and a source, respectively, voltage control of the transfer gate 3 allows complete charge transfer and no afterimage occurs.

[Effects of the Invention] The solid-state imaging device of this invention includes a photodiode and a CCD.
By providing an impurity region of another conductivity type with an impurity concentration similar to that of the photodiode impurity region at the interface below the transfer gate between the photodiode and the photodiode, the charge generated in the photodiode is transferred to the COD. In this case, no potential barrier is formed between the photodiode and the CCD. Therefore, charge can be smoothly transferred from the photodiode to the CCD, and no afterimage occurs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a solid-state imaging device according to an embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of a conventional solid-state imaging device. 1...Photodiode, 2...n channel CC
D, 3... Transfer gate, 4... P-type substrate, 5...
n-type impurity region

Claims (1)

[Scope of Claims] A photodiode in which an impurity region of another conductivity type is provided on the main surface of a semiconductor substrate of one conductivity type, a CCD comprising a region of the other conductivity type, and a transfer gate for transferring data to a CCD, and an impurity region of another conductivity type having the same impurity concentration as the impurity region of the photodiode is provided in an interface portion under the transfer gate. Solid-state imaging device.