JPS589361A - Solid state image pickup element - Google Patents

Abstract

PURPOSE:To prevent vertical smears caused by leak of light by a method wherein the part of a well region just below a field oxide film is made thinner than other parts of the region, when a well region is diffusedly formed on a semiconductor substrate and a field oxide film is provided to divide said substrate and individual well regions after division are provided with a photoelectronic conversion element corresponding to a picture element. CONSTITUTION:A P type well region 2 is diffusedly formed on an N type Si substrate 1 and a thick field oxide film 6 divides the region 2 into a multiplicity of units. An element is constituted when an N type drain region 4 and a source region etc., not illustrated, are provided in the region 2 located on the both sides of the film 6. After this, a coverage is provided by an interlayer insulating film 7, an opening is provided, and Al wirings 9 are attached to the picture element region. In this construction, a part of the region 2 positioned under the film 6 is made thinner so that a depletion layer 13 formed by the region 2 and the substrate 1 reaches a location immediately below the film 6. Thereby the photoelectrons generated by leak of the light 11 are made to flow into the substrate 1 without reaching the region 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state imaging device having a three-layer structure including a well layer.

This type of solid-state image sensor that has been used conventionally is called Maguro 1#AK.
show. In the figure, a Kp type well layer 2 is formed on the entire surface of a shaped substrate 1, and a MOlt transistor consisting of a type 1 source 3, drain 4, and gate electrode 5 is constructed at ζζ. The source 3 also constitutes a photodiode together with the p-type well layer 2, and each photoelectric conversion element consisting of this photodiode and the MoB transistor is formed by a field oxide film 6 and interlayer insulating films 7, 8. They are insulated from each other and connected by AI wiring 9. Further, an interlayer insulating film 1 is provided above each field oxide III.

In the solid-state imaging device having the above configuration, the A1 layer 10 is provided, the source 3 and the p-type well layer 2
1j from the part other than the photodiode formed by !
A structure is adopted to prevent light from entering the 1# photoelectric conversion element.

However, although the AI layer 10 is an effective means for preventing light that is incident directly on the A4 layer 10, the light incident on the A4 layer 10 in an oblique direction as shown in FIG. The photoelectrons enter the photoelectric conversion element while avoiding the photoelectrons 12, and generate photoelectrons 12 near the drain 4. The generated photoelectrons 12 enter the tray 74 by diffusion or drift, causing vertical smear.

The zero launch was made in view of this situation.
The purpose is to prevent vertical smear due to leakage light components and provide a solid-state image sensor.

In order to achieve such an object, the solid-state imaging device according to the present invention has a well layer width under the field oxide film that is thinner than other parts.

Hereinafter, the solid-state imaging device according to the present invention will be described in detail using Examples.

FIG. 3 is a sectional view showing an embodiment of the solid-state image sensing device according to the present invention, and the same parts as in FIG. 2 are denoted by the same symbols, and detailed explanation thereof will be omitted. In FIG. 3, the rectangular well layer 2 on the shaped substrate 1 is formed to be thinner in the portion below the field oxide film 6 than in other portions. Therefore, the depletion layer 1 formed by the p-type well layer 2, the n-type substrate 1, and K
3 has reached just 15 below the field oxide film 6.

In the solid-state imaging device having the above configuration, the depletion layer ISK
, a positive electric field is applied in the direction of the n-type substrate 1.

Therefore, phototravel electrons 12 generated inside the p-type well layer 2 due to the leakage light component 11 are transferred to the n-type substrate 1 by this electric field.
, and almost no flow to the drain 4 side.

Therefore, the occurrence of vertical smear can be significantly reduced.

In the embodiment described above, the p-type well layer 2 is provided on the shaped substrate 1, and the Km-type source is formed on top of the p-type well layer 2.

We will only explain the n-p-n structure in which the drain etc. are formed, but even if the conductivity type is reversed and the conductivity type is reversed, the charge generated by the leaked light component will be treated in exactly the same way. It goes without saying that the effect of preventing vertical smear by absorbing it on the substrate side can be obtained.

As explained above, according to the solid-state imaging device according to the present invention, the width of the well layer under the field oxide film is made thinner than other parts, so that the muj layer above the field oxide film can be avoided. Charges generated in the well layer at this portion due to the leaked light components entering the well layer can be caused to flow out to the substrate side by using the depletion layer generated there. Therefore, charges generated by the leakage current component can be prevented from flowing into the drain, and vertical smear can be reduced, resulting in an excellent effect of significantly increasing the S/N ratio and improving performance.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing a conventional solid-state image sensor, and FIG. 3 is a cross-sectional view of a solid-state image sensor according to the present invention. 1... shape substrate, 2... p-shaped L layer, 3...
... Source, 4...Φ drain, 5... Gate electrode, 6... Field oxide film. 2

Claims (1)

[Claims] A well layer made of a semiconductor having a second conductivity type is provided on one main surface of a semiconductor substrate having a first conductivity type, and a photodiode and a switching transistor having the photodiode as a component are formed on the well layer. In other words, a plurality of photoelectric conversion elements corresponding to one pixel are separated by a field oxide film, and the well layer is made thinner than other parts below the field oxide film. A solid-state image sensor characterized by the following.