JPS6150550B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a CCD (charge coupled device) type solid-state imaging device.

A general CCD type solid-state image sensor has charge storage electrodes and charge transfer electrodes arranged alternately on a semiconductor substrate with an insulating film interposed between them. The electric charge excited therein is stored at the storage electrode position to obtain a charge image. This charge follows the movement of the potential well caused by clock pulses applied to each of the charge storage electrode and the charge transfer electrode, and is taken out from the edge of the semiconductor substrate as image information.

Blooming phenomenon is a problem when capturing images using such a solid-state image sensor. This blooming phenomenon is when a CCD type solid-state image sensor is locally exposed to strong light, the amount of charge excited in the semiconductor substrate by this light increases, and this charge is diffused from the point where the light is incident. This means that a charge image is formed as if the light was incident over a wider area than it actually is.

As a result, the resulting reproduced image has white bleeding and becomes very unsightly.

To prevent this kind of blooming phenomenon,
There is an urgent need for CCD type solid-state image sensors.
Improvement research for this purpose has been ongoing.

FIG. 1 shows the configuration of a conventional solid-state image sensor. Figure a is a plan view, figure b is a cross-sectional view taken along line X-X, and figure c is a cross-sectional view taken along line Y-Y. A semiconductor substrate made of P-type silicon, 2... a plurality of channel parts formed in parallel to the semiconductor substrate 1, 3...
are channel stoppers formed along both sides of the channel portion 2, and the semiconductor substrate 1
P-type impurities are diffused to a higher concentration. 4...
is an overflow drain formed between the channel stoppers 3 . 5
are the above-mentioned channel section 2..., channel stopper 3..., and overflow drain 4...,
The transparent insulating film 6 made of distributary silicon or the like is formed on the semiconductor substrate containing a plurality of transparent insulating films 6 provided on the insulating film 5 in parallel in a direction orthogonal to the channel portion 2... A transparent charge storage electrode of the book, for example made of polysilicon.
7... are a plurality of charge transfer electrodes made of aluminum and provided alternately in parallel with the charge storage electrodes 6.... Note that the thickness of the insulating film 5 below the charge transfer electrode 7 is formed to be thicker than that of the charge storage electrode 6 below, and the same voltage is applied to the charge storage electrode 6 and the charge transfer electrode 7. In this case, the depth of the potential formed from the semiconductor surface under the charge storage electrode 6 is made deeper than that under the charge transfer electrode 7.

A solid-state image sensor having such a configuration has a plurality of light-transmissive charge storage electrodes 6 in each channel portion 2.
The area where ... is located constitutes the light receiving part, and in the plurality of light receiving parts arranged in rows and columns in this way, an amount of charge, in this case electrons, is excited depending on the intensity of the incident light. and will be accumulated on the surface of the substrate 1.

FIG. 2 shows the potential form in the cross section shown in FIG. 1b of the light receiving section in the charge accumulation state in this case, and FIG. 3 shows the potential form in the cross section shown in FIG. 1c. As is clear from these potential diagrams, the light receiving section at this time is based on the difference between the potential φ ₁ due to the positive voltage applied to the charge transfer electrodes 7 and the potential φ ₂ due to the positive voltage applied to the charge storage electrode 6. Potential barrier for electrons φ 1 −φ ₂ expressed by φ ₁ −φ 2 and potential barrier for electrons φ 3 _−φ expressed by the difference between potentials φ ₃ and φ ₂ of channel stopper 3...
It forms a potential well surrounded by ₂ and . At this time, if strong light is incident on a specific light-receiving part, the amount of electrons excited in the P-type silicon of channel part 2 increases, and excess electrons are formed as described above. It will flow out from the potential well. Among these excess electrons, those flowing out beyond the channel stopper 3 are absorbed by the overflow drain section 4, which maintains a low potential _φ4 with respect to electrons by applying a positive voltage. As a result, excess electrons are prevented from diffusing to other channel sections 2.

However, in the conventional solid-state image sensor as described above, although the overflow drain 4 prevents the blooming phenomenon between the channel sections 2..., adjacent light receiving within the same channel section 2... The risk of blooming occurring between departments remains unresolved.

The present invention has been made in view of the current situation, and an overflow drain is partially extended between adjacent light receiving sections within the same channel section 2.

FIG. 4 shows the configuration of the solid-state image sensing device of the present invention.

Figure a is a partial plan view, and figure b is its X-X
These are cross-sectional views along the line, and in these figures, 5, 6, and 7 are the same insulating film, charge storage electrode, and charge transfer as in the conventional solid-state image sensor shown in FIG. It is an electrode. 8 is a channel portion, and the channel width at the portion where the charge transfer electrodes 7 are located is smaller than that at the portion where the charge storage electrodes 6 are located, and is formed in a meandering state. 9... is the meandering channel portion 8...
The channel stopper 10 is formed with a constant width along both sides of the channel stopper 9.
It is an overflow drain narrowed by ... and each channel portion 8 at the transfer electrode 7 position.
... and is formed in a comb-teeth shape extending to the center line (X-X line in FIG. 4a).

Incidentally, these channel portions 8...channel stoppers 9...and overflow drains 10...
... consists of a semiconductor region having the same impurity as shown in FIG.

In the solid-state imaging device of the present invention configured as described above,
The potential form in the light receiving state is shown in FIG. 5 in the XX direction of FIG. 4, and in FIG. 6 in the Y-Y direction. As is clear from these potential diagrams, the channel portion 8...
Around the light receiving part where the charge storage electrode 6 is located, there are channel stoppers 9 not only in the channel direction but also in places that partially obstruct the channel direction.
potential φ ₃ and the charge storage electrode 6 at this time...
Potential φ ₂ due to positive voltage applied to...
A potential barrier φ 3 −φ ₂ for electrons is formed, which is represented by the difference between φ ₃ and φ 2 . Furthermore, a low potential _φ4 for electrons is maintained outside this potential barrier by an overflow drain 10 to which a positive voltage is applied. If strong light is incident on such a light receiving part and excess electrons are generated,
Along with the electrons flowing out in the direction perpendicular to the channel direction, most of the electrons flowing out in the channel direction are also absorbed by the overflow drains 10 .

On the other hand, the charges accumulated in the light receiving section are transferred to the channel section 8 depending on the clock pulses applied to the charge storage electrode 6 and the charge transfer electrode 7, respectively.
By sequentially moving through the channels, image information depending on the amount of charge can be obtained from each end of the plurality of channel sections 8.

Although the CCD type solid-state imaging device of the present invention uses a P-type semiconductor substrate and uses electrons as carriers, it goes without saying that an N-type semiconductor substrate may also be used.

As is clear from the above description, the solid-state imaging device of the present invention is composed of a plurality of channel portions, a channel stopper, and an overflow drain, and the overflow drain is formed in a comb-like shape by extending to the transfer electrode location. Therefore, each light receiving section formed at each charge storage electrode position can be sufficiently separated in terms of potential from other light receiving sections by the channel stopper and overflow drain. Therefore, even if excess charge is generated in each light receiving section, this excess charge is not only prevented from flowing to the light receiving section of another adjacent channel section, but also prevented from flowing to the next light receiving section within the same channel section. Since this can be sufficiently prevented, it is possible to obtain an image free of any blooming phenomenon.

[Brief explanation of the drawing]

FIG. 1 shows a conventional solid-state image sensor, in which a is a plan view thereof, b is a cross-sectional view in the X-X direction at a,
c is a cross-sectional view in the Y-Y line direction in a, Figures 2 and 3 are potential diagrams in the X-X line and Y-Y line direction in Figure 1 a, and Figure 4 is the main The solid-state imaging device of the invention is shown in which a is a plan view thereof, b is a cross-sectional view taken along line X-X at a, and FIGS. 5 and 6 are 4
Potential diagrams in the X-X line direction and the Y-Y line direction in Figure a are shown, respectively. 1... Semiconductor substrate, 2, 8... Channel part,
3, 9... Channel stopper, 4, 10... Overflow drain, 5... Insulating film, 6... Charge storage electrode, 7... Charge transfer electrode.

Claims (1)

[Claims] 1. In a CCD solid-state image sensor in which a plurality of band-shaped charge storage electrodes and band-shaped charge transfer electrodes are alternately arranged in parallel on a semiconductor substrate with an insulating film interposed therebetween, the extension of the band-shaped storage electrodes and transfer electrodes is A plurality of channel portions extending in a direction crossing the direction are arranged in parallel in a semiconductor substrate, and channel stoppers are provided on both sides of each channel portion to separate each channel, and the channel portions are further sandwiched between adjacent channel stoppers. An overflow drain is formed at a location where the transfer electrode is located, and the width of the channel portion at the transfer electrode location is made smaller than the width at the storage electrode location, and the overflow drain is extended to the transfer electrode location to form a comb-like shape. A solid-state image sensor characterized by forming a solid-state image sensor.