JPH04115678A - Solid-state image pickup element and its driving method therefor - Google Patents

Abstract

PURPOSE:To suppress the weight of a smear electric charge by providing an optical means to lead a light radiated on a light shielding electrode on a non- light-shielding electrode or to the interval side of a transfer electrode so as to cover the transfer electrode. CONSTITUTION:Transfer electrodes 10b and 10d of a lower layer side among transfer electrodes 10a to 10d of a 2-layer-constitution are formed by the high melting point metal of w-Si (tungsten silicide) and so on opaque to incident light or the alloy of it and a microlens layer 11 to refract light radiated on the transfer electrodes 10b and 10d to an open part side is provided on an insulating film 7. That is, the microlens layer 11 which consists of acrylic resin is provided to prevent a smear electric charge from being mixed in the information electric charge of a transfer process with the lower layer side of the transfer electrodes 10a to 10d as light shielding electrodes and moreover to prevent the lowering of sensitivity owing to the light shielding electrodes so as to converge the light to the open part of the transfer electrodes 10a to 10d. Thus, a smear electric charge component can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a solid-state image sensor and a method for driving the same that reduce the generation of smear charges.

(b) Prior art FIG. 4 is a plan view of the imaging section of a CCD solid-state imaging device with a vertical overflow drain structure, and FIG. 5 is an x-y
FIG.

A P-Well region (2) is formed on one surface of an N-type Si substrate (1), and an N-type diffusion region partitioned by a separation region (3) within this P-Well region (2). The zero isolation regions (3), which are arranged in parallel with each other to form a buried storage and transfer channel, are composed of, for example, P'-type diffusion regions, and form horizontal pixel isolation. On the diffusion region (4), there are a plurality of Po1s perpendicular to the separation region (3).
y-Si transfer electrode (5a) (5b) (5c)
(5d) is formed into an array. This transfer electrode (5a)
(5b) (5c) (5d) have a two-layer structure that partially overlaps each other, and each has a four-phase transfer lock φ, ~φ
4 is applied. In addition, the transfer electrode (5a) on the upper layer side (
5c) is narrow (formed) on the separation region (3) and connects the upper layer side transfer electrode (5a) (5c) and the lower layer side transfer electrode (5c).
5b) An opening is formed between (5d).

Furthermore, the diffusion region (4) exposed from the opening has N-
A mold diffusion region (6) is formed. These transfer electrodes (5a) (5b) (5c) (5d) are 5
It is protected by an insulating film (7) such as idlL.

On the other hand, a substrate clock that controls the potential inside the Si substrate (1) is applied to the Si substrate (1), and information charges accumulated in the storage and transfer channels due to the action of the transfer locks φ1 to φ4 are transferred to the Si substrate. (1) It is constructed so that it can be discharged to the side.

FIG. 6 is a diagram showing the state of the potential in the vertical direction of FIG. 5, and shows the state of the potential in the vertical direction when information charges are accumulated (solid line) and when they are discharged (broken line).

When accumulating information charges, P-
A potential barrier is formed near the well region (2), and information charges are accumulated between this potential barrier and the potential barrier on the surface of the diffusion region (4).

On the other hand, when discharging information charges, the substrate clock is set to a high potential and the transfer lock φ2 is set to a low potential to eliminate the potential barrier formed near the P-well region (2), contrary to the case when storing information charges. Therefore, the information charges accumulated between the potential barriers are discharged to the Si substrate (1) side according to the potential gradient as shown by the broken line in FIG.

FIG. 7 is a waveform diagram-c of transfer locks φ and φ4, and FIG. 8 is a diagram showing the potential at each timing.

Transfer locks φ1 to φ4 have a duty ratio of 50%, for example.
The transfer electrodes (5aH5bH5c
) (5d) is applied. The information charge accumulated under the transfer electrode (5b) at timing T1 is transferred to the next timing T.
Transfer lock with 2! , φ are inverted, and furthermore, at timing T3, transfer locks φ2 and φ4 are inverted, and the transfer electrode (5d) is transferred. Then, at timing T4, transfer locks φ3 and φ3 are reversed, and then transfer locks φ2 and
φ is inverted and becomes the state at timing T1. By repeating the operations at timings T1 to T4, the information charges in the storage and transfer channel are transferred and output in a predetermined direction.

(c) Problems to be Solved by the Invention As mentioned above, in a frame transfer type COD solid-state image sensor in which the light receiving part directly functions as a transfer part, even in the process of transferring and outputting information charges, the storage and transfer channel is created by light irradiation. A charge is generated within the information charge, and this charge is superimposed on the information charge as a smear charge. Since the smear charge superimposed on the information charge appears in the form of vertical stripes on the reproduction screen, it is suppressed by being corrected at the processing stage of the video signal obtained from the solid-state image sensor.

In order to correct such smear charge components, a special circuit configuration as disclosed in, for example, Japanese Patent Publication No. 56-35067 is required, which causes an increase in cost.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a driving method that suppresses the superimposition of smear charges by configuring the solid-state image sensor itself so that smear charges are difficult to superimpose on information charges.

(d) Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the first feature is that a plurality of charge transfer regions are provided on one principal surface of a semiconductor substrate. In a solid-state imaging device in which a plurality of transfer electrodes having a multilayer structure are formed in an array and parallel to each other and intersect with the charge transfer region, one layer of the transfer electrodes is formed from a light-shielding electrode that blocks incident light. An optical means for guiding the light irradiated onto the light-shielding electrode onto the non-light-shielding electrode or onto the gap side of the transfer electrode is provided to cover the transfer electrode.

The second feature is that it is a solid state in which a plurality of charge transfer regions are arranged and formed on one main surface of a semiconductor substrate, and a plurality of transfer electrodes of a multilayer structure in which one layer blocks incident light are formed in parallel to each other. In the imaging device, when the information charge is under the light shielding electrode during the process of transferring the information charge within the charge transfer region, the charge transfer region under the non-light shielding electrode and the adjacent excess charge absorption The purpose is to eliminate the potential barrier between the charge transfer region and the charge transfer region, and discharge smear charges generated by light incident into the charge transfer region through the non-light-shielding electrode to the excess charge absorption region.

(E) Effect According to the present invention, when information charges are present under the light-shielding electrode during the process in which information charges are transferred within the storage and transfer channel, the generation of smear charges itself in the region where the information charges are present is suppressed. , smear charges are no longer mixed into information charges.

Furthermore, smear charges generated by light irradiated onto the diffusion region through the non-light-shielded transfer electrode are discharged to the substrate side if there is no information charge in that region. Therefore, the smear charge is superimposed on the information charge only when the information charge passes under the non-light-shielding electrode, and theoretically the amount of smear charge mixed into the information charge is 1/4.

(f) Example An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of the imaging section of the solid-state imaging device of the present invention, and FIG. 2 is an X-Y sectional view thereof. In this diagram,
The Si substrate (1), P-Well region (2), isolation region (3), and diffusion region (4) are the same as in FIG. 4, and the same parts are given the same reference numerals.

The feature of the present invention is that the transfer electrode has a two-phase structure (1
0a) (10b) (IOC) Among (10d), the lower transfer electrode (10b) (10d) is formed of a high melting point metal such as W-5i (tungsten silicide) or its alloy, which is opaque to incident light. and this transfer type i
(]Ob) (10d) A microlens layer (11) is provided on the insulating film (7) to refract light irradiated onto the opening toward the opening. That is, the transfer electrode (10a) (1
0b) (10c) The lower layer side of (10d) is used as a light-shielding electrode to prevent smear charges from being mixed into the information charges during the transfer process, and a microlens layer made of acrylic resin is used to prevent a decrease in sensitivity due to the light-shielding electrode. (11) and transfer electrodes (10a) (10b) (10c) (
10d) is configured to condense light into the opening.

In such a solid-state image sensor, when the information charge is under the transfer electrode (Job) (10d), the generation of the smear charge itself is suppressed, so the smear charge is prevented from being superimposed on the information charge. can.

FIG. 3 is a diagram showing potential states for explaining the driving method of the present invention. Here, the timings T1 to T4 correspond to the timings T1 to T4 in FIG. 7.

Transfer locks φ0 and φ3 form a potential barrier near the P-Well region (2) as shown by the solid line in Figure 6 when the potential is high, and a potential barrier is formed near the P-Well region (2) as shown by the broken line in Figure 6 when the potential is low. The potential is set so that it disappears. Transfer electrodes (Jo) to which transfer locks φ2 and φ4 are applied
b) (10d) is a light-shielding electrode that is not irradiated with light and has no sensitivity to incident light.Therefore, as shown in Figure 3, due to the action of transfer locks φ and φ3, 3/4 of the process in which information charges are transferred by the area of the transfer electrode (10a) (]Oc) that is an insensitive area and the area of the transfer electrode (10b) (10d) that blocks light is sensitive to incident light. The smear charge is superimposed on the information charge only when it passes under the transfer electrode (10a) <10c).

Here, the transfer electrode (1
0a) (]Oc) Transfer locks φ1 to φ4 so that the time for information charges to pass through the lower storage transfer channel is shortened.
By setting the duty ratio of , it is possible to further reduce the inclusion of smear charges.

According to applicants' measurements, the transfer electrode (10a) (10
b) (10c) By using one of (10d) as a light-shielding electrode, the smear ratio could be improved by 3.5 dB. Further, by optimizing the duty ratios of transfer locks φ1 to φ4, a further improvement of 9.5 dB can be expected.

On the other hand, when information charges are accumulated, the transfer electrodes (10a) (10
By eliminating the insensitive region caused by C), necessary information charges are prevented from leaking to the substrate side, thereby preventing a decrease in sensitivity.

(g) Effects of the Invention According to the present invention, it is possible to reduce the mixing of smear charges into information charges in a solid-state image sensor, so there is no need to perform correction processing for smear charge components on video signals, and the circuit configuration can be simplified. Increase can be prevented.

Therefore, it is possible to suppress smear charge components without significantly increasing cost, and to realize a solid-state imaging device that can obtain high-quality images at low cost.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the solid-state image sensing device of the present invention, and FIG.
3 is a potential diagram explaining the driving method of the present invention, FIG. 4 is a plan view of a conventional solid-state image sensor, FIG. 5 is a sectional view of FIG. 4, and FIG. 7 is a waveform diagram of a transfer lock, and FIG. 8 is a potential diagram explaining a conventional driving method. (1)・=Si substrate, (2)--P-Well region,
(3) = - Separation region, (4) - = Diffusion region, (5aH
5b) (5c) (5d) (10a> (1ob) (
10c) (]0dl-transfer electrode, (IJ,)-= fibrolens layer.

Claims (3)

[Claims] (1) A solid-state imaging device in which a plurality of charge transfer regions are arranged and formed on one main surface of a semiconductor substrate, and a plurality of transfer electrodes having a multilayer structure are formed in parallel to each other and intersect with the charge transfer regions. One layer of the transfer electrode is a light-shielding electrode that blocks incident light, and an optical means that guides the light irradiated onto the light-shielding electrode onto the non-light-shielding electrode or onto the gap between the transfer electrodes covers the transfer electrode. A solid-state imaging device characterized in that it is provided in. (2) The solid-state image pickup device according to claim 1, wherein information charges generated upon receiving incident light are accumulated in the charge transfer region. (3) In a solid-state imaging device in which a plurality of charge transfer regions are arranged and formed on one principal surface of a semiconductor substrate, and a plurality of transfer electrodes of a multilayer structure in which one layer blocks incident light are formed in parallel to each other, the above-mentioned During the process in which the information charge is transferred within the charge transfer region, when the information charge is under the light-shielding electrode, a potential barrier is formed between the charge transfer region under the non-light-shielding electrode and the adjacent excess charge absorption region. A method for driving a solid-state image sensor, characterized in that smear charges generated by light incident on a charge transfer region through a non-light-shielding electrode are discharged to the excess charge absorption region.