JPH0697415A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To make it possible to increase a charge transfer capacity of a transfer electrode next to a charge detection part without degrading charge transfer efficiency. CONSTITUTION:A first transfer electrode 2A which is adjacent to a charge detection part 1 is formed in the shape of an arc. Due to this. a maximum transfer distance of signal charges in a lower part of the first transfer electrode 2A in a charge transfer channel 9 is equivalent to a gate length of the first transfer electrode 2A and the gate length is increased more than required, which serves to protect the transfer efficiency of the first transfer electrode 2A on its lower part from being degraded. In addition to that, a part connected to the charge detection part 1 in the charge transfer channel 9 is formed to keep the same width with the other parts in the charge detection channel 9. Therefore, this construction increases a transfer capacity of signal charges compared with the charge transfer channel 9 which is reduced in tapered shape in a part connected to the charge detection part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device.

[0002]

2. Description of the Related Art A conventional solid-state image pickup device will be described below with reference to FIG.

In FIG. 1, reference numeral 1 is a charge detecting portion for taking out signal charges formed on a semiconductor substrate and transferred as an output signal, and 2 is a rectangular first portion formed in a portion adjacent to the charge detecting portion 1. 1 transfer electrode, 3 is a rectangular second transfer electrode formed in a portion adjacent to the first transfer electrode 2, 4 is a rectangular third transfer electrode formed in a portion adjacent to the second transfer electrode 3, Reference numeral 5 is a rectangular fourth transfer electrode formed in a portion adjacent to the third transfer electrode 4, 6 is a rectangular fifth transfer electrode formed in a portion adjacent to the fourth transfer electrode 5, and 7 is a fifth. A rectangular sixth part formed in a region adjacent to the transfer electrode 6.
Transfer electrodes, 8 is a rectangular seventh transfer electrode formed in a portion adjacent to the sixth transfer electrode 7, and 9 is connected to the charge detection unit 1 below the first to seventh transfer electrodes on the semiconductor substrate. The charge transfer channel is formed as described above and is used to transfer the signal charge to the charge detection unit 1. As shown in the figure, the signal charge 10 is transferred from the seventh transfer electrode 8 to the first charge transfer channel 9 through the first transfer electrode 8.
The charges are sequentially transferred toward the transfer electrode 2 and transferred to the charge detection unit 1.

Conventionally, the charge transfer channel 9 is provided with a tapered portion 9a which is tapered toward the charge detection portion 1 at a portion connected to the charge detection portion 1, and the tapered portion 9a is provided. It is usual that the charge detection unit 1 is formed at the narrowest part of the. Therefore, the tapered portion 9a of the charge transfer channel 9 is formed.
Also, in order to secure the same signal charge transfer capacity as the other portion 9b, the gate length A of the first transfer electrode 2 or the first and second transfer electrodes 2 and 3 located above the tapered portion 9a is , And is longer than the gate length of the transfer electrode located above the other portion 9b.

[0005]

However, as described above, in order to secure the signal charge transfer capacitance in the charge transfer channel 9 below the first transfer electrode 2 adjacent to the charge detection portion 1, the first transfer electrode is required. If the gate length A of 2 is increased, there is a problem that the maximum transfer distance B for transferring the signal charges 10 is increased in the lower part of the first transfer electrode 2 in the charge transfer channel 9.

As described above, if the maximum transfer distance B for transferring the signal charges 10 becomes long, the transfer efficiency of the signal charges decreases, so that the transfer efficiency of the signal charges is maintained in the conventional solid-state image pickup device. However, it is difficult to sufficiently increase the signal charge transfer capacity.

In view of the above, an object of the present invention is to make it possible to secure a sufficiently large signal charge transfer capacity while maintaining the transfer efficiency of signal charges.

[0008]

In order to achieve the above object, the invention according to claim 1 provides a transfer electrode adjacent to a charge detecting portion in a substantially arc shape having a point on the charge detecting portion as a center. To do.

Specifically, the means for solving the problems according to the first aspect of the present invention is to provide a charge detection unit for taking out, as an output signal, a signal charge formed and transferred on a semiconductor substrate, and the charge detection unit on the semiconductor substrate. The charge transfer channel is formed so as to be connected to the charge transfer channel and transfers the signal charge to the charge detection unit, and the plurality of transfer electrodes are formed side by side so as to be adjacent to each other above the charge transfer channel. Assuming a solid-state imaging device including a transfer electrode group for sequentially transferring signal charges to a channel toward the charge detection unit, a front end of a plurality of transfer electrodes forming the transfer electrode group in a signal charge transfer direction. The final transfer electrode located in the
The configuration is such that it is formed in a substantially arcuate shape with one point on the charge detection portion as the center.

Further, the invention of claim 2 suppresses a decrease in transfer efficiency of a lower part of one or a plurality of transfer electrodes adjacent to the final transfer electrode in the charge transfer channel, and specifically, In the configuration of claim 1, among the plurality of transfer electrodes forming the transfer electrode group, one transfer electrode adjacent to the final transfer electrode or a plurality of transfer electrodes adjacent to each other including the one transfer electrode are: A configuration is added in which it is formed in a substantially arcuate shape with one point on the charge detection portion as the center.

Furthermore, the invention of claim 3 is intended to increase the transfer capacity of the signal charge of the portion connected to the charge detection portion in the charge transfer channel, and specifically, the structure of claim 1 or 2. In addition, a configuration is added in which the portion of the charge transfer channel connected to the charge detection portion is formed to have the same width as the other portions of the charge transfer channel.

[0012]

According to the structure of claim 1, the shape of the final transfer electrode located at the end on the front side in the signal charge transfer direction among the plurality of transfer electrodes forming the transfer electrode group is centered on one point on the charge detection part. Since it is formed in a substantially arc shape, the maximum transfer distance of the signal charge in the lower portion of the final transfer electrode in the charge transfer channel and the gate length of the final transfer electrode become substantially the same length, and the gate length is longer than necessary. Since the length does not become long, the transfer efficiency of the lower part of the final transfer electrode in the charge transfer channel does not decrease.

According to the structure of claim 2, one of the plurality of transfer electrodes forming the transfer electrode group is adjacent to the final transfer electrode.
Since the shape of one transfer electrode or a plurality of transfer electrodes adjacent to each other including the one transfer electrode is formed in a substantially arc shape centering on a point on the charge detection portion, it is adjacent to the final transfer electrode in the charge transfer channel. Since the maximum transfer distance of the signal charge in the lower part of one or a plurality of transfer electrodes and the gate length of the one or a plurality of transfer electrodes are substantially the same, the lower side of the final transfer electrode in the charge transfer channel is The transfer efficiency of the part does not decrease.

According to the third aspect of the invention, since the portion of the charge transfer channel connected to the charge detection portion is formed to have the same width as the other portion of the charge transfer channel, the portion connected to the charge detection portion is tapered. The transfer capacity of the signal charge is increased as compared with the existing charge transfer channel.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a solid-state image pickup device according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a charge detection unit for taking out a signal charge formed on a semiconductor substrate and transferred as an output signal, Reference numeral 2A denotes a semi-circular first transfer electrode formed at a portion adjacent to the charge detection portion 1 and having a point O on the charge detection portion 1 as a center, and 3A is formed at a portion adjacent to the first transfer electrode 2. The semi-circular second transfer electrode 4A centering on the one point O is formed in a portion adjacent to the second transfer electrode 3A, and the semi-circular third transfer electrode 4A centering on the one point O is provided.
A is an arc-shaped fourth transfer electrode formed at a portion adjacent to the third transfer electrode 4A and having the above-mentioned one point O as a center, and 6A is a fourth
An arc-shaped fifth transfer electrode formed in a portion adjacent to the transfer electrode 5A and having the above-mentioned one point O as a center, and 7A is formed in a portion adjacent to the fifth transfer electrode 6A and having an arc-shaped as the center. Of the sixth transfer electrode, 8A is formed in a portion adjacent to the sixth transfer electrode 7A, and is an arc-shaped seventh transfer electrode having the above-mentioned one point O as a center, and 9 is the first to seventh parts on the semiconductor substrate.
Charge transfer channels that are formed below the transfer electrodes 2A to 8A so as to be connected to the charge detection unit 1 and transfer signal charges to the charge detection unit 1. 8A constitutes a transfer electrode group for sequentially transferring signal charges to the charge transfer channel 9 toward the charge detection unit 1. In this case, the width of the charge transfer channel 9 is formed to have the same size over the entire area in the signal charge transfer direction.

As described above, since the first transfer electrode 2A adjacent to the charge detection portion 1 is formed in an arc shape, the maximum transfer of the signal charge in the lower part of the first transfer electrode 2A in the charge transfer channel 9 is performed. Since the distance B is equal to the gate length A of the first transfer electrode 2 and the gate length A does not become longer than necessary, the transfer efficiency of the lower portion of the first transfer electrode 2A in the charge transfer channel 9 is Does not fall.

Further, the width of the charge transfer channel 9 is formed to have the same size over the entire area in the signal charge transfer direction, and the portion of the charge transfer channel 9 connected to the charge detection portion 1 is formed to have the same width as the other portions. Therefore, when the gate length A of the first transfer electrode 2A is the same as that of the conventional charge transfer channel 9 which is tapered in the portion connected to the charge detection unit 1, the transfer of the signal charge is performed. Larger capacity.

Further, since the second transfer electrode 3A to the seventh transfer electrode 8A are also formed in an arc shape centering on a point O on the charge detection portion 1, the second to the second transfer electrodes in the charge transfer channel 9 are formed.
Since the maximum transfer distance of the signal charges in the lower part of each of the seventh transfer electrodes 3A to 8A and the gate length of each of the second to seventh transfer electrodes 3A to 8A become the same length, The transfer efficiency of the lower parts of the second to seventh transfer electrodes 3A to 8A does not decrease.

FIG. 2 shows a solid-state image pickup device according to the second embodiment of the present invention. In the second embodiment, each of the first to fourth transfer electrodes 2B to 5B has a point O on the charge detecting section 1. The fifth to eighth transfer electrodes 6 </ b> B to 9 </ b> B are formed in a circular shape centering on a center, and each of the fifth to eighth transfer electrodes 6 </ b> B to 9 </ b> B is formed in an arc shape centering on a point O on the charge detection unit 1.

As described above, in the second embodiment, since the first to fourth transfer electrodes 2B to 5B are formed in the shape of a quarter circle centered on one point O on the charge detection portion 1, the charge is reduced. Since the transfer channel 9 has a shape projecting toward the charge detection portion 1, when the transfer electrodes having the same gate length are used, a larger charge transfer capacitance can be obtained than in the case of the first embodiment.

FIG. 3 shows a solid-state image pickup device according to a third embodiment of the present invention. In the third embodiment, the first to eighth transfer electrodes 2C to 9C are located at one point O on the charge detecting section 1. It is formed in a polygonal shape close to a circular arc as the center. As described above, even if the shapes of the first to eighth transfer electrodes 2C to 9C are polygonal, the same effect as that of the first embodiment can be obtained as long as it is a polygon close to an arc, that is, a substantially arcuate shape. . In this case, as the number of sides of the polygon is increased and the shape is closer to a circular arc, the effect that a sufficiently large signal charge transfer capacity can be obtained while maintaining the transfer efficiency of the signal charges becomes greater.

[0023]

As described above, according to the solid-state image pickup device of the first aspect of the present invention, the shape of the final transfer electrode located at the front end in the signal charge transfer direction is centered on a point on the charge detection part. Therefore, since the maximum transfer distance of the signal charges in the lower portion of the final transfer electrode in the charge transfer channel and the gate length of the final transfer electrode are substantially the same, The transfer efficiency of the lower part of the transfer electrode does not decrease. Therefore, according to the first aspect of the invention, it is possible to secure a sufficiently large signal charge transfer capacity while maintaining the signal charge transfer efficiency.

According to the solid-state imaging device of the second aspect of the present invention, one transfer electrode adjacent to the final transfer electrode among the plurality of transfer electrodes forming the transfer electrode group or a plurality of adjacent transfer electrodes including the one transfer electrode. Since the shape of the transfer electrode is formed in a substantially arc shape centering on a point on the charge detection portion, the maximum transfer of the signal charge of the lower part of one or more transfer electrodes adjacent to the final transfer electrode in the charge transfer channel is achieved. Since the distance and the gate length of the one or more transfer electrodes are substantially the same, the transfer efficiency of the lower part of the final transfer electrode in the charge transfer channel does not decrease. Therefore, according to the invention of claim 2, it is possible to secure a larger signal charge transfer capacity while maintaining the transfer efficiency of the signal charges.

According to the solid-state imaging device of the third aspect of the present invention, the portion connected to the charge detection portion in the charge transfer channel is formed to have the same width as the other portion in the charge transfer channel, so that the transfer capacity of the signal charge is increased. Can be made.

[Brief description of drawings]

FIG. 1 is a plan view showing a charge transfer channel, a transfer electrode, and a charge detection unit in a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a charge transfer channel, a transfer electrode, and a charge detection unit in the solid-state imaging device according to the second embodiment of the present invention.

FIG. 3 is a plan view showing a charge transfer channel, a transfer electrode, and a charge detection unit in a solid-state imaging device according to a third embodiment of the present invention.

FIG. 4 is a plan view showing a charge transfer channel, a transfer electrode, and a charge detection unit in a conventional solid-state imaging device.

[Explanation of symbols]

1 charge detection part 2A, 2B, 2C 1st transfer electrode (final transfer electrode) 3A, 3B, 3C 2nd transfer electrode 4A, 4B, 4C 3rd transfer electrode 5A, 5B, 5C 4th transfer electrode 6A, 6B, 6C Fifth transfer electrode 7A, 7B, 7C Sixth transfer electrode 8A, 7B, 7C Seventh transfer electrode 9 Charge transfer channel 10 Signal charge

Claims (3)

[Claims] 1. A charge detection unit for extracting a signal charge formed and transferred on a semiconductor substrate as an output signal, and a signal charge formed on the semiconductor substrate so as to be connected to the charge detection unit. And a plurality of transfer electrodes formed side by side so as to be adjacent to each other on the upper side of the charge transfer channel to sequentially transfer signal charges to the charge detection channel toward the charge detection unit. In the solid-state imaging device including a transfer electrode group for transfer, a final transfer electrode located at an end portion on the front side in the signal charge transfer direction of the plurality of transfer electrodes forming the transfer electrode group is on the charge detection unit. A solid-state imaging device, wherein the solid-state imaging device is formed in a substantially arc shape with one point as a center. 2. Among the plurality of transfer electrodes forming the transfer electrode group, one transfer electrode adjacent to the final transfer electrode or a plurality of transfer electrodes adjacent to each other including the one transfer electrode is the charge detection circuit. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is formed in a substantially arc shape with a point on the portion as a center. 3. The solid according to claim 1, wherein a portion of the charge transfer channel that is connected to the charge detection unit is formed to have the same width as other portions of the charge transfer channel. Imaging device.