JP3118325B2 - Solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device such as a CCD solid-state imaging device having two or more different gate structures.

[0002]

2. Description of the Related Art Conventionally, CCD solid-state imaging devices used in home video cameras and the like are roughly classified into frame transfer type and interline type. In the case of the frame transfer type, for example, the document “Solid-state imaging device” (Shokodo Co., Ltd., first edition first published on July 30, 1986)
As shown in page 4.6 of FIG. 4.6, the image pickup section (image section), storage section, horizontal shift register (horizontal read register), and output section (detection / amplification section).

[0005] The signal charges of the imaging section based on the reception of the imaging light are sequentially transferred from the imaging section to the output section by the CCD of each section, and are read out from the output section to the outside as a video signal (image signal).

In the case of the interline type, for example, as described in FIG.
D) is provided, and signal charges are sequentially transferred from the vertical register to the output unit via a horizontal register (horizontal CCD). An imaging unit for transferring signal charges, regardless of whether it is a frame transfer type or an interline type,
Storage unit (vertical shift register), horizontal shift register,
The gate structure of the CCD of the output unit may be different.

For example, in the case of a frame transfer type CCD solid-state image pickup device, as shown in FIG. 4, a CCD gate electrode 2 of the image pickup unit 1 and a gate electrode of the CCD of the storage unit 3 are provided as shown in FIG. 4 is different. In FIG. 4, reference numeral 5 denotes a channel separation region (channel stop diffusion region), and a region between the regions 5 forms a CCD channel as a signal charge transfer path.

Reference numeral 7 denotes an incident light window formed around the narrow channel portion 2 'of each gate electrode 2, which improves the reduction in blue sensitivity as described on page 92 of the above-mentioned document. Then, for example, two-phase or three-phase
The transfer gate pulse is sequentially applied by the phase driving method, and the signal charges are transferred in the direction of the arrow line s in the figure.

At this time, if the signal charge is not completely transferred not only at the same gate structure of the imaging unit 1 and the storage unit 3 but also at the boundary of the gate structure changing from the gate electrode 2 to the gate electrode 4, the image quality will be high. Significantly deteriorated. However, at the boundary portion, even if a gate pulse of the same voltage (magnitude) is applied to the transfer side CCD of the gate electrode 2 and the transfer side CCD 4 of the gate electrode 4 based on the difference in the gate structure, the original surface is not affected. The depth of the potential (potential) differs, and a situation occurs in which a sufficient surface potential difference required for transfer is not formed.

Therefore, conventionally, as shown in FIG.
High voltage Va of the gate pulse P ₂ of the receiving CCD than the gate pulse P ₁ of the CD. In this case, the gate pulse P
Based on the application of P ₁ and P ₂ , the surface potential of the imaging unit 1 becomes sufficiently shallower than that of the storage unit 3 as shown in FIG.
A sufficiently large surface potential difference φa that changes from a shallow state to a deep state in the transfer direction occurs at a boundary portion 8 between the two portions 1 and 3.

Due to the large surface potential difference φa, signal charges are completely transferred even at the boundary portion 8 as shown by the arrow line e in FIG. In order to perform the complete transfer of the signal charge, the transfer gate pulse on the transfer side and the transfer gate on the receive side are used not only between the imaging unit 1 and the storage unit 3 but also between the units having different signal charge transfer path gate structures. It is necessary to provide a sufficiently large surface potential difference at the boundary by giving a voltage difference to the pulse.

[0010]

In the case of the above-mentioned conventional solid-state imaging device, there is a problem that a complicated gate pulse generating circuit is required because the voltage of the transfer gate pulse is changed between the parts having different gate structures. In addition, when the gate structure changes at a plurality of locations, it is necessary to sequentially increase the voltage of the transfer gate pulse to make the surface potential deeper in the later stage, but the potential of the transfer gate pulse cannot be increased without limit. And incomplete transfer is likely to occur.

According to the present invention, the surface potential (potential) between CCDs having different gate structures is changed in a concentrated manner at a boundary portion thereof, and a transfer gate pulse between the transfer side and the reception side at the boundary portion is not subjected to a voltage difference. It enables complete transfer of signal charges.

[0012]

In order to achieve the above object, in a solid-state image pickup device according to the present invention, a transfer-side CCD or a transfer-side CCD of one of the gate structures at a CCD boundary where a gate structure of a signal charge transfer path changes. Receiving side C of the other gate structure
The CD is formed by a CCD whose surface potential gradually changes from a deep state to a shallow state in the transfer direction at the boundary,
The surface potential difference of the CD is concentrated on the boundary,
At the boundary of the CD, a surface potential difference is formed that changes sharply from a shallow state to a deep state in the transfer direction.

[0013]

In the solid-state imaging device according to the present invention having the above-described structure, for example, in a portion where the gate structure of the signal charge transfer path is different, for example, the range in which the original surface potential on the signal charge transfer side does not cause transfer deterioration is generated. Thus, a large surface potential difference that changes gradually and sharply changes is applied to a boundary where incomplete transfer is likely to occur.

Therefore, the signal charges can be completely transferred without level shifting the transfer gate pulses of the transfer side CCD and the transfer side CCD. Even if the gate structure is different at a plurality of points in the signal transfer path, it is not necessary to gradually increase the transfer gate pulse and gradually increase the surface potential as in the conventional case.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described with reference to FIGS. In FIG. 2A showing the gate structure,
The same reference numerals as those in FIG.
Is the delivery side CC of one of the gate structures such as the imaging unit 1 in FIG.
D and 10 are receiving CCDs of the other gate structure of the storage unit 3 and the like in FIG. 4, α is a boundary where the gate structure of the boundary portion 11 between the two CCDs 9 and 10 changes, and 12 is a surface potential variable unit of the receiving CCD 9. .

If each of the CCDs 9 and 10 is regarded as a shift register and one bit is transferred by one gate electrode 2 or 4, the boundary portion 11 is substantially equivalent to three bits of each of the transfer side and the receive side. Is formed by the shift register of FIG. Further, the transfer-side 3-bit shift register of the two 3-bit shift registers forms the variable section 12, and the CCD of the variable section 12 gradually reduces the ion implantation amount (ion implantation amount) at the time of manufacturing. Is created.

Therefore, only the variable portion 12 of the CCDs 9 and 10 on both sides gradually loses its original surface potential (potential) within a range where transfer deterioration does not occur as shown in FIGS. 1 (a) and 2 (b). It becomes shallow. 1 (a) and 2 (b) show the surface potential on the lines a and a 'in FIG. 2 (a).

Since the surface potential of the variable portion 12 becomes shallow at the boundary α, the original surface potential of the receiving CCD 10 is the same as the surface potential of the receiving CCD 9 before the boundary portion, as shown in FIG. As shown in (a), a large surface potential difference φb that sharply changes in the transfer direction is formed at the boundary α.

Therefore, as shown in FIG.
The voltage of the transfer gate pulse Pa of D9 and the receiving CCD 10
Even if the voltage of the transfer gate pulse Pb of
In D9, the signal charges are gradually transferred from the wells having a large surface potential to the wells having a small surface potential. At the boundary α, the signal charges are completely transferred to the receiving side based on the large surface potential difference. And
Since it is not necessary to change the transfer gate pulses Pa and Pb by level shifting, both gate pulses Pa and Pb can be formed by the same pulse, and the conventional complicated pulse generation circuit becomes unnecessary.

Even if a different portion of the gate structure occurs after the receiving CCD 10, the original surface potential of the receiving CCD is gradually changed at the boundary in the same manner as described above, so that the same as the transfer gate pulses Pa and Pb. Complete transfer can be performed using a pulse as a transfer gate pulse.

The boundary portion 1 where the variable portion 12 is provided
The range of 1 is not limited to the embodiment. In the above embodiment, the surface potential of the variable portion 12 was changed by changing the ion implantation amount. However, for example, the shape of the gate electrode 2 of the variable portion 12 was changed to realize the change of the surface potential by a so-called narrow channel effect. Is also possible.

Further, in the above embodiment, both CCDs 9, 1
Since the original surface potential of 0 is deep, a variable portion 12 is provided in the delivery side CCD 9 to change the surface potential only from a deep state to a shallow state. However, as shown in FIG.
When the original surface potential of 0 is shallow, a variable surface potential portion corresponding to the variable portion 12 may be provided in the receiving CCD 10, and only the surface potential of this variable portion may be changed from a deep state to a shallow state.
Further, it is needless to say that the present invention can be applied to not only a CCD solid-state imaging device but also a solid-state imaging device using a CCD as a part of a CID solid-state imaging device or the like.

[0023]

Since the present invention is configured as described above, the following effects can be obtained. Delivery CC
D9 or the surface potential (potential) of the receiving CCD 10
Changes from a deep state to a shallow state in the transfer direction of signal charges only at the boundary portion 11, the surface potential difference between the CCDs 9, 10 on both sides concentrates on the boundary portion 11, and the boundary α steeply changes from a shallow state to a deep state in the transfer direction. Since a large changing surface potential difference is formed, the signal charges can be completely transferred between the CCDs 9 and 10 having different gate structures without causing a voltage difference between the transfer gate pulses of the signal charges, and a pulse generation for generating a transfer gate pulse is performed. A circuit can be easily formed.

Further, since the transfer gate pulse of the same voltage can be used even when the gate structure changes, when there are a plurality of places where the gate structure changes in the signal charge transfer path, the transfer gate pulse is changed as in the related art. Complete transfer can be performed without gradually shifting the level to a high voltage.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory diagrams of one example and another example of a surface potential change at a boundary portion of a solid-state imaging device according to the present invention.

FIGS. 2A and 2B are explanatory diagrams of the structure of a gate electrode and its surface potential according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a transfer gate pulse according to one embodiment of the present invention.

FIG. 4 is an explanatory diagram of a conventional gate structure.

FIG. 5 is an explanatory diagram of a transfer gate pulse of a conventional example.

FIG. 6 is an explanatory diagram of a surface potential change in a conventional English boundary part.

[Explanation of symbols]

 2, 4 Gate electrode 9 Delivery side CCD 10 Receiving side CCD 11 Boundary part α boundary

Claims (1)

(57) [Claims] In a solid-state imaging device having a structure in which a gate structure of a CCD forming a signal charge transfer path changes in the middle of the transfer path, a transfer side CCD having one gate structure or a reception side CCD having another gate structure is provided on a surface thereof. A potential is formed by a CCD that gradually changes from a deep state to a shallow state in a transfer direction at a boundary portion between the two-side CCDs, and a surface potential difference between the two-side CCDs is concentrated at the boundary portion;
A solid-state image sensing device, wherein a surface potential difference which sharply changes from a shallow state to a deep state in a transfer direction is formed at a boundary between the two CCDs.