JPH0770704B2 - Charge transfer device and driving method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a structure and a driving method of a charge transfer device.

[Conventional technology]

A four-phase drive charge transfer device having a plurality of channel regions which are signal charge paths has been conventionally known. FIG. 4 shows a schematic plan view of a conventional four-phase drive charge transfer device having two channel regions. Transfer electrode groups 41 to 48 are provided on the first n-type channel region 21 and the second n-type channel region 22 partitioned by the p-type element isolation region 10, and the transfer electrode groups 41 to 48 are Every four transfer electrodes are electrically connected. In order to distinguish the four electrically separated transfer electrodes by the clock voltage applied to each of them, each electrode will be referred to as G ₁ , G ₂ , G ₃ and G ₄ . In this conventional example, the transfer electrodes 41 to 48 are shared between the first and second n-type channel regions, and the arrangement of the transfer electrodes along the channel region is equal. That is, from left to right in FIG. 4, the transfer electrodes of both channels are arranged in the order of ..., G ₁ , G ₂ , G ₃ , G ₄ ,.

Next, a conventional driving method of the four-phase drive charge transfer element will be described. FIG. 5 shows the transfer electrode of the conventional element shown in FIG.
Clock voltage φ ₁ , applied to G ₁ , G ₂ , G ₃ and G ₄ ,
6 shows a timing chart of φ ₂ , φ ₃ and φ ₄ . φ
_{1 to} φ ₄ are periodic pulses whose phases are shifted by 1/4. To show the principle of charge transfer, FIG. 6 shows the transfer electrodes G ₁ , G ₂ , at the times T ₁ , T ₂ , ..., T ₅ in FIG.
The potential diagrams of the first and second channel regions immediately below G ₃ and G ₄ are shown. Needless to say, both channel regions have the same potential distribution at each time because the arrangement of the transfer electrodes is the same. White circles in FIG. 6 represent signal charges. At time T ₂ , the signal charges accumulated directly under the electrodes G ₁ and G _{2 are} immediately under the electrodes G ₂ and G _{3 at} time T ₃ , and further at the time T ₃ .
At T ₄ , they are transferred to just below the electrodes G ₃ and G ₄ . That is, the signal charge is transferred from left to right in FIG. 6 with the passage of time.

[Problems to be Solved by the Invention]

As described above, the first and second channel regions 21,22
In this case, since the arrangement of the transfer electrodes is the same, if the clock voltage for transferring the signal charges is applied to the transfer electrodes, the charge transfer is surely performed simultaneously in both channel regions. It was impossible to obtain a selective transfer function of transferring signal charges existing only in some of the plurality of channel regions and not transferring signal charges existing in other channel regions. .

Therefore, in the CCD image sensor, which is an application of the charge transfer element, the signal charge photoelectrically converted to all pixels at the same time is output by interlaced scanning.
It was also impossible to realize a CCD image sensor with functions that had been desired to be developed when applied to TV cameras.

An object of the present invention is to provide a charge transfer device having a selective transfer function and a driving method thereof.

[Means for Solving the Problems]

The charge transfer element of the first invention of the present application has a plurality of channel regions which are paths for signal charges, and an arbitrary transfer electrode provided on the channel region is arranged between the plurality of channel regions. In a four-phase drive charge transfer device, the arrangement of the transfer electrodes is repeated with an arrangement of four transfer electrodes along the signal charge transfer direction as one cycle.
The arrangement of any two adjacent transfer electrodes of the four transfer electrodes is reversed between the plurality of channels, and the arrangement of the remaining two transfer electrodes is the same between the plurality of channels. .

The second invention of the present application is the method of driving a charge transfer element according to the first invention, wherein at any one time, any one of two transfer electrodes having the same electrode arrangement among a plurality of channels is provided. Signal charges are accumulated in the channel region below the first transfer electrode by turning on only the transfer electrode (hereinafter referred to as the first transfer electrode), and then the electrode arrangement is the same between the channels. Of the two transfer electrodes, the other transfer electrode that is not the first transfer electrode (hereinafter referred to as the fourth transfer electrode) is held in the OFF state, and all three transfer electrodes other than the fourth transfer electrode are turned on. After the state, the arrangement is reversed between the first transfer electrode and the plurality of channels 2
By sequentially turning off any one transfer electrode (hereinafter, referred to as a second transfer electrode) of the two transfer electrodes, the signal charge is transferred from the channel region under the first transfer electrode to a plurality of channels. Of the two transfer electrodes whose arrangement is reversed, the transfer is performed to the channel region below the other transfer electrode (hereinafter referred to as the third transfer electrode) which is not the second transfer electrode, and then the second transfer electrode. By holding all the three transfer electrodes other than the second transfer electrode in the on state while keeping the off state, and sequentially turning off the third transfer electrode and the fourth transfer electrode, The signal charge is transferred from the channel region below the third transfer electrode to the channel region below the first transfer electrode.

[Action]

In the charge transfer device of the present invention, since the arrangement of the transfer electrodes differs among the plurality of channel regions, the arrangement of potential wells and barriers can be different. Further, when the driving method of the present invention is applied, charge transfer is performed by moving the potential well in some channel regions in the transfer direction, while moving the potential well in only one direction in other channel regions. It is possible not to complete the charge transfer, and the selective transfer function can be realized.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic plan view of a charge transfer device which is an embodiment of the first invention of the present application. In this embodiment, transfer electrode groups 31 to 38 are provided on the first n-type channel region 21 and the second n-type channel region 22 divided by the p-type element isolation region 10, and this transfer electrode group is provided. Reference numerals 31 to 38 are four-phase drive charge transfer elements electrically connected to every four transfer electrodes.
In order to distinguish the four electrically separated transfer electrodes by the clock voltage applied to each, each electrode is labeled G ₁ ,
If G ₂ , G ₃ and G ₄ are used, the arrangement of transfer electrodes in the first n-type channel region 21 is ..., G ₁ , G ₂ , G ₃ , G ₄ ... In the shaped channel region 22, the arrangement of transfer electrodes is ..., G ₁ , G ₃ , G ₂ , G ₄ ,.

FIG. 2 shows transfer electrodes G ₁ , G ₂ , G _{3 of} the device shown in FIG. 1 for explaining an embodiment of the second invention of the present application, and
Clock voltages applied to G ₄ φ ₁ , φ ₂ , φ ₃ and φ ₄
The timing chart of is shown. Each clock voltage is at time T ₁
It is a clock voltage with one cycle from T ₅ to T ₅ . The difference from the conventional driving method is that at time T ₁ , T ₃ and T ₅ , both clock voltages φ ₂ and φ ₄ are off. In order to explain the state of charge transfer, an electric potential diagram immediately below the transfer electrode of the first n-type channel region at each time T _{1 to} T ₅ shown in FIG. 2 is shown in FIG. N
Figure 3 (b) shows the potential diagram directly under the transfer electrode in the channel region
Shown in. White circles in the figure represent signal charges. G ₁ at time T ₁
The signal charge accumulated directly under the electrode is G ₁ , at time T ₂ ,
It is distributed immediately below the G ₂ and G ₃ electrodes and is transferred to immediately below the G ₃ electrode at time T ₃ . Furthermore, at time T ₄ , the signal charge is
G _3, G _4, and distributed in the G ₁ electrode immediately below, G ₁ at time T ₅
Transferred directly under the electrode. The above description of charge transfer is the first
And the second n-type channel region, as shown in FIG. 3 (a), in the first n-type channel region 21, the signal charge accumulated immediately below the G ₁ electrode 31 at the time T ₁ . Is transferred to four electrodes at time T ₅ , and the next G ₁ electrode 35
While it is transferred directly below, in the second n-type channel region 22, as shown in FIG. 3B, the signal charge returns directly below the same G ₁ electrode 31. In the second n-type channel region 22, the G ₃ electrode 32 and the G ₁ electrode located on the right side of the G ₃ electrode
Since the G ₂ and G ₄ electrodes 33 and 34 are not turned on between 35, the signal charges are not transferred.

One embodiment of the second invention of the present application described above is a driving method in which the signal charges in the first n-type channel region 21 are transferred but the signal charges in the second n-type channel region 22 are not transferred. ,
By exchanging the clock voltages φ ₂ and φ ₃ , it is possible to realize a driving method in which the signal charges in the second n-type channel region 22 are transferred but the signal charges in the first n-type channel region 21 are not transferred.

〔The invention's effect〕

As described above, according to the present invention, in a charge transfer device having a plurality of channel regions sharing a transfer electrode,
Transfers only the signal charges existing in some channel regions,
It is possible to realize the selective transfer function of not transferring the signal charges existing in the other channel region.

Thus, in a frame transfer type or frame interline transfer type CCD image pickup device having an image pickup unit and a storage unit, two vertical channels are provided in the storage unit for each vertical channel of the image pickup unit to form a multiplexer, By storing the signal charges of the odd-numbered rows and the signal charges of the even-numbered rows of the image pickup section by dividing them into the above-described two pairs of vertical channels of the accumulation section and performing the selective transfer when reading the signal charges of the accumulation section ,
It is possible to realize a CCD image pickup device suitable for an EDTV camera in which signal charges photoelectrically converted at the same time are converted into interlaced scanning by a storage unit and output.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a charge transfer element according to an embodiment of the first invention, and FIG. 2 is a timing chart of clock voltages applied to charge transfer electrodes for explaining an embodiment of the second invention. 3 (a) and 3 (b) are potential diagrams of the first and second n-type channel regions at respective times in FIG. 2, and FIG. 4 is a schematic plan view of a conventional charge transfer device, FIG. FIG. 6 is a timing chart showing a clock voltage for charge transfer in the conventional driving method, and FIG. 6 is a potential diagram at each time in FIG. 10 ... P-type element isolation region, 21 ... First n-type channel region, 22 ... Second n-type channel region, 31-38, 41-48 ...
… Transfer electrodes.

Claims (2)

[Claims] 1. A four-phase drive charge transfer having a plurality of channel regions which are paths of signal charges, and arbitrary transfer electrodes provided on the channel regions being arranged between the plurality of channel regions. In the element, the arrangement of the transfer electrodes is repeated with an arrangement of four transfer electrodes along the transfer direction of the signal charges as one cycle, and any two adjacent transfer electrodes of the four transfer electrodes are repeated. Is reversed among a plurality of channels, and the arrangement of the remaining two transfer electrodes is the same among the plurality of channels. 2. The method of driving a charge transfer device according to claim 1, wherein at any one time, any one of the two transfer electrodes having the same electrode arrangement among a plurality of channels (hereinafter referred to as “transfer electrode”). Only the first transfer electrode) is turned on to store the signal charge in the channel region below the first transfer electrode, and then two transfer in which the arrangement of electrodes is the same between a plurality of channels. After holding the other transfer electrode (hereinafter referred to as the fourth transfer electrode) that is not the first transfer electrode of the electrodes in the off state, all three transfer electrodes other than the fourth transfer electrode are turned on. , A first transfer electrode and an arbitrary one of the two transfer electrodes whose arrangement is reversed between the plurality of channels (hereinafter, referred to as a second transfer electrode) are sequentially turned off to obtain a signal. Charge
From the channel region below the first transfer electrode, below the other transfer electrode (hereinafter referred to as the third transfer electrode) that is not the second transfer electrode of the two transfer electrodes whose arrangement is reversed between the plurality of channels. Of the three transfer electrodes other than the second transfer electrode while keeping the second transfer electrode in the off state,
The signal charges are transferred from the channel region below the third transfer electrode to the channel region below the first transfer electrode by sequentially turning off the third transfer electrode and the fourth transfer electrode. A method of driving a charge transfer device, comprising: