JPS58212167A - Interline transfer charge coupled element - Google Patents

Abstract

PURPOSE:To exhaust charges of a vertical transfer unit channel and a photoreceptor photodiode array adjacent at both sides by aligning overflow drains of adjacent element units at the transfer channel of a vertical transfer unit without providing a channel stopper. CONSTITUTION:In order to transfer a signal charge of vertical direction, two different voltage levels VIL and VIH at middle level of two voltages VL, VH are applied as transfer voltage and a transfer is performed. It is adjusted that the height of a voltage barrier between the photodiode array 1 and the buried channel 3-2 is higher than that between the array 1 and adjacent overflow array 2. Unnecessary charge is simultaneously and totally exhausted to the adjacent drains 2 by applying the voltage VL to the vertical transfer electrode 3-1 from the channel 3-2 of the vertical transfer unit 3 by the overflow control gate 4 from the photodiode array 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an interline transfer charge-coupled device (CCD) for a solid-state image sensor.
LED Devlce)K related.

An electronic still camera, for example, a still image having an electronic imaging means as shown in Japanese Patent Application Laid-open No. 49-52912 and an electric or magnetic recording means capable of recording or reproducing the electrical signal obtained thereby. camera for recording photography,
Alternatively, when electronically providing a shutter function to a solid-state image sensor used in a video camera or the like with variable shutter time, it has been known to use an interline transfer COD as the solid-state image sensor.

By the way, a typical example of the structure of a conventional interline transfer COD is partially shown in FIGS. 1a and 1b. That is, a photodiode array (1) serving as a light receiving section is sandwiched between the overflow drain (2) serving as a means for discharging excess charge on one side, and the vertical transfer section (3) serving as a CCD for vertical transfer of signal charges on the other side. )
are arranged in parallel, and an overflow control case is installed between the photodiode array (1) and the overflow drain (2) to control the overflow potential.
)(4), and a photodiode array (1) is provided between the photodiode array (1) and the vertical transfer section (3).
A transfer gate (5) is provided to transfer the signal charges accumulated in 1) to the buried channel (3-2) under the transfer electrode (3-1) of the saliva direct transfer section (3), and this is connected to the interface. As one element unit of the vertical light receiving/transfer channel of the line transfer CCD, a plurality of these element units are arranged by placing a channel stop (6) between each unit to prevent the spread of charge in the horizontal direction. Therefore, it is configured as a two-dimensional image sensor. In addition, the vertical transfer electrode (3-1) and the buried channel (
In the vertical transfer section (3) formed by 3-2), the 1b
As shown in the potential diagram in Fig. 1c, which is shown in the lower part of the figure, the electrodes (3-2
) will rise and fall between the solid line position and the broken line position.

In order to provide an electronic shutter function to a conventional interline transfer COD having such a structure, the charges accumulated in the light receiving photodiode array are first discharged all at once, and then exposure is performed for the required time. At the time of completion of this process, an operational function is required to transfer the signal charge of the photodiode obtained by the exposure to the vertical transfer electrode from which unnecessary charges have already been discharged by some means. For this reason, in the past, for the bulk discharge of unnecessary charges from the photodiode array (1) prior to exposure, the overflow control game (1) applied a high K voltage to lower the potential barrier between the photodiode and the overflow drain. Vertical transfer electrode (3-1)
Unnecessary charge below is transferred vertically to the transfer CCD.
The shutter function was obtained by sequentially discharging the liquid to the outside.

However, the electronic shutter function using the conventional interlie/transfer COD has several problems as described below.

That is, the first is the transfer gate (5),
Overflow control key) (4) -? , the vertical transfer electrode (3-1), etc. must be formed on the CCD, resulting in a complicated structure, and therefore defects are likely to occur. The problem is that the same path as the signal charge transfer is used to discharge unnecessary charge under the vertical transfer electrode, such as charge due to dark current, so no matter how fast the transfer is performed, it takes a non-negligible amount of time to discharge the unnecessary charge. It is.

For example, if we consider the case where exposure control is performed using the TTL direct metering method, the vertical transfer section (
If the unnecessary charge generated in step 3) is discharged after the photometry is completed, the unnecessary charge discharge time will be added to the exposure time, especially in the case of a high-speed shutter (when the exposure time is very short), so There is a risk of overexposure. Therefore, it is conceivable to finish discharging unnecessary charges from the vertical transfer section (3) before the photometry is completed, but since the shutter speed cannot be known in advance with the TTL direct photometry method, it is possible to finish discharging unnecessary charges from the vertical transfer section (3) before the start of exposure or after the start of exposure. Unnecessary charge must be discharged from the beginning, and for this reason, in the case of a slow shutter (when the exposure time is very long), the transfer lock must be maintained for a long time, which reduces power consumption. This results in the problem of increase.

In the case shown in FIGS. 2a and 2b, the vertical transfer electrode (3-1) is enlarged to the side of the photodiode array (1) without using a transfer gate, and in this way, This is an example in which the complexity of the electrode structure, which is the first drawback, is reduced.

In other words, as shown in the potential diagram in Figure 2C,
By applying the high voltage vR shown by the broken line to the vertical transfer electrode (6-1), the photodiode (1) and the transfer section channel (3
-2) is the lowest potential barrier, and charges at a potential level that exceeds it are transferred from the photodiode (1) to the channel (3-2), and thus Transfer electrode (3-1) stretched to
Applying a high voltage V to is equivalent to the function of a transfer gate. After that, in order to transfer the charge in the vertical direction, two voltages V and VL are required as shown by the solid line in Figure 2C.
It is sufficient to repeatedly apply two voltages to the electrode (3-1). In this case, the barrier potential between the photodiode (1) and the photodiode (1) due to the vertical transfer electrode voltages V1 and vL is (2) is adjusted to be higher than the barrier potential between the photodiode (1) and the photodiode (1) during vertical transfer.
2) Hot water is discharged through the pipe and does not interfere with vertical transfer.

However, even with this improved device, the second drawback, the discharge of unnecessary charges in the vertical transfer section (3), is exactly the same as in the examples shown in Figures 1a and 1b. When applied to an electronic still camera using an electronic shutter function or a video camera with variable shutter time and a strobe effect, the same problem as mentioned above occurred, and the performance could not be said to be practically satisfactory.

The present invention eliminates the drawbacks of these conventional devices and provides a solid-state image sensor with a simple structure, high pixel density, and high resolution, particularly an electronic still camera with a high-performance electronic shutter function or a variable shutter time type. In order to provide an interline/sun-ar CCD image sensor suitable for solid-state imaging devices such as video cameras, the hoe is designed to simultaneously discharge unnecessary charges from the photodiode in the light receiving section and unnecessary charges from the vertical transfer section. At the same time, it is an attempt to simplify the element structure.

That is, in order to achieve such an object, the interline transfer COD of the present invention is arranged in multiple rows of elements in which an overflow drain is arranged on one side of the photodiode array of the light receiving section and a vertical transfer section is arranged on the other side. The device is characterized in that overflow drains of adjacent elements are juxtaposed to the transfer channel of the vertical transfer section without providing a channel stopper, and in one aspect, the overflow drain is Charges from both the vertical transfer section channel and the light receiving section photodiode array adjacent to each other on both sides are discharged together.

In this way, the interline transfer CO of the present invention
In D, the conventional one has an overflow of the vertical transfer section channel and the light receiving section photodiode eye of the adjacent element unit.
, ′, 'i, and the channel stop that existed between the rays and the rays were removed, and each element unit/space was made to be adjacent to each other with a common overflow drain1. Previously, unnecessary charges were first transferred vertically and then transferred to the horizontal transfer section CCD to be discharged.
In the present invention, this can be discharged all at once to the adjacent overflow drain, so there is no need for transfer time for discharging unnecessary charges, and the time required for discharging unnecessary charges can be significantly shortened. At the same time, this overflow drain can also drain the false charge of the adjacent light receiving photodiode array, and the common overflow drain can drain the unnecessary charge of the vertical transfer section between adjacent element units and the light receiving photodiode array. Unnecessary charges can be discharged all at once, and the device structure can be simplified and unnecessary charges can be discharged in a short time at the same time.

The present invention will be described in detail below along with the illustrated embodiments. 68 and 6b are a plan view and a sectional view schematically showing a part of an interline transfer CCD according to the first practical example of the present invention, and as shown in FIG. ) is absent, and the vertical transfer electrode (3-1) is provided apart from the adjacent overflow drain (2).

In FIG. 6b, the embedded channel (3) of the transfer section (3)
The right side of -2) is adjacent to the overflow drain (2) of the adjacent element unit, and is designed to discharge charges from the channel (3-2) to the overflow drain (2). As can be seen from the left side of FIG. 6b, unnecessary charges can also be discharged from the light-receiving portion photodiode array (1) for each element.

As shown in Fig. 6b, the vertical transfer electrode (3-1) is designed so that the entire potential well can be formed only in the left side of the buried channel (3-2) near the photodiode array (1). The electrode (3-1) is extended on the left side by the photodiode array (1) and is separated from the adjacent overflow drain (2) on the right side.

Therefore, in the case of FIGS. 31 and 6b, only the vertical transfer electrode (3-1) and the overflow control gate electrode (4) are required as electrodes, and the electrode structure may also be simpler than that of the conventional one. .

The driving method for electronically shuttering the image sensor using the interline transfer COD of this embodiment will be described below with reference to the potential diagram in FIG. 6c.

When the potential of the vertical transfer electrode (3-1) is set to the lowest voltage VL, the potential of the buried channel (3-2) of this CCD becomes the highest potential as shown in FIG. If -2) had any charge, all of it would be discharged to the adjacent overflow drain (2). Further, when the potential of the vertical transfer electrode (3-1) reaches the highest potential V, the voltage barrier between the vertical transfer electrode (3-1) and the photodiode (1) is low. , from the photodiode (1) to the buried channel (
Signal charges can be transferred to the potential well formed on the left side in the figure 3-2).

To transfer signal charges in the vertical direction, another 22 voltage levels VIL and Vlll, which are at an intermediate level between the two potentials vL and VH, may be applied as transfer potentials to perform the transfer. In this case, no matter which voltage VIL or VIH is applied to the vertical electrode (3-1), the photodiode array (1) and the buried channel (3-2)
) is higher than the potential barrier height between the photodiode array (1) and the adjacent photodiode array (2), VI
L+! : Of course, adjust the VIR and overflow control gate voltages.

If you do K like this, photodiode array (1) Karaha overflow control cable) (4) K
In addition, by applying a voltage vL from the channel (3-2) of the vertical transfer section (3) to the vertical transfer electrode (3-1), the overflow drain (2) adjacent to each
Each unnecessary charge can be discharged simultaneously and all at once.

Figures 4m, 4b, and 4c are similar plan views, cross-sectional views, and button diagrams schematically showing another embodiment of the present invention; Compared to the one shown in Figure 3b, an overflow drain control (4) is not required, and the structure is simple with only the vertical transfer electrode (3-1) provided as an electrode.

In this embodiment, the potential barrier between the photodiode array (1) and the overflow drain (2) is formed by a fourth n-shaded region with a lower donor concentration than both of them.
It is fixed in the area indicated by reference numeral (7) in Figure b.

To explain the operation of the CCD of this embodiment with reference to Fig. 4c, as in the case of the first embodiment shown in Figs.
IL + ■Summer I r Vll is applied, and the operation is the same as in the first embodiment. However, this second embodiment is essentially different from the first embodiment in that there is no overflow control gate electrode (4), so that the charge accumulated in the photodiode array (1) is This is because it cannot be discharged all at once to the adjacent overflow drain (2). However, in the second embodiment, unnecessary charges cannot be discharged from the photodiode array (1) to the overflow drain (2) at all, and unnecessary charges can be discharged from the vertical transfer channel in a much shorter time than in the conventional example. This is very easily possible.

That is, unnecessary charges of the photodiode array (1) are once transferred to the buried channel (3-2) below by applying a high voltage vH to the vertical transfer electrode (3-1),
This can be achieved by subsequently applying a low voltage V to the vertical transfer electrode (3-1) and discharging the unnecessary charge transferred to the channel (3-2) to the adjacent overflow drain (2). be.

In this way, unnecessary charges in the vertical transfer section (3) can be discharged in one stage of transfer, and the photodiode array (3) can be discharged in one stage.
The discharge of unnecessary charges in 1) is achieved through two stages of transfer. Therefore, when this is used as an image sensor with a shutter function such as an electronic still camera, a short period of only 1 or 2 clocks is required before the start of exposure. Within the camera, all unnecessary charges have been discharged and the camera is ready for shooting.

As another example (not shown), instead of eliminating the channel stopper (6) that was conventionally located between the vertical transfer section (3) and the overflow drain (2), a horizontal CCD structure may be constructed using the usual method. from the vertical transfer section (3) to the overflow drain (2)! A similar effect can be obtained by making it possible to discharge loads all at once.

511.5b and 50 show a sixth embodiment of the present invention, and in this embodiment, the distance between the vertical transfer section (3) and the overflow drain (2) is different from that in the second embodiment. The difference is that another gate electrode (8) is provided at the gate electrode.

By providing another gate electrode (8) as in
Even if the vertical transfer channel (3-2) and the overflow drain (2) of the adjacent element are substantially separated from each other, the voltage applied to the gate electrode (8) can be controlled. ) can adjust the potential directly under the second electrode, although this makes the electrode structure somewhat complicated.
It is possible to obtain the same effects as in Example Σ.

It should be noted that in the above description, the display and description on the drawings of elements that are not essentially related to the description of the present invention, such as the means for shielding the vertical rotation part (3) from light, are omitted. It is. Furthermore, in the above explanation, an example in which a photodiode is used in the light receiving section has been described, but the present invention is not limited to this, and the present invention can also be applied to, for example, a photoconductive film stacked solid-state image sensor. It is possible.

As described above, according to the present invention, the vertical transfer section C
Since unnecessary charges can be discharged from the CD to the overflow drain all at once, exposure preparation can be completed in just 1 to 2 clock periods.Also, the solid-state with electronic shutter function is capable of high-speed shutter operation as before even with COD. It is possible to realize an image sensor, and since unnecessary charges from both the adjacent light receiving section and vertical transfer section can be discharged to the overflow drain, it greatly contributes to the simplification of the device configuration, and the unnecessary charges can be discharged in a short time. Therefore, there is no need for a transfer operation to discharge σ unnecessary charges from the 111i' vertical transfer unit COD before or during exposure, and the power consumption for transfer drive can be reduced by that much, and the CCD By simplifying the configuration itself, it is possible to increase pixel density and therefore achieve higher resolution.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1a, 1b, and 1c are a plan view, a sectional view, and a potential diagram schematically showing essential parts of an example of a conventional interline transfer COD, and FIG.
2B, and 2C are a plan view, a sectional view, and a potential diagram schematically showing the main parts of another conventional example,
6a, 6b, and 6c are a plan view, a sectional view, and a potential diagram schematically showing the main parts of the first embodiment of the present invention, and FIGS. 4a, 4b, and 4c. 5A, 5B, and 5C schematically show a plan view, a sectional view, and a potential diagram of the main parts of the second embodiment of the present invention, and FIGS. FIG. 2 is a plan view, a cross-sectional view, and a potential diagram schematically showing the part. (1): Light receiving part photodiode array, <2) Niober flow drain, (3): Vertical transfer part, (3-1
): vertical transfer electrode, (3-2): buried channel, (4) nitrogen flow control gate, (5)
: ) Transfer gate, (6): Channel stop, (7): Low concentration n shadow region, (8): Gate electrode. Agent Patent Attorney Kimura 3 Akira 1 o + 16 listening o / C mouth 1 ° spear 2 theta flash: A'720 figure sum l: 2 'c genius 3a mouth 36 figure + 3 G1 illusion 4 theta closing + 4? Sen-A=4C Eyesai 5/2 Figure-151, - Zuga 5C Ward: □. 325-

Claims (1)

[Claims] In an interline transfer charge-coupled device that is arranged in multiple rows of element units with an over 70 and a drain on one side of a light receiving part and a vertical transfer part juxtaposed on the other side, an element unit adjacent to the channel of the vertical transfer part. An interline transfer charge coupling characterized in that overflow drains are arranged in parallel, and the overflow drain discharges charges from both a vertical transfer section channel and a light receiving section provided on both sides thereof. element.