JPH0714045B2 - Charge transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides a charge transfer device (CCD), and in particular, a function capable of switching and selecting whether to introduce the transfer charge from an output end or to eliminate it during transfer. Involved in CCD.

[Outline of Invention]

The present invention provides a charge discharge path having a drain region for discharging charges to a required charge storage section of the charge transfer section. In particular, this charge discharge path is connected to the charge transfer section from the charge transfer section. A switching unit that switches whether to introduce charges or to transfer the charges as they are in the charge transfer unit;
A potential barrier portion that prevents the reverse flow of charges from the drain region, and a charge delivery portion that overcomes this barrier portion and pumps out the charges from the charge transfer portion to the drain region and sends them out are provided. It is possible to reliably switch to the excluded / non-excluded state without causing the backflow of charges from the drain region.

[Conventional technology]

The magnetic tracks on the magnetic tape in the video tape recorder VTR change the inclination of the magnetic field with respect to every other magnetic track to cause azimuth loss between adjacent magnetic tracks to reduce crosstalk between adjacent tracks. I'm wearing. In this case, in a special mode, for example, in still reproduction, a correction circuit is provided to correct a skew jump of 0.5H (H is a horizontal cycle) of the horizontal sync signal interval caused by the magnetic head scanning across a plurality of tracks. Used. This correction circuit is provided with a second signal line having a delay line that delays by 0.5H as compared with the first signal line used in a normal reproduction state, and detects the reproduction of the reproduced video signal by detecting a skew jump. By switching to the second signal line, the reproduced video signal output delayed by 0.5H is taken out from this second signal line.

As such a correction circuit, there has been proposed a configuration in which the above-described first line and the second line that obtains a delay of 0.5H in comparison with the above-mentioned first line are each configured by a CCD formed on a common semiconductor substrate. . In this case, in order to selectively introduce the reproduced video signal output from the first and second lines, that is, the CCDs shown in FIGS. 1 and 2, in each CCD, the charge discharge path for discharging the transfer signal charge to the drain region is removed. Is provided, and the introduction of electric charges to this discharge path is interlocked to be switched to any one, and the reproduction video signal output is derived from either one.

A CCD having such a charge discharge path is shown, for example, in its schematic top view in FIG. 4 and in FIG.
As shown in the sectional view on the line, for example, at least one main surface (1a) side is composed of a semiconductor substrate (1) made of one conductivity type, for example, n-type semiconductor having a relatively low impurity concentration.
Then, a channel stopper region CS in which another conductivity type, for example, P-type impurity is introduced by selective diffusion is formed facing the one main surface (1a) of the semiconductor substrate (1), and the charge of the CCD is A transfer passage is defined. In the charge transfer passage defined by the channel stopper region CS, the above-mentioned one conductivity type, that is, for example, an n-type impurity is selectively diffused by maintaining a predetermined interval along the transfer direction. The charge storage regions (3s) that have been introduced and have a higher impurity concentration than other parts are formed, and these regions (3s)
A charge transfer region (3t) is formed therebetween. On the main surface (1a) of the substrate (1), a dielectric film (4) such as SiO ₂ is formed on the front surface, and, for example, a large number of dielectric films (4) are formed on each charge storage region (3a) through the dielectric film (4). The charge storage part (6s) is formed by selectively forming the electrode (5a) made of a crystal and a silicon layer, and is formed on the charge transfer region (3t) by, for example, thermally oxidizing the surface of the electrode (5s). These electrodes (5
An electrode (5t) made of, for example, a metal electrode electrically insulated from s) is selectively formed to form a charge transfer section (6t). In this way, the charge storage portions (6s) and the charge transfer portions (6t) are arranged alternately along the original charge transfer direction shown by the solid arrows a and b in FIG. Then, the electrodes (5t) and (5s) of the adjacent charge storage section (6s) and charge transfer section (6t) are electrically connected to each other,
And one of these mutually connected electrodes (5t) and (5s)
Every other pair is electrically connected to each other to derive terminals t ₁ and t ₂ to which two-phase clock voltages φ ₁ and φ ₂ are applied. In this way, the charge transfer section (9) having the CCD structure is constructed.

Then, a side path for eliminating the transferred charges is provided for the charge transfer section (9). This bypass extends a region surrounded by the channel stopper region CS laterally from _one storage unit (6s ₁ ) forming the charge transfer unit (9), and within this region, each region (3t) and (3s). ) And an n-type impurity of the same conductivity type are introduced at a high concentration to form a drain region (10). A drain electrode (11) is ohmicly deposited on the drain region (10) to introduce a terminal D. Then, the drain region (10) is formed through the dielectric film (4).
A switching electrode (12) formed at the same time as the above-mentioned electrode (5) is deposited between the charge storage section ( ₁ ) and _one charge storage section (6s ₁ ),
The switching unit (13) is configured here. SW is this electrode (1
Introducing terminal from 2) is shown.

In such a configuration, in order to discharge and remove the transferred charges by the charge transfer unit (9) to the drain region (10), the switching unit (1
As shown in the potential diagram by the solid line in FIG. 5, a positive positive voltage, for example, a voltage of 11.6V is applied to the electrode (12) of 3) so that a potential deeper than the potential in the storage portion (6s ₁ ) is applied. By forming the signal charges, the signal charges in the storage portion (6s ₁ ) are sent to the drain region (10) and are eliminated as schematically shown by the arrow j.

However, in the case of such a configuration, since the potential for the signal charge in the switching unit (13) and the storage unit (6s ₁ ) is higher than the potential of the drain region (10), that is, the power source potential, as shown by the broken line in FIG. When the clock voltage for the storage section (6s ₁ ) drops, the transient charge is fast, and before the signal charge is discarded to the drain side, the next charge transfer of the storage section (6s ₁ ) in the transfer section (9) is performed. In some cases, backflow from the power supply occurred in the section (6t).

[Problems to be solved by the invention]

As described above, it has the function of switching to eliminate or not exclude the signal charge of the CCD during charge transfer.
In the CCD configuration, there is a problem that the charges to be removed are not sufficiently removed and may flow back, and in the present invention, charge transfer designed to solve such a problem. It provides a device CCD.

[Means for solving problems]

The present invention relates to a charge transfer unit that should originally be a signal charge, a drain region, and a switching unit that switches between a required charge storage unit and a drain region of the charge transfer unit between discharging and non-discharging the charge of the charge transfer unit. In particular, a sending-out part for sending out the charge from the switching part to the drain region side between the switching part and the drain region and a fixed potential barrier is formed between the sending-out part and the drain region. Set up barriers. Then, a voltage synchronized with the above-mentioned voltage applied to the one charge accumulating section of the charge transfer section is applied to the charge sending section, so that the charge can be sent out over the potential barrier in the drain region.

[Action]

As described above, in the present invention, the switching unit for discharging or non-discharging the charge in the charge transfer unit is provided between the charge transfer unit for performing the original charge transfer and the drain region. In particular, by forming a fixed potential barrier between the switching portion and the drain region, backflow from the drain side to the charge transfer portion is prevented.

〔Example〕

Next, an example of the CCD according to the present invention will be described with reference to FIGS. FIG. 1 is an enlarged top view of an essential part of a CCD according to the present invention, and FIG. 2 is a voltage diagram of an applied voltage used for the explanation.
FIG. 3A is an enlarged sectional view taken along the line AA in FIG. 1, and FIG.
E is the potential diagram. In FIGS. 1 to 3, parts having the same configurations as those described in FIGS. 4 and 5 are designated by the same reference numerals, and redundant description thereof will be omitted as much as possible. In the present invention, the charge storage section (6s) and the charge transfer section (6t) are arranged alternately to form a charge transfer section (9) having a CCD configuration for transferring the original signal charge,
A bypass is provided for the _first storage section (6s ₁ ), but especially between the drain region (10) and the storage section (6s ₁ ) in this side path from the storage section (6s ₁ ) side. For example, a switching unit (22) for switching between discharging and non-discharging charges forming a stepwise potential having a low potential for signal charges toward the drain side, and a sending section (23) for forming a similar stepwise potential. ) And a potential barrier section (24) forming a fixed potential barrier are sequentially provided. SW, F, and OG denote terminals of the switching section (22), the sending section (23), and the potential barrier section (24), respectively.

The stepwise potentials of the switching section (22) and the sending section (23) are formed by selectively introducing, for example, n-type impurities simultaneously with the formation of the charge storage region (3s) in the charge transfer section (9), respectively. Regions (22a) and (23a) formed by forming the low impurity concentration regions (22b) and (22b) and (22a) and (23a) on the regions (22a) and (23a) and on the regions where the regions (22a) and (22b) are not formed. 23b), for example, electrodes (5s) and (5t) and electrodes (32a) (33a) (32b) (33b) simultaneously formed, respectively, are formed by depositing via a dielectric film (4). obtain. The electrodes (32a) and (32b), (33a) and (33b) are electrically connected to each other and are respectively connected to the terminals S described above.
W and F are derived.

The barrier section (24) is an electrode on the n-type region (24b) of low impurity concentration between the region (23a) of the sending section (23) and the drain region (10) via the dielectric film (4). (34) is formed by being attached.

A positive power supply voltage of, for example, 9V is applied to the drain region (10), and a positive voltage shallower than this power supply voltage, for example, a fixed voltage of 5V is applied to the terminal OG of the barrier section (24). ~ E
As shown in, the potential barrier bp is always formed.

On the other hand, the two-phase clock voltages φ ₁ and φ ₂ shown in FIGS. 2A and 2B are applied to the terminals t ₁ and t ₂ . Further, as shown in FIG. 2C, a clock φ ₁ is applied to the terminal F, that is, a voltage φ _F synchronized with the voltage applied to the charge storage section (6s ₁ ).

Now, to see the case where the transfer charge is removed from the charge transfer section (9) that transfers the original charge, in this case, the terminal S
A predetermined deep voltage, for example, 12.6V is applied to the electrodes W (32a) and (32b) of the switching unit (22). In this state, surface potential diagrams in the discharge path for discharging and removing charges at respective times T ₁ , T ₂ , T ₃ , and T ₄ in FIG. 2 are shown in FIGS. 3B, 3C, 3D, and 3E, respectively. In the figure, the switching unit (22)
The deeper region of the staircase potential at (22
The shaded portion in a) indicates the potential generated by the residual charge in the previous charge elimination.

First, looking at the state at time T ₁ with reference to FIG. 3B,
In this case, the potential of the charge storage portion (6s ₁ ) is higher than that of the charge transfer portion (6t) to which the adjacent clock φ ₁ is applied, so that no charge is applied to the charge storage portion (6s ₁ ). by the potential is lowered in the charge accumulating portion as shown in FIG. 3 C (6s ₁₎ in time T _2, the signal charges e arrives here. At this time, since a predetermined switching voltage is applied to the switching section (22) and the potential thereof is lowered, the charge e of the storage section (6s ₁ ) is changed to the switching section (22) side as shown by an arrow d. Move to.

Next, as shown at time T ₃ , a predetermined clock voltage is applied to the charge storage section (6s ₁ ) and its potential is lowered, so that the charge storage section (6s 1 _The electric charge e in ₁ ) moves to the low potential portion (23a) in the sending portion (23). Second
When the voltage state at the time point T ₄ shown in the figure is applied, the potential state of the potential state is increased as shown in FIG. After passing through the fixed potential barrier bp, it shifts to the drain region (10) side as shown by an arrow g, and the charge is eliminated. Next, the state returns to the state at time T ₅ , that is, the state of FIG. 3B showing the same potential state as at time T ₁ , but in this case,
Since the fixed barrier potential bp is formed on the charge storage portion (6s ₁ ) side of the drain region, the backflow of charges from the drain side to the charge storage portion (6s ₁ ) side does not occur.

In this way, the original charge transfer section (9) is applied in the state where a predetermined voltage is applied to the switching section (22) to form a potential valley.
The charge can be removed from the charge storage portion (6s ₁ ) to the drain as indicated by the broken line arrow c in FIG.

Further, in such a configuration, in order to carry out regular charge transfer and introduce from the output side in the charge transfer section (9) as shown by an arrow b without removing the charge, the charge is transferred to the switching section (22). by lowering the applied voltage, the potential, by performing the original charge transfer without flowing the charge accumulation units (6s ₁₎ on the drain side by increasing than that of the storage section (6s _1), a charge transfer section (9 ) Output.

In the example described above, in the charge transfer section (9), the charge storage section (6s), the charge transfer section (6t), and the switching section (2
2) and each potential step in the sending part (23) is formed by the difference in impurity concentration in the main surface (1a), but various CCD configurations such as changing the thickness of the insulating layer in each part It will be clear that the invention can be applied in.

[Effects of the Invention] As described above, according to the CCD having the configuration of the present invention, the signal charge of the charge transfer unit that performs the original charge transfer is surely discharged and non-discharged as necessary to prevent the charge from the drain side. Since it can be performed without causing backflow, for example, as described at the beginning, 0.5H of special mode playback in VTR
It is suitable to be used as a CCD having a function of switching between sending out and not sending out electric charges in each of the two signal lines that are switched in the two signal lines that are different from each other. Moreover, despite having such a special configuration,
Compared to the conventional CCD described in FIG. 4, no increase in the number of manufacturing steps occurs, so that it is practically profitable.

[Brief description of drawings]

1 is a schematic top view of an example of a charge transfer device according to the present invention, FIG. 2 is a voltage diagram for explaining the operation thereof, FIG. 3A is a sectional view taken along line AA of FIG. 1, and FIG. B, C, D and E are potential diagrams, FIG. 4 is a schematic top view of a conventional charge transfer device, FIG. 5A is a sectional view taken along the line AA, and FIG. 5B is its potential diagram. Is. (1) is a semiconductor substrate, (9) is a charge transfer unit, (3s) is its charge storage region, (3t) is a charge transfer region, (6s) is a charge storage unit, and (6s ₁ ) is a charge storage unit. , (6t) is the charge transfer part,
(22) is a switching part, (23) is a sending part, (24) is a barrier part, (10) is a drain region, and (4) is a dielectric film.

Claims (1)

[Claims] 1. A charge transfer portion; (b) a drain region; (c) a required charge storage portion of the charge transfer portion between the drain region and (d) a charge transfer portion of the charge transfer portion. A switching unit that switches between discharging and non-discharging a charge; (e) a sending unit that sends out the charges from the switching unit to the drain region side; and (f) a fixed potential between the sending unit and the drain region. (G) a voltage synchronized with the voltage applied to the charge storage unit is applied to the charge delivery unit, and the charge delivery unit overcomes the potential barrier in the drain region and then passes from the switching unit. The electric charge transfer device is characterized in that the electric charge of the electric charge is sent out.