JPH07273314A - Electric charge transmitting device and switching device - Google Patents

Abstract

PURPOSE: To provide a charge transfer device and a switching element, in which the difference of potential barrier voltage can be kept constant between first and second gates. CONSTITUTION: This charge transfer device comprises first gates 11-19 formed for transmitting a charge signal, second gates 21-27 lapped partially over the region of adjacent first gates and formed for transmitting a charge signal such that the work function will be different from that of the first gate, a first gate group to be applied simultaneously with a first clock signal ϕ1 from a set of adjacent first and second gates, and a second gate group to be applied simultaneously with a second clock signal ϕ2 from a set of adjacent first and second gates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge transfer device and a switching element, and more particularly, to the first and second gates made of the same kind of material having different work functions and different kinds of materials having different work functions doped with different impurities. The present invention relates to a charge transfer device that is formed to keep a potential barrier voltage constant and can operate even with a two-phase clock signal, and a switching element that is a reset gate used at a transfer end of a charge coupled device.

[0002]

2. Description of the Related Art Generally, a charge transfer device that transfers a charge signal at high speed causes a difference in channel doping concentration by barrier ion implantation, or a thickness of an insulating film between a gate electrode and a silicone substrate. Differently, by generating a potential barrier voltage, it is driven by a two-phase clock signal.

In forming a conventional charge transfer device, first, an impurity is ionized in a region where a horizontal charge transfer end is formed by using a mask layer after forming a first gate made of polycrystalline silicon. A second gate is formed on the first gate by using polycrystalline silicon so that the second gate is injected and overlaps with the first gate. Then, barrier ion implantation is performed in order to cause a difference between the potential barrier voltage of the second gate and the potential barrier voltage of the first gate. Alternatively, in order to cause a difference between the potential barrier voltage of the second gate and the potential barrier voltage of the first gate, the thickness of each insulating film formed under the first gate and the second gate may be different. There is.

In such a conventional charge transfer device, one clock signal is applied to the first gate and the second gate pair,
It is driven by a two-phase clock signal.

However, in the former manufacturing process which causes the difference in potential barrier voltage between the first and second gates, a photolithography process for forming a mask and a barrier ion implantation process are additionally required. Therefore, there is a problem that the manufacturing process becomes complicated. Further, in the latter manufacturing process that causes the difference in the potential barrier voltage described above, it is difficult to accurately control the difference in the thickness of the insulating film, which causes a problem that the potential barrier voltage changes. To have.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a charge transfer device and a switching element capable of making the difference in potential barrier voltage between the first gate and the second gate constant. The purpose is to provide.

[0007]

In order to achieve the above object, a charge transfer device according to the present invention comprises a first gate which is formed so as to transfer a charge signal, and a first gate which is adjacent to the first gate.
A second gate, which overlaps with a partial region of the gate and has a work function different from that of the first gate to transmit a charge signal, and the first and second gates adjacent to each other, form a set. A first gate group to which a first clock signal is simultaneously applied and the first gate group are alternately formed, and the first and second gates adjacent to each other are combined to apply a second clock signal simultaneously. And a second gate group that is formed.

In addition, in a switching element that is formed at a transmission end of a charge coupled device that transmits a charge signal and periodically restores a potential barrier by a clock signal, a first gate formed of a first material; A second gate which is overlapped with a partial region of one gate and which is formed of a second material so as to have a work function different from that of the first gate and to which the same clock signal is applied simultaneously. It has a feature.

[0009]

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

FIG. 1 is a diagram showing a state in which clock signals φ1 and φ2 are applied to a gate according to the first embodiment of the present invention.

First, by a normal process, first gates 11, 13, 15, 17, and 19 made of polycrystalline silicon in which N-type impurities such as phosphorus and arsenic are ion-implanted are formed at predetermined intervals. Then, the second gates 21 and 2 made of polycrystalline silicone ion-implanted with P-type impurities such as boron.
3, 25, 27 are connected to the first gates 11, 13, 15,
It is formed so as to overlap with 17 and 19 by a predetermined portion and be adjacent to each other. At this time, the first gate and the second gate may be formed of different materials having different work functions such as polycrystalline silicon and metal silicide. First and second gates 13, 21, 1 adjacent to each other
The first gate group composed of 7 and 25 etc. is simultaneously applied with the clock signal φ1, while the first and second gates 11, 15, 23 and 1 adjacent to the first gate group are provided.
A clock signal φ2 is simultaneously applied to the second gate group composed of 9, 27 and the like.

2 (a) to 2 (c) show the state of the potential due to the change of the clock signal applied to the gate according to the first embodiment of the present invention.

First, when the clock signal φ1 is in the low state and the clock signal φ2 is in the high state, the potential becomes a state as shown in FIG. 2 (a), and the charges are stored in the first gates 11, 15 and.
Accumulate in the lower well such as 19. Then, while the clock signal φ1 changes from the low state to the high state and the clock signal φ2 changes from the high state to the low state, the potential becomes a state as shown in FIG. 2B, and the first gate 1
The charge accumulated in the well below the first and second gates 2
The charges accumulated in the well below the first gate 15 at the same time as being transmitted to the first and second gates 15 and 17,
Be transmitted to. Further, the electric charge accumulated in the well under the first gate 19 is also transmitted in the same manner as above. After that, when the clock signal φ1 is in the high state and the clock signal φ2 is in the low state, the potential becomes a state as shown in FIG. 2 (c), and the above-mentioned charges to be transferred are wells under the first gates 13 and 17. Accumulated in each. Therefore, the charge transfer device configured as described above and driven by the two-phase clock makes the difference in potential barrier constant.

FIG. 3 is a diagram showing a state in which the clock signal φ1 is applied to the switching element formed at the transmission end of the charge coupled device according to the second embodiment of the present invention and used as a reset gate.

As shown in FIG. 3, the first gate 31 of polycrystalline silicon, which is ion-implanted with N-type impurities such as phosphorus and arsenic, is formed with a predetermined width b by a normal process. . Next, a second gate 33 of polycrystalline silicon, in which a P-type impurity such as boron is ion-implanted, is formed (with a width a) so as to overlap one side upper portion of the first gate 31. . The first and second gates 31, 33
Are simultaneously applied with the clock signal φ1. At this application, the first gate 31 and the second gate 33 can be formed of different materials having different work functions, such as polycrystalline silicone and metal silicide.

FIG. 4 shows the state of the potential according to the change of the clock signal applied to the gate according to the second embodiment of the present invention.

While the clock signal φ1 changes from the high state to the low state and the potential barrier is raised, the charge in the well under the second gate 33 is transferred to the both sides of the second gate. The charges in the well under the gate 31 are transferred only in one direction due to the higher potential barrier under the second gate 33. The switching element configured as described above is formed such that the width of the potential barrier by the second gate 33 is narrow, noise can be reduced, and the potential barrier is stabilized.

As described above, in the charge transfer device of the present invention, the first and second gate electrodes are formed of the same kind of material having different work functions and different kinds of materials doped with different types of impurities. After the difference between the potential barriers is made constant, a two-phase clock signal is applied to the first and second gates so that they are driven. A switching element that periodically restores the potential barrier at the transmission end of the charge coupled device is also formed by the same method.

[0019]

Therefore, the charge transfer device and the switching element according to the present invention have the advantages that the potential barrier is stabilized and the reliability is improved while being manufactured by a simple manufacturing process. Further, in the present invention, there is an advantage that noise due to charge transfer of the switching element can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a clock signal is applied to a gate according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a state of a potential according to a change of a clock signal applied to a gate according to the first exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a state in which a clock signal is applied to the gate according to the second exemplary embodiment of the present invention.

FIG. 4 is a diagram showing a state of a potential according to a change of a clock signal applied to a gate according to a second embodiment of the present invention.

[Explanation of symbols]

 11, 13, 15, 17, 19 First gate 21, 23, 25, 27 Second gate φ1, φ2 Clock signal 31 First gate 33 Second gate

Claims (6)

[Claims] 1. A first gate formed to transmit a charge signal and an adjacent partial region of the first gate are overlapped with each other, and a work function is different from that of the first gate. A second part formed on the surface and transmitting a charge signal
Gates, first gate groups to which the first and second gates adjacent to each other are simultaneously applied and a first clock signal are simultaneously applied, and the first gate groups are alternately formed. And a second gate group to which a second clock signal is simultaneously applied in combination with a second gate. 2. The charge transfer device according to claim 1, wherein the first and second gates are formed of different materials having different work functions. 3. The charge transfer device as claimed in claim 1, wherein the first and second gates are formed of the same material having different work functions by being doped with impurities of different types. 4. The charge transfer device of claim 1, wherein the first and second gates have opposite conductivity types. 5. The charge transfer device according to claim 1, wherein the first and second clock signals are applied in mutually opposite states. 6. A switching device, which is formed at a transmission end of a charge-coupled device for transmitting a charge signal and periodically restores a potential barrier by a clock signal, comprising: a first gate formed of a first material; A switching device including a second gate which is overlapped with a partial region of one gate and which is formed of a second material so as to have a work function different from that of the first gate and to which the same clock signal is simultaneously applied. .