JP2890483B2 - Charge coupled device and driving method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge-coupled device having a charge transfer channel having a storage region and a barrier region, and a method of driving the same.

[Conventional technology]

FIG. 3 (a) is a plan view showing a conventional example of a charge-coupled device, FIG. 3 (b) is a schematic cross-sectional view of a semiconductor chip taken along a line BB in FIG. 3 (a), FIG. 3C is a signal waveform diagram of the driving pulse, and FIG. 3D is a potential diagram for explaining signal charge transfer.

In this example, a buried channel type charge-coupled device having a buried layer 302 having a conductivity type opposite to that of the semiconductor substrate 301 in a semiconductor substrate 301 is assumed, and the conductivity type opposite to that of the buried layer is ion-implanted into the buried channel surface. Are formed to form barrier regions 304 to 307. The storage electrodes 308 to 312 and one of the barrier electrodes 313 to 316 adjacent to the storage electrodes 308 to 312 are respectively connected inside the element, and in this example, it is assumed that they are driven by two-phase pulses φ ₁ and φ _2. Therefore, terminals 317, 31 for applying a drive pulse to the outside of the element are connected in common every other pair of electrodes of the storage electrode and the barrier electrode.
8 are provided.

Consider a case where drive pulses φ ₁ and φ ₂ are applied to external terminals 317 and 318, respectively. phi ₁ is high level at time t ₁ phi ₂ is at low level, the signal charge 319 and 320 are accumulated under the storage electrode 309, 311. At time t _2, t _3, a low level of phi _1, by the phi ₂ to the high level, the signal charge 319 and 320 is transferred to under the storage electrode 308 and 310 from the bottom, respectively the storage electrodes 309 and 311, are accumulated. By repeating such operations, signal charges are transferred in the charge transfer channel in a direction from the right side to the left side in the figure.

[Problems to be solved by the invention]

As described above, in the conventional charge-coupled device, the transfer direction of the signal charge is uniquely determined because the storage electrode and the barrier electrode that is paired with the storage electrode are connected inside the device.

FIG. 4 is a diagram schematically showing a relationship between a drive pulse amplitude of the charge-coupled device and a transfer signal charge amount. Where Δψ
Represents the potential difference between the storage electrode and the barrier electrode in FIG. When the potential difference Δψ is large, the maximum transfer signal charge amount increases, but the transferable minimum drive pulse amplitude also increases. Conversely, when Δψ is small, the maximum transfer signal charge amount decreases, but the minimum drive pulse amplitude can also be reduced. When the same drive pulse is applied to the storage electrode and the barrier electrode as shown in FIG. 3, the magnitude of Δψ is determined by the amount of impurity implanted by ion implantation. That is, the maximum signal charge amount and the minimum drive pulse amplitude depend only on the manufacturing conditions, and cannot be changed by the drive method.

SUMMARY OF THE INVENTION An object of the present invention is to provide a new charge-coupled device that eliminates such conventional disadvantages and a driving method thereof.

[Means for solving the problem]

The charge-coupled device of the present invention includes a semiconductor substrate provided on one main surface side of a charge transfer channel in which storage regions and barrier regions are alternately arranged, a storage electrode covering the storage region, and a storage electrode provided thereabove. , And a barrier electrode is provided above the cover electrode, wherein the wiring to the storage electrode is provided independently of the wiring to the barrier electrode.

Further, in the method of driving the charge-coupled device of the present invention, a charge transfer channel in which storage regions and barrier regions are alternately provided is provided on one main surface side of a semiconductor substrate, the storage region is covered, and a storage electrode is provided above the storage region. A charge-coupled device comprising a barrier electrode provided above and covering the barrier region, wherein a wiring to the storage electrode is provided to a storage electrode of the charge-coupled device provided independently of a wiring to the barrier electrode. A pulse having the same phase as that of the storage electrode is applied to one of the adjacent barrier electrodes.

[Action]

In the present invention, since the storage electrode and the barrier electrode are independently wired, the transfer direction of the charge can be determined by the method of applying the drive pulse. Further, by applying drive pulses having different amplitudes to the storage electrode and the barrier electrode that is paired with the storage electrode, it is possible to change the maximum transfer signal charge amount and the minimum drive pulse amplitude.

〔Example〕

FIG. 1 (a) is a plan view showing a charge-coupled device of the present invention, FIG. 1 (b) is a schematic cross-sectional view of a semiconductor chip cut along a line AA in FIG. 1 (a), and FIG. FIG. 3C is a signal waveform diagram of the driving pulse.

In this embodiment, as in the conventional example shown in FIG.
This is a buried channel type charge-coupled device having a buried layer 102 having a conductivity type opposite to that of the semiconductor substrate, and an impurity of a conductivity type opposite to that of the buried layer is introduced into the buried channel surface by ion implantation to form a barrier region. 104 to 107 are formed. In this embodiment as well, it is basically assumed that driving is performed by two-phase pulses. However, the storage electrode and the barrier electrode which are different from the conventional example of FIG. Four terminals 117 to 120 which are connected in common and apply a driving pulse to the outside of the element are provided.

In the following description, the external terminal connected to the storage electrode
It is assumed that drive pulses φ _1S and φ _2S are applied to 117 and 118, respectively.

If the same drive pulses φ _1S and φ _2S as those of the external terminals 117 and 118 are applied to the external terminals 119 and 120 connected to the barrier electrodes, respectively, the state becomes exactly the same as the conventional example of FIG. Transferred in the direction to go. When drive pulses φ _2S and φ _1S are applied to the external terminals 119 and 120, respectively, the signal charges are transferred in the direction from the left to the right in the figure. That is, the transfer direction of the signal charge can be controlled by the drive pulse applied to the barrier electrode.

It is assumed that drive pulses φ _1B and φ _2B having the same phase as φ _1S and φ _2S are applied to external terminals 119 and 120 connected to the barrier electrode, respectively. When the amplitudes of φ _1B and φ _2B are the same as those of φ _1S and φ _2S, it is the same as the above-described example. phi _1B, the amplitude of phi _2B phi
_1S, by a different value and phi _2S, it is possible to change the potential difference Δψ between the storage electrode and the barrier electrode shown in Figure 3. That is, as shown in FIG.
The values of the maximum transfer signal charge amount and the minimum drive pulse amplitude can be set to optimal conditions according to the operation state. Also, by applying drive pulses φ _2B and φ _1B having the same phase as φ _2S and φ _1S to the external terminals 119 and 120, respectively, it is possible to transfer the signal charges in the opposite direction as in the above-described example.

FIG. 2 is a block diagram showing an application example of the present invention.
An example in which the charge-coupled device shown in the figure is applied to a horizontal register of an interline transfer type solid-state imaging device is shown. This example is different from the conventional interline transfer type solid-state imaging device in that horizontal registers 204 and 205 are arranged at both ends of a vertical register 203, and charge detection units 206 to 209 are provided at both ends of each horizontal register. It is. Vertical register 203
Is a four-phase drive, and the horizontal registers 204 and 205 are wired independently of the storage electrode and the barrier electrode as shown in FIG.
In order to obtain a normal reproduced image, the signal charges stored in the photodiode are read out to a vertical register via a transfer gate and vertically transferred to the horizontal register 204 side, and then the horizontal signal is horizontally transferred to the charge detection unit 206 side in the horizontal register 204. The signal is transferred and output as a signal to the outside by the charge detection unit 206. In addition, by horizontally transferring the data in the horizontal register 204 to the charge detection unit 207 side and outputting the signal as an external signal by the charge detection unit 207, a reproduced image that is inverted left and right from normal can be obtained. On the other hand, the signal charge stored in the photodiode is read out to the vertical register via the transfer gate and vertically transferred to the horizontal register 205, and then the charge in the horizontal register 205 is transferred to the charge detection unit 208 or the charge detection unit.
Horizontal transfer to 209 side, charge detection unit 208 or charge detection unit
By outputting it as a signal by 209,
It is possible to obtain a reproduced image which is turned upside down or rotated by 108 degrees from the normal. As described above, in this application example, it is possible to obtain a reproduced image that cannot be obtained with the conventional interline transfer type solid-state imaging device.

As described above, the buried channel type charge-coupled device is assumed and the barrier region is formed on the buried channel surface by the ion implantation method. However, the present invention can be applied to the surface channel type charge-coupled device. The present invention is also effective when the barrier region is formed by other means, for example, by changing the thickness of the gate insulating film below the storage electrode and below the barrier electrode, instead of the ion implantation method. Further, although the example of the two-phase driving has been described, the present invention can be realized by an operation using a driving pulse of three or more phases.

〔The invention's effect〕

As described above, in the charge-coupled device of the present invention, since the storage electrode and the barrier electrode are independently wired, the transfer direction of the charge can be determined by the driving pulse application method. Further, by applying drive pulses having different amplitudes to the storage electrode and the barrier electrode that is paired with the storage electrode, it is possible to change the maximum transfer signal charge amount and the minimum drive pulse amplitude. Further, by applying the charge-coupled device of the present invention to an interline transfer type solid-state imaging device, it is possible to obtain a reproduced image that cannot be obtained with a conventional imaging device.

[Brief description of the drawings]

1 (a) to 1 (c) are plan views, schematic sectional views and signal waveforms of driving pulses showing an embodiment of a charge-coupled device and a method for driving the same according to the present invention, and FIG. 3 (a) to 3 (d) are plan views showing a conventional charge-coupled device and its driving method, schematic sectional views, and driving pulse signals. FIG. 4 is a waveform diagram and a potential diagram for explaining signal charge transfer. FIG. 4 is a schematic diagram showing the relationship between the drive pulse oscillation of the charge coupled device and the amount of transfer signal charge. 101,301 ... semiconductor substrate, 102,302 ... buried layer, 103,30
3 ... Charge transfer channel. 104 to 107, 304 to 307: barrier region, 108 to 112, 308 to 312: storage electrode, 113 to 116, 313
... 316 ... barrier electrode, 117-120,317,318 ... external terminal, 319,320 ... signal charge, 201 ... photodiode,
202 ... transfer gate, 203 ... vertical register,
204, 205 ... horizontal registers, 206 to 209 ... charge detection units.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) H01L 21/339 H01L 29/762 H01L 27/148

Claims (3)

(57) [Claims] A semiconductor substrate is provided on one main surface side of a charge transfer channel in which storage regions and barrier regions are alternately arranged, a storage electrode is provided above the storage region, and a storage electrode is provided above the storage region. A barrier electrode is provided above the
A phase-driven charge-coupled device, wherein a wiring to the storage electrode is provided independently of a wiring to the barrier electrode, and the storage electrode and the barrier electrode are commonly connected to every third electrode and taken out to the outside. A charge-coupled device capable of independently applying a clock signal to each clock signal input terminal taken out. 2. A pulse having the same phase as the pulse applied to the storage electrode and having a different amplitude is applied to one of the barrier electrodes adjacent to the storage electrode of the charge-coupled device according to claim 1. A method for driving a charge-coupled device. 3. The method according to claim 2, wherein the amplitude of the pulse applied to the storage electrode is different from the amplitude of the pulse applied to the barrier electrode.