JPH03163836A - Charge coupled device - Google Patents

Abstract

PURPOSE:To avoid the deterioration in the transfer efficiency thereby enabling the title charge coupled device to be highly integrated by a method wherein an electrode group exhibiting no overlap structure as well as an electrode impressed with DC voltage as an upper layer of the electrode group is provided. CONSTITUTION:An upper layer electrode 10 is provided above a lower layer electrode group comprising electrodes 3-6 through the intermediary of an insulating film 9 comprising e.g. an SiO2 film while the electrode 10 is impressed with DC voltage from a DC power supply 11. That is, the electrode 10 is provided as if overlapping with the electrode group 3-6 and then the electrode 10 is impressed with DC voltage to control the potential below the lower layer electrode group 3-6 so that the electrode length of said group may not be restricted just like in case of an overlap electrode structure to abolish the potential barrier between said electrode group causing the deterioration in transfer efficiency. Through these procedures, the title charge coupled device can highly be integrated for improving the transfer efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a charge coupled device that has good transfer efficiency and is suitable for high density.

[Conventional technology]

FIG. 2(a) is a cross-sectional view of a conventional charge-coupled device. In the figure, 1 is a p-type semiconductor substrate, and 2 is a semiconductor substrate formed on the semiconductor substrate 1 by, for example, thermal oxidation. Formally precepted S
It is an iO film and acts as an insulating film. 3, 4, 5.6
is a group of electrodes made of polycrystalline silicon, for example, provided on the insulating film 2, and the spacing between each electrode is indicated by S in the figure.
This electrically isolates each electrode.

The charge-coupled device in FIG. 2(a) shows the case of four-phase drive, and the electrodes 3.4 and 5.6 have clocks φl and φ1, respectively.
φ2. φ3. φ4 is given, and these four electrodes are one of the CCDs.
Corresponds to a stage. Here φ1. Figure 2 (b) shows the potential distribution for electrons in the semiconductor substrate 1 when φ2 is in the clock high state and φ3 and φ4 are in the clock low state.
). 7 in the figure indicates the electrons to be transferred,
It is confined in a potential well formed under the electrode 3.4 to which the clock I4high is applied. Since the electrodes 3, 4, 5, 6 are provided with a spacing S, the electric field exerted from the electrodes into the semiconductor substrate becomes weak in this portion, and a potential halia Δφ occurs. This potential barrier Δφ becomes a factor that deteriorates transfer efficiency. This situation will be explained using FIG. 2(C). Fig. 2(C) shows that φ3 is in the High state and φ1 is in the L state from the state of Fig. 2(b).
The potential distribution is shown in the OW state and the charge is transferred by l electrodes. As seen in the figure, a residual charge 8 is generated under the electrode 3 due to the potential barrier Δφ,
Transfer efficiency will deteriorate.

A generally widely used method for solving this problem is called an overlap electrode structure, and the structure is shown in FIG. The difference from the conventional example shown in FIG. 2(a) is that the electrodes 3.4 and 5.6 have a two-layer electrode structure, and the lower layer electrode 4.6 and the upper layer electrode 3.5 have an overlap portion I! 1 is provided and has an overlapping structure.

With such a structure, there is no portion S without electrodes as shown in FIG. 2(a), and no potential barrier is generated. However, when such a structure is adopted, when increasing the density of the CCD, the distance l, determined by the mask alignment accuracy of the lower layer electrode and the upper layer electrode, and the interval I!, determined by the processing accuracy of the upper layer electrode, are determined. ．． 2, the electrode length is limited. That is, the length of each electrode in the lower electrode group is 21+ +
It cannot be made shorter than p2. On the other hand, in the conventional example shown in FIG. 2, from the viewpoint of processing only, the only factor that limits the increase in density is the spacing S.

[Problem to be solved by the invention]

Since conventional charge-coupled devices are constructed as described above, the device shown in FIG.
In the device shown in the figure, the electrode length of the electrode group is limited as described above.
There was a problem that high density could not be achieved.

This invention was made to solve the above-mentioned problems, and aims to provide a charge-coupled device that is suitable for high density and has good transfer efficiency.

[Means to solve the problem]

The electrode-coupled device according to the present invention has a plurality of electrode groups that do not overlap each other on a semiconductor substrate via an insulating film, a new electrode is provided on the upper layer of this electrode group, and a DC voltage is applied to this electrode. This is what I did.

? Effect] In this invention, an additional electrode is provided in the upper layer of the electrode group, and a DC voltage is applied to the electrode to control the potential between the electrodes of the lower electrode group, so that an overlap electrode structure is achieved. The potential barrier between the electrode groups, which causes deterioration in transfer efficiency, can be eliminated without limiting the electrode length of the electrode groups.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1(a) is a diagram showing a charge-coupled device according to an embodiment of the present invention. In the figure, 1 is a semiconductor substrate, 2 is an insulating film, 3, 4, 5.6 is a group of electrodes. The interval between
It is shown in The structure up to this point is exactly the same as the conventional example shown in FIG. 2(a). In the present invention, electrodes 3, 4, 5
．． An upper layer electrode 10 is provided on the upper layer of the lower layer electrode group 6 with an insulating film 9 made of, for example, a SiO2 film interposed therebetween, and a DC voltage is applied to this electrode from a DC power source 11.

Next, the operation will be explained.

Corresponding to FIG. 2(b), the clock H ig is applied to the electrodes 3 and 4.
Figure 1(b) shows the potential distribution when the h level is applied and the clock low level is applied to the electrode 5.6.
1 (C) shows the potential distribution when the clock high level is applied to the electrode 5.4 and the clock low level is applied to the electrodes 3 and 6, corresponding to FIG. 2(C). ). As shown in these figures, in this embodiment, the electric field caused by the DC voltage applied to the electrode 10 can eliminate the potential barrier that conventionally occurs between the electrodes.

By the way, if the voltage applied to the electrode 10 is too large, the potential will conversely be depressed, so it is necessary to adjust it appropriately according to the electrode interval S and the distance from the electrode 10 to the surface of the semiconductor substrate.

As described above, in this embodiment, the upper layer electrode 10 is provided on the upper layer of the electrode groups 3 to 6 via the insulating film 9, and a DC voltage is applied to the electrode 10 so as to eliminate the potential barrier generated between the electrode groups. Therefore, the charge transfer efficiency can be greatly improved without limiting the electrode length of the electrode group.

In the above embodiment, a surface channel type charge coupled device was shown, but the present invention can also be applied to a buried channel type charge coupled device. Since a potential depression is created, the power source 11 shown in the embodiment of FIG.
It is necessary to reverse the polarity of

Furthermore, although the above embodiments have been described with reference to a four-phase drive charge coupled device, it goes without saying that the present invention can also be applied to a three-phase drive charge coupled device.

〔Effect of the invention〕

As described above, according to the present invention, by providing an electrode group that does not have an overlapping structure and an electrode to which a DC voltage is applied in the upper layer of the electrode group, unevenness in potential due to the electrode spacing of the electrode group is reduced. Therefore, there is no deterioration in transfer efficiency, and there is no limit on the electrode length that occurs in the case of the Ohara wrap structure, so there is an effect that a charge coupled device suitable for high density can be obtained.

[Brief explanation of the drawing]

FIG. 1(a) is a diagram showing the cross-sectional structure of a charge coupled device according to an embodiment of the present invention, FIGS. 1(b) and (C) are diagrams showing the potential distribution for electrons of the present invention, and FIG. a
) is a diagram showing the cross-sectional structure of a conventional charge-coupled device, and Figure 2 (
b) and (C) are diagrams showing the potential distribution for electrons in the charge coupled device of FIG. 1 is a semiconductor substrate, 2 is an insulating film, 3,456 is an electrode group, 9
1 is an insulating film, IO is an upper layer electrode, and 11 is a DC power source. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A plurality of non-overlapping electrode groups provided on a semiconductor substrate via an insulating film, and a plurality of electrode groups provided in an upper layer of the electrode group to be insulated from the electrode group, and between the electrode groups in the semiconductor substrate. and an upper layer electrode to which a DC voltage is applied for controlling the potential in the semiconductor substrate so as to cancel a potential barrier formed in the region.