JPH084133B2 - Solid-state imaging device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device, particularly a two-dimensional image pickup device.

2. Description of the Related Art Conventionally, in an image pickup device using a horizontal scanning CCD shift register, formation of a barrier electrode required to move the horizontal CCD by two-phase driving is performed by, for example, n-type buried channel CCD in order to lower the potential for signal charges. In the above-mentioned method, boron was formed by ion implantation of p-type impurities only under the barrier electrode.

The operation will be briefly described below with the interline CCD image pickup device (hereinafter referred to as IL-CCD) shown in FIG. 1 is the channel part of the horizontal CCD, 11 is the vertical C
The channel part of the CD is connected to the channel part 1 of the horizontal CCD. In FIG. 2a, the electrode indicated by the broken line is the electrode formed of the first-layer polysilicon. However, an n-type buried channel is formed in the horizontal and vertical CCD channel parts 1 and 11 before forming the first layer electrode. After forming the first layer electrode, p-type impurities are selectively introduced only in the perspective view shown in the drawing. After that, the second-layer polysilicon electrode shown by the solid line in the drawing is formed. Next, let's follow the flow of signal charges. The signal charge passes from the upper part of the figure through the channel portion 11 of the vertical CCD, and from the final stage electrode 2 of the vertical CCD to the horizontal CCD.
The electrode 32 along the path 6 through the electrode 4 which also serves as the transfer electrode of
Carried under. In addition, since the electrodes of the channel portion 1 of the horizontal CCD are driven in two phases, the electrodes 4 and 32, the electrodes 52 and 31, and the electrodes 51 and 31 are connected, and the electrodes 4 and 3 are connected.
A pulse of φ H ₁ is applied to electrode 2, electrode 31 and electrode 5
A pulse of φH ₂ is applied to 1 and the electrode 31. The second is to schematically show the horizontal CCD pontent at that time.
Figure c. The solid line is the potential when φH ₁ is LOW and φH ₂ is HIGH, and is the opposite of the broken line, showing the potential when φH ₁ is HIGH and φH ₂ is LOW.

The electric charge that has passed through the above-mentioned path 6 is carried under the electrode 32. At that time, φH ₁ must be HIGH and φH ₂ must be LOW. And the next drive timing, that is, φH ₁
When φH ₂ becomes HIGH at LOW, path 7 (electrode 32 to electrode 52
Flow to the electrode 31), and the electric charge is carried by a half pitch. After that, φH ₁ and φH ₂ alternately repeat HIGH and LOW, so that the charges sequentially move to the left.

Problems to be Solved by the Invention However, in such a configuration, for example, in the process of charge transfer from the path 8 to the path 9 in FIG.
The electric charge stored in is spread over the entire electrode 32,
There is a problem that a part of the electric charge passes from the route 8'to the route 9 ', and transfer loss occurs at this portion. The present invention solves such a problem, and an object of the present invention is to provide a structure for two-phase driving which does not cause deterioration of horizontal transfer efficiency.

Means for Solving the Problems In order to solve this problem, the present invention provides a photoelectric conversion element group on a semiconductor substrate, a vertical scanning CCD shift register group for reading and transferring signal charges from the photoelectric conversion element group, or a vertical scanning element. A signal line group and a horizontal scanning CCD shift register are provided, and in a first region under a first electrode and a second region under a second solid line adjacent to each other, which constitute the horizontal scanning CCD shift register. A two-phase drive CCD having the second region as a main storage part by additionally introducing an impurity of the same conductivity type as that of the first region, which raises the potential for signal charges to the second region more than the first region. And the second electrode for each jump of the second electrode is connected to the last electrode of the vertical scanning CCD shift register group or the vertical signal line group. It

Operation With this configuration, the charge transfer in the horizontal direction is limited to the substantially horizontal CCD portion, and thus the deterioration of the horizontal transfer efficiency is suppressed.

Embodiment FIG. 1 shows an interline type according to an embodiment of the present invention.
FIG. 5 is a plan view, a cross-sectional view, and a potential diagram of a vertical to horizontal CCD shift register section of the CCD image pickup device.

Reference numeral 1 is a horizontal CCD channel portion, and 11 is a vertical CCD channel portion, which is connected to the horizontal CCD channel portion 1. In FIG. 1A, the broken line indicates an electrode made of the first layer polysilicon. However, in this case, in the horizontal and vertical CCD channel portions 1 and 11, an n-type buried channel is formed before the formation of the first-layer polysilicon electrode. Then, after forming the first-layer polysilicon electrode, n-type impurities are selectively introduced only into the hatched portions shown in the drawing. After that, the second-layer polysilicon electrode shown by the solid line in the drawing is formed. In the present invention, the flow of the signal charge enters the horizontal CCD from the upper side of the figure and is directed to the left. Therefore, the electrode of the horizontal CCD channel part 1 is 2
In order to perform the phase drive, the electrode 4 and the electrode 31, the electrode 51 and the electrode 32, and the electrode 52 and the electrode 32 are coupled, and a pulse of φH ₁ is applied to the set of the electrode 4 and the electrode 31 and the electrode 51 and the electrode 32. electrode
A pulse of φH ₂ is applied to the set of 52 and the electrode 32. FIG. 1c schematically shows the potential of the horizontal CCD at that time. The solid line shows that φH ₁ is HIGH and φH ₂ is LOW.
The potential at the time of φH ₁ is LOW and φH ₂ is HIG.
The potential diagram for H is shown.

The flow of the signal charge passes through the final electrode 2 of the channel portion 11 of the vertical CCD, and when φH ₁ is HIGH, the path 6 is formed under the electrode 4.
Enter the shaded portion of the electrode 4 along. Then φH ₁ is LOW, φH
_{When 2} goes high, the signal charge is carried through path 7 and under electrode 52 without backflowing path 6. After that, φH ₁
The charges sequentially move to the left by alternately repeating HIGH and LOW with and φ H ₂ . In that case, the place where the potential for electric charge is high, that is, the accumulation part of the horizontal CCD, is the original horizontal C
Since it is provided only in the CD section, the deterioration of transfer efficiency caused by the signal charge entering the vertical CCD side, which has been a problem in the conventional example, is eliminated.

In the embodiment, the starting channel is an n-type buried channel, but it may be a surface channel or a p-channel CC.
In D, it is obvious that a similar effect can be obtained by adding a p-type impurity to increase the potential.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to suppress deterioration of the horizontal transfer efficiency without increasing the number of process steps, and thus it is possible to obtain a very effective effect such as realizing a high-performance imaging device.

[Brief description of drawings]

1A, 1B, 1C are plan views, sectional views and potential diagrams of an interline CCD image pickup device according to an embodiment of the present invention, and FIGS. 2A, 2B and 2C are conventional interline CCD image pickup devices. It is a top view, a sectional view, and a potential figure of a device. 1 …… Horizontal CCD channel part, 2,31,32 …… First layer polysilicon electrode, 4,51,52 …… Second layer polysilicon electrode, 11 …… Vertical CCD channel part.

Claims (1)

[Claims] 1. A vertical scanning CC for reading and transferring a signal charge from a photoelectric conversion element group on a semiconductor substrate.
A D shift register group or a vertical signal line group and a horizontal scan CCD shift register are provided.
In the first region under the first electrode and the second region under the second electrode, which are adjacent to each other and constitute the CD shift register, the second region is formed.
An impurity of the same conductivity type as that of the first region, which raises the potential for the signal charge higher than that of the first region, is additionally introduced into the second region, and the second region is used as a main storage portion 2
The phase drive CCD is configured, and the second electrode for each step of the second electrode is connected to the vertical scanning CCD shift register group or the final electrode of the vertical signal line group. A characteristic solid-state imaging device.