JPS5951673A - solid-state imaging device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a solid-state imaging device, and particularly to a MOS-type integrated imaging device and a combined-type solid-state imaging device of a MOS and a charge transfer element.

[Prior art]

FIGS. 1 and 2 show the configurations of a conventional MO8 type solid-state imaging device and a MOS and charge-coupled device combination type solid-state imaging device.

In FIG. 1, at 2, 1 and 3 are a vertical shift register and a horizontal shift register, respectively, and 9.2 is a photoelectric conversion element consisting of a photodiode.

The light incident on the photodiode 2 is converted into a signal charge,
The parasitic capacitance CaK of the original diode is accumulated. Accumulated 1
The signal charge of a line, for example, the top line, passes through the vertical switch 21 during the horizontal retrace period, and is divided by the capacitance Cv of the vertical line 4 and the parasitic capacitance C6 of the photodiode 2. 4. The signal charge read out to the vertical line 4 turns the vertical switch 21 OFF.
After preventing the new signal charge from moving to the vertical line 4 by F, it is transferred to the horizontal shift register by the vertical shift register 1, and after being read into the horizontal shift register 3 by opening and closing the horizontal switch 5, The signal is read out as a video signal by transfer through the horizontal shift register 3.

Figure 2 shows a combined solid-state imaging device of MOS and charge-coupled device (CCLI).The difference from Figure 1 is that, instead of the horizontal switch 5 in Figure 1, a horizontal charge transfer element
CCU) and the signal charge from the vertical line 4 to the horizontal force direction COD
The light incident on the element, which would have been provided with a transfer circuit 7 to be transferred to the photodiode 2, is converted into a signal charge and stored in the photodiode 2 in the same manner as the element shown in FIG. It is read out into the capacitance Cv of the line 4 in the direction. The signal charge transferred to the vertical line 4 causes the vertical switch 21 to turn
After being turned off, the signal is sent to the CCD 6 in the horizontal direction by the transfer circuit 7.

Thereafter, by driving the COD in the horizontal direction, it is read out as a video signal.

By the way, in these devices, the transfer of signal charge from the photoelectric conversion section consisting of a photodiode to the vertical line 4 is as follows.
Capacitance Cv of vertical line 4 and parasitic capacitance C of photodiode 2
This is done by dividing the capacity with a. If Cv is significantly larger than 06, almost all the signal charge will be transferred to the photodiode 2 or to the vertical line 4, but in reality this is not the case, so some of the signal charge will be transferred to the photoelectric conversion. (photodiode 2), resulting in an afterimage.

In particular, when trying to increase the aperture ratio (the proportion of the light-receiving surface of the entire image sensor) in order to increase the sensitivity, the width of the vertical line 4 must be narrowed. The capacitance Cv of the line 4 also becomes smaller, and the afterimage further increases.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an MO8 type solid-state imaging device and a combination type solid-state imaging device of MOS and charge transfer device, which have improved the above-mentioned conventional drawbacks and do not cause afterimages.

[Summary of the invention]

In order to achieve the above object, the present invention provides a light receiving section comprising a plurality of two-dimensionally arranged photoelectric conversion elements and a vertical readout switch for reading signal charges accumulated in the photoelectric conversion elements; Captures and accumulates signal charges,
In the solid-state imaging device, the solid-state imaging device further comprises a horizontal drive circuit section or a charge transfer element that sequentially reads and outputs a video signal, and a vertical drive circuit section that includes a shift register for generating scanning pulses that sequentially selectively scans the rows of the photoelectric conversion elements. It is assumed that the photoelectric conversion element is constituted by a depletion layer that is formed under the transparent electrode when a voltage is applied to the transparent electrode.

[Embodiments of the invention]

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

FIG. 3 is an embodiment of the present invention, and shows a cross-sectional structure of a photoelectric conversion element portion of a solid-state imaging device.

In the structure shown in FIG. 3(a), the signal charge is transferred from the photoelectric conversion element portion 2' to the vertical line 4 in the following q manner. That is, during the video period, the vertical switch 21 is OFF, as shown in the potential diagram in FIG. 3(b).
While maintaining the F state, a positive voltage (for N channel, negative voltage for P channel) is applied to the transparent electrode 9 to form a depletion layer 2' in the photoelectric conversion element portion. Depletion layer 2'
The light P incident through the transparent electrode 9 while the
is converted into a signal charge and accumulated in the depletion layer 2'.

To transfer the accumulated charge to the vertical line 4, first turn on the vertical switch 21 and lower the voltage of the transparent electrode 9, so that the potential level of the depletion layer 2' is lower than the potential level below the vertical switch 21. Increase (C)
.

By performing such an operation, all the signal charges in the depletion layer 2' can be transferred to the vertical line 4 in a short time. This makes it possible to prevent afterimages caused by signal charges remaining unread in the photoelectric conversion element portion.

FIG. 4 shows an embodiment of the present invention in an MO8 type solid-state imaging device. The transparent electrode is constituted by a horizontal band 42, one end of which is connected to an external terminal φ'vo through a switch 44 which is opened and closed by the output of the vertical shift register 1.

FIG. 5 shows driving of the MO8 type solid-state imaging device of FIG.
It is a figure showing a driving method.

In the apparatus of FIG. 4, the horizontal blanking pulse II-BL
When entering the horizontal retrace period T u Rt, the vertical shift register is first operated by the φV pulse, and after transferring the signal charge accumulated in the Cv of the vertical line 4, the switch corresponding to the next line is activated. Turn on 44. By operating this switch 44, it becomes possible to perform either sequential scanning or interlaced scanning. After that, the vertical switch 21 is turned on by φv6, and φ′v
When o is turned off, the potential level of the depletion layer 2' under the transparent electrode is not high, and all the signal charges in the depletion layer 2' are not left behind and are transferred to the vertical line 4 through the vertical switch 21. transferred inside.

Next, after turning off the vertical switch 21, the transparent electrode φ'vo is turned on, so that the depletion layer 2
Accumulation of signal charges begins within ', and a running period begins.

As described above, all the signal charges accumulated in the depletion layer 2' are transferred into the vertical line 4 without being left behind, and the transferred signal charges are used to operate the horizontal shift register. By extracting the image, a video signal without afterimage can be obtained.

FIG. 6 shows a second embodiment of the present invention in an MO8 type solid-state imaging device.

The operating principle of the device shown in FIG. 6 is a modification of the operation shown in FIG. 3. As shown in FIGS. 7(a) and (b), the vertical switch 2
The potential under the depletion layer 2' is always kept constant, and the potential inside the depletion layer 2' is changed only by turning on and off the transparent electrode voltage, so that signal charges are transferred without being left behind. A similar operation can be performed in the device shown in FIG. 4, but in FIG. 6, in order to simplify the element structure, the vertical switch 21 is directly connected to the external terminal φv0 without passing through the switch 44.

FIG. 8 shows a third embodiment of the present invention in an MO8 type solid-state imaging device.

The operating principle of the device shown in FIG. 8 is a modification of the operation shown in FIGS. 3 and 7. As shown in FIG. 9, the potential below the transparent electrode 2' is kept constant, and the vertical switch 21 O of
By only turning off the N, OFF operation, a difference is made in the potential between the depletion layer 2' and the bottom of the vertical switch 21, and all of the signal charges in the depletion layer 2' are transferred to the vertical line 4 through the vertical switch 21 without leaving any signal charges behind. I tried to transfer it. A similar operation can be performed in the device shown in FIG. 4, but in order to simplify the device structure in FIG.
It is directly connected to the external terminal φVQ without passing through the terminal 4.

In FIG. 8, the transparent electrode 2' can also be a transparent electrode film.

Although only the MO8 type solid-state imaging device has been described above, the fourth
By replacing the horizontal shift register 3 and the horizontal switch 5 in FIGS. 6, 8 with the horizontal CCD 6 and the transfer circuit section 7, it is possible to obtain a solid-state imaging device of the combination type of MOS and charge transfer element without image retention. can.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain an MO8 type solid-state imaging device and a combination type solid-state imaging device of a MOS and a charge transfer element, which do not cause afterimages, and improve image quality.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing the configuration of a conventional solid-state imaging device;
FIG. 3 is a cross-sectional view of the photoelectric conversion element section and a diagram explaining its operation in the two embodiments printed in this press, and FIGS. 4 and 5 show the structure of one embodiment of the solid-state imaging device according to the present invention. Figures 6 and 7 and Figures 8 and 9 are diagrams showing the structure of another embodiment of the solid-state imaging device according to the present invention and diagrams explaining its operation, respectively. It is. 1... Vertical shift) L/register 2... Photoelectric conversion element part (photodiode), 2'... Photoelectric conversion element part (depletion layer under transparent electrode), 3... Horizontal shift register, 4・
...Vertical line, 21...Vertical switch, 42...
Transparent electrode, 44...Scanning line designation switch, φVQ
...Vertical switch control pulse, φ'vo...Transparent electrode control pulse No. 1 n 2 Fig. figure

Claims (1)

[Claims] 1. A light receiving section comprising a plurality of two-dimensionally arranged photoelectric conversion elements and a vertical readout switch for reading out the signal charges accumulated in the photoelectric conversion elements, which receives and accumulates the signal charges. In the solid-state imaging device described above, the solid-state imaging device further comprises a horizontal drive section or a charge transfer element that sequentially reads and outputs a video signal, and a vertical drive circuit section that includes a shift register for generating scanning pulses that sequentially selectively scans the rows of the photoelectric conversion elements. A solid-state imaging device characterized in that a photoelectric conversion element is constituted by a depletion layer formed by applying a voltage to a transparent electrode. 2. The solid-state imaging device according to claim 1, wherein signal charges are read from the transparent electrode by a vertical drive circuit operated via a switch that sequentially selectively scans each row. 3. The solid-state imaging device according to claim 1, further comprising circuits that respectively control the voltage of the transparent electrode and the vertical readout switch.