JPS6033347B2 - solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state imaging device, in which a photoconductor is formed on a semiconductor substrate constituting a circuit element having a charge transfer function, and an electrode formed on the photoconductor is charged with a photoconductor. It is an object of the present invention to provide a solid-state green image device in which the blooming phenomenon is suppressed by applying a high voltage that cannot be turned on by a clock pulse applied to a circuit element during transfer.

Conventionally, in a structure in which a photoconductor is formed on a semiconductor substrate having a charge transfer function, and the same gate electrode is used to read the charge generated in the photoconductor to the transfer stage and transfer the signal charge, , the electrode on the photoconductor was kept at the same potential as the semiconductor substrate (ground potential).

Therefore, when the amount of incident light is large, the charge photogenerated in the photoconductor decreases the source potential electrically connected to the photoconductor, and the threshold voltage between the source region and the transfer stage drain region decreases. is equal to or lower than the threshold voltage between the source and drain of the transfer stage. At this time, although the read operation and the transfer operation are originally independent in time, the read operation is also performed during the transfer.
This was the cause of the blooming phenomenon. The present invention provides a solid-state imaging device having the above configuration, in which a voltage higher than the potential of a source region electrically connected to the photoconductor is applied to the electrode on the photoconductor, which can be set by a drive voltage during transfer. The present invention provides a solid-state imaging device in which the above-described blooming phenomenon is suppressed by applying .

The solid-state imaging device of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a cross-sectional structure of one unit of the solid-state imaging device of the present invention, which has a circuit element having a charge transfer function formed on a silicon substrate and a photoconductor formed thereon.

An n+ type region 11 is formed in a p-type semiconductor substrate 10 to provide a diode. 12 is a potential well in an n+ type region.

A first gate electrode 13 has a portion overlapping with the n+ type region 11.

14 is an insulating film between the semiconductor substrate 10 and the first gate electrode 13, which is a gate oxide film.

Reference numeral 15 denotes an insulating layer for electrically separating the first electrode 16 from the semiconductor substrate 10 and the first gate electrode 13.

A first electrode 16 is an electrode of a diode electrically connected to the n+ type region 11, and also serves as an electrode of the hole blocking layer 17. 18 is (Zn, -xCdxTe), -
It is a photoconductor made of y(1 ratio Te3)y, on which a transparent electrode 19 is formed, and is set to a potential according to the present invention by two voltage sources.

In the configuration shown in FIG. 1, a driving pulse as shown in FIG. 2a is applied.

At time t, electrode 13 is set to a potential (VcH-VT) as shown in FIG. 2b). Here, VT is n
This is the threshold voltage of the FET composed of the positive regions 11 and 12 and the first gate electrode 13. When there is now incident light 21, electron-hole pairs are generated in the photoconductor 18, which reach the electrodes 16 and 19, respectively, and the potential of the electrode 16 decreases. Furthermore, when voltage VcH is applied to the first gate electrode 13 at time t2, signal charges are transferred from the n+ region 11 to the n+ region 12, and as a result, the potential of the n+ region 11 rises again to (VcH - VT). . n+ area 12
The signal charge transferred to is then transferred to the output section by the transfer pulse VO shown in FIG. Now, incident light 21
Consider a case where the voltage is very strong and the potential according to the present invention is not set on the transparent electrode 19.

At this time, the potential of the electrode 16 described above is greatly reduced, and the transfer pulse applied to the first gate electrode 13 also transfers signal charges from the n+ region 11 to the n+ region 12 in the same manner as the read pulse, and is transferred to the transfer line. This causes the blooming phenomenon. However, as in the present invention, when a voltage Va higher than the potential of the source region electrically connected to the photoconductor is applied to the transparent electrode 19, which can be set by the transfer pulse applied to the first gate electrode 13. When the potential of the first electrode 16 is lowered to Va due to the photo-generated signal charges, the potential difference in the photoconductor disappears, and the photo-generated charges do not reach the electrode 16 and disappear by recombination.

Therefore, even in the case of strong incident light, it is clipped to the potential Va of the electrode 16, and a read operation by the transfer pulse applied to the first gate electrode 13 cannot occur, and the blooming phenomenon is suppressed. FIG. 3 specifically shows this effect.

In this case, when the voltage of the transparent electrode 19 becomes about 3 V or higher, blooming is drastically reduced. However, as can be seen from FIG. 3, if the voltage applied to the transparent electrode 19 is further increased, the signal amount also decreases from around 5 V, so this voltage becomes the upper limit of the voltage that can be applied to the transparent electrode 19. . Therefore, in this case, the optimal condition for the voltage applied to the transparent electrode 19 is 3 to 5V. However, this value is limited and is not 0, but changes depending on other device conditions.
As described above, in the present invention, a transparent electrode on a photoconductor is connected to a reading stage FET using a clock pulse during transfer.
The blooming phenomenon is suppressed by applying a voltage that does not allow the switch to turn on.

If the present invention is used, even if there is locally strong incident light, images of other parts can be captured without being disturbed by blooming, so it can be said to have extremely great industrial significance. 0 Brief Description of the Drawings FIG. 1 is a diagram showing a cross-sectional structure of one unit of the solid-state imaging device of the present invention, in which a photoconductor is provided on a circuit element having a charge transfer function, and FIGS. FIG. 3, which is a diagram for explaining the operation of the illustrated solid-state imaging device, is a characteristic diagram of the solid-state imaging device of the present invention.

10...p-type semiconductor substrate, 11...n+ source region, 12...n+ drain region, 13...
・First gate electrode, 14...Gate oxide film, 1
5... Insulating film, 16... First electrode, 1
7...Hole blocking layer, 0 18...(Znr
xCdxTe), -y(IQTe3)y layer, 19...
...Transparent electrode, 20...Voltage source.

Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A semiconductor substrate having one conductivity type is provided with a first source and a first drain region having an opposite conductivity type, and the first drain region is used as a second source region. forming a second drain region;
An identical gate electrode is formed between the two source and drain regions, an insulating layer is formed except for a part of the first source region, and an electrical connection between the first source region and the first source region is formed on the insulating layer. forming a first electrode coupled to the first electrode, forming a photoconductor on the first electrode and the insulating layer, forming a second electrode on the photoconductor, and photoconducting the photoconductor. In a solid-state imaging device in which a plurality of solid-state devices are arranged as a unit, a voltage is applied to the second electrode from the first source region potential which can be set by the drive voltage of the second source and drain regions. A solid-state imaging device characterized by a high voltage.