JPH05136395A - Solid-state imaging device - Google Patents

Abstract

PURPOSE:To provide a solid-state imaging device capable of preventing noise charges occurred on the surface of a substrate from flowing into a signal charge storage part, and capable of reducing outputs and unevenness during dark periods. CONSTITUTION:A solid-state imaging device is made up of a plurality of signal charge storage parts 11 which are formed on a p-type silicon substrate 10 and made of an n-type layer, signal charge read parts for reading signal charges stored in the signal charge storage part 11, signal charge transfer parts 12 made of an n-type layer for transferring the signal charges read by the signal charge read part, transfer gate electrodes 14 and 15 formed over the signal charge read part and the signal charge transfer part 12, and element isolating regions for isolating the signal charge storage part 11 from the signal charge transfer part 12. The signal charge storage part 11 is partially surrounded by a p-type impurity diffusing layer 6 for raising the electric potential of the periphery of the storage part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a charge coupled device (CC
The present invention relates to a solid-state image pickup device using D), and more particularly to a solid-state image pickup device having an improved peripheral structure of a signal charge storage portion.

[0002]

2. Description of the Related Art In recent years, the number of pixels of a solid-state image pickup device using a CCD has been increased, the element characteristics have been dramatically improved, and it is being widely applied to various applications. In particular, a solid-state image pickup device having a two-story structure in which a photoconductive layer is laminated on a solid-state image pickup element chip can have a large opening area of the photosensitive portion, and thus has excellent characteristics of high sensitivity and low smear. For this reason, various monitoring televisions and HDTV (High Definition Tele)
vision) is expected to be applied to cameras.

FIG. 10 shows a conventional laminated solid-state image pickup device.
It is sectional drawing which shows a pixel structure. In the figure, 60 is a p-type Si substrate, 61 is a signal charge storage section (storage diode) made of an n-type layer, 62 is a signal charge transfer section (vertical CCD channel) made of an n-type layer, and 63 is a p-type layer. An element isolation layer, 64 is a first transfer gate electrode also serving as a read gate, 65 is a second transfer gate electrode, 66 is a planarization insulating layer, 67 is a protruding electrode, and 68 is a pixel electrode. To form a solid-state image sensor chip.
Then, a photoelectric conversion film 70 is deposited on the solid-state image sensor chip, and a transparent electrode 71 such as ITO is formed on the photoelectric conversion film 70.

FIG. 11 shows a plan configuration of this device. Further, FIG. 12 shows a potential distribution in a cross section taken along the line EE ′ of the signal charge storage portion. In the case of the conventional image pickup device, noise charges generated on the surface of the substrate at the time of signal storage flow into the signal charge storage section 61 to increase the dark output and increase the dark unevenness. In particular, in the case of a stacked solid-state image pickup device, since the photoelectric conversion film 70 and the signal charge storage unit 61 are connected by the metal wiring 67, the surface of the signal charge storage unit 61 is formed like a buried photodiode of a normal CCD image pickup device. Cannot be transformed. Therefore, the stacked solid-state imaging device cannot reduce the dark output and the dark unevenness.

[0005]

As described above, in the conventional stacked type solid-state image pickup device, noise charges generated from the surface of the substrate flow into the signal charge storage portion, so that the dark output is increased and the dark unevenness is increased. There was a problem to do.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent noise charges generated on the surface of a substrate from flowing into a signal charge storage portion, and to output at dark and dark. An object of the present invention is to provide a solid-state image pickup device capable of reducing unevenness in time.

[0007]

The essence of the present invention is to increase the potential of the peripheral portion of the signal charge storage portion in order to prevent noise charge generated on the substrate surface from flowing into the signal charge storage portion. It is in.

That is, according to the present invention (claim 1), a plurality of signal charge accumulating portions formed on the main surface of the semiconductor substrate and a signal charge reading portion for reading out the signal charges accumulated in these signal charge accumulating portions. In the solid-state imaging device, the signal charge transfer section for transferring the signal charge read by the signal charge reading section, and the element isolation region for separating the signal charge storage section and the signal charge transfer section are provided. A diffusion layer for increasing the potential of the peripheral portion is provided in the peripheral portion of the storage portion.

According to the present invention (claim 2), a plurality of signal charge accumulating portions formed on the main surface of the semiconductor substrate and a signal charge reading portion for reading out the signal charges accumulated in these signal charge accumulating portions. And a signal charge transfer section for transferring the signal charge read by these signal charge read sections, an element isolation region for separating the signal charge storage section and the signal charge transfer section, and a signal charge transfer section formed on the signal charge transfer section. In a solid-state imaging device including a transfer gate electrode and a read gate electrode formed on the signal charge reading unit, an auxiliary gate electrode for increasing the potential of the signal charge storage unit is provided on the peripheral unit. It is the one. Further, the present invention (claim 3) includes a plurality of signal charge accumulating portions formed on the main surface of the semiconductor substrate, a signal charge reading portion for reading the signal charges accumulated in these signal charge accumulating portions, and these. Formed on the signal charge transfer section and the signal charge read section, the signal charge transfer section that transfers the signal charge read by the signal charge read section, the element isolation region that separates the signal charge storage section and the signal charge transfer section from each other. In the solid-state imaging device including the first transfer gate electrode also serving as the read gate and the second transfer gate electrode formed on the signal charge transfer portion, the element isolation region below the second transfer gate electrode is formed. It is designed to be removed.

[0010]

According to the present invention (claims 1 and 2), a diffusion layer is formed in the peripheral portion of the signal charge storage portion, or an auxiliary gate electrode is formed on the peripheral portion to increase the potential around the signal charge storage portion. Therefore, the noise charges generated on the substrate surface during signal storage flow out to the signal charge transfer unit side without flowing into the signal charge storage unit. Therefore, it is possible to reduce the dark output and the dark unevenness of the signal charge storage portion.

According to the present invention (claim 3), the second aspect
Since the element isolation layer under the transfer gate electrode of is removed,
The noise charge generated on the surface of the substrate during signal storage does not collect only in the signal charge storage part, but also flows into the signal charge transfer part side. Therefore, although not as high as in claims 1 and 2, it is possible to reduce the dark output and the dark unevenness of the signal charge storage portion.

[0012]

The details of the present invention will be described below with reference to the illustrated embodiments.

FIG. 1 is a plan view showing the schematic arrangement of a solid-state image pickup device according to the first embodiment of the present invention, and FIG. 2 is a view A in FIG.
It is a figure which shows a -A 'cross section and an electric potential distribution. 10 in the figure is p
Type silicon substrate (semiconductor substrate), an n-type layer 11 acting as a storage diode (signal charge storage portion) is arranged in a matrix on the surface layer of the substrate 10, and further adjacent to these storage diodes 11. The n-type layers (vertical CCD channels) 12 that act as signal charge transfer units are arranged in a column. A first transfer gate electrode 14 also serving as a read gate is provided on the vertical CCD channel 12.
And a second transfer gate electrode 15 used only for transferring signal charges is formed.

Here, the transfer gate electrode (readout gate)
Reference numeral 14 is for reading out the signal charge of the storage diode 11 to the vertical CCD channel 12, and extends from the top of the vertical CCD channel 12 to the end of the storage diode 11. Then, the storage diode 11 and the CCD channel 12
Is a charge reading section.

The basic structure up to this point is similar to that of the conventional device, but in this embodiment, in addition to this, a diffusion layer (barrier layer) 16 is formed adjacent to the peripheral portion of the storage diode 11. That is, a p-type impurity diffusion layer 16 having a conductivity type opposite to that of the diode 11 is formed on the side and bottom of the storage diode 11.
Is formed. However, the diffusion layer 16 is not formed at the charge reading port for the vertical CCD channel 12.

With such a structure, as shown in the potential distribution diagram of FIG. 2, the p-type diffusion layer 16 increases the potential of the peripheral portion of the storage diode 11, so that the noise charge generated from the substrate surface is stored. It will not collect in the diode 11 but will flow into the vertical CCD channel 12. Note that the noise charge flowing into the vertical CCD channel 12 is
Since the CCDs are driven when the signal charges are accumulated, they are dispersed in one vertical line, which causes almost no problem. As a result, it is possible to reduce the dark output of the storage diode 11 and also reduce the dark unevenness.

As described above, according to this embodiment, by providing the p-type diffusion layer 16 in the peripheral portion of the storage diode 11 and increasing the potential in the peripheral portion of the storage diode 11, the dark output of the storage diode 11 can be obtained. It can be reduced, and unevenness in darkness can be reduced. Therefore, the quality of the reproduced image can be improved. Further, as in the present embodiment, if it is a laminated type in which the light receiving part and the storage part are independent, there is no inconvenience that the sensitivity is lowered even if the peripheral part of the storage diode 11 is made p-type. Furthermore, by providing the p-type diffusion layer 16 as a barrier layer, it is possible to omit the element isolation layer which was conventionally required.

FIG. 3 is a plan view showing the schematic arrangement of a solid-state image pickup device according to the second embodiment of the present invention, and FIG. 4 is a view B in FIG.
It is a figure which shows a -B 'cross section and an electric potential distribution. The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

This embodiment is different from the first embodiment described above in that the p-type diffusion layer provided in the peripheral portion of the storage diode 11 is a plurality of layers. That is, the p-type layer 16 has the highest potential with respect to the storage diode 11, and the potential is lowered stepwise as the distance from the periphery increases, for example.
6'and 16 "are formed. Even with such a configuration, the same effect as that of the first embodiment can be obtained.

FIG. 5 is a plan view showing a schematic structure of a solid-state image pickup device according to a third embodiment of the present invention, and FIG. 6 is a view C in FIG.
It is a figure which shows -C 'cross section and a potential distribution. The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

The difference of this embodiment from the first embodiment is that an auxiliary gate electrode 26 is provided instead of the p-type diffusion layer 16. That is, the storage diode 11
An auxiliary gate electrode 26 for increasing the potential of the peripheral portion is formed on the peripheral portion. A p-type element isolation layer 13 is formed between the storage diode 11 and the vertical CCD channel 12 and between the adjacent storage diodes.

With such a configuration, as shown in the potential distribution diagram of FIG. 6, by applying a negative voltage to the auxiliary gate electrode 26, the potential of the peripheral portion of the storage diode 11 can be increased, and Holes are not accumulated on the surface of the n-type diffusion layer of the diode 11 to generate noise charges.
Further, the noise charge generated on the surface of the substrate 10 flows into the vertical CCD channel 12 without flowing into the storage diode 11 because the potential under the electrode is increased by the auxiliary gate electrode 26. This makes it possible to reduce the dark output of the storage diode 11,
Moreover, it has become possible to reduce unevenness in darkness.

FIG. 7 is a plan view showing the schematic arrangement of a solid-state image pickup device according to the fourth embodiment of the present invention. Note that FIG.
The same parts as those of the above are denoted by the same reference numerals, and detailed description thereof will be omitted.

The difference between this embodiment and the third embodiment is that the auxiliary gate electrode 26 is formed in a portion excluding the signal charge reading port. In this case, the read gate 14 can be read without applying a voltage to the auxiliary gate electrode 26 during signal reading.
Signal voltage can be transferred to the vertical CCD channel 12 by applying a voltage only to the vertical CCD channel 12. That is, a constant negative voltage may be applied to the auxiliary gate electrode 26. Even in this embodiment, the same effect as that of the first embodiment can be obtained.

FIG. 8 is a plan view showing the schematic arrangement of a solid-state image pickup device according to the fifth embodiment of the present invention, and FIG. 9 is a view D in FIG.
It is a figure which shows -D 'cross section and electric potential distribution. The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

The difference of this embodiment from the first embodiment is that the pattern of the element isolation layer 13 is devised instead of providing the diffusion layer 16. That is, in this embodiment, the element isolation layer 13 is provided only under the read gate 14, and the element isolation layer 13 is not formed under the transfer gate 15.

With such a structure, as shown in the potential distribution diagram of FIG. 9, the element isolation layer 13 is formed under the transfer gate 15.
Since the noise charge generated from the surface of the substrate 10 is not collected only in the storage diode 11, the vertical CCD does not exist.
It will also flow into the channel 12. That is, the noise charge is dispersed in the storage diode 11 and the vertical CCD channel 12. As a result, the storage diode 11
The output in darkness decreased, and it became possible to reduce unevenness in darkness. Further, compared to the conventional device, there is an advantage that it can be realized by only changing the pattern of the element isolation layer 13 without adding a new process.

The present invention is not limited to the above embodiments. In the embodiment, the laminated solid-state image pickup device is taken as an example, but the invention is not limited to the laminated type, and can be applied to a normal CCD type image pickup device. In addition, various modifications can be made without departing from the scope of the present invention.

[0029]

As described above in detail, according to the present invention, since the diffusion layer and the auxiliary gate electrode are provided in the peripheral portion of the signal charge storage portion, noise charges generated on the substrate surface are stored in the signal charge storage portion. It does not flow in, so that it is possible to reduce the dark output and the dark unevenness of the signal charge storage portion.

[Brief description of drawings]

FIG. 1 is a plan view showing a schematic configuration of a solid-state imaging device according to a first embodiment of the present invention,

FIG. 2 is a view showing a cross section taken along the line AA ′ of FIG. 1 and a potential distribution,

FIG. 3 is a plan view showing a schematic configuration of a solid-state imaging device according to a second embodiment of the present invention,

FIG. 4 is a diagram showing a cross section and a potential distribution taken along line BB ′ of FIG.

FIG. 5 is a plan view showing a schematic configuration of a solid-state imaging device according to a third embodiment of the present invention,

6 is a diagram showing a cross section CC-C ′ in FIG. 5 and a potential distribution,

FIG. 7 is a plan view showing a schematic configuration of a solid-state imaging device according to a fourth embodiment of the present invention,

FIG. 8 is a plan view showing a schematic configuration of a solid-state imaging device according to a fifth embodiment of the present invention,

9 is a diagram showing a cross section taken along the line DD ′ of FIG. 8 and a potential distribution,

FIG. 10 is a cross-sectional view showing a schematic configuration of a conventional stacked solid-state imaging device,

FIG. 11 is a plan view showing a schematic configuration of a conventional stacked solid-state imaging device,

FIG. 12 is a diagram showing a cross section taken along the line EE ′ of FIG. 11 and a potential distribution.

[Explanation of symbols]

 10 ... p-type silicon substrate (semiconductor substrate), 11 ... n-type storage diode (signal charge storage part), 12 ... n-type vertical CCD channel (signal charge transfer part), 13 ... p-type element isolation layer, 14 ... first Transfer gate electrode (readout gate), 15 ... second transfer gate electrode, 16 ... p-type impurity diffusion layer (barrier layer), 26 ... auxiliary gate electrode.

Front page continuation (72) Inventor Naomi Nomi 1 Komukai Toshiba-cho, Kawasaki-shi, Kanagawa Kanagawa Prefecture Inside the Toshiba Research Institute Co., Ltd.

Claims (4)

[Claims] 1. A plurality of signal charge accumulating portions formed on a main surface of a semiconductor substrate, a signal charge reading portion for reading signal charges accumulated in these signal charge accumulating portions, and a signal charge reading portion. A signal charge transfer unit that transfers the read signal charges, an element isolation region that separates the signal charge storage unit and the signal charge transfer unit, and a potential formed in the peripheral portion of the signal charge storage unit. A solid-state imaging device, comprising: a diffusion layer for increasing the height. 2. A plurality of signal charge accumulating portions formed on the main surface of a semiconductor substrate, a signal charge reading portion for reading the signal charges accumulated in these signal charge accumulating portions, and these signal charge reading portions. A signal charge transfer unit that transfers the read signal charge, an element isolation region that separates the signal charge storage unit and the signal charge transfer unit, a transfer gate electrode formed on the signal charge transfer unit, and the signal charge A solid-state imaging device comprising: a read gate electrode formed on a read section and an auxiliary gate electrode formed on a peripheral portion of the signal charge storage section. 3. A plurality of signal charge accumulating portions formed on the main surface of a semiconductor substrate, a signal charge reading portion for reading the signal charges accumulated in these signal charge accumulating portions, and these signal charge reading portions. A signal charge transfer unit that transfers the read signal charge, an element isolation region that separates the signal charge storage unit and the signal charge transfer unit, and a read gate formed on the signal charge transfer unit and the signal charge read unit A first transfer gate electrode that also serves as a second transfer gate electrode, and a second transfer gate electrode formed on the signal charge transfer portion.
In the solid-state imaging device including the transfer gate electrode of, the element isolation region under the second transfer gate electrode is removed. 4. A pixel electrode electrically connected to the signal charge storage portion is formed on a substrate on which the respective portions are formed, and a photoelectric conversion film is formed on the substrate on which the pixel electrode is formed. The solid-state imaging device according to claim 1, 2, or 3, wherein