JP2000022134A - Solid-state image-pickup device and method for driving the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image-pickup device having a large area for photoelectric transfer parts and exhibiting high sensitivity by reducing the number of wires formed between photoelectric transfer parts in vertical direction on a semiconductor substrate. SOLUTION: A solid-state image-pickup device is provided with plural photoelectric transfer parts 12, disposed in rows on a semiconductor substrate 10 and vertical charge transferring parts for transferring signal charge from the photoelectric transfer parts 12 in the vertical direction, which are disposed adjacent to the rows formed by the photoelectric transfer parts 12. The vertical charge transferring parts are provided with a group of transferring electrodes, including a first transferring electrode 14a and a second transferring electrode 13, corresponding to each of the photoelectric transfer parts 12. Each of first transfer electrodes 14 is formed into the shape of an isolated island. At least a part of the electrical connection between the first transferring electrode 14a is made via a metal light blocking film 16 formed on the vertical charge transferring part via an interlayer insulating film 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state imaging device and a driving method thereof.

[0002]

2. Description of the Related Art In recent years, charge coupled devices (charge coupled devices) have been developed.
evice; hereinafter, "CCD". The solid-state imaging device using a charge transfer device represented by ()) has been remarkably put into practical use due to its superiority such as low noise characteristics. In particular, as a structure for realizing low power consumption, a structure in which a plurality of transfer electrodes constituting a charge transfer device are formed in a single layer without overlapping each other (hereinafter, referred to as a “single-layer electrode structure”) has been proposed. (For example, JP-A-5-114617). Less than,
A conventional solid-state imaging device having a single-layer electrode structure will be described with reference to the drawings.

FIG. 7 is a plan view showing the structure of a pixel portion of a conventional solid-state imaging device, and FIG. 8 is a cross-sectional view taken along the line CC 'of FIG. Photoelectric conversion units (usually, photodiodes) 32 are two-dimensionally arranged on the semiconductor substrate 30, and a plurality of vertical charge transfer units (usually, CCDs) are formed by the photoelectric conversion units 32. It is formed to be adjacent to the row. In other words, the pixel unit of the solid-state imaging device has a structure in which pixels each formed by one photoelectric conversion unit and a charge transfer unit including two transfer electrodes are two-dimensionally arranged. The vertical charge transfer section includes an n-type diffusion region 31 formed in a p-type semiconductor substrate (or p-type well) 30.
And a single-layered transfer electrode formed on the n-type diffusion region 31 via an insulating film. The transfer electrodes constituting the vertical charge transfer unit are photoelectric conversion units in a direction (hereinafter, “horizontal direction”) orthogonal to the charge transfer direction (hereinafter, “vertical direction”) in the vertical charge transfer unit. Are electrically connected to another adjacent transfer electrode through the column. The connection between the transfer electrodes is achieved by forming a comb-shaped electrode 33 in which a plurality of transfer electrodes arranged in the horizontal direction are integrated. That is, in the comb-shaped electrode 33, the portion corresponding to the teeth of the comb functions as a substantial transfer electrode for driving the vertical charge transfer unit, and the portion corresponding to the body of the comb functions as a wiring connecting the transfer electrodes. I have.

A metal light-shielding film 36 is formed above the vertical charge transfer section via an interlayer insulating film 35. The metal light-shielding film 36 is formed in order to suppress generation of a false signal called smear, which is caused by light incident on a region other than the photoelectric conversion unit (mainly, the vertical charge transfer unit). is there. Further, although not shown, the vertical charge transfer section is connected to a horizontal charge transfer section, and the horizontal charge transfer section is connected to an output amplifier section also serving as charge detection.

In the solid-state imaging device having the above structure, the signal charges generated in the photoelectric conversion unit 32 are sequentially transferred by the vertical charge transfer unit and the horizontal charge transfer unit, converted into a voltage by the output amplifier unit, and output. . FIG. 9 shows an example of a pulse for driving a conventional solid-state imaging device. In FIG. 9, H1 and H2 are pulses for driving the horizontal charge transfer unit, and V1, V2, V3 and V4 are pulses for driving the vertical charge transfer unit. As described above, in the vertical charge transfer unit, a drive pulse of at least three phases (four phases in FIG. 9) is used to transfer a signal charge without mixing it with a signal from another pixel. The potential distribution and signal charge transfer in the vertical charge transfer unit when the conventional solid-state imaging device is driven by the pulse shown in FIG. 9 are as shown in FIG.

[0006]

In a conventional solid-state imaging device having a single-layer electrode structure, as described above, a plurality of transfer electrodes are periodically arranged in a horizontal direction by forming a comb-shaped electrode. The transfer electrodes adjacent in the horizontal direction are electrically connected. Since two transfer electrodes are formed in one pixel, two wirings (portions corresponding to the comb body of the comb-shaped electrode) for connecting horizontally adjacent transfer electrodes are also formed per pixel. The Rukoto.
Therefore, in the solid-state imaging device as described above, as shown in FIG. 7, it is necessary to secure an area for forming two wirings between the photoelectric conversion units, and thus the area of the photoelectric conversion units is limited.
Therefore, the effective area of the photoelectric conversion unit is reduced, which has been a problem in improving the sensitivity of the solid-state imaging device.

An object of the present invention is to provide a solid-state imaging device having good sensitivity and a driving method thereof.

[0008]

In order to achieve the above object, a solid-state imaging device according to the present invention has a plurality of photoelectric conversion units arranged in a matrix on a semiconductor substrate, and is adjacent to each column formed by the photoelectric conversion units. A solid-state imaging device in which a vertical charge transfer unit that transfers a signal charge from the photoelectric conversion unit in a vertical direction so as to fit is provided, wherein the vertical charge transfer unit is a first charge conversion unit corresponding to each of the photoelectric conversion units. And a transfer electrode group including a second transfer electrode and a second transfer electrode. Each of the first transfer electrodes is formed in an independent island shape, and an electrical connection between the first transfer electrodes is formed. At least a portion is formed via a metal light-shielding film formed on the vertical charge transfer section via an interlayer insulating film.

With this configuration, a part of the connection between the transfer electrodes constituting the vertical charge transfer portion is implemented by the metal light-shielding film. Therefore, compared with the conventional solid-state imaging device shown in FIG. It is possible to reduce the number of wirings formed between the photoelectric conversion units. Therefore, the element that limits the interval between the photoelectric conversion units in the vertical direction is smaller than that in the conventional solid-state imaging device, so that the effective photoelectric conversion unit area can be increased and the sensitivity can be improved.

In the solid-state imaging device, it is preferable that the transfer electrodes constituting the transfer electrode group are formed in a single layer without being laminated. According to this preferred example, since the vertical charge transfer section has a so-called single-layer electrode structure, power consumption can be reduced.

Further, in the solid-state imaging device, a diffusion region serving as a transfer channel of the vertical charge transfer portion is formed in the semiconductor substrate, and a transfer electrode constituting the transfer electrode group among the diffusion regions is formed. It is preferable that the impurity concentration of a region located below and behind the signal charge transfer direction in the vertical charge transfer unit is lower than the impurity concentration of the other region of the diffusion region. According to this preferred example, in the vertical charge transfer section, charge transfer by two-phase driving can be performed without inconvenience such as mixing of signal charges.

In the solid-state imaging device, it is preferable that the metal light-shielding film is divided in a signal charge transfer direction in the vertical charge transfer section. That is,
It is preferable that the structure has a structure in which a plurality of metal light shielding films are arranged in a vertical direction. According to this preferred example, the transfer electrodes of the vertically adjacent pixels can be electrically independent from each other. Therefore, when a desired pixel is selected and read from the vertical pixel column, a metal light shielding is applied to the wiring. A transfer electrode using a film can be used as a readout electrode.

In the solid-state imaging device, the transfer electrodes constituting the transfer electrode group may be made of a metal having a light-shielding property, a silicon compound of the metal, or a laminate of the metal or the silicon compound and polysilicon. Is preferably formed. This is because generation of smear can be suppressed. Examples of such a material include W, Mo, WSi, and a laminate of these and polysilicon.

To achieve the above object, a method for driving a solid-state imaging device according to the present invention is a solid-state imaging device according to the present invention,
Of the diffusion region that becomes the transfer channel of the vertical charge transfer unit,
The impurity concentration of a region located below each of the transfer electrodes constituting the transfer electrode group and located rearward with respect to the transfer direction of the signal charge in the vertical charge transfer portion is an impurity concentration of another region of the diffusion region. The transfer of signal charges in the vertical charge transfer section is performed by two-phase driving using a solid-state imaging device having a lower density. According to this driving method, it is easy to generate a pulse, so that high-speed driving can be realized.

Another driving method of the solid-state imaging device according to the present invention is the solid-state imaging device according to the present invention, wherein the metal light-shielding film is divided into a signal charge transfer method in a vertical charge transfer unit. And applying a low-level voltage to a transfer electrode group located below a gap formed by dividing the metal light-shielding film during a signal charge transfer stop period in the vertical charge transfer section. According to this driving method, it is possible to suppress an increase in smear due to the presence of the gap in the metal light shielding film.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A solid-state imaging device according to the present invention is a pixel including a photoelectric conversion unit for converting an optical signal into a charge and a vertical charge transfer unit for transferring a signal charge from the photoelectric conversion unit. And a horizontal charge transfer unit that transfers the signal charges transferred from the pixel unit, and an output amplifier unit that detects the transferred signal charges, amplifies the signal charges, and outputs the amplified signal charges. FIG. 1 is a plan view of a pixel portion constituting a solid-state imaging device according to a first embodiment of the present invention, and FIG.
FIG. 3 shows a cross-sectional view along A ′. Hereinafter, the structure of the solid-state imaging device according to the present embodiment will be described with reference to these drawings.

The photoelectric conversion unit 12 includes, for example, a p-type semiconductor substrate (or a p-type well formed in the semiconductor substrate) 10.
The photodiode is formed by introducing an n-type impurity such as arsenic or phosphorus therein, and is arranged in a matrix on the main surface of the semiconductor substrate 10. The plurality of vertical charge transfer units are formed so as to be adjacent to each of the columns formed by the photoelectric conversion units arranged in the vertical direction. That is, the semiconductor substrate 10
As shown in FIG. 1, vertical charge transfer sections and photoelectric conversion section rows are alternately arranged in the horizontal direction. Further, the semiconductor substrate 1
A metal light-shielding film 16 is formed on a region including the upper part of the vertical charge transfer portion on the substrate 0 via an interlayer insulating film 15. The metal light-shielding film 16 has an opening above the photoelectric conversion unit 12, as shown in FIG.

The vertical charge transfer portion includes an impurity diffusion region 11a formed by introducing an n-type impurity such as arsenic or phosphorus into a p-type semiconductor substrate (or a p-type well formed in the semiconductor substrate) 10. A CCD having a single-layer electrode structure formed by using a transfer electrode formed on the impurity diffusion region 11a via an insulating film, wherein the impurity diffusion region 11a
Is the channel area of the CCD.

[0019] The impurity diffusion region 11a constituting the vertical charge transfer portion, as shown in FIG. 2, a region of low respectively impurity concentration below the respective transfer electrodes (n ^- -type region) 11b is formed (provided that In FIG. 1, n ⁻
The mold region 11b is omitted. ). n ^- type region 11b
Are formed below the transfer electrodes in portions located rearward in the charge transfer direction. That is, in the channel opposed to one transfer electrode, the potential of the portion located rearward in the charge transfer direction is adjusted to be lower than that of the other region (n-type region) 11a. As a result, in the channel below one transfer electrode, the n-type region 11 a
^The -type region 11b functions as a barrier region that suppresses mixing with signals from other pixels, and enables charge transfer by two-phase driving. This will be described later.

The transfer electrodes constituting the vertical charge transfer section are formed periodically corresponding to the arrangement period of the photoelectric conversion sections. For example, as shown in FIG. Transfer electrodes are arranged. That is, the pixel unit of the solid-state imaging device according to the present embodiment includes one photoelectric conversion unit and two photoelectric conversion units.
A pixel including a charge transfer unit including a plurality of transfer electrodes (each of which is a first transfer electrode and a second transfer electrode) is arranged in a matrix.

The second transfer electrode is formed in a shape integrated with the second transfer electrode constituting another pixel adjacent in the horizontal direction. More specifically, comb-shaped electrodes (13a, 13b and 13 in the figure) in which a portion functioning as a transfer electrode for substantially driving the vertical charge transfer portion is regarded as a comb tooth
formed as c). By forming the electrodes in a comb shape in this manner, a plurality of transfer electrodes are periodically arranged in the horizontal direction, and at the same time, a portion corresponding to the body of the comb functions as a wiring, and the transfer electrodes adjacent to each other in the horizontal direction are formed. Electrical connection is realized.

On the other hand, the first transfer electrode (1 in the figure)
4a, 14b and 14c) are formed in an island shape independent of each other in pattern. The first transfer electrode and the first transfer electrode forming another pixel adjacent in the horizontal direction are electrically connected by using the metal light-shielding film 16 as a wiring. That is, as shown in FIG. 2, the first transfer electrodes 14a, 14a
b and 14c, an opening for making a contact is formed.
Are electrically connected to each other. Therefore, in the first transfer electrode, there is no need for an element that limits the interval between the photoelectric conversion units arranged in the vertical direction, such as the wiring part in the comb-shaped electrode.

In the solid-state imaging device according to the present embodiment having the above-described structure, the element that limits the vertical interval of the photoelectric conversion unit on the semiconductor substrate is the comb-shaped electrode 13.
Since only the portions (corresponding to the body of the comb) of a, 13b and 13c function as wiring, the effective photoelectric conversion area is increased compared to the conventional solid-state imaging device as shown in FIG. And the sensitivity can be improved. The solid-state imaging device according to the present embodiment has a structure in which charge transfer by two-phase driving can be performed in the vertical charge transfer unit. Pulse generation is easier than in the case of driving, and high-speed driving can be realized.

It should be noted that the same materials as those conventionally used can be used for the materials of the members constituting the solid-state imaging device of the present embodiment. For example, as the metal light-shielding film, metals such as aluminum, tungsten, titanium, and molybdenum, and alloys of these metals can be used. For other members,
For example, a single crystal silicon substrate may be used for a semiconductor substrate, a silicon oxide film may be used for an insulating film and an interlayer insulating film, and polysilicon may be used for a transfer electrode.

The solid-state imaging device according to the present embodiment is the same as the conventional solid-state imaging device except that at least a part of the electrodes is formed in an independent island shape and a contact is formed in an interlayer insulating film on the island electrode. It can be manufactured by a conventional method. An example of the manufacturing method will be briefly described below. First, impurity ions are implanted into a p-type silicon substrate to form diffusion regions of a photoelectric conversion unit and a vertical charge transfer unit. Next, after a silicon oxide film is formed on the substrate surface by thermal oxidation, a polysilicon film is deposited by a CVD method. The polysilicon film is patterned by a photolithography method to form the above-mentioned comb-shaped electrode and an electrode having an independent shape. Subsequently, a silicon oxide film is deposited on the substrate on which the electrodes are formed by a CVD method to form an interlayer insulating film. After an opening for making contact with the interlayer insulating film on the electrode having an independent shape is formed by etching, an aluminum film is formed by an evaporation method or a sputtering method. The aluminum film is patterned by a photolithography method, and an opening is formed in a portion above the photodiode to form a metal light shielding film.

Next, the operation of the solid-state imaging device according to the present embodiment will be described. FIG. 3 is a diagram illustrating an example of a pulse for driving the solid-state imaging device according to the present embodiment, where H1 and H2 are pulses for driving the horizontal charge transfer unit, and V1 and V
Reference numeral 2 denotes a pulse for driving the vertical charge transfer unit. FIG. 4 shows the potential distribution and signal charge transfer in the vertical charge transfer unit when the solid-state imaging device of the present embodiment is driven by the pulse shown in FIG.

The signal charge generated in the photoelectric conversion unit is transferred to the vertical charge transfer unit (hereinafter, transfer of the charge from the photoelectric conversion unit to the vertical charge transfer unit is referred to as “reading”). Reading is performed by using one of the transfer electrodes constituting the pixel as a reading electrode, and applying a voltage higher than a voltage applied during charge transfer to the reading electrode. In addition, when a desired pixel is selected and read out from the vertical pixel column, drive for independently controlling the transfer electrode is required. Therefore, the second pixel which is electrically independent from other pixels in the vertical direction is required. Transfer electrodes (comb-shaped electrodes 13a, 13b
And 13c) are used as readout electrodes.

The read signal charges are transferred by the vertical charge transfer section. Note that, as shown in FIG. 3, during a period in which charge transfer is performed in the vertical charge transfer unit, the pulse applied to the horizontal charge transfer unit has a flat waveform, and the charge transfer in the horizontal charge transfer unit stops.

As shown in FIG. 3, the vertical charge transfer section of the solid-state imaging device is driven by two-phase pulses of V1 and V2, and one of the transfer electrodes constituting the pixel has V1 and the other has V2. Is applied. The driving waveforms of V1 and V2 can be waveforms in which the phases are inverted.

Hereinafter, the second transfer electrode 13 in FIG.
The state of charge transfer will be described by taking as an example a case where a pulse of V1 is applied to a, 13b and 13c and a pulse of V2 is applied to the first transfer electrodes 14a, 14b and 14c. Actually, any of the two-phase pulses applied to the transfer electrode is a ternary pulse, and when the highest pulse is applied, the signal charge is read out, and the charge transfer is performed with the remaining binary pulses. However, in FIG. 3, the pulse at the time of reading is omitted, and V1 and V2 are shown as binary pulses. In the following description, the higher one of the binary pulses used for charge transfer is referred to as “high level”, and the lower one is referred to as “low level”.

As described above, impurities are formed under each transfer electrode.
High and low because regions with different concentrations are formed
Even when a pulse of a shift level is applied, 1
Regions with high potential (n-type
The region 11a) and the low region (n ^-Mold region 11b) is formed
Have been. Therefore, charge is accumulated under a certain transfer electrode.
The charge is more potential at its transfer electrode
N-type region 11a (hereinafter referred to as “charge storage region”).
You. ).

First, at t = t1, V1 is at a low level,
Since V2 is at the high level, the potential below the transfer electrode 13b to which V2 is applied increases. Therefore, the signal charges are stored in the charge storage region below the transfer electrode 13b.
Next, at t = t2, since V1 is at a high level and V2 is at a low level, the potential under the transfer electrode 14b to which V1 is applied becomes high, and the signal stored in the charge storage region under the transfer electrode 13b. The charge is transferred to the charge storage region below the transfer electrode 14b. At this time, the n ⁻ -type region having a low potential formed below the transfer electrode 13b functions as a barrier region, and suppresses mixing with a signal from another pixel and transfer of charges in the reverse direction. Similarly, at t = t3, the signal charge is transferred from the charge storage region below the transfer electrode 14b to the charge storage region below the transfer electrode 13c. Thus, the signal charge moves by one pixel in one cycle.

As shown in FIG. 3, when the transfer of one stage is completed in the vertical charge transfer section, the stopped horizontal charge transfer section is driven. During the period in which the horizontal charge transfer unit is driven, the pulse applied to the vertical charge transfer unit has a flat waveform, and the charge transfer in the vertical charge transfer unit stops.

As described above, the signal charges are transferred from the photoelectric conversion unit to the output amplifier unit via the vertical charge transfer unit and the horizontal charge transfer unit, converted into a voltage, and output.

(Second Embodiment) FIG. 5 is a plan view of a pixel portion constituting a solid-state imaging device according to a second embodiment of the present invention, and FIG. 6 is a cross-sectional view taken along the line BB 'of FIG. It is. The structure of the solid-state imaging device according to the present embodiment is substantially the same as that of the first embodiment except for the shape of the metal light shielding film.

The photoelectric conversion units 22 are arranged in a matrix on the main surface of the semiconductor substrate 20, and a plurality of vertical charge transfer units are formed so as to be adjacent to each of the columns formed by the photoelectric conversion units 22 arranged in the vertical direction. ing. The vertical charge transfer section includes an n-type impurity diffusion region 21a formed in a p-type semiconductor substrate (or a p-type well formed in the semiconductor substrate) 20;
CCD having a single-layer electrode structure constituted by using a transfer electrode formed on the impurity diffusion region 21a via an insulating film.
It is. Two transfer electrodes are formed for each pixel, and one of them (second transfer electrode) is a comb-shaped electrode 2 integrated with one of the transfer electrodes constituting the horizontally adjacent pixels.
3a, 23b and 23c and the other (first
Are formed as independent island-shaped electrodes 24a, 24b and 24c. Further, within the n-type impurity diffusion region 21a, an n ⁻ -type region 21a is formed at a portion located below each transfer electrode and rearward in the charge transfer direction.

In this embodiment, as in the first embodiment, a metal light-shielding film 26 is formed above a transfer electrode with an interlayer insulating film 25 interposed therebetween.
Island-shaped first transfer electrode 24 constituting vertical charge transfer portion
a, 24b, and 24c function as wiring for electrically connecting to the first transfer electrode of another pixel adjacent in the horizontal direction.

However, in the solid-state imaging device of this embodiment, as shown in FIGS. 5 and 6, a plurality of metal light-shielding films 26 divided in the vertical direction in accordance with the arrangement cycle of the transfer electrodes are provided.
Are formed. That is, the first transfer electrodes 24a, 2a
4b and 24c are connected to the transfer electrode of another pixel adjacent in the horizontal direction by the metal light shielding film 26,
The structure is such that the transfer electrodes of vertically adjacent pixels are electrically independent.

As described above, by dividing the metal light-shielding film in the vertical direction and making the transfer electrodes of the vertically adjacent pixels electrically independent from each other, a desired pixel can be selected from the vertical pixel column. In the case of reading, the second transfer electrodes 23a, 23b and 23c, which are comb-shaped electrodes, and the first transfer electrode 24a using a metal light shielding film for wiring,
Either 24b or 24c can be used as the readout electrode. In particular, it is preferable to use the first transfer electrode as a readout electrode because the length of an electrode contributing to readout can be increased and a voltage can be reduced.

The materials of the members constituting the solid-state imaging device according to the present embodiment can be the same as those conventionally used, as in the first embodiment. Has a light-shielding refractory metal (for example,
Tungsten, molybdenum, etc.), a silicon compound of a high melting point metal or a laminate of these and polysilicon is preferably used. This is because generation of smear can be suppressed.

The operation of the solid-state imaging device according to this embodiment is the same as that of the first embodiment. That is, the solid-state imaging device according to the present embodiment can drive the vertical charge transfer unit in two phases by the pulse shown in FIG. 3, and the potential distribution in the vertical charge transfer unit when driven by the pulse shown in FIG. The state of signal charge transfer is as shown in the schematic diagram of FIG.

However, when the vertical charge transfer section is driven by the pulse shown in FIG. 3, of the two transfer electrodes constituting the pixel, the transfer electrode disposed below the gap between the metal light shielding films (see FIG. 5). Applies a pulse of V1 to the second transfer electrodes 23a, 23b and 23c) and the other transfer electrode (the first transfer electrodes 24a, 24b and 24c in FIG. 5).
It is preferable to apply a pulse of V2 to. That is, a pulse is applied to the transfer electrode disposed below the gap of the metal light-shielding film so that the voltage is maintained at the low level during the charge transfer stop period in the vertical charge transfer unit, and the other transfer electrode is It is preferable to apply a pulse so that the voltage is maintained at a high level.

The solid-state imaging device according to the present embodiment is not limited to two-phase driving, but can be driven by three-phase driving or four-phase driving. As described above, even when the solid-state imaging device according to the present embodiment is driven by a pulse different from the waveform shown in FIG. It is preferable that a low-level voltage is applied during the transfer stop period.

In this embodiment, a gap is formed in the metal light-shielding film due to the divided shape of the metal light-shielding film, and light may directly enter the vertical charge transfer portion from this gap, thereby causing smear. However, in the preferred example described above, this gap is formed on the transfer electrode to which a low-level voltage is applied during the charge transfer stop period in the vertical charge transfer unit, that is, on a region where the depletion layer has a small spread. In addition, the area related to generation of smear can be minimized.

[0045]

As described above, according to the solid-state imaging device of the present invention, a plurality of photoelectric conversion units are arranged in a matrix on a semiconductor substrate so that the photoelectric conversion units are adjacent to each other. A solid-state imaging device in which a vertical charge transfer unit that transfers signal charges from the photoelectric conversion unit in a vertical direction is arranged,
The vertical charge transfer unit includes a transfer electrode group including a first transfer electrode and a second transfer electrode corresponding to each of the photoelectric conversion units, wherein the first transfer electrodes are independent islands. Since at least a part of the electrical connection between the first transfer electrodes is made via a metal light-shielding film formed on the vertical charge transfer portion via an interlayer insulating film, The number of wirings formed between the photoelectric conversion units in the vertical direction on the semiconductor substrate can be reduced, the effective photoelectric conversion unit area can be increased, and the sensitivity can be improved.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line A-A 'of FIG.

FIG. 3 is an example of a driving waveform diagram when the solid-state imaging device according to the present invention is driven.

FIG. 4 is a potential distribution diagram when the solid-state imaging device according to the present invention is driven by the driving waveform of FIG.

FIG. 5 is a plan view of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 6 is a sectional view taken along the line B-B 'of FIG.

FIG. 7 is a plan view of a conventional solid-state imaging device.

FIG. 8 is a sectional view taken along the line C-C 'of FIG.

FIG. 9 is a driving waveform diagram when a conventional solid-state imaging device is driven.

FIG. 10 is a potential distribution diagram when the conventional solid-state imaging device is driven by the driving waveform of FIG.

[Explanation of symbols]

10, 20, 30 p-type semiconductor substrate 11a, 21a, 31 n-type diffusion region 11b, 21b n ^- type diffusion region 12, 22, 32 photoelectric conversion unit 13a, 13b, 13c, 23a, 23b, 23c Second transfer electrode (Comb-shaped electrode) 14a, 14b, 14c, 24a, 24b, 24c First transfer electrode (island-shaped electrode) 33 Transfer electrode (comb-shaped electrode) 15, 25, 35 Interlayer insulating film 16, 26, 36 Metal light shielding film

Claims (7)

[Claims] 1. A plurality of photoelectric conversion units are arranged in a matrix on a semiconductor substrate, and vertical charges for vertically transferring signal charges from the photoelectric conversion units so as to be adjacent to respective columns formed by the photoelectric conversion units. A solid-state imaging device in which a transfer unit is arranged,
The vertical charge transfer unit includes a transfer electrode group including a first transfer electrode and a second transfer electrode corresponding to each of the photoelectric conversion units, wherein the first transfer electrodes are independent islands. And that at least a part of the electrical connection between the first transfer electrodes is made via a metal light-shielding film formed on the vertical charge transfer portion via an interlayer insulating film. Characteristic solid-state imaging device. 2. The transfer electrode constituting the transfer electrode group,
The solid-state imaging device according to claim 1, wherein the solid-state imaging device is formed in a single layer without being stacked. 3. A diffusion region serving as a transfer channel of the vertical charge transfer portion is formed in the semiconductor substrate, and the diffusion region is located below each of the transfer electrodes constituting the transfer electrode group in the diffusion region. The solid-state imaging device according to claim 1, wherein an impurity concentration of a region of the vertical charge transfer unit located rearward in a signal charge transfer direction is lower than an impurity concentration of another region of the diffusion region. . 4. The metal light-shielding film is divided in a signal charge transfer direction in the vertical charge transfer section.
4. The solid-state imaging device according to any one of claims 3 to 3. 5. The transfer electrode forming the transfer electrode group,
The solid-state imaging device according to claim 1, wherein the solid-state imaging device is formed of a metal having a light-shielding property, a silicon compound of the metal, or a laminate of the metal or the silicon compound and polysilicon. 6. A method for driving a solid-state imaging device, comprising using the solid-state imaging device according to claim 3 to transfer signal charges in the vertical charge transfer unit by two-phase driving. 7. A transfer electrode group located below a gap formed by dividing the metal light-shielding film during a signal charge transfer stop period in the vertical charge transfer unit using the solid-state imaging device according to claim 4. A low-level voltage is applied to the solid-state imaging device.