JPH06120477A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To improve an aperture coefficient in the vertical direction of the photoelectric converting means by forming a first wiring electrode and a second wiring electrode for mutually connecting the other portions of a plurality of vertical electrodes of vertical transfer means along the vertical transfer channel. CONSTITUTION:A transfer signal by the 2-phase drive system is impressed to a plurality of first layer electrodes 4 through a first wiring electrode 6 and to a plurality of second layer electrode 3 through a second wiring electrode 2. The second layer electrode 3 and the first layer electrode 4 of the vertical transfer channel 2 are mutually connected and integrated through the first wiring electrode 6 and the second wiring electrode 5. The first wiring electrode 6 and the second wiring electrode 5 are formed in the vertical direction along the direction opposed to the photoelectric conversion means 1. Thereby, the second layer electrodes 3 and the first layer electrodes 4 can be led in the vertical direction and a sufficient numerical aperture can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device, and more particularly to an interline transfer type solid-state image pickup device.

[0002]

2. Description of the Related Art As a charge transfer device used in a solid-state image pickup device, a charge coupled device (CCD [Charge C
oupled Device]) is excellent. A solid-state imaging device using this charge-coupled device (hereinafter referred to as “CCD”) has an interline transfer system and a frame transfer system as a transfer system of charges from a photoelectric conversion unit, but has a short wavelength sensitivity and smear. At present, an interline transfer method, which is called false signal and has a small chip size, is widely used.

A conventional configuration of the interline transfer type CCD solid-state image pickup device will be described with reference to FIG.

In this CCD solid-state image pickup device, a large number of photoelectric conversion units 1 formed of photodiodes are formed in a matrix on a P-type silicon substrate. Further, strip-shaped vertical transfer channels 2 are formed on the sides (on the left side in the drawing) of the columns of the photoelectric conversion units 1 arranged in the vertical direction. In this vertical transfer channel 2, a surface layer portion of a P-type silicon substrate is an N ⁻ -type layer, and a second-layer electrode 3 and a first-layer electrode 4 are alternately arranged on the upper layer with an insulating film interposed therebetween. ing. Also, each vertical transfer channel 2
The second-layer electrode 3 and the first-layer electrode 4 arranged in the horizontal direction between each other are mutually interposed via the second wiring electrode 5 and the first wiring electrode 6 formed between the photoelectric conversion units 1 arranged in the vertical direction. Connected and integrated. The shaded area in the drawing is a channel stop area. Further, the upper layers other than the photoelectric conversion unit 1 are covered with a light shielding film (not shown).

In the CCD solid-state image pickup device having the above-described structure, the second layer of each vertical transfer channel 2 is provided through the second wiring electrode 5 and the first wiring electrode 6 which are drawn out to the end portion in the horizontal direction of the chip. Four-phase transfer clocks φV1 to φV4 are applied to the electrode 3 and the first-layer electrode 4. That is, the transfer clock φV1 and the transfer clock φV4 are applied to the second-layer electrode 3 and the first-layer electrode 4 of one set, and the second-layer electrode 3 and the first-layer electrode of the other set vertically adjacent thereto are applied. The transfer clock φV3 and the transfer clock φV2 are applied to the circuit 4. Then, when the transfer clocks φV1 and φV3 applied to the second layer electrode 3 become a high-voltage read pulse, the charges accumulated in the photoelectric conversion unit 1 are transferred to the vertical transfer channel 2 on the side, and thereafter. When the transfer clocks .phi.V1 to .phi.V4 become 4-phase transfer pulses, charges are transferred in the vertical direction in the vertical transfer channel 2 in order. Further, the charges transferred in the vertical transfer channel 2 in this way are
It will be sent to a horizontal transfer channel (not shown).

[0006]

However, in the above-mentioned conventional CCD solid-state image pickup device, when the pixel pitch in the vertical direction is LV and the widths of the second wiring electrode 5 and the first wiring electrode 6 are L0, The vertical aperture ratio of the photoelectric conversion unit 1 is represented by (LV-L0) / LV. Therefore, this C
When it is desired to reduce the vertical pixel pitch LV of the CD solid-state image pickup device, in order to maintain the aperture ratio of the photoelectric conversion unit 1, it is necessary to reduce the width L0 according to the pixel pitch LV. However, when the width L0 is reduced, the resistances of the second wiring electrode 5 and the first wiring electrode 6 increase, so that the second layer electrode 3 and the first layer electrode 4 which are far from the supply position of the transfer clocks φV1 to φV4 are formed. There is a problem in that the applied pulse waveform deteriorates due to rounding, and a transfer failure occurs in the vertical transfer channel 2.

The present invention has been made in order to solve the above problems, and an object of the present invention is to draw out the electrodes of the vertical transfer channels in the vertical direction to sufficiently ensure the vertical aperture ratio of the photoelectric conversion portion. Another object of the present invention is to provide a solid-state imaging device that can be secured.

[0008]

A solid-state imaging device according to the present invention comprises a plurality of photoelectric conversion units arranged in a matrix, a vertical transfer channel, and a plurality of vertical transfer unit transfer electrodes formed on the vertical transfer channel. A plurality of vertical transfer units and a horizontal transfer unit, and the signal charges from the photoelectric conversion unit are transferred in the vertical direction by the vertical transfer unit, and the signal charges from the vertical transfer unit are transferred in the horizontal direction by the horizontal transfer unit. An interline transfer type solid-state imaging device, wherein a first wiring electrode interconnecting a part of the plurality of vertical transfer part transfer electrodes and a second interconnecting part of the plurality of vertical transfer part transfer electrodes are interconnected. And the first and second wiring electrodes are formed along the vertical transfer channel, the above object can be achieved.

The vertical transfer portion transfer electrodes are divided into a plurality of first layer electrodes and a plurality of second layer electrodes, and the plurality of first layer electrodes and the plurality of second layer electrodes are alternately arranged on the vertical transfer channels. Solid-state imaging in which a transfer signal by a two-phase driving method is applied to a plurality of first-layer electrodes through a first wiring electrode and a plurality of second-layer electrodes through a second wiring electrode. It may be a device.

Further, a wire connecting both ends of the first wiring electrode to both ends of the adjacent first wiring electrode, and a wire connecting both ends of the second wiring electrode to both ends of the adjacent second wiring electrode, respectively. It is preferable to have wiring.

[0011]

According to the invention of claim 1, since the second layer electrode and the first layer electrode of the vertical transfer channel are drawn out by the second wiring electrode and the first wiring electrode along the vertical direction, each photoelectric conversion section Can be arranged in the vertical direction via only the pixel separation region. Therefore, the vertical aperture ratio of these photoelectric conversion units is restricted only by the width of the pixel separation region, and a sufficient aperture ratio can be obtained even if the pixel pitch is reduced in the vertical direction. .

With the structure of claim 1 only, the transfer clock can be supplied only from the end of the second wiring electrode and the first wiring electrode in the vertical direction opposite to the horizontal transfer channel. For this reason, conventionally, the transfer clock can be supplied from both ends in the horizontal direction, but if the transfer clock can be supplied from only one end in this way, the second layer electrode and the first layer electrode close to the horizontal transfer channel can be provided. There is a possibility that the pulse waveform applied to the circuit will be severely deteriorated. However, according to the invention of claim 3, the transfer clock can be supplied from both ends of the horizontal transfer channel. Therefore, it becomes possible to prevent the deterioration of the pulse waveform to the extent of the conventional level and prevent the vertical transfer efficiency from decreasing.

[0013]

EXAMPLES The present invention will be described below with reference to examples.

1 to 6 show an embodiment of the present invention,
1 shows a CCD solid-state imaging device in which a vertical transfer unit has a structure of a two-phase drive system. 1 is a plan view showing the structure of a vertical transfer channel in the CCD solid-state image pickup device, FIG. 2 is a potential distribution diagram showing the charge transfer operation in the AA cross section of FIG. 1, and FIG. 3 is a vertical view in the CCD solid-state image pickup device. FIG. 4 is a plan view showing the structure of an intersection of a transfer channel and a horizontal transfer channel, FIG. 4 is a plan view showing the structure of a CCD solid-state image sensor in the field accumulation mode, and FIG. 5 is a structure of a CCD solid-state image sensor in the frame accumulation mode. FIG. 6 is a plan view showing the configuration of a CCD solid-state image sensor in the all-pixel reading mode. In addition, the same numbers are added to the constituent members having the same functions as those of the conventional example shown in FIG.

In the CCD solid-state image pickup device of this embodiment, as shown in FIG. 1, a large number of photoelectric conversion parts 1 are formed in a matrix on a P-type silicon substrate at a horizontal pitch LH and a vertical pitch LV. A strip-shaped vertical transfer channel 2 is formed on the side (on the left side in the drawing) of each column of the photoelectric conversion units 1 arranged in the vertical direction.

In the vertical transfer channel 2, an N ⁻ type layer is formed as a buried channel in the surface layer portion of a P type silicon substrate, and the second layer electrode 3 and the first layer electrode 4 are formed on the upper layer of the N ⁻ type layer via an insulating film. Are arranged alternately. The second layer electrode 3 and the first layer electrode 4 of each vertical transfer channel 2 are
The vertical transfer channels 2 are connected to each other through a second wiring electrode 5 and a first wiring electrode 6 which are formed in the vertical direction along the side opposite to the photoelectric conversion section 1 and are integrally formed. There is. That is, the second-layer electrode 3 and the second wiring electrode 5, and the first-layer electrode 4 and the first wiring electrode 6 are simultaneously and integrally formed of polysilicon or an aluminum thin film.

In the lower layer of the boundary portion where the second-layer electrode 3 and the first-layer electrode 4 of the vertical transfer channel 2 overlap, the impurity concentration (type of impurity and its doping amount) is adjusted to adjust the N of the surface layer of the substrate. ^An N ^-- type layer having an impurity concentration lower than that of the --type layer is formed, and a vertical barrier region 7 that directs the vertical transfer of charges is formed. In addition, in the portion between the photoelectric conversion portion 1 and the vertical transfer channel 2 which is the lower layer of the second layer electrode 3 or the first layer electrode 4, the substrate surface layer portion has a lower impurity concentration than the N ⁻ type layer. ^-
The mold layer is formed, and the photoelectric conversion unit 1 and the vertical transfer channel 2 are formed.
A transfer barrier region 8 is formed for partitioning the space between and. The shaded area in the figure other than the photoelectric conversion section 1, the transfer barrier area 8 and the vertical transfer channel 2 serves as a channel stop area. Further, the upper layers other than the photoelectric conversion unit 1 are covered with a light shielding film (not shown).

The above-mentioned second wiring electrode 5 and first wiring electrode 6
Are supplied with two-phase transfer clocks φV1 and φV2 from one end (the upper end in the figure) in the vertical direction. Here, for example, the transfer clock φV1
2 as a high-voltage read pulse, the storage region in the lower layer of the second-layer electrode 3 deepens to the position shown by the alternate long and short dash line, and the charge accumulated in the photoelectric conversion unit 1 is transferred to the transfer barrier region as shown in FIG. 8 is transferred to the storage region of the lower layer of the second layer electrode 3. After that, the transfer clock φV1,
By setting φV2 as a two-phase transfer pulse, the potential of the vertical transfer channel 2 alternately repeats the states of the solid line and the broken line in the figure, so that the charges in the storage region are sequentially directed in one of the vertical directions ( In the figure, it will be transferred downward). The vertical barrier region 7 must be formed so as to be exactly aligned with the boundary of the second-layer electrode 3 or the first-layer electrode 4, and if there is a mismatch, the potential becomes uneven and vertical transfer failure occurs. This method includes masking and Japanese Patent Application No. 1-1425.
There is a method disclosed in 91.

As described above, in the solid-state image pickup device of this embodiment, the second layer electrode 3 and the first layer electrode 4 of the vertical transfer channel 2 are vertically arranged by the second wiring electrode 5 and the first wiring electrode 6. Since it is drawn out, it is not necessary to form electrodes between the photoelectric conversion units 1 arranged in the vertical direction. Therefore,
Shows the vertical aperture ratio of this photoelectric conversion unit 1 (LV-L
The width L0 in (0) / LV is not the width of the electrode but the width of the channel stop region for separating pixels, so that a sufficient aperture ratio can be obtained even when the pixel pitch LV in the vertical direction is reduced. become. Further, since the vertical transfer channel 2 is driven by the two-phase transfer clocks φV1 and φV2, the second wiring electrode 5 and the first wiring electrode 6 are superposed on each other for each vertical transfer channel 2 with the insulating layer interposed therebetween. Therefore, the second wiring electrode 5 and the first wiring electrode 6 formed in the vertical direction limit the aperture ratio in the horizontal direction of the photoelectric conversion unit 1 more than necessary, and the vertical transfer channel is provided. There is no need to narrow the width of 2.

In the structure shown in FIG. 1, the transfer clocks φV1 and φV2 are supplied to the second wiring electrode 5 and the first wiring electrode 6 only from the upper end portion in the vertical direction. However, in this case, since the distance to the second layer electrode 3 and the first layer electrode 4 on the lower side becomes long, deterioration due to rounding of the pulse waveform may occur, which may reduce the vertical transfer efficiency.

Therefore, as shown in FIG. 3, redundant second layer electrodes 3 and first layer electrodes 4 may be formed at the lower end where each vertical transfer channel 2 intersects with the horizontal transfer channel 9. These redundant second layer electrode 3 and first layer electrode 4
Since the photoelectric conversion unit 1 is not formed on the side, it can be extended in the horizontal direction and integrally connected between the adjacent vertical transfer channels 2 as illustrated. Therefore, if the transfer clocks φV1 and φV2 are supplied to the redundant second-layer electrode 3 and the first-layer electrode 4 from both ends in the horizontal direction, the second wiring electrode 5 and the first wiring electrode 6 are vertically moved. Since the transfer clocks φV1 and φV2 are supplied from the upper and lower ends, the deterioration of the pulse waveform can be prevented.

The CCD solid state image pickup device of the above embodiment is shown in FIG.
It can be used in both the field storage mode shown in FIG. 5 and the frame storage mode shown in FIG. Further, not only such a one-electrode / one-pixel configuration but also a two-electrode / one-pixel configuration as shown in FIG. 6 may be used in the all-pixel reading mode. The selection of these modes is determined depending on which of the vertical resolution and sensitivity of the pixel and the presence or absence of the frame afterimage is important.

[0023]

As is apparent from the above description, according to the solid-state image pickup device of the present invention, the second layer electrode and the first layer electrode of the vertical transfer channel are vertically connected by the second wiring electrode and the first wiring electrode. By pulling out in the vertical direction, it becomes possible for the photoelectric conversion unit to secure a sufficient vertical aperture ratio even when the vertical pixel pitch is reduced.
It is also possible to prevent the transfer efficiency of the vertical transfer channel from being lowered.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, which is a CCD
It is a top view showing the composition of the vertical transfer channel in a solid-state image sensor.

2 is a potential distribution diagram showing an embodiment of the present invention and showing a charge transfer operation in a cross section taken along the line AA of FIG. 1. FIG.

FIG. 3 shows an embodiment of the present invention, which is a CCD
It is a plan view showing a configuration of an intersection of a vertical transfer channel and a horizontal transfer channel in the solid-state imaging device.

FIG. 4 shows an embodiment of the present invention and is a plan view showing a configuration of a CCD solid-state imaging device in a field storage mode.

FIG. 5 is a plan view showing an embodiment of the present invention and showing a configuration of a CCD solid-state imaging device in a frame accumulation mode.

FIG. 6 shows an embodiment of the present invention and is a plan view showing a configuration of a CCD solid-state imaging device in an all-pixel reading mode.

FIG. 7 shows a conventional example and is a plan view showing a configuration of a vertical transfer channel in a CCD solid-state imaging device.

[Explanation of symbols]

 1 Photoelectric Converter 2 Vertical Transfer Channel 3 Second Layer Electrode 4 First Layer Electrode 5 Second Wiring Electrode 6 First Wiring Electrode 7 Vertical Barrier Area 8 Transfer Barrier Area 9 Horizontal Transfer Channel

Claims (3)

[Claims] 1. A plurality of photoelectric transfer units arranged in a matrix, a plurality of vertical transfer units having a vertical transfer channel and a plurality of vertical transfer unit transfer electrodes formed on the vertical transfer channel, and a horizontal transfer unit. An interline transfer type in which the signal charges from the photoelectric conversion unit are transferred in the vertical direction by the plurality of vertical transfer units, and the signal charges from the vertical transfer unit are transferred in the horizontal direction by the horizontal transfer unit. A solid-state imaging device, further comprising a first wiring electrode interconnecting a part of the plurality of vertical transfer unit transfer electrodes and a second interconnect interconnecting another part of the plurality of vertical transfer unit transfer electrodes. With electrodes,
The solid-state imaging device, wherein the first and second wiring electrodes are formed along the vertical transfer channel. 2. The vertical transfer unit transfer electrodes are divided into a plurality of first layer electrodes and a plurality of second layer electrodes, and the plurality of first layer electrodes and the plurality of second layer electrodes are the vertical transfer channels. They are alternately arranged on the upper side, and the plurality of first-layer electrodes are provided with the first wiring electrodes, and the plurality of second-layer electrodes are provided with the second wiring electrodes. The solid-state imaging device according to claim 1, wherein a transfer signal is applied. 3. A wire connecting both ends of the first wiring electrode to both ends of the adjacent first wiring electrode, and both ends of the second wiring electrode adjacent to both ends of the second wiring electrode. The solid-state imaging device according to claim 1 or 2, further comprising: