JPH08195485A - Solid image pickup device and its manufacture - Google Patents

Abstract

PURPOSE: To improve the transfer efficiency with low-voltage drive by shallowly setting the potential to the charge of the region on the opposite side to the direction of transfer of the transfer channel under the transfer electrode in the vicinity of the end of the deep well in an un-light-receiving region. CONSTITUTION: Transfer electrodes V1 and V2 are divided into two electrodes (polysilicon 7 and 8), and a barrier region 6 is made in the transfer channel under the electrode (polysilicon 8) on the opposite side to the direction of transfer. Hereby, the shape of potential in each transfer electrode V1 and V2 becomes deep in the direction of charge transfer, and as the voltage of the transfer electrode V2 changes from H to L, the charge is carried completely under the transfer electrode 3. This way, there is no transfer deterioration by the deep p-type well 3, and also this can cope enough with the position of formation of the p-type well 3 and the change of impurity distribution, so the transfer efficiency can be improved with low-voltage drive, and high-speed transfer can be materialized.

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 a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional solid-state image pickup device will be described with reference to FIG. 2A is a plan view of a conventional solid-state imaging device, FIG. 2B is a sectional view taken along the line ABC, and FIG. 2C is a potential diagram taken along the section. In FIG. 2, 21 is an N-type silicon substrate, 22 is P
Type region, 23 is a deep P type well, 24 is a P type region, 25
Is an N-type region to be a buried channel, 27 and 28 are first and second polysilicons which are transfer electrodes of the vertical transfer section 31, and
Reference numeral 29 is polysilicon of the horizontal shift register, 30 is a photodiode, 32 is a unit pixel, 33 is a light receiving portion, 34 is a horizontal shift register, and 35 is a non-light receiving area between the light receiving portion 33 and the horizontal shift register 34. In addition, V1, V
2, V3 and V4 are transfer electrodes in the non-light receiving area 35. Further, H (high) and L (low) are shown as examples of voltage application to the transfer electrodes V1, V2, V3, V4 and the electrodes (polysilicon 29) of the horizontal shift register 34.

This conventional solid-state image pickup device has a vertical overflow drain structure in order to suppress blooming.
After forming the P-type region 22 on the type silicon substrate 21, the two-layer polysilicon 27, 28 is used because of the ease of manufacturing the manufacturing surface. In addition, an N-type region 2 to be a buried channel has a buried channel structure for transfer efficiency and dark current suppression.
5 is provided. Then, in order to increase the amount of charge handled by the vertical transfer unit 31 that determines the dynamic range of the image pickup device, the P-type region 24 is provided so as to increase the P-type impurity concentration below the N-type region 25 forming the buried channel. It has a well structure. Further, the horizontal shift register 34
Has a low surface concentration and a deep P due to the high-speed / low-voltage driving and the breakdown voltage of the floating diffusion part which is the output part.
It is formed by the mold well 23.

[0004]

However, in the above-mentioned conventional configuration, the vertical transfer unit 31 to the horizontal shift register 3 are connected.
In the case of transfer to No. 4, since the deep P-type well 23 of the horizontal shift register 34 is formed in the charge transfer direction, this modulates the potential under the transfer electrode, and as shown in the potential diagram of FIG. In addition, when the voltage of the transfer electrode V2 is changed from high (H) to low (L), the potential shape under the transfer electrode V2 becomes a barrier of the transfer charge due to the influence of the deep P-type well 23, which significantly deteriorates the transfer efficiency. Was there.
Then, in order to improve the transfer efficiency, it was necessary to increase the driving voltage in order to eliminate the potential barrier and increase the potential difference between the electrodes.

An object of the present invention is to provide a solid-state image pickup device capable of improving the transfer efficiency by driving at a low voltage and a manufacturing method thereof.

[0006]

According to a first aspect of the present invention, there is provided a solid-state image pickup device, wherein a light receiving portion having a plurality of photoelectric conversion elements arranged two-dimensionally and a signal charge arranged via the light receiving portion and a non-light receiving area. A horizontal shift register for transferring the
A plurality of transfer electrodes and a vertical transfer unit having a transfer channel below the transfer electrodes and transferring signal charges of a plurality of photoelectric conversion elements to a horizontal shift register; A solid-state imaging device in which a setting means for setting a shallow potential for electric charges in a region opposite to a transfer direction of a transfer channel in a lower portion of a transfer electrode near an end of a deep well in a non-light-receiving region is provided. It is characterized by that.

According to a second aspect of the present invention, there is provided the solid-state image pickup device according to the first aspect.
In the solid-state imaging device described above, the setting means includes two electrodes formed by dividing the transfer electrode near the end of the deep well in the non-light-receiving region, and a barrier region formed in the transfer channel below the electrode opposite to the transfer direction. Consists of. The method for manufacturing a solid-state imaging device according to claim 3 is the same as that when forming the barrier region of the horizontal shift register, and at the same time, it is opposite to the transfer direction of the transfer channel below the transfer electrode near the end of the deep well in the non-light-receiving region. A barrier region is formed in the side region.

[0008]

According to the present invention, the potential for charges in the region opposite to the transfer direction of the transfer channel under the transfer electrode in the vicinity of the end of the deep well in the non-light receiving region between the light receiving portion and the horizontal shift register. Setting means is provided for shallowly setting. The setting means is composed of two electrodes obtained by dividing the transfer electrode near the end of the deep well in the non-light-receiving region and a barrier region formed in the transfer channel below the electrode on the side opposite to the transfer direction. This reduces the potential for charges, eliminates the potential barrier due to the influence of the end of the deep well for the horizontal shift register, and the potential shape under each transfer electrode of the vertical transfer section in the non-light-receiving region is always in the charge transfer direction. Formed deeply. Therefore, obstacles to charge transfer are eliminated, and transfer efficiency is improved by low voltage driving.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG. 1A is a plan view of a solid-state imaging device according to an embodiment of the present invention, FIG. 1B is a sectional view taken along the line ABC, and FIG. 1C is a sectional view taken along the line. It is a potential diagram. In FIG. 1, 1 is an N-type semiconductor substrate, 2 is a P-type region, 3 is a deep P-type well, 4 is a P-type region, 5 is an N-type region to be a buried channel, 6 is a barrier region, and 7 and 8 are. First and second polysilicon that are transfer electrodes of the vertical transfer unit (VCCD) 11, 9 are polysilicon that are electrodes of the horizontal shift register, 10 is a photodiode (photoelectric conversion element), 12 is a unit pixel, and 13 is A light receiving portion, 14 is a horizontal shift register (HCCD), and 15 is a non-light receiving area between the light receiving portion 13 and the horizontal shift register 14. In addition, V
Reference numerals 1, V2, V3, V4 are transfer electrodes in the non-light-receiving area 15, and transfer electrodes V1, V2 are transfer electrodes divided into two electrodes (polysilicon 7, 8). Further, H (high) and L (low) are shown as examples of voltage application to the transfer electrodes V1, V2, V3, V4 and the electrodes (polysilicon 9) of the horizontal shift register 14.

In this solid-state image pickup device, the transfer electrodes V1 and V2 of the vertical transfer portion 11 near the end of the deep P-type well 3 in the non-light-receiving region 15 are composed of two electrodes (polysilicon 7 and 8), and the transfer direction is The barrier region 6 is formed in the transfer channel below the electrode (polysilicon 8) on the side opposite to, and the potential for charges is made shallow. The transfer electrodes V1 and V2 and the barrier region 6 correspond to the setting means.

A method of manufacturing the solid-state image pickup device of this embodiment will be briefly described below. First, the P-type region 2 common to the horizontal shift register 14 and the vertical transfer unit 11 is formed on the N-type semiconductor substrate 1. Next, a deep P-type well 3 is formed in the horizontal shift register 14 and the vertical transfer portion 11 of the non-light-receiving region 15,
The P-type region 4 is selectively formed only in the vertical transfer unit 11.
Then, a normal two-layer polysilicon CCD process is performed. At that time, after the electrodes are selectively formed by the first polysilicon 7, the barrier region 6 is formed near the end of the deep P-type well 3 at the same time when the barrier region of the two-phase driving HCCD (horizontal shift register 14) is formed. Then, the second polysilicon 8 is selectively formed. The electrodes V1 and V2 near the end of the deep P-type well 3 in the non-light-receiving region 15 are made of polysilicon 7 and 8, and the polysilicon 7 and 8 are connected by aluminum wiring.

The barrier region 6 below the electrode V3 may be omitted. Further, the electrodes V3 and V4 may have the same structure as the electrodes V1 and V2. The N-type region 5 is formed before forming the first polysilicon 7. The barrier region 6 is formed by selectively implanting a P-type impurity (boron) into the N-type region 5. That is, the order of the steps is as follows:
First polysilicon 7 → barrier region 6 → second polysilicon 8 is obtained.

According to this embodiment, the transfer electrodes V1 and V2 are
Is divided into two electrodes (polysilicon 7, 8) and the barrier region 6 is formed in the transfer channel below the electrode (polysilicon 8) on the side opposite to the transfer direction. The potential shape becomes deeper in the charge transfer direction, and as the voltage of the transfer electrode V2 changes from H to L, the charges are completely carried below the transfer electrode V3. As described above, there is no transfer deterioration due to the deep P-type well 3, and it is possible to sufficiently cope with the variation of the formation position of the deep P-type well 3 and the impurity distribution, and it is possible to improve the transfer efficiency by the low voltage driving and to achieve high speed. Transfer can be realized.

In this embodiment, the deep P-type well 3 is used.
Although the barrier region 6 is provided below the transfer electrodes V1, V2 and V3 at the end of the above, the effect can be expected even if the barrier region is provided only below the transfer electrode V1. Although the N-type semiconductor substrate 1 is used in this embodiment, the same effect can be obtained even if the P-type semiconductor substrate is used and the conductivity types of the other regions are all reversed.

[0015]

As described above, according to the present invention,
Providing setting means for shallowly setting the potential for charges in the region opposite to the transfer direction of the transfer channel under the transfer electrode near the end of the deep well in the non-light receiving region between the light receiving unit and the horizontal shift register. There is. The setting means is composed of two electrodes obtained by dividing the transfer electrode near the end of the deep well in the non-light-receiving region and a barrier region formed in the transfer channel below the electrode on the side opposite to the transfer direction. This reduces the potential for charges, eliminates the potential barrier due to the influence of the end of the deep well for the horizontal shift register, and the potential shape under each transfer electrode of the vertical transfer section in the non-light-receiving region is always in the charge transfer direction. Deeply formed, smooth charge transfer is performed. As described above, there is no transfer deterioration due to the deep well, and it is possible to sufficiently cope with the variation of the formation position of the deep well and the impurity distribution, the transfer efficiency is improved by the low voltage driving, and the high speed transfer can be realized.

[Brief description of drawings]

1A is a plan view of a solid-state imaging device according to an embodiment of the present invention, FIG. 1B is a cross-sectional view thereof, and FIG. 1C is a potential diagram along the cross-section.

FIG. 2A is a plan view of a conventional solid-state imaging device, and FIG.
Is a cross-sectional view, and (c) is a potential diagram along the cross-section.

[Explanation of symbols]

 1 N-type semiconductor substrate 2, 4 P-type region 3 Deep P-type well 5 N-type region (buried channel) 6 Barrier region 7 First polysilicon (transfer electrode) 8 Second polysilicon (transfer electrode) 10 Photo Diode (photoelectric conversion element) 11 Vertical transfer section 12 Unit pixel 13 Light receiving section 14 Horizontal shift register 15 Non-light receiving area V1, V2, V3, V4 Transfer electrodes in non-light receiving area

Claims (3)

[Claims] 1. A light receiving section having a plurality of photoelectric conversion elements arranged two-dimensionally, a horizontal shift register arranged via the light receiving section and a non-light receiving area to transfer signal charges in a horizontal direction, and a plurality of transfer sections. An electrode and a vertical transfer unit having a transfer channel below the transfer electrode and transferring the signal charges of the plurality of photoelectric conversion elements to the horizontal shift register, and deep below the horizontal shift register and the non-light-receiving region. A solid-state imaging device in which a well is formed, wherein a potential for charges in a region opposite to a transfer direction of the transfer channel in a lower portion of the transfer electrode near an end of the deep well in the non-light-receiving region is set to be shallow. A solid-state image pickup device comprising: 2. The setting means comprises two electrodes formed by dividing a transfer electrode near an end of a deep well in a non-light receiving region, and a barrier region formed in a transfer channel below the electrode on the side opposite to the transfer direction. The solid-state imaging device according to claim 1. 3. A light receiving section having a plurality of photoelectric conversion elements arranged two-dimensionally, a horizontal shift register arranged via the light receiving section and a non-light receiving area to transfer signal charges in a horizontal direction, and a plurality of transfer sections. An electrode and a vertical transfer unit having a transfer channel below the transfer electrode and transferring the signal charges of the plurality of photoelectric conversion elements to the horizontal shift register, and deep below the horizontal shift register and the non-light-receiving region. A method of manufacturing a solid-state imaging device in which a well is formed, the transfer being performed at a lower portion of the transfer electrode near an end of the deep well in the non-light-receiving region at the same time when a barrier region of the horizontal shift register is formed. A method of manufacturing a solid-state imaging device, comprising forming a barrier region in a region opposite to a channel transfer direction.