JP2001144280A - Solid-state imaging device - Google Patents

Abstract

(57) Abstract: Provided is a solid-state imaging device having the same dark output of an effective pixel portion and an optical black portion, and having good imaging characteristics. SOLUTION: The pixel structure of an effective pixel section 15 and an optical black section 16 are the same, and a solid-state imaging device 1 in which a light shielding film 11 is formed on the optical black section 16 is configured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device such as a CCD solid-state imaging device having an optical black portion and an effective pixel portion.

[0002]

2. Description of the Related Art Usually, in a CCD solid-state imaging device,
In order to set the black level, an optical black portion in which the light receiving portion is covered with a light-shielding film made of a metal having high light-shielding properties such as Al is provided outside the effective pixel portion, and a signal from the optical black portion is set as a black level I have.

FIG. 2 is a plan view showing an example of a CCD solid-state imaging device. The CCD solid-state imaging device 50 includes an imaging unit 51 in which a plurality of light receiving units 53 serving as pixels are arranged in a matrix, and a vertical transfer register 52 having a CCD structure is provided on one side of each light receiving unit 53 column. The horizontal transfer register 54 is provided on one side of the horizontal transfer register 51, and an output unit 59 connected to the output side of the horizontal transfer register 54 is provided. The imaging unit 51 includes an effective pixel unit 56 that requires light reception, and an optical black unit 57 for defining a black level in the imaging unit 51.
A light-shielding film is formed on the entire surface of the horizontal transfer register 54 as shown in FIG. Reference numeral 58 in FIG. 2 denotes a peripheral portion where other output circuits, wirings, and the like exist.

FIG. 3 is a schematic sectional view of a conventional CCD solid-state imaging device. FIG. 3 corresponds to a cross-sectional view taken along line AA of FIG. This CCD solid-state imaging device 21
In the semiconductor substrate 22, a light receiving unit 23 for performing photoelectric conversion and a vertical transfer register 24 for transferring signal charges read from the light receiving unit 23 are formed. The portion between the light receiving section 23 and the vertical transfer register 24 is a read gate section or a channel stop area (not shown).

A gate insulating film 25 is formed on the semiconductor substrate 22.
A vertical transfer electrode 26 is formed through the interlayer insulating film 27. An interlayer insulating film 27 made of, for example, an SiO ₂ film is formed to cover the vertical transfer electrode 26. A first metal film 28 made of a high-metal or the like is formed. In the first metal film 28, an opening 30 is formed on the light receiving portion 23 in the effective pixel portion 35,
Light enters the light receiving section 23. On the other hand, in the optical black section 36, the optical black section 36 is formed continuously over the light receiving section 23 so that light does not enter the light receiving section 23.

The planarization film 2 is formed on the first metal film 28.
9 are formed and the surface is flattened. Further, although not shown, a color filter, an on-chip lens, and the like are formed as necessary.

In the peripheral portion 37, a second metal film 31 of Al or the like is formed on the flattening film 29 to constitute a wiring of a peripheral circuit.

[0008]

However, when the first metal film 28 is made of a material that absorbs hydrogen, such as titanium, or is made of a material that does not easily pass hydrogen,
In the optical black portion 36, sufficient hydrogen annealing is not performed. In this case, the dark current increases in the light receiving section 23 of the optical black section 36 and the vertical transfer register 24.

As a result, the effect of reducing the interface state caused by defects of the semiconductor substrate 22 due to hydrogen differs between the effective pixel portion 35 and the optical black portion 36. Therefore, the dark level (black reference output) as noise caused by a signal or the like due to the charge generated due to the interface state when the device is completely dark increases in the optical black unit 36, and the output of the effective pixel unit 35 is increased. A phenomenon of sinking, that is, a so-called "black sink" occurs, which has a significant effect on imaging characteristics.

FIG. 4 shows a change in the CCD output voltage V during a lapse of time T during _one horizontal line period T1 in the case of occurrence of black sun. As shown in FIG. 4, the dark output (black level) V _{2 of the} optical black portion, which is output thereafter, is compared with the dark output (black level) V ₁ of the effective pixel portion.
Is larger, a "black sink" is caused by the difference ΔV.
As a result, the dark level of the optical black
It becomes higher than the dark level of the effective pixel portion, and the image quality deteriorates due to the difference in the dark level.

In another CCD solid-state image pickup device, if the optical black portion is not provided with a light receiving portion comprising a photodiode, the signal output is reduced by the absence of the light receiving portion. A phenomenon that the output of the portion floats, that is, a so-called "black float" occurs.
Also in this case, image quality is deteriorated due to the difference between the dark level of the optical black portion and the dark level of the effective pixel portion.

In addition, it is conceivable that the width of the vertical transfer register and the width of the photodiode in the light receiving section are different between the effective pixel section and the optical black section. However, in this configuration, even if the amount of dark current in the effective pixel portion and the optical black portion was adjusted to be the same at room temperature, the temperature increased because the photodiode widths of the vertical transfer register and the sensor portion were different. In such a case, there is a problem that a difference occurs in the amount of dark current.

In order to solve the above-mentioned problem, the present invention provides a solid-state image pickup device that can make the output of the effective pixel portion and the optical black portion dark at the same time and has good image pickup characteristics. is there.

[0014]

The solid-state imaging device according to the present invention has the same pixel structure as the effective pixel portion and the optical black portion, and has a light-shielding film formed on the optical black portion.

According to the configuration of the present invention described above, since the effective pixel portion and the optical black portion have the same pixel structure, the same amount of dark current can be generated. Further, since the light-shielding film is formed on the optical black portion, light-shielding is performed by the light-shielding film even if the pixel structure is the same as that of the effective pixel portion.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a solid-state imaging device in which a pixel structure of an effective pixel portion and an optical black portion are the same, and a light shielding film is formed on the optical black portion.

FIG. 1 is a schematic sectional view of a CCD solid-state imaging device according to an embodiment of the present invention. FIG. 1 also corresponds to a cross-sectional view taken along line AA of the plan view of FIG. In the CCD solid-state imaging device 1, a light receiving unit 3 for performing photoelectric conversion and a vertical transfer register 4 for transferring signal charges read from the light receiving unit 3 are formed in a semiconductor substrate 2, respectively. still,
The portion between the light receiving unit 3 and the vertical transfer register 4 is
Although not shown, it is, for example, a readout gate unit for reading out signal charges from the light receiving unit 3 or a channel stop region for separation from an adjacent pixel.

A vertical transfer electrode 6 is formed on the semiconductor substrate 2 with a gate insulating film 5 interposed therebetween.
An interlayer insulating film 7 made of, for example, an SiO ₂ film is formed so as to cover the first metal film 8, and a first metal film 8 made of a metal having a high light-shielding property such as Al or tungsten is formed through the interlayer insulating film 7.

A flattening film 9 is formed on the first metal film 8 to flatten the surface. Further, although not shown, a color filter, an on-chip lens, and the like are formed as necessary.

The first metal film 8 has an opening 10 formed on the light receiving portion 3 in the effective pixel portion 15 so that light is incident on the light receiving portion 3. That is, the effective pixel section 15 is the same as that of the conventional CCD solid-state imaging device 21 shown in FIG.

In this embodiment, the opening 10 is formed in the first metal film 8 on the light receiving section 3 of the optical black section 16 in the same manner as the effective pixel section 15. And
The pixel structure composed of the light receiving section 3 and the vertical transfer register 4 is the same in the effective pixel section 15 and the optical black section 16.

Thus, the optical black portion 16
In the same manner as in the effective pixel section 15, the charges accumulated in the photodiode can be read out, and the charges read out from the pixels of the optical black section 16
Black level can be set.

Further, in the present embodiment, the entire optical black portion 16 is covered with the second metal film 11 such as Al on the flattening film 9 used in the peripheral portion 17 to shield light. Therefore, the first of the optical black section 16
Even if the opening 10 is formed in the metal film 8, the second metal film 11
Thereby, the light can be sufficiently shielded so that light does not enter the light receiving section 3 of the optical black section 16.

In the case where the first metal film 8 is a tungsten film, the first metal film 8 can be made thin because of good light-shielding properties and coverage. High-temperature heat treatment can be performed.

According to the above-described embodiment, the pixel structure of the optical black section 16 is the same as the pixel structure of the effective pixel section 15, so that the dark current can be the same in both the optical black section 16 and the floating black section. The problem of the black sun can be solved. Therefore, it is possible to avoid image quality deterioration due to a difference in dark level between the optical black section 16 and the effective pixel section 15.

Also, in the optical black portion 16, since the opening 10 is formed in the first metal film 8 on the light receiving portion 3, the first metal film 8 is made of a material such as titanium which absorbs hydrogen. Also, it is possible to supply hydrogen to the substrate 2 through the opening 10, and it is possible to recover a defect of the substrate 2 and reduce a dark current similarly to the effective pixel portion 15.
Therefore, the film type of the first metal film 8 covering the transfer electrode 6 can be freely selected regardless of the hydrogen storage ability and the hydrogen blocking ability.

Further, since the pixel structure is the same, each pixel of the effective pixel portion 15 and the optical black portion 16 can be formed in the same pattern, and the manufacturing process can be easily performed without complicating the manufacturing process. it can.

The applicant of the present invention has previously proposed a solid-state imaging device having a configuration in which the optical black portion is covered with a black dyed film to shield light (see Japanese Patent Application Laid-Open No. 8-78654). According to the present embodiment, by shielding the optical black portion 16 with the metal film 11 to shield light, it is possible to further improve the light shielding property as compared with the case where a black stain film is used.

In the above embodiment, the present invention is applied to the CCD solid-state image pickup device. However, other types of solid-state image pickup devices having an optical black portion for the effective pixel portion can be used. The present invention can be similarly applied to a solid-state imaging device.

The present invention is not limited to the above-described embodiment, and may take various other configurations without departing from the gist of the present invention.

[0031]

According to the present invention described above, since the pixel structure of the optical black portion is the same as the pixel structure of the effective pixel portion, the dark current generated in both portions can be made the same. Therefore, it is possible to solve the problem of black floating or black sunken with the same dark output from both parts, and to realize good imaging characteristics.

Further, the material of the metal film covering the transfer electrode can be freely selected irrespective of the hydrogen storage capacity and the hydrogen blocking capacity.

Further, the manufacturing process can be easily performed without complicating the manufacturing process.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a CCD solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a plan view of a CCD solid-state imaging device.

FIG. 3 is a schematic sectional view of a conventional CCD solid-state imaging device.

FIG. 4 is a diagram showing a change in CCD output voltage over time during one horizontal line period when black sun phenomenon occurs.

[Explanation of symbols]

1,50 CCD solid-state imaging device, 2 semiconductor substrate, 3,
53 light receiving section, 4,52 vertical transfer register, 5 gate insulating film, 6 vertical transfer electrode, 7 interlayer insulating film, 8 first
Metal film, 9 planarization film, 10 opening, 11 second metal film, 15, 56 effective pixel portion, 16, 57 optical black portion, 17, 58 peripheral portion, 51 imaging portion, 54
Horizontal transfer register, 59 output section

Claims (1)

[Claims] 1. A solid-state imaging device, wherein a pixel structure of an effective pixel portion and an optical black portion are the same, and a light-shielding film is formed on the optical black portion.