JPH02230768A - Solid-state image sensing element - Google Patents

Abstract

PURPOSE:To prevent the generation of dark current difference between picture elements caused by heat treatment during manufacturing process by a method wherein an optical black picture element region of a solid state image sensing element is formed by installing a black color filtering layer using black coating in a specified region on a semiconductor substrate, via a dyestuff protecting layer. CONSTITUTION:After a substrate protecting layer 5a is formed, a light shielding layer of aluminum is formed only on a channel stopper 3 on an effective picture element region 14. A black color filtering layer 9 is formed in a region for forming an optical black element region 15 on such a solid-state image sensing element substrate. For this purpose, after a covering process for forming a substrate protecting layer 5b is finished, a dye protecting layer 6 is firstly formed as a base layer, thereby flattening the substrate surface and preventing the substrate inside from being dyed. Material wherein photosensitivity is imparted to protein such as casein and gelatin is used as the matrix of the black color filtering layer 9, and dyed with dyestuff excellent in light absorbing property. In this image sensing element, unit picture elements 13 and unit black picture elements 13a are not covered with a light shielding layer of aluminum, so that the difference in dark current between both of the picture elements is not caused by heat treatment process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device, and particularly to a solid-state imaging device having an optical black pixel for setting a black level standard.

[Prior Art] In a solid-state image sensor, in order to set a black level standard during light irradiation, an optical black pixel area is formed in a part of the pixel formed by a plurality of photodiodes of the solid-state image sensor. There is a need to. A plan view of one example is shown in FIG.

As shown in the figure, there are unit pixels 13 on the solid-state image sensor.
A two-dimensional photoelectric conversion region 12 is provided, in which the unit pixels 13 are arranged in a matrix, and some of the unit pixels 13 are made into black pixels 13a included in the optical black pixel region 15, and the other unit pixels is included in the effective pixel area 14 and performs photoelectric conversion.

Conventionally, such optical black pixel regions have been formed by the following two methods. First, an example of a solid-state image sensor according to the first method is shown in FIGS. 5(a) and 5(b). Figure 5(a) shows the line A-A' in Figure 4. Figure 5(b)
) is a sectional view taken along line BB' in Figure 4. Figure 5(a)
and (b), a p-well region 2 is formed on an n-type semiconductor substrate 1, and in this p-well region, an n-well region constituting a photodiode together with the well region is formed.
A type region 4 and a channel stop 3 separating this n-type region are formed. On the semiconductor substrate, S i 02
Substrate protection layers 5a and 5b formed by laminating films, BPSG layers, etc. are provided. Then, the portion where the optical black pixel area 15 is to be formed and the effective pixel area 1
An aluminum light shielding layer 7 is formed on the substrate surface of the channel stop 3 portion in 4 with a substrate protective layer 5a interposed therebetween. Next, an example of a solid-state image sensor according to the second method is shown in FIG.
) and (b). Figure 6(a) is A-A in Figure 4.
6(b) is a sectional view taken along line BB' in FIG. 4. In these figures, the same reference numerals are given to the parts common to the parts in FIGS. However, this layer is not provided in the optically black pixel area 15.Instead, a black and white filter 18 is formed in which a light transmitting layer 17a and a chrome light shielding layer 17b are formed on a transparent glass substrate 16.
The light transmitting layer 17a covers the effective pixel area and the chrome light shielding layer 17b covers the optically black pixel area using a single adhesive. [Problems to be Solved by the Invention] Now, solid-state imaging devices in which optical black pixel regions are formed using these two types of methods have the following drawbacks.

First, in the solid-state image sensor according to the first method, when the entire solid-state image sensor is operated with light blocked, the output signal from the unit pixel 13 in the effective pixel area and the unit black pixel in the optical black pixel area 15 This has the disadvantage that a level difference that should not occur in the first place occurs between the output signal of 13a and the output signal of 13a. The reason why such a difference occurs has not been fully elucidated, but depending on whether or not an aluminum layer is present on the n-type region 4 constituting the photodiode, impurities in the substrate protective layer 5a may be removed during the heat treatment process. It is thought that the distribution state and the interface state of the n-type region 4 are affected. When a solid-state image sensor formed in this way is used in a video camera or the like, a level difference of 10 mV to 10 mV appears in an operating temperature environment of around 40°C, although it depends on the heat treatment conditions. , this cannot be ignored. Next is the case where the black and white filter 18 is glued onto the solid-state image sensor, but in this case, neither the n-type region on the effective pixel region 14 nor the n-type region on the black pixel region 15 is covered with aluminum. Although the heat treatment does not cause a difference in dark current as in the case of the first method, this device has the disadvantage that flare appears in the edict. This causes a decrease in the contrast of the captured and reproduced image, greatly reducing the image quality. The reason why this flare occurs will be explained using FIGS. 7 and 8. FIG. 7 is a plan view of a product in which a solid-state imaging device is housed in a package, a glass cap, etc., and FIG. 8 is a sectional view taken along line cc'. As shown in FIGS. 7 and 8, the solid-state image sensor 11 has a black-and-white filter 18, in which a light-transmitting layer 17a and a chromium light-shielding layer 17b are formed on a transparent glass substrate 16, bonded to a semiconductor substrate. mounted within 20,
It is hermetically sealed with a glass cap 21 made of transparent glass. Now, a solid-state image sensor, for example, an interline transfer CCD.
In the image sensor, in order to prevent photoelectric conversion in the vertical transfer CCD within the effective pixel area and to prevent oblique light from entering each pixel,
A light-shielding layer is required above the vertical transfer CCD that separates each pixel and above the channel stop [FIG. 6(a) shows only the light-shielding layer portion above the channel stop].

For such a light-shielding layer, an aminium thin film is generally used for common use with wiring. However, since this aluminum thin film reflects about 90% of the light, the incident light 22 to the effective pixel area of the solid-state image sensor 11 is transmitted through the aluminum light-shielding layer, which occupies about 50% of the effective pixel area of the solid-state image sensor 11. About 50% of the light becomes reflected light 23 and returns to the black-and-white filter 18. The reflected light 23 reaches the glass interface 16a of the black and white filter without being attenuated much. At the glass interface 16a of this black-and-white filter, if the inside of the package 20 is filled with nitrogen gas, the difference in refractive index between the glass and nitrogen gas is approximately 4
% reflection occurs, so a part of the reflected light 23 from the surface of the aluminum light-shielding layer enters the effective pixel area of the solid-state image sensor 11 again. This kind of reflection occurs at the glass cap interface 2.
1a, and as a result, flare occurs.

In the solid-state image sensor according to the second method, a portion of the light reflected on the surface of the aluminum light-shielding layer 7 enters the optically black pixel region. This reflected light is reflected again by the chrome light-shielding layer 17, enters the unit black pixel, and changes the reference black level. [Means for Solving the Problems] The solid-state image sensing device according to the present invention has a plurality of pixels formed on the surface of a semiconductor substrate, and the plurality of pixels are divided into those belonging to an effective pixel area and those belonging to an optical black pixel area. A black filter layer using a black dye is formed on the semiconductor substrate in the optically black pixel area via an anti-dying layer.

[Example] Next, an example of the present invention will be described with reference to the drawings.

1 (a> and (b) are diagrams showing the first embodiment of the present invention, respectively, line A-A' and line B of FIG. 4.
-B' line sectional view. In these figures, parts common to the conventional example shown in FIG. 5 or 6 are given the same reference numerals. In this embodiment, after forming the substrate protection layer 5a, an aluminum light shielding layer is formed only on the channel stop 3 above the effective pixel area. A black filter layer 9 is formed in a region on such a solid-state image sensor substrate where an optical black pixel region is to be formed. To this end, after the cover step of forming the substrate protective layer 5b is completed, an anti-staining layer 6 is first formed as a base layer to planarize the surface of the substrate and provide an anti-staining effect to the inside of the substrate. As an anti-dyeing layer,
Considering the steps after the formation of the optical black pixel region, such as the opening of the bonding butt part (not shown), it is convenient to use a material that emits light, such as PGMA (polyglycidyl methacrylate) or PMMA. (polymethyl methacrylate), etc. are used. Subsequently, a black filter N9 is formed, and this layer is generally made of casein or zebra as a base material. It is formed by using a photosensitive material such as latin and dyeing it with a dye with good light absorption, such as BLACKOO6 or BLACK205 manufactured by Nippon Kayaku. All filter layers using these dyes have an average light transmittance of 1%/μ
By forming a black filter layer with an appropriate thickness, it can be made into an effective light-shielding layer. Finally, a protective film 8 is formed. This protective film 8 is desirably made of a photosensitive material similar to the anti-dyeing layer 6 in consideration of later steps.

In this embodiment, since neither the unit pixel 13 nor the unit black pixel 13a is covered with an aluminum light shielding layer, there is no difference in dark current between the two pixels due to the heat treatment process. Further, since the black and white filter using a transparent glass substrate is not bonded, there is no reflection on the surface of the glass substrate, and flare is reduced. However, when this solid-state image sensor is enclosed in a package, flare occurs due to light being re-reflected from the glass cap surface, but the distance between the aluminum light-shielding layer and the glass cap is large, so flare is not a major problem. . Furthermore, since the light reflected by the aluminum light-shielding layer and incident on the optically black pixel area is absorbed by the black filter layer, this reflected light no longer changes the reference black level. Next, regarding the second embodiment of the present invention, FIG. 2(a),
This will be explained with reference to (b). Figures 2 (a) and (b) are
5. They are sectional views taken along line AA' and line BB' in FIG. 4, respectively. This embodiment differs from the first embodiment in that an aluminum light-shielding layer is not formed within the substrate protection layer 5 even on the effective pixel area, but instead channel stops 3 separate each pixel in the effective pixel area. A black filter layer 9 is formed on top with an anti-dyeing layer 6 interposed therebetween.

According to this embodiment, flare can be further reduced.

Next, with reference to FIGS. 3(a) and 3(b), an embodiment of the color solid-state image sensing device of the present invention will be described. Third
Figures (a) and (b) are sectional views taken along the lines AA' and BB' in FIG. 4, respectively. The difference between this embodiment and the first embodiment is that after the black filter layer 9 is formed in the optical black pixel area on the anti-dyeing layer 6a, the anti-dyeing layers 6b to 6d and the color filter layers 10a to 10c are formed. This is the point where the layers are laminated. 1
0a, 10b, and 10c are red, green, and blue color filter layers, respectively, and are arranged on each pixel in the effective pixel area. These color filter layers are
Like the black filter layer, it is formed by dyeing a photosensitive protein such as casein or seratin as a base material with a dye corresponding to a predetermined color.

[Effects of the Invention] As explained above, the present invention provides an optical black pixel area of a solid-state image sensor by providing a black filter layer using a black dye in a predetermined area on a semiconductor substrate via an anti-dying layer. Therefore, according to the present invention, unlike the case where an optical black pixel area is formed using an aluminum light-shielding layer, there is a difference in dark current between each pixel due to heat treatment during the manufacturing process. Never. Furthermore, since the transparent glass substrate is not bonded, the device of the present invention does not cause re-reflection on the surface of the glass substrate, and can reduce the flare phenomenon. Furthermore, if the light reflected by the aluminum light-shielding layer is incident on the optically black pixel region, this light will be absorbed by the black filter layer, so that this light will no longer fluctuate the reference black level. Furthermore, if the light shielding layer in the effective pixel area is also formed of a black filter layer, the step of forming an aluminum light shielding layer can be omitted, and flare can be extremely reduced.

[Brief explanation of the drawing]

The fourth figure is a plan view showing the present invention and a conventional example, FIG.
2 and 3 are diagrams showing embodiments of the present invention, respectively, and in FIGS. 1 to 3, (a) and (b)
) are sectional views taken along line A-A' and line B-B' in FIG. 4, respectively, and FIGS. 5 and 6 are views showing conventional examples, respectively. In Figure 6 (a),
(b) is a cross-sectional view taken along line AA' and line B-B' in FIG. 4, respectively, FIG. 7 is a plan view showing the packaging state of the conventional device, and FIG. , c-c' in Fig. 7
This is a line cross-sectional view. 1... N-type semiconductor substrate, 2... P-well region, 3
... Channel stop, 4... N-type region, 5,
5a, 5b...Substrate protective layer, 6, 6a to 6d...
Anti-dyeing layer, 7... Aluminum light shielding layer, 8...
Protective film, 9... Black filter layer, 10a to 10c
... color filter layer, 11 ... solid-state image sensor,
12... Two-dimensional photoelectric conversion area, 13... Unit pixel, 13a... Unit black pixel, 14... Effective pixel area, 15... Optical black pixel area, 16... Transparent glass substrate, 17a ...Light transmission layer, 17b. Chrome light shielding layer, 18.. Black and white filter, 19.. Adhesive, 20.. Package, 21.. Glass cap.

Claims (2)

[Claims] (1) In a solid-state image sensor in which a plurality of pixels are formed on the surface of a semiconductor substrate, and the plurality of pixels are divided into those belonging to an effective pixel area and those belonging to an optical black pixel area, the optical black pixel 1. A solid-state image sensing device, characterized in that a black filter layer using black dye is formed on a semiconductor substrate in the region via an anti-dyeing layer. (2) In a solid-state image sensor in which a plurality of pixels are formed on the surface of a semiconductor substrate, and the plurality of pixels are divided into those belonging to an effective pixel area and those belonging to an optical black pixel area, the effective pixel area is 1. A solid-state image pickup device, characterized in that a black filter layer using a black dye is formed on the semiconductor substrate in a region excluding the pixel portion and on the semiconductor substrate in the optically black pixel region via an anti-dyeing layer.