JPH02114780A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To suppress flair or ghost and to reduce interference fringe at the incidence of single wavelength light by providing a film with a prescribed thickness with respect to a specific wavelength of an incident light to a part on a face of a photodiode and making the area with the said film of the prescribed thickness provided thereto equal to a film without the said film each other on the face of the said photodiode. CONSTITUTION:The solid-state image pickup element is a solid-state image pickup element in which a filter 12 is adhered onto a substrate via a medium 15 with a refractive index lower than that of the filter and an oxide film 16 is formed on the photodiode 13. The thickness of the oxide film 16 is selected as (n+1)lambda/4. The area with the oxide film 16 is equal to the area 17 without the oxide film. A light B in a wavelength lambda radiated from a light source 11 is interferred with a light B1 through the oxide film 16 on the surface of the oxide film 16 and then reflected in the filter 12 and again interferred with a light B2 made incident on the surface of the oxide film 16. The incident lights A, B are radiated on the equal area and they have a contrast with each other, then the luminous quantity is uniform and no interference fringe takes place.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device that prevents the occurrence of ghosts and flares in the solid-state imaging device, and further reduces the occurrence of interference fringes.

[Conventional technology]

The solid-state image sensor includes a photoelectric conversion section and a signal processing section, and the photoelectric conversion section includes a plurality of photodiodes arranged in one row. −
Arranged in two dimensions, the signal processing section includes a transfer register that transfers the charge generated in the photoelectric conversion section, and an amplifier that amplifies and outputs the charge from the transfer register. FIG. 5 shows an example of a solid-state imaging device in which photodiodes are arranged two-dimensionally. In such a solid-state image sensor, as shown in FIG. 3(a), conventionally, a filter 32 is placed on the surface of a substrate 340 including a photodiode 33, and a resin whose refractive index is about 1.5 times that of the filter is used. 3
It has a structure with 5. However, in this structure, as shown in FIG.
4, the light is totally reflected on the top surface of the filter 32 and enters the surface of the substrate 34 again. Therefore, when an intense point light source is imaged, the light is reflected on the playback screen as shown in Figure 3 fb). A circular ghost image 37 with a radius d centered around the light source image 31 appears.

On the other hand, in the method shown in FIG. 4 in which the filter 42 is bonded to the surface of the solid-state image sensor through a gap of a medium (for example, air) with a lower refractive index than the filter 42, the light incident from the light source 41 is transmitted to the surface of the substrate 44. Since the light is reflected at the edge of the filter 42 and scattered at the end of the filter 42, a ghost image 371d as shown in FIG. 3(b) does not appear. However, while this method has a very strong ability to suppress defects such as flare ghosts, interference occurs due to multiple reflections on the lower surface of the filter 42 and the surface of the photodiode 43. This interference does not affect multispectral light such as sunlight because it is integrated over all spectra, but in the case of single wavelength light, it depends on the distance between the bottom surface of the filter 42 and the photodiode 43.
The intensity of the incident light changes. Also, the distance of this gap w7i
It is very difficult to uniformly bond the entire surface of the substrate of a two-dimensional sensor with a constant value, and when a single wavelength light is incident on the substrate, two-dimensional interference fringes will occur.

In recent years, solid-state image sensors have also improved in sensitivity and S/N [7], making it possible to take pictures even indoors, and they are often used under light sources with a single-wavelength spectrum peak, such as fluorescent lights. Therefore, the occurrence of interference fringes becomes a big problem.

[Problem to be solved by the invention]

As mentioned above, conventional solid-state image sensors use a method in which a filter is bonded to the surface of the solid-state image sensor through a gap in a medium that has a lower refractive index (than the filter's refractive index), making it possible to suppress flare and ghosting. However, interference fringes occur under fluorescent light illumination, which impairs the quality of the screen.The present invention suppresses flare and ghosting, and reduces interference fringes when light of a single wavelength is incident, thereby solving the above-mentioned problems. The purpose is to resolve the issue.

[Failure to solve the problem]

The solid-state image sensor of the present invention includes a glass filter on a substrate that has at least a photoelectric conversion section consisting of photodiodes arranged one-dimensionally or two-dimensionally, and a signal processing section that outputs the electric charge generated in the photoelectric conversion section to the outside. The glass filter is pasted through a medium with a refractive index lower than the refractive index, and a part of the photodiode surface is set at a specific wavelength λ of 1 unit ±0.05 (n is an integer). ), and the area of the area of the photodiode surface where the film of the thickness described above is provided is equal to the area of the area where the film is not provided.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1(a) is a longitudinal section of a first embodiment of the present invention.

This figure only depicts the photodiode, which is a feature of the present invention, and omits the signal processing section and other parts that are the same as in the prior art. It is a solid-state imaging device in which a filter 12 is bonded to a substrate 14 via a medium 15 having a refractive index lower than that of the filter, and an oxide film 16 is formed on a photodiode 13. The thickness of the oxide film 16 is (n
+t)J (λ is the wavelength of the incident light, n is an integer). The portion (spotted portion) where this oxide film 16 is formed is shown in FIG.
As shown in b) (which shows a plan view of the light-receiving surface of the photodiode), the area is equal to that of the portion (shaded portion) 17 of the photodiode 13 where the oxide film is not formed.

The light (2) with wavelength λ emitted from the light source 11 is reflected on the substrate surface, further reflected on the filter 12, and interferes with the light that is incident on the substrate surface again. On the other hand, the light (2) with a wavelength λ emitted from the light source 11 passes through the oxide film 16 and is reflected by the surface of the oxide film 160, further reflected by the filter 12, and enters the surface of the oxide film 16 again. Interferes with O.

At this time, when the oxide film 16 interferes with the light O having the wavelength λ, the interference of the light (2) weakens each other, and when the interference of the light (2) weakens each other, the interference of the light (2) strengthens each other. In this way, the light beams ■ and ■ incident on one photodiode have the same incident area,
Since they are both bright and dark, the amount of light is uniform and no interference fringes occur.

[Example 2] FIG. 2(a) is a longitudinal section of Example 2 of the present invention.

The basic structure is the same as the first embodiment shown in FIG. 1, and like the first embodiment, no interference fringes occur.

In Examples 1 and 2, the areas of the light-receiving surface of the photodiode where the oxide film was formed (spotted areas) and the areas where the oxide film was not formed (hatched areas) 17 were equal in area, but the areas where the oxide film was formed were the same. (spotted areas) are different.

That is, in Example 1, the part where the oxide film 16 is formed is provided in the right half of the photodiode 13 as shown in FIG. Since the rectangular portion on which the film 16 is formed is provided at a distance α from the outer periphery of the photodiode 13, the oxide film 16 can be formed if the mask for forming the oxide film 16 is shifted within the distance α both vertically and horizontally. The area of the oxidized portion (spotted portion) and the portion (shaded portion) 17 where no oxide film is formed can be made equal, which facilitates manufacturing.

However, in all of the embodiments described above, it is necessary to accurately control the film thickness, but errors inevitably occur during the manufacturing process. In order to reduce the intensity of interference fringes to a level that does not pose a practical problem, assuming that the reflectance on the film surface and the reflectance on the bottom surface of the filter are 10%, there is almost no problem if they are 30% of the level of conventional interference fringes. From this judgment, it can be seen that the film thickness should be controlled to (n+1)'±0.05λ.

〔Effect of the invention〕

As explained above, in the present invention, when light of wavelength λ is incident on the photodiode in a solid-state image sensor in which the filter is bonded via a medium having a refractive index lower than the refractive index of the filter, (n+1 ) The thickness of the oxide film is set to λ 7−, and the area of the portion where the oxide film is formed is made equal to the area of the portion of the photodiode where no oxide film is formed, thereby reducing interference fringes of light. It also has the effect of fully suppressing flare and ghosting.

[Brief explanation of the drawing]

Fig. 1(a) Fi is a vertical cross-sectional view of the first embodiment of the present invention, Fig. 1(b) fd is a view of the photodiode viewed from above,
FIG. 2(a) is a vertical cross-sectional view of the second embodiment of the present invention;
Figure (b) is a view of the photodiode from above.
Figure (a) tI'i Longitudinal cross-sectional view of a conventional solid-state image sensor, No. 3
Figure (b) is the playback screen of Figure 3 (a), Figure 4 is an explanatory diagram of a conventional solid-state image sensor in which a ghost image does not occur,
FIG. 5 is a plan view showing an example of a solid-state image sensor. In the figure, 11.41... light source, 12,32
゜42...Filter, 13.33.43...
...Photodiode, 14.34.44...
... Substrate, 15 ... Medium having a refractive index lower than that of the filter, 35 ... Resin, 16 ... Oxide film, 37 ... Bost image. Agent Patent Attorney Susumu Uchihara (θ) (b) Chen

Claims (1)

[Claims] A substrate with a refractive index lower than the refractive index of the glass filter is provided, which includes at least a photoelectric conversion section consisting of photodiodes arranged in one or two dimensions, and a signal processing section that outputs the electric charge generated in the photoelectric conversion section to the outside. through the medium of
In the solid-state image sensor to which the glass filter is bonded, a part of the light-receiving surface of the photodiode has a specific wavelength λ of ((n+1)λ/4)±0.05λ of the incident light.
(n is an integer), and a solid-state image pickup device characterized in that a film having a thickness of (n is an integer) is provided, and the area of a portion of the light-receiving surface of the photodiode where the film of the film thickness is provided and a portion without the film are equal to each other. .