JPH0465163A - Manufacture of solid state image sensor - Google Patents

Abstract

PURPOSE:To simply and easily form a color filter layer by coating the layer with a material which exhibits photochromism characteristics. CONSTITUTION:A color filter layer 6 is provided on a semiconductor substrate l formed on photoelectric converters 2. The layer 6 is made of a red light transmitting layer 3, a green color transmitting layer 4, a blue color transmitting layer 5 and a transparent resin protective layer 7. Colors correspond to the converters 2 to be formed by using photographic printing plate method. The layers 3, 4, 5 are covered with the layer 7 upon each formation, and the layer 6 is coated with a material 8 exhibiting photochromism characteristics. The material 8 is composed, for example, by dispersing organic compounds exhibiting photochromism in a transparent polymer material having high permeability to a visible light. Thus, its cost can be reduced, a term can be shortened, its quality can be improved, stabilized, and its yield can be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a solid-state image sensor, and more particularly to a method for manufacturing a solid-state image sensor in which a filter layer whose light transmittance changes depending on the amount of incident light is provided on a light-receiving surface. It is something.

[Conventional technology]

In a solid-state image sensor, when strong light enters some pixels on the light-receiving surface and the amount of signal charge generated there exceeds the charge storage capacity of the photodiode, for example, the excess charge flows into the surrounding photodiodes. As a result, charges accumulate in surrounding pixels even though they are not illuminated by light, and a false signal is generated at the timing when each pixel is selected. This phenomenon is called blooming, and is a major problem with solid-state image sensors. Many methods have been proposed to eliminate this blooming phenomenon, and one of them is to provide a filter layer on the light-receiving surface of the solid-state image sensor whose light transmittance changes depending on the amount of incident light. . The material used for this filter layer is generally a glass containing silver halide microcrystals called photochromic glass, or a glass containing an element serving as a color center.

Next, the operation will be explained. For example, Japanese Patent Publication No. 537391
6, photochromic glass refers to glass whose transmittance decreases in proportion to the intensity of irradiated light. When such glass is attached to the light-receiving surface of a solid-state image sensor, when intense light is incident on a part of the light-receiving surface, it is possible to partially and reversibly suppress the amount of incident light without disturbing the hack's optical information. , This makes it possible to eliminate the blooming phenomenon.

[Invention or problem to be solved]

Like other well-known glasses, these photochromic glasses have silicic acid (SiO2) as their main component, and their production involves mixing raw material oxides and melting them at high temperatures (around 1000 yen). Therefore, as a method for forming the filter layer, it is difficult to decide whether it is easier or easier to attach a flat plate of synthesized glass to the light-receiving surface of the element.
It was thought that this could lead to a decrease in overall sensitivity due to absorption of the adhesive, or uneven sensitivity due to uneven adhesive application. Also, is it possible to synthesize it directly on the wafer? Considering the semiconductor manufacturing process, exposing the wafer to such high temperatures may seriously deteriorate the performance of the device itself. It becomes difficult to control the film thickness. On the other hand, considering that the glass may break when dicing the chips, the manufacturing process involves a complicated process as it is necessary to bond each chip together after dicing.
An increase in costs is unavoidable.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method for manufacturing a solid-state image sensor in which the filter layer can be formed more simply and easily.

[Means to solve the problem]

This invention relates to a method for manufacturing a solid-state imaging device in which a semiconductor substrate is provided with a photoelectric conversion element and a layer exhibiting photochromism with respect to light incident on the photoelectric conversion element, and a step of applying the layer exhibiting photochromism as described above. This includes:

[Effect]

According to the method of the present invention, when forming a filter layer whose transmittance changes depending on the amount of incident light on the light-receiving surface of a solid-state image sensor, a spin code method, etc., which is often used in normal semiconductor processes, can be used. Since it can be reused, it is easy to control the thickness of the desired filter layer, and there is no need for high temperatures that would adversely affect the semiconductor substrate. In addition, since single wafer processing is possible, it is possible to manufacture in large quantities more easily and quickly than with conventional methods.

〔Example〕

Hereinafter, FIG. 1 showing an embodiment of the present invention will be explained. FIG. 1 shows an example in which the present invention is applied to a color solid-state image sensor with a color separation function, in which a color filter layer (6) is formed on the upper surface of a semiconductor substrate (1) on which a photoelectric conversion section (2) is formed.
has. This filter layer (6) includes a red light transmitting layer (3).
), a green light transmitting layer (4), a blue light transmitting layer (5),
It consists of a transparent resin protective layer (7), and is formed using a photolithography technique to correspond to each charging conversion section 2 in one color. Also, each transparent layer (3).

f4), (5) is a transparent resin protective layer (
7). A material (8) exhibiting photochromic properties is applied onto the color filter layer (6) thus formed. Specifically, this material (8) is, for example, a material in which an organic compound exhibiting photochromism is dispersed in a transparent polymeric material with high visible light transmittance. For example, the polymer material may be any organic or inorganic polymer material that is transparent and has high visible light transmittance, such as polyethylene or polystyrene, in addition to acrylic or ester polymer compounds. Further, as the organic substance to be dispersed, it is preferable to use a mixture of spiropyran compounds, which have absorption bands from green to red, and thioindigo and fulgide compounds, which have absorption bands from near ultraviolet to blue, in appropriate proportions. As for the mixing ratio at this time, there is a method of determining the transmittance in consideration of reducing the transmittance equally in each wavelength range of light, or adjusting the transmittance according to the sensitivity of the solid-state image sensor in each wavelength range. You can also make a decision by taking into consideration what you will do. In addition, it is also possible to dim only a part of the wavelength band of visible light for special purposes. On the other hand, when using the spin code method,
The viscosity of the material to be coated is a problem in terms of film thickness and uniformity after coating, but the viscosity can be easily adjusted because the solvent can be, for example, ethyl cellosolve acetate, which is the same as that used in general film resists. Further, in order to obtain the required film thickness and uniformity of the film thickness, it is also possible to change the coating rotation speed and rotation time depending on the viscosity. For example, as an example of specific manufacturing conditions, 2μm-3μm
In order to obtain a film thickness of
The coating may be applied at a rotation speed of about -250 rpm.

Although the present invention has been illustrated above, the above-mentioned example can be further modified based on the technical idea. For example, (3),
For (4) and (5), a complementary color filter consisting of the three colors cyan, macenda, and green can be used, and if color resolution is not required, the color filter layer (6) can be omitted. good.

In addition, if there is an organic or inorganic material that has the characteristic of decreasing its light transmittance as the intensity of the irradiated light increases, and it satisfies the appropriate conditions, it is also possible to use materials such as (8). However, for example, it is also possible to synthesize and use a polymer in which a compound exhibiting photochromism as described above is introduced into the side chain. Moreover, it is needless to say that it is not always necessary to use the spin code method, and that a dipping method, other coating methods, or thin film forming method can be applied.

〔Effect of the invention〕

According to the present invention, by applying a material exhibiting photochromism as described above, it is possible to prevent blooming much more simply and conveniently than conventional means without increasing the number of special devices or processes. In addition, since it can be manufactured more easily and quickly in large quantities than conventional methods, it is expected to reduce costs, shorten production time, improve and stabilize quality, and improve yields as a result.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a solid-state image sensor showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a conventional solid-state image sensor. In the figure, (1)...semiconductor substrate, (2)...photoelectric conversion section, (3), (4), (5)...red, green, blue filter layers, (6)...on・Chip type color filter layer, (7) ・Transparent resin protective layer, (8)...
Polymer photochromic material, (9)・Photochromic glass, α0)・Adhesive. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] A method for manufacturing a solid-state imaging device in which a semiconductor substrate is provided with a photoelectric conversion element and a layer exhibiting photochromism with respect to light incident on the photoelectric conversion element, including the step of applying the layer exhibiting photochromism as described above. A method for manufacturing a solid-state image sensor, characterized by: