JPS6022323B2 - Solid-state color image sensor and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state color image sensor, and more particularly to a solid-state color group image sensor equipped with a color filter.

Recently, with the spread of industrial and household VTRs,
Demand for 4-inch, lightweight, and easy-to-use television cameras is increasing.

Therefore, solid-state television cameras using semiconductor integrated circuits (generally IC or LSI) are attracting attention. In this solid-state television camera, the face plate and electron beam generating portion of the conventional cylindrical tube are replaced with an IC board, making it an independent solid-state imaging device. This does not use an electron beam, so
They are superior to image pickup tubes in that they are more stable, have less magnetic force, and are easier to handle, and are expected to be the next generation of television cameras. This solid-state imaging device is formed in a layered manner and consists of a semiconductor substrate portion and a color filter portion. When a brown filter is used as a color filter, a method is generally used in which four sets of cyan, yellow, green, and white are used to measure color reproduction.

In that case, as shown in FIG. 1, green is produced by laminating cyan 1 and yellow 2. Note that FIG. 1 is a sectional view of a main part of a solid-state image sensor.

In the figure, 8 is a semiconductor substrate provided with at least a light receiving area.

Numerals 4 to 7 are light receiving areas, and a color filter section is provided above the light receiving area, with each color filter area facing the light receiving area.

Generally, film filters use gelatin containing a photosensitizer such as ammonium dichromate or bisazide, or a water-soluble photoresist such as polyvinyl alcohol, which is exposed through a mask, developed and patterned, and then formed into a predetermined pattern. It is stained by immersion in a staining solution. After forming the pattern of the first color, it is coated with an organic material that is not dyed by the dyeing solution, and then the same process is repeated to form the filter pattern of the second color. At this time, the spectral transmission characteristics of the filter vary greatly depending on the thickness of the gelatin or the like.

Therefore, in order to realize a good color filter, it is necessary to accurately form the film thickness of the filter base material.

However, when manufacturing a filter base material by imparting a photosensitive characteristic to the filter base material and utilizing this photosensitive characteristic as described above, the amount of light used to expose the pattern on the filter base material may vary depending on the amount of light used to expose the pattern on the filter base material. Depends on film thickness. When forming a color filter directly on a solid-state image sensor using this method, unlike when forming a color filter on a light-transmitting substrate such as ordinary glass, reflected light from the substrate surface becomes a big problem. Become.

This is because the substrate of a solid-state image pickup device is different from a transparent substrate such as glass, and the amount of reflected light is large. When performing exposure on a solid-state image sensor, the amount of light for exposure is determined by the sum of light directly incident from the light source and light reflected from the substrate surface.

Therefore, if a color filter (for example, yellow) that absorbs irradiation light such as ultraviolet rays is formed on the first color, and cyan is formed as the second color on top of the first color, if the base is silicon, the cyan filter will be In the evening, the amount of light on Yellow is about 30% insufficient compared to non-Yellow areas.
The photosensitive properties of gelatin tend to become saturated if the amount of light is increased beyond a certain level, but in this saturated region there is a lot of fogging, making it impossible to form a highly accurate pattern. It is optimal to expose to light just before saturation, but in this case, there is a difference of about 30% in the gelatin film thickness between yellow and non-yellow, and the spectral characteristics shown in FIG. 2 are exhibited. That is, while the spectral transmittance curve of the cyan filter formed as a single layer is 25, it changes to the curve 23 on the yellow filter. Therefore, the green transmittance curve formed by the yellow and cyan layering should be the main button 24, but the curve on the longer wavelength side is shifted to the longer wavelength, and becomes the curve 22.
SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a solid-state color imaging device having an optically good color filter.

The key point of the Sonodai image sensor of the present invention is that a plurality of color filters are installed on the upper part of the substrate of the solid-state image sensor having at least a plurality of light receiving areas, and the overlapping portion of the first color filter layer and the second color filter layer is used to form a first color filter layer. When configuring the third color filter,
The point is that the filter formed in the lower layer close to the substrate has a spectral transmission characteristic that substantially transmits the exposure light beam used for forming the filter layer.

When forming a color on a solid-state image sensor substrate using an organic material such as gelatin using photolithography technology, the exposure light is the sum of the light that is directly incident from the light source and the light that is reflected from the substrate surface. determined by

As shown in the above purchase, a color filter that transmits light such as ultraviolet rays used for exposure, such as cyan, is first formed, and a color filter that absorbs the fuzzy light rays is partially overlapped on top of the color filter, such as yellow. When a color filter is formed, even if there is an overlapping area, the yellow filter will be properly exposed to the direct incident light from the light source and the reflected light from the substrate, so both the overlapping and non-overlapping areas will be the same film. Can be formed thickly.
In this way, even if there is an overlap between the color filter and other color filters, the film thickness of the color filter can be made uniform.
The filter has good spectral transmission characteristics and can provide high quality images.

This will be explained in detail below using examples. FIG. 1 is a schematic cross-sectional view of a solid-state color imaging device as an embodiment of the present invention. In the semiconductor substrate, light receiving regions 4, 5, 6, and 7 as light receiving elements are formed on a Si substrate 8, and furthermore, predetermined discontinuities (not shown) and metal wiring (
(not shown), and a passivation film (not shown) is formed as necessary.

Figures 3 to 7 show schematic process diagrams of the process.

A polyglycidyl methacrylate layer 30 is formed on the semiconductor substrate shown in FIG. 3, and then a cyan color filter 1 dyed with a cyan dye is formed. Furthermore, gelatin 21 is coated on the color mixture prevention protective film layer 30 made of polyglycidyl methacrylate (abbreviated as PGMA) by a spin coating method, as shown in FIG. Here, as a photosensitizer for gelatin, ammonium dichromate (NH4-207, generally AD
A 5% solution of 40° C. (abbreviated as C) is used. The thickness of this gelatin coating layer is approximately 1 mm. Next, as shown in FIG. 5, using a chromium (Cr) mask 31, ultraviolet rays are applied to polymerize and harden the gelatin layer, and a dyeable gelatin pattern layer 22 is formed by development. Next, as shown in FIG. 6, the gelatin layer 22 is dyed yellow by heating a dyeing solution for yellow color at about 70:00 and soaking the above-mentioned element in it. form 2. The cyan dye mentioned above is Chibaku. A 2.2% aqueous solution of turmeric and a yellow dye of canol yellow.
% aqueous solution is used. In this example, a complementary color filter is used for the color filter, and four colors of cyan, yellow, green, and white are used.
A method is used to measure color reproduction using sets. The light receiving area corresponding to cyan is 5, green is 6, yellow is 7 and white is 4.
correspond to each other. Next, as shown in FIG. 7, a protective film 3 made of polyglycidimethacrylate is formed on the filter layers 1 and 2 to constitute a color filter for a solid-state color image sensor.

In addition to the gelatin described above, polyvinyl alcohol or glue can also be used as the material for the color film.

In this way, since the yellow color filter 2 is formed on the upper layer of the cyan color filter, even if there is an overlapping part in the color filter 2, the amount of ultraviolet light for exposure can be used for flashing without running out of light. can.

In addition, since the reflected light from the substrate is also effectively used for exposure, a highly accurate pattern can be formed without causing "fogging", which is caused by an unnecessary increase in the amount of directly incident ultraviolet light. Figure 2 is a schematic characteristic diagram showing the spectral transmission characteristics of the present invention and the conventional element, focusing on the wavelength of light.
The vertical axis shows the spectral transmittance T.

Curve 25 is the spectral transmittance of cyan, and curve 26 is the spectral transmittance of yellow.

Now, consider the case where yellow is formed in the lower layer and cyan is formed in the upper layer, and green is obtained in the overlapped area. Generally, ultraviolet rays or light with a wavelength of around 43 m are used as exposure light for forming a filter layer, but in this case, this exposure light is not transmitted due to the spectral characteristics of yellow. Therefore, the amount of exposure light for the cyan filter layer placed to obtain green color is reduced,
The thickness of this filter layer becomes thinner. As a result, the spectral transmittance of this cyan color exhibits a characteristic as shown by curve 23. As a result, the green color synthesized from the yellow of the curve 24 and the cyan of the curve 23 has a spectral transmittance as shown by the curve 22. On the other hand, the cyan spectral transmittance of the portion where yellow is not formed in the lower layer is shown by a curve 25.

In the case of color reproduction, R (red) = W (white) - Cy (cyan) 10 Ye (yellow) - G (green) 8 (blue) = W (white) - Ye (yellow)
The three primary colors are reproduced by the following calculation: 10 Cy (cyan) 1 G (green) G (green) = G (green) This calculation is as follows: Cy (cyan) = B (blue) 1 G (green) Ye ( Yellow) = G (green) + R (red) This cannot be true unless the following relationship is established.

That is, if green among the three primary colors has characteristics that do not match the green components contained in cyan and yellow, R, G, and B cannot be displayed as desired. On the other hand, when cyan, which transmits the exposure light, is disposed in the lower layer as in the present invention, the characteristic curves of each filter are curves 25 (cyan) and 24 (green) in FIG.
, 26 (yellow).

This is because when cyan is disposed in the lower layer, the filter formed on the upper layer is exposed to a predetermined amount of light and a desired film thickness can be obtained. The element of the present invention was not affected by differences in film thickness during imaging, and therefore good spectral characteristics were obtained without wavelength shift.

In this embodiment, only yellow and cyan color filters have been described, but the present invention can be applied to a combination of color filters of other colors to make the filter film thickness in the overlapping part equal to that in the non-overlapping part. Needless to say, this applies.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a solid-state color imaging device as an embodiment of the present invention, FIG. 2 is a schematic characteristic diagram of the device according to the present invention, and FIGS. 3 to 7 are schematic portions of the device according to the present invention. It is a process diagram. 1...Color filter (Cy), 2...Color filter (Y
e), 3... Mixing prevention protective film, 4-7... Light receiving area, 8... Si substrate. Fang diagram vs. 2 diagram Ji 3 box younger brother Mu diagram 3 Sae S diagram Shizuka 7 diagram

Claims (1)

[Scope of Claims] 1. A semiconductor substrate having at least a plurality of light-receiving parts, and a color filter layer disposed on the substrate corresponding to the light-receiving part, each of the filter layers having at least two different types of spectral transmission. and has at least a configuration in which a third spectral transmission characteristic is obtained by combining the spectral transmission characteristics of the first and second filter layers as the spectral transmission characteristic of the filter provided corresponding to the light receiving section. The solid-state color imaging device includes a filter layer having spectral transmission characteristics that substantially transmits an exposure light beam used for processing the first and second filter layers when laminating the first and second filter layers. A solid-state color image sensor characterized by being arranged in the lower layer. 2. The solid-state color imaging device according to claim 1, wherein the lower filter layer is cyan, and the upper filter layer is yellow. 3. The solid-state color imaging device according to claim 1 or 2, wherein the semiconductor substrate having at least a plurality of light-receiving parts has a light-transmitting organic polymer layer on its surface. 4. On a semiconductor substrate having at least a plurality of light receiving parts,
a step of forming a first filter base material having predetermined photosensitive characteristics; a step of exposing and processing the first filter base material into a predetermined shape; and a step of making the first filter base material have predetermined spectral transmission characteristics. A step of forming a first filter element, a step of forming a transparent organic polymer resin layer on the semiconductor substrate prepared up to the previous step, and a step of forming a second filter element having predetermined photosensitive characteristics on the resin layer.
a step of exposing and processing this second filter base material into a predetermined shape having at least a portion overlapping with the first filter base material;
at least the step of imparting predetermined spectral transmission characteristics to the filter base material to form a second filter element, and the spectral transmission characteristics of the first filter element substantially transmit the exposure light of the filter base material. A method for manufacturing a solid-state color image sensor characterized by transmitting properties. 5. The method of manufacturing a solid-state color imaging device according to claim 4, wherein the semiconductor substrate having at least a plurality of light-receiving parts has a transparent organic polymer layer formed on its surface. 6. The method of manufacturing a solid-state color imaging device according to claim 4, wherein the first filter element is cyan and the second filter element is yellow.