JP2802999B2 - Method for manufacturing color solid-state imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color solid-state imaging device, and more particularly to a so-called on-chip color solid-state imaging device in which a color filter is formed directly on a solid-state imaging device. It relates to a manufacturing method.

[Conventional technology]

Currently, as a method for manufacturing a color solid-state imaging device, there are a method of forming a color separation filter on a transparent substrate such as glass and bonding this filter to a solid-state imaging device such as a CCD, and a method of flattening a solid-state imaging device such as a CCD. A method of forming a color separation filter directly via a chemical layer is known, and each is industrialized. In particular, the solid-state imaging device formed by the latter method is called an on-chip type, and there is no alignment work between the solid-state imaging device and the color separation filter. Positioning is possible.

An outline of a conventional method for manufacturing an on-chip color solid-state imaging device will be described with reference to FIG. First,
As shown in FIG. 3 (b), a flattening agent 12 is applied on the solid-state imaging device 11 of FIG. 3 (a) and cured. As the flattening agent, a resin that is transparent to visible light and has high heat resistance and water resistance, such as a polyurethane resin, a silicone resin, an acrylic resin, an epoxy resin, and a polyimide resin, is used.

Next, as shown in FIG.
On the solid-state imaging device 11, predetermined colored pixels 13 are accurately aligned and sequentially formed in a predetermined pattern, and a protective film 14 is applied thereon as shown in FIG. Then, as shown in FIG. 3 (e), a photosensitive resin 15 (positive type in the figure) is applied, and is accurately aligned with the image pickup element 11 using a mask 16 having a desired pattern. Make a plate. Using the photosensitive resin 15 made as a resist as a resist, dry etching is performed using oxygen plasma or the like to ashing and removing a flattening agent on a predetermined portion, for example, on an electrode pad or a scribe line (FIG. 3 (f) )). Finally, when the photosensitive resin 15 is peeled off, an on-chip type color image sensor as shown in FIG. 3 (g) is obtained.

[Problems to be solved by the invention]

By the way, even if the surface of the solid-state imaging device is flattened by a flattening agent, unevenness still remains. The surface steps of the solid-state imaging device vary widely depending on the location, but the large ones include (a) individual sensors and transfer units (IL-CCD)
1.5 μm, and (b) 2 at the boundary between the sensor group and the wiring section
It is about μm. Due to the formation of the flattening layer, the level difference in (a) becomes about 0.7 μm, but the level difference in (b) remains almost 2 μm, and there is not much effect of flattening. There is a problem that the color filters existing on the uneven steps are easily cracked.

Although various causes can be considered, in the manufacturing process of the color filter, through the steps of dyeing, anti-dyeing, heating, etc., the swelling and shrinkage of the colored pixels occur, and the stress acts on the step portion of the unevenness, and finally, Is considered to have cracks here. Further, it is considered that a liquid pool of the dyeable photosensitive substrate occurs in the step portion, and the colored pixel formed in this portion becomes a thick film, and cracks are particularly likely to occur.

FIG. 2 shows a part of a cross section of a conventional color solid-state imaging device. The colored pixels 4 are formed on the solid-state imaging device 6,
At the same time, the thick film portion 5 is formed below the step, and cracks are easily generated here.

[Means for Solving the Problems] The present invention has been obtained as a result of study to solve the above problems.

That is, in the first invention, fine colored pixels are repeatedly located on the solid-state imaging device, and the thickness of the colored pixel located on the step edge portion of the surface of the solid-state imaging device is reduced to the thickness of another portion. In a method for manufacturing a color solid-state imaging device having a relatively thin film, a negative-type dyeable photosensitive substrate is coated on the solid-state imaging device, and when the solid-state imaging device is exposed to ultraviolet light through a photomask, the solid-state imaging device A method for manufacturing a color solid-state imaging device, wherein a portion of the dyeable photosensitive substrate located on a step edge portion of a surface is shielded from light by a light shield having a line width of 500 nm or less; The invention is characterized in that fine colored pixels are repeatedly located on the solid-state imaging device, and the thickness of the colored pixel located on the step edge portion of the surface of the solid-state imaging device is thinner than the thickness of other portions. In the method for manufacturing a color solid-state imaging device, A negative-type water-soluble dyeable photosensitive substrate is coated on an image element, and when exposed to ultraviolet light through a photomask, the dyeable photosensitive substrate located on a step edge of the surface of the solid-state image sensor is removed. A method for manufacturing a color solid-state imaging device, wherein a part is shielded from light by a light-shielding body having a line width of 2000 nm or less.

That is, the color solid-state imaging device manufactured according to the present invention is such that the thickness of the colored pixel located on the step edge portion of the surface of the solid-state imaging device is thinner than the thickness of other portions. Thus, it is possible to prevent the cracks caused by the local stress, which is a problem of the prior art described above. FIG. 1 shows a part of a cross section of an example of a color solid-state imaging device manufactured according to the present invention. The colored pixel 1 is formed on the solid-state imaging device 2, and the thin film portion 3 of the colored pixel is formed at each step edge portion of the solid-state imaging device 2.

The first and second inventions are a method for manufacturing the above-described color solid-state imaging device.

According to a first aspect of the invention, in order to manufacture the above-described color solid-state imaging device, a portion where a colored pixel becomes a thick film, that is, a portion of a negative type dyeable photosensitive substrate on a step edge portion is formed by using a photomask. The light is shielded by a light shield having a line width of 500 nm or less. When exposed, the dyeable photosensitive substrate has a resolution limit due to light diffraction. In the ultraviolet exposure, the resolution limit is limited by an exposure method (contact exposure method or reduced projection exposure method), or a condition peculiar to an exposure apparatus (difference in light source, aperture ratio of a projection lens), and properties of a dyeable photosensitive substrate. Although it varies, the resolution limit of i-line and g-line photolithography such as a so-called mercury lamp is approximately 500 nm. A light-shielding body having a resolution lower than this limit does not completely shield the dyeable photosensitive substrate even when exposed, and partially exposes the dyeable photosensitive substrate by diffracted light of ultraviolet rays, but the exposure amount is Because it is small, a thin film remains. For this reason, a portion thinner than a normal exposed portion is formed in a portion where the light shield below the resolution limit is located. That is, the first aspect of the present invention is to manufacture a color solid-state imaging device by obtaining the thin film portion 3 shown in FIG. 1 using diffracted light of ultraviolet rays.

In the case of exposure with ultraviolet light, the thickness of the portion shielded by a mask having a line width of 500 nm cannot be unconditionally defined by the type (characteristics) of the photosensitive substrate and the amount of irradiation at the time of exposure. About 90%. In this case, as the photosensitive substrate, acrylic, vinyl cinnamate, or styrene can be used, but (a) it is transparent and can be dyed by any means, and (b) the resolution limit is due to light diffraction. It is necessary to meet the conditions.

The second invention is also a method for manufacturing a color solid-state imaging device, and shows a method for manufacturing a color solid-state imaging device when a so-called negative water-soluble dyeable photosensitive substrate is used as the dyeable photosensitive substrate. It is a thing. As described above, the resolution limit is determined by some restrictions, but mainly water-soluble dyeable photosensitive substrates, for example, natural proteins such as gelatin, casein, and glue, and dichromate is added as a crosslinking agent. In this method, even when exposed through a photomask having a line width of 2000 nm or less, a gel component which can be said to be in a semi-crosslinked state remains between lands, and this becomes a residual film. Since the remaining film has a thickness smaller than that of a normal exposed portion, the thin film portion 3 in FIG. 1 is formed using a photomask having such a line width as in the first invention. That is, the second invention is to manufacture the above-described color solid-state imaging device by utilizing the exposure characteristics of a water-soluble dyeable photosensitive substrate. In this case, 2000
The film thickness of the portion shielded by a photomask having a line width of nm or less also depends on the type (characteristics) of the photosensitive substrate, as in the case of the first invention.
Although it cannot be unconditionally specified by the irradiation dose at the time of exposure, it is generally about 10 to 90% of the pixel film thickness.

Next, a dyeable photosensitive substrate is applied and dried, and the first and second dyeable substrates are dried.
In the invention of the present invention, it is assumed that exposure is performed with light shielding by a light shielding body having a line width equal to or more than the limited line width, and development and drying are performed. During development, the exposed dyeable photosensitive substrate swells shortly thereafter and shrinks during drying, so adjacent pixels will attract each other,
Finally, a gap is formed. In other words, the film thickness of the portion 3 in FIG. 1 formed under such conditions is too small, and the film thickness is insufficient to connect the adjacent pixels to each other, so that a gap is formed. Since this gap extends beyond the light-shielded line width, it becomes a white drop of the color filter. Therefore,
Based on such knowledge, the line width to be shielded is examined by experiments, and as a method of manufacturing a color solid-state imaging device,
This is the first and second inventions.

(Operation)

According to the present invention, since the thick film portion is not formed under the step, there is an effect of preventing occurrence of cracks and the like, and reliability is improved in a manufacturing process.

〔Example〕

Hereinafter, the color solid-state imaging device of the present invention and a method for manufacturing the same will be described in detail with reference to examples.

Example 1 PGMA was applied to a solid-state imaging device immobilized on a 5 ″ φ silicon wafer so as to have a thickness of 1 μm, dried, and exposed to far ultraviolet light through a photomask. Developed to form a planarization layer, where PGMA is an abbreviation for polyglycidyl methacrylate, which is an electron beam, X-ray, or deep ultraviolet photosensitive resin and has the following structure: .

Next, 10 parts by weight of gelatin and 1 part by weight of potassium dichromate are added to 100 parts by weight of water and dissolved sufficiently, and then applied on the flattening layer to a thickness of 1 μm. Then, it was heated and dried at 90 ° C. for 30 minutes.

Using a first photomask that shields a portion located at a step portion of the solid-state imaging device with a line width of 1.5 μm, the substrate was exposed to ultraviolet light, immersed in hot water at 40 ° C. for 1 minute, and developed. Then, it is dried by heating at 100 ° C. for 30 minutes, dyed in a red dyeing bath, immersed in a 1% tannic acid solution for 5 minutes, and further heated at 150 ° C. for 30 minutes.
After heating and drying for 1 minute, a red colored pixel of the first layer was obtained.

Similarly, green and blue colored pixels of the second and third layers were sequentially formed. At this time, as the second and third photomasks, similarly to the first photomask, ones that shield the portions located at the steps of the solid-state imaging device with a line width of 1.5 μm were used.

Further, PGMA was applied to the surface so as to have a thickness of 1 μm, dried, exposed to far ultraviolet light through a photomask, and developed to form a protective film. In addition, the dyeing bath composition of each color is as follows.

Red dyeing bath (liquid temperature 60 ° C) Kayanol Milling Red RS ・ ・ ・ ・ 3 (wt%) Acetic acid ・ ・ ・ ・ 4 (wt%) Water ・ ・ ・ ・ 93 (wt%) Green dyeing bath (liquid temperature 60) ° C) Alizarin green ··· 10 (wt%) Acetic acid ··· 2 (wt%) Water ··· 88 (wt%) Blue dye bath (liquid temperature 60 ° C) Eriobrilliant cyanine ··· 10 (% By weight) Ionette D-70 ··· 1 (% by weight) Acetic acid ··· 2 (% by weight) Water · ··· 87 (% by weight) Finally, this color solid-state image sensor was placed along the scribe line. After cutting and mounting, and photographing, good image quality was obtained.

Example 2 A flattening layer was formed in the same manner as in Example 1 on a solid-state image sensor mounted on a 5 ″ φ silicon wafer.

Polyvinyl cinnamate (10 wt%) dissolved in xylene is applied on the surface to a thickness of 2 μm,
For 30 minutes.

Using a first photomask that shields a portion located at a step portion of the solid-state image sensor with a line width of 0.3 μm, the substrate is exposed to ultraviolet light through the first photomask, and developed with a mixed solution of xylene: ethylcellsolve = 2: 3. And dried by heating at 120 ° C for 30 minutes, and dyed with a red dyeing bath.
, Dried at 90 ° C. for 30 minutes, exposed to ultraviolet light in a desired pattern, and developed with methyl ethyl ketone to form a stain protective film.

Similarly, green and blue colored pixels of the second and third layers were sequentially formed. At this time, as the second and third photomasks, similarly to the first photomask, those that shield the portions located at the steps of the solid-state imaging device with a line width of 0.3 μm were used.

Further, a protective film was formed in the same manner as in Example 1. In addition,
The composition of the dyeing bath for each color is as follows.

Red dyeing bath (liquid temperature 90 ° C) Kayarus Supra Red BWS ··· 7 (% by weight) Sodium sulfate (anhydrous) · · · 10 (% by weight) Water · · · 83 (% by weight) Green dyeing bath ( Liquid temperature 80 ° C) Kayarus Supra Green F4G ··· 7 (% by weight) Sodium sulfate (anhydrous) ··· 10 (% by weight) Water · ··· 83 (% by weight) Blue dyeing bath (liquid temperature 70 ° C) Kayarus Supra Blue 4BL conc ··· 5 (% by weight) Sodium sulfate ··· 10 (% by weight) Water · ··· 85 (% by weight) Finally, this color solid-state imaging device is placed along the scribe line. After cutting, mounting on a camera and photographing, good image quality was obtained.

〔The invention's effect〕

According to the present invention, even in a solid-state imaging device having irregularities, since a thick film portion is not formed in a colored pixel portion located below a step, generation of cracks and the like can be prevented, and reliability of a color filter on the solid-state imaging device can be reduced. It is possible to improve the performance and the image quality of the color solid-state imaging device. Further, reliability in the manufacturing process can be improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of one example of a color solid-state imaging device according to the present invention, FIG. 2 is a partial cross-sectional view of a conventional color solid-state imaging device, and FIG. It is. 1: colored pixel, 2: solid-state imaging device, 3: thin-film portion of the colored pixel at the step edge portion, 4: colored pixel, 5: thick-film portion of the colored pixel formed below the step, 6: solid-state imaging device, 11: solid-state image sensor, 12: flattening layer, 13: colored pixel, 14: protective film, 15: photosensitive resin, 16: mask.

Claims (2)

(57) [Claims] A fine colored pixel is repeatedly located on a solid-state imaging device, and the thickness of the colored pixel located on a step edge portion of the surface of the solid-state imaging device is larger than the thickness of other portions. In a method of manufacturing a color solid-state imaging device having a thin film,
Apply a negative type dyeable photosensitive substrate on the solid-state imaging device,
When exposing to ultraviolet light through a photomask, the site of the dyeable photosensitive substrate located on the step edge of the surface of the solid-state imaging device is shielded from light by a light shield having a line width of 500 nm or less. Of manufacturing a color solid-state imaging device. 2. A fine colored pixel is repeatedly located on a solid-state imaging device, and the thickness of the colored pixel located on a step edge portion of the surface of the solid-state imaging device is larger than the thickness of other portions. In a method of manufacturing a color solid-state imaging device having a thin film,
A negative-type water-soluble dyeable photosensitive substrate is coated on a solid-state imaging device, and when exposed to ultraviolet light through a photomask, the dyeable photosensitive substrate located on a step edge of the surface of the solid-state imaging device. A method for manufacturing a color solid-state imaging device, wherein light is shielded by a light-shielding body having a line width of 2000 nm or less.