Patent Application
20050270594
1. Field of the Invention
The present invention relates to solid-state imaging devices that contain color on-chip filters, methods for manufacturing the same, and to cameras provided with the solid-state imaging devices.
2. Description of Related Art
Conventionally, solid-state imaging devices such as CCD solid-state imaging devices that have photo-electric conversion portions for converting light to an electric charge, and MOS solid-state imaging devices have been used in various image input apparatuses such as video cameras and digital still cameras, or facsimiles.
Color solid-state imaging devices that have color filters also are known as these solid-state imaging devices. Conventional color solid-state imaging devices have a configuration in which, for example, primary color filters made of a combination of red (R), blue (B) and green (G), or complementary color filters made of a combination of cyan (C), magenta (M), yellow (Y) and green (G) are laminated in a predetermined pattern onto light receiving faces of light receiving elements that are arranged in a two-dimensional array on the solid-state imaging elements, such that a single light receiving element corresponds to a single color. Color filters that are laminated onto the light receiving faces of light receiving elements in this way generally are called “on-chip filters”.
However, the light beams that are incident on the light receiving face of a color solid-state imaging element are not necessarily perpendicular to the light receiving surface and parallel to each other. There is a problem in that color mixing occurs when light that is incident on the light receiving face from a direction that is inclined with respect to the light receiving face passes through a single color filter at an angle and is incident on an adjacent light receiving element.
In order to solve the problem of such color mixing, a color solid-state imaging device 91 that is provided with black light blocking films 96a to 96c on border portions of light receiving pixel regions formed by photodiodes (PD) (pixel border portions), such as shown in
Firstly, first light blocking films 96a are formed by patterning a dyeable resin to a predetermined film thickness onto the pixel border portion of the imaging surface of the solid-state imaging element 91, and dyeing with a black dye. Next, a first color filter (R) 93 is formed by patterning and dyeing a dyeable resin onto a predetermined region of the regions that are divided by the light blocking films 96a.
Next, a transparent dye repellent film 97 is formed on the light receiving face on which the first light blocking film 96a and the first color filter 93 are formed, and second light blocking films 96b are formed by patterning a dyeable resin to a predetermined film thickness onto the pixel border portion on the transparent dye repellent film 97, and dyeing with a black dye. Then, a second color filter (G) 94 is formed by patterning and dyeing a dyeable resin onto a predetermined region of the regions that are divided by the light blocking films 96b.
Moreover, in the same manner as described above, a transparent dye repellent film 98, third light blocking films 96c and a third color filter (B) 95 are formed, and lastly, a transparent dye repellent film 99 is formed as a protective layer.
In this way, by forming the black light blocking films 96a to 96c on the pixel boundary portions, light that is incident on, for example, the B color filter 95 at an angle, and that passes through this color filter is blocked by the light blocking films 96a to 96c, and is not incident on the adjacent light receiving pixel region (PD portion) 92. Thus, color mixing due to angled light can be prevented.
However, in the conventional configuration noted above, there is the problem that a multitude of steps are necessary, ie. (1) forming the black light blocking film, (2) forming the first color filter, (3) forming the dye repellent film, (4) forming the black light blocking film, (5) forming the second color filter, (6) forming the dye repellent film, (7) forming the black light blocking film, (8) forming the third color filter and (9) forming the protective layer.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a solid-state imaging device that has an on-chip filter capable of preventing color mixing from adjacent pixels due to angled light and can be made with a simpler manufacturing method.
In order to achieve the above-noted object, the solid-state imaging device according to the present invention provides a semiconductor substrate, light receiving elements that are formed in a matrix pattern on the semiconductor substrate, and a color filter layer that is formed above the light receiving elements, and that is constituted by color filters of three or more colors, wherein in the color filter layer, at least one part of a pixel border portion in which the color filters of two colors are adjacent contains a color filter wall of a color that is different from the two colors.
Furthermore, the method for manufacturing the solid-state imaging device according to the present invention provides a step of forming light receiving elements onto a semiconductor substrate in a matrix pattern, and a step of forming at least color filters of a first color to a third color in order, onto an upper layer of the light receiving elements, wherein in at least one step of the steps for forming the color filters of the first color to the third color, a color filter wall of the same color as the color filter formed in the one step is formed in at least a part of a pixel border portion in which color filters of two colors that differ from the one color filter are adjacent.
With the present invention, it is possible to provide, at a lower cost, a solid-state imaging device that has an on-chip filter capable of preventing color mixing from adjacent pixels due to angled light.
The solid-state imaging device according to the present invention is constituted by a semiconductor substrate, light receiving elements that are formed in a matrix pattern on the semiconductor substrate, and a color filter layer that is formed above the light receiving elements, and that is constituted by color filters of three or more colors, wherein in the color filter layer, at least one part of a pixel border portion in which the color filters of two colors are adjacent contains a color filter wall of a color that is different from the two colors.
With this configuration, when angled light that has passed through a color filter of a pixel is incident on a color filter wall, the colors of the color filter and the color filter wall are different and thus there is the effect that the angled light is eliminated. Thus, color mixing from adjacent pixels due to angled light can be prevented. The manufacturing step is simplified because conventional black light blocking films are unnecessary, and it is possible to provide the solid-state imaging device at lower cost.
In the solid-state imaging device having the above-noted configuration, the color filter layer can be constituted by, for example, color filters in a primary color Bayer pattern, color filters in a primary color stripe array, or color filters having complementary colors.
In the solid-state imaging device having the above-noted configuration, if the color filter layer has a configuration in which it is formed by a colored photoresist, then the solid-state imaging device can be manufactured without a step of dyeing, and thus it is possible to reduce the manufacturing cost further.
The solid-state imaging device having the above-noted configuration may be embodied such that the color filter wall has substantially the same thickness as the color filter layer, and is formed with a substantially uniform width. Furthermore, the solid-state imaging device having the above-noted configuration may be embodied such that the color filter wall is formed with a thickness that is lower than that of the color filter layer. Alternatively, it may be embodied such that the width of the color filter wall decreases toward the side of the color filter layer on which the light is incident. With the latter two aspects, there is the advantage that it is possible to ensure that the area of the pixel aperture is broad, while preventing color mixing due to angled light.
The present invention may also be embodied as a camera provided with the solid-state imaging device having any of the configurations noted above.
The method for manufacturing the solid-state imaging device according to the present invention includes a step of forming light receiving elements onto a semiconductor substrate in a matrix pattern, and a step of forming at least color filters of a first color to a third color in order, onto an upper layer of the light receiving elements, wherein in at least one step of the steps for forming the color filters of the first color to the third color, a color filter wall of the same color as the color filter formed in the one step is formed in at least a part of a pixel border portion in which color filters of two colors that differ from the one color filter are adjacent.
With this manufacturing method, it is possible to manufacture a solid-state imaging device that can prevent color mixing from adjacent pixels due to angled light. That is to say, in this solid-state imaging device, when angled light that has passed through a pixel of a color filter is incident on a color filter wall, the colors of the color filter and the color filter wall are different, and thus there is the effect that the angled light is eliminated. Thus, color mixing due to angled light can be prevented. Further, the manufacturing step is simplified because the color filter wall can be formed in the same step as the color filter of the same color and the step of forming conventional black light blocking films are unnecessary, and it is possible to provide the solid-state imaging device at lower cost.
In the manufacturing method noted above, the color filter and the color filter wall can be formed by photolithography. In this case, it is preferable that a colored photoresist is used as the material of the color filter and the color filter wall. This is because the manufacturing step can be further simplified, because a step of dyeing is not necessary. Moreover, by using a halftone mask or a grey tone mask when forming the color filter wall, it is possible to form a color filter wall having a thickness that is lower than that of the color filter layer, or a color filter wall whose width decreases toward the side of the color filter layer on which the light is incident.
The aforementioned manufacturing method may also include a step of using a dyeable resin as the material of the color filter and the color filter wall, and patterning the dyeable resin, and a step of dyeing the patterned dyeable resin. In this case, it is preferable that the aforementioned manufacturing method also includes a step of treating with a hardening liquid after the step of dyeing the dyeable resin. This is because the manufacturing step can be simplified since a dye repellent film is unnecessary, and it is possible to make the on-chip filter thinner.
More specific embodiments of the solid-state imaging device of the present invention are described below with reference to the drawings.
A solid-state imaging device according to one embodiment of the present invention is described below. It should be noted that a CCD solid-state imaging device is illustrated here as one embodiment, however the present invention is not limited to CCD solid-state imaging devices, and may also be applied to, for example, MOS solid-state imaging devices.
The solid-state imaging device according to the present embodiment has a color filter layer that is in what is known as a basic Bayer pattern, in which G color filters 4 are arranged on two diagonally opposite pixels of four 2 (h)×2 (w) pixels, wherein an R color filter 6 is arranged on one pixel of the remaining two pixels, and a B color filter 5 is arranged on the further remaining one pixel, such as shown in
As shown in
A color filter layer is formed above the first flat film 3. As can be understood from
As can be understood from
Moreover, a second flat film 7 made from transparent acrylic resin, for example, is provided above the color filter layer made up of the G color filters 4, the B color filter 5, the R color filter 6, the R color filter walls 6w and the B color filter walls 5w described above. Microlenses 8 for focusing incident light onto the photodiodes 2 then are provided above the second flat film 7, aligned with the positions of the respective photodiodes 2.
Furthermore, since the overlap of the transmittance curves of the G light and the R light is small, as shown in
In the same way, the transmittance of the angled light that has passed through the G color filter 4 and the adjacent B color filter 5w, as shown in
As given above, color mixing from adjacent pixels due to angled light can be prevented effectively in the solid-state imaging device 10. Furthermore, in the solid-state imaging device 10, the R, G and B color filters 4, 5 and 6, and the color filter walls 5w and 6w are formed as a single layer color filter layer having a uniform thickness. Therefore it is possible to make the on-chip filter thinner than that of a conventional configuration in which the R, G, and B color filters are formed as a plurality of layers, such as shown in
A method for manufacturing the solid-state imaging device 10 according to the present embodiment is described next.
Firstly, as shown in
Next, a positive photoresist that has been colored blue is coated by spin coating so as to cover the entirety of the G color filter 4s and the first flat film 3. A mask having a pattern such as is shown in
When light is irradiated from above the mask in this condition, in a cross-section c-c′ shown in
In a cross-section d-d′ shown in
Next, a positive photoresist that has been colored red is spin coated so as to cover the entirety of the G color filters 4 and the B color filter 5, and the color filter walls 5w that are formed as shown in
When light is irradiated from above the mask in this condition, in a cross-section e-e′ shown in
Furthermore, in a cross-section f-f′ shown in
Continuing, the second flat film 7 is formed on the color filter layer that is formed as shown in
With the manufacturing method given above, the color filter layer can be formed by the three steps of (1) forming the G color filters, (2) forming the B color filter and the color B filter walls, and (3) forming the R color filter and the R color filter walls. Therefore, the manufacturing step can be made simpler than the conventional configuration that contains black light blocking films in the pixel border regions, as described previously.
It should be noted that the above-noted manufacturing method is no more than a single example, and that various alternatives are possible. For example, in this case, an example has been shown in which the color filters are formed in the order of G, B and R, however the order in which the color filters are formed is not limited to this, and may be any order desired. Furthermore, a negative photoresist may also be used as a substitute for the positive photoresist. In this case, the pattern of the mask may be altered such that the regions that allow light to pass and the regions that block the light are the opposite of those in
Furthermore, a dyeable resin or the like may be used as the material for the color filter layer, as a substitute for the colored resist described above. In this case, a transparent dyeable resin is first patterned to the shape of any color filter (for example, G), after which it is dyed with dye. After forming a dye repellent film thereon, the transparent dyeable resin is again patterned to the shape of the color filter and the color filter walls, and dyed with the next color (for example, B). Then, after forming the dye repellent film thereon, the transparent dyeable resin further is patterned to the shape of the color filter and the color filter walls, and dyed with the next color (for example, R).
If a dyeable resin is used, then a step of treating with a hardening liquid may be added after the dying step as a substitute for using the dye repellent film described above. In this case, the dyeable resin treated with the hardening liquid will not be colored even if later exposed to other dyes. Thus the dye-repellent film is unnecessary and there is the advantage that the color filter layer does not become thick.
The R or B color filter walls 5w or 6w shown in
Color filter walls 6w′ shown in
It should be noted that in
Furthermore, the width of the color filter walls may also be non-uniform. For example, the width of the color filter walls 6w″ as shown in
It should be noted that the color filter walls 6w″ shown in
It is preferable that the angled faces of the color filter walls 6w″ are formed at an angle at which the light that is incident perpendicular to the light receiving face and that is focused with the microlenses 8 toward the photodiodes 2 is not incident on the color filter walls 6w″.
In
In the above-noted description, a configuration has been illustrated in which the basic array of the color filter is a primary color Bayer pattern, however, the present invention also may be applied to a case in which the color filter is a striped array of three primary colors. In this case also, the B, G and R color filter walls may be arranged on the R and G pixel border portion, the R and B pixel border portion and the G and B pixel border portion respectively.
Moreover, it is also possible to embody the present invention with complementary color filters. The spectral characteristics of the colors C, M, Y and G are as shown in
Another embodiment of the present invention is described with reference to
If the solid-state imaging device described in Embodiment 1 is applied to a digital camera, then a digital camera that has superior picture quality due to prevention of color mixing can be realized at low cost.
The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-153726 | May 2004 | JP | national |
