Image sensor capable of improving color shading effect

An image sensor includes: a pixel array where a plurality of pixel groups are arrayed in two dimensions, wherein each of the plurality of the pixel groups includes: a first pixel suitable for sensing a first color signal that is color-separated through a first color filter; and a second pixel suitable for sensing a second color signal that is color-separated through a second color filter and has a longer wavelength than the first color signal, and a volume of a first color filter or a second color filter that is positioned in a peripheral area of the pixel array is different from a volume of a first color filter or a second color filter that is positioned in a central area of the pixel array.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of Korean Patent Application No. 10-2017-0035289, filed on Mar. 21, 2017, which is herein incorporated by reference in its entirety.

BACKGROUND

Exemplary embodiments of the present invention relate to a semiconductor device, and more particularly, to an image sensor capable of improving a color shading effect.

2. Description of the Related Art

An image sensor is a device capable of converting an optical image into electrical signals. An image sensor may include a plurality of pixels, for example, a plurality of red pixels, a plurality of green pixels, and a plurality of blue pixels, which are arrayed in a two-dimensional structure.

FIG. 1Ais a graph showing cut-off characteristics for each wavelength according to an incidence angle of an infrared cut-off filter, andFIG. 1Bis a graph showing light receiving rate for each color signal of incident light (IL) according to a position in a pixel array of an image sensor.

In general, red color signals have a wavelength ranging from approximately 620 nm to approximately 780 nm, green color signals have a wavelength ranging from approximately 490 nm to approximately 570 nm, and blue color signals have a wavelength ranging from approximately 450 nm to approximately 490 nm.

Referring toFIG. 1A, the red color signals show much difference in wavelength that is cut off by an infrared cut-off filter according to incidence angles. When the incidence angle of the red color signals is 0 degree (°), the infrared cut-off filter may cut off red color signals having a wavelength of approximately 680 nm or more and pass red color signals having a wavelength of less than approximately 680 nm. When the incidence angle of the red color signals is 45 degrees (°), the infrared cut-off filter may cut off red color signals having a wavelength of approximately 620 nm or more and pass red color signals having a wavelength of less than approximately 620 nm.

Referring toFIG. 1Bwhich is an example of an image sensor that includes a central area and a peripheral area, in which the light receiving rate of the red color signals is remarkably decreased due to the cut-off characteristics of the infrared cut-off filter being as close to the peripheral area where the incidence angle of light is greater than the incidence angle in the central area, compared with other color signals. Therefore, an imbalance occurs due to the difference in the light receiving rate, which causes a color shading effect.

SUMMARY

Embodiments of the present invention are directed to an image sensor with improved performance.

In accordance with an embodiment of the present invention, an image sensor includes: a pixel array where a plurality of pixel groups are arrayed in two dimensions, wherein each of the plurality of the pixel groups includes: a first pixel suitable for sensing a first color signal that is color-separated through a first color filter; and a second pixel suitable for sensing a second color signal that is color-separated through a second color filter and has a longer wavelength than the first color signal, and a volume of a first color filter or a second color filter that is positioned in a peripheral area of the pixel array is different from a volume of a first color filter or a second color filter that is positioned in a central area of the pixel array.

The first color filter positioned in the peripheral area of the pixel array may have a greater volume than the first color filter positioned in the central area of the pixel array.

The first color filter positioned in the peripheral area of the pixel array may be thicker than the first color filter positioned in the central area of the pixel array.

A volume of the second color filter positioned in the peripheral area of the pixel array may be the same as a volume of the second color filter positioned in the central area of the pixel array.

The image sensor may further include: a photoelectric conversion device that is formed in a lower portion of the first color filter; and a first buffer layer that is formed between the first color filter and the photoelectric conversion device, includes a concave and convex pattern contacting a lower surface of the first color filter that is positioned in the peripheral area, and includes a material having a refraction index which is different from a refraction index of the first color filter.

The image sensor may further include: a micro lens that is formed in an upper portion of the first color filter; and a second buffer layer that is formed between the first color filter and the micro lens, includes a concave and convex pattern contacting an upper surface of the first color filter that is positioned in the peripheral area, and includes a material having a refraction index which is different from a refraction index of the first color filter.

The peripheral area may include a first peripheral area where a first incident light enters at a first incidence angle and a second peripheral area where a second incident light enters at a second incidence angle, which is greater than the first incidence angle, and a volume of the first color filter that is formed in the second peripheral area may be greater than a volume of the first color filter that is formed in the first peripheral area.

The peripheral area may include a first peripheral area where a first incident light enters at a first incidence angle and a second peripheral area where a second incident light enters at a second incidence angle, which is greater than the first incidence angle, and a total volume of convex patterns of the concave and convex pattern formed in the second peripheral area may be smaller than a total volume of convex patterns of the concave and convex pattern formed in the first peripheral area, and a volume of the first color filter that is formed in the second peripheral area may be greater than a volume of the first color filter that is formed in the first peripheral area.

The second color filter positioned in the peripheral area of the pixel array may have a smaller volume than the second color filter positioned in the central area of the pixel array.

The second color filter positioned in the peripheral area of the pixel array may have a smaller volume than the second color filter positioned in the central area of the pixel array.

A volume of the first color filter positioned in the peripheral area of the pixel array may be the same as a volume of the first color filter positioned in the central area of the pixel array.

A thickness of the first color filter positioned in the peripheral area of the pixel array may be the same as a thickness of the first color filter positioned in the central area of the pixel array.

The image sensor may receive an incident light from an infrared cut-out filter.

In accordance with another embodiment of the present invention,

an image sensor includes: a pixel array having a plurality of pixel groups are arrayed in two dimensions, wherein each of the plurality of the pixel groups includes: a first pixel suitable for sensing a first color signal that is color-separated through a first color filter; and a buffer layer that includes a concave and convex pattern contacting an upper surface or a lower surface of a first color filter which is positioned in a peripheral area of the pixel array and is formed of a material having a refraction index different from a refraction index of a material of the first color filter, and a volume of the first color filter that is positioned in the peripheral area of the pixel array may be greater than a volume of a first color filter that is positioned in a central area of the pixel array.

A thickness of the first color filter positioned in the peripheral area of the pixel array may be greater than a thickness of the first color filter positioned in the central area of the pixel array.

The peripheral area may include a first peripheral area where a first incident light enters at a first incidence angle and a second peripheral area where a second incident light enters at a second incidence angle, which is greater than the first incidence angle, and a volume of the first color filter that is formed in the second peripheral area may be greater than a volume of the first color filter that is formed in the first peripheral area.

A total volume of convex pattern of the concave and convex pattern of the buffer layer contacting the upper surface or the lower surface of the first color filter that is positioned in the second peripheral area may be smaller than a total volume of convex pattern of the concave and convex pattern of the buffer layer formed in the first peripheral area.

The image sensor of claim15, wherein each of the plurality of the pixel groups may further include: a second pixel suitable for sensing a second color signal that is color-separated through a second color filter and has a longer wavelength than the first color signal, and a volume of a second color filter that is positioned in the peripheral area of the pixel array is the same as a volume of a second color filter that is positioned in a central area of the pixel array.

DETAILED DESCRIPTION

The following embodiments of the present invention provide an image sensor with improved performance. Herein, the image sensor with improved performance is an image sensor capable of improving a color shading effect.

Before the embodiments of the present invention are described, a conventional image sensor is described. An image sensor is a semiconductor device that converts an optical image into electrical signals. Image sensors may be largely divided into Charge-Coupled Device (CCD) image sensors and CMOS (Complementary Metal Oxide Semiconductor) image sensors. The CMOS image sensors are easy to operate and capable of adopting diverse scanning schemes, compared with the CCD image sensors. Also, since the CMOS image sensors are capable of integrating circuits for processing signals that are outputted from pixels into one chip through a CMOS fabrication process, they are favorable for miniaturizing product sizes and reducing production costs while consuming a small amount of power. For this reason, researchers and the industry are studying to develop CMOS image sensors. CMOS image sensors may also be divided into a front-side illumination type and a back-side illumination type. The technological concept of the present invention may be applied to both of the front-side illumination type and the back-side illumination type. It is known, however, that the back-side illumination type has superior operation characteristics for example, sensitivity, to the front-side illumination type. Therefore, the embodiments of the present invention, which will be described in detail hereafter, are described by taking a back-side illumination type of a CMOS image sensor as an example. Also, in order to increase the volume of a color filter in the embodiments of the present invention, the thickness of the color filter may be increased, or a concave and convex pattern may be formed in an upper portion and/or a lower portion of the color filter.

FIGS. 2A and 2Bare a cross-sectional view and a plane view illustrating an image sensor system in accordance with an embodiment of the present invention.

Referring toFIG. 2A, the image sensor system in accordance with the embodiment of the present invention may include an image sensor100, an infrared cut-off filter200, and a module lens300. The module lens300may pass incident light (IL) to the infrared cut-off filter200and the image sensor100. The infrared cut-off filter200may be disposed between the module lens300and the image sensor100, and may cut off infrared ray from the incident light (IL) while passing the remainder of the incident light (IL) to a micro lens (not shown) of the image sensor100. The image sensor100may convert the incident light (IL) that is received from the infrared cut-off filter200into electrical signals.

Referring toFIGS. 2A and 2B, the image sensor100may receive the incident light (IL) at an incidence angle (θ). The incidence angle (θ) is an angle between an optical axis (C) and the incident light (IL). The image sensor100in accordance with the embodiment of the present invention may include a plurality of peripheral areas, for example, first to fourth peripheral areas S1, S2, S3and S4, according to the distance from the optical axis (C). The first peripheral area S1closest to the optical axis (C) may be referred to as a central area of a pixel array of the image sensor100, and the second to fourth peripheral areas S2, S3and S4may be referred to as a peripheral area of the pixel array. The incidence angle (θ) may increase as it goes from the central area of the pixel array to the peripheral area of the pixel array. The incidence angle (θ) may have a minimal value (θmin) of approximately 0 degree at the optical axis (C) corresponding to the first peripheral area S1, and the incidence angle (θ) may have a maximal value (θmax) at an edge of the peripheral area of the pixel array corresponding to the fourth peripheral area S4.

FIG. 3is a plane view illustrating a portion of a color filter array of the image sensor100in accordance with an embodiment of the present invention. Specifically,FIG. 3is a plane view illustrating a plurality of color filter arrays110corresponding to the pixel array of the image sensor100illustrated inFIGS. 2A and 2B.

The image sensor100may include the color filter arrays110which corresponds to the pixel arrays. Each of the color filter arrays110may include a plurality of pixel groups110A that are arrayed in a two-dimensional structure. Each of the pixel groups110A may include a Bayer pattern where a first green color filter Gr and a red color filter R of a red line and a second green color filter Gb and a blue color filter B of a blue line are disposed. Particularly, the light receiving rate of red color signals may be decreased in the pixel arrays that are disposed in the peripheral areas S2, S3and S4of the image sensor100, compared with the light receiving rate of blue color signals and green color signals. Therefore, the light receiving rate of the plurality of color signals becomes imbalanced, which causes a color shading effect.

In order to reduce the color shading effect caused in the peripheral area of the pixel arrays of the image sensor100, the volume of the blue color filter B disposed in the peripheral area of each of the pixel arrays may be increased greater than the volume of the blue color filter B disposed in the central area of each of the pixel arrays. In this way, the light receiving rate of the blue color signals whose wavelength is shorter than that of the green or red color signals may be decreased in the peripheral area, thus improving the imbalance between the light receiving rate of the red color signals whose wavelength is longer, and the light receiving rate of the other color signals, such as the blue color signals and the green color signals. This will be described in detail later with reference toFIGS. 4A and 4B.

FIG. 4Ais a cross-sectional view illustrating an example of the image sensor100in accordance with a first embodiment of the present invention. Specifically,FIG. 4Ashows a cross-sectional view of the pixel group110A taken along a line A-A′ inFIG. 3.

Referring toFIG. 4A, each pixel group110A of the image sensor100may include a substrate20, a photoelectric conversion device30, a first buffer layer40, a color filter area50, a second buffer layer60, and a micro lens70.

An isolation layer (not shown) for isolating neighboring pixels from the photoelectric conversion device30may be formed over the substrate20including a plurality of pixels. The first buffer layer40, the color filter area50, the second buffer layer60, and the micro lens70may be formed over the substrate.

The substrate20may include a semiconductor substrate. The semiconductor substrate may be of a monocrystalline state, and the semiconductor substrate may include a silicon-containing material. That is, the substrate20may include a monocrystalline silicon-containing material. For example, the substrate20may be a bulk silicon substrate, or a Silicon-On-Insulator (SOI) substrate including a silicon epitaxial layer.

The photoelectric conversion device30may include a plurality of photoelectric conversion unit (not shown) that may vertically overlap with each other, and the photoelectric conversion device30may be formed to correspond to each of the color pixels. Each of the photoelectric conversion unit may be a photodiode which includes an N-type impurity region and a P-type impurity region. The photoelectric conversion device30may be formed in the substrate20by penetrating the substrate20. Also, the photoelectric conversion device30may be formed to contact one side of the substrate20and to be spaced apart from another side of the substrate20by a predetermined distance.

The first buffer layer40may be formed over the substrate20, and under the color filter area50, that is, formed between the substrate20and the color filter area50. The first buffer layer40may function as an anti-reflection layer with respect to the incident light (IL) as well as removing a step difference due to a predetermined structure that is formed in the substrate20. The first buffer layer40may be a single layer of one selected from a group including an oxide layer, a nitride layer, and an oxynitride layer, or a multi-layer where two or more of them are stacked.

The color filter area50may be formed over the first buffer layer40, and include a plurality of color filters Gr, R, Gb and B. The color filters Gr, R, Gb and B may be formed to respectively correspond to the photoelectric conversion device30, and provide the photoelectric conversion device30with the incident light (IL) of the wavelength band required by each pixel. That is, the photoelectric conversion unit of the photoelectric conversion device30may receive the incident light (IL) that is color-separated by the color filters Gr, R, Gb and B. The color filters Gr, R, Gb and B may be one single filter selected from a group including a red color filter R, green color filters Gr and Gb, a blue color filter B, a cyan filter, a yellow filter, a magenta filter, a white filter, a black filter, an infrared pass filter, an infrared cut-off filter, and a band pass filter which passes a particular wavelength band, or a multi-filter including two or more of them.

The second buffer layer60may be formed over the color filter area50, and the second buffer layer60may be formed of the same material as the material of the first buffer layer40. In this embodiment of the present invention, the second buffer layer60may be used as a planarization layer.

The micro lens70may be formed over the second buffer layer60, and concentrate the incident light (IL) entering from the infrared cut-off filter200illustrated inFIG. 2Ainto the photoelectric conversion device30through the color filter area50.

Referring toFIG. 4A, the volumes of the first green color filter Gr, the red color filter R, the second green color filter Gb, and the blue color filter B may be decided based on the wavelength of the color signals. For example, the volumes of the first green color filter Gr, the red color filter R, and the second green color filter Gb that are included in the central area S1may be the same as the volumes of the first green color filter Gr, the red color filter R, and the second green color filter Gb that are included in the peripheral areas S2, S3and S4.

However, in case of the blue color filter, the volume of a blue color filter50E_B included in the peripheral areas S2, S3and S4may be formed to be greater than the volume of a blue color filter50C_B included in the central area S1. As a result, the light receiving rate of the blue color signals in the peripheral areas S2, S3and S4may be decreased while maintaining the light receiving rate of the blue color signals in the central area S1. To increase the volume, the blue color filter50E_B included in the peripheral areas S2, S3and S4may be formed to be thicker than the blue color filter50C_B included in the central area S1.

The first buffer layer40may include a substrate20or a silicon epitaxial layer (not shown) in the inside of the substrate20. If the first buffer layer40is a silicon epitaxial layer (not shown) doped with a P-type impurity, the first buffer layer40may be able to suppress the generation of dark current on the surface of the substrate. Also, the first buffer layer40may be formed of a material having a different refraction index from the blue color filter B.

The embodiment of the present invention may be able to suppress a color shading effect that is caused due to imbalance between the light receiving rate of a red color whose wavelength becomes longer as it goes from the central area S1of each pixel array of the image sensor100to the peripheral areas S2, S3and S4, and the light receiving rate of the other color signals. To this end, the volume of the blue color filter50E_B of the peripheral areas S2, S3and S4may be formed greater than the volume of the blue color filter50C_B of the central area S1.

FIG. 4Bis a cross-sectional view illustrating the first buffer layer40and the blue color filter50E_B of the peripheral areas S2, S3and S4, according to a modified example of the image sensor ofFIG. 4A.

Referring toFIG. 4B, in which the peripheral areas S2, S3and S4are divided into the second peripheral area S2, the third peripheral area S3, and the fourth peripheral area S4according to the distance from the incident optical axis (C), first buffer layers40_S2,40_S3and40_S4and blue color filters50E_B_S2,50E_B_S3and50E_B_S4have different thicknesses for each area. Herein, the total thickness of the first buffer layer and the blue color filter in each of the second to fourth peripheral areas S2, S3and S4may be uniform regardless of the distance from the incident optical axis (C).

The volume of the blue color filter50E_B_S3of the third peripheral area S3may be greater than the volume of the blue color filter50E_B_S2of the second peripheral area S2, and the volume of the blue color filter50E_B_S4of the fourth peripheral area S4may be greater than the volume of the blue color filter50E_B_S3of the third peripheral area S3. The thickness of the first buffer layer40_S3of the third peripheral area S3may be thinner than the thickness of the first buffer layer40_S2of the second peripheral area S2, and the thickness of the first buffer layer40_S4of the fourth peripheral area S4may be thinner than the thickness of the first buffer layer40_S3of the third peripheral area S3.

According to the modified example illustrated inFIG. 4B, the blue color filters B of various volumes are provided according to the distance from the optical axis (C) of the incident light (IL). In this way, the light receiving rate of the blue color pixels positioned in the peripheral areas may be controlled diversely based on the distance from the optical axis (C) of the incident light (IL).

In order to decrease the color shading effect that is caused in the peripheral areas of the pixel arrays of the image sensor, a concave and convex pattern may be formed at a boundary surface between the blue color filters B positioned in the peripheral areas of the pixel arrays and at least one of the first buffer layer40and the second buffer layer60. Accordingly, the volume of the blue color filters B positioned in the peripheral areas may be greater than the volume of the blue color filters B positioned in the central area, so as to decrease the light receiving rate of blue color signals whose wavelength is shorter in the peripheral areas. In this way, the imbalance between the light receiving rate of the red color signals having longer wavelength, and the light receiving rate of the other color signals may be improved. This will be described below with reference toFIGS. 5A and 5BandFIGS. 6A and 6B.

FIG. 5Ais a cross-sectional view illustrating an example of an image sensor in accordance with a second embodiment of the present invention.FIG. 5Ashows a cross-sectional view of the pixel groups110A taken along a line A-A′ inFIG. 3. Since the constituent elements shown inFIG. 5Aare substantially the same as those shown inFIG. 4A, except for a concave and convex pattern BB, further description may be omitted.

Referring toFIG. 5A, the concave and convex pattern BB may be formed at a boundary surface between the first buffer layer40and blue color filters50E_B of the peripheral areas. That is, the first buffer layer40of the peripheral areas may have an upper portion having the concave and convex pattern BB, and the blue color filters50E_B of the peripheral areas may have a lower portion having the concave and convex pattern BB. The blue color filters50E_B of the peripheral areas may be formed to have a volume greater than that of blue color filters50C_B of the central area. Accordingly, the concave and convex pattern BB may be able to prevent color shading by increasing the volume of the blue color filters50E_B positioned in the peripheral areas more than the volume of the blue color filters50C_B positioned in the central area and thus decreasing the light receiving rate of the blue color signals in the peripheral areas.

Moreover, the boundary surface between the blue color filters50E_B and the first buffer layer40may have the concave and convex pattern BB so as to provide an effect of improving the optical characteristics based on the difference for example, refraction index and transmission rate, in the characteristics of the two materials. To this end, the first buffer layer40may be formed of a material having a different refraction index from that of the blue color filters50E_B.

If the first buffer layer40does not exist, the concave and convex pattern BB may be formed on the back side of the substrate20or a silicon epitaxial layer (not shown). If the first buffer layer40is a silicon epitaxial layer (not shown), the first buffer layer40may be a layer doped with a P-type impurity. In this case, generation of dark current may be suppressed on the back side of the substrate.

Particularly, a convex pattern of the upper portion of the first buffer layer40may contact a concave pattern of the lower portion of the blue color filter50E_B, and a concave pattern of the upper portion of the first buffer layer40may contact a convex pattern of the lower portion of the blue color filter50E_B. The blue color filter50E_B formed over the convex pattern of the upper portion of the first buffer layer40may be a low refraction index region having a lower refraction index, and the blue color filter50E_B formed over the concave pattern of the upper portion of the first buffer layer40may be a high refraction index region having a higher refraction index. However, the concept and spirit of the present invention are not limited to it, and the opposite may be included as an embodiment of the present invention according to the structures and materials of the first buffer layer40and the blue color filter50E_B.

The volume of the blue color filter50E_B may be controlled to be different according to the distance from the optical axis (C) by adjusting the gap between the convex patterns of the upper portion of the first buffer layer40according to the distance from the optical axis (C). This will be described later with reference toFIG. 5B.

FIG. 5Bis a cross-sectional view illustrating the first buffer layer40and the blue color filter50E_B of the peripheral areas S2, S3and S4, according to a modified example of the image sensor ofFIG. 5A.

Referring toFIG. 5B, when the peripheral areas S2, S3and S4are divided into the second peripheral area S2, the third peripheral area S3, and the fourth peripheral area S4according to the distance from the optical axis (C) of the incident light (IL), concave and convex patterns may be formed at boundary surfaces between first buffer layers40_S2,40_S3and40_S4and blue color filters50E_B_S2,50E_B_S3and50E_B_S4, and may have a different gap between the convex patterns of the upper portions of the first buffer layers40_S2,40_S3and40_S4. Herein, the total thickness of the first buffer layer and the blue color filter may be uniform regardless of the distance from the incident optical axis (C).

A gap G3between the convex patterns of the first buffer layer40_S3in the third peripheral area S3may be wider than a gap G2between the convex patterns of the first buffer layer40_S2in the second peripheral area S2. A gap G4between the convex patterns of the first buffer layer40_S4in the fourth peripheral area S4may be wider than the gap G3of the third peripheral area S3. The volume of the first buffer layer40_S3having the gap G3in the third peripheral area S3may be smaller than the volume of the first buffer layer40_S2having the gap G2in the second peripheral area S2. The volume of the first buffer layer40_S4having the gap G4in the fourth peripheral area S4may be smaller than the volume of the first buffer layer40_S3having the gap G3in the third peripheral area S3. The volume of the blue color filter50E_B_S3of the third peripheral area S3may be greater than the volume of the blue color filter50E_B_S2of the second peripheral area S2. The volume of the blue color filter50E_B_S4of the fourth peripheral area S4may be greater than the volume of the blue color filter50E_B_S3of the third peripheral area S3.

That is, in the embodiment of the present invention, the light receiving rate of the blue color signals may be controlled differently according to the area by controlling the volume of the blue color filter50E_B differently according to the peripheral area S2, S3or S4.

FIG. 6Ais a cross-sectional view illustrating an example of an image sensor in accordance with a third embodiment of the present invention.FIG. 6Ashows a cross-sectional view of the pixel groups110A taken along a line A-A′ inFIG. 3. Since the constituent elements shown inFIG. 6Aare substantially the same as those shown inFIG. 4A, except for a concave and convex pattern CC, further description may be omitted.

Referring toFIG. 6A, the concave and convex pattern CC may be formed at a boundary surface between the second buffer layer60and the blue color filters50E_B of the peripheral areas S2, S3and S4. That is, the second buffer layer60of the peripheral areas may have a lower portion having the concave and convex pattern CC, and the blue color filters50E_B of the peripheral areas may have an upper portion having the concave and convex pattern CC. At this time, the blue color filters50E_B of the peripheral areas may be formed to have a volume greater than that of blue color filters50C_B of the central area. Accordingly, the concave and convex pattern CC may be able to prevent color shading by increasing the volume of the blue color filters50E_B positioned in the peripheral areas and thus decreasing the light receiving rate of the blue color signals in the peripheral areas.

Moreover, the boundary surface between the blue color filters50E_B and the second buffer layer60may have the concave and convex pattern CC so as to provide an effect for improving the optical characteristics based on the difference for example, refraction index and transmission rate, in the characteristics of the two materials.

FIG. 6Bis a cross-sectional view illustrating the blue color filter50E_B and the second buffer layer60of the peripheral areas S2, S3and S4, according to a modified example of the image sensor ofFIG. 6A.

Referring toFIG. 68B, when the peripheral areas S2, S3and S4are divided into the second peripheral area S2, the third peripheral area S3, and the fourth peripheral area S4according to the distance from the optical axis (C) of the incident light (IL), the concave and convex pattern CC may be formed at boundary surfaces between blue color filters50E_B_S2,50E_B_S3and50E_B_S4and second buffer layers60_S2,60_S3and60_S4, and may have a different gap between the convex patterns of the lower portions of the second buffer layers60_S2,60_S3and60_S4. Herein, the total thickness of the second buffer layer60and the blue color filter B may be uniform regardless of the distance from the incident optical axis (C).

A gap G3between the convex patterns of the second buffer layer60_S3in the third peripheral area S3may be wider than a gap G2between the convex patterns of the second buffer layer60_S2in the second peripheral area S2. A gap G4between the convex patterns of the second buffer layer60_S4in the fourth peripheral area S4may be wider than the gap G3of the third peripheral area S3. The volume of the second buffer layer60_S3having the gap G3in the third peripheral area S3may be smaller than the volume of the second buffer layer60_S2having the gap G2in the second peripheral area S2. The volume of the second buffer layer60_S4having the gap G4in the fourth peripheral area S4may be smaller than the volume of the second buffer layer60_S3having the gap G3in the third peripheral area S3. The volume of the blue color filter50E_B_S3of the third peripheral area S3may be greater than the volume of the blue color filter50E_B_S2of the second peripheral area S2. The volume of the blue color filter50E_B_S4of the fourth peripheral area S4may be greater than the volume of the blue color filter50E_B_S3of the third peripheral area S3. That is, in the embodiment of the present invention, the light receiving rate of the blue color signals positioned in the peripheral areas may be controlled differently according to the distance from the optical axis (C) by controlling the volume of the blue color filter50E_B differently according to the peripheral area S2, S3or S4.

FIGS. 7A and 7Bare cross-sectional views illustrating an example of an image sensor in accordance with a fourth embodiment of the present invention. In a peripheral area where light is received at a greater incidence angle than in a central area, a wavelength of red color signals becomes shorter, decreasing the light receiving rate remarkably.

In the fourth embodiment of the present invention illustrated inFIGS. 7A and 7B, in order to prevent the light receiving rate of the red color signals from decreasing remarkably, compared with green color signals and blue color signals, the volume of a red color filter50E_R of the peripheral areas S2, S3and S4is smaller than the volume of a red color filter50C_R of the central area S1may be reduced. Thus, the light receiving rate of the red color signals may be increased up to the light receiving rate of the green color signals and the blue color signals, so as to prevent a color shading effect caused in the peripheral areas S2, S3and S4of the image sensor. In this case, the volume of the red color filter50E_R may be reduced by increasing the volume of the first buffer layer40of the peripheral areas S2, S3and S4as illustrated inFIG. 7A, or by increasing the volume of the second buffer layer60of the peripheral areas S2, S3and S4as illustrated inFIG. 7B.

Referring toFIG. 7A, the red color filter50E_R of the peripheral areas S2, S3and S4may have a recessed lower portion by a certain depth, compared with green color filters Gr and Gb and a blue color filter B. Referring toFIG. 7B, the red color filter50E_R of the peripheral areas S2, S3and S4may have a recessed upper portion by a certain depth, compared with the green color filters Gr and Gb and the blue color filter B. Thus, referring toFIGS. 7A and 7B, the red color filter50E_R of the peripheral areas S2, S3and S4may have a smaller thickness than the red color filter50C_R of the central area S1while the green color filters Gr and Gb and the blue color filter B of the peripheral areas S2, S3and S4may have the same thickness as the red color filter50C_R of the central area S1.

According to the embodiments of the present invention, images with suppressed color shading may be obtained in the peripheral area of an image sensor by controlling the volume or thickness of a color filter in the peripheral area to be different from the volume or thickness of the color filter in the central area.

According to the embodiments of the present invention, an image with effectively suppressed color shading may be obtained by controlling the volumes of color filters that are formed in a plurality of peripheral areas, which is distinguished according to the distance from an optical axis, and which are different from each other.