KR100278983B1 - Solid state imaging device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid state image pickup device, and in order to reduce the nonuniformity caused by light having a specific focal length passing through each color filter layer having a different focal length, the height of the underlying layer of the color filter layer is adjusted thereon. Place each of the color filter layers and the microlenses to be formed at appropriate heights, or adjust the height of the second flattening layer between the color filters and the microlenses to position each microlens formed thereon at the appropriate heights, By forming each microlens having a predetermined radius of curvature and adjusting the focal length of each light, each light is focused on the PD, which is the light receiving part, and is focused on the microlens and passes through each color filter layer. All of the lights in the PD are equally focused on the PD to improve color reproduction and color balance. There.

Description

Solid state imaging device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid state image pickup device, and more particularly, to a solid state image pickup device in which light is focused on a PD by adjusting a distance between a microlens and a photo diode (hereinafter referred to as PD) by a focal length of light. .

A solid state image pickup device generates electrons by light, arranges a charge coupled device so as to have a directionality, and detects the signal charges transmitted thereby. In other words, it is a device that transfers the electric charges excited by light through a directional CCD array and then amplifies the signal to obtain an output signal. As shown in FIG. 1, the solid state image pickup device, a device for converting an image signal into an electrical signal, includes a PD array unit formed of unit cells formed of PD and a vertical charge coupled device (VCCD), and a horizontal charge coupled device (HCCD). ), And a signal detection unit. The signal charges generated and accumulated in the PD are sequentially transferred to the VCCD and the HCCD and output through the signal detector.

2A to 2D are views for explaining a manufacturing process diagram of a solid state image pickup device according to the related art, and schematically illustrate some cross-sections of a PD array unit.

Referring to FIG. 2A, a substrate 200 in which a PD for generating signal charges and a VCCD, which is a charge transfer region for transferring signal charges generated in the PD in a vertical direction, are alternately formed according to the intensity of light incident by a conventional process. After the insulating layer 21 is formed on the exposed front surface of the Ns, a light shielding layer 22 is formed on the VCCD to prevent the VCCD from being injected from the light. Thereafter, a protective film 23 for protecting such a solid state image pickup device is formed.

Referring to FIG. 2B, a first planarization layer 25 is formed to cover the exposed entire surface. Subsequently, color filter layers 26-1, 26-2 and 26-3 are formed on the first planarization layer 25, respectively. That is, a first resin layer is formed on the first planarization layer 25, and the first resin layer 26-1, for example, a RED layer is formed by dyeing and fixing the first resin layer in a first color. By repeating the above steps, the second and third color filter layers 26-2 and 26-3, for example, the GREEN layer and the BLUE layer, are formed on the first planarization layer 25, respectively, to thereby form the first. Three color filter layers 26-1, 26-2 and 26-3 are sequentially formed on the planarization layer 25.

Referring to FIG. 2C, after the process of forming the color filter layer is completed, the second planarization layer 27 is formed on the first planarization layer 25 including the color filter layer to planarize the substrate again. Thereafter, a microlens material, which is an acrylic resin, is coated on the second planarization layer 27, and then the applied microlens material is photo-etched to form a microlens material layer positioned on each PD. . Subsequently, a thermal reflow process is performed on the microlens material layer to form a convex lens-type microlens 28.

Thereafter, a subsequent process is performed to complete the manufacture of the solid state imaging device.

The operation of the solid state image pickup device manufactured as described above will be described with reference to FIG. 3.

The light focused by the microlens 28 is selectively transmitted through the color filter layer. That is, the first color filter layer 26-1 of the color filter layers selectively transmits only the light for the first color among the light focused by the microlens 28, and applies the light to the PD corresponding to the first color among the plurality of PDs. The second color filter layer 26-2 selectively transmits light for the second color and applies it to the PD corresponding to the second color, and the third color filter layer 26-3 selectively transmits light for the third color. To the PD corresponding to the third color. Light incident on each PD is photoelectrically converted to generate signal charges, and the charges generated by the PD are transmitted to the VCCD by a signal transmission operation of a conventional solid-state image pickup device and then to the HCCD (not shown in the drawing). . Subsequently, the signal charge transmitted to the HCCD is sensed by a voltage by floating diffusion at the end of the device, and then amplified by an amplifier (not shown) to be transmitted to the peripheral circuit.

As such, the light collected by the microlens passes through the color filter layer, and only light of a specific wavelength band corresponding to the predetermined color filter layer on each pixel is selectively transmitted. By the way, each light passing through the color filters has a specific wavelength and therefore has a unique refractive index. Thus, the position of the focal point that is refracted and focused is different for each light. When the first color filter layer 26-1 is RED, the second color filter layer 26-2 is GREEN, and the third color filter layer 26-3 is BLUE, the focal length of the light transmitted through the second color filter layer In reference to, the focal length is long from the lens because the refractive index of the light passing through the first color filter layer is the smallest, and the focal length is short because the light passing through the third color filter layer is large. Therefore, as shown in the drawing, the light passing through each color filter layer does not focus correctly on the PD. As a result, the intensity of light that is sensitive and converted in the PD is different, resulting in poor color reproduction and color balance.

The present invention aims to precisely focus the light on the PD by adjusting the light path to the focal length of the light in order to reduce the nonuniformity caused by the light having a different focal length from the specific wavelength band passing through each color filter layer. .

The present invention adjusts the height of the first planarization layer, which is the underlying layer of the color filter layer, and places each of the color filter layers and the microlenses formed thereon at an appropriate height so that each light having a different focal length is focused on the PD receiving part. It is to be concluded.

The present invention adjusts the height of the second flattening layer between the color filter and the microlens and positions each microlens formed thereon at an appropriate height so that each light having a different focal length is focused on the PD having the light receiving portion. I want to.

The present invention is to form a microlens having a predetermined radius of curvature to adjust the focal length of each light, so that each light is focused on the PD, the light receiving portion.

The present invention provides a semiconductor substrate comprising first to third photoelectric conversion regions in which first to third light are focused to generate signal charges, and charge transfer regions alternately arranged between the photoelectric conversion regions, and the semiconductors. An insulating layer covering the substrate, a color filter layer of first to third colors formed at a position corresponding to the first to third light conversion regions on the insulating layer, and a color filter layer of the first to third colors In the solid-state image pickup device including the first to third microlenses formed at the position where the first micro lens and the third microlens are formed, the first to third spacing between the first to third photoelectric conversion region and the first to the third microlens are It is characterized by being adjusted according to the focal length of the first to third lights. In this case, the insulating layer may have a first to third stepped portion formed on the upper portion so as to adjust the first to third intervals. In addition, a stepped layer for adjusting the first to third intervals may be formed between the first to third color filter layers and the first to third microlenses.

The present invention provides a semiconductor substrate comprising first to third photoelectric conversion regions in which first to third light are focused to generate signal charges, and charge transfer regions alternately arranged between the photoelectric conversion regions, and the semiconductors. A first planarization layer covering the substrate, a color filter layer of first to third colors formed at a position corresponding to the first to third light conversion regions on the first planarization layer, and the first to third color filter layers; And a second planarization layer covering the entire exposed substrate, and first to third microlenses formed on the second planarization layer at positions corresponding to the color filter layers of the first inner third color. The first to third microlenses may have first to third curvature radii according to first to third focal lengths of the first to third lights.

1 is a general plan view of a solid state imaging device

2A to 2C are manufacturing process diagrams of a solid state image pickup device according to the related art.

3 is a view for explaining a path of light in a conventional solid state image pickup device.

4 is a cross-sectional view of the solid state image pickup device according to the first embodiment of the present invention.

5A to 5D are manufacturing process diagrams of the solid state image pickup device shown in FIG.

6 is a cross-sectional view of the solid state image pickup device according to the second embodiment of the present invention.

7A to 7D are manufacturing process diagrams of the solid state image pickup device shown in FIG.

8 is a cross-sectional view of a solid state image pickup device according to a third embodiment of the present invention.

9A to 9D are manufacturing process diagrams of the solid state image pickup device shown in FIG.

In the embodiments of the present invention described below, for convenience, the first color filter layer is a color that transmits the first light having the first focal length, and the second color filter layer is a color that transmits the second light having the second focal length, The third color filter layer is formed with a color that transmits third light having a third focal length (first focal length> second focal length> third focal length) as an example.

4 is a view for explaining the first embodiment of the solid state image pickup device according to the present invention, and shows a part of the cross-sectional structure of the PD array unit.

The insulating layer 41 is exposed on the exposed front surface of the substrate 400 on which the PD for generating signal charge and the VCCD, which is a charge transfer region for transferring signal charge generated in the PD in a vertical direction, are alternately formed according to the intensity of incident light. Is formed, a light shielding layer 42 for preventing the VCCD from being injected from light is formed on the VCCD, and a protective film 43 for protecting such a substrate is formed. The stepped layer 45 is formed thereon, and the color filter layers 46-1, 46-2, 46-3 and the microlens 48 are formed on the planarization layer 45. The stepped layer 45 has a stepped portion so that each color filter layer can be located at a different height. That is, the first color filter layer 46-1 has a height of a1 from the PD in the first step portion, and the second color filter layer 46-3 has a height of a2 in the second step portion with the third color. The filter layer 46-3 is located in the third stepped portion having the height of a3. At this time, the heights of the first, second and third stepped portions are determined to the extent that the lights can focus on the respective PDs in consideration of the focal lengths of the respective lights passing through the color filter. Therefore, each of the lights passing through the microlens 48 and the color filter has a focus on the PD appropriately located at the respective focal length, thereby making it possible to make the light conversion uniform.

5A to 5D show a manufacturing process diagram of the solid state image pickup device according to the first embodiment of the present invention described above.

Referring to FIG. 5A, a substrate 400 alternately formed with a PD for generating signal charges and a VCCD, which is a charge transfer region for transferring signal charges generated in the PD in a vertical direction, according to the intensity of light incident by a conventional process. After the insulating layer 41 is formed on the exposed front surface of the Ns, a light shielding layer 42 is formed on the VCCD to prevent the VCCD from being injected from the light. Thereafter, a protective film 43 for protecting such a solid state image pickup device is formed, and a planarization layer 45L covering the entire exposed surface is formed. At this time, the planarization layer 45L is formed to be spaced about a1 from the PD in consideration of the first focal length of the first light.

Referring to FIG. 5B, an etching process is performed on the planarization layer 45L a predetermined number of times to form a stepped layer 45 having stepped parts having different heights. That is, the first stepped portion A1 having the height of a1, the second stepped portion A2 having the height of a2, and the third stepped portion A3 having the height of a3 are formed from the PD. In this process, after forming the first etching blocking film on the planarization layer on the first PD (PD1), the planarization layer is etched to a thickness of [a2-a1] using the mask as a mask. Thereafter, after removing the first photo film, a second photo film is formed on the planarization layer on the first PD (PD1) and the second PD (PD2), and then the planarization layer etched with the mask is [a3-a2] thick. Etch with. Thereafter, the second photo film is also removed. As a result of the two etching processes, as shown in the drawing, the planarization layer becomes a stepped layer 45 in which the first stepped part A1, the second stepped part A2, and the third stepped part A3 are defined.

Referring to FIG. 5C, the first, second, and third color filter layers 46-1, 46-2, and 46-3 may be disposed on the first, second, and third stepped portions of the stepped layer 45. Form each. That is, the first resin layer is formed on the first stepped portion of the stepped layer 45, and the first resin layer 46-1 is formed by dyeing and fixing the first resin layer in the first color. By repeating the above steps, the second and third color filter layers 46-2 and 46-3 are formed on the second and third stepped portions of the stepped layer 45, respectively, so that the stepped layer 45 is formed. Three color filter layers 46-1, 46-2, 46-3 are sequentially formed on the substrate.

Referring to FIG. 5D, after the process of forming the color filter layer is completed, an acrylic microlens material is coated on the stepped layer including the first, second, and third color filter layers, and then the applied microlens material is applied. Photolithography forms a microlens material layer on the first, second, and third color filter layers 46-1, 46-2, and 46-3, respectively. Subsequently, a thermal reflow process is performed on the microlens material layer to form a convex lens-type microlens 48.

Thereafter, a subsequent process is performed to complete the manufacture of the solid state imaging device.

As mentioned, in order to focus the light on each PD, it is necessary to form the distance between the microlens and the PD by the focal length. In the first embodiment of the present invention, the planarization layer is formed on the passivation layer, and the gap between the microlens and the PD is controlled by forming a stepped portion having different heights according to the focal length of the light on the planarization layer.

The present invention can be variously implemented using the above contents, and the second and third embodiments of the present invention using the same will be described below.

FIG. 6 is a view for explaining a second embodiment of the solid state image pickup device according to the present invention, showing a part of the cross-sectional structure of the cell array unit. Unlike the first embodiment, the second embodiment forms a color filter layer on the first planarization layer, forms a second planarization layer thereon, and then forms the second planarization layer as a stepped layer by etching. After that, a microlens is formed. That is, the distance between the microlens and the PD to be determined by the focal length is adjusted by the second planarization layer.

A plurality of charge transfer VCCDs and a plurality of photoelectric conversion PDs corresponding to the first to third colors between the VCCDs are alternately arranged on the substrate 600 at predetermined intervals. A light shielding layer 62 covering the VCCD is formed on the insulating layer 61, and a protective film 63 is formed. A first planarization layer 64 is formed on the passivation layer 63, and color filter layers 65-1, 65-2, and 65-3 are formed on the first planarization layer 64. . Then, a stepped layer 66 and a microlens 68 are formed thereon, which allows the microlenses to be positioned at different heights. Thus, the distance between the microlens and the PD may be adjusted according to the respective light by the stepped layer 66 on the first planarization layer 64. As a result, as shown in the figure, lights having different focal lengths can be properly focused on each PD.

7A to 7D show manufacturing process drawings of the solid state image pickup device according to the second embodiment of the present invention described above.

Referring to FIG. 7A, an insulating layer 61 is disposed on an exposed front surface of a substrate 600 in which PD for generating signal charge and VCCD, which is a charge transfer region, are alternately formed according to the intensity of light incident by a conventional process. After the formation, the light shielding layer 62 is formed on the VCCD, and the protective film 63 is formed.

Referring to FIG. 7B, after the first planarization layer 64 is formed to cover the exposed entire surface, the color filter layer 65-1 may be formed by a conventional process as mentioned on the first planarization layer 64. (65-2) and (65-3) are formed, respectively. Subsequently, a second planarization layer 66L covering the color filter layer and the exposed entire surface is formed to a thickness of b1. At this time, the thickness of the second planarization layer 66L is formed to be spaced from b to PD in consideration of the first focal length of the first light.

Referring to FIG. 7C, an etching process is performed on the second planarization layer 66L a predetermined number of times to form a stepped layer 66 having stepped parts having different heights. That is, the first stepped portion B1 having the height of b1, the second stepped portion B2 having the height of b2, and the third stepped portion B3 having the height of b3 are formed from the PD. In this process, after forming the first etching blocking film on the second planarization layer on the first PD (PD1), the planarization layer is etched to a thickness of [b2-b1] as a mask. Thereafter, after removing the first photo film, a second photo film is formed on the planarization layer on the first PD (PD1) and the second PD (PD2), and then the planarization layer etched with the mask is [b3-b2] thick. Etch with. Thereafter, the second photo film is also removed. As a result of the two etching processes, the planarization layer becomes a stepped layer 66 in which the first stepped part B1, the second stepped part B2, and the third stepped part B3 are defined as shown in the drawing.

Referring to FIG. 7D, the microlenses 68 are formed on the first, second, and third stepped portions of the stepped layer 66 corresponding to the respective PDs by the conventional process mentioned above.

Thereafter, a subsequent process is performed to complete the manufacture of the solid state imaging device.

FIG. 8 is a view for explaining a third embodiment of the solid state image pickup device according to the present invention, showing a part of the cross-sectional structure of the cell array unit. Unlike the first and second embodiments, the third embodiment forms microlenses having different curvature radii, respectively, thereby adjusting the focal length of the light according to the distance between the defined microlenses and the PD.

As for the cross-sectional structure, VCCD, PD for photoelectric conversion, insulating layer 82, light shielding layer 83 covering VCCD, protective film 84, and the like are formed on a substrate 800, as in the conventional art. The first planarization layer 84 is formed thereon, and the color filter layers 85-1, 85-2, and 85-3 are formed on the first planarization layer 84. The second planarization layer 86 and the microlenses 88-1, 88-2, and 88-3 are formed thereon, respectively. However, the microlens in this embodiment adjusts its radius of curvature so that each transmitted light can be refracted at a predetermined rate so as to focus on the PD. When referring to the second focal length of the second light, the first focal length of the first light should be reduced and the third focal length of the third light needs to be increased. Therefore, a microlens having a large radius of curvature is formed at a portion where the first light is focused, and a microlens having a small radius of curvature is formed at a portion where the third light is focused. That is, the focal length of the light is adjusted by the radius of curvature of the microlenses.

9A to 9D show a manufacturing process diagram of the solid state image pickup device according to the third embodiment of the present invention described above.

Referring to FIG. 9A, an insulating layer 81 is disposed on an exposed front surface of a substrate 800 in which PD for generating signal charge and VCCD, which are charge transfer regions, are alternately formed according to the intensity of light incident by a conventional process. After forming, the light shielding layer 82 is formed on the VCCD, and a protective film 83 is formed.

Referring to FIG. 9B, the first planarization layer 84 is formed on the entire exposed substrate, and the color filter layers 85-1, 85-2, 85 are formed on the first planarization layer 86 by a conventional process. -3) are formed respectively.

Referring to FIG. 9C, the entire surface of the exposed substrate is formed by forming the second planarization layer 86. The microlens material layers 88a, 88b, and 88c are formed on the second planarization layer 86 to correspond to the color filter layers, respectively. That is, after applying the microlens material, which is an acrylic resin, on the second planarization layer 86, the coated microlens material is patterned to correspond to the first color filter layer 85-1 corresponding to the first PD (PD1). The first microlens material layer 88a having a thickness of c1 is formed on the upper side of the? Subsequently, the process of coating and etching the microlens material is repeated to form second and third microlens material layers 88b and 88c having thicknesses of c2 and c3, respectively.

Referring to FIG. 9D, each microlens 88-1, 88-2, and 88-3 in which a curvature radius is appropriately adjusted by performing a thermal reflow process on each microlens material layer. Is formed on the second planarization layer 86.

Thereafter, a subsequent process is performed to complete the manufacture of the solid state imaging device.

The solid state image pickup device according to the present invention has an improved structure in which each of the lights focused on the microlenses and passing through the respective color filter layers is equally focused on the PD. This is because the PD's role is that light enters and generates a corresponding charge, and the PD receives light of the same intensity in the PD of each pixel, thereby improving color reproduction and color balance.

Claims (5)

A semiconductor substrate comprising first to third photoelectric conversion regions in which first to third light are focused to generate signal charges, and charge transfer regions formed to be alternately arranged between the photoelectric conversion regions, and covering the semiconductor substrate; An insulating layer, a color filter layer of first to third colors formed on a position corresponding to the first to third light conversion regions on the insulating layer, and a position corresponding to the color filter layer of the first to third colors; In the solid-state imaging device comprising the first to third microlenses formed, And the first to third intervals between the first to third photoelectric conversion regions and the first to third microlenses are adjusted according to a focal length of the first to third lights. The method according to claim 1, The insulating layer is a solid-state imaging device, characterized in that the first to third stepped portion is formed on the upper portion so as to adjust the first to third intervals. The method according to claim 1 or 2, And the first to third microlenses are positioned on an upper end of the first to third color filter layers. The method according to claim 1, And a stepped layer for adjusting the first to third intervals between the first to third color filter layers and the first to third microlenses. The method according to claim 1 or 4, And the insulating layer is a planarization layer covering the semiconductor substrate evenly.

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