KR20020091985A - Method for forming micro lens of solid state image sensor - Google Patents

Abstract

PURPOSE: A method for forming a microlens of a solid state imaging device is provided to reduce ineffective light transmitted to the remaining region except for a light receiving portion by forming the microlens of a uniform shape on the solid state imaging device. CONSTITUTION: A planarization layer is formed on a semiconductor substrate(10) including a color filter(12). A photoresist pattern is formed on the planarization layer in order to cover a light receiving portion(11) of an optical diode. An auxiliary lens pattern(24) having a projection portion(25) is formed on an upper portion of the light receiving portion(11) by etching the planarization layer. A shape and a curvature of the next microlens are determined according to height of the projection portion(25). A transparent layer(26) is formed on a whole surface of the above structure. A microlens(28) is formed on an upper portion of the light receiving portion(11).

Description

METHOOD FOR FORMING MICRO LENS OF SOLID STATE IMAGE SENSOR}

The present invention relates to a method of manufacturing a solid state image pickup device, and more particularly, to a method of forming a micro lens of a solid state image pickup device.

The solid state imaging device refers to a device that receives an optical image of a subject and converts the signal into an electrical signal in time series using a television scanning principle. The solid state image pickup device obtains an image by focusing light incident through a micro lens and a color filter onto a light receiving unit of a photodiode. Therefore, in order to obtain an image of excellent quality, a process capable of forming a structure that minimizes light other than effective light incident on a micro lens and a light receiving unit having a uniform focusing capability is required.

1 and 2 are process cross-sectional views for explaining a conventional method for manufacturing a solid state image pickup device.

As shown in FIG. 1, in the conventional solid state imaging device, an insulating film is formed on a semiconductor substrate 10 on which a cell array including a photodiode and a charge transfer layer is formed, and an upper portion of the light receiving unit of the optical pickup device is formed on the insulating film. The covering color filter 12 is formed. Subsequently, a planarization layer 14 for protecting the color filter 12 and adjusting the effective focal length is formed on the entire surface of the resultant product on which the color filter 12 is formed.

Subsequently, a photoresist pattern 22 covering the upper portion of the light receiving portion is formed on the planarization layer 14. Since the photoresist pattern 22 includes a photosensitive agent, the chemical bond structure is modified when exposed to light. Therefore, a bleaching process is performed to make the photoresist pattern 22 into a light saturation state so as not to react to light. The photoresist pattern 22 is flowed by applying a heat treatment process to the resultant product on which the photoresist pattern 22 is formed. As a result, as shown in FIG. 8, the photoresist pattern 22 is fluidized to form a convex lens type micro lens 18 on the planarization layer 14 by surface tension.

As described above, the prior art forms a convex lens using surface tension by fluidizing a photoresist pattern by thermal energy. Therefore, since a difference in thermal energy applied to each region of the semiconductor substrate occurs during the heat treatment process, the microlenses of the solid state imaging device may not be uniformly formed. In addition, a difference in the interfacial tension between the fluidized photoresist and the planarization layer may occur due to contamination of the planarization layer surface or defects in molecular structure. For this reason, there is a problem in that the photoresist does not flow uniformly and the microlenses are not formed in a uniform form. As described above, if the microlenses are not formed uniformly on the entire surface of the solid state image pickup device, the light collected by the optical pickup device is uneven, so that image quality of excellent quality cannot be obtained.

Another problem is the interference of the effective light due to the scattering of light incident on the lens and the area between the lens. As shown in FIG. 3, in the solid state image pickup device using the prior art, there are regions spaced at regular intervals between the lens due to the non-uniformity of the photoresist flow. Therefore, the light incident to the spaced apart area is reflected and scattered in a region other than the light receiving unit, and the scattered light causes interference with the effective light incident through the microlens. For this reason, there is a problem that the solid state image pickup device cannot obtain a uniform image of high quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a micro lens having a uniform shape in a solid state image pickup device, in order to solve the above problems of the prior art. In addition, the present invention provides a method for forming a microlens that can significantly reduce the ineffective light incident on a region other than the light receiving unit because there is no separation distance between the microlens and the microlens.

1 and 2 are process cross-sectional views for explaining a conventional method for manufacturing a solid state image pickup device.

3 is a view for explaining the problem of the conventional solid-state image pickup device.

4 to 6 are process cross-sectional views illustrating a method of manufacturing a solid state image pickup device according to a preferred embodiment of the present invention.

7 is a view for explaining the effect of the solid state image pickup device according to an embodiment of the present invention.

※ Explanation of code about main part of drawing ※

10 semiconductor substrate 12 color filter

14 planarization layer 16, 22 photoresist pattern

18, 28: microlens 24: spare microlens pattern

25: protrusion 26: transparent film

In order to achieve the above object, the present invention forms a planarization layer on the entire surface of the semiconductor substrate on which the substructure including the photodiode is formed, and a photoresist pattern covering the upper portion of the photodiode on the planarization layer. Subsequently, the planarization layer is etched using the photoresist pattern as an etching mask to form a lens auxiliary pattern having protrusions on the photodiode. Subsequently, after the photoresist pattern is removed, a microlens is formed by forming a transparent film surrounding the protrusion on the entire surface of the resultant body in which the lens auxiliary pattern is formed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed subject matter is thorough and complete, and that the scope of the invention to those skilled in the art will fully convey. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Also, if it is mentioned that the layer is on another layer or substrate, it may be formed directly on the other layer or substrate or a third layer may be interposed therebetween. Like numbers refer to like elements throughout.

4 to 6 are process cross-sectional views illustrating a method of forming a micro lens of a solid state image pickup device according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the planarization layer 14 is formed on the entire surface of the semiconductor substrate 10 on which the photodiode, the charge transfer layer, and the color filter 12 are formed. A photoresist pattern 22 is formed on the planarization layer 14 to cover the top surface of the photodiode 11. The color filter 12 is dyed to selectively transmit light having a characteristic wavelength in incident light. The color filter is a conventional method, and a flattened semiconductor substrate on which a cell array including the photodiode and the charge transfer layer is formed with an insulating film, and a dyed photoresist covering the upper portion of the light receiving portion 11 on the insulating film, respectively. Can be formed. The planarization layer 14 is a material film having excellent light transmittance, and is preferably formed using, for example, polyimide resin or polyacrylic resin.

Referring to FIG. 5, using the photoresist pattern 22 as an etch mask, the planarization layer 14 is etched to form a lens auxiliary pattern 24 having a protrusion 25 formed on the light receiving part 11. Form. At this time, the shape and curvature of the micro lens (28 of FIG. 6) to be formed in a later process are determined according to the height of the protrusion 25. Thus, by adjusting the etching amount of the planarization layer 14, it is possible to form a micro lens of a desired shape.

Referring to FIG. 6, a transparent film 26 surrounding the protrusion 25 is formed on the entire surface of the resultant body in which the lens auxiliary pattern 24 is formed. As a result, a microlens 28 having a constant curvature is formed on the light receiving portion 11. The transparent film 26 is a material film having excellent light transmittance, and may be formed of a photoresist, polyimide resin, or polyacrylic resin. When the transparent film 26 is formed of a photoresist, after the photoresist is formed, the photoresist is placed in a light saturation state in order to prevent deformation of the microlenses by a photoactive compound in the photoresist. It is desirable to carry out a bleaching process to make. However, in the microlens of the present invention, the transparent film 26 may be formed of polyimide resin or polyacrylic resin to omit the bleaching process.

The microlenses according to the present invention may be formed of a patterned protrusion part using a photo process and a transparent film surrounding the protrusion part, thereby forming a uniform microlens as compared with a conventional microlens using a heat treatment process.

7 is a schematic cross-sectional view for explaining a micro lens of a solid state image pickup device according to the present invention.

As shown in FIG. 7, unlike the conventional micro lens, the micro lens of the solid state image pickup device according to the present invention is formed without a separation distance between the lens and the lens. Therefore, the focusing efficiency of focusing the light incident from the outside to the light receiving unit 11 is superior to the prior art. In addition, in the prior art, the ineffective light (b) incident between the lens and the lens can be focused to the light receiving unit 11, so the light collecting efficiency is excellent, and the uniform image can be obtained by preventing the interference of the ineffective light and the effective light.

As described above, the present invention can form a uniform micro lens as compared with the prior art. In addition, since there is no separation distance between the micro-lenses, it is possible to prevent the interference phenomenon of the incident light. As a result, a solid-state imaging device capable of obtaining a uniform and excellent image quality can be manufactured.

Claims (4)

Forming a planarization layer on an entire surface of the semiconductor substrate on which the substructure including the photodiode is formed; Forming a photoresist pattern covering the photodiode on the planarization layer; Etching the planarization layer by using the photoresist pattern as an etching mask to form a lens auxiliary pattern having protrusions on the photodiode; Removing the photoresist pattern; and And forming a transparent film surrounding the protrusion on the entire surface of the resultant product on which the preliminary lens pattern is formed. According to claim 1, And the planarization layer is formed of a polyimide resin or a polyacrylic resin. According to claim 1, And said transparent film is formed of photoresist, polyimide resin or polyacrylic resin. The method of claim 3, wherein After forming the photoresist, And performing a bleaching process to make the photoresist into a light saturation state.