JPH04233759A - Solid-state image sensing device and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide the title solid-state image sensing device in enhanced sensitivity and the manufacture thereof by providing improved convex lenses on individual sensing part. CONSTITUTION:The title solid-state image sensing device is composed of multiple each of picture elements having photodiodes (sensing parts) 2 formed on a semiconductor substrate 1 and optical means positioned above the sensing parts 2 so as to converge the exterior light on the sensing parts 2 provided that on a first convex lens is laminated a second lens 6b which is different from the first convex lens 6a in curvature radius or refractive index, or in both curvature radius and refractive index.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device that uses an improved convex lens to improve sensitivity and reduce the occurrence of smear or flare, and to a method for manufacturing the same.

0002

[Prior Art] A solid-state imaging device generally consists of a plurality of photosensitive sections and a transfer stage that transfers the output signal charge converted by the photosensitive sections.Incoming external light is converted into an electrical signal by a photosensitive section such as a photodiode. and get the output signal. In such a solid-state imaging device, in order to increase the light-receiving sensitivity without increasing the size of the photosensitive section, a convex lens is provided above the photosensitive section, and the convex lens focuses incident light onto the photosensitive section.

A conventional solid-state imaging device will be explained below. FIG. 4 is a sectional view of a main part of a conventional solid-state imaging device. As shown in FIG. 4, a photodiode 2 that converts incident light into an electrical signal is formed on a semiconductor substrate 1.
A light shielding film 3 is formed in a region other than the photodiode 2, and a transparent film 4 and a filter layer 5 are laminated thereon. Further, a convex lens 6 is placed above the photodiode 2, and the convex lens 6 focuses the incident light 7 onto the photodiode 2, making it possible to increase the photoelectric sensitivity compared to a case without a lens.

0004

However, in the conventional configuration described above, the cross section of the convex lens 6 is semicircular with a radius of curvature r3, as shown in the enlarged sectional view of the convex lens portion shown in FIG. The incident light 7 near the center of the convex lens 6 is focused on the photodiode 2, but the incident light from the periphery of the convex lens 6 protrudes from the area of the photodiode 2. In order to solve this problem, the radius of curvature r4 of the convex lens 6 is increased as shown in FIG. 7 into the photodiode 2 becomes difficult. Further, as shown in FIG. 7, after forming the convex lens 6, a transparent resin film 9 may be coated on the surface of the convex lens 6.
Since it is difficult to control the curvature of the transparent resin film 9, the incident light 7 focused on the photodiode 2 varies.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a solid-state imaging device in which incident light is efficiently focused on a photodiode, and a method for manufacturing the same.

[0006]

[Means for Solving the Problems] In order to achieve this object, the solid-state imaging device of the present invention includes a photosensitive portion formed on a semiconductor substrate and a portion located above the photosensitive portion to collect external light onto the photosensitive portion. A plurality of pixels having an optical means for emitting light are arranged, and the optical means overlays a second convex lens having a radius of curvature or a refractive index, or a radius of curvature and a refractive index different from those of the first convex lens. It has a similar configuration.

[0007] Furthermore, the method for manufacturing a solid-state imaging device of the present invention includes:
forming a first convex lens on each photosensitive portion formed on a semiconductor substrate; and forming a second convex lens on the first convex lens with a radius of curvature or a refractive index different from that of the first convex lens. and a step of forming.

[0008]

[Operation] With this configuration, even if external light passes through either the center or the peripheral area of the convex lens, it is focused on the photodiode area, and the light can be used efficiently.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Note that the same parts as in the conventional example shown in FIGS. 4 to 7 are given the same reference numerals, and detailed explanations are omitted.

FIG. 1 is a sectional view of a solid-state imaging device according to an embodiment of the present invention. As shown in FIG. 1, a first convex lens 6a is formed on the transparent film 4, and a second convex lens 6b is formed overlappingly at the center of the first convex lens 6a. FIG. 2 is an enlarged cross-sectional view of the convex lenses 6a and 6b in FIG. The first convex lens 6a is formed to have a radius of curvature 8a of r1 and a refractive index of n1, and the second convex lens 6b
is formed so that its radius of curvature 8b is r2 and its refractive index is n2. In this case, if the lens design is r1≧r2 and the material selection is n1≦n2, the incident light 7 that enters from either the center or the peripheral area of the convex lens can be efficiently focused as shown in FIG. Ru.

FIG. 3 is a process diagram showing a method of manufacturing a solid-state imaging device according to an embodiment of the present invention. Note that in FIG. 3, the photodiode 2 and filter layer 5 of the semiconductor substrate 1 are
was omitted. First, as shown in FIG. 3(a), a material for forming the first convex lens 6a, such as a positive type photosensitive material with high transparency, is coated on the transparent film 3.
After drying at a low temperature of 00° C., exposure and development are performed to form the first pattern 10. Next, as shown in FIG. 3(b), 1
The first pattern 10 is caused to flow and harden by heating at 50 to 240° C. to form the first convex lens 6a. Next, as shown in FIG. 3C, a second pattern 11 having a smaller area than the first convex lens 6a is formed on the first convex lens 6a using a different material. Next, add these to 150-240
The second pattern 11 is caused to flow and harden by heating to a temperature of .degree. C. to form the second convex lens 6b. In this way, a solid-state imaging device whose cross-sectional view is shown in FIG. 1 is obtained.

The material for forming the convex lens may be a negative photosensitive material in addition to the positive photosensitive material shown in this embodiment. Furthermore, even a transparent material without photosensitivity can be used as a material for forming a convex lens by patterning it using photoresist and dry etching. Furthermore, the planar shape of the convex lens may be circular, rectangular or similar. In this embodiment, an example is shown in which convex lenses are stacked in two stages, but they may be stacked in n stages. In this case, it is effective to make the radius of curvature of the n-th convex lens smaller and the refractive index larger than that of the first-stage convex lens.

[0013]

As described above, the present invention provides optical means for condensing external light onto the photosensitive portion of a solid-state imaging device, in which a second convex lens having a different radius of curvature or a different refractive index is superimposed on a first convex lens. By adopting such a structure, it is possible to realize a solid-state imaging device in which incident light passing through a convex lens is effectively focused on a photosensitive portion, and a method for manufacturing the same.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a convex lens portion of a solid-state imaging device according to an embodiment of the present invention.

FIG. 3 is a process diagram showing a method for manufacturing a solid-state imaging device according to an embodiment of the present invention.

[Figure 4] Cross-sectional view of a conventional solid-state imaging device

[Figure 5] Enlarged cross-sectional view of the convex lens section of a conventional solid-state imaging device

[Figure 6] Enlarged cross-sectional view of the convex lens section of a conventional solid-state imaging device

[Figure 7] Cross-sectional view of a conventional solid-state imaging device in which a transparent resin film is formed on a convex lens.

[Explanation of symbols]

1 Semiconductor substrate 2 Photodiode (photosensitive part) 6a First convex lens 6b Second convex lens

Claims (4)

[Claims] 1. A plurality of pixels each having a photosensitive section formed on a semiconductor substrate and an optical means located above the photosensitive section for focusing external light onto the photosensitive section, the optical means being A solid-state imaging device in which a second convex lens having a radius of curvature or a refractive index, or a radius of curvature and a refractive index different from those of the first convex lens is superimposed on a first convex lens. 2. The solid-state imaging device according to claim 1, wherein the radius of curvature of the second convex lens is smaller than the radius of curvature of the first convex lens. 3. The solid-state imaging device according to claim 1, wherein the second convex lens has a larger refractive index than the first convex lens. 4. A step of forming a first convex lens on each photosensitive portion formed on a semiconductor substrate, and a first convex lens having a radius of curvature or a refractive index on the first convex lens. and forming a different second convex lens.