JPH06163866A - Solid-state image pickup device and its manufacture - Google Patents

Abstract

(57) [Summary] [Objective] The sensitivity is improved, manufacturing is facilitated, and light from an adjacent pixel is suppressed from entering. [Structure] A photosensitive element 30 is formed on a semiconductor substrate 33,
The microlens 34 is formed thereon, and the microlens 38 is further formed thereon. Then, the light incident on the microlens 38 is condensed on the lower microlens 34, and the light incident on the microlens 34 is further condensed on the photosensitive element 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device suitable for use in, for example, a video camera, an electronic still camera and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, for example, in a video camera or the like, a solid-state image pickup device has been used as an image pickup element instead of an image pickup tube. In the image pickup tube, the charges generated corresponding to the incident light are scanned by the electron beam, so that the image pickup surface can be effectively used.

On the other hand, in the solid-state image pickup device,
Since the photosensitive element that generates electric charges corresponding to the amount of incident light and the charge reading mechanism section for reading the electric charges generated in the photosensitive element must be formed on the same plane, the photosensitive element in the entire area of the solid-state imaging device is exposed. The range that can be used as the area of the element is limited (the part of the area is
Must be reserved for the charge readout mechanism). As a result, for example, in a MOS type XY address type image pickup device, the ratio of the area of the photosensitive element to the entire area of the solid-state image pickup device is 30% to 50%.

In recent years, in order to form a finer image, the number of photosensitive elements in a solid-state image pickup device tends to increase, but the shape of the charge reading mechanism cannot be reduced so much. Therefore, the area per photosensitive element is inevitably reduced, and the sensitivity of the solid-state imaging device is reduced.

Therefore, conventionally, as shown in FIG. 4, one microlens 11 is formed corresponding to one photosensitive element 12, and the light incident by the microlens 11 is condensed on the photosensitive element 12. It is suggested to do so. With this configuration, the light incident on the charge reading mechanism 13 can be efficiently focused on the photosensitive element 12, and thus the sensitivity can be improved.

[0006]

However, when the occupancy rate per unit area of the unit pixel 14 of the photosensitive element 12, that is, the aperture ratio is made extremely small, the light incident on the pixel 14 is exposed by the corresponding microlens 11. In order to focus the light on the element 12, it is necessary to increase the curvature, the refractive index, and the like of the microlens 11, and as a result, it is difficult to manufacture the microlens 11. Therefore, it is difficult to completely collect the light incident on the unit pixel on the photosensitive element, and there is a problem that the sensitivity cannot be sufficiently improved.

Furthermore, the distance between the photosensitive element 12 and the microlens 11 must be increased, and as a result, incident light from adjacent pixels is mixed in, resulting in a blurred image.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to facilitate manufacturing and obtain a clearer image. Further, the sensitivity can be improved by effectively utilizing the incident light to the pixel.

[0009]

A solid-state image pickup device according to the present invention includes a photosensitive element 30 for generating charges corresponding to incident light.
In a solid-state imaging device including a charge read-out mechanism section 40 that reads out charges generated by the photosensitive element 30, a first microlens 34 formed at a position where light is condensed on the photosensitive element 30, and a first microlens. At least a second microlens 38 formed at a position for condensing light is provided at 34.

The first microlens 34 and the second microlens 38 control at least one of the position, the refractive index, the curvature, the radius, and the thickness of the first microlens 34 and the second microlens 38 to form incident light on the photosensitive element. The light can be focused on 30.

One of the first microlenses 34 is formed so that light is focused on one photosensitive element 30, and the second microlens 34 is formed.
The microlenses 38 of the above are two first microlenses 34, one of which is arranged in the first direction and two first microlenses 34 of which are arranged in the second direction perpendicular to the first direction. The microlenses 34 can be formed so as to focus light on a total of four first microlenses 34.

The four photosensitive elements 30 to which the light from the second microlenses 38 is incident via the corresponding first microlenses 34 are the second microlenses 38.
It can be formed concentrated near the center of.

In the method of manufacturing a solid-state image pickup device according to a fifth aspect, the photosensitive element 30 is formed on the semiconductor substrate 33, and the light from the second microlens 38 is condensed on the photosensitive element 30. Corresponding to the first microlens 3
4 is formed on the four first microlenses 34,
It is characterized in that the incident second light forms a corresponding second microlens 38 at a position where the light is condensed on the corresponding photosensitive element 30.

[0014]

In the solid-state image pickup device according to the first aspect, the first microlens 34 is arranged on the photosensitive element 30, and the second microlens 38 is further arranged thereon. Therefore, it is not necessary to increase the refractive index, curvature, radius, thickness, etc. of the microlenses 34, 38 so much, which facilitates manufacturing. Further, the light can be effectively condensed on the photosensitive element 30, and the possibility that the light from the adjacent pixels is incident is reduced.

Further, in the method of manufacturing a solid-state image pickup device according to the fifth aspect, the photosensitive element 30 is formed on the semiconductor substrate 33, the microlens 34 is formed thereon, and the microlens 38 is further formed thereon. To be done. Therefore, it is possible to easily manufacture a solid-state imaging device that can efficiently collect light on the photosensitive element 30.

[0016]

1 is a plan view showing the configuration of an embodiment of a solid-state image pickup device according to the present invention. FIG. 2 shows a sectional view taken along the line AA ′ of FIG. In this embodiment, a transparent flattening film 32 is formed on a photosensitive element 30 formed on a semiconductor substrate 33, and a first (lower layer) microlens 34 is formed thereon. This micro lens 34
Is covered with a transparent flattening film 35.
A second (upper layer) microlens 38 is further formed on the above.

The photosensitive element 30 is provided corresponding to the pixel 41. That is, one photosensitive element 30 is provided for one pixel 41. Then, one microlens 34 is formed corresponding to one photosensitive element 30. Further, in FIG. 1, a total of four microlenses 34 (that is, two microlenses 34 arranged in the horizontal direction and two microlenses 34 arranged vertically in the horizontal direction) (that is, One microlens 38 is formed corresponding to four pixels).

As shown in FIG. 1, most of the light incident on the four pixels can be captured by the microlens 38. The microlenses 38 focus the received light on the corresponding four microlenses 34. Then, the four microlenses 34 further condense light onto the corresponding four photosensitive elements 30. In this way, the light incident on each pixel 41 is focused on the corresponding photosensitive element 30.

As shown in FIG. 2, the microlens 38
Since the change in the curvature of the surface is larger toward the outer circumference, the refraction angle at the outer circumference is larger than the refraction angle at the inner circumference. That is, of the light incident on the microlens 38, the light incident on the outer periphery is refracted more in the inner peripheral direction than the light incident on the inner periphery. Therefore, as shown in FIG. 1, the microlenses 34 are concentrated near the center of the microlenses 38.

As described above, the incident angles of light incident on the microlenses 34 from the microlenses 38 are not necessarily uniform. Therefore, as shown in FIGS. 1 and 2, the photosensitive element 30 is not arranged at the center of the microlens 34 but is arranged so as to be concentrated at a position deviated from the center of the microlens 38.

Since the lens for condensing the light incident on the photosensitive element 30 is constituted by two layers as described above,
The microlenses 34 and 38 formed in each layer may have a smaller refractive index, curvature, radius, or thickness than the case where light is condensed by one microlens. By controlling at least one of the position, the refractive index, the curvature, the radius, and the thickness of the microlenses 34 and 38, the incident light is effectively incident on the photosensitive element 30. .

Next, a method of manufacturing such a solid-state image pickup device will be described with reference to FIG. First, the photosensitive element 30 is formed on the semiconductor substrate 33. Then, on the semiconductor substrate 33 on which the photosensitive element 30 is formed in this manner, a flattening film 32 made of, for example, transparent isobutyl methacrylate having a relatively small refractive index is formed, and further, for example, a novolac-based film. A resist film 31 made of resin or the like (lens material) is formed (FIG. 3A).

Next, a predetermined pattern is exposed on the resist film 31 by ordinary photolithography, and this is developed to leave the resist film 31 at the position where the microlens 34 is to be formed (FIG. 3B. )).

Then, the resist film 31 is heated to an appropriate temperature to form a microlens 34 (FIG. 3).
(C)).

After the microlenses 34 are formed in this way, a flattening film 35 made of transparent isobutyl methacrylate, which also has a low refractive index, is formed on the microlenses 34 (FIG. 3D). Then, a lens material 36 made of, for example, isopropyl methacrylate is applied on the flattening film 35, and a resist film 37 is further formed thereon.
To form. Then, as in the case of FIG. 3B, a predetermined pattern is exposed on the resist film 37 by ordinary photolithography, and this is developed to remove unnecessary portions (FIG. 3E).

Next, using the resist film 37 as a mask, wet etching or etching in gas plasma is performed to remove unnecessary portions of the lens material 36 (FIG. 3 (f)). Further, by removing the resist film 37 used as a mask, the microlens 3
8 is formed (FIG. 3 (j)).

In the above manufacturing process, one microlens 34 is formed so as to focus light on one photosensitive element 30, and one microlens 38 is arranged in the horizontal and vertical directions. It is formed so as to collect light on the four microlenses 34 in total.

In the above embodiments, the microlens has a two-layer structure, but it may have three or more layers.

[0029]

As described above, according to the solid-state image pickup device of the first aspect, the first microlens is formed on the photosensitive element, and the second microlens is further formed thereon. So the first and second microlenses
The refractive index, curvature, radius or thickness of the layer can be reduced as compared with the case where the layer is composed of microlenses, which facilitates manufacturing. Further, the light can be effectively condensed on the photosensitive element, and the incidence of the light of the adjacent pixels can be suppressed.

According to the method of manufacturing a solid-state image pickup device according to a fifth aspect, a photosensitive element is formed on a semiconductor substrate, a first microlens is formed thereon, and a second microlens is formed thereon. Since it is formed, it is possible to easily manufacture a solid-state imaging device that can effectively collect light on a photosensitive element.

[Brief description of drawings]

FIG. 1 is a plan view showing a configuration of an embodiment of a solid-state imaging device of the present invention.

FIG. 2 is a sectional view taken along the line A-A ′ in FIG.

FIG. 3 is a cross-sectional view illustrating a manufacturing process of a method for manufacturing a solid-state imaging device according to the present invention.

FIG. 4 is a plan view showing the configuration of an example of a conventional solid-state imaging device.

[Explanation of symbols]

 11 Microlens 12 Photosensitive Element 13 Charge Readout Mechanism Section 14 Pixel 30 Photosensitive Element 31 Resist Film 32 Flattening Film 33 Semiconductor Substrate 34 Microlens 35 Flattening Film 36 Lens Material 37 Resist Film 38 Microlens 40 Charge Readout Mechanism Section 41 Pixel

Claims (5)

[Claims] 1. A solid-state imaging device comprising: a photosensitive element that generates electric charges corresponding to incident light; and a charge reading mechanism that reads out the electric charges generated by the photosensitive element. A position at which light is condensed on the photosensitive element. A solid-state imaging device comprising: at least a first microlens formed on the first microlens; and a second microlens formed at a position where light is condensed on the first microlens. 2. The first microlens and the second microlens control incident light by controlling at least one of a position, a refractive index, a curvature, a radius, and a thickness formed by the first microlens and the second microlens. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is configured to collect light on an element. 3. One of the first microlenses is formed so as to collect light on one of the photosensitive elements, and one of the second microlenses is formed of the first microlens. Two said first microlenses arranged in the direction of
2 arranged in a second direction perpendicular to the first direction
A total of four of the first microlenses
The solid-state imaging device according to claim 1 or 2, wherein the microlens is formed so as to collect light. 4. The four photosensitive elements on which light from one of the second microlenses is incident through the corresponding one of the first microlenses are near the center of the second microlens. The solid-state imaging device according to claim 3, wherein the solid-state imaging device is formed in a concentrated manner. 5. The method for manufacturing a solid-state imaging device according to claim 3, wherein the photosensitive element is formed on a semiconductor substrate, and the second photosensitive element is formed on the photosensitive element. The corresponding first microlens is formed at a position where the light from the microlens is collected, and the light incident thereon is formed on the four first microlenses. A method for manufacturing a solid-state imaging device, comprising forming the corresponding second microlens at a position where light is condensed on an element.