JPH06326284A - Color sold-state imaging device - Google Patents

Abstract

PURPOSE:To effectively obtain sensitivity without being affected by the lens iris of a video camera. CONSTITUTION:A transparent film 8 whose refractive index is lower than that of microlens material is formed on the microlens 7 formed on a light receiving part 2 of a solid state image sensor formed on a semiconductor substrate. In the above structure, a light entering a color solid-state imaging device from the oblique direction is refracted on account of the difference of refractive index between the air and the transparent film on the microlens, so that the incident angle to the microlens 7 is reduced. Thereby the deviation of light converging position of the microlens 7 is restrained to be small when the light is converged at the light receiving part 2, and sensitivity degradation at the time of lens iris opening of the video camera can be restrained. Hence sensitivity can be effectively obtained without being affected by the lens iris of the video camera.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color solid-state image pickup device having a microlens effective for improving sensitivity when a lens aperture of a video camera is opened and a film having a lower refractive index than a microlens material as an upper layer. is there.

[0002]

2. Description of the Related Art In recent years, there has been a problem in that the sensitivity of the solid-state image pickup device is reduced due to the reduction of the area of the light-receiving portion accompanying the miniaturization and increase in the number of pixels. In order to solve this problem, a color solid-state image pickup device having a microlens on a light receiving portion has come to be used.

FIG. 4 is a sectional view of a main part of a conventional color solid-state image pickup device having a microlens. In FIG. 4, 1 is a semiconductor substrate made of silicon, 2 is a light receiving portion made of a photodiode, and 3 is aluminum. The light-shielding portion 4 made of is a flattening layer made of an acrylic transparent film having a refractive index n of around 1.5 (1.4 to 1.6) and a light transmittance of 98% or more in the visible light region. Rate n is around 1.5
(1.4 to 1.6) a color filter layer made of a natural organic resist and dyed in a desired color, and 6 is an intermediate layer made of an acrylic transparent film having the same refractive index n and light transmittance as the flattening layer 4. The layer 7 is made of an acrylic resin having a refractive index n of about 1.5 (1.4 to 1.6) and a light transmittance of 98% or more in a visible light region, and has a semicircular cross section. Is.

The operation of the color solid-state image pickup device configured as described above will be described.

First, light incident not only above the light receiving portion 2 but also above the light shielding portion 3 is condensed through the microlens 7 and passes through the intermediate layer 6. Then, only light having a desired wavelength passes through the color filter layer 5, and further the flattening layer 4
And enters the light receiving unit 2. The light incident on the light receiving unit 2 is converted into signal charges by the light receiving unit 2 according to the amount thereof.

[0006]

In the structure of the conventional microlens as described above, as shown in FIGS. 4 and 5, the lens aperture diameter of the video camera is sufficiently small so that the light incident on the color solid-state image pickup device can be prevented. , Vertical light shown in FIG. 4 (incident angle θ =
0) or less than the arbitrary incident angle shown in FIG. 5 (here, the arbitrary incident angle is the limit incident angle of oblique light that can be condensed on the light receiving portion by the microlens. In the case of oblique light (where the angle is α) (θ <α), the incident light is focused on the light receiving section 2 without any problem, but as shown in FIG. When the incident oblique light component increases above α (θ> α), the oblique light component that cannot be condensed on the light receiving unit 2 increases, and the sensitivity of the color solid-state imaging device is not effectively improved. It was

The present invention solves the above-mentioned conventional problems, and provides a color solid-state image pickup device capable of effectively improving the sensitivity without being affected by the lens aperture of the video camera. With the goal.

[0008]

In order to achieve the above object, the present invention comprises a microlens formed on a light receiving portion of a solid-state image pickup device, and a transparent film having a refractive index lower than that of the microlens material. Is.

[0009]

According to the present invention, due to the difference in the refractive index between the air and the layer film on the microlens, the light which is vertically incident on the color solid-state image pickup device is not affected and is incident from an oblique direction. By refracting only the light and making the incident angle to the microlens small, the amount of deviation of the microlens condensing position can be minimized, and the incident light can be efficiently condensed in the light receiving part. It is possible to suppress a decrease in sensitivity of the color solid-state imaging device when the diaphragm is opened.

[0010]

FIG. 1 is a sectional view of a main part of a color solid-state image pickup device according to an embodiment of the present invention. The same parts as those in the conventional example shown in FIG. Omit it. Here, 8 shown in FIG. 1 is a transparent material having a light transmittance of 98% or more in the visible light region on the microlens 7 and a refractive index n (1.2 to 1.3) lower than that of the microlens material (for example, It is a transparent film (hereinafter referred to as a transparent film on a microlens) formed of a kind of polyvinyl alcohol resin or the like.

The operation of the color solid-state image pickup device configured as described above will be described. As shown in FIG. 1, when the light is vertically incident on the color solid-state imaging device (θ = 0), the incident light is transmitted through the microlens transparent film 8 without being refracted and is incident on the microlens 7. . Then, the light condensed by the microlens 7 passes through the intermediate layer 6, only the light having a desired wavelength passes through the color filter layer 5, the flattening layer 4, and enters the light receiving portion 2. Further, the light incident on the light receiving unit 2 is converted into signal charges according to the amount thereof.

Next, FIG. 2 shows a state (θ <α) when light is incident at an angle smaller than the incident angle α. Thus, when light is incident on the color solid-state imaging device at an angle, the light is refracted at the boundary surface due to the difference in refractive index between the air and the microlens-on-transparent film 8 and is incident on the microlens-on-transparent film 8. The incident angle becomes smaller than the angle at which the light enters, and the light enters the microlens 7. Then, the light collected by the microlens 7 passes through the intermediate layer 6, the color filter layer 5, and the flattening layer 4, and then enters the light receiving unit 2.

Next, FIG. 3 shows a state (θ> α) when light is incident at an angle equal to or larger than the incident angle α. Similar to the state of FIG. 2, incident light having an angle is refracted at the boundary surface between the air and the transparent film 8 on the microlens, and the incident angle becomes less than α and enters the microlens 7. The light collected by the microlens 7 sequentially passes through the intermediate layer 6, the color filter layer 5, and the flattening layer 4, and then enters the light receiving unit 2.

By forming the transparent film 8 having a refractive index lower than that of the microlens material on the microlens 7 as described above, even with respect to the light incident on the color solid-state image pickup device in an oblique direction, It is possible to obtain a light-collecting effect that is almost the same as that of vertically incident light.

The transparent film 8 on the microlens described above
The refraction angle of light due to can be controlled by the refractive index of the transparent film material formed on the microlens (refractive index difference from air). Further, since a transparent film having a refractive index between air and the microlens material is formed on the microlens, the difference in the refractive index between the microlens and the upper medium thereof is small.
Therefore, the light collecting distance of the microlens is longer than that of the color solid-state imaging device including the conventional microlens, and it is necessary to adjust the distance between the light receiving unit 2 and the microlens 7 to the optimum distance.

As described above, according to this embodiment, the light incident on the microlens 7 is irrespective of the incident angle of the light with respect to the transparent film 8 on the microlens, that is, the aperture state of the lens of the video camera. 2 can be focused.

In the present embodiment, the color solid-state image pickup device in which the color filter layer is directly formed on the solid-state image pickup element formed on the semiconductor substrate has been described. The same effect can be obtained with the device.

Further, since the monochrome solid-state image pickup device does not have the color filter layer 5 which requires a natural organic material, the flattening layer, the intermediate layer and the microlens have a refractive index n of about 1.6 to 1.8. If a transparent resin (for example, a polyimide resin) is used and the transparent film on the microlens is made of a transparent resin having a refractive index n of 1.4 to 1.6, the refractive index between air and the transparent film on the microlens increases, Light having a smaller incident angle can be made incident on the microlens, and a greater effect can be obtained.

[0019]

As described above, the color solid-state image pickup device of the present invention has a lower refractive index than the microlens material on the microlens formed on the light receiving portion of the solid-state image pickup element formed on the semiconductor substrate. By providing the transparent film of
It is possible to realize an excellent color solid-state imaging device in which there is little reduction in sensitivity when the aperture of the lens of the video camera is opened.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of a main part of a color solid-state imaging device for explaining a state in which light is obliquely incident at an incident angle of less than α in FIG.

FIG. 3 is a cross-sectional view of a main part of a color solid-state imaging device for explaining a state in which light is obliquely incident at an incident angle α or more in FIG.

FIG. 4 is a cross-sectional view of a main part of a conventional color solid-state imaging device.

5 is a cross-sectional view of a main part of the color solid-state image pickup device for explaining a state in which light is obliquely incident at an incident angle of less than α in FIG.

FIG. 6 is a cross-sectional view of a main part of the color solid-state imaging device for explaining a state in which light is obliquely incident at an incident angle α or more in FIG.

[Explanation of symbols]

1 ... Semiconductor substrate, 2 ... Light receiving part, 3 ... Light shielding part, 4 ...
Flattening layer, 5 ... Color filter layer, 6 ... Intermediate layer, 7
… Microlens, 8… Transparent film on microlens.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirotatsu Kodama 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electronics Industrial Co., Ltd.

Claims (1)

[Claims] 1. A color solid-state imaging device comprising a microlens formed on an upper surface of a color filter formed on a solid-state imaging device and having a film having a lower refractive index than that of a microlens material and a flat surface.