JPH06132502A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To improve the sensitivity of a solid-state image sensing device having a microlens layer in a state where its diaphragm is open. CONSTITUTION:A photoelectric conversion element part 2 is prepared on the surface of a semiconductor substrate 1. On the part 2 a microlens layer 5 is formed with an intermediate layer 4 in between. A plate condensing layer 6 which is made of a material having a larger refractive index than that of the layers 4 and 5 is formed in the layer 4. Thus the incident angle range of diagonal incident light Lt to be collected will become wider and the decrease in sensitivity in a peripheral part be prevented while the diaphragm is open. Especially, by making the layer 6 to become like a convex lens in the central part of the part 2, the condensing range of vertical incident light is widen in the central part where there are much vertical incident light and the incident angle range to collect the diagonal incident light is also widen in the peripheral part where are relatively much diagonal incident light, so that high sensing effect can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a solid-state image pickup device in which a microlens layer is provided on a photoelectric conversion portion on a semiconductor substrate via an intermediate layer such as a filter.

[0002]

2. Description of the Related Art In recent years, a solid-state image pickup device having a photoelectric conversion element formed on a semiconductor substrate has been reduced in size of a camera-integrated VTR,
In response to the weight reduction, the optical size has been rapidly reduced. At that time, a lens made of a resin film called a microlens layer is formed on the photoelectric conversion element to reduce the size of the photoelectric conversion element. It is designed to prevent a decrease in light collection rate.

The conventional structure of the solid-state image pickup device will be described below with reference to FIG.

FIG. 4 is a sectional view of a light receiving portion of a conventional general solid-state image pickup device. In the figure, 1 is a semiconductor substrate, 2
Is provided on the surface of the semiconductor substrate 1, and is a photoelectric conversion element section for converting incident light into signal charges, 3 is a light shielding section, and 5 is for converging light incident through the camera lens on the photoelectric conversion element section 2. The microlens layer 4 provided on the photoelectric conversion element portion 2 is an intermediate layer interposed between the photoelectric conversion element portion 2 and the microlens layer 5, and the intermediate layer layer 4 is provided with the microlens on the upper portion. In the case of a color solid-state imaging device, a flattening film for forming the layer 5, a color filter film necessary for colorization, and the like are formed.

[0005]

By the way, since both the microlens layer 5 and the intermediate layer 4 have a refractive index of about 1.5, when the microlens layer 5 enters the filter layer 4, the light is refracted. The light Ls incident perpendicularly to the photoelectric conversion element 2 and the photoelectric conversion element portion 2
On the other hand, any of the light Lt that is obliquely incident goes straight in the intermediate layer 4. In addition, A is a range in which the vertically incident light Ls can be effectively condensed on the photoelectric conversion element unit 2.

However, in the conventional solid-state image pickup device as described above, the light which is vertically incident from the outside of the effective condensing range A or the oblique incident light Lt shown in FIG. The incident light was blocked by the light shielding portion 3 and could not reach the photoelectric conversion element portion 2. Then, the ratio of obliquely incident light increases when the diaphragm is opened, but the condensing ratio is reduced because the condensing range of such obliquely incident light is narrowed, and especially in the peripheral portion of the photoelectric conversion element, the obliquely incident light is obliquely incident. Since the incident angle of light is extremely low, the sensitivity of the solid-state imaging device is reduced due to the reduction of the light collection rate, which is a serious problem.

The present invention has been made in view of the above points, and an object thereof is to provide a solid-state image pickup device in which a microlens layer is provided on a photoelectric conversion element portion via an intermediate layer, and the microlens layer is provided inside the intermediate layer. By providing the layer having a high refractive index, it is intended to expand the range in which obliquely incident light can be effectively condensed.

[0008]

Means for Solving the Problems To achieve the above object, the means taken by the invention of claim 1 is, as shown in FIG. 1, a photoelectric conversion element portion formed on a semiconductor substrate, and the photoelectric conversion element portion. It is premised on a solid-state image pickup device having a microlens layer which is provided on the element section via an intermediate layer such as a filter and collects light in the photoelectric conversion element section.

Then, a plate-shaped light collecting layer made of a material having a higher refractive index than the microlens layer and the intermediate layer is provided in the intermediate layer.

As shown in FIG. 2, the means taken by the invention of claim 2 is the invention of claim 1 in which the light collecting layer is formed in the shape of a convex lens near the center of the photoelectric conversion element part. .

[0011]

With the above structure, in the invention of claim 1, the vertically incident light is slightly inwardly bent by the microlens, and then is shifted to the outside of the photoelectric conversion element portion by the light-collecting layer having a high refractive index. The effective condensing range of the vertically incident light is slightly reduced accordingly. On the other hand, the obliquely incident light incident at a low angle shifts from the light shielding part to the photoelectric conversion element part side in the light collecting layer, so that the incident angle range in which the obliquely incident light can be condensed is expanded.

Particularly, in the peripheral portion of the photoelectric conversion element with the diaphragm open, the proportion of obliquely incident light increases, but by expanding the incident angle range of obliquely incident light that can be condensed in this way, The light collection rate at the peripheral portion is increased, and the sensitivity at the peripheral portion, which is a problem, is improved.

According to the second aspect of the present invention, in the central portion of the photoelectric element portion, the vertically incident light is bent inwardly of the photoelectric conversion element portion by the light-condensing layer having the convex lens shape, and the light condensing range of the vertically incident light is expanded. On the other hand, the incident angle range of the obliquely incident light that can be condensed does not change so much.

Further, in the vicinity of the periphery of the photoelectric conversion element portion, the incident angle range of obliquely incident light that can be condensed by the plate-like condensing layer is expanded by the same operation as that of the above-mentioned invention.

Therefore, the sensitivity is improved in both the central portion where the proportion of vertically incident light is large and the peripheral portion where the proportion of oblique incident angle is large.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

First, the first embodiment will be described with reference to FIG. FIG. 1 shows the configuration of the solid-state imaging device according to the first embodiment. The same parts as those in the conventional example of FIG. As a feature of the present invention, a plate made of a material having a higher refractive index than the microlens layer 5 or the intermediate layer 4 is included in the intermediate layer 4 sandwiched between the microlens layer 5 and the photoelectric conversion element 2. The light-collecting layer 6 having a shape of a circle is formed.

Here, the vertically incident light Ls vertically incident on the microlens layer 5 of the solid-state image pickup device is bent toward the inside of the microlens layer 5, that is, toward the inside of the photoelectric conversion element portion 2. Then, when the light enters the intermediate layer 4 and reaches the light collecting layer 6, the light collecting layer 6 is formed of a material having a higher refractive index than the material forming the intermediate layer 4, so that the upper surface of the light collecting layer 6 is formed. At the boundary between the intermediate layer 4 and the intermediate layer 4, and is bent at a refraction angle smaller than the incident angle.
At the boundary between and, it is bent again to be parallel to the incident angle. As a result, the vertical incident angle Ls is shifted slightly outward of the photoelectric conversion element section 2 by the light-collecting layer 6, so that the vertical incident light L
The condensing range A of s is slightly reduced.

On the other hand, the obliquely incident light Lt has a path from the end of the microlens layer 5 to the vicinity of the end on the opposite side of the photoelectric conversion element 2, that is, the light incident at a low angle. Although it is incident on 2, the oblique incident light Lt shifts to the photoelectric conversion element section 2 side, so that the range of the incident angle of the oblique incident light Lt to be condensed is expanded.

Therefore, as described above, the condensing range of the obliquely incident light Lt that increases in the state where the diaphragm is opened is expanded, which causes a problem particularly in the peripheral portion when the diaphragm is opened. It is possible to effectively prevent a decrease in sensitivity.

Next, the invention of claim 2 will be described with reference to FIGS. FIG. 2 shows the overall structure of the solid-state imaging device according to the second embodiment. The basic structure of the solid-state imaging device is the same as that of the first embodiment shown in FIG. 6 is formed on the convex lens-shaped light-collecting layer 6a at the center of the photoelectric conversion element portion 2, the convex lens-shaped light-collecting layer 6b having a larger radius of curvature than the center at the portion adjacent to the center, and the plate-shaped light-collecting layer 6c at the peripheral portion. Has become.

FIG. 3 is an enlarged detailed view of the vicinity of the center of the photoelectric conversion element portion 2 shown in FIG. 2. In this case, the range of the incident angle at which the oblique incident light Lt is condensed does not change so much. The condensing range A of the vertically incident light Ls is significantly expanded by the diaphragm effect of the convex lens-shaped condensing layer 6a. On the other hand, in the peripheral portion where the plate-shaped light collecting layer 6c is provided, the range of the incident angle at which the obliquely incident light Lt can be collected is expanded similarly to the effect of the first embodiment.

Therefore, in the central portion of the photoelectric conversion element portion 2 in which the proportion of vertically incident light is large, the convex lens-like condensing layer 6a expands the condensing range A of the vertically incident light Ls, and the photoelectric ratio in which the proportion of obliquely incident light Lt is large. In the peripheral portion of the conversion element unit 2, the incident angle range of the oblique incident light Lt that can be condensed by the plate-shaped condensing layer 6c is expanded, and the sensitivity of the solid-state imaging device is further improved as compared with the first embodiment. Become.

[0024]

As described above, according to the invention of claim 1, as a solid-state image pickup device in which the microlens layer is provided on the photoelectric conversion element portion via the intermediate layer, the microlens is provided in the intermediate layer. Since the plate-shaped light condensing layer having a higher refractive index than the layers and the intermediate layer is provided, it is possible to improve the sensitivity in a state where the diaphragm having a large proportion of obliquely incident light is opened.

According to the invention of claim 2, in the invention of claim 1, the condensing layer is formed in a convex lens shape in the central portion of the photoelectric conversion element portion, so that the photoelectric conversion element portion in which the proportion of vertically incident light is high is large. The convex lens-shaped light condensing layer expands the condensing range of vertically incident light in the central part, and expands the incident angle range where oblique incident light can be condensed in the peripheral part of the photoelectric conversion element part where the ratio of oblique incident light is large. Therefore, it is possible to exert a remarkable effect in improving the sensitivity.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing the overall structure of a solid-state imaging device according to a second example.

FIG. 3 is a partial cross-sectional view showing the structure near the center of the solid-state imaging device according to the second example.

FIG. 4 is a partial cross-sectional view of a conventional general solid-state imaging device.

[Explanation of symbols]

 1 semiconductor substrate 2 photoelectric conversion element part 3 light shielding part 4 intermediate layer 5 microlens layer 6 light collecting layer

Claims (2)

[Claims] 1. A photoelectric conversion element portion formed on a semiconductor substrate, and a microlens layer provided on the photoelectric conversion element portion with an intermediate layer such as a filter interposed therebetween to collect light in the photoelectric conversion element portion. A solid-state imaging device having: a plate-shaped light condensing layer made of a material having a higher refractive index than the microlens layer and the intermediate layer in the intermediate layer. 2. The solid-state imaging device according to claim 1, wherein the light-collecting layer is formed in a convex lens shape in the vicinity of the center of the photoelectric conversion element portion.