JP3044734B2 - Solid-state imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid-state imaging device having a multiple lens structure.

[Conventional technology]

As a solid-state imaging device such as a CCD imager,
An element in which a lens forming layer is provided on a chip in order to increase the amount of light incident on a sensor unit as described in Japanese Patent No. 10666 is known.

The lens forming layer is a layer obtained by processing an inorganic or organic transparent material layer into, for example, a convex surface, and converges by refraction of light rays on the convex surface.

Conventionally, in a solid-state imaging device having a lens forming layer, as shown in FIG. 9, an electrode layer 102 having a light-shielding property is formed on a silicon substrate 101, and the electrode layer 102 faces the bottom of the opening 103 of the electrode layer 102. A sensor unit 104 for photoelectric conversion is formed. The electrode layer 102 is covered with a flattening layer 105, and a dye layer 106 as a color filter is formed on the electrode layer 102. Then, the lens forming layer 1 is provided on the upper part of the staining layer 106.
07 is provided, and a convex surface portion 108 is formed at a position of the lens forming layer 107 facing the opening portion 103 of the sensor.

Light incident from the surface of the chip is refracted by the convex portion 108 and guided to the sensor portion 104 on the substrate surface. Then, photoelectric conversion is performed in the sensor unit 104, and a required image signal is obtained.

[Problems to be solved by the invention]

By the way, the above-described solid-state imaging device has a lens forming layer 107.
Since the amount of light condensed or the like is determined only by the size and shape of the convex portion 108, when the convex portion 108 is formed to have an enlarged diameter or the like, light originally received as a signal is also indicated by an arrow W in FIG. Phenomena such as reflection on the surface of the electrode layer 102 occur like light rays, and in fact, problems such as a decrease in the amount of condensed light occur.

Accordingly, an object of the present invention is to provide a solid-state imaging device having a multiple lens structure that solves the above-described problems and realizes stable light collection.

[Means for solving the problem]

A solid-state imaging device according to the present invention proposed to achieve the above-described object includes a lens integrally formed on a chip, and this lens has a diameter larger than at least the sensor opening. A multi-lens structure including at least a convex first lens for condensing, and a second convex lens for refracting the light beam condensed by the first lens toward the sensor opening. It was done.

Here, the first lens and the second lens are formed of different layers, respectively, and are formed so that the first lens and the second lens have different refractive indexes.

[Action]

The solid-state imaging device according to the present invention has a convex second lens for refracting a light beam condensed by the first lens toward a sensor opening in addition to the convex first lens for condensing. Therefore, the light incident on the sensor opening comes from a more vertical direction. When the angle of the incident light received is closer to the vertical direction, the optical path is closer to the center of the light receiving part, and even if the shape of the lens is slightly deformed in the process, the amount reflected by the edge of the opening decreases. Is done.

〔Example〕

A specific embodiment of the solid-state imaging device according to the present invention will be described with reference to the drawings.

First Embodiment This embodiment is an example in which a lens including two lens forming layers is formed on a CCD solid-state imaging device.

In the solid-state imaging device according to the first embodiment, as shown in FIG. 1, a sensor unit 2 is formed on the surface of a silicon substrate 1, and light incident on the sensor unit 2 is photoelectrically converted. The electrode layer 4 formed on the silicon substrate 1 is patterned on the surface of the sensor unit 2 so that the sensor opening 3
Is provided. The electrode layer 4 is formed of a light-shielding film such as aluminum. A first transparent material layer 5 is formed so as to cover the electrode layer 4 in which the sensor opening 3 is provided, and a region corresponding to the sensor opening 3 of the first transparent material layer 5 includes: A convex lens 6 is formed. The first transparent material layer 5 has a refractive index of n ₂ , a diameter of the lens 6 is W ₂ , a radius of curvature is r ₂ , and a height from the substrate is h ₂ . A second transparent material layer 7 is formed on the first transparent material layer 5 on which the lens 6 is formed, and a region corresponding to the sensor opening 3 of the second transparent material layer 7. Is formed with a lens 8 having a convex shape. The lens 8 has a diameter W ₁ larger than the area of the sensor opening 3, the radius of curvature is r ₁ , and the height from the interface with the first transparent material layer 5 is h ₁ . Have been.
The refractive index of the second transparent material layer 7 is n ₁ .

Here, an example of the relationship between the two convex lenses 6 and 8 will be described. For example, by setting the radius of curvature to be r ₁ <r ₂ and the refractive index to be n ₁ > n _2. The light incident on the lens 8 is refracted so as to converge on the surface of the lens 8, and further refracted and the light incident on the lens 6 is bent on the surface of the lens 6 in a direction perpendicular to the substrate. . That is, even if the light is not refracted on the surface of the lens 6 in a direction completely perpendicular to the main surface of the substrate, the light is refracted in a direction close thereto. In FIG. 1, a light ray P is an example of a light ray that travels through two convex lenses 6 and 8, and a light ray P incident at a distance from the optical axis toward the focal point of the lens 8 on the surface of the lens 8. The light advances and enters the lens 6. In the lens 6, a deeper position becomes the focal point f in relation to the refractive index and the radius of curvature. By such a vertical direction, incident light having a high degree in the vertical direction enters the sensor unit 2, and photoelectric conversion is performed. Will be

With such a multi-lens structure, in the solid-state imaging device of the present embodiment, first, since the convex first lens 8 has a larger aperture W ₁ than the area of the sensor opening 3, It is possible to increase the amount of light collection. In addition, since it is bent in the vertical direction by the convex second lens 6,
With a structure that is resistant to deviation from the design that occurs in the process, irregular reflection at the sensor non-opening part etc. is suppressed, and
The area of the sensor unit 2 can be maximized. Further, even when the thickness of the electrode layer 4 is increased due to the multi-layer structure of the electrodes due to the incident light having a high degree in the vertical direction, it is possible to sufficiently cope with the case.

Next, the lens structure of the solid-state imaging device according to the present embodiment will be described with reference to FIGS. 3 to 8 while comparing it with a conventional single-layer lens structure.

First, when comparing FIG. 3 and FIG. 4 regarding the characteristics with respect to the oblique incident light, it can be seen that the multiple lens structure of FIG. 3 is superior. That is, the F value is 14, the incident angle θ
Assuming that i is 19.7 °, when the element surface indicating the position of the sensor unit and the like is relatively changed from the lens position, the multiple lens structure of the solid-state imaging device according to the present embodiment in FIG. The ratio of receiving the light amount is higher on both the element surface A and the element surface B than in the conventional single-layer lens structure shown in FIG. Further, in the multi-lens structure according to the solid-state imaging device of the present embodiment shown in FIG. 3, it is possible to receive the condensed light on the element surface A and the element surface B without much change. In the single-layer lens structure described above, the sensitivity that was maximum on the element surface A decreases toward the element surface B. This indicates that the position of the lens and the position of the sensor unit 2 have a structure that is more resistant to variation in the solid-state imaging device of the present embodiment, and that it is advantageous in design.

Second, comparing the incident light around the angle of view of the oblique incident light with FIG. 5 and FIG. 6, similarly, the multiple lens structure of FIG. 5 is superior. For example, if the F value is 14,
Assuming that the incident angle θi is 19.7 ° and the tilt angle θt is 6.1 °, even if the element surface of the solid-state imaging device is relatively changed from the position of the lens, as in the previous comparison, the book shown in FIG. The multi-lens structure of the solid-state imaging device according to the embodiment receives a higher amount of light on both the element surface A and the element surface B than the conventional single-layer lens structure shown in FIG.

7 and 8 are diagrams showing shading amounts,
FIG. 7 shows the characteristics of the multi-lens structure according to the solid-state imaging device of the present embodiment, and FIG. 8 shows the characteristics of the conventional single-layer lens structure. Comparing the characteristics in FIG. 7 and FIG.
Relative shading of FIG that is s _1, shading of Figure 8 is a s _2, have a relationship of s ₁ <s _2. Therefore, it can be seen that, as shown in FIG. 7, the multi-lens structure of the solid-state imaging device according to the present embodiment also reduces the shading amount and also increases the condensing amount as a whole. .

As described above, it can be seen that the solid-state imaging device of the present embodiment has high sensitivity to oblique incidence of light and has a reduced shading amount. Further, since the incident light is made vertical by the convex lens 6, even if the thickness of the electrode layer 4 is increased or the height of the lens changes, stable sensitivity can be obtained.

Second Embodiment This embodiment is an example of a solid-state imaging device having a three-layer lens structure.

As shown in FIG. 2, in this solid-state imaging device, a sensor unit 12 is formed on the surface of a silicon substrate 11, and incident light is photoelectrically converted by the sensor unit 12. Sensor part 12
An electrode layer 14 formed on a silicon substrate 11 is patterned on the surface thereof, and a sensor opening 13 is provided.
The electrode layer 14 is formed of a light shielding film made of aluminum or the like.

The multi-lens structure of the solid-state imaging device of the present embodiment has three convex lenses 16, 18, and 20. That is, the first transparent material layer 15 is formed so as to cover the electrode layer 14 in which the sensor opening 13 is provided. A convex lens 16 is formed in a region corresponding to the sensor opening 13 of the first transparent material layer 15. This first transparent material layer 15
Has a refractive index n ₀₃ , the aperture of the lens 16 is W ₀₃ ,
The radius of curvature is r ₀₃ . Then, a second transparent material layer 17 is formed on the first transparent material layer 15 provided with the lens 16 and corresponds to the sensor opening 13 of the second transparent material layer 17. A lens 18 is formed in the area. The lens 18 has a diameter W _02, its radius of curvature is r _02. The refractive index of the second transparent material layer 17 is n ₀₂ . Further, a third transparent material layer 19 is formed on the second transparent material layer 17 on which the convex lens 18 is formed. A convex lens 20 is formed in a region corresponding to the sensor opening 13 in the third transparent material layer 19. The lens 20 has an aperture _W01 having a larger area than the sensor opening 13, and has a radius of curvature _r01 and a refractive index _n01 .

The three convex lenses 16, 18, and 20 will be described. For example, the radius of curvature is set to be r ₀₁ <r ₀₂ <r ₀₃ and the refractive index is set to be n ₀₁ > n ₀₂ > n _03. . With this setting, the light incident on the lens 20 is refracted so as to converge on the surface of the lens 20, and the light is directed on the surfaces of the lenses 18 and 16 in a direction perpendicular to the substrate. Can be bent. In FIG. 2, a light ray P ₁ is an example of a light ray that travels through three convex lenses 20, 18, and 16, and a light ray P _{1 that} is incident slightly away from the optical axis is focused by the first lens 20. And the second lens 18, 16 bends in a more vertical direction.

The solid-state imaging device of the present embodiment has a multi-lens structure,
It is possible to increase the amount of light collection, and the first lens 20
Is converged by the second lenses 18 and 16 in the vertical direction toward the sensor opening 13, so that irregular reflection at the sensor non-opening portion and the like is suppressed and the area of the sensor unit 12 is maximized. Can be used for Further, the solid-state imaging device according to the present embodiment can sufficiently cope with the multilayer structure of the electrodes, and can suppress the shading amount.

Each lens described above is formed by, for example, patterning a heat-deformable film on a transparent material layer for each sensor opening, reflowing the heat-deformable film, and then etching. In the solid-state imaging device, a dye layer and a flattening film can be provided on the chip as needed.

〔The invention's effect〕

The solid-state imaging device according to the present invention can increase the amount of light condensed by the multiple lens structure as described above, and at the same time, the light incident on the sensor unit is bent in the vertical direction. It has a structure that is resistant to manufacturing variations, and can cope with higher density and higher pixels. In addition, the thickness of the electrode layer increases as the number of electrodes increases, but the light is incident in the vertical direction, so that the electrode can be sufficiently applied to increase the number of electrodes. Further, the amount of shading when mounted on a camera or the like can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a main part of a first embodiment of a solid-state imaging device according to the present invention, and FIG. 2 is a main part of a second embodiment of the solid-state imaging device according to the present invention. FIG. 3 is a diagram schematically showing an example of an optical path of the solid-state imaging device according to the first embodiment of the present invention in the case of oblique incident light, and FIG. FIG. 5 is a diagram illustrating an example of an optical path in the case of oblique incident light with respect to an example of the solid-state imaging device of FIG. 5. FIG. 5 illustrates a case of oblique incident light with respect to the solid-state imaging device of the first embodiment according to the present invention. FIG. 6 is a diagram showing another optical path, FIG. 6 is a diagram showing another optical path in the case of oblique incident light with respect to an example of a conventional solid-state imaging device, and FIG. 7 is a first embodiment according to the present invention. FIG. 8 is a diagram showing a shading amount of an example solid-state imaging device, and FIG. Is a diagram showing the shading of an example of an image element. FIG. 9 is a cross-sectional view schematically showing one example of a conventional solid-state imaging device. 1,11 ... Silicon substrate, 2,12 ... Sensor part, 3,13 ...
Sensor opening, 4,14 ... Electrode layer, 5,7,15,17,19 ... Transparent material layer, 6,8,16,18,20 ... Lens

Claims (3)

(57) [Claims] A lens formed integrally on a chip, wherein the lens has a first convex lens for condensing having a diameter larger than at least a sensor opening;
A solid-state imaging device having a multi-lens structure having at least a convex second lens that refracts a light beam condensed by the lens toward the sensor opening. 2. The method according to claim 1, wherein the first lens and the second lens are
2. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is formed of different layers. 3. The solid-state imaging device according to claim 1, wherein said first lens and said second lens have different refractive indexes.