JP2001077339A - Solid-state image sensing element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solid-state image sensing element which is constructed so that an area of an opening part can be enlarged practically. SOLUTION: A solid-state image sensing element 20 is formed by providing a light receiving sensor 3 which performs photoelectric conversion to a surface layer of a base 2, and providing transfer electrodes 4, 5 for transferring charge formed in a light receiving sensor onto the base 2 and a light screening film 6 covering the same. A lattice-like or stripe-like light screening wall 21 which becomes a partition for picture element isolation is provided on the light screening film 6. Each picture element partitioned by a light screening wall is provided with inlay lenses 22, 23 positioned in part immediately above a light receiving sensor part 3. A flattened passivation film 27 is provided on the light screening wall. A color filter layer 28 is provided on the passivation film 27. An on-chip lens 29 is provided on the color filter layer 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solid-state image pickup device having improved light-collecting efficiency to a light-receiving sensor unit.

[0002]

2. Description of the Related Art As a solid-state imaging device, for example, FIG.
The structure shown in (a) is known. In this solid-state imaging device 1, a light receiving sensor unit 3 for performing photoelectric conversion is formed on a surface layer of a substrate (base) 2 made of a silicon substrate or the like.
A first transfer electrode 4 and a second transfer electrode 5 for transferring charges formed by the light receiving sensor unit 3 and a light-shielding film 6 covering the transfer electrodes 4 and 5 are formed thereon. An opening 6 a of the light-shielding film 6 is formed directly above the light receiving sensor unit 3, and a surface facing the opening 6 a is a substantial light receiving surface of the light receiving sensor unit 3.

[0003] Further, on the substrate 2, between the light shielding films 6, 6,
A buried flattening layer 7 is formed on the light-shielding film 6, and a passivation film 8 is further formed thereon.
A color filter layer 9 is formed on the passivation film 8, and an on-chip lens 10 is formed on the color filter layer 9.

[0004] In recent years, in solid-state imaging devices, the unit pixel size has been reduced along with the reduction in chip size and the increase in the number of pixels. However, such reduction in the unit pixel size is almost always reduced in the plane direction (horizontal direction) of the substrate 2, and is reduced in the thickness direction (vertical direction) of the substrate 2.
The current situation is that the reduction in size is delayed because it is technically more difficult than in the plane direction. For this reason, when attention is paid to the unit pixel, the aspect ratio (the ratio in the vertical direction to the surface direction of the substrate) is only increasing.

For example, as shown in FIG. 3A, the cell size is 4 μm square, and the first transfer electrode 4 and the second transfer electrode 5
Considering the case where the thickness of the first transfer electrode 4 and the second transfer electrode 5 are overlapped with each other, the on-chip lens 1
The thickness up to the bottom portion of 0 (the level on the upper surface of the color filter layer 10) is about 4.5 μm. Therefore, the aspect ratio in this case is 4.5 / 4 = 1.125.

On the other hand, as shown in FIG. 3B, when the cell size is 3 μm square, the aspect ratio is 4.5 if there is no change from the light receiving sensor unit 3 to the layer thereabove.
/3=1.5. At this time, the on-chip lens 10
Is about 1 μm, the cross-sectional shape is as shown in FIG. That is, the state shown in FIG. 3A is changed from the state shown in FIG.
If the thickness of the on-chip lens 10 does not change even though the single pixel size (cell size) is reduced, FIG.
As shown in (b), the radius of curvature of the on-chip lens 10 is reduced, and the focal point thereof is located not above the light receiving surface of the light receiving sensor unit 3 but above the light receiving surface. As a result, the light collection efficiency is reduced. It will be. Such a decrease in light collection efficiency is expected to worsen as the size of a single pixel decreases in the future.

[0007]

Conventionally, optimization of the shape of the on-chip lens 10 and the like have been studied in order to improve the light collection efficiency. Since it largely depends on the processing limit of the lens 10, there is a limit in improving the light-collecting state and increasing the light-collecting efficiency. Particularly, in the case of a single pixel having a large aspect ratio, the light is efficiently collected on the light receiving sensor unit 3. It was difficult to do.

Accordingly, as described above, when the light-collecting efficiency is reduced, characteristics such as sensitivity gradient in the plane of the solid-state image sensor, color mixing due to incidence on adjacent pixels, and further, sensitivity reduction and smear level deterioration are caused. Will be reduced.
For example, light transmitted through the on-chip lens 10 and the color filter layer 9 enters adjacent pixels as shown by an arrow A in FIG. The light reaches the light-shielding film 6 and is reflected by the light-shielding film 6, so that the light does not enter the light-receiving sensor unit 3, and as a result, the sensitivity is reduced. It is also conceivable to make some improvement on the layer above the surface of the substrate 2 to reduce the layer thickness. However, in that case, restrictions on electric characteristics and deterioration of characteristics are induced, and device design and fabrication are performed. Is restricted, and the degree of freedom is reduced.

On the other hand, regarding the reduction in the plane direction, the first transfer electrode 4 and the second transfer electrode 5
Is simply reduced, the characteristics of the amount of electric charges to be handled are remarkably deteriorated, so that the reduction ratio of the transfer electrodes 4 and 5 cannot be made equal to the reduction ratio of the single pixel size. Therefore, when the surface direction is reduced from the state shown in FIG. 3A to the state shown in FIG. 3B, the opening of the light-shielding film 6 which becomes a substantial light receiving surface of the light receiving sensor unit 3 The area of 6a is reduced, which causes a decrease in sensitivity.

The present invention has been made in view of the above circumstances, and an object of the present invention is not to largely depend on an aspect ratio of a single pixel size, and to provide an opening 6a.
It is an object of the present invention to provide a solid-state imaging device having a structure capable of substantially increasing the area of the solid-state imaging device.

[0011]

Means for Solving the Problems The inventor of the present invention has made intensive studies to solve the above-mentioned problems. As a result, the present inventors have developed a conventional solid-state imaging device having a structure as shown in FIGS. 3 (a) and 3 (b). Noted that only a semiconductor material layer such as silicon oxide or a resin layer was provided above the light-shielding film 6, and no structure for preventing light transmission or reflecting light was provided. . That is, since such a configuration is not provided, when the light-collecting efficiency is reduced, the incidence on the adjacent pixels cannot be suppressed, and the light incident above the light shielding film 6 contributes to the sensitivity. He could not do anything at all.

Therefore, in the solid-state imaging device of the present invention, a light receiving sensor unit for performing photoelectric conversion is provided on the surface layer of the base, and a transfer electrode for transferring electric charges formed by the light receiving sensor on the base and the transfer electrode are provided. In a solid-state imaging device provided with a light-shielding film that covers an electrode, on the light-shielding film, a lattice-shaped or stripe-shaped light-shielding wall serving as a partition for separating pixels is provided, and each of the light-shielding walls is partitioned by the light-shielding wall. For each pixel, an in-layer lens is provided immediately above the light receiving sensor unit, a flattened passivation film is provided on the light shielding wall, and a color filter layer is provided on the passivation film. Providing an on-chip lens on the filter layer is a means for solving the above problem.

According to this solid-state imaging device, a lattice-shaped or stripe-shaped light-shielding wall is provided as a partition for separating pixels on the light-shielding film, and the light-shielding wall allows the incident light to reach the light-shielding wall. It is possible to prevent the incident light from being incident on the adjacent pixels, and furthermore, it is possible to improve the light-collecting efficiency by reflecting the incident light on the light-shielding wall and causing the incident light to enter the light-receiving sensor unit. .

Further, the provision of the in-layer lens and the on-chip lens makes it possible to further improve the light collection efficiency. Further, since the color filter layer is provided on the flattened passivation film, the film thickness of the color filter layer becomes constant, and therefore, there is no difference in the spectral characteristics over the entire color filter layer. Color display becomes possible.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solid-state imaging device according to the present invention will be described in detail. FIG. 1 is a diagram showing an embodiment of a solid-state imaging device according to the present invention. In FIG. 1, reference numeral 20 denotes a solid-state imaging device. In the solid-state imaging device 20, a light-receiving sensor unit 3 that performs photoelectric conversion is formed on a surface layer of a substrate (base) 2 made of a silicon substrate or the like as in a conventional device, and the light-receiving sensor unit 3 is formed on the substrate 2. A first transfer electrode 4 and a second transfer electrode 5 for transferring the transferred charges, and a light shielding film 6 covering the transfer electrodes 4 and 5 are formed. An opening 6 a of the light-shielding film 6 is formed directly above the light receiving sensor unit 3, and a surface facing the opening 6 a is a substantial light receiving surface of the light receiving sensor unit 3.

On the light-shielding film 6, a lattice-shaped light-shielding wall 21 serving as a partition for pixel separation is provided.
The light-shielding wall 21 is formed of the same material as the light-shielding film 6 made of a light-shielding material such as a metal in this example, and is formed so as to surround the opening 6a of the rectangular light-shielding film 6. That is, it is formed continuously with the light shielding film 6. Further, in this example, the light shielding wall 21 is formed to have a width smaller than the width of the light shielding film 6 covering the transfer electrode 4 (5).

On the substrate 2, convex and concave inner lenses 22, 23 are formed for each pixel partitioned by the light shielding walls 21, 21. The convex and concave inner lenses 22, 23
Are formed so as to be located directly above the light receiving sensor unit 3, respectively, and are designed so that the light is condensed in the opening 6 a of the light shielding film 6. A low-refractive-index layer 24 made of a low-refractive-index material such as an oxide film is formed, a high-refractive-index layer 25 made of a high-refractive-index material such as a silicon nitride film is formed thereon, and an SOG (Spin On Grass) low refractive index layer 2
6 is formed. That is, since the interface between the low-refractive index layer 24 and the high-refractive index layer 25 is concave upward, the concave inner lens 22 is formed at the interface between the low-refractive index layer 24 and the high-refractive index layer 25,
Since the interface between the high refractive index layer 25 and the low refractive index layer 26 is convex upward, the high refractive index layer 25 and the low refractive index layer 26
The convex inner lens 23 is formed at the interface with the substrate.

On the low refractive index layer 26 and the light shielding wall 21, a passivation film 2 made of a silicon nitride film is formed.
7 are formed. This passivation film 27
As described below, the passivation film 27 itself is also flattened because the low refractive index layer 26 and the light-shielding wall 21 which are the bases are flattened. Then, the passivation film 27 thus planarized
On the color filter layer 28, an on-chip lens 29 is formed.

In manufacturing the solid-state image pickup device 20 having such a structure, in particular, in order to form the intralayer lenses 22, 23 and the light-shielding wall 21, the light-shielding film 6 is formed on the substrate 2 in the same manner as in the prior art. Opening on the light receiving sensor section 3 to form an opening 6
After forming a, a low refractive index material is deposited. Then, the film made of the low-refractive-index material is patterned by a conventionally known lithography technique and etching technique, and is processed into a curved surface shape that is concave upward at a position immediately above the light receiving sensor unit 3 as shown in FIG. Thus, a low refractive index layer 24 is formed.

Next, a high refractive index material is formed on the low refractive index layer 24. The film made of the high-refractive-index material is patterned by lithography and etching in the same manner as in the case of the low-refractive-index layer 24, so that the film has a curved surface shape that is upwardly convex just above the light-receiving sensor unit 3. It is processed to form the high refractive index layer 25. As a result, a concave inner lens 22 is formed between the high refractive index layer 25 and the low refractive index layer 24. Next, an SOG film is formed on the high-refractive-index layer 25 to form a low-refractive-index layer 26. As a result, a convex inner lens 23 is formed between the low refractive index layer 26 and the high refractive index layer 25.

After the inner lenses 22 and 23 are formed in this manner, the low refractive index layer 26 and the high refractive index layer 2 are formed by a conventionally known lithography technique and etching technique.
5, the low refractive index layer 24 is patterned, and the light shielding film 6 on the transfer electrode 4 (5) is surrounded by the opening 6a of the light shielding film 6.
Lattice-shaped grooves (not shown) communicating with the upper surface of the light shielding film 6
To form Since the grooves are formed so as to communicate with the light shielding film 6, the materials of the low refractive index layer 26, the high refractive index layer 25, and the low refractive index layer 24 are the light shielding film 6.
It is desirable to select a material having a high selectivity to the material. Next, a light-shielding material such as metal is deposited so as to fill the groove, and then etched back or C
Low refractive index layer 26 by MP method (chemical mechanical polishing method)
The upper light shielding material is removed, the light shielding wall 21 is formed in the groove, and the upper surface of the light shielding film 21 and the surface of the low refractive index layer 26 are flattened.

In the solid-state imaging device 20 shown in FIG. 1, a grid-shaped light-shielding wall 21 is formed on the light-shielding film as a partition for separating pixels. As shown by C, it is possible to prevent the light that has reached the light-shielding wall 21 out of the incident light from being incident on an adjacent pixel. 3, the light collection efficiency can be improved.

Further, since the width of the light-shielding wall 21 is formed smaller than the width of the light-shielding film 6, the opening width between the light-shielding walls 21 and 21 must be sufficiently larger than the opening width of the opening 6a of the light-shielding film 6. Therefore, the aperture 6a of the light-shielding film 6 can be substantially expanded to further improve the light-collecting efficiency. further,
Since such a light-shielding wall 21 is formed, the conventional opening of the light-shielding film 6 can be replaced by an opening substantially surrounded by the light-shielding wall 21, and thus this opening is raised to just below the passivation film 27. As a result, it is possible to obtain an effect equivalent to a state where the overall layer pressure is reduced, that is, the unit pixel size is reduced in the vertical direction of the substrate.

In addition, since the substantial opening can be raised to just below the passivation film 27, the influence of the thickness of each layer below the passivation film 27 on the characteristics can be reduced. Thus, the degree of freedom of the structure below the passivation film 27 can be increased.

Further, since the light shielding wall 21 is formed continuously with the light shielding film 6, it is possible to reliably prevent light from passing between the light shielding wall 21 and the light shielding film 6. In addition, by providing the inner lenses 22 and 23, as shown by an arrow D in FIG. 1, the light-collecting efficiency can be improved not only for parallel light but also for F-value light in which oblique light is mixed. . Further, since the color filter layer 28 is provided on the flattened passivation film 27, the film thickness of the color filter layer 28 becomes constant, so that there is no difference in spectral characteristics over the entire area of the color filter layer 28. Thereby, good color display can be achieved.

In the above embodiment, the concave inner lens 22 and the convex inner lens 23 are formed directly above the light receiving sensor section 3, but the present invention is not limited to this. For example, only the concave inner lens 22 may be formed as shown in FIG. 2, or only a convex inner lens (not shown) may be formed.

In the above embodiment, the light-shielding wall 21 is formed in a lattice shape. However, the light-shielding wall 21 may be formed in a stripe shape so as to sandwich the opening 6a of the light-shielding film 6.
Here, the opening 6a of the light-shielding film 6, which is substantially the light-receiving surface of the light-receiving sensor unit 3, is usually formed in a rectangular shape. In this case, the light-shielding wall 21 is formed along the long side of the rectangle. It is desirable to do.

This is because the on-chip lens 29 formed on the rectangular opening 6a is formed in a substantially elliptical shape (oval shape) in plan view corresponding to the shape of the opening 6a.
In this case, the radius of curvature decreases in the short side direction of the opening 6a, the refraction increases, and the refracted light is collected at a position above the light receiving surface of the light receiving sensor unit 3, and the incidence rate on the light receiving surface decreases. Since the incidence rate of light incident obliquely along the short side direction on the light receiving surface decreases as described above,
By forming the light shielding wall 21 along the long side, light deviating from the light receiving surface can be reflected by the light shielding wall 21 to be incident on the light receiving surface, or can be prevented from being incident on an adjacent pixel. .

Further, in the above embodiment, the width of the light shielding wall 21 is formed narrower than the width of the light shielding film 6, but the present invention is not limited to this, and is formed to be equal to the width of the light shielding film 6. You may do so.

[0030]

As described above, the solid-state imaging device according to the present invention is provided with a lattice-shaped or stripe-shaped light-shielding wall as a partition for separating pixels on the light-shielding film. In addition, it is possible to prevent the light that has reached the light-shielding wall out of the incident light from being incident on an adjacent pixel, and further reflects the incident light on the light-shielding wall to make it incident on the light-receiving sensor unit, thereby condensing the light. Efficiency can be improved.

Further, by providing the inner lens and the on-chip lens, the light collection efficiency can be further improved, and in particular, by providing the inner lens,
The focusing efficiency can be improved not only for the parallel light but also for the F-value light in which the oblique light is mixed. In addition, since the color filter layer is provided on the flattened passivation film, the thickness of the color filter layer can be made constant, so that there is no difference in spectral characteristics over the entire color filter layer. And good color display can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a side sectional view of a main part showing a schematic configuration of another embodiment of the solid-state imaging device of the present invention.

FIGS. 3 (a) and 3 (b) are cross-sectional side views of main parts showing a schematic configuration of an example of a conventional solid-state imaging device.

[Explanation of symbols]

Reference numeral 2 denotes a substrate (substrate), 3 denotes a light receiving sensor unit, 4 denotes a first transfer electrode, 5 denotes a second transfer electrode, 6 denotes a light shielding film, 6a denotes an opening, 2
0: solid-state imaging device, 21: light-shielding wall, 22: intra-layer lens,
23: intra-layer lens, 24: low refractive index layer, 25: high refractive index layer, 26: low refractive index layer, 27: passivation film, 2
8 ... Color filter layer, 29 ... On-chip lens

Claims (2)

[Claims] 1. A light receiving sensor unit for performing photoelectric conversion is provided on a surface layer of a base, and a transfer electrode for transferring electric charges formed by the light receiving sensor on the base and a light shielding film covering the transfer electrode are provided. In the solid-state imaging device, a grid-shaped or stripe-shaped light-shielding wall serving as a partition for separating pixels is provided on the light-shielding film, and the light-receiving sensor is provided for each pixel partitioned by the light-shielding wall. An inner lens is provided immediately above the portion, a flattened passivation film is provided on the light shielding wall, a color filter layer is provided on the passivation film, and a color filter layer is provided on the passivation film. An on-chip lens is provided on the solid-state imaging device. 2. The solid-state imaging device according to claim 1, wherein said light-shielding wall is formed continuously with a light-shielding film.