JPH11284162A - Solid-state imaging element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light gathering ratio by reducing thickness of a solid-state imaging element. SOLUTION: On a photodetecting sensor part 12, an inter layer film 21 comprising a recessed part at the photodetecting sensor part 12 is provided, and on the inter layer film 21, a plurality of micro lenses 27 wherein, a side facing the photodetecting sensor 12 filling a recessed part 21a of the inter layer film, the curved surface of the recessed part 21a forms a protruding part 27a are provided, while each of the micro lenses is a colored micro lens comprising any color among a plurality of colors.

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, particularly to a color solid-state image pickup device.

[0002]

2. Description of the Related Art In recent years, in solid-state imaging devices, the miniaturization and the increase in the density of pixels have progressed, and with this, the light receiving area has been reduced, resulting in deterioration in characteristics such as sensitivity reduction. As a countermeasure against the decrease in sensitivity, it has been proposed to provide a microlens, for example, a so-called on-chip lens or an in-layer lens to increase the light-collecting efficiency in the light-receiving sensor unit. Hereinafter, the structure of a conventional solid-state imaging device will be described.

FIG. 6 is a schematic sectional view of a main part of a solid-state imaging device 100 having a conventional structure. As shown in FIG.
1, a large number of light receiving sensor units 102 for performing photoelectric conversion
Are arranged in rows and columns. A charge transfer unit 104 is formed for the light receiving sensor units 102 on each common column. The signal charges obtained by the photoelectric conversion in the light receiving sensor unit 102 are read out to the charge transfer unit 104 and transferred in the column direction.

[0004] An insulating film (not shown) is laminated on the substrate 101, and a transfer electrode 107 is formed almost directly above the charge transfer section 104 via the insulating film. On this transfer electrode 107, a light shielding film 109 made of a high melting point metal is formed so as to cover the transfer electrode.

[0005] Covering the light shielding film 109, for example, BP
An interlayer film 111 made of SG (boron / phosphor / silicate glass) is formed. The interlayer electrode 111 is subjected to a reflow process (thermal softening process) so that the transfer electrode 1 is formed.
A concave portion 111a is formed on the light receiving sensor portion 102 between the positions 07 and 07. These concave portions 111a are adjusted to concave surfaces having a required curvature.

On the interlayer film 111, a concave portion 111 of the interlayer film is formed.
a is embedded with an in-layer lens material such as plasma silicon nitride, and the in-layer lens 114 having a convex portion having a curvature necessary for condensing incident light on the light receiving sensor unit 102 by the curved surface of the concave portion 111a. Is formed. The upper surface of the inner lens 114 is planarized by a known so-called resist etch-back method or a CMP method (chemical mechanical polishing method).

On the planarized inner lens 114,
A color filter layer 116 is formed. The color filter layer 116 is formed by a known method using a resin in which a dye is dispersed.

[0008] On the color filter layer 116, a micro lens 117 having a convex lens shape is formed. The microlenses 117 are for condensing incident light on the light receiving sensor unit 112 via the inner lens 114. Therefore, the curvature of the convex micro lens 117 is selected to a desired value according to the distance from the light receiving sensor unit 102 to the micro lens 117 in the solid-state imaging device 100 shown in FIG.

[0009]

However, the solid-state imaging device 100 having the structure shown in FIG. 6 has the following disadvantages. That is, in the solid-state imaging device 100 having the structure having the inner lens 114 shown in FIG.
Are provided, the thickness from the light receiving sensor unit 102 to the surface on which the micro lens 117 is formed is 4 to 5 μm.
m or more, and the distance from the light receiving sensor unit 102 to the surface on which the microlenses 117 are formed becomes large.

As described above, when the distance from the light receiving sensor unit 102 to the microlens 117 becomes large, as shown in FIG. When the light incident obliquely increases, as shown by a broken line L ′ in FIG.
When the light incident at an angle is condensed by the microlenses 117, the condensing at the center of the opening of the light shielding film 109 is reduced.
That is, the F-number dependence is deteriorated, and the sensitivity to the central parallel light is good, but the sensitivity is significantly reduced on the aperture open side.
When the condensed light approaches the opening end of the light-shielding film 109, signal charges are mixed into the adjacent light receiving sensor unit 102 and the charge transfer unit, so that so-called smear is generated.

The present invention provides a solid-state imaging device having a structure in which the distance from the light receiving sensor unit 102 to the microlens 117 is reduced to solve the above-mentioned disadvantage.

[0012]

The solid-state imaging device of the present invention has a light-receiving sensor unit for performing photoelectric conversion on a substrate, an interlayer film having a concave portion on the light-receiving sensor unit, and , Having a plurality of microlenses having a convex upper surface,
This microlens is formed by embedding a concave part of an interlayer film and forming a convex part by a curved surface of the concave part, and a curvature of the convex part of the microlens is a curvature necessary for condensing incident light on a light receiving sensor part. It is assumed that each of the microlenses is a colored microlens having any one of a plurality of colors.

The solid-state imaging device of the present invention has a colored microlens in which a lens in a layer constituting a conventional solid-state imaging device, a color filter, and a microlens are integrated. In the solid-state imaging device of the present invention, the colored microlens has the functions of an inner lens, a color filter, and a microlens. In the case of manufacturing the solid-state imaging device of the present invention, it is only necessary to manufacture a colored microlens in which an in-layer lens, a color filter, and a microlens are integrated, and it is not necessary to separately manufacture these. . Further, according to the structure of the solid-state imaging device of the present invention, since the colored microlens also functions as the inner lens, the color filter, and the microlens, the inner lens, the color filter, and the microlens are used. There is no need to provide the microlens separately, so that the distance from the light receiving sensor unit to the microlens is reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid-state imaging device according to the present invention has a light-receiving sensor unit for performing photoelectric conversion on a substrate, and has an interlayer film having a concave portion in the light-receiving sensor unit on the light-receiving sensor unit. It has a plurality of micro lenses on the top,
The side facing the light receiving sensor is formed by embedding a concave portion of the interlayer film and forming a convex portion having a curvature necessary for condensing incident light on the light receiving sensor portion by the curved surface of the concave portion, and each of the micro lenses has a plurality of It is assumed that the color microlens has any one of the colors.

Hereinafter, an example of the solid-state imaging device of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following example. FIG. 1 shows a solid-state imaging device 1 of the present invention.
FIG. 1 shows a schematic cross-sectional view of a main part of one example. As shown in FIG. 1, for example, on a silicon substrate 11, a large number of light receiving sensor units 12 for performing photoelectric conversion are arranged and formed in rows and columns. A charge transfer section 14 is formed on one side of the light receiving sensor section 12 on each common column. The signal charges obtained by photoelectric conversion in the light receiving sensor unit 12 are read out by the one charge transfer unit 14 and transferred in the column direction.

A transfer electrode 17 made of, for example, polysilicon is formed almost immediately above the charge transfer section 14.
Further, another transfer electrode is formed so as to partially overlap the transfer electrode 17.

On this transfer electrode 17, a light-shielding film 19 made of a refractory metal and having a light-receiving window 12a formed thereon is formed on the light-receiving sensor section 12, covering the transfer electrode.

The light shielding film 19 is covered, and
An interlayer film 21 made of PSG (boron phosphorus silicate glass) is formed. By performing a reflow process (thermal softening process) on the interlayer film 21, a concave portion 21 a is formed on the light receiving sensor unit 12 between the transfer electrodes 17. The concave portion 21a is adjusted to a required curvature.

On the interlayer film 21, a passivation film 22 is formed of, for example, plasma silicon nitride.

On this passivation film 22, a micro lens 27 is formed. The micro lens 27 has a concave portion 21a of the interlayer film 21 buried on the side facing the light receiving sensor 12, and a convex portion 27a is formed by a curved surface of the concave portion 21a. This micro lens 27
Is formed as a convex surface having a curvature necessary for condensing incident light on the light receiving sensor unit 12. Also,
Each of the microlenses 27 is a colored microlens having any one of a plurality of colors.

The surface of the micro lens 27 is coated with a low reflection film 28. The reflection of the incident light on the surface of the microlens 27 is reduced by the low reflection film 28, so that the incident light can be efficiently taken into the element.

The solid-state imaging device according to an embodiment of the present invention shown in FIG. 1 can be manufactured as follows. That is, first, the light receiving sensor unit 12, the charge transfer unit 14, and the transfer electrode 17 are formed on the silicon substrate 11 by a conventionally known method.
Next, an interlayer insulating film (not shown) is formed so as to cover the transfer electrode 17, and then a light-shielding film 19 is formed by depositing a high melting point metal such as tungsten (W). A light receiving window 12 a is formed in the light shielding film 19 on the light receiving sensor unit 12.

Next, for example, using BPSG, this is converted to, for example, CVD (Chemical Vapor Depo).
An interlayer film 21 is formed on the entire surface so as to cover the light-shielding film 19 by a position (method). Next, the interlayer film 21 is subjected to a thermal softening process (reflow process) at a predetermined condition, for example, about 700 ° C. to 800 ° C. to form a recess 21a of the interlayer film 21. The center of the recess 21a is It is formed so as to coincide with the center of the light receiving sensor unit 12 at the opening 19.
A colored microlens 27 is finally formed on the concave portion 21a. The microlens 27 is such that the concave portion 21a is embedded and a convex portion is formed by the curved surface of the concave portion 21a. Since the micro lens 27 also functions as an intra-layer lens of a conventional solid-state imaging device, the concave portion 21a of the interlayer film 21 is formed.
Is formed so as to have a curvature necessary for condensing incident light on the light receiving element.

On the interlayer film 21, for example, a SiN film or Si
The passivation film 22 of the ON film is formed by, for example, a plasma CVD method. This passivation film 2
Reference numeral 2 has a role of preventing ions from entering the lower interlayer film 21 from the upper layer.

Next, as shown in FIG. 2, for example, the three primary colors of red, green, and blue are formed on the passivation 22 by using a material in which a synthetic dye is contained in polyvinyl alcohol or a material in which a pigment is dispersed. The filter layer 30 is formed.

Thereafter, a photoresist is applied on the color filter layer 30 and its surface is flattened to form a photoresist layer 31.

Next, as shown in FIG. 3, the photoresist layer 31 is exposed and then developed to form a required pattern. That is, the photoresist layer 31
Among them, the pattern is formed in such a manner that the one at the opening of the light shielding film 19 is left.

Next, as shown in FIG. 4, the photoresist layer 31 is subjected to a thermal softening treatment (reflow treatment),
The surface is formed into a spherical surface having a required curvature, and a lens-type forming layer 31a is formed. For this reason, a material in which the melting point of the material of the photoresist layer 31 is lower than the melting point of the material of the color filter layer 30 is selected in advance, and the photoresist layer 31 is formed at a temperature lower than the melting point of the material of the color filter layer 30. Heat treatment. Melted photoresist layer 3
1 has a spherical surface due to surface tension, and the lens-type forming layer 31a can be obtained.

Next, a lens-type forming layer 31a having a spherical surface is formed.
RIE (Reactive Ion)
Etching is performed to etch the lens type forming layer 31a and the color filter layer 30 to form each color filter into a convex lens shape as shown in FIG. The convex lens-shaped color filters constitute the microlenses 27 in the finally obtained solid-state imaging device 10.

Next, the surface of the microlens 27 is coated with a low-reflection film 28 capable of reducing the reflection of incident light on the surface of the microlens 27, and finally, the intended solid-state imaging device 10 is manufactured. be able to.

The solid-state imaging device 10 thus obtained is
In this case, the light condensed on the upper convex surface of the microlens 27 and further condensed on the lower portion of the microlens 27, that is, the convex portion 27 a on the side facing the light receiving sensor unit 12, And enters the light receiving sensor unit 12, where photoelectric conversion is performed.

According to the solid-state imaging device of the present invention, the colored microlens 27 is a function of the in-layer lens 114, the color filter 116, and the microlens 117 of the conventional solid-state imaging device 100 described with reference to FIG. Having.

In the solid-state image pickup device of the present invention, it is sufficient to form only a colored microlens without separately forming an inner lens, a color filter, and a microlens. Can be formed small. In addition, since the distance from the light receiving sensor unit to the microlens is formed small as shown in FIG. 5, as shown in FIG. Fig. 5
As indicated by the broken line in the middle, the light condensed by the microlens 27 is condensed on the light receiving sensor unit 12 even when deviated from the center of the opening of the light-shielding film 19, and compared with the solid-state imaging device having the conventional structure. As a result, the light collection rate is improved. That is,
It is possible to reduce the reduction in sensitivity even on the aperture open side. In addition, since the collected light can avoid mixing signal charges into the adjacent light receiving sensor unit 12 and the charge transfer region (not shown), so-called smear can be prevented.

In the embodiment described above, the surface of the photoresist layer 31 formed on the color filter layer 30 is formed into a spherical shape by heat treatment, but the present invention is not limited to this example. . That is, the present invention can be similarly applied to a case where a so-called chemical treatment of forming a spherical shape on the surface by partially dissolving the photoresist layer 30 with a solution is performed.

In the above-described embodiment, the interlayer film 21 is formed by BPSG. However, the present invention is not limited to this example.
A conventionally known material can be applied as long as it is a material that can form the concave portion 21a having a required curvature by subjecting 1 to a heat softening treatment (reflow treatment).

[0036]

According to the solid-state imaging device of the present invention, the light receiving sensor has a structure in which a colored microlens having the functions of an inner lens, a color filter, and a microlens and integrated with each other is formed. The distance from the part to the microlens could be reduced. As a result, even when the light obliquely incident on the microlens increases, such as when the aperture of the imaging lens of the camera is opened, the light collected by the microlens remains at the center of the opening of the light shielding film. There was no deviation, and it was possible to effectively avoid a decrease in the light collection rate.

Further, the solid-state image pickup device of the present invention only forms a colored microlens in which an inner lens, a color filter, and a microlens are integrated. Were not separately formed, so that the manufacturing process of the solid-state imaging device could be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a solid-state imaging device according to the present invention.

FIG. 2 shows a manufacturing process diagram of the solid-state imaging device of the present invention.

FIG. 3 shows a manufacturing process diagram of the solid-state imaging device of the present invention.

FIG. 4 shows a manufacturing process diagram of the solid-state imaging device of the present invention.

FIG. 5 is a diagram showing a state where light incident on a lens is collected by the solid-state imaging device of the present invention.

FIG. 6 is a schematic sectional view of a conventional solid-state imaging device.

FIG. 7 shows a state of condensing incident light in a solid-state imaging device having a conventional structure.

[Explanation of symbols]

10, 100: solid-state imaging device, 11, 101: substrate, 1
2, 102: light receiving sensor unit, 12a: light receiving window, 14, 1
04 ... Charge transfer part, 17,107 ... Transfer electrode, 19,1
09: light shielding film, 21, 111: interlayer film, 21a, 111
a: concave portion, 22: passivation film, 114: internal lens, 116: color filter layer, 27, 117: micro lens, 27a: convex portion, 28: low reflection film, 30:
Color filter layer, 31 ... photoresist layer, 31a
… Lens type forming layer

Claims (2)

[Claims] 1. A solid-state imaging device having a light-receiving sensor unit for performing photoelectric conversion on a substrate, comprising an interlayer film having a concave portion on the light-receiving sensor unit, wherein an upper surface has a convex surface on the interlayer film. A plurality of microlenses, the side of the microlens facing the light-receiving sensor embeds a concave portion of the interlayer film, and the curved surface of the concave portion focuses incident light on the light-receiving sensor portion. A solid-state imaging device having a convex surface having a required curvature, wherein each of the microlenses is a colored microlens having any one of a plurality of colors. 2. The solid-state imaging device according to claim 1, wherein said microlens is coated with a low reflection film.