JPH065829A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To improve the sensitivity of a photoelectric conversion device by a method wherein a luminous power which is lost from the surface of a condensing lens by reflection is suppressed and a luminous power which enters an optoelectric transducer is increased. CONSTITUTION:A photoelectric conversion device is composed of optoelectric transducers 11 and condensing lenses 19 corresponding to the optoelectric transducers 11. A transparent film 20 which has a smaller refractive index than the condensing lens 19 is formed over the condensing lenses 19. As the transparent film 20 which has the smaller refractive index than the condensing lens 19 is provided on the surface of the condensing lenses 19, the reflectance of a condensing lens system composed of the condensing lens 19 and the transparent film 20 is lowered, so that the sensitivity of the photoelectric conversion device can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device, and more particularly to a photoelectric conversion device having a condenser lens covered with a transparent film.

[0002]

2. Description of the Related Art In a photoelectric conversion device such as a solid-state image pickup device, as the density of pixels of the device increases, it is an important development subject to increase the sensitivity of the photoelectric conversion device corresponding to the miniaturization of pixels. . Since the improvement of sensitivity due to the improvement of semiconductor elements is approaching the limit, recently, a method of providing a plurality of condenser lenses on the surface of the device and condensing incident light on a photoelectric conversion element has come to be widely used. The related art will be described below with reference to the drawings.

FIG. 3 is a cross-sectional view of the periphery of the photoelectric conversion element portion of a typical color solid-state image pickup device. A plurality of photoelectric conversion elements 41 and a plurality of charge transfer portions (not shown) are formed on the surface of the semiconductor substrate 40. Is formed, and the flattening layer 42 made of a translucent resin is formed thereon. Further on top of that
A color filter layer 43, a first intermediate layer 44, a second color filter layer 45, a second intermediate layer 46, and a third color filter layer 47 are sequentially formed, and an overcoat layer 48 made of a translucent resin is formed thereon. To form a filter layer. The first intermediate layer 44 and the second intermediate layer 46 are also made of a translucent resin and are used to prevent color mixing between the color filter layers. As the color filter layer, casein, gelatin, and the like, to which a photosensitive material is added, and dyed with an appropriate dye, such as cyan, yellow, and magenta, are used.

Then, a condenser lens 49 is formed on the overcoat layer 48 by using a novolac type photoresist or the like to complete a color solid-state image pickup device. A protective layer 50 made of the same material as the first intermediate layer 44 and the second intermediate layer 46 may be formed on the condenser lens 49 in order to prevent the shape of the lens from changing. (JP-A-3-14288
1, see JP-A-3-190169). Since this protective layer 50 may or may not be used, FIG.
Is shown with a dotted line.

[0005]

In the above structure, the flattening layer, the color filter layer, the intermediate layer, the overcoat layer, the condenser lens, and the protective layer are usually made of an organic material. Acrylic resin, casein, gelatin, polystyrene resin, novolac resin, etc. are used as the material, and their refractive indexes are all about 1.5 to 1.6.

On the other hand, a part of the incident light is reflected on the surface or interface of a lens / filter system composed of a condenser lens (protective layer and condenser lens if there is a protective layer), color filter layer, intermediate layer, etc. Therefore, 5 to 10% of the incident light is lost as reflected light. That is, 5 to 10 of the incident light
% Is lost, and the sensitivity of the photoelectric conversion device is reduced accordingly.

Therefore, the present invention aims to provide a photoelectric conversion device in which the amount of light lost from the lens / filter system due to reflection is reduced and the amount of light entering the photoelectric conversion element is increased to improve the sensitivity. .

[0008]

In order to achieve the above object, according to the present invention, in a photoelectric conversion device having a photoelectric conversion element and a condenser lens corresponding to the photoelectric conversion element, the collector lens is provided on the condenser lens. It is characterized in that a transparent film having a refractive index lower than that of the optical lens is formed.

[0009]

[Function] When a transparent film having a refractive index lower than that of the condenser lens is formed on the condenser lens with an appropriate thickness,
Since the reflectance of the condenser lens system including the transparent film and the condenser lens can be minimized, the amount of light lost to the outside of the condenser lens system can be reduced, and therefore the sensitivity of the photoelectric conversion device can be increased. be able to.

Generally, when a transparent film having a refractive index lower than that of the lens is formed on the lens with a film thickness corresponding to a quarter wavelength of the incident light wavelength, the reflection of the light is suppressed by the interference of light and the light is transmitted. It is known that the rate will increase. If the thickness of the transparent film is 0.10 to 0.18 μm, the wavelength in the normal visible light range
A quarter wavelength of 0.40 to 0.70 μm can be covered, and a low reflectance can be realized over the entire visible light region.

As for the light reflected from the lower interface of the condenser lens and the filter layer, the refractive index of the transparent film is smaller than that of the condenser lens. , The probability of total reflection is increased, and the amount of light lost to the outside of the condenser lens system is reduced.

[0012]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment of the present invention. In FIG. 1, a plurality of photoelectric conversion elements 11 are arranged on a semiconductor substrate 10 with a horizontal pitch of 9.6 μm and a vertical pitch of 9.9 μm. On top of that, a flattening layer 12 made of acrylic resin, a first color filter layer 13 made of casein dyed in cyan, a first intermediate layer 14 made of acrylic resin, and a second colored casein made in yellow. A color filter layer 15, a second intermediate layer 16 made of acrylic resin, a third color filter layer 17 obtained by dyeing casein with magenta color, and an overcoat layer 18 made of acrylic resin are sequentially formed, and a filter layer having a thickness of 7 μm is formed. Was formed. Then, using a novolac-based positive photoresist (refractive index 1.60), patterning with ordinary photolithography technology, and performing the photoelectric conversion in a well-known process such as transparency treatment by re-exposure and shape imparting by heat melt. A condenser lens 19 was formed on the element 11. The size of the condenser lens 19 is 9.0 μm in length and 9.0 μ in width.
m and the height was 2.6 μm. In addition, CYTOP solution (transparent fluororesin made by Asahi Glass, refractive index 1.34) is applied on the lens
The transparent film 20 having a low refractive index was formed by spin coating to a thickness of 0.14 μm to complete the photoelectric conversion device.

Next, referring to FIG. 2, the transparent film 20 (thickness 0.14 μm)
A comparison of relative sensitivities when the lens film thickness of the condenser lens 19 is changed is shown with and without. In FIG. 2, a curve 31 represents the case of the conventional technique without the transparent film 20,
The curve 32 is a transparent film having a low refractive index shown in the embodiment of the present invention, and the curve 33 is used as a comparison. Indicates. The height of the condenser lens 19
In a low region of 2.0 μm or less, when the Cytop solution is applied, the solution accumulates at the boundary (recess) of the plurality of condensing lenses 19 arranged, and the lens effect is reduced. Therefore, the curve 32 and the curve 33 when the transparent film 20 is present
In the low region where the height is 2.0 μm or less, the sensitivity is lower than the sensitivity of the curve 31 when the transparent film 20 is not provided.

However, the height of the condenser lens 19 is
When it exceeds 2.0 μm, the curve 32 with the transparent film 20 having a low refractive index has a higher sensitivity than the curve 31 without the transparent film 20. The curve 33 with the transparent film 20 having a refractive index (1.56) similar to the refractive index (1.60) of the condenser lens 19 does not exceed the maximum sensitivity of the curve 31 without the transparent film 20. The thickness of the condenser lens 19 is 2.0
In the region exceeding μm, the curve 32 is different from the other curves 31, 33.
A maximum sensitivity improvement of 5% was observed.

In this embodiment, the color solid-state image pickup device has been described, but it goes without saying that the present invention can be applied to a monochrome solid-state image pickup device in which a condenser lens is directly formed after forming a flattening layer. Further, the present invention can be applied not only to the solid-state image pickup device but also to general light receiving type photoelectric conversion devices.

[0016]

Since the transparent film having the refractive index lower than that of the condenser lens is provided on the surface of the condenser lens, the reflectance of the condenser lens system composed of the condenser lens and the transparent film is improved. It is possible to improve the sensitivity of the photoelectric conversion device.

[Brief description of drawings]

FIG. 1 is a sectional view of a photoelectric conversion device according to an embodiment of the present invention.

FIG. 2 is a comparative sensitivity comparison diagram with and without a transparent film.

FIG. 3 is a cross-sectional view of a photoelectric conversion device according to a conventional technique.

[Explanation of symbols]

 10 Semiconductor substrate 11 Photoelectric conversion element 12 Flattening layer 13 First color filter layer 14 First intermediate layer 15 Second color filter layer 16 Second intermediate layer 17 Third color filter layer 18 Over Coating layer 19 ... Condensing lens 20 ... Transparent film

Claims (2)

[Claims] 1. A photoelectric conversion device having a photoelectric conversion element and a condenser lens corresponding to the photoelectric conversion element, wherein a transparent film having a refractive index lower than that of the condenser lens is provided on the condenser lens. A photoelectric conversion device characterized by being formed. 2. The photoelectric conversion device according to claim 1, wherein the transparent film has a thickness of 0.10 to 0.18 μm.