JP2005166992A - Solid-state imaging element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging element where reflected light from an unopening part is reduced by good reproducibility and stably without burying a gap between lenses with resin even in a fine pixel. <P>SOLUTION: An exposed surface between microlenses 15 is an infrared absorbing layer containing color material having an infrared absorbing function, and minute protrusions 13 of ≤0.2μm pitch are formed on the exposure surface. The color material of the infrared absorbing layer is a color layer obtained by blending an organic pigment and an inorganic pigment. The exposure surface between the microlenses is a color filter 31 containing the color material, and the minute protrusions of ≤0.2μm pitch are formed on the exposure surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a solid-state imaging device typified by a light-receiving device such as a C-MOS or CCD, and more particularly to a solid-state imaging device that improves image quality by reducing reflected light from a flat portion on the surface of the imaging device.

  A region (opening) that contributes to photoelectric conversion of a light receiving element such as a CCD depends on the element size and the number of pixels, but is limited to about 20% to 40% of the total area. A small aperture leads to a decrease in sensitivity as it is, and therefore it is common to form a condensing microlens on the light receiving element to compensate for this.

  However, recently, the demand for high-definition CCD image sensors with more than 3 million pixels has increased, and the aperture ratio of the microlenses associated with these high-definition CCDs (that is, sensitivity reduction) and noise such as flare, ghost, smear, etc. The decrease in image quality due to the increase has become a major problem. Imaging devices such as C-MOS and CCD are approaching a substantially sufficient number of pixels, and the competition among these device manufacturers is changing from the number of pixels to the competition of image quality.

The microlens formation technique is shown in relatively detail as a known technique, for example, in JP-A-60-53073. Japanese Patent Application Laid-Open No. 60-53073 also discloses a technique that uses the thermal fluidity (heat flow) of a resin by heat flow as a technique for forming a lens into a round and hemispherical shape, and a technique for processing a lens by several etching techniques. It is disclosed in detail.
In addition, the formation of an organic film such as PGMA or an OCD (SiO ₂ -based) inorganic film on the lens surface is also disclosed. A technique for dry-etching a microlens is described in detail in JP-A-1-10666, in addition to the above technique.

A technique for making the surface of the microlens porous is well known in Japanese Patent Application Laid-Open No. 2003-37257, but it is a relatively difficult technique to form a porous layer with good reproducibility and stability on the resin surface. There were instabilities that the surface was not flat, but became a flat surface, or the resin surface was simply wrinkled.
In addition, coating and forming a resin on the microlens often has the opposite effect of filling the gap between the lenses and forming a narrow gap.
JP 60-53073 A Japanese Patent Laid-Open No. 1-10666 JP 2003-37257 A

Re-reflected light and scattered light between the surface of the image sensor device and the inner surface of the cover glass cause noise to the image sensor, which is a problem. In particular, the non-opening portion that is a flat surface between the microlenses is 3 μm or less, that is, the area of the non-opening portion increases as the pixel becomes finer, and thus the adverse effect of the reflected light from the flat surface becomes stronger. This reflected light becomes re-reflected light from the cover glass disposed on the upper surface of the image sensor and the optical lens group on the cover glass and re-enters another adjacent image sensor to reduce image quality. It becomes the noise light to be connected.
An object of the present invention is to provide a solid-state imaging device in which reflected light from a non-opening portion is reproducibly and stably reduced without filling a gap between lenses even in a fine pixel. It is. This leads to an improvement in the S / N ratio of the solid-state imaging device, and finally an improvement in image quality is obtained.

  The present invention relates to a solid-state imaging device having a two-dimensionally arranged photoelectric conversion element and a substantially hemispherical microlens laminated on each of the photoelectric conversion elements, and an exposed surface between the microlenses is red. A solid-state imaging device comprising an infrared absorption layer containing a color material having an external absorption function, and having fine protrusions with a pitch of 0.2 μm or less formed on the exposed surface.

  The present invention is the solid-state imaging device according to the invention, wherein the color material of the infrared absorption layer is a color material in which an organic pigment and an inorganic pigment are mixed.

  In addition, the present invention provides a solid-state imaging device including a two-dimensionally arranged photoelectric conversion element and a substantially hemispherical microlens stacked on each of the photoelectric conversion elements, and an exposed surface between the microlenses is The solid-state imaging device is characterized in that it is a color filter containing a coloring material, and fine protrusions having a pitch of 0.2 μm or less are formed on the exposed surface.

  Further, according to the present invention, in the solid-state imaging device according to the invention, the color material of the color filter is a color material in which one or more organic pigments are mixed, and the difference in film thickness between the color filters of different colors is 0. It is a solid-state image sensor characterized by being within 1 μm.

The present invention has an advantage that a reflected light reduction that leads to an improvement in image quality of a solid-state imaging device can be achieved by a simple method without increasing the number of manufacturing steps. That is, at the same time as dry etching for reducing the thickness of the image sensor, microprojections can be formed to reduce reflected light.
According to the present invention, it is possible to easily form minute protrusions, which have conventionally been difficult to reproduce stably, by using a heat-resistant color material. The present invention can simultaneously provide the functions of reducing reflected light and cutting infrared rays. With the solid-state imaging device of the present invention, high image quality with little noise could be obtained.

Hereinafter, embodiments of the present invention will be described in detail.
1 and 2 are partial cross-sectional views of an embodiment of a solid-state imaging device according to the present invention. FIG. 4 shows a partial plan view of an embodiment of the solid-state imaging device according to the present invention.

1 is a partial cross-sectional view in the BB ′ direction in FIG. 4, and FIG. 2 is a partial cross-sectional view in the AA ′ direction in FIG. 4. 1 is a cross section in the diagonal direction (BB ′) of the microlens in FIG. 4, the gap 17 between the microlenses in FIG. 1 is wider than the gap 17 ′ between the microlenses in FIG. Become.
5A to 5D are partial cross-sectional views showing the method of manufacturing the solid-state imaging device according to the present invention in the order of steps.

  The invention relating to claim 1 and claim 2 of the solid-state imaging device of the present invention includes a planarizing layer 16 and a color filter on a semiconductor substrate 10 on which a photoelectric conversion device 12 is formed as shown in FIGS. 11, an infrared absorption layer 14, and a microlens 15. Microprojections 13 are formed on the surface of the infrared absorption layer 14 exposed between the microlenses. The infrared absorption in the present invention is defined as having near infrared absorption performance mainly in the region of 650 nm to 1100 nm at the wavelength of light.

The inventors of the present invention have used an infrared absorption layer constituting the exposed surface as a colored resin in which a color material mixed with a heat-resistant organic pigment or inorganic pigment is dispersed, thereby exposing the surface where no microlens is formed. It has been found that microprojections having a pitch of 0.2 μm or less can be formed very easily on the surface (the surface of the infrared absorption layer).

  The formation of the microprojections 13 brings about an effect of reducing the surface reflectance by about 0.5% compared to the case where no projections are formed. In the case of a gap between microlenses on a flat surface without protrusions, the intensity of reflected light in a certain direction is increased for parallel incident light having a certain angle, and the back surface of the cover glass located on the upper surface of the image sensor is increased. Reflects and re-enters the image sensor, adversely affecting image quality. However, the formation of the minute protrusions 13 can reduce the reflected light and eliminate the re-incident light of this intensity.

  FIG. 3 is a partial cross-sectional view of an example of a solid-state imaging device according to the inventions related to claims 3 and 4. In the present invention, as shown in FIG. 3, the semiconductor substrate 30 on which the photoelectric conversion element 32 is formed includes a planarization layer 36, a color filter 31, and a microlens 35, and the surface of the color filter exposed between the microlenses. Are formed with minute protrusions 13.

Since the microprotrusions in the present invention are intended to reduce the reflection of light at the site where the microprotrusions are formed, the height of the microprotrusions (the etching amount to be described later) is ¼ to the light wavelength λ. At most, it may be up to the wavelength of light. For this reason, in order to form microprotrusions on the color filter surfaces of different colors, it is necessary to reduce the film thickness difference between the color filters.
The film thickness difference between these color filters is preferably within 0.2 μm and about 0.1 μm. If the film thickness difference between the color filters is large, the size of the fine protrusions formed on each color filter tends to be different.

The microprotrusions in the present invention are basically formed by hitting a colored resin surface in which a heat-resistant pigment (including a pigment having an infrared absorption function) is dispersed in a transparent resin with plasma or an electron beam, or coloring. It is formed by removing a small amount of the resin component on the surface of the resin by etching or the like, and leaving fine protrusions centered on the pigment on the surface.
More specifically, a microlens is directly formed on the color filter, and the surface of the color filter (including a heat-resistant pigment as a color material) exposed between the microlenses is dry-etched. Alternatively, when an infrared absorption layer and a transparent resin are laminated in this order on a color filter and a microlens matrix is formed, and then the microlens matrix is transferred to the lower transparent resin by a dry etching technique. In addition, the surface of the infrared absorption layer is dry-etched.

  In order to selectively leave the pigment, it is important to select a pigment that is more heat resistant than the resin. Alternatively, after forming the transparent resin and the microlens matrix on the color filter without forming the infrared absorption layer, the microlens may be transferred and formed on the transparent resin by dry etching. An ultraviolet absorbing colorant may be added to the infrared absorbing layer. Furthermore, a light stabilizer such as a hindered compound or a quencher (for example, a singlet oxygen quencher) may be added.

  The formation of the minute protrusions in the present invention is simple by dry etching such as ECR, parallel plate magnetron, DRM, ICP, or dual frequency RIE. The gas used for dry etching is not particularly limited as long as it is an oxidizing or corrosive gas. There is no particular limitation on a gas having a halogen element such as fluorine, chlorine or bromine, or a gas having oxygen or sulfur elements in the same manner. However, it is practically preferable to use a fluorocarbon gas that is not flammable and has low toxicity.

  In order to reduce the gap of the microlens to be transferred and formed, a slight reducing gas may be used in combination, or a gas such as helium, argon, or carbon monoxide may be used in combination to improve the etching distribution. The target semiconductor substrate may be heated or cooled to improve the distribution and microlens shape during dry etching. Although dry etching is strongly dependent on a dry etching apparatus, the gas pressure, power, gas flow rate, etc. at the time of etching may be appropriately adjusted by each apparatus.

  The gist of the present invention utilizes a heat-resistant pigment (a fine particle of several tens of nanometers) to form a microprojection with good reproducibility and to use the microprojection to reduce the surface reflection of light. This is to improve the image quality of the image sensor.

  Examples of pigments having infrared absorption performance include fine particles of metal oxides such as indium oxide, tin oxide, antimony oxide, zirconia, and ceria, metal compounds such as lanthanum compounds, and phthalocyanine organic pigments represented by cyan pigments. Both are finely pulverized fine particles and can be applied to the present invention. The size of the fine particles is preferably smaller at the nanometer level. It is desirable to use a surfactant, a pigment derivative, and other dispersants in combination.

However, these heat-resistant pigments include anthraquinone compounds, phthalocyanine compounds, cyanine compounds, polymethylene compounds, aluminum compounds, diimonium compounds, imonium compounds, azo compounds, and the like, low-heat-resistant materials, and dye-based pigments. It is also possible to add a coloring material for the purpose of improving infrared absorption performance.
As the organic pigment of the color filter, most of organic pigments (pigments) represented by CI numbers can be adopted. However, these organic pigments also preferably employ the same fine particle size as described above and use a dispersant in combination.

  The resin that disperses the pigment having the infrared absorption performance or the pigment used in the color filter is not limited as long as it is a heat-resistant transparent resin that does not change color at 180 ° C., preferably 230 ° C. to 260 ° C., for example. An acrylic resin, an epoxy resin, a polyester resin, a urethane resin, a melamine resin, a urea resin, a styrene resin, a phenol resin, or a copolymer thereof can be used.

In order to improve coatability and dispersibility, the color resist and the coating solution for the infrared absorption layer may be added with a surfactant, mixed with a plurality of solvents, or may be adjusted with the molecular weight of the resin or added with other resins. . Further, as a pretreatment for coating, the surface of each layer may be subjected to plasma treatment or ultraviolet cleaning.
A resin film having a low refractive index may be applied and formed on the surface of the solid-state imaging device according to the present invention with a thin film thickness of about ¼ of the light wavelength λ. The low refractive index film may be formed by vacuum film formation or photolithography.

  The solid-state imaging device according to claims 1 and 2 of the present invention will be described in detail below. In FIG. 1, the planarization layer 16, the color filter 11, the infrared absorption layer 14, the microlens 15, and the infrared absorption layer 14 between the microlenses 15 are minute on the semiconductor substrate 10 on which the photoelectric conversion element 12 is formed. An embodiment of the solid-state imaging device according to the present invention in which the protrusions 13 are formed is shown. The diagonal microlens gap 17 shown in FIG. 1 is about 0.8 μm. FIG. 2 shows a sectional view in the side direction, and the gap 17 ′ between the microlenses in the side direction is set to 0.05 μm.

The manufacturing method of the solid-state image sensor of this invention is demonstrated using Fig.5 (a)-(d).
First, the planarization layer 56 is formed on the semiconductor substrate 50 on which the photoelectric conversion element 52 and the light shielding layer 53 are formed. The planarizing layer 56 was formed by applying an acrylic resin containing an ultraviolet absorber at a film thickness of 0.6 μm by spin coating, and drying and hardening at 180 ° C. (See Fig. 5 (a))
As shown in FIG. 5B, R, G, and B color filters are formed on the flattening layer 56 by three photolithography processes (color resist coating → drying → exposure → development → hardening). did. Each color filter film thickness was about 0.9 μm.
In addition, the organic pigment shown below was used for the color resist used for the color filter (R, G, B). First, green (G) is C.I. I. Pigment yellow 139, C.I. I. Pigment green 36, C.I. I. Pigment Blue 15: 6 dispersed in a photosensitive acrylic resin was used as a green resist. Red (R) is C.I. I. Pigment red 177 and C.I. I. Pigment yellow 139 dispersed therein was used. Blue (B) is C.I. I. Pigment blue 15: 6 and C.I. I. Pigment violet 23 dispersed therein was used.

  As shown in FIG. 5C, a lens matrix 59 having a thickness of 1.2 μm, a lens transfer layer 58 having a thickness of 0.8 μm, and a height of 0.8 μm was laminated. The lens matrix 59 was formed by a photolithography process using a photosensitive resin material having heat flow. Infrared absorbing layer 54 is an alkali-soluble type photosensitizer of 10 parts of a phthalocyanine-based organic pigment as a cyan pigment, 3 parts of antimony tin oxide having a fine particle of 50 nm or less, and 3 parts of a mixed lanthanum compound and zirconia having a fine particle of 50 nm or less. It was formed by spin coating using a coating liquid dispersed in a conductive acrylic resin. It should be noted that unnecessary portions such as the periphery of the imaging element chip for forming the infrared absorption layer 54 were previously removed by alkali development.

Using a dry etching apparatus, the lens matrix 59 shown in FIG. 5C is dry-etched and transferred to the lens transfer layer 58 to form a microlens 55 having a height of 0.7 μm shown in FIG. . The etching amount was 0.9 to 0.95 μm, and microprojections having a height of approximately 0.1 μm were formed on the surface of the inter-lens gap 57 of the infrared absorption layer 54. CF ₄ was used as a dry etching gas.

Hereinafter, the solid-state imaging device according to claims 3 and 4 of the present invention will be described in detail with reference to FIG.
In FIG. 3, a solid-state imaging device in which a planarization layer 36, a color filter 33, a microlens 35, and a microprojection 33 are formed on the color filter 33 between the microlenses 35 on the semiconductor substrate 30 on which the photoelectric conversion element 32 is formed. showed that. The gap 37 between the diagonal microlenses is about 0.8 μm. The color filter and the organic pigment used for the color filter are the same as in Example 1. The film thicknesses of green, blue, and red were 0.95 μm, 0.9 μm, and 0.9 μm, respectively, and the film thickness difference was within 0.1 μm. The dry etching amount was 0.95 μm.
The infrared absorption layer shown in Example 1 is omitted in Example 2, and the minute protrusions 33 are formed only on the exposed surface of the inter-lens gap 37 of the color filter.

It is a fragmentary sectional view of one example of a solid-state image sensing device by the present invention. It is a fragmentary sectional view of one example of a solid-state image sensing device by the present invention. It is a fragmentary sectional view of an example of the solid-state image sensor by the invention concerning Claim 3 and Claim 4. It is a partial top view of one Example of the solid-state image sensor by this invention. (A)-(d) is explanatory drawing of the manufacturing method of the solid-state image sensor by this invention.

Explanation of symbols

10, 30, 50 ... Semiconductor substrate 11, 31, 51 ... Color filters 12, 32, 52 ... Photoelectric conversion elements 13, 33, 53 ... Micro projections 14, 54 ... Infrared absorption Layers 15, 35, 55... Microlenses 16, 36, 56... Flattening layers 17, 17 ′, 37, 57. Type

Claims (4)

  In a solid-state imaging device having a two-dimensionally arranged photoelectric conversion element and a substantially hemispherical microlens laminated on each of the photoelectric conversion elements, an exposed surface between the microlenses has an infrared absorption function. A solid-state imaging device, comprising: an infrared absorption layer containing a coloring material having a colorant, and fine protrusions having a pitch of 0.2 μm or less formed on the exposed surface.   The solid-state imaging device according to claim 1, wherein the color material of the infrared absorption layer is a color material obtained by mixing an organic pigment and an inorganic pigment.   In a solid-state imaging device including a two-dimensionally arranged photoelectric conversion element and a substantially hemispherical microlens stacked on each of the photoelectric conversion elements, an exposed surface between the microlenses contains a color material. A solid-state imaging device which is a color filter and has fine protrusions with a pitch of 0.2 μm or less formed on the exposed surface.   The color material of the color filter is a color material in which one or more organic pigments are mixed, and the film thickness difference between the color filters of different colors is within 0.1 μm. Solid-state image sensor.

Images