JP2016225338A - Solid state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid state imaging device in which formation of a color filter layer, achieving miniaturization and thinning of a color filter layer along with the progress of miniaturization, is achieved with low defect.SOLUTION: In a solid state imaging device 200 where a planarization layer 13 composed of transparent resin, a color filter layer 14 formed corresponding to a photodiode 12, a smoothing layer 15 and a microlens 16 are formed in this oder, on the photodiode formed in matrix on a substrate 11, a first undercoat layer 17 is formed below a first color filter layer 24, that is formed at first on the planarization layer. The undercoat layer uses a material having the surface free energy larger than that of the planarization layer, and the thickness is 100 nm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solid-state image sensor.

  The solid-state imaging device is a semiconductor device in which an imaging region in which a plurality of pixels are arranged in a matrix in the horizontal direction and the vertical direction is provided on the surface of a substrate. In this imaging region, a plurality of photoelectric conversion units that receive light from the subject image and generate signal charges are formed so as to correspond to the respective pixels. For example, a photodiode is formed as the photoelectric conversion portion.

  In the upper layer of the photoelectric conversion portion, a color filter layer is provided so as to correspond to each pixel. The photoelectric conversion unit is configured to receive light passing through the color filter layer. As an example, the color filter layer is a colored layer of three primary colors of red, green, and blue, and the colored layers of the three primary colors are arranged in a Bayer arrangement, for example, in accordance with the pixel matrix. .

  In addition, in the upper layer of the color filter layer, a microlens is provided corresponding to each pixel. The light condensed by the microlens is configured to enter the photoelectric conversion unit through the color filter layer.

  FIG. 3 shows an example of a pixel arrangement diagram of a conventional solid-state imaging device. In FIG. 3, the pixel arrangement is a Bayer arrangement, and a structure in which color filters of three primary colors are arranged corresponding to the respective pixels in the pixels 10 (A), 10 (B), and 10 (C). I'm taking it.

  FIG. 2 shows a schematic cross-sectional view of the color filter layer and the microlens in the case of the conventional solid-state imaging device cut along the line A-A ′ in the solid-state imaging device 100 shown in FIG. 3. On the semiconductor substrate 11, a photodiode 12 made of CMOS or CCD is formed as a light receiving element. A silicon oxide film or a silicon nitrogen oxide film (not shown) is formed on the surface of the semiconductor substrate 11, and a planarizing layer (PL) 13 made of a transparent resin is formed on the semiconductor substrate 11. ing. On the planarizing layer (PL) 13, a color filter layer 14 in which a coloring material such as a pigment or a dye is dispersed in a transparent resin is formed corresponding to the photodiode 12. A smoothing layer (FL) 15 made of a transparent resin is formed on these color filter layers 14, and a microlens 16 is formed thereon corresponding to the photodiode.

  In recent years, miniaturization of pixels has progressed in line with the progress of miniaturization of electronic devices with cameras such as digital cameras and mobile phones, and the increase in the number of pixels of solid-state imaging devices.

  As the pixel miniaturization of the solid-state image sensor progresses, the patterning dimension of the color filter layer needs to be similarly miniaturized. Along with the miniaturization, there are problems such as a decrease in light receiving sensitivity characteristics per pixel and an increase in the ratio of noise incident from adjacent pixels. For this reason, in the color filter layer, it is required that the spectral transmittance is improved and the film thickness is reduced at the same time.

In order to reduce the film thickness while maintaining or improving the spectral characteristics of the color filter, it is necessary to increase the pigment ratio of the solid content forming the color filter layer and reduce the other solid content ratio. The components that need to be reduced are components related to photolithography characteristics, color pigments, and components related to dispersion thereof. The reduction of the photolithographic component has a problem that the patterning property, which is increasing in difficulty due to pixel miniaturization, becomes more difficult.

With the progress of miniaturization such that the pixel size is 1.5 μm square or less or 1.2 μm square or less, the film thickness is 0.8 μm or less and the film thickness is 0.6 μm or less while maintaining the spectral characteristics of the color filter layer Such thinning is also progressing.
Therefore, there is a situation in which the total amount of photolithography components such as an alkali-soluble resin, a polymerizable monomer, and a photopolymerization initiator must be reduced while increasing the pigment ratio in the solid content forming the color filter layer.

  By reconsidering the material composition by thinning the color filter layer as described above, a reduction in the amount of the polymerizable monomer of the photosensitive component and a reduction in the amount of the photopolymerization initiator required for performing photolithography occur. This affects the adhesion with the underlying layer, causing a problem that it tends to peel off. In particular, this is a significant problem in the color filter layer formed first in the color filter layer.

  Further, with the miniaturization of the pattern, the decrease in the amount of the alkali-soluble resin, and the increase in the pigment concentration, the occurrence of residues on the surface of the underlayer at the locations where the resist has been removed by alkali development after pattern formation has become prominent.

  For example, in Japanese Patent Application Laid-Open No. H10-260707, the film peeling is less likely to occur by making the green layer into two layers and reducing the film thickness of the first layer with respect to the problem of film peeling caused by pixel miniaturization. Have gained. However, such a method has a problem that it is impossible to cope with the generation of residues due to the miniaturization of pixels.

JP 2009-152315 A

  The present invention has been made in view of the above problems, and in accordance with the progress of pixel miniaturization, a solid-state imaging device that realizes the formation of a color filter layer that realizes miniaturization and thinning of the color filter layer with low defects. It is an issue to provide.

According to a first aspect of the present invention, there is provided a planarization layer made of a transparent resin on a photodiode formed in a matrix on a semiconductor substrate, a color filter layer formed corresponding to the photodiode, and a smoothing layer. In the solid-state imaging device in which the formation layer and the micro lens are formed in this order,
The undercoat layer is provided under the first color filter layer, which is a color filter layer that is first formed on the flattening layer, and the undercoat layer has a surface free energy larger than that of the flattening layer. A solid-state imaging device using a material and having a thickness of the undercoat layer of 100 nm or less.

The second invention according to the present invention is characterized in that the surface free energy of the undercoat layer is 3 mJ / m ² or more larger than the surface free energy of the planarization layer. It is an element.

  According to a third aspect of the present invention, there is provided the solid-state imaging device according to claim 1 or 2, wherein the first color filter layer is a color filter layer that transmits green light.

  According to a fourth aspect of the present invention, the solid-state imaging device according to claim 1 or 2, wherein the first color filter layer is a color filter layer that transmits blue light.

  According to a fifth aspect of the present invention, there is provided the solid-state imaging device according to claim 1 or 2, wherein the first color filter layer is a color filter layer that transmits red light.

  Moreover, the 6th invention which concerns on this invention is the solid-state image sensor of any one of Claims 1-5 characterized by the transmittance | permeability of the said undercoat layer being 90% or more in wavelength 550nm. is there.

  The seventh invention according to the present invention is the solid-state imaging device according to any one of claims 1 to 6, wherein a pixel arrangement period of the solid-state imaging device is 1.2 μm or less. .

  The eighth invention according to the present invention is any one of claims 1 to 7, wherein the thickness of the color filter layer of the solid-state imaging device is 0.1 to 0.8 μm. This is a solid-state imaging device.

According to the present invention, it is possible to form a color filter layer that is free from defects such as residue and peeling in the formation of the color filter layer for pixels with fine dimensions.
As a result, it is possible to form a solid-state imaging device having fine pixels with low defects.

1 is a schematic cross-sectional view showing an example of a solid-state imaging device of the present invention. It is a schematic sectional drawing which shows an example of the conventional solid-state image sensor. It is a schematic explanatory drawing which shows the example of a Bayer arrangement as an example of pixel arrangement | positioning of a solid-state image sensor.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a schematic cross-sectional view of the color filter layer and the microlens taken along the line AA ′ in the solid-state imaging device 100 shown in FIG. On the semiconductor substrate 11, photodiodes 12 made of CMOS or CCD as light receiving elements are formed in a matrix. A silicon oxide film or a silicon nitrogen oxide film (not shown) is formed on the surface of the semiconductor substrate 11, and a planarizing layer (PL) 13 made of a transparent resin is formed on the semiconductor substrate 11. ing. On the planarizing layer (PL) 13, a color filter layer 14 made of a transparent resin in which a coloring material such as a pigment or a dye is dispersed is formed corresponding to the photodiode. A smoothing layer (FL) 15 made of a transparent resin is formed on these color filters, and a microlens 16 is formed thereon corresponding to the photodiode.

  FIG. 1 shows an example of a cross-sectional view of the color filter layer 14 and the microlens 16 in the solid-state imaging device 200 of the present invention taken along the line A-A ′ shown in FIG. 3. A photodiode 12 made of CMOS or CCD is formed as a light receiving element on the semiconductor substrate 11, and a silicon oxide film or a silicon nitrogen oxide film (not shown) is formed on the surface of the semiconductor substrate 11. A planarizing layer (PL) 13 made of a transparent resin is formed on the semiconductor substrate 11. A first undercoat layer 17 is formed on the flattening layer 13 so as to correspond to the photodiode and to be positioned at the position where the first color filter layer is formed.

On the first undercoat layer 17, a first color filter layer 24 that is formed first among the color filter layers 14 made of a transparent resin in which a coloring material such as a pigment or a dye is dispersed is formed. . The color filter layers other than the first color filter layer are formed on the planarizing layer 13.
A smoothing layer (FL) 15 made of a transparent resin is formed on these color filters 14, and a microlens 16 is formed thereon corresponding to the photodiode.
Note that the pixel arrangement and the color of the first color filter layer 24 are not limited to these. In addition to the three primary colors, the color combination may be a combination provided with a color filter such as yellow or clear (transparent).

In the solid-state imaging device of the present invention shown in FIG. 1, the surface free energy of the first undercoat layer 17 is made of a material that is higher than that of the planarizing layer 13.
The difference in surface free energy between the first undercoat layer and the planarizing layer 13 is preferably ³ mJ / m ² or more, more preferably 5 mJ / m ² or more.
The surface free energy of the first undercoat layer 17 is desirably in the range of ^{20 to} 80 mJ / m ² . The thickness of the film formed as the first undercoat layer is preferably a thin film of 100 nm or less, more preferably 60 nm or less.

  In the conventional configuration, the pixel size is 1.2 μm or less, and the color filter layer thickness is 0.8 μm or less. With the progress of miniaturization and thinning, the pigment ratio in the color filter layer increases. The color resist components are being reviewed. In particular, it is necessary to reduce the amount of the photolitho component in the color resist component and the amount of the pigment dispersant, and it is difficult to obtain the color filter layer 14 in a desired pattern shape.

  In particular, the first color filter layer 24 formed first in the color filter layer has a large problem in pattern formation by photolithography, such that film peeling is likely to occur and generation of residue is remarkable.

  Therefore, in the present invention, the surface free energy of the first undercoat layer 17 formed below the first color filter layer 24 formed first in the color filter layer 14 is used as the surface free energy of the planarizing layer 13. And a thin film of 100 nm or less. By doing so, it is possible to obtain the first color filter layer 24 with no film peeling when the first color filter layer 24 is formed and with little generation of residue. As a result, the color filter layer can be miniaturized and thinned with low defects.

  Next, the coloring material of the color filter layer in the present invention contains an organic pigment or dye, a dispersant, an alkali-soluble resin, a polymerizable monomer, a photopolymerization initiator, and a solvent that are conventionally used for forming the color filter layer. A composition can be suitably selected. In addition, it can utilize also about the material which added the additive currently used conventionally as needed. In particular, when an organic pigment is used, the average particle size of the pigment is desirably 20 nm to 100 nm. Here, the average particle diameter is a volume average diameter by a dynamic light scattering method.

  Next, the material of the first undercoat layer 17 in the present invention has a material structure mainly including a resin component such as an acrylic resin, a styrene resin, an epoxy resin, and is transparent and heat resistant after film formation. It is required that the material composition has Further, the light transmittance at a wavelength of 550 nm needs to be 90% or more.

In addition, the material of the first undercoat layer 17 in the present invention has a composition containing a polymerizable monomer, a photopolymerization initiator, and a solvent in addition to a resin component such as an acrylic resin, a styrene resin, and an epoxy resin. A material composition having both photolithographic properties, transparency, and heat resistance is selected. As the composition, a composition conventionally used for photolithography can be selected, and a material to which an additive is added can be used as necessary.

  In addition, the formation of the first undercoat layer 17 and the color filter layer 14 can be applied by manufacturing methods such as a photolithography method, an etching method, and a printing method that are conventionally used. In addition, conventionally used materials can be applied to the formation of the microlens.

  Further, the pixel size in the present invention is desirably 0.1 μm to 1.2 μm, and the film thickness of the first color filter layer 24 is desirably 0.1 to 0.8 μm. The pixel array period is desirably 1.2 μm or less.

<Example 1>
A plurality of photodiodes made of CMOS as light receiving elements are arranged in a Bayer array. A semiconductor substrate on which a silicon oxide film is formed is used on the surface of the semiconductor substrate. Here, the arrangement period of the pixels of the light receiving element is 1.1 μm.

  Next, after a film made of a styrene-based transparent resin is formed by spin coating, a heat treatment is performed at 200 ° C. for 10 minutes to form a flattened film. The thickness of the planarizing film was 40 nm.

  Subsequently, a photosensitive resist composed of an acrylic resin, an acrylic polymerizable monomer, and a polymerization initiator was applied by a spin coating method. Then, after aligning with a pixel, it exposed through the photomask and then developed with the alkaline developing solution. By doing in this way, a predetermined pattern is formed in the location in which the first color filter layer is formed in the next step. Then, heat processing (200 degreeC, 10 minutes) was performed in clean oven, and the 1st undercoat layer was formed. The film thickness was 55 nm and the line width was 1.11 μm.

The surface free energy of the planarized film formed here was 36.4 mJ / m ² , and the surface free energy of the first undercoat layer was 41.5 mJ / m ² .

  Subsequently, a negative pigment dispersion resist having a green spectral characteristic was applied by a spin coating method. After alignment with the pixels, exposure was performed through a photomask, followed by development with an alkaline developer, and a predetermined pattern in the pixel array was formed on the first undercoat layer. Then, heat processing (200 degreeC, 10 minutes) was performed in clean oven, and the 1st color filter layer was formed. The film thickness was 0.58 μm and the line width was 1.10 μm. The negative pigment dispersion resist having a green spectral characteristic was a material having a pigment ratio of 62.1% by weight, a photolitho component of 12.6% by weight, and a dispersion component of 25.3% by weight.

  Next, SEM observation of the pattern shape of the first color filter layer was performed. As a result, the straightness of the pattern was a good result, the entire semiconductor substrate was not peeled off, and the residue area found in the pixel was 0.5%.

  Subsequently, a negative pigment dispersion resist having red spectral characteristics was applied by spin coating. After alignment with the pixels, exposure was performed through a photomask. Thereafter, development processing was performed with an alkali developer to form a predetermined pattern in accordance with the pixel arrangement. Next, heat treatment was performed at 200 ° C. for 10 minutes in a clean oven to form a color filter layer. The film thickness was 0.63 μm, and the line width was 1.10 μm.

Subsequently, a negative pigment dispersion resist having a blue spectral characteristic was applied by spin coating. After alignment with the pixels, exposure was performed through a photomask, and then development processing was performed with an alkaline developer, thereby forming a predetermined pattern in accordance with the pixel arrangement. Thereafter, a heat treatment was performed at 200 ° C. for 10 minutes in a clean oven to form a color filter layer. The film thickness was 0.62 μm and the line width was 1.10 μm.

  A thermosetting acrylic resin layer having a flattening effect on these three color pixels and containing an ultraviolet absorber is applied by a spin coating method, and is subjected to a heat treatment at 200 ° C. for 10 minutes in a clean oven. The color filter layer was formed to a thickness of 1.5 μm.

  Subsequently, microlenses were formed on the red, green and blue color filter layers. First, a negative pigment dispersion resist (product name, manufacturer name) was applied by spin coating. A predetermined pattern suitable for the pixel array was formed by aligning with the pixel through a photomask, and after exposure, developing with an alkaline developer. Here, a gray-tone mask is used as the photomask, and a mask pattern with concentric gradations is used so that the transmitted light at the center of the lens is the strongest and the transmitted light becomes weaker toward the end of the lens. Went. Thereafter, heat treatment was performed at 200 ° C. for 10 minutes in a clean oven to form a first microlens. The film thickness of the top portion of the formed microlens was 0.42 μm.

<Comparative Example 1>
Next, a comparative example will be described.
Sample preparation conditions were that the first undercoat layer was not formed, the film thickness of the first color filter layer (green) was 0.60 μm, the line width was 1.19 μm, and the film thickness of the red color filter layer was 0. .62 μm, line width was 1.01 μm, blue color filter layer thickness was 0.62 μm, and line width was 1.01 μm.

  Next, as a result of confirming the pattern shape of the first color filter layer by SEM observation, the rectilinearity of the rectangular pattern is poor and jagged (sawtooth state), and the residual area seen in the pixel is 9.7%. It was a bad result. In addition, the occurrence of defects due to film peeling was confirmed in a part of the area on the semiconductor substrate. The results are shown in Table 1 together with Example 1 and the results.

10 (A), 10 (B), 10 (C): pixel 11 (of solid-state imaging device): semiconductor substrate 12: photodiode 13: planarization layer 14: color filter layer 15: smoothing layer 16: microlens 17 : First undercoat layer 24: first color filter layer 100: solid-state image sensor 200: solid-state image sensor

Claims (8)

On a photodiode formed in a matrix on a semiconductor substrate, a planarizing layer made of a transparent resin, a color filter layer formed corresponding to the photodiode, a smoothing layer, and a microlens are arranged in this order. In the formed solid-state imaging device,
The undercoat layer is provided under the first color filter layer, which is a color filter layer that is first formed on the flattening layer, and the undercoat layer has a surface free energy larger than that of the flattening layer. A solid-state imaging device using a material and having a thickness of an undercoat layer of 100 nm or less. ^2. The solid-state imaging device according to claim 1, wherein a surface free energy of the undercoat layer is 3 mJ / m ² or more larger than a surface free energy of the planarization layer.   The solid-state imaging device according to claim 1, wherein the first color filter layer is a color filter layer that transmits green light.   The solid-state imaging device according to claim 1, wherein the first color filter layer is a color filter layer that transmits blue light.   The solid-state imaging device according to claim 1, wherein the first color filter layer is a color filter layer that transmits red light.   The solid-state imaging device according to claim 1, wherein the undercoat layer has a transmittance of 90% or more at a wavelength of 550 nm.   The solid-state imaging device according to claim 1, wherein a pixel array period of the solid-state imaging device is 1.2 μm or less.   The film thickness of the color filter layer of the said solid-state image sensor is 0.1-0.8 micrometer, The solid-state image sensor of any one of Claims 1-7 characterized by the above-mentioned.

Images