JP2016219703A - Solid-state imaging element and method for manufacturing solid-state imaging element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing solid-state imaging element, in which a resist in forming a pattern of a color filter by a dry etching method does not penetrate into a color material, a resist can be removed without damaging a color filter, and a high-density color filter that can cope with higher definition and thinner thickness can be formed, and thereby a highly sensitive solid-state imaging element can be formed.SOLUTION: In a solid-state imaging element including a semiconductor substrate on which a plurality of photodiodes are formed and a color filter formed to correspond to each of the photodiodes, a pattern of a green color filter is formed using a color material formed in a two-layer structure including one layer of a first green color material that does not contain a photosensitive component and the other layer of a second green color material laminated on the one layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solid-state imaging device and a manufacturing method thereof.

  Video cameras and digital cameras are increasing in pixel count. Therefore, a solid-state image sensor incorporated in a video camera or a digital camera also has high pixels, and the pixel size is expected to be reduced to 1 μm or less. As the pixel size is further miniaturized, the amount of light incident on the pixel is reduced as the pixel area is reduced, and the sensitivity of the photodiode is lowered. In addition, when the line width of the wiring is reduced and the dielectric layer is thinned, the pixel is easily affected by noise. In order to solve these problems, a microlens is placed above the color filter formed corresponding to the photodiode formed on the semiconductor substrate that will be a solid-state image sensor, and the light sensitivity is collected by collecting the incident light. Is increasing.

  However, even if a microlens is disposed, incident light cannot be efficiently collected if the distance between the microlens and a photodiode made of CMOS or CCD as a light receiving element is large. For example, if the pixel size is 1.5 μm and the distance from the microlens to the photodiode is 5 μm, even if the light incident from the camera lens has an angle of 20 °, the angle from the microlens to the photodiode is 10 °. Only light within a range of a certain angle can be taken in, and the light collection efficiency is deteriorated, leading to a decrease in sensitivity of the solid-state imaging device. Therefore, a thin color filter layer is required.

  A conventional solid-state imaging device having an on-chip color filter (a color color filter formed on a semiconductor substrate on which a photodiode is formed and allowing light of a predetermined wavelength to enter the corresponding photodiode) A silicon oxide film or a silicon nitrogen oxide film (not shown) is formed on the surface of the semiconductor substrate. A planarizing layer (PL) made of a transparent resin is formed on the semiconductor substrate. Corresponding to the photodiode, a green color filter, a blue color filter, and a red color filter made of a transparent resin in which pigments such as pigments and dyes are dispersed are formed on the planarization layer (PL). A smoothing layer (FL) made of a transparent resin is formed on these color filters, and a plurality of microlenses are formed thereon corresponding to the photodiodes.

  The color filter is formed as follows, for example. That is, first, a color resist including a photosensitive resin, a pigment such as a pigment or a dye, a solvent, and an additive is formed on the planarization layer (PL) by a coating apparatus such as a spinner. Next, a color resist in a predetermined region is selectively exposed (pattern exposure) through a photomask for pattern exposure using an exposure apparatus such as a stepper. Next, the resist pattern is cured at a temperature of 200 ° C. or more after leaving a color resist pattern at a predetermined site by developing with an aqueous alkali solution and rinsing with pure water or the like. By repeating such a process three times with a red resist, a green resist, and a blue resist, a green color filter, a red color filter, and a blue color filter are obtained.

  The color filter takes, for example, a so-called Bayer array. First, a green color resist is applied on the planarizing layer, and pattern exposure, development, and heat curing are performed to dispose a green color filter in a checkered pattern in the green region. Next, a blue color resist is applied to the entire surface, and pattern exposure, development, and thermal curing are performed to arrange blue color filters vertically and horizontally in the blue region. Further, a red color resist is applied to the entire surface, pattern exposure, development and heat curing are performed, and red color filters are arranged vertically and horizontally in the red region.

  However, in the conventional color filter manufacturing method described above, since the color resist contains a photosensitive component in the pigment paste, it cannot cope with the thinning of the color filter. If the color resist is to be thinned, the necessary spectral characteristics cannot be obtained unless the pigment concentration is increased due to the thinning. Although it is possible to increase the concentration of the pigment, it is difficult to produce a color resist with a high concentration because there is no room for including a photosensitive component.

  Therefore, Patent Document 1 describes a method of patterning a color material by etching instead of lithography. In this method, a resist is applied on a color material, and a resist pattern is formed by pattern exposure and development on the resist. Thereafter, the color material is dry-etched using the resist pattern as a mask to form a color filter pattern. In this step, since the color material can be patterned even if it does not contain a photosensitive component, it is possible to increase the concentration of the color material, and there is no problem even when the pigment is thinned.

JP 2007-79154 A

However, in the color filter pattern forming method described in Patent Document 1, when a resist is applied on the color material, the resist may penetrate into the color material. In addition, the resist on the color material may remain as a residue. Due to these phenomena, the spectral characteristics of the original color filter may not be obtained. For these phenomena, there is a means for removing the resist by a chemical mechanical polishing (CMP) process, but the CMP process has a problem of damaging the color filter.
An object of the present invention is to provide a solid-state image sensor having high sensitivity and high density color filter formation and high sensitivity.

  In order to solve the problem, a solid-state imaging device according to one embodiment of the present invention includes a semiconductor substrate on which a plurality of photodiodes are formed, and a color filter formed corresponding to each photodiode. And forming a green color filter pattern using a color material formed in a two-layer configuration of a first green color material that does not contain a photosensitive component and a second green color material laminated thereon. And

In addition, a method for manufacturing a solid-state imaging device which is one embodiment of the present invention includes a semiconductor substrate on which a plurality of photodiodes are formed, and green, blue, and red color filters formed corresponding to the photodiodes. In the method for manufacturing a solid-state imaging device,
Applying a green pigment paste not containing a photosensitive component on the entire surface of the semiconductor substrate and performing thermosetting;
Applying a green color resist containing a photosensitive component on the entire surface of the green pigment paste, and heating;
Applying a resist on the green color resist and performing pattern exposure and development to form a resist pattern in a green region; and
Etching the green pigment paste and the green color resist by dry etching using the patterned resist as a mask;
Removing the resist and the green color resist by peeling film cleaning or whole surface exposure and development to form a green color filter pattern;
Applying a blue color resist on the entire surface, pattern exposure, development and thermosetting to form a blue color filter pattern in the blue region;
Applying a red color resist to the entire surface, pattern exposure, development and thermosetting to form a red color filter pattern in the red region; and
It is characterized by having.

  According to the aspect of the present invention, the resist when forming the pattern of the color material by the dry etching method does not penetrate into the color material, and the resist can be removed without damaging the color filter. A high-density color filter that can cope with the above can be formed. Therefore, it is possible to provide a solid-state imaging device having a color filter having an excellent shape, a short distance from the microlens to the photodiode, and high sensitivity.

Sectional drawing explaining the formation order of the green color filter which concerns on embodiment of this invention. The top view explaining arrangement and formation order of a color filter concerning an embodiment of the present invention. 1 is a cross-sectional view of a solid-state image sensor according to an embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings.
First, a method for patterning a first green color material containing no photosensitive component and a second green color material containing a photosensitive component by etching will be described with reference to FIG.
As shown in FIG. 1A, a plurality of photodiodes 12 are formed on a 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 planarization layer (PL) 13 made of a transparent resin is applied on the semiconductor substrate 11. The planarization layer (PL) 13 functions as an adhesive layer between the color filter and the semiconductor substrate while planarizing the irregularities on the surface of the semiconductor substrate.
Further, a first green color material 20 that does not contain a photosensitive component and in which pigments such as pigments and dyes are dispersed is applied on the planarizing layer 13.

The first green color material 20 is preferably adjusted so that pigment green (PG) 36 or PG58 and pigment yellow (PY) 150 have a one-to-one composition, and the pigment concentration is 50% or more.
The film thickness of the first green color material 20 was 500 nm at a coating rotation speed of 1500 rpm of the coating apparatus. In addition, thermosetting is performed at a temperature of 300 ° C. or less which does not affect the actual device. For example, the first green color material 20 is thermally cured by heating at 230 degrees.

Next, as shown in FIG. 1B, a second green color material 21 (color resist) in which a photosensitive component is added to a transparent resin in which a pigment such as a pigment or a dye is dispersed is applied.
Regarding the film thickness of the second green color material 21, the coating rotation speed of the coating apparatus is set to 800 rpm, for example, and the film thickness is set to 200 nm, for example. Further, by heating at 150 ° C. or lower, for example, heating is performed at 100 ° C. in order to impart a certain degree of resistance, although not completely cured.

  Next, as shown in FIG. 1C, a positive resist 22 is applied on the second green color material 21. As the positive resist 22, a general i-line positive resist 22 made of a novolac resin or the like may be used. The film thickness of the positive resist 22 is, for example, 2800 rpm at the coating rotation speed of the coating apparatus, and the film thickness is, for example, 1000 nm.

Next, as shown in FIG. 1D, corresponding to the photodiode, a positive resist 22 is subjected to pattern exposure and development to form a checkered pattern in the green region.
Next, as shown in FIG. 1E, the second green color material 21 and the first green color material 20 are sequentially etched using the positive resist 22 as an etching mask.
Next, as shown in FIG. 1F, the positive resist 22 and the second green color material 21 are removed by developing the entire surface by exposure. This step can be performed in the same manner by stripping cleaning with a solvent such as cyclohexanone.

The first green color material 20 heated at 230 degrees is also resistant to peeling cleaning, but the second green color material 21 heated at 100 degrees can be exposed by exposure and removed by development, and the curing is weak even after peeling cleaning. Removed.
By these steps, the positive resist 22 does not penetrate into the first green color material 20, and the resist residue and the like adhering to the second green color material 21 are removed at the same time, so that a high-quality green color filter is manufactured. can do. It is confirmed that the positive resist 22 has not penetrated into the first green color material 20 by actually performing the above process.

Next, the arrangement and formation order of the color filters will be described with reference to FIG.
This color filter has a so-called Bayer arrangement in this embodiment.
The first green color material 20 patterned in FIG. 1 (f) has a checkered pattern corresponding to the green color filter 31 in FIG. 2 (a).
Next, as shown in FIG. 2B, a blue color resist is applied to the entire surface, pattern exposure, development and thermal curing are performed, and blue color filters 32 are arranged vertically and horizontally in the blue region.

Further, as shown in FIG. 2C, a red color resist is applied to the entire surface, pattern exposure, development and thermal curing are performed, and red color filters 33 are arranged vertically and horizontally in the red region.
With reference to FIG. 3, the material used for the microlens of this invention and its manufacturing method are demonstrated.
A smoothing layer 17 is applied on the color filter formed in FIG. A transparent resin layer is formed on the smoothing layer 17 using, for example, an acrylic resin coating solution.

  The smoothing layer 17 eliminates the steps between the pixels of the three color filters and makes it easier to form the microlens 18 with a good shape. In order to improve the light condensing property, the microlens 18 preferably has a gap between individual lenses as narrow as possible and a lens shape close to an ideal curve. If the level difference between pixels is large and the flatness of the smoothing layer 17 is poor, the lens shape may not be a desired shape, and the lens characteristics may vary between pixels.

Next, on the transparent resin layer, for example, a lens matrix material made of, for example, a phenol resin having alkali solubility, photosensitivity, and heat flow is applied.
Next, using a known photolithography process, the lens matrix material is patterned so as to leave a region that becomes the lens matrix.
The remaining lens matrix material is heat-treated and thermally reflowed, and deformed into a hemisphere to form a lens matrix. By setting the reflow amount to an appropriate amount of about 0.1 μm on one side, a smooth hemispherical shape with a gap between the unit lens molds of, for example, about 0.24 μm can be obtained.

Next, using a mixed gas of CF ₄ and C ₄ F ₈ with a dry etching apparatus, the lens matrix is transferred to the transparent resin layer using the lens matrix as a mask to form the microlens 18. . If the lens matrix and the transparent resin layer are uniformly etched from above, the etching proceeds downward while maintaining the shape of the lens matrix. Therefore, the shape of the transparent resin layer may be etched to the same shape as the lens matrix. it can.
The microlens 18 has a height of, for example, 1 μm and a gap between unit lenses of, for example, 0.04 μm.

Here, FIG. 3A shows a cross section of the green (G), blue (B), and green (G) columns, and FIG. 3 (b) shows the green (G), red (R), and green (G) columns. It is sectional drawing of the solid-state image sensor which shows the cross section of a row | line | column.
In the solid-state imaging device obtained as described above, three color filter patterns are formed on the planarization layer 13 formed thinly on the surface of the semiconductor substrate 11, and the first green color of the first color is formed. The material 20 did not contain a photosensitive component, and the concentration of the color material in the solid content was increased, so that the color filter pattern could be formed thin.
Furthermore, a color filter having an excellent shape can be formed by etching, and the distance from the microlens to the photodiode is shortened, so that a highly sensitive solid-state imaging device can be provided.

11 Semiconductor substrate 12 Photodiode 13 Flattening layer 17 Smoothing layer 18 Micro lens 20 First green color material 21 Second green color material 22 Positive resist 31 Green color filter 32 Blue color filter 33 Red color filter

Claims (8)

In a solid-state imaging device having a semiconductor substrate on which a plurality of photodiodes are formed and a color filter formed corresponding to each photodiode,
A pattern of a green color filter is formed using a color material formed by a two-layer structure of a first green color material not containing a photosensitive component and a second green color material laminated thereon. Solid-state image sensor.   The solid-state imaging device according to claim 1, wherein the first green color material is a green pigment paste containing no photosensitive component.   3. The solid-state imaging device according to claim 2, wherein the green pigment paste has a one-to-one composition of PG36 or PG58 and PY150, and the pigment concentration of the green pigment paste is 50% or more.   The solid-state imaging device according to any one of claims 1 to 3, wherein the second green color material is a green color resist containing a photosensitive component.   5. The solid-state imaging device according to claim 1, wherein the green color filter has a thickness of 50 nm to 600 nm.   The solid-state imaging device according to claim 1, further comprising a smoothing layer and a microlens on the color filter. In a method for manufacturing a solid-state imaging device having a semiconductor substrate on which a plurality of photodiodes are formed, and green, blue and red color filters formed corresponding to each photodiode,
Applying a green pigment paste not containing a photosensitive component on the entire surface of the semiconductor substrate and performing thermosetting;
Applying and heating a green color resist containing a photosensitive component on the entire surface of the green pigment paste; and
Applying a resist on the green color resist and performing pattern exposure and development to form a resist pattern in a green region; and
Etching the green pigment paste and the green color resist by dry etching using the patterned resist as a mask;
Removing the resist and the green color resist by peeling film cleaning or whole surface exposure and development to form a green color filter pattern;
Applying a blue color resist on the entire surface, pattern exposure, development and thermosetting to form a blue color filter pattern in the blue region;
Applying a red color resist to the entire surface, pattern exposure, development and thermosetting to form a red color filter pattern in the red region; and
A method for manufacturing a solid-state imaging device, comprising:   8. The method of manufacturing a solid-state imaging device according to claim 7, wherein the green color resist has a one-to-one composition of PG36 or PG58 and PY150, and the pigment concentration is the same as that of the green pigment paste.

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