JP2024044717A - Solid-state image sensor and its manufacturing method - Google Patents

Abstract

[Problem] To provide a technology that can prevent color mixing in a solid-state imaging element. [Solution] A solid-state imaging element 1A includes a substrate 2 on which a plurality of photodiodes 21 are provided, a plurality of filter sections 51, 52 respectively provided on the plurality of photodiodes, a color separation filter 5 in which one or more of the plurality of filter sections have a different transmission spectrum from one or more of the plurality of filter sections, and a partition layer 4 including a plurality of partition sections each sandwiched between adjacent ones of the plurality of filter sections, the plurality of partition sections having a refractive index greater than 1.0 and less than 1.4 over the entire wavelength range from 380 nm to 700 nm. [Selected Figure] Figure 1

Description

The present invention relates to a solid-state imaging device.

Some solid-state imaging devices (or image sensors) have a color separation filter and a partition layer provided on a substrate on which a photodiode is formed. The color separation filter is made of a large number of filter sections. The partition layer includes partition sections sandwiched between adjacent filter sections. The partition sections are made of, for example, an oxide (see Patent Document 1).

JP 2019-125757 A

An object of the present invention is to provide a technique that can make it difficult for color mixture to occur in a solid-state image sensor.

According to one aspect of the present invention, there is provided a solid-state imaging device comprising a substrate on which a plurality of photodiodes are provided, a plurality of filter sections respectively provided on the plurality of photodiodes, a color separation filter having a transmission spectrum different from that of at least one of the plurality of filter sections and at least one of the plurality of filter sections, and a partition layer including a plurality of partition sections each sandwiched between adjacent ones of the plurality of filter sections, the plurality of partition sections having a refractive index greater than 1.0 and less than 1.4 over the entire wavelength range from 380 nm to 700 nm.

According to another aspect of the present invention, there is provided a solid-state imaging device according to the above aspect, in which each of the plurality of partitions is wider at the upper portion.

According to yet another aspect of the present invention, there is provided a solid-state imaging device in which each of the plurality of filter sections has a convex upper surface, and the peripheral portion of the upper surface of each of the plurality of filter sections is in contact with the side surface of the partition section adjacent to the filter section at a position where the partition section is widened.

According to another aspect of the present invention, there is provided a solid-state imaging device including a substrate on which a plurality of photodiodes are provided, a plurality of filter sections respectively provided on the plurality of photodiodes, a color separation filter having a transmission spectrum different from that of at least one of the plurality of filter sections and at least one of the plurality of filter sections, and a plurality of partition sections each sandwiched between adjacent ones of the plurality of filter sections, each of the plurality of partition sections being provided with a partition layer which is widened at the upper portion, each of the plurality of filter sections having a convex upper surface, and the upper peripheral portion of each of the plurality of filter sections being in contact with the side surface of the partition section adjacent to the filter section at the position where the partition section is widened.

According to yet another aspect of the present invention, there is provided a solid-state imaging device according to any of the above aspects, in which the partition layer is made of a cured product of a non-photosensitive resin.

According to yet another aspect of the present invention, there is provided a solid-state imaging device according to the above aspect, in which the non-photosensitive resin contains a silanol group.

According to still another aspect of the present invention, a dummy layer including a plurality of island portions arranged corresponding to the plurality of photodiodes is formed on a substrate provided with a plurality of photodiodes; forming a non-photosensitive resin layer on the dummy layer so as to fill the gaps between the plurality of island-like parts; and removing a surface area of the non-photosensitive resin layer to fill the gaps between the plurality of island-like parts; exposing a top surface; removing the plurality of island portions with exposed top surfaces to form a partition layer having a plurality of through holes at the positions of the plurality of photodiodes; and forming a partition layer having a plurality of through holes at the positions of the plurality of photodiodes. A method of manufacturing a solid-state imaging device is provided, which includes forming a color separation filter including a plurality of filter sections each provided within the color separation filter.

According to yet another aspect of the present invention, there is provided a method for manufacturing a solid-state imaging device according to the above aspect, in which the dummy layer is formed using a positive photoresist, and the removal of the plurality of island-shaped portions is performed by exposing the dummy layer to light and developing it.

According to still another aspect of the present invention, the partition layer has a refractive index greater than 1.0 and less than 1.4 over the entire wavelength range of 380 nm to 700 nm. A manufacturing method is provided.

According to still another aspect of the present invention, there is provided a method for manufacturing a solid-state imaging device according to any of the above aspects, wherein the non-photosensitive resin contains a silanol group.

According to still another aspect of the present invention, the dummy layer is formed such that each of the plurality of island-shaped portions has a convex upper surface, and the side surface that widens each of the plurality of partition portions at an upper portion. A method of manufacturing a solid-state image sensor according to any of the above is provided.

According to still another aspect of the present invention, in the color separation filter, each of the plurality of filter parts has a convex upper surface, and a peripheral edge of the upper surface of each of the plurality of filter parts is adjacent to the filter part. There is also provided a method for manufacturing a solid-state imaging device, in which the side surface of the partition wall portion is formed so as to be in contact with the side surface of the partition wall portion at a position where the partition wall portion is widened.

According to the present invention, a technique is provided that can make it difficult for color mixture to occur in a solid-state image sensor.

FIG. 1 is a cross-sectional view showing a part of a solid-state imaging device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a first step in the manufacture of the solid-state imaging device shown in FIG. FIG. 3 is a cross-sectional view showing the second step in manufacturing the solid-state image sensor shown in FIG. FIG. 4 is a cross-sectional view showing the third step in manufacturing the solid-state image sensor shown in FIG. FIG. 5 is a cross-sectional view showing a fourth step in the manufacture of the solid-state imaging device shown in FIG. FIG. 6 is a cross-sectional view showing the fifth step in manufacturing the solid-state image sensor shown in FIG. FIG. 7 is a cross-sectional view showing a part of a solid-state imaging device according to the second embodiment of the present invention. FIG. 8 is a cross-sectional view showing one step in the manufacture of the solid-state imaging device shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are more specific implementations of any of the above aspects. The matters described below can be incorporated into each of the above aspects singly or in combination.

In addition, the embodiments shown below illustrate configurations for embodying the technical idea of the present invention, and the technical idea of the present invention includes the materials, shapes, structures, etc. of the following constituent members. It is not limited by. Various changes can be made to the technical idea of the present invention within the technical scope defined by the claims.

Note that elements having the same or similar functions will be designated by the same reference numerals in the drawings referred to below, and overlapping explanations will be omitted. In addition, the drawings are schematic, and the relationship between dimensions in one direction and dimensions in another direction, and the relationship between the dimensions of a certain member and the dimensions of other members, etc. may differ from the actual one. It can be different.

<1> First Embodiment FIG. 1 is a sectional view showing a part of a solid-state image sensor according to a first embodiment of the present invention.

The solid-state imaging element 1A shown in FIG. 1 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge-Coupled Device) image sensor. The solid-state imaging element 1A includes a substrate 2, an undercoat film 3, a partition layer 4, a color separation filter 5, and a microlens array 6.

Note that in each figure, the X direction is a direction parallel to the main surface of the substrate 2 facing the microlens array 6. The Y direction is parallel to the previous main surface and intersects with the X direction. The Z direction is a direction perpendicular to the X direction and the Y direction, that is, the thickness direction of the substrate 2. Here, as an example, it is assumed that the X direction and the Y direction are perpendicular to each other.

The substrate 2 is a semiconductor substrate such as a silicon substrate. A plurality of photodiodes 21, which are photoelectric conversion elements, are provided on the surface region of the substrate 2. The photodiodes 21 are arranged in the X and Y directions.

The base film 3 is provided on the main surface of the substrate 2 on the photodiode 21 side. The base film 3 provides a flat base for the color separation filter 5. The base film 3 is colorless and transparent, and exhibits high transmittance to light that should be incident on the photodiode 21. The base film 3 is made of a polymer such as acrylic resin, for example. The base film 3 can be omitted.

The color separation filter 5 is provided on the base film 3. The color separation filter 5 includes a plurality of types of filter sections having different transmission spectra and spaced apart from each other. Here, the color separation filter 5 includes a first filter section 51, a second filter section 52, and third and fourth filter sections (not shown). The number of types of filter sections included in the color separation filter 5 does not need to be four, as long as there are two or more types.

The first filter section 51 and the second filter section 52 each extend in the X direction and form a plurality of first rows arranged in the Y direction. In each of the first rows, the first filter sections 51 and the second filter sections 52 are arranged alternately in the X direction. The third filter section and the fourth filter section each extend in the X direction and form a plurality of second rows arranged in the Y direction. In each of the second rows, the third filter section and the fourth filter section are arranged alternately in the X direction. The first and second columns are arranged alternately in the Y direction.

The first filter section 51, the second filter section 52, the third filter section, and the fourth filter section have different transmission spectra. Each of the first filter section 51, the second filter section 52, the third filter section, and the fourth filter section is, for example, a red layer, a blue layer, a green layer, a yellow layer, a magenta layer, a cyan layer, a colorless transparent layer, a near-infrared transmitting layer, or a near-infrared absorbing layer. According to one example, the first filter section 51, the second filter section 52, and the third filter section are a red layer, a blue layer, and a green layer, and the fourth filter section is a colorless transparent layer, a near-infrared transmitting layer, or a near-infrared absorbing layer. According to another example, the first filter section 51, the second filter section 52, and the third filter section are a yellow layer, a magenta layer, and a cyan layer, and the fourth filter section is a colorless transparent layer, a near-infrared transmitting layer, or a near-infrared absorbing layer.

The partition layer 4 is provided on the base film 3. The partition layer 4 is a layer having a through hole at the position of the filter section. That is, the partition layer 4 includes a plurality of partition wall sections, each of which is sandwiched between adjacent filter sections.

Here, the shape of the through hole observed from the Z direction is a square with rounded corners. The shape of the through hole observed from the Z direction may be another shape such as a circle.

The partition has a refractive index greater than 1.0 and less than 1.4 throughout the wavelength range of 380 nm to 700 nm. In one example, the partition has a refractive index in the range of 1.1 to 1.3 throughout this wavelength range.

The thickness of the partition layer 4 is preferably within the range of 0.35 μm to 0.70 μm, and more preferably within the range of 0.50 μm to 0.70 μm. Here, the upper surface of the partition layer 4 and the upper surface of the color separation filter 5 are flush with each other. The heights of the upper surfaces of the substrate 2 or the base film 3 with respect to the surface thereof may be different.

The partition layer 4 is made of, for example, a cured product of a non-photosensitive resin, preferably a cured product of a non-photosensitive resin containing a silanol group. Inorganic oxides such as silicon oxide, silicon nitride, and aluminum oxide have a high refractive index for light in the above wavelength range. Further, the photosensitive resin also has a large refractive index for light in the above wavelength range. In order to form a partition having a small refractive index over the entire wavelength range, it is preferable to use a non-photosensitive resin, particularly a non-photosensitive resin containing a silanol group.

The microlens array 6 is provided on the partition layer 4 and the color separation filter 5. The microlens array 6 is made of transparent material. This transparent material may be organic or inorganic.

Microlens array 6 includes a plurality of microlenses 61. These microlenses 61 each face the photodiode 21 with the base film 3 and color separation filter 5 in between.

Each of the microlenses 61 is a convex lens having a convex upper surface. Each microlens 61 has a rectangular shape with rounded corners when orthogonally projected onto a plane perpendicular to the Z direction. This orthographic projection may have other shapes, such as circular.

A flattening film may be provided between the microlens array 6 and the composite consisting of the partition wall layer 4 and the color separation filter 5. The flattening film is colorless and transparent, and exhibits high transmittance to light that should be incident on the photodiode 21. The flattening film provides a flat base for the microlens array 6. The planarization film is made of a polymer such as acrylic resin, for example.

This solid-state imaging element 1A includes a plurality of pixels arranged in the X and Y directions. Here, each pixel includes first to fourth sub-pixels. The first sub-pixel includes a first filter portion 51, a photodiode 21 facing it, and a microlens 61. The second sub-pixel includes a second filter portion 52, a photodiode 21 facing it, and a microlens 61. The third sub-pixel includes a third filter portion, a photodiode 21 facing it, and a microlens 61. The fourth sub-pixel includes a fourth filter portion, a photodiode 21 facing it, and a microlens 61.

In the solid-state imaging device 1A, color mixing is unlikely to occur. This will be described below.
A part of the light incident on the microlens 61 passes through the filter section immediately below the microlens 61 and the base film 3, and is incident on the photodiode 21 facing the microlens 61. However, another part of the light incident on the microlens 61 is incident on the filter section immediately below the microlens 61, and then travels obliquely downward toward the side surface of the partition section.

If the refractive index of the partition is large, at least a portion of this light is not reflected by the side of the partition, but enters the partition, and then passes through the base film 3, etc., and may enter another photodiode 21 (hereinafter referred to as the adjacent photodiode) adjacent to the photodiode 21 facing the previous microlens 61. In this way, color mixing occurs.

In contrast, in this solid-state imaging element 1A, the refractive index of the partition is small. Therefore, most of the light that travels diagonally downward toward the side of the partition is reflected by the side of the partition and does not enter the adjacent photodiode 21. Furthermore, the light that enters the partition moves closer to the Z direction due to refraction upon incidence. Therefore, this light also rarely enters the adjacent photodiode 21. Therefore, color mixing is less likely to occur in the solid-state imaging element 1A.

This solid-state image sensor 1A can be manufactured, for example, by the following method.
2 to 6 are cross-sectional views showing the first to fifth steps in manufacturing the solid-state image sensor shown in FIG. 1, respectively.

In this method, first, as shown in FIG. 2, a base film 3 and a dummy layer 15 are sequentially formed on a substrate 2 on which a plurality of photodiodes 21 are provided (first step). Base film 3 is a continuous film. The dummy layer 15 includes a plurality of island-shaped portions arranged corresponding to the photodiodes 21 . The dummy layer 15 can be removed with a sufficiently high selectivity with respect to the partition layer 4 in a fourth step to be described later.

The dummy layer 15 is made of, for example, a photosensitive resin. In this case, the dummy layer 15 can be formed, for example, by a method including forming a coating film made of a photosensitive resin, exposing the coating film to pattern light, and developing the coating film. As the photosensitive resin, it is preferable to use a positive photoresist. A positive photoresist does not contain an initiator (initiator-free), and its solubility in a developer increases upon exposure. As the positive photoresist, for example, IK02 or E02 manufactured by Tokyo Ohka Kogyo Co., Ltd. can be used.

Next, as shown in FIG. 3, a non-photosensitive resin layer, here a partition layer 4 further including a portion covering the upper surface of the dummy layer 15, is formed on the dummy layer 15 so as to fill the gaps between the island-shaped portions (second step). This non-photosensitive resin layer is formed, for example, by a method including applying a coating liquid to the substrate 2 on which the dummy layer 15 is provided and curing the coating film.

As this coating liquid, for example, SC550 manufactured by PI bond can be used. This coating liquid contains propylene glycol propyl ether as a solvent. Therefore, when this coating liquid is used, the coating film is cured by a method that includes a drying step. Note that the cured product layer obtained using this coating liquid has a refractive index of 1.2 over the entire wavelength range.

Next, as shown in FIG. 4, the surface region of the non-photosensitive resin layer is removed to expose the upper surface of the island-shaped portion (third step). That is, the thickness of the partition layer 4 is reduced to expose the upper surface of the dummy layer 15. Surface areas of the non-photosensitive resin layer are removed, for example, by etching, polishing, chemical mechanical polishing, or a combination thereof.

Thereafter, as shown in FIG. 5, the island-shaped portion with its upper surface exposed is removed to form a partition layer 4 having a plurality of through holes TH at the positions of the photodiodes 21. These islands can be removed by dissolution. For example, when the dummy layer 15 is made of a positive photoresist, the island-like portions can be removed by exposing the entire surface and then developing. If a residue is generated during this development, O ₂ etching may be performed to remove the residue.

Note that the partition layer 4 may be baked after removing the island portion. According to one example, after removing the island portion, the partition layer 4 is baked at 230° C. for 180 seconds.

Next, as shown in FIG. 6, a color separation filter 5 including a plurality of filter parts each provided in the through hole TH is formed. In forming the first filter section 51 included in the color separation filter 5, a coating film made of a photosensitive material is formed, and patterning including pattern exposure and development is performed on this coating film. The second filter section 52, the third filter section, and the fourth filter section are also formed by the same method as the first filter section 51. The first filter section 51, the second filter section 52, the third filter section, and the fourth filter section may be formed in any order.

Then, a microlens array 6 is formed on the color separation filter 5. In this manner, the solid-state imaging device 1A shown in FIG. 1 is obtained.

In order to form the partition layer 4 having through holes using a non-photosensitive material, it is necessary to form a continuous film made of the non-photosensitive material, form an etching mask on it, and etch the film made of the non-photosensitive material. There is. However, when etching is performed, the photodiode 21 may be damaged.

In the method described with reference to FIGS. 2 to 6, the partition layer 4 having through holes can be formed without etching. Therefore, it is possible to prevent the photodiode 21 from being damaged by etching.

<2> Second Embodiment FIG. 7 is a sectional view showing a part of a solid-state image sensor according to a second embodiment of the present invention.
The solid-state image sensor 1B shown in FIG. 7 is the same as the solid-state image sensor 1A except for the following points.

That is, in solid-state imaging device 1B, each partition section is wider at the top. Each filter section has a convex upper surface. The peripheral portion of the upper surface of each filter section is in contact with the side surface of the partition section adjacent to that filter section at the position where the partition section is wider.

As described above, in the solid-state image sensor 1B, each of the filter sections has a convex top surface. Therefore, each of the filter sections can act as a convex lens. In this structure, the partition wall portion has a small refractive index and covers the upper peripheral edge of the filter portion, thereby enhancing the function of the filter portion as a convex lens. Therefore, in this solid-state imaging device 1B, compared to the solid-state imaging device 1A, the proportion of light that travels obliquely downward toward the side surface of the partition wall portion of the light that enters the filter portion is small. Therefore, color mixture is less likely to occur in the solid-state image sensor 1B than in the solid-state image sensor 1A.

Each of the partition wall portions has a ratio ΔW/T of the difference ΔW between the maximum value W _MAX and the minimum width W _MIN of the width of the partition wall portion to the thickness T of the partition layer 4 within the range of 0.10 to 0.25. It is preferably within the range of 0.100 to 0.167, and more preferably within the range of 0.100 to 0.167. When the ratio ΔW/T is increased, the function of the filter section as a convex lens is enhanced. However, if the ratio ΔW/T is made excessively large, the yield may decrease.

The maximum width W _MAX and the minimum width W _MIN of the partition portion are measured from a photograph of a cross section that is parallel to the arrangement direction of the photodiodes and the thickness direction of the substrate 2 and crosses the center of the through hole provided in the partition layer 4, for example, a cross section that is perpendicular to the Y direction and crosses the center of the through hole provided in the partition layer 4, or a cross section that is perpendicular to the X direction and crosses the center of the through hole provided in the partition layer 4.

The solid-state imaging device 1B can be manufactured, for example, by the following method.
FIG. 8 is a cross-sectional view showing one step in the manufacture of the solid-state imaging device shown in FIG.

In this method, first, the first step described with reference to FIG. 2 is carried out. However, in this case, as shown in FIG. 8, the dummy layer 15 is formed so that each island-shaped portion has a convex upper surface. The island-shaped portions having a convex upper surface can be formed, for example, by appropriately setting the exposure conditions or by heating and melting the island-shaped portions formed in a columnar shape.

Next, the second step described with reference to FIG. 3, the third step described with reference to FIG. 4, and the fourth step described with reference to FIG. 5 are sequentially performed. As mentioned above, each of the islands has a convex upper surface. Therefore, in the partition layer 4 obtained by performing the second to fourth steps, each of the partition parts is widened at the upper part.

Next, the fifth step described with reference to FIG. 6 is carried out. Here, in the fifth step, the color separation filter 5 is formed so that the peripheral portion of the upper surface of each filter portion contacts the side surface of the partition portion adjacent to this filter portion at the position where the partition portion widens. This results in a color separation filter 5 in which the upper surface of each filter portion is convex and the peripheral portion of this upper surface contacts the side surface of the partition portion at the position where the partition portion widens.

Then, as described above for the solid-state imaging element 1A, a microlens array 6 is formed on the color separation filter 5. In this manner, the solid-state imaging element 1B shown in FIG. 7 is obtained.

In this method, the island-shaped portion constituting the dummy layer 15 is used as a mold for forming the partition layer 4 having through holes. Then, the partition layer 4 having the through holes is used as a mold for forming the filter section. Therefore, if the island portion is formed with high shape accuracy, the partition layer 4 having the through holes can also be formed with high shape accuracy, and therefore the filter portion can also be formed with high shape accuracy.

<3> Modifications Various modifications are possible to the above-described solid-state imaging devices 1A and 1B and the manufacturing methods thereof.

For example, in the solid-state imaging devices 1A and 1B, the microlens array 6 may be omitted. In particular, in the solid-state imaging device 1B, the filter portion functions as a convex lens, and therefore can serve as the microlens 61.

In the solid-state imaging element 1B, the refractive index of the partition layer 4 for light having any wavelength within the above wavelength range may be 1.4 or more. Even in this case, each filter portion can function as a convex lens. However, as described above, if the refractive index of the partition layer 4 is low, the incident light can be largely refracted at the upper peripheral portion of the filter portion, which is highly effective in preventing color mixing.

Furthermore, in the method for manufacturing the solid-state imaging devices 1A and 1B, the refractive index of the partition layer 4 for light having any wavelength within the above wavelength range may be 1.4 or more. Even in this case, various materials including non-photosensitive materials can be used as the material for the partition layer 4, and the partition layer 4 and the filter section can be formed with high shape accuracy.

1A...solid-state image sensor, 1B...solid-state image sensor, 2...substrate, 3...base film, 4...partition layer, 5...color separation filter, 6...microlens array, 15...dummy layer, 21...photodiode, 51... 1st filter part, 52...2nd filter part, 61...microlens, TH...through hole.

Claims (7)

A substrate on which a plurality of photodiodes are provided;
a color separation filter including a plurality of filter sections respectively provided on the plurality of photodiodes, the color separation filter having a transmission spectrum different from that of one or more of the plurality of filter sections and a transmission spectrum different from that of another or more of the plurality of filter sections;
a partition layer including a plurality of partition sections each sandwiched between adjacent ones of the plurality of filter sections,
The plurality of partition portions have a refractive index greater than 1.0 and less than 1.4 over the entire wavelength range from 380 nm to 700 nm. The solid-state imaging device according to claim 1, wherein the partition layer is made of a cured product of a non-photosensitive resin. 3. The solid-state imaging device according to claim 2, wherein the non-photosensitive resin contains a silanol group. The solid-state imaging device according to claim 1, wherein each of the plurality of partitions is wider at the top. The solid-state imaging device according to claim 4, wherein each of the plurality of filter sections has a convex upper surface, and the peripheral portion of the upper surface of each of the plurality of filter sections contacts the side surface of the partition section adjacent to the filter section at a position where the partition section is widened. A substrate provided with a plurality of photodiodes,
a color separation filter including a plurality of filter sections each provided above the plurality of photodiodes, and one or more of the plurality of filter sections and one or more of the other one or more of the plurality of filter sections have different transmission spectra;
including a plurality of partition walls, each of which is sandwiched between adjacent ones of the plurality of filter parts, each of the plurality of partition walls including a partition layer whose width is widened at an upper part;
Each of the plurality of filter parts has a convex upper surface, and a peripheral edge of the upper surface of each of the plurality of filter parts is widened by a side surface of the partition wall adjacent to the filter part and the partition wall part. A solid-state image sensor that is in contact at certain positions. forming a dummy layer including a plurality of island-shaped portions arranged corresponding to the plurality of photodiodes on a substrate provided with a plurality of photodiodes;
forming a non-photosensitive resin layer on the dummy layer so as to fill the gaps between the plurality of island-shaped parts;
Removing a surface region of the non-photosensitive resin layer to expose the upper surfaces of the plurality of island-shaped parts;
removing the plurality of island-shaped portions with exposed upper surfaces to form a partition layer having a plurality of through holes at the positions of the plurality of photodiodes;
A method of manufacturing a solid-state imaging device, comprising: forming a color separation filter including a plurality of filter sections respectively provided in the plurality of through holes.