JP2000304906A - Microlens array for solid-state imaging device and solid-state imaging device using the same - Google Patents

Abstract

(57) Abstract: An object is to provide a microlens array and a solid-state imaging device that can increase the light-receiving efficiency of a light-receiving section of a solid-state imaging device and improve the sensitivity and image quality of a solid-state imaging device. A light receiving unit and a light shielding unit are provided on a semiconductor substrate.
3. A positive resist (JSR (Co., Ltd.), in which a flattening layer 14, a color filter layer 15, and an overcoat layer 16 are formed and the extinction coefficient at a wavelength of 450 nm is adjusted in advance to 0.57 × 10 ^−3. The solid-state imaging device 10 having the convex lens-shaped microlenses 21 and the microlens array 22 is obtained by forming a resin pattern layer and heating and softening the resin pattern layer at 130 ° C. Further, on the microlens 21, there is provided a microlens array 32 in which a filling rate improving layer 31 having a thickness of 0.09 μm is formed of an acrylic resin prepared so that the refractive index at a wavelength of 450 nm is 1.45. The solid-state imaging device 20 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device provided with a microlens array, and more particularly to a microlens array for improving light use efficiency.

[0002]

2. Description of the Related Art In general, a solid-state imaging device is provided with a light receiving section and a charge transfer section on a semiconductor substrate, and transfers charges photoelectrically exchanged by the light receiving section to the charge transfer section. For this reason, 100% of the area on the semiconductor substrate cannot be used as the light receiving portion. As a method for improving the light receiving efficiency of the light receiving portion, a light receiving device comprising photodiodes arranged two-dimensionally in the horizontal and vertical directions is used. The microlenses 27 are arranged on the unit as shown in FIG. 6 and are focused on the light receiving unit 12 to improve the sensitivity of the solid-state imaging device.

FIG. 6 is a partial cross-sectional view schematically showing the structure of a conventional solid-state imaging device 30, in which 11 is a semiconductor substrate made of silicon, 12 is a light receiving portion made of a photodiode, 13 is a light shielding portion, and 14 is a light shielding portion. A flattening layer, 15 is a color filter layer for color separation, 16 is an overcoat layer, 41 is a micro lens, and 42 is a micro lens array.

The incident light is condensed by a micro lens 41,
The light enters the light receiving section 12 through the overcoat layer 16, the color filter layer 15, and the flattening layer 14, is converted into electric charge according to the amount of incident light, and is transferred. At this time, all of the incident light does not enter the light receiving unit 12 but also enters the light shielding unit 13, and the amount of light incident on the light shielding unit 13 is not converted into electric charge, which causes a decrease in sensitivity of the solid-state imaging device. It is a factor.

In recent years, solid-state imaging devices have been developed as solid-state imaging devices such as a handy movie (trade name) and a digital still camera in which the number of pixels of the solid-state imaging device is increased. There is no problem if the optical system including the solid-state image sensor can be simply increased by the amount of pixels of the solid-state image sensor.
There is a strong tendency to reduce the weight, and the number of pixels increases, but the solid-state imaging device tends to be the same size as before or smaller.

[0006] If a large number of pixels are to be accommodated within a certain size, the pixel area must be reduced, resulting in a reduction in characteristics such as a decrease in sensitivity and a decrease in saturation output voltage. For this reason, it is necessary to increase the amount of light incident on the photodiode. However, in the conventional method of forming a microlens array, there is a limit in controlling the lens shape and the positional accuracy, and at present, no further effect can be expected for improving the sensitivity. Specifically, when the pixel pitch of the micro lens is 5 μm, the diameter is 4.5 μm
The limit is to form a microlens.

Further, a photosensitive organic resin is currently used as the material of the microlens. Particularly, the light absorption in a short wavelength region is large, the transmittance of the short wavelength is reduced, and the solid-state imaging device is changed depending on the wavelength. There is a problem that the sensitivity and the image quality are reduced.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned problems, and a microlens array and a solid-state imaging device capable of improving the light-receiving efficiency of a light-receiving portion of a solid-state imaging device and improving the sensitivity and image quality of a solid-state imaging device. An object is to provide an imaging device.

[0009]

In order to achieve the above object, according to the present invention, first, a microlens array is provided on a light receiving portion arranged two-dimensionally in a horizontal direction and a vertical direction. In the solid-state imaging device formed,
A microlens array for a solid-state imaging device, wherein an extinction coefficient of a microlens constituting the microlens array is 1.82 × 10 ⁻³ or less at a wavelength of 450 nm.

According to a second aspect of the present invention, there is provided the microlens array for a solid-state imaging device according to the first aspect, wherein a filling rate improving layer is provided on the surface of the microlens.

According to a third aspect of the present invention, there is provided a microlens array for a solid-state imaging device according to the first or second aspect, wherein a refractive index of the filling factor improving layer is 1.46 or less at a wavelength of 450 nm. It was done.

According to a fourth aspect of the present invention, the filling thickness improving layer has an optical thickness of 100 to 150 nm at a wavelength of 450 nm.
4. The method according to claim 1, wherein
A microlens array for a solid-state imaging device according to any one of the above.

According to a fifth aspect of the present invention, there is provided a solid-state imaging device comprising the solid-state imaging device microlens array according to any one of the first to fourth aspects. is there.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies in order to solve the above problems, and focused on the extinction coefficient (K) of the organic resin forming the microlens. As a result of examining the relationship with the transmittance, the extinction coefficient was changed to the wavelength (450
When a microlens is formed of a resin of 1.82 × 10 ⁻³ or less in terms of nm), a blue peak sensitivity wavelength of 450 n is practically used.
It was found that the transmittance was 85% or more at m.

FIG. 2 shows the results of simulating the transmittance of various resin layers having a different extinction coefficient (K) of 1.2 μm thickness for each wavelength. As can be seen from FIG.
When the transmittance at 50 nm is set to 85% or more 1.8
It can be seen that forming a microlens using a resin having an extinction coefficient of 2 × 10 ⁻³ or less can contribute to improvement in sensitivity of a solid-state imaging device.

In the case of a micro-lens array, if the gap between the micro-lenses can be formed to be zero, the light-collecting efficiency can be improved. However, considering the variation in the process (material, exposure optical system, process, etc.) for manufacturing the micro-lenses, The gap between microlenses is limited to 0.5 μm. It has been found that it is effective to form a filling factor improving layer (transparent thin film layer) on the surface of the microlens as a method for bringing the gap between the microlenses close to zero.

By forming the filling rate improving layer, a gap between microlenses can be filled, and a microlens array for a solid-state imaging device with higher light-collecting efficiency can be manufactured. Further, the surface reflection of the microlens can be reduced, the light-collecting efficiency can be increased comprehensively, and the sensitivity of the solid-state imaging device can be improved.

In order to reduce the surface reflection of the microlens, a material having a lower refractive index than that of the microlens may be used as the filling rate improving layer and may be formed to have a predetermined thickness. Specifically, on the surface of a microlens having an extinction coefficient of 1.82 × 10 ⁻³ or less, the refractive index at a wavelength of 450 nm is 1.46 or less and the optical film thickness (refractive index × film thickness) at a wavelength of 450 nm. By providing the filling rate improving layer having a thickness of 100 to 150 nm, the surface reflectance of the microlens at a wavelength of 450 nm can be reduced to 3% or less.

As described above, if the microlens array of the present invention is formed of a material having an extinction coefficient of 1.82 × 10 ⁻³ or less, the transmittance of the microlens alone is 85% or more at a wavelength of 450 nm. Is provided on the microlens surface with a filling rate improving layer having a refractive index at a wavelength of 450 nm of 1.46 or less and an optical film thickness (refractive index × film thickness) at a wavelength of 450 nm of 100 to 150 nm. As a result, a transmittance of 85% or more at a wavelength of 450 nm can be obtained, and at the same time, the surface reflectance of the microlens can be reduced to 3% or less. This can contribute to an improvement in the sensitivity of the imaging device.

[0020]

The present invention will be described in detail with reference to the following examples.
1A is a partial cross-sectional view schematically showing a microlens array for a solid-state imaging device and a solid-state imaging device according to a first embodiment of the present invention, and FIG. 1B is a microlens for a solid-state imaging device according to the present invention. A partial cross-sectional view schematically showing Example 2 of an array and a solid-state imaging device is shown.

Embodiment 1 First, an acrylic resin solution is applied by a spinner on a semiconductor substrate 11 on which a light receiving portion 12 made of a photodiode and a light shielding portion 13 made of aluminum are formed, and a planarizing layer 14 having a predetermined thickness is formed. Was formed.

Next, a photosensitive pigment solution is applied on the flattening layer 14 by a spinner to form a photosensitive pigment layer having a predetermined thickness, and is patterned to form a first color filter on the light receiving portion. did. This process is sequentially repeated to form a second color filter and a third color filter, and Red, Gr
color filter layer 1 of three colors consisting of eeen and Blue
Formed 5

Next, an acrylic resin solution was spin-coated on the color filter layer 15 with a spinner to form an overcoat layer 16 having a predetermined thickness.

Next, on the overcoat layer 16, a positive resist (MER-35) adjusted in advance so that the extinction coefficient at a wavelength of 450 nm is 0.57 × 10 ^-3.
4: JSR Corp.) was spin-coated with a spinner to form a photosensitive layer, and pattern exposure was performed to form a resin pattern layer of a predetermined size corresponding to the light receiving section 12. Further, this resin layer pattern layer was heated and softened at 130 ° C. to form a microlens 21 having a convex lens shape, thereby obtaining a solid-state imaging device 10 having a microlens array 22 (see FIG. 1A).

FIG. 3 shows the results of measuring the spectral transmittance of a sample in which the microlens array 22 was separately formed on a glass substrate of the same size. 450nm wavelength
Showed 88.5%, which confirmed the validity of claim 1 of the present invention.

<Embodiment 2> An acrylic resin solution previously prepared so that the refractive index at a wavelength of 450 nm is 1.45 is spin-coated on the microlens 21 obtained in Embodiment 1 with a spinner. A solid-state imaging device 20 having a microlens array 32 on which a filling factor improving layer 31 having a thickness of 0.09 μm was formed (see FIG. 1B).

By forming the filling rate improving layer 31,
The gap between the micro lenses became 0.2 μm, and the optical filling factor of the lens could be improved from 76% to 90%.

The microlens 21 has a filling rate improving layer 3
FIG. 4 shows the result of measuring the spectral transmittance of a sample in which the microlens array 32 in which the sample No. 1 was formed was separately formed on a glass substrate of the same size. The transmittance at a wavelength of 450 nm was 90%, and the transmittance was further improved by 1.5% as compared with the microlens array 22 having a single microlens.

FIG. 5 shows the results of measuring the spectral reflectance characteristics of a sample in which a microlens array 32 in which the filling factor improving layer 31 is formed on the microlens 21 is separately formed on a glass substrate of the same size. 450nm wavelength
Shows a reflectance of 2.4%, which is less than half the reflectance of the conventional microlens array 42 with a single microlens.

<Comparative Example> On the overcoat layer 16 of the solid-state imaging device obtained in Example 1, a wavelength of 450
A positive resist (manufactured by JSR Corporation) adjusted to have an extinction coefficient in nm of 1.94 × 10 ⁻³ is spin-coated with a spinner, a photosensitive layer is formed, pattern exposure is performed, and a light receiving portion is formed. A resin pattern layer of a predetermined size corresponding to No. 12 was formed. Further, the resin pattern layer was heated and softened at 130 ° C. to form a microlens 41 having a convex lens shape, thereby obtaining a solid-state imaging device 30 having a microlens array 42 (see FIG. 6).

Here, FIG. 7 shows the result of measuring the spectral transmittance of a sample in which the microlens array 42 was separately formed on a glass substrate of the same size, and FIG. 8 shows the result of measuring the spectral reflectance. The transmittance at a wavelength of 450 nm was 84.5%, and the target of 85% could not be cleared. The reflectance at a wavelength of 450 nm was 4.9%.

Finally, the resin layer formed on the terminal electrodes of the solid-state imaging device is patterned by a known dry etching method to produce the solid-state imaging devices 10 and 20 shown in FIGS. 1A and 1B. However, it was confirmed that the photoelectric conversion efficiency was improved as compared with the conventional solid-state imaging device 30.

[0033]

As described above, at a wavelength of 450 nm, 1.
If a microlens having an extinction coefficient of 82 × 10 ⁻³ or less is used, a transmittance of at least 85% or more can be obtained, which can contribute to improvement in sensitivity of the solid-state imaging device. Furthermore, by forming a filling improvement layer on the microlenses, the gap between the microlenses can be filled to form a microlens array for a solid-state imaging device with a higher light-collecting efficiency. In addition, since the transmittance can be improved, it is possible to contribute to improvement in sensitivity of the solid-state imaging device and downsizing of the solid-state imaging device.

[Brief description of the drawings]

FIG. 1A is a partial cross-sectional view schematically illustrating a microlens array for a solid-state imaging device and a solid-state imaging device according to a first embodiment of the present invention. (B) is a partial sectional view schematically showing Example 2 of the microlens array for a solid-state imaging device and the solid-state imaging device of the present invention.

FIG. 2 is an explanatory diagram showing the results of simulating the transmittance for various wavelengths of various resin layers having a thickness of 1.2 μm having different extinction coefficients (K).

FIG. 3 is an explanatory diagram illustrating a spectral transmittance characteristic of the microlens array for a solid-state imaging device according to the first embodiment.

FIG. 4 is an explanatory diagram showing a spectral transmittance characteristic of a microlens array for a solid-state imaging device according to a second embodiment.

FIG. 5 is an explanatory diagram illustrating spectral reflectance characteristics of a microlens array for a solid-state imaging device according to a second embodiment.

FIG. 6 is a partial cross-sectional view schematically illustrating a conventional microlens array for a solid-state imaging device and a solid-state imaging device.

FIG. 7 is an explanatory diagram showing a spectral transmittance characteristic of a conventional (comparative example) microlens array for a solid-state imaging device.

FIG. 8 is an explanatory diagram showing a spectral reflectance characteristic of a conventional (comparative example) microlens array for a solid-state imaging device.

[Explanation of symbols]

 10, 20, 30 ... solid-state image sensor 11 ... semiconductor substrate 12 ... light receiving unit 13 ... light shielding unit 14 ... flattening layer 15 ... color filter layer 16 ... overcoat layer 21, 41 ... microlens 22, 32, 42... Microlens array 31... Filling rate improving layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M118 AA10 AB01 BA09 CA02 EA20 FA06 GB03 GB07 GB11 GC08 GD04 GD07 5C024 AA01 CA00 EA04 EA08 FA01 GA01 5F088 BA01 BB03 EA06 HA02 HA20 JA12 LA03

Claims (5)

[Claims] 1. A microlens array formed on a solid-state imaging device having a light receiving portion two-dimensionally arranged in a horizontal direction and a vertical direction, wherein an extinction coefficient of a microlens constituting the microlens array is provided. Has a wavelength of 450 nm
A microlens array for a solid-state imaging device, which is 1.82 × 10 ⁻³ or less. 2. The microlens array for a solid-state imaging device according to claim 1, wherein a filling rate improving layer is provided on a surface of said microlens. 3. The filling factor improving layer has a refractive index of 450 nm.
3. The microlens array for a solid-state imaging device according to claim 1, wherein m is 1.46 or less. 4. The optical film thickness of the filling rate improving layer is 450 wavelengths.
4. The microlens array for a solid-state imaging device according to claim 1, wherein the range is 100 to 150 nm in nm. 5. 5. A solid-state imaging device comprising the microlens array for a solid-state imaging device according to claim 1.