JP2008060323A - Solid-state imaging device, method for manufacturing solid-state imaging device, and camera - Google Patents

Abstract

A solid-state imaging device that performs color imaging using a dichroic filter and can achieve high productivity even if pixels are miniaturized.
In a solid-state imaging device, a P-type semiconductor layer, an interlayer insulating film, a polarization cut filter, and a condenser lens are sequentially stacked on an N-type semiconductor layer. On the side of the interlayer insulating film 104 of the P-type semiconductor layer 102, a photodiode 103 is formed for each pixel. In the interlayer insulating film 104, a light shielding film 107, a dichroic filter 106, and a support 105 are formed. The dichroic filter 106 selectively transmits light in any one of the red (R), green (G), and blue (B) wavelength ranges for each pixel. The support 105 has a tapered surface with an inclination angle of 45 degrees with respect to the main surface of the P-type semiconductor layer 102, and supports the dichroic filter 106 on the tapered surface.
[Selection] Figure 1

Description

  The present invention relates to a solid-state imaging device, a method for manufacturing the solid-state imaging device, and a camera, and more particularly to a spectroscopic technique used for color imaging.

In recent years, the application range of solid-state imaging devices such as digital cameras and mobile phones is explosively expanding, and it is required to realize high sensitivity in various environments.
For this reason, for example, a solid-state imaging device that performs color imaging using a dichroic filter has been proposed (Patent Document 1). FIG. 6 is a cross-sectional view showing a configuration of a solid-state imaging device according to the conventional technique.

As shown in FIG. 6, the solid-state imaging device 6 is formed by laminating a silicon substrate 601, a sensor substrate 610, an optical substrate 620, and a glass substrate 630. A photoelectric conversion unit 602 is provided on the silicon substrate 601. The glass substrate 630 is transparent.
The sensor substrate 610 includes a waveguide 611, aluminum wirings 612 and 613, and an interlayer film 614. The optical substrate is a dichroic filter layer 621 and 622, a first refractive index layer 624, a second refractive index layer 623, and a microlens. 625 and a low refractive index layer 626.

In this way, since the reflected light from the dichroic filter layers 621 and 622 is guided to the adjacent pixels by the first refractive index layer 624 and the second refractive index layer 623, the utilization efficiency of incident light is improved. Sensitivity can be increased.
JP 2005-64385 A

  However, since the solid-state imaging device 6 according to the above-described prior art is manufactured by laminating an optical substrate and a sensor substrate that are individually manufactured, when these pixels are miniaturized and the pixel size is increased, these substrates are used. It must be bonded with high assembly accuracy. For this reason, if the pixel size is miniaturized to several μm or less, a sufficient yield cannot be achieved and productivity is lowered.

In addition, the dichroic filter layers 621 and 622 included in the solid-state imaging device 6 according to the above-described prior art only show materials such as silicon dioxide (SiO ₂ ) and titanium dioxide (TiO ₂ ), and the manufacturing method is not limited. Since even the configuration is not disclosed, it is poor in the first place.
The present invention has been made in view of the above problems, and is a solid-state imaging device that performs color imaging using a dichroic filter, and can achieve high productivity even if pixels are miniaturized. An object is to provide a solid-state imaging device.

  To achieve the above object, a solid-state imaging device according to the present invention is a solid-state imaging device in which a plurality of unit pixels are arranged two-dimensionally, and each unit pixel is a flat photoelectric conversion region that photoelectrically converts incident light. And a flat dichroic filter that is formed above the photoelectric conversion region and has a dielectric layer stacked thereon and separates the wavelength of incident light, and the main surface of the dichroic filter is the main surface of the photoelectric conversion region. It arrange | positions so that it may cross with respect to, It is characterized by the above-mentioned.

In this way, a dichroic filter is formed by a semiconductor process on a semiconductor substrate having a photoelectric conversion region, so that high assembly accuracy can be achieved. Therefore, the pixels can be miniaturized to increase the number of pixels in the solid-state imaging device.
In this case, the dichroic filter has an insulator layer sandwiched between λ / 4 multilayer films. The λ / 4 multilayer film has two types of dielectric layers having the same optical film thickness and different refractive indexes. They may be stacked alternately. The dichroic filter may transmit incident light in a different wavelength range depending on the presence or absence of the insulator layer, and the dichroic filter is supposed to transmit incident light in the green wavelength region when there is no insulator layer. Is preferable.

  The solid-state imaging device according to the present invention includes a polarization cut filter, and the dichroic filter wavelength-separates incident light that has passed through the polarization cut filter. In this way, it is possible to stabilize the transmission characteristics of the dichroic filter 106 and prevent a decrease in color reproducibility. In this case, the polarization cut filter may be made of a photonic crystal.

Further, the dichroic filter is characterized in that its main surface obliquely intersects with the main surface of the photoelectric conversion region by 45 degrees. In this way, incident light reflected by the dichroic filter can be guided to other pixels, so that sensitivity can be improved.
In the method for manufacturing a solid-state imaging device according to the present invention, a plurality of unit pixels that are two-dimensionally arranged are respectively formed on a flat photoelectric conversion region that photoelectrically converts incident light, and above the photoelectric conversion region, and a dielectric layer is formed And a flat dichroic filter that separates wavelengths of incident light, and the dichroic filter is disposed so that its main surface is oblique to the main surface of the photoelectric conversion region. A manufacturing method comprising: forming a translucent support layer on a photoelectric conversion region; forming a dichroic filter on the support layer; and forming a support layer under the dichroic filter as a tapered surface. And a step of causing the main surface of the dichroic filter to cross the main surface of the photoelectric conversion region along the dichroic filter. In this way, it is possible to realize a solid-state imaging device that performs color imaging using a dichroic filter.

The camera according to the present invention includes the solid-state imaging device as described above. In this way, it is possible to obtain a camera with high pixels and high productivity while using a dichroic filter.
As described above, according to the present invention, it is possible to realize a solid-state imaging device that includes a dichroic filter having an RGB color function, has extremely high production stability, and can reduce the size of pixels.

Hereinafter, a solid-state imaging device, a method for manufacturing a solid-state imaging device, and an embodiment of a camera according to the present invention will be described with reference to the drawings, taking a digital still camera as an example.
[1] Configuration of Solid-State Imaging Device First, the configuration of a solid-state imaging device according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view illustrating a configuration of a pixel portion of a solid-state imaging device according to an embodiment of the present invention. As shown in FIG. 1, the solid-state imaging device 1 is formed by sequentially stacking a P-type semiconductor layer 102, an interlayer insulating film 104, a polarization cut filter 108, and a condenser lens 109 on an N-type semiconductor layer 101. On the side of the interlayer insulating film 104 of the P-type semiconductor layer 102, a photodiode 103 in which N-type impurities are ion-implanted is formed for each pixel. A P-type semiconductor layer is interposed between adjacent photodiodes 103, which is called an element isolation region.

A light shielding film 107, a dichroic filter 106, and a support 105 are formed in the interlayer insulating film 104. The light shielding film 107 prevents light transmitted through the condenser lens 109 from entering the photodiode 103.
The dichroic filter 106 is a multilayer interference filter, and selectively transmits light in any one of the red (R), green (G), and blue (B) wavelength ranges for each pixel. The multilayer interference filter includes a spacer layer sandwiched between λ / 4 multilayer films, and transmits light in a wavelength region corresponding to the optical film thickness of the spacer layer.

Further, λ is called a set wavelength and is the center wavelength of the reflection wavelength region of the λ / 4 multilayer portion. For example, when the set wavelength λ is 550 nm, the optical film thickness of the dielectric layers constituting the λ / 4 multilayer film is 137.5 nm. Here, the optical film thickness is an index obtained by multiplying the physical film thickness of the dielectric layer by the refractive index.
In the present embodiment, the dichroic filter 106 is formed by alternately laminating two types of dielectric layers, a high refractive index layer made of titanium dioxide (TiO ₂ ) and a low refractive index layer made of silicon dioxide (SiO ₂ ). Become. Since the refractive indexes of titanium dioxide and silicon dioxide are 2.51 and 1.45, respectively, the physical film thickness of the titanium dioxide layer and the silicon dioxide layer is 54.7 nm, respectively, in order to make the optical film thickness 137.5 nm. 94.8 nm.

The spacer layer is made of silicon dioxide, and its physical film thickness is 30 nm, 0 nm, and 130 nm for the dichroic filter 106 that transmits light in the red (R), green (G), and blue (B) wavelength regions, respectively. .
Note that the two titanium dioxide layers sandwiching the spacer layer having a physical thickness of 0 nm in the dichroic filter 106 that transmits light in the green (G) wavelength region have a physical thickness of 109.4 nm as a whole. For the dichroic filter 106 that transmits light in the green (G) wavelength region, this titanium dioxide layer may be referred to as a spacer layer.

  Further, the total number of layers of the dichroic filter 106, that is, the total number of layers including the λ / 4 multilayer film and the spacer layer is the dichroic filter 106 that transmits light in the red (R) and blue (B) wavelength regions. Is 8 layers, and the dichroic filter 106 that transmits light in the green (G) wavelength region has 6 layers. In this way, the dichroic filter 106 can be easily formed.

The support 105 is a triangular prism-shaped member made of silicon dioxide, and has a tapered surface with an inclination angle of 45 degrees with respect to the main surface of the P-type semiconductor layer 102. The dichroic filter 106 is formed on the tapered surface.
The polarization cut filter 108 will be described later.
[2] Manufacturing Method of Dichroic Filter 106 Next, a manufacturing method of the dichroic filter 106 will be described. FIG. 2 is a diagram showing various processes for manufacturing the dichroic filter 106. In FIG. 2, the manufacturing process of the dichroic filter 106 proceeds from (a) to (f). Further, the N-type semiconductor layer 101, the P-type semiconductor layer 102, the photodiode 103, the light shielding film 107, and the condenser lens 109 are not shown.

First, a silicon dioxide film 201 is formed on the P-type semiconductor layer 102 (FIG. 2A).
Next, a resist agent is applied onto the silicon dioxide film 201, and after exposure baking (pre-baking), exposure is performed by an exposure apparatus such as a stepper, resist development, and final baking (post-baking), thereby forming a triangular prism shape. The resist pattern 202 is formed (FIG. 2B).

Next, the silicon dioxide film 201 is physically etched using a tetrafluoromethane (CF ₄ ) -based etching gas to form the support 105 (FIG. 2C).
Next, a region other than the support 105 on the P-type semiconductor layer 102 is exposed by an exposure device such as a stepper to form a resist pattern 203 (FIG. 2D).
Then, a dichroic filter 106 is formed on the tapered surface of the support 105 using a sputtering apparatus (FIG. 2 (e)).

Finally, when the resist is removed by organic cleaning or the like, the dichroic filter 106 is obtained (FIG. 2 (f)).
[4] Pixel Arrangement Next, the pixel arrangement according to the present embodiment will be described.
FIG. 3 is a plan view showing an array of pixels of the solid-state imaging device 1 according to the present embodiment. As shown in FIG. 3, the pixels are two-dimensionally arranged with four pixels each receiving light in the wavelength ranges of green (G), magenta (Mg), red (R), and cyan (Cy) as one unit. .

Further, a condensing lens 109 is formed on the green (G) and red (R) pixels, whereas no condensing lens is formed on the magenta (Mg) and cyan (Cy) pixels. Of the incident light collected by the condenser lens 109, light in the wavelength range of green (G) and red (R) is transmitted through the dichroic filter 106 and is incident on the photodiode 103.
On the other hand, light in the wavelength range of magenta (Mg) and cyan (Cy), which are complementary colors of green (G) and red (R), respectively, is reflected by the dichroic filter 106 and enters the dichroic filter 106 of the adjacent pixel. .

[5] Transmission Characteristics of Dichroic Filter 106 Next, transmission characteristics of the dichroic filter 106 will be described.
FIG. 4 is a graph showing the transmission characteristics of the dichroic filter 106, where (a) shows the transmission characteristics of the dichroic filter 106 that transmits light in the blue (B) wavelength region, and (b) shows the red (R) characteristics. The transmission characteristic of the dichroic filter 106 that transmits light in the wavelength band is shown, and (c) shows the transmission characteristic of the dichroic filter 106 that transmits light in the green (G) wavelength band.

As shown in FIG. 4, when the dichroic filter 106 is used, light in each wavelength region of red (R), green (G), and blue (B) can be dispersed, while p-wave (solid line) and s Transmission characteristics differ from waves (broken lines).
Here, the p-wave refers to linearly polarized light in which the vibration direction of the electric vector of light incident on the dichroic filter 106 is included in the main surface of the dichroic filter 106. The s-wave is a straight line perpendicular to a plane in which the vibration direction of the electric vector of light incident on the dichroic filter 106 includes the normal of the main surface of the dichroic filter 106 and the normal of the wavefront that is the traveling direction of light. This refers to polarized light.

For any of the dichroic filters 106 that split light in the red (R), green (G), and blue (B) wavelength regions, the peak wavelength is generally the same between the s wave and the p wave, but the transmission bandwidth For, the s wave is narrower than the p wave.
Since natural light contains both s-wave and p-wave components in a random ratio, when color imaging is performed with natural light, the transmission characteristics are not constant, and the color reproducibility may be reduced.

  In order to solve this problem, either the s wave or the p wave may be removed before entering the dichroic filter 106. For this reason, in this embodiment, a polarization cut filter 108 having a photonic crystal structure is provided between the interlayer insulating film 104 and the condenser lens 109. Note that the photonic crystal structure is a structure in which materials having different refractive indexes overlap in a multidimensional manner with a period of about the wavelength of light.

In this embodiment, the polarization cut filter 108 is formed by alternately laminating titanium dioxide layers and silicon dioxide layers, and each layer has a sawtooth shape in cross section. The polarization cut filter 108 transmits the p-wave on the main surface of the dichroic filter 106 and reflects the s-wave.
As a result, it is possible to stabilize the transmission characteristics of the dichroic filter 106 and to prevent a decrease in color reproducibility.

[6] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) In the above embodiment, the case where the support body 105 is formed prior to the formation of the dichroic filter 106 has been described. Needless to say, the present invention is not limited to this. Anyway.

FIG. 5 is a diagram showing various steps in the manufacturing method according to this variation of the dichroic filter 106.
First, a silicon dioxide film 501 is formed on the P-type semiconductor layer 102 (FIG. 5A).
Next, a multilayer film 502 having the same configuration as that of the dichroic filter 106 is formed on the silicon dioxide film 501 (FIG. 5B).

Then, a resist pattern 503 is formed by a normal lithography process (FIG. 5C), and the multilayer film 502 and the silicon dioxide film 501 are physically removed by dry etching or the like (FIG. 5D).
In this case, when anisotropic etching is performed by adjusting the gas flow rate and pressure so that the portion of the silicon dioxide film 501 sandwiched between the multilayer film 502 and the P-type semiconductor layer 102 is etched obliquely, A tapered surface of the support 105 is obtained (FIG. 5E).

Thereafter, the resist pattern 503 is removed (FIG. 5F), the resist pattern 504 is formed (FIG. 5G), and the multilayer film 502 and the silicon dioxide film 501 are removed by etching. Finally, the dichroic filter is obtained. 106 and the support 105 are obtained (FIG. 5 (h)).
In this case, since the dichroic filter 106 is formed in a horizontal state, the uniformity and stability of the film thickness are higher than when the manufacturing method according to the above embodiment is used. Therefore, the color resolution of the dichroic filter 106 can be dramatically improved.

(2) In the above embodiment, the case where titanium dioxide is used as the material of the high refractive index layer has been described. However, it goes without saying that the present invention is not limited to this, and the following may be used instead. . In other words, instead of titanium dioxide, other materials such as silicon nitride (Si ₃ N ₄ ), tantalum trioxide (Ta ₂ O ₃ ), zirconium dioxide (ZrO ₂ ) are used as the material for the high refractive index layer. Also good. Further, a material other than silicon dioxide may be used for the material of the low refractive index layer. The effects of the present invention can be obtained regardless of the material used for the multilayer interference filter.

  (3) In the above embodiment, the total number of layers of the dichroic filter 106, that is, the total number of layers including the λ / 4 multilayer film and the spacer layer is the wavelength range of red (R) and blue (B). In the above description, the dichroic filter 106 that transmits light of 8 layers has 8 layers and the dichroic filter 106 that transmits light in the green (G) wavelength region has 6 layers. However, the present invention is not limited to this. Alternatively, the number of layers may be 4 layers, 12 layers, 16 layers, or more.

The spacer layer may be made of the same material as the high refractive index layer of the λ / 4 multilayer film, or may be made of the same material as the low refractive index layer. Further, a material different from the material of any layer constituting the λ / 4 multilayer film may be used.
(4) Although the case where silicon dioxide is used as the material of the support 105 has been described in the above embodiment, it goes without saying that the present invention is not limited to this, and a material other than silicon dioxide is used instead. Also good. Regardless of the material, the effect of the present invention can be obtained as long as it is a transparent material that does not absorb visible light.

(5) In the above embodiment, the case where the pixels are arranged as shown in FIG. 3 has been described. However, it goes without saying that the present invention is not limited to this, and other arrangements may be used instead. good. The effect of the present invention can be obtained regardless of the arrangement of the pixels.
(6) In the above embodiment, the case where the solid-state imaging device 1 is provided with the polarization cut filter has been described. Needless to say, however, the present invention is not limited to this. good. If a polarization cut filter is not provided, the transmission characteristics are not stable and the color reproducibility is lowered, but the effect of the present invention is still obtained.

  The solid-state imaging device, the manufacturing method of the solid-state imaging device, and the camera according to the present invention have very high production stability and are useful as a dichroic filter technology that can reduce the size of pixels.

It is sectional drawing which shows the pixel part of the solid-state imaging device which concerns on embodiment of this invention. It is a figure which shows the various processes which manufacture the dichroic filter 106 which concerns on embodiment of this invention. It is a top view which shows the arrangement | sequence of the pixel of the solid-state imaging device 1 which concerns on embodiment of this invention. 5 is a graph showing the transmission characteristics of a dichroic filter according to an embodiment of the present invention, where (a) shows the transmission characteristics of the dichroic filter 106 that transmits light in the blue (B) wavelength region, and (b) shows the red characteristics. (R) represents the transmission characteristic of the dichroic filter 106 that transmits light in the wavelength band, and (c) represents the transmission characteristic of the dichroic filter 106 that transmits light in the green (G) wavelength band. It is a figure which shows the various processes which manufacture the dichroic filter 106 which concerns on the modification (1) of this invention. It is sectional drawing which shows the structure of the solid-state imaging device concerning a prior art.

Explanation of symbols

1, 6 …………………………………… Solid-state imaging device 101 …………………………… N-type semiconductor layer 102 ……………………………… … P-type semiconductor layer 103 ………………………………… Photodiode 104 ………………………………… Interlayer insulating film 105 …………………………… …… Support 106 …………………………………… Dichroic filter 107 ………………………………… Shading film 108 ………………………………… Polarization cut filter 109 ……………………………… Condensing lens 201 ………………………… Silicon dioxide films 202, 203, 503, 504... Resist pattern 501. …………………………… Silicon dioxide film 502 ………………………………… Multilayer film 601 …………………………………… Silicon Plate 602 …………………………………… Photoelectric converter 610 ………………………………… Sensor substrate 611 ……………………………………… Waveguide 612, 613 ……………………… Aluminum wiring 614 …………………………… Interlayer film 620 ………………………………… Sensor substrate 621, 622… …………………… Dichroic filter layer 624 ………………………………… First refractive index layer 623 ………………………………… Second refractive index Layer 625 ………………………………… Microlens 626 ………………………………… Low refractive index layer 630 ………………………………… Glass substrate

Claims (9)

A solid-state imaging device in which a plurality of unit pixels are arranged two-dimensionally,
Each unit pixel has a flat photoelectric conversion region that photoelectrically converts incident light, and
A flat dichroic filter that is formed above the photoelectric conversion region, is formed by laminating dielectric layers, and separates the wavelength of incident light; and
The dichroic filter is disposed so that its main surface is oblique to the main surface of the photoelectric conversion region. The dichroic filter consists of an insulator layer sandwiched between λ / 4 multilayer films.
2. The solid-state imaging device according to claim 1, wherein the λ / 4 multilayer film is formed by alternately laminating two types of dielectric layers having the same optical film thickness and different refractive indexes. The solid-state imaging device according to claim 2, wherein the dichroic filter transmits incident light having different wavelength ranges depending on the presence or absence of an insulator layer. The solid-state imaging device according to claim 2, wherein the dichroic filter transmits incident light in a green wavelength region when there is no insulator layer. With polarization cut filter,
The solid-state imaging device according to claim 1, wherein the dichroic filter wavelength-separates incident light that has passed through the polarization cut filter. The solid-state imaging device according to claim 5, wherein the polarization cut filter is made of a photonic crystal. 2. The solid-state imaging device according to claim 1, wherein the main surface of the dichroic filter obliquely intersects with the main surface of the photoelectric conversion region by 45 degrees. A plurality of unit pixels arranged two-dimensionally are each formed as a flat photoelectric conversion region that photoelectrically converts incident light, and a flat plate that is formed above the photoelectric conversion region and has a dielectric layer stacked thereon to separate wavelengths of incident light. A dichroic filter, and the dichroic filter is a method for manufacturing a solid-state imaging device in which a main surface thereof is arranged obliquely with respect to a main surface of a photoelectric conversion region,
Forming a translucent support layer on the photoelectric conversion region;
Forming a dichroic filter on the support layer;
A solid layer characterized by comprising: a support layer under a dichroic filter as a tapered surface, a dichroic filter along the tapered surface, and a main surface of the dichroic filter obliquely intersecting with a main surface of the photoelectric conversion region. Manufacturing method of imaging apparatus. A camera comprising the solid-state imaging device according to claim 1.

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